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Vibratory stress, induced by turbulent flow, has been shown to alter the structural properties in arteries. Since turbulent flow can exist in the lungs it seems important to know whether a similar effect can occur in bronchi. To answer that question air was passed through isolated dog bronchi. Turbulent flow was created by having, at one end, a cannula acting as a stenosis, producing vibrations or a "flitter" in the wall. A measure of the elastic properties was obtained by coupling pressure-volume data with photographs taken at different pressures. The results demonstrate a significant alteration in the structural properties, localized to ares under maximum vibration. A "yielding" in the direction of maximum stress was observed with a corresponding structural rearrangement (radius decreased, length increased). This effect and its relation to structural fatigue is discussed. The physiological significance of the results are that the bronchi become more resistant to deformation under positive pressures and less resistant to collapse under negative pressures.
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PMID:Effect of vibration on isolated dog bronchi. 112 86

One of the most important nutritional goals amongst athletes is to maintain adequate energy and fluid balance, since these are subject to relatively rapid changes and are directly related to performance and health. This may especially be the case when exercise intensity is high. Furthermore, when due to exercise and environmental stress food and fluid intake become depressed. In such conditions there may be a dramatic increase in the utilization of carbohydrate (CHO), fluid, and in some instances protein. These increased requirements may then not be covered. Insufficient replacement of CHO may lead to hypoglycemia, altered protein metabolism, central fatigue and exhaustion. Large sweat losses may pose a risk to health by inducing severe dehydration, impaired blood circulation and heat transfer, leading to heat exhaustion and collapse. Inadequate CHO and protein intake leads to a negative nitrogen balance, which over the long term will lead to a loss of muscle mass. In the scope of this presentation we will refer to the most important nutritional factors which are known to affect performance over a short term, at sea level and altitude.
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PMID:Nutritional aspects of health and performance at lowland and altitude. 148 43

Metabolic fatigue is a characteristic muscle response to intense exercise that has outstripped the rate of ATP replacement. The accumulation of metabolic by-products, namely hydrogen ions and diprotonated phosphate, interferes with actin-myosin interaction, effectively preserving muscle ATP levels by preventing further ATP hydrolysis. Muscle force and metabolite concentrations return to normal in about 5 minutes. Less intense exercise causes a more subtle, non-metabolic fatigue due to a still-undefined disturbance of excitation-contraction coupling, which can last for several hours. In this type of fatigue, greater effort is required to generate submaximal forces. Endurance exercise is mainly limited by the size of muscle glycogen stores and how efficiently they are used. Endurance training permits an athlete to work aerobically at high rates, consuming a mixture of lipid and carbohydrate fuels. When muscle glycogen is used up, exercise can only continue at the relatively low rate supportable by lipid metabolism. Anaerobic exercise is also limited by subjective factors such as dyspnoea and muscle pain, which have objective determinants. Extremely prolonged exercise can lead to general collapse because of dehydration, hyperthermia, or hypoglycaemia. None of these factors explains the phenomenon of asthenia, a subjective sense of exhaustion that produces no objective impairment of physical performance. The metabolic myopathies are experiments of nature that promise to shed new light on the biochemical basis of muscle fatigue. This will require quantitative studies of the kind provided by topical magnetic resonance spectroscopy, correlating physiology and metabolism in vivo.
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PMID:Muscle metabolism during fatigue and work. 226 24

