development of meissner corpuscle of mouse toe pad

Development of Meissner Corpuscle of Mouse Toe Pad CHIZUKA IDEZ Department of Anatomy, Faculty of Medicine, University of Tokyo, Tokyo, 113 J n p n n

ABSTRACT The cytologic development of Meissner corpuscles of the mouse toe pad has been studied using light and electron microscopy, and correlated with silver impregnations of frozen sections. By 18 days of gestation, neurites are seen near the epidermis, but intraepidermal neurites are few. One day after birth, the number of intraepidermal neurites increases, and some accompanying Schwann cells extend their cytoplasmic processes penetrating the basal lamina of the epidermis. Four days after birth, Schwann cells invade the epidermis further, extending many cytoplasmic processes which are intimately associated with basal cells of epidermis. These specialized Schwann cells which contact the epidermis proper also begin to develop cytoplasmic lamellae and thus denote the onset of lamellar cell development. By eight days after birth, the developing lamellar cells become more elaborated, and their cytoplasmic processes contain caveolae and filaments, characteristic features of lamellar cells. This developmental sequence supports the concept that lamellar cells are derived from Schwann cells. Through all stages of development, neurites and Schwann cells interact closely with epidermal cells. Epidermal cells may be essential for corpuscle formation. By 20 to 25 days after birth, mouse toe pad Meissner corpuscles are cytologically mature.

There have been few studies to date on the development of Meissner corpuscles; Cauna (‘53) described by light microscopy the human digital Meissner development. Munger (‘73, ’76) has described by electron microscopy the developmental sequence of Meissner corpuscles present in the tongue and palatal regions of rhesus monkey. The origin of lamellar cells of Meissner corpuscles has been controversial. Cauna and Ross (‘60) observed that lamellar cells of human Meissner corpuscles directly abut the nerve fibers as do Schwann cells and thus considered that lamellar cells were specialized Schwann cells. The inner core cells of Pacinian corpuscles, perhaps equivalent to lamellar cells of Meissner corpuscles, have been suggested as Schwann cell in origin (Cauna and Mannan, ’59; Munger, ’66; Andres, ’69; Nava, ’74). The most convincing evidence that inner bulb cells of Herbst corpuscles, equivalent to inner core cells of Pacinian corpuscles, are Schwann cell in origin has been provided by Saxod (‘73) who trans- planted frontal buds and sensory ganglia between quail and chick and traced migra- tion of cells to Herbst corpuscles. On the

ANAT. REC., 188: 49-68.

contrary, Pease and Quillium (’57) and Quillium (’65) did not regard the inner core cells of Pachian corpuscle as Schwann cell derivatives. The origin of lamellar cells of Meissner corpuscles has not been studied by electron microscopy to date. The present study concerns the origin of lamellar cells as determined by tracing the cytologic development of Meissner corpuscles in mouse toe pads. The use of the term “Meissner corpuscle” for sensory corpuscles in mouse toe pads has been justified in a previous study of serial sections of the corpuscle (Ide, ’76). Preliminary findings have been reported elsewhere (Ide, ’75).

MATERIALS AND METHODS

Albino mouse fetuses of 18 days of gestation, and suckling mice from 1 day to 30 days after birth were fixed by perfusion through the heart with Karnovsky’s fixative

Received Aug. 23, ’76. Accepted Nov. 17, ’76. 1 This study was supported in part by U S . Public

Health Service Grant NIH-N01-HD-4-2869 from the Na- tional Institute of Child Health and Human Develop- ment.

2 Present address: Department of Anatomy, College of Medicine. The Pennsvlvania State University. The Milton S. Hershey Medical Center, Hershey, Pennsyl- vania 17033 U.S.A.

49

50 CHIZUKA IDE

(Karnovsky, '65). Toe pad skin was excised and immersed in fixative for three hours, post-fixed in 1% osmium tetroxide in 0.1 M phosphate buffer at 4°C for two hours, dehydrated in graded alcohol, and em- bedded in Epon 812. Epon sections 1-1.5 pm thick were stained with toluidine blue. Selected areas were sectioned for electron microscopy with glass knives, and double- stained with uranyl acetate and lead citrate (Venable and Coggeshall, '65). For- malin-fixed frozen sections were impreg- nated with silver (Winkelmann, '57).

