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1.
Effect of luteal phase elevation in core temperature on forearm blood flow during exercise 总被引:1,自引:0,他引:1
Kolka, Margaret A., and Lou A. Stephenson. Effect ofluteal phase elevation in core temperature on forearm blood flow duringexercise. J. Appl. Physiol. 82(4):1079-1083, 1997.Forearm blood flow (FBF) as an index of skinblood flow in the forearm was measured in five healthy women by venousocclusion plethysmography during leg exercise at 80% peak aerobicpower and ambient temperature of 35°C (relative humidity 22%;dew-point temperature 10°C). Resting esophagealtemperature (Tes) was 0.3 ± 0.1°C higher in the midluteal than in the early follicular phase ofthe menstrual cycle (P < 0.05).Resting FBF was not different between menstrual cycle phases. TheTes threshold for onset of skinvasodilation was higher (37.4 ± 0.2°C) in midluteal than inearly follicular phase (37.0 ± 0.1°C; P < 0.05). The slope of the FBF toTes relationship was not different between menstrual cycle phases (14.0 ± 4.2 ml · 100 ml1 · min1 · °C1for early follicular and 16.3 ± 3.2 ml · 100 ml1 · min1 · °C1for midluteal phase). Plateau FBF was higher during exercise inmidluteal (14.6 ± 2.2 ml · 100 ml1 · min1 · °C1)compared with early follicular phase (10.9 ± 2.4 ml · 100 ml1 · min1 · °C1;P < 0.05). The attenuation of theincrease in FBF to Tes occurred when Tes was 0.6°C higher andat higher FBF in midluteal than in early follicular experiments(P < 0.05). In summary, the FBF response is different during exercise in the two menstrual cycle phasesstudied. After the attenuation of the increase in FBF and whileTes was still increasing, thegreater FBF in the midluteal phase may have been due to the effects ofincreased endogenous reproductive endocrines on the cutaneousvasculature. 相似文献
2.
Novel transitions in MHC isoforms: separate and combined effects of thyroid hormone and mechanical unloading 总被引:1,自引:0,他引:1
Caiozzo Vincent J.; Baker Michael J.; Baldwin Kenneth M. 《Journal of applied physiology》1998,85(6):2237-2248
Single-fiber(n = 3,818 fibers) electrophoreticanalyses were used to delineate the separate and combined effects ofhyperthyroidism (T3) andhindlimb suspension (HS) on the myosin heavy chain (MHC) isoformcomposition (1-, 2-, and 4-wk time points) of the rat soleus muscle.The key findings of this study are as follows. First,T3 and HS both altered thedistribution of MHC isoforms at the single-fiber level; however, thepopulations of fibers produced by these two interventions were clearlydifferent from one another. Second,T3 + HS rapidly converted thesoleus into a fast muscle, producing large increases in the relativecontents of the fast type IIx and IIb MHC isoforms which were primarily expressed in several populations of hybrid fibers (e.g., types I/IIa/IIx, I/IIx/IIb, I/IIa/IIx/IIb). Finally,T3 + HS produced uniquepopulations of hybrid fibers that did not adhere to the IIIaIIxIIb sequential scheme of MHC plasticity. Collectively, the findings of this study demonstrate that the intervention of T3 + HS is a powerful model formanipulating and studying MHC isoform plasticity in slow skeletal muscle. 相似文献
3.
Ameredes Bill T.; Brechue William F.; Stainsby Wendell N. 《Journal of applied physiology》1998,84(6):1909-1916
Repetitiveisometric tetanic contractions (1/s) of the caninegastrocnemius-plantaris muscle were studied either at optimal length(Lo) or shortlength (Ls;~0.9 · Lo),to determine the effects of initial length on mechanical and metabolicperformance in situ. Respective averages of mechanical and metabolicvariables were(Lo vs.Ls, allP < 0.05) passive tension (preload) = 55 vs. 6 g/g, maximal active tetanic tension(Po) = 544 vs. 174 (0.38 · Po)g/g, maximal blood flow () = 2.0 vs. 1.4 ml · min1 · g1,and maximal oxygen uptake(O2) = 12 vs. 9 µmol · min1 · g1.Tension at Lodecreased to0.64 · Po over20 min of repetitive contractions, demonstrating fatigue; there were nosignificant changes in tension atLs. In separatemuscles contracting atLo, was set to that measured atLs (1.1 ml · min1 · g1),resulting in decreased O2(7 µmol · min1 · g1),and rapid fatigue, to0.44 · Po. Thesedata demonstrate that 1)muscles at Lohave higher andO2 values than those at Ls;2) fatigue occurs atLo with highO2, adjusting metabolic demand (tension output) to match supply; and3) the lack of fatigue atLs with lowertension, , andO2 suggestsadequate matching of metabolic demand, set low by shortmuscle length, with supply optimized by low preload. Thesedifferences in tension andO2 betweenLo andLs groupsindicate that muscles contracting isometrically at initial lengthsshorter than Loare working under submaximal conditions. 相似文献
4.
