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Biomedical subjects

L Edström

Publications and source records attributed to L Edström.

At least 73 records · Page 4Linked to original sources
PubMed1987

Force, relaxation and energy metabolism of rat soleus muscle during anaerobic contraction.

Isolated soleus muscle of rat was stimulated electrically (2 Hz) for 7 min under anaerobic conditions. Isometric twitch tension decreased progressively and was 30% of the initial value at the end of stimulation. The decline in relative force was similar to that previously observed in fast twitch muscle and soleus can thus not be termed fatigue-resistant under anaerobic conditions. Phosphocreatine (PCr) decreased from (mean +/- SD) 61.1 +/- 4.4 at rest to 4.0 +/- 1.8 mmol kg-1 dry muscle (d.m.) after 7 min of stimulation, while lactate increased from 3.7 +/- 1.6 to 30 +/- 8 mmol kg-1 d.m. Energy was thus derived from complete utilization of PCr and a low rate of glycolysis resulting in an almost unchanged calculated intracellular pH. It is concluded that tension decline in soleus muscle is not due to decreased intracellular pH but is more related to the capacity to regenerate ATP at a sufficient rate. Contraction and relaxation time of the twitch remained practically constant during the stimulation period. In contrast prolonged activation of fast-twitch muscle results in a slowing of the relaxation of the twitch (Sahlin et al. 1981) and it has been suggested that this is caused by the decrease of intracellular pH. The constancy of both relaxation time and calculated pH in the fatigued soleus muscle is consistent with the hypothesis that there is a connection between these two parameters. In contrast to the twitch, relaxation of tension after a tetanus was prolonged in soleus. Hence, it appears that the rate limiting step for relaxation is different for a twitch than for a tetanus in soleus.

Adenosine Triphosphate↗
PubMed1987

Effects of age on contractile and enzyme-histochemical properties of fast- and slow-twitch single motor units in the rat.

1. Contractile, enzyme-histochemical and morphometrical properties of muscle fibres were studied in single motor units of tibialis anterior (t.a.) and soleus muscles in young (3-6 months) and old (20-24 months) male albino rats. The technique of measuring glycogen depletion as a marker of previous muscle contraction was used for direct correlation of enzyme-histochemical and contractile parameters within single motor units of the fast- and slow-twitch type. 2. In t.a., the fast-twitch motor units covered 18 +/- 9 and 22 +/- 16% (P = not significant, n.s.) of t.a. cross-sections, included 148 +/- 65 and 162 +/- 63 muscle fibres per unit (P = n.s.) and had a cross-sectional area of 0.50 +/- 0.32 and 0.44 +/- 0.22 mm2 (P = n.s.) in the young and old animals, respectively (means +/- S.D.). 3. In soleus, the slow-twitch motor units covered 53 +/- 11 and 71 +/- 12% (P = n.s.), included 55 +/- 10 and 83 +/- 13 muscle fibres per unit (P less than 0.01) and had a total cross-sectional area of 0.14 +/- 0.02 and 0.22 +/- 0.06 mm2 (P less than 0.01) in the young and the old animals, respectively. The calculated number of motor units in soleus accordingly decreased (P less than 0.01) from 49 +/- 10 in the young to 29 +/- 10 in the old animals resulting in a loss of muscle fibres and an increased innervation ratio in old age (mean +/- S.D.). 4. Clusters of more than three muscle fibres were rarely seen in any of the glycogen-depleted motor units in either the young or the old animals. However, in the slow-twitch motor units of old animals the muscle fibres were less randomly distributed within the motor unit territory (P less than 0.05), indicating a denervation-reinnervation process. 5. The contraction and half-relaxation times of the isometric twitch were significantly prolonged in old age. In 274 randomly isolated single motor units of t.a. the contraction time increased from 13 +/- 1 in young animals to 17 +/- 3 ms in old ones and the half-relaxation time from 12 +/- 2 to 16 +/- 5 ms (P less than 0.01 in both cases). In 236 randomly isolated soleus single motor units, the contraction and half-relaxation times increased (P less than 0.001) from 24 +/- 5 to 31 +/- 7 ms and from 26 +/- 8 to 35 +/- 9 ms, respectively (mean +/- S.D.).(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Triphosphatases↗
PubMed1987

Muscle biopsy findings, conduction velocity and refractory period of single motor nerve fibres in schizophrenia.

