Author Archives: HelenHu

Can We Predict the Next Mass Extinction?

Posted on March 11, 2019 | 1 comment

Asteroid Impact that killed the dinosaurs (Source: Wikimedia Commons)

Sixty-six million years ago, a massive asteroid crashed into Earth. The explosion from the impact released energy equivalent to 100 trillion tons of TNT. The mass extinction that occurred afterwards wiped out about 80% of all species at the time, including the dinosaurs. What if there was a way to predict such a catastrophe?

Do Mass Extinctions Follow a Pattern?

In 1984, researchers Raup and Sepkoski compiled data on twelve recent extinction events. Using statistics, they analyzed the data and found that a mass extinction seemed to occur about every 26 million years. This finding led to a torrent of research as scientists sought to replicate and explain this phenomenon.

The Solar System’s Journey through the Milky Way

One of the most prominent explanations were suggested by Rampino and Stothers. They proposed this pattern had something to do with our sun’s movement within the Milky Way galaxy. Just like how the earth revolves around the sun, the sun also revolves around the centre of our spiral galaxy. As the sun orbits, it also oscillates above and below the spiral arm. The gravity within our solar system fluctuates along with this vertical movement.

The sun’s orbit around Milky Way (Source: Wikimedia Commons)

According to Rampino and Stothers, the changes in gravity has an important impact on the Oort Cloud, a cluster of asteroids in the outer reaches of our solar system. When the sun is located right within the galaxy arm, the gravity from this densely packed region disturbs the Oort Cloud. As a result, Oort Cloud comets are deflected into the inner solar system, where any one of them can crash onto Earth, potentially causing a mass extinction similar to the one that killed the dinosaurs.

Oort Cloud (Source: Wikimedia Commons)

Counterargument

Equally many scientists have also criticized the existence of the 26-million-year pattern. For example, in his study, John Alroy claimed that the proposed pattern did not agree with data documenting mass extinctions of marine animals. In addition, Bailer-Jones pointed out flaws in Raup and Sepkoski’s statistics. She wrote that there were extinction events in the data that Raup and Sepkoski had omitted from the calculations. Furthermore, she noted the dates of the extinction events were uncertain, which Raup and Sepkoski did not account for. As a result, Bailer-Jones felt that Raup and Sepkoski’s calculations were not significant enough to draw such bold conclusions. Instead, she felt there’s more evidence that mass extinctions are sporadic, caused by multiple factors, including climate change.

Conclusion

The idea that mass extinctions occur at a predictable rate is both terrifying and fascinating. However, scientists are still debating whether such a pattern really exists. In the meantime, we can focus on other causes of mass extinctions. Specifically, ones we can control. Asides from meteor impacts, global warming  is also a major cause of mass extinctions and there’s not need to predict that our planet is warming at an unprecedented rate.

-Written by Helen Hu

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Parkinson’s Disease: mystery solved by a protein?

Posted on January 21, 2019 | 1 comment

Source: Army US

Parkinson’s disease is a lifelong disease with no cure. According to this website, out of all the diseases associated with the brain, Parkinson’s is the second most common. Parkinson’s is characterized by problems with movement, such as uncontrollable shaking and difficulty walking.

Unexplained Cell Death is the cause of Parkinson’s Disease

On a cellular level, Parkinson’s is the result of nerve cell death. Neurons are the cells that make up our nervous system. Since the nervous system is responsible for our ability to think, feel and move, neurons are pretty important. Especially, since, after a certain age, we stop producing new neurons.

Essentially, Parkinson’s Disease is caused by the massacre of these precious neurons. Specifically, Parkinson’s is caused by the nerve cell death in a specific part of the brain,  the Substantia Nigra. Nerve cells in this region produce dopamine, a chemical signal involved in producing movement.

As of now, we have yet to find a clear culprit responsible for the cell death in Parkinson’s. However, active research has shed some light on the matter.

Relative location of the Substantia Nigra. Source: Wikimedia Commons

Lewy Bodies’ association with Parkinson’s Disease

Lewy bodies are essentially clumps of broken protein, of different types and sizes. According to this study, Lewy bodies are especially common in the dopamine-producing cells belonging to patients with Parkinson’s. Because they have such a strong association with the disease, Lewy Bodies and their protein contents have piqued scientists’ interests.

One protein of note, is alpha-synuclein. In the healthy body, the function of this protein is unknown. In diseased state, however, scientists have found they make up a large portion of Lewy Bodies. With this, we turn to another study that investigated alpha-synuclein’s role in hereditary Parkinson’s Disease.

Example of a Lewy Body (the dark red circle). Source: Wikimedia Commons

Alpha-Synuclein’s role in Hereditary Parkinson’s

There are two broad categories of Parkinson’s: hereditary and non-hereditary. The hereditary type is rare and, like most hereditary disease, the cause can be found in the patient’s genes. Specifically, researchers have found a mutation in the gene that codes for alpha-synuclein. The mutation ended up producing proteins with the wrong shape. The correct proteins should have what is called an alpha helix shape; meanwhile, the defective protein had a beta sheet shape instead (refer to diagram below). Unlike alpha helices, beta sheets have the ability to stack on top of each other to form an amyloid fibril. These structures start to pose a problem because they are hard to degrade and are useless, just hanging around inside the cell. Amyloid fibrils have the potential to kill neurons and explains the cell death seen in this particular type of Parkinson’s.

Source: Wikimedia Commons

The researchers for this study feel that the same mutation is probably no the cause for the more common, non-hereditary version of this disease. However, they also feel that a similar process may be at play here and their findings have provided groundwork for future research.

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