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K Tanabe

Publications and source records attributed to K Tanabe.

At least 181 records · Page 10Linked to original sources
PubMed1999

Selenophosphate as a substrate for mammalian selenocysteine synthase, its stability and toxicity.

The mechanism of selenocysteine synthesis on tRNASec in mammals was previously studied by means of HSe- as a Se donor to synthesize selenocysteine. It has been recently established that HSe- in E. coli is activated by ATP to become selenophosphate (SeP). In this study, we provide evidence that [75Se]selenocysteine is produced by bovine selenocysteine synthase from Ser-tRNASec and [75Se]Sep, synthesized from elemental 75Se and Tris(trimethylsilyl)phosphite. We also studied the stability of SeP by NMR measurement. SeP was stable during storage under nitrogen at -80 degrees C for 3 months in 0.2 M Hepes buffer at pH 6.8. However, SeP decomposed at 0 degree C in air (half life 32 hrs) or at 22 degrees C under nitrogen (half life 30 hrs) at pH 6.8. The half lives of SeP at -19 degrees C in air and at 0 degree C under nitrogen at pH 6.8 were 740 and 840 hrs, respectively. At pH 4 under nitrogen at 22 degrees C, the half life was 240 hrs. The half life was only 9.2 hrs at pH 9 under nitrogen at 0 degree C. Thus, SeP was proved to be stable at low temperature, under acidic and anaerobic conditions, but labile under neutral and alkaline conditions. The LD50 of SeP administered i.p. to mice was 37.5 mg/kg body weight.

Air↗
PubMed1999

Overexpression of dominant negative mutant hepatocyte nuclear factor (HNF)-1alpha inhibits arginine-induced insulin secretion in MIN6 cells.

AIMS/HYPOTHESIS: To explain the mechanisms whereby mutations in the HNF-1alpha gene cause insulin secretory defects. METHODS: A truncated mutant HNF-1alpha (HNF-1alpha288t) was overexpressed in hepatoma cells (HepG2) and murine insulinoma cells (MIN6) using a recombinant adenovirus system and expression of the HNF-1alpha target genes and insulin secretion were examined. RESULTS: Expression of phenylalanine hydroxylase and alpha1-antitrypsin genes, the target genes of HNF-1alpha, was suppressed in HepG2 cells by overexpression of HNF-1alpha288t. In MIN6 cells, overexpression of HNF-1alpha288t did not change insulin secretion stimulated by glucose (5 mmol/l and 25 mmol/l) or leucine (20 mmol/l). Potentiation of insulin secretion by arginine (20 mmol/l, in the presence of 5 mmol/l or 25mmol/l glucose) was, however, reduced (p < 0.0001 and p = 0.027, respectively). Similarly reduced responses were observed when stimulated with homoarginine. Expression of the cationic amino acid transporter-2 was not reduced and insulin secretory response to membrane depolarization by 50 mmol/l KCl was intact. CONCLUSION/INTERPRETATION: The HNF-1alpha288 t, which is structurally similar to the mutant HNF-1alpha expressed from the common MODY3 allele, P291fsinsC, exerts a dominant negative effect. Suppression of HNF-1alpha in MIN6 cells severely impaired potentiation of insulin secretion by arginine, whereas glucose-stimulated and leucine-stimulated insulin secretion was intact. Our findings delineate the complex nature of beta-cell failure in patients with MODY3. This cell model will be useful for further investigation of the mechanism of insulin secretory defects in these patients.

Animals↗
PubMed1999

Identification of 1-aminocyclopropane-1-carboxylic acid synthase genes controlling the ethylene level of ripening fruit in Japanese pear (Pyrus pyrifolia Nakai).

