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Biomedical subjects

A Hirai

Publications and source records attributed to A Hirai.

At least 163 records · Page 9Linked to original sources
PubMed1992

[Anti-thrombotic and anti-atherogenic action of eicosapentaenoic acid].

Epidemiological studies performed in Greenland Eskimos and Japanese indicated that ingestion of fish meat rich in omega-3 polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA), reduces the incidence of cerebro- and cardiovascular thrombotic diseases. Therefore, the effect of administration of purified EPA, derived from sardine oil, on hemorrheological properties and serum lipids in patients with thrombotic disorders was studied. Dietary supplementation of EPA resulted in decrease in platelet aggregability with reduction of TXA2 production, prolongation of bleeding time, decrease of platelet adhesiveness, increase of red cell deformability, and improvement of serum lipid concentration. Decrease in platelet TXA2 production may be ascribed to the decrease in arachidonate (AA) content of platelet membrane, inhibition of AA release from platelet membrane and competitive inhibition of AA metabolism at the level of cyclo-oxygenase, by EPA. Administration of EPA increased PGI2 production in the rat thoracic aorta and co-culture of rat aorta smooth muscle cell with EPA also increased PGI2 production, but suppressed smooth muscle cell proliferation. This may be explained by a EPA-derived peroxide stimulation of cyclo-oxygenase activity. Administration of EPA decreased platelet-derived growth factor (PDGF) production in rat peritoneal macrophages. In EPA-rich peritoneal macrophages from rat given EPA, incorporation of acetyl LDL and accumulation of cholesterol in macrophages decreased. This may indicate that dietary supplementation of EPA suppress foam cell formation. An interesting finding is that EPA-rich LDL obtained from rabbits given EPA is less susceptible to Cu(2+)-catalyzed oxidative modification. This seems to indicate that EPA may also suppress lipid peroxidation of lipoprotein.(ABSTRACT TRUNCATED AT 250 WORDS)

Arachidonic Acid↗
PubMed1991

The rice mitochondrial nad3 gene has an extended reading frame at its 5' end: nucleotide sequence analysis of rice trnS, nad3, and rps12 genes.

The nucleotide sequences of the tRNASer (trnS), pseudo-tRNA, NADH dehydrogenase subunit 3 (nad3), and ribosomal protein S12 (rps12) genes from rice mitochondrial DNA (mtDNA) were determined. Both trnS and nad3 were confirmed to be single copy genes by Southern blot analysis. The nad3 and rps12 genes were arranged in tandem, and the two were co-transcribed. The order of the above four genes in rice mtDNA differed from the linear order observed for the wheat and maize genes. In rice mitochondria, the trnS and pseudo-tRNA genes were found upstream of the cytochrome c oxidase subunit I gene, instead of the nad3 and rps12 genes as observed in maize and wheat. Additionally, while the rice nad3 and rps12 genes remain paired, they too are in a different sequence environment from the wheat and maize genes. The apparent split of the two pairs of genes indicates the occurrence of a mitochondrial intramolecular recombinational event. Another peculiarity is that the sequence upstream of the translational initiation codon of the rice nad3 gene is different from that of the wheat and maize versions. The ATG initiation codon of wheat and maize nad3 is replaced by TTG in the rice nad3. A subsequent deduction of the amino acid sequence, accompanied by a primer extension analysis, indicates that the predicted rice NAD3 protein has an additional 37 amino acid residues at its N-terminus compared to the wheat and maize NAD3 proteins. cDNA sequence analysis showed no introns or the occurrence of RNA editing at the newly replaced TTG codon.

Amino Acid Sequence↗
PubMed1991

Enhancement of finger blood flow response of postprandial human subjects to the increase in body temperature during exercise.

