Search PubMed⌕ Search

Biomedical subjects

W L Chick

Publications and source records attributed to W L Chick.

At least 55 records · Page 3Linked to original sources
PubMed1987

Multipotential phenotypic expression of genes encoding peptide hormones in rat insulinoma cell lines.

The developmental origin of the four phenotypically distinct hormone-producing islet cells (insulin, glucagon, somatostatin, pancreatic polypeptide) is unclear. To investigate the potential for phenotypic differentiation of islet cells, we prepared several clonal cell lines from a radiation-induced rat islet tumor and analyzed them for insulin, glucagon, and somatostatin gene expression by cDNA hybridization, immunocytochemistry, and radioimmunoassay. We found expression of all three genes in the tumor and in the parental cell line and mixed variable phenotypes in the clonal lines derived from the parental line. We also observed the ectopic expression of the angiotensinogen gene in the tumor and the cell lines. The relative levels of hormonal gene expression differed among the cell lines but remained fixed during continuous passage. The three islet hormone mRNAs were larger compared to the pancreas owing to longer poly(A) tracts. These observations indicate that neoplastic islet cells retain the potential to differentiate into hormone-specific cellular phenotypes and may mimic developmental pathways of the pancreatic islets.

Adenoma, Islet Cell↗
PubMed1985

111Indium-labelled lymphocytes do not image or label the pancreas of the BB/W rat.

Autologous transfusions of 111indium-labelled peripheral blood lymphocytes reportedly image the pancreas of patients with Type 1 (insulin-dependent) diabetes at the time of onset. We attempted to apply this technique to the spontaneously diabetic BB/W rat. First, acutely diabetic BB/W rats, diabetes-prone BB/W rats, diabetes-resistant W-line BB/W rats, and Wistar Furth rats were given autologous transfusions of labelled peripheral blood lymphocytes. Radioactivity recovered from the pancreas was similar in all groups. No correlation was found between the intensity of imaging and the presence or intensity of insulitis. To decrease non-specific intravascular radioactivity, acutely diabetic, diabetes-prone, and W-line rats were perfused 48 h after autologous transfusion of labelled lymphocytes. Again, the intensity of recovered activity was similar in all groups, using both macroautoradiography and numerical counting techniques. A second set of experiments studied diabetes and insulitis induced by passive transfer of concanavalin A-treated splenic lymphocytes from acutely diabetic donors. Activated lymphocytes were labelled with 111Indium and given to groups of diabetes-prone and diabetes-resistant rats. There were no differences in pancreatic localization 72-96 h after injection. Groups of diabetes-prone and diabetes-resistant rats were also given concanavalin A-activated lymphocytes and then challenged 2-10 days later with autologous transfusions of labelled peripheral blood lymphocytes. Again, no differences in organ labelling or imaging were detected. We conclude that the autologous transfusions of 111indium-labelled lymphocytes do not label or image the pancreas of the BB/W rat.

Acute Disease↗
PubMed1985

Passive transfer of diabetes from BB/W to Wistar-Furth rats.

Autoimmune diabetes can be transferred to young, diabetes prone BB/W rats by injecting them intravenously with concanavalin A (Con A)-treated spleen cells from acute diabetic BB/W donors. This study describes the transfer of diabetes to the normal Wistar-Furth strain of rats using a similar procedure. For the successful transfer of diabetes it was necessary to immunosuppress recipient animals with a single intraperitoneal injection of cyclophosphamide 24-48 h before administering Con A-stimulated spleen cells from acute diabetic BB/W rats. Of 68 Wistar-Furth rats in immunosuppressed with a dose of 100-150 mg cyclophosphamide/kg body wt, 10 (15%) became diabetic. None of the control rats receiving either Con A-stimulated Wistar-Furth spleen cells (n = 28), freshly isolated BB/W spleen cells (n = 14), or fresh RPMI medium (n = 11) became diabetic. These data indicate that diabetes can be transferred from BB/W to Wistar-Furth rats. In addition, they support the hypothesis that cell-mediated immune processes are involved in the development of insulin-dependent diabetes and rule out any absolute requirement for BB-derived genes in the target pancreatic beta cells.

Animals↗
PubMed1985

Biohybrid artificial pancreas. Long-term insulin secretion by devices seeded with canine islets.

