2,102 research outputs found
Work capacity of permanent residents of high altitude
No full textMarconi, Claudio, Mauro Marzorati, and Paolo Tibetan and Andean natives at altitude have allegedly a greater work capacity and stand fatigue better than acclimatized lowlanders. The principal aim of the present review is to establish whether convincing experimental evidence supports this belief and, should this be the case, to analyze the possible underlying mechanisms. The superior work capacity of high altitude natives is not based on differences in maximum aerobic power (V(O2 peak)), mL kg(-1)min(-1)). In fact, average V (O2 peak) of both Tibetan and Andean natives at altitude is only slightly, although not significantly, higher than that of Asian or Caucasian lowlanders resident for more than 1 yr between 3400 and 4700 m (Tibetans, n = 152, vs. Chinese Hans, n = 116: 42.4 +/- 3.4 vs. 39.2 +/- 2.6 mL kg(-1)min(-1), mean +/- SE; Andeans, n = 116, vs. Caucasians, n = 70: 47.1 +/- 1.7 vs. 41.6 +/- 1.2 mL kg(-1)min(-1)). However, compared to acclimatized lowlanders, Tibetans appear to be characterized by a better economy of cycling, walking, and running on a treadmill. This is possibly due to metabolic adaptations, such as increased muscle myoglobin content and antioxidant defense. All together, the latter changes may enhance the efficiency of the muscle oxidative metabolic machinery, thereby supporting a better prolonged submaximal performance capacity compared to lowlanders, despite equal V(O2 peak). With regard to Andeans, data on exercise efficiency is scanty and controversial and, at present, no conclusion can be drawn as to the origin of their superior performance
Economy of locomotion in high-altitude Tibetan migrants exposed to normoxia
No full textHigh-altitude Tibetans undergo a pattern of adaptations to chronic hypoxia characterized, among others, by a more efficient aerobic performance compared with acclimatized lowlanders. To test whether such changes may persist upon descent to moderate altitude, oxygen uptake of 17 male Tibetan natives lifelong residents at 3500-4500 m was assessed within 1 month upon migration to 1300 m. Exercise protocols were: 5 min treadmill walking at 6 km h-1 on increasing inclines from +5 to +15% and 5 min running at 10 km h-1 on a +5% grade. The data (mean (plus or minus) S.E.M.) were compared with those obtained on Nepali lowlanders. When walking on +10, +12.5 and +15% inclines, net VO2 of Tibetans was 25.2 (plus or minus) 0.7, 29.1 (plus or minus) 1.1 and 31.3 (plus or minus) 0.9 ml kg-1 min-1, respectively, i.e. 8, 10 and 13% less (P < 0.05) than that of Nepali. At the end of the heaviest load, blood lactate concentration was lower in Tibetans than in Nepali (6.0 (plus or minus) 0.9 versus 8.9 (plus or minus) 0.6 mM; P < 0.05). During running, VO2 of Tibetans was 35.1 (plus or minus) 0.8 versus 39.3 (plus or minus) 0.7 ml kg-1 min-1 (i.e. 11% less; P < 0.01). In conclusion, during submaximal walking and running at 1300 m, Tibetans are still characterized by lower aerobic energy expenditure than control subjects that is not accounted for by differences in mechanical power output and/or compensated for by anaerobic glycolysis. These findings indicate that chronic hypoxia induces metabolic adaptations whose underlying mechanisms still need to be elucidated, that persist for at least 1 month upon descent to moderate altitude
Postal de Claudio Vivas a Maruja Vieira, junio 23 de 1955
No full textPostal de Claudio Vivas a Maruja Vieira, felicitándola por el reconocimiento que le fue otorgado a la autora de poemasPostcard from Claudio Vivas to Maruja Vieira, congratulating her for the recognition given to the author of poems.Publicación, fondo Maruja Vieira, carpeta 1, folio
Age-related heart rate response to exercise in heart transplant recipients. Functional significance
