Perfluoroalkyl substances (PFAS) and lead (Pb) as "cardiovascular disruptors" in 9-11-year-old children living in Syracuse, New York, United States.

OBJECTIVE: Per- and polyfluoro-alkyl substances (PFAS) and lead (Pb) are ubiquitous environmental toxicants with apparent impact on cardiovascular disease (CVD) risk. As one possible mechanism for this increased risk, we have previously demonstrated an association between Pb exposure and heightened cardiovascular reactivity to acute psychological stress, a CVD risk factor. The present study expands this approach and considers both PFAS and Pb exposures (and the possible interaction). METHODS: We assessed 14 serum PFAS and whole blood Pb concentrations in a sample of 9-11 year-old children (N = 291; 43.2% White, 56.8% Black; 53.5% female). We measured cardiovascular functioning at rest and during psychological stress as well as multiple indicators of subclinical CVD including resting blood pressure (BP), carotid-femoral pulse wave velocity (cfPWV), carotid intima-media thickness (cIMT), and left ventricular mass (LVM). Data analysis included general linear modeling as well as a non-parametric approach to study metal mixtures, specifically Bayesian Kernel Machine Regression (BKMR). RESULTS: Significant interactions between different PFAS and with Pb suggest the importance of considering toxicant mixtures when assessing potential disruption of the cardiovascular system. The pattern of findings suggests that greater "vascular reactivity" (elevated BP and vascular resistance during acute psychological stress) was associated with higher concentrations of perfluorononanoic acid (PFNA), perfluorohexane sulfonate (PFHxS), and Pb, but only when perfluorooctanoic acid (PFOA) was concurrently elevated. With respect to subclinical outcomes, increasing perfluorodecanoic acid (PFDA) was associated with greater cIMT (ß = 0.21, p = 0.010). CONCLUSION: To our knowledge this is the first study to consider how PFAS exposures might affect cardiovascular functioning and subclinical disease. Although a complex pattern of associations emerged, it does appear that PFAS and Pb can be classified as "cardiovascular disruptors" in children. Further research is needed to replicate these novel findings and determine whether these disruptions produce future cardiovascular disease.

Airborne levels of cadmium are correlated with urinary cadmium concentrations among young children living in the New York state city of Syracuse, USA.

Air pollution is a serious public health issue with early childhood exposure being of high concern because of the greater risk that children might experience negative health outcomes. Industrial sources in and near communities are one potential path of exposure that children might face with greater levels of air pollution correlating with higher levels of toxicants detected in children. We compare estimated ambient air concentrations of Cadmium (Cd) to a cohort (n = 281) of 9 to 11-year old children during their early childhood years (0-5 years of age) in a mid-size city in Upstate New York. Levels of Cd air pollution are compared to children's urine-Cd levels. Urine has been shown to be a superior biomarker to blood for Cd exposure particularly for longer-term exposures. We find that participants who reside in households that faced greater Cd air pollution during the child's early years have higher urine-Cd levels. This association is stable and stronger than previously presented associations for blood-Cd. Findings support expanded use of air modelling data for risk screening to reduce the potential health burden that industrial pollution can have.

Arterial stiffness and augmentation index are associated with balance function in young adults.

OBJECTIVE: Arterial stiffness and pulsatile central hemodynamics have been shown to affect various aspects of physical function, such as exercise capacity, gait speed, and motor control. The aim of this study was to examine the potential association between arterial stiffness and balance function in healthy younger men and women. METHODS: 112 participants (age = 21 ± 4 years, n = 78 women) underwent measures of arterial stiffness, pulsatile central hemodynamics, balance function and physical fitness in this cross-sectional study. Postural sway was measured in triplicate while participants stood on a foam surface with their eyes closed for 20 s. The average total center of pressure path length from the three trials was used for analysis. Measures of vascular function were estimated using an oscillometric blood pressure device while at rest and included pulse wave velocity (PWV), augmentation index (AIx), and pulse pressure amplification. Measures of physical fitness used as covariates in statistical models included handgrip strength determined from a handgrip dynamometer, lower-body flexibility assessed using a sit-and-reach test, estimated maximal aerobic capacity (VO2max) using heart rate and a step test, and body fat percentage measured from air displacement plethysmography. RESULTS: The results from linear regression indicated that after considering sex, mean arterial pressure, body fat, estimated VO2max, handgrip strength, and sit-and-reach, PWV (ß = 0.44, p < 0.05) and AIx (ß = - 0.25, p < 0.01) were significant predictors of postural sway, explaining 10.2% of the variance. CONCLUSION: Vascular function is associated with balance function in young adults independent of physical fitness. Increased arterial stiffness may negatively influence balance, while wave reflections may be protective for balance.

