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Biomedical subjects

S Ohta

Publications and source records attributed to S Ohta.

At least 19 recordsLinked to original sources
PubMed1992

Bone morphogenetic proteins (BMP-2 and BMP-3) induce the late phase expression of the proto-oncogene c-fos in murine osteoblastic MC3T3-E1 cells.

Here we report that bone morphogenetic proteins 2 and 3 (BMP-2 and BMP-3) induced marked expression of c-fos mRNA in a biphasic manner, i.e. the late phase (48 to 60 h) as well as the immediate-early phase (0.5 h), in murine osteoblastic MC3T3-E1 cells in vitro. The BMP-induced late phase c-fos gene expression was temporally associated with the onset of marked expression of the genes for osteocalcin and alkaline phosphatase, differentiation markers of mature osteoblasts. In contrast, none of TGF-beta 1, 10% FBS, IGF-I and IGF-II, which induced only the immediate-early c-fos mRNA expression, stimulated the expression of osteocalcin and alkaline phosphatase genes. These data suggest that in osteoblasts BMP-2 and BMP-3 induce the late phase expression of c-fos, which may play a role in transcriptional activation of the genes involved in differentiation of osteoblasts.

Animals↗
PubMed1992

The effect of active vitamin D3 analogs and dexamethasone on the expression of osteocalcin gene in rat tibiae in vivo.

We tested the effects of 1 alpha,25-dihydroxyvitamin D3 (1,25-(OH)2D3), 2 beta-(3-hydroxypropoxy)-1 alpha,25-dihydroxyvitamin D3 (ED-71) and dexamethasone on osteocalcin mRNA levels in rat tibiae in vivo. Northern blot analysis showed that both 1,25-(OH)2D3 and ED-71 caused an increase in osteocalcin mRNA levels in bone: 1,25-(OH)2D3 induced a transient increase in the mRNA levels followed by a decrease in the control level by 12 h post administration. In contrast, ED-71 caused a persistent increase in osteocalcin mRNA level for seven days post administration. Serum osteocalcin levels paralleled the osteocalcin mRNA level in bone in both groups. Dexamethasone caused a marked reduction in both osteocalcin mRNA and serum osteocalcin levels. Suppressive effect of dexamethasone on osteocalcin expression was persistent for seven days at higher dose. Our results represent the first demonstration of the effect of active vitamin D and corticosteroid on the expression of osteocalcin mRNA in bone in vivo.

Amino Acid Isomerases↗
PubMed1992

The alpha 3 beta 3 and alpha 1 beta 1 complexes of ATP synthase.

Two catalytic structures of H(+)-motive ATP synthase (Fig. 1), the alpha 3 beta 3 oligomer (M(r) = 319,581) and alpha 1 beta 1 promoter (M(r) = 106,527) (Fig. 2), were isolated using high pressure liquid chromatography (Fig. 3) and polyacrylamide gel electrophoresis (Figs. 4 and 5). These were reconstituted from the alpha and beta subunits of thermophilic F1 (TF1), and the alpha 3 beta 3 oligomer was also crystallized. Common to both F1 and the alpha 3 beta 3 oligomer were the nucleotide specificity, the two Km values, the presence of protomer-oligomer activities, and the one-hit--one-kill phenomenon. A synchrotron experiment on the ATP hydrolysis cycle revealed the dynamic shrinkage and expansion of F1(44) that correspond, respectively, to the ATP-induced association and ADP-induced dissociation of the alpha 3 beta 3 oligomer. The oligomer, like mitochondrial F1 and TF1, exhibited two kinds of ATPase activity: one was cooperative and was inhibited by only one inhibitor per hexamer, and the other was inhibited by three inhibitors per hexamer.

Adenosine Triphosphate↗
PubMed1992

Comparison of anticonvulsant effects of valproic acid entrapped in positively and negatively charged liposomes in amygdaloid-kindled rats.

Intraperitoneal injection of free valproic acid (VPA) suppressed amygdaloid-kindled seizure 1 h after injection in rats, but had no effect at 24 h. VPA entrapped in positively charged liposomes showed a prolonged anticonvulsant effect lasting for 2 days, while the effect evaluated at 1 h was not different from that with free VPA. VPA entrapped in negatively charged liposomes exerted a significantly stronger effect at 1 h than did free VPA, while it had no significant effect at 24 h. These results suggest that surface charges on liposomes play an important role in modifying the anticonvulsant effect of VPA.

Amygdala↗
PubMed1992

Thrombin-induced human platelet aggregation is inhibited by protein-tyrosine kinase inhibitors, ST638 and genistein.

