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Biomedical subjects

K Nagata

Publications and source records attributed to K Nagata.

At least 793 records · Page 44Linked to original sources
PubMed1989

Role of growth hormone in modulating the constitutive and phenobarbital-induced levels of two P-450(6)beta (testosterone 6 beta-hydroxylase) mRNAs in rat livers.

The role of growth hormone in the expression of two forms of hepatic cytochrome P-450(P-450), P-450(6)beta-1(6 beta-3), and P-450(6)beta-4, was investigated using RNA blots. The level of P-450(6)beta-1(6 beta-3) mRNA was twenty times higher than that of P-450(6) beta-4 mRNAs in untreated male rat livers. The levels of P-450(6)beta-1(6 beta-3) and P-450(6)beta-4 mRNAs were increased two fold and three fold, respectively, by hypophysectomy of adult male rats. By intermittent injection of human growth hormone (hGH) into hypophysectomized male rats, both mRNAs were decreased to the level of normal rats, and almost disappeared after continuous infusion of hGH. In female rats, these two mRNAs were not detected, but were increased remarkably by hypophysectomy. The increases in these mRNAs were almost abolished after continuous infusion of hGH in hypophysectomized female rats. The effect of hGH on PB-mediated induction of P-450(6)beta-1(6 beta-3) and P-450(6)beta-4 mRNAs was also examined. The PB-mediated increases in P-450(6)beta-1(6 beta-3) and P-450(6)beta-4 mRNAs were higher in hypophysectomized male rats (2.5-fold and 10.9-fold, respectively) than in normal male rats (1.5-fold and 5.2-fold, respectively). Thus, the levels of P-450(6)beta-1(6-beta-3) and P-450(6)beta-4 mRNAs were 4.1-fold and 7.3-fold, respectively, higher in PB-induced hypophysectomized rats than in normal male rats. Concerning the postnatal developmental profiles, P-450(6)beta-1(6 beta-3) mRNA was detectable at neonate and reached a maximal level at around 17 days of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1989

Site-directed mutagenesis of human pancreatic secretory trypsin inhibitor.

Arg-42 or Lys-43 or Arg-44 of human pancreatic secretory trypsin inhibitor (PSTI) was replaced by Thr or Ser by site-directed mutagenesis, and the inactivation rates of the mutants after mixing with human trypsin were compared with that of the natural form. The inactivation rate decreased for one mutant (Arg-44----Ser), whereas no change was observed for another (Arg-42----Thr) and an increase was observed for a third (Lys-43----Thr). Kinetic studies on the interactions between human trypsin and synthetic peptides, comprising the regions of Phe39-Ser47 of the respective PSTI species, showed that human trypsin cleaved the Arg42-Lys43 bond preferentially to the Arg44-Gln45 bond. However, it is cleavage of the latter bond that is thought to cause inactivation of human PSTI. These results suggest that the Arg44-Gln45 bond of human PSTI is responsible for its inhibitory activity, and inactivation of human PSTI is probably caused by deletion of the dipeptide Lys43-Arg44.

Amino Acids↗
PubMed1989

Correlation between cell-cell contact formation and activation of protein kinase C in a human squamous cell carcinoma cell line.

Formation of desmosomal cell-cell contact associated with reorganization of keratin intermediate filaments (KIFs) was observed when cultured cells of a cell line of human skin squamous cell carcinoma were transferred from low (0.07 mM) calcium to high (1.87 mM) calcium medium. At low calcium, cells were dispersed without desmosomal cell-cell contact and the KIFs were mostly concentrated around the nucleus. After 15 min of the transfer, cells contacted each other and formed small colonies and the KIFs initiated to show a radial arrangement. In addition to the cell-cell contact formation and rearrangement of KIFs, the transfer induced fourfold increase of particulate-associated protein kinase C (C-kinase) activity. When 12-O-tetradecanoyl phorbol-13-acetate (PMA), which specifically activates C-kinase, was added to the cells grown at low calcium medium, cell-cell contact formation and radial arrangement of KIF bundles almost identical to those induced by the transfer to high calcium medium were observed. These data suggest a correlation between an increase in C-kinase activity and formation of cell-cell contacts associated with rearrangements of KIFs.

