Asthma and obesity: endotoxin another insult to add to injury?

Low-grade inflammation is often an underlying cause of several chronic diseases such as asthma, obesity, cardiovascular disease, and type 2 diabetes mellitus (T2DM). Defining the mediators of such chronic low-grade inflammation often appears dependent on which disease is being investigated. However, downstream systemic inflammatory cytokine responses in these diseases often overlap, noting there is no doubt more than one factor at play to heighten the inflammatory response. Furthermore, it is increasingly believed that diet and an altered gut microbiota may play an important role in the pathology of such diverse diseases. More specifically, the inflammatory mediator endotoxin, which is a complex lipopolysaccharide (LPS) derived from the outer membrane cell wall of Gram-negative bacteria and is abundant within the gut microbiota, and may play a direct role alongside inhaled allergens in eliciting an inflammatory response in asthma. Endotoxin has immunogenic effects and is sufficiently microscopic to traverse the gut mucosa and enter the systemic circulation to act as a mediator of chronic low-grade inflammation in disease. Whilst the role of endotoxin has been considered in conditions of obesity, cardiovascular disease and T2DM, endotoxin as an inflammatory trigger in asthma is less well understood. This review has sought to examine the current evidence for the role of endotoxin in asthma, and whether the gut microbiota could be a dietary target to improve disease management. This may expand our understanding of endotoxin as a mediator of further low-grade inflammatory diseases, and how endotoxin may represent yet another insult to add to injury.

The control of respiratory pressures and neuromuscular activation to increase force production in trained martial arts practitioners.

PURPOSE: The mechanisms that explain the ability of trained martial arts practitioners to produce and resist greater forces than untrained individuals to aid combat performance are not fully understood. We investigated whether the greater ability of trained martial arts practitioners to produce and resist forces was associated with an enhanced control of respiratory pressures and neuromuscular activation of the respiratory, abdominal, and pelvic floor musculature. METHODS: Nine trained martial arts practitioners and nine untrained controls were instrumented with skin-surface electromyography (EMG) on the sternocleidomastoid, rectus abdominis, and the group formed by the transverse abdominal and internal oblique muscles (EMGtra/io). A multipair oesophageal EMG electrode catheter measured gastric (Pg), transdiaphragmatic (Pdi), and oesophageal (Pe) pressures and EMG of the crural diaphragm (EMGdi). Participants performed Standing Isometric Unilateral Chest Press (1) and Standing Posture Control (2) tasks. RESULTS: The trained group produced higher forces normalised to body mass2/3 (0.033 ± 0.01 vs. 0.025 ± 0.007 N/kg2/3 mean force in Task 1), lower Pe, and higher Pdi in both tasks. Additionally, they produced higher Pg (73 ± 42 vs. 49 ± 19 cmH2O mean Pg) and EMGtra/io in Task 1 and higher EMGdi in Task 2. The onset of Pg with respect to the onset of force production was earlier, and the relative contributions of Pg/Pe and Pdi/Pe were higher in the trained group in both tasks. CONCLUSION: Our findings demonstrate that trained martial arts practitioners utilised a greater contribution of abdominal and diaphragm musculature to chest wall recruitment and higher Pdi to produce and resist higher forces.

Comparable reductions in hyperpnoea-induced bronchoconstriction and markers of airway inflammation after supplementation with 6·2 and 3·1 g/d of long-chain n-3 PUFA in adults with asthma.

