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J F Rehfeld

Publications and source records attributed to J F Rehfeld.

At least 91 records · Page 5Linked to original sources
PubMed1997

[Research in Copenhagen hospitals--a bibliometric evaluation].

The aim of this study was to measure size and quality of the research carried out in Copenhagen (H:S) hospitals using conventional bibliometry. Based on the H:S-report on scientific publications in 1995, the research performed in each hospital and each department has been measured as the sum of publications and as journal impact factor score. Publication numbers and impact factor score varied eighty-fold between the individual H:S-hospitals. With a close relation between publication numbers and impact factor score, the Rigshospital produced 60%, Hvidovre Hospital 20% and Bispebjerg Hospital 11%, while the four remaining hospitals (Frederiksberg Hospital, the Copenhagen Community Hospital, Sct. Hans Hospital and Sundby Hospital) together produced 9% of the research. The departmental research activities as such showed correlation neither to clinical specialty nor to specific hospitals. In conclusion, the Rigshospital is responsible for most of the research in H:S. Generally, departments headed by university professors showed the highest research activity.

Bibliometrics↗
PubMed1997

Disturbed progastrin processing in carboxypeptidase E-deficient fat mice.

The fat mouse strain exhibits a late-onset obesity syndrome associated with a mutation in the gene encoding carboxypeptidase E (CPE). Since CPE plays a central role in the biosynthesis of a number of regulatory peptides, including gastrin, we examined the biogenesis and processing of progastrin in fat/fat mice by measuring gastrin mRNA, carboxyamidated gastrin and its processing intermediates in the stomach. The tissue concentration of carboxyamidated (i.e. bioactive) gastrin was only slightly reduced (601 +/- 28 pmol/g in fat/fat mice vs. 715 +/- 43 pmol/g in wild-type controls). However, progastrin processing intermediates accumulated excessively with an 86-fold increase in the concentration of the CPE substrate, glycyl-arginine extended gastrin, and a seven-fold increase in the concentration of glycine-extended gastrin. Accordingly, the total progastrin product was doubled, as was the concentration of gastrin mRNA. Plasma concentrations of carboxyamidated gastrin were, however slightly reduced both in fasted fat/fat mice and postprandially. The results show that the CPE mutation diminishes the efficiency of progastrin processing, but gastrin synthesis is nevertheless increased to maintain an almost normal production of bioactive gastrins. By comparison with other neuroendocrine prohormones, progastrin processing in CPE-deficient mice is unique. Hence, the increase of glycine-extended gastrin in combination with normal levels of carboxyamidated gastrin suggests that G-cells may have another biosynthetic pathway for gastrin.

Animals↗
PubMed1997

Elasmobranchs express separate cholecystokinin and gastrin genes.

The peptide hormone gastrin was long believed to be specific for higher vertebrates, whereas its homologue, cholecystokinin (CCK), has been assumed to represent the original ancestor of the CCK/gastrin family. To trace the divergence of the CCK/gastrin family beyond birds, reptiles, and amphibians we have now examined sharks. Distinct CCK and gastrin peptides were identified in two shark species, the spiny dogfish (Squalus acanthias) and the porbeagle (Lamna cornubica). The corresponding genes and cDNAs were isolated and sequenced from the spiny dogfish. Comparison with several vertebrate species show that the CCK gene and peptide structures have been considerably more conserved than the corresponding gastrin structures. Alignment of the dogfish prepropeptides displays similarities that support the hypothesis that they share a common ancestor. Our findings move the CCK/gastrin family segregation back to at least 350 million years ago. This event must have occurred before, or perhaps during, the evolution of cartilagenous fishes, probably concomitant with the occurrence of gastric acid secretion.

Amino Acid Sequence↗
PubMed1997

New consensus features for tyrosine O-sulfation determined by mutational analysis.

