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  • 1
    Online Resource
    Online Resource
    Microneurographic characterization of sympathetic responses during 1-leg exercise in young and middle-aged humans
    Canadian Science Publishing ; 2019
    In:  Applied Physiology, Nutrition, and Metabolism Vol. 44, No. 2 ( 2019-02), p. 194-199
    Details
    In: Applied Physiology, Nutrition, and Metabolism, Canadian Science Publishing, Vol. 44, No. 2 ( 2019-02), p. 194-199
    Abstract: Muscle sympathetic nerve activity (MSNA) at rest increases with age. However, the influence of age on MSNA recorded during dynamic leg exercise is unknown. We tested the hypothesis that aging attenuates the sympatho-inhibitory response observed in young subjects performing mild to moderate 1-leg cycling. After predetermining peak oxygen uptake, we compared contra-lateral fibular nerve MSNA during 2 min each of mild (unloaded) and moderate (30%–40% of the work rate at peak oxygen uptake, halved for single leg) 1-leg cycling in 18 young (age, 23 ± 1 years (mean ± SE)) and 18 middle-aged (age, 57 ± 2 years) sex-matched healthy subjects. Mean height, weight, resting heart rate, systolic blood pressure, and percent predicted peak oxygen uptake were similar between groups. Middle-aged subjects had higher resting MSNA burst frequency and incidence (P 〈 0.001) and diastolic blood pressure (P = 0.04). During moderate 1-leg cycling, older subjects’ systolic blood pressure increased more (+21 ± 5 vs. +10 ± 1 mm Hg; P = 0.02) and their fall in MSNA burst incidence was amplified (−19 ± 2 vs. −11 ± 2 bursts/100 heart beats; P = 0.01) but because heart rate rose less (+15 ± 3 vs. +19 ± 2 bpm; P = 0.03), exercise induced similar reductions in burst frequency (P = 0.25). Contrary to our initial hypothesis, with advancing age, mild- to moderate-intensity dynamic leg exercise elicits a greater rise in systolic blood pressure and a larger fall in MSNA.
    Type of Medium: Online Resource
    ISSN: 1715-5312 , 1715-5320
    URL: Article
    DOI: 10.1139/apnm-2018-0101
    Language: English
    Publisher: Canadian Science Publishing
    Publication Date: 2019
    SSG: 31
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  • 2
    Online Resource
    Online Resource
    The Effects of Ischemic Preconditioning on Human Exercise Performance
    Springer Science and Business Media LLC ; 2016
    In:  Sports Medicine Vol. 46, No. 4 ( 2016-4), p. 531-544
    Details
    In: Sports Medicine, Springer Science and Business Media LLC, Vol. 46, No. 4 ( 2016-4), p. 531-544
    Type of Medium: Online Resource
    ISSN: 0112-1642 , 1179-2035
    URL: Article
    DOI: 10.1007/s40279-015-0433-5
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2016
    detail.hit.zdb_id: 2025521-4
    SSG: 31
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  • 3
    Online Resource
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    Interindividual variability in muscle sympathetic responses to static handgrip in young men: evidence for sympathetic responder types?
    American Physiological Society ; 2018
    In:  American Journal of Physiology-Regulatory, Integrative and Comparative Physiology Vol. 314, No. 1 ( 2018-01-01), p. R114-R121
    Details
    In: American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, American Physiological Society, Vol. 314, No. 1 ( 2018-01-01), p. R114-R121
    Abstract: Negative and positive muscle sympathetic nerve activity (MSNA) responders have been observed during mental stress. We hypothesized that similar MSNA response patterns could be identified during the first minute of static handgrip and contribute to the interindividual variability throughout exercise. Supine measurements of multiunit MSNA (microneurography) and continuous blood pressure (Finometer) were recorded in 29 young healthy men during the first (HG1) and second (HG2) minute of static handgrip (30% maximal voluntary contraction) and subsequent postexercise circulatory occlusion (PECO). Responders were identified on the basis of differences from the typical error of baseline total MSNA: 7 negative, 12 positive, and 10 nonresponse patterns. Positive responders demonstrated larger total MSNA responses during HG1 ( P 〈 0.01) and HG2 ( P 〈 0.0001); however, the increases in blood pressure throughout handgrip exercise were similar between all groups, as were the changes in heart rate, stroke volume, cardiac output, total vascular conductance, and respiration (all P 〉 0.05). Comparing negative and positive responders, total MSNA responses were similar during PECO ( P = 0.17) but opposite from HG2 to PECO (∆40 ± 46 vs. ∆-21 ± 62%, P = 0.04). Negative responders also had a shorter time-to-peak diastolic blood pressure during HG1 (20 ± 20 vs. 44 ± 14 s, P 〈 0.001). Total MSNA responses during HG1 were associated with responses to PECO ( r = 0.39, P 〈 0.05), the change from HG2 to PECO ( r = −0.49, P 〈 0.01), and diastolic blood pressure time to peak ( r = 0.50, P 〈 0.01). Overall, MSNA response patterns during the first minute of static handgrip contribute to interindividual variability and appear to be influenced by differences in central command, muscle metaboreflex activation, and rate of loading of the arterial baroreflex.
