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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
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↗
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

Monomer-dimer equilibria of a Bence Jones protein and its variable fragment.

The circular dichroic (CD) spectra of a type lambda Bence Jones protein (Tod), its variable (VL) fragment, and the constant (CL) fragment of a type lambda protein (Nag) were measured under various conditions. In the pH region from 5.5 to 7.5, the CD spectra of Tod protein with intact interchain disulfide bond (L(SS)) and and CL did not change with pH, while the spectra of Tod protein in which the interchain disulfide bond had been reduced and alkylated (L(RA)) and VL did not change with pH. The dimerization reactions of L(RA) and VL were studied by following the CD change with protein concentration. The CD spectrum of CL did not change with the protein concentration. The dimerization constant for L(RA) was 4 X 10(4) M-1 at at pH 7.5 and 25 degrees C, which was smaller than that for VL (1 X 10(5) M-1). The ellipticity at 278 nm for the L(RA) dimer was different from that for the L(SS) dimer and changed with pH. These findings indicate that the L(RA) dimer and L(SS) dimer have different conformations. The differences in the conformation and L-L interaction between the L(RA) dimer and L(SS) dimer are discussed on the basis of the conformations of VL and CL and the interactions between the paired domains.

Alkylation↗