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Biomedical subjects

K Yasuda

Publications and source records attributed to K Yasuda.

At least 631 records · Page 35Linked to original sources

Hamster gastric inhibitory polypeptide receptor expressed in pancreatic islets and clonal insulin-secreting cells: its structure and functional properties.

We have isolated a cDNA encoding a gastric inhibitory polypeptide (GIP) receptor from a hamster insulinoma (HIT-T15) cDNA library. The hamster GIP receptor is a 462 amino acid protein having seven transmembrane segments. Expression of recombinant of hamster GIP receptors in Chinese hamster ovary (CHO) cells shows that it binds specifically to GIP with high affinity (IC50 = 9.6 nM) and is positively coupled to adenylate cyclase, but not to phospholipase C. RNA blot analysis reveals that a 3.8-kb GIP receptor mRNA is expressed at high levels in rat pancreatic islets as well as in HIT-T15 cells.

Amino Acid Sequence↗

Phorbol ester and insulin stimulate protein kinase C isoforms in rat adipocytes.

We examined effect of insulin or 12-O-tetradecanoyl phorbol 13-acetate (TPA) on the subcellular redistribution of protein kinase C isoforms in rat adipocytes. Total Mono Q column-elutable novel PKCs (nPKCs) which are Ca(2+)-independent and phospholipid-dependent protein kinases, decreased in the cytosolic fraction and increased in the membrane fraction during treatment with insulin or phorbol ester for 10 min. Immunoblot analysis of novel PKCs, -epsilon, -delta and -zeta, showed that insulin stimulated the translocation of these PKC isoforms from cytosol to membrane, similar to the translocation of conventional Ca2+/phospholipid-dependent PKCs (cPKCs), -alpha, -beta, and -gamma. Phorbol esters stimulated the translocation of PKC-alpha, -beta, -gamma, -epsilon and -delta, but not PKC-zeta. These results suggest that (a) insulin and phorbol esters similarly stimulate the translocation of each PKC isoform except for PKC-zeta, and (b) the translocation of both nPKCs and cPKCs occurs during insulin and TPA actions in rat adipocytes.

Adipocytes↗

Regional induction of tumor necrosis factor alpha expression in the mouse brain after systemic lipopolysaccharide administration.

Tumor necrosis factor alpha (TNF-alpha) is a cytokine that is responsible, in part, for several aspects of the acute-phase response to inflammation, including the generation of fever. TNF-alpha has direct effects on central nervous system neurons deep within the hypothalamus that are involved in producing the febrile response, but the blood-brain barrier prevents circulating TNF-alpha from having access to these sites. We therefore have hypothesized that TNF-alpha may be produced in the brain and used as a mediator in the cerebral components of the acute-phase response. We used in situ hybridization to determine the distribution of production of TNF-alpha mRNA in the mouse brain after systemic administration of lipopolysaccharide. During the initial phase of fever, hybridization was observed in perivascular cells and neurons in circumventricular organs, including the vascular organ of the lamina terminalis, median eminence, and area postrema, as well as along the ventral surface of the medulla; hybridization was also prominent over many cell in the meninges. During the late phase of the response, hybridization was observed over neurons in the pericircumventricular nuclei such as the anteroventral periventricular and arcuate nuclei of the hypothalamus and the nucleus of the solitary tract. TNF-alpha produced by a cascade of neurons within the brain may participate in the complex autonomic, neuroendocrine, metabolic, and behavioral responses to infection and inflammation.

Acute-Phase Reaction↗

Multiple effector coupling of somatostatin receptor subtype SSTR1.