Tyrosine sulfation is an ubiquitous modification of proteins synthesized along the secretory pathway. It enhances protein-protein interactions and may be necessary for the bioactivity of secreted proteins and peptides. To predict tyrosine sulfation, a consensus has been proposed based on sequence comparisons of known substrates and on in vitro studies using synthetic peptides. This consensus predicts the presence of acidic residues on the amino-terminal side of the target tyrosine as the key feature. Using site-directed mutagenesis, we have examined the role of residues neighboring the sulfation site of an intact protein, human progastrin, in vivo. The results show that the charge of the residue in the amino-terminal position (-1) of the tyrosine is critical and can be neutral or acidic, whereas a basic residue abolishes sulfation. In addition, the degree of sulfation is influenced by the residues in positions -2 and -3. Hence, surprisingly a basic residue in position -2 enhances sulfation. Our data suggest a considerably broader range of substrates for the tyrosylprotein sulfotransferase than hitherto assumed and that the tyrosylprotein sulfotransferase is cell-specifically expressed.

Amino Acid Sequence↗
PubMed1997

Heterologous expression of human cholecystokinin in Saccharomyces cerevisiae. Evidence for a lysine-specific endopeptidase in the yeast secretory pathway.

Precursors of the human regulatory peptide cholecystokinin (CCK) have been expressed in Saccharomyces cerevisiae, and the post-translational processing of secreted CCK-related products analyzed. Recombinant plasmids expressing native human prepro-CCK and a hybrid molecule encompassing the prepro leader of the yeast alpha-mating pheromone fused to pro-CCK were examined. The latter construct resulted in considerably higher levels of pro-CCK secretion and was therefore analyzed in more detail. Two of the protein modifications essential for CCK bioactivity, C-terminal alpha-amidation and tyrosyl sulfation, were not detected in S. cerevisiae. Proteolytic cleavage of pro-CCK occurred C-terminally of three basic sites; (i) Arg105-Arg106 which, upon exposure to carboxypeptidase activity, leads to the production of glycine-extended CCK; (ii) Arg95 to produce CCK-8 related processing intermediates; and (iii) Lys81 resulting in CCK-22 related products. To elucidate which protease(s) are involved in these endoproteolytic cleavage events, pro-CCK was expressed in yeast mutants lacking various combinations of the Mkc7, Yap3, and Kex2 proteases. Only in S. cerevisiae strains deficient in Kex2 function was any of the above mentioned pro-CCK cleavages abolished, namely processing at the Arg105-Arg106 and Arg95 sites. This suggests that mammalian Kex2-like serine proteases may process pro-CCK at single arginine residues. Our data suggests that an as yet uncharacterized endopeptidase(s) in the S. cerevisiae secretory pathway is responsible for the lysine-specific cleavage of pro-CCK.

Amino Acid Sequence↗
PubMed1997

Expression of gastrin and transforming growth factor-alpha during duct to islet cell differentiation in the pancreas of duct-ligated adult rats.

In adult rats islet cell neogenesis can be stimulated by partial duct ligation. Duct to islet cell differentiation is thought to be regulated by growth factors such as gastrin and transforming growth factor-alpha (TGF alpha). To test this hypothesis, we examined the expression of gastrin and TGF alpha at the mRNA and protein level in pancreatic tissue following partial duct ligation. Pancreatic specimens were investigated on days 3, 5, 7 and 14 after duct ligation by means of non-isotopic in situ hybridization, immunocytochemistry and Western blotting. Gastrin mRNA was strongly expressed in newly developed duct-like cell structures in the ligated tail portion of the pancreas before the period of pronounced islet cell neogenesis (days 5 and 7), and immunostaining for gastrin peptides was positive at days 5-7. In the non-ligated head portion and in control pancreases, gastrin was not expressed. Expression of TGF alpha was found to be increased in the ligated tail portion of the pancreas on day 3 and particularly on day 5, while there was no enhanced signal in the non-ligated part. Western blotting revealed two different TGF alpha isoforms (18 kDa and 42 kDa) in the ligated tail part and three isoforms (18 kDa, 24 kDa and 42 kDa) in the non-ligated head part and in untreated pancreases. The induction of gastrin and TGF alpha expression preceded the peak in the bromodeoxyuridine pulse labelling index of beta cells, known from a previous study to occur on day 7. We conclude that pancreas duct ligation induces the overexpression of gastrin and TGF alpha in the first days following ligation. Since ductal cells are known to give rise to endocrine cells after duct ligation, gastrin and TGF alpha may play a role as growth factors in islet neogenesis.