    Type of Medium: Online Resource
    ISSN: 0363-6119 , 1522-1490
    URL: Article
    DOI: 10.1152/ajpregu.00266.2017
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2018
    detail.hit.zdb_id: 1477297-8
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  • 4
    Online Resource
    Online Resource
    Remote ischemic conditioning for acute respiratory distress syndrome in COVID-19
    American Physiological Society ; 2021
    In:  American Journal of Physiology-Lung Cellular and Molecular Physiology Vol. 320, No. 3 ( 2021-03-01), p. L331-L338
    Details
    In: American Journal of Physiology-Lung Cellular and Molecular Physiology, American Physiological Society, Vol. 320, No. 3 ( 2021-03-01), p. L331-L338
    Abstract: Acute respiratory distress syndrome and subsequent respiratory failure remains the leading cause of death ( 〉 80%) in patients severely impacted by COVID-19. The lack of clinically effective therapies for COVID-19 calls for the consideration of novel adjunct therapeutic approaches. Though novel antiviral treatments and vaccination hold promise in control and prevention of early disease, it is noteworthy that in severe cases of COVID-19, addressing “run-away” inflammatory cascades are likely more relevant for improvement of clinical outcomes. Viral loads may decrease in severe, end-stage coronavirus cases, but a systemically damaging cytokine storm persists and mediates multiple organ injury. Remote ischemic conditioning (RIC) of the limbs has shown potential in recent years to protect the lungs and other organs against pathological conditions similar to that observed in COVID-19. We review the efficacy of RIC in protecting the lungs against acute injury and current points of consideration. The beneficial effects of RIC on lung injury along with other related cardiovascular complications are discussed, as are the limitations presented by sex and aging. This adjunct therapy is highly feasible, noninvasive, and proven to be safe in clinical conditions. If proven effective in clinical trials for acute respiratory distress syndrome and COVID-19, application in the clinical setting could be immediately implemented to improve outcomes.
    Type of Medium: Online Resource
    ISSN: 1040-0605 , 1522-1504
    URL: Article
    DOI: 10.1152/ajplung.00223.2020
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2021
    detail.hit.zdb_id: 1477300-4
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  • 5
    Online Resource
    Online Resource
    Arterial baroreflex regulation of muscle sympathetic single-unit activity in men: influence of resting blood pressure
    American Physiological Society ; 2020
    In:  American Journal of Physiology-Heart and Circulatory Physiology Vol. 318, No. 4 ( 2020-04-01), p. H937-H946
    Details
    In: American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 318, No. 4 ( 2020-04-01), p. H937-H946
    Abstract: The arterial baroreflex has dominant control over multiunit muscle sympathetic nerve activity (MSNA) burst occurrence, but whether this extends to all single units or is influenced by resting blood pressure status is unclear. In 22 men (32 ± 8 yr), we assessed 68 MSNA single units during sequential bolus injections of nitroprusside and phenylephrine (modified Oxford). Sympathetic baroreflex sensitivity (sBRS) was quantified as the weighted negative linear regression slope between diastolic blood pressure (DBP) and single-unit spike firing probability and multiple spike firing. Strong negative linear relationships ( r ≥ −0.50) between DBP and spike firing probability were observed in 63/68 (93%) single units (−2.27 ± 1.27%·cardiac cycle −1 ·mmHg −1 [operating range, 18 ± 8 mmHg]). In contrast, only 45/68 (66%) single units had strong DBP-multiple spike firing relationships (−0.13 ± 0.18 spikes·cardiac cycle −1 ·mmHg −1 [operating range, 14 ± 7 mmHg]). Participants with higher resting DBP (65 ± 3 vs. 77 ± 3 mmHg, P 〈 0.001) had similar spike firing probability sBRS (low vs. high, −2.08 ± 1.08 vs. −2.46 ± 1.42%·cardiac cycle −1 ·mmHg −1 , P = 0.33), but a smaller sBRS operating range (20 ± 6 vs. 16 ± 9 mmHg, P = 0.01; 86 ± 24 vs. 52 ± 25% of total range, P 〈 0.001) and a higher proportion of single units without arterial baroreflex control outside this range [6/31 (19%) vs. 21/32 (66%), P 〈 0.001]. Participants with higher resting DBP also had fewer single units with arterial baroreflex control of multiple spike firing (79 vs. 53%, P = 0.04). The majority of MSNA single units demonstrate strong arterial baroreflex control over spike firing probability during pharmacological manipulation of blood pressure. Changes in single-unit sBRS operating range and control of multiple spike firing may represent altered sympathetic recruitment patterns associated with the early development of hypertension. NEW & NOTEWORTHY Muscle sympathetic single units can be differentially controlled during stress. In contrast, we demonstrate that 93% of single units maintain strong arterial baroreflex control during pharmacological manipulation of blood pressure. Interestingly, the operating range and proportion of single units that lose arterial baroreflex control outside of this range are influenced by resting blood pressure levels. Altered single unit, but not multiunit, arterial baroreflex control may represent changes in sympathetic recruitment patterns in early stage development of hypertension.
