вход по аккаунту


Localization of serotonin-like immunoreactivity in the merkel cells of pig snout skin.

код для вставкиСкачать
THE ANATOMICAL RECORD 225:267-271 (1989)
Localization of Serotonin-Like lmmunoreactivity in
the Merkel Cells of Pig Snout Skin
Departamento de Ciencias Morfologicas (Catedra de Histologia Humana), Servicio de
Microscopia Electronica, Facultad de Medicina, Hospital General de Galicia, Uniuersidad
de Santiago de Compostela, Galicia, Spain (T.G.-C., R.G., E.R., D.B., A.B.); CNRS U R A
559, Laboratorie d‘Histologie-Embryologie, Facultd de Mkdecine Lyon Sud, France (G.M.)
The presence of serotonin in the Merkel cells of pig snout epidermis was investigated by the peroxidase-antiperoxidase immunohistochemical
technique. Serotonin-like immunoreactive Merkel cells were found in groups located a t the base of epidermal rete pegs and in the external root sheath of sinus
hair follicles (vibrissae). Immunoreactivity was stronger on the basal side of the
Merkel cells, where dense-cored granules are most numerous. Neither the nerve
terminal associated with the Merkel cell nor the neighbouring epidermal cells
were immunostained.
These results are the first evidence of serotonin-like immunoreactivity in mammalian Merkel cells. The fact that immunoreactivity is strongest in those parts of
the Merkel cells with the highest granule density suggests that in these cells
serotonin is probably localized in the dense-cored granules.
Merkel cells were first described in 1875 by Friedrich
Sigmund Merkel as “Tastzellen” (touch cells). Merkel
suggested that these specialized epidermal cells, which
appeared associated with nerve terminals, were receptors and transducers of mechanical stimuli (see Camisa
and Weissmann, 1982).
The mechanoreceptor function of Merkel corpuscles
has been generally accepted. In mammals they act as
slowly adapting type I units (Iggo and Muir, 1969; Tapper, 1970; Munger, 1971; Pubols et al., 1971; Andres
and During, 1973; Burgess and Perl, 1973; Winkelmann and Breathnach, 1973; Horch et al., 1974; Smith,
1977). However, the function of the Merkel cells themselves is still unclear (Winkelmann and Breathnach,
1973). The roles suggested by morphological or physiological studies include their activity as: a) the actual
mechanoelectric transducer as Merkel originally postulated (Andres, 1966; Iggo and Muir, 1969; Burgess
and Perl, 1973; Chen et al., 1973; Mihara et al., 1979;
Breathnach, 1980; Hartschuh and Weihe, 1980); b)
neuromodulators of the response generated directly in
the nerve ending by mechanical stimulus (Hartschuh
et al., 1983; Diamond et al., 1986); c) tropic and/or
trophic elements for the nerve terminals (Ram6n y Cajal, 1919; Smith and Creech, 1967; Munger et al., 1971;
English, 1974, 1977; Diamond et al., 1976; Killackey,
1980; Scott et al., 1981; Gottschaldt and Vahle-Hinz,
1981, 1982); and d) passive abutments for the nerve
endings (Gottschaldt and Vahle-Hinz, 1981). It has also
been suggested that Merkel cells may affect neighbouring epidermal cells by paracrine action (Pearse, 1980;
Hartschuh et al., 1984; Tachibana et al., 1984). Whatever the function of Merkel cells is, it involves the secretion of the contents of their dense-cored granules
(Fox and Whitear, 1978; Tachibana et al., 1984; Salomon et al., 1987). Knowledge of the chemical nature
0 1989 ALAN
of these granules is essential for elucidation of Merkel
cells functiods).
Zaccone (1986) reported immunoreactivity for serotonin in Merkel cells in the skin of the conger-eel (Conger conger).The purpose of the work described here was
to investigate immunohistochemically whether serotonin is present in Merkel cells of the pig.
Samples were taken from the skin of pig snouts in
which Merkel cells are abundant and exhibit morphologic and immunohistochemical similarities to human
Merkel cells. The specimens were fixed by immersion
in Bouin’s solution for 2 hrs and embedded in paraffin.
