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Biomedical subjects

S Hosoda

Publications and source records attributed to S Hosoda.

At least 109 records · Page 6Linked to original sources
PubMed1994

Aftereffects of high-intensity DC stimulation on the electromechanical performance of ventricular muscle.

To clarify the mechanisms underlying cardiac dysfunction after electrical defibrillation, we investigated the effects of direct current field stimulation (10 ms, 1-80 V/cm) on isolated guinea pig papillary muscles. Shocks (S2) > 15 V/cm lowered the plateau height of the S2-induced action potential and inhibited its terminal repolarization. Subsequent responses to basic stimuli (S1, 1.0 Hz) for 1-3 min were characterized by a decrease in the maximum diastolic potential, a shortening of action potential duration, and an increase of the developed tension. With S2 > 30 V/cm, a marked delay in repolarization of the S2-induced action potential was followed by oscillation of membrane potential, resulting in repetitive spontaneous activity and often refractoriness to S1 stimulation. The aftereffects were independent of the phase of S2 application. Most of the aftereffects were preserved in the presence of nifedipine (1 microM) or ryanodine (1 microM). Only sodium channel blockade by tetrodotoxin (10 microM) modified the aftereffects by depressing the generation of spontaneous activity. These findings suggest that strong shocks (> 15 V/cm) will produce abnormal arrhythmogenic responses probably through a transient rupture of sarcolemmal membrane (electroporation) leading to a disturbance of the ionic equilibrium of the myocyte.

Animals↗
PubMed1994

A simple method for predicting the cyclosporin A erythrocyte-to-plasma distribution ratio in blood, and its clinical assessment.

To adapt the monitoring of cyclosporin A (CyA) to clinical practice, we have developed a model to predict the CyA erythrocyte-to-plasma distribution ratio (CyA-EP), and evaluated its utility in clinical practice. We monitored CyA trough concentrations in whole blood and performed a series of biochemical tests during disease states in patients undergoing immunosuppressive therapy with CyA after transplantation. An estimate of CyA-EP (EPpr) was thus given by the following equation: EPpr = 6.0831 - 0.2944 x (TG+CHO) - 0.0037 x (CyAblood) - 0.0553 x (HCT) + 0.0463 x (BW) + 0.4447 x (CRE) - 0.0366 x (AGE). In this predictive model, EPpr is given as a function of the plasma lipid levels (TG+CHO, mM), the CyA concentration in whole blood (CyAblood, ng/ml), and the hematocrit (HCT, %), as well as the patient's body weight (BW, kg), serum creatinine (CRE, mg/dl) and age (AGE, years). The parameters TG+CHO, CyAblood, HCT, and AGE were negatively correlated with the CyA-EP, whereas BW and CRE exhibited a positive correlation. The predictive performance of this model was satisfactory for clinical use and changes in CyA-EP in transplant patients were obtained from monitoring CyA in whole blood and routine biochemical tests, without directly measuring CyA-EP. Since CyA-EP is an useful indicator for predicting a shift of CyA into tissues and its systemic clearance in plasma, our model to predict the CyA-EP will help the physician select a CyA regimen during immunosuppressive therapy in a variety of disease states after transplantation.

Adult↗
PubMed1994

Improvement of regional wall motion in medically treated myocardial infarction with single-vessel coronary artery disease.

Long-term changes in regional wall motion (RWM) following acute myocardial infarction (AMI) in 42 patients with uncomplicated single-vessel disease were examined retrospectively by repeat cardiac catheterizations. The first and second cardiac catheterizations were performed at an average of 28 days and 6.6 years after the onset of AMI, respectively. All 42 patients underwent first and second cardiac catheterizations without undergoing coronary artery bypass surgery or coronary angioplasty. Regional left ventricular functions were analyzed by the centerline method using a right anterior oblique left ventriculogram. The wall motion abnormality score (WMAS) was defined as [# chord below -2SD] x [mean SD chord below -2SD]. The improvement in the WMAS was more prominent in cases with an occluded infarct-related artery. Thus, we concluded that 1) RWM improves significantly with medical treatment in long-term follow-up in cases of uncomplicated AMI with single-vessel disease, and 2) the improvement of RWM is completed within the first few weeks after AMI in cases with a patent infarct-related artery.

Adult↗
PubMed1994

[Evaluation of gastric motility using vector analysis of electrogastrography].

