http://www.nature.com/news/2007/070423/full/070423-3.html / Published online: 23 April 2007; | doi:10.1038/news070423-3

Migraines may slow memory loss

Sufferers show less cognitive decline as they age.

Heidi Ledford

A migraine is not just a headache, it is an über-headache - a pounding, queasy, searing pain that can incapacitate its victims for hours on end. And as if the pain weren't bad enough, sufferers were also thought to show diminished memory and verbal skills.

But new research now suggests that although migraines are sometimes associated with diminished cognitive skills, sufferers may in fact show less memory loss as they age than those who are migraine-free.

The results are puzzling, admits Amanda Kalaydjian of the National Institute of Mental Health in Bethesda, Maryland, who led the study. "We originally hypothesized that migraineurs would be doing worse," she says, "so I was really surprised."

Slower decline

More than 28 million people in the United States suffer from migraines, and women are three times more likely than men to have the condition. The cause is still unknown, and different theories have blamed nervous-system malfunctions, chemical imbalances, over-reactive blood vessels, or a combination of factors.

Meanwhile, attempts to catalogue the damage wrought by a lifetime of migraine attacks have met with conflicting results. Some studies suggest that migraineurs have poorer memories and less verbal ability than those without the condition, whereas other studies show no difference at all between sufferers and non-sufferers. Most of these studies were small and relied on patients in headache clinics, meaning that the study population can be skewed towards those with more severe cases of the condition, Kalaydjian points out.

Kalaydjian decided to test how cognitive function in migraineurs changes over time. She and her colleagues tested word recall and overall cognitive function in 1,448 people, including 204 migraine sufferers selected from a broad epidemiological study and not from headache clinics.

The results, published today in Neurology, show that sufferers do perform worse on memory tests than non-sufferers, both during the initial screens performed from 1993 to 1996 and in follow-up interviews in 2005. But although both groups tended to show signs of cognitive decline in the roughly 12 years between the two tests, many migraineurs did not decline as rapidly. In particular, the ability to remember specific words did not weaken as much in migraineurs who suffer from migraines with 'aura', the flashing lights, squiggly lines and other visual interruptions that accompany some migraines. And in other tests of cognitive function, migraineurs who were older than 50 did not weaken as quickly as people in the same age group who do not suffer from migraines.

Exactly why the migraineurs would be more protected from cognitive decline remains a mystery. "Since no one really knows what causes migraines, it's really difficult to say what about them may or may not decrease the cognitive decline," says Kalaydjian.

Brains trained?

One possibility is that lifestyle differences in those with migraines could have a protective effect. Migraineurs may take non-steroidal anti-inflammatory medications such as ibuprofen to relieve their pain, and some studies have suggested that these drugs may help to protect against cognitive decline. People with migraines may also be better stewards of their own health. A lifestyle designed to stave off migraines would include regular exercise, attention to diet and adequate sleep, all of which could boost overall health and cognitive function.

It will take more targeted studies to untangle all of these contributing factors, says Kalaydjian. When she factored information about sleeping habits, exercise and medication into analyses of her current data, the difference was still there, suggesting that these theories may not represent the whole answer.

It is also possible that migraines may genuinely deliver fundamental cognitive benefits in addition to these lifestyle factors, says Karen Waldie, a neuroscientist at the University of Auckland in New Zealand. Waldie speculates that decades of cerebral insult could train a migraineur's brain to better protect itself on a cellular level, and that sufferers' brains are "used to problems that the non-migraineur might not have experienced".

References : Kalaydjian A., Zandi P. P., Swartz K. L., Eaton W.W. & Lyketsos C. Neurology, 68. 1417 - 1424 (2007).

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http://www.futura-sciences.com/news-migraines-ameliorent-elles-memoire_10728.php
Par Jean Etienne, Futura-Sciences, le 26/04/2007 à 11h03

C'est ce qu'on pourrait penser, si l'on en croit les résultats obtenus par une équipe de scientifiques américains, en se basant sur des tests passés auprès de sujets migraineux à partir de 1993, et dont les résultats ne manquent pas de surprendre.

Amanda Kalaydjian et ses collègues de l'Ecole de Santé Publique Johns Hopkins Bloomberg, à Baltimore, a évalué sur le long terme l'évolution des facultés de mémorisation, entre autres, de 1448 femmes volontaires, membres de la Baltimore Epidemiologic Catchment Area Study. Parmi elles, 204 migraineuses chroniques.

