Our blood-brain barrier stops bugs and toxins getting to our brain. Here’s how it works
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Our brain is an extremely complex and delicate organ. Our body fiercely protects it by holding onto things that help it and keeping harmful things out, such as bugs that can cause infection and toxins.
It does that though a protective layer called the blood-brain barrier. Here’s how it works, and what it means for drug design.
First, let’s look at the circulatory system
Adults have roughly 30 trillion cells in their body. Every cell needs a variety of nutrients and oxygen, and they produce waste, which needs to be taken away.
Our circulatory system provides this service, delivering nutrients and removing waste.
Where the circulatory system meets your cells, it branches down to tiny tubes called capillaries. These tiny tubes, about one-tenth the width of a human hair, are also made of cells.
But in most capillaries, there are some special features (known as fenestrations) that allow relatively free exchange of nutrients and waste between the blood and the cells of your tissues.
It’s kind of like pizza delivery
One way to think about the way the circulation works is like a pizza delivery person in a big city. On the really big roads (vessels) there are walls and you can’t walk up to the door of the house and pass someone the pizza.
But once you get down to the little suburban streets (capillaries), the design of the streets means you can stop, get off your scooter and walk up to the door to deliver the pizza (nutrients).
We often think of the brain as a spongy mass without much blood in it. In reality, the average brain has about 600 kilometres of blood vessels.
The difference between the capillaries in most of the brain and those elsewhere is that these capillaries are made of specialised cells that are very tightly joined together and limit the free exchange of anything dissolved in your blood. These are sometimes called continuous capillaries.
This is the blood brain barrier. It’s not so much a bag around your brain stopping things from getting in and out but more like walls on all the streets, even the very small ones.
The only way pizza can get in is through special slots and these are just the right shape for the pizza box.
The blood brain barrier is set up so there are specialised transporters (like pizza box slots) for all the required nutrients. So mostly, the only things that can get in are things that there are transporters for or things that look very similar (on a molecular scale).
The analogy does fall down a little bit because the pizza box slot applies to nutrients that dissolve in water. Things that are highly soluble in fat can often bypass the slots in the wall.
Why do we have a blood-brain barrier?
The blood brain barrier is thought to exist for a few reasons.
First, it protects the brain from toxins you might eat (think chemicals that plants make) and viruses that often can infect the rest of your body but usually don’t make it to your brain.
It also provides protection by tightly regulating the movement of nutrients and waste in and out, providing a more stable environment than in the rest of the body.
Lastly, it serves to regulate passage of immune cells, preventing unnecessary inflammation which could damage cells in the brain.
What it means for medicines
One consequence of this tight regulation across the blood brain barrier is that if you want a medicine that gets to the brain, you need to consider how it will get in.
There are a few approaches. Highly fat-soluble molecules can often pass into the brain, so you might design your drug so it is a bit greasy.
Another option is to link your medicine to another molecule that is normally taken up into the brain so it can hitch a ride, or a “pro-drug”, which looks like a molecule that is normally transported.
Using it to our advantage
You can also take advantage of the blood brain barrier.
Opioids used for pain relief often cause constipation. They do this because their target (opioid receptors) are also present in the nervous system of the intestines, where they act to slow movement of the intestinal contents.
Imodium (Loperamide), which is used to treat diarrhoea, is actually an opioid, but it has been specifically designed so it can’t cross the blood brain barrier.
This design means it can act on opioid receptors in the gastrointestinal tract, slowing down the movement of contents, but does not act on brain opioid receptors.
In contrast to Imodium, Ozempic and Victoza (originally designed for type 2 diabetes, but now popular for weight-loss) both have a long fat attached, to improve the length of time they stay in the body.
A consequence of having this long fat attached is that they can cross the blood-brain barrier, where they act to suppress appetite. This is part of the reason they are so effective as weight-loss drugs.
So while the blood brain barrier is important for protecting the brain it presents both a challenge and an opportunity for development of new medicines.
Sebastian Furness, ARC Future Fellow, School of Biomedical Sciences, The University of Queensland
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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6 Signs Of Stroke (One Month In Advance)
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Most people can recognise the signs of a stroke when it’s just happened, but knowing the signs that appear a month beforehand would be very useful. That’s what this video’s about!
The Warning Signs
- Persistently elevated blood pressure: one more reason to have an at-home testing kit and use it regularly! Or a smartwatch or similar that’ll do it for you. The reason this is relevant is because high blood pressure can lead to damaging blood vessels, causing a stroke.
- Excessive fatigue: of course, this one can have many possible causes, but one of them is a “transient ischemic attack” (TIA), which is essentially a micro-stroke, and can be a precursor to a more severe stroke. So, we’re not doing the Google MD thing here of saying “if this, then that”, but we are saying: paying attention to the overall patterns can be very useful. Rather than fretting unduly about a symptom in isolation, see how it fits into the big picture.
- Vision problems: especially if sudden-onset with no obvious alternative cause can be a sign of neural damage, and may indicate a stroke on the way.
- Speech problems: if there’s not an obvious alternative explanation (e.g. you’ve just finished your third martini, or was this the fourth?), then speech problems (e.g. slurred speech, trouble forming sentences, etc) are a very worrying indicator and should be treated as a medical emergency.
- Neurological problems: a bit of a catch-all category, but memory issues, loss of balance, nausea without an obvious alternative cause, are all things that should get checked out immediately just in case.
- Numbness or weakness in the extremities: especially if on one side of the body only, is often caused by the TIA we mentioned earlier. If it’s both sides, then peripheral neuropathy may be the culprit, but having a neurologist take a look at it is a good idea either way.
Click Here If The Embedded Video Doesn’t Load Automatically!
Want to learn more?
You might also like to read:
Two Things You Can Do To Improve Stroke Survival Chances
Take care!
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Behaving During the Holidays
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It’s Q&A Day at 10almonds!
Have a question or a request? You can always hit “reply” to any of our emails, or use the feedback widget at the bottom!
In cases where we’ve already covered something, we might link to what we wrote before, but will always be happy to revisit any of our topics again in the future too—there’s always more to say!
As ever: if the question/request can be answered briefly, we’ll do it here in our Q&A Thursday edition. If not, we’ll make a main feature of it shortly afterwards!
So, no question/request too big or small
❝It’s hard to “behave” when it comes to holiday indulging…I’m on a low sodium, sugar restricted regimen from my doctor. Trying to get interested in bell peppers as a snack…wish me luck!❞
Good luck! Other low sodium, low sugar snacks include:
- Nuts! Unsalted, of course. We’re biased towards almonds 😉
- Mixed nuts are an especially healthy way to snack, though (assuming you don’t have an allergy, obviously)
- Air-popped popcorn (you can season it, just not with salt/sugar!)
- Fruit (but not fruit juice; it has to be in solid form)
- Peas (not a classic snack food, we know, but they can be enjoyed many ways)
- Seriously, try them frozen or raw! Frozen/raw peas are a great sweet snack.
- Chickpeas are great dried/roasted, by the way, and give much of the same pleasure as a salty snack without being salty! Obviously, this means cooking them without salt, but that’s fine, or if using tinned, choose “in water” rather than “in brine”
- Hummus is also a great healthy snack (check the ingredients for salt if not making it yourself, though) and can be enjoyed as a dip using raw vegetables (celery, carrot sticks, cruciferous vegetables, whatever you prefer)
Enjoy!
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- Nuts! Unsalted, of course. We’re biased towards almonds 😉
Here’s Looking At Ya!
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This Main Feature Should Take You Two Minutes (and 18 Seconds) To Read*
*Or at least, that’s what we’re told by our powerful software that checks things for readability!
Curious what that looks like? Try Out Hemingway App Online Here!
There’s a problem nobody wants to talk about when it comes to speed-reading
If you’re not very conscientious in your method, information does get lost. Especially, anything over 500 words per minute is almost certainly skimming and not true speed-reading.
One of the reasons information gets lost is because of a weird and wonderful feature of our eyes and brain: saccades.
Basically, our eyes can either collect visual information or they can move; they can’t do both at once. And as you may know, our eyes are almost always moving. So why aren’t we blind most of the time?
We actually are.
Did you know: your eyes take two upside-down 2D images and your brain presents you one 3D image the right way around instead? You probably did know that. So: it’s a bit like that.
Your brain takes a series of snapshots from whenever your eyes weren’t moving, and mentally fills in the blanks for you, just like a studio animation. We have a “frame rate” of about 60 frames per second, by the way—that’s why many computer monitors use that frequency. Lower frequencies can result in a noticeable flicker, and higher frequencies are wasted on us mere mortals!
Our eyes do some super-speedy movements called saccades (up to 500º per second! Happily no, our eyes don’t rotate 500º, but that’s the “per second” rate) and our brain fills in the gaps with its best guesses. The more you push it, the more it’ll guess wrong.
We’re not making this up, by the way! See for yourself:
Eye Movements In Reading And Information Processing: 20 Years Of Research
Fortunately, it is possible to use your eyes in a way that reduces the brain’s need to guess. That also means it has more processing power left over to guess correctly when it does need to.
Yes, There’s An App For That
Actually there are a few! But we’re going to recommend Spreeder as a top-tier option, with very rapid improvement right from day one.
