segunda-feira, abril 28, 2014

As aves de Chernobyl

"1986, ano que o terrível desastre nuclear de Chernobyl (Ucrânia) aconteceu.

Com o ocorrido, a usina de Chernobyl liberou uma quantidade letal de material radioativo que contaminou uma quilométrica região atmosférica. Em termos comparativos, o material radioativo disseminado naquela ocasião era assustadoramente quatrocentas vezes maior que o das bombas utilizadas no bombardeio às cidades de Hiroshima e Nagasaki, no fim da Segunda Guerra Mundial.

Estudos científicos revelam que a população atingida pelos altos níveis de radiação sofre uma série de enfermidades. Além disso, os descendentes dos atingidos apresentam uma grande incidência de problemas congênitos e anomalias genéticas".

Desde que a cidade foi evacuada, se tornou uma cidade fantasma.....


.....a não ser pela fauna silvestre.


Li um trabalho muito interessante que mostra os efeitos da radiação nas aves que vivem na região isolada.

A exposição a radiação ionizante causa danos às células e produz compostos chamados de radicais livres. O corpo se protege contra estes compostos usando antioxidantes, mas quando a taxa de radicais livres é muito alta, os antioxidantes não dão conta, causando envelhecimento acelerado, câncer e morte. 

Foram capturadas 152 aves de 16 espécies diferentes em regiões diversas dentro do perímetro de isolamento (algumas mais e outras menos afetadas pela radiação).

Eles coletaram sangue (para medir níveis de antioxidantes, danos no DNA e stress oxidativo) e penas (para medir os níveis de dois tipos de melanina - a eumelanina e a feomelanina) de cada ave .

A maior parte dos resultados foram surpreendentes: os níveis de antioxidantes estavam aumentados e o estado geral das aves era ótimo, já o nível de stress oxidativo e os danos no DNA estavam baixos.

No entanto, as aves que produzem mais feomelanina (coloração avermelhada e rosada) obtiveram resultados negativos: os níveis de antioxidantes estavam diminuidos e o estado geral das aves era ruim, já o nível de stress oxidativo e os danos no DNA estavam aumentados.

O motivo disso? A feomelanina utiliza uma grande quantidade de antioxidantes para a sua produção.

Este é o primeiro estudo que mostra que animais conseguem se adaptar a exposição a radiação ionizante.

Desculpa o post longo, mas era um tema meio complexo :)
Boa semana!
Verônica Pardini, DVM
Nearly three decades since the disaster and it seems the birds living in the exclusion zone around Chernobyl are adapting to long-term radiation exposure. And some of them aren’t even just coping, they appear to be benefiting.
Ionizing radiation damages cells by producing reactive compounds called free radicals. The body protects itself using antioxidants, but if their levels are too low, then the radiation produces genetic damage and oxidative stress (when free radicals overwhelm the bodies defenses), leading to aging and death. 
Previous studies of wildlife at Chernobyl showed that chronic radiation exposure depleted antioxidants and increased oxidative damage. “We found the opposite,” Ismael Galván of the Spanish National Research Council says in a news release.
Using mist nets, Galván and colleagues captured 152 birds from 16 different species at eight different sites inside or near the exclusion zone, an area that spans 30 kilometers in radius. Humans can’t live here, although the area has become somewhat of an accidental ecological experiment. (Pictured, mist nets strung along a pasture near the power plant.) The team measured the background radiation levels of each site -- these ranged from 0.02 to 92.90 micro Sieverts per hour. 
They took feather and blood samples from each bird before releasing them. In the blood samples, they measured levels of the antioxidant glutathione, oxidative stress, and DNA damage. With the feathers, they measured levels of melanin pigments. Eumelanin (black and brown) and pheomelanin (red and pink) are types of melanin. Because the production of the latter uses up antioxidants, animals who produce the most pheomelanins are likely to be more susceptible to the effects of ionizing radiation. They just don’t have enough antioxidants left over to fend off the free radicals. 
The results reveal that with increasing background radiation, the birds’ overall body condition and antioxidant levels increased, while oxidative stress and DNA damage decreased. 
However, birds who produce larger amounts of pheomelanin and lower amounts of eumelanin pay a cost: poorer body condition, decreased glutathione, and increased oxidative stress and DNA damage. The two negatively affected birds -- the great tit (Parus major) and the barn swallow (Hirundo rustica) -- both produce large amounts of the pinkish pigment in their feathers. 
Previous lab experiments have shown that, with prolonged exposure to low doses, humans and other animals can adapt to radiation. And that it increases resistance to larger, subsequent doses. This study shows the first evidence that animals in the wild can adapt to ionizing radiation. 

Read more at http://www.iflscience.com/plants-and-animals/birds-adapting-chernobyls-radiation#tRwRJAkzgtMvDU6B.99
Nearly three decades since the disaster and it seems the birds living in the exclusion zone around Chernobyl are adapting to long-term radiation exposure. And some of them aren’t even just coping, they appear to be benefiting.
Ionizing radiation damages cells by producing reactive compounds called free radicals. The body protects itself using antioxidants, but if their levels are too low, then the radiation produces genetic damage and oxidative stress (when free radicals overwhelm the bodies defenses), leading to aging and death. 
Previous studies of wildlife at Chernobyl showed that chronic radiation exposure depleted antioxidants and increased oxidative damage. “We found the opposite,” Ismael Galván of the Spanish National Research Council says in a news release.
Using mist nets, Galván and colleagues captured 152 birds from 16 different species at eight different sites inside or near the exclusion zone, an area that spans 30 kilometers in radius. Humans can’t live here, although the area has become somewhat of an accidental ecological experiment. (Pictured, mist nets strung along a pasture near the power plant.) The team measured the background radiation levels of each site -- these ranged from 0.02 to 92.90 micro Sieverts per hour. 
They took feather and blood samples from each bird before releasing them. In the blood samples, they measured levels of the antioxidant glutathione, oxidative stress, and DNA damage. With the feathers, they measured levels of melanin pigments. Eumelanin (black and brown) and pheomelanin (red and pink) are types of melanin. Because the production of the latter uses up antioxidants, animals who produce the most pheomelanins are likely to be more susceptible to the effects of ionizing radiation. They just don’t have enough antioxidants left over to fend off the free radicals. 
The results reveal that with increasing background radiation, the birds’ overall body condition and antioxidant levels increased, while oxidative stress and DNA damage decreased. 
However, birds who produce larger amounts of pheomelanin and lower amounts of eumelanin pay a cost: poorer body condition, decreased glutathione, and increased oxidative stress and DNA damage. The two negatively affected birds -- the great tit (Parus major) and the barn swallow (Hirundo rustica) -- both produce large amounts of the pinkish pigment in their feathers. 
Previous lab experiments have shown that, with prolonged exposure to low doses, humans and other animals can adapt to radiation. And that it increases resistance to larger, subsequent doses. This study shows the first evidence that animals in the wild can adapt to ionizing radiation. 

Read more at http://www.iflscience.com/plants-and-animals/birds-adapting-chernobyls-radiation#tRwRJAkzgtMvDU6B.99
Related Posts Plugin for WordPress, Blogger...

2 comentários: