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Biomedical subjects

M Hamada

Publications and source records attributed to M Hamada.

At least 451 records · Page 25Linked to original sources
PubMed1989

[Exercise radionuclide ventriculography in evaluating successful percutaneous transluminal coronary angioplasty (PTCA)].

To evaluate late success of PTCA in 29 patients with coronary artery disease, exercise radionuclide ventriculography was performed. Twenty-nine patients were classified into two groups according to the presence of restenosis (Group N: 19 patients without restenosis, Group R: 10 patients with restenosis). LVEF improved significantly in Group N, and the sensitivity, specificity and overall accuracy for detecting restenosis were 100%, 68% and 79%, respectively. Regional wall motion abnormality during exercise did not worsened in Group N, and the sensitivity, specificity and overall accuracy for detecting restenosis were 89%, 96%, and 94%, respectively. The left ventricular end-systolic volume during exercise increased in group R but decreased in Group N. The exercise response of the ratio of systolic blood pressure to end-systolic volume in Group N was significantly larger than that of Group R, and was considered to be useful parameter for detecting restenosis.

Adult↗
PubMed1989

[A patient with olivopontocerebellar atrophy combined with sleep apnea syndrome].

A 52-year-old man with olivopontocerebellar atrophy was admitted to Ehime University Hospital for examination of sleep apnea. Overnight polysomnographic study revealed that his sleep apnea was predominantly the central type. With progress of the disease, the dominance of apnea pattern changed from the central type to the obstructive type. After tracheostomy, the apnea index decreased from 15 per hour to 12.4 per hour. However, the apnea index of the central type increased from 1.5 per hour to 12.4 per hour. These findings suggest that the effect of tracheostomy is not always beneficial in sleep apnea, and that the frequency and the pattern of apnea are not always indicators of tracheostomy.

Humans↗
PubMed1989

[Inhalation of a precursor analogue of vasoactive intestinal polypeptide (Leu17 VIP-Gly-Lys) protects ascaris-induced bronchoconstriction in dog].

We studied in vivo the effects of pre-inhalations of vasoactive intestinal polypeptide (VIP) and a precursor analogue of VIP (Leu17 VIP-Gly-Lys: preVIP) in mongrel dogs bronchoconstricted by ascaris. An inhalation of preVIP solution (2 mg/5 ml saline) gave significant protection for 120 min against increases in respiratory resistance (Rrs) and decreases in dynamic compliance (Cdyn) induced by ascaris challenges. An inhalation of VIP solution (2 mg/ml saline) also gave significant protection for 120 min against increases in Rrs induced by ascaris challenges. Protective effect of the inhalation of preVIP against ascaris-induced bronchoconstriction was more potent than that of VIP. The inhalations of preVIP and VIP solution did not change systemic blood pressure or heart rate. These results indicate that inhalations of preVIP or VIP solution would attenuate ascaris-induced bronchoconstriction in dogs without affecting cardiovascular dynamics.

Administration, Inhalation↗
PubMed1989

[Clinical significance of exercise induced ST segment depression after successful percutaneous transluminal coronary angioplasty--assessment by thallium-201 SPECT].

To evaluate the clinical significance of ST segment depression during repeated Treadmill exercise after successful PTCA, Thallium-201 SPECT was performed. The Thallium-201 SPECT was performed before, one week after and 3-6 months after PTCA. All thirty-five patients had one vessel disease and positive Thallium-201 exercise test. During follow-up period for 3-6 months, 11 of 35 patients had persistent ST segment depression. Restenosis of dilated coronary lesion was demonstrated in 6 of 11 patients. In another 3 of 35 patients, exercise induced ST segment depression was disappeared during follow-up Treadmill exercise. In 14 patients with persistent or transient ST segment depression after PTCA, Thallium-201 SPECT demonstrated transient ischemia in 5 of 6 patients with restenosis. In other 8 patients without restenosis, SPECT images did not demonstrate myocardial ischemia and coronary arteriographic findings could not verify side branch stenosis or intimal dissection which might cause myocardial ischemia. The etiology of ST segment depression after successful PTCA in one vessel disease is not produced by exercise induced myocardial ischemia but still unknown mechanisms may be present.

Adult↗
PubMed1989

[Acute and chronic effects of a new oral inotropic agent, ibopamine hydrochloride, on hemodynamic and metabolic responses to ergometer exercise in patients with severe congestive heart failure].

The hemodynamic and metabolic effects of ibopamine, an orally active 3,4-diisobutylic ester of N-methyl-dopamine, at rest and during exercise, were evaluated in 8 patients with severe congestive heart failure, initially at 2 hrs after oral 100 mg and after 4 weeks of maintenance therapy (100 mg, 3 times a day). At rest, a single dose of ibopamine increased CI, SVI and SWI, and reduced PCWP, PAm, RA and PVR. These beneficial hemodynamic effects were maintained during supine bicycle exercise: CI and SVI increased markedly (p less than 0.05) and PCWP, PAm, RA and SVR increased at a lower extent (p less than 0.05) after ibopamine than on control conditions. After chronic therapy with the drug, LVDd and CTR decreased (p less than 0.05) and exercise tolerance time increased (p less than 0.01). HR, BPm, double product, norepinephrine, epinephrine, renin activity, aldosterone and lactate/pyruvate did not change significantly after administration of ibopamine. Clinical responses after 4 weeks of maintenance therapy were good in 4 cases and fair in 1 case. No adverse effects were observed. Therefore, ibopamine seems to have not only a positive inotropic action, but also a potent vasodilating action, leading to both afterload and preload reduction and so to be useful for the treatment of severe congestive heart failure at rest and during exercise after acute and chronic therapy with the drug.