We have investigated the involvement of protein-tyrosine kinases in thrombin-induced aggregation of human platelets, using ST638 and genistein which are known inhibitors of protein-tyrosine kinase. Preincubation of platelets with 50 microM of ST638 or 25 micrograms/ml of genistein completely blocked the platelet aggregation induced with 0.05 unit/ml of thrombin. The increase of protein-tyrosine phosphorylation bands (135-, 124-, 76-, 64-, and 60-kDa) induced with thrombin was also inhibited by these inhibitors in a dose-dependent manner. These inhibitors also blocked the platelet aggregation and protein-tyrosine phosphorylation induced with thrombin in aspirin-treated platelets. Increase of the intracellular Ca2+ concentration induced by thrombin was also inhibited by higher concentrations of genistein. These results suggest that the protein-tyrosine phosphorylation plays a certain role in platelet activation having some relation to the intracellular Ca2+ concentration.

Amino Acid Sequence↗
PubMed1992

Protein-tyrosine kinase p72syk is activated by wheat germ agglutinin in platelets.

We previously reported a molecular cloning of porcine gene syk encoding a non-receptor type 72-kDa protein-tyrosine kinase (Taniguchi et al. (1991) J. Biol. Chem. 266, 15790-15796). In this study, we have demonstrated that p72syk is expressed in porcine platelets at 0.1-0.2% of total protein and that the lectin wheat germ agglutinin induces an activation of p72syk against both auto- and exogenous-substrate-phosphorylation in porcine platelets. The activation of p72syk was abrogated by the coexistence of N-acetyl-D-glucosamine with wheat germ agglutinin. These data suggest that p72syk is a candidate of responsible protein-tyrosine kinase for platelet activation and that cell surface glycoprotein is involved in the activation of p72syk in platelets.

Acetylglucosamine↗
PubMed1992

Upstream region of a genomic gene for human mitochondrial transcription factor 1.

A genomic gene for human mitochondrial transcription factor 1 was cloned from a human genomic library and its 5' flanking region was sequenced. No typical TATA and three consensus sequences for potential Sp1 binding site were found in its 5' flanking region of 2 kilobase pairs. There were, at least, four common sequences among some nuclear genes for mitochondrial-related proteins.

Amino Acid Sequence↗
PubMed1992

Protein-tyrosine phosphorylations induced by concanavalin A and N-formyl-methionyl-leucyl-phenylalanine in human neutrophils.

The ability of the lectin concanavalin A (ConA) and N-formyl-methionyl-leucyl-phenylalanine (fMLF) to induce protein-tyrosine phosphorylation in human neutrophils was examined by immunoblot analysis. ConA caused an increase in tyrosine phosphorylation of protein bands with apparent molecular masses of 120, 80, 76, 66 and 40 kDa; on the other hand, fMLF caused an increase in those of only 80-kDa and 40-kDa proteins. These protein-tyrosine phosphorylations were time- and dose-dependent. The tyrosine phosphorylation of 40-kDa protein induced by fMLF was suppressed but that by ConA was not suppressed by pertussis toxin pretreatment. At the same time, pertussis toxin pretreatment also inhibited lysozyme release and aggregation of neutrophils induced by fMLF but did not inhibit those responses induced by ConA. These results suggest that the tyrosine phosphorylation of 40-kDa protein may be involved in a part of neutrophil activation and be regulated via pleiotropic signal transduction pathways. In addition, immunoblot analysis employing antibodies against microtubule-associated protein 2 (MAP2) kinase suggested that this tyrosine-phosphorylated 40-kDa protein might be the MAP2 kinase.

Blood Proteins↗
PubMed1992

Molecular cloning of dihydrolipoamide acetyltransferase of the rat pyruvate dehydrogenase complex: sequence comparison and evolutionary relationship to other dihydrolipoamide acyltransferases.

A complementary DNA (cDNA) clone of dihydrolipoamide acetyltransferase (E2) of the rat pyruvate dehydrogenase complex (PDC) was isolated from a lambda gt11 rat heart cDNA library. The amino acid sequence of a full mature protein of rat PDC-E2 was predicted by combination of the cDNA nucleotide sequence and the N-terminal amino acid sequence determined chemically. The amino acid sequence of rat PDC-E2 was well consistent with those of the E2 components of other alpha-ketoacid dehydrogenase complexes. These E2 components possess the sequence G-X-G-X-X-G, which is the consensus sequence for nucleotide binding sites of nucleotide binding proteins, in the E3 and/or E1 binding domains. The E2 components of the three alpha-ketoacid dehydrogenase complexes are suggested to be classified into three clusters separated during evolution.

Acetyltransferases↗
PubMed1992

Cytochrome P450 isozymes catalyzing 4-hydroxylation of parkinsonism-related compound 1,2,3,4-tetrahydroisoquinoline in rat liver microsomes.

