PubMed · 9100210
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I H Ullrich, R A Yeater. 1997. Postexercise oxygen consumption.. https://doi.org/10.1080/07315724.1997.10718660
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ATP synthase is conceived as a rotatory engine with two reversible drives, the proton-transporting membrane portion, F0, and the catalytic peripheral portion, F1. They are mounted on a central shaft (subunit gamma) and held together by an eccentric bearing. It is established that the hydrolysis of three molecules of ATP in F1 drives the shaft over a full circle in three steps of 120 degrees each. Proton flow through F0 probably generates a 12-stepped rotation of the shaft so that four proton-translocating steps of 30 degrees each drive the synthesis of one molecule of ATP. We addressed the elasticity of the transmission between F0 and F1 in a model where the four smaller steps in F0 load a torsional spring which is only released under liberation of ATP from F1. The kinetic model of an elastic ATP synthase described a wealth of published data on the synthesis/hydrolysis of ATP by F0F1 and on proton conduction by F0 as function of the pH and the protonmotive force. The pK values of the proton-carrying group interacting with the acidic and basic sides of the membrane were estimated as 5.3-6.4 and 8.0-8.3, respectively.
Both endurance and strength training are generally agreed to be necessary components of a balanced fitness programme. These two types of training are complementary; strength training improves neuromuscular function, prevents injuries, and is a prerequisite for effective endurance training. Whereas endurance training results in high energy expenditure during exercise, strength training, being associated with increased muscle mass, may result in increased energy expenditure at rest. In conjunction with endurance training, the most striking finding in skeletal muscle is its remarkable adaptability. Indeed, it is usually possible for the muscles to acquire the characteristics necessary to meet prevailing functional demands. This is true even if the demand is continuous contractile activity, 24 hours a day, week after week. The physiological effects of strength training are the result of hypertrophy of individual motor units, mostly comprising type II (fast-twitch) fibres, but are also secondary to neural changes affecting the recruitment and frequency modulation of motor units and co-ordination.
PURPOSE: In contrast to full-term infants, premature neonates generate accelerated growth rates after birth in an attempt to "catch up" to normal weight-for-age levels. Because this catch-up ability is related to gestational age, the authors postulated that there would be significant differences in anabolic recovery based on the degree of prematurity. To evaluate this hypothesis in surgical and septic neonates, we used serial postoperative prealbumin (PA) serum concentrations as an index of the return to anabolic metabolism after surgical stress. METHODS: Serum PA concentrations were measured on the day of surgery (DOS) and daily for a 10-postoperative day (POD) period in 73 acutely ill neonates after surgery. These infants were divided into two groups: mature infants with gestational ages > or =35 weeks (average, 38.2+/-1.84; n = 55), and premature infants with gestational ages < or =34 weeks (average, 29.7+/-2.93; n = 18). Infants were subgrouped based on insult type into either surgery (n = 56), or sepsis (n = 17). Statistical significance between groups at the given postoperative times was established using independent unpaired t tests assuming unequal variances. RESULTS: There was no significant difference in the daily nitrogen and caloric intake between the groups. Although recovery of hepatic prealbumin synthesis after the resolution of injury insult increased progressively in both gestational age groups, premature infants increased prealbumin production significantly earlier and to a greater degree than their nearer-term counterparts. CONCLUSIONS: These results suggest an earlier return of anabolic protein metabolism after acute injury in premature neonates versus infants that are born nearer term in both the surgery and the sepsis subgroups. These findings may be useful in modifying strategies for protein and nutritional repletion in acutely stressed preterm infants.