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Comment by Dr. Krishna Kumari Challa on July 16, 2024 at 6:48am

Study identifies epigenetic 'switches' that regulate the developmental trajectories of single cells

Individual cells in the human body develop progressively over time, ultimately becoming specialized in specific functions. This process, known as cell differentiation or specialization, is central to the formation of distinct cell populations that serve different purposes.

Past studies suggest that the fate of cells is also modulated by epigenetic mechanisms (i.e., interactions between genes and environmental factors). These epigenetic mechanisms, however, have so far been proved difficult to pinpoint.

Researchers recently carried out a study aimed at exploring the epigenetic processes influencing the developmental trajectories of individual cells, using human brain and retina organoids derived from pluripotent stem cells.  

Their paper, published in Nature Neuroscience, outlines a single-cell epigenome-wide map that could aid the study of human cell fate determination.

This paper was inspired by the need to better understand the epigenetic mechanisms that regulate cell fate decisions during human brain and retina development.

The primary objective was to create a comprehensive single-cell epigenomic map that could capture the transitions from pluripotent stem cells to differentiated neural cells.

To study the epigenetic mechanisms underpinning the diversification of human cells, the researchers carried out experiments on human brain and retina organoids, three-dimensional (3D), miniaturized versions of human organs created in laboratory settings, using pluripotent stem cells.

Part 1

Comment by Dr. Krishna Kumari Challa on July 15, 2024 at 11:22am

The Exact Part of The Brain Behind Your Curiosity
Being curious is a quintessential part of being human, driving us to learn and adapt to new environments. For the first time, scientists have pinpointed the spot in the brain where curiosity emerges.
The discovery was made by researchers  who used functional magnetic resonance imaging (fMRI) scans to measure oxygen levels in different parts of the brain, indicating how busy each region is at any one time.

Knowing where curiosity originates could help us understand more about how human beings tick, and potentially lead to therapies for conditions where curiosity is lacking, such as chronic depression.
This is really the first time we can link the subjective feeling of curiosity about information to the way your brain represents that information.
In the experiments conducted on curiosity and fMRI scans, notable activity was spotted in three regions: the the occipitotemporal cortex (linked to vision and object recognition), the ventromedial prefrontal cortex or vmPFC (which manages perceptions of value and confidence), and the anterior cingulate cortex (used for information gathering).
The vmPFC appears to act as a sort of neurological bridge between levels of certainty recorded by the occipitotemporal cortex, and subjective feelings of curiosity – almost like a trigger telling us when to be curious. The less confident the volunteers were about the image subject, the more curious they were about it.
These results illuminate how perceptual input is transformed by successive neural representations to ultimately evoke a feeling of curiosity," write the researchers in their published paper.

https://www.jneurosci.org/content/early/2024/07/04/JNEUROSCI.0974-2...

Comment by Dr. Krishna Kumari Challa on July 15, 2024 at 10:42am

LUCA, they found, was probably very similar to a prokaryote, a single-celled organism that doesn't have a nucleus. It was obviously not reliant on oxygen, since there would have been little oxygen available; that's not unexpected for a microbe. As such, its metabolic processes probably produced acetate.

But there was something else interesting. LUCA appears not to have been alone.
This study showed that LUCA was a complex organism, not too different from modern prokaryotes.
But what is really interesting is that it's clear it possessed an early immune system, showing that even by 4.2 billion years ago, our ancestor was engaging in an arms race with viruses.
Because its metabolic processes would have produced waste products that could be used by other lifeforms, they could have emerged not long after LUCA did.

This implies that it takes relatively little time for a full ecosystem to emerge in the evolutionary history of a planet – a finding that has implications far beyond our own little pale blue dot.

https://www.nature.com/articles/s41559-024-02461-1

Part 2

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Comment by Dr. Krishna Kumari Challa on July 15, 2024 at 10:41am

Study Finds Life on Earth Emerged 4.2 Billion Years Ago

Once upon a time, Earth was barren. Everything changed when, somehow, out of the chemistry available early in our planet's history, something started squirming – processing available matter to survive, to breed, to thrive.