The shelf life of Japanese pear fruit is determined by its level of ethylene production. Relatively high levels of ethylene reduce storage potential and fruit quality. We have identified RFLP markers tightly linked to the locus that determines the rate of ethylene evolution in ripening fruit of the Japanese pear. The study was carried out using sequences of two types of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase genes (PPACS1 and pPPACS2) and a ACC oxidase gene (PPAOX1) as probes on 35 Japanese pear cultivars expressing different levels of ethylene (0.0 to approximately 300 microl/kg fresh weight/h) in ripening fruit. When total DNA was digested with HindIII and probed with pPPACS1, we identified a band of 2.8 kb which was specific to cultivars having very high ethylene levels (> or = 10 microl/kg f.w./h) during fruit ripening. The probe pPPACS2 identified a band of 0.8 kb specific to cultivars with moderate ethylene levels (0.5 microl/kg f.w./h-10 microl/kg f.w./h) during fruit ripening. The cultivars that produce high levels of ethylene possess at least one additional copy of pPPACS1 and those producing moderate levels of ethylene have at least one additional copy of pPPACS2. These results suggest that RFLP analysis with different ACC synthase genes could be useful for predicting the maximum ethylene level during fruit ripening in Japanese pear.

Amino Acid Oxidoreductases↗
PubMed1999

Contribution of TAP genes to genetic predisposition for diffuse panbronchiolitis.

Diffuse panbronchiolitis is a chronic obstructive pulmonary disease found in Asian populations. Although diffuse panbronchiolitis is considered to be a multifactorial disease of unknown etiology, the disease susceptibility appears to be determined by a genetic predisposition unique to Asians. An earlier study showed that human leukocyte antigen (HLA)-B54 predominantly found in East Asians was strongly associated with the disease. A possible interpretation of this association is that the class I molecule or class I antigen presenting system is directly involved in its pathogenesis. Recent observations in which impaired expression of class I molecules causes a syndrome resembling diffuse panbronchiolitis further prompted us to test this possibility. Genes of the molecules implicated in the class I pathway, TAP1, TAP2 and LMP2, which are located in the HLA region of the sixth chromosome were analyzed in 76 patients with diffuse panbronchiolitis and 120 normal controls. The combination of Ala-665 and Gln-687 in exon 11 of the TAP2 gene was associated with the disease (P=0.0028, Pc<0.05). Although this positive association might be partly explained by linkage disequilibrium with HLA-B*5401, this TAP2 variation was associated with the disease even in the B*5401-negative subgroup. On the other hand, the His-60 substitution within the LMP2 gene exhibited a negative association with the disease. This negative association, however, could be explained by a strong linkage disequilibrium with HLA-B44 which showed a negative association with the disease in the previous study. These results support the notion that diffuse panbronchiolitis is influenced by genetic factors in the HLA region. Besides the class I gene itself, genes relevant to the class I antigen presenting system might contribute to its genetic predisposition.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Pregnancy in women receiving renal dialysis or transplantation in Japan: a nationwide survey.

BACKGROUND: Since a report on the first successful pregnancy of a woman on long-term haemodialysis in Japan in 1977, there has been a growing number of case reports on successful pregnancy in patients on dialysis. We undertook a nationwide survey on pregnancy in women on renal replacement therapy in 1996. METHODS: A preliminary questionaire was sent to 2504 dialysis units and 143 renal transplant units in Japan. For each reported pregnancy, a more detailed questionaire was sent to collect nephrological, obstetric and neonatal information. RESULTS: There were 172 pregnancies (0.44%) reported in 38889 women on dialysis, with 90 successful pregnancies (0.23%), and 194 pregnancies reported in 852 female renal transplant recipients. Detailed pregnancy information was collected from 74 women on dialysis and 194 renal transplant recipients. Of the 74 pregnancies in the women on dialysis, 36 (48.6%) resulted in surviving infants, nine (12.2%) in neonatal death, nine (12.2%) spontaneous abortions and 14 (18.9% elective abortions were reported. The outcome of six pregnancies (8.1%) was unknown. Of 194 pregnancies in renal transplant recipients, 159 (82.0%) resulted in surviving infants, two (1.4%) in neonatal death and 28 (14.4%) in spontaneous or elective abortion. In five cases the pregnancy outcome was not reported. No congenital anomalies were reported, except two infants with mental retardation and one with epilepsy. CONCLUSION: The current survey revealed that the rate of successful pregnancy in women on dialysis has improved. More than half of the pregnancies resulted in infant survival. But, premature birth is a major problem for the children of women on dialysis and there is a higher rate of neonatal death. There are significant differences in gestational age, birth weight, frequency and severity of prematurity and rates of neonatal death between pregnancies of women undergoing dialysis and those who are renal transplant recipients.

