Do infections speed up memory loss in Alzheimer’s?

How does an infection affect the progression of Alzheimer’s disease?

Microglia and neurons Do infections speed up memory loss in Alzheimer’s?

Microglia (green) and neurons (red) living in harmony…for now. Image by Gerry Shaw, EnCor Biotechnology Inc. (Wikicommons).

Alzheimer’s disease (AD) is the most common form of dementia. It’s a neurodegenerative condition characterized by ongoing cognitive decline, loss of functions such as memory, and behavioural abnormalities. AD usually occurs amongst the elderly, and its prevalence is now so high, that its estimated overall cost to society is 5 times that of cancer, heart disease and stroke. While AD was first identified over a century ago, research into its causes has only really begun to gather momentum over the past 30 years. Some think that damage may stem from the formation of toxic ‘plaques’ and ‘tangles’ that appear to be associated with brain cell death. Unfortunately, understanding the triggers of neurodegeneration has become a much more troublesome challenge.

Some teams have begun to look at the contribution of inflammation to the development of brain atrophy (shrinkage). Inflammation is the first response of the immune system to infection/injury. You can recognise inflammation when you graze your skin or sprain an ankle: as well as pain, there may be redness, swelling and the area may feel hot to the touch. This is thanks to the extra blood carrying immune cells to the site of injury to prevent infection and aid repair. The inflammatory response is an innate and usually protective reaction to injury or infection and requires the co-operation between local, ‘resident’ immune cells at the site of injury and circulating immune cells in the bloodstream.

Hippocampus Do infections speed up memory loss in Alzheimer’s?

The hippocampi (red) as seen from below the human brain, looking up. (Image from Wikicommons).

The main resident immune cells of the brain are called microglia; they respond to infection and injury to trigger an inflammatory response. Microglia are hyper-sensitive to changes in their local environment. When the brain is injured, they become ‘activated’. They change shape and behave differently, releasing different chemicals which can be toxic to brain cells. Some research has suggested that it’s possible that activated microglia break down the connections between cells in the memory centre of the brain, the hippocampus. Intriguingly, hippocampal damage and memory loss are the primary symptoms of AD.

Several lines of evidence have implicated microglial inflammation in AD, including the observation of activated microglia in the brains with Alzheimer’s, and the possibility that anti-inflammatory drugs may be neuroprotective. However, clinical trials have failed to show any efficacy yet.

Professor Hugh Perry and his research group at the University of Southampton investigate how inflammation contributes to outcome of brain diseases. About ten years ago Perry and his team developed an animal model (the prion mouse) to better understand the complex role of inflammation in AD. A chemical that causes neurodegeneration was injected into the mouse hippocampus (the memory centre of the brain), and the researchers studied the evolution of the resulting prion disease, which bears some similarities to AD. Thirteen weeks after the injection, although the mice appeared normal, there were more activated microglia found in the hippocampus, even compared to surrounding areas of the brain. The researchers then claimed that this microglial activation was pathological, since the mice showed some behavioural disturbances and deficits in learning tasks.

Perry and his team suggested that systemic infections in patients with AD could worsen cell death in the brain, speeding up neuron deterioration and memory loss. (‘Systemic’ infections are so-named because they infect a number of organs and tissues or affect the body ‘system’ as a whole, instead of being localized in one area.)

Mikroglej 1 Do infections speed up memory loss in Alzheimer’s?

Makrofagi 2 Do infections speed up memory loss in Alzheimer’s? Resting (top) and activated (bottom) rat microglia after a brain injury. Images by Grzegorz Wicher (Wikicommons).

To look into this idea, researchers looked at differences between the prion mouse with an ‘infection’ (or rather, an injection of a toxin released by bacteria to mimic an infection) or without infection. The prion mouse given a fake infection had twice as many dead brain cells as the uninfected prion mouse. Researchers concluded that the microglia are primed by the ongoing prion disease and so, when the infection is added, they overreact. They then drive the production of a number of inflammatory chemicals, which triggers a whole host of damaging effects on brain cells.

