Comparison of clonogenic assay with premature chromosome condensation assay in prediction of human cell radiosensitivity.

AIM: To determine whether the number of non-rejoining G2-chromatid breaks can predict the radiosensitivity of human cell lines. METHODS: Cell lines of human ovary carcinoma cells (HO8910), human hepatoma cells (HepG2) and liver cells (L02) were irradiated with a range of doses and assessed both of cell survival and non-rejoining G2-chromatid breaks at 24 h after irradiation. Cell survival was documented by a colony assay. Non-rejoining G2-chromatid breaks were measured by counting the number of non-rejoining G2 chromatid breaks at 24 h after irradiation, detected by the prematurely chromosome condensed (PCC) technique. RESULTS: A linear-quadratic survival curve was observed in three cell lines, and HepG2 was the most sensitive to gamma-radiation. A dose-dependent linear increase was observed in radiation-induced non-rejoining G2-PCC breaks measured at 24 h after irradiation in all cell lines, and HepG2 was the most susceptible to induction of non-rejoining G2-PCC breaks. A close correlation was found between the clonogenic radiosensitivity and the radiation-induced non-rejoining G2-PCC breaks (r = 0.923). Furthermore, survival-aberration correlations for two or more than two doses lever were also significant. CONCLUSION: The number of non-rejoining G2 PCC breaks holds considerable promise for predicting the radiosensitivity of normal and tumor cells when two or more than two doses lever is tested.

Comparative study on radiosensitivity of various tumor cells and human normal liver cells.

AIM: To investigate the radiation response of various human tumor cells and normal liver cells. METHODS: Cell lines of human hepatoma cells (SMMC-7721), liver cells (L02), melanoma cells (A375) and cervical tumor (HeLa) were irradiated with (60)Co gamma-rays. Cell survive was documented by a colony assay. Chromatid breaks were measured by counting the number of chromatid breaks and isochromatid breaks immediately after prematurely chromosome condensed by Calyculin-A. RESULTS: Linear quadratic survival curve was observed in all of four cell lines, and dose-dependent increase in radiation-induced chromatid and isochromatid breaks were observed in GB2B phase. Among these four cell lines, A375 was most sensitive to radiation, while, L02 had the lowest radiosensitivity. For normal liver cells, chromatid breaks were easy to be repaired, isochromatid breaks were difficult to be repaired. CONCLUSION: The results suggest that the gamma-rays induced chromatid breaks can be possibly used as a good predictor of radiosensitivity, also, unrejoined isochromatid breaks probably tightly related with cell cancerization.

Study in vitro and in vivo of nociceptin/orphanin FQ(1-13)NH2 analogues substituting N-Me-Gly for Gly2 or Gly3.

In the present study, two analogues containing N-Me-Gly (Sarcosine, Sar) were synthesized to further investigate the structural-activity relationships of orphanin FQ/nociceptin (OFQ/NC, NC). The replacement of Gly(2) or Gly(3) with Sar increased the flexibility and decreased the hydrophobicity of the N-terminal tetrapeptide. The activity of the analogues was investigated in a series of assays in vivo and in vitro. [Sar(2)]NC(1-13)NH(2) was found to (1) produce dose-dependent inhibition of the electrically induced contraction in MVD assay (pEC(50) = 6.14); (2) produce significant hyperalgesia effects in a dose-dependent manner when intracerebroventricularly (i.c.v.) injected in mice. The inhibitive effects of [Sar(2)]NC(1-13)NH(2) in MVD assay could be significantly antagonized by [Nphe(1)]NC(1-13)NH(2), and partially antagonized by naloxone; the hyperalgesic effect of [Sar(2)]NC(1-13)NH(2) could be significantly antagonized by naloxone, and partially antagonized by [Nphe(1)]NC(1-13)NH(2). On the contrary, [Sar(3)]NC(1-13)NH(2) showed no effects in these assays. All the findings suggest that the flexibility of the peptide bond between Phe(1) and Gly(2) and between Gly(2) and Gly(3) play an important role in NC-OP(4) receptor interaction, and the hydrophobicity of the N-terminal tetrapeptide showed no significant effect on this interaction. The present work also helps to provide a novel method to elucidate structural and conformational requirements of the opioid peptide-receptor interaction.

Effects of nociceptin (13-17) in pain modulation at supraspinal level in mice.

This work was designed to observe the effects of nociceptin(13-17), one of the main metabolites of nociceptin (also termed orphanin FQ), in pain modulation at supraspinal level in mice. Intracerebroventricular (i.c.v.) administration of nociceptin/orphanin FQ(13-17) (N/OFQ(13-17)) (5, 0.5, 0.05, 0.005 nmol/mouse) dose-dependently induced potent hyperalgesic effects in the 48 degrees C warm-water tail-flick test in mice. I.c.v. pretreatment with N/OFQ(13-17) (5, 0.5, 0.05 nmol/mouse) potentiated the analgesic effects induced by morphine (i.p., 2 mg/kg) and reversed the hyperalgesic effects induced by N/OFQ (i.c.v., 5 nmol/mouse). The hyperalgesic effects induced by N/OFQ(13-17) could not be antagonized by [Nphe((1))]N/OFQ(1-13)NH((2)) or naloxone. These findings suggest that N/OFQ(13-17) may play important roles in pain modulation at supraspinal level in mice and elicits these effects through a novel mechanism independent of the N/OFQ receptor and the mu, delta and kappa opioid receptors.