No abstract

In the central nervous system (CNS), nerve regeneration after traumatic injury fails. The formation of a dense fibrous scar is thought to restrict in part the growth of axonal projections, providing one of the many reasons that complete lesions of neural pathways in the adult mammalian CNS are rarely followed by significant functional recovery. In order to determine which mechanisms mediate scar formation in the CNS and to investigate whether they can be modulated in vim, we have attempted to define the potential role of trophic factors. Our previous studies have shown the focal elevation of transforming growth factor P1 (TGFP,) expression in lesioned CNS tissue. In the studies described here, we demonstrate that TGFP, participates in the scarring response in the rat brain. First, the elevated protein levels of TGFP, are localized to specific populations of injury-responsive cells in the traumatized CNS. Furthermore, the injection of TGFP, into the brains of injured rats causes a dramatic increase in the scarring response. Conversely, when neutralizing TGFP, antibodies are administered, the deposition of fibrous scar tissue and the formation of a limiting glial membrane that borders the lesion is significantly attenuated, thus establishing a role for the endogenous growth factor in regulation of the non-glial component of the scar. In implicating TGFP, in the scarring response in the CNS, the potential use for TGFP, antagonists as inhibitors of scar formation in the injured mammalian CNS is self-evident.

Apomixis is a route of asexual reproduction through seeds, that progresses in the absence of meiosis and fertilization to generate maternal clonal progenies. Gametophytic apomicts are usually polyploid and probably arose from sexual ancestors through a limited number of mutations in the female reproductive pathway. A differential display analysis was carried out on immature inflorescences of sexual and apomictic tetraploid genotypes of Paspalum notatum, in order to identify genes associated with the emergence of apospory. Analysis of approximately 10,000 transcripts led to the identification of 94 high-quality differentially expressed sequences. Assembling analysis, plus validation, rendered 65 candidate unigenes, organized as 14 contigs and 51 singletons. Thirty-four unigenes were isolated from apomictic plants and 31 from sexual ones. A total of 45 (69.2%) unigenes were functionally categorized. While several of the differentially expressed sequences appeared to be components of an extracellular receptor kinase (ERK) signal transduction cascade, others seemed to participate in a variety of central cellular processes like cell-cycle control, protein turnover, intercellular signalling, transposon activity, transcriptional regulation and endoplasmic reticulum-mediated biosynthesis. In silico mapping revealed that a particular group of five genes silenced in apomictic plants clustered in a rice genomic area syntenic with the region governing apospory in Paspalum notatum and Brachiaria brizantha. Two of these genes mapped within the set of apo-homologues in P. notatum. Four genes previously reported to be controlled by ploidy were identified among those expressed differentially between apomictic and sexual plants. In situ hybridization experiments were performed for selected clones.

No abstract

The therapeutic effects of individual neurotrophic factors (NTF) have proved disappointing in clinical trials for neuronal repair and axon regeneration. Here, we demonstrate NTF synergistic neuronal responses after a combination of basic fibroblast growth factor, neurotrophin-3 and brain derived growth factor delivered to the somata of retinal ganglion cells promoted greater survival and axon growth than did the sum of the effects of each NTF alone. Triple and not single NTF treatments potentiated regulated intramembraneous proteolysis of p75(NTR), and ectodomain shedding of Nogo receptor, correlated with a 30% decrease in activation of Rho-A, a key signalling molecule in the axon growth inhibitory cascade. Thus, combinatorial NTF administration synergistically enhanced neuronal survival, disinhibited axon growth and promoted axon regeneration through the hostile CNS environment without the intervention of scar tissue at the lesion site.

BackgroundThe content and composition of cerebrospinal fluid (CSF) is determined in large part by the choroid plexus (CP) and specifically, a specialized epithelial cell (CPe) layer that responds to, synthesizes, and transports peptide hormones into and out of CSF. Together with ventricular ependymal cells, these CPe relay homeostatic signals throughout the central nervous system (CNS) and regulate CSF hydrodynamics. One new candidate signal is augurin, a newly recognized 14 kDa protein that is encoded by esophageal cancer related gene-4 (Ecrg4), a putative tumor suppressor gene whose presence and function in normal tissues remains unexplored and enigmatic. The aim of this study was to explore whether Ecrg4 and its product augurin, can be implicated in CNS development and the response to CNS injury.MethodsEcrg4 gene expression in CNS and peripheral tissues was studied by in situ hybridization and quantitative RT-PCR. Augurin, the protein encoded by Ecrg4, was detected by immunoblotting, immunohistochemistry and ELISA. The biological consequence of augurin over-expression was studied in a cortical stab model of rat CNS injury by intra-cerebro-ventricular injection of an adenovirus vector containing the Ecrg4 cDNA. The biological consequences of reduced augurin expression were evaluated by characterizing the CNS phenotype caused by Ecrg4 gene knockdown in developing zebrafish embryos.ResultsGene expression and immunohistochemical analyses revealed that, the CP is a major source of Ecrg4 in the CNS and that Ecrg4 mRNA is predominantly localized to choroid plexus epithelial (CPe), ventricular and central canal cells of the spinal cord. After a stab injury into the brain however, both augurin staining and Ecrg4 gene expression decreased precipitously. If the loss of augurin was circumvented by over-expressing Ecrg4 in vivo, BrdU incorporation by cells in the subependymal zone decreased. Inversely, gene knockdown of Ecrg4 in developing zebrafish embryos caused increased proliferation of GFAP-positive cells and induced a dose-dependent hydrocephalus-like phenotype that could be rescued by co-injection of antisense morpholinos with Ecrg4 mRNA.ConclusionAn unusually elevated expression of the Ecrg4 gene in the CP implies that its product, augurin, plays a role in CP-CSF-CNS function. The results are all consistent with a model whereby an injury-induced decrease in augurin dysinhibits target cells at the ependymal-subependymal interface. We speculate that the ability of CP and ependymal epithelium to alter the progenitor cell response to CNS injury may be mediated, in part by Ecrg4. If so, the canonic control of its promoter by DNA methylation may implicate epigenetic mechanisms in neuroprogenitor fate and function in the CNS.