Griffin, M. Pamela. Role for anions in pulmonaryendothelial permeability. J. Appl.Physiol. 83(2): 615-622, 1997.-Adrenergic stimulation reduces albumin permeation across pulmonary artery endothelial monolayers and induces changes in cell morphology that aremediated by Cl flux. Wetested the hypothesis that anion-mediated changes in endothelial cellsresult in changes in endothelial permeability. We measured permeationof radiolabeled albumin across bovine pulmonary arterial endothelialmonolayers when the extracellular anion was Cl,Br,I,F, acetate(Ac), gluconate(G), and propionate(Pr). Permeability toalbumin (Palbumin)was calculated before and after addition of 0.2 mM of thephosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX), whichreduces permeability. InCl, thePalbumin was 3.05 ± 0.86 × 106 cm/s andfell by 70% with the addition of IBMX. The initialPalbumin was lowest forPr andAc. InitialPalbumin was higher inBr,I,G, andF than inCl. A permeability ratiowas calculated to examine the IBMX effect. The greatest IBMX effect wasseen when Cl was theextracellular anion, and the order among halide anions wasCl > Br > I > F. Although the level ofextracellular Ca2+ concentration([Ca2+]o)varied over a wide range in the anion solutions,[Ca2+]odid not systematically affect endothelial permeability in this system.When Cl was theextracellular anion, varying[Ca2+]ofrom 0.2 to 2.8 mM caused a change in initialPalbumin but no changein the IBMX effect. The anion channel blockers4-acetamido-4-isothiocyanotostilbene-2,2-disulfonic acid(0.25 mM) and anthracene-9-carboxylic acid (0.5 mM) significantly altered initialPalbumin and the IBMXeffect. The anion transport blockers bumetanide (0.2 mM) and furosemide(1 mM) had no such effects. We conclude that extracellular anionsinfluence bovine pulmonary arterial endothelial permeability and thatthe pharmacological profile fits better with the activity of anionchannels than with other anion transport processes. 相似文献
5.
Changes in maximum oxygen uptake during prolonged training, overtraining, and detraining in horses 总被引:2,自引:0,他引:2
Tyler Catherine M.; Golland Lorraine C.; Evans David L.; Hodgson David R.; Rose Reuben J. 《Journal of applied physiology》1996,81(5):2244-2249
Tyler, Catherine M., Lorraine C. Golland, David L. Evans,David R. Hodgson, and Reuben J. Rose. Changes in maximum oxygenuptake during prolonged training, overtraining, and detraining inhorses. J. Appl. Physiol. 81(5):2244-2249, 1996.Thirteen standardbred horses were trained asfollows: phase 1 (endurance training, 7 wk),phase 2 (high-intensity training, 9 wk),phase 3 (overload training, 18 wk), andphase 4 (detraining, 12 wk). Inphase 3, the horses were divided intotwo groups: overload training (OLT) and control (C). The OLT groupexercised at greater intensities, frequencies, and durations than groupC. Overtraining occurred after 31 wk of training and was defined as asignificant decrease in treadmill run time in response to astandardized exercise test. In the OLT group, there was a significantdecrease in body weight (P < 0.05).From pretraining values of 117 ± 2 (SE)ml · kg1 · min1,maximal O2 uptake(O2 max) increased by15% at the end of phase 1, and when signs of overtraining werefirst seen in the OLT group,O2 max was 29%higher (151 ± 2 ml · kg1 · min1in both C and OLT groups) than pretraining values. There was nosignificant reduction inO2 max until after 6 wk detraining whenO2 max was 137 ± 2 ml · kg1 · min1.By 12 wk detraining, meanO2 max was134 ± 2 ml · kg1 · min1,still 15% above pretraining values. When overtraining developed, O2 max was notdifferent between C and OLT groups, but maximal values forCO2 production (147 vs. 159 ml · kg1 · min1)and respiratory exchange ratio (1.04 vs. 1.11) were lower in the OLTgroup. Overtraining was not associated with a decrease inO2 max and, afterprolonged training, decreases inO2 max occurredslowly during detraining. 相似文献
6.
