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1.
Mechanical advantage of the canine triangularis sterni 总被引:3,自引:0,他引:3
De Troyer, André, and Alexandre Legrand.Mechanical advantage of the canine triangularis sterni.J. Appl. Physiol. 84(2): 562-568, 1998.Recent studies on the canine parasternal intercostal,sternomastoid, and scalene muscles have shown that the maximal changesin airway opening pressure (Pao) obtained per unit muscle mass(Pao/m) during isolatedcontraction are closely related to the fractional changes in musclelength per unit volume increase of the relaxed chest wall. In thepresent study, we have examined the validity of this relationship for the triangularis sterni, an important expiratory muscle of the rib cagein dogs. Passive inflation above functional residual capacity (FRC)induced a virtually linear increase in muscle length, such that, with a1.0-liter inflation, the muscle lengthened by 17.9 ± 1.6 (SE) % of its FRC length. When the muscle in one interspace wasmaximally stimulated at FRC, Pao increased by 0.84 ± 0.11 cmH2O. However, in agreement withthe length-tension characteristics of the muscle, when lung volume wasincreased by 1.0 liter before stimulation, the rise in Pao amounted to1.75 ± 0.12 cmH2O. At thehigher volume, Pao/m thereforeaveraged + 0.53 ± 0.05 cmH2O/g, such that the coefficientof proportionality between the change in triangularis sterni lengthduring passive inflation and Pao/m was the same as that previously obtained for the parasternalintercostal and neck inspiratory muscles. These observations,therefore, confirm that there is a unique relationship between thefractional changes in length of the respiratory muscles, bothinspiratory and expiratory, during passive inflation and theirPao/m. Consequently, the maximal effect of a particular muscle on the lung can be predicted on the basisof its change in length during passive inflation and its mass. Ageometric analysis of the rib cage also established that thelengthening of the canine triangularis sterni during passive inflationis much greater than the shortening of the parasternal intercostalsbecause, in dogs, the costal cartilages slope downward from thesternum. 相似文献
2.
Yan, Sheng, Pawel Sliwinski, and Peter T. Macklem.Association of chest wall motion and tidal volume responses during CO2 rebreathing.J. Appl. Physiol. 81(4):1528-1534, 1996.The purpose of this study is to investigate theeffect of chest wall configuration at end expiration on tidal volume(VT) response duringCO2 rebreathing. In a group of 11 healthy male subjects, the changes in end-expiratory andend-inspiratory volume of the rib cage (Vrc,E andVrc,I, respectively) and abdomen (Vab,E and Vab,I, respectively) measured by linearizedmagnetometers were expressed as a function of end-tidalPCO2(PETCO2). The changes inend-expiratory and end-inspiratory volumes of the chest wall(Vcw,E and Vcw,I,respectively) were calculated as the sum of the respectiverib cage and abdominal volumes. The magnetometer coils were placed atthe level of the nipples and 1-2 cm above the umbilicus andcalibrated during quiet breathing against theVT measured from apneumotachograph. TheVrc,E/PETCO2 slope was quite variable among subjects. It was significantly positive (P < 0.05) in fivesubjects, significantly negative in four subjects(P < 0.05), and not different fromzero in the remaining two subjects. TheVab,E/PETCO2slope was significantly negative in all subjects(P < 0.05) with a much smallerintersubject variation, probably suggesting a relatively more uniformrecruitment of abdominal expiratory muscles and a variable recruitmentof rib cage muscles during CO2rebreathing in different subjects. As a group, the meanVrc,E/PETCO2,Vab,E/PETCO2, andVcw,E/PETCO2slopes were 0.010 ± 0.034, 0.030 ± 0.007, and0.020 ± 0.032 l / Torr, respectively;only theVab,E/PETCO2 slope was significantly different from zero. More interestingly, theindividualVT/PETCO2slope was negatively associated with theVrc,E/PETCO2(r = 0.68,P = 0.021) and Vcw,E/PETCO2slopes (r = 0.63,P = 0.037) but was not associated withtheVab,E/PETCO2slope (r = 0.40, P = 0.223). There was no correlation oftheVrc,E/PETCO2 andVcw,E/PETCO2slopes with age, body size, forced expiratory volume in 1 s, orexpiratory time. The groupVab,I/PETCO2 slope (0.004 ± 0.014 l / Torr) was not significantlydifferent from zero despite theVT nearly being tripled at theend of CO2 rebreathing. Inconclusion, the individual VTresponse to CO2, althoughindependent of Vab,E, is a function ofVrc,E to the extent that as theVrc,E/PETCO2slope increases (more positive) among subjects, theVT response toCO2 decreases. These results maybe explained on the basis of the respiratory muscle actions andinteractions on the rib cage. 相似文献
3.
