Schistosomes: beware the water

Over 700 million people worldwide are at risk from parasitic worms called schistosomes (blood flukes), which are transmitted via swimming in contaminated water. The worms are a major problem and can cause a severe debilitating disease called schistosomiasis in their hosts, which, sadly, kills nearly 200 million people each year.

This is an adult male blood fluke. Note its highly developed mouth piece on the right, which is uses to 'clamp' onto the inside of blood vessels and anchor itself against the blood flow. Once secured, it feeds on the nutrients carried in the host's blood. The fold that you can see running through the centre of the worm is called the gynacophoric canal, in which the much smaller female worm lies in permanent copulation.

Due to the large distribution of the schistosomes and their prevalence in third world countries that have very little infrastructure, they are of huge concern to the World Health Organisation, who is trying to reduce the levels of infection by educating people in endemic areas of the dangers, improving sanitation and by ensuring that the drug praziquantel is readily available to as many patients as possible.

Unfortunately, praziquantel treatment is extremely unpleasant and results in a range of negative side effects in humans, including: dizziness, somnolence, seizures, arachnoiditis and diarrhoea. To make matters worse, the parasites themselves actually worsen these side effects and patients undergoing treatment can also suffer from urticaria, rashes and pruritus. This is due to the sheer volume of dead parasitic material that is released into the blood at any one time, which can also cause eosinophilia in leukocytes.

Schistosomes are waterborne and infect human hosts when they swim in contaminated water. As the host swims, they leave a trail of fatty acids from their skin in the water behind them. The parasite is attracted to these fatty acids (L-arginine inparticular) and then attaches itself to the host's skin. Once attached, schistosomes secrete acids and enzymes from acetabular glands and literally burn through the skin until they enter the bloodstream! The distinctive and unpleasant rash that results is often called 'swimmers itch'.

Due to the problems associated with praziquantel, many health agencies are beginning to acknowledge that the best way to combat schistosomiasis is to prevent human infection in the first place. The easiest way to do this is to treat infected waters with insecticides that kill water snails – another vector that is essential to the schistosome life cycle. Without water snails, schistosomes will be completely unable to infect humans and the problem of schistosomiasis is thereby solved!

Like most parasites, schistosomes have an extremely complicated life cycle where they morph through a range of different forms and, at different stages, live in more than one host.

One of the reasons schistosomes are such a major problem is because males and females live in permanent copulation with each other inside the human body so can literally release thousands of eggs in a very short space of time. Rather than the parasites themselves, it is actually these eggs that cause the symptoms of schistosomiasis – a chronic, severely debilitating disease that is usually fatal. The exact symptoms of schistosomiasis vary (depending on the species that has infected the host and where the worms prefer to take up residence), but the most common symptoms are given below:

• Intestinal schistosomiasis is caused by the bowel-living species of blood flukes Schistoma mansoni and S. japonicum, and is associated with abdominal pain, diarrhoea and bloody faeces. Liver enlargement is frequently seen in advanced cases, which leads to gross abdominal swelling as fluid is forced into the host's peritoneal cavity as a side effect of abnormally high blood pressure
• Urogenital schistosomiasis is caused by S. haematobium, which lives in the bladder, and is commonly characterised by haematuria (blood in the urine); lesioning and scarring of bladder tissue; ureter and kidney damage; genital lesions that lead to pain during sexual intercourse; and, in advanced cases, can lead to infertility and a variety of cancers

Liver enlargement is one of the most debilitating symptoms of schistosomiasis and is fatal in almost all cases. This is due to the large-scale, irreversible damage it causes to the host's body.

What makes schistosome eggs so problematic is the large spike that protrudes from their surface. This spike is designed to slice through the walls of blood vessels so the eggs can pass into their hosts urine or faeces (and thereby be passed back into water where they hatch and infect more snails), but can become caught in the host’s tissues upon occasional. Once an egg has become lodged, the host’s immune system identifies it as 'foreign material' and a type of leukocyte called a macrophage activates in response. Macrophages quickly form a granuloma around the egg, which is essentially just a tough wall of inert proteins that prevents the egg from interacting with the body’s tissues. Ordinarily, granulomas are beneficial and are eventually removed from the body, but this cannot happen with the trapped egg. Due to this long-term presence, the surrounding tissue begins to inflame and no longer functions correctly. This problem is exacerbated as an ever increasing amount of eggs build up in the organ and are themselves enclosed by granulomas! Eventually, the organ becomes so blocked and damaged that it is unable to function correctly - leading to the symptoms of schistosomiasis!

Scientists are currently working on a waterproof cream that mask the fatty acids on our skin when we swim (which will help prevent schistosomes from invading our body), but this research is still in its early stages and doesn't look likely to have a practical application anytime soon. For now, you should simply avoid swimming in any water where schistosomiasis is prevalent (no matter how inviting it may look). If you are travelling aboard, such as to Africa (where schistosomiasis is a particular problem), I strongly recommend that you consult your doctor and travel professionals to familiarise yourself with the risks of the area before you head out.

Ghost organs: the future of transplant medicine?

The human body is far from perfect, being at risk from numerous degenerative diseases that 'break' essential organs and lead to our deaths. Aging, disease and poor lifestyle choices are the obvious causes of such organ failure and our current level of science and technology is largely unable to cure such damage.

Organ transplants provide patients with the best hope of survival, in which the defective organ is replaced by a healthy one from a donor. Needless to say, such operations are dangerous and carry high risks of patients' dying during the operation, from the patient’s own body rejecting the new organ and secondary infections (caused by post-surgery immunosuppressant drugs).

Last year, 166 people in the UK went under the knife in heart transplant operations [source]. Needless to say such operations are dangerous and, despite recent advancement in aftercare treatments, 1 in 10 patients will die within the following year. Their body rejecting the new organ is the main cause of these deaths, which kills most patients within the first month from the surgery.

