Biomedical subjects

M Higuchi

Publications and source records attributed to M Higuchi.

At least 55 records · Page 3Linked to original sources

PubMed1993

[Relation of habitual exercise to basal metabolic rate and energy expenditure during exercise in older people].

The relation between habitual exercise and the basal metabolic rate, energy expenditure during exercise (lactic threshold and maximal oxygen uptake) was examined in 291 older people. Metabolic rate was highest in old players of gatebowl (a form of croquet) (male; 23.3 +/- 2.3, female; 22.7 +/- 3.0 kcal/kg/day), higher in old untrained people (male; 21.9 +/- 2.5, female; 20.8 +/- 2.4 kcal/kg/day), and lower in old people in a home for the aged (male; 20.6 +/- 3.5, female; 20.8 +/- 3.7 kcal/kg/day). Energy expenditure while walking at a speed of less than 100 m/min was similar in trained and untrained old people aged 60-69 years. However, lactic threshold was higher in trained (30.2 +/- 4.8 ml/kg/min) than in untrained (20.9 +/- 2.8 ml/kg/min) females aged 60-69 years. Maximal oxygen uptake was higher in trained (male; 50.4 +/- 4.1, female; 36.6 +/- 3.9) than in untrained (male; 30.9 +/- 3.7, female; 26.8 +/- 2.8) old people aged 60-69 years. It was suggested that a higher basal metabolic rate, lactic threshold and maximal oxygen uptake resulted in higher daily physical activity and larger daily energy consumption in trained old people.

Aged↗

PubMed1993

Regulation of two forms of the TNF receptors by phorbol ester and dibutyryl cyclic adenosine 3',5'-monophosphate in human histiocytic lymphoma cell line U-937.

Recently the cDNA for two different forms of TNF receptor, with gene products of molecular masses of 60 and 80 kDa, have been cloned. In the present report, we investigated the effects of phorbol ester and dibutyryl cAMP on the regulation of the transcript for each type of TNF receptor in U-937 cells. Our results indicate that exposure of these cells to either phorbol ester or dibutyryl cAMP increases the steady state mRNA levels of the 80 kDa form. This effect is dose- and time-dependent. The induction of the p80 receptor transcript by PMA and dibutyryl cAMP was additive suggesting independent mechanisms of induction. Under identical conditions, both agents failed to induce the transcript for the p60 form of the TNF receptor. As demonstrated by actinomycin D pulse-chase experiment, the mRNA for the p80 receptor was found to be highly stable with an approximate half-life of 16 h. No significant change in the half-life was observed when cells were treated with phorbol ester. The mechanisms by which phorbol ester and dibutyryl cAMP induce the upregulation of p80 receptor mRNA appear to be different. Induction of receptor transcript by cycloheximide suggests the presence of a labile repressor protein. Interestingly, the effect of cycloheximide on the induction of the p80 mRNA was found to be additive with that of dibutyryl cAMP but not with phorbol ester. 1-(5-Isoquinolinylsufonyl)-2-methylpiperazine (H7) and N[2-(methylamino) ethyl]-5-isoquinolinesulfonamide (H-8), inhibitors of protein kinase C and protein kinase A, respectively, both inhibited the phorbol ester-mediated induction of the p80-transcript but not that mediated through dibutyryl cAMP. Since dibutyryl cAMP undergoes intracellular dissociation into cAMP and butyric acid, we found that exposure of cells to sodium butyrate alone could induce p80 mRNA in a dose-dependent manner, thus suggesting the role of histone hyperacetylation. Furthermore forskolin treatment, an intracellular inducer of cAMP, increased the receptor transcript level whereas isobutylmethylxanthine, an inhibitor of phosphodiesterase, had no effect. Interestingly, while the p80 form of the TNF receptor mRNA levels was elevated by both phorbol ester and dibutyryl cAMP, only dibutyryl cAMP increased the TNF binding; phorbol ester treatment decreased the binding activity. Thus, our results demonstrate that the genes for the two forms of TNF receptors are differentially regulated. Furthermore, the mechanism of regulation by PMA differs from that by dibutyryl cAMP.

1-Methyl-3-isobutylxanthine↗

PubMed1993

Effects of pilsicainide on systemic hemodynamics and cardiac function of anesthetized dogs.