Administration, Oral↗
PubMed1989

[Clinical significance of reverse redistribution in exercise thallium-201 SPECT after percutaneous transluminal coronary angioplasty].

Clinical significance of reverse redistribution on thallium image was evaluated in 54 patients who had undergone PTCA. Thallium SPECT imaging was performed one week and three to six months after PTCA. Reverse redistribution was detected eight of 54 patients one week after PTCA and five of 38 patients three to six months after PTCA. In the segments with reverse redistribution, reduced regional wall motion and lesser degree of coronary stenosis was common features (p less than 0.05) angiography. In conclusion, reverse redistribution had a tendency to appear in the region with mild myocardial injury and relatively high coronary blood flow after PTCA. But in cases with new occurrence and disappearance of reverse redistribution during follow up period, we can not assess the factors to explain these phenomena. In these segments, "coronary flow reserve", "stunned myocardium", "hibernating myocardium" or other factors may be related.

Angioplasty, Balloon, Coronary↗
PubMed1988

Grayanotoxin opens Na channels from inside the squid axonal membrane.

External application of alpha-dihydro-grayanotoxin II (alpha-H2-GTX II) to squid giant axon under nonperfused condition caused substantial membrane depolarization. Intracellular perfusion of the fibers retarded this depolarization appreciably. Tritium-labeled alpha-dihydro-grayanotoxin II ([3H]alpha-H2-GTX II) in the external medium can permeate through the cell membrane, but permeation of alpha-H2-GTX II does not occur either with the carrier-mediated system or through the pores of the Na channel. The finding that the most hydrophilic grayanotoxin analogue, desacyl asebotoxin VII, is effective only when applied internally, strongly suggests that the receptor for grayanotoxin does not exist on the external surface of the membrane. The linear relationship between the concentration of [3H]alpha-H2-GTX II in the external medium and the count in the effluent from the perfused axon indicates that GTX II diffuses through the cell membrane's lipid phase and reaches the site of action only approached from the internal medium.

Aconitine↗
PubMed1988

Drosophila homolog of the murine Int-1 protooncogene.

We have isolated phage clones from Drosophila melanogaster genomic and cDNA libraries containing a sequence homologous to the murine Int-1 protooncogene. The Drosophila gene is represented by a single locus at position 28A1-2 on chromosome 2. The gene is expressed as a 2.9-kilobase-long polyadenylylated mRNA in embryo, larval, and pupal stages. It is hardly detectable in adult flies. The longest open reading frame of the cDNA clone corresponds to a protein 469 amino acids long. Alignment of the predicted amino acid sequences shows that the Drosophila protein is 86 amino acids longer than its murine counterpart. In spite of the difference in length, the two proteins are highly conserved with an overall sequence homology of 54%. Both Drosophila and murine Int-1 proteins begin with a hydrophobic leader sequence and contain cysteine residues and sites for glycosylation (four in the murine protein and one in the Drosophila protein) in conserved positions, suggesting that they play important functional roles.

Amino Acid Sequence↗
PubMed1988

Ca2+ uptake in bovine adrenocortical microsomes: formation of phosphorylated intermediate of Ca2+ dependent ATPase.

Bovine adrenocortical microsomes were prepared and partially purified by discontinuous sucrose density gradient. Light fractions of the microsomes at the interface between 15 and 30% sucrose solution, exhibited ATP dependent Ca2+ uptake. The Ca2+ uptake was dependent on temperature and stimulated by free Ca2+ (the concentration for half maximal activation = 1.0 microM) and Mg2+. The Ca2+ uptake was inhibited by ADP but not affected by 10 mM NaN3 or 0.5 mM ouabain. Calcium release from the microsomes was accelerated by a Ca2+ ionophore, A23187, but not by a Ca2+ antagonist, diltiazem. A microsomal protein with a molecular weight of 100-110 kDa was phosphorylated by [gamma-32P]ATP in the presence of Ca2+, and the Ca2+ dependency was over the same range as the Ca2+ uptake (the concentration for half maximal activation = 3.0 microM). The phosphorylated protein (EP) was stable at acidic pH but labile at alkaline pH and sensitive to hydroxylamine. The rate of EP formation at 0 degrees C in the presence of 1 microM ATP and 10 microM Ca2+ (half time = 0.2 s) was less than that in the sarcoplasmic reticulum (SR) of rabbit skeletal muscle (half time = 0.1 s). The rate of EP decomposition at 0 degrees C after adding EGTA was about 6.7 times slower (rate constant: kd = 4.3 X 10(-3) s-1) than that of SR. It was suggested that adrenocortical microsomes contain a Ca2+ dependent ATPase which function as a Ca2+ pump with similar properties to that of SR.

Adenosine Diphosphate↗
PubMed1988

Disparate difference in preload reserve between myocardial hypertrophy due to essential hypertension and hypertrophic cardiomyopathy.

To investigate the left ventricular preload reserve in essential hypertensives, the legs-up procedure was performed and the data were compared with those in patients with non-obstructive hypertrophic cardiomyopathy and in normal subjects. Stroke volume index and the following systolic time intervals were measured before and after the legs-up procedure: left ventricular ejection time, pre-ejection period and the ratio of pre-ejection period to left ventricular ejection time (PEP/ET). No changes in blood pressure, heart rate or plasma catecholamine levels were noted before and after the legs-up procedure in all groups. A shortening in the pre-ejection period, a prolongation of ejection time, a decrease in the PEP/ET ratio and an increase in the stroke volume index were observed in essential hypertensives and in normal subjects. However, the changes in these parameters were not observed in patient with hypertrophic cardiomyopathy. The legs-up procedure is known to increase left ventricular end-diastolic volume. These results suggest that myocardial hypertrophy due to essential hypertension preserves the same preload reserve as in normals, but hypertrophic cardiomyopathy does not.

Blood Pressure↗