Biomedical subjects

K Tatemoto

Publications and source records attributed to K Tatemoto.

At least 73 records · Page 4Linked to original sources

PubMed1988

Isolation and primary structure of human peptide YY.

The isolation, primary structure and chemical synthesis of human peptide YY (PYY) are described. The peptide was purified from human colonic extracts using a chemical method which detected the C-terminal tyrosine amide structure of PYY. Human PYY consists of 36 amino acid residues and the complete amino acid sequence is: Tyr-Pro-Ile-Lys-Pro-Glu-Ala-Pro-Gly-Glu- Asp-Ala-Ser-Pro-Glu-Glu-Leu-Asn-Arg-Tyr-Tyr-Ala-Ser-Leu-Arg-His-Tyr-Leu- Asn-Leu-Val-Thr-Arg-Gln-Arg-Tyr-NH2. The differences between the structures of porcine and human PYY are at positions 3 (Ala/Ile replacement) and 18 (Ser/Asn). Synthetic human PYY prepared using a solid-phase synthetic technique was found to be structurally identical to the natural peptide.

Amino Acid Sequence↗

PubMed1988

Effect of natural peptide YY on blood flow and exocrine secretion of pancreas in dogs.

Little is known regarding the mechanism by which peptide YY exerts an inhibitory effect on exocrine pancreatic secretion. The purpose of this study is to determine if peptide YY affects pancreatic blood flow with simultaneous measurement of exocrine pancreatic secretion in dogs. Pancreatic blood flow was measured by a laser Doppler flowmeter which allows continuous measurement of tissue blood flow. Natural peptide YY (0.1, 0.5, 1 microgram/kg) was infused intravenously as a bolus under background infusion of secretin (1 unit/kg/hr) in combination with cholecystokinin-octapeptide (0.1 microgram/kg/hr). Peptide YY caused a reduction of pancreatic blood flow in a dose-dependent manner as well as inhibition of pancreatic protein output, attaining the maximal reduction (28 +/- 4%) and inhibition (45 +/- 9%) at a dose of 1 microgram/kg, respectively. Simultaneous and continuous observation on tissue blood flow and exocrine secretion of the pancreas revealed that there was a highly significant correlation between the percent reduction of pancreatic blood flow and that of volume of pancreatic juice in response to peptide YY (r = 0.849, P less than 0.001). This study provides evidence that the mechanism of peptide YY-induced inhibition of exocrine pancreatic secretion is mediated, at least partly, through the decreased pancreatic blood flow.

Animals↗

PubMed1988

The occurrence of pancreastatin in tumours of the diffuse neuroendocrine system.

We have reported previously the localization of the 49 amino acid peptide pancreastatin to all identifiable endocrine cells of porcine gut, pancreas and adrenal, thyroid and pituitary glands. In this study, we have investigated the occurrence of pancreastatin in a series of human neuroendocrine tumours using an antibody to whole synthetic porcine pancreastatin. The most consistent immunostaining for pancreastatin was found in carcinoid tumours of ileum (four out of six), rectum (four out of six), ovary (two out of two) and lung (nine out of 10). Radioimmunoassay of tumour extracts showed that the concentrations of pancreastatin in ileal carcinoids were very high (mean 71.6, range 31.0-184.0 pmol g-1). The high rate of positivity in lung carcinoids contrasted sharply with the results of 10 pulmonary small cell carcinomas which displayed no immunoreactivity and contained minimal concentrations of pancreastatin (mean 2.0, range 0-6.0 pmol g-1). Extra-adrenal paragangliomas also contained pancreastatin (seven out of 10), but although radioimmunoassay detected peptide in phaeochromocytomas (mean 29.8, range 8.0-69.0 pmol g-1), immunocytochemistry did not. Porcine pancreastatin shows structural homology with bovine chromogranin A, an observation which has led to suggestions that chromogranin is a precursor for the peptide. More recently, a sequence homologous to porcine pancreastatin has been identified in the human chromogranin A molecule. In this study, immunostaining with an antiserum to human chromogranin gave positive results in most cases of each tumour type except the small cell carcinomas. The lack of consistent relationships between chromogranin and pancreastatin immunoreactivities may reflect the fact that the antiserum to pancreastatin was raised against the porcine peptide. When antibodies to human pancreastatin become available, the peptide may prove to be a more consistent marker for neuroendocrine tumours.

