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Biomedical subjects

T Nishihara

Publications and source records attributed to T Nishihara.

At least 163 records · Page 9Linked to original sources
PubMed1994

Fractal dimension analysis of mandibular bones: toward a morphological compatibility of implants.

In addition to biological and mechanical compatibilities for promising implant materials, a morphological compatibility is proposed by the authors. It has been reported by many investigators that implant surface with appropriate roughness and pore size exhibit better bone ingrowth activities. However, these parameters cannot characterize the complexity of surface textures. In the present study, dentulous and edentulous mandibular alveolar bones were utilized. Four segments from each mandible were subjected to the Fractal Dimension (DF) analysis. It was found that the dentulous mandible showed the DF of 1.81 +/- 0.03 while the edentulous mandible exhibited DF of 1.55 +/- 0.07, indicating that the former has more complex surface texture. It was also found that there could be a linear relationship between the surface roughness and the fractal dimension.

Alveolar Process↗
PubMed1993

Activin A induces apoptotic cell death.

Activins, members of a family of the transforming growth factor beta (TGF beta), are involved in the regulation of multiple biological events. We found a novel effect of activin A on hybridoma and myeloma cell lines. Activin A exhibited a cytotoxic effect on interleukin-6 (IL-6)-dependent B9 cells and induced a significant increase in the proportion of fragmented DNA. B9 cells exposed to activin A released high amounts of lactate dehydrogenase (LDH) and exhibited the typical ladder pattern of DNA fragmentation of apoptotic cells. IL-6 did not prevent apoptosis of B9 cells induced by activin A. The cytotoxicity of activin A to B9 cells was suppressed by follistatin. On the other hand, TGF beta showed no cytotoxic effect on B9 cells. These findings indicate that apoptosis induced by activin A could be one of the mechanisms to prevent uncontrolled cell growth.

Activins↗
PubMed1993

Vitamin D receptor zinc finger region binds to a direct repeat as a dimer and discriminates the spacing number between each half-site.

1 alpha,25-Dihydroxyvitamin D3, the most active metabolite of vitamin D3, is a multifunctional agent. The actions of 1 alpha,25-dihydroxyvitamin D3 are mediated through its receptor that activates the specific genes in a ligand-dependent manner. In order to investigate the details of DNA binding properties of vitamin D receptor, we have developed the overexpression and purification system of vitamin D receptor DNA binding domain. The purified peptide could specifically bind to the osteopontin-derived vitamin D responsible element (VDRE) but not to the osteocalcin and the calbindin D-9k-derived VDREs, as determined by bandshift analysis. The osteopontin VDRE contains a direct repeat of GGTTCA motif separated by 3 nucleotides, whereas the osteocalcin and calbindin D-9k VDREs have inadequate direct repeat. Further analyses using synthetic oligonucleotides revealed that vitamin D receptor DNA binding domain could discriminate the spacing number between the consensus steroid-responsible element motif and had different affinities to direct repeats that consisted of various related sequences. These studies give insight into ways in which vitamin D receptor mediates the signal of 1 alpha,25-dihydroxyvitamin D3.

Animals↗
PubMed1993

Secretion and purification of hepatitis C virus NS1 glycoprotein produced by recombinant baculovirus-infected insect cells.

Recombinant baculoviruses that produce a putative non-structural protein 1 (NS1) of hepatitis C virus (HCV), predicted to be the second envelope glycoprotein, were constructed. The recombinant NS1 protein (re-NS1) produced in infected insect cells was localized on the cell surface and was apparently glycosylated, because it was susceptible to treatment with both tunicamycin and N-glycanase. Furthermore, re-NS1 was effectively secreted into the culture supernatant when the putative NS1 signal peptide (SP) was replaced by the SP of rabies virus G protein, and the C-terminal hydrophobic region was eliminated. The secreted re-NS1 was tagged with six His residues at the C terminus and purified simply by native Ni(2+)-nitrilotriacetic acid (Ni(2+)-NTA) affinity column chromatography. An enzyme-linked immunosorbent assay (ELISA) was developed for the serological diagnosis of HC using purified re-NS1. Anti-NS1 antibody (Ab) was detected in 55 of 60 patients (92%) with chronic HC liver diseases. Thus, this ELISA for Ab directed against HCV re-NS1 produced in insect cells is useful for the detection of chronic HC patients.

