The incidence of barley yellow dwarf virus isolates in perennial ryegrass (Lolium perenne) in south-western Victoria

Barley yellow dwarf virus (BYDV) was detected in perennial ryegrass cultivars examined from three sites in south-western Victoria (Balmoral, Mininera and Hamilton); the frequency of BYDV infection varied with cultivar. PAV-related isolates were prevalent at all sites, but the incidence of MAV- and RPV-related isolates varied with the site and cultivar. The PAV-related isolate was less frequent in cv. Ellett than in cv. Victorian at all sites. The implications for the epidemiology of the disease and its agronomic importance in Victoria are discussed.     

The Functional Role of Oxytocin in the Induction of Oocyte Meiotic Resumption in Cattle

The aim of the present study was to examine the role of oxytocin (OT) in the progesterone (P4) and prostaglandins (PGs) pathway to induce oocyte meiotic resumption. Cumulus–oocyte complexes were co‐cultured with follicular hemisections for 15 h to determine the effects of different doses of OT or atosiban (ATO; oxytocin receptor antagonist) on oocyte meiotic resumption. In another experiment, we examined the effect of the interaction between P4, OT and PGs on the regulatory cascade of the oocyte meiotic resumption. Oxytocin at 1 μm was effective in inducing meiotic resumption in oocytes co‐cultured with follicular cells (84.0%), not differing from the positive control group (74.4%). Atosiban inhibited in a dose‐dependent manner the positive effect of OT on the meiotic resumption (27.6% metaphase I with 10 μm of ATO, which did not differ from the 25.5% of the negative control group). Furthermore, a third experiment showed that P4 was able to induce oocyte meiotic resumption, which was inhibited by ATO. However, the OT positive effect was not blocked by mifepristone (P4 antagonist), but was inhibited by indomethacin (a non‐selective PTGS2 inhibitor). Collectively, these data suggest a sequential role of P4, OT and PGs in the induction of oocyte meiotic resumption.     

Regulation of platelet activating factor-induced equine platelet activation by intracellular kinases

Lipopolysaccharide (LPS) can activate equine platelets directly or indirectly, via leukocyte-derived platelet activating factor (PAF). Thromboxane (Tx) production by LPS-stimulated equine platelets requires p38 MAPK and this kinase has been suggested as a therapeutic target in endotoxaemia. The present study has utilised selective inhibitors to investigate the role of p38 MAPK and two other kinases, phosphatidylinositol-3 kinase (PI3K) and protein kinase C (PKC), in regulating PAF-induced Tx production, aggregation and 5-HT release in equine platelets, and the modification of these responses by LPS. LPS enhanced PAF-induced 5-HT release, an effect that was reduced by the p38 MAPK inhibitor, SB203580 (60 ± 8% reduction; n  = 6). SB203580 did not affect responses to PAF alone; whereas inhibition of PKC reduced PAF-induced 5-HT release, Tx production and aggregation (maximal inhibition by the PKCδ inhibitor, rottlerin: 69 ± 13%, 63 ± 14% and 97 ± 1%, respectively; n  = 6). Wortmannin and LY249002, which inhibit PI3K, also caused significant inhibition of PAF-induced aggregation (maximal inhibition 78 ± 3% and 88 ± 2%, respectively; n  = 6). These data suggest that inhibition of platelet p38 MAPK may be of benefit in equine endotoxaemia by counteracting some of the effects of LPS. However, detrimental effects of platelet activation mediated by PAF and not enhanced by LPS are unlikely to be markedly affected.     

动物疫苗及其合理使用（一）

疫苗接种是预防动物传染病发生的重要举措。依据免疫学理论,疫苗作为抗原,通过激发动物机体免疫系统,产生特异的体液免疫和细胞免疫,从而获得针对某种疾病的特异性免疫。疫苗一般分为细菌疫苗、病毒疫苗和类毒素疫苗等。用于防病治病的各种疫苗、菌苗又是特殊的生物药品,与普通化学药品具有完全不同的成分、功能和特性,疫苗中含有多种蛋白质（除细菌或病毒外,有的还含有保护剂、鸡胚尿囊液或细胞培养液）,它们均适合许多病原体的生长,有些制品还是活的微生物,一旦污染后果不堪设想。疫苗在保存、运输和使用时有其特别要求。如果方法不当,不但会使活性物质失活,起不到免疫防病作用;而且还可能适得其反,引发动物新的疾病,造成重大损失。     

Identification of Chlamydia gallinacea in a parrot and in free‐range chickens in Australia

Chlamydia gallinacea is a recently described bacterial species in a genus known to infect and cause disease in animals and humans. Our report describes the identification of C. gallinacea infection in free‐range laying chickens (Gallus gallus) in Australia, and the identification of C. gallinacea infection in a parrot, a wild Australian galah (Eolophus roseicapillus). There is currently little knowledge of the effects of C. gallinacea infection on avian hosts, but it has been linked to respiratory disease in humans and could potentially cause similar disease in other species. Our report highlights the need for further study and surveillance of Chlamydia species in both wild and domestic hosts in Australia.     

Qualitative and quantitative ultrasound attributes of maternal‐foetal structures in pregnant ewes

The aim of this study was to examine foetal organs and placental tissue to establish a correlation between the changes in the composition of these structures associated with their maturation and the ultrasonographic characteristics of the images. Twenty‐four pregnant ewes were included in the study. Ultrasonography assessments were performed in B‐mode, from the ninth gestational week until parturition. The lungs, liver and kidneys of foetuses and placentomes were located in transverse and longitudinal sections to evaluate the echogenicity (hypoechoic, isoechoic, hyperechoic or mixed) and echotexture (homogeneous and heterogeneous) of the tissues of interest. For quantitative evaluation of the ultrasonographic characteristics, it was performed a computerized image analysis using a commercial software (Image ProPlus^®). Mean numerical pixel values (NPVs), pixel heterogeneity (standard deviation of NPVs) and minimum and maximum pixel values were measured by selecting five circular regions of interest in each assessed tissue. All evaluated tissues presented significant variations in the NPVs, except for the liver. Pulmonary NPVmean, NPVmin and NPVmax decreased gradually through gestational weeks. The renal parameters gradually decreased with the advancement of the gestational weeks until the 17th week and later stabilized. The placentome NPVmean, NPVmin and NPVmax decreased gradually over the course of weeks. The hepatic tissue did not show echogenicity and echotexture variations and presented medium echogenicity and homogeneous echotexture throughout the experimental period. It was concluded that pixels numerical evaluation of maternal‐foetal tissues was applicable and allowed the identification of quantitative ultrasonographic characteristics showing changes in echogenicity related to gestational age.