Search

The endocrine islets of Triturus carnifex consisted mainly of a core of B cells and a peripheral mantle of A cells. A rich supply of nerve terminals innervated the endocrine cells. The A and B cells showed a cytoplasm filled with secretory granules, glycogen, lipid droplets, microtubules and microfilaments, a well‐developed RER, and Golgi. To study the hormonal control of the secretion and the eventual morphological changes of the cells evoked by the hormonal stimulus, the newts were treated with 100 and 3×100 ug of epinephrine that caused dose‐dependent variations in pancreatic endocrine cells. B cells were inhibited by the lowest and stimulated by the highest doses, whereas A cells were always stimulated.

In early spring, neuropeptide Y injections in the lizard Podarcis s. sicula caused an increase of appetite in animals compared with those injected with saline alone. Glycemia determination showed an annual cycle with a maximum of blood glucose in summer when animals feed, and a minimum in winter when they undergo a semi‐hibernation period during which they do not eat. In NPY‐treated lizards, blood glucose dropped as the NPY dose increased to reach significantly lower values than those of controls fed for the whole time of treatment. Both endocrine and exocrine pancreas was affected by the treatment. In particular, the insulin immunoreactive B cells appeared less intensely immunostained than those of the controls, with a progressive reduction of immunostaining, according to the NPY doses used. Optical density of immunostaining measurements of B cells, showing a progressive reduction of this parameter in the treated lizards, supported the morphological observations. Acinar cells, too, exhibited red...

In this study, we investigated the presence of leptin receptor in pancreatic islets and the effect of exogenous leptin administration in Podarcis sicula on glucose metabolism. Our data show the presence of leptin receptor immunoreactivity in the endocrine pancreas suggesting that leptin may act at a peripheral level as previously postulated in mammals. The effects of short- and long-term and dose–response treatment with supraphysiological concentrations of leptin on circulating levels of insulin, glucagon and glucose in the blood have been evaluated. Taken together, our results indicate that leptin treatment was followed by an increase in insulin, glucagon and glucose in the blood, depending on the dose of leptin. Moreover, leptin treatment brought about a decrease of glycogen and the appearance of tyrosine-phosphorylated proteins in the liver. This study shows that in the lizard P. sicula leptin is involved in glucose metabolism. J. Exp. Zool. 305A, 2006. © 2006 Wiley-Liss, Inc.

In this study we investigated comparative morphology of the endocrine pancreas of several species belonging to the family Gekkonidae and apoptotic processes of the pancreas which may be correlated to the seasonal cycle. The following species of the family Gekkonidae were studied: Phelsuma lineata, P. madagascariensis, P. dubia, P. abotti, Gekko gecko, G. vittatus, and Geckonia chazaliae. In all these species the pancreas consisted of large and medium islets as well as endocrine cells which were scattered throughout the acinar cells. Exocrine parenchyma consisted of tubuli-acini. Four mayor cell types were identified in the endocrine pancreas, using immunocytochemistry: glucagon-immunoreactive (A) cells, insulin-immunoreactive (B) cells, somatostatin-immunoreactive (D) cells, and pancreatic polypeptide immunoreactive (PP) cells. In the endocrine pancreas the amount of A cells and B cells was either equal or a prevalence of A cells was observed. In the wet season the pancreatic morphology presented normal features with very rare apoptotic cells. The animals belonging to the genus Phelsuma taken in the dry season (July) showed numerous vacuolated, Caspase 3, 9 and 11-immunoreactive acinar and some endocrine cells containing picnotic nuclei which were positive to tunel reaction. The animals belonging to the genus Gekko taken at the end of the dry season (October) exhibited strongly vacuolated, Caspase 3, 9 and 11-immunoreactive endocrine and some acinar cells containing nuclei which were positive to tunel reaction. These apoptosis events could be a reaction in response to stress mechanisms, such as a starvation period during the dry season.

The effects of acetylcholine (ACh) administration on the endocrine pancreas of the lizard Podarcis sicula were studied by histological and immunocytochemical methods at light and electron microscopy, and in situ hybridization, and the results were evaluated by image analysis. In control lizards, the endocrine islet cells, especially B cells, displayed heterogeneity in the immunoreactive content of secretory granules in both the splenic and duodenal pancreatic lobes; however, this feature was more evident in the former. Following ACh administration, the differences in B cells between the splenic and duodenal lobes were more marked. In fact, splenic lobe B cells showed a bubbling aspect caused by a massive exocytosis testified by the greatly swollen s secretory granules devoid of their content. The duodenal lobe B cells exhibited images of exocytosis to a lesser extent and ‘disorganized’ granules. The secretion of A cells was also stimulated by ACh. These morphological observations were supported b...