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A Perrelet

Publications and source records attributed to A Perrelet.

At least 73 records · Page 4Linked to original sources
PubMed1980

Opposite polarity of filipin-induced deformations in the membrane of condensing vacuoles and zymogen granules.

Filipin binding to membrane sterols induces deformations of the membrane that are detected by freeze-fracture either as 20- to 25-nanometer protuberances or as pits on the fracture faces. By using the filipin probe in pancreatic acinar cells, it was found that the polarity of filipin-induced deformations in the membrane limiting the Golgi condensing vacuoles is opposite that in the membrane limiting the mature zymogen granules. This asymmetry could be due to unequal partitioning of cholesterol between the membrane leaflets in these two compartments during the transformation of the condensing vacuole into the zymogen granule.

Cholesterol↗
PubMed1980

Gap junction development is correlated with insulin content in the pancreatic B cell.

The development of gap junctions between insulin-containing B cells was quantitatively analyzed in islets of Langerhans isolated from rats treated with the sulfonylurea glibenclamid for 1, 2, or 7 days. Glibenclamid treatment was associated with a marked depletion of the insulin content of B cells and with an increase in the number and size of gap junctions between these cells. A significance correlation was found between these two events.

Animals↗
PubMed1980

Distribution of filipin-cholesterol complexes at sites of exocytosis - a freeze-fracture study of degranulating mast cells.

The distribution of membrane cholesterol at sites of exocytosis was studied with the cytochemical probe, filipin, in freeze-fractured rat peritoneal mast cells. When degranulation was induced in mast cells by polymyxin B, the membrane of all secretory granules, as well as the plasma membrane, including bulged areas signaling incipient exocytosis, appeared heavily labeled with filipin-sterol complexes (recognizable as 25-nm protuberances). This is evidence that cholesterol depletion is not an absolute requirement for membrane fusion.

Animals↗
PubMed1980

Nonrandom distribution of gap junctions between pancreatic beta-cells.

The numerical and spatial distribution of gap junctions between insulin-containing cells (beta-cells) under resting and stimulated conditions of insulin secretion were quantitatively analyzed in freeze-fracture replicas of isolated rat islets of Langerhans. The results show that the beta-cells located at the periphery of the islet have twice as many gap junctions per unit membrane area as the beta-cells situated in the islet center. In both locations, gap junctions assumed a nonrandom clustering on the beta-cell membranes. During stimulation of insulin secretion, the gap junctions were found increased between the central and between the peripheral beta-cells. The degree of their clustering was also modified. The latter change depended both on the location of the gap junctions in the islet and on the type of stimulation used (high glucose or glibenclamide).

Animals↗
PubMed1980

Quantitative immunocytochemical localization of pancreatic secretory proteins in subcellular compartments of the rat acinar cell.

The recently developed protein A-gold technique for the detection of intracellular antigenic sites on thin sections was utilized to localize nine different secretory proteins in the rat exocrine pancreas. Amylase, chymotrypsinogen, trypsinogen, lipase, elastase, carboxypeptidases A and B, RNase and DNase, were detected at the level of the rough endoplasmic reticulum, the Golgi area, and the zymogen granules of the acinar cells, as well as in the acinar lumen. A quantitative evaluation of the labeling showed that its intensity was not identical for all enzymes studied nor in all cellular compartments analyzed. An increasing gradient of the labeling from the rough endoplasmic reticulum to the Golgi and to the zymogen granules was found for amylase, carboxypeptidases A and B, chymotrypsinogen, trypsinogen, and RNase, while a comparable low degree of labeling in the Golgi apparatus and in the zymogen granules was observed for DNase, lipase, and elastase. These results suggest that the nine enzymes are processed through the same intracellular compartments, but that they may be concentrated to different degrees in the zymogen granules before being released in the acinar lumen.

Animals↗
PubMed1980

Gap junctions and B-cell function.

The development of gap junctions between pancreatic B-cells was quantitatively assessed in freeze-fracture replicas of isolated rat islets under various conditions of insulin secretion. Stimulation of insulin secretion by glucose in vitro and by glibenclamide in vivo raised the number of gap junctions between B-cells; glibenclamide alone caused an increase in the size of individual gap junctions. In addition, gap junctions of control and stimulated B-cells showed a packing of particles different from that observed under experimental conditions causing functional uncoupling. The results suggest that gap junctions (and probably coupling) are involved in the secretory activity of B-cells.

Animals↗
PubMed1979

Endocrine pancreas: three-dimensional reconstruction shows two types of islets of langerhans.

