PubMed · 9752302
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J J Mazeron, G Boisserie. 1998. [The alpha/beta connection].. https://pubmed.ncbi.nlm.nih.gov/9752302/
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In this work, we shed new light on the highly debated issue of chromatin fragmentation in cryopreserved cells. Moreover, for the first time, we describe replicating cell-specific DNA damage and higher-order chromatin alterations after freezing and thawing. We identified DNA structural changes associated with the freeze-thaw process and correlated them with the viability of frozen and thawed cells. We simultaneously evaluated DNA defects and the higher-order chromatin structure of frozen and thawed cells with and without cryoprotectant treatment. We found that in replicating (S phase) cells, DNA was preferentially damaged by replication fork collapse, potentially leading to DNA double strand breaks (DSBs), which represent an important source of both genome instability and defects in epigenome maintenance. This induction of DNA defects by the freeze-thaw process was not prevented by any cryoprotectant studied. Both in replicating and non-replicating cells, freezing and thawing altered the chromatin structure in a cryoprotectant-dependent manner. Interestingly, cells with condensed chromatin, which was strongly stimulated by dimethyl sulfoxide (DMSO) prior to freezing had the highest rate of survival after thawing. Our results will facilitate the design of compounds and procedures to decrease injury to cryopreserved cells.
Immunohistochemistry was used to determine the expression of granulocyte colony-stimulating factor (G-CSF) and its receptor (G-CSFR) in primary ovarian carcinomas. The expression of G-CSFR was observed in the malignant cells of each of the 46 primary carcinomas examined; G-CSF was coexpressed in both the malignant epithelial cells and the stroma of 56.5% of the specimens. Thus the majority of ovarian carcinomas harbor both potential autocrine and paracrine G-CSF axes. In 37% of the samples, G-CSF was expressed only within stromal cells, suggesting that only a potential paracrine system is in place. In a preliminary, retrospective, evaluation, the survival of patients whose tumors expressed only the apparent paracrine loop was significantly worse than patients whose tumors expressed both potential autocrine and paracrine G-CSF-based regulatory loops (14.5 vs. 42.5 months, respectively). Studies on the potential function of G-CSF were performed using the G-CSFR-expressing OVCAR-3 ovarian carcinoma line. As a single agent, rhG-CSF failed to stimulate [3H]-thymidine incorporation in these cells, but enhanced the mitogenic action of epidermal growth factor (EGF) in a dose-dependent manner. Thus, potential autocrine and/or paracrine loops involving G-CSF and its receptor occur in over 90% of primary ovarian carcinomas, and may act to modulate the action of growth factors.
BACKGROUND: The use of conventional fluorescence microscopy to image biological systems at the cellular level is limited by its inability to spatially resolve thick tissues. We have applied the technique of multi-photon fluorescence microscopy to study the structure and function of endothelial cells in living human saphenous vein taken from patients undergoing coronary artery bypass surgery. MATERIALS AND METHODS: Vein segments were preserved for 1-4 h to determine the temporal effects of storage. The effect of pH on endothelial and smooth muscle cell viability was examined by storing segments at pH 6.0, 7.4, and 8.0. Calcein-mediated green fluorescence and ethidium homodimer-mediated red fluorescence were used to differentiate cell viability. Increases in diaminofluorescein fluorescence were used to measure bradykinin activation of endothelial nitric oxide synthase (eNOS) with or without N-nitro-l-arginine (L-NNA). Multi-photon imaging was performed with the BioRad MRC1024ES system. RESULTS: Successful imaging of endothelial and smooth muscle cells of vein segments was achieved. Cell viability was well preserved up to 3 h of storage but dramatically decreased after 4 h. Cell viability was maintained at pH 7.4, diminished at pH 8.0, and was completely lost at pH 6.0. A two- to threefold increase in eNOS activity was observed upon activation by bradykinin which was completely inhibited in L-NNA-treated samples. CONCLUSIONS: We have demonstrated the successful application of multi-photon microscopy in imaging and quantifying nitric oxide production and cell viability under various storage conditions in human saphenous veins. This imaging technique allows for the functional imaging of cellular processes and may have diagnostic potential in cardiovascular surgery for patients undergoing bypass operations.