No abstract

Using a flow cytometric technique to analyse DNA content and chromatin structure simultaneously, the following parameters of cell cycle progression were estimated in control and drug-treated L1210 cell cultures: (a) the kinetics of cell exit from the GI phase; (b) the probability of cell exit from the indeterminate portion of the GI phase, measured as the half-time of cell residence in that state; (c) the duration of the deterministic portion of GI phase; (d) the rates of cell transit through selected "windows" in S phase; (e) the rate of cell entrance into mitosis; (f) the mean duration of the cell cycle (Tc). These parameters are obtained in a single stathmokinetic experiment from measurements of individual samples withdrawn a t 30 min-1 hr intervals from Vinblasatinetreated cultures. In the same experiment mitotic indices are obtained with high statistical accuracy, and may be used to determine the terminal point of drug action. In addition to cell cycle analysis the method makes it possible to detect drug-induced changes in nuclear chromatin that are manifested by varying sensitivity of DNA in situ to denaturation by acid. Such changes were found to be associated with defective chromatin condensation, altered histone modifications or intercalation of the drugs into DNA. Using this technique the effects of sodium n-butyrate and two new antitumor drugs on L1210 cells were investigated.

Shedding of TNFR1 may help reduce apoptosis of hepatocytes induced by TNFalpha. Membrane-anchored metalloprotases could play a role in shedding membranous TNFR1. At the same time, PKC may take part in regulation of this shedding process.

The interphase NIH3T3 cells were vitally fluorescentstained with calcium indicator fluo-3 and Glogi probe C 6-NBD-ceramide, and then the single cells were examined by laser scanning confocal microscopy (LSCFM) for subcellular distributions of Ca 2+ and the location of Golgi apparatus. In these cells, the intracellular Ca 2+ were found to be highly concentrated in the Golgi apparatus. The changes of distribution of cytosolic high Ca 2+ region and the Golgi apparatus coincided with the cell cycle phase. In calcium free medium, when the plasma membrane of the cells which had been loaded with fluo-3/AM were permeated by digitonin, the fluorescence of the Golgi region decreased far less than that of the cytosol. Our results indicated that the Glogi lumen retained significantly high concentration of free calcium.