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Lawrenson, L., J. Hoff, and R. S. Richardson. Aging attenuates vascular and metabolic plasticity but does not limit improvement in muscle V[o.sub.2 max]. Am J Physiol Heart Circ Physiol 286: H1565-H1572, 2004. First published December 18, 2003; 10.1152/ ajpheart.01070.2003.--The interactions between exercise, vascular and metabolic plasticity, and aging have provided insight into the prevention and restoration of declining whole body and small muscle mass exercise performance known to occur with age. Metabolic and vascular adaptations to normoxic knee-extensor exercise training (1 h 3 times a week for 8 wk) were compared between six sedentary young (20 [+ or -] 1 yr) and six sedentary old (67 [+ or -] 2 yr) subjects. Arterial and venous blood samples, in conjunction with a thermodilution technique facilitated the measurement of quadriceps muscle blood flow and hematologic variables during incremental knee-extensor exercise. Pretraining, young and old subjects attained a similar maximal work rate (W[R.sub.max]) (young = 27 [+ or -] 3, old = 24 [+ or -] 4 W) and similar maximal quadriceps [O.sub.2] consumption (muscle V[o.sub.2 max]) (young = 0.52 [+ or -] 0.03, old = 0.42 [+ or -] 0.05 1/min), which increased equally in both groups posttraining (W[R.sub.max], young = 38 [+ or -] 1, old = 36 [+ or -] 4 W, Muscle V[o.sub.2 max], young = 0.71 [+ or -] 0.1, old = 0.63 [+ or -] 0.1 l/min). Before training, muscle blood flow was ~500 ml lower in the old compared with the young throughout incremental knee-extensor exercise. After 8 wk of knee-extensor exercise training, the young reduced muscle blood flow ~700 ml/min, elevated arteriovenous [O.sub.2] difference ~1.3 ml/dl, and increased leg vascular resistance ~17 mmHg * [ml.sup.-1] * [min.sup.-1], whereas the old subjects revealed no training-induced changes in these variables. Together, these findings indicate that after 8 wk of small muscle mass exercise training, young and old subjects of equal initial metabolic capacity have a similar ability to increase quadriceps muscle W[R.sub.max] and muscle V[o.sub.2 max], despite an attenuated vascular and/or metabolic adaptation to submaximal exercise in the old. vascular resistance; quadriceps; pulse pressures; [O.sub.2] diffusional conductance; exercise training

To determine the effect of age on quadriceps muscle blood flow (QMBF), leg vascular resistance (LVR), and maximum oxygen uptake (QV[O.sub.2.max]), a thermal dilution technique was used in conjunction with arterial and venous femoral blood sampling in six sedentary young (19.8 [+ or -] 1.3 yr) and six sedentary old (66.5 [+ or -] 2.1 yr) males during incremental knee extensor exercise (KE). Young and old attained a similar maximal KE work rate (W[R.sub.max]) (young: 25.2 [+ or -] 2.1 and old: 24.1 [+ or -] 4 W) and QV[O.sub.2.max] (young: 0.52 [+ or -] 0.03 and old: 0.42 [+ or -] 0.05 1/min). QMBF during KE was lower in old subjects by ~500 ml/min across all work rates, with old subjects demonstrating a significantly lower QMBF/W (old: 174 [+ or -] 20 and young: 239 [+ or -] 46 ml*[min.sup.-1]*[W.sup.-1]). Although the vasodilatory response to incremental KE was 142% greater in the old (young: 0.0019 and old: 0.0046 mmHg* min*[ml.sup.-1]*[W.sup.-1]), consistently elevated leg vascular resistance (LVR) in the old, 80% higher LVR in the old at 50% WR and 40% higher LVR in the old at W[R.sub.max] (young: 44.1 [+ or -] 3.6 and old: 31.0 [+ or -] 1.7 mmHg* min*[ml.sup.1]), dictated that during incremental KE the LVR of the old subjects was never less than that of the young subjects. Pulse pressures, indicative of arterial vessel compliance, were 36% higher in the old subjects across all work rates. In conclusion, well-matched sedentary young and old subjects with similar quadriceps muscle mass achieved a similar W[R.sub.max] and Q[Vo.sub.2.max] during incremental KE. The old subjects, despite a reduced QMBF, had a greater vasodilatory response to incremental KE. Given that small muscle mass exercise, such as KE, utilizes only a fraction of maximal cardiac output, peripheral mechanisms such as consistently elevated leg vascular resistance and greater pulse pressures appear to be responsible for reduced blood flow persisting throughout graded KE in the old subjects. vascular resistance; quadriceps; pulse pressures; [O.sub.2] conductance