Training-induced alterations of carbohydrate metabolism in women: women respond differently from men 总被引:4,自引:0,他引:4
Friedlander Anne L.; Casazza Gretchen A.; Horning Michael A.; Huie Melvin J.; Piacentini Maria Francesca; Trimmer Jeffrey K.; Brooks George A. 《Journal of applied physiology》1998,85(3):1175-1186
We examined the hypothesis that glucose flux wasdirectly related to relative exercise intensity both beforeand after a 12-wk cycle ergometer training program [5days/wk, 1-h duration, 75% peakO2 consumption(O2 peak)] inhealthy female subjects (n = 17; age23.8 ± 2.0 yr). Two pretraining trials (45 and 65% of O2 peak)and two posttraining trials [same absolute workload (65% of oldO2 peak)and same relative workload (65% of new O2 peak)] wereperformed on nine subjects by using a primed-continuous infusion of[1-13C]- and[6,6-2H]glucose.Eight additional subjects were studied by using[6,6-2H]glucose.Subjects were studied postabsorption for 90 min of rest and 1 h ofcycling exercise. After training, subjects increased O2 peak by 25.2 ± 2.4%. Pretraining, the intensity effect on glucose kinetics wasevident between 45 and 65% ofO2 peak with rates ofappearance (Ra: 4.52 ± 0.25 vs. 5.53 ± 0.33 mg · kg1 · min1),disappearance (Rd: 4.46 ± 0.25 vs. 5.54 ± 0.33 mg · kg1 · min1),and oxidation (Rox: 2.45 ± 0.16 vs. 4.35 ± 0.26 mg · kg1 · min1)of glucose being significantly greater(P 0.05) in the 65% thanin the 45% trial. Training reducedRa (4.7 ± 0.30 mg · kg1 · min1),Rd (4.69 ± 0.20 mg · kg1 · min1),and Rox (3.54 ± 0.50 mg · kg1 · min1)at the same absolute workload (P 0.05). When subjects were tested at the same relative workload,Ra,Rd, andRox were not significantlydifferent after training. However, at both workloads after training,there was a significant decrease in total carbohydrate oxidation asdetermined by the respiratory exchange ratio. These results show thefollowing in young women: 1)glucose use is directly related to exercise intensity;2) training decreasesglucose flux for a given power output;3) when expressed asrelative exercise intensity, training does not affect the magnitude ofblood glucose flux during exercise; but4) training does reduce totalcarbohydrate oxidation. 相似文献
7.
Diffusional permeability (P) to sucrose(Psuc) andNa+(PNa+)was determined in specimens of rabbit sternal parietal pericardium,which may be obtained without stripping. Specimens were mounted in anUssing apparatus with 3H-labeledsucrose and22Na+in a luminal (L) or interstitial (I) chamber.Psuc was 2.16 ± 0.44 for LI and 2.63 ± 0.45 (SE) × 105 cm/s for IL,i.e., ~10 times smaller than that previously obtained in strippedspecimens of pleura despite the similarity of intercellular junctionsin pericardium and pleural mesothelium of various species. Thesefindings suggest that previousPsuc wasoverestimated because stripping damages the mesothelium.PNa+ (×105 cm/s) was 7.07 ± 0.71 for LI and 7.37 ± 0.69 × 105 cm/s for IL.Measurements were also done with phospholipids, which are adsorbed onthe luminal side of mesothelium in vivo. With phospholipids in L,Psuc was 0.75 ± 0.10 and 0.65 ± 0.08 andPNa+was 3.80 ± 0.32 and 3.76 ± 0.15 × 105 cm/s for LI andIL, respectively, i.e., smaller than without phospholipids.With phospholipids in I (where they are not adsorbed), Psuc (2.33 ± 0.42 × 105 cm/s) andPNa+(7.01 ± 0.45 × 105 cm/s) were similar tothose values without phospholipids. Hence, adsorbed phospholipidsdecrease P of mesothelium. If themesothelium were scraped away from the specimen,Psuc of theconnective tissue would be 13.2 ± 0.76 × 105 cm/s.Psuc of themesothelium, computed fromPsuc of theunscraped and scraped specimens, corrected for the effect of unstirredlayers (2.54 and 19.4 × 105 cm/s, respectively),was 2.92 and 0.74 × 105 cm/s without and withphospholipids, respectively. Hence, most of the resistance to diffusionof the pericardium is provided by the mesothelium. 相似文献
8.
Endothelial cell dilatory pathways link flow and wall shear stress in an intact arteriolar network 总被引:3,自引:0,他引:3
Frame, Mary D. S., and Ingrid H. Sarelius. Endothelialcell dilatory pathways link flow and wall shear stress in an intactarteriolar network. J. Appl. Physiol.81(5): 2105-2114, 1996.Our purpose was to determine whether theendothelial cell-dependent dilatory pathways contribute to theregulation of flow distribution in an intact arteriolar network. Cellflow, wall shear stress (T),diameter, and bifurcation angle were determined for four sequentialbranches of a transverse arteriole in the superfused cremaster muscleof pentobaribtal sodium (Nembutal, 70 mg/kg)-anesthetized hamsters(n = 51). Control cell flow wassignificantly greater into upstream than into downstream branches[1,561 ± 315 vs. 971 ± 200 (SE) cells/s,n = 12]. Tissue exposure to 50 µMN-nitro-L-arginine + 50 µM indomethacin (L-NNA + Indo) produced arteriolar constriction of 14 ± 4% and decreasedflow into the transverse arteriole. More of the available cell flow wasdiverted to downstream branches, yet flow distribution remainedunequal. Control T was higherupstream than downstream (31.3 ± 6.8 vs. 9.8 ± 1.5 dyn/cm2).L-NNA + Indo decreasedT upstream and increasedT downstream to become equal inall branches, in contrast to flow. To determine whether constriction ingeneral induced the same changes, 5%O2 (8 ± 4% constriction) or109 M norepinephrine (NE;4 ± 3% constriction) was added to the tissue (n = 7). WithO2, flow was redistributed tobecome equal into each branch. With NE, flow decreased progressivelymore into the first three branches. The changes in flow distributionwere thus predictable and dependent on the agonist. WithO2 or NE, the spatial changes inflow were mirrored by spatial changes inT. Changes in diameter and incell flux were not related forL-NNA + Indo (r = 0.45),O2(r = 0.07), or NE(r = 0.36). For all agonists, when thebifurcation angle increased, cell flow to the branch decreasedsignificantly, whereas if the angle decreased, flow was relativelypreserved; thus active changes in bifurcation angle may influence redcell distribution at arteriolar bifurcations. Thus, when theendothelial cell dilatory pathways were blocked, the changes in flowand in T were uncoupled; yet when they were intact, flowand T changed together. 相似文献
9.
