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Electron Microscopic Studies on the Skin of Zovawk (Mizo Local Pig)

A. Lalramliana P. C. Kalita Arup Kalita O. P. Chaudhary P. J. Doley Hemen Das
Vol 8(4), 202-205
DOI- http://dx.doi.org/10.5455/ijlr.20171010105017

The electron microscopic study was conducted on skin by using two male and two female adult Zovawk pig. The stratum basale consisted mainly of a single layer of cuboidal to low columnar cells which had large ovoid nuclei with numerous indentations, cytoplasmic melanin granules, and many tonofilaments. The stratum basale were also added by some suprabasal cells which might contribute to proliferation. A stratum spinosum rested upon the proliferating stratum basale and consisted of a layer of irregular–shaped keratinocytes two to four cells deep which were increasingly flattened in the outermost layers. These cells had large spherical nuclei with sparse chromatin, electron lucent cytoplasm containing small mitochondria. A stratum granulosum layers also contained irregularly shaped, non-membrane-bounded, electron dense keratohylin granules. A stratum corneum layer appeared clear cytoplasmic organelles without nuclei. The dermis consisted of dense irregular connective tissue with a felt work of collagen, reticular and elastic fibers embedded in an amorphous ground substance. The fine structure of the cuboidal secretory cells comprised of coiled, deep fundic zone of the apocrine glands. The nuclei of these cells were basally situated and sometimes cleft and were in close proximity to small mitochondria with densely packed cristae. Most of the cytoplasm was filled with closely packed, electron lucent, spherical or ovoid secretory granules.


Keywords : Electron Microscopic Skin Ultrastructural Zovawk Pig

Introduction

The skin is composed of epidermis and dermis. The skin of Zovawk shows abundance of hair on the dorsal surface of the body. Monteiro-Rievere and Stromberg (1985) reported that the nucleus was large and ovoid and occupied most of the cells along with melanosomes and tonofilaments under Transmission electron microscope (TEM) in Large White Yorkshire. The skin of Zovawk has no record on histological and ultrastructural studies. Therefore the objective of the present study was undertaken to observe the histological and ultrastructural details of Zovawk skin.

Materials and Methods

Ultrastructural studies of skin were conducted on two male and two female adult Zovawk pig of Mizoram. The skin samples were collected  from eight different sites namely dorsal neck, lateral neck, ventral neck, dorsal thorax, lateral thorax, ventral thorax, dorsal loin and lateral loin tissue  samples (1-2 mm) were fixed in Karnovsky’s fixative (2.5% glutaraldehyde in 0.1M Sodium cacodylate or Phosphate buffer at pH 7.2) for 2-4 hours at 4ºC for TEM . After washing in 0.1M buffer (3 changes of 15 minutes each) the tissues were embedded in pure embedding medium using gelatin capsules and sectioned with diamond knives using a ultra-microtome (Leica ultracut)  and mounted on copper grids. The photography was taken with the help of the digital camera which was inbuilt with the microscope. Interpretations were made by viewing the tissues in the TEM and with the help of photomicrographs.

Results and Discussion

The study observed that the stratum basale, the germinativum layer of the Zovawk epidermis, consisted mainly of a single layer of cuboidal to low columnar cells, along with some suprabasal cells which also might contribute to proliferation. Basal cells rested upon a distinct basemen membrane that separated the stratum basale from the subjacent, dermal collagenous connective tissue. Large ovoid nuclei with numerous indentations, cytoplasmic melanin granules, and many tonofilaments were present in Zovawk stratum basale cells. Lateral interdigitations of thin cytoplasmic processes and desmosomes between adjacent stratum basale cells were present, which was inconsonant with the observation of Wolf and Wolf-schreiner (1976) in pig.  Some cells of the stratum basale had a relatively flat non-serrated base, and fewer had cytoplasmic tonofilaments, whereas others had a highly serrated base with deep projections extending into the underlying dermis with larger congregations of tonofilaments. This finding was in agreement with the finding of Dellmann and Eurell (1998) on the skin in cattle.  In the serrated cells the tonofilaments extended into the basal cytoplasmic projections and connected to the hemidesmosomes. Melanin granules were observed in the cytoplasm.

