| 1. |
- Burggren, Warren, et al.
(författare)
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Breathing patterns and associated cardiovascular changes in intermittently breathing animals: (Partially) correcting a semantic quagmire
- 2024
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Ingår i: Experimental Physiology. - : WILEY. - 0958-0670 .- 1469-445X.
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Forskningsöversikt (refereegranskat)abstract
- Many animal species do not breathe in a continuous, rhythmic fashion, but rather display a variety of breathing patterns characterized by prolonged periods between breaths (inter-breath intervals), during which the heart continues to beat. Examples of intermittent breathing abound across the animal kingdom, from crustaceans to cetaceans. With respect to human physiology, intermittent breathing-also termed 'periodic' or 'episodic' breathing-is associated with a variety of pathologies. Cardiovascular phenomena associated with intermittent breathing in diving species have been termed 'diving bradycardia', 'submersion bradycardia', 'immersion bradycardia', 'ventilation tachycardia', 'respiratory sinus arrhythmia' and so forth. An examination across the literature of terminology applied to these physiological phenomena indicates, unfortunately, no attempt at standardization. This might be viewed as an esoteric semantic problem except for the fact that many of the terms variously used by different authors carry with them implicit or explicit suggestions of underlying physiological mechanisms and even human-associated pathologies. In this article, we review several phenomena associated with diving and intermittent breathing, indicate the semantic issues arising from the use of each term, and make recommendations for best practice when applying specific terms to particular cardiorespiratory patterns. Ultimately, we emphasize that the biology-not the semantics-is what is important, but also stress that confusion surrounding underlying mechanisms can be avoided by more careful attention to terms describing physiological changes during intermittent breathing and diving. What is the topic of this review? This review examines the rather confusing semantics that has been used to describe patterns in the field of cardiorespiratory physiology as it applies to intermittent breathing, particularly in diving species. What advances does it highlight? This review highlights the various cardiorespiratory phenomena associated with intermittent breathing and diving. It highlights the semantic issues associated with describing each and offers a rationale for standardizing terms based on underlying mechanisms to reduce confusion and advance the study of cardiorespiratory phenomena in both medical and comparative physiological investigations.
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| 2. |
- Cannon, Barbara, et al.
(författare)
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Human brown adipose tissue : Classical brown rather than brite/beige?
- 2020
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Ingår i: Experimental Physiology. - 0958-0670 .- 1469-445X. ; 105:8, s. 1191-1200
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Tidskriftsartikel (refereegranskat)abstract
- New Findings What is the topic of this review? It has been suggested that human brown adipose tissue (BAT) is more similar to the brite/beige adipose tissue of mice than to classical BAT of mice. The basis of this is discussed in relationship to the physiological conditions of standard experimental mice.
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| 3. |
- Elia, Antonis, et al.
(författare)
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Splenic responses to a series of repeated maximal static and dynamic apnoeas with whole-body immersion in water
- 2020
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Ingår i: Experimental Physiology. - : Blackwell Publishing Ltd. - 0958-0670 .- 1469-445X.
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Tidskriftsartikel (refereegranskat)abstract
- New Findings: What is the central question of this study? Splenic contractions occur in response to apnoea-induced hypoxia with and without face immersion in water. However, the splenic responses to a series of static or dynamic apnoeas with whole-body water immersion in non-divers and elite breath-hold divers are unknown. What is the main finding and its importance? Static and dynamic apnoeas were equally effective in stimulating splenic contractions across non-divers and elite breath-hold divers. These findings demonstrate that the magnitude of the splenic response is largely dictated by the degree of the hypoxemic stress encountered during voluntary apnoeic epochs. Abstract: Splenic contractions occur in response to apnoea-induced hypoxia with and without facial water immersion. However, the splenic responses to a series of static (STA) or dynamic (DYN) apnoeas with whole-body water immersion in non-divers (NDs) and elite breath-hold divers (EBHDs) are unknown. EBHD (n = 8), ND (n = 10) and control participants (n = 8) were recruited. EBHD and ND performed a series of five maximal DYN or STA on separate occasions. Control performed a static eupnoeic (STE) protocol to control against any effects of water immersion and diurnal variation on splenic volume and haematology. Heart rate (HR) and peripheral oxygen saturation (SpO2) were monitored for 30 s after each apnoea. Pre- and post-apnoeic splenic volumes were quantified ultrasonically, and blood samples were drawn for haematology. For EBHD and ND end-apnoeic HR was higher (P < 0.001) and SpO2 was lower in DYN (P = 0.024) versus STA. EBHD attained lower end-apnoeic SpO2 during DYN and STA than NDs (P < 0.001). Splenic contractions occurred following DYN (EBHD, −47 ± 6%; ND, −37 ± 4%; P < 0.001) and STA (EBHD, −26 ± 4%; ND, −26 ± 8%; P < 0.01). DYN-associated splenic contractions were greater than STA in EBHD only (P = 0.042). Haemoglobin concentrations were higher following DYN only (EBHD, +5 ± 8g/L, +4 ± 2%; ND, +8 ± 3 g/L, +4.9 ± 3%; P = 0.019). Haematocrit remained unchanged after each protocol. There were no between group differences in post-apnoeic splenic volume or haematology. In both groups, splenic contractions occurred in response to STA and DYN when combined with whole-body immersion. DYN apnoeas, were effective at increasing haemoglobin concentrations but not STA apnoeas. Thus, the magnitude of the splenic response relates to the hypoxemic stress encountered during apnoeic epochs.
