Stores from old reservoirs: Sediment Hg and Hg methylation in Ontario hydroelectric developments

We sampled several Ontario Hydro reservoirs to deteimine the changes in mercury (Hg) and organic profiles of sediment cores with reservoir development We also examined Hg methylation among reservoirs of different age and water chemistry. In sediment cores from four Ontario reservoirs, reservoir (watershed) specific differences appeared to supersede general trends, with the differences between headpond and run-of-river reservoirs particularly important In general, the rate of Hg and organic accumulation appeared to increase with reservoir impoundment, but we were unable to discern consistent changes in concentrations of Hg or loss on ignition (LOI) with reservoir impoundment We also observed significant positive correlations of sediment Hg with concentrations of chlorophyll derivatives and bacterial photopigments. Our results are in agreement with earlier studies which indicated that an increase in Hg supply caused by erosion and release from flooded soils is central to the changes in Hg dynamics within reservoirs following impoundment Although Hg methylation activity of sediments, from a series of reservoirs on the Mississagi River was positively correlated with organic content of the sediment, the observed rates were sufficiently variable that the potential effects of reservoir age or preparation methods could not be resolved. Similarly, in our measurements of net methylmercury (MeHg) flux in two older reservoirs, the large range of variation in net MeHg flux observed among replicate samples obscured the potential effects of differences in geology and water chemistry. Future studies should focus on resolving the underlying causes of this variability and in consolidating the ‘microscale’ measurements obtained using sediment core incubation techniques and the ‘macroscale’ values obtained by whole lake mass balance techniques.     

Mechanism of the Zonal Displacements of the Pacific Warm Pool: Implications for ENSO

The western equatorial Pacific warm pool is subject to strong east-west migrations on interannual time scales in phase with the Southern Oscillation Index. The dominance of surface zonal advection in this migration is demonstrated with four different current data sets and three ocean models. The eastward advection of warm and less saline water from the western Pacific together with the westward advection of cold and more saline water from the central-eastern Pacific induces a convergence of water masses at the eastern edge of the warm pool and a well-defined salinity front. The location of this convergence is zonally displaced in association with El Nino-La Nina wind-driven surface current variations. These advective processes and water-mass convergences have significant implications for understanding and simulating coupled ocean-atmosphere interactions associated with El Nino-Southern Oscillation (ENSO).     

Demography of the Namibian cheetah, Acinonyx jubatus jubatus

Namibian cheetahs have suffered, and continue to suffer, high levels of removal due to conflict with local farmers, and it is important to understand the demography of this population in order to determine its likely persistence. Examination of cheetahs reported live-trapped or killed by local farmers, combined with subsequent information from radio-telemetry, allowed demographic parameters such as sex ratios, age and social structure, litter size, interbirth intervals and survivorship to be estimated for cheetahs on Namibian farmlands. Cub mortality was relatively low, but adult mortality was high, particularly for males, and peaked at 5-6 years of age. Neither marking nor relocating cheetahs seemed to affect survivorship, and there was no difference in survivorship between the sexes. Time spent in captivity did not appear to affect survival after release. These findings will be useful in formulating recommendations regarding the conservation and sustainable utilization of cheetah populations outside protected areas.     

Avenanthramides are bioavailable and accumulate in hepatic, cardiac, and skeletal muscle tissue following oral gavage in rats

Avenanthramides (AVA), polyphenols found exclusively in oats ( Avena sativa L.), may play a role in the anti-inflammatory and antiatherogenic activity of oats. The bioavailability of AVA has been demonstrated previously, but its distribution at the organ and tissue level and the extent of conjugation following ingestion have been unexplored. Synthetic AVA was administered to 24 rats by oral gavage, whereas 6 control rats received saline. AVA concentrations were measured via HPLC in plasma, liver, heart, and gastrocnemius (GAS) obtained over a 12 h period (0, 2, 4, 12 h; n = 6 at each time point). Samples were extracted with and without glucuronidase-sulfatase to assess the level of conjugation. We conclude that AVA are bioavailable to the blood circulation following oral ingestion in the rat and reach peripheral tissues where they can be taken up by various organs differentially. With AVA remaining in the organs for up to 12 h, it seems possible to maintain an increased level of AVA in the rat via repeated feedings.     