Although high dose n-3 PUFA supplementation reduces exercise- and hyperpnoea-induced bronchoconstriction (EIB/HIB), there are concurrent issues with cost, compliance and gastrointestinal discomfort. It is thus pertinent to establish the efficacy of lower n-3 PUFA doses. Eight male adults with asthma and HIB and eight controls without asthma were randomly supplemented with two n-3 PUFA doses (6·2 g/d (3·7 g EPA and 2·5 g DHA) and 3·1 g/d (1·8 g EPA and 1·3 g DHA)) and a placebo, each for 21 d followed by 14 d washout. A eucapnic voluntary hyperpnoea (EVH) challenge was performed before and after treatments. Outcome measures remained unchanged in the control group. In the HIB group, the peak fall in forced expiratory volume in 1 s (FEV1) after EVH at day 0 (-1005 (sd 520) ml, -30 (sd 18) %) was unchanged after placebo. The peak fall in FEV1 was similarly reduced from day 0 to day 21 of 6·2 g/d n-3 PUFA (-1000 (sd 460) ml, -29 (sd 17) % v. -690 (sd 460) ml, -20 (sd 15) %) and 3·1 g/d n-3 PUFA (-970 (sd 480) ml, -28 (sd 18) % v. -700 (sd 420) ml, -21 (sd 15) %) (P<0·001). Baseline fraction of exhaled nitric oxide was reduced by 24 % (P=0·020) and 31 % (P=0·018) after 6·2 and 3·1 g/d n-3 PUFA, respectively. Peak increases in 9α, 11ß PGF2 after EVH were reduced by 65 % (P=0·009) and 56 % (P=0·041) after 6·2 and 3·1 g/d n-3 PUFA, respectively. In conclusion, 3·1 g/d n-3 PUFA supplementation attenuated HIB and markers of airway inflammation to a similar extent as a higher dose. Lower doses of n-3 PUFA thus represent a potentially beneficial adjunct treatment for adults with asthma and EIB.

A prebiotic galactooligosaccharide mixture reduces severity of hyperpnoea-induced bronchoconstriction and markers of airway inflammation.

Gut microbes have a substantial influence on systemic immune function and allergic sensitisation. Manipulation of the gut microbiome through prebiotics may provide a potential strategy to influence the immunopathology of asthma. This study investigated the effects of prebiotic Bimuno-galactooligosaccharide (B-GOS) supplementation on hyperpnoea-induced bronchoconstriction (HIB), a surrogate for exercise-induced bronchoconstriction, and airway inflammation. A total of ten adults with asthma and HIB and eight controls without asthma were randomised to receive 5·5 g/d of either B-GOS or placebo for 3 weeks separated by a 2-week washout period. The peak fall in forced expiratory volume in 1 s (FEV1) following eucapnic voluntary hyperpnoea (EVH) defined HIB severity. Markers of airway inflammation were measured at baseline and after EVH. Pulmonary function remained unchanged in the control group. In the HIB group, the peak post-EVH fall in FEV1 at day 0 (-880 (sd 480) ml) was unchanged after placebo, but was attenuated by 40 % (-940 (sd 460) v. -570 (sd 310) ml, P=0·004) after B-GOS. In the HIB group, B-GOS reduced baseline chemokine CC ligand 17 (399 (sd 140) v. 323 (sd 144) pg/ml, P=0·005) and TNF-α (2·68 (sd 0·98) v. 2·18 (sd 0·59) pg/ml, P=0·040) and abolished the EVH-induced 29 % increase in TNF-α. Baseline C-reactive protein was reduced following B-GOS in HIB (2·46 (sd 1·14) v. 1·44 (sd 0·41) mg/l, P=0·015) and control (2·16 (sd 1·02) v. 1·47 (sd 0·33) mg/l, P=0·050) groups. Chemokine CC ligand 11 and fraction of exhaled nitric oxide remained unchanged. B-GOS supplementation attenuated airway hyper-responsiveness with concomitant reductions in markers of airway inflammation associated with HIB.

Effects of Oral Lactate Supplementation on Acid-Base Balance and Prolonged High-Intensity Interval Cycling Performance.

Lactate is an important energy intermediate and metabolic buffer, and may be ergogenic. We investigated if lactate supplementation is an effective approach to enhance the exercise performance and acid-base balance of trained cyclists during exercise devised to simulate the demands of endurance road race cycling. Sixteen endurance-trained male cyclists (V·O2max 59 ± 7 mL·kg-1·min-1) consumed 120 mg·kg-1 body mass of lactate or a placebo 70 min prior to performing an exercise performance test, comprising five repeated blocks consisting of 1 km and 4 km time trials interspersed with 10 min of moderate-intensity exercise. Blood acid-base balance (including [H+] and [HCO3-]), heart rate, perceived exertion, and gastro-intestinal tolerance were assessed. There was no effect of lactate supplementation on exercise performance (p = 0.320), despite a reduction in RPE (p = 0.012) and increases in [SID] (p = 0.026) and [HCO3-] (p = 0.041). In addition, gastro-intestinal side effects were observed, but there was no effect on heart rate. Lactate supplementation did not improve exercise performance, despite positive changes in acid-base balance and RPE. This suggests that the alkalising effects of the supplement can reduce perceived effort, but these benefits do not translate into performance improvements.

