Search PubMed⌕ Search

Biomedical subjects

J Nakao

Publications and source records attributed to J Nakao.

At least 55 records · Page 3Linked to original sources
PubMed1983

Calcium dependency of aortic smooth muscle cell migration induced by 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid. Effects of A23187, nicardipine and trifluoperazine.

We have previously reported that 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE), a 12-lipoxygenase product of arachidonic acid in platelets, is a potent chemoattractant for rat aortic smooth muscle cells. In the present study, the mechanism involved in 12-HETE-associated smooth muscle cell migration was investigated in relation to calcium mobilization in the cells. Migration of smooth muscle cells was measured by a filter membrane technique in modified Boyden chambers. Smooth muscle cell migration induced by 12-HETE increased with the increase of extracellular Ca2+ concentration and became maximal at the physiological Ca2+ concentration of 1.25 mM. The calcium ionophore A23187, at concentrations of 0.2 and 2.0 microM, significantly stimulated cell migration. Nicardipine, a potent calcium-entry blocker, significantly inhibited 12-HETE-associated smooth muscle cell migration at concentrations from 10(-9) to 10(-5) M. Concentrations of trifluoperazine from 10(-9) to 10(-5) M and W-7 at 10(-5) M, which are specific inhibitors of calmodulin, also significantly inhibited cell migration induced by 12-HETE. Cytochalasin B at 1.0 and 10 microM, and colchicine at 0.1 and 1.0 microM concentrations drastically inhibited cell migration, indicating that actin-containing microfilaments and microtubules are involved in smooth muscle cell migration. These findings indicated that the stimulation of smooth muscle cell migration by 12-HETE is a highly calcium-dependent process and suggest that 12-HETE might act at the initial stage of smooth muscle cell migration through enhancing calcium influx through plasma membrane and thus stimulating cell migration.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1983

Induction of fatty acid cyclooxygenase in rat aortic smooth muscle cells by estradiol.

We have previously reported that estradiol stimulates prostacyclin biosynthesis in cultured rat aortic smooth muscle cells by increasing fatty acid cyclooxygenase activity, and induction of new protein biosynthesis is involved since the effect of estradiol is blocked by cycloheximide treatment. In order to see whether estradiol stimulates de novo biosynthesis of fatty acid cyclooxygenase in cells, a specific radioimmunoassay of fatty acid cyclooxygenase was used to measure the enzyme. Estradiol significantly increased immunoreactive fatty acid cyclooxygenase in cells. Consequently, increase in cyclooxygenase activity results in the production of more prostaglandin endoperoxides for final increased synthesis of prostacyclin in these cells.

Animals↗
PubMed1983

Antitumor activity in the culture supernatant fluid of Fusobacterium nucleatum strain KO-31.

Antitumor activity of Fusobacterium nucleatum strain KO-31, which had been isolated from the oral cavity, was investigated in Ehrlich carcinoma-bearing mice. The strain KO-31 was cultured in TF medium for 48 hr. One-half ml of the culture supernatant fluid was injected intraperitoneally during a 7-day period to mice with Ehrlich ascites carcinoma. The survival time of the treated mice prolonged remarkably. A significant reduction in size of the solid Ehrlich tumor was also achieved with the supernatant. Antitumor activity was not observed in the cell extract.

Animals↗
PubMed1982

Stimulation of 12-lipoxygenase activity in rat platelets by 17 beta-estradiol.

The effects of estradiol on the endogenous fatty acid (specifically, arachidonic acid) composition of cellular phospholipid fractions and the 12-lipoxygenase activity in rat platelets in vivo were studied. Estradiol had no significant effect on the endogenous fatty acid composition of cellular phospholipid fractions. However, estradiol significantly increased 12-lipoxygenase activity in platelets in a dose-dependent manner. The stimulatory effect of estradiol on platelet lipoxygenase was blocked by the anti-estrogen nafoxidine hydrochloride which was injected simultaneously together with estradiol in vivo, suggesting that the effect in target cells was due directly to estradiol.

