Biomedical subjects

M H Greider

Publications and source records attributed to M H Greider.

At least 19 recordsLinked to original sources

PubMed1987

Enhanced preservation of endosecretory granules in PP-cells of the canine pancreas.

Standard fixation techniques commonly used for light and electron microscopic studies have resulted in reported differences in the ultrastructural appearance of endosecretory granules of the pancreatic polypeptide (PP) cell. To clarify these differences, canine pancreatic tissues of intact and cultured pseudoislets were studied using a variety of ingredients, additives and fixatives in an effort to better preserve the endosecretory granules of PP cells. Results show that preservation of PP granules is enhanced by addition in zinc chloride (0.5%) to a glutaraldehyde-paraformaldehyde fixative in 0.1 M cacodylate buffer, followed by osmium tetroxide fixation. This fixative is recommended for all light and electron microscopic studies of the pancreatic polypeptide cell.

Animals↗

PubMed1979

Studies of the functional and morphologic status of islets maintained at 24 C for four weeks in vitro.

Isolated rat islets were maintained in vitro at 24 C for 1-4 weeks in tissue culture medium containing D-glucose (1.5 mg/ml). The rate of insulin release at 24 C remained stable for three weeks (2.2 muU/islet/hr) and decreased to 1.2 muU/islet/hr during the fourth week. Increasing the temperature from 24 C to 37 C at the end of 1, 2, 3, or 4 weeks produced a 5--7-fold increase in the rate of insulin release in the presence of glucose (1.5 mg/ml). This rate of secretion was comparable to control islets maintained at 37 C for 1--4 weeks. Light- and electron-microscopic studies revealed minimal central necrosis of large islets maintained at 24 C for 3 weeks. In contrast, extensive central necrosis was present in large islets maintained at 37 C for only 1 week. Degranulation of B cells occurred at 24 C with almost complete degranulation at 28 days. Regranulation occurred when the temperature was increased to 37 C. These findings indicate that isolated islets maintained at 24 C remain functionally and morphologically intact for 4 weeks. Initial studies have shown that maintenance of islets at 24 C for 1 week in conjunction with a single injection of antilymphocyte serum will produce marked prolongation of survival of islet allografts. The finding that isolated islets will survive for prolonged periods of time at 24 C should be of importance to future studies on islet transplatation, immune rejection, and investigations on hormonal release from islets maintained under these conditions.

Animals↗

PubMed1979

Regional distribution and concentration of pancreatic polypeptide in the human and canine pancreas.

The regional concentrations of pancreatic polypeptide (PP), insulin, and glucagon and the cellular distribution of PP were studied in 13 human and nine canine pancreases by radioimmunoassay, immunoperoxidase localization, and cell quantitation. PP concentration was highest in both the uncinate process and the head of the human pancreas and in the right lobe of the canine pancreas. In contrast, glucagon and insulin levels were higher in the body and tail of both the human and canine pancreases. Human F-cells, which contain PP, were located primarily at the periphery of the islets, although a few F-cells were scattered throughout the ducts and acini. Canine F-cells were located in ducts, acini, and islets; the relative proportion of canine F-cells in the endocrine and exocrine tissues differed according to location. Cellular quantitation of F-cells in both species correlated significantly with the tissue concentration of PP in all regions studied, validating the use of morphometric techniques to quantitate the regional distribution of PP.

Adult↗

PubMed1978

Elevated levels of pancreatic polypeptide in obese-hyperglycemic mice.

The concentration and distribution of pancreatic polypeptide (PP) was studied in hyperglycemic obese (ob/ob) mice and homozygous (+/+) controls. By radioimmunoassay, the concentration of PP in the pancreas of ob/ob mice was greater both in the duodenal lobe (70.7%) and in the body and tail (66.3%) when compared to identical areas of control pancreases. Analysis of immunostained pancreatic tissue indicated that the number of PP cells per islet cross-section was significantly increased (58%) in the ob/ob tissue. The calculated total number of PP cells per average islet was elevated three times in the ob/ob islet. However, the proportion PP cell volume relative to the islet volume in ob/ob was one-half that of control islets. These results clearly demonstrate an elevation in both the number of PP cells per islet and the concentration of PP in the diabetic ob/ob murine pancreas.

