In Vivo Voltammetric Monitoring of Catecholamine Metabolism in the A1 and A2 Regions of the Rat Medulla Oblongata

Catecholaminergic metabolism was estimated in A1 and A2 noradrenergic nuclei of the rat medulla oblongata using differential normal pulse voltammetry combined with electrochemically treated carbon fiber microelectrodes. In both areas an oxidation peak appearing at +50 mV was recorded. Electrochemical data and pharmacological experiments indicated that 3,4-dihydroxyphenylacetic acid (DOPAC) synthesized by noradrenergic neurons was the major contributor to this signal. Indeed, alpha-methyl-p-tyrosine, by inhibiting tyrosine hydroxylase, and pargyline, by inhibiting monoamine oxidase, both totally suppressed the peak appearing at +50 mV in A1 and A2 areas. Conversely, FLA-63, an inhibitor of dopamine-beta-hydroxylase, increased it. Moreover, a local and unilateral injection of catecholaminergic neurotoxin (6-hydroxydopamine) in the vicinity of A1 induced a 60% decrease in the peak height. This effect was prevented by pretreatment with desipramine, an inhibitor of noradrenaline reuptake, which is known to protect noradrenergic neurons against the action of 6-hydroxydopamine. Finally, specific drugs acting on alpha-2-noradrenergic receptors (clonidine and piperoxane) modulated the peak height recorded from both structures. Thus, as previously shown in the locus ceruleus, the variations in the extracellular DOPAC levels reflect the metabolic activity of A1 and A2 noradrenergic neurons.     

Chemical composition of bone marrow after exposure of rabbits to nitrogen mustard

Rabbits were injected with 2.5 mg./kg. of methylbis(2-chloroethyl)-amine hydrochloride while the marrow of the right leg was protected by clamping the blood vessels which supply it. There was a marked lowering of the lipide-free solid content of the affected marrow. The lipide concentration was increased, but the change was not of the order of magnitude one would expect from the morphological appearance.     

Spontaneous reactivation of acetylcholinesterase following organophosphate inhibition. I. An analysis of anomalous reactivation kinetics.

The first kinetic studies on the spontaneous reactivation of Sarin-inhibited acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) are reported. With increasing pH the extent of reactivation increases while the observed rate constant decreases. An analysis of the change in aging rate constant as a function of pH suggests that the aging of alkyl-alkoxy phosphonylated acetylcholinesterases is not solely acid catalyzed.     

Dissociation of the lipid-enzyme complex of hormone-sensitive lipase using high density lipoprotein or apolipoprotein A-I

Hormone-sensitive lipase in homogenates of adipose tissue occurs as a large, lipid-rich complex including several acylhydrolase activities that emerge quantitatively in the void volume on gel filtration chromatography (2% agarose). Incubation with intact human plasma high density lipoprotein or with lipid-free apolipoprotein A-I, however, disrupted the lipid-rich complex almost completely and most of the enzyme activity eluted from a 2% agarose column at about Ve = 2.3 x Vo. This use of the detergent-like properties of apolipoprotein A-I may be of value for dissociation of other lipid-associated or membrane-bound enzymes.     

A Swedish comment on ‘review: the availability of life-cycle studies in Sweden’

The International Journal of Life Cycle Assessment -     

G protein-coupled time travel: evolutionary aspects of GPCR research

The common seven-transmembrane-domain (TMD) architecture of G protein-coupled receptors (GPCRs) has been preserved over a vast period of time, and highly conserved amino acid motifs and residues have evolved to establish ligand and signal transduction specificities. The mining of evolutionary data from sequenced genomes and targeted retrieved orthologs has proven helpful for understanding the physiological relevance of individual GPCRs and for interpreting the clinical significance of GPCR mutations in structural terms. Sequence analysis of GPCR pseudogenes, which are considered as genomic traces of past functions, as well as recent success in sequence analysis of GPCR genes from extinct species, provide further information. This review discusses recent advances and approaches aimed at developing a better understanding of GPCR biology based on evolutionary data.     

Phosphopantetheinyl transferase CfwA/NpgA is required for Aspergillus nidulans secondary metabolism and asexual development

Polyketide synthases (PKSs) and/or nonribosomal peptide synthetases (NRPSs) are central components of secondary metabolism in bacteria, plants, and fungi. In filamentous fungi, diverse PKSs and NRPSs participate in the biosynthesis of secondary metabolites such as pigments, antibiotics, siderophores, and mycotoxins. However, many secondary metabolites as well as the enzymes involved in their production are yet to be discovered. Both PKSs and NRPSs require activation by enzyme members of the 4'-phosphopantetheinyl transferase (PPTase) family. Here, we report the isolation and characterization of Aspergillus nidulans strains carrying conditional (cfwA2) and null (DeltacfwA) mutant alleles of the cfwA gene, encoding an essential PPTase. We identify the polyketides shamixanthone, emericellin, and dehydroaustinol as well as the sterols ergosterol, peroxiergosterol, and cerevisterol in extracts from A. nidulans large-scale cultures. The PPTase CfwA/NpgA was required for the production of these polyketide compounds but dispensable for ergosterol and cerevisterol and for fatty acid biosynthesis. The asexual sporulation defects of cfwA, DeltafluG, and DeltatmpA mutants were not rescued by the cfwA-dependent compounds identified here. However, a cfwA2 mutation enhanced the sporulation defects of both DeltatmpA and DeltafluG single mutants, suggesting that unidentified CfwA-dependent PKSs and/or NRPSs are involved in the production of hitherto-unknown compounds required for sporulation. Our results expand the number of known and predicted secondary metabolites requiring CfwA/NpgA for their biosynthesis and, together with the phylogenetic analysis of fungal PPTases, suggest that a single PPTase is responsible for the activation of all PKSs and NRPSs in A. nidulans.