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Biomedical subjects

K Nishimura

Publications and source records attributed to K Nishimura.

At least 1,369 records · Page 76Linked to original sources
PubMedDate not supplied

Hepatic circulation during nonpulsatile cardiopulmonary bypass.

The arterial ketone body ratio, which reflects the hepatic mitochondrial redox potential (NAD+/NADH), decreases markedly during cardiopulmonary bypass (CPB). One of the reasons for arterial ketone body ratio reduction may be hepatic hypoperfusion during CPB. To evaluate the hepatic circulation under nonpulsatile CPB, the authors used color Doppler ultrasonography to measure the portal venous flow (PVF) in 24 adult patients before, during (aortic clamping and rewarming period), and after CPB. Nonpulsatile hypothermic CPB was performed at a flow rate of 2.4 L/min/m2. PVF was calculated from the product of mean flow velocity and cross-sectional area of the portal vein. PVF was maintained during CPB at 0.44 +/- 0.13 and at 0.54 +/- 0.18 L/min/m2. PVF (%) in relation to systemic blood flow was obtained by calculating PVF/CI or PVF/PI, where CI is the cardiac index and PI is the perfusion index. PVF (%) before, during, and after CPB was 18.3 +/- 9.3, 18.5 +/- 5.5, and 17.4 +/- 6.7%, respectively. In conclusion, PVF was maintained during nonpulsatile CPB at a flow rate of 2.4 L/min/m2 and depended upon systemic blood flow.

Adult↗
PubMedDate not supplied

Applicability of the latissimus dorsi muscle in situ as a biomechanical energy source.

The purpose of this study was to assess the applicability of the latissimus dorsi muscle in situ as an energy source for a circulatory assist device. A pneumatic chamber, devised by the authors, was inserted beneath the muscle and compressed by contractions of the muscle so that muscle contractile power was converted into pneumatic pressure. The optimal insertion position of the chamber beneath the latissimus dorsi muscle, and the influence of chamber size on generated pneumatic pressure, were investigated. The pneumatic chamber functioned better when it was placed in a proximal position (third intercostal space) than in a middle or distal position. Using a mock circuit, the performance of the pneumatic chamber as an energy source for a circulatory assist device was evaluated. The pneumatic chamber was able to generate power sufficient to drive a right ventricular assist device as far as stroke work was involved. When the pneumatic chamber was operated with a high afterload, it could even be an energy source for aortic counterpulsation.

Animals↗
PubMedDate not supplied

A compressive type skeletal muscle pump as a biomechanical energy source.

The purpose of this study was to assess the applicability of the conditioned latissimus dorsi muscle as an energy source for circulatory assist devices. The authors developed a pneumatic chamber as a muscle actuator. The pneumatic chamber placed between latissimus dorsi muscle and chest wall was compressed by the burst stimulated muscle and, thereby, converted muscle contractile power into pneumatic pressure. The authors report the performance of the implanted pneumatic chamber at a chronic phase, and the capability of the conditioned muscle in situ as an energy source for circulatory assist devices. Six adult mongrel dogs were used. At the first operation, a pacemaker for muscle conditioning and the pneumatic chamber were implanted. After 12 weeks of muscle conditioning, the performance of the pneumatic chamber with conditioned muscle was evaluated. The pressure generating capability of a chamber buried in fibrous adhesions was reduced to approximately 65% of that of a chamber without adhesions. The stroke volume and stroke work of the assist device driven by the developed pneumatic pressure were measured. The maximum stroke work of the circulatory assist was greater than the stroke work of the right ventricle, but less than that of the left ventricle. In respect to stroke volume, the pneumatic chamber could drive the circulatory assist device against not only a pulmonary range of afterload, but also a systemic range of afterload, when high pre load was available. These results indicate that the compressive skeletal muscle pump with conditioned latissimus dorsi muscle generates acceptable hemodynamic work for right ventricular bypass or aortic counterpulsation. In the long-term, the interface between tissue and actuator is the major obstacle to developing a muscle powered assist device.

Animals↗
PubMedDate not supplied

Results of chronic animal experiments with a new version of a magnetically suspended centrifugal pump.

