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Scientists have found that human beings age at a molecular level in two accelerated bursts – first at the age of 44, and then again at 60.

In a study published in the journal Nature Aging, scientists at Stanford University and Nanyang Technological University in Singapore followed 108 participants over several years to observe aging changes in their molecules — RNA, proteins and participants’ microbiomes.

The scientists found that human aging does not happen in a gradual, linear way. Rather, the majority of the molecules they studied showed accelerated, non-linear changes at the ages of 44 and 60.

Xiaotao Shen, an assistant professor in microbiome medicine at Nanyang Technological University and first author of the study, told CNN that the results show “we are not becoming old gradually.” Some points in time are particularly important for our aging and health, he added.

For example, the ability to metabolize caffeine notably decreases – first around the age of 40 and once more around 60. Components involved in metabolizing alcohol also diminish, particularly around the age of 40, Michael Snyder, chair of the department of genetics at Stanford and an author of the study, told CNN, referring to the two waves of aging.

Snyder added that, anecdotally, “people often get muscle injuries and see their fat accumulation hit in their 40s (related to lipid metabolism), and definitely sarcopenia (muscle loss) hit people in their 60s — this is a very big deal.”

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Generation X and millennials face a higher risk of getting certain types of cancer when compared to earlier generations, according to a large new study published Wednesday.

In the study, published in the Lancet Public Health journal, researchers from the American Cancer Society (ACS) studied 34 of the most common cancers. They found that cancer incidence rates continued to rise in progressively younger generations in 17 of the cancers, including breast, pancreatic and gastric cancers.

For eight of the 17 cancers, researchers found that cancer incidence rates rose for each successive birth cohort since 1920. For nine of them, incidence rates increased in younger cohorts, after first declining in older birth cohorts.

“These findings add to growing evidence of increased cancer risk in post-Baby Boomer generations, expanding on previous findings of early-onset colorectal cancer and a few obesity-associated cancers to encompass a broader range of cancer types,” Hyuna Sung, lead author of the study, said in a statement.

The study highlighted the need to identify and address the “underlying risk factors in Gen X and Millennial populations” to explain and address these rising cancer rates in younger generations, said Ahmedin Jemal, a senior author of the study.

“Birth cohorts, groups of people classified by their birth year, share unique social, economic, political, and climate environments, which affect their exposure to cancer risk factors during their crucial developmental years,” Sung added.

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An international team of scientists has studied 33 years of satellite data and found that Earth is actually getting significantly greener as a result of rising carbon dioxide levels, with greater carbon emissions over the past three decades leading to a huge increase in the amount of leaves on plants and trees.

"We were able to tie the greening largely to the fertilising effect of rising atmospheric CO2 concentration by tasking several computer models to mimic plant growth observed in the satellite data," said researcher Ranga Myneni from Boston University.

But how are airborne pollutants spurring vegetation growth? The process, called the carbon fertilisation effect, results from leaves absorbing CO2 from the air as part of photosynthesis. With greater levels of carbon in the atmosphere, plants and trees and even crops actually grow faster, particularly in warm climates.

And with the levels of carbon in the atmosphere as high as they are now, that's seen a massive increase in the amount of vegetation over the surface of the planet.

"The greening over the past 33 years reported in this study is equivalent to adding a green continent about two times the size of mainland USA (18 million km2), and has the ability to fundamentally change the cycling of water and carbon in the climate system," said one of the team, Zaichun Zhu from Peking University in China.

As a result of the growth in recent decades, vegetation now covers almost a third (32 percent) of the planet's total surface area, occupying about 85 percent of all ice-free land.

But while extra greenery – and its ability to absorb atmospheric carbon – sounds like a positive for the environment, the scientists warn that this side effect of high carbon levels will only be temporary, and won't ultimately help against other consequences of climate change, such as severe weather, and rising temperatures and sea levels.

"[S]tudies have shown that plants acclimatise, or adjust, to rising CO2 concentration and the fertilisation effect diminishes over time," said Philippe Ciais from the Laboratory of Climate and Environmental Sciences in France.

Nor is CO2 the only factor behind the current green trends. The scientists say nitrogen use in agricultural fertilisers, climate change generally, and land management also contribute to the phenomenon in lesser amounts.

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Wild sharks off the coast of Brazil have tested positive for cocaine, according to new study by Brazilian scientists, in the latest research to demonstrate how illegal drug consumption by humans is harming marine life.

According to a study entitled Cocaine Shark and published in the journal Science of the Total Environment, scientists dissected the bodies of 13 sharpnose sharks (Rhizoprionodon lalandii) caught in fishermen’s nets off a beach in Rio de Janeiro.

All 13 tested positive for the drug.

Previous studies have found cocaine in river, sea and sewage water, and traces of the drug have been found in other sea creatures such as shrimps.

A separate study recently revealed that high levels of cocaine residue were causing “serious toxicological effects” in animals such as brown mussels, oysters and eels in Santos Bay, in the Brazilian state of São Paulo.

But the concentration found in the Rio sharks was 100 times higher than had been found in other marine animals, the researchers said.

How the cocaine ended up in the sharks remains a mystery.

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