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A Suyama

Publications and source records attributed to A Suyama.

70 records · Page 4Linked to original sources
PubMed1984

Mechanisms of the ergonovine-induced vasoconstriction in the rabbit main coronary artery.

The mean membrane potential of smooth muscle cells of the rabbit main coronary artery was -60.3 mV and an evoked action potential could be recorded in response to acetylcholine (ACh). Ergonovine or 5-hydroxytryptamine (5-HT) slightly depolarized the membrane and methysergide, a relatively selective antagonist for the 5-HT receptor, had a slight inhibitory action on these depolarizations. 5-HT produced larger contractions than ergonovine, and the concentration-effect relationships obtained for both agents shifted to higher concentrations following pre-equilibration with methysergide. ACh (10(-11)M) slightly hyperpolarized the membrane and relaxed the tissue, and high concentrations of ACh (greater than 10(-8)M) depolarized the membrane, increased the membrane resistance and produced a contraction. ACh but not ergonovine or 5-HT, produced a contraction in Ca-free EGTA-containing solution. Following a 60 min pre-equilibration with indomethacin, the ergonovine-induced contraction was markedly enhanced but the 5-HT- or ACh-induced contractions were not. Removal of the endothelium by rubbing the vascular lumen enhanced the ergonovine- or ACh-induced contractions, but not those to 5-HT. The results obtained can be summarized as follows: ergonovine probably accelerates Ca influx and thereby produces contraction in the rabbit main coronary artery. This contraction is due to activation of the 5-HT receptor as an agonist, but the ergonovine-induced contraction is attenuated due to activation of the endothelium from which inhibitory prostanoid substances may be released. Ergonovine, therefore, may produce greater contractions in coronary arteries with damaged endothelium than in intact tissues.

Acetylcholine↗
PubMed1984

Stability distribution in the phage lambda-DNA double helix: a correlation between physical and genetic structure.

Statistical analyses on the positional correlation of physical-stability and base-sequence distribution maps with genetic map are made for the whole DNA (48502 bases) of lambda-phage. The susceptibility to a double-helix unfolding perturbation and the fraction of the transient opening of a particular region of the double helix are adopted to define this physical stability. The principal features obtained are: A) The DNA double strand of protein coding regions is found to have homostabilizing propensity around a defined stability which is characteristic to each individual gene. B) The stability of the double helix in non-protein coding region fluctuates, on average over the whole region, more than that in protein coding region. C) Boundary regions of protein coding and non-protein coding regions are regions of high stability-fluctuation. Stability especially fluctuates at the protein-coding-region side of the boundary. Contrary to the quiet feature of the interior part of protein coding region rather noisy part exists at its edge. D) One frequently opening region coincides with the attaching site for the site specific recombination between phage and bacterial DNA. There are two possible ways to explain the noisy feature in the stability distribution in non-protein coding regions: 1) The region has been used as the locus of recombination as evolution took place. Thus DNAs which were homostabilized around a different value characteristic to each individual DNA, have been joined there many times, so that the noise has accumulated as a remnant of evolutional history; and/or 2) the base-composition homogenizing or double-helix homostabilizing mechanism does not work in unneeded region such as non-protein coding region or introns. Since corresponding characteristics have been found in our previous analyses on other viral and globin-gene DNAs, the rules mentioned above may be comprehensively extended to other DNAs.

Bacteriophage lambda↗
PubMed1983

Reconstitution mechanism of nucleosome core particles mediated by poly(L-glutamic acid).

