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  • 1
    Electronic Resource
    Electronic Resource
    Pentamerism and the ancestral echinoderm (1974)
    [s.l.] : Nature Publishing Group
    Nature 250 (1974), S. 82-83 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. 1 Nichols' hypothetical ancestral echinoderm, in cross section. Nichols' reconstruction, like many primitive echinoderms, has mouth, hydropore and anus in a straight line. Such an animal must live with the anus on the downstream side, to carry waste products away from mouth and hydro-pore ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/250082a0
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  • 2
    Electronic Resource
    Electronic Resource
    Fossil Burrows on the Coast of Kenya (1965)
    [s.l.] : Nature Publishing Group
    Nature 207 (1965), S. 850-851 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The rock containing the burrows resembles the coquinas described by Thompson1. It is cream-coloured granular limestone which in thin section is seen to consist of fragments of shell, with some foraminifera and a few quartz grains, cemented together by calcite. In outcrop the bedding is picked out ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/207850a0
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  • 3
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    "Cardiac Myocyte - Connective Tissue Interactions in Health and Disease", edited by T.F. Robinson and R.K.H. Kinne (Book Review) (1992)
    Baltimore : Periodicals Archive Online (PAO)
    Human Biology. 64:2 (1992:Apr.) 263 
    Details
    ISSN: 0018-7143
    Topics: Biology
    Notes: Book Reviews
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:5243-1992-064-02-000015
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  • 4
    Electronic Resource
    Electronic Resource
    Non-uniform ion distributions and electrical potentials in sarcoplasmic regions of skeletal muscle fibres (1981)
    [s.l.] : Nature Publishing Group
    Nature 289 (1981), S. 690-692 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We used mechanically skinned single muscle fibres of the barnacle1 (Balanus nigrescens), subsequently treated with a nonionic detergent which disrupted and removed all cellular membranes. Electron microscopic observations confirmed this and showed that the only regions which could be distinguished ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/289690a0
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  • 5
    Electronic Resource
    Electronic Resource
    Mesospheric and lower thermospheric wind changes over Canada during the January 1975 stratospheric warming (1975)
    [s.l.] : Nature Publishing Group
    Nature 258 (1975), S. 62-64 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. 1 Zonal component of daily median wind, for one hour around noon, and in the altitude ranges 60-85, 88-100 and 〉 103 km, at Saskatoon. There seem to be at least two related classes of stratospheric temperature changes. The first is an aspect of a travelling planetary wave-changes in the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/258062a0
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  • 6
    Electronic Resource
    Electronic Resource
    Pentameral Symmetry in Echinoderms (1967)
    [s.l.] : Nature Publishing Group
    Nature 216 (1967), S. 994-994 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Nichols has looked for a reason for pentamerism in the life of modern echinoderms, but the evolution of echino-derms is a continuous process which has gone on since Pre-Cambrian times3. Once the pentameral condition had been established at some time in the past, in many members of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/216994a0
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  • 7
    Electronic Resource
    Electronic Resource
    Theory and observation of spontaneous oscillatory contractions in skeletal myofibrils (1994)
    Springer
    Journal of muscle research and cell motility 15 (1994), S. 369-389 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary At low levels of activation, an isometrically-held myofibrillar preparation on the descending limb may exhibit persistent oscillations of period 1–6 s in tension and sarcomere lengths. We propose a sarcomeric theory of spontaneous oscillatory contraction, based on the phenomena of force creep and delayed length activation. The time delay leads to oscillations and controls their period. A computer model using these ideas simulates spontaneous oscillatory contraction for fixed-end fibres only if isometric tension capacity varies slightly along the fibre. The form of this inhomogeneity controls a diversity of spontaneous oscillatory contraction behaviour: the tension waveform can vary from large and sinusoidal to small-amplitude pulses or chaotic behaviour, and these variations are observed in slow-twitch soleus fibres from the same animal (rat). The model predicts that oscillatory and quiescent regions coexist in the fibre, with large-amplitude sawtooth waveforms in sarcomere length in the former as observed. It can also generate travelling-wave structures, similar to those found by the Tokyo group, in oscillating regions when there is a spatial gradient in isometric tension capacity. Phase discontinuities in sarcomere length occur near the oscillatory-quiescent boundary. Predictions for the Ca2+ concentrations and sarcomere lengths in which spontaneous oscillatory contraction occurs and for differences in the spontaneous oscillatory contraction frequencies of fast-and slow-twitch fibres compare well with experiment. Spontaneous oscillatory contraction is also predicted under isotonic conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00122112
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  • 8
    Electronic Resource
    Electronic Resource
    Activation of skinned arthropod muscle fibres by Ca2+ and Sr2+ (1980)
    Springer
