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Fig. 5.4 A mammalian
centrosome is composed of
two centrioles surrounded by
a meshwork of a proteins
embedded in matrix called
the pericentriolar material
(PCM). Gamma-tubulin and
the gamma-tubulin ring
complex that nucleate
microtubules along with
associated proteins are
embedded in the PCM.
Highlighted in this diagram
are two centrosomal
complexes, the microtubule
nucleating complex and the
microtubule anchoring
complex (Schatten 2008 )
cleavage-stage embryos were examined by routine TEM. Centrosomes were also
examined in several mature and immature oocytes during IVF, and 25 sperm
samples (fertile and infertile) to characterize maternal and paternal centrosomes.
Early cleavage-stage embryos were examined by serial sectioning up to the
hatching blastocyst stage. Our investigation also extended to oogonia in fetal
ovaries, testis and testicular biopsies, and embryonic stem cells. TEM is the best
method currently available to reveal the structure of centrioles within centrosomes.
Most other studies use confocal fluorescent microscopy (FM) to reveal chromo-
somes and microtubules (MTs) by immunocytochemistry (Schatten 1994 ; Simerly
et al. 1995 ) or labeling of centrosomes with specific antibodies for proteins-like
alpha tubulin and centrin associated with centrioles. These images elegantly
demonstrate whole asters, spindles, and chromosomes, while TEM demonstrates
the fine structure of the centrosome in serial sections. These two techniques are
complimentary in the visualization of nearly all components of meiotic and mitotic
figures in oocytes and early embryos. Locating centrosomes in oocytes and
embryonic cells is both laborious and time-consuming in serial sections. They are
usually found close to the nucleus during interphase and located at spindle poles in
mitosis. It is, however, easier to locate the sperm centriole which is found below
the basal plate in the neck of the sperm cell (Fig. 5.6 ). An optimal method to
analyse sperm centrioles is by cutting a pellet of sperm which allows visualization
of centrioles in all planes of sectioning. Our atlas (Sathananthan 1996 ) and website
www.sathembryoart.com show some of these images.
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