Calcium↗
PubMed1989

Characterization of monoclonal antibodies against human parvovirus B19.

Eleven hybridoma cell lines producing mouse monoclonal antibodies (mAbs) against human parvovirus B19 were established. Their specificity was as follows. Approximately 5% of fetal erythroid cells inoculated with B19 reacted with all the mAbs and with anti-B19 positive human serum, but not with negative serum by indirect double immunofluorescence staining. All the mAbs recognized both VP-1 (84 kDa) and VP-2 (58 kDa) capsid proteins of B19 virions propagated in vitro and in vivo by Western blotting, and immunoprecipitated B19 virions.

Animals↗
PubMed1989

Endotoxin-induced serum factor that stimulates gamma interferon production.

Serum from Mycobacterium bovis BCG-infected mice that had been challenged with lipopolysaccharide (LPS) exhibited a marked ability to induce gamma interferon (IFN-gamma) in cultures of spleen cells of normal mice in the presence of interleukin-2 (IL-2). The inducing activity became detectable in the circulatory system about 90 min after LPS challenge, disappeared at around 5 h, and was observable upon 640x dilution of the serum. Addition of monoclonal anti-IL-2 receptor antibody to the culture inhibited the induction by the serum. The activity induced high levels of IFN-gamma even in nylon wool-nonadherent cells, while concanavalin A failed to do so. Serum from uninfected mice challenged with LPS contained no such activity. The molecular weight of the active substance, estimated by gel filtration, was about 70,000. There were pronounced differences among mouse strains in the activities of the sera prepared, which paralleled the amounts of IFN-gamma produced in vivo. However, the levels of IFN-gamma produced in whole spleen cells and in nylon wool-nonadherent cells from mice of various strains were the same when stimulated with competent serum. These results indicate the existence of an unidentified factor that induces IFN-gamma in cooperation with IL-2 in macrophage-depleted splenocytes. They also suggest that IFN-gamma production in vivo is not genetically controlled at the lymphocyte level but, rather, at the level of synthesis of the unknown factor.

Animals↗
PubMed1989

Activation of endogenous c-fos proto-oncogene expression by human T-cell leukemia virus type I-encoded p40tax protein in the human T-cell line, Jurkat.

We examined the ability of the trans-acting factor p40tax of human T-cell leukemia virus type I (HTLV-I), which is thought to be a crucial molecule in T-cell transformation by HTLV-I, to activate expression of a set of endogenous cellular genes related to T-cell proliferation. For this purpose we established a subclone (JPX-9) of Jurkat cells that was stably transfected with an expression plasmid containing the p40tax gene, whose expression is definitely dependent on heavy-metal ions. Expression of the interleukin-2 receptor alpha chain in JPX-9 cells was induced in response to the induction of p40tax expression, as has been demonstrated by others in transient transfection experiments with Jurkat cells. In addition, we found that significant enhancement of expression of the nuclear proto-oncogene c-fos was closely associated with expression of p40tax. Continous enhancement in the level of c-fos mRNA was observed in the presence of p40tax. In contrast, mRNA levels of other nuclear proto-oncogenes (c-myc, c-myb, and c-jun) were not appreciably effected by the expression of p40tax. These results suggest that (i) in addition to the interleukin-2-interleukin-2 receptor system, cellular genes such as c-fos, which regulate normal T-cell growth, are also activated directly or indirectly by p40tax and (ii) p40tax-induced modulation of gene expression plays a crucial role in T-cell transformation by HTLV-I.

Blotting, Northern↗
PubMed1989

Differential vasodilator effect of nitroglycerin on systemic capacitance and resistance vessels in anesthetized dogs, and the mechanism of its action--a study by measuring mean circulatory pressure and total peripheral resistance.

