Effect of temporary submandibular duct-ligation on the myoepithelial cells in albino rat. A light and electron microscopic studies

The duct of the right submandibular gland was doubly ligated with metal clips to study the effects of duct ligation and ligature removal in albino rat submandibular gland to elucidate the relationship between duct ligation and removal of the ligature and to determine whether proliferation of myoepithelial cells occur in atrophic rat submandibular glands. Twenty adult male albino rats were used in this study. Rats were divided randomly into 3 main groups: a submandibular gland atrophy group [Ligated Group] in which the right main submandibular duct was ligated for 1, 2 and 4 weeks; a recovery group in which duct ligation was in place for 2 weeks and then removed and the rats were sacrificed after 2 weeks and the 3rd group was not subjected to operation and used as control group. At the assigned date, the animals were sacrificed. The right submandibular glands were thoroughly-dissected and removed. Specimens of the gland were cut at 6-8 micro m thickness and stained with haematoxylin and eosin. Other specimens of the gland were taken and prepared for electron microscopy study. Duct ligation of the submandibular gland was accompanied by progressive atrophy of the gland. After 4 weeks of duct-ligation, light microscopy showed that the acini became atrophied and contained few secretory granules. There was dilated inter-lobular and intralobular ducts that lined by cuboidal flat cells. The inter-lobular connective tissue was increased in thickness. Persistent myoepithelial cells were also found in atrophic rat sumandibular gland. After removal of the ligature, the gland revealed histological evidence of regeneration and persistent myoepithelial cells. All cellular components manifested recovery and became similar to the control condition. The present observations also suggest that ligation of the main duct of the rat submandibular gland produces a pronounced atrophy that is reversed upon ligature removal

protective effect of co- supplementation of propolis and vitamin B6 against gentamicin induced nephrotoxicity on proximal tubules in albino rat

Thirty albino rats were used in this work. Rats were divided into five groups, six rats each. Sham control group [Group A] were injected intraperitoneaily, with 5ml of 0.9% NaCI for ten successive days. Gentamicin group [Group B] rats were injected with gentamicin, intraperitoneally, at a dose of 100 mg /kg/day for a period of 10 days. Gentamicin and Vit. B6 group [Group C] rats were injected with gentamicin in the same dose simultaneously with Vit. 36 [2.5 mg/Kg/ day] for ten successive days. Gentamicin and Propolis group [Group D] rats were intraperitoneally injected with same does of gentamicin and propolis 10% solution and given orally by gastric gavage in a dose of 100 mg/kg/day for ten days. Gentamicin, vitamin B6 and propolis group [Group E] rats were injected intraperitoneally with gentamicin, vitamin B6 with the same previous doses and propolis of the same dose orally for ten successive days. On the 11[th] day, the animals were sacrificed. Samples of blood were analyzed for blood urea and serum creatinine. Excised kidneys were fixed in 10% phosphate buffered formalin, dehydrated with ascending grades of ethanol, cleared and, then, embedded in paraffin. The paraffin embedded tissue was cut at 6 Um section and stained with haematoxyline and eosin stains. Small specimens of the kidneys were prepared for ultrathin sections and examined under electron microscope. Gentamicin administration produced a significant increase in serum creatinine [P < 0.001 Vs control] which was avoided by simultaneous vitamin B[6] and propolis treatment for 10 days [P < 0.001]. Vitamin B6 or propolis treatment reduced gentamicin induced elevation in serum creatinine, but still significant over than that of the control by day eleven. The re-suits of the blood urea nitrogen determination were similar. Light microscopic examination of the renal tissues from gentamicin treated rats revealed severe histopathological changes of the proximal convoluted tubules, whereas specimens obtained from group C, or Group D - treated rats revealed only mild changes. In group E rats treated with both vitamin B[6] and propolis, histological examination revealed a normal renal parenchymal picture without any sign of inflammatory or degenerative changes. This finding was further validated by electron microscopic examination. In electron microscopic examination, the cells of the proximal convoluted tubules from group B contained multiple large lysosomes, the mitochondria lost their cristae, some luminal microvilli were disrupted. The protective effect of vitamin B6 against gentamicin-induced nephrotoxicity was supported by electron microscopic examination. While vitamin B6 and propolis-treated rats showed milder histopathological findings similar to that of control. Proximal tubular epithelial cells were regaining normal structure. In a few areas, the tubular cells were lower with few organelles and rudimentary villi. There was little protection by propolis alone against the nephrotoxic effects of gentamicin treatment. The present study could conclude that co-administration of vitamin B6 and propolis has beneficial effects on renal preservation in gentamicin induced nephrotoxicity

Myoepithelial cells after duct ligation and de-ligation of rat submandibular gland, light and electron microscopic study

Myoepithelial cells are observed in several exocrine glands. They are star-shaped cells that lie in between the basal lamina and the acinar and ductal cells [Ogawa et al., 1999][30]. These cells have the structural features and function of both smooth muscle cells and epithelium [Frank et al., 1980][31]. They contract when the gland is stimulated to secret. They aid expulsion of glandular secretion through compressing or reinforcing the underlying parenchymal cells. It was suggested that the major function of myoepithelial cells in salivary glands is to support the glandular structure through isometric contraction [Segawa et al., 1995][36]. They also display the characteristics of epithelium in that they are situated within the glandular epithelium between secretory cells and the basement membrane [Tandler, 1965; Harrop, 1968; Leeson and Leeson, 1971][45, 19, 26]. Myoepithelial cells have speculated to play an important role in histogenesis of some salivary gland tumors, such as pleomorphic adenoma, Myoepith-elloma, adenoid cystic carcinoma and certain other tumors [Batsakis et al., 1983; Dardick and Buford-Mason, 1993; Redman, 1994][2,9,33]. Studies of the responses of SMG to ligation of the main excretory duct have established that both acinar cells and cells of the granular ducts are markedly altered morphologically and functionally [Kasai, et al., 1993; Kern, 1993] [24, 25]. Moreover, ligation of the main excretory duct of the rat submandibular gland [SMG] produces a pronounced atrophy that is reversed upon ligature removal. The altered morphology and function of ligated salivary glands recover toward the normal state after removal of ligature [Junqueira and Rabinovitch, 1954; Harrison and Garrett, 1976; Randriamampita and Tsien, 1993; Ahn et al., 2000][23, 17,32,1]. However, it is not established whether myoepithelial cells are able to proliferate in atrophic rat submandibular gland, which differ histologically from parotid glands. Burgess et al. [1996][6] observed that atrophy of the rat parotid glands which induced by duct ligation was associated with proliferation of myoepithelid cells. However, Bataskis et at. [1989][3] found low proliferation in myoepithelial cells in atrophied rat salivary glands. Therefore, the present study was undertaken to clarify the effects of duct ligation and ligature removal on the myoepithelial cells of rat SMG. Also, it is an attempt to determine the crucial role of myoepithelial cells upon the integrity of acinar cells in both ligated and de-ligated ducts of SMG of rat