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ISSN 00124966, Doklady Biological Sciences, 2014, Vol. 456, pp. 199–202. © Pleiades Publishing, Ltd., 2014. Original Russian Text © O.F. Chernova, 2014, published in Doklady Akademii Nauk, 2014, Vol. 456, No. 3, pp. 374–377.

GENERAL BIOLOGY

Scanning Electron Microscopy of the Hair Medulla of Orangutan, Chimpanzee, and Man O. F. Chernova Presented by Academician E.I. Vorob’eva January 13, 2014

Received January 15, 2014

DOI: 10.1134/S0012496614030065

Human and animal hairs are studied in various fields of knowledge, from evolutionary biology to criminology, and these studies have both theoretical and practical implications. At the level of the light optical microscopy, the hair structure of humans and various mammalian species has been well studied; there are numerous atlases and descriptions; diagnos ing of animal species and human races is now possible. The published data suggest that hair cuticle and cortex are similar in humans and animals, while the medullar structure of human hair is fundamentally different from that of other mammals; this structure is defined as “intermediate, amorphous, and filamentous” in contrast to usually one or multilane ladder medulla of the animal hair. In view of this, specific human hair structure is assumed to demonstrate the remoteness of man and animals. The filamentous, fibrillar hair struc ture resulting from compression is believed to be spe cific for humans. This confuses the scientists that do not follow theological or anthropocentric views on human origin [1]. Another peculiar feature of human hair is that the relative thickness of the hair medulla does not exceed onethird of the hair shaft thickness. Nevertheless, the fine structure (inner architectonics) of the hair medulla is difficult to discern by means of the light optical microscopy and the data obtained are some times doubtful. Because of this, hairs are often studied using electron microscopy, as well as the molecular genetic, immunogenetic, biochemical, Xray, refrac tometric, and nanomechanical methods and electro phoresis. Some authors [2, 3], including us [4, 5], have used successfully the scanning electron microscopy (SEM). By this method, the outer surface of the cuti Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Leninskii pr. 33, Moscow, 117071 Russia email: [email protected]

cle of an intact hair and its cortex and medulla were examined on cross sections of the hair shaft, as well as the maceration products of hair medulla in alkaline [3]. By means of SEM, a classification scheme of the mammalian hair medulla has been developed on the basis of its mechanical design, the “inert air” distribu tion in keratinized “cells,” the volume of cellular remains, and the degree of either vacuolization or per foration of keratinous septa [1, 4]. At the same time, only in our studies has the structure of mammalian hair medulla been studied by SEM on the longitudinal sections of the hair shaft. This approach yielded the most complete pattern of the medullar architectonics, which is necessary for diagnosing of a taxon [4]. There is no similar data in scientific literature, because dis section of the longitudinal hair preparations is diffi cult, although some methodical recommendations are available [6]. Since we have acquired experience in SEM examination of longitudinal hair sections, we decided to compare the human hair architectonics with that of the anthropoid apes. Analysis of similarity and distinctions between the human hair medulla and that of the phylogenetically related species, namely chimpanzee and orangutan, is a scientific novelty of our study. We have examined (1) the top hairs from the back of adult orangutan Pongo pygmaeus and common chimpanzee Pan troglodytes exposed in the Moscow Zoo, (2) the terminal hairs from the head of adult women and men of Slavic appearance, (3) the hairs from the back and chest of an adult men of Slavic ori gin (Caucasian race). At least five hairs were purified, dried, cut crosswise, and both the crosspieces and intact hairs were glued onto the sample stage; after wards, the intact hairs were cut lengthwise with a razor blade. The preparations were goldsputtered using the method of ionassisted sputtering by means of an Edwards S150A device (United Kingdom). After wards, they were examined using a JEOL840A (Japan) and a TESCAN (Czech Republic) scanning

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(a)

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Fig. 1. Hair medulla architectonics on the longitudinal sections of the primate hairs: (a, e, inset) orangutan; (b, f, inset) chim panzee. Hairs of a Slavic man: (c, g) from the back; (d, h) from the head. SEM. Scale:(a–d) 10 µm; (e–h) 1 µm.

electron microscopes at an accelerating voltage of 10 and 15 kV, and the electronograms have been obtained. The results of our study demonstrate that each of the species has its own individual features of the hair medulla structure, which confirms the diagnostic sig nificance of its architectonics [4]; nevertheless, some features are shared by all of the three species. Not all human hairs contain hair medulla; it is especially rare in the head hairs. Even if there is a hair medulla, it is

underdeveloped and often looks fragmentary and beaded. As mentioned above, the hair medulla makes up at most 30% of the human hair thickness; in our case, it makes up 17–28% at a hair shaft thickness of 45–101 µm. In the apes studied, the hair medulla is also poorly developed: it makes up 16–27% in orangu tan and 21–22% in chimpanzee at a hair shaft thick ness of 140–170 and 101–113 µm, respectively. Con figuration of the medulla chord in apes is almost regu lar, cylindrical, while in man, it is a little flattened, DOKLADY BIOLOGICAL SCIENCES

