Deep Impact: excavating comet Tempel 1

Deep Impact collided with comet Tempel 1, excavating a crater controlled by gravity. The comet's outer layer is composed of 1- to 100-micrometer fine particles with negligible strength (<65 pascals). Local gravitational field and average nucleus density (600 kilograms per cubic meter) are estimated from ejecta fallback. Initial ejecta were hot (>1000 kelvins). A large increase in organic material occurred during and after the event, with smaller changes in carbon dioxide relative to water. On approach, the spacecraft observed frequent natural outbursts, a mean radius of 3.0 +/- 0.1 kilometers, smooth and rough terrain, scarps, and impact craters. A thermal map indicates a surface in equilibrium with sunlight.     

In vitro production of porcine zygotes using intracytoplasmic injection of vitrified sperm

The objectives of this study were to evaluate if vitrified porcine spermatozoa are able to maintain their capacity to produce zygotes in vitro using intracytoplasmic sperm injection (ICSI) and to evaluate the zygote development in two in vitro atmospheric conditions: 5% CO₂ and tri‐gas. A group of porcine oocytes maturated in vitro were injected with vitrified‐warmed sperm (treatment group) and another group, with sperm diluted and conserved at 17°C (control group). To evidence parthenogenetic activation, some oocytes were submitted to a Sham test. The injected oocytes were cultured in G1 medium at 38°C, 100% humidity and 5% CO₂ or tri‐gas. No significant differences (p > .05) were observed in embryo development between the oocytes injected with vitrified‐warmed sperm (31.8%; 36/113), and those injected with semen diluted and conserved at 17°C (35.5%; 32/90), when cultured in 5% CO₂ or under tri‐gas atmosphere (42.9%; 39/91 vs. 34.2%; 26/76, respectively). No significant differences (p > .05) were observed in the percentage of pronuclei (PN) obtained between 5% CO₂ and tri‐gas, within each treatment either. Of the 52 oocytes submitted to the Sham test, only two presented a female PN (activation) indicating that the PN observed in the treatment group were a product of fertilization and not parthenogenetic activation. To conclude, porcine sperm vitrified using spheres, at a concentration of 5 × 10⁶ spermatozoa/ml in TALP medium with 1% bovine serum albumin (BSA), conserve condensed and intact chromatin capable of producing early embryo development up to the pronuclear stage.     

科学构建国家兽医药品公共信息平台促进产业发展

文章探讨了兽医药品信息对政府、企业、消费者以及产业发展的重要意义，国家如何科学地构建行业专业的信息平台，实施兽医药品产业、政务、公共信息数字化网络化，通过信息化建设推进产业发展。     

Failure to identify non-bovine reservoirs of Mycobacterium bovis in a region with a history of infected dairy-cattle herds

The State of Texas had the most (cumulative) tuberculous cattle herds of any state in the United States during the decade ending in 1997. Of the cumulative 18 infected herds in Texas, 12 herds were concentrated in El Paso County (designated the 'El Paso milkshed'). To identify whether non-bovine reservoirs were a source of Mycobacterium bovis infection of cattle in this region, an investigation was conducted on the premises of 14 dairy herds (12 tuberculous and 2 non-affected herds) between May 1995 and June 1997. None of the 670 mammalian, avian and environmental (soil, water and air) samples collected and cultured from the premises of these herds was positive for the presence of M. bovis. None of the 119 human urine samples obtained from employees of these dairies was culture positive for M. bovis. Of 124 dairy-farm workers with tuberculin skin-test results, 48 showed positive test results. There was, however, no difference in percentages of positive skin-test results between farms without, and farms having, bovine tuberculosis within the last two years or longer. The percentage of positive reactions did not increase with length of time employed at a dairy with a history of confirmed tuberculosis. These findings suggest that non-bovine reservoirs appear not to be a factor responsible for tuberculosis of cattle in the El Paso milkshed.     

Molecular mechanisms influencing efficiency of RNA interference in insects

RNA interference (RNAi) is an endogenous, sequence‐specific gene‐silencing mechanism elicited by small RNA molecules. RNAi is a powerful reverse genetic tool, and is currently being utilized for managing insects and viruses. Widespread implementation of RNAi‐based pest management strategies is currently hindered by inefficient and highly variable results when different insect species, strains, developmental stages, tissues, and genes are targeted. Mechanistic studies have shown that double‐stranded ribonucleases (dsRNases), endosomal entrapment, deficient function of the core machinery, and inadequate immune stimulation contribute to limited RNAi efficiency. However, a comprehensive understanding of the molecular mechanisms limiting RNAi efficiency remains elusive. Recent advances in dsRNA stability in physiological tissues, dsRNA internalization into cells, the composition and function of the core RNAi machinery, as well as small‐interfering RNA/double‐stranded RNA amplification and spreading mechanisms are reviewed to establish a global understanding of the obstacles impeding wider understanding of RNAi mechanisms in insects. © 2018 Society of Chemical Industry     

Absorption by sheep of dieldrin from contaminated soil

Objective To study the accumulation of dieldrin residues in sheep from ingestion of contaminated soils was studied in two experiments.
Design A controlled feeding study of sheep fed contaminated soils of different type at varying intervals.
Animals and procedure Thirty-four 2-years-old wethers were divided into four groups (one control sheep only) and fed water-soluble dieldrin or soil contaminated with aldrin and dieldrin at varying intervals in the first study. In a second study 34 similar sheep were divided into four treatments with one being a control. Sheep were fed sandy, high clay or high organic matter soils with similar dieldrin and aldrin concentrations.
Results In the first study the concentration of dieldrin in the body fat of sheep dosed with dieldrin-contaminated soil was about half that in the body fat of sheep dosed with an equivalent amount of water-soluble dieldrin. The concentration of dieldrin was almost the same in sheep fed 500 μg of total dieldrin per day as it was in sheep fed 5000 μg every tenth day, over a 50-day period. In the second experiment sheep accumu-lated nearly three times as much pesticide from a soil with a high organic matter content, and about four times as much from a soil with a high clay content, as from a sandy soil with the same dieldrin content, over a 100-day period. The half-life of dieldrin in the fat of all sheep varied between 96 and 116 days after sheep ceased ingesting contaminated soil.
Conclusions Dieldrin concentrations in the fat of sheep that consume dieldrin contaminated soil fall within 10 days of removal from the source of contamination. However, dieidrin accumulates in the wool of sheep that consume dieldrin-contaminated soil.