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Human Reproduction Update 1998, Vol. 4, No. 2 pp. 153–168

European Society for Human Reproduction and Embryology

Recent developments in endocrinology and paracrinology of blastocyst implantation in the primate* Debabrata Ghosh and Jayasree Sengupta1 Department of Physiology, All India Institute of Medical Sciences, New Delhi 110 029, India

TABLE OF CONTENTS Introduction Hormonal regulation of endometrial receptivity Oviductal and endometrial support to preimplantation embryo Correlates of endometrial receptivity Cytokines and other factors in embryo growth and implantation Acknowledgements References

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It is becoming increasingly evident that growth factors and cytokines play crucial roles in the process of blastocyst implantation. Endometrial differentiation and secretions, embryo development and secretions, and embryo–endometrium interaction leading to implantation require continuous and synchronous dialogue between these two compartments involving endocrine and paracrine regulators. In this review, a model of the endocrinology and paracrinology of blastocyst implantation in the primate is described. Key words: cytokines/embryo/endometrium/growth factors/implantation/progesterone Introduction Recent studies in the area of assisted human reproduction and in the area of post-ovulatory, post-coital contraception have resulted in significant expansion of our information on blastocyst development and implantation in the human. Studies with small animals and non-human primates, especially in areas which cannot be investigated with human

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samples for ethical and technical constraints, have elaborated the conceptual background of the process of blastocyst implantation in general. Taken together, it is possible to develop a hypothetical model of the endocrinology and paracrinology of blastocyst implantation in the primate (Figure 1), a brief account of which is presented in this review. Interestingly, the complex regulatory system involving several endocrine–paracrine factors, which operates at the level of endometrium and embryo during the implantation window, may not be operative when embryo implants at an ectopic site. However, in the present essay, our aim is to develop a working scheme of endocrinology and paracrinology of embryo implantation in the endometrium of the primate, with a special reference to the human. Hormonal regulation of endometrial receptivity The term uterine ‘receptivity’ refers to a state when endometrium allows blastocyst to attach, penetrate and induce localized changes in the stroma resulting in decidualization. These changes are initiated in the human by around day 7 after fertilization, and by day 16 secondary villi begin to form. Although the physiological and biochemical determinants which allow endometrium to enter into the state of receptivity for human embryo attachment and implantation remain poorly understood (Johannisson, 1991), various endocrine correlates of endometrial receptivity and implantation are well documented. Synchronous development of embryo and endometrium is a prerequisite for blastocyst implantation. Generally, this is dependent upon the actions of oestrogen and progesterone. Normal implantation, gestation and delivery can be experimentally obtained from surrogate embryo transfer combined with oestrogen plus progesterone in ovariectom-

whom correspondence should be addressed

*This article is based on a lecture delivered at the International Symposium on Post-Coital and Post-Ovulatory Contraception, Budapest, Hungary, March 6–7, 1997.

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D.Ghosh and J.Sengupta

Figure 1. A scheme of endocrine–paracrine regulation of blastocyst implantation. Under progesterone dominance, various endometrial cellular compartments differentiate and undergo cell–cell interaction. This allows endometrium to secrete into the luminal milieu a variety of active biomolecules which support embryo growth. A viable embryo in turn secretes different types of biomolecules which influence embryo growth (autocrine effect) and endometrial receptivity (paracrine effect). 1: Endometrial epithelial cells (EEC) secrete cytokines [e.g. leukaemia inhibitory factor (LIF)] and growth factors (e.g. vascular endothelial growth factor) which influence the vascular compartment (VC). 2: Paracrine interaction between EEC and stromal cells (SC) influences platelet activating factor (PAF)–prostaglandin (PG) milieu, which affects VC, and emigration and activation (*) of blood-derived cells (BDC). During receptivity, there is a higher bias towards PGE resulting in increased blood flow, low vascular impedence and inhibition of BDC emigration and activation, otherwise chemical agents [e.g. nitric oxide, superoxides, PAF, prostaglandins, interleukins (IL), tumour necrosis factors (TNF)] liberated by activated BDC may affect EEC, SC and VC (3). SC play a crucial role in regulating vasoactive peptides (e.g. nitric oxide synthase, endothelin, parathyroid hormone-related protein and cytokines [e.g. transforming growth factor-β (TGFβ)] which also influence VC (4). Factors (matrix metalloproteinases, proteases, plasminogen activator, tissue inhibitors of proteinases, plasminogen activator inhibitor) liberated from SC and BDC influence the integrity and turnover of extracellular matrix (ECM) (5). During the receptive period, endometrium secretes several chemical agents (e.g. EGF, IGF-I, LIF) which may help to support embryo growth (6). While some embryo-derived factors (e.g. TGFα, IGF-II) may influence its own growth in an autocrine manner (7), other factors (e.g. IL-1, PAF, PGE, spermine–spermidine, proteases) may influence endometrial preparation towards blastocyst implantation (8).

ized rhesus monkeys (Hodgen, 1983), and in women having primary ovarian failure (Lutjen et al., 1984; Navot et al., 1986). It is pragmatically assumed that mid-luteal phase rise of oestradiol is also required for blastocyst implantation in the human. However, luteal support with progesterone alone to women with inadequate or absent ovaries led to normal secretory maturation of endometrium (de Ziegler et al., 1992). In a study aimed to investigate whether luteal phase ovarian oestrogen is essential for blastocyst implantation and pregnancy maintenance, rhesus monkey embryos were transferred either to acutely ovariectomized or to long-term ovariectomized, primed surrogate recipients; implantation and live births were obtained in both groups following supplementation with

progesterone alone (Ghosh et al., 1994). Examination of endometrial histology also failed to indicate any insufficiency in glandular and stromal characteristics of mid-luteal phase monkey endometrium in the absence of mid-luteal phase ovarian oestrogen. It appears that luteal phase ovarian oestrogen is not essential for progesteronedependent endometrial receptivity and responses leading to implantation and pregnancy maintenance in the rhesus monkey (Ghosh et al., 1994; Ghosh and Sengupta, 1995). Luteal phase oestrogen support is also not required for the establishment of pregnancy in women (Zegers-Hochschild and Altieri, 1995). High serum oestradiol concentrations on the day of human chorionic gonadotrophin (HCG) administration in patients undergoing ovulation induction

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demonstrated that endometrial receptivity and not oocyte quality was affected (Simon et al., 1995a). The simplicity of natural ovulatory cycles in in-vitro fertilization (IVF) programmes has been recently analysed to show that unstimulated IVF cycles are a clinically viable alternative to stimulated cycles (Paulson et al., 1994). However, the possibility that luteal phase oestradiol may none the less be permissive for implantation cannot be ruled out. There are reports that luteal phase treatment with anti-oestrogen (e.g. tamoxifen) or with anti-oestradiol antibody may inhibit implantation (Ravindranath and Moudgal, 1987; 1990). Furthermore, a putative role of locally available oestrogen, either from endometrial stromal cells (Tseng et al., 1986; Noble et al., 1997), or from blastocysts (Edgar et al., 1993) around the time of blastocyst implantation remains to be explored in primates (de Ziegler, 1995; Edgar, 1995; Ghosh and Sengupta, 1995). Progesterone is essential for endometrial preparation for blastocyst implantation in most mammals including the monkey and the human. Inadequate endometrial maturation and progesterone insufficiency are well known causes of infertility. Progesterone maintains embryo viability, presumably indirectly through its action on uterus (see Mead, 1989). Also, application of a high-affinity antiprogestin such as mifepristone (RU486) and onapristone (ZK98.299) during early luteal phase can delay or inhibit endometrial maturation for implantation resulting in contragestion (Li et al., 1988; GemzellDanielsson et al., 1993, 1994, 1997; Ghosh and Sengupta, 1993; Katkam et al., 1995; Ghosh et al., 1996; Cameron et al., 1997; Dockery et al., 1997). Despite the fact that serum concentration of progesterone is highest during the mid-luteal phase of the ovulatory cycle, it appears possible that endometrial maturation towards receptivity does not require a very high concentration of progesterone in peripheral circulation, and implantation stage embryos can withstand a partial lack of progesterone for a limited period for time (Edwards, 1994; Ghosh et al., 1997a; Milligan and Finn, 1997). It has been suggested that progesterone induces a basic drive and an innate releasing mechanism towards implantation in both embryo and endometrium, and thus it proceeds through certain steps in a fixed action pattern, even in the presence of vaccum stimuli (Ghosh and Sengupta, 1995). Some of the paracrine modules in this process will be addressed in the following sections. Relaxin is a luteal peptide hormone which has been shown to increase at the time of implantation and suggested to be regulated at least partially by chorionic gonadotrophin (CG) (Castracane et al., 1985; Bell et al., 1987a; Johnson et al., 1994). In embryo transfer experiments using normally cycling rhesus monkeys, it

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was observed that the delay in the appearance of CG in circulation correlated well with a delay of appearance of relaxin (Ghosh et al., 1997a). The questions whether relaxin is essential for blastocyst implantation and what are the functional correlates of relaxin in this process in the human remain to be investigated. Relaxin has been shown to promote uterine growth and to affect uterine contractility (Pusey et al., 1980; Rogers et al., 1983; Vasilenko et al., 1986; Vasilenko and Mead, 1987), and it presumably exerts permissive action regarding the role of progesterone in endometrial differentiation around the time of implantation (Tseng et al., 1992; Bryant-Greenwood et al., 1993). Relaxin also causes vasodilation (Bani Sacchi et al., 1995), inhibits mast cell degranulation (Masini et al., 1994), depresses platelet activation (Bani et al., 1995) and counteracts immune reaction induced by antigen exposure (Bani et al., 1997) in various tissue systems. Whether such functions of relaxin are essential for blastocyst implantation remains only speculative at this time, because it has been observed that normal pregnancy in women can be achieved following ovum transfer with no detectable relaxin in peripheral circulation (Johnson et al., 1991).

Oviductal and endometrial support to preimplantation embryo The concept that paracrine factors of oviductal and endometrial origin could help in promoting embryo growth and differentiation in vivo is not novel (Dey, 1996). Recently it has been shown by several groups that improved embryo morphology, development and hatching as well as better implantation rate are obtained following embryo co-culture on feeder layers of autologous cumulus or granulosa cells, human or bovine oviduct cells, and sequential oviductal–endometrial cells (Weimer et al., 1993; Bongso et al., 1994a,b). Interestingly, a number of studies have demonstrated the beneficial effect of a monkey kidney cell line (Vero cells) monolayer as well as human skin fibroblasts on embryo development (Ménézo et al., 1990, 1995; Wetzels et al., 1992; Lai et al., 1994; Jassenswillen et al., 1995). There is evidence that growth factors from oviduct and uterus stimulate cell proliferation and differentiation of preimplantation embryos (Gandolfi and Moor, 1987a; Brigstock et al., 1989). It is evident that growth factors including epidermal growth factor (EGF), transforming growth factor (TGF)-α or -β and insulin-like growth factor (IGF)-I or -II improve the development of preimplantation stage embryos (Paria and Dey, 1990; Smith et al., 1993). Also, various growth factors (e.g. TGFα, EGF, IGF-I) are found in Fallopian tube and endometrial epithelial cells, receptors for which are observed in human

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embryos (Smotrich et al., 1996). The means by which co-culture with cells derived from non-reproductive tissues exert beneficial effects on blastocyst development are only speculative. Cells in the feeder layer for embryo cultures might produce embryotrophic factors (Gandolfi et al., 1987b; Maguiness et al., 1992; Mermillod, 1993; Liu et al., 1995a). It has also been demonstrated that human endometrial cells, oviductal cells and Vero cells produce insulin-like growth factor binding proteins (IGFBP) which may possess direct or indirect embryotrophic activity (Liu et al., 1995a; Lai et al., 1996). However, it is still debated whether embryotrophic factor(s) secreted by co-cultured cells is indeed responsible for improved embryo development in co-culture studies (Bavister and Boatman, 1997). Additionally, it is also possible that factors from co-cultured cells may help embryo development in relatively non-specific ways. For example, poor quality of embryo growth in vitro has been associated with reduced free-radical scavenging potential in embryo spent medium in the human (Paszkowski and Clarke, 1996), and 2-cell stage developmental block in mouse embryos grown in vitro has also been associated with a rise in reactive oxygen species (Nasr-Esfahani et al., 1990; Noda et al., 1991). It is possible that a feeder layer in embryo co-culture secretes proteins and other factors in culture medium, which help to reduce toxic damage from superoxide radicals (Edwards and Brody, 1995). Bavister and Boatman (1997) suggest that the co-culture system modulates the glucose milieu in the culture environment in a favourable manner for growing embryos. However, the superiority of co-culture was not observed in a study showing no difference in embryo development profiles as judged from incidence of fragmentation, development arrest, degree of mutinucleation and frequency of blastocyst formation when normally fertilized human embryos were grown in balanced salt solution with 15% maternal serum with or without co-culture on a confluent monolayer of cells derived from non-reproductive tissues (Van Blerkom, 1993). Additionally, no consensus exists about the pregnancy rates using co-cultured embryos. Several groups failed to confirm (Cohen et al., 1990; Sakkas et al., 1994) the observation that pregnancy rates are improved with co-cultured blastocysts (Bongso et al., 1992; Freeman et al., 1995). Recently, Turner and Lenton (1996) have observed that human embryos cultured on Vero cells had a higher blastocyst formation rate, but blastocyst viability in terms of hatching ability and HCG production in vitro was not improved as compared to blastocysts grown in routine culture conditions.

