Pasteurella haemolytica A1 and Bovine Respiratory Disease: Pathogenesis

The severe fibrinonecrotic pneumonia associated with pneumonic pasteurellosis usually results from colonization of the lower respiratory tract by Pasteurella haemolytica biotype A, serotype 1(A1). Despite recent research efforts, the authors lack a detailed understanding of the interactions and host response to P. haemolytica in the respiratory tract. The authors hypothesize that management and environmental stress factors or viral infection alters the upper respiratory tract (URT) epithelium allowing P. haemolytica to colonize the epithelium. Once the URT is colonized, large numbers of organisms enter the lung where they interact with alveolar macrophages. Endotoxin, released from the bacteria, crosses the alveolar wall where it activates pulmonary intravascular macrophages, endothelium, neutrophils, lymphocytes, platelets, complement, and Hageman factor leading to complex interactions of cells and mediators. It is the progression of this inflammatory response with neutrophil influx that is ultimately responsible for the pulmonary injury. Leukotoxin is a major virulence factor of P. haemolytica that allows it to survive by destroying phagocytic cells. At subcytolytic concentrations it may also enhance the inflammatory response by activating cells to produce mediators and release reactive oxygen metabolites and proteases.     

Genetics of Body Color in Tilapia mossambica

Gold, bronze, and black (normal pigmentation) body colors in Tilapia mossambica are controlled by a single autosomal gene with incomplete dominant gene action: GG fish are black gg fish are gold; Gg fish are bronze. Because gold body color is produced by the recessive genotype, it is easy to produce and to maintain a truebreeding population of gold T. mossambica for commercial purposes. If all other colors are culled, the population will breed true, because gold × gold will always produce 100% gold offspring. The G gene will be a valuable genetic marker for many genetic studies, such as the production of gynogenetic T. mossambica .     

Mycorrhizal colonization and lead distribution in root tissues of Norway spruce seedlings

Non-inoculated spruce seedlings (Picea abies Karst.) and spruce seedlings colonized with Lactarius rufus Fr., Pisolithus tinctorius Coker & Couch or Paxillus involutus Fr. were grown for 35 or 37 weeks in a microcosm system on two types of natural forest humus differing in Pb content. Using X-ray microanalysis, the distribution and content of Pb in the tissues of mycorrhizal and non-mycorrhizal root tips were compared. No significant difference in the Pb contents of root cortex cell walls of non-mycorrhizal and seedlings colonized by Lactarius rufus, Pisolithus tinctorius, or indigenous mycorrhizal fungi (mainly Tylospora sp.) was found. However, in root tips of seedlings colonized by Paxillus involutus, due to a higher binding capacity for cations, the Pb content in cell walls of the root cortex were higher than in non-mycorrhizal roots. Pb contents in cell walls of the cortex of mycorrhizal and non-mycorrhizal roots were 3 times higher in plants growing in humus with a high Pb content than in plants growing in humus with a low Pb content. It is concluded that increasing contents of Pb in the organic matter may lead to an increased loading of the apoplast with Pb. The mycobionts tested in this investigation did not exclude Pb from root tissues.     

Effects of tilling no-till soil on losses of atrazine and glyphosate to runoff water under variable intensity simulated rainfall

Herbicides released through agricultural activities to surface waters and drinking water systems represent a risk to human and environmental health, as well as a cost to municipalities for removal. This study focuses on the viability of glyphosate tolerant cropping systems as an alternative to atrazine-based systems, and the impact of tilling historically no-till ground on the runoff pollution potential of these systems. Variable intensity field rainfall simulations were performed on 2 m long × 1 m wide plots within a field in first-year disk and harrow following no-till (CT), and within a long-term no-tilled (NT) field, both treated with atrazine and glyphosate according to label. Rainfall sequence was: 50 mm h⁻¹ for 50 min followed by 75 mm h⁻¹ for 15 min, 25 mm h⁻¹ for 15 min, and 100 mm h⁻¹ for 15 min. Runoff was collected at regular time intervals during two simulated rainfall events and analyzed for herbicide concentration, sediment content, and volume. Maximum glyphosate concentration in runoff was 233 μg L⁻¹ for NT and 180 μg L⁻¹ for CT (approximately 33% and 26% of the maximum contaminant limit (MCL) for glyphosate (700 μg L⁻¹), respectively, while maximum atrazine concentrations in runoff was 303 μg L⁻¹ for NT and 79 μg L⁻¹ for CT (approximately 100 times and 26 times the atrazine MCL (3 μg L⁻¹)). Atrazine concentration and loading were significantly higher in runoff from NT plots than from CT plots, whereas glyphosate concentration and loading were impacted by tillage treatment to a much lesser degree. Results suggest that glyphosate-based weed management may represent a lower drinking water risk than atrazine-based weed management, especially in NT systems.     