Perry and his team collaborated with other research groups to identify whether the evidence they had gathered would be relevant to AD patients. In a small pilot study of 85 AD patients with moderate cognitive impairment scores over 2 months, they found that those who had infections showed a more cognitive decline than the other patients in the study. This was the first evidence in a clinical setting that systemic infection may affect neurological disease progression. The next study involved 300 AD patients, 50% of whom had a systemic infection within the recorded 6 months. The researchers saw that patients that got an infection within the 6 months suffered three times the rate of cognitive decline, compared to a small cognitive decline in those who had not had an infection.

These fascinating studies have provided the first clinical evidence that as well as inflammation in the brain driving damage, infection and inflammation in the body can also worsen and speed up neurodegeneration. It appears that brain-resident microglia become primed for activation, so that when patients suffer from a bodily infection, their brain cells become more vulnerable to the damaging effects of an inflammatory response.

Not only did this research provide ideas to potentially help AD patients today, but it also formed the basis for an important direction for current disease research. The evidence on the highly complex interplay between the diseased brain and systemic inflammation can be applied, not just to AD, but as a generic concept to many nervous system diseases.

Post by Isabelle Abbey-Vital

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Hating greens and “taster” genes: the bitter truth

sprouts Hating greens and “taster” genes: the bitter truthYou’d be hard pushed nowadays to find anyone unaware of the “five-a-day” rule surrounding fruit and vegetables in our diets. Green vegetables, in particular, are associated with numerous health benefits, such as reduced risk of coronary heart disease.1 Yet consuming enough of these foods on a daily basis can be hard, especially if you find greens like Brussels sprouts unpleasantly bitter. But why do some of us find these vegetables less palatable? And can anything help make sprouts more appetising? Scientists in the fields of genetics and food science (or bromatology) are working to find the answers.

We all carry a unique set of instructions within our genes, defining who and what we are. Our genes encode the protein building blocks that form our bodies, including protein receptors (or sensors) within our taste buds. These receptors interact with food passing through our mouths telling us how bitter, salty, sweet, sour or umami it tastes. A special group of genetically determined receptors, known as the TAS2R group, detect bitter tastes, meaning that our genes play a key role in determining how bitter our food tastes.

The genetics behind bitterness is complex, but scientists have established a common test to explain why some people experience certain foods as being more bitter than others. This test involves the TAS2R38 bitter taste receptors and two substances they detect, phenylthiocarbamine (PTC) and 6-n-propylthiouracil (PROP). In general, the functionality of a person’s TAS2R38 receptors determines to what degree they taste PTC or PROP as bitter, with people being divided into three groups: non-tasters with non-functional TAS2R38 receptors (PTC and PROP do not taste bitter), medium tasters (PTC and PROP taste slightly bitter) and “super tasters” (PTC and PROP taste very bitter).2,3 But what does this have to do with green vegetables?

yuck Hating greens and “taster” genes: the bitter truthIn 2006, a lab group from Yale and Connecticut Universities set out to investigate PROP as a marker for bitterness in green vegetables (Brussels sprouts, kale and asparagus) and whether this related to peoples’ intake and preference. 110 individuals were asked to rate these vegetables, along with PROP, for bitterness and likability whilst also being asked to complete a questionnaire regarding their daily diet.

Interestingly, the results showed that people who tasted PROP as most bitter (i.e. super tasters) also found the green vegetables very bitter, inferring PROP could be a marker of bitterness for this food group as well and suggesting TAS2R38 receptors may be involved in green vegetables’ bitterness.2 These people also tended to dislike greens more and eat less of them, suggesting a strong (and logical) relationship between a food’s bitterness and a lack of it in one’s diet. Thus, it seems for super tasters our genetic predisposition to produce functional TAS2R38 receptors may be working against us getting our five a day; making us find green vegetables bitter and unpalatable.

But all is not lost! Food scientists are now working on a solution to the super taster’s quandary. Mastaneh Sharafi and colleagues from the Allied Health Sciences Department at Connecticut University recently investigated the use of additives (aspartame, sodium chloride and sodium acetate) in a pilot study aimed at reducing or ‘masking’ green vegetables’ bitterness. Sharafi began by grouping 37 participants into non-, medium and super taster groups using PROP. They were then asked to rate plain and bitter green vegetables (asparagus, Brussel sprouts and kale), served together with one of the above masking agents, for likability.

