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Biomedical subjects

R Suzuki

Publications and source records attributed to R Suzuki.

At least 505 records · Page 28Linked to original sources
PubMed1991

Experimental lethal infection of Leptospira interrogans in mice treated with cyclophosphamide.

After preadministration of cyclophosphamide (300 mg/kg), BALB/c mice were lethally infected with Leptospira interrogans serovar lai and a virulent strain of Leptospira interrogans serovar copenhageni, and leptospiral cells were detected in both kidneys of infected mice by indirect immunofluorescent assay. Nonpathogenic leptospirae, Leptospira biflexa serovar patoc, Leptonema illini, and an avirulent strain of L. interrogans serovar copenhageni, were not parasitic to the mice treated with cyclophosphamide. The cyclophosphamide-treated mice were protected from the homologous leptospiral infection by passive immunization with anti-leptospiral monoclonal antibody or with rabbit antiserum and by active immunization with lyophilized organisms or with protective antigen. The results of active immunization in mice treated with cyclophosphamide agreed well with those in nontreated hamsters, which were sensitive to the organisms. Furthermore, these experiments were reproducible with any lot of cyclophosphamide used. These results indicated that cyclophosphamide-treated mice can be used in the experimental infection of Leptospira in place of hamsters or guinea pigs.

Animals↗
PubMed1991

Effects of parathyroid hormone-related protein on systemic and regional hemodynamics in conscious rats. A comparison with human parathyroid hormone.

PTHrp was discovered as a humoral hypercalcemic factor of malignancy and has been shown to bind the same receptor as PTH in rat bone cells, canine renal membranes, and rabbit renal microvessels. We investigated the global effect of human PTH(hPTH) and PTHrp on systemic and regional hemodynamics in conscious rats. The hypotensive response to PTHrp was more potent than that to hPTH. Although hPTH (15 micrograms/kg/min, i.v.) caused a significant increase in cardiac output, whereas PTHrp (5 micrograms/kg/min, i.v.) caused no change in cardiac output despite a similar hypotensive effect to hPTH, the effects of PTHrp and hPTHrp on regional hemodynamics were quite similar, and both peptides had a prominent vasodilatory effect on the coronary and hepatic arteries. Therefore, PTHrp appears to have an important role in blood pressure and regional hemodynamics as does hPTH.

Animals↗
PubMed1991

Erythromycin reduces the severity of bronchial hyperresponsiveness in asthma.

It has been demonstrated that bronchial hyperresponsiveness is a characteristic feature of bronchial asthma, and airway inflammation plays an important role in bronchial hyperresponsiveness. Erythromycin is an antibiotic extensively used worldwide which is also reported to have anti-inflammatory action. This study was designed to clarify whether erythromycin could favorably alter bronchial responsiveness in patients with bronchial asthma. To estimate bronchial responsiveness, histamine challenge was performed in 23 patients with bronchial asthma (atopic type, 11; nonatopic type, 12). All patients were treated for ten weeks with erythromycin, 200 mg three times daily, orally. After ten weeks' treatment, PC20, an index of bronchial sensitivity, was increased significantly. There was no difference between atopic and nonatopic patients in the improvement of PC20. It was concluded that erythromycin reduces the severity of bronchial responsiveness in patients with bronchial asthma.

Adult↗
PubMed1991

Effects of encephalo-duro-arterio-synangiosis on childhood moyamoya patients--swift disappearance of ischemic attacks and maintenance of mental capacity.

The effect of encephalo-duro-arterio-synangiosis (EDAS) upon chronic cerebrovascular ischemia in 65 pediatric moyamoya patients was evaluated by the postoperative interval before complete disappearance of ischemic attacks and changes in pre- and postoperative intelligence (IQ) or development quotients (DQ). The ischemic attacks disappeared after a mean period of 239 days, in three-fourths of patients within a year and in about one-fourth within the second year. This was very fast compared with the natural course of the disease. There was no significant difference in DQ/IQ before and after the operation. The mentally normal (IQ/DQ greater than or equal to 86) population in the postoperative patients was greater than in the natural course of the disease, although fewer in the preoperative group. This shows that EDAS delayed or prevented the deterioration in mental capacity usually present but often overlooked in the natural course of pediatric moyamoya disease.

Adolescent↗
PubMed1991

The medical evaluation of patients with diabetes mellitus in exercise therapy.