The signal transduction pathways of a cloned human somatostatin receptor subtype, SSTR1, have been investigated in CHO cells stably expressing this receptor. In SSTR1-expressing CHO cells, somatostatin-14 inhibits forskolin-stimulated cAMP formation in a dose-dependent manner with an ED50 of 1.0 x 10(-9) M. Somatostatin-14 also stimulates inositol 1,4,5-trisphosphate formation in a dose-dependent manner with an ED50 of 4.0 x 10(-8) M. Somatostatin-14 inhibitory action on adenylyl cyclase and stimulatory action on inositol 1,4,5-trisphosphate formation are both blocked by pertussis toxin, indicating that these effects of SSTR1 are mediated by pertussis toxin-sensitive G protein(s). Antiserum against Gi alpha 3 blocked the inhibitory effects of somatostatin-14 on forskolin-stimulated adenylyl cyclase, but antiserum against Gi alpha 1/Gi alpha 2 did not, indicating that Gi alpha 3 dominantly couples SSTR1 to adenylyl cyclase. These results demonstrate that SSTR1 can be coupled to different signaling pathways to exert multiple biological effects, one of which is mediated by Gi alpha 3.

Adenylyl Cyclases↗

Characterization of high-molecular-mass heat shock proteins and 42 degrees C-specific heat shock proteins of murine cells.

There are two isoforms of high-molecular-mass heat shock protein (HMM-HSP), hsp105A and hsp105B, in murine FM3A cells. To characterize the HMM-HSPs, we here purified hsp105A and hsp105B, as well as 42 degrees C-specific HSPs that are specifically induced by continuous heating at 42 degrees C, from the cytoplasmic extracts of the FM3A cells heat-shocked at 42 degrees C for 8 h. Digestion of the hsp105A, hsp105B, and 42 degrees C-specific HSPs with lysyl endopeptidase generated 17,000-Da polypeptide fragments in common, and the N-terminal amino acid sequences of the fragments revealed a homology with those of the adenosine binding domain of hsp70 family proteins and actin. Thus, the two isoforms of hsp105 and the 42 degrees C-specific HSPs seemed to be very similar proteins having a ATP binding domain in common, and these HSPs may constitute a HMM-HSP family in murine cells.

Amino Acid Sequence↗

Two major types of premotoneurons in the feline trigeminal nucleus oralis as demonstrated by intracellular staining with horseradish peroxidase.

Previous studies suggest that neurons in the dorsomedial subdivisions of trigeminal nucleus oralis (Vo) may contribute to reflex control of jaw movements and to modulation of sensory information. The present study has addressed this possibility by the use of intracellular staining with horseradish peroxidase of physiologically identified neurons in Vo to examine functional and morphological properties of these neurons. Of 14 labeled neurons, eight had axon collaterals terminating exclusively in the dorsolateral subdivision of the trigeminal motor nucleus (DL neurons) and four in its ventromedial subdivision (VM neurons); axon collaterals of two neurons were not traced. Both groups of neurons sent terminal arbors into other nuclei of the lower brainstem. The DL neurons were distinguishable from the VM neurons in their receptive field (RF) location, neuronal position, somadendritic architecture, and projections to other brainstem nuclei. All neurons, except for two that were exclusively activated by noxious stimuli applied to the tongue, were responsive to light mechanical stimulation of peri- and intraoral structures. The RFs of the DL neurons were located in more posterior oral structures than those of the VM neurons. The RF of nearly all low-threshold DL neurons was located in the maxillary region, and that of the VM neurons, in contrast, involved the mandibular region. The VM neurons were located medial or ventral to the DL neurons. The soma size of the VM neurons was significantly larger than that of the DL neurons. Dendritic arbors of both groups could be separated into medial and lateral components. The ratio of the dendritic transverse areas in the medial vs. lateral component was significantly higher in the VM neurons than in the DL neurons. The DL neurons also issued collaterals that terminated in larger brainstem areas than those of the VM neurons. These observations provide new evidence on the morphological and functional properties of Vo neurons that contribute to reflex control of jaw and facial movements and modulation of sensory information.

Animals↗

Human somatostatin receptor, SSTR2, is coupled to adenylyl cyclase in the presence of Gi alpha 1 protein.

