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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.
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
3.
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
4.
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
5.
Padilla Jaime; Garcia-Villalon Angel Luis; Fernandez Nuria; Monge Luis; Gomez Bernardino; Dieguez Godofredo 《Journal of applied physiology》1998,85(6):2205-2212
To analyze the effect of hyperthermia on thevascular response, the isometric response of isolated rabbit femoralartery segments was recorded at 37°C and hyperthermia (41 and44°C). Contraction to potassium (5 × 103-5 × 102 M) was significantlygreater at 41 and 44 than at 37°C and increased by inhibition ofnitric oxide (NO) synthesis withN-nitro-L-arginine(L-NNA;104 M) or endotheliumremoval at 37°C but not at 41 or 44°C. Norepinephrine (109-104M) produced a concentration-dependent contraction greater at 41 or 44 than at 37°C and not modified by endothelium removal orL-NNA at either temperature.Phenylephrine(109-104M) produced a contraction increased by warming to 44°C but not to41°C. The specific2-adrenoceptor agonist BHT-920produced a weak contraction, reduced by the1-adrenoceptor antagonist prazosin (106 M) andincreased at 44°C but not at 41°C. The concentration-dependent contraction to endothelin-1 (ET-1;1011-107M) was increased by warming to 41 and 44°C and by endothelium removal or L-NNA at 37°C butnot at 41 or 44°C. Response to ET-1 was reduced by endothelinETA-receptor antagonist BQ-123(105 M) andETB-receptor antagonist BQ-788(105 M). In arteriesprecontracted with ET-1(108-3 × 108 M), relaxation tosodium nitroprusside(108-104M) was increased at 41 and 44°C vs. at 37°C, but that of ACh (108-104M) or adenosine(108-104M) was not different at all temperatures studied. Relaxation to ACh,but not adenosine, was reduced similarly byL-NNA at all temperaturesstudied. These results suggest hyperthermia in muscular arteries mayinhibit production of, and increase dilatation to, NO, resulting inunchanged relaxation to ACh and increased constriction to KCl and ET-1,and may increase constriction to stimulation of1-adrenoceptors byNO-independent mechanisms. 相似文献
6.
Effect of inhibition of nitric oxide synthesis on the diaphragmatic microvascular response to hypoxia 总被引:1,自引:0,他引:1
Ward, Michael E. Effect of inhibition of nitric oxidesynthesis on the diaphragmatic microvascular response to hypoxia. J. Appl. Physiol. 81(4):1633-1641, 1996.The purpose of this study was to determine theeffect of inhibition of nitric oxide (NO) release on the diaphragmaticmicrovascular responses to hypoxia. In -chloralose-anesthetizedmongrel dogs, the microcirculation of the vascularly isolated ex vivoleft hemidiaphragm was studied by intravital microscopy. The diaphragmwas pump perfused with blood diverted from the femoral artery through aseries of membrane oxygenators. The responses to supramaximalconcentrations of sodium nitroprusside, moderate hypoxia (phrenicvenous PO2 27 Torr), andsevere hypoxia (phrenic venous PO2 15 Torr) were recorded before and after an infusion ofNG-nitro-L-arginine(L-NNA; 6 × 104 M) into the phreniccirculation for 20 min. Under control conditions, diaphragmatic bloodflow was 12.4 ± 1.1 ml · min1 · 100 g1. Diaphragmatic bloodflows recorded during moderate and severe hypoxia were 15.6 ± 1.2 and 24.3 ± 1.5 ml · min1 · 100 g1, respectively(P < 0.05 for both compared withcontrol values). Treatment withL-NNA reduced diaphragmaticblood flow to 9.6 ± 0.8 ml · min1 · 100 g1 under control conditions(P < 0.05) and caused arteriolarvasoconstriction to a degree that was dependent on vessel size (i.e.,larger vessels constricted more than smaller vessels).L-NNA eliminated the increase inblood flow during moderate hypoxia and inhibited arteriolar dilation byan amount that was related to vessel size (i.e., dilation of largervessels was inhibited more than that of smaller vessels). Inhibition ofNO synthesis had no effect on the increase in diaphragmatic blood flow(23.6 ± 1.9 ml · min1 · 100 g1;P > 0.05 compared with that duringsevere hypoxia before treatment withL-NNA) or arteriolar diametersduring severe hypoxia. NO release plays a role in the diaphragmaticvascular response to hypoxia, but this role is limited to dilation oflarger arterioles during hypoxia of moderate severity. 相似文献
7.