The effects of pilsicainide, propafenone and flecainide on systemic hemodynamics and cardiac function were compared in anesthetized open-chest dogs. Pilsicainide, propafenone and flecainide given intravenously at 1 and 3 mg/kg produced dose-dependent decreases in the mean aortic pressure. The heart rate was decreased by pilsicainide and flecainide, but not by propafenone. The three drugs increased the left ventricular end-diastolic pressure and reduced the first derivative of left ventricular pressure and myocardial oxygen consumption. Pilsicainide decreased aortic, vertebral, coronary and renal blood flows in a dose-dependent manner at 1 and 3 mg/kg. Propafenone increased aortic and vertebral blood flows at 1 mg/kg and decreased coronary and renal blood flows at 3 mg/kg. Flecainide did not significantly change blood flow, except for an increase in the aortic blood flow with 3 mg/kg. The total peripheral, vertebral, coronary and renal vascular resistances were increased by pilsicainide, but not by flecainide. Propafenone decreased total peripheral and vertebral vascular resistances, but hardly affected the coronary and renal vascular resistances. The stroke volume was decreased by 1 and 3 mg/kg pilsicainide in a dose-dependent manner, and increased by 1 and 3 mg/kg propafenone, but not significantly changed by 1 or 3 mg/kg flecainide. The stroke work index was decreased by 3 mg/kg pilsicainide and 3 mg/kg flecainide. The effects of pilsicainide correlated with the changes in its plasma concentration with time. The results indicate that pilsicainide has a negative inotropic activity similar to that of propafenone and flecainide. Pilsicainide and flecainide show almost the same effects with a slightly different efficacy, while propafenone exerts different effects upon some cardiovascular functions.

Anesthesia, Intravenous↗

PubMed1993

[Pharmacokinetics of MX2, a new morpholino anthracycline, in CSF following intravenous injection].

MX2 x HCl is a new morpholino anthracycline derivative with molecular weight 622.07, and highly lipophilic. In the animal experiments, MX2 was found to cross the blood brain barrier after i.v. injection. Its distribution into the brain was increased by intracarotid injection. In the present study, we examined the distribution of MX2 into the cerebrospinal fluid (CSF) after i.v. administration (5 mg/kg) in normal rabbits. Five min after injection, plasma concentration of MX2 reached to the maximum level (4344.5 ng/ml). CSF concentration of MX2 was at the highest level (75.8 ng/ml) 10 min after injection, and thereafter decreased gradually in parallel with plasma concentration. At 5 hrs after injection, CSF concentration became 26.7 ng/ml, AUC half time of elimination, and mean residence time were 3093.8 ng.hr/ml, 4.57 hrs and 5.10 hrs in plasma and 212.3 ng.h/ml, 5.23 hrs and 7.14 hrs in CSF, respectively. These results indicate that MX2 is able to distribute into CSF after i.v. injection, and expected to be a new anticancer drug for brain and leptomeningeal tumors.

Animals↗

PubMed1993

[In vitro ENU-induced carcinogenesis of rat fetal astroglia--biological character of mutant glial cell].

To investigate glial carcinogenesis in vitro, fetal rat brain cells were cultured and exposed to ENU (approximately 200 micrograms/ml). The cells were passaged weekly thereafter. Morphological changes were observed under the phase contrast microscope. When mutant colonies where the cells lost contact inhibition and grew in a multilayer fashion appeared, the cells were cloned. To assess the biological characters of cells, expression of GFAP, vimentin, A2B5 and p53 product were determined by immunohistochemistry and flow cytometry. Tumor forming ability of the cells was evaluated by both colony forming efficiency in low serum medium (LSM; 2% FBS, 300 cells/100 mm dish) and transplantability to nude mice. Both primary cultured and ENU-treated cells were positive for GFAP and vimentin, but population of A2B5 positive cells was less than 5%, thus indicating that these cells were astroglial in origin. The mutant colonies appeared 7 weeks after ENU treatment. These cells grew rapidly with cell doubling time ranging between 18 to 26 hours, while non-ENU-treated astroglias had a longer cell doubling time (48 to 55 hours). The cloned mutant glial cell lines formed large colonies in LSM (efficiency 20-40%), but astroglial cells did not. The mutant astroglial cells also developed tumors in nude mice. p53 protein was never detected in normal astroglia, however, some glial cells treated by ENU abruptly became p53 positive after several passages. These p53 positive cells formed stratified colonies thereafter. These results indicate that mutant astroglial cells can be induced by a single dose of ENU in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Inherited WT1 mutation in Denys-Drash syndrome.