Immunohistochemistry Diagnosis of an Ovarian Dysgerminoma in One Bitch

An ovarian enlargement (diameter, 8 cm) was identified and surgically excised from a 5-year-old female dog. Microscopic examination of the multinodular neoplasm revealed sheets of polygonal neoplastic cells with large nuclei, frequent mitosis, necrosis and haemorrhage. Immunohistochemically, the neoplastic cells were positive for vimentin and alkaline phosphatase but were negative for CD3, CD79a, cytokeratin, alpha-fetoprotein, inhibin-α and S-100. The histopathological diagnosis of the mass was unilateral ovarian dysgerminoma.     

Effect of hCG Treatment on the Oestrous and Ovulation Responses to FSH in Prepubertal Gilts

To ensure sufficient numbers of pregnant females, particularly at hotter times of the year, hormonal induction of gilt oestrus may be necessary. However, the gilt oestrus and ovulation responses to gonadotrophin treatment have often proven unpredictable. The objective of this study was to examine possible reasons for this unpredictability. Prepubertal gilts (approximately 150 days of age, n = 63) were assigned to one of three treatments: injection of 300 IU hCG (n = 15); pre-treatment with 100 mg FSH in polyvinylpyrrolidinone administered as 2 × 50 mg injections 24 h apart, followed by 600 IU eCG at 24 h after the second FSH injection (n = 23); or FSH pre-treatment as above followed by 300 IU hCG at 24 h after the second FSH injection (n = 25). To facilitate oestrus detection, gilts were exposed to a mature boar for 15 min daily for 7 days. Blood samples were obtained on the day of eCG or hCG injection and again 10 days later and gilt ovulation responses determined based on elevated progesterone concentrations. The oestrus responses by 7 days were 6.7%, 17.5% and 64.0% for gilts treated with hCG, FSH + eCG and FSH + hCG, respectively (p < 0.001). The oestrous gilt receiving hCG alone and one oestrous FSH + hCG gilt did not ovulate, all other oestrous gilts ovulated. A further two anoestrous FSH + eCG-treated gilts ovulated. These data suggest that FSH pre-treatment facilitated the development of ovarian follicles to the point where they became responsive to hCG, but had little effect on the response to eCG.     

A cross-sectional study to show Eperythrozoon ovis infection is prevalent in Western Australian sheep farms

A serological survey and risk factor study was conducted to estimate the prevalence of Eperythrozoon ovis infection in Western Australian weaner sheep, the prevalence of farms with infected sheep, and to identify factors affecting initiation and maintenance of infection on the farm. The study was conducted on 91 farms, purposively chosen from 41 randomly selected regional shires stratified by sheep number and rainfall zones. Twenty sheep were selected systematically from a mixed-sex flock on each farm and tested for serum antibody to E ovis using an enzyme-linked immunosorbent assay. Information on putative risk factors was collected using an interview questionnaire. Antibody to E ovis was detected in 4.5% of sheep on 47% of the farms sampled. The prevalence of E ovis infection in sheep was estimated at the 95% confidence level to be between 3.6 and 5.5%, and the prevalence of farms with infected sheep was estimated to be between 37.5 and 56.5%. Most farms with serological evidence of infection occurred in the Great Southern agricultural region (79.5%), south-east of Perth through to Albany (latitude 32 to 34 degrees S, longitude 116 to 120 degrees E), and in the Northern region (12.8%) surrounding Geraldton (latitude 29 degrees S, longitude 114 degrees E). There were significantly more farms (P less than 0.05) with evidence of infection in the Great Southern region compared to the Central region between Geraldton and Perth, and on farms in the region south compared to north of latitude 32 degrees S. None of the putative risk factors examined in the questionnaire were associated with serological evidence of infection on the farm.(ABSTRACT TRUNCATED AT 250 WORDS)