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Successful Regeneration (successful + regeneration)
Selected AbstractsInhibition of Rho-dependent pathways by Clostridium botulinum C3 protein induces a proinflammatory profile in microgliaGLIA, Issue 11 2008Anja Hoffmann Abstract Successful regeneration in the central nervous system crucially depends on the adequate environment. Microglia as brain immune-competent cells importantly contribute to this task by producing pro- and anti-inflammatory mediators. Any environmental change transforms these cells towards an activated phenotype, leading to major morphological, transcriptional and functional alterations. Rho GTPases affect multiple cellular properties, including the cytoskeleton, and C3 proteins are widely used to study their involvement. Especially C3bot from Clostridium botulinum has been considered to promote neuronal regeneration by changing Rho activity. Yet C3bot may exert cellular influences through alternative mechanisms. To determine the role of Rho-dependent pathways in microglia we investigated the influence of C3bot on functional properties of cultivated primary mouse microglial cells. Nanomolar concentrations of C3bot transformed microglia towards an activated phenotype and triggered the release of nitric oxide and several proinflammatory cyto- and chemokines. These inductions were not mediated by the ROCK-kinase pathway, since its selective inhibitors Y27632 and H1152 had no effect. C3-induced and Rho-mediated NO release was instead found to be under the control of NF,B, as revealed by treatment with the NF,B inhibitor PDTC. Thus, C3bot induces a proinflammatory response in microglia resembling the classical proinflammatory phenotype elicited by bacterial LPS. The findings are relevant for the use of C3bot in regenerative approaches. © 2008 Wiley-Liss, Inc. [source] Regeneration potential of CIMMYT durum wheat and triticale varieties from immature embryosPLANT BREEDING, Issue 4 2001N. E. Bohorova Abstract Twenty-five durum wheat elite advanced lines and released varieties, and five triticale varieties were evaluated for their ability to produce embryogenic callus using three different media. For callus initiation and maintenance there were basal Murashige and Skoog (MS) medium containing double strains of macroelements and 2.5 mg/l 2,4D (DW1), basal MS medium containing 2.0 mg/l 2,4D (DW2), or basal MS medium supplemented with 1.0 mg/l 2,4 D and coconut milk (DW3). Plant regeneration was achieved on basal MS medium with indoleacetic acid and 6-benzylaminopurine, and plants rooted on MS with 1-naphthale-neacetic acid. DW3 medium proved better than the other media tested for embryogenic callus initiation and maintenance. Regeneration rates varied widely with both genotype and initiation medium, with values ranging from no regeneration to 100% regeneration; the plantlets produced per embryo ranged from five to 20. Fourteen of the durum wheat genotypes showed 63,100% regeneration from DW3 callus formation medium, four lines from DW1 medium, and two lines from DW2. Four of the triticale varieties had regeneration of 48,100% from DW3 medium. After six subcultures, over a 6-month period, genotypes lost their ability to regenerate plants. Only 10 lines retained some plant regeneration potential but regeneration was at reduced levels. Successful regeneration of durum wheat and triticale varieties will be used as an integral part of the transformation process. [source] Beyond early development: Xenopus as an emerging model for the study of regenerative mechanismsDEVELOPMENTAL DYNAMICS, Issue 6 2009Caroline W. Beck Abstract While Xenopus is a well-known model system for early vertebrate development, in recent years, it has also emerged as a leading model for regeneration research. As an anuran amphibian, Xenopus laevis can regenerate the larval tail and limb by means of the formation of a proliferating blastema, the lens of the eye by transdifferentiation of nearby tissues, and also exhibits a partial regeneration of the postmetamorphic froglet forelimb. With the availability of inducible transgenic techniques for Xenopus, recent experiments are beginning to address the functional role of genes in the process of regeneration. The use of soluble inhibitors has also been very successful in this model. Using the more traditional advantages of Xenopus, others are providing important lineage data on the origin of the cells that make up the tissues of the regenerate. Finally, transcriptome analyses of regenerating tissues seek to identify the genes and cellular processes that enable successful regeneration. Developmental Dynamics 238:1226,1248, 2009. © 2009 Wiley-Liss, Inc. [source] Overexpression of the transcription factor Msx1 is insufficient to drive complete regeneration of refractory stage Xenopus laevis hindlimbsDEVELOPMENTAL DYNAMICS, Issue 6 2009Donna M. Barker Abstract Xenopus laevis tadpoles are capable of hindlimb