RESULTS

There is no evidence of corpuscle formation prior to birth. By eight days after birth, the lamellar cells can definitely be identified in the developing corpuscles. Corpus- cle formation is completed by 20 to 25 days after birth.

Eighteen days of gestation (figs. 1-3) The epidermis is stratified and surface

cells are squamous in shape. Large cells with round nuclei can be identified in the superficial dermis, distinguishable from small, flattened cells deep in the dermis overlying developing cartilage. Corpuscles, as such, cannot be identified. Presumptive neurite profiles are seen in the superficial dermis (n: fig. l ) , corresponding in position to nerve bundles as visualized in silver stained sections (fig. 2). In electron micrographs, the growing neurites, forming bundles, approach the epidermis and a few of them penetrate the basal lamina of the epidermis (inset, fig. 3) . Some profiles of isolated neurites abut on cells with large nuclei, which are considered the same as those large cells seen in figure 1 (fig. 3). These large cells have no basal lamina. The growing neurites conpin mitochondria and vesicles 500-800 A in diameter.

One day after birth (figs. 4-7) The toe pad is markedly elevated, and

polygonal cells are aggregated below the epidermis (fig. 4). There is no sign of distinct corpuscle formation. Nerve bundles ascend between developing sweat glands to the epidermis. It is not unusual to en- counter intraepidermal neurites extending almost the entire length of the basal cells (fig. 6). Schwann cells are closely associ-

ated with the epidermal cells, but they have not been observed to penetrate the basal lamina of the epidermis (fig. 6). Schwann cells contain abundant free ribosomes. A distinct basal lamina is now discernible on these Schwann cells. At somewhat more advanced stages, both Schwann cell processes and neurites penetrate the basal lamina of epidermis (fig. 7). The superficial dermis bulges into the epidermis at the site of intraepidermal neurites forming small dermal papillae (fig. 7). The somewhat more mature Schwann cells at this stage contain polysomes and a scant rough endoplasmic reticulum, as contrasted to the abundant free ribosomes observed in less mature Schwann cells (figs. 6, 7). The neurites contain vesicles and mitochondria similar to those described in the previous stage (figs. 6, 7).

Four days after birth (figs. 8-10) Neurites penetrating the epidermis are

frequently encountered at this stage (fig. 9), and presumable Schwann cell profiles are seen in the superficial dermal connective tissue compartment (fig. 8). Small nerve bundles are now present which are often associated with flattened cells (arrowhead: fig. 8). These flattened cells appear to be developing perineural epitheli- oid cells. Schwann cells, which are intimately associated with neurites in the subepidermal connective tissue in previous stages, appear somewhat modified at this stage (figs. 8, 10). The modified Schwann cells have numerous large cytoplasmic processes that abut epidermal cells without intervening basal lamina. By electron microscopy, these modified Schwann cells clearly surround small diameter neurite profiles (fig. 10). Some neurite profiles are not invested by the Schwann cell processes, but abut directly on epidermal cells (fig. lo). A distinct basal lamina is present on Schwann cell bodies, but is fragmentary on its cytoplasmic processes (fig. lo). The distal extent of Schwann cell cytoplasmic processes contain for the most part only free ribosomes.

E i g h t days after birth (figs. 11-14) The beginning of definitive Meissner cor-

puscle formation is evident at this stage. The dermal papillae are markedly enlarged. Clusters of cells are located at the apex

MOUSE MEISSNER CORPUSCLE DEVELOPMENT 51

of the papillae and extend cytoplasmic processes to the epidermal cells (fig. 11). These cytoplasmic processes contain filaments and caveolae, and surround neurite profiles as depicted in figures 12 and 13. These features are characteristic of mature lamellar cells as discussed in detail subsequently. Lamellar cell bodies contain well-developedrough endoplasmic reticulum (fig. 14). The basal lamina is distinct on the cell body, but fragmentary on its cytoplasmic processes. The neurite profiles surrounded by developing lamellar cells are large in diameter and contain mitochondria and vesicles (figs. 12-14). Coated vesicles are also observed (fig. 14). The cytoplasmic processes surrounding neurites are associated with epidermal cells without interposition of basal lamina. Some neurites are not confined within the dermal region, but extend into the epidermis (fig. 13).

