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Biomedical subjects

Y Takami

Publications and source records attributed to Y Takami.

At least 91 records · Page 5Linked to original sources
PubMed1996

Pump power loss and heat generation in a pivot bearing-supported Gyro centrifugal pump (C1E3).

Pump power loss is defined as input power that is not used for the output work of the pump. Less pump power loss means a higher pump efficiency. A common opinion is that the pump power loss is closely related to heat generation of the pump, which may affect not only the endurance of pump materials, but also blood damage in a blood pump. In this study, the relationship between pump power loss and heat generation in centrifugal blood pumps was investigated using the pivot-bearing supported Gyro C1E3 pump (C1E3) and Bio-Medicus pump (BP-80) under four different total pressure heat/flow conditions. A single special torque measuring driver motor was used for operating both the C1E3 and BP-80 in the four conditions. The pump power loss was calculated from the measured motor torque and hydraulic power. The changes in blood temperature were measured while the pump was operated at room temperature (25 degrees C) to obtain the following findings: First, the C1E3 caused less pump power loss and less temperature increase in blood than the BP-80 in all clinical simulated conditions that were tested; and second, the pump power loss and heat generation had a linear correlation with temperature rise from 22 to 25 degrees C in both the C1E3 and BP-80. During this period, approximately 30% of the pump power loss was transformed to heat, independent of the centrifugal blood pump type, provided that heat conduction through the pump housing and tubing was negligible during this particular period.

Animals↗
PubMed1996

Safety margin of magnetic coupling distance in decoupling of a pivot bearing-supported Gyro centrifugal pump (C1E3).

The pivot bearing-supported Gyro C1E3 centrifugal pump is driven by magnetic coupling. The magnetic coupling distance (MCD) between the impeller magnet and the driver magnet affects both hydraulic performance and hemolysis. Although a greater MCD causes less hemolysis, it increases the risk of decoupling of the impeller magnet. Therefore, it is important to consider the effect of the MCD on both hemolysis and decoupling when the C1E3 pump is applied in various circulatory assist conditions. This study investigates the effect of the MCD on decoupling in a C1E3 pump that is driven by the Nd-Fe-B composite ring-shaped magnets. The results will determine which MCD is the most practical in all assist device conditions. The MCD of the C1E3 pump was varied from 9.5 to 14.5 mm by inserting spacers between the bottom pump housing and the driver magnet. At a rotational speed just before the decoupling occurred, the flow rate and total pressure head were measured. The results revealed that a MCD between 9.5 and 14.5 mm was enough to produce a flow rate of more than 10 L/min without decoupling, and a MCD of less than 11.5 mm was required when the total pressure head was more than 500 mm Hg. Thus, the limiting factor for the MCD of the C1E3 pump is the total pressure head rather than the flow rate. An MCD of less than 11.5 mm is required to prevent decoupling of the impeller of the C1E3 pump with the specific Nd-Fe-B magnets in the full range of clinical circulatory assist conditions.

Centrifugation↗
PubMed1996

Hemolytic characteristics of a pivot bearing supported Gyro centrifugal pump (C1E3) simulating various clinical applications.

Centrifugal blood pumps are playing a key role in circulatory mechanical assist systems including cardiopulmonary bypass (CPB), right and left ventricular assist devices (RVAD and LVAD), percutaneous cardiopulmonary support (PCPS), and extracorporeal membrane oxygenation (ECMO). Each of these circulatory assist systems requires specific flow and pressure conditions. In vitro hemolysis tests were performed using five compact mock loops with flow and pressure set equivalent to clinical conditions. These studies determined the hemolytic characteristics and clinical applicability of the pivot bearing-supported Gyro centrifugal pump with an eccentric port (C1E3) compared with the Bio-Medicus pump (BP-80). Normalized index of hemolysis (NIH) values of the C1E3 were less than those of the BP-80 under all conditions; in particular, they were significantly less in the CPB, LVAD, and RVAD conditions. In addition, linear correlation was observed between NIH values, rotational pump speed (RPM), total pressure head (delta P), and flow rate (Q) with both the C1E3 and BP-80: NIH = a(RPM/Q) + b, NIH = c(delta P/Q) + d. However, the slopes (a and c) of these equations were smaller with the C1E3 than those with the BP-80, which suggests that the C1E3 has decreased hemolytic characteristics when increasing the RPM and delta P. In other words, the increase of RPM and delta P results in less shear stress with the C1E3 than with the BP-80. One cause of these decreased hemolytic characteristics of the C1E3 is thought to be less pump power loss against an increase of RPM and delta P than with the BP-80. Furthermore, the average exposure time is shorter with the C1E3 than with the BP-80 because the priming volume of the C1E3 (30 ml) is smaller than that of the BP-80 (80 ml). From the point of both shear stress and exposure time, the C1E3 has less hemolytic features than the BP-80.

