P2 receptor-mediated modulation of neurotransmitter release—an update

Presynaptic nerve terminals are equipped with a number of presynaptic auto- and heteroreceptors, including ionotropic P2X and metabotropic P2Y receptors. P2 receptors serve as modulation sites of transmitter release by ATP and other nucleotides released by neuronal activity and pathological signals. A wide variety of P2X and P2Y receptors expressed at pre- and postsynaptic sites as well as in glial cells are involved directly or indirectly in the modulation of neurotransmitter release. Nucleotides are released from synaptic and nonsynaptic sites throughout the nervous system and might reach concentrations high enough to activate these receptors. By providing a fine-tuning mechanism these receptors also offer attractive sites for pharmacotherapy in nervous system diseases. Here we review the rapidly emerging data on the modulation of transmitter release by facilitatory and inhibitory P2 receptors and the receptor subtypes involved in these interactions.     

Phylogenetic analyses of complete mitochondrial genome sequences suggest a basal divergence of the enigmatic rodent <Emphasis Type="Italic">Anomalurus</Emphasis>

Background  

Phylogenetic relationships between Lagomorpha, Rodentia and Primates and their allies (Euarchontoglires) have long been debated. While it is now generally agreed that Rodentia constitutes a monophyletic sister-group of Lagomorpha and that this clade (Glires) is sister to Primates and Dermoptera, higher-level relationships within Rodentia remain contentious.     

Environment and virulence factors of Vibrio cholerae strains isolated in Argentina

AIMS: To determine the presence of Vibrio cholerae in different areas of Argentina in three sample types, to determine the composition of planktonic communities in areas at which this pathogen was detected and to characterize the virulence properties and antimicrobial resistance of the recovered environmental isolates. METHODS AND RESULTS: Water and plankton samples were collected in marine, brackish and freshwater environments. Vibrio cholerae non-O1, non-O139 was isolated in 36.1% of the samples analysed. The micro-organism was detected in freshwater but not in marine or brackish samples. No relationship was found between isolation of V. cholerae and presence of any species of plankton. All the isolates presented very similar virulence profiles by PCR, lacking ctxA and tcpA El Tor and containing hlyA (98.7%), rtxA (99.0%), toxR (98.7%) and stn-sto (1.9%). Resistance to ampicillin was found in both Tucumán (21%) and Buenos Aires isolates (45%). CONCLUSIONS: We identified two geographic areas in Argentina where V. cholerae was present: freshwaters of the rivers from Tucumán and the Río de la Plata. SIGNIFICANCE AND IMPACT OF THE STUDY: The identification of V. cholerae strains in the environment, carrying both virulence factors and resistance to antimicrobial agents, highlight the need for a continuous and active surveillance of this pathogen.     

Variability of the mitochondrial genome in mammals at the inter-species/intra-species boundary

Genomic variations represent the molecular basis of the biodiversity of living organisms on which selection operates to generate evolution. In eukaryotes, genomic variability can be experienced in both nuclear and organellar, i.e. mitochondrial and plastid (where present), genomes, which can follow completely different evolution pathways, as revealed by comparative genomics analyses. In Metazoa, for which a substantial number of complete genome sequences are available (nuclear, but mainly mitochondrial), we are just starting to grasp the selective pressures operating on some basic features of the genome as a whole. In this brief review, we discuss the variability of the mitochondrial metazoan genome, with particular reference to mitochondrial DNA in mammals. In light of the recent assumption that a small segment of mitochondrial DNA may be used, particularly in Metazoa, as a species marker, some data on mitochondrial gene variability at the inter-species/intra-species boundary are reported. Intra-species variability has been evaluated in four mammalian species, Homo sapiens, Bos taurus, Sus scrofa and Canis familiaris, whereas the relationship between intra- and inter-species variability has been investigated in Bos taurus and Bos indicus.     