Total brachial artery reactivity and incident heart failure and heart failure subtypes: multi-ethnic study of atherosclerosis.

Endothelial dysfunction may be a phenotypic expression of heart failure (HF). Total brachial artery reactivity (TBAR) is a non-invasive measurement of endothelial function that has been associated with increased risk of cardiovascular outcomes. Limited information is currently available on the impact of TBAR on incident HF and its subtypes. The aim of this study was to investigate whether TBAR is associated with overall incident HF, and the two HF subtypes, HF with reduced ejection fraction (HFrEF) and HF with preserved ejection fraction (HFpEF) in a community-based study. The sample included 5499 participants (45-84 years of age) from the Multi-Ethnic Study of Atherosclerosis who were free of cardiovascular disease at baseline. Brachial artery was imaged via ultrasound after five minutes of cuff occlusion at the right forearm. TBAR was calculated as the difference between maximum and minimum brachial artery diameters following cuff release, divided by the minimum diameter multiplied by 100%. A dichotomous TBAR variable was created based on the median value (below or above 7.9%). Participants with EF ≤ 40% were considered HFrEF and those with EF ≥ 50% were considered HFpEF. Cox proportional hazards regression models were used to calculate hazard ratios (HR) and 95% confidence intervals (CI). Over a mean follow-up period of 12.5 years, incident HF was diagnosed in 250 participants: 98 classified as HFrEF, 106 as HFpEF, and 46 with unknown or borderline EF (41-49%). Crude analysis revealed that those with TBAR below the median had a significantly greater risk of HF (HR 1.46; 95% CI 1.13-1.88, p < 0.01) and HFrEF (HR 1.61; 95% CI 1.07-2.43, p < 0.05). Following adjustment for known HF risk factors (e.g., age, sex, race, blood pressure), the strength of these relationships was attenuated. Borderline significant results were revealed in those with HFpEF (HR 1.43; 95% CI 0.97-2.12, p = 0.06). Kaplan-Meier curves suggest significantly lower risks of developing HF and HFrEF in those with TBAR above the median (log-rank p ≤ 0.05 for both). When examined as a continuous variable, with a cut point of 50% for EF, every 1-standard deviation (9.7%) increase in TBAR resulted in a 19 and 29% decrease in risk of HF (p < 0.05) and HFrEF (p = 0.05), respectively. Lower TBAR values were associated with higher rates of incident HF and HFrEF, suggesting a possible role of endothelial dysfunction in HF pathogenesis. The impact of other known HF risk factors may mediate this relationship, thus further research is warranted.

Association of Sleep Quality With Greater Left Ventricular Mass in Children Aged 9 to 11 Years.

OBJECTIVE: Research has consistently found associations between sleep characteristics and cardiovascular disease risk in children, adolescents, and adults. Although primarily investigated in clinical samples (e.g., in those with sleep disorders), greater left ventricular mass is associated with poor sleep quality in nonclinical adult populations as well; however, this has not been evaluated in children or adolescents. Our study aim was to consider the relationship between objectively measured sleep characteristics and left ventricular mass in children. METHODS: We assessed sleep and cardiac structure in a biracial sample of 9- to 11-year-old children (n = 176; 41% White, 59% Black; 50% female). Sleep was assessed with actigraphy for five nights. Cardiac dimensions were assessed using echocardiography. RESULTS: After adjusting for covariates, we found that poor sleep quality was associated with significantly greater left ventricular mass (ß = 0.13, t(167) = 2.14, p = .034, Cohen d = 0.16, for activity during sleep; ß = 0.15, t(167) = 2.43, p = .016, Cohen d = 0.18, for sleep fragmentation). Other cardiac dimensions (namely, relative wall thickness and right ventricular dimension) were also significantly associated with sleep characteristics. Notably, associations did not differ as a function of sex or race. CONCLUSIONS: The present findings are novel and unique because no prior reports have systematically documented the association between poor sleep quality with potentially detrimental cardiac remodeling in a nonclinical sample of children. However, the novelty and importance of these findings require additional research for confirmation.