The aim of our studies was to examine if the baroreceptor reflex induced by intravenous injection of nitroglycerin (NG) nearly nullifies the vasodilator action of NG on the systemic capacitance vessels in dogs anesthetized with pentobarbital. We performed total spinal anesthesia (TSA) in open-chest dogs to eliminate the baroreceptor reflex. Dogs in which mean blood pressure (MBP) was maintained at about 100 mmHg by continuous intravenous infusion of epinephrine formed the TSA 100 group, and those in which MBP was maintained at about 70 mmHg formed the TSA 70 group. Dose-response curves relating 5-6 different doses (0.8 to 200 micrograms/kg) of intravenous NG, to changes in mean circulatory pressure (% delta MCP) and to changes in total peripheral resistance (% delta TPR), were constructed. These data were compared with those from untreated dogs. In addition, we also studied plasma catecholamine (CA) concentrations before and after the intravenous injection of NG. (1) There was no significant difference in the dose-response curves of NG for % delta TPR between the 3 groups. (2) There was no significant difference in the dose-response curves for % delta MCP between the 2 TSA groups. However, there was significant difference in the dose-response curves for % delta MCP between the TSA groups and the untreated dogs. The dose-response curves for % delta MCP in the TSA groups shifted upwards as compared with that of the untreated dogs. (3) In the TSA 100 group, there was no significant increase in the plasma CA concentrations with 100 micrograms/kg of NG. In the untreated group, intravenous injection of 12.5 micrograms/kg and 100 micrograms/kg of NG caused a dose-related fall in MBP and a dose-related rise in the plasma norepinephrine and epinephrine concentrations. Our results suggest that the vasodilator action of NG on the systemic capacitance vessels in the untreated dogs was counterbalanced partly by the vasoconstriction produced by the baroreceptor reflex, with its direct vasodilator effect masked when the hypotensive doses of NG were given acutely.

Anesthesia, Spinal↗
PubMed1989

Hepatic level of mRNA in relation to polymorphism and strain difference in expression of cytochrome P-450g.

Hepatic level of mRNA for P-450g was determined in male and female rats of Sprague-Dawley, ACI and Fischer strains using a specific oligonucleotide probe. The mRNA level in female Sprague-Dawley and Fischer rats was undetectable in accordance with a very low or undetectable level of P-450g protein. The mRNA was detected in all male ACI rats, in which high levels of P-450g protein were detected. In Fischer male rats, mRNA for P-450g was clearly detected in the liver, but P-450g protein was not detected. Moreover, the mRNA was detected in the liver of all male Sprague-Dawley rats, irrespective of the expressed level or absence of P-450g protein. As a most plausible explanation of the observed discordance in the levels of P-450g mRNA and protein, translation of unstable protein for microheterogeneous P-450g is discussed.

Animals↗
PubMed1989

[Bonding durability of various adhesion systems of dental alloy in aciditic solution].

Previous studies found that the adhesive resin provided strong adhesion to alloys. Also, the bond durability was improved by oxidation of alloys. In oral, many aciditic substances exist. However, the oxides yielded by oxidation are unstable in aciditic environment. Thereupon, the adhesive resin systems should be studied in aciditic environment. In this study, half of the alloy disks were air-brushed with alumina and the remaining half were polished with #600 emery. They were then ion-coated. One third of the disks were with Cu oxide another one third were Cu.Sn oxide, and remaining were Sn oxide. The handle was affixed by the 4-META resin. For reference, Co-Cr specimen oxidized ultrasonically was fabricated. Completed specimens emery polished were stored in lactic acid at 37 degrees C for 3 months, and sand-blasted were for 6 months. Then the tensile strength was measured. In 0.002% solution, initial bond strength of all the specimens was maintained after immersion. After 1.0% immersion, bond strength of Cu oxide coating specimen polished with emery decreased rapidly. Bond strength of Cu.Sn oxide and Sn oxide coated specimens decreased slowly. Sand-blasted specimens showed higher durability than emery polished. Co-Cr alloy specimen showed the highest durability, and 260 kgf/cm2 was maintained after 6 months in 2.0%.

Dental Alloys↗
PubMed1989

[Study on ion-coating surface treatment of dental alloys for adhesion. 2. Effect of Sn and Cu-Sn target on Au-Ag-Pd alloy].

