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Biomedical subjects

J Karlsson

Publications and source records attributed to J Karlsson.

At least 253 records · Page 14Linked to original sources
PubMed1982

Changes in muscle metabolites in females with 30-s exhaustive exercise.

The purpose of this study was to quantify the changes in selected intramuscular metabolites associated with non-oxidative energy metabolism after performance of the Wingate Test (WT), a widely used, exhaustive, 30-s cycle test of short-time muscular power. Muscle biopsies were taken from the m. vastus lateralis of nine female physical education students at rest and immediately after performance of the WT. The concentrations of adenosine triphosphate (ATP), creatine phosphate (CP), lactate, and glycogen were determined. The ATP decreased from 20.9 to 13.8; CP decreased from 62.7 to 25.1; lactate increased from 9.0 to 60.5; and glycogen decreased from 360 to 278 (all concentrations are mmol X kg-1 dry muscle). The absolute changes in CP and lactate were not as large as those reported in other exercise studies. Based on the metabolite changes, it was concluded that the WT is a satisfactory test of the maximal muscular power that can be generated from non-oxidative metabolism, but that the 30-s duration of the test probably does not tax the maximal capacity of such energy metabolism.

Adenosine Triphosphate↗
PubMed1981

Relevance of muscle fibre type to fatigue in short intense and prolonged exercise in man.

It has been suggested that the histological and histochemical features of human muscle are important in determining performance capacity. The relationship between muscle fibre types (Type I, slow twitch fibres; Type II, fast twitch fibres) and performance on standardized tests has been studied in subjects accustomed to physical exercise, and related to their patterns of lactate metabolism, expressed as the onset of blood lactate accumulation (OBLA). This variable was found to be the best predictor of endurance capacity of the variables studied. It is suggested that in healthy male subjects muscle lactate is crucial in short, intense forms of exercise (the higher the lactate formation, the better the performance) and also in prolonged, "endurance' forms of exercise (the later the onset of lactate formation, the higher the sustainable exercise intensity). In subjects with a high proportion of fast twitch fibres, more lactate will be formed at the same exercise intensity. This is advantageous for short intense exercise but impairs endurance performance. The deleterious effects induced by glycogen depletion were studied and found to be most pronounced in subjects rich in fast twitch (glycogen-dependent) fibres. Indications were also obtained that muscular performance is regulated in different ways in males and females. In women an inverse relationship was found between fast twitch fibres and muscle power, and between fatigue and lactate concentration, whereas direct relations were found in men.

Biopsy↗
PubMed1981

Increase of lipoprotein-lipase activity in skeletal muscle during heavy exercise. Relation to epinephrine excretion.

As part of the training programme for Swedish elite soldiers, a 10 day march is carried out with a heavy pack under active-service conditions. Six soldiers volunteered to take part in an investigation on the energy consumption with special regard to the lipid metabolism at different levels of physical effort. The degree of physical work was evaluated by continuous heart-rate recording and analysis of the excretion of epinephrine and norepinephrine in the urine. Fasting values of triglycerides and free fatty acids in blood plasma were determined and muscle biopsies (taken in the morning and in the afternoon) were analysed for lipoprotein-lipase (LPL) activity. After an overnight fast the free fatty acids were increased only in the mornings following days of heavy physical work. The plasma triglyceride concentrations were lowest in a morning proceeded by 3 days of heavy work. The muscle LPL activity in the morning was highest after a day of heavy work and lowest after days of rest. During days of heavy work this activity increased and was higher in the afternoon than in the morning. Muscle LPL activity in the afternoon was closely related to urinary excretion of epinephrine. The data indicate that LPL activity is elevated in the working skeletal muscle increasing the access of fatty acids. The degree of elevation is related to the degree of effort as described by the urinary excretion of morning. Muscle LPL activity in the afternoon was closely related to urinary excretion of epinephrine. The data indicate that LPL activity is elevated in the working skeletal muscle increasing the access of fatty acids. The degree of elevation is related to the degree of effort as described by the urinary excretion of morning. Muscle LPL activity in the afternoon was closely related to urinary excretion of epinephrine. The data indicate that LPL activity is elevated in the working skeletal muscle increasing the access of fatty acids. The degree of elevation is related to the degree of effort as described by the urinary excretion of epinephrine.

Catecholamines↗
PubMed1981

Effect of electrical stimulation on human skeletal muscle.