Amino Acid Sequence↗
PubMed1993

Modulation of glutathione S-transferase activity by a thiol/disulfide exchange reaction and involvement of thioltransferase.

Low concentrations of cystamine and cystine inactivated human placenta glutathione S-transferase (GST-pi) in cytosolic fraction very effectively, as did the purified enzyme, through the thiol/disulfide exchange reaction. Mixed disulfide formation of GST-pi in cytosol was prevented by thioltransferase existing in cytosol with a low concentration of GSH. This protection of GST-pi activity was more effective with the participation of glutathione reductase. The incorporation of half-[14C]cystine into a GST-pi molecule according to the inactivation was provided by autoradiography. Purified human placenta thioltransferase (1900-fold from cytosol) could release the incorporated half-[14C]cystine from a GST-pi molecule with restoration of enzyme activity. Thioredoxin in placenta cytosol could not protect the GST-pi activity from inactivation at all.

Chromatography, Affinity↗
PubMed1993

Difference in glutathione S-transferase response to oxidative stress between porcine and bovine lens.

Porcine and bovine lens GSTs were compared in the stability against various oxidative stress which is a major factor of cataract formation in order to clarify the role of lens glutathione S-transferase (GST) and its relation to cataractogenesis. Class pi porcine lens GST was inactivated reversibly by biological disulfides, cystine and cystamine, and also inactivated by active oxygen species such as O2- generated through xanthine-xanthine oxidase system and H2O2. On the other hand, class mu bovine lens GST was insensitive to such applied oxidative stress. Furthermore, 1,2-naphthoquinone, which is a metabolite of naphthalene and an actual inducer of naphthalene cataract, strongly inactivated porcine lens GST though it did not affect bovine enzyme. Thus, porcine and bovine lens GSTs had different sensitivity to various oxidative stress which could induce cataract formation. The results suggest that the differential expression of GST isozymes among animals may explain the variation in the cataract formation caused by oxidative stress.

Animals↗
PubMed1993

Comparison of purified lens glutathione S-transferase isozymes from rabbit with other species.

Two glutathione S-transferase (GST) isozymes, GST-rl1 and GST-rl2, were purified from rabbit lenses and their properties were compared with those of other animals. GST-rl1 and GST-rl2 are dimeric enzymes whose subunit sizes are 24,000 and 21,500, respectively. The substrate specificities and inhibitor sensitivities of GST-rl1 and GST-rl2 are different from each other and from those of the isozymes from other animals. GST-rl1 immunologically crossreacted with the antibody against class mu GST (rat GST Yb1-Yb1), and GST-rl2 crossreacted with the antibody against class pi GST (rat GST Yp-Yp). N-Terminal amino acid sequences of GST-rl1 and GST-rl2 have great homology with other class mu and class pi enzymes, and thus indicate that they belong to class mu and class pi, respectively. Class pi GST-rl2 is inactivated by 1,2-naphthoquinone, an oxidized metabolite of naphthalene, but class mu GST-rl1 is insensitive to it. These results are similar to those of class pi pig lens GST and class mu bovine lens GST. Thus, the expression pattern of GST isozymes in lens varies with animal species, and may relate to their variation in sensitivity to oxidative stress.

Amino Acid Sequence↗
PubMed1993

Modulation of 3 alpha-hydroxysteroid dehydrogenase activity by the redox state of glutathione.

