Effect of exercise intensity and apnea on splenic contraction and hemoglobin increase in well-trained cross-country skiers.

The human spleen acts as a reservoir for red blood cells, which is mobilized into the systemic circulation during various conditions such as hypoxia and physical exertion. Cross-country (XC) skiers, renowned for their exceptional aerobic capacity, are regularly exposed to high-intensity exercise and local oxygen deficits. We investigated a putative dose-dependent relationship between splenic contraction and concomitant hemoglobin concentration ([Hb]) elevation across four exercise intensities in well-trained XC skiers. Fourteen male XC skiers voluntarily participated in a 2-day protocol, encompassing a serial apnea test and a V ˙ O2max test (day 1), followed by three submaximal exercise intensities on a roller skiing treadmill corresponding to 55, 70, and 85% of V ˙ O2max (day 2). Spleen volume was measured via ultrasonic imaging, and venous blood samples were used to determine [Hb] levels. Baseline spleen volume was similar (266(35) mL) for all conditions (NS). Notably, all conditions induced significant splenic contractions and transient [Hb] elevations. The V ˙ O2max test exhibited the most pronounced splenic contraction (35.8%, p < 0.001) and a [Hb] increase of 8.1%, while the 85% exercise intensity led to 27.1% contraction and the greatest [Hb] increase (8.3%, < 0.001) compared to baseline. The apnea test induced relatively smaller responses (splenic contraction: 20.4%, [Hb] = 3.3%, p < 0.001), akin to the response observed at the 70% exercise intensity (splenic contraction = 23%, [Hb] = 6.4%, p < 0,001) and 55% (splenic contraction = 20.0%, [Hb] = 4.8%, p < 0.001). This study shows a discernible dose-dependent relationship between splenic contraction and [Hb] increase with levels of exercise, effectively distinguishing between submaximal and maximal exercise intensity.

Sexual selection for extreme physical performance in a polygynous bird is associated with exceptional sex differences in oxygen carrying capacity.

In many animals, males compete for access to fertile females. The resulting sexual selection leads to sex differences in morphology and behaviour, but may also have consequences for physiology. Pectoral sandpipers are an arctic-breeding polygynous shorebird in which males perform elaborate displays around-the-clock and move over long distances to sample potential breeding sites, implying the need for physiological adaptations to cope with extreme endurance. We examined the oxygen carrying capacity of pectoral sandpipers, measured as the volume percentage of red blood cells in blood (haematocrit, Hct). We found a remarkable sex difference in Hct levels, with males having much higher values (58.9 ± 3.8 s.d.) than females (49.8 ± 5.3 s.d.). While Hct values of male pectoral sandpipers are notable for being among the highest recorded in birds, the sex difference we report is unprecedented and more than double that of any previously described. We also show that Hct values declined after arrival to the breeding grounds in females, but not in males, suggesting that males maintain an aerobic capacity during the mating period equivalent to that sustained during trans-hemispheric migration. We conclude that sexual selection for extreme physical performance in male pectoral sandpipers has led to exceptional sex differences in oxygen carrying capacity.

Targeting erythrocyte-mediated hypoxia to alleviate lung injury induced by pyrrolizidine alkaloids.

Pyrrolizidine alkaloids (PAs) are widely distributed natural toxins and have been extensively studied for their hepatotoxicity. However, PA-induced pulmonary toxicity remains less studied regarding the initiating mechanism and treatment approaches. Our previous study demonstrated the formation of pyrrole-hemoglobin adducts after PA exposure in vivo, which is suspected to affect the oxygen-carrying capacity of erythrocytes [red blood cells (RBCs)] consequently. The present study aimed to investigate the effects of PAs on the oxygen-carrying capacity of RBCs and the potential of targeting RBC-mediated hypoxia to alleviate PA-induced lung injury. First, rats were treated with retrorsine (RTS) or monocrotaline (MCT) intravenously at 0.2 mmol/kg. The results of Raman spectrometry analysis on blood samples revealed both RTS and MCT significantly reduced the oxygen-carrying capacity of RBCs. Further, MCT (0.2 mmol/kg) was orally given to the rats with or without pretreatment with two doses of erythropoietin (Epo, 500 IU/kg/dose every other day), an RBC-stimulating agent. Biochemical and histological results showed pretreatment with Epo effectively reduced the cardiopulmonary toxicity induced by MCT. These findings provide the first evidence that adduction on hemoglobin, and the resulting RBC damage and impaired oxygen-carrying capacity, are the major initiating mechanism underlying PA-induced pulmonary arterial hypertension (PAH), while targeting the RBC damage is a potential therapeutic approach for PA-induced lung injury.

