The octadecaneuropeptide ODN prevents 6‐hydroxydopamine‐induced apoptosis of cerebellar granule neurons through a PKC‐MAPK‐dependent pathway

Oxidative stress, induced by various neurodegenerative diseases, initiates a cascade of events leading to apoptosis, and thus plays a critical role in neuronal injury. In this study, we have investigated the potential neuroprotective effect of the octadecaneuropeptide (ODN) on 6‐hydroxydopamine (6‐OHDA)‐induced oxidative stress and apoptosis in cerebellar granule neurons (CGN). ODN, which is produced by astrocytes, is an endogenous ligand for both central‐type benzodiazepine receptors (CBR) and a metabotropic receptor. Incubation of neurons with subnanomolar concentrations of ODN (10^?18 to 10^?12 M) inhibited 6‐OHDA‐evoked cell death in a concentration‐dependent manner. The effect of ODN on neuronal survival was abrogated by the metabotropic receptor antagonist, cyclo_1–8[DLeu⁵]OP, but not by a CBR antagonist. ODN stimulated polyphosphoinositide turnover and ERK phosphorylation in CGN. The protective effect of ODN against 6‐OHDA toxicity involved the phospholipase C/ERK MAPK transduction cascade. 6‐OHDA treatment induced an accumulation of reactive oxygen species, an increase of the expression of the pro‐apoptotic gene Bax, a drop of the mitochondrial membrane potential and a stimulation of caspase‐3 activity. Exposure of 6‐OHDA‐treated cells to ODN blocked all the deleterious effects of the toxin. Taken together, these data demonstrate for the first time that ODN is a neuroprotective agent that prevents 6‐OHDA‐induced oxidative stress and apoptotic cell death.     

High levels of diversity in Fusarium oxysporum from non-cultivated ecosystems in Australia

The Fusarium oxysporum species complex (FOSC) is a ubiquitous ascomycetous group that includes both pathogenic and non-pathogenic strains, the former being responsible for disease in over 100 cultivated plant species. Previous phylogenetic studies have uncovered at least four major clades within the FOSC, with Clade 1 hypothesised as being ancestral. However, the origin of these clades and pathogenic strains is poorly understood. Due to an emphasis on agricultural isolates in previous studies, the underlying diversity of this species complex in non-cultivated soils is largely unknown. To address this imbalance an extensive survey of isolates associated with native vegetation geographically isolated from cultivation throughout the Australian continent was conducted. A multi-gene phylogenetic analysis of the translation elongation factor (EF-1α) and the mitochondrial small subunit (mtSSU) rDNA loci did not recover any novel clades. However, the Australian isolates had high levels of intra-Clade diversity based on EF-1α sequence type (ST) comparison with a global dataset. The ST diversity was not equally distributed across the four clades, with the majority of novel STs recovered from Clade 1. Implications on the origin of the FOSC are discussed.     

Intestinal colonization by enteroaggregative Escherichia coli supports long-term bacteriophage replication in mice

Bacteriophages have been known to be present in the gut for many years, but studies of relationships between these viruses and their hosts in the intestine are still in their infancy. We isolated three bacteriophages specific for an enteroaggregative O104:H4 Escherichia coli (EAEC) strain responsible for diarrhoeal diseases in humans. We studied the replication of these bacteriophages in vitro and in vivo in a mouse model of gut colonization. Each bacteriophage was able to replicate in vitro in both aerobic and anaerobic conditions. Each bacteriophage individually reduced biofilms formed on plastic pegs and a cocktail of the three bacteriophages was found to be more efficient. The cocktail was also able to infect bacterial aggregates formed on the surface of epithelial cells. In the mouse intestine, bacteriophages replicated for at least 3 weeks, provided the host was present, with no change in host levels in the faeces. This model of stable and continuous viral replication provides opportunities for studying the long-term coevolution of virulent bacteriophages with their hosts within a mammalian polymicrobial ecosystem.     

Reciprocal regulation of brain and muscle Arnt-like protein 1 and peroxisome proliferator-activated receptor alpha defines a novel positive feedback loop in the rodent liver circadian clock

Recent evidence has emerged that peroxisome proliferator-activated receptor alpha (PPARalpha), which is largely involved in lipid metabolism, can play an important role in connecting circadian biology and metabolism. In the present study, we investigated the mechanisms by which PPARalpha influences the pacemakers acting in the central clock located in the suprachiasmatic nucleus and in the peripheral oscillator of the liver. We demonstrate that PPARalpha plays a specific role in the peripheral circadian control because it is required to maintain the circadian rhythm of the master clock gene brain and muscle Arnt-like protein 1 (bmal1) in vivo. This regulation occurs via a direct binding of PPARalpha on a potential PPARalpha response element located in the bmal1 promoter. Reversely, BMAL1 is an upstream regulator of PPARalpha gene expression. We further demonstrate that fenofibrate induces circadian rhythm of clock gene expression in cell culture and up-regulates hepatic bmal1 in vivo. Together, these results provide evidence for an additional regulatory feedback loop involving BMAL1 and PPARalpha in peripheral clocks.     