Animals↗
PubMed1997

Abnormal gastric histology and decreased acid production in cholecystokinin-B/gastrin receptor-deficient mice.

BACKGROUND & AIMS: The cholecystokinin (CCK)-B/gastrin receptor is one of several regulators of gastric acid secretion and mucosal growth. To elucidate the contribution of this receptor relative to other trophic and secretory factors, mice that lack the CCK-B/gastrin receptor have been generated and studied. METHODS: Both alleles of the CCK-B/gastrin receptor were inactivated by targeted gene disruption. Analysis of the mice included measurement of basal gastric pH and plasma gastrin levels. In addition, multiple gastric mucosal cell types were identified by immunostaining and quantified. RESULTS: Homozygous mutant mice were viable, fertile, and appeared grossly normal into adulthood. The receptor-deficient mice exhibited a marked increase in basal gastric pH (from 3.2 to 5.2) and an approximately 10-fold elevation in plasma gastrin concentration compared with wild-type controls. In the stomach of mutant animals, parietal and enterochromaffin-like cells were decreased, providing a likely explanation for the reduction in acid output. In the antrum, a decrease in somatostatin cell density and an increase in the gastrin cell number were observed, consistent with the concomitant elevation in circulating gastrin. CONCLUSIONS: Together, these findings demonstrate the importance of the CCK-B/gastrin receptor in maintaining the normal cellular composition and function of the gastric mucosa.

Animals↗
PubMed1997

Plasma cholecystokinin and its precursors in hepatic cirrhosis.

BACKGROUND/AIMS: The liver influences the metabolism of several peptide hormones. The metabolic effect may, however, change considerably by diseases in the liver. This study examined whether hepatic cirrhosis influences the occurrence and concentrations of procholecystokinin (proCCK) and its products in plasma. METHODS: The sum of proCCK and its products (both processing intermediates and bioactive fragments) in plasma were measured by a recently developed "processing-independent analysis". Bioactive forms of CCK in plasma were measured using a highly specific radioimmunoassay directed against the C-terminal epitope of CCK. RESULTS: In plasma from patients with primary biliary cirrhosis the basal concentration of the total proCCK product was increased. Moreover, a mixed meal increased plasma concentrations of both bioactive CCK (i.e. carboxyamidated an 0-sulfated CCK peptides) and the total proCCK product in primary biliary cirrhosis. In contrast, plasma concentrations of bioactive CCK and the total proCCK product were normal in patients with alcoholic liver cirrhosis-both pre- or postprandially. The fraction of bioactive CCK in plasma from patients with both biliary and alcoholic cirrhosis was also normal. Hence, in primary biliary cirrhosis, alcoholic cirrhosis and in controls, respectively, bioactive CCK constituted 15%, 15% and 17% of the total proCCK product in the basal state; 70%, 58% and 53% 30 min after and 48%, 56% and 51% 90 min after the meal. As shown by gel chromatography, plasma from patients with primary biliary cirrhosis and controls sampled 30 min after a meal contained CCK-33, -22 and -8-like peptides. In addition, plasma contained non-amidated (approximately non-bioactive) proCCK products corresponding in size to CCK-83, -58 and -33. Ninety minutes after a meal, CCK-8 predominated in plasma from patients with primary biliary cirrhosis, whereas plasma from controls displayed a CCK profile similar to that obtained 30 min post-prandially. CONCLUSIONS: The results show that CCK-8 is metabolized at a slower rate in patients with primary biliary cirrhosis.

Adult↗
PubMed1997

Gastric lipase secretion after sham feeding and cholinergic blockade.