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
8.
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
9.
Laughlin M. Harold; Schrage William G.; McAllister Richard M.; Garverick H. A.; Jones A. W. 《Journal of applied physiology》2001,90(1):216-227
The purpose of the presentstudy was to test the hypothesis that gender influences exercisetraining-induced adaptations of vascular reactivity of porcine arteriesthat provide blood flow to skeletal muscle and femoral and brachialarteries. Male and female Yucatan miniature swine were exercise trainedon a motor-driven treadmill or cage confined for 16-20 wk.Contractile responses of arterial rings were evaluated in vitro bydetermining concentration-response curves for endothelin-1 (ET-1;1010 to 107 M) and norepinephrine (NE;1010 to 104 M). Relaxationresponses of arteries precontracted with 30 µM PGF2were examined for endothelium-dependent agents [bradykinin (BK;1011 to 106 M), ACh (1010 to104 M), and a Ca2+ ionophore, A-23187(106 M)] and a endothelium-independent agent [sodiumnitroprusside (1010 to 104 M)].Arteries from female pigs developed greater contractile force inresponse to ET-1 than arteries from male pigs, whereas contractileresponses to NE and KCl were similar in arteries from both genders.Femoral arteries from females exhibited greater endothelium-mediatedvasorelaxation (BK and ACh) than did those from males. In contrast,brachial arteries of males were more responsive to BK and ACh thanbrachial arteries of females. Exercise training increased ET-1-inducedcontractions in arteries from males (without endothelium) but not inarteries from females. Training had no effect on endothelium-dependentrelaxation in arteries from males but increased relaxation responses inbrachial arteries from females. We conclude that both gender andanatomic origin of the artery influence exercise training-inducedadaptations of vascular reactivity of porcine skeletal muscle conduit arteries. 相似文献
10.
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
11.
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
12.
Klokker M.; Secher N. H.; Madsen P.; Pedersen M.; Pedersen B. K. 《Journal of applied physiology》1997,83(5):1492-1498
Klokker, M., N. H. Secher, P. Madsen, M. Pedersen, and B. K. Pedersen. Adrenergic 1-and 1+2-receptor blockade suppress the natural killer cell response to head-up tilt in humans. J. Appl. Physiol. 83(5):1492-1498, 1997.To evaluate stress-induced changes in bloodleukocytes with emphasis on the natural killer (NK) cells, eight malevolunteers were followed during three trials of head-up tilt withadrenergic 1- (metoprolol) and1+2- (propranolol) blockade andwith saline (control) infusions. The 1- and1+2-receptor blockade did notaffect the appearance of presyncopal symptoms, but the head-up tiltinduced a transient lymphocytosis that was abolished by1+2-receptor blockade but notby 1-receptor blockade. Head-uptilt also resulted in delayed neutrophilia, which was insensitive to-receptor blockade. Lymphocyte subset analysis revealed that thehead-up tilt resulted in a twofold increase in the percentage andabsolute number of CD3/CD16+andCD3/CD56+NK cells in peripheral blood and that this increase was partially blocked by metoprolol and abolished by propranolol. The NKcell activity on a per NK cell basis did not change during head-up tilt, indicating that the cytotoxic capability of NK cells recruited tocirculation is unchanged. The data suggest that the head-up tilt-induced lymphocytosis was due mainly toCD16+ andCD56+ NK cells and that theirrecruitment to the blood was inhibited by1- and especially1+2-receptor blockade. Thusstress-induced recruitment of lymphocytes, and of NK cells inparticular, is mediated by epinephrine through activation of-receptors on the lymphocytes. 相似文献
13.
