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Biomedical subjects

J C Thompson

Publications and source records attributed to J C Thompson.

At least 307 records · Page 17Linked to original sources
PubMed1987

Somatostatin secretion in cultured human islet cells from patients with nesidioblastosis: a compensatory mechanism?

Two patients with nesidioblastosis, one with persistent hypoglycemia and another who was asymptomatic, underwent pancreatic resection. Dispersed pancreatic islets were prepared from each patient. Insulin secretion from cultured islet cells was increased and somatostatin decreased in the symptomatic patient compared with the asymptomatic patient. Immunocytochemistry showed increased somatostatin-containing cells in the asymptomatic patient. We hypothesize that this may be the mechanism by which some patients with nesidioblastosis maintain normal serum glucose levels.

Cell Separation↗
PubMed1987

Insulin and glucagon production in experimental cirrhosis.

The release of insulin and glucagon in cirrhotic rats was examined. Rats were made cirrhotic by a combination treatment of carbon tetrachloride (CCl4) and phenobarbitone. Liver cirrhosis was verified by histologic findings. Both basal and stimulated release of insulin from isolated pancreatic islets, in vitro, were decreased significantly in cirrhotic rats, as compared with control rats. Basal, but not stimulated, levels of glucagon, in vitro, were reduced significantly in cirrhotic rats. Circulating levels of plasma insulin, glucagon, glucose, bilirubin, and amylase levels were unaffected in cirrhotic rats when compared with control rats. There were no signs of pancreatitis. The results indicated that the release of insulin and glucagon is depressed in cirrhotic rats and in rats treated with phenobarbitone and CCl4. Clearance of circulating insulin and glucagon by the liver was apparently reduced, since circulating levels of insulin and glucagon were unaltered in all treated rats.

Animals↗
PubMed1987

Correlation of cholecystokinin receptors with gallbladder contractility in patients with gallstones.

The authors have previously identified two groups of patients with gallstones: those whose gallbladders contract the same as those of normal volunteers and show an increased sensitivity to endogenous cholecystokinin (CCK) ("contractors") and those whose gallbladders are relatively unresponsive ("noncontractors"). To define the mechanism responsible for these differences in contractility, the authors have measured CCK receptors on gallbladder muscle of patients with gallstones. Twenty-three patients with gallstones and 10 healthy volunteers (controls) fasted overnight. Simultaneous plasma samples for radioimmunoassay of CCK release and ultrasonographic measurements of gallbladder volume were obtained before and at intervals for 60 minutes after ingestion of Lipomul. Patients with gallstones had cholecystectomy, and CCK receptors were determined on cell membranes from gallbladder specimens by use of radiolabeled analogs of CCK-8-SO4. Histologic sections were graded for the degree of inflammation and scarring. Thirteen patients with gallstones were identified as contractors and 10 as noncontractors. Basal gallbladder volumes were not significantly different between patients in either group. The total integrated output of CCK for contractors was 1.6 +/- 0.2 ng X min/ml compared with 5.5 +/- 1.2 ng X min/ml for controls, while the integrated output for noncontractors was 11.1 +/- 2.1 ng X min/ml. Contractors had a higher number of CCK-binding sites (27.6 +/- 6.8 fmol/mg protein) than did noncontractors (4.8 +/- 1.0 fmol/mg protein). CCK receptors in gallbladders of all patients with gallstones correlated closely with gallbladder motility (y = 1.149, x = 0.624, r = 0.7, p less than 0.001). Although contractors had more mild inflammation and scarring, 40% of noncontractors had mild inflammation and scarring; there was no correlation. A decrease in CCK receptors may be an early event in the pathogenesis of gallstone formation by causing a decrease in gallbladder motility in some patients.

Adult↗
PubMed1987

Peptide YY inhibits nutrient-, hormonal-, and vagally-stimulated pancreatic exocrine secretion.

