Detection of Escherichia coli strains producing cytotoxic necrotizing factor type two (CNF2) by enzyme-linked immunosorbent assay

Sheep and rabbit antisera were produced against lysates of E. coli strain 711 (pVir). This K-12 strain carries the Vir plasmid which codes for Cytotoxic Necrotizing Factor type 2 (CNF2). Immunoglobulin G (IgG) fractions of both immune sera were subsequently purified by a two-step precipitation method. To increase the specificity for CNF2, the sheep IgG preparation was extensively adsorbed against both a sonicated extract of isogenic K-12 strain 711 and intact phenol-treated cells of vaccine strain 711 (pVir). An enzyme-linked immunosorbent assay (ELISA) was developed to detect clinical isolates of E. coli producing CNF2, using the final preparations of rabbit and sheep IgG in a double sandwich technique. The results obtained with this CNF2-ELISA were compared to those obtained with the conventional HeLa cell cytotoxicity assay. The testing of 133 E. coli strains (49 CNF2 positive strains and 84 negative strains) resulted in no false-negative and no false-positive. Therefore, the CNF2-ELISA offers a good alternative to the HeLa cell culture assay for the detection of CNF2-producing strains where facilities for and experience with cell cultures is lacking.     

Economic evaluation of alternative crossbreeding systems involving four breeds of swine. I. The simulation model

A static, deterministic computer model, programmed in Microsoft Basic for IBM PC and Apple Macintosh computers, was developed to calculate production efficiency (cost per kg of product) for nine alternative types of crossbreeding system involving four breeds of swine. The model simulates efficiencies for four purebred and 60 alternative two-, three- and four-breed rotation, rotaterminal, backcross and static cross systems. Crossbreeding systems were defined as including all purebred, crossbred and commercial matings necessary to maintain a total of 10,000 farrowings. Driving variables for the model are mean conception rate at first service and for an 8-wk breeding season, litter size born, preweaning survival rate, postweaning average daily gain, feed-to-gain ratio and carcass backfat. Predictions are computed using breed direct genetic and maternal effects for the four breeds, plus individual, maternal and paternal specific heterosis values, input by the user. Inputs required to calculate the number of females farrowing in each sub-system include the proportion of males and females replaced each breeding cycle in purebred and crossbred populations, the proportion of male and female offspring in seedstock herds that become breeding animals, and the number of females per boar. Inputs required to calculate the efficiency of terminal production (cost-to-product ratio) for each sub-system include breeding herd feed intake, gilt development costs, feed costs and labor and overhead costs. Crossbreeding system efficiency is calculated as the weighted average of sub-system cost-to-product ratio values, weighting by the number of females farrowing in each sub-system.     

The crossbred sire: experimental results for swine

Experiments aimed at comparing crossbred and purebred boars were reviewed. These experiments showed that crossbred boars matured sexually more quickly than corresponding purebred boars: they exhibited greater testis weight, large ejaculate volume and had better semen quality. Young crossbred boars were more aggressive sexually and achieved a higher conception rate, particularly on first service. Differences between the two types of boars for litter size and weight were generally small and variable in direction. Growth rate, feed efficiency and carcass characteristics of progeny of purebred and crossbred boars were generally similar. In addition, there was little evidence that use of crossbred sires had any effect on variability of pig performance.     

Economic evaluation of alternative crossbreeding systems involving four breeds of swine. II. System efficiency

A static, deterministic computer model was used to calculate production efficiency (cost per kg of product) for four purebred and 69 alternative crossbreeding systems involving the Duroc, Yorkshire, Landrace and Spotted breeds of swine. Crossbreeding systems were defined as including all purebred, crossbred and commercial matings necessary to maintain a total of 10,000 farrowings. Driving variables for the model were predicted mean conception rates, litter size born, preweaning survival rate, postweaning average daily gain, feed-to-gain ratio and carcass backfat. Predictions were computed using breed effect and heterosis estimates obtained from experimental data involving the four breeds collected at the Oklahoma Agricultural Experiment Station between 1976 and 1979. The most efficient breed combinations for each of the nine types of crossbreeding systems evaluated were predicted to reduce cost per kg of product by 6.7 to 10.5%, relative to the most efficient purebred (Duroc). The Duroc X (Yorkshire, Landrace, Spotted) four-breed rotaterminal was predicted to be the most efficient system, followed by the Duroc X (Yorkshire, Landrace) rotaterminal. Duroc X (Spotted X Landrace) and Duroc X (Spotted X Yorkshire) static systems ranked third and fourth overall, respectively. Sensitivity analysis indicated that ranking of systems predicted to be most efficient under the default model was reasonably robust to varying input economic, genetic and management parameter values. Results of this study suggested that three- or four-breed rotaterminal or static systems should maximize effective use of heterosis and breed complementarity in swine production systems.     

Using 3D animations to teach intracellular signal transduction mechanisms: taking the arrows out of cells

Traditional methods of teaching intracellular biological processes and pathways use figures or flowcharts with the names of molecules linked with arrows. Many veterinary students, presented with such material, simply memorize the names or chemical structures of the molecules and are then likely to forget the material once the examination is completed. To address this problem, the authors designed, created, and field-tested new teaching media that incorporate realistic three-dimensional (3D) animations depicting the dynamic changes that occur in intracellular molecules during cellular activation. Testing found that veterinary students taught using traditional teaching media (e.g., lectures, handouts, textbooks) are proficient in memorizing the names and order of intracellular molecules but unable to appreciate the interactions between these elements or their spatial relationships within cells. In contrast, more than 90% of veterinary students taught using 3D animations not only recall the facts about the intracellular elements but also develop accurate mental images of the interactions among these molecules and their spatial relationships. These findings strongly suggest that the comprehension of complex biological processes by veterinary students can be enhanced by the use of dynamic 3D depictions of these processes in the classroom.     

Pharmaceutical and nutraceutical management of canine osteoarthritis: present and future perspectives

Osteoarthritis (OA) is one of the most common chronic musculoskeletal diseases and causes of lameness in the dogs. The osteoarthritic disease process involves the entire synovial joint, encompassing the synovium, cartilage and underlying bone. Joint failure results from an abnormal mechanical strain causing damage to normal tissue or failure of pathologically impaired articular cartilage and bone under the influence of normal physiological strain or a combination of both. In both cases, the end point is cartilage loss and joint impairment. Osteoarthritic chondrocytes show an altered phenotype characterised by an excess production of catabolic factors, including metalloproteinases and reactive oxygen species. These factors constitute potential therapeutic targets and some new drugs and nutraceuticals have been proposed to promote the return to homeostasis. Until now, the therapeutic management of OA in dogs has been dominated by nonsteroidal anti-inflammatory drugs, but some new compounds, including diacerhein, with potential structure-modifying effects, are already used to treat OA in humans and could be helpful to manage OA in the dog. In addition, novel nutraceuticals, such as avocado/soybean unsaponifiable substances, have shown symptomatic effects in knee OA in humans, and could offer an alternative to prevent OA progression. This paper provides an overview of recent discoveries in the pathophysiology and in the therapeutic management of osteoarthritis in dogs.