B7+CTLA4+ T cells engage in T-T cell interactions that mediate apoptosis: a model for lentivirus-induced T cell depletion

Apoptosis in lymph node (LN) T cells of feline immunodeficiency virus (FIV)-infected cats is associated with cells co-expressing B7.1 and B7.2 costimulatory molecules, and their ligand CTLA4. To study the possibility of B7.1/B7.2-CTLA4 mediated T-T interactions and the predicted induction of T cell apoptosis in vitro, costimulatory molecules were up-regulated on CD4+ and CD8+ T cells by mitogen stimulation. B7.1 expression on in vitro stimulated CD4+ and CD8+ cells increased within 24h; B7.2 and CTLA4 expression increased after 48-72 h. Apoptosis, as analyzed by terminal deoxynucleotidyl transferase (transferase nick end labeling, TUNEL)-based staining followed by three color flow cytometric analysis, correlated to the cells expressing B7 and/or CTLA4. Blocking experiments revealed that CD4+ and CD8+ T cell apoptosis could be significantly inhibited with anti-B7 antibodies. As FIV infection results in immune activation with a T cell phenotype similar to that of the in vitro activated T cells, the data support the hypothesis that the chronic expansion of B7+CTLA4+ LN T cells in infected cats allows for T-T cell interactions resulting in T cell depletion and eventually the development of AIDS.     

Learning from outbreaks of bovine tuberculosis near Riding Mountain National Park: applications to a foreign animal disease outbreak

Riding Mountain National Park, Manitoba, is home to a population of free-roaming elk (Cervus elaphus manitobensis) that have been found to be infected with Mycobacterium bovis, the agent of bovine tuberculosis (TB). The disease has also been found in a number of cattle herds near the Park and, as a result, Manitoba has been assigned a split status for bovine TB. A number of government agencies, with input from representatives from the wildlife and agricultural sectors, have responded by devising a program to detect, investigate, control, eradicate, and prevent TB in both wild and domestic animals. Experience from these efforts can be applied to the control of other diseases, such a foreign animal disease, elsewhere in Canada.     

Demand for red meats: principles, research evidence, and issues.

Demand is not measured by per capita consumption. Demand is a schedule of the quantities consumers will take at alternative prices. The level of demand and demand changes over time are tied to consumer incomes, prices of substitutes, and consumer tastes and preferences. Critical to increasing meat demand is a greater understanding of consumer preferences for new meat products. Developing branded products such as "natural" or "guaranteed-tender" beef may not be the answer for all cattle producers, but research suggests that there are segments of the population willing to pay premiums for such products. Differentiating meat products through technology and branding provides a means of better meeting consumers' desires and increasing overall demand for meat and livestock.     

Discrimination among Listeria monocytogenes isolates using a mixed genome DNA microarray

Listeria monocytogenes can cause serious illness in humans, usually following the ingestion of contaminated food. Epidemiologic investigation requires identification of specific isolates, usually done by a combination of serotyping and subtyping using pulsed-field gel electrophoresis (PFGE). DNA microarrays provide a new format to resolve genetic differences among isolates and, unlike PFGE, to identify specific genes associated with the infecting pathogen. A 585 probe, mixed genome microarray was constructed and 24 strains of L. monocytogenes were hybridized to the array. Microarray analysis allowed discrimination among L. monocytogenes isolates within a serotype and obtained from similar geographic and epidemiologic sources. Importantly, the microarray results preserved previously described phylogenetic relationships between major serogroups and, in a limited comparison, agreed with PFGE subtypes. The association of individual probes with isolates allowed identification of specific genes. Sequencing of 10 polymorphic probes identified nine matches with previously described bacterial genes including several suspected virulence factors. These results demonstrate that mixed genomic microarrays are useful for differentiating among closely related L. monocytogenes isolates and identifying genetic markers that can be used in epidemiologic and possibly pathogenesis studies.     