Animals↗
PubMed1982

Effects of reduced glutathione on the 12-lipoxygenase pathways in rat platelets.

Arachidonic acid is converted into several more polar products in addition to 12-l-hydroperoxyeicosa-5,8,10,14-tetraenoic acid (12-HPETE) and 12-l-hydroxyeicosa-5,8,10,14-tetraenoic acid (12-HETE) by the cytosol fractions of rat platelets. The more polar products are formed via the lipoxygenase pathways in the same way as are 12-HPETE and 12-HETE, since their formation is not inhibited by indomethacin but by eicosa-5,8,11,14-tetraynoic acid (ETYA). The presence of 0.5-1.5mm-reduced glutathione (GSH) in the reaction mixture prevents the formation of the more polar products and produces 12-HETE as the only metabolite from arachidonic acid by the 12-lipoxygenase pathway. l-Cysteine has the same effect as GSH. However, oxidized glutathione (GSSG) and l-cystine are not able to prevent the formation of the more polar products. The results indicate that 12-HPETE peroxidase in the 12-lipoxygenase pathway is a GSH-dependent peroxidase and the more polar products might be formed from the non-enzymic breakdown of the primary 12-lipoxygenase product of 12-HPETE, owing to insufficient capability of the subsequent peroxidase system to completely reduce 12-HPETE to 12-HETE. Thus the presence of GSH in the reaction mixture offers a convenient and precise cell-free assay system for 12-lipoxygenase in rat platelets. Routine assays of 12-lipoxygenase are carried out in the presence of 1mm-GSH in the reaction mixture. The synthesis of 12-HETE by 12-lipoxygenase is linear during the first 4 min of incubation at 37 degrees C, and has a pH optimum of 7.7. The 12-lipoxygenase reaches half-maximal activity at an arachidonate concentration of 20mum. Fractionation of cell homogenates indicates that the cytosol fraction possesses almost all the 12-lipoxygenase activity, whereas the microsomal fraction exhibits little enzyme activity.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1982

Comparative effect of lipoxygenase products of arachidonic acid on rat aortic smooth muscle cell migration.

We investigated the effects of mono-hydroxyeicosatetraenoic acids (HETEs) and N-formyl-methionyl-leucyl-phenylalanine (F-Met-Leu-Phe) on rat aortic smooth muscle cell migration in modified Boyden chambers. 12-HETE showed the most potent stimulatory effect on smooth muscle cell migration among the mono-HETEs tested. The optimal concentrations for cell migration were 3 X 10(-15) and 3 X 10(-13) g/ml for 12-HETE and 10(-8) g/ml for 15-HETE, 5-HETE and F-Met-Leu-Phe were inactive with these cells. As 12-HETE is biosynthesized from arachidonic acid by the 12-lipoxygenase pathway in platelets and macrophages, and 15-HETE by the 15-lipoxygenase pathway in granulocytes, the present results indicate an important role for such cells in the early phase of atherosclerosis.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1982

Platelets stimulate aortic smooth muscle cell migration in vitro. Involvement of 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid.

The migration of rat aortic smooth muscle cells was measured in modified Boyden chambers. Smooth muscle cells were motile in vitro and their migration was stimulated (time- and dose-dependently) by a platelet-derived factor. Treatment of platelets with indomethacin resulted in a significant increase in smooth muscle cell migration, whereas treatment with 5,8,10,14-eicosatetraenoic acid inhibited it. Purified 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid at a very low concentration (6 x 10(-15)-6 x 10(-13) g/ml) significantly stimulated smooth muscle cell migration. The locomotion induced by 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid was chemokinetic. These findings point to the physiological importance of a platelet 12-lipoxygenase product of arachidonic acid in the early phase of atherosclerosis.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1981

Effects of estradiol on the metabolism of arachidonic acid by aortas and platelets in rats.