To investigate myocardial ischemia during exercise, submaximal exercise testing with electrocardiogram and thallium 201-myocardial scintigraphy was performed in non-insulin-dependent diabetics. The relationship between plasma atrial natriuretic polypeptide (ANP) levels in response to exercise and cardiac function assessed by echocardiography was also examined. The following results were obtained: 1) Twelve of the 66 diabetics (18.2%) had ischemic ST-segment changes in exercise ECGs, compared with 4 of 75 control subjects (5.3%)(p less than 0.05). Of the 12 diabetics with positive exercise ECGs, 10 were asymptomatic. 2) The washout rate in thallium-201 myocardial scintigraphy was significantly less in diabetics with positive exercise ECGs (36.5 +/- 4.1%) than in controls (51.9 +/- 2.8%)(p less than 0.05). 3) Although no difference in heart rate were observed between diabetics and controls, diabetic patients had significantly higher systolic blood pressure than controls during all stages of exercise and at maximal exertion. Rate pressure products in stages 1 and 2 were significantly higher in diabetics than in controls. 4) The increase of plasma ANP concentration during moderate exercise (VO2 max 60%) was significantly greater in diabetics than in controls (32.3 +/- 11.9 pg/ml vs. 15.0 +/- 1.7 pg/ml)(p less than 0.02). 5) There was a significant correlation between the increase in plasma ANP during exercise and the levels of left ventricular diastolic function (A/R:r = 0.504, p less than 0.05, IRT:r = 0.587, p less than 0.02), assessed by echocardiography, in diabetics. In conclusion, this study demonstrated that the frequency of asymptomatic myocardial ischemia during exercise was higher in diabetics than in controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Natriuretic Factor↗
PubMed1990

Protection by ethanol of cortical neurons from N-methyl-D-aspartate-induced neurotoxicity is associated with blocking calcium influx.

Effect of ethanol on N-methyl-D-aspartate (NMDA)-induced neurotoxicity in rat dissociated cortical cells (8-12 day cultures) was studied. Treatment of cells with NMDA (50 and 500 microM) for 15 min caused cytotoxic effects on the cells, as examined by microscopic observations and lactate dehydrogenase release from cells 18 h after the treatment. Ca2+ is essential for these effects in medium during treatment. Presence of ethanol (50-300 mM) simultaneously with NMDA protected cells from the cytotoxicity depending on the concentration of ethanol. Calcium accumulation in cells on addition of NMDA, as monitored by fluorescence ratio (F405/F485) of Indo-1-preloaded cortical cells, was also decreased depending on the concentration of added ethanol. APV (200 microM) and ketamine (100 microM) blocked both the cytotoxicity and cellular calcium accumulation due to NMDA. These results suggest that ethanol effects its protection of neurons from NMDA-induced cytotoxicity by blocking the receptor-mediated calcium influx.

2-Amino-5-phosphonovalerate↗
PubMed1990

The role of lipocortin I in macrophage-mediated immunosuppression in tumor-bearing mice.

The soluble mediators and/or mechanisms involved in immunosuppression in tumor-bearing hosts are not well characterized, although macrophages have long been recognized as major participants. We have investigated the role of lipocortin I, a phospholipid-binding protein, in macrophage-mediated immunosuppression in tumor-bearing mice. Proliferation of splenic lymphocytes in response to the mitogens (PHA, Con A, LPS, and PWM) was severely suppressed in tumor (Sqc-NH-1 carcinoma)-bearing mice. This immunosuppression was associated with a decrease in T and B lymphocytes and an increase in macrophages in these spleens. Mac-2+ macrophages were found only in spleens from tumor-bearing mice. Splenic macrophages from tumor-bearing, but not normal, mice were responsible for this immunosuppression, as revealed by negative and positive selection experiments. The levels of lipocortin I mRNA expression were markedly increased in peripheral blood cells from tumor-bearing mice as compared with those from normal mice. Lipocortin I mRNA was strongly induced in splenic mononuclear cells from tumor-bearing mice. Furthermore, these cells displayed increased expression of lipocortin I protein, as judged by Western blot analysis with polyclonal anti-lipocortin I serum. Some nonimmune organs such as the heart, submaxillary gland, muscle, and bladder also displayed increased levels of lipocortin I mRNA expression in tumor-bearing mice. Mac-2+ macrophages among the splenic mononuclear cells in tumor-bearing mice expressed lipocortin I mRNA, as judged by negative and positive selection experiments. Most of these Mac-2+ macrophages also had Mac-1 and Mac-3 Ag. Lipocortin I protein was increased in the serum of tumor-bearing mice as compared with normal mice. The culture supernatants of splenic cells from tumor-bearing mice suppressed the mitogenic responses of splenic cells from normal mice, and addition of anti-lipocortin I antiserum inhibited this suppression. Furthermore, recombinant mouse lipocortin I suppressed mitogenic responses of splenic cells from normal mice. In summary, Mac-2+ macrophage-derived lipocortin I was largely involved in immunosuppression in tumor-bearing mice.

