Tritrichomonas foetus.

Tritrichomonas foetus is a venereal disease of cattle that has a clear pattern of adverse reproductive sequela in the affected female, with a carrier state in the bull in which he shows no outward signs. Given sexual rest and symptomatic treatment, the female returns to reproductive viability. In contrast, the male remains infective and is a risk to other female contacts. Prevention of the disease relies on excluding infected males and females from the population of susceptible cattle. Control of this disease requires a plan to identify, isolate, and treat infected females, and eliminate or cull infected males. Improvements in culture technique and the application of newer methods, such as polymerase chain reaction, enhance the likelihood of detecting infected animals.     

Cellular Composition and Viability of Cloned Bovine Embryos Using Exogene-Transfected Somatic Cells

The present study compared the efficiency of transgenic (TG) cloned embryo production by somatic cell nuclear transfer (SCNT) with fetal-derived fibroblast cells (FFCs) which were transfected with pEGFP-N1 to in vitro-fertilized (IVF), parthenogenetic and SCNT counterparts by evaluating the rates of cleavage and blastocyst formation, apoptosis rate at different developmental stages, cell number, ploidy and gene expression in blastocysts. In SCNT and TG embryos, the rates of cleavage and blastocyst formation were significantly lower (p < 0.05) than those of IVF controls, but it did not differ between SCNT and TG embryos. In IVF control, 86.7% embryos displayed diploid chromosomal complements and the rates were significantly (p < 0.05) higher than those of SCNT and TG embryos. Most TG embryos (79%) with FFCs expressed the gene by both PCR and under fluorescence microscopy. The expression of apoptosis by TUNEL was first detected at six to eight cell stages in all embryos of IVF, SCNT and TG groups, but the expression rate at each developmental stages was significantly higher (p < 0.05) in SCNT and TG embryos than in IVF counterparts. The expression rate in inner cell mass (ICM) of TG embryos was significantly higher (p < 0.05) than in SCNT and IVF embryos. These results indicate that the high occurrence of apoptosis observed in SCNT and TG embryos compared with IVF counterparts might influence the developmental competence. Moreover, the SCNT embryos derived using non-transfected donor cells exhibited a lower apoptosis expression in ICM cells than in TG embryos derived using pEGP-N1-transfected donor cells suggesting a possible role of negative gene effect in TG embryos.     

Efficacy of tulathromycin in the treatment of bovine respiratory disease associated with induced Mycoplasma bovis infections in young dairy calves

The efficacy of tulathromycin in the treatment of bovine respiratory disease (BRD) due to Mycoplasma bovis was determined following experimental infection. Two highly pathogenic strains of M. bovis (with minimum inhibitory concentration values for tulathromycin of 1 and >64 microg/ml) were inoculated into 145 calves. Four days after inoculation, calves with clinical BRD were treated subcutaneously with saline or tulathromycin (2.5 mg/kg). Compared with saline, BRD-related withdrawals, peak rectal temperatures, and lung lesion scores were significantly lower for tulathromycin-treated calves (P < .01). Tulathromycin was highly effective in the treatment of BRD due to M. bovis in calves regardless of the minimum inhibitory concentration of the challenge strain (1 or >64 microg/ml).     

The first European congress on agricultural and food ethics and follow-up workshop on ethics and food biotechnology: A US perspective

The first European Congress on Agriculturaland Food Ethics was held at Wageningen University andResearch Center (WUR), Wageningen, The Netherlands, March 4–6, 1999. This was the inaugural conference forthe newly forming European Society for Agricultural andFood Ethics – EUR-SAFE – and around two hundredpeople from across Europe (and a handful of NorthAmericans) participated. Following theCongress/conference, a small (16 people), two-dayworkshop funded in part by the US National ScienceFoundation focused on similarities and differencesbetween the US and the EU regarding publicdiscourse/debate on food biotechnology. A briefoverview of the Congress and the follow-up workshopsuggests what lessons AFHVS and ASFS might learn fromEuropean experience of agricultural and food ethics.     

Tail reconnection triggering substorm onset

Magnetospheric substorms explosively release solar wind energy previously stored in Earth's magnetotail, encompassing the entire magnetosphere and producing spectacular auroral displays. It has been unclear whether a substorm is triggered by a disruption of the electrical current flowing across the near-Earth magnetotail, at approximately 10 R(E) (R(E): Earth radius, or 6374 kilometers), or by the process of magnetic reconnection typically seen farther out in the magnetotail, at approximately 20 to 30 R(E). We report on simultaneous measurements in the magnetotail at multiple distances, at the time of substorm onset. Reconnection was observed at 20 R(E), at least 1.5 minutes before auroral intensification, at least 2 minutes before substorm expansion, and about 3 minutes before near-Earth current disruption. These results demonstrate that substorms are likely initiated by tail reconnection.     

机油乳剂防治策略对柑橘园害虫天敌群落结构与动态的影响

不同防治策略对果园害虫天敌群落的影响试验结果表明,与果农常规防治策略(主要使用化学合成农药防治害虫)试区相比,机油乳剂防治策略(主要使用机油乳剂防治害虫)试区柑橘害虫天敌群落丰富度较高,且随该防治策略的继续实施而进一步逐年提高,天敌群落均匀度指数较稳定,而天敌群落多样性指数则无明显变化。     

Effect of polychlorinated biphenyls on the physical properties of soils

Model experiments were performed for studying the effect of different concentrations (2 and 20 mg/kg) of polychlorinated biphenyls (PCBs) on the physical properties of natural materials (samples from the A horizon of loamy gray forest soil, river sand, and mantle loam). It was found that PCBs affect the aggregation of micro-and macroparticles in samples from the A horizon of gray forest soil and loam and the reflective properties of sand. It was also found that the coefficient of filtration in the substrates studied varies under the effect of PCBs. The rate of the water rising in the loam samples in the presence of PCBs decreases by 5.9 times for particles <3 mm and remains constant for particles <0.25 mm; in the samples from the A horizon of gray forest soil, the rate of the water rising increases by a factor of 1.3–1.9 for particles of all sizes. The water-retaining capacity of loam and gray forest soil from the A horizon decreases in the presence of PCBs.     

The epidemiology of the sea lice, Caligus elongatus Nordmann, in marine aquaculture of Atlantic salmon, Salmo salar L., in Scotland

Although Caligus elongatus is one of two major species of sea lice that parasitize farmed salmon, its epidemiology has not been extensively studied. In this communication, the abundances of the adult stage of C. elongatus in salmon populations from 33 farms in the West of Scotland between 1997 and 2000 have been analysed for evidence of seasonal and annual patterns. The findings indicate that the pattern of C. elongatus is remarkably consistent from year to year, and directly opposed to that reported for Lepeophtheirus salmonis, the other major caligid species. In particular, adult infestations rapidly increase from the start of July each year, and are more prevalent on salmon in the first year of production than the second year. Treatment is seen to have an effect on levels of infestation but it is not clear why this species should have significantly lower levels of abundance in the second year of production. There is also evidence that fallowing has no effect on abundance. Strategic management programmes for the control of sea lice on salmon farms, which are increasingly effective in controlling L. salmonis , may also have to give greater consideration to C. elongatus .