El bentos y su fracción derivante: composición y estructura en un arroyo regulado (Achiras, Córdoba)

Flow regulation modifies the physico-chemical conditions of the fluvial system and consequently its biota. The aim of this study was to analyze the composition and structure of benthic and drift, upstream and downstream of the Achiras dam before and after construction. Sampling of benthos (Surber nets, 0.09 m2 and 300 μ) and drift (nets 1 m long, 300 μ and 0.0192 m2) were performed in high water and low water periods. The organisms were identified to the lowest possible taxonomic level and benthic Feeding Functional Groups were identified. Density, taxonomic richness, Shannon diversity and evenness for benthos and drift were calculated. Data were compared by three-way ANOVAs. The structure of both assemblages varied spatially and temporally. Benthic community showed a total of 110 taxa, corresponding to 8 phyla, while drift assemblage 55 taxa corresponding to 6 phyla. In both assemblages, the phylum Arthropoda was the most abundant. In the site below the dam and in the post-construction period, the benthos richness was greater, while drift evenness exhibited the highest value at the site below the dam during low water period. The filtering collectors and scrapers showed significant differences between year, site and hydrological period. The chironomids Tanytarsus sp. and Rheotanytarsus sp. were the most abundant among collectors while filtering Camelobaetidius penai and Stenophysa sp. among the scrapers. Data obtained in this study show that both data of benthic structure and its drifting fraction as the GFA data would indicate no significant changes attributable to dam effect. Longer studies would be required since in regulated systems most ecological changes happen more slowly than observed immediately.Facultad de Ciencias Naturales y Muse

El bentos y su fracción derivante: composición y estructura en un arroyo regulado (Achiras, Córdoba)

Flow regulation modifies the physico-chemical conditions of the fluvial system and consequently its biota. The aim of this study was to analyze the composition and structure of benthic and drift, upstream and downstream of the Achiras dam before and after construction. Sampling of benthos (Surber nets, 0.09 m2 and 300 μ) and drift (nets 1 m long, 300 μ and 0.0192 m2) were performed in high water and low water periods. The organisms were identified to the lowest possible taxonomic level and benthic Feeding Functional Groups were identified. Density, taxonomic richness, Shannon diversity and evenness for benthos and drift were calculated. Data were compared by three-way ANOVAs. The structure of both assemblages varied spatially and temporally. Benthic community showed a total of 110 taxa, corresponding to 8 phyla, while drift assemblage 55 taxa corresponding to 6 phyla. In both assemblages, the phylum Arthropoda was the most abundant. In the site below the dam and in the post-construction period, the benthos richness was greater, while drift evenness exhibited the highest value at the site below the dam during low water period. The filtering collectors and scrapers showed significant differences between year, site and hydrological period. The chironomids Tanytarsus sp. and Rheotanytarsus sp. were the most abundant among collectors while filtering Camelobaetidius penai and Stenophysa sp. among the scrapers. Data obtained in this study show that both data of benthic structure and its drifting fraction as the GFA data would indicate no significant changes attributable to dam effect. Longer studies would be required since in regulated systems most ecological changes happen more slowly than observed immediately.Facultad de Ciencias Naturales y Muse

El bentos y su fracción derivante: composición y estructura en un arroyo regulado (Achiras, Córdoba)

Flow regulation modifies the physico-chemical conditions of the fluvial system and consequently its biota. The aim of this study was to analyze the composition and structure of benthic and drift, upstream and downstream of the Achiras dam before and after construction. Sampling of benthos (Surber nets, 0.09 m2 and 300 μ) and drift (nets 1 m long, 300 μ and 0.0192 m2) were performed in high water and low water periods. The organisms were identified to the lowest possible taxonomic level and benthic Feeding Functional Groups were identified. Density, taxonomic richness, Shannon diversity and evenness for benthos and drift were calculated. Data were compared by three-way ANOVAs. The structure of both assemblages varied spatially and temporally. Benthic community showed a total of 110 taxa, corresponding to 8 phyla, while drift assemblage 55 taxa corresponding to 6 phyla. In both assemblages, the phylum Arthropoda was the most abundant. In the site below the dam and in the post-construction period, the benthos richness was greater, while drift evenness exhibited the highest value at the site below the dam during low water period. The filtering collectors and scrapers showed significant differences between year, site and hydrological period. The chironomids Tanytarsus sp. and Rheotanytarsus sp. were the most abundant among collectors while filtering Camelobaetidius penai and Stenophysa sp. among the scrapers. Data obtained in this study show that both data of benthic structure and its drifting fraction as the GFA data would indicate no significant changes attributable to dam effect. Longer studies would be required since in regulated systems most ecological changes happen more slowly than observed immediately.Facultad de Ciencias Naturales y Muse

