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Biomedical subjects

K Tatemoto

Publications and source records attributed to K Tatemoto.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1992

Synthesis of receptor antagonists of neuropeptide Y.

We report the synthesis of receptor antagonists of neuropeptide Y (NPY) by a strategy based on synthesis of mixtures of analogs and the subsequent isolation and identification of receptor antagonists from these mixtures. After screening a series of mixtures of NPY analogs by using an NPY antagonist assay, two potent receptor antagonists, designated PYX-1 and PYX-2, were isolated from an antagonist-containing mixture. Structural analysis revealed these analogs to be Ac-[3-(2,6-dichlorobenzyl)Tyr27, D-Thr32]NPY-(27-36) amide and Ac-[3-(2,6-dichlorobenzyl)Tyr27,36,D-Thr32]NPY-(27-36) amide, respectively. The receptor antagonists inhibited release of intracellular calcium elicited by NPY in human erythroleukemia cells and displaced 3H-labeled NPY from NPY receptors in rat brain membrane. The approach of screening and identifying useful analogs from synthetic mixtures may significantly reduce the time and resources previously required for development of receptor antagonists.

Amino Acid Sequence↗
PubMed1992

Isolation and characterization of two novel peptide amides originating from myelin basic protein in bovine brain.

During a systematic search for peptides that possess the C-terminal amide structure, two novel peptide amides, one with a tyrosine amide and the other with an alanine amide were isolated from bovine brain by acid extraction and sequential steps of reversed phase HPLC. Microsequence, amino acid and mass spectral analyses revealed the structures: Ac-Ala-Ala-Gln-Lys-Arg-Pro-Ser-Gln-Arg-Ser-Lys-Tyr-amide and Ac-Ala-Ala-Gln-Lys-Arg-Pro-Ser-Gln-Arg-Ser-Lys-Tyr-Leu-Ala-Ser-Ala-amide . These 12 and 16 residues peptides had the primary structure identical to the N-terminal fragment of myelin basic protein (MBP). The peptides were therefore designated myelin peptide amide-12 (MPA-12) and -16 (MPA-16). Unlike other amidated peptides, MPA might be generated from MBP by hydroxyl radicals produced via a Fenton reaction in situ. However, this unique amidation seems to occur exclusively to MBP in a site specific manner in the brain.

Amino Acid Sequence↗
PubMed1992

Pancreastatin inhibits pancreatic enzyme secretion by presynaptic modulation of acetylcholine release.

Pancreastatin (PST), a 49-amino acid polypeptide, inhibits endocrine and exocrine pancreatic functions. In this study, we examined the mechanism of the inhibitory action of PST on exocrine pancreatic secretion in the rat. In anesthetized rats prepared with pancreatic fistulas, intravenous administration of PST (500 pM.kg-1.h-1) completely inhibited 2-deoxyglucose (75 mg/kg)-stimulated amylase output to below basal levels. Because 2-deoxyglucose acts to stimulate the vagus, we assessed the ability of PST to inhibit carbachol-stimulated amylase release from isolated rat pancreatic acini. PST suppressed neither carbachol- nor cholecystokinin-stimulated amylase release, indicating that PST inhibits exocrine secretion via indirect mechanisms. To examine neural pathways for inhibition, we used pancreatic lobules to examine the action of PST on intrapancreatic neurons. Incubation of pancreatic lobules in 75 mM potassium buffer stimulated amylase release by a cholinergic pathway. PST dose dependently inhibited potassium-evoked amylase release, with maximal inhibition of 49.6 +/- 11%. In addition, when lobules were incubated with [3H]choline, PST inhibited KCl-stimulated release of synthesized [3H]acetylcholine by 43 +/- 5.7%. Other studies demonstrate that PST inhibits rat pancreatic enzyme secretion via presynaptic modulation of acetylcholine release.

Acetylcholine↗
PubMed1991

Effects of pancreastatin and chromogranin A on insulin release stimulated by various insulinotropic agents.

