Biomedical subjects

R Nustede

Publications and source records attributed to R Nustede.

62 records · Page 4Linked to original sources

PubMed1989

Role of ornithine decarboxylase and polyamines in camostate (Foy-305)-induced pancreatic growth in rats.

This study was designed to investigate changes of ornithine decarboxylase and polyamines during pancreatic adaptation in response to feeding of the synthetic protease inhibitor camostate. alpha-Difluoromethylornithine, an irreversible and specific inhibitor of ornithine decarboxylase, was applied simultaneously to elucidate the essential role of polyamines in pancreatic growth. Cholecystokinin (CCK) plasma levels in camostate-fed rats increased from basal values of 3-4 pmol/l to a maximal level of 27.4 pmol/l after 2h; they then decreased up to 12 h but remained elevated above controls throughout the 30-day experiments. In the camostate group pancreatic ornithine decarboxylase activity was elevated after 2 h, reaching a maximum after 6 h (1,858.5 pmol 14CO2/h/mg DNA, about 200-fold above controls) followed by a significant increase in putrescine after 4 h and spermidine after 24 h while spermine remained unchanged. The trophic parameters increased in the following time sequence: thymidine kinase (12 h), DNA polymerase (12 h), protein (24 h), pancreatic weight (24 h) and DNA (5 days). alpha-Difluoromethylornithine significantly delayed and reduced the camostate-induced increase in ornithine decarboxylase activity and polyamine concentrations as well as the trophic parameters. Application of the CCK receptor antagonist L-364,718 resulted in complete inhibition of the increases in ornithine decarboxylase, polyamines and all trophic parameters. These data indicate an important role for ornithine decarboxylase and polyamines in camostate-induced pancreatic growth and hormonal mediated pancreatic adaptation in rats.

Animals↗

PubMed1989

Influence of CCK antagonist L-364,718, pancreastatin (33-49) and a somatostatin analogue on camostate-induced rat pancreatic hypertrophy.

Since endogenous cholecystokinin (CCK) is released after oral administration of camostate, it has been suggested that camostate-induced pancreatic growth is mediated via circulating CCK. To test this concept, we investigated the effects of three potentially inhibitory substances on rat pancreatic hypertrophy caused by feeding of camostate over 2 weeks: (1) L-364,718, the novel specific highly potent nonpeptide CCK receptor antagonist, (2) octreotide (SMS 201-995), a potent long-lasting somatostatin analogue and (3) pancreastatin (33-49), the biologically active C-terminal fragment of the novel gastrointestinal peptide pancreastatin. Camostate feeding (200 mg/kg) once daily for 14 days induced a significant increase in pancreatic weight, total protein, trypsinogen and polyamine levels, whereas total amylase content was substantially diminished. Simultaneous oral or subcutaneous treatment with L-364,718 (0.3 mg/kg twice daily) completely suppressed all trophic effects of camostate. Octreotide (25 micrograms/kg twice daily s.c.) and pancreastatin (33-49) (10 micrograms/kg twice daily s.c.) did not change any trophic parameter. In case of octreotide it could be shown that two daily injections only partially suppressed elevated CCK levels. Pancreatic DNA and putrescine levels were slightly reduced in rats receiving the CCK antagonist alone. These results demonstrate that camostate-induced pancreatic hypertrophy in rats is caused by the release of endogenous CCK which may contribute to the maintenance of normal pancreatic DNA and putrescine concentrations.

Animals↗

PubMed1989

Characterization of five mouse monoclonal antibodies to apolipoprotein[a] from human Lp[a]: evidence for weak plasminogen reactivity.

