Search PubMed⌕ Search

Biomedical subjects

T Yamane

Publications and source records attributed to T Yamane.

At least 199 records · Page 11Linked to original sources
PubMed1998

Development of design methods of a centrifugal blood pump with in vitro tests, flow visualization, and computational fluid dynamics: results in hemolysis tests.

There are few established engineering guidelines aimed at reducing hemolysis for the design of centrifugal blood pumps. In this study, a fluid dynamic approach was applied to investigate hemolysis in centrifugal pumps. Three different strategies were integrated to examine the relationship between hemolysis and flow patterns. Hemolytic performances were evaluated in in vitro tests and compared with the flow patterns analyzed by flow visualization and computational fluid dynamic (CFD). Then our group tried to establish engineering guidelines to reduce hemolysis in the development of centrifugal blood pumps. The commercially available Nikkiso centrifugal blood pump (HPM-15) was used as a standard, and the dimensions of 2 types of gaps between the impeller and the casing, the axial and the radial gap, were varied. Four impellers with different vane outlet angles were also prepared and tested. Representative results of the hemolysis tests were as follows: The axial gaps of 0.5, 1.0, and 1.5 mm resulted in normalized index of hemolysis (NIH) values of 0.0028, 0.0013 and 0.0008 g/100 L, respectively. The radial gaps of 0.5 and 1.5 mm resulted in NIH values of 0.0012 and 0.0008 g/100 L, respectively. The backward type vane and the standard one resulted in NIH values of 0.0013 and 0.0002 g/100 L, respectively. These results revealed that small gaps led to more hemolysis and that the backward type vane caused more hemolysis. Therefore, the design parameters of centrifugal blood pumps could affect their hemolytic performances. In flow visualization tests, vortices around the impeller outer tip and tongue region were observed, and their patterns varied with the dimensions of the gaps. CFD analysis also predicted high shear stress consistent with the results of the hemolysis tests. Further investigation of the regional flow patterns is needed to discuss the cause of the hemolysis in centrifugal blood pumps.

Animals↗
PubMed1998

Washout hole flow measurement for the development of a centrifugal blood pump.

Washout holes in the impeller of a centrifugal blood pump reduce thrombus formation in areas where blood is apt to stagnate, especially in the back gap of the impeller. In this study, flow through the washout holes is quantified by pressure measurement and flow visualization with a 300% scaled-up model to understand the force driving flow through the washout holes and the flow itself. When external circuit resistance is constant, pressure distribution normalized by the square of the tip speed is constant and independent of the impeller rotational speed. The ratio of the flow rate through the washout holes to the flow rate of the external circuit is also constant. When the external circuit resistance increases, the pressure difference at the washout holes between the front and back gap of the impeller increases and generates a greater flow rate through the washout holes.

Biomechanical Phenomena↗
PubMed1998

Computational fluid dynamic analyses to establish design process of centrifugal blood pumps.

To establish quantitative, efficient design theories for centrifugal blood pumps, computational fluid dynamics (CFD) analyses were compared to the results of flow visualization tests and hemolysis tests, mainly on the Nikkiso centrifugal blood pump. The results turned out to coincide in the velocity vector plots. CFD analysis revealed that the smaller the gap is, the greater the shear stress becomes. This tendency becomes even greater with a radial gap change. Hemolysis study also indicated that the smaller the gap is, the greater the hemolysis. CFD analysis in comparison with hemolysis tests could be a useful index for developing blood pumps in the future.

Biomechanical Phenomena↗
PubMed1998

CD4- and TCRalphabeta-positive T lymphocytes predominantly infiltrated into well-moderately differentiated colon adenocarcinoma tissues.

Intraepithelial T lymphocytes have been reported as being functional in the growth of epithelial cells and also in the discrimination of aberrant cells, whereas their function against colon adenocarcinoma cells is obscure. The phenotype of colon intraepithelial T lymphocytes has been found in patients with inflammatory bowel diseases but not in patients with colon adenocarcinoma. In this study, we investigated cell surface markers of tumor-infiltrating T lymphocytes of adenocarcinoma of the colon and rectum at various grades of differentiation and intraepithelial T lymphocytes of adjacent normal colon by enzyme immunostaining. Among intraepithelial T lymphocytes of the normal colon, CD8-and TCRgammadelta-positive T lymphocytes were predominant as described. In contrast, tumor-infiltrating T lymphocytes of well-moderately differentiated adenocarcinoma of the colon and rectum were predominantly CD4- and TCRalphabeta-positive. The decrease of TCRgammadelta-positive T lymphocytes and the increase of CD4 and TCRalphabeta-positive T lymphocytes in adenocarcinoma tissues of the colon and rectum suggests that an alteration of the local immune system participates in the formation of adenoma and/or adenocarcinoma of the colon and rectum, resulting in infiltration of CD4-positive T lymphocytes that have certain activity against transformed cells.