Linking metal (Pb, Hg, Cd) industrial air pollution risk to blood metal levels and cardiovascular functioning and structure among children in Syracuse, NY.

BACKGROUND: Exposure to air pollution has been linked to individual health effects in occupational environments and communities proximate to air pollution sources. Use of estimated chemical concentrations from the Risk Screening Environmental Indicators (RSEI) model, derived from the Toxics Release Inventory, can help approximate some contributions to individual lifetime exposure to risk from air pollution and holds potential for linkages with specific health outcome data. OBJECTIVES: Our objectives were: (1) use regression modeling to test for associations between observed blood metal concentrations in children and RSEI total air concentrations of the same metals released from proximate manufacturing facilities; (2) determine the relative contribution of RSEI air pollution to blood metal concentrations; and (3) examine associations between chronic metal exposure and cardiovascular functioning and structure in study participants. METHODS: Using data synthesis methods and regression modeling we linked individual blood-based levels of lead, mercury, and cadmium(Pb, Hg, Cd) and cardiovascular functioning and structure to proximate industrial releases of the same metals captured by the Environmental Protection Agency's (EPA) RSEI geographic microdata. RESULTS: We found that RSEI-derived ground-level ambient air concentrations of Hg and Cd were a significant predictor of blood metal levels, when controlling for covariates and other exposure variables. In addition to associations with blood metal findings, RSEI concentrations also predicted cardiovascular dysfunction and risk including changes in left-ventricular mass, blood pressure, and heart rate. DISCUSSION: Right-to-know data, such as EPA's RSEI, can be linked to objective health outcomes, rather than simply serving as a non-specific risk estimate. These data can serve as a proxy for hazard exposure and should be used more widely to understand the dynamics of environmental exposure. Furthermore, since these data are both a product of and contribute to regulatory decision making, they could serve as an important link between disease risk and translation-orientated national environmental health policy.

Sex differences in cardiovascular adaptations in recreational marathon runners.

INTRODUCTION: There are well-established sex differences in central hemodynamic and cardiac adaptations to endurance exercise; however, controversial evidence suggests that excessive endurance exercise may be related to detrimental cardiovascular adaptations in marathoners. PURPOSE: To examine left ventricle (LV) structure, LV function, 24-h central hemodynamics and ventricular-vascular coupling in male and female marathoners and recreationally active adults. METHODS: 52 marathoners (41 ± 5 years, n = 28 female, completed 6 ± 1 marathons/3 years) and 49 recreationally active controls (42 ± 5 years, n = 25 female) participated in the study. Three-Dimensional Echocardiography (3DE) was used to measure LV mass index and LV longitudinal (LS) circumferential (CS), area (AS), and radial strain (RS). An ambulatory blood pressure (BP) cuff was used to measure 24-h central hemodynamics (BP, pulse wave velocity, PWV, wave reflection index, RIx). Hemodynamic and 3DE measures were combined to derive the ratio of arterial elastance (Ea) to ventricular elastance (Elv) as a global measure of ventricular-vascular coupling. RESULTS: There were no sex or group differences in LS, CS, AS, and RS (p > 0.05). Females marathoners had similar aortic BP (116 ± 9 vs. 113 ± 1 mmHg), and PWV (5.9 ± 0.5 vs. 5.9 ± 1.1 m/s) compared to female controls but lower aSBP (116 ± 9 vs. 131 ± 10 mmHg) and PWV (5.9 ± 0.5 vs. 6.2 ± 0.5 m/s) compared to male marathoners (p < 0.05). Female marathoners had lower Ea/Elv than female controls (0.67 ± 0.20 vs. 0.93 ± 0.36) and male marathoners (0.67 ± 0.20 vs. 0.85 ± 0.42, p < 0.05). CONCLUSIONS: Women that have completed multiple marathons do not have reduced LV function or increased aortic stiffness and may have better ventricular-vascular coupling compared to male marathoners and their female untrained counterparts.

The Inverse Association of Muscular Strength with Carotid Intima-media and Extra-media Thickness in Women.

