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Biomedical subjects

O Hazeki

Publications and source records attributed to O Hazeki.

At least 55 records · Page 3Linked to original sources
PubMed1994

Involvement of the pertussis toxin-sensitive GTP-binding protein in regulation of expression and function of granulocyte complement receptor type 1 and type 3.

Human polymorphonuclear leukocytes (PMN) express receptors for complement (C) C3b and C3bi termed CR1 and CR3, respectively. The addition of PMA or fMLP to PMN enhances the capacity of these receptors to promote binding of C3b- and C3bi-coated erythrocytes. fMLP-dependent increase of the binding of these ligand-coated erythrocytes was completely abolished by prior exposure of the PMN to pertussis toxin (IAP). GTP-binding protein (Gi alpha) was ADP-ribosylated and dysfunctional by this treatment. On the other hand, PMA-dependent binding of these ligands, as well as control binding, was inhibited only slightly, if at all, by the IAP treatment. The levels of C receptor expression on cell surface were determined by flow cytometry using monoclonal antibody against CR1 and those against the alpha and beta chains of CR3 (CR3 is composed of alpha and beta chain). Upon exposure of PMN to the chemotactic factor or PMA, or upon incubation of the cells at 37 degrees C, the surface expression of CR1 and CR3 alpha was increased. IAP also blocked an fMLP-induced increase of CR1 and CR3 alpha, but did not block the temperature- or PMA-dependent increase of these receptors. Opsonized zymosan (SOZ), another ligand for CR3, also led to an increase of both CR1 and CR3 alpha. Neither PMA nor SOZ brought about an increase of the surface expression of CR3 beta, but fMLP caused a slight increase of CR3 beta in an IAP-sensitive manner. Based on the IAP-sensitivity of the receptor expression, therefore, it appears that at least two separate mechanisms are operative in the control of C receptors. In addition, the alpha and beta chains of CR3 are regulated independently. The present data offer evidence suggesting that C receptor functions are in part regulated through a GTP-binding protein via modulation of their surface expression.

Adenosine Diphosphate Ribose↗
PubMed1993

Insulin-stimulated GLUT4 translocation is relevant to the phosphorylation of IRS-1 and the activity of PI3-kinase.

We examined the role of 185-kDa insulin receptor substrate-1 (IRS-1) and phosphatidylinositol 3-kinase (PI3-kinase) in the signaling pathway of insulin-stimulated GLUT4 translocation. We had already developed a novel cell line to detect GLUT4 on the cell surface, directly and sensitively (Kanai, F., Nishioka, Y., Hayashi, H., Kamohara, S., Todaka, M., and Ebina, Y. (1993) J. Biol. Chem. 268, 14523-14526). We stably expressed a mutant insulin receptor in which Tyr972 was replaced with phenylalanine. Insulin-stimulated tyrosyl phosphorylation of IRS-1 and GLUT4 translocation were decreased in cells expressing the mutant receptor, as compared to findings in cells expressing the normal receptor. Wortmannin, an inhibitor of PI3-kinase, inhibits the insulin-stimulated PI3-kinase activity and GLUT4 translocation at 50 nM, but not the NaF-stimulated GLUT4 translocation. These results suggest that the tyrosine phosphorylation of IRS-1 and activation of PI3-kinase may be involved in the signaling pathway of the insulin-stimulated GLUT4 translocation.

Androstadienes↗
PubMed1993

cAMP stimulates human immunodeficiency virus (HIV-1) from latently infected cells of monocyte-macrophage lineage: synergism with TNF-alpha.

