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Biomedical subjects

K Tatemoto

Publications and source records attributed to K Tatemoto.

At least 19 recordsLinked to original sources
PubMed1997

Hyperpolarization-activated Cl- current elicited by pituitary adenylate cyclase activating polypeptide in Xenopus oocytes.

We examined the electrophysiological effect of pituitary adenylate cyclase activating polypeptide (PACAP) in isolated Xenopus laevis oocytes in vitro. In conventional two-electrode voltage clamp experiments, PACAP (1-10 microM) activated an inward rectifier current at membrane potentials more negative than -60 mV without causing any significant change in currents at potentials more positive than -60 mV both in the follicle-enclosed oocyte and in the defolliculated oocyte. This current reversed at -22.5 mV, close to the theoretical value of Cl- equilibrium potential and the reversal potential of this current was shifted positively by reducing [Cl-]o. This current was blocked by Cl- channel blocker SITS and Ba2+. Furthermore, VIP and adenylate cyclase activator forskolin did not elicit the currents. In conclusion, PACAP elicited the hyperpolarization-activated Cl- current in Xenopus laevis oocytes. This current may modulate the membrane potential of the oocyte, thereby affecting the oocyte physiology.

Animals↗
PubMed1997

Uric acid changes in serum during different forms of hepatic vascular inflow occlusion.

The present study was conducted to develop an efficient marker which can evaluate the influence of the occlusion of hepatic vascular inflow, which technique is commonly used in major liver surgery or in liver transplantation. Serum samples from the rats induced by hepatic vascular inflow occlusion were analyzed with high performance liquid chromatography with the electrochemical detection, and a substance which changed in accordance with the duration of the occlusion was obtained. Both the retention time and the ultraviolet absorption spectra of the substance completely agreed with those of an authentic uric acid and the substance was ultimately determined to be uric acid. To evaluate the changes in serum uric acid during different forms of hepatic vascular inflow occlusion we devised the four types of experimental model, viz. the occlusion of hepatic artery, portal vein, both hepatic artery and portal vein and both hepatic artery and portal vein of left hepatic lobes. From the device of experiments our results indicated that in the early stage of hepatic vascular inflow occlusion the high values of serum uric acid did not reflect the damage of hepatic circulation but rather responded to the intestinal congestion. Our results also indicated that even after the declamping of hepatic vascular inflow if high values of serum uric acid are prolonged it means the deterioration of the portocaval circulation including both intestinal and hepatic circulation. So that the evaluation of the severity of injured liver due to hepatic vascular inflow occlusion should be done with the caution especially in vivo study when uric acid values are used as a marker.

Animals↗
PubMed1997

Islet hormone secretion in pancreatic cancer patients with diabetes.

The diabetes or impaired glucose tolerance that occurs in most patients with pancreatic cancer is characterized by profound insulin resistance. Recent evidence suggests that the diabetes may result from the presence of the tumor rather than being a predisposing factor to development of the malignancy. Some islet hormones have been shown to exhibit diabetogenic effects. To investigate the potential role of these hormones in the diabetic state associated with pancreatic cancer, we measured islet hormones during fasting in pancreatic cancer patients (n = 30), patients with other malignancies (n = 43), and healthy controls (n = 25). Preoperative pancreatic cancer patients were classified as normal glucose tolerance (NGTT), impaired glucose tolerance (IGTT), non-insulin-requiring diabetes (NIRD), and insulin-requiring diabetes (IRD). Nine pancreatic cancer patients were studied after tumor removal by subtotal pancreatectomy. Some preoperative pancreatic cancer patients (n = 19), postoperative patients (n = 9), and controls (n = 8) were also studied during hyperglycemia and following glucagon injection. Fasting plasma C-peptide was elevated in NIRD pancreatic cancer patients compared to controls. Fasting levels of islet amyloid polypeptide (IAPP), glucagon, and somatostatin were elevated in NIRD and IRD patients. IAPP and glucagon, but not somatostatin, normalized following subtotal pancreatectomy. During hyperglycemia, increases in C-peptide and IAPP were seen only in controls and in NGTT and postoperative pancreatic cancer patients. After glucagon infusion, IAPP levels increased in controls and nondiabetic cancer patients; C-peptide levels increased in controls, nondiabetic patients, and NIRD. Responses of C-peptide and IAPP to glucagon normalized after pancreatectomy. During hyperglycemia, glucagon levels fell in all groups except IGTT patients and a decrease in somatostatin concentrations was seen in controls.

