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1.
Effects of dopamine and domperidone on ventilatory sensitivity to hypoxia after 8h of isocapnic hypoxia 总被引:1,自引:0,他引:1
Pedersen Michala E.F.; Dorrington Keith L.; Robbins Peter A. 《Journal of applied physiology》1999,86(1):222-229
Acclimatization to altitude involves an increase in the acutehypoxic ventilatory response (AHVR). Because low-dose dopamine decreases AHVR and domperidone increases AHVR, the increase in AHVR ataltitude may be generated by a decrease in peripheral dopaminergicactivity. The AHVR of nine subjects was determined with and without aprior period of 8 h of isocapnic hypoxia under each of threepharmacological conditions: 1)control, with no drug administered;2) dopamine (3 µg · min1 · kg1);and 3) domperidone (Motilin, 40 mg).AHVR increased after hypoxia (P 0.001). Dopaminedecreased (P 0.01), and domperidone increased (P 0.005) AHVR. The effect of both drugs on AHVR appearedlarger after hypoxia, an observation supported by a significantinteraction between prior hypoxia and drug in the analysis of variance(P 0.05). Although the increasedeffect of domperidone after hypoxia of 0.40 l · min1 · %saturation1[95% confidence interval (CI) 0.11 to 0.92 l · min1 · %1]did not reach significance, the lower limit for this confidence interval suggests that little of the increase in AHVR after sustained hypoxia was brought about by a decrease in peripheral dopaminergic inhibition. 相似文献
2.
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
3.
Schwanke Uwe; Strauss Harald; Arnold Gunther; Schipke Jochen D. 《Journal of applied physiology》1996,81(5):2115-2122
Schwanke, Uwe, Harald Strauss, Gunther Arnold, and Jochen D. Schipke. Analysis of respiratory watera new method for evaluation of myocardial energy metabolism. J. Appl.Physiol. 81(5): 2115-2122, 1996.Aerobic ATPsynthesis via oxidative phosphorylation causes a proportionalproduction of respiratory water. Thus the amount of respiratory waterproduced at a given time should be a reliable measure of the currentATP demand of the mammalian myocardium. Respiratory water from isolatedrabbit hearts was labeled by using the stable oxygen isotope18O. The hearts were perfusedaccording to the method of Langendorff (O. Langendorff.Pfluegers Arch. 61: 291-332,1895) with18O2-equilibratedKrebs-Henseleit solution. Control hearts were exclusively perfused withcarbogen-equilibrated Krebs-Henseleit solution. Myocardial tissue wasthen lyophilized; the extracted water and samples from the coronaryvenous effluent were converted toCO2 by using the guanidinehydrochloride technique. The18O values within theCO2 samples were determined bymass spectrometry and related to the standard mean ocean water(SMOW) scale. Compared with controlhearts, the 18O-labeled heartsexhibited a significant increase of18O values from tissue water(47.50 ± 0.64 vs. 40.35 ± 2.05SMOW; P < 0.05). The values were alsosignificantly increased in the coronary venous effluent after aperfusion time of only 50 s (47.50 ± 0.64 vs. 43.66 ± 0.91 SMOW;P < 0.05). Thus this firstadaptation of the guanidine hydrochloride technique on microlitersamples of myocardial tissue water and coronary venous effluentdemonstrates that this method can be used to evaluate both respiratoryactivity and the kinetics of cardiac metabolic processes. 相似文献
4.
