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Biomedical subjects

H Howald

Publications and source records attributed to H Howald.

At least 73 records · Page 4Linked to original sources
PubMed1984

Improved resolution with one-dimensional polyacrylamide gel electrophoresis: myofibrillar proteins from typed single fibers of human muscle.

Standard procedures for one-dimensional discontinuous sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis and silver staining were modified to give more effective separation and an improved resolution of human skeletal muscle proteins. In this system, an electrophoresis buffer composed of 100 mM L-isoleucine, 25 mM Tris base, and 0.1% SDS was used. The separating gel consisted of 16% acrylamide with N,N'-methylenebisacrylamide as a crosslinker (1:23), 0.4% SDS, 1.5 M Tris-HCl, pH 8.8. By the present procedure, the slow and the fast forms of myosin light chains (LCs, LCf) and other contractile proteins from human muscle could be better separated. The silver stain is based on a combination of methods previously described. The modified method requires a small fragment of a single fiber to observe as few as 10 ng of myofibrillar muscle proteins. The described simplifications made it possible to assay and compare up to 40 single fibers in the same electrophoretic run. Improved separation of other proteins migrating at basic pH could be achieved by a similar approach.

Electrophoresis, Polyacrylamide Gel↗
PubMed1984

The relationship of oxygen uptake to superoxide dismutase and catalase activity in human skeletal muscle.

A considerable amount of evidence now makes it clear that aerobic tissues require an elaborate enzyme system to remove the harmful reaction products of oxygen reduction. A portion of this protective system has been studied in human muscle and rat tissues. The VO2 max as well as the superoxide dismutase and catalase activity of vastus lateralis muscle of 12 healthy, male subjects was measured. The subjects with a high aerobic capacity (VO2 max greater than 60 ml . kg-1 . min-1) had significantly greater levels of both superoxide dismutase and catalase. There was also a linear relationship between both superoxide dismutase and catalase and VO2 max. The tissue oxygen consumption, and enzyme activity of the liver, heart, lung, and gastrocnemius from 24 rats was also studied. There VO2 and tissue enzyme activity of both superoxide dismutase and catalase.

Adolescent↗
PubMed1983

Morphometric analysis of the capillary supply in skeletal muscles of trained and untrained subjects--its limitations in muscle biopsies.

Muscle fiber area, capillary density, and capillary to fiber ratio were determined in needle biopsy samples of M. vastus lateralis processed for electron microscopy from 9 untrained men (average VO2 max = 43.7 ml/min kg) and 5 well trained orienteers (VO2 max = 76.1 ml/min kg). The volume density of mitochondria was previously reported to be significantly higher in orienteers (7.32%) than in untrained men (5.19%) and in untrained women (4.08%) in the same material (Hoppeler et al. 1973). The mean fiber area was found to be somewhat larger in orienteers (6,410 microns 2) than in untrained men (5,350 microns 2, not significant), but significantly smaller values were found in untrained women (3,390 microns 2). The capillary density was almost identical in the three experimental groups, it ranged from 416 to 431 mm-2. The absolute values reported for both of the above variables are subjected to a bias due to fiber shrinkage, fiber shortening and fiber kinking occurring during the needle biopsy procedure and the subsequent steps of tissue preparation. The capillary to fiber ratio is much less affected by tissue handling and significantly higher values were found in orienteers (2.70) than in untrained men (2.07) and in untrained women (1.37). There was a significant linear relationship between the capillary to fiber ratio and both VO2 max and the volume density of mitochondria for all subjects analysed, suggesting an adjustment of the capillary supply to the maximal aerobic capacity as well as to the mitochondrial content in M. vastus lateralis.

Adult↗
PubMed1983

Nutrient intake and energy regulation in physical exercise.

Rates of energy expenditure as well as total daily energy cost can be considerable during periods of exercise. In trained athletes, expenditure can be as high as 380 kJ/min during short-term maximal exercise. Training programmes of several hours' duration lead to a daily nutrient intake of 25-35 MJ in most Olympic sports. The mobilization of the energetic fuels of the body is modulated by the nature of the exercise. ATP and creatine phosphate stores in muscle cells are depleted within seconds during maximal work. Glycogen is the main fuel for heavy exercise of a few minutes' duration where performance capacity is limited by the degree of lactate accumulation and intracellular acidosis. Oxidation of both glucose and free fatty acids supplies the energy needed for exercise lasting more than two minutes, the relative contribution of lipids increasing with a longer duration or a lower intensity of the muscular work. Intramuscular stores of glycogen and triglycerides may be almost completely depleted in long-lasting exercise, e.g. a 100 km run. Under these conditions, glycogen stores in the liver and triglycerides in adipose tissue contribute approximately 70% of the energy need whereas 5-10% of the supply comes from oxidation of amino acids. Although adequate nutrition for exercise could be achieved through the intake of a well-balanced diet, the regulation of energy utilization can be influenced by the sources of food energy, by dietary modifications before exercise or by nutrient supplements during exercise. Intake before exercise of fructose or medium-chain triglycerides, both only weakly insulinogenic compared to glucose, leads to changes in blood substrates and metabolites. However, neither glycogen depletion in the working muscles nor performance capacity was influenced by a single meal containing this particular carbohydrate or lipid. Mobilization of free fatty acids in adipose tissue can be enhanced by caffeine or depressed by nicotinic acid. Since the rate of free fatty acid oxidation in skeletal muscle depends on the blood concentration of this substrate, energy regulation during exercise and work output are considerably influenced by the ingestion of such substances.