Patients with the Denys-Drash syndrome (Wilms' tumor, genital anomalies, and nephropathy) have been demonstrated to carry de novo constitutional mutations in WT1, the Wilms' tumor gene at chromosome 11p13. We report three new cases, two carrying a previously described WT1 exon 9 mutation and one with a novel WT1 exon 8 mutation. However, unlike patients in previous reports, one of our three patients inherited the affected allele from his phenotypically unaffected father. This observation indicates that the WT1 exon 9 mutation affecting 394Arg demonstrated in over one-half of the patients with the Denys-Drash syndrome may exhibit incomplete penetrance. Consequently, familial studies in patients affected by this syndrome are recommended.

Adolescent↗

PubMed1992

Modulation of two forms of tumor necrosis factor receptors and their cellular response by soluble receptors and their monoclonal antibodies.

Recently, two different receptors for human tumor necrosis factor (TNF) with molecular masses of 60 kDa (p60) and 80 kDa (p80) have been identified. In this report, we investigated the effect of the soluble forms of these receptors and monoclonal antibodies against them on ligand interaction, receptor down-regulation, and mediation of cellular response in U-937 cells. Our results indicate that p60 and p80 constitute 20-30 and 60-80% of the total TNF-binding sites on U-937 cells, respectively. However, by cross-linking, only the p80 form of the receptor could be detected. In contrast to unlabeled TNF, the anti-p60 and anti-p80 antibodies together only partially inhibited ligand binding, and this inhibition was not additive. Lack of additive inhibition of binding was found to be not due to stereo-chemical hindrance. TNF binding to cells can be completely displaced by soluble forms of either the p60 or p80 receptor. However, 100-fold more of the p80 than the p60 form of the soluble receptor is needed for equivalent displacement. Under optimum conditions, TNF and the anti-p80 and anti-p60 antibodies down-regulated 30, 80, and 20% of the TNF receptors, respectively. The anti-p60 and anti-p80 antibodies down-regulated not only their own receptors, but also reciprocal receptors, suggesting a cross-communication between the p60 and p80 forms of the TNF receptor. In spite of inhibiting as much as 80% of TNF binding, none of the receptor antibodies significantly inhibited the cytotoxic response to TNF in U-937 cells. Soluble forms of both receptors, however, completely abrogated the cellular response to TNF. Thus, overall, our results indicate that the antibodies against both receptors together inhibit the majority of the receptor-ligand interaction without any significant effect on the biological response to TNF.

Antibodies, Monoclonal↗

PubMed1992

Hemophilia A due to mutations that create new N-glycosylation sites.

In studying the molecular defects responsible for cross-reacting material-positive hemophilia A, we have identified two patients in whom the nonfunctional factor VIII-like protein has abnormal, slower-moving heavy or light chains on SDS/PAGE. Both patients have severe hemophilia A (less than 1% of normal factor VIII activity) with a normal plasma level of factor VIII antigen. The molecular defects were identified by denaturing gradient gel electrophoresis screening of PCR-amplified products of the factor VIII-coding DNA sequence followed by nucleotide sequencing of the abnormal PCR products. In patient ARC-21, a methionine-to-threonine substitution at position 1772 in the factor VIII light chain creates a potential new N-glycosylation site at asparagine-1770. In patient ARC-22, an isoleucine-to-threonine substitution at position 566 creates a potential new N-glycosylation site at asparagine-564 in the A2 domain of the factor VIII heavy chain. The mobility of these chains on SDS/PAGE was normal after N-Glycanase digestion and procoagulant activity was generated--to a maximum of 23% and 45% of control normal plasma. Abnormal N-glycosylation, blocking factor VIII procoagulant activity, represents a newly recognized mechanism for the pathogenesis of severe hemophilia A.

Amidohydrolases↗

PubMed1992

Heteromeric NMDA receptors: molecular and functional distinction of subtypes.

The N-methyl D-aspartate (NMDA) receptor subtype of glutamate-gated ion channels possesses high calcium permeability and unique voltage-dependent sensitivity to magnesium and is modulated by glycine. Molecular cloning identified three complementary DNA species of rat brain, encoding NMDA receptor subunits NMDAR2A (NR2A), NR2B, and NR2C, which are 55 to 70% identical in sequence. These are structurally related, with less than 20% sequence identity, to other excitatory amino acid receptor subunits, including the NMDA receptor subunit NMDAR1 (NR1). Upon expression in cultured cells, the new subunits yielded prominent, typical glutamate- and NMDA-activated currents only when they were in heteromeric configurations with NR1. NR1-NR2A and NR1-NR2C channels differed in gating behavior and magnesium sensitivity. Such heteromeric NMDA receptor subtypes may exist in neurons, since NR1 messenger RNA is synthesized throughout the mature rat brain, while NR2 messenger RNA show a differential distribution.

