GROSS, LIGHT MICROSCOPIC AND ULTRASTRUCTURAL STUDIES OF MAMMARY GLAND IN KOSALI COW
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Date
2024
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DEPARTMENT OF VETERINARY ANATOMY, Chhattisgarh Kamdhenu Vishwavidyalaya Durg
Abstract
The present study was conducted on 36 samples of mammary gland of
Kosali cows procured from central plain region of the Chhattisgarh and divided
into two groups - lactating and non-lactating/ non-pregnant stages with 18 cows in
each group. Lactating and non-lactating/ non-pregnant stages were further
categorized as early, mid and late groups, each with 6 animals. After recording
gross parameters, the tissue samples were processed for histological,
histochemical and ultrastructural studies.
Grossly, the udder of lactating Kosali cow was large and bowl shaped,
whereas it was small and round in non-lactating/ non-pregnant Kosali cows. Teat
of Kosali cow was cylindrical or conical shaped in lactating and funnel or pear
shaped in non-lactating/ non-pregnant Kosali cow. The rear quarter teats were
shorter and thicker than the front teats in lactating as well as non-lactating/ nonpregnant
cows. Distance between front teats was higher as compared to rear teats
in both the groups.
Histologically, the mammary gland was ensheathed by the skin and
capsule from outside to in. Glomus organs were observed in the reticular layer of
dermis of the skin in both stages of cows. The amount of interalveolar,
interlobular and interlobar connective tissue increased in mid and late lactation to
dry stage and was maximum in late nonlactating/ nonpregnant cows. Varied
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shaped lobules containing alveoli of different shape and adipose tissue were
found. The percentage of small alveoli showed increasing trend, while medium
and large alveoli decreased from lactating to non-lactating stage. The alveolar
epithelium changed from high cuboidal in early lactation to squamous in late
nonlactating stage. The duct system was lined by low cuboidal with patches of
bistratified cuboidal in lactating and low cuboidal to squamous in nonlactating
cows. “Corpora amylacea” were intra alveolar in lactating stage and were found,
mostly in stromal connective tissue non-lactating cows. Myoepithelial cells were
more in non-lactating Kosali cows. Epithelium of gland cistern was high cuboidal
in lactating and low cuboidal in non-lactating stage. The degenerating
rudimentary lobules were ten to twenty times smaller in non-lactating stage. In
annular fold region, the epithelium was high cuboidal in lactating and low
cuboidal in non-lactating cows. In lactating stage, the glandular lobules were
approximately three time larger in size than non-lactating stage.
The lining epithelium of teat cistern was mostly cuboidal with patches of
bistratified cuboidal and columnar in lactating and non-lactating Kosali cows.
Mucosa showed mostly circular folds in lactating and longitudinal folds in nonlactating
stage. The stratum corneum of the epidermis was apparently two times
thicker in lactating than non-lactating stage. Mucosal folds of Furstenberg’s
rosette were primary as well as secondary. In both stages, Furstenberg’s rosette
was lined by cuboidal, bistratified cuboidal and stratified squamous
nonkeratinized epithelium. Furstenberg’s rosette associated lymphoid tissue
(FALT) were present in diffuse and dense form as lymphoid follicles. The teat
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canal was lined by a stratified squamous epithelium in initial part, distally
keratinization was increased.
All the gross and histomorphometrical parameters except thickness of
capsule of different regions of mammary gland were significantly higher in early
lactation as compared to mid and late, in lactating Kosali cows and were
significantly higher in early dry period as compared to mid and late, in nonlactating
Kosali cows. Further, they were significantly higher in lactating as
compared to non-lactating cows in early, mid and late stages. The percentage
decrease in the above parameters between mid and late stages was higher (60%)
as compared to early and mid stages (40%) in lactating as well as non-lactating
Kosali cow. Average diameters were increased orderly from mammary alveoli to
intralobular duct, interlobular duct, and lactiferous duct. Average diameters of teat
canal were higher at orifice than midpart and near the rosette of Furstenberg.
Histochemically, collagen was the most abundant fiber followed by
reticular and elastic. Their density was apparently increased with advancement of
lactation from early to late stage. These fibers were more compact and denser in
non-lactating/ non-pregnant Kosali cows. In the capsule and connective tissue
stroma, PAS positive reaction was intense in lactating Kosali cows and moderate
reaction in non-lactating/non-pregnant cows. Moderate to intense reaction for
PAS positive material was noticed in epithelium, intraluminal secretions,
basement membranes and smooth muscles of alveoli and duct system in lactating
group, whereas weak reaction was found in non-lactating Kosali cows. Epithelium
of alveoli, and duct system of lactating cows showed mild to moderate reaction
and basement membrane and secretory material showed strong reaction for acid
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mucopolysaccharides in lactating mammary gland. In non-lactating gland, it was
mild. Corpora amylacea was moderately PAS positive in non-lactating and
intensely positive in lactating Kosali cows. Epithelium of gland cistern and
annular folds, teat cistern, rosette of Furstenberg and teat canal were positive for
PAS and AB-PAS reactive substances in both the groups but reaction was weak in
non-lactating group.
Ultra-structurally, three types of cells were seen in mammary alveoli viz.
alveolar epithelial cells, myoepithelial cells and wandering cells. The glandular
epithelial cells of lactating Kosali cows were active and polar in nature in lactating
stage and became inactive and apolar in non-lactating stage. The amount of
euchromatin was decreased and simultaneously heterochromatin increased in
proportion with progression in lactation. The cytoplasmic nuclear ratio in alveolar
epithelial cells was more in early lactation than in advance lactation. The alveolar
epithelial cells of early and mid lactating Kosali cows were densely packed with
well-developed cytoplasmic organelles, which were reduced almost thrice in late
lactating stage. The luminal border of lactating epithelial cells showed numerous
irregular microvilli projecting in the lumen. Three types of stasis vesicles viz.
intermediate electron dense/ electron dense/ electron dense with granular protein
were noted in the apical portion of cells in the late lactating stage. The alveolar
epithelial cells contained two distinct types of secretory material viz. lipid droplets
and casein micelle. In early and mid lactating stage casein particle and lipid
droplets were almost equal, whereas in late lactation, casein droplet predominated
over lipid droplet. The alveolar lumen was either empty or filled with little
secretory material in non-lactating/ nonpregnant Kosali cows.
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During lactation, the tight junctions of the alveolar epithelial cells were
intact and impermeable. The same were loose and leaky during late lactation in
non-lactating/ non-pregnant Kosali cows. The corpora amylacea were noted in the
alveolar lumen of lactating and nonlactating stage. Dense lamellated corpora
amylacea had alternate thin electron dense and thick intermediate electron dense
granules arranged in circular fashion. The myoepithelial cells were irregular
flattened, elongated to fusiform in shape. In non-lactating/ non-pregnant Kosali
cows, the cytoplasmic processes of myoepithelial cells protruded deeper into the
underlying stroma. The lymphocyte and macrophages were more prevalent in
lactating cows. In nonlactating/ nonpregnant Kosali cows, many macrophages and
lymphocytes were observed. Monocytes were also observed at some places.