Spermidine/spermine N1-acetyltransferase (SSAT) activity in human small-cell lung carcinoma cells following transfection with a genomic SSAT construct.

Spermidine/spermine N (1)-acetyltransferase (SSAT) activity is typically highly inducible in non-small-cell lung carcinomas in response to treatment with anti-tumour polyamine analogues, and this induction is associated with subsequent cell death. In contrast, cells of the small-cell lung carcinoma (SCLC) phenotype generally do not respond to these compounds with an increase in SSAT activity, and usually are only moderately affected with respect to growth. The goal of the present study was to produce an SSAT-overexpressing SCLC cell line to further investigate the role of SSAT in response to these anti-tumour analogues. To accomplish this, NCI-H82 SCLC cells were stably transfected with plasmids containing either the SSAT genomic sequence or the corresponding cDNA sequence. Individual clones were selected based on their ability to show induced SSAT activity in response to exposure to a polyamine analogue, and an increase in the steady-state SSAT mRNA level. Cells transfected with the genomic sequence exhibited a significant increase in basal SSAT mRNA expression, as well as enhanced SSAT activity, intracellular polyamine pool depletion and growth inhibition following treatment with the analogue N (1), N (11)-bis(ethyl)norspermine. Cells containing the transfected cDNA also exhibited an increase in the basal SSAT mRNA level, but remained phenotypically similar to vector control cells with respect to their response to analogue exposure. These studies indicate that both the genomic SSAT sequence and polyamine analogue exposure play a role in the transcriptional and post-transcriptional regulation and subsequent induction of SSAT activity in these cells. Furthermore, this is the first production of a cell line capable of SSAT protein induction from a generally unresponsive parent line

Challenges for the maintenance and cryopreservation of multiple isolates of model microorganisms : an example using the marine diatom Skeletonema marinoi

Modern genomic and metabolomic tools have provided the possibility of generating and interrogating large datasets that can provide answers to previously imponderable taxonomic, evolutionary, ecological, and physiological questions. However, the curatorial tools needed to provide and maintain the relevant biological resources on which new knowledge can be built have not kept pace with this meteoric rise in scientific capacity, its associated activity, or the huge increase in published science. The availability of biological material of guaranteed identity and quality in Biological Resource Centers is fundamental for scientific research, but it crucially depends on there being adequate preservation/maintenance methods that are capable of ensuring phenotypic, genotypic, and functional security of the biological material(s). This article highlights the challenges to the long-term maintenance of genetic resources in general, focusing specifically on the issues associated with the maintenance of a large collection of strains of the ecologically significant diatom Skeletonema marinoi. This research collection, held at the Department of Marine Sciences, University of Gothenburg, has been systematically tested for its capacity to survive cryopreservation. A method, involving incubation in the dark for 20-24 hours before cryopreservation, followed by cryoprotection employing 10% dimethysulphoxide (DMSO) and conventional cooling in a passive cooler, before plunging into liquid nitrogen was successfully applied to similar to 80% of the strains tested. In addition, the growth characteristics of exemplar strains were confirmed after storage