Sections 5 pm thick were immunostained using the
peroxidase-antiperoxidase (PAP) technique (Sternberger et al., 1970) by succesive incubation in: 1) hydrogen peroxide (3%) for 10 min at room temperature;
2) normal goat serum (1:lO) for 30 min at room temperature; 3) anti-serotonin raised in rabbits (Immuno
Nuclear, Stillwater, MN, lot no. 8616010) at a dilution
of 1:2,000, overnight at 4°C;4) anti-rabbit IgG developed in goats (Sigma, St Louis, MO) at a dilution of
150, for 1 hr at room temperature; 5) PAP (rabbit)
complex (Dakoppatts, Glostrup, Denmark) at 1:100, for
1 hr at room temperature; and 6) 3,3’diaminobenzidine-tetrahydrochloride (DAB) (Sigma, St Louis,
MO) solution with 0.003% HzOZ,for 10 min. All the
solutions were made up in PBS of pH 7.4. After steps
Received December 5, 1988; accepted March 24, 1989.
Address reprint requests to Prof. Andres Beiras, Servicio de Microscopia Electrbnica, Facultad de Medicina, CiSan Francisco s/n, 15705
Santiago de Compostela, La Coruna, Spain.
1,3,4, and 5 the sections were washed twice for 5 min
with PBS of pH 7.4, and with distilled water after step
6. After step 2 the normal goat serum was drawn off
before the primary antibody was applied.
The serotonin-specificity of the antiserum was
checked by preadsorbing diluted serotonin antiserum
(1:2,000) with 5-HT creatinine sulphate (Sigma, St
Louis, MO) at 100 pg/ml. The vials were placed in a
37°C oven for 1 hr and then stored overnight at 4°C.
Additional vials of diluted antiserum were subjected to
the same procedure and employed for staining controls.
In addition, sections were incubated with normal (nonimmune) rabbit serum instead of anti-serotonin serum.
For ultrastructural analysis, specimens were processed as previously described (Beiras et al., 1986).
Briefly, samples were fixed by immersion in 2.5% glutaraldehyde in 0.15 M sodium cacodylate buffer of pH
7.3. Postfixation was performed in 2% osmium tetroxide in the same buffer. Tissue blocks were then dehydrated and embedded in Spurr’s epoxy resin (Spurr,
Serotonin-like immunoreactive Merkel cells were
found parallel to the surface a t the tips of epidermal
rete pegs of pig snout skin (Fig. 1). They appeared both
isolated or, more frequently, forming groups (the latter
generally at the tips of the widest rete pegs) (Fig. 1).No
other epidermal cells were immunostained. The strongest immunoreactivity was seen on the basal side of the
epidermal Merkel cells (Fig. 1).The area exhibiting the
most intense immunostaining was the region of the
Merkel cells that was closest to the nerve ending (Fig.
l),where dense-cored granules are concentrated (Fig.
2). Neither the expanded nerve terminals associated
with the Merkel cells nor the myelinated axons found
in the superficial dermis were positive for serotonin
(Fig. 1).
Sinus hair follicles (vibrissae) exhibited immunostained Merkel cells in a row in the external root sheath
(Fig. 3). Unlike epidermal Merkel cells, vibrissal Merkel cells were most intensely stained on the side facing
into the follicle (Fig. 3). In vibrissae, the nerve endings
were not situated on the dermal side of the Merkel cells
(as in epidermis), but on their epithelial side, so that
the Merkel cells lay between the nerve disc and the
basal membrane (not shown).
Control assays were performed in serial sections.
Slides incubated with serotonin antiserum exhibited
numerous immunostained Merkel cells (Fig. 4), but
there was no immunoreaction in sections incubated
with antiserum preadsorbed by serotonin (Fig. 5 ) , nor
when the antiserum was replaced by normal rabbit serum.
ence of serotonin in the Merkel cells of conger-eel epidermis (Zaccone, 1986). Our results confirm that
Merkel cells exhibit serotonin-like immunoreactivity
and, to our knowledge, are the first observations of
serotonin in mammalian Merkel cells. The specificity
of the serotonin antiserum used in this study was verified by the absence of immunostaining after preadsortion of the antiserum by serotonin or replacement of
the antiserum by normal rabbit serum.
The finding of more intense immunostaining on the
side of the Merkel cells with the highest granule density leads us to suppose that serotonin is stored in the
Merkel cells’ dense-cored granules, as has been postulated by Zaccone (1986) for the Merkel cells of congereel (Conger conger). The different situations of the
nerve disc described in the epidermal and vibrissal
Merkel corpuscles (Andres and During, 1973; Hartschuh and Weihe, 1980) explain the difference in the
localization of immunostaining in both Merkel corpuscles.