We have previously reported that estradiol treatment stimulates prostacyclin production by cultured rat aortic smooth muscle cells, through the stimulation of fatty acid cyclooxygenase and prostacyclin synthetase activities. In order to see whether estradiol stimulates the fatty acid cyclooxygenase activity in platelets, intact rats were treated with estradiol, and thromboxane biosynthesis in platelets and prostacyclin production by aortas were investigated. Estradiol significantly stimulates prostacyclin production by aortas. However, no significant effect on thromboxane biosynthesis in platelets is observed. Our present results support the idea that estradiol would be a protective hormone in atherosclerotic heart disease.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1981

Triiodothyronine stimulates prostacyclin production by rat aortic smooth muscle cells in culture.

The effect of triiodothyronine (T3) on prostacyclin production in rat aortic smooth muscle cells was investigated by using an intact cell assay system. T3 at its physiological concentrations has no significant effect on smooth muscle cell proliferation, but it does significantly stimulate prostacyclin production by the cells. Maximum stimulation of prostacyclin production is obtained when cells are treated with T3 for 4 consecutive days. The dose--response curve shows a linear relationship between the stimulation of prostacyclin production and T3 concentrations in the range 0.007--10 microgram/dl. The maximal prostacyclin production by T3-treated cells (at a concentration of 10 microgram/dl), is 270% compared with control cells. T3 treatment shows no significant effect on phospholipase (and/or lipase) activities. Our results suggest that thyroid hormone might play an important physiological role in the protection of arteries from atherosclerotic changes by stimulating prostacyclin production in arterial smooth muscle cells.

Animals↗
PubMed1981

Testosterone inhibits prostacyclin production by rat aortic smooth muscle cells in culture.

The effects of testosterone on cell proliferation and prostacyclin production were investigated using rat aortic smooth muscle cells in culture. Testosterone at 10(-10)-10(-6) M did not have any significant effect on cell proliferation, but it significantly inhibited prostacyclin production by the cells. Maximal inhibition of prostacyclin production (70%) was observed when cells were treated with a physiological concentration of 19(-8) M testosterone for 5 consecutive days. These results suggest that testosterone may stimulate thrombus formation and accelerate atherosclerosis by suppressing prostacyclin production in arterial smooth muscle cells.

Animals↗
PubMed1980

Stimulation of prostaglandin cyclooxygenase and prostacyclin synthetase activities by estradiol in rat aortic smooth muscle cells.

The effects of estradiol on the arachidonic acid pool and prostacyclin biosynthetic activity in rat aortic smooth muscle cells were studied. Estradiol has no significant effect on the distribution of [14C]arachidonic acid in cells with respect to prostacyclin production assay, the endogenous fatty acid (specifically, arachidonic acid) composition of cellular phospholipid fractions and cellular phospholipase (or/and lipase) activities. However, estradiol significantly stimulates both prostaglandin cyclooxygenase and prostacyclin synthetase activities of cells, and induction of new protein biosynthesis is involved in the effect of estradiol on the stimulation of prostacyclin biosynthetic activity.

Animals↗
PubMed1980

Age-related decrease in prostacyclin biosynthetic activity in rat aortic smooth muscle cells.

Prostaglandin biosynthetic activity in cultured rat aortic smooth muscle cells was investigated as a function of age by both intact cell and cell-free homogenate assays. The total cyclooxygenase activity for prostaglandin biosynthesis is the same in cells from young and old rats. However, cells from young rats proceduce more prostacyclin than prostaglandin E2, and cells from old rats produce more prostaglandin E2 than prostacyclin. Age-related decrease in prostacyclin biosynthesis is also found when protaglandin H2 is used as substrate. Lower prostacyclin and higher prostaglandin E2 biosynthetic activity in aortic smooth muscle cells from aged rats may contribute to the direct explanation of pathogenesis of spontaneous atherosclerosis and artial thrombosis in aged humans and other mammals.

