Search PubMed⌕ Search

Biomedical subjects

K Yamazaki

Publications and source records attributed to K Yamazaki.

At least 235 records · Page 13Linked to original sources
PubMed1999

Sealing properties of mechanical seals for an axial flow blood pump.

A miniature intraventricular axial flow blood pump for left ventricular support is under development. One of the key technologies required for such pumps is sealing of the motor shaft. In this study, to prevent blood backflow into the motor side, mechanical seals were developed and their sealing properties investigated. In the experimental apparatus, the mechanical seal separated the bovine blood on the chamber side from the cooling water on the motor side. A leakage of the blood was measured by inductively coupled plasma (ICP) light emission analysis. The rate of hemolysis was measured by the cyanmethemoglobin method. Frictional torque acting on the shaft was measured by a torque transducer. In the experiments, the rotational speed of the shaft was changed from 1,000 to 10,000 rpm, and the contact force of the seal faces was changed from 1.96 to 4.31 N. To estimate lubrication regimes, the Stribeck curve, a diagram of the coefficient of friction against the bearing characteristic G number, was drawn. The results of the experiments showed that both the leakage of blood and the rate of hemolysis were very small. The friction loss was also very small. The mechanical seal was operated in various lubrication regimes, from a fluid lubrication regime to a mixed lubrication regime.

Animals↗
PubMed1999

Rotary blood pump flow spontaneously increases during exercise under constant pump speed: results of a chronic study.

Many types of rotary blood pumps and pump control methods have recently been developed with the goal of clinical use. From experiments, we know that pump flow spontaneously increases during exercise without changing pump control parameters. The purpose of this study was to determine the hemodynamics associated with the long-term observation of calves implanted with centrifugal blood pumps (EVAHEART, Sun Medical Technology Research Corporation, Nagano, Japan). Two healthy female Jersey calves were implanted with devices in the left thoracic cavity. A total of 22 treadmill exercise tests were performed after the 50th postoperative day. During exercise, the following parameters were compared with conditions at rest: heart rate, blood pressure, central venous oxygen saturation (SvO2), pump speed, and pump flow. The pump flow in a cardiac cycle was analyzed by separating the systole and diastole. Compared to the base data, statistically significant differences were found in the following interrelated parameters: the heart rate (66.8 +/- 5.2 vs. 106 +/- 9.7 bpm), mean pump flow (4.8 +/- 0.2 vs. 7.0 +/- 0.3 L/min), and volume of pump flow in diastole (26.0 +/- 1.8 vs. 13.5 +/- 2.5 ml). During exercise, the volume of pump flow in systole was 3 times larger than that measured in diastole. Blood pressure, SvO2, and pump speed did not change significantly from rest to exercise. These results suggested that the mean pump flow depends on the systolic pump flow. Therefore, the increase in the mean pump flow during exercise under constant pump speed was caused by an increase in the heart rate.

Animals↗
PubMed1999

Immunoglobulins of untreated Graves' patients with or without thyrotropin receptor antibody (determined by porcine thyrocytes) universally elicit potent thyroid hormone-releasing activity in cultured human thyroid follicles.

