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While p53 is dispensable for development, an excess of p53 has dramatic consequences on the embryogenesis and on the cell dierentiation. In an attempt to analyse in vivo the eects of p53 activity, we have generated transgenic mice expressing the wild-type p53 under the control of the metallothionein I promoter. In the three transgenic lines established, exogenous p53 is expressed constitutively in the postmeiotic cells of transgenic males and two lines are subfertile. Transgenic males expressing the upper level of p53 produce few spermatozoa since the majority of developing spermatids undergo apoptosis. In the subfertile males exhibiting an intermediate amount of p53, teratozoospermia is obvious suggesting an altered terminal dierentiation of postmeiotic cells. In contrast lower level of p53 does not lead the third line to sterility. These results suggest that the activity of p53 is dependent in vivo on the amount of p53 present within cells, as it has been already demonstrated in vitro.

International audienceMultiphoton and electron microscopic analyses show that acido-soluble collagen I prepared in 5 mM acetic acid (pH 3.5) at concentration above 45 mg mL−1 spontaneously generates liquid crystal phases mimicking plywood organization found in cornea tissues. Those organizations extend for several hundred micrometers. Transmission electron microscopy reveals the presence of small nanofibrils organized in a complex phase, coupling overall smectic and cholesteric organizations together with local order. Those nanofibrils could be the mesogen elements giving rise to this plywood organization. These data provide clues to physico-chemical events that may take place in cornea morphogenesis in vivo. This result is invaluable for bioengineering fields, as this liquid crystal organization paves the way for the generation of collagen based bio-mimetic cornea matrices

The simultaneous use of cytochemical techniques and X-ray spectrograph^ reveals the presence of diverse cations (Ca, Mg, Mn, Zn, and Fe) in various organs of P. varia. These elements may be linked to MPSA in salivary ducts, they are associated with pigments in the eye or hypodermis and form phosphate concretions in the Malpighian tubules, the midgut and adipose tissue. The distribution and abundance of metals as well as the development of storage products have been studied during the whole of the postembryonic development. Our results are compared with data in other orders of terrestrial insects. Life in a aquatic environment produces an absence of accumulations of potassium and purine wastes. The formation of mineral salts seems necessary for some ionic exchanges in this Insect which has no problem of water economy for the greater part of its life.

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