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Y Hata

Publications and source records attributed to Y Hata.

At least 19 recordsLinked to original sources
PubMed1992

Site-directed mutagenesis at aspartate and glutamate residues of xylanase from Bacillus pumilus.

To elucidate the reaction mechanism of xylanase, the identification of amino acids essential for its catalysis is of importance. Studies have indicated the possibility that the reaction mechanism of xylanase is similar to that of hen's egg lysozyme, which involves acidic amino acid residues. On the basis of this assumption, together with the three-dimensional structure of Bacillus pumilus xylanase and its amino acid sequence similarity to other xylanases of different origins, three acidic amino acids, namely Asp-21, Glu-93 and Glu-182, were selected for site-directed mutagenesis. The Asp residue was altered to either Ser or Glu, and the Glu residues to Ser or Asp. The purified mutant xylanases D21E, D21S, E93D, E93S, E182D and E182S showed single protein bands of about 26 kDa on SDS/PAGE. C.d. spectra of these mutant enzymes show no effect on the secondary structure of xylanase, except that of D21E, which shows a little variation. Furthermore, mutations of Glu-93 and Glu-182 resulted in a drastic decrease in the specific activity of xylanase as compared with mutation of Asp-21. On the basis of these results we propose that Glu-93 and Glu-182 are the best candidates for the essential catalytic residues of xylanase.

Aspartic Acid↗
PubMed1992

Methotrexate decreases thymidine kinase activity.

MTX cytotoxicity is not fully explained by its well-known inhibition of dihydrofolate reductase activity which leads to a decrease in the dTMP synthase reaction, since TdR kinase which converts TdR to dTMP could readily circumvent MTX action through this salvage activity. TdR kinase is of particular significance, since in various types of carcinoma cells its activity is orders of magnitude higher than that of dTMP synthase. To throw light on this problem, we tested the hypothesis that the impact of MTX treatment might in fact involve an inhibition or decrease in TdR kinase activity. Injection in rat of MTX (i.p.) decreased TdR kinase activity in a time- and dose-dependent fashion in liver (t1/2 = 46 h; IC50 = 95 mg/kg), bone marrow (t1/2 = 10 h; IC50 = 5 mg/kg) and rapidly growing transplantable hepatoma 3924A (t1/2 = 56 h; IC50 = 5 mg/kg). Injection in rat of cycloheximide (15 mg/kg, i.p.), an inhibitor of protein biosynthesis, rapidly decreased TdR kinase activity in the hepatoma (t1/2 = 3.6 h); activities of other purine and pyrimidine synthetic enzymes, dTMP synthase, IMP dehydrogenase, GMP reductase and GMP synthase, declined at a markedly slower rate (t1/2 = 11, 11.6, 12 and 22 h, respectively). MTX, by curtailing purine and pyrimidine biosynthesis, limits product of TdR kinase which is more sensitive to unopposed protein degradation than other enzymes of nucleic acid biosynthesis. TdR kinase is a newly discovered target of MTX treatment.

Animals↗
PubMed1992

Structure of acidic phospholipase A2 for the venom of Agkistrodon halys blomhoffii at 2.8 A resolution.

The crystal structure of acidic phospholipase A2 from the venom of Agkistrodon halys blomhoffii has been determined by molecular replacement methods based on the known structure of Crotalus atrox PLA2, a same group II enzyme. The overall structures, except the calcium-binding regions, are very similar to each other. A calcium ion is pentagonally ligated to two carboxylate oxygen atoms of Asp-49 and each carbonyl oxygen atoms of Tyr-28, Gly-30 and Ala-31. A reason why the former enzyme functions as monomeric form, while the latter one does as dimer, could be presumed by the structural comparison of these calcium-binding regions. Although Gly-32 is usually participated as a ligand in the coordination with calcium ion in group I PLA2, it is characteristically replaced to Ala-31 in the present structure, and thus the coordination geometry of calcium ion is rather different from the usually observed one.

Amino Acid Sequence↗
PubMed1992

Functional elements of the promoter region of the Aspergillus oryzae glaA gene encoding glucoamylase.