Adenocarcinoma↗
PubMed1998

High energy radiofrequency catheter ablation for common atrial flutter targeting the isthmus between the inferior vena cava and tricuspid valve annulus using a super long tip electrode.

There have been controversies concerning the optimal target sites and approaches in radiofrequency catheter ablation of common atrial flutter. We attempted high energy radiofrequency catheter ablation targeting the isthmus between the inferior vena cava and tricuspid valve annulus (IVC-TV isthmus) with a super long (8 mm) tip electrode, and compared the efficacy of this anatomical approach with the electrophysiological approach targeting the posteroseptal right atrium posterior to the coronary sinus using a standard 4-mm tip electrode. Atrial flutter was successfully ablated in 12 of 12 patients (100%) without recurrence with the anatomical approach, while, in 7 of 9 patients (64%) with 2 recurrences with the electrophysiological approach. In comparison of ablation data between the anatomical and electrophysiological approaches, there were significant differences in the mean number of application pulses (anatomical vs electrophysiological: 2.3 +/- 0.8 vs 9.9 +/- 6.4, P < 0.01), applied wattage (39 +/- 12 W vs 24 +/- 6 W, P < 0.01), applied energy per application (1,986 +/- 426 J vs 659 +/- 323 J, P < 0.01), fluoroscopic time (26 +/- 11 min vs 74 +/- 30 minutes, P < 0.01), and procedure time (59 +/- 8 min vs 181 +/- 53 min, P < 0.01). In conclusion, the anatomical approach is superior to the electrophysiological one with respect to procedure and radiation time, and linear ablation at the IVC-TV isthmus with an 8-mm tip electrode and high energy application is highly effective and safe.

Aged↗
PubMed1998

Retrograde multiple and multifiber accessory pathway conduction in the Wolff-Parkinson-White syndrome: potential precipitating factor of atrial fibrillation.

INTRODUCTION: The determinants of susceptibility to atrial fibrillation (AF) and the existence of accessory pathway conduction have remained unidentified in the Wolff-Parkinson-White (WPW) syndrome. We tested the hypothesis that excitation inputs into the atrium over a retrograde multiple or multifiber accessory pathway during AV reentrant tachycardia (AVRT) could precipitate initiation of AF. METHODS AND RESULTS: Two hundred fifty consecutive patients with WPW syndrome underwent electrophysiologic study and radiofrequency catheter ablation. The patients were classified into two groups according to the study results: 29 with retrograde multiple or multifiber accessory pathway (MP) and 221 with retrograde single accessory pathway (SP). Compared with the SP patients, the MP patients showed a significantly higher incidence of clinical AF (MP vs SP: 19/29 vs 51/221, P < 0.01), induced AF (12/29 vs 32/221, P < 0.01), and initiated AF during ventricular pacing and AVRT (10/12 vs 17/32, P < 0.05). There were no differences between the two groups in incidence of clinical and induced AVRT (24/29 vs 200/221 and 25/29 vs 206/221, respectively), mean cycle length of induced AVRT, or electrophysiologic parameters of the accessory pathway. AF inducibility during AVRT or ventricular pacing was eliminated by partial ablation in 7 of 10 patients with MP. After total ablation, the incidence of induced AF was similar between the two groups (MP vs SP: 1/29 vs 11/221). CONCLUSION: The existence of a retrograde multiple or multifiber accessory pathway in patients with WPW syndrome is associated with a higher incidence of clinical and induced AF. Successful ablation of the retrograde multiple or multifiber accessory pathway can eliminate the induction of both AVRT and AF.

Adult↗
PubMed1998

[Treatment of hepatosplenic candidiasis with liposomal amphotericin B in a patient with acute leukemia; a case report of the experience of use of liposomal amphotericin B].

