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Biomedical subjects

T Z Liu

Publications and source records attributed to T Z Liu.

69 records · Page 4Linked to original sources
PubMed1977

Biochemical basis of skeletal defects induced by hydralazine: inhibiton of collagen synthesis and secretion in embryonic chicken cartilage in vitro.

Hydralazine (1-hydrazinophthalazine) produces skeletal defects resembling those observed in experimentally induced manganese deficiencies. Since glycosylation of collagen, a step preceding its secretion, requires Mn2+, the effect of hydralazine on collagen secretion and the formation hydroxylysine glycosides was examined in explants of embryonic chicken long-bone rudiments. Auto-radiographic studies showed that hydralazine blocked collagen secretion. Secretion was restored by Fe2+ alone or Fe2+ + Mn2+ but not by Mn2+ alone, suggesting that a Fe2+-requiring step was involved. Biochemical analyses showed that hydralazine inhibited the formation of hydroxylysine, a step requiring Fe2+, but it did not inhibit the formation of hydroxylysine-glocosides by Mn2+-requiring steps, although the reaction was inhibited in vitro. Hydralazine also failed to inhibit intracellular mucopolysaccharide synthesis which involves several Mn2+-requiring enzymes. These observations suggest that the deleterious effects of hydralazine on bones are caused by its inhibition of hydroxylation steps in collagen synthesis.

Abnormalities, Drug-Induced↗
PubMed1977

Measurement of serum magnesium with a centrifugal analyzer.

We show how serum magnesium can be determined with a centrifugal analyzer. The method is based upon a manual procedure involving magnesium/calmagite complex formation in an alkaline reagent mixture. The assay, performed at 30 degrees C, requires 5 mul of serum in a final reaction volume of 405 mul, including 350 mul of reagent mixture. The stable color produced at 1 min is measured at 520 nm. Linearity studies showed that Beer's law was followed to 50 mg/liter. Average analytical recovery was 97.3%. Within-day studies showed CV's of 3.36% and 1.09%, compared to day-to-day variations of 5.32% and 3.04% at 18.8 and 46.6 mg of magnesium per liter, respectively. Correlation studies with the manual method, the Du Pont aca (methylthymol blue compleximetric) procedure, and atomic absorption spectroscopy showed correlation coefficients of 0.996, 0.976, and 0.950, respectively. Results compare excellently with those by common present methods. The method is fast, economical, reliable, and applicable to small specimen volumes.

Azo Compounds↗
PubMed1977

Interference of sodium azide with measurement of serum uric acid by the direct acid ferric reduction procedure.

We examined the effect of sodium azide on the quantitation of serum uric acid by the direct acid ferric reduction procedure. Ferric phenanthroline was used as redox indicator. Sodium azide, in a concentration commonly used as preservative (2 g/liter, 27.2 mmol/liter), increased the absorption at 505 nm and increased apparent uric acid values in specimens, as shown by calculations based on an azide-free standard. Spectral studies indicated that this interference was a result of the color produced by sodium azide in the reaction mixture. The mechanism for azide interference was the interaction of sodium azide and ferric ions to form ferric azide, which also absorbs extensively at 505 nm.

Azides↗
PubMed1975

Loss of ability to synthesize collagen in fibroblasts transformed by rous sarcoma virus.

Transformation of chick embryo fibroblasts by Rous sarcoma virus inhibited their ability to synthesize collagen. Kinetic experiments showed that 72 hours after infection, collagen synthesis was reduced by 90%. Nontransforming Rous-associated viruses did not inhibit collagen synthesis. The inhibition resulted from the failure of the cells to synthesize collagen polypeptides rather than from a decrease in the activity of prolyl hydroxylase; the levels of prolyl hydroxylase were fourfold those in uninfected cells. The addition of dibutyryl cyclic AMP and theophylline, alone or together, did not restore collagen synthesis.

Animals↗
PubMedDate not supplied

The isoprostanes: unique bioactive products of lipid peroxidation. An overview.

The development of a specific, reliable and noninvasive method for measuring oxidative stress in humans is essential for establishing the role of free radicals in human diseases. Currently, accurate techniques to assess oxidant injury in vivo are extremely limited although a number of approaches are being investigated. Of these, the measurement of specific products of nonenzymatic lipid peroxidation, the F2-isoprostanes (F2-IsoPs), appears to be a more accurate marker of oxidative stress in vivo in humans than other available methods. The purpose of this brief review is to acquaint the reader with the IsoPs from a biochemical perspective and to provide information regarding the utility of quantifying these compounds as indicators of oxidant stress.

Animals↗
PubMedDate not supplied

Inhibition of creatine kinase activity and alterations in electrophoretic mobility by palladium ions.

The toxicological consequences of increased levels of palladium in the environment have not yet been assessed. In this paper, the effect of palladium ions (Pd) on purified rabbit muscle creatine kinase (CPK-MM) and on human serum CPK-MM was examined. When rabbit muscle CPK-MM was treated with Pd, a concentration-dependent inhibition of enzyme activity with a calculated Ki of 0.16 mumol, associated with a marked increase in a electrophoretic mobility of the enzyme toward the anode, was observed. Pd exerted the same effect of human serum CPK-MM, but to a lesser extent. Analysis of binding of Pd to CPK-MM by a colorimetric competitive-binding technique, using chlorpromazine-chromophore, as well as by a dialyzing technique, indicated that the cation may form an extremely strong complex with essential SH groups of the enzyme.

Animals↗