Browsing by Author "Pun, Matiram"

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    Differential Effects of High-Altitude Exposure on Markers of Oxidative Stress, Antioxidant Capacity and Iron Profiles, Supplementary Figures S1-S3, Rytz et al
    (2022-07-07) Rytz, Chantal; Pun, Matiram; Mawhinney, Jamie; Mounsey, Craig; Mura, Mathilde; Martin, Agnes; Pialoux, Vincent; Hartmann, Sara; Furian, Michael; Lopez, Ivan; Rawling, Jean; Soza, Daniel; Moraga, Fernando; Lichtblau, Mona; Bader, Patrick; Ulrich, Silvia; Bloch, Konrad; Frise, Matthew; Poulin, Marc
    Supplementary tables S1-S3 for manuscript entitled "Differential Effects of High-Altitude Exposure on Markers of Oxidative Stress, Antioxidant Capacity and Iron Profiles"
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    Effect of Acute, Subacute, and Repeated Exposure to High Altitude (5050 m) on Psychomotor Vigilance
    (Frontiers in Physiology, 2018-01) Pun, Matiram; Hartmann, Sara E.; Furian, Michael; Dyck, Adrienna M.; Muralt, Lara; Lichtblau, Mona; Bader, Patrick R.; Ulrich, Silvia; Bloch, Konrad E.; Rawling, Jean M.; Poulin, Marc J.
    Aim: High altitude (HA) hypoxia may affect cognitive performance and sleep quality. Further, vigilance is reduced following sleep deprivation. We investigated the effect on vigilance, actigraphic sleep indices, and their relationships with acute mountain sickness (AMS) during very HA exposure, acclimatization, and re-exposure. Methods: A total of 21 healthy altitude-naive individuals (25 ± 4 years; 13 females) completed 2 cycles of altitude exposure separated by 7 days at low altitude (LA, 520 m). Participants slept at 2900 m and spent the day at HA, (5050 m). We report acute altitude exposure on Day 1 (LA vs. HA1) and after 6 days of acclimatization (HA1 vs. HA6). Vigilance was quantified by reaction speed in the 10-min psychomotor vigilance test reaction speed (PVT-RS). AMS was evaluated using the Environmental Symptoms Questionnaire Cerebral Score (AMS-C score). Nocturnal rest/activity was recorded to estimate sleep duration using actigraphy. Results: In Cycle 1, PVT-RS was slower at HA1 compared to LA (4.1 ± 0.8 vs. 4.5 ± 0.6 s-1, respectively, p = 0.029), but not at HA6 (4.6 ± 0.7; p > 0.05). In Cycle 2, PVT-RS at HA1 (4.6 ± 0.7) and HA6 (4.8 ± 0.6) were not different from LA (4.8 ± 0.6, p > 0.05) and significantly greater than corresponding values in Cycle 1. In both cycles, AMS scores were higher at HA1 than at LA and HA6 (p < 0.05). Estimated sleep durations (TST) at LA, 1st and 5th nights were 431.3 ± 28.7, 418.1 ± 48.6, and 379.7 ± 51.4 min, respectively, in Cycle 1 and they were significantly reduced during acclimatization exposures (LA vs. 1st night, p > 0.05; LA vs. 5th night, p = 0.012; and 1st vs. 5th night, p = 0.054). LA, 1st and 5th nights TST in Cycle 2 were 477.5 ± 96.9, 430.9 ± 34, and 341.4 ± 32.2, respectively, and we observed similar deteriorations in TST as in Cycle 1 (LA vs. 1st night, p > 0.05; LA vs. 5th night, p = 0.001; and 1st vs. 5th night, p < 0.0001). At HA1, subjects who reported higher AMS-C scores exhibited slower PVT-RS (r = -0.56; p < 0.01). Subjects with higher AMS-C scores took longer time to react to the stimuli during acute exposure (r = 0.62, p < 0.01) during HA1 of Cycle 1. Conclusion: Acute exposure to HA reduces the PVT-RS. Altitude acclimatization over 6 days recovers the reaction speed and prevents impairments during subsequent altitude re-exposure after 1 week spent near sea level. However, acclimatization does not lead to improvement in total sleep time during acute and subacute exposures.
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    Effect of Selective and Nonselective Cyclooxygenase Enzyme Inhibition on Arterial Blood Pressure and Cerebral Blood Flow with Exposure to Intermittent Hypoxia in Humans
    (2013-04-23) Pun, Matiram; Poulin, Marc J.
