Sarah J. Thurston

Short exposures to 60 Hz magnetic fields do not alter MYC expression in HL60 or daudi cells

Analysis of changes in gene expression induced by 60 Hz magnetic fields has been considered to support an association between exposure to magnetic fields and cancer risk. Several reports have indicated that these fields rapidly activate many genes in mammalian cells. However, previous studies in this area have not provided sufficient information to support the conclusions drawn. To clarify this controversial research, we have attempted to validate, under rigorously controlled conditions, key experiments on induction of gene expression by magnetic fields. An extensive series of experiments, incorporating critical improvements in experimental design, most notably blind exposures and internal standards, was performed with human HL60 and Daudi cells. Exposure conditions covered a range of flux densities (5.7 microT to 10 mT) and times (20-60 min). No alteration in the human MYC gene, commonly referred to as c-myc, or beta-actin steady-state mRNA levels was observed. The lack of an effect was not attributable to exposure geometry, timing of RNA preparation, or serum lot and concentration. To eliminate any remaining variables, exact replication was performed in one of the laboratories previously reporting gene expression effects; again, no evidence for altered MYC expression was found. Finally, differential display PCR indicated that extremely low-frequency magnetic field-induced changes in gene expression were not prevalent.

Ultraviolet shadowing nucleic acids on nylon membranes

We describe a method for the direct visualization of nucleic acids on nylon membranes. Nylon is weakly fluorescent under short wave ultraviolet light allowing membrane-bound nucleic acids to be detected with a sensitivity of 10 ng. This procedure involves no staining or destaining of the gels prior to transfer, does not require duplicate sample lanes or blots, and does not interfere with transfer of the nucleic acid to the membrane or subsequent hybridization.

Localization of the gene for the trans-acting transcription factor Sp1 to the distal end of mouse chromosome 15.

The mouse chromosomal location for the gene (Sp1-1) encoding the trans-acting transcription factor Sp1 has been determined. Analysis of restriction fragment length polymorphisms in recombinant inbred, congenic, and interspecific backcross mice using human and mouse cDNA probes demonstrated that Sp1-1 is a single gene closely linked to the mammary tumor virus integration site-1 (Int-1) on the distal end of chromosome 15. Sp1 is a zinc finger protein, but Sp1-1 is not closely linked to any of the other zinc finger protein genes that have been mapped in mouse. Int-1 and other markers flanking the Sp1-1 locus are part of a conserved linkage group represented on human chromosome 12q.