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PubMed2002

Recombinant human alpha-2a interferon promotes an atypical process of mast cell secretion with ultrastructural features suggestive for piecemeal degranulation.

Purified mast cells (MC), isolated from the rat peritoneum, were stimulated in vitro with recombinant human IFN-alpha 2a (rhIFN-alpha 2a) and studied ultrastructurally. Quantitative determination of histamine release was also performed. The following ultrastructural features were observed: (1) dilation of single granules, leading to the formation of cytoplasmic cavities filled with dissolved or eroded matrices; (2) induction of partially empty, nonfused granule containers close to unaltered resting granules, a process very suggestive of piecemeal degranulation; (3) focal exocytosis, characterized by opening of single granules to the cell exterior and/or fusion of a few granules into small secretory channels. Histamine release was slightly increased in rhIFN-alpha 2a-treated MC, although not to significant levels. These results indicate that rhIFN-alpha 2a induces a characteristic pattern of degranulation in rat peritoneal MC and that a small proportion of rhIFN-alpha 2a-stimulated MC shows ultrastructural features suggestive for piecemeal degranulation.

Animals↗
PubMed2003

Ultrastructural correlates of synapse withdrawal at axotomized neuromuscular junctions in mutant and transgenic mice expressing the Wld gene.

We carried out an ultrastructural analysis of axotomized synaptic terminals in Wld(s) and Ube4b/Nmnat (Wld) transgenic mice, in which severed distal axons are protected from Wallerian degeneration. Previous studies have suggested that axotomy in juvenile (< 2 months) Wld mice induced a progressive nerve terminal withdrawal from motor endplates. In this study we confirm that axotomy-induced terminal withdrawal occurs in the absence of all major ultrastructural characteristics of Wallerian degeneration. Pre- and post-synaptic membranes showed no signs of disruption or fragmentation, synaptic vesicle densities remained at pre-axotomy levels, the numbers of synaptic vesicles clustered towards presynaptic active zones did not diminish, and mitochondria retained their membranes and cristae. However, motor nerve terminal ultrastructure was measurably different following axotomy in Wld transgenic 4836 line mice, which strongly express Wld protein: axotomized presynaptic terminals were retained, but many were significantly depleted of synaptic vesicles. These findings suggest that the Wld gene interacts with the mechanisms regulating transmitter release and vesicle recycling.

Animals↗
PubMed1999

Direct ultrastructural imaging of macrophages using a novel x-ray contact microscopy.

A compact, high-resolution, laser-plasma, x-ray contact microscopy method using a table-top Nd:glass laser system has been developed. This x-ray microscopy system was applied for the observation of macrophage ultrastructures. These images were produced using proximity imaging in which a 5-ns pulse of soft x-rays with wavelengths near and inside the water windows (23A-44A) produced by the laser-plasma were absorbed by the specimen and then registered on a photo resist. The x-ray images imprinted on the photo resist were then developed and analyzed with an atomic force microscope (AFM). Mouse thioglycollate-elicited peritoneal macrophages in suspension were examined by this new x-ray microscope. The x-ray images of the macrophages were compared with those observed by conventional transmission electron microscopy (TEM). The x-ray images showed no obvious organelles, including the nucleus and endoplasmic reticulum, as can be seen with TEM, but high- and low-contrast structures caused by mass distribution of carbon were observed. Thus, using the x-ray microscopy we visualized the first x-ray images of macrophage ultrastructures. The successful x-ray imaging of macrophage ultrastructure indicates that proximity x-ray microscopy may be of value in studying physiology linked to the dynamics of a cell.

Animals↗
PubMed2003

Ultrastructural identification of peripheral myelin proteins by a pre-embedding immunogold labeling method.

Ultrastructural immunolabeling of peripheral nervous system components is an important tool to study the relation between structure and function. Owing to the scarcity of certain antigens and the dense structure of the peripheral nerve, a pre-embedding technique is likely appropriate. After several investigations on procedures for pre-embedding immunolabeling, we propose a method that offers a good compromise between detection of antigenic sites and preservation of morphology at the ultrastructural level, and that is easy to use and suitable for investigations on peripheral nerve biopsies from humans. Pre-fixation by immersion in paraformaldehyde/glutaraldehyde is necessary to stabilize the ultrastructure. Then, ultrasmall gold particles with silver enhancement are advised. Antibodies against myelin protein zero and myelin basic protein were chosen for demonstration. The same technique was applied to localize a 35 kDa myelin protein.

