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Biomedical subjects

H Tsuru

Publications and source records attributed to H Tsuru.

At least 145 records · Page 8Linked to original sources
PubMed1983

Routes of drug delivery to the middle segment of the canine inferior vena cava in vivo.

Noradrenaline (1-3 micrograms/kg) administered into the right femoral vein caused a two-step increase in tension of the middle segment of the canine inferior vena cava, whereas noradrenaline administered into the right external jugular vein or the aortic arch caused a single-step one. The analysis of these vascular responses showed that noradrenaline administered into the femoral vein affected the inferior vena cava first from the endothelial side, distributed systemically and, then, affected the vein again from the adventitial side via the vasa vasorum. Acetylcholine (3 micrograms/kg) administered into the femoral vein caused a single-step increase in tension and could hardly reach the arterial side, while the same dose of acetylcholine administered into the aortic arch contracted the vein more largely as compared with noradrenaline. The response to noradrenaline administered topically through the vasa vasorum was augmented by administration of cocaine (2 X 10(-5) M) through the same route, while that to acetylcholine was not. These results show that acetylcholine reaches the middle segment of the inferior vena cava through the vasa vasorum in vivo more effectively than noradrenaline partly because it is not taken up by nerve terminals in the vein.

Acetylcholine↗
PubMed1982

Comparative study of supersensitivity to K+ after denervation and decentralization in rabbit ear artery.

The contractile response to potassium following denervation or decentralization of the central artery of the rabbit ear was studied in vitro. Denervation or decentralization for 8 weeks caused comparable supersensitivity to potassium: mean EC50 values obtained with isotonic high potassium solution were 21.3 mM in the denervated artery and 18.7 mM in the decentralized artery, and these values were significantly less than those (25-26 mM) of their respective contralateral control arteries (P less than 0.005, paired t-test). The maximum responses to potassium did not differ among the control, denervated and decentralized arteries. Phentolamine (3 X 10(-7) M) and propranolol (3 X 10(-7) M) had no significant effect on the response to potassium. Sensitivities to potassium with hypertonic high KCl solution and hypertonic high K2SO4 solution were virtually identical to those obtained with isotonic high potassium solution. The results suggest that denervation and decentralization produce identical postjunctional supersensitivity to potassium and that the lack of tonic activity of sympathetic nerves may be responsible for the phenomenon in the rabbit ear artery.

Animals↗
PubMed1981

Functional and structural changes in the rabbit ear artery after sympathetic denervation.

We studied the tissue weight, dimensions, contractility, elasticity, and sensitivity to exogenous norepinephrine (NE) of denervated and innervated segments of the central ear arteries of white New Zealand rabbits. Three different age groups received unilateral superior cervical ganglionectomies, "growing" at 3-4 weeks, "young adult" at 9-11 weeks, and "mature" at 16-20 weeks. In the growing group, 8 weeks after ganglionectomy, the denervated arteries showed mean decreases in tissue weight (11%), total wall thickness (12+), cross-sectional area of media (17%), contractility (16%), and increases in the tangential modulus of elasticity and sensitivity to NE (2.3-fold) compared to the contralateral control vessels. The change in medial cross-sectional area was significant in the growing and young adult but not the mature animals. The other changes, however, although consistently seen, differed quantitatively among the groups. These results indicate that an intact innervation is necessary for normal development and maintenance of the artery wall. However, the precise consequences of this influence vary at different ages. Whether this influence involves a special trophic factor is not known.

Animals↗
PubMed1981

A new method for recording vascular tone with an intravascular cuff and its application to canine inferior vena cava in vivo.

An intravascular cuff was devised with a short plastic cylinder and a latex membrane wrapping it, in order to examine the responsiveness of the canine inferior vena cava in vivo. The cuff was inflated by injecting saline through a catheter to make the membrane contact the vascular wall closely, and the change in the cuff pressure was recorded. An in vitro experiment with an isolated segment of the vein proved that the cuff detected quantitatively the active response of the vascular smooth muscle to norepinephrine (NE). The sensitivity to NE under this experimental condition was equal to that obtained previously with the isolated strip preparation. In the in vivo experiments, the cuff inserted into the segment between the liver and the renal veins of the inferior vena cava exhibited spontaneous rhythmic changes in pressure. In response to NE injected intravenously, dose-dependent increases in cuff pressure were observed. The responses recorded with the intravascular cuff were considered to be predominantly the active tension of the vascular smooth muscle, since influences of intestinal motion and changes in venous pressure on the cuff pressure were ruled out. The cuff picked up the response of the supradiaphragmatic segment of the inferior vena cava as well. The method seems to be useful for measuring the tone of larger veins.

Animals↗
PubMed1980

An extension of pA principle to the potentiation of drug effects, and its application to the biological assay of some anticholinesterases and cardenolides.

A new scale for the potentiation was introduced and was termed pA1/2. The value can be calculated by using an equation; (Formula: see text), which is similar to that which is used for the calculation of pA2. For the use of the equation, the parallel shift of the dose-response curve and the unchanged maximum response are prerequisites. This experiment showed the validity and the usefulness of calculating the pA1/2 values, in the biological assay. In the assay of anticholinesterases, the potentiating effects of neostigmine or physostigmine on the acetylcholine-induced contraction were examined, by using frog's rectus abdominis. The pA1/2 values obtained in the presence of two different concentrations of anticholinesterases were the same, indicating that pA1/2 is a parameter which is specific to the potentiator. The potentiating effects of some cardenolides on the K-induced contracture were examined, by using the frog's ventricular muscles. The relative potencies of four cardenolides obtained from the pA1/2 values well agreed with those reported earlier. The amount of the cardenolides required for this assay was smaller than required for other methods.

Animals↗
PubMed1980

Effect of thyroid hormone on cyclic AMP phosphodiesterase in rat kidney.

The effect of thyroid hormone on the activity of low Km cyclic AMP) phosphodiesterase of the particulate fraction from the kidney was investigated. This enzyme activity increased in the cortex from hypothyroid rats and reverted to the normal level after the subcutaneous administration of L-3,5,3'-triiodothyronine (T3) daily for 3 days. However, this hormone did not affect the enzymes from the normal rats. In vitro experiments revealed that T3 as well as various known phosphodiesterase inhibitors similarly inhibited the activity of low Km cyclic AMP phosphodiesterase from both normal and hypothyroid rat kidneys. The results of the present study suggest that the effect of thyroid hormone on cyclic AMP phosphodiesterase was not direct but was mediated by a modulation of the rate of protein synthesis and an unknown mechanism in the kidney.

1-Methyl-3-isobutylxanthine↗