It works by presenting the text with a single unmoving focal point. This is the opposite of traditional speed-reading methods that involve a rapidly moving pacer (such as your finger on the page, or a dot on the screen).
This unmoving focal point (while the words move instead) greatly reduces the number of saccades needed, and so a lot less information is lost to optical illusions and guesswork.
Try Spreeder (any platform) Here Now!
If you find that easy to use and would like something with a few more features, you might like another app that works on the same principle: Spritz.
It can take a bit more getting-used-to, but allows for greater integrations with all your favourite content in the long-run:
Check Out Spritz: Android App / iOS App / Free Chrome Extension
Lastly, if you don’t want any of those fancy apps and would just like to read more quickly and easily with less eye-strain, Beeline has you covered.
For free, unless you want to unlock some premium features!
How Beeline works is by adding a color gradient to text on websites and in documents. This makes it a lot easier for the eye to track without going off-piste, skipping a line, or re-reading the same bit again, etc.
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Why are tall people more likely to get cancer? What we know, don’t know and suspect
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People who are taller are at greater risk of developing cancer. The World Cancer Research Fund reports there is strong evidence taller people have a higher chance of of developing cancer of the:
- pancreas
- large bowel
- uterus (endometrium)
- ovary
- prostate
- kidney
- skin (melanoma) and
- breast (pre- and post-menopausal).
But why? Here’s what we know, don’t know and suspect.
Pexels/Andrea Piacquadio 
Height does increase your cancer risk – but only by a very small amount. Christian Vinces/Shutterstock A well established pattern
The UK Million Women Study found that for 15 of the 17 cancers they investigated, the taller you are the more likely you are to have them.
It found that overall, each ten-centimetre increase in height increased the risk of developing a cancer by about 16%. A similar increase has been found in men.
Let’s put that in perspective. If about 45 in every 10,000 women of average height (about 165 centimetres) develop cancer each year, then about 52 in each 10,000 women who are 175 centimetres tall would get cancer. That’s only an extra seven cancers.
So, it’s actually a pretty small increase in risk.
Another study found 22 of 23 cancers occurred more commonly in taller than in shorter people.
Why?
The relationship between height and cancer risk occurs across ethnicities and income levels, as well as in studies that have looked at genes that predict height.
These results suggest there is a biological reason for the link between cancer and height.
While it is not completely clear why, there are a couple of strong theories.
The first is linked to the fact a taller person will have more cells. For example, a tall person probably has a longer large bowel with more cells and thus more entries in the large bowel cancer lottery than a shorter person.
Scientists think cancer develops through an accumulation of damage to genes that can occur in a cell when it divides to create new cells.
The more times a cell divides, the more likely it is that genetic damage will occur and be passed onto the new cells.
The more damage that accumulates, the more likely it is that a cancer will develop.
A person with more cells in their body will have more cell divisions and thus potentially more chance that a cancer will develop in one of them.
Some research supports the idea having more cells is the reason tall people develop cancer more and may explain to some extent why men are more likely to get cancer than women (because they are, on average, taller than women).
However, it’s not clear height is related to the size of all organs (for example, do taller women have bigger breasts or bigger ovaries?).
One study tried to assess this. It found that while organ mass explained the height-cancer relationship in eight of 15 cancers assessed, there were seven others where organ mass did not explain the relationship with height.
It is worth noting this study was quite limited by the amount of data they had on organ mass.
Is it because tall people have more cells? Halfpoint/Shutterstock Another theory is that there is a common factor that makes people taller as well as increasing their cancer risk.
One possibility is a hormone called insulin-like growth factor 1 (IGF-1). This hormone helps children grow and then continues to have an important role in driving cell growth and cell division in adults.
This is an important function. Our bodies need to produce new cells when old ones are damaged or get old. Think of all the skin cells that come off when you use a good body scrub. Those cells need to be replaced so our skin doesn’t wear out.
However, we can get too much of a good thing. Some studies have found people who have higher IGF-1 levels than average have a higher risk of developing breast or prostate cancer.
But again, this has not been a consistent finding for all cancer types.
It is likely that both explanations (more cells and more IGF-1) play a role.
But more research is needed to really understand why taller people get cancer and whether this information could be used to prevent or even treat cancers.
I’m tall. What should I do?
If you are more LeBron James than Lionel Messi when it comes to height, what can you do?
Firstly, remember height only increases cancer risk by a very small amount.
Secondly, there are many things all of us can do to reduce our cancer risk, and those things have a much, much greater effect on cancer risk than height.
We can take a look at our lifestyle. Try to:
- eat a healthy diet
- exercise regularly
- maintain a healthy weight
- be careful in the sun
- limit alcohol consumption.
And, most importantly, don’t smoke!
If we all did these things we could vastly reduce the amount of cancer.