    Journal of muscle research and cell motility 1 (1980), S. 73-87 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Mechanically skinned skeletal muscle fibres of three crustaceans (barnacle, crayfish and crab) and two insects (cockroach and cricket) were activated in Ca2+- and Sr2+-buffered solutions of different concentrations and the isometric force response was determined. The maximum force response induced by Sr2+ (P 0 Sr ) was only 0–10% of that induced by Ca2+ (P 0 Ca ) in all crustacean muscles, but approached 90% in insects. Experiments on barnacle muscle fibres activated simultaneously by Ca2+ and Sr2+ suggested that Sr2+ competes with Ca2+ for binding onto the regulatory sites without, however, being able to turn all of them ‘on’ as efficiently as Ca2+. Interestingly, the ratioP 0 Sr /P 0 Ca and the sensitivity for both Sr2+ and Ca2+ increased substantially after 4–6 h following the dissection of the animals in most intact decapod muscle fibres and after 24 h in most barnacle muscle fibres. The steepness of the activation curves for both Ca2+ and Sr2+ was similar for each muscle regardless of the age of the fibre and implied that more than 2 Ca2+ (2 Sr2+) were involved in the activation process of each muscle. A Ca2+-induced Ca2+ release mechanism of physiological importance was found to operate in all arthropod muscle fibres investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00711926
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  • 9
    Electronic Resource
    Electronic Resource
    Calcium and strontium activation characteristics of skeletal muscle fibres from the small marsupialSminthopsis macroura (1990)
    Springer
    Journal of muscle research and cell motility 11 (1990), S. 12-24 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Mechanically skinned skeletal muscle fibres from the soleus and tibialis anterior muscles of the small marsupialSminthopsis macroura were activated by Ca2+ and Sr2+ so that their isometric force properties could be determined. The properties characterized were the shape, slope and positions of the curves generated by plotting isometric force vs. pCa (−log10[Ca2+]) and pSr (−log10[Sr2+]), the maximum Ca2+-activated and Sr2+-activated tension (Ncm−2) and the frequency of force oscillations of myofibrillar origin during submaximal activations. The effect of caffeine on force activation was also studied. Apart from the fibres which exhibited physiological characteristics similar to those observed previously in mammalian fibres, a large proportion of fibres exhibited characteristics or combinations of characteristics which have not previously been described from healthy adult mammals. The results from 32 soleus fibres showed that only 23 could be categorized as either typical fast-twitch or slow-twitch fibres. The rest possessed unusual physiological characteristics which suggested the co-existence in the same fibre of Ca2+-regulatory and contractile properties from different categories of fast-twitch and slow-twitch fibres. We could distinguish two major fast twitch populations of tibialis anterior fibres which occurred in similar proportions. There were significant differences in the maximum tension produced by some of these groups of fibres. The tibialis anterior population fibres produced the highest maximum tension (T o Ca 44.6±4.6 Ncm−2, n=7) while the soleus combined type fibres produced the lowest maximum tension (T o Ca 18.1±2.1 Ncm−2, n=8). Our physiological observations of the Ca2+-activation and Sr2+-activation properties of soleus fibres in this study provide new evidence that there can be combinations of characteristics in single fibres and a continuum of properties between fibre types in normal mammalian skeletal muscles. These animals can therefore be used as a source of fibres with a wide range of properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01833322
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of temperature on contractile activation of intact and chemically skinned ‘catch’ muscle fibre bundles of Mytilus edulis (1995)
    Springer
    Journal of muscle research and cell motility 16 (1995), S. 285-294 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effect of temperature (5–35° C) on maximum force production was examined in intact and chemically skinned muscle fibre bundles (10–25 fibres) from the anterior byssus retractor muscle of Mytilus edulis. In intact fibre bundles, 10 μm acetylcholine induced a tonic contraction which had a magnitude of 65.4±4.0 N cm-2 (n=30) at 23° C. Activation by caffeine (20 mm) produced a force response which was 157.1±7.9% (n=16) of the acetylcholine response at 23° C and acetylcholine and caffeine together produced force which was not significantly different from the response to caffeine alone. At 5° C the acetylcholine and caffeine responses were decreased by 9.6±3.4% (n=6) and 14.6±2.8% (n=8) compared with the respective responses at 23° C. However, there was no significant reduction of the response induced by the combined action of acetylcholine and caffeine when the temperature was decreased from 23° C to 5° C. The 20–80% of peak force activation time increased by about one order of magnitude for all acetylcholine, caffeine and combined acetylcholine-caffeine-induced responses when the temperature was decreased from 23–5° C. Repeated exposure of the intact preparation to caffeine caused a marked decrease in the caffeine-induced response (complete abolition of force after the third exposure to caffeine), but the response to caffeine could be fully restored following one acetylcholine-induced activation. The maximum Ca2+-activated force after skinning the preparation with saponin was not significantly different from the caffeine or combined acetylcholine-caffeine-induced responses before skinning. In the saponin skinned fibre preparation a drop in temperature from 23° C to 15° C or 5° C decreased the maximum Ca2+-activated force by 13.2±1.4% (n=8) and 41.4±3.1% (n=5) respectively. The activation time between 20–80% of the peak Ca2+-activated force increased at 15° C and 5° C by a factor of 1.5±0.1 (n=5) and 6.8±1.1 (n=5) respectively when compared to corresponding values at 23° C. The relaxation half-time decreased by a factor of 1.7±0.2 (n=5) and 3.0±0.2 (n=5) at 15° C and 5° C respectively compared with that at 23° C. It was possible to distinguish between the temperature effects on the contractile apparatus per se and the Ca2+ regulatory system with the results indicating that the contractile apparatus was more sensitive to a change in temperature than the Ca2+-regulatory system. Increasing the temperature to 35° C irreversibly affected the ability to develop and maintain force in both intact and skinned muscle preparations. These results indicate that: (1) acetylcholine does not fully activate the intact ‘catch’ muscle at 23° C; (2) acetylcholine is able to replenish the internal stores after depletion by caffeine; (3) compensatory mechanisms which oppose the inhibitory effect of lower temperatures on the contractile apparatus and the Ca2+-regulatory system must be operating in the intact fibre preparations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00121137
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