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Biomedical subjects

C L Tai

Publications and source records attributed to C L Tai.

45 records · Page 3Linked to original sources
PubMed1980

9-Hydroxyprostaglandin dehydrogenase from rat kidney. Purification to homogeneity and partial characterization.

A 9-hydroxyprostaglandin dehydrogenase has been purified from rat kidney to apparent homogeneity. The molecular weight of the enzyme as determined by gel filtration was 33,000. Electrophoresis in sodium dodecyl sulfate gave a value of 34,000 indicating the absence of subunits. The enzyme catalyzes NAD+-specific irreversible oxidation of 15-keto-13,14-dihydro-prostaglandin F2 alpha as well as of 15-keto-PGF2 alpha and PGF2 alpha although at a lesser degree. It does not catalyze the oxidation of 6-keto-PGF1 alpha. The enzyme was sensitive to sulfhydryl inhibitors and was inhibited by prostaglandins, fatty acids, triiodothyroacetic acid, and indomethacin.

Animals↗
PubMed1980

Synthesis of [5,6-3H]arachidonic acid and its use in development of a sensitive assay for prostacyclin synthetase.

[5,6-3H]arachidonic acid has been prepared by catalytic reduction of eicosa-cis-8,11,14-trien-5-ynoic acid (IV) over Lindlar catalyst. When either [5,6-3H]arachidonic acid or [5,6-3H]PGH2 is converted into PGI2 by swine aortic microsomes, the tritium at C-6 is lost to the medium. Thus, the progress of this enzymic rearrangement may be monitored by following the rate of tritium release. As swine aortic microsomes contain only low levels of cyclooxygenase, it is necessary to fortify the system with ram seminal vesicular microsomes (rich in cyclooxygenase) when [5,6-3H]arachidonic acid is used as the indirect substrate.

8,11,14-Eicosatrienoic Acid↗
PubMed1980

Radioimmunological assay of prostacyclin synthetase activity.

A radioimmunoassay for 6-oxoprostaglandin F1 alpha has been developed. 6-Oxoprostaglandin F1 alpha antiplasma was produced in rabbits by repeated immunization with 6-oxoprostaglandin F1 alpha coupled to bovine serum albumin. [125I] -labelled hapten with high specific radioactivity was prepared by radioiodination of 6-oxoprostaglandin F1 alpha-tyrosine methyl ester conjugate followed by purification with thin layer chromatography. The antibodies showed good specificity toward 6-oxoprostaglandin F1 alpha and crossreacted only significantly with prostaglandin F1 alpha. The radioimmunoassay was applied to the determination of prostacyclin synthetase activity in swine aorta microsomes using arachidonic acid and prostaglandin H2 as indirect and direct substrates. The enzyme assay was validated by the criteria that the formation of 6-oxoprostaglandin F1 alpha, immunoreactivity from either substrates was both time and enzyme protein dependent, and was inhibitable by specific inhibitors of the enzyme system.

6-Ketoprostaglandin F1 alpha↗
PubMed1980

Inhibition of thromboxane synthesis and platelet aggregation by pyridine and its derivatives.

Pyridine inhibited the conversion of PG endoperoxide to TXA2 catalyzed by TX synthetase from human platelet and swine lung microsomes. The inhibitory potency of pyridine is abolished by derivatizing pyridine at the 2-position but is increased by introducing hydrophobic substituents at 3- or 4-positions, with 3-substituted pyridines being the most potent inhibitors. Inhibition by pyridine and its derivatives was also selective, since other enzymes in the arachidonic acid cascade were not significantly affected. Pyridine and the active derivatives also inhibited human platelet aggregation induced by arachidonic acid or ADP.

Animals↗
PubMed1976

Biosynthesis of prostaglandins in rabbit kidney medulla. Properties of prostaglandin synthase.

A simple radioactive-substrate assay for prostaglandin synthase (EC 1.14.99.1), which uses t.l.c. to measure simultaneously different prostaglandins synthesized from one precursor substrate, was developed. Rabbit kidney-medulla prostaglandin synthase catalyses the formation of prostaglandin E2, prostaglandin F2alpha and prostaglandin D2 from arachidonic acid. Fractionation of crude homogenates indicated that the microsomal fraction possessed the highest specific activity of prostaglandin synthase, whereas the soluble fraction exhibited little enzyme activity but rather contained a heat-labile inhibitory macromolecular factor(s), which might be attributed to the serum albumin present in this fraction. The microsomal fraction possessed low intrinsic enzyme activity, but the actvity could be fully stimulated by the presence of both GSH (reduced glutathione) and a phenolic cofactor. Only cysteine could partially replace GSH, whereas other thiols were inactive and some were even inhibitory. A variety of phenolic compounds, including catecholamines, dopamine (3,4-dihydroxyphenethylamine), 5-hydroxytryptamine and quinol, were active in stimulating prostaglandin synthase. In all cases, the stimulation was reflected in the synthesis of all three prostaglandins with ratios not significantly altered by different phenolic cofactors. The synthesis of each of the different prostaglandins appeared to have similar pH optima. The enzyme system was not inhibited by thiol-group inhibitors or a variety of metal chelators except for cyanide and 8-hydroxyquinoline. Characterization of the kidney-medulla prostaglandin synthase system indicated that it exhibited properties similar to those of the enzyme system present in seminal vesicles.

Animals↗
PubMedDate not supplied

Treatment of ununited femoral shaft fractures associated with locked nail breakage: comparison between closed and open revision techniques.

OBJECTIVES: To investigate and compare closed and open revision techniques in the treatment of ununited femoral shaft fractures associated with locked nail breakage. DESIGN: Retrospective. SETTING: University hospital. METHODS: Ununited femoral shaft fractures associated with locked nail breakage were treated with either closed or open revision (nine or eighteen cases, respectively). The closed technique entailed closed removal of the broken nail and reinsertion of a stable intramedullary nail after reaming the marrow cavity. The open technique included open removal of the broken nail, reinsertion of a stable intramedullary nail or plate, and cancellous bone graft supplementation. Union rate, union period, perioperative course, and complications were compared. RESULTS: Eight closed and fifteen open technique cases were followed for at least one year (median two years). Cases treated with the closed technique had a union rate of 100 percent, a union period of 4.4+/-0.9 months, an operating time of 1.5+/-0.4 hours, no blood transfusion, and no complications. Open technique cases demonstrated a union rate of 100 percent, a union period of 5.7+/-1.5 months (p = 0.033), an operating time of 2.4+/-0.4 hours (p < 0.001), blood transfusion of 1,000+/-500 milliliters (p < 0.001), and no complications. CONCLUSIONS: We recommend the closed revision technique because its union period and operating time are shorter, and it does not require a blood transfusion. Because there is no local wound dissection, infection rates should also be lower. However, the procedure is technically demanding. If it cannot be completed successfully, using the open technique can still achieve a satisfactory outcome.

Adolescent↗