Heat acclimation, aerobic fitness, and hydration effects on tolerance during uncompensable heat stress 总被引:4,自引:0,他引:4
The purpose ofthe present study was to determine the separate and combined effects ofaerobic fitness, short-term heat acclimation, and hypohydration ontolerance during light exercise while wearing nuclear, biological, andchemical protective clothing in the heat (40°C, 30% relativehumidity). Men who were moderately fit [(MF); <50ml · kg1 · min1maximal O2 consumption;n = 7] and highly fit[(HF); >55ml · kg1 · min1maximal O2 consumption;n = 8] were tested while theywere euhydrated or hypohydrated by ~2.5% of body mass throughexercise and fluid restriction the day preceding the trials. Tests wereconducted before and after 2 wk of daily heat acclimation (1-htreadmill exercise at 40°C, 30% relative humidity, while wearingthe nuclear, biological, and chemical protective clothing). Heatacclimation increased sweat rate and decreased skin temperature andrectal temperature (Tre) in HF subjects but had no effecton tolerance time (TT). MF subjects increased sweat rate but did notalter heart rate, Tre, or TT. In both MF and HF groups, hypohydration significantly increased Tre and heart rate and decreasedthe respiratory exchange ratio and the TT regardless of acclimationstate. Overall, the rate of rise of skin temperature was less, whileTre, the rate of rise of Tre, and the TTwere greater in HF than in MF subjects. It was concluded thatexercise-heat tolerance in this uncompensable heat-stress environmentis not influenced by short-term heat acclimation but is significantlyimproved by long-term aerobic fitness. 相似文献
10.
Training-induced alterations of glucose flux in men 总被引:5,自引:0,他引:5
Friedlander Anne L.; Casazza Gretchen A.; Horning Michael A.; Huie Melvin J.; Brooks George A. 《Journal of applied physiology》1997,82(4):1360-1369
Friedlander, Anne L., Gretchen A. Casazza, Michael A. Horning, Melvin J. Huie, and George A. Brooks. Training-induced alterations of glucose flux in men. J. Appl.Physiol. 82(4): 1360-1369, 1997.We examined thehypothesis that glucose flux was directly related to relative exerciseintensity both before and after a 10-wk cycle ergometer trainingprogram in 19 healthy male subjects. Two pretraining trials [45and 65% of peak O2 consumption(O2 peak)] andtwo posttraining trials (same absolute and relative intensities as 65%pretraining) were performed for 90 min of rest and 1 h of cyclingexercise. After training, subjects increasedO2 peak by9.4 ± 1.4%. Pretraining, the intensity effect on glucose kinetics was evident with rates of appearance(Ra; 5.84 ± 0.23 vs. 4.73 ± 0.19 mg · kg1 · min1),disappearance (Rd; 5.78 ± 0.19 vs. 4.73 ± 0.19 mg · kg1 · min1),oxidation (Rox; 5.36 ± 0.15 vs. 3.41 ± 0.23 mg · kg1 · min1),and metabolic clearance (7.03 ± 0.56 vs. 5.20 ± 0.28 ml · kg1 · min1)of glucose being significantly greater(P 0.05) in the 65% than the 45%O2 peak trial. WhenRd was expressed as a percentage of total energy expended per minute(Rd E), there was nodifference between the 45 and 65% intensities. Training did reduceRa (4.63 ± 0.25),Rd (4.65 ± 0.24),Rox (3.77 ± 0.43), andRd E (15.30 ± 0.40 to12.85 ± 0.81) when subjects were tested at the same absolute workload (P 0.05). However, whenthey were tested at the same relative workload,Ra,Rd, andRd E were not different,although Rox was lowerposttraining (5.36 ± 0.15 vs. 4.41 ± 0.42, P 0.05). These results show1) glucose use is directly relatedto exercise intensity; 2) trainingdecreases glucose flux for a given power output;3) when expressed as relativeexercise intensity, training does not affect the magnitude of bloodglucose use during exercise; 4)training alters the pathways of glucose disposal. 相似文献
11.