The present study was performed to investigate the effect of food intake on thermoregulatory vasodilatation in seven healthy male volunteers. The changes in oesophageal (Toes) and mean skin temperatures, finger and forearm blood flows (BF), oxygen consumption (VO2) and heart rate (fc) with and without food intake were measured before and during a 40-min exercise at an intensity of 35% maximal O2 consumption at an ambient temperature of 25 degrees C. Exercise commenced 60 min after food intake. Ingestion of food equivalent to 50.2 kJ.kg body mass-1 elevated mean body temperature, BF, VO2 and fc in 60 min. Four subjects responded to exercise with a marked increase in finger BF and with no sweating (non-sweating group), while the other three responded with perspiration over almost the whole skin area and with little change in finger BF. Further analyses were made mainly in the non-sweating group. The postprandial increases in Toes, BF, VO2 and fc were persistent during exercise. The rate of increase in finger BF with the increase in Toes and mean body temperature was significantly greater with food intake than without. However, there was no difference in the response of forearm BF to exercise between the two conditions. These results suggested that food intake enhanced finger BF response to the increase in deep body temperature during exercise. It was also concluded that there was a regional difference in cutaneous vasomotor response to thermal load in the postprandial subjects.

Adult↗
PubMed1991

Prolonged exposure to industrial noise causes hearing loss but not high blood pressure: a study of 2124 factory laborers in Japan.

To determine the role of noise exposure in the etiology of hypertension, a cross-sectional study was performed by measuring the blood pressure of 2124 male laborers working in a noisy factory. The prevalence of hypertension was 10.2% in group I (85-115 dB), 10.9% in group II (less than 85 dB) and 12.5% in group III (office workers). There was no difference in systolic or diastolic blood pressure among the three groups. There were 358, 439 and 71 laborers in groups I, II and III, respectively, all having worked in the same noise area for more than 10 years. Blood pressure was lower 10 years previously in each group, but the degree of increment did not significantly differ among the three groups. The prevalence of hearing loss was 16.5% in group I, which was significantly higher than that in group II (7.5%) and group III (2.8%). Blood pressure of laborers with hearing loss was equal to that of laborers with intact hearing acuity. There was no significant relationship between hearing loss and the prevalence of hypertension. Thus, prolonged exposure to industrial noise contributes to hearing loss. However, elevation of blood pressure was not found in laborers working in a noisy factory. This finding was not consistant with previously reported findings in the rat. An adaptability to prolonged noise in man may account for this discrepancy.

Adult↗
PubMed1991

Leiomyosarcoma of the skin with generalized metastases: electron microscopic and immunohistochemical study.

A 62-year-old woman with numerous (more than 50) tumors between 25 and 75 mm in diameter disseminated over most of her body surface is reported. Biopsied tissue specimens demonstrated that the tumors consisted mainly of spindle-shaped cells with nuclear pleomorphisms and relatively high mitotic rates. They were irregularly arranged; they sometimes mimicked storiform- and palisading-patterns. Immunohistochemistry revealed that the tumor cells were positive for muscle-specific actin, desmin, and myosin, but negative for S-100 protein. Electron microscopy confirmed myofilaments and dense patches in the cytoplasm. The metastatic potential of such leiomyosarcoma of the skin is indicated.

Cytoskeletal Proteins↗
PubMed1991

A method of measuring the peak flow rate and the regurgitant volume of regurgitation based on the characteristics of turbulent free jets.

The issuing flow rate of a jet, Q0, is given by Q0 = U0A, where U0 is the issuing velocity of the jet and A is the cross-sectional area of the orifice. However, measurement of A of a regurgitant jet in the cardiovascular system is difficult. On the assumption that the jet is 'free' and turbulent, the following relations apply between the diameter of the orifice D, the length of the core region of the jet L, the centerline velocity of the jet Uc(chi) at an arbitrary distance chi(greater than L) from the orifice, and U0:L = 6.8D and Uc(chi)/U0 = L/chi. From these equations we obtain Q0 = 0.017 (chi Uc(chi))2/U0. Pulsatile jets issuing into an aqueous glycerol bath through orifices with various diameters were studied. U0, chi and Uc(chi) were measured with a color Doppler system. There was a good linear correlation between the peak flow rates estimated from the above equation and those measured with a flowmeter irrespective of the diameter of orifices (y = 0.93 chi + 3.8, r = 0.95, SEE = 6.6 ml/s). Assuming that the flow rate waveform is similar to the issuing velocity waveform, we estimated the issuing volume per stroke by integrating the issuing velocity. There was a good linear correlation between the estimated issuing volume and the known stroke volume of the pump (y = 1.0 chi + 2.6, r = 0.92, SEE = 2.8 ml).

Blood Flow Velocity↗
PubMed1991

Sterol carrier protein2 (SCP2)-like protein in rat aorta.