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| 4. |
- Elia, Antonis, et al.
(författare)
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Whole-body vibration preconditioning reduces the formation and delays the manifestation of high-altitude-induced venous gas emboli.
- 2021
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Ingår i: Experimental Physiology. - : Wiley. - 0958-0670 .- 1469-445X. ; 106:8, s. 1743-1751
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Tidskriftsartikel (refereegranskat)abstract
- NEW FINDINGS: What is the central question of this study? Is performing a 30-min whole-body vibration (WBV) prior to a continuous 90-min exposure at 24,000 ft sufficient to prevent venous gas emboli (VGE) formation? What is the main finding and its importance? WBV preconditioning significantly reduces the formation and delays the manifestation of high-altitude-induced VGE. This study suggests that WBV is an effective strategy in lowering decompression stress.ABSTRACT: Rapid decompression may give rise to formation of venous gas emboli (VGE) and resultantly, increase the risk of sustaining decompression sickness. Preconditioning aims at lowering the prevalence of VGE during decompression. The purpose of this study was to investigate the efficacy of whole-body vibration (WBV) preconditioning on high-altitude-induced VGE. Eight male subjects performed, on separate days in a randomised order, three preconditioning strategies: 40-min seated-rest (control), 30-min seated-rest followed by 150 knee-squats performed over a 10-min period (exercise) and 30-min WBV proceeded by a 10-min seated-rest. Thereafter, subjects were exposed to an altitude of 24,000 ft (7315 m) for 90 min whilst laying in a supine position and breathing 100% oxygen. VGE were assessed ultrasonically both during supine rest (5-min intervals) and after three fast, unloaded knee-bends (15-min intervals) and were scored using a 5-grade scale and evaluated using the Kisman Integrated Severity Score (KISS). There was a significant difference in VGE grade (P < 0.001), time to VGE manifestation (P = 0.014) and KISS score following knee-bends (P = 0.002) across protocols, with a trend in KISS score during supine rest (P = 0.070). WBV resulted in lower VGE grades (median (range), 1 (0-3)) and KISS score (2.69 ± 4.56 a.u.) compared with control (2 (1-3), P = 0.002; 12.86 ± 8.40 a.u., P = 0.011) and exercise (3 (2-4) , P < 0.001; 22.04 ± 13.45 a.u., P = 0.002). VGE were detected earlier during control (15 ± 14 min, P = 0.024) and exercise (17 ± 24 min, P = 0.032) than WBV (54 ± 38 min). Performing a 30-min WBV prior to a 90-min continuous exposure at 24,000 ft both delays the manifestation and reduces the formation of VGE compared with control and exercise preconditioning.
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| 5. |
- Fahlman, Andreas
(författare)
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Cardiorespiratory adaptations in small cetaceans and marine mammals
- 2023
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Ingår i: Experimental Physiology. - : WILEY. - 0958-0670 .- 1469-445X.
