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Biomedical subjects

M Hirata

Publications and source records attributed to M Hirata.

At least 397 records · Page 22Linked to original sources
PubMed1992

Effect of glutathione content on cellular uptake and growth inhibitory activity of prostaglandin A2 in L-1210 cells.

Prostaglandin A2 (PGA2) is known to be actively incorporated into mammalian cells and thereby evokes its biological effects. To explore the transport mechanism of PGA2 and the possible role of cellular glutathione (GSH) in the transport process, we prepared GSH-enriched and -depleted L-1210 cells and then incubated with [3H] PGA2. In GSH-depleted cells, the total amount of PGA2 incorporated was reduced to about 50% of that in the control and GSH-enriched cells, accompanied by marked reduction of the PG in the cytosol but not in the nuclei. The kinetics of uptake revealed that the apparent Vmax was reduced by GSH depletion. Subsequent study of L-1210 cells under culture conditions provided similar results; GSH-depletion caused suppression of PG uptake and a reduction in the amount of PGA2 in cytosol, while its nuclear accumulation was little influenced. Comparison of the effect of PGA2 on the growth of control and GSH-depleted cells showed that the PG suppressed cell proliferation to the same extent. Our results suggest that, though uptake of PGA2 may be significantly influenced, its accumulation, and hence the manifestation of its biological effects are not influenced by GSH status.

Animals↗
PubMed1991

Synthetic inositol 1,3,4,5-tetrakisphosphate analogs and their effect on the binding to microsomal fraction of rat cerebellum.

Binding activity of [3H]inositol 1,3,4,5-tetrakisphosphate (InsP4) was characterized with rat cerebellar membranes. Two types of InsP4 analog with either the aminobenzoyl or the aminocyclohexanecarbonyl group on the 2nd position of InsP4 have been synthesized and their effects on the binding activity were also examined. [3H]InsP4 binding was gradually displaced by increasing amounts of unlabeled InsP4, with an IC50 of 60-170 nM, depending on the pH values. The binding was sharply increased at acidic pH and millimolar concentrations of Ca2+, this being in clear contrast with [3H]InsP3 binding noted in the same species of tissue. Heparin inhibited the binding, with an IC50 of 1.7, 3 or 20 micrograms/ml at pH 8.3, 7.2 or 5.0, respectively. Adenine nucleotide inhibited the binding more potently than did [3H]InsP3 binding. InsP4 analogs were as effective as InsP4 in displacing [3H]InsP4 from rat cerebellar membranes, thereby indicating that the 2nd hydroxyl group may not be involved in recognition of InsP4 by its binding sites.

Animals↗
PubMed1991

Differential expression of the beta I- and beta II-PKC subspecies in the postnatal developing rat brain; an immunocytochemical study.

Differential expression of protein kinase C subspecies, beta I- and beta II-PKC, derived from a single gene by alternative splicing was evidenced in the postnatal developing rat brain. Immunoblot analysis of the PKC subspecies in the whole developing brain showed that beta I-PKC was present at birth and then gradually increased, while beta II-PKC was not present at birth or on postnatal day 3, then increased rapidly from day 7 to the maximum value seen in the adult brain. Under light microscopy, beta I-PKC immunoreactivities seen at birth were the most intense in the brainstem and intense in the diagonal bundle and globus pallidus. beta I-PKC immunoreactivities in these neurons weakened from day 7 and disappeared in the adult brain, while in the cerebral cortex, triangular septal nucleus and pontine nucleus beta I-PKC immunoreactivities were week at birth and then gradually increased. beta II-PKC immunoreactivities were first visible in neurons on day 7 and increased progressively. beta I- and beta II-PKCs were not co-localized in a neuron, as far as examined. The immunoreactivities of beta I-PKC at birth were localized in growth cone-like structures as well as in the dendrites and perikarya. Similarly, alpha-PKC was also present at birth in the growth cone-like structure. Immunoblot analysis revealed that beta I-PKC was present at birth in the growth cone-rich fraction from the hindbrain but not in that from the forebrain, while alpha-PKC was found in the growth cone-rich fraction from both the forebrain and the hindbrain. beta II- and gamma-PKC were not detected in the growth cone-rich fraction from either forebrain or hindbrain. These findings suggest that beta I- and beta II-PKC play a role in different stages of development and in different neurons; both beta-subspecies may be involved in postnatal developing neuronal functions while only beta I-PKC plays functional roles in the growth cone, in the prenatal developmental stage.