Immunoblot analysis using affinity-purified antibody against sterol carrier protein2 (SCP2) showed that SCP2-like protein exists in 105,000 x g supernatant of rat aorta. Analysis of subcellular distribution of SCP2-like protein in rat aorta was determined with enzyme immunoassay (EIA). The highest level of SCP2-like protein was observed in cytosolic fraction, while the lowest level was in nuclear fraction. Analysis of marker enzymes in subcellular fractions showed that catalase, a marker enzyme of peroxisomes, leaked to cytosolic fraction to a significant extent during subcellular preparation, suggesting that SCP2-like protein in cytosolic fraction of rat aorta might be partially originated from peroxisomes. In vitro addition of homogenous SCP2 purified from rat liver dose-dependently stimulated the formation of [14C]cholesteryl esters from exogenously added [14C]cholesterol by acyl-CoA:cholesterol acyltransferase (ACAT) in microsomal preparation of rat aorta. However the addition of cytosolic fraction did not enhance cholesterol esterification by ACAT, most likely due to a markedly low level of SCP2-like protein in this fraction. The role of SCP2 in the formation of cholesteryl esters by ACAT in rat aorta was discussed.

Animals↗
PubMed1990

Hypersensitivity to thromboxane A2 in cholesterol-rich human platelets.

The effect of changes in platelet membrane cholesterol content on thromboxane A2 (TXA2)-induced platelet activation was studied. Concentrations of 9,11-epithio-11,12-methano-TXA2 (STA2), a stable analogue of TXA2 which can cause half-maximal aggregation and release of [14C]serotonin in cholesterol-rich platelets were significantly lower than those in cholesterol-normal platelets. STA2-induced increase in cytosolic calcium concentration and [32P]phosphatidic acid formation in cholesterol-rich platelets were significantly greater than those in cholesterol-normal platelets. The maximal concentration of binding site (Bmax) for SQ29548 was significantly increased in cholesterol-rich platelets compared with cholesterol-normal platelets, while the equilibrium dissociation rate constant (Kd) for SQ29548 did not differ between cholesterol-rich and cholesterol-normal platelets. The present study suggested that sensitivity to TXA2 was increased by the incorporation of cholesterol into platelet membrane and that the cause of hypersensitivity to TXA2 in cholesterol-rich platelets may be partly explained by an increase in binding capacity for TXA2.

Blood Platelets↗
PubMed1990

Possible involvement of arachidonic acid metabolites of cytochrome P450 monooxygenase pathway in vasopressin-stimulated glycogenolysis in isolated rat hepatocytes.

Arachidonic acid (AA) is reported to be metabolized by three major pathways, i.e., cyclooxygenase (CO), lipoxygenase (LO), and NADPH-dependent cytochrome P450 monooxygenase (MO) pathways. Monooxygenase metabolites of AA have been proposed to play an important role in hormone action in various cells. Recently it was reported that the MO pathway may exist in rat liver. The present study was carried out to investigate the role of MO metabolites in vasopressin-induced glycogenolysis in isolated rat hepatocytes. The pretreatment of isolated rat hepatocytes with eicosatetraynoic acid (ETYA), an inhibitor of CO, LO, and MO pathways, and ketoconazole and SKF 525A, inhibitors of the MO pathway, dose-dependently reduced vasopressin-induced phosphorylase activation, while the pretreatment with indomethacin, an inhibitor of the CO pathway, had no effect. The increment of cytosolic calcium concentration in vasopressin-stimulated hepatocytes was also dose-dependently decreased by ETYA, ketoconazole, and SKF 525A. In vitro addition of epoxyeicosatrienoic acid (EET) dose-dependently increased both phosphorylase a activity and cytosolic calcium concentration. 14,15-EET was the most potent among four regioisomeric EETs. These results suggest that MO metabolites of AA, most likely EETs, may be involved in vasopressin-induced glycogenolysis probably via the activation of phosphorylase by increasing the cytosolic calcium concentration.

8,11,14-Eicosatrienoic Acid↗
PubMed1990

Transformation of arachidonic acid by 5- and 15-lipoxygenase pathways in bovine adrenal fasciculata cells.