We measured leg blood flow (LBF), drew arterial-venous (A-V) blood samples, and calculated muscle [O.sub.2] consumption (V[O.sub.2]) during incremental cycle ergometry exercise [15, 30, and 99 W and maximal effort (maximal work rate, W[R.sub.max])] in nine sedentary young (20 [+ or -] 1 yr) and nine sedentary old (70 [+ or -] 2 yr) males. LBF was preserved in the old subjects at 15 and 30 W. However, at 99 W and at W[R.sub.max], leg vascular conductance was attenuated because of a reduced LBF (young: 4.1 [+ or -] 0.2 1/min and old: 3.1 [+ or -] 0.3 1/rain) and an elevated mean arterial blood pressure (young: 112 [+ or -] 3 mmHg and old: 132 [+ or -] 3 mmHg) in the old subjects. Leg A-V [O.sub.2] difference changed little with increasing WR in the old group but was elevated compared with the young subjects. Muscle maximal V[O.sub.2] and cycle W[R.sub.max] were significantly lower in the old subjects (young: 0.8 [+ or -] 0.05 1/min and 193 [+ or -] 7 W; old: 0.5 [+ or -] 0.03 1/rain and 117 [+ or -] 10 W). The submaximally unchanged and maximally reduced cardiac output associated with aging coupled with its potential maldistiribution are candidates for the limited LBF during moderate to heavy exercise in older sedentary subjects. V[O.sub.2max]; vascular conductance; skeletal muscle

The interactions between exercise, vascular and metabolic plasticity, and aging have provided insight into the prevention and restoration of declining whole body and small muscle mass exercise performance known to occur with age. Metabolic and vascular adaptations to normoxic knee-extensor exercise training (1 h 3 times a week for 8 wk) were compared between six sedentary young (20 ± 1 yr) and six sedentary old (67 ± 2 yr) subjects. Arterial and venous blood samples, in conjunction with a thermodilution technique facilitated the measurement of quadriceps muscle blood flow and hematologic variables during incremental knee-extensor exercise. Pretraining, young and old subjects attained a similar maximal work rate (WRmax) (young = 27 &plusmnl 3, old = 24 ± 4 W) and similar maximal quadriceps O2 consumption (muscle Vo2 max) (young = 0.52 ± 0.03, old = 0.42 ± 0.05 1/min), which increased equally in both groups posttraining (WRmax, young = 38 &plusm; 1, old = 36 ± 4 W, Muscle Vo2 max young = 0.71 ± 0.1, old = 0.63 ± 0.1 l/min). Before training, muscle blood flow was ∼500 ml lower in the old compared with the young throughout incremental knee-extensor exercise. After 8 wk of knee-extensor exercise training, the young reduced muscle blood flow ∼700 ml/min, elevated arteriovenous O2 difference -1.3 ml/dl, and increased leg vascular resistance ∼17 mmHg·ml- ∼·min-1, whereas the old subjects revealed no training-induced changes in these variables. Together, these findings indicate that after 8 wk of small muscle mass exercise training, young and old subjects of equal initial metabolic capacity have a similar ability to increase quadriceps muscle WRmax and muscle Vo2 max, despite an attenuated vascular and/or metabolic adaptation to submaximal exercise in the old. [ABSTRACT FROM AUTHOR]

