Trans-disciplinary diagnosis for an in-depth reform of regulatory expertise in the field of environmental toxicology and security.

Repeated health and environmental scandals, the loss of biodiversity and the recent burst of chronic diseases constantly remind us the inability of public authorities and risk assessment agencies to protect health and the environment. After reviewing the main shortcomings of our evaluation system of chemicals and new technologies, supported by some concrete examples, we develop a number of proposals to reform both the risk assessment agencies and the evaluation processes. We especially propose the establishment of an independent structure, a High Authority of Expertise, supervising, either at European level or at national level, all the evaluation agencies, and ensuring the transparency, the methodology and the deontology of the expertise. In addition to modifying the evaluation protocols, both in their nature and in their content, especially in order to adapt them to current pollutants such as endocrine disruptors, we propose a reform of the expertise processes based on transparency, contradiction, and greater democracy, including close collaboration between the institutional and scientific parties on the one hand and the whole civil society on the other. All the proposals we make are inspired by the desire to prevent, through appropriate mechanisms, the human, health, ecological, but also economic consequences of contemporary technological choices.

The telomerase activity of adult mouse testis resides in the spermatogonial alpha6-integrin-positive side population enriched in germinal stem cells.

Testis is one of the organs with the most telomerase activity in the adult. This activity protects chromosomes from telomere attrition and ensures the transmission of full-length chromosomes to progeny. Little is known about telomerase activity during adult germ cell differentiation, however. We demonstrate here that the telomerase activity of adult mouse testis resides in the alpha6-integrin-positive Side Population containing spermatogonia and enriched in spermatogonial stem cells. The telomerase activity of these cells fell upon entry into meiosis and during the subsequent spermiogenesis. In addition, the telomerase activity of cells in various stages of differentiation was unaffected by aging and, notably, remained high in the alpha6-integrin-positive Side Population.

[Cytokeratins 7 and 20 immunohistochemistry in ampullary carcinomas]. / Expression immunohistochimique des cytokératines 7 et 20 dans les carcinomes ampullaires.

UNLABELLED: Ampullary carcinomas (AC) account for 33% of all surgically operable pancreatoduodenal tumors. The 5-year relative survival rate is 50% and tumoral stage is the main prognostic factor. However, among the three AC histological subtypes (intestinal, pancreatobiliary and mixed), a favorable prognostic has been reported for the intestinal subtype. BACKGROUND: The aims of this study were to determine the prognostic impact of AC histologic subtype and of cytokeratins (CK) 7 and 20 immunostaining profile in these tumors. PATIENTS AND METHODS: Clinical data of 54 AC were obtained retrospectively. Macroscopic and histologic documents were reviewed and immunostainings for CK7 and CK20 were performed. RESULTS: The classification of tumors, according to histological subtype, was: intestinal 26%, pancreatobiliary 65% and mixed 9%. No correlation was found between histological subtype and tumor stage. The 5-year survival rate varied from 100% for intestinal subtype to 35% for pancreatobiliary subtype. A strong correlation (p < 0.0001) was found between histological subtype and CK7/CK20 immunostaining profile. The 5-year survival rate varied from 100% for CK7-/CK20 + AC to 40% for CK7 + /CK20- AC. CONCLUSION: In our study, the intestinal histological subtype had a favorable prognostic value. CK7/CK20 immunostaining profile was helpful for the identification of histological subtype and appears to provide additional prognostic information.

Mouse differentiating spermatogonia can generate germinal stem cells in vivo.

In adults, stem cells are responsible for the maintenance of many actively renewing tissues, such as haematopoietic, skin, gut and germinal tissues. These stem cells can self-renew or be committed to becoming progenitors. Stem-cell commitment is thought to be irreversible but in male and female Drosophila melanogaster, it was shown recently that differentiating germ cells can revert to functional stem cells that can restore germinal lineage. Whether progenitors are also able to generate stem cells in mammals remains unknown. Here we show that purified mouse spermatogonial progenitors committed to differentiation can generate functional germinal stem cells that can repopulate germ-cell-depleted testes when transplanted into adult mice. We found that GDNF, a key regulator of the stem-cell niche, and FGF2 are able to reprogram in vitro spermatogonial progenitors for reverse differentiation. This study supports the emerging concept that the stem-cell identity is not restricted in adults to a definite pool of cells that self-renew, but that stemness could be acquired by differentiating progenitors after tissue injury and throughout life.