The effects of age on dyspnea and respiratory mechanical and neural responses to exercise in healthy men.

The respiratory muscle pressure generation and inspiratory and expiratory neuromuscular recruitment patterns in younger and older men were compared during exercise, alongside descriptors of dyspnea. Healthy younger (n = 8, 28 ± 5 years) and older (n = 8, 68 ± 4 years) men completed a maximal incremental cycling test. Esophageal, gastric (Pga ) and transdiaphragmatic pressures, and electromyography (EMG) of the crural diaphragm were measured using a micro-transducer and EMG catheter. EMG of the parasternal intercostals, sternocleidomastoids, and rectus abdominis were measured using skin surface electrodes. After the exercise test, participants completed a questionnaire to evaluate descriptors of dyspnea. Pga at end-expiration, Pga expiratory tidal swings, and the gastric pressure-time product (PTPga ) at absolute and relative minute ventilation were higher (p < 0.05) for older compared to younger men. There were no differences in EMG responses between older and younger men. Younger men were more likely to report shallow breathing (p = 0.005) than older men. Our findings showed younger and older men had similar respiratory neuromuscular activation patterns and reported different dyspnea descriptors, and that older men had greater expiratory muscle pressure generation during exercise. Greater expiratory muscle pressures in older men may be due to compensatory mechanisms designed to offset increasing airway resistance due to aging. These results may have implications for exercise-induced expiratory muscle fatigue in older men.

Inspiratory muscle training abolishes the blood lactate increase associated with volitional hyperpnoea superimposed on exercise and accelerates lactate and oxygen uptake kinetics at the onset of exercise.

We examined the effects of inspiratory muscle training (IMT) upon volitional hyperpnoea-mediated increases in blood lactate ([lac(-)](B)) during cycling at maximal lactate steady state (MLSS) power, and blood lactate and oxygen uptake kinetics at the onset of exercise. Twenty males formed either an IMT (n = 10) or control group (n = 10). Prior to and following a 6-week intervention, two 30 min trials were performed at MLSS (207 ± 28 W), determined using repeated 30 min constant power trials. The first was a reference trial, whereas during the second trial, from 20 to 28 min, participants mimicked the breathing pattern commensurate with 90% of the maximal incremental exercise test minute ventilation ([Formula: see text]). Prior to the intervention, the MLSS [lac(-)](B) was 3.7 ± 1.8 and 3.9 ± 1.6 mmol L(-1) in the IMT and control groups, respectively. During volitional hyperpnoea, [Formula: see text] increased from 79.9 ± 9.5 and 76.3 ± 15.4 L min(-1) at 20 min to 137.8 ± 15.2 and 135.0 ± 19.7 L min(-1) in IMT and control groups, respectively; [lac(-)](B) concurrently increased by 1.0 ± 0.6 (+27%) and 0.9 ± 0.7 mmol L(-1) (+25%), respectively (P < 0.05). Following the intervention, maximal inspiratory mouth pressure increased 19% in the IMT group only (P < 0.01). Following IMT only, the increase in [lac(-)](B) during volitional hyperpnoea was abolished (P < 0.05). In addition, the blood lactate (-28%) and phase II oxygen uptake (-31%) kinetics time constants at the onset of exercise and the MLSS [lac(-)](B) (-15%) were reduced (P < 0.05). We attribute these changes to an IMT-mediated increase in the oxidative and/or lactate transport capacity of the inspiratory muscles.

Exercise-induced bronchoconstriction in university field hockey athletes: Prevalence, sex differences, and associations with dyspnea symptoms.