Changes in muscle proteomics in the course of the Caudwell Research Expedition to Mt. Everest

This study employed differential proteomic and immunoassay techniques to elucidate the biochemical mechanisms utilized by human muscle (vastus lateralis) in response to high altitude hypoxia exposure. Two groups of subjects, participating in a medical research expedition (A, n = 5, 19d at 5300 m altitude; B, n = 6, 66d up to 8848 m) underwent a ≈ 30% drop of muscular creatine kinase and of glycolytic enzymes abundance. Protein abundance of most enzymes of the tricarboxylic acid cycle and oxidative phosphorylation was reduced both in A and, particularly, in B. Restriction of α‐ketoglutarate toward succinyl‐CoA resulted in increased prolyl hydroxylase 2 and glutamine synthetase. Both A and B were characterized by a reduction of elongation factor 2alpha, controlling protein translation, and by an increase of heat shock cognate 71 kDa protein involved in chaperone‐mediated autophagy. Increased protein levels of catalase and biliverdin reductase occurred in A alongside a decrement of voltage‐dependent anion channels 1 and 2 and of myosin‐binding protein C, suggesting damage to the sarcomeric structures. This study suggests that during acclimatization to hypobaric hypoxia the muscle behaves as a producer of substrates activating a metabolic reprogramming able to support anaplerotically the tricarboxylic acid cycle, to control protein translation, to prevent energy expenditure and to activate chaperone‐mediated autophagy.     

Haemoglobin modulates salicylate and jasmonate/ethylene-mediated resistance mechanisms against pathogens

Nitric oxide (NO) plays a role in defence against hemibiotrophic pathogens mediated by salicylate (SA) and also necrotrophic pathogens influenced by jasmonate/ethylene (JA/Et). This study examined how NO-oxidizing haemoglobins (Hb) encoded by GLB1, GLB2, and GLB3 in Arabidopsis could influence both defence pathways. The impact of Hb on responses to the hemibiotrophic Pseudomonas syringae pathovar tomato (Pst) AvrRpm1 and the necrotrophic Botrytis cinerea were investigated using glb1, glb2, and glb3 mutant lines and also CaMV 35S GLB1 and GLB2 overexpression lines. In glb1, but not glb2 and glb3, increased resistance was observed to both pathogens but was compromised in the 35S-GLB1. A quantum cascade laser-based sensor measured elevated NO production in glb1 infected with Pst AvrRpm1 and B. cinerea, which was reduced in 35S-GLB1 compared to Col-0. SA accumulation was increased in glb1 and reduced in 35S-GLB1 compared to controls following attack by Pst AvrRpm1. Similarly, JA and Et levels were increased in glb1 but decreased in 35S-GLB1 in response to attack by B. cinerea. Quantitative PCR assays indicated reduced GLB1 expression during challenge with either pathogen, thus this may elevate NO concentration and promote a wide-ranging defence against pathogens.     

Host association of Spodoptera frugiperda (Lepidoptera: Noctuidae) corn and rice strains in Argentina, Brazil, and Paraguay

Spodoptera frugiperda (J.E. Smith) is composed of two genetically distinct strains, the so-called corn strain and the rice strain. Whether the two strains differ in their host use is unclear, because laboratory experiments have not been able to show consistent host performance or preference differences between them, and field studies showed high rates of hybridization, as well as some degree asymmetric host use. To determine the distribution of the two strains and their association with host plants, we collected fall armyworm larvae from different crops (corn, rice, alfalfa, and sorghum) and grasses in 15 different localities over 4 yr in Argentina, Brazil, and Paraguay. The strain identity was analyzed using two polymorphisms in the mitochondrial cytochrome oxidase subunit I gene. We identified the corn and rice haplotypes and three types of populations were characterized based on the frequencies of the individuals that belonged to any of these haplotypes: in 44% of populations the corn haplotype predominated, in 44% of populations the rice haplotype was the most frequent, and 11% of populations showed both haplotypes at similar proportions. In total, eight populations (47%) showed the expected pattern, two populations (12%) were polymorphic within the same field, and seven populations (41%) showed the inverse pattern. Taken together, there was no consistent pattern of host association between the two sympatric genotypes and their respective host plants. This investigation supports the need for additional studies to determine which other forces keep the genotypes separate, and what is the degree of genetic differentiation between these populations.     

