The products of the bvgAS locus coordinately regulate expression of the Bordetella pertussis virulence regulon in response to environmental signals. Transcription of bvgAS-activated genes is nearly eliminated by several modulating conditions, induding the presence of sulfate anion or nicotinic acid and growth at low temperature. We have isolated spontaneous mutations that result in the constitutive synthesis of multiple bvg-regulated loci. Several of these mutations have been analyzed and were found to result from single-nucleotide substitutions within bvgS, in a region encoding a 161-amino-acid segment which links the transmembrane sequence with cytoplasmic domains that appear to be involved in signaling events. The effect of signal transduction mutations in Escherichia coli was determined by measuring the expression of anJhaB-lacZYA transcriptional fusion, and that in B. pertussis was determined by measuring expression of both luaB-cat and ptxA3201-cat fusions. The constitutive mutations have little effect on flJaBcat or JhaB-lacZYA expression in the absence of modulating signals but result in a nearly complete insensitivity to MgSO4, nicotinic acid, or growth at low temperature. Furthermore, insertion and deletion mutations in bvgS sequences encoding the periplasmic domain eliminate activity of the wild-type product, whereas constitutive mutants remain active. In B. pertussis cultures grown in Stainer-Scholte broth, expression of ptxA3201-cat differed from that of flaBcat in several respects. In combination with a wild-type bvgS allele, ptxA3201-cat expression required the addition of heptakis-(2,6-0-dimethyl)-,-cyclodextrin, and this requirement was eliminated by the presence of the constitutive mutations.A majority of the known virulence factors expressed by Bordetella pertussis, the etiologic agent of whooping cough, are coordinately regulated by a sensory transduction system encoded by the bvgAS (vir) locus (3,36,40). Transcription of the pertussis toxin operon (ptxA-E), the adenylate cyclase toxin-hemolysin gene (cyaA), the locus encoding filamentous hemagglutinin (fhaB), fimbrial subunit genes (fim), and the bvg operon itself requires the bvgAS gene products in trans (6,10,18,22,28,30,42). In addition, expression of dermonecrotic toxin, a 69-kDa outer membrane protein, cytochrome d629, and several other loci is positively controlled by bvg by mechanisms which remain to be determined (20,40). In Escherichia coli, the wild-type bvgAS locus is sufficient for activation of thejhaB and bvgA promoters but does not trans-activate expression of ptxA-E or cyaA (9, 22). It has therefore been suggested that there are additional requirements for expression of these two loci (9,11,23 (15,17,22,41

Background Ethanol and anesthetic drugs trigger neuroapoptosis in the developing mouse brain. Recently, it was found that ethanol-induced neuroapoptosis is preceded by suppressed phosphorylation of extracellular signal-regulated protein kinase (ERK), and lithium counteracts both the phosphorylated ERK suppressant action and ethanol-induced neuroapoptosis. The present study was undertaken to address the following questions: 1) Do ketamine and propofol mimic ethanol in suppressing ERK phosphorylation? 2) If they do, does lithium prevent this suppressant action, and also prevent these anesthetic drugs from triggering neuroapoptosis? Method Postnatal day 5 mice were treated with propofol, ketamine, lithium, a combination of propofol or ketamine and lithium or saline and their brains prepared for western blot analysis or histology. For western blot, cytosolic lysates of caudate putamen were analyzed for expression of phosphorylated ERK and phosphorylated serine/threonine-specific protein kinase. For histology, brains were stained immunohistochemically with antibodies to activated caspase-3 and the density of activated caspase-3 positive cells determined. Results Ketamine and propofol suppressed phosphorylated ERK, and lithium counteracted both the phosphorylated ERK suppressant action and neuroapoptotic action of these anesthetic drugs. Conclusion If further testing finds lithium to be safe for use in pediatric/obstetric medicine, administration of a single dose of lithium prior to anesthesia induction may be a suitable means of mitigating the risk of anesthesia-induced developmental neuroapoptosis.

Drugs that suppress neuronal activity, including general anesthetics used in pediatric and obstetric medicine, trigger neuroapoptosis in the developing rodent brain. Exposure of infant rats for 6 hours to a combination of anesthetic drugs (midazolam, nitrous oxide, isoflurane) reportedly causes widespread apoptotic neurodegeneration, followed by lifelong cognitive deficits. Isoflurane, the dominant ingredient in this triple cocktail, has not been evaluated individually for apoptogenic potential. It was recently reported that (1) the minimum alveolar concentration (MAC) for anesthetizing infant mice with isoflurane is 2.26%, and; (2) that infant mice, without assisted respiration, maintain normal arterial oxygen values but become hypoglycemic when exposed to isoflurane 3% for 30 minutes, then 1.8% for 1 hour (1.46 MAC-hours). In the present experiments, infant mice were exposed to isoflurane at various sub-MAC concentrations and durations, and the brains were evaluated quantitatively 5 hours after initiation of anesthesia exposure to determine the number of neuronal profiles undergoing apoptosis. Blood glucose values were also determined under each of these conditions. All conditions tested (isoflurane at 0.75% for 4 h, 1.5% for 2 h, 2.0% for 1 h) triggered a statistically significant increase in neuroapoptosis compared with the rate of spontaneous apoptosis in littermate controls. Blood glucose determinations ruled out hypoglycemia as a potential cause of the brain damage. It is concluded that exposure to sub-MAC concentrations of isoflurane for one or more hours triggers neuroapoptosis in the infant mouse brain. These findings are consistent with other recent evidence demonstrating that brief exposure to ethanol, ketamine, or midazolam triggers neuroapoptosis in the developing mouse brain.