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  • 1
    Electronic Resource
    Electronic Resource
    Relaxation and force during fatigue and recovery of the human quadriceps muscle: relations to metabolite changes (1991)
    Springer
    Pflügers Archiv 418 (1991), S. 153-160 
    Details
    ISSN: 1432-2013
    Keywords: ATP ; Electrical stimulation ; Force ; Phosphate ; Phosphocreatine ; Relaxation ; Skeletal muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Force and relaxation were measured during electrical stimulation of the quadriceps muscle of 14 volunteers. Stimulation produced 51.2 s of intermittent ischaemic contractions either as 16 3.2-s tetani or as 64 0.8-s tetani. Changes during recovery were followed for 180 s. On 8 subjects muscle biopsies were taken during work and after the rest period for determination of ATP, phosphocreatine and intermediates in glucolysis. The stimulation using 0.8-s contractions gave more pronounced fatigue and slowing of relaxation. There was a good correlation between force and relaxation during work but this relation changed during recovery, indicating that no general relation exists between these two contraction characteristics. In the 0.8-s stimulation more ATP was utilized and there were more profound changes in metabolite levels. We found a correlation between estimated [H2PO 4 − ] and relaxation covering both work and recovery and hypothesize that inorganic phosphate and its removal by phosphocreatine resynthesis during recovery might be important. Since stimulation patterns differ in force and relaxation even after the recovery period we suggest that additional factors, such as pH, are of importance in this work model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370464
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  • 2
    Electronic Resource
    Electronic Resource
    Contraction characteristics of the human quadriceps muscle during percutaneous electrical stimulation (1990)
    Springer
    Pflügers Archiv 417 (1990), S. 136-141 
    Details
    ISSN: 1432-2013
    Keywords: Electrical stimulation ; Fatigue ; Force ; Frequency ; Skeletal muscle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Percutaneous electrical stimulation was used to study the force response of the quadriceps muscle. The normal frequency dependence of force was investigated in muscles at rest and after fatiguing contractions. A comparison between force response during fatigue induced by electrical stimulation at different frequencies and by voluntary work suggested equal changes in contractility, irrespective of the fatigue-inducing procedure. In fresh muscle we found a linear relation between stimulation period (10–100 ms) and force. At fatigue the relation changes with maximal deviation from linearity at a 50-ms period (20 Hz). There is a rapid recovery of high frequency force whereas the low frequency response remains low even after 30 min rest. At very low frequencies there is initially unexpectedly high force in fatigued muscle. This could be a result of increased fusion of twitches with initially prolonged relaxation time. To study the twitch summation we compared experimental results in a wide frequency range with computer-simulated twitch summations and present the frequency dependence of summation processes in human quadriceps muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370690
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Attenuation profiles of the petrous bone with acoustic neuroma (1980)
    Springer
    Neuroradiology 19 (1980), S. 123-129 
    Details
    ISSN: 1432-1920
    Keywords: Computed tomography ; Acoustic neuroma ; Internal auditory meatus ; Attenuation profiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Attenuation profiles across the petrous bone covering the whole internal auditory meatus (IAM) were constructed from the printouts obtained by computed tomography (CT) with narrow collimation performed on 12 patients with 13 acoustic neuromas. In healthy patients the attenuation profiles of right and left petrous bone were very similar in shape. The attenuation values of the individual pixels in the pixel columns of the printout located at the site of the porus and the IAM reflected the demineralization of the petrous bone and the widening of the porus and the IAM caused by the acoustic neuroma. A widening deep in the meatus was demonstrated in a patient with an intracanalicular tumor, and therefore it seems possible to make this diagnosis by CT scanning combined with the construction of attenuation profiles across the petrous bone. In the presence of unilateral acoustic neuroma there was a significant and characteristic difference in shape between the attenuation profiles of the two sides with generally lower attenuation values on the tumor side together with signs of widening of the porus and the IAM. In cases of bilateral acoustic neuroma comparison of the attenuation profiles can be made with mean attenuation curves obtained from scanning normal petrous bones. The prevailing physical limitations for demonstrating a narrow bony canal like the IAM with CT was experimentally analyzed using bone-simulating plastic material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00342386
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    Paper (German National Licenses)
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