Analysis was made of the promoter region of the Aspergillus oryzae glaA gene encoding glucoamylase. Northern blots using a glucoamylase cDNA as a probe indicated that the amount of mRNA corresponding to the glaA gene increased when expression was induced by starch or maltose. The promoter region of the glaA gene was fused to the Escherichia coli uidA gene, encoding beta-glucuronidase (GUS), and the resultant plasmid was introduced into A. oryzae. Expression of GUS protein in the A. oryzae transformants was induced by maltose, indicating that the glaA-GUS gene was regulated at the level of transcription in the presence of maltose. The nucleotide sequence 1.1 kb upstream of the glaA coding region was determined. A comparison of the nucleotide sequence of the A. oryzae glaA promoter with those of A. oryzae amyB, encoding alpha-amylase, and A. niger glaA showed two regions with similar sequences. Deletion and site-specific mutation analysis of these homologous regions indicated that both are essential for direct high-level expression when grown on maltose.

Aspergillus niger↗
PubMed1992

Liver regeneration following portacaval shunt in rats: 3',5'-cyclic AMP changes in plasma and liver tissue.

Hepatic regeneration following portacaval shunt was evaluated in the light of the changes of 3',5'-cyclic AMP (cAMP) levels in plasma and liver tissue, and also plasma cAMP levels after glucagon administration, using a 70% hepatectomy and portacaval shunt model in rats. Ratios of liver to body weight recovered to 60% of pre-operative ratios 2 weeks after the operation. Plasma cAMP level decreased slightly, but insignificantly, 1 day and 3 days after the operation, then recovered to the pre-operative level. Hepatic cAMP concentration increased for 2 weeks after the operation. Plasma cAMP levels induced after glucagon administration did not increase until 3 days after the operation and were only 50% of pre-operative levels 4 weeks after the operation. From these results, liver regeneration following the portacaval shunt was remarkably delayed, but continued until at least 2 weeks after the operation.

Animals↗
PubMed1992

Inflammatory pseudotumor of the liver in children: report of cases and review of the literature.

Two pediatric cases of inflammatory pseudotumor of liver were reported and compared with seven previously reported cases. Clinical presentation was variable but often consisted of fever and vague abdominal symptoms. These two cases were considered to be clinically malignant because angiographically one showed hypervascularity and the other showed the portal vein draining into the lesion to be occluded. There are four previous reports of similar cases complicated with occlusive phlebitis within and around the lesion. All but two of the reported cases underwent major hepatectomy or liver transplantation. However, because of the benign nature of the lesion, the treatment might be more conservative after adequate diagnostic procedures, including needle biopsy, are applied.

Child↗
PubMed1992

Solidifying liquid with novel initiation system for detachable balloon catheters.

In endovascular surgery, to permanently hinder blood inflow into an aneurysm for example, a catheter is percutaneously introduced into an artery and the balloon is positioned and inflated by a solidifying liquid and then released into the diseased part. A novel solidifying liquid for the inflated balloon curable under the continuous feeding of oxygen through the wall of the balloon is described here. Glucose oxidase which oxidizes glucose producing hydrogen peroxide was used for polymerization of the solidifying liquid. This solidifying liquid cured even in the presence of oxygen and water. It was radiopaque when mixed with the iodinated X-ray contrast chemical iopamidol. In addition, the solidified liquid had appropriate mechanical properties. The endovascular surgery could be carried out safely using it.

Catheterization↗
PubMed1992

Laminin and procollagen-III-peptide as a serum marker for hepatic fibrosis in congenital biliary atresia.

The extracellular matrix (ECM) is a complex of macromolecules that includes collagens, proteoglycans, and complex glycoproteins. In fibrotic liver tissue there is an increase in all of these matrix components, and they increase in serum in the patients with alcoholic hepatitis or liver cirrhosis. These ECM components have been used as a serum marker of hepatic fibrosis. Prolonged obstruction of bile flow results in morphologic and biochemical changes and the development of secondary biliary cirrhosis. In congenital biliary atresia (CBA) there is a close correlation between the degree of the hepatic fibrosis and bile flow after the operation. We estimated that, in CBA, ECM increased in serum, and it would reflect the degree of the hepatic fibrosis. To clarify this we examined the serum procollagen-III-peptide (P-III-P) and laminin in CBA patients. P-III-P was elevated in all preoperative patients but in two of the three postoperative patients whose jaundice disappeared P-III-P was in the normal range. In the all 3 patients whose jaundice continued, P-III-P was in normal range. Serum laminin was elevated in 12 preoperative patients with CBA, but there is no correlation between day of diagnosis and level of laminin. Mean concentration in CBA without jaundice after operation was 3.18 U/mL, 3.226 U/mL in CBA with jaundice and 3.3 U/mL in infantile hepatitis. There were no significant differences among three groups. With the elevation of serum alanine aminotransferase, aspartate aminotransferase, and total bilirubin, serum laminin level was also increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Biliary Atresia↗
PubMed1992