Our purpose was to examine gastric lipase secretion after cephalic stimulation (sham feeding) and to examine the effect of cholinergic blockade. Eight healthy volunteers, four women and four men, age 21-58 years, were studied twice on separate days. They were sham fed with and without infusion of atropine. Gastric content was measured and the amount as well as the activity of gastric lipase output were determined. Plasma concentrations of gastrin, secretin, and cholecystokinin (CCK) were measured simultaneously by radioimmunoassays. Cephalic stimuli can evoke human gastric lipase secretion, and this effect was almost ablated by atropine blockade of cholinergic receptors. The concentrations of CCK and secretin in plasma were unaffected by sham feeding with or without atropine blockade, whereas gastrin was stimulated by sham feeding after atropine blockade. Gastric lipase secretion in man is apparently controlled by interacting vagal and hormonal mechanisms.

Adult↗
PubMed1997

Calcitonin gene-related peptide (CGRP), a potent regulator of biliary flow.

This study was designed to investigate the effect of porcine calcitonin gene-related peptide (CGRP) on the motility of the porcine biliary tract in vivo. We measured the pressure in the gallbladder and sphincter of Oddi and, in separate experiments, the biliary flow into the duodenum during local intraarterial infusions of CGRP. To determine if the observed effect could be caused by release of cholecystokinin (CCK), we measured the CCK release. The basal pressure in the sphincter of Oddi increased dose-dependently from 5.9 +/- 0.5 mmHg to 11.5 +/- 2.1 mmHg and the motility index of phasic contractions (amplitude x frequency) from 47 +/- 8 to 347 +/- 64 mmHg s-1, at an infusion rate of 32.6 pmol kg-1 min-1. No effect was observed on the gallbladder pressure. CGRP at 6.5 pmol kg-1 min-1 significantly reduced the biliary flow into the duodenum to 47.7 +/- 6% of the basal level. Atropine, injected intravenously, completely abolished the contractile effect of CGRP. CGRP had no effect on the release of CCK. We conclude that CGRP increases biliary motility and hereby reduces bile flow, an effect which involves cholinergic but not cholecystokininergic mechanisms.

Animals↗
PubMed1997

Reduced frequency of extracolonic cancers in hereditary nonpolyposis colorectal cancer families with monoallelic hMLH1 expression.

Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal dominant disease caused by mutations in one of at least four different DNA mismatch repair genes, hMLH1, hMSH2, hPMS1, and hPMS2. Phenotypically, HNPCC is characterized by the early onset of colorectal cancers and various extracolonic cancers. Depending on the presence or absence of extracolonic tumors, HNPCG-has been divided into two syndromes (Lynch syndrome I and Lynch syndrome II), but, so far, no correlation to distinct genotypes has been demonstrated. In this study, we present a frequent hMLH1 intron 14 founder mutation that is associated with a highly reduced frequency of extracolonic tumors. The mutation disrupts the splice donor site and silences the mutated allele. Tumors exhibited microsatellite instability, and loss of the wild-type hMLH1 allele was prevalent. We propose that the mutation results in a milder phenotype, because the mutated hMLH1 protein is prevented from exerting a dominant negative effect on the concerted action of the mismatch repair system.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Chronic endogenous hypercholecystokininemia promotes pancreatic carcinogenesis in the hamster.