Adolescent↗
PubMed1999

Effect of propofol on arachidonate cascade by vasopressin in aortic smooth muscle cells: inhibition of PGI2 synthesis.

BACKGROUND: The mechanisms underlying the vascular effects of propofol are not fully understood. Vasopressin, a potent vasoactive peptide, stimulates the arachidonate cascade and the synthesis of prostacyclin (PGI2; the main metabolite of the cascade in vascular smooth muscle cells). Arachidonic acid (AA) release by phospholipases is the rate-limiting step in the cascade. We investigated the mechanisms underlying vasopressin-induced AA release and the effect of propofol on PGI2 synthesis in a rat aortic smooth muscle cell line: A10 cells. METHODS: In cultured A10 cells pretreated with propofol, the stimulation by vasopressin of AA release and PGI2 synthesis was evaluated by measuring [3H]AA and 6-keto PGF1alpha, respectively, in the culture medium. The effects of propofol on vasopressin-induced activation of phosphoinositide-hydrolyzing phospholipase C and phosphatidylcholine-hydrolyzing phospholipase D were evaluated by measuring inositol phosphate formation and choline formation, respectively. RESULTS: A phospholipase C inhibitor and a phosphatidic acid phosphohydrolase inhibitor both attenuated vasopressin-induced AA release and PGI2 synthesis, as did a phospholipase A2 inhibitor. Propofol inhibited vasopressin-induced activation of phosphoinositide-hydrolyzing phospholipase C and phosphatidylcholine-hydrolyzing phospholipase D, but this effect of propofol was significant only at supraclinical concentration (0.1 mM). Propofol reduced vasopressin-induced PGI2 synthesis. The inhibitory effect was observed at concentrations (10 microM-0.1 mM) higher than those used clinically. CONCLUSIONS: Propofol suppresses the arachidonate cascade caused by vasopressin at least partly by inhibiting phosphoinositide-hydrolyzing phospholipase C and phosphatidylcholine-hydrolyzing phospholipase D, resulting in the inhibition of PGI2 synthesis. Propofol-mediated inhibition of vasopressin-stimulated synthesis of PGI2 may reduce the vasorelaxation by propofol.

Anesthetics, Intravenous↗
PubMed1999

[Bacteriological survey of diarrheal epidemics in the 1998 Bangladesh floods].

In 1998, the worst flood disaster in Bangladesh ravaged more than half of its land and diarrheal epidemics broke out. We examined fecal specimens of diarrheal patients at rural hospitals in Chandpor district located 140 km southeast of Dhaka to analyze the enteric bacterial pathogens in post-flood period October. Of the 76 patients stools examined, Vibrio cholerae O1 biotype El Tor, serotype Ogawa, and Vibrio cholerae O139 Bengal were detected in 25 (33%) and in 14 (18%) respectively. Other enteropathogenic bacteria confirmed were Vibrio cholerae O5, Vibrio fluvialis and Enteropathogenic Escherichia coli O44. Neither Shigella nor Salmonella species was detected in this study. A drug susceptibility test was performed using TC, DOXY, CPFX, NA, and AMPC disks to cholera Vibrios. The O1 Vibrios showed the same susceptible pattern as O139 excluding NA susceptibility. TC resistant strain among the Vibrios was not detected though TC is a common therapeutic drug for diarrhea in this area. Our result clearly suggested that the epidemic potentiality of O139 still existed in rural Bangladesh.

Bangladesh↗