Previous study found that ion coating treatment with Cu target demanded 10 minutes of treatment to achieve the durable adhesion with 4-META resin. For clinical application, it's indispensable to shorten the treatment period. Sn and Cu-Sn target were examined in this study. 4 minutes of treatment with Sn target showed high bond strength of adhesion. However, the excess of treatment time over 8 minutes caused the remarkable decrease of adhesion durability against thermal cycling. In clinical situation, many of the prosthesis possess the wings of complex shape and it's difficult to attain the uniform coating by only once treatment. However, the repetition of treatment with Sn target is undesirable because of the decrease of adhesion durability. Favorable result was shown by 4 minutes of treatment with Cu-Sn target and even by 30 minutes of treatment, same result was attained. With this ion treated specimens of Au-Ag-Pd alloy sandblasted, the adhesive bond strength of above 200 kgf/cm2 was maintained after 100,000 thermocycles.

Acrylic Resins↗
PubMed1989

The relation between phenytoin-receptor and glucocorticoid in the induction of cleft palate with phenytoin in mice.

Both phenytoin (PHT) and glucocorticoid (GC) have been reported to be an effective teratogen for the production of cleft palate. The authors suggest the possibility that a part of GC-receptor to which PHT competitively bind (common receptor with PHT), participate in the production of cleft palate. In the present study, as one of the studies for the elucidation of the mechanism of cleft palate induction with PHT, we investigated the PHT-receptors and its relation with GC in the lung tissue of mice, which were either sensitive (CF1) or resistant (C57BL/6) to PHT or GC. Scatchard analysis of the specific binding of 14C-PHT to the cytosol protein revealed that the total capacity of PHT-receptor for CF1 (1,571 fmole/mg protein) was much greater than that for C57BL/6 (994 fmole/mg). The value of the Kd's for these strains, however, were 18.1 and 16.5 nM, respectively, indicating the absence of any great difference between both strains. The capacity of the common receptors with GC for CF1 (236 fmole/mg) was greater than that for C57BL/6 (126 fmole/mg). But, the value of the Kd's for these strains were 5.4 and 3.1 nM, respectively, indicating the absence of a great difference between the strains. The analysis indicated that the lung tissue cytosols of both strains also contain the proper receptor for PHT, which is in a much greater amount than that of the common receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities, Drug-Induced↗
PubMed1989

Structure and regulation of P-450s in the rat P450IIA gene subfamily.

The rat P450IIA subfamily was characterized at the protein, cDNA, and gene level. The purified IIA1 and IIA2 P-450s displayed distinct positional specificities toward hydroxylation of the prototype substrate testosterone. The IIA1 and IIA2 genes were also regulated differently during development; IIA1 was expressed within 1 week after birth in both males and females, and was specifically suppressed in males at puberty, while IIA2 was not expressed in females and was activated at puberty in males. The cDNA-deduced amino acid sequences of these enzymes showed 88% similarity with interspersed regions of high and low similarity indicative of former gene conversion events. Both the IIA1 and IIA2 genes contained nine exons.

Aging↗
PubMed1989

Inhibition of the in vitro growth of blast progenitors from acute myeloblastic leukemia patients by transforming growth factor-beta (TGF-beta).

The effects of transforming growth factor-beta (TGF-beta) on the blast progenitors from nine acute myeloblastic leukemia patients were studied in methylcellulose and suspension cultures. Leukemic blast progenitors undergo terminal divisions with a limited differentiation in methylcellulose culture, making blast colonies. Blast progenitors can renew themselves. The self-renewal can be reflected by secondary colony formation after replating primary blast colonies in fresh methylcellulose media and by the exponential growth of clonogenic cells in suspension culture. TGF-beta suppressed primary and secondary colony-formation in methylcellulose culture. Furthermore, TGF-beta suppressed the recovery of clonogenic cells in suspension. The results indicate that TGF-beta is effective in inhibiting not only terminal divisions but also self-renewal of leukemic blast progenitors.

Adolescent↗
PubMed1989

Autocrine growth mechanisms of the progenitors of blast cells in acute myeloblastic leukemia.