The effects of porcine pancreastatin on insulin release stimulated by insulinotropic agents, glucagon, cholecystokinin-octapeptide (CCK-8), gastric inhibitory polypeptide (GIP) and L-arginine, were compared to those of bovine chromogranin A (CGA) using the isolated perfused rat pancreas. Pancreastatin significantly potentiated glucagon-stimulated insulin release (first phase: 12.5 +/- 0.9 ng/8 min; second phase: 34.5 +/- 1.6 ng/25 min in controls; 16.5 +/- 1.1 ng/8 min and 44.0 +/- 2.2 ng/25 min in pancreastatin group), whereas CGA was ineffective. The first phase of L-arginine-stimulated insulin release was also potentiated by pancreastatin (6.9 +/- 0.5 ng/5 min in controls, 8.4 +/- 0.6 ng/5 min in pancreastatin group), but not by CGA. Pancreastatin did not affect CCK-8 or GIP-stimulated insulin release. Similarly, CGA did not affect insulin release stimulated by CCK-8 or GIP. These findings suggest that pancreastatin stimulates insulin release in the presence of glucagon. Because pancreastatin can have multiple effects on insulin release, which are dependent upon the local concentration of insulin effectors, pancreastatin may participate in the fine tuning of insulin release from B cells.

Animals↗
PubMed1990

Isolation and characterization of a novel peptide amide from porcine brain.

Peptide with C-terminal tyrosine amide was isolated from porcine brain by acid extraction and sequential steps of reverse phase HPLC. Microsequence, amino acid and mass spectral analyses revealed the structure: Ac-Ala-Ser-Glu-Lys-Arg-Pro-Ser-Glu-Arg-His-Gly-Ser-Lys- Tyr-amide. Since this peptide had the identical sequence to N-terminus of porcine myelin basic protein (pMBP) 1-14, we have designated porcine myelin peptide amide 14 (pMPA14). The final HPLC step yielded 20 micrograms of homogeneous peptide preparation from 20 kg brain tissue. Unlike other amidated peptides, pMPA14 may be produced by non enzymatic mechanism or unknown amidating enzyme. This unique amidation seems to occur exclusively to MBP in the brain.

Amino Acid Sequence↗
PubMed1990

Preliminary report: role of peptide YY in defence against diarrhoea.

To investigate whether peptide YY (PYY) has a role in minimising fluid loss during diarrhoea, its effect on hypersecretion induced by vasoactive intestinal peptide (VIP) was studied in seven subjects with ileostomies. An isotonic electrolyte solution containing polyethylene glycol 4000 was infused directly into the duodenum and the effluent was collected for 40 min (baseline), then VIP was infused intravenously at 5 pmol.kg-1.min-1 for 500 min. PYY was infused intravenously at low doses (0.4 and 0.2 pmol.kg-1.min-1) for 100 min each during the continuous VIP infusion. Small-intestinal secretion was assessed by effluent weight and by polyethylene glycol dilution, which gave similar results. Plateau ileal output was 501 (SEM 33) ml/h during VIP infusion. PYY caused significant falls in secretion--to 404 (48) ml/h for the lower dose and to 323 (75) ml/h for the higher. It also prolonged small-bowel transit. These findings suggest that PYY is a natural inhibitor of diarrhoea and that its therapeutic potential merits investigation.

Diarrhea↗
PubMed1990

Stimulatory effect of pancreastatin on gastric acid secretion in conscious dogs.

Pancreastatin, a new 49-amino acid peptide, has recently been isolated and characterized from extracts of the porcine pancreas. The objective of the present study was to examine the effect of various doses of pancreastatin on gastric acid secretion in conscious dogs that were prepared with chronic gastric cannulas. Pancreastatin, administered IV at 400 pmol.kg-1 x h-1, enhanced peptone meal [peptone (5%), phenylalanine (90 mmol/L), glucose (12 g/dL)]-stimulated gastric acid secretion by 50%; pancreastatin at 800 pmol.kg-1 x h-1 enhanced peptone meal secretion by 165% (P less than 0.05). Intravenous administration of pancreastatin did not affect basal or peptone-stimulated release of gastrin. In addition, IV pancreastatin (400 pmol.kg-1 x h-1) failed to influence basal gastric acid secretion. Pancreastatin did not affect acid secretion stimulated by 2-deoxyglucose, histamine, or pentagastrin. The present study shows that pancreastatin can selectively enhance gastric acid secretion by a mechanism independent of cholinergic, histaminergic, or gastrin input.

Animals↗