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Biomedical subjects

T Ohhashi

Publications and source records attributed to T Ohhashi.

126 records · Page 7Linked to original sources
PubMed1979

Effect of microvibration on activity of ureteral and portal smooth muscles.

Spontaneous contractions were elicited by microvibrations (1--80 Hz, 50--400 micron) imposed upon quiescent ureter and portal venous smooth muscles of dogs. The microvibrations increased the rate of spontaneous contractions. A microvibration of larger amplitude gave rise to a more profound increase at each frequency. The acceleration was often accompanied by a reduction in contractile force. The positive chronotropic effect was enhanced by increases in frequency from 20 to 40 Hz and not affected by administration of autonomic blocking agents and tetrodotoxin, but disappeared in a Ca-free environment and reappeared on addition of Ba2+. the simulating action of microvibration was almost proportional to external Ca2+ concentrations ranging from 2.2 to 6.2 mM. The microvibrations were able to elicit spontaneous activity in the preparation, which had been made quiescent by administration of Mn2+. These findings suggested that the positive chronotropic effect may be closely related to an increased Ca2+ influx through the membrane of smooth muscle. Active tension in the ureter in a state of contracture was depressed by imposed microvibrations.

Action Potentials↗
PubMed1979

Electrical activity and ultrastructure of bovine mesenteric lymphatics.

Membrane action potentials of bovine mesenteric lymphatics were recored simultaneously with isometric contractions by use of the sucrose gap method. The action potentials always had one-to-one correspondence to the contraction waves. From the effects of tetrodotoxin, manganese, cal-calcium-free environment, and barium chloride on the spontaneous contractions, it was suggested that calcium current may probably play a major role in producing spike discharge in the smooth muscles. Blood capillaries were found within the smooth muscle layers as well as in the adventitia.

Action Potentials↗
PubMed1978

The response of lymphatic smooth muscles to vasoactive substances.

A study was made of the isotonic response of bovine mesenteric lymphatics to several physiological vasoactive substances. Contractions of lymphatic smooth muscles were induced by serotonin (5-HT), prostaglandin F2alpha (PGF2alpha), noradrenaline (NA), histamine, dopamine and acetylcholine (ACh). The smooth muscles were particularly sensitive to 5-HT. Excepting PGF2alpha no other substances could equal 5-HT in the magnitude of the maximum response. The majority of 5-HT receptors seemed to be the D receptors. The decreasing order of the contractile responses was as follows: 5-HT greater than PGF2alpha greater than NA greater than histamine greater than dopamine greater than ACh. The contractile response to ACh was observed only in specimens involving valvular region. It was very likely that, in the lymphatics, there were 2 kinds of receptors for catecholamines, i.e. alpha and beta receptors, and the stimulation of the former induced smooth muscle contraction and that of the latter relaxation. A difference was noticed between the responses of valvular and intervalvular segments to NA. Relaxations of lymphatic smooth muscles were induced not only by isoproterenol but also by adenosine and adenine nucleotides. The decreasing order of the relaxant responses was as follows: ISP greater than adenosine greater than ATP greater than ADP greater cyclic AMP greater than or equal to AMP. The relaxant responses to adenine nucleotides tended to reduce with decrease in the number of high energy phosphates.

Adenine Nucleotides↗
PubMed1978

Vibration-induced hyperresponsiveness of arterial smooth muscle to noradrenaline with special reference to Raynaud's phenomenon in vibration disease.

Effects of in vitro and in vivo vibratory stimulations were studied on dose-response relationships of noradrenaline in excised femoral arteries of dogs and rats. The responsiveness of these arteries were enhanced after the application of the stimulation. The degree of the hyperresponsiveness was dependent upon frequency, amplitude, and duration of the stimulation. Based on the experimental results, a possible explanation was offered for Raynaud's phenomenon in vibration disease.

Animals↗
PubMed1978

Isolated, blood-perfused canine arteries: different vasoconstrictor responses of internal and external carotid arteries to 5-hydroxytryptamine.