Amino Acid Sequence↗

PubMed1992

Role of sugar chains in the expression of the biological activity of human erythropoietin.

Various deglycosylated derivatives of recombinant human erythropoietin (hEPO) were prepared and used to determine the role of the sugar chains in the expression of its biological activity in vivo and in vitro. Three N-linked oligosaccharides of hEPO have been partially or fully removed to obtain N-glycan (NG) (2)-, NG(1)-, and NG(0)-hEPO carrying two, one, and no N-linked sugar chains, respectively. The preparation lacking only O-linked sugar chain O O-glycan (OG) (0)-hEPO was also used. As de-N-glycosylation proceeded, the in vivo activity of the hormone decreased drastically, and the activity of these derivatives was correlated with the number of sialic acids bound to them. On the contrary, the in vitro activity was increased by the de-N-glycosylation; NG(0)-hEPO showed a 3-fold higher specific activity than the intact hormone. This was confirmed by binding experiments of the derivatives to target cells. The in vitro activity and the affinity also correlated with the number of sialic acids bound to the deglycosylated hEPO preparations. On the other hand, OG(0)-hEPO was as active as the intact hormone in vivo and in vitro. In conclusion, the N-linked sugar chains are not required for in vitro activity but required for in vivo activity, acting as anchors for the essential terminal sialic acids. The O-linked sugar chain has no essential role in the biological activity of the hormone in vivo or in vitro.

Amino Acids↗

PubMed1992

Inhibition of ligand binding and antiproliferative effects of tumor necrosis factor and lymphotoxin by soluble forms of recombinant P60 and P80 receptors.

Tumor necrosis factor (TNF) is one of the mediators of inflammatory responses. Recently, the cDNA for two distinct receptors of TNF with predicted molecular masses of 60 kDa and 80 kDa, respectively, were isolated. In this report, we compare the inhibitory effects of these two forms of recombinant soluble TNF receptors (extracellular domains) on the ligand binding and on the antiproliferative effects of TNF and lymphotoxin (LT) in a human histiocytic lymphoma cell line (U-937). Our results show that the soluble form of the p60 receptor is approximately 100-fold more potent than the soluble form of the p80 receptor in inhibiting both the antiproliferative effects of TNF as well as in blocking TNF binding to U-937 cells. In contrast, the antiproliferative effects of LT and its binding to cells is inhibited equally by both the p60 and p80 forms of the soluble receptor. Thus, overall our results indicate that the two soluble receptors differ in their ability to inhibit TNF and LT. The impotance of these soluble receptors in blocking the harmful effects of TNF and LT is discussed.

Cell Division↗

PubMed1992

The relation between amniotic fluid surfactant concentration in preterm labour and histological evidence of chorioamnionitis.

Concentration of amniotic fluid disaturated phosphatidylcholine (DSPC), factors related to cervical ripening, and histopathological evidence of chorioamnionitis were studied in 38 patients in preterm labour with intact membranes; all of them delivered spontaneously before 37 weeks. There was no correlation between the amniotic fluid DSPC level and gestational age at the time of amniocentesis. However, a significant inverse correlation was found between the amniotic fluid DSPC level and the interval between the onset of labour and delivery. The amniotic fluid DSPC level in cases with onset-delivery interval of less than 48 h was significantly higher than that in cases with an onset-delivery interval of 48 h or more. The gestational age in the former group was significantly lower than in the latter (28.6 vs 32.0 weeks). The amniotic fluid DSPC level in the patients with chorioamnionitis was significantly higher than that in the patients without chorioamnionitis, although the gestational age did not differ between the two groups. All 3 infants with RDS were associated with cervical incompetence. Patients in preterm labour with chorioamnionitis may be refractory to tocolysis and have higher amniotic fluid surfactant levels.

Adult↗

PubMed1992

Microtiter plate radioreceptor assay for tumor necrosis factor and its receptors in large numbers of samples.

We developed a rapid radioreceptor assay for tumor necrosis factor (TNF) and its receptors by utilizing serum-coated 96-well plates. This assay has an advantage over the traditional tube assay in speed, number of simultaneous samples, and amount of material needed for the assay. As many as 200 samples were assayed in less than 3 h. The usefulness of this assay to determine TNF and its cell surface receptors and to screen for TNF inhibitors in large numbers of biological fluids from patients is demonstrated. This assay may also prove useful for determining the activity of competitive antagonists of TNF.

