Social and Behavioral Sciences Commons^™

Plasma Fetuin-A Concentrations In Young And Older High- And Low-Active Men, Nathan T. Jenkins, Jennifer A. Mckenzie, James M. Hagberg, Sarah Witkowski

Exercise and Sport Studies: Faculty Publications

Fetuin-A is a liver-derived factor that may play a role in insulin resistance and age-related chronic diseases (eg, type 2 diabetes mellitus and cardiovascular [CV] disease). Regular exercise improves CV risk and insulin sensitivity; however, it is unknown whether chronic exercise training is related to circulating levels of fetuin-A. Therefore, this study examined whether plasma fetuin-A levels were related to age and chronic physical activity in men. We hypothesized that chronic physical activity would be related to lower plasma fetuin-A levels in younger and older men. In healthy high-active (HI) and low-active (LO) young (HI, n = 7; LO, n …

Akt1 G205t Genotype Influences Obesity-Related Metabolic Phenotypes And Their Responses To Aerobic Exercise Training In Older Caucasians, Jennifer A. Mckenzie, Sarah Witkowski, Andrew T. Ludlow, Stephen M. Roth, James M. Hagberg

Exercise and Sport Studies: Faculty Publications

As part of the insulin signalling pathway, Akt influences growth and metabolism. The AKT1 gene G205T (rs1130214) polymorphism has potential functional effects. Thus, we determined whether the G205T polymorphism influences metabolic variables and their responses to aerobic exercise training. Following dietary stabilization, healthy, sedentary, 50- to 75-year-old Caucasian men (n= 51) and women (n= 58) underwent 6 months of aerobic exercise training. Before and after completing the intervention, dual-energy X-ray absorptiometry was used to measure percentage body fat, computed tomography to measure visceral and subcutaneous fat, and oral glucose tolerance testing to measure glucose total area under the curve (AUC), …

High-Frequency Electrically Stimulated Skeletal Muscle Contractions Increase P70S6k Phosphorylation Independent Of Known Igf-I Sensitive Signaling Pathways, Sarah Witkowski, Richard M. Lovering, Espen E. Spangenburg

Exercise and Sport Studies: Faculty Publications

Insulin-like growth factor (IGF-I) is hypothesized to be a critical upstream regulator of mammalian target of rapamycin (mTOR)-regulated protein synthesis with muscle contraction. We utilized a mouse model that expresses a skeletal muscle specific dominant-negative IGF-I receptor to investigate the role of IGF-I signaling of protein synthesis in response to unilateral lengthening contractions (10 sets, 6 repetitions, 100. Hz) at 0 and 3. h following the stimulus. Our results indicate that one session of high frequency muscle contractions can activate mTOR signaling independent of signaling components directly downstream of the receptor.

Thrombin And Exercise Similarly Influence Expression Of Cell Cycle Genes In Cultured Putative Endothelial Progenitor Cells, Michael M. Lockard, Sarah Witkowski, Nathan T. Jenkins, Espen E. Spangenburg, Thomas O. Obisesan, James M. Hagberg

Exercise and Sport Studies: Faculty Publications

Acute exercise and exercise training may influence putative endothelial progenitor cell (EPC) number and colony forming units (CFU-ECs), although the mechanisms remain unclear. This study examined the effects of in vitro thrombin supplementation and acute exercise on CFU-EC gene expression, associated with cellular proliferation and differentiation. The effect of habitual physical activity was evaluated through analysis of EPCs from chronically high- and low-active men. Participants were healthy high- and low-active men (n = 23), aged 55-80 yr. Circulating CD34+/VEGFR2+ number, CFU-ECs, plasma prothrombin fragment (F1+2), and thrombin-antithrombin III were measured at rest and after 30 min of exercise. Gene expression …

Endurance Exercise Training Effects On Body Fatness, Vo2max Hdl-C Subfractions, And Glucose Tolerance Are Influenced By A Plin Haplotype In Older Caucasians, Nathan T. Jenkins, Jennifer A. Mckenzie, Coleen M. Damcott, Sarah Witkowski, James M. Hagberg

