Ultrastructural changes in pancreatic beta cells treated with NGF and dbcAMP.

Nerve growth factor (NGF) induces morphological and physiological changes in cultured pancreatic beta-cells, including the extension of neurite-like processes. This latter effect is potentiated by dibutyryl cAMP (dbcAMP). beta-cells cultured under these conditions maintain their immunoreactivity to insulin and gamma-amino-butyric acid (GABA). NGF, dbcAMP, and high glucose concentrations also increase the expression of the GABA-synthesizing enzyme glutamic acid decarboxylase-65 in cultured beta-cells. The aim of this work was to study the effect of NGF alone or in combination with dbcAMP on pancreatic beta-cell ultrastructural morphology, after 10 days in culture. We used light microscopy, scanning electron microscopy, and transmission electron microscopy to analyze the modifications in cell surface and neurite-like projections. Morphometric analysis showed that NGF and/or dbcAMP treatment substantially increased the insulin and GABA content in granules and rough endoplasmic reticulum. Given that pancreatic beta-cells express NGF receptors and that NGF is synthesized and secreted by beta-cells, these results further suggest that NGF could have trophic actions on pancreatic hormone synthesis and/or storage.

Newly hatched chick ovarian cell subpopulations metabolize distinctively progestin and androgen precursors.

The aim of this study was to characterize the ability of four different cell fractions (F1, F2, F3, and F4), isolated from the ovary of newly hatched chick by means of subsequent metrizamide gradients (0-15%), to metabolize progestins and androgens. The results showed the presence of 17 alpha-hydroxylase/C17-20 lyase and 3 beta-hydroxysteroid dehydrogenase/isomerase (3 beta-HSD) activities in the typical steroidogenic cells isolated in F1 (d = 1.012 g/ml). Primary oocytes present in F2 (d = 1.037 g/ml) did not show relevant steroid metabolism in the various assays that were carried out. Fractions 3 (d = 1.055 g/ml) and 4 (d = 1.071 g/ml), which contained a mixture of prefollicular and poorly differentiated epithelial cells, presented both 5 beta-reductase and aromatase activities, whereas 17 beta-HSD activity was mainly located in the cells of fraction 3. It is highly possible that poorly differentiated epithelial cells of fractions 3 and 4 are responsible for the steroidogenic activity. We conclude that in newly hatched chick ovary, typical steroidogenic cells metabolize progestins to androgens, and poorly differentiated epithelial cells further aromatize androgens to estrogens. In addition, we suggest the existence of at least two metabolically distinct poorly differentiated epithelial cell subpopulations, one presenting 5 beta-reductase and aromatase activities and another exhibiting 17 beta-HSD activity.

Morphological changes in the thecal layer during the maturation of the preovulatory ovarian follicle of the domestic fowl (Gallus domesticus).

The aim of the present study was to evaluate changes in the steroidogenic tissue, the blood vessels and the undifferentiated cell islets observed in the theca of developing follicles in the hen ovary. Samples of preovulatory follicles (F1 to F5 in order of decreasing size) and small yellow follicles (SYF) were obtained from White Leghorn hens for light microscopy studies. Cell suspensions of the whole theca obtained from follicles at the same stage of development were analyzed for 17 beta-estradiol and testosterone secretion. Typical steroidogenic cells with abundant cytoplasmic lipid droplets were identified in the theca interna beside blood vessels and nerve fibers. Islets of undifferentiated cells were observed in the theca externa. The steroidogenic tissue of the theca interna was evident in the small yellow follicle. However, considering the growth of the developing follicle, the total volume of steroidogenic cells increased from the SYF up to F1 follicle. The blood vessels reached the maximum development in the largest follicle (F1). On the other hand, undifferentiated cell islets were markedly reduced in the F1 follicle. The structural changes herein described could be correlated to modifications in the steroid hormone secretion during the maturation of the ovarian follicle.

Steroidogenic cell subpopulations obtained from the theca of preovulatory follicles in the ovary of the domestic fowl.

The purpose of the present study is to provide further evidence in support of the theory which suggests that two cells are involved in the secretion of estrogens and androgens in the theca of the preovulatory ovarian follicles in the domestic fowl. The third (F3), the fourth (F4), and the fifth (F5), in order of decreasing size follicles, were obtained from white Leghorn hens. Theca cells were dispersed by trypsin treatment, and isolated cells were centrifuged in a continuous Percoll gradient (0-100%). Testosterone and 17 beta-estradiol secretion from cell samples in each density gradient fraction were radioimmunologically assayed. The highest secretion of 17 beta-estradiol was registered in cells isolated in density fractions ranging from 1.059 to 1.070 g/ml, while the maximal testosterone production was found in fractions from 1.037 to 1.048 g/ml. The different results were obtained from the three types of follicles studied (F3-F5). Morphological study of the F4 follicle showed typical steroidogenic cells with abundant lipid droplets in the cytoplasm in the theca interna, whereas clusters of poorly differentiated epithelial cells were visualized between fibroblast layers of the theca externa. The secretion of aromatizable androgens by the typical steroidogenic cells of the theca interna and estrogen production in the epithelial cells of the theca externa are postulated.