    Type of Medium: Online Resource
    ISSN: 0363-6135 , 1522-1539
    URL: Article
    DOI: 10.1152/ajpheart.00700.2019
    RVK:
    WA 15000
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2020
    detail.hit.zdb_id: 1477308-9
    SSG: 12
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  • 6
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    Signal-averaged resting sympathetic transduction of blood pressure: is it time to account for prevailing muscle sympathetic burst frequency?
    American Physiological Society ; 2021
    In:  American Journal of Physiology-Regulatory, Integrative and Comparative Physiology Vol. 321, No. 3 ( 2021-09-01), p. R484-R494
    Details
    In: American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, American Physiological Society, Vol. 321, No. 3 ( 2021-09-01), p. R484-R494
    Abstract: Calculating the blood pressure (BP) response to a burst of muscle sympathetic nerve activity (MSNA), termed sympathetic transduction, may be influenced by an individual’s resting burst frequency. We examined the relationships between sympathetic transduction and MSNA in 107 healthy males and females and developed a normalized sympathetic transduction metric to incorporate resting MSNA. Burst-triggered signal averaging was used to calculate the peak diastolic BP response following each MSNA burst (sympathetic transduction of BP) and following incorporation of MSNA burst cluster patterns and amplitudes (sympathetic transduction slope). MSNA burst frequency was negatively correlated with sympathetic transduction of BP ( r = −0.42; P 〈 0.01) and the sympathetic transduction slope ( r = −0.66; P 〈 0.01), independent of sex. MSNA burst amplitude was unrelated to sympathetic transduction of BP in males ( r = 0.04; P = 0.78), but positively correlated in females ( r = 0.44; P 〈 0.01) and with the sympathetic transduction slope in all participants ( r = 0.42; P 〈 0.01). To control for MSNA, the linear regression slope of the log-log relationship between sympathetic transduction and MSNA burst frequency was used as a correction exponent. In subanalysis of males (38 ± 10 vs. 14 ± 4 bursts/min) and females (28 ± 5 vs. 12 ± 4 bursts/min) with high versus low MSNA, sympathetic transduction of BP and sympathetic transduction slope were lower in participants with high MSNA (all P 〈 0.05). In contrast, normalized sympathetic transduction of BP and normalized sympathetic transduction slope were similar in males and females with high versus low MSNA (all P 〉 0.22). We propose that incorporating MSNA burst frequency into the calculation of sympathetic transduction will allow comparisons between participants with varying levels of resting MSNA.
    Type of Medium: Online Resource
    ISSN: 0363-6119 , 1522-1490
    URL: Article
    DOI: 10.1152/ajpregu.00131.2021
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2021
    detail.hit.zdb_id: 1477297-8
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  • 7
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    Effects of dynamic arm and leg exercise on muscle sympathetic nerve activity and vascular conductance in the inactive leg
    American Physiological Society ; 2019
    In:  Journal of Applied Physiology Vol. 127, No. 2 ( 2019-08-01), p. 464-472
    Details
    In: Journal of Applied Physiology, American Physiological Society, Vol. 127, No. 2 ( 2019-08-01), p. 464-472
    Abstract: The influence of muscle sympathetic nerve activity (MSNA) responses on local vascular conductance during exercise are not well established. Variations in exercise mode and active muscle mass can produce divergent MSNA responses. Therefore, we sought to examine the effects of small- versus large-muscle mass dynamic exercise on vascular conductance and MSNA responses in the inactive limb. Thirty-five participants completed two study visits in a randomized order. During visit 1, superficial femoral artery (SFA) blood flow (Doppler ultrasound) was assessed at rest and during steady-state rhythmic handgrip (RHG; 1:1 duty cycle, 40% maximal voluntary contraction), one-leg cycling (17 ± 3% peak power output), and concurrent exercise at the same intensities. During visit 2, MSNA (contralateral fibular nerve microneurography) was acquired successfully in 12/35 participants during the same exercise modes. SFA blood flow increased during RHG ( P 〈 0.0001) and concurrent exercise ( P = 0.03) but not cycling ( P = 0.91). SFA vascular conductance was unchanged during RHG ( P = 0.88) but reduced similarly during concurrent and cycling exercise (both P 〈 0.003). RHG increased MSNA burst frequency ( P = 0.04) without