Somatostatin has been shown to exert diverse biological effects in various tissues. Recently, the human genes encoding five subtypes of somatostatin receptor (SSTR1-SSTR5) were cloned. Among these subtypes SSTR2 is present in many endocrine tumors as well as normal tissues and may mediate the effects of somatostatin analog, SMS201-995. In this study, we have investigated the intracellular effect of SSTR2 stably expressed in Chinese hamster ovary cells. Somatostatin-14 does not affect the forskolin stimulated cAMP formation when human SSTR2 is expressed in CHO cells, which lack internal Gi alpha 1 protein. However, somatostatin-14 inhibits the adenylyl cyclase in a dose dependent and pertussis toxin-sensitive manner when human SSTR2 is co-expressed with Gi alpha 1 in CHO cells. These results indicate that human SSTR2 is functionally coupled to Gi alpha 1 protein but not to Gi alpha 2 or Gi alpha 3 when expressed in CHO cells.

Adenylate Cyclase Toxin↗

A cloned rat CD38-homologous protein and its expression in pancreatic islets.

Cyclic ADP-ribose recently has been suggested to be an important intracellular signal for insulin secretion. CD38, which was originally isolated from human lymphocytes as a surface marker, is active in the synthesis of cyclic ADP-ribose. We report here the cloning of a rat CD38-homologous protein (CD38H) which is expressed in pancreatic islets. The deduced amino acid sequence shows that rat CD38H is a protein of 303 amino acids (M(r), 34.4 kD) and contains one possible membrane-spanning domain, consistent with a type II transmembrane glycoprotein. The overall identity and similarity of the amino acid sequences between the human CD38 and the rat CD38H are 58% and 76%, respectively. RNA blot analysis showed a strong signal of 3.4 kb in rat brain, duodenum, and heart. CD38H also is shown to be expressed in pancreatic islets by the RT-PCR procedure, but its expression is not significantly different in Wistar and GK rats, a genetic model of non-insulin-dependent diabetes mellitus. The presence of rat CD38H in the pancreatic islets suggests that CD38H may be involved in insulin secretion by synthesizing cADP-ribose.

ADP-ribosyl Cyclase↗

Molecular cloning and characterization of the genes encoding the immunoreactive major cell-surface proteins of Porphyromonas gingivalis.

A 72-kDa major cell-surface protein (72K-CSP) was purified from the wash fluid of Porphyromonas gingivalis OMZ409. Using the synthetic oligonucleotide probes corresponding to the determined amino-terminal amino acid sequence of 72K-CSP, recombinant plasmid clones carrying approx. 3.4-kb KpnI-XhoI fragments in XL1-Blue libraries of P. gingivalis OMZ409 and 381 were obtained. The premature form proteins of 558 and 563 amino acids led by putative signal sequences were thought to be processed to form the mature proteins of a predicted size of 55,655 Da for strain OMZ409 and of 55,654 for strain 381. Both proteins had unusual proline-rich regions in their carboxyl-terminal regions. No homologous sequences could be found in protein databases. Examination of antigen-specific antibody responses in the serum of patients with adult periodontitis by ELISA revealed that 72K-CSP had a different immunoreactivity from that of P. gingivalis 381 fimbriae.

Adult↗

High density cultivation of hybridoma in charged porous carriers.

A porous carrier whose surface is charged with polyethyleneimine (PEI) was evaluated for high-density cultivation of immobilized hybridoma cells. The carrier was used either in suspension or in fixed bed. For suspended carriers, the effect of carrier pore size, ion-exchange capacity (IEC), mixing intensity and inoculum concentration on the attachment and growth of HBs MAb-producing hybridoma cells in carrier CELLSNOW EX were studied. The carrier with 100 microns pore size was more efficient than that with 500 microns in supporting cell attachment. In addition, the amount of antibody which was detected by PHA (passive hemagglutination assay) was 4-times higher in 100 microns compared with 500 microns pore size. At low initial cell concentration, 2.8 x 10(5) ml-1, the attached cells did not grow in the first 7 d as indicated by a negligible glucose consumption. However, cell proliferation was observed at high inoculum, 9 x 10(5) ml-1. Hybridoma cells were expected to attach faster to EX with high IEC than with low IEC but results showed no significant difference. A different hybridoma cell line producing monoclonal antibody (MAb) against penicillin-G-amidase was successfully cultivated in an axial-flow fixed bed containing CELLSNOW carriers. The specific glucose uptake rate as an indicator for cell activity was 24-times higher compared with conventional chemostat cultures. The CELLSNOW carriers offers many advantages over other carriers.

