Energy drinks are very popular nonalcoholic beverages among adolescents and young adults for their stimulant effects. Our study aimed to investigate the effect of repeated intraoral Red Bull (RB) infusion on dopamine transmission in the nucleus accumbens shell and core and in the medial prefrontal cortex and on cardiac contractility in adult rats exposed to chronic RB consumption. Rats were subjected to 4 weeks of RB voluntary consumption from adolescence to adulthood. Monitoring of in vivo dopamine was carried out by brain microdialysis. In vitro cardiac contractility was studied on biomechanical properties of isolated left-ventricular papillary muscle. The main finding of the study was that, in treated animals, RB increased shell dopamine via a nonadaptive mechanism, a pattern similar to that of drugs of abuse. No changes in isometric and isotonic mechanical parameters were associated with chronic RB consumption. However, a prolonged time to peak tension and half-time of relaxation and a slower peak rate of tension fall were observed in RB-treated rats. It is likely that RB treatment affects left-ventricular papillary muscle contraction. The neurochemical results here obtained can explain the addictive properties of RB, while the cardiovascular investigation findings suggest a hidden papillary contractility impairment.

Hemodynamic changes during exercise in acute hypoxia (AH) have not been completely elucidated. The present study aimed to investigate hemodynamics during an acute bout of mild, dynamic exercise during moderate normobaric AH. Twenty-two physically active, healthy males (average age; range 23–40 years) completed a cardiopulmonary test on a cycle ergometer to determine their maximum workload (W_max). On separate days, participants performed two randomly assigned exercise tests (three minutes pedaling at 30% of W_max): (1) during normoxia (NORMO), and (2) during normobaric AH at 13.5% inspired oxygen (HYPO). Hemodynamics were assessed with impedance cardiography, and peripheral arterial oxygen saturation (SatO₂) and cerebral oxygenation (Cox) were measured by near-infrared spectroscopy. Hemodynamic responses (heart rate, stroke volume, cardiac output, mean arterial blood pressure, ventricular emptying rate, and ventricular filling rate) were not any different between NORMO and HYPO. However, the HYPO test significantly reduced both SatO₂ (96.6 ± 3.3 vs. 83.0 ± 4.5%) and Cox (71.0 ± 6.6 vs. 62.8 ± 7.4 A.U.) when compared to the NORMO test. We conclude that an acute bout of mild exercise during acute moderate normobaric hypoxia does not induce significant changes in hemodynamics, although it can cause significant reductions in SatO₂ and Cox.

New Findings What is the central question of this study? On the papillary muscle from Type I diabetic rats, we investigated whether diabetes‐associated altered ventricular function had to be ascribed to changes of acto‐myosin interactions and if these modifications were attributable to a possible sarcomere rearrangement. What is the main finding and its importance? For the first time, we showed that type‐I diabetes altered sarcomeric ultrastructure, as seen by transmission electron microscopy, consistently with physiological parameters. Diabetic condition induced slower timing parameters, which are coherent with a principle of diastolic dysfunction. Indeed, at the sarcomeric level, augmented β‐MHC content, increased sarcomere length and crossbridges’ number preserve myocardial stroke and could concur to maintain the ejection fraction. Abstract We investigated whether diabetes‐associated altered ventricular function, in a Diabetes Type I animal model, had to be ascribed to a modification of acto‐myosin interactions, through the in vitro recording of left papillary muscle mechanical parameters and of sarcomeres morphology by electron transmission microscopy (TEM). Experiments were performed on streptozotocin‐induced Diabetic and age‐matched Control female Wistar rats. Mechanical isometric and isotonic indexes and timing parameters were determined. Using Huxley's equations, we calculated mechanics, kinetics and energetics of myosin crossbridges. Sarcomere and A‐band lengths were measured on TEM images. Type I and III Collagen and β‐MHC expression was determined by immunoblotting. No variation in resting and developed tension as well as maximum extent of shortening were evident between groups, but Diabetic rats showed lower maximum shortening velocity, and prolonged timing parameters. Compared to Controls, Diabetics also displayed a higher number of crossbridges with lower unitary force. Moreover, no change in type I and III Collagen was associated to diabetes, but pathological rats showed a two‐fold enhancement of β‐MHC content, longer sarcomeres and A‐band, detected by ultrastructural morphometry. Overall, these data address for a preserved systolic function accompanied by an altered diastolic phase, this has probably to be ascribed to a recruitment of super relaxed myosin heads or to the phosphorylation of regulatory light chain in myosin. Although the early signs of diabetic cardiomyopathy were well expressed, the striking finding of our study was that, in Diabetics, sarcomere modification may be a possible compensatory mechanism that preserves the systolic function. This article is protected by copyright. All rights reserved

Background: Ureteral peristalsis is the result of coordinated mechanical motor performance of longitudinal and circular smooth muscle layer of the ureter wall. The main aim of this study was to characterize in smooth muscle of proximal segments of human ureter, the mechanical properties at level of muscle tissue and at level of myosin molecular motors.Methods: Ureteral samples were collected from 15 patients, who underwent nephrectomy for renal cancer. Smooth muscle strips longitudinally and circularly oriented from proximal segments of human ureter were used for the in vitro experiments. Mechanical indices including the maximum unloaded shortening velocity (V_max), and the maximum isometric tension (P₀) normalized per cross-sectional area, were determined in vitro determined in electrically evoked contractions of longitudinal and circular smooth muscle strips. Myosin cross-bridge (CB) number per mm²(Ψ) the elementary force per single CB (Ψ) and kinetic parameters were calculated in muscle strips, using Huxley's equations adapted to nonsarcomeric muscles.Results: Longitudinal smooth muscle strips exhibited a significantly (p<0.05) faster V_max(63%) and a higher P₀(40%), if compared to circular strips. Moreover, longitudinal muscle strips showed a significantly higher unitary force (Ψ) per CB. However, no significant differences were observed in CB number, the attachment (f1) and the detachment (g²) rate constants between longitudinal and circular muscle strips.Conclusions: The main result obtained in the present work documents that the mechanical, energetic and unitary forces per CB of longitudinal layer of proximal ureter are better compared to the circular one; these preliminary findings suggested, unlike intestinal smooth muscle, a major role of longitudinal smooth muscle layer in the ureter peristalsis.

The use of hypoxic devices among athletes who train in normobaric hypoxia has become increasingly popular; however, the acute effects on heart and brain metabolism are not yet fully understood. This study aimed to investigate the mitochondrial bioenergetics in trained male and female Wistar rats after acute hypoxia training. The experimental plan included exercising for 30 min on a treadmill in a Plexiglas cage connected to a hypoxic generator set at 12.5% O₂ or in normoxia. After the exercise, the rats were sacrificed, and their mitochondria were isolated from their brains and hearts. The bioenergetics for each complex of the electron transport chain was tested using a Clark-type electrode. The results showed that following hypoxia training, females experienced impaired oxidative phosphorylation through complex II in heart subsarcolemmal mitochondria, while males had an altered ADP/O in heart interfibrillar mitochondria, without any change in oxidative capacity. No differences from controls were evident in the brain, but an increased electron transport system efficiency was observed with complex I and IV substrates in males. Therefore, the study’s findings suggest that hypoxia training affects the heart mitochondria of females more than males. This raises a cautionary flag for female athletes who use hypoxic devices.