Biomedical Engineering Reference
In-Depth Information
can be approximated by 1.8
2
2.1
3
10
2
3
m
3
/kg, when considering a mixture of
all the components of a typical cell
[4]
. A direct application of this relationship is to study
the DM production rate and the dry mass surface density (DMSD) in the cell cycle. This
interpretation had been first proposed by Barer in 1950s, but due to the difficulty of
manipulating an interferometric set-up it did not show any biological applications until
recently when many groups using QPM techniques started to exploit this phase
content.
α
DM
relationship
[19,39,131
134]
. Some other applications in the quantitative monitoring of the
cell division will be discussed in Chapter 5.
Cells need to double their content during each cell cycle to stay a constant size. Hence, a
good indicator of the biomass is the DM (nonaqueous material), defined as the weight of
the cell when water has evaporated and which mainly depends on protein concentration.
Consequently, monitoring the DM production provides a dynamic indicator of the real-time
evolution of the cell cycle in a noninvasive manner, thus providing a label-free tool to
screen for quantitative analysis of the cell.
Most cells reproduce by duplicating their content and then dividing to produce daughters of
equal size. The ability to genetically manipulate yeast cells, coupled with their rapid growth
rate, has made them an attractive model to study cell growth and division. In a recent study,
Rappaz et al.
[39]
illustrated this application by comparing the evolution of DM
concentration during a complete cell cycle in wild-type and mutant fission yeast cells. Cells
of the fission yeast
Schizosaccharomyces pombe
may be modeled as cylinders capped by
hemispherical ends; they grow mainly by tip-elongation and divide by formation of a
medially placed septum, which is cleaved to produce two daughter cells. In this study, we
showed a marked difference between the DM production during the cell cycle of wild-type
yeasts compared to a
cdc16-116
mutant. Cdc16p is required to limit the cell to a single
septum per cell cycle; if it is inactivated, the cell synthesizes multiple additional septa,
producing anucleate cell compartments
[135]
(
Figure 5.2
).
In this study, we observed that the DM production rates of the mutant and wild-type cells are
significantly different. The wild-type DMSD shows a specific pattern resulting from the
cytokinesis process, which is absent in the mutant. DM accumulation can be combined to other
parameters easily measured by DHM, including cell volume and refractive index, to provide a
better understanding of the cell cycle for DHM techniques can thus be further used for
high-throughput, label-free screening, allowing a rapid quantitative characterization of the cell
cycle, and the effects of specific pharmacological agents likely to affect cell cycle progression.
5.3.3 Biophysical Parameters in Hematology
In addition to the DM, the phase signal can be interpreted in many other ways, allowing to
calculate clinically important RBC parameters including mean corpuscular volume (MCV),
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