To the researchers surprise, it seemed the masking agent’s effectiveness differed depending on both the vegetable and whether participants were non-, medium or super tasters. For super tasters, for instance, the two salt solutions reduced bitterness in asparagus but not sprouts or kale. Aspartame decreased bitterness across all the vegetables for super and medium tasters but had no effect for non-tasters. Participants with a significant dislike of greens and subsequent lack of these in their diets, reported improved likability with aspartame, suggesting masking agents could be useful to increasing green vegetable intake in disinclined individuals.3

So, it appears green veg haters can take some comfort in knowing that their dislike of sprouts is more likely due to their genetics than a desire to be difficult at dinnertime. And that masking these unpleasantly bitter tastes may hold the key to a palatable and balanced diet. Shafari’s small, yet noteworthy experiment certainly shows good prospects for aspartame and salt-based masking additives, but further work is still needed before us super tasters can comfortably achieve our “five-a-day”.

Guest Post by Megan Barrett

Megan is currently working as an associate writer at a medical communication company. You can follow her on Twitter @Meg_an12.

  1. Drewnowski A, Gomez-Carneros C. 2000. Bitter taste, phytonutrients, and the consumer: a review. Am J Clin Nutr. 72(6): 1424-35.
  2. Dinehart M, Hayes J, Bartoshuk L, et al. 2006. Bitter taste markers explain variability in vegetable sweetness, bitterness, and intake. Physiol Behav. 87(2): 304-13.
  3. Sharafi M, Hayes J, Duffy V. 2013. Masking vegetable bitterness to improve palatability depends on vegetable type and taste phenotype. Chem. Percept. 6:8-19.
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Excellent scientists that you probably haven’t heard of

There are some scientists that everyone has heard of; Darwin, Newton and Curie all spring to mind. Of course, their scientific discoveries were all legendary. But what about the people who have contributed just as much to the world of science but who maybe aren’t so famous? Here I’ve compiled a small list of some of the scientists I think have contributed just as much to our understanding of the modern world as those mentioned above. Although many of these people have been recognised in their fields and some have even won Nobel Prizes, their names have never entered the wider public consciousness.

1.       Rosalind Franklin (1920 – 1958) and Maurice Wilkins (1916  – 2004)

DNA 300x225 Excellent scientists that you probably haven’t heard of

The Structure of DNA.

Whilst Franklin and Wilkins are probably the best-known names on this list, they are not as well-known as they should be.  The discovery that DNA is a double helix is now forever associated with (James) Watson and (Francis) Crick. However, there were other names involved in this remarkable achievement, including Wilkins and Franklin who were working at King’s College London at the time of the discovery. Maurice Wilkins even shared the 1962 Nobel Prize with Watson and Crick, yet somehow his name has been lost from the public consciousness. His student was Rosalind Franklin, whose work with X-Ray diffraction was the key to confirming that DNA is indeed a double helix. Much has been made of Franklin not winning the Nobel Prize along with Watson, Crick and Wilkins. But, the sad fact is that the Nobel Prize is not awarded posthumously and by the time the discovery received this honourable recognition she had sadly passed away – at the tragically young age of 37. However, what I believe to be even more scandalous, is that her contribution seems to have been entirely overlooked until a few years ago when the deserved recognition began to flow in.

As for Wilkins, Watson himself states in his autobiography ‘The Double Helix’: “I proceeded to forget about Maurice, but not his DNA photograph”1. There is no doubt that the work done by Wilkins and Franklin was instrumental in aiding Crick and Watson with their ground-breaking discovery and their names certainly deserve to be remembered!

2.       George Gey (1899 – 1970)

Lamp1 copy 300x287 Excellent scientists that you probably haven’t heard of

HeLa Cells. Stained for lysosomes (green) and DNA (blue). Photo credit: Louise Walker, 2011.

Although he is a figure of some controversy, I think George Gey (pronounced “guy”) deserves to be on this list. Gey was the first person to propagate the HeLa cell line – the first human cells to be successfully grown in a laboratory environment. Since then, scientists have used HeLa cells, and other cell lines created since, to make many important breakthroughs, including the discovery of a treatment for polio. And they are still used in thousands of labs across the world, including mine (see picture).