Correlates of endometrial receptivity Several endometrial factors and functions which have been shown to be influenced by luteal phase progesterone appear to be robust associates of endometrial receptivity and ovo-implantation. The luminal surface is considered to play a critical role in embryo–uterine interaction. Based on experimentations performed in rodent models, luminal epithelium has been suggested to act as a transducer in transmitting embryonic signals to uterine stromal cells for induction of decidualization, an integral endometrial response to implantation (Glasser and McCormack, 1982). Pinopodes differentiate on the apical surface of luminal epithelium in human receptive stage uterus under the influence of progesterone, and these may allow absorption of luminal fluid and thereby facilitate embryo adhesion (Nikas et al., 1995). Also, progesterone inhibits uterine contractility which facilitates embryo immobilization and adhesion (Mead, 1989). Features including glandular hyperplasia and changes in vascular bed in endometrium during receptivity and implantation in conception cycles are also evident (Hertig, 1964; Ghosh et al., 1993). However, endometrial samples classified as normal based on histology may be found to be abnormal on the basis of endometrial protein expression (Manners, 1990). Progesterone during the luteal phase is known to modulate the synthesis and secretion of a number of endometrial proteins (Okulicz et al., 1996). Pregnancy associated endometrial α2 globulin (α2 PEG, also known as placental protein 14, PP14, or glycodelin) appears in mid-luteal phase and is a glandular marker of endometrial function (Bell et al., 1987b). Estimates of uterine luminal concentrations of PP14 collected on day LH+6 have revealed significantly low levels of PP14 in washings collected from a group of women with recurrent miscarriage having both histologically normal and retarded endometrial development as compared with normal fertile women (Dalton et al., 1995). The functional relevance of PP14 in peri-implantation endometrium (Wahlstrom et al., 1985) is not known, but there is evidence to suggest that this polypeptide may play a role in immunomodulation (Seppala et al., 1994). A 24 kDa heat shock protein (HSP) has been shown to exhibit maximal expression in luminal epithelial cells of human endometrium around the time of implantation (Ciocca et al., 1983, 1993). Based on circumstantial evidence, it appears possible that 24 kDa HSP may be involved in pinopode differentiation through influencing the organization of microfilament resulting in at least two broad functions: facilitating embryo apposition and influencing signal transduction (Arrigo and Landry, 1994;


Edwards, 1994). Even in the absence of precise knowledge about the physiological significance of PP14 and 24 kDa HSP, there is evidence indicating that the expression of these protein factors in endometrial cells may potentially be used for identifying a receptive stage endometrium (Rizk et al., 1992). Furthermore, progesterone-induced uterine protein-1 (PUP-1) and prolactin by endometrial cells during luteal phase may be involved in embryo–endometrium interaction, implantation and decidualization (Maslar and Riddick, 1979; Sharpe-Timms et al., 1995; Seppala and Tiitinen, 1995). Leukaemia inhibitory factor (LIF) secretion in vitro by human endometrium during different phases of cycle has been studied from tissue biopsies collected from normal fertile women (Delage et al., 1995; Laird et al., 1997). This cytokine is secreted throughout the menstrual cycle, and its expression is high in progesterone-dominated implantation stage endometrium (Kojima et al., 1994; Laird et al., 1997). Endometrial LIF concentration is lower in infertile women with recurrent embryo transfer failure after IVF (Delage et al., 1995) and in women with unexplained infertility (Laird et al., 1997). Blockade of progesterone receptor inhibits the endometrial maturation along with repressed expression of mid-luteal phase endometrial LIF (Gemzell-Danielsson et al., 1997). It has been suggested that endometrial LIF influences blastocyst implantation through an antocrine–paracrine interaction at the luminal epithelium level and blastocyst stage (Cullinan et al., 1996). It has also been demonstrated that LIF can influence endometrial angiogenesis which is, at least partially, dependent on progesterone (Pepper et al., 1995; Ghosh et al., 1998a). Progesterone inhibits superoxide radical formation (Sugino et al., 1996a,b) and tumour necrosis factor (TNF)-α in endometrium (Hunt et al., 1992; Laird et al., 1996). Both these factors may induce degenerative changes in the tissue. Superoxide dismutase (SOD) is a scavenging system for superoxide radicals and is highest in endometrium at mid-secretory stage of the cycle; it has been recovered in human uterine fluid in pre- and peri-implantation stages (Narimoto et al., 1990) and it could play a prominent role in protecting blastocysts from superoxide radical damage. Thus, luteal phase antiprogestin (mifepristone) treatment may result in increased superoxide radical formation and increase in TNFα production compromising endometrial maturation, embryo viability and blastocyst implantation (Zimmerman et al., 1989; Rotello et al., 1992; Gemzell-Danielsson et al., 1993; Ghosh and Sengupta, 1993; Ghosh et al., 1996, 1997b; Dockery et al., 1997).

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Despite the fact that expression of TGFβ is high in preimplantation stage endometrium of mouse (Tamada et al., 1990; Das et al., 1992), and that its expression is enhanced by oestradiol and progesterone in human endometrial stromal cells (Arici et al., 1996), the level of TGFβ1 in primate luteal endometrium is low at the time of implantation (Ghosh et al., 1998a). Indeed, administration of luteal phase antiprogestin (RU486) results in increased endometrial TGFβ associated with inhibition of epithelial cell maturation, increased epithelial cell degeneration and failure of implantation in monkeys (Rotello et al., 1991, 1992; Ghosh et al., 1996, 1998a). Mucin (Muc-1) is a cell-surface and secretory product of endometrial epithelium (Hey et al., 1995), and its level is higher in uterine luminal fluid during days 7–13 post-ovulation in normal volunteers. But in women suffering from recurrent spontaneous miscarriage, the concentration of Muc-1 in uterine flushings was significantly lower on days 7 and 13 (Hey et al., 1995). The physiological significance of Muc-1 production and loss during the anticipated time of implantation in the human remains to be defined. It has however been reported that progesterone down-regulates uterine Muc-1 expression, suggesting that the loss of Muc-1 contributes to generation of a receptive state for implantation in the mouse (Pimental et al., 1995) and the baboon (Hild-Petito et al., 1996). Surface glycoproteins may play an important role in regulating maternal–fetal interactions at implantation. The composition and profile of glycoproteins, degree of glycosylation, charge properties of the glycocalyx and the proteoglycans secreted into luminal fluid are known to change during the receptive phase of the uterus (Solter and Knowles, 1978; Shevensky et al., 1982). Antigens involving α1–3-fucosylated type 2 chain (Lex and Ley) secreted by glandular epithelium may have a potential in mediating embryo adhesion; Ley antigen has also been detected in embryonic cells in a stage-specific manner and could play a role in trophectoderm recognition during implantation (Fenderson et al., 1991). In the rhesus monkey, the expression of Ley is maximal on luminal and glandular epithelium of endometrium around the time of implantation in normal menstrual cycles as well as in mated, fecund cycles (Ghosh et al., 1998b); its expression is inhibited by a single dose of early luteal phase antiprogestin (mifepristone) treatment (Ghosh et al., 1998b) which also inhibits blastocyst implantation in this species (Ghosh and Sengupta, 1993). CD44 is a cell surface glycoprotein and known to be a hyaluronate receptor; it is postulated to function through cell–cell and cell–mtarix interaction with respect to

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lymphocyte homing (Haynes et al., 1991; Underhill, 1992). Besides lymphocytes, it is also expressed on many types of epithelium (Fox et al., 1993; Heider et al., 1993; Screaton et al., 1993). There is now evidence that CD44 is expressed by glandular epithelial cells during mid- to late-secretory endometrium under progesterone dominance (Yaegashi et al., 1995), suggesting that such adhesion molecules may be involved in the process of embryo–endometrium attachment. Cell adhesion molecules (CAM) involved in cell–cell and cell–matrix interactions have been recognized to contribute to cell migration, matrix organization and transduction of differentiation signals (Ruoslahti, 1991). The co-expression of αvβ3 and α4β1 in human endometrium during the ‘implantation window’ has been documented and the lack of αvβ3 in luteal phase deficiency, minimal or mild endometriosis and infertility are consistent with the suggestion that these integrins are involved in the implantation process (Lessey et al., 1992; 1994; Tabibzadeh, 1992). Furthermore, there is evidence to suggest that several types of cell adhesion molecules including integrin, cadherins, CAM families and other adhesion molecules are expressed by preimplantation embryos and trophoblast cells (Turpeeniemi-Hujanen et al., 1992; Campbell et al., 1995; Check et al., 1995; Blankenship and Enders, 1997); these may be involved in the process of interaction between embryo and endometrium during implantation in primates (Edwards, 1995; Sueoka et al., 1997). Non-invasive studies indicate that uterine blood flow is highest around the time of implantation in normal cycling women (Bourne et al., 1996; Gannon et al., 1997) and that downstream impedence is reduced with increased blood flow on the side of corpus luteum (Scholtes et al., 1989). In the study by Scholtes et al. (1989), comparison of the pulsatility index (PI) from the left and right ovarian and uterine arteries revealed a significantly lower PI on the dominant side, i.e. on the side of the ovary bearing the developing corpus luteum on day 21 compared with day 7 of the menstrual cycle, suggesting reduced down-stream impedence and increased blood flow in implantation stage endometrium on the dominant side. Vascular impedance in uterus is known to be lowest during days 6–8 of the luteal phase (Fraser and Peek, 1992; Ferenczy, 1994; Edwards and Brody, 1995) suggesting that good blood flow in endometrium is essential for its maturation at the time of implantation. Clinical studies have shown that embryos fail to implant in women with impaired uterine perfusion (Battaglia et al., 1990; Steer et al., 1992). Improved pregnancy rates in women with impaired uterine perfusion have been reported after the addition of low-dose aspirin to

hormone replacement therapy (Wada et al., 1994); this could result from improved uterine blood flow since aspirin is known to shift the balance towards prostacyclin production (Thorp et al., 1988; Tulppala et al., 1997). Increased endometrial vascular permeability is one of the earliest distinguishable features of implantation in several mammalian species (Psychoyos, 1973). In the mouse, onset of enhanced endometrial permeability occurs in the vicinity of zonal blastocyst even prior to commencement of attachment and implantation (Mclaren, 1969) and a similar situation is found in the monkey on day 6 of gestation when most blastocysts remain zona-encased (Ghosh et al., 1993). The cellular mechanism responsible for increases in vascular permeability has not been clearly defined but endometrial prostaglandin (PG) E2 and platelet activating factor (PAF) have been suggested as possible candidates. A network of prostaglandins and PAF operative in endometrial cells and modulated by endocrine and paracrine factors at the time of implantation has been proposed (Alecozay et al., 1991; Ghosh and Sengupta, 1996). According to this model, progesterone stimulates PAF production by endometrial stromal cells; PAF along with oestradiol in turn acts on glandular epithelial cells and promotes PGE production; PGE in turn stimulates PAF production and aromatase activity in stromal cells. Thus, a positive feedback ensues. It now appears that various other factors such as interleukin (IL-1), LIF, endothelin (ET)-1 and epidermal growth factor (EGF) may influence this network (Cameron et al., 1991; Jacobs and Carson, 1993; Edwards, 1994; Bany and Kennedy, 1995a,b). The net result is an increase in the PGE:PGF ratio, which may mediate vasodilatation, immunosuppression and decidualization in the endometrium at the time of implantation (Edwards and Brody, 1995; Ghosh and Sengupta, 1996; Grbovic et al., 1996). When vascular impedence and blood flow are compromised around the time of implantation by a single dose application of antiprogesterone, the blastocyst fails to implant (Johannisson et al., 1989; Ghosh et al., 1996). Recently, the involvement of cytokines and vasoactive peptides in the vascular reaction of endometrium during receptivity and implantation has gained attention. Vascular endothelial growth factor (VEGF) promotes angiogenesis and vascular permeability. VEGF expression is high in secretory phase endometrium in women (Charnock-Jones et al., 1993) and monkeys (Greb et al., 1997), and it is inhibited by the early luteal phase administration of antiprogestin in monkeys (Greb et al., 1995, 1997; Ghosh et al., 1998a). An endometrial vasoactive peptide system has been shown to be operative in which vasoactive peptides, synthesized by stromal cells