Combined heart rate and activity improve estimates of oxygen consumption and carbon dioxide production rates 总被引:1,自引:0,他引:1
Moon, Jon K., and Nancy F. Butte. Combined heart rateand activity improve estimates of oxygen consumption and carbon dioxideproduction rates. J. Appl. Physiol.81(4): 1754-1761, 1996.Oxygen consumption(O2) andcarbon dioxide production (CO2) rates were measuredby electronically recording heart rate (HR) and physical activity (PA).Mean daily O2 andCO2 measurements by HR andPA were validated in adults (n = 10 women and 10 men) with room calorimeters. Thirteen linear and nonlinear functions of HR alone and HR combined with PA were tested as models of24-h O2 andCO2. Mean sleepO2 andCO2 were similar to basalmetabolic rates and were accurately estimated from HR alone[respective mean errors were 0.2 ± 0.8 (SD) and0.4 ± 0.6%]. The range of prediction errorsfor 24-h O2 andCO2 was smallestfor a model that used PA to assign HR for each minute to separateactive and inactive curves(O2, 3.3 ± 3.5%; CO2, 4.6 ± 3%). There were no significant correlations betweenO2 orCO2 errors and subject age,weight, fat mass, ratio of daily to basal energy expenditure rate, orfitness. O2,CO2, and energy expenditurerecorded for 3 free-living days were 5.6 ± 0.9 ml · min1 · kg1,4.7 ± 0.8 ml · min1 · kg1,and 7.8 ± 1.6 kJ/min, respectively. Combined HR and PA measured 24-h O2 andCO2 with a precisionsimilar to alternative methods. 相似文献
4.
Muscle capillarization, O2 diffusion distance, and VO2 kinetics in old and young individuals 总被引:1,自引:0,他引:1
Chilibeck P. D.; Paterson D. H.; Cunningham D. A.; Taylor A. W.; Noble E. G. 《Journal of applied physiology》1997,82(1):63-69
Chilibeck, P. D., D. H. Paterson, D. A. Cunningham, A. W. Taylor, and E. G. Noble. Muscle capillarization,O2 diffusion distance, andO2 kinetics in old andyoung individuals. J. Appl. Physiol.82(1): 63-69, 1997.The relationships between muscle capillarization, estimated O2diffusion distance from capillary to mitochondria, andO2 uptake(O2) kineticswere studied in 11 young (mean age, 25.9 yr) and 9 old (mean age, 66.0 yr) adults. O2kinetics were determined by calculating the time constants () forthe phase 2 O2 adjustment to andrecovery from the average of 12 repeats of a 6-min, moderate-intensityplantar flexion exercise. Muscle capillarization was determined fromcross sections of biopsy material taken from lateral gastrocnemius.Young and old groups had similarO2 kinetics(O2-on = 44 vs. 48 s;O2-off = 33 vs. 44 s, for young and old, respectively), muscle capillarization, andestimated O2 diffusion distances.Muscle capillarization, expressed as capillary density or averagenumber of capillary contacts per fiber/average fiber area, and theestimates of diffusion distance were significantly correlated toO2-off kinetics in theyoung (r = 0.68 to 0.83;P < 0.05). We conclude that1) capillarization andO2 kinetics during exerciseof a muscle group accustomed to everyday activity (e.g., walking) arewell maintained in old individuals, and2) in the young, recovery of O2 after exercise isfaster, with a greater capillary supply over a given muscle fiber areaor shorter O2 diffusion distances. 相似文献
5.
