Nogo Receptor Inhibition Enhances Functional Recovery following Lysolecithin-Induced Demyelination in Mouse Optic Chiasm

Background

Inhibitory factors have been implicated in the failure of remyelination in demyelinating diseases. Myelin associated inhibitors act through a common receptor called Nogo receptor (NgR) that plays critical inhibitory roles in CNS plasticity. Here we investigated the effects of abrogating NgR inhibition in a non-immune model of focal demyelination in adult mouse optic chiasm.

Methodology/Principal Findings

A focal area of demyelination was induced in adult mouse optic chiasm by microinjection of lysolecithin. To knock down NgR levels, siRNAs against NgR were intracerebroventricularly administered via a permanent cannula over 14 days, Functional changes were monitored by electrophysiological recording of latency of visual evoked potentials (VEPs). Histological analysis was carried out 3, 7 and 14 days post demyelination lesion. To assess the effect of NgR inhibition on precursor cell repopulation, BrdU was administered to the animals prior to the demyelination induction. Inhibition of NgR significantly restored VEPs responses following optic chiasm demyelination. These findings were confirmed histologically by myelin specific staining. siNgR application resulted in a smaller lesion size compared to control. NgR inhibition significantly increased the numbers of BrdU+/Olig2+ progenitor cells in the lesioned area and in the neurogenic zone of the third ventricle. These progenitor cells (Olig2+ or GFAP+) migrated away from this area as a function of time.

Conclusions/Significance

Our results show that inhibition of NgR facilitate myelin repair in the demyelinated chiasm, with enhanced recruitment of proliferating cells to the lesion site. Thus, antagonizing NgR function could have therapeutic potential for demyelinating disorders such as Multiple Sclerosis.     

A Preliminary Study of Viral Metagenomics of French Bat Species in Contact with Humans: Identification of New Mammalian Viruses

The prediction of viral zoonosis epidemics has become a major public health issue. A profound understanding of the viral population in key animal species acting as reservoirs represents an important step towards this goal. Bats harbor diverse viruses, some of which are of particular interest because they cause severe human diseases. However, little is known about the diversity of the global population of viruses found in bats (virome). We determined the viral diversity of five different French insectivorous bat species (nine specimens in total) in close contact with humans. Sequence-independent amplification, high-throughput sequencing with Illumina technology and a dedicated bioinformatics analysis pipeline were used on pooled tissues (brain, liver and lungs). Comparisons of the sequences of contigs and unassembled reads provided a global taxonomic distribution of virus-related sequences for each sample, highlighting differences both within and between bat species. Many viral families were present in these viromes, including viruses known to infect bacteria, plants/fungi, insects or vertebrates, the most relevant being those infecting mammals (Retroviridae, Herpesviridae, Bunyaviridae, Poxviridae, Flaviviridae, Reoviridae, Bornaviridae, Picobirnaviridae). In particular, we detected several new mammalian viruses, including rotaviruses, gammaretroviruses, bornaviruses and bunyaviruses with the identification of the first bat nairovirus. These observations demonstrate that bats naturally harbor viruses from many different families, most of which infect mammals. They may therefore constitute a major reservoir of viral diversity that should be analyzed carefully, to determine the role played by bats in the spread of zoonotic viral infections.     

Dendritic Signals Command Firing Dynamics in a Mathematical Model of Cerebellar Purkinje Cells

Dendrites of cerebellar Purkinje cells (PCs) respond to brief excitations from parallel fibers with lasting plateau depolarizations. It is unknown whether these plateaus are local events that boost the synaptic signals or they propagate to the soma and directly take part in setting the cell firing dynamics. To address this issue, we analyzed a likely mechanism underlying plateaus in three representations of a reconstructed PC with increasing complexity. Analysis in an infinite cable suggests that Ca plateaus triggered by direct excitatory inputs from parallel fibers and their mirror signals, valleys (putatively triggered by the local feed forward inhibitory network), cannot propagate. However, simulations of the model in electrotonic equivalent cables prove that Ca plateaus (resp. valleys) are conducted over the entire cell with velocities typical of passive events once they are triggered by threshold synaptic inputs that turn the membrane current inward (resp. outward) over the whole cell surface. Bifurcation analysis of the model in equivalent cables, and simulations in a fully reconstructed PC both indicate that dendritic Ca plateaus and valleys, respectively, command epochs of firing and silencing of PCs.     

Polymorphism ofTcrb andTcrg genes in Biozzi mice: Segregation analysis of a newTcrg haplotype with antibody responsiveness

Tcrb andTcrg gene polymorphism was investigated in high (H) and low (L) responder Biozzi mice from selection I, II, and GS by Southern blot analysis with appropriateV andC probes. No polymorphism of theTcrb haplotype was detected between H and L mice in all selections which were all found to be of the BALB/c type. The H-I and H-II g genotype was of BALB/c and DBA/2 type, respectively. In contrast, a newTcrg haplotype shared by L-I and L-II mice was identified and characterized by C1, 2, 3, C4, V1, 2, 3, V5, and V6 restriction fragment length polymorphisms (RFLPs).Tcrg genotypes were not fixed in the GS selection and two additional new haplotypes were identified in two L-GS mice. An attempt was made to correlate the L-Ig genotype with the low responder status by analyzingg haplotypes among highest and lowest responder (H-1 x L-I)F₂ hybrids immunized with sheep red blood cells (SRBC). No correlation was found in this segregation study, whereas a highly significant one was established with theH-2 haplotype, a locus already known to participate in the genetic control of H-I/L-I difference. The lack of correlation between SRBC response and theTcrg genotype was consistent with the heterogenousg haplotypes found in mice of the GS selection. Together, the present results suggest that H and L mice have the sameTcrab potential repertoire and that T-cell receptor (Tcr) genes cannot be considered as immune response genes in this model. Our results also indicate that the F₂ segregation analysis, given a polymorphic gene, is suitable for an investigation of its immune response functions.     

