Impacts of previous heatstroke history on physiological parameters eHSP72 and biomarkers of oxidative stress in military working dogs.

Heatstroke (HS) is an acute, progressive life-threatening emergency. Animals, including military working dogs (IDFMWD), rapidly activate cytoprotective processes, e.g., heat shock proteins (HSPs) and antioxidative molecules, in response to heat stress. We hypothesized that serum HSPs (eHSP72) and oxidative stress markers would differ in IDFMWD with a history of HS compared with controls and thus could be used to detect susceptibility to recurrent HS. eHSPs concentration, oxidative stress markers, and systemic physiological parameters were studied in dogs with and without histories of HS, undergoing indoor or outdoor training. Treadmill physical performance tests (PPTs) were conducted indoors at 22 °C (groups C-I and HS-I) or outdoors under heat stress conditions of 36 °C; 60% humidity (groups C-O and HS-O). Pre-, immediately post-, and 45 min post-PPT heart rate (HR), respiratory rate, and rectal temperature (Tre) were recorded in all dogs. Likewise, blood samples were collected and eHSP72, venous blood gas analysis, and lactate and creatine kinase activity (CK) were assayed. Serum uric acid (sUA) and total serum redox potential (TRP) were measured only in the indoor group. Immediately post-PPT under both environmental conditions, Tre, HR, eHSP, sUA, and TRP (only measured in indoor PPT) significantly (P < 0.05) increased, whereas venous blood pH and bicarbonate decreased significantly (P < 0.05). Between groups comparisons demonstrated significant differences in basal HR and post-PPT Tre immediately after outdoor PPT. eHSP72 induction, CK, sUA, and serum TRP remained significantly higher in the HS group during post-PPT recovery. Taken together, animals with a history of HS have different results, and this signature of previous HS may predict altered heat sensitivity.

Fluorine-18-fluoro-2-deoxy-d-glucose PET-CT aids in detection of soft-tissue injuries for dogs with thoracic or pelvic limb lameness.

Fluorine-18-fluoro-2-deoxy-d-glucose positron emission tomography (FDG PET) provides physiologic images of tissues based on their glucose metabolism. The combination of FDG PET and CT (FDG PET-CT) has been utilized in human musculoskeletal imaging to localize soft tissue lesions, however, this modality has not been thoroughly investigated for the diagnosis of canine lameness. This prospective, descriptive study evaluated FDG PET-CT findings in 25 client-owned dogs with inconclusive origin of thoracic or pelvic limb lameness (thoracic limb n = 15/25, 60%; pelvic limb n = 6/25, 24%; and combination of both limbs n = 4/25, 16%). We hypothesized that FDG PET-CT would aid the detection of soft tissue lesions not visible with other imaging modalities. Combined FDG PET-CT detected soft tissue lesions in 40% (n = 10/25) and osteoarthritis in 64% (n = 16/25) of the patients. FDG PET detected more soft tissue lesions than contrast-enhanced CT (n = 15/15, 100% and n = 12/15, 80%, respectively), while CT identified more osteoarthritis lesions than FDG PET (n = 26/26, 100% and n = 18/26, 69%, respectively). The three imaging-diagnoses based on the FDG PET component included the following: flexor carpi ulnaris muscle tear, psoas major myopathy, and tarsal desmopathy. No diagnosis for the lameness was obtained in three dogs. Findings supported FDG PET-CT as a useful adjunct imaging modality for detection of certain soft tissue injuries of the musculoskeletal system. Combined FDG PET-CT should be considered for cases where the cause of lameness is thought to be of soft tissue origin and cannot be diagnosed by conventional means.

Diagnostic Ultrasound Detection of Changes in Femoral Muscle Mass Recovery after Tibial Plateau Levelling Osteotomy in Dogs.

OBJECTIVE: The goal of this study was to develop a clinically feasible ultrasound (US) protocol that can detect changes in thigh muscle mass in dogs after stifle surgery. The primary aim of this study was to compare previously described US measurement locations of the canine thigh for detecting changes in muscle mass in dogs recovering from tibial plateau levelling osteotomy (TPLO). STUDY DESIGN: This was a prospective, exploratory pilot study. Adult dogs (n = 7) undergoing pet-owner elected TPLO were enrolled. Twelve different US measurements were performed in triplicate by a single experienced observer. Measurements were performed at 0, 2, 4 and 8 weeks after surgery at a proximal and distal location along the femur. Data from all available time points and locations were analysed for the main effect of time within modalities. RESULTS: A total of 1,008 US measurements were performed. Measurements of the transverse sectional area of the rectus femoris muscle detected significant (p ≤ 0.05) muscle loss between weeks 0 and 2 at the lateral and medial aspects of the distal location (19% and 15% respectively). Measurements of the thigh muscle thickness were significantly (p < 0.01) increased between 2nd- and 8th- week time points at the lateral aspect of the proximal location (26%). CONCLUSION: The proximal femoral location, measured from the lateral aspect, appears to be the most suitable US measurement for detecting increases in femoral muscle mass in dogs recovering from TPLO. The provided pilot data suggest that further research evaluating this outcome measure is indicated.

Two years of combined high-intensity physical training and heat acclimatization affect lymphocyte and serum HSP70 in purebred military working dogs.

Military working dogs in hot countries undergo exercise training at high ambient temperatures for at least 9 mo annually. Physiological adaptations to these harsh conditions have been extensively studied; however, studies focusing on the underlying molecular adaptations are limited. In the current study, military working dogs were chosen as a model to examine the effects of superimposing endurance exercise on seasonal acclimatization to environmental heat stress. The lymphocyte HSP70 profile and extracellular HSP70 were studied in tandem with physiological performance in the dogs from their recruitment for the following 2 yr. Aerobic power and heat shock proteins were measured at the end of each summer, with physical performance tests (PPTs) in an acclimatized room (22°C). The study shows that together with a profound enhancement of aerobic power and physical performance, hsp72 mRNA induction immediately post-PPT and 45 min later, progressively increased throughout the study period (relative change in median lymphocyte hsp72 mRNA first PPT, 4.22 and 12.82; second PPT, 17.19 and 109.05, respectively), whereas induction of HSP72 protein was stable. These responses suggest that cellular/molecular adaptive tools for maintaining HSP72 homeostasis exist. There was also a significant rise in basal and peak median optical density extracellular HSP at the end of each exercise test (first PPT, 0.13 and 0.15; second PPT, 1.04 and 1.52, respectively). The relationship between these enhancements and improved aerobic power capacity is not yet fully understood.