Introduction: Exercise-induced bronchoconstriction (EIB) is a prevalent condition in athletes. EIB screening studies identify many athletes with undiagnosed EIB. Moreover, there is a poor relationship between EIB and dyspnea symptoms recalled from memory. Purpose: This study investigated: (I) the prevalence of EIB in British university field hockey athletes; (II) the effect of sex and diagnostic criteria on EIB prevalence; and (III) the association between EIB and contemporaneous dyspnea symptoms. Methods: 52 field hockey athletes (age: 20 ± 2 years; height: 173 ± 9 cm; body mass: 72 ± 10 kg; male = 31; female = 22) completed a eucapnic voluntary hyperpnea (EVH) test with multi-dimensional dyspnea scores measured 3-10 mins post-EVH. A test was deemed positive (EIB+) if a fall index (FI) ≥10% in FEV1 occurred at two consecutive time points post-test (FIATS). Two further criteria were used to assess the effect of diagnostic criteria on prevalence: FI≥10%, determined by a pre-to-post-EVH fall in FEV1 of ≥10% at any single time-point; and FI≥10%-NORM calculated as FI≥10% but with the fall in FEV1 normalized to the mean ventilation achieved during EVH. Results: EIB prevalence was 19% and greater in males (30%) than females (5%). In EIB+ athletes, 66% did not have a previous diagnosis of EIB or asthma and were untreated. Prevalence was significantly influenced by diagnostic criteria (P = 0.002) ranging from 19% (FIATS) to 38% (FI≥10%-NORM). Dyspnea symptoms were higher in EIB+ athletes (P ≤ 0.031), produced significant area under the curve for receive operator characteristics (AUC ≥ 0.778, P ≤ 0.011) and had high negative prediction values (≥96%). Conclusion: Overall, 19% of university field hockey athletes had EIB, and most were previously undiagnosed and untreated. EVH test diagnostic criteria significantly influences prevalence rates, thus future studies should adopt the ATS criteria (FIATS). Contemporaneous dyspnea symptoms were associated with bronchoconstriction and had high negative prediction values. Therefore, contemporaneous dyspnea scores may provide a useful tool in excluding a diagnosis of EIB.

Pressure measurement characteristics of a micro-transducer and balloon catheters.

Respiratory pressure responses to cervical magnetic stimulation are important measurements in monitoring the mechanical function of the respiratory muscles. Pressures can be measured using balloon catheters or a catheter containing integrated micro-transducers. However, no research has provided a comprehensive analysis of their pressure measurement characteristics. Accordingly, the aim of this study was to provide a comparative analysis of these characteristics in two separate experiments: (1) in vitro with a reference pressure transducer following a controlled pressurization; and (2) in vivo following cervical magnetic stimulations. In vitro the micro-transducer catheter recorded pressure amplitudes and areas which were in closer agreement to the reference pressure transducer than the balloon catheter. In vivo there was a main effect for stimulation power and catheter for esophageal (Pes ), gastric (Pga ), and transdiaphragmatic (Pdi ) pressure amplitudes (p < 0.001) with the micro-transducer catheter recording larger pressure amplitudes. There was a main effect of stimulation power (p < 0.001) and no main effect of catheter for esophageal (p = 0.481), gastric (p = 0.923), and transdiaphragmatic (p = 0.964) pressure areas. At 100% stimulator power agreement between catheters for Pdi amplitude (bias =6.9 cmH2 O and LOA -0.61 to 14.27 cmH2 O) and pressure areas (bias = -0.05 cmH2 O·s and LOA -1.22 to 1.11 cmH2 O·s) were assessed. At 100% stimulator power, and compared to the balloon catheters, the micro-transducer catheter displayed a shorter 10-90% rise time, contraction time, latency, and half-relaxation time, alongside greater maximal rates of change in pressure for esophageal, gastric, and transdiaphragmatic pressure amplitudes (p < 0.05). These results suggest that caution is warranted if comparing pressure amplitude results utilizing different catheter systems, or if micro-transducers are used in clinical settings while applying balloon catheter-derived normative values. However, pressure areas could be used as an alternative point of comparison between catheter systems.

