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Biomedical subjects

S I Said

Publications and source records attributed to S I Said.

At least 181 records · Page 10Linked to original sources
PubMed1977

Vasoactive intestinal peptide (VIP) cells in the pancrease and gastro-intestinal mucosa. An immunohistochemical and ultrastructural study.

Using antibodies against pure porcine VIP in immunoperoxidase and immunofluorescence tests, VIP-immunoreactive cells have been detected in the pancreas-especially in the islets-and gastrointestinal mucosa of the dog, guinea-pig and man. VIP immunoreactive cells were widely distributed in these tissues, never being numerous at any site. Some parallelism has been noted between such cells and ultrastructurally identified D1 cells fo the pancreas and gastrointestinal mucosa. The presence of VIP cells in normal pancreas may help explain the occurrence of pancreatic endocrine tumors producing VIP.

Animals↗
PubMed1977

Effects of prostaglandin endoperoxide analogs on contractile elements in lung and gastrointestinal tract.

Prostaglandin endoperoxides are formed in the lung as intermediate compounds in the biosynthesis of prostaglandins and thromboxanes. The effects of different doses of two analogs of prostaglandin endoperoxide PGH2 were compared with those of PGF2alpha and PGE2 on superfused preparations of isolated trachea, bronchiole, peripheral lung, pulmonary artery and gastrointestinal smooth-muscle tissues. Endoperoxide analogs induced contraction of all smooth-muscle structures in the lung and airway. Compared to PGF2alpha, analog I was approximately 71 times as potent on guinea-pig trachea, 214 times as potent on guinea-pig lung, and 57 times as potent on guinea-pig pulmonary artery. Analog II was moderately less potent on all tissues than analog I. On gastrointestinal smooth-muscle organs, the PGH2 analogs were generally closer in activity to PGF2alpha and PGE2, or even weaker. The findings show that PG endoperoxide analogs are potent constrictors of airways, lung and pulmonary vessels, and suggest that the naturally occurring compounds may participate in the mediation of bronchoconstriction and pulmonary vasoconstriction in disease states.

Animals↗
PubMed1977

Synthesis and pharmacological properties of the N-terminal decapeptide of the vasoactive intestinal peptide (VIP).

The decapeptide derivative, L-histidyl-L-seryl-L-aspartyl-L-alanyl-L-valyl-L-phenylalanyl-L-threonyl-L-aspartyl-L-asparaginyl-L-tyrosine methyl ester, corresponding to the N-terminal sequence of both porcine and chicken VIP was synthesized in solution, by the stepwise strategy. Its pharmacological properties resemble those of VIP itself, but with a much lower potency, comparable to that of peptides with C-terminal sequences. The presence of two independent sequences carrying similar instructions was recognized in VIP.

Amino Acid Sequence↗
PubMed1977

Vasoactive intestinal polypeptide in brain: localization in and release from isolated nerve terminals.

The vasoactive intestinal polypeptide was present in synaptosomal (nerve ending) preparations from cerebral cortex, hypothalamus, and striatum of rat brain in higher concentrations than in these tissues as a whole. The total content and relative specific activity of the peptide increased with progressive purification of the synaptosomal fractions and generally followed the distribution of known synaptosomal constituents--dopamine, norepinephrine, and lactate dehydrogenase (L-lactate:NAD+ oxidoreductase, EC 1.1.1.27). The peptide was also released from synaptosomal pellets with increased K+ concentration, and this release was Ca2+-dependent. The findings suggest a role for vasoactive intestinal polypeptide as a transmitter or modulator of synaptic function.

Animals↗
PubMed1977

Stimulation of insulin and glucagon secretion by vasoactive intestinal peptide.

In vivo, vasoactive intestinal peptide (VIP) produces simultaneous increases in blood glucose and insulin levels. In order to determine whether VIP, like its homologues, also stimulates insulin secretion directly, studies were made in controlled glucose media employing the vascularly perfused cat pancreas. VIP stimulated insulin secretion significantly in the presence of constant physiological concentrations of glucose. The highest insulin response to VIP (100.3+/-8.1 muU/min) approached the highest insulin response to glucose (119.9 +/- 12.0 muU/min). In the absence of glucose, the insulin response to VIP was insignificant. Unexpectedly, VIP was found to be a more effective stimulant of glucagon than of insulin secretion. The highest glucagon response to VIP (327+/-51% of control levels) was attained in the presence of physiological concentrations of glucose and equalled the glucagon response obtained upon withdrawal of glucose from the perfusate. The glucagon response to VIP was blocked by increasing the glucose in the perfusate. These studies indicate the VIP present in pancreatic islets might play a role in the local control of pancreatic endocrine function.

Animals↗
PubMed1976

Vasoactive intestinal polypeptide: abundant immunoreactivity in neural cell lines and normal nervous tissue.

