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Biomedical subjects

J F Jiang

Publications and source records attributed to J F Jiang.

9 recordsLinked to original sources
PubMed2000

Antioxidant and antiapoptotic function of metallothioneins in HL-60 cells challenged with copper nitrilotriacetate.

Antioxidant activity is believed to be an important intracellular function of metallothioneins (MT), yet the specific mechanisms of their antioxidant action are not known. Under conditions when cells are challenged with elevated concentrations of free copper as a result of metabolic disturbances or environmental and occupational exposures, MTs may be ideally suited for antioxidant function as effective copper chelators. In the study presented here, we tested this hypothesis using a recently established model of copper nitrilotriacetate-induced oxidative stress in HL-60 cells. Since copper-induced oxidative stress triggers apoptosis, we further investigated antiapoptotic function of MTs in HL-60 cells. Using a Sephadex G-75 chromatographic partial purification of MTs from cell homogenates with subsequent immuno-dot-blot assay, we showed that zinc pretreatment yielded a pronounced induction of MTs in HL-60 cells. We report that zinc-induced MTs were able to (i) completely bind intracellular copper, (ii) completely quench redox-cycling activity of copper, (iii) significantly inhibit copper-dependent oxidative stress in membrane phospholipids, and (iv) prevent copper-dependent apoptosis and its characteristic biochemical features (cytochrome c release from mitochondria into cytosol, caspase-3 activation, and externalization of phosphatidylserine in plasma membranes). In separate experiments, we used lung fibroblasts derived from MT1, MT2 knockout mice (MT(-)(/)(-)) and MT wild-type (MT(+/+)) mice. ZnCl(2) pretreatment resulted in a more than 10-fold induction of MTs in MT(+/+) cells, whereas the MT content in MT(-)(/)(-) cells remained low, at levels approximately 100-fold lower than in their MT wild-type counterparts. MT(-)(/)(-) cells were very sensitive to Cu-NTA and, most importantly, showed no response to ZnCl(2) pretreatment. In contrast, MT(+/+) cells were relatively more resistant to Cu-NTA, and this resistance was remarkably enhanced by ZnCl(2) pretreatment. Combined, our results demonstrate that metallothioneins function as effective antioxidants and an antiapoptotic mechanism in copper-challenged HL-60 cells.

Animals↗
PubMed2000

Differentiation-inducing action of 10-hydroxycamptothecin on human hepatoma Hep G2 cells.

AIM: To study the mechanism of differentiation-inducing action of 10-hydroxycamptothecin (HCPT) on human hepatoma Hep G2 cells. METHODS: The proliferating cell nuclear antigen (PCNA) expression was studied by immunocytochemical staining method. The cell cycle distribution and the wild-type protein p53 expression were measured by flow cytometry. Telomerase activity was assayed with telomeric repeat amplification protocol (TRAP). RESULTS: After treatment with HCPT at differentiation-inducing concentrations 5-20 micrograms.L-1 for 6 d, Hep G2 cells were mainly arrested at G2/M phase and the PCNA expression rate was lower than that of control cells. When Hep G2 cells grew in a medium containing HCPT 5 micrograms.L-1 for 6 d, the p53 expression level markedly increased in comparison with the control cells. The telomerase activity did not change in Hep G2 cells treated with HCPT 5-20 micrograms.L-1 for 8 d. CONCLUSION: The differentiation-inducing effect of HCPT on Hep G2 cells is related with the cell cycle arrest at G2/M phase, down-regulation of PCNA and up-regulation of wild-type protein p53.

Antineoplastic Agents, Phytogenic↗
PubMed2000

Regulation of telomerase activity in camptothecin-induced apoptosis of human leukemia HL-60 cells.