Fifteen days after birth (figs. 15, 16) The dermal papillae are enlarged and

relatively mature developing corpuscles occupy the apex of the papillae. Neurites entering these developing corpuscles have distinct myelin sheaths (fig. 15). The cytoplasmic processes of the developing lamellar cells are stacked on each other to form several lamellae around neurites. Caveolae are prominent in these cytoplasmic processes (fig. 16). The neurite profiles are much enlarged, and contain mitochondria and vesicles. There is no discernible basal lamina interposing between epidermal cells and developing lamellar cells. The corpuscle formation is near its completion at this stage (fig. 16). By approximately one week later, the corpuscle attains the adult form.

(1) Origin of lamellar cell and corpuscle formation

As the maturational sequence of lamellar cells in the mouse Meissner corpuscle is traced following birth, lamellar cells seem clearly derived from Schwann cells. At the eighth day after birth, the cells en- veloping neurites with their cytoplasmic processes can clearly be identified as developing lamellar cells (fig. 12). These developing lamellar cells are characteristic in that they surround neurite profiles with their long cytoplasmic processes and then

DISCUSSION

are intimately associated with epidermal cells with interposition of only scanty or no basal lamina. Earlier in development, cells in this position are identified as Schwann cells (figs. 6-8, lo). The inner bulb cells of Herbst corpuscles, equivalent to inner core cells of Pacinian corpuscles, have been demonstrated to be derived from Schwann cells migrating from spinal sensory ganglia and Gasserian ganglia following transplantation of frontal buds or ganglia between quail and chick (Saxod, '73). Therefore, the lamellar cells of Meissner corpuscles, inner core cells of Pacinian corpuscles, and inner bulb cells of Herbst corpuscles all appear to be derived from Schwann cells.

The basal lamina of Schwann cells is not always distinct early in development. Munger ('73, '76) has described the neurite profiles associated with polygonal cells evidencing scant basal lamina. He considered the possibility that these polygonal cells may be Schwann cells differentiating into lamellar cells. Gamble ('66) did not observe the basal lamina on Schwann cells of sural nerve in a human fetus of ten weeks of menstrual age. Webster and Bil- lings ('72) and Webster ('75) stated that Schwann cells have no discernible basal lamina in Xenopus in the early stages of development. As shown in figure 3, some neurite profiles abut large cells with round nuclei. Although these cells have no distinct basal lamina, the possibility is not excluded that these cells are presumptive Schwann cells.

Modified Schwann cells deeply invade the epidermis, forming a small pocket surrounded by epidermal cells at four days after birth. These pockets may represent the formation of dermal papillae, in which Meissner corpuscles will subsequently develop. The close association of lamellar and epidermal cells during Meissner corpuscle development has been observed by Cauna ('53). He stated that Meissner corpuscle development is in part intraepidermal and in part extraepidermal in the perinatal period. The close association of Meiss- ner corpuscle development with epidermal cells suggests that the epidermal cells pos- sibly are essential components for the corpuscle formation (Dijkstra, '33). The nerve fibers which will form Meissner corpuscles sometimes retain intraepidermal compo-

52 CHIZUKA IDE

nents even in the adult form (Dogiel, '03; Cauna, '53; Ide, '76).

(2) Cytology of neurite development In general, mitochondria and various

kinds of vesicles are abundant in the growing neurites. Growth cones, i.e., growing tips of neurites of cultured neurons contain many mitochondria and vesicles (Ya- mada et al., '71; Bunge, '73; Nakai and Ide, '73). Far more abundant accumulation of mitochondria and vesicles are observed in proximal stumps, i.e., regenerating tips, of severed nerve fibers of peripheral nerves (Estable et al., '57; Blumcke et al., '66; Pellegrino de Iraldi and De Robertis, '68; Morris et al., '72; Rodriguez-Echandia and Schoebitz, '72) and in the hypophysecto- mized animals (Dellmann, '73). Such or- ganelles are also seen in regenerating nerves in taste buds (Fujimoto and Mur- ray, '72) and in regenerating nerves of salamander limbs (Hay, '67). While growth cones observed in very young rabbit embryos (Tennyson, '70) or in chick embryos (Ide, unpublished observation) contain relatively few mitochondria and vesicles, developing neurites in the skin of perinatal mice as shown in the present study contain many mitochondria and vesicles. These observations suggest that mitochondria and vesicles may gradually accumulate in distal portions of neurites during later stages of development as these neurites reach their target organs. Vesicles con- tained in regenerating nerves have been postulated as responsible for trophic ac- tion of the nerve fibers in taste buds (Fuji- mot0 and Murray, '72) and in regenerating limbs of salamanders (Hay, '67). Munger ('65) considered that the mito- chondrial accumulations in neurites in the opossum snout skin could reflect the activity of continuous growth of the neurites. The abundant mitochondria and vesicles in neurites of developing tissue could indi- cate the growing activity as well as trophic function of developing neurites.