Mortality from coronary artery disease is a common problem in treated hypertensive patients, and these people have a high prevalence of elevated cholesterol levels. A study was undertaken to determine whether cholesterol could be lowered effectively without major side effects in patients with treated hypertension. Forty-nine patients (mean age 67.6 years) with cholesterol greater than 5.5 mmol/l were placed on a reduced-fat (less than 30% of calories from fat with a ratio of polyunsaturated to saturated fats of less than 1) diet for 3 months. If the cholesterol was between 5.5 and 7.5 mmol/l and total cholesterol divided by high-density lipoprotein cholesterol was greater than 4.5, the patients were randomly allocated either to the simvastatin (24 patients) or the placebo group (25 patients). Diet and placebo caused minor and insignificant falls in cholesterol and no change in triglycerides or lipids. Treatment with simvastatin reduced cholesterol levels from 6.85 to 4.75 mmol/l (P less than 0.001), triglycerides from 2.7 to 2.1 mmol/l (P less than 0.01), low-density lipoproteins from 4.6 to 2.6 mmol/l (P less than 0.001) and high-density lipoproteins rose from 1.09 to 1.18 mmol/l (P less than 0.01). Total cholesterol divided by high-density lipoprotein cholesterol fell from 6.3 to 4.0 (P less than 0.001). The drug was well tolerated and the side-effect profile did not differ from the placebo in clinical or biochemical events. The active drug was stopped in one patient (abdominal pain, dizziness, headache, tiredness) and in two patients taking the placebo (elevated creatine phosphokinase, cardiovascular collapse). Simvastatin effectively lowered total cholesterol and improved the lipoprotein profile. The dose required in most patients was 40 mg/day. Simvastatin may be an acceptable drug to improve the lipoprotein profile in order to determine whether this improves the prognosis in patients treated for hypertension.
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PMID:Simvastatin in the treatment of hypercholesterolaemia in patients with essential hypertension. 233 14

The Patient was a 72-year-old man who presented with dyspnea and general fatigue. Chest X-ray and CT-scan at the admission showed bilateral pleural effusion with collapse of the left lung and pericardial effusion. Cytology from the left pleural effusion suggested malignant mesothelioma. For this reason, malignant mesothelioma of the left pleura was diagnosed clinically and it was supposed to have spread subsequently to the pericardium. At autopsy, entire surface of the heart was found to be encroached in a diffuse fashion by a thick layer of mesothelioma tissues, which formed a small mass around the left pulmonary vein over the left atrium and invaded deep into the myocardium of all cardiac chambers. The endocardium and the intima of the left pulmonary vein were free of the invasion. The parietal pericardium adhered in places to the cardiac lesion, but no direct invasion to the adjacent pleurae through the pericardial wall was present. The left pleura over the lung and chest cavity disclosed only a superficial invasion by similar mesothelioma which was identifiable only on microscopic study. No distant metastasis was present in any thoracic and other organs as well as lymph nodes including the hilar ones of the lung. It seemed most likely from this anatomical finding that the primary site of the present mesothelioma was in the pericardium (visceral) and the tumor spread to the left pleura by a continuous extension along the outside of the left pulmonary vein. Primary malignant mesothelioma of the pericardium is of very rare occurrence and we found only 51 cases of it in the Japanese literature since 1915.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Primary malignant mesothelioma of the pericardium masquerading as malignant pleural mesothelioma: report of an autopsy case and review of the reported cases in Japan as to its invasion to neighboring organs]. 268 98

The hip with rheumatoid arthritis (RA) is characterized by reduced bone resistance. Protrusion, fatigue fractures and femoral head collapse are the typical consequences. The survival rate of total hip prostheses in hips with RA seems to be higher than for hips with osteoarthritis (OA), possibly due to lower demands. When isolated loosening of the acetabular and femoral component are compared, there is a definite shift towards acetabular loosening in RA compared to OA. This is definitely due to the reduction in the mentioned bone resistance at the acetabular level. In primary joint replacement, well-cemented femoral components provide more reliable clinical results. They will remain the gold standard for long-term performance as well. On the other hand, it is very likely that non-cemented acetabular components, fixed by means of screws in the direction of the resulting force or based on a compression principle, may prove at least as effective as well-cemented acetabuli. For revision of the loose acetabular component, the use of special metal rings fixed with screws and bridging severe bony defects with a bone graft and frequently also bone cement, have proved to be of value. For loose femoral components with a thin and brittle cortical wall, special non-cemented prostheses combined with a bone graft seem to promise a more reliable long-term solution than cemented versions. The follow-up of our revision cases confirms the value of the described methods - at least at the short and medium-term follow-up. More definite conclusions can only be arrived at after long-term follow-ups which have been carried out with different systems and where the results are compared using the same documentation procedure.
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PMID:[Loosening of hip prostheses in chronic rheumatoid polyarthritis]. 281 74