You can also take part in cancer screening programs that help pick up cancers of the breast, cervix and bowel early so they can be treated successfully.
Finally, take heart! Research also tells us that being taller might just reduce your chance of having a heart attack or stroke.
Susan Jordan, Associate Professor of Epidemiology, The University of Queensland and Karen Tuesley, Postdoctoral Research Fellow, School of Public Health, The University of Queensland
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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Retrain Your Brain – by Dr. Seth Gillihan
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15-Minute Arabic”, “Sharpen Your Chess Tactics in 24 Hours”, “Change Your Life in 7 Days”, “Cognitive Behavioral Therapy in 7 weeks”—all real books from this reviewer’s shelves.
The thing with books with these sorts of time periods in the titles is that the time period in the title often bears little relation to how long it takes to get through the book. So what’s the case here?
You’ll probably get through it in more like 7 days, but the pacing is more important than the pace. By that we mean:
Dr. Gillihan starts by assuming the reader is at best “in a rut”, and needs to first pick a direction to head in (the first “week”) and then start getting one’s life on track (the second “week”).
He then gives us, one by one, an array of tools and power-ups to do increasingly better. These tools aren’t just CBT, though of course that features prominently. There’s also mindfulness exercises, and holistic / somatic therapy too, for a real “bringing it all together” feel.
And that’s where this book excels—at no point is the reader left adrift with potential stumbling-blocks left unexamined. It’s a “whole course”.
Bottom line: whether it takes you 7 hours or 7 months, “Cognitive Behavioral Therapy in 7 Weeks” is a CBT-and-more course for people who like courses to work through. It’ll get you where you’re going… Wherever you want that to be for you!
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Dodging Dengue In The US
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Dengue On The Rise
We wrote recently about dengue outbreaks in the Americas, with Puerto Rico declaring an epidemic. Cases are now being reported in Florida too, and are likely to spread, so it’s good to be prepared, if your climate is of the “warm and humid” kind.
If you want to catch up on the news first, here you go:
- UN health agency cites tenfold increase in reported cases of dengue over the last generation
- Puerto Rico has declared an epidemic following a spike in dengue cases
- Dengue fever confirmed in Florida Keys as US on watch for rise in mosquito illness
Note: dengue is far from unheard of in Florida, but the rising average temperatures in each year mean that each year stands a good chance of seeing more cases than the previous. It’s been climbing since at least 2017, took a dip during the time of COVID restrictions keeping people at home more, and then for the more recent years has been climbing again since.
What actually is it?
Dengue is a viral, mosquito-borne disease, characterized by fever, vomiting, muscle pain, and a rash, in about 1 in 4 cases.
Which can sound like “you’ll know if you have it”, but in fact it’s usually asymptomatic for a week or more after infection, so, watch out!
What next, if those symptoms appear?
The good news is: the fever will usually last less than a week
The bad news is: a day or so after that the fever subsided, the more serious symptoms are likely to start—if they’re going to.
If you’re unlucky enough to be one of the 1 in 20 who get the serious symptoms, then you can expect abdominal cramps, repeat vomiting, bleeding from various orifices (you may not get them all, but all are possible), and (hardly surprising, given the previous items) “extreme fatigue and restlessness”.
If you get those symptoms, then definitely get to an ER as soon as possible, as dengue can become life-threatening within hours of such.
Read more: CDC | Symptoms of Dengue and Testing
While there is not a treatment for dengue per se, the Emergency Room will be better able to manage your symptoms and thus keep you alive long enough for them to pass.
If you’d like much more detail (on symptoms, seriousness, at-risk demographics, and prognosis) than what the CDC offers, then…
Read more: BMJ | Dengue Fever
Ok, so how do we dodge the dengue?
It sounds flippant to say “don’t get bitten”, but that’s it. However, there are tips are not getting bitten:
- Use mosquito-repellent, but it has to contain >20% DEET, so check labels
- Use mosquito nets where possible (doors, windows, etc, and the classic bed-tent net is not a bad idea either)
- Wear clothing that covers your skin, especially during the day—it can be light clothing; it doesn’t need to be a HazMat suit! But it does need to reduce the area of attack to reduce the risk of bites.
- Limit standing water around your home—anything that can hold even a small amount of standing water is a potential mosquito-breeding ground. Yes, even if it’s a crack in your driveway or a potted bromeliad.
Further reading
You might also like to check out:
Stickers and wristbands aren’t a reliable way to prevent mosquito bites. Here’s why
…and in case dengue wasn’t bad enough:
Mosquitoes can spread the flesh-eating Buruli ulcer. Here’s how you can protect yourself
Take care!
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Did you arrive here from our newsletter? Don’t forget to return to the email to continue learning!
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