Home About us Contact
|
Home About us Contact | ||
|
|
||
Reduced Viability (reduced + viability)
Selected AbstractsHydrologic Connectivity and the Contribution of Stream Headwaters to Ecological Integrity at Regional Scales,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 1 2007Mary C. Freeman Abstract:, Cumulatively, headwater streams contribute to maintaining hydrologic connectivity and ecosystem integrity at regional scales. Hydrologic connectivity is the water-mediated transport of matter, energy and organisms within or between elements of the hydrologic cycle. Headwater streams compose over two-thirds of total stream length in a typical river drainage and directly connect the upland and riparian landscape to the rest of the stream ecosystem. Altering headwater streams, e.g., by channelization, diversion through pipes, impoundment and burial, modifies fluxes between uplands and downstream river segments and eliminates distinctive habitats. The large-scale ecological effects of altering headwaters are amplified by land uses that alter runoff and nutrient loads to streams, and by widespread dam construction on larger rivers (which frequently leaves free-flowing upstream portions of river systems essential to sustaining aquatic biodiversity). We discuss three examples of large-scale consequences of cumulative headwater alteration. Downstream eutrophication and coastal hypoxia result, in part, from agricultural practices that alter headwaters and wetlands while increasing nutrient runoff. Extensive headwater alteration is also expected to lower secondary productivity of river systems by reducing stream-system length and trophic subsidies to downstream river segments, affecting aquatic communities and terrestrial wildlife that utilize aquatic resources. Reduced viability of freshwater biota may occur with cumulative headwater alteration, including for species that occupy a range of stream sizes but for which headwater streams diversify the network of interconnected populations or enhance survival for particular life stages. Developing a more predictive understanding of ecological patterns that may emerge on regional scales as a result of headwater alterations will require studies focused on components and pathways that connect headwaters to river, coastal and terrestrial ecosystems. Linkages between headwaters and downstream ecosystems cannot be discounted when addressing large-scale issues such as hypoxia in the Gulf of Mexico and global losses of biodiversity. [source] Antibacterial activity of silver inorganic agent YDA fillerJOURNAL OF ORAL REHABILITATION, Issue 4 2004S. Ohashi summary, YDA filler is an antibacterial agent that is currently in commercial dental use. In this study, we attempted to determine whether it exerts an antibacterial effect on human saliva bacteria, and to determine whether it can be used in dental materials. CFUs in 1 mL stimulated human saliva were examined using blood agar and mitis salivarius agar after immersion, with or without YDA filler. The antibacterial effect was compared with that of Ketac-Silver. Dental materials containing 5% wt YDA filler were prepared for in vitro testing on S. mutans and A. viscosus. Furthermore, we examined the in vitro cytotoxicity of experimental MMA resin containing YDA filler on HeLa cells. Human saliva bacteria and mutans streptococci showed reduced viability following exposure to YDA filler after 12 h. The concentration of silver ions released by YDA filler was below 1 ppm after 12 h. Two tested strains showed reduced viability following exposure to dental materials containing YDA filler. In another experiment, MMA resin containing YDA filler did not show cytotoxicity on HeLa cells after 24- and 48-h exposure. Thus, YDA filler may help in the development of antibacterial dental materials, such as composite resin, glass,ionomer or temporary cement. [source] Ovarian dynamics and oosorption in two species of predatory lady beetles (Coleoptera: Coccinellidae)PHYSIOLOGICAL ENTOMOLOGY, Issue 2 2009YUKIE KAJITA Abstract Ovarian development and oviposition dynamics of two species of lady beetle, Coccinella septempunctata L. and C. transversoguttata richardsoni Brown, are examined in laboratory experiments in which pea aphids (Acyrthosiphon pisum Harris) are provided ad libitum and then removed. Both species respond to prey removal by stabilizing at lower body weights, and by laying progressively fewer and smaller eggs of reduced viability, until oviposition ceases altogether after several days of starvation. Dissections of females after prey removal reveal similar patterns of oosorption in both species. However, C. septempunctata reduces oviposition more rapidly after prey removal than does C. transversoguttata. When prey are again provided, C. septempunctata soon lay as many eggs as previously but C. transversoguttata lay fewer. Females, especially of C. septempunctata, that stop producing and resorb eggs in the absence of prey lay more eggs subsequently than do females that feed continually on prey provided ad libitum and lay eggs throughout the experiment. Thus, although both species are responsive to a rapid change in prey availability, C. septempunctata appears to be especially responsive. Rapid responses to changes in prey availability may contribute to the greater abundance and reproductive success of this introduced species relative to the native C. transversoguttata in western North American alfalfa fields that exhibit widely varying pea aphid densities. However, both species engage in oosorption as a means of reserving resources under poor prey conditions and enhancing future reproductive effort when prey conditions improve. [source] Dendritic cells from spondylarthritis-prone HLA,B27,transgenic rats display altered cytoskeletal dynamics, class II major histocompatibility complex expression, and viabilityARTHRITIS & RHEUMATISM, Issue 9 2009Maarten Dhaenens Objective Spondylarthritis (SpA) is characterized by spinal and peripheral joint inflammation, frequently combined with