Animals↗
PubMed1996

[Coronary artery bypass grafting for ischemic heart disease associated with acromegaly: a case report].

Coronary artery bypass grafting (CABG) for ischemic heart disease associated with acromegaly has never been reported in Japan, though coronary artery sclerosis is known as complicating factor in acromegaly. A 44-year-old man with ischemic heart disease was admitted to our hospital and emergency percutaneous transluminal coronary recanalization was performed. After admission, he was diagnosed as acromegaly from endocrinological studies and operated on CABG. The peri- and post-operative course was uneventful in spite of our fear for complications due to acromegalic heart muscle disease.

Acromegaly↗
PubMed1996

Development of a pivot bearing supported sealless centrifugal pump for ventricular assist.

Since 1991, in our laboratory, a pivot bearing-supported, sealless, centrifugal pump has been developed as an implantable ventricular assist device (VAD). For this application, the configuration of the total pump system should be relatively small. The C1E3 pump developed for this purpose was anatomically compatible with the small-sized patient population. To evaluate antithrombogenicity, ex vivo 2-week screening studies were conducted instead of studies involving an intracorporeally implanted VADs using calves. Five paracorporeal LVAD studies were performed using calves for longer than 2 weeks. The activated clotting time (ACT) was maintained at approximately 250 s using heparin. All of the devices demonstrated trouble-free performances over 2 weeks. Among these 5 studies, 3 implantations were subjected to 1-month system validation studies. There were no device-induced thrombus formations inside the pump housing, and plasma-free hemoglobin levels in calves were within the normal range throughout the experiment (35, 34, and 31 days). There were no incidents of system malfunction. Subsequently, the mass production model was fabricated and yielded a normalized index of hemolysis of 0.0014, which was comparable to that of clinically available pumps. The wear life of the impeller bearings was estimated at longer than 8 years. In the next series of in vivo studies, an implantable model of the C1E3 pump will be fabricated for longer term implantation. The pump-actuator will be implanted inside the body; thus the design calls for substituting plastic for metallic parts.

Blood Cell Count↗
PubMed1996

Evaluation of the wear of the pivot bearing in the Gyro C1E3 pump.

To estimate the lifetime of the pivot bearing system of the sealless centrifugal Gyro C1E3 pump, pivot bearing wear phenomena of the C1E3 were studied. The pivot bearing system consisted of a male and female pivot made of ceramics and ultrahigh molecular weight polyethylene (UHMWPE), respectively. First, many pumping tests were performed with the C1E3 under various pumping conditions, and the effects of impeller position and fluid on wear were analyzed. Through these preliminary tests, it was found that the wear progress of the pivot bearing consisted of initial wear and stationary wear. Most of this initial wear is caused by the plastic deformation of the polyethylene female pivot. It also was observed that bovine blood was almost comparable to water in its effect on the stationary wear rate at the same rotational speed. Based on these results, a long-term pumping test was performed with the C1E3, and initial and stationary wear rates were determined. At the same time, the maximal loosening distance (LDmax) (permissible total wear) of the C1E3 was determined experimentally from hemolytic and hydraulic performance perspectives. By using experimentally determined parameters the lifetime of the pivot bearing system of the C1E3 was typically 10 years for right ventricular assist, 8 years for left ventricular assist, and 5 years for cardiopulmonary bypass.