We have developed a magnetically suspended centrifugal pump (MSCP) for long-term ventricular support. This study reports results of chronic animal experiments using a new version of the MSCP. Three sheep weighing 50-70 kg were used in this study. A left heart assist system was established with cannulas into the descending aorta and the left ventricular apex. In two sheep the MSCP was positioned outside the body and in one sheep implanted on the chest wall. The pumping flow was estimated by the motor current and motor speed. The temperature of the pump and the muscle near the pump was recorded for 10 days after operation. The duration of continuous pumping was 60, 140, and 230 days+ (ongoing), respectively. The cause of termination was infection associated with thrombus formation in the first, and failure of magnetic suspension in the second sheep. No thrombus or embolus was observed after sacrifice of the second sheep. The third sheep has been going well despite skin necrosis around the pump pocket. The estimation of pumping flow was reliable even at 140 days. Temperature of the pump surface was 42 degrees C immediately after the operation and gradually reduced to 41 degrees C. The MSCP is a reliable pump for long-term circulatory assist.

Animals↗
PubMedDate not supplied

Hemodynamics on abrupt stoppage of centrifugal pumps during left ventricular assist.

A magnetically suspended centrifugal pump (MSCP), developed for long-term ventricular assist, is reliable and durable because it has no shaft or seal. However, with nonvalve pumps such as a MSCP, regurgitation occurs when they accidentally stop without cannula clamping. We investigated the hemodynamics during temporary stoppage of a MSCP being used as a left ventricular assist system (LVAS), comparing two inflow cannulation sites. In four sheep (weight, 35-45 kg), microspheres were injected into the left main coronary artery to induce heart failure. An outflow cannula was sutured onto the descending aorta, and two inflow cannulae were inserted into the left atrium and the left ventricle. The MSCP was stopped with both the left ventricular cannula and left atrial cannula clamped, and the hemodynamics and P-V loops were recorded. Each cannula was then unclamped in order, and similar parameters were recorded. LVEDP increased at unclamping of the left ventricular cannula (ULVC), and rose further at unclamping of the left atrial cannula (ULAC). Aortic pressure did not change at ULVC, but decreased at ULAC. The effective systemic flow that subtracted the regurgitant flow through the MSCP from left ventricular output was half at ULVC and almost 0 at ULAC. When stopping centrifugal pumps without circuit clamping, hemodynamic deterioration is less at ULVC than at ULAC. This finding suggests that left ventricular inflow cannulation is recommended to allow more time in emergency situations.

Animals↗
PubMedDate not supplied

Computed tomography of hydrosalpinx following tubal ligation.

The CT findings in three cases of surgically proven hydrosalpinx following tubal ligation are described. In every case a cystic mass of characteristic tubular shape was detected in the pelvic adnexal region. These findings can be considered diagnostic of iatrogenic hydrosalpinx.

Adult↗
PubMedDate not supplied

MR imaging of cavernous hemangioma of the face and neck.

Four patients with cavernous hemangioma of face and neck were evaluated with magnetic resonance imaging. Pathologically, soft tissue cavernous hemangiomas are characterized by small feeding arteries and large blood poolings. Arteriography usually fails to demonstrate the extent of the lesion. Computed tomography does not allow differentiation between these lesions and surrounding normal tissues. Magnetic resonance clearly demonstrates hemangiomas with good contrast between lesion and normal tissues. Spin-echo technique with long echo time appears to be particularly useful to delineate these lesions.

Adolescent↗
PubMedDate not supplied

Anterior and posterior lobes of the pituitary gland: assessment by 1.5 T MR imaging.

