Phospho-mimetic CD3ε variants prevent TCR and CAR signaling.

Introduction: Antigen binding to the T cell antigen receptor (TCR) leads to the phosphorylation of the immunoreceptor tyrosine-based activation motifs (ITAMs) of the CD3 complex, and thereby to T cell activation. The CD3ε subunit plays a unique role in TCR activation by recruiting the kinase LCK and the adaptor protein NCK prior to ITAM phosphorylation. Here, we aimed to investigate how phosphorylation of the individual CD3ε ITAM tyrosines impacts the CD3ε signalosome. Methods: We mimicked irreversible tyrosine phosphorylation by substituting glutamic acid for the tyrosine residues in the CD3ε ITAM. Results: Integrating CD3ε phospho-mimetic variants into the complete TCR-CD3 complex resulted in reduced TCR signal transduction, which was partially compensated by the involvement of the other TCR-CD3 ITAMs. By using novel CD3ε phospho-mimetic Chimeric Antigen Receptor (CAR) variants, we avoided any compensatory effects of other ITAMs in the TCR-CD3 complex. We demonstrated that irreversible CD3ε phosphorylation prevented signal transduction upon CAR engagement. Mechanistically, we demonstrated that glutamic acid substitution at the N-terminal tyrosine residue of the CD3ε ITAM (Y39E) significantly reduces NCK binding to the TCR. In contrast, mutation at the C-terminal tyrosine of the CD3ε ITAM (Y50E) abolished LCK recruitment to the TCR, while increasing NCK binding. Double mutation at the C- and N-terminal tyrosines (Y39/50E) allowed ZAP70 to bind, but reduced the interaction with LCK and NCK. Conclusions: The data demonstrate that the dynamic phosphorylation of the CD3ε ITAM tyrosines is essential for CD3ε to orchestrate optimal TCR and CAR signaling and highlights the key role of CD3ε signalosome to tune signal transduction.

Brevundimonas and Serratia as host systems for assessing associated environmental viromes and phage diversity by complementary approaches.

Focusing on visible plaques for phage isolation leaves the question if we miss the diversity of non-plaque forming phages. We addressed this question through direct plaque-based isolation by employing the new hosts Brevundimonas pondensis LVF1 and Serratia marcescens LVF3 dsDNA, ssDNA, dsRNA, and ssRNA host-associated metavirome analysis. Of the 25 distinctive dsDNA phage isolates, 14 were associated with Brevundimonas and 11 with Serratia. TEM analysis revealed that 6 were myoviruses, 18 siphoviruses and 1 podovirus, while phages infecting Brevundimonas belonged all to siphoviruses. The associated viromes suggested a higher phage diversity in summer than in winter, and dsDNA phages were the dominant group. Isolation of vB_SmaP-Kaonashi was possible after investigating the viromes associated with Serratia, demonstrating the great potential of accompanying host-associated metavirome analysis. The ssDNA virome analysis showed that the B. pondensis LVF1 host is associated with Microviridae and Inoviridae phages, although none of them were isolated. The results demonstrated that the classical isolation technique is not exhausted, leading to the isolation of new dsDNA phages. It can be further improved by combination with metavirome techniques, which revealed further diversity.

A Cysteine Residue within the Kinase Domain of Zap70 Regulates Lck Activity and Proximal TCR Signaling.

