Control of asgE expression during growth and development of Myxococcus xanthus.

One of the earliest events in the Myxococcus xanthus developmental cycle is production of an extracellular cell density signal called A-signal (or A-factor). Previously, we showed that cells carrying an insertion in the asgE gene fail to produce normal levels of this cell-cell signal. In this study we found that expression of asgE is growth phase regulated and developmentally regulated. Several lines of evidence indicate that asgE is cotranscribed with an upstream gene during development. Using primer extension analyses, we identified two 5' ends for this developmental transcript. The DNA sequence upstream of one 5' end has similarity to the promoter regions of several genes that are A-signal dependent, whereas sequences located upstream of the second 5' end show similarity to promoter elements identified for genes that are C-signal dependent. Consistent with this result is our finding that mutants failing to produce A-signal or C-signal are defective for developmental expression of asgE. In contrast to developing cells, the large majority of the asgE transcript found in vegetative cells appears to be monocistronic. This finding suggests that asgE uses different promoters for expression during vegetative growth and development. Growth phase regulation of asgE is abolished in a relA mutant, indicating that this vegetative promoter is induced by starvation. The data presented here, in combination with our previous results, indicate that the level of AsgE in vegetative cells is sufficient for this protein to carry out its function during development.

Screening for stimulant use in adult emergency department seizure patients.

OBJECTIVE: The objective of this study was to determine the prevalence of positive plasma drug screening for cocaine or amphetamine in adult emergency department seizure patients. METHODS: This prospective study evaluated consecutive eligible seizure patients who had a plasma sample collected as part of their clinical evaluation. Plasma was tested for amphetamine and the cocaine metabolite benzoylecgonine using enzyme-mediated immunoassay methodology. Plasma samples with benzoylecgonine greater than 150 ng/mL or an amphetamine greater than 500 ng/mL were defined as positive. Patient demographics, history of underlying drug or alcohol-related seizure disorder, estimated time from seizure to sample collection, history or suspicion of cocaine or amphetamine abuse, results of clinical urine testing for drugs of abuse, and assay results were recorded without patient identifiers. RESULTS: Fourteen of 248 (5.6%, 95% CI 2.7%-8.5%) plasma samples were positive by immunoassay testing for benzoylecgonine and no samples (0%, 95% CI 0-1.2%) were positive for amphetamine. Positive test results were more common in patient visits where there was a history or suspicion of cocaine or amphetamine abuse (p < 0.0005). CONCLUSIONS: During this study period, routine plasma screening for cocaine and amphetamines in adult seizure patients had a low yield. As a result, routine plasma screening would yield few cases of stimulant drug in which there was neither a history nor suspicion of drug abuse in this population.