Li, M. H., J. Hildebrandt, and M. P. Hlastala.Quantitative analysis of transpleural flux in the isolated lung.J. Appl. Physiol. 82(2): 545-551, 1997.In this study, the loss of inert gas through the pleura of anisolated ventilated and perfused rabbit lung was assessed theoreticallyand experimentally. A mathematical model was used to represent an idealhomogeneous lung placed within a box with gas flow(box) surrounding the lung. Thealveoli are assumed to be ventilated with room air(A) andperfused at constant flow () containinginert gases (x) with various perfusate-air partition coefficients(p,x).The ratio of transpleural flux of gas(plx)to its total delivery to the lung via pulmonary artery( ),representing fractional losses across the pleura, can be shown todepend on four dimensionless ratios:1)p,x,2) the ratio of alveolar ventilation to perfusion(A/), 3) the ratioof the pleural diffusing capacity(Dplx) to the conductance ofthe alveolar ventilation (Dplx /Ag,where g is the capacitancecoefficient of gas), and 4) theratio of extrapleural (box) ventilation to alveolar ventilation(box/A).Experiments were performed in isolated perfused and ventilated rabbitlungs. The perfusate was a buffer solution containing six dissolvedinert gases covering the entire 105-fold range ofp,x usedin the multiple inert gas elimination technique. Steady-state inert gasconcentrations were measured in the pulmonary arterial perfusate,pulmonary venous effluent, exhaled gas, and box effluent gas. Theexperimental data could be described satisfactorily by thesingle-compartment model. It is concluded that a simple theoreticalmodel is a useful tool for predicting transpleural flux from isolatedlung preparations, with known ventilation and perfusion, for inertgases within a wide range of . 相似文献
6.
Harms Craig A.; Babcock Mark A.; McClaran Steven R.; Pegelow David F.; Nickele Glenn A.; Nelson William B.; Dempsey Jerome A. 《Journal of applied physiology》1997,82(5):1573-1583
Harms, Craig A., Mark A. Babcock, Steven R. McClaran, DavidF. Pegelow, Glenn A. Nickele, William B. Nelson, and Jerome A. Dempsey.Respiratory muscle work compromises leg blood flow during maximalexercise. J. Appl. Physiol.82(5): 1573-1583, 1997.We hypothesized that duringexercise at maximal O2 consumption (O2 max),high demand for respiratory muscle blood flow() would elicit locomotor muscle vasoconstrictionand compromise limb . Seven male cyclists(O2 max 64 ± 6 ml · kg1 · min1)each completed 14 exercise bouts of 2.5-min duration atO2 max on a cycleergometer during two testing sessions. Inspiratory muscle work waseither 1) reduced via aproportional-assist ventilator, 2)increased via graded resistive loads, or3) was not manipulated (control).Arterial (brachial) and venous (femoral) blood samples, arterial bloodpressure, leg (legs;thermodilution), esophageal pressure, andO2 consumption(O2) weremeasured. Within each subject and across all subjects, at constantmaximal work rate, significant correlations existed(r = 0.74-0.90;P < 0.05) between work of breathing(Wb) and legs (inverse), leg vascular resistance (LVR), and leg O2(O2 legs;inverse), and between LVR and norepinephrine spillover. Mean arterialpressure did not change with changes in Wb nor did tidal volume orminute ventilation. For a ±50% change from control in Wb,legs changed 2 l/min or 11% of control, LVRchanged 13% of control, and O2extraction did not change; thusO2 legschanged 0.4 l/min or 10% of control. TotalO2 max was unchangedwith loading but fell 9.3% with unloading; thusO2 legsas a percentage of totalO2 max was 81% incontrol, increased to 89% with respiratory muscle unloading, anddecreased to 71% with respiratory muscle loading. We conclude that Wbnormally incurred during maximal exercise causes vasoconstriction inlocomotor muscles and compromises locomotor muscle perfusion andO2. 相似文献
7.
