Metabolic disease in animals

Rickets is a metabolic bone disorder characterized by osteopenic changes resulting from the failure of calcification of the osteoid matrix and absent mineralization of hypertrophic cartilage cells at the epiphyseal growth plates in growing primates, herbivores, swine, carnivores, and birds. The causes of rickets include inadequate dietary provision of calcium, phosphorus, and vitamin D. Osteomalacia in reptiles, simian bone disease in nonhuman primates, and osteodystrophia fibrosa (secondary hyperparathyroidism) or "bran disease" in herbivores are caused by a diet that has a much higher content of phosphorus than calcium, combined with inadequate exposure to direct sunlight. Medullary bone consists of interconnected spicules of bone resembling embryonic bone and is established in relation to the shell formation cycle of laying birds. Hypertrophic osteodystrophy develops in large-breed growing dogs, chickens, and guinea pigs and is possibly caused by vitamin C deficiency. Tibial dyschondroplasia is a defect in endochondral ossification characterized by a widened proximal tibial physis that is not penetrated by metaphyseal vascular sprouts, commonly found in growing broiler chickens, turkeys, and exotic birds.     

Metabolic micromilieu in tumours

Solid malignant tumours are characterized by a heterogeneous metabolic micromilieu with the intra-individual variability within single tumours being substantially smaller than the inter-individual differences between tumours. Despite this variability, there are some hallmarks which are characteristic for the majority of malignancies. They include hypoxia, tissue acidosis, and abnormal microcirculation. Peculiarities of the carbohydrate metabolism and specifically of glycolysis in tumours receive increasing attention in experimental and clinical research. As shown by our research with induced bioluminescence, different tumours from various entities exhibit a large spectrum of lactate accumulation. Interestingly, primary lesions with metastasis contain significantly higher amounts of lactate as compared to non-metastatic tumours. Classification into high and low lactate tumours according to the median lactate concentration in combination with a Kaplan-Meier analysis reveals that survival of patients with high lactate tumours is significantly worse than that with low lactate carcinomas. Furthermore, there is a positive correlation between tumour lactate content and radio-resistance. Conclusion: High lactate tumours are characterized by a higher degree of malignancy and therapeutic resistance.     

Metabolic testing in the office

The three most commonly used metabolic tests are the Resting Metabolic Rate, Anaerobic Threshold Testing, and V.O2max. For several decades, these metabolic tests have been confined to the setting of university-based physiology laboratories and cardiopulmonary environments, i.e., metabolic carts in the intensive care units. The information gathered is used as a research and clinical tool in evaluating metabolic activity in a variety of physiological states from a body at rest, to exercise (aerobic and anaerobic), in certain medical states like illness, fed/starvation, and medicinal or supplementation affective states. Over the last decade, as technology has improved, so have the metabolic testing carts. They have become widely available for mainstream use by a variety of health care professionals. The purpose of this article is to review these three tests and how they may be useful in a medical practice.     

Metabolic factors in fatigue.

The supply of energy is of fundamental importance for the ability to sustain exercise. The maximal duration of exercise is negatively related to the relative intensity both during dynamic and static exercise. Since exercise intensity is linearly related to the rate of energy utilisation this suggests that energetic deficiency plays a major role in the aetiology of muscle fatigue. Characteristic metabolic changes in the muscle are generally observed at fatigue--the pattern being different after short term exercise (lactate accumulation and phosphocreatine depletion) from after prolonged exercise at moderate intensity (glycogen depletion). A common metabolic denominator at fatigue during these and many other conditions is a reduced capacity to generate ATP and is expressed by an increased catabolism of the adenine nucleotide pool in the muscle fibre. Transient increases in ADP are suggested to occur during energetic deficiency and may be the cause of fatigue. Experimental evidence from human studies demonstrate that near maximal power output can be attained during acidotic conditions. Decreases in muscle pH is therefore unlikely to affect the contractile machinery by a direct effect. However, acidosis may interfere with the energy supply possibly by reducing the glycolytic rate, and could by this mechanism be related to muscle fatigue.     