Effects of Prior Voluntary Hyperventilation on the 3-min All-Out Cycling Test in Men.

INTRODUCTION: The ergogenic effects of respiratory alkalosis induced by prior voluntary hyperventilation (VH) are controversial. This study examined the effects of prior VH on derived parameters from the 3-min all-out cycling test (3MT). METHODS: Eleven men ( = 46 ± 8 mL·kg-1·min-1) performed a 3MT preceded by 15 min of rest (CONT) or VH ( = 38 ± 5 L·min-1) with PETCO2 reduced to 21 ± 1 mm Hg (HYP). End-test power (EP; synonymous with critical power) was calculated as the mean power output over the last 30 s of the 3MT, and the work done above EP (WEP; synonymous with W') was calculated as the power-time integral above EP. RESULTS: At the start of the 3MT, capillary blood PCO2 and [H+] were lower in HYP (25.2 ± 3.0 mm Hg, 27.1 ± 2.6 nmol·L-1) than CONT (43.2 ± 2.0 mm Hg, 40.0 ± 1.5 nmol·L-1) (P < 0.001). At the end of the 3MT, blood PCO2 was still lower in HYP (35.7 ± 5.4 mm Hg) than CONT (40.6 ± 5.0 mm Hg) (P < 0.001). WEP was 10% higher in HYP (19.4 ± 7.0 kJ) than CONT (17.6 ± 6.4 kJ) (P = 0.006), whereas EP was 5% lower in HYP (246 ± 69 W) than CONT (260 ± 74 W) (P = 0.007). The ΔWEP (J·kg-1) between CONT and HYP correlated positively with the PCO2 immediately before the 3MT in HYP (r = 0.77, P = 0.006). CONCLUSION: These findings suggest that acid-base changes elicited by prior VH increase WEP but decrease EP during the all-out 3MT.

Effects of Prior Upper Body Exercise on the 3-min All-Out Cycling Test in Men.

INTRODUCTION: Prior upper body exercise reduces the curvature constant (W') of the hyperbolic power-duration relationship without affecting critical power. This study tested the hypothesis that prior upper body exercise reduces the work done over the end-test power (WEP; analog of W') during a 3-min all-out cycling test (3MT) without affecting the end-test power (EP; analog of critical power). METHODS: Ten endurance-trained men (V˙O2max = 62 ± 5 mL·kg·min) performed a 3MT without (CYC) and with (ARM-CYC) prior severe-intensity, intermittent upper body exercise. EP was calculated as the mean power output over the last 30 s of the 3MT, whereas WEP was calculated as the power-time integral above EP. RESULTS: At the start of the 3MT, plasma [La] (1.8 ± 0.4 vs 14.1 ± 3.4 mmol·L) and [H] (42.8 ± 3.1 vs 58.6 ± 5.5 nmol·L) were higher, whereas the strong ion difference (41.4 ± 2.2 vs 30.9 ± 4.6 mmol·L) and [HCO3] (27.0 ± 1.9 vs 16.9 ± 3.2 mmol·L) were lower during ARM-CYC than CYC (P < 0.010). EP was 12% lower during the 3MT of ARM-CYC (298 ± 52 W) than CYC (338 ± 60 W; P < 0.001), whereas WEP was not different (CYC: 12.8 ± 3.3 kJ vs ARM-CYC: 13.5 ± 4.1 kJ, P = 0.312). EP in CYC was positively correlated with the peak [H] (r = 0.78, P = 0008) and negatively correlated with the lowest [HCO3] (r = -0.74, P = 0.015). CONCLUSIONS: These results suggest that EP during a 3MT in endurance-trained men is sensitive to fatigue-related ionic perturbation.

Inspiratory flow-resistive breathing, respiratory muscle-induced systemic oxidative stress, and diaphragm fatigue in healthy humans.