ACKNOWLEDGMENTS

The author wishes to thank Professor J . Nakai of the University of Tokyo for his continuous support throughout this study, and Professor B. L. Munger for reviewing the manuscript and his inspiring discus- sions.

LITERATURE CITED

Andres, K. H. 1969 Zur Ultrastruktur der ver- schiedenen Mechanorezeptoren von hoheren Wirbeltieren. Anat. Anz., 124: 551-567.

Bliimcke, S., H. R. Neidorf and J. Rode 1966 Axoplasmic alterations in the proximal and distal stumps of transected nerves. Acta Anat., 7: 44-61.

Bunge, M . B. 1973 Fine structure ofnerve fibers and growth cones of isolated sympathetic neurons in culture. J . Cell Biol., 56: 713-735.

Cauna, N. 1953 Some observations on the structure and development of Meissner's corpuscle. J. Anat., 87: 4 4 0 4 4 1 .

Cauna, N., and G. Mannan 1959 Development and postnatal changes of digital Pacinian corpuscle (corpuscula lamellosa) in the human hand. J. Anat., 93: 271-286.

Cauna, N., and L. Ross 1960 The fine structure of Meissner's touch corpuscles of human fingers. J. biophys, biochem., Cytol., 8: 467-482.

Dellmann, H. D. 1973 Degeneration and regeneration of neurosecretory systems. Int. Rev. Cy- tol., 36: 2 1 5 3 1 5 .

Dijkstra, C. 1933 Die De- und Regeneration der sensiblen Endkorperchen des Entenschnabels (Grandry- und Herbst-Korperchen) nach Durch- schneidung des Nerven, nach Fortnahme der ganzen Haut und nach Transplantation des Hautstiickchens. Z. mikrosk. anat. Forsch., 34:

Dogiel, A. S. 1903 Uber die Nervenapparate in der Haut des Menschen. 2. wissensch. Zool., 75:

Estable, C., W. Acosta-Ferreira and J. R. Sotelo 1957 An electron microscope study of regenerating nerve fibers. 2. Zellforsch., 46: 387-399.

Fujimoto, S., and R. G. Murray 1970 Fine structure of degeneration and regeneration in de- nervated rabbit vallate taste buds. Anat. Rec., 168: 393-613.

Gamble, H. J. 1966 Further electron microscope studies of human foetal peripheral nerves. J. Anat., 100: 487-502.

Hay, E. D. 1960 The fine structure of nerves in the epidermis of regenerating salamander limbs. Exp. Cell Res., 19: 299-317.

Ide, C. 1975 Morphological studies on the development of the Meissner-type corpuscle of the mouse. In: Proceedings of 10th International Congress of Anatomists, p. 305, (Abstract).

1976 The fine structure of the digital corpuscle of the mouse toe pad, with special reference to nerve fiber. Am. J. Anat., 147: 329- 355.

Karnovsky, M. J. 1965 A formaldehyde-glutar- aldehyde fixative. High osmolarity for use in electron microscopy. J. Cell Biol., 27: 137A.

1972 A study of degeneration and regeneration in the divided rat sciatic nerve based on electron microscopy. 11. Changes in the axons of the proximal stumps. Z. Zellforsch., 124: 131-164.

Munger, B. L. 1965 The intraepidermal innerva- tion of the snout skin of the opossum. A light and electron microscope study with observations on the nature of Merkel's Tastzellen. J. Cell Biol., 26: 79-97.

The discussion on nature of lamel-

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46-1 11 .