Long-term insulin secretion was investigated in seven biohybrid capillary devices seeded with canine islets. Approximately 50,000 islets could be isolated from a single canine pancreas using collagenase digestion in conjunction with the recently described Velcro technique. Devices were perfused with tissue culture medium 199 containing 300 mg/dl glucose. Insulin secretion fell during the first 1-2 days of culture from approximately 18 to 6 U/day. After 3-4 wk of perfusion, however, there was a gradual rise in insulin output that reached greater than 15 U/day after 7 wk. Insulin output eventually stabilized at 18-20 U/day. Two of these devices were studied for 80 and 86 days, respectively, and continued to secrete these same amounts of insulin. Glucose-induced insulin release was studied after 1 and 4 wk of culture and was well preserved.

Animals↗
PubMed1984

Contrasting patterns of insulin biosynthesis, compartmental storage, and secretion. Rat tumor versus islet cells.

A series of 3H-leucine pulse-labeling experiments was carried out with dispersed cells freshly isolated from transplanted rat insulinomas. After secreted fractions were separated, insulin was purified and specific activities were determined for both secreted and average cellular insulins. Labeling patterns in this line of tumor cells were compared with those previously established for isolated rat islets. With both tumors and islets, conversion of labeled proinsulin to insulin occurred to the same extent by 2.5 h, suggesting similar onset and half-time of proteolysis in these cells. However, total cellular insulin in tumors attained a threefold higher specific activity than in islets. Because total B-cell mass in these tumors was unknown, either a more rapid proinsulin biosynthesis or diminished cellular storage (or both) could lead to this faster fractional replacement of total stored insulin. Insulin secretion in these tumor cells was insensitive to high glucose but responded, albeit poorly, to leucine plus 3-isobutyl-1-methylxanthine (IBMX). Under all secretory conditions tested, tumor cells continuously secreted insulin at elevated fractional rates, which were slightly higher than fractional insulin secretory rates in maximally glucose-stimulated islets. In contrast with normal islets, newly synthesized insulin was stored homogeneously in tumor cells, and compartmental storage characteristics were not generated by incubation with either 20 mM glucose or leucine plus IBMX in the marking period. Thus, preferential secretion of insulin was never observed in tumor cells.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-3-isobutylxanthine↗
PubMed1983

Identification and significance of glucokinase in transplantable insulinomas.

Glucose 6-phosphotransferases were investigated in two transplantable rat insulinoma tumor lines. Homogenates of tumors contained glucose phosphorylating activities of both high (e.g. supernatant Km = 0.060 mM and pellet Km = 0.077 mM) and low (Km = 7.6 mM) affinities for glucose. Chromatography of supernatants (105,000 X g) of insulinomas on DEAE-Cibacron Blue F3GA agarose evidenced glucose 6-phosphotransferase activity which eluted similarly to glucokinase from rat liver. Kinetic studies of insulinoma glucokinase also indicated similarity with liver glucokinase, i.e. cooperative rate dependence on glucose concentration and comparable Km values for glucose, and it did not phosphorylate N-acetylglucosamine. These characteristics of glucose 6-phosphotransferase in insulinomas are similar to those of the enzyme found in islets of Langerhans. Since glucokinase is thought to serve as glucose sensor of insulin secretory pancreatic beta-cells, these transplantable insulinomas offer great promise for biochemical and biophysical studies of the nature of glucose-induced insulin release.

Adenoma, Islet Cell↗
PubMed1981

Insulin secretion by a transplantable rat islet cell tumour.

Investigation of the subcellular and molecular components of insulin secretion has been made difficult by the small quantities of material available. The recent development of a transplantable rat islet cell tumour of high insulin content and state of differentiation suggested a system more amenable to analysis. To validate the tumour as a model of secretion we have studied its release of insulin. In acute experiments in vitro immunoreactive insulin release was increased by leucine, glucagon, theophylline and dibutyryl cyclic AMP, though not by glucose. Leucine (20 mmol/l) plus theophylline (5 mmol/l) caused an abrupt, sustained and rapidly reversible stimulation of two- to fivefold. The response was inhibited by antagonists of cellular oxidative phosphorylation (cyanide, 2,4-dinitrophenol, antimycin A), calcium flux (EGTA, verapamil, Mg2+), calmodulin (trifluoperazine), microtubules (vinblastine, colchicine) and by adrenaline and somatostatin. These findings suggest that the tumour secretes insulin by an exocytotic mechanism similar to that of normal islet tissue.

Adenoma, Islet Cell↗
PubMed1981

Transfer plate radioassay using adsorbed anti-insulin antibody to detect insulin secreted by islet cell cultures.