Rac1 and Rac3 GTPases Regulate the Development of Hilar Mossy Cells by Affecting the Migration of Their Precursors to the Hilus

We have previously shown that double deletion of the genes for Rac1 and Rac3 GTPases during neuronal development affects late developmental events that perturb the circuitry of the hippocampus, with ensuing epileptic phenotype. These effects include a defect in mossy cells, the major class of excitatory neurons of the hilus. Here, we have addressed the mechanisms that affect the loss of hilar mossy cells in the dorsal hippocampus of mice depleted of the two Rac GTPases. Quantification showed that the loss of mossy cells was evident already at postnatal day 8, soon after these cells become identifiable by a specific marker in the dorsal hilus. Comparative analysis of the hilar region from control and double mutant mice revealed that synaptogenesis was affected in the double mutants, with strongly reduced presynaptic input from dentate granule cells. We found that apoptosis was equally low in the hippocampus of both control and double knockout mice. Labelling with bromodeoxyuridine at embryonic day 12.5 showed no evident difference in the proliferation of neuronal precursors in the hippocampal primordium, while differences in the number of bromodeoxyuridine-labelled cells in the developing hilus revealed a defect in the migration of immature, developing mossy cells in the brain of double knockout mice. Overall, our data show that Rac1 and Rac3 GTPases participate in the normal development of hilar mossy cells, and indicate that they are involved in the regulation of the migration of the mossy cell precursor by preventing their arrival to the dorsal hilus

Promises of stem cell therapy for retinal degenerative diseases

With the development of stem cell technology, stem cell-based therapy for retinal degeneration has been proposed to restore the visual function. Many animal studies and some clinical trials have shown encouraging results of stem cell-based therapy in retinal degenerative diseases. While stem cell-based therapy is a promising strategy to replace damaged retinal cells and ultimately cure retinal degeneration, there are several important challenges which need to be overcome before stem cell technology can be applied widely in clinical settings. In this review, different types of donor cell origins used in retinal treatments, potential target cell types for therapy, methods of stem cell delivery to the eye, assessments of potential risks in stem cell therapy, as well as future developments of retinal stem cells therapy, will be discussed

Effective transplantation of photoreceptor precursor cells selected via cell surface antigen expression

Retinal degenerative diseases are a major cause of untreatable blindness. Stem cell therapy to replace lost photoreceptors represents a feasible future treatment. We previously demonstrated that postmitotic photoreceptor precursors expressing an NrlGFP transgene integrate into the diseased retina and restore some light sensitivity. As genetic modification of precursor cells derived from stem cell cultures is not desirable for therapy, we have tested cell selection strategies using fluorochrome-conjugated antibodies recognizing cell surface antigens to sort photoreceptor precursors. Microarray analysis of postnatal NrlGFP-expressing precursors identified four candidate genes encoding cell surface antigens (Nt5e, Prom1, Podxl, and Cd24a). To test the feasibility of using donor cells isolated using cell surface markers for retinal therapy, cells selected from developing retinae by fluorescence-activated cell sorting based on Cd24a expression (using CD24 antibody) and/or Nt5e expression (using CD73 antibody) were transplanted into the wild-type or Crb1(rd8/rd8) or Prph2(rd2/rd2) mouse eye. The CD73/CD24-sorted cells migrated into the outer nuclear layer, acquired the morphology of mature photoreceptors and expressed outer segment markers. They showed an 18-fold higher integration efficiency than that of unsorted cells and 2.3-fold higher than cells sorted based on a single genetic marker, NrlGFP, expression. These proof-of-principle studies show that transplantation competent photoreceptor precursor cells can be efficiently isolated from a heterogeneous mix of cells using cell surface antigens without loss of viability for the purpose of retinal stem cell therapy. Refinement of the selection of donor photoreceptor precursor cells can increase the number of integrated photoreceptor cells, which is a prerequisite for the restoration of sight. STEM CELLS 2011;29:1391-140