Advances in veterinary science and comparative medicine最新文献_第2页

Respiratory gas exchange during exercise. 运动时的呼吸气体交换。

Advances in veterinary science and comparative medicine Pub Date : 1994-01-01

F L Powell

引用次数: 0

Exercise performance of mammals: an allometric perspective. 哺乳动物的运动表现:异速视角。

Advances in veterinary science and comparative medicine Pub Date : 1994-01-01

S L Lindstedt, R G Thomas

{"title":"Exercise performance of mammals: an allometric perspective.","authors":"S L Lindstedt, R G Thomas","doi":"","DOIUrl":"","url":null,"abstract":"We have examined aerobic exercise performance among the mammals with particular attention to the constraints that body size places on all aspects of muscle biomechanics, aerobic energetics, tissue oxygen diffusion, cardiovascular oxygen delivery, and pulmonary oxygen uptake. Several body-size-dependent patterns emerge that seemingly govern aerobic performance in mammals, with the caveat that at any given body size there is a range of aerobic capacities, the result of natural selection operating on the size-dependent \"default values\" of structure and function. Among these default values, the following apparent functional clusters surface: 1. In general, concentrations and pressures (e.g., of proteins and gases) are roughly independent of body size. Inspiratory and expiratory ventilation pressures, blood pressure and the partial pressures of O2 and CO2 in lungs, blood, and tissues do not vary with body size. Likewise, concentrations of hemoglobin, myoglobin, and hematocrit are independent of body size. 2. Most volumes and capacities scale linearly with body size (i.e., as a constant function of body mass). In addition to heart, lung, and total blood volumes, important examples relevant to exercise performance are the diffusing capacities for oxygen in the lung and, apparently, in the tissues. 3. Finally, most time-dependent variables related to oxygen delivery scale allometrically with body mass; they are of shorter duration in small animals than in large ones. Biological rates, for example, Vmax of working muscle, heart and respiratory rates, and transit times of blood through the muscles and lungs, all vary roughly as the -1/5 to -1/4 power of body mass.","PeriodicalId":75456,"journal":{"name":"Advances in veterinary science and comparative medicine","volume":"38B ","pages":"191-217"},"PeriodicalIF":0.0,"publicationDate":"1994-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18811008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Beyond the vertebrates: achieving maximum power during flight in insects and hummingbirds. 超越脊椎动物:昆虫和蜂鸟在飞行中获得最大的力量。

Advances in veterinary science and comparative medicine Pub Date : 1994-01-01

D J Wells, C P Ellington

{"title":"Beyond the vertebrates: achieving maximum power during flight in insects and hummingbirds.","authors":"D J Wells, C P Ellington","doi":"","DOIUrl":"","url":null,"abstract":"Hummingbirds and insects are clearly extreme aerobic athletes. Hovering hummingbirds and insects exhibit the highest mass-specific metabolic rates found in vertebrates and invertebrates, respectively. Both groups of fliers have high mitochondrial volume densities in their locomotor muscles, but these do not exceed 35-40% of the fiber volume, presumably from a need to conserve myofibrils for force generation. A possible adaptation to this constraint is the observed greater packing of the inner mitochondrial membranes than occurs in mammalian mitochondria. Both hummingbirds and insects show higher rates of oxygen consumption per unit volume of mitochondria than do mammals. Additionally, volume-specific mitochondrial oxygen consumption in insects increases as body size decreases, unlike the size-independent pattern in mammals. Aerodynamic analysis of power output during hovering flight strongly suggests that both insects and hummingbirds operate with considerable elastic storage of kinetic energy, thereby decreasing their inertial power requirements. Both groups appear to hover with muscle power output close to 100 W kg-1. Muscle efficiency in hummingbirds is near 10%; in insects, muscle efficiency varies with body size, but at similarly low values. Scaling of efficiency with body size has also been reported in terrestrial mammals, suggesting a possible common mechanism. Both groups of hovering fliers can markedly increase their metabolic power inputs and mechanical power outputs above those required for basic hovering flight. These elite aerial athletes offer considerable insight into the constraints and demands on animal design for maximal aerobic capacity. Additionally, the similarities shown between the different phyla suggest the existence of common mechanisms and limitations in metabolic and mechanical performance. Insects in particular offer a number of advantages in pursuing questions such as the cause of the allometric scaling of muscle efficiency; this scaling can be examined within families, genera, or species with the additional benefit that insect muscles also perform well in vitro.","PeriodicalId":75456,"journal":{"name":"Advances in veterinary science and comparative medicine","volume":"38B ","pages":"219-32"},"PeriodicalIF":0.0,"publicationDate":"1994-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18811010","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Exercise performance of fish. 鱼的运动表现。