Adenocarcinoma↗

PubMed1988

A comparison of the insulinotropic and the insulin-inhibitory actions of gut peptides on newborn and adult rat islet cells.

The objective of this study was to examine the release of insulin from cultured islet cells, taken from the pancreas of newborn and adult rats, in response to gastric inhibitory polypeptide (GIP), cholecystokinin-8 (CCK-8), calcitonin gene-related peptide (CGRP), and pancreastatin. GIP (10(-9)-10(-7) M) potentiated glucose-stimulated release of insulin in a dose-dependent fashion from both newborn and adult islet cells. CCK-8 (greater than 10(-8) M) also increased glucose-stimulated release of insulin from newborn islet cells, however its effect was not significant and not as strong as that observed with adult islet cells. Culture of newborn islet cells for 3 weeks with media containing high concentrations of glucose (16.7 mM) enhanced insulin release in response to CCK-8. CGRP did not affect the release of insulin from newborn islet cells, whereas at 10(-10) M, it reduced the release of insulin from adult islet cells by 66 +/- 4%. Pancreastatin (10(-9)-10(-8) M) did not affect the release of insulin from newborn islet cells when cells were incubated with 4.2 mM glucose, whereas it stimulated the release of insulin from adult islet cells in a dose-dependent fashion. When incubated with 16.7 mM glucose, pancreastatin inhibited the release of insulin from both newborn and adult islet cells. These results indicate that newborn islet cells experience developmental changes which render them responsive to enteric peptides.

Age Factors↗

PubMed1988

Localization of pancreastatin immunoreactivity in porcine endocrine cells.

Pancreastatin is a peptide isolated from the porcine pancreas and shown to inhibit insulin release. We have studied the immunocytochemical distribution of pancreastatin in three porcine endocrine tissues: pancreas, gut, and adenohypophysis. Pancreastatin-specific immunoreactivity was found in all three locations and distributed to numerous cells. In the pancreas, we performed the alternate labeling of consecutive thick (immunofluorescence) or thin (protein A-gold) sections and we observed that pancreastatin colocalizes to secretory granules of insulin and somatostatin-containing cells. The relationship of pancreastatin to chromogranin A is discussed.

APUD Cells↗

PubMed1988

Pancreastatin inhibits insulin secretion and stimulates glucagon secretion in mice.

Recently a new peptide, pancreastatin, was isolated from porcine pancreatic extracts. It contains 49 amino acids and shows a structural similarity to chromogranin A, which occurs in secretory granules of the endocrine pancreas. Furthermore, pancreastatin has been found to inhibit glucose-induced insulin secretion in the perfused rat pancreas. However, its effects under in vivo conditions have never been studied. We have therefore investigated the effects of this peptide on insulin and glucagon secretion in vivo in the mouse. We found that an intravenous injection of pancreastatin (4.0 nmol/kg) lowered basal plasma insulin concentration at 6 min from 55 +/- 8 microU/ml in control mice to 21 +/- 7 microU/ml (P less than .01). The peptide also inhibited the plasma insulin response to both glucose (P less than .01) and the cholinergic agonist carbachol (P less than .001). Furthermore, 2 min after injection of pancreastatin, plasma glucagon concentration had increased to 301 +/- 19 pg/ml compared to 190 +/- 12 pg/ml in control mice (P less than .001). The peptide did not, however, affect the carbachol-induced plasma glucagon response. In addition, pancreastatin induced a transient hyperglycemia. Combined adrenergic blockade by means of a pretreatment of phentolamine and propranolol did not prevent pancreastatin from exerting its effects on plasma insulin levels, whereas the increase in plasma glucagon levels was abolished. Thus, in the mouse, the newly discovered intrapancreatic peptide pancreastatin 1) lowers baseline plasma insulin levels, 2) inhibits glucose- and cholinergically induced insulin secretion, 3) stimulates baseline glucagon secretion, and 4) induces hyperglycemia.

Animals↗

PubMed1987

Chemical sympathectomy reveals pre- and postsynaptic effects of neuropeptide Y (NPY) in the cardiovascular system.