A stratum spinosum rested upon the proliferating stratum basale and consisted of a layer of irregular–shaped keratinocytes two to four cells deep which were increasingly flattened in the outermost layers. These cells had large spherical nuclei with sparse chromatin, electron lucent cytoplasm containing small mitochondria, a few small (0.5 μm) electron dense granules and sparsely scattered short tonofilaments. Other organelles and melanin granules were seldomly observed. Cells of the stratum spinosum were joined by numerous desmosomes. A stratum granulosum layers also contained irregularly shaped, nonmembrane-bound, electron dense keratohylin granules that can be observed. Similar findings were also observed by Marcarian and Calhoun (1966) on the integuments of adult swine. High tonofilaments were observed in this region (Fig. 1). A stratum corneum layer appeared clear and contained no nuclei or cytoplasmic organelles.

Fig. 1: Stratum granulosum in the epidermal cells of Zovawk, as in other species displayed a greater concentration of tonofilaments (arrow) than were seen in underlying stratum spinosum cells. X 9800; scale bar ꞊ 1 μm.

The fine structure of the cuboidal secretory cells comprised of coiled apocrine glands, located in deep fundic zone of the glands, was similar to that observed in many other species. The nuclei of these cells were basally situated and were in close proximity to small mitochondria with densely packed cristae (Fig. 2).

Fig 2: Secretory granules (S) of apocrine tubular gland in Zovawk, basally placed nuclei (N). X8100, scale bar ꞊2 μm.

A variety of other cell types like eosinophils, mast cells and fibroblasts were observed in the dermis. Numerous capillaries, small arterioles, veins and small neurons near the vasculature were also seen in the dermis. Smooth muscle cells found mainly in arrector pili muscles attached to hair follicles or in arteriolar walls were seen in the dermis of Zovawk pig. The ultrastructure of arrector pili muscles had numerous fusiform densities, centrally placed nuclei, mitochondria, and pinocytotic vesicles as typically found in smooth muscle. A thick (0.3μm) basement membrane encircled the myocytes and collagenous fibres were observed between the cells.

Conclusion

After conducting the electron microscopic studies of Zovawk skin, the ultrastructural character of Zovawk showed that the stratum basale, the germinativum layer of the Zovawk epidermis, consisted mainly of a single layer of cuboidal to low columnar cells, along with some suprabasal cells which also might contribute to proliferation. Basal cells rested upon a distinct basemen membrane that separated the stratum basale from the subjacent, dermal collagenous connective tissue. Large ovoid nuclei with numerous indentations, cytoplasmic melanin granules, and many tonofilaments were present in Zovawk stratum basally cells. A stratum spinosum rested upon the proliferating stratum basale and consisted of a layer of irregular–shaped keratinocytes, two to four cells deep which were increasingly flattened in the outermost layers. A stratum corneum layer appeared clear and contained no nuclei or cytoplasmic organelles.

References

  1. Dellmann HD and Eurell J. 1998. Integuments in: Textbook of Veterinary Histology, 5th Edn .Lippincott        Williams and Wilkins, New York, pp 303.
  2. Marcarian H and Calhoun ML. 1966. Microscopic anatomy of the integuments of adult swine. J. Vet. Res. 118: 765-772.
  3. Monteiro-Riviere NA and Stromberg MW. 1985. Ultrastructure of the integuments of the domestic pig (Sus scrofa) from one week to fourteen week of age. Histol. Embryol .14: 97-101.
  4. Wolff K and Wolff-Schreiner E. 1976. Trends in electron microscopy of skin. Invest. Dermatol67:39-57.
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