Animals↗
PubMedDate not supplied

Ultrastructure of human platelets processed for transfusion under standard blood bank conditions.

Platelets processed for transfusion are routinely subjected to centrifugation, mechanical agitation and storage at either room temperature or 4 C. To evaluate morphologic changes associated with standard blood bank conditions, platelet units were grouped into four categories: linear agitation at room temperature, agitation at a 90 degrees arc with a Hemolater at room temperature, agitation at a 360 degrees arc with a commercial platelet agitator, and refirgeration at 4 C without agitation. Cold (4 C) preservation resulted in a surprisingly good preservation of platelet ultrastructure, even at 72 hours of storage. By contrast, harsh linear agitation at room temperature brought about marked alterations in platelet ultrastructure beginning at 24 hours. The Hemolator agitator with 90 degrees arc was associated with good preservation of platelet organelles even at 72 hours, whereas marked degenerative changes were observed at this time in platelets processed with a commercial agitator with a 360 degrees arc. These results indicate that platelets stored at 4 C or processed at room temperature with an agitator with 90 degrees arc show the best preservation of ultrastructure.

Blood Banks↗
PubMed1980

The effects of pig follicular fluid upon the ultrastructure of rat granulosa cells in tissue culture.

The ultrastructure of rat granulosa cells from preovulatory follicles has been investigated after incubation in control fetal calf serum (FCS) medium with or without LH (1 micron/ml), and in total or steroid-free pig follicular fluid (FF) medium. While the cells had a similar ultrastructure after 1 day of incubation in these media, significant differences were detectable after 3 days. In FCS supplemented with LH, autolysis and phagocytotic activity remained elevated, and cells did not develop any of the typical ultrastructural features of steroid-secreting cells. In contrast, total FF induced complete differentiation of mitochondrial cristae from the lamelliform to the villiform type. Steroid-free FF induced the same array of effects as total FF, except that mitochondrial differentiation was not complete. These observations together with those of previous studies, in which progesterone secretion was measured in cells incubated in the same media, suggested that the development of the capacity to secrete progesterone in rat luteal cells could be directly related only to mitochondrial differentiation.

Animals↗
PubMed2000

Lipomatous hemangiopericytoma: a fat-containing variant of solitary fibrous tumor? Clinicopathologic, immunohistochemical, and ultrastructural analysis of a series in favor of a unifying concept.

The dinicopathologic, immunohistochemical and ultrastructural features of 13 lipomatous hemangiopericytomas are presented. There were 6 male and 7 female patients whose ages at diagnosis ranged from 27 to 75 years (median 48) all presenting with a mass of variable duration. The tumor sizes ranged from 1.7 cm to 19 cm (median 5.5 cm). The locations included the orbit (1), neck (1), mediastinum (1), epicardium (1), retroperitoneum (3), right iliac fossa (1), and upper (1) and lower (4) extremity. Histologically, the lesions were composed of a varying admixture of spindle-shaped to round cells, variably collagenous stroma, adipose tissue, and branched, often thick-walled, hemangiopericytoma-like vessels. For 11 tumors, the mitotic activity ranged from 1 to 3 mitoses per 10 high-power fields (HPF). One tumor which contained hypercellular areas showed 13 mitoses per 10 HPF, and another hypercellular lesion showed up to 43 mitoses per 10 HPF, abnormal mitoses, and necrosis. Immunohistochemically, tumor cells were invariably positive for vimentin and CD99, and mostly for CD34 but negative for desmin, keratin, CD31, CD117 (c-kit), and inhibin. About half of the tumors showed reactivity for bcl-2. Occasionally, focal reactivity was also observed for smooth muscle actin, muscle-specific actin, S100 protein, and epithelial membrane antigen. Ultrastructural examination of seven cases showed features in keeping with fibroblastic, myofibroblastic, or pericytic differentiation. Treatment consisted of simple tumorectomy in 10 cases and wide excision in 3. Follow-up information on 10 patients (range: 6 to 77 months; median: 18 months) showed no recurrence. Lipomatous hemangiopericytoma which share the clinical, pathologic, immunohistochemical, and ultrastructural features of solitary fibrous tumor (SFT) is likely to represent, in most cases, a fat-containing variant of SFT.

Actin Cytoskeleton↗
PubMed2001

Natural history of experimental intestinal atresia: morphologic and ultrastructural study.

