Dynamic exercise elicits robust changes in sympathetic activity in part due to accumulation of metabolites within the active skeletal muscle which activates group III and IV afferents triggering the muscle metaboreflex. This reflex raises cardiac output via tachycardia, increased ventricular contractility, and central blood volume mobilization which improves perfusion to the active skeletal muscle. An important component of maintaining exercise performance is optimal ventricular ‐ vascular coupling which can change with exercise, aging, as well as pathophysiological conditions. The effect of muscle metaboreflex activation (MMA) on ventricular ‐ vascular interactions is unknown. We hypothesized that MMA increases Effective Arterial Elastance (Ea). We utilized two previously published methods of evaluating Ea (End Systolic Pressure / Stroke Volume (M1) and Heart Rate x Vascular Resistance (M2)) at rest, during mild treadmill exercise, and during MMA induced via partial reductions in hindlimb blood flow imposed during exercise. At rest Ea averaged 3.0 ± 0.1 and 3.0 ± 0.2 mmHg/mL for M1 and M2, respectively. With the transition from rest to mild exercise little change in Ea occurred, whereas with subsequent MMA, Ea increased significantly by 33.6% ± 2.7 and 20.5% ± 2.3 for M1 and M2. We conclude that MMA elicits robust increases in Ea which parallel the substantial increases in ventricular performance thereby optimizing ventricular ‐ vascular coupling. Support or Funding Information Supported by HL‐55473, HL‐126706, HL120822 and R25 GM058905 This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Exercise intolerance is a hallmark symptom of cardiovascular disease and likely occurs via enhanced activation of muscle metaboreflex- induced vasoconstriction of the heart and active skeletal muscle which, thereby limits cardiac output and peripheral blood flow. Muscle metaboreflex vasoconstrictor responses occur via activation of metabolite-sensitive afferent fibers located in ischemic active skeletal muscle, some of which express Transient Receptor Potential Vanilloid 1 (TRPV1) cation channels. Local cardiac and intrathecal administration of an ultra-potent noncompetitive, dominant negative agonist resiniferatoxin (RTX) can ablate these TRPV1 sensitive afferents. This technique has been used to attenuate cardiac sympathetic afferents and nociceptive pain. We investigated whether intrathecal administration (L4-L6) of RTX (2 μg/kg) could chronically attenuate subsequent muscle metaboreflex responses elicited by reductions in hindlimb blood flow during mild exercise (3.2 km/h) in chronically instrumented conscious canines. RTX significantly attenuated metaboreflex induced increases in mean arterial pressure (27 ± 5.0 mmHg vs. 6 ± 8.2 mmHg), cardiac output (1.40 ± 0.2 L/min vs. 0.28 ± 0.1 L/min) and stroke work (2.27 ± 0.2 L*mmHg vs. 1.01 ± 0.2 L*mmHg). Effects were maintained until 78 ± 14 days post RTX at which point the efficacy of RTX injection was tested by intra-arterial administration of capsaicin (20 μg/kg). A significant reduction in the mean arterial pressure response (+45.7 ± 6.5 mmHg pre RTX vs +19.7 ± 3.1mmHg post RTX) was observed. We conclude that intrathecal administration of RTX can chronically attenuate the muscle metaboreflex and could potentially alleviate enhanced sympatho-activation observed in cardiovascular disease states.

Escherichia coli, Listeria spp. and Salmonella typhimurium are common food pathogens and responsible for frequent and widespread outbreaks of foodborne illness annually. This study examines the potential of radiant catalytic ionization (RCI) as a food decontamination technology through its reduction of inoculations of these bacteria on representative food items (apples, cantaloupes, and spinach). RCI exposure resulted in ≥99% reduction in the recovery of these bacteria within a 90-min exposure, with two exceptions (E. coli and S. typhimurium inoculated on cantaloupe: 94% reduction; 88% reduction, respectively). When E. coli, L. innocua and S. typhimurium were inoculated onto apple slices, the percentages remaining after exposure to RCI for 0, 30, 60 and 90 min were: 100, 2, 0, 0; 100, 30, 9, 0.01; and 100, 21, 0.004, 0.02, respectively. When E. coli, L. innocua and S. typhimurium were inoculated onto the rough outer skin of cantaloupes, the percentages remaining after exposure to RCI for 0, 30, 60 and 90 min were: 100, 19, 15, 6; 100, 9, 10, 1; and 100, 24, 22, 12, respectively. When E. coli, L. innocua and S. typhimurium were inoculated onto spinach leaves, the percentages remaining after exposure to RCI for 0, 30, 60 and 90 min were: 100, 16, 0.001, 0.002; 100, 19, 11, 0.005; and 100, 0.007, 0, 0, respectively (SE = ± 0.1 maximum). These results indicate that RCI is an effective technology for reducing foodborne pathogens.