The interactions between exercise, vascular and metabolic plasticity, and aging have provided insight into the prevention and restoration of declining whole body and small muscle mass exercise performance known to occur with age. Metabolic and vascular adaptations to normoxic knee-extensor exercise training (1 h 3 times a week for 8 wk) were compared between six sedentary young (20 ± 1 yr) and six sedentary old (67 ± 2 yr) subjects. Arterial and venous blood samples, in conjunction with a thermodilution technique facilitated the measurement of quadriceps muscle blood flow and hematologic variables during incremental knee-extensor exercise. Pretraining, young and old subjects attained a similar maximal work rate (WRmax) (young = 27 &plusmnl 3, old = 24 ± 4 W) and similar maximal quadriceps O2 consumption (muscle Vo2 max) (young = 0.52 ± 0.03, old = 0.42 ± 0.05 1/min), which increased equally in both groups posttraining (WRmax, young = 38 &plusm; 1, old = 36 ± 4 W, Muscle Vo2 max young = 0.71 ± 0.1, old = 0.63 ± 0.1 l/min). Before training, muscle blood flow was ∼500 ml lower in the old compared with the young throughout incremental knee-extensor exercise. After 8 wk of knee-extensor exercise training, the young reduced muscle blood flow ∼700 ml/min, elevated arteriovenous O2 difference -1.3 ml/dl, and increased leg vascular resistance ∼17 mmHg·ml- ∼·min-1, whereas the old subjects revealed no training-induced changes in these variables. Together, these findings indicate that after 8 wk of small muscle mass exercise training, young and old subjects of equal initial metabolic capacity have a similar ability to increase quadriceps muscle WRmax and muscle Vo2 max, despite an attenuated vascular and/or metabolic adaptation to submaximal exercise in the old. [ABSTRACT FROM AUTHOR]

Diagnosis of acute HIV infection (AHI) presents an opportunity to prevent HIV transmission during a highly infectious period. Disclosure is important during AHI as a means to facilitate safer sex practices and notify partners, particularly as those with AHI may be better able to identify the source of their infection because of the recency of HIV acquisition. However, little is known about disclosure during AHI. We conducted 40 semi-structured interviews with Malawians diagnosed with AHI (24 men; 21 married). Most participants reported disclosing to a sexual partner within a month of diagnosis, and knew or had a strong suspicion about the source of their infection. Participants often assumed their source had knowingly infected them, contributing to anger and feeling that disclosure is futile if the source already knew their HIV status. Assisted partner notification, individual and couples counseling, and couples HIV testing may facilitate disclosure during AHI., Clinical Trial Registration Number: NCT01450189., Competing Interests: The authors have declared that no competing interests exist.

Purpose: Pancreatic fiducials have proven superior over other isocenter localization surrogates, including anatomical landmarks and intratumoral or adjacent stents. The more clinically relevant dosimetric impact of image guided radiation therapy (IGRT) using intratumoral fiducial markers versus bony anatomy has not yet been described and is therefore the focus of the current study., Methods and Materials: Using daily orthogonal kV or cone beam computed tomography (CBCT) images and positional and dosimetric data were analyzed for 12 consecutive patients treated with fiducial based IGRT and volumetric modulated arc therapy to the intact pancreas. The shifts from fiducial to bone (ΔFid-Bone) required to realign the daily fiducial-matched pretreatment images (kV, CBCTs) to the planning computed tomography (CT) using bony anatomic landmarks were recorded. The isocenter was then shifted by (ΔFid-Bone) for 5 evenly spaced treatments, and the dosimetric impact of ΔFid-Bone was calculated for planning target volume coverage (PTV50.4 and PTV47.9) and organs at risk (liver, kidney, and stomach/duodenum)., Results: The ΔFid-Bone were greatest in the superoinferior direction (ΔFid-Bone anteroposterior, 2.7 ± 3.0; left-right, 2.8 ± 2.8; superoinferior, 6.3 ± 7.9 mm; mean ± standard deviation; P = .03). PTV50.4 coverage was reduced by 13% (fiducial plan 95 ± 2.0 vs bone plan 82 ± 12%; P = .005; range, 5%-52%; >5% loss in all; and >10% loss in 42% of patients), and to a lesser degree for PTV47.9 (difference, -8%; range, 1%-30%; fiducial plan 100 ± 0.3% vs bone plan 92 ± 7.6%; P = .003; with reductions of >5% in 66% and >10% in 33% of patients). The dosimetric impact of ΔFid-Bone on the organs at risk was not significant. Positional shifts for kV- and CBCT-based realignments were nearly identical., Conclusion: Compared with matching by fiducial markers, IGRT matched by bony anatomy substantially reduces the PTV50.4 and PTV47.9 coverage, supporting the use of intratumoral pancreatic markers for improved targeting in IGRT for pancreatic cancer., (Copyright © 2016 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.)

