Amniocentesis:- It is a technique in which the
amniotic fluid is analyzed in early stage of foetal development. The amniotic
fluid surrounds the developing foetus in uterus and also contains the cells of
developing foetus. It is done on about 14 or 15 weeks after conception.
During it,
-Ultrasonography is done to locate the position of the foetus in uterus.
-The amniotic fluid is taken out from the
uterus by the help of surgical needle.
-The amniotic fluid is centrifuged to separate the
cells of foetus and
-The cells are cultured for some time and are analyzed.
In karyotype analysis the nucleus of the cell
is analyzed and the chromosomal abnormalities of the foetus are identified. If
any genetic disorder like Down syndrome, Klinefelter's syndrome are present then that is also identified. By examining the
sex chromosome sex of the developing foetus is also identified.
In biochemical analysis the metabolic features
of the cell is identified. If any metabolic disorders like sickle cell anaemia is present, then that is
identified.
If the foetus is suffering from any serious congenital
disease, the pregnancy will be terminated. However, this technique is widely
misused to terminate normal female foetus. Thus, it is banned nowadays.
Test-tube baby: - It refers to child born by the use of IVF- technology. The term IVF
refers to in vitro fertilization which means fertilization in glass ware. It is
applicable for those women who are not able to conceive and give birth to child
normally due to some disorders.
This technique was first successfully done by Robert
Edwards and Patrick Steptoe of England to develop first test tube baby "Louis
joy Brown" in 25 July, 1978.
In Nepal first
test tube baby was born in 21st falgun, 2061 at Om hospital and
research centre in Kathmandu and was "Om Mani Tamang".
In this technique the egg is taken out from mother's
body and is cultured in glass ware. The egg is fertilized by the sperm of her
husband in the glass ware (test tube). The fertilized egg is cultured in glass
ware for up to 32 celled stage and is implanted in the uterus of another woman.
The another woman is called as surrogate mother who acts as animal incubator
and gives birth to a child after completion of normal pregnancy period. She has
no any contribution in the genetic makeup of the child.
This is a great achievement of medical science and is
boon to childless couple who are having problems to give birth to child naturally. However, it has raised a number of ethical and legal
problems like right over the child.
Antibiotics:- The chemical substances obtained
from micro-organisms which are capable to inhibit the growth of micro-organisms
or to kill the micro-organisms are called as antibiotics.
The first antibiotic is Penicillin which was
discovered by Sir Alexander Fleming in 1928. It was extracted from Penicillium
notatum.
On the basis of their effects on micro-organisms
antibiotics are of two types:-
* Bacteriostatic antibiotics: - Those
antibiotics which are capable to stop or inhibit the growth of micro-organisms
are called bacteriostatic antibiotics.
*Bactericides antibiotics: - Those antibiotics
which are capable to kill or destroy the micro-organisms are called as
bactericides antibiotics.
On the basis of varieties of micro-organisms on which
antibiotics act, they are categorized in to two types:-
*Broad spectrum antibiotics: - Those
antibiotics which show their action on different types of micro-organisms are
called as broad spectrum antibiotics.
*Specific antibiotics: - Those antibiotics
which show their action on particular type of micro-organisms are called as
specific antibiotics.
Some common antibiotics are penicillin, streptomycin,
Tetracycline, Erythromycin etc.
The antibiotics are used as:
* Medicine to control different diseases.
* Preservatives to preserve fresh meat, fish, fruits,
vegetables etc.
* Supplementary food for animals to enhance their
growth.
Vaccines:- The vaccines are liquid chemical substances
which stimulate immunity of body when administered into body. They contain
modified, dead or attenuated microorganisms or their antigens. They are injected
or taken orally in advance so body get time to set active immunity before the
entry of germs. When any pathogen enters inside body, it produces chemical
called as antigen to destroy the human immune system. The human immune system
produces a specific chemical to destroy the antigen and this substance is
called as antibody which is also called as immunoglobin.
The first immunization was done by Louis Pasteur to
treat rabies. He extracted the fluid from spinal cord of a rabid dog and
injected it to a boy who was bitten several times by a rabid dog.
Types of vaccines:- Vaccines are of following types;
* Attenuated
viruses as vaccines:- In this
method, viruses are weakened or attenuated by chemical treatment and are used
as vaccine. Eg. BCG, Vaccines for Rabies, Polio, yellow fever etc.
* Dead organisms as vaccines:- In this type, dead bodies of micro-organisms are treated
chemically and used as vaccines. Eg. Typhoid vaccines, cholera vaccine, vaccine
of woophing cough etc.
