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81.
Structural basis of Wnt recognition by Frizzled 总被引:1,自引:0,他引:1
Wnts are lipid-modified morphogens that play critical roles in development principally through engagement of Frizzled receptors. The 3.25 angstrom structure of Xenopus Wnt8 (XWnt8) in complex with mouse Frizzled-8 (Fz8) cysteine-rich domain (CRD) reveals an unusual two-domain Wnt structure, not obviously related to known protein folds, resembling a "hand" with "thumb" and "index" fingers extended to grasp the Fz8-CRD at two distinct binding sites. One site is dominated by a palmitoleic acid lipid group projecting from serine 187 at the tip of Wnt's thumb into a deep groove in the Fz8-CRD. In the second binding site, the conserved tip of Wnt's "index finger" forms hydrophobic amino acid contacts with a depression on the opposite side of the Fz8-CRD. The conservation of amino acids in both interfaces appears to facilitate ligand-receptor cross-reactivity, which has important implications for understanding Wnt's functional pleiotropy and for developing Wnt-based drugs for cancer and regenerative medicine. 相似文献
82.
SB Grant JD Saphores DL Feldman AJ Hamilton TD Fletcher PL Cook M Stewardson BF Sanders LA Levin RF Ambrose A Deletic R Brown SC Jiang D Rosso WJ Cooper I Marusic 《Science (New York, N.Y.)》2012,337(6095):681-686
Humans create vast quantities of wastewater through inefficiencies and poor management of water systems. The wasting of water poses sustainability challenges, depletes energy reserves, and undermines human water security and ecosystem health. Here we review emerging approaches for reusing wastewater and minimizing its generation. These complementary options make the most of scarce freshwater resources, serve the varying water needs of both developed and developing countries, and confer a variety of environmental benefits. Their widespread adoption will require changing how freshwater is sourced, used, managed, and priced. 相似文献
83.
Infectivity of porcine circovirus type 2 DNA in semen from experimentally-infected boars 总被引:1,自引:0,他引:1
Madson DM Ramamoorthy S Kuster C Pal N Meng XJ Halbur PG Opriessnig T 《Veterinary research》2009,40(1):10-Feb;40(1):10
Porcine circovirus type 2 (PCV2) is an economically important pathogen. It has been demonstrated that PCV2 DNA can be detected in boar semen by PCR; however, the biological relevance of this is unknown. The objectives of this study were to determine if semen positive for PCV2 DNA is infectious (1) in a swine bioassay, or (2) when used for artificial insemination. For the first objective, 4-week-old pigs were inoculated intraperitoneally with PCV2 DNA-negative (bioassay-control; n = 3), PCV2a DNA-positive (bioassay-PCV2a; n = 3), or PCV2b DNA-positive (bioassay-PCV2b; n = 3) raw semen, or PCV2 live virus (bioassay-positive; n = 3), respectively. Pigs inoculated with PCV2 DNA-positive semen and PCV2 live virus became viremic and developed anti-PCV2 antibodies indicating that the PCV2 DNA present in semen was infectious. For the second objective, three Landrace gilts were inseminated with PCV2 DNA-negative semen (gilts-controls) from experimentally-infected boars, and six gilts were artificially inseminated with semen positive for PCV2a DNA (gilts-PCV2a; n = 3) or PCV2b DNA (gilts-PCV2b; n = 3). Serum samples collected from the gilts in all groups remained negative for anti-PCV2 antibodies for the duration of the experiment. In addition, fetal serum samples from all 105-day-gestation fetuses were negative for anti-PCV2 antibodies or PCV2 DNA. Under the conditions of this study, PCV2 DNA-positive semen was not infectious when used to artificially inseminate gilts; however, it was demonstrated to be infectious in a swine bioassay model and therefore is a potential means of PCV2 transmission amongst swine herds. 相似文献
84.
