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over 3 years ago
I'd like to tell you a curious story. Jane was a 52 year old woman in need of a kidney transplant. Thankfully she had three loving sons who were all very happy to give her one of theirs. So Jane's doctors performed tests to find out which of the three boys would be the best match, but the results surprised everyone. In the words of Jeremy Kyle, the DNA test showed that Jane was not the mother of two of the boys... Hang on, said Jane, child birth is not something you easily forget. They're definitely mine. And she was right. It turns out Jane was a chimera. Chimerism is the existence of two genetically different cell lines in one organism. This can arise for a number of reasons- it can be iatrogenic, like when someone has an organ transplant, or it can be naturally occurring. In Jane's case, it began in her mum's womb, with two eggs that had been fertilised by different sperm creating two embryos. Ordinarily, they would develop into two non-identical twins. However in Jane's case the two balls of cells fused early in development creating one person with both cell lines. Thus when doctors did the first tissue typing tests on Jane, just by chance they had only sampled the 'yellow' cell line which was responsible for one of her sons. When they went back again they found the 'pink' cell line which had given rise to the other two boys. This particular type of human chimerism is thought to be pretty rare- there are only 30 case reports in the literature. (Though remarkably both House and CSI's Gil Grissom have encountered cases.) What happens far more frequently is fetal microchimerism- which occurs in pregnant women when cells cross the placenta from baby to mum. This is awesome because we used to think the placenta was this barrier which prevented any cells crossing over. Now we've found both cells and free floating DNA cross the placenta, and that the cells can hang around for decades after the baby was born. Why? As is often the case in medicine we're not sure but one theory is that the fetal cells might have healing properties for mum. In pregnant mice who've had a heart attack, fetal cells can travel to the mum's heart where the develop into new heart muscle to repair the damage. Whilst we're still in the early stages of understanding why this happens, we already have a practical application. In the United States today, a pregnant woman can have a blood test which isn't looking for abnormalities in her DNA but in that of her fetus. The DNA test isn't conclusive enough to be used to diagnose genetic conditions, but it is a good screening test for certain trisomies including Down's syndrome. Now, we started with a curious tale, so lets close with a curious fact, and one that's appropriate for Mother's Day: This exchange of cells across the placenta is a two way process. So you may well have some of your mum's cells rushing through your veins right now. In my case they're probably the ones that tell me to put on sensible shoes and put that boy down... (FYI: This is a story I originally posted on my own blog)
Dr Catherine Carver
over 4 years ago
Your heart is a pump that is responsible for delivering blood to all parts of your body. Arteries carry oxygen-rich blood from the lungs to nourish the cells, and veins transport oxygen-poor blood on its way back to the heart and lungs.
about 1 year ago
Covers the very early development of the human heart. We go from the flat trilaminar stage to the looped heart and its five regions. Part two will then take us from this stage to the four-chambered heart we know so well. I hope you enjoy it.
over 1 year ago
The heart's conductions system controls the generation and propagation of electric signals or action potentials causing the hearts muscles to contract and the heart to pump blood.
over 3 years ago
Watch this medical education video about heart failures and prepare for your next cardiology exam! You can also watch this video and many other free lectures...
over 1 year ago
As a larger volume of blood flows into the ventricle, the blood will stretch the walls of the heart, which in turn increases the force of the contraction and thus the quantity of blood that is pumped into the aorta during systole.
about 3 years ago
A review of the EKG findings in MIs, including their morphological classification, a determination of their age, and localization to region of the heart and ...
over 2 years ago
Written by Dr John L Gibbs, Consultant Paediatric Cardiologist, Yorkshire Heart Centre, Leeds General Infirmary. This presentation covers the many types of bradyarthymias, their ECG findings, investigation of them and finally some of the common treatment methods.
over 8 years ago