Alterations in both the expression and function of the non-receptor tyrosine kinase Zap70 are associated with numerous human diseases including immunodeficiency, autoimmunity, and leukemia. Zap70 propagates the TCR signal by phosphorylating two important adaptor molecules, LAT and SLP76, which orchestrate the assembly of the signaling complex, leading to the activation of PLCγ1 and further downstream pathways. These events are crucial to drive T-cell development and T-cell activation. Recently, it has been proposed that C564, located in the kinase domain of Zap70, is palmitoylated. A non-palmitoylable C564R Zap70 mutant, which has been reported in a patient suffering from immunodeficiency, is incapable of propagating TCR signaling and activating T cells. The lack of palmitoylation was suggested as the cause of this human disease. Here, we confirm that Zap70C564R is signaling defective, but surprisingly, the defective Zap70 function does not appear to be due to a loss in palmitoylation. We engineered a C564A mutant of Zap70 which, similarly to Zap70C564R, is non-palmitoylatable. However, this mutant was capable of propagating TCR signaling. Moreover, Zap70C564A enhanced the activity of Lck and increased its proximity to the TCR. Accordingly, Zap70-deficient P116 T cells expressing Zap70C564A displayed the hyperphosphorylation of TCR-ζ and Zap70 (Y319), two well-known Lck substrates. Collectively, these data indicate that C564 is important for the regulation of Lck activity and proximal TCR signaling, but not for the palmitoylation of Zap70.

Acute high altitude exposure, acclimatization and re-exposure on nocturnal breathing.

Background: Effects of prolonged and repeated high-altitude exposure on oxygenation and control of breathing remain uncertain. We hypothesized that prolonged and repeated high-altitude exposure will improve altitude-induced deoxygenation and breathing instability. Methods: 21 healthy lowlanders, aged 18-30y, underwent two 7-day sojourns at a high-altitude station in Chile (4-8 hrs/day at 5,050 m, nights at 2,900 m), separated by a 1-week recovery period at 520 m. Respiratory sleep studies recording mean nocturnal pulse oximetry (SpO2), oxygen desaturation index (ODI, >3% dips in SpO2), breathing patterns and subjective sleep quality by visual analog scale (SQ-VAS, 0-100% with increasing quality), were evaluated at 520 m and during nights 1 and 6 at 2,900 m in the 1st and 2nd altitude sojourn. Results: At 520 m, mean ± SD nocturnal SpO2 was 94 ± 1%, ODI 2.2 ± 1.2/h, SQ-VAS 59 ± 20%. Corresponding values at 2,900 m, 1st sojourn, night 1 were: SpO2 86 ± 2%, ODI 23.4 ± 22.8/h, SQ-VAS 39 ± 23%; 1st sojourn, night 6: SpO2 90 ± 1%, ODI 7.3 ± 4.4/h, SQ-VAS 55 ± 20% (p < 0.05, all differences within corresponding variables). Mean differences (Δ, 95%CI) in acute effects (2,900 m, night 1, vs 520 m) between 2nd vs 1st altitude sojourn were: ΔSpO2 0% (-1 to 1), ΔODI -9.2/h (-18.0 to -0.5), ΔSQ-VAS 10% (-6 to 27); differences in acclimatization (changes night 6 vs 1), between 2nd vs 1st sojourn at 2,900 m were: ΔSpO2 -1% (-2 to 0), ΔODI 11.1/h (2.5 to 19.7), ΔSQ-VAS -15% (-31 to 1). Conclusion: Acute high-altitude exposure induced nocturnal hypoxemia, cyclic deoxygenations and impaired sleep quality. Acclimatization mitigated these effects. After recovery at 520 m, repeated exposure diminished high-altitude-induced deoxygenation and breathing instability, suggesting some retention of adaptation induced by the first altitude sojourn while subjective sleep quality remained similarly impaired.

Differential effects of high-altitude exposure on markers of oxidative stress, antioxidant capacity, and iron profiles.