The controversy surrounding Gey2 is the fact that the HeLa cells were taken from a cervical cancer patient, Henrietta Lacks, without her permission. Gey did not ask Henrietta or her family for permission to use or distribute the cells. The cell line was later patented and has made those who patented it (incidentally, not Gey or his family) very rich. Henrietta’s family received no money for the use of her cells, and until recently, Henrietta’s contribution went unacknowledged. George Gey however, did not have such financial motives; once he managed to successfully grow the HeLa cells, he gave them away to fellow scientists.

Whilst controversy remains as to how much money the Lacks family should be entitled to, I like to remember George Gey; the man who started it all out of altruism with no financial motives, a quality that should be admired.

3.       Sir Edwin Southern (1938 – )

Tsg101 blot 300x79 Excellent scientists that you probably haven’t heard of

A Western Blot. Showing the protein Tsg101 after elution from a gel filtration column, if you’re really that interested.
Credit: Louise Walker, 2011

Here’s one for fellow biochemists. Edwin Southern is a British molecular biologist and inventor of the Southern blot. This is a method for detection of DNA, now commonly used in DNA fingerprinting and genetic profiling. The Southern blot was later developed into the cleverly-named Northern Blot – modified to detect the other form of genetic material, RNA. Even better, the development of the Southern Blot finally led to development of the Western Blot – a method used to detect proteins. These methods are probably used by every biochemistry lab across the world, including mine (see picture).

The Southern blot and its offshoots have become staple practices in the lab and have made way for many important discoveries. Yet I know few biochemists who have even heard of Edwin Southern or his contributions to the scientific methods they use on a daily basis.

4.       Dorothy Crowfoot Hodgkin (1910 – 1994)

Insulin 300x231 Excellent scientists that you probably haven’t heard of

The Crystal Structure of Insulin Credit:

Another British scientist, Dorothy Hodgkin, won the Nobel Prize in Chemistry in 1964 for discovering the structure of vitamin B12. She was a pioneer in the field of X-Ray crystallography, working on solving the crystal structure of proteins. Her knowledge was instrumental in the discovery of the structure of several proteins, but arguably her greatest achievement was in leading the team that solved the structure of insulin. This discovery led to the development of synthetic insulin – now widely used to treat people with type I diabetes.

Hodgkin has been recognised for her work in the scientific community. Along with the Nobel Prize she was also the first woman to win the prestigious Copley Medal. Some of her fellow recipients include Charles Darwin and Stephen Hawking. She was a true pioneer, not just for women in science but also for promoting peace and aid for developing countries. (According to her Wikipedia page, she did teach Margaret Thatcher, but I guess nobody’s perfect.)

While you could argue that most of these names are well-known in scientific circles, they have not become household names along with the likes of Darwin and Hawking. And this is by no measure an exhaustive list!

Perhaps one of the most endearing qualities of great scientists is that they rarely do what they do for fame or fortune. In fact, many actively shy away from the limelight. People like George Gey and Dorothy Hodgkin were certainly more interested in curing disease and adding to our understanding of the world than earning money or becoming famous. So this is just my way of thanking them for their tireless work and recognising the contributions they have made to modern science.

Post by: Louise Walker

1 The Double Helix by James Watson, Simon and Schuster, first published 1968

2To find out more about Henrietta Lacks and George Gey, see The Immortal Life of Henrietta Lacks by Rebecca Skloot, Pan MacMillan, 2011

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Attacked by your own hand: when the brain acts against you

Sometimes it might feel like your brain acts against your own interests. Who hasn’t regretted that extra pint or an unaffordable shopping spree? But what if your brain was controlling a part of your body against your will?

