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Biomedical subjects

H Xiang

Publications and source records attributed to H Xiang.

76 records · Page 5Linked to original sources
PubMed1988

Effect of L-carnitine treatment on lipid metabolism and cardiac performance in chronically diabetic rats.

The beneficial effects of L-carnitine administration were studied in vivo in isolated perfused working hearts from control and diabetic rats. Control and streptozocin-induced diabetic (STZ-D) rats were treated daily for 6 wk with high-dose L-carnitine (3 g.kg-1.day-1 i.p.). STZ-D results in loss of body weight and hypoinsulinemia. These effects were not altered by L-carnitine treatment. Myocardial free-carnitine levels were decreased in the untreated diabetic rats. L-Carnitine treatment of the diabetic rats increased myocardial free-carnitine levels, which were comparable with those of control rats. Six weeks after STZ administration, hearts from untreated diabetic animals exhibited depressed left ventricular developed pressure, cardiac contractility, and ventricular relaxation rates compared with control animals. However, this depression was not seen in the L-carnitine-treated diabetic animals. L-Carnitine treatment of diabetic rats significantly reduced plasma glucose and lipid levels but had no effect on control rats. Furthermore, thyroid hormone levels were higher in the L-carnitine-treated diabetic rats than in the untreated diabetic group. The data suggest that high-dose L-carnitine treatment may reduce the severity of diabetes and result in improved cardiac performance.

Animals↗
PubMed1988

Effect of myo-inositol and T3 on myocardial lipids and cardiac function in streptozocin-induced diabetic rats.

Numerous experimental studies have implied a link between diabetes-induced abnormal lipid buildup in the myocardium and the development of cardiomyopathy. Because the diabetic state in rats is associated with lowered T3 (triiodothyronine) and T4 levels and because diabetic patients excrete large amounts of myo-inositol, a lipotropic agent, we investigated the effects of myo-inositol and T3 on the elevated myocardial lipid levels and depressed cardiac performance of streptozocin (55 mg/kg i.v.)-induced diabetic (STZ-D) rats. myo-inositol (2.5 g.kg-1.day-1 in the drinking water) and T3 (30 micrograms.kg-1.day-1 s.c.) were given for an 8-wk period 3 days after diabetes induction. Untreated diabetic rats were characterized by a decreased rate of body weight gain, hyperglycemia, and hypoinsulinemia, which were not altered after myo-inositol and/or T3 treatment. Thyroid status of diabetic animals was normalized by T3 alone or in combination with myo-inositol but not by myo-inositol alone. The elevations in plasma and myocardial lipids associated with the diabetic state were prevented by myo-inositol treatment. However, the plasma lipid and myocardial cholesterol levels in diabetic rats remained elevated or were further increased with treatment with T3 or myo-inositol plus T3. myo-inositol treatment partially improved cardiac performance in STZ-D rats. T3 treatment alone did not prevent cardiac dysfunction in diabetic rats. There was, however, some improvement in heart function in the groups treated with both myo-inositol and T3, coinciding with a significant decrease in the myocardial triacylglycerol level. The data indicate that a possible correlation may exist between elevated myocardial triacylglycerol levels and cardiac dysfunction in diabetic rats.

Animals↗
PubMedDate not supplied

Production and utilization of detyrosinated tubulin in developing Artemia larvae: evidence for a tubulin-reactive carboxypeptidase.

The reversible, enzymatically driven removal and readdition of its carboxy-terminal tyrosine are major posttranslational modifications of alpha-tubulin. To study these processes isoform-specific antibodies were produced and subsequently used to characterize tyrosinated and detyrosinated tubulin in the brine shrimp, Artemia. Tyrosinated tubulin existed in relatively constant amounts on western blots of cell-free protein extracts from Artemia at all developmental stages examined, whereas detyrosinated tubulin was present after 20-24 h of postgastrula growth. In agreement with the blots, the detyrosinated isoform was observed in immunofluorescently stained larvae after 24 h of incubation, appearing first in structures of a transient nature, namely spindles and midbodies. The elongated muscle cells encircling the gut and the epithelium bordering the gut lumen were stained extensively with antibody to detyrosinated tubulin. Detyrosination was accompanied by the appearance of a tubulin-reactive carboxypeptidase, which used both nonpolymerized and polymerized tubulin as substrate. The enzyme bound to microtubules very poorly, if at all, under conditions used in this work. Several inhibitors of carboxypeptidase A had no effect on the carboxypeptidase from Artemia and revealed similarities between this enzyme and others thought to be tubulin specific. The use of inhibitors also indicated that the carboxypeptidase from Artemia recognized aspects of tubulin structure in addition to the carboxy-terminal tyrosine. Our results support the idea that detyrosinated tubulin appears in microtubules of varying stability, and they demonstrate that Artemia possess a carboxypeptidase with the potential to detyrosinate tubulin during growth of larvae.

Amino Acid Sequence↗