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Biomedical subjects

M Murase

Publications and source records attributed to M Murase.

At least 181 records · Page 10Linked to original sources
PubMed1986

Evaluation by pulsed Doppler echocardiography of the atrial contribution to left ventricular filling in patients with DDD pacemakers.

To evaluate the significance of the left atrial (LA) contribution to left ventricular (LV) filling in cardiac pacing, LV inflow velocity was recorded with pulsed Doppler echocardiography in 20 patients with a DDD pacemaker. The pacemaker was programmed to atrioventricular (AV) sequential pacing with AV intervals of 50, 100, 150, 200 and 250 ms, and then to VVI pacing at a fixed rate of 70 beats/min. To evaluate the relative changes of LV filling volume in individual patients, the percent change in time-velocity integral of LV inflow velocity in each pacing mode was calculated as the ratio to that of AV sequential pacing with an AV interval of 150 ms. To estimate the degree of LA contribution to LV filling, the ratio of time-velocity integral during LA ejection phase to that during total LV filling phase was measured at the optimal AV interval. The percent LV inflow volume in AV sequential pacing was 74% for an AV interval of 50 ms, 87% for 100 ms, 98% for 200 ms and 90% for 250 ms. The percent LV inflow volume in VVI pacing was 72%. The percent LV inflow volume at AV intervals of 150 ms was significantly greater than that at an AV interval of 50, 100 and 250 ms, and in VVI pacing (p less than 0.05). The degree of LA contribution to LV filling showed a positive correlation with the percent increase of LV inflow volume with mode conversion from VVI to AV sequential pacing (p less than 0.005) and also with age (p less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

A model of flagellar movement based on cooperative dynamics of dynein-tubulin cross-bridges.

A theoretical model based on molecular mechanisms of both dynein cross-bridges and radial spokes is used to study bend propagation by eukaryotic flagella. Though nine outer doublets are arranged within an axoneme, a simplified model with four doublets is constructed on the assumption that cross-bridges between two of the four doublets are opposed to those between the other two, corresponding to the geometric array of cross-bridges on the 6-9 and the 1-4 doublets in the axoneme. We also assume that external viscosity is zero, whereas internal viscosity is non-zero in order to reduce numerical complexity. For demonstrating flagellar movement, computer simulations are available by dividing a long flagellum into many straight segments. Considering the fact that dynein cross-bridge spacing is almost equal to attachment site spacing, we may use a localized cross-bridge distribution along attachment sites in each straight segment. Dynamics of cross-bridges are determined by a three-state model, and effects of radial spokes are represented by a periodic mechanical potential whose periodicity is considered to be a stroke distance of the radial spoke. First of all, we examine the model of a short segment to know basic properties of the system. Changing parameters relating to "activation" of cross-bridges, our model demonstrates various phenomena; for example "excitable properties with threshold phenomena" and "limit cycle oscillation". Here, "activation" and "inactivation" (i.e. switching mechanisms) between a pair of oppositely-directed cross-bridges are essential for generation of excitable or oscillatory properties. Next, the model for a flagellar segment is incorporated into a flagellum with a whole length to show bending movement. When excitable properties of cross-bridges, not oscillatory properties, are provided along the length of the flagellum and elastic links between filaments are presented at the base, then our model can demonstrate self-organization of bending waves as well as wave propagation without special feedback control by the curvature of the flagellum. Here, "cooperative interaction" between adjacent short segments, based on "cooperative dynamics" of cross-bridges, is important for wave propagation.

Adenosine Triphosphatases↗
PubMed1986

A three-state model for oscillation in muscle: sinusoidal analysis.