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Forskningsöversikt (refereegranskat)abstract
- The dive response, or the master switch of life, is probably the most studied physiological trait in marine mammals and is thought to conserve the available O-2 for the heart and brain. Although generally thought to be an autonomic reflex, several studies indicate that the cardiovascular changes during diving are anticipatory and can be conditioned. The respiratory adaptations, where the aquatic breathing pattern resembles intermittent breathing in land mammals, with expiratory flow exceeding 160 litres s(-1) has been measured in cetaceans, and where exposure to extreme pressures results in alveolar collapse (atelectasis) and recruitment upon ascent. Cardiorespiratory coupling, where breathing results in changes in heart rate, has been proposed to improve gas exchange. Cardiorespiratory coupling has also been reported in marine mammals, and in the bottlenose dolphin, where it alters both heart rate and stroke volume. When accounting for this respiratory dependence on cardiac function, several studies have reported an absence of a diving-related bradycardia except during dives that exceed the duration that is fuelled by aerobic metabolism. This review summarizes what is known about the respiratory physiology in marine mammals, with a special focus on cetaceans. The cardiorespiratory coupling is reviewed, and the selective gas exchange hypothesis is summarized, which provides a testable mechanism for how breath-hold diving vertebrates may actively prevent uptake of N-2 during routine dives, and how stress results in failure of this mechanism, which results in diving-related gas emboli.
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| 6. |
- Holmström, Pontus K., et al.
(författare)
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Differential splenic responses to hyperoxic breathing at high altitude in Sherpa and lowlanders
- 2024
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Ingår i: Experimental Physiology. - : Wiley. - 0958-0670 .- 1469-445X. ; 109:4, s. 535-548
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Tidskriftsartikel (refereegranskat)abstract
- The human spleen contracts in response to stress-induced catecholamine secretion, resulting in a temporary rise in haemoglobin concentration ([Hb]). Recent findings highlighted enhanced splenic response to exercise at high altitude in Sherpa, possibly due to a blunted splenic response to hypoxia. To explore the potential blunted splenic contraction in Sherpas at high altitude, we examined changes in spleen volume during hyperoxic breathing, comparing acclimatized Sherpa with acclimatized individuals of lowland ancestry. Our study included 14 non-Sherpa (7 female) residing at altitude for a mean continuous duration of 3 months and 46 Sherpa (24 female) with an average of 4 years altitude exposure. Participants underwent a hyperoxic breathing test at altitude (4300 m; barrometric pressure = ∼430 torr; (Formula presented.) = ∼90 torr). Throughout the test, we measured spleen volume using ultrasonography and monitored oxygen saturation ((Formula presented.)). During rest, Sherpa exhibited larger spleens (226 ± 70 mL) compared to non-Sherpa (165 ± 34 mL; P < 0.001; effect size (ES) = 0.95, 95% CI: 0.3–1.6). In response to hyperoxia, non-Sherpa demonstrated 22 ± 12% increase in spleen size (35 ± 17 mL, 95% CI: 20.7–48.9; P < 0.001; ES = 1.8, 95% CI: 0.93–2.66), while spleen size remained unchanged in Sherpa (−2 ± 13 mL, 95% CI: −2.4 to 7.3; P = 0.640; ES = 0.18, 95% CI: −0.10 to 0.47). Our findings suggest that Sherpa and non-Sherpas of lowland ancestry exhibit distinct variations in spleen volume during hyperoxia at high altitude, potentially indicating two distinct splenic functions. In Sherpa, this phenomenon may signify a diminished splenic response to altitude-related hypoxia at rest, potentially contributing to enhanced splenic contractions during physical stress. Conversely, non-Sherpa experienced a transient increase in spleen size during hyperoxia, indicating an active tonic contraction, which may influence early altitude acclimatization in lowlanders by raising [Hb].
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| 7. |
- Holmström, Pontus, et al.
(författare)
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The effects of high altitude ascent on splenic contraction and the diving response during voluntary apnea
- 2021
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Ingår i: Experimental Physiology. - 0958-0670 .- 1469-445X. ; 106:1, s. 160-174
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Tidskriftsartikel (refereegranskat)abstract
- Voluntary apnea causes splenic contraction and reductions in heart rate (HR; bradycardia), and subsequent transient increases in hemoglobin 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 hematological 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, apnea-induced responses in HR, SpO2 and splenic volume were measured before and after two separate voluntary maximal apneas (A1-A2) at 1400 m, 3440 m and 4240 m. Resting spleen volume decreased -14.3% (-15.2 mL)/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 (1400 m) to 128±10.4 g/L (3440 m), 138.8±12.7 g/L (4240 m) and 157.5±8 g/L (5160 m; P = 0.021). Apnea-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 apnea-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 apnea-induced [Hb] increases in hypoxia. We suggest that tonic splenic contraction may contribute to hematological acclimatization early in HA ascent in humans.
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| 8. |
- Iacomino, G., et al.