Objective: To ascertain the rates and patterns of prostate-specific antigen (PSA) screening in New Zealand men., Methods: The study population included 35,958 men aged 40+ years, with no prior diagnosis of prostate cancer, enrolled in 31 general practices in the Midland Cancer Network Region of New Zealand in 2010. Computerized practice records were searched for information, including reasons for testing, for men with elevated PSA test results in 2010. PSA results for 2007-2010 were obtained from community laboratories. Screened men were identified and screening rates calculated by age., Results: Of 9344 men who underwent one or more PSA tests in 2010, 84.9% were classified as having been screened. The overall screening rate was 22.1%, with 24.4% of men aged 70+ years screened. Elevated PSA levels were found in 2.1% of screened men. Of the men screened in 2010, 57.3% had had a screening test in the previous three years., Conclusions: General practitioners in New Zealand commonly screen men (including those aged 70+) for prostate cancer, despite the lack of trial evidence that these men would benefit from screening. The value of annual PSA testing in men with previous normal PSA levels is unproven. Longer intervals between tests would be appropriate.

Cancer progression represents an evolutionary process where overall genome level changes reflect system instability and serve as a driving force for evolving new systems. To illustrate this principle it must be demonstrated that karyotypic heterogeneity (population diversity) directly contributes to tumorigenicity. Five well characterized in vitro tumor progression models representing various types of cancers were selected for such an analysis. The tumorigenicity of each model has been linked to different molecular pathways, and there is no common molecular mechanism shared among them. According to our hypothesis that genome level heterogeneity is a key to cancer evolution, we expect to reveal that the common link of tumorigenicity between these diverse models is elevated genome diversity. Spectral karyotyping (SKY) was used to compare the degree of karyotypic heterogeneity displayed in various sublines of these five models. The cell population diversity was determined by scoring type and frequencies of clonal and non-clonal chromosome aberrations (CCAs and NCCAs). The tumorigenicity of these models has been separately analyzed. As expected, the highest level of NCCAs was detected coupled with the strongest tumorigenicity among all models analyzed. The karyotypic heterogeneity of both benign hyperplastic lesions and premalignant dysplastic tissues were further analyzed to support this conclusion. This common link between elevated NCCAs and increased tumorigenicity suggests an evolutionary causative relationship between system instability, population diversity, and cancer evolution. This study reconciles the difference between evolutionary and molecular mechanisms of cancer and suggests that NCCAs can serve as a biomarker to monitor the probability of cancer progression.

Both antioxidant supplementation and exercise training have been identified as interventions which may reduce oxidative stress and thus improve cardiovascular health, but the interaction of these interventions on arterial BP (blood pressure) and vascular function has not been studied in older humans. Thus in six older (71+/-2 years) mildly hypertensive men, arterial BP was evaluated non-invasively at rest and during small muscle mass (knee-extensor) exercise with and without a pharmacological dose of oral antioxidants (vitamins C and E, and alpha-lipoic acid). The efficacy of the antioxidant intervention to decrease the plasma free radical concentration was verified via EPR (electron paramagnetic resonance) spectroscopy, while changes in endothelial function in response to exercise training and antioxidant administration were evaluated via FMD (flow-mediated vasodilation). Subjects were re-evaluated after a 6-week aerobic exercise training programme. Prior to training, acute antioxidant administration did not change resting arterial BP or FMD. Six weeks of knee-extensor exercise training reduced systolic BP (from 150+/-8 mmHg at pre-training to 138+/-3 mmHg at post-training) and diastolic BP (from 91+/-5 mmHg at pre-training to 79+/-3 mmHg at post-training), and improved FMD (1.5+/-1 to 4.9+/-1% for pre- and post-training respectively). However, antioxidant administration after exercise training negated these improvements, returning subjects to a hypertensive state and blunting training-induced improvements in FMD. In conclusion, the paradoxical effects of these interventions suggest a need for caution when exercise and acute antioxidant supplementation are combined in elderly mildly hypertensive individuals.

