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Biomedical subjects

N D Christofides

Publications and source records attributed to N D Christofides.

At least 73 records · Page 4Linked to original sources
PubMed1983

Molecular forms of human enteroglucagon in tissue and plasma: plasma responses to nutrient stimuli in health and in disorders of the upper gastrointestinal tract.

A means of estimating human enteroglucagon (glucagon-like immunoreactivity of intestinal origin) in tissues and plasma is described, based on the subtraction of RIA values obtained with the C-terminal-directed glucagon antiserum RCS5 from the total glucagon-like immunoreactivity determined with the N-terminal- to midmolecule-directed glucagon antiserum R59. Gel filtration on Sephadex G-50 of human plasma and extracts of normal human intestine separated the R59 immunoreactivity into three peaks: a small peak of void volume material, a major peak coeluting with porcine glicentin, and a smaller peak coeluting with pancreatic glucagon. No RCS5 immunoreactivity was detected in the human gut, except for a small amount constituting less than 2% of the total glucagon-like immunoreactivity in the ileum and rectum only. In extracts of human pancreas, the chromatographic profiles obtained with RCS5 and R59 assays differed from the intestinal patterns, but were identical to each other, giving no evidence of a significant amount of pancreatic R59 immunoreactivity that was not also reactive with RCS5. Chromatography of plasmas from healthy subjects and patients with dumping syndrome, active coeliac disease, and tropical sprue showed that only the second major peak of R59 immunoreactivity reflected the basal or postnutrient increases in the plasma enteroglucagon concentration. In patients with exaggerated enteroglucagon release, the rise was again found to be entirely due to an increase in this peak of immunoreactivity. This major molecular form of human enteroglucagon, similar in size to porcine glicentin, is, thus, the form most likely to be of physiological and pathophysiological significance.

Adult↗
PubMed1983

Gut hormones in inflammatory bowel disease.

We have studied fasting levels and the response to a standard test breakfast of blood glucose and several gut hormones in 24 patients with ulcerative colitis, in 14 patients with Crohn's disease, and in 14 healthy control subjects. Patients with ulcerative colitis had significantly elevated fasting human pancreatic polypeptide (HPP) concentrations, and both basal and postprandial levels of gastrin, gastric inhibitory polypeptide (GIP), and motilin were greater than normal. In contrast, patients with Crohn's disease had normal gastrin levels but had increased fasting and postprandial levels of GIP and motilin and, in addition, of enteroglucagon, compared with controls. These patients also had greater than normal HPP concentrations 30 min after the breakfast. Normal levels of insulin, pancreatic glucagon, neurotensin, and vasoactive intestinal polypeptide were found in both groups of patients. Much remains to be known about the pathophysiology of these two debilitating diseases, and the abnormal release of gut hormones may be of importance.

Adolescent↗
PubMed1982

Decreased plasma motilin concentrations in pregnancy.

Plasma motilin concentrations were measured in 37 women during the second and third trimester of pregnancy and one week after delivery. The mean plasma motilin concentrations, both fasting and after a glucose load and a mixed meal, were significantly (p less than 0.001) reduced during pregnancy, returning to the normal range one week post partum. Pregnancy appears to have a profound inhibitory effect on plasma motilin, and this may in part be responsible for the gastrointestinal hypomotility associated with pregnancy.

Female↗
PubMed1982

PHI stimulates intestinal fluid secretion.

Regulatory peptides are likely to have a role in the control of net intestinal fluid transport. PHI is a peptide recently isolated from porcine duodenum which has been shown to have sequence homologies with other peptides of the glucagon-secretin family. We have studied the effect of intravenous infusion of synthetic PHI on net intestinal fluid transport in the rat small intestine. During PHI infection net absorption was reduced in the duodenum and jejunum and net secretion was observed in the ileum. Thus synthetic PHI appears to be capable of strongly stimulating intestinal secretion in the rat.

Animals↗
PubMed1982

Duodenal perfusion with sodium taurocholate inhibits biliary but not pancreatic secretion in man.

1. A standard duodenal perfusion technique was used to study the effects of luminally perfused sodium taurocholate on basal and stimulated biliary and pancreatic secretion and gastrointestinal hormone release in man. 2. During duodenal perfusion with sodium taurocholate alone, both basal and caerulein/secretin-stimulated bilirubin secretion were suppressed. A successive perfusion with a mixture of the bile salt and essential amino acids in combination overcame the biliary suppression and biliary secretion rose above basal levels. A further increase in bilirubin secretion was not observed in a subsequent perfusion with essential amino acids alone in these studies. 3. No inhibitory effect on basal or caerulein/secretin-stimulated trypsin secretion was observed during the bile salt perfusion; basal trypsin secretion was in fact slightly increased during a prolonged (4 h) perfusion of the bile salt. 4. During bile salt perfusion, basal bicarbonate secretion remained unchanged but caerulein/secretin-stimulated bicarbonate secretion was slightly increased. 5. Plasma levels of pancreatic polypeptide, gastric inhibitory peptide and gastrin did not change significantly during duodenal perfusion with bile salt, but plasma levels of motilin were suppressed. 6. These results support the view that bile salts in the duodenum may regulate biliary and pancreatic secretion in man and affect plasma levels of motilin.