The crossbridge mechanism leading to oscillation in insect flight muscle is studied theoretically based on a three-state model proposed by Nishiyama et al. [Biochim. biophys. Acta 460, 523-36 (1977)]. Skeletal muscle as well as insect flight muscle shows. oscillatory contraction. We demonstrate this oscillatory contraction in muscle by choosing proper rate constants among the three states of the model. It is established that our model gives out not only Hill's force-velocity relation but also other mechanical properties of skeletal muscle. The model is then compared with two types of experiment by Kawai & Brandt [J. Musc. Res. Cell Motility 1, 279-303 (1980)] and by Steiger & Rüegg [Pflügers Arch. 307, 1-21 (1969)]. Kawai & Brandt obtained the Nyquist plot showing the relation between the phase shift and the amplitude of tension change in response to sinusoidal length changes at various frequencies. Steiger & Rüegg studied the power output and ATPase activity at various frequencies of the length change. Our theoretical results are in good agreement with the results of these two experiments. To determine the crossbridge mechanism which produces the positive power output, spatio-temporal crossbridge distributions in the three states are calculated. It is shown that, after the stretching phase of sinusoidal change in muscle length, the delayed rise of tension is caused by attachment of crossbridges to the active state via the preactive state while the delayed fall is caused by detachment from the active state after release. To obtain the oscillatory property it is not necessary to assume that stretch in muscle length increases the attaching rate as originally proposed by Thorson & White [Biophys. J. 9, 360-90 (1969)].

Animals↗
PubMed1986

Effects of castration and testosterone administration on serum lipoproteins and their apoproteins in male spontaneously hypertensive rat.

Serum triglyceride and very low density lipoprotein (VLDL) concentrations were higher in male spontaneously hypertensive rat than in male control Wistar Kyoto rat, whereas serum cholesterol, phospholipids, and high density lipoprotein (HDL) concentrations were lower. Castration of hypertensive rats induced an increase in serum cholesterol, phospholipids, and HDL, and a decrease in serum triglyceride and VLDL. The cholesterol content of HDL increased, whereas the triglycerides decreased after gonadectomy of hypertensive rats. These changes in serum lipids and lipoproteins could be reversed by the administration of testosterone. Apolipoprotein E contents in VLDL and HDL of hypertensive rats were low when compared with control rats but rose after castration and could be reduced by testosterone administration. Hypertensive rats accumulated triglycerides and cholesterol in the liver, which resulted in an increase of liver weight. Castration reduced the hepatic lipids as well as liver weight. The effects of castration and testosterone treatment on lipids and lipoproteins were more prominent in spontaneously hypertensive rats than in control rats. These results suggest that testosterone reduces VLDL catabolism which is related to changes of apolipoprotein composition, and that hypertensive rats are more sensitive to testosterone than control rats.

Animals↗
PubMed1986

Long term results of mitral commissurotomy.

This study aims to evaluate the different surgical procedures used in 358 patients undergoing mitral commissurotomy. 89 patients underwent closed mitral commissurotomy by finger fracture (CMCF) and 162 by transventricular dilator (CMCD). 107 patients underwent open mitral commissurotomy (OMC). The following conclusions can be made: Commissurotomy is one of the better palliative procedures for mitral stenosis (MS). It is logical to continue the use of CMCD for selected patients with MS. A careful follow-up study of patients with mitral commissurotomy is necessary, and reoperation should be carried out positively when indicated. It has been confirmed in the survey that 7 patients out of 358 succumbed to sudden death. It is one of the goals of future work to determine the causes of sudden death and to develop an effective method of prevention. It can be expected that a patient with MS who undergoes a flawless operation at the right time will survive and recover full strength.

Actuarial Analysis↗
PubMed1986

[A ruptured cerebral aneurysm of the fronto-orbital artery and a coexisting anastomosis with the anterior ethmoidal artery--a case report].

The authors present a case with a ruptured saccular aneurysm of the left fronto-orbital artery and the coexisting anastomosis with the left anterior ethmoidal artery, accompanied by subarachnoid hemorrhage and intracerebral hematoma in the left frontal lobe. A 44-year-old male, whose past history had been uneventful, was admitted complaining severe headache and vomiting, followed by confusion. CT examinations revealed subarachnoid hemorrhage and intracerebral hematoma in the left frontal lobe. Left carotid angiograms disclosed a saccular aneurysm described above. Emergency operation in a state of grade 3 according to Hunt and Kosnik revealed a saccular aneurysm and its parent artery which was thought to be proximally a left fronto-orbital artery and distally a left anterior ethmoidal artery, which was seen to penetrate the anterior cranial fossa at the lamina cribrosa. Then the aneurysm was excised following clipping of the neck. Thereafter, the patient showed favorable recovery. The histological examination revealed absence of the media and the internal elastic lamina in the wall of the aneurysm with slight infiltration of round cells. Generally speaking, distal anterior cerebral artery aneurysms, which arise on branches beyond the anterior communicating artery, occupy 2-5% of all cerebral aneurysms, and most of them are found at the branching site of the pericallosal artery. As far as the authors know, there was few or no report referring to the aneurysm arising on the fronto-orbital artery, as shown in this case. Also, as for the aneurysm arising on the anterior ethmoidal artery, there are a few reports.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

[Fundamental and clinical studies on cefixime in pediatric field].