We report a 26-year-old male patient with acute myelocytic leukemia and hepatosplenic candidiasis during his clinical course. His hepatosplenic candidiasis was refractoty to itraconazole and fluconazol. He developed serious side-effect such as renal dysfunction, when conventional amphotericin B was given. Then he was treated with liposomal amphotericin B (Abelcet). This therapy was safe and effective for him. He was able to be treated with 3075 mg of a liposomal amphotericin B. This was ten times as much as the dose of conventional amphotericin B which was given earlier until amphotericin B was stopped because of renal dysfunction. Liposomal amphotericin B seems to be a safe and effective therapy for systemic fungal infectin and should be considered more in Japan.

Adult↗
PubMed1998

Determination of hematopoietic stem cells in peripheral blood by an automated hematology analyzer (SE-9000).

We evaluated the usefulness of an automated hematology analyzer (SE-9000) for the identification and counting of peripheral blood stem cells (PBSCs). The samples tested were from 14 patients with hematological malignancies. Peripheral blood samples were collected from the subjects before and after a course of chemotherapy. From the leukapheresis sample, CD34+ cells, assumed to be hematopoietic stem cells, were obtained with an immunomagnetic cell separator. The CD34+ cells obtained accumulated in the gate corresponding to low recurrent frequencies of the automated hematology analyzer. This gate shows results of the 'immature information' (IMI) channel. Software for detection of only the cells that accumulated in this gate was therefore developed. With this trial program, the regression coefficient between the percentage of leukocytes from the blood samples that were CD34+ and the percentage of such leukocytes that appeared on the IMI channel was 0.79. With this analyzer, the number of PBSC could be counted in about 80 s. The identification and counting of cells picked up by the IMI channel should be clinically useful for the monitoring of changes in PBSC after chemotherapy for mobilization.

Adult↗
PubMed1998

Peripheral blood stem cell transplantation for non-Hodgkin's lymphoma in complete remission.

High-dose chemotherapy with PBSCT as consolidation therapy was administered to 15 patients with non-Hodgkin's lymphoma admitted to our department between November 1991 and March 1998. The average number of CD34-positive cells harvested was 3.1 x 10(6)/kg and the median time to a granulocyte count above 500/microliter was 12.8 days. Of the patients, one died from cytomegalovirus pneumomonia after WBC count recovered, 2 relapsed, and 12 patients are still alive and disease-free. The average disease-free survival period was 50.0 months. Stem cell harvesting is relatively simple and hematopoietic recovery is mory rapid with PBSCT than with ABMT. Our findings suggest that PBSCT can be used for consolidation therapy in NHL patients who have achieved complete remission with standard chemotherapy.

Adolescent↗
PubMed1998

Commitment and differentiation of stem cells to the osteoclast lineage.

Osteoclasts are hematopoietic cells which play important roles in bone remodeling and resorption. They have phenotypic characteristics of the monocyte/macrophage lineages. In this review we first describe the phylogeny of osteoclasts. Osteoclast generation is closely linked to the presence of bone tissues. The formation of bone cavities in aquatic animals is underdeveloped, even though they have cells which have the potential to differentiate into osteoclasts. Next we describe recent advances in our understanding of osteoclastogenesis that have resulted from the identification of critical molecules and mutated genes of osteopetrotic mice. Reports that transcriptional factors PU.1 and c-Fos are essential for commitment and (or) differentiation into the osteoclast lineage and novel culture systems, which have clarified some characteristics of osteoclast precursors, are also described. We are now able to induce mature osteoclasts from hematopoietic stem cells and even from totipotent embryonic stem cells. Cell lines that differentiate into osteoclasts are also available. Using these culture systems and cell lines, the interactions of osteoclasts with osteoblastic stromal cells, which produce critical molecules for osteoclastogenesis, have been studied. Very recently, one of these critical molecules, osteoclast differentiation factor/osteoprotegerin-ligand, was cloned. The presence of this factor and macrophage-colony-stimulating factor is sufficient to induce osteoclast development in cultures inoculated only with an osteoclast precursor cell line. We review the present status and the remaining questions in osteoclast biology.

Animals↗
PubMed1998

[Factitious anemia with severe iron deficiency caused by self-venesection].

