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Biomedical subjects

K Nishimura

Publications and source records attributed to K Nishimura.

At least 1,405 records · Page 78Linked to original sources
PubMedDate not supplied

Cardiohemodynamic effect of a novel calcium antagonist, SD-3211, in the dog.

The cardiohemodynamic effects of SD-3211, a calcium antagonist possessing a unique structure, were studied in anesthetized open-chest dogs and in conscious dogs. SD-3211 (10-300 micrograms/kg, i.v.) increased coronary and vertebral artery blood flow dose-dependently while lowering blood pressure, indicating a vasodilatation of these arteries. SD-3211 caused a significant increase in heart rate at 10-100 micrograms/kg, but a significant decrease at 300 micrograms/kg. Left ventricular dp dtmax was dose-dependently decreased at the dose range examined, and the change was significant at 300 micrograms/kg. When compared with the cardiohemodynamic effects of diltiazem (10 300 micrograms/kg, i.v.) and nicardipine (1-30 micrograms/kg, i.v.), the selectivity of SD-3211 with regard to vasodilatation as compared to cardiac depression, manifested by a reduction in heart rate and myocardial contractility, was greater than that of diltiazem, but less than that of nicardipine. Furthermore, a comparative study of the effects of orally administered SD-3211 and diltiazem on blood pressure and atrioventricular conduction in conscious, normotensive dogs, demonstrated that SD-3211 had a more potent and long-lasting hypotensive effect, but a much weaker effect on atrioventricular conduction prolongation than diltiazem. Thus, these in vivo cardiohemodynamic studies show that SD-3211 possesses a tissue-selectivity for vasculature, respectively cardiac tissues, which is intermediate between diltiazem and nicardipine.

Anesthesia↗
PubMedDate not supplied

A comparison of swine abdominal temperature distribution after heating with BSD-1000, an annular phased array system (APAS), and Thermotron RF-8.

External hyperthermia for deep-seated tumors is still a difficult problem. We compared the abdominal temperature distribution in a pig after heating with BSD-1000, an annular phased array system (APAS), and Thermotron RF-8. Thirty elastic tubes were inserted into the upper abdomen of the pig and a thermocouple was inserted into each of the tubes. After heating, these thermocouples were moved at 1-cm intervals and the three-dimensional temperature distribution was obtained. The temperature distribution after heating with APAS and Thermotron RF-8 was compared by using the distribution on the longitudinal center line of each sagittal plane at 1-cm intervals from the center. The temperature was much higher and its distribution more homogeneous with APAS than Thermotron RF-8.

Abdomen↗
PubMedDate not supplied

Effect of a leukocyte-platelet removal filter on ischemia induced reperfusion injury.

The effect of leukocyte and platelet depletion on reperfusion injury using a leukocyte-platelet removal filter (LRF) in intracoronary thrombolysis is reported. To better define the usefulness of LRF in evaluating the effectiveness of intracoronary thrombolysis with this device, several cardiovascular variables were examined in rabbits during ischemia followed by reperfusion. The rabbits underwent cytoapheresis with LRF (n = 5) and were compared with controls without LRF (n = 5). LRF was composed of a nonwoven polyester fabric (1.8 microns, 4.6 gm). Removal of leukocytes and platelets by LRF was 98% for both. A period of 30 min equilibration was allowed before any experimental intervention, at which time the diagonal artery was occluded for 20 min and then reperfused. All arrhythmias were defined and quantified in accordance with the Lambeth Convention. Regional wall thickening was examined by a pulsed Doppler dimension system. No significant differences were observed in hemodynamic variables between the two groups; however, rabbits treated with a LRF demonstrated greater regional wall thickening (LRF group: 17 +/- 0.9%, control group: 11 +/- 0.3%, p less than 0.01), as well as significant improvement in the frequency of ventricular arrhythmias (LRF group: 12.5%, control group: 47.2%, p less than 0.01). The data suggest that LRF may help prevent arrhythmias, and preserve left ventricular contraction, during and after intracoronary thrombolysis.

