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  • 1
    Electronic Resource
    Electronic Resource
    The microanatomy of canine islets of Langerhans: implications for intra-islet regulation (1992)
    Springer
    Anatomy and embryology 185 (1992), S. 131-141 
    Details
    ISSN: 1432-0568
    Keywords: Dogs ; Islets of Langerhans ; Extrainsular endocrine cells ; Immunohistochemistry ; Regulation of islets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In recent years models for the internal (“intra-islet”) regulation of hormone secretion have been proposed to explain how different islet cells might regulate each other by means of their respective secretory peptides. Models that emphasize the importance of a directed intra-islet blood flow and sequence of perfusion of islet cells rely on a certain type of islet microanatomy and vascular supply. The experimental studies underlying these models have partly been performed in dogs. To extend the incomplete morphological knowledge of the canine endocrine pancreas both canine islets of Langerhans and extrainsular cells have been analysed in immunostained serial semithin (0.5 μm) sections. In addition to their occurrence within islets of Langerhans, all endocrine cell types are also found at extrainsular sites (about 9% of all endocrine cells) where they are distributed in different quantities among the epithelial lining of exocrine acini or excretory ducts and the connective tissue. There are continuous transitions from single extrainsular cells to small mono-and polycellular cell groups to islets. In a comprehensive analysis of whole islets, including computer-assisted three-dimensional reconstructions, the size, shape and vascularization of the islets as well as their cellular composition and the microtopology of islet cells have been studied. We have found marked intra-and inter-islet heterogeneities of the parameters investigated that are not compatible with concepts of a uniform and directed vascular perfusion of the various islet cell populations. Instead, their paracrine regulation may occur primarily via hormonal secretion into the intercellular spaces or vascular hormonal delivery to adjacent cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185914
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  • 2
    Electronic Resource
    Electronic Resource
    Heterogeneities of the islets in the rabbit pancreas and the problem of “paracrine” regulation of islet cells (1988)
    Springer
    Anatomy and embryology 178 (1988), S. 297-307 
    Details
    ISSN: 1432-0568
    Keywords: Rabbits ; Islands of Langerhans ; Electron microscopy ; Immunohistochemistry ; Regulation of islands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In addition to “external” signals conveyed by the circulation or the nervous system, the pancreatic islets obviously are regulated also by “internal” (intra-islet) signals, e.g. by the islet hormones: insulin (B-), glucagon (A-), and somatostatin (D-) cells are able to affect the secretion of the heterologous cell types. It is, however, unclear whether this functional cooperation between islet cells occurs by an intercellular route (paracrinia sensu strictore), by intraislet “portal” vessels, or by the systemic circulation. These likely interactions are limited by islet anatomy. To identify the anatomical basis for the mutual functional relationships between the islet cells, islets of Langerhans in the rabbit pancreas were completely analyzed in immunostained serial semithin (0.5 μm) sections. The islets were found to be largely heterogenous. They were classified in three basic types: a) polycellular islets, composed of all established endocrine cells, and including two subtypes of islets, b) bicellular islets, containing only B- and A-cells or B- and D-cells, and c) monocellular islets, exclusively made up of B-cells. Concerning the modes of paracrine regulation of islet cells, the findings suggest primarely an endocrinous route of transport of the islet peptides to heterologous endocrine cells. The corresponding functional cooperation between islet cells probably is mediated rather by the systemic circulation than by intra-islet portal vessels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00698661
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  • 3
    Electronic Resource
    Electronic Resource
    Immunocytochemical and ultrastructural heterogeneities of normal and glibenclamide stimulated pancreatic beta cells in the rat (1994)
    Springer
    Virchows Archiv 425 (1994), S. 305-313 
    Details
    ISSN: 1432-2307
    Keywords: Rat ; Pancreatic beta cells ; Immunocytochemistry ; Ultrastructure ; Insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract When studied morphologically in semi-thin sections in the rat in vivo, pancreatic beta cells displayed heterogeneous immunoreactivities for insulin and amylin, depending on the islet size and the intra-islet position of the beta cells. In larger islets, cortical beta cells (beta cells with contacts with all islet cell types and with the exocrine parenchyma) which are located in the periphery were more densely immunostained for insulin and amylin than medullary beta cells (beta cells with contacts only with other beta cells) which are located in the centre of the islet. Ultrastructurally, these findings were accompanied by differences in the number of secretory granules and mitochondria. Beta cells in small islets and at extra-islet sites exhibited a dense immunoreactivity. After administration of glibenclamide, immunoreactivities for insulin and amylin were diminished in a time-dependent manner, decreasing first in medullary and thereafter in cortical beta cells of larger islets. Ultrastructurally, the beta cells exhibited the typical signs of stimulation. A minority of beta cells in small islets and all beta cells in extra-islet locations remained unchanged. Thus pancreatic beta cells under basal and stimulatory conditions in vivo exhibit heterogeneity in hormone content and in ultrastructural features. These differences may represent the basis for a functional heterogeneity of the insulin secretory response of the individual beta cell both in vivo and in vitro in states of normal and impaired insulin secretion. As heterogeneity was observed only among beta cells in islets, while single beta cells surrounded by acinar cells exhibited no changes in insulin immunoreactivity, interactions between beta cells as well as between beta cells and other endocrine cells may be critical for expression of heterogeneity within the beta cell population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196154
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  • 4
    Electronic Resource
    Electronic Resource
    Loss of GLUT2 glucose transporter expression in pancreatic beta cells from diabetic Chinese hamsters (1996)
    Springer
    Virchows Archiv 428 (1996), S. 177-185 
    Details
    ISSN: 1432-2307
