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  • 1
    Electronic Resource
    Electronic Resource
    Muscle glycogen depletion patterns in fast twitch fibre subgroups of man during submaximal and supramaximal exercise (1979)
    Springer
    Pflügers Archiv 379 (1979), S. 105-108 
    Details
    ISSN: 1432-2013
    Keywords: Glycogen depletion ; Human muscle ; Fibre types ; Fast twitch subgroups
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Muscle glycogen depletion in ST, FTa and FTb fibres were studied in human subjects undergoing two distinctly different modes of bicycle exercise. Two hours of submaximal exercise (60% of V02 max) produced a 77% decline in muscle glycogen concentration accompanied by only minor elevations in muscle and blood lactate levels, whereas 10 one minute supramaximal work bouts resulted in a 52% decrease in total glycogen concentration and substantially elevated muscle and blood lactate contents. Moreover the patterns of glycogen depletion in the two conditions were also distinctly different. Based on the PAS staining intensity, glycogen was depleted the most in ST fibres and least in FTb fibres, during submaximal work. During supramaximal work FTb fibres were the lightest in PAS staining, with little loss of glycogen from ST fibres. In both situations the loss of glycogen in the FTa fibres was intermediate compared to the other two fibre types. These data support a selective recruitment of muscle fibres during work of different intensities, and further, suggest a physiological basis for the subgrouping of FT fibres in man.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00622912
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  • 2
    Electronic Resource
    Electronic Resource
    Myosin light chain phosphorylation and isometric twitch potentiation in intact human muscle (1985)
    Springer
    Pflügers Archiv 403 (1985), S. 348-352 
    Details
    ISSN: 1432-2013
    Keywords: Twitch potentiation of human skeletal muscle ; P-light chain phosphorylation ; Myosin light chain kinase ; Myosin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of a single voluntary contraction of the quadriceps muscle group on phosphate incorporation into the phosphorylatable light chains (P-light chains) of fast and slow myosin isolated from the vastus lateralis muscle and potentiation of the electrically stimulated twitch tension was studied in intact human muscle. Twitch potentiation was maximal 20 s after the voluntary contraction. Thereafter, twitch potentiation declined, but was still significantly higher than pre-contraction values 2 min after the voluntary contraction. Phosphate incorporation into the P-light chain of fast myosin followed a similar time course to twitch potentiation, but no phosphate was incorporated into slow myosin P-light chains. These observations suggest that myosin light chain kinase activity is mainly associated with fast-twitch muscle fibers and, in agreement with previous studies, suggests that twitch potentiation associated with P-light chain phosphorylation is confined to the fast-twitch fibers of human muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00589245
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  • 3
    Electronic Resource
    Electronic Resource
    Myosin light chain phosphorylation during staircase in fatigued skeletal muscle (1993)
    Springer
    Pflügers Archiv 425 (1993), S. 9-15 
    Details
    ISSN: 1432-2013
    Keywords: Potentiation ; Myosin light chain kinase ; Muscle stimulation ; Fatigue
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract It has been reported that the peak of the staircase or the enhanced tension response during low frequency stimulation is delayed in fatigued fast muscle. Our purpose was to determine if the rate and extent of regulatory myosin light chain (P-LC) phosphorylation, a molecular mechanism associated with the positive staircase, are also altered by fatigue. The staircase contractile response, muscle metabolites and phosphate incorporation by the P-LC were assessed at 0, 5, 10 or 20 s of 10-Hz stimulation, in either non-fatigued (control) or fatigued (10 Hz for 5 min, followed by 20 min of recovery) rat gastrocnemius muscle in situ. The concentration of adenosine triphosphate (ATP) in fatigued muscles, 21 ±0.9 mmol · kg−1 (dry weight) was significantly lower (P〈0.05) than in the control muscles, 26.1±1.5 mmol · kg−1. In both groups, ATP content was significantly lower after 20 s of 10 Hz stimulation. The P-LC phosphate content (in mol phosphate · mol−1 P-LC) was 0.10, 0.38, 0.60 and 0.72 after 0, 5, 10 or 20 s of 10 Hz stimulation in control muscles, but only 0.03, 0.08, 0.11 and 0.19 at these times in fatigued muscles. Although the absolute magnitude of tension potentiation was attenuated in proportion to the depressed twitch amplitude, these surprisingly low levels of phosphorylation were associated with 0, 48, 79 and 86% potentiation of the developed tension at these times in contrast with 0, 71, 87 and 49% potentiation in control muscles. These data demonstrate that while the rate and extent of phosphate incorporation is depressed in fatigued muscle, tension potentiation is still evident. The persistence of potentiation in the fatigued state indicates that either this condition results in greater potentiation for a given level of P-LC phosphorylation, or that factors in addition to P-LC phosphorylation are responsible for the staircase response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374497
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  • 4
    Electronic Resource
    Electronic Resource
    Mechanical measures during maximal velocity knee extension exercise and their relation to fibre composition of the human vastus lateralis muscle (1988)
