Development and application of a competitive enzyme-linked immunosorbent assay for the detection of serum antibodies to porcine circovirus type 2.

We report the development of a competitive enzyme-linked immunosorbent assay (c-ELISA) for the detection of antibodies to porcine circovirus type 2 (PCV2), the agent associated with the recently described postweaning multisystemic wasting syndrome in pigs. At present, no method has been published describing a c-ELISA for the detection of antibodies to PCV2, and currently employed tests are impractical for use in some laboratories. The assay described here uses a cell culture isolate of porcine circovirus type 2 as antigen and a PCV2-specific monoclonal antibody as the competing reagent. Evaluation of the ELISA was performed by comparison with results obtained using an indirect immunofluorescent test on 484 sera from pig herds in the United Kingdom, Canada, France, and the USA and serial bleeds from pigs experimentally infected with porcine circoviruses. The sensitivity and specificity of the ELISA were determined as 99.58% and 97.14%, respectively, at 2 standard deviations (SD) from the mean or 95.81% and 100% at 3 SD from the mean. Using this ELISA, a serologic survey of 461 sera collected from commercial pig herds in Northern Ireland between 1973 and 1999 was undertaken. Analysis of the results of this survey demonstrated that the number of ELISA-positive sera detected in an individual year during this period ranged from 55% to 100%. This c-ELISA has applications for large-scale rapid diagnosis of PCV2 infection in pig populations worldwide and for immunoscreening of sera from other species for antibodies to PCV2.     

Flower and corm development in gladiolus as affected by photoperiod

Gladiolus plants cultivar ‘Spick and Span’ were grown in winter under natural short day (SD) or under long day (LD), with 4 hours low intensity light at midnight. Growth of the various organs was followed by periodic sampling. SD promoted flower development and advanced anthesis but reduced the final size of the flower. LD increased weight and size of leaves and flowers.Initial growth of the corm was similar under both photoperiods, but while corm growth continued throughout the growing-period under SD, it was checked under LD when flowers were developed at an enhanced rate and until anthesis. At this stage, the allocation of assimilates was directed towards the flower sink and away from the corm sink.Final corm weight was also promoted by LD. This is interpreted as an indirect effect due to increased photosynthesis of the larger LD plants. In non-flowering plants raised from cormels, SD specifically promoted corm growth, although no competing flower sink was present.It is concluded that photoperiod affects growth and development of gladiolus in two ways: directly — by affecting the partitioning of assimilates between the flower or the corm; and indirectly — by affecting the total photosynthates available to the plants by influencing foliage size and the total growth period.     

Measurement and simulation of the movement and degradation of atrazine and metribuzin in a fallow soil

The movement and persistence of atrazine and metribuzin, in a sandy loam soil following application in spring, was simulated using two models. The first model, based on the physical laws describing water and solute movement and using measured values of soil hydraulic properties, underestimated herbicide mobility in the soil and predicted too rapid drying of the deeper soil layers. The accuracy of the simulations was improved by empirically reducing the measured hydraulic conductivities by a factor of 4. This probably reflects the difficulties of obtaining reliable measurements of soil hydraulic properties. A second and simpler model, which simulated water and herbicide movement using mobile and immobile water categories, accurately predicted soil water contents. It tended to underestimate herbicide movement at short times after application, and to overestimate movement later in the experiments. A comparison of different methods of simulating herbicide degradation showed that prediction of degradation rates in the field from laboratory data can be unsatisfactory with some compounds.     

Ascites and portal hypertension in three young dogs with non-fibrosing liver disease

Three young dogs were evaluated because of the sudden development of ascites. In each case ascites was referable to non-fibrosing hepatic disease associated with portal hypertension. Obstruction to portal flow was pre-sinusoidal in two cases and post sinusoidal in the other. In all cases ascites developed in the absence of severe hypoalbuminaemia. The ratio of the protein content of ascitic fluid in relation to the protein content of plasma proved useful in differentiating between pre- and post sinusoidal portal hypertension. All three animals died or were euthanased because of the sequelae of portal hypertension.     

Reduction of deer browsing of Douglas-fir (Pseudotsuga menziesii) seedlings by quadrivalent selenium

The feasibility of using selenite ion as a systemic deer repellent for the protection of Douglas-fir (Pseudotsuga menziesii) seedlings is evaluated. When applied to the soil, the selenite ion is absorbed by the seedling roots, transported to the foliage, and thereafter volatilized. Acute phytotoxicity is observed only when selenium foliar concentrations exceed 100 ppm, while animal repellency is demonstrated at concentrations as low as 1–2 ppm. The design of a slow release device, based on a sparingly soluble salt of selenious acid, is reported, and its evaluation in a series of field trials is described. Preliminary results indicate that statistically significant reduction of browse damage can be achieved.     

Significance of Habitat and Stock Re-Testing for Enhancement of Natural Fisheries: Experimental Analyses with Queen Conch Strombus gigas

The queen conch Strombus gigas is a large, commercially important gastropod mollusc native to the Caribbean region that has become severely depleted because of overfishing and habitat destruction. Over the last 10 yr attempts have been made to rehabilitate conch stocks through releases of hatchery-reared stocks, but successes have been few. Some of the reasons for high mortality in hatchery-reared conch are elucidated by recent experiments conducted at Lee Stocking Island in the central Bahamas.
Field experiments with juvenile queen conch indicate that sites with similar depths, sediments, and macrophyte cover do not provide equivalent food and shelter for conch. Transplants of conch were successful only in sites known to be historically significant as nursery grounds. While small-scale transplants can be used to screen potential outplant sites, only comprehensive understanding of the habitat requirements, behavior, feeding ecology, and predator-prey relationships will lead to long-term enhancement of fishery stocks. Differences in morphology, behavior, and habitat utilization between wild and hatchery-reared stocks also had significant effects on the survivorship and growth of outplanted stock. Therefore, hatcheries must develop culture methods that do not reduce the natural fitness of wild stock. Successful enhancement of natural fisheries through outplanting of hatchery-reared stocks depends upon: 1) development of hatchery animals sufficiently well adapted to survive in the field; and 2) release of the stock in suitable habitats at the optimal time. Close linkage between laboratory and field research, and hatchery operators will he necessary for the ultimate success of stock enhancement efforts.     

Neutropenia with a probable hereditary basis in Border Collies

This paper documents a disease of Border Collies characterised by chronic neutropenia which probably resulted in recurrent bacterial infections manifesting as osteomyelitis and sometimes gastroenteritis. The neutropenia occurred despite hyperplasia of the myeloid cells in the bone marrow and a shift to the right in myeloid cell maturation. The underlying defect is currently unknown but may result from the inability of neutrophils to escape from the bone marrow into the peripheral circulation. Necrosis and new bone formation commonly involved the metaphyseal regions of long bones. Other findings included a fasting hypercholesterolaemia and the occasional presence of nucleated red blood cells in circulation, despite a non-regenerative anaemia. An autosomal recessive mode of inheritance is suspected. This condition has some features of a rare human disease called myelokathexis which is also believed to have in autosomal recessive mode of inheritance.