Biomedical subjects

Toshio Ohhashi

Publications and source records attributed to Toshio Ohhashi.

26 records · Page 2Linked to original sources

PubMed2003

Flow-mediated release of nitric oxide from lymphatic endothelial cells of pressurized canine thoracic duct.

We examined the effects of flow on lymphatic endothelial cells by using conventional cascade preparations of isolated coronary arteries without intact endothelium. The pressurized thoracic ducts were intraluminally perfused at a constant flow rate ranging from 0.5 to 2.0 ml/min. A linear relationship was observed between the flow rate and the normalized amount of relaxing substance(s) released from the lymphatic endothelial cells. Thus the flow rate of 2.0 ml/min produced approximately 39% of sodium nitroprusside (SNP)-produced maximal relaxation in the cascade arterial rings. The acetylcholine (ACh, 10(-5) M)- and flow-induced relaxations of the cascade arterial rings were completely reduced by the mechanical rubbing of lymphatic endothelial cells in the pressurized lymph vessels. Pretreatment with 5 x 10(-5) M N(G)-nitro-L-arginine methyl ester (L-NAME) on the lymphatic endothelial cells caused a significant reduction of the ACh- and flow-induced vasodilations of the cascade arterial rings. Pretreatment with 10(-5) M indomethacin on the lymphatic endothelial cells produced no significant effect on the ACh- and flow-induced vasodilations. These findings suggest that lymphatic endothelial cells of canine thoracic ducts can produce and release endogenous nitric oxide by stimulation of flow (approximately 2.0 ml/min).

Acetylcholine↗

PubMed2003

Estrogen-induced augmentation of endothelium-dependent nitric oxide-mediated vasodilation in isolated rat cerebral small arteries.

We examined chronic effects of 17beta-estradiol (E(2)beta) on the responses of isolated rat anterior cerebral small arteries to vasoactive substances with special reference to endothelial function. Female Sprague-Dawley rats were separated into four groups: (1) sham-operated group (Sham), (2) sham-operated plus E(2)beta treated group (Sham+E), (3) ovariectomized group (OVX), (4) ovariectomized plus E(2)beta treated group (OVX+E). 5-Hydroxytryptamine (5-HT) (10(-10)-10(-3) M) and U46619 (10(-15)-10(-8) M) induced concentration-dependent contractions in the cerebral small arteries. The 5-HT- and U46619-induced contractions were not affected by pretreatment with 3 x 10(-5) M N(omega)-nitro-L-arginine methyl ester (L-NAME). No significant difference in high potassium (80 mM)- and the agonists-mediated contractions was observed among the four groups. Administration of acetylcholine (ACh) (10(-9)-10(-3) M) and sodium nitroprusside (SNP) (10(-8)-10(-3) M) caused dose-related relaxations in the cerebral small arteries precontracted by 10(-8) M U46619. Chronic treatment with E(2)beta caused a significant potentiation of the ACh-induced relaxations in the Sham+E and OVX+E groups. The dose-response curve for ACh in the OVX group was quite similar to that obtained with the Sham group. The ACh-induced relaxation was reduced significantly by pretreatment with 3 x 10(-5) M L-NAME, and an additional treatment with 10(-3) M L-arginine reversed significantly the L-NAME-induced inhibition. The removal of endothelial cells produced a significant reduction of the ACh-induced relaxation. Indomethacin (10(-5) M) did not alter the ACh-induced relaxation. The findings suggest that E(2)beta potentiates ACh-induced endothelium-dependent relaxation in rat anterior cerebral arteries and that the potentiation may be, in part, mediated by increasing production and release of endogenous NO from the endothelial cells.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed2003

Age-dependent changes in the regulatory roles of nitric oxide and vasodilator prostanoids on the mechanical activities of isolated rabbit spinal arterioles.

The developmental changes in acetylcholine (ACh)-induced vasodilator response in isolated rabbit spinal arterioles were investigated with special reference to endogenous nitric oxide (NO) and vasodilator prostaglandins. Spinal arterioles from juvenile (1-3 months) and adult (12-14 months) Japanese white rabbits were dissected, cannulated, and perfused. In both age groups, ACh produced a comparable vasodilation of the arterioles preconstricted with KCl (20-40 mM). In juveniles, a major part of the ACh-induced vasodilation was eliminated by the cyclo-oxygenase inhibitor indomethacin (10 microM), whereas the effect of the NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 30 microM) was smaller. In contrast, L-NAME completely eliminated the ACh-induced vasodilation in the adult group, which was partially restored with additional treatment with L-arginine (1 mM). Vasodilations induced by isocarbacyclin (a prostacyclin analogue) and cilostazol (a cAMP-phosphodiesterase inhibitor) was attenuated in the adult, whereas that induced by sodium nitroprusside was unaltered. These results suggest that the mechanisms of ACh-induced vasodilation of rabbit spinal arterioles change with the development: prostanoid-associated in juveniles and NO-associated in the adult. Such age-related modulation of the mediator roles of prostanoids and NO might represent an increase in NO production and a decreased sensitivity of the vascular smooth muscle to cAMP-mediated responses with age.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2002