Three-dimensional reconstructions of islets of Langerhans, based on immunofluorescent staining of successive serial sections with antiserums to insulin, glucagon, somatostatin, and pancreatic polypeptide reveal a marked difference in the number of cells containing glucagon and pancreatic polypeptide depending on the anatomical location of the islet in the pancreas. The two types of islets are situated in regions of exocrine tissue that are drained by different excretory ducts. This demonstration contradicts the assumption that all islets in the pancreas are similar in their endocrine cell content.

Animals↗
PubMed1979

Pancreatic fat.

Explore the source record for details and available documents.

Adipose Tissue↗
PubMed1979

Inhomogeneity of surface labelling of B-cells at prospective sites of exocytosis.

Using ferritin-labelled Ricinus communis agglutinin to detect lectin-binding sites of the pancreatic B-cell surface, we show that limited regions of the plasma membrane are deprived of lectin-binding sites over marginated secretory granules. Such deprived regions increased during glucose stimulation of B-cells in monolayer culture: 56 +/- 8 of them were found in high (300 mg/100 ml) glucose as compared to only 27 +/- 5 in low (50 mg/100 ml) glucose (p less than 0.005). In addition, non-membrane, intracytoplasmic bridges were detected between the plasma membrane and the membrane of the marginated granule suggesting the involvement of cell web components in promoting the change in surface labelling.

Animals↗
PubMed1979

Identification of a lobe in the adult human pancreas rich in pancreatic polypeptide.

Systematic sampling of human necropsy pancreases has revealed that pancreatic polypeptide (PP) cells are not distributed equally in the gland. PP-cells are the most abundant cell type in the posterior part of the pancreatic head while they are scarce or absent in the remainder of the gland. The PP-rich part of the head can be separated by blunt dissection from the pancreas as a discrete lobe. This lobe probably originates from the ventral pancreatic bud during embryogenesis. A quantitative study of the immunofluorescent endocrine cell types (insulin, glucagon, somatostatin and pancreatic polypeptide cells) in PP-rich and PP-poor regions of pancreases in 8 subjects with ages ranging from 33 fetal weeks to 80 years, showed that the proportions of the cell types were different in youngs and adults.

Adult↗
PubMed1979

Absence of filipin-sterol complexes from large coated pits on the surface of culture cells.

Monolayer cultures of normal or transformed fibroblasts and of liver cells fixed in a glutaraldehyde solution containing 300 microM filipin, a sterol-specific polyene antibiotic, were freeze-fractured to study the distribution of cholesterol within their plasma membranes. Filipin-sterol complexes, recognizable as 25- to 30-nm protuberances scattered in the fracture face of plasma membrane, were absent from invaginations corresponding to large, bristle-coated pits (and possibly also from small, flask-shaped invaginations). These results suggest that invaginating regions on the cell surface are specialized plasma membrane domains with a lower cholesterol content than the surrounding membrane. The localized change in membrane fluidity due to the low cholesterol concentration could play a role in endocytosis.

Animals↗
PubMed1979

Increase of gap junctions between pancreatic B-cells during stimulation of insulin secretion.

The development of gap junctions between pancreatic B-cells was quantitatively assessed in freeze-fracture replicas of isolated rat islets under different conditions of insulin secretion. The results show that in resting B-cells, gap junctions are small and scarce but that these junctions increase when insulin secretion is stimulated. Both a short (90 min) stimulation by glucose in vitro and a prolonged (2.5 d) stimulation by glibenclamide in vivo raise the number of gap junctions; in addition, the glibenclamide stimulation causes an increase in the size of individual gap junctions. As a consequence, the total area occupied by gap junctions on the B-cell membrane and the ratio of this area to the cell volume were found significantly increased in the latter condition. The slight increase of these values observed after the glucose stimulation did not reach significance. These data indicate a change of gap junctions during the secretory activity of the pancreatic B-cells. The possibility that the coupling of the cells is affected by the treatment is discussed.

Animals↗
PubMed1978

Orthogonal arrays of particles in plasma membranes of the gastric parietal cell.

Freeze-fracture of rat gastric mucosa revealed a specific set of intramembranous particles in the plasma membrane of the parietal cells. The particles were small and of square shape and formed orthogonal arrays in the P-face with corresponding orthogonal arrays of pits in the E-face. Arrays, scattered among usual globular particles, were particularly numerous at the basal pole of the cell and less concentrated on the lateral side. They were not present in the apical microvillar membrane nor in the membranes of intracellular tubulovesicles. As in other cell types in which similar arrays were described previously (e.g., astrocytes, "light" cells of the kidney collecting tubule), their presence in parietal cell membranes suggest some specialized function of these membranes not shared by plasma membranes showing only a population of globular particles. This function has yet to be identified.

Animals↗