We questioned whether the respiratory muscles of humans contribute to systemic oxidative stress following inspiratory flow-resistive breathing, whether the amount of oxidative stress is influenced by the level of resistive load, and whether the amount of oxidative stress is related to the degree of diaphragm fatigue incurred. Eight young and healthy participants attended the laboratory for four visits on separate days. During the first visit, height, body mass, lung function, and maximal inspiratory mouth and transdiaphragmatic pressure (Pdimax) were assessed. During visits 2-4, participants undertook inspiratory flow-resistive breathing with either no resistance (control) or resistive loads equivalent to 50 and 70% of their Pdimax (Pdimax50% and Pdimax70%) for 30 min. Participants undertook one resistive load per visit, and the order in which they undertook the loads was randomized. Inspiratory muscle pressures were higher (P < 0.05) during the 5th and Final min of Pdimax50% and Pdimax70% compared with control. Plasma F2-isoprostanes increased (P < 0.05) following inspiratory flow-resistive breathing at Pdimax70%. There were no increases in plasma protein carbonyls or total antioxidant capacity. Furthermore, although we evidenced small reductions in transdiapragmaic twitch pressures (PdiTW) after inspiratory flow-resistive breathing at Pdimax50% and Pdimax70%, this was not related to the increase in plasma F2-isoprostanes. Our novel data suggest that it is only when sufficiently strenuous that inspiratory flow-resistive breathing in humans elicits systemic oxidative stress evidenced by elevated plasma F2-isoprostanes, and based on our data, this is not related to a reduction in PdiTW.NEW & NOTEWORTHY We examined whether the respiratory muscles of humans contribute to systemic oxidative stress following inspiratory flow-resistive breathing, whether the amount of oxidative stress is influenced by the level of resistive load, and whether the amount of oxidative stress is related to the degree of diaphragm fatigue incurred. It is only when sufficiently strenuous that inspiratory flow-resistive breathing elevates plasma F2-isoprostanes, and our novel data show that this is not related to a reduction in transdiaphragmatic twitch pressure.

Machine Learning Analysis for Quantitative Discrimination of Dried Blood Droplets.

One of the most interesting and everyday natural phenomenon is the formation of different patterns after the evaporation of liquid droplets on a solid surface. The analysis of dried patterns from blood droplets has recently gained a lot of attention, experimentally and theoretically, due to its potential application in diagnostic medicine and forensic science. This paper presents evidence that images of dried blood droplets have a signature revealing the exhaustion level of the person, and discloses an entirely novel approach to studying human dried blood droplet patterns. We took blood samples from 30 healthy young male volunteers before and after exhaustive exercise, which is well known to cause large changes to blood chemistry. We objectively and quantitatively analysed 1800 images of dried blood droplets, developing sophisticated image processing analysis routines and optimising a multivariate statistical machine learning algorithm. We looked for statistically relevant correlations between the patterns in the dried blood droplets and exercise-induced changes in blood chemistry. An analysis of the various measured physiological parameters was also investigated. We found that when our machine learning algorithm, which optimises a statistical model combining Principal Component Analysis (PCA) as an unsupervised learning method and Linear Discriminant Analysis (LDA) as a supervised learning method, is applied on the logarithmic power spectrum of the images, it can provide up to 95% prediction accuracy, in discriminating the physiological conditions, i.e., before or after physical exercise. This correlation is strongest when all ten images taken per volunteer per condition are averaged, rather than treated individually. Having demonstrated proof-of-principle, this method can be applied to identify diseases.

The effects of inspiratory muscle training in older adults.

