Biomedical subjects

S Toyonaga

Publications and source records attributed to S Toyonaga.

11 recordsLinked to original sources

PubMed2000

Effects of cilostazol on heart rate and its variation in patients with atrial fibrillation associated with bradycardia.

BACKGROUND: Heart-rate (HR) variability is an important predictor of mortality in patients with heart disease. We examined the effects of cilostazol, a quinolinone derivative, on HR and HR variability in patients with chronic atrial fibrillation associated with bradycardia episodes. PATIENTS AND METHODS: Thirteen patients with chronic atrial fibrillation associated with bradycardia episodes (minimal HR <40/min and/or pauses, ie, episodes with an RR interval > 2.5 sec) received cilostazol (100 or 200 mg/day) orally for at least 2 months and 24-hour Holter electrocardiography was performed before and after the start of cilostazol administration. RESULTS: Minimal HR was significantly increased, by an average of 14 beats/min (bpm), at 3.3 +/- 0.8 weeks (mean +/- SD) after the start of cilostazol treatment. The number of pauses was significantly decreased. As a consequence, mean HR was increased by an average of 18 bpm. Maximal HR was also increased by an average of 19 bpm. The circadian variation of the HR, determined by cosine fitting, was not changed by cilostazol treatment. The time-domain HR variabilities, ie, the SD of the mean RR interval and the SD of the 5-minute mean RR intervals, were also unchanged. New York Heart Association functional class was significantly improved and the plasma atrial natriuretic polypeptide level was significantly decreased after the initiation of cilostazol treatment. CONCLUSION: Cilostazol improves the slow HR episodes associated with chronic atrial fibrillation and maintains the HR circadian variation and time-domain variability, indicating that cilostazol has therapeutic utility for the treatment of the slow HR associated with chronic atrial fibrillation.

Aged↗

PubMed1999

Early decrease of P-glycoprotein in the endothelium of the rat brain capillaries after moderate dose of irradiation.

In this study, we examined the degree of disruption of blood-brain barrier (BBB) in irradiated rat brains using P-glycoprotein, one of the functional molecules of BBB, as a marker. In the animal experiments, disruption of BBB has been mainly studied at the acute stage of brain edema caused by a lethal dose of irradiation. However, they do not mimic the clinical situation of radiotherapy for malignant brain tumors. Therefore, we examined effects of a clinically compatible dose of radiation on BBB. The rat hemisphere received a single application of 25 Gy of X-rays, and P-glycoprotein was analyzed 5 days later by immunohistochemistry and Western blotting. Immunoreactivity of P-glycoprotein was found to be strong in endothelial cells of the brain of the nonirradiated rat as well as in the nonirradiated hemisphere of the irradiated rat. In contrast, very weak or no immunoreactivity was observed in the majority of endothelial cells in the irradiated hemisphere. Western blotting quantitatively showed that P-glycoprotein in the irradiated hemisphere decreased to nearly 60% that of the controls. The present study indicated that even a clinically applicable dose of radiation causes early disruption of BBB in the rat model.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1998

Double-sector Lorenz plot scattering in an R-R interval analysis of patients with chronic atrial fibrillation: incidence and characteristics of vertices of the double-sector scattering.

Animal experiments have demonstrated that the minimum R-R interval during atrial fibrillation is proportional to the functional refractory period of the atrioventricular node. On Lorenz plots, atrial fibrillation is characterized by sector-shaped scattering; the vertex of the sector (ie, the minimum R-R interval) represents the functional refractory period. According to the atrioventricular nodal dual-pathway theory, it was hypothesized that the dual atrioventricular nodal pathways associated with chronic atrial fibrillation represent two vertices with two sectors. Detection of two-sector Lorenz plot scattering was attempted in 48 patients with chronic atrial fibrillation who underwent 24-hour ambulatory electrocardiography. Lorenz plot scattering was constructed by means of a computer. Two sectors, suggesting dual pathways, were detected in 19 (40%) of the 48 patients. The two vertices, located at 388 +/- 61 ms (mean +/- SD) and 580 +/- 60 ms were considered to represent the functional refractory periods of the fast and slow pathways, respectively. The vertex indicating the fast pathway showed greater circadian variation than that indicating the slow pathway. In one patient with dual-sector Lorenz plot scattering, whose atrial fibrillation spontaneously converted to sinus rhythm, an electrophysiologic study demonstrated dual atrioventricular nodal pathways. Thus, the Lorenz plot analysis identified two sectors, indicating the dual pathways, in approximately 40% of the patients with chronic atrial fibrillation, and the characteristics of the functional refractory periods of both pathways were estimated from the characteristics of the vertices. Although this study did not provide direct evidence of the dual atrioventricular nodal pathways, the analysis of Lorenz plot scattering may be clinically useful for studying the effects of drugs and/or ablation on the ventricular response in patients with atrial fibrillation based on the dual atrioventricular nodal pathway theory.