What that something was, and when it first squirmed, have been burning questions that have puzzled humanity probably for as long as we've been able to ask "what am I?"

Now, a new study has found some answers – and life emerged surprisingly early.

By studying the genomes of organisms that are alive today, scientists have determined that the last universal common ancestor (LUCA), the first organism that spawned all the life that exists today on Earth, emerged as early as 4.2 billion years ago.

Earth, for context, is around 4.5 billion years old. That means life first emerged when the planet was still practically a newborn.

Back when it was new, Earth was a very different place, with an atmosphere that we would find extremely toxic today. Oxygen, in the amount current life seems to need, didn't emerge until relatively late in the planet's evolutionary history, only as early as around 3 billion years ago.

But life emerged prior to that; we have fossils of microbes from 3.48 billion years ago. And scientists think that conditions on Earth may have been stable enough to support life from around 4.3 billion years ago.

But our planet is subject to erosional, geological, and organic processes that make evidence of that life, from that time, almost impossible to find.

a team of scientists went looking somewhere else: in genomes from living organisms, and the fossil record.

Their study is based on something called a molecular clock. Basically, we can estimate the rate at which mutations occur, and count the number to determine how much time has passed since the organisms in question diverged from common ancestors.

All organisms, from the humblest microbe to the mightiest fungus, have some things in common. There's a universal genetic code. The way we make proteins is the same. There's an almost universal set of 20 amino acids that are all oriented the same way. And all living organisms use adenosine triphosphate (ATP) as a source of energy in their cells.

Researchers  worked out, based on these similarities and differences, how long it has been since LUCA's successors started to diverge. And, using complex evolutionary modeling, they were able to learn more about LUCA itself – what it was, and how it survived on an Earth so very inhospitable to its descendants.

Part1

Comment by Dr. Krishna Kumari Challa on July 15, 2024 at 9:17am

Urban animals modify their behaviors, learning, and problem-solving skills to cope with urban challenges, reflecting a dynamic response to urban landscapes," they write. "Similarly, humans alter their urban spaces, influencing wildlife behavior and evolution. This reciprocal adaptation between humans and wildlife is fundamental to understanding co-culture."
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Future research is also needed to examine the possibility of cultural and genetic co-evolution—the idea that species' cultures and genomes are evolving in concert. A key question, the researchers say, is "In the context of co-culture, how do cultural adaptations influence genetic evolution, and vice versa, across different species and environments?"
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Cédric Sueur et al, Co-cultures: exploring interspecies culture among humans and other animals, Trends in Ecology & Evolution (2024). DOI: 10.1016/j.tree.2024.05.011

Part 2

• Animals interact both within and between species, sharing common spaces.
• Animals exhibit cultural behaviours.
• Animals can influence and learn from each other, including interactions with other species.
• The co-culture concept suggests that two populations of different species can influence each other's cultures through synchronised activities.
• Co-culture emphasises cultural adaptations within ecological niches.

Comment by Dr. Krishna Kumari Challa on July 15, 2024 at 9:16am

Introducing co-cultures: When co-habiting animal species share culture

Cooperative hunting, resource sharing, and using the same signals to communicate the same information—these are all examples of cultural sharing that have been observed between distinct animal species. In an opinion piece published June 19 in the journal Trends in Ecology & Evolution, researchers introduce the term "co-culture" to describe cultural sharing between animal species. These relationships are mutual and go beyond one species watching and mimicking another species' behavior—in co-cultures, both species influence each other in substantial ways.

Co-culture challenges the notion of species-specific culture, underscoring the complexity and interconnectedness of human and animal societies, and between animal societies," write the authors.

These cross-species interactions result in behavioral adaptations and preferences that are not just incidental but represent a form of convergent evolution.

Co-cultures have been observed between humans and nonhuman animals—for example, between humans and honeyguides in Tanzania and Mozambique, where the birds lead humans to honeybee nests. They are also evident between different species of nonhuman animals—for example, cooperative scavenging between ravens and wolves, cooperative hunting between false killer whales and bottlenose dolphins, and signal sharing between distinct species of tamarin. Ultimately, this inter-species sharing of culture could drive evolution, the researchers say.