We describe the development of five murine monoclonal antibodies (14A12, 39A1, 53A9, 73A7, and 128A6) specific to human apolipoprotein[a] (Mr approximately 570,000), and their characterization by a number of procedures including cotitration, competition and inhibition enzyme-linked immunosorbent assays (ELISA), immunoblotting of native lipoproteins and of SDS-solubilized apolipoproteins electrophoresed in polyacrylamide gels, and dot immunobinding assays. The patterns of immunoreactivity of these antibodies were similar. Each reacted in ELISA assays and upon electroimmunoblotting with purified apo[a], with apo[a] liberated by reduction of Lp[a], and with delipidated Lp[a] solubilized in SDS, but by contrast, they reacted with native Lp[a] to a significant degree only upon electroimmunoblotting. No reactivity was seen with LDL-apoB-100 or with other apolipoproteins. The cross-reactivity of these antibodies with the homologous protein, plasminogen, was examined by comparison of the amount of plasminogen or apo[a] required for 50% inhibition of antibody binding to apo[a], and by an ELISA assay. The inhibition assay showed reactivity with plasminogen to be 37- to 50-fold lower than with apo[a], while dot immunobinding showed the lower limit of detection of plasminogen and of apo[a] to be approximately 320 and 31 micrograms, respectively. In an ELISA sandwich assay based on monoclonal antibodies LHLP-1, 14A12, and 53A9, the lower limit of Lp[a] detection (approximately 1 ng/ml protein) was about 100-fold less than that of plasminogen. Chemical modification of apo[a] revealed a significant contribution of arginine residues to the epitopes of 14A12, 39A1, and 53A9. Modification of cysteine residues with iodoacetamide was without effect, thereby distinguishing these antibodies from LHLP-1. Each antibody reacted with the six major size forms of apo[a] (Mr approximately 450,000-750,000) in immunoblots of human sera electrophoresed in SDS-polyacrylamide gels. Marked heterogeneity in apo[a] phenotype was detected and both single and double band phenotypes were observed in a randomized study. Cotitration and competition binding studies showed varying degrees of interaction between all five epitopes, with the exception of 128A6 which appeared to be independent of 39A1 and 53A9 (and vice versa). These data suggest that our five monoclonal antibodies recognize epitopes on apolipoprotein[a] that are exposed and accessible on the native Lp[a] particle. We conclude that our monoclonal antibodies recognize a specific region of apo[a], and that this region undergoes a conformational change upon adsorption of Lp[a] to plastic thereby diminishing epitope recognition.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1989

[Does the stomach balloon modify the function of the esophagus and lower esophageal sphincter, stomach emptying and release of gastrointestinal peptides?].

The Willmen gastric bubble has been used as an adjunct to weight loss in morbidly obese patients. 35 patients with morbid obesity were studied with routine manometry, esophageal 24-h-pH-measurement, and gastric emptying studies before and 4 weeks after bubble placement. During emptying studies blood samples were taken to measure gastrin, PP, CCK, VIP, neurotensin and insulin. No patient developed heartburn or regurgitation after bubble placement. Esophageal motility and LES function remained unchanged. There was no important pathological gastroesophageal reflux before and after gastric bubble. The gastric emptying time of solid food was unchanged by gastric bubble placement and the emptying time of liquids was accelerated up to normal. In patients with fasting gastrin levels less than 20 pg/ml at the beginning of the first test we found no differences in gastrin release before and after bubble insertion. In patients with primary high fasting values gastrin release was significantly increased. CCK, VIP, neurotensin and insulin levels were unchanged. With PP we measured significantly raised fasting levels after gastric bubble. We conclude that esophageal and LES functions are not altered by Willmen gastric bubble placement and that primary retardation of fluids is changed to normal. Bubble induced gastric tension increases fasting PP. In case of high fasting gastrin the bubble leads to an extremely high food response without any clinical signs.

Adult↗

PubMed1988

Pancreatic trophism following colectomy in rats: the potential role of gastrointestinal hormones.