Cell Line↗

PubMed1992

Correlation of contractile dysfunction and abnormal tissue energy metabolism during hypoperfusion with norepinephrine in isolated rat hearts: differences between normal and diabetic hearts.

The relationship of myocardial high-energy phosphate depletion and lactate accumulation with contractile dysfunctions was investigated in streptozotocin-diabetic (DM) and normal rat hearts. The isolated hearts were perfused with 10(-6) M norepinephrine (NE) at various low-flow rates (0.4-6 ml/min/g heart wt) for 1 h. Left ventricular pressure (LVP) and contractile force (CF) were monitored, through a water-filled balloon in LV and through a hook attached to the apex, respectively. In DM hearts resting CF (diastolic tension) increased, when the perfusion flow rate was reduced below 6 ml and reached a maximum at a flow rate of less than 3 ml. The large increase in LV stiffness correlated with an elevation in diastolic LVP. In normal hearts these parameters were elevated at a flow rate below 1 ml. A flow-dependent decrease in developed CF was more prominent in DM than in normal hearts, while developed LVP and perfusion pressure were slightly higher in DM hearts with a marked increase in the LV stiffness. A flow-dependent decrease in high-energy phosphates and increases in inorganic phosphate and lactate were more prominent in the inner than in the outer layer of LV free wall in both groups. The change of ATP in the inner layer was greater, while increases of lactate in both layers were smaller in DM hearts. Changes in mechanical parameters correlated well with the ATP decrease and lactate increase in the inner layer in both groups. The correlation curves, however, were not coincidental: at the same low ATP and high lactate level, the LV stiffness was higher in DM hearts. Results indicate that DM hearts are more susceptible to flow-reduction with NE and depletion of total ATP in their tissue, and easily suffer from increased LV stiffness. This cannot be explained by the rate of decrease in total ATP and lactate accumulation alone.

Adenosine Triphosphate↗

PubMed1992

A comparative study on tissue distribution and metabolic adaptation of IMP-GMP 5'-nucleotidase.

1. Activity of a cytoplasmic 5'-nucleotidase which preferentially hydrolyzes IMP and GMP (IMP-GMP 5'-nucleotidase) was determined by a specific immunochemical method in two species of birds and two species of mammals. 2. The activity was markedly high in avian liver, and it increased two-fold in response to a high protein diet in chicken liver. 3. In mammals, the activity was high in testis and spleen. In the rat, the activities in liver, kidney and heart extracts increased by about 30% in response to the high protein diet, while they increased three-fold in regenerating liver. 4. Low activities were detected in skeletal muscles and in erythrocytes of all the species studied.

5'-Nucleotidase↗

PubMed1992

Effects of ouabain on contractile response to norepinephrine in isolated rat aorta.

1. Inhibition of sodium(Na+), potassium(K+)-ATPase activity was dependent on the concentration of ouabain and inverse to the concentration of potassium ([K+]) in the reaction mixture. 2. Contractility of isolated rat aorta preparation in response to norepinephrine was augmented by ouabain and low [K+]. 3. Results suggest that inhibition of Na+,K(+)-ATPase activity will be correlated with augmentation of vascular contractility maybe through activation of Na(+)-calcium exchange system.

Animals↗

PubMed1992

Enhancement of vascular contractility by plasma substances obtained from pregnancy-induced hypertension.

1. Augmentation of norepinephrine (NE)-induced contraction of isolated dog mesenteric arteries by ouabain was significantly enhanced under 4 mM potassium ([K+]) medium condition compared with usual medium condition at 6 mM [K+]. 2. Vascular contractility to NE was significantly enhanced by plasma substances obtained from pregnancy-induced hypertension (PIH) patients compared with that from normotensive pregnant women under 4 mM [K+] medium condition despite of no difference between them under 6 mM [K+] medium condition. 3. These results suggest the possible involvement of the ouabain-like substance in development of hypertension in PIH patients.

Adult↗

PubMed1992

Damage to mitochondrial respiration chain is related to phospholipase A2 activation caused by tumor necrosis factor.

Tumor necrosis factor (TNF) has been shown to be cytotoxic to tumor cell lines in vitro, but the mechanism by which TNF exerts its cell growth-regulatory effects is not known. In this report, we used various inhibitors to investigate the sequence of events that lead to cytotoxic effects of TNF on L.P3 cells, a highly sensitive, murine fibroblast cell line. Our results indicate that mitochondrial respiration chains are damaged by a hydroxyl radical at an early stage of the cell lysis after TNF treatment. This event is followed by the activation of phospholipase A2, and finally leads to cell lysis.

Animals↗