High-altitude (HA) exposure may stimulate significant physiological and molecular changes, resulting in HA-related illnesses. HA may impact oxidative stress, antioxidant capacity, and iron homeostasis, yet it is unclear how both repeated exposure and HA acclimatization may modulate such effects. Therefore, we assessed the effects of weeklong repeated daily HA exposure (2,900-5,050 m) in altitude-naïve individuals (n = 21 individuals, 13 females, mean ± SD, 25.3 ± 3.7 yr) to mirror the working schedule of HA workers (n = 19 individuals, all males, 41.1 ± 9.4 yr) at the Atacama Large Millimeter Array (ALMA) Observatory (San Pedro de Atacama, Chile). Markers of oxidative stress, antioxidant capacity, and iron homeostasis were measured in blood plasma. Levels of protein oxidation (P < 0.001) and catalase activity (P = 0.023) increased and serum iron (P < 0.001), serum ferritin (P < 0.001), and transferrin saturation (P < 0.001) levels decreased with HA exposure in both groups. HA workers had lower levels of oxidative stress, and higher levels of antioxidant capacity, iron supply, and hemoglobin concentration as compared with altitude-naïve individuals. On a second week of daily HA exposure, changes in levels of protein oxidation, glutathione peroxidase, and nitric oxide metabolites were lower as compared with the first week in altitude-naïve individuals. These results indicate that repeated exposure to HA may significantly alter oxidative stress and iron homeostasis, and the degree of such changes may be dependent on if HA is visited naïvely or routinely. Further studies are required to fully elucidate differences in HA-induced changes in oxidative stress and iron homeostasis profiles among visitors of HA.

A prospective cohort study about the effect of repeated living high and working higher on cerebral autoregulation in unacclimatized lowlanders.

Cerebral autoregulation (CA) is impaired during acute high-altitude (HA) exposure, however, effects of temporarily living high and working higher on CA require further investigation. In 18 healthy lowlanders (11 women), we hypothesized that the cerebral autoregulation index (ARI) assessed by the percentage change in middle cerebral artery peak blood velocity (Δ%MCAv)/percentage change in mean arterial blood pressure (Δ%MAP) induced by a sit-to-stand maneuver, is (i) reduced on Day1 at 5050 m compared to 520 m, (ii) is improved after 6 days at 5050 m, and (iii) is less impaired during re-exposure to 5050 m after 7 days at 520 m compared to Cycle1. Participants spent 4-8 h/day at 5050 m and slept at 2900 m similar to real-life working shifts. High/low ARI indicate impaired/intact CA, respectively. With the sit-to-stand at 520 m, mean (95% CI) in ΔMAP and ΔMCAv were - 26% (- 41 to - 10) and - 13% (- 19 to - 7), P < 0.001 both comparisons; mean ± SD in ARI was 0.58 ± 2.44Δ%/Δ%, respectively. On Day1 at 5050 m, ARI worsened compared to 520 m (3.29 ± 2.42Δ%/Δ%), P = 0.006 but improved with acclimatization (1.44 ± 2.43Δ%/Δ%, P = 0.039). ARI was less affected during re-exposure to 5050 m (1.22 ± 2.52Δ%/Δ%, P = 0.027 altitude-induced change between sojourns). This study showed that CA (i) is impaired during acute HA exposure, (ii) improves with living high, working higher and (iii) is ameliorated during re-exposure to HA.

Extravascular lung water and cardiac function assessed by echocardiography in healthy lowlanders during repeated very high-altitude exposure.

BACKGROUND: High-altitude pulmonary edema is associated with elevated systolic pulmonary artery pressure (sPAP) and increased extravascular lung water (EVLW). We investigated sPAP and EVLW during repeated exposures to high altitude (HA). METHODS: Healthy lowlanders underwent two identical 7-day HA-cycles, where subjects slept at 2900 m and spent 4-8 h daily at 5050 m, separated by a weeklong break at low altitude (LA). Echocardiography and EVLW by B-lines were measured at 520 m (baseline, LA1), on day one, two and six at 5050 m (HA1-3) and after descent (LA2). RESULTS: We included 21 subjects (median 25 years, body mass index 22 kg/m2, SpO2 98%). SPAP rose from 21 mmHg at LA1 to 38 mmHg at HA1, decreased to 30 mmHg at HA3 (both p < 0.05 vs LA1) and normalized at 20 mmHg at LA2 (p = ns vs LA1). B-lines increased from 0 at LA1 to 6 at HA2 and 7 at HA3 (both p < 0.05 vs LA1) and receded to 1 at LA2 (p = ns vs LA1). Overall, in cycle two, sPAP did not differ (mean difference (95% confidence interval) -0.2(-2.3 to 1.9) mmHg, p = 0.864) but B-lines were more prevalent (+2.3 (1.4-3.1), p < 0.001) compared to cycle 1. Right ventricular systolic function decreased significantly but minimally at 5050 m. CONCLUSIONS: Exposure to 5050 m induced a rapid increase in sPAP. B-lines rose during prolonged exposures to 5050 m, despite gradual decrease in sPAP, indicating excessive hydrostatic pressure might not be solely responsible for EVLW-development. Repeated HA-exposure had no acclimatization effect on EVLW. This may affect workers needing repetitive ascents to altitude and could indicate greater B-line development upon repeated exposure.