Intravenous injection of neuropeptide Y (NPY) caused short-lasting dose-dependent pressor responses in anesthetized rats. NPY was equipotent with noradrenaline in producing proportional pressor effects. Chemical sympathectomy, following the administration of 100 mg/kg 6-hydroxydopamine (6-OHDA), significantly potentiated the systemic pressor effects elicited by NPY or noradrenaline. Pretreatment with 2 nmol NPY enhanced the noradrenaline-induced pressor response in control rats. NPY did not change the basal tension of isolated rat aortic strips but significantly potentiated the contractile activity induced by 16 nM noradrenaline. This effect of NPY was not observed in aortic strips from rats pretreated with 6-OHDA. The presence of pre- and postsynaptic sites of action for NPY in the cardiovascular system of the rat is discussed.

Animals↗

PubMed1987

Identification and molecular characterization of galanin receptor sites in rat brain.

Receptors for galanin are identified and characterized in rat brain membranes. Interaction of [125I]-galanin with its receptors is saturable, time, pH, and ionic strength-dependent. It is reversible and highly peptide specific. Scatchard analysis of binding data reveals the existence of one single class of high affinity binding sites with a KD of 0.9 nM and a capacity of 101 fmoles/mg membranes protein. Chemical cross-linking of [125I]-galanin to its brain receptor followed by SDS-PAGE analysis leads to the identification of one major protein of 56 kD corresponding to the galanin-receptor complex. Our findings provide the first biochemical characterization of galanin receptors in the central nervous system supporting a role for galanin in the control of brain functions.

Animals↗

PubMed1987

Molecular cloning of a brain-specific calcium/calmodulin-dependent protein kinase.

A calcium/calmodulin-dependent protein kinase type II (CaM-K) alpha-subunit cDNA has been cloned from rat brain. This enzyme is encoded by a 5.1-kilobase mRNA expressed exclusively in the brain. Hybridization histochemistry reveals that the CaM-K mRNA expression corresponds to the distribution of the immunoreactive alpha-subunit protein, suggesting that the high enzyme levels in specific brain areas reflect regional differences in gene expression. The sequence of CaM-K alpha-subunit cDNA indicates a 478-amino acid (54-kDa) protein with three functional domains. The domain organization suggests a structural model for calcium/calmodulin-dependent and independent states that might subserve short- and long-term responses to transient stimuli.

Amino Acid Sequence↗

PubMed1987

Pancreastatin and islet hormone release.

The effect of pancreastatin on the release of insulin, glucagon, and somatostatin was studied in the isolated perfused rat pancreas. After an initial equilibration period (-20 to 0 min) with a basal glucose concentration (3.3 mM), the pancreata were perfused with either 16.7 mM glucose (0-40 min) or with 20 mM arginine (0-20 min). Pancreastatin was introduced 10 min prior to and throughout the administration of the high glucose and arginine and continued during their perfusion. As expected, the glucose and the arginine augmented insulin and somatostatin release. Pancreastatin (1 and 10 nM) markedly suppressed the first phase of insulin release with both insulinogogues used, while the early somatostatin secretion was not significantly decreased. However, the peak incremental somatostatin response to arginine was reduced by 50% (P less than 0.05). Conversely, the peptide (10 nM) tended to augment arginine-induced glucagon release. Pancreastatin (100 nM) also suppressed glucose-stimulated insulin release from isolated rat islets. These pancreastatin-mediated alterations in islet hormone release are reminiscent of those known to characterize non-insulin-dependent diabetes. Therefore, the significance of pancreastatin in islet physiology and pathophysiology deserves special consideration.

Animals↗

PubMed1987

Galanin receptors in a hamster pancreatic beta-cell tumor: identification and molecular characterization.

High affinity binding sites for galanin are identified and characterized in membranes from a hamster pancreatic beta-cell tumor. Using the radioiodinated peptide [125I] galanin, interaction of the peptide with pancreatic membranes is shown to be saturable, reversible, and time, temperature, membrane protein concentration, pH, and ionic strength dependent. In optimized equilibrium conditions of binding (90 min at 10 C), native galanin competitively inhibits the binding of [125I]galanin in a dose-dependent manner (from 10(-11)-10(-8) M); half-maximal inhibition is induced by 1 nM peptide. Scatchard analysis indicates the existence of a single population of sites of high affinity (Kd = 1.5 nM) and low capacity (44 fmol/mg protein). The monophasic dissociation process confirms the homogeneity of galanin-binding sites. Galanin-binding sites are highly specific, since apart from native galanin, none of the numerous biologically active peptides tested competes with [125I] galanin for binding to pancreatic membranes. The cross-linking of [125I]galanin to beta-cell membranes is performed using the chemical bifunctional reagent ethylene glycol bis-(succinimidyl succinate). After sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis in the presence or absence of dithiothreitol, one single band of 57,000 mol wt is observed, which may be corresponding to the [125I]galanin-receptor complex. Indeed, labeling of this 57,000 mol wt component is abolished only by native galanin but is unaffected by various other digestive peptides. Assuming one molecule of [125I]galanin is bound per molecule of protein, a 54,000 mol wt protein is identified as the pancreatic galanin receptor. In conclusion, our results indicate for the first time the identification of galanin receptors. Their presence in pancreatic beta-cells suggests a direct role of galanin in regulating endocrine beta-cell function.