in a sex hormone-dependent fashion, act on the adventitial surface of the spiral artery and arterioles to regulate endometrial vascular function. The components of this system include parathyroid hormone-related protein (PTHrP, a vasorelaxant) and endothelin-1 (ET-1, a vasocontractant); both are synthesized in stromal cells of human endometrium (Economos et al., 1992; Casey et al., 1993). The tissue levels of ET-1 may in turn be regulated by enkephalinase, which is a plasma membrane ectoenzyme localized in stromal cells, the activity of which increases in response to progesterone (Casey et al., 1991). Nitric oxide synthase (NOS) has been detected in human endometrium and myometrium, suggesting that nitric oxide, which is a potent vasodilator (Palmer et al., 1987), may also play a role in the paracrine control of the uterine vascular bed (Telfer et al., 1995). It is conceivable that this network, involving VEGF, ET, PTHrP and NOS modulating flow, tonicity and permeability of blood vessels of endometrium functionalis, could play a crucial role in the process of endometrial receptivity to blastocyst implantation. Under progesterone dominance, a significant degree of association has been observed between endometrial maturation and the concentrations of several cytokines in endometrial cells (Giudice, 1994; Tabibzadeh, 1994; Tabibzadeh and Babaknia, 1995). Endometrial secretory maturation and vascular competence were compromised along with marked changes in LIF–TGFβ–VEGF profiles in glandular and vascular compartments of endometrium functionalis around the time of implantation following progesterone receptor blockade by early luteal phase mifepristone administration (Ghosh et al., 1996, 1998a). In functional terms, such changes associated with dysregulated glandular maturation and vascular competence following progesterone receptor blockade result in endometrial inadequacy and luminal insufficiency (Ghosh et al., 1996), which in turn reduce embryo viability (Ghosh et al., 1997b) and inhibit blastocyst implantation (Ghosh and Sengupta, 1993). Additionally, cytoskeletal proteins of epithelial cells and stromal fibroblasts, as well as extracellular matrix (ECM) proteins of the endometrium, undergo differential regulation under progesterone dominance during blastocyst implantation and decidualization (Loke et al., 1989; Christenson et al., 1995; Edwards, 1995; Iwahashi et al., 1996). Endometrial plasminogen activator inhibitor and other protease inhibitors are also increased around the time of blastocyst implantation (Casslen, 1986; Schatz et al., 1993; Sayegh et al., 1995). Furthermore, progesterone inhibits the expression of matrix metalloproteinases (MMP) and stimulates the release of tissue inhibitors of metalloproteinases (TIMP) in endometrium, and thereby

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influences ECM organization (Marbaix et al., 1992, 1996). Thus, luteal phase administration of antiprogestin results in high tissue plasminogen activity and high levels of MMP causing dysregulation of endometrial maturation (Berthois et al., 1991). Thus, a complex network of cytokines and other cellular factors involving endometrial cells, ECM and implantation stage embryo under progesterone dominance plays a role in endometrial receptivity and blastocyst implantation.

Cytokines and other factors in embryo growth and implantation The importance of many cytokines and growth factors and their receptors in the control of cellular proliferation and blastocyst formation during the preimplantation stage as well as implantation is now well documented (Harvey et al., 1995; Sharkey et al., 1995). Various studies performed mainly in murine species and some reports available from human studies indicate that embryos produce several growth factors and cytokines and their receptors in a stage-specific manner, so that these factors may exert anabolic, mitogenic and differentiation-inducing effects on embryo development (autocrine actions). At the same time, some embryonic factors may exert specific actions on endometrium in a stage-specific manner (paracrine effects). Besides, oviductal and endometrial functions generate a milieu which is conducive for embryo growth, as discussed earlier. The growing body of knowledge tends to support a pragmatic model in which early cleavage stage embryos possess a higher degree of autocrine control, while paracrine interaction between embryo and endometrium increases as implantation ensues. Stage-specific distribution of receptors for TGFα, EGF and IGF-I at 4-cell and 8–14-cell stages have been observed in human embryos, while ligand growth factors have been found in Fallopian tube epithelial cells (Smotrich et al., 1996). Human embryos also produce TGFα and IGF-II and cannot produce EGF and IGF-I in culture (Hemmings et al., 1992). EGF and TGFα may share receptors, and both may promote preimplantation embryo growth (Paria and Dey, 1990; Dardik et al., 1993), as well as trophoblast invasion and postimplantation embryo growth (Haimovici and Anderson, 1993; Nielsen et al., 1991). The involvement of IGF in the autocrine and paracrine control of embryo growth and implantation is not very clear. Few investigators observed no influence of IGF-I and IGF-II on embryo growth in the mouse (Paria and Dey, 1990; Rao et al., 1990), others have observed that IGF stimulates metabolism, inner cell mass (ICM) proliferation

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and differentiation in mammalian embryos (Harvey and Kaye, 1992a,b; Rappolle et al., 1992; Smith et al., 1993; Xia et al., 1994). Preimplantation embryos express mRNA encoding IGF-II and receptors for IGF-I and IGF-II (Rappolle et al., 1990; Schultz and Heyner, 1993). It now appears that IGF alone cannot effectively stimulate embryo growth: it requires IGFBP which are primarily produced by endometrial cells or other cells (Liu et al., 1995b; Lai et al., 1996). IGFBP-1, -2 and -3 as well as and IGF-I and -II are differentially expressed in secretory endometrium under progesterone dominance (Giudice et al., 1993; Giudice, 1994), while embryos can secrete IGF-II and accumulate IGFBP (Hemmings et al., 1992; Lai et al., 1996). Furthermore, the production of IGFBP by human oviductal cells, endometrial cells and Vero cells was stimulated by embryo co-culture (Liu et al., 1995b; Lai et al., 1996). Interestingly, relaxin is a homologue member of the IGF family and it stimulates IGFBP production by endometrial cells (Tseng et al., 1992). While TGFα and IGF-II are produced by early embryos, fibroblast growth factor (FGF) is produced at blastocyst stage, and mRNA encoding FGF receptors are also seen in blastocysts in mice (Campbell et al., 1992). FGF induces primitive streak formation in rabbit preimplantation embryos in vitro (Deangelis and Kirchner, 1993). Besides growth factors, other cytokines also play crucial role in the paracrine modulation of embryo growth and implantation (Yoshinaga, 1994). IL-1, IL-6 and colony stimulating factor (CSF) show increased concentrations in spent media of human embryos grown in vitro (Zolti et al., 1991). In another study, no significant correlation between IL-1, IL-6 and TGFβ production rates and human embryo morphological score could be found over the 48 h period of the study (Austgulen et al., 1995). Again, higher levels of IL-1α were observed in 24 h spent media of embryos transferred in cycles where pregnancy ensued (Sheth et al., 1991), yet IL-1 inhibits mouse embryo development in vitro (Sueldo et al., 1990). Interestingly IL-1β, which inhibits blastocyst attachment, stimulates the outgrowth of attached blastocyst (Hartshorne and Edwards, 1996). However, human endometrial epithelial cells exhibit IL-1 binding sites (Tabibzadeh et al., 1990), immunoreactive IL-1 receptor subtype I (IL-1RtI, Simon et al., 1993) and functional IL-RtI (Laird et al., 1994). Interleukin-1 receptor inhibitor (IL-1ra) was identified as a major component of the IL-1 family of polypeptides (Dinarello, 1988), and blockade of maternal IL-1RtI with recombinant human IL-1ra prevented implantation in the mouse by interfering with embryonic attachment (Simon et al., 1994). Immunoreactivity for IL-1 receptor antagonist has been detected in the human endometrial luminal

epithelium (Simon et al., 1995b) and mouse uterus (Dang and Polan, 1994). Recently, it has been demonstrated that embryo-derived IL-1 may up-regulate the expression of integrin β3 by endometrial epithelial cells. Endometrial β3 up-regulation appears relevant because it increases the ability of blastocyst to adhere to endometrial epithelial cells (Simon et al., 1997). Furthermore, embryo-derived IL-1β may influence the endometrial vascular compartment (Li et al., 1995). Although it has been doubted whether embryo-derived IL-1 is an artefact of endotoxin exposure in culture (Kauma et al., 1992), it does appear to be a functional entity which is primarily addressed to endometrial epithelial cells, and it acts in a stage-specific and vectorial manner, presumably resulting in paracrine modulation of endometrium towards implantation (Polan et al., 1995; Simon et al., 1995c). Lachapelle et al. (1993) observed that human embryos secreted TNFα in the medium till morula stage, not at blastocyst stage, and mouse embryo development was not affected by a high concentration of TNFα in vitro, possibly for a lack of TNF receptors on embryos. On the contrary, TNFα could be detected only in media of embryos at the 6–8 cell stage (Zolti et al., 1991) and, in another study, TNFα remained non-detectable in embryo spent medium (Austgulen et al., 1995). Also, addition of TNFα was found to be deleterious to mouse embryo development in vitro (Hill et al., 1987). A developmentally regulated expression of TNFα receptors was demonstrated in mouse embryos, and its ligand led to the down regulation of ICM proliferation (Pampfer et al., 1994). The selective inhibitory action of TNFα on ICM cell lineage supports the hypothesis that TNFα could contribute to the aetiology of many unexplained reproductive failures with high levels of TNFα in the reproductive tract (Eisermann et al., 1988; Taketani et al., 1992). Indeed, progesterone also depresses TNFα production in endometrium (see above). Taken together, it appears that high concentrations of TNFα in the local milieu is not beneficial for preimplantation embryo growth, although it may influence trophoblast invasion through endometrial epithelial cells and endometrial decidual reaction (Edwards, 1995; Tabibzadeh et al., 1995; Vince and Johnson, 1995). Recently, there has been considerable interest about the role of LIF in the implantation process. Mice rendered genetically deficient in the LIF gene fail to implant (Stewart et al., 1992). These animals ovulate and their ova fertilize; however, the developing blastocysts fail to implant but could successfully implant after their transfer to normal surrogate female mice. The role of LIF gene expression in promoting preimplantation stage embryo development in the human is not clear. LIF inhibits


embryonic stem cell differentiation (Rathjen et al., 1990) and selectively inhibits formation of primitive ectoderm, while it permits differentiation of primitive endoderm (Shen and Leder, 1992). mRNA for LIF receptor has been identified in human preimplantation stage blastocysts produced by IVF, suggesting that the human embryo at this stage may be capable of responding to a maternal LIF signal which is synthesized and secreted by endometrial glands at the mid-secretory stage of cycle (Charnock-Jones et al., 1994a). Blastocyst formation was higher when human embryos were co-cultured with endometrial cells capable of LIF secretion into the culture medium (Plachot et al., 1995). Using a complex serum-free medium, the addition of LIF significantly increased the quality and number of human blastocysts in vitro (Dunglison et al., 1996). Embryo-derived signals may also include oestradiol, prostaglandin and PAF. The characteristics and putative functions of such embryo-derived signals in different mammalian species have been reviewed elsewhere (Kennedy, 1994). Human blastocysts also possess the machinery to metabolize steroids and secrete oestradiol between days 5 and 8 after fertilization and this correlates well with blastocyst HCG secretion rate (Edgar et al., 1993). The functional role of embryo-derived steroid is uncertain; however, it is possible that the capacity of preimplanting blastocysts to biotransform steroids could be associated with the initiation of the process of implantation (Ghosh and Sengupta, 1995). Embryos also secrete gonadotrophin releasing hormone in a stage-specific manner (Fishel et al., 1984; Seshagiri et al., 1994). Human embryos can produce HCG at 8-cell stage onwards (Fishel et al., 1984) and it requires interaction between ICM and trophectodermal cells (Summers et al., 1993). Thus, HCG production is high by blastocysts with good morphology and maturation in vitro (Dokras et al., 1991; Hartshorne and Edwards, 1996). The issue of blastocyst-derived prostaglandin in human and other non-human primate species is largely unattended. Holmes et al. (1989) have shown that human preimplantation stage embryos (early cleavage stage, 4 cell and blastocyst stage) can release PGE2 but not PGF2 in culture over a 48 h period. In rhesus monkeys, among different stages of preimplantation embryos (pre-morula, morula and blastocyst) only blastocysts were observed to secrete PGE2 in vitro, while PGF2 remained non-detectable (Ghosh and Sengupta, 1996). PGE2 is known to increase vascular permeability, immunosuppression and decidualization in implantation stage endometrium. There is no robust evidence to support the fact that embryo-derived prostaglandins mediate these

