Deuterium oxide (heavy water) arrests the cell cycle of PtK2 cells during interphase.

Deuterium oxide (D2O, heavy water) exerts an antiproliferative effect on a variety of cells in vitro and on some organisms. This effect is mainly ascribed to a tubulin-mediated antimitotic action. We evaluated the morphology, the mitotic activity, and the dynamics of the cell cycle of PtK2 cells grown in vitro in the presence of 75% D2O for up to eight weeks by microspectrophotometric DNA measurements as well as flow cytometric analysis and a determination of mitotic indices.

Extinction of the HPV18 upstream regulatory region in cervical carcinoma cells after fusion with non-tumorigenic human keratinocytes under non-selective conditions.

'Universal fuser' clones of a human papillomavirus type 16 positive cervical carcinoma cell line (SiHa) were established to study the effect of a non-tumorigenic fusion partner on the regulation of a stably integrated chloramphenicol acetyltransferase (CAT) gene controlled by the HPV18 upstream regulatory region under non-selective conditions. The CAT expressing cells were fused with both non-tumorigenic, spontaneously immortalized human keratinocytes (HaCaT) and non-modified SiHa cells. The resulting hybrids were characterized by restriction enzyme fragment length polymorphism analysis and flow cytometry.

Application of laser optical tweezers in immunology and molecular genetics.

Optical tweezers, based on a compact diode pumped Nd:YAG laser providing 350 mW at 1,064 nm coupled into a Zeiss IM 35 microscope, were used to sort CD4+ T cells into a capillary for further mechanical handling and to establish contact between single human natural killer (NK) cells and human erythroleukemia cells (K562) as targets. After contact and a lag phase of a few tens of seconds, the target cell starts to change its morphology and membrane blebbing occurs. The kinetics of the attack of the NK cell on K562 cells is not straightforward but governed by temporal oscillations in the shape of the target cell (zeosis).

Comparison of S-phase fractions measured by flow cytometry and autoradiography in human transplant tumors.

The 3H-thymidine labeling index (TLI) and the percentage of cells in the S-phase have been determined by autoradiography and by flow cytometry, (FCM), respectively, in six malignant tumors of human origin transplanted on athymic nude mice. The Dean and Jett model and the graphical model were used to determine the percent of S-phase cells by FCM. Cell cycle analysis was performed using 1) no correction for background; 2) an algebraic function for background correction; and 3) an exponential function for background subtraction.

Cytostatic and cytotoxic response of Ehrlich ascites tumor cells in vivo on chronic treatment with cytarabine, bleomycin, and peplomycin.

The cytokinetic response of Ehrlich ascites tumor (EAT) cells in vivo upon chronic treatment at low dosage levels with cytarabine (1-beta-D-arabinofuranosylcytosine, ara-c) bleomycin (BLM) and peplomycin (PEP) was estimated. Bivariate DNA histograms allow the simultaneous evaluation of the cell cycle status of living and killed cells. It could be confirmed that ara-C is cytostatic on cells in S phase.