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1.
DB ADAMS JJ LYNCH† BH ANDERSON LR FELL‡ GN HINCH§ RK MUNRO¶ 《Australian veterinary journal》1990,67(12):443-445
Three-year-old, non-lactating and non-pregnant Merino ewes, raised on pasture under a program of strategic treatment with anthelmintic and found to be extremely resistant to "trickle" infection with Haemonchus contortus, were given single-dose infections with either H. contortus or Trichostrongylus colubriformis or both species together. The purpose was to ascertain the intensity of protective immunity against the 2 parasites in sheep with immunity acquired from a presumably slight exposure to infection. To provide a criterion, some infected ewes were immunosuppressed with corticosteroid, dexamethasone. Untreated ewes were extremely resistant to challenge infection with either 15,000 or 150,000 H. contortus or 15,000 T. colubriformis. Surprisingly, when mixed infection was given, egg counts for H. contortus were significantly elevated compared with infection by that species alone. Antibody to antigens from infective larval and adult H. contortus was measured in serum by enzyme-linked-immunosorbent assay (ELISA) during the course of infection. Serum titres against larval antigens were significantly depressed when infections with either H. contortus or T. colubriformis were permitted by immunosuppression with dexamethasone, whereas those against adult antigen were depressed when infection with T. colubriformis was permitted. 相似文献
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Prevalence of cpb2, encoding beta2 toxin,in Clostridium perfringens field isolates: correlation of genotype with phenotype 总被引:4,自引:0,他引:4
Beta2 toxin, encoded by the cpb2 gene, has been implicated in the pathogenesis of porcine, equine and bovine enteritis by type A Clostridium perfringens. By incorporating primers to cpb2 into a multiplex genotyping PCR, we screened 3270 field isolates of C. perfringens. Of these, 37.2% were PCR positive for the cpb2 gene. The majority of isolates from cases of porcine enteritis were positive for cpb2 (>85%), and this was even more true for C. perfringens isolated from cases of porcine neonatal enteritis (91.8%). In contrast, isolates from normal pigs only contained cpb2 in 11.1% of cases. The correlation between enteritis in other animal species and the presence of cpb2 was not so strong. cpb2 was found in 21.4% of C. perfringens isolates from cattle with enteritis, and in 47.3% of isolates from calves with enteritis or abomastitis. The prevalence of cpb2 varied with genotype, with type A isolates being positive for this gene in 35.1% of cases. Furthermore, enterotoxigenic type D or type E strains almost always carried cpb2. We cloned a 6xHIS-tagged beta2 (HIS-beta2) and used this protein to raise antiserum against beta2. Culture supernatants from 68 cpb2-positive and 13 cpb2-negative strains were tested for the presence of beta2 by Western blotting. In cpb2-positive isolates of porcine origin, beta2 was almost always detected (96.9%). However, in cpb2-positive isolates from other animal species, only 50.0% expressed beta2 protein. The high rate of cpb2-positivity among strains from neonatal pigs with enteritis and the high correlation of genotype with phenotype, supports the contention that beta2 toxin plays a role in the pathogenesis of these infections. However, it may be important to consider the use of an additional method for the detection of beta2 toxin in non-porcine cpb2-positive isolates when making claims about the role of beta2 in enteritis in non-porcine species. 相似文献
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Steed PM Tansey MG Zalevsky J Zhukovsky EA Desjarlais JR Szymkowski DE Abbott C Carmichael D Chan C Cherry L Cheung P Chirino AJ Chung HH Doberstein SK Eivazi A Filikov AV Gao SX Hubert RS Hwang M Hyun L Kashi S Kim A Kim E Kung J Martinez SP Muchhal US Nguyen DH O'Brien C O'Keefe D Singer K Vafa O Vielmetter J Yoder SC Dahiyat BI 《Science (New York, N.Y.)》2003,301(5641):1895-1898
Tumor necrosis factor (TNF) is a key regulator of inflammatory responses and has been implicated in many pathological conditions. We used structure-based design to engineer variant TNF proteins that rapidly form heterotrimers with native TNF to give complexes that neither bind to nor stimulate signaling through TNF receptors. Thus, TNF is inactivated by sequestration. Dominant-negative TNFs represent a possible approach to anti-inflammatory biotherapeutics, and experiments in animal models show that the strategy can attenuate TNF-mediated pathology. Similar rational design could be used to engineer inhibitors of additional TNF superfamily cytokines as well as other multimeric ligands. 相似文献
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Changes in the volatile composition of strawberries (cv. Cigaline) at six stages of maturity, from 28 to 44 days after anthesis, were investigated over two harvesting seasons. Volatiles were isolated by direct solvent extraction and analyzed by means of GC-FID and GC-MS, with special attention to the quantification of furanones. Firmness, skin color, soluble solids (SS), titratable acidity (TA), SS/TA ratio, organic acids, and sugars were also determined. With increasing maturity, soluble solids, SS/TA ratio, Minolta a value, and levels of sucrose, glucose, fructose, and malic acid increased, whereas Minolta L value, hue angle (), titratable acidity, and levels of citric acid decreased. Furanones and esters were generally not detected before half-red fruits, whereas C(6) compounds were the main compounds in immature fruits. During maturation, levels of these so-called green components decreased drastically, whereas levels of key flavor compounds increased significantly and were closely correlated with skin color development. Maximum volatile production was observed in fully red fruits. 相似文献
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M Jost 《Schweizer Archiv für Tierheilkunde》1983,125(4):205-212