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Biomedical subjects

W Z Yang

Publications and source records attributed to W Z Yang.

51 records · Page 3Linked to original sources
PubMed1992

Role of glutathione and glutathione S-transferase in chlorambucil resistance.

A chlorambucil (CLB)-resistant cell line, N50-4, was developed from the established mouse fibroblast cell line NIH 3T3, by multistep drug selection. The mutant cells exhibited greater than 10-fold resistance to CLB. Alterations in GSH and glutathione S-transferase (GST) were found in CLB-resistant variants. A 7-10-fold increase in cellular GSH content and a 3-fold increase in GST activity were detected in N50-4 cells, compared with parental cells, as determined by enzymatic assays. An increase in steady state levels of the GST-alpha isozyme mRNA was found in the CLB-resistant cells, as analyzed by Northern blotting. No GST gene amplification or rearrangement was shown by Southern blot analysis. To test the relative roles of GSH and GST in CLB resistance, a number of GSH- and GST-blocking agents were used. The CLB toxicity was significantly enhanced in N50-4 cells by administration of either the GSH-depleting agent buthionine sulfoximine or the GST inhibitors ethacrynic acid or indomethacin. The resistance to CLB cytotoxicity in N50-4 cells, however, was still significantly higher than that of parental cells. The resistance of N50-4 cells to CLB was almost completely abolished by combination pretreatment yielding both GSH depletion and GST inhibition. The results indicate that both increased cellular GSH content and increased GST activity play major roles in CLB resistance in N50-4 mutant cells.

3T3 Cells↗
PubMed1991

[Study on targeting drug delivery system--the animal behavior in vivo after hepatic arterial embolization of methotrexate microsphere].

The cross-linked MTX-gelatin microsphere was chosen as an experimental model. Pharmacokinetics and biodegradable period of the microsphere were studied after hepatic arterial embolization in vivo in dogs. After hepatic arterial infusion, the concentration of MTX-ms in peripheral vein blood increased rapidly and declined slowly. In contrast, the peak time of the drug concentration of infused MTX solution appeared at once and decreased rapidly. The half-life of MTX-ms in vivo was 2.14 times as much as that of MTX solution. During the assay period of sixteen hours the drug concentration of MTX-ms in hepatic vein blood was constantly higher than that of MTX solution. The follow-up angiography revealed that microsphere is a kind of peripheral embolic agent and its degradable time in vivo is about one month. Both sustained release and embolization effectiveness of microsphere will be significant in treatment of hepatic cancer.

Animals↗
PubMed1990

[A nutritional survey among day-school pupils].

A comprehensive nutritional survey conducted in Chengdu, 1986 among 488 day-school pupil aged 6 to 12 years showed that definite improvement in the dietary intake of heat energy, protein, iron, thiamin, niacin and ascorbic acid and other nutrients as compared with 1982, apparently the result of improved living standards. Nevertheless, the intake of energy food in breakfast meals were still inadequate. The findings revealed that 38.3% of the pupils suffered mild anemia. Special attention should be paid to the pupils' nutritional status during the adolescent growth spurt.

Adolescent↗
PubMed1989

Role of hyperventilation in hypoxia on lung growth in rats.

This study was conducted in an attempt to differentiate the contribution of hyperventilation, if any, from that of low PO2 on adaptive lung growth in response to hypoxia. Male albino rats were exposed to one of the following: (1) Room air for 7 days, as control; (2) 10% O2 in N2 for 7 days; (3) 10% O2 for 6 h, 1 day or 2 days and air for the remaining of 7 days; (4) 10% O2 for 2 days and 7% CO2 in air for 5 days; (5) air for 2 days and 7% CO2 for 5 days; or (6) 7% CO2 in air for 7 days. Lung growth was assessed by measuring the lung weight, lung air volume, lung DNA content and rate of DNA synthesis in lung explants. Hypoxia stimulated lung DNA synthesis even when administered for only 6 h, and the effects persisted for a few days after discontinuation of hypoxia. Hypercapnia did not stimulate DNA synthesis in lung. In 2 day hypoxic 5 day air rats the lung weight and lung DNA content increased, in 2 day air 5 day hypercapnic rats only the lung volume increased, and in 2 day hypoxic 5 day hypercapnic rats all parameters of lung growth, i.e., lung weight, DNA content and air volume increased as in 7 day hypoxic rats. The results suggest that adaptive or compensatory lung growth in hypoxia is brought about on one hand by the direct effect of low PO2 on lung cells, resulting in lung hyperplasia, and on the other hand by the mechanical stimulation of lung tissue by hyperventilation, causing lung distension.