PURPOSE: The aim of this study was to evaluate a natural history of congenital intestinal atresia (IA) in the chick embryo and to assess the type and nature of changes in the intestine at various developmental stages. METHODS: Chick embryos underwent operative induction of IA on the 12th day of incubation. The procedure consisted of electrocoagulation of the mesenteric vessels supplying a 7- to 8-mm intestinal segment. The embryos were subjected to macroscopic examination, histologic and ultrastructural studies of the preatretic and postatretic bowel using the light microscope, scanning, and transmission electron microscopes. All investigations were performed in an experimental group (operated embryos), in a control group, and in a sham-operated group on the 15th, 17th, 19th, and 21st day of incubation. RESULTS: The original technique of an iatrogenic "vascular event" proved to be effective because IA developed in 96% of embryos surviving the procedure. The affected portion of the bowel underwent progressive necrosis, and signs of bowel obstruction could be observed 48 hours after operation. Cord atresia (type II) developed in 81% of embryos. Histologic investigations showed progressive thinning of mucosa, flattening of mucosal folds, and epithelial detachment within the intestine proximal to atresia. There was only mild hypertrophy of the muscular layers. All these pathomorphologic changes were of rapidly progressive nature until the 17th day of incubation. Later, the rate of distension of preatretic bowel and histologic changes were less. Ultrastructural investigation of the proximal bowel showed progressive flattening of the enterocytes associated with their apical bulging, widening of the intercellular spaces, and microvilli atrophy. Surprisingly, at days 19 and 21 of incubation, signs of induction of adaptive mechanisms with partial restoration of near-normal microvilli pattern were observed. CONCLUSIONS: Study of natural history of experimental IA indicates that histologic and ultrastructural lesions of the bowel are of dynamic nature and are not only the effect of pathologic intraluminal pressure.

Animals↗
PubMedDate not supplied

Structural differentiation of human uterine luminal and glandular epithelium during early pregnancy: an ultrastructural and immunohistochemical study.

The differentiation of human endometrial epithelium is a dynamic event that occurs throughout the menstrual cycle and early pregnancy. The structural transformation and differentiation of human uterine luminal and glandular epithelium of early human pregnancy (n=14) was investigated ultrastructurally and immunohistochemically using antibodies against cytokeratin (CT), endothelial marker CD31, Fas, and proliferating cell nuclear antigen (PCNA). Ultrastructurally, luminal epithelial cells showed distinctive euchromatic nuclei with prominent nucleoli and relatively loose cell membranes in all poles (apical to basal). Subcellular components were easily recognized in luminal epithelium except in degenerating cells. Mainly two cell types, dark and clear cells, formed the glandular epithelium. In the early gestation period, microvilli were abundant on the apical and apico-lateral poles of these cells. Only a few cytoplasmic projections were observed in dark cells. Numerous cilia were observed on the apical pole of some clear cells, located at the adluminal segment. In contrast, dark cells lacked cilia, nuclear channels, or giant mitochondrial profiles. Glycogen synthesis and apocrine secretion were recognizable for several days during early gestation. The apocrine secretory activity differed among dark cells of the glandular epithelium. The immunoreactivity of PCNA and Fas, and ultrastructural observations in the glandular epithelium suggest that, even in different segments of the same gland, epithelial cells do not regress during early gestation, but proliferate, perhaps representing a resistance against trophoblastic invasion. These morphological and molecular changes suggest that both luminal and glandular epithelium may play an important role in cellular defense and limitation for trophoblastic invasion during early pregnancy since plasma membrane alterations of the surface epithelium take place at the apical, basal and lateral poles compared to early secretory phase endometrial cells. Besides glandular epithelium may be consequently responsible for uterine secretions, which may be critical for early embryo development.

Adult↗
PubMed2001

Neuronal free Ca(2+)and BBB permeability and ultrastructure in head injury with secondary insult.

