Transmission of tobraviruses by trichodorid nematodes1

Transmission of tobacco rattle tobravirus by Paratrichodorus and Trichodorus has been known since 1961. However many of the studies of these virus-vector associations have been uncritical. Here we describe a system to study acquisition and transmission of individual tobravirus isolates by given species of Paratrichodorus and Trichodorus. Results from initial experiments in which this system was used suggest that different isolates of tobacco rattle tobravirus differ in vector specificity.     

The association between serotypes of tobraviruses and Trichodorus and Paratrichodorus species1

New procedures developed for studying virus transmission by Trichodorus and Paratrichodorus species permit accurate characterization of the virus and identification of the nematode species. Results obtained using this virus transmission system show that serologically distinct isolates (serotypes) of tobraviruses are transmitted by different vector species. Furthermore, one species may be associated with the same virus serotype in several countries. These results suggest that a high degree of specificity occurs between tobraviruses and their vector nematodes. These new methods also permit the application of stringent criteria which are considered necessary to establish that a Trichodorus or Paratrichodorus species is a vector of a tobravirus. Only 11 of 36 published associations between Trichodorus or Paratrichodorus and tobraviruses fulfil these criteria.     

The efficiency of herbicide incorporation into soil with different implements

The distribution of trifluralin in soil was measured following its incorporation with the rotavator, rotary power harrow, reciprocating harrow, spring-tined harrow, tandem disc cultivator and drag harrow. A single pass with the rotavator gave an even distribution In the top 5 cm of soil and similar results were obtained by cross cultivations with the rotary power harrow, reciprocating harrow, spring-tined harrow and disc cultivator. A single cultivation with the spring-tined harrow, reciprocating harrow and rotary power harrow left much of the herbicide close to the soil surface as did both a single and cross cultivation with the drag harrow. With the tandem discs, although a single pass did incorporate the herbicide, a cross cultivation was necessary to ensure that incorporation was even enough across the treated area. A single pass of the rotavator gave a uniform mixing throughout its working depth, whereas cross cultivations with each of the other implements gave a relatively uniform mixing to about half of their working depth.     

Apparent digestibilities of common feedstuffs for bluegill Lepomis macrochirus and largemouth bass Micropterus salmoides using individual test ingredients

Apparent digestibility of dry matter and energy, and availability of amino acids from blood meal (BM), fish meal (FM), meat and bone meal (MBM), poultry by-product meal (PBM), soybean meal (SBM), corn, wheat and yellow grease (YG) were determined for bluegill Lepomis macrochirus (mean weight, 57 g), and likewise, but not for BM or wheat, for largemouth bass Micropterus salmoides (mean weight, 30 g). To avoid nutrient interaction from a reference diet, diets containing 98.5% (985 g kg⁻¹) of test ingredients were used, except for semi-solid, YG which was mixed with corn to permit pelletization. Faeces were collected by a siphoning method. Apparent dry matter digestibility values ranged from 50% (corn) to 87% (BM) for bluegill and from 53% (MBM) to 76% (PBM) for largemouth bass. Apparent energy digestibility values ranged from 53% (corn) to 92% (BM) for bluegill and from 63% (MBM) to 93% (YG) for largemouth bass. Apparent digestibility of most amino acids exceeded 90% for evaluated protein sources, except for MBM which showed slightly lower values (80–90%) for both fishes. Isoleucine digestibility from BM was relatively low (82%) for bluegill. High digestibility values for SBM, PBM and BM, indicate good potential for replacing FM in diets for both fishes.     

Plasticity in vertical behaviour of migrating juvenile southern bluefin tuna (Thunnus maccoyii) in relation to oceanography of the south Indian Ocean

Electronic tagging provides unprecedented information on the habitat use and behaviour of highly migratory marine predators, but few analyses have developed quantitative links between animal behaviour and their oceanographic context. In this paper we use archival tag data from juvenile southern bluefin tuna ( Thunnus maccoyii , SBT) to (i) develop a novel approach characterising the oceanographic habitats used throughout an annual migration cycle on the basis of water column structure (i.e., temperature-at-depth data from tags), and (ii) model how the vertical behaviour of SBT altered in relation to habitat type and other factors. Using this approach, we identified eight habitat types occupied by juvenile SBT between the southern margin of the subtropical gyre and the northern edge of the Subantarctic Front in the south Indian Ocean. Although a high degree of variability was evident both within and between fish, mixed-effect models identified consistent behavioural responses to habitat, lunar phase, migration status and diel period. Our results indicate SBT do not act to maintain preferred depth or temperature ranges, but rather show highly plastic behaviours in response to changes in their environment. This plasticity is discussed in terms of the potential proximate causes (physiological, ecological) and with reference to the challenges posed for habitat-based standardisation of fishery data used in stock assessments.     

Relationship between plasma creatinine concentration and glomerular filtration rate in dogs

Glomerula filtration rate (GFR), plasma creatinine concentration (CR), and plasma urea nitrogen concentration (BUN) were measured in 129 adult dogs with reduced renal mass. A preliminary examination of the relationship between CR and GFR was conducted, and the inverse model (GFR vs. 1/CR) was chosen for further evaluation. The slope of the regression of GFR on 1/CR which was computed from actual data was not statistically different from a theoretical regression line generated from the clearance equation.
Evaluation of subsets of the population revealed no significant difference between male ( n = 69) and female (n = 60) dogs on the slope of the regression equations. Diets differing in protein concentration (16% protein, n = 35: 21% protein, n = 75: 32% protein, n = 19) did not cause a significant difference in the slope of the regression equations.
The regression equation and the confidence intervals generated in this study may be used to predict a probable range of GFR values from CR in individual dogs. Such values may be useful in adjusting drug dosages in dogs with renal disease. However, since the derived equation did not differ significantly from the theoretical inverse relationship between GFR and CR, it remains to be established whether the equation is advantageous.     

Incorporation of Fresh and Cryopreserved Bone in Osteochondral Autografts in the Horse

The structural integrity of subchondral bone in fresh and frozen osteochondral autografts was investigated at month 3 in 10 horses. Two osteochondral autografts were harvested from the lateral aspect of the lateral trochlear ridge of the left talus in each of 10 anesthetized horses. Grafts were frozen in 7.5% DMSO. After 14 days, the thawed grafts were press-fitted into drill holes in the trochlear ridges of the right stifles. A fresh graft from the right hock was implanted in each left stifle. To control for the effects of surgery, a fresh graft was transferred from the right stifle to the left stifle. The end result was two grafts in each femoropatellar joint. Fresh and frozen bone grafts maintained a structurally intact support for the cartilage surface. Graft stability and surface congruency were determining factors in the outcome of the grafts. Incorporation of both types of graft was complete at month 3, but remodeling of the fresh grafts was more active.