Adenocarcinoma↗
PubMed1996

Diazepam binding inhibitor is a potent cholecystokinin-releasing peptide in the intestine.

Pancreatic proteases in the duodenum inhibit the release of cholecystokinin (CCK) and thus exert feedback control of pancreatic exocrine secretion. Exclusion of proteases from the duodenum either by the diversion of bile-pancreatic juice or by the addition of protease inhibitors stimulates exocrine pancreatic secretion. The mechanism by which pancreatic proteases in the duodenum regulate CCK secretion is unknown. In this study, we isolated a trypsin-sensitive peptide that is secreted intraduodenally, releases CCK, and stimulates pancreatic enzyme secretion in rats. This peptide was found to be identical to the porcine diazepam binding inhibitor by peptide sequencing and mass spectrometry analysis. Intraduodenal infusion of 200 ng of synthetic porcine diazepam binding inhibitor1-86 in rats significantly stimulated pancreatic amylase output. Infusion of the CCK antagonist MK-329 completely blocked the diazepam binding inhibitor-stimulated amylase secretion. Similarly, diazepam binding inhibitor33-52 [corrected] also stimulated CCK release and pancreatic secretion in a dose-dependent manner although it was 100 times less potent than the whole peptide. Using a perfusion system containing isolated mucosal cells from the proximal intestine of rats, porcine diazepam binding inhibitor 10(-12) M) dose dependently stimulated CCK secretion. In separate studies, it was demonstrated that luminal secretion of the diazepam binding inhibitor immunoreactivity (7.5 X 10(11) M) could be detected in rat's intestinal washing following the diversion of bile-pancreatic juice. The secretion of this peptide was inhibited by atropine. In conclusion, we have isolated and characterized a CCK-releasing peptide that has a sequence identical to the porcine diazepam binding inhibitor from pig intestinal mucosa and that stimulates CCK release when administered intraduodenally in rat. This peptide may mediate feedback regulation of pancreatic enzyme secretion.

Amino Acid Sequence↗
PubMed1996

Activation of iron handling system within the gerbil hippocampus after cerebral ischemia.

Analyzing the distribution pattern of transferrin (Tf) and ferritin, we investigated the changes in iron metabolism related proteins in the process of neuronal death induced by 5 min ischemia. In the control animals, Tf immunoreactivity was localized in the oligodendrocytes. Ferritin was distributed in both neurons and gliacytes, particularly microglia. In parallel with the delayed neuronal death, Tf-positive atrophied neurons and numerous ferritin-positive gliacytes appeared in the CA1 subfield of the hippocampus 4 days after ischemia, when glia fibrillary acidic protein (GFAP)-positive astrocytes also appeared throughout the hippocampal structure. A considerable number of ferritin-positive phagocytes (reactive microglia) appeared in the stratum pyramidale from the seventh day. Our data show clearly that the mobilization of Tf and ferritin-positive phagocytes are linked with the degeneration of neurons induced by cerebral ischemia. These events may suggest an activation of iron handling system under the postischemic condition.

Animals↗
PubMed1996

Bradykinin increases intracellular free Ca2+ concentration and promotes insulin secretion in the clonal beta-cell line, HIT-T15.