Treppo Steven; Mijailovich Srboljub M.; Venegas Jose G. 《Journal of applied physiology》1997,82(4):1163-1176
Treppo, Steven, Srboljub M. Mijailovich, and José G. Venegas. Contributions of pulmonary perfusion and ventilation toheterogeneity in A/measured by PET. J. Appl. Physiol. 82(4): 1163-1176, 1997. To estimate the contributions of the heterogeneity in regionalperfusion () and alveolar ventilation(A) to that of ventilation-perfusionratio (A/), we haverefined positron emission tomography (PET) techniques to image localdistributions of andA per unit of gas volume content(s and sA,respectively) and VA/ indogs. sA was assessed in two ways:1) the washout of 13NN tracer after equilibrationby rebreathing (sAi), and2) the ratio of an apneic image after a bolus intravenousinfusion of 13NN-saline solution to an image collectedduring a steady-state intravenous infusion of the same solution(sAp).sAp was systematically higher than sAi in allanimals, and there was a high spatial correlation betweens andsAp in both body positions(mean correlation was 0.69 prone and 0.81 supine) suggesting thatventilation to well-perfused units was higher than to those poorlyperfused. In the prone position, the spatial distributions ofs, sAp, and A/ were fairlyuniform with no significant gravitational gradients; however, in thesupine position, these variables were significantly more heterogeneous,mostly because of significant gravitational gradients (15, 5.5, and10%/cm, respectively) accounting for 73, 33, and 66% of thecorresponding coefficient of variation (CV)2 values. Weconclude that, in the prone position, gravitational forces in blood andlung tissues are largely balanced out by dorsoventral differences inlung structure. In the supine position, effects of gravity andstructure become additive, resulting in substantial gravitationalgradients in s andsAp, with the higherheterogeneity inA/ caused by agravitational gradient in s, only partially compensated by that in sA. 相似文献
8.
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
9.
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
10.
Hyde Richard W.; Geigel Edgar J.; Olszowka Albert J.; Krasney John A.; Forster Robert E. II; Utell Mark J.; Frampton Mark W. 《Journal of applied physiology》1997,82(4):1290-1296
Hyde, Richard W., Edgar J. Geigel, Albert J. Olszowka, JohnA. Krasney, Robert E. Forster II, Mark J. Utell, and Mark W. Frampton.Determination of production of nitric oxide by the lower airwaysof humanstheory. J. Appl. Physiol.82(4): 1290-1296, 1997.Exercise and inflammatory lung disorderssuch as asthma and acute lung injury increase exhaled nitric oxide(NO). This finding is interpreted as a rise in production of NO by thelungs (NO)but fails to take into account the diffusing capacity for NO(DNO) that carries NO into thepulmonary capillary blood. We have derived equations to measureNO from thefollowing rates, which determine NO tension in the lungs(PL) at any moment from 1) production(NO);2) diffusion, whereDNO(PL) = rate of removal by lung capillary blood; and3) ventilation, whereA(PL)/(PB 47) = the rate of NO removal by alveolar ventilation(A) and PB is barometric pressure. During open-circuit breathingwhen PL is not in equilibrium,d/dtPL[VL/(PB 47)] (where VL is volumeof NO in the lower airways) = NO DNO(PL) A(PL)/(PB 47). When PL reaches asteady state so that d/dt = 0 andA iseliminated by rebreathing or breath holding, then PL = NO/DNO.PL can be interpreted as NOproduction per unit of DNO. Thisequation predicts that diseases that diminishDNO but do not alterNO willincrease expired NO levels. These equations permit precise measurementsof NO thatcan be applied to determining factors controlling NO production by thelungs. 相似文献
11.
Khimenko Pavel L.; Bagby G. J.; Fuseler J.; Taylor Aubrey E. 《Journal of applied physiology》1998,85(6):2005-2011
The effects ofboth recombinant rat tumor necrosis factor- (TNF-) and ananti-TNF- antibody were studied in isolated buffer-perfused ratlungs subjected to either 45 min of nonventilated[ischemia-reperfusion (I/R)] or air-ventilated(/R) ischemia followed by 90 min of reperfusion and ventilation. In the I/R group, the vascularpermeability, as measured by the filtration coefficient(Kfc),increased three- and fivefold above baseline after 30 and 90 min ofreperfusion, respectively (P < 0.001). Over the same time intervals, theKfc for the/R group increased five- and tenfold above baseline values, respectively (P < 0.001).TNF- measured in the perfusates of both ischemic modelssignificantly increased after 30 min of reperfusion. Recombinant ratTNF- (50,000 U), placed into perfusate after baseline measurements,produced no measurable change in microvascular permeability in controllungs perfused over the same time period (135 min), but I/R injury wassignificantly enhanced in the presence of TNF-. An anti-TNF-antibody (10 mg/rat) injected intraperitoneally into rats 2 h beforethe lung was isolated prevented the microvascular damage in lungsexposed to both I/R and /R (P < 0.001). These results indicatethat TNF- is an essential component at the cascade of events thatcause lung endothelial injury in short-term I/R and/R models of lung ischemia. 相似文献
12.