Adipose Tissue↗
PubMed1983

Energy metabolism of medium-chain triglycerides versus carbohydrates during exercise.

Medium-chain triglycerides (MCT) are known to be rapidly digested and oxidized. Their potential value as a source of dietary energy during exercise was compared with that of maltodextrins (MD). Twelve subjects exercised for 1 h on a bicycle ergometer (60% VO2 max), 1 h after the test meal (1MJ). The metabolism of MCT was followed using 1-13C-octanoate (Oc) as tracer and U-13C-glucose (G) was added to the 13C-naturally enriched MD. After MCT ingestion no insulin peak was observed with some accumulation of ketone bodies (KB), blood levels not exceeding 1 mM. Total losses of KB during exercise in urine, sweat and as breath acetone were small (less than 0.2 mmol X h-1). Hence, the influence of KB loss and storage on gas exchange data was negligible. The partition of fat and carbohydrate utilization during exercise as obtained by indirect calorimetry was practically the same after the MCT and the CHO meals. Oxidation over the 2-h period was 30% of dose for Oc and 45% for G. Glycogen decrements in the Vastus lateralis muscle were equal. It appears that with normal carbohydrate stores, a single meal of MCT or CHO did not alter the contribution of carbohydrates during 1 h of high submaximal exercise. The moderate ketonemia after MCT, despite substantial oxidation of this fat, led to no difference in muscle glycogen sparing between the diets.

Adolescent↗
PubMed1983

Human muscle adaptations to chronic hypoxia.

Maximal aerobic power (V02max) decreases with increasing altitude, the drop being about the same in acute and chronic hypoxia. To elucidate this well established but still rather inexplicable finding, experiments were carried out on a group of participants before and immediately after return from a mountaineering expedition to Mount Lhotse Shar (8398 m). The results of a typical subject exposed over a period of 5 weeks to an altitude of at least 5200 m indicate that: A) In the vastus lateralis muscle the number of capillaries to the number of fibers ratio was unchanged, the mean fiber diameter was reduced from 77.3 to 67.9 mu while the mitochondrial to fiber volume ratio increased from 6.7 to 7.9%; in addition, muscle protein concentration diminished by 37% and succinate dehydrogenase activity (SDH) was 48% less than in control conditions; B) Cardiac output and muscular (vastus lateralis) blood flow at submaximal work loads were reduced by 21% and 53%, respectively; C) The V02 on-response kinetics at the mouth upon rectangular submaximal work loads was delayed (t 1/2 = 37.5 vs. 27.0 s). From the above results it is concluded that the apparent lack of beneficial effects of acclimatization on maximal aerobic power is likely the consequence of the interaction of a number of positive (increased hematocrit, rightward shift of the 02 dissociation curve) and negative (reduced thoracic and peripheral blood flow, decreased muscle mass and oxidative enzymes activity) changes induced by hypoxia.

Adaptation, Physiological↗
PubMed1982

Training-induced morphological and functional changes in skeletal muscle.

In addition to the histochemical ATPase staining techniques, immunohistochemistry and two-dimensional gel electrophoresis lead to a better understanding of the molecular structure of the contractile proteins actin, myosin, tropomyosin, and troponin in the different fiber types of human skeletal muscle. A great plasticity enables muscle fibers to adapt to different genetic and environmental influences not only on the level of cellular ultrastructure and metabolic function, but also on the molecular level of the contractile proteins. Fiber type transformation is possible with cross-innervation and specific electrical stimulation. Prolonged and intense endurance training probably also transforms type II fibers into type I fibers, whereas with spring or strength training changes in the different fiber types are restricted to ultrastructure (e.g., myofibrillar to mitochondrial volume ration) and metabolic function. The fiber type distribution pattern in top athletes seems to be determined by both hereditary and environmental factors.

