Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The separation of the germ line from the soma is a classic concept in animal biology, and depending on species is thought to involve fate determination either by maternally localized germ plasm (''preformation'' or ``maternal inheritance'') or by inductive signaling (classically termed ``epigenesis'' or ``zygotic induction''). The latter mechanism is generally considered to operate in non-bilaterian organisms such as cnidarians and sponges, in which germ cell fate is determined at adult stages from multipotent stem cells. We have found in the hydrozoan cnidarian Clytia hemisphaerica that the multipotent ``interstitial'' cells (i-cells) in larvae and adult medusae, from which germ cells derive, express a set of conserved germ cell markers: Vasa, Nanos1, Piwi and PL10. In situ hybridization analyses unexpectedly revealed maternal mRNAs for all these genes highly concentrated in a germ plasm-like region at the egg animal pole and inherited by the i-cell lineage, strongly suggesting i-cell fate determination by inheritance of animal-localized factors. On the other hand, experimental tests showed that i-cells can form by epigenetic mechanisms in Clytia, since larvae derived from both animal and vegetal blastomeres separated during cleavage stages developed equivalent i-cell populations. Thus Clytia embryos appear to have maternal germ plasm inherited by i-cells but also the potential to form these cells by zygotic induction. Reassessment of available data indicates that maternally localized germ plasm molecular components were plausibly present in the common cnidarian/bilaterian ancestor, but that their role may not have been strictly deterministic.
ISSN: 0012-1606

hal-01544487
https://hal.archives-ouvertes.fr/hal-01544487
DOI : 10.1016/j.ydbio.2012.01.018

Éditeur(s) : Springer
Résumé : The transforming growth factor (TGF)-beta superfamily is a group of important growth factors involved in multiple processes such as differentiation, cell proliferation, apoptosis and cellular growth. In the Pacific oyster Crassostrea gigas, the oyster gonadal (og) TGF-beta gene was recently characterized through genome-wide expression profiling of oyster lines selected to be resistant or susceptible to summer mortality. Og TGF-beta appeared specifically expressed in the gonad to reach a maximum when gonads are fully mature, which singularly contrasts with the pleiotropic roles commonly ascribed to most TGF-beta family members. The function of og TGF-beta protein in oysters is unknown, and defining its role remains challenging. In this study, we develop a rapid bacterial production system to obtain recombinant og TGF-beta protein, and we demonstrate that og TGF-beta is processed by furin to a mature form of the protein. This mature form can be detected in vivo in the gonad. Functional inhibition of mature og TGF-beta in the gonad was conducted by inactivation of the protein using injection of antibodies. We show that inhibition of og TGF-beta function tends to reduce gonadic area. We conclude that mature og TGF-beta probably functions as an activator of germ cells development in oyster.
Marine Biotechnology (1436-2228) (Springer), 2011-10 , Vol. 13 , N. 5 , P. 971-980

Droits : Springer Science+Business Media, LLC 2011
http://archimer.ifremer.fr/doc/00042/15371/13438.pdf
DOI:10.1007/s10126-010-9361-4
http://archimer.ifremer.fr/doc/00042/15371/

Éditeur(s) : HAL CCSD Public Library of Science
Résumé : International audience
The capacity of testicular somatic cells to promote and sustain germ cell differentiation is largely regulated by sexual steroids and notably androgens. In fish species the importance of androgens is emphasized by their ability to induce sex reversal of the developing fries and to trigger spermatogenesis. Here we studied the influence of androgens on testicular gene expression in trout testis using microarrays. Following treatment of immature males with physiological doses of testosterone or 11-ketotestosterone, 418 genes that exhibit changes in expression were identified. Interestingly, the activity of testosterone appeared stronger than that of 11-ketotestosterone. Expression profiles of responsive genes throughout testis development and in isolated germ cells confirmed androgens to mainly affect gene expression in somatic cells. Furthermore, specific clusters of genes that exhibit regulation coincidently with changes in the natural circulating levels of androgens during the reproductive cycle were highlighted, reinforcing the physiological significance of these data. Among somatic genes, a phylogenetic footprinting study identified putative androgen response elements within the proximal promoter regions of 42 potential direct androgen target genes. Finally, androgens were also found to alter the germ line towards meiotic expression profiles, supporting the hypothesis of a role for the somatic responsive genes in driving germ cell fate. This study significantly increases our understanding of molecular pathways regulated by androgens in vertebrates. The highly cyclic testicular development in trout together with functions associated with regulated genes reveal potential mechanisms for androgen actions in tubule formation, steroid production, germ cell development and sperm secretion.
ISSN: 1932-6203

inserm-00825763
http://www.hal.inserm.fr/inserm-00825763
http://www.hal.inserm.fr/inserm-00825763/document
http://www.hal.inserm.fr/inserm-00825763/file/Rolland_et_al.pdf
DOI : 10.1371/journal.pone.0053302