Cognitive Effects of Repeated Acute Exposure to Very High Altitude Among Altitude-Experienced Workers at 5050 m.

Background: We investigated altitude effects on different cognitive domains among perennial shift-workers at the Atacama Large Millimeter/submillimeter Array Observatory (5050 m), Chile. Materials and Methods: Twenty healthy male workers were recruited and assigned to either a moderate-altitude first (MAF group, Test 1: 2900 m and Test 2: 5050 m) or to a high-altitude first (HAF group, Test 1: 5050 m and Test 2: 2900 m). Test 1 was conducted at the beginning and Test 2 at the end of the shift-work week. Processing speed (RTI, reaction time), attention (AST, attention-switching task, and RVP, rapid visual processing), and executive function (OTS, One Touch Stockings of Cambridge) were assessed. Results: Of the three cognitive domains assessed, only processing speed showed altitude-at-test group interaction (RTI median five choice reaction time: F1, 17 = 6.980, [Formula: see text] = 0.291, p = 0.017). With acclimatization, there was a decrease in AST reaction latency mean (t17 = -2.155, dz = 1.086, p = 0.046), an increase in RVP accuracy (t17 = 2.733, dz = 1.398, p = 0.014), and a decrease in OTS mean latency first choice (t17 = -2.375, dz = 1.211, p = 0.03). Decreased variability in cognitive function was observed in AST reaction latency standard deviation (t17 = -2.524, dz = 1.282, p = 0.022) and in RVP response latency standard deviation (t17 = -2.35, dz = 1.177, p = 0.03) with acclimatization. At 5050 m of elevation, SpO2 was positively correlated with executive function in the MAF group (OTS problems solved on first choice: r(5) = 0.839, p = 0.018) and negatively correlated with executive function latency standard deviations in the HAF group (OTS latency to first choice standard deviation: r(10) = -0.618, p = 0.032). Conclusions: Our findings highlight the importance of acclimatization and improvement of blood oxygen level, even among high altitude-experienced workers, to optimize performance of cognitively demanding work and reduce high altitude-associated health risks.

Effects on Cognitive Functioning of Acute, Subacute and Repeated Exposures to High Altitude.

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.

Effect of Acute, Subacute, and Repeated Exposure to High Altitude (5050 m) on Psychomotor Vigilance.

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.

Exercise Performance of Lowlanders with COPD at 2,590 m: Data from a Randomized Trial.

