Sunday 28 January 2024

Ants & lions, immune system & ageing, stress & bacteria in the intestine | Last Week in Science (28th Jan 2024)

The ants and the lions

The old moral story of how small ants can fight off an animal as huge as an elephant was true in the forests of Kenya until big headed ants started showing up. Scientists observed that the big head ants started to kill the native acacia ants which would have saved the acacia trees from being eaten up by the elephants.

You must be wondering how elephants getting more food to eat can affect the lions.

These acacia trees provide hiding spots to lions for hunting zebras. The absence of acacia ants, increased grazing of acacia trees by elephants that decreased the tree cover. Scientists at Wyoming University studied number of zebras in areas where big head ants had invaded comparing it to areas where they had not invaded. They also looked at how many zebras got killed in these two different regions. They also tracked the movement of lionesses in these different regions by bugging them with GPS.

After three years of tracking, the result was as the trees started getting less dense, creating more open space, the lions had trouble in hunting zebras. So, the lions started hunting buffaloes. But how can that be a big deal? For one it takes lions more energy to hunt buffaloes and at times the lions get killed in the process. Second, the increase in zebras could cause unexpected changes to the existing ecosystem of the forests in Kenya.

This study is a beautiful example of how one small change in the ecosystem can have big effects. 

Can we use the immune system to slow ageing?

Our immune system have a specific type of cells called as the T cells which are trained to recognize specific cell types - pathogens or infected cells. With the recent advances, these T cells can be trained outside the body to recognize other types of cells - like cancer cells. These trained cells are called as CAR-T cells for chimeric antigen receptor T - cell. These T cells recognize specific molecules that are present on the surface of a specific cell type.

The aged and defective cells are called as senescent cells are the ones that have stopped growing and dividing because of damage. These cells usually release signals to call immune system to destroy them and are important for preventing cancer and causing healing after injury. The senescent cells increase in different tissues as we age. Their removal becomes less effective because of the decline in the immune system as we age. In the recent study, scientists at Cold Spring Harbor Lab generated CAR-T cells to recognize aged cells of mice. What they found was when these CAR-T cells were introduced in aged mice then they prevented some of the diseases that come with ageing or because of consumption of high fat diet. These mice were also physically more active after this one time treatment.

But it still remains to be seen whether it can prolong life and whether we can use such an approach in humans.

Stress and the bacteria in the intestine

We all have heard examples of how stress can upset one's stomach. In severe cases, a disease called as Inflammatory Bowel Disease (IBD) is seen with stress that persists for a long time - called as chronic stress, which causes swelling of the intestines, stomach pain, and diarrhea. 

In the recent study, scientists at China Pharmaceutical University found that when mice were given chronic stress, for 2 weeks, they could not produce enough cells in their intestines to protect from infections and so causing swelling or inflammation. A specific type of bacteria of the Lactobacillus genus was found to be increased in their gut. These bacteria produced a chemical - indole-3-acetate (IAA). This chemical did not let the stem cells of the intestine to form the cells that would have protected the gut from infections.

What is interesting is scientists also found Lactobacillus and IAA in feces of humans who have depression. The scientists could treat the mice by giving a chemical called as alpha ketoglutarate. But it will still take time to see whether the same treatment would work in individuals suffering from inflammatory bowel disease or not. 

The scientists are still seeking answers to how the brain affects the bacteria in the intestines. These answers will help in understanding and treating many diseases that happen because of stress.

Saturday 20 January 2024

The tail wag, the sick chimps, reversing memory loss | Last Week in Science (21st Jan 2024)

The tail wag

Can't get enough of your dancing dog with their tail wagging on seeing you? Do you wonder why they wag their tails?

In a recent compilation of existing studies, researchers have made some interesting findings. Tail wagging is seen in many other animals like wolves for communicating. In the wild, wolves may show a sign of submission to a more aggressive wolf by tugging their tails between their legs or moving it slowly, which is also true for dogs. Dogs not only wag their tails more often than wolves but also show an asymmetry when it comes to their preference towards the object that they are wagging their tail after looking at. When they want to approach towards an object then their tail wags more towards the right side while it is towards the left when they want to move away from the object. The speed of their tail movement does help in distinguishing whether they are happy or aggressive.

But we still do not have clear answers to whether they feel happy and so less stressed after they dance with their tails wagging fervently, how does their brain control the movement of their tails and is this a behaviour that they can control voluntarily.

The sick chimps

It's not only animals who transfer disease causing microbes to humans but the reverse is also true. Remember how you were asked to stay away from your pets if you caught COVID-19. The cases of cheetah and deers getting affected of COVID-19 were also reported, which created a fear of SARS-COV2 evolving in these animals into more deadly forms. What we overlook is how we can affect the different species especially of apes like chimpanzees and gorillas who are closely related to us. There have been disease outbreaks in the wilderness of sanctuaries because of microbes that may not harm humans that much but have been deadly for the apes. The situation is more pertinent because many of these species have such low numbers that we cannot afford to lose them to such infections. 59% of deaths of these apes which had a known cause were because of infections coming from humans.