Aging↗
PubMed1991

Purification, characterization, and molecular cloning of lactonizing lipase from Pseudomonas species.

An extracellular lipase catalyzing the synthesis of macrocyclic lactones in anhydrous organic solvents was purified to homogeneity from Pseudomonas nov. sp. 109, and characterized. The lipase showed a pI of 5.3 on isoelectric focusing and a Mr of 29,000 +/- 1,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. With respect to substrate specificity, optimum chain length for acyl moiety varied depending on the type of reaction catalyzed: C18 in monomer lactone formation, C11 or shorter in dimer lactone formation, and C8 in ester hydrolysis. The amino-terminal 19 amino acid residues of the purified lipase were determined as Ser-Thr-Tyr-Thr-Gln-Thr-Lys-Tyr-Pro-Ile-Val-Leu-Ala-His-Gly-Met-Leu-Gly- Phe, and the gene encoding the lipase was identified by hybridization to a synthetic 20-nucleotide probe, cloned, and sequenced. Nucleotide sequence analysis predicted a 311-amino acid open reading frame, a putative ribosome-binding site, and a 26-amino acid sequence at the amino terminus of the sequence that is not found in the mature protein. This 26-amino acid sequence has many of the characteristics common to known signal peptides. The lipase gene encoded a sequence of Val-Asn-Leu-Ile-Gly-His-Ser-His-Gly-Gly which is very well conserved among lipases, and showed 38-40% overall homology to the amino acid sequences of lipases from Pseudomonas fragie and Pseudomonas cepacia, but showed little homology to those of other lipases, suggesting that some structural features are required for catalyzing macrocyclic lactone synthesis in organic solvents and are restricted to lipases of the Pseudomonas origin.

Amino Acid Sequence↗
PubMed1991

Evidence for coupling of bradykinin receptors to a guanine-nucleotide binding protein to stimulate arachidonate liberation in the osteoblast-like cell line, MC3T3-E1.

The effect of bradykinin on the activation production of inositol 1,4,5-trisphosphate and prostaglandin E2 (PGE2) was examined in the murine osteoblastic cell line, MC3T3-E1. Bradykinin, at concentrations ranging from 1 to 1000 nM, stimulated the production of inositol 1,4,5-trisphosphate 2.5- to 3-fold within 10 s, and elevated cytosolic-free Ca2+, even in the absence of external Ca2+. This process is mediated through the activation of phospholipase C. Bradykinin at the same concentration also stimulated the production of PGE2 and caused a release of 3H radioactivity from the cells prelabeled with [3H]arachidonic acid, probably via the activation of phospholipase A2. Pretreatment of the cells with pertussis toxin inhibited the stimulation of PGE2 production and 3H radioactivity release, while the elevation in cytosolic Ca2+ and the production of inositol 1,4,5-trisphosphate were not altered by toxin-pretreatment. The addition of an unhydrolyzable analog of GTP, guanosine 5'-[gamma-thio]triphosphate (GTP gamma S) to the beta-escin-permeabilized cells prelabeled with [3H]arachidonic acid enhanced the release of 3H radioactivity. The simultaneous presence of bradykinin with GTP gamma S further activated the 3H radioactivity release in the beta-escin-permeabilized cells. These results provide evidence that receptors for bradykinin in the MC3T3-E1 couple stimulating arachidonate release, probably via the activation of phospholipase A2, through a guanine nucleotide binding protein sensitive to pertussis toxin.

Animals↗
PubMed1991

Complementary DNA sequence of rabbit CAP18--a unique lipopolysaccharide binding protein.

