Des chercheurs ont remplacé le génome entier d'une bactérie par celui d'une espèce très proche et ainsi fait un nouveau pas dans la construction d'un génome à partir de zéro. La création de génomes synthétiques pourrait permettre aux scientifiques de développer des microorganismes capables de produire des biocarburants, de traiter les déchets toxiques, de retenir le carbone et d'autres applications... http://www.techno-science.net/?onglet=news&news=4246

http://www.nature.com/news/2007/070702/multimedia/070702-1-m1.html

Galapagos National Park

Arabian Oryx Sanctuary, Oman

Florida Everglades

Niokolo-Koba National Park, Senegal

Río Plátano Biosphere Reserve, Honduras

Madagascan rainforests

Southern China karst region

Jeju Island, South Korea

Teide National Park, Spain

Beech forests of the Carpathian Mountains

 

Par Laurent Sacco, Futura-Sciences

On ne saurait minimiser la découverte faite en 1905 par Bernard Brunhes alors qu'il était le directeur de l'observatoire du Puy de Dôme à Clermont-Ferrand en Auvergne. Ce géophysicien avait alors mis en évidence que certaines roches, capables de garder en mémoire la direction du champ magnétique de la Terre à une époque donnée, indiquaient clairement qu'autrefois une boussole aurait pointé, non pas en direction du nord, mais bien vers le sud. Sa découverte ne convainquit pas grand monde à l'époque mais, à partir des années 50, et surtout suite à la publication retentissante de Vines et Matthews en 1963, l'existence de séries d'inversions globales de l'orientation du champ magnétique terrestre s'est non seulement imposée mais s'est trouvée être au cœur de la confirmation de la théorie de la dérive des continents de Wegener. La commémoration de cet événement s'est faite du 27 au 28 Juin 2007, notamment sur le lieu même de sa découverte. Futura-Sciences y était.

http://www.futura-sciences.com/fr/sinformer/actualites/news/t/geologie-1/d/la-decouverte-des-inversions-du-champ-magnetique-de-la-terre-100-ans-deja_12257/

Par Jean-Luc Goudet - Futura-Sciences

Pour construire ses ailes, l'embryon de poule utilise une horloge génétique afin de lire et relire un même gène de façon répétitive, organisant ainsi des cycles de production calés à quelques minutes près. Un travail orchestré de main de maître...

http://www.futura-sciences.com/fr/sinformer/actualites/news/t/genetique-1/d/des-horloges-rythment-la-fabrication-de-lembryon_12177/  

Published online: 2 July 2007; | doi:10.1038/news070702-2 / http://www.nature.com/news/2007/070702/full/070702-2.html

Doctors announce new fertility feat

Baby is first to be born from eggs matured and frozen in the lab.

Michael Hopkin

Ever more work is helping infertility patients to become parents. Alamy

Doctors in Canada have announced the birth of the first baby to be created from an egg that was matured in a test tube and then frozen and thawed for later use. The method offers hope for women who fall victim to sudden ovarian failure or who cannot be given drugs that promote egg maturation in the ovaries themselves.

The baby girl, now around one year old, was born in Canada as a result of work at the McGill Reproductive Centre in Montreal. Her mother suffers from polycystic ovarian syndrome, meaning that her ovaries were at risk of being over-stimulated if she were given the hormone injections that are routinely used by fertility doctors to obtain mature eggs.

So instead, researchers led by Hananel Holzer removed unmatured egg cells from the woman's ovaries and used hormones to coax them to maturity in the laboratory. The eggs were then frozen and later thawed for use.

The maturation of eggs in the lab has been done before, leading to healthy births. And the freezing of eggs is a well established procedure. But this is the first time that all these steps - each important to infertility patients in different ways - have been strung together into a successful birth.

Three more women from the 20 participants in the study are also now pregnant, giving a 20% overall success rate. The success shows that eggs that have been matured in the test tube and then frozen can still generate a full-term pregnancy.

"We have demonstrated for the first time that it is possible to do this," Holzer told the meeting of the European Society for Human Reproduction and Embryology in Lyon, France, where he announced the birth.

Stimulating

The technique could benefit women with cancers, such as breast cancer, that can be worsened by the hormones given to stimulate egg production within the ovary. Women undergoing in vitro fertilization (IVF) are typically given female hormone supplements to boost the number of mature eggs they produce, allowing more embryos to be created.

Ovarian stimulation is also time-consuming, taking between two and six weeks. Women who suffer sudden ovarian failure would not have time to wait for traditional methods, and so the new technique could therefore help them save and freeze several eggs before it is too late, Holzer told the meeting.

In his study, which involved women with an average age of 30, Holzer and his colleagues collected a total of 295 immature eggs, 68% of which could successfully be encouraged to mature in the laboratory. Of these, 74% survived the freezing and thawing and were fertilized. An average of three embryos was implanted in each of the 20 volunteers to maximize the chances of success, although all four of the resulting pregnancies were single babies.

The technique has not yet successfully been demonstrated in cancer patients, who might be expected to make up the majority of those wishing to preserve their fertility using this method, Holzer admits.

But the technique could hopefully replace the practice currently on offer to cancer patients, whereby doctors simply freeze entire chunks of ovarian tissue that could later be re-implanted. This has led to fears that the re-implanted tissue may not be completely free of cancer cells.

Healthy women could even use the new method to preserve their fertility as they near middle-age, Holzer suggests, without the need for hormone injections. "Women in their mid-30s with no partner could freeze their eggs in this way," he told the meeting.

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Fécondation par ovocytes immatures, le nouvel espoir

Par Jean Etienne, Futura-Sciences

Envisagée comme une méthode fiable pour résoudre certains problèmes de fertilité, la fécondation à partir d'ovocytes congelés est encore rare puis qu'on ne compte que moins de 150 naissances dans le monde. Mais un récent progrès suscite l'espoir.

 http://www.futura-sciences.com/fr/sinformer/actualites/news/t/medecine/d/fecondation-par-ovocytes-immatures-le-nouvel-espoir_12285/