| Basal Sliding and the Mechanics of Oscillation in a Mammalian Sperm Flagellum Biophysical Journal, Volume 87, Issue 6, 1 December 2004, Pages 3934-3944 Geraint G. Vernon and David M. Woolley Abstract The mechanism of oscillation in cilia and flagella has been a long-standing mystery. This article raises the possibility of a mechanical explanation based on new findings relating to where in the flagellum microtubule sliding can occur—and where it cannot occur. All theoretical analyses of flagellar bending have until now made the assumption that sliding displacements at the base of the flagellum cannot occur. One consequence of this has been the need to accept that sliding must be transmitted through propagating bends, an idea that has been tolerated even though it becomes paradoxical if bends are the result of resistance to sliding. Our observations, of spermatozoa from the chinchilla, have led us to a contradictory view. We have shown directly, by light microscopy and by two methods of electron microscopy, that basal sliding does occur. Also, evidence from video microscopy indicates that a propagating bend cannot transmit sliding through it. We have analyzed a movement pattern in which the beat frequency increases fourfold in a phasic manner. Our analysis of this suggests that new bends terminate when no further sliding is possible. At this point the bend direction immediately reverses. That is, the flagellar beat frequency increases when there is a limitation to sliding. One can see directly the alternation in basal sliding direction under these circumstances. This suggests a mechanism for the initiation of a new bend in the opposite direction to the bend just completed: we propose that the initiating trigger is the reversal of elastic deformations at the base, which reverses the direction of interdoublet sliding. Abstract | Full Text | PDF (584 kb) |
| Tissue-specific expression and subcellular localisation of mammalian δ-tubulin Current Biology, Volume 10, Issue 7, 1 April 2000, Pages 413-416 Oskar W. Smrzka, Nathalie Delgehyr and Michel Bornens Summary The properties of the microtubule network are regulated at various levels including tissue-dependent isotype switching, post-translational modification of α- and β-tubulin, and by a variety of microtubule-associated molecules (for reviews, see ). Microtubule nucleation is attributed to γ-tubulin, which is present in protein complexes at the centrosome and in the cytoplasm . A screen for flagellar mutants in the green alga has led to the identification of a fourth member of the tubulin gene superfamily, δ-tubulin. In this unicellular organism, the lack of a functional δ-tubulin gene copy causes aberrant numbers of flagella, depending on the age of the corresponding basal bodies; mutants also show abnormal ultrastructure of the basal bodies and a misplacement of the cleavage furrow at mitosis . Here, we report the isolation of the mouse δ-tubulin homologue and show that the gene is highly expressed in testis. In the elongating spermatid, δ-tubulin associated with the manchette, a specialised microtubule system present during reshaping of the sperm head. The protein specifically localised at the perinuclear ring of the manchette, at the centriolar vaults and along the principal piece of the sperm flagellum. In somatic cell lines, unlike most other tubulins, mammalian δ-tubulin was both cytoplasmic and nuclear and did not colocalise with microtubules. The protein was enriched at the spindle poles during mitosis and we found that γ-tubulin coimmunoprecipitated with δ-tubulin. Together, the data indicate a specialised role for mammalian δ-tubulin that is distinct from other known tubulins. Summary | Full Text | PDF (238 kb) |
| A centriole protein that does something Trends in Cell Biology, Volume 8, Issue 7, 1 December 1998, Pages 265 W Marshall Abstract 141, 455–467 Abstract | Full Text | PDF (31 kb) |
Copyright © 1975 The Biophysical Society. All rights reserved.
Biophysical Journal, Volume 15, Issue 8, 831-841, 1 August 1975
doi:10.1016/S0006-3495(75)85857-7
Research Article
R. Rikmenspoel
The results of previous radiation experiments, which indicated that the centriole serves as a control center for bull sperm motility, appear to be in conflict with experiments showing that the bull sperm flagellum is an autonomous oscillator. To resolve this conflict experiments were conducted to calibrate absolutely the dose-response curves for the radiation damage, and to measure the force production and the mechanochemical energy conversion after irradiation in bull sperm. The results indicate that the centriole acts as a mechanical anchor for the contractile fibers.