Poly(L-glutamic acid) has been reported to mediate in vitro nucleosome assembly (Stein, A., Whitlock, J.P., Jr. and Bina, M. (1979) Proc. Natl. Acad. Sci. U.S.A. 76,5000-5004). To study the reaction mechanism, we have reconstituted nucleosome core particles from chicken erythrocyte core DNA and core histones in the presence of poly(L-glutamic acid) and analyzed the assembly products by polyacrylamide gel electrophoresis. Poly(L-glutamic acid), which binds and forms a large complex with core histones, is replaced with core DNA in the reconstitution process. When histone-poly(L-glutamic acid) complex and core DNA are mixed with a histone:DNA ratio of 1.0, the yield of core particles increases by prolonged reconstitution time. Two phases with a distinct time range appear in the process. In the fast phase within 30 min, 60% of the DNA is involved in products containing histones: reconstituted core particles, a larger nucleoprotein complex and aggregation. In the second phase, the remaining DNA and the DNA in the aggregation decrease, and the core particles increase slowly. The yield of core particles is approx. 60% after 24 h. The slow phase is not observed by reconstitution with a histone:DNA ratio of 2.0 in the initial mixture. The reaction scheme of the assembly process derived from these data is given. Based on the in vitro reaction scheme, the possible role of in vivo 'nucleosome assembly factors' is also discussed.

Animals↗
PubMed1983

Correlation between thermal stability maps and genetic maps of double-stranded DNAs.

The positional correlation of boundaries of cooperatively melting regions with boundaries of protein coding regions and mere open reading frames, and with cleavage sites of restriction enzymes and S1 nuclease are statistically examined for phi X174, G4, fd, SV40, BKV, and polyoma DNAs. A statistically significant correlation does exist in the case of boundaries of protein coding regions, but none is detected for boundaries of mere open reading frames or cleavage sites of restriction enzymes and S1 nuclease. The significant correlation disappears when the cooperativity of melting of the DNA double strand decreases to a nonphysiological condition. The result presents the first evidence showing that a physical property of DNAs correlates with their biological function.

Base Composition↗
PubMed1983

Multiple actions of cocaine on neuromuscular transmission and smooth muscle cells of the guinea-pig mesenteric artery.

1. The effects of cocaine on the neuromuscular transmission and smooth muscle cells of the guinea-pig mesenteric artery were observed using various experimental procedures.2. Cocaine (10(-7) M) depolarized the membrane and increased the membrane resistance of single smooth muscle cells. Outward current pulses produced neither spikes nor graded responses in Krebs solution, but in the presence of 10(-5) M-cocaine, outward current did produce spikes.3. Perivascular nerve stimulation evoked excitatory junction potentials (e.j.p.s). Repetitive stimulation (0.25-1.0 Hz) produced a frequency-dependent facilitation. Application of cocaine (10(-7) M) reduced the amplitude of the first e.j.p. (e.j.p.(f)) and also after completion of facilitation (e.j.p.(s)). However, the facilitation process was not affected by cocaine (10(-5) M).4. On pre-treatment with phentolamine (3 x 10(-7) M), both e.j.p.(f) and e.j.p.(s) were enhanced, but on pre-treatment with yohimbine (3 x 10(-7) M), e.j.p.(f) was inhibited and e.j.p.(s) was enhanced. Both phentolamine and yohimbine accelerated the facilitation of e.j.p.s in the absence and presence of cocaine (10(-7) M).5. The conduction velocity of nerve excitation measured from the latency of generation of e.j.p.s was slightly lowered by cocaine. The number of nerve fibres or varicosities contributing to the generation of an e.j.p. was not reduced in the presence of cocaine (10(-5) M).6. Mechanical responses could be recorded on perivascular nerve stimulation, and direct muscle stimulation on treatment with tetrodotoxin. Cocaine (10(-7) to 10(-4) M) enhanced the contraction evoked by direct muscle stimulation and inhibited the contraction evoked by perivascular nerve stimulation.7. Cocaine (10(-5) M) enhanced the contraction evoked by 5 x 10(-6) M-noradrenaline (NA) and direct muscle stimulation (5 sec pulse) but no effect was observed on the K-induced contraction (39.2 mM-K). On pre-treatment with guanethidine (10(-6) M) these effects of cocaine were not affected.8. In the presence of cocaine (10(-5) M), the depolarization of the membrane induced by NA was additively increased, and the dose response curve for NA was shifted to the left with no change in the maximum amplitude of contraction.9. When 10(-5) M-cocaine was applied during contractions evoked by alternate perivascular nerve stimulation and exogenously applied NA, the contraction evoked by perivascular nerve stimulation was reduced, while that evoked by NA was enhanced.10. In saponin-treated skinned muscles, the pCa-tension relationship was not affected by application of 10(-4) M-cocaine. The effects of cocaine on the Ca accumulation and release from the store site were estimated. It was found that cocaine (10(-4) M) slightly inhibited the Ca accumulation (0.89 times the control) but did not modify the Ca-release mechanism.11. The overflow of NA, 3,4-dihydroxyphenylglycol (DOPEG) and 3-methoxy-4-hydroxyphenylglycol (MOPEG) were measured in the same tissue before and after application of perivascular nerve stimulation in the presence or absence of cocaine (10(-7) to 10(-5) M). Cocaine induced a concentration-dependent increase in the overflow of NA and a reduction in the amounts of DOPEG and MOPEG.12. We conclude from these studies that cocaine mainly inhibits the sensitivity of the intra-junctional adrenoceptor, but increases the sensitivity of the extrajunctional adrenoceptor distributed on the post-junctional muscle membrane, with increase in the overflow of NA. The enhancement of mechanical response in the presence of cocaine is probably due to an increased sensitivity of the extra-junctional adrenoceptor and changes in the post-junctional muscle membrane, without any marked effect on the prejunctional mechanism.