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endometrial changes, since PG of endometrial origin also increase at implantation sites. However, it has been suggested that the stimulus for their release by endometrial cells is provided by the blastocyst (Kennedy, 1983). A physiologically important chemical agent which enhances the synthesis and release of PG in various cell types is PAF. Although several groups have failed to detect PAF from embryos of different mamalian species including rabbit (Angel et al., 1988), mouse (Smal et al., 1990) and human (Amiel et al., 1989), it has been suggested by O’Neill (1991) based on several lines of evidence that embryoderived PAF influences locally arachidonic acid metabolism and PG milieu in endometrium. Indeed, the notion that embryo-derived factors may directly or indirectly influence endometrial physiology towards receptivity and implantation is substantiated by several lines of evidence. Studies in the rhesus monkey indicate that endometrial physiology during mid-luteal phase in the presence of conceptus is discernibly different compared with that in non-fecund mid-luteal phase without any significant change in the serum concentrations of oestradiol-17β and progesterone (Ghosh and Sengupta, 1988a,b; Sengupta et al., 1988; Ghosh et al., 1993). Several embryo-derived endocrine and paracrine factors, including CG, IL-1, inhibin, pregnancy-specific β1 glycoprotein (SP1), early pregnancy factor (EPF), PAF, PG, spermine–spermidine and histamine releasing factor may be involved in local modulation of endometrial function around the time of implantation (Clark et al., 1989; Segars et al., 1989; Maly et al., 1990; Lea et al., 1991; O’Neill, 1991; Sueoka, 1992; Dimitriadou et al., 1992; Phocas et al., 1992; Polan et al., 1995; Simon et al., 1995c, 1997). Further studies are required to delineate the nature of paracrine influence of preimplantation blastocyst on hormone-primed endometrium, and this may help to improve the success rate in assisted reproduction. Despite the fact that there are substantial studies on the morphological details of invasion and placentation in the human and in non-human primates, our knowledge about the involvement of paracrine factors at different stages of trophoblast invasion and differentiation is very poor and indirect, mainly based on studies with abortion and term placental materials, and using cytotrophoblast culture. It appears that LIF reduces the production of HCG and influences trophoblast differentiation towards an anchoring phenotype which is associated with the higher expression of oncofetal fibronectin and α5-integrin subunit along with a decrease in protease activity (Bischof et al., 1995; Kojima et al., 1996; Nachtigall et al., 1996). TGFβ up-regulates integrin expression and reduces migratory ability of the invasive trophoblasts, and it also exerts an

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inhibitory effect on cytotrophoblast invasiveness by stimulating secretion of decidual TIMP which inhibits MMP activity of invading cytotrophoblast (Graham and Lala, 1992; Graham et al., 1992; Irving and Lala, 1995). On the other hand, EGF, TGFα, IL-1 and IL-6 have opposite effects (Morrish et al., 1987; Masuhiro et al., 1991; Li et al., 1992; Bass et al., 1994). It is thus possible that, as the early conceptus begins to implant, embryo- and endometrium-derived cytokines and growth factors result in trophoblast invasion, while some of these cytokines activate LIF and TGFβ, which in turn induce extravillous and villous differentiation. Such a controlled cascade of proliferation, invasion and differentiation presumably play a critical role in the process of progressive implantation and placentation. Human placenta-derived growth factor (PlGF) is a secreted, dimeric glycoprotein of 46–50 kDa molecular weight, shares with VEGF a high degree of sequence similarity in the cysteine-rich domain, and is chemotactic, mitogenic and angiogenic in nature (Maglione et al., 1991; DiSalvo et al., 1995; Cao et al., 1996; Ziche et al., 1997). Furthermore, trophoblast cells express both KDR (kinase-insert-domain containing receptor) and Flt-1 (fms-like tyrosine kinase) which show differential binding affinity for VEGF (Charnock-Jones et al., 1994b; Ahmed et al., 1997) and PlGF (Park et al., 1994). Maternal decidua secrete VEGF (Ahmed et al., 1995). Studies to delineate the interaction between different variants of VEGF and their receptors in the process of trophoblast invasion and differentiation has only recently been initiated. It appears that a multifactorial, complex and dynamic regulation is operative between embryonic and endometrial compartments in order to manifest controlled proliferation and invasion of trophoblast cells. Further studies are warranted using primate models to delineate the endocrine and paracrine regulation of cell–cell and cell–ECM interactions during trophoblast invasion, differentiation and placentation. Acknowledgements The studies reported from the authors’ laboratory were funded by grants from the Rockefeller Foundation, the Special Programme of Research, Development and Research Training in Human Reproduction, World Health Organization, the NIH, US-held India Rupee Fund, the Indian Council of Medical Research and the Council of Scientific and Industrial Research, India.

References Ahmed, A., Li, X.-F., Dunk, C. et al. (1995) Colocalisation of vascular endothelial growth factor and its Flt-1 receptor in human placenta. Growth Factors, 12, 235–243.

Ahmed, A., Dunk, C., Kniss, D. and Wilkes, M. (1997) Role of VEGF receptor-1 (Flt-1) in mediating calcium-dependent nitric oxide release and limiting DNA synthesis in human trophoblast cells. Lab. Invest., 76, 779–791. Alecozay, A.A., Harper, M.J.K., Schenken, R.S. and Hanahan, D.J. (1991) Paracrine interactions between platelet-activating factor and prostaglandins in hormonally-treated human luteal phase endometrium. J. Reprod. Fertil., 91, 301–312. Amiel, M.L., Duquenne, C., Benveniste, J. and Testard, J. (1989) Platelet aggregating activity in human embryo culture media free of PAF-acether. Hum. Reprod., 4, 327–330. Angel, J., Jones, M.S., McManus, L.M. et al. (1988) Platelet activating factor in the rabbit uterus during early pregnancy. J. Reprod. Fertil., 83, 711–722. Arici, A., MacDonald, P.C. and Casey, M.L. (1996) Modulation of the levels of transforming growth factor β messenger ribonucleic acids in human stromal cells. Biol. Reprod., 54, 436–469. Arrigo, A.P. and Landry, J. (1994) Expression and function of the low-molecular-weight heat shock proteins. In Morimoto, R.I., Tissieres, A. and Georgopoulos, C. (eds), The Biology of Heat Shock Proteins and Molecular Chaperones. Cold Spring Harbor Laboratory Press, New York, pp. 335–373. Austgulen, R., Arntzen, K.J., Vatten, L.J. et al. (1995) Detection of cytokines (interleukin-1, interleukin-6, transforming growth factor-β) and soluble tumour necrosis factor receptors in embryo culture fluids during in vitro fertilization. Hum. Reprod., 10, 171–176. Bani, D., Bigazzi, M., Masini, E. et al. (1995) Relaxin depresses platelet aggregation. In vitro studies on isolated human and rabbit platelets. Lab. Invest., 73, 709–716. Bani, D., Ballati, L., Masini, E. et al. (1997) Relaxin counteracts asthma-like reaction induced by inhaled antigen in sesitized guinea pigs. Endocrinology, 138, 1909–1915. Bani Sacchi, T., Bigazzi, M., Bani, D. et al. (1995) Relaxin induced increased coronary flow through stimulation of nitric oxide production. Br. J. Pharmacol., 116, 1589–1594. Bany, B.M. and Kennedy, T. (1995a) Regulation by epidermal growth factor of prostaglandin production and cyclooxygenase activity in sensitized rat endometrial stromal cells in vitro. J. Reprod. Fertil., 104, 57–62. Bany, B.M. and Kennedy, T. (1995b) Interleukin-1α regulates prostaglandin production and cyclooxygenase activity in sensitized rat endometrial stromal cells in vitro. Biol. Reprod., 53, 126–132. Bass, K.E., Morrish, D., Roth, I. et al. (1994) Human cytotrophoblast invasion is up-regulated by epidermal growth factor: evidence that paracrine factors modify this process. Dev. Biol., 164, 550–561. Battaglia, C, Larocca, E., Lanzani, A. et al. (1990) Doppler ultrasound studies of the uterine arteries in spontaneous and IVF stimulated ovarian cycles. Gynecol. Endocrinol., 4, 245–250. Bavister, B.D. and Boatman, D.E. (1997) The neglected human blastocyst. Hum. Reprod., 8, 1607–1613. Bell, R.J., Eddie, L.W., Lester, A.R. et al. (1987a) Relaxin in human pregnancy measured with a homologous radioimmunoassay. Obstet. Gynecol., 69, 585–589. Bell, S.C., Keyle, J.W. and Waites, G.T. (1987b) Pregnancy-associated endometrial α2-globulin, the major secretory protein of the luteal phase and first trimester pregnancy endometrium is not glycosylated prolactin but related to β-lactoglobulins. J. Clin. Endocrinol. Metab., 65, 1067–1071. Berthois, Y., Brux, J.D., Salat-Baroux, J. et al. (1991) A multiparametric analysis of endometrial estrogen and progesterone receptors after the post-ovulatory administration of mifepristone. Fertil. Steril., 55, 547–554. Bischof, P., Haenggeli, L. and Campana, A. (1995) Gelatinase and oncofetal fibronectin secretion is dependent on integrin expression on human cytotroblasts. Mol. Hum. Reprod., 1 see Hum. Reprod., 10, 734–742. Blankenship, T.N. and Enders, A.C. (1997) Expression of platelet–endothelial cell adhesion molecule-1 (PECAM) by macaque trophoblast cells during invasion of the spiral arteries. Anat. Rec., 247, 413–417. Bongso, A., Ng, S.C., Fong, C.Y. et al. (1992) Improved pregnancy rate after transfer of embryos grown in human Fallopian tubal cell coculture. Fertil. Steril., 58, 569–574.