Ecological and life-history correlates of erythrocyte size and shape in Lepidosauria.

Blood oxygen-carrying capacity is shaped both by the ambient oxygen availability as well as species-specific oxygen demand. Erythrocytes are a critical part of oxygen transport and both their size and shape can change in relation to species-specific life-history, behavioural or ecological conditions. Here, we test whether components of the environment (altitude), life history (reproductive mode, body temperature) and behaviour (diving, foraging mode) drive erythrocyte size variation in the Lepidosauria (lizards, snakes and rhynchocephalians). We collected data on erythrocyte size (area) and shape (L/W: elongation ratio) from Lepidosauria across the globe (N = 235 species). Our analyses show the importance of oxygen requirements as a driver of erythrocyte size. Smaller erythrocytes were associated with the need for faster delivery (active foragers, high-altitude species, warmer body temperatures), whereas species with greater oxygen demands (diving species, viviparous species) had larger erythrocytes. Erythrocyte size shows considerable cross-species variation, with a range of factors linked to the oxygen delivery requirements being major drivers of these differences. A key future aspect for study would include within-individual plasticity and how changing states, for example, pregnancy, perhaps alter the size and shape of erythrocytes in Lepidosaurs.

Impairment in maximal lactate steady state after carbon monoxide inhalation is related to training status.

NEW FINDINGS: What is the central question of this study? What is the effect of an elevated carboxyhaemoglobin (COHb) concentration following carbon monoxide inhalation on the maximal lactate steady state (MLSS) in humans and is this effect dependent on aerobic fitness? What is the main finding and its importance? An elevated COHb concentration intensified physiological responses to exercise at the MLSS - including heart rate, ventilation and peripheral fatigue - in general and reduced the MLSS (i.e., destabilized the blood lactate concentration) in trained but not untrained males and females. ABSTRACT: This study investigated whether a lower effective [Hb], induced by carbon monoxide (CO) inhalation, reduces the peak oxygen uptake ( V ̇ O 2 peak ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{peak}}}$ ) and the maximal lactate steady state (MLSS) and whether training status explains individual variation in these impairments. Healthy young participants completed two ramp incremental tests (n = 20, 10 female) and two trials at MLSS (n = 16, eight female) following CO rebreathe tests and sham procedures (SHAM) in random orders. All fitness variables were normalized to fat-free mass (FFM) to account for sex-related differences in body composition, and males and females were matched for aerobic fitness. The V ̇ O 2 peak ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{peak}}}$ (mean (SD): -4.2 (3.7)%), peak power output (PPO) (-3.3 (2.2)%) and respiratory compensation point (RCP) (-6.3 (4.5)%) were reduced in CO compared with SHAM (P < 0.001 for all), but the gas exchange threshold (-3.3 (7.1)%) was not (P = 0.077). Decreases in V ̇ O 2 peak ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{peak}}}$ (r = -0.45; P = 0.047) and PPO (r = -0.49; P = 0.029) in CO were correlated with baseline aerobic fitness. Compared to SHAM, physiological and perceptual indicators of exercise-related stress were exacerbated by CO while cycling at MLSS. Notably, the mean blood lactate concentration ([La]) increased (i.e., Δ[La] >1.0 mM) between 10 min (5.5 (1.4) mM) and 30 min (6.8 (1.3) mM; P = 0.026) in CO, with 9/16 participants classified as unstable. These unstable participants had a higher V ̇ O 2 peak ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}{\rm{peak}}}$ (66.2 (8.5) vs. 56.4 (8.8) ml kg FFM-1  min-1 , P = 0.042) and V ̇ O 2 ${\dot{V}}_{{{\rm{O}}}_{\rm{2}}}$ at MLSS (55.8 (7.0) vs. 44.3 (7.0) ml kg FFM-1  min-1 , P = 0.006) compared to the stable group. In conclusion, a reduced O2 -carrying capacity decreased maximal and submaximal exercise performance, with higher aerobic fitness associated with greater impairments in both.

The effects of high altitude ascent on splenic contraction and the diving response during voluntary apnoea.