Immunotargeting chemotherapy for AFP-producing pediatric liver cancer using the conjugates of anti-AFP antibody and anti-tumor agents.

The effect of immunotargeting chemotherapy for hepatoblastoma (HB) and hepatocellular carcinoma (HCC) following the application of adriamycin (ADM) or cis-platinum conjugated with anti-alpha-fetoprotein (AFP) antibody was evaluated experimentally and clinically. The conjugate was made from mouse monoclonal antihuman AFP antibody linked to ADM or CDDP, with a weight ratio of 2.5:1 via a dextran bridge. Experimentally, AFP-producing human HCC transplanted subsequently on nude mice was used. A mixture of the antibody and ADM or CDDP was prepared with the same ratio. Each drug was injected intraperitoneally, three times at the total dose of 14.4 mg/kg as ADM and one time at the dose of 8 mg/kg as CDDP. Tumor growth was inhibited significantly in the conjugate group compared with the other mixture group, the ADM or CDDP group, and the control group. Clinically, the conjugates were administered intraarterially in 4 cases (2 HBs and 2 HCCs) and intravenously in one case (1 HB). ADM and CDDP conjugated with anti-AFP antibody were used in 2 cases and 3 cases, respectively. Antitumor effects from the viewpoint of volume suppression rate showed partial response in 2 cases and no change in 3 cases. The immunotargeting chemotherapy using anti-AFP monoclonal antibodies may be a promising method for treatment of malignant epithelial liver cancer in children.

Adolescent↗
PubMed1992

An experimental study of ischemia following subcutaneous heterotopic intestinal graft: influence of arterial or venous occlusion.

A subcutaneously transferred intestinal model was prepared in the rat and experimental observations were conducted of serial histologic changes in the intestine and of acceptance rates, when the artery or vein in the pedicle was ligated at various times after transfer. Results showed 50 percent take in the artery-ligated group and 12.5 percent in the vein-ligated group, when performed 5 days after transfer; 87.5 percent take in the artery-ligated group and 50 percent in the vein-ligated group, when performed 7 days after transfer; and 100 percent take for both groups, when ligation was performed 14 days after transfer. Consequently, it was concluded that venous occlusion constitutes a greater danger to successful transfer of intestine than arterial occlusion.

Abdominal Muscles↗
PubMed1992

The effects of acid secretagogues on protective agents of gastric cells from adult rabbits in vitro.

Endogenous prostaglandin and mucus have been recognized as important protective factors in the gastric mucosa. However, the regulatory mechanisms of these agents have not been well studied. The aim of the present study was to investigate the effects of acid secretagogues on cyclic adenosine monophosphate (cAMP) formation, prostaglandin E2 (PGE2) production, and mucus secretion by isolated parietal cells and culture mucous cells from adult rabbits. Rabbit parietal cells were enriched by nonlinear Percoll gradients after the isolation of rabbit gastric mucosal cells with collagenase and ethylenediaminetetraacetic acid (EDTA). Rabbit gastric mucous cells were cultured in 10% fetal bovine serum added to Ham's F12 medium. As gastric acid secretagogues, histamine, carbachol, gastrin, and 2-chloroadenosine were tested. To evaluate the effects of the second messengers of cellular signal transduction on protective agents, A23187, which is a calcium ionophore, and cAMP were used. PGE2 and cAMP were measured by radioimmunoassay. The release of [3H]glucosamine from prelabeled cells was used as an indicator of mucus secretion. Histamine, carbachol, gastrin, and 2-chloroadenosine did not modulate PGE2 production by parietal cells. Exogenously administered cAMP did not affect PGE2 production by parietal cells, whereas it was significantly increased by A23187. 2-Chloroadenosine but not histamine or carbachol significantly increased cAMP formation by mucous cells. Histamine, carbachol, and gastrin did not have significant effects on PGE2 production by mucous cells. 2-Chloroadenosine, which increased cAMP, also did not modulate PGE2 production. A23187 but not cAMP increased PGE2 production by mucous cells. None of the acid secretagogues used in the present study modulated mucus secretion. A23187 but not cAMP significantly increased mucus secretion by cultured mucus cells.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Chloroadenosine↗
PubMed1992