Eight untreated and eight neuroleptic treated male schizophrenic patients were studied. Light and electron microscopical analysis of muscle biopsies from the anterior tibial muscle showed a spectrum of pathological changes without significant quantitative or qualitative differences between the two groups. The changes included atrophic fibres, central nuclei, "moth-eaten fibres", "ring fibres", fibre splitting and subsarcolemmal and intermyofibrillar glycogen droplets. Electrophysiological investigation of single motor unit properties showed impaired peripheral impulse propagation in both patient groups while the conduction velocity and the refractory period of single motor nerve fibres were within the same range as in healthy subjects. In conclusion there are neuromuscular abnormalities in schizophrenic patients which cannot be attributed to medication or drug abuse.

Adult↗
PubMed1987

Muscle fibre type composition, motoneuron firing properties, axonal conduction velocity and refractory period for foot extensor motor units in dystrophia myotonica.

Seven patients with dystrophia myotonica were investigated using neurophysiological combined with histochemical techniques to elucidate motor unit properties in foot extensor muscles, which are often involved in the early stages of this disorder. For the 25 extensor digitorum brevis motor units studied the axonal conduction velocity, the axonal refractory period and the voluntary firing properties were within normal limits. However, high threshold motor units were not observed and the mean value of the axonal conduction velocities was lower (p less than 0.02) for the dystrophia myotonica motor units when compared with corresponding data from healthy subjects. There were also signs of impaired impulse propagation in the terminal part of the motor unit. In muscle biopsy specimens from the anterior tibial muscle, fibre type composition and structure were demonstrated using enzyme histochemical techniques for adenosine-triphosphate and immunohistochemical techniques for identification of the types of myosin isoform present. The histochemical findings indicated a type I fibre dominance, which was most obvious in the more seriously affected muscles. Neonatal myosin was observed preferentially in small but also in some normal sized fibres. Furthermore, some ring fibres were present and these showed staining with antineonatal myosin in their superficial portion. This indicates that an abnormal regeneration is one cause of the myopathic appearance of the muscle fibres in dystrophia myotonica. These investigations show that there is a reduced proportion of type II motor units in foot extensor muscles involved in the myopathy in dystrophia myotonica although it cannot definitely be established whether this is due to a loss of high threshold type II motor units or type II to type I transformation.

Action Potentials↗
PubMed1986

Effect of exercise on the motor unit.

The motoneuron part of this review deals with the changes in recruitment and firing rates of the motor unit types upon changes from a physically inactive life to endurance or strength training. The muscle fibers react to prolonged exercise by adaptation to a higher level of performance. A matter of discussion is the prerequisites for a transformation between the basic muscle fiber types, slow twitch and fast twitch, during voluntary (transsynaptic) activity, which is demonstrated after artificial nerve stimulation. The review includes current knowledge of muscle fiber transformation as an adaptive response to increased usage either by electrical stimulation or by transsynaptic neuronal activity. The metabolic adaptation related to increased endurance is reviewed with special reference to effects on muscle fibers. The increase in strength as a result of high resistance training is mainly the result of increased muscle cross-section. Whether this is solely the result of an increase in size of individual fibers or an increased fiber number is a controversial matter.

Action Potentials↗
PubMed1986

Type distribution of muscle fibres and their ultrastructure related to intracellular elemental composition as revealed by energy dispersive X-ray microanalysis. A study of multicore myopathy.

Four cases of congenital myopathy, two children and two adults, are described whose light-microscopical and ultrastructural findings are consistent with a multicore myopathy. In all cases a hereditary etiology to the disorders is obvious presumably by an autosomal recessive trait. Fibres with central nuclei and multiple minicores was a prominent finding in all cases. Energy dispersive X-ray microanalysis of single muscle fibres revealed a normal intracellular content of elements (sodium, potassium and chlorine). This is in contrast to the findings in some cases of s.c. myotubular myopathy earlier described from our group where content of sodium and chlorine is markedly increased while that of potassium is decreased. It is suggested that in myotubular myopathy membrane dysfunction causing decreased ionic gradients is an important feature of the pathophysiology while in multicore myopathy other mechanisms, as a suggestion related to mitochondrial and myofibrillar function play a more prominent part. From a diagnostic point of view it seems that X-ray microanalysis can be used to differentiate the two conditions.

Adult↗
PubMed1986

Effects of age on enzyme-histochemical fibre spectra and contractile properties of fast- and slow-twitch skeletal muscles in the rat.