Interferon-gamma has immunomodulatory effects with minor endocrine and metabolic effects in humans 总被引:1,自引:0,他引:1
de Metz J.; Sprangers F.; Endert E.; Ackermans M. T.; ten Berge I. J.M.; Sauerwein H. P.; Romijn J. A. 《Journal of applied physiology》1999,86(2):517-522
To evaluatewhether interferon- (IFN-) is involved in the interaction betweenthe immune and endocrine systems in vivo, we studied six healthysubjects twice in a placebo-controlled trial: once after administrationof recombinant human IFN- and, on another occasion, afteradministration of saline. The rate of appearance of glucose wasdetermined by infusion of[6,6-2H2]glucoseand resting energy expenditure by indirect calorimetry. Human leukocyteantigen-DR gene expression on monocytes and serum neopterin increased after administration of IFN-(P < 0.05 vs. control). IFN-increased serum interleukin-6 levels significantly. Levels of tumornecrosis factor- remained below detection limits. IFN- increasedplasma concentrations of ACTH and cortisol(P < 0.05 vs. control), IFN- didnot alter concentrations of growth hormone,(nor)epinephrine, insulin, C peptide, glucagon, or insulin-like growthfactor I. IFN- did not alter plasma concentrations of glucose andfree fatty acids nor the rate of appearance of glucose. IFN-increased resting energy expenditure significantly. We conclude thatIFN- is a minor stimulator of the endocrine and metabolic pathways.Therefore, IFN- by itself is probably not a major mediator in theinteraction between the immune and the endocrine and metabolic systems. 相似文献
5.
Magnitude and time course of hemodynamic responses to Mueller maneuvers in patients with congestive heart failure 总被引:2,自引:0,他引:2
Hall Michael J.; Ando Shin-Ichi; Floras John S.; Bradley T. Douglas 《Journal of applied physiology》1998,85(4):1476-1484
To simulate theimmediate hemodynamic effect of negative intrathoracic pressure duringobstructive apneas in congestive heart failure (CHF), without inducingconfounding factors such as hypoxia and arousals from sleep, eightawake patients performed, at random, 15-s Mueller maneuvers (MM) attarget intrathoracic pressures of 20 (MM 20) and40 cmH2O (MM 40),confirmed by esophageal pressure, and 15-s breath holds, as apneic timecontrols. Compared with quiet breathing, at baseline, before theseinterventions, the immediate effects [first 5 cardiac cycles(SD), P values refer to MM 40compared with breath holds] of apnea, MM 20, and MM 40 were, for left ventricular (LV) systolic transmural pressure (Ptm), 1.0 ± 1.9, 7.2 ± 3.5, and 11.3 ± 6.8 mmHg(P < 0.01); for systolic bloodpressure (SBP), 2.9 ± 2.6, 5.5 ± 3.4, and 12.1 ± 6.8 mmHg (P < 0.01); and forstroke volume (SV) index, 0.4 ± 2.8, 4.1 ± 2.8, and6.9 ± 2.3 ml/m2(P < 0.001), respectively.Corresponding values over the last five cardiac cycles were for LVPtm6.4 ± 4.4, 5.4 ± 6.6, and 4.5 ± 9.1 mmHg (P < 0.01); for SBP6.9 ± 4.2, 8.2 ± 7.7, and 24.2 ± 6.9 mmHg (P < 0.01); and for SVindex 0.4 ± 2.1, 5.2 ± 2.8, and 9.2 ± 4.8 ml/m2(P < 0.001), respectively.Thus, in CHF patients, the initial hemodynamic response to thegeneration of negative intrathoracic pressure includes an immediateincrease in LV afterload and an abrupt fall in SV. The magnitude ofresponse is proportional to the intensity of the MM stimulus. By theend of a 15-s MM 40, LVPtm falls below baseline values, yet SVand SBP do not recover. Thus, when 40cmH2O intrathoracic pressure issustained, additional mechanisms, such as a drop in LV preload due toventricular interaction, are engaged, further reducing SV. The neteffect of MM 40 was a 33% reduction in SV index (from 27 to 18 ml/min2), and a 21% reductionin SBP (from 121 to 96 mmHg). Obstructive apneas can have adverseeffects on systemic and, possibly, coronary perfusion in CHF throughdynamic mechanisms that are both stimulus and timedependent. 相似文献
6.