Aged↗

PubMed1997

A large right coronary artery-left ventricle fistula with mild volume overload on the left ventricle owing to its capacitive action--pulsed Doppler and cineangiographic analyses in a patient.

A 54-year-old woman was admitted to our hospital because of a heart murmur without subjective symptoms. Angiography disclosed an enlarged right coronary artery and flow drainage into the left ventricle, ie, a large right coronary artery-left ventricle fistula. Analysis of pulsed Doppler studies and cineangiograms indicated considerable capacitance of this fistula owing to Windkessel action, which attenuated volume overload on the left ventricle. The features in this case suggest that evaluation of fistula hemodynamics is important in determining the overload on the ventricle through the fistula.

Blood Flow Velocity↗

PubMed1997

Decremental oscillation curve fitting of heart rate response following face immersion into cold water.

Using 18 healthy volunteers, we attempted to fit the heart rate response to a decremental oscillation curve by the least-squares method following facial immersion into cold water. The decremental oscillation equation was as follows: HR = alpha.e(-betat) sin omegat + gamma, where HR is the instantaneous heart rate at t s, alpha the maximum amplitude of the decremental oscillation, beta the decremental rate, omega the angular velocity and gamma the basal heart rate. Each subject immersed his/her face fully in a basin filled with ice-cold water (4 degrees C) for 30 s. The heart rate response to facial immersion was significantly fitted to the decremental oscillation curve with a correlation coefficient > 0.75 in all the trials. Double trials with a 15-min intertrial interval did not show any significant change in the coefficients. Atropine sulfate decreased the value of coefficient omega and increased that of gamma but did not change alpha or beta, indicating that omega is determined mainly by parasympathetic tone. There were no differences for any coefficient between men and women. The coefficients beta and gamma increased in association with age. Given the significant fitting to the decremental oscillation curve of the heart rate response, we propose that the corresponding electrical circuit consists of a resistance and an inductor connected in series, with a condenser in a parallel circuit with a direct current impulse. This method of fitting with the corresponding electric circuit may be useful for analysis of the heart rate response to physiological stimulus.

Age Factors↗

PubMed1996

[The correlation of immunohistochemical expression of human manganase-superoxide dismutase and outcome of the patients with medulloblastomas].

There in no clear indicator for making a prognosis in patients with medulloblastoma. The effects of adjuvant therapy on the tumor are exerted through free radicals that emerge in the cytoplasm of tumor cells following chemotherapy and/or radiotherapy. Thus, free radical scavengers, such as superoxide dismutase (SOD), in tumor cells may antagonize the effects of adjuvant therapy. In order to determine whether there is a correlation between SOD levels and the prognosis of medulloblastoma patients, SOD expression in tumor tissue was investigated immunohistochemically in eleven cases of medulloblastoma by using a polyclonal antibody against human manganase SOD. Abundant SOD was expressed in the tumors of patients with poor outcomes whereas there was little SOD expression in patients with good outcomes. This suggests that resistance to adjuvant therapy depends on the level of SOD in tumor tissue. The effect of adjuvant therapy on medulloblastoma depends on the production of oxygen free radicals. Thus, if the tumor cells contain free radical scavengers, such a SOD, the effects of adjuvant therapy may be reduced. Measurement of SOD in tumor tissue is useful as a prognostic indicator in medulloblastoma.