This is a relatively rare but mind-boggling condition called alien hand syndrome, where patients have the sensation of a limb acting without their control. It can feel like their arm is disobedient, and has “a will of its own”. The condition appears in the 1964 film Dr Strangelove, where the eponymous character is shown to have the condition. Medically, it was first documbetween the two hemispheres of the brain (the corpus callosum) cut. ented in patients who had undergone surgery to treat epilepsy, though it can occur after other types of brain surgery, stroke, brain tumours, infections or certain degenerative brain diseases. It is best understood in patients with epilepsy who have had the connection Following this surgery patients are generally able to continue their lives as normal, but in some cases the effects can be dramatic.

hand2 Attacked by your own hand: when the brain acts against you

Patients with alien hand syndrome report that following the surgery one arm (and sometimes leg) feels like someone else’s, and describe the arm’s behaviour as not their own. Some patients may even be unaware of the actions of their hand. One patient who suffered a severe case of alien hand syndrome and appeared in the 2011 BBC documentary “The Brain: a Secret History”, described how her “alien” left hand would take things out of her handbag without her knowledge, or stub out a cigarette that her right hand had just lit. In cases where the “alien” hand performs goal-directed behaviours such as these, it may perform actions directly opposed to the unaffected hand, leaving the hands apparently bickering. For instance, while the unaffected hand tries to pick up a mug, the other moves it away. Conversely, the affected hand may involuntarily mirror the actions of the other hand. For these patients, when instructed to perform an action with the unaffected hand, they may be unable to do so without the affected hand attempting the same movement. In another case, reminiscent of a horror film plotline, following serious heart surgery, a patient found that her left hand was no longer under her control, and would even try to choke her. Frighteningly she had to physically restrain it with her right hand to avoid injury.

So what is going on in the brain to allow this to happen? Brain imaging research has found that alien hand movements, like normal hand movements, are accompanied by activity in the primary motor cortex (a part of the brain critical to producing movements). But this occurs without the usual preceding activity in the premotor cortex (another part of the brain involved in planning and producing motor actions), and other regions involved in planning behaviours. In patients who have had the connection between the hemispheres cut, it is possible that interhemispheric premotor to motor cortex activity is disrupted. So, in effect, the motor cortex is acting without the usual sequence of brain activity that controls it and gives us a sense of the action being one we’ve chosen to do. In addition, in the healthy brain, motor actions are accompanied by a signal to the sensory parts of the brain that will experience it (an efferent signal; see an earlier post on this blog about how this stops us from being able to tickle ourselves here). If this efferent signal is absent or faulty, your own actions may feel like someone else’s.

brain Attacked by your own hand: when the brain acts against you

Although it is still not fully understood what changes in the brain lead to alien hand syndrome, it seems possible that a combination of these disturbances in the brain may contribute to the sensation of the hand being autonomous. This condition has fascinated scientists for many years, and raises interesting questions about how we experience physical sensations.

Post by: Claire Scofield

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Controlling the brain with light: Where are we at with optogenetics?

Optogenetics has had a blockbuster billing. This remarkable neuroscience tool has been lauded to have the potential to illuminate the inner workings of the brain and allow us to understand and treat neurological diseases. But how far off are we from these goals and what have we achieved thus far?

Optogenetics has been explained before on this blog and elsewhere and is explained excellently in the video below.

Briefly, in order to understand the way the brain works we need to be able to investigate how circuits of cells communicate with each other. Previously, we have used electrodes to record what is going on inside the brain. By presenting a stimulus and recording the brain’s response, we can try and interpret what this response means. The true test of our understanding, however, relies on us being able to produce the required behavioural response by stimulating the brain.

Using electrodes, we can record the response of a nerve cell when a mouse wants to turn right. Then we can replay this response back to the mouse’s brain and see whether he turns right. The problem with this is that we will not only stimulate the nerve cells we want, but all of their neighbours as well. The brain is precisely organised and neighbouring cells may carry out completely different roles so this will commonly be a large interference.

What optogenetics allows us to do is insert a light-sensitive ion channel into the cells that we want to activate. This channel will open when we flash a burst of light onto it, in turn activating our cell. This technology thus allows us look at the actions of specific population of cells without the interference that comes with using electrodes.

So in just over a decade since optogenetics was first described, what have we managed to do? I’ve split my summary into two main headings. The first highlights basic research that increases our understanding of the brain. The second, the possibilities for understanding and treating disease.

Basic research

Svoboda Controlling the brain with light: Where are we at with optogenetics?