Yet despite the risks thousands of people are on transplant waiting lists all over the world, being desperate for the chance of getting a replacement organ to extend their lives. Improvements in operation procedures and aftercare have reduced the risk of dying during surgery in recent years, but rejection is still a major issue that patients must consider and is something that we are unable to prevent in every case.

Transplanted organs are rejected by leukocytes (white blood cells), which make up our body's natural immune system. All cells have proteins on their surface called antigens, which allow leukocytes to identify 'friendly' tissues. Foreign material has different antigens on its surface which, when detected by leukocytes, causes them to destroy the invading cells. This is usually beneficial and allows us to 'fight off' bacteria and viruses, but in organ transplants the donor actually needs the foreign material to live!

Anti-rejection drugs (which suppress our immune system), have had some success in preventing rejection, but they put the patient at risk of dying from common illnesses (such as colds and intestinal bugs) and aren't successful in all cases. The perfect solution to this problem would be to clone the patient’s organ so their body doesn't recognise it as 'foreign’ material' post-transplantation. But - thanks to all of the media’s unfounded nonsense and scare-mongering about stem cell research - our cloning technology is still a long way off being able to do this. We do have something similar in the pipeline though – ‘ghost’ organs.

This sounds ridiculous, right? But actually it’s not and a ghost organ is simply an organ that has been decellularized. Chemicals that are commonly found in detergents and shampoos are used to ‘wash away’ all of the organ’s cells until only a ‘scaffolding’ of extracellular connective proteins are left. Healthy cells are then taken from the patient and are grown over the connective proteins to repopulate the organ. Once this repopulation process is complete, the donor has a heart comprised of their own cells so rejection is EXTREMELY unlikely!

This is a ghost organ made from a decellularized pig's heart. All of the cardiac cells have been stripped away, leaving only the connective tissue.

If perfected, ghost organs have the potential to be transplant’s equivalent of cancer's 'magic bullet' and may save uncountable human lives in the future. But, despite having repopulated ghost organs with cells successfully, the technology still has its problems and scientists must find a way to make the cells functional if they are to used as replacement organs.

For example, the cells in ghost hearts beat discordantly as individuals, which means they would only pump half the fluid as a healthy heart around a host's body. Obviously, this means they aren't viable for transplants yet and scientists must devise a way to get them to pump in a propagated wave (as healthy heart cells do), before they will be of any medicinal use!

But prominent researchers in this field, such as Dr Doris Taylor from the University of Minnesota, are optimistic and predict that human trials will likely begin taking place in years rather than decades! Ghost lungs are proving to be particularly successful and research is progressing in using ghost organs to replace almost the entire human viscera!

Hangovers: what are they & can we avoid them?

With Christmas and New Years over, many of us will be looking back over the festive periods to remember the glittering decorations that adorned our homes, opening our presents, spending time with our loved ones and indulging in rich, expensive foods. And of course, no memories of the Christmas holidays are complete without those of the hangover and it's safe to say that many of us will have just as vivid memories of times spent inebriated and of those nursing the unpleasant headaches and tender stomachs that inevitably followed a night's heavy drinking. The hangover is unarguably the bane of many of our celebrations and often leads to promises of “never again”. 

Of course, there always is an again and we all know full well that we’re not fooling anyone when we make that particular promise. The call to drink when we're enjoying ourselves is just too strong! So, we will all drink again and will all suffer for it again. Yet despite knowing to expect a hangover the next morning, do we really know what one is? 

The British National Health Service (NHS) recommends that men should not regularly consume more than 3-4 units of alcohol per day and women should not regularly consume more than 2-3 units. By 'regularly', the NHS means drinking these amounts on most (more than four) days of the week.

The answer to this question is in the properties of ethanol, the alcohol present in drinks, itself. Basically, ethanol is a powerful diuretic drug (like those discussed in the earlier post: 'Coca Cola: Christmas in the toilet'), and dehydrates us by making our body absorb less water. As our body becomes dehydrated and less begin to lose water, the cells that form it shrink and contract – leading to severe problems for the brain! 

This is because the human brain is surrounded by three thin membranes that are collectively known as the meninges. Thus, as we become dehydrated and the cells in these membranes shrink, the meninges contracts and squeezes our brain. It is this squeezing effect that is responsible (predominantly) for the headache we suffer the next morning and, obviously, the more we drink, the more dehydrated we become so the brain is squeezed more and we have a worse headache for it! 

Furthermore, this squeezing effect is also slightly responsible for any memories we may have lost, working in conjunction with the disruptive effects that ethanol has on the normal activities of the brain’s neurotransmitters (which leads to the associated behavioural changes and loss of coordination and response speed that are also experienced when drinking alcohol). And, as the brain is squeezed, it compresses the areas of our brain that deal with the formation and storage of memory - impairing its blood flow. This means that these areas work less much efficiently than they do normally and we end up with ‘holes’ in the night’s events when we look back on it. 

Whereas dehydration is responsible for our headaches, it is not the cause of the feeling of nausea that is also associated with hangovers. This feeling is due to another of ethanol’s particular properties, in that it is one of the few chemicals to be absorbed straight into our bodies through our stomach lining (paracetamol is another, which is why the drug alleviates pain so quickly). As well as meaning that alcohol affects us very quickly, particularly on an empty stomach, large amounts of ethanol passing through the stomach lining can leave it feeling sore and inflamed – which is also what causes the stomach ulcers that are a common symptom of long-term alcohol abuse! 

Fairly obviously then, if our stomachs are sore then they are not going to be very welcoming of food – particularly those that are heard to digest. Furthermore, vomiting the night before (which is actually beneficial for the body as it’s a protect reflex it uses to expel ethanol once it knows that much more is being absorbed than can be broken down safely), would make the feeling worse as it could itself damage the stomach lining and leave the stomach muscles strained and fatigued. 

