OBJECTIVE: To investigate the distribution of T-cell markers (CD4 and CD8α) in lymphoid organs of newborn, juvenile, and adult yaks. ANIMALS: 15 healthy male yaks of various ages from highland plateaus. PROCEDURES: Yaks were allocated to groups on the basis of age (newborn [1 to 7 days old; n = 5], juvenile [5 to 7 months old; 5], and adult [3 to 4 years old; 5]). The thymus, spleen, 5 mesenteric lymph nodes, and 5 hemal nodes were harvested from each yak within 10 minutes after euthanasia. Morphological characteristics of those lymphoid organs were assessed by histologic examination; expression of CD4 and CD8α mRNAs and proteins were measured by quantitative real-time PCR assay and immunohistochemical staining. RESULTS: Among the lymphoid organs evaluated, expressions of CD4 and CD8α mRNAs were highest in the thymus in all age groups. In newborn lymphoid organs, CD4 mRNA expression and CD4+ cell distribution were more predominant, whereas in juvenile and adult lymphoid organs, CD8α mRNA expression and CD8α+ cell distribution were more predominant. The CD4+ and CD8α+ cells were mainly located in the cortex and medulla of the thymus, the medulla of the hemal nodes and mesenteric lymph nodes, the periarteriolar lymphoid sheaths, and the red pulp of the spleen. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that the CD4 mRNA expression and CD4+ T-cell distribution in yak lymphoid organs decreased and CD8α mRNA expression and CD8α+ T-cell distribution increased with age. Moreover, CD8α+ cells were present in the follicles of yaks’ secondary lymphoid organs, which differs from findings for other mammals.

OBJECTIVE To determine the scan delay for use in performing cardiac CT angiography in dogs. ANIMALS 4 clinically normal adult Beagles. PROCEDURES In a crossover study, 12 formulations of iohexol solutions differing in iodine dose (300, 400, and 800 mg/kg) and concentration (undiluted and diluted 1:1, 1:2, and 1:3 with saline [0.9% NaCl] solution) were administered IV to each dog. Dynamic CT angiography was performed to evaluate enhancement characteristics of each formulation, with the region of interest set over the aorta. Time-attenuation curves (TACs) were obtained and analyzed. RESULTS Peak arc–type TACs were obtained after administration of all undiluted formulations. Curve shape changed from peak arc type to plateau type as the total volume of the contrast solution (ie, dilution) increased. Prolonged peaks characteristic of plateau-type TACs suggested that a sufficient period of homogeneous attenuation could be achieved for CT scanning with administration of higher iohexol dilutions (1:2 or 1:3) containing higher iodine doses (400 or 800 mg/kg). In particular, attenuation values for plateau-type TACs remained between 200 and 300 Hounsfield units for > 16 seconds after the plateau endpoint was reached for 1:2 and 1:3 dilutions containing an iodine dose of 800 mg/kg. Scan delays of 13 to 17 seconds were computed for those 2 formulations. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that for clinically normal dogs, a scan delay of 13 to 17 seconds could be used to perform cardiac CT angiography with iohexol solutions containing an iodine dose of 800 mg/kg at dilutions of 1:2 or 1:3.

Objective: To assess the prevalence of Mycobacterium bovis infection in cattle and wild ruminants (WRs) in a wildlife-livestock interface area (WLIA) of the Mexican highland plateau. Animals: 24,400 cattle from 793 herds (including 17,351 commercially slaughtered cattle) and 142 WRs (110 white-tailed deer [Odocoileus virginianus], 20 red deer [Cervus elaphus], and 12 North American elk [Cervus canadensis]) harvested via controlled hunting. Procedures: Cattle were serially tested for M bovis infection via caudal fold tuberculin and comparative cervical tuberculin tests during field surveillance. Carcasses of cattle and WRs were inspected for gross lesions; samples suggestive of tuberculosis were analyzed via histologic evaluation and mycobacterial culture (HMC). A PCR assay to detect Mycobacterium tuberculosis complex organisms was performed to confirm positive results of HMC. Results: WRs had inflammatory lesions in lungs and lymph nodes, although HMC results did not indicate M bovis infection. Eight cattle had positive results for both tuberculin tests, and 31 had positive results for HMC of grossly detected lesions; all were from 7 herds, and ≥ 1 cow in each herd had positive PCR assay results. These 7 herds were depopulated; adjacent herds and herds related via commerce were quarantined. Calculated true prevalence of M bovis infection was 0.86% (95% confidence interval, 0.24% to 1.49%) in cattle; M bovis was not detected in any WRs. Conclusions and Clinical Relevance: M bovis infection was present in cattle. Although transmission to WRs in this WLIA was not detected, diagnosis and prevention activities should be implemented and consolidated to prevent potential M bovis transmission between cattle and WRs.