| |
|
Headlines:
|
 |
Back to table of contents
Submitted by Dr. Hesham Al-Inany, M.D. Lecturer,
Gynaecology & Obstetrics dept. Kasr El-Aini hospital, Cairo University,
Egypt.
|
|
|
During Gamete Micromanipulation sperms are injected into an ovum to assist in
union of the gametes.
|
|
| |
|
|
| |
| |
| |
|
|
| |
|
|
|
Transmission electron microscopy (TEM) after SUZI
Sathananthan et al,(1989) , studied the ultrasrtucural features of
spermatozoa-oocyte incorporation after sperm transfer Of 100 spermatozoa
examined by TEM in the PVS of 16 oocytes after transfer of 5-10 spermatozoa
from oligozoospermic men , 76% had intact acrosomes and 33% of intact
spermatozoa were morphologically abnormal . Nuclear, acrosomal, midpiece
and tail defect were entered in these abnormal sperm forms.
Ng et al, (1990), also studied the spermatozoa undergoing sperm head decondensation
and formation of a pronucleus. Between 10-30 sperm were transferred into
11 donated human embryos between pronuclear and 16-cell stages. After
culture for 24 hours, the embryos were fixed TEM.
Both acrosome-intact and acrosome-reacted sperm were located in the PVS
and between blastomeres. Sperm-blastomere membrane fusion was not observed.
The study clearly showed that sperm heads are incapable of expanding their
chromatin to form typical male pronuclei following SUZI into early human
embryos.
|
|
|
|
Are you a doctor or a nurse?
Do you want to join the Doctors Lounge online medical community?
Participate in editorial activities (publish, peer review, edit) and
give a helping hand to the largest online community of patients.
Click on the link below to see the requirements:
Doctors Lounge Membership
Application |
|
Intracytoplasmic sperm injection
Assisted-fertilization methods e.g., partial zona dissection and subzonal
insemination have been successful in some couples with severe male-factor
infertility who could not be helped by IVF. Pregnancies and births have
been reported, but despite use of these methods some women still do not
conceive .
Intracytoplasmic sperm injection (ICSI) is a promising assisted-fertilization
technique. It is the direct injection of spermatozoon into the ooplasm
of the oocyte. It is indicated in situations where the spermatozoal count
so low that SUZI is not possible and possibly when there is a structural
abnormality preventing gamete fusion e.g round -headed acrosomeless spermatozoa
(Lalonde et al , 1988) .
With recent advances of technology and lab tools, TEM studies show that
a spermatozoon could be injected with minimal injury to the ooplasm and
possible sperm-oocyte membrane fusion could occur in the ooplasm (Sathananthan
et al, 1989).
Lanzendorf et al, (1988) showed that human oocytes are capable of surviving
the mechanical insertion of spermatozoon directly into ooplasm. However,
mechanical damage to the oocyte may still occur, the likelihood of which
may be influenced by characteristics of the injection pipette or of the
micromanipulation technique.
In rabbits and cattle , embryos obtained by such injections have been
transferred to recipient mothers and live offspring have resulted (Iritani
, 1991) .
It needs using very fine micropipettes handling gametes very gently by
highly experienced person to avoid oocyte injury which is the major side
effects of this technique (Markert et al, 1983).
The outer and inner diameters of the holding and injection pipettes are,
respectively, 60 and 20 um and 7 and 5um. The injection pipette has a
bevel angle of 50 and a sharp spike to assist penetration through the
oolemma . An immotile sperm is aspirated tail-first into the tip of the
microinjection pipette .
Then the micropipette is pushed through the zona pellucida and into the
ooplasm. The injection pipette is withdrawn gently and the oocyte is released
from the holding pipette.
Palermo et al ,(1992) described successful intracytoplasmic injection
into 47 metaphase-II oocytes of single spermatozoa from men severely impaired
spermatozoa characteristics after IVF and SUZI had failed. 38 oocytes
remained intact after injection, 31 become fertilized, and 15 embryos
were replaced in utero .
Four pregnancies occurred after eight treatment cycles-two singleton and
one twin pregnancy, and a preclinical abortion. Two healthy boys have
been delivered from the singleton pregnancies and a healthy boy and girl
from the twin pregnancy.
ICSI bypasses many steps in the fertilization process i.e., the spermatozoon's
binding to penetration into ZP and its fusion with the oolemma. ICSI may
allow fertilization by spermatozoa with deficient kinetic properties or
anomalies of the acrosome. However, further studies are necessary to confirm
the high survival and fertilization rates obtained after ICSI.
|
|
send
to a friend
printer
friendly version