As well as due to ethanol, the feeling of illness and lethargy experienced in hangovers are also caused by impurities in the drinks themselves, which are a result from the brewing or fermenting process. These impurities affect the body in many different ways and often require investments of large amounts of energy to break them down (which is why you should avoid mixing drinks). Due to the nature by which these impurities are created, different drinks contain different culprit chemicals. So your body might be coping, say, with those present in your red wine, but when you switch to whiskey later, it will have to start synthesising different enzymes to break the new chemicals in the whiskey down. As there are only so many enzymes that can be made at any one time (and a finite allocation of resources to use), the body ends up not producing enough enzymes to cope with either of the chemicals – meaning of course, that your hangover will be much worse! 

And so, now that you have a fair understanding of what hangovers are you might want to know whether or not they're possible to avoid. Sadly, they're not – not unless you cease drinking anyway, which let’s face it, isn't going to happen and seems a little excessive... But hangovers are possible to minimise, with surprisingly little effort. 

1. Don’t drink on an empty stomach. Eating a large meal of foods that are high in carbohydrates, such as pasta- or rice-based dishes, before you begin drinking will absorb some of the alcohol and so slow the rate it passes into your bloodstream. Likewise, drinking full-cream milk or eating high fat foods beforehand are beneficial since fat actually inhibits alcohol absorption, so less will be absorbed into your system. 
2. Avoid ‘dark’ drinks. As a general rule, darker beverages such as red wine, brandy and whiskey, contain more of the contaminants discussed above so will harder for your body to process. Instead, try drinking clear drinks like white wine, vodka and gin. 
3. If you're out and about, avoid buying ‘rounds’. Everyone drinks at different rates and have their own limits and so, by drinking rounds, you are having to match your own consumption to those around you (and let’s face it, the quickest drinkers always pressurise others to hurry up so “we can get the next round in”), which may be more than you can handle or want to drink that night. 
4. Stop drinking early. Usually, we drink to get drunk. So when we are finally drunk, we've normally got a lot of surplus alcohol in our stomachs’ that has yet to be absorbed. If you take this into consideration and stop drinking once you've reached your limit (or at least slow down), your body will have longer before the morning to have cleared the alcohol from your system and your hangover will be less severe as the result. 
5. Drink as much water as you can before bed and take a bottle of water with you. This way, you’re drinking water that will not only dilute the alcohol left in your stomach and system, but will rehydrate some of the water that you've lost over the course of the night - alleviating the crushing pressure on your brain. 
6. Try and force a ‘full-English breakfast’ down in the morning, or something similar (like McDonald's). As discussed earlier, fatty foods inhibit alcohol absorption so by eating foods such as sausage, bacon and eggs, you can stop the last ‘dregs’ of alcohol in your digestive tract from being absorbed. 
7. Avoid drinking caffeine. Caffeine is another diuretic, so although they may make you feel better in the short term, drinks like tea and coffee will only make you more dehydrated. This will not only make your headache worse, but will prolong it as well. Instead, drink fruit juices (not from concentrates if possible), as the sugars and vitamins they contain will ‘refresh’ your body and help to restore its vitality.

If you're concerned about the effects and dangers of alcohol or want more information, click here to be taken to the NHS' alcohol help and guidance pages.

Coca Cola: Christmas in the toilet!

Christmas is fast approaching and, as it gets nearer, we all make more and more excuses to indulge in fatty foods and sweet drinks that we know can be very bad for our health! Chief candidates among these luxury foods and beverages are the family of carbonated drinks, such as Coca Cola and Pepsi, which are often drunk in much greater quantities than normal throughout the festive season.

Coca Cola and Pepsi are both examples of carbonated drinks, which essentially means that they have had carbon dioxide gas dissolved in them under high pressure to improve their taste, texture and to give them their fizzy characteristics.

Most of us understand that such carbonated drinks can be damaging to our health if we drink them excessively, over long periods of time, and know that they are associated with a range of clinical problems that include obesity, tooth decay and diabetes, which are all related to their high sugar content.

What many of us don't know however, is that drinking large quantities of drinks like Coca Cola and Pepsi in one sitting also has side-effects; mainly, in making us need the toilet more often! Although this isn't quite as serious as, say, becoming diabetic, having to regularly queue for the toilet during Christmas festivities can be highly irritating to say the least!

Basically Coca Cola and Pepsi (along with tea - another popular drink here in the UK), contain chemicals in them that belong to a family of compounds called diuretics, which essentially alter the body so that it absorbs less water; meaning that its bladder fills up faster and we have to urinate more regularly. The diuretics found in these drinks are not particularly strong however and are not associated with any negative side-effects like any of artificial powerful diuretic drugs you may know, so don't worry - they carry no cause for concern!

Although the diuretics found in Coca Cola and Pepsi are weaker than medicinal drugs, they do however, work in the same manner and assert their effects by modulating the synthesis of antidiuretic hormone* (ADH), which controls how much water is absorbed and secreted from the body.

As you may have guessed by its name, ADH stimulates the body so that it retains water in its kidneys - making us urinate less often. ADH does this by activating normally dormant protein carriers called aquaporins, causing them to bind to the walls of the Distal Convoluted Tubule (DCT) in the kidney and to those of the collecting duct that the DCT opens into. Once present in the walls of these vessels, the tiny aquaporins actively collect molecules of water and transport them back into the bloodstream via the vasa recta.

Diuretic compounds then, interfere with the expression of ADH and cause less to be secreted by the brain's posterior pituitary gland. Thus, less water is reabsorbed back into the bloodstream and our bladders fill up faster - meaning that if we drink glasses and glasses of Coca Cola or Pepsi, the only place for the liquid to go is out!