Exercise and Sport Studies: Faculty Publications

Perilipins are lipid droplet-coating proteins that regulate intracellular lipolysis in adipocytes. A haplotype of two perilipin gene (PLIN) single nucleotide polymorphisms, 13041A>G and 14995A>>T, has been previously associated with obesity risk. Furthermore, the available data indicate that this association may be modified by sex. We hypothesized that this haplotype would associate with body fatness, aerobic fitness, and a number of cardiovascular (CV) risk factor phenotypes before and after a 6-mo endurance exercise training program in sedentary older Caucasians. The major haplotype group (13041A/14995A; n = 57) had significantly lower body mass index (BMI) and body fatness compared with …

Relationship Between Circulating Progenitor Cells, Vascular Function And Oxidative Stress With Long-Term Training And Short-Term Detraining In Older Men, Sarah Witkowski, Michael M. Lockard, Nathan T. Jenkins, Thomas O. Obisesan, Espen E. Spangenburg, James M. Hagberg

Exercise and Sport Studies: Faculty Publications

Exercise may contribute to the maintenance of vascular function via enhanced liberation and action of bone-marrow-derived progenitor cells. Activity related changes in oxidative stress may also influence the number and function of these cells. In the present study, we sought to determine (i) whether adaptations in reactive hyperaemic FBF (forearm blood flow) response associated with long-term endurance exercise and short-term detraining were related to resting putative progenitor cell number and function, and (ii) whether oxidative stress affected these factors. Participants included men with a history of more than 30 years of moderate-to-high-intensity exercise (HI group) and healthy low-active age- and …

Effects Of Acute And Chronic Endurance Exercise On Intracellular Nitric Oxide In Putative Endothelial Progenitor Cells: Role Of Napdh Oxidase, Nathan T. Jenkins, Sarah Witkowski, Espen E. Spangenburg, James M. Hagberg

Exercise and Sport Studies: Faculty Publications

We sought to delineate the effects of acute and chronic exercise on the regulation of intracellular nitric oxide (NOi) production in putative endothelial progenitor cells (EPCs). Putative EPC colony-forming units (CFUEC) were cultured from blood drawn before and after 30 min of treadmill exercise at 75% of maximal oxygen uptake in active (n = 8) and inactive (n = 8) men. CFU-EC were similar between groups at baseline, but increased after exercise in active men only (P = 0.04). CFU-EC expressed lower NADPH oxidase subunit gp91 phox mRNA and elevated endothelial nitric oxide synthase mRNA in active relative to inactive …

Same-Sex Social Behavior In Meadow Voles: Multiple And Rapid Formation Of Attachments, Annaliese K. Beery, David M. Routman, Irving Zucker

Neuroscience: Faculty Publications

Adult meadow voles (Microtus pennsylvanicus) are solitary in the spring–summer reproductive season, but during winter months, females and males are socially tolerant and aggregate in groups. This behavioral difference is triggered by day length: female meadow voles housed in short, winterlike day lengths form same-sex partner preferences, whereas those housed in long, summer-like day lengths are less social. The present study demonstrates that same-sex social attachments in short day lengths are not exclusive; females formed concurrent attachments with more than one individual, and with non-kin as well as siblings. Partner preferences between females were established within one day of cohousing …

Maternal Photoperiodic History Affects Offspring Development In Syrian Hamsters, Annaliese K. Beery, Matthew J. Paul, Irving Zucker

Neuroscience: Faculty Publications

During the first 7 weeks of postnatal life, short day lengths inhibit the onset of puberty in many photoperiodic rodents, but not in Syrian hamsters. In this species, timing of puberty and fecundity are independent of the early postnatal photoperiod. Gestational day length affects postnatal reproductive development in several rodents; its role in Syrian hamsters has not been assessed. We tested the hypothesis that cumulative effects of pre- and postnatal short day lengths would restrain gonadal development in male Syrian hamsters. Males with prenatal short day exposure were generated by dams transferred to short day lengths 6 weeks, 3 weeks, …