Dishart Michael K.; Schlichtig Robert; Tonnessen Tor Inge; Rozenfeld Ranna A.; Simplaceanu Elena; Williams Donald; Gayowski Timothy J.P. 《Journal of applied physiology》1998,84(3):791-797
Dysoxia canbe defined as ATP flux decreasing in proportion toO2 availability with preserved ATPdemand. Hepatic venous -hydroxybutyrate-to-acetoacetate ratio(-OHB/AcAc) estimates liver mitochondrial NADH/NAD and may detectthe onset of dysoxia. During partial dysoxia (as opposed to anoxia),however, flow may be adequate in some liver regions, diluting effluentfrom dysoxic regions, thereby rendering venous -OHB/AcAc unreliable.To address this concern, we estimated tissue ATP whilegradually reducing liver blood flow of swine to zero in a nuclearmagnetic resonance spectrometer. ATP flux decreasing withO2 availability was taken asO2 uptake(O2) decreasing inproportion to O2 delivery(O2);and preserved ATP demand was taken as increasingPi/ATP.O2, tissuePi/ATP, and venous -OHB/AcAcwere plotted againstO2to identify critical inflection points. Tissue dysoxia required meanO2for the group to be critical for bothO2 and forPi/ATP. CriticalO2values for O2 andPi/ATP of 4.07 ± 1.07 and 2.39 ± 1.18 (SE) ml · 100 g1 · min1,respectively, were not statistically significantly different but notclearly the same, suggesting the possibility that dysoxia might havecommenced after O2 begandecreasing, i.e., that there could have been"O2 conformity." CriticalO2for venous -OHB/AcAc was 2.44 ± 0.46 ml · 100 g1 · min1(P = NS), nearly the same as that forPi/ATP, supporting venous -OHB/AcAc as a detector of dysoxia. All issues considered, tissue mitochondrial redox state seems to be an appropriate detector ofdysoxia in liver. 相似文献
13.
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
14.
Grassi Bruno; Marconi Claudio; Meyer Michael; Rieu Michel; Cerretelli Paolo 《Journal of applied physiology》1997,82(6):1952-1962
Grassi, Bruno, Claudio Marconi, Michael Meyer, Michel Rieu,and Paolo Cerretelli. Gas exchange and cardiovascular kinetics with different exercise protocols in heart transplant recipients. J. Appl. Physiol. 82(6): 1952-1962, 1997.Metabolicand cardiovascular adjustments to various submaximal exercises wereevaluated in 82 heart transplant recipients (HTR) and in 35 controlsubjects (C). HTR were tested 21.5 ± 25.3 (SD) mo (range1.0-137.1 mo) posttransplantation. Three protocols were used:protocol A consisted of 5 min of rectangular 50-W load repeatedtwice, 5 min apart [5 min rest, 5 min 50 W (Ex 1), 5 minrecovery, 5 min 50 W (Ex 2)]; protocol B consistedof 5 min of rectangular load at 25, 50, or 75 W; protocol Cconsisted of 15 min of rectangular load at 25 W. Breath-by-breathpulmonary ventilation (E),O2 uptake (O2),and CO2 output(CO2) were determined.During protocol A, beat-by-beat cardiacoutput () was estimated by impedance cardiography. The half times (t1/2) of the on- andoff-kinetics of the variables were calculated. In all protocols,t1/2 values forO2 on-,E on-, andCO2 on-kinetics were higher(i.e., the kinetics were slower) in HTR than in C, independently ofworkload and of the time posttransplantation. Also,t1/2 on- was higher in HTRthan in C. In protocol A, no significant difference of t1/2 O2on- was observed in HTR between Ex 1 (48 ± 9 s) and Ex2 (46 ± 8 s), whereas t1/2 on- was higher during Ex 1 (55 ± 24 s)than during Ex 2 (47 ± 15 s). In all protocols and for all variables, the t1/2 off-values were higher in HTRthan in C. In protocol C, no differences of steady-stateE,O2, andCO2 were observed in bothgroups between 5, 10, and 15 min of exercise. We conclude that1) in HTR, a "priming" exercise, while effective inspeeding up the adjustment of convective O2 flow to muscle fibers during a second on-transition, did not affect theO2 on-kinetics, suggestingthat the slower O2 on- inHTR was attributable to peripheral (muscular) factors; 2) thedissociation between on- andO2 on-kinetics in HTRindicates that an inertia of muscle metabolic machinery is the mainfactor dictating theO2 on-kinetics; and 3) theO2 off-kinetics was slowerin HTR than in C, indicating a greater alactic O2 deficitin HTR and, therefore, a sluggish muscleO2 adjustment. 相似文献
15.
