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D Grube

Publications and source records attributed to D Grube.

At least 37 records · Page 2Linked to original sources
PubMed1991

Immunocytochemical localization of cathepsins B, H, and L in the rat gastro-duodenal mucosa.

Cathepsins B, H, and L are representative cysteine proteinases in lysosomes of a large variety of cells. Previous immunochemical studies indicated the presence of these enzymes also in the gastrointestinal wall. Using specific antisera, the cellular and subcellular distribution of cathepsins B, H, and L in rat gastric (oxyntic and pyloric part) and duodenal mucosa was investigated by light and electron microscopical immunocytochemistry. The subtypes of cathepsins were distributed differently in the cellular constituents of the epithelia: Cathepsin B was localized to lysosomes of all cells except goblet cells. Cathepsin H was found predominantly in gastric parietal cells (lysosomes) and in secretion granules of pyloric gastrin and duodenal cholecystokinin cells. Cathepsin L immunoreactivities were weak and restricted to a minority of cells (gastric mucous cells, enterocytes). Interstitial cells of the lamina propria immunoreactive for cathepsins H and L were identified as macrophages. The present findings suggest a dual function of cathepsins in the gastro-duodenal mucosa. They (1) cleave enzymatically proteins and peptides ingested in lysosomes, and (2) they may be involved in the processing of biologically active peptides (enteric hormones) from their precursor proteins.

Animals↗
PubMed1991

Topology of chromogranin A and secretogranin II in the rat anterior pituitary: potential marker proteins for distinct secretory pathways in gonadotrophs.

Chromogranins (Cg)/secretogranins (Sg) are representative acidic glycoproteins in secretory granules of many endocrine cells where they are co-stored and co-released with resident amines or peptides. The exact distribution of these proteins in the rat anterior pituitary is unknown. Therefore, pituitaries from untreated male rats were investigated by light- and electron-microscopical immunocytochemistry for the cellular and subcellular localization of CgA, CgB, and SgII. Endocrine cells, identified light-microscopically as gonadotrophs in adjacent semithin sections immunostained for follicle-stimulating hormone (FSH) and luteinizing hormone (LH), concomitantly were immunoreactive for CgA, CgB, and SgII. Ultrastructurally, gonadotrophs exhibited two types of secretory granules which varied in their immunoreactivities for gonadotropins and Cg/Sg. Large-sized (500 nm), moderately electron-dense granules showed antigenicities for FSH, LH, and CgA. Smaller-sized (200 nm), electron-dense granules were immunoreactive exclusively for LH and SgII. The distinct localization of CgA and SgII to morphologically and hormonally different secretory granules indicates the existence of two regulated secretory pathways in rat pituitary gonadotrophs. Hence, these proteins are considered as valuable tools to analyze the intracellular trafficking during granule biogenesis and the possible different regulation of FSH and LH secretion.

Animals↗
PubMed1991

Topology of chromogranins in secretory granules of endocrine cells.

Chromogranins A and B are glycoproteins originally detected in the adrenal medulla. These proteins are also present in a variety of neuroendocrine cells. The subcellular distribution of the chromogranins, and particularly their intra-granular topology are of special interest with respect to their putative functions. Endocrine cells of the guinea pig adrenal medulla, pancreas and gastric mucosa were investigated immunoelectron microscopically for the subcellular distribution of both chromogranins. Out of 13 established endocrine cell types in all locations, only two endocrine cell types showed immunoreactivity for both chromogranin A and B, and eight endocrine cell types showed immunoreactivities only for chromogranin A. These immunoreactivities varied inter-cellularly. Three endocrine cell types were unreactive for the chromogranins. Moreover, some hormonally non-identified endocrine cells in the pancreas and the gastric mucosa also contained chromogranin A immunoreactivities. Subcellularly, chromogranin A or B were confined to secretory granules. In most endocrine cells, the secretory granules showed chromogranin immunoreactivities of varying densities. Furthermore, the intra-granular topology of chromogranin A or B in the secretory granules varied considerably: in some endocrine cell types, i.e. chromaffin-, gastrin- and enterochromaffin-like-cells, chromogranin A immunoreactivity was localized in the perigranular and/or dense core region of the secretory granules; in others, i.e. insulin-, pancreatic polypeptide- and bovine adrenal medulla dodecapeptide-cells, it was present preferentially in the electron-opaque centre of the secretory granules; chromogranin B immunoreactivity was localized preferentially in the perigranular region of the secretory granules of chromaffin cells and gastrin-cells. The inter-cellular and inter-granular variations of chromogranin A and B immunoreactivities point to differences in biosynthesis or processing of the chromogranins among endocrine cells and their secretory granules.

