FIRST ATTEMPTS
In 1881 a physician named William Halsted successfully
carried out a blood transfusion injecting his blood in his sister Minnie who
was dying for a hemorrhage after giving birth to her child. This was one of the
few successful cases, in
which that was possible, because they had the same blood type (which is not guaranteed
even among close relatives). One of the first experiments was made in 1667 by
Jean Baptiste Denys, who
tested this practice on a man called Antoine Mauroy using the blood of a sheep to
treat his psychosis. At the first try everything
seemed good, but after the second one he started to run a
fever, had a pain in his lower back and a sting in his arm, then he urinated a
thick black liquid.
WHY DID THAT HAPPEN?
This phenomenon
was caused by the immune response of the body that started producing antibodies,
a type of proteins which distinguish home cells from foreign proteins embedded
in an intruder’s cell membrane (antigen), then they bound to them so as to indicate them to other
proteins which degrade them. Another effect is the creation of colts that
hinder the blood flow between organs overloading the kidney causing the organs failure.
Fortunately, Antoine survived, but this practice caused a lot of demises and
the same Mauroy renounced his career
after causing the death of a patient.
FURTHER STEPS TOWARD SUCCESS
In 1670 blood transfusions became forbidden in Europe
because of the large number of failures, the experiments with animal blood and
ethical controversies.
In 1901 Karl Landsteiner discovered blood types: the
crucial step for the success of human to human transfusions. He mixed different
type of human blood in order to study the clump-formation, so doing he
discovered that it didn’t happen mixing blood of the same type.
In 1907 the practice spread everywhere thanks to the
greater reliability. The transfusion happened in real time directly between two
individuals after mixing two blood samples to see if they were compatible.
Another crucial step was the discovery of the
properties of sodium citrate, which in contact with blood removes calcium
avoiding the coagulation caused by the contact with air. This fundamental
defense mechanism prevents an excessive blood loss after injuries.
In 1916 the heparin was discovered, this substance (more
effective than sodium citrate) could inhibit the same enzymes, that caused the
coagulation to form. In this way the transfusion didn’t have to happen directly
between two individuals and you could collect the blood for future emergencies.
The blood banks actually were introduced for the first time in field hospitals during
the First World War.
BLOOD TYPES
White blood cells interact with some proteins on the
membrane of blood cells named antigen, this process permits to distinguish your
own body cells without attacking them as extraneous corpuscles.
There are two main antigens (A; B) whose presence
determines your blood type: if the blood cells have no antigens on their
membrane your blood type is 0.
We have 46 chromosomes of which 23 from each parent,
every match of chromosome presents in a specific place (called locus) some genes which encode for the
same protein and this determines the appearance of a specific feature (blond hair,
green eyes, freckles). Since there are two genes, the one which manifests is
called dominant and the other recessive, but there are other cases, for example, in which they can both be
present or the recessive can contaminate the dominant ( i.e. a violet flower
with some white speckles). This feature is linked to the amount of proteins
that a gene can produce.
 |
| An allele is simply the variant of the same gene |
So if your parents
are an A type and a B type the dominance of one determine your blood type,
while whether they produce the same amount of proteins you are an AB type. The
0 type is always recessive this means that both your parents should be 0 type
to inherit this feature. 0 types can donate to everyone because of the absence
of antigens on their blood cells membrane, while they can receive blood only
from 0 type . AB types can donate only to AB types, but can receive blood from
everyone so they are universal recipient.
Finally, there is another type of factor ( rh+ / rh- )
which determines the presence of another antigen D.
And that is all for this
post. My aim was to share with you about the scope of biology and the bizarre
history of blood transfusions, which I find very interesting. I hope you
enjoyed reading and you find it interesting. Till next time!
GIORDANO C.
No comments:
Post a Comment