* commonly called vasopressin

Age of first sexual encounter may effect relationship happiness and success in later life

It is widely accepted that modern society runs at a faster pace than it used to, with children and teenagers experiencing many life events at much younger ages than did their parents and grandparents. This 'growing up fast' way-of-life is of great concern to many parents, especially when their children's ventures into sexual relationships are concerned, who are worried that their children are not ready such encounters. Is there really a cause for concern, however, or are parents just fussing and worrying for nothing?

Humans are a very social species and, in resource-abundant environments, usually favour a mating pattern called monogamy, where one person has just one sexual partner for a long period of time. Such relationships are rewarding and healthy when they work, creating stable conditions in which to raise a family.

Recent research from the University of Texas has suggested that, unfortunately, there is. The study, which was carried out by psychologist Paige Harden, has tried to determine whether the timing of an individual's first sexual encounter affects their romantic relationships later in life and whether it can predict factors like relationship satisfaction, the likelihood to marry and the number of sexual partners.

Dr. Harden conducted this research via a meta-analysis, using data from the [US] National Longitudinal Study on Adolescent Health and followed 1659 people from their early teens to young adulthood (<29 years old). As part of this research, Harden classified each participant in one of three categories in regard to their age at their first experience of having sexual intercourse: Early (<15), On-time (15-19) or Late (>19), before comparing the qualities of their romantic relationships/encounters.

As she predicted, the most highly educated participants from greater income families were older at the time of their first experience of sexual intercourse. The study appears to show that first experiencing sex at a later age is beneficial to an individual, as those in the study showed greater levels of marriage (or living with their partner), were less likely to be dissatisfied with their partner, were less likely to persist in an abusive relationship and typically had less sexual partners over the course of their life.

In contrast, those who were younger at their first encounter tended to have many more sexual partners and typically showed a greater level of romantic dissatisfaction. This data also fit with a clear pattern: those in the 'Early' group showed much more exaggerated trends than those in the 'On-Time' category.

Dr. Harden explains these results by suggesting that waiting until later to first have sexual intercourse may be beneficial to an individual as it allows their cognitive and mental development to have finished first. As well as having obvious benefits such as greater confidence, which makes an individual more likely to walk away from abuse and inappropriate pressure, being fully developed [mentally] also appears to enable an individual to learn more 'healthy' relationship skills. Harden suggests that it is these skills in particular that allow an individual to form healthier and happier relationships, which are more likely to endure for longer periods of time.

Although these findings are worrying, and seem to show that being young when having sexual intercourse for the first time can have series and long-term negative side-effects,  more research needs to be carried out into these ideas before any significant statement can be made. Dr. Harden has acknowledged this, saying that "we are just beginning to understand how adolescents' sexual experiences influence their future developments and relationships". For the time being, however, it looks like parents are right after all, and children may indeed, be 'growing up too fast'.

Black mamba venom may be a super painkiller!

French scientists have recently identified that the toxic venom of the black mamba, one of Africa's most dangerous and feared snakes, has a huge potential for its use in medicine. The research, carried out by Dr. Eric Lingueglia from the Institute of Molecular and Cellular Pharmacology near Nice, has identified that the snake's poison contains a unique class of chemicals called mambalgins, which act as painkillers in mice that are as strong as morphine but have none of its associated side effects.

The black mamba, Dendroaspis polylepis, is named after the dark skin inside its mouth rather than after the colour of its scales. As well as being among the most poisonous snakes in the world, the 3 metre long mamba is also the fastest and can even outrun humans. These attributes, along with its highly aggressive nature, have made the snake highly feared among all the African peoples that live alongside it.

These properties of black mamba venom are of huge interest to the healthcare sector because, despite its heavy use, morphine is highly addictive and has many severe side effects for those taking the drug, which include headaches, a reduction in their thinking capacity, nausea and muscle spasms. A new painkiller then, which is effective enough to remove the same agonising pains as morphine but with none of its side effects would be like a 'magic bullet' in pharmacology, being hugely popular among both doctors and their patients.

Research has identified that these useful mambalgins may work in such a beneficial way because they operate via a previously unseen neural pathway that is not targeted by any other studied venom or by the palliative drugs currently in production. Dr. Nicholas Casewell, a world-leading expert in snake venom from the Liverpool School of Tropical Medicine, is avid over the potential implications of black mamba toxins to medicine and has said that mambalgins are "a really great example of drugs from venom, we're talking about an entirely new class of analgesics".

Dr. Lingueglia believes that this rather surprising property of black mamba venom may be as an intentional effect of the poison, which helps to incapacitate the snake's prey so that it is less likely to escape; or may be due to a chance, but useful, fluke in mice, resulting from the differences in brain chemistry between the rodents and the snake's usual prey.

Whatever the reason for the venom's remarkable analgesic properties in mice however, scientists are excited about the discovery and are hopeful that the toxins will have the same effects in humans as our brain chemistry is very similar to that of the rodents (which is why mice are often used in scientific studies). It is likely that there will be extensive research into mambalgins in the near future, which will hopefully lead to a new drug that acts as a safer alternative to morphine.

From black to white: is calcium really that important?

The majority of us are at ease with Darwin's concept of evolution and understand how the 'survival of the fittest' has led to the vast abundance of life on Earth. Obviously, humans are no exception to this rule and evolution has moulded us into what we are today. Evolution, for example, selected for the first of us who began to move on two legs as this freed up our hands for better tool use; and selected for those who chose to live in social groups, which provided much more protection and help than did living alone. Without evolution it is doubtful that any life would exist on Earth at all, especially not in the form of hugely sophisticated organisms like humans.