No full textThe heart rate (HR) and O(2) uptake (VO(2)) responses to cycle ergometer exercise and the role of O(2) transport in limiting submaximal and maximal aerobic performance were assessed in 33 heart transplant recipients (HTR) [14 children (P-HTR), 11 young adults (YA-HTR) and 8 middle-age adults (A-HTR)] and in 28 age-matched control subjects (CTL). In 7 P-HTR ("responders") the HR response to the onset of exercise (on-response) was as fast as that of CTL, whereas in all other patients ("non-responders") the HR on-response was typical of the denervated heart. Compared with non-responder P-HTR, responder P-HTR were also characterized by a normal peak HR (177+/- 16 vs. 151+/- 25 beats/min), an equally slow time constant for the VO(2) on-response (tau: 54 +/- 11 vs. 62+/- 13 s) and a similar low (approximately 60% of that of CTL) peak VO(2) (28 +/- 7 vs. 26 +/- 10 ml/kg per min). On the other hand non-responder YA-HTR and A-HTR were characterized by a relatively low peak HR (151 +/- 21 and 144 +/- 29 beats/min, respectively), a slow tau for the on-response (63 +/- 12 and 70 +/- 11 s) and a low peak (28 +/- 7 and 19 +/- 6 ml/kg per min). In conclusion, a sizeable number of paediatric patients (responder P-HTR) may reacquire the normal HR response to exercise, both in terms of kinetics and maximal level. Despite the almost complete recovery of cardiovascular function, and, probably, oxygen delivery, both the kinetics of the VO(2) on-response and the maximal aerobic power of the responder P-HTR were similar to those of non-responder P-HTR. The latter finding is probably attributable to peripheral limitations, due to inborn and/or pharmacological muscle deterioration
“Dialogue between Translators and Authors. The Example of Claudio Magris”
No full textThe paper focuses on the forms of cooperation between authors and their translator(s) in all cases in which the two operate simultaneously. This issue is explored on the example of the Trieste-born author Claudio Magris, who cultivates a very close relationship with most of his translators.
Writing and translation have been coexisting in this author throughout his career and have resulted in the heightened sensitivity of Magris the author with regards to translation, as the first part of the analysis shows. The second part describes the dialogue between Magris and the translators of his works, and ends with the more general question of the significance and role of such a form of exchange
Consideraciones sobre la poética de Claudio Rodríguez
No full textThe purpose of this paper is to study the poetics of Claudio Rodríguez, delimiting its components and trying to clarify them and to present them as a whole. The author left some pages written on his conception of poetry that encourage reflection and, in some cases, interpretation. So with his conception of poetry as a gift and inebriation, as an alliance and condemnation or celebration (giving title to his collections of poems), or with notions such as «participation», «living contemplation», «living expression » or «personal rhythm» that make up his way of understanding the poetic process.El propósito de este artículo es estudiar la poética de Claudio Rodríguez, deslindando sus componentes y tratando de clarificarlos y presentarlos en su conjunto. El autor dejó escritas algunas páginas sobre su concepción de la poesía que animan a la reflexión y, en algunos casos, a la interpretación. Así sucede con su concepción de la poesía como un don y una ebriedad, como alianza y condena o como celebración (que dan título a sus poemarios), o con nociones como las de «participación», «contemplación viva», «expresión viva» o «ritmo personal», que configuran su forma de entender el proceso poético
Gas exchange and cardiovascular kinetics with different exercise protocols in heart transplant recipients