BACKGROUND: Effects of hypobaric hypoxia at altitude on exercise performance of lowlanders with chronic obstructive pulmonary disease (COPD) have not been studied in detail. OBJECTIVES: To quantify changes in exercise performance and associated physiologic responses in lowlanders with COPD travelling to moderate altitude. METHODS: A total of 31 COPD patients with a median age (quartiles) of 66 years (59; 69) and FEV1 of 56% predicted (49; 69) living below 800 m performed a constant-load bicycle exercise to exhaustion at 60% of the maximal work rate at 490 m (Zurich) and at an identical work rate at 2,590 m (Davos) in randomized order. Pulmonary gas exchange, pulse oximetry (SpO2), cerebral tissue oxygenation (CTO; near-infrared spectroscopy), and middle cerebral artery peak blood flow velocity (MCAv) by Doppler ultrasound during 30 s at end exercise were compared between altitudes. RESULTS: With ascent from 490 to 2,590 m, the median endurance time (quartiles) was reduced from 500 s (256; 795) to 205 s (139; 297) by a median (95% CI) of 303 s (150-420) (p < 0.001). End exercise SpO2 decreased from 92% (89; 94) to 81% (77; 84) and CTO from 62% (56; 66) to 55% (50; 60); end exercise minute ventilation increased from 40.6 L/min (35.5; 47.8) to 47.2 L/min (39.6; 58.7) (p < 0.05; all comparisons 2,590 vs. 490 m). MCAv increased similarly from rest to end exercise at 490 m (+25% [17; 36]) and at 2,590 m (+21% [14; 30]). However, the ratio of MCAv increase to SpO2 drop during exercise decreased from +6%/% (3; 12) at 490 m to +3%/% (2; 5) at 2,590 m (p < 0.05). CONCLUSIONS: In lowlanders with COPD travelling to 2,590 m, exercise endurance is reduced by more than half compared to 490 m in association with reductions in systemic and cerebral oxygen availability.

Human cerebral blood flow control during hypoxia: focus on chronic pulmonary obstructive disease and obstructive sleep apnea.

The brain is a vital organ that relies on a constant and adequate blood flow to match oxygen and glucose delivery with the local metabolic demands of active neurons. Thus exquisite regulation of cerebral blood flow (CBF) is particularly important under hypoxic conditions to prevent a detrimental decrease in the partial pressure of oxygen within the brain tissues. Cerebrovascular sensitivity to hypoxia, assessed as the change in CBF during a hypoxic challenge, represents the capacity of cerebral vessels to respond to, and compensate for, a reduced oxygen supply, and has been shown to be impaired or blunted in a number of conditions. For instance, this is observed with aging, and in clinical conditions such as untreated obstructive sleep apnea (OSA) and in healthy humans exposed to intermittent hypoxia. This review will 1) provide a brief overview of cerebral blood flow regulation and results of pharmacological intervention studies which we have performed to better elucidate the basic mechanisms of cerebrovascular regulation in humans; and 2) present data from studies in clinical and healthy populations, using a translational physiology approach, to investigate human CBF control during hypoxia. Results from studies in patients with chronic obstructive pulmonary disease and OSA will be presented to identify the effects of the disease processes on cerebrovascular sensitivity to hypoxia. Data emerging from experimental human models of intermittent hypoxia during wakefulness will also be reviewed to highlight the effects of intermittent hypoxia on the brain.

Blood Flow during Handgrip Exercise in COPD: Effect of Vitamin C.

PURPOSE: Chronic obstructive pulmonary disease (COPD) is associated with vascular dysfunction, possibly related to increased oxidative stress. Exercise hyperemia may similarly be impaired, which could have implications for exercise limitations in COPD. We tested if brachial blood flow (BBF) was reduced during handgrip exercise in COPD and if this response would be improved after vitamin C infusion. METHODS: Doppler ultrasound was used to measure brachial blood flow and vascular conductance (BBF and BVC, respectively) during mild, rhythmic handgrip exercise (EX) under conditions of sham-saline and vitamin C. Measures of flow-mediated dilation (FMD) and nitroglycerine-mediated dilation were used to assess endothelial-dependent and independent dilation, respectively. Biomarkers of antioxidants (vitamin C, superoxide dismutase [SOD], catalase), oxidative stress (malondialdehyde [MDA], advanced oxidation protein products [AOPP]), and nitric oxide metabolism (NOx) were measured in blood plasma. RESULTS: Ten COPD patients with moderate COPD and 10 healthy age-matched controls participated. COPD patients had similar increases in BBF and BVC during EX, compared with controls. Vitamin C was not found to have an effect on blood flow parameters during exercise (P > 0.05). Markers of endothelial-dependent dilation (FMD) and nitroglycerin-mediated dilation were similar between groups at baseline; FMD improved similarly in both groups after vitamin C. CONCLUSIONS: Moderate COPD patients have a preserved BBF response during handgrip exercise and do not exhibit endothelial dysfunction. Despite an increase in endothelial-dependent dilation after vitamin C, BBF remained unchanged, suggesting a limited impact of endothelial-derived NO in determining the blood flow response to handgrip exercise in older individuals. COPD patients of moderate severity, screened for cardiovascular disease, do not exhibit endothelial dysfunction and have similar exercise blood flow responses to healthy controls.