Animals↗
PubMedDate not supplied

Isolated interruption of the aortic arch.

We report a case of a 4-year-old girl with interruption of the aortic arch without a patent ductus arteriosus or intracardiac shunts. The anomaly was successfully corrected with the use of a 14 mm Dacron prosthetic graft to bypass the interrupted segment. The postoperative course was uneventful.

Aorta, Thoracic↗
PubMedDate not supplied

Spinocerebellar degeneration: qualitative and quantitative MR analysis of atrophy.

Magnetic resonance imaging at 1.5 T was performed in 27 patients with either the cerebellar or spinocerebellar form of spinocerebellar degeneration and in 10 control subjects. Neither T1- nor T2-weighted images (T1WIs and T2WIs) of the patients showed any abnormal intensity areas within the cerebellum or in any other structures of the brain. The T2WIs delineated normal configurations of symmetrical dentate and red nuclei. On T1WIs two patterns of atrophy were detected: (a) moderate to severe shrinkage of the basis pontis and the middle cerebellar peduncles associated with atrophy of the cerebellum, and (b) moderate atrophy of the cerebellum with a preserved basis pontis. The former morphological changes are consistent with the pathology of pontocerebellar atrophy (PCA) and the latter with those of cerebellar cortical degeneration (CCD). In 11 patients, only after a quantitative analysis of the images were we able to classify them in one of the two morphological categories (PCA or CCD). There was a significant correlation between atrophy of the cerebellum and atrophy of the basis pontis. Furthermore, in the PCA group the anterior portion of the body of the corpus callosum was significantly smaller in comparison with the control subjects.

Adult↗
PubMedDate not supplied

Posterior lobe of the pituitary: identification by lack of chemical shift artifact in MR imaging.

The posterior aspect of the normal sellar content usually displays high intensity signal on T1-weighted images. The shape, size, and location of this high intensity seem to be compatible with the posterior lobe of the pituitary gland. But fatty tissues such as intrasellar fat pad or fatty marrow of the dorsum sellae or both must be excluded as other possible sources of this high intensity signal. Two sellar phantoms were prepared. Both included high intensity posterior parts, one due to high concentration of a paramagnetic ion and the other due to fat. Magnetic resonance imaging of these phantoms showed that the fatty component was accompanied by distinct chemical shift artifacts in a predictable way. The absence of chemical shift artifact in the sellar content of normal volunteers excluded the fatty tissue as representing the high intensity posterior part. The high intensity posterior part of the normal sellar content appears to represent the posterior lobe of the pituitary gland.

Adipose Tissue↗
PubMedDate not supplied

A human isolate of Exophiala (Wangiella) dermatitidis forming a catenate synanamorph that links the genera Exophiala and Cladophialophora.

A strain of the black yeast Exophiala dermatitidis displayed a hydrophobic synanamorph consisting of acropetal chains of lemon-shaped conidia, morphologically similar to those of Cladophialophora bantiana. The occurrence of the two conidial types in a single strain suggests a taxonomic affinity between Exophiala and Cladophialophora and provides support to the supposition that Cladophialophora, a possible anamorph genus of Herpotrichiellaceae, is related to black yeasts rather than to Cladosporium, which has teleomorphs in the Mycosphaerellaceae.

Exophiala↗
PubMedDate not supplied

A magnetically suspended centrifugal pump. In vitro and in vivo assessment.