No full text 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.—Metabolic and cardiovascular adjustments to various submaximal exercises were evaluated in 82 heart transplant recipients (HTR) and in 35 control subjects (C). HTR were tested 21.5 ± 25.3 (SD) mo (range 1.0–137.1 mo) posttransplantation. Three protocols were used: protocol A consisted of 5 min of rectangular 50-W load repeated twice, 5 min apart [5 min rest, 5 min 50 W ( Ex 1), 5 min recovery, 5 min 50 W ( Ex 2)]; protocol B consisted of 5 min of rectangular load at 25, 50, or 75 W; protocol Cconsisted of 15 min of rectangular load at 25 W. Breath-by-breath pulmonary ventilation (V˙e), O2 uptake (V˙o 2), and CO2 output (V˙co 2) were determined. During protocol A, beat-by-beat cardiac output (Q˙) was estimated by impedance cardiography. The half times ( t 1/2) of the on- and off-kinetics of the variables were calculated. In all protocols, t 1/2 values forV˙o 2 on-,V˙e on-, andV˙co 2 on-kinetics were higher (i.e., the kinetics were slower) in HTR than in C, independently of workload and of the time posttransplantation. Also, t 1/2 Q˙ on- was higher in HTR than in C. In protocol A, no significant difference of t 1/2 V˙o 2on- was observed in HTR between Ex 1 (48 ± 9 s) and Ex 2 (46 ± 8 s), whereas t 1/2Q˙ on- was higher during Ex 1 (55 ± 24 s) than during Ex 2 (47 ± 15 s). In all protocols and for all variables, the t 1/2 off-values were higher in HTR than in C. In protocol C, no differences of steady-stateV˙e,V˙o 2, andV˙co 2 were observed in both groups between 5, 10, and 15 min of exercise. We conclude that 1) in HTR, a “priming” exercise, while effective in speeding up the adjustment of convective O2 flow to muscle fibers during a second on-transition, did not affect theV˙o 2 on-kinetics, suggesting that the slower V˙o 2 on- in HTR was attributable to peripheral (muscular) factors; 2) the dissociation between Q˙ on- andV˙o 2 on-kinetics in HTR indicates that an inertia of muscle metabolic machinery is the main factor dictating theV˙o 2on-kinetics; and 3) theV˙o 2 off-kinetics was slower in HTR than in C, indicating a greater alactic O2 deficit in HTR and, therefore, a sluggish muscleV˙o 2 adjustment. </jats:p
Blood lactate accumulation and muscle deoxygenation during incremental exercise
No full text Near-infrared spectroscopy (NIRS) could allow insights into controversial issues related to blood lactate concentration ([La]b) increases at submaximal workloads (w˙). We combined, on five well-trained subjects [mountain climbers; peak O2 consumption (V˙o 2peak), 51.0 ± 4.2 (SD) ml ⋅ kg−1 ⋅ min−1] performing incremental exercise on a cycle ergometer (30 W added every 4 min up to voluntary exhaustion), measurements of pulmonary gas exchange and earlobe [La]b with determinations of concentration changes of oxygenated Hb (Δ[O2Hb]) and deoxygenated Hb (Δ[HHb]) in the vastus lateralis muscle, by continuous-wave NIRS. A “point of inflection” of [La]b vs.w˙ was arbitrarily identified at the lowest [La]b value which was >0.5 mM lower than that obtained at the following w˙. Total Hb volume (Δ[O2Hb + HHb]) in the muscle region of interest increased as a function ofw˙ up to 60–65% ofV˙o 2 peak, after which it remained unchanged. The oxygenation index (Δ[O2Hb − HHb]) showed an accelerated decrease from 60– 65% ofV˙o 2 peak. In the presence of a constant total Hb volume, the observed Δ[O2Hb − HHb] decrease indicates muscle deoxygenation (i.e., mainly capillary-venular Hb desaturation). The onset of muscle deoxygenation was significantly correlated ( r 2 = 0.95; P < 0.01) with the point of inflection of [La]bvs. w˙, i.e., with the onset of blood lactate accumulation. Previous studies showed relatively constant femoral venous[Formula: see text] levels at w˙ higher than ∼60% of maximal O2consumption. Thus muscle deoxygenation observed in the present study from 60–65% ofV˙o 2 peak could be attributed to capillary-venular Hb desaturation in the presence of relatively constant capillary-venular[Formula: see text] levels, as a consequence of a rightward shift of the O2Hb dissociation curve determined by the onset of lactic acidosis. </jats:p
Heart rate variability in the human transplanted heart: Nonlinear dynamics and QT vs RR-QT alterations during exercise suggest a return of neurocardiac regulation in long-term recovery