Advances in veterinary science and comparative medicine Pub Date : 1994-01-01

P W Webb

引用次数: 0

Cellular energetics during exercise. 运动时的细胞能量。

Advances in veterinary science and comparative medicine Pub Date : 1994-01-01

K E Conley

{"title":"Cellular energetics during exercise.","authors":"K E Conley","doi":"","DOIUrl":"","url":null,"abstract":"How is the muscle fiber designed to accomplish the diversity of tasks performed by striated muscle? Basically, a common contractile mechanism and a similar organization of metabolism in striated muscles are used to generate a wide spectrum of speeds and durations of contraction. The speed of contraction ranges from manyfold within an animal to over a hundred-fold between animals, owing to variation in the intrinsic velocities of the myosin isoforms. Recruiting fibers that contain the myosin isoform that contracts at the appropriate velocity varies the speed of locomotion at minimal cost. The magnitude and duration of the energy supply required to meet this contractile demand depends on the size of the cellular energy buffer and the capacities of the metabolic pathways. The faster the contractile speed, the larger the PCr pool and the greater the glycolytic capacity to meet a high rate of ATP use. Slower-contracting fibers have a smaller buffer for the short term, but an increased oxidative capacity for continuous energy supply to maintain energy balance over the long term. In general, fibers trade contractile speed for duration of performance, but a number of exceptions exist where rapid contractions are maintained for extended periods. In the face of this heterogeneity of properties, common features are found that assure an energy balance. The PCr/ATP buffer system offers a simple mechanism of feedback control of energy supply despite the wide range of high-energy phosphate concentrations and oxidative capacities found in skeletal muscle. An oxygen balance system also appears to be present in the terminal structures of the respiratory system, the capillaries, and mitochondria. Despite the diversity of these structures, a rather constant ratio of oxygen delivery capacity to mitochondrial oxidative capacity is found in vertebrate striated muscles. Finally, a critical feature of muscle energy balance that remains unresolved is (are) the mechanism(s) controlling mitochondrial respiration in heart. Feedback control appears to account for linking ATP supply to demand in skeletal muscle, but the mechanisms governing respiratory control in heart are still under vigorous investigation. Thus, the links between contractile demand and oxidative phosphorylation are still unresolved in this tissue, which may indicate that a key element is missing in our understanding of the cellular energetics of exercise.","PeriodicalId":75456,"journal":{"name":"Advances in veterinary science and comparative medicine","volume":"38A ","pages":"1-39"},"PeriodicalIF":0.0,"publicationDate":"1994-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18801019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Structural basis of muscle performance. 肌肉表现的结构基础。

Advances in veterinary science and comparative medicine Pub Date : 1994-01-01

R Billeter, H Oetliker, H Hoppeler

引用次数: 0

Exercise performance of birds. 鸟类的运动表现。

Advances in veterinary science and comparative medicine Pub Date : 1994-01-01

D K Saunders, M R Fedde

引用次数: 0

Circulatory function during exercise: integration of convection and diffusion. 运动时的循环功能:对流与扩散的结合。