Animals↗
PubMed1983

An algorithm for the bonding-probability map of nucleic acid secondary structure.

We report a more efficient and well-defined algorithm for predicting a secondary structure of single-stranded nucleic acid from a primary nucleotide sequence. Using this algorithm, one- and two-dimensional bonding-probability maps of 5S rRNA of thermus thermophilus HB8 were calculated. These maps well express the stability of the secondary structure.

Chemical Phenomena↗
PubMed1982

Correlation between thermal stability maps and genetic maps of double-stranded DNAs.

The positional correlation of boundaries of cooperatively melting regions with boundaries of genes and with cleavage sites of restriction enzymes are statistically examined for phiX174, G4, fd, SV40, BKV, and polyoma DNAs. A statistically significant correlation does exist in the case of gene boundaries, but none is detected for cleavage sites.

Base Composition↗
PubMed1981

Comparative hepatic transport of sulfobromophthalein and its glutathione conjugate in rats.

The hepatic transport of sulfobromophthalein (BSP) and its glutathione conjugate (BSP-GSH) were compared in rats by pharmacokinetic analysis in an attempt to determine the effect of conjugation on the over-all transfer of BSP from blood into bile. In the control rats, the plasma disappearance of BSP was faster than that of BSP-GSH, while the biliary excretion rate of BSP-GSH was significantly higher than that of BSP for the first 10 min. No significant difference in the total amount excreted in the bile for 4 hr was observed between two dyes. In the rats chronically intoxicated with carbon tetrachloride, typical delays were shown in both the plasma disappearance and the biliary excretion of BSP-GSH. In the control rats, the pharmacokinetic parameters, k12 and k23 of BSP-GSH were significantly smaller than those of BSP, while k34 was significantly greater than those of BSP. In the intoxicated rats, significant decreases were observed in k12, k23 and k34. The binding of BSP and BSP-GSH to the Y-fraction prepared from the control and intoxicated rats were studied by equilibrium dialysis. In the control rats, the number of high affinity bindings sites (n1) of BSP-GSH was significantly smaller than that of BSP, while no significant difference was revealed in the binding constant of the high affinity binding site (K1). In the intoxicated rats, both n1 and K1 of BSP-GSH were significantly smaller than those of the control rats. It was suggested that the glutathione conjugation might not play as the rate-determining step in the over-all hepatic transport of BSP.