The purpose of this study was to determine the relationship between strength and atherosclerotic cardiovascular disease (CVD) risk in young women. Carotid intima-media thickness (IMT) and extra-media thickness (EMT) were used as measures of subclinical atherosclerosis and CVD risk. Muscular strength, IMT, and EMT were measured in 70 young women (mean age=21±4 years). Strength was determined using a handgrip dynamometer and expressed relative to body mass. IMT and EMT were measured using ultrasonography of the left common carotid artery. Objectively measured moderate-vigorous physical activity (MVPA) was assessed with accelerometry. Higher relative handgrip strength was associated with lower IMT (r=-0.23; p<0.05) and lower EMT (r=-0.27; p<0.05). Associations between relative handgrip strength and IMT (r=-0.24) as well as EMT (r=-0.25) remained significant after adjusting for potential confounders including traditional CVD risk factors and MVPA (p<0.05). These results show that there is an inverse association between handgrip strength with carotid IMT and EMT in young women. Muscular strength may reduce CVD risk in young women via favorable effects on subclinical carotid atherosclerosis independent of physical activity.

Influence of sprint exercise on aortic pulse wave velocity and femoral artery shear patterns.

PURPOSE: Aortic stiffness may affect shear patterns in the peripheral vasculature. This study examined if sprint exercise, which typically increases aortic stiffness is associated with increased peripheral retrograde blood flow and impaired microvascular function. METHODS: Twenty participants (10 women; age: 27 ± 5 years) underwent arterial stiffness, shear rate, and microvascular function assessment at three time points: baseline; following time control; ~ 2 min post a 30-s cycle ergometer sprint against 7.0% body mass. Aortic stiffness was assessed using carotid-femoral pulse wave velocity (cfPWV). Superficial femoral artery (SFA) diameter and blood velocity were assessed using Doppler-ultrasound and were used to calculate shear rates and resistance index (RI). SFA wave reflections were obtained via wave intensity analysis. Vastus medialis microvascular function was measured as tissue saturation index reactivity pre-post exercise via near-infrared spectroscopy. RESULTS: cfPWV increased by + 0.8 ± 0.7 m·s-1 following exercise (p < 0.001). Retrograde shear was reduced following exercise compared with time control (- 4.9 ± 3.8 s-1; p < 0.001), while tissue saturation index was increased post-exercise from baseline (+ 2.3 ± 4.6%; p = 0.04). Reductions in SFA wave reflections (- 1.70 ± 1.96 aU) and RI (- 0.17 ± 0.13 aU) were also noted following exercise (p < 0.001). CONCLUSION: These data suggest sprint exercise-mediated changes in peripheral shear patterns and microvascular function in the exercised vasculature occur independent from increases in aortic stiffness. Exercise-induced reductions in SFA retrograde shear may be related to decreased wave reflections and peripheral vascular resistance.

Effect of external compression on femoral retrograde shear and microvascular oxygenation in exercise trained and recreationally active young men.

INTRODUCTION: Retrograde shear causes endothelial damage and is pro-atherogenic. The purpose of our study was to examine the impact of vascular remodeling from habitual exercise training on acute changes in retrograde shear and microvascular oxygenation (SMO2) induced via 30 min of external compression. METHODS: Participants included 11 exercise trained (ET) men (Division I track athletes; age 20 ± 3 years) and 18 recreationally active (RA) men (age 23 ± 5 years). Near-infrared spectroscopy (NIRS) was used to measure vastus medialis SMO2. Doppler-ultrasound was used to assess SFA intima-media thickness, diameter and flow velocity to derive retrograde shear. Vascular measures were made at baseline (BASELINE), during a sham condition (calf compression to 5 mmHg, SHAM) and during the experimental condition (calf compression to 60 mmHg, EXP). RESULTS: Compared to RA, ET had larger SFA diameters (0.66 ± 0.06 vs 0.58 ± 0.06 cm, p < 0.05) and lower SFA IMT (0.33 ± 0.03 vs 0.36 ± 0.07 mm, p < 0.05). Retrograde shear increased similarly in both groups during EXP (p < 0.05) but ET men had lower overall retrograde shear during the conditions (BASELINE 75.8 ± 26.8 vs EXP 88.2 ± 16.9 s-1) compared to RA men (BASELINE 84.4 ± 23.3 vs EXP 106.4 ± 19.6 s-1p < 0.05). There was a similar increase in SMO2 from BASELINE to SHAM (ET + 8.1 ± 4.8 vs RA + 6.4 ± 9.7%) and BASELINE to EXP (ET + 8.7 ± 6.4 vs RA + 7.1 ± 9.0%) in both groups. CONCLUSION: Beneficial vascular remodeling in ET men is associated with lower retrograde shear during external compression. Acute increases in retrograde shear with external compression do not detrimentally impact microvascular oxygenation.