Endocrinology and paracrinology of implantation Bongso, A., Fong, C.Y., Ng, S.C. and Ratnam, S. (1994a) Human embryonic behavior in a sequential human–oviduct–endometrial co-culture system. Fertil. Steril., 61, 976–978. Bongso, A., Fong, C.Y., Ng, S.C. and Ratnam, S. (1994b) Blastocyst transfer in human in vitro fertilization: the use of embryo co-culture. Cell Biol. Int., 18, 1181–1189. Bourne, T.H., Hagstrom, H.G., Granberg. S. et al. (1996) Ultrasound studies of vascular and morphological changes in the human uterus after a positive self-test for the urinary luteinizing hormone surge. Hum. Reprod., 11, 369–375. Brigstock, D.R., Heap, R.B. and Brown, K.D. (1989) Polypeptide growth factors in uterine tissues and secretions. J. Reprod. Fertil., 85, 747–758. Bryant-Greenwood, G.D., Rutanen, E.-M, Partanen, S. et al. (1993) Sequential appearance of relaxin, prolactin and IGF-BP1 during growth and differentiation of the human endometrium. Mol. Cell. Endocrinol., 95, 23–29. Cameron, L.T., Davenport, A.P., Brown, M.J. and Smith, S.K. (1991) Endothelin-1 stimulates prostaglandin release from human endometrium. Prostaglandins Leukot. Essent. Fatty Acids, 42, 155–157. Cameron, S.T., Critchley, H.O.D., Buckely, C.H. et al. (1997) Effect of two antiprogestins (mifepristone and onapristone) on endometrial factors of potential importance for implantation. Fertil. Steril., 67, 1046–1053. Campbell, W.J., Miller, K.A., Anderson, T.M. et al. (1992) Expression of fibroblast growth factor receptors by embryonical carcinoma cells and early mouse embryos. In Vitro Cell. Dev. Biol., 28, 61–66. Campbell, S., Swann, H.R., Seif, M.W. et al. (1995) Cell adhesion molecules on oocyte and preimplantation human embryo. Hum. Reprod., 10, 1571-1578. Cao, Y., Chen, H., Zhou, L. et al. (1996) Heterodimers of placenta growth factor/vascular endothelial growth factors: endothelial activity, tumour cell expression, and high affinity binding to Flk-1/KDR. J. Biol. Chem., 271, 3154–3162. Casey, M.L., Smith, J.W., Nagai, K. et al. (1991) Progesterone regulated cyclic modulation of membrane metalloendopeptidase (enkaphalinase) in human endometrium. J. Biol. Chem., 266, 23041–23047. Casey, M.L., Mibe, M. and MacDonald, P.C. (1993) Regulation of parathyroid hormone related protein gene expression in stromal cells in culture. J. Clin. Endocrinol. Metab., 77, 188–194. Casslen, B. (1986) Inhibitors of trypsin, chymotrypsin and elastase in human uterine fluid. Acta Obstet. Gynaecol., Scand., 65, 121–124. Castracane, D.V., D’Eletto, R. and and Weiss, G. (1985) Relaxin secretion in the baboon (Papio cynocephalus). In Greenwald, G.S. and Terranove, P.F. (eds), Factors Regulating Ovarian Function. Raven Press, New York, pp. 415–419. Charnock-Jones, D.S, Sharkey, A.M., Rajput-Williams, J. et al. (1993) Identification and localization of alternately spliced mRNAs for vascular endothelial growth factor in human uterus and steroid regulation in endometrial carcinoma cell lines. Biol. Reprod., 48, 1120–1128. Charnock-Jones, D.S., Sharkey A.M., Lechene, C.P. et al. (1994a) Leukaemia inhibitory factor mRNA concentration peaks in human endometrium at the time of implantation and the blastocyst contains mRNA for the receptor at this time. J. Reprod. Fertil., 101, 421–426. Charnock-Jones, D.S., Sharkey A.M., Boocock, C.A. et al. (1994b) Vascular endothelial growth factor receptor localization and activation in human trophoblast and choriocarcinoma cells. Biol. Reprod., 51, 524–530. Check, J.H., Bollendorf, A. and Askari, H.A. (1995) Evidence for a leukocyte adhesion factor produced by the early embryo. Am. J. Reprod. Immunol., 34, 20–25. Christenson, S., Verhage, H.G., Nowak, G. et al. (1995) Smooth muscle myosin II and alpha smooth muscle actin expression in the baboon (Papio anubis) uterus is associated with glandular secretory activity and stromal cell transformation. Biol. Reprod., 53, 598-608. Ciocca, D.R., Asch, R.H., Adams, D.J. and McGuire, W.I. (1983) Evidence for modulation of a 24K protein in human endometrium. J. Clin. Endocrinol. Metab., 57, 496–499. Ciocca, D.R., Oesterreich, S., Chamness, G.C. et al. (1993) Biological and clinical implications of heat shock protein 27000 (Hsp 27): a review. J. Natl. Cancer Inst., , 85, 1558–1570. Clark, D.A., Lee, S., Fishell, S. et al. (1989) Immunosuppressive activity in human in vitro fertilization (IVF) culture supernatants and prediction of

163

the outcome of embryo transfer: multicenter trial. J. In Vitro Fertil. Embryo Transfer, 6, 51–53. Cohen, J., Elsner, C., Kort, H. et al. (1990) Impairment of the hatching process following IVF in the human and improvement by assisting hatching using micromanupulation. Hum. Reprod., 5, 7–13. Cullinan, E.B., Abbondanzo, S.J., Anderson, P.S. et al. (1996) Leukemia inhibitory factor (LIF) and LIF receptor expression in human endometrium suggests a potential autocrine/paracrine function in regulating embryo implantation. Proc. Natl. Acad. Sci. USA, 93, 3115–3120. Dalton, C.F., Laird, S.M., Serle, E. et al. (1995) The measurement of CA 125 and placental protein 14 in uterine flushings in women with recurrent miscarriage: relation to endometrial morphology. Hum. Reprod., 10, 2680–2684. Dang, W. and Polan, M.L. (1994) Embryonic implantation in mice is blocked by interleukin-1 receptor antagonist. Endocrinology, 134, 521–528. Dardik, A., Doherty, A.S. and Schultz, R.M. (1993) Protein secretion by the mouse blastocyst: stimulatory effect on secretion into blastocoel by transforming growth factor-α. Mol. Reprod. Dev., 34, 396–401. Das, S.K., Flanders, K.C., Andrews, G.K. and Dey, S.K. (1992) Expression of transforming growth factor-β isoforms (β2 and β3) in mouse uterus: analysis of the periimplantation period and effects of ovarian steroids. Endocrinology, 130, 3459–3466. Deangelis, M.H. and Kirchner, C. (1993) Fibroblast growth factor induced primitive streak formation in rabbit preimplantation embryos in vitro. Anat. Embryol., 187, 269–273. de Ziegler, D. (1995) Hormonal control of endometrial receptivity. Hum. Reprod., 10, 4–7. de Ziegler, D., Bergeron, C., Cornel, C., Medalie, D.A. et al. (1992) Effects of luteal estradiol on the secretory transformation of human endometrium and plasma gonadotropins. J. Clin. Endocrinol. Metab., 74, 322–331. Delage, G., Moreau, J.-F., Taupin, J.-L. et al. (1995) In-vitro endometrial secretion of human interleukin for DA cells/leukaemia inhibitory factor by explant cultures from fertile and infertile women. Hum. Reprod., 10, 2483–2488. Dey, S.K. (1996) Implantation. In Adashi, E.Y., Rock, J.A. and Rosenwaks, Z. (eds), Reproductive Endocrinology, Surgery, and Technology. Philadelphia, Lippincott–Raven, pp. 421–434. Dinarello, C.A. (1988) Biology of interleukin 1. FASEB J., 2, 108–115. Dimitriadou, F., Phocas, I., Mantzavinos, M. et al. (1992) Discordant secretion of pregnancy specific beta-1-glycoprotein and human chorionic gonadotropin by human pre-embryos cultured in vitro. Fertil. Steril., 57, 631–636. DiSalvo, J., Bayne, M.L., Conn, G. et al. (1995) Purification and characterization of a naturally occurring vascular endothelial growth factor–placenta growth factor heterodimer. J. Biol. Chem., 270, 7717–7723. Dockery, P., Ismail, R.M.J., Li, T.C. et al. (1997) The effect of a single dose of mifepristone (RU486) on the fine structure of the human endometrium during the early luteal phase. Hum. Reprod., 12, 1778–1784. Dokras, A., Sargent, I.L., Gardner, R.L. and Barlow, D.H. (1991) Human trophectoderm biopsy and secretion of chorionic gonadotrophin. Hum. Reprod., 6, 1453–1459. Dunglison, G.F., Barlow, D.H. and Sargent, L.L. (1996) Leukaemia inhibitory factor significantly enhances the blastocyst formation rates of human embryos cultured in serum-free medium. Hum. Reprod., 11, 191–196. Economos, K., MacDonald, P.C. and Casey, M.L. (1992) Endothelin-1 gene expression and protein biosynthesis in human endometrium: potential modulator of endometrial blood flow. J. Clin. Endocrinol. Metab., 74, 14–19. Edgar, D.H. (1995) Oestrogen and human implantation. Hum. Reprod., 10, 2–3. Edgar, D.H., James, J.B. and Mills, J.A. (1993) Steroid secretion by human early embryos in culture. Hum. Reprod., 8, 277–278. Edwards, R.G. (1994) Implantation, contraception and interception. Hum. Reprod., 9, 985–989.

164


Edwards, R.G. (1995) Physiological and molecular aspects of human implantation. Hum. Reprod., 10 (Suppl. 2), 1–13. Edwards, R.G. and Brody, S.A. (1995) Principles and Practice of Assisted Human Reproduction. W.B.Saunders, Philadelphia. Eisermann, J., Gast, M.J., Pineda, J. et al. (1988) Tumour necrosis factor in peritoneal fluid of women undergoing laparoscopic surgery. Fertil. Steril., 50, 573–577. Fenderson, B.A., Kojima, N., Zhu, Z.M. et al. (1991) Specific interaction between Ley and H as a possible basic for trophectoderm-endometrium recognition during implantation. Glyoconjugate J., 8, 177a. Ferenczy, A. (1994) Anatomy and histology of the uterine corpus. In Kurman, R.J. (ed.), Blausteins’s Pathology of the Female Genital Tract. Springer-Verlag, New York, pp, 327–366. Fishel, S.B., Edwards, R.G. and Evans, C.J. (1984) Human chorionic gonadotrophin secreted by preimplantation embryos cultured in vitro. Science, 223, 816–818. Fox, S.B., Gatter, K.C., Jackson, D.G. et al. (1993) CD44 and cancer screening. Lancet, 342, 548–549. Fraser, I.S. and Peek, M.J. (1992) Effects of exogenous hormones on endometrial capillaries. In Alexander, A.J. and d’Arcangues, C. (eds), Steroid Hormones and Uterine Bleeding. AAAS Press, Washington, DC, pp. 67–79. Freeman, M.R., Whitworth, C.M. and Hill, G.A. (1995) Granulosa cell coculture enhances human embryo development and pregnancy rate following in-vitro fertilization. Hum. Reprod., 10, 408–414. Gandolfi, F. and Moor, R.M. (1987a) Stimulation of early embryonic development in the sheep by co-culture with oviduct epithelial cells. J. Reprod. Fertil., 81, 23–28. Gandolfi, F., Brezini, J., Richardson, L. et al. (1987b) Characterization of proteins secreted by sheep oviduct epithelial cells and their function in embryonic development. Development, 106, 303–312. Gannon, B.J., Carati, C.J. and Verco, C.J. (1997) Endometrial perfusion across the normal human menstrual cycle assessed by laser Doppler fluxmetry. Hum. Reprod., 12, 132–139. Gemzell-Danielsson, K., Swahn, M.L., Svalander P. and Bygdeman, M. (1993) Early luteal phase treatment with mifepristone (RU486) for fertility regulation. Hum. Reprod., 8, 870–873. Gemzell-Danielsson, K, Swahn M.L., Svalander, P. and Bygdeman, M. (1994) Effect of a single post-ovulatory dose of RU 486 on endometrial maturation in the implantation phase. Hum. Reprod., 9, 2398–2400. Gemzell-Danielsson, K, Swahn M.L. and Bygdeman, M. (1997) The effect of various doses of mifepristone on endometrial leukaemia inhibitory factor expression in the midluteal phase — an immunohistochemical study. Hum. Reprod., 12, 1293–1297. Ghosh, D. and Sengupta, J. (1988a) A comparative study of endometrial acid phosphatase activity in the mid-luteal phase of the menstrual cycle and in the peri-implantation stage in the rhesus monkey (Macaca mulatta). J. Endocrinol., 116, R7–R9. Ghosh, D. and Sengupta, J. (1988b) Patterns of estrogen and progesterone receptors in rhesus monkey endometrium during secretory phase of normal menstrual cycle and preimplantation stages of gestation. J. Steroid Biochem., 31, 223–229. Ghosh, D. and Sengupta, J. (1993) Anti-nidatory effect of a single, post-ovulatory administration of mifepristone (RU486) in the rhesus monkey. Hum. Reprod., 8, 552–558. Ghosh, D. and Sengupta, J. (1995) Endometrial receptivity for implantation. Another look at the issue of periimplantation oestrogen. Hum. Reprod., 10, 1–2. Ghosh, D. and Sengupta, J. (1996) Prostaglandins and blastocyst implantation in primates. In Sengupta, J. and Ghosh, D. (eds), Cellular and Molecular Signaling in Reproduction. New Age International, New Delhi, pp. 145–162. Ghosh. D., Roy, A., Sengupta, J. and Johannisson, E. (1993) Morphological characteristics of preimplantation stage endometrium in the rhesus monkey. Hum. Reprod., 8, 1579–1587. Ghosh, D., De, P. and Sengupta, J. (1994) Luteal phase oestrogen is not essential for implantation and maintenance of pregnancy from surrogate embryo transfer in the rhesus monkey. Hum. Reprod., 9, 629–637. Ghosh, D., Sengupta, J. and Hendrickx, A.G. (1996) Effect of a single-dose, early luteal phase administration of mifepristone (RU486) on