Day Length And Estradiol Affect Same-Sex Affiliative Behavior In The Female Meadow Vole, Annaliese K. Beery, Theresa J. Loo, Irving Zucker

Neuroscience: Faculty Publications

Non-sexual social bonding between adult mammals remains poorly understood, despite its importance in many species. Female meadow voles are territorial and nest alone in long summer day lengths when circulating estradiol concentrations are high, but cohabit in groups in short winter photoperiods when estradiol secretion is low. The influence of day length and estradiol on same-sex huddling behavior was assessed in adult female pairs housed together in long day lengths (LDs) or short day lengths (SDs) from weaning. The behavior of intact, ovariectomized, and estradiol-treated ovariectomized females from each photoperiod was assessed during 3 hour partner preference tests. Intact SD …

Exercise, Apoe, And Working Memory: Meg And Behavioral Evidence For Benefit Of Exercise In Epsilon4 Carriers, Sean P. Deeny, David Poeppel, Jo B. Zimmerman, Stephen M. Roth, Josef Brandauer, Sarah Witkowski, Joseph W. Hearn, Andrew T. Ludlow, José L. Contreras-Vidal, Jason Brandt, Bradley D. Hatfield

Exercise and Sport Studies: Faculty Publications

Performance on the Sternberg working memory task, and MEG cortical response on a variation of the Sternberg task were examined in middle-aged carriers and non-carriers of the APOE ε4 allele. Physical activity was also assessed to examine whether exercise level modifies the relationship between APOE genotype and neurocognitive function. Regression revealed that high physical activity was associated with faster RT in the six- and eight-letter conditions of the Sternberg in ε4 carriers, but not in the non-carriers after controlling for age, gender, and education (N = 54). Furthermore, the MEG analysis revealed that sedentary ε4 carriers exhibited lower right temporal …

Relationship Between Physical Activity Level, Telomere Length, And Telomerase Activity, Andrew T. Ludlow, Jo B. Zimmerman, Sarah Witkowski, Joe W. Hearn, Bradley D. Hatfield, Stephen M. Roth

Exercise and Sport Studies: Faculty Publications

The purpose of this study was to examine the relationship of exercise energy expenditure (EEE) with both telomere length and telomerase activity in addition to accounting for hTERT C-1327T promoter genotype.

Progenitor Cells And Age: Can We Fight Aging With Exercise?, Sarah Witkowski, James M. Hagberg

Exercise and Sport Studies: Faculty Publications

No abstract provided.

Transcranial Doppler Estimation Of Cerebral Blood Flow And Cerebrovascular Conductance During Modified Rebreathing, Jurgen A.H.R. Claassen, Rong Zhang, Qi Fu, Sarah Witkowski, Benjamin D. Levine

Exercise and Sport Studies: Faculty Publications

Clinical transcranial Doppler assessment of cerebral vasomotor reactivity (CVMR) uses linear regression of cerebral blood flow velocity (CBFV) vs. end-tidal CO2 (PETCO2) under steady-state conditions. However, the cerebral blood flow (CBF)-PETCO2 relationship is nonlinear, even for moderate changes in CO2. Moreover, CBF is increased by increases in arterial blood pressure (ABP) during hypercapnia. We used a modified rebreathing protocol to estimate CVMR during transient breath-by-breath changes in CBFV and PETCO2. Ten healthy subjects (6 men) performed 15 s of hyperventilation followed by 5 min of rebreathing, with supplemental O2 to maintain arterial oxygen saturation constant. To minimize effects of changes …

Sex Differences In The Onset Of Seasonal Reproductive Quiescence In Hamsters, Annaliese K. Beery, Justin J. Trumbull, Jyeming M. Tsao, Ruth M. Costantini, Irving Zucker