3 alpha-Hydroxysteroid dehydrogenase (EC 1.1.1.50), purified to homogeneity from rat liver, was strongly inactivated by incubation with a disulfide such as GSSG, L-cystine or L-cystamine, as well as an SH-reagent such as DTNB (5,5'-dithiobis(2-nitrobenzoic acid)), NEM (N-ethylmaleimide) or iodoacetic acid. The inactivation advanced with incubation time. Coenzyme (NADP+) completely protected the enzyme from this inactivation by disulfides, but neither of the substrates (androsterone and benzenedihydrodiol) did. The activity of inactivated enzyme was restored by treatment with thiols such as DTT (dithiothreitol) or GSH. In the GSH/GSSG redox buffer, the enzyme existed in an equilibrium between active (reduced) and inactive (oxidized) forms.

3-Hydroxysteroid Dehydrogenases↗
PubMed1993

[Expression of hepatitis C virus genome].

Complementary DNAs from HCV genome were expressed and analyzed. C8-2 protein, a part of NS5, and core protein were synthesized in E. coli. Core protein (JCC) was appeared to be very useful for diagnostic probe of HCV infection. Predicted envelope glycoproteins (E1 and E2/NS1) produced in infected insect cells were glycosylated and secreted into the culture media when the signal sequence of rabies virus G protein was introduced. An ELISA was developed using each purified recombinant protein. Anti-E1 antibody was detected in 20% of patients with non-A, non-B chronic liver diseases, whereas anti-E2/NS1 antibody was detected in more than 88%. These results indicate that the immune responses against these glycoproteins are different.

Animals↗
PubMed1992

Identification of non heparin-binding endothelial cell growth factor from rat myofibroblasts.

Myofibroblasts (Mfs) from rat fat tissues produced a potent endothelial cell growth factor (Mf-ECGF). The growth factor activity found in the conditioned media from primary cultures of Mfs, was labile to heat (80 degrees C for 10 min) and proteinase (trypsin), and did not bind to heparin in the presence of 0.2 M NaCl. Mf-ECGF was partially purified 4760-fold with a recovery of 25% from serum-free conditioned media by sequential carboxymethyl (CM) ion-exchange column chromatography and gel filtration. This Mf-ECGF activity was recovered from the 40 kD region of a non-reducing SDS-PAGE, and from the pH region between 6.5 and 7 of isoelectric focusing, with recoveries of 20% and 65%, respectively. These results indicated that a major portion of ECGF activity in the conditioned media was clearly distinct from other well-known endothelial cell growth factors including fibroblast growth factors (FGFs).

Adipose Tissue↗
PubMed1992

Characterization of bovine liver cytosolic 3 alpha-hydroxysteroid dehydrogenase and its aldo-keto reductase activity.

1. 3 alpha-Hydroxysteroid dehydrogenase was purified to homogeneity from bovine cytosolic fraction, which was monomeric and its molecular weight was estimated to be about 35 kDa. 2. The enzyme had ability to catalyze NADP(H)-dependent oxidoreduction of position 3 alpha-hydroxy and keto group of steroids and also could catalyze the reduction of some ketones and quinones. 3. In addition, benzenedihydrodiol was one of the substrates of dehydrogenase activity with NADP+. 4. Indomethacin, synthetic steroids and SH-reagents were potent inhibitors for this enzyme. 5. Inactivation of the enzyme by GSSG-treatment was restored to its original activity by the addition of DTT. 6. The presence of coenzyme, 0.33 mM NADP+, completely protected from the DTNB-inactivation. 7. Bovine liver cytosolic enzyme immunologically crossreacted with rat liver 3 alpha-hydroxysteroid dehydrogenase.

3-Hydroxysteroid Dehydrogenases↗
PubMed1992

Purification and characterization of glutathione S-transferase isozymes in dog lens.

1. Two isozymes of glutathione S-transferase (GST-dl1 and GST-dl2) were purified to homogeneity from dog lens. 2. The subunit size and the isoelectric point were determined to be 24,000 and > pI 9.5 for GST-dl1 and 22,000 and pI 8.1 for GST-dl2. 3. It was judged that GST-dl1 is a class alpha enzyme and GST-dl2 belongs to class pi on the basis of their immunological properties and N-terminal amino acid sequences. 4. The expression pattern of glutathione S-transferase isoenzymes in dog lens is different from that in pig, rat and bovine lenses.