Use of scintigraphy for assessment of fracture healing and early diagnosis of osteomyelitis following fracture repair in rabbits

OBJECTIVE: To evaluate use of technetium Tc 99m disodium hydroxymethylene diphosphonate (99m-Tc-HDP) for assessing fracture healing and 99m-Tc-HDP and technetium Tc 99m ciprofloxacin (99m-Tc-CIPRO) for early diagnosis of osteomyelitis in rabbits. ANIMALS: 32 skeletally mature New Zealand White rabbits. PROCEDURE: A femoral fracture defect stabilized with bone plates and cortical screws was used. Scintigraphy was performed 4, 8, 12, and 16 weeks after surgery. The 99m-Tc-CIPRO scan was performed 48 hours after the 99m-Tc-HDP scan. The uptake ratio of the experimental limb to the normal limb was calculated by use of multiple regions of interest. Results of radiography performed to determine external callus and lysis grade and percentage defect ossification at 16 weeks were compared with scintigraphy results. RESULTS: Infected fractures had a higher uptake ratio for 99m-Tc-HDP and 99m-Tc-CIPRO than noninfected fractures. Infected fractures could be differentiated from noninfected fractures late in healing by use of 99m-Tc-HDP. Although 99m-Tc-CIPRO was better than 99m-Tc-HDP for identifying infection, there was a high incidence of false positive and negative results with 99m-Tc-CIPRO. There was an association between 99m-Tc-HDP uptake ratio and callus formation and a good correlation between 99m-Tc-HDP uptake ratio and defect ossification after 4 weeks. CONCLUSIONS AND CLINICAL RELEVANCE: 99m-Tc-HDP and 99m-Tc-CIPRO may be useful for diagnosing osteomyelitis late in fracture healing; however, false positive and false negative results occur. Technetium Tc 99m disodium hydroxymethylene diphosphonate may be useful for evaluating fracture healing.     

Clinical findings associated with prairie rattlesnake bites in dogs: 100 cases (1989-1998)

OBJECTIVE: To identify clinically relevant variables and treatments for dogs bitten by prairie rattlesnakes (Crotalus viridis viridis). DESIGN: Retrospective study. ANIMALS: 100 client-owned dogs. PROCEDURE: Records of dogs evaluated for rattlesnake envenomation from 1989 to 1998 were reviewed. Analysis was performed to test for significant associations among clinical variables or treatments and cell counts, costs, and duration of hospitalization. RESULTS: Most prairie rattlesnake bites occurred between May and September. Dogs were 3 months to 12 years old (median, 3.7 years); most were bitten on the head in the late afternoon. There was no sex predilection. Median time to evaluation was 1 hour (range, 15 minutes to 13 hours). Swelling in the area of the bite was the primary physical abnormality. Principal initial laboratory findings were echinocytosis, thrombocytopenia, leukocytosis, and prolonged activated clotting time. Ninety-four dogs were hospitalized; 48 were discharged the following day. Antimicrobials and crystalloid fluids, glucocorticoids, antihistamines, and antivenin administered i.v. were the most commonly used treatments. One dog died, and small dogs were hospitalized longer than large dogs. Antivenin administration was not significantly associated with duration of hospitalization but was associated with higher platelet counts after treatment and higher total hospital costs. CONCLUSIONS AND CLINICAL RELEVANCE: Prairie rattlesnake envenomation in dogs is associated with high morbidity rate but low mortality rate. The efficacy of administration of antivenin for dogs with bites from this snake species is questionable.     

Arthroscopic evaluation of menisci in dogs with cranial cruciate ligament injuries: 100 cases (1999-2000)

OBJECTIVE: To determine prevalence of meniscal injuries by use of arthroscopic examination in dogs with cranial cruciate ligament (CCL) injuries. DESIGN: Retrospective study. ANIMALS: 94 dogs with 100 injured CCLs. PROCEDURE: Records for 94 large dogs (> 20 kg [44 lb]) with 100 naturally occurring CCL injuries that were examined arthroscopically were reviewed. Pathologic findings in the CCL (complete or partial tears), prevalence and type of meniscal injuries, and periarticular osteophytes were recorded. RESULTS: 77% of joints had tears of the lateral meniscus; most were a series of small radial tears of the cranial horn. Fifty-eight percent of joints had tears of the medial meniscus. Positive correlation between complete tears of the CCL and medial meniscal damage was found. No significant relationships were detected between periarticular osteophyte formation and meniscal injury, medial and lateral meniscal injury, or degree of CCL tear and lateral meniscal injury. CONCLUSIONS AND CLINICAL RELEVANCE: There is a strong association between CCL injury and lateral and medial meniscal injuries in dogs. Clinical importance of lateral meniscal lesions is not known; a much higher percentage of dogs had such injuries than has been reported previously, possibly because of use of arthroscopy.     

