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Biomedical subjects

T Azuma

Publications and source records attributed to T Azuma.

At least 361 records · Page 20Linked to original sources
PubMed1983

A preliminary study on clinical application of Nd:YAG laser to the face and head.

Preliminary experiments were carried out for use of the Nd:YAG laser therapy of malignant tumors of the head and face. Because bone and brain tissue lie under the soft tissues in the face and head, the authors prepared two experimental models and examined the thermal effects of laser irradiation using three irradiating methods, single-pulse, automatic running, and manual. In experiments using results from these models, a temperature rise inducing protein coagulation did not occur under the surface of the soft tissue under the bone in both models. With automatic running irradiation, the temperature rise in the surface of the soft tissue under the bone was about 5 degrees C at 60 W with a running speed of 4 mm/sec in model I. These conditions were considered to be sufficiently within safe limits. In the second model, it was estimated that no thermal effects would be exerted on the soft tissue under the bone at 60 W or less with a running speed of 8 mm/sec or less. Using manual irradiation, no thermal disturbance of the soft tissue under the bone was induced in the first model, but without a shortening of irradiation time or an increase in irradiation distance this method could cause thermal damage to the second model and must be taken into consideration.

Animals↗
PubMed1983

Effect of potassium on adrenergic nerve endings in bovine mesenteric lymphatics.

This work concerned the effect of KCl (60 mM) on noradrenaline efflux from aminergic nerve endings in bovine mesenteric lymphatics. In high potassium Krebs solution containing cocaine (10(-7) M), the lymphatics showed some phasic contractions followed by a tonic contraction with a high initial peak. The high KCl solution also caused a transient but statistically significant increase of tritiated noradrenaline efflux (P less than 0.01) which was not blocked by tetrodotoxin (10(-7) M). However, 5 X 10(-6) M 5-hydroxytryptamine or 10(-5) M prostaglandin F2 alpha produced a contraction of the lymphatic smooth muscle similar in magnitude to the contraction by 60 mM KCl. In this case, however, no increase was observed in 3H efflux. A Ca-antagonist, D-600 (10(-4) M) inhibited the potassium-induced rise in tritiated noradrenaline efflux and suppressed dose-dependently the contractile response to high potassium solution. These observations support the suggestion that the effect of KCl on 3H-release reflects an effect of kinetics of exchange across the nerve ending rather than an effect of contraction per se on isotope exchange through the complex extracellular matrix, and that the activation of Ca channels in the adrenergic nerve terminals may contribute to the release of noradrenaline in high KCl solution.

Adrenergic Fibers↗
PubMed1983

Factors modifying the local arterial hyperresponsiveness of vibration-induced white finger.

The extent and duration of the vibration-induced hyperresponsiveness of arterial smooth muscle to noradrenaline increased as the period of vibratory stimulation became longer. Division of a fixed stimulation time into a few shorter units interposed by intermissions decreased the extent and duration of the hyperresponsiveness. The shorter the length of each unit, the less the hyperresponsiveness. Verapamil effectively suppressed the appearance of the hyperresponsiveness, whereas pretreatment with phentolamine only partially inhibited its appearance. Administration of vitamin E was effective in suppressing the vibration-induced rise of responsiveness to noradrenaline in plasma.

Animals↗
PubMed1983

Bradykinin-induced contractions of bovine mesenteric lymphatics.

The mode of action of bradykinin (BK) on bovine mesenteric lymphatics was investigated by recording isometric tensions and action potentials in the isolated longitudinal segments. Addition of BK in concentrations from 10(-10) to 4 X 10(-6) M caused dose-related tonic contractions. BK in a low concentration accelerated the rhythm of action potential discharges in the spontaneously beating preparations and elicited frequent discharges of action potentials and a rapid rise in smooth muscle tone associated with phasic contractions. BK in high concentrations (more than 10(-7) M) caused a further rise of tension in the preparations which had already been depolarized in a high-K solution. The contraction induced by 4 X 10(-9) M-BK in the standard solution was abolished in a Ca-free environment or in the presence of a Ca-antagonist, 10(-4) M-D-600, though more than 50% of the contraction caused by 10(-6) M-BK still remained in both circumstances. In a Ca-free solution containing 1 mM-EGTA (Ca-free standard solution), 10(-6) M-BK caused a slight contraction even after high-K-induced contractions were completely blocked. The contractile response to 10(-6) M-BK in the Ca-free standard solution was augmented after activation of beta-receptors. It is concluded that the BK-induced contractions may be closely related to an increased Ca influx through the membrane and release of membrane-bound and intracellular Ca. The increased uptake of Ca into the BK-sensitive intracellular store may contribute to the relaxing effect of beta-agonist.

Action Potentials↗
PubMed1983

[Characteristics of alpha adrenoceptors of lymphatics and their physiological significance].

We studied isolated bovine mesenteric lymphatics to investigate the pharmacological properties of the postjunctional-adrenoceptors. Rings of the lymph vessels were mounted for isometric tension recording in organ chambers filled with Krebs-Ringer bicarbonate solution. The lymph vessels contracted when exposed to phenylephrine and clonidine. The relative sensitivity of the vessels to clonidine was larger than to phenylephrine. Yohimbine was a competitive antagonist against phenylephrine and clonidine in the lymph vessels. Prazosin caused a parallel shift to the right of the dose-response curve to phenylephrine, and not to clonidine in the vessels. The Schild's plot for yohimbine in the lymph vessels suggests that the presence of both alpha 1- and alpha 2-like adrenoceptors on lymphatic smooth muscle cells.

