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Biomedical subjects

J Karlsson

Publications and source records attributed to J Karlsson.

At least 307 records · Page 17Linked to original sources
PubMed1975

Relationship between isometric endurance and fibre types in human leg muscles.

Relationship between isometric endurance performance at 50% of maximal voluntary isometric contraction (MCV) and skeletal muscle fibre composition has been elucidated in 19 physical education students. This was found to be linear and the equation corresponded to: y=9.35 + 1.093x; r=0.70 (endurance time expressed in seconds and fibre composition as percent slow twitch muscle fibres (ST) of the vastus lateralis muscle). As it is assumed from previous studies that similar isometric tensions preferentially recruit fast twitch muscle fibres (FT) and that the muscle at the point of exhaustion exhibits maximal values for lactate accumulation, it is suggested that lactate formed in FT fibres is released and stored in nonrecruited ST fibres. The ability to sustain similar isometric tension would then be depending on how large the fraction of ST fibres is that can serve as a lactaterecipient for lactate producing FT fibres.

Adult↗
PubMed1975

LDH isozymes in skeletal muscles of endurance and strength trained athletes.

Muscle biopsy samples were obtained from arm and leg muscles of endurance and strength trained athletes, respectively. Total LDH activity as well as occurrence and activity of LDH isozymes were determined. Comparing the results from the athletes with those from non-trained subjects with corresponding fibre compositions, it was found that the endurance athletes had a lower total LDH activity, a higher relative activity of the most heart-specific isozymes. LDH (1 + 2), and, on electrophoretic separation, a complete absence of LDH (4 + 5) in both arm and leg muscles. As compared to the untrained material the strength trained athletes tended to have a higher total LDH activity, a similar distribution of relative isozyme activities, and, in the leg muscles, a strong electrophoretic band corresponding to LDH 5, the most skeletal muscle specific isozyme.

Adult↗
PubMed1975

Enzyme activities and muscle strength after "sprint training" in man.

Sprint type strength training was performed 3-4 times a week for 8 weeks by 4 healthy male students (16-18 yrs). The training was carried out on a treadmill at high speed and with high inclination. Muscle biopsies were obtained from vastus lateralis before and after the training period for histochemical classification of slow and fast twitch muscle fibres and for biochemical determination of metabolites and enzyme activities. Muscle fibre type distribution was unchanged, whereas fibre area indicated an increase for both fibre types in 3 subjects after training. The muscle enzyme activities of Mg2+ stimulated ATPase, myokinase and creatine phosphokinase increased 30, 20, and 36 percent, respectively. Muscle concentration of ATP and creatine phosphate (CP) did not change with training. Sargent's jump increased with on average 4 cm (from 47 to 51 cm), maximal voluntary contraction (MVC) with 19 kp (from 165 to 184 kp), and endurance at 50 percent of MVC with 9 s (from 47 to 56 s), respectively. After training all subjects showed a gain in body weight (mean 1.4 kg) and in thigh circumference (mean 1.5 cm) indicating a larger leg muscle volume and consequently also an increase in total ATP and CP.

Actomyosin↗
PubMed1975

Constituents of human muscle in isometric fatigue.

Three subjects performed five successive isometric contractions to fatigue; the tension in any one experiment was constant at tensions varying from 20 to 80% of the maximal voluntary contraction (MVC). The interval between contractions was held constant at 11 min. Muscle biopsy specimens were obtained at the start of the experiment, after the first, fourth, and fifth, and before the second and fifth of the successive contractions. The concentrations of ATP, CP, glycogen, and lactate were measured in each sample of muscle. Changes in ATP and glycogen were insufficient to be held accountable for the development of isometric fatigue. Changes in CP and lactate were large after fatigue at intermediate tensions, but those of CP were considered unlikely to be responsible for the fatigue. At tensions of 30-50% MVC the increase in lactate could be responsible for fatigue either directly or by indirect changes in pH; at higher and lower tensions the possibility that lactate is directly implicated in the development of fatigue seems remote.

Adenosine Triphosphate↗
PubMed1975

Effects of previous exercise with arms or legs on metabolism and performance in exhaustive exercise.

