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Cell cycle analysis by DNA flow cytofluorimetry and autoradiography has been utilized to investigate the effects of 3-methoxybenzamide (MBA), a potent inhibitor of ADP-ribosylation reactions, on cell cycle progression in N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-treated C3H10T1/2 cells. Following a dose of 6.8 microM MNNG, the presence of MBA resulted in an increased length of S phase from approximately 6.5 h to 10 h and in an accumulation of cells in G2 with a mitosis delay of 12 h. Progression to the next S phase occurred 5-10 times more slowly and the cells ultimately accumulated in G2. Increasing the dose of MNNG resulted in a complete block in cell division in the absence of ADP-ribosylation. These results suggest that ADP-ribosylation reactions, which do not seem to be necessary for DNA excision repair in nondividing cells, are essential for coordinating the events of DNA excision repair with DNA replication and events related to progression through the cell cycle.

Flow cytometry has become the preferred technique by which critical clinical evaluations are made such as CD4 counts and aneuploid analyses. Mounting concern has arisen over the numerous techniques, reagents, and different flow cytometers employed to determine these data. Several studies have documented significant differences in results when different flow cytometers are utilized to analyze the same sample. Fluorochrome-dependent instrument sensitivity also has been reported by numerous investigators. As more and more procedures are performed by cytometric analysis, light scatter and fluorescence limitations, which appear to be instrument dependent, demonstrate that not all flow cytometers have the same capabilities. Attempts were made to calculate molecules of equivalent soluble fluorochrome (MESF) values on nine different flow cytometers using fluorescein isothiocyanate (FITC) and R-phycoerythrin (R-PE) labeled microsphere reference standards produced by Flow Cytometry Standards Corporation (FCSC). Dramatiic differences were observed in the ability of some cytometers to resolve these microspheres. The diminished resolution appeared to be instrument model and fluorochrome dependent. We propose that diminished fluorescence resolution in certain flow cytometers could be responsible for significant variability in clinical values reported from laboratories utilizing different flow cytometers. o 1995 Wiley-Liss, Inc.*

A 27-year-old woman was maintained in an isolated state for 131 days in Carlsbad Caverns, New Mexico. Her diet was vitamin D-depleted. Determinations on the effects of such isolation on levels and activities of peripheral blood cells that are important for hematological homeostasis and immunological function were carried out. Throughout the duration of the study, the percentage of lymphoid cells that expressed CD3, CD4, CD8, CD19, Leu 8, and other markers remained relatively constant although the absolute numbers of these cells varied. Although the percentage of natural killer (NK) cells did not vary, the activity of these cells did change. NK cell activity became elevated as the isolation study progressed. Production of interferon-gamma (IFN-gamma) in response to mitogen stimulation was higher than expected throughout the isolation periods, but returned to the normal range after termination of the isolation. Red and white cell counts dropped significantly upon entering isolation, but soon returned to normal.

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