A nevetés hatására csökken a leptin (étvégytalanságot okoz) és növekedik a ghrelin (étvágyfokozó) koncentrációja.
"Egyre több adat gyűlik össze arról, hogy a személyes kapcsolati hálónk sokkal inkább meghatározza a sorsunkat, semmint azt hinnénk. (…)
A hálózatok viselkedést meghatározó másik példájaként az önmagukról a közösségi portálokra (iwiw-re, Facebook-ra, myvip-re, stb.) mosolygó arcképet felrakó embereknek általában sok és mosolygó arcképű ember az ismerőse, és fordítva: a savanyúképűeket kevés, de hasonlóan savanyúképű ismerős veszi körül. A hálózatok meghatározó szerepe nemcsak egyéni, hanem társadalmi méretekben is igaz. Magyarországon jelenleg a továbblépés egyik legnagyobb akadálya az, hogy a társadalmi háló befelé forduló, és szűk csoportokra töredezett."
Ennek az észak-amerikai verébfajnak (Ammodramus caudacutus) a legcsalfábbak - hogy szépen fejezzük ki magunkat - a tojói: egy fészekaljra átlagban több mint 2.5 apa jut, minden harmadik fészekaljban pedig minden fiókának más az apja.
Ceruza végén is elfér ez a most felfedezett gekkó faj. Az equadori Cerro Pata de Pájaro esőerdeiben új kétéltű és hüllőfajokat fedeztek fel. A Föld azon kevés régiói közé tartozik ahol aránylag kis területen akár 20-30 békafajjal is találkozhatunk (vagyis mintegy két-háromszor több békafajjal mint ahány egy Közép-Európai országban él!).
For the first time, scientists have found a rage-inducing pheromone and the neuron that detects it in fruit flies. The research, detailed in the journal Nature, could help explain everything from bar fights to species-wide population control.
“Not only did we identify the pheromone that leads to aggression and its neuron,” said David Anderson, a scientist at Cal Tech and co-author of the Nature study, “but we were able to manipulate the ability of the flies to increase aggression.”
For the most part, fruit flies are a peaceful species. Give a group of flies a piece of food, and they graze peacefully. Give them some land, and they usually share the territory without incident.
These idyllic scenes, however, can quickly turn violent. Drop filter paper soaked in artificially produced pheromone, known as 11-cis-vaccenylacetate (CVA), into the air around six flies, and they quickly start karate chopping and judo wrestling their opponents, rearing up on their hind legs and snapping down violently, and grappling with their forelegs.
Eventually one fly dominates, scaring all other flies away.
Natural CVA, found in the hard exoskeletons of flies and theoretically released when the flies bump against each other, also enrages flies. Anderson and colleagues crammed up to 100 fruit flies into a container with tiny holes on the top and watched as the flies fought, releasing ever greater amounts of CVA.
The CVA rose through the container and out of the holes on top, where two other flies were waiting. The two flies on top had plenty of food and plenty of space. However, when they smelled the CVA produced by the fighting flies under them, the two flies on top started fighting as well.
When scientists remove the flies from inside the lower container, the two flies on top become peaceful again.
After identifying the pheromone, the scientists set out to find the part of the fly’s antennae, the receptor, that binds to CVA. They removed five genes that encode for specific receptors in fruit flies.
These genetically modified flies were unable to smell CVA, and no amount of the CVA could trigger aggressive behavior.
Other scientists had previously identified CVA as an aggression promoting pheromone. Other researchers had even identified the neuron that detects CVA. Anderson’s new work links the pheromone with the neuron in the flies antennae and the genes that produce those neurons.
This pheromone is a way to keep fly populations in check. When the number of flies becomes too large, some flies decide to forgo the fighting and find another food source.
Waiting for Synthia
“Waiting for Synthia - that has been the script for enthusiasts of synthetic life for the past two years, ever since genomics pioneer Craig Venter promised to unveil a living bacterial cell carrying a genome made from scratch in the lab. 2010 is the year for him to deliver.
Synthia is the popular name for a species containing a lab-built set of genetic instructions that are close to the minimum necessary to support bacterial life - based on the DNA of a microbe called Mycoplasma genitalium.
When Venter announced the creation of a synthetic M. genitalium genome in January 2008, Synthia’s birth was thought to be imminent. Just months before, his team had demonstrated the technology for smuggling the DNA into a living bacterial cell, by performing a “genome transplant” between two differentMycoplasma species.
But perfecting the method so that Synthia’s DNA will “boot up” inside a bacterial cell stripped of its own genome has proved harder than Venter anticipated. His team has had to battle various problems, including host-cell enzymes that seek and destroy alien DNA.
Elsewhere, other researchers are working on the component parts of an entirely synthetic cell. George Church of Harvard University has already announced that his team has made a self-assembling ribosome - the cellular factory responsible for making proteins. He expects the next step - to get synthetic ribosomes to self-replicate - to happen in 2010.
A completely synthetic cell remains a distant goal, however. So let’s hope “Waiting for Synthia” gets a new final act sometime soon. Venter has shown that he can handle being criticised for playing God. But for someone with his reputation for achievement, playing Godot can’t be so much fun.”
Kósa Ferenc
Egy biológus Biológiáról szóló bejegyzései.
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