Regional scale analysis of denitrification in north temperate forest soils

Large scale analyses of biogeochemical processes are necessary for understanding anthropogenic effects on global climate and environmental quality. Regional scale estimates of denitrification from forest soils in southern lower Michigan USA were produced by stratifying the region into landscape experimental units using soil texture and natural drainage classes, and extrapolating data to larger areas using a geographic information system (GIS). Previous landscape-scale research established relationships between soil texture and drainage and denitrification and quantified annual denitrification N loss in nine soil texture/drainage groups. All forest soils within the region (64 series) were assigned to one of these nine groups based on their texture and drainage characteristics and were assigned an annual denitrification N loss value. A regional estimate of denitrification was produced by multiplying the areal extent of each of the nine soil groups by their annual denitrification N loss value. Loam-textured soils underlie 47% of the regional forest and accounted for 73% of the forest denitrification. Sandy soils were found under 44% of the regional forest but produced only 5% of the regional denitrification. Clay loam soils underlie 9% of the regional forest and produced 22% of the denitrification. Annual denitrification N loss for the region was estimated as 1.4×10⁷ kg N/yr. We used denitrification enzyme activity (DEA) as a proxy for annual denitrification N loss to determine if the relationship between denitrification and soil texture and natural drainage that we observed at the landscape scale held up at the regional scale. DEA was measured in 22 soils across the region and was strongly related to soil texture and natural drainage (r²=0.61), suggesting that extrapolation of data from the landscape to the regional scale was justified.     

Approaches to increase recovery of bacterial and fungal abortion agents in domestic ruminants

Abortions in domestic ruminants cause significant economic losses to farmers. Determining the cause of an abortion is important for control efforts, but it can be challenging. All available diagnostic methods in the bacteriology laboratory should be employed in every case due to the many limiting factors (autolysis, lack of history, range of samples) that complicate the investigation process. The purpose of this study was to determine whether the recovery of diagnostically significant isolates from domestic ruminant abortion cases could be increased through the use of a combination of the existing aerobic culture and Brucella selective method with methods that are commonly recommended in the literature reporting abortion investigations. These methods are examination of wet preparations and impression smears stained by the modified Ziehl–Neelsen method, anaerobic, microaerophilic, Leptospira, Mycoplasma and fungal culture. Samples of placenta and aborted foetuses from 135 routine clinical abortion cases of cattle (n = 88), sheep (n = 25) and goats (n = 22) were analysed by the new combination of methods. In 46 cases, bacteria were identified as aetiological agents and in one case a fungus. Isolation of Brucella species increased to 7.4% over two years compared with the previous 10 years (7.3%), as well as Campylobacter jejuni (n = 2) and Rhizopus species (n = 1). Salmonella species (5.9%) and Trueperella pyogenes (4.4%) were also isolated more often. In conclusion, the approach was effective in removing test selection bias in the bacteriology laboratory. The importance of performing an in-depth study on the products of abortion by means of an extensive, combination of conventional culture methods was emphasised by increased isolation of Brucella abortus and isolation of C. jejuni. The combination of methods that yielded the most clinically relevant isolates was aerobic, microaerophilic, Brucella and fungal cultures.     

pH对鱼类化学感觉的影响

关于硬骨鱼类的嗅、味感觉器官在解剖学和生理学方面的研究成果，许多学者都发表过综述文章(Kleerekoper1969，Bardach和Atema1971，Bardach和Villars1974，Kapoor等1975，Brown和Hara1982，Tucker1983)，最近十几年，对于鱼类化学感觉的电生理研究，主要在于一些天然物质、氨基酸及其衍生物对于嗅、味觉系统的相对刺激效果，刺激物的分子结构与刺激效果的关系，以及刺激物与感受细胞膜上的感受点相互作用的机制，而对于人为因素如捕捞、环境因素pH、污染对鱼类嗅、味觉的影响报导甚少(Hara1976，1978，Konishi等1969，Tucker1973，Silver，1978，Cancolon1980，Hidaka1970)。鱼类的嗅、味觉在鱼类生命活动如摄食、洄游、生殖、逃避敌害、群体的控制等等行为中起重要的作用，当人们利用鱼类嗅、味觉的一些生理活动规律为生产实践服务时，pH是不可忽视的一个因素，本试验以重要的生物信息分子氨基酸为刺激物，研究pH对于鱼类嗅、味觉系统对氨基酸敏感性的影响。     

猪繁殖与呼吸综合征引起的疾病风险评估

起始于2003年的开发工作已经完成了一个PRRS风险评估系统,利用该系统能够对会影响PRRS病毒被清除后的猪群是否能够保持PRRS阴性的风险因素进行评估.     

Tracer Dyes Food Green No. 4 and Food Blue No. 3 in Antibiotic and Chemotherapeutic Preparations for Intramammary Application Iv

Comparison has been made between Food Green No. 4 and Food Blue No. 3 as tracer dyes for indirect detection of the drugs in milk after intramammary application of a number of commonly used preparations containing antibiotics and chemotherapeutic agents.The tracer dyes had no effect on the stability of the preparations containing penicillin, penicillin ester, and sulphonamide (I, II, III, V and VI) ; after six months’ storage at room temperature, 75 to 100 per cent of the drugs could be recovered. The Oxytetracycline content in preparation IV recovered by 70 to 100 per cent after two months. There were great differences in the irritating effect of the various preparations, as determined by the cell counts of the milk, but the addition of tracer dye did not alter this effect. A direct relationship was demonstrated between concentrations of, on the one hand, tracer dye and, on the other hand, penicillin (preparations I, II, and III), Oxytetracycline (preparation IV) and sulphonamide (preparations V and VI) in milk from ten treated cows.In all quarter samples tracer dye could be demonstrated for just as long as the drugs, and often one or two milkings longer. Thus the experiments confirm the great certainty with which triphenylmethane dyes can reveal indirectly the presence of very small residues of antibiotics and sulphonamides in the milk after intramammary infusion.     

Validating an empiric sulfadiazine–trimethoprim dosage regimen for treatment of Escherichia coli and Staphylococcus delphini infections in mink (Neovison vison)

Antimicrobial agents are used extensively off‐label in mink, as almost no agents are registered for this animal species. Pharmacokinetic (PK) and pharmacodynamic (PD) data are required to determine antimicrobial dosages specifically targeting mink bacterial pathogens. The aims of this study were to assess, in a PKPD framework, the empirical dosage regimen for a combination of trimethoprim (TMP) and sulfadiazine (SDZ) in mink, and secondarily to produce data for future setting of clinical breakpoints. TMP and SDZ PK parameters were obtained experimentally in 22 minks following IV or oral administration of TMP/SDZ (30 mg/kg, i.e. 5 mg/kg TMP and 25 mg/kg SDZ). fAUC/MIC with a target value of 24 hr was selected as the PKPD index predictive of TMP/SDZ efficacy. Using a modeling approach, PKPD cutoffs for TMP and SDZ were determined as 0.062 and 16 mg/L, respectively. By incorporating an anticipated potentiation effect of SDZ on TMP against Escherichia coli and Staphylococcus delphini, the PKPD cutoff of TMP was revised to 0.312 mg/L, which is above the tentative epidemiological cutoffs (TECOFF) for these species. The current empirical TMP/SDZ dosage regimen (30 mg/kg, PO, once daily) therefore appears adequate for treatment of wild‐type E. coli and S. delphini infections in mink.