Age-related declines in maximal aerobic capacity in regularly exercising vs. sedentary women: a meta-analysis 总被引:3,自引:0,他引:3
Fitzgerald Margaret D.; Tanaka Hirofumi; Tran Zung V.; Seals Douglas R. 《Journal of applied physiology》1997,83(1):160-165
Fitzgerald, Margaret D., Hirofumi Tanaka, Zung V. Tran, andDouglas R. Seals. Age-related declines in maximal aerobic capacityin regularly exercising vs. sedentary women: a meta-analysis. J. Appl. Physiol. 83(1): 160-165, 1997.Our purpose was to determine the relationship between habitualaerobic exercise status and the rate of decline in maximal aerobiccapacity across the adult age range in women. A meta-analytic approachwas used in which mean maximal oxygen consumption(O2 max) values fromfemale subject groups (ages 18-89 yr) were obtained from thepublished literature. A total of 239 subject groups from 109 studiesinvolving 4,884 subjects met the inclusion criteria and werearbitrarily separated into sedentary (groups = 107; subjects = 2,256),active (groups = 69; subjects = 1,717), and endurance-trained (groups = 63; subjects = 911) populations.O2 max averaged 29.7 ± 7.8, 38.7 ± 9.2, and 52.0 ± 10.5 ml · kg1 · min1,respectively, and was inversely related to age within each population (r = 0.82 to 0.87, allP < 0.0001). The rate of decline inO2 max withincreasing subject group age was lowest in sedentary women (3.5ml · kg1 · min1· decade1), greater inactive women (4.4ml · kg1 · min1· decade1), andgreatest in endurance-trained women (6.2ml · kg1 · min1 · decade1)(all P < 0.001 vs. each other). Whenexpressed as percent decrease from mean levels at age ~25 yr, therates of decline inO2 max were similarin the three populations (10.0 to 10.9%/decade). Therewas no obvious relationship between aerobic exercise status and therate of decline in maximal heart rate with age. The results of thiscross-sectional study support the hypothesis that, in contrast to theprevailing view, the rate of decline in maximal aerobic capacity withage is greater, not smaller, in endurance-trained vs. sedentary women.The greater rate of decline inO2 max in endurance-trained populations may be related to their higher values asyoung adults (baseline effect) and/or to greater age-related reductions in exercise volume; however, it does not appear to berelated to a greater rate of decline in maximal heart rate with age. 相似文献
7.
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
8.
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
9.
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
10.
Lynch Nicole A.; Nicklas Barbara J.; Berman Dora M.; Dennis Karen E.; Goldberg Andrew P. 《Journal of applied physiology》2001,90(1):99-104
The accumulation ofvisceral fat is independently associated with an increased risk forcardiovascular disease. The aim of this study was to determine whetherthe loss of visceral adipose tissue area (VAT; computed tomography) isrelated to improvements in maximal O2 uptake(O2 max) during a weight loss(250-350 kcal/day deficit) and walking (3 days/wk, 30-40 min)intervention. Forty obese [body fat 47 ± 1 (SE) %], sedentary(O2 max 19 ± 1 ml · kg1 · min1)postmenopausal women (age 62 ± 1 yr) participated in the study. The intervention resulted in significant declines in body weight (8%), total fat mass (dual-energy X-ray absorptiometry; 17%), VAT(17%), and subcutaneous adipose tissue area (17%) with no changein lean body mass (all P < 0.001). Women with anaverage 10% increase in O2 max reducedVAT by an average of 20%, whereas those who did not increaseO2 max decreased VAT by only 10%,despite comparable reductions in body fat, fat mass, and subcutaneousadipose tissue area. The decrease in VAT was independently related tothe change in O2 max(r2 = 0.22; P < 0.01) andfat mass (r2 = 0.08; P = 0.05). These data indicate that greater improvements inO2 max with weight loss and walking areassociated with greater reductions in visceral adiposity in obesepostmenopausal women. 相似文献
11.
