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Tag: cells

  • Life on Earth: A Trillion Times More Cells than Sand Grains

    Life on Earth: A Trillion Times More Cells than Sand Grains

    New calculations indicate that the number of living cells on Earth surpasses the estimated count of sand grains and stars in the universe. Researchers estimate that there are one trillion times more cells than grains of sand on Earth and one million times more cells than there are stars in the universe. These calculations provide critical insights into our planet’s biological diversity and could help predict how lifeforms will utilize carbon in the future.

    living cells

    These calculations are essential for scientists in their quest to ask meaningful questions and comprehend the world around us. Being able to count and measure different aspects of our environment is fundamental for conducting scientific research.

    Peter Crockford, a geologist at Carleton University, led the study. The research began with an inventory of the number of microbes in the ocean, soil, and Earth’s subsurface, combined with the count of cells in larger organisms, to determine the number of cells currently alive, which amounts to an astonishing 10^30 cells, primarily cyanobacteria.

    The key to this calculation was primary productivity, the process that transforms carbon dioxide (CO2) into carbon-based compounds that sustain life. These compounds, such as sugars and starches, travel up the food chain: photosynthesizing microbes and plants are consumed by other organisms, which, in turn, are eaten by larger organisms. All of these eventually die, decompose, and return CO2 to the atmosphere, completing the carbon cycle.

    To understand how primary productivity has evolved over Earth’s history, the researchers analyzed various factors, such as the numbers and types of photosynthesizing organisms at different points in time, as well as the amount of food they produced. By examining the primary productivity of modern cells, they could estimate the number of cells needed to sustain past productivity levels. They also adjusted their calculations for factors like the emergence of different lifeforms and the impact of ice ages on their activity.

    The research reveals that, over time, the number of cells on Earth has cycled through all of the planet’s carbon about 100 times. However, it also suggests that there is an upper limit to these numbers. Earth cannot support more than 10^41 cells.

    The findings have been met with support from scientists in various fields. The numbers are seen as reasonable and realistic, providing insights into the evolution of life on Earth. The calculations also offer a glimpse into the future, where it’s suggested that changes in the Earth’s environment, including alterations in CO2 levels, could impact life on the planet, possibly leading to the decline of biomass and a radically transformed Earth in the distant future.

  • Beyond Motor Coordination: Surprising Functions of Purkinje Cells in Cerebellum

    Beyond Motor Coordination: Surprising Functions of Purkinje Cells in Cerebellum

    A recent study from the University of Chicago has revealed exciting new findings about brain cells called Purkinje cells. These cells are found in the cerebellum, which is a part of the brain responsible for coordinating movement and processing sensory information.

    Purkinje cells

    For over a century, scientists believed that Purkinje cells had only one main branch, or dendrite, that connected to a single climbing fiber from the brain stem. However, a closer look at thousands of these cells in both humans and mice showed that the conventional idea was not entirely accurate.

    The study found that almost all human Purkinje cells have multiple primary dendrites, which are like large branches sprouting from the cell body. This discovery matched the illustrations made by the Spanish researcher Santiago Ramón y Cajal, who received the Nobel Prize in 1906 for his work on brain structures. Cajal’s drawings depicted multiple dendrites, and now it seems he was right.

    About 50% of Purkinje cells in mice also have multiple primary dendrites. Interestingly, 25% of these cells receive input from multiple climbing fibers, which connect to different branches of the dendrites. This challenges the long-standing belief that each Purkinje cell connects to only one climbing fiber.

    To investigate the functional implications of these findings, the researchers conducted experiments on live mice. They found that each branch could be activated independently in cells with multiple primary dendrites, responding to different stimuli. For example, some branches respond more to light, while others are more sensitive to sound or touch.

    Multiple dendrites and climbing fibers in Purkinje cells provide more computational power to the brain. This allows brain circuits to adapt and respond to different situations that require various movements.

    Understanding the structure and connectivity of Purkinje cells could also have implications for certain diseases. Studies have shown that the connections between these cells and climbing fibers are weaker in some movement disorders, like cerebellar ataxia. On the other hand, stronger connections have been observed in genetic duplication and overexpression models of autism.

    Overall, this study has challenged the conventional understanding of Purkinje cells and their connections, shedding new light on the complexities of the cerebellum. By unraveling the mysteries of these brain cells, researchers hope to gain a deeper understanding of brain function and potential implications for neurological conditions.