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
14.
Ventilatory long-term facilitation in unanesthetized rats 总被引:5,自引:0,他引:5
Olson E. B. Jr.; Bohne C. J.; Dwinell M. R.; Podolsky A.; Vidruk E. H.; Fuller D. D.; Powell F. L.; Mitchel G. S. 《Journal of applied physiology》2001,91(2):709-716
Wetested the hypothesis that unanesthetized rats exhibit ventilatorylong-term facilitation (LTF) after intermittent, but not continuous,hypoxia. Minute ventilation (E) and carbon dioxide production (CO2) were measured inunanesthetized, unrestrained male Sprague-Dawley rats via barometricplethysmography before, during, and after exposure to continuous orintermittent hypoxia. Hypoxia was either isocapnic [inspiredO2 fraction (FIO2) = 0.08-0.09 and inspired CO2 fraction(FICO2) = 0.04] or poikilocapnic(FIO2 = 0.11 andFICO2 = 0.00). Sixty minutes afterintermittent hypoxia, E orE/CO2 wassignificantly greater than baseline in both isocapnic and poikilocapnicconditions. In contrast, 60 min after continuous hypoxia,E andE/CO2 were notsignificantly different from baseline values. These data demonstrateventilatory LTF after intermittent hypoxia in unanesthetized rats.Ventilatory LTF appeared similar in its magnitude (after accounting forCO2 feedback), time course, and dependence on intermittenthypoxia to phrenic LTF previously observed in anesthetized,vagotomized, paralyzed rats. 相似文献
15.
Effect of nitric oxide synthase inhibition on cardiorespiratory responses in the conscious rat 总被引:3,自引:0,他引:3
Gozal David; Torres Jose E.; Gozal Yair M.; Littwin Sanford M. 《Journal of applied physiology》1996,81(5):2068-2077
Gozal, David, José E. Torres, Yair M. Gozal, andSanford M. Littwin. Effect of nitric oxide synthase inhibition on cardiorespiratory responses in the conscious rat. J. Appl. Physiol. 81(5): 2068-2077, 1996.Nitricoxide synthase (NOS) blockade was used to test the cardioventilatoryresponses to hypercapnia and hypoxia in freely behaving animals.Chronically instrumented adult Sprague-Dawley rats were studied beforeand after intravenous administration of either 100 mg/kg ofNG-nitro-L-arginine methylester (L-NAME), a nonspecificNOS blocker, or 10 mg/kg ofS-methyl-L-thiocitrulline(SMTC), a selective neural NOS inhibitor.L-NAME injection inducedsustained blood pressure (BP) elevation with transient tachycardia andincreased minute ventilation (E), whichreturned to baseline within minutes. SMTC elicited similar, althoughtransient, BP increases; however, heart rate andE decreased.L-NAME and SMTC did not modifyoverall steady-state hypercapnic responses. In controlconditions, hypoxia induced early Eincreases with further E enhancementsat 30 min. L-NAME increased theearly E response to 10%O2 but induced lateE reductions in hypoxia. SMTC did notchange early E responses but inducedmarked reductions in the later Ehypoxic responses. In control animals, hypoxia induced a significantheart rate increase. This increase was absent during the early response after SMTC and was followed in bothL-NAME- and SMTC-treated animals by significant heart rate reductions to values below room air. Similarly, the sustained BP response to hypoxia in control animals wasabsent after administration of NOS inhibitors. These findings suggestthat NOS activity exerts excitatory influences on respiration andcardiac chronotropy and sustained vasomotor tone during hypoxia. Wespeculate that NOS-mediated mechanisms may play an important role inhypoxia-induced ventilatory roll-off during wakefulness. 相似文献
16.