Life on Earth began sometime around 4 billion years ago. It is believed that single-celled organisms first evolved on the shores of primordial oceans, which were abundant in the resources needed for life. Over time, these cells eventually evolved into the countless forms of life that we see on Earth today.

Most of you won't be surprised by any of this; it makes sense, after all. Something you might find surprising however, is why scientists believe that the early humans settling Europe evolved from being black to white. Obviously the sun's rays are less intense in Europe than they are in Africa, meaning that European settlers wouldn't have needed to produce as much of the pigment melanin in their skin, which absorbs ultraviolet (UV) radiation. Producing less melanin then would have provided such individuals with an advantage as they wouldn't have been wasting energy producing proteins their body didn't really need. This saved energy could then have been dedicated to more important processes (like keeping warm in the colder climate, for one thing).

Although this theory makes sense logically and saving energy by producing less melanin could quite plausibly have been the difference between life and death in the harsh European winters, is it really enough to have driven the evolution of one of our most noticeable racial polymorphisms?

Many scientists believe not, at least not by itself anyway, and research into this question has provided a rather odd alternative. Simply put, many scientists now believe that Europeans evolved from having black skin to white skin due to calcium!

Calcium is an fundamental resource for our bodies, with its ions having essential roles in muscle contraction; in propagating nerve impulses; and, arguably most importantly, in forming our skeletons (via binding with phosphorous to form a very stable salt called calcium phosphate). Despite its importance, calcium is rare in nature and is extremely difficult to acquire naturally as part of our diets. As always however, Nature provided early man with an ingenious way around this and all humans are able to make vitamin D in their skin when it is exposed to sunlight (in much the same way as plants photosynthesise sugars from sunlight to use as energy). Vitamin D greatly increases the affinity of calcium absorption in the gut, allowing the body to absorb much more of any calcium that it consumed than it would otherwise be able to.

Due to this ability, most people are able to acquire enough calcium (especially during the summer) to lead normal and healthy lives, and indeed, our African ancestors would have had strong bones and efficient muscles. The problems arose however, when early explorers entered Europe where the sun's rays are much less intense. This meant that the melanin pigments in their black skin were able to absorb much more sunlight than they could while in Africa and, as a result, vitamin D could no longer be produced.

Fossil evidence suggests that it was not long before the health of these explorers deteriorated, and many adult skeletons from the period show symptoms of osteomalacia (a disease where bones soften due to lack of calcium and deform under the weight of walking), and many may have suffered from a range of muscle weakness and epileptic disorders as their reserves of calcium were depleted and less and less could be replaced from bone stripping. Obviously such ill effects greatly reduced an individual's chances of survival and those with slightly lighter skin would have been more likely to live longer. Being healthier and living longer meant that they would have been more likely to survive to reproduce and slowly, the 'lighter' genes (which produced less melanin), would have spread through the population. In each generation the palest individuals would have been most successful at surviving and breeding so, over time, European humans would have got paler and paler until their skin was as white as it is in their descendants now.

As if this selection pressure wasn't enough to drive for whiter skin, having low levels of calcium and brittle bones had another major problem for women in particular - it hindered childbirth. Many women had such brittle pelvises that they broke under the strain of labour, virtually guaranteeing that both the infant and the mother would die. Furthermore, many children suffered from severe rickets due to a lack of calcium during childhood and puberty. This meant that such individuals were physically smaller than they should have been and many women suffered from underdeveloped hips that were too narrow for a baby to pass through. As a result, such a mother and her baby would have died during labour. Thus, many of the darker individuals would have been unable to give birth so that the darker genes disappeared from the European populations very quickly - being strongly selected against by Nature!

The degree of deformity that rickets can lead to can be very extreme, almost completely debilitating a child suffering with the condition throughout their entire life.

Scientists also believe that this explains why the vast majority of Europeans (and those in their descendent colonies such as Australia and the USA) can eat dairy as a stable component of their diet. This is actually quite abnormal, both in the animal kingdom and among other ethnicities of humans, as rennin (the enzyme required to digest milk) usually stops being produced by the body in infancy after the individual has been fully weaned. Thus, most humans are lactose intolerant and experience unpleasant symptoms if they drink milk or eat too much dairy-based produce. Humans evolving in Europe however, needed as much calcium as possible and would have been under strong selection pressure to continue producing rennin throughout their lives as milk is an unrivalled source of calcium.

Thus, the importance of calcium to the human body has made it an invaluable component that we need to survive. Too little calcium leads to severe health conditions that are so extreme that they can even drive evolution into turning black humans, who have very active melanocytes (melanin-producing skin cells), into white humans who have very little sun-protective pigments in their skin (allowing them to produce more vitamin D).

Skinchangers: fact or fiction?

Throughout much of sub-Saharan Africa a disease called African trypanosomiasis (or sleeping sickness) is rife that affects both humans and animals alike. The main characteristic of the disease is the disruption of sleeping patterns that causes suffers to be awake at night and asleep during the day. Other symptoms of sleeping sickness include fever, sweating, headaches and the tendency to experience rapid mood swings. If the disease is left untreated, those infected with sleeping sickness could die from heart failure within 6 months of infection and, even if they get medical help in time, are likely to suffer from permanent damage to their nervous system so that their ability to live a normal life is impinged. Over 60 million people are at risk from African trypanosomiasis, which affects 50% of people in endemic areas. Furthermore, the loss of domestic cattle has had significant socio-economic consequences and the reduced ability for cattle farming has cost a staggering US$12, 000 million!

African trypanosomes are extracellular parasites, which means that they live freely in their hosts blood rather than inside of cells. Humans can be infected by two types of African trypanosome: Trypanosoma brucei gambiense and Trypanosoma brucei rhodiense, which is the most common and most deadly type, and is featured in this photo.