Thyrotropin receptor antibody (TRAb), comprising thyrotropin binding inhibitor immunoglobulin (TBII) and thyroid-stimulating antibody (TSAb), both of which are conventionally determined using porcine thyrocytes in Japan, is not always positive in patients with untreated Graves' disease. To elucidate whether immunoglobulin G (IgG) obtained from TBII/TSAb-positive (+) or negative (-) Graves' disease patients are responsible for hyperthyroidism, we investigated the thyroid hormone-releasing activity (THRA) of these IgGs in human thyroid follicles in suspension culture, in which bovine thyrotropin (bTSH) is detectable even at 0.1 microU/mL. Human thyroid follicles, obtained from Graves' disease patients by subtotal thyroidectomy, were cultured in serum-free F-12/RPMI-1640 medium supplemented with bTSH or purified Graves' IgGs. After preculturing for 3 days, 125I was added, and after an additional 3 days of culture, 1251 incorporated into the thyroid follicles and organic 125I released into the culture medium (mainly 1251 -T4 + 125I-T3) were counted. Seventy TBII(+)/TSAb( + )-, 3 TBII( + )/TSAb( - )-, and 3 TBII( - )/TSAb( + )- patients with untreated Graves' disease were all positive for THRA, which became undetectable in spontaneous remission obtained after several years of medical treatment. The THRA was equivalent to 0.8-230 microU/mL bTSH. Furthermore, 2 TBII(-)/TSAb(-) patients were significantly positive for THRA. This TBII(-)/TSAb(-)IgG stimulated human thyrocytes to produce cyclic adenosine monophosphate (cAMP), and this was partially inhibited by antihuman IgG antibody. The THRA induced by TBII(+)/TSAb(+) IgGs as well as TBII(-)/TSAb(-) IgG was inhibited by blocking-type TRAb obtained from TBII(+) patients with myxedema. There was a significant correlation between THRA and TSAb. These in vitro findings suggest that all IgGs obtained from untreated Graves' patients (n = 78) elicit potent THRA in human thyroid follicles in suspension culture. Because the TBII(-)/TSAb(-) IgGs can stimulate cAMP production in human but not in porcine thyrocytes, they probably recognize epitope(s) of TSH-binding sites specific to the human thyrotropin (hTSH) receptor. Furthermore, we have demonstrated that the thyroid gland of hyperthyroid Graves' patients is stimulated by IgG(s) equivalent to at least 0.8 microU/mL bTSH (about 5 microU/mL hTSH) in vitro.

Animals↗
PubMed1999

Primary hepatic lymphoma associated with primary biliary cirrhosis.

We report a case of primary hepatic lymphoma in a 55-yr-old female patient with primary biliary cirrhosis and Sjögren's syndrome. On July 1994, a tumor measuring 11 mm in diameter was detected in the right lobe of the liver by abdominal ultrasonography. A needle biopsy specimen showed the lesion to contain small- and medium-sized lymphoid cells without obvious atypia, and a provisional diagnosis of pseudolymphoma was made. About 2 yr later, the tumor increased to 15 mm in diameter, necessitating a second needle biopsy. Histological and genetic examinations confirmed non-Hodgkin's lymphoma of diffuse, mixed small and large cell, B-cell type. However, the size of the tumor remained almost stable (16 mm in diameter) over a period of 7 months after diagnosis, without any treatment for lymphoma, indicating a low grade malignancy. We document hepatic lymphoma as an additional complication of primary biliary cirrhosis.

Adult↗
PubMed1999

Invasive thymoma with long-term survival by extensive reoperation.

The recurrence of invasive thymoma is often observed; however, no accepted treatment of recurrent invasive thymoma has yet been established. We herein report a 41-year-old woman with invasive thymoma and pleural dissemination who demonstrated long-term survival after undergoing 4 operations. Based on our findings, reoperation is thus suggested in patients with intrathoracic recurrence and long-term survival can be expected.

Adult↗
PubMed1999

Syncope caused by nonsteroidal anti-inflammatory drugs and angiotensin-converting enzyme inhibitors.

A 85-year-old woman with diabetes mellitus and prior myocardial infarction was transferred to the emergency room with loss of consciousness due to marked bradycardia caused by hyperkalemia. The T wave during right ventricular pacing was tall and tent-shaped while the concentration of serum potassium was high, and its amplitude during pacing was decreased after correction of the serum potassium level. Simultaneously with the correction, normal sinus rhythm was restored. The cause of hyperkalemia was considered to be several doses of loxoprofen, a nonsteroidal anti-inflammatory drug (NSAID), prescribed for her lumbago by an orthopedic specialist, in addition to the long-term intake of imidapril, an angiotensin-converting enzyme inhibitor (ACEI), prescribed for her hypertension by a cardiologist. This case warns physicians that the combination of NSAID and ACEI can produce serious side effects in aged patients who frequently suffer from hypertension, diabetes mellitus, ischemic heart disease, and degenerative joint disease.

Aged↗
PubMed1999

Parathyroid hormone-related protein regulates proliferation of condylar hypertrophic chondrocytes.

