Principal cell types in the pancreatic islet of a teleost fish,Xiphophorus helleri H.

Summary By means of correlative light and electron microscopy, five pancreatic islet cell categories are described in the teleost fish, Xiphophorus helleri, each of which has specific light microscopic appearance and fine structure. Different histochemical techniques have been used, including immunofluorescence with antiporcine insulin and glucagon sera. In addition to B- and A₁-cells, two categories of A₂-cells have been observed, both reacting with antiporcine glucagon serum: A₂-cells with round granules gave a positive reaction for tryptophan; A₂-cells with crystalline granules gave a negative reaction with the same staining technique on the same section. The clear cells, the last category, were not specifically stained by any of the staining methods carried out in this investigation. The influence of fixation on staining affinities and on ultrastructure was shown to be considerable.Supported in part by the Deutsche Forschungsgemeinschaft, Bonn-Bad Godesberg (grant La 229/4) and by the Deutscher Akademischer Austauschdienst, Bonn-Bad Godesberg.     

Cytochemical localization of ATPase in axon-myelin-Schwann cell complex type

ATPase activity was studied in the structures of axon-myelin-Schwann cell complex of sciatic nerves of rabbits of pre-and postnatal development. Positive reaction was observed on the plasma membrane, mitochondria and endoplasmic reticulum of Schwann cells, on the intraperiod lines of the compact myelin, in the split myelin lamellae in the paranodal regions and Schmidt-Lanterman clefts, in segment of outermost lamellae split off from the interparanodal myelin, in the mesaxons, in the loose myelin lamellae in the earlier stages of myelinization, on the axolemma (periaxonal space) and axoplasm. The ATPase activity on the Schwannian plasmalemma, axolemma and myelin sheath surface was found to be heterogeneously distributed. An accumulated of reaction deposits at the origin of the outer mesaxon, at the axoglial contacts as well as at the terminal part of the myelin sheath was respectively observed. Alterations of the enzyme activity distribution in axon-myelin-Schwann cell complex during rabbit's development were found to be associated with the growing myelin sheath and its node-paranode. Using controls with ouabain an attempt was made the possibilities of Wachstein and Meisel's method to be shown and the place of alpha+ form of Na+, K+-ATPase in the axon-myelin-Schwann cell Complex to be establish.     

Cytochemical localization of alkaline phosphatase in the cell membrane ofDictyostelium discoideum amebae

Histochemistry and Cell Biology - We demonstrated that alkaline phosphatase was localized on the cell membrane ofDictyostelium discoideum amebae and on isolated plasma membranes. The enzyme...     

Long-acting somatostatin analogues in pancreatic islet cell carcinoma

In secreting islet cell carcinoma, the long-acting somatostatin analogue, Sandostatin, reduces symptoms of endocrine secretion both by inhibiting peptide secretion and by acting on the target organs. It could be used during the initial evaluation of patients with such tumors and thereafter when the tumor cannot be found or is metastatic. Its efficacy depends upon the tumor type and probably the presence of somatostatin receptors on the tumoral cells. It could decrease with time, especially in VIPomas. Side effects are few and usually mild. Hypoglycemia attacks in insulinoma could be worsened during treatment by the complete inhibition of hyperglycemic hormones. The inhibition of tumoral growth, based on animal models, appears infrequent in clinical practice.     

Noninvasive in vivo imaging of pancreatic islet cell biology

Advanced imaging techniques have become a valuable tool in the study of complex biological processes at the cellular level in biomedical research. Here, we introduce a new technical platform for noninvasive in vivo fluorescence imaging of pancreatic islets using the anterior chamber of the eye as a natural body window. Islets transplanted into the mouse eye engrafted on the iris, became vascularized, retained cellular composition, responded to stimulation and reverted diabetes. Laser-scanning microscopy allowed repetitive in vivo imaging of islet vascularization, beta cell function and death at cellular resolution. Our results thus establish the basis for noninvasive in vivo investigations of complex cellular processes, like beta cell stimulus-response coupling, which can be performed longitudinally under both physiological and pathological conditions.     

Cytochemical localization of alkaline phosphatase in the cell membrane of Dictyostelium discoideum amebae

We demonstrated that alkaline phosphatase was localized on the cell membrane of Dictyostelium discoideum amebae and on isolated plasma membranes. The enzyme activity was specifically inhibited by 0.01 M KCN or cysteine. The same method could also be applied to baker's yeast and MDCK cells (dog kidney cells in vitro).     

