Toxicokinetic profile of swainsonine following exposure to locoweed (Oxytropis sericea) in naïve and previously exposed sheep

AIM: To determine the toxicokinetic profiles of swainsonine (SW) in sheep previously (subacute) and not previously (acute) exposed to locoweed. METHODS: Twenty-nine wethers were stratified by bodyweight (BW; 68.0 (SE 7.6) kg) and randomly assigned to one of six treatments. Treatments were: 0 (n=5), 0.4 (n=5), and 1.6 (n=5) mg SW/kg BW for Trial 1, and 0 (n=4), 0.2 (n=5), and 0.8 (n=5) mg SW/kg BW for Trial 2. Acute exposure in both trials included adaptation to blue grama (Bouteloua gracilis) hay for 14 days and no previous exposure to locoweed (i.e. SW), followed by administration of a single oral dose of SW prepared from an extract of locoweed, in the doses described above. Subacute exposure comprised ingestion of a blue grama and locoweed (428 microg SW/g locoweed) diet for 21 days in Trial 1 and 28 days in Trial 2, followed by removal from locoweed for 5 days, then an oral dose of SW, as above. Quantities of locoweed fed in the diet were adjusted to achieve the dose rates specified for each treatment. Blood samples were collected via jugular venepuncture twice daily for 3 days prior to initial exposure to SW and then every 7 days for the duration of the trials, to monitor serum alkaline phosphatase (Alk-P) and aspartate aminotransferase (AST) activities. For intensive sampling periods, SW was administered immediately following blood sampling at 0 h, and blood samples were collected at hourly intervals from 0-12 h, 3-h intervals from 15-24 h, 6-h intervals from 30-48 h, and 12-h intervals from 60-168 h. Concentrations of SW in serum and locoweed extract were determined using the alpha-mannosidase inhibition assay (detection limit=25 ng/ml). Rates of absorption and elimination of SW from serum were calculated for each animal, using exponential curve fits of the concentration of SW in serum concentration vs time plots. RESULTS: In both trials, SW was detected in serum in all animals exposed to locoweed. Elevated (p<0.05) serum Alk-P and AST activities indicated that subclinical SW intoxication was induced during the subacute exposure phase. Calculated rates of elimination were faster (p<0.001) for the 1.6 vs 0.4 (Trial 1) and 0.8 vs 0.2 (Trial 2) mg SW/kg BW doses. Rates of elimination indicated that, in both trials, SW was removed from serum faster (p<0.06) following acute exposure than subacute exposure. Higher exposure rates to SW resulted in higher concentrations of SW in serum within a trial. CONCLUSIONS: Multiple compartments were involved in the kinetics of SW, and dose and previous exposure altered the toxicokinetics of SW. CLININCAL RELEVANCE: Should the true elimination half-life prove to be as high or higher than the 95 h demonstrated for the treatment using 0.4 mg SW/kg BW in Trial 1, then withdrawal periods for clearing SW from sheep should be >40 days (assuming 10 half-lives to clear the compound).     

Isolation and characterization of porcine circovirus type 2 from pigs showing signs of post‐weaning multisystemic wasting syndrome in the Netherlands

Summary

Pigs with wasting syndrome were examined for macroscopic and histopathological lesions, and for porcine circovirus (PCV). Histopathological lesions were comparable to those previously documented for post‐weaning multisystemic wasting syndrome (PMWS). In addition, in seven out of ten examined PMWS‐affected pigs focal‐to‐slight mononuclear meningitis and focal cerebral mononuclear infiltrates (4 out of 10) were observed. A virus was isolated from organs and sera from pigs showing wasting syndrome. An immunoperoxidase monolayer assay and an indirect immunofluorescence assay were performed on the infected PK‐15 and Dulac cell cultures, respectively, and both assays indicated the presence of PCV type 2 (PCV2). The nested‐polymerase chain reaction (nPCR) technique, based on the use of PCV2 specific oligonucleotides, revealed specific amplified products of 481 bp. Nucleotide sequence analysis of the entire genome of the Dutch PCV isolate 24657 NL showed a homology with known nucleotide sequences of porcine PCV type 1 (PCV1) and PCV2 isolates of 77.1% and >96%, respectively. This is the first report of the isolation and characterization of PCV2 in PMWS‐affected pigs in the Netherlands.     

Transfer of β-hydroxy-β-methylbutyrate from sows to their offspring and its impact on muscle fiber type transformation and performance in pigs

Background: Previous studies suggested that supplementation of lactating sows with β-hydroxy-β-methylbutyrate(HMB) could improve the performance of weaning pigs, but there were little information in the muscle fiber type transformation of the offspring and the subsequent performance in pigs from weaning through finishing in response to maternal HMB consumption. The purpose of this study was to determine the effect of supplementing lactating sows with HMB on skeletal muscle fiber type transformation and growth of the offspring during d 28 and180 after birth. A total of 20 sows according to their body weight were divided into the control(CON, n = 10) or HMB groups(HMB, n = 10). Sows in the HMB group were supplemented with β-hydroxy-β-methylbutyrate calcium(HMB-Ca) 2 g/kg feed during d 1 to 27 of lactation. After weaning, 48 mixed sex piglets were blocked by sow treatment and fed standard diets for post-weaning, growing, finishing periods. Growth performance was recorded during d 28 to 180 after birth. Pigs were slaughtered on d 28(n = 6/treatment) and 180(n = 6/treatment) postnatal and the longissimus dorsi(LD) was collected, respectively.Results: The HMB-fed sows during lactation showed increased HMB concentration(P 0.05) in milk and LD of weaning piglets(P 0.05). In addition, offsprings in HMB group had a higher finishing BW and lean percentage than did pigs in CON group(P 0.05), meanwhile, compared with pigs from sows fed the CON diet, pigs from sows fed HMB diet showed higher type Ⅱ muscle fiber cross-sectional area(CSA), elevated myosin heavy chain(MyHC) Ⅱb and Sox6 mRNA, and fast-MyHC protein levels in LD(P 0.05).Conclusions: HMB supplemented to sow diets throughout lactation increases the levels of HMB in maternal milk and skeletal muscle of pigs during d 28 after birth and promotes subsequent performance of pigs between d 28 and 180 of age by enhancing glycolytic muscle fiber transformation.     

A preliminary study to understand the effect of Fasciola hepatica tegument on naïve macrophages and humoral responses in an ovine model

Fasciola hepatica, the liver fluke, is a highly evolved endo-parasite that uses various mechanisms to evade the host immune system. The immunosuppressive capabilities of the parasite's excretory/secretory products have been well demonstrated by previous independent studies. However, the role of the parasite's tegument in the immune responses remains to be investigated. In this study, the effect of the tegument and other fractions of adult F. hepatica (excretory/secretory, liver fluke homogenate and liver fluke homogenate without tegument) in the activation of naïve macrophages in vitro was investigated using an ovine model. In addition, an immunoproteomic approach was used to investigate the characteristics of humoral antibody responses developed in sheep against the tegument fraction. The results indicated significantly increased arginase expression in macrophages incubated with the tegument and excretory/secretory fractions. Two dimensional gel electrophoresis of the tegument demonstrated approximately 100 protein spots, with only four of these spots were highly reactive with the positive serum as determined by 2-DE immunoblotting. These results give a preliminary indication that the liver fluke tegument may play role in avoiding hosts’ protective immune responses against itself.