Magnesium in the 1990's: Implications for Veterinary Critical Care

Magnesium is the second most abundant intracelular cation, exceeded only by potassium. The majority of magnesium is found in bone and muscle. This cation is required for many metabolic functions, most notably as a coenzyme for the sodium-potassium ATPase pump. Magnesium functions to maintain the electrolyte gradient across all membranes. Interference with this gradient may result in changes in the resting membrane potential and disturbances in repolarization, resulting in cardiovascular and neuromuscular abnormalities.
Hypomagnesemia may be the most underdiagnosed electrolyte disorder. Incidence rates greater than 50 percent have been reported in critically ill human patients. Currently there is little or no information available regarding the incidence and significance of hypomagnesemia in hospitalized animals. Causes of magnesium deficiency can be divided into four general categories: gastrointestinal, renal, endocrine and miscellaneous. The diagnosis of magnesium depletion can be difficult since less than one percent of total body magnesium is located in serum. Alternative methods of evaluating magnesium status include determining ultrafilterable magnesium levels, mononuclear blood cell magnesium levels or by quantifying magnesium retention of an administered loading dose.     

Incidence of brucellosis in domestic livestock in Saudi Arabia

Summary The results of an extensive serological survey for brucellosis antibodies using the standard plate agglutination procedure on 14,000 serum samples from native domestic animals and imported livestock over a five year period are reported. The incidence of brucellosis was highest (11.6%) in small ruminants reared intensively in breeding establishments, next highest (2.6%) in imported animals sacrificed during the Hajj season of 1977 and somewhat lower (1.5%) in local livestock sacrificed during the same Hajj season. The incidence was very low among the following groups of livestock: small ruminants raised on desert ranges (0.5%), small ruminants raised in small groups around individual homes (0.4%) and in commercial dairy herds (0.2%).

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Incidencia De Brucelosis En Animales Domesticos En Arabia Saudita

Resumen Se describen los resultados de un extenso estudio sobre brucelosis, utilizando la prueba de aglutinación en placa, en 14,000 muestras de suero proveniente de animales nativos e importados, estudio que duró cinco años. La prevalencia de brucelosis fue alta (11.6%) en pequeños rumiantes criados intensivamente, menor (2.6%) en animales importados sacrificados durante la estación Hajj de 1.977 y baja (1.5%) en animales locales sacrificados durante la misma estación. La prevalencia fué muy baja en los siguientes grupos de ganado: pequeños rumiantes criados en el desierto (0.5%), pequenos rumiantes criados cerca de las casas de habitación (0.4%) y en hatos lecheros comerciales (0.2%).

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Incidence De La Brucellose Chez Le Cheptel Domestique D'Arabie Saoudite

Résumé Sont présentés les résultats d'une vaste enquête sérologique sur la brucellose portant sur 14000 échantillons de sérum prélevés sur des animaux domestiques et du bétail importé pendante une période de 5 ans. La méthode standard d'agglutination sur lame a été utilisée. L'incidence de la brucellose était la plus élevée (11,6 p. 100) chez les petits ruminants des Centres d'Elevage intensif. Ensuite venaient les animaux importés (2,6 p. 100) sacrifiés pendant la période du Hajj 1977. Enfin, on a trouvé une incidence quelque peu plus faible chez le bétail local (1,5 p. 100) sacrifié la même période du Hajj. L'incidence était très faible parmi les groupes suivants de bétail: petits ruminants élevés sur des parcours désertiques (0,5 p. 100), petits ruminants élevés en petit groupe autour de maisons individuelles (0,4 p. 100) et dans les troupeaux laitiers industriels (0,2 p. 100).