Amino Acid Sequence↗
PubMed1992

Study on human erythrocyte thioltransferase: comparative characterization with bovine enzyme and its physiological role under oxidative stress.

Thioltransferase, an enzyme which catalyzes the thiol/disulfide exchange reaction in the presence of GSH, was purified to homogeneity on 15% SDS-PAGE from human (36,000-fold purification) and bovine (23,000-fold) erythrocyte hemolysates. These enzymes had similar properties in their monomeric structures (M(r) = 11,000) and broad specificities for substrates ranging from low-molecular disulfides (S-sulfocysteine, cystamine, and cystine) to protein disulfides (trypsin and insulin). They were highly sensitive to SH-reagents (monoiodoacetic acid and mercuric chloride), but were protected from inactivation by the presence of disulfides (GSSG, cystamine, and cystine). Phosphofructokinase and pyruvate kinase that had been inactivated by disulfides were reactivated effectively by the addition of thioltransferase with GSH. In addition, disulfides in membrane proteins of human erythrocytes that have been oxidatively damaged by diamide treatment were reduced to the SH-free form more effectively by incubation with thioltransferase.

Amino Acids↗
PubMed1992

A novel dihydrodiol dehydrogenase in bovine liver cytosol: purification and characterization of multiple forms of dihydrodiol dehydrogenase.

Three enzymes (DD1, DD2, and DD3) having dihydrodiol dehydrogenase activity were purified to homogeneity from bovine cytosol. DD1 and DD2 were identified as 3 alpha-hydroxysteroid dehydrogenase and high-Km aldehyde reductase, respectively, as judged from their molecular weights, substrate specificities and inhibitor sensitivities. DD3 was a unique enzyme which could specifically catalyze the dehydrogenation of trans-benzenedihydrodiol and trans-naphthalenedihydrodiol without any activity toward the other tested alcohols, aldehydes, ketones, and quinones. The Km value of DD3 (0.18 mM) for benzenedihydrodiol was lower than those of other dihydrodiol dehydrogenases so far reported. DD3 immunologically crossreacted with DD1, but showed no crossreactivity with DD2. Additionally, DD3 was inhibited in a competitive manner, with a low Ki value of 1 microM, by androsterone, which was a good substrate for DD1. It was assumed that DD3 is a novel enzyme which is specific to dihydrodiols, exhibiting similarity to DD1 in immunological and structural properties.

3-Hydroxysteroid Dehydrogenases↗
PubMed1992

Biochemical defects of outermost layer deficient mutants during sporulation of Bacillus megaterium.

To determine the regulation of morphogenesis of the outermost layer, the thick layer outside the inner coat, of the Bacillus megaterium spore, we isolated 15 outermost layer deficient mutants of B. megaterium using transposon Tn917. Three mutant strains lacked both synthesis of the 48-kDa outermost layer protein and induction of two initial enzymes for galactosamine-6-phosphate polymer synthesis, evidence that these biochemical events are regulated in the cascade system during morphogenesis of the outermost layer.

Bacillus megaterium↗
PubMed1992

Characterization of multiple forms of carbonyl reductase from chicken liver.

Three enzyme forms (CR1, CR2 and CR3) of carbonyl reductase were purified from chicken liver with using 4-benzoylpyridine as a substrate. CR1 was a dimeric enzyme composed of two identical 25-kD subunits. CR2 and CR3 were monomeric enzymes whose molecular weights were both 32 kD. CR1 exhibited 17 beta-hydroxysteroid dehydrogenase activity as well as carbonyl reductase activity in the presence of both NADP(H) and NAD(H). CR2 and CR3 had similar properties with regard to substrate specificity and inhibitor sensitivity. They could exhibit the activity only with NADPH and had no hydroxysteroid dehydrogenase activity. CR2 and CR3 cross-reacted with anti-chicken kidney carbonyl reductase antibody, though CR1 did not. The results suggest that CR1 is a hydroxysteroid dehydrogenase, and CR2 and CR3 are similar to each other and to the kidney enzymes.

17-Hydroxysteroid Dehydrogenases↗