NEW FINDINGS: What is the central question of this study? What is the relative contribution of a putative tonic splenic contraction to the haematological acclimatization process during high altitude ascent in native lowlanders? What is the main finding and its importance? Spleen volume decreased by -14.3% (-15.2 ml) per 1000 m ascent, with an attenuated apnoea-induced [Hb] increase, attesting to a tonic splenic contraction during high altitude ascent. The [Hb]-enhancing function of splenic contraction may contribute to restoring oxygen content early in the acclimatization process at high altitude. ABSTRACT: Voluntary apnoea causes splenic contraction and reductions in heart rate (HR; bradycardia), and subsequent transient increases in haemoglobin concentration ([Hb]). Ascent to high altitude (HA) induces systemic hypoxia and reductions in oxygen saturation ( SpO2 ), which may cause tonic splenic contraction, which may contribute to haematological acclimatization associated with HA ascent. We measured resting cardiorespiratory variables (HR, SpO2 , [Hb]) and resting splenic volume (via ultrasound) during incremental ascent from 1400 m (day 0) to 3440 m (day 3), 4240 m (day 7) and 5160 m (day 10) in non-acclimatized native lowlanders during assent to HA in the Nepal Himalaya. In addition, apnoea-induced responses in HR, SpO2 and splenic volume were measured before and after two separate voluntary maximal apnoeas (A1-A2) at 1400, 3440 and 4240 m. Resting spleen volume decreased -14.3% (-15.2 ml) per 1000 m with ascent, from 140 ± 41 ml (1400 m) to 108 ± 28 ml (3440 m; P > 0.99), 94 ± 22 ml (4240 m; P = 0.009) and 84 ± 28 ml (5160 m; P = 0.029), with concomitant increases in [Hb] from 125 ± 18.3 g l-1 (1400 m) to 128 ± 10.4 g l-1 (3440 m), 138.8 ± 12.7 g l-1 (4240 m) and 157.5 ± 8 g l-1 (5160 m; P = 0.021). Apnoea-induced splenic contraction was 50 ± 15 ml (1400 m), 44 ± 17 ml (3440 m; P > 0.99) and 26 ± 8 ml (4240 m; P = 0.002), but was not consistently associated with increases in [Hb]. The apnoea-induced bradycardia was more pronounced at 3440 m (A1: P = 0.04; A2: P = 0.094) and at 4240 m (A1: P = 0.037 A2: P = 0.006) compared to values at 1400 m. We conclude that hypoxia-induced splenic contraction at rest (a) may contribute to restoring arterial oxygen content through its [Hb]-enhancing contractile function and (b) eliminates further apnoea-induced [Hb] increases in hypoxia. We suggest that tonic splenic contraction may contribute to haematological acclimatization early in HA ascent in humans.

Splenic contraction is enhanced by exercise at simulated high altitude.

PURPOSE: Splenic contraction increases circulating hemoglobin (Hb) with advantages during hypoxia. As both hypoxia and exercise have been shown to be important separate triggers of splenic contraction we aimed to investigate if the spleen response to simulated high altitude (HA) is enhanced by superimposing exercise. METHOD: Fourteen healthy volunteers (seven females) performed the following protocol in a normobaric environment sitting on an ergometer cycle: 20 min rest in normoxia; 20 min rest while breathing hypoxic gas simulating an altitude of 3500 m; 10 min exercise at an individually set intensity while breathing the hypoxic gas; 20 min rest in hypoxia; and finally 20 min rest in normoxia. Spleen measurements were collected by ultrasonic imaging and venous Hb measured at the end of each intervention. RESULT: Mean ± SD baseline spleen volume during normoxic rest was 280 ± 107 mL, the volume was reduced by 22% during rest in hypoxia to 217 ± 92 mL (p < 0.001) and by 33% during exercise in hypoxia (189 mL; p < 0.001). Hb was 140.7 ± 7.0 g/L during normoxic rest and 141.3 ± 7.4 g/L during hypoxic rest (NS), but increased by 5.3% during hypoxic exercise (148.6 ± 6.3 g/L; p < 0.001). Spleen volume and Hb were stepwise changed back to baseline at cessation of exercise and return to normoxia. CONCLUSION: Splenic contraction is induced by hypoxia and further enhanced by superimposing exercise, and reduced when exercise ceases, in a step-wise manner, showing that the tonic but partial contraction observed in long-term field expeditions to HA may occur also in the short term. This "graded response" may be beneficial during acclimatization to HA, to cope with moderate chronic hypoxia during rest while allowing additional enhancement of oxygen carrying capacity to overcome short bouts of extreme hypoxia caused by exercise.