altering burst amplitude ( P = 0.69) or total MSNA ( P = 0.26). In contrast, cycling and concurrent exercise had no effects on MSNA burst frequency (both P ≥ 0.10) but increased burst amplitude (both P ≤ 0.001) and total MSNA (both P ≤ 0.007). Across all exercise modes, the changes in MSNA burst amplitude and SFA vascular conductance were correlated negatively ( r = −0.43, P = 0.02). In summary, the functional vascular consequences of alterations in sympathetic outflow to skeletal muscle are most closely associated with changes in MSNA burst amplitude, but not frequency, during low-intensity dynamic exercise. NEW & NOTEWORTHY Low-intensity small- versus large-muscle mass exercise can elicit divergent effects on muscle sympathetic nerve activity (MSNA). We examined the relationships between changes in MSNA (burst frequency and amplitude) and superficial femoral artery (SFA) vascular conductance during rhythmic handgrip, one-leg cycling, and concurrent exercise in the inactive leg. Only changes in MSNA burst amplitude were inversely associated with SFA vascular conductance responses. This result highlights the functional importance of measuring MSNA burst amplitude during exercise.
    Type of Medium: Online Resource
    ISSN: 8750-7587 , 1522-1601
    URL: Article
    DOI: 10.1152/japplphysiol.00997.2018
    RVK:
    WA 15000
    RVK:
    XA 52094
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2019
    detail.hit.zdb_id: 1404365-8
    SSG: 12
    SSG: 31
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  • 8
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    Relevance of differential control of sympathorespiratory response magnitudes in clinical assessments
    Wiley ; 2021
    In:  The Journal of Physiology Vol. 599, No. 10 ( 2021-05), p. 2517-2520
    Details
    In: The Journal of Physiology, Wiley, Vol. 599, No. 10 ( 2021-05), p. 2517-2520
    Type of Medium: Online Resource
    ISSN: 0022-3751 , 1469-7793
    URL: Issue
    URL: Article
    DOI: 10.1113/tjp.v599.10
    DOI: 10.1113/JP281277
    RVK:
    WA 15000
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 1475290-6
    SSG: 12
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  • 9
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    Thinking from the heart: arrhythmia‐induced reduction in cerebral blood flow and the cumulative burden on cognitive function in cardiovascular disease
    Wiley ; 2022
    In:  The Journal of Physiology Vol. 600, No. 19 ( 2022-10), p. 4255-4258
    Details
    In: The Journal of Physiology, Wiley, Vol. 600, No. 19 ( 2022-10), p. 4255-4258
    Type of Medium: Online Resource
    ISSN: 0022-3751 , 1469-7793
    URL: Issue
    URL: Article
    DOI: 10.1113/tjp.v600.19
    DOI: 10.1113/JP283651
    RVK:
    WA 15000
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 1475290-6
    SSG: 12
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  • 10
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    Arterial baroreflex regulation of muscle sympathetic nerve activity at rest and during stress
    Wiley ; 2019
    In:  The Journal of Physiology Vol. 597, No. 18 ( 2019-09), p. 4729-4741
    Details
    In: The Journal of Physiology, Wiley, Vol. 597, No. 18 ( 2019-09), p. 4729-4741
    Abstract: The arterial baroreflex controls vasoconstrictor muscle sympathetic nerve activity (MSNA) in a negative feedback manner by increasing or decreasing activity during spontaneous blood pressure falls or elevations, respectively. Spontaneous sympathetic baroreflex sensitivity is commonly quantified as the slope of the relationship between MSNA burst incidence or strength and beat‐to‐beat variations in absolute diastolic blood pressure. We assessed the relationships between blood pressure inputs related to beat‐to‐beat blood pressure change or blood pressure rate‐of‐change (variables largely independent of absolute pressure) and MSNA at rest and during exercise and mental stress. The number of participants with strong linear relationships between MSNA and beat‐to‐beat diastolic blood pressure change variables or absolute diastolic blood pressure were similar at rest, although during stress the beat‐to‐beat diastolic blood pressure change variables were superior. Current methods may not fully characterize the capacity of the arterial baroreflex to regulate MSNA.
    Type of Medium: Online Resource
    ISSN: 0022-3751 , 1469-7793
    URL: Issue
    URL: Article
    DOI: 10.1113/tjp.v597.18
    DOI: 10.1113/JP278376
    RVK:
    WA 15000
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 1475290-6
    SSG: 12
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