Electrical stimulation-induced alpha1- and alpha2-adrenoceptors-mediated contractions of isolated canine lymph nodes.

The contractile effects of alpha-adrenoceptor agonists and field electrical stimulation were investigated pharmacologically in canine isolated tracheobronchial lymph nodes. Addition of noradrenaline (NA), phenylephrine (Phe) and UK14,304 caused dose-related contractions of the isolated lymph nodes. Pretreatment with prazosin (3 x 10(-9), 3 x 10(-8) and 3 x 10(-7) M) shifted the concentration-response curve for phenylephrine to the right, whereas yohimbine (3 x 10(-7) M) did not affect the contractile responses to phenylephrine. On the other hand, the concentration-response curve for UK 14,304 shifted to the right by treatment with yohimbine (3 x 10(-9), 3 x 10(-8) and 3 x 10(-7) M) but not by prazosin (3 x 10(-7) M). Field electrical stimulation (25 V, 0.7 ms, 16 Hz) produced contractile responses of the lymph nodes. The electrical stimulation-induced contractions were completely reduced by pretreatment with tetrodotoxin (TTX) (3 x 10(-7) M) or bretylium (10(-6) M). Furthermore, phentolamine (10(-8), 10(-7) and 10(-6) M), prazosin (3 x 10(-9) and 3 x 10(-8) M) and yohimbine (3 x 10(-8) and 3 x 10(-7) M) significantly reduced the electrical stimulation-induced contractions in the preparations. The present findings suggest that there are both alpha1- and alpha2-adrenoceptors located on the smooth muscle cells in canine tracheobronchial lymph nodes, and that the adrenoceptors-mediated excitatory mechanisms of adrenergic innervation exist in the lymph nodes.

Adrenergic alpha-Agonists↗

PubMed2002

Development of pressurized retinal resistance-sized arteriolar preparation with special reference to acetylcholine-induced nitric-oxide-mediated vasodilatation.

We examined the responses of pressurized bovine retinal functional arterioles (97-185 microm in diameter and approximately 3 mm long) to vasoactive substances and the mode of action of acetylcholine (ACh) on the pressurized arterioles. The retinal arterioles were cannulated at both ends with glass micropipettes and perfused at a constant pressure of 60 mmHg. Vasoconstrictions of the retinal arterioles were induced by prostaglandin F(2 alpha) (PG F(2 alpha)), U46,619, noradrenaline (NA), and 5-hydroxytryptamine (5-HT) in a dose-dependent manner. The decreasing order of potency (pD(2) value) in the constrictive responses was as follows: 5-HT = U46,619 > NA > PG F(2 alpha). On the other hand, sodium nitroprusside (SNP), isocarbacyclin (a stable prostaglandin I(2) analog), ACh, and isoproterenol (ISP) caused dose-dependent vasodilatation in the pressurized retinal arterioles preconstricted with high-potassium solution (40 mM K+). The decreasing order of potency in the vasodilative responses was as follows: isocarbacyclin > SNP > ACh. The ACh-induced vasodilatation was suppressed significantly by pretreatment with N omega-nitro-L-arginine methyl ester (L-NAME) (3 x 10(-5) M). A treatment with L-arginine (10(-3) M) in the presence of 3 x 10(-5) M L-NAME reversed completely the L-NAME-induced reduction of the vasodilatation. These results suggest that ACh causes the production and release of endogenous nitric oxide or its related compounds, which results in vasodilatation of the pressurized bovine retinal functional arterioles.

Acetylcholine↗

PubMed2002

Plasma-mediated potentiation in prostanoid-induced contractions in isolated canine external jugular veins.