The pancreatic islet endothelial cell: emerging roles in islet function and disease

The pancreatic islets are one of the most vascularized organs of the body. This likely reflects the requirements of the organ for a rich supply of nutrients and oxygen to the tissue, as well as the need for rapid disposal of metabolites and secreted hormones. The islet endothelium is richly fenestrated to facilitate trans-endothelial transport of secreted hormones, has a unique expression of surface markers, and produces a number of vasoactive substances and growth factors. The islet endothelial cells play a critical role in the early phase of type 1 diabetes mellitus by increasing the expression of surface leucocyte-homing receptors, thereby enabling immune cells to enter the endocrine tissue and cause beta-cell destruction. Following transplantation, pancreatic islets lack a functional capillary system and need to be properly revascularized. Insufficient revascularization may severely affect the transport properties of the islet endothelial system, resulting in a dysfunctional islet graft.     

The pancreatic islet endothelial cell: emerging roles in islet function and disease

The pancreatic islets are one of the most vascularized organs of the body. This likely reflects the requirements of the organ for a rich supply of nutrients and oxygen to the tissue, as well as the need for rapid disposal of metabolites and secreted hormones. The islet endothelium is richly fenestrated to facilitate trans-endothelial transport of secreted hormones, has a unique expression of surface markers, and produces a number of vasoactive substances and growth factors. The islet endothelial cells play a critical role in the early phase of type 1 diabetes mellitus by increasing the expression of surface leucocyte-homing receptors, thereby enabling immune cells to enter the endocrine tissue and cause beta-cell destruction. Following transplantation, pancreatic islets lack a functional capillary system and need to be properly revascularized. Insufficient revascularization may severely affect the transport properties of the islet endothelial system, resulting in a dysfunctional islet graft.     

Postnatally disturbed pancreatic islet cell distribution in human islet amyloid polypeptide transgenic mice

OBJECTIVE: Islet amyloid polypeptide (IAPP)/amylin is produced by the pancreatic islet beta-cells, which also produce insulin. To study potential functions of IAPP, we have generated transgenic mice overexpressing human IAPP (hIAPP) in the beta-cells. These mice show a diabetic phenotype when challenged with an oral glucose load. In this study, we examined the islet cytoarchitecture in the hIAPP mice by examining islet cell distribution in the neonatal period, as well as 1, 3 and 6 months after birth. RESULTS: Neonatal transgenic mice exhibited normal islet cell distribution with beta-cells constituting the central islet portion, whereas glucagon and somatostatin-producing cells constituted the peripheral zone. In contrast, in hIAPP transgenic mice at the age of 1 month, the glucagon-immunoreactive (IR) cells were dispersed throughout the islets. Furthermore, at the age of 3 and 6 months, the islet organisation was similarly severely disturbed as at 1 month. Expression of both endogenous mouse IAPP and transgenic hIAPP was clearly higher in 6-month-old mice as compared to newborns, as revealed by mRNA in situ hybridisation. CONCLUSIONS: Mice transgenic for hIAPP have islets with disrupted islet cytoarchitecture in the postnatal period, particularly affecting the distribution of glucagon-IR cells. This islet cellular phenotype of hIAPP transgenic mice is similar to that of other mouse models of experimental diabetes and might contribute to the impaired glucose homeostasis.     

Phosphoinositide phosphorylation and hydrolysis in pancreatic islet cell membrane

Membranes were isolated from dispersed rat pancreatic islet cells by attachment to Sephadex beads. When these membranes were exposed to [gamma-32P]ATP, formation of 32P-labeled phosphatidate, phosphatidylinositol 4-phosphate, and phosphatidylinositol 4,5-bisphosphate was observed. Carbamylcholine, added 10 s prior to lipid extraction, caused a dose-related fall in 32P-labeled phospholipids. The effect of the cholinergic agent was suppressed by atropine, ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid, and verapamil, and simulated, in part, by an increase in Ca2+ concentration. When the membranes were derived from islet cells prelabeled with [U-14C]arachidonate, carbamylcholine stimulation, in addition to decreasing labeled polyphosphoinositides, was accompanied by an increased production of labeled diacylglycerol, without a concomitant increase in labeled phosphatidylinositol. These results indicate that activation of a plasma membrane-associated phospholipase C directed against polyphosphoinositides represents a primary event in the functional response of the pancreatic beta cell to cholinergic agents.     

Studies on the function of pancreatic islet cell membranes.

