Cases, What's this?

What’s this? #5 Amyloidosis

Last week we asked “what’s this?”. Alicia D got it right with renal glomerular amyloidosis, and paleomanuel also correctly spotted some swelling! To understand what’s going wrong in this kidney, we first need to understand the problem with proteins.

When proteins go wrong, all sorts of chaos can occur in the body. One particularly interesting abnormality is when the proteins fold incorrectly when being made, and stick together in clumpy plaques (called proteinopathies = protein + pathology).

You are nothing without your proteins. They act out the instructions written in your DNA – making and holding us together (connective proteins), allowing us to grow and move (contractile and cell division proteins), giving us energy (metabolic and oxygen transport proteins), defending us (immune proteins), giving us colour (pigmentary proteins), and so on and so on and so on!

File:Main protein structure levels en.svg

All proteins are built up from long chains of smaller molecules called ‘amino acids’ (a protein’s primary structure; the lego blocks of life).  These chains fold into different shapes (secondary structure).  Sometimes these fold further – tertiary structure.  And some proteins are made up of multiple folded chains – quaternary structure (super complicated lego mansion).

The accummulation of protein gives the kidney a yellow colour

The accummulation of protein gives the kidney a yellow colour

‘Amyloidosis’ is actually a group of diseases caused by a build up of sticky protein plaques.  Some types of amyloidosis are inherited, like ‘Shar-Pei Fever’ (not to be confused with Sharpie Fever) in Shar-Pei dogs.

Shar-pei dogs, which can actually become airborne in strong winds

Shar-pei dogs can actually use their skin folds to become airborne in strong winds…maybe

In affected dogs, the liver over-produces a protein called serum amyloid A (SAA) involved in inflammation. Some of the SAA proteins fold incorrectly, making sheets that stick together.

Congo red (x100) stains the amyloid fibrils orange-red within the glomeruli

Congo red (x100) stains the amyloid fibrils orange-red within the glomeruli

The sticky sheets of protein float around in the blood, and get lodged in the kidney’s blood filtering machinery (the glomerulus). They stick together and clog up the filter, making the kidneys appear swollen and discoloured with proteinaceous gunk. The delicate blood vessels in the glomerulus are a bit like coffee filter paper: they are easily torn and damaged by trying to push past the protein clogs and keep filtering the blood clean. Once damaged, normal molecules are lost rather than filtered (like coffee granules leaking past the filter paper in to your cup). Once the kidneys lose their ability to filter, we call it kidney failure. Because the whole thing is triggered by repeated episodes of inflammation and SAA release, it is often associated with fever in Shar-pei dogs.

Iodine stains the amyloid deposits in the glomeruli black

Iodine staining the amyloid deposits in the glomeruli dark brown

Amyloid reacts with iodine and forms big brown blobs, so we can see the clumpy SAA plaques in the kidney with the naked eye. We can also stain it with Congo Red under the microscope, which stains the proteins red.  In fact, the Congo Red dye binds in a very regular pattern, almost crystal like, so that when polarised light is shone through it, it becomes apple green…

Polarised light reveals the Congo Red dye as apple green, when bound to amyloid fibrils

Polarised light reveals the Congo Red dye as apple green, when bound to amyloid fibrils

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Cases

I’m sticking with you.

It’s almost the Easter weekend, which means the UK lambing season is well underway! For the past couple of months, exhausted farmers tend their flocks and we all get to see cute lambs springing around in the fields. However most of us know it’s not all nice, with shows like Lambing Live  illustrating the unique problems of this time of year.

It unfortunately comes with the territory that with vast numbers of animals being born all at once, there are inevitably mortalities. With such huge numbers of births, there is also a good chance that at some point you’ll encounter some very strange developmental abnormalities.

One head good, two necks baaa-d

One head good, two necks baaa-d

 

One such abnormality is conjoined lambs, where two foetuses develop stuck together. These lambs had one body, two necks and a shared head. They also had partially separate organ systems.

