PubMed Health⌕ Search

Biomedical subjects

D Grube

Publications and source records attributed to D Grube.

At least 19 recordsLinked to original sources
PubMed1992

Mutual relationships between chromogranins A and B and gastrin in individual gastrin cells.

The chromogranins A and B (CgA and CgB, respectively), originally detected in the adrenal medulla, are present in various endocrine organs. Remarkably, their immunoreactivities vary among different endocrine cell types and also within a given endocrine cell population. With densitometric techniques at the cellular level, individual gastrin cells (n = 318) from guinea pig antral mucosa were studied to measure their content of immunoreactive CgA, CgB, and gastrin. The composition of these secretory proteins in individual gastrin cells varied considerably but with predictable components. Statistical evaluation of the data showed that immunoreactivities for gastrin and CgA correlated negatively in these cells; CgA and CgB immunoreactivities also correlated inversely. On the other hand, immunoreactivities for gastrin and CgB exhibited a high positive correlation. The mutual relationships between gastrin, CgA, and CgB suggest that under physiological conditions biosynthetic pathways of these secretory constituents are linked to each other in individual gastrin cells.

Animals↗
PubMed1992

The microanatomy of canine islets of Langerhans: implications for intra-islet regulation.

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 microns) 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.

Animals↗
PubMed1992

Serotonin storage and chromogranins: an experimental study in rat gastric endocrine cells.

Chromogranins (Cg) and secretogranins (Sg) are acidic proteins localized in the secretory granules of a large variety of endocrine cells collectively named APUD cells (amine precursor uptake and decarboxylation). To examine the possible function of Cg/Sg as amine storage proteins, enteroendocrine cells of the rat gastric antral mucosa, i.e., serotonin-containing enterochromaffin (EC)-cells, gastrin (G)-, and somatostatin (D)-cells, were investigated immunohistochemically in serial semi-thin sections of controls and after intervention in serotonin synthesis. CgA and CgB immunoreactivity was determined semiquantitatively by optical density measurements. Experiments included inhibition of serotonin synthesis by p-chlorophenylalanine (pCPA), exogenous application of the serotonin precursor 5-hydroxytryptophan (5-HTP), and a combination of both treatments. The cellular distribution of Cg and the density of its immunoreactivity were closely related to the primary content of serotonin and the ability to store serotonin after 5-HTP application. Thus, Cg may act as amine-binding proteins in enteroendocrine cells, binding most probably being due to ionic interactions between Cg and the biogenic amines. EC- and G-cells, however, differed in their amine-handling properties and in the response of their Cg immunoreactivity after intervention in serotonin synthesis. We conclude, therefore, that the physiological function of Cg as amine storage proteins is restricted to endocrine cells with an endogenous content of amines. In other endocrine cells, exhibiting only a potential amine production, APUD may be considered as a kind of supravital staining without physiological significance.

5-Hydroxytryptophan↗
PubMed1992

[Synaptophysin in the nervous system and endocrine cells].

Synaptophysin is a major integral membrane glycoprotein of neuronal synaptic vesicles that is present in virtually all synapses and shows a high degree of evolutionary conservation in mammalian species. It has also been detected in numerous endocrine cell types where it is localized in the membrane of small synaptic-like vesicles which are thought to constitute a previously unknown secretory pathway. Antibodies directed against synaptophysin are a valuable tool for the immunohistochemical quantitation of synapses. Moreover, synaptophysin is a most reliable and specific marker molecule for normal and neoplastic neuroendocrine cells. In the nervous system, synaptophysin-positive tumors comprise ganglioneuromas, ganglioneuroblastomas, neuroblastomas, paragangliomas and primitive neuroectodermal tumors.

Animals↗
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↗
PubMed1979

The Merkel cell--a member of the APUD cell system. Fluorescence and electron microscopic contribution to the neurotransmitter function of the Merkel cell granules.

Merkel cells of sinus hair follicles of nude mice were investigated by fluorescence and electron microscopy following pretreatment with amine precursors (L-Dopa, L-5-Hydroxytryptophan) and monoaminoxidase-inhibitors (Marsilid, Harmaline). Neither in control animals nor in pretreated animals any evidence for an involvement of Merkel cells in monoamine metabolism could be found. Therefore, the hypothesis that Merkel cells might share the most constant cytochemical characteristics of the cells of the APUD series, i.e., to take up amine precursors, should definitely be left. Following Harmaline treatment, however, Merkel cells were found fluorescent; cytophotometric analysis of the fluorescence emission spectra of formaldehyde-treated tissue ascertained that this fluorescence was due merely to a specific Harmaline fluorescence. The significance of Harmaline uptake in Merkel cells, most probably in the Merkel cell granules, is discussed.

5-Hydroxytryptophan↗
PubMed1978

Pancreatic glucagon cells contain endorphin-like immunoreactivity.

Semithin and thin serial sections of rat pancreas were investigated by immunocytochemical techniques using antisera against glucagon and endorphin. The immunocytochemical staining methods revealed that in the rat endocrine pancreas endorphin-like immunoreactivity is contained in glucagon (A-) cells. All secretion granules of glucagon cells that could be identified in adjacent thin sections exhibited glucagon as well as endorphin immunoreactivity. Since glucagon cells are devoid of ACTH-like immunoreactivity it is concluded that the biosynthetic pathway of pancreatic endorphin is not the same as in the pituitary.

Animals↗