The acute and adaptive effects of electrical stimulation of the quadriceps muscle were investigated in healthy male volunteers. The acute effects, i.e., depletion of phosphagen and glycogen stores and formation of lactate as well as decreases in certain enzyme activities, were similar to those found earlier for intense muscular exercise. Intermittent electrical stimulation for 4 to 5 weeks did not cause any significant changes in enzyme activities, muscle fiber characteristics, or mitochondrial properties. A 4-week period of electrical stimulation resulted in improvements of muscle strength comparable to the results of a corresponding program of voluntary training. However, the effects of electrical stimulation appeared more "position-specific" and less "speed-specific" than those of voluntary training with slow isokinetic contractions.

Adult↗
PubMed1981

Effects of beta-adrenergic blockade on endurance and short-time performance in respect to individual muscle fiber composition.

Nine physically active males were studied three times with four different exercise tests after administration of placebo, 0.1 g atenolol, or 0.08 g propranolol in random order. The test modals were: bicycle ergometer exercise at 50% of VO2max, peak torque during knee extension, the Wingate muscle power test, and 2000 m track running. Muscle fiber composition had previously been determined. In subjects with a high percentage of slow-twitch fibers the beta-blockers caused a more marked impairment in the exercising muscles. This effect was more pronounced with the unselective beta-blocker propranolol than with atenolol. One interpretation of our findings is that peripheral sympathetic beta 2-receptors in skeletal muscles may contribute to regulating muscle metabolism.

Adrenergic beta-Antagonists↗
PubMed1981

Performance and muscle metabolite changes in exercise with repeated maximal dynamic contractions.

Maximal voluntary contractions (MVC) were performed by five male subjects as repeated knee extensions separated by 13-s rest periods for the purposes of studying performance capability, physiologic responses, and recruitment patterns among fast-twitch (FT) and slow-twitch (ST) extrafusal muscle fibers for this type of exercise. Exercise was performed on an isokinetic ergometer (Cybex II) as 4 MVC per min for 1 h, each contraction lasting 2 s and resulting in knee extension at a velocity of 18 degrees x s-1 from 90 forward to 57. Biopsies were taken from the m. vastus lateralis before, at the midpoint, and at the end of the 60-min period of exercise and analyzed for ATP, CP, lactate, and glycogen. Fiber type was determined by staining sections for myofibrillar ATPase and fiber glycogen content by PAS stain. Ability to produce force (torque) declined form an average of 250 Nm during the first minute to 200 Nm during the last minute of exercise. Oxygen uptake and heart rate were relatively constant for each subject and averaged 0.94 l x min-1 and 110 beat x min-1 throughout exercise. Muscle values in mmol x kg-1 at rest, at midpoint, and at end of exercise were for ATP 5.3, 5.4, and 4.1; for CP 19.4, 15.7, and 12.1; and for lactate 1.7, 3.9, and 4.5, respectively. It was estimated that approximately one third of the energy requirement for exercise was obtained from the endogenous muscle glycogen. Glycogen depletion patterns indicated the involvement of both FT and ST fibers in this type of exercise.

Adenosine Triphosphate↗
PubMed1981

Muscle metabolism, lactate breaking point, and biomechanical features of endurance running.

Nine subjects ranging in muscle fiber composition (m, vastus lateralis) from 38% to 100% slow twitch (ST) were filmed while running on a treadmill at a speed corresponding to the onset of blood lactate accumulation (VOBLA). The film analysis concentrated on several kinetic features of running, such as mechanical work (W) and average power output (W) for the total step cycle including the positive and negative work phases. The results indicated that %ST was related significantly (r = 0.78) with VOBLA and with the average speed of a marathon race (Vm; r = 0.80), which followed the treadmill test. The values of VOBLA and Vm were 4.27 +/- 0.51 and 3.74 +/- 0.64 m x s-1, respectively. Capillary density as calculated from amylase PAS staining of the muscle samples demonstrated also a significant relationship with Vm (r = 0.80). The value of W was not significantly related to either %ST or VOBLA. However, the average mechanical power output at VOBLA (WOBLA) demonstrated high correlations with %ST (r = 0.75), VOBLA (r = 0.90), Vm (r = 0.92), and with capillary density (r = 0.77). The findings suggest that mechanical power at VOBLA is an important parameter, which indicates the maximum power output of the runner under pure aerobic conditions.

Capillaries↗
PubMed1981

Onset of blood lactate accumulation and enzyme activities in m. vastus lateralis in man.

