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  • 1
    Electronic Resource
    Electronic Resource
    Responses of mouse fast and slow skeletal muscle to streptozotocin diabetes: Myosin isoenzymes and phosphorous metabolites (1995)
    Springer
    Molecular and cellular biochemistry 148 (1995), S. 147-154 
    Details
    ISSN: 1573-4919
    Keywords: 31P-nuclear magnetic resonance ; streptozotocin ; myosin ; insulin-dependent diabetes ; ATP chemical potential ; energy metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract A condition similar to insulin-dependent diabetes mellitus (IDDM) was induced in male CD-1 mice by injection of streptozotocin (STZ). Five weeks after treatment, the fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus (SOL) muscles were isolated for analysis. Phosphorous metabolites were quantified by31P-NMR and HPLC, native myosin was characterized electrophoretically, and activities of metabolic enzymes were measured spectrophotometrically. Relative to control animals, STZ-diabetes resulted in a significant 32% decrease in the FM1 isoform of myosin in EDL and a 24% decrease in IM myosin of SOL. Mass-specific activities of phosphofructokinase, citrate synthase, and cytochrome oxidase were significantly lower in SOL from STZ-diabetic mice than in controls by 23, 18, and 36%, respectively. Intracellular ATP was significantly lower in SOL from STZ-diabetic mice than in controls (3.44±0.20 μmol g−1 wet weight vs. 4.61±0.20 μmol g−1, respectively), as was creatine phosphate (11.98±0.80 μmol g−1 wet weight vs. 14.22±0.44 μmol g−1). In contrast to results from SOL, there were no significant changes in phosphorus metabolites or enzyme activity in EDL. These results show that the effects of IDDM on levels of phosphorus containing metabolites and maximal activities of key regulatory enzymes in muscle are markedly fibertype specific. It is suggested that the muscle type-specific effects of STZ-diabetes may be a consequence of differential accumulation of intracellular fatty acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00928152
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  • 2
    Electronic Resource
    Electronic Resource
    Regulation of the Ascaris major sperm protein (MSP) cytoskeleton by intracellular pH (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 193-205 
    Details
    ISSN: 0886-1544
    Keywords: amoeboid motility ; fluorescence ratio imaging ; BCECF ; nematodes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The development and locomotion of the amoeboid sperm of the nematode, Ascaris suum, depend on precise control of the assembly of their unique major sperm protein (MSP) filament system. We used fluorescence ratio imaging of cells loaded with BCECF to show that intracellular pH (pHi) is involved in controlling MSP polymerization in vivo. Spermatogenesis is marked by a cycle of MSP assembly-disassembly-reassembly that coincides with changes in pHi. In spermatocytes, which contain MSP in paracrystalline fibrous bodies, pHi was 6.8, 0.6 units higher than in spermatids, which disassemble the fibrous bodies and contain no assemblies of MSP filaments. Activation of spermatids to complete development resulted in rapid increase in pHi to 6.4 and reappearance of filaments. Treatment of spermatocytes with weak acids caused the fibrous bodies to disassemble whereas incubation of spermatids in weak bases induced MSP assembly. The MSP filaments in spermatozoa are organized into fiber complexes that flow continuously rearward from the leading edge of the pseudopod. These cells established a pseudopodial pH gradient with pHi 0.15 units higher at the leading edge, where fiber complexes assemble, than at the base of the pseudopod, where disassembly occurs. Acidification of these cells caused the MSP cytoskeleton to disassemble and abolished the pH gradient. Acid removal resulted in reassembly of the cytoskeleton, re-establishment of the pH gradient, and re-initiation of motility. MSP assembly in sperm undergoing normal development and motility and in cells responding to chemical manipulation of pHi occurs preferentially at membranes. Thus, we propose that filament assembly in sperm is controlled by pH-sensitive MSP-membrane interaction. © 1994 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970270302
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  • 3
    Electronic Resource
    Electronic Resource
    The eurythermal myofibrillar protein complex of the mummichog (Fundulus heteroclitus): adaptation to a fluctuating thermal enviroment (1983)
    Springer
    Journal of comparative physiology 153 (1983), S. 167-173 
    Details
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Mummichogs from salt marshes of the Atlantic coast of Maine (USA) experience a mean seasonal temperature range of −1 °C to +15 °C. However, during summer tidal cycles they may experience rapid temperature changes between 15 °C and 30 °C. Observations of animals in the wild suggest that swimming capability is maintained during acute temperature fluctuations which would substantially impair contractile function in other fishes. Myofibrils were isolated from the fast epaxial musculature and APTase activity determined in a medium of 40 mM imidazole, pH 7.2 (20 °C), 50 mM KCl, 5 mM ATP, 6 mM MgCl2, 5 mM EGTA, 0.4 mg/ml protein (I=0.124) in the presence (pCa 5.15) and absence (pCa 7.15) of 5 mM CaCl2. More than 90% of the ATPase activity was calcium dependent over the temperature range 0–35 °C. Arrhenius plots of Mg2+ Ca2+ myofibrillar ATPase activity showed a discontinuity in slope at 12.5 °C. Values for activation enthalpy (ΔH≠) of the ATPase were 28,100 cal/mole in the range 0–12.5 °C and 11,900 cal/mole between 12.5–35 °C. The pCa's required to give onehalf maximal ATPase activity were 6.39 (0.407 μM), 6.18 (0.661 μM), and 6.24 (0.575 μM) at 5, 15 and 25 °C, respectively. Thermal denaturation of Ca2+-sensitivity and ATPase activity proceed essentially in parallel. At 0.5 mg/ml in standard incubation medium the temperature required to denature 50% of activity over 30 min is 40–41 °C. Identical results were obtained for groups of fish acclimated for 6 weeks to either 5 °C, 15 °C or 25 °C. The higher temperature dependence and relatively low ATPase activity at very cold temperatures suggest a relatively torpid state for overwintering fish. Compared to other fishes previously studied, results with mummichogs indicate that both Ca2+ regulatory function and catalytic activity of the myofibrillar complex has low temperature sensitivity over the range of 12–35 °C. These factors apparently obviate the need for acclimatory modifications of the contractile proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00689620
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