PURPOSE: Declining inspiratory muscle function and structure and systemic low-level inflammation and oxidative stress may contribute to morbidity and mortality during normal ageing. Therefore, we examined the effects of inspiratory muscle training (IMT) in older adults on inspiratory muscle function and structure and systemic inflammation and oxidative stress, and reexamined the reported positive effects of IMT on respiratory muscle strength, inspiratory muscle endurance, spirometry, exercise performance, physical activity levels (PAL), and quality of life (QoL). METHODS: Thirty-four healthy older adults (68 ± 3 yr) with normal spirometry, respiratory muscle strength, and physical fitness were divided equally into a pressure-threshold IMT or sham-hypoxic placebo group. Before and after an 8-wk intervention, measurements were taken for dynamic inspiratory muscle function and inspiratory muscle endurance using a weighted plunger pressure-threshold loading device; diaphragm thickness by using B-mode ultrasonography; plasma cytokine concentrations by using immunoassays; DNA damage levels in peripheral blood mononuclear cells by using comet assays; spirometry, maximal mouth pressures, and exercise performance by using a 6-min walk test; PAL by using a questionnaire and accelerometry; and QoL using a questionnaire. RESULTS: Compared with placebo, IMT increased maximal inspiratory pressure (+34% ± 43%, P = 0.008), diaphragm thickness at residual volume (+38% ± 39%, P = 0.03), and peak inspiratory flow (+35% ± 42%, P = 0.049) but did not change other spirometry measures, plasma cytokine concentrations, DNA damage levels in peripheral blood mononuclear cells, dynamic inspiratory muscle function, inspiratory muscle endurance, exercise performance, PAL, or QoL. CONCLUSION: These novel data indicate that in healthy older adults, IMT elicits some positive changes in inspiratory muscle function and structure but neither attenuates systemic inflammation and oxidative stress nor improves exercise performance, PAL, or QoL.

Human keratinocytes express multiple P2Y-receptors: evidence for functional P2Y1, P2Y2, and P2Y4 receptors.

Extracellular nucleotides are agonists at the family of receptors known as the P2 receptors, and in keratinocytes the P2Y2 subtype is known to elevate the intracellular free calcium concentration (Cai) and stimulate proliferation. In this study, we have investigated the presence of other functional members of the P2Y subgroup in both normal human keratinocytes and the HaCaT cell line. Using reverse transcription polymerase chain reaction, the expression of mRNA for P2Y1, P2Y2, P2Y4, and P2Y6 receptors was demonstrated in HaCaT cells and differentiated and undifferentiated normal human keratinocytes. Cai was monitored in response to a panel of P2Y receptor agonists. To couple mobilized Cai to a downstream cellular response, cell proliferation was also addressed. In both cell types, adenosine 5'-triphosphate and uridine 5'-triphosphate induced Cai transients of approximately equal duration, magnitude, and shape, confirming the presence of functional P2Y2 receptors. In HaCaT cells, additional characteristic responses were observed in a subpopulation of cells; adenosine 5'-triphosphate failed to elevate Cai in some cells responding to uridine 5'-triphosphate, indicating the presence of P2Y4 receptors, whereas the P2Y1-specific agonist 2-methylthio-5'-adenosine diphosphate was, again, only effective in a small subpopulation. Uridine 5'-diphosphate was ineffective, indicating the absence of functional P2Y6 receptors. Adenosine 5'-triphosphate and uridine 5'-triphosphate equally promoted cell growth in normal human keratinocytes in comparison with the control. In HaCaT cells, adenosine 5'-triphosphate, uridine 5'-triphosphate, and adenosine 5'-diphosphate significantly increased proliferation in comparison to the controls, with a 30% higher response to uridine 5'-triphosphate than with adenosine 5'-triphosphate. These data demonstrate that multiple P2Y receptors (P2Y1, P2Y2, and P2Y4 subtypes) are differentially involved in the regulation of proliferation in human keratinocytes and therefore may be important in wound healing.

Determinants of inspiratory muscle strength in healthy humans.

We investigated (1) the relationship between the baseline and inspiratory muscle training (IMT) induced increase in maximal inspiratory pressure (P(I,max)) and (2) the relative contributions of the inspiratory chest wall muscles and the diaphragm (P(oes)/P(di)) to P(I,max) prior to and following-IMT. Experiment 1: P(I,max) was assessed during a Müeller manoeuvre before and after 4-wk IMT (n=30). Experiment 2: P(I,max) and the relative contribution of the inspiratory chest wall muscles to the diaphragm (P(oes)/P(di)) were assessed during a Müeller manoeuvre before and after 4-wk IMT (n=20). Experiment 1: P(I,max) increased 19% (P<0.01) post-IMT and was correlated with baseline P(I,max) (r=-0.373, P<0.05). Experiment 2: baseline P(I,max) was correlated with P(oe)/P(di) (r=0.582, P<0.05) and after IMT PI,max increased 22% and Poe/Pdi increased 5% (P<0.05). In conclusion, baseline P(I,max) and the contribution of the chest wall inspiratory muscles relative to the diaphragm affect, in part, baseline and IMT-induced P(I,max). Great care should be taken when designing future IMT studies to ensure parity in the between-subject baseline P(I,max).