Adenoma, Islet Cell↗

PubMed1987

Synthesis of neuropeptide Y.

Neuropeptide Y (NPY), a hexatriacontapeptide amide, was synthesized on benzhydrylamine resin. The peptide product obtained by HF treatment contained 63% of the target peptide, NPY. A comparison of the chemical, immunochemical and biological properties of the synthetic peptide with natural NPY indicated that they were identical.

Amino Acid Sequence↗

PubMed1986

Galanin: an inhibitory neural peptide of the canine small intestine.

Galanin injected intraarterially during phasic activity of the canine small intestine in vivo produced inhibition. Fifty percent inhibition occurred at 1.5 +/- 0.5 X 10(-10) mols lasting for 0.7 min. The inhibitory response was not decreased by treatment with atropine, hexamethonium, yohimbine or naloxone, suggesting that muscarinic, nicotinic, alpha 2 adrenergic or opiate receptors were not being stimulated. Since tetrodotoxin blockade of nerves did not reduce the response and galanin at 10(-10) mols was able to eliminate the smooth muscle response to intraarterial acetylcholine, we suggest that galanin acts to inhibit smooth muscle directly. Galanin 10(-9) M added to the muscle bath also inhibited phasic activity of the canine ileum circular muscle in vitro in the presence of tetrodotoxin. These results suggest that the neural peptide galanin may be a non-adrenergic, non-cholinergic, non-opioid neurotransmitter in the canine small intestine.

Animals↗

PubMed1986

Interaction of peptide YY with rat intestinal epithelial plasma membranes: binding of the radioiodinated peptide.

High affinity binding sites for peptide YY (PYY) have been identified and characterized in plasma membranes prepared from rat jejunal epithelium by studying the kinetics, stoichiometry, and chemical specificity of the interaction of 125I-labeled PYY with membranes. Binding of [125I]PYY was rapid, saturable, reversible, specific, and depended on temperature, pH, and ionic strength. In optimized steady state conditions of binding (2 h of incubation at 15 C), the degradation of both [125I] PYY and binding sites did not exceed 20%. The concentration dependence of PYY binding, determined by adding increasing concentrations of [125I]PYY, indicated that specific binding saturated at 2-3 nM peptide. Scatchard analysis revealed a single class of binding sites with a dissociation constant (Kd) of 434 +/- (SE) 56 pM and a binding capacity of 336 +/- 41 fmol/mg protein (n = 11). Identical results were obtained when increasing concentrations of unlabeled PYY were added to a fixed concentration of [125I]PYY, indicating that the radioiodinated peptide has the same apparent affinity as native PYY. Peptides structurally unrelated to PYY, such as members of the vasoactive intestinal peptide family, insulin, or cholecystokinin octapeptide, were unable to compete with [125I]PYY for binding to membranes. Rat, human, and avian pancreatic polypeptides, which display, respectively, 42%, 47%, and 53% homology with PYY, did inhibit [125I]PYY binding but with an approximate or equal to 100,000-fold lower potency than PYY, indicating the strict structural requirement for recognition by PYY binding sites. In contrast, natural or synthetic neuropeptide Y, which has 25 out of 36 amino acids in common with PYY, retained a high affinity for PYY binding sites [only 4.7 +/- 1.2 (n = 5) times lower than that of PYY]. Specific [125I]PYY binding was particularly high in the upper small intestine and could not be detected in stomach, large intestine, or liver. These findings indicate that rat small intestinal epithelium expresses specific binding sites for the candidate gut hormone PYY that also binds the neuropeptide Y with high affinity, suggesting that the two peptides may regulate the function of small intestinal epithelium, through interaction with a common receptor site.

Animals↗

PubMed1986

The distribution of polypeptide YY-like immunoreactivity in rat tissues.