Aging↗
PubMed1980

Stimulation of prostacyclin biosynthetic activity by estradiol in rat aortic smooth muscle cells in culture.

Effects of estradio on cell proliferation and prostacyclin biosynthetic activity in cultured rat aortic smooth muscle cells are investigated. Prostacyclin is the major product formed from arachidonic acid by the cells, both in a cell-free homogenate system and in intact cells. When cells are treated with estradiol, no effect on cell proliferation is observed. However, a significantly stimulatory effect on prostacyclin biosynthetic activity in cells is evident. The maximal effect of estradiol on the stimulation of prostacyclin biosynthetic activity is observed after 5-day treatment of the cells with estradiol at its physiological concentration (10(-9) M). Our results support the idea that estradiol would be a protective hormone in atherosclerotic heart disease.

Adenosine Diphosphate↗
PubMed1980

Elastinolytic activity in the rat aortic smooth muscle cells in culture.

Elastinolytic activity was examined in cultured rat aortic smooth muscle cells, using Congo Red elastin as a substrate. Elastinolytic activity was demonstrated in the soluble fraction of sonicated smooth muscle cells, with an optimal pH around 10.0. The soluble fraction also showed elastase-like esterolytic activity against the synthetic substrate, N-succinyl-trialanyl-paranitroanilide.

Animals↗
PubMed1980

Classification of glucose intolerance in the aged based on hemoglobin A1.

While the incidence of glucose intolerance increases with age, the diagnostic criteria of diabetes mellitus in the aged have been controversial. In this study, glucose intolerance in the aged was classified according to the changes in Hb A1 concentrations and plasma glucose levels at the time of 50 g oral glucose tolerance test. Ninety-six aged Japanese (60-90 years old, mean 72 years) were studied. Hb A1 was measured by Fast Hb Test System. The results suggested the existence of critical plasma glucose levels for the increment in Hb A1 in the aged, and the critical values were around 120 mg/100 ml at fasting, and around 240 mg/100 ml at 60 or 120 min after glucose load. Using these critical plasma glucose levels, glucose intolerance in the aged was classified into two groups, i.e., Group 1 with fasting plasma glucose below 120 mg/100 ml and both plasma glucose levels at 60 and 120 min below 240 mg/100 ml, and Group 2 with fasting plasma glucose above 120 mg/100 ml and both plasma glucose levels at 60 and 120 min above 240 mg/100 ml. The incidence of elevated Hb A1 in Group 1, 4.3%, was significantly lower than 94.1% in Group 2, and insulinogenic index at 30 min in Group 1, 0.74, was significantly higher than 0.07 in Group 2. In conclusion, it was proposed that subjects in Group 2 represent diabetes mellitus, while subjects in Group 1 might not be of pathological glucose intolerance in the aged.

Aged↗
PubMed1979

Low serum estradiol levels in subjects with arterial calcification.

The relationship between arterial calcification and serum estradiol levels was studied in 72 postmenopausal female and 59 male subjects. In both sexes, subjects with iliac artery calcification had rather lower serum estradiol levels (8.4 +/- 1.4 pg/ml in the females, and 19.2 +/- 2.5 pg/ml in the males) than controls (16.1 +/- 1.6 pg/ml in the females, and 29.7 +/- 2.4 pg/ml in the males). The bone mineral content of females with iliac artery calcification (0.44 +/- 0.02 g/cm2) was lower than controls (0.52 +/- 0.01 g/cm2); a positive correlation between serum estradiol levels and bone mineral content was found in the females. However, bone mineral content did not significantly differ between males with and without arterial calcification (0.67 +/- 0.03 g/cm2 in the former, and 0.65 +/- 0.02 g/cm2 in the latter). These results indicate that arterial calcification and increased bone resorption are both individual results of estrogen deficiency.

Adult↗