Prior upper body exercise reduces cycling work capacity but not critical power.

PURPOSE: This study examined whether metabolite accumulation, induced by prior upper body exercise, affected the power-duration relationship for leg cycle ergometry. METHODS: Seven males performed, to the limit of tolerance and both without (L) and with (AL) prior severe-intensity arm-cranking exercise, an incremental cycling test and four constant power cycling tests to determine the parameters of the power-duration relationship: critical power (CP) and W'. RESULTS: At the onset of cycling exercise plasma lactate (L vs AL: 1.2 ± 0.1 vs 11.6 ± 2.9 mEq · L) and hydrogen ion (40.4 ± 1.3 vs 53.1 ± 4.3 nEq · L), concentrations were higher during AL compared with L, whereas the strong ion difference (37.8 ± 1.8 vs 32.4 ± 2.0 mEq · L) and bicarbonate concentration (25.7 ± 0.7 vs 18.3 ± 1.9 mEq · L) were lower during AL compared with L (P < 0.01). During incremental exercise, maximum cycling power (358 ± 15 vs 332 ± 21 W) and peak oxygen uptake (VO2peak) (4.31 ± 0.36 vs 3.71 ± 0.44 L · min) were lower during AL compared with L (P < 0.05). The rate of increase in plasma potassium concentration during constant power cycling was greater during AL compared with L (0.09 ± 0.08 vs 0.14 ± 0.13 mEq · L · min) (P < 0.05), and exercise duration was 35 ± 15% shorter (P < 0.01). CP was not different between L and AL (267 ± 19 vs 264 ± 20 W), whereas W' was lower in AL (17.3 ± 5.7 vs 11.8 ± 4.2 kJ) (P < 0.01). CONCLUSION: The reduced W' after prior upper body exercise indicates that the magnitude of W' is partly dependent on metabolite accumulation.

Influence of oxidative stress, diaphragm fatigue, and inspiratory muscle training on the plasma cytokine response to maximum sustainable voluntary ventilation.

The influence of oxidative stress, diaphragm fatigue, and inspiratory muscle training (IMT) on the cytokine response to maximum sustainable voluntary ventilation (MSVV) is unknown. Twelve healthy males were divided equally into an IMT or placebo (PLA) group, and before and after a 6-wk intervention they undertook, on separate days, 1 h of (1) passive rest and (2) MSVV, whereby participants undertook volitional hyperpnea at rest that mimicked the breathing and respiratory muscle recruitment patterns commensurate with heavy cycling exercise. Plasma cytokines remained unchanged during passive rest. There was a main effect of time (P < 0.01) for plasma interleukin-1ß (IL-1ß) and interleukin-6 (IL-6) concentrations and a strong trend (P = 0.067) for plasma interleukin-1 receptor antagonist concentration during MSVV. Plasma IL-6 concentration was reduced after IMT by 27 ± 18% (main effect of intervention, P = 0.029), whereas there was no change after PLA (P = 0.753). There was no increase in a systemic marker of oxidative stress [DNA damage in peripheral blood mononuclear cells (PBMC)], and diaphragm fatigue was not related to the increases in plasma IL-1ß and IL-6 concentrations. A dose-response relationship was observed between respiratory muscle work and minute ventilation and increases in plasma IL-6 concentration. In conclusion, increases in plasma IL-1ß and IL-6 concentrations during MSVV were not due to diaphragm fatigue or DNA damage in PBMC. Increases in plasma IL-6 concentration during MSVV are attenuated following IMT, and the plasma IL-6 response is dependent upon the level of respiratory muscle work and minute ventilation.