Adrenal Medulla↗
PubMed1991

Immunoreactivities for chromogranin A and B, and secretogranin II in the guinea pig entero-endocrine system: cellular distributions and intercellular heterogeneities.

The family of the chromogranin/secretogranin proteins consists of three major subtypes: chromogranin A (CgA), chromogranin B (CgB) and secretogranin II (SgII). These proteins are present in various endocrine cells and organs. Using immunohistochemistry on serial semithin sections, we have investigated ten endocrine cell types of the guinea pig gastro-intestinal tract for their content of chromogranin/secretogranin proteins. The gastrin cell was the only cell type containing immunoreactivities for all three chromogranin subtypes. The majority of entero-endocrine cells showed immunoreactivities for CgA and SgII. Somatostatin cells lacked immunoreactivities for any of the chromogranins. Moreover, the densities of the corresponding immunoreactivities varied among the different endocrine cell types or even among endocrine cells of a given population. Aminergic endocrine cells (e.g., enterochromaffin and enterochromaffin-like cells) regularly exhibited strong immunoreactivities for CgA but failed to react for SgII. In peptidergic endocrine cells, the immunoreactivities for both CgA and SgII ranged from dense to faint. This was also true for CgB in gastrin cells. Hence, only CgA and SgII can be considered as regular constituents of entero-endocrine cells. The intercellular differences in immunoreactivities for all three chromogranin subtypes indicate that every endocrine cell has its own composition of chromogranin/secretogranin proteins. This may be due to differences in the regulation of biosynthesis or processing of the chromogranins in individual endocrine cells; this in turn might be related to the functional states of endocrine cells.

Animals↗
PubMed1991

Synaptophysin immunoreactivity in the mammalian endocrine pancreas.

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.

Animals↗
PubMed1991

The endocrine pancreas of glucagon-and somatostatin-immunized rabbits. I. Light microscopy and immunohistochemistry.

Peptide antibodies raised in rabbits are widely used in biology and medicine. During immunization of the animals, the respective antibodies may affect the endocrine cells physiologically responsible for the synthesis of peptides used as antigens. Since corresponding morphological data are still sparse, the rabbit endocrine pancreas was systematically investigated by light microscopy and immunocytochemistry after long-term immunization against glucagon and somatostatin. Both immunizations led to an increase in the number of islets (nesidioblastosis), to the development of giant islets (macronesia), and to changes in the relative proportions of the major types of endocrine cells or their hormonal content. The latter changes differed after either immunization: glucagon immunization resulted in hypertrophy and hyperplasia of glucagon cells and a decrease in their hormonal content; somatostatin immunization led to an increased proportion of somatostatin cells and a lowered hormonal content of insulin cells. The various alterations were expressed differently according to islet type; islets of the rabbit pancreas differ in size or angioarchitecture, and in the proportion and distribution of endocrine cells. The present findings point to autocrine or paracrine effects of the respective peptides. These effects, however, are obviously of differing significance in morphologically heterogeneous islets.

Animals↗
PubMed1991

The endocrine pancreas of glucagon- and somatostatin-immunized rabbits. II. Electron microscopy.