Peptide YY (PYY) is a recently isolated gut peptide that is found primarily in the mucosal endocrine cells of the terminal ileum, colon, and rectum of several mammalian species, including humans. The purpose of this study was to characterize the effect of PYY on pancreatic exocrine secretion in six conscious dogs prepared with pancreatic and gastric fistulas. In control experiments, pancreatic exocrine secretion was stimulated by either intravenous (i.v.) administration of secretin (100 ng/kg/h), cholecystokinin-8 (50 ng/kg/h), neurotensin (5 micrograms/kg/h), or 2-deoxy-D-glucose (75 mg/kg); or by the intraduodenal infusion of hydrochloric acid (4 mEq/h), a mixture of amino acids (phenylalanine + tryptophan at 5 mmol/h), sodium oleate (9 mmol/h), or a liquid meal. On separate days, PYY (12.5, 25, 50, 100, 200, or 400 pmol/kg/h) was given intravenously in combination with one of the above pancreatic secretagogues. Intravenous PYY at 200 and 400 pmol/kg/h inhibited secretin-stimulated pancreatic bicarbonate output significantly (p less than 0.05). Pancreatic bicarbonate and protein responses to all pancreatic secretagogues were reduced significantly (p less than 0.05) by PYY at 400 pmol/kg/h. Intravenous administration of atropine (0.6 mg bolus, followed by 0.02 mg/kg/h) did not abolish the ability of PYY to inhibit secretin-stimulated pancreatic bicarbonate secretion. This study demonstrates that PYY can inhibit nutrient-, hormonal-, and vagally-stimulated pancreatic exocrine secretion in the dog; its mechanism of action appears to be independent of cholinergic innervation.

Amino Acids↗
PubMed1987

Effect of gastrin-releasing peptide analogues on gastrin and somatostatin release from isolated rat stomach.

A differential biological potency of bombesin (BBS), compared with its mammalian counterpart gastrin-releasing peptide (GRP), has been reported in several biological systems in rodents. In the present study we have examined the relative potency of BBS, GRP-(1-27) (GRP-L), and GRP-(14-27) (GRP-S) on the release of gastrin and somatostatin (SRIF) from the isolated perfused rat stomachs. Male rats were fasted overnight and the stomachs perfused via the celiac artery. Increasing doses of BBS, GRP-L, and GRP-S were perfused for 15 min each and the effluent collected for measurement of gastrin and SRIF. The release of gastrin and SRIF in response to the GRP analogues was biphasic, with a peak increase occurring within the first 5 min, followed by a sustained increased secretion. The release of gastrin in response to 10(-10)-10(-9) M concentrations of the peptides was strongest with GRP-S (1.5-2.0 times higher than that released by BBS and GRP-L), although at higher concentrations (10(-8) M), the response to all three analogues was similar. The release of SRIF, on the other hand, was significantly higher in the presence of BBS compared with that in response to GRP-S, while GRP-L was ineffective. These studies indicate that the biological potency of BBS compared with its mammalian counterpart, GRP, is different on the two cell populations [gastrin (G) and SRIF (D)].

Animals↗
PubMed1987

Inhibitory action of peptide YY on gastric acid secretion.

The purpose of this study is to investigate the effect of peptide YY (PYY) on pentagastrin-, histamine-, and bethanechol-stimulated gastric acid secretion and the possible mechanisms by which PYY inhibits gastric acid secretion. Six mongrel dogs with chronic gastric and duodenal fistulas were given an intravenous infusion of pentagastrin (0.5 microgram . kg-1 . h-1), histamine (18 micrograms . kg-1 . h-1), or bethanechol (80 micrograms . kg-1 . h-1) either alone or simultaneously with intravenous PYY (100, 200, 400, pmol . kg-1 . h-1). PYY (100, 200, 400 pmol . kg-1 . h-1) inhibited pentagastrin-stimulated gastric acid secretion in a dose-dependent manner. PYY (400 pmol . kg-1 . h-1) did not depress bethanechol-stimulated gastric acid secretion. PYY (400 pmol . kg-1 . h-1) also failed to inhibit histamine-stimulated gastric acid secretion. Furthermore, PYY inhibit pentagastrin-stimulated gastric acid secretion in the face of atropine, vagotomy, or indomethacin treatment. These findings indicate that the inhibitory action of PYY on gastric acid secretion is in part independent of long and short cholinergic pathways. These findings also indicate that the inhibitory mechanism of PYY is independent of prostaglandin synthesis. Our findings are discussed in relation to previous reports regarding the effects of PYY on gastric acid secretion.