The distribution of peptide YY (PYY)-like immunoreactivity (IR) in rat tissues was determined by specific RIA after extraction with boiled 1 N acetic acid. The high concentration of PYY-IR was observed in the gastrointestinal tract, with concentrations gradually increasing from the duodenum to the end of colon. The concentration of PYY-IR in the colon was 298.7-449.5 pmol/g tissue (approximately 100-200 times more than that in the duodenum). Pituitary and pancreas contained measurable amounts of PYY-IR (6.8 and 6.3 pmol/g tissue). The concentration of PYY-IR in the mucosa was higher than that in the muscular layer in the small intestine, cecum, colon, and rectum. The ratio of the mucosal PYY-IR to the muscular PYY-IR was highest in the distal small intestine (4.7-6.8). Sephadex G-50 gel chromatography of the colon extracts revealed the one PYY-IR peak which corresponds to [125I]PYY. The gradual increase of PYY-IR from the duodenum to the end of the colon is different from the distribution of other known gut peptides.

Animals↗

PubMed1986

The effect of galanin on canine plasma glucose and gastroenteropancreatic hormone responses to oral nutrients and intravenous arginine.

Intravenous infusion of galanin into conscious dogs during ingestion of oral glucose or a mixed meal or during iv infusion of arginine resulted in significant blunting of plasma insulin responses and significant increases in plasma glucose levels compared to those in control experiments. Galanin infusions did not significantly alter plasma gastric inhibitory peptide responses to oral glucose or a mixed meal, or plasma gastrin, pancreatic polypeptide, or pancreatic glucagon responses to a mixed meal. Similarly, galanin infusions did not significantly alter pancreatic glucagon responses to iv arginine. In all experimental situations, on cessation of the galanin infusions, prompt elevation of plasma insulin levels occurred. These results suggest that in the conscious dog, galanin administration produces a relatively selective, but readily reversible, inhibition of insulin secretion stimulated by oral nutrients or iv arginine.

Animals↗

PubMed1985

Isolation and characterization of substance P, substance P 5-11, and substance K from two metastatic ileal carcinoids.

Using an antiserum directed at the COOH-terminus of tachykinins, we have examined postmortem tissue from two cases of metastatic ileal carcinoid for the presence of tachykinin-like immunoreactivity. The vast majority of the immunoreactive tachykinin-like material eluted from a Sephadex G-50 column as two peaks at positions corresponding to molecular weights of 1300 and 850. The 1300 dalton peak was resolved by reverse-phase-HPLC into two components which by Edman sequencing, amino acid analysis, and fast atom bombardment (FAB)-mass spectrometry criteria, were identified as substance P and substance K. The 850 dalton peak was also resolved on RP-HPLC into two peaks which were resistant to Edman degradation but from amino acid analysis and FAB-mass spectrometry criteria were identified as pyro-Glu-substance P 5-11 and oxidized pyro-Glu-substance P 5-11. In control experiments substance P 5-11 was converted to pyro-Glu-substance P 5-11 during the extraction procedure. Both tumors also contained a minor immunoreactive peak which eluted from a Sephadex G-50 sizing column at a position corresponding to a molecular weight of 4000 which probably represents neuropeptide K. These results suggest that beta-preprotachykinin is preferentially expressed in carcinoid tumors and that substance K may also play a role in the carcinoid syndrome.

Amino Acid Sequence↗

PubMed1985

Neuropeptide Y-induced pressor responses: activation of a non-adrenergic mechanism, potentiation by reserpine and blockade by nifedipine.

Intravenous administration of neuropeptide Y (NPY) to pentobarbital anesthetized rats produced a short-lasting concentration-dependent increase in systolic and diastolic blood pressure. Pretreatment of rats with 2 mg/kg reserpine potentiated the NPY-induced pressor responses causing a leftward shift of the NPY concentration-response curve. In addition, reserpinization lengthened the duration of the NPY pressor effects. Reserpine also potentiated the noradrenaline-induced pressor effect but not that caused by angiotensin II. The NPY-induced increase in blood pressure was not antagonized by phenoxybenzamine. On the contrary, some degree of potentiation was observed, particularly with the larger doses of NPY. The NPY pressor responses were reduced by nifedipine in control and in reserpinized rats. The results demonstrate that the NPY-induced pressor responses were not related to adrenergic mechanisms. NPY may activate calcium channels in the cardiovascular system to promote an influx of calcium, causing peripheral vasoconstriction.

Angiotensin II↗