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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 352 (1991), S. 640-643 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Progress in analysing the structure and function of dynein has been hindered by the lack of primary sequence information resulting from the difficulty of cloning a complementary DNA encoding such a large polypeptide. We have now used a poly-merase chain reaction (PCR)-directed procedure to obtain ...
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 309 (1984), S. 560-562 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Sperm from the sea urchin, Tripneustes gratilla, were demem-branated in the presence of Ca2+(refs 2, 3) and reactivated at 22-23 C (Fig. 1). In these conditions the waveforms of the sperm flagella are nearly symmetrical when they are reactivated with Mg-ATP2" at low (〈106M) Ca2+concentration, ...
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 292 (1981), S. 85-86 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The effects of methanol and dimethylformamide on the asymmetry of reactivated sperm in the presence or absence of added Ca2+ are shown in Fig. 1. Methanol increases the asymmetry in both cases. On the other hand, dimethylformamide decreases the asymmetry induced by Ca2+ and has almost no effect on ...
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  • 4
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 3 Ill.
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  • 5
    ISSN: 0886-1544
    Keywords: eel sperm ; 9+0 flagellum ; motility ; helicoidal bending ; reactivation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The sperm flagella of the eel, Anguilla anguilla, are capable of vigorous motion in spite of having an axoneme with reduced structure that lacks the outer dynein arms, radial spokes and spoke heads, the two central tubules and the central tubule projections that are all part of the standard “9+2” axoneme. These sperm progress forward rapidly as a result of the propagation of helicoidal waves distally along the flagellum. Their flagellar beat frequencies are high, 93 Hz at 21°C, and they roll at a frequency of about 19 Hz. Eel sperm could be demembranated with Nonidet P-40 and reactivated with MgATP2- in 0.22 M K acetate at pH 8.1. The reactivated motility closely resembles that of the live sperm, with a beat frequency of 69 Hz, but the demembranated flagella are unusually fragile, and commonly disintegrate by a combination of splitting, coiling, and sliding within a few minutes. Little reactivation is obtained if acetate is replaced by Cl- in the reactivating medium. The Michaelis constant for beat frequency (0.2 mM) is similar to that obtained for several “9+2” flagella. These sperm, however, appear to lack the mechanism by which Ca2+ regulates waveform. Our results indicate that eel sperm flagella, which at rest are straight, are induced to bend helicoidally by ATP, as the result of sliding between tubules that is blocked at both the base and tip of the organelle. The flagellar waveform consists of a series of planar bends separated by short regions of right-handed twist, which give it an overall left-handed helicoidal form.
    Additional Material: 9 Ill.
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  • 6
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Previous work has shown that the dynein from axonemes of sea urchin sperm consists of two distinct fractions which differ substantially in their extractability by salt. Upon gel electrophoresis of whole demembranated axonemes solubilized with sodium dodecyl sulfate, the dynein fraction shows two closely spaced bands with apparent molecular weights of 520,000 and 460,000; the proteins in these bands are termed the A and B components of the dynein. Similar electrophoresis of the soluble fraction obtained by extracting the axonemes with 0.5 M NaCl shows a single prominent band containing approximately half of the A component of the dynein (A1 component). The residue of extracted axonemes contain the other half of the A component of the dynein (A2 component) and all the B component. Densitometry of the bands indicates that the A1, A2 and B components of the dynein are present in approximately equal molar quantity. Electron microscopic studies show that the A1 component of the dynein constitutes the outer arms on the doublet tubules. Assay of ATPase activity in 0.05 M KCl and l mM ATP indicates about 65% of the total ATPase activity becomes soluble when the A1 component of the dynein is extracted with salt.
    Additional Material: 3 Ill.
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  • 7
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Flagellar waveforms have been studied during the stopping and starting transients of light-induced, Ca2+-mediated, intermittent swimming of live sperm of the sea urchinTripneustes gratilla. Tracings of successive frames of movie film made at about 200 frames s−1 were used to determine the bend propagation velocity, beat frequency, and bend angles during three stopping and four starting transients chosen as representative of the range of variation among sperm in the preparations. A stopping transient begins with a transitional stage in which the asymmetry of the bending waves increases steadily over 2–6 beat cycles (40–120 ms), with the angles of successive fully developed principal bends increasing and those of reverse bends decreasing. This is followed by a blocked stage, lasting one beat cycle (20 ms), in which a principal bend becomes arrested and then decays in the mid-region of the flagellum. The next principal bend forms but remains unpropagated at the base, apparently because no following reverse bend is initiated, and the flagellum becomes quiescent. Quiescent flagella have a characteristic, highly asymmetric waveform consisting of a sharp principal bend of about 3.2 rad at the basal end, a nearly straight mid-region and a gentle principal bend of about 0.4 rad near the tip. After a quiescent period of 0.2–2 s, motility is resumed with the initiation of a new reverse bend at the base. This bend and the proximal principal bend remaining from quiescence begin to propagate but they decay before passing more than halfway along the flagellum. In this blocked stage of the starting transient, which lasts 1–15 beat cycles (20–300 ms), successive principal and reverse bends are propagated progressively further along the flagellum but they decay before reaching the tip and the asymmetry remains at the high value characteristic of quiescence. The first propagation of a principal bend to the tip marks the beginning of the transitional stage of the transient, during which the asymmetry of the bending waves gradually decreases until after 2–5 beat cycles (40–100 ms) it reaches the value characteristic of steady-state beating. In both stopping and starting flagella the beat frequency and the mean of the principal and reverse bend angles remain constant throughout the transient (except for the beat cycle immediately pre- or post-quiescence), indicating that they are regulated by mechanisms almost completely independent of that regulating wave symmetry. The bend propagation velocity remains constant during stopping transients but it is diminished during the blocked stage of starting transients, indicating that the bend velocity, and hence the wavelength, can be altered by changes in the internal resistance to bend propagation.
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