implantation stage endometrium in the rhesus monkey. Hum. Reprod., 11, 2026–2035. Ghosh, D., Stewart, D. R., Nayak, N.R. et al. (1997a) Serum concentrations of oestradiol-17β progesterone, relaxin and chorionic gonadotrophin during blastocyst implantation in natural pregnancy cycle and in embryo transfer cycle in the rhesus monkey. Hum. Reprod., 12, 914–920. Ghosh, D., Kumar, P.G.L.L. and Sengupta, J. (1997b) Early luteal phase administration of mifepristone inhibits preimplantaion embryo development and viability in the rhesus monkey. Hum. Reprod., 12, 575–582. Ghosh, D., Kumar, P.G.L.L. and Sengupta, J. (1998a) Effects of early luteal phase administration of mifepristone (RU486) on leukaemia inhibitory factor, transforming growth factor β and vascular endothelial growth factor in the implantation stage endometrium of the rhesus monkey. J. Endocrinol. (In press). Ghosh, D., Liu, N., Zhu, Z.M. and Sengupta, J. (1998b) Immunolocalization of Ley oligosaccharide in endometrium during menstrual cycle and effect of early luteal phase mifepristone administration on its expression in implantation stage endometrium of the rhesus monkey. Hum. Reprod., 13, 1374–1379. Giudice, L.C. (1994) Growth factors and growth modulators in human uterine endometrium: their potential relevance to reproductive medicine. Fertil. Steril., 61, 1–17. Giudice. L.C., Dsupin, B.A., Jin, I.H. et al. (1993) Differential expression of messenger ribonucleic acids encoding insulin-like growth factors and their receptors in human uterine endometrium and decidua. J. Clin. Endocinol. Metab., 76, 1115–1122. Glasser, S.R. and McCormack, S.A. (1982) Cellular and molecular aspects of decidualization and implantation. In Beier, H.M. and Karlson, P. (eds), Proteins and Steroids in Early Pregnancy. Springer-Verlag, Berlin, pp. 245–310. Graham, C.H. and Lala, P.K. (1992) Mechanisms of placental invasion of the uterus and their control. Biochem. Cell Biol., 70, 867–874. Graham, C.H., Lysiak, J.J., McCrae, K.R. and Lala, P.K. (1992) Localisation of transforming growth factor at the human fetal–maternal interface: role in trophoblast growth and differentiation. Biol. Reprod., 46, 561–572. Grbovic, L., Jovanovic, A. and Tulic, I. (1996) Indomethacin reduces contraction of isolated non-pregnant human uterine artery induced by prostaglandin F2α. Hum. Reprod., 11, 1998–2002. Greb, R.R., Bukowski, R., Hsiu, J.G. et al. (1995) Vascular endothelial growth factor (VEGF) in primate endometrium. Immunohistochemical patterns during the cycle and after chronic RU486 treatment in cynomolgus monkeys. Ann. NY Acad. Sci., 761, 376–382. Greb, R.R., Heikinheimo, O., Williams, R.F. et al. (1997) Vascular endothelial growth factor in primate endometrium is regulated by oestrogen-receptor and progesterone-receptor ligands in vivo. Hum. Reprod., 12, 1280–1292. Haimovici, G. and Anderson, D. (1993) Effects of growth factors and growth factor-extracellular matrix interactions on mouse trophoblast outgrowth in vitro. Biol. Reprod., 19, 124–130. Hartshorne, G.M. and Edwards, R.G. (1996) Early embryo development. In Adashi, E.Y., Rock, J.A. and Rosenwaks, Z. (eds), Reproductive Endocrinology, Surgery, and Technology. Lippincott–Raven, Philadelphia, pp. 435–450. Harvey, M.B. and Kaye, P.L. (1992a) Insulin-like growth factor-I stimulates growth of mouse preimplantation embryos in vitro. Mol. Reprod. Dev., 31, 195–199. Harvey, M.B. and Kaye, P.L. (1992b) IGF-2 stimulates growth and metabolism of early mouse embryos. Mechan. Dev., 38, 169–173. Harvey, M.B., Leco, K.J., Arcellana-Panlilio, M.Y. et al. (1995) Roles of growth factors during preimplantation development. Mol. Hum. Reprod., 1, see Hum. Reprod., 10, 712–718. Haynes, B.F., Liao, H.-X. and Patton, K.I. (1991) The transmembrane hyaluronate receptor (CD44): multiple functions, multiple form. Cancer Cells, 3, 347–350. Heider, K.-H., Hofmann, M., Hors, E. et al. (1993) A human homologue of the rat metastasis-associated variant of CD44 is exposed in colo-rectal carcinomas and adenomatous polyps. J. Cell Biol., 120, 227–233.

Endocrinology and paracrinology of implantation Hemmings, R., Langlais, J., Falcone, T. et al. (1992) Human embryos produce transforming growth factors a activity and insulin like growth factors II. Fertil. Steril., 58,101–104. Hertig, A.T. (1964) Gestational hyperplasia of endometrium. Lab. Invest., 13, 1153–1191. Hey, N.A., Li, T.C., Devine, P.L. et al. (1995) MUC1 in secretory phase endometrium: expression in precisely dated biopsies and flushings from normal and recurrent miscarriage patients. Hum. Reprod., 10, 2685–2662. Hild-Petito, S., Fazleabas, A.T., Julian, J. and Carson, D.D. (1996) Mucin (Muc-1) expression is differently regulated in uterine luminal and glandular epithelia of the babbon (Papio anubis). Biol. Reprod., 34, 939–947. Hill, J.A., Haimovici, F and Anderson, D.J. (1987) products of activated lymphocytes and macrophages inhibit mouse embryo development in vitro. J. Immunol., 139, 2250–2254. Hodgen, G.D. (1983) Surrogate embryo transfer combined with estrogen-progesterone therapy in monkeys. J. Am. Med. Assoc., 250, 2167–2171. Holmes, P.V., Sjogren, A. and Hamberger, L. (1989) Prostaglandin-E2 released by preimplantation human conceptus. J. Reprod. Immunol., 17, 79–86. Hunt, J.S., Chen, H.L., Hu, X. and Tabibzadeh, S. (1992) Tumour necrosis factor-α messenger ribonucleic acid and protein in human endometrium. Biol. Reprod., 47, 141–147. Irving, J.A. and Lala, P.K. (1995) Functional role of cell surface integrins on human trophoblast cell migration: Regulation by TGF-β, IGF-II and IGFBP-1. Exp. Cell Res., 217, 419–427. Iwahashi, M., Muragaki, Y., Ooshima, A. et al. (1996) Alterations in distribution and composition of the extracellular matrix during decidualization of the human endometrium. J. Reprod. Fertil., 108, 147–155. Jacobs, A.L. and Carson, D.D. (1993) Uterine epithelial cell secretion of interleukin-1α induces prostaglandin E2 (PGE2) and PGF2α secretion by uterine stromal cells in vitro. Endocrinology, 132, 300–308. Janssenswillen, C., Nagy, Z.P. and Van Steirteghem, A. (1995) Maturation of human cumulus-free germinal vesicle-stage oocytes to metaphase II by coculture with monolayer Vero cells. Hum. Reprod., 10, 375–378. Johannisson, E. (1991) Morphological and biochemical factors related to implantation. Ballière’s Clin. Obstet. Gynecol. 5, 191–209. Johannisson, E., Oberholzer, M., Swahn, M.L. and Bygdeman, M. (1989) Vascular changes on the human endometrium following the administration of the progesterone antagonist, RU486. Contraception, 39, 103–117. Johnson, M.R., Abdalla, H., Allman, A.C.J. et al. (1991) Relaxin in ovum donation pregnancies. Fertil. Steril., 56, 59–61. Johnson, M.R., Abbas, A.A., Allman, A.C.J. et al. (1994) The regulation of plasma relaxin levels during pregnancy. J. Endocrinol., 142, 261–265. Kauma, S.W., Walsh, S.W., Nestler, J.E. and Turner, T.T. (1992) Interleukin-1 is induced in the human placenta by endotoxin and isolation procedures for trophoblasts. J. Clin. Endocrinol. Metab., 75, 951–955. Katkam, R.R., Gopalkrishnan, K., Chwalisz, K. et al. (1995) Onapristone (ZK 98.299): a potential antiprogestin for endometrial contraception. Am. J. Obstet. Gynecol., 173, 779–787. Kennedy, T.G. (1983) Embryonic signals and the initiation of blastocyst implantation. Australian J. Biol. Sci., 36, 531–543. Kennedy, T.G. (1994) Involvement of local mediators in blastocyst implantation. In Glasser, S.R., Mulholland, J. and Psychoyos, A. (eds), Endocrinology of Embryo–Endometrium Interaction. Plenum Press, New York, pp. 183–194. Kojima, K., Kanzaki, H., Iwai, M. et al. (1994) Expression of leukemia inhibitory factor (LIF) in human endometrium and placenta. Biol. Reprod., 50, 882–887. Lachapelle, M.H., Miron, P., Hemmings, R. et al. (1993) Embryonic resistance to tumour necrosis factor-α mediated cytotoxicity: novel mechanism underlying maternal immunological tolerance to fetal growth. Hum. Reprod., 8, 1032–1038. Lai, Y.M., Chang, S.Y., Chang, M.Y. and Soong, Y.K. (1994) Coculture human zygotes on Vero cell monlayers. In Rodriguez-Arms, O. (ed.),

165

Proceedings of the 14th World Congress on Fertility and Sterility. Parthenon, New York, pp. 401–405. Lai, Y.M., Wang, H.S., Lee, C.L. et al. (1996) Insulin-like growth factor-binding proteins produced by Vero cells, human oviductal cells and human endometrial cells, and the role of insulin-like growth factor-binding protein-3 in mouse embryo coculture systems. Hum. Reprod., 11, 1281–1286. Laird , S.M., Tuckerman, E., Li, T.C. and Bolton, A.E. (1994) Stimulation of human endometrial epithelial cell interleukin 6 production by interleukin 1 and placental protein 14. Hum. Reprod., 9, 1339–1343. Laird, S.M., Tuckerman, E. M., Saravelos, H. and Li, T.C. (1996) The production of tumour necrosis factor-α (TNF-α) by human endometrial cells in culture. Hum. Reprod., 11, 1318–1323. Laird, S.M., Tuckerman, E.M., Dalton, C.F. et al. (1997) The production of leukaemia inhibitory factor by human endometrium: presence in uterine flushings and production by cells in culture. Hum. Reprod., 12, 569–574. Lea, R.G., Porat, O., Daya, S. et al. (1991) The detection of spermine and spermidine in human in vitro fertilization supernatants and their relation to early embryo-associated supressor activity. Fertil. Steril., 56, 771–775. Lessey, B.A., Damjanovich, L., Coutfaris, C. et al. (1992) Integrin adhesion moelcules in the human endometrium. Correlation with the normal and abnormal menstrual cycle. J. Clin. Invest., 90, 188–195. Lessey, B.A., Castelbaum, A.J., Buck, C.A. et al. (1994) Further characterization of endometrial integrins during the menstrual cycle and in pregnancy. Fertil. Steril., 62, 497–506. Li, T.C., Rogers, A.W., Dockery, P. et al. (1988) The effects of progesterone receptor blockade in the luteal phase of normal fertile women. Fertil., Steril., 50, 732–742. Li, Y., Matsuzaki, N., Masuhiro, K. et al. (1992) Trophoblast-derived tumour necrosis factor-α induces release of human chorionic gonadotropin using IL-6 and IL-6 receptor dependent system in the normal human trophoblasts. J. Clin. Endocrinol. Metab., 74, 184–191. Li, J., Perrella, M.A., Tsai, J-C. et al. (1995) Induction of vascular endothelial growth factor gene expression by IL-1b in rat aortic smooth muscle cells. J. Biol. Chem., 270, 308–312. Liu, L.P.S., Chan, S.T.H., Ho, P.C. and Yeung, W.S.B. (1995a) Human oviductal cells produce high molecular weight factor(s) that improves the development of mouse embryo. Hum. Reprod., 10, 2781–2786. Liu, H.C., Mele, C., Catz, D. et al. (1995b) Production of insulin-like growth factor binding proteins (IGFBPs) by human endometrial stromal cells is stimulated by the presence of embryos. J. Assist. Reprod., 12, 78–87. Loke, Y.W., Gardner, L., Burland, K. and King, A. (1989) Laminin in human trophoblast and decidua interaction. Hum. Reprod., 4, 457–463. Lutjen, P.J., Trounson, A., Leeton, J. et al. (1984) The establishment and maintenance of pregnancy using in vitro fertilization and embryo donation in a patient with primary ovarian failure. Nature, 307, 174–175. Maly, F.E., Sterzik, K., Henderson, D. and de Weck, A.L. (1990) Enhancement of macrophage cell oxidative burst by early post-transfer sera from patients after unsuccessful embryo transfer. Hum. Reprod., 5, 342–344. Maglione, D., Guerriero, V., Viglietto, G. et al. (1991) Isolation of a human placenta cDNA coding for a protein related to the vascular permeability factor. Proc. Natl. Acad. Sci. USA, 88, 9267–9271. Maguiness, S.D., Shrimanker, K., Djahanbakheh, O. and Grudzinska, J.G. (1992) Oviductal proteins. Contemp. Rev. Obstet. Gynaecol., 4, 42–50. Manners, C.V. (1990) Endometrial assessment in a group of infertile women stimulated cycles for IVF: immunohistochemical findings. Hum. Reprod., 5, 128–132. Marbaix, E., Donnez, J., Courtoy, P.J. and Eeckhout, Y. (1992) Progesterone regulates the activity of collagenase and related gelatinases A and B in human endometrium. Proc. Natl. Acad. Sci. USA, 89, 11789–11793. Marbaix, E., Kokorine, I., Donnez, J. et al. (1996) Regulation and restricted expression of interstitial collagenase suggest a pivotal role in the initiation of menstruation. Hum. Reprod., 11 (Suppl. 2), 134–143. Masini, E., Bani, D., Bogazzi, M. et al. (1994) Effect of relaxin on mast cells. In vitro and in vivo studies in rats and guinea pigs. J. Clin. Invest., 94, 1974–1980.