Several peptides found in Merkel cell cytoplasm are
also thought t o be stored in the dense-cored granules,
namely met-enkephalin in various rodents (Hartschuh
et al., 1979b, 1980); vasoactive intestinal polypeptide
in man, cat, dog, and pig (Hartschuh et al., 1983,19841,
and calcitonin gene-related peptide in cats (Alvarez et
al., 1988). The coexistence of serotonin and polypeptides in the same cell is not an exceptional circumstance and has been long recognized in neurons
(Hokfelt et al., 1980, 1984; Pelletier et al., 1981) and in
a variety of endocrine cells (Gylfe, 1978; Larsson 1980;
Nunez et al., 1980).
Merkel corpuscles may be considered analogous to
the neuroepithelial bodies (NEBS) of the respiratory
mucosa since both consist of granulated cells in close
contact with nerve endings (Chen et al., 1973; Winkelmann, 1977; Stahlman et al., 1985). NEBS have been
shown t o contain various peptides (bombesin, calcitonin, leu-enkephalin, calcitonin gene-related peptide,
and somatostatin) and serotonin (Lauweryns et al.,
1973; Wharton et al., 1978; Becker et al., 1980; Cutz et
al., 1981; Dayer et al., 1985; Lauweryns and Van
Ranst, 1987; Scheuermann et al., 1987). The presence
of serotonin in Merkel cells thus increases the analogy.
The role of serotonin in most paracrine cells is not
well known. In the gastrointestinal tract it seems to act
on both neural elements (Eklund et al., 1980; Johnson
et al., 1980) and smooth muscle cells (Paton and Aboo
Zar, 1968). For NEBS it has been suggested that serotonin has: 1) a role in the mechanism of hypoxia-induced pulmonary vasoconstriction (Lauweryns et al.,
1982); 2) specific interaction with efferent vagal impulses (Lauweryns et al., 1982); and 3) a trophic role in
the process of capillary invasion during fetal lung development (Stahlman et al., 1985).For the Merkel cells
The morphological similarity between Merkel cell
granules and monoamine storing granules led to the
suggestion that the former contained monoamines too
(Mustakallio and Kiistala, 1967; Winkelmann and
Fig. 1. Isolated Merkel corpuscles located a t the tips of epidermal
Breathnach, 1973). However, Smith (1967, 19701, rete pegs, showing immunoreactivity for serotonin on the side closest
Hartschuh et al. (1979a1, and Diamond et al. (1986) to the associated nerve endings (arrowheads), which are not immu( x 1,100).
failed to confirm this hypothesis by pharmacological nostained.
Fig. 2. Ultrastructural appearance of a Merkel corpuscle. Most
procedures or fluorescence techniques. Immunohisto- dense-cored granules are on the side of the Merkel cell apposed to the
chemical techniques have recently revealed the pres- nerve terminal (N). ( x 31,200).
Figs. 1-2.
Fig. 3.Sinus hair follicle (vibrissa), showing immunoreactivity on
the epithelial side of Merkel cells ( X 500).
Figs. 4 and 5. Antibody specificity controls. Serial sections were
incubated with serotonin antiserum (Fig. 4) and with the antiserum
preadsorbed by serotonin (Fig. 5). Observe the absence of immunostaining in the Merkel cells of the control (Fig. 5) ( X 270).
of Conger conger, Zaccone (1986) postulated that serotonin may either stimulate the attached nerve ending,
thus acting as a neurohormone or be a synaptic mediator that transduces received stimuli from the cell to
the nerve ending. However, all these hypotheses are
quite speculative; and it has also been suggested that
serotonin coexisting in cells with polypeptides is involved in the synthesis, storage, andlor release of the
latter (Owman et al., 1973).
To sum up, serotonin is present in Merkel cells in pig
snout skin, probably located in the dense cored granules of these cells. Further investigations are needed to
confirm the subcellular localization of this amine and
to discover the exact role that serotonin plays in the
physiology of Merkel corpuscles.
related peptide and vasoactive intestinal polypeptide in cat Merkel cells and cutaneous free nerve endings: Light and electron
microscopic study. Cell Tissue Res., 254:429-437.