Animals↗
PubMed1990

Inhibition of actomyosin subfragment 1 ATPase activity by analog peptides of the actin-binding site around the Cys(SH1) of myosin heavy chain.

The synthetic heptapeptide, Ile-Arg-Ile-Cys-Arg-Lsy-Gly-ethoxy, an analog of one of the actin binding sites on myosin head (S-site) (Suzuki, R., Nishi, N., Tokura, S., and Morita, F. (1987) J. Biol. Chem. 262, 11410-11412) was found to completely inhibit the acto-S-1 (myosin subfragment 1) ATPase activity. The effect of the heptapeptide on the binding ability of S-1 for F-actin was determined by an ultracentrifugal separation. Results indicated that the heptapeptide scarcely dissociated the acto-S-1 complex during the ATPase reaction. Consistent results were obtained from the acto-S-1 ATPase activities determined as a function of S-1 concentrations in the absence or presence of the heptapeptide at a fixed F-actin concentration. The heptapeptide reduced the maximum acto-S-1 ATPase activity without affecting the apparent dissociation constant of the acto-S-1 complex. The heptapeptide bound by a site on actin complementary to the S-site probably inhibits the activation of S-1 ATPase by F-actin. These results suggest that S-1 ATPase is necessary to rebind transiently with F-actin at the S-site in order to be activated by F-actin. This is consistent with the activation mechanism proposed assuming the two actin-binding sites on S-1 ATPase (Katoh, T., and Morita F. (1984) J. Biochem. (Tokyo) 96, 1223-1230).

Actins↗
PubMed1990

Trajectory formation of arm movement by cascade neural network model based on minimum torque-change criterion.

We proposed that the trajectory followed by human subject arms tended to minimize the time integral of the square of the rate of change of torque (Uno et al. 1987). This minimum torque-change model predicted and reproduced human multi-joint movement data quite well (Uno et al. 1989). Here, we propose a neural network model for trajectory formation based on the minimum torque-change criterion. Basic ideas of information representation and algorithm are (i) spatial representation of time, (ii) learning of forward dynamics and kinetics model and (iii) relaxation computation based on the acquired model. The model can resolve ill-posed inverse kinematics and inverse dynamics problems for redundant controlled object as well as ill-posed trajectory formation problems. By computer simulation, we show that the model can produce a multi-joint arm trajectory while avoiding obstacles or passing through viapoints.

Algorithms↗
PubMed1990

Mental outcome following encephaloduroarteriosynangiosis in children with moyamoya disease with the onset earlier than 5 years of age.

The mental prognosis of children with moyamoya disease, in whom the onset was when they were younger than 5 years of age, has been reported to be very poor. We studied the mental outcome of these patients after encephaloduroarteriosynangiosis (EDAS) in relation to the age at the onset of the disease and the age at operation. For patients in whom the onset of moyamoya disease occurs when they are younger than 2 years of age, the prognosis is very poor with regard to mental abilities even if they have an operation within a year after the onset. Slight hope remains if the operation is within 3 months of the onset. For patients in whom the disease begins when they are 2-5 years of age, EDAS performed before the age of 9 years may result in a good outcome with regard to mental ability, as well as resolution of the paroxysmal symptoms and cerebral revascularization.

Adolescent↗
PubMed1990

Oral dosage regimen in the nonlinear pharmacokinetics of sulphadimethoxine in pigs.