Transmission from tourists who do not follow safety guidelines of wearing masks and not going close to the animals are one of the causes.

A study that was conducted in Kibale National Park, Uganda traced the transmission from scientists working at the Park who had young children studying in schools. By testing children, their parents and the chimpanzees' stool samples the link was established. This brought to light the unhygienic conditions of the schools where these kids used to study and the initiation of Happy Children Happy Apes program with measures like creating awareness about infections in children. It is hoped that making scientist, tourists, Park officials, and nearby residents aware would help in keeping the apes safe. 

Reversing memory loss

Athletes like football players often get hit by the football on their heads. Multiple mild hits on the head can cause memory loss or what is known as amnesia. It was earlier thought that such a memory loss is because of the death of neurons in the brain, an event that cannot be reversed. But in a recent study scientists have shown that this isn't true. 

They gave multiple mild head injuries to mice to see the effects on its memory. These mice had neurons tagged in a manner that the scientists can switch them on and off. What they discovered was it is the connections between the neurons that are responsible for remembering a memory get affected and when the scientists switched on the specific neurons they could reverse the memory loss seen after the head injuries.

Although, we are still too far from using this finding in humans but what gives hope is the possibility of reversing memory loss in instances of mild brain injuries.

Sunday 14 January 2024

The lost great apes, EU ancestors and human fetal brain organoids | Last Week in Science (14th Jan 2024)

The lost great apes

Gigantopithecus blacki
 are the largest apes known that went extinct 210,000 years ago. They would weigh 200-300 kgs and would be as tall as 3 meters or more than 9 feet.

What changed in this ape's environment that made it extinct? To answer this question, researchers studied teeth excavated from caves in China, these apes were native to China. They found that older teeth samples indicated a healthy and balanced diet being taken by G blacki but in the teeth samples which were more recent the diet seemed to be less balanced.

By dating - finding how old the teeth samples are and comparing it with how the environment would have been at that time the researchers found further clues.

Around 3.2 million years back, G blacki were living in surroundings that were covered with dense forests mixed with open grasslands. But this environment changed in to a less dense and more open grasslands at around the time the great apes went extinct. 

The researchers are looking out for more fossils because so far they could only find teeth, especially the thigh bones so that they can better understand what made these giants apes go extinct.

Reference: Why did the world’s biggest ape go extinct?

The European ancestors

When it comes to study ancestry and human migration around the globe, researchers study the genetic material that they extract from fossils of humans. In a recent study that looked at 1000 different European ancestors, the researchers found that the current day European Union has had three different waves of human migration. The earliest coming from hunter gatherers from Asia 45,000 years ago followed by farmers from Middle East, 11,000 years ago and the most recent being the animal herders that came from Western Aisa some 5,000 years ago. 

There is a mixing of these populations but there are also clear distinctions between northern and southern Europe. This was because the animal herders mostly settled in the northern part of the Europe while the farmers went to the southern and western parts.

The northern population being at high risk of diabetes and Alzheimer's while the southern population being at high risk of developing a neurological condition known as multiple sclerosis can be explained by the ancestors being different in two geographically different regions of the EU.

Multiple Sclerosis is a disease where the body's immune system starts to attack the nerves of the body. As the animal herder started to settle in the northern regions the instances of disease would have increased because of the microbes being introduced by the animals in the environment. Individuals with an overactive immune system would be at an advantage in this change in the environment. This would explain why the northern population have more individuals that have an over active immune system and increasing the chances of developing auto immune disease like Multiple Sclerosis.

The study also revealed that in certain places like in Denmark the migrants completely replaced the existing local population by killing them. I wonder if an in depth analysis might be able to reveal more about the evolution of the killer instinct of humans as we advanced towards the modern world. 

Reference: Ancient DNA reveals origins of multiple sclerosis in Europe 

Mini brains from human fetus

Brain organoids are mini brains grown in the lab that help scientists to study how the brain develops or what goes wrong in diseases where the brain is not able to develop properly.

Till now, scientists have grown brain organoids from stem cells that can be created in the lab by taking cells from adult humans. While these brain organoids do help in understanding how different brain cells form but further development and forming of connections between different brain regions cannot be studied. This is where tissue from fetus can help. But using human fetal tissue especially the brain is banned in many countries like the USA. The current research happened in the EU where there is no ban. The researchers also ensured that the mini brains were not conscious or feeling pain, an ethical concern that surrounds research around growing mini brains in the lab.

The researchers used brain tissue from 12 to 15 week old aborted fetuses. They could grow different parts of the brain in a dish by taking slices from the fetal brain. These formed balls of cells that resembled the different parts of the brain. They tested drugs for brain cancer on these mini fetal brain organoids after creating cancerous cells in them and the drugs were found to be effective. The researchers now plan to use these mini brains for screening new drugs to treat brain cancer along with better studying the development of brain.