Microsomal 4-hydroxylase of 1,2,3,4-tetrahydroisoquinoline (TIQ), a possible candidate for causing Parkinson disease, was characterized by using rat hepatic microsomes and purified P450 isozymes. Kinetic analysis revealed that Km and Vmax values (mean +/- SE) for hepatic microsomal TIQ 4-hydroxylase of male Wistar rats were 319.6 +/- 26.8 microM and 12.13 +/- 1.43 pmol.min-1.mg-1 protein, respectively. When TIQ 4-hydroxylase activity was compared in Wistar (an animal model of extensive debrisoquine metabolizers) and Dark Agouti (an animal model of poor debrisoquine metabolizers) rats, significant strain (Wistar greater than Dark Agouti) and sex (male greater than female) differences were observed. The microsomal activity toward TIQ 4-hydroxylation was increased by pretreatment of male Wistar rats with P448 inducers (beta-naphthoflavone and sudan I), but not with phenobarbital. Pretreatment with propranolol, an inhibitor of P450 isozymes belonging to the P450 IID gene subfamily, decreased TIQ 4-hydroxylase activity. P450 BTL, a P450 isozyme belonging to the IID subfamily, showed TIQ 4-hydroxylase activity of 64.1 pmol.min-1.nmol P450(-1), which was 3.2-fold that of microsomes (20.9 pmol.min-1.nmol P450(-1)). Antibody (IgG) against this isozyme suppressed microsomal TIQ 4-hydroxylase activity concentration-dependently. A male-specific P450 ml (P450IIC11) catalyzed this reaction to a much lesser extent (10.0 pmol.min-1.nmol P450(-1)), and its antibody did not affect the microsomal activity. These results suggest that TIQ 4-hydroxylation in hepatic microsomes are catalyzed predominantly by a P450 isozyme (or isozymes) belonging to the IID gene subfamily in non-treated rats and its immunochemically related P450 isozyme (or isozymes), and that a P450 isozyme (or isozymes) belonging to the IA subfamily also participates in TIQ 4-hydroxylation in rats pretreated with P448-inducers.

Amino Acid Sequence↗
PubMed1992

The alpha beta complexes of ATP synthase: the alpha 3 beta 3 oligomer and alpha 1 beta 1 protomer.

The basic structures of the catalytic portion (F1, alpha 3 beta 3 gamma delta epsilon) of ATP synthase are the alpha 3 beta 3 hexamer (oligomer with cooperativity) and alpha 1 beta 1 heterodimer (protomer). These were reconstituted from the alpha and beta subunits of thermophilic F1 (TF1), and the alpha 3 beta 3 hexamer was crystallized. On electrophoresis, both the dimer and hexamer showed bands with ATPase activity. Using the dimer and hexamer, we studied the nucleotide-dependent rapid molecular dynamics. The formation of the hexamer required neither nucleotide nor Mg. The hexamer was dissociated into the dimer in the presence of MgADP, while the dimer was associated into the hexamer in the presence of MgATP. The hexamer, like mitochondrial F1 and TF1, showed two kinds of ATPase activity: one was cooperative and was inhibited by only one BzADP per hexamer, and the other was inhibited by three BzADP per hexamer.

Nucleotides↗
PubMed1992

Bilateral multiple renal adenocarcinomas in a patient with acquired renal cystic disease: correlation of imaging with pathological study.

The findings of computed tomography (CT), magnetic resonance imaging (MRI), and angiography were correlated with the histopathological findings in a patient with acquired renal cystic disease (ARCD) and bilateral multiple renal adenocarcinomas. Hemodialysis patients, especially with ARCD, should have a follow-up imaging study for an early detection of renal adenocarcinomas because multiple renal adenocarcinomas would arise frequently and simultaneously from ARCD.

Carcinoma, Renal Cell↗
PubMed1992

Density of perfused capillaries in living human brain during functional activation.

Recent evidence has indicated that functional activation of cerebral cortex is accompanied by increases of blood flow and glucose consumption but not oxygen consumption. No explanation has been advanced for this change of the flow-metabolism couple. We formulated the hypothesis that oxygen delivery to brain tissue is diffusion-limited by the enormous hemoglobin binding, and rate-limiting for the oxygen consumption of the tissue. One prediction of this hypothesis is very low oxygen tensions in the tissue. A second prediction is the inability of oxygen consumption to increase during functional activation in the absence of recruitment of capillaries for the oxygen diffusion capacity. We designed a study to test the latter prediction by calculating the density of functioning capillaries during vibrotactile stimulation of the parietal cortex. We defined functioning capillaries as capillaries that transport glucose and therefore calculated the capillary density from the glucose diffusion capacity (K1) of the cerebral capillaries. We confirmed the presence of a partial flow-CMRglc couple (2:1) during the functional activation. Oxygen consumption did not change despite an increase of capillary density in proportion to the change of blood flow.

Brain↗
PubMed1992

Oxygen consumption of the living human brain measured after a single inhalation of positron emitting oxygen.