No full textRATIONALE: Functional reinnervation of the transplanted human heart by the autonomic nervous system has not been demonstrated. A lack of autonomic control of the transplanted allograft is reflected by an increased resting heart rate, a sluggish heart rate response to dynamical exercise and a reduced heart rate variability. Recent evidence suggests that a measure of deterministic chaos in the heartbeat interval series (point correlation dimension, PD2i) is superior to the conventional power spectrum or other stochastic measures in detecting changes in the mechanism underlying heartbeat generation. METHODS: The PD2i is based on the presumption that the variability is determined and patterned, whereas the stochastic measures all assume that the variability is around a stationary mean and is noise. The PD2i reconstructs the degrees of freedom (number of independent variables) in the system that generates the time series examined, and does this irrespective of whether the system is stochastic or deterministic and is stationary in time. RESULTS: PD2i was determined for heartbeat intervals (RR, ECG digitized at 1200 Hz; supine posture) of 23 heart transplant recipients (HTR: 9 adults, 14 children; 0.04-7.7 years after transplantation) and 21 healthy control subjects (CTL; 13 adults, 8 children). The PD2i (+/-SD) averaged 5.4 +/- 0.7 for the CTL adults and 5.4 +/- 0.6 for the CTL children. Mean PD2i was reduced after transplantation to 1.1 +/- 0.1 in 6 HTRs recorded within 1 year after surgery; in one HTR recorded 2 weeks after surgery the mean PD2i was 3.7. Between 1 to 2 years PD2i was found increased in 2 of 3 subjects and between 2 to 8 years it was increased in 13 of 13, but not to control levels. In normal hearts the QT subinterval of each heartbeat cycle is associated with inotropy and the RR-QT remainder with chronotropy (i.e., the dyastolic interval during which RR is primarily regulated). To examine more closely the residual and returning heartbeat dynamics of the HTR subjects, these subinterval series were examined during mild exercise (40 to 90 Watts) and its recovery. In recent HTRs, resting QT and RR-QT were moderately reduced and modulated by exercise and recovery, but with an approximate 100 beat latency. In long-term (7-8 years) HTR subjects there was a rapid and larger response to exercise/recovery, but compared to normal the range was smaller and the complexity of the subinterval trajectories in time was simpler. CONCLUSIONS: Recurrence of low-dimensional deterministic dynamics after transplantation suggests recovery of neurocardiac control attributable to 1) reorganization of the viable intrinsic cardiac nervous system, 2) reinnervation by the extrinsic autonomic nervous system, or 3) both
The heart rate response to exercise and circulating catecholamines in heart transplant recipients
No full textThe plasma concentration of noradrenaline ([NA]) is higher than that of adrenaline ([A]) both in normal subjects and in heart transplant recipients (HTR). Since in both groups the myocardial density of beta1-adrenergenic receptors is much greater than that of beta2-adrenergenic receptors, the chronotropic response of a denervated heart to changes in plasma [NA] and [A] in the absence of reinnervation should be similar to that of agonist stimulation of beta1-receptors. To test this hypothesis, 17 HTR and 9 healthy subjects (CTL) performed incremental exercise on a cycle ergometer to voluntary exhaustion. Heart rate (HR) was recorded by electrocardiography. [NA] and [A] were measured by high-pressure liquid chromatography at rest and at increasing workloads (w). In both groups, HR and [NA+A] increased with w, and HR with [NA+A]. Normalized HR values, plotted against the logarithm of [NA+A], fitted significantly logistic curves. The affinity constants were different, i.e. 2599+/-350 and 487+/-37 ng.l(-1), for HTR and CTL, respectively. The chronotropic effect of changes in [NA+A] in HTR was similar to that of combined beta1- and beta2-adrenergic activation evoked by applying isoprenaline to isolated heart myocytes (Brodde OE, Pharmacol Ther 60:405-430, 1993). These findings suggest that over time sympathetic reinnervation and the modulation of beta-receptors may take place in HTR, ruling out the hypothesis of persistent heart denervation
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