Enzyme-histochemical fibre spectra and contractile properties were studied in fast-twitch (extensor digitorum longus (EDL) or tibialis anterior (TA)) and slow-twitch (soleus (S)) muscles of young adult (6 months) and old (20-24 months) male albino rats. It was found that ageing affected fibre size, fibre type proportions, and contractile properties of muscle tissue in both qualitative and quantitative terms and that these age-related alterations differed between fast- and slow-twitch muscles. In the fast-twitch TA and EDL, no differences were observed in either the total number of fibres, the cross-sectional area or the absolute and relative numbers of different muscle fibre types and subtypes between young adult and old animals. In the slow-twitch S, on the other hand, both the total number of muscle fibres and the average cross-sectional fibre area were smaller in the old animals. The fibre loss and fibre atrophy were most pronounced in type II fibres, especially type IIA. In TA, twitch force was higher and tetanus force was unaltered in the old as compared with the young adult animals, resulting in an increased twitch:tetanus ratio in old age. In S, on the other hand, both these forces were lower in the old animals and the twitch:tetanus ratio was accordingly unchanged with age. When the tetanus force was related to age-related differences in total muscle fibre cross-sectional area, no differences were found in the maximum force-generating capacity of maintained contractile material in either fast- or slow-twitch muscles between the two age groups. Probable mechanisms underlying the above alterations are discussed.

Adenosine Triphosphatases↗
PubMed1985

Activation of glycogen phosphorylase by electrical stimulation of isolated fast-twitch and slow-twitch muscles from rat.

The influence of muscle contraction, induced by electrical stimulation, on the activity of glycogen phosphorylase, the contents of high-energy phosphates, hexose-monophosphates and lactate have been studied in isolated extensor digitorum longus (EDL) and soleus muscles from rats. The activity of phosphorylase a + b was about nine times higher in fast twitch muscles (EDL) than in slow-twitch soleus and remained unchanged during the stimulation. A pronounced increase of phosphorylase a occurred during the stimulation in EDL muscle. Stimulation with a frequency of 50 Hz for 10 s and 2 Hz for 90 s resulted in a 44-fold and five-fold increase in phosphorylase a, respectively. In contrast, stimulation of soleus muscle resulted in only a minor increase of phosphorylase a. The rate of glycogenolysis increased in both muscles during the stimulation but the increase was four to five times higher in the EDL than in soleus muscle. The content of phosphocreatine (PCr) before stimulation was much higher in EDL than in soleus but similar after the stimulation. This resulted in a three- to four-fold higher release of inorganic phosphate (Pi) in EDL than in soleus during contraction. Pi has previously been shown to be present in a limiting amount for the activity of phosphorylase and the increase during contraction is of importance for increasing the glycogenolytic rate. It is concluded that the higher glycogenolytic capacity in fast-twitch muscles compared to slow-twitch muscles is due to: (1) higher content of phosphorylase a + b, (2) higher degree of transformation of the enzyme into the a form during contraction, and (3) higher content of PCr, which liberates a large amount of Pi during contraction.

Animals↗
PubMed1985

Contractile properties, fatiguability and glycolytic metabolism in fast- and slow-twitch rat skeletal muscles of various temperatures.

The influence of muscle temperature (28 and 36 degrees C) on fatiguability and glycolytic metabolism was studied during 5 min of intermittent stimulation of motor nerves of the tibialis anterior, extensor digitorum longus (fast-twitch) and soleus (slow-twitch) muscles in the rat at 100 Hz (200 ms per s). The decline in isometric tension was not affected by muscle temperature either in fast- or in slow-twitch muscles. In fast-twitch muscles the utilization of glycogen during stimulation was the same at 28 and 36 degrees C, while in the soleus muscle it was lower at 28 degrees C. The concentration of glucose-6-phosphate immediately after stimulation was higher in the muscles at 28 degrees C than in those at 36 degrees C, whereas no difference in lactate concentration was found between the two temperature groups. These observations indicate that compared with the rate at 36 degrees C, the rate of glycogenolysis at 28 degrees C is unchanged in fast-twitch, but decreased in slow-twitch muscle. This might imply increased economy of ATP turnover during contraction in the soleus muscle at 28 degrees C.

Animals↗
PubMed1985

Freeze-drying and related preparation techniques for biological microprobe analysis.