In order to examine the effect of cholecystokinin on spontaneous and induced pancreatic carcinogenesis in the hamster, two sets of experiments were carried out, one involving long-term hypercholecystokininemia and one involving cancer induction during hypercholecystokininemia. The effect of hypercholecystokininemia, induced by pancreaticobiliary diversion (PBD), was studied for 8 months. Neither PBD animals nor sham-operated controls developed premalignant or malignant pancreatic lesions. However, in the PBD group the mean pancreatic weight, total protein content and DNA content were increased by 30, 29 and 27% respectively. No such increases were found in PBD animals receiving a cholecystokinin-A receptor antagonist during the last 24 days of the experiment. In the cancer induction study, the effect of PBD on N-nitrosobis(2-oxopropyl)amine-induced pancreatic carcinogenesis was studied for 3 months. Putative premalignant pancreatic lesions were diagnosed in all PBD hamsters and in four of 15 sham-operated controls. Pancreatic ductular carcinoma in situ was only found in PBD animals. The [3H]thymidine labeling index of the pancreatic lesions was significantly higher in the PBD group than in the controls. No such increase was observed in PBD animals receiving a cholecystokinin-A receptor antagonist during the last 5 days of the experiment. It is concluded that chronic endogenous hypercholecystokininemia promotes early phase pancreatic carcinogenesis, but does not per se cause development of premalignant or malignant pancreatic lesions in the hamster.

Animals↗
PubMed1997

Biliodigestive shunt evokes hyperCCKemia and trophic effects in the rat pancreas, but not in the liver or gastrointestinal tract.

The influence of bile on the release of cholecystokinin (CCK) and, thereby, on the regulation of exocrine pancreatic function and growth is unsettled. The aim of this study was to elucidate the effect of long-term diversion of bile from the upper small intestine of CCK release and on the pancreas, liver, and gastrointestinal tract. A surgical biliodigestive shunt was performed in rats, diverting the bile flow directly to the middle of the small intestine. The animals were killed after 4 or 12 weeks. Plasma CCK and trophic effects on the pancreas, liver, and gastrointestinal tract were determined, as were the trypsin and chymotrypsin contents in the intestine. The CCK concentration in plasma increased 10-fold at both time points studied. The pancreas doubled its weight from 4 weeks onward. Also, pancreatic protein, DNA, and amylase contents were increased throughout the study. The liver and gastrointestinal tract were unaffected. Intraluminal bile plays a role in the feedback regulation of CCK release and is involved in this way in the control of pancreatic growth but has no similar effects on the liver or gastrointestinal tract.

Amylases↗
PubMed1997

Effect of chronic endogenous hypergastrinaemia on pancreatic growth and carcinogenesis in the hamster.

BACKGROUND: To examine the effect of gastrin on spontaneous and induced pancreatic carcinogenesis in the hamster. METHODS AND RESULTS: Two sets of experiments were carried out, one involving long term hypergastrinaemia and one involving cancer induction during hypergastrinaemia. The effect of hypergastrinaemia accomplished by gastric fundectomy was studied for eight months. Neither fundectomised hamsters nor sham operated controls developed premalignant or malignant pancreatic lesions. In the fundectomy group, the mean pancreatic weight, total protein content, and DNA content was increased by 28%, 25%, and 25% respectively. No such increases were found in fundectomised animals receiving a cholecystokinin-B receptor antagonist during the last 24 days of the experiment. In the cancer induction study, the effect of fundectomy on N-nitrosobis(2-oxopropyl) amine induced pancreatic carcinogenesis was studied for three months. There were no significant differences in the incidence or [3H]-thymidine labelling index of focal pancreatic lesions between fundectomised and sham operated control animals. CONCLUSIONS: Fundectomy with chronic hypergastrinaemia induces pancreatic hypertrophy, but does not enhance N-nitrosobis (2-oxopropyl)amine induced pancreatic carcinogenesis in the hamster. The increases in growth were inhibited by a cholecystokinin-B receptor antagonist, indicating that the trophic effect of fundectomy is mediated by gastrin.

Animals↗
PubMed1997

Characterization of the cholecystokinin and gastrin genes from the bullfrog, Rana catesbeiana: evolutionary conservation of primary and secondary sites of gene expression.