Top row shows the behavioural set-up. Mice detect whether the pole is in the right (right) or wrong (left) position and are trained to either lick (right) to receive a water reward or not lick (left). Bottom row shows the optogenetic intervention. When a laser beam is crossed (red dot), the cortex is stimulated. Mice were fooled into licking in the left condition, even though their whisker hadn’t touched a pole. From O’Connor et al. (2013).

Optogenetics has been used successfully to understand more about perception and the senses. Karel Svoboda’s group at the Janelia Farm Research Campus in the US have been able to create what they call ‘illusory touch’ in the brain of awake, behaving mice. Mice were trained to detect the position of a vertical pole, presented near to their whiskers. When the mice sensed that the pole was in the right position, they were trained to expect a drink of water and would lick (see left). When the pole was in a wrong position, they were trained to do nothing. Once trained, mice were able to give the correct response 75% of the time.

The researchers suspected they knew the area of the brain that was telling the mouse when their whiskers touched the pole, a part of the cerebral cortex. To test this, they injected an optogenetic channel into this area and replaced the pole with a laser beam and detector. The detector was linked to a light on the skull so that when the whisker passed through the laser light beam, a signal was sent to shine light onto the cerebral cortex and activate the specific cells they were interested in. They found that by activating the cortex when the whisker passed through the beam, the mouse would lick even though the whisker hadn’t touched a pole. They had created an illusion in the mouse’s brain that his whisker had touched a pole!

Another optogenetics study that hit the headlines recently looked into memory formation in the hippocampus. Susumu Tonegawa and his team from the RIKEN-MIT Center for Neural Circuit Genetics in the USA were interested in proving the crucial role of the hippocampus in memory formation. They inserted optogenetic channels into the hippocampus of mice in such a way that when new memories were formed, the cells that were connected by this memory would also contain these light-sensitive channels.

By placing mice in an arena and allowing them to explore, the mice would form spatial memories of the arena within their hippocampus. The new cells and connections generated would form a circuit that could be stimulated with light. The next day, the researchers placed the mice in a new arena that the mouse had no knowledge of. The researchers shone a light on the head of the mouse to activate the cells formed the previous day. They simultaneously gave the mouse an electric shock. Now, when placed back in the first arena, the mouse froze. It had associated the memory of the first arena with an electric shock, even though the mouse had never been shocked in the first arena! The researchers described this as creating a false memory within the brain.


Treating disease

Perhaps the most exciting aspect of optogenetics is its potential to treat disease, with the fantastic Karl Deisseroth leading the way. Arguably, the most natural place to start when talking about the therapeutic options of light-responsive channels is with blindness.

A collaborative group led by Botond Roska at the Friedrich Miescher Institute for Biomedical Research in Switzerland has looked into retinitis pigmentosa, a form of blindness caused by degeneration of the retina at the back of the eye. Using two animal models, they have been able to restore vision by inserting a light-sensitive channel into the retina. This therapy worked well enough to allow the previously blind mice to be able to carry out visually guided behaviours.

eye Controlling the brain with light: Where are we at with optogenetics?A further use of therapeutic optogenetics has been mooted for the treatment of Parkinson’s disease. In Parkinson’s, a region of the brain called the basal ganglia degenerates, leading to an inability of the patient to co-ordinate movement. Increasing the activity of this region has been shown to have therapeutic benefit and the lab of Anatol Kreitzer at the University of California, US have shown potential in an optogenetic approach. They were able to mould the activity of the basal ganglia in such a way to create Parkinsonian-like symptoms in mice and also to reduce Parkinsonian-like symptoms in a mouse model of Parkinson’s.

So has optogenetics lived up to the hype so far? Well despite its application in humans lacking somewhat at this point, it appears that optogenetics has already answered some vital questions we have. The challenge now is to develop the technology further so that we have more accurate and controllable tools for when we’d like to start using them in humans. The excitement surrounding optogenetics is still widespread and there is no evidence yet that the bubble is set to burst anytime soon.

Post by: Oliver Freeman @ojfreeman

Papers Referenced:

Sensory Perception – O’Connor et al. Nature Neuroscience (2013)

Memory Formation – Ramirez et al. Science (2013)

Blindness – Busskamp et al. Science (2010)

Parkinson’s Disease – Kravitz et al. Nature (2010)

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Body disorders that you never knew existed- Part 1

Welcome to the world of the weird and wonderful. You will be taken on a run down through five of the most unusual, rare, fascinating and possibly unthinkable disorders that we know exist.

