Role of endogenous carbon monoxide in central regulation of arterial pressure

We investigated the contribution of neural mechanisms to the arterial pressure increase produced by zinc deuteroporphyrin 2,4-bis glycol (ZnDPBG), an inhibitor of endogenous carbon monoxide synthesis. The arterial baroreceptor reflex control of heart rate was examined in rats with and without ZnDPBG pretreatment (45 micromol/kg IP) by analysis of the arterial pressure-heart rate relationship during infusions of phenylephrine or sodium nitroprusside to vary arterial pressure. ZnDPBG increased arterial pressure from 110 +/- 3 to 126 +/- 2 mm Hg without eliciting bradycardia. The maximum gain of the heart rate response to changes in arterial pressure was attenuated by ZnDPBG treatment (-1.9 +/- 0.3 versus -4.8 +/- 1.0 bpm/mm Hg). The possibility that ZnDPBG elevates arterial pressure by attenuating baroreceptor reflex function was addressed by comparing the pressor response to ZnDPBG (45 micromol/kg IP) in rats with and without sinoaortic denervation. The pressor effect of ZnDPBG was similar in rats with and without arterial baroreceptor deafferentation, implying that the increase in pressure is not simply the consequence of attenuated baroreceptor reflex function per se. The possibility that ZnDPBG increases arterial pressure via an effect on the nucleus tractus solitarii (NTS) also was investigated. ZnDPBG (1 nmol in 100 nL) injected into the NTS of rats increased arterial pressure from 111 +/- 4 to 126 +/- 5 mm Hg, and this effect was reversed by an ipsilateral microinjection of carbon monoxide into the NTS. Accordingly, the pressor effect of ZnDPBG may rely on inhibition of carbon monoxide production in the NTS. This implies that carbon monoxide formed by brain heme oxygenase plays a role in the central regulation of arterial pressure.     

Archaeal nucleosomes

Archaea contain histones that have primary sequences in common with eukaryal nucleosome core histones and a three-dimensional structure that is essentially only the histone fold. Here we report the results of experiments that document that archaeal histones compact DNA in vivo into structures similar to the structure formed by the histone (H3+H4)2 tetramer at the center of the eukaryal nucleosome. After formaldehyde cross-linking in vivo, these archaeal nucleosomes have been isolated from Methanobacterium thermoautotrophicum and Methanothermus fervidus, visualized by electron microscopy on plasmid and genomic DNAs, and shown by immunogold labeling, SDS/PAGE, and immunoblotting to contain archaeal histones, cross-linked into tetramers. Archaeal nucleosomes protect approximately 60 bp of DNA and multiples of approximately 60 bp from micrococcal nuclease digestion, and immunoprecipitation has demonstrated that most, but not all, M. fervidus genomic DNA sequences are associated in vivo with archaeal histones.     

Buspirone metabolite structure profile using a standard liquid chromatographic-mass spectrometric protocol

A rapid and systematic LC-MS protocol is utilized to profile buspirone metabolites. Analysis of rat bile, urine and liver S9 samples using a standard LC-MS method provides structural information for 25 metabolites. The resulting buspirone metabolite structure database contains characteristic retention time, molecular mass and MS-MS product ion information for each compound. Metabolites are categorized according to profile groups, which illustrate that substitution reactions are primarily associated with the azaspirone decane dione and pyrimidine substructures. Structures of new buspirone metabolites are reported and include the despyrimidinyl, despyrimidinylpiperazine, glucuronide, hydroxyglucuronide (four isomers), methoxyglucuronide and hydroxymethoxyglucuronide (two isomers) buspirone metabolites.