interior (typically over the course of a few milliseconds,
although the crystal growth velocity may vary by an order of
magnitude), whereas concomitant changes in cell opacity are
minimal. Example high-speed video recordings that depict
intracellular freezing are available in the online supplementary
materials of previously published articles [12, 23]. If the video
acquisition rate is less than 1000 fps, then intracellular ice
formation will typically appear in the form of so-called
“twitching” events [27], which are more difficult to discern.
103. When searching for intracellular ice crystallization events in
high-speed video recordings, especially when the acquisition
frame rate is too slow (e.g., less than 1000 fps), it is possible to
misidentify as intracellular ice formation certain unrelated
changes in cell appearance that are not caused by ice crystals
within the cell. For example, a small change in the vertical
position of the cell relative to the camera focal plane may alter
the appearance of the cell image in a manner similar to the
changes caused by the “twitching” form of intracellular ice
formation. To avoid such misidentifications, one should keep
in mind that true intracellular ice formation events are typically stochastic (random) and relatively independent (especially in cell suspensions). Thus, if changes in cell appearance
occur at the same time as similar changes in appearance of
other cells in the field of view, it is unlikely that these events
represent intracellular freezing (which seldom occurs simultaneously in two cells)—a change of focal plane is a more
likely explanation. Likewise, if changes in the appearance of
a cell are spatially and temporally correlated with movements
in the surrounding extracellular ice field, one should consider
interactions with the external ice as an alternative explanation
for the observed cellular changes. Finally, especially in the
absence of clear view of the advancing intracellular solidification front, one may use the duration of the observed event as
a criterion to confirm whether or not the recorded phenomenon represent intracellular ice formation. In particular, for
somatic cells (with diameters in the range 5–50 μm) that are
frozen rapidly (with minimal cell dehydration), the duration
of intracellular crystallization processes typically falls in the
range 0.1–10 ms. Thus, cellular events that occur over a much
longer time scale should be critically evaluated before a decision is made to classify the observation as an intracellular ice
formation event.
104. To convert a Linksys32 data file, first go to the “File” menu
and select “Open” and then “Data File”; select the desired
data file (.iml extension) and click the “Open” button. A
“Data Chart” window showing the recorded temperature
data will be displayed; click the “Export” icon in the toolbar
266
Jens O. M. Karlsson
although the crystal growth velocity may vary by an order of
magnitude), whereas concomitant changes in cell opacity are
minimal. Example high-speed video recordings that depict
intracellular freezing are available in the online supplementary
materials of previously published articles [12, 23]. If the video
acquisition rate is less than 1000 fps, then intracellular ice
formation will typically appear in the form of so-called
“twitching” events [27], which are more difficult to discern.
103. When searching for intracellular ice crystallization events in
high-speed video recordings, especially when the acquisition
frame rate is too slow (e.g., less than 1000 fps), it is possible to
misidentify as intracellular ice formation certain unrelated
changes in cell appearance that are not caused by ice crystals
within the cell. For example, a small change in the vertical
position of the cell relative to the camera focal plane may alter
the appearance of the cell image in a manner similar to the
changes caused by the “twitching” form of intracellular ice
formation. To avoid such misidentifications, one should keep
in mind that true intracellular ice formation events are typically stochastic (random) and relatively independent (especially in cell suspensions). Thus, if changes in cell appearance
occur at the same time as similar changes in appearance of
other cells in the field of view, it is unlikely that these events
represent intracellular freezing (which seldom occurs simultaneously in two cells)—a change of focal plane is a more
likely explanation. Likewise, if changes in the appearance of
a cell are spatially and temporally correlated with movements
in the surrounding extracellular ice field, one should consider
interactions with the external ice as an alternative explanation
for the observed cellular changes. Finally, especially in the
absence of clear view of the advancing intracellular solidification front, one may use the duration of the observed event as
a criterion to confirm whether or not the recorded phenomenon represent intracellular ice formation. In particular, for
somatic cells (with diameters in the range 5–50 μm) that are
frozen rapidly (with minimal cell dehydration), the duration
of intracellular crystallization processes typically falls in the
range 0.1–10 ms. Thus, cellular events that occur over a much
longer time scale should be critically evaluated before a decision is made to classify the observation as an intracellular ice
formation event.
104. To convert a Linksys32 data file, first go to the “File” menu
and select “Open” and then “Data File”; select the desired
data file (.iml extension) and click the “Open” button. A
“Data Chart” window showing the recorded temperature
data will be displayed; click the “Export” icon in the toolbar
266
Jens O. M. Karlsson