Cerebrovascular and ventilatory responses to acute isocapnic hypoxia in healthy aging and lung disease: effect of vitamin C.

Acute hypoxia increases cerebral blood flow (CBF) and ventilation (V̇e). It is unknown if these responses are impacted with normal aging, or in patients with enhanced oxidative stress, such as (COPD). The purpose of the study was to 1) investigate the effects of aging and COPD on the cerebrovascular and ventilatory responses to acute hypoxia, and 2) to assess the effect of vitamin C on these responses during hypoxia. In 12 Younger, 14 Older, and 12 COPD, we measured peak cerebral blood flow velocity (V̄p; index of CBF), and V̇e during two 5-min periods of acute isocapnic hypoxia, under conditions of 1) saline-sham; and 2) intravenous vitamin C. Antioxidants [vitamin C, superoxide dismutase (SOD), glutathione peroxidase, and catalase], oxidative stress [malondialdehyde (MDA) and advanced protein oxidation product], and nitric oxide metabolism end products (NOx) were measured in plasma. Following the administration of vitamin C, vitamin C, SOD, catalase, and MDA increased, while NOx decreased. V̄p and V̇e sensitivity to hypoxia was reduced in Older by ∼60% (P < 0.02). COPD patients exhibited similar V̄p and V̇e responses to Older (P > 0.05). Vitamin C did not have an effect on the hypoxic V̇e response but selectively decreased the V̄p sensitivity in Younger only. These findings suggest a reduced integrative reflex (i.e., cerebrovascular and ventilatory) during acute hypoxemia in healthy older adults. Vitamin C does not appear to have a large influence on the cerebrovascular or ventilatory responses during acute hypoxia.

Increased ventilatory response to carbon dioxide in COPD patients following vitamin C administration.

Patients with chronic obstructive pulmonary disease (COPD) have decreased ventilatory and cerebrovascular responses to hypercapnia. Antioxidants increase the ventilatory response to hypercapnia in healthy humans. Cerebral blood flow is an important determinant of carbon dioxide/hydrogen ion concentration at the central chemoreceptors and may be affected by antioxidants. It is unknown whether antioxidants can improve the ventilatory and cerebral blood flow response in individuals in whom these are diminished. Thus, we aimed to determine the effect of vitamin C administration on the ventilatory and cerebrovascular responses to hypercapnia during healthy ageing and in COPD. Using transcranial Doppler ultrasound, we measured the ventilatory and cerebral blood flow responses to hyperoxic hypercapnia before and after an intravenous vitamin C infusion in healthy young (Younger) and older (Older) subjects and in moderate COPD. Vitamin C increased the ventilatory response in COPD patients (mean (95% CI) 1.1 (0.9-1.1) versus 1.5 (1.1-2.0) L·min-1·mmHg-1, p<0.05) but not in Younger (2.5 (1.9-3.1) versus 2.4 (1.9-2.9) L·min-1·mmHg-1, p>0.05) or Older (1.3 (1.0-1.7) versus 1.3 (1.0-1.7) L·min-1·mmHg-1, p>0.05) healthy subjects. Vitamin C did not affect the cerebral blood flow response in the young or older healthy subjects or COPD subjects (p>0.05). Vitamin C increases the ventilatory but not cerebrovascular response to hyperoxic hypercapnia in patients with moderate COPD.

Cerebrovascular responses to submaximal exercise in women with COPD.