Xiao Ming Shi Xiao Gang Li Rui Jun Long Bhupinder Pal Singh Zhuo Ting Li Feng Min Li 《Biology and Fertility of Soils》2010,46(2):103-111
This study is aimed at quantifying organic carbon (C) and total nitrogen (N) dynamics associated with physically separated
soil fractions in a grassland-cultivation sequence in the Qinghai-Tibetan plateau. Concentrations of organic C and N of soil,
free and occluded particulate organic matter (OM), and aggregate- and mineral-associated OM in different land uses are increased
in the following order: 50 years cultivation < 12 years cultivation ≤ native grassland. The prolonged cropping of up to 50 years
markedly affected the concentrations of free and occluded particulate OM and mineral-associated OM. After wet-sieving, 43%
of native grassland soil mass was found in >1−10 mm water-stable aggregates that stored 40% of bulk soil organic C and N;
only 16% and 7% of soil mass containing 16% and 7% of bulk soil organic C and N was >1−10 mm water-stable aggregates of soils
cultivated for 12 years and 50 years, respectively. This indicated that losses of soil organic C and N following cultivation
of native grassland would be largely related to disruption of >1–10 mm size aggregates and exposure of intra-aggregate OM
to microbial attack. Organic C and N concentrations of soil aggregates were similar among aggregate size fractions (>0.05−10 mm)
within each land use, suggesting that soil aggregation process of these soils did not follow the hierarchy model. The increase
of the C-to-N ratio of free and occluded particulate fractions in the cultivated soils compared to the grassland soil indicated
a greater loss of N than C. 相似文献
85.
Shifts in oxic and anoxic conditions in soil are most frequently caused by water table fluctuations, heavy rain, snowmelt or flooding, with potentially significant impacts on microbial processes and the ability of soils to convert mineral nitrogen to nitrogen gases efficiently. The impact of oxic/anoxic cycles on nitrogen transformation rates was therefore explored in the upper layer (0-30 cm) of partially degraded peat soil. We hypothesized that high denitrification potential would be conserved due to the high organic matter content of this soil. Mineral nitrogen was applied to approximately 1-cm deep layers of homogenized soil in microcosms, with no external source of readily degradable carbon. Microcosms were subjected to three cycles, each consisting of an oxic phase of 8-11 days and an anoxic phase of 21-28 days. Approximately 2% of the ammonium load was lost through ammonia volatilization during oxic phases and the remainder was nitrified. The accumulated nitrate decreased soil pH from 8.0 to 6.8 before its transformation through denitrification. Nitrification and denitrification rates during the three oxic/anoxic cycles (approximately three months) were 2.9-3.2 kg N ha−1 d−1 and 1.0-2.3 kg N ha−1 d−1, respectively. Extrapolation of these values to 30-cm deep soil layers gave rates that were sufficient for complete transformation of at least 1700 kg N ha−1 of ammonium to nitrogen gases, which is ten-fold greater than the annual nitrogen application of 170 kg N ha−1 permitted by the European directive. Denitrification rates decreased linearly during the three cycles (from 36 ± 2 to 16 ± 1 μg N g−1 d−1 dry soil), projecting cessation of denitrification activity and CO2 production during the fifth cycle. Storage of peat soil at 4 °C most probably allowed slow degradation of organic matter that was completely oxidized to CO2 after the soil was exposed to higher temperature (28 °C). Storage of soil for one year did not affect nitrification rate, but reduced denitrification rate, unless soil was amended with a readily degradable carbon source. The data suggest that, despite the high carbon content of this soil, it cannot sustain transformations of high N loads to nitrogen gases for prolonged periods without amendment with readily available carbon. 相似文献
86.
Keeping in mind to reduce chilling injury and retain quality; pomegranate (Punica granatum L., cv. Mridula) fruits were treated with putrescine, carnauba wax and putrescine + carnauba wax prior to cold storage at 2 °C. Before analyzing physical, physiological and biochemical parameters fruits were subjected to post cold storage exposure at 20 °C for 3 days. Untreated fruits developed rapidly chilling injury, with main symptoms being brown discolouration of the skin, surface pitting, weight and firmness loss during storage. All these undesirable changes were significantly delayed by putrescine + carnauba wax application. Respiration and ethylene evolution rate were also brought down by combined application of putrescine and carnauba wax treatment. The superiority of combine treatment over other applications seems arises due to additive benefit of antisenescence and barrier properties of putrescine and carnauba wax, respectively. 相似文献
87.