Pancreatic islets rich in beta-cells were isolated from non-inbred ob/ob-mice and used for studying various aspects of the function of the plasma membrane. A review is given of the authors' work along the following lines: the role of transmembrane transport or membrane binding in the recognition of insulin-releasing sugars, amino acids, sulfonylureas, and sulphydryl-blocking agents; the role of cyclic 3',5'-AMP and cations in the coupling of stimulus recognition to insulin discharge; alloxan beta-cytotoxicity in vitro and its prevention by sugars; the isolation of a subcellular fraction enriched by plasma membranes. 1. It is suggested that D-glucose is recognized as an insulin secretagogue by being metabolized in the beta-cells; the teleological purpose of the transmembrane transport system being to allow fluctuations of the extracellular glucose concentration to be rapidly transmitted to the cell interior. Insulin-releasing sulfonyluraes and sulphydryl reagents are thought to act directly on the beta-cell plasma membrane, however. 2. Although cyclic 3',5'-AMP may amplify the expression of a secretory signal induced by D-glucose, studies with cholera toxin suggest that activation of the adenylate cyclase does not per se elicit secretion. The increase of islet cyclic 3',5'-AMP observed in response to several secretagogues, including D-glucose, may be secondary to membrane depolarization. 3. The possible role of an electrodiffusional mechanism in controlling the electrical potential is emphasized; a decrease of K+ permeability, rather than an increase of Na+ permeability, is suggested to be involved in the depolarizing action of D-glucose. Studies with the lanthanum-wash technique indicated that D-glucose causes a net flux of Ca2+ from the outside to the inside of the beta-cells. Although this uptake may relate to the enhancement of insulin secretion, the detailed mechanisms are unclear. 4. Inhibition of the Na+/K+ pump may be one of the earliest events in damage to the beta-cell by alloxan, on the basis of Rb+ studies. Protective effects of glucose against alloxan toxicity appear to be close related. 5. Studies of enzyme markers, the binding of wheat germ agglutinin, and electron microscopy indicate the presence of plasma membranes in a smooth-membrane fraction obtained by fractionating islet homogenates at consecutive sucrose gradients.     

Histochemical localization of NADPH-diaphorase in the rat accessory olfactory bulb

The distribution of NADPH-diaphorase activity was examined inthe accessory olfactory bulb of the rat using a direct histochemicaltechnique. Labeled fibers and somata were found in all layersof the accessory olfactory bulb. The entire vomeronasal nerveand all vomeronasal glomeruli were strongly labeled, contraryto the main olfactory bulb, where only dorsomedial olfactoryglomeruli displayed NADPH-diaphorase activity. NADPH-diapborasepositive neurons were identified as periglomerular cells inthe glomerular layer and external plexiform layer, horizontalcells in the internal plexiform layer, and granule cells anddeep short-axon cells in the granule cell layer. The labeleddendrites of the granule cells formed a dense neuropile in thegranule cell layer, internal plexiform layer and external plexiformlayer. The staining pattern in the accessory olfactory bulbwas more complex than what has been previously reported, anddemonstrated both similarities and differences with the distributionof NADPH-diaphorase in the main olfactory bulb.     

Pancreastatin producing cell line from human pancreatic islet cell tumor

It has been characterized that cell line QGP-1 derived from human non-functioning pancreatic islet cell tumor produces human pancreastatin. Exponentially growing cultures produced 5.7 fmol of pancreastatin/10(6) cells/hr. Human pancreastatin immunoreactivities in plasma and tumor after xenografting with QGP-1 into nude mouse were 92.7 fmol/ml and 160.2 pmol/g wet weight, respectively. Immunocytochemical study revealed both chromogranin A and pancreastatin immunoreactive cells in the tumor. Gel filtrations of culture medium and tumor extract identified heterogenous molecular forms of PST-LI which eluted as large and smaller molecular species. These results suggest that plasma pancreastatin levels may be useful as a tumor marker of endocrine tumor of the pancreas, and the pancreastatin producing cell line may be useful for studies of the mechanism of secretions and processing of chromogranin A and pancreastatin.     

Cytochemical localization and biochemical analysis of the enzyme markers in human hepatoma cell lines

Three enzyme makers, glucose-6-phosphatase, ATPase and gamma-glutamyl transpeptidase, have been used in studying carcinogenesis of hepatocellular carcinoma. They have been investigated in animal models and human hepatocellular carcinoma in vivo and in vitro. But the inconsistent levels of these three enzymes associated with this type of carcinoma raised the possibility that the carcinoma cells might have derived from the cells originating from different stages of differentiation. To evaluate this possibility, three human cell lines, Hep G2, Hep 3B, and HA 22T, all thought to be arrested in different stages of differentiation based on their biochemical and morphological characteristics, were used as models. The three enzyme markers glucose-6-phosphatase, ATPase and gamma-glutamyl transpeptidase were examined cytochemically and biochemically. Our results showed that there was no correlation between the ATPase levels and the stages of the cell line's differentiation. But both glucose-6-phosphatase and gamma-glutamyl-transpeptidase were higher in cells that were more differentiated.     

Cytochemical localization of alkaline phosphatase in the cell membrane ofDictyostelium discoideum amebae

Summary We demonstrated that alkaline phosphatase was localized on the cell membrane ofDictyostelium discoideum amebae and on isolated plasma membranes. The enzyme activity was specifically inhibited by 0.01 M KCN or cysteine. The same method could also be applied to baker's yeast and MDCK cells (dog kidney cells in vitro).