The validity of amplitude analysis was studied by means of vector analysis of cutaneous electrogastrography (EGG) recorded from two sets of bipolar electrodes placed at the upper abdomen. In a basic study on the dog, it was found that the vector locus area obtained by vector analysis of EGG expresses contractile activity in the stomach, and that the extreme ellipsoid's long axis of EGG corresponds well to the electrical axis of the stomach. In a clinical study on the healthy male volunteers, vector analysis of EGG in response to gastroprokinetic and cold stress showed potential utility. In summary, vector analysis of cutaneous EGG enables the measurement of gastric motor activity and the location of electrical axis, and is valuable in the evaluation of gastric motor activity together with the analysis of EGG frequency. In is concluded that cutaneous EGG is a simple, and clinically relevant technique for the measurement of functional abnormalities of the stomach.

Action Potentials↗
PubMed1994

Differential fibrotic stromal responses of host tissue to low- and high-metastatic cloned Lewis lung carcinoma cells.

BACKGROUND: The relationship between host stromal responses and tumor invasion and metastasis is poorly understood. To gain new insights into this relationship, we compared the stromal response in tumor tissues formed by low- and high-metastatic murine lung carcinoma cell lines. EXPERIMENTAL DESIGN: Mouse Lewis-lung-carcinoma-derived cloned cell lines with different metastatic potentials (P29, LM12-3, and LM60-D6 cells with low-, medium-, and high-metastatic potentials, respectively) were subcutaneously injected, and the resultant tumor tissue was analyzed immunohistochemically for the localization of type I collagen, fibronectin, and tenascin, and biochemically for the levels of glycosaminoglycans. The activities of conditioned media of cultured tumor cells to stimulate DNA synthesis in BALB/c 3T3 cells in vitro were also examined. RESULTS: In the subcutaneous low-metastatic P29 tumor, fibrillar extracellular matrices and fibroblast-like cells surrounding tumor cells were stained strongly for type I collagen, fibronectin, and tenascin, but only weakly stained in the more highly metastatic LM12-3 and LM60-D6 tumors. Implantation of these cell lines into cerebrum, which does not normally contain interstitial stroma, gave same results. Morphometric analysis of the subcutaneous tumor tissues revealed significantly more fibroblast-like cells and mast cells in the P29 tumor than in the more highly metastatic tumors. Quantitative analysis of glycosaminoglycans present in tumor tissues showed that the hyaluronic acid content of the P29 tumor was more than 5 times that in the more highly metastatic tumors. Furthermore, serum-free conditioned medium prepared from the culture of P29 cells exhibited about 10 times higher mitogenic activity toward BALB/c 3T3 cells than the conditioned medium from the more highly metastatic cells. CONCLUSIONS: We found an inverse relationship between the host stromal response and spontaneous lung metastasis. The stromal response in the P29 tumor may be induced directly by tumor cells and/or indirectly via mast cell activation. This metastasis model should be useful in understanding the role of stromal response in tumor metastasis.

Animals↗
PubMed1994

[Effects of 16,16-dimethyl prostaglandin E2 on pancreatic exocrine function in vivo and in vitro in rat experiments].

The effects of exogenous and endogenous prostaglandin on rat pancreatic exocrine function were investigated in vivo and in vitro. Under stimulation by endogenous CCK or exogenous caerulein, protein output was significantly reduced by intravenous drip infusion of 16,16-dimethyl prostaglandin E2 (DMPGE2), and under stimulation by exogenous secretin, volume and bicarbonate output were markedly reduced by DMPGE2. Amylase release from isolated pancreatic acini was significantly reduced by DMPGE2 under stimulation by 10(-11)-3 x 10(-11) M CCK-8, and was not influenced by DMPGE2 under stimulation by secretin or by indomethacin under stimulation by caerulein. Basal amylase release was not influenced by DMPGE2 or indomethacin. Basal cellular cyclic AMP and cyclic GMP contents were not influenced by DMPGE2, and elevated cyclic GMP content under stimulation by caerulein was significantly reduced by DMPGE2. These findings suggest that pancreatic enzyme secretion is reduced by DMPGE2 under stimulation by physiological or pharmacological concentration of CCK, and one of which mechanism is direct effect of DMPGE2 on pancreatic acini, may be coupling with phosphatidylinositol breakdown system and without cyclic AMP.

16,16-Dimethylprostaglandin E2↗