    Keywords: Diabetic Chinese hamster ; Pancreatic beta cell ; Immunocytochemistry ; Insulin ; GLUT2 glucose transporter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The diabetic Chinese hamster is a well-established animal model for NIDDM with a defective glucose-induced insulin secretory response. In the pancreas of nondiabetic hamsters, the GLUT2 glucose transporter was localized in the plasma membrane of insulin-positive beta cells. At variance with the rat, immunoreactivity was also detected in the cytoplasm. Other islet cell types were not GLUT2 positive. GLUT2 immunoreactivity was already significantly reduced in beta cells from mildly diabetic animals in spite of a normal insulin immunoreactivity. In severely diabetic animals the majority of the beta cells had lost GLUT2 immunostaining. This observation was confirmed in a Western blot analysis of the GLUT2 protein in isolated pancreatic islets. Only beta cells that were densely immunostained for insulin were still GLUT2 positive. However, around 40% of the beta cells devoid of GLUT2 immunoreactivity were still insulin immunoreactive. Thus, the loss of GLUT2 immunoreactivity, which is an important component of the glucose recognition apparatus of the pancreatic beta cell, is an early indicator of beta cell dysfunction before the development of degenerative lesions or the loss of insulin immunoreactivity. GLUT2 loss may be important in the deterioration of glucose-induced insulin secretion in the diabetic Chinese hamster.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00200660
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  • 5
    Electronic Resource
    Electronic Resource
    Nutrient-dependent distribution of insulin and glucokinase immunoreactivities in rat pancreatic beta cells (1999)
    Springer
    Virchows Archiv 434 (1999), S. 75-82 
    Details
    ISSN: 1432-2307
    Keywords: Key words Rat ; Pancreatic beta cell ; Insulin ; GLUT2 glucose transporter ; Glucokinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Functional heterogeneity among pancreatic beta cells is a characteristic feature of the islets of Langerhans. Under physiological conditions, beta cells in the pancreas of fed rats exhibited heterogeneous immunohistochemical staining for insulin and glucokinase. Intracellular beta cell glucokinase staining was either faint or dense. In the pericapillary space beta cell glucokinase immunoreactivity had a polar orientation, with the highest density in cytoplasmic regions close to the blood vessels. Starvation resulted in a loss of heterogeneity with homogeneous insulin staining in all beta cells of the islets, and this was accompanied by a loss of heterogeneous glucokinase staining. The intracellular polarity of glucokinase staining in contact to blood vessels also disappeared after starvation. Refeeding resulted in the reappearance of intercellular heterogeneity. In dependence on the functional demand, the endocrine pancreas recruited insulin from beta cells according to a well-defined hierarchy, with an initial preferential mobilization of medullary beta cells. In the course of this process intracellular polarity of glucokinase staining reappeared in areas of the beta cell with functional contact to the GLUT2 glucose transporter in the plasma membrane. This can be regarded as the morphological correlate of an activation of the glucose signal recognition apparatus. Interestingly, the study also provides evidence that the changes in glucokinase distribution apparently preceded those in insulin distribution, which is in keeping with the central role of glucokinase as the glucose sensor of the pancreatic beta cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004280050308
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  • 6
    Electronic Resource
    Electronic Resource
    Chromogranin A (CGA) in the gastro-entero-pancreatic (GEP) endocrine system (1986)
    Springer
    Histochemistry and cell biology 85 (1986), S. 441-452 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Chromogranin A (CGA), a protein at first detected in the adrenal medulla, has recently been found also in other organs, e.g. the endocrine pancreas. However, immunohistochemical findings concerning the cellular source of pancreatic CGA were controversial. Therefore, the endocrine pancreas of 10 mammalian species (man, tupaia, mole, cat, dog, pig, guinea pig, rabbit, rat) was investigated immunohistochemically for CGA-like immunoreactivities on serial semithin plastic sections using a high-titer polyclonal antiserum against bovine CGA. The results show that basically all pancreatic endocrine cell types are CGA-immunoreactive; however, every species has its own pattern of CGA-immunoreactive cell types. Other findings of the present studies indicate that the physiological function of CGA in pancreatic endocrine cells is related to the storage mechanisms of peptide hormones. Finally, a methodological approach is given to obtain not only qualitative but also semiquantitative data during immunohistochemical investigations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00508425
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  • 7
    Electronic Resource
    Electronic Resource
    Synaptophysin immunoreactivity in the mammalian endocrine pancreas (1991)
    Springer
    Cell & tissue research 264 (1991), S. 461-467 
    Details
    ISSN: 1432-0878
    Keywords: Synaptophysin ; P38 ; Membrane proteins ; Endocrine pancreas ; Islet cells ; Immunohistochemistry ; Human ; Dog ; Gerbil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Synaptophysin, a major membrane glycoprotein of small presynaptic vesicles in neurons, has also been found in microvesicles of endocrine cells, e.g., of the endocrine pancreas. In the present study, the endocrine pancreas in 9 mammalian species (man, dog, mink, bovine, rabbit, guinea pig, rat, mouse, gerbil) has been investigated immunohistochemically for synaptophysin immunoreactivity. Synaptophysin-positive cells have been identified and localized on semithin plastic sections. Our study demonstrates that, in all species examined, all pancreatic endocrine cell types are consistently synaptophysin-positive independent of their location within the tissue, or the conditions of tissue processing. In addition, a few cells that cannot be hormonally identified show synaptophysin immunoreactivity. Hence, synaptophysin appears to be a regular constituent of all pancreatic endocrine cells in mammals. In several species, a subpopulation of endocrine cells, consisting of glucagon-containing and/or pancreatic-polypeptide-containing cells, exhibits a significantly higher degree of synaptophysin immunoreactivity. In the gerbil, this heterogeneity can readily be detected from the day of birth onwards. Our findings indicate that closely related endocrine cell types may differ with respect to the content of synaptophysin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319036
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