Adult↗
PubMed1982

Effects of intravenous somatostatin and motilin on the blood glucose and hormonal response to oral glucose.

Exogenous intravenous infusions of control saline, somatostatin, motilin and somatostatin and motilin together were compared in normal volunteers for their effects on the rise of blood glucose following 50 g oral glucose and for their effects on gastric emptying and plasma hormone concentrations. All regulatory peptide infusions increased the rate of gastric emptying by between 182% and 198% at 60 min post-ingestion. The glucose response during the oral glucose tolerance test was suppressed when somatostatin with or without motilin was infused but was increased during motilin. The somatostatin infusion reduced concentrations of motilin, insulin, gastric inhibitory polypeptide, gastrin and neurotensin whilst the motilin infusion was associated with an increased initial rise in insulin and gastric inhibitory polypeptide. The metabolic effects of the motilin infusion were overriden by the effects of somatostatin when both peptides were infused together; this suggests that somatostatin inhibits both the effects and secretion of motilin.

Adult↗
PubMed1982

Gut hormone release after intestinal resection.

To investigate the possible role of gut and pancreatic hormones in the adaptive responses to gut resection, plasma concentrations of the circulating hormones were measured, in response to a test breakfast, in patients with either small or large intestinal resection and in healthy control subjects. In 18 patients with partial ileal resection a significant threefold rise was found in basal and postprandial levels of pancreatic polypeptide, a fourfold increase in motilin, and more than a twofold increase in gastrin and enteroglucagon levels compared with healthy controls. In contrast, nine patients with colonic resection had a threefold rise in levels of pancreatic polypeptide only. One or more of these peptides may have a role in stimulating the adaptive changes found after gut resection.

Adult↗
PubMed1982

Interdigestive biliary output in man: relationship to fluctuations in plasma motilin and effect of atropine.

The fasting output of bile into the bowel was investigated in nine healthy volunteers by hepatobiliary scanning. Subjects were studied twice, on each occasion for 2.5 hours. A significant flow of radioactivity from the gall bladder to the duodenum was observed on one or two occasions during each experiment. A 32 +/- 4% mean decrease in counts over the gall bladder was recorded, indicating partial emptying of this organ in the interdigestive state. The output of bile into the bowel was found to be related to fluctuations in fasting plasma motilin levels in that a significant motilin increment (18 +/- 4 pmol/l, p less than 0.005) paralleled the appearance of radioactivity in the duodenum. The onset of gall-bladder emptying regularly preceded the peak in plasma motilin (mean: 25 +/- 2 minutes). Atropine, intravenously, 0.6 mg followed by 0.3 mg, nearly abolished both fasting biliary output and plasma motilin fluctuations. Thus, bile output appears to occur frequently in fasting humans, but our data do not allow any conclusions as to the possible causal relationship between fasting gall-bladder emptying and release of motilin. Cholinergic influences appear to be of importance in the regulation of interdigestive biliary output in man.

Adult↗
PubMed1982

Pancreatic and gastrointestinal hormones in chronic pancreatitis.

Pancreatic and gut hormones have been measured in 39 patients with chronic pancreatitis, 16 of whom had severe pancreatic insufficiency. Patients with pancreatic insufficiency had significantly diminished fasting levels and postprandial rises of pancreatic polypeptide which were less than 20% of normal. Patients with chronic pancreatitis, with or without exocrine insufficiency, had two- to threefold higher plasma levels of motilin and enteroglucagon than controls. Plasma levels of insulin, pancreatic glucagon, gastric inhibitory polypeptide and gastrin were similar to normal in these patients. The pattern of response of these hormones to a test breakfast differs markedly from those seen in other gut disease states and may reflect pathophysiological mechanisms.

Adult↗
PubMed1982

Elevated motilin levels in patients treated with antidepressant and neuroleptic drugs.

Constipation is a frequent effect of treatment with antidepressant and neuroleptic drugs as a result of interference with neuronal control of colonic muscular activity. Motilin, a circulating peptide, is involved in induction of myoelectric complexes in the colon. Significantly elevated circulating basal motilin levels were found in patients receiving tricyclic antidepressant drugs, mean 128 +/- 33 pmol/l (control 48 +/- 6 pmol/l) or neuroleptic therapy, mean 213 +/- 29 pmol/l (control 87 +/- 8 pmol/l).

Antidepressive Agents, Tricyclic↗
PubMed1982

Bombesin: action on gut hormones and calcium in man.