[1-14C]Arachidonic acid was incubated with isolated bovine adrenal fasciculata cells for 15 min at 37gC. The metabolites were separated and purified by reverse- and straight-phase high performance liquid chromatography, and identified by gas chromatography-mass spectrometry or radioimmunoassay. Identified metabolites were 5-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE), 15-hydroxy-5,8,11,13-eicosatetraenoic acid (15-HETE), leukotriene B4 and 11,14,15-trihydroxy-5,8,12-eicosatrienoic acid (11,14,15-THET). Addition of 15-hydroperoxy-5,8,11,13-eicosatetraenoic acid (15-HPETE), an intermediate metabolite of 15-lipoxygenase pathway to microsomes of bovine adrenal fasciculata cells resulted in the formation of 11,14,15-THET. The formation of 11,14,15-THET by microsomes was not dependent on the presence of NADPH, while it was dose-dependently suppressed by ketoconazole, a potent inhibitor of cytochrome P-450 dependent enzymes. These results indicate that 5- and 15-lipoxygenase pathways of arachidonic acid may exist in bovine adrenal fasciculata cells and that 15-HPETE is further metabolized to 11,14,15-THET by adrenal microsomal cytochrome P-450.

Animals↗
PubMed1990

The participation of sterol carrier protein2 in cholesterol esterification in rat adrenal microsomes.

The effect of sterol carrier protein2 (SCP2) purified from rat liver on the formation of cholesterol esters by acyl-CoA: cholesterol acyl-transferase (ACAT: EC 2.3.1.26) in rat adrenal microsomes was studied. The rate of incorporation of [1-14C]oleoyl-CoA into cholesteryl oleate was determined in the presence or absence of exogenously added cholesterol or SCP2, or both. The addition of SCP2 had no effect on the formation of cholesterol esters from endogenous cholesterol by ACAT in rat adrenal microsomes. In contrast, the formation of cholesterol esters from exogenous cholesterol by ACAT was dose-dependently increased by the addition of SCP2. These experiments showed that SCP2 had an enhancing effect on cholesterol esterification by ACAT in rat adrenal microsomes most likely by modulating the availability of exogenous cholesterol and that SCP2 may participate in the formation of cholesterol esters in the rat adrenal gland.

Adrenal Cortex↗
PubMed1989

TSK-Toyopearl gels for the preparative separation of sterol carrier protein2 from rat liver.

The application of TSK-Toyopearl gels to the preparative separation of a basic and low-molecular-weight protein, sterol carrier protein2 (SCP2), was studied. SCP2 was purified from 105,000 g supernatant of rat liver (S105) by ion-exchange chromatography on CM-Toyopearl 650M and gel permeation on Toyopearl HW60S. Separation of S105 by CM-Toyopearl 650M was carried out at a high flow-rate in the presence of 10% (v/v) glycerol, a stabilizer of the protein. Toyopearl HW60S showed a significant ion-exchange effect on the elution of SCP2. Using an elution buffer of ionic strength of 45 mM, a highly efficient purification of SCP2 on HW60S was achieved. SCP2 was purified approximately 5000-fold to apparent homogeneity with an overall yield of 69%.

Animals↗
PubMed1989

Arachidonic acid metabolites by cytochrome P-450 dependent monooxygenase pathway in bovine adrenal fasciculata cells.

[1-14C]Arachidonic acid was incubated with microsomes of bovine adrenal fasciculata cells in the presence of 1 mM NADPH for 30 min at 37 degrees C. The metabolites were separated and purified by reverse phase high performance liquid chromatography, and identified by gas chromatography-mass spectrometry. Identified metabolites were four dihydroxyeicosatrienoic acids (DHTs) (5,6-, 8,9-, 11,12-, 14,15-DHTs), 20-hydroxyeicosatetraenoic acid and eicosatetradioic acid. The formation of these metabolites was dependent on NADPH and inhibited by SKF-525A. 14,15-DHT was also formed by isolated bovine adrenal fasciculata cells. These results indicate that cytochrome P-450 dependent arachidonate monooxygenase pathway may exist in bovine adrenal fasciculata cells. Addition of the chemically synthesized epoxyeicosatrienoic acids (EETs) to isolated bovine adrenal fasciculata cells stimulated cortisol production. Among four regioisomeric EETs, 14,15-EET was most potent and stimulated steroidogenesis in a dose-related manner over a range of 0.5 to 5.0 microM.

8,11,14-Eicosatrienoic Acid↗