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
17.
Hebestreit H.; Kriemler S.; Hughson R. L.; Bar-Or O. 《Journal of applied physiology》1998,85(5):1833-1841
The objective of this study was to compare theO2 uptake(O2) kinetics at the onsetof heavy exercise in boys and men. Nine boys, aged 9-12 yr, and 8 men, aged 19-27 yr, performed a continuous incremental cyclingtask to determine peak O2(O2 peak).On 2 other days, subjects performed each day four cycling tasks at 80 rpm, each consisting of 2 min of unloaded cycling followed twice bycycling at 50%O2 peak for 3.5 min,once by cycling at 100%O2 peak for 2 min,and once by cycling at 130%O2 peak for 75 s.O2 deficit was not significantlydifferent between boys and men (respectively, 50%O2 peak task: 6.6 ± 11.1 vs. 5.5 ± 7.3 ml · min1 · kg1;100% O2 peak task:28.5 ± 8.1 vs. 31.8 ± 6.3 ml · min1 · kg1;and 130%O2 peaktask: 30.1 ± 5.7 vs. 35.8 ± 5.3 ml · min1 · kg1).To assess the kinetics, phase I was excluded from analysis. Phase IIO2 kinetics could bedescribed in all cases by a monoexponential function. ANOVA revealed nodifferences in time constants between boys and men (respectively, 50%O2 peaktask: 22.8 ± 5.1 vs. 26.4 ± 4.1 s; 100%O2 peak task: 28.0 ± 6.0 vs. 28.1 ± 4.4 s; and 130%O2 peak task: 19.8 ± 4.1 vs. 20.7 ± 5.7 s). In conclusion, O2 deficit and fast-componentO2 on-transientsare similar in boys and men, even at high exercise intensities, whichis in contrast to the findings of other studies employing simplermethods of analysis. The previous interpretation that children relyless on nonoxidative energy pathways at the onset of heavy exercise isnot supported by our findings. 相似文献
18.
Scheuermann Barry W.; Kowalchuk John M.; Paterson Donald H.; Cunningham David A. 《Journal of applied physiology》1998,85(4):1384-1393
Inhibition of carbonic anhydrase (CA) isassociated with a lower plasma lactate concentration([La]pl)during fatiguing exercise. We hypothesized that a lower[La]plmay be associated with faster O2uptake (O2) kinetics during constant-load exercise. Seven men performed cycle ergometer exercise during control (Con) and acute CA inhibition with acetazolamide (Acz,10 mg/kg body wt iv). On 6 separate days, each subject performed 6-minstep transitions in work rate from 0 to 100 W (below ventilatory threshold,<ET)or to a O2 corresponding to~50% of the difference between the work rate atET and peakO2(>ET).Gas exchange was measured breath by breath. Trials were interpolated at1-s intervals and ensemble averaged to yield a single response. The mean response time (MRT, i.e., time to 63% of total exponential increase) for on- and off-transients was determined using a two- (<ET) or athree-component exponential model(>ET).Arterialized venous blood was sampled from a dorsal hand vein andanalyzed for[La]pl.MRT was similar during Con (31.2 ± 2.6 and 32.7 ± 1.2 s for onand off, respectively) and Acz (30.9 ± 3.0 and 31.4 ± 1.5 s for on and off, respectively) for work rates<ET. Atwork rates >ET, MRTwas similar between Con (69.1 ± 6.1 and 50.4 ± 3.5 s for on andoff, respectively) and Acz (69.7 ± 5.9 and 53.8 ± 3.8 s for on and off, respectively). On- and off-MRTs were slower for>ET thanfor <ETexercise.[La]plincreased above 0-W cycling values during<ET and>ET exercise but was lower at the end of the transition during Acz (1.4 ± 0.2 and 7.1 ± 0.5 mmol/l for<ET and>ET,respectively) than during Con (2.0 ± 0.2 and 9.8 ± 0.9 mmol/lfor <ETand >ET,respectively). CA inhibition does not affectO2 utilization at the onset of<ET or>ETexercise, suggesting that the contribution of oxidative phosphorylationto the energy demand is not affected by acute CA inhibition with Acz. 相似文献
19.