The condylar cartilage, an important growth site in the mandible, shows characteristic modes of growth and differentiation, e.g., it shows delayed appearance in development relative to the limb bud cartilage, originates from the periosteum rather than from undifferentiated mesenchymal cells, and shows rapid differentiation into hypertrophic chondrocytes as opposed to the epiphyseal growth plate cartilage, which has resting and proliferative zones. Recently, attention has been focused on the role of parathyroid hormone-related protein (PTHrP) in modulating the proliferation and differentiation of chondrocytes. To investigate further the characteristic modes of growth and differentiation of this cartilage, we used mice with a disrupted PTHrP allele. Immunolocalization of type X collagen, the extracellular matrix specifically expressed by hypertrophic chondrocytes, was greatly reduced in the condylar cartilage of homozygous PTHrP-knockout mice compared with wild-type mice. In contrast, immunolocalization of type X collagen of the tibial cartilage did not differ. In wild-type mice, proliferative chondrocytes were mainly located in both the flattened cell layer and hypertrophic cell layer of the condylar cartilage, but were limited to the proliferative zone of the tibial cartilage. The number of proliferative chondrocytes was greatly reduced in both cartilages of homozygous PTHrP-knockout mice. Moreover, apoptotic chondrocytes were scarcely observed in the condylar hypertrophic cell layer, whereas a number of apoptotic chondrocytes were found in the tibial hypertrophic zone. Expression of the type I PTH/PTHrP receptor was localized in the flattened cell layer and hypertrophic cell layer of the condylar cartilage, but was absent from the tibial hypertrophic chondrocytes. It is therefore concluded that, unlike tibial hypertrophic chondrocytes, condylar hypertrophic chondrocytes have proliferative activity in the late embryonic stage, and PTHrP plays a pivotal role in regulating the proliferative capacity and differentiation of these cells.

Animals↗
PubMed1999

Short-term longitudinal changes in subcutaneous fat distribution and body size among Japanese women in the third decade of life.

This research clarified the changes in body shape among Japanese women aged in their 20's, by measuring the subcutaneous fat distribution over the whole body and its circumference at certain points. The subjects, 13 healthy women, were measured twice, once in their early 20's and 5 years later in their late 20's. Subcutaneous fat thickness was measured at 14 points on the body using the B-mode ultrasound method and the body size was measured directly at 8 points on the body using a steel measure. Subcutaneous fat thickness tends to increase with age, except at the cheek, neck, bust and leg. Significant increases were detected especially at lower parts of the trunk such as the waist and infragluteal region. Meanwhile, despite the significant change in subcutaneous fat thickness, the circumferences measured did not change, and also weight tended to decrease with age. Based on this finding, except for fat, body mass, such as muscle and bone, decreases with age due to decreased exercise and changes in calorie intake. Cluster analysis of the accumulation patterns of subcutaneous fat indicated that there were the following 3 patterns of subcutaneous fat accumulation from the early 20's to the late 20's. I. Accumulation on the whole trunk (bust, abdomen, waist and back) and upper arm--trunk/upper arm accumulation pattern. II. Significant accumulation around waist--waist accumulation pattern. III. Even accumulation at abdomen, side abdomen, hip and lower hip--abdomen/hip accumulation pattern.

Adipose Tissue↗
PubMed1999

An aged male patient with autoimmune hepatitis complicated by hepatocellular carcinoma.

An 82-year-old male patient was admitted for liver dysfunction. Laboratory test showed the following data; aspartate aminotransferase (AST) 79 IU/l, alanine aminotransferase (ALT) 28 IU/l, total bilirubin (T. Bil) 0.9 U, zinc sulfate turbidity test (ZTT) 48.9 U, gamma-globulin 4.9 g/dl, immunoglobulin G (IgG) 5,046 mg/dl, anti-nuclear antibodies x 320, anti-mitochondrial antibodies (-), hepatitis B virus surface antigen (HBsAg) (-), HBcAb (-), anti-hepatitis C virus (anti-HCV) (-), hepatitis C virus (HCV-RNA) (-), anti-hepatitis G virus (anti-HGV) (-), alpha-fetoprotein 306.8 ng/ml, carcinoembryonic antigen (CEA) 2.3 ng/ml, carbohydrate antigen (CA) 19-9 77.2 U/ml. Abdominal ultrasonography and computed tomography showed a large mass occupying most of the right lobe and portal thrombosis in the liver. Liver biopsy revealed cirrhosis with inactive hepatitis in the nontumorous lesion and well-differentiated hepatocellular carcinoma in the tumorous lesion. We report a rare case of an aged male patient with autoimmune hepatitis complicated by hepatocellular carcinoma.