An active or passive immunization against hormones and the subsequent neutralization of hormones by circulating antibodies is a valuable tool for the identification of hormonal action. To recognize presumed local (autocrine, paracrine) effects exerted by pancreatic hormones, the endocrine pancreas of rabbits was investigated electron-microscopically after long-term immunization against glucagon or somatostatin. Glucagon immunization resulted in hyperplasia and hypertrophy of glucagon- (A-) cells and in their increased metabolic activities: They showed prominent nucleoli, increased amounts of endoplasmic reticulum, Golgi areas, and mitochondria. These changes were paralleled by alterations in secretion granules (increased size, decreased hormonal content), increased numbers of lysosomes (crinophagic bodies), and an increment of the filamentous system. Basically, these findings point to an autocrine regulation of A-cells. Following somatostatin immunization, somatostatin- (D-) cells were hyperplastic but unchanged in their metabolic state. Instead, insulin-(B-) cells and A-cells exhibited equivalents of increased cellular activities (parameters, see above). This stimulation most probably is caused by cancelled paracrine (inhibitory) effects of somatostatin. The changes observed after both immunizations were differently expressed in morphologically heterogeneous islet types (size, angioarchitecture, cellular composition, microtopology of the various cell types). It is concluded, therefore, that the regulation of islets is not uniform. Autocrine and paracrine effects exerted by islet hormones are of different significance in individual islets, or they interfere differently with other regulatory signals.

Animals↗
PubMed1990

Immunoreactivities for chromogranin A and B, and secretogranin II in the guinea-pig endocrine pancreas.

The chromogranins are acidic proteins present in various endocrine cells and organs. They consist of chromogranin A (CgA), chromogranin B (CgB) and secretogranin II (SgII). In the pancreas, these proteins or their breakdown products are possibly involved in the regulation of pancreatic hormone secretion. The guinea-pig endocrine pancreas was now investigated immunohistochemically for the presence of the chromogranins in five endocrine cell types. CgA is a regular constituent of insulin (B-), pancreatic polypeptide (PP-) and enterochromaffin (EC-) cells. In addition, a minority of somatostatin (D-) cells were immunoreactive for CgA. CgB immunoreactivities were very faint and exclusively observed in B-cells. SgII was found in B- and PP-cells; a faint immunostaining for SgII was also seen in a few glucagon (A-) cells. Typically, the densities of CgA or SgII immunoreactivities varied among the members of a given cell population, e.g. among individual B- or PP-cells. The present findings about the heterogeneities of immunoreactivities for the chromogranins are in line with findings obtained in pancreatic endocrine cells of other species. The true reasons for these heterogeneities are enigmatic. It seems probable, however, that the corresponding immunoreactivities depend on the intracellular processing of the chromogranins which in turn might be related to the metabolic state of endocrine cells. This has to be examined in future by experimental investigations.

Adrenal Medulla↗
PubMed1990

Immunohistochemical localization of synaptophysin (p38) in the pineal gland of the Mongolian gerbil (Meriones unguiculatus).

Synaptophysin (protein p38), a major integral membrane glycoprotein of small presynaptic vesicles, was localized immunohistochemically in semithin sections of the superficial pineal gland of the Mongolian gerbil (Meriones unguiculatus). Synaptophysin immunoreactivity could be detected in all pinealocytes, which were visualized with antibodies directed against neuron-specific enolase (NSE) in adjacent sections. No p38 immunoreactivity was discernible in the interstitial glial cells, which showed a heterogeneous pattern of immunostaining for the intermediate filament proteins glial fibrillary acidic protein (GFAP) and vimentin. Pinealocytes exhibited considerable intercellular differences in the densities of immunostaining. The various degrees of synaptophysin immunoreactivities in pinealocytes were not correlated with the densities of NSE immunostaining. Nerve terminals and varicosities displayed stronger immunoreactivities than pinealocytes. They were particularly numerous in the perivascular spaces. It is not clear whether this distribution indicates an innervation of pineal capillaries in addition to the functionally important innervation of pinealocytes. Several highly p38-positive dots of variable size were a conspicuous feature throughout the gland. By the consecutive semithin-thin section technique, they could be identified as processes of pinealocytes, filled with accumulations of small clear vesicles. Obviously, these vesicles represent the major site of synaptophysin immunoreactivity in pinealocytes. In the gerbil, similar vesicles have been ascribed a role in the secretory activity of the gland, and/or in the transport of calcium. The intercellular differences in the degrees of p38 immunostaining may, therefore, reflect different states of a specific cellular activity. The presence of synaptophysin in pinealocytes of the normal pineal, including the deep portions of the gland, emphasizes the paraneuronal character of these cells.

Animals↗
PubMed1989

Immunocytochemical localization of cathepsins B and H in human pancreatic endocrine cells and insulinoma cells.

