S-adenosyl-l-methionine inhibits phosphoinositide metabolism in the rat brain synaptosomal suspensions

S-adenosyl-l-methionine (AdoMet) has been reported to affect events linked to noradrenergic neurotransmission. In the present work, we studied the effect of AdoMet on norepinephrine (NE)-stimulated inositol phosphate production in³H-inositol-labelled crude synaptosomal suspensions of rat brain. AdoMet (50–1000 M) decreased both the synthesis of labelled polyphosphoinositide (30–50%) and the release of inositol mono- and bisphosphate (40–50%). The AdoMet effect was not dependent on NE concentration (10–1000 M), suggesting that the inhibition of inositol phosphate release was not the result of a modification of the norepinephrine binding to its receptor sites. S-adenosyl-L-homocysteine (AdoHcy) (1 mM) an inhibitor of methyltransferase activities, partially inhibited (70%) the AdoMet (0.1 mM) effect, indicating that the methylation processes cannot explain all the effects observed. We conclude that, in addition to previously reported effects of AdoMet on NE transport, AdoMet may reduce NE-linked intracellular signalling.     

Writing failure: knowledge production,temporalities, ethics,and traces

This volume follows failures out into the world, exploring how they unfold ethnographically. Taking a longer view shows how objects, narratives, and diagnoses of failures may be crafted, acted on, suffered, resisted – unmade or recomposed. Thus while tropes and diagnoses of failure can temporarily (re)organize, narrate, and stabilize the world, the kinds of failures explored here also indicate a mode of uncontainable excess that refuses the boundedness of knowledge objects, temporalities, and spaces. This volume offers three main interventions. The first concerns knowledge production: how objects of failure are crafted through selective ways of knowing that occlude both other modes of apprehension at different scales and failure's many affective valences. The second thinks through the knotted temporalities – whether pasts, futures, suspended presents, or repetition and sedimentation – that make and are made by failure. Finally, writing about unfurling failures requires careful attention to non-linear reverberations and traces as well as to open-ended and mobile narratives that produce different social and material effects.     

Growth and respiratory oxidation of reduced sulfur compounds by intact cells ofThiobacillus novellus (type strain) grown on thiosulfate

Thiobacillus novellus (type strain) was grown chemolithoautrophically on thiosulfate in batch cultures under microaerophilic conditions. Under these conditions,T. novellus grew exponentially (=0.05–0.06 h^–1). The respiratory oxidation rates of tetrathionate, thiosulfate, elemental sulfur (S^o), and sulfite were measured respirometrically with an oxygen electrode, with exponentially growing cells. Cells growing on thiosulfate as the unique energy source retain thiosulfate-oxidizing activity, S^o-oxidizing activity (SOA), and very high sulfite-oxidizing activity, but lack respiratory tetrathionate-oxidizing activity. HQNO (50 m), an inhibitor of the quinone-cytochrome b region, strongly inhibited the SOA (70%), moderately the sulfite-oxidizing activity (45%), and poorly the thiosulfate-oxidizing activity (15%), 1mm KCN totally inhibited (>89%) all respiratory activities. This study confirms that inThiobacillus novellus, as well as in otherThiobacilli, SOA is present in cells grown with thiosulfate as sole electron donor. SOA appears not to be an oxygenase; it is linked to the respiratory chain, and the electrons are probably released in the quinone-cytochrome b region.     

Cobalamin producers and prokaryotic consumers in the Northwest Atlantic

Cobalamin availability can influence primary productivity and ecological interactions in marine microbial communities. The characterization of cobalamin sources and sinks is a first step in investigating cobalamin dynamics and its impact on productivity. Here, we identify potential cobalamin sources and sinks on the Scotian Shelf and Slope in the Northwest Atlantic Ocean. Functional and taxonomic annotation of bulk metagenomic reads, combined with analysis of genome bins, were used to identify potential cobalamin sources and sinks. Cobalamin synthesis potential was mainly attributed to Rhodobacteraceae, Thaumarchaeota, and cyanobacteria (Synechococcus and Prochlorococcus). Cobalamin remodelling potential was mainly attributed to Alteromonadales, Pseudomonadales, Rhizobiales, Oceanospirilalles, Rhodobacteraceae, and Verrucomicrobia, while potential cobalamin consumers include Flavobacteriaceae, Actinobacteria, Porticoccaceae, Methylophiliaceae, and Thermoplasmatota. These complementary approaches identified taxa with the potential to be involved in cobalamin cycling on the Scotian Shelf and revealed genomic information required for further characterization. The Cob operon of Rhodobacterales bacterium HTCC2255, a strain with known importance in cobalamin cycling, was similar to a major cobalamin producer bin, suggesting that a related strain may represent a critical cobalamin source in this region. These results enable future inquiries that will enhance our understanding of how cobalamin shapes microbial interdependencies and productivity in this region.     