Animals↗
PubMed1987

Treatment of hamster pancreatic cancer with alpha-difluoromethylornithine, an inhibitor of polyamine biosynthesis.

Polyamines are essential for cell division and growth. Inhibition of polyamine biosynthesis by alpha-difluoromethylornithine (DFMO) on the growth of hamster H2T pancreatic cancer was investigated both in vitro and in vivo. Cell-doubling time (TD) and survival fraction were determined after a single treatment with DFMO (5 mM). We examined the ability of putrescine to reverse the growth-inhibitory effect of DFMO. The TD for cells treated with DFMO in vitro was 49.6 +/- 5.7 versus 25.4 +/- 2.6 hours for control. The addition of putrescine to DFMO-treated H2T cells showed a reversal of the growth-inhibitory effect of DFMO. Cytotoxicity in vitro increased with prolonged treatment; the survival fraction after 24 hours of treatment was 32%; after 48 hours, 19%; after 72 hours, 13%; and after 92 hours, 8%. We performed two separate animal experiments. In experiment I, H2T cells were injected into the cheek pouch of male Syrian golden hamsters; controls did not receive DFMO. Continuous treatment with 3% DFMO in the drinking water was begun 7 days before, on the day of, or 7 days after tumor cell injection. In experiment II, 4 groups were treated identically to those in experiment I. An additional group of 10 hamsters received 3% DFMO and no tumor, and another additional group of 10 hamsters were housed individually with 3% DFMO begun 7 days after tumor cell injection. Tumor size, body weight, water, and food intake were measured. DFMO treatment in vivo significantly inhibited tumor size and inhibited growth of pancreatic cancer by as much as 50% of control. Our results demonstrate a significant antiproliferative effect of DFMO on the growth of pancreatic adenocarcinoma both in vitro and in vivo.

Adenocarcinoma↗
PubMed1987

Bile enhances release of insulin: an incretin-mediated effect.

Ingestion of food stimulates secretion of bile and release of gut hormones that enhance nutrient-stimulated release of insulin. The extent of physiologic participation of bile in the enteroinsular axis was examined in seven conscious dogs (weight: 20 +/- 2 kg) that were prepared for study with chronic cannulas placed in the duodenum opposite the ampulla of Vater. On separate days, a meal consisting of 10 gm (MG-10), 25 gm (MG-25), or 62 gm (MG-62) of glucose (dextrose) was given orally in the presence of normal bile flow or during bile diversion. Bile diversion was achieved by catheterization of the common bile duct via the duodenal cannula. The insulin responses (given as ng [0-120] min/ml) to the different glucose meals, with bile present (BP) or absent (BA) in the lumen, were as follows: MG-10, 81 +/- 8 BP and 72 +/- 11 BA; MG-25, 172 +/- 25 BP and 100 +/- 6 BA (p less than 0.05); and MG-62, 390 +/- 79 BP and 153 +/- 32 BA (p less than 0.05). Only MG-25 and MG-62 produced a significant elevation of plasma glucose concentrations. Release of gastrin was not affected by either the presence of bile or the glucose content of the meal. We conclude that endogenous bile enhances nutrient-stimulated release of insulin, this effect is glucose-dependent with a threshold of approximately 1 gm/kg of glucose, and bile may facilitate the release of insulinotropic hormones other than gastrin.

Animals↗
PubMed1987

Calcitonin gene-related peptide: possible tumor marker for medullary thyroid cancer.