A solid-phase radioimmunoassay for detection of insulin synthesized by islet cell clones is described. This assay employs anti-insulin antibody adsorbed onto fenestrated polyvinyl chloride 96-well plates ('transfer plates'). The calibrated aperture in the bottom of each transfer plate well permits fluid to enter the wells when transfer plates are lowered into microculture wells containing insulin. With this assay it is possible to rapidly screen hundreds of islet cell cultures for insulin production. We have used this assay to facilitate cloning of the RIN rat insulinoma cell line. The assay readily detects insulin synthesis by RIN cells and [125I]insulin is not displayed by culture medium from cells which do not produce insulin. The transfer plate format should be applicable to semiautomate other radioimmunoassays.

Adsorption↗
PubMed1981

Hormones and factors that stimulate growth of a rat islet tumor cell line in serum-free medium.

A number of hormones and factors were found to stimulate growth of cultured rat islet tumor cells, the RIN-r cell line. A serum-free supplemented medium from RIN-r cells was formulated. It consisted of a 1:1 mixture of Ham's F12 and DME media with the addition of insulin, transferrin, triiodothyronine, prolactin, growth hormone, and an extract of proteose peptone (medium IM). The growth rate of RIN-r cells in this medium is as great as it is in 10% serum-supplemented medium. Up to 10 populations doublings occurred over a period of 20 days. Insulin is a very effective mitogen for RIN-r cells and has an effect on concentrations as low as 30 ng/ml. In addition, the insulin-like somatomedin, multiplication stimulating activity (MSA), is a growth factor at 50 ng/ml. It was found that RIN-r cells proliferate and continue to produce immunoreactive insulin in a hormonally and nutritionally defined medium. This medium is derived from medium IM, in which insulin is replaced with MSA and proteose peptone is omitted. Variations of this medium may prove useful in studies on the growth and function of the normal islets in long-term primary culture.

Adenoma, Islet Cell↗
PubMed1980

Continuous, clonal, insulin- and somatostatin-secreting cell lines established from a transplantable rat islet cell tumor.

Continuous cell lines that secrete both insulin and somatostatin were established by two cooperating groups of investiagtors from a serially transplantable, radiation-induced, rat islet cell tumor. The cell lines, named RIN-r and RIN-m, were initiated from tumors maintained in inbred rats or in athymic nude mice, respectively. The cultured cells are epithelioid, free of fibroblast contamination, and can be cloned. They have a hypodiploid chromosome number, are tumorigenic, and posses amine-handling properties, including high levels of L-dopa decarboxylase and formaldehyde-induced fluorescence. Preliminary analysis of clones revealed a spectrum of insulin secretion from undetectable to relatively high. These clonal cell lines provide important systems to study the biology of insulin and somatostatin.

Adenoma, Islet Cell↗
PubMed1980

Serially transplantable chemically induced rat islet cell tumor.

A serially transplantable, chemically induced pancreatic islet cell tumor was developed in Lewis rats. The original tumor was induced by the administration of streptozotocin and nicotinamide. It was subsequently maintained by ip or sc transplantation of tissue fragments into recipient animals. Tumors generally grew to 0.5--2.0 cm in diameter within 3--4 months of transplantation. They were well encapsulated, without gross evidence of metastasis. Peroxidase immunocytochemical staining revealed a predominance of insulin-positive cells. Somatostatin-positive cells were also present and varied widely in numbers between different tumors. In addition, small numbers of glucagon-positive cells were observed in all of the tumors. On electron microscopy, cells containing secretory granules, indistinguishable from nonneoplastic beta-cells, were most abundant. Other granulated cells were also observed, but the granule morphology was not identical to that of any of the other classically described islet cell types. Tumor extracts contained an average of 3260 micrograms insulin, 22.6 micrograms somatostatin, and 0.84 micrograms glucagon per g wet wt of tissue. Tumors caused marked, progressive hypoglycemia in recipients, with plasma glucose levels frequently falling below 30 mg/dl before death. Furthermore, the recipients' islets were markedly reduced in size due to a decreased beta-cell volume.

Adenoma, Islet Cell↗
PubMed1978

A bacterial clone synthesizing proinsulin.

