in vitro fertilization paper

8/13/2019 In Vitro Fertilization Paper

1/11

In vitro fertilization (IVF) is a procedure where an egg taken from a

females body is fertilized by sperm taken from a male in a laboratory dish. IVF is

commonly known as an alternative way for infertile couples to become pregnant.

his techni!ue is useful in many other ways as well. IVF can be used to

determine if a child possesses a genetic disorder in the earliest stages of

development (embryonic stage). It can also be used as a tool for studying se"ual

reproduction.

Infertility is a condition which prevents a couple from becoming pregnant

by normal se"ual intercourse. #ppro"imately $.% million people in the &nited

'tates are affected by infertility. owever fewer than *+ of infertile couples

choose to use IVF. IVF is usually chosen by women who suffer from blocked

badly damaged or no fallopian tubes. It may also be used when the woman

suffers from endometriosis or the man suffers from problem with sperm such as

low sperm count (,arcia).

In vitro fertilization is a procedure where eggs taken from a females body

and sperm taken from a males body are combined in a laboratory dish. -nce the

eggs are fertilized they are then implanted in the females uterus through a

process called embryo transfer (In Vitro Fertilization/ IVF0). In this process the

embryos are inserted into the womans uterus using a catheter. If the eggs attach

to the uterine wall and grow the pregnancy test result is positive (,arcia).

he success rate of this procedure depends on individual patients as well

as treatment methods. 1regnancy rates are not e!uivalent to live birth rates. In

the &nited 'tates the live birth rate for each IVF cycle started is appro"imately/


2/11


3/11

(FI') was produced in early %==2. It allowed chromosomal disorders to be

found through the e"amination of single nuclei. 1reimplantation genetic diagnosis

is becoming a popular medical alternative in reproductive medicine (0)

&ntil 1,< was established couples had few favorable reproductive

options. -ne option was to take their chances of producing a child with a genetic

disorder. #nother option was using prenatal diagnosis such as chorionic villus

sampling or amniocentesis to check if the baby possessed a genetic defect. In

this option a couple should be prepared to abort the pregnancy if a genetic defect

is discovered. #bortion of the pregnancy is not an easy alternative for it can

result in psychological and physical pain. -ther options included the use of

donated gametes with all its ethical and financial difficulties not to procreate at

all or to adopt (0).0

here are many reasons patients decide to use 1,


4/11

disorders and chromosomal structural aberrations. 8ore and more diseases are

becoming detectable through 1,


5/11

accurate and reliable results. hese 1,< techni!ues are making it possible for

an increasing amount of genetic disorders to be discovered (0).

Fertilization in plants is difficult to study because their gametes are located

inside a protected part of the plant. herefore there is a narrow grasp of what

happens in fertilization in particular plants. Fortunately in vitro fertilization has

enabled researchers to study fertilization in plants by eliminating most of the

surrounding somatic tissues and nearby maternal gametophytic cells. IVF has

made it possible to investigate hypotheses on gamete recognition and zygote

activation. It is currently a very important tool concerning plant development and

reproduction in higher plants (Gang).

#s reported by @ass in %=52 living sperm cells were first isolated using

male gametes from barley (Hordeum vulgare). hese gametes were isolated by

bursting anthesis pollen grains in a 43+ sucrose solution (Gang.)0 #fter a mass

of sperm cells were isolated in %=6$ the isolation of male gametes was

continued with revision in a variety of angiosperms (flowering plants). he first

reports regarding isolation of egg and central cells was completed by u et al. in

%=6* and uang and Aussel in Plumbagoin %=6=. # common way to isolate

female gametes was to use a dilute enzyme treatment to loosen surrounding cell

walls followed of accompanied by micromanipulation to separate remaining

ovule cells from embryo sacs (Gang).0 @omponents contained within the embryo

sacHthe egg cell two synergids central cell and three variably present

antipodalsHare then available to be isolated without restraint. he first effective


6/11

IVF e"periments as conveyed by ranz and others (%==%) Coined sperm and

egg cells from maize to produce an in vitro zygote by using electrofusion. hese

researchers adapted this process and by using in vitro:created zygotes were

able to accomplish restoration of fertile plants (Gang).

In vitro fertilization of angiosperms has e"perienced only limited success

so far. #lthough tobacco would appear to be an ideal prototype for in vitro

fertilization its gametes did not merge easily to create embryos. Ghen gametes

were e"posed to a polyethylene glycol solution fusion occurredE however there

was no further development. #lthough limited grasses remain the best group for

in vitro fertilization. ovJcs et al. (%==*) succeeded in combining wheat gametes

with the same IVF process. Kecause the in vitro zygotes ceased to grow a

multicellular structure was generated (Gang).

#side from using plants with superior living gametes the cell cycle is

another important factor in effectively fusing gametes. For most eukaryotes

fertilization takes place during the ,%phase of the cell cycle but for many

angiosperms fertilization takes place during the ,4phase. here are numerous

ways fertilization may occur in angiosperms. For e"ample pollen could be

e"pelled before the development of sperm in bicellular pollen species. In

tricelluar pollen species the stage of the cell cycle that sperm formation occurs

can vary from ,% ' or ,4. #lso sperm cells do not always occur in harmony with

the female gametes. he phase of the cell cycle that fertilization takes place has

only been reported for a small amount of plants which show significant diversity.

hese studies have indicated that grasses are the most proficient species for in


7/11

vitro fertilization since their gametes are usually released in the ,%phase which

is the same phase that they combine in naturally (Gang).