Effects of Prolonged Dietary Curcumin Exposure on Skeletal Muscle Biochemical and Functional Responses of Aged Male Rats.

Oxidative stress resulting from decreased antioxidant protection and increased reactive oxygen and nitrogen species (RONS) production may contribute to muscle mass loss and dysfunction during aging. Curcumin is a phenolic compound shown to upregulate antioxidant defenses and directly quench RONS in vivo. This study determined the impact of prolonged dietary curcumin exposure on muscle mass and function of aged rats. Thirty-two-month-old male F344xBN rats were provided a diet with or without 0.2% curcumin for 4 months. The groups included: ad libitum control (CON; n = 18); 0.2% curcumin (CUR; n = 18); and pair-fed (PAIR; n = 18) rats. CUR rats showed lower food intake compared to CON, making PAIR a suitable comparison group. CUR rats displayed larger plantaris mass and force production (vs. PAIR). Nuclear fraction levels of nuclear factor erythroid-2 related-factor-2 were greater, and oxidative macromolecule damage was lower in CUR (vs. PAIR). There were no significant differences in measures of antioxidant status between any of the groups. No difference in any measure was observed between CUR and CON rats. Thus, consumption of curcumin coupled with reduced food intake imparted beneficial effects on aged skeletal muscle. The benefit of curcumin on aging skeletal muscle should be explored further.

Menstrual phase and the vascular response to acute resistance exercise.

INTRODUCTION: Aerobic exercise has a favorable effect on systemic vascular function, reducing both central (large elastic artery) and peripheral (smaller muscular artery) stiffness. The effects of resistance exercise (RE) on arterial stiffness are more complex. Acute RE increases central artery stiffness while decreasing peripheral stiffness. To date, the majority of studies have been performed in predominantly male participants. PURPOSE: To examine the effect of acute RE on central and peripheral arterial stiffnesses in women, a secondary purpose was to explore the influence of cyclic changes in estrogen status across the menstrual cycle on the arterial response to acute RE. METHODS: 18 healthy women [28 ± 7 years, body mass index (BMI) 22.6 ± 2.9 kg/m2] completed an acute RE bout during the early follicular and the early luteal phase of their menstrual cycle. Salivary 17ß-Estradiol concentration was measured during each phase, using a passive drool technique. Pulse-wave velocity (PWV) was obtained from the carotid-femoral and carotid-radial pulse sites to measure central and peripheral stiffness, respectively, using applanation tonometry. PWV was measured at rest, immediately, 10, 20, and 30 min post-RE. RESULTS: 17ß-Estradiol concentration was significantly lower in the early follicular vs. the early luteal phase of the menstrual cycle (1.78 ± 0.51 vs. 2.40 ± 0.26 pg/ml, p = 0.01). Central PWV significantly increased (p < 0.05) and peripheral PWV significantly decreased (p < 0.05) post-RE in both the early follicular and early luteal phases. No phase-by-time interaction was detected for either vascular segment (p > 0.05). CONCLUSION: Women experience increases in central arterial stiffness and reductions in peripheral arterial stiffness following acute RE. Menstrual cycle phase may not influence changes in arterial stiffness in response to acute RE.

Aortic stiffness, central pulse pressure and cognitive function following acute resistance exercise.

INTRODUCTION: While resistance exercise (RE) is known to be beneficial for overall health, one bout of RE acutely increases aortic stiffness and pulse pressure (PP). Increases in aortic stiffness and PP in a setting of aging has been shown to detrimentally impact cognitive function. This study examined whether increased aortic stiffness and PP from an acute bout of RE is associated with cognitive function. METHODS: Thirty-five participants (21 ± 2 years) underwent cognitive testing before and after either an acute bout of RE or a non-exercise time-control condition. Cognitive function was assessed as reaction time and accuracy during memory recognition, attention (Flanker) and working memory (N-back) tasks. Aortic stiffness and PP were measured via pulse wave velocity (PWV) and pulse wave analysis, respectively, using a brachial oscillometric device. RESULTS: There were significant increases in aortic PWV and aortic PP following RE (p < 0.05) with no change in PWV or PP following the non-exercise control condition (p > 0.05). There was no change in accuracy metrics (% hits) across conditions for any cognitive task (p > 0.05). There was a condition-by-time interaction for reaction time for the memory task (p < 0.05) driven by a significant decrease in reaction times following RE (p < 0.05) with no change in reaction time following the non-exercise control (p > 0.05). CONCLUSION: Functional increases in aortic stiffness and pulse pressure following acute RE occur in the absence of detrimental changes in cognitive function in young, healthy adults.