Influence of muscle fiber type and pedal frequency on oxygen uptake kinetics of heavy exercise 总被引:9,自引:0,他引:9
Barstow Thomas J.; Jones Andrew M.; Nguyen Paul H.; Casaburi Richard 《Journal of applied physiology》1996,81(4):1642-1650
Barstow, Thomas J., Andrew M. Jones, Paul H. Nguyen, andRichard Casaburi. Influence of muscle fiber type and pedal frequency on oxygen uptake kinetics of heavy exercise.J. Appl. Physiol. 81(4):1642-1650, 1996.We tested the hypothesis that the amplitude ofthe additional slow component ofO2 uptake(O2) during heavy exerciseis correlated with the percentage of type II (fast-twitch) fibers inthe contracting muscles. Ten subjects performed transitions to a workrate calculated to require aO2 equal to 50% betweenthe estimated lactate (Lac) threshold and maximalO2 (50%).Nine subjects consented to a muscle biopsy of the vastus lateralis. Toenhance the influence of differences in fiber type among subjects,transitions were made while subjects were pedaling at 45, 60, 75, and90 rpm in different trials. Baseline O2 was designed to besimilar at the different pedal rates by adjusting baseline work ratewhile the absolute increase in work rate above the baseline was thesame. The O2 response after the onset of exercise was described by a three-exponential model. Therelative magnitude of the slow component at the end of 8-min exercisewas significantly negatively correlated with %type I fibers at everypedal rate (r = 0.64 to 0.83, P < 0.05-0.01). Furthermore,the gain of the fast component forO2 (asml · min1 · W1)was positively correlated with the %type I fibers across pedal rates(r = 0.69-0.83). Increase inpedal rate was associated with decreased relative stress of theexercise but did not affect the relationships between%fiber type and O2parameters. The relative contribution of the slow component was alsosignificantly negatively correlated with maximalO2(r = 0.65), whereas the gainfor the fast component was positively associated(r = 0.68-0.71 across rpm). Theamplitude of the slow component was significantly correlated with netend-exercise Lac at all four pedal rates(r = 0.64-0.84), but Lac was notcorrelated with %type I (P > 0.05).We conclude that fiber type distribution significantly affects both thefast and slow components ofO2 during heavy exerciseand that fiber type and fitness may have both codependent andindependent influences on the metabolic and gas-exchange responses toheavy exercise. 相似文献
12.
Turcotte Lorraine P.; Petry Carsten; Kiens Bente; Richter Erik A. 《Journal of applied physiology》1998,84(5):1788-1794
To evaluate the effects of contractions on thekinetics of uptake and oxidation of palmitate in a physiological musclepreparation, rat hindquarters were perfused with glucose (6 mmol/l),albumin-bound [1-14C]palmitate, andvarying amounts of albumin-bound palmitate (200-2,200 µmol/l) atrest and during muscle contractions. When plotted against the unboundpalmitate concentration, palmitate uptake and oxidation displayedsimple Michaelis-Menten kinetics with estimated maximal velocity(Vmax)and Michaelis-Menten constant(Km) values of42.8 ± 3.8 (SE)nmol · min1 · g1and 13.4 ± 3.4 nmol/l for palmitate uptake and 3.8 ± 0.4 nmol · min1 · g1and 8.1 ± 2.9 nmol/l for palmitate oxidation, respectively, at rest.Whereas muscle contractions increased theVmaxfor both palmitate uptake and oxidation to 91.6 ± 10.1 and 16.5 ± 2.3 nmol · min1 · g1,respectively, theKm remainedunchanged.Vmaxand Km estimates obtained from Hanes-Woolf plots (substrate concentration/velocity vs.substrate concentration) were not significantly different. In theresting perfused hindquarter, an increase in palmitate delivery from31.9 ± 0.9 to 48.7 ± 1.2 µmol · g1 · h1by increasing perfusate flow was associated with a decrease in thefractional uptake of palmitate so that the rates of uptake andoxidation of palmitate remained unchanged. It is concluded that therates of uptake and oxidation of long-chain fatty acids (LCFA) saturatewith an increase in the concentration of unbound LCFA in perfusedskeletal muscle and that muscle contractions, but not an increase inplasma flow, increase theVmaxfor LCFA uptake and oxidation. The data are consistent with the notion that uptake of LCFA in muscle may be mediated in part by a transport system. 相似文献
13.