We have sought to determine whether medullary thyroid carcinoma (MTC) released calcitonin gene-related peptide (CGRP) in vivo. MTC cells were inoculated from tissue culture into eight Wag-Rij rats. One month later blood was drawn before and after the intravenous injection of calcium, and plasma levels of CGRP and calcitonin (CT) levels in that blood were determined by radioimmunoassay. The tumor was examined for content of CGRP and of CT by means of radioimmunoassay and immunocytochemistry. The tumor was divided and portions were passed to another eight rats. One month later, the studies were repeated. The tumor was passed two additional times (four passages in all). Controls consisted of non-tumor-bearing Wag-Rij rats. Basal levels of plasma CGRP in control rats (7 +/- 1 ng/ml) were unaffected by calcium stimulation. In tumor-bearing rats, the plasma CGRP level, which was initially slightly elevated (15 +/- 7 ng/ml), rose progressively with passages to 279 +/- 79 ng/ml in the third passage and fell to normal values at the end of passage four. Hypercalcemia had no effect on plasma CGRP levels in tumor-bearing rats but did stimulate the release of CT in both control and tumor-bearing rats, although it is not clear whether this release was from the tumor or from normal thyroid parafollicular cells in these tumor-bearing rats. We conclude that rat MTC synthesizes and releases CGRP but, unlike CT, CGRP appears unresponsive to calcium stimulation.

Animals↗
PubMed1987

The effects of gamma-irradiation on haemopoiesis and red blood cell destruction in hamsters infected with Leptospira interrogans serovar ballum.

Irradiated hamsters were infected with Leptospira interrogans serovar ballum in order to study the effects of impairment of the reticulo-macrophage system on the progression of the disease and the development of haemoglobinaemia. Infected and irradiated hamsters were compared with infected controls, irradiated controls and untreated controls. Red blood cells (RBCs) from untreated controls were biconcave disks while those from irradiated controls were echinocytes. Red blood cells from animals of both infected groups which were severely affected and moribund were in the form of pitted spherocytes and were associated with increased icteric indices and haemoglobinaemia. Red blood cells from less severely affected animals were echinocytic. Pitted spherocytes, however, were seen in some irradiated-infected hamsters before increased icteric indices and haemoglobinaemia were present. Both irradiated-infected and irradiated hamsters showed severe depletion of haemopoietic cells and lymphoid cells, with regeneration occurring in those animals which survived for longer. Red cell sequestration and erythrophagocytosis were present in infected-only hamsters. In irradiated-infected animals, severe anaemia was caused by both persistence of fixed macrophages, RBC sequestration and erythrophagocytosis, and haemorrhage due to vascular damage and renal papillary necrosis. A severe leucopaenia affected the irradiated hamsters' ability to suppress leptospiral multiplication resulting in the presence of larger numbers of organisms.

Animals↗
PubMed1986

Distribution of bombesin-like peptides in the alimentary canal of several vertebrate species.

The objective of this study was to quantitate and characterize the variants of bombesin-like immunoreactivity in the alimentary canal of the rat, rabbit, hawk, owl, dog, monkey and human. Bombesin-like immunoreactivity was found throughout the entire gastrointestinal tract of all species studied. In the rat, the highest concentration of bombesin-like immunoreactivity was found in the colon. Gel chromatography showed that bombesin-like immunoreactivity corresponded to gastrin-releasing peptide (GRP-27) and GRP-10. In the dog, the greatest concentration of bombesin-like immunoreactivity was observed in the mucosal layer of the fundus, whereas the concentration of bombesin-like immunoreactivity in the muscle layer of the dog did not vary significantly from region to region. Gel chromatography showed that bombesin-like immunoreactivity in the dog corresponded to GRP-27, bombesin, GRP-10, and a smaller fragment. In the human, the concentration of bombesin-like immunoreactivity did not vary significantly from region to region in the mucosal and muscular layers. Gel chromatography of human fundal mucosa showed that bombesin-like immunoreactivity peaks occur in the regions of GRP-27, bombesin and GRP-10. These findings substantiate the observation that bombesin-like peptides play a variety of roles in the regulation of gut function.

Animals↗
PubMed1986

Blood-CSF barrier to CCK and effect of centrally administered bombesin on release of brain CCK.