Coirault Catherine; Samuel Jane-Lyse; Chemla Denis; Pourny Jean-Claude; Lambert Francine; Marotte Francoise; Lecarpentier Yves 《Journal of applied physiology》1998,85(5):1762-1769
We investigatedthe hypothesis that diaphragm compliance was abnormal incardiomyopathic Syrian hamsters (CSH), an experimental model ofmyopathy. The passive elastic properties of isolated diaphragm muscleswere analyzed at both the muscle and sarcomere levels. We used thefollowing passive exponential relationship between stress () andstrain (): = (Eo/)(e 1), where Eo is the initialelastic modulus and is the stiffness constant. Immunocytochemistryprocedures were used to analyze the distribution of two key elasticcomponents of muscle, extracellular collagen and intracellular titinelastic components, as well as the extracellular matrix glycoproteinlaminin. Muscle and sarcomere values of were nearly twofold lowerin CSH (8.7 ± 1.9 and 8.3 ± 1.4, respectively) than in controlanimals (19.7 ± 1.7 and 16.8 ± 2.1, respectively)(P < 0.01 for each). Compared withcontrols, Eo was higher in CSH.Sarcomere slack length was significantly longer in CSH than in controlanimals (2.1 ± 0.1 vs. 1.9 ± 0.1 µm,P < 0.05). The surface area ofcollagen I was significantly larger in CSH (17.4 ± 1.8%) than incontrol animals (12.4 ± 0.7%, P < 0.05). There was no change in the distribution of titin or lamininlabelings between the groups. These results demonstrate increaseddiaphragm compliance in cardiomyopathic hamsters. The increase in CSHdiaphragm compliance was observed despite an increase in the surfacearea of collagen and was not associated with an abnormal distributionof titin or laminin. 相似文献
20.
Hasday Jeffrey D.; Bannerman Douglas; Sakarya Sirhan; Cross Alan S.; Singh Ishwar S.; Howard Deborah; Drysdale Beth-Ellen; Goldblum Simeon E. 《Journal of applied physiology》2001,90(1):90-98
Fever is an important regulator ofinflammation that modifies expression and bioactivity of cytokines,including tumor necrosis factor (TNF)-. Pulmonary vascularendothelium is an important target of TNF- during the systemicinflammatory response. In this study, we analyzed the effect of afebrile range temperature (39.5°C) on TNF--stimulatedchanges in endothelial barrier function, capacity for neutrophilbinding and transendothelial migration (TEM), and cytokine secretion inhuman pulmonary artery endothelial cells (EC). Permeability for[14C]BSA tracer was increased by treatment with TNF-,and this effect was augmented by incubating EC at 39.5°C. Treating ECwith 2.5 U/ml TNF- stimulated an increase in subsequent neutrophiladherence and TEM. Incubating EC at 39.5°C caused a 30% increase inTEM but did not modify the enhancement of neutrophil adherence or TEMby TNF- treatment. Analysis of cytokine expression in EC culturesexposed to TNF- at either 37° or 39.5°C revealed three patternsof temperature and TNF- responsiveness. Granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin (IL)-8 were notdetectable in untreated EC but were increased after TNF- exposure,and this increase was enhanced at 39.5°C. IL-6 expression was alsoincreased with TNF- exposure, but IL-6 expression was lower in39.5°C EC cultures. Transforming growth factor-1 was constitutively expressed, and its expression was not influenced eitherby TNF- or exposure to 39.5°C. These data demonstrate thatclinically relevant shifts in body temperature might cause importantchanges in the effects of proinflammatory cytokines on the endothelium. 相似文献