Hyperactivation is the mode conversion from constant‐curvature beating to constant‐frequency beating under a constant rate of microtubule sliding

Ohmuro, Junko; Ishijima, Sumio

doi:10.1002/mrd.20521

Cited by 33 publications

(33 citation statements)

References 26 publications

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“…The velocity of the microtubule sliding of the sperm flagella in each species remained constant before and after the hyperactivation because of the balanced decrease in the beat frequency and increase in the maximum shear angle [Ohmuro and Ishijima, 2006;Kaneko et al, 2007]. However, the value of the sliding velocity was apparently different among the golden hamster, monkey, and Suncus spermatozoa [Kaneko et al, 2007].…”

Section: Load Dependency Of Microtubule Sliding Velocitymentioning

confidence: 95%

“…In fact, a comparison of the shear angle of the flagellar bends of the hyperactivated spermatozoa with that of the nonhyperactivated spermatozoa revealed that the large bends at the flagellar base of the hyperactivated spermatozoa were induced by an increase in the total length of the microtubule sliding [Ohmuro and Ishijima, 2006]. An important role of the basal regions in the ciliary movement has been emphasized by Kinoshita and Kamada [1939].…”

Section: Biphasic Characteristic Of Flagellar Beatingmentioning

confidence: 99%

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The velocity of microtubule sliding: Its stability and load dependency

Ishijima

2007

Cell Motil. Cytoskeleton

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It is now well understood that ATP-driven active sliding between the doublet microtubules in the sperm axoneme generates flagellar movement. However, much remains to be learned about how this movement is controlled. Detailed analyses of the flagellar beating of the mammalian spermatozoa revealed that there were two beating modes at a constant rate of microtubule sliding: that is, a nearly constant-curvature beating in nonhyperactivated spermatozoa and a nearly constant-frequency beating in hyperactivated spermatozoa. The constant rate of microtubule sliding suggests that the beat frequency and waveform of the flagellar beating are dependently regulated. Comparison of the sliding velocity of several mammalian and sea urchin sperm flagella with their mechanical property clarified that the sliding velocity of the microtubule was determined by the stiffness of the flagellum at its base, and that its relationship was expressed by a logarithmic equation that is similar to the classical force-velocity equation of the muscle contraction. Data from sea urchin spermatozoa also satisfied the equation, suggesting that the same microtubule sliding system functions in both the mammalian and echinoderm spermatozoa. Cell Motil. Cytoskeleton 64: 809-813, 2007

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Section: Load Dependency Of Microtubule Sliding Velocitymentioning

confidence: 95%

Section: Biphasic Characteristic Of Flagellar Beatingmentioning

confidence: 99%

The velocity of microtubule sliding: Its stability and load dependency

Ishijima

2007

Cell Motil. Cytoskeleton

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“…For example, comparisons between mutants of Chlamydomonas can provide a powerful analysis of the defects present in the sperm of sub-fertile men and identify potential interactions of novel signalling complexes (see Zhang et al 2004). Detailed imaging of the flagella motion (Ohmuro & Ishijima 2006) will allow a clear understanding of how the dynamics of the signalling complexes affect waveform. In addition to the studies on the axoneme, there is also data on the sperm accessory structures (fibrous sheath, outer dense fibres).…”

Section: Calcium Oscillations In Sperm -A New Signalling System?mentioning

confidence: 99%

Counting sperm does not add up any more: time for a new equation?