Background and Purpose: Serotonin is a major regulator of structural brain plasticity, which may occur following cortical resection in humans. In this study we used positron emission tomography (PET) with alpha[11C]methyl-l-tryptophan (AMT) to evaluate serotonergic alterations in subcortical structures following cortical resection in children with intractable epilepsy., Methods: AMT uptake in the thalamus and lentiform nucleus was evaluated postoperatively (1-89 months following resection) in 19 children (mean age: 8.7 years) with a previous cortical resection due to intractable epilepsy. Ten children with partial epilepsy but without resection and seven normal children served as controls., Results: There was an increased AMT uptake in the lentiform nucleus ipsilateral to the resection as compared to the contralateral side (mean asymmetry: 4.2+/-3.0%), and the asymmetries were significantly higher than those measured in the control groups (p

To further explore the limitations to maximal O(2) consumption (.VO(2 max)) in exercise-trained skeletal muscle, six cyclists performed graded knee-extensor exercise to maximum work rate (WR(max)) in hypoxia (12% O(2)), hyperoxia (100% O(2)), and hyperoxia + femoral arterial infusion of adenosine (ADO) at 80% WR(max). Arterial and venous blood sampling and thermodilution blood flow measurements allowed the determination of muscle O(2) delivery and O(2) consumption. At WR(max), O(2) delivery rose progressively from hypoxia (1.0 +/- 0.04 l/min) to hyperoxia (1.20 +/- 0.09 l/min) and hyperoxia + ADO (1.33 +/- 0.05 l/min). Leg .VO(2 max) varied with O(2) availability (0.81 +/- 0.05 and 0.97 +/- 0.07 l/min in hypoxia and hyperoxia, respectively) but did not improve with ADO-mediated vasodilation (0.80 +/- 0.09 l/min in hyperoxia + ADO). Although a vasodilatory reserve in the maximally working quadriceps muscle group may have been evidenced by increased leg vascular conductance after ADO infusion beyond that observed in hyperoxia (increased blood flow but no change in blood pressure), we recognize the possibility that the ADO infusion may have provoked vasodilation in nonexercising tissue of this limb. Together, these findings imply that maximally exercising skeletal muscle may maintain some vasodilatory capacity, but the lack of improvement in leg .VO(2 max) with significantly increased O(2) delivery (hyperoxia + ADO), with a degree of uncertainty as to the site of this dilation, suggests an ADO-induced mismatch between O(2) consumption and blood flow in the exercising limb.

Originally thought of as simply damaging or toxic "accidents" of in vivo chemistry, free radicals are becoming increasingly recognized as redox signaling molecules implicit in cellular homeostasis. Indeed, at the vascular level, it is plausible that oxidative stress plays a regulatory role in normal vascular function. Using electron paramagnetic resonance (EPR) spectroscopy, we sought to document the ability of an oral antioxidant cocktail (vitamins C, E, and alpha-lipoic acid) to reduce circulating free radicals, and we employed Doppler ultrasound to examine the consequence of an antioxidant-mediated reduction in oxidative stress on exercise-induced vasodilation. A total of 25 young (18-31 yr) healthy male subjects partook in these studies. EPR spectroscopy revealed a reduction in circulating free radicals following antioxidant administration at rest ( approximately 98%) and as a consequence of exercise ( approximately 85%). Plasma total antioxidant capacity and vitamin C both increased following the ingestion of the antioxidant cocktail, whereas vitamin E levels were not influenced by the ingestion of the antioxidants. Brachial artery vasodilation during submaximal forearm handgrip exercise was greater with the placebo (7.4 +/- 1.8%) than with the antioxidant cocktail (2.3 +/- 0.7%). These data document the efficacy of an oral antioxidant cocktail in reducing free radicals and suggest that, in a healthy state, the aggressive disruption of the delicate balance between pro- and antioxidant forces can negatively impact vascular function. These findings implicate an exercise-induced reliance upon pro-oxidant-stimulated vasodilation, thereby revealing an important and positive vascular role for free radicals.