Animals↗

Cellular localization of high-molecular-mass heat shock proteins in murine cells.

We have previously prepared an antiserum raised against hsp105 of murine FM3A cells. The anti-hsp105 serum reacted to two isoforms of high-molecular-mass heat shock protein (HMM-HSP) having a molecular mass of 105,000 Da (hsp105A and hsp105B) in FM3A cells. While hsp105A and hsp105B were both synthesized and accumulated under non-stressed conditions, upon exposure to heat shock much more hsp105B was induced than hsp105A. When the cellular distribution of these hsp105s in murine 3T3 Swiss albino and C3H 10T1/2 cells was examined by immunofluorescence methods using the anti-hsp105 serum, the HMM-HSPs were localized in the cytoplasm and nuclei and were never found in the nucleoli of both 3T3 and C3H cells under non-stressed and stressed conditions.

3T3 Cells↗

Cloning of a complete protein-coding sequence of human platelet-type phosphofructokinase isozyme from pancreatic islet.

We have cloned a full length protein-coding sequence of human platelet-type phosphofructokinase (PFK) from pancreatic islet cDNA library. The platelet-type PFK was composed of 784 amino acids and had a deduced molecular weight of 85,590. Homologies in the primary structure with muscle- and liver-type PFK were 71 and 67%. Clear similarities of the amino and carboxyl halves with a prokaryotic PFK indicated an evolutionary event that duplicated genes of a prototype PFK fused into larger genes of eukaryotic PFKs. Amino acid residues constituting the binding sites for various allosteric modulators were well conserved, while a couple of different residues at the inhibitory ATP sites among three isozymes may partly explain their varied degree of sensitivities to ATP. Considerable amount of platelet-type PFK expression was demonstrated in brain, heart, kidney, colon and testis.

Amino Acid Sequence↗

Correlative retention time peak identification method for glycated haemoglobin in high-performance liquid chromatography.

A convenient peak identification method in stepwise elution was investigated and correlation among the retention times of peaks in ion-exchange chromatography of glycated haemoglobin was assessed. By using a correlation method, accuracy of peak identification among columns with degradation and product deviations can be maintained. The correlative retention time identification procedure is treated theoretically.

Chromatography, High Pressure Liquid↗

[Unique type of Cushing's disease in clinical profile: cyclic Cushing's syndrome and Cushing's disease with favorable outcome to a high daily dose of bromocriptine].

A rare case of cortisol-responsive, dexamethasone-non-responsive cyclic Cushing's disease for whom a high daily dose of bromocriptine was effective was presented, and 58 cases of cushing's syndrome with variable hormonogenesis from the literature were reviewed with our own case (a total of 59 cases). In addition, the results of the high daily dose of bromocriptine treatment in our 7 cases of Cushing's disease were described. The presented case, a 57-year-old female, had a clinically and biochemically proven 3-8 day cycle length. With 40mg daily of bromocriptine, periodic hypercortisolemia disappeared and the patient was in remission with normal suppression of plasma cortisol by dexamethasone. Out of 59 cases of cyclic Cushing's syndrome, 39 were pituitary Cushing's disease or Cushing's syndrome with bilateral adrenal hyperplasia. 15 cases (25%) were adrenal adenoma and ectopic ACTH syndrome. In 22 out of 34 cases (62%), paradoxical response of plasma cortisol to dexamethasone was observed. Only 4 out of 16 cases (25%) on whom Hardy's operation was performed remitted completely. Our own presented case alone showed long-term remission with medical treatment. Seven Cushing's disease patients were treated with a high daily dose of bromocriptine (17.5-55mg/day). Three cases, in whom the highest dose of bromocriptine was 40, 55, and 35mg/day, showed clinical and biochemical long-term remission. In these 3 cases, an escape phenomenon was observed during the early treatment period with a decreased dose of bromocriptine. Thereafter the dose was increased, resulting in a beneficial outcome.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