Aged↗
PubMed1999

Linearly and circularly polarized, 50 Hz magnetic fields did not alter intracellular calcium in rat immune cells.

This study was conducted to determine if exposure to 50 Hz magnetic field (MF) affects intracellular calcium ([Ca2+]i). We employed flow cytometry for real-time detection of possible changes in [Ca2+]i in a large number of cells. A solenoid coil for vertical MF exposure and a multiple-loop square-coil for horizontal MF were utilized. In the laboratory, background 50 Hz MF was less than 0.08 microT when all necessary equipment was powered. Rat thymocytes were exposed to 0.1 mT horizontal or vertical field, or to 0.14 mT circularly polarized field for 30 min; the effects of consecutive exposures to vertical and horizontal MFs, or vice versa, for 20 min each also were examined. In addition, intact thymocytes or lectin-activated thymocytes, splenocytes and peripheral blood lymphocytes were exposed to the 5 mT vertical field for 30 min. In all these experiments, no alteration in [Ca2+]i was evident. As a positive control, a calcium ionophore always was added to the medium following MF exposure to verify that the cells were capable of increasing [Ca2+]i and the system would record the response. The data indicate that MF exposure had no effect on [Ca2+]i under any of the conditions examined.

Animals↗
PubMed1999

Absence of limiting amino acids in calves fed a corn and soybean meal diet past three months of age.

We conducted three nitrogen balance trials using Holstein bull calves older than 16 wk (Trial 1; n = 8), 13 wk (Trial 2; n = 6), and 15 wk of age (Trial 3; n = 9) in a 4 x 4 (Trial 1) or 3 x 3 Latin square design (Trials 2 and 3) to identify limiting amino acids for a corn and soybean meal diet. All calves were trained to maintain reflex closure of the reticular groove after weaning at 5 wk of age. The basal diet was fed daily at 20 or 27 g/kg BW (Trial 1) and at 20 g/kg BW (Trials 2 and 3). The lower feeding level resulted in reduced urinary excretion of purine derivatives, suggesting reduced synthesis of ruminal microbial protein (Trial 1). In Trials 1 and 2, administration of DL-methionine plus L-lysine monohydrochloride through the reticular groove did not increase N retention compared with the supplement of isonitrogenous L-glutamine at either level of intake. In Trial 3, administration of either casein or isonitrogenous monosodium glutamate increased N retention to a similar extent above that observed with a N-free supplement. Results suggested that no specific amino acids were limiting for the corn-soybean meal diet. Administration of methionine plus lysine resulted in a remarkable increase in plasma methionine (Trials 1 and 2), especially at the lower intake level (Trial 1), and a decrease in plasma branched-chain amino acids at either intake level. Glutamine supplementation did not increase plasma branched-chain amino acids compared with the supplementation of diammonium citrate (Trial 2).

Animal Feed↗
PubMed1999

[Surgical management of chest wall tumors].

Twenty-four patients with chest wall tumors underwent resection during the past twenty years. There were 12 female and 12 male patients with ages ranging from 7 months to 78 years (mean 44 years). Five patients had primary malignant neoplasms, 7 had metastases, and 12 had benign tumors. The tumor was located in the soft tissue in 14 patients and in the ribs and the sternum in 10. Ninety-two percent of tumors were diagnosed correctly if they were benign or malignant before resection, however the final diagnosis was made in only 25% of benign tumors and 54% of malignant tumors before surgery. Thirty-one operations were performed in 24 patients and 10 reconstruction with prosthetic materials were done. Concerning malignant neoplasms patients with primary tumors had better prognosis than those with metastases and patients underwent reconstruction had better prognosis than those underwent resection only. We conclude that wide resection with reconstruction is potentially curative treatment.

