1,720,967 research outputs found
Retinoic acid regulation of human spermatogonial genes
No full textThe retinoic acid (RA) is a vitamin A metabolite that, in the mouse, has been demonstrated to regulate the spermatogonial differentiation, the meiotic entry, the initiation of the spermatid elongation and the release of spermatozoa. Over the years several RA responsive genes have been identified. They have been involved in the mediation of one or more events. Among others Stra8 is crucial to induce the spermatogonial differentiation and the meiotic entry [1]. In our study we tested the hypothesis that the RA is able to regulate the same genes in the human spermatogonia
Retinoic acid down-regulates GDNF expression in immature Sertoli cells
No full textThe balance between retinoic acid (RA) and GDNF (Glial cell-derived neurotrophic factor) determines the behavior of the spermatogonial stem cell
compartment. Importantly, RA inhibits GDNF expression during the cycle of the seminiferous epithelium [1]. However, the molecular mechanism
by which RA impinge on GDNF regulation within the testis is not known.
The aim of the present project is to clarify the molecular mechanisms underlying RA-dependent gdnf regulation in mouse testis. Deepening these
dynamics could ameliorate the comprehension of SSCs niche and the mechanism behind SSCs self-renewal
Inactivation of Numb and Numblike in spermatogonial stem cells by cell-permeant Cre recombinase
No full textSpermatogonial stem cells (SSC) ensure continuous production of mammalian male gametes. In rodents, the SSC are Asingle spermatogonia (As). Gene loss and gain-of-function mutations have provided some clues into SSC function, but genetic dissection of SSC physiology has not yet been accomplished. The adaptor protein Numb is an evolutionarily conserved protein originally implicated in the control of the fate of sibling cells. Mice homozygous for deficient Numb die before embryonic day 11.5, hampering the analysis of its inactivation in postnatal male germline. Here, we have developed an experimental strategy to conditionally inactivate Numb and its homolog Numb like in the postnatal germline by in vitro delivery of cell-permeant Cre recombinase. Cre-transduced SSC isolated from wild-type mice retained their ability to self-renew and to differentiate in vivo, as shown by their ability to give rise to normal spermatogenic colonies when transplanted in recipient testes. Cre-transduced SSC from conditional mutant mouse line were able to colonize recipient testes upon transplantation. Inactivation of either Numb or Numb like in SSC did not impair the development of normal donor-derived spermatogenesis. However, compared to single-null SSC, double-null SSC generated shorter colonies in which the germ cells failed to differentiate beyond the round spermatid stage, underscoring the essential roles of both Numb and Numblike in spermatogenesis. We demonstrate the feasibility of gene inactivation in adult SSC by ex vivo Cre delivery. This provides a means to analyze the function of genes that operate on a cell-autonomous basis or those that are coupled to signals that SSC receive from bystander cells. (C) 2009 Published by Elsevier Ltd. on behalf of International Society of Differentiatio
Expression of the adaptor protein m-Numb in mouse male germ cells
No full textJCR Subject Category: Reproductive Biology IF= 3.1
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Analysis of spermatogonial marker expression in non-human primate
No full textHuman and non-human primate spermatogonia (SPG) share important similarities [1]. Recently, a new classification was proposed for the human SPG compartment based on protein markers such as, MAGEA4, GFRA1, KIT, etc. [2]. Even though, the kinetic of monkey SPG has been previously investigated [3], less is known about the expression profile of spermatogonial markers. Here we tested the hypothesis that SPG marker expression and progression in human and non-human primates is conserved. To this end, we analyzed the expression of human markers, in Macaca fascicularis SPG and their proliferation activity during the stages of the seminiferous epithelium cycle [4, 5]
Variations on the Author
Full text link“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
Distribution of the spermatogonial subpopulations during the stages of the epithelial cycle
No full textThe maintenance of seminiferous epithelium function hinges on the biological activity of spermatogonial stem cells (SSCs), they play a pivotal role in maintaining spermatogenesis, the process by which spermatozoa are produced, and ensuring continuous sperm production throughout a male's reproductive life. Despite their critical importance, our understanding of SSC biology, particularly their spatial distribution within the testicular microenvironment, remains limited, prompting investigations into their precise localization and the existence of specialized microenvironments known as spermatogonial stem cell niches. In rodents, research has revealed that undifferentiated spermatogonia, including SSCs, exhibit non-random distribution within the seminiferous tubules, preferring areas adjacent to interstitial regions rather than tubule-tubule contact regions at specific stages of the seminiferous epithelium cycle (SEC). Here, we present a pioneering investigation into the topological localization of undifferentiated spermatogonia (undiff-SPG) in primates, specifically Macaca Fascicularis, using immunofluorescence (IF) and immunohistochemistry (IHC) analyses with specific markers. Remarkably, our examination of undiff-SPG subsets' relative positioning along the basal membrane in relation to interstitial tissue uncovers significant distinctions. While PIWIL4+ and NANOS3+ undiff-SPG exhibit random distribution along the basal compartment across all SEC stages, GFRA1+ undiff-SPG display stage-dependent localization patterns. During the first half of the cycle, GFRA1+ undiff-SPG preferentially inhabit regions adjacent to the interstitium, while in the second half, they predominantly occupy tubule-tubule contact regions. This spatial organization appears to be coordinated with the stages of the SEC, suggesting dynamic regulation of SSC behavior throughout the process of sperm production. Our study contributes to the growing body of literature aimed at deciphering the complexities of SSC biology and the regulation of spermatogenesis in mammalian species, with implications for understanding male fertility, reproductive health, and the development of novel therapeutic interventions targeting SSCs
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