Andres, K.H. 1966 Uber die Feinstruktur der Rezeptoren an Sinushaaren. Z. Zellforsch., 75t339-365.
Andres, K.H., and M.V. During 1973 Morphology of cutaneous receptors. In: Handbook of Sensory Physiology. A. Iggo, ed. Springer
Verlag, Berlin, Vol. 11, pp. 3-28.
Becker, K.L., K.G. Monaghan, and O.L. Silva 1980 Immunocytochemical localization of calcitonin in Kulchitsky cells of human lungs.
Arch. Pathol. Lab. Med., 104t196-198.
Beiras, A., T. Garcia-Caballero, J. Espinosa, and R. Gallego 1986
Staining of Merkel cells of pig snout epidermis using the uranaffin reaction. Morphometric analysis of neuroendocrine granules.
Differentiation, 32539-92.
Breathnach, A S . 1980 Branched cells in the epidermis: An overview.
J . Invest. Dermatol., 75t6-11.
Burgess, P.R., and E.R. Per1 1973 Cutaneous mechanoreceptors and
nociceptors. In: Handbook of Sensory Physiology. A. Iggo, ed.
Springer Verlag, Berlin, Vol. 11, pp. 30-72.
Camisa, C., and A. Weissmann 1982 Friedrich Sigmund Merkel. Part
11. The Cell. Am. J. Dermatopathol., 4t527-535.
Chen, S.Y., S. Gerson, and J. Meyer 1973 The fusion of Merkel cell
granules with a synapse-like structure. J . Invest. Dermatol., 61;
Cutz, E., W. Chan, and N.S. Track 1981 Bombesin, calcitonin and
leu-enkephalin immunoreactivity in endocrine cells of human
lung. Experientia, 37t765-767.
Dayer, A.M., J . De Mey, and J.A .Will 1985 Location of somatostatinbombesin- and serotonin-like immunoreactivity in the lung of the
fetal Rhesus monkey. Cell Tissue Res., 239:621-625.
Diamond, J., E. Cooper, C. Turner, and L. Macintyre 1976 Trophic
regulation of nerve sprouting. Science, 193:371-377.
Diamond, J . , M. Holmes, and C.A. Nurse 1986 Are Merkel cell-neu-
This work was supported in part by grant No.
6090275290 from the Xunta de Galicia (Conselleria de
Educacion), and also by grant No. 65140-1988 (Accion
Integrada Hispano Francesa) from the Ministerio de
Educacion, Madrid, Espafia. The authors thank D.
Fernandez Roe1 and V. Garcia Castro for technical assistance, M. Rios-Curras for photographic work, and I.
Coleman for correction of the English text.
Alvarez, F.J., C. Cervantes, R. Villalba, I. Blasco, J.M. Polak, and J .
Rodrigo 1988 Immunocytochemical analysis of calcitonin gene
rite reciprocal synapses involved in the initiation of tactile responses in salamander skin? J . Physiol. (Lond.),376t101-120.
Eklund, S., J . Fahrenkrug, M. Jodal, 0. Lundgren, O.B. Schaffalizky
de Muckadell, and A. Sjoqvist 1980 Vasoactive intestinal polypeptide, 5-hydroxytryptamine and reflex hyperaemia in small
intestine of the cat. J . Physiol. (Lond.) 302.549-557.
English, K.B. 1974 Cell types of cutaneous type I mechanoreceptors
(Haarscheiben) and their alterations with injury. Am. J. Anat.,
English, K.B. 1977 Morphogenesis of Haarscheiben in rats. J. Invest.
Dermatol., 6958-67.
Fox, H., and M. Whitear 1978 Observations on Merkel cells in amphibians. Biol. Cell., 32t223-232.
Gottschaldt, K.M., and C. Vahle-Hinz 1981 Merkel cell receptors:
Structure and transducer function. Science, 214:183-186.
Gottschaldt, K.M., and C. Vahle-Hinz 1982 Evidence against transmitter function of met-enkephalin and chemosynaptic impulse
generation in “Merkel cell” mechanoreceptor. Exp. Brain Res.,
Gylfe, E. 1978 Association between 5-hydroxytryptamine release and
insuline secretion. J. Endocrinol., 78:239-248.
