What even are cats?

Cats are strange. They constantly seem to be plotting to kill you or to take over the world. They lend their name to quantum physics thought experiments or grinning characters from children’s tales. They come up with creative yet actually very annoying ways to brighten your day, and they only participate in science experiments when they feel like it.

Cats are strange and the scientific community at least agrees on this fact. A 2014 study wondered what the physical nature of cats was, asking the very important question: are cats solid or fluid?*

Fluid dynamics for some very fluid cats.

Marc-Antoine Fardin used a scientific approach to answer the question “Can a Cat Be Both a Solid and a Liquid?”

Here was his conundrum:
Cat’s are generally assumed to be solid. You know, you can touch them and they feel pretty solid. But on the other hand, cat’s fit into really small spaces and can seemingly adjust their form to the container they are in – a property usually attributed to fluids. This is commonly known in internet circles as I fits, I sits.”

A kitten fitting in a wine glass to illustrate that cats can fit into any small space.
Who needs a glass of whine when you can drink fur?
(Image credit: unknown)

The author takes a rheological approach (rheology = the study of flow of matter) to try to differentiate between whether the deformation of a cat is solid deformation or fluid flow. Solids can be deformed, especially if they are soft. Think Play-Doh, which can take any shape while keeping the same volume as opposed to honey, which can also take any shape while keeping the same volume but can be poured.

To me, “Can a cat be poured?” is the question worth asking, and this might be difficult to test without ending up with a lot of scratches.

Reading the paper, I was starting to think the author didn’t take his research very seriously (among his acknowledgements he thanks two people – or cats, I don’t know – for “providing a reliable technique to load Felis catus in different geometries: 1.Bring an empty box; 2. Wait.”). That said, studying the physical nature of cats could bring us closer to understanding the nature of matter itself. More recent experiments are promising:

It seems that the duality of cats extends beyond dead or alive.


Source:
On the Rheology of Cats,” Marc-Antoine Fardin, Rheology Bulletin, vol. 83, 2, July 2014, pp. 16-17 and 30.

* The study won the 2017 Ig Nobel prize for Physics. The prize awarded to science that first makes you laugh and then makes you think. To be honest, it makes you think that the whole thing was a joke in the first place. It probably was.

Twinsies

The twin paradox states the following:

There are two identical twins. One of them travels through space in a high-speed rocket. When they return home, the Earth-bound twin has aged more. This is a result of special relativity. Very briefly, this is due to time slowing down as higher speeds are reached, and why Matthew McConaughey returned to Earth only to find his 90-something year old daughter on her dying bed.

This thought experiment has long been exactly that, a though experiment. But recently, we actually were able to learn what happens to twins when one is in space (granted, not in a high-speed rocket, but on the ISS) for almost a year, while the other twin stays on Earth.

Real Space Twinsies

On March 27 2015, astronaut Scott Kelly arrived at the International Space Station (ISS), while his brother, astronaut Mark Kelly, remained on Earth. (One can have a discussion on who was the luckier of the two.) They did the same activities, ate the same things, and followed the same schedule*, the only difference being that Scott was 400 km from the Earth’s surface, travelling at a speed of 7.66 km/s, while Mark was 0 km from the Earth surface, travelling at a speed of merely 460 m/second, as we all are.

340 days later, March 1 2016, Scott returned to Earth. For the full duration of his time on the ISS, as well as after his return, numerous samples were collected and tests were conducted to monitor his health and compare the physiological and biological changes that happened as a consequence of spacelife. Using his twin brother, a perfect genetic duplicate, as a control.

twins patch
The Twin Study, a massive undertaking involving lots of collaboration and fancy badge design.

The effects of space

There are many “unusual” aspects about living in space, compared to living on Earth, including the odd noises of the ISS, the isolation (Scott was in contact with a mere 12 people during those 340 days), the ultra-controlled environment, a disruption of the normal body clock (imagine perpetually being jet-lagged because of constant switching of time zones), living in micro gravity and the excess of radiation.

An ultra-combined effort, i.e. a major collaboration between a lot of different labs that looked at all possible aspects of physiological and biological function, the effects of 340 days in space (in this specific set of twins) was published last month. There are a lot of changes that occur to the human body in space, some more severe than others.

An immense effort and a lot of numbers went into creating, collecting and comparing samples from the twins. Credit: NASA

There are some changes that don’t really matter much, like changes in the gastrointestinal microbiome and changes in biomass, which were affected during Scott’s time in space, but rapidly returned to normal after he returned. Not much to worry about.