The gastrin and cholecystokinin (CCK) genes, and the complementary DNAs they encode, have been isolated and sequenced from the bullfrog, Rana catesbeiana. The CCK gene promoter region possess the same four well characterized transcriptional control elements as the human CCK gene, namely an E-box, AP-1 binding site, Sp1 site, and TATA box. In contrast, no obvious regulatory motifs are conserved in the gastrin gene. Alignment of the bullfrog preprohormone sequences with other members of the CCK/gastrin peptide family showed that preproCCK has been conserved to a greater degree during evolution than preprogastrin. In mammalian species, gastrin gene expression is typically associated with the antrum, and CCK with the small intestine and brain. However numerous secondary sites of CCK/gastrin gene expression have also been found. RT-PCR showed a high degree of conservation of both primary and secondary sites of CCK/gastrin production between mammals and the bullfrog, with gastrin messenger RNA being detected in the antrum, duodenum, colon, pancreas, brain, and testes, whereas CCK mRNA was observed in the brain, lung, testes, and throughout the length of the small intestine. In situ hybridization using radiolabeled gene specific antisense oligonucleotides uncovered CCK and gastrin messenger RNA in distinct areas of the bullfrog central nervous system and pituitary gland. Notably, the gastrin gene was expressed in the pituitary gland and hypothalamus of the bullfrog, as previously seen in mammals. This highly preserved tissue expression pattern suggests that gastrin plays specific roles in the hypothalamus and pituitary gland that are distinct from those of CCK. Our findings show that in spite of the structural resemblance, bullfrog CCK and gastrin constitute independent neuroendocrine peptide systems.

Amino Acid Sequence↗
PubMed1997

Basal chromogranin A and gastrin concentrations in circulation correlate to endocrine cell proliferation in type-A gastritis.

BACKGROUND: It is not known whether plasma chromogranin analysis could be a complement to histology for detection and grading of gastric fundic mucosal endocrine cell proliferation in hypergastrinemic (type-A) atrophic gastritis. METHODS: Gastric biopsy sections (body and antrum) from 43 patients with type-A gastritis (9 with gastric carcinoid) were examined for density and micronodules of argyrophil endocrine cells. Fasting blood samples were analyzed for chromogranin A and B, gastrin, and somatostatin. RESULTS: All patients with carcinoid and 17 of the 34 without carcinoid had micronodules in the gastric fundic mucosa. The median plasma chromogranin A concentration was 5.7 (3.5-40.0) nmol/l in patients with carcinoid, 4.5 (3.0-9.5) nmol/l in patients with micronodules, and 3.7 (0.8-6.0) nmol/l in patients without micronodules. Overall, chromogranin A concentrations correlated to endocrine cell densities in the fundic mucosa (r = 0.64, P < 0.001) and to gastrin concentrations (r = 0.71, P < 0.001). Plasma somatostatin and chromogranin B concentrations did not differ significantly between the groups. CONCLUSION: In type-A gastritis, analysis of plasma chromogranin A may be a useful complement to histology in estimating the endocrine cell mass. Moreover, subclinical type-A gastritis may be a source of error when chromogranin A analysis is used in the search for neuroendocrine neoplasia.

Aged↗
PubMed1997

Deficient gastric lipase secretion in pancreatic insufficiency.

BACKGROUND: Gastrin is an important stimulator of gastric lipase secretion in man. In advanced pancreatic insufficiency gastric lipases might compensate for the lack of pancreatic lipases, but the role of gastrin in such compensation remains to be evaluated. The aim of this study was to examine the effect of gastrin on the gastric lipase secretion in patients with pancreatic insufficiency. METHODS: Eight patients with pancreatic insufficiency secondary to alcohol abuse were studied, and six healthy subjects volunteered as controls for the study. All volunteers received identical doses of intravenous gastrin-17 (10, 30, and 60 pmol/kg/h). The gastric content was measured, using a nasogastric tube for aspiration, and the amount and activity of gastric lipase output were determined. Plasma concentrations of gastrin, secretin, and cholecystokinin were measured by radioimmunoassays. RESULTS: The increased plasma levels of gastrin were accompanied by a dose-dependent increase in the amount and activity of gastric lipase in controls, but in the patients the response was almost abolished. CONCLUSIONS: Gastrin in postprandial concentrations does not influence the secretion of gastric lipase in patients with pancreatic insufficiency due to chronic pancreatitis.

Adult↗