Interaction of cross-sectional area, driving pressure, and airflow of passive velopharynx 总被引:2,自引:0,他引:2
Isono Shiroh; Feroah Thom R.; Hajduk Eric A.; Brant Rollin; Whitelaw William A.; Remmers John E. 《Journal of applied physiology》1997,83(3):851-859
Isono, Shiroh, Thom R. Feroah, Eric A. Hajduk, Rollin Brant,William A. Whitelaw, and John E. Remmers. Interaction ofcross-sectional area, driving pressure, and airflow of passive velopharynx. J. Appl. Physiol. 83(3):851-859, 1997.Previous studies have shown that, when thepharyngeal muscles are relaxed, the velopharynx is a highly compliantsegment of the pharynx. Thus, under these circumstances,cross-sectional area of the velopharynx (AVP), drivingpressure across the velopharynx (P), and inspiratory airflow(I) willbe mutually interdependent variables. The purpose of the presentinvestigation was to describe the interrelation among these threevariables during inspiration. We studied 15 sleeping patients withobstructive sleep apnea/hypopnea when the pharyngeal muscles wererendered hypotonic by applying continuous positive airway pressure tothe nasal airway.AVP, determined by endoscopic imaging, was significantly greater at onset ofI limitationthan at minimum oropharyngeal pressure(P < 0.01). Snoring was neverobserved duringIlimitation. In a subgroup of six patients, values for P,I, andAVP were obtainedat 0.1-s intervals at various levels of mask pressure. For these sixpatients, the mathematical expressionI = 0.657(AVP/Amax) · P0.332,where Amax ismaximal AVP,described the relationship among the three variables(R2 = 0.962) forflow-limited and non-flow-limited inspirations. The impedance of thepassive velopharynx, defined asP0.33/,was inversely related toAVP and increaseddramatically when AVP was <0.3cm2. In summary, we observed aprogressive decrease inAVP during flow-limited inspiration in patients with obstructive sleep apnea. Thisconstriction of the velopharynx contributes to an increase invelopharyngeal impedance that, in turn, counterbalances the increase inP during flow limitation. 相似文献
12.
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
13.
Carvalho Paula; Johnson Shane R.; Charan Nirmal B. 《Journal of applied physiology》1998,84(1):215-221
Carvalho, Paula, Shane R. Johnson, Nirmal B. Charan.Non-cAMP-mediated bronchial arterial vasodilation in response toinhaled -agonists. J. Appl.Physiol. 84(1): 215-221, 1998.We studied thedose-dependent effects of inhaled isoetharine HCl, a -adrenergicbronchodilator (2.5, 5.0, 10.0, and 20.0 mg), on bronchial blood flow(br) in anesthetized sheep. Isoetharine resulted ina dose-dependent increase in br. With atotal dose of 17.5 mg, br increased from baselinevalues of 22 ± 3.4 (SE) to 60 ± 16 ml/min(P < 0.001), an effect independentof changes in cardiac output and systemic arterial pressure. To furtherstudy whether synthesis of endogenous nitric oxide (NO) affects-agonist-induced increases in br, weadministered isoetharine (20 mg) by inhalation before and after theNO-synthase inhibitorN-nitro-L-argininemethyl ester (L-NAME).Intravenous L-NAME (30 mg/kg) rapidly decreased br by ~80% of baseline,whereas L-NAME via inhalation(10 mg/kg) resulted in a delayed and smaller (~22%) decrease.Pretreatment with L-NAME viaboth routes of administration attenuated bronchial arterialvasodilation after subsequent challenge with isoetharine. We concludethat isoetharine via inhalation increases br in adose-dependent manner and that -agonist-induced relaxation ofvascular smooth muscle in the bronchial vasculature is partiallymediated via synthesis of NO. 相似文献
14.
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
15.
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
16.