Pituitary glands of 60 normal volunteers (30 men 20-36 years old, and 30 women 18-42 years old) were studied by 1.5 T magnetic resonance (MR) imaging. The T1-weighted images (T1WI) [repetition time (TR) = 400 ms; echo time (TE) = 25 ms] were obtained in the coronal, sagittal, and axial planes. Proton density (PD)/T2-weighted images (PDWI/T2WI) (TR = 2,000 ms; TE = 25/100 ms) were obtained in the sagittal plane using 3 mm slice thickness. On T1WIs of all subjects the posterior part (PP) of the pituitary fossa showed the highest signal, which was indistinguishable from fatty tissue. This study reveals that this region of high signal intensity (PP) corresponds to the posterior lobe and not intrasellar fat because its shape, size, and position are compatible with the posterior lobe; its signal intensity differs from that of fatty tissue on PDWI and T2WI; the absence of an intrinsic chemical shift artifact (CSA) characteristic of fat; and due to CSA, a dorsum with fatty marrow is shifted relative to the PP (or may be made to merge with it). Regarding the differentiation of the two lobes of the pituitary gland on MR, the morphology of the anterior and posterior lobes was evaluated and great variation found. Appreciation of normal is particularly important in evaluating coronal images for small pituitary lesions.

Adolescent↗
PubMedDate not supplied

Posterior lobe of the pituitary in diabetes insipidus: MR findings.

The posterior lobe of the pituitary gland was evaluated by 1.5 T magnetic resonance (MR) in five cases of diabetes insipidus (DI), including one primary (idiopathic) and four secondary DI cases due to germinomas (two), teratoma (one), and histiocytosis X (one). The normal posterior lobe displays high signal indistinguishable from fatty tissue on T1-weighted images (T1WI) (short T1 value). In all five DI cases the normal high signal of the posterior lobe was not detected in the pituitary fossa on T1WI. Hence, because of this characteristic finding, MR may greatly assist in the diagnosis of DI. We may speculate that the short T1 value of the posterior lobe is closely related to its functional integrity and may be due to the neurosecretory materials in the axons of the hypothalamohypophyseal tract.

Adolescent↗
PubMedDate not supplied

Stratified impairment of pulmonary ventilation in "diffuse panbronchiolitis:" PET and CT studies.

Positron emission tomography with radioactive nitrogen gas as well as CT were performed in seven patients with diffuse panbronchiolitis (DPB) to evaluate regional changes on pulmonary ventilation and lung attenuation values. Special focus of this study was on the difference between the central and peripheral parts of the lung. Mean ventilatory time constants measured in the peripheral parts of the lung were significantly greater than those in the central parts. Moreover, mean CT attenuation values in the peripheral parts were also significantly lower than those in the central parts, indicating that hyperinflation of the lung in DPB was located mainly in the peripheral parts. Such stratified distribution of ventilatory impairment is considered to be characteristic of diffuse bronchiolar narrowing because, in the peripheral parts of the lung, there are no large airways. In addition, different branching patterns of airways between the central and peripheral parts of the lung may play an important role in the mechanism of selective injury of bronchioles in the peripheral parts.

Adult↗
PubMedDate not supplied

Preduodenal portal vein and anomalous continuation of inferior vena cava: CT findings.

Four cases of a rare congenital anomaly, preduodenal portal vein (PPV), are presented. Preduodenal portal vein is known to be frequently associated with other anomalies including intestinal malrotation, situs inversus, biliary atresia, and pancreatic, splenic, and cardiac anomalies. Of our four cases, three had azygos or hemiazygos continuation of the inferior vena cava and other anomalies. We want to call attention to association of azygos or hemiazygos continuation of inferior vena cava with PPV.

Abnormalities, Multiple↗
PubMedDate not supplied

Intravenous leiomyomatosis of uterus: MR appearance.

We report a case with intravenous leiomyomatosis of uterus that showed characteristic appearances on MR. Magnetic resonance demonstrated a tangle of distended and folded tubular structures, well enhanced by Gd-diethylenetriamine pentaacetic acid. It was confirmed by surgery that these tubular structures reflected the vessels markedly dilated by intravascular tumor.

Adult↗
PubMedDate not supplied

Optimized scanning conditions of high resolution CT in the follow-up of pulmonary emphysema.