Animals↗
PubMed1982

A small hypervariable segment in the variable domain of an immunoglobulin light chain stimulates formation of anti-idiotypic suppressor T cells.

The induction in BALB/c mice of suppressor T cells that block a delayed-type hypersensitivity (DTH) response to the idiotype of M315, a myeloma protein of BALB/c origin, was examined with a variety of immunoglobulin chains and fragments whose amino acid sequences are known. Normal BALB/c mice receiving either the light chain of M315 (L315, lambda 2 isotype) or the variable (V) domain of this chain prior to sensitization with M315 showed marked suppression of DTH to the M315 idiotype. In contrast, neither the heavy chain nor the variable domain of the heavy chain of M315 affected the DTH response. Two other lambda 2 chains were tested and they also failed to suppress DTH to M315. Comparison of amino acid sequences in the three lambda 2 chains indicates that in L315 at most four V region amino acid substitutions (each resulting from a somatic mutation in the V lambda 2 germ-line gene) determine the specificity of the T-cell suppressor pathway. One of the four is in the framework and probably of negligible importance; the other three, however, are all clustered in the third hypervariable loop of the L315 V domain. The tertiary structure of L315 may also be essential, because disruption of intrachain disulfide bonds abolished the ability of the chain to induce suppression.

Amino Acid Sequence↗
PubMed1982

Numerical analysis of blood flow in the vertebral artery.

Abnormal hemodynamic forces associated with distortions of blood vessel lumen have been thought to play an important role in the pathogenesis of focal vascular lesions. In the vertebral artery, segments located between osseous rings are ectatic compared with those surrounded by the rings. Based on the assumption that arterial blood flow was quasi-steady, this work was undertaken to investigate the structure of flow through arterial models with one or two sinusoidal stenoses. Numerical analysis was performed by an integral-momentum method. The validity of the method was examined by comparison of experimental data so far reported with theoretical results. Velocity and wall shear stress distributions were explored in a model with two stenoses simulating a part of the vertebral artery. The ectatic segments of the vertebral artery have been known as predilection sites for atherosclerotic lesions. The present study suggested that the ectatic wall was under unstable shear stresses, the direction of which was dependent upon the magnitude of the Reynolds number.

Blood Flow Velocity↗
PubMed1982

Contraction of arterial smooth muscle induced by magnesium ions.

Dose-response relationships for Mg2+ in a Mg2+-free bathing solution were obtained with isolated canine femoral arteries. At concentrations less than 5 mM, relaxant responses appeared in the preparations. In a concentration range of 10-20 mM, however, every one of the preparations invariably showed dose-dependent contractions. The relaxant and contractile responses were induced by the action of Mg2+ per se but not by the hyperosmolarity associated with the addition of Mg2+. Neither response was affected by the drugs that inhibited the actions of catecholamine, acetylcholine, serotonin, or histamine. The contractile response was kept unchanged in Ca2+-free Locke's solution and was almost independent of environmental calcium concentrations ranging from 2.2 to 8.2 mM. The contractile response was not affected under the influence of Ca antagonists, verapamil, or Mn2+. The presence of Ba2+ or Sr2+ enhanced the relaxant response and dose dependently suppressed the contractile response. The contractile response was still evoked in smooth muscles that were in the state of K+ contracture. These results suggest the possibility that the contractile action of Mg2+ was mediated by a release of intracellular Ca2+ or exerted directly on the contractile machinery of arterial smooth muscle.

Animals↗
PubMed1982

The horseshoe vortex: a secondary flow generated in arteries with stenosis, bifurcation, and branchings.

In order to elucidate the fluid dynamic feature of arterial blood flow, the present flow visualization study was carried out with various transparent blood vessel models having a protuberance, a bifurcation, or branchings. The observed flow patterns could be understood in terms of occurrence of a secondary flow, named the horseshoe vortex. The mode of generation of the horseshoe vortex in a tube with a protuberance projecting into the boundary layer was explained as follows. A radial pressure gradient toward the tube wall was produced along the upstream surface of the protuberance because of the interaction between the viscous sheared flow and the wall. This pressure gradient made fluid particles turn round downward directly before the obstacle. Then they curled round on themselves and formed a bound vortex tube, the horseshoe vortex, which in turn passed round the front of the protuberance in both directions. In a tube with a Y-shaped bifurcation or rectangular side branch, the flow divider at the branching site acted in place of the protuberance to produce a vortex tube similar in pattern to the horseshoe vortex. The vortex tube extended from the high pressure region, i. e. the apex of the flow divider, to the low pressure region, i. e. the lateral margin of the branch orifice, and generated swirling secondary flows in the main and branched tubes. These results suggested that the following mechanical factors might initiate or facilitate athero- and thrombogenesis: collision of blood cells captured by the horseshoe vortex with blood vessel walls, the interaction of the walls and blood cells due to turbulence, and the occurrence of localized high wall shear stresses.

Aorta, Abdominal↗