We have cloned double-stranded cDNA copies of a rat preproinsulin messenger RNA in Escherichia coli chi1776, using the unique Pst endonuclease site of plasmid pBR322 that lies in the region encoding amino acids 181-182 of penicillinase. This site was reconstructed by inserting the cDNA with an oligo(dG)-oligo(dC) joining procedure. One of the clones expresses a fused protein bearing both insulin and penicillinase antigenic determinants. The DNA sequence of this plasmid shows that the insulin region is read in phase; a stretch of six glycine residues connects the alanine at position 182 of penicillinase to the fourth amino acid, glutamine, of rat proinsulin.

Base Sequence↗
PubMed1978

Pancreatic beta-cell replication: relation to insulin secretion.

The relationship between beta-cell replication and insulin release was investigated utilizing neonatal rat pancreatic monolayer cell cultures. Glucose-induced insulin release was either inhibited using diazoxide or mannoheptulose, or potentiated using theophylline. The corresponding effects on the frequency of beta-cell replication were determined by incubating cultures with [3H]thymidine and estimating the frequency of beta-cell labeling in aldehyde thionine-stained radioautographs. beta-Cell replication and insulin release were shown to be dissociable processes in two ways. First, in the presence of diazoxide (1-100 microgram/ml), insulin release was inhibited by as much as 86%, while the frequency of beta-cell replication was not reduced. Second, in the presence of theophylline (1 mM), insulin release was increased by 23%, while beta-cell replication was inhibited. Finally, the inhibition of both beta-cell replication and insulin release by mannoheptulose (5.5 mM) indicated that glucose utilization may be important for both of these beta-cell processes.

Animals↗
PubMed1977

Artificial pancreas using living beta cells:. effects on glucose homeostasis in diabetic rats.

An artificial pancreas consisting of beta cells cultured on synthetic semipermeable hollow fibers was tested in rats with alloxan-induced diabetes. When implanted ex vivo as arteriovenous shunts in the circulatory system these devices lowered concentrations of plasma glucose from 533 to between 110 and 130 milligrams per 100 milliliters, increased concentrations of plasma insulin, and restored intravenous glucose tolerance tests essentially to normal.

Animals↗
PubMed1977

"Somatostatinoma": a somatostatin-containing tumor of the endocrine pancreas.

We studied the pancreatic and enteric hormone profile of a 46-year-old woman who had hyperglycemia and a pancreatic tumor. Before operation, there was no evidence of overproduction of glucagon or insulin. The tumor's ultrastructure had a distinctive endocrine morphology, resembling D cells. Prompted by the recent demonstration of somatostatin in D cells of pancreatic islets, we analyzed the tumor and found a large quantity of immunoreactive somatostatin (301 ng per milligram of tissue). Insulin, glucagon, gastrin, vasoactive intestinal polypeptide and human pancreatic polypeptide were present in only trace quantities. The tumor cells were cultured in monolayers, which remained viable up to 51 days and released somatostatin into the culture medium. In seven insulinomas and two glucagonomas, we found the somatostatin content either much lower (less than 0.6 ng per milligram of tissue) or undetectable. After complete resection of the tumor, our patient became euglycemic and has remained so for the past 20 months.

Cells, Cultured↗
PubMed1977

A transplantable insulinoma in the rat.

A transplantable insulinoma was developed in inbred albino rats of the NEDH strain. The original tumor, 1 cm in diameter, was removed from the pancreas of a male parabiont 566 days folowing 1000 rads (10J/kg) of total body x-irradiation. The time required for implanted fragments to grow to 0.5-1.5 cm in diameter decreased from 5-8 months in the first generation to 2-5 months in the seventh generation. Successful transplantation in male animals followed for 4 or more months after transplantation was significantly greater than in female animals followed for a similar period of time (96% versus 69%). Light and electron microscopy revealed that the tumors consisted predominantly of well-granulated beta cells. Ultrastructural studies also showed small numbers of D-cells. Tumor extracts contained an average of 223 units of immunoreactive insulin and 25.9 mug of immunoreactive somato-statin per gram wet weight of tissue. Tumors generally produced increasingly profound hypoglycemia within 2-4 months following transplantation, with plasma glucose levels frequently falling to 40 mg/100 ml or lower prior to death. Removal of tumors from chronically hypoglycemic animals resulted in transient rebound hyperglycemia with plasma glucose levels above 300mg/100 ml within the first 24 hr and a gradual decline to normal levels of 129 mg/100ml in 2-4 days. These observations correlated with findings of marked atropy and degranulation of the beta cells in the pancreata of tumor-bearing animals, and with gradual return of normal light microscopic morphology following tumor removal.

Adenoma, Islet Cell↗