To overcome problems derived from the shaft within conventional centrifugal pumps, we have developed a new centrifugal pump, the magnetically suspended centrifugal pump (MSCP), which has no shaft and operates as a bearingless centrifugal pump. The impeller is suspended freely and centrally by magnetic force within the pump. Hemolysis tests were performed in comparison with the Biopump. Index of hemolysis and destruction of platelets were significantly lower in the MSCP than in the Biopump. Animal studies were designed to evaluate the durability and antithrombogenicity of the MSCP. Short-term animal studies were performed using two mongrel dogs. Left heart bypass was established with the MSCP. After 3 hr, the layer of thrombus adherent to the surface of the polycarbonate impeller impaired pumping efficiency. However, using the impeller coated with silicone, no thrombus was observed on the impeller after continuous pumping for 24 hr. In addition, long-term animal studies were performed using two sheep. Left heart bypass was established with the MSCP containing an impeller coated with silicone. In one sheep, the MSCP ran for 14 days without problems in pumping performance and showed no thrombus within the pump. In the other sheep, the MSCP ran for 15 days, and showed no thrombus on the impeller. During each experiment, plasma free hemoglobin levels were less than 15 mg/dl. The MSCP induced less hemolysis than did the Biopump, and the MSCP containing an impeller coated with silicone demonstrated the potential to run for 14 days without thrombus formation within the pump.

Animals↗
PubMedDate not supplied

Mitochondrial DNA analysis of Sporothrix schenckii in Costa Rica.

Mitochondrial DNA (mtDNA) types using restriction patterns with HaeIII were investigated in 21 clinical isolates of Sporothrix schenckii in Costa Rica. Nineteen isolates were found to be a new mtDNA type (Type 14), while the remaining two were Type 3 and Type 6. Based on the phylogeny of 14 mtDNA types constructed by estimating sequence divergences of mtDNA, S. schenckii were clustered into two main groups: Group A and Group B, with Type 14 and Type 3 included in Group A, and Type 6 in Group B. The results suggest that isolates of Group A may exist mainly in Central America including Costa Rica.

Costa Rica↗
PubMedDate not supplied

Development of a magnetically suspended centrifugal pump as a cardiac assist device for long-term application.

To overcome problems with the shaft seal in conventional centrifugal pumps, the authors have been developing a magnetically suspended centrifugal pump (MSCP) that operates as a valveless, sealless, and bearingless pump. The prototype of the MSCP was modified with respect to size of the volute diffuser and impeller blade profiles. A hemolysis test in vitro using a new version of the MSCP was performed in comparison with a commercially available centrifugal pump. The test circuit for the hemolysis test comprised a blood reservoir, a pump, and polyvinyl tubes, and was filled with fresh heparinized bovine blood. The pumping conditions were a flow rate of 5 L/min and a pump head afterload of 100 mmHg. The index of hemolysis in the MSCP was significantly lower than that in the Biomedicus pump (0.0035 +/- 0.0025 versus 0.0097 +/- 0.0056 g/100 L, p < 0.05). Reduction in the platelet count during pumping also was lower in the MSCP compared with the Biomedicus pump at both 6 hrs and 12 hrs of pumping (p < 0.01). This MSCP may be advantageous for extended use of assist devices, not only from the theoretical point of view, but in a practical sense after the results of the current hemolysis test.

Centrifugation↗
PubMedDate not supplied

Determination of ploidy in Cryptococcus neoformans by flow cytometry.

We determined the ploidy of Cryptococcus neoformans (28 strains) isolated from patients and nature. The cellular DNA content of these strains, which stained with propidium iodide in comparison to that of two authentic haploid strains, was determined by flow cytometry. All the strains exhibited diphasic histograms. In case of the authentic haploid strains, the first peak was centred around channel 9, and the second peak around channel 18. Most strains exhibited this type of histogram. Some strains exhibited another type of histogram: the first peak was centred around channel 18, and the second one around channel 35. In flow cytometry, the channel number is correlated with the intensity of fluorescence, namely, in proportion to the channel number the DNA content in the cells increases. The cellular DNA content of the second type of histograms showed twice that of the authentic haploid strains, and thus, five of 28 isolates were concluded to be diploid, and the others haploid.

Cryptococcosis↗
PubMedDate not supplied

Long-term results of ethanol embolization of renal cell carcinoma.

