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    Sex-dependent metabolic and behavioural alterations in a rat model of forced exertion-induced myopathy
    (BioMed Central Ltd, 2025-12-01) Lubbe C; Harvey BH; Viljoen FP; Meyer L; Wolmarans DW
    Background: Mass boma capture (MBC) of ungulates may trigger a metabolic condition known as capture myopathy (CM), resulting in myoglobinuria and hyperthermia (rhabdomyolysis). Its pathobiology is poorly understood, especially the role of contextual reminders; a preclinical model system could thus be useful. Sixty (60) adult Sprague Dawley rats (30 rats per sex), divided into three experimental series (n = 12—24), were exposed to MBC-like exertion, viz., forced treadmill running (FTR) at 75% of VO2MAX (30 m/min) with and without aversive noise (context) until physical exhaustion. Rectal and surface temperatures were measured before and after reaching exhaustion. Urine myoglobin, plasma lactate dehydrogenase (LDH), lactate, and creatine kinase (CK) were measured immediately and 15 days after MBC. Anxiety was assessed in the light-dark and social interaction tests. Results: Male and female MBC rats presented with significant hyperthermia, with females showing significantly increased urine myoglobin immediately after MBC, although this was not sustained until day 15 post MBC. LDH was significantly elevated in female rats at baseline but not day 15 post-MBC. Contextual re-exposure prior to testing on day 15 resulted in significant sex-dependent differences in myoglobin and CK concentrations, with female rats being significantly more affected. Only female rats trended towards increased anxiety-like behaviour immediately post-MBC exposure, which was not sustained until day 15 post MBC. Conclusions: This work builds on previous research using a rodent model of capture myopathy (CM) that confirmed the running protocol to effectively elicite the necessary muscular response. The MBC protocol emphasizes hyperthermia and increased urine myoglobin, sensitivity to contextual reminder (noise), and a trend towards anxiety, particularly in females, highlighting sex-specific physiological responses. By incorporating behavioural and biochemical assessments, acute versus delayed response and environmental triggers, the study enhances model validity and deepens insights into CM-related responses.
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    Does cooling affect skeletal muscle glycogen replenishment after an acute bout of fear-induced exertional hyperthermia in blesbok (Damaliscus pygargus phillipsi)?
    (Elsevier Inc, 2025-11-01) Kohn TA; Martin M; van Boom KM; Donaldson B; Blackhurst DM; Fitte A; Burroughs R; Steyl JCA; Goddard A; Meyer LCR
    Rhabdomyolyses is a clinical sign of capture myopathy in wild animals and may be linked to glycogen metabolism. To study potential mechanisms, 26 wild blesbok were chased for 15 min and immobilised, whereafter 12 of these blesbok were doused with ice-water (n = 14 chased only group; n = 12 chased + cooled group). An additional 12 blesbok served as resting (not chased) uncooled controls. Vastus lateralis biopsies were obtained after immobilisation for biochemical analyses. Biopsies obtained at initial capture, 3- and 16-days post exercise were analysed for glycogen content. Blesbok muscles contained predominantly myosin heavy chain (MHC) IIA (∼50 ± 9 %), followed by IIX (32 ± 10 %) and MHC I (18 ± 5 %), with no difference between groups. Citrate synthase (mean: 87 ± 48), 3-hydroxyacetyl co A dehydrogenase (47 ± 17), lactate dehydrogenase (1567 ± 654), phosphorylase (162 ± 94), phosphofructokinase (250 ± 123) and creatine kinase (12,455 ± 6372) activities (in μmol/min/g prot) were not different between groups. Similarly, superoxide dismutase (7.9 ± 7 U/mg prot), catalase (8.8 ± 5.8 mmol/min/g prot), and overall antioxidant capacity (ORAC: 23055 ± 18,460 μmol/g prot) were not different between groups. Glycogen content was reduced in both chased groups and not replenished by day 3. Glycogen supercompensation was observed on day 16 in both chased groups (∼33 % higher than resting control group). The results confirm that blesbok have high muscle metabolic capacities, and that glycogen resynthesis is slow, which could lead to metabolite deficiency during prolonged chase events (>15 min).