An X-ray microanalytical and morphological investigation has been carried out on rapidly frozen, freeze-dried or freeze-substituted tissues. A comparison was made between different embedding and polymerisation procedures following freeze-substitution and freeze-drying. The investigation also included an analysis of specimens infiltrated, embedded and polymerised by ultraviolet irradiation at low temperatures with Lowicryl HM20. The morphological preservation of Lowicryl embedded tissue was adequate for the identification of different cell structures like nuclei, mitochondria, lysosomes and different types of endoplasmic reticulum. X-ray microanalytical investigation of low temperature embedded material displayed an elemental composition of cells and organelles similar to that found in freeze-dried cyosections. Compared with freeze-dried cryosections, low temperature embedded material could be sectioned for light microscopy and area of interest chosen for further thin sectioning. This is of great importance in work with tissues with complicated morphology and heterogenous cell populations.

Animals↗
PubMed1984

Muscle fibre type composition in distal myopathy (Welander). An analysis with enzyme- and immuno-histochemical, gel-electrophoretic and ultrastructural techniques.

The myopathic muscle of distal myopathy (Welander's disease), the dominantly inherited neuromuscular disorder which occurs frequently in Sweden, has been characterized by electron microscopy, enzyme- and immuno-histochemistry (using antibodies against embryonic, neonatal, fast and slow myosin, and against the muscle-specific intermediate filament protein, desmin), and with gel electrophoretic techniques. Of special interest is the fact that the ultrastructural appearance of the fibres with regard to M- and Z-band structures does not fit the proposed classification criteria for ultrastructural fibre typing of normal human muscle. Furthermore, contrary to previous results, we conclusively demonstrate that the predominating fibres are of a slow-twitch type. Unexpectedly, we also observed that embryonic and neonatal myosin was expressed in some residual fibres. This emphasises the importance of supplementing stains to demonstrate activity of ATPase with myosin immuno-histochemistry in order to improve understanding of fibre type characteristics in myopathic muscles. The origin of the myopathic muscle fibres in distal myopathy could not be definitely determined, but it is suggested that neurogenic disturbances play an important part in the pathophysiology of Welander's disease.

Adenosine Triphosphatases↗
PubMed1984

Sodium, phosphorus, sulphur, chlorine and potassium shifts in rat brain during embryonic development.

Concentrations of sodium (Na), phosphorus (P), sulphur (S), chlorine (Cl) and potassium (K) and their variations during brain development were measured in freeze-dried thick sections from rat brain (16-20 micron). Sprague-Dawley rats were bred and the day of finding vaginal spermatozoa was considered as day zero of pregnancy. On days 12E, 13E, 14E, 16E, 19E, 21E (embryonic) and postnatal day one whole embryos or fetal heads were rapidly frozen in liquid Freon 22 cooled with liquid nitrogen (-180 degrees C), sectioned in a cryostat (-20 to -40 degrees C), and processed for X-ray microanalysis on pure carbon plates. Concentrations of Na and Cl differed in the cells of the cerebral cortex, ependyma, choroid plexus and cerebral spinal fluid (CSF). During cerebral development, Na and Cl concentrations appeared to be correlated, while K was more related to P. S was low and unchanged in all compartments during development and was thus considered as an internal control. K was inversely related to Na and Cl fluctuations within the choroid plexus epithelia. Sharp phase changes of elemental composition appeared in all tissues at specific growth stages, e.g. days 14E and 19E. These results demonstrate rhythmic changes in the inorganic components of developing rat brain cells and fluid environment presumably reflecting physiological fluctuations and cell cycle phenomena. Such changes may also be related directly or indirectly to known 'growth phase changes' in the developing rat.

Animals↗
PubMed1984

Recent applications of X-ray microanalysis in muscle pathology.

X-ray microanalysis of single muscle fibres visualized in the scanning- and scanning-transmission mode of electron microscopy has been applied to human muscle biopsies to quantify changes of intracellular elements in different muscle disorders. To detect elements representing diffusible ions, cryofixation and cryosectioning was performed and analyses were conducted on freeze-dried cryosections 6 micron thick. Changes in the concentration of elements were found to differentiate certain muscular disorders. A large increase in sodium (Na) and chlorine (Cl), and a decrease in potassium (K) was typical of myotubular myopathy, while a moderate increase in Na and Cl was found in central core disease and nemaline myopathy. The normal elemental spectrum was found in multicore myopathy and facio- scapulo -humeral muscle dystrophy. In dystrophia myotonica there was constantly a decrease in K whereas in myotonia congenita an increase in K was a common finding. In myotonic dystrophy an increase in Na and Cl seemed to be related to the increase in the ring fibre formation. Experimental tenotomy of the soleus muscle of the rat is characterized by plasma membrane changes and the formation of core fibres. A marked increase in Na and Cl and a decrease in K was found to be a prominent elemental change in such core fibres. We conclude that changes in the concentration of certain intracellular elements demonstrable by X-ray microanalysis on cryosectioned freeze-dried muscle biopsies seem to be an indication of muscle fibre membrane disturbances.

