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Fibrous Sheath (fibrous + sheath)

Distribution by Scientific Domains

Medical Sciences	50%
Life Sciences	50%

Selected Abstracts

TEM, FISH and molecular studies in infertile men with pericentric inversion of chromosome 9

ANDROLOGIA, Issue 4 2006
G. Collodel
Summary Pericentric inversions involving the secondary constriction (qh) region of chromosome 9 are considered to be normal variants of human karyotype. A number of investigators have suggested that chromosomal anomalies can contribute to human infertility causing spermatogenetic derangement. The present study was aimed at verifying the influence of chromosome 9 inversion on human spermatogenesis. Semen samples of 18 male carriers of chromosome 9 inversion, analysed by light microscopy, revealed that five patients were azoospermic. PCR analysis demonstrated that two of them also had Y microdeletions. The other 13 showed generally normal sperm concentrations and reduced motility. The morphological characteristics of sperm were studied by TEM and the data were elaborated by a mathematical formula. Sperm pathologies resulted more frequently in the studied group compared to controls, particularly apoptosis. Partial sequences of the A-kinase anchoring protein (Akap) 4 and 3 genes were performed in all patients, as a previous study by our group highlighted Dysplasia of Fibrous Sheath (DFS) defect in two men with inv 9 investigations. The possible effect of chromosome 9 inversion on meiotic chromosome segregation was investigated by FISH, which showed an increased incidence of diploidy. We hypothesized that this inversion could have variable effects on spermatogenesis, from azoospermia to severely altered sperm morphology, motility and meiotic segregation. [source]

Ultrastructure of spermatozoa of lizards in the genus Mabuya from Central Brazil

ACTA ZOOLOGICA, Issue 1 2009
S. M. De Sá Mandel
Abstract This is the first description of spermatozoal ultrastructure of Mabuya skinks. The spermatozoa of the species studied are filiform, consisting of a head region, a midpiece and a tail. The head is characterized by the following features: a depressed acrosome anteriorly, an acrosome vesicle divided into cortex and medulla, paracrystalline subacrosomal material, a pointed tip perforatorium, a circular perforatorium base plate inside the subacrosomal cone, an epinuclear lucent zone separated from the subacrosomal cone by a membrane, a large nuclear rostrum, and round nuclear shoulders. The midpiece presents a bilateral stratified laminar structure, a distal centriole, peripheral fibres 3 and 8 grossly enlarged, columnar mitochondria with linear cristae, dense body rings and a triangular annulus. Finally, the tail is composed of a principal piece and an end piece. An axoneme and a fibrous sheath characterize the principal piece, and the end piece is formed only by an axoneme, which loses its pattern in the last portion. Comparisons with members of Teiidae revealed differences in the numbers of dense rings. A well-developed epinuclear lucent zone in Mabuya is less prominent among teiids. In the spermatozoa of Mabuya, the first ring of dense bodies is very large, uniquely resembling the condition present in snakes. [source]

Ultrastructure of the spermatozoon of Apus apus (Linnaeus 1758), the common swift (Aves; Apodiformes; Apodidae), with phylogenetic implications

ACTA ZOOLOGICA, Issue 4 2005
Barrie G. M. Jamieson
Abstract The spermatozoon of Apus apus is typical of non-passerines in many respects. Features shared with palaeognaths and the Galloanserae are the conical acrosome, shorter than the nucleus; the presence of a proximal as well as distal centriole; the elongate midpiece with mitochondria grouped around an elongate distal centriole; and the presence of a fibrous or amorphous sheath around the principal piece of the axoneme. The perforatorium and endonuclear canal are lost in A. apus as in some other non-passerines. All non-passerines differ from palaeognaths in that the latter have a transversely ribbed fibrous sheath whereas in non-passerines it is amorphous, as in Apus, or absent. The absence of an annulus is an apomorphic but homoplastic feature of swift, psittaciform, gruiform and passerine spermatozoa. The long distal centriole, penetrating the entire midpiece, is a remarkably plesiomorphic feature of the swift spermatozoa, known elsewhere only in palaeognaths. The long centriole of Apus, if not a reversal, would be inconsistent with the former placement of the Apodiformes above the Psittaciformes from DNA,DNA hybridization. In contrast to passerines, in A. apus the microtubules in the spermatid are restricted to a transient single row encircling the cell. The form of the spermatozoon fully justifies the exclusion of swifts from the passerine family Hirundinidae. [source]

Ultrastructure of the spermatid of Caprimulgus europaeus Linnaeus 1758, the European nightjar (Aves; Caprimulgidae), with phylogenetic implications

JOURNAL OF MORPHOLOGY, Issue 10 2006
Sandro Tripepi
Abstract The sperm of Caprimulgus europaeus is typical of other nonpasserines in many respects. Features shared with Paleognathae and Galloanserae are the conical acrosome, shorter than the nucleus; the presence of a perforatorium and endonuclear canal; the presence of a proximal as well as distal centriole; the elongate midpiece with mitochondria grouped around a central axis (here maximally six mitochondria in ,10 tiers); and the presence of a fibrous or amorphous sheath around the principal piece of the axoneme. A major (apomorphic) difference from paleognaths and galloanserans is the short distal centriole, the midpiece being penetrated for most of its length by the axoneme and for only a very short proximal portion by the centriole. Nonpasserines differ from paleognaths in that the latter have a transversely ribbed fibrous sheath, whereas in nonpasserines it is amorphous, as in Caprimulgus, or absent. The absence of an annulus is an apomorphic feature of Caprimulgus, apodiform, psittaciform, gruiform, and passerine sperm, homoplastic in at least some of these. In contrast to passerines, in Caprimulgus the cytoplasmic microtubules in the spermatid are restricted to a transient longitudinal manchette. The structure of the spermatid and spermatozoon is consistent with placement of the Caprimulgidae near the Psittacidae, but is less supportive of close proximity to the Apodidae, from DNA,DNA hybridization and some other analyses. J. Morphol. © 2006 Wiley-Liss, Inc. [source]

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells.