Zhang Haibo; Rogiers Peter; Smail Nadia; Cabral Ana; Preiser Jean-Charles; Peny Marie-Odile; Vincent Jean-Louis 《Journal of applied physiology》1997,83(4):1164-1173
Zhang, Haibo, Peter Rogiers, Nadia Smail, Ana Cabral,Jean-Charles Preiser, Marie-Odile Peny, and Jean-Louis Vincent.Effects of nitric oxide on blood flow distribution andO2 extraction capabilities duringendotoxic shock. J. Appl. Physiol.83(4): 1164-1173, 1997.The effects of the nitric oxide (NO)synthase inhibitorNG-monomethyl-L-arginine(L-NMMA) and the NO donor3-morpholinosydnonimine (SIN-1) were tested in 18 endotoxic dogs. L-NMMA infusion(10 mg · kg1 · h1)increased arterial and pulmonary artery pressures and systemic andpulmonary vascular resistances but decreased cardiac index, leftventricular stroke work index, and blood flow to the hepatic, portal,mesenteric, and renal beds. SIN-1 infusion (2 µg · kg1 · min1)increased cardiac index; left ventricular stroke work index; andhepatic, portal, and mesenteric blood flow. It did not significantly influence arterial and pulmonary artery pressures but decreased renalblood flow. The critical O2delivery was similar in the L-NMMA group and in the controlgroup (13.3 ± 1.6 vs. 12.8 ± 3.3 ml · kg1 · min1)but lower in the SIN-1 group (9.1 ± 1.8 ml · kg1 · min1,both P < 0.05). The criticalO2 extraction ratio was alsohigher in the SIN-1 group than in the other groups (58.7 ± 10.6 vs.42.2 ± 7.6% in controls, P < 0.05; 43.0 ± 15.5% inL-NMMA group,P = not significant). We conclude thatNO is not implicated in the alterations inO2 extraction capabilitiesobserved early after endotoxin administration. 相似文献
14.
Hogan Michael C.; Gladden L. Bruce; Grassi Bruno; Stary Creed M.; Samaja Michele 《Journal of applied physiology》1998,84(6):1882-1888
The purpose ofthis study was to examine the bioenergetics and regulation ofO2 uptake(O2) and force productionin contracting muscle when blood flow was moderately reduced during asteady-state contractile period. Canine gastrocnemius muscle(n = 5) was isolated, and 3-minstimulation periods of isometric, tetanic contractions were elicitedsequentially at rates of 0.25, 0.33, and 0.5 contractions/s (Hz)immediately followed by a reduction of blood flow [ischemic (I)condition] to 46 ± 3% of the value obtained at 0.5 Hz with normal blood flow. TheO2 of thecontracting muscle was significantly (P < 0.05) reduced during the Icondition [6.5 ± 0.8 (SE) ml · 100 g1 · min1]compared with the same stimulation frequency with normal flow (11.2 ± 1.5 ml · 100 g1 · min1),as was the tension-time index (79 ± 12 vs. 123 ± 22 N · g1 · min1,respectively). The ratio ofO2 to tension-time indexremained constant throughout all contraction periods. Musclephosphocreatine concentration, ATP concentration, and lactate effluxwere not significantly different during the I condition compared withthe 0.5-Hz condition with normal blood flow. However, at comparable rates of O2 andtension-time index, muscle phosphocreatine concentration and ATPconcentration were significantly less during the I condition comparedwith normal-flow conditions. These results demonstrate that, in thishighly oxidative muscle, the normal balance ofO2 supply to force output wasmaintained during moderate ischemia by downregulation of forceproduction. In addition,1) the minimal disruption inintracellular homeostasis after the initiation of ischemia waslikely a result of steady-state metabolic conditions having alreadybeen activated, and 2) thedifference in intracellular conditions at comparable rates ofO2 and tension-time index between the normal flow and I condition may have been due to altered intracellular O2 tension. 相似文献
15.
Becker Patrice M.; Buchanan Wendy; Sylvester J. T. 《Journal of applied physiology》1998,84(3):803-808
Cessation of bloodflow during ischemia will decrease both distending and shearforces exerted on endothelium and may worsen ischemic lung injury bydecreasing production of nitric oxide (NO), which influences vascularbarrier function. We hypothesized that increased intravascular pressure(Piv) during ventilated ischemia might maintain NO productionby increasing endothelial stretch or shear forces, thereby attenuatingischemic lung injury. Injury was assessed by measuring the filtrationcoefficient(Kf) and theosmotic reflection coefficient for albumin(alb) after 3 h of ventilated(95% O2-5%CO2; expiratory pressure 3 mmHg) ischemia. Lungs were flushed with physiological salt solution, and then Piv was adjusted to achieve High Piv (mean 6.7 ± 0.4 mmHg, n = 15) or Low Piv (mean0.83 ± 0.4 mmHg, n = 10).NG-nitro-L-arginine methyl ester(L-NAME;105 M,n = 10),NG-nitro-D-argininemethyl ester (D-NAME;105 M,n = 11), orL-NAME(105M)+L-arginine (5 × 104 M,n = 6) was added at the start ofischemia in three additional groups of lungs with High Piv.High Piv attenuated ischemic injury compared with Low Piv(alb 0.67 ± 0.04 vs. 0.35 ± 0.04, P < 0.05). Theprotective effect of High Piv was abolished byL-NAME(alb 0.37 ± 0.04, P < 0.05) but not byD-NAME(alb 0.63 ± 0.07). The effects of L-NAME were overcomeby an excess of L-arginine(alb 0.56 ± 0.05, P < 0.05).Kf did not differsignificantly among groups. These results suggest that Piv modulatesischemia-induced barrier dysfunction in the lung, and theseeffects may be mediated by NO. 相似文献
16.