Sleeping sickness is spread by blood-sucking tsetse flies, which inject parasites called African trypanosomes* into their host's bloodstream along with the anticoagulants in their saliva. Once inside their host's bloodstream the parasites rapidly divide by binary fission and spread through various fluids throughout their body. What is interesting about African trypanosomes is the fact that they remain free-living in their host's body throughout their entire life cycle. This is highly unusual and most parasites (with the exception of worms), are intracellular and invade a specific type of cell to live and divide in as soon as they enter their host. The main reason many parasites do this, to put it simply, is to avoid their host's immunodefences. It is quite remarkable that African trypanosomes can manage to survive in the bloodstream,  which is a very hostile environment that is full of leukocytes (white blood cells)!

How they survive here is amazing and African trypanosomes are quite literally skinchangers! The parasites have special proteins on the surface of their 'skin' called variable surface glycoproteins (VSGs), which are encoded for by over 1, 000 different genes. The many proteins produced by these genes can be spliced together at random so that an infinite number of unique VSGs can be produced. This plays havoc for the host's defences and effectively renders the infection unclearable. This is because our immune system relies on shape: foreign invaders (or pathogens) have very specifically shaped antigens on their surfaces to which our bodies produce antibodies against in order to kill them. So, by changing the VSGs that they are displaying, African trypanosomes prevent their host's immune system from killing them off.

To explain this further, most of the parasites display the same unique VSG on their surface that their host's body cannot fight against so that they can divide unchecked. Eventually, and after a delay, the host's immune system produces new antibodies against this VSG and all of the parasites expressing that particular phenotype are killed. However a small number of the parasite population have already changed their skins by then and survive. These parasites then divide very rapidly (as they have less competition with other parasites), until the body 'learns' how to kill them and the whole cycle starts again. Eventually the parasites have done so much damage to the host, that it dies. Thus, outside medical treatment is required to kill all of the parasites at once that entails using powerful drugs such as Pentamidine or Melarsoprol.

The population of African trypanosomes in their host's bloodstream cycles depending on whether their host can kill them off or whether it is trying to produce new antibodies against them. The peaks in their population, which coincide with peaks in the symptoms of the disease, are called trypanolytic crises and were first discovered in 1910 by an Italian doctor.

So there you have it! African trypanosomes quite literally change their skin to avoid being detected and killed by their host's immune system, which allows them to persist in their host's body nearly indefinitely. 

* note that African trypanosomes are fundamentally very different to their cousins, South American trypanosomes, which cause Chagas Disease and have very different life cycles.

New drug could save countless lives!

Scientists from Queen Mary, University of London, have recently announced that a new drug is in the pipelines that could potentially slash the numbers of fatal and debilitating cases of heart attacks and the ailments associated with high blood pressure/cholesterol each year. The drug, which has not yet been named commercially, is a 'polypill' formed from a statin (a class of drugs that lower cholesterol) and three drugs that lower blood pressure. All of the polypill's components have been used pharmaceutically for decades so that the new drug is considered safe, although any risks or side-effects that may be associated with its use cannot be determined until large-scale testing has been carried out on human volunteers.

The various drug components of the polypill are ground into a fine powder and mixed within an insoluble shell (that is often based on glycerol), which is broken down by enzymes secreted in the small intestine.

The scientists developing the pill have called for it to be made available as "a matter of urgency" and expect the pill to be available upon prescription within two years. Should this be the case, then the drug may reduce the blood pressure of over 50's by 12% and their 'bad' cholesterol (formed by Low-Density Lipoproteins) by 39%. This effectively reduces their likelihood of having a heart attack or a stroke for example, to the same levels of risk experienced by reasonably healthy 20 years olds - preventing an estimated 94, 000 a year!

Although the polypill has been heralded as a "milestone" in our ability to help fight these illnesses, which are becoming disturbingly more and more common, they are not a substitute for healthy living. The British Heart Foundation (BHF) stresses that although the positive benefits of the drug are obvious in the small-scale study carried out to provide this data, much more research into its application and effects needs to be carried out before the drug is ready for production. Particularly on the long-term effects of the drug on healthy people, who may buy it in order to stave of such conditions.

Despite the misgivings arising from the drug's lack of testing, the commercial use of this polypill looks likely. Combined with a balanced diet and healthy lifestyle, the drug could save up to 200, 000 lives in the United Kingdom every year and greatly reduce the numbers of patients suffering from permanent disabilities resulting from strokes.

Save Peoples' Sight!

Hi everyone,

This weekend one of my friends is taking part in the Great Manchester Swim, hoping to raise money in support of the Royal National Institute for Blind People (RNIB). As you may or may not be aware, the RNIB is a charity that aims to prevent people from losing their sight unnecessarily and to support blind and partially sighted people so that they can live as independent lives as possible. Personally, I think that sight loss is one of the worst and most distressing ailments of man that sadly effects millions worldwide and any money that you could donate would be greatly appreciated by Charlotte and her brother, Malcolm, as well by the charity and the many individuals that it helps. If you are interested, more information is available on Charlotte's blog and you can sponsor their swim via their JustGiving page.

Obviously this is a very worthy cause and every penny counts! So please sponsor Charlotte and Malcolm for their efforts and help the RNIB to provide a better quality of life for many people less fortunate than ourselves.

Thanks,

David

Legionnaires' outbreak claims its second life

As many of you may already be aware, there has been a sudden outbreak of Legionnaires' Disease in Edinburgh that has sadly claimed lives the lives of two men. The source of the outbreak is still unknown and although scientists doubt that they will ever be able to identify it definitively due to the large size of the industrial estate in the western district of the city, it is believed that the bacteria is spreading in the steam released from the cooling towers of certain factories. The outbreak already has 41 confirmed cases* and the number of suspected cases stands at 48*.