An oral high dosage regimen of sulphadimethoxine (SDM) was examined in pigs. The dose (50 mg/kg) in the therapeutic range, showed nonlinear pharmacokinetics, and administered by drench once a day for 4 days. The unbound plasma concentration-time profile was compared with that of the dosage regimen based on nonlinear pharmacokinetics, where a pharmacokinetic model and parameters were used except for the first order absorption rate constant (ka) and bioavailability (F). F and ka were obtained from oral and intravenous administration of 20 and 10 mg/kg of SDM. The unbound plasma concentration was observed almost within the setting range by the dosage regimen through the experimental period. This result suggested that the dosage regimen, based on the nonlinear pharmacokinetic model, resulted in an appropriate effect in the clinical use.

Absorption↗
PubMed1990

Roles of the amino acid side chains in the actin-binding S-site of myosin heavy chain.

The heptapeptide Ile-Arg-Ile-Cys-Arg-Lys-Gly-OEt is the analog of the S-site, one of the actin-binding sites in myosin [Suzuki et al. (1987) J. Biol. Chem. 262, 11410-11412]. Various substituted heptapeptides were synthesized, and the dissociation constants of each acto-heptapeptide complex was measured. Comparison of the dissociation constants indicated that the hydrophobic side chain of Ile-1 was critical for the binding with F-actin, but not that of Ile-3. The positive charge and the side chain length of Arg-2 were also important. The presence of a sulfur atom in the Cys-4 was also necessary. The affinity of the N-terminal Ile-Arg-Ile part for F-actin was influenced by the kind of residues in the C-terminal tetrapeptide part. Based on these results, the side chains of Ile(702), Arg(703), and Cys(SH1)(705) in myosin subfragment-1 heavy chain were assigned to be critical for the binding with F-actin. The amino acid sequence of S-1 heavy chain containing these critical residues for the S-site from residue number 700 to 717 can be predicted as an analogue of the segment B of the ATP-binding site [Walker et al. (1982) EMBO J. 1, 945-951]. The actin-binding S-site possibly shares a part of the ATP-binding site in myosin. We discuss the possibility that the S-site is an inhibitory site of myosin ATPase and the so-called actin-activation of myosin ATPase is a deinhibition induced by transient binding of F-actin to the S-site.

Actins↗
PubMed1990

Saccular aneurysms of the distal anterior cerebral artery.

We report a series of 42 consecutive patients with aneurysms of the distal anterior cerebral artery (ACA). Of these, 36 patients had one aneurysm, 5 had two aneurysms, and one had three aneurysms. Thirty patients had a ruptured distal ACA aneurysm; among these patients, the size of the aneurysm was less than 5 mm in diameter in 20, 6 to 10 mm in 7, and larger than 11 mm in 3. Eighteen patients (42.9%) had multiple aneurysms, and distal ACA aneurysms were responsible for a subarachnoid hemorrhage in 10. Thirty-four patients underwent direct surgery, and 30 of these had excellent outcomes 3 months after surgery. The treatment of patients with distal ACA aneurysms is often technically difficult, because of their broad neck configuration and the coexistence of other aneurysms. Nevertheless, the present study emphasizes that distal ACA aneurysms tend to bleed, irrespective of their size, and that excellent outcomes are obtainable by direct surgery.

Adult↗
PubMed1990

Protective activity of glycolipid antigen against infection by Leptospira interrogans serovar canicola.

A protective glycolipid antigen (PAg) was extracted from Leptospira interrogans serovar canicola with chloroform/methanol/water (1:2:0.8, by vol.) and partially purified by silica gel column chromatography. The PAg elicited a protective response in hamsters and in cyclophosphamide-treated mice subsequently challenged with homologous Leptospira. The PAg band was detected as a single smear-like band, corresponding to a protein of 23-30 kDa, by silver-staining in SDS-PAGE. In immunoblots, this band reacted with a monoclonal antibody, A5, which agglutinated serovar canicola and recognized a serovar-specific antigen. Furthermore, the PAg did not migrate on silica gel TLC, but was detected at the origin as a ninhydrin- and naphthol-positive spot. This suggests that PAg is a hydrophilic molecule with a carbohydrate chain that contains amino groups, possibly as amino sugars.

Animals↗
PubMed1990

Microlamellar structures in lobular glomerulonephritis associated with monoclonal IgG lambda paraproteinemia. A case report and review of the literature.