Neuroscience: Faculty Publications

Day length is the primary cue used by many mammals to restrict reproduction to favourable spring and summer months, but it is unknown for any mammal whether the seasonal loss of fertility begins at the same time and occurs at the same rate in females and males; nor it established whether the termination of mating behaviour in males and females coincides with the loss of fertility. We speculated that females, owing to their greater energetic investment in reproduction, are the limiting sex in terminating offspring production in short days (SDs). Oestrous cycles and production of young were monitored in Syrian …

Cerebral Hemodynamics After Short- And Long-Term Reduction In Blood Pressure In Mild And Moderate Hypertension, Rong Zhanf, Sarah Witkowski, Qi Fu, Jurgen A.H.R. Claassen, Benjamin D. Levine

Exercise and Sport Studies: Faculty Publications

This study tested the hypothesis that acute reduction in blood pressure (BP) at the initial stage of antihypertensive therapy compromises brain perfusion and dynamic cerebral autoregulation in patients with hypertension. Cerebral blood flow velocity and BP were measured in patients with mild and moderate hypertension and in healthy volunteers at baseline upon reduction of BP within 1 to 2 weeks of administration of losartan/hydrochlorothiazide and after 3 to 4 months of treatment. The transfer function between beat-to-beat changes in BP and cerebral blood flow velocity was estimated to assess dynamic autoregulation. After 1 to 2 weeks of treatment, BP was …

Effects Of Gender And Hypovolemia On Sympathetic Neural Responses To Orthostatic Stress, Qi Fu, Sarah Witkowski, Kazunobu Okazaki, Benjamin D. Levine

Exercise and Sport Studies: Faculty Publications

We tested the hypothesis that women have blunted sympathetic neural responses to orthostatic stress compared with men, which may be elicited under hypovolemic conditions. Muscle sympathetic nerve activity (MSNA) and hemodynamics were measured in eight healthy young women and seven men in supine position and during 6 min of 60° head-up tilt (HUT) under normovolemic and hypovolemic conditions (randomly), with ∼4-wk interval. Acute hypovolemia was produced by diuretic (furosemide) administration ∼2 h before testing. Orthostatic tolerance was determined by progressive lower body negative pressure to presyncope. We found that furosemide produced an ∼13% reduction in plasma volume, causing a similar …

Persistent Sympathetic Activation During Chronic Antihypertensive Therapy, Qi Fu, Rong Zhang, Sarah Witkowski, Armin Arbab-Zadeh, Anand Prasad, Kazunobu Okazaki, Benjamin D. Levine

Exercise and Sport Studies: Faculty Publications

Previous studies have demonstrated that antihypertensive treatment resets baroreflex control of heart rate (HR) and increases cardiac vagal baroreflex sensitivity. However, it is uncertain whether baroreflex control of muscle sympathetic nerve activity (MSNA) also resets after treatment. We tested the hypothesis that chronic antihypertensive therapy alters baroreflex regulation of MSNA in patients with untreated moderate hypertension. Seven newly diagnosed patients with systolic blood pressure (BP) of 159 5 mm Hg (mean SE) and diastolic BP of 103 4 mm Hg were studied before and after 1 to 2 weeks ´ and 3 months (chronic) of antihypertensive treatment with losartan– hydrochlorothiazide …

Vasoconstrictor Reserve And Sympathetic Neural Control Of Orthostasis, Qi Fu, Sarah Witkowski, Benjamin D. Levine

Exercise and Sport Studies: Faculty Publications

Background—We tested the hypothesis that individual variability in orthostatic tolerance is dependent on the degree of neural and vasomotor reserve available for vasoconstriction.