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SCANNING ELECTRON MICROSCOPY OF THE HAIR MEDULLA OF ORANGUTAN

sometimes beaded, and intermittent; in all of the spe cies compared, the medulla chord is uneven especially in chimpanzee and man (Figs. 1a–1d). The boundary between the hair medulla and cortex is uneven; the cortex juts into the medulla in the form of three rounded outgrowths (Figs. 1a–1d). The architectonics of orangutan hair medulla (Figs. 1a, 1e) is similar to that of predatory mammals (wolfs and cats) [4]. It is “delicate” and consists of randomly interwoven kera tin septa separating numerous middlesized round or oval air cavities. The thickened nonperforated fila mentous septa are also encountered; they are oriented across the medulla chord or obliquely to its longitudi nal axis. In chimpanzee, the sparse large polymorphic cavities are well discernible, as are thickened fila ments, which are arcuate and oriented across the cord (Figs. 1b, 1f). In human hair medulla, there are few air cavities, which are small, nondilated, polymorphic, and resemble the hair medulla of chimpanzee. In the apes, the septal walls contain sometimes two or three large perforations, which are absolutely absent in humans. In human hairs, the relatively large slitshaped round or polymorphic cavities are rare (Fig. 1d). Most of the hair medulla is formed by a tightly interwoven ornament of keratin filaments which are variable in configuration, thickness, and orientation. In human hairs, all of the structural elements are stretched longi tudinally; the thick filamentous septa are observed sometimes across the hair medulla cord (Fig. 1c) or they are arcuate in shape (Fig. 1d) as in chimpanzee hair. Our data are in accordance with the reports sug gesting that the human hair medulla has a fibrillar structure. The ultrastructural features of the medulla that is formed in hair follicle demonstrate distinctions between primates and other animals: in some mam malian species, the metabolically active medullar cells have either amorphous or granular contents, while in humans and anthropoid apes, these cells contain macro and microfibrils [7]; the genus Homo has a specific medullar structure, though it cannot be used to distinguish different individuals [8]. The fibrillar structure of the human head hair has been confirmed by Xray studies; both the fibrils and protofibrils looks like randomly arranged cylindrical structural elements immersed into an amorphous matrix [9]. There were pigmented granules in the hair medulla of orangutan and chimpanzee; these were round or oval in shape and up to 1 µm in diameter (insets in Figs. 1e and 1f), which is typical of mammalian hairs [4]. In the human hair medulla, we failed to find any pigmented granules, although we examined the hair of a blackhaired man. SEM examination revealed both oval and elongated granules up to 1 µm in diameter [3]; i.e., these granules were similar to those of apes (especially in chimpanzee). DOKLADY BIOLOGICAL SCIENCES

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In summary, we have come to a conclusion that general structure of the human hair medulla does not differ significantly from that of the anthropoid apes, especially chimpanzee. Some peculiar features are characteristic of the primate hairs, such as weak heat insulating properties (underdevelopment of the hair medulla, its airbearing cavities, and septal perfora tions), a diversity of polymorphic keratic filaments of complex configuration, and varying spatial orienta tion. Architectonics of the human hair medulla is quite similar to that of chimpanzee, but in hairs of the back, the crimped and tightly packed filaments are mostly stretched along the hair shaft. Under a light optical microscope, this hair medulla looks probably like a tight interweaving of the longitudinally elon gated and twisted bundles. Thus, the human hair medulla is quite similar to that of chimpanzee, which is not surprising if the relat edness of these species is accepted, because they con stitute the same subfamily Homidinae, which has been confirmed by various methods. Nevertheless, the human hair medulla differs from that of orangutan, which is a member of another subfamily Ponginae. The ancient ancestors of this subfamily and those of the chimpanzee–man branch have diverged earlier (6.2–8.4 million years ago) than the ancestors of chimpanzee and man (4.6–6.2 million years ago), as it was determined by molecular genetic analysis [10]. Specific features of the human hairs has been con firmed by electrophoresis of their keratins, proteins that are different from those of other mammals, but to a lesser extent from hair keratins of the anthropoid apes (a sequential reduction of the keratin fractions is characteristic of both the apes and man) [11]. More extensive SEM analysis of hairs from humans and closely related primates would make it possible to find some novel diagnostic traits of species and races and to discuss evolution of the mammalian hair, including that of humans. ACKNOWLEDGMENTS I am grateful to N.N. Spasskaya for the help in col lection of the material and to T.N. Tselikova for the technical assistance. REFERENCES 1. Clement, J.L., Hagege, R., Le Pareux, A., Connet, J., and Gastaldi, G., Forens. Sci. Int., 1981, vol. 26, no. 3, pp. 447–458. 2. Verhoeven, L.E., J. Criminal Law Criminol. Police Sci., 1972, vol. 63, no. 1, pp. 125–132. 3. Kisin, M.V. and Golovin, A.V., Microscope, 1992, vol. 40, pp. 259–264.

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4. Chernova, O.F. and Tselikova, T.N., The Atlas of Mam malian Hair, Moscow: KMK, 2004. 5. Chernova, O.F., Perfilova, T.V., Spasskaya, N.N., Kiladze, A.B., and Ibraev, M.V., The Atlas of Horse Hair Microstructure, Moscow: GFTsSE, 2011. 6. Kempson, I.M., Skinner, W.M., and Kirkbride, K.P., Forensic Sci. Int., 2002, vol. 47, no. 4, pp. 889–892. 7. Clement, J.L., Le Pareux, A., and Ceccaldi, P.F., Ann. Dermatol. Venerol., 1981, vol. 108, no. 11, pp. 849–857. 8. Clement, J.L., Le Pareux, A., and Ceccaldi, P.F., J. Forensic Sci. Soc., 1982, vol. 22, no. 4, pp. 396–398.

9. Wilk, K.E., James, V.J., and Amemiya, Y., Biochim. Biophys. Acta Gen. Subj., 1995, vol. 1245, no. 3, pp. 392–396. 10. Chen, F.Ch. and Li, W.H., Am. J. Hum. Genet., 2001, vol. 68, pp. 444–456. 11. Spitsyn, V.A., Afanas’eva, I.S., Bychkovskaya, L.S., and Spitsyna, N.Kh., Vestn. Mosk. Univ., Ser. 23 Antropol., 2009, no. 4, pp. 71–82.

Translated by A. Nikolaeva

DOKLADY BIOLOGICAL SCIENCES

Vol. 456

2014