Biochemical kinetics of cell proliferation regulated by extremely low frequency electromagnetic field.

To study the mechanism of cells subjected to external electromagnetic fields, the expression of cyclin kinase inhibitor p27 is analyzed in the four cell cycle phases. The regulatory functions are investigated in gap phase1 to synthesis, gap phase 2 to mitotic phase and post mitotic phase transition in the mammalian cell cycle processes. A mathematical model is developed to meet the general cell cycle regulatory network based on the molecular dynamics method. Phase plane analysis results show that the p27 over-expression can lead to the hysteresis effect of cell cycle processes and phase transition delay. It is an universal approach to predict the key regulatory gene in signal transduction pathway.

The alteration of PTEN tumor suppressor expression and its association with the histopathological features of human primary hepatocellular carcinoma.

PURPOSE: Although deletions or inactivating mutations of the tumor suppressor gene PTEN (phosphatase and tensin homolog deleted on chromosome 10) are involved in the development of a variety of tumors including glioblastoma, melanoma, prostate cancer, breast cancer, endometrial cancers etc., the role of PTEN expression in human primary hepatocellular carcinoma (HCC) has not yet been clarified. The aim of this study is to investigate the involvement of PTEN mRNA and protein expression in HCC. METHODS: The level of PTEN mRNA expression in HCC specimens was analyzed by Northern blot. PTEN poly-clonal antibody was raised by immunizing New Zealand white rabbit with (His)(6)-tagged PTEN fusion protein and characterized by Western blot. The level of PTEN protein expression was determined by immunohistochemistry. The significance of PTEN in HCC was analyzed by comparing its expression level with the clinicopathological parameters of HCC patients. RESULTS: Four transcripts of PTEN mRNA at 5.5 kb, 4.4 kb, 2.4 kb, and 1.8 kb were detected in most para-carcinoma liver tissues, and the expression level of PTEN mRNA in carcinoma liver tissues was found to decrease significantly. The poly-clonal antibody raised against histidine-tagged fusion PTEN protein showed specific immuno-reactivity to PTEN protein. Using the specific poly-clonal antibody prepared and characterized by ourselves, we found that PTEN protein was significantly down-regulated in HCC tissues compared with paired para-carcinoma tissues. The protein expression of PTEN is negatively associated with the pathological grading and presence of cancer thrombus of HCC. CONCLUSIONS: Down-regulation of PTEN expression may play an important role in the development of HCC and the level of PTEN expression may be a potential adjuvant parameter in forecasting the progression and prognosis of HCC patients.

Levels of immunoreactive dynorphin A1-13 during development of morphine dependence in rats.

AIM: To study the relationship between the levels of immunoreactive dynorphin A1-13 (ir-dynorphin A1-13) and the degree of morphine dependence. METHODS: The levels of ir-dynorphin A1-13 in discrete brain regions, spinal cord, and plasma in rats were determined by radioimmunoassay, and the degree of morphine dependence was assessed by scoring withdrawal signs on d 3, d 6, and d 12. RESULTS: Morphine injection s.c. decreased the levels of ir-dynorphin A1-13 in spinal cord, pituitary, and plasma. The levels of ir-dynorphin A1-13 in hippocampus and hypothalamus were increased. No changes in cortex, midbrain, cerebellum, pons, and medulla were observed. With continuous injection of morphine, withdrawal signs scores were increased on d 6, but there was no difference between the scores of d 6 and d 12. CONCLUSION: The changes of the levels of endogenous ir-dynorphin A1-13 in pituitary, spinal cord, and plasma were compatible with the degree of morphine dependence.