Ecology and Evolution of Blood Oxygen-Carrying Capacity in Birds.

Blood oxygen-carrying capacity is one of the important determinants of the amount of oxygen supplied to the tissue per unit time and plays a key role in oxidative metabolism. In wild vertebrates, blood oxygen-carrying capacity is most commonly measured with the total blood hemoglobin concentration (Hb) and hematocrit (Hct), which is the volume percentage of red blood cells in blood. Here, I used published estimates of avian Hb and Hct (nearly 1,000 estimates from 300 species) to examine macroevolutionary patterns in the oxygen-carrying capacity of blood in birds. Phylogenetically informed comparative analysis indicated that blood oxygen-carrying capacity was primarily determined by species distribution (latitude and elevation) and morphological constraints (body mass). I found little support for the effect of life-history components on blood oxygen-carrying capacity except for a positive association of Hct with clutch size. Hb was also positively associated with diving behavior, but I found no effect of migratoriness on either Hb or Hct. Fluctuating selection was identified as the major force shaping the evolution of blood oxygen-carrying capacity. The results offer novel insights into the evolution of Hb and Hct in birds, and they provide a general, phylogenetically robust support for some long-standing hypotheses in avian ecophysiology.

Phenotypic flexibility in respiratory traits is associated with improved aerial respiration in an amphibious fish out of water.

Amphibious fishes have evolved multiple adaptive strategies for respiring out of water, but there has been less focus on reversible plasticity. We tested the hypothesis that when amphibious fishes leave water, enhanced respiratory performance on land is the result of rapid functional phenotypic flexibility of respiratory traits. We acclimated four isogenic strains of Kryptolebias marmoratus to air for 0, 1, 3 or 7 days. We compared respiratory performance out of water with traits linked to the O2 cascade. Aerial O2 consumption rate was measured over a step-wise decrease in O2 levels. There were significant differences between strains, but time out of water had the largest impact on measured parameters. Kryptolebiasmarmoratus had improved respiratory performance [lower aerial critical oxygen tension (Pcrit), higher regulation index (RI)] after only 1 day of air exposure, and these changes were strongly associated with the change in hematocrit and dorsal cutaneous angiogenesis. Additionally, we found that 1 h of air exposure induced the expression of four angiogenesis-associated genes - vegfa, angpt2, pecam-1 and efna1 - in the skin. After 7 days in air, respiratory traits were not significantly linked to the variation in either aerial Pcrit or RI. Overall, our data indicate that there are two phases involved in the enhancement of aerial respiration: an initial rapid response (1 day) and a delayed response (7 days). We found evidence for the hypothesis that respiratory performance on land in amphibious fishes is the result of rapid flexibility in both O2 uptake and O2 carrying capacity.

A Physiological Signature of the Cost of Reproduction Associated with Parental Care.

Costs of reproduction are an integral and long-standing component of life-history theory, but we still know relatively little about the specific physiological mechanisms underlying these trade-offs. We experimentally manipulated workload during parental care in female European starlings (Sturnus vulgaris) using attachment of radios and/or wing clipping and assessed measures of workload, current breeding productivity, future fecundity, and survival (local return rate) in relation to treatment. Females with wing clipping and radio attachment paid a clear cost of reproduction compared with all other treatment groups: they had lower future fecundity and lower return rates despite having lower current breeding productivity. We then measured 13 physiological traits, including measures of aerobic/metabolic capacity, oxidative stress and muscle damage, intermediary metabolism and energy supply, and immune function. Our results show that the cost of reproduction in females with wing clipping and radio attachment was associated with lower oxygen-carrying capacity (lower hematocrit and hemoglobin levels), lower energy reserves (plasma nonesterified fatty acid and triglyceride levels), decreased immune function (lower haptoglobin levels), and elevated levels of oxidative stress (higher levels of dROMs [reactive oxygen metabolites] and lower levels of the endogenous antioxidant uric acid). Our study provides evidence that costs of reproduction involve a widespread decline in physiological function across multiple physiological systems consistent with long-standing ideas of cumulative "wear and tear" and allostatic load.

Long-term hypoxia exposure alters the cardiorespiratory physiology of steelhead trout (Oncorhynchus mykiss), but does not affect their upper thermal tolerance.