Morris, J. H., A. R. Hudson and G. Weddell

1966

MOUSE MEISSNER CORPUSCLE DEVELOPMENT 53

lar cells of encapsulated end-organs. In: Touch, Heat and Pain. A Ciba Foundation Symposium, A. V. S. DeReuck and J. Knight, eds. Churchill, London, pp. 132-135.

1973 Cytology and ultrastructure of sensory receptors in the adult and newborn primate tongue. In: Fourth Symposium on Oral Sensation and Perception: Development in the fetus and infant. J. F. Bosma, ed. DHEW Publi- cation No. NIH 73-546, pp. 75-95.

Specificity in the development of sensory receptors in primate oral mucosa. In: Development of Upper Respiratory Anatomy and Function: Implication for Sudden Infant Death Syndrome. J. F. Bosma, ed., U.S. Govt.

Nakai, J., and C . Ide 1973 Fine structure of the cultured nerve growth cones. Acta Anat. Nippon 48: 56 (Abstract). (In Japanese).

Nava, P. B., Jr. 1974 The developmental fine structure of Pacinian corpuscles. Anat. Rec., 178: 4 2 4 4 2 5 (Abstract).

Pease, D. C., and T. A. Quillium 1957 Electron microscopy of the Pacinian corpuscle. J. Cell Biol., 3 : 331-342.

1968 The neurotubular system of the axon and the origin of granulated and non-granulated vesicles in regenerating nerve. Z . Zellforsch., 87: 330- 344.

Quillium, T. A. 1966 Structure of receptor organs. Unit design and array pattern in receptor organs. In: Touch, Heat and Pain. A Ciba Foun-

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Pellegrino de Iraldi, A., and E. De Robertis

dation Symposium. A. V. S. DeReuck and J. Knight, eds. Churchill, London', pp. 86-116.

Rodriguez-Enchandia, E. L. , and K . Schoebitz 1972 The smooth endoplasmic reticulum in regenerating nerve fibers of the anuran Calrpto- cephalla gayi. Z . Zellforsch., 132: 257-262.

Saxod, R. 1973 Developmental origin of the Herbst cutaneous sensory corpuscle. Experimen- tal analysis using cellular markers. Dev. Biol., 3 2 : 167-178.

Tennyson, V. M. 1970 The fine structure of the axon and growth cone of the dorsal root neuro- blast of the rabbit embryo. J. Cell Biol., 44: 62- 79.

Venable, J. H . , and R. Coggeshall 1965 A sim- plified lead citrate stain for use in electron microscopy. J. Cell Biol., 25: 407408 .

Webster, H. deF. 1975 Development of peripheral myelinated and unmyelinated nerve fibers. In: Peripheral Neuropathy. Vol. 1 . P. J . Dyck, P. K. Thomas and E. H. Lambert, eds. Saunders, pp. 37-61.

Webster, H. deF., and S . M. Billings 1972 My- elinated nerve fibers in Xenopus tadpoles: In uitro observations and fine structure. J. neuro- pathol., exp. Neurol., 31: 102-112.

Winkelmann, R. K . 1957 A simple silver meth- od for nerve axoplasm. Proceedings. of Staff Meetings of Mayo Clinic, 3 2 : 217-223.

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PLATE I

EXPLANATION O F FIGURES

Eighteen days of gestation.

1 Cross section of toe pad. The basal cells of epidermis are arranged i n a row with long axis of nuclei vertical to the basal lamina. Cells with large nuclei (arrows) are scattered beneath the epidermis and small, flattened cells (fc) are located near the cartilage. Profiles of presumptive neurites are seen in the dermal compartment (n). X 500.

Longitudinal section of toe pad. Digital nerve trunk (N) and its branches (n) are demonstrated. The branches are approaching the epidermis. Silver impregnation. X 220.

Growing nerve bundle (nb) reaches near the epidermis. Isolated neurite profiles abut on the cells with large nuclei (arrows). Neurites contain mitochondria (m) and vesicles (v). X 10,800. Inset. The neurite

2

3

intrudes into the epidermis. The growing tip contains vesicles (v). X 14,500.

54

MOUSE MEISSNER CORPUSCLE DEVELOPMENT Chizuka Ide

PLATE 1

55

PLATE 2

EXPLANATION OF FIGURES

One day after birth.