3T MRI上鼠脑多体素1H-MRS成像因素及其代谢物比值研究

目的:探讨影响鼠脑多体素1H-MRS的成像因素及在3T MRI上正常鼠脑代谢物值.材料和方法:40只正常雄性SD大鼠,体重200～250g.利用3T MRI扫描机、大鼠专用线圈对SD大鼠尾状核行二维多体素1H-MRS检查,采用点分辨波谱(PRESS)序列,TR/TE=1000ms/35ms,FOV 60mm,层厚4mm,NEX 1;利用波谱后处理软件FuncTool重建SD大鼠正常尾状核Cho/Cr、Cho/NAA、NAA/Cr的比值.结果:40只行多体素1H-MRS检查的正常SD大鼠,其尾状核Cho/Cr的平均值为0.97±0.20、Cho/NAA为0.79±0.33、NAA/Cr为1.34±0.34.在多体素1H-MRS检查中,关键要选择合适的体素位置,并对匀场进行优化,同时要恰如其分的放置饱和带.结论:在3T MRI上进行鼠脑多体素1H-MRS切实可行;通过测定正常鼠脑的代谢物比值,为以后的科研工作提供有价值的参考值.     

长期中低强度健身锻炼对老年代谢综合征危险因素影响的追踪观察

目的:观察长期健身锻炼对老年代谢综合征及其危险因素的影响。方法:293名60～85岁门诊患者按健身锻炼方式不同分为对照组(无规律性健身锻炼)、锻炼1组(坚持琴棋书画、气功等传统养生健身锻炼5年以上)、锻炼2组(长期有规律参加健身运动,每周至少3次,每次30分钟以上,运动强度为10～20METs-h/week)和锻炼3组(运动项目、时间、频率同锻炼2组,运动强度为20～40METs-h/week)。对代谢综合征危险因素进行为期3年的追踪观察。结果:随着年龄增长,代谢综合征各项危险因素发病率逐渐增高,但速度放缓。锻炼1组和锻炼2组体重指数、血压、血糖控制好于对照组(P<0.05)。对照组老年人代谢综合征发病率达29.9%,高于各锻炼组。锻炼1组和锻炼2组代谢综合征危险因素在观察期间新发病率低于对照组,亦低于未加饮食控制的锻炼3组。结果提示:传统养生健身锻炼和低强度锻炼对控制老年人代谢综合征危险因素发生率有一定作用。在老年人群中开展各种形式的健身锻炼,并辅以饮食控制,对预防控制代谢综合征及其危险因素具有重要作用。     

Chronic Fatigue Syndrome

The major symptom of chronic fatigue syndrome is extreme fatigue and an increase in fatigue following exertion. Many patients reduce physical activity to avoid such fatigue and thus become increasingly weaker and less fit. Exercise testing does not exacerbate symptoms. Even though a fair amount of variability exists in symptoms from one day to another, low- to moderate- intensity, intermittent exercise therapy appears to improve functional capacity and reduce fatigue and other symptoms.     

Metabolic Repair of Premutational Damage in Paramecium

The problems of experimental analysis of the post-irradiation processes leading to mutation are considered in some detail. In particular, methods for separating the effects of various modifiers on the rate of these processes from the effects on the time available for them to occur are discussed. Data are presented for recessive lethal mutations in Paramecium to show that all metabolic inhibitors tried (caffeine, iodoacetate, chloramphenicol and streptomycin) decrease the rate of loss of premutational damage and decrease mutation only because they increase the time available for loss. The results are shown to fit the hypothesis of metabolic repair of radiation-induced lesions of the chromosomes.     

氚水在小鼠体内的代谢

本文利用高氯酸-过氧化氢(HClO₄H₂O₂)消化和液闪计数测定生物样品中氚的方法, 研究亍腹腔注入氚水后65天内氚在小鼠各脏器干、湿组织中的分布与滞留, 并估算了剂量.实验结果表明。氚进入机体属迅速而均匀地分布于全身各脏器, 并在经历了大约l～8天的蓄积期之后约有l～8%的氚转化为组织结合氚。无论是湿组织中的总氚, 还是干组织中的组织结合氚, 其滞留系数曲线一般都能表述为两项措致函数。总氚的第一生物半排出期约2天。在本实验用量条件下, 每注入l徽居里, 克体重的氚水将在65天内使各脏器受到0.8拉德左右的剂量, 其中组织结台氘的贡献j般不大于1q%.氚在脂肪组织中的行径和其他各脏器不同, 总氚及其所致剂量要低得多, 但组织结合氚所占的比例却要高得多。