A 22-year-old unmarried female student of nurse school was admitted to our hospital because of hypochromic anemia and fever of unknown origin. She was diagnosed as having iron-deficiency anemia and was treated with iron, but progressive anemia recurred periodically. In particular, rapidly progressive anemia was observed after the patient stayed overnight, so we strongly suspected factitious anemia. A search of her locker in the sickroom and her room at home revealed many syringes, injection needles and a bottle of blood. Factitious anemia was diagnosed and she confessed to self blood-drawing. After a psychiatric consultation, anemia tended to to resolve gradually. However she did not go to the hospital after 6 months from her discharge. Physicians should consider factitious anemia in a patient with severe chronic hypochromic anemia who dose not respond to adequate iron therapy, particularly in a patient with medical training.

Adult↗
PubMed1998

[Simple method for determination of hematopoietic stem cells].

We investigated on the rapid and easy method for the determination of peripheral blood stem cell (PBSC) using the immature information channel (IMI) of the automated hematology analyzer (SE-9000). The IMI channel provides information regarding immature leukocytes, including blast cells and immature granulocytes. CD34 positive cells, which are detected as the CD34 antigen on hematopoietic stem cells, were purified from the fractionated peripheral blood stem cell harvesting samples using Isolex. These purified CD34 positive cells accumulated in the gate corresponding to low Recurrent Frequency values which was presented on IMI channel analysis. Thus, the software for the IMI channel analysis to detect only the cells accumulated in this gate was developed (HPC program). The peripheral blood samples were collected from the subjects (22 cases) before and after chemotherapy. Using HPC program, the regression coefficient value between the ratio of IMI positive cells and CD34 positive cells in the peripheral blood samples was 0.81 (n = 122). As SE-9000 enables to determine the number of PBSC easily and rapidly, the measurement of IMI positive cells is clinically useful for the monitoring of the rise in PBSC after chemotherapy for mobilization.

Adult↗
PubMed1998

[Peripheral blood stem cell transplants: clinical considerations and observations in practice in a general hospital].

Of 36 patients with malignant tumors who had been subjected to peripheral blood stem cell harvests (PBSCHs), 22 had undergone peripheral blood stem cell transplants (PBSCTs) since 1993. Flow cytometry recorded higher CD34+ cell yields in the PBSCHs of those patients with high white blood cell (WBC) counts as well as those who had been under intensive chemotherapy. Also, higher CD34+ cell yields were recorded in patients whose peripheral blood WBCs recovered more rapidly from their nadir state. WBC counts recovered rapidly in patients who received transfusions of at least 2.0 x 10(6) CD34+ cells/kg. However, patients with acute non-lymphocytic leukemia (ANLL) demonstrated a delayed recovery in their platelet counts following PBSCT. The mean disease-free survival rate and mean disease-free period were 60% and 12.8 months for the 5 patients with ANLL; and 100% and 11.3 months for the 4 patients with acute lymphocytic leukemia. These findings suggest PBSCT is a safe and effective treatment for patients with malignant tumors following high-dose chemotherapy, and can be performed in a private general hospital.

Adolescent↗
PubMed1998

[Acute myelogenous leukemia with hyperkalemia induced by pentamidine administration].

A 27-year-old male with acute myelogenous leukemia received an allogeneic bone marrow transplantation (allo-BMT). Pneumocystis carinii pneumonia developed on day 65 after the allo-BMT. The patient was intravenously treated with pentamidine. This resulted in a prompt improvement of his dyspnea and fever, but hyperkalemia occurred during the pentamidine therapy. Treatment with pentamidine was stopped and emergent treatment was started. Nevertheless, the serum potassium level rose to 7.7 mEq/l. Urgent dialysis was performed and the serum potassium level fell to 5.0 mEq/l after treatment. Careful monitoring of the serum potassium level is recommended during intravenous therapy with pentamidine.

Adult↗
PubMed1998

[Postoperative management of the preserved rectal segment in patients with familial polyposis: the use of 5-fluorouracil suppositories and green tea extract to inhibit tumor growth].

We report the clinical details of seven patients with familial polyposis. They underwent subtotal colectomy with ileorectostomy, and were treated with 5-fluorouracil suppositories and green tea extract after surgery. Some regression of the polyps in the preserved rectal segment was observed, and no rectal cancer developed in any of these patients.

Adenomatous Polyposis Coli↗