BACKGROUND: COPD patients have decreased physical fitness, and have an increased risk of vascular disease. In the general population, fitness is positively associated with resting cerebral blood flow velocity, however, little is known about the cerebrovascular response during exercise particularly in COPD patients. We hypothesized that COPD patients would have lower cerebral blood flow during exercise secondary to decreased physical fitness and underlying vascular disease. METHODS: Cardiopulmonary exercise testing was conducted in 11 women with GOLD stage I-II COPD, and 11 healthy controls to assess fitness. Cerebro- and cardio-vascular responses were compared between groups during two steady-state exercise tests (50% peak O2 consumption and 30 W). The main outcome variable was peak middle cerebral artery blood flow velocity (VP) during exercise using transcranial Doppler ultrasonography. RESULTS: Physical fitness was decreased in COPD patients. VP was comparable between COPD and controls (25 ± 22% versus 15 ± 13%, respectively; P > 0.05) when exercising at the same relative intensity, despite patients having higher blood pressure and greater arterial desaturation. However, VP was elevated in COPD (31 ± 26% versus 13 ± 10%; P ≤ 0.05) when exercising at the same workload as controls. CONCLUSIONS: Our results are contradictory to our a-priori hypothesis, suggesting that during matched intensity exercise, cerebral blood flow velocity is similar between COPD and controls. However, exercise at a modestly greater workload imposes a large physical demand to COPD patients, resulting in increased CBF compared to controls. Normal activities of daily living may therefore impose a large cerebrovascular demand in COPD patients, consequently reducing their cerebrovascular reserve capacity.

Decreased cerebrovascular response to CO2 in post-menopausal females with COPD: role of oxidative stress.

Chronic obstructive pulmonary disease (COPD) is associated with cerebrovascular abnormalities and an overproduction of reactive oxygen species. We hypothesised that COPD patients have oxidant-related cerebrovascular dysfunction. Our main objective was to evaluate cerebrovascular reactivity and its relationship with oxidative stress in females with COPD. We studied eight females with moderate COPD and 10 healthy female control subjects of similar age. Transcranial Doppler ultrasound assessed cerebral blood flow (CBF) velocity during hypercapnia. Plasma was assessed at rest for DNA oxidation, advanced oxidation protein products, lipid peroxidation, nitrotyrosine, antioxidant enzyme activity (glutathione peroxidase and catalase) and end-products of nitric oxide metabolism. Moderate COPD patients showed decreased cerebrovascular sensitivity to carbon dioxide (CO(2)) (COPD 1.17 ± 0.54 versus control 2.15 ± 0.73 cm · s(-1) · mmHg(-1); p<0.01). COPD patients had higher levels of DNA and lipid oxidation, advanced oxidation protein products and higher glutathione peroxidase activity (p<0.05). Controlling for measures of oxidative stress (DNA and lipid oxidation, and advanced oxidation protein product) eliminates statistically significant differences between the COPD and control groups in the CBF sensitivity to CO(2). Females with moderate COPD were found to have cerebrovascular dysfunction. Our results suggest that increased levels of systemic oxidative stress may have implications in the cerebrovascular dysfunction observed during hypercapnia in COPD.

Entre a escrita e a expressão: vias para a produção de conhecimento / Between writing and expression: pathways for the production of knowledge / Entre la escritura y la expresión: vías para la producción de conocimiento

A escrita é a forma majoritariamente utilizada para produção e divulgação de conhecimentos. O seu papel na comunicação já é um consenso. No que diz respeito à sua parte na criação, entretanto, a escrita abre um campo de possibilidades das quais a universidade faz um aproveitamento, no mínimo, exíguo. Este artigo pretende adentrar um espaço de diluição das figuras tradicionais da escrita - como o eu que escreve e os regimes imutáveis de significação - a fim de espreitar a expressão, com a crença na possibilidade de reunir as funções da ciência com os afectos da escritura. A contribuição à escrita acadêmica assemelha-se, então, a um sopro de inesperado quando tudo parece estar demasiado claro. É o aparecimento de inúmeras possibilidades de experiências com a palavra, através das quais o escrever acadêmico pode investigar suas zonas informes.(AU)