    Background: Intermittent hypoxia (IH) simulating obstructive sleep apnea raises blood pressure (BP) and impairs cerebral blood flow response. The pathophysiology of intermittent hypoxia-mediated increase in BP involves multiple mechanisms but the role of cyclooxygenase (COX) catalyzed vasoactive prostaglandins (PG) is unclear. Methods: A placebo controlled double-blind randomized cross-over trial was designed using nonselective COX inhibitor indomethacin (50 mg tid/po), selectively COX-2 inhibitor celecoxib (200 mg bid/po) comparing with placebo. Healthy males ingested either of drugs for 4 days and physiological measurements were taken on 5th day with an acute isocapnic-hypoxia challenge pre- and post 6 hrs of IH exposure. Urinary PGs were assayed pre- and post- IH exposure. Results: After 4 days of drug, INDO increased BP compared to PLBO and CLBX; and lowered CBF compared to PLBO (air and baseline breathing). Mean arterial pressure gain with INDO increased followed by CLBX in response to acute isocapnic hypoxia and it was driven by increased gains in both systolic BP and diastolic BP (statistically not significant). CBF gain was blunted with CLBX while it was similar between INDO and PLBO although they were not statistically significant. With 6 hrs of IH (post-IH), CBF gain remained blunted with CLBX but was augmented with INDO (statistically not significant). CVC gain was lower with CLBX (statistically not significant). Both drugs lowered vasodilator and vasoconstrictor PGs compared to PLBO. Pre-IH PGI2:TxA2 was higher with INDO compared to PLBO (p < 0.001) and CLBX (p < 0.001). Conclusion: Indomethacin perturbs cardio- and cerebrovascular homeostasis in more robust manner as compared to placebo and celecoxib after 4 days of ingestion.
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    Effects on Cognitive Functioning of Acute, Subacute and Repeated Exposures to High Altitude
    (Frontiers, https://www.frontiersin.org, 2018-08-21) Pun, Matiram; Guadagni, Veronica; Aitken, Julie; Furian, Michael; Lichtblau, Mona; Ulrich, Silvia; Bettauer, Kaitlyn M.; Drogos, Lauren L.; Hartmann, Sara E.; Bader, Patrick R.; Rawling, Jean M.; Protzner, Andrea B.; Bloch, Konrad Ernst; Giesbrecht, Barry L.; Poulin, Marc J.; Rawling, Jean M.
    Objective: Neurocognitive functions are affected by high altitude, however the altitude effects of acclimatization and repeated exposures are unclear. We investigated the effects of acute, subacute and repeated exposure to 5,050 m on cognition among altitude-naïve participants compared to control subjects tested at low altitude. Methods: Twenty-one altitude-naïve individuals (25.3 ± 3.8 years, 13 females) were exposed to 5,050 m for 1 week (Cycle 1) and re-exposed after a week of rest at sea-level (Cycle 2). Baseline (BL, 520 m), acute (Day 1, HA1) and acclimatization (Day 6, HA6, 5,050 m) measurements were taken in both cycles. Seventeen control subjects (24.9 ± 2.6 years, 12 females) were tested over a similar period in Calgary, Canada (1,103 m). The Reaction Time (RTI), Attention Switching Task (AST), Rapid Visual Processing (RVP) and One Touch Stockings of Cambridge (OTS) tasks were administered and outcomes were expressed in milliseconds/frequencies. Lake Louise Score (LLS) and blood oxygen saturation (SpO2) were recorded. Results: In both cycles, no significant changes were found with acute exposure on the AST total score, mean latency and SD. Significant changes were found upon acclimatization solely in the altitude group, with improved AST Mean Latency [HA1 (588 ± 92) vs. HA6 (526 ± 91), p < 0.001] and Latency SD [HA1 (189 ± 86) vs. HA6 (135 ± 65), p < 0.001] compared to acute exposure, in Cycle 1. No significant differences were present in the control group. When entering Acute SpO2 (HA1-BL), Acclimatization SpO2 (HA6-BL) and LLS score as covariates for both cycles, the effects of acclimatization on AST outcomes disappeared indicating that the changes were partially explained by SpO2 and LLS. The changes in AST Mean Latency [ΔBL (-61.2 ± 70.2) vs. ΔHA6 (-28.0 ± 58), p = 0.005] and the changes in Latency SD [ΔBL (-28.4 ± 41.2) vs. ΔHA6 (-0.2235 ± 34.8), p = 0.007] across the two cycles were smaller with acclimatization. However, the percent changes did not differ between cycles. These results indicate independent effects of altitude across repeated exposures. Conclusions: Selective and sustained attention are impaired at altitude and improves with acclimatization.The observed changes are associated, in part, with AMS score and SpO2. The gains in cognition with acclimatization during a first exposure are not carried over to repeated exposures.