166


Maslar, I.A. and Riddick, D.H. (1979) Prolactin production by human endometrium during the normal menstrual cycle. Am. J. Obstet. Gynecol., 135, 751-–754. Masuhiro, K., Matsuzaki, N., Nishino, E. et al. (1991) Trophoblast derived interleukin-1 (IL-1) stimulates the release of human chorionic gonadotropin by activating IL-6 and IL-6 receptor systemin first trimester human trophoblast. J. Clin. Endocrinol. Metab., 72, 594–601. Mclaren, A. (1969) Can mouse blastocysts stimulate a uterine response before losing the zona pellucida? J. Reprod. Fertil., 19, 199–201. Mead, R.A. (1989) Role of the mammalian corpus luteum in the maintenance of early pregnancy. In Yoshinaga, K. (ed.), Blastocyst Implantation. Serono Symposia, Adams Publishing Group, Boston, pp. 189–194. Ménézo, Y.J.R, Guerin, J.F. and Czyba, J.C. (1990) Improvement of human early embryo development in vitro by coculture on monolayers of Vero cells. Biol. Reprod., 42, 301–306. Ménézo, Y.J.R, Sakkas, D. and Janny, L. (1995) Co-culture of the early human embryo: factors affecting human blastocyst formation in vitro. Microsc. Res. Tech., 32, 50–56. Mermillod, P., Vansteenburgge, A., Wils, C. et al. (1993) Characterization of the embryotrophic activity of exogenous protein-free oviduct conditioned medium used in culture of cattle embryos. Biol. Reprod., 49, 582–587. Milligan, S.R. and Finn, C.A. (1997) Minimal progesterone support required for the maintenance of pregnancy in mice. Hum. Reprod., 12, 602–607. Morrish, D.W., Bhardwaj, D., Dabbagh, L.K. et al. (1987) Epidermal growth factor induces differentiation and secretion of human chorionic gonadotropin and placental lactogen in normal placenta. J. Clin. Endocrinol. Metab., 65, 1282–1290. Nachtigall, M.J., Kliman, H.J., Feinberg, R.F. et al. (1996) The effect of leukemia inhibitory factor (LIF) on trophoblast differentiation: a potential role in human implantation. J. Clin. Endocrinol. Metab., 81, 801–806. Narimoto, K., Noda, Y., Shiotani, M. et al. (1990) Immunohistochemical assessment of superoxide dismutase expression in the human enodmetrium throughout the menstrual cycle. Acta Histochem. Cytochem., 24, 85–91. Nasr-Esfahani, M.H., Aitken, J.R. and Johnson, M.H. (1990) Hydrogen peroxide levels in mouse oocytes and early cleavage stage embryos developed in vitro or in vivo. Development, 109, 501–507. Navot, D., Anderson, T.L., Droesch, K. et al. (1986) Hormonal manipulation of endometrial maturation. J. Clin. Endocrinol. Metab., 68, 801–807. Nielsen, L.L., Werb, Z. and Pederson, R.A. (1991) Induction of c-fos transcripts in early postimplantation mouse embryos by TGF-α, EGF, PDGF and FGF. Mol. Reprod. Dev., 29, 227–237. Nikas, G., Drakakis, P, Loutradis, D. et al. (1995) Uterine pinopodes as markers of the ‘nidation’ window in cyclic women receiving exogenous oestradiol and progesterone. Hum. Reprod., 10, 1208–1213. Noble, L.S., Takayama, K., Zeitoun, K.M. et al. (1997) Prostaglandin E2 stimulates aromatase expression in endometriosis-derived stromal cells. Endocrinology, 82, 600–605. Noda, Y., Matsumoto, H., Umaoka, Y and Mori, T. (1991) Involvement of superoxide radicals in mouse two-cell block phenomenon. Mol. Reprod. Dev., 28, 356–360. Okulicz, W.C., Ace, C.I., Longcope, C. and Tast, J. (1996) Analysis of differential gene regulation in adequate versus inadequate secretory-phase endometrial complementary deoxyribonucleic acid populations from the rhesus monkey. Endocrinology, 137, 4844–4850. O’Neill, C. (1991) Viability and development of preimplantation embryos. Baillières Clin. Obstet. Gynaecol., 5, 159–178. Palmer, R.M.J., Ferrige, A.G. and Moncada, S. (1987) Nitric oxide release accounts for the biological activity of endothelium-derived relaxing factor. Nature, 327, 524–526. Pampfer, S., Wuu, Y.D., Vanderheyden, I. and De Hertogh, R. (1994) Expression of tumor necrosis factor-α (TNF-α) receptors and selective effect of TNF-α on the inner cell mass in mouse blastocysts. Endocrinology, 134, 206–212. Paria, B.C. and Dey, S.K. (1990) Preimplantation embryo development in vitro: cooperative interactions among embryos and the role of growth factors. Proc. Natl. Acad. Sci. USA, 87, 4756–4760.

Park, J.E., Chen, H.H., Winer, J. et al. (1994) Placenta growth factor. Potentiation of vascular endothelial growth factor bioactivity in vitro and in vivo, and high affinity binding to Flt-1 but not Flk-1/KDR. J. Biol. Chem., 269, 25646–25654. Paszkowski, T. and Clarke, R.N. (1996) Antioxidative capacity of preimplantation embryo culture medium declines following the incubation of poor quality embryos. Hum. Reprod., 11, 2493–2495. Paulson, R.J., Sauer, M.V., Francis, M.M. et al. (1994) Factors affecting pregnancy success of human in-vitro fertilization in unstimulated cycles. Hum. Reprod., 9, 1571–1573. Pepper, M.S., Ferrara, M., Orci, L. and Montesano, R. (1995) Leukemia inhibitory factor (LIF) inhibits angiogenesis in vito. J. Cell Sci., 108, 73–83. Phocas, I., Sarandakou, A., Rizos, D. et al. (1992) Secretion of alpha-immunoreactive inhibin by human pre-embryos cultured in vitro. Hum. Reprod., 7, 545–549. Pimental, R.A., Wegner, C.C., Dey, S.K. and Carsom, D.D. (1995) Expression and steroid hormonal control of Muc-1 in the mouse uterus. Endocrinology, 136, 3639–3647. Plachot, M., Godard, A. and Geenan, V. (1995) Secretion of leukemia inhibiting factor by human endometrium alone and in co-cultre with embryos. Hum. Reprod., 11 (Suppl. 1), 185–186. Polan, M.L., Simon, C., Frances, A. et al. (1995) Role of embryonic factors in human implantation. Hum. Reprod., 10 (Suppl. 2), 22–29. Psychoyos, A. (1973) Endocrine control of egg implantation. In Greep, R.O. and Astwood, E.B. (eds), Handbook of Physiology. Washington, DC, pp. 187–215. Pusey, J., Kelly, W.A., Bradshaw, J.M.C. and Porter, D.G. (1980) Myometrial activity and the distribution of blastocysts in the uterus of the rat. Biol. Reprod., 23, 394–397. Rao, L.V., Wikarczuk, M.L. and Heyner, S. (1990) Functional roles of insulin and insulin-like growth factors in mouse preimplantation development. In Vitro Cell. Dev. Biol., 26, 1043–1048. Rappolle, D.A., Strum, K.S., Schultz, G.A. et al. (1990) The expression of growth factor ligand and receptors in preimplantation embryos. In Heyner, S. (ed.), Early Embryo Development and Paracrine Relationships, UCLS Symposium on Molecular and Cellular Biology, New Series 117, A.R.Liss, New York, pp. 11–25. Rappolle, D.A., Strum, K.S., Behrendtsen, O. et al. (1992) Insulin-like growth factor II acts through an endogenous growth pathway regulated by imprinting in early mouse embryo. Genes Dev., 6, 939–952. Rathjen, P.D., Toth, S., Willis, A. et al. (1990) Differentiation inhibiting activity is produced in matrix-associated and diffusible forms that are generated by alternative promoter usage. Cell, 62, 1105–1114. Ravindranath, N. and Moudgal., N.R. (1987) Use of tamoxifen, an anti-oestrogen, in establishing a need for oestrogen in early pregnancy in the bonnet monkey (Macaca radiata). J. Reprod. Fertil., 81, 327–336. Ravindranath, N. and Moudgal., N.R. (1990) Effect of a specific estrogen antibody on pregnancy establishment in the bonnet monkey (Macaca radiata). Fertil. Steril., 54, 1162–1167. Rizk, B., Manners, C.V., Davies, M.C. et al. (1992) Immunocytochemical expression of endometrial proteins and pregnancy outcome in frozen embryo replacement cycles. Hum. Reprod., 7, 413–417. Rogers, P.A.W., Murphy, C.R., Squires, K.R. and MacLennan, A.H. (1983) Effects of relaxin on the intrauterine distribution and antimesometrial positioning and orientation of rat blastocysts before implantation. J. Reprod. Fertil., 68, 431–435. Rotello, R.R., Lieberman, R.C., Purchio, A.F. and Gerschenson, L.E. (1991) Coordinated regulation of apoptosis and cell proliferation by transforming growth factor β1 in cultured uterine epithelial cells. Proc. Natl. Acad. Sci. USA, 88, 3412–3415. Rotello, R.R., Lieberman, R.C., Lepoff, R.B. and Gerschenson, L.E. (1992) Characterization of uterine epithelium apoptotic cell death kinetics and regulation by progesterone and RU486. Am. J. Pathol., 140, 449–456. Ruoslahti, E. (1991) Integrins. J. Clin. Invest., 87, 1–5. Sakkas, D., Jaquenoud, N., Leppens, G. and Campana, A. (1994) Comparison of results after in vitro fertilized human embryos are cultured in routine medium and in coculture on Vero cells: a randomized study. Fertil. Steril., 61, 521–525.