Henke, Kathe G. Upper airway muscle activity and upperairway resistance in young adults during sleep. J. Appl. Physiol. 84(2): 486-491, 1998.To determinethe relationship between upper airway muscle activity and upper airwayresistance in nonsnoring and snoring young adults, 17 subjects werestudied during sleep. Genioglossus and alae nasi electromyogramactivity were recorded. Inspiratory and expiratory supraglotticresistance (Rinsp and Rexp, respectively) were measured at peak flow,and the coefficients of resistance(Kinsp andKexp,respectively) were calculated. Data were recorded during control,with continuous positive airway pressure (CPAP), and on the breathimmediately after termination of CPAP. Rinsp during control averaged 7 ± 1 and 10 ± 2 cmH2O · l1 · sand Kinspaveraged 26 ± 5 and 80 ± 27 cmH2O · l1 · s2in the nonsnorers and snorers, respectively(P = not significant). Onthe breath immediately after CPAP,Kinsp did notincrease over control in snorers (80 ± 27 for control vs. 46 ± 6 cmH2O · l1 · s2for the breath after CPAP) or nonsnorers (26 ± 5 vs. 29 ± 6 cmH2O · l1 · s2).These findings held true for Rinsp.Kexp did notincrease in either group on the breath immediately after termination ofCPAP. Therefore, 1) increases inupper airway resistance do not occur, despite reductions inelectromyogram activity in young snorers and nonsnorers, and2) increases in Rexp and expiratoryflow limitation are not observed in young snorers. 相似文献
17.
Effects of respiratory muscle work on cardiac output and its distribution during maximal exercise 总被引:9,自引:0,他引:9
Harms Craig A.; Wetter Thomas J.; McClaran Steven R.; Pegelow David F.; Nickele Glenn A.; Nelson William B.; Hanson Peter; Dempsey Jerome A. 《Journal of applied physiology》1998,85(2):609-618
We have recently demonstrated that changes inthe work of breathing during maximal exercise affect leg blood flow andleg vascular conductance (C. A. Harms, M. A. Babcock, S. R. McClaran, D. F. Pegelow, G. A. Nickele, W. B. Nelson, and J. A. Dempsey. J. Appl. Physiol. 82: 1573-1583,1997). Our present study examined the effects of changesin the work of breathing on cardiac output (CO) during maximalexercise. Eight male cyclists [maximalO2 consumption(O2 max):62 ± 5 ml · kg1 · min1]performed repeated 2.5-min bouts of cycle exercise atO2 max. Inspiratorymuscle work was either 1) at controllevels [inspiratory esophageal pressure (Pes): 27.8 ± 0.6 cmH2O],2) reduced via a proportional-assistventilator (Pes: 16.3 ± 0.5 cmH2O), or 3) increased via resistive loads(Pes: 35.6 ± 0.8 cmH2O).O2 contents measured in arterialand mixed venous blood were used to calculate CO via the direct Fickmethod. Stroke volume, CO, and pulmonaryO2 consumption(O2) were not different(P > 0.05) between control andloaded trials atO2 max but were lower(8, 9, and 7%, respectively) than control withinspiratory muscle unloading atO2 max. Thearterial-mixed venous O2difference was unchanged with unloading or loading. We combined thesefindings with our recent study to show that the respiratory muscle work normally expended during maximal exercise has two significant effectson the cardiovascular system: 1) upto 14-16% of the CO is directed to the respiratory muscles; and2) local reflex vasoconstriction significantly compromises blood flow to leg locomotor muscles. 相似文献
18.
Smaller lungs in women affect exercise hyperpnea 总被引:2,自引:0,他引:2
McClaran Steven R.; Harms Craig A.; Pegelow David F.; Dempsey Jerome A. 《Journal of applied physiology》1998,84(6):1872-1881
We subjected 29 healthy young women (age: 27 ± 1 yr) with a wide range of fitness levels [maximal oxygenuptake (O2 max): 57 ± 6 ml · kg1 · min1;35-70ml · kg1 · min1]to a progressive treadmill running test. Our subjects had significantly smaller lung volumes and lower maximal expiratory flow rates, irrespective of fitness level, compared with predicted values for age-and height-matched men. The higher maximal workload in highly fit(O2 max > 57 ml · kg1 · min1,n = 14) vs. less-fit(O2 max < 56 ml · kg1 · min1,n = 15) women caused a higher maximalventilation (E) with increased tidal volume (VT)and breathing frequency (fb) atcomparable maximal VT/vitalcapacity (VC). More expiratory flow limitation (EFL; 22 ± 4% ofVT) was also observed duringheavy exercise in highly fit vs. less-fit women, causing higherend-expiratory and end-inspiratory lung volumes and greater usage oftheir maximum available ventilatory reserves.HeO2 (79% He-21%O2) vs. room air exercise trialswere compared (with screens added to equalize external apparatusresistance). HeO2 increasedmaximal expiratory flow rates (20-38%) throughout the range ofVC, which significantly reduced EFL during heavy exercise. When EFL wasreduced with HeO2, VT,fb, andE (+16 ± 2 l/min) weresignificantly increased during maximal exercise. However, in theabsence of EFL (during room air exercise),HeO2 had no effect onE. We conclude that smaller lungvolumes and maximal flow rates for women in general, and especiallyhighly fit women, caused increased prevalence of EFL during heavyexercise, a relative hyperinflation, an increased reliance onfb, and a greater encroachment onthe ventilatory "reserve." Consequently,VT andE are mechanically constrained duringmaximal exercise in many fit women because the demand for highexpiratory flow rates encroaches on the airways' maximum flow-volumeenvelope. 相似文献
19.