It has been suggested that exposure to high temperature or hypoxia may confer tolerance to the other oxygen-limited stressor (i.e., 'cross-tolerance'). Thus, we investigated if chronic hypoxia-acclimation (>3 months at 40% air saturation) improved the steelhead trout's critical thermal maximum (CTMax), or affected key physiological variables that could impact upper thermal tolerance. Neither CTMax (24.7 vs. 25.3°C) itself, nor oxygen consumption ( [Formula: see text] ), haematocrit, blood haemoglobin concentration, or heart rate differed between hypoxia- and normoxia-acclimated trout when acutely warmed. However, the cardiac output (Q̇) of hypoxia-acclimated fish plateaued earlier compared to normoxia-acclimated fish due to an inability to maintain stroke volume (SV), and this resulted in a ~50% lower maximum Q̇. Despite this reduced maximum cardiac function, hypoxia-acclimated trout were able to consume more O2 per volume of blood pumped as evidenced by the equivalent [Formula: see text] . These results provide additional evidence that long-term hypoxia improves tissue oxygen utilization, and that this compensates for diminished cardiac pumping capacity. The limited SV in hypoxia-acclimated trout in vivo was not associated with changes in cardiac morphology or in vitro maximum SV, but the affinity and density of myocardial ß-adrenoreceptors were lower and higher, respectively, than in normoxia-acclimated fish. These data suggest that alterations in ventricular filling dynamics or myocardial contractility constrain cardiac function in hypoxia-acclimated fish at high temperatures. Our results do not support (1) 'cross-tolerance' between high temperature and hypoxia when hypoxia is chronic, or (2) that cardiac function is always the determinant of temperature-induced changes in fish [Formula: see text] , and thus thermal tolerance, as suggested by the oxygen- and capacity-limited thermal tolerance (OCLTT) theory.

Blue blood on ice: modulated blood oxygen transport facilitates cold compensation and eurythermy in an Antarctic octopod.

INTRODUCTION: The Antarctic Ocean hosts a rich and diverse fauna despite inhospitable temperatures close to freezing, which require specialist adaptations to sustain animal activity and various underlying body functions. While oxygen transport has been suggested to be key in setting thermal tolerance in warmer climates, this constraint is relaxed in Antarctic fishes and crustaceans, due to high levels of dissolved oxygen. Less is known about how other Antarctic ectotherms cope with temperatures near zero, particularly the more active invertebrates like the abundant octopods. A continued reliance on the highly specialised blood oxygen transport system of cephalopods may concur with functional constraints at cold temperatures. We therefore analysed the octopod's central oxygen transport component, the blue blood pigment haemocyanin, to unravel strategies that sustain oxygen supply at cold temperatures. RESULTS: To identify adaptive compensation of blood oxygen transport in octopods from different climatic regions, we compared haemocyanin oxygen binding properties, oxygen carrying capacities as well as haemolymph protein and ion composition between the Antarctic octopod Pareledone charcoti, the South-east Australian Octopus pallidus and the Mediterranean Eledone moschata. In the Antarctic Pareledone charcoti at 0°C, oxygen unloading by haemocyanin was poor but supported by high levels of dissolved oxygen. However, lower oxygen affinity and higher oxygen carrying capacity compared to warm water octopods, still enabled significant contribution of haemocyanin to oxygen transport at 0°C. At warmer temperatures, haemocyanin of Pareledone charcoti releases most of the bound oxygen, supporting oxygen supply at 10°C. In warm water octopods, increasing oxygen affinities reduce the ability to release oxygen from haemocyanin at colder temperatures. Though, unlike Eledone moschata, Octopus pallidus attenuated this increase below 15°C. CONCLUSIONS: Adjustments of haemocyanin physiological function and haemocyanin concentrations but also high dissolved oxygen concentrations support oxygen supply in the Antarctic octopus Pareledone charcoti at near freezing temperatures. Increased oxygen supply by haemocyanin at warmer temperatures supports extended warm tolerance and thus eurythermy of Pareledone charcoti. Limited haemocyanin function towards colder temperatures in Antarctic and warm water octopods highlights the general role of haemocyanin oxygen transport in constraining cold tolerance in octopods.

The amphibious fish Kryptolebias marmoratus uses different strategies to maintain oxygen delivery during aquatic hypoxia and air exposure.