Canine carotid arteries were isolated, suspended in a bath and perfused under a constant flow rate with arterial blood led from a support dog. Resting perfusion pressure was set at a constant level over 50 mm Hg. Drugs were administered into the endothelial side of the artery through a cannulated tubing and the response was obtained as pressure changes. This preparation was proved to be superior to usual isolated arterial strips, since its reactivity was kept in a stable condition over 5-10 hours at 37 degrees C. Using this preparation, effects of 5-hydroxytryptamine (5-HT) on the internal and external carotid arteries were investigated in comparison with effects of norepinephrine. In the internal carotid artery, 5-HT caused a much more potent vasoconstriction than norepinephrine. On the other hand, in the external carotid artery, 5-HT caused only slight vasoconstriction, while norepinephrine produced a marked vasoconstriction.

Animals↗
PubMed1976

Microvibration: capable of inducing spontaneous contractions in smooth muscles.

Spontaneous contractions were elicited by the vibration of small amplitude (microvibration) imposed upon the quiescent strips prepared from the ureter and portal vein of dogs. An acceleration of the existing rhythm in the spontaneously contracting strips was also brought about by microvibration. Frequencies and amplitudes of microvibration ranged from 1 to 90 Hz and from 50 to 150 mum, respectively. Imposed cyclic strains were less than 1% at their maximum. Up to the amplitude of 150 mum, the greater the amplitude, the faster the induced rhythm. Stepwise increase of the frequencies up to 30 Hz brought about a gradual acceleration of rhythmicity. At frequencies of above 30 Hz, no appreciable frequency-dependent differences were observable among the responses induced. Local adrenergic mechanism proved to have nothing to do with these effects.

Animals↗
PubMedDate not supplied

The effects of pancreatic polypeptides and neuropeptide Y on the rat vas deferens.

In order to study the physiological significance of the coexistence of pancreatic polypeptide and norepinephrine (NE) in peripheral noradrenergic nerves, the effects of pancreatic polypeptides of several species were tested on the isolated rat vas deferens. Neuropeptide Y (NPY) was also studied because of its sequence homology to the pancreatic polypeptides. The contractile responses, which were mediated predominantly by activation of noradrenergic nerves following electrical stimulation, were inhibited by bovine pancreatic polypeptide (BPP), human pancreatic polypeptide (HPP), avian pancreatic polypeptide (APP) and NPY in a dose-dependent manner using a constant flow bath. The decreasing order of the inhibitory responses was as follows: BPP = HPP greater than NPY greater than APP. The inhibitory responses produced by BPP and HPP lasted more than 1 hr and displayed a marked tachyphylaxis. In contrast, the inhibitory effects induced by NPY and APP usually returned to the control level after 20-30 min and had minimal tachyphylaxis. The inhibitory action of NPY was still present during alpha-adrenergic blockade. Contractions produced by a single submaximal dose of exogenous NE or serotonin (5-HT) in unstimulated preparations were not affected by pretreatment with NPY. The amplitude of contractions was partially reduced 1 min after pretreatment with BPP or HPP; recovery occurred about 15 min after peptide pretreatment in a constant flow bath. These results suggest that an NPY receptor exists presynaptically in the rat vas deferens and that stimulation of the receptor by NPY inhibits the release of NE from noradrenergic nerves.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic Fibers↗
PubMedDate not supplied

Effect of calcitonin gene-related peptide on the neuroeffector mechanism of sympathetic nerve terminals in rat vas deferens.