Dissecting mechanisms of immunodominance to the common tuberculosis antigens ESAT-6, CFP10, Rv2031c (hspX), Rv2654c (TB7.7), and Rv1038c (EsxJ)

Diagnosis of tuberculosis often relies on the ex vivo IFN-γ release assays QuantiFERON-TB Gold In-Tube and T-SPOT.TB. However, understanding of the immunological mechanisms underlying their diagnostic use is still incomplete. Accordingly, we investigated T cell responses for the TB Ags included in the these assays and other commonly studied Ags: early secreted antigenic target 6 kDa, culture filtrate protein 10 kDa, Rv2031c, Rv2654c, and Rv1038c. PBMC from latently infected individuals were tested in ex vivo ELISPOT assays with overlapping peptides spanning the entirety of these Ags. We found striking variations in prevalence and magnitude of ex vivo reactivity, with culture filtrate protein 10 kDa being most dominant, followed by early secreted antigenic target 6 kDa and Rv2654c being virtually inactive. Rv2031c and Rv1038c were associated with intermediate patterns of reactivity. Further studies showed that low reactivity was not due to lack of HLA binding peptides, and high reactivity was associated with recognition of a few discrete dominant antigenic regions. Different donors recognized the same core sequence in a given epitope. In some cases, the identified epitopes were restricted by a single specific common HLA molecule (selective restriction), whereas in other cases, promiscuous restriction of the same epitope by multiple HLA molecules was apparent. Definition of the specific restricting HLA allowed to produce tetrameric reagents and showed that epitope-specific T cells recognizing either selectively or promiscuously restricted epitopes were predominantly T effector memory. In conclusion, these results highlight the feasibility of more clearly defined TB diagnostic reagent.     

Dissection of the network of interactions that links RNA processing with glycolysis in the Bacillus subtilis degradosome

The RNA degradosome is a multiprotein macromolecular complex that is involved in the degradation of messenger RNA in bacteria. The composition of this complex has been found to display a high degree of evolutionary divergence, which may reflect the adaptation of species to different environments. Recently, a degradosome-like complex identified in Bacillus subtilis was found to be distinct from those found in proteobacteria, the degradosomes of which are assembled around the unstructured C-terminus of ribonuclease E, a protein not present in B. subtilis. In this report, we have investigated in vitro the binary interactions between degradosome components and have characterized interactions between glycolytic enzymes, RNA-degrading enzymes, and those that appear to link these two cellular processes. The crystal structures of the glycolytic enzymes phosphofructokinase and enolase are presented and discussed in relation to their roles in the mediation of complex protein assemblies. Taken together, these data provide valuable insights into the structure and dynamics of the RNA degradosome, a fascinating and complex macromolecular assembly that links RNA degradation with central carbon metabolism.     

Yeast and yeast-like fungi associated with dry indehiscent fruits of Nothofagus nervosa in Patagonia, Argentina

Nothofagus nervosa (Raulí) is a native tree species that yields valuable timber. It was overexploited in the past and is currently included in domestication and conservation programs. Several research programs have focused on the characterization of epiphytic microorganisms because it has been demonstrated that they can affect plant-pathogen interactions and/or promote plant growth. Although the microbial ecology of leaves has been well studied, less is known about microorganisms occurring on seeds and noncommercial fruits. In this work, we analyzed the yeast and yeast-like fungi present on N.?nervosa fruits destined for the propagation of this species, as well as the effects of fruit preservation and seed dormancy-breaking processes on fungal diversity. Morphological and molecular methods were used, and differences between fungal communities were analyzed using a similarity index. A total of 171 isolates corresponding to 17 species were recovered, most of which belong to the phylum Ascomycota. The majority of the species develop mycelia, produce pigments and mycosporines, and these adaptation strategies are discussed. It was observed that the preservation process considerably reduced yeast and yeast-like fungal diversity. This is the first study concerning microbial communities associated with this ecologically and economically important species, and the information presented is relevant to domestication programs.