Changes in flagellar movement of rat spermatozoa along the length of the epididymis: Manual and computer-aided image analysis
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The different patterns of motility of rat spermatozoa during epididymal transit were studied in vitro using high-speed videomicroscopy. The sperm images were analysed after manual tracing as well as with a computer imaging system. The present work is the first which reports both the swimming path of the sperm head and the characteristics of flagellation in this species. The hook-shaped head of the rat spermatozoa allowed us to demonstrate the two-dimensional (2D) swmming movement compared to the three-dimensional (3D) sperm motion which was mainly related to rotation of the head. Immotile spermatozoa entered the initial segment of the testis and showed rigid flagella. The potential for sperm motility occured abruptly in the proximal caput region, and different patterns of flagellation were observed: vibrating, motile in place, motile with a static curvature of the midpiece resulting in a spinning motion or a circular path, and forward progressive movement with regular rotation of the head. The pattern of sperm movement became homogeneous in the distal cauda where the whole sperm population swam in a straight line. A static curvature appeared in the midpiece portion when the spermatozoa reached the proximal caput region. The formation of the static curvature was observed on both sides of the rat flagellum which were easily indicated by the head-shaped projection of the head and the axonemal side of the principal wave. As soon as they moved, the spermatozoa successively initiated principal (P) and reverse (R) waves, but the waves were visible only distal to the static curvature. The midpiece stiffness progressively decreased during the epididymal maturation; simultaneously the static curvature showed a larger radius and then disappeared. Consequently, the initiation of waves which was first seen in the distal part of the flagellum of immature cells occurred progressively near the junction with the head of maturing spermatozoa. These changes in sperm motion previously shown in rams and now in rats might be a general phenomenon in mammals. The high resolution of this computer imaging system applied tosperm motion showing a well-characterized “side of the flagellum” should allow sensitive detection of biochemical effects on flagellar beating. © 1996 Wiley-Liss, Inc.The presence of motility inhibitors in seminal plasma and within spermatozoa from control and infertile men with poor sperm motility was investigated using demembranated reactivated human spermatozoa. No difference was found in the inhibitory capacities in seminal plasma of patients with poor sperm motility (< 50%) when compared with that of fertile controls with motility above 50%. No correlation was observed between inhibitory capacity and sperm motility. However, when extracts of spermatozoa from these patients were tested for the presence of inhibitor, it was observed that three of nine patients had an inhibitor in their sperm extract. By contrast, all sperm extracts from fertile control subjects were devoid of inhibitor. It was concluded that the presence of a motility inhibitor in seminal plasma does not explain the poor sperm motility observed in patients. The presence of a motility inhibitor within spermatozoa, however, may represent an important factor in the etiology of the poor sperm motility observed in some patients.
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Capacitation
Acrosome reaction
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Basal (medicine)
Basal body
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After leaving the testis, sperm undergo two sequential maturational processes before acquiring fertilizing capacity: sperm maturation in the male epididymis, and sperm capacitation in the female reproductive tract. During their transit through the epididymis, sperm experience several maturational changes; the acquisition of motility is one of them. The molecular basis of the regulation of this process is still not fully understood. Sperm are both transcriptionally and translationally silent, therefore post-translational modifications are essential to regulate their function. The post-translational modification by the addition of O-linked β-N-acetylglucosamine (O-GlcNAc) can act as a counterpart of phosphorylation in different cellular processes. Therefore, our work was aimed to characterize the O-GlcNAcylation system in the male reproductive tract and the occurrence of this phenomenon during sperm maturation. Our results indicate that O-GlcNAc transferase (OGT), the enzyme responsible for O-GlcNAcylation, is present in the testis, epididymis and immature caput sperm. Its presence is significantly reduced in mature cauda sperm. Consistently, caput sperm display high levels of O-GlcNAcylation when compared to mature cauda sperm, where it is mostly absent. Our results indicate that the modulation of O-GlcNAcylation takes place during sperm maturation and suggest a role for this post-translational modification in this process.
Capacitation
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Axoneme
Gliding motility
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Charactering the sperm specific proteins is to elucidate the function in the process of reproduction and to develop them as effective targets for reproductive regulation.Mammalian sperm after spermiogenisis in testis seminiferous tubules,although they are tadpole-like,are neither able to swim nor to fertilize the egg.Sperm must undergo modification in epididymis to be mature,which is called epididymal sperm maturation.This process mainly includes the sperm membrane protein modification.During sperm traveling through the epididymis tubes,some proteins are removed away,some are binding on,and some proteins are glycosylated or phosphorylated.Therefore,the identification of epididymal protein,especially the epididymal-specific protein,is one of the most important points to reveal the function of sperm.The function of epididymal-specific protein,especially on sperm maturation and sperm protection,is reviewed in this paper.
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Significance Trypanosoma brucei is a highly invasive pathogen capable of penetrating deeply into host tissues. To understand how flagellar motility facilitates cell penetration, we used cryo-electron tomography (cryo-ET) to visualize two genetically anucleate mutants with different flagellar motility behaviors. We found that the T. brucei cell body is highly deformable as defined by changes in cytoskeletal twist and spacing, in response to flagellar beating and environmental conditions. Based on the cryo-ET models, we proposed a mechanism of how flagellum motility is coupled to cell shape changes, which may facilitate penetration through size-limiting barriers.
Penetration (warfare)
Limiting
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Flagella and motility are widespread virulence factors among pathogenic bacteria. Motility enhances the initial host colonization, but the flagellum is a major antigen targeted by the host immune system. Here, we demonstrate that pathogenic E. coli strains employ a mechanosensory function of the flagellar motor to activate flagellar expression under high loads, while repressing it in liquid culture. We hypothesize that this mechanism allows pathogenic E. coli to regulate its motility dependent on the stage of infection, activating flagellar expression upon initial contact with the host epithelium, when motility is beneficial, but reducing it within the host to delay the immune response.
Pathogenic bacteria
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Prokaryotes use a wide variety of structures to facilitate motility. The majority of research to date has focused on swimming motility and the molecular architecture of the bacterial flagellum. While intriguing questions remain, especially concerning the specialized export system involved in flagellum assembly, for the most part the structural components and their location within the flagellum and function are now known. The same cannot be said of the other apparati including archaeal flagella, type IV pili, the junctional pore, ratchet structure and the contractile cytoskeleton used by a variety of organisms for motility. In these cases, many of the structural components have yet to be identified and the mechanism of action that results in motility is often still poorly understood. Research on the bacterial flagellum has greatly aided our understanding of not only motility but also protein secretion and genetic regulation systems. Continued study and understanding of all prokaryotic motility structures will provide a wealth of knowledge that is sure to extend beyond the bounds of prokaryotic movement.
Gliding motility
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