In order to evaluate the mode of action of calcitonin gene-related peptide (CGRP) on the neuroeffector mechanism of peripheral sympathetic nerve fibers, the effects of CGRP were tested on the electrical stimulated and the non-stimulated preparations of the isolated rat vas deferens. The contractile responses, which were mediated predominantly by activation of postganglionic noradrenergic nerve fibers, were dose-dependently inhibited by CGRP in concentrations ranging from 0.1 to 10 nM. The inhibitory response produced by CGRP in high concentrations (greater than 2 nM) usually returned to the control level at 20-30 min and were rarely tachyphylactic. The inhibitory action of CGRP was not modified by pretreatment with 10(-7) M propranolol or 10(-7) M atropine. Contractions produced by exogenous norepinephrine (NE) and 5-hydroxytryptamine (5-HT) in unstimulated preparations were not affected by pretreatment with CGRP in a low concentration (less than 2 nM). On the other hand, the contractions were slightly reduced 1 min after pretreatment with CGRP in high concentrations (greater than 5 nM), which recovered in 15 min after constant flow washout. High concentrations of CGRP also caused a concentration-dependent relaxation on the precontracted preparations produced by high potassium (60 mM K+) solution. These results suggest that CGRP in high concentrations (greater than 5 nM) may have a non-specific inhibitory action on the postsynaptic plasma membrane of the smooth muscle cell and a postulated CGRP receptor exists presynaptically in the rat vas deferens and that CGRP may inhibit the release of NE during adrenergic nerve stimulation.

Animals↗
PubMedDate not supplied

Effects of calcitonin gene-related peptide on neuromuscular transmission in the isolated rat diaphragm.

The present study was undertaken to investigate a possible interaction between the cholinergic nerve neurotransmitter and CGRP on neuromuscular transmission in the isolated rat diaphragm. Electrical stimulation of the isolated phrenic nerve resulted in twitch contractions which were dose-dependently potentiated by CGRP in concentrations ranging from 1.2 x 10(-9) M to 3 x 10(-7) M. The potentiating action of CGRP (3 x 10(-7) M) disappeared in about 25 min. The same dose of CGRP 40 min later produced an augmentation of contraction amplitude similar to that observed prior to the administration of CGRP. The action of CGRP was dependent upon the stimulation pulse width ranging from 0.2 to 1.0 msec. Rat calcitonin (4.5 x 10(-7) M) caused a minimal change in the amplitude of twitch contractions. CGRP had no effect on the quiescent striated muscle. Twitch responses to direct electrical stimulation were also enhanced by CGRP (6 x 10(-8) M-6 x 10(-7) M) in the absence and presence of 10(-5) M d-tubocurarine. These results suggest that CGRP modulates the action of acetylcholine at the motor end plates of striated muscle.

Animals↗
PubMedDate not supplied

Immunohistochemical detection of retinal cones in monkey retina: light and electron microscopic study.

PURPOSE: Retinal cones have wave-length-specific visual pigments. To identify subclasses of cones, opsin-specific antibodies were previously established for the immunohistochemical studies of frozen sections. In this study, we produced retinal cone antibodies and examined (1) the specificity of these antibodies with Western blot analysis, (2) the application of these antibodies to paraffin-embedded monkey retinal sections, and (3) the use of these antibodies in light and electron microscopic immunohistochemical analyses of the localization of retinal cones. METHODS: The N-terminal peptide of blue opsin, and the C-terminal peptide of green/red opsin were used as immunogens in New Zealand White rabbits. Immunohistochemical staining was performed using the ABC method and immunogold method. As antigen retrieval treatment, paraffin-embedded cynomolgus monkey retinas were subjected to enzyme and microwave treatment. RESULTS: Both anti-red/green and anti-blue cone opsin antibodies detected 40 kDa native cone opsins in crude retina extract. The red/green and blue cone opsin immunostaining after trypsin treatment revealed that a positive signal was observed in the cone outer segment. Immunogold labeling also showed that gold particles were concentrated on the cone outer segment. CONCLUSION: In the antigen retrieval method, trypsin treatment is the appropriate method to obtain optimal staining of paraffin sections of retina. Using this method, retinal cone in conserved old paraffin sections can be identified immunohistochemically.

Animals↗
PubMedDate not supplied

Comparison of the vascular effects of adenosine, AMP, ADP and ATP on isolated blood-perfused internal and external carotid arteries of dogs.

1. The effects of adenosine and adenine nucleotides were studied on arterial vasculature in blood-perfused arterial preparations of dogs which were isolated from the internal and external carotid arteries. Each compound was administered directly into the cannulated artery over a period of 4 s. 2. In both arterial preparations, adenosine produced a dose-related vasodilatation and was more potent than AMP. On the other hand, ATP produced a dose-related vasoconstriction and was more potent than ADP.

Adenine Nucleotides↗