* Bacterial toxoids as vaccines:- The exotoxins of bacteria are treated chemically to
remove their harmful nature and are used
as vaccines. Eg. Tetanus toxoid, vaccine of dipthrea etc.
* Immunizing sera
as vaccines:- The blood serum of a
person or animal contains antibody and are used to treat diseases like diphtheria,
rabies etc. rather than to prevent.
Now a days vaccine are also prepared by DNA
recombinant technology of genetic engineering and such vaccines are called as
second generation vaccines. These are safer and more effective. Eg. Vaccine of
Hepatitis, Influenza etc.
Classification of vaccines:
vaccines are classified as follows:
*First generation Vaccines:- The vaccines produced by conventional methods using whole organisms are called first generations vaccines.
*Second generation Vaccines:- The vaccines produced by genetic engineering or DNA recombinant technology are called second generation vaccines. These are safer, simpler and more effective. Eg. vaccine of Hepatitis-B.
*Third generation vaccines:- The vaccines which are prepared artificially are called third generation vaccines. They are highly effective. Eg. Vaccine of Diphtheria.
Vaccines develop immunity against infectious disease and kill or destroy disease causing organisms.
Tissue and organ transplantation:- The process of
replacement of dead or damaged tissue or organ by similar tissue or organ from
same body or another body is called as transplantation.
The recipient's body
regards the transplanted organ as antigen and produces antibodies which must
match with the antigen otherwise the transplanted tissue or organ is rejected
by the recipient's body. The antigen- antibody reaction may damage the transplanted organ.The success rate of transplantation depends up on the
relationship of donor and recipient.
In human, the genes responsible for the rejection of transplanted organ are called H-genes or histocompatibility genes or human lymphocyte antigens (HLA). The success of transplantation depends upon the matching of HLA that occurs in all cells of body. The test carried out to match the HLA antigens of donor and recipient is called tissue typing. The success rate of transplantation increases significantly when HLA types are matched.
On the basis of relationship of donor and recipient,
the transplantations are of following types,
* Autograft:-
It is transplant of tissue from one part of body to another part of body. There
is no problem of rejection. Eg. Skin transplant from one part of body to
another part of same body.
*Isograft:-
It is transplantation between genetically identical individuals like identical
twins. There is no problem of rejection.
*Allograft:-
it is transplantation between individuals of same species. The success rate of
transplant depends upon relationship of donor and recipient. Closure the
relationship, the transplant becomes more successful.
*Xenograft or heterograft: - It is
transplantation between individuals of different species like man and monkey.
In this type of transplant success rate is very low and till now it is carried
out for research.
Tissue transplantation:- In it, damaged tissues are replaced by similar tissue
from another part of body. The most common type of tissue transplantation is
skin transplant. Nowadays a small part of tissue is taken out from body and is
cultured to obtain sheets of tissues and is kept in tissue banks and is used
for transplantation. It needs corrective surgery.
Organ transplantation: - In it, a whole organ like kidney, heart, lungs etc are
replaced. It is a very decisive process which is done only when the life of an
individual is saved by the transplantation. The success rate becomes high if the
donor and recipient are genetically similar as far as possible.
The most common and successful organ transplant is of cornea as it is
not related with immune system and blood supply. It is easiest organ
transplantation. However, transplantation of organs like kidney, liver, heart
etc. are very complicated. The main problem of organ transplantation is that
the recipient body regards transplanted organ as foreign part or antigen and
produces antibodies against the transplanted organ and is rejected by the
immune system of recipient's body. This is called as rejection. The rejection
can be prevented by following ways;
*By using immunosuppressive drugs called as immunosuppressant.
However, these drugs are very expensive and suppress the immunity of whole body
and body become highly susceptible to infection. Imuran, cyclosporine are examples of immunosuppressants.
*The transplanted organ must be taken from siblings
i.e. brother or sister or from genetically identical member.
* The immune system is also suppressed by radiation.
*Tissue typing i.e. matching of HLA of donor and recipient should be done.
* The researches are going on to develop immunosuppressant
which can suppress only the immunity of transplanted area which only stop
rejection while the immunity of other parts remain active.
*The researches are also going to develop artificial
organs. Like plastics are used to replace valves, vessels, bones etc.
= first corneal transplant was done in 1905 by Eduard Zirm.
=first heart transplant was done in 1967 by Christian Barnard.
=first kidney transplant was done in 1954 by Joseph Murray.