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Fig. 1. Synchronous oscillations of NADH and FAD++ autofluorescence at
fertilisation. (A) Ca2+ fluxes and oxidative phosphorylation in the
mitochondria. The supply of substrate (such as pyruvate) to the Kreb’s
cycle promotes the reduction of NAD+ to NADH and of
FAD++ to FADH2. NADH is then oxidised by complex I in
the respiratory chain, whereas FADH2 is oxidised at complex II. The
electrons are then transferred to complexes III and IV to reduce O2
to H2O. In the process, protons are translocated across the inner
mitochondrial membrane, generating a potential gradient of approximately
–150 mV (
). ATP synthesis takes place at complex V or F0/F1
synthase, the inward flux of protons through the synthase provides the energy
necessary to phosphorylate ADP. ATP is then transported out of the
mitochondria by the adenine nucleotide translocase (ANT). Ca2+
enters the mitochondria through the Ca2+ uniporter, while it is
extruded via the action of a Na+/Ca2+ exchanger. The
actions of CN- and FCCP are also indicated. (B) Variations in NADH
(blue trace) and FAD++ (green trace) observed at fertilisation of a
mouse egg (n=6). Time 0 corresponds to the time of insemination. F
indicates the time of fertilisation. (C) Changes in NADH (blue trace) and
FAD++ (green trace) autofluorescence measured inside the ROI shown
in (i), upon perfusion of 2 mM CN– (provoking full reduction
of NADH and FAD++) and of 1 µM FCCP (provoking full oxidation of
NADH and FAD++). (i-iv) Images of FAD++ autofluorescence
of a mouse egg at times indicated on the graph.
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