Animals↗
PubMed1989

Role of cyclic AMP in proliferation of lung tissue in organ culture.

The role of cyclic AMP in cell proliferation and division has been the subject of study by a number of investigators in the past 30 years, but the argument of whether cyclic AMP is a negative or a positive regulator has not been settled. We studied the effect of cyclic AMP on proliferation of normal and postpneumonectomized lung tissues in young adult rats by measuring the incorporation of tritiated thymidine into lung DNA in organ culture. In normal lung tissues the incorporation of [3H]thymidine was increased by exogenous dibutyryl cyclic AMP, or by isoproterenol or forskolin to stimulate adenylate cyclase, or by caffeine, which inhibits cAMP phosphodiesterase. The effect of isoproterenol, but not forskolin, was abolished by the beta-adrenergic blocking agent propranolol. The effect of caffeine on [3H]thymidine incorporation was further enhanced in normal lung tissues in the presence of dibutyryl cyclic AMP and in postpneumonectomized lung tissues. Imidazole, a cAMP phosphodiesterase stimulator, also increased [3H]thymidine incorporation in culture, but the effect was not magnified in the presence of exogenous dibutyryl cyclic AMP, nor in postpneumonectomized lung tissues. The data suggest that cyclic AMP acts as a positive regulator in proliferation of lung tissues.

Animals↗
PubMed1988

[Differences in nitrogen and RNA contents between free bacteria and bacteria fixed to food particles in the rumen contents, in the case of different diets; consequences for estimating the ratio of bacterial nitrogen in duodenal nitrogen].

Differences in nitrogen and RNA contents were found between liquid-associated and solid-adherent bacteria isolated from the reticulo-rumen of ruminants offered various diets. Consequences on the estimation of the bacterial nitrogen flow to the duodenum are discussed.

Animal Feed↗
PubMed1985

The biological effects of photodynamic therapy on normal skin in mice--I. A light microscopic study.

A light microscopic investigation of the biological effects of photodynamic therapy using hematoporphyrin derivative and red light irradiation has been carried out. HpD alone, even used at a dose of 50 mg/kg, did not cause histologically discernible changes. The irradiation alone used in this experiment caused only slight or moderate dilatation and congestion of blood vessels, which disappeared completely within several hours after light exposure. In the PDT treated mouse ears severe degeneration and necrosis of skin tissue occurred within 1-2 days. The importance of adequate drug and light doses and proper interval chosen for obtaining best therapeutic effects and protection of surrounding normal tissues was pointed out. The possible mechanism of the PDT action in vivo was briefly discussed.

Animals↗
PubMed1985

The biological effects of photodynamic therapy on normal skin in mice--II. An electron microscopic study.

In the present study it has been demonstrated that the ultrastructural changes in mouse ear skin after PDT action occurred much more distinct and earlier than those observed in the histological study. Various types of cells in the skin respond to the photodynamic action differently. The endothelial cells, fibroblasts and nerve fibers are most sensitive. In contrast, the keratinocytes and chondrocytes often remain rather well preserved after PDT treatment. The possible mechanism of PDT action was briefly discussed.

Animals↗
PubMed1984

Circadian organization of running-wheel activity, food intake and drinking of old male rats.

Circadian rhythms of running-wheel activity, food intake and drinking were monitored in old male rats of Long-Evans strain over 22 months of age in both entrained (light:dark 12:12, LD) and free running condition (continuous illumination, LL) and were compared with those of young adult male rats of 3.5 to 6.5 months of age. Twenty-four hour distribution of running activity, feeding events and licking events of young rats as well as old rats showed bi- or tri-modal patterns during the 12 hr dark period of the LD schedule. In the light period, 2 out of 8 old rats, 6 out of 10 old rats and 1 out of 6 old rats had 1 or 2 medium or high peaks in running activity, feeding events and licking events, respectively, leading to equal distribution between the dark and light period. In the LD schedule, old rats showed a decrease in running-wheel activity, its patterns and power spectra, a decrease in feeding events and its power spectra in 6 rats which lost circadian rhythms and increase in feeding events and its power spectra in 4 rats which still showed circadian rhythms and increase in licking events. LL suppressed running-wheel activity, its patterns and power spectra, licking events and its power spectra and feeding events in young rats. However, LL could suppress only feeding events of 4 rats which still showed circadian rhythms and licking events and its spectral level in old rats. The possible causes of decreased response to LL in old rats and its implication are discussed.

Aging↗