Animals↗
PubMedDate not supplied

Chronic active "lupoid" hepatitis and HLA system; report of 6 cases.

During the 12 years from 1977 to 1988 in Tottori University Hospital, 6 cases (4.2%) with chronic active "lupoid" hepatitis were encountered among 143 patients with histologically proven chronic active hepatitis. HLA antigens were studied; BW 22 and CW 1 were strongly associated, and A 11 was rather associated with the rare disorder in Japan. These results suggested that Japanese patients with chronic active "lupoid" hepatitis have different HLA markers from those in Caucasian patients, which may be attributable to rare specificity in the HLA system rather than different mechanisms of pathogenesis.

Adult↗
PubMedDate not supplied

Preoperative and postoperative study of left ventricular function, hemodynamics and plasma catecholamine concentrations during dynamic exercise in patients with chronic mitral regurgitation.

We studied 7 patients before and after mitral valve replacement (MVR) for chronic mitral regurgitation (MR) and 5 control subjects by echocardiography and right heart catheterization to assess left ventricular function, hemodynamics and plasma catecholamine concentrations during supine bicycle exercise. Left ventricular (LV) end-systolic dimension decreased and LV systolic function increased significantly during exercise in patients and control subjects. LV systolic function (fractional shortening and mean velocity of circumferential fiber shortening) was significantly lower in patients after MVR than before MVR (p < 0.05). Cardiac index at peak exercise was significantly higher in patients after MVR than before MVR (p < 0.05). Significantly greater augmentation in plasma norepinephrine (NE) levels were observed during exercise in patients both before and after MVR than in control subjects (p < 0.05). No significant differences in mean pulmonary artery pressure (PAP) and pulmonary capillary wedge pressure (PCWP) were observed between the patients before and after MVR. Thus, it is concluded that LV systolic and pump function (CI) during exercise were augmented by a compensatory activation of sympathetic nervous system in patients both before and after MVR for chronic MR.

Adult↗
PubMedDate not supplied

Characteristic differences of hepatocellular carcinoma in Japan, with special reference to liver weight at autopsy.

BACKGROUND/AIMS: Liver weight at autopsy in patients with hepatocellular carcinoma (HCC) has been found to differ by geographic region. The clinicopathological characteristics of HCC in relation to liver weight at autopsy have not been reported for Japanese cases. METHODOLOGY: From 1980 to 1992, a total of 107 consecutive HCC autopsy cases were studied. Seven cases were excluded (5 surgically resected cases and 2 cases of occult-type HCC (Berman) which were diagnosed at autopsy for the first time). The 100 cases of HCC were divided into 4 groups according to liver weight at autopsy: less than 999 g (group A, n = 15, 15%); 1000-1999 g (group B, n = 50, 50%); 2,000-2,999 g (group C, n = 20, 20%); and more than 3,000 g (group D, n = 15, 15%). Various clinical and pathological findings, including age, sex, hepatitis B surface antigen (HBsAg) status, history of blood transfusions, treatment, cause of death, underlying liver disease, survival after diagnosis, tumor size, macroscopic findings, microscopic findings, splenic weight and liver weight were studied. RESULTS: Significant differences between groups were found in sex (p < 0.01), underlying liver disease (p < 0.001), tumor size (p < 0.0001), microscopic findings (p < 0.001) and survival (p < 0.01). The lowest liver weight group (group A) had a significantly longer mean survival rate than the other three groups (p < 0.001). CONCLUSIONS: These results showed that 15% of HCC occurred in large size livers (more than 3,000 g), 15% occurred in small size livers (less than 999 g) and 70% occurred in livers between 1,000 g and 2,999 g, and that tumor size (p < 0.0001) and microscopic findings (p < 0.001) were the major determinants of liver weight in HCC patients. The total liver volume reflected by liver weight in HCC cases may be valuable for the assessment of the clinicopathological features of HCC and its prognosis.

Carcinoma, Hepatocellular↗