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 4 2010
Part 3: Developmental changes in spermatid flagellum, cytoplasmic droplet, egg plasma membrane, interaction of sperm with the zona pellucida
Abstract Spermiogenesis constitutes the steps involved in the metamorphosis of spermatids into spermatozoa. It involves modification of several organelles in addition to the formation of several structures including the flagellum and cytoplasmic droplet. The flagellum is composed of a neck region and middle, principal, and end pieces. The axoneme composed of nine outer microtubular doublets circularly arranged to form a cylinder around a central pair of microtubules is present throughout the flagellum. The middle and principal pieces each contain specific components such as the mitochondrial sheath and fibrous sheath, respectively, while outer dense fibers are common to both. A plethora of proteins are constituents of each of these structures, with each playing key roles in functions related to the fertility of spermatozoa. At the end of spermiogenesis, a portion of spermatid cytoplasm remains associated with the released spermatozoa, referred to as the cytoplasmic droplet. The latter has as its main feature Golgi saccules, which appear to modify the plasma membrane of spermatozoa as they move down the epididymal duct and hence may be partly involved in male gamete maturation. The end product of spermatogenesis is highly streamlined and motile spermatozoa having a condensed nucleus equipped with an acrosome. Spermatozoa move through the female reproductive tract and eventually penetrate the zona pellucida and bind to the egg plasma membrane. Many proteins have been implicated in the process of fertilization as well as a plethora of proteins involved in the development of spermatids and sperm, and these are high lighted in this review. Microsc. Res. Tech., 2010. © 2009 Wiley-Liss, Inc. [source]

Spermatid manchette: Plugging proteins to zero into the sperm tail

MOLECULAR REPRODUCTION & DEVELOPMENT, Issue 4 2001
Abraham L. Kierszenbaum
Spermiogenesis pursues three major objectives: (1) The safeguard of the male genome within the confines of a compact nucleus. (2) The accumulation of enzymes in the acrosome of be released at fertilization. (3) The development of a sperm propelling tail consisting of an axoneme surrounded by a scaffold of keratin-containing outer dense fibers and a fibrous sheath. Recent experimental data indicate that three keratins-Sak57, 0df1 and 0df2-and other proteins (the 26S proteasome and the 0df1-binding protein Spag4) are temporarily stored in the manchette before being sorted to the developing sperm tail. These findings support a general model for the manchette as an ephemeral structure timely developed and strategically positioned to provide a transient storage to both structural and signaling proteins. Some of the proteins are later sorted to the developing tail; others may participate in the reciprocal nuclear-cytoplasmic signaling pathways as the gene activity of the male genome gradually becomes silent. Mol. Reprod. Dev. 59: 347,349, 2001. © 2001 Wiley-Liss, Inc. [source]

Testicular protein Spag5 has similarity to mitotic spindle protein Deepest and binds outer dense fiber protein Odf1

MOLECULAR REPRODUCTION & DEVELOPMENT, Issue 4 2001
Xueping Shao
Abstract Outer dense fibers (ODF) and the fibrous sheath (FS) are major cytoskeletal structures in the mammalian sperm tail. The molecular mechanisms underlying their morphogenesis along the axoneme or their function are poorly understood. Recently, we reported the cloning and characterization of Odf2, a major ODF protein, and Spag4, an axoneme-binding protein, by virtue of their strong interaction with Odf1, the 27 kDa major ODF protein. We proposed a crucial role for leucine zippers in molecular interactions during sperm tail morphogenesis. Here we report the cloning and characterization of a novel gene, Spag5, which encodes a 200 kDa testicular protein that interacts strongly with Odf1. Spag5 is transcribed and translated in pachytene spermatocytes and spermatids. It bears 73% similarity with the mitotic spindle protein Deepest of unknown function. We identified two putative leucine zippers in the C-terminal part of the Spag5 protein, the downstream one of which is involved in interaction with Odf1. Interestingly, these motifs are present in Deepest. These results highlight the importance of the leucine zipper in sperm tail protein interactions. Mol. Reprod. Dev. 59: 410,416, 2001. © 2001 Wiley-Liss, Inc. [source]

Sperm morphology and aneuploidies: defects of supposed genetic origin

ANDROLOGIA, Issue 6 2006
G. Collodel
Summary As individuals with genetic sperm defects are intracytoplasmic sperm injection candidates, the study of the chromosomal constitution of their spermatozoa is of great interest. This study is a review of the current literature concerning fluorescence in situ hybridisation studies in spermatozoa with genetic sperm defect as ,round head', ,dysplasia of fibrous sheath' (DFS), ,primary ciliary dyskinesia' (PCD), the ,detached tail' and the ,absence of fibrous sheath'. Regarding sperm head defects, elevated XY disomy and diplodies were detected. Genetic defects affecting the sperm tail seemed to have a different correlation with chromosome meiotic segregation. Only chromosome 18, among the autosomes, was studied and the percentage of frequency of disomy was generally within the normal range. In the more frequently studied defect, DFS, the alterations in gonosome disomy and diploidy were recorded by different groups. Regarding PCD defects, elevated frequencies of disomy of sex chromosomes and diploidy were observed, whereas the absence of the fibrous sheath and the detached tail did not show any meiotic disturbance. The problem of genetic sperm defects should be seriously considered when these sperm are used for assisted reproduction, owing to the high risk of transmission of chromosomal imbalance and of mutations that could cause genetic sperm defects in offspring. [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]