Quantitative ultrastructural changes induced by sucrose administration in the pancreatic B cells of normal hamsters

We have previously reported that young male Syrian hamsters receiving a sucrose-rich diet presented increased B-cell replication rate and size. The aim of the present study was to analyze, under the same experimental conditions, the ultrastructural changes in B cells. For this purpose, young male Syrian hamsters were fed with a commercial diet and 10 sucrose in their drinking water (S group) while the control group (C) received the same diet and tap water, for 5 weeks. Samples of the pancreas removed after that period were processed for the immunohistochemical identification of B cells as well as for measuring several ultrastructural parameters. S hamsters showed higher serum insulin levels, while similar serum glucose values were obtained in animals from both groups. The B cells from S group exhibited lesser number of dense secretory granules at expenses of an increase of the pale ones, increased number of both exocytosis profiles and fusion-granule images, as well as enlargement of the intercellular space and mitochondrial area. Marked expansions of this space, limited by junctional complexes, were observed between adjacent B cells. These results would indicate that sucrose administration to normal hamsters not only increases the pancreatic B-cell mass but also induces measurable subcellular changes in the individual B-cell characteristic of an enhanced secretory activity. The present model would represent a useful tool for testing strategies in preventing the damage or promoting the recovery of the pancreatic B cells.

Ultrastructural study of the endocrine pancreas of the toad Bufo arenarum

The aim of the present report was to identify by electron microscopy the different endocrine cell types of the toad pancreas. Thus, we studied the pancreas from male specimens of Bufo arenarum with routine techniques for transmission electron microscopy. The results showed the presence of four endocrine cells types which would correspond to those responsible for the different pancreatic hormonal secretions in other species (B, A, D and PP cells). Type 1 cells contained rounded secretory granules with a clear halo which responded to two varieties: a) measuring 200 to 400 mm, and b) having a crystalloid core and a diameter of 400 to 600 nm; these cells would correspond to B cells showed rounded or irregular granules of 104 to 400 nm; they would be equivalent to A cells. Type 3 cells presented polymorphic ganules, most of them peanut-shaped, measuring 115 to 850 nm; they would resemble D cells. Finally, Type 4 cells contained rounded granules of 80 to 400 nm; these cells would correspond to PP cells. In addition, we also observed mixed cells exhibiting similar characteristics to acinar cells, but containing secretory granules resembling those found in some of the endocrine cell types; these would correspond to the acinar-islet cells reported in other animals. In conclusion, we described the ultrastructure of the toad endocrine pancreas and compare it with previous observations made in other amphibians.

Estructura y ultraestructura del pancreas endocrino de ratones transgenicos diabeticos / Structure and ultrastructure of the endocrine pancreas in diabetic transgenic mice

El objetivo del trabajo fue corroborar los cambios estructurales y determinar las alteraciones ultraesctructurales ocurridas en el páncreas endocrino de ratones con un síndrome inducido de diabetes mellitus insulinodependiente (DMID). Para ello se utilizaron ratones transgénicos (OVE 27) que sobreexpresan el gen de calmodulina en las células beta del páncreas endocrino; en estos animales, el aumento de calmodulina disminuye los niveles de calcio citosólico de las células beta, produciendo alteraciones morfológicas y funcionales que desencadenan una DMID de curso severo. Para nuestro estudio se obtuvieron y procesaron porciones del páncreas (cola) de 4 ratones transgénicos machos diabéticos de 5 semanas de edad (glucemia: 376 + 2 mg/del) y de 4 controles no transgénicos de la misma cepa, sexo y edad (glucemia: 113 + 13 mg/dl). El estudio inmunohistoqu­mico con microscop­a de luz confirmó que los ratones transgénicos presentan una disminución del número y tama o de los islotes con distorsión de su arquitectura, sin respuesta inflamatoria asociada. Los estudios ultraestructurales demostraron diversos grados de da o en las células Beta, tales como la presencia de interdigitaciones de membrana y alteraciones de sus organelas y de sus gránulos de secreción. Estos hallazgos coinciden con el deterioro cuantitativo y funcional de las células beta y la conservación de las problaciones celulares no-beta de los islotes. Estos cambios ultraestructurales en las células beta del páncreas del modelo experimental estudiado, sumados a las alteraciones inmunohistoquímicas previamente descriptas, contribuyen a explicar la manifestación de la diabetes.