Lefièvre¹,

Bedu-Addo²,

Conner³

et al. 2007

Reproduction

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Although sperm dysfunction is the single most common cause of infertility, we have poor methods of diagnosis and surprisingly no effective treatment (excluding assisted reproductive technology). In this review, we challenge the usefulness of a basic semen analysis and argue that a new paradigm is required immediately. We discuss the use of at-home screening to potentially improve the diagnosis of the male and to streamline the management of the sub-fertile couple. Additionally, we outline the recent progress in the field, for example, in proteomics, which will allow the development of new biomarkers of sperm function. This new knowledge will transform our understanding of the spermatozoon as a machine and is likely to lead to non-ART treatments for men with sperm dysfunction. Reproduction (2007) 133 675-684

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“…It was later shown to be essential in fertilization (Burkman, 1984;Suarez et al, 1991). It is characterized by sperm changing from a linear, forward-progressing swimming, where the flagellar beat is of lower amplitude and high frequency, to a somewhat lower frequency and a much larger beat amplitude (Cooper and Woolley, 1982; Ishijima and Mohri, 660 Lindemann and Lesich CYTOSKELETON 1985; Suarez and Osman, 1987;Ohmuro and Ishijima, 2006). After conversion to the greater amplitude form of beating, the swimming behavior becomes less forwardly progressive and more of an in-place tumbling motion.…”

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confidence: 99%

Functional anatomy of the mammalian sperm flagellum

2016

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The eukaryotic flagellum is the organelle responsible for the propulsion of the male gamete in most animals. Without exception, sperm of all mammalian species use a flagellum for swimming. The mammalian sperm has a centrally located 9 1 2 arrangement of microtubule doublets and hundreds of accessory proteins that together constitute an axoneme. However, they also possess several characteristic peri-axonemal structures that make the mammalian sperm tail function differently. These modifications include nine outer dense fibers (ODFs) that are paired with the nine outer microtubule doublets of the axoneme, and are anchored in a structure called the connecting piece located at the base. The presence of the ODFs and connecting piece, and the absence of a basal body, dictate that physical forces generated by the dynein motors are transmitted to the base of the flagellum through the ODFs. Mammalian sperm flagella also possess a mitochondrial and a fibrous sheath that encircle most of the axoneme. These sheaths and the ODFs add mechanical rigidity to the flagellum creating the functional effect of increasing bend wavelength, which requires the entrainment of more dynein motors in the production of a single wave. The sheaths also act as a retinaculum and maintain the integrity of the central axoneme when large bending torques are generated by dynein. Large torque production is crucial to the process of hyperactivation and the unique motility transitions associated with effective fertilizing capacity. Consequently, these specialized anatomical features are essential for the effective interaction of sperm with the female reproductive tract and ovum. V C 2016 Wiley Periodicals, Inc.Key Words: axoneme; outer dense fibers; fibrous sheath; outer doublets; dynein; connecting piece; hyperactivation; sperm motility Introduction E ukaryotic cilia and flagella are highly conserved and ubiquitous organelles present in most animals, as well as many lower plants and eukaryotic protozoa. In the vertebrate lineage, the eukaryotic flagellum is universally employed to propel the male gamete. In the mammalian branch of the vertebrates, the sperm tail is always a modified flagellum with some characteristic accessory features that are added onto the basic 9 1 2 axoneme of microtubules found in most cilia and flagella. Figure 1 shows transmission electron micrographs (TEMs) of a mouse sperm flagellum in cross section at several positions along the length of the flagellum. The central axoneme is visible with its nine outer doublets surrounding a pair of single central microtubules (central pair or CP). Each of the outer microtubule doublets bears two rows of projections called the inner row and outer row of dynein arms. These arms are composed of the dynein motor proteins that power motility. The dynein arms are the source of the motive force that bends the flagellum. The dynein heavy chains (DHC) of the arms form bridges between the outer doublets and undergo a Mg-ATP driven power stroke that generates a sliding (or shearing) action between t...

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Hyperactivation is the mode conversion from constant‐curvature beating to constant‐frequency beating under a constant rate of microtubule sliding

Cited by 33 publications

References 26 publications

The velocity of microtubule sliding: Its stability and load dependency

The velocity of microtubule sliding: Its stability and load dependency

Counting sperm does not add up any more: time for a new equation?

Functional anatomy of the mammalian sperm flagellum

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