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Wucheria bancrofti is a filarial nematode that can cause filariasis, also known as elephantiasis. The nematode grows between 4-10cm in length and is spread by mosquitoes. The nematode travels to the lymph nodes and its offspring (microfilaria) are released into the circulation in order to be taken up by a mosquito, inside which it develops into an infective larvae.
Much of the pathology of Wucheria infection is caused by the immune response to the pathogen, which causes an inflammatory response. This causes lymph returning to the lymph node to be obstructed and results in the dilation of the affected duct. Fibrous connective tissue infiltrates the lymph node and results in swollen apendages. The most commoly affected areas are the legs, arms and scrotum.
Onchocerca volvulus is a filarial nematode that causes river blindness. The nematode grows between 20-50cm and is spread by blackfly. Upon infecting a host, it forms subcutaneous nodules and from this point releases it offspring (microfilaria) into the skin so they can be taken up by blackfly. Inside the blackfly, the microfilaria mature into infective larvae and the cycle continues.
The microfilaria released into the skin may invade the eye and cause inflammation followed by a build-up of fibrous tissue. In some areas endemic with Onchocerca, there may be up to 1500 blind persons per 10000. The adult worms, inversely, are less pathogenic though occasionally causing elephantiaisis and dermatisis.
Both Wucheria bancrofti and Onchocerca volvulus contain a bacterial intracellular symbiote from the Wolbachia genus. Indeed, Wolbachia is responsible for many of the symptoms of filarial nematode infection; the bacteria triggering innate and adaptive immune responses. Treatment of infected patients with antibiotics reduces the lifespan of adults from 10-14 years to 1-2 years. Additionally, adults often become sterile due to the nature of the symbiosis between the nematode and the bacteria.
Pictured: Onchocerca volvulus
Image Source: maksumprocedure.blogspot.com
Hookworms are a family of parasitic nematodes that infect mammals. Two species commonly infect humans; these are Ancylostoma duodenale and Necator americanus. Combined, hookworms are believed to infect 600million people across the world. Growing up to 1cm in length, hookworms have an interesting lifecycle. The free living larvae enter the host through penetrating the skin and entering the circulation. Next the parasite migrates to the lung, penetrates into alveoli, and is coughed up and swallowed. Eventually, the adult hookworm winds up in the small intestine where it feeds on the blood of its host. Adults can live up to 15 years (Necator americanus) with females producing around 10,000 eggs per day.
Hookworms also secrete a number of molecules to combat the host’s defenses. These include an acetylcholine esterase, which acts as an anti-inflammatory, and superoxide dismutase, which causes inactivation of reactive oxygen intermediates (ROIs). Proteinases (enzymes that degrade proteins) are also produced in order to break down chemokines produced by the host, as is a pro-apoptotic factor that causes any in range T cells to die.
The host is damaged in a variety of ways. Firstly, parasite feeding can result in the host loosing up to 200ml of blood a day in a heavy infection of hookworm. This can result in anaemia and malnutrition; in children, this can result in stunted physical and cognitive development.
Pictured below: Male and Female Necator americanus (the male is the smaller worm)
Image Source: theonion.com
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Ascaris lumbricoides is a parasitic nematode that infects up to ¼ of the world’s population. Reaching between 15-35cm as an adult, the parasite lives on average for one year. Transmitted through the faecal-oral route (yummy), the infective larvae take a rather unusual route to replicate. In summary, one the larvae hatch within the small intestine they penetrate a villus and enter the portal circulation. Once they’ve hitched a ride on their hosts blood stream they exit at the lungs and penetrate into the alveoli. From here, they migrate up the respiratory tract and are swallowed; winding up in the small intestine again. At this point they mate and produce eggs to be passed out with the faeces and help the nematode spread. The eggs, whilst sensitive to UV, are very resilient under optimal conditions and can survive up to 10 years.
The results of being infected with Ascaris include lung damage from the nematodes migration, a deficiency in Vitamin A, lactose intolerance, and decreased protein and fat utilisation. An allergic response to worm metabolites, generating strong TH2 cell response, can lead to rashes, eye pain and asthma. In particularly heavy infections, with over several hundred worms, death can result from intestinal blockage.
Ascaris is a major health issue; on average there are 80,000-100,000 deaths per year due to the nematode. In addition, approximately 1.5million children suffer permanent negative effects in their development, both physical and cognitive, due to being infected by the parasite.
Pictured below: Ascaris lumbricoides
Image Source: http://ascarislumbricoides.org/
Sometimes a blog is used for spreading science, other times its used for self-promotion. Sometimes its used for both.
Vis-à-vis, I’m involved in a really cool project at the moment. ICSJ (or The International Collegiate Science Journal) is a project which aims to produce an international student science magazine. They’re so far nine universities involved and the people involved are keen as anything. Science communication is important for furthering greater understanding of science in the public, and this project looks set to help further the aim.