The purpose of this study, in part, was to determine the ability of cholecystokinin (CCK-33/39 and CCK-8) to penetrate the blood cerebrospinal fluid (CSF) barrier in dogs by measuring these forms of CCK in plasma and in CSF. In addition, the effectiveness of centrally administered bombesin in releasing brain CCK-33/39 and CCK-8 was evaluated. Six groups of five dogs each were studied. Each group received one of the following: (1) intravenous infusion of CCK-33/39 (1.3 micrograms/kg/hr); (2) intravenous infusion of CCK-8 (0.4 micrograms/kg/hr); (3) intrathecal infusion of CCK-33/39 (1.3 micrograms/kg/hr); (4) intrathecal infusion of CCK-8 (0.5 micrograms/kg/hr); (5) intravenous infusion of bombesin (1 micrograms/kg/hr); and (6) intrathecal infusion of bombesin (1 microgram/kg/hr). Plasma concentrations of CCK-33/39 significantly increased during intravenous infusion of CCK-33/39 (from basal of 84 +/- 8 to 142 +/- 2 pg/ml) or bombesin (from basal of 78 +/- 13 to 325 +/- 87 pg/ml); however, CSF perfusate concentrations of CCK-33/39 did not increase. CCK-33/39 levels of the CSF perfusate increased significantly (P less than .05) from 211 +/- 84 to 9,873 +/- 3,368 pg/ml during intrathecal infusion of CCK-33/39, but failed to rise simultaneously in the systemic circulation. Similarly, intravenous infusion of CCK-8 caused a fivefold elevation in plasma CCK-8 levels and no change in CSF perfusate levels of CCK-8; moreover, intrathecal infusion of CCK-8 failed to elevate peripheral CCK-8 levels, despite CSF perfusate CCK-8 levels of 92,300 +/- 18,598 pg/ml. Intrathecal concentrations of neither CCK-33 nor CCK-8 were affected by intravenous or intrathecal administration of bombesin. We conclude that CCK-33/39 and CCK-8 do not penetrate the blood-cerebrospinal fluid barrier in dogs, and centrally administered bombesin is ineffective in causing release of cholecystokinin from brain tissue into the CSF.

Animals↗
PubMed1986

Central versus peripheral effects of bombesin on the release of gastrointestinal hormones in dogs.

This study compared the effects of bombesin given intracerebroventricularly and intravenously on circulating levels of gastrin, pancreatic polypeptide (PP), and cholecystokinin (CCK-33). Bilateral cannulas were implanted permanently into the lateral cerebral ventricles of five dogs. An intravenous (IV) bolus injection of bombesin (0.25 microgram/kg) significantly elevated circulating levels of gastrin, PP, and CCK-33. Vagotomy inhibited the release of PP that was induced by IV bombesin, but vagotomy did not affect gastrin and CCK-33 responses. Intracerebroventricular injection of bombesin (5.0 micrograms) significantly elevated circulating gastrin levels but did not affect circulating levels of CCK-33 and PP. Vagotomy did not alter gastrin release induced by intracerebroventricular injection of bombesin.

Animals↗
PubMed1986

Superoxide dismutase and catalase: a possible role in established pancreatitis.

The mechanism of cerulein-induced acute pancreatitis may involve the production of free radicals in excess of the capacity of endogenous intracellular scavengers. These radicals destroy the cellular membranes, releasing digestive enzymes and cellular proteins into the interstitium. Thereafter, a cascade of events, including polymorphonuclear infiltration and complement activation, leads to pancreatic destruction. The present study demonstrates that superoxide dismutase and catalase reduce the ultrastructural and biochemical injury associated with cerulein-induced acute pancreatitis in rats. Pretreatment with superoxide dismutase and catalase 30 minutes before injury did not appear to be protective, presumably because the half-life of intravenous superoxide dismutase is only 6 minutes. This and similar studies suggest a potential clinical role for free radical scavengers in acute established pancreatitis.

Acute Disease↗