Endocrinology and paracrinology of implantation Sayegh, R., Awwad, J.T., Maxwell, C. et al. (1995) α2-Macroglobulin production by the human endometrium. J. Clin. Endocrinol. Metab., 80, 1021–1026. Schatz, F. and Lockwood, C.J. (1993) Progestin regulation of plasminogen activator inhibitor type 1 in primary cultures of endometrial stromal and decidual cells. J. Clin. Endocrinol. Metab., 77, 621–625. Scholtes, M.C.W., Wladimiroff, J.W., van Rijen, H.J.M. and Hop, W.C.J. (1989) Uterine and ovarian flow velocity waveforms in the normal menstrual cycle: a transvaginal Doppler study. Fertil. Steril., 52, 981–985. Schultz, G.A. and Heyner, S. (1993) Growth factors in preimplantation mammalian embryos. Oxford Rev. Reprod. Biol., 15, 43–81. Screaton, G.R., Bell, M.V., Bell, J.I. et al. (1993) The identification of a new alternative exon with highly restricted tissue expression in transcripts encoding the mouse Pgp-1 (CD44) homing receptor. Comparison of all 10 variable exons between mouse, human and rat. J. Biol. Chem., 268, 12235–12238. Segars, J.H., Rogers, B.J., Niblack, G.D. et al. (1989) The human blastocyst produces a soluble factor(s) that interferes with lymphocyte proliferation. Fertil. Steril., 52, 381–386. Sengupta, J., Sakhuja, D., Paria, B.C. and Ghosh, D. (1988) Endometrial phosphatases, β glucuronidase, and cathepsin D during the menstrual cycle and pre-implantation stages of gestation in the rhesus monkey (Macaca mulatta). Acta Endocrinol., 118, 142–146. Seppala, M. and Tiitinen, A. (1995) Endometrial reponses to corpus luteum products in cycles with induced ovulation: theoretical and practical consideration. Hum. Reprod., 10 (Suppl. 2), 67–76. Seppala, M., Koistinen, R. and Rutanen, E.-M. (1994) Uterine endocrinology and paracrinology: insulin-like growth factor binding protein-1 and placental-14 revisited. Hum. Reprod., 9, 917–925. Seshagiri, P.B. Terasawa, E. and Hearn, J. P. (1994) Secretion of gonadotrophin-releasing hormone by peri-implantation embryos of the rhesus monkey: comparison with the secretion of chorionic gonadotrophin. Hum. Reprod., 9, 1300–1307. Sharkey, A.M., Dellow, K., Blayney, M. et al. (1995) Stage-specific expression of cytokine and receptor messenger ribonucleic acids in human preimplantation embryos. Biol. Reprod., 53, 955–962. Sharpe-Timms, K.L., Zimmer, R.L., Trammell, S.E. et al. (1995) Immunolocalization of progesterone-induced uterine protein-1 in human endometrium during the menstrual cycle and in the placenta throughout gestation. Am. J. Obstet. Gynecol., 173, 1569–1578. Shevensky, L.H., Knowles, B.B., Damjanov, I. and Solter, D. (1982) Monoclonal antibody to murine embryos defines a stage specific embryonic antigen on mouse embryos and human teratocarcinoma cells. Cell, 30, 697–705. Shen, M.M. and Leder, P. (1992) Leukemia inhibitory factor is expressed by the preimplantation uterus and selectively blocks primitive ectoderm formation in vitro. Proc. Natl. Acad. Sci. USA, 89, 8240–8244. Sheth, K.V., Roca, G.L., Al-Sedairy, S.T. et al. (1991) Prediction of successful embryo implantation by measuring interleukin-1-a and immunosuppressive factor(s) in preimplantation embryo culture fluid. Fertil. Steril., 55, 952–957. Simon, C., Piquette, G.N., Frances. A. et al. (1993) Interleukin-1 type I receptor messenger ribonucleic acid expression in human endometrium throughout the menstrual cycle. Fertil. Steril., 59, 791–796. Simon, C., Frances, A., Piquette, N. et al. (1994) Embryonic implantation in mice is blocked by interleukin-1 receptor anatgonist. Endocrinology, 134, 521–528. Simon, C, Cano, F., Valbuena, D. et al. (1995a) Clinical evidence for a detrimental effect on uterine receptivity of high serum oestradiol concentrations in high and normal responder patients. Hum. Reprod., 10, 2432–2437. Simon, C., Frances, A., Lee. B.Y. et al. (1995b) Immunohistochemical localization, identification and regulation of the interleukin-1 receptor antagonist in the human endometrium. Hum. Reprod., 10, 2472–2477. Simon, C., Pellicer, A. and Polan, M.L. (1995c) Interleukin-1 system crosstalk between embryo and endometrium in implantation. Hum. Reprod., 10 (Suppl. 2), 43–54. Simon, C., Gimeno, M.J., Mercader, A. et al. (1997) Embryonic regulation if integrins β3, α4, and α1 in human endometrial epithelial cells in vitro. J. Clin. Endocrinol. Metab., 82, 2607–2616.

167

Smal, M.A., Dziadek, M., Cooney, S.J. et al. (1990) Examination for platelet-activating factor production by preimplantation mouse using a specific radioimmunoassay. J. Reprod. Fertil., 90, 419–425. Smith, R.M., Garside, W.T., Aghayan, M. et al. (1993) Mouse preimplantation embryos exhibit receptor-mediated binding and transcytosis of maternal insulin-like growth factor I. Biol. Reprod., 49, 1–12. Smotrich, D.B., Stillman, R.J., Widra, E.A. et al. (1996) Immunocytochemical localization of growth factors and their receptors in human pre-embryos and Fallopian tubes. Hum. Reprod., 11, 184–190. Solter, D. and Knowles, B.B. (1978) Monoclonal antibody defining a stage-specific mouse embryonic antigen (SSEA-1). Proc. Natl. Acad. Sci. USA, 75, 5565–5569. Steer, C.V., Mill, C, Campbell, S. et al. (1992) The use of transvaginal color flow imaging after in vitro fertilization to identify optimum uterine conditions before embryo transfer. Fertil. Steril., 57, 372–376. Stewart, C.L., Kaspar,P., Bhatt, H. et al. (1992) Blastocyst implantation depends on maternal expression of leukemia inhibitory factor. Nature, 359, 76–79. Sueldo, C.E., Kelly, E., Montoro, L., et al. (1990) Effect of interleukin-1 on gamete interaction and mouse embryo development. J. Reprod. Med. Obstet. Gynecol., 35, 868–872. Sueoka, K. (1992) Comphensive study on the expression mechanism of the early pregnancy associated substances and the implication for embryo development — structural determination of early pregnancy factor molecule and analysis of its homologous peptides. Nippon Sanka Fujinka Gakkai Zasshi, 44, 930–938. Sueoka, K., Shiokawa, S., Miyazaki, T. et al. (1997) Integrins and reproductive physiology: expression and modulation in fertilization, embryogenesis, and implantation. Fertil. Steril., 67, 799–811. Sugino, N., Shimamura, K,, Takiguchi, S. et al. (1996a) Changes in activity of superoxide dismutase in the human endometrium throughout the menstrual cycle and in early pregnancy. Hum. Reprod., 11, 1073–1078. Sugino, N., Shimamura, K., Tamura, H. et al. (1996b) Progesterone inhibits pseudopregnant superoxide radical production by mononuclear phagocytes in pseudopregnant rats. Endocrinology, 137, 740–754. Summers, P.M., Taylor, C.T. and Miller, M.W. (1993) Requirement of inner cell mass for efficient chorionic gonadotrophin secretion by blastocysts of common marmosets. (Callithrix jacchus). J. Reprod. Fertil., 97, 321–327. Tabibzadeh, S. (1992) Patterns of expression of integrin molecules in human endometrium throughout the menstrual cycle. Hum. Reprod., 7, 876–882. Tabibzadeh, S. (1994) Cytokines and the hypothalamic–pituitary– ovarian–endometrial axis. Hum. Reprod., 9, 947–967. Tabibzadeh, S. and Babaknia, A. (1995) The signals and molecular pathways involved in implantation, a symbiotic interaction between blastocyst and endometrium involving adhesion and tissue invasion. Hum. Reprod., 10, 1579–1602. Tabibzadeh, S.S. Kaffka, K.L., Satyaswaroop, P.G. and Kilan, P.L. (1990) IL-1 regulation of human endometrial function: presence of IL-1 receptor correlates with IL-1 stimulated PGE2 production. J. Clin. Endocrinol. Metab., 70, 1000–1009. Tabibzadeh, S., Kong, Q.F., Kapu, S. et al. (1995) Tumour necrosis factor mediated dyscohesion of epithelial cells is associated with disordered expression of cadherins/β-catenin and dissembly of actin filaments. Hum. Reprod., 10, 994–1004. Taketani, Y., Kuo, T.M. and Mizuno, M. (1992) Comparison of cytokine levels and embryo toxicity in peritoneal fluid in infertile women with untreated or treated endometriosis. Am. J. Obstet. Gynecol., 167, 265–270. Tamada, H., McMaster, M.T., Flanders, K.C. et al. (1990) Cell type-specific expression of transforming growth factor-β1 in the mouse uterus during the periimplantation period. Mol. Endocrinol., 4, 965–972. Telfer, J.F., Lyall, F., Norman, J.E. and Cameron, L.T. (1995) Identification of nitric oxide synthase in human uterus. Hum. Reprod., 10, 19–23. Thorp, J., Waksh, S. and Brath, P. (1988) Low-dose aspirin inhibits thromboxane, but not prostacyclin production by human placental arteries. Am. J. Obstet. Gynaecol., 159, 1381–1384.

168


Tseng, L., Mazella, J. and Sun, B. (1986) Modulation of aromatase activity in human endometrial stromal cells by steroids, Tamoxifen and RU486. Endocrinology, 118, 1312–1318. Tseng, L., Gao, J.G., Zhu, H.H. et al. (1992) Effect of progestin, antiprogestin and relaxin on the accumulation of PRL and insulin like growth factor binding protein-1 messenger ribonucleic acid in human endometrial stromal cells. Biol. Reprod., 47, 441–450. Tulppalla, M., Marttunen, M., Soderstorm-Anttila, V. et al. (1997) Low-dose aspirin in prevention of miscarriage in women with unexplained or autoimmune related recurrent miscarriage: effect on prostaglandin and thromboxane A2. Hum. Reprod., 12, 1567–1572. Turner, K. and Lenton, E.A. (1996) The influence of Vero cell culture on human embryo development and chorionic gonadotrophin production in vitro. Hum. Reprod., 11, 1966–1974. Turpeeniemi-Hujanen, T., Ronnberg, L., Kaupila, A. and Puistola, V. (1992) Laminin in human embryo implantation: analogy to the invasion by malignant cells. Fertil. Steril., 58, 105–113. Underhill, C. (1992) CD44: the hyaluronan receptor. J. Cell Sci., 103, 293–298. Van Blerkom, J. (1993) Development of human embryos to the hatched blastocyst stage in the presence or absence of a monolayer of Vero cells. Hum. Reprod., 8, 1525–1539. Vasilenko, P. and Mead, J.P. (1987) Growth-promoting effects of relaxin and related compositional changes in the uterus, cervix, and vagina of the rat. Endocrinology, 120, 1370–1376. Vasilenko, P., Mead, J.P. and Weidmann, J.E. (1986) Uterine growth-promoting effects of relaxin: a morphometric and histological analysis. Biol. Reprod., 35, 987–995. Vince, G.S. and Johnson, P. (1995) Maternal–fetal immunobiology in normal pregnancy and its possible failure in recurrent spontaneous abortion? Hum. Reprod., 10 (Suppl. 2), 107–113. Wada, I., Hsu, C.C., Williams, G. et al. (1994) The benefits of low dose aspirin therapy in women with impaired uterine perfusion during assisted conception. Hum. Reprod., 9, 1954–1957.

Wahlstrom, T., Koskimies, A.I., Tenhunen, A. et al. (1985) Pregnancy proteins in endometrium after follicle aspiration for in vitro fertilization. Ann. NY Acad. Sci., 442, 402–407. Weimer, K.E., Hoffman, D.L., Maxson, W.S. et al. (1993) Embryonic morphology and rate of implantation of human embryos following co-culture on bovine oviductal epithelial cells. Hum. Reprod., 8, 97–101. Wetzels, A.M.M., Punt-Van der Zalm, A.P.E.M., Bastiaans, B.A., et al. (1992) The effects of human skin fibroblast monolayers on human sperm motility and mouse zygote development. Hum. Reprod., 7, 852–856. Xia, P., Tekpetey, F. and Armstrong, D.T. (1994) Effect of IGF-I on pig oocyte maturation, fertilization, and early embryonic development in vitro, and on granulosa and cumulus cell biosynthetic activity. Mol. Reprod. Dev., 38, 373–379. Yaegashi, N., Fujita, N., Yajima, A. and Nakamura, M. (1995) Menstrual cycle dependent expression of CD44 in normal human endometrium. Hum. Pathol., 26, 862–865. Yoshinaga, K. (1994) Future prospect of research on endocrinology of embryo–endometrial interactions. In Glasser, S.R. et al. (eds), Endocrinology of Embryo–Endometrium Interactions. Plenum Press, New York. pp. 391–400. Zegers-Hochschild, F. and Altieri, E. (1995) Luteal phase estrogen is not required for establishment of pregnancy in the human. J. Assist. Reprod. Genet., 12, 224–228. Ziche, M., Maglione, D., Ribatti, D. et al. (1997) Placenta growth factor-1 is chemotactic, mitogenic, and angiogenic. Lab. Invest., 76, 517–531. Zimmerman, R.J., Chan, A. and Leadon, S.A. (1989) Oxidative damage in murine tumour cells treated in vitro by recombinant human tumour necrosis factor. Cancer Res., 49, 1644–1648. Zolti, M., Ben-Rafael, Z., Meirom, R. et al. (1991) Cytokine involvement in oocytes and early embryos. Fertil. Steril., 56, 265–272.

Received on January 23, 1998; accepted on March 31, 1998