We have examined the effects of bradykinin (BK) on both the intracellular free calcium concentration ([Ca2+]i) and insulin secretion in the hamster beta-cell line, HIT-T15 cells. BK evoked a rise in [Ca2+]i in a dose-dependent manner. This response was suppressed by neomycin, suggesting that BK mobilizes Ca2+ from intracellular store via promotion of the phosphatidyl inositol turnover. Furthermore, BK also evoked insulin secretion. Both the BK-evoked rise in [Ca2+]i and insulin secretion were suppressed by the BK2 receptor antagonist, but not by the BK1 receptor antagonist. These results indicate that BK increases [Ca2+]i via BK2 receptor, thereby promoting insulin secretion in HIT-T15 cells.

Animals↗
PubMed1996

GLP-1 depolarizes the rat pancreatic beta cell in a Na(+)-dependent manner.

An intestinal hormone glucagon-like-peptide-1 (GLP-1) is a prominent candidate for incretin. In vitro experiment showed (Fridolf and Ahren, Mol. Cell. Endocrinol., 96 (1993) 85-90) that GLP-1 increased both insulin secretion and the efflux of 45Ca2+ in a Na(+)-dependent manner. Further, GLP-1 depolarizes the pancreatic beta cells in the presence of high concentration of glucose. Here, we report the effect of GLP-1 on the membrane potential with a physiological concentration of glucose in perforated patch clamp of primary cultured rat beta cells. 10 nM GLP-1 depolarized the beta cell, which was completely reversed by replacing Na+ with the impermeant molecule N-methyl-D-glucamine (NMDG). The Ca2+ channel blocker, Co2+ suppressed the Ca2+ spikes without hyperpolarizing the cell. GLP-1-induced insulin secretion in perifused islets was also suppressed by a prior replacement of Na+ with NMDG. In addition, GLP-1 slightly augmented the long-lasting Ba2+ current, which was reverted to the control level by a selective inhibitor of protein kinase A, H-89. These results indicate: (i) GLP-1 depolarizes the beta cell by activating the membrane Na+ permeability; (ii) GLP-1 slightly modulates the L-type Ca2+ channel probably through protein kinase A; and (iii) at least in part, these mechanisms may be involved in the insulin secretion induced by GLP-1.

Animals↗
PubMed1996

Effects of pancreastatin and somatostatin on secretagogues-induced rise in intracellular free calcium in single rat pancreatic islet cells.

Pancreastatin (PST) is known to inhibit glucose-stimulated insulin release both in vivo and in vitro, but it has not been determined whether PST acts directly on pancreatic B-cells and no study has been reported on the effect of PST on the intracellular free Ca2+ concentration ([Ca2+]i) in pancreatic islet cells. In the present study, by using the dissociated rat pancreatic B-cells, we examined the effects of PST on the increase in [Ca2+]i induced by several insulin secretagogues, and compared them with those of somatostatin (SRIF). PST (1-100 nM) dose-dependently inhibited the glucose-induced rise in [Ca2+]i in single pancreatic islet cells. SRIF (10 nM) also suppressed the glucose-induced rise in [Ca2+]i. These demonstrated direct inhibitory actions of PST and SRIF on the pancreatic B-cells. Acetylcholine (ACh, 10 microM) with 5.5 mM glucose induced a biphasic increase in [Ca2+]i in single islet cells. SRIF (10 nM) suppressed the second phase in [Ca2+]i increase without affecting the first phase. In contrast, PST (100 nM) had no effect on the ACh-induced response. Gastric inhibitory polypeptide (100 nM) with 5.5 mM glucose induced a rise in [Ca2+]i in single islet cells. SRIF inhibited this increase, but PST did not. Both PST and SRIF failed to affect the sustained rise in [Ca2+]i evoked by excess K+. These results suggest that PST and SRIF suppress the glucose-induced insulin secretion at least partly by inhibiting the rise in [Ca2+]i in pancreatic B-cells. Furthermore, PST may suppress the glucose-induced rise in [Ca2+]i via a mechanism different from that of SRIF.

Acetylcholine↗
PubMed1996

Effects of bradykinin on the intracellular calcium concentration of pancreatic acinar AR42J cells.