Hartschuh, W., M. Reinecke, E. Weihe, and N. Yanaihara 1984 VIPimmunoreactivity in the skin of various mammals: Immunohistochemical, radioimmunological and experimental evidence for a
dual location in cutaneous nerves and Merkel cells. Peptides, 5:
Hartschuh, W., and E. Weihe 1980 Fine structural analysis of the
synaptic junction of Merkel cell-axon complexes. J . Invest. Dermatol., 75t159-165.
Hartschuh, W., E. Weihe, and M. Buchler 1980 Met-enkephalin-like
immunoreactivity in Merkel cells of various species (Abstract). J .
Invest. Dermatol., 74t453.
Hartschuh, W., E. Weihe, M. Biichler, and P. Kalmbach 1979a Experimental investigation of the Merkel cell. J. Invest. Dermatol.,
Hartschuh, W., E. Weihe, M. Buchler, V. Helmstaedter, G.E. Feurle,
and W.G. Forssmann 19791, Met-enkephalin-like immunoreactivity in Merkel cells. Cell Tissue Res., 201t343-348.
Hartschuh, W., E. Weihe, N. Yanaihara, and M. Reinecke 1983 Immunohistochemical location of vasoactive intestinal polypeptide
(VIP) in Merkel cells of various mammals: Evidence for a neuromodulator function of the Merkel cell. J. Invest. Dermatol., 81:
Hokfelt, T., 0. Johansson, and M. Goldstein 1984 Chemical anatomy
of the brain. Science, 225t1326-1334.
Hokfelt, T., 0. Johansson, A. Ljungdahl, J.M. Lundberg, and M.
Schultzberg 1980 Peptidergic neurones. Nature, 284515-521.
Horch, K.W., D. Whitehorn, and P.R. Burgess 1974 Impulse generation in type I cutaneous mechanoreceptors. J. Neurophysiol., 37:
Iggo, A., and A.R. Muir 1969 The structure and function of a slow
adapting touch corpuscle in hairy skin. J. Physiol. (Lond.), 200:
Johnson, S.M., Y. Katayama, and R.A. North 1980 Multiple actions of
5-hydroxytryptamine on myenteric neurones of the guinea-pig
ileum. J . Physiol. (Lond.), 304:459-470.
Killackey, H.P. 1980 Pattern formation in the trigeminal system of
the rat. Trends Neurosci., 3:303-305.
Larsson. L.I. 1980 On the oossible existence of multide endocrine.
paracrine, and neurocrine messengers in secretory cell systems.
Invest. Cell. Pathol., 3:73-85.
Lauweryns, J.M., M. Cokelaere, and P. Theunynck 1973 Serotonin
producing neuroepithelial bodies in rabbit respiratory mucosa.
Science, 180:410-413.
Lauweryns, J.M., V. de Bock, A.A.J. Verhofstad, and H.W.M. Steinbusch 1982 Immunohistochemical localization of serotonin in intrapulmonary neuro-epithelial bodies. Cell Tissue Res., 226t215 223.
Lauweryns, J.M., and L. Van Ranst 1987 Calcitonin gene-related peptide immunoreactivity in rat lung: A light and electron microscopic study. Thorax, 42t183-189.
Merkel, F. 1875 Tastzellen und Tastkorperchen bei den Haustieren
und beim Menschen. Arch. Mikr. Anat., 11t636-652.
Mihara, M., K. Hashimoto, K. Ueda, and M. Kumariki 1979 The
specialized junctions between Merkel cell and neurite: An electron microscopic study. J. Invest. Dermatol., 73t325-334.
Munger, B.L. 1971 Patterns of organization of peripheral sensory receptors. Handbook of Sensory Physiology, W.R. Loewenstein, ed.
Springer Verlag, Berlin, Vol. I, pp. 523-556.
Munger, B.L., L.M. Pubols, and B.H. Pubols 1971 The Merkel rete
papilla, a slowly adapting sensory receptor in mammalian glabrous skin. Brain Res., 29t47-61.
Mustakallio, K.K., and U. Kiistala 1967 Electron microscopy of Merkel’s “Tastzelle,” a potential monoamine storing cell of human
epidermis. Acta Derm. Venereol. (Stokh.), 47:323-326.
Nunez, E.A., A. Silverman, and M.D. Gershon 1980 Pituitary serotonin: Responsiveness of levels to hormonal change and ultrastructural alterations associated with amine depletion. Cell Tissue
Res., 211t487-492.
