Search PubMed⌕ Search

Biomedical subjects

Y Takada

Publications and source records attributed to Y Takada.

At least 559 records · Page 31Linked to original sources
PubMed1988

Graft transection and warm perfusion in situ in canine partial orthotopic liver transplantation.

Liver transplantation is now proven therapy for various forms of end-stage liver disease in children; however, the problem of donor liver shortage remains. To investigate the feasibility of graft procurement from living, genetically related adult donors without injury to either donor or recipient, partial orthotopic liver transplantation (PLT) using a graft transected and warm perfused in situ was evaluated in beagles; the viability of the graft was assessed in terms of energy metabolism, including blood ketone body ratio (KBR), as well as of recipient survival. PLT was performed in two groups with venovenous bypass. The left half of the donor liver was transected in situ, flush perfused with 2 l lactated Ringer's solution (4 degrees C in group A, 20 degrees C in group B), and immediately implanted into the recipient, who was totally hepatectomized, care having been taken to leave the inferior vena cava intact. Four of seven dogs survived for 5 days or longer (longest, 8 days) in group A and six of eight dogs (longest, 20 days) in group B. Causes of death were gastrointestinal bleeding, intussusception, or infection but not graft dysfunction. In both groups the KBR decreased significantly during the anhepatic period, recovered rapidly to the pre-anhepatic level after revascularization, and was maintained within a normal range thereafter. No significant differences in the time course of changes in KBR were seen between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Enhanced activator activity of the mixture of streptokinase and a modified form of plasminogen (Lys-plasminogen) in the presence of fibrin: role of conformational change of plasminogen.

Equimolar concentrations of Lys-plasminogen (Lys-PLG) and streptokinase (SK) were mixed with various concentrations of fibrin, fibrinogen, fragment D or E (potentiating agents). The activity of the mixture was measured by the hydrolysis of S-2251. Kinetic analyses indicated that catalytic rate constant (kcat) of the hydrolysis of S-2251 increased in the presence of increasing amounts of potentiating agents. Km did not change in their presence. Effectiveness of the enhancement of the hydrolysis of S-2251 was in the order of fibrin greater than fibrinogen greater than E greater than D. It could be concluded that a complex of SK, Lys-PLG and potentiating agent is a better enzyme, thus activator, than a complex of SK and Lys-PLG. Since Lys-PLG does not change its conformation and its activation rate upon interaction with fibrin, the enhanced activator activity of complex of SK, Lys-PLG and potentiating agent may not be due to the conformational change of Lys-PLG.

Chromogenic Compounds↗
PubMed1988

Comparison of kinetic parameters of the activation of Glu-plasminogen by tissue plasminogen activator obtained from various sources.

Kinetic analyses were made for the activation of Glu-plasminogen (Glu-Plg) by tissue plasminogen activator (t-PA) obtained from various sources. We compared kinetic parameters for three t-PA preparations. t-PA(M) was obtained from cultured melanoma cell line, and t-PA(W) and t-PA(TD) were obtained from cells with recombinant DNA. t-PA(W) had two chains whereas t-PA(TD) had one chain. Although values of kinetic parameters were different in the three t-PA preparations, there were following general tendencies. The presence of catalytic amounts of fibrin resulted in a decrease in Km, whereas the presence of larger amounts of fibrin resulted in an increase in kcat with a slight decrease in Km. The presence of fibrinogen also enhanced the activation of Glu-Plg by t-PA with an increase in kcat and without change in Km. When the effects of fragment D or E were compared, the presence of increasing amounts of E resulted in an increase in kcat, but the presence of increasing amounts of D resulted in an increase in kcat and a decrease in Km. The results suggest that roles of D and E domains of fibrin may be different in the enhanced activation of plasminogen by t-PA.

Animals↗
PubMed1988

Physiology of plasminogen: with special reference to activation and degradation.