We examined the effects of bradykinin (BK) on the intracellular free calcium concentration ([Ca2+]i) in rat pancreatic acinar AR42J cells. BK induced a dose-dependent rise in [Ca+2]i in AR42J cells between the concentrations of 10(-12)M and 10(-7)M. The BK-evoked response was not affected by the presence of Co2+ or the absence of extracellular calcium. This response was suppressed by neomycin or the B2 antagonist, but not by the B1 antagonist. The response was also attenuated by treatment with dexamethasone. These results suggest that BK increases [Ca2+]i through the B2 receptors by promoting the phosphatidyl inositol turn-over and that, in the process of azaserine-induced undifferentiation, the pancreatic acinar cells strongly express the BK receptors.

Animals↗
PubMed1996

Cultured leptomeningeal cells secrete cerebrospinal fluid proteins.

To extrapolate the function of the leptomeninges, we examined the profile of the proteins secreted from the cultured leptomeningeal cells prepared from 1-2-day-old rats. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the medium conditioned with the cultured cells, 20-25 differentially distinctive protein bands were noted. Through several chromatographic procedures (Sephadex G-75, Mono Q, and 7C8-300), altogether 18 proteins were purified to homogeneity, and the partial amino acid sequence of each protein was determined. Homology search revealed that the major proteins included prostaglandin-D-synthase or beta-trace protein, insulin-like growth factor (IGF)-II, IGF-binding protein-2, apolipoprotein E, beta 2-microglobulin, cystatin C, transferrin, peptidyl-prolyl cis-trans isomerase or cyclophilin C, secreted protein acidic and rich in cysteine, ubiquitin, lysozyme C, extracellular superoxide dismutase, and collagen alpha-1 (III). Most of these proteins are known to be the major brain-derived protein constituents of CSF and are thought to play important roles in certain biological events in the brain. Considering the morphological features, the present findings suggest the importance of the leptomeninges as an origin of such proteins in CSF.

Amino Acid Sequence↗
PubMed1995

Synthesis and secretion of insulin-like growth factor (IGF)-II and IGF binding protein-2 by cultivated brain meningeal cells.

The meninges (the pia mater and the arachnoid) covering the surface of brain parenchyma are known to participate in the regulation of blood circulation and the blood-cerebrospinal fluid barrier. In the present study, we isolated and characterized some of the major proteins secreted into the conditioned medium of the meningeal cell cultures prepared from 1-2-day-old rats. Five protein molecules (7 kDa, 16 kDa, 18 kDa, 27 kDa and 32 kDa) were recognized as major proteins in the conditioned medium by SDS-PAGE. The major proteins were isolated and purified to homogeneity, respectively. Their N-terminal sequences, except that of 27 kDa protein, were successfully determined. Homology search has revealed that the N-terminal sequences of the 7 kDa protein and the 32 kDa protein were identical with those of insulin-like growth factor-II (IGF-II) and IGF-binding protein-2 (IGFBP-2), respectively. The N-terminal sequences of the 16 kDa and 18 kDa molecules were identical with those of the corresponding fragments of IGFBP-2. The present study demonstrates that cultured meningeal cells produce and secrete large amounts of IGF-II and IGFBP-2. The meninges may, therefore, be one of the main sources of these proteins in the cerebrospinal fluid and involved in the modulation of neuronal and/or glial cell survival or functioning.

Amino Acid Sequence↗
PubMed1995

Isolation and characterization of novel antimicrobial peptides, rugosins A, B and C, from the skin of the frog, Rana rugosa.

Three antimicrobial peptides were isolated from the skin of Rana rugosa. The major component, designated rugosin A, consisted of 33 amino acid residues and had structural homology (45%) with brevinin-2 of Rana porosa brevipoda. This peptide strongly inhibited the growth of gram-positive bacteria (e.g. Staphylococcus aureus 209P). The second peptide (rugosin B), a minor component, also had 33 amino acid residues, but was less homologous (33%) with brevinin-2. This peptide exhibited a striking antimicrobial activity against both gram-negative (e.g., Escherichia coli NIHJ) and gram-positive bacterial species. The third one, named rugosin C, composed of 37 amino acid residues, exhibited an antimicrobial activity against gram-positive bacteria. All three peptides had an intramolecular disulfide bond at the C-terminus.