1.  Hypertrichosis- ‘Werewolf syndrome’

Hypertrichosis 224x300 Body disorders that you never knew existed  Part 1 Imagine having a body covered in so much hair that people mistake you for a werewolf. This is something that sufferers of hypertrichosis have to deal with on a daily basis. Hair growth isn’t restricted to the areas of the body that we consider ‘normal’, instead spreading to areas over their body and face in men, women and children alike. The disorder is extremely rare with fewer than 100 known cases worldwide. But how does this unusual condition come about? Scientists think that there are two causes; one of a genetic nature, and the other developing due to certain external factors. Researchers in China tested the DNA of two unrelated patients with the condition and found that there were extra genes present in the same region of the X chromosome. This extra DNA sits near to a gene involved in hair growth (SOX3) and is thought to switch on this gene, stimulating mass hair production. Next time you have a moan about having to shave or wax to get rid of your unwanted hair, spare a thought for hypertrichosis sufferers.

2. Foreign Accent Syndrome

Speech 2 Body disorders that you never knew existed  Part 1 Whilst this sounds like something from a very strange medical drama, foreign accent syndrome really does exist. Usually occurring as a result of severe brain injury such as stroke or trauma, the patient ends up speaking with an accent distinct from the one they had before. One of the most recent cases occurred after a women suffered from a severe migraine. She woke up in hospital to find that she was speaking with a Chinese accent despite never having visited China. What is to blame for this sudden change in dialect? Scientists have found that damage to the parts of the brain required for speech and movement of muscles during speaking affects how we pronounce words. This changes the timing and rhythm of our speaking. As our tongue forms words in a different way, it sounds as if we are speaking with an accent.

3. Congenital pain insensitivity

Splinter 240x300 Body disorders that you never knew existed  Part 1 A condition where you are unable to feel any pain sounds like an absolute blessing. No headaches, no pain when you’ve broken a bone, or when you whack your knee on the side of a table. But now think about it seriously, imagine not being able to tell if you’ve pushed your body too far exercising or cut your finger whilst chopping up a carrot. Pain is one of our body’s most protective mechanisms, alerting us that something is wrong and needs our attention. Without this basic mechanism we would have no way of knowing when something has gone wrong.  Individuals born with this condition have what we call a loss of sensory perception: they are unable to feel pain but can feel pressure and touch. A mutation affecting how the nerve cells form during development is thought to cause the improper functioning of these nerves in response to pain. Sadly, this is likely to occur with other deficits such as mental retardation and in some cases the ability to regulate body temperature. Not being able to feel pain would be extremely advantageous-…if you are a superhero that is. For us mere mortals, not so helpful.

4) Fibrodysplasia Ossificans Progressiva- ‘Stone man syndrome’

FOP 199x300 Body disorders that you never knew existed  Part 1 Stone man syndrome does what it says on the tin. Cue an image of The Thing from the Fantastic Four- a body essentially made of rock. Slowly over time, sufferers of this excruciatingly painful disorder start turning to bone. Due to a malfunction of the bodies repair mechanism, the gene that is responsible for ossification (bone growing) during development remains active. This gene is usually switched off after the development of bones in the fetus. In time, muscles, tendons and ligaments slowly begin to harden and turn to bone. As the degree of ossification worsens, everyday tasks such as tying your shoelaces or walking to the shop become an impossible task. Would surgery provide suitable relief? In short, no. Surgery is not considered an option as this type of trauma causes the body to attempt to repair the damaged area – creating more bone and more damage than before. Although there are around 700 confirmed cases of FOP worldwide, there is very little known about how to treat it. Remember next time your body feels stiff and uncomfortable that what you are experiencing couldn’t even scratch the surface of what these people of made of stone are subjected to.