Although Legionnaires' Disease is caused by a range of bacteria from the genus Legionella, approximately 90% of cases are due to infection with Legionella pneumophila. L. pneumophila can cause a potentially fatal form of pneumonia in 'Legion Fever' or in some forms, can produce a milder illness that resembles the flu.

Named after an outbreak of pneumonia in a conference of the American Legion in the Bellevue-Stratford Hotel in 1977, Legionnaires' Disease is caused by small bacteria  from the genus Legionella and can be fatal in severe cases. The bacteria are found in water and are spread to people when they drink or wash in water from contaminated sources - a fact that can play havoc in hotels, apartment blocks and hotels as many individuals' in such buildings use water from the same source, meaning that infection can spread very rapidly. Legionnaires' Disease is rare in the UK however, due to the enforcement of strict regulations for the control and maintenance of water control systems (e.g. heating water to at least 60C) and as such, there was only 245 reported cases of the disease in England and Wales in 2009.

Poor maintenance of the cooling systems in the factory(s) involved is believed to have allowed the bacteria to build up and divide in the steam produced and then be disseminated over large areas of land in the airborne water vapour ejected from their cooling towers; infecting people who unknowingly come into contact with it and breathe in the droplets. Symptoms of the disease includes mild headaches, muscle pains, a persistent cough and occasionally vomiting and diarrhoea - anyone in south-west Edinburgh suffering from such symptoms should contact NHS Direct or their local GP if they are concerned (although the outbreak is believed to have already reached its peak). The disease is rarely fatal however and, as in the tragic cases of the two deaths earlier this week, is usually only so when it infects individuals who already have underlying health problems.

* as of publishing this post

Parasites can cause schizophrenia?!

Everyone's heard of parasites, how can you not have? They are everywhere - infecting billions of animals, plants and bacteria worldwide and are found in almost every ecosystem imaginable. In fact, parasitism is the most successful form of life on the planet and countless species choose to live in this manner; having evolved over millions of years to take advantage of their hosts and to avoid their defensive capabilities.

Unfortunately parasites also exploit humans and tens of millions of individuals die each year as a result of parasites, with countless more suffering from chronic and debilitating diseases. Probably the most well-known deadly parasites of  man are those from the genus Plasmodium, which affect over half the world's population and are responsible for causing malaria - a disease that kills a person every 12 seconds and has killed more humans throughout our history than all of our wars combined! Of course many other parasites prey on man as well, with other fairly well-known examples including African sleeping sickness (which is caused by African trypanosomes) and the debilitating disease leishmaniasis (which is caused by Leishmania parasites).

A child suffering from leishmaniasis, a protozoan parasite that inhabits macrophages - the same type of white blood cell that the AIDS virus (HIV) lives in. Depending on the strain of the parasite this lesion will either disappear by itself or, without medical intervention, could continue to grow until the child's death.

However many of these diseases occur in hot and distant countries, such as Africa which is plagued by the examples mentioned above, and it is easy to forget that parasites regularly effect us here in Europe, the United Kingdom and the USA as well. In fact, anyone who's ever had an itch in a rather private place knows that we can catch 'worms' - intestinal nematode parasites that latch onto the walls of our gut and shed their eggs through our faeces. However, although unpleasant, catching 'worms' is rarely life threatening and can even help to alleviate the symptoms of asthma and other inflammatory diseases as the body shifts the dominance of its immune response away from the inflammatory causing Th1 response to a Th2 response, which is more suitable for killing worms in the gut! Cases such as this, where parasites can to help reduce the symptoms of 'modern diseases' that have only recently appeared in the civilised world, have led many scientists to believe that our hygiene and healthcare is now so good it it actually harming us in some ways as with less infection our leucocyctes (white blood cells) have nothing to fight and actually begin to harm our own bodies!

However, many of the parasites that can effect us in Europe are much more sinister and do not have such helpful side effects. One such parasite is Toxoplasma gondii, an intracellular protozoan that is arguably the most successful parasite in the world as it can effect almost any warm blooded animal (most parasites can only inhabit one or a very small number of specific species) and is found on every continent of the globe. The parasite is spread through cat  faeces, by ingesting under-cooked meat or across a mother's placenta to her unborn baby (which is known as congenital or 'vertical' transmission) and can affect up to 80% of human populations depending on where you live. For example, the incidence of T. gondii is about 16% in the UK where eating rare meat is unpopular; yet in France, where rare meat and blue meats are in high demand, 8 in every 10 people are infected by the parasite!

While all felids can contract T. gondii and pass sporolating oocysts (which are essentially just 'bags' of membrane that contains multiple parasites) with their faeces, is the domestic cat (Felis catus) that mainly transmits them to humans. This is usually when their owner has changed their litter or stroked them near to their tail and then prepared food without first washing their hands.

It may be confusing then, why so few people have heard of T. gondii or about toxoplasmosis (the disease that it causes) and even more so, why we do not have a vaccine against the parasite. The answer however, is fairly mundane - it is because the parasite does not cause any symptoms in individuals with a normally functioning immune system meaning that healthcare organisations around the world largely ignore the parasite. In fact, healthcare institutions only bother worrying about the parasites in patients in a state of  immunodeficiency, such as AIDS or chemotherapy patients; and during pregnancy, as congenital infection can result in the baby being born  blind, deformed or even in a miscarriage (don't worry - the parasite is checked for during routine baby checks throughout pregnancy and can be killed safely by the antibiotic Spiramycin, which builds up and persists for long periods of time in placental tissue).

The lack of symptoms that T. gondii parasites cause has led many scientists to believe for years that the parasite is safe and doesn't merit further study, despite the parasite forming life-long cysts in our brains that contain bradyzoites (parasites that become active by turning into tachyzoites when the cyst is eaten by another organism. Obviously, this is a 'dead end' for the parasites in humans since we are only rarely eaten). However, recent research suggests that the parasites are in fact harmful to us - slowing down our reaction times, altering our behaviour and inducing many psychotic diseases like the infamous schizophrenia (which despite popular belief, is NOT a split-personality disorder!).