 

Unusually for conjoined lambs, the face was almost normal  (more often there are two distorted faces)

Unusually for conjoined lambs, the face was almost normal (more often there are two distorted faces)

These twins are similar to the skeletal specimen, sharing a head with an almost normal face.

Probably how the lambs would have looked – these taxidermied lambs also share a head with an almost normal face

 

Two spinal cords are seen entering the skull and there is a cleft palate.

From underneath, you can see there is a cleft palate.

These lambs also had a cleft palate in their shared head – a hole in the roof of the mouth, where the bony plate between the nose and mouth hasn’t formed properly. If the lambs had lived, it is likely the milk they drank would have passed into the nose and been inhaled, causing pneumonia.

Side view

Side view

 

Twins conjoined at the chest and head.

Twins conjoined at the chest and head.

Conjoined twinning is a relatively common developmental problem in animals, and similar to the parasitic twin phenomenon. It is more often seen in domesticated animals since they have more care and better chances of survival than their wild counterparts.

Happy Easter!

Happy Easter!

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What's this?

What’s this? #4 Horse Parasites

Parasites often live inside animals without causing trouble (in fact, it’s better for them to keep their meaty landlords alive and kicking, since it ensures a consistent food source and a place to call home!).  The mystery picture in What’s this? #4 is from the liver of a horse, and correctly identified by a number of people (well done!) as the cystic stage of a tapeworm called Echinococcus granulosus.  This is actually a parasite which has evolved to cycle through dogs and sheep, rather than horses. The dog is its Final host, where the adult lives and lays eggs in the intestines. The eggs are pooped out, hatch into larvae and wriggle free onto pasture, where sheep eat them. Dogs are then re-infected by eating sheep organs. Alas, the best laid plans of mites and men (and tapeworms) often go awry, and other animals like horses and humans can become infected accidentally.  In humans it can form fatal cysts within the brain and other organs, which is a no-win for the parasite.

Hydatid cysts in the liver of a horse.

Hydatid cysts in the liver of a horse. Each cyst contains a developing tapeworm.

Another tapeworm which can be found in the horse, is called Anoplocephala perfoliata and looks like little leaves.  They are often found in the small intestine where they can cause ulceration and inflammation of the intestine.  Generally they do not cause the horse any problems, but sometimes they dig too deep and lead to rupture of the intestine, peritonitis and death.

Circled is the tapeworm Anoplocephala perfoliate within the small intestine of a horse.

Circled is the tapeworm Anoplocephala perfoliata within the small intestine of a horse.

A worm called Strongylus vulgaris (also known as a large strongyle) can be found in the large intestine and caecum (appendix) of horses.  It is particularly nasty as it digs in and invades the wall of the intestine so it can travel along the arteries. Eventually it migrates to a branch of the aorta (the large artery leaving the heart).  It can damage the blood vessels so much that the intestines die, which can kill the horse.

These are the intestinal vessels branching off the aorta (mesenteric arteries) - notice how inflamed they are.

These are the intestinal vessels branching off the aorta (mesenteric arteries) – notice how thick and inflamed they are.

The worm can be seen attached to the wall of a mesenteric artery - inflammation of arteries caused by worms is called verminous arteritis.

The worms can be seen attached to the wall of a mesenteric artery – inflammation of arteries caused by worms is called verminous arteritis.

Another strongyle, commonly known as a small strongyle (Cyathostomum) lives in the large intestines and caecum of horses.  Like other worms, enough of them can cause diarrhoea and weight loss.  However, a cystic stage can also occur, with thousands of larvae in tiny cysts within the lining of the intestine.  Sometimes, these will all emerge at once, bursting the intestinal wall and causing huge injury.  Gut toxins can then leak into the blood and cause toxic shock, which is often fatal.

Thousands of encysted cyathostome larvae within the wall of the large intestine.

Thousands of encysted cyathostome larvae within the wall of the large intestine.

 

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