CAP18 is a novel 18 kDa cationic protein [pI approximately 10] originally purified from rabbit granulocytes using as an assay the agglutination of lipopolysaccharide (LPS) coated erythrocytes. cDNA clones encoding CAP18 were isolated from a rabbit bone marrow cDNA library using a PCR generated oligonucleotide probe derived from the N-terminal amino acid sequence. The deduced amino acid sequence reveals a putative signal sequence of 29 amino acids and a mature protein of 142 amino acid residues. The predicted size of the encoded protein is 16.6 kDa with a pI of 10. There are no N-linked glycosylation sites. The CAP18 sequence bears no homology with other known LPS-binding proteins including human bacterial permeability increasing protein (BPI)(1) and rabbit LPS binding protein (LBP)(2).

Amino Acid Sequence↗
PubMed1991

Synthetic inositol 1,3,4,5-tetrakisphosphate analogues.

Inositol 1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P4] analogues were synthesized and their effects on [3H]Ins(1,3,4,5)P4 5-phosphatase, [3H]Ins(1,3,4,5)P4 3-phosphatase and [3H]inositol 1,4,5-trisphosphate [3H]Ins(1,4,5)P3] 5-phosphatase activities were examined. The Ins(1,3,4,5)P4 analogue with the aminobenzoyl group at the 2-position of Ins(1,3,4,5)P4 inhibited the hydrolysis of 5-phosphate of [3H]Ins(1,3,4,5)P4 catalysed by erythrocyte ghosts, with a lower Ki value than seen with Ins(1,3,4,5)P4, whereas the analogue with the aminocyclohexanecarbonyl group at the same position had a higher Ki value. The Ins(1,4,5)P3 analogues that we had previously synthesized were also capable of inhibiting this process, with the same tendency as Ins(1,3,4,5)P4 analogues. Such differences in the potency among Ins(1,3,4,5)P4 and Ins(1,4,5)P3 analogues were applicable to other phosphatase activities, namely [3H]Ins(1,3,4,5)P4 3-phosphatase and [3H]Ins(1,4,5)P3 5-phosphatase. These results suggest that the active sites of these enzymes may catalyse the dephosphorylation in a similar fashion.

Erythrocyte Membrane↗
PubMed1991

Sympathetic inhibition and attenuation of spontaneous hypertension by PVN lesions in rats.

To determine whether the paraventricular nucleus (PVN) contributes to the development of hypertension in spontaneously hypertensive rats (SHR), we compared cardiovascular responses to ganglionic blockade with hexamethonium or vasopressin antagonism with dPVAVP in sham-operated or PVN lesioned SHR and Wistar-Kyoto rats (WKY). Lesions were produced electrolytically when the rats were 5 weeks old. During the next 3 weeks, tail-cuff measurements showed that the development of hypertension in SHR was inhibited, while systolic pressure in WKY was unaffected. Mean pressures recorded directly from the femoral artery at 8 weeks of age were lower in lesioned than in sham-operated SHR (141 +/- 5 vs 110 +/- 3 mm Hg, P less than 0.05), but did not differ in corresponding WKY groups (110 +/- 4 vs 112 +/- 5 mm Hg). Depressor responses to ganglionic blockade induced by i.v. injection of hexamethonium (25 mg/kg) were significantly larger in sham-operated than in lesioned SHR (-41 +/- 4% vs -28 +/- 3%, P less than 0.05). By contrast, vasopressin antagonism with dPVAVP did not alter blood pressure in all rat groups. In 24-h urine samples, excretion of vasopressin was unaffected, but that of norepinephrine was significantly reduced in lesioned SHR. These findings suggest that the PVN contributes to the development of spontaneous hypertension by sympathetic activation without increasing vasopressin secretion.

Animals↗
PubMed1991

Cloning and expression of cDNA for a human thromboxane A2 receptor.