The ability of additional muscles to perform after certain other muscles of the body had been exercised to exhaustion was studied in three male subjects. Exhaustive exercise was performed in two series: series L-A, a bout of leg exercise preceded a bout of arm exercise; series A-L, arm preceded leg (6-min recovery between bouts). Biopsies were taken during the course of each experiment from both the deltoideus and vastus lateralis muscles for determination of ATP, creatine phosphate, lactate, and pyruvate. Exhaustive exercise led to marked elevations in lactate and decreases in ATP and CP in exercised muscle and marked increases in blood lactate concentration. Similar changes, especially in lactate, were observed during and after the first exercise bout in nonexercised muscle. When arm or leg exercise was performed as the second bout, decreases in performance time were observed as compared to performance as the initial bout. It is suggested that the performance potential of muscle is decreased because of internal changes elicited by elevated blood lactate and/or blood H+ concentrations brought about by other muscle groups previously exercised to exhaustion.

Adenosine Triphosphate↗
PubMed1975

Relationship between myocardial metabolism and epicardial ST segment alterations during myocardial ischemia.

Acute myocardical ischemia was produced by ligating the midlevel left anterior descending coronary artery for 17 min in anesthetized dogs. Epicardial electrocardiograms were recorded from 15 sites surrounding the area of left anterior descending coronary artery ligation with a smooth tip, rounded epicardial electrode. Sites of ST segment elevation and isoelectric sites within the grossly ischemic portion of the left ventricle were needle biopsied to obtain tissue samples of less than 6 mg wet weight to assess myocardial metabolism at these precise sites. Epicardial areas of ST segment elevation had marked lactate accumulation and high energy phosphate depletion. Isoelectric sites were areas of either no lactate accumulation or mild lactate accumulation and high energy phosphate concentrations that were greater than those found at site of ST segment elevation. Thus, the data obtained indicate that epicardial sites of ST segment elevation are locations of profound anaerobic metabolism and of both epicardial and endocardial ischemia.

Acute Disease↗
PubMed1975

Skeletal muscle metabolites in patients with cardiogenic shock or severe congestive heart failure.

Skeletal muscle metabolite concentrations were determined in 19 patients in either cardiogenic shock or severe left ventricular failure by obtaining a needle biopsy specimen of lateral thigh muscle. Evidence of anaerobic skeletal muscle metabolism was found in both patient groups with the greatest lactate accumulation and most severe high-energy phosphate depletion present in the patients in cardiogenic shock. The skeletal muscle lactate accumulation was most pronounced in the patients that died. Blood lactate values did not absolutely predict skeletal muscle lactate concentrations in those patients in whom skeletal muscle lactate concentrations were the highest. The patients in cardiogenic shock and severe left ventricular failure who survived demonstrated a reduction in skeletal muscle lactate levels and a restoration of high-energy phosphates over several days which correlated with clinical and hemodynamic improvement.

Adenosine Triphosphate↗
PubMed1974

Selective glycogen depletion in skeletal muscle fibres of man following sustained contractions.

1. Six healthy males performed sustained contractions with different tensions related to their maximal voluntary contraction (MVC). The isometric exercise consisted of efforts to extend the knee when flexed at an angle of 90 degrees .2. Biopsy samples were taken from the lateral portion of M. quadriceps femoris before and after different periods (6-45 min) during a series of sustained contractions. Total glycogen content was determined on each muscle sample. In order to evaluate whether the glycogen depletion occurred preferentially in slow twitch (ST) or fast twitch (FT) fibres, serial sections of the muscle samples were stained for myofibrillar ATPase and glycogen (PAS reaction).3. In all experiments a selective glycogen depletion was observed. At low tensions, the ST fibres and at higher tensions the FT fibres became glycogen depleted. The critical tension at which this conversion in glycogen depletion from ST to FT fibres took place was 20% MVC.4. It is concluded that at sustained contractions of less than 20% MVC there is a major reliance upon ST fibres and above that level a primary dependence upon FT fibres. It is further suggested that restriction of blood flow and thus availability of oxygen at forces higher than 20% MVC may be the explanation for the present findings.

Adenosine Triphosphatases↗