PURPOSE: To address the optimal scanning condition of high resolution computerized tomography from the perspective of minimizing exposed dose. METHOD: The influence of the electric current, the slice number, and the slice thickness on precise percent ratio of the low attenuation area to whole lung field (LAA%) of chronic obstructive pulmonary disease patients was examined. The standard conditions were 250 mA, 3 slices, 2 mm slice thickness, and a varied parameter. RESULTS: In cases showing an LAA% less than 30, LAA% obtained by < or =150 mA were significantly larger than those by 250 mA. The mean LAA% with 3 and 10 slices were well correlated and the correlation with lung function was similar. The correlation of LAA% with lung function was approximately the same between the 2 and 5 mm slice thicknesses. CONCLUSION: The electrical current must be > or =200 mA, and 3 slices and 2 mm slice thickness are appropriate.

Electricity↗
PubMedDate not supplied

PMEA coating of pump circuit and oxygenator may attenuate the early systemic inflammatory response in cardiopulmonary bypass surgery.

We investigated the effects of coating a cardiopulmonary bypass (CPB) circuit and oxygenator with poly-2-methoxy-ethyl acrylate (PMEA) on the systemic inflammatory response during and after CPB. Thirty patients undergoing elective cardiac surgery were randomized into three groups (each group n = 10): noncoated (group N), heparin coated (group H), and PMEA coated circuit and oxygenator (group X). Bradykinin (BK), complement 3 activation (C3a) and interleukin-6 (IL-6) levels were measured as early phase indicators of inflammatory response, as were maximum C reactive proteins (CRP) and white blood cell (WBC) levels. The alveolar-arterial oxygen gradient (A-a DO2) was measured as a parameter of respiratory function. IL-6 levels after CPB were significantly higher in group N than in groups H and X (p < 0.05). Serum BK and C3a levels showed similar patterns in all groups. A-a DO2 was lower at the end of and 3 hours after CPB in groups H and X than in group N (p < 0.05). Maximum CRP levels were lower in group X than in groups N (p < 0.05). This prospective study suggests that PMEA coated CPB may improve respiratory function and decrease systemic inflammatory response after cardiac surgery, possibly because this circuit is as biocompatible as heparin coated CPB circuit.

Acrylates↗
PubMedDate not supplied

Aspergillus arvii spec. nov., a new animal pathogen?

Aspergillus arvii sp. nov. Aho, Horie, Nishimura & Miyaji isolated from liver lesions of a dairy cow in Finland, is suggested to represent a new species. It differs from the other members of the Aspergillus fumigatus group by its stable brown colony colour, the ornamentation of its conidia as well as the shape of the vesicles and length of conidiophores.

Animals↗
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Pathogenicity of strains of the black yeast Exophiala (Wangiella) dermatitidis: an evaluation based on polymerase chain reaction.

Strains of Exophiala dermatitidis, mainly originating from patients with systemic neurotropic mycosis in Asia and from the lungs of patients with cystic fibrosis (CF) in Europe, were analysed by ribotyping of the small subunit rDNA and by random amplification of polymorphic DNA (RAPD). A characteristic banding pattern for the species was found after restriction analysis of amplified fragments V9 and ITS4. The small subunit rDNA gene of five strains was about 1800 base pairs (bp) long, while in 16 strains its length was about 3000 bp. Using RAPD, seven populations could be distinguished. European CF strains as well as Asian strains from systemic mycoses are mainly distributed over two populations, one of which contained both CF strains and a systemic strain. It is concluded that the two clinical pictures are caused by genetically similar strains. The differences in pathogenicity may be explained by immunological differences in the hosts or by differences in exposure to the fungal propagules.

Base Sequence↗
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Cell-surface hydrophobicity and lipolysis as essential factors in human tinea nigra.

Hydrophobic adhesion of cells of the black yeast Hortaea werneckii (Horta) Nishimura & Miyaji, causative agent of human tinea nigra, was established by microbial adhesion to hexadecane (MATH) and adhesion to polystyrene, and compared with adhesion of other species of black yeasts. Additional ecophysiological tests were performed. Hortaea werneckii cells proved to have a high degree of hydrophobicity (98.5% MATH). The species is unable to degrade keratin, but shows significant lipolytic activity. It is concluded that H. werneckii is a commensal, that shows lipophilic adhesion to human skin and survives by the assimilation of excretion products.

Animals↗