The Journals Facebook group, kickstarter, and website are linked below.
tl;dr: Groovy science journalism project is occurring, any support would be wonderful.
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Did you know dragons exist? Members of the Draco genus are lizards that are capable of gliding up to 60m due to possessing an extension of skin known as a Patagium. Don’t worry though, your livestock and homes are safe. The lizards, only measuring up to 20cm (including tail), are insectivores and (as far as is reasonably known) incapable of breathing fire and wreaking havoc upon society.
Pictured below, an image of Draco taeniopterus in flight.
Image Credit: Psumusum
Dr. Prior, whose authority is great in the origin of popular names, says “It seems probably that the name was in the first place, foxes’ glew, or music, in reference to the favourite instrument of an earlier time, a ring of bells hung on an arched support, the tintinnabulum”… we cannot quite agree with Dr. Prior for it seems quite probable that the shape of the flowers suggested the idea of a glove, and that associated with the name of the botanist Fuchs, who first gave it a botanical name, may have been easily corrupted into foxglove. It happens, moreover, the name foxglove is a very ancient one and exists in a list of plants as old as the time of Edward III. The “folks” of our ancestors were the fairies and nothing is more likely than that the pretty coloured bells of the plant would be designated “folksgloves,” afterwards, “foxglove.” In Wales it is declared to be a favourite lurking-place of the fairies, who are said to occasion a snapping sound when children, holding one end of the digitalis bell, suddenly strike the other on the hand to hear the clap of fairy thunder, with which the indignant fairy makes her escape from her injured retreat. In south of Scotland it is called “bloody fingers” more northward, “deadman’s bells” whilst in Wales it is known as “fairy-folks-fingers” or “lambs-tongue-leaves”.
English Botany, Or, Coloured Figures of British Plants
(on the origin of foxgloves, the common name for Digitalis)
How many times have we seen a story about how a compound that increases the immune system may help fight cancer (I’m looking at you Daily Mail)? Whilst often we recognise these stories as over-glamorised and technically false, there is an assumption made that is rarely challenged; that the immune system regulates cancer. This assumption is false and based on misinterpretations of old studies.
In studies of both immune suppressed humans and mice, it was found that there was no major difference in occurrences of cancer compared with humans and mice with normal immune systems.
There is one exception to this finding; cancers associated with viral infections. It is found that tumours with a known viral cause are more likely to be found in those with a compromised immune system (cancers such as Kaposi’s Sarcoma).
This can be turned on its head. If a type of cancer shows different rates in individuals with normal immune systems and those with compromised immune systems, then it is likely to have a viral influence.
Image below of Kaposi’s Sarcoma
The last case of wild polio in the WHO Region of the Americas occurred in 1991. Indeed it was the last case of wild polio in the western hemisphere. His name was Luis Fermin Tenorio. At the time of contracting polio he was three years old and was currently living in Junin, Northern Peru.
Image shows Luis Fermin Tenorio (centre).
Image source: www.paho.org
First Updates, then Science.
I’m now contributing to a blog on plant sciences called PLANeT. The link is http://cambridgeplanet.wordpress.com . Its a really awesome project and a load of cool people are involved so it’s worth checking out. Like totally.
Now Science! Sometimes when male deer fight, their horns become entangled to such an extent that they are unable to break free. The obvious and sad conclusion is that they starve to death. Don’t believe? The picture below shows the result of such a misfortune a while down the line.
Image source: http://i.imgur.com/9aUqnZg.jpg
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Listeria monocytogenes is an intracellular pathogen that causes listeriosis and is one of the most virulent food-borne pathogens in the world. Unlike species of Salmonella, Listeria monocytogenes actively moves through it’s host cell.
How does it do this? By means of Actin assembly-inducing protein (ActA). ActA is is found at one end of the bacteria only, and induces host actin polymerisation.
This causes the bacteria to be propelled forward and results in the production of Actin Comet tails, which can be viewed by fluorescence microscopy. The resulting image is surprisingly beautiful.
An image of this phenomenon can be viewed below, the actin is green and the listeria are orange/red.
Image Source: http://labrat.fieldofscience.com/
Alternative Title: Little Feathery Psychos—Why you don’t fuck with a Great Spotted Cuckoo
You’ve probably heard about Cuckoo. The go to example for when people need to demonstrate parasites don’t have to be slimy; they can be feathery too.
Parasitic cuckoo’s come in one of two forms. The first is the Common Cuckoo, which lays it’s eggs in the nests of other birds. Upon hatching the cuckoo chick ‘evicts’ the remaining eggs; if any chicks are unlucky to have hatched before the cuckoo then they are also ‘evicted’.
But it’s the second species that takes the metaphorical biscuit for feathered-spawn-o’-satan. They tend to lay their eggs in the nests of magpies, and when the the cuckoo eggs hatch they allow their adopted kleptomaniac brothers and sisters to survive.