regeneration, although this ability declines with age. Bmp signaling is one pathway known to be necessary for successful regeneration to occur. Using an inducible transgenic line containing an activated version of the Bmp target Msx1, we assessed the ability of this transcription factor to enhance regeneration in older limbs. Despite considerable evidence correlating msx1 expression with regenerative success in vertebrate regeneration models, we show that induction of msx1 during hindlimb regeneration fails to induce complete regeneration. However, we did observe some improvement in regenerative outcome, linked to morphological changes in the early wound epithelium and a corresponding increase in proliferation in the underlying distal mesenchyme, neither of which are maintained later. Additionally, we show that Msx1 is not able to rescue limb regeneration in a Bmp signalling-deficient background, indicating that additional Bmp targets are required for regeneration in anuran limbs. Developmental Dynamics 238:1366,1378, 2009. © 2009 Wiley-Liss, Inc. [source] The effect of past changes in inter-annual temperature variability on tree distribution limitsJOURNAL OF BIOGEOGRAPHY, Issue 7 2010Thomas Giesecke Abstract Aim, The northern limits of temperate broadleaved species in Fennoscanndia are controlled by their requirements for summer warmth for successful regeneration and growth as well as by the detrimental effects of winter cold on plant tissue. However, occurrences of meteorological conditions with detrimental effects on individual species are rare events rather than a reflection of average conditions. We explore the effect of changes in inter-annual temperature variability on the abundances of the tree species Tilia cordata, Quercus robur and Ulmus glabra near their distribution limits using a process-based model of ecosystem dynamics. Location, A site in central Sweden and a site in southern Finland were used as examples for the ecotone between boreal and temperate forests in Fennoscandia. The Finnish site was selected because of the availability of varve-thickness data. Methods, The dynamic vegetation model LPJ-GUESS was run with four scenarios of inter-annual temperature forcing for the last 10,000 years. In one scenario the variability in the thickness of summer and winter varves from the annually laminated lake in Finland was used as a proxy for past inter-annual temperature variability. Two scenarios were devised to explore systematically the effect of stepwise changes in the variance and shape parameter of a probability distribution. All variability scenarios were run both with and without the long-term trend in Holocene temperature change predicted by an atmospheric general circulation model. Results, Directional changes in inter-annual temperature variability have significant effects on simulated tree distribution limits through time. Variations in inter-annual temperature variability alone are shown to alter vegetation composition by magnitudes similar to the magnitude of changes driven by variation in mean temperatures. Main conclusions, The varve data indicate that inter-annual climate variability has changed in the past. The model results show that past changes in species abundance can be explained by changes in the inter-annual variability of climate parameters as well as by mean climate. Because inter-annual climatic variability is predicted to change in the future, this component of climate change should be taken into account both when making projections of future plant distributions and when interpreting vegetation history. [source] Postdispersal seed predation and seed viability in forest soils: implications for the regeneration of tree species in Ethiopian church forestsAFRICAN JOURNAL OF ECOLOGY, Issue 2 2010Alemayehu Wassie Abstract Almost all dry Afromontane forests of Northern Ethiopia have been converted to agricultural, grazing or scrub lands except for small fragments left around churches (,Church forests'). Species regeneration in these forests is limited. We investigated (i) how intense postdispersal seed predation was in church forest, and if this seed predation varied with species and/or habitat, and (ii) for how long tree seeds maintained their viability while buried in forest soil. In the seed predation experiment, we monitored seeds of six tree species in four habitats for a period of 14 weeks (the peak seeding season). In the seed viability experiment, we assessed seed viability of five species in four habitats after being buried 6, 12, or 18 months. Ninety-two percent of the tree seeds were predated within 3.5 months. Predation was mainly dependent on species whereas habitat had a weaker effect. Seed viability decreased sharply with burial time in soil for all species except for Juniperus. To minimize seed availability limitation for regeneration of such species in the forest, the standing vegetation needs to be persistently managed and conserved for a continuous