In an earlier study, we reported close relationships between marathon running performance and the running velocity (V) at which the "onset of blood lactate accumulation" (VOBLA) occurs in a group of marathon runners. Using biopsy material from the m. vastus lateralis of the same subjects (n = 19), we have evaluated the relationship of VOBLA to different muscle enzyme activities together with muscle fiber composition and capillary density in the present study. The activities of lactate dehydrogenase (LDH EC 1.1.1.27), phosphofructokinase (PFK EC 2.7.1.11), and citrate synthase (CS EC 4.1.3.7) were determined. VOBLA was negatively correlated to LDH (r = -0.54) and PFK/CS (r = -0.68). Using multiple regression analysis, the PFK/CS ratio together with the capillary density accounted for 61% of the variation in VOBLA. Absolute training kilometrage was the most significant variable measured and accounted for 77% of the variation in VOBLA. Subjects were divided into elite runners (n = 6) and nonelite runners (n = 13) for an additional analysis of the relationship between VOBLA and the ratios of PFK/CS or LDH/CS. Significant relationships between VOBLA and the ratios were observed only in the nonelite runners (r = -0.77 and -0.66, respectively). The vertical distances between the regression lines for these two subject groups could not be explained only on the basis of the enzyme activity ratios. A greater adaptation to fat combustion in the elite runners might explain the disproportionally high VOBLA in relation to the PFK/CS or LDH/CS activity ratios.

Adult↗
PubMed1981

Leg blood flow during exercise in man in relation to muscle fibre composition.

Fibre composition in the vastus lateralis muscle, leg blood flow, oxygen uptake and respiratory exchange ratio were determined in 12 healthy male volunteers during submaximal exercise (50% of V02 max). The percentage of slow-twitch fibres varied from 26 to 66. Mean leg blood flow during exercise was 4.68 +/- 0.191.min-1. The blood flow and respiratory exchange ratio correlated positively to the percentage of slow-twitch fibres in the vastus muscles. No correlation was found between the muscle fibre composition and either oxygen uptake heart rate or mechanical efficiency. The results with a dependence of muscle blood flow and carbon dioxide release to muscle fibre composition support the view that the arrangement of the vascular bed and blood supply differ between fast-twitch and slow-twitch muscle fibres in humans.

Adolescent↗
PubMed1981

Regeneration from duplicating fragments of the Drosophila wing disc.

It is a general rule that of two complementary Drosophila imaginal disc fragments, one regenerates and the other duplicates. This paper reports an investigation of an exception to this rule. Duplicating fragments from the periphery of the wing disc which lacked presumptive notum were found to regenerate notum structures during and after duplication. The propensity for this was greatest in fragments lying close to the presumptive notum, with the exception of a fragment confined to the posterior compartment, which did not regenerated notum. Structures were added sequentially, and regeneration stopped once most of the notum was present. These results are not easily explained by the polar coordinate model, which states that regeneration cannot occur from duplicating fragments. Since compartments appear to be involved in this type of regeneration as in others, it is suggested that a new type of model is required, one which permits simultaneous regeneration and duplication, and assigns a major role to compartments.

Animals↗
PubMed1981

The distribution of regenerative potential in the wing disc of Drosophila.

The distribution of regulative potential was investigated in the wing disc of Drosophila. Ten complementary pairs of fragments were tested for their capacity to regenerate or duplicate. The distribution of positional values resulting from this data was found to be very unequal; six of the twelve clockface values were tightly clustered round the anterior--posterior compartment boundary. Despite this, complementarity between regeneration and duplication was generally maintained.

Animals↗
PubMed1980

Effects of castration and testosterone substitution on body composition and muscle metabolism in rats.

Male weanling Wistar rats were castrated or sham-operated and followed for 12 weeks without substitution or with large (2 mg . 14 days-1) or small (0.2 mg . 14 days-1) intramuscular dose of testosterone enantate. Castration without substitution was associated with lower body weight and smaller fat cell sizes in different adipose tissue depots. The epididymal and caudal subcutaneous depots were the most sensitive to castration. The percentage of fast-twitch high-oxidative (type II A) muscle fibers decreased in the non-substituted castrated animals. There was a decrease in phosphorylase and lactate dehydrogenase activities in the white portion of the gastrocnemius muscle of the castrates. These changes were reversed by the large dose of testosterone. Removal of testosterone by castration thus seems to "feminize" male rats with respect to body composition and muscle metabolism.

Adipose Tissue↗
PubMed1980

Distal regeneration in proximal fragments of the wing disc of Drosophila.