Zschauer A. O.A.; Sielczak M. W.; Smith D. A.S.; Wanner A. 《Journal of applied physiology》1997,82(6):1918-1925
Zschauer, A. O. A., M. W. Sielczak, D. A. S. Smith, and A. Wanner. Norepinephrine-induced contraction of isolated rabbit bronchial artery: role of 1-and 2-adrenoceptor activation. J. Appl. Physiol. 82(6):1918-1925, 1997.The contractile effect of norepinephrine (NE) onisolated rabbit bronchial artery rings (150-300 µm in diameter)and the role of 1- and2-adrenoceptors (AR) on smoothmuscle and endothelium were studied. In intact arteries, NE increasedtension in a dose-dependent manner, and the sensitivity for NE wasfurther increased in the absence of endothelium. In intact but not inendothelium-denuded arteries, the response to NE was increased in thepresence of both indomethacin (Indo; cyclooxygenase inhibitor) andNG-nitro-L-argininemethyl ester [L-NAME;nitric oxide (NO) synthase inhibitor], indicating that twoendothelium-derived factors, NO and a prostanoid, modulate theNE-induced contraction. The1-AR antagonist prazosinshifted the NE dose-response curve to the right, and phenylephrine(1-AR agonist) induced adose-dependent contraction that was potentiated byL-NAME or removal of theendothelium. The sensitivity to NE was increased slightly by the2-AR antagonists yohimbine andidazoxan, and this effect was abolished by Indo or removal of theendothelium. Similarly, contractions induced by UK-14304(2-AR agonist) were potentiatedby Indo or removal of the endothelium. These results suggest thatNE-induced contraction is mediated through activation of1- and2-ARs on both smooth muscle andendothelium. Activation of the1- and2-ARs on the smooth musclecauses contraction, whereas activation of the endothelial 1- and2-ARs induces relaxationthrough release of NO (1-ARs) and a prostanoid (2-ARs). 相似文献
16.
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
17.
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
18.
Susceptibility to periodic breathing with assisted ventilation during sleep in normal subjects 总被引:6,自引:0,他引:6
Meza Sonia; Mendez Manuel; Ostrowski Michele; Younes Magdy 《Journal of applied physiology》1998,85(5):1929-1940
Assisted ventilation with pressure support (PSV)or proportional assist (PAV) ventilation has the potential to produceperiodic breathing (PB) during sleep. We hypothesized that PB willdevelop when PSV level exceeds the product of spontaneous tidal volume (VT) and elastance(VTsp · E)but that the actual level at which PB will develop[PSV(PB)] will be influenced by thePCO2 (difference between eupneicPCO2 andCO2 apneic threshold) and by RR[response of respiratory rate (RR) to PSV]. We also wishedto determine the PAV level at which PB develops to assess inherentventilatory stability in normal subjects. Twelve normal subjectsunderwent polysomnography while connected to a PSV/PAV ventilatorprototype. Level of assist with either mode was increased in smallsteps (2-5 min each) until PB developed or the subject awakened.End-tidal PCO2,VT, RR, and airway pressure (Paw) were continuously monitored, and the pressure generated byrespiratory muscle (Pmus) was calculated. The pressure amplification factor (PAF) at the highest PAV level was calculated from[(Paw + Pmus)/Pmus], where Paw is peak Paw continuous positive airway pressure. PB with central apneas developedin 11 of 12 subjects on PSV. PCO2ranged from 1.5 to 5.8 Torr. Changes in RR with PSV were small andbidirectional (+1.1 to 3.5min1). With use ofstepwise regression, PSV(PB) was significantly correlated withVTsp(P = 0.001), E(P = 0.00009),PCO2 (P = 0.007), and RR(P = 0.006). The final regressionmodel was as follows: PSV(PB) = 11.1 VTsp + 0.3E 0.4 PCO2 0.34 RR 3.4 (r = 0.98). PBdeveloped in five subjects on PAV at amplification factors of1.5-3.4. It failed to occur in seven subjects, despite PAF of upto 7.6. We conclude that 1) aPCO2 apneic threshold exists duringsleep at 1.5-5.8 Torr below eupneicPCO2,2) the development of PB during PSVis entirely predictable during sleep, and3) the inherent susceptibility to PBvaries considerably among normal subjects. 相似文献
19.