5) Trimethylaminuria- ‘Fish odour syndrome’

Fish 225x300 Body disorders that you never knew existed  Part 1 Trimethylaminuria is a rare metabolic condition that can be embarrassing for individuals suffering from it. An enzyme (FM03) that is needed to breakdown trimethylamine (TMO) into a substance called trimethylamineoxide is absent from the body. TMO gradually builds up without the enzyme to break it down, and so has to be removed from the body through other outlets such as the skin, urine and breath.  Whilst sweating out toxins isn’t unusual, it is the strong fish-like odour that comes partnered with it that is considered abhorrent. The condition is more common in women, possibly irritated by female hormones. Despite the putrid odour, there are no other symptoms associated with it.

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Humans – Why Are We So Gross?

Our bodies, all in all, are pretty impressive. We’ve got big brains, mighty muscles and intricate insides. Human bodies are remarkable, finely tuned machines. Unfortunately these machines have a lot of by-products. We make sick, snot, pus and poop. There are no two ways about it, these things are pretty disgusting. But what are they, what are they made from and why have our bodies evolved to make so much unpleasant stuff?

Read on if you have a strong stomach and you’re not currently eating. This isn’t one for the squeamish.

What is Sick Made Out Of?

old pic of vomitting 231x300 Humans – Why Are We So Gross?Sick is just undigested food and liquid from your stomach mixed with gastric acid. The gastric acid is what makes throwing up hurt. It is a mix of HCl and KCl that the stomach uses to kill microbes present in food and has a low pH (around pH1). Food is churned around in the stomach for a bit with a few digestive enzymes and the gastric acid. Once the food is nice and slurry-like it passes into the intestines for absorption.  When you’re sick, whatever hasn’t made it to the intestine does a reverse anti-gravity manoeuvre and comes back up. Lovely stuff.


What is Snot Made Out Of?

Licensing info needed1 231x300 Humans – Why Are We So Gross?

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Snot is infected mucus. Mucus is constantly secreted by the delightfully named Goblet cells that adorn your airways. Mucus is largely made out of proteins with massive chains of sugar attached. These molecules cling on to water, which gives mucus its slimy consistency. Most of the time mucus is a good thing, trapping dust and microbes. The cells of the airways are covered in hair-like structures that can then waft the dust-microbe-mucus combo out of the airways and down into the stomach where it can be digested.

This all goes a bit awry during a cold when the cells in your airways get infected with cold viruses and the mucus becomes snot. Your immune system declares war on the virus but unfortunately during the battles, there are a few casualties to your own cells. Some of these are white blood cells that can explode to release chemicals, which kill invading nasties. One of the thing that spills out of these exploding cells is a green coloured anti-bacterial enzyme called MPO. So green snot isn’t so bad, it just means your white blood cells are doing their job and fighting infection.

What is Pus Made Out Of?

pus 2 Humans – Why Are We So Gross?Pus isn’t too dissimilar to snot as it’s made out of a lot of debris from battles between the immune system and infection. Pus is essentially the remnants of all the white blood cells that have rushed to a site of infection and died fighting the invading microbes. Pus isn’t harmful, it’s a sign your body has been fighting infection the way it should and eventually the body will clear pus from sites that were infected. If pus doesn’t clear, it may be a sign your body is struggling to fight an infection.

What is Poop Made Out Of?

Yep, the grossest of all gross things. We all know what poop is, but what is it actually made from? Well, unsurprisingly undigested food makes up a large proportion. Dietary fibre – the stuff that keeps you regular – is the stuff you can’t digest and gives your poop a bit of form. So that’s good. There’s also a LOT of bacteria in there, which along with methane, causes the smell. It’s brown because of bile, which is a yellowing-green substance secreted by the gallbladder to help digest fat. When bile passes through the digestive system it changes colour and turns brown. The gallbladder is situated inside the liver, so if the liver gets swollen and inflamed it can block the bile duct and this results in poop that is white as a sheet. So if your poop looks like it’s seen a ghost, I suggest you see a doctor.

So there you have it – that is why human beings are gross.  It’s quite possible we’ve evolved to find these things disgusting as a way to avoid illness and infections.  Whatever the reason we find them off-putting, they are all just part of being human.

Congratulations if you made it the whole way through the post – you’re made of strong stuff.

Post by Liz Granger

Twitter: @Bio_Fluff

Posted in Liz Granger | 2 Comments