OBJECTIVE: To study changes in free calcium (Ca(2+)), neuronal and blood-brain barrier (BBB) permeability and ultrastructure in brain after diffuse axonal injury (DAI) with secondary brain insults (SBIs). METHOD: One hundred and twenty Sprague-Dawley (SD) rats were randomised into control, DAI alone and DAI with SBI groups which were sub-divided into 5 groups that were 0.5 h, 2 h, 12 h, 24 h, 48 h post trauma. The animal models of DAI and DAI with SBI have been described before (2). Fluorescence probe Fluo-3/Am was used to measure free Ca(2+)in neurons. Laser scan microscopy was used to detect fluorescence intensity. After the animals were anesthetized, Lanthanum nitrate liquid was used for intracardiac perfusion to assess BBB permeability. Under the transmission electron microscope, changes in cerebral ultrastructure and BBB permeability were observed. RESULTS: The fluorescence intensity was weak in the control. The concentration of free Ca(2+)in neurons was obviously increased at 30 min after brain injury, reached a peak at 12 h-24 h (P< 0.01), and appeared to decrease at 48 h after injury. In the DAI alone group, BBB tight junction opening with particles of Lanthanum nitrate outside the vessels was found at 30 min after injury, and peaked at 24 h. In DAI with SBI, the changes in ultrastructure and BBB permeability were more severe than that in the DAI alone group at the same time interval. The shape of the fluorescence concentration curve was basically the same for both kinds of brain injury. The intensity of fluorescence in DAI with SBI was higher than that in the DAI alone group at the same time interval (P< 0.05). CONCLUSION: In DAI alone and DAI with SBI, Ca(2+)overload and BBB permeability changes interact and both play important roles in the aggravation of brain damage.

Animals↗
PubMed2001

An ultrastructural study of connective tissue in mollusc integument: II. Gastropoda.

We studied the ultrastructure of the subepidermal connective tissue (SEC) in different zones of the integument in terrestrial, marine and freshwater gastropods (eight species). In all cases, the SEC was a layer of loose connective tissue between the basal membrane (BM) of the epidermis and the connective tissue of the deeper muscle layers. It was of monotonous structure and not differentiated into layers such as are found in mammalian dermis. The extracellular matrix (ECM) consisted of a network of collagen fibrils of variable diameter, with abundant anchoring devices and proteoglycans. In six species, variables quantities of haemocyanin were present within haemocoelic sinuses present in the SEC. The thickness and density of the BM varied from species to species, as well as within species in the various zones of integument. The ultrastructure of the lamina densa (LD) was indistinguishable from that of BM in bivalves and similar to that in mammals, although basotubules and double pegs were absent. An irregularly spaced lamina lucida was usually present and was often shot thorough with filaments and small protrusions of the LD that connected with epithelial plasma membrane or with hemidesmosomes. A lamina fibroreticularis was not present. LD protrusions characterize the connection between BM and the ECM of SEC. In the terrestrial gastropods, a spongy matrix with ultrastructure closely similar to LD occupied large tracts of the SEC. In the mantle region of Arion rufus, the integumental SEC contained large cavities filled with spherical concretions, probably representing rudiments of a shell. In the mantle where the integument contained abundant muscle fibres, the BM was thick and directly connected to the ECM of the SEC which consisted of compact laminae of collagen fibrils with abundant anchoring devices. Along the edge of the foot of Patella ulyssiponensis, the SEC contained a layer of paramyosinic muscle fibres adhering to the epidermis. No differences or gradations in integumental SEC structure could be related to the phylogenetic position of the species examined.

Animals↗
PubMed2001

Immunocytochemical and ultrastructural characterization of endocrine cells in the larval stomach of the frog Rana temporaria tadpoles: a comparison with adult specimens.

According to immunostaining and ultrastructural patterns, Rana temporaria tadpole stomach displays a well-differentiated endocrine population comprising, at least, six cellular types: ECL, EC [serotonin], D [somatostatin] - all three of them abundant -, P [bombesin] - less numerous -, CCK-8 [cholecystokinin/gastrin] and A [glucagon/glicentin] - both very scarce. Larval endocrine cells are mainly located in the surface epithelium and show open or closed morphologies. Cellular diversity is similar in tadpoles and frogs, with the exception of immunoreactivity for gastrin-17, found in adults in numerous cells. Larval cells display mature ultrastructural traits, although with smaller secretory granules. The different distribution of endocrine cells, which in adults are preferentially located in the glands, probably refers to different functional requirements. However, the rich vascular plexus present in larval mucosa may be an efficient transport medium of surface hormones to-gastric targets. The enhancement in adults of endocrine population and correlative increase in hormonal secretion indicates a more active functional role, probably related to the shift from herbivorous to carnivorous habits. In summary, the tadpole gastric endocrine population, although not as numerous as that of adult frogs, displays histological traits that indicate a relevant (immunoreactive and ultrastructural properties, cellular diversity) and specific (surface location, relative abundance of open-type cells) role of local regulatory factors in amphibian larval gastric function.

Animals↗
PubMed1976

[Different ultrastructure of the right and left myocardium after preservation for 24 hours (author's transl)].