Writing is the most commonly used form in production and dissemination of knowledge. Its role in communication is already a consensus. Regarding to its part in creation; however, writing unfolds to a vast range of possibilities, of which the university usage is, at least, meager. This article aims at entering a space of dilution of the traditional figures of writing - for instance, the "I" that writes and the immutable systems of meaning - in order to stalk the expression, with the belief in the possibility of merging functions of science and the affection of writing. The contribution to academic writing resembles, thus, to an unexpected blow, when everything seems too settled. It is the appearing of innumerous opportunities of experience with words, through which the academic writing can investigate its own shapeless areas.(AU)

La escritura es la forma principal utilizada para la producción y difusión de conocimientos. Su papel en la comunicación es ya un consenso. Por su parte en la creación, sin embargo, la escritura se abre a un campo de posibilidades que la Universidad hace una recuperación al menos escasa. Este artículo pretende introducir un espacio de diluición de las figuras tradicionales de escritura - como el yo que escribe y los regímenes inmutables de significado - a fin de escuchar la expresión, con la creencia en la posibilidad de reunir las funciones de la ciencia con la calidez de la escritura. La contribución a la escritura académica es similar, pues, un golpe inesperado cuando todo parece ser demasiado claro. Es la aparición de numerosas posibilidades de experimentar con la palabra, a través del cual la escritura académica puede investigar sus zonas informes.(AU)

Entre a escrita e a expressão: vias para a produção de conhecimento / Between writing and expression: pathways for the production of knowledge / Entre la escritura y la expresión: vías para la producción de conocimiento

A escrita é a forma majoritariamente utilizada para produção e divulgação de conhecimentos. O seu papel na comunicação já é um consenso. No que diz respeito à sua parte na criação, entretanto, a escrita abre um campo de possibilidades das quais a universidade faz um aproveitamento, no mínimo, exíguo. Este artigo pretende adentrar um espaço de diluição das figuras tradicionais da escrita - como o eu que escreve e os regimes imutáveis de significação - a fim de espreitar a expressão, com a crença na possibilidade de reunir as funções da ciência com os afectos da escritura. A contribuição à escrita acadêmica assemelha-se, então, a um sopro de inesperado quando tudo parece estar demasiado claro. É o aparecimento de inúmeras possibilidades de experiências com a palavra, através das quais o escrever acadêmico pode investigar suas zonas informes.

Writing is the most commonly used form in production and dissemination of knowledge. Its role in communication is already a consensus. Regarding to its part in creation; however, writing unfolds to a vast range of possibilities, of which the university usage is, at least, meager. This article aims at entering a space of dilution of the traditional figures of writing - for instance, the "I" that writes and the immutable systems of meaning - in order to stalk the expression, with the belief in the possibility of merging functions of science and the affection of writing. The contribution to academic writing resembles, thus, to an unexpected blow, when everything seems too settled. It is the appearing of innumerous opportunities of experience with words, through which the academic writing can investigate its own shapeless areas.

La escritura es la forma principal utilizada para la producción y difusión de conocimientos. Su papel en la comunicación es ya un consenso. Por su parte en la creación, sin embargo, la escritura se abre a un campo de posibilidades que la Universidad hace una recuperación al menos escasa. Este artículo pretende introducir un espacio de diluición de las figuras tradicionales de escritura - como el yo que escribe y los regímenes inmutables de significado - a fin de escuchar la expresión, con la creencia en la posibilidad de reunir las funciones de la ciencia con la calidez de la escritura. La contribución a la escritura académica es similar, pues, un golpe inesperado cuando todo parece ser demasiado claro. Es la aparición de numerosas posibilidades de experimentar con la palabra, a través del cual la escritura académica puede investigar sus zonas informes.