Cathepsins B and H are representative cysteine proteinases localized to lysosomes of a variety of mammalian cells. Previous studies indicated the presence of these enzymes also in secretory granules of endocrine cells. Therefore, the human endocrine pancreas and human insulinomas were investigated by light microscopical immunohistochemistry on serial semithin plastic sections immunostained sequentially for cathepsins B or H and pancreatic hormones. Out of the four established endocrine cell types, insulin (B-) and glucagon (A-) cells showed immunoreactivities for these cathepsins. Cathepsin B immunoreactivities showed a dot-like appearance in A- and B-cells and in insulinoma cells. Immunoreactivities for cathepsin H additionally were found in cell parts containing secretory granules of B-cells and insulinoma cells. By single and double immunoelectron microscopy the dot-like immunoreactivities for cathepsin B were identified as immunoreactive lysosomes of A- and B-cells and insulinoma cells. In addition, some of the secretory granules of A- and B-cells showed cathepsin B immunoreactivities. Cathepsin H immunoreactivities showed an other pattern: they were found regularly in the secretory granules of A- and B-cells and insulinoma cells, and in lysosomes of A-cells. These findings suggest that cathepsins B and H in lysosomes of A- and/or B-cells are involved in the degradation of lysosomal constituents. In secretory granules of these cells, these cysteine proteinases may participate in the processing of the corresponding hormones from their precursor proteins.

Adenoma, Islet Cell↗
PubMed1989

Chromogranin A (CgA) in the gastro-entero-pancreatic (GEP) endocrine system. II. CgA in mammalian entero-endocrine cells.

Chromogranin A (CgA) and related acidic proteins are widely distributed in the organism. They are also present in entero-endocrine cells and in other members of the paraneuron family. Therefore, CgA has been claimed as an universal marker of this cellular community. To yield precise data about the distribution of CgA in entero-endocrine cells, all segments of the gastro-intestinal tract of five mammalian species (man, cattle, pig, cat, guinea-pig) were investigated immunohistochemically for CgA. In serial semithin plastic sections, all CgA-immunoreactive endocrine cells were identified for resident amines or peptides. CgA could be found in ten hormonally identified endocrine cell types and in two or three other endocrine cell types. Entero-endocrine cells containing amines (histamine, serotonin) regularly exhibited CgA-immunoreactivities. In contrast, peptide-containing endocrine cells were largely heterogeneous: Their CgA-immunoreactivities varies among the species, among the gastro-intestinal segments, and even among the members of the same cell population. Hence, seen histochemically, CgA is no universal marker for entero-endocrine cells. Seen biochemically, the observed heterogeneities of CgA-immunoreactivities theoretically can be attributed to various factors (species-specificities of CgA, subclasses of chromogranins, processing of CgA or its pro-protein). Most probably, these heterogeneities are caused by species- or cell-specific differences in the extent of processing of CgA. In addition, some findings point to certain interrelations between the processing or storage of CgA and resident peptides in the secretion granules of enteroendocrine cells.

Animals↗
PubMed1989

Immunohistochemistry of chromogranin A and B, and secretogranin II in the canine endocrine pancreas.

The chromogranins are large acidic proteins contained in secretion granules of adrenal medullary cells. These proteins are also presumed to be regular constituents of other endocrine cells, e.g., pancreatic endocrine cells. In our previous immunohistochemical studies performed in the endocrine pancreas of 10 mammalian species, only canine endocrine cells lacked any immunoreactivity for chromogranin A. Therefore, this problem was reinvestigated in the present study. Antisera against bovine and rat chromogranin A, B, and C (= secretogranin II) were applied under various conditions of the immunohistochemical protocol. Upon meeting certain requirements, chromogranin-immunoreactivities were found also in canine pancreatic B- (insulin), PP- (pancreatic polypeptide), and EC- (enterochromaffin) cells. The immunohistochemical data suggest that canine chromogranins partially differ structurally or immunologically from bovine chromogranins and completely from rat chromogranins. In addition, the present findings confirm our previous findings about both interspecies differences in the cellular localization of chromogranins in the endocrine pancreas and the peculiar localization of secretogranin II to pancreatic PP-cells. Finally, the present methodological studies have shown that even the buffer used in the immunohistochemical protocol may be decisive for a false-positive or false-negative immunostaining.