Hypoxia- and normoxia-induced reversibility of autonomic control in Andean guinea pig heart 总被引:2,自引:0,他引:2
Leon-Velarde Fabiola; Richalet Jean-Paul; Chavez Juan-Carlos; Kacimi Rachid; Rivera-Chira Maria; Palacios Jose-Antonio; Clark Daniel 《Journal of applied physiology》1996,81(5):2229-2234
León-Velarde, Fabiola, Jean-Paul Richalet, Juan-CarlosChavez, Rachid Kacimi, Maria Rivera-Chira, José-Antonio Palacios, and Daniel Clark. Hypoxia- and normoxia-induced reversibility ofautonomic control in Andean guinea pig heart. J. Appl.Physiol. 81(5): 2229-2234, 1996.We hereindescribe the regulation of cardiac receptors in a typical high-altitudenative animal. Heart rate response to isoproterenol(HRIso)(beats · min1 · mgIso · kg1)and atropine, the density of -adrenergic(AR) and muscarinic (M2) receptors, and theventricular content of norepinephrine (NE) and dopamine (DA) werestudied in guinea pigs (Caviaporcellus). Animals native to Lima, Peru (150 m) werestudied at sea level (SL) and after 5 wk at 4,300-m altitude (SL-HA).Animals native to Rancas [Pasco, Peru (4,300 m)] werestudied at high altitude (HA) and after 5 wk at SL (HA-SL). HA animalshad a lower HRIso, maximum numberof AR binding sites(Bmax),AR dissociation constant (Kd), NE, andDA (P < 0.05) and a higherM2Bmax(P < 0.001) when compared with theSL group. HA-SL showed an increase of theHRIso, ARKd, and NE(P < 0.05) and a decrease of theM2Bmax andKd (P < 0.0001) when compared with theHA group. The present study demonstrates the differential regulationand reversibility of the autonomic control in the guinea pig heart. 相似文献
20.
Greater rate of decline in maximal aerobic capacity with age in physically active vs. sedentary healthy women 总被引:8,自引:0,他引:8
Tanaka Hirofumi; Desouza Christopher A.; Jones Pamela P.; Stevenson Edith T.; Davy Kevin P.; Seals Douglas R. 《Journal of applied physiology》1997,83(6):1947-1953
Tanaka, Hirofumi, Christopher A. DeSouza, Pamela P. Jones,Edith T. Stevenson, Kevin P. Davy, and Douglas R. Seals. Greater rate of decline in maximal aerobic capacity with age in physically active vs. sedentary healthy women. J. Appl.Physiol. 83(6): 1947-1953, 1997.Using ameta-analytic approach, we recently reported that the rate of declinein maximal oxygen uptake(O2 max) with age inhealthy women is greatest in the most physically active and smallest inthe least active when expressed in milliliters per kilogram per minuteper decade. We tested this hypothesis prospectively underwell-controlled laboratory conditions by studying 156 healthy, nonobesewomen (age 20-75 yr): 84 endurance-trained runners (ET) and 72 sedentary subjects (S). ET were matched across the age range forage-adjusted 10-km running performance. Body mass was positivelyrelated with age in S but not in ET. Fat-free mass was not differentwith age in ET or S. Maximal respiratory exchange ratio and rating ofperceived exertion were similar across age in ET and S, suggestingequivalent voluntary maximal efforts. There was a significant butmodest decline in running mileage, frequency, and speed with advancingage in ET.O2 max(ml · kg1 · min1)was inversely related to age (P < 0.001) in ET (r = 0.82) and S(r = 0.71) and was higher atany age in ET. Consistent with our meta-analysic findings,the absolute rate of decline inO2 max was greater inET (5.7ml · kg1 · min1 · decade1)compared with S (3.2 ml · kg1 · min1 · decade1;P < 0.01), but the relative (%)rate of decline was similar (9.7 vs 9.1%/decade; notsignificant). The greater absolute rate of decline inO2 max in ET comparedwith S was not associated with a greater rate of decline in maximalheart rate (5.6 vs. 6.2beats · min1 · decade1),nor was it related to training factors. The present cross-sectional findings provide additional evidence that the absolute, but not therelative, rate of decline in maximal aerobic capacity with age may begreater in highly physically active women compared with theirsedentary healthy peers. This difference does not appear to be relatedto age-associated changes in maximal heart rate, bodycomposition, or training factors. 相似文献