Experimental Physiology Research Papers - Academia.edu (original) (raw)

Seven men were studied during 40 min of exercise at 70% VO2 peak, in an environmental chamber maintained at either 20 or 40 degrees C, to examine the effect of heat stress on ammonia metabolism during exercise. Heart rate and rectal and... more

Seven men were studied during 40 min of exercise at 70% VO2 peak, in an environmental chamber maintained at either 20 or 40 degrees C, to examine the effect of heat stress on ammonia metabolism during exercise. Heart rate and rectal and muscle temperatures were higher during exercise in the heat, while no differences were observed in pulmonary oxygen uptake or respiratory exchange ratio. Plasma ammonia levels and muscle ammonia accumulation were higher during exercise at 40 degrees C compared with 20 degrees C. Such metabolic alterations may be associated with reduced performance during exercise in the heat.

Temperature-sensitive mechanisms may contribute to blood flow regulation, but the influence of temperature on perfusion to exercising and non-exercising human limbs is not established. Blood temperature (TB ), blood flow and oxygen uptake... more

Temperature-sensitive mechanisms may contribute to blood flow regulation, but the influence of temperature on perfusion to exercising and non-exercising human limbs is not established. Blood temperature (TB ), blood flow and oxygen uptake (VO2 ) in the legs and arms were measured in 16 healthy humans during 90 min of leg and arm exercise and during exhaustive incremental leg or arm exercise. During prolonged exercise, leg blood flow (LBF) was 4-fold higher than arm blood flow (ABF) in association with higher TB and limb VO2 . Leg and arm vascular conductance during exercise compared to rest was related closely to TB (R(2) = 0.91; P < 0.05), plasma adenosine triphosphate (ATP) (R(2) = 0.94; P < 0.05) and limb VO2 (R(2) = 0.99; P < 0.05). During incremental leg exercise, LBF increased in association with elevations in TB and limb VO2 whereas ABF, arm TB and VO2 remained largely unchanged. During incremental arm exercise, both ABF and LBF increased in relation to similar in...

Exposure to maternal hyperglycemia induces hypertension and vascular dysfunction in adult male offspring. Because female offspring from several fetal programming models are protected from the effects of fetal insult, in this study we... more

Exposure to maternal hyperglycemia induces hypertension and vascular dysfunction in adult male offspring. Because female offspring from several fetal programming models are protected from the effects of fetal insult, in this study we analyzed possible differences relative to gender in blood pressure and vascular function in hyperglycemia-programmed offspring. Hyperglycemia was induced on gestation day 7 (streptozotocin, 50 mg.kg(-1) ). Blood pressure, acetylcholine and phenylephrine/noradrenaline responses were analyzed in aorta and mesenteric resistance arteries (MRA) of 3-, 6- and 12-month-old male and female offspring. TxA2 release was analyzed by commercial kits and superoxide anion (O2(-) ) production by dihydroethidium-emitted fluorescence. Male but not female offspring of hyperglycaemic dams (O-DR) had increased blood pressure than controls (O-CR). Contraction to phenylephrine increased and relaxation to acetylcholine was decreased only in aorta from 12-month-old male O-DR th...

What is the central question of this study? Continuous-wave near-infrared spectroscopy, coupled with venous and arterial occlusions, offers an economical, non-invasive alternative to measuring skeletal muscle blood flow and oxygen... more

What is the central question of this study? Continuous-wave near-infrared spectroscopy, coupled with venous and arterial occlusions, offers an economical, non-invasive alternative to measuring skeletal muscle blood flow and oxygen consumption, but its reliability during exercise has not been established. What is the main finding and its importance? Continuous-wave near-infrared spectroscopy devices can reliably assess local skeletal muscle blood flow and oxygen consumption from the vastus lateralis in healthy, physically active adults. The patterns of response exhibited during exercise of varying intensity agree with other published results using similar methodologies, meriting potential applications in clinical diagnosis and therapeutic assessment. Near-infrared spectroscopy (NIRS), coupled with rapid venous and arterial occlusions, can be used for the non-invasive estimation of resting local skeletal muscle blood flow (mBF) and oxygen consumption (mV̇O2), respectively. However, th...

It is now well established that brain plasticity is an inherent property not only of the developing but also of the adult brain. Numerous beneficial effects of exercise, including improved memory, cognitive function and neuroprotection,... more

It is now well established that brain plasticity is an inherent property not only of the developing but also of the adult brain. Numerous beneficial effects of exercise, including improved memory, cognitive function and neuroprotection, have been shown to involve an important neuroplastic component. However, whether major adaptive cardiovascular adjustments during exercise, needed to ensure proper blood perfusion of peripheral tissues, also require brain neuroplasticity, is presently unknown. This review will critically evaluate current knowledge on proposed mechanisms that are likely to underlie the continuous resetting of baroreflex control of heart rate during/after exercise and following exercise training. Accumulating evidence indicates that not only somatosensory afferents (conveyed by skeletal muscle receptors, baroreceptors and/or cardiopulmonary receptors) but also projections arising from central command neurons (in particular, peptidergic hypothalamic pre-autonomic neuron...

Angiotensin 1-7 (ANG 1-7) is generated by type 2 angiotensin converting enzyme (ACE 2) and binds to MAS receptor. Although it is well known that angiotensin 1-7 functionally antagonizes the effects of the classical renin-angiotensin... more

Angiotensin 1-7 (ANG 1-7) is generated by type 2 angiotensin converting enzyme (ACE 2) and binds to MAS receptor. Although it is well known that angiotensin 1-7 functionally antagonizes the effects of the classical renin-angiotensin system (RAS) in several situations, the role of ANG 1-7 in hydromineral homeostasis is not clear. This study aimed to assess the role of ANG 1-7 on neuroendocrine responses to hyperosmolality in rats. Male Wistar rats were divided into the following three groups: control, 24 hours of water deprivation (WD) and 24 hours of salt loading (SL, 1.8% NaCl). Intracerebroventricular (icv) injections of ANG 1-7 or vehicle were given to assess water intake and vasopressin (AVP) plasma levels. Additionally, the brains from control and WD groups were collected to evaluate gene expression in the subfornical (SFO), paraventricular (PVN), and supraoptic (SON) nuclei. Icv ANG 1-7 did not change water and salt intake in control rats; however, ANG 1-7 increased water inta...

Tricarballylic acid is a non-metabolizable rumen bacterial fermentation product of the naturally occurring tricarboxylic acid trans-aconitic acid. The aim of the present study was to investigate intestinal absorption of tricarballylate... more

Tricarballylic acid is a non-metabolizable rumen bacterial fermentation product of the naturally occurring tricarboxylic acid trans-aconitic acid. The aim of the present study was to investigate intestinal absorption of tricarballylate using brush-border membrane vesicles (BBMVs) isolated from the proximal jejunum of steers by a Ca2+ precipitation method with subsequent differential centrifugation. Transport of tricarballylate was investigated indirectly (influence of tricarballylate on the uptake of 14C-labelled citrate) as well as directly (uptake of 3H-labelled tricarballylate). Citrate as well as tricarballylate uptake (at a concentration of 0.05 mmol l-1) was strongly stimulated by an inwardly directed initial Na+ gradient. Furthermore, transport of both tricarboxylates under Na+ gradient conditions was clearly enhanced by lowering the extravesicular pH from 7.8 to 5.6. The imposition of an inwardly directed H+ gradient (pH(out)/pH(in) = 5.6/7.8) further enhanced the intravesic...