(författare)
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Circulating miRNAs are associated with sleep duration in children/adolescents: Results of the I.Family Study
- 2020
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Ingår i: Experimental Physiology. - : Wiley. - 0958-0670 .- 1469-445X. ; 105:2, s. 347-356
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Tidskriftsartikel (refereegranskat)abstract
- New Findings What is the central question of this study?Are differential patterns of circulating miRNAs associated with sleep duration in normal-weight European children and adolescents? What is the main finding and its importance?Differences in the expression level of circulating miR-26b-3p and miR-485-5p are positively associated with total sleep duration in healthy normal-weight children and adolescents. It is commonly recognized that sleep is essential for children's health, and that insufficient sleep duration is associated with negative health outcomes. In humans, sleep duration and quality are influenced by genetic, environmental and social factors. Epigenetic mechanisms, likewise, regulate circadian rhythms and sleep patterns. In the present study, we aimed to identify circulating microRNAs associated with sleep duration in a subsample of normal-weight European children/adolescents (n = 111) participating in the I.Family Study. Subjects were divided into two groups based upon self-reported sleep duration, according to the recommended amount of sleep for paediatric populations. Sleep needs for children <13 years were at least 9 h per day, and for children >13 were at least 8 h per day. There were group differences (short sleepers versus normal sleepers) in circulating levels of miR-26b-3p (mean (95% CI) = 2.0 (1.3-2.7) versus 2.3 (1.9-2.7), P = 0.05) and miR-485-5p (mean (95% CI) = 0.6 (0.3-0.9) versus 0.9 (0.7 - 1.0), P < 0.001), adjusting for country of origin, age, sex, pubertal status, screen time and highest educational level of parents. Our findings show for the first time that sleep duration reflects the profile of specific circulating microRNAs in school-aged children and adolescents. It is conceivable that epigenetic modifications, mainly related to circadian rhythm control, may be modulated or interfere with sleep duration.
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| 9. |
- Keramidas, Michail E., Assistant Professor, et al.
(författare)
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Hypoxia gradually augments metabolic and thermoperceptual responsiveness to repeated whole-body cold stress in humans
- 2020
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Ingår i: Experimental Physiology. - 0958-0670 .- 1469-445X. ; 105, s. 2123-2140
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Tidskriftsartikel (refereegranskat)abstract
- We examined whether hypoxia would modulate thermoeffector responses during repeated cold stress encountered in a single day. Eleven men completed two ∼10 h sessions, while breathing, in normobaria, either normoxia or hypoxia (PO2 : 12 kPa). During each session, subjects underwent sequentially three 120 min immersions to the chest in 20◦C water (CWI), interspersed by 120 min rewarming. In normoxia, the final drop in rectal temperature (Trec) was greater in the third (∼1.2◦C) than in the first and second (∼0.9◦C) CWIs (P < 0.05). The first hypoxic CWI augmented the Trec fall (∼1.2◦C; P = 0.002), but the drop in Trec did not vary between the three hypoxic CWIs (P = 0.99). In normoxia, the metabolic heat production (Ṁ ) was greater during the first half of the third CWI than during the corresponding part of the first CWI (P = 0.02); yet the difference was blunted during the second half of the CWIs (P = 0.89). In hypoxia, by contrast, the increase in Ṁ was augmented by ∼25% throughout the third CWI (P < 0.01). Regardless of the breathing condition, the cold-induced elevation in mean arterial pressure was blunted in the second and third CWI (P < 0.05). Hypoxia aggravated the sensation of coldness (P = 0.05) and thermal discomfort (P = 0.04) during the second half of the third CWI. The present findings therefore demonstrate that prolonged hypoxia mediates, in a gradual manner, metabolic and thermoperceptual sensitization to repeated cold stress.
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| 10. |
- Keramidas, Michail E., Assistant Professor, et al.
(författare)
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Short-term sleep deprivation and human thermoregulatory function during thermal challenges
- 2021
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Ingår i: Experimental Physiology. - : Wiley. - 0958-0670 .- 1469-445X. ; 106:5, s. 1139-1148
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Tidskriftsartikel (refereegranskat)abstract
- bstractRelatively short periods of inadequate sleep provoke physiological and psychological perturbations, typically leading to functional impairments and degradation in performance. It is commonly accepted that sleep deprivation also disturbs thermal homeostasis, plausibly enhancing susceptibility to cold- and heat-related illnesses. Herein, we summarize the current state of human-based evidence on the impact of short-term (i.e., ≤4 nights) sleep deprivation on autonomic and behavioural thermoeffectors during acute exposure to low and high ambient temperatures. The purpose of this brief narrative review is to highlight knowledge gaps in the area and stimulate future research to investigate whether sleep deprivation constitutes a predisposing factor for the development of thermal injuries.
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