extraarticular manifestations. Despite the well-established association of SpA with the class I major histocompatibility complex (MHC) allele HLA,B27, there are still different, parallel hypotheses on the relationship between HLA,B27 and disease mechanisms. The present study was undertaken to investigate several characteristics of mature dendritic cells (DCs), which are believed to be essential for triggering disease in a model of SpA in HLA,B27,transgenic rats. Methods We combined different whole-proteome approaches (2-dimensional polyacrylamide gel electrophoresis and iTRAQ) to define the most aberrant molecular processes occurring in spleen DCs. Videomicroscopy and flow cytometry were used to confirm both cytoskeletal and class II MHC expression deficiencies. Results Our proteome studies provided evidence of up-regulation of proteins involved in class I MHC loading, and unfolded protein response, along with a striking down-regulation of several cytoskeleton-reorganizing proteins. The latter result was corroborated by findings of deficient motility, altered morphology, and decreased immunologic synapse formation. Furthermore, class II MHC surface expression was reduced in DCs from B27-transgenic rats, and this could be linked to differences in class II MHC,induced apoptotic sensitivity. Finally, we found reduced viability of the CD103+CD4, DC subpopulation, which likely exerts tolerogenic function. Conclusion Taken together, our findings have different important implications regarding the physiology of B27-transgenic rat DCs, which have a putative role in spontaneous disease in these rats. In particular, the reduced motility and viability of putatively tolerogenic CD4+ DCs could play an important role in initiating the inflammatory process, resulting in SpA. [source] NS0 cell damage by high gas velocity sparging in protein-free and cholesterol-free culturesBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2008Ying Zhu Abstract Recent developments in high cell density and high productivity fed-batch animal cell cultures have placed a high demand on oxygenation and carbon dioxide removal in bioreactors. The high oxygen demand is often met by increasing agitation and sparging rates of air/O2 in the bioreactors. However, as we demonstrate in this study, an increase of gas sparging can result in cell damage at the sparger site due to high gas entrance velocities. Previous studies have showed that gas bubble breakup at the culture surface was primarily responsible for cell damage in sparged bioreactors. Such cell damage can be reduced by use of surfactants such as Pluronic F-68 in the culture. In our results, where NS0 cells were grown in a protein-free and cholesterol-free medium containing 0.5 g/L Pluronic F-68, high gas entrance velocity at the sparger site was observed as the second mechanism for cell damage. Experiments were performed in scaled-down spinners to model the effect of hydrodynamic force resulting from high gas velocities on antibody-producing NS0 cells. Cell growth and cell death were described by first-order kinetics. Cell death rate constant increased significantly from 0.04 to 0.18 day,1 with increasing gas entrance velocity from 2.3 to 82.9 m/s at the sparger site. The critical gas entrance velocity for the NS0 cell line studied was found to be ,30 m/s; velocities greater than 30 m/s caused cell damage which resulted in reduced viability and consequently reduced antibody production. Observations from a second cholesterol-independent NS0 cell line confirmed the occurrence of cell damage due to high gas velocities. Increasing the concentration of Pluronic F-68 from 0.5 to 2 g/L had no additional protective effect on cell damage associated with high gas velocity at the sparger. The results of gas velocity analysis for cell damage have been applied in two case studies of large-scale antibody manufacturing. The first is a troubleshooting study for antibody production carried out in a 600 L bioreactor, and the second is the development of a gas sparger design for a large bioreactor scale (e.g., 10,000 L) for antibody manufacturing. Biotechnol. Bioeng. 2008;101: 751,760. © 2008 Wiley Periodicals, Inc. [source] CP27 affects viability, proliferation, attachment and gene expression in embryonic fibroblastsCELL PROLIFERATION, Issue 4 2002X. Luan CP27 is a gene that has been cloned from an E11 early embryonic library and has been suggested to mediate early organogenesis (Diekwisch et al., 1999, Gene 235, 19). We have hypothesized that CP27 exhibits its effects on organogenesis by affecting individual cell function. Based on the CP27 expression pattern we have selected the CP27 expressing embryonic fibroblast cell line BALB/c 3T3 to determine the effects of CP27 on cell function. CP27 loss of function strategies were performed by adding 5, 12.5 or 25 µg/ml anti-CP27 antibody to cultured BALB/c 3T3 cells and comparing the results to controls in which identical concentrations of rabbit serum were added to the culture medium. Other controls included an antibody against another extracellular matrix protein amelogenin (negative control) and anti-CP27 antibodies directed against other areas of the CP27 molecule (positive control). Following cell culture, cell viability, apoptosis, cell proliferation, cell shape, cellular attachment and fibronectin matrix production were assayed using MTT colourimetric assay, BrdU staining, morphometry, immunostaining and western blot analysis. Block of CP27 function using an antibody strategy resulted in the following significant changes: (i) reduced viability, (ii) increased number of apoptotic cells, (iii) reduced proliferation, (iv) alterations in cell shape, (v) loss of attachment, and (vi) reduction in fibronectin matrix production. There was also a redistribution in fibronectin matrix organization demonstrated by immunohistochemistry. We conclude that CP27 plays an important role in the maintance of normal cell function and that CP27 block leads to significant changes in cellular behaviour. [source] | |||||||||||||