AIM: To explore the regulation of telomerase activity in camptothecin induced apoptosis of human leukemia HL-60 cells. METHODS: Apoptosis of HL-60 cells was induced by camptothecin (1 mg/L) for 2, 4, and 6 h. Apoptosis was determined by agarose electrophoresis and flow cytometry analysis. To assess telomerase activity, a PCR-based telomeric repeat amplification protocol assay (TRAP) was used. RT-PCR was performed to examine the mRNA levels of hTR (human telomerase RNA component), hEST2/hTERT (human telomerase reverse transcriptase), TLP1/TP1 (telomerase association protein 1), and bcl-2 (B cell leukemia/lymphoma 2 gene) in HL-60 cells before and after camptothecin treatment. RESULTS: Telomerase activity was decreased in a time-dependent manner during the camptothecin induced apoptosis of HL-60 cells. However, no difference in expression of each telomerase subunit was detected, while expression of bcl-2 was progressively down-regulated. CONCLUSION: These lines of evidences indicated that down-regulation of the telomerase activity in HL-60 cells was closely related to camptothecin-induced apoptosis, and the telomerase activity was not blocked at the transcriptional levels of the genes of the known ribonucleoprotein (RNP) complex components. We also found that bcl-2 did not regulate the mRNA expressions of telomerase subunits directly.

Apoptosis↗
PubMed1993

Clinical and experimental studies of cigarette smoking in microvascular tissue transfers.

Circulatory crisis, attributed to cigarette smoking, in three microvascular cases (two toe transfers, one musculocutaneous flap) is reported. After anticoagulation and antispasm treatment only one transfer survived. Coordinated experimental studies in the rat demonstrated that cigarette smoking delayed anastomotic healing. Five days after anastomoses were performed, endothelial cells completely covered the sutures in the experimental smoking group in only 16-19% of sutures, while the control group had a 75% coverage rate. Mechanisms and characteristics of circulatory crisis caused by cigarette smoking are discussed.

Adult↗
PubMed1993

Circulatory crisis caused by cigarette smoking in tissue transfer. Clinical and experimental studies.

Cigarette smoking-induced circulatory crisis occurred in two patients receiving toe transfer and one patient having musculocutaneous flap. After anticoagulation and antispasm treatment, one survived and two failed. Experimental studies demonstrated that cigarette smoking is harmful to the healing of endothelia at the anastomotic site of vessels. Five days after operation, the complete recovery rate of the endothelium over sutures of anastomotic sites was 16%-19% in smoking groups, but 75% in the control group. The mechanism and characteristics of circulatory crisis caused by cigarette smoking are discussed.

Adult↗
PubMed1992

Experimental study of free toe replantation in rats.

A rat model for free second toe replantation, free hallux-to-thumb transplantation, and combined free hallux-to-thumb transplantation and free second-toe-to-index transfer is described. Experimental devices, operative methods, and the keys to success are discussed.

Animals↗
PubMed1990

A new embedding method for tendon suturing.

A new embedding method in tendon suture was designed for interembedding of tendon ends to obtain interlock and strengthen antitension strength. Experiments showed that the embedding method might result in greater antitension strength than the conventional end-to-end method (Bunnell's method) or weaving method. Statistically, difference was significant. Dynamic studies on tendon healing showed that a prominent reaction of surrounding tissues occurred in 3 to 5 days after operation. In this period the antitension strength is likely to decrease and be broken with a rate of 28.1% in Bunnell's method, 5.25% in weaving method and 0% in embedding method. Clinically, the embedding method has been used in 125 cases of tendon-broken repair in which a 87.8% of good and excellent effect was resulted.

Animals↗
PubMed1989

Scanning electron microscopic observations on the endothelial healing mechanism of vessels.

Systematic scanning electron microscopic observations of the healing mechanism in the endothelium of rat carotid arteries were carried out at the site of anastomosis. The site of needle holes and stitches are the main locations for thrombocyte adhesion and aggregation in normal vascular anastomosis. The repair process in endothelial injury can be divided into three stages. A thrombocyte-adhesion and filling stage is apparent at 1 hr postoperatively; this is also the period when thrombus is most likely to occur. A fibrin-covering stage is apparent at 2 hr after operation and reaches its peak in 24 hr. The formation of fibrin provides a framework for endothelial growth. In this period, there is still the possibility of thrombus formation. At 48 hr postoperatively, endothelial growth can be seen at the site of some needle holes. At 72 hr after operation, 47 percent of needle holes have endothelial growth, and the possibility of thrombus formation at the anastomotic site declines. The data suggest that eversion of the intima in vascular anastomosis and minimization of endothelial injury by considering the size of the needle hole, the duration of ischemia time, and perfection of surgical technique, are keys to the prevention of thrombus formation at the anastomotic site.

Anastomosis, Surgical↗