Life-history correlates of steroid concentrations in wild peripartum baboons

Steroid concentrations during late pregnancy and early lactation may be affected by both a female's reproductive history and her current condition, and may in turn predict subsequent life-history events, such as offspring survival. This study investigated these relationships in a wild primate population through the use of fecal steroid analysis in repeated sampling of peripartum baboons (Papio cynocephalus). Fecal samples were collected from 32 females in five groups within the Amboseli basin during 8 weeks prior to parturition and 13 weeks postpartum. From December 1999 through February 2002, 176 fecal samples were collected from individuals representing 39 peripartum periods. Fecal concentrations of progestins (fP), estrogen metabolites (fE), glucocorticoids (fGC), and testosterone metabolites (fT) were measured by radioimmunoassay. Steroid concentrations declined from late pregnancy to lactation, and the decline was greatest and most precipitous for fE and fP. Primiparous females had significantly higher mean fE concentrations in each of the last 2 months of pregnancy compared to multiparous females. Among multiparous females, fE and fT were significantly higher during late pregnancy in females carrying a male fetus compared to those carrying a female fetus. During early lactation, high fT in young mothers predicted subsequent infant death during the first year of life. These findings illustrate the potential power of repeated fecal-steroid sampling to elucidate mechanisms of life-history variability in natural populations. They also document significant differences in hormone profiles among subgroups, and highlight that such normative subgroup information is essential for interpreting individual variability in hormone-behavior associations.     

Impact of exogenous lysolipids on sensitive and multidrug resistant K562 cells: 1H NMR studies

The ability of lysolipids to enter into a membrane bi-layer and disturb the membrane structure was used to study the behavior of K562 erythroleukemic cells, K562 wild type (K562wt) as well as the multidrug resistant cells K562adr. Both types of cells, when analyzed by proton NMR spectroscopy exhibit the high resolution signals assigned to so-called "mobile lipid" signals, which, in most cases, are located outside the lipid bi-layer as lipid droplets. In order to perform these studies, the K562wt and K562adr cells were treated for 48h with lysophosphatidylcholine oleoyl (LPC18), lysophosphatidylcholine palmitoyl (LPC16) and L-alpha-lysophosphatidyslerine (LPS). After evaluating toxicity of lysolipids, proton NMR of whole treated cells was used to analyze the mobile lipid content. Nile red staining and fluorescence microscopy were used to detect the presence of intracellular lipid droplets. Membrane lipid asymmetry perturbation was estimated by annexin V staining with use of flow cytometry. Using fluorescence spectroscopy the functioning of P-glycoprotein (P-gp) responsible for multidrug resistance was also evaluated after the treatment with lysolipids. Lysolipids were found to be more toxic for K562wt than for K562adr cells. LPS and LPC16 produced an increased of a mobile lipid NMR signal and amount of lipid droplets in K562wt cells only. LPC18, with the lowest toxicity, has shown more intense effects on NMR spectra with a large increase of lipid NMR signal without changes in lipid droplet staining. The functioning of the P-gp pump and membrane asymmetry were not modified by any of the lysolipids used.     

Leaf yellowing and anthocyanin accumulation are two genetically independent strategies in response to nitrogen limitation in Arabidopsis thaliana

For the first time in Arabidopsis thaliana, this work proposes the identification of quantitative trait loci (QTLs) associated with leaf senescence and stress response symptoms such as yellowing and anthocyanin-associated redness. When Arabidopsis plants were cultivated under low nitrogen conditions, we observed that both yellowing of the old leaves of the rosette and whole rosette redness were promoted. Leaf yellowing is a senescence symptom related to chlorophyll breakdown. Redness is a symptom of anthocyanin accumulation related to whole plant ageing and nutrient limitation. In this work, Arabidopsis is used as a model system to dissect the genetic variation of these parameters by QTL mapping in the 415 recombinant inbred lines of the Bay-0xShahdara population. Fifteen new QTLs and two epistatic interactions were described in this study. The yellowing of the rosette, estimated by visual notation and image processing, was controlled by four and five QTLs, respectively. The visual estimation of redness allowed us to detect six QTLs among which the major one explained 33% of the total variation. Two main QTLs were confirmed in near-isogenic lines (heterogenous inbred family; HIF), thus confirming the relevance of the visual notation of these traits. Co-localizations between QTLs for leaf yellowing, redness and nitrogen use efficiency described in a previous publication indicate complex interconnected pathways involved in both nitrogen management and senescence- and stress-related processes. No co-localization between QTLs for leaf yellowing and redness has been found, suggesting that the two characters are genetically independent.