Advances in veterinary science and comparative medicine Pub Date : 1994-01-01

J H Jones

{"title":"Circulatory function during exercise: integration of convection and diffusion.","authors":"J H Jones","doi":"","DOIUrl":"","url":null,"abstract":"The cardiovascular system has frequently been hypothesized to be the limiting step for O2 transport that determines VO2 max in many species of mammals. Careful analysis of the factors that determine how O2 is transported by the circulation demonstrate that such a single-step limitation cannot exist. Evaluation of the results of experiments in which circulatory O2 transport capacity was experimentally altered demonstrates no direct or absolute relationship between changes in O2 transport capacity and changes in VO2 max. Furthermore, experimental evidence collected during maximal exercise in hypoxia and hyperoxia supports the concept that multiple components of the O2 transport system contribute to limiting O2 flux at VO2 max. Consideration of the basic equations that describe O2 transport through the respiratory system shows that changes in PO2 at each step of the system required to increase O2 flux through that step conflict with the changes in PO2 required to increase flux through adjacent steps. Changes in convection, capacitance, or conductance at one step affect gas transport through the adjacent steps. Hence, no single-step limitation to O2 transport is possible, because the convective and diffusive gas exchangers are interdependent. Increasing QT at VO2 max always increases O2 flux (although not necessarily in proportion to the increase in QT), unless VO2 max is limited by mitochondrial oxidative capacity, as in goats. Cardiovascular structure and function in mammals reflects allometric, adaptive and induced variation. Maximal heart rate is determined strictly by body size, thus maximal QT/Mb is inevitably lower in larger mammals. Adaptive and induced variation elicit hypertrophy of muscle, capillaries, and mitochondria, increasing circulatory capacity and VO2 max. When selection for maximal respiratory function is weak, as in most species of mammals, any component(s) of the respiratory system may be underdeveloped, relative to other structures in the system, and contribute disproportionately to limiting O2 flux. When selection for aerobic capacity is strong, as in racehorses, malleable elements of the respiratory system, including the cardiovascular structures, may hypertrophy until their capacities for O2 transport match that of the least malleable structure, the lung. Amplifying circulatory function so greatly in a large animal may lead to functional demand exceeding structural capacity, resulting in the nearly ubiquitous occurrence of exercise-induced pulmonary hemorrhage in racehorses.","PeriodicalId":75456,"journal":{"name":"Advances in veterinary science and comparative medicine","volume":"38A ","pages":"217-51"},"PeriodicalIF":0.0,"publicationDate":"1994-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18801022","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Jumping ability of anuran amphibians. 无脊椎两栖动物的跳跃能力。

Advances in veterinary science and comparative medicine Pub Date : 1994-01-01

R L Marsh

引用次数: 0

Solving the common problem: matching ATP synthesis to ATP demand during exercise. 解决常见的问题:使ATP合成与运动时的ATP需求相匹配。

Advances in veterinary science and comparative medicine Pub Date : 1994-01-01

P W Hochachka

{"title":"Solving the common problem: matching ATP synthesis to ATP demand during exercise.","authors":"P W Hochachka","doi":"","DOIUrl":"","url":null,"abstract":"Biologists have long known that rates of adenosine triphosphate utilization and production need to be extremely closely balanced in all cells at all work rates. To put it in molecular rather than molar terms, in human muscle engaged in a 15-min work protocol, some 3.3 x 10(20) ATP molecules g-1 are used and resynthesized at close to 100 times the resting cycling rates before fatigue occurs. However, during this interval only a 20-25% decrease in the ATP pool is sustained. Review of recent studies as to how such remarkable regulatory precision is achieved suggests that in resting muscle, myosin behaves as a latent catalyst for which the full catalytic capacity is (a) realized with the arrival of its activator signal (Ca2+) and (b) attenuated with reaction products. These proactive controls, initiated at the onset of ATP utilization, set the required flux through ATP-producing pathways. For any given enzyme step in ATP-producing pathways, reaction velocity (upsilon) becomes the independent parameter, whereas substrate concentration ([s], the dependent parameter) must be adjusted accordingly. Because the dynamic range for muscles (change from resting to maximum ATP turnover rates) can exceed 100-fold, in many studies of working muscle the percentage change in ATP turnover rate usually greatly exceeds the percentage change in substrate concentrations. These kinds of observations are not easily explained by current metabolic regulation models, but are consistent with pathway enzymes behaving as latent catalysts in resting muscle. In this view, the unmasking of such latent catalytic potential is the main explanation for how large changes in upsilon can be achieved with modest (sometimes immeasurable) changes in [s]. In terms of the basic enzyme velocity equation, Vmax = kcat.e0 for pathways of ATP utilization and of ATP synthesis, the dominant (coarse level) regulation is achieved through e0 adjustments, whereas fine-tuning of flux is achieved by effective kcat adjustment.","PeriodicalId":75456,"journal":{"name":"Advances in veterinary science and comparative medicine","volume":"38A ","pages":"41-56"},"PeriodicalIF":0.0,"publicationDate":"1994-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"18801024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0