Bombesin, a peptide with widespread biological actions, has been demonstrated in human tissues by immunological methods. To investigate its effect in man, synthetic bombesin was infused at low doses in six male volunteers. Bombesin at 2.4 pmol kg-1 min-1 produced significant rises in plasma insulin, glucagon, pancreatic polypeptide, gastrin, cholecystokinin, motilin, glucose-dependent insulinotropic polypeptide, neurotensin, enteroglucagon, vasoactive intestinal polypeptide, and serum calcium. In contrast, bombesin caused a profound fall in parathyroid hormone levels and reduced plasma glucose concentrations. A late rise in plasma calcitonin was also observed. Bombesin had no significant effect on the pituitary hormones, TSH, GH, PRL, or cortisol. No hormonal changes or alterations in calcium were noted during saline infusions. Bombesin has a marked stimulatory effect on gastrointestinal hormones, which is unique and opposite to the effect of somatostatin, a potent inhibitor of gut hormone release. Bombesin also influences calcium-regulating hormones, either directly or through its action on gut hormones. The bombesin concentrations achieved with the dosages used were low enough to indicate a possible physiological role for the endogenous peptide.

Adult↗
PubMed1982

Interdigestive motor activity in patients with systemic sclerosis.

Fasting antral, duodenal, and jejunal motor activity and plasma motilin and pancreatic polypeptide were studied in 14 patients with systemic sclerosis, 6 and 9 without clinical evidence of small bowel involvement, and 8 healthy control subjects. Normal interdigestive motor activity was present in control subjects and patients without intestinal involvement. However, cyclic motor activity was absent in 3 of the patients with intestinal disease and the motility index per interdigestive cycle (or per 6-h recording period in those without cyclic activity) was significantly less in the antrum (181 +/- 103 mm2 compared with 760 +/- 86 and 1116 +/- 96 mm2 for patients without involvement and healthy control subjects, respectively), duodenum (153 +/- 101 mm2 compared with 1425 +2- 186 nd 1055 +/- 241 mm2), and jejunum (268 +/- 131 mm2 compared with 1166 +/- 97 and 1105 +/- 128 mm2). Metoclopramide and bethanechol significantly increased motor activity at the three sites in all subjects but the magnitude of the metoclopramide response was less in patients with intestinal involvement. Fasting concentrations of motilin and pancreatic polypeptide exhibited cyclic variation with peak values occurring during phase 3 of the interdigestive cycle. Plasma motilin during each phase of motor activity was significantly higher in patients with scleroderma, with or without intestinal involvement, than in control subjects. The abnormal motor activity demonstrated here indicates a possible mechanism by which intestinal stasis and bacterial overgrowth could occur and by which clinical disturbances of intestinal transit might arise.

Adult↗
PubMed1982

The effects of naloxone and morphine on postprandial gastrointestinal hormone secretion.

Postprandial gastrointestinal hormone secretion was not affected by the intravenous administration of naloxone. However, after the administration of morphine, multiple effects were observed. Postprandial pancreatic polypeptide, motilin, and enteroglucagon secretion were abolished and there was a reduction in the secretion of insulin, gastric inhibitory polypeptide, and neurotensin. There was prolonged secretion of gastrin. Levels of vasoactive intestinal polypeptide, somatostatin, and pancreatic glucagon were not affected. Many of these changes can be accounted for by the ability of morphine to delay gastric emptying. The prolonged secretion of gastrin could result from a combination of impaired gastric emptying and reduced postprandial gastric acid secretion. Inhibition of vagal acetylcholine release is the most likely explanation for the abolition of pancreatic polypeptide secretion. With the exception of the effects on motilin, pancreatic polypeptide, and enteroglucagon secretion this study provides no evidence that opiate substances directly affect the secretion of gastrointestinal hormones.

Adult↗
PubMed1981

Effect of motilin on the gastric emptying of glucose and fat in humans.

The effect of natural motilin on the rate of gastric emptying of 200 ml 25% glucose was studied in seven subjects using a 99mtechnetium tin colloid marker. On the control day the subjects received intravenous saline while on the test day they received a motilin infusion of 0.2 pmol/kg/min. Infusions were blind and given in random order. Thirty minutes after glucose ingestion, 25.5 +/- 2% of the isotope had emptied during motilin infusion, compared with 11.0 +/- 1.5% with saline (p < 0.005). Plasma motilin concentrations rose from a basal value of 23 +/- 5 pM to 57 +/- 9 pM during the motilin infusion. The faster emptying rates after motilin were reflected in a faster rise of plasma glucose and insulin. The rate of emptying of 99mtechnetium-labeled double cream (200 ml, 24 g fat) was measured in 5 subjects. The rate of gastric emptying of the cream was unaffected by exogenous motilin. Gel chromatographic analysis of basal plasmas revealed two immunoreactive motilin peaks. After ingestion of cream during motilin infusion, there was an increase of the second peak but a reduction of the first peak whereas both peaks rose on the control day. Thus low-dose exogenous motilin stimulates the gastric emptying of glucose but not of fat.

Adult↗
PubMed1981

The gut hormone profile of fulminant hepatic failure.

Twenty-five patients with fulminant hepatic failure and grade III or IV hepatic encephalopathy were studied. Plasma insulin, glucagon, pancreatic polypeptide and enteroglucagon were significantly raised. Levels of secretin and gastrin were normal, while motilin concentrations were significantly depressed. Vasoactive intestinal polypeptide was increased in six patients and was significantly higher in those patients who were hypotensive or who had marked prolongation of prothrombin time.

Acute Kidney Injury↗