    Springer
    European journal of applied physiology 58 (1988), S. 1-7 
    Details
    ISSN: 1439-6327
    Keywords: Maximal velocity of knee extension ; Acceleration ; Peak torque ; Electromechanical delay-Muscle fibre type
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A method for measuring the maximal velocity of knee extension exercise is described using a very light lever arm. Instrumentation of the lever arm with a potentiometer and accelerometer also allows for the measurement of peak acceleration, time to peak acceleration, the average rate of development of acceleration (jerk) and peak torque. With this apparatus and surface electromyography, electromechanical delay (EMD) was also determined. This apparatus was tested using 17 female and 10 male subjects, and the measures obtained were related to the percentage of fast twitch fibres (% FT) and the relative area of fast twitch fibres (% FTA) in the vastus lateralis determined from duplicate muscle biopsy samples. Peak velocity of unloaded knee extension averaged 12.1±1.2 and 12.2±1.7 rad · s−1 for females and males, respectively, and were not significantly different. As well, peak acceleration, time to peak acceleration jerk and EMD values were not significantly different between the female and male subjects, but the mean peak torque for the female subjects (73.5±14.7 N · m) was significantly lower than that for the males (98.4±31.5 N · m). Peak acceleration was significantly correlated with %FT (r=0.40,P=0.04) for the total subject population. None of the other measures was significantly related to either %FT or %FTA for the male and female subjects or the combined population of subjects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00636595
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Lactam bridge stabilization of α-helical peptides: Ring size, orientation and positional effects (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Peptide Science 1 (1995), S. 274-282 
    Details
    ISSN: 1075-2617
    Keywords: Lactam bridges ; α-helical stability ; cyclization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of 14 residue amphipathic α-helical peptides, in which the sidechains of glutamic acid and lysine have been covalently joined, was synthesized in order to determine the effect of spacing, position and orientation of these lactam bridges. It was found that although an (i, i+3) spacing would position the lactam bridge on the same face of the helix, these lactams with 18-member rings were actually helix-destabilizing regardless of position or location. On the other hand, (i, i+4) lactams with 21-member rings were helix-stabilizing but this was dependent on orientation. Glutamic acid-lysine lactams increased the helical content of the peptide when compared with their linear homologue in benign conditions (50 mM KH2PO4, 100 mM KCl, pH 7). Two Glu-Lys (i, i+4) lactams located at the N- and C-termini gave rise to a peptide with greater than 99% helical content in benign conditions. Peptides with Lys-Glu oriented lactams were random structures in benign conditions but in the presence of 50% TFE could be induced into a helical conformation. The stability of the single-stranded α-helices, as measured by thermal denaturations in 25% TFE indicated that Glu-Lys oriented lactam bridges stabilized the helical conformation relative to the linear unbridged peptide. One Glu-Lys lactam in the middle of the peptide was more effective at stabilizing helical structure than two Glu-Lys lactams positioned one at each end of the molecule. The lactams with the Lys-Glu orientation were destabilizing relative to the unbridged peptide. This study demonstrates that correct orientation and position of a lactam bridge is critical in order to design peptides with high helical content in aqueous media.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/psc.310010408
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  • 6
    Electronic Resource
    Electronic Resource
    Phosphorylation of rabbit skeletal muscle myosin in situ (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 125 (1985), S. 301-305 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Myosin light chain (P light chain) is phosphorylated by Ca2+. calmodulindependent myosin light chain kinase. Based on studies with rat skeletal muscles, it has been shown that P light chain phosphorylation correlated to the extent of potentiation of isometric twitch tension. It is not clear whether this correlation exists in rabbit skeletal muscle, which has been the primary source of contractile proteins for biochemical studies. Therefore, phosphorylation of myosin P light chain in rabbit slow-twitch soleus and fast-twitch plantaris muscles in situ was examined. Electrical stimulation (5 Hz, 20 seconds) of plantaris muscle produced an increase in the phosphate content of P light chain from 0.17 to 0.45 mol phosphate/mol P light chain. This increase in phosphate content was accompanied by a 58% increase in maximal isometric twitch tension. Tetanic stimulation (100 Hz, 15 seconds) of rabbit soleus muscle resulted in only a small increase in P light chain phosphate content from 0.02 to 0.10 mol phosphate/mol P light chain, and posttetanic twitch tension did not increase significantly. The correlation between potentiated isometric twitch tension and P light chain phosphorylation in rabbit fast-twitch muscle is similar to that observed in rat skeletal muscle. These results were consistent with the hypothesis that phosphorylation of rabbit skeletal muscle myosin, which results in an increase in actin-activated ATPase activity, may be related to isometric twitch potentiation.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041250219
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