The most common symptoms of patients with heart failure are shortness of breath and fatigue. The causes of these symptoms may be different in various entities encompassed by the general term heart failure, such as acute pulmonary edema, circulatory collapse and chronic heart failure. In patients with acute heart failure, shortness of breath is closely related to left atrial pressure. In patients with chronic heart failure, optimally treated with diuretics, the body fluid compartments are usually of normal size. Recent work strongly suggests that, in such patients, central hemodynamic abnormalities are not the sole determinants of symptoms. Impaired vasodilation and altered metabolism in skeletal muscle, circulating metabolites and pulmonary ventilation-perfusion mismatch with consequent increased physiologic dead space may all contribute to the genesis of symptoms. Consequently, it may be possible to alleviate symptoms by treatments that are not aimed directly at improving central hemodynamics. Whether such an approach could also modify prognosis is unknown.
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PMID:Causes of symptoms in chronic congestive heart failure and implications for treatment. 329 93

The effects of necrotic laryngitis on the mechanics of breathing and gas exchange were investigated in five Belgian blue double muscled calves two to three months old. All the animals showed the typical clinical picture of the respiratory syndrome associated with naturally occurring necrotic laryngitis. Highly significant increases in total pulmonary resistance, minute viscous work of breathing and alveolar-arterial oxygen gradient, and highly significant decreases in dynamic lung compliance and arterial oxygen tension were recorded in the infected animals, when compared to reference values for healthy cattle. The ratio of inspiratory to expiratory viscous work of breathing was also significantly increased probably because of a partial collapse of the extrathoracic trachea during inspiration. It was concluded that necrotic laryngitis disturbs pulmonary function to such an extent that it impedes the growing process and predisposes the infected animals to secondary bronchopneumonia and ventilatory failure due to respiratory muscle fatigue.
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PMID:Functional changes induced by necrotic laryngitis in double muscled calves. 368 95

Some aspects of the early collapse biomechanics of the segmentally necrotic adult human femoral head were studied, using a small-deformation plane strain, elasto-plastic finite element model. The computational procedure used was based upon the initial stress technique, and permitted study of stress and strain fields and of the progression of failure regions as a function of incrementally applied joint loads. The results consistently demonstrated both subchondral and deep cancellous failure patterns similar to those seen clinically. There was a clear distinction, however, between these two failure regimes, dependent primarily upon the relative strength deficits input for the subchondral versus the deep cancellous regions. Usually, the failure zone was appreciable only at significantly supra-physiological loads, reflecting the likely importance of fatigue events in the clinical collapse process. Although subchondral failure was always limited to the entire base region of the infarction wedge, the zones of deep failure varied considerably with changes in lesion geometry, usually being concentrated within the infarct near the underlying necrotic/viable interface.
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PMID:A non-linear finite element analysis of some early collapse processes in femoral head osteonecrosis. 717 2

A case of cardiac tamponade showing the characteristic flow pattern in the superior vena cava is reported. An 80-year-old man was admitted to our hospital complaining of anorexia and general fatigue. We observed a paradoxical pulse of 25 mmHg, dilatation of the jugular vein, and marked cardiomegaly on chest radiography. A two-dimensional echocardiogram demonstrated a massive pericardial effusion and collapse of the right atrial and right ventricular walls. On the basis of his echocardiograms and clinical signs, we diagnosed his condition as cardiac tamponade. Pulsed Doppler echocardiograms showed two-peaked flow in the superior vena cava in systole. To assess the diagnostic significance of this characteristic flow pattern, the superior vena cava flow was recorded simultaneously with the intrapericardial pressure and the right atrial pressure. The intrapericardial pressure was higher than the right atrial pressure in early systole. After pericardial drainage, these pressures became reversed and the two-peaked flow disappeared. The two-peaked flow is attributed to collapse of the right atrial wall caused by the higher intrapericardial pressure than the right atrial pressure. The superior vena cava flow represents the right heart filling dynamics in cardiac tamponade.
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PMID:[The characteristic flow of the superior vena cava in cardiac tamponade: a case report]. 816 29


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