Flow cytometric characterization of viable meiotic and postmeiotic cells by Hoechst 33342 in mouse spermatogenesis.

BACKGROUND: Spermatogenesis in adult is a complex stepwise process leading to terminally differentiated spermatozoa. The cellular heterogeneity of testis renders complex the studies on molecular aspects of this differentiation process. Analysis of the regulation of adult spermatogenesis would undoubtedly benefit from the development of techniques to characterize each germinal differentiation step. METHODS: Hoechst 33342 staining of mouse testicular cells allows characterization of an enriched population in germinal stem cell and spermatogonia, called side population. In this study, we examined the definition of the various germinal populations stained by Hoechst 33342, notably meiotic and postmeiotic cells. RESULTS: Preleptotene spermatocytes, spermatocyte I, spermatocyte II, and round and elongated spermatids were discriminated by Hoechst 33342 staining. In addition, we associated differentiation of spermatocyte I through leptotene to diplotene with changes in Hoechst 33342 red fluorescence pattern. CONCLUSIONS: Hoechst 33342 staining of viable germinal cells constitutes a valuable tool to study normal and impaired mouse adult spermatogenesis or to isolate viable cells from various differentiation stages for studies of molecular mechanisms regulating spermatogenesis.

Herpesvirus, cytomegalovirus, human sperm and assisted fertilization.

BACKGROUND: The effect of viral particles on the motility of human sperm and the relationship between sperm and virus are of importance particularly in assisted fertilization. METHODS: We incubated ejaculated sperm with or without seminal fluid with either herpes simplex virus type 2 (HSV2) or human cytomegalovirus (HCMV). For each experiment, 5 x 10(5) sperm were incubated with a viral load of between 10(4) and 10(6) plaque-forming units. RESULTS: We detected no apparent variations in the percentage of motile forms when sperm were incubated with either HSV2 or HCMV. Using a computer-aided semen analysis system, a slight difference was reported in the percentage of motile forms when seminal fluid-free sperm were incubated with HSV2 (57.18 versus 64.43 in the control). Although the mean amplitude of lateral head displacement and the curvilinear velocity were significantly higher in infected sperm, the difference in straight line velocity was not statistically significantly different. Few viral particles (HSV2 or HCMV) adhered to the sperm membrane in the presence of seminal fluid. However, more particles stuck when in the absence of seminal fluid, particularly with HSV2 (8% of sperm sections for HSV2; 4% for HCMV). CONCLUSIONS: The relationship between sperm and viruses depends on the type of virus present as well as the presence or absence of seminal fluid. Motility is not a good enough criterion on which to prove the presence of viral elements, either in the medium or on the sperm.

'Side Population' cells in adult mouse testis express Bcrp1 gene and are enriched in spermatogonia and germinal stem cells.

Stem cells in various somatic tissues (bone marrow, skeletal muscle) can be identified by the 'Side Population' marker based on Hoechst 33342 efflux. We show that mouse testicular cells also display a 'Side Population' that express Bcrp1 mRNA, the ABC transporter responsible for Hoechst efflux in hematopoietic cells. Inhibition of Hoechst efflux by specific BCRP1 inhibitor Ko143 show that germinal 'Side Population' phenotype is dependent on BCRP1 activity. Analysis of two well-defined models of altered spermatogenesis (W/Wv mutants and cryptorchid male mice) and RNA expression studies of differentiation markers demonstrate that germinal 'Side Population' contains spermatogonial cells. In addition, alpha 6-integrin and Stra8 germinal stem cell markers, are expressed in the 'Side Population'. In vivo repopulation assay clearly establishes that testis 'Side Population' in adult mice is highly enriched in male germ stem cells.

Investigaciones sobre el embrión humano / Research on human embryos

In this article the author examines the diferent proposals by researchers and doctors who for years have addressed the issue of the urgent need for research using human embryos. The proposals from France in 1994 are reviewed, together with new projects for embryo research (AU)

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