This retrospective study was conducted to evaluate the long-term results of transarterial embolization with absolute ethanol (ethanol-TAE) for patients with renal cell carcinoma (RCC). Twenty-eight patients, including 15 stage IVb patients, underwent ethanol-TAE, with 12 of them followed by nephrectomy. The cumulative survival rates after 1, 3, and 5 years were 71%, 54%, and 54% in the surgical group, and 54%, 33%, and 22% in the non-surgical group. From the results, we recommend ethanol-TAE for advanced stage patients for the following reasons: first, it can be a useful alternative to nephrectomy in high-risk patients; second, ethanol-TAE can decrease the primary tumor size increasing operability; and third, local tumor control may result in longer survival.

Aged↗
PubMedDate not supplied

More than 1 year continuous operation of a centrifugal pump with a magnetically suspended impeller.

The authors have been developing a centrifugal pump with a magnetically suspended impeller (MSCP) designed for total artificial heart and long-term ventricular support. The MSCP consists of a magnetic bearing, an impeller and housing, and a driving motor. The impeller is suspended by a magnetic bearing, therefore providing contact free rotation of the impeller inside the pump. This study was designed to evaluate long-term durability and nonthrombogenicity of the MSCP in a chronic sheep model. The blood contacting surfaces of the pump and conduits were completely modified by a heparin immobilization technique (Hepaface). The MSCP was placed paracorporeally as a left heart bypass between left ventricle and descending aorta in three adult sheep. Coumadin was given orally to maintain prothrombin time at 15-20 sec. The coagulation and hematologic parameters, including plasma free hemoglobin, were periodically monitored throughout the experiment. Under daily movement in the cage, the pump could produce average flow rates of 3-6 L/min (50-100 ml/kg) at 1,700-2,000 rpm. Although the arterial pulse contour decreased, there was no physiologic deterioration. The axial impeller excursion monitored by a position sensor was < 25 microns. Plasma free hemoglobin level remained at < 5 mg/dl throughout the experiment. There was no increase in the motor current, which indicates no massive thrombus formation around the impeller. One experiment was terminated at 70 days due to Hall sensor dysfunction of the motor. The retrieved pump was entirely free from thrombus formation. There was no detectable thrombus formation inside the pump or the inflow and outflow conduits. Hematologic, renal, and hepatic parameters remained within the normal range throughout the experiment. The other two sheep have survived for more than 395 and 41 days without major complication. These studies demonstrated that the MSCP has significant potential for long-term use.

Animals↗
PubMedDate not supplied

Control of the pressure flow relationship with a magnetically suspended centrifugal pump in a chronic animal experiment.

A magnetically suspended centrifugal pump (MSCP) has been developed for long-term ventricular support. Effective torque to blood of the MSCP is exactly proportional to a motor current because of no friction inside the MSCP. The authors have devised new driving modes using these characteristics and applied it to a chronic animal experiment. Three driving modes were compared: 1) a constant rotational speed (N), 2) a constant motor current (I), and 3) a controlled motor current (CI). In two of nine sheep, the MSCPs were operated by the N and in seven by the I mode. The motor current and the rotational speed were always monitored. The CI mode was studied by altering the resistance of the vessels. In the I mode, the rotational speed varied depending upon the pressure head, and the slope of the pressure-flow (P-Q) relationship was steeper than that of the N mode, so that the pump flow was stabilized. In the CI mode, in which the motor current increased to compensate for the decrease in pump flow as the rotational speed increased, the P-Q slope was effectively controlled when the resistance was changed. The MSCP was able to control the P-Q slope without monitor of the pump flow. Various driving modes could be selected according to changes in resistance.

Animals↗
PubMedDate not supplied

In vivo and in vitro evaluation of the pulsatile mode of a magnetically suspended centrifugal pump.

