The persistence of Brucella melitensis in experimentally infected ewes through three reproductive cycles

The authors studied the persistence of infection in 46 ewes experimentally infected with Brucella melitensis biovar 3 and monitored through three subsequent reproductive cycles. The entire experimental period lasted for 151 weeks. Infection of ewes and elimination of Brucella in milk, or its presence in vaginal discharges, persisted throughout the duration of the trial, as demonstrated by recurrent elimination of Brucella in milk and vaginal discharges. Brucella melitensis was recovered from the tissues of one ewe killed at the end of the trial. The strain was recovered from vaginal swabs and milk following parturition in the third reproductive cycle from an ewe that had aborted in the first cycle but was not pregnant in the second cycle. From a public health point of view, the periodical recovery of Brucella from the milk during the entire trial period illustrated that brucellosis in sheep remains a continuous occupational risk and a significant public health problem for consumers of fresh milk and milk products. That risk may persist for at least 3 years following the initial infection of the flock. Lamb antibody titres became negative in all lambs within 5 months after birth. This suggested that serological tests on lambs may have no practical diagnostic significance if performed during the first 5 months of life. Nevertheless, the birth of three infected lambs suggested that the phenomenon of latent carrier state may represent another way for B. melitensis to persist in a flock.     

多价伊氏锥虫灭活疫苗制备及免疫保护试验

用湖北株、广西株和江苏株伊氏锥虫经体外培养增殖，再等量混合，制备多价伊氏锥虫灭活苗。疫苗免疫接种小鼠后，再分别用强毒湖北株、广西株和江苏株伊氏锥虫攻击，结果3组小鼠均获12／12保护。免疫保护鼠于免疫后105d时，再作第二次攻虫，结果湖北、广西和江苏组分别获得1／5，3／5，4／5保护，对照组小鼠均100％发病死亡。结果表明多价伊氏锥虫灭活苗对多种虫株均产生了良好免疫保护作用，免疫期达3个月，从而为大面积推广伊氏锥虫病苗提供了有效途径。     

A Single Sample Method for Evaluating 51Chromium-Ethylene Diaminic Tetraacetic Acid Clearance in Normal and Hyperthyroid Cats

Background: Chronic kidney failure is frequently seen in middle-aged and elderly cats. ⁵¹Chromium-ethylene diaminic tetraacetic acid (⁵¹Cr-EDTA) clearance and single blood sample (SBS) method are used in several species to estimate the glomerular filtration rate (GFR).
Hypothesis: The hypothesis of this study was that ⁵¹Cr-EDTA clearance could be determined using an SBS method in normal and hyperthyroid cats.
Animals: Forty-six cats were included in this study, with an average age of 9.5 years. Of these cats, 27 had hyperthyroidism; 19 were healthy.
Methods: After IV injection of ⁵¹Cr-EDTA (average dose: 4.25 MBq), 7 blood samples were obtained between 5 and 240 minutes. Reference clearance was calculated in mL/min and mL/min/kg body weight, using a 2-compartment model. Optimal time for clearance measurement with SBS was then determined by systematically comparing each individual plasma concentration to the reference multisample clearance.
Results: The average reference plasma clearance of ⁵¹Cr-EDTA for all cats was 14.9 mL/min (3.7 mL/min/kg). The clearance in hyperthyroid cats averaged 16.4 mL/min (4.3 mL/min/kg) and in normal cats averaged 10.3 mL/min (2.4 mL/min/kg).
The optimal time for the SBS was 48 minutes after injection of tracer ⁵¹Cr-EDTA ( R ²= 0.9414), giving the following converting equation: clearance = (0.0066 × DV_{48 minutes}) – 0.9277 (in mL/min).
Conclusions and Clinical Importance: In this study, the single sample ⁵¹Cr-EDTA clearance method was used to estimate the global GFR in cats. The method identified differences in clearance between normal and hyperthyroid cats. The optimal time for an SBS was 48 minutes.     

