An Introduction
Cryobanking (i.e. the preservation of biological materials
at very low temperatures for use in reproductive technology [YD, 2012]), was
first introduced for use in the livestock industry as early as 1949 in France.
Technological advances continued to develop throughout the 1950s and 60s. The
first commercial human semen cryobank was established in the 1970s in the
United States (CBS, 2012). Cryopreservation for non-domestic animal species is
still considered to be emerging due to the fact that they are not widely
practiced; there is limited knowledge of the reproductive biology of many
species, and few have been tested (Pukazhenthi, et. al., 2006).
Preserving tissue requires blocking intracellular functions,
while maintaining the physiochemical structure of the cell (CBS, 2012).
Decreasing temperature slows down cellular activity and eventually stops it
entirely (CBS, 2012). All types of life forms have various sensitivity and
resistance to cold. Freezing biological material can be very arduous. Sudden
cooling can damage cells due to ice crystallization both inside and outside of
the cell membrane; causing changes in the overall physical environment of the
cell (CBS, 2012). In addition, dehydration can occur due to increased salt
levels that rise when water freezes (CBS, 2012). Another impediment that can
occur by lowering temperatures too quickly is thermal shock. Thermal shock can
occur even with the absence of crystals [i.e. at +15°C] (CBS, 2012). These
effects can be alleviated through the use of cryoprotective agents, slower
cooling methods and preconditioning the cells in a high salt medium (CBS,
2012). All cells have a dehydration threshold and cannot tolerate losing their
baseline water content (CBS, 2012).
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References:
CBS (Cryo Bio
Systems), 2012. Online. Available at:
http://www.cryobiosystem-imv.com/Portals/3/PDF/Monograph.pdf
Pukazhenthi,
B., Cinuzzoli, P., Travis, A., and Wildt, D., 2006. Applications of emerging
technologies to the study of conservation of threatened and endangered species.
Reproduction, Fertility and Development. V. 18. Pp.77-90. Online. Available
from Science Direct.
YD (Your Dictionary), 2012. Online. Available
at: http://medical.yourdictionary.com/cryobank