The authors have been developing a magnetically suspended centrifugal pump (MSCP). They have devised a pulsatile mode for the MSCP, which was generated by altering rotational speed. This article describes in vitro and in vivo studies with the pulsatile mode of the MSCP. Hemolysis tests were performed in two identical circuits to compare the nonpulsatile (NP) mode and the pulsatile (P) mode. In vivo studies were performed in sheep. First, biventricular assisted circulation was instituted in the left heart with the MSCP and in the right heart with the Biopump. The native heart was induced to ventricular fibrillation. Second, a left ventricular assisted circulation was instituted as the native heart was beating. An inflow cannula was inserted into the left atrium in one sheep and into the left ventricle in the other. The normalized indices of hemolysis of the NP and P groups were 0.0025 +/- 0.0018 g/100 L, and 0.0032 +/- 0.0024 g/100 L (N = 4, not significant). During ventricular fibrillation in the P mode, the pulse pressure was 14 mmHg (the rotational speed: 1,500 to 2,600 rpm). In a beating heart, at atrial withdrawal, the pulse pressure increased from 10 to 24 mmHg (2,100 +/- 500 rpm), while at ventricular withdrawal, it decreased from 17 to 40 mmHg (2,000 +/- 500 rpm) on P mode. The MSCP in pulsatile mode did not increase hemolysis. At ventricular withdrawal, it was easier to produce a pulsation than at atrial withdrawal. The pulsatile mode of the MSCP is applicable to a left ventricular assist system.

Animals↗
PubMedDate not supplied

A computer simulation study of isometric contraction of latissimus dorsi muscle used for cardiac assistance.

This study was designed to investigate the feasibility of a skeletal muscle pump employing latissimus dorsi muscle (LDM) for cardiac assistance. We developed and used a 2-dimensional mathematical model for LDM to investigate how the size of pneumatic balloons (30, 38, and 45 ml) and the three different locations (proximal, center, and distal) affect the pressure applied to the balloon by LDM. The computer simulation was performed by coding a visco-elastic and nonlinear 2-dimensional program that employed the finite element method (FEM). The muscle specific parameters of LDM were obtained from animal experiment results. The model is based on Hill's characteristic equation and composed of a contractile component and a passive element. The simulation results indicated that the intermediate and largest sized balloon lead to the highest and the lowest power (volume reduction per unit time interval), respectively. On the other hand, when the balloon is inserted in the distal LDM, the power is lower than in the other two positions, regardless of the balloon size. The above results suggest that the optimal size of the balloon should be selected depending on the muscle specific parameters of the actuator, and that the balloon should be inserted either in the proximal portion or center of the actuator.

Animals↗
PubMedDate not supplied

Histopathological and electron microscopical studies on experimental Penicillium marneffei infection in mice.

Experimental Penicillium marneffei infection in mice was investigated histopathologically and by electron microscopy. Viable conidia (5 x 10(6) cells) of P. marneffei were inoculated into each mouse of group A (BALB/c mice) and group B (BALB/c-nu/nu-SIc mice) through the tail vein. All the mice were sacrificed at intervals and the livers were examined. In group A, the conidia were phagocytosed by Kupffer cells soon after inoculation, and proliferated by fission in the cytoplasm. Marked proliferation of yeast cells was observed 7 and 14 days after inoculation. With proliferation of the fungus, the number of lysosomes in Kupffer cells increased, and numerous granulomas were formed in the liver. These granulomas consisted mainly of macrophages with yeast cells, together with a few polymorphonuclear leukocytes, lymphocytes and giant cells. From 28 days on yeast cells were gradually cleared from the granulomas, and 56 days after inoculation almost all the granulomas disappeared. In group B, at an early stage of infection, similar pathological changes to those seen in mice of group A were observed. However, as the infection progressed, the number of granulomas continued to increase and yeast cells continued to proliferate although lymphocytes did not infiltrate these granulomas. With proliferation of yeast cells the liver tissue was replaced with both yeast cells engulfed by macrophages and extracellular yeasts, and dissemination occurred.

Animals↗