PubMed Health⌕ Search

Biomedical subjects

C Vens

Publications and source records attributed to C Vens.

5 recordsLinked to original sources
PubMed2002

Rapid fluorescence ratio assay for detecting changes in radiosensitivity.

To test modifications in sensitization to radiation or drugs in preclinical studies of cancer therapy, the colony-forming assay is regarded as the gold standard. Because this assay is time consuming, somewhat laborious, and unsuitable for rapid screening, development of other assays is desirable. We describe here an assay based on the detection of enhanced green fluorescence protein (EGFP) with flow cytometry that is particularly suitable for genetic manipulation studies in which the gene of interest is introduced together with EGFP as reporter. It is easily adaptable to other reporters, however, whether naturally fluorescent or requiring immunochemical staining. Cells are irradiated as mixed populations of a known standard cell line (nonfluorescent) together with the genetically manipulated cell line expressing EGFP. Ratios of fluorescent and nonfluorescent cells are measured before treatment and several days after treatment. If the cell populations have equal radiosensitivities, the ratio remains unchanged. Changes in the ratio indicate changes in radiosensitivity. The assay was validated for two situations in which dominant negative peptides inhibiting DNA repair were expressed in A549 human lung cells and affected radiosensitivity.

Cell Death↗
PubMed1999

T cell activation responses are differentially regulated during clinorotation and in spaceflight.

Studies of T lymphocyte activation with mitogenic lectins during spaceflight have shown a dramatic inhibition of activation as measured by DNA synthesis at 72 h, but the mechanism of this inhibition is unknown. We have investigated the progression of cellular events during the first 24 h of activation using both spaceflight microgravity culture and a ground-based model system that relies on the low shear culture environment of a rotating clinostat (clinorotation). Stimulation of human peripheral blood mononuclear cells (PBMCs) with soluble anti-CD3 (Leu4) in clinorotation and in microgravity culture shows a dramatic reduction in surface expression of the receptor for IL-2 (CD25) and CD69. An absence of bulk RNA synthesis in clinorotation indicates that stimulation with soluble Leu4 does not induce transition of T cells from G0 to the G1 stage of the cell cycle. However, internalization of the TCR by T cells and normal levels of IL-1 synthesis by monocytes indicate that intercellular interactions that are required for activation occur during clinorotation. Complementation of TCR-mediated signaling by phorbol ester restores the ability of PBMCs to express CD25 in clinorotation, indicating that a PKC-associated pathway may be compromised under these conditions. Bypassing the TCR by direct activation of intracellular pathways with a combination of phorbol ester and calcium ionophore in clinorotation resulted in full expression of CD25; however, only partial expression of CD25 occurred in microgravity culture. Though stimulation of purified T cells with Bead-Leu4 in microgravity culture resulted in the engagement and internalization of the TCR, the cells still failed to express CD25. When T cells were stimulated with Bead-Leu4 in microgravity culture, they were able to partially express CD69, a receptor that is constitutively stored in intracellular pools and can be expressed in the absence of new gene expression. Our results suggest that the inhibition of T cell proliferative response in microgravity culture is a result of alterations in signaling events within the first few hours of activation, which are required for the expression of important regulatory molecules.

Antigens, CD↗
PubMed1996

The C5 Unit: a semi-automatic cell culture device suitable for experiments under microgravity.

This paper presents data on a novel, semi-automatic cell culturing device called 'C5 Unit' (connectable circuit cell culture chamber) which was developed and adapted to the quality and size criteria set by the characteristics of the ESA Biorack. The suitability of the hardware for culturing cells under microgravity conditions was demonstrated by successful culture of primary mouse cells from neonatal cerebellum and testis aboard the Space Shuttle during the IML-2 mission.

Animals↗
PubMed1994

Ectopic expression of NCAM in mouse fibroblasts stimulates self-aggregation, and promotes integration into primary cerebellum cell aggregates.

We have undertaken aggregation experiments using mouse LMTK(-)-fibroblasts transfected with various isotypes of the neural cell adhesion molecule, NCAM. We found that self-aggregation of NCAM-positive fibroblasts is enhanced compared to control-transfected cells. The aggregation properties are partly dependent on the expressed NCAM isotype. Fibroblasts expressing a NCAM 140 isotype with exons a3 and pi were further tested in primary cerebellum cell re-aggregation experiments. While control-transfected fibroblasts could not be found in forming aggregates, fibroblasts ectopically expressing NCAM were integrated into neural cell aggregates. Time-lapse photography indicated that the nascent primary cell aggregates actively participated in the integration process by migration and attachment to nearby NCAM-positive fibroblasts.

Animals↗