Adrenal Medulla↗
PubMed1989

Chromogranins in mammalian GEP endocrine cells: their distribution and interrelations with co-stored amines and peptides.

Chromogranins (Cg) are large acidic proteins, co-stored with amines or peptides in the secretory granules of a wide variety of paraneurons. By immunohistochemistry performed on serial semithin sections, the distribution of Cg in the gastroenteropancreatic (GEP) system was analyzed in the endocrine pancreas of 10 mammalian species and in enteroendocrine cells of 6 species. Of the Cg families, CgA is primarily localized in GEP endocrine cells. CgA was regularly present in amine containing cells (EC and EC-like cells). In 11 other endocrine cell types, CgA-immunoreactivities showed inter-species and intra-species variations in their distribution or in the intensity of staining. However, no endocrine cell type lacked CgA-immunoreactivities in all species investigated. Findings from extended studies indicate that CgA is involved in the intracellular storage of resident amines, and in the storage of newly formed amines after exogenous application of the corresponding precursors. Finally, densitometric findings on possible reciprocal relationships between CgA- and peptide-immunoreactivities suggest that CgA also participates in the intragranular storage of peptide hormones in certain GEP endocrine cells.

Amines↗
PubMed1988

Heterogeneities of the islets in the rabbit pancreas and the problem of "paracrine" regulation of islet cells.

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 intra-islet "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 micron) 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 primarily 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.

Aging↗
PubMed1988

Cellular distribution and amount of chromogranin A in bovine endocrine pancreas.

We determined the cellular distribution and the amount of chromogranin A in endocrine cells of bovine pancreas using a polyclonal antibody against bovine adrenomedullary chromogranin A. The relative amounts of chromogranin A in the different cells of the endocrine pancreas were determined by computer-assisted analyses of the optical densities of the immunoreactivities in the stained sections. More than 80% of the immunoreactive chromogranin A was located in the pancreatic B-cells. In immunoblots of acid tissue extracts, only one chromogranin A band (MW 74 KD) was observed. Quantification of the immunoblots revealed that 3 micrograms of chromogranin A and 918 micrograms of insulin were present per gram pancreas (wet weight), equivalent to a molar ratio of 460 mumol chromogranin A per mol insulin.

Animals↗
PubMed1988

Cytology and arrangement of enterochromaffin (EC) cells in the human stomach.

Serotonin containing enterochromaffin (EC) cells in the human gastric mucosa were observed using serial semithin sections immunostained by Sternberger's PAP method and reconstructed by computer-assisted methods. In oxyntic glands, EC cells displayed a marked pleomorphism which suggests their plasticity or active movement. They sometimes possessed multipolar cytoplasmic processes directly contacting the neighboring epithelial cells and/or gastric lumen. In the antropyloric glands, they are exclusively the "closed-type," which fails to contact the lumen, and are often arranged touching other EC cells (cluster formation), apparently exhibiting polynuclear enterochromaffin syncytia. This syncitium-like arrangement is interpreted as the morphological counterpart of a possibly synchronized function of these cells. The morphological differences of EC cells in their shape, luminal endings and arrangement between both regions may be indicative of regional differences in their functions. Furthermore, the present study provides the first three-dimensional visualization of EC cells in the human stomach.

Chromaffin System↗
PubMed1987

Immunological characterization of chromogranins A and B and secretogranin II in the bovine pancreatic islet.

Antisera against chromogranin A and B and secretogranin II were used for analysing the bovine pancreas by immunoblotting and immunohistochemistry. All three antigens were found in extracts of fetal pancreas by one dimensional immunoblotting. A comparison with the soluble proteins of chromaffin granules revealed that in adrenal medulla and in pancreas antigens which migrated identically in electrophoresis were present. In immunohistochemistry, chromogranin A was found in all pancreatic endocrine cell types with the exception of most pancreatic polypeptide-(PP-) producing cells. For chromogranin B, only a faint immunostaining was obtained. For secretogranin II, A- and B-cells were faintly positive, whereas the majority of PP-cells exhibited a strong immunostaining for this antigen. These results establish that chromogranins A and B and secretogranin II are present in the endocrine pancreas, but that they exhibit a distinct cellular localization.

Adrenal Medulla↗