After a 24 hrs' preservation of rat hearts, in 22% the viability test with allogenic perfusion showed a singular recovery of the right ventricle (57 of 257 experiments). The ultrastructural aspects correlate with the differences of the function. The micrographs of the right myocardium show--except a mild edema--ultrastructural integrity, but the micrographs of the left myocardium show marked alterations of the ultrastructure: edema, swollen mitochondria with destroyed cristal membranes, swelling of the sacrotubular system and alterations of myofibrils.

Animals↗
PubMed2002

Effect of Vitamin C and E supplementation on biochemical and ultrastructural indices of muscle damage after a 21 km run.

This study investigated whether 4 weeks of daily supplementation with 500 or 1000 mg of Vitamin C and 500 or 1000 IU of Vitamin E could modify biochemical and ultrastructural indices of muscle damage following a 21 km run. Fifteen experienced male distance runners were divided into two groups (vitamin or placebo) and received supplementation for four weeks before completing the first 21 km run in as fast a time as possible. A four-week "washout" period followed before the subjects crossed over and received the alternate supplement for the next four weeks. They then completed a second 21 km run. Before, immediately after and 24 h after each run venous blood samples were taken and analysed for serum creatine kinase, myoglobin, malondialdehyde and vitamin C and E (before-samples only) concentrations. A subgroup of six subjects also had muscle biopsy (gastrocnemius) samples taken 24 h before and 24 h after each 21 km run, which were later analysed by electron microscopy. The two dosages of supplementation produced similar results, so a single vitamin group was formed for further analysis of results. Significant increases (p < 0.05) in creatine kinase and myoglobin, but not in malondialdehyde, were found post-run in both groups. However, no significant differences were found between the vitamin and placebo groups for creatine kinase, myoglobin and malondialdehyde concentrations recorded after the 21 km runs. A qualitative ultrastructural examination of pre-run muscle samples revealed changes consistent with endurance training, but little further change was seen after the 21 km run in either the vitamin or placebo groups. It was concluded that vitamin C and E supplementation (500 or 1000 mg or IU per day) for four weeks does not reduce either biochemical or ultrastructural indices of muscle damage in experienced runners after a half marathon.

Administration, Oral↗
PubMed2004

Ultrastructure of right ventricular myocardium subjected to acute pressure load.

BACKGROUND: Ultrastructural data on acute right ventricular pressure load in pigs are rare. MATERIALS AND METHODS: In control (n = 7) and banding groups (n = 6), right ventricular pressure (micromanometry) and function (sonomicrometry) were measured. Right ventricular pressure was increased 2.5-fold in the banding group by pulmonary artery constriction. Right ventricular biopsies were taken at baseline and after 6 h and processed for electron microscopy. Parameters of cellular injury were determined stereologically. Three perfusion -fixed hearts were investigated qualitatively in each group. RESULTS: Stereology revealed an increase in the sarcoplasmic volume fraction and the cellular edema index in the banding group ( p < 0.05). Mitochondrial surface-to-volume ratio and volume fraction did not show significant alterations. Subendocardial edema and small amounts of severely injured myocytes were observed in the perfusion-fixed hearts after banding. Ultrastructure was normal in controls. After an initial increase, the right ventricular work index declined progressively in the banding group but remained unchanged in controls. CONCLUSIONS: Ultrastructural alterations resulting from acute right ventricular pressure load were characterized by edema of subendocardial myocytes and single cell necrosis. Focal adrenergic overstimulation and mechanical stress are probably more relevant in the pathogenesis of these lesions than ischemia.

Acute Disease↗
PubMed2005

Ultrastructure and lipid alterations induced by cadmium in tomato (Lycopersicon esculentum) chloroplast membranes.

