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Biomedical subjects

T Azuma

Publications and source records attributed to T Azuma.

At least 397 records · Page 22Linked to original sources
PubMed1981

[The mode of action of ATP on the isolated internal carotid artery (author's transl)].

Adenosine triphosphate (ATP) has been known to induce vasodilation in various vascular beds. Recently, we reported that ATP produced vasoconstrictions in isolated internal and external carotid arteries of dogs. In the present study, the mode of the ATP-induced vasoconstriction in the internal carotid artery was analysed from the physiological and pharmacological points of view. The results obtained were as follows: 1) ATP (5 X 10(-6) approximately 2 X 10(-4) M) caused dose-dependent vasoconstrictions in the internal carotid artery. 2) The ATP-induced vasoconstriction was not affected by pretreatment with phenoxybenzamine, propranolol, atropine, cyproheptadine, or tetrodotoxin. 3) Verapamil suppressed dose-dependently the contractile response. 4) ATP caused no vasoconstriction in a calcium-free Krebs solution containing Im M EGTA. 5) ATP produced no further vasoconstriction in the preparation which had been in a state of contracture in a high potassium Krebs solution. These results suggest that an increase of potential-dependent Ca++ influx into the arterial smooth muscle cells may play a major role in the ATP-induced vasoconstriction.

Adenosine Triphosphate↗
PubMed1980

A camera-type diameter gauge applicable to small blood and lymph vessels.

A camera-type diameter gauge was constructed and used in physiological experiments. The distinctive features of the design and use of the gauge may be summarized as follows. Installation of an image sensor in the focal plane of a single-lens reflex camera equipped with a set of extension tubes which makes it possible to measure outer diameters of blood and lymph vessels as small as 100 micrometer. Using the gauge, we can distinguish a diameter change of about 12 micrometer. Simultaneous measurements of the diameters of two different vessels can be made using two window signals generated independently at desired moments for appropriate periods within the video scans.

Animals↗
PubMed1980

An approach to the pathogenesis of "white finger" induced by vibratory stimulation: acute but sustained changes in vascular responsiveness of canine hindlimb to noradrenaline.

A fixed vibratory stimulation (60 Hz in frequency, 3 g in acceleration, and 2.2 mm in amplitude) was applied to a hindlimb (test limb) of dogs anaesthetised with sodium pentobarbital. Peripheral vascular resistance in the test limb was calculated as the ratio of mean pressure difference between the femoral artery and the femoral vein to the rate of femoral arterial blood flow. By means of a highly sensitive clinical thermometer, interdigital temperature was recorded not only from the test limb but also from a forelimb (control limb). The vibratory stimulation significantly reduced the peripheral resistance in the test limb. The increase in peripheral resistance induced by noradrenaline administration was suppressed during, and enhanced 1 h after, the stimulation. With the start of the vibratory stimulation, interdigital temperature in the test limb rose gradually and reached a constant level. The temperature first went below, and then returned to, the initial level after interruption of the stimulation. No change in the temperature was produced in the control limb. The decrease of temperature induced by noradrenaline administration was suppressed during, and enhanced 1 h after, the stimulation. These results indicate that, even in the living body, the conclusion of our previously report is valid: ie the responsiveness of arterial smooth muscle to noradrenaline decreases during, and increases soon after, vibratory stimulation. Assuming that our results obtained from acute experiments can be applicable to human digital arteries, the occurrence of "white fingers" on vibration disease may be understood in terms of vibration-induced hyperresponsiveness following stimulation.

Animals↗
PubMed1980

Active and passive mechanical characteristics of bovine mesenteric lymphatics.

Pressure-volume and pressure-radius relationships in lymphangions isolated from bovine mesenteric lymphatics were similar in pattern with those in the vein. Circumferential modulus of elasticity of the lymphatics ranged from 4.2 x 10(4) tatic walls. The contractile force increased in early stages of distension and decreased after an optimal intraluminal pressure was attained. The spontaneous activity was also affected by the rate of wall deformation. The pacemaker site of spontaneous activity seemed to be in the wall in the immediate vicinity of the inlet valve of a lymphangion. The activity propagated with a velocity of 4-5 mm/s. Ejection fraction of a lymphangion was between 45 and 65%. The endurance limit of the lymphatic valve was 68.4 +/- 7.6 cmH2O in specimens of about 3 mm in outer diameter. These findings suggested that lymphatic smooth muscle seemed to play a major role in elastic behavior of the wall and in regulation of the spontaneous activity, thereby affecting significantly passive and active lymph transport.

Animals↗
PubMed1980

Paradoxical relaxation of arterial strips induced by vasoconstrictive agents.

Longitudinal strips isolated from canine distributing muscular arteries were relaxed by noradrenaline and contracted by papaverine. This paradoxical relaxation and contraction may be due to a helical and circular arrangement of smooth muscle in the wall which is incompressible. Various vasoconstrictive agents, including noradrenaline, produced a circumferential contraction and longitudinal relaxation in muscular arteries. Vasodilator agents produced the opposite effect. The direction and magnitude of response of a helical strip to a vasoactive substance depended upon its sectioning angle from the transverse axis of the vessel.

Adenosine↗
PubMed1979

A photoelectric diameter gauge utilizing the image sensor.

We have designed and constructed a blood vessel diameter gauge, utilizing a high resolving power and stability of the image sensor which has become of major interest lately as a new photoelectric transducer. The distinct feature of the gauge is summarized as follows. (1) Contact-free measurements of blood vessel diameter (1--14 mm) are possible. (2) The cuff-type probe is small in size and easy to put to use. (3) The lightguide consisting of optical fibers makes incident light cold. (4) The resolving power of the gauge is 28 micrometer in principle. (5) The frequency response of the gauge is flat up to 100 Hz. A few results of its preliminary application to in vitro and in vivo experiments are also demonstrated.

Animals↗
PubMed1979

Refolding of the immunoglobulin light chain.

The kinetics of the refolding reactions of type lambda Bence Jones proteins from 4 M GuHCl were studied by CD, ultraviolet absorption, and fluorescence spectrophotometry. The kinetics were complex and consisted of at least three phases, an undetectable fast phase, a detectable fast phase, and a slow phase. The slow phase followed first-order kinetics and the three experimental methods used gave similar rate constants for all the Bence Jones proteins (about 3 X 10(-3) s-1). The refolding reaction of VL fragment was too fast to be measured in the present experiments. The refolding process of CL fragment was very similar to those of Bence Jones proteins except that the detectable fast phase was less significant. The rate constant of the slow phase observed for the CL fragment was similar to those of the slow phase observed for Bence Jones proteins. The activation energy of the slow phase was the same for a Bence Jones protein and its CL fragment. These results indicate that the refolding kinetics of the CL domain are very similar to those of isolated CL fragment and that refolding of the VL domain precedes refolding of the CL domain, even though both domains have similar immunoglobulin folds. However, the results of refolding experiments on Bence Jones proteins, and VL and CL fragments in the presence of ANS, as well as the other lines of evidence, indicate that the refolding kinetics of the Bence Jones protein molecule cannot be expressed as simple sum of the refolding reactions of isolated VL and CL fragments.

Bence Jones Protein↗
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↗