Despite the abundance of oxygen in atmospheric air relative to water, the initial loss of respiratory surface area and accumulation of carbon dioxide in the blood of amphibious fishes during emersion may result in hypoxemia. Given that the ability to respond to low oxygen conditions predates the vertebrate invasion of land, we hypothesized that amphibious fishes maintain O2 uptake and transport while emersed by mounting a co-opted hypoxia response. We acclimated the amphibious fish Kryptolebias marmoratus, which are able to remain active for weeks in both air and water, for 7 days to normoxic brackish water (15‰, ~21kPa O2; control), aquatic hypoxia (~3.6kPa), normoxic air (~21 kPa) or aerial hypoxia (~13.6kPa). Angiogenesis in the skin and bucco-opercular chamber was pronounced in air- versus water-acclimated fish, but not in response to hypoxia. Aquatic hypoxia increased the O2-carrying capacity of blood via a large (40%) increase in red blood cell density and a small increase in the affinity of hemoglobin for O2 (P50 decreased 11%). In contrast, air exposure increased the hemoglobin O2 affinity (decreased P50) by 25% without affecting the number of red blood cells. Acclimation to aerial hypoxia both increased the O2-carrying capacity and decreased the hemoglobin O2 affinity. These results suggest that O2 transport is regulated both by O2 availability and also, independently, by air exposure. The ability of the hematological system to respond to air exposure independent of O2 availability may allow extant amphibious fishes, and may also have allowed primitive tetrapods to cope with the complex challenges of aerial respiration during the invasion of land.

The effect of chronic habitual exercise on oxygen carrying capacity and blood compartment volumes in older adults.

Absolute total hemoglobin mass (tHbmass) and blood compartment volumes are often considered to be higher in endurance athletes compared with nonathletes, yet little data support a fitness effect in older age. Therefore, we measured tHbmass and blood compartment volumes (carbon monoxide rebreathing) in 77 healthy individuals (23% female; aged, 60-87 yr). Participants were recruited into groups based upon their lifelong (>25 yr) exercise "dose": 1) 15 sedentary individuals, <2 sessions/wk; 2) 25 casual exercisers, 2-3 sessions/wk; 3) 24 committed exercisers, 4-5 sessions/wk; and 4) 13 competitive Masters athletes, 6-7 sessions/wk, plus regular competitions. Absolute (L/min) and relative (mL/kg/min) V̇o2peak were higher with increasing exercise "dose" (P = 0.0005 and P < 0.0001, respectively). Hemoglobin concentration, hematocrit, and absolute tHbmass and blood compartment volumes were not significantly different between groups (all, P > 0.1328). When scaled to body mass, tHbmass (Sedentary, 9.2 ± 1.7 mL/kg; Casual, 9.2 ± 1.3; Committed, 10.2 ± 1.4; Competitive, 11.5 ± 1.4, ANOVA P < 0.0001) and blood volume were significantly different between groups [Sedentary, 63.4 (59.2-68.5) mL/kg; Casual, 67.3 (64.4-72.6); Committed, 73.5 (67.5-80.2); Competitive, 83.4 (78.9-88.6), ANOVA P < 0.0001], whereby all values were highest in Masters athletes. However, when scaled to fat-free mass (FFM), tHbmass and blood compartment volumes were greater in Competitive compared with Casual exercisers (all, P < 0.0340) and tHbmass and erythrocyte volume were also higher in Committed compared with Casual exercisers (both, P < 0.0134). In conclusion, absolute tHbmass and blood compartment volumes are not different between groups, with dose-dependent differences only among exercisers when scaled for FFM, with the highest tHbmass and blood compartment volumes in competitive Masters athletes.NEW & NOTEWORTHY We observed that absolute oxygen carrying capacity (total hemoglobin mass, tHbmass) and blood compartment volumes were not associated with lifelong exercise dose. However, hematological adaptations associated with lifelong habitual exercise are only present among exercisers, whereby competitive Masters athletes have a greater oxygen carrying capacity (tHbmass) and expanded blood compartment volumes when scaled to fat-free mass.

Sex Differences in Orthostatic Tolerance Are Mainly Explained by Blood Volume and Oxygen Carrying Capacity.