Adolescent↗
PubMed1983

Changes in elemental composition of single muscle fibers following tenotomy of the rat soleus muscle.

Cores were produced in type 1 muscle fibers by tenotomy of rat soleus muscle. The morphology and histochemistry of the muscle fibers was established by light microscopy on cryostat sections stained for hematoxylin-eosin or myofibrillar ATPase and on semithin plastic sections. The ultrastructure was visualized on thin plastic sections. On 6 micrometers of freeze-dried cryosections, energy dispersive X-ray microanalysis was performed on muscle fibers visualized in the scanning-transmission mode of electron microscopy. This procedure permitted quantification of different intracellular elements such as sodium (Na), chlorine (Cl), potassium (K), magnesium (Mg), sulphur (S), and phosphorus (P). Spectra from core fibers could easily be compared with those of normal fibers. A conspicuous finding was an increased Na and Cl content and a decreased K content in core fibers compared to normal fibers. It is known that core fibers produced after tenotomy exhibit distinct changes in plasma membrane morphology similar to that found in Duchenne muscular dystrophy (DMD). The results in this study point to a change in normal intracellular ion composition which could be a result of a deficiency of mechanisms maintaining normal membrane ion gradients.

Animals↗
PubMed1983

Quantitative estimation of anaerobic and oxidative energy metabolism and contraction characteristics in intact human skeletal muscle in response to electrical stimulation.

A set up for electrical stimulation of the human quadriceps femoris muscle and registration of tension is described. Normal values for the frequency-tension relations and relaxation time are presented. There was no relationship between contraction characteristics and fibre type distribution. Muscle tissue was sampled after electrical stimulation by percutaneous biopsy technique. Phosphocreatine (PCr) decreased during a 75 s isometric contraction from 76 mmol per kg dry muscle down to a mean value of 9 mmol. Lactate increased during the same time period from 5 mmol per kg dry muscle to 100 mmol. At end of contraction there was a rapid resynthesis of PCr with a half time of about 20 s while the lactate content decreased slowly. The relaxation time of the muscle was prolonged from 38 ms, in non-fatigued muscle, to 128 ms after 75 s of isometric contraction. The relaxation time was normalized after the contraction at the same rate as the resynthesis of PCr. It is proposed that the relationship between PCr and lactate of contracting muscle can be used as an index of glycolytic capacity and that the rate of resynthesis of PCr after contraction is a measure of oxidative capacity. Relaxation time measurements alone may be used as a non-invasive estimation of the oxidative capacity.

Adenosine Diphosphate↗
PubMed1983

Fatigue and phosphocreatine depletion during carbon dioxide-induced acidosis in rat muscle.

Isolated extensor digitorum longus muscles from rat were exposed to atmospheres of 30% CO2 (high-CO2 muscles) or 6.5% CO2 (control muscles) in O2 for 95 min. Muscle contraction characteristics were studied before and after the incubation. Tetanic tension decreased in high-CO2 muscles to 55% of initial value but remained unchanged in control muscles. Relaxation time was prolonged in high-CO2 muscles but not in control muscles. Intracellular pH was 6.67 +/- 0.04 (SD) in high-CO2 muscles and 7.01 +/- 0.04 in control muscles. CO2-induced acidosis had a marked influence on the intermediary energy metabolism as shown by a fourfold increase of glucose 6-phosphate, a 14% increase of ADP, and a decrease of phosphocreatine to 44% of the control value. Lactate and pyruvate contents were unchanged. The observed metabolic changes can be explained by an effect of H+ on the activity of phosphofructokinase and on the creatine kinase equilibrium. It can be concluded that H+ concentration causes muscular fatigue. It is, however, uncertain whether this is an effect of increased H+ per se or by high-energy phosphate depletion induced by acidosis.

Acidosis↗