Jan Lännergren

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Prolonged activation of skeletal muscle leads to a decline of force production known as fatigue. In this review we outline the ionic and metabolic changes that occur in muscle during prolonged activity and focus on how these changes might lead to reduced force. We discuss two distinct types of fatigue: fatigue due to continuous high-frequency stimulation(More)
The respiratory and limb skeletal muscles become weakened in sepsis, congestive heart failure, and other inflammatory diseases. A potential mediator of muscle weakness is tumor necrosis factor (TNF)-alpha, a cytokine that can stimulate muscle wasting and also can induce contractile dysfunction without overt catabolism. This study addressed the latter(More)
1. Isometric tension responses to electrical stimulation have been studied at 7.5 37.5 degrees C in single, intact fibres of the flexor digitorum brevis muscle of the mouse. A large number of reproducible tetani could be obtained at temperatures less than or equal to 35 degrees C. 2. The tetanic force per cross-sectional area generated at 25.0 degrees C was(More)
Muscle performance declines during prolonged and intense activity; important components are a reduction in force production and shortening velocity and a prolongation of relaxation. In this review we consider how the changes in metabolites (particularly H+, inorganic phosphate (Pi), ATP and ADP) and changes in sarcoplasmic reticulum Ca2+ release lead to the(More)
Force recovery from fatigue in skeletal muscle may be very slow. Gross morphological changes with vacuole formation in muscle cells during the recovery period have been reported and it has been suggested that this is the cause of the delayed force recovery. To study this we have used confocal microscopy of isolated, living muscle fibres from Xenopus and(More)
Isolated, living muscle fibres from either Xenopus or mouse were observed in a confocal microscope and t-tubules were visualized with sulforhodamine B. Observations were made before and after fatiguing stimulation. In addition, experiments were performed on fibres observed in an ordinary light microscope with dark-field illumination. In Xenopus fibres,(More)
The Schwann cell basal lamina (BL) is required for normal myelination. Loss or mutations of BL constituents, such as laminin-2 (alpha2beta1gamma1), lead to severe neuropathic diseases affecting peripheral nerves. The function of the second known laminin present in Schwann cell BL, laminin-8 (alpha4beta1gamma1), is so far unknown. Here we show that absence(More)
1. The effect of altered intracellular pH (pHi) on isometric contractions and shortening velocity at 12, 22 and 32 degrees C was studied in intact, single fibres of mouse skeletal muscle. Changes in pHi were obtained by exposing fibres to solutions with different CO2 concentrations. 2. Under control conditions (5% CO2), pHi (measured with carboxy SNARF-1)(More)
1. Single skeletal muscle fibres of Xenopus laevis were used to investigate the involvement of a mechano-sensitive link in excitation-contraction coupling (EC coupling). 2. Fibres were stimulated by intermittent tetani until tension fell to about 40% of its initial level. Fibres were then stressed either by briefly stretching the fibres to 120% of their(More)