seed rain supply. Additional seed sowing, and seed and seedling protection (by e.g. animal exclosures) may increase successful regeneration of important species in these forests. Résumé Presque toutes les forêts afromontagnardes sèches du nord de l'Ethiopie ont été converties en terres agricoles, pâturages ou broussailles, à l'exception de petits fragments laissés autour des églises (« Forêts d'églises »). La régénération des espèces dans ces fragments reste limitée. Nous avons étudié (1) l'intensité de la prédation sur les semences après leur dispersion dans ces forêts et si cette prédation variait selon les espèces et/ou les habitats, (2) combien de temps les semences d'arbres gardaient leur viabilité lorsqu'elles étaient enterrées dans le sol d'une forêt. Dans l'expérience sur la prédation des semences, nous avons suivi des semences de six espèces d'arbres dans quatre habitats pendant 14 semaines (le pic de la saison des semences). Dans l'expérience sur la viabilité des semences, nous avons évalué la viabilité de semences de cinq espèces dans quatre habitats après avoir été enterrées depuis 6, 12 ou 18 mois. 92% des semences avaient été consommées en 3,5 mois. La prédation dépendait principalement de l'espèce, et l'habitat avait un effet moins important. La viabilité des semences diminuait fortement avec l'allongement de la durée d'enfouissement pour toutes les espèces sauf Juniperus. Pour diminuer autant que possible la limitation de la disponibilité des semences destinées à la régénération de telles espèces dans la forêt, il faut gérer continuellement la végétation présente et la conserver pour une production continue de semences. Un ensemencement supplémentaire ainsi que la protection des semences et des jeunes plants (par exemple en les clôturants pour écarter les animaux) pourraient améliorer la régénération des espèces importantes de ces forêts. [source] Starch,poly(,-caprolactone) and starch,poly(lactic acid) fibre-mesh scaffolds for bone tissue engineering applications: structure, mechanical properties and degradation behaviourJOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE, Issue 5 2008M. E. Gomes Abstract In scaffold-based tissue engineering strategies, the successful regeneration of tissues from matrix-producing connective tissue cells or anchorage-dependent cells (e.g. osteoblasts) relies on the use of a suitable scaffold. This study describes the development and characterization of SPCL (starch with ,-polycaprolactone, 30:70%) and SPLA [starch with poly(lactic acid), 30:70%] fibre-meshes, aimed at application in bone tissue-engineering strategies. Scaffolds based on SPCL and SPLA were prepared from fibres obtained by melt-spinning by a fibre-bonding process. The porosity of the scaffolds was characterized by microcomputerized tomography (µCT) and scanning electron microscopy (SEM). Scaffold degradation behaviour was assessed in solutions containing hydrolytic enzymes (,-amylase and lipase) in physiological concentrations, in order to simulate in vivo conditions. Mechanical properties were also evaluated in compression tests. The results show that these scaffolds exhibit adequate porosity and mechanical properties to support cell adhesion and proliferation and also tissue ingrowth upon implantation of the construct. The results of the degradation studies showed that these starch-based scaffolds are susceptible to enzymatic degradation, as detected by increased weight loss (within 2 weeks, weight loss in the SPCL samples reached 20%). With increasing degradation time, the diameter of the SPCL and SPLA fibres decreases significantly, increasing the porosity and consequently the available space for cells and tissue ingrowth during implantation time. These results, in combination with previous cell culture studies showing the ability of these scaffolds to induce cell adhesion and proliferation, clearly demonstrate the potential of these scaffolds to be used in tissue engineering strategies to regenerate bone tissue defects. Copyright © 2008 John Wiley & Sons, Ltd. [source] Nervous system,derived chondroitin sulfate proteoglycans regulate growth cone morphology and inhibit neurite outgrowth: A light, epifluorescence, and electron microscopy studyMICROSCOPY RESEARCH AND TECHNIQUE, Issue 5 2001Diane M. Snow Abstract Proteoglycans influence aging and plasticity in the nervous system. Particularly prominent are the chondroitin sulfate proteoglycans (CSPGs), which are generally inhibitory to neurite outgrowth. During development, CSPGs facilitate normal guidance, but following nervous system injury and in diseases of aging (e.g., Alzheimer's disease), they block successful regeneration, and are associated with axon devoid regions and degenerating nerve cells. Whereas previous studies used non-nervous system sources of CSPGs, this study analyzed the morphology and behavior of sensory (dorsal root ganglia) neurons, and a human nerve cell model (SH-SY5Y neuroblastoma