Thromboxane A2 is a very unstable arachidonate metabolite, yet a potent stimulator of platelet aggregation and a constrictor of vascular and respiratory smooth muscles. It has been implicated as a mediator in diseases such as myocardial infarction, stroke and bronchial asthma. Using a stable analogue of this compound we recently purified the human platelet thromboxane A2 receptor to apparent homogeneity. Using an oligonucleotide probe corresponding to its partial amino-acid sequence, we have obtained a complementary DNA clone encoding this receptor from human placenta and a partial clone from cultured human megakaryocytic leukaemia cells. The placenta cDNA encodes a protein of 343 amino acids with seven putative transmembrane domains. The protein expressed in COS-7 cells binds drugs with affinities identical to those of the platelet receptor, and that in Xenopus oocytes opens Ca2(+)-activated Cl- channel on agonist stimulation. Northern blot analysis and nucleotide sequences of the two clones suggest that an identical species of the thromboxane A2 receptor is present in platelets and vascular tissues. This first report on the molecular structure of an eicosanoid receptor will promote the molecular pharmacology and pathophysiology of these bioactive compounds.

Amino Acid Sequence↗
PubMed1991

Histopathological study of oesophageal mucosa in patients with varices: a comparison between bleeders and non-bleeders.

Thirty-six patients with oesophageal varices underwent a non-shunting operation including oesophageal transection. Of these, 16 had an emergency or elective operation (bleeders) and the remaining 20 had prophylactic surgery (non-bleeders). A comparative study was performed between the bleeders and non-bleeders in terms of preoperative endoscopic findings and histopathology of the oesophagus. The severity of red colour sign showed no significant difference between the two groups. The venous dilatation in each of the three layers of the oesophageal mucosa was demonstrated histologically to be of the same degree in bleeders and non-bleeders. In addition, the hepatic venous pressure gradient in cirrhotic patients did not differ between the two groups; for bleeders this was a mean(s.d.) of 15.2(6.1) mmHg and for non-bleeders 14.4(2.9) mmHg. We were unable to find any factors differentiating bleeders from non-bleeders, although these results do not justify prophylactic surgery for oesophageal varices.

Aged↗
PubMed1991

Induction of experimental murine granuloma formation against Schistosoma japonicum eggs produced by in vitro ova deposition, in vitro tissue extraction, or lyophilization.

Fresh eggs, laid by Schistosoma japonicum adult worms in vitro or recovered from tissue after trypsin digestion, as well as non-viable lyophilized eggs were injected into mice via the cecal vein. The freshly laid eggs induced a marked, maximal reaction at 2 weeks after implantation. This reaction was indistinguishable from that seen early in naturally infected mice. Lyophilized eggs induced granulomas only one-tenth the size of those formed around freshly laid eggs. Maximal granulomatous reactivity was not seen until the 4th week after implantation and the intensity of cellular reactivity and associated histopathological change was much lower than that observed with freshly laid eggs. Reactions against live, tissue-extracted eggs were quantitatively and temporally intermediate between those observed against laid and those surrounding lyophilized eggs. The results suggests that these differences in granuloma formation are due to variable quantities of locally produced cytotoxic materials and/or antigen that stimulate immune reactions of different intensities.

Animals↗
PubMed1991

Glycyrrhizin withdrawal followed by human lymphoblastoid interferon in the treatment of chronic hepatitis B.

Seventeen patients with chronic hepatitis B were treated with a 4-week administration of glycyrrhizin followed by a 4-week treatment with human lymphoblastoid interferon, then followed for 6 months after the end of treatment. All were positive for hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg), and hepatitis B virus-associated DNA polymerase (DNA-p) for at least 6 months before entry. All patients were Japanese and none of them were homosexuals. Eleven patients lost DNA-p activity and 10 of them lost HBeAg. Three of these 10 patients had antibody to HBeAg. In 10 patients who became HBeAg-negative, alanine aminotransferase levels after glycyrrhizin administration were higher and initial DNA-p activities relatively lower than the levels found in seven patients who remained HBeAg-positive. The immunomodulator provided by a short course of glycyrrhizin before administration of human lymphoblastoid interferon may be an effective treatment for patients with chronic hepatitis B.

Adult↗
PubMed1991

Effect of L-methionine on 2-carboxybenzaldehyde reductase induction by phenobarbital in primary cultures of rat hepatocytes.