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
BACKGROUND: Phthalic acid esters are widely used in the manufacture of plastics. Numerous studies have shown that these phthalates impair testicular testosterone production in the rat. However, the scarce and contradictory data concerning humans have cast doubt over whether these compounds are also anti-androgenic in man. We therefore investigated the direct effects of di-(2-ethylhexyl) phthalate (DEHP) and mono-(2-ethylhexyl) phthalate (MEHP) on organo-cultured adult human testis and a human cell line. METHODS: Adult human testis explants or NCI-H295R adrenocortical human cells were cultured with DEHP or MEHP. The effects of ketoconazole, used as a reference molecule, were also assessed. RESULTS: In both models, DEHP and MEHP significantly inhibited testosterone production. The effects of both phthalates appeared to be specific for steroidogenesis, as INSL3 production by Leydig cells was not altered. Furthermore, the phthalates of interest had no effect on inhibin B production by Sertoli cells or on germ cell apoptosis. As only a small fraction of the phthalates added was found in the testis explants, and as these compounds were found to be metabolized, we estimate that the anti-androgenic effects observed occurred at concentrations of phthalates that are of the same order of magnitude as exposures reported in the literature for men. CONCLUSIONS: We provide the first evidence that DEHP and MEHP can inhibit testosterone production in the adult human testis. This is consistent with recent epidemiological findings of an inverse correlation between exposure to MEHP and testosterone concentrations.
ISSN: 0268-1161

hal-00876965
https://hal.archives-ouvertes.fr/hal-00876965
DOI : 10.1093/humrep/des069
PUBMED : 22402212

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : International audience
Parapneumonic pleural effusions represent the main cause of pleural infections. Their incidence is constantly increasing. Although by definition they are considered to be a “parapneumonic” phenomenon, the microbial epidemiology of these effusions differs from pneumonia with a higher prevalence of anaerobic bacteria. The first thoracentesis is the most important diagnostic stage because it allows for a distinction between complicated and non-complicated parapneumonic effusions. Only complicated parapneumonic effusions need to be drained. Therapeutic evacuation modalities include repeated therapeutic thoracentesis, chest tube drainage or thoracic surgery. The choice of the first-line evacuation treatment is still controversial and there are few prospective controlled studies. The effectiveness of fibrinolytic agents is not established except when they are combined with DNase. Antibiotics are mandatory; they should be initiated as quickly as possible and should be active against anaerobic bacteria except for in the context of pneumococcal infections. There are few data on the use of chest physiotherapy, which remains widely used. Mortality is still high and is influenced by underlying comorbidities.
Les épanchements pleuraux parapneumoniques représentent la principale étiologie des pleurésies infectieuses. Leur incidence est en constante augmentation. Bien qu’ils soient qualifiés de « parapneumoniques », l’épidémiologie microbienne est différente de celle des pneumonies avec notamment une plus grande fréquence des germes anaérobies. La ponction pleurale exploratrice représente l’étape diagnostique centrale qui permet de distinguer les épanchements parapneumoniques compliqués et non compliqués. Seuls les épanchements parapneumoniques compliqués doivent faire l’objet d’un traitement évacuateur reposant sur la mise en œuvre de ponctions pleurales répétées (PPR), d’un drainage thoracique ou d’une prise en charge chirurgicale. Le choix de la technique évacuatrice première reste débattu car il existe peu d’études prospectives comparatives. L’utilisation d’agents fibrinolytiques n’a pas fait la preuve de son efficacité sauf lorsqu’ils sont utilisés en association à la DNAse. L’antibiothérapie doit être systématique, précoce et couvrir les germes anaérobies, sauf en cas d’infection à pneumocoque. Il existe peu de données sur la place de la kinésithérapie qui reste largement utilisée. La mortalité est élevée et directement influencée par les comorbidités sous-jacentes.
ISSN: 0761-8425

hal-01117905
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01117905
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01117905/document
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01117905/file/Les%20%C3%A9panchements%20pleuraux%20parapneumoniques_accepted.pdf
DOI : 10.1016/j.rmr.2014.12.001

Éditeur(s) : HAL CCSD National Academy of Sciences
Résumé : International audience
Stem cells are pivotal for development and tissue homeostasis of multicellular animals, and the quest for a gene toolkit associated with the emergence of stem cells in a common ancestor of all metazoans remains a major challenge for evolutionary biology. We reconstructed the conserved gene repertoire of animal stem cells by transcriptomic profiling of totipotent archeocytes in the demosponge Ephydatia fluviatilis and by tracing shared molecular signatures with flatworm and Hydra stem cells. Phylostratigraphy analyses indicated that most of these stem-cell genes predate animal origin, with only few metazoan innovations, notably including several partners of the Piwi machinery known to promote genome stability. The ancestral stem-cell transcriptome is strikingly poor in transcription factors. Instead, it is rich in RNA regulatory actors, including components of the ``germ-line multipotency program'' and many RNA-binding proteins known as critical regulators of mammalian embryonic stem cells.
ISSN: 0027-8424

hal-01544480
https://hal.archives-ouvertes.fr/hal-01544480
DOI : 10.1073/pnas.1514789112