Methods and Results—Muscle sympathetic nerve activity (MSNA) and hemodynamics were measured in 12 healthy young volunteers during 60° head-up tilt (HUT), followed by a cold pressor test (CPT) in HUT. Orthostatic tolerance was determined by progressive lower-body negative pressure (LBNP) to presyncope. The same protocols were performed randomly in normovolemic and hypovolemic conditions. We found that mean arterial pressure increased and stroke volume decreased, whereas heart rate (HR), MSNA, and total peripheral resistance (TPR) increased during HUT …

Inhibition Of Nitric Oxide Inhibition Of Nitric Oxide Synthase Does Not Alter Dynamic Cerebral Autoregulation In Humans, Rong Zhang, Thad E. Wilson, Sarah Witkowski, Jian Cui, Craig G. Crandall, Benjamin D. Levine

Exercise and Sport Studies: Faculty Publications

The aim of this study was to determine whether inhibition of nitric oxide synthase (NOS) alters dynamic cerebral autoregulation in humans. Beat-to-beat blood pressure (BP) and cerebral blood flow (CBF) velocity (transcranial Doppler) were measured in eight healthy subjects in the supine position and during 60° head-up tilt (HUT). NOS was inhibited by intravenous N G-monomethyl-L-arginine (L-NMMA) infusion. Dynamic cerebral autoregulation was quantified by transfer function analysis of beat-to-beat changes in BP and CBF velocity. Pressor effects of L-NMMA on cerebral hemodynamics were compared with those of phenylephrine infusion. In the supine position, L-NMMA increased mean BP from 83 ± …

Nitric Oxide Synthase Inhibition Does Not Affect Regulation Of Muscle Sympathetic Nerve Activity During Head-Up Tilt, Jian Cui, Rong Zhang, Thad E. Wilson, Sarah Witkowski, Craig G. Crandall, Benjamin D. Levine

Exercise and Sport Studies: Faculty Publications

To test the hypothesis that systemic inhibition of nitric oxide (NO) synthase does not alter the regulation of sympathetic outflow during head-up tilt in humans, in eight healthy subjects NO synthase was blocked by intravenous infusion of NG-monomethyl-L-arginine (L-NMMA). Blood pressure, heart rate, cardiac output, total peripheral resistance (TPR), and muscle sympathetic nerve activity (MSNA) were recorded in the supine position and during 60° head-up tilt. In the supine position, infusion of L-NMMA increased blood pressure, via increased TPR, and inhibited MSNA. However, the increase in MSNA evoked by head-up tilt during L-NMMA infusion (change in burst rate: 24 ± …

Determinants Of Erythropoietin Release In Response To Short-Term Hypobaric Hypoxia, Ri Li Ge, S. Witkowski, Y. Zhang, C. Alfrey, M. Sivieri, T. Karlsen, G. K. Resaland, M. Harber, J. Stray-Gundersen, B. D. Levine

Exercise and Sport Studies: Faculty Publications

We measured blood erythropoietin (EPO) concentration, arterial O2 saturation (SaO2), and urine PO2 in 48 subjects (32 men and 16 women) at sea level and after 6 and 24 h at simulated altitudes of 1,780, 2,085, 2,454, and 2,800 m. Renal blood flow (Doppler) and Hb were determined at sea level and after 6 h at each altitude (n = 24) to calculate renal O2 delivery. EPO increased significantly after 6 h at all altitudes and continued to increase after 24 h at 2,454 and 2,800 m, although not at 1,780 or 2,085 m. The increase in EPO varied markedly …

Skin Cooling Maintains Cerebral Blood Ffow Velocity And Orthostatic Tolerance During Tilting In Heated Humans, Thad E. Wilson, Jian Cui, Rong Zhang, Sarah Witkowski, Craig G. Crandall

Exercise and Sport Studies: Faculty Publications

Orthostatic tolerance is reduced in the heat-stressed human. The purpose of this project was to identify whether skin-surface cooling improves orthostatic tolerance. Nine subjects were exposed to 10 min of 60° head-up tilting in each of four conditions: normothermia (NT-tilt), heat stress (HT-tilt), normothermia plus skin-surface cooling 1 min before and throughout tilting (NT-tiltcool), and heat stress plus skin-surface cooling 1 min before and throughout tilting (HT-tiltcool). Heating and cooling were accomplished by perfusing 46 and 15°C water, respectively, though a tube-lined suit worn by each subject. During HT-tilt, four of nine subjects developed presyncopal symptoms resulting in the termination …