Biomedical Engineering Reference
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FIgurE 14.7 SHG/THG time series of the mitosis process in the 1-k-cell-stage zebrafish embryo. During (a) the
prophase stage, (b) the metaphase, (c) the anaphase, and (d) the telophase, the cell nuclear membrane (arrowhead),
centrosomes (arrows in (a)), and mitotic spindles (arrow in (b)) can be visualized through THG and SHG, respec-
tively. Scale bar: 10 μm. SHG images corresponding to (a)-(d) are shown in (a-S)-(d-S), respectively.
14.3.2.2 nervous System Development
Without any fluorescence markers, nonstop long-term observation of the brain development in the
same live zebrafish embryo for more than 20 h has been accomplished by using SHG/THG microscopy
(Chen et  al. 2006). Through SHG modality, the dynamics of the cell mitosis, neuron differentiation,
and the nerve fibers in the brain can be recorded. On the other hand, structure-sensitive THG modal-
ity can help to pick up the morphogenetic changes of the brain from neural plate to neural keel, neural
rod, and then neural tube (Figure 14.8). At the right beginning of the brain development, bud stage,
there is only a cluster of cells, which are still under differentiation and division, forming a plate-like
structure named neural plate but no neural fibers in the neural plate. Through strong SHG signals from
spindles, the cells under mitosis for differentiation or division can be clearly recognized, while THG
images can help to localize the position of those cells (Figure 14.8a). After about 1 h, the embryo was
FIgurE 14.8 Continuous 20 h in vivo HGM imaging of the brain development in the same zebrafish embryo
from the bud stage to the prim-15 stage. The structural changes of brain from (a) neural plate (NP) at the bud stage;
(b) neural keel (NK) at the three-somite stage; (c) NK at the five-somite stage; (d) neural tube (NT) at the 14-somite
stage; (e) midbrain at the 22-somite stage; to (f) NT and eye at the prim-15 stage can be revealed by THG micros-
copy. The nerve fibers (arrows) in both the NT and the retina (R) can be revealed by SHG. SHG images correspond-
ing to (a)-(f) are shown in (a-S)-(f-S), respectively. Scale bar: 50 μm.
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