We measured the rate of washout of 15O-labeled water generated from labeled oxygen accumulated in brain after bolus [15O]O2 inhalation, and compared the washout with that of labeled water measured with H215O. Contrary to the original expectation, the radioactive water generated from labeled oxygen failed to leave the brain tissue at the rate predicted by exogenous water. Therefore, the use of a separately measured value for exogenous water clearance led to an error in the calculation of oxygen consumption. A new method presented in this paper eliminated the error by yielding oxygen consumption in a single oxygen study. We used time-weighted integration to estimate three parameters, including the unidirectional clearance from blood to brain (KO2(1)), the fractional clearance of the distribution volume in brain (kO2(2)), and the vascular volume correction (VO). We showed that the clearance of oxygen from blood to brain can be estimated with acceptable precision by this new approach, and that the new method yields a reliable measure of oxygen consumption.

Administration, Inhalation↗
PubMed1992

Influence of ischemia on blood-brain and blood-CSF calcium transport.

The objective was to explore whether the increased incorporation of 45Ca into selectively vulnerable neurons, observed after transient ischemia, can be explained by enhanced blood-tissue and/or enhanced blood-CSF transfer. Anesthetized rats were subjected to 15 min of forebrain ischemia, with recirculation for 20 or 60 min, or 24 h. The transfer constants (Kin) and unidirectional fluxes (Jin) for calcium in tissue and CSF were determined following i.v. injection of 45Ca, integration of the curve for plasma-specific activity over 10 min, and sampling of cisternal CSF, and tissue (cortex, caudoputamen, hippocampus, and cerebellum). Predictably, values for Kin and Jin in control animals were much larger in CSF than in tissues, and hippocampus had higher values than the other areas, probably because of its closeness to the lateral ventricle. Ischemia failed to alter the Kin and Jin values, demonstrating that the low permeability of blood-brain and blood-CSF barriers to calcium is upheld both in the immediate recirculation period, and after 24 h of recirculation. The results support the contention that the increased 45Ca incorporation during recovery is due to increased calcium cycling across functionally altered cell membranes.

Animals↗
PubMed1992

Functional neuroanatomy of face and object processing. A positron emission tomography study.

Studies of brain-damaged patients have revealed the existence of a selective impairment of face processing, prosopagnosia, resulting from lesions at different loci in the occipital and temporal lobes. The results of such studies have led to the identification of several cortical areas underlying the processing of faces, but it remains unclear what functional aspects of face processing are served by these areas and whether they are uniquely devoted to the processing of faces. The present study addresses these questions in a positron emission tomography (PET) study of regional cerebral blood flow in normal adults, using the 15 oxygen water bolus technique. The subjects participated in six tasks (with gratings, faces and objects), and the resulting level of cerebral activation was mapped on images of the subjects' cerebral structures obtained through magnetic resonance and was compared between tasks using the subtraction method. Compared with a fixation condition, regional cerebral blood flow (rCBF) changes were found in the striate and extrastriate cortex when subjects had to decide on the orientation of sine-wave gratings. A face-gender categorization resulted in activation changes in the right extrastriate cortex, and a face-identity condition produced additional activation of the fusiform gyrus and anterior temporal cortex of both hemispheres, and of the right parahippocampal gyrus and adjacent areas. Cerebral activation during an object-recognition task occurred essentially in the left occipito-temporal cortex and did not involve the right hemisphere regions specifically activated during the face-identity task. The results provide the first empirical evidence from normal subjects regarding the crucial role of the ventro-medial region of the right hemisphere in face recognition, and they offer new information about the dissociation between face and object processing.

Adult↗
PubMed1992

The vasculature and clinical application of the posterior tibial perforator-based flap.

Use of the posterior tibial flap pedicled on the posterior tibial vessels has been described by several authors, but with it there is the major disadvantage of an unavoidable transection of the posterior tibial artery. To overcome this disadvantage, we anatomically studied the perforators from the posterior tibial artery and used posterior tibial perforator-based flaps clinically. Based on our anatomic study of 25 cadaveric legs, the cutaneous perforators were considered to be distributed from the distal to the proximal sides of the lower leg through the medial border of the tibia, and they were classified into three types: septocutaneous perforators mainly located in the distal third of the leg, muscle perforators located in the proximal half, and periosteal perforators in the proximal third of the leg. The average size and number of perforators was 0.8 mm and 3.1 in one leg, respectively. A considerable number were located at sites from 70 to 140 mm superior to the medial malleolus. Based on our clinical cases repaired with flaps, we consider this flap to be useful as a free flap for the repair of defects of the extremities and as an island flap for reconstruction of defects on the anteromedial aspect of the lower leg. The territory of the flap is relatively wide, being 19 x 13 cm. The long saphenous vein can be used safely as the venous drainage system in the case of free-flap transfer.

Adult↗