OBJECTIVES: The reduced orthostatic tolerance (OT) that is characteristic of the female sex may be explained by multiple phenotypic differences between sexes. This study aimed to elucidate the mechanistic role of blood volume (BV) and oxygen carrying capacity on sex differences in OT. DESIGN: Experimental intervention. SETTING: University of Calgary, Main Campus, Calgary, AB, Canada. SUBJECTS: Healthy women and men (n = 90) throughout the adult lifespan (20-89 yr) matched by age and physical activity. INTERVENTIONS: Incremental lower body negative pressure (LBNP) in all individuals. Blood withdrawal and oxygen carrying capacity reduction in men to match with women's levels. MEASUREMENTS AND MAIN RESULTS: Transthoracic echocardiography and central blood pressures were assessed throughout incremental LBNP for 1 hour or until presyncope. Blood uniformization resulted in a precise sex match of BV and oxygen carrying capacity (p ≥ 0.598). A third of women (14/45) and two thirds of men (31/45) prior to blood uniformization completed the orthostatic test without presyncopal symptoms (p-for-sex < 0.001). After blood uniformization, seven out of 45 men completed the test (p-for-sex = 0.081). Left ventricular end-diastolic volume (LVEDV) and stroke volume (SV) were progressively reduced with LBNP in both sexes, with women showing markedly lower volumes than men (p < 0.001). Blood uniformization did not eliminate sex differences in LVEDV and SV. CONCLUSIONS: Sex differences in OT are not present when BV and oxygen carrying capacity are experimentally matched between sexes throughout the adult lifespan.

Sex-Specific Effect of Blood Oxygen-Carrying Capacity on Orthostatic Tolerance in Older Individuals.

Blood oxygen (O2)-carrying capacity is reduced with aging and has been previously linked with the capacity to withstand the upright posture, that is, orthostatic tolerance (OT). This study experimentally tested the hypothesis that a definite reduction in blood O2-carrying capacity via hemoglobin manipulation differently affects the OT of older women and men as assessed by lower body negative pressure (LBNP). Secondary hemodynamic parameters were determined with transthoracic echocardiography throughout incremental LBNP levels for 1 hour or until presyncope in healthy older women and men (total n = 26) matched by age (64 ± 7 vs 65 ± 8 years, p < .618) and physical activity levels. Measurements were repeated within a week period after a 10% reduction of blood O2-carrying capacity via carbon monoxide rebreathing and analyzed via 2-way analysis of covariance. In the assessment session, OT time was similar between women and men (53.5 ± 6.1 vs 56.4 ± 6.0 minutes, p = .238). Following a 10% reduction of blood O2-carrying capacity, OT time was reduced in women compared with men (51.3 ± 7.0 vs 58.2 ± 2.8 minutes, p = .003). The effect of reduced O2-carrying capacity on OT time differed between sexes (mean difference [MD] = -5.30 minutes, p = .010). Prior to presyncope, reduced O2-carrying capacity resulted in lower left ventricular end-diastolic volume (MD = -8.11 mL∙m-2, p = .043) and stroke volume (MD = -8.04 mL∙m-2, 95% confidence interval = -14.36, -1.71, p = .018) in women relative to men, even after adjusting for baseline variables. In conclusion, present results suggest that reduced blood O2-carrying capacity specifically impairs OT and its circulatory determinants in older women.

To Research the Effects of Storage Time on Autotransfusion based on Erythrocyte Oxygen-Carrying Capacity and Oxidative Damage Characteristics.

Autotransfusion refers to a blood transfusion method in which the blood or blood components of the patient are collected under certain conditions, returned to himself when the patient needs surgery or emergency after a series of storing and processing. Although autotransfusion can avoid blood-borne diseases and adverse reactions related to allogeneic blood transfusion, a series of structural and functional changes of erythrocytes will occur during extension of storage time, thus affecting the efficacy of clinical blood transfusion. Our research was aimed to explore the change of erythrocyte oxygen-carrying capacity in different storage time, such as effective oxygen uptake (Q), P50, 2,3-DPG, Na+-K+-ATPase, to detect membrane potential, the change of Ca2+, and reactive oxygen species (ROS) change of erythrocytes. At the same time, Western blot was used to detect the expression of Mitofusin 1 (Mfn1) and Mitofusin 2 (Mfn2) proteins on the cytomembrane, from the perspective of oxidative stress to explore the function change of erythrocytes after different storage time. This study is expected to provide experimental data for further clarifying the functional status of erythrocytes with different preservation time in patients with autotransfusion, achieving accurate infusion of erythrocytes and improving the therapeutic effect of autologous blood transfusion, which has important clinical application value.

The effect of different storage times on the oxygen-carrying capacity of the exosomes of red blood cells.