The effects of cadmium (Cd) uptake on ultrastructure and lipid composition of chloroplasts were investigated in 28-day-old tomato plants (Lycopersicon esculentum var. Ibiza F1) grown for 10 days in the presence of various concentrations of CdCl2. Different growth parameters, lipid and fatty acid composition, lipid peroxidation, and lipoxygenase activity were measured in the leaves in order to assess the involvement of this metal in the generation of oxidative stress. We first observed that the accumulation of Cd increased with external metal concentration, and was considerably higher in roots than in leaves. Cadmium induced a significant inhibition of growth in both plant organs, as well as a reduction in the chlorophyll and carotenoid contents in the leaves. Ultrastructural investigations revealed that cadmium induced disorganization in leaf structure, essentially marked by a lowered mesophyll cell size, reduced intercellular spaces, as well as severe alterations in chloroplast fine structure, which exhibits disturbed shape and dilation of thylakoid membranes. High cadmium concentrations also affect the main lipid classes, leading to strong changes in their composition and fatty acid content. Thus, the exposure of tomato plants to cadmium caused a concentration-related decrease in the fatty acid content and a shift in the composition of fatty acids, resulting in a lower degree of fatty acid unsaturation in chloroplast membranes. The level of lipid peroxides and the activity of lipoxygenase were also significantly enhanced at high Cd concentrations. These biochemical and ultrastructural changes suggest that cadmium, through its effects on membrane structure and composition, induces premature senescence of leaves.

Cadmium Chloride↗
PubMed1999

Time-dependent efficacy of initial reperfusion with 2,3 butanedione monoxime (BDM) on release of cytosolic enzymes and ultrastructural damage in isolated hearts.

BACKGROUND: Reperfusion injury after cardioplegia may not be sufficiently addressed by conventional cardioplegic techniques in open heart surgery. 2,3-butanedione monoxime (BDM) has the potential to reduce myocardial reperfusion injury by uncoupling myocyte contraction from the intracellular calcium concentration, thus reducing reperfusion contracture. The aim of this study was to investigate the effects of different application periods of BDM during initial reperfusion on myocardial tissue injury after cardioplegia. METHODS: Isolated guinea-pig hearts underwent 50 min of cardioplegic arrest in St. Thomas' Hospital II solution at 37 C. Control hearts (n = 8) were immediately reperfused with normal Krebs-Henseleit solution for 30 min. In the therapy groups BDM-5, BDM-20, and BDM-40 (n = 8, each), hearts were initially reperfused with BDM (20mmol/L) for either 5, 20, or 40 min, respectively, followed by 30 min of reperfusion with normal Krebs-Henseleit solution. Coronary venous effluent was collected to estimate myocardial tissue damage through release of cytosolic enzymes (LDH and CK) and cardiac troponin 1. Ultrastructural alterations were qualitatively assessed by electron microscopy. RESULTS: Initial reperfusion with BDM markedly reduced LDH and CK release, as long as BDM was present. After washout of the protective agent a rebound of enzyme release occurred in BDM-5 hearts which was effectively reduced in BDM-20 and BDM-40 hearts. Troponin I release was similarly increased in all groups at the onset of reperfusion and rapidly decreased thereafter. Myocardial ultrastructural damage was most pronounced in control hearts, intermediate in BDM-5 and BDM-40 hearts, but markedly attenuated in BDM-20 hearts. CONCLUSIONS: Both 20 and 40 min of initial reperfusion effectively protected the hearts from reperfusion damage as indicated by cytosolic enzyme release, while 5 min of treatment were clearly insufficient. Toxic effects of BDM during the longer treatment period of 40 min or induction of edema by the long-term perfusion of non-beating hearts in this group may account for the worse preservation of myocardial ultrastructure in BDM-40 hearts. Thus, contraction uncoupling during initial reperfusion by BDM or similarly acting drugs may prove a viable principle for reduction of myocardial reperfusion injury. However, the ideal duration of treatment for the best therapeutic effect must be carefully evaluated.

Animals↗
PubMed1982

Glucocorticoid-induced changes in insulin secretion related to the metabolism and ultrastructure of pancreatic islets.

The effect of adrenalectomy and dexamethasone-treatment on insulin secretion was studied and related to the changes observed in the glucose oxidation, calcium uptake, cAMP and insulin content, as well as the ultrastructure of pancreatic rat islets. It was found that adrenalectomy was followed by a decreased glucose-induced insulin secretion, glucose oxidation, calcium uptake, cAMP and insulin content without any remarkable change observed at the ultrastructural level. Conversely, adrenalectomized-rats supplemented with dexamethasone showed an increased glucose-induced insulin secretion, glucose oxidation, calcium uptake and cAMP content but a diminished islet insulin content. At the ultrastructural level, a clear picture of increased secretory activity was found, with diminished number of mature B granules and greater number of pale granules, while rough endoplasmic reticulum and Golgi complex frequently appeared hypertrophic. These changes were only observed in the B cells. On account of our results, we might suggest that insulin secretion is partially controlled by glucocorticoid circulating levels throughout their effect on pancreatic islet metabolism.

Animals↗