Effects of phenobarbital (PB) and L-methionine on 2-carboxybenzaldehyde (CBA) reductase in rat hepatocyte primary culture were examined. Inclusion of PB in the culture medium markedly enhanced the CBA reductase activity while L-methionine, which elevates the cellular glutathione (GSH) level, suppressed the stimulatory effect of PB. This suppression, though less pronounced, was also found with other precursors of GSH biosynthesis. GSH-depletors, buthionine sulfoximine (BSO) or diethylmaleate (DEM), enhanced the CBA reductase activity suggesting that GSH plays an important role in enzyme induction.

Alcohol Oxidoreductases↗
PubMed1991

Protective effect of prostaglandin A2 against menadione-induced cell injury in cultured porcine aorta endothelial cells.

Prostaglandin A2 (PGA2) stimulates the biosynthesis of gamma-glutamylcysteine synthetase and elevates glutathione (GSH) contents in cultured mammalian cells. To clarify the importance of gamma-glutamylcysteine synthetase induction in the defence of endothelial cells against oxidative stress, the effect of PGA2 on menadione (2-methyl-1,4-naphthoquinone)-induced cell injury was examined. Incubation of porcine aorta endothelial cells with menadione produced marked loss of cellular GSH and protein sulfhydryl groups, followed by leakage of lactic dehydrogenase (LDH) into the culture medium. The LDH leakage and modification of protein thiol was, however, completely prevented by pretreatment of the cells with PGA2. The protective effect of PGA2 was more potent than that of cysteine delivery agents such as methionine, N-acetylcysteine or 2-oxo-4-thiazolidine carboxylic acid (OTC). The results suggest that cellular GSH plays an important role in the defence against oxidative stress, and induction of gamma-glutamylcysteine synthetase is effective for protecting vascular endothelial cells.

Animals↗
PubMed1991

Experimental regulation of granulomatous reactions around Schistosoma japonicum eggs implanted into the liver of mice.

Using a liver model, various granulomatous responses against Schistosoma japonicum eggs were studied in C57BL/6 mice immunized with tissue-extracted eggs prior to challenge implantation with freshly laid eggs. In mice receiving two ip injections of 20,000 eggs, there was little effect on early granuloma formation. Three weeks after implantation, however, tissue reaction accompanied by marked fibrosis was significantly augmented, compared to that in the untreated mice. In contrast, when mice were given four ip injections, the early reaction was accelerated and the subsequent fibrosis came to an end earlier than in the twice immunized or untreated mice. Different routes of injection produced differing effects on 2-week granulomas, with an augmented reaction following two sc injections and a diminished reaction following the same number of ip injections. Histologically, the diminished reaction was characterized by less cellularity, especially in the case of eosinophil infiltration.

Animals↗
PubMed1991

Decrease of hepatitis A and B virus infections in the population of Okinawa, Japan.

In 1988 1282 serum samples were collected from healthy Japanese persons living on Hateruma Island (574 samples) and Iriomote Island (708 samples) in Okinawa, Japan. Serological markers of hepatitis B virus (HBV) infection [hepatitis B surface antigen (HBsAg), antibody to hepatitis B core antigen (anti-HBc) were investigated and the findings compared with samples taken in 1980 on Hateruma Island and in 1970 and 1980 on Iriomote Island. The samples collected in 1988 on Iriomote Island were also tested for antibody to hepatitis A virus (anti-HAV) and the findings compared with the results of the 1970 and 1980 surveys. The overall prevalence of HBsAg and anti-HBc was 3.7 and 64.8% for Hateruma Island and 3.8 and 44.9% for Iriomote Island. In both areas the overall prevalence of anti-HBc was lower than in 1980, the decrease being significant for the 10-19 year age group on Hateruma Island and the age groups under 39 years on Iriomote Island. The overall prevalence of anti-HAV had fallen to 50.9%. This remarkable decrease had occurred in children and young adults. These data suggest that Virus A (HAV) and HBV infections have dramatically decreased among children in Okinawa within the past 2 decades.

Adolescent↗