Neurexins.

Explore the source record for details and available documents.

Amino Acid Sequence↗
PubMed1992

Activity-dependent potentiation and depression of visual cortical responses to optic nerve stimulation in kittens.

1. To see whether long-lasting changes in synaptic efficacy are induced in the developing visual cortex (VC), field potentials evoked by test stimulation given alternatively to each of the optic nerves (ONs) were recorded from VC of kittens ranging in age from 4 to 8 wk. In some experiments, field potentials were recorded simultaneously from the dorsal lateral geniculate nucleus (LGN) in addition to VC. 2. Tetanic stimulation was applied to one of the ONs for 1-60 min at 5 Hz. Homosynaptic potentiation of cortical responses, defined as an increase lasting > 2.5 h in the cortical field potential evoked by test stimulation of the ON that was tetanized, was induced without any changes in LGN responses in 3 of the 12 kittens tested. Heterosynaptic depression, defined as a decrease lasting > 0.5 h in the field potential evoked by stimulation of the ON that was not tetanized, was also induced in two of those three kittens. 3. To elucidate a role of inputs originating from spontaneous activity of retinal ganglion cells in induction of potentiation and depression in the cortex, tetrodotoxin (TTX) was injected into both eyes of 11 kittens. After we confirmed the suppression of retinal activity by TTX, tetanic stimulation was applied to ON. Homosynaptic potentiation of cortical responses was induced in 6 of the 11 kittens, and the ratio of the mean amplitude of posttetanic responses to that of pretetanic responses for the 11 kittens was on average larger than that for the 12 control kittens. Heterosynaptic depression was not observed in any of the 11 kittens. 4. To see a role of postsynaptic activity in induction of potentiation and depression, gamma-aminobutyric acid (GABA) was applied continuously to the VC by an infusion pump in 10 kittens. Tetanic stimulation was given to ON while cortical activities were suppressed by GABA. After recovery of cortical activities, homosynaptic depression was found to be induced in 3 of the 10 kittens, but homosynaptic potentiation was not observed at all. The ratio of amplitude of posttetanic to pretetanic responses at the tetanized side for the 10 kittens was on average smaller than that for the 11 TTX-injected kittens. 5. These results can be accounted for by the modified covariance model in which the relation of postsynaptic activity and direction of changes in synaptic efficacy is formulated.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

[Protective effects of naftidrofuryl oxalate against hypoxia-induced death].

To analyze the effects of naftidrofuryl oxalate (LS-121) on the central nervous system exposed to critical hypoxia, survival duration was employed as a parameter of the protective effects of the drug against hypoxia-induced death. In the control group (no drug administration), the electroencephalogram (EEG) was flattened promptly after changing to hypoxia from aerobic conditions, and it was impossible to recognize precisely what time the EEG disappeared because of vigorous body movements. Arterial blood pressure (BP) was clearly recognized, and rats never recovered after BP decreased to 0 mmHg, although the electrocardiogram (ECG) was still recorded. Thus, survival duration recognized by measuring the time from the onset of hypoxia to the time when BP became 0 mmHg was considered to be a good indicator. After LS-121 (10 mg/kg) administration, survival duration was significantly prolonged compared to the control. Combination therapy of LS-121 (25 mg/kg) and bifemelane hydrochloride (BI) (25 mg/kg) also revealed the prolongation of survival duration. Neither idebenone (10 mg/kg) nor nicergoline (10 mg/kg) showed significant changes in survival duration. These findings suggest that LS-121, either with or without BI, could improve cerebrovascular disorders induced by hypoxia.

Animals↗