VO2 max is associated with ACE genotype in postmenopausal women 总被引:6,自引:0,他引:6
Hagberg James M.; Ferrell Robert E.; McCole Steve D.; Wilund Kenneth R.; Moore Geoffrey E. 《Journal of applied physiology》1998,85(5):1842-1846
Relationships have frequently been found betweenangiotensin-converting enzyme (ACE) genotype and various pathologicaland physiological cardiovascular outcomes and functions. Thuswe sought to determine whether ACE genotype affected maximalO2 consumption (O2 max) and maximalexercise hemodynamics in postmenopausal women with different habitualphysical activity levels. Age, body composition, and habitual physicalactivity levels did not differ among ACE genotype groups. However, ACEinsertion/insertion (II) genotype carriers had a 6.3 ml · kg1 · min1higher O2 max(P < 0.05) than the ACEdeletion/deletion (DD) genotype group after accounting for the effectof physical activity levels. The ACE II genotype group also had a 3.3 ml · kg1 · min1higher O2 max(P < 0.05) than the ACEinsertion/deletion (ID) genotype group. The ACE ID group tended to havea higher O2 max thanthe DD genotype group, but the difference was not significant. ACEgenotype accounted for 12% of the variation inO2 max among womenafter accounting for the effect of habitual physical activity levels.The entire difference inO2 max among ACEgenotype groups was the result of differences in maximal arteriovenousO2 difference (a-vDO2).ACE genotype accounted for 17% of the variation in maximal a-vDO2 inthese women. Maximal cardiac output index did not differ whatsoeveramong ACE genotype groups. Thus it appears that ACE genotype accountsfor a significant portion of the interindividual differences inO2 max among thesewomen. However, this difference is the result of genotype-dependentdifferences in maximala-vDO2 andnot of maximal stroke volume and maximal cardiac output. 相似文献
17.
Hardarson Thorir; Skarphedinsson Jon O.; Sveinsson Torarinn 《Journal of applied physiology》1998,84(2):411-416
Hardarson, Thorir, Jon O. Skarphedinsson, and TorarinnSveinsson. Importance of the lactate anion in control ofbreathing. J. Appl. Physiol. 84(2):411-416, 1998.The purpose of this study was to examine theeffects of raising the arterialLa andK+ levels on minute ventilation(E) in rats. EitherLa or KCl solutions wereinfused in anesthetized spontaneously breathing Wistar rats to raisethe respective ion arterial concentration ([La] and[K+]) gradually tolevels similar to those observed during strenuous exercise.E, blood pressure, and heart rate wererecorded continuously, and arterial[La],[K+], pH, and bloodgases were repeatedly measured from blood samples. To prevent changesin pH during the Lainfusions, a solution of sodium lactate and lactic acid was used. Raising [La] to13.2 ± 0.6 (SE) mM induced a 47.0 ± 4.0% increase inE without any concomitant changes ineither pH or PCO2. Raising[K+] to 7.8 ± 0.11 mM resulted in a 20.3 ± 5.28% increase inE without changes in pH. Thus ourresults show that Laitself, apart from lactic acidosis, may be important in increasing E during strenuous exercise, and weconfirm earlier results regarding the role of arterial[K+] in the control ofE during exercise. 相似文献
18.
Training improves endothelium-dependent vasodilation in resistance vessels of patients with heart failure 总被引:3,自引:0,他引:3
Katz Stuart D.; Yuen Jeannette; Bijou Rachel; Lejemtel Thierry H. 《Journal of applied physiology》1997,82(5):1488-1492
Katz, Stuart D., Jeannette Yuen, Rachel Bijou, and ThierryH. LeJemtel. Training improves endothelium-dependent vasodilation in resistance vessels of patients with heart failure.J. Appl. Physiol. 82(5):1488-1492, 1997.The effects of physical training onendothelium-dependent vasodilation in skeletal muscle resistance vessels were investigated in patients with heart failure. Forearm bloodflows(ml · min1 · 100 ml1) in response tobrachial arterial administration of acetylcholine (5 × 105 and 5 × 104 M at 1 ml/min) andnitroglycerin (5 × 106 and 5 × 105 M at 1 ml/min) weredetermined by strain-gauge venous occlusion plethysmography before andafter 8 wk of daily handgrip exercise in 12 patients with chronic heartfailure. After 8 wk of daily handgrip exercise, the vasodilatoryresponses to acetylcholine significantly increased from pretrainingvalues, i.e., 16.6 ± 2.0 vs. 8.6 ± 1.3 ml · min1 · 100 ml1(P < 0.05) and 27.5 ± 1.5 vs. 14.6 ± 1.7 ml · min1 · 100 ml1(P < 0.05), respect- ively,whereas the vasodilatory responses to nitroglycerin did notchange. Handgrip exercise training appears to specificallyenhance endothelium-dependent vasodilation in the forearm skeletalmuscle circulation of patients with heart failure. 相似文献
19.