Deux séries de tests ont été pratiquées, d'abord entre 1993 et 1996, puis entre 2004 et 2005. Ceux-ci consistaient essentiellement en des exercices de mémorisation, ce que l'on appelle communément un "Mini-Mental State Examination".

Sans surprise, les chercheurs ont d'abord constaté que les femmes migraineuses obtenaient de moins bons scores en comparaison aux sujets ne souffrant pas de cette affection. Mais la mise en corrélation des résultats des deux séries de tests a surpris toute l'équipe, car il apparaissait nettement que si les facultés cognitives diminuent avec l'âge, celles des migraineuses se réduisent nettement moins vite.

Comment expliquer ces résultats ? A cette question, Amanda Kalaydjian ne peut qu'émettre des hypothèses. Même si les causes de la migraine paraissent essentiellement liées à des anomalies vasculaires entraînant vasodilatation et augmentation de la perméabilité vasculaire, elles restent incomplètement élucidées, et difficiles à identifier. Actuellement, les chercheurs ignorent par quel mécanisme cette pathologie pourrait freiner la perte de facultés liée au vieillissement.

L'équipe ne pense pas que cet effet bénéfique soit lié à la prise de médicaments anti-inflammatoires. Cependant, elle n'exclut pas que le mode de vie des migraineux, rendu plus sain par suite de périodes de repos plus longues, de séances de relaxation anti-stress, et surtout de la volonté de réduire la consommation d'alcool, source de déclenchement de cette pathologie, pourrait expliquer en partie ces résultats.

Mais Amanda Kalaydjian estime qu'il existe vraisemblablement un facteur biologique à la base de cette différence, basé sur l'activité neuronale et la vasodilatation, qui jouerait un rôle de protection chez les migraineux.

http://www.nature.com/news/2007/070423/full/070423-1.html / Published online: 23 April 2007; | doi:10.1038/news070423-1

Ancient fossil forest found by accident

Treasure trove of extinct species discovered in old coal mine.

Katharine Sanderson

Geologists have found the remains of a huge underground rainforest hidden in a coal mine in Illinois. The fossil forest, buried by an earthquake 300 million years ago, contains giant versions of several plant types alive today.

Experts say the forest was growing on top of peaty soil when an ancient tremor plunged it about 5 metres down, allowing it to be buried and fossilized beneath further layers of more recent rock. It dates from a time when North America and Europe were joined together, at the Equator - similar forests went on to be transformed into the rich coal seams of the two continents.

The forest was discovered in 2005 by John Nelson of the Illinois State Geological Survey, who was making routine measurements in a mine in Vermilion County. He called in a team of palaeontologists to investigate the forest. As they drove down to 100 metres below ground, they saw the forest's remains in the glare from their miners' lamps as they looked up at the ceiling. "You actually see roots coming down; you see tree trunks lying in the ceiling," says Howard Falcon-Lang of the University of Bristol, UK, a member of the research team.

The forest is not the oldest to be discovered - others are known that are up to 370 million years old - it is the sheer size of the forest that is significant. It has allowed Falcon-Lang and his colleagues to show that the distribution of plant species that made up the forests in the Carboniferous era differed from region to region, rather than being randomly mixed.

"Forests closer to the coast differed from forests slightly further inland," says Falcon-Lang. "It is a subtle point but one that could not have been made without the great size of the sampled area," says Kirk Johnson, chief curator at the Denver Museum of Nature and Science, Colorado. "Without a large area to sample, there was really no way to know."

The ancient forest bears little resemblance to modern equivalents. "The diversity of the first rainforests was bizarre," says Falcon-Lang. He and his team found the remains of tree-sized clubmosses, horsetails and ferns - plants that today grow 2 or 3 metres tall, but in the ancient forest reached heights of up to 40 metres. Also surprising is the presence of remains from mangrove-like plants. "It was always assumed that mangrove plants had evolved fairly recently," says Falcon-Lang.

The forest probably had about 50 different plant species, although Falcon-Lang says that this is a conservative estimate. We probably lumped several similar species together as one," he explains. Modern rainforests are more diverse, containing as many as 500 plant species per hectare.

This discovery also shows that the fundamental processes that guide the complexity and evolution of forests has been around for hundreds of millions of years, says Scott Hocknull, a curator at the Queensland Museum in Brisbane, Australia. "Knowing this and how it has played out so many times in history will allow ecologists to better understand the complexity of modern forest systems," he adds.