The present experiments were designed to study whether GTP binding protein activation and the resulting cAMP plays any role in HIV replication. The results showed that cholera toxin (CT) enhanced HIV replication dose dependently in myelo-monocytic cell lines latently infected with HIV-1, U1 and J22HL-60. Three- to 4-fold enhancement of virus production was observed in U1 cells and 4- to 11-fold enhancement in J22HL-60 cells 4 days after treatment with 100 ng/ml of CT. The increment of intracellular cAMP accumulation was parallel with HIV augmentation by CT in both cells. Even at the low concentration 0.1 ng/ml, TNF enhanced virus production to about an 80-fold higher level than the untreated U1 control cells as described previously (11). However, a synergistic effect (80- to 238-fold enhancement) was observed, when TNF-alpha and CT were added together to U1 cells. Similar synergism was seen in J22HL-60 cells. HIV antigen positive cells and gp120 expression were also increased to a similar degree. Phosphodiesterase inhibitor IBMX had no effect on HIV production alone, but potentiated HIV induction by CT and TNF. Adenylate cyclase activator, forskolin (FK), at 100 microM also significantly augmented HIV production (> 4-fold) and potentiated TNF induction in J22HL-60 and U1 cells. On the other hand, CT did not show any effect on HIV replication as well as TNF induction in HIV-1-infected T cell line. Northern blot experiment confirmed that this enhancement was mediated through the activation of HIV transcription. These data suggest that cAMP augments HIV replication and potentiates TNF induction in a particular monocyte-macrophage system.

1-Methyl-3-isobutylxanthine↗
PubMed1993

Oxygen dependence of redox state of copper in cytochrome oxidase in vitro.

To obtain quantitative information about tissue oxygenation from near-infrared signals, the oxygen dependencies of the redox states of both heme a+a3 and copper in cytochrome oxidase of isolated mitochondria were determined at low oxygen concentrations (10(-6)-10(-9) M) using leghemoglobin as an oxygen indicator. The maximum absorbance changes caused by the aerobic-anaerobic transition measured at 830-760 nm of copper in state 3, state 4, and the uncoupled state were 10, 17, and 5% of those at 605-620 nm of heme a+a3, respectively. Thus the relative absorbance ratio of copper to heme a+a3 could be used as a sensitive indicator for the mitochondrial energy state. The oxygen concentrations required for the half-maximal reduction of heme a+a3 varied with the energy state and the respiratory rate and were 7.8 x 10(-8) and 1.6 x 10(-7) M in state 4 and state 3, respectively. In contrast, that of copper was 7.5 x 10(-8) M and was independent of both the energy state and the respiratory rate. The relationship between the percent oxidation of heme a+a3 and copper in the aerobic-anaerobic transition did not show a straight-line relationship. This was referred to as the difference in oxygen affinity between these two chromophores. The deviation from the straight line was larger in state 3 than in state 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerobiosis↗
PubMed1992

Suppression by wortmannin of platelet responses to stimuli due to inhibition of pleckstrin phosphorylation.

Studies were made of inhibition by wortmannin, a fungal metabolite, of human platelet responses to various stimuli. Wortmannin at concentrations as low as 1-100 nM inhibited several receptor-agonist-induced 5-hydroxytryptamine release from platelets, without affecting agonist-induced increases in the intracellular concentration of Ca2+. Phorbol 12-myristate 13-acetate (PMA), an active tumour promoter, caused 5-hydroxytryptamine release when combined with a low concentration of ionomycin, and platelet aggregation by itself; these effects of the phorbol ester were also inhibited by wortmannin as well as by staurosporine, a potent, although non-specific, protein kinase C (PKC) inhibitor, in a similar molar concentration range. The platelet responses to the receptor agonists or PMA were accompanied by increased incorporation of [32P]Pi into pleckstrin, a protein selectively expressed in platelets and other blood cells arising from haematopoietic stem cells, as a result of PKC activation in the intact cells. The pleckstrin phosphorylation was inhibited by wortmannin in ways mostly similar to those in which it inhibited the 5-hydroxytryptamine-release responses. Nevertheless, wortmannin failed to inhibit PKC activity measurable in a cell-free assay system which is highly susceptible to staurosporine. Nor did it inhibit the translocation of cytosolic PKC to membranes induced by addition of PMA to platelet cells. Thus wortmannin, which is not a direct inhibitor of PKC, could interfere with the kinase-dependent phosphorylation of pleckstrin, which may play an important role in the cellular responses to receptor stimulation.

Alkaloids↗
PubMed1989

Near infrared quadruple wavelength spectrophotometry of the rat head.