The present study determined if acute exercise increased free radical formation in human skeletal muscle. Vastus lateralis biopsies were obtained in a randomized balanced order from six males at rest and following single-leg knee extensor exercise performed for 2 min at 50% of maximal work rate (WR(MAX)) and 3 min at 100% WR(MAX). EPR spectroscopy revealed an exercise-induced increase in mitochondrial ubisemiquinone (UQ*-) [0.167 +/- 0.055 vs. rest: 0.106 +/- 0.047 arbitrary units (AU)/g total protein (TP), P < 0.05] and alpha-phenyl-tert-butylnitrone-adducts (112 +/- 41 vs. rest: 29 +/- 9 AU/mg tissue mass, P < 0.05). Intramuscular lipid hydroperoxides also increased (0.320 +/- 0.263 vs. rest: 0.148 +/- 0.071 nmol/mg TP, P < 0.05) despite an uptake of alpha-tocopherol, alpha-carotene and beta-carotene. There were no relationships between mitochondrial volume density and any biomarkers of oxidative stress. These findings provide the first direct evidence for intramuscular free radical accumulation and lipid peroxidation following acute exercise in humans.

We sought to identify the relationship between shear stimuli and flow-mediated vasodilation and to determine whether small muscle mass exercise training could provoke limb-specific improvements in endothelial function in older subjects. In five young (22 +/- 1 yr old) and six old (71 +/- 2 yr old) subjects, ultrasound Doppler measurements were taken in the arm (brachial artery) and leg (deep and superficial femoral arteries) after suprasystolic cuff occlusion with and without ischemic exercise to evaluate flow-mediated dilation (FMD) in both limbs. Older subjects were reevaluated after 6 wk of single-leg knee extensor exercise training. Before the training, a significant FMD was observed in the arm of young (3 +/- 1%) but not old (1 +/- 1%) subjects, whereas a significant leg FMD was observed in both groups (5 +/- 1% old vs. 3 +/- 1% young). However, arm vasodilation was similar between young and old when normalized for shear rate, and cuff occlusion with superimposed handgrip exercise provoked additional shear, which proportionately improved the FMD response in both groups. Exercise training significantly improved arm FMD (5 +/- 1%), whereas leg FMD was unchanged. However, ischemic handgrip exercise did not provoke additional arm vasodilation after training, which may indicate an age-related limit to shear-induced vasodilation. Together, these data demonstrate that vascular reactivity is dependent on limb and degree of shear stimuli, challenging the convention of diminished endothelial function typically associated with age. Likewise, exercise training improved arm vasodilation, indicating some preservation of vascular plasticity with age.

Aging appears to attenuate leg blood flow during exercise; in contrast, such data are scant and do not support this contention in the arm. Therefore, to determine whether aging has differing effects on blood flow in the arm and leg, eight young (22 +/- 6 yr) and six old (71 +/- 15 yr) subjects separately performed dynamic knee extensor [0, 3, 6, 9 W; 20, 40, 60% maximal work rate (WRmax)] and handgrip exercise (3, 6, 9 kg at 0.5 Hz; 20, 40, 60% WRmax). Arterial diameter, blood velocity (Doppler ultrasound), and arterial blood pressure (radial tonometry) were measured simultaneously at each of the submaximal workloads. Quadriceps muscle mass was smaller in the old (1.6 +/- 0.1 kg) than the young (2.1 +/- 0.2 kg). When normalized for this difference in muscle mass, resting seated blood flow was similar in young and old subjects (young, 115 +/- 28; old, 114 +/- 39 ml x g(-1) x min(-1)). During exercise, blood flow and vascular conductance were attenuated in the old whether expressed in absolute terms for a given absolute workload or more appropriately expressed as blood flow per unit muscle mass at a given relative exercise intensity (young, 1,523 +/- 329; old, 1,340 +/- 157 ml x kg(-1) x min(-1) at 40% WRmax). In contrast, aging did not affect forearm muscle mass or attenuate rest or exercise blood flow or vascular conductance in the arm. In conclusion, aging induces limb-specific alterations in exercise blood flow regulation. These alterations result in reductions in leg blood flow during exercise but do not impact forearm blood flow.