Animals↗

PubMed1978

Ultrastructural localization of pancreatic polypeptide in the F cell of the dog pancreas.

The F cell of the dog pancreas has been identified as the specific cell type containing pancreatic polypeptide. This localization of pnacreatic polypeptide was accomplished by immunocytochemical staining of ultrathin sections and direct electron microscopic identification. Verification of the specificity of the reaction was obtained by blocking experiments on serial sections of the same cell. It is proposed that the name F cell be used for defining in all species the islet cell that contains pancreatic polypeptide.

Animals↗

PubMed1977

Pancreatic perinuclear inclusions in diabetes mellitus and other diseases.

Unusual perinuclear inclusions in pancreatic duct cells were observed by electron microscopy in 23 diabetic pancreases, in nine pancreases with islet hyperplasia, and in 10 of 27 pancreases without islet pathology. The origin and significance of the perinuclear inclusions could not be determined, but it is suggested that they may be of viral origin or may represent a cellular response to an unknown stimulus.

Adolescent↗

PubMed1977

The gastrin-producing cells in tissue cultures of the rat pyloric antrum.

Tissue culture methods were used to study the gastrin-producing cells isolated from the pyloric antral mucosa of rats. Cultures were maintained for up to 7 days. Gastrin cells were identified by means of immunofluorescent and unlabeled antibody-enzyme techniques. The tissue culture medium was monitored for basal gastrin secretion. In addition, stimulation of gastrin release was achieved by the use of dibutyryl cyclic-AMP and theophylline. This is the first report of the successful application of tissue culture methods to the functional study of antral gastrin cells. The procedure has proven to be useful in assessing the mechanisms of gastrin secretion.

Adenosine Monophosphate↗

PubMed1976

Gastrin in the perinatal rat pancreas and gastric antrum: immunofluorescence localization of pancreatic gastrin cells and gastrin secretion in monolayer cell cultures.

The presence and development of immunoreactive gastrin (IRGa) in the fetal and neonatal pancreas and pyloric antrum of the rat were studied. IRGa appeared in both organs at least as early as the 16th day of fetal life. Antral IRGa increased rapidly and continuously in the neonatal period, while pancreatic IRGa concentration increased and was maintained at a relatively constant level from days 5 to 35. Monolayer cell cultures of the neonatal rat pancreas were used to evaluate the role of cyclic AMP mediated release of gastrin. The addition of N6,O2'-dibutyryl cyclic AMP (4 mM) or theophylline (4 mM) to the culture medium induced significant release of gastrin. The stimulation of adenylate cyclase with cholera toxin (10 ng/ml) also resulted in significant gastrin release. Long-term cultures (18-24 days) were shown to release gastrin continuously at a relatively constant rate. The cellular localization of pancreatic gastrin in 7-day-old cultures was performed by immunological techniques, using fluorescein-labeled antibodies to gastrin. The gastrin-containing cells were located at the periphery of most of the endocrine cell clusters. Immunofluorescence techniques for insulin and glucagon also showed that the alpha cells had a similar peripheral distribution, although they were more frequent in number. In contrast, insulin-containing cells were numerous and were present in all areas of the endocrine cell clusters. The studies support the following conclusions: a) Gastrin is present in the rat pancreas, even as early as late fetal life; b) Gastrin-producing cells are present and functionally competent in monolayer cell cultures of the neonatal rat pancreas for prolonged periods of time (24 days); c) Gastrin is released from these cells when intracellular levels of cyclic AMP are increased; d) By immunofluorescence methods, the gastrin-producing cells in pancreatic cell cultures are found to be located at the periphery of the endocrine cell clusters.

Animals↗

PubMed1974