Animals↗
PubMed1982

Anaerobic muscle enzyme changes after interval training.

In contrast to endurance training, little evidence is available concerning the effects of sprint-type training programs on the anaerobic metabolism of skeletal muscle. Four male subjects completed a mean of 16 training sessions consisting of eight 200-m runs at 90% of maximal speed, which were separated by 2-min rest periods. Before and after the 5-week training period, muscle biopsies were taken out of the lateral head of m. gastrocnemius and analyzed for the activities of phosphorylase, phosphofructokinase (PFK), glyceraldehyde phosphate dehydrogenase (GAPDH), lactate dehydrogenase (LDH), succinate dehydrogenase (SDH), and malate dehydrogenase (MDH). Following training there was a significant increase in the subjects' performance time in a treadmill test at a speed of 16 km/h speed and 15% grade. Significant increases were observed in the activities of phosphorylase, PFK, GAPDH, LDH, and MDH, whereas the 17.5% increase in SDH was not statistically significant. It is concluded that interval training with high intensity and a 1:4 work-rest ratio leads to increased activities of key enzymes involved in glycogenolysis and anaerobic glycolysis of skeletal muscle.

Adult↗
PubMed1981

Analysis of myosin light and heavy chain types in single human skeletal muscle fibers.

In this study, myosin types in human skeletal muscle fibers were investigated with electrophoretic techniques. Single fibers were dissected out of lyophilized surgical biopsies and typed by staining for myofibrillar ATPase after preincubation in acid or alkaline buffers. After 14C-labelling of the fiber proteins in vitro by reductive methylation, the myosin light chain pattern was analysed on two-dimensional gels and the myosin heavy chains were investigated by one-dimensional peptide mapping. Surprisingly, human type I fibers, which contained only the slow heavy chain, were found to contain variable amounts of fast myosin light chains in addition to the two slow light chains LC1s and LC2s. The majority of the type I fibers in normal human muscle showed the pattern LC1s, LC2s and LC1f. Further evidence for the existence in human muscle of a hybrid myosin composed of a slow heavy chain with fast and slow light chains comes from the analysis of purified human myosin in the native state by pyrophosphate gel electrophoresis. With this method, a single band corresponding to slow myosin was obtained; this slow myosin had the light chain composition LC1s, LC2s and LC1f. Type IIA and IIB fibers, on the other hand, revealed identical light chain patterns consisting of only the fast light chains LC1f, LC2f and LC3f but were found to have different myosin havy chains. On the basis of the results presented, we suggest that the histochemical ATPase normally used for fibre typing is determined by the myosin heavy chain type (and not by the light chains). Thus, in normal human muscle a number of 'hybrid' myosins were found to occur, namely two extreme forms of fast myosins which have the same light chains but different heavy chains (IIA and IIB) and a continuum of slow forms consisting of the same heavy chain and slow light chains with a variable fast light chain composition. This is consistent with the different physiological roles these fibers are thought to have in muscle contraction.

Adenosine Triphosphatases↗
PubMed1981

Biochemical changes in a 100 km run: carbohydrates, lipids, and hormones in serum.

During the 100 km race in Biel, Switzerland, seven-well trained men (age 33.3 +/- 3.5 years; V02 max. 59.9 +/- ml/kg) have been investigated. Their mean running time over the 100 km distance averaged 10.41 +/- 1.25 h. In contrast to almost unchanged blood glucose and lactate concentrations, blood lipids showed significant changes. Triglycerides decreased about two-fold, whereas glycerol and free fatty acids increased to extremely high concentrations (0.628 and 2.44 mmol/l respectively). Plasma insulin after the run was unaffected, whereas growth hormone, aldosterone and cortisol concentrations were significantly increased. With the exceptions of a still significantly elevated aldosterone and lactate concentration as well as a decreased triglyceride concentration all other values in the blood are restored to normal 24 h after completion of the run.

Adult↗
PubMed1981

[Physical activity and capacity in 4 Swiss cities].

As part of the Swiss National Research Program for the Prevention of Cardiovascular Disease, the degree of physical activity at work and during leisure time ws investigated in 3614 men and 4221 women living in four Swiss cities. Some 50% of the men and more than 60% of the women were considered insufficiently active. Since their jobs involve little physical activity, the quantity and quality of exercise needed for prevention of coronary heart disease can only be obtained from sports during leisure time. Of the men and women investigated in Aarau, 65 and 61% respectively volunteered for a bicycle ergometer test while in Nyon the participation in this part of the study was considerably lower (29 and 24% of the men and women). In both sexes and all age groups the mean values for the extrapolated maximum oxygen uptake were comparable to those reported from other highly industrialized countries.

Adolescent↗