Owman, C., R. HBkanson, and F. Sundler 1973 Occurrence and function of amines in endocrine cells producing polypeptide hormones.
Fed. Proc., 32t1785-1791.
Paton, W.D.M., and M. Aboo Zar 1968 The origin of acetylcholine
released from guinea-pig intestine and longitudinal muscle
strips. J. Physiol. (Lond.), 194t13-33.
Pearse, A.G.E. 1980 The neuroendocrine (APUD) cells of the skin.
Am. J. Dermatopathol., 2:121-123.
Pelletier, G., H.W.M. Steinbusch, and A.A.J. Verhofstad 1981 Immunoreactive substance P and serotonin present in the same dense
core vesicles. Nature, 293.5’-72.
Pubols, L.M., B.H. Pubols, and B.L. Munger 1971 Functional properties of mechanoreceptors in glabrous skin of the raccoon’s forepaw.
Exp. Neurol., 31t165-182.
Ram6n y Cajal, S. 1919 Accion neurotropica de 10s epitelios. n a b .
Inst. Cajal Invest. Biol., 17t181-228.
Salomon, D., P. Carraux, Y. Merot, and J.H. Saurat 1987 Pathway of
granule formation in Merkel cells: An ultrastructural study. J.
Invest. Dermatol., 89t362-365.
Scheuermann D.W., J.P. Timmermans, D. Adriaensen, and M.H.A. De
Groodt-Laesseel 1987 Immunoreactivity for calcitonin gene-related peptide in neuroepithelial bodies of the newborn cat. Cell
Tissue Res., 249t337-340.
Scott, S.A., E. Cooper, and J . Diamond 1981 Merkel cells as targets of
the mechanosensory nerves in salamander skin. Proc. R. Soc.
Lond. [Biol.], 211t455-470.
Smith, K.R. 1967 The structure and function of Haarscheibe. J. Comp.
Neurol., 131t459-474.
Smith, K.R. 1970 The ultrastructure of the human Haarscheibe and
Merkel cell. J . Invest. Dermatol., 54t150-159.
Smith, K.R., Jr. 1977 The Haarscheibe. J. Invest. Dermatol., 69t6874.
Smith, K.R., and B.J. Creech 1967 Effects of pharmacological agents
on the physiological responses of hair discs. Exp. Neurol., 19:
Spurr, A.R. 1969 A low viscosity epoxy resin embedding medium for
electron microscopy. J. Ultrastruct. Res., 26:31-43.
Stahlman, M.T., A.G. Kasselberg, D.N. Orth, and M.E. Gray 1985
Ontogeny of neuroendocrine cells in human fetal lung. 11. An
immunohistochemical study. Lab. Invest., 52t52-60.
Sternberger, L.A., P.H. Hardy Jr., J.J. Cuculis, and H.G. Meyer 1970
The unlabeled antibody enzyme method of immunohistochemistry. Preparation and properties of soluble antigen-antibody complex (horseradish peroxidase-antihorseradish peroxidase) and its
use in the identification of spirochetes. J. Histochem. Cytochem.,
Tachibana, T., K. Ishizeki, Y. Sakakura, and T. Nawa 1984 Ultrastructural evidence for a possible secretory function of Merkel
cells in the barbels of a teleost fish, Cyprinus carpzo. Cell Tissue
Res., 235:695-697.
Tapper, D.N. 1970 Behavioral evaluation of the tactile pad receptor
system in hairy skin of the cat. Exp. Neurol., 26t447-459.
Wharton, J., J.M. Polak, S.R. Bloom, M.A. Ghatei, E. Solcia, M.R.
Brown, and A.G.E. Pearse 1978 Bombesin-like immunoreactivity
in the lung. Nature, 273r769-770.
Winkelmann, R.K. 1977 The Merkel cell system and a comparison
between it and the neurosecretory or APUD cell system. J . Invest.
Dermatol., 69t41-46.
Winkelmann, R.K., and A S . Breathnach 1973 The Merkel cell. J.
Invest. Dermatol., 60t2-15.
Zaccone, G. 1986 Neuron-specific enolase and serotonin in the Merkel
cells of conger-eel (Conger conger) epidermis. An immunohistochemical study. Histochemistry, 85t29-34.
Без категории
Размер файла
1 718 Кб
like, merkel, serotonin, pig, localization, snout, skin, immunoreactivity, cells
Пожаловаться на содержимое документа