Adolescent↗
PubMed1999

[Pneumonitis induced by the drug ougon].

We report a case of drug-induced pneumonitis associated with the herbal medications Sho-saiko-to and Ouren-gedoku-to. A 62-year-old man experienced fever and dry cough after using Ouren-gedoku-to for 2 months. He was admitted to our hospital because a subsequent 5-day course of Sho-saiko-to for suspected bronchitis aggravated these symptoms and caused exertional dyspnea. Chest X-ray films revealed a ground-glass appearance in both lower lung fields. Cessation of these medications improved the patient's clinical and X-ray findings. Bronchoalveolar lavage showed an increase in lymphocytes with a decreased CD 4/CD 8 ratio. While drug-induced lymphocyte stimulation tests gave negative results, challenge tests for Ouren-gedoku-to and Sho-saiko-to were both positive. A diagnosis of drug-induced pneumonitis was made. Our findings suggested the involvement of Ougon, the only common ingredient in the two medications.

CD4-CD8 Ratio↗
PubMed1999

[Emergent coronary artery bypass grafting within twenty-four hours following acute myocardial infarction].

We experienced 43 patients with acute myocardial infarction who underwent emergent coronary artery bypass grafting within twenty-four hours from the onset. Twenty-six patients (group S) were in cardiogenic shock preoperatively and fourteen patients of this group had total or subtotal obstruction of the left main trunk. Fourteen of the other seventeen patients (group N) had a left main trunk disease. More patients underwent PTCA and the time required for reperfusion of the infarction-related coronary artery with PTCA was shorter in group S than group N. Preoperative hemodynamics improved in twenty patients in group S. The time required for completion of a coronary artery bypass to the infarction-related coronary artery was also shorter in group S. The operative mortality was 15% in group S and 6% in group N. One noncardiac late death occurred in group S. The postoperative segmental wall motion score of the infarcted left ventricle was much improved in patients with subtotal occlusion of the infarction-related coronary artery. Thus, preoperative hemodynamic improvement by early reperfusion leads to satisfying operative results and salvage of the infarcted myocardium.

Aged↗
PubMed1999

[Hypereosinophilic syndrome associated with antineutrophil cytoplasmic antibody].

A 68-year-old man was admitted to our hospital with complaints of fever, cough, and shortness of breath. He had several erythematous maculae on the trunk and experienced hypesthesia in his lower extremities. Laboratory data showed marked eosinophilia (20,235/mm3) and enhanced hepatobiliary enzymes. Chest X-ray films and computed tomographic scans revealed diffuse patchy infiltrative changes in the lungs. Histologic findings confirmed eosinophilic infiltration of the skin, liver, and lungs. A diagnosis of hypereosinophilic syndrome (HES) was made in accordance with clinical criteria proposed by Chusid et al. The patient was positive for antineutrophil cytoplasmic antibodies (a marker for vasculitis). This suggested a clinical picture resembling Churg-Strauss syndrome (CSS) despite the lack of bronchial asthma. The findings in this report could contribute to a better understanding of the diversity of HES cases, several of which are considered to represent a continuum of pathologies sharing an etiology similar to that of CSS.

Aged↗
PubMed1999

[Correlation between clinical aggressiveness of thymic epithelial tumors and expression of tumor suppressor gene products (p53, p27)].

It is impossible to predict malignant potential of thymomas by conventional histopathological examination. In order to find a malignant marker of thymoma, we immunohistochemically examined the expression of the products of p53 and p27kip1, potential tumor suppressor genes in thymic epithelial tumors. The thymic epithelial tumors examined in the present study included 13 non-invasive thymomas, 7 invasive thymomas, and 4 thymic carcinomas. The thymic epithelial cells showed abnormal accumulation of p53 protein in 2 of 13 non-invasive thymomas (15.4%), 4 of 7 invasive thymomas (50%), and 3 of 4 thymic carcinomas (75%). The frequency of p53-expression paralleled with clinical aggressiveness. On the other hand, p27 showed no correlation with clinical aggressiveness. In conclusion, the present results suggest that the presence of p53-positive epithelial cells might be a useful indicator to predict malignant potential of thymoma.

Cell Cycle Proteins↗