The forest's long life will now be cut short - the mine is likely to collapse in the next few years and there are no plans to preserve it for the sake of the fossils. But Falcon-Lang is philosophical about losing the forest, pointing out that if it weren't for mining, the forest would never have been discovered in the first place.

References : DiMichele W. A., et al. Geology, 35. 415 - 418 (2007).

Photo de la Nasa montrant les images en trois dimensions du soleil, transmises par les deux sondes de la mission Stereo (Photo Nasa/AP).

La Nasa a montré lundi 23 avril les premières images en trois dimensions (3D) du soleil transmises par les deux sondes de la mission Stereo qui vont permettre de mieux comprendre et prévoir les éruptions solaires pour en prévenir l'impact sur l'atmosphère terrestre.

Les deux satellites identiques de la taille d'une voiturette de golf et d'un poids de 620 kg chacun, avaient été lancés en octobre dernier depuis la base militaire de Cap Canaveral en Floride (sud-est) et sont en orbite autour du soleil.

"Les deux engins s'éloignent l'un de l'autre de 45 degrés par an et commencent maintenant à être dans des positions respectives permettant d'effectuer des mesures stéréographiques", a expliqué Michael Kaiser, le chef scientifique du projet à la Nasa, lors d'une conférence de presse.

"La principal objectif de Stereo est d'étudier les tempêtes solaires (...) qui affectent tous les systèmes de communications des avions et engins spatiaux, perturbent la distribution électrique sur la terre et présentent un danger pour les astronautes dans l'espace", a-t-il rappelé.

"Les météorologues sont capables de prédire avec précision les cyclones une semaine à l'avance et nous voudrions pouvoir en faire autant avec les tempêtes solaires", a expliqué ce scientifique.

"Stereo représentera un nouvelle étape vers cet objectif en nous permettant d'étudier de façon plus détaillée les éruptions solaires", a-t-il ajouté.

Durant leur mission de deux ans, ces deux sondes jumelles vont pouvoir explorer l'origine, l'évolution et les conséquences interplanétaires de ces éjections de masse coronale (EMC), le plasma solaire projeté dans l'espace à la suite de puissantes explosions.

Ces gigantesques éruptions projettent plusieurs milliards de tonnes de plasma chauffé à un million de degrés Celsius en direction de la terre qui dérèglent le champ electro-magnétique. En mars 1989 elles ont été à l'origine d'une panne d'électricité au Québec.

Elles sont aussi responsables des aurores australes et boréales. Les cycles solaires durent 11 ans et sont marqués par deux pics d'activité. Lors du précédent pic en 2000, on a compté près de 2.000 EMC dont une centaine se sont produites en direction de la Terre.

En période creuse comme actuellement il y a moins de 200 éruptions par an. Le coût total de la mission Stereo, fruit d'une coopération euro-américaine, est de 550 millions de dollars y compris le lancement, a précisé la Nasa.

AFP / http://www.la-croix.com/photo2/index.jsp?docId=2301125&rubId=4085

Sur Internet : Les photos du soleil en 3D sur le site de la Nasa

http://www.nature.com/news/2007/070416/full/070416-15.html / Published online : 20 April 2007 | doi:10.1038/news070416-15

Fruit proves better than vitamin C alone

Tests show that it isn't just the vitamin that protects the body.

Matt Kaplan

If you're after an antioxidant, try oranges. AddStyle

If you're in the market for an antioxidant to keep your body young and healthy, new research suggests you'd be much better off with oranges than vitamin C tablets.

Although vitamin C is best known for its protection against scurvy [scorbut] and, possibly, the common cold [rhume], fruits rich in vitamin C are also powerful antioxidants that protect cellular DNA from being damaged by oxidation. Going without such foods leads to DNA damage long before the iconic bleeding [saignement] gums [gencives] of scurvy are seen.

But do vitamin C pills on their own have the same protective effect as fruit ? Serena Guarnieri and a team of researchers in the Division of Human Nutrition at the University of Milan, Italy, designed a simple experiment to find out.

The team gave test subjects a single glass of blood-orange juice, vitamin-C-fortified water, or sugar water to drink. The blood-orange juice and the fortified water had 150 milligrams of vitamin C each, whereas the sugar water had none. Blood samples were taken from the test subjects 3 hours and 24 hours after their drink. Unsurprisingly, blood plasma vitamin C levels went up after drinking both the juice and the fortified water.