-n the other hand tobacco has been shown to be an ineffective e"ample

for in vitro fertilization. his is likely because its sperm cells form during the , %

phase but do not fuse until the ,4 phase naturally. It is very difficult if not

impossible to obtain a sperm cell at the right time in tobacco plants. his is

because the sperm cells finish the ' phase within the synergid (cell near the egg

inside a mature embryo sac) and instantly fuse after entering the , 4 phase.

Aesponsive egg cells are probably Cust as challenging to ac!uire because egg

cells develop in synchrony with sperm cells. 8atching the cell cycle of gametes

with their normal fusion condition thus represents a potentially grace pitfall in

meeting IVF congruity re!uirements (Friedman %===) (Gang).0

Fortunately all that has been achieved with in vitro fertilization of grasses

is a positive sign that IVF may be effective on some essential crop plants and

offer a helpful understanding of zygote activation. 'uccessful IVF into new fertile

plants may prove to be a useful approach for investigating epigenetic effects

nucleocytoplasmic interactions typical to gametes (Gang).

In vitro fertilization can also allow gametes from different species of plants

to be fused creating hybrids. he production of hybrid plants has encountered

many problems because of differences in chromosome number. 'ometimes

fusion of the gametes of two different species is successful but the product plant

is infertile. #n interesting occurrence in some hybrid cells is the total removal of

one parents chromosomes. here are several other problems involved in IVF of


8/11

different species including the failure of cells to divide properly and genetic

instability. 'till there has been some success in creating hybrid plants such as

the making of potato:tomato hybrids (Gang).

#ll in all there have been numerous setbacks involved with in vitro

fertilization in plants. -ne of the most maCor complications has been the isolation

of gametes. In vitro fertilization has been very successful in grasses but

unsuccessful in tobacco. #lthough creating hybrid plants has e"perienced a

variety of problems the production of potato:tomato hybrids was accomplished.

oday many more tools are offered to allow e"amination of plant gametes.

hese advances will hopefully allow many !uestions concerning reproduction in

angiosperms to be answered (Gang).

In vitro fertilization has caused some side effects such as ovarian

hyperstimulation syndrome and multiple pregnancies. -ther concerns involving

the risks of taking ovulation:stimulating drugs have risen within the past few

years. he possible connection between these drugs and ovarian cancer was

discussed in a collection of articles regenerating concern among the public

(Derner:geva).

here has actually only been a few cases of ovarian cancer among

women that underwent IVF treatments. # fast:developing tumor was detected

soon after IVF treatment in the maCority of these cases. #lthough these cases do

not confirm a link between IVF treatment and the occurrence of ovarian cancer

they do suggest the ovarian stimulation or oocyte e"traction may !uicken the

development of a present tumor. 'tudies that analyzed the occurrence of cancer


9/11

in a group of women who went through in vitro fertilization treatments generally

showed no increased risks of ovarian or breast cancer. he obCective of the

current study was to investigate the development of cancer in a group of infertile

women who underwent IVF treatment. Gomen who developed cancer within the

first year were focused on especially (Derner:geva).

his research was based on a group of women treated for infertility from

%=67 to %==4 at an IVF unit in el #viv Israel. -nly women who underwent at

least one IVF treatment were used in this study. # variety of demographic

information was collected such as age and continent of birth.


10/11

latency period between IVF treatments and the development of cancer (Derner:

geva).

he data was analyzed by comparing the observed to e"pected

occurrence of cancerHstandardized incidence ratios ('IA). he e"pected values

were determined by age se" continent of birth and the rate of year:specific

national cancer fre!uency. he risk period was calculated from the initial

treatment date to either the last follow:up date or malignancy diagnosis date

(Derner:geva).

# total of %364 women were involved in this study. he average age of

initial IVF treatment was 24.5 M 7.6 and the average age of the last follow:up

was 26.5 M *.4. he e"pected number of patients who would develop cancer was

%% but 4% cases were actually observed. hese included five cases of breast

cancer compared to 7.66 that were e"pected three cases of ovarian cancer as

compared to 3.$3 e"pected and three cases of cervical cancer as compared to

3.$* e"pected (Derner:geva).0

In the cases that cancer was detected within the first year were e"cluded

from the evaluation Cust %$ cancer cases were detected opposed to 4% cases.

he occurrence of ovarian cancer was eliminated. he occurrence of cervical

cancer was still higher than e"pected but not significantly. -verall the ratio

between the observed and e"pected number of cancer cases displayed not

significantly greater risk for cancer development (Derner:geva).

his study which included determining whether or not IVF treatments

were related to the development of cancer found no significantly increased risk


11/11

of cancer. In fact infertility alone has been considered to be responsible for a

higher possibility of cancer. 'imilar studies have shown that the incidence of

breast and ovarian cancer was no higher than predicted. he greater than

e"pected rate of cancer development was reduced by e"cluding the women who

were diagnosed with cancer within the first year receiving IVF treatment. hese

numbers may possibly be due to pre:e"isting cancer that was simply triggered by

the hormonal drugs involved with IVF treatment. IVF treatments may actually

help to diagnose cancer earlier by activating pre:e"isting malignancies (Derner:

geva).

In vitro fertilization or the fertilization of egg and sperm outside of the

reproductive organs has proved to be a very useful tool in science. #side from

allowing infertile couples to produce a biologically related baby it also allows

preimplantation genetic diagnosis (1,

in vitro fertilization paper

Documents