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Sperm Flagellum (sperm + flagellum)

Distribution by Scientific Domains

Medical Sciences	50%
Life Sciences	50%

Selected Abstracts

Measurement of the force and torque produced in the calcium response of reactivated rat sperm flagella

CYTOSKELETON, Issue 1 2001
Mark J. Moritz
Abstract Rat sperm that are demembranated with Triton X-100 and reactivated with Mg-ATP show a strong mechanical response to the presence of free calcium ion. At pCa < 4, the midpiece region of the flagellum develops a strong and sustained curvature that gives the cell the overall appearance of a fishhook [Lindemann and Goltz, 1988: Cell Motil. Cytoskeleton 10:420,431]. In the present study, the force and torque that maintain the calcium-induced hook have been examined quantitatively. In addition, full-length and shortened flagella were manipulated to evaluate the plasticity of the hooks and determined the critical length necessary for maintaining the curvature. The hooks were found to be highly resilient, returning to their original configuration (>95%) after being straightened and released. The results from manipulating the shortened flagella suggest that the force holding the hook in the curved configuration is generated in the basal 60 ,m of the flagellum. The force required to straighten the calcium-induced hooks was measured with force-calibrated glass microprobes, and the bending torque was calculated from the measured force. The force and torque required to straighten the flagellum were found to be proportional to the change in curvature of the hooked region of the flagellum, suggesting an elastic-like behavior. The average torque to open the hooks to a straight position was 2.6 (±1.4) × 10 -7 dyne × cm (2.6 × 10 -14 N × m) and the apparent stiffness was 4.3 (±1.3) × 10 -10 dyne × cm2 (4.3 × 10 -19 N × m2). The stiffness of the hook was determined to be approximately one quarter the rigor stiffness of a rat sperm flagellum measured under comparable conditions. Cell Motil. Cytoskeleton 49:33,40, 2001. © 2001 Wiley-Liss, Inc. [source]

A gene trap knockout of the abundant sperm tail protein, outer dense fiber 2, results in preimplantation lethality,

GENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 11 2006
Nicholas A. Salmon
Abstract Outer dense fiber 2 (Odf2) is highly expressed in the testis where it encodes a major component of the outer dense fibers of the sperm flagellum. Furthermore, ODF2 protein has recently been identified as a widespread centrosomal protein. While the expression of Odf2 highlighted a potential role for this gene in male germ cell development and centrosome function, the in vivo function of Odf2 was not known. We have generated Odf2 knockout mice using an Odf2 gene trapped embryonic stem cell (ESC) line. Insertion of a gene trap vector into exon 9 resulted in a gene that encodes a severely truncated protein lacking a large portion of its predicted coil forming domains as well as both leucine zipper motifs that are required for protein,protein interactions with ODF1, another major component of the outer dense fibers. Although wild-type and heterozygous mice were recovered, no mice homozygous for the Odf2 gene trap insertion were recovered in an extended breeding program. Furthermore, no homozygous embryos were found at the blastocyst stage of embryonic development, implying a critical pre-implantation role for Odf2. We show that Odf2 is expressed widely in adults and is also expressed in the blastocyst stage of preimplantation development. These findings are in contrast with early studies reporting Odf2 expression as testis specific and suggest that embryonic Odf2 expression plays a critical role during preimplantation development in mice. genesis 44:515,522, 2006. Published 2006 Wiley-Liss, Inc. [source]

Tyrosine phosphorylation of a 38-kDa capacitation-associated buffalo (Bubalus bubalis) sperm protein is induced by L -arginine and regulated through a cAMP/PKA-independent pathway

INTERNATIONAL JOURNAL OF ANDROLOGY, Issue 1 2008
S. C. Roy
Summary The aim of the present study was to determine the effect of l -arginine on nitric oxide (NO,) synthesis, capacitation and protein tyrosine phosphorylation in buffalo spermatozoa. Ejaculated buffalo spermatozoa were capacitated in the absence or presence of heparin, or l -arginine or N, -nitro- l -arginine methyl ester (l -NAME), an inhibitor of nitric oxide synthase (NOS) for 6 h. Capacitating spermatozoa generated NO, both spontaneously and following stimulation with l -arginine and l -NAME quenched such l -arginine-induced NO, production. Immunolocalization of NOS suggested for existence of constitutive NOS in buffalo spermatozoa. l -Arginine (10 mm) was found to be a potent capacitating agent and addition of l -NAME to the incubation media attenuated both l -arginine and heparin-induced capacitation and suggested that NO, is involved in the capacitation of buffalo spermatozoa. Two sperm proteins of Mr 38 000 (p38) and 20 000 (p20) were tyrosine phosphorylated extensively by both heparin and l -arginine. Of these, the tyrosine phosphorylation of p38 was insensitive to both induction by cAMP agonists as well as inhibition by a protein kinase A (PKA) inhibitor. Further, most of these l -arginine-induced tyrosine phosphorylated proteins were localized to the midpiece and principal piece regions of flagellum of capacitated spermatozoa and suggested that sperm flagellum takes active part during capacitation. These results indicated that l -arginine induces capacitation of buffalo spermatozoa through NO, synthesis and tyrosine phosphorylation of specific sperm proteins involving a pathway independent of cAMP/PKA. [source]

Arrest of flagellum morphogenesis with fibrous sheath immaturity of human spermatozoa

ANDROLOGIA, Issue 2 2006
D. Escalier
Summary Morphogenesis of the mammalian sperm flagellum is characterized by the assembly of axonemal and peri-axonemal structures. The incorporation of mitochondria into the flagellum results from complex cellular events, including flagellum compartmentalization and membrane and organelle reorganization. These events are striking in the annulus, which progressively relocates from the neck to the principal piece of the flagellum. This study presents a human sperm phenotype with failure of the annulus relocation, absence of mitochondrial sheath and a fibrous sheath at intermediate step of assembly. The sperm nucleus was fully condensed but with deep invaginations engulfing the acrosome. The distal pole of some mitochondria exhibited an unusual dense substance. This rare human sperm phenotype was found in a consanguineous patient, suggesting a genetic origin. These anomalies raise the question of the mechanisms that lead to impairment of both the annulus relocation and the deposit of proteins on the fibrous sheath during spermiogenesis. [source]