Adolescent↗

PubMed1995

Syntaxin 1 (HPC-1) is associated with chromaffin granules.

Syntaxin 1 (HPC-1), a component of the receptor for SNAPs (soluble N-ethylmaleimide-sensitive factor attachment proteins), has been implicated in the docking and fusion of synaptic vesicles with the plasma membrane. It was reported that syntaxin 1 in rat brain and chromaffin cells (PC12) is exclusively located on the plasma membrane (Bennett, M. K., Calakos, N., and Scheller, R. H. (1992) Science 257, 255-259; Söllner, T., Bennett, M. K., Whiteheart, S. W., Scheller, R. H., and Rothman, J. E. (1993) Cell 75, 409-418). By means of biochemical and morphological analyses, we now show that syntaxin 1 is associated with chromaffin granules in the adrenal medulla. This finding raises the possibility that syntaxin 1 in chromaffin cells is a component of vesicle-SNAP receptor as well as one of target-SNAP receptor on the plasma membrane.

Adrenal Medulla↗

PubMed1995

Spontaneous rhabdomyosarcomas in aged Mastomys (Praomys coucha).

Two spontaneous tumours in the hind leg of 2 aged Mastomys were diagnosed as poorly differentiated rhabdomyosarcomas. In both cases, the neoplastic cells had no evidence of cross-striation, but had a positive reaction for muscle-specific proteins. This is the second report of rhabdomyosarcomas in Mastomys, and the first described in detail.

Animals↗

PubMed1994

Two isolectins from leaves of winged bean, Psophocarpus tetragonolobus (L.) DC.

Two isolectins were isolated from leaves of winged bean and characterized. They differed from each other in terms of their immunological properties, hemagglutinating activities, sugar inhibition patterns, and amino acid compositions. Both lectins were acidic and one of them (L-I), which was inactive toward trypsinized human type O erythrocytes, was similar to one of green shell lectins (WGS-1); which resembled basic seed lectin in its immunological properties. The amino-terminal sequence of L-I was homologous to that of WGS-1. The amino acid composition of L-I was similar to that of basic seed lectin, but the extent of the homology between amino-terminal sequences was low when L-I and basic seed lectin were compared. Examination by ELISA revealed that L-I and WGS-1 were distinct from the basic lectins of seeds and tuberous roots. L-I had a disulfide bridge between two subunits and it exhibited high hemagglutinating activity toward human type A erythrocytes, as compared to its activity toward other erythrocytes. By contrast, the properties of a second acidic lectin from winged bean leaves (L-II) were very similar to those of acidic lectins from seeds and tuberous roots, and the similarities extended as far as the immunological properties.

Amino Acid Sequence↗

PubMed1992

Cerebral paragonimiasis--report of five cases.

Five cases of cerebral paragonimiasis presenting with hemianopsia, convulsion, and gait disturbance are discussed. The cases were all in the chronic stage. The intradermal paragonimiasis reaction, complement fixation, and Ouchterlony tests were not useful for diagnosis. Computed tomography demonstrated calcifications in all cases in sites consistent with the foci of symptoms. Surgical treatment in two cases failed to improve symptoms.

Adult↗

PubMedDate not supplied

Relationship between body mass index and anti-hypertensive efficacy of doxazosin according to a survey of Japanese patients.

In this cross-sectional study, we surveyed a population of 101 hypertensive patients in Japan to determine the efficacy of the blood pressure lowering effect of alpha 1-blockers in relation to their body mass index (BMI). We found that doxazosin was frequently administered to obese hypertensive patients; many patients treated with doxazosin were taking concomitant medication. We also demonstrated that the higher the dose of doxazosin, the lower the ambulatory blood pressure measured in the out-patient clinic. Doxazosin showed a more favourable blood pressure lowering effect in patients with a higher BMI. These results suggest that anti-hypertensive drugs are useful when used in obese patients receiving multiple concomitant medications. These patients would normally be considered to show a poor response to anti-hypertensive treatment. Furthermore, we expect the alpha 1-blocker doxazosin to demonstrate a dose-dependent effect in obese patients with hypertension.

Adult↗