The neo-Darwinian theory and pesticide resistance

The development of resistance to pesticides in populations of organisms as diverse as those of bacteria, insects and mammals, provides outstanding examples of adaptation by natural selection. The integration of Mendelian genetics and the Darwinian hypothesis, known as the neo-Darwinian theory of evolution, can account for such genetic responses to changes in environment. There is one problem: that of its weak falsifiability. Selected subsets of theory can explain almost anything. An attempt is made to identify phenomena that are involved in adaptive responses of higher organisms to changes in environment. These are discussed with particular reference to the development of resistance in mammalian populations. Recent developments in genetics pertinent to this problem are outlined.     

Innate immune traits differ between Meishan and Large White pigs

A panel of innate immune traits were compared between Meishan and Large White pigs. These pigs were of similar age and kept under the same environmental conditions to reduce non-genetically derived variation in immune traits. The animals were all apparently healthy and were not experimentally challenged with any pathogen during the study. The measures only required a small blood sample. Total white cell counts were similar between the pig breeds. However, the numbers of lymphocytes, neutrophils and monocytes differed significantly, with Meishans having higher neutrophil and monocyte counts and lower lymphocyte counts. Flow cytometric methods were used to determine quantitatively the characteristics and function of neutrophils and monocytes. Meishan neutrophils were smaller and less complex than Large White neutrophils, and phagocytosis of Escherichia coli and the ensuing oxidative burst was lower in Meishan neutrophils compared to Large White neutrophils. Monocyte phagocytosis of E. coli was significantly less than that of neutrophils in both breeds but the function of Meishan monocytes as measured by phagocytosis and tumour necrosis factor alpha (TNFalpha) release did not differ from that of Large White monocytes. Levels of acute phase proteins also differed between the breeds with a significantly higher proportion of Meishans having elevated serum amyloid A levels. However, Meishans had lower alpha(1)-acid glycoprotein levels than Large Whites and haptoglobin levels were similar. Such differences in innate immune traits may have implications in the resistance to infection by a broad range of pathogens and subsequent disease effects in these breeds. Further studies are warranted to investigate the genes underlying these traits.     

Topographic placement of management practices in riparian zones to reduce water quality impacts from pastures

Riparian buffers, a best management practice (BMP), lessen environmental impacts caused by pasture-based agriculture by excluding livestock from streams and removing sediment and nutrients from overland flow before they enter the watercourse. Geospatial data analysis of digital elevation models (DEMs) can improve BMP placement by ensuring that BMPs intercept flow paths. Livestock heavy use areas and riparian buffers within 100?m of the stream were digitized using aerial photography of Spring Creek watershed (Pennsylvania, USA). Flow path lengths and stream entry points from heavy use areas, from all agricultural land uses, and from a random sample of points were calculated using 1, 10, and 30?m DEM resolutions. Euclidean distances identified the nearest stream entry point regardless of topography. Drainage areas for each streambank cell were evaluated using each DEM resolution. Topographic calculations differed significantly from Euclidean, with median differences of 14.3?m for flow path length and 24.1?m between stream entry points for the 10?m DEM. Existing buffers intercepted runoff from only 23?% of heavy use areas. Drainage areas ranged from one to hundreds of DEM cells. Any DEM is an arbitrary representation of a continuous surface; both resolution and processing method affect the suitability of such a representation for any given purpose. We found that 30?m DEMs did not provide reasonable flow path estimates at the scale of grazing agriculture in this region, while Pennsylvania 1?m DEMs were minimally smoothed during DEM preparation, resulting in erratic flow paths. The 10?m DEMs were the most suitable available DEM product, and should be used in conjunction with site visits for planning pasture BMP placement.     

Antiproliferative activity of Saponaria vaccaria constituents and related compounds

Total methanolic extracts of Saponaria vaccaria seed derived from several varieties, as well as various purified components obtained through successive chromatographic separations of total extracts were evaluated for their growth inhibitory activity in WiDr (colon), MDA-MB-231 (breast), NCI-417 (lung) and PC-3 (prostate) human cancer cells as well as the non-tumorigenic fibroblast BJ (CRL-2522) cell line using MTT colorimetric assay. Purified bisdesmosidic saponins segetoside H and I were further examined using microscopy and apoptosis assays. Bisdesmosidic saponins exhibited dose-dependent growth inhibitory and selective apoptosis-inducing activity. Growth inhibitory effects were particularly strong in a breast (MDA-MB-231) and a prostate (PC-3) cancer cell line. Total extracts exhibited a different preference being most active against a colon cancer cell line (WiDr). In a comparison of varieties, all of the total seed extracts exhibited similar dose-dependent activities, but with some variation in potency. Monodesmosidic saponins vaccarosides A and B, phenolic vaccarin, and cyclopeptide segetalin A, co-occurring seed substituents, did not exhibit activity. The non-tumorigenic fibroblast cell line BJ (CRL 2522) was growth inhibited but did not undergo apoptosis when treated with bisdesmosidic saponins at low micromolar concentrations. Saponin-rich extracts from Kochia scoparia seed and Chenopodium quinoa were also evaluated alongside Saponaria saponins but did not exhibit activity. Closely related Quillaja saponins exhibited activity but were less potent.