Effects of dietary molybdenum on nematode and host during Haemonchus contortus infection in lambs.

The addition of molybdenum (0.05 mmol kg-1 dry-matter) to the diet of lambs given a trickle infection of Haemonchus contortus larvae (500 third stage larvae d-1 over six weeks) reduced mean faecal egg counts (epg) from 3952 to 2312 +/- 402 by 32 days (P less than 0.02) and greatly reduced the mean number of worms recovered from the abomasum 14 days after infection ceased (907 compared with 4167: P less than 0.01). Infection reduced haemoglobin concentrations less in lambs given molybdenum although the difference was small relative to the reduction in worm burden. Lambs not given molybdenum had low intraepithelial mast cell counts in the abomasal mucosa and less abomasal hypertrophy than expected from abomasal parasitism. Molybdenum did not consistently reduce the copper status of the host or the parasite. Previous exposure to molybdenum greatly reduced protein but not proteinase activity in, or secreted by, adult worms cultured for eight hours. It is suggested that molybdenum either increased the inflammatory response which preceded worm rejection or that it indirectly enhanced that reaction by reducing the effectiveness of copper-dependent, anti-inflammatory enzymes in the gastrointestinal mucosa.     

Copper metabolism in experimental Border disease.

The proposal that hypocupraemia and hypocuprosis are characteristic manifestations of Border disease and of aetiological significance has been investigated. Mean plasma copper concentrations in 65 affected and 47 unaffected lambs were similar and in a controlled experiment, plasma and tissue copper concentrations tended to be higher in affected lambs than in controls. It is concluded that hypocupraemia and hypocuprosis are not consistent features of Border disease and thus have no aetiological significance.     

An assessment of the efficacy and safety of selenium and cobalt included in an anthelmintic for sheep

A trial was devised to assess whether the administration of selenium and cobalt together with the anthelmintic mebendazole (Ovitelmin S&C) was safe and could improve the supplies of selenium and cobalt for adult sheep fed a whole grain diet, low in both elements, which produced a steady decrease in blood glutathione peroxidase (GSHPx) and plasma vitamin B12 concentrations. Ovitelmin S&C, when given orally in a single dose as a suspension containing 0.34 mg selenium/ml, and 0.44 mg cobalt/ml (to provide 0.11 mg selenium and 0.15 mg cobalt/kg liveweight) significantly increased the GSHPx activity in blood. After a second dose given 28 days later the rate of change increased from 2.5 to 3.5 u/g haemoglobin/day. The responses in GSHPx were similar for a preparation which contained twice the concentration of selenium. Ovitelmin S&C increased the concentration of vitamin B12 in the plasma by about 1000 pg/ml for four to seven days after each dose and the increases were similar to those observed in sheep treated with an Ovitelmin preparation containing 45 times more cobalt (providing 6.7 mg cobalt/kg liveweight). After 63 days, liver vitamin B12 concentrations were 43 per cent higher in the cobalt treated than in the untreated groups (P less than 0.01) with no differences among the groups given cobalt. Neither adverse reactions nor signs of toxicity followed the administration of Ovitelmin S&C or Ovitelmin containing the higher concentrations of selenium and cobalt.     

Metagenomic analysis of coastal RNA virus communities

RNA viruses infect marine organisms from bacteria to whales, but RNA virus communities in the sea remain essentially unknown. Reverse-transcribed whole-genome shotgun sequencing was used to characterize the diversity of uncultivated marine RNA virus assemblages. A diverse assemblage of RNA viruses, including a broad group of marine picorna-like viruses, and distant relatives of viruses infecting arthropods and higher plants were found. Communities were dominated by distinct genotypes with small genome sizes, and we completely assembled the genomes of several hitherto undiscovered viruses. Our results show that the oceans are a reservoir of previously unknown RNA viruses.     

Three-dimensional deformation measured in an alaskan glacier

Measurements of movement along 28 boreholes reveal the three-dimensional flow field in a 6 million cubic meter reach of Worthington Glacier, a temperate valley glacier located in Alaska. Sliding at the bed accounted for 60 to 70 percent of the glacier's surface motion. Strain rates in the ice were low from the surface to a depth of about 120 meters, but then increased rapidly toward the bed. Ice deformation was not affected by temporal changes in the sliding rate. The three-dimensional pattern of motion indicates that plane strain, which is often assumed by models, is a poor approximation of this viscous flow.     

Problems in the diagnosis and anticipation of trace element deficiencies in grazing livestock

Three principles governing the interpretation of biochemical criteria of trace element status are identified; they concern the relationships between the concentration of the marker and the intake of the element, the time on an adequate regimen and disturbances of tissue function. From these principles, the concentrations of liver copper, liver vitamin B12 and ovine serum vitamin B12 are shown to be insensitive indices of deficiency but good indices of surfeit. Plasma copper less than 9 mumol/litre is a good index of marginally deficiency but values may have to fall below 3 mumol/litre before there is risk of dysfunction and loss of production in sheep and cattle. Serum vitamin B12 values below 188 pmol/litre are indicative of functional deficiency in sheep whereas cattle with values between 38 and 76 pmol/litre may be only marginally deficient. Concentrations of methylmalonic acid in the plasma greater than 5 mumol/litre may offer a surer guide to diagnosis of functional vitamin B12 deficiency. Blood selenium or glutathione peroxidase concentrations may be unreliable in diagnosing selenium-responsive conditions because other nutrients determine what is adequate. For all elements the surest diagnosis is an improvement in growth or health in response to a specific supplement. The adoption of preventive measures should be prompted by biochemical evidence of marginal deficiencies in animals (rather than soils or pastures) although economic responses will not necessarily follow.