We report a 49-year-old woman who developed lobular glomerulonephritis with prevalent deposition of material positive for IgG, C1q and lambda light chain, but which was not stained by Congo red. Glomeruli revealed massive electron-dense deposits with a microlamellar structure in the mesangial matrix and peripheral capillary loops. Clinically, the patient had nephrotic syndrome, microhematuria and hypertension. No Bence-Jones protein or cryoglobulin was found in the urine or serum. Anti-DNA antibody was positive, but systemic lupus erythematosus (SLE) was ruled out by repeated serological examinations. Immunoelectrophoresis of blood and urine revealed increased IgG-lambda paraprotein, but no free light chains were found. We reviewed 54 cases reported in the literature, which showed organized crystalline structures on ultrastructural examination, but were unassociated with amyloidosis, SLE, cryoglobulinemia or multiple myeloma. The present patient is the first reported to have exhibited a combination of glomerulonephritis with organized deposits, monoclonal IgG lambda paraproteinemia, and the presence of anti-DNA antibody.

Female↗
PubMed1990

Electrophysiological effects of AFD-21 and AFD-19, new antiarrhythmic compounds on papillary muscles and single ventricular myocytes isolated from guinea-pig hearts.

1. The effects of AFD-21, a newly synthesized antiarrhythmic compound, and AFD-19, its active metabolite, on transmembrane action potentials were examined in right ventricular papillary muscles and single ventricular myocytes isolated from guinea-pig hearts. 2. In papillary muscles, AFD-21 10(-5) M caused a slight prolongation of action potential duration (APD), while AFD-19 above 10(-6) M shortened APD in a dose-dependent manner. 3. Both AFD-21 and AFD-19 above 10(-6) M caused a significant and dose-dependent decrease in the maximum upstroke velocity (Vmax) of the action potential without affecting the resting membrane potential. 4. In the presence of AFD-21 or AFD-19, trains of stimuli at rates greater than or equal to 0.2 Hz led to an exponential decline in Vmax. This use-dependent block was enhanced at higher stimulation frequencies. A time constant for the recovery of Vmax from the use-dependent block was 2.9 s for AFD-21 and 3.6s for AFD-19. 5. The curves relating membrane potential and Vmax were shifted by AFD-21 (10(-5) M), or AFD-19 (10(-5) M) to the direction of more negative potentials by 5.3 mV and 5.1 mV respectively. 6. In single ventricular myocytes treated with AFD-21 (10(-5) M) or AFD-19 (10(-5) M), Vmax of test action potentials preceded by conditioning clamp pulses to 0 mV was decreased progressively as the clamp pulse duration was prolonged. 7. These findings suggest that both AFD-21 and AFD-19 have use- and voltage-dependent inhibitory action on the sodium channel by binding to the channel during its inactivated state, and that the unbinding rate is comparable to that of Class I antiarrhythmic drugs with intermediate kinetics.

Action Potentials↗
PubMed1990

[Effects of anti-androgens on sexual function. Double-blind comparative studies on allylestrenol and chlormadinone acetate Part I: Nocturnal penile tumescence monitoring].

Allylestrenol (ALE) and chlormadinone acetate (CMA) were administered to patients with prostatomegaly by the double-blind method, and the effects of these antiandrogens on their sexual function were objectively compared. Each agent was orally administered to 58 patients in a dosage of 50 mg/day for 12 consecutive weeks. For the objective evaluation of the sexual function, nocturnal penil tumescence (NPT) was measured using an erectometer. For the subjective evaluation the conventional interview method was employed. The levels of hormones relating to sexual function were also determined. A decrease in NPT was noted in both the ALE and CMA groups, but the degree of the decrease was significantly smaller in the ALE group than in the CMA group (p less than 0.001). The results of the interview, revealed a large between the two drug groups; in the CMA group, marked worsening for all items. In the determination of hormones, levels of luteinizing hormone, follicle stimulating hormone, testosterone and estradiol were decreased in both drug groups, while the prolactin level was increased in both groups. The changes in the testosterone, estradiol and prolactin levels in the CMA group were significantly dominant compared with those in the ALE group. In addition, drop-out cases due to a decrease in the sexual function numbered 7 (12.1%) in the CMA group, while there were no such drop-out cases in the ALE group; the difference in the drop-out rate was thus significant. In conclusion, ALE's effects on the sexual function were concluded to be smaller than those of CMA.

Aged↗