Amino Acid Sequence↗
PubMed1995

Meninges play a neurotrophic role in the regeneration of vasopressin nerves after hypophysectomy.

Following hypophysectomy the regenerating fibers of magnocellular neurons are known to establish new neurohemal connections with reorganized vasculatures in the median eminence, which lead to establishment of a posterior pituitary-like structure. In order to examine the role of the meninges (the pia mater and the arachnoid) in this regeneration process, we implanted the meningeal tissues obtained from neonatal rat pups into the third ventricle of the adult rats, and then hypophysectomized the host animals. Ten days after hypophysectomy, the meningeal tissue grafts were found to be densely innervated by regenerating vasopressin-immunoreactive fibers. Such fibers had dots and frequently formed large punctuations. On the contrary, few vasopressin fibers were found within the cortical tissue grafts. Further, the exposure of primary hypothalamic cell cultures to the medium conditioned by meningeal cell cultures promoted not only the survival of vasopressin-immunoreactive neurons but also the outgrowth and aborization of the neurites. The survivals of cortical and cerebellum neurons in culture were also promoted by the conditioned medium. These findings raise the possibility that the meninges play an important role in the axonal regeneration process after hypophysectomy.

Animals↗
PubMed1995

Differentiation-inducing factor of D. discoideum raises intracellular calcium concentration and suppresses cell growth in rat pancreatic AR42J cells.

DIF (differentiation-inducing factor) is a putative morphogen that induces stalk cell differentiation in the lower eukaryote, Dictyostelium discoideum. In this study, we have examined the effects of DIF on growth and the intracellular calcium concentration ([Ca2+]i) in rat pancreatic acinar AR42J cells. Growth of AR42J cells was inhibited when DIF was present in the media, and approximately 50% growth inhibition was attained with 20 microM DIF. DIF was also found to raise [Ca2+]i in a dose-dependent manner (1-40 microM), both in the presence and absence of extracellular Ca2+. These results suggest that DIF elicits both calcium influx from the extracellular space and calcium release from intracellular pool(s), thereby inhibiting cell growth in AR42J.

Animals↗
PubMed1994

Biotinyl C-terminal-extended motilin as a biologically active receptor probe.

The synthesis, purification, and characterization of biotinylated analogues of motilin are reported. The C-terminal of canine motilin was extended by the addition of a cysteine residue, and then biotinylated. Biotinyl motilin was purified by following HPLC and characterized by amino acid analysis. Biotinylation of the ligand was confirmed by ELISA assay with the avidin-biotin system. Biotinyl motilin showed similar affinity for binding to rabbit gastric membrane fraction compared to unlabeled canine motilin, and also retained functional activity in its ability to cause contraction of rabbit duodenal segments. To determine the binding of biotinyl motilin in isolated rabbit antral smooth muscle, cells were incubated with the biotinyl motilin with and without excess of unlabeled motilin. Subsequent addition of avidin-biotinylated peroxidase complex showed the distribution of reaction products over the cell surface. Bioactive biotinyl motilin provides a useful probe for the demonstration of cell surface motilin receptors and will facilitate receptor purification and characterization.

Amino Acid Sequence↗
PubMed1994

Magnetic resonance imaging for aspirated peanut in the bronchus.

Peanut inhalation in the right main bronchus of a 15-month-old boy was diagnosed using a T1-weighted image produced by magnetic resonance imaging (MRI) because of the high fat content of the peanut. The T1-weighted MRI image may also be useful in diagnosing other kinds of aspirated nuts with high lipid content as well as peanuts. This method does not involve any X-ray exposure.

Arachis↗