Parents' Beliefs About Physical Activity for Their Children With Visual Impairments.

Despite having the desire to become physically active as a family, parents of children with visual impairments often lack the skills and resources needed to provide appropriate physical activities (PAs) for their children. The purpose of this study was to explore the intentions of parents of children with visual impairments toward including their children in PAs after participating in a PA program. In this descriptive qualitative study, the participants were 10 parents of children with visual impairments. A series of workshops were designed to provide parents with the skills and resources needed to promote PA for their family. Upon completion of the workshops, parents took part in one-on-one semistructured interviews that were subsequently transcribed and analyzed using a thematic line-by-line process. Two interdependent themes emerged from the data analyses: (a) eye-opening experiences and (b) transformed, more hopeful, and optimistic outlook. The results revealed that through the PA intervention, parents learned teaching strategies that were intended to increase their PA opportunities and garnered resources that allowed them to teach their children to participate in PA.

Racial Differences in Aortic Stiffness in Children.

OBJECTIVE: To investigate racial differences in central blood pressure and vascular structure/function as subclinical markers of atherosclerotic cardiovascular disease in children. STUDY DESIGN: This cross-sectional study recruited 54 African American children (18 female, 36 male; age 10.5 ± 0.9 years) and 54 white children (27 female, 26 male; age 10.8 ± 0.9 years) from the Syracuse City community as part of the Environmental Exposures and Child Health Outcomes study. Participants underwent blood lipid and vascular testing on 2 separate days. Carotid artery intima-media thickness and aortic stiffness were measured by ultrasonography and carotid-femoral pulse wave velocity, respectively. Blood pressure was assessed at the brachial artery and estimated in the carotid artery using applanation tonometry. RESULTS: African American children had significantly higher pulse wave velocity (4.8 ± 0.8 m/s) compared with white children (4.2 ± 0.7 m/s; P < .05), which remained significant after adjustment for confounding variables including socioeconomic status. African American children had significantly higher intima-media thickness (African American 0.41 ± 0.06, white 0.39 ± 0.05 mm), and carotid systolic blood pressure (African American 106 ± 11, white 102 ± 8 mm Hg; P < .05) compared with white children, although these racial differences were no longer present after covariate adjustments for height. CONCLUSIONS: Racial differences in aortic stiffness are present in childhood. Our findings suggest that racial differences in subclinical cardiovascular disease occur earlier than previously recognized.

Carotid artery reactivity during sympathetic activation following acute resistance exercise.

OBJECTIVE: Acute resistance exercise has been shown to reduce brachial endothelial function. Whether there are concomitant reductions in carotid endothelial function remains unexplored. METHODS: Cold pressor test-mediated vasodilation of the carotid artery was used to assess carotid endothelial function in 15 young and healthy participants (age 26 ± 1 years, body mass index 24 ± 1 kg/m2) after acute resistance exercise or an inactive time control condition. RESULTS: Acute resistance exercise had no effect on the cold pressor test-mediated vasodilation compared to time control (5.8 ± 0.8 vs 6.2 ± 0.9% dilation, p > 0.05). INTERPRETATION: Carotid endothelial function may not be compromised following acute resistance exercise in young healthy adults.

Effect of acute nitrate ingestion on central hemodynamic load in hypoxia.