The rules governing proximo-distal regeneration in the wing disc of Drosophila were investigated. It was found that proximal fragments confined to either anterior or posterior compartments could not regenerate distally, although many fragments having tissue from both compartments could do so even in the absence of circumferential regeneration. Fragments containing the ventral but not the dorsal end of the anterior-posterior border were able to regenerate distally. The use of a cuticular marker in the posterior compartment very close to the border permitted precise localization of the tissue required to cause anterio fragments to regenerate distally; in anterior fragments cut close to the border, there was an almost perfect correlation between possession of this marker and distal regeneration. It was found however, that distal regeneration was not an all-or-none phenomenon; its extent was dependent on the total amount of tissue present from both compartments.

Animals↗
PubMed1979

A major difference between transdetermination and homeosis.

IN Drosophila, the adult structures arise from nests of larval cells called imaginal disks, whose state of determination with respect to disk type is usually fixed. However, two processes are known which can change determination from one disk type to another; one occurs in situ and is due to homeotic mutations, and the other is seen after culture of disk material and is called transdetermination. Similarities between the two, notably the lack of intermediate states, have led to the idea that they are different aspects of the same phenomenon(1,2). The existence of homeotic mutations argues that determination in normal development is underlain by a genetic switching mechanism(3,4); transdetermination could result from epigenetic changes in this system. If this is so then the two phenomena should have characteristics in common. Studies of homeotic mutants have shown that a structure in one disk is always transformed into a specific structure from the other disk(5,6); for example clones of bithorax in an anterior dorsal position in the haltere show anterior dorsal wing structures(5). This is used as a criterion of homology, and also indicates that all disks use the same positional information(7). Differences between disks must be due to different interpretation of this information, mediated in some way by the wild-type alleles of the homeotic genes. It is not yet known whether transdetermination also shows position-specific transformation; if the two phenomena are closely related then this should be the case. It is often assumed to be so, because there have been reports of transdetermination between leg and antenna in which structures such as claw and arista, thought from homeotic mutants to be homologous, are found adjacent to one another in implants(1). However, these findings could also be explained by non-homologous transdetermination followed by either movement together of homologous structures due to preferential cell affinities, or intercalary regeneration between the non-homologous structures. Also, regeneration before transdetermination can give misleading results. One cannot simply ask to what structures a given disk fragment will transdetermine as the fragment might regenerate the rest of the disk first, and non-regenerating (that is duplicating) fragments do not appear to transdetermine (unpublished observations, and ref. 8). One solution to these problems is to find a disk in which transdetermination occurs only in one part, and this is the case in the foreleg disk. The experiments reported here were designed to find whether this part transdetermines to a homologous part of the wing disk.

Journal Article↗
PubMed1979

Metabolic changes in muscle on long-term alprenolol therapy.

Muscle biopsies from the vastus muscle were taken at rest and immediately after upright bicycle exercise at 50% of the individual VO2max, before and during 6 wk of alprenolol treatment (200 to 400 mg twice daily) in 6 untrained patients with essential hypertension. Resting muscle concentrations (mmole - kg-1 - wet weight) of glycogen, glucose, lactate, and high-energy phosphates [adenosine triphosphate (ATP) and creatine phosphate (CP)] were not affected by alprenolol treatment, but after 10 min after exercise the glycogenolysis increased and depletion of ATP and CP was enhanced. The relationship between blood and muscle lactate was altered by alprenolol, indicating that alprenolol prevents lactate translocation from the muscle to the blood. The results show that during moderate exercise, leg muscle metabolism is influenced by long-term antihypertensive therapy.

Adenosine Triphosphate↗
PubMed1979

Central and peripheral circulation in relation to muscle-fibre composition in normo- and hyper-tensive man.

1. Fibre composition in the vastus lateralis muscle, and blood pressure, were determined in age-matched normotensive (n = 22) subjects and previously untreated patients (n = 19) with essential hypertension. 2. In all subjects the muscle fibres were classified, as fast-twitch (FT) and slow-twitch (ST), and blood pressure was recorded. Eleven patients and seven of the normotensive subjects participated in an extended haemodynamic study with intra-arterial pressure measurements and determinations of leg blood flow. 3. In both normo- and hyper-tensive subjects, ambulant and intra-arterial blood pressure and leg vascular resistance were negatively correlated to the percentage of ST fibres; no significant correlation was found to total leg blood flow. 4. The findings show that muscles with a high proportion of FT fibres have a higher resistance than muscles rich in ST fibres and suggest that the type of fibre in skeletal muscle might be of importance for the development of the hypertensive disease.

Adult↗