A quadruple wavelength method to monitor the changes in concentration of oxygenated and deoxygenated hemoglobin and the redox state of cytochrome oxidase within a living tissue is presented. The expected advantages of this technique over the triple wavelength method are (i) that it can compensate for the light scattering change of tissue itself or for instabilities of light source and photomultiplier, (ii) that it can treat the optical properties of the red blood cell in a tissue in the same way as in an in vitro model system, and (iii) that it requires no estimation of the absorption coefficient of cytochrome oxidase in situ.

Animals↗
PubMed1989

The oxygen dependency of the redox state of heme and copper in cytochrome oxidase in vitro.

The oxidation-reduction state of cytochrome oxidase in isolated mitochondria at low oxygen concentrations was measured by the use of leghemoglobin as an oxygen indicator. P50 a + a3 varied with energy state as well as the respiratory rate. In contrast to heme a + a3, copper was slower to reduce than heme a + a3. The P50Cu of 8 x 10(-8)M in State 4 and 7.4 x 10(-8)M in State 3 was independent of both the energy state and the respiratory rate.

Aerobiosis↗
PubMed1988

The simultaneous measurements of tissue oxygen concentration and energy state by near-infrared and nuclear magnetic resonance spectroscopy.

The oxygenation and energy states of brain tissues were measured simultaneously by near-infrared photometry and nuclear magnetic resonance spectroscopy in situ. In both cat and dog, the critical hemoglobin oxygenation was 10%, below which the ratio of phosphocreatine (PCr) to inorganic phosphate (Pi) started to fall. The fall of PCr/Pi paralleled the reduction of copper in cytochrome aa3. The separation of the cytochrome aa3 signal from that of hemoglobin by our optical method was confirmed by the substitution of blood by fluorocarbon solution. The energy-oxygen diagram (PCr/Pi against hemoglobin oxygenation, HbO2) was the same in normal- and fluorocarbon substituted cats, but energy curve shifted to the right in the latter when PCr/Pi plotted against the inspired oxygen, FiO2.

Animals↗
PubMed1988

Noninvasive quantitative analysis of blood oxygenation in rat skeletal muscle.

Using the isolated perfused rat hindlimb and the fluorocarbon-transfused rat, we have examined the optical characteristics of the rat skeletal muscle in the near-infrared region. The total contribution of myoglobin and cytochromes to the overall absorbance change was less than 10%. Analyzing transmitted light at 700, 730, and 805 nm, we found linear relationships between the absorbance and the hemoglobin concentrations at hematocrit values from 15 to 50% in the inflowing perfusate. Based on the relationship, we determined the ratio of absorption coefficients at 700, 730, and 805 nm of oxy- and deoxy-hemoglobins of blood in the thigh muscle. The values in thigh muscle were significantly smaller than those in hemoglobin solutions for deoxygenated blood. On the other hand, the values in thigh muscle were larger than those in hemoglobin solutions for oxygenated blood. Solving simultaneous equations by the use of these absorption coefficients, we calculated the changes in the contents of oxy-, deoxy-, and total hemoglobins in the anesthetized rat hindlimb under various conditions. The oxygen saturation of blood determined by our optical method in the thigh muscle was very close to that in the vena cava measured directly with a gas analyzer.

Animals↗
PubMed1988

Quantitative analysis of hemoglobin oxygenation state of rat brain in situ by near-infrared spectrophotometry.

The light in the near-infrared region (700-900 nm) was illuminated on the rat head, and absorption spectra were measured with the transmitted light under various conditions. The absorbance changes less than 780 nm were attributable to hemoglobin in the brain tissue, whereas those greater than 780 nm were associated with both hemoglobin and cytochrome oxidase. The changes of oxy- and total (oxy- plus deoxy-) hemoglobin content in the rat head could be monitored quantitatively by expressions of delta A700--1.20 delta A730 and delta A700--1.52 delta A730, respectively. The oxyhemoglobin content in the tissue was decreased as the O2 tension in inspired gas was lowered. At 10% O2 approximately 50% of hemoglobin was deoxygenated. The total hemoglobin content was increased under anoxic conditions. Inhalation of 5% CO2 and intravenous injection of a Ca2+ blocker nicardipine increased the O2 saturation of hemoglobin in the brain. These conclusions were confirmed by measuring the difference absorption spectra in the near-infrared region.

Animals↗