Animals↗
PubMed1995

Purification, characterization, and molecular cloning of a novel rat liver Dopa/tyrosine sulfotransferase.

A novel sulfotransferase was purified from the rat liver cytosol to electrophoretic homogeneity via five column chromatography steps (hydroxylapatite I, DEAE Bio-Gel, ATP-agarose I, hydroxylapatite II, and ATP-agarose II). The minimum molecular weight of the purified enzyme was determined by sodium dodecyl sulfatepolyacrylamide gel electrophoresis to be approximately 33,000. Gel filtration chromatography revealed a native molecular weight of approximately 34,000, indicating the enzyme being present in the monomeric form. The purified sulfotransferase displayed enzymatic activities, with a pH optimum of 9.25, toward various tyrosine and 3,4-dihydroxyphenylalanine (Dopa) isomers, except DL-ortho-tyrosine. Thyroid hormones, as well as dopamine and p-nitrophenol, could also be used as substrates. The apparent Km value of the enzyme (designated the Dopa/tyrosine sulfotransferase) for L-Dopa, determined at a constant 14 microM of 3'-phosphoadenosine 5'-phosphosulfate, was 0.76 mM. The intact enzyme was found to be N-blocked when subjected to N-terminal sequencing. Three internal partial amino acid sequences, obtained by analyzing its proteolytic fragments, were found to be distinct from the homologous sequences of other known rat liver sulfotransferases. The deduced amino acid sequence of a full-length cDNA isolated from a rat liver cDNA library confirmed the identity of the Dopa/tyrosine sulfotransferase as a new type of aryl sulfotransferase. Upon transfection of COS-7 cells with an expression vector (pMSG-CMV) harboring the full-length cDNA, a 33-kDa protein displaying enzymatic and immunological properties similar to those of the purified Dopa/tyrosine sulfotransferase was expressed.

Amino Acid Sequence↗
PubMed1995

Targeted disruption of H2B-V encoding a particular H2B histone variant causes changes in protein patterns on two-dimensional polyacrylamide gel electrophoresis in the DT40 chicken B cell line.

The chicken H2B gene family comprises eight members (H2B-I to H2B-VIII), which are all located in two major histone gene clusters. All of them have been shown to encode four different protein variants (classes I to IV). In the DT40 chicken B cell line, the H2B-V gene, encoding the class III H2B variant, constituted about 10% of the total intracellular mRNA from all the H2B genes. To study the nature of this particular variant in vivo, we generated heterozygous (H2B-V, +/-) and homozygous (H2B-V, -/-) DT40 mutants by targeted integration. The remaining H2B genes were shown to be expressed more in these mutants than in the wild-type cell lines. The growth rate of DT40 cells was unchanged in the absence of the H2B-V gene. Two-dimensional polyacrylamide gel electrophoresis showed that the protein patterns were, on the whole, similar between the wild-type and homozygous cell lines. However, within this constant background, some cellular proteins disappeared or decreased quantitatively in the homozygous mutants, and several other proteins increased or newly appeared. These results suggest that the class III H2B variant participates negatively or positively in regulation of the expression of particular genes that encode the proteins that vary in DT40 cells. This type of regulation is possibly mediated through alterations in nucleosome structure over the restricted regions involving the putative genes of the DT40 genome.

Animals↗
PubMed1995

Targeted disruption of 01H1 encoding a particular H1 histone variant causes changes in protein patterns in the DT40 chicken B cell line.

Six members of the chicken H1 gene family, all of which are located in two major histone gene clusters, have been shown to encode six different protein variants. The intracellular mRNA level from one of them, 01H1, encoding the 01H1 variant composed of 218 amino acid residues, constitutes 9.9% of the total H1 mRNA in the DT40 chicken B cell line. To study the specific role of this particular H1 variant, besides its well-known functions as a linker in chromatin maintenance and as a general repressor of transcription, we used targeted integration to construct heterozygous and homozygous DT40 mutants with disruption of one and two 01H1 alleles, respectively. Analyses of the stable transfectants showed that the growth rate of DT40 was unchanged in the absence of two 01H1 alleles. Moreover, the remaining H1 genes were shown to be expressed more in these mutants than in the wild-type cell lines. Two-dimensional polyacrylamide gel electrophoresis showed that within an almost constant background in the homozygous mutants several cellular proteins newly appeared or increased, while some other proteins disappeared or decreased quantitatively. These variable proteins all differed from those that varied in DT40 mutants deprived of one of the eight chicken H2B genes, H2B-V, encoding a particular H2B variant. These results suggest that the 01H1 variant is involved in the regulation of expression of genes that encode the proteins that vary in 01H1-deleted mutants of DT40 cells.