Increases in phosphatase and β‐glucosidase activities in wheat seedlings in response to phosphorus‐deficient growth

The ability of plants to utilize P efficiently is important for crops growing in P‐deficient soils or on soils with a high P‐fixing capacity. The purpose of this work was to investigate early physiological changes which occur when wheat (Triticum aestivum L.) seedlings were grown under P‐deficient conditions. Wheat plants were grown in a greenhouse and watered with nutrient solution containing or lacking P. During the interval 12 to 18 days after planting, the dry weight of wheat seedlings was similar regardless of P treatment, although the P‐deficient plants had a greater proportion of the total plant weight in the roots. Sixteen days after planting, the roots and leaves of P‐deficient plants had only 20 to 30% the P content of P‐sufficient plants. After 16 days, plants grown under P stress had 41% more p‐nitrophenol phosphatase activity and 70% more β‐glucosidase activity in shoot homogenates than was found in P‐sufficient plants. Changes in both enzyme activities may be involved in the mobilization of plant resources during the early stages of P‐deficient growth.     

Application of Electrochemical Degradation of Wastewater Composed of Mixtures of Phenol–Formaldehyde

The industrial wastewater from resin production plants contains as major components phenol and formaldehyde, which are traditionally treated by biological methods. As a possible alternative method, electrochemical treatment was tested using solutions containing a mixture of phenol and formaldehyde simulating an industrial effluent. The anode used was a dimensionally stable anode (DSA?) of nominal composition Ti/Ru_0.3Ti_0.7O₂, and the solution composition during the degradation process was analyzed by liquid chromatography and the removal of total organic carbon. From cyclic voltammetry, it is observed that for formaldehyde, a small offset of the beginning of the oxygen evolution reaction occurs, but for phenol, the reaction is inhibited and the current density decreases. From the electrochemical degradations, it was determined that 40?mA?cm^?2 is the most efficient current density and the comparison of different supporting electrolytes (Na₂SO₄, NaNO₃, and NaCl) indicated a higher removal of total organic carbon in NaCl medium.     

Intestinal stem cell replacement follows a pattern of neutral drift

With the capacity for rapid self-renewal and regeneration, the intestinal epithelium is stereotypical of stem cell-supported tissues. Yet the pattern of stem cell turnover remains in question. Applying analytical methods from population dynamics and statistical physics to an inducible genetic labeling system, we showed that clone size distributions conform to a distinctive scaling behavior at short times. This result demonstrates that intestinal stem cells form an equipotent population in which the loss of a stem cell is compensated by the multiplication of a neighbor, leading to neutral drift dynamics in which clones expand and contract at random until they either take over the crypt or they are lost. Combined with long-term clonal fate data, we show that the rate of stem cell replacement is comparable to the cell division rate, implying that neutral drift and symmetrical cell divisions are central to stem cell homeostasis.     

应用绵羊粪便的近红外光谱方程评定其日粮的可消化有机物

利用近红外光谱法 (NIRS)对绵羊粪便的扫描值和日粮的体内测定值来建立定标方程式。以绵羊为试验动物 ,日粮主要由各种牧草、作物秸秆和棉花籽壳组成 ,试验动物日粮设计了 78个蛋白水平。在 2 0 0 2年和 2 0 0 3年分别用 15只和 2 0只成熟母羊 (体重为 5 5± 2 .4kg)进行了为期 7周的实验。体内收粪法测定出的日粮可消化有机物(DOM)水平为 5 2 .4 %至 75 .8% ,日粮的可消化有机物的定标方程式决定系数r2 =0 .80 ,定标标准误差SEC =1.5 1。随机选取 2 0 0 3年试验第 3周第 7d的 10个粪便样品利用可消化有机物定标方程预测其日粮的可消化有机物 ,其结果是决定系数r2 =0 .94 5 ,预测标准误差SEP =0 .5 5 2 ,斜率Slope =1.0 83,表明利用近红外光谱法 (NIRS)对粪便的扫描值可以有效预测绵羊日粮的可消化有机物