D. R. Batish K. Lavanya H. Pal Singh R. K. Kohli 《Journal of Agronomy and Crop Science》2007,193(1):37-44
A study was conducted to determine the potential and nature of root‐mediated allelopathic interference of Chenopodium murale on wheat. Early growth of wheat reduced significantly in agar medium where C. murale seedlings were previously growing as well as in rhizosphere soil of C. murale. The reduction in wheat growth was due to the presence of inhibitory metabolites released by roots of C. murale in the growth media. Even the soil incorporation of root residues also reduced the wheat growth in terms of seedling length and seedling dry weight. Only a partial amelioration in growth inhibition occurred upon charcoal supplementation or nitrogen fertilization in these amended soils. Root residues did not reduce the available nutrients in the soil, which was rather nutrient rich. These results indicated the definite role of allelopathy of C. murale roots in retarding wheat growth. Root amended soils contained significantly higher amount of phytotoxic phenolics as the putative allelochemicals, which were ferulic acid, vanillic acid, p‐coumaric acid and benzoic acid. The study concluded that C. murale roots and their exudates exerted allelopathic effects on wheat by releasing water‐soluble phenolic acids as putative allelochemicals in soil. 相似文献
88.
Postnatal persistence of foetal haemoglobin in yaks 总被引:2,自引:0,他引:2
Sarkar M Pal RN Das DN Mondal DB Mohanty TK Pattanaik S 《Australian veterinary journal》1999,77(3):190-190
89.
The inoculation of 2000 colony-forming units of Corynebacterium pseudotuberculosis into one teat canal of each of three cows resulted in severe, chronic, pyogranulomatous mastitis. Within three days the cows had a reduced haematocrit, haemoglobin concentration and red cell count. The anaemia was initially normocytic, normochromic and non-regenerative, and was associated with a brief peak of neutrophilia; a regenerative response became evident two to three weeks later. Clinical signs of mastitis appeared seven to 14 days after the inoculation, with a peak of high fever, more severe anaemia, a second peak of neutrophilia and the complete cessation of milk production from all quarters; extensive and severe pyogranulomatous mastitis developed in the inoculated quarters. No other lesions were detected postmortem, and C pseudotuberculosis was cultured from the affected quarters but not from the supramammary lymph nodes and viscera. 相似文献
90.
Epidemiology ofVerticillium dahliae on olive trees (cvs. ‘Barnea’ and ‘Souri’) irrigated with saline water was studied over a period of 3 years. Disease incidence
in cv. Barnea increased from 18.9% to 40.5% in the first year, while disease severity decreased from 4.2 to 2.4 (on a scale
of 2–10). In the first month after pruning of diseased branches (June 1999), disease incidence was 26.9% and it increased
to 60.6% by May 2000. No changes in disease severity were observed from this time until the end of the study. In cv. Souri,
disease incidence doubled during the 3 years of the study (from 22.1% to 44.8%), and disease severity increased from 2.4 to
2.9. The disease caused significant reduction of yield in cv. Barnea in 1999 and 2000 (48.3% and 12.0%, respectively). In
cv. Souri yield was measured only in 2001, where a reduction of 66.8% was observed.V. dahliae was isolated from both diseased and symptomless trees. A significant decrease in the isolation rate ofV. dahliae from diseased cv. Barnea trees occurred between the first year (47.9%) and the third year (5.3%); positive isolations were
obtained in all seasons, without differences between seasons. In cv. Souri, the fungus was isolated in significantly higher
rates during the winter and spring (55% and 50%, respectively). Our findings strongly support the assumption that natural
recovery occurs in cv. Barnea 4–5 years after planting, but not in cv. Souri.
http://www.phytoparasitica.org posting July 10, 2003. 相似文献