Somatic embryogenesis in wild cherry (Prunus avium)

Indirect somatic embryogenesis was obtained inPrunus avium L. from either somatic or zygotic embryos. An embryogenic line was established by reinduction of embryogenic calluses from somatic embryos. The line was maintained for more than 3 years through 6 generations of embryogenic cultures. In the last 2 generations, more than 50% of the explants were embryogenic. Embryos at different stages of development were produced. Among cotyledonary-stage embryos, 50% had two cotyledons and a distinct hypocotyl, 43% had one or more than 2 cotyledons and 7% had fused cotyledons. Most of the embryos were translucent and conversion into plantlets was very rare. Secondary embryos could be observed to occur with low frequency from cultured somatic embryos and from embryos emerging from calluses. Indirect somatic embryogenesis was also induced from immature zygotic embryos. From one donor tree, 51% of the explants were embryogenic when cultured on a medium containing 0.9 μM kinetin, 0.9 μM BA and 0.5 μM NAA. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of nandrolone decanoate on respiratory and peripheral muscles in male and female rats

Bisschop, Anja, Ghislaine Gayan-Ramirez, HélèneRollier, P. N. Richard Dekhuijzen, René Dom, Vera de Bock, andMarc Decramer. Effects of nandrolone decanoate on respiratory and peripheral muscles in male and female rats. J. Appl.Physiol. 82(4): 1112-1118, 1997.Thirty maleand 18 female adult rats received weekly an intramuscular injection ofeither saline (control; C), 1.5 mg/kg (low-dose; LD) nandrolonedecanoate or 7.5 mg/kg (high-dose; HD) nandrolone decanoate during 5 wk. Compared with respective C, growth rate was stunted in male HD ratsfrom 2 wk of treatment on, whereas it was enhanced in female LD and HDrats after 1 wk. Mass of all muscles studied varied proportionally tobody weight, except for the gastrocnemius (males: 0.49 ± 0.04 vs. C: 0.52 ± 0.03%, not significant; females: 0.17 ± 0.01 vs. C: 0.15 ± 0.01%, P < 0.05). In vitro contractile andfatigue properties of the diaphragm remained unchanged, except for adecrease in twitch kinetics (time to peak tension: C, 21 ± 2; LD,19 ± 1; HD, 19 ± 2 ms, P < 0.05; half-relaxation time: C, 26 ± 5, LD, 25 ± 5, HD, 23 ± 3 ms, P < 0.01).Histochemistry of the diaphragm and the gastrocnemius revealed asignificant increase in type IIx/b dimensions. In the gastrocnemius,type I fiber dimensions also increased. A pair-fed study, includinganother 24 female rats, showed that the changes in oral food intakeonly partly accounted for the observed anabolic effects.

     

Comparative Genomic Analysis of Drechmeria coniospora Reveals Core and Specific Genetic Requirements for Fungal Endoparasitism of Nematodes

Drechmeria coniospora is an obligate fungal pathogen that infects nematodes via the adhesion of specialized spores to the host cuticle. D. coniospora is frequently found associated with Caenorhabditis elegans in environmental samples. It is used in the study of the nematode’s response to fungal infection. Full understanding of this bi-partite interaction requires knowledge of the pathogen’s genome, analysis of its gene expression program and a capacity for genetic engineering. The acquisition of all three is reported here. A phylogenetic analysis placed D. coniospora close to the truffle parasite Tolypocladium ophioglossoides, and Hirsutella minnesotensis, another nematophagous fungus. Ascomycete nematopathogenicity is polyphyletic; D. coniospora represents a branch that has not been molecularly characterized. A detailed in silico functional analysis, comparing D. coniospora to 11 fungal species, revealed genes and gene families potentially involved in virulence and showed it to be a highly specialized pathogen. A targeted comparison with nematophagous fungi highlighted D. coniospora-specific genes and a core set of genes associated with nematode parasitism. A comparative gene expression analysis of samples from fungal spores and mycelia, and infected C. elegans, gave a molecular view of the different stages of the D. coniospora lifecycle. Transformation of D. coniospora allowed targeted gene knock-out and the production of fungus that expresses fluorescent reporter genes. It also permitted the initial characterisation of a potential fungal counter-defensive strategy, involving interference with a host antimicrobial mechanism. This high-quality annotated genome for D. coniospora gives insights into the evolution and virulence of nematode-destroying fungi. Coupled with genetic transformation, it opens the way for molecular dissection of D. coniospora physiology, and will allow both sides of the interaction between D. coniospora and C. elegans, as well as the evolutionary arms race that exists between pathogen and host, to be studied.     

High-performance liquid chromatography of ecdysone metabolites applied to the cabbage butterfly, Pieris brassicae L

HPLC allowed separation of twelve major labeled compounds after injection of ³H-ecdysone into Pieris pharate pupae. These compounds were identified as six pairs of metabolites (3α and 3β epimers), comprising ecdysone, 20-hydroxyecdysone, 26-hydroxyecdysone, 20,26-dihydroxy-ecdysone and the polar metabolites P and 20-hydroxy-P. These last two products could not be enzymatically split by any hydrolase tested and are weak acids arising respectively from 26-hydroxyecdysone and 20,26-dihydroxyecdysone. They might be 26-oic compounds.Epimerization appears as a fundamental inactivation process in Pieris and could well be a general characteristic of closed systems (eggs and pupae). No significant amounts of hydrolyzable conjugates were detected in our biological system (pharate pupae and pupae).