Vasoactive intestinal polypeptide immunoreactivity is present in high concentrations in clonal lines of neuronal and glial origin. The central nervous system and sympathetic ganglia are also rich in the peptide. The findings suggest that this peptide, hitherto thought limited to the gastrointestinal tract, is widely distributed in neural tissue and may have broad physiological significance.

Animals↗
PubMed1976

A re-examination of the conformation of secretin in water.

An examination of a series of peptides corresponding to partial sequences of secretin and the application of empirical conformational parameters to the sequence has reopened the question about the position of the short helical stretch in the folded chain. In earlier studies, this was tentatively placed near the N-terminus, while newly accumulated evidence points to the C-terminal area. The possible role of ion pairs in the stabilization of the folding was investigated by the preparation and examination of synthetic analogues of the C-terminal tricosapeptide part of secretin. The carboxyl groups of glutamic acid (in position 9) and of aspartic acid (in position 15) were replaced by carboxamides. The 9-glutamine and the 15-asparagine analogues show a significant decrease in helical character. This loss of "structure" is even more pronounced in the 9-glutamine-15-asparagine tricosapeptide. Thus, ion-pair formation is indeed implicated as one of the forces which stabilize the folded conformation of the chain. Possible correlations between biological activity and secretin-like architecture were studied on several smooth muscle preparations.

Amino Acid Sequence↗
PubMed1976

Evidence for secretion of vasoactive intestinal peptide by tumours of pancreas, adrenal medulla, thyroid and lung: support for the unifying APUD concept.

Levels of vasoactive intestinal polypeptide (VIP) were measured by radioimmunoassay in plasma or tissue from thirty-five patients with watery diarrhoea, and in plasma of twenty-five normal controls. Plasma levels were between 0.6 and 11.0 ng/ml in thirty-one of the thirty-three patients in whom it was measured and too low to measure (less than 200 pg/ml) in the other two. Peptide levels were less than 200 pg/ml in twenty-three of the controls, but higher in the remaining two. All tissues from patients were "rich" in VIP (10 ng to 35 microgram per g). The aetiologic diagnoses included pancreatic islet-cell adenoma or adenocarcinoma, islet-cell hyperplasia, bronchogenic carcinoma, pheochromocytoma, ganglioneuroblastoma, medullary thyroid carcinoma, and retroperitoneal histiocytoma. The findings support the conclusions that: (1) VIP is a likely mediator of the water-diarrhoea syndrome; (2) the syndrome may result from a variety of tumours; (3) this or a related peptide hormone may be secreted by these tumours; and (4) these tumours may have a common embryonic origin.

APUD Cells↗
PubMed1975

Elevated plasma and tissue levels of vasoactive intestinal polypeptide in the watery-diarrhea syndrome due to pancreatic, bronchogenic and other tumors.

The actions of the vasoactive intestinal polypeptide make it a potential candidate for mediating certain manifestations of the watery-diarrhea syndrome. Peptide levels were measured by radioimmunoassay in 25 controls and 30 patients with chronic watery diarrhea. Plasma levels were too low to measure (smaller 200 pg per milliliter) in 22 of the controls, averaging 79 plus or minus 64 pg per milliliter (S.D.). Levels were elevated in 26 of 28 plasma samples (5.1 plus or minus 2.5 ng per milliliter), and in each of 13 tissue extracts (5.1 plus or minus 10.9 mug per gram); in all, 28 patients had elevated levels in plasma or tissue or both. Thirteen patients had pancreatic islet-cell adenoma, four islet-cell hyperplasia, five bronchogenic carcinoma, and one each pheochromocytoma and ganglioneuroblastoma. The findings indicate that the peptide is a probable mediator of the watery-diarrhea syndrome, that the syndrome may result from a variety of non-pancreatic tumors, and that this or a related peptide may also be secreted by these tumors.

Adenoma, Islet Cell↗
PubMed1975

Vasoactive intestinal polypoptide: inactivation in liver and potentiation in lung of anesthetized dogs (384699).

The role of the liver and the lung in the inactivation or potentiation of the biological activity of the vasoactive intestinal polypeptide (VIP) was examined in five anesthetized dogs. Infusions of the peptide were made into the right ventricle, the left ventricle, and the portal vein. Each animal received 4 doses, ranging from 0.29 to 2.23 mug/kg. Systemic arterial blood pressure, tidal volume, breathing frequency, and minute ventilation were continually monitored. The biological effects of the peptide were measured in terms of (a) the fall in arterial blood pressure; and (b) respiratory stimulation. Infusions of the peptide into the portal vein produced either no effect or significantly weaker effects (p smaller than 0.01) than infusions into the right ventricle. The latter infusions were moderately more potent (p smaller than 0.05) than infusions into the left ventricle VIP thus appears to be effectively inactivated during passage through the liver. The apparent increase in biological potency of the peptide during its passage through the lung may be attributable to the release of additional vasodilator substances, or to further activation of the peptide.

Animals↗