Patterns of Integration and Expression of Retroviral, Non-Replicative Vectors in Avian Embryos: Embryo Developmental Stage and Virus Subgroup Envelope Modulate Tissue-Tropism

We previously demonstrated that Avian Leukemia Viruses (ALV) carrying the v-myc gene specifically induce two types of tumors, cardiomyocytic tumors when the virus is injected before embryonic day 3 (E3), skin tumors when the virus is injected at E3 or E5.

Aiming to elucidate the mechanisms which determine this time-dependent change in target, we infected chick and quail embryos at E3 and E5 with replication-deficient, lacZ gene-carrying, ALV-based viruses produced by a packaging cell line. Three constructs driven by 3 different Long Terminal Repeats (LTRs) were tested and yielded similar results. When the constructs were inoculated at E3 and the lacZ gene product revealed 5 days later, around 70% of the embryos carried lacZ+ clones in the heart, around 50% had positive clones in the skin anywhere on the body, while a few embryos displayed clones in internal organs (liver, stomach, lungs). Immunocytological identification of the heart cell type(s) expressing the virus revealed that the only cells infected were cardiomyocytes. When the constructs were inoculated at E5, no lacZ+ clones appeared in the heart but all were located in the cephalic skin. In order to examine the relationship between viral integration and expression, DNA of different organs or tissues from lacZ stained embryos was analyzed by PCR. A tight correlation between integration and expression in the heart and in the skin was revealed in most cases. In contrast, a significant PCR signal was often detected in the liver or the stomach despite weak or absent expression as revealed by lacZ+ clones.

We then investigated the influence of envelope glycoprotein subgroups on the tropism of these constructs. The lacZ vector driven by RAV-2 LTRs was packaged as subgroups A, B or E viral particles. The A subgroup, used in the part of the study described above, infects both chick and quail while the B and E subgroups are specific for chick or quail respectively. These B and E subgroups induced lacZ+ clones in the heart (after E3 injection) while no clones or only a few were detected in the skin either after E3 or E5 injection. The following conclusions can be drawn: 1) cardiomyocytes are at E3 the major target for integration and expression of ALV-derived viruses in vivo; 2) targets change rapidly with embryonic age; and 3) tissue-specific infections depend on the envelope subgroup, thus presumably on the presence of the cognate receptor. This study clearly indicates that E3 inoculation of ALV-based retroviral vectors is a simple and powerful method to transfer gene sequences into cardiomyocytes and epidermal cells.     

Wax as a Mechanism for Protection against Photoinhibition — A Study of Cotyledon orbiculata

The leaves of the Crassulacean acid metabolism plant Cotyledon orbiculata have a waxy coating which is highly reflective but can be easily removed by brushing. This provided an ideal system in which to investigate the role of epidermal wax as a possible photoprotectant. Removal of the wax, prior to exposure to natural sunlight, resulted in substantial decreases in F_v/F_m and in severe cases evidence of photoinhibitory damage, as indicated by a rise in F_o. Leaves from which wax had been removed also showed higher conversion of violaxanthin to zeaxanthin than waxed leaves. Recovery of brushed leaves over a 12 day period was correlated with an increase in the total pool of xanthophyll cycle components. This study suggests that the presence of highly reflective wax on the epidermis may confer significant photoprotection to plants exposed to high solar radiation environments.     

Cyclooxygenase and 5-lipoxygenase inhibitory activity of 2,6 di-t-butylphenols linked by a sulfur atom to 1,3,4-thiadiazoles and 1,3,4-oxadiazoles

The preparation of a series of 1,3,4-thiadiazoles and 1,3,4-oxadizoles linked by a thioether to 2,6-di-t-butylphenol and the inhibition of cyclooxygenase (CO) and 5-lipoxygenase (5-LO) by these compounds is dicussed.