UNLABELLED: Acute hypoxia results in local vasodilation that may temporarily unload the left ventricle (LV) through nitric oxide (NO)-mediated mechanisms. Whether increasing NO levels augments LV unloading and improves ventricular-vascular coupling in hypoxia remains unknown. PURPOSE: Investigate the effect of acute nitrate ingestion on central hemodynamic load in hypoxia. METHODS: 20 Healthy men (23 ± 3 yrs, BMI 24.6 ± 2.8 kg m(-2)) consumed 70 mL of either a) 0.45 g nitrate (NIT) or b) an inert placebo (PLA) prior to 105 min of normobaric hypoxia (11.6 ± 0.1%) in this randomized, double-blind, crossover-design study. Wave reflection index (RIX; ratio of forward to reflected wave pressure), augmentation index (AIX75) and pulse wave velocity were calculated as measures of wave reflection magnitude and aortic stiffness, respectively, from the aortic blood pressure (BP) waveform. LV wasted pressure effort (WPE) was calculated as an index of LV work due to wave reflections. Subendocardial viability ratio (SEVR) was assessed a measure of myocardial O2 supply/demand ratio. RESULTS: Aortic diastolic BP decreased in hypoxia compared to normoxia (p < 0.05). Aortic RIX, AIX75, and LV WPE significantly decreased in hypoxia compared to normoxia (p < 0.05). Aortic systolic BP, SEVR, and PWV were unaffected by hypoxia (p > 0.05). Compared to placebo, nitrate ingestion did not significantly alter central hemodynamics in hypoxia (p > 0.05). CONCLUSIONS: Acute hypoxic exposure unloads the LV (WPE, AIX75, and RIX) without disturbing myocardial O2 supply-demand ratio (SEVR). Reductions in LV work with hypoxia are likely due to reductions in pressure from wave reflections as hypoxia had negligible effects on aortic stiffness. Nitrate ingestion did not affect the central hemodynamic response to acute systemic hypoxia.

Evidence for natural hybridization between native and introduced lineages of Phragmites australis in the Chesapeake Bay watershed.

PREMISE OF THE STUDY: The introduction of nonnative taxa into areas occupied by conspecifics can lead to local extinction of native taxa via habitat modification and competitive dominance, and be exacerbated by outbreeding depression or the formation of invasive hybrid lineages following intraspecific gene flow. The expansion of Eurasian Phragmites australis into tidal wetlands of North America has been accompanied by a dramatic decline of native P. australis, with few relic populations remaining along the Atlantic coastline of the United States, particularly in the Virginia portion of the Chesapeake Bay. METHODS: We sampled populations from the York River and its two major tributaries to determine the pattern of Phragmites invasion and identify remnant native populations that warrant conservation. We used chloroplast DNA haplotypes and nuclear DNA microsatellite profiles to classify individuals as belonging to the native or introduced lineage. KEY RESULTS: Although native Phragmites stands were identified in the brackish upstream reaches of the two York River tributaries, the majority of Phragmites stands surveyed contained the introduced lineage. We also identified a single putative hybrid plant, based on its microsatellite profile. This plant possessed the native cpDNA haplotype and was located in an otherwise native Phragmites stand that is adjacent to an isolated patch of introduced Phragmites. CONCLUSIONS: Although evidence of field hybridization between native and introduced lineages of Phragmites in North America is still relatively rare, the continued encroachment of the introduced lineage into native wetlands may increase the likelihood of future hybrid formation. Careful genetic monitoring to identify remnant native and potential hybrid Phragmites is essential for prioritizing ongoing management efforts.

Vascular and central hemodynamic changes following exercise-induced heat stress.

This study examined the effects of moderate exercise-induced heat stress (EIHS) on vascular function, central hemodynamic load and indices of coronary perfusion. Vascular-hemodynamic measures were collected in 12 healthy men (aged 22±3 years) pre and post 100 minutes of moderate, intermittent exercise in two randomized conditions: heat stress (HS; wearing firefighter personal protective equipment (PPE)), and no heat stress (NHS; wearing a cooling shirt and equivalent PPE weight). Aortic blood pressure, reflected wave pressure (Pb), systolic (SPTI) and diastolic pressure time-integral (DPTI), and aortic stiffness were assessed before and after each condition. SPTI was significantly greater, and DPTI and Pb were significantly lower for HS-post compared to NHS-post (p<0.05). Pulse wave velocity was not different between conditions. In conclusion, EIHS does not affect aortic stiffness, but increases indices of myocardial work and reduces indices of coronary perfusion which may be related to chronotropic responses to EIHS. The mismatch between oxygen demand and oxygen supply may increase cardiac vulnerability to ischemia during strenuous work in the heat.