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In the present study we have examined the effect of dexamethasone on ob gene mRNA expression and leptin release from isolated human subcutaneous adipocytes. Dexamethasone stimulated leptin release from cultured adipocytes in a time- and dose-dependent manner. A two-fold increase in leptin release was detectable by 36 h of treatment with 10(-7) M dexamethasone. Leptin release was preceded by a significant 83 +/- 30% increase in ob mRNA after 24 h exposure to the compound. Co-incubation of cells with dexamethasone (10(-7) M) and insulin (10(-7) or 10(-9) M) completely blocked the dexamethasone-stimulated increase in ob mRNA and leptin release. These data demonstrate that insulin and glucocorticoids regulate leptin synthesis and release from human adipocytes in vitro.

Subtractive hybridization was used to isolate genes expressed uniquely in the immortalized human breast epithelial cell (HBEC) line MCF-10F and not in the mortal HBEC line S-130, from which MCF-10F cells were derived. We identified a 233-bp cDNA that was expressed in MCF-10F cells and not in their mortal counterpart S-130 cells. Sequence comparison with the GenBank database revealed that the cDNA was identical to the gene encoding human ferritin heavy H chain. Northern blot analysis using the isolated cDNA as a probe showed a differentially expressed 1.1-kb transcript of ferritin H in total RNA from the immortal MCF-10F cells, MCF-10F cells treated with the chemical carcinogens 7,12-dimethylbenz[a]anthracene and benzo[a]pyrene, and the breast cancer cell lines MCF-7, HBL-100, T-47D, and BT-20. No ferritin H transcript was detected in the mortal line S-130 or in other primary HBEC cultures. Increased levels of mRNA transcript signals were also detected in total RNA from breast cancer tissue samples. Tissue with ductal hyperplasia had higher expression levels than normal adjacent mammary tissue. In situ hybridization showed high levels of ferritin H transcript in mammary tissue areas with ductal hyperplasia, carcinoma in situ, and infiltrating ductal carcinoma. This is the first report of the differential expression and upregulation of human ferritin H chain gene in immortal HBECs. It may be an important factor in the process of immortalization, possibly an early stage of malignant transformation of HBECs, providing cells with iron necessary for growth and clonal expansion. Also, ferritin iron, once released, may increase the level of reactive iron, leading to an increase in oxygen free-radical generation, oxidative DNA damage, and mutation.

Elimination gasoline vapor in oil tank by mechanical ventilation has disadvantages of long vent time poor safety, and low efficiency, however, those shortcomings can be better conquered if combusted gas is used in the process of the mechanical ventilation. Based on former studies, the research on the effects of inlet location on gasoline vapor’s inert replacement in oil tank by combusted inert gas is studied experimentally in this paper. The conclusions in this paper can provide some useful guidance for the field project of gasoline vapor’s inert replacement in oil tank.