The blood samples were then exposed to hydrogen peroxide, a substance known to cause DNA damage through oxidation. The damage was significantly less in the samples taken from volunteers who had ingested orange juice, in both the samples collected 3 hours after consumption and 24 hours after the drink. Unsurprisingly, the sugar water had no protective effect. But neither did the vitamin-C-fortified water.

At least one other study, which looked at larger quantities of vitamin C, has shown a protective effect from the vitamin alone. But the fact that it doesn't show up here indicates that something more complicated is going on, says Guarnieri. "It appears that vitamin C is not the only chemical responsible for antioxidant protection ; there is something more at work here," she says. The find is reported in the British Journal of Nutrition.

"It is an important observation," says David Heber, director of the Center for Human Nutrition at the University of California, Los Angeles. It suggests that people studying the effects of the vitamin should be careful to note where in the diet it comes from. "Vitamin C is provided in a matrix in fruits with many other beneficial substances," he says; and all of these may interact with each other.

Other nutrition researchers have suggested that sugars in juice interact with vitamin C to generate the antioxidant effect. But Guarnieri suspects that the phytochemicals found in oranges (cyanidin-3-glucoside, flavanones and carotenoids) are the substances that need further study. "But how they are interacting is still anyone's guess," she adds.

References

1. Guarnieri S., Riso P. & Porrini M.Brit. J. Nutr., 97. 639 - 643 (2007).
2. Lotito S. B. & Frei B. Free Rad. Biol. Med., 37. 251 - 258 (2004).

Les antirides, produits à risque et mort cellulaire
Par Jean-Luc Goudet - Futura-Sciences, le 17/04/2007 à 09h14

Selon des chercheurs canadiens, plusieurs cosmétiques, et spécialement des antirides, déclencheraient dans la peau des réactions pathologiques qui mériteraient beaucoup plus d'attention.

Pas vraiment rassurants, les tests in vitro effectués par trois chercheurs de l'université de Laval, au Québec, montrent que certains produits cosmétiques génèrent dans la peau des effets plutôt dévastateurs. Dans un récent article publié dans la revue British Journal of Dermatology, ils mettent en cause le DMAE (2-diméthylaminoéthanol), un cousin de la choline, une molécule fabriquée par l'organisme. Depuis des années, l'industrie cosmétique l'utilise comme antiride mais aussi dans des crèmes, des rouges à lèvres, des shampoings, des savons et des lotions pour bébés. Pourtant, personne ne savait jusqu'à présent comment il agissait.

François Marceau, Guillaume Morissette et Lucie Germain pensent avoir trouvé comment : par une réaction qu'ils qualifient de pathologique. Sur des cultures cellulaires, les chercheurs ont observé que le DMAE provoque un gonflement immédiat des fibroblastes, une famille de cellules que l'on trouve dans la peau. Ce sont les vacuoles, petites vésicules intracellulaires, qui augmentent brusquement de taille. L'équipe pense qu'elles absorbent massivement le DMAE et de l'eau. Sur la peau, ce gonflement provoque une tension plus grande qui réduit effectivement les rides.

Mort cellulaire

Pourquoi cette réaction serait-elle pathologique ? Parce que, rapportent les trois scientifiques, les fibroblastes ainsi gonflés se divisent beaucoup moins et subissent une perturbation de leur métabolisme tandis que leur taux de mortalité augmente. Or celui-ci est proportionnel à la quantité de DMAE introduite dans la culture. Avec des doses qui correspondent à une application normale d'une crème antiride, 25 % des cellules meurent après 24 heures.

L'équipe n'affirme pas pour autant que les produits à base de DMAE sont dangereux pour la santé. Mais leur avis est qu'il faudrait mieux étudier les effets de cette molécule, s'étonnant de ce que ce genre de produits, qui agissent au sein du corps humain, sont soumis à une réglementation légère. « Même si le DMAE est un produit quasiment médicamenteux et que d'autres produits de la même famille sont des médicaments, il existe très peu de documentation scientifique sur ses effets pharmacologiques et toxicologiques », commente François Marceau dans le journal de l'université de Laval. Et d'enfoncer le clou : « Plusieurs composés qui se retrouvent dans les cosmétiques sont aussi complexes que les médicaments, ils sont absorbés par la peau, ils sont concentrés dans les cellules, ils circulent dans le sang, ils sont éliminés par les reins ou peut-être même stockés dans le foie. Pourtant, le cadre réglementaire qui régit leur usage est beaucoup moins strict que celui des médicaments ».

http://www.futura-sciences.com/news-antirides-produits-risque-mort-cellulaire_10666.php