猪气喘病实验猪模型的建立

目的 研究建立猪气喘病人工发病模型。方法 将分离得到的一株猪肺炎支原体(Mycoplasma hyopneumoniae,Mhp)Js株进行各种试验鉴定,证实其为Mhp强毒株。每头猪肺内接种Js株培养物2ml,15～25d后观察临床症状和病理变化,采集病变组织,经冻干制成攻毒用组织毒。安检合格,批号为20000324。给15头小梅山二元杂交猪分别气管内注射以KM₂培养基作10^-2、10^-3、10^-4和10^-5稀释的强毒,每头猪5ml,对照组注射培养基。攻毒后25d观察试验猪临诊症状,X线透视,记录病理变化。结果 10^-2、10^-3、10^-4稀释的强毒试验组猪均出现了典型的猪气喘病临床症状和病理变化。结论 人工发病试验测得Mhp Js株组织强毒接种气管内注射最小发病剂量为10^-4稀释5ml,正式试验人工发病可用100个最小发病剂量即强毒冻干物1:100稀释气管内注射5ml,可确保攻毒成功。     

Production of swine pepsinogen by protein-producing Bacillus brevis carrying swine pepsinogen cDNA

Summary An expression-secretion vector, pNU100, was constructed, utilizing the promoter and coding sequences for the signal peptide and nine amino-terminal amino acids of the middle wall protein, to produce foreign proteins by protein-producing Bacillus brevis. Expression of swine pepsinogen cDNA in B. brevis was examined with pNU100 as a vector. The recombinant swine pepsinogen synthesized by B. brevis was found to accumulate extracellularly in the form of a soluble protein and to have acid protease activity. The acid protease activity was completely inhibited by pepstatin. Furthermore, the recombinant pepsinogen was converted autocatalytically to pepsin under acidic conditions. This indicates that B. brevis produces a pepsinogen with the same conformation as authentic pepsinogen. Efficient production of the enzyme (11 mg/l) was achieved by regulating the pH of the medium. The enzyme produced by B. brevis remained stable on cultivation for a long period, up to 40 h. This is suggested to be due to a unique property of protein-producing B. brevis, i. e. a deficiency in extracellular protease production.     

Embryo recovery in swine

Embryos were surgically recovered 63 times from 13 purebred donor sows for an average of 4.8 times per donor. Recoveries were completed at three or six week intervals. An average of 15.6 transferable embryos were collected per surgery. Based on these limited observations it would appear that multiple surgical embryo recoveries may be completed on a specific donor at three and/or six week intervals without impairing future production.     

Plasminogen polymorphism in swine

1. Plasminogen polymorphism in swine (Sus scrofa) plasma was demonstrated by immunoblotting. 2. Eleven plasminogen phenotypic patterns, including a null pattern, were detected. 3. The null pattern was associated with extremely low plasma triglyceride and increased unesterified cholesterol levels. 4. Changes in plasminogen polymorphic patterns from the fetal to neonate status were observed after nursing commenced.     

Brucellosis in feral swine

Some 255 feral hogs were serologically tested for Brucella titers at a location in the lower coastal plain of South Carolina. Eighteen percent were reactors. The organism was cultured from lymph node tissues in one 3+ years old boar and identified as Brucella suis biotype 1. Prevalence of sero-positive animals increased with age. There were no important differences between sexes.     

Nitrification of swine waste

Complete oxidation of ammonia nitrogen (approximately 1000 mg/L) to nitrite was observed in stabilized swine waste after 49 days in incubation at 400 rpm and 29 degrees C, only if 10% (v/v) activated sludge from a wastewater treatment unit and 1.5% (w/v) CaCO3, were added. Stabilized swine waste contains less than 0.09 most probable number (MPN) per millilitre of nitrosobacteria and 2.3 MPN/mL of nitrobacteria. In activated sludge, the concentrations of these bacteria were 2.4 MPN/mL for nitrosobacteria and 4.2 x 10(5) MPN/mL for nitrobacteria. In the swine waste where ammonia was oxidized to nitrite, the nitrosobacteria growth increased to 5.5 x 10(5) MPN/mL, while the nitrobacteria growth decreased to 2.3 MPN/mL. Inoculation of a freshly stabilized swine waste with 10% (v/v) of the active nitrifying waste and addition of 1.5% (w/v) CaCO3, accelerated the oxidation of ammonia nitrogen to nitrite; the reaction was completed after only 5 days of incubation. Increasing the incubation period to 10 days resulted in the complete oxidation of the accumulated nitrite to nitrate. In the stabilized swine waste, complete nitrification without accumulation of nitrite was obtained in only 5 days of incubation when the waste was inoculated with both enriched nitrifying populations (10(6)-10(7) MPN/mL).