Plasminogen is said to be synthesized in many organs, but the major source of its production is considered to be the liver. The production of plasminogen is observed in fetal life, but its plasma level is low in new born infants, rising rapidly to attain adult levels in about 13 weeks. The plasma levels do not change much with age. Although the fibrinolytic enzyme system is influenced by many factors such as hormones, exercise, emotion, age, sex, nutritional states etc., the plasma levels of plasminogen are relatively stable. In this presentation we would like to discuss three important subjects related to the physiology of plasminogen. The first subject is the activation pathway of the native form of plasminogen (Glu-plg) by various activators in the plasma or clotted plasma. Glu-plg was not easily activated by activators such as urokinase (UK) or tissue plasminogen activator (t-PA), but activated very easily in the presence of fibrin clot. In the presence of purified clot, Glu-plg was partly activated by activators to Glu-plasmin, but also converted to Lys-plg by preformed plasmin, subsequently being activated to plasmin. Glu-plg I (containing two carbohydrate chains) changed conformation more easily upon interaction with fibrin than Glu-plg II (containing one carbohydrate chain) and Glu-plg I was also more easily activated by activators than Glu-plg II. Although Glu-plg was hardly activated by activators in the plasma, Glu-plg was activated easily in the presence of plasma clot. Results of immunoblotting experiments indicated that Glu-plg was mainly activated by activators directly to plasmin, not via Lys-plg in contrast to purified systems. The second subject is the degradation of plasminogen by elastase. Plasminogen may be degraded by proteolytic enzymes such as cathepsin or elastase. The degradation of plasminogen by elastase is shown to give rise to K1 to K3, K4, and mini-plg (containing K5). We have shown that the degradation rate to Glu-plg by elastase increased in the presence of tranexamic acid, indicating that the conformational change of Glu-plg in the presence of tranexamic acid resulted in the exposure of the hydrophobic regions connecting K3, K4 and K5, thus making them accessible to elastase. Consequently, Lys-plg or conformationally altered Glu-plg (possibly bound to fibrin or FDP) is more easily degraded in vivo. The last subject is relationship between plasma plasminogen levels and fibrinolytic activity in various ages. Although plasma plasminogen levels do not change with age, the fibrinolytic activity lowers.(ABSTRACT TRUNCATED AT 400 WORDS)

Enzyme Activation↗
PubMed1987

Characterization of the cell surface heterodimer VLA-4 and related peptides.

A monoclonal antibody (B-5G10) was produced which specifically recognizes the Mr 150,000/130,000 VLA-4 complex on the surface of human cells. Cross-linking studies indicated that the Mr 150,000 alpha 4 subunit of VLA-4 is in noncovalent 1:1 association with the Mr 130,000 VLA beta subunit. In the absence of cross-linking, the VLA-4 alpha 4 beta subunit complex was easily dissociated, especially in Nonidet P-40 detergent, or at elevated pH (above 8.0). Studies of dissociated subunits showed that B-5G10 recognizes an epitope on the Mr 150,000 alpha 4 subunit of VLA-4, whereas the beta subunit is immunologically identical to the Mr 130,000 beta subunit common to all VLA heterodimers. VLA-4 is widely distributed on hematopoietic cells, including thymocytes, peripheral blood lymphocytes, monocytes, activated T cells, T and B lymphoblastoid cell lines, and myeloid cell lines. However, VLA-4 is only weakly expressed on most adherent cell lines tested. Immunoprecipitates of VLA-4 often contain additional proteins of Mr 80,000 and Mr 70,000. These are probably derived from the Mr 150,000 alpha 4 subunit because: 1) they are both recognized by anti-alpha 4 sera, but not anti-beta sera; 2) the sum of their sizes is equal to the size of alpha 4; 3) they are selectively coexpressed with alpha 4 and not other VLA alpha subunits; 4) the Mr 80,000 protein has an identical NH2-terminal sequence to alpha 4; 5) like alpha 4, the Mr 70,000 and 80,000 peptides can variably associate with the VLA beta subunit; and 6) trypsin appears to cleave the Mr 150,000 alpha 4 subunit into products of Mr 70,000 and 80,000.

Amino Acid Sequence↗
PubMed1987

Relationship between age and plasma t-PA, PA-inhibitor, and PA activity.

A positive correlation between age and the occurrence of thrombosis has been suggested. We studied the relationship between age and fibrinolytic activities; namely levels of tissue plasminogen activator (t-PA) antigen, plasminogen activator inhibitor (PA inhibitor) activity, and plasminogen activator activity (PA activity). A dramatic increase in both t-PA antigen and PA inhibitor was shown in persons with increasing age. PA activity decreased with age. Therefore it is suggested that the tendency of decreased PA activity with increasing age may be related to the high incidence of thrombosis in older persons.

Adolescent↗