"Cultural behaviors that enhance survival or reproductive success in a particular setting can lead to changes in population habits that, over time, could drive genetic selection," they write.

To extend our understanding of co-cultures, the researchers say that future studies could start by investigating wild animals in urban environments.

Part 1

Comment by Dr. Krishna Kumari Challa on July 15, 2024 at 9:12am

New study finds 40% of cancer cases and almost half of all deaths  linked to modifiable risk factors

A study led by researchers at the American Cancer Society (ACS) finds four in 10 cancer cases and about one-half of all cancer deaths in adults 30 years old and older could be attributed to modifiable risk factors, including cigarette smoking, excess body weight, alcohol consumption, physical inactivity, diet, and infections.

Cigarette smoking was by far the leading risk factor, contributing to nearly 20% of all cancer cases and 30% of all cancer deaths. The findings are published in the journal CA: A Cancer Journal for Clinicians.

The risk factors included cigarette smoking (current and former smoking); secondhand smoke; excess body weight; alcohol consumption; consumption of red and processed meat; low consumption of fruits and vegetables, dietary fiber, and dietary calcium; physical inactivity; ultraviolet (UV) radiation; and infection with Epstein-Barr virus (EBV), Helicobacter pylori, hepatitis B virus (HBV), hepatitis C virus (HCV), human herpes virus-8 (HHV-8; also called Kaposi sarcoma herpesvirus), human immunodeficiency virus (HIV), and human papillomavirus (HPV). 

CA: A Cancer Journal for Clinicians (2024)

Comment by Dr. Krishna Kumari Challa on July 15, 2024 at 9:01am

These new results reveal a mystery. In the largest animals, there is something preventing brains from getting too big. Whether this is because big brains beyond a certain size are simply too costly to maintain remains to be seen. But as we also observe similar curvature in birds, the pattern seems to be a general phenomenon—what causes this 'curious ceiling' applies to animals with very different biology.

Chris Venditti et al, Co-evolutionary dynamics of mammalian brain and body size, Nature Ecology & Evolution (2024). DOI: 10.1038/s41559-024-02451-3

Part 2

Comment by Dr. Krishna Kumari Challa on July 15, 2024 at 9:00am

Brain size riddle solved as humans exceed evolutionary trend

The largest animals do not have proportionally bigger brains—with humans bucking this trend—a study published in Nature Ecology & Evolution has revealed.

Researchers collected an enormous dataset of brain and body sizes from around 1,500 species to clarify centuries of controversy surrounding brain size evolution.

Bigger brains relative to body size are linked to intelligence, sociality, and behavioral complexity—with humans having evolved exceptionally large brains. The new research reveals the largest animals do not have proportionally bigger brains, challenging long-held beliefs about brain evolution.

For more than a century, scientists have assumed that this relationship was linear—meaning that brain size gets proportionally bigger, the larger an animal is. We now know this is not true. The relationship between brain and body size is a curve, essentially meaning very large animals have smaller brains than expected.

The research reveals a simple association between brain and body size across all mammals which allowed the researchers to identify the rule-breakers—species which challenge the norm.

Among these outliers includes our own species, Homo sapiens, which has evolved more than 20 times faster than all other mammal species, resulting in the massive brains that characterize humanity today. But humans are not the only species to buck this trend.

All groups of mammals demonstrated rapid bursts of change—both towards smaller and larger brain sizes. For example, bats very rapidly reduced their brain size when they first arose, but then showed very slow rates of change in relative brain size, suggesting there may be evolutionary constraints related to the demands of flight.

There are three groups of animals that showed the most pronounced rapid change in brain size: primates, rodents, and carnivores. In these three groups, there is a tendency for relative brain size to increase in time (the "Marsh-Lartet rule"*). This is not a trend universal across all mammals, as previously thought.

* a tendency for relative brain sizes to increase with time. But, as the study notes, this rule is not universally applicable across all mammals
part 1

Comment by Dr. Krishna Kumari Challa on July 13, 2024 at 11:41am

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