Cefixime (CFIX) was evaluated for pharmacokinetics, therapeutic effectiveness on infection, safety, and bacteriological effectiveness in pediatrics. The following is a summary of the results. Pharmacokinetics in 4 children, 2 each receiving a single dose of 1.5 mg or 6.0 mg per kg body weight, were examined. Peak serum CFIX concentrations after the dose of 1.5 mg/kg were 1.12 and 1.34 micrograms/ml, and the serum half-lives were 1.83 and 3.53 hours. For the children administered with 6.0 mg/kg of CFIX, the respective figures were 2.50 and 7.46 micrograms/ml, and 6.77 and 6.64 hours. The 12-hour urinary recoveries were 4.9 and 34.1% and 9.4 and 25.4% for the small and the large doses, respectively. Therapeutic effectiveness in 19 children with infections was "excellent" in 14 and "good" in 5, with an effectiveness rate of 100%. Bacteriological effectiveness was evaluated in 10 children. Classified by causative organisms, 5 cases had H. influenzae, 2 each H. parainfluenzae and S. pyogenes, and 1 mixed infection by H. influenzae and S. pneumoniae. Only the H. influenzae in the child with mixed infection resisted the therapy, and all the other pathogens were successfully eradicated. No side effects were recorded. The only abnormal laboratory test finding attributed to CFIX was eosinophilia in 2 children.

Acute Disease↗
PubMed1985

Aging changes of riboflavin concentration and glutathione reductase activity in erythrocytes.

Aged erythrocytes obtained by fractionation using gradient centrifugation with Dextran 40, showed lower glutathione reductase activity and riboflavin content than young cells. However, both young and old cells displayed almost the same increase in enzyme activity upon addition of flavin adenine dinucleotide to the test hemolysate in vitro. The lipid peroxide content in the cell membranes showed no consistent changes with aging.

Centrifugation, Density Gradient↗
PubMed1985

Problems of artificial pacemaker therapy.

Four hundred and sixty-seven cases with implantation of an artificial pacemaker were studied. The postoperative survival rate was 63% for 15 years. Seventy-two percent of type III patients of the sick sinus syndrome were free from postoperative thromboembolism and the lowest of the three types of the sick sinus syndrome. Comparing postoperative physical activity, cardiothoracic ratio and exercise tolerance time, physiological pacing was superior to ventricular pacing in hemodynamic effects and clinical symptoms. In a hundred cases of physiological pacing, complications and problems of physiological pacing were discussed. Atrial sensing failure and over-sensing were observed in seven and two cases respectively. A low amplitude of atrial potential and use of unipolar atrial leads were considered to be the main causes of these complications. Bipolar lead should be used as the atrial lead to avoid such complications, because the atrial potential by bipolar leads is not less than that by unipolar leads. Atrial sensing may be more sensitive without electromagnetic interference. The fixed A-V delay time whenever the atrium is sensed or paced, often results in a ventricular fusion beat and hemodynamic change on every beat, according to the interval of atrial and ventricular contractions. The A-V delay time should be changed in accordance with atrial sensing or pacing.

Cardiac Pacing, Artificial↗
PubMed1985

[Serum and prostatic tissue concentration of ceftizoxime (CZX) after intravenous administration in cases of benign prostatic hypertrophy].

One gram of ceftizoxime (CZX) was administrated before transurethral resection in 38 cases of benign prostatic hypertrophy. Then the serum and tissue concentration of CZX was measured, and compared with the sensitivity of CZX to the bacteria separated from the urine of inpatients. The concentration of CZX in prostatic tissue was higher than the MIC80 for E. coli for 16.7 hr, for Klebsiella for 18.7 hr, for Proteus for 14.7 hr and for Serratia for 8.86 hr. Therefore, CZX was considered to be an effective drug against bacterial prostatitis.

Aged↗