Grassi Bruno; Gladden L. Bruce; Samaja Michele; Stary Creed M.; Hogan Michael C. 《Journal of applied physiology》1998,85(4):1394-1403
The mechanism(s)limiting muscle O2 uptake(O2) kinetics wasinvestigated in isolated canine gastrocnemius muscles(n = 7) during transitions from restto 3 min of electrically stimulated isometric tetanic contractions(200-ms trains, 50 Hz; 1 contraction/2 s; 60-70% of peakO2). Two conditions weremainly compared: 1) spontaneousadjustment of blood flow () [control, spontaneous (C Spont)]; and2) pump-perfused, adjusted ~15 s before contractions at aconstant level corresponding to the steady-state value duringcontractions in C Spont [faster adjustment ofO2 delivery (FastO2 Delivery)]. During FastO2 Delivery, 1-2 ml/min of102 M adenosine wereinfused intra-arterially to prevent inordinate pressure increases withthe elevated . The purpose of the study was todetermine whether a faster adjustment ofO2 delivery would affectO2 kinetics. was measured continuously; arterial(CaO2) and popliteal venous(CvO2)O2 contents were determined atrest and at 5- to 7-s intervals during contractions;O2 delivery was calculated as · CaO2,and O2 was calculated as · arteriovenous O2 content difference. Times toreach 63% of the difference between baseline and steady-stateO2 during contractions were23.8 ± 2.0 (SE) s in C Spont and 21.8 ± 0.9 s in FastO2 Delivery (not significant). Inthe present experimental model, elimination of any delay inO2 delivery during therest-to-contraction transition did not affect muscleO2 kinetics, which suggeststhat this kinetics was mainly set by an intrinsic inertia of oxidativemetabolism. 相似文献
20.
Influence of age and gender on cardiac output-VO2 relationships during submaximal cycle ergometry 总被引:2,自引:0,他引:2
Proctor David N.; Beck Kenneth C.; Shen Peter H.; Eickhoff Tamara J.; Halliwill John R.; Joyner Michael J. 《Journal of applied physiology》1998,84(2):599-605
Proctor, David N., Kenneth C. Beck, Peter H. Shen, Tamara J. Eickhoff, John R. Halliwill, and Michael J. Joyner. Influence ofage and gender on cardiacoutput-O2 relationshipsduring submaximal cycle ergometry. J. Appl.Physiol. 84(2): 599-605, 1998.It is presentlyunclear how gender, aging, and physical activity status interact todetermine the magnitude of the rise in cardiac output(c) during dynamic exercise. To clarify this issue,the present study examined thec-O2 uptake(O2) relationship duringgraded leg cycle ergometry in 30 chronically endurance-trained subjects from four groups (n = 6-8/group): younger men (20-30 yr), older men (56-72yr), younger women (24-31 yr), and older women(51-72 yr). c (acetylene rebreathing), strokevolume (c/heart rate), and whole bodyO2 were measured at restand during submaximal exercise intensities (40, 70, and ~90% of peakO2). Baseline restinglevels of c were 0.6-1.2 l/min less in theolder groups. However, the slopes of thec-O2relationship across submaximal levels of cycling were similar among allfour groups (5.4-5.9 l/l). The absolute cassociated with a given O2(1.0-2.0 l/min) was also similar among groups. Resting andexercise stroke volumes (ml/beat) were lower in women than in men butdid not differ among age groups. However, older men and women showed areduced ability, relative to their younger counterparts, to maintainstroke volume at exercise intensities above 70% of peakO2. This latter effect wasmost prominent in the oldest women. These findings suggest that neitherage nor gender has a significant impact on thec-O2 relationships during submaximal cycle ergometry among chronically endurance-trained individuals. 相似文献