1,720,960 research outputs found
Phospholipid hydroperoxide glutathione peroxidase: Expression pattern during testicular development in mouse and evolutionary conservation in spermatozoa
No full textPhospholipid hydroperoxide glutathione peroxidase (PHGPx) is a selenoprotein belonging to the family of glutathione peroxidases and has been implicated in antioxidative defense and spermatogenesis. PHGPx accounts for almost the entire selenium content of mammalian testis. In an attempt to verify the expression pattern of PHGPx, testes of mouse mutants with arrest at different stages of germ cell development and testes of mice at different ages were subjected to immunostaining with a monoclonal anti-PHGPx antibody. PHGPx was detected in Leydig cells of testes in all developmental stages. In the seminiferous tubuli, the PHGPx staining was first observed in testes of 21-day-old mice which is correlated with the appearance of the first spermatids. This result was confirmed when the testes of mutant mice with defined arrest of germ cell development were used. An immunostaining was observed in the seminiferous tubuli of olt/olt and qk/qk mice which show an arrest at spermatid differentiation. In Western blot analysis of proteins extracted from testes of mutant mice and from developing testes, two signals at 19- and 22-kDa were observed which confirm the existence of two PHGPx forms in testicular cells. In mouse spermatozoa, a subcellular localization of PHGPx and sperm mitochondria-associated cysteine-rich protein (SMCP) was demonstrated, indicating the localization of PHGPx in mitochondria of spermatozoa midpiece. For verifying the midpiece localization of PHGPx in other species, spermatozoa of Drosophila melanogaster, frog, fish, cock, mouse, rat, pig, bull, and human were used in immunostaining using anti-PHGPx antibody. A localization of PHGPx was found in the midpiece of spermatozoa in all species examined. In electronmicroscopical analysis, PHGPx signals were found in the mitochondria of midpiece. These results indicate a conserved crucial role of PHGPx during sperm function and male fertility. (C) 2004 Wiley-Liss, Inc
Triple knockouts reveal gene interactions affecting fertility of male mice
No full textTriple knockout mice were used to investigate the interactions of five genes that were expressed in meiotic and haploid spermatogenic cells in mice, transition protein 2 (Tnp2), proacrosin (Acr), histone H1.1 (H1.1), histone H1t (H1t), and sperm mitochondria-associated cysteine-rich protein (Smcp). TNP2 functions in the replacement of histones and the initial condensation of the spermatid nucleus. The linker histone subtypes H1.1 and H1t are expressed at high levels in meiotic and early haploid cells. ACR, a protease that is stored as a proenzyme in the acrosome, is activated during the acrosome reaction and functions in binding of sperm to the zona pellucida . SMCP is a structural protein in the outer membranes of sperm mitochondria that functions in motility. Previous work demonstrates that homozygous knockout mice lacking each of these proteins individually exhibit no defect in fertility on mixed genetic backgrounds. In contrast, the present study demonstrates that five triple knockout lines, Acr/H1.1/Smcp, Acr/Tnp2/Smcp, Tnp2/H1.1/Smcp, Acr/H1t/Smcp, Tnp2/H1t/Smcp, exhibit drastic reductions in fertility on mixed genetic backgrounds. Analysis of fertility parameters reveal that the decreased fertility is due to line-dependent defects in sperm motility in vitro correlated with reduced migration in the female reproductive tract, and decreased fertilization due to defects in adhesion of sperm to the zona pellucida, the membrane surrounding the egg. It was also found that triple knockout males, that are hemizygous for one locus and homozygous for two other loci, are as subfertile as homozygous triple knockout males, a phenomenon known as haploinsufficiency. These findings demonstrate that male fertility involves synergistic interactions of genes that function in sperm motility and sperm-egg adhesion during fertilization. (C) 2005 Wiley-Liss, Inc
Prm3, the fourth gene in the mouse protamine gene cluster, encodes a conserved acidic protein that affects sperm motility
No full textThe protamine gene cluster containing the Prm1, Prm2, Prm3, and Tnp2 genes is present in humans, mice, and rats. The Prm1, Prm2, and Tnp2 genes have been extensively studied, but almost nothing is known about the function and regulation of the Prm3 gene. Here we demonstrate that an intronless Prm3 gene encoding a distinctive small acidic protein is present in 13 species from seven orders of mammals. We also demonstrate that the Prm3 gene has not generated retroposons, which supports the contention that genes that are expressed in meiotic and haploid spermatogenic cells do not generate retroposons. The Prm3 mRNA is first detected in early round spermatids, while the PRM3 protein is first detected in late spermatids. Thus, translation of the Prm3 mRNA is developmentally delayed similar to the Prm1, Prm2, and Tnp2 mRNAs. In contrast to PRM1, PRM2, and TNP2, PRM3 is an acidic protein that is localized in the cytoplasm of elongated spermatids and transfected NIH-3T3 cells. To elucidate the function of PRM3, the Prm3 gene was disrupted by homologous recombination. Sperm from Prm3(-/-) males exhibited reductions in motility, but the fertility of Prm3(-/-) and Prm3(+/+) males was similar in matings of one male and one female. We have developed a competition test in which a mutant male has to compete with a rival wildtype male to fertilize a female; the implications of these results are also discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Sexual selection, genetic conflict, selfish genes, and the atypical patterns of gene expression in spermatogenic cells
No full textAbstractThis review proposes that the peculiar patterns of gene expression in spermatogenic cells are the consequence of powerful evolutionary forces known as sexual selection. Sexual selection is generally characterized by intense competition of males for females, an enormous variety of the strategies to maximize male reproductive success, exaggerated male traits at all levels of biological organization, co-evolution of sexual traits in males and females, and conflict between the sexual advantage of the male trait and the reproductive fitness of females and the individual fitness of both sexes. In addition, spermatogenesis is afflicted by selfish genes that promote their transmission to progeny while causing deleterious effects. Sexual selection, selfish genes, and genetic conflict provide compelling explanations for many atypical features of gene expression in spermatogenic cells including the gross overexpression of certain mRNAs, transcripts encoding truncated proteins that cannot carry out basic functions of the proteins encoded by the same genes in somatic cells, the large number of gene families containing paralogous genes encoding spermatogenic cell-specific isoforms, the large number of testis-cancer-associated genes that are expressed only in spermatogenic cells and malignant cells, and the overbearing role of Sertoli cells in regulating the number and quality of spermatozoa
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