Autocrine growth mechanisms of leukemic blast progenitors in acute myeloblastic leukemia (AML) were investigated. Colony formation of leukemic blast progenitors was observed in 14 of 14 patients tested when purified blast cell fraction depleted of both T cells and monocytes was plated in methylcellulose without any colony-stimulating factor (CSF). However, there existed a minimal cell density required to initiate blast progenitor growth with marked patient-to-patient variation. To clarify the role of cell density on the spontaneous growth of blast progenitors, we tested whether leukemic cells produced and secreted some stimulatory humoral factor(s). Production of colony-stimulating activity (CSA) by blast cells was observed in 17 of 18 patients tested. Following further depletion of monocytes, the CSA levels decreased markedly in 14 patients, indicating that blast cells with monocytoid differentiation were responsible for CSA production. We also confirmed granulocyte colony-stimulating factor (G-CSF) and/or granulocyte macrophage-colony-stimulating factor (GM-CSF) production by leukemic blasts using specific immunologic assays. When leukemic cells were divided into nonadherent nonphagocytic cell fraction and adherent cell fraction, only nonadherent nonphagocytic cells showed clonogenecity and adherent blast cells lacked the colony-forming capacity. The results indicate that there are at least two blast cell subpopulations in AML: one is proliferating subpopulation with self-renewal capacity and the other is supporting subpopulation with functions such as CSF production. The quite intimate relationship between these two blast cell subpopulations in AML may play an important role on the growth of leukemic blast progenitors in vitro.

Adult↗
PubMed1989

[The investigation of asthmatic children by multiple factor analysis. III. The changes in allergic factors selected by multiple factor analysis in 3 anti-allergic during treated groups over one year].

We investigated the difference in the influence on 10 allergic factors of 3 anti-allergic drugs: azelastine, tranilast, ketotifen. We determined the ranking of 10 allergic factors using the relative range ratio calculated by Multiple factor analysis. The ranking as follows: (1) Eosinophil count (2) IgE RAST score to H.D. (3) IgG4 antibody titers to egg white (4) IgE RAST score to egg white (5) IgE RAST score to D.f. (6) IgG4 antibody titers to milk (7) IgE RIST (8) IgG4 antibody titers to soybean (9) IgE RAST score to soybean (10) IgE RAST score to milk. Then we split 122 asthmatic children (mean age: 9.3) into 3 groups and gave each group a different one of the 3 anti-allergic drugs for one year. From daily records of asthma attacks and clinical findings, we classified the children into improved and not-improved groups within their respective anti-allergic drug group, and we investigated the changes in and the change ratios of the 10 allergic factors by the Student t method over this one year. The results were as follows. 1) There was no difference in the chang of 3 allergic factors (Eosinophil count, IgG4 antibody titers to egg white and IgE RIST) among the 3 anti-allergic drug treated groups. 2) The specific IgE antibodies to H.D. and D.f. had a remarkable decline tendency in treated groups by azelastine and tranilast. 3) The specific IgE antibody to egg white had a remarkable decline tendency in treated group by ketotifen.

Adolescent↗
PubMed1989

[Bonding of MMA-TBB resin to bovine tooth coated by poly (methyl methacrylate-co-p-styrene sulfonic acid)].

The objective of this study was to prepare a new type water soluble bonding agent, methyl methacrylate (MMA)-p-styrene sulfonic acid copolymer (MS), and to investigate the effect of MS on bonding between resins and tooth substrates. MS is cross-linked with Ca2+ supplied by hydroxyapatite in a smeared layer on ground enamel and dentin and sticks to their surface. Samples were prepared by bonding an acrylic rod with MMA-TBB resin to ground enamel and dentin coated with an aqueous mixture of FeCl3 and 10 wt% MS. After immersed in water for 24 hrs, the tensile bond strength was measured. The bond strengths to both enamel and dentin were higher than 11 MPa and cohesive failure of cured MMA-TBB resin was observed in every case. This suggested that MS could adhere to tooth substrates with a new bonding mechanism different from the previously reported mechanism of the monomer interpenetration and polymerization.

Adhesives↗