Mid-level risks included known effects of living in microgravity such changes in bone density (you don’t really need to use your skeletal muscles while floating around) and changes in how the heart pumps around blood (you don’t need to fight gravity to pump blood to the head). NASA already knows this and therefore has a rigorous rehabilitation program for returning astronauts to re-acclimatize to Earth’s gravity.

However, it’s the high-risk findings that we all have to worry about, which a mostly due to prolonged floating and prolonged radiation exposure. Due to changes in air pressure as well as that thing I mentioned about blood pumping, a lot of astronauts experience ocular issues after their return, a risk that only increases with increased dwell time off-Earth. This can severely compromise vision. There is also evidence of some cognitive decline. Both those aspects are worrying in the light of long term space travel, we would hope that space-explorers can see and think clearly while carrying out dangerous tasks in dangerous conditions. And that’s without considering a final severe risk…

Who’s the oldest twin?

In addition, the radiation that Scott experienced on ISS is pretty much equivalent to 50 years of normal exposure on Earth. This causes significant genomic instability and DNA damage, and consequentially an increased risk of developing cancer.

One example of this genomic instability has to do with telomeres**. Telomeres are bits of DNA that cap the end of chromosomes. Every time a cell divides, and in the process duplicates its whole DNA library, the telomeres get shorter. When they get too short, the cell can no longer divide. This is something that happens naturally during aging: shortening of telomeres phases out cells until they can no longer divide. Eventually, this leads to cell death.

1 year of space had an odd effect on Scott’s telomeres. Some of them grew longer, while others showed shortening. However, the lengthened telomere returned to normal after Scott’s landing on Earth, while the shortening persisted. So even though Scott was the space twin in our paradox, he seems to have ended up aging faster than Mark…

At a glance, the different effects of one year in space on a human body. Well, it probably takes more than a glance to read this.

A lot happens to a body in space

Overall, the results are pretty surprising, prolonged living in space had more of an effect on the human body than researchers expected. And there is probably a lot more to learn, even just with the data collected from Scott and Mark.

On one hand, the twin study showed how resilient and robust the human body is. 91.3% of Scott’s gene expression levels returned to his baseline level within six months of landing, and some of the changes that occurred to his DNA and microbiome were no different than what occurs in high-stress situations on Earth. That’s amazing, the human body has not evolved to survive in space, but it seems to do pretty well considering how outlandish the conditions are!

On the other hand, the prolonged exposure to microgravity and high radiation does have severe effects on the human health, leading to increased risk for compromised vision, cardiovascular disease, and cancer development. Even with the rigorous preparation and rehabilitation programs astronauts go through before and after spaceflight, some of these effects will be impossible to avoid.

The massive study, combining the effort of 84 researchers in 12 different universities is a feat of collaboration (though nothing compared to the black hole telescope, if I’m honest) and it’s definitely a first that the genomes of space vs. Earth could be compared with a true genetic control. This compiled study, and the many pieces of research that are expected to be published in the next year with the results from the individual studies, provide crucial insight on the effects of space in the long term. If we think that it takes approximately 1 year for a return journey to Mars, this research is valuable for the health of future astronauts and mankind’s ambition to explore further into space.


Want to know more? Watch NASA’s video on the three key findings, or read more in the Science paper or the NASA website (links below).


Sources:

Markus Löbrich and Penny A. Jeggo. Hazards of human spaceflight. Science 364 (6436) p. 127-128. 2019. DOI: 10.1126/science.aaw7086

Francine E. Garrett-Bakelman, et al. The NASA Twins Study: A multidimensional analysis of a year-long human spaceflight.
Science 364 (6436) eaau8650. 2019. DOI: 10.1126/science.aau8650

Twin study on the NASA website: https://www.nasa.gov/twins-study

Cover image: The International Space Station crosses the terminator above the Gulf of Guinea, image credit NASA


*I remember reading this somewhere, but I cannot find the source anymore. It is thus possible that Mark just went about his normal life. Regardless, it is amazing that NASA had the opportunity to do this experiment with a perfect genetic control.

** Fun fact, my spelling check does not know the word “telomeres” and suggests that I mean “omelettes”. Well, I guess they both get super scrambled up in space? (Eeeeh for an inaccurate joke, sorry).