4 Cross section of toe pad. Polygonal cells (arrows) aggregate beneath the epidermis. sg, sweat gland. X 470.

Longitudinal section of toe pad. Nerve bundles ascend to the epidermis and one of them invades to some extent into the epidermis (arrow). Silver impregnation. X 450.

5

6 Neurites (n) intrude into the epidermis almost to the upper margin of basal cells. Neurites contain vesicles (v), mitochondria (m), neuro- filaments (f) and neurotubules (t). Basal lamina (B) is distinct on the Schwann cell (S). X 17,000.

56


PLATE 2

57

PLATE 3

EXPLANATION OF FIGURE

One day after birth

7 The cytoplasmic process (p) of Schwann cell ( S ) invades into epidermis with neurites (n). Neurites contain mitochondria (m) and vesicles (v). Vesicles with double membranes (dv) are seen occasionally. X 17,000.

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PLATE 3

59

PLATE 4


Four days after birth.

8 Cross section of toe pad. Presumable Schwann cell profiles (s) are seen, and they are surrounded by flattened cells (arrowhead). But the Schwann cell beneath the epidermis is not enclosed by such flattened cells. There is a cell ("1 resembling this Schwann cell i n the small pocket of the epidermis. This cell sends several cytoplasmic processes to the epidermal cells (arrow). X 880.

9 Longitudinal section of toe pad. The nerve bundles approaching the epidermis are separated into smaller ones. The neurite (arrow) extends into the epidermis (E). Silver impregnation. X 440.

This micrograph shows the same kind of cell as depicted in figure 8. Cytoplasmic processes (p) of this cell surround many neurite profiles (n), and they are associated with epidermal cells (E), sometimes without interposition of basal lamina (B). One neurite profile abuts on the epidermal cells directly (arrow). X 12,500.

10

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PLATE 4

61

PLATE 5

EXPLANATION O F FIGURES

Eight days after birth.

11 Cross section of toe pad. The dermal papillae are markedly developed. Neurites (n) extending into the dermal papilla have no distinct myelin sheath. Every dermal papilla contains at its apex one to several cells which extend cytoplasmic processes (arrows) to the epidermal cells. The epidermal cells (E) on the apex of dermal papillae have large clear nuclei and light cytoplasm. X 560.

Higher magnification of the apex of dermal papilla such a s shown in figure 1 1 . The cells (L) extend long cytoplasmic processes (p) to surround the neurites (n). These cytoplasmic processes are in contact with epidermal cells without interposition of any well-constituted basal lamina (B). Caveolae (c) are seen o n the plasma membrane. Neurites are enlarged, and contain mitochondria (m) and vesicles (v). The neurite (arrow) extends further into the epidermis. X 7,400.

12

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PLATE 5

63

PLATE 6


Eight days after birth

13 High magnification of a part of figure 12. The intraepidermal neurite (n) is an extension of a neurite seen in the dermal papillae of figure 12. Cytoplasmic processes of developing lamellar cell contain caveolae (c), filaments (f), and free ribosomes. There is no interposition of basal lamina between these cytoplasmic processes and epidermal cells. Neu- rite contains mitochondria (m) and vesicles (v). X 16,000.

Cell body of the developing lamellar cells contain abundant rough endoplasmic reticulum (er). The neurite contains mitochondria (m) and some coated vesicles (cv). X 18,000.

14

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PLATE 6

65

PLATE 7

E X P L A N A T I O N O F FIGURES

Fifteen days after birth

15 Cross section of toe pad. The developing Meissner corpuscles (dc) are clearly demonstrated in the apex of the dermal papillae. The myelin sheath (arrows) is distinct on the neurites entering the developing corpuscles. 1, cell bodies of developing lamellar cells. X 560.

Cytoplasmic processes of developing lamellar cells are elongated and elaborated to make lamellae around neurites. Caveolae (C) are abundant in the cytoplasm of these processes. Aggregations of ribosomes (r) are only occasionally seen. Neurites are markedly enlarged, and contain mitochondria (rn) and vesicles (v). There is a neurite profile in the epidermal region (arrow). X 14,000.

16

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PLATE 7

67

development of meissner corpuscle of mouse toe pad

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