Alleles↗
PubMed1995

Possible involvement of a ubiquitous and several distinct elements in the transcription regulation of the chicken H3 histone gene family.

We have studied possible modes of transcription regulation of four members (H3-II, H3-III, H3-IV and H3-V) of the twelve chicken H3 genes. Results of transient CAT assays using 5'-truncated mutants of H3-IV, together with those reported previously for H3-II and H3-III, indicated that all these four H3 genes possessed a ubiquitous element, the CCAAT sequence, in addition to several distinct elements. Transient CAT assays using the 5'-extended mutants of these four H3 genes showed that the promoter activities decreased with increasing lengths of the 5'-extended fragments, and that the effects were strong for H3-IV and H3-V, but only moderate for H3-II and H3-III.

Animals↗
PubMed1995

Targeted disruption of an H3-IV/H3-V gene pair causes increased expression of the remaining H3 genes in the chicken DT40 cell line.

The chicken H3 gene family contains 12 members (H3-I to H3-XII). Nine of them belong to two major histone gene clusters, but the genomic locations of the others are unknown. In the DT40 chicken B cell line, H3-IV and H3-V, which are located in inverted orientation and share a 3'-untranslated region of 531 bp, produce about 24% of the steady-state level of total mRNAs from all the H3 genes. To study the nature of these two genes, we carried out targeted integration into DT40 cells of constructs of the H3-IV/H3-V locus. Analysis of the stable transfectants showed that the growth rate of DT40 cells was unchanged in the absence of two copies of the H3-IV/H3-V locus. Furthermore, the remaining H3 genes were shown to be expressed more in the mutants lacking one or two H3-IV/H3-V alleles than DT40 cells, and the steady-state level of total H3 mRNAs remained constant in all the mutant cell lines tested. The levels of mRNAs from the H2B and H1 genes, which are located close to the H3 genes, were unchanged. These results demonstrate that the chicken H3 gene family has the ability to compensate for disruption of H3-IV/H3-V, which are normally responsible for about 24% of total H3 mRNAs.

Alleles↗
PubMed1995

Disappearance of Langerhans cells and melanocytes after cryopreservation of skin.

Cryopreserved skin allografts have been extensively reported to remain viable for longer periods after grafting, both in the laboratory and in the clinic, than skin stored by other methods. We investigated the immunocytochemical and electron microscopic properties of samples of cryopreserved human skin (-196 degrees C) for comparison with fresh samples. In an immunocytochemical study of fresh skin, reagents S-100 and CDIa indicated numerous mesenchymal origin cells in the squamous cell layer, basal layer and dermis; 2B7 identified these cells in the basal layer and PC-10 identified them in the basal and squamous cell layers. In cryopreserved skin, however, few cells reacted to these reagents. An electron microscopic study of the cryopreserved skin showed Langerhans cells (LC); however, these had suffered degeneration, with partial defects of the cell membrane and vacuolation in the cytoplasm. We speculate these effects are responsible for the virtually complete abolition of LC membrane and cytoplasm markers. In summary, we detected few mesenchymal origin cells, melanocytes, Langerhans cells, or S-phase cells, in cryopreserved skin by immunocytochemical methods. Langerhans cells existed but had degenerated. These results indicate that cryopreservation at -196 degrees C causes degeneration of Langerhans cells, and that is the reason for the prolonged viability of cryopreserved allograft.

Adolescent↗
PubMed1993

The chicken histone gene family.