One printed heart, please

It goes without saying that 3D printing is cool*. The ability to think up any three dimensional structure, design it in a 3D design software and have it materialize blows my mind. Granted, I’m making it sound like it’s a very easy and fast process and I know that’s often not the case, but I also know that for a lot of engineering and physics laboratories, the ability to relatively quickly print a model or prototype for anything is extremely useful. In addition, it’s an amazing educational resource. You can print model organs, molecular structures, planets, … and have something physical to show or throw around during a science demo.

Just to name a few reasons why 3D printing is cool.

What is possible even cooler is the potential of printing tissues and organs. And now, for the first time according to a group of researchers in Tel Aviv, it has happened: a complete 3D heart was printed.

They started with some cells isolated from a sheet of fatty tissue from a human patient. These cells were reprogrammed to what’s called pluripotent stem cells. Pluripotent stem cells have the potential to give rise to many different cell types , depending on the biochemical cues they get – for example by changing the formulation of the culture media, which contains nutrients, hormones and other components to “feed” the cells.

In this case, the cells were driven towards being heart muscle cells and blood vessel cells. By mixing these cells with a personalized hydrogel, consisting of collagen (remember, from the reindeer eyes?) and glycoproteins (proteins have a sugar molecule connected to it), the researchers created a “bioink”, a material that could be used to print cardiac tissue in the same way a 3D printer prints 3D structures using a plastic “ink”.

3D printing a mini-heart (image credit AFP or licensors)

While the 3D printed heart – currently around the size of a rabbit’s heart – cannot beat yet, the possibility to be able to print custom organs, starting from a patient’s own cells and therefore eliminating an immune response, is of major importance for medical applications. To enable heart function, the heart cells would have to be taught how to contract in an organized manner, and create a beating heart.

Beating has already been achieved in heart organoids. Organoids are little mini-organs grown in a petri dish, that mimic the organization and function of an organ in a living organism. The difference between 3D printed organs and organoids, is that organoids are allowed to form their own structure and cell types, driven by the media cocktail they are given, while 3D printing positions already differentiated cells in a 3D scaffold. Heart organoids, starting from one or a few reprogrammed cells, grow into structured groups of cells that spontaneously start beating.

Beating heart organoids (gif from Popular Mechanics US)

These organoids, however, don’t really mimic the structure of the heart unless you “force” structure by growing these mini-hearts in a mold, basically geometrically confining the cells to form a predefined structure.

A model of a pumping heart was developed last year, creating an in vitro biomimetic system that could help with drug discovery and studying cardiac diseases. While it doesn’t look as much as a heart as the 3D printed one developed by the Israeli research group, it’s still pretty amazing to watch this little blob of tissue beating under electrical stimulation:


In any case, I hope to see a combined version of all of the above: a 3D printed, functional heart. Nevertheless, this first (though debatable if they actually were the first) 3D printed heart is pretty awesome and has a lot of potential applications in medicine and clinical research. Not to mention that it looks pretty cool:

3D confocal image of the printed heart (Advanced Science, scale bar = 1mm)

Sources used:

Noor N., Shapira A., Edri R., Gal I., Wertheim L., Dvir T. 3D Printing of Personalized Thick and Perfusable Cardiac Patches and HeartsAdv. Sci. (2019), 1900344. https://doi.org/10.1002/advs.201900344

Ma Z., Wang J., Loskill P., Heubsch N., Koo S., Svedlund F.L., Marks N.C., Hua E.W., Grigoropoulos C.P., Conklin B.R., Healy K.E. Self-organizing human cardiac microchambers mediated by geometric confinement. Nat. Comm. 6 (2015), 7413. https://doi.org/10.1038/ncomms8413

Li R.A., Keung A., Cashman T.J., Backeris P.C., Johnson B.V., Bardot E.S., Wong
A.O.T., Chan P.K.W., Chan C.W.Y, Costa K.D. Bioengineering an electro-mechanically functional miniature ventricular heart chamber from human pluripotent stem cells. Biomaterials 163 (2018), 116-127. https://doi.org/10.1016/j.biomaterials.2018.02.024


*Sudden realization that most (if not all) of this blog is me saying “Hey, did you hear about this science thing, it’s really cool!!”

Supermassive black hole

Step one – press play on this video:

Step two – stare into this picture for the full 3-and-a-half minutes (that’s the length of the song, you’re free to stare for longer):

20190410-78m

Credit: Event Horizon Telescope Collaboration

Step three – find out more

Oh hey, scientists have taken the first ever picture of a black hole. This is amazing.


Note: I intend to write another blog post this week, I just wanted to share this black hole news!