Serikov Vladimir B.; Jerome E. Heidi; Fleming Neal W.; Moore Peter G.; Stawitcke Frederick A.; Staub Norman C. 《Journal of applied physiology》1997,83(2):668
Serikov, Vladimir B., E. Heidi Jerome, Neal W. Fleming,Peter G. Moore, Frederick A. Stawitcke, and Norman C. Staub.Airway thermal volume in humans and its relation to body size.J. Appl. Physiol. 83(2): 668-676, 1997.The objective of this study was to investigate the influence ofvolume ventilation(E) andcardiac output () on the temperature of the expiredgas at the distal end of the endotracheal tube in anesthetized humans.In 63 mechanically ventilated adults, we used a step decrease in thehumidity of inspired gas to cool the lungs. After change from humid todry gas ventilation, the temperature of the expired gas decreased. Weevaluated the relationship between the inverse monoexponential timeconstant of the temperature fall (1/) and eitherE or . WhenE wasincreased from 5.67 ± 1.28 to 7.14 ± 1.60 (SD) l/min(P = 0.02), 1/ did not changesignificantly [from 1.25 ± 0.38 to 1.21 ± 0.51 min1,P = 0.81]. In the 11 patients in whom changed during the study period(from 5.07 ± 1.81 to 7.38 ± 2.45 l/min,P = 0.02), 1/ increasedcorrespondingly from 0.89 ± 0.22 to 1.52 ± 0.44 min1(P = 0.003). We calculated the airwaythermal volume (ATV) as the ratio of the measured values to 1/ and related it to the body height (BH):ATV (liters) = 0.086 BH (cm) 9.55 (r = 0.90). 相似文献
20.
Combined myofibrillar and mitochondrial creatine kinase deficiency impairs mouse diaphragm isotonic function 总被引:2,自引:0,他引:2
Watchko Jon F.; Daood Monica J.; Sieck Gary C.; Labella John J.; Ameredes Bill T.; Koretsky Alan P.; Wieringa Be 《Journal of applied physiology》1997,82(5):1416-1423
Watchko, Jon F., Monica J. Daood, Gary C. Sieck, John J. LaBella, Bill T. Ameredes, Alan P. Koretsky, and BeWieringa. Combined myofibrillar and mitochondrialcreatine kinase deficiency impairs mouse diaphragm isotonic function.J. Appl. Physiol. 82(5): 1416-1423, 1997.Creatine kinase (CK) is an enzyme central to cellular high-energy phosphate metabolism in muscle. To characterize the physiological role of CK in respiratory muscle during dynamic contractions, we compared the force-velocity relationships, power, andwork output characteristics of the diaphragm (Dia) from mice withcombined myofibrillar and sarcomeric mitochondrial CK deficiency (CK[/]) with CK-sufficient controls (Ctl).Maximum velocity of shortening was significantly lower inCK[/] Dia (14.1 ± 0.9 Lo/s,where Lo isoptimal fiber length) compared with Ctl Dia (17.5 ± 1.1 Lo/s)(P < 0.01). Maximum power wasobtained at 0.4-0.5 tetanic force in both groups; absolute maximumpower (2,293 ± 138 W/m2) andwork (201 ± 9 J/m2) werelower in CK[/] Dia compared with Ctl Dia(2,744 ± 146 W/m2 and 284 ± 26 J/m2, respectively)(P < 0.05). The ability ofCK[/] Dia to sustain shortening duringrepetitive isotonic activation (75 Hz, 330-ms duration repeated eachsecond at 0.4 tetanic force load) was markedly impaired, withCK[/] Dia power and work declining to zero by 37 ± 4 s, compared with 61 ± 5 s in Ctl Dia. We conclude that combined myofibrillar and sarcomeric mitochondrial CK deficiency profoundly impairs Dia power and work output, underscoring the functional importance of CK during dynamic contractions in skeletal muscle. 相似文献