Arm and leg vascular responsiveness to comparable shear stimuli during isolated dynamic exercise has not been assessed in humans. Consequently, six young cyclists performed incremental, intermittent handgrip exercise (arm) and knee-extensor exercise (leg) from 5 to 60% of maximal work rate (WR). Ultrasound Doppler measurements were taken in the brachial artery (BA), common femoral artery (CFA), and deep femoral artery (DFA) at rest and at each WR to assess diameter and sheer rate changes. Exercise at 60% maximum WR increased shear rate to the same degree in the CFA (314.3 +/- 33.3 s(-1)) and BA (303.3 +/- 26.3 s(-1)), but was significantly higher in the DFA (712.6 +/- 88.3 s(-1)). Compared with rest, exercise at 60% maximum WR did not alter CFA vessel diameter, but increased BA diameter (0.42 +/- 0.01 to 0.49 +/- 0.01 cm) and DFA diameter (0.59 +/- 0.05 to 0.64 +/- 0.04 cm). These data from the DFA demonstrate for the first time a substantial improvement in vascular reactivity in a conduit vessel only slightly distal to the CFA. However, despite comparable dilation between the BA and DFA, the slope of the relationship between vessel diameter and shear rate was much greater in the arm (2.4 x 10(-4) +/- 4.6 x 10(-5) cm/s) than in either the DFA (8.9 x 10(-5) +/- 1.5 x 10(-5) cm/s) or CFA (2.1 x 10(-5) +/- 1.1 x 10(-5) cm/s). Together, these findings reveal a substantial heterogeneity in vascular responsiveness in the leg during dynamic exercise but demonstrate that conduit vessel dilation for a given change in shear rate is, nonetheless, reduced in the leg compared with the arm.

Incremental knee extensor (KE) exercise performed at 25, 70, and 100% of single-leg maximal work rate (WR(MAX)) was combined with ex vivo electron paramagnetic resonance (EPR) spectroscopic detection of alpha-phenyl-tert-butylnitrone (PBN) adducts, lipid hydroperoxides (LH), and associated parameters in five males. Blood samples were taken from the femoral arterial and venous circulation that, when combined with measured changes in femoral venous blood flow, permitted a direct examination of oxidant exchange across a functionally isolated contracting muscle bed. KE exercise progressively increased the net outflow of LH and PBN adducts (100% > 70% > 25% WR(MAX), P < 0.05) consistent with the generation of secondary, lipid-derived oxygen (O(2))-centered alkoxyl and carbon-centered alkyl radicals. Radical outflow appeared to be more intimately associated with predicted decreases in intracellular Po(2) (iPo(2)) as opposed to measured increases in leg O(2) uptake, with greater outflow recorded between 25 and 70% WR(MAX) (P < 0.05 vs. 70-100% WR(MAX)). This bias was confirmed when radical venoarterial concentration differences were expressed relative to changes in the convective components of O(2) extraction and flow (25-70% WR(MAX) P < 0.05 vs. 70-100% WR(MAX), P > 0.05). Exercise also resulted in a net outflow of other potentially related redox-reactive parameters, including hydrogen ions, norepinephrine, myoglobin, lactate dehydrogenase, and uric acid, whereas exchange of lipid/lipoproteins, ascorbic acid, and selected lipid-soluble anti-oxidants was unremarkable. These findings provide direct evidence for an exercise intensity-dependent increase in free radical outflow across an active muscle bed that was associated with an increase in sarcolemmal membrane permeability. In addition to increased mitochondrial electron flux subsequent to an increase in O(2) extraction and flow, exercise-induced free radical generation may also be regulated by changes in iPo(2), hydrogen ion generation, norepinephrine autoxidation, peroxidation of damaged tissue, and xanthine oxidase activation.