Ultrastructure of the ovarian medulla in the newly hatched chick treated with human chorionic gonadotropin.

The ultrastructural characteristics of the ovarian medulla of the newly hatched white leghorn chick were studied in control animals and compared with chicks that were treated with human chorionic gonadotropin during embryonic development. The ovarian medulla was mainly occupied by epithelial cells which formed cords or islets surrounded by a basal lamina. Within this epithelial compartment, steroidogenic cells, poorly differentiated cells and a lacunary system could be recognized. When chicks were treated with human chorionic gonadotropin, steroidogenic cells became discernible; there was an increment in the amount of cytoplasm and the area of mitochondria. Poorly differentiated cells exhibited signs of stimulation, and transitional images suggested the transformation of these cells into steroidogenic cells. The epithelial cells of the lacunar system also displayed stimulated cytoplasmic organelles. Evidence was supplied suggesting that relatively undifferentiated cells persist in the ovarian medulla until hatching and can develop into steroidogenic cells under gonadotropic stimulation.

Identification of steroidogenic cell subpopulations in the ovary of the newly hatched chicken.

The aim of the present study is the isolation of subpopulations of steroid-producing cells in the ovary of the newly hatched chicken. Cells were obtained by fractional trypsin dissociation of the ovary and isopycnic separation in a continuous metrizamide gradient (0-30%). Testosterone and 17 beta-estradiol secretion was measured by radioimmunoassay in the incubation medium of the isolated cells. Six fractions of ovarian cells were studied. Fraction II (density 1.080) contained typical steroidogenic cells with a positive reaction for 3 beta-hydroxysteroid dehydrogenase, delta 5-isomerase. This fraction secreted testosterone (3.7 ng/10(6) cells/2 hr) but no 17 beta-estradiol secretion was detectable. The majority (85%) of cells obtained in fraction VI (density 1.150) were relatively undifferentiated and contained polyribosomes, mitochondria with lamellar cristae, and few rough endoplasmic reticulum; only 3-5% of the cells of this fraction were similar to those of fraction II. In fraction VI the highest level of 17 beta-estradiol secretion was found (2.9 ng/10(6) cells/2 hr) whereas testosterone was at a minimum level (0.06 ng/10(6) cells/2 hr). Results strongly suggest the existence of two cell subpopulations in the inmature chicken ovary: typical steroidogenic and poorly differentiated cells which secrete testosterone and 17 beta-estradiol, respectively.

Morphological changes in the ovary of newly hatched chickens treated with chorionic gonadotropin during embryonic development.

The present study describes morphological changes produced in the ovary of newly hatched chickens by treatment with human chorionic gonadotropin (hCG). Morphometric measurements of the volume of steroidogenic cells and structures of the ovarian medulla were performed in controls and experimental chickens treated with hCG (1.0 IU/embryo) at 13, 15, and 17 days of embryonic development. After hCG treatment, the volume of interstitial cell cords increased, and modifications in poorly differentiated cells neighbouring the interstitial cells were also observed. Other changes obtained after hCG treatment were an increment in the development of the lacunar system and blood capillaries, as well as a reduction in the number of germ cells in the stroma of the ovarian medulla.

Estudio de la superficie endocardica de auricula derecha del raton con microscopia electronica de barrido. / Study of endocardial surface of right atrium of mice with scanning electron microscopy

En este estudio describimos la configuracion de superficie de la auricula derecha del raton, con particular interes en la desembocadura de los vasos sanguineos del sistema venoso profundo del corazon (SVP) mediante microscopia electronica de barrido. La superficie endocardica auricular se observo rugosa y finamente granulosa, con surcos moderadamente profundos de longitud variable. En el tabique auricular se visualizo el patron de fibras musculares subendocardicas. Se observo que las foraminulas de Lannelongue tenian distribucion irregular por toda la superficie auricular, y eran mas numerosas en la pared de la auricula que en el tabique auricular.El diametro de estas foraminulas fue variable. El aspecto submicroscopico de la superficie del anillo de las foraminulas fue similar al de la superficie de la pared auricular adyacente

Study of the trophozoite surface of Entamoeba histolytica with high resolution cytochemical studies and scanning electron microscopy.

A study of positive and negative electrical surface charges of Entamoeba histolytica trophozoites axenically cultured was carried out by means of incubation with colloidal iron solutions at pH 4.0 and 1.8, respectively. The samples were examined under the transmission electron microscope. Human erythrocytes were studied using the same experimental conditions as controls. In these cells the surface negative charges were homogeneously distributed on the surface, whereas the positive charges were observed as irregularly distributed patches. No electrical charges were labelled into the trophozoite surface with the colloidal iron solutions employed. It can be correlated with previous biochemical and cytochemical studies, as well as with experimental data obtained by other authors. Likewise surface configuration was studied using the scanning electron microscope in three pathogenic strains of E. histolytica cultured in axemic or monoxenic conditions. A detailed description of the trophozoite surface configuration was made and findings were correlated with data obtained from transmission electron microscopy studies of the parasite. There were no differences in the trophozoite surface structure which could be related to the strains of E. histolytica examined or to the culture conditions employed.