It has been shown that the large bowel contains substances with a potential to inhibit exocrine pancreatic function. Following large bowel removal in rats, there is an increase of pancreatic weight, digestive enzyme concentration, and secretion capacity in vitro. To evaluate the role of various GI hormones in the exocrine pancreatic adaptation following colectomy, we measured plasma cholecystokinin (CCK), neurotensin, glucagon, and insulin after meal stimulation. The test meal was applied via a transabdominal gastric tube in eight colectomized Wistar rats after a median of 18 days following surgery. Ten rats with a gastric tube without previous bowel surgery served as controls. After large bowel removal, there was impaired glucose tolerance and attenuated plasma insulin secretion. Baseline plasma glucagon levels were increased after colon removal, whereas the total postprandial glucagon release was decreased. Baseline and postprandial neurotensin values were comparable in both the experimental and control animals. Baseline and postprandial CCK plasma levels were intensely increased in the colectomized rats. It is assumed that the baseline and postprandial CCK pattern in rats after subtotal colectomy is responsible for exocrine pancreatic adaptation.

Animals↗

PubMed1988

Vagal influence on cholecystokinin and neurotensin release in conscious dogs.

Cholecystokinin (CCK) release in seven conscious dogs was investigated by means of modified sham feeding. After sham feeding mean CCK concentrations rose from a basal value of 1.0 +/- 0.2 pmol/l to a peak value of 2.4 +/- 0.3 pmol/l (p less than 0.005). The release in response to sham feeding amounted to half of that seen after normal feeding. Atropine significantly altered CCK output after sham feeding (basal, 1.0 +/- 0.2 pmol/l; peak 1.3 +/- 0.3 pmol/l). Sham feeding did not affect neurotensin release. It is concluded that an important cephalic phase of CCK release exists which seems to be dependent on a cholinergic mechanism.

Animals↗

PubMed1987

Isolation of apolipoprotein-B-48 from chylomicrons by high-performance liquid chromatography.

Apolipoprotein-B-48 (B-48) is a component of chylomicrons and chylomicron remnants and originates in the human gut wall. Its molecular weight represents 48% of the hepatic apolipoprotein-B-100 (B-100). So far, immunochemical assays are only available for B-100 and do not permit the specific determination of B-48. As a convenient immunochemical method is necessary for clinical and biochemical investigations of chylomicron remnants, we isolated B-48 in amounts sufficient to permit the production of monoclonal antibodies. After delipidation of the chylomicron fraction from 3 1 of human chylous ascites, size-exclusion chromatography was performed by using two serially connected TSK columns. B-48 was eluted as a second peak at about 35% of the total volume, well separated from B-100 (eluted as a first peak). After detection by UV absorption at 280 nm, the fractions collected from 25 automated runs were combined, ultrafiltered and examined for their protein composition by sodium dodecyl sulphate polyacrylamide gel electrophoresis. This indicated that we were able to isolate rapidly 3.4 mg of B-48 in a purity sufficient to perform immunization.

Apolipoprotein B-48↗

PubMed1987

Exocrine pancreatic function in dogs with denervated pancreas.

There is strong evidence that the vagus nerve plays an important role in exocrine pancreatic secretion. In the present study we examined the effect of total extrinsic denervation of the pancreas on exocrine pancreatic secretion to different stimuli in dogs. In the experiments we used the model of the orthotopic autotransplanted dog pancreas as described by Debas et al. Denervation of the gland did not significantly alter water and bicarbonate response to secretin. The dose-response curve of caerulein showed the denervated pancreas as sensitive as the intact gland. However, autotransplantation of the pancreas caused a significant decrease (p less than 0.05) in protein secretion during intraintestinal L-tryptophan in increasing doses. Furthermore, bicarbonate and protein secretion after food intake was significantly decreased in the denervated pancreas (protein: peak levels 380 mg/15 min and 135 mg/15 min; bicarbonate: 3.2 mEq/15 min and 1.4 mEq/15 min) (p less than 0.02). From our data we conclude that the denervated pancreas is as sensitive as the intact pancreas to stimulation by exogenous secretin and caerulein, whereas denervation of the pancreas causes an important influence in the intestinal phase of pancreatic secretion.

Animals↗