"Aha!", you may say, "this proves that they’re lovely birds with nothing but kindness in their little avian hearts."
Wrong. For, you see, the parent cuckoo returns to the magpies nest a few days after laying and, if it finds it’s precious egg missing, goes a little ‘cuckoo’ (pun intended and may the gods of comedy forgive me) and destroys all of the hosts eggs in an extreme case of “If I can’t then no one can”.
This is not a case of blind rage, it is crafty calculation on the Cuckoo’s part. It actually confers an advantage to Great Spotted Cuckoos overall, as it only allows for the evolutionary selection of magpies that allow cuckoo’s eggs to stay.
Further details can be found in this research paper: http://www.eeza.csic.es/eeza/documentos/soler_1004.pdf
Don’t worry it’s not dry as death- they refer to cuckoo’s as the Mafia.
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As a pathology student, the festive season is not a good time for reading; there’s too much "Peace on earth and good will to all men" floating around. Driven out of curiosity/boredom/ curioredom, I searched the internet for "Christmas Disease" and, low and behold, it exists!
Giving proof to the thought that the only consolation of of having a rare disease is the possibility it will be named after you, the disease gains it’s name from the person the disease was identified in: Stephen Christmas. The disease, also known as Haemophilia B, is characterised by a mutation in the Factor IX gene. Factor IX is one of the serine proteases involved in the coagulation cascade; in short, without it your blood doesn’t clot. The condition accounts for 15% of haemophiliacs and even has a royal following—it is the form of haemophilia that afflicted the royal families of Europe throughout the 20th century.
Somewhat humourously, the paper detailing the discovery of the condition was published in the British Medical Journal in 1952 on the 27th of December; the Christmas issue.
In a somewhat sad conclusion, Stephen Christmas died of HIV/AIDS in 1993 after contracting it through a contaminated transfusion; a horrendous fate bore by many haemophiliacs at the time. (This blog post has nothing to do with Christmas trees)
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The final battle against malaria is a battle against vivax.
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How does one figure out the value of Pi? You could draw a circle on some paper/in the ground/ on your friend’s back. But how could you guarantee your circle was accurate? Chances are it would be a little bit off and you would be left with a false value- no matter how accurate you thought it was. One way to solve the problem would be to introduce boundaries, to say that the value of pi is between X and Y.
This was the method undertaken by Archimedes, who knowing how to calculate the circumference of simpler shape, calculated the first estimation of pi. Using simpler shapes to estimate the value of pi is known as the polygon approximation method. The simplest form of this is to use two squares, one just inside the circle and the other just outside (see picture). The larger square will have a side length equal to the diameter of the circle, and so its perimeter will be equal to 4d. The inner square will have the length from one corner to the opposite as equal to the circle’s diameter. The smaller square can then be thought of as being two right handed triangles each with a hypotenuse equal to d. Using Pythagoras’ Theorem it can be found that each of the sides of the small square are equal in length to d/sqrt(2), giving a total perimeter of 4d/sqrt(2) (roughly 2.83d). As the circle lies between the two squares it’s perimeter (or circumference) must lie between 2.83d and 4d, and as pi is related to these two properties by the equation C=pi*d, then pi must lie between 2.83 and 4.
This can be repeated using polygons with more sides for greater accuracy and indeed pi was calculated to 38 places using this method, involving polygons exceeding 4 billion billion sides. Sounds fun.
For once there is no picture credit as produced by me.
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Behold the mighty dinosaur,
Famous in prehistoric lore,
Not only for his weight and length,
But for his intellectual strength.
You will observe by these remains
The creature had two sets of brains,
The one in his head, the usual place,
The other at his spinal base.
Thus he could reason a priori
As well as a posteriori.
No problem bothered him a bit,
He made both head and tail of it.
So wise he was
So wise and solemn
Each thought filled just a spinal column.
If one brain found the pressure strong,
It passed a few ideas along.
It something slipped the forward mind
’Twas rescued by the one behind.
And if in error he was caught
He had a saving afterthought.
As he thought twice before he spoke
He had no judgment to revoke.
For he could think without congestion
Upon both sides of every question.
O gaze upon this noble beast,
Defunct ten million years at least.
This poem by Bert Leston Taylor represents a peculiarity found in some dinosaurs and also illustrates one of the most steadfast rumours in science. Sadly, dinosaurs did not have a second brain (in the true sense of the word) in their rump, though some (such as the stegosaurus) did possess a concentration of nerve cells thought to give some independent control to the tail and rear legs and so allow the dinosaur to remain balanced. Far from being unique to dinosaurs this neural arrangement is also found in some lizards and even ostriches!
Pictured below is an illustration of a stegosaurus skeleton with the approximate location of the primary brain and the false second ‘brain’.
Image source (http://gildedgreen.notart.org)
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