Tag: zero gravity

Study: Long periods of weightlessness caused changes in the brain

9:55 am

Scientists studying the brains of 30 astronauts who spent from two weeks to one year on ISS have found that the longer a person stayed in weightlessness the greater the changes caused in the brain, and the longer it takes to recover.

Their findings, reported today in Scientific Reports, reveal that the brain’s ventricles expand significantly in those who completed longer missions of at least six months, and that less than three years may not provide enough time for the ventricles to fully recover.

Ventricles are cavities in the brain filled with cerebrospinal fluid, which provides protection, nourishment and waste removal to the brain. Mechanisms in the human body effectively distribute fluids throughout the body, but in the absence of gravity, the fluid shifts upward, pushing the brain higher within the skull and causing the ventricles to expand.

“We found that the more time people spent in space, the larger their ventricles became,” said Rachael Seidler, a professor of applied physiology and kinesiology at the University of Florida and an author of the study. “Many astronauts travel to space more than one time, and our study shows it takes about three years between flights for the ventricles to fully recover.”

You can read the paper here. The expansion of ventricles is a normal process due to aging, but I could not find any description in the paper noting its impact, for good or ill. Long periods of weightlessness brings it about quickly, but only temporarily.

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Research: Flies on ISS benefited greatly from simulated gravity

10:52 am

Scientists have found that providing fruitflies 1g of artificial gravity on ISS using a centrifuge acted to reduce the medical changes that weightlessness produces.

In this study, scientists sent flies to the space station on a month-long mission in a newly developed piece of hardware called the Multi-use Variable-gravity Platform (MVP), capable of housing flies at different gravity levels. The flies in this hardware had access to fresh food as they lived and reproduced. By using distinct compartments, the MVP allowed for different generations of flies to be separated. On the space station, one group of fruit flies experienced microgravity similar to their human counterparts. Another group was exposed to artificial gravity by simulating Earth’s gravity on the space station using a centrifuge – an instrument that spins to simulate gravity. While on the space station, cameras in the hardware recorded behavior of these “flyonauts”. At different points in time, some of the flies were frozen and returned to Earth to study their gene expression.

…More in-depth analysis on the ground immediately post-flight revealed neurological changes in flies exposed to microgravity. As the flies acclimated to being back on Earth after their journey, the flies that experienced artificial gravity in space aged differently. They faced similar but less severe challenges to the flies that were in microgravity.

You can read the paper here.

To some extent, this study tells us nothing. We already know from a half century of research that zero gravity causes negative physical changes in both fruit flies and humans. What we really need to know is the lowest level of artificial gravity that would be beneficial. It is much easier to engine a spacecraft to produce 0.1g of artificial gravity than 1g. Even 0.5g would ease the engineering problem. The problem is that we do not yet know the right number.

It is a shame the scientists didn’t subject some flies to 0.5g, just to find out if that level of artificial gravity worked to provide benefits.

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New changes to the brain found from long space missions

8:38 am

Scientists have discovered a “significant increase” in the brain’s white matter that occurs after astronauts have completed long missions in weightlessness.

The team conducted brain MRIs of 11 astronauts before they traveled to the ISS, and then again one day after they returned. Scans were then performed at several interval across the following year. “What we identified that no one has really identified before is that there is a significant increase of volume in the brain’s white matter from preflight to postflight,” Kramer says. “White matter expansion in fact is responsible for the largest increase in combined brain and cerebrospinal fluid volumes postflight.”

These changes remained visible one year after spaceflight, which the researchers say indicates they could be permanent alterations. Past research has suggested that changes in the volume of cerebrospinal fluid (CSF) specifically could be a key driver of Visual Impairment Intracranial Pressure in astronauts. The authors of the new study also observed an increase in the velocity of CSF through the cerebral aqueduct, along with deformation of the pituitary gland, which they believe is related to higher intracranial pressure in microgravity.

The uncertainties for this work remain very large. For one thing, the sample (11 astronauts) is very small. For another, the permanence of this change is only suggested and remains unproven.

Nonetheless, this research adds to the growing body of research that suggests that long term weightlessness is generally not good for the human body. It also reinforces the desperate need for research into the effects of even a small amount of artificial gravity. To most efficiently design spacecraft that provide some form of centrifugal force as artificial gravity, we need to find out the minimum required. It could be providing only 10% or 30% Earth gravity could be sufficient. Or not. We just don’t know.

The engineering challenges however go up significantly the more gravity you need to create. For future interplanetary travel this information is critical.

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Does zero gravity cause intestinal issues?

9:23 am

The uncertainties of science: New research simulating microgravity on Earth now suggests that zero gravity might weaken the walls of the intestines.

The barrier function of the intestinal epithelium, he added, is critical for maintaining a healthy intestine; when disrupted, it can lead to increased permeability or leakiness. This, in turn, can greatly increase the risk of infections and chronic inflammatory conditions such as inflammatory bowel disease, celiac disease, Type 1 diabetes, and liver disease.

McCole’s team used a rotating wall vessel — a bioreactor that maintains cells in a controlled rotation environment that simulates near weightlessness — to examine the impact of simulated microgravity on cultured intestinal epithelial cells.

Following culture for 18 days in the vessel, the team discovered intestinal epithelial cells showed delayed formation of “tight junctions,” which are junctions that connect individual epithelial cells and are necessary for maintaining impermeability. The rotating wall vessel also produces an altered pattern of tight junction assembly that is retained up to 14 days after the intestinal epithelial cells were removed from the vessel.

This is good research, but it has not proved anything, merely indicated an area of research that needs a follow-up in space. I also wonder if there has been any evidence of this phenomenon from astronauts returning from long missions. As far as I know, intestinal issues have never been mentioned as a problem post flight.

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