We examined the effects of plasma on contractile responses of isolated dog external jugular veins to a thromboxane A(2) analog, U46619, and noradrenaline. Pretreatment with 1.0% plasma in Krebs-bicarbonate solution, but not 0.1%, caused a significant left and upward shift in the concentration-contractile response curve for U46619. The plasma-mediated potentiation of the response to U46619 was found in the venous segments without intact endothelium. The administration of 2x10(-5) M lysophosphatidylcholine in Krebs-bicarbonate solution with no plasma also produced a significant left and upward shift of the concentration-contractile response curve for U46619, the shift being quite similar to that obtained with 1.0% plasma. In contrast, pretreatment with 1.0% plasma or 2x10(-5) M lysophosphatidylcholine produced no significant effect on the noradrenaline-mediated contractions in the venous segments. Pretreatment with 10(-4) M L-ascorbate or 0.1 mg/ml alpha-tocopherol in the presence of 1.0% plasma caused a significant reduction in the plasma-mediated potentiation of the contractile responses to U46619. These findings suggest that lysophosphatidylcholine, a major phospholipid component of oxidized low-density lipoproteins, may contribute, in part, to the plasma-mediated potentiation of contractile responses of the isolated veins to U46619, and that the antioxidant vitamin, L-ascorbate, or alpha-tocopherol significantly reduces the plasma-mediated potentiation of the contractile responses to U46619, which may be related to inhibiting the production of lysophosphatidylcholine in plasma.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed2002

Effects of cilostazol, a selective cyclic AMP phosphodiesterase inhibitor on isolated rabbit spinal arterioles.

Cilostazol, a potent inhibitor of guanosine 3':5'-cyclic monophosphate (cGMP)-inhibited adenosine 3':5'-cyclic monophosphate (cAMP) phosphodiesterase (PDE3), has been used clinically for the treatment of chronic peripheral arterial occlusive disease. The beneficial effect of cilostazol is attributed to both anti-platelet aggregating activity and vasodilation. However, the effect of cilostazol on resistance-sized vasculature is not well documented. Furthermore, mechanisms of vasodilation and influence on endothelium function are not fully understood. Thus, we investigated the vasodilator action of cilostazol using isolated, pressurized rabbit spinal arterioles with special reference to the functional endothelium. Cilostazol, acetylcholine (ACh), isocarbacyclin (prostacyclin analogue), and sodium nitroprusside (SNP) all produced concentration-dependent vasodilations of isolated spinal arterioles with endogenous myogenic tone. The order of potency of these agonists was isocarbacyclin>ACh>SNP>cilostazol. Indomethacin (10 micro M, a cyclo-oxygenase inhibitor), N(omega)-nitro-L-arginine methyl ester (L-NAME, a nitric oxide synthase inhibitor, 30 micro M), or chemical denudation of the endothelial cells did not significantly alter the cilostazol-induced arteriolar dilation. Furthermore, stimulating the release of endothelium-derived relaxing factors by administering ACh (100 nM), or treating with isocarbacyclin (1 nM) or SNP (3 nM) did not significantly modify the cilostazol-induced vasodilation. These results suggest that cilostazol produces the vasodilation of isolated, pressurized rabbit spinal arterioles independent of the functional endothelium. We infer that the vasodilator action of cilostazol in the spinal arterioles may be attributed to a yet unknown mechanism that is independent of the PDE3 inhibition.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMedDate not supplied

Recanalization of the collecting lymphatics in rabbit hind leg.

OBJECTIVE: This study was designed to examine whether mature collecting lymphatics can regenerate in the adult tissue or not. MATERIALS AND METHODS: The X-ray lymphograms were used to detect network of the collecting lymphatics in rabbit hind leg. Regeneration of the lymphatics was observed after surgical removal of the popliteal lymph node or a part of the popliteal afferent lymphatic. Structure and mechanical properties of the lymphatics were also examined by light and electron microscopes and in vitro functional experiments. RESULTS: One week after removal of the lymph node, only an afferent lymphatic and a deposit of the contrast medium at the popliteal region were observed. Four weeks after the removal, the connection of the afferent and efferent lymphatics at the popliteal region, and collateral lymphatics were present in the leg. Further, 4 weeks after 1-mm excisions of a part of the lymphatic, recanalization was observed between the central and peripheral cut ends of the lymphatic but not after 3- and 10-mm excisions. Endothelial cells and smooth muscle cells could be observed by electron microscope, and contractile proteins, and alpha-smooth muscle actin SM1 and SM2 were immunofluorescently detected in both intact and the regenerated lymphatic walls. In both lymphatics, norepinephrine and acetylcholine induced dose-dependent constriction and dilation of the vessels, respectively. CONCLUSION: The present study demonstrated that mature collecting lymphatics are able to regenerate in the adult tissues.

Animals↗