Toxoplasma gondii tachyzoites can be seen here, after absorbing an intracellular blue/purple dye. The parasites can enter almost any nucleated cell and illicit a strong Th1 immune response. Oddly, they want this response from their host and even promote it by secreting their own chemicals! These chemicals can also be beneficial for their host in other ways, helping them to overcome long-established intestinal worm infections and even develop immunity to Leishmania parasites!

It is still not clear exactly how the parasites alter our behaviour, with the outcome appearing to be dependent on gender and personality-type in humans but the changes are believed to be similar to those altered in rodents, where the animals become more likely to take risks; have delayed reaction times; become less able to learn; spend more time in open spaces; and lose their fear of cats - one of their major natural predators! Amazingly, the behavioural changes are so profound that infected mice have been seen to start running in circles with their eyes closed whenever they see a cat! It is believed that these changes are induced in rodent behaviour to increase the changes of them being eaten by a felid - a fact that is highly beneficial to the parasite as T. gondii can only enter the sexual stage of its life cycle inside a cat! Thus, cats are its definitive host and the parasites effectively spend their entire lives trying to get inside a cat. The changes in human behaviour are not believed to be aimed at us directly, but are thought to take place due to the similarities that our brains have to those of rodents.

Research has found that individuals infected with T. gondii are 2.65 times more likely to be involved in a car crash. This is not surprising really, given that the parasites slow down our reaction times and make us more likely to take risks.

Although inducing changes in our behaviour is undesirable and no-one wants to think that they are being manipulated by a parasite so that they get eaten by a cat, it may not really matter in the grand scheme of things - are most of us ever going to be in a position where a cat could eat us? The most worrying problem that is caused by T. gondii then, is the fact that they alter our brain chemistry. Studies have found that the parasite increases the production of the neurotransmitter dopamine in our brains and that this in turn, can lead to schizophrenia - a debilitating disease that is characterised by a range of symptoms including social withdrawal, delusions, self neglect, hallucinations and altered perception and thinking patterns. Schizophrenia is the ninth most prevalent cause of disability worldwide and frequently leaves its sufferers unable to function normally in society. Furthermore, the parasites have been found to be positively correlated with the risk of having a stroke, developing Alzheimer's disease, epilepsy and depression!

Thus, catching and living with T. gondii may not be as unproblematic as previously thought, especially because once you've been infected with the parasites, you will unfortunately have them for the rest of your life. To further complicate matters, it is unlikely that a drug can be developed against T. gondii parasites because once they switch to bradyzoites and form cysts throughout brain and muscle tissue, killing them becomes more trouble than its worth - killing that many parasites at once could release huge amounts of toxins into the host's bloodstream, causing them to die very rapidly from anaphylactic shock. Therefore, the only real protection against T. gondii is to prevent yourself from catching it in the first place. The easiest way you can do this is to ensure that you cook all meat thoroughly at temperatures above 65C for a least 10 minutes, even if the meat has been frozen as the parasites can survive for very long periods of time in temperatures as low as -12C!

Paralysed rats walk again!

An interesting new study has revealed that it has been successful in enabling artificially paralysed rats to regain motor function and walk again! These findings have exciting implications for helping humans to recover from spinal damage and Dr. Vissel from the Garvan Institute of Medical Research in Sidney has said that: "we are on the edge of a truly profound advance in modern medicine - the prospect of repairing the spinal cord after injury".

Much of the physiology of the common rat (Rattus norvegicus) is very similar to that of humans, which makes the animal extremely useful for scientific study.

The study, carried out by researchers at the Swiss Federal Institute of Technology (EPFL), involved severing the spinal cord of rats in two separate places at their 7th and 10th thoracic vertebrae (which form the section of your spine behind your ribs). This was sufficient to completely disrupt their voluntary muscle control; leaving the rats paralysed and unable to move. The researchers then injected their spinal cords with a solution of various electrolytes such as serotonin and dopamine receptor agonists, which increased the activity levels of the nerves and stimulated the rats' nerves even further using electricity (at 40Hz if anyone's interested...) by attaching diodes to various segments of their spines near their base.

By supporting the movement of the rats in a robotic harness, researchers found that they were eventually able to walk, run and even climb stairs when their spine was being stimulated! This behaviour was gradually 'built up' however, as the rats appeared to have had to relearn how to move so the research doesn't suggest that there is an 'instant fix' to spinal damage; rather that it is possible with extensive physiotherapy in conjunction with modern medical techniques, such as those used in this experiment.

"It is completely unexpected to see this level of recovery." Professor Courtine (EPFL)

Thus, this exciting experiment suggests that recovery after spinal damage is perfectly possible for humans and that such individuals will eventually be able to live normal and independent lives. Experts point out however that although this technique has worked well in rats, it may not work in humans. 'Real life' injuries to the spine are much more complicated than those that were artificially introduced in this experiment and humans are much larger, more complicated organisms than rats. The study does provide hope however, and, as stated by Dr. Bacon (the director of research at Spinal Research): "this is a robust demonstration that medical research is moving in the right direction and restoring function after paralysis can no longer be dismissed as a pipedream".

Reference

van den Brand R., Heutschi J., Barraud Q., DiGiovanna J., Bartholdi K., Huerlimann M., Friedli L., Vollenweider I., Moraud E. M., Duis S., Dominici N., Micera S., Musienko P. & Courtine G. (2012). Restoring Voluntary Control of Locomotion after Paralyzing Spinal Cord Injury. Science 336, 1182-1185.