Group A rotaviruses are the most common cause of dehydrating diarrhea in infants and young children worldwide, with more than 2 million hospitalizations yearly and approximately 440,000 deaths. It is estimated that 82% of rotavirus deaths occur in children in the poorest countries (23). Rotavirus transmission occurs mainly by the fecal-oral route, although respiratory transmission has been suggested to occur (7).Rotavirus infection was thought to be limited to the gastrointestinal tract. However, respiratory symptoms and rotavirus shedding in nasopharyngeal secretions have been reported in children with and without gastrointestinal symptoms (19,26,42). Rotavirus antigen was detected in the lung of 1 of 13 experimentally infected 3-week-old conventional pigs at postinoculation day 2 (30) and in liver and kidney specimens from immunodeficient children (9). Rotavirus RNA has also been detected in cerebrospinal fluid and blood of children with central nervous system disease (20,34). Recently, Blutt and colleagues (2) detected rotavirus antigenemia in the serum of children, mice, rabbits, and calves. They further demonstrated that serum from infected mice induced rectal rotavirus antigen shedding after oral inoculation of rotavirus-negative adult mice with the serum. Previously, another enteric virus, the porcine enteric calicivirus (PEC), has also been associated with transient viremia (infectious virus in serum) after oral inoculation of gnotobiotic pigs (11).We choose gnotobiotic pigs because they constitute an animal model of HRV-induced disease. Their gastrointestinal tract physiology and their development of mucosal immunity resemble that of humans. These similarities with HRV infections of infants allow us to establish correlations which could be applied for rotavirus vaccine development (14,25) The question addressed in our study was whether an attenuated human rotavirus and virulent HRV causes upper respiratory tract infections or viremia in naïve neonatal gnotobiotic pigs after various routes of inoculation. In this study we evaluated nasal and rectal virus shedding and viremia after oral, intranasal, feeding tube (gavage), and intravenous inoculation of neonatal gnotobiotic pigs with the Wa strain of attenuated HRV or virulent HRV. The presence of infectious virus in serum of gnotobiotic pigs after oral inoculation with Wa HRV was also investigated by oral and intravenous reinoculation of gnotobiotic pigs with a pool of the HRV-positive sera. MATERIALS AND METHODSVirus. The attenuated cell culture-adapted Wa strain HRV (P1A [8]G1), derived from the 27th HRV passage in African Green monkey kidney cells (MA104) and the virulent Wa HRV from pooled intestinal contents of gnotobiotic pigs were used for inoculation of the gnotobiotic pigs at doses of 5 ϫ 10 7

Human rotavirus-specific CD4؉ and CD8 ؉ T-cell responses in peripheral blood lymphocytes were studied using a flow cytometric assay that detects the intracellular accumulation of cytokines after short-term in vitro antigen stimulation. The frequencies of virus-specific T cells that secrete gamma interferon and interleukin-13 (IL-13) were determined in adults and children during the acute or convalescent phase of rotavirus-induced diarrhea, in asymptomatically infected adults and laboratory workers who worked with human stool samples containing rotavirus, and in healthy adults. Significantly higher frequencies of rotavirus-specific interferon gamma-secreting CD8؉ and CD4 ؉ T cells, but not IL-13-secreting T cells, were detected in symptomatically infected adults and exposed laboratory workers than in healthy adults and children with acute rotavirus diarrhea. The levels of rotavirus-specific T cells returned to levels found in healthy adults by 32 days after the onset of rotavirus diarrhea in most adult subjects. Children with rotavirus diarrhea had undetectable or very low levels of CD4 ؉ and CD8 ؉ T cells that secrete gamma interferon. Adult cytomegalovirus-seropositive individuals had frequencies of cytomegalovirus-specific T cells that secrete gamma interferon that were approximately 20 times the level of rotavirus-specific T cells. This result suggests that rotavirus is a relatively poor inducer of circulating memory T cells that secrete gamma interferon. The frequencies of gamma interferon-secreting CD4؉ and CD8 ؉ T cells and the frequencies of IL-13-secreting CD4 ؉ T cells responding to the T-cell superantigen staphylococcal enterotoxin B (SEB) were lower in children than in adults. In both adults and children, the frequencies of CD4 ؉ cells secreting gamma interferon in response to SEB were higher than the frequencies of cells secreting IL-13.Rotaviruses (RV) are the most important cause of severe dehydrating diarrhea in children worldwide, resulting in an estimated 480,000 to 640,000 deaths annually (5). The first vaccine approved for use in humans has recently been withdrawn by the manufacturer because it was associated with increased numbers of cases of intussusception (1). For these reasons, investigators are exploring alternative vaccination strategies to develop improved second-generation vaccine candidates. A detailed knowledge of the immune response against RV in humans will be useful for the design and/or evaluation of new RV vaccines.The RV-specific cell-mediated immune response is relatively well studied in the murine model: CD4 ϩ T cells are essential for the development of more than 90% of the RV-specific intestinal immunoglobulin A (IgA) (14). Moreover, the antibody response seems to be the main mechanism that mediates protection against RV reinfection (14,15,31). Murine RVspecific CD8 ϩ T cells have a direct antiviral effect, are involved in the timely resolution of primary RV infection, and can mediate partial protection against reinfection (13,15,31).Because RV replication is restricted to...