cells) as they contacted nervous system,derived CSPGs, using a variety of microscopy techniques. The results of these qualitative analyses show that growth cones of both nerve cell types contact CSPGs via actin-based filopodia, sample the CSPGs repeatedly without collapse, and alter their trajectory to avoid nervous system,derived CSPGs. Turning and branching are correlated with increased filopodial sampling, and are common to both neurons and Schwann cells. We show that CSPG expression by rat CNS astrocytes in culture is correlated with sensory neuron avoidance. Further, we show for the first time the ultrastructure of sensory growth cones at a CSPG-laminin border and reveal details of growth cone and neurite organization at this choice point. This type of detailed analysis of the response of growth cones to nervous system,derived CSPGs may lead to an understanding of CSPG function following injury and in diseases of aging, where CSPGs are likely to contribute to aberrant neurite outgrowth, failed or reduced synaptic connectivity, and/or ineffective plasticity. Microsc. Res. Tech. 54:273,286, 2001. © 2001 Wiley-Liss, Inc. [source] Heterogeneous genetic structure in a Fagus crenata population in an old-growth beech forest revealed by microsatellite markersMOLECULAR ECOLOGY, Issue 5 2004Y. Asuka Abstract The within-population genetic structure of Fagus crenata in a 4-ha plot (200 × 200 m) of an old-growth beech forest was analysed using microsatellite markers. To assess the genetic structure, Moran's I spatial autocorrelation coefficient was calculated. Correlograms of Moran's I showed significant positive values less than 0.100 for short-distance classes, indicating weak genetic structure. The genetic structure within the population is created by limited seed dispersal, and is probably weakened by overlapping seed shadow, secondary seed dispersal, extensive pollen flow and the thinning process. Genetic structure was detected in a western subplot of 50 × 200 m with immature soils and almost no dwarf bamboos (Sasa spp.), where small and intermediate-sized individuals were distributed in aggregations with high density because of successful regeneration. By contrast, genetic structure was not found in an eastern subplot of the same size with mature soils and Sasa cover, where successful regeneration was prevented, and the density of the small and intermediate-sized individuals was low. Moreover, genetic structure of individuals in a small-size class (diameter at breast height < 12 cm) was more obvious than in a large-size class (diameter at breast height , 12 cm). The apparent genetic structure detected in the 4-ha plot was therefore probably the result of the structure in the western portion of the plot and in small and intermediate-sized individuals that successfully regenerated under the favourable environment. The heterogeneity in genetic structure presumably reflects variation in the density that should be affected by differences in regeneration dynamics associated with heterogeneity in environmental conditions. [source] Potential of Fortified Fibrin/Hyaluronic Acid Composite Gel as a Cell Delivery Vehicle for ChondrocytesARTIFICIAL ORGANS, Issue 6 2009Sang-Hyug Park Abstract Numerous treatment methods have been applied for use in cartilage repair, including abrasion, drilling, and microfracture. Although chondrocyte transplantation is the preferred treatment, it has some shortcomings, such as difficulty of application (large and posterior condylar regions), poor chondrocyte distribution, and potential cell leakage from the defect region. The cell delivery system of the tissue engineering technique can be used to overcome these shortcomings. We chose fibrin/hyaluronan (HA) composite gel as an effective cell delivery system to resolve these issues. Both components are derived from natural extracellular matrix. In the first trial, fortified fibrin/HA composite gels with rabbit chondrocytes were tested by implantation in nude mice. At 4 weeks, glycosaminoglycan contents in the fibrin/HA composite (0.186 ± 0.006 mg/mg) were significantly higher than those in the presence of fibrin alone (0.153 ± 0.017 mg/mg). As a next step, we applied the fibrin/HA composite gel to animal cartilage defects using full thickness cartilage defect rabbit models. The fibrin/HA composite gel with rabbit chondrocytes (allogenic) was implanted into the experimental group, and the control group was implanted with the fibrin/HA composite gel alone. Implanted chondrocytes with the fibrin/HA composite showed improved cartilage formation. In conclusion, the key to successful regeneration of cartilage is to provide the repair site with a sufficient supply of chondrogenic cells with a suitable delivery vehicle to ensure maximal differentiation and deposition of the proper extracellular matrix. This study suggests the feasibility of tissue-engineered cartilage formation using fibrin/HA composite gel. [source] | |||||||||||||