Adenosine Inhibition of 45Ca Uptake by Synaptosomes as Function of Time of Electrical Stimulation

Abstract

The effect of adenosine on ⁴⁵Ca uptake by rat brain synaptosomes electrically stimulated was studied as function of time of stimulation (10, 30, 120 s). Inhibition of ⁴⁵Ca uptake was more evident for 120 s.     

High interleukin-4 expression and interleukin-4 gene polymorphisms are associated with susceptibility to human paracoccidioidomycosis

Paracoccidioidomycosis (PCM) is caused by dimorphic fungi fromtheParacoccidioides brasiliensis complex. Previous studies havedemonstrated that the severity of disease is associated with a T-helper 2 immuneresponse characterised by high interleukin (IL)-4 production. In the present study weanalysed two polymorphisms in the IL-4 gene (-590 C/T and intron-3microsatellite) in 76 patients with PCM and 73 control subjects from an endemic area.The production of IL-4 by peripheral blood mononuclear cells after antigen orphytohaemagglutinin stimulation was determined by ELISA. A significant correlationwas observed between the RP2/RP2 intron-3 genotype and infection withParacoccidioides sp. (p = 0.011), whereas the RP1/RP1 genotypewas correlated with resistance. No significant correlation was observed forthe IL-4 promoter polymorphism. Furthermore, the low IL-4expression observed in the control group compared with patients was associated withthe RP1/RP1 genotype. These results suggest that IL-4polymorphismsmight be associated with the ability of the host to control Paracoccidioidessp. infection. The relevance of this polymorphism is supported by theobservation that patients with disease produce high levels of IL-4 following mitogenor antigen stimulation. The IL-4 gene is located in the cytokinecluster region of chromosome 5 where other polymorphisms have also beendescribed.     

Accumulation of a polyisoprene-linked amino sugar in polymyxin-resistant Salmonella typhimurium and Escherichia coli: structural characterization and transfer to lipid A in the periplasm

Polymyxin-resistant mutants of Escherichia coli and Salmonella typhimurium accumulate a novel minor lipid that can donate 4-amino-4-deoxy-l-arabinose units (l-Ara4N) to lipid A. We now report the purification of this lipid from a pss(-) pmrA(C) mutant of E. coli and assign its structure as undecaprenyl phosphate-alpha-l-Ara4N. Approximately 0.2 mg of homogeneous material was isolated from an 8-liter culture by solvent extraction, followed by chromatography on DEAE-cellulose, C18 reverse phase resin, and silicic acid. Matrix-assisted laser desorption ionization/time of flight mass spectrometry in the negative mode yielded a single species [M - H](-) at m/z 977.5, consistent with undecaprenyl phosphate-alpha-l-Ara4N (M(r) = 978.41). (31)P NMR spectroscopy showed a single phosphorus atom at -0.44 ppm characteristic of a phosphodiester linkage. Selective inverse decoupling difference spectroscopy demonstrated that the undecaprenyl phosphate group is attached to the anomeric carbon of the l-Ara4N unit. One- and two-dimensional (1)H NMR studies confirmed the presence of a polyisoprene chain and a sugar moiety with chemical shifts and coupling constants expected for an equatorially substituted arabinopyranoside. Heteronuclear multiple-quantum coherence spectroscopy analysis demonstrated that a nitrogen atom is attached to C-4 of the sugar residue. The purified donor supports in vitro conversion of lipid IV(A) to lipid II(A), which is substituted with a single l-Ara4N moiety. The identification of undecaprenyl phosphate-alpha-l-Ara4N implies that l-Ara4N transfer to lipid A occurs in the periplasm of polymyxin-resistant strains, and establishes a new enzymatic pathway by which Gram-negative bacteria acquire antibiotic resistance.     

Insulin Accelerates Seedling Growth of Canavalia ensiformis (Jack bean)

Insulin is a 6 kDa peptide hormone that activates several metabolic processes and cellular growth. Germination studies showed that insulin, vanadyl sulphate (an insulin mimetic compound), tyrphostin (an inhibitor of insulin receptor kinase activity), pinitol (a chiro inositol analogue) and glucose were able to accelerate Canavalia ensiformis (Jack bean) seedling radicle and epicotyl development. Immunofluorescence microscopy analysis showed that proteins binding to insulin, insulin receptor and phosphoserine antibodies are localized in an internal layer of the C. ensiformis seed coat. These results and others previously reported from our laboratory suggest that insulin, insulin receptor and phosphoserine proteins could be components of signalling pathways akin to those present in animals.     

Effects of antibody on viral kinetics in simian/human immunodeficiency virus infection: implications for vaccination

Passive antibody treatment of macaques prior to simian/human immunodeficiency virus infection produces "sterilizing immunity" in some animals and long-term reductions in viral loads in others. Analysis of viral kinetics suggests that antibody mediates sterilizing immunity by its effects on the initial viral inoculum. By contrast, reduction in peak viral load later in infection prevents CD4 depletion and contributes to long-term viral control.     

Functional Characterization of a Novel Family of Acetylcholine-Gated Chloride Channels in Schistosoma mansoni

Acetylcholine is the canonical excitatory neurotransmitter of the mammalian neuromuscular system. However, in the trematode parasite Schistosoma mansoni, cholinergic stimulation leads to muscle relaxation and a flaccid paralysis, suggesting an inhibitory mode of action. Information about the pharmacological mechanism of this inhibition is lacking. Here, we used a combination of techniques to assess the role of cholinergic receptors in schistosome motor function. The neuromuscular effects of acetylcholine are typically mediated by gated cation channels of the nicotinic receptor (nAChR) family. Bioinformatics analyses identified numerous nAChR subunits in the S. mansoni genome but, interestingly, nearly half of these subunits carried a motif normally associated with chloride-selectivity. These putative schistosome acetylcholine-gated chloride channels (SmACCs) are evolutionarily divergent from those of nematodes and form a unique clade within the larger family of nAChRs. Pharmacological and RNA interference (RNAi) behavioral screens were used to assess the role of the SmACCs in larval motor function. Treatment with antagonists produced the same effect as RNAi suppression of SmACCs; both led to a hypermotile phenotype consistent with abrogation of an inhibitory neuromuscular mediator. Antibodies were then generated against two of the SmACCs for use in immunolocalization studies. SmACC-1 and SmACC-2 localize to regions of the peripheral nervous system that innervate the body wall muscles, yet neither appears to be expressed directly on the musculature. One gene, SmACC-1, was expressed in HEK-293 cells and characterized using an iodide flux assay. The results indicate that SmACC-1 formed a functional homomeric chloride channel and was activated selectively by a panel of cholinergic agonists. The results described in this study identify a novel clade of nicotinic chloride channels that act as inhibitory modulators of schistosome neuromuscular function. Additionally, the iodide flux assay used to characterize SmACC-1 represents a new high-throughput tool for drug screening against these unique parasite ion channels.