BACKGROUND: After storing blood for a period of time, the structure and properties of the red blood cells (RBC) will change, which results in a decrease in the oxygen-carrying capacity, and further has a certain impact on their exosomes. OBJECTIVES: Effective oxygen uptake (Q), P50, 2,3-DPG, and Na+-K+-ATP of RBC after different storage times were detected. Electron microscopy was used to observe the morphology of RBC and the characteristics of secreting exosomes. Western blot was used to detect the expression of phenotypes CD63 and CD81 of exosomes, and the expression of mitochondrial riboprotein MRPS35 of exosomes was also detected to explore the mechanism of decreased function of RBC with the extension of preservation time. MATERIAL AND METHODS: After the RBC suspension was prepared, the effective oxygen-carrying capacity (Q) and P50, as well as 2,3-DPG and Na+-K+-ATP were prepared. This was followed by morphology observation of erythrocyte exosomes using transmission electron microscope (TEM), and by western blot analysis of exosome phenotypes CD63 and CD81. RESULTS: Erythrocytes secrete exosomes, which results in abnormal expression of related proteins in mitochondria. This leads to increased ROS production, mitochondrial apoptosis and, finally, changes in or damage to erythrocytes. CONCLUSIONS: Changes in the rheological properties and oxygen-carrying functions of erythrocytes during preservation are all observable manifestations, and underlying these manifestations are mechanisms of damage to erythrocytes at a molecular level. Erythrocytes secrete exosomes, which results in abnormal expression of related proteins in mitochondria, increasing ROS production, mitochondrial apoptosis and, finally, changes or damage to erythrocytes.

To study the effect of oxygen carrying capacity on expressed changes of erythrocyte membrane protein in different storage times.

Erythrocyte membrane is crucial to maintain the stability of erythrocyte structure. The membrane protein on the surface of erythrocyte membrane enables erythrocyte to have plasticity and pass through the microcirculation without being blocked or destroyed. Decreased deformability of erythrocyte membrane protein will lead to a series of pathological and physiological changes such as tissue and organ ischemia and hypoxia. Therefore, this research collected 30 cases of healthy blood donors, and explored erythrocyte stored at different times relating indicators including effective oxygen uptake (Q), P50, 2,3-DPG, Na+-k+-ATP. Erythrocyte morphology was observed by electron microscopy. Western blot and immunofluorescence assay were used to detect membrane protein EPB41, S1P, GLTP, SPPL2A expression changes of erythrocyte. To explore the effective carry oxygen capacity of erythrocyte at different storage time resulting in the expression change of erythrocyte surface membrane protein.

The metabolism and swimming performance of sheepshead minnows (Cyprinodon variegatus) following thermal acclimation or acute thermal exposure.

Ectothermic animals are especially susceptible to temperature change, considering that their metabolism and core temperature are linked to the environmental temperature. As global water temperatures continue to increase, so does the need to understand the capacity of organisms to tolerate change. Sheepshead minnows (Cyprinodon variegatus) are the most eurythermic fish species known to date and can tolerate a wide range of environmental temperatures from - 1.9 to 43.0 °C. But little is known about the physiological adjustments that occur when these fish are subjected to acute thermal challenges and long-term thermal acclimation. Minnows were acclimated to 10, 21, or 32 °C for 4 weeks or acutely exposed to 10 and 32 °C and then assessed for swimming performance [maximum sustained swimming velocity (Ucrit), optimum swimming velocity (Uopt)] and metabolic endpoints (extrapolated standard and maximum metabolic rate [SMR, MMR), absolute aerobic scope (AS), and cost of transport (COT)]. Our findings show that the duration of thermal exposure (acute vs. acclimation) did not influence swimming performance. Rather, swimming performance was influenced by the exposure temperature. Swimming performance was statistically similar in fish exposed to 21 or 32 °C (approximately 7.0 BL s-1), but was drastically reduced in fish exposed to 10 °C (approximately 2.0 BL s-1), resulting in a left-skewed performance curve. There was no difference in metabolic end points between fish acutely exposed or acclimated to 10 °C. However, a different pattern was observed in fish exposed to 32 °C. MMR was similar between acutely exposed or acclimated fish, but acclimated fish had a 50% reduction in extrapolated SMR, which increased AS by 25%. However, this enhanced AS was not associated with changes in swimming performance, which opposes the oxygen-capacity limited thermal tolerance concept. Our findings suggest that sheepshead minnows may utilize two distinct acclimation strategies, resulting in different swimming performance and metabolic patterns observed between 10 and 32 °C exposures.