1. Most of the chicken 43 core and H1 histone genes belong to two major histone gene clusters. 2. Each of six H1 genes encodes a different H1 protein sequence. 3. The known core histone genes, four H2A, seven H2B, and seven H3 genes, respectively, encode two, three and three different protein variants, whereas the four known H4 genes encode the same amino acid sequence. 4. The core histone genes have particular transcription regulatory elements within the 5'-flanking regions and the regulations of their expressions are distinct, even though they are members of the same core histone gene family. 5. There are some undefined differences in the DNA structures of the particular core histone genes in various chicken tissues and these structural variations probably result in differences in their transcriptional regulation.

Animals↗
PubMed1993

Properties of gamma-glutamyl transpeptidase in squamous cell carcinoma.

gamma-Glutamyl transpeptidase (GGT) was extracted from squamous cell carcinoma tissues of human skin (SCC) by Triton X-100 and bromelain treatment, and some of its biochemical properties were compared with those of GGT extracted from eccrine gland-rich tissue and normal kidney. GGT activity significantly increased in SCC, but there was no definitive differences in enzymological properties between GGT of SCC and normal tissue enzyme. However, GGT of SCC was distinguishable from those of normal tissues by isoelectric point, electrophoretic mobility, and sensitivity to neuraminidase treatment. These results indicate that GGT of SCC has some variant properties which may be related to skin carcinogenesis.

Carcinoma, Squamous Cell↗
PubMed1993

Isolation of flat revertants from human papillomavirus type 18 E6E7 transformed 3Y1 cells by transfection with a rat embryo fibroblast cDNA expression library.

A rat embryo fibroblast (REF) cDNA expression library was transfected into 3Y1 cells transformed by human papillomavirus type 18 E6 and E7 genes and 10 flat revertants were isolated. These revertants expressed the same levels of E6 and E7 mRNA as the parent cells, but had greatly reduced ability to form colonies in soft agar. Suppression of transformation was dominant in cell hybrids generated by fusing each revertant with the parental transformed cells. Furthermore, loss of transfected cDNA was observed in re-transformed cell hybrids derived from one flat revertant. Overexpression of the cDNA suppresses the colony-forming efficiency of the cells transformed by E6 and E7 genes.

Animals↗
PubMed1992

Presence of distinct transcriptional regulatory elements in the 5'-flanking region shared by the chicken H3 histone gene homopair.

The chicken H3 histone gene family contains nine members belonging to two major histone gene clusters. Six of these genes have been sequenced and shown to encode two different H3 protein variants. Five H3 genes (H3-I, -II, -IV, -V, and -VI) encode the same amino acid sequence (class I) and another H3 gene (H3-III) differs from class I in a single amino acid (IIe113-Met) (class II). H3-II and H3-III have inverted orientations and share a 5' intergenic region of about 900 bp. To understand the regulation of expression of these two genes, we fused the 5'-flanking region to the CAT gene in inverted orientations to generate two chimeric plasmids, pH3-II-900 and pH3-III-900. Transient CAT assays using these constructs indicated that the promoter of H3-III is more active than that of H3-II. CAT assays with deletion mutants showed that H3-II and H3-III each possess a particular transcription regulatory sequence 5' adjacent to their coding sequence. In addition, the functional sequences of H3-II have no effect on expression of H3-III and vice versa. These results suggest that the regulations of expression of the two H3 genes are distinct.

3T3 Cells↗
PubMed1992

The ramification of the superficial branch of the superior gluteal artery. Anatomical basis of a new gluteus maximus myocutaneous flap.

In order to design a new gluteus maximus myocutaneous flap, the ramification of the superficial branch of the superior gluteal artery was investigated in 56 sides of 33 Japanese cadavers. The superficial branch constantly divides into two main branches, which are called the ascending and transverse branches in this study. Of the ascending and transverse branches, one or both usually give off at least one well developed division running on the undersurface of the gluteus maximus muscle (98.2%). This division, which is called the intermediate branch in this study, generally reaches the superior edge of the muscle giving off only a couple of muscular branches and pierces the muscle and its deep fascia to supply skin (83.6%). Perforators of the intermediate branch constantly emerge from the fascia near the middle or lower one-third point on a line extending from the middle of the iliac crest to the tip of the greater trochanter.

Aged↗