Characterization and purification of the F17 adhesin on the surface of bovine enteropathogenic and septicemic Escherichia coli

The F17 antigen from bovine enterotoxigenic Escherichia coli strain (E coli 25KHO9), which adhered to calf intestinal villi, was isolated. An enterotoxin-negative derivative (25KHO9st) was used for further studies. Using an immunogold-labeling technique, the F17 antigen was characterized as a fimbrial protein. Pure fimbriae with a subunit molecular weight of 20,000 were obtained by homogenization and use of a sucrose gradient. The adhesion of E coli 25KHO9st was mediated by the F17 fimbriae, as both F17 antibodies and F17 protein blocked the adhesion of the strain 25KHO9st. The F17 fimbriae were serologically distinct from K88, K99, F41, and 987P fimbriae and did not agglutinate bovine, ovine, guinea pig, human, or chicken erythrocytes. Peptide fingerprint analysis revealed F17 and F(Y) adhesins to be homologous, if not identical.     

花椒抗旱性研究进展

花椒是我国重要的油料和经济作物,在干旱半干旱地区分布较广。近年来,随着全球气候变暖的加剧,水资源短缺的形势更加严峻,干旱已成为影响花椒生产的主要环境因子。本文从花椒生长形态特征、生理生化变化和抗旱分子机制3个方面阐述了花椒抗旱性的国内外研究现状,并分析了花椒抗旱性评价的方法。结果表明：花椒主要通过根、茎、叶特征的变化实现形态上的抗旱;通过保持较高的光合色素含量和调整气孔开度维持较高的光合效率、积累较多的渗透物质以增强叶片保水能力和细胞的渗透调节性能,保持较高的抗氧化酶活性减轻活性氧对细胞的伤害来提高其生理上的抗旱性;长链非编码RNA(Incrna)和ZbWRKY转录因子在花椒的抗旱过程中发挥了重要作用,其通过调控代谢途径、合成代谢物和产生植物激素应对干旱胁迫。隶属函数法、主成分分析法、聚类分析法、灰色关联度分析法可作为花椒抗旱性评价的主要方法。今后应继续加强花椒抗旱生理研究,并建立系统的抗旱性鉴定评价体系,以期为花椒抗逆性研究提供参考。     

"十五"期间重庆雾水化学特征研究

“十五”期间重庆市区雾水呈酸性,近郊区雾水呈弱酸性,远郊区基本未酸化;由市区向外,雾水的电导率逐步降低,阴离子浓度逐步降低,钙离子、铵根离子和钾离子浓度也逐步降低,但钠离子和镁离子则有所不同;重庆雾水的酸化类型以硫酸型为主,其次是盐酸型和硝酸型.雾水的碱化类型在市区和远郊区以钙—铵型为主,在近郊区以钙型为主.雾水中离子浓度比雨水高出数倍.     

不同施肥水平对双低油菜产量和含油率的影响

本试验研究了不同施肥水平对优质双低油菜青油46号产量、产油量和含油率的影响。结果表明;在一定范围内,增施磷、钾肥有利于油菜含油率的提高;而增施氮、钾肥有利于油菜产量的增加。     

半干旱地区杨树新品种选育初报

通过青杨派的种间杂交,在半干旱地区的杨树新品种选育中,初选出四龄树的金科5号优良无性系。对金科5号在耐干旱、耐盐碱、速生等方面的特性进行了试验研究,发现其表现优良,适于在兰干旱地区推广。     

Artificial neural network models of the rumen fermentation pattern in dairy cattle

The objectives of this study were: (1) to predict the rumen fermentation pattern from milk fatty acids using a machine learning technique, i.e. artificial neural networks (ANN) combined with feature selection and (2) to compare the prediction accuracy of the resulting model to that of a statistical multi-linear regression model, based on odd and branched chain milk fatty acids. Data were collected from 10 experiments with rumen fistulated dairy cows, resulting in a dataset of 138 observations. Feature selection was based on correlation and principal component analysis, and background physiological knowledge. Different ANN architectures and training algorithms were assessed. The evaluation of the model performance, based on the test dataset, showed a root mean square prediction error, expressed relative to the observed mean, of 2.65%, 7.67% and 7.61% of the observed mean for acetate, propionate and butyrate, respectively. Compared to a multi-linear regression model, the ANN revealed not to perform significantly better. However, the results confirm that milk fatty acids have great potential to predict molar proportions of individual volatile fatty acids in the rumen.