30
R. W. Taylor and V. Sandoghdar
in refractive index or path length [26, 32], would lead to declining interest in the
method. Nevertheless, the technique would undergo a new lease of life in the late
1980s under the helm of Erich Sackmann (born 1934) who sought to implement
greater quantitative rigor, initially studying cell membrane elasticity [33] and later
the interaction of synthetic vesicle membranes to their substrates [34, 35].
Other interferometric methods would also find a revival in the 1980s, following the
realization that analogue controls for camera gain and offset could be used to increase
the dynamic range and contrast of microscopic images. This contrast enhancement
facilitated real-time observations of structures that were previously too faint to see
by the naked eye. Indeed, weak contrast variations composing an image are more
easily detected by the video camera owing to its linear response to light intensity.
While this fact was known since the invention of the video camera in the 1940s, the
better resolution and historical success of photography cemented the latter as the
dogma in microscopic documentation. It would not be until 1975 for this view to
change [36], and another 6 years before the first implementations of this analogue
contrast enhancement [37, 38].
The improvement in analogue contrast immediately precipitated a new problem
of how to remove unwanted background signals such as speckle originating from
uneven illumination or the presence of dust, etc. By digitizing the analogue video
signal, these problems could be readily tackled because the live video signal could
undergo in-line digital processing including static image subtraction, averaging and
differential subtraction [39, 40]. This technique was referred to as digital contrast
enhancement, and along with its analogue cousin, would collectively become known
as video-enhanced microscopy [41, 42] and often paired with DIC imaging. Following its introduction in the early 1980s, video-enhanced microscopy quickly led to
a flurry of efforts to explore previously hidden aspects of cellular architecture and
function, including the network structure of cellular microtubules and actin filaments,
or transport of particles and vesicles in and around the cell [43–47].
Following these demonstrations, the video-enhanced microscopy of the late 1980s
and early 1990 quickly advanced efforts to monitor intracellular dynamics of specific proteins in living cells through introduction of sub-hundred nanometer colloidal
particles. Michael Sheetz and colleagues pioneered this microscopy under the
moniker Nanovid-microscopy (nanometer video-enhanced microscopy) and investigated in vitro mobility assays on microtubules, receptor-mediated endocytosis and
single-protein diffusion in the plasma membrane of cells [48–53]—a body of work
that serves as the foundation for single-particle tracking microscopy. In the latter half
of the 1990s to early 2000s, Akihiro Kusumi and colleagues would use this technique to advance the study of single-protein diffusion in the plasma membrane of
cells [54, 55].
It is worth noting that the challenge of detecting and analyzing micro- and submicroscopic particulates were also confronted in the field of aerosol science, dating
from the period of the 1970s. Whilst employing intensity-based detection, in 1982
Pettit and Peterson [56] introduced an interferometric scheme derived from the Jamin
interferometer to detect the phase shift induced by microscopic particles upon the
incident illuminating beam. By using phase a better estimate of the particle size was
R. W. Taylor and V. Sandoghdar
in refractive index or path length [26, 32], would lead to declining interest in the
method. Nevertheless, the technique would undergo a new lease of life in the late
1980s under the helm of Erich Sackmann (born 1934) who sought to implement
greater quantitative rigor, initially studying cell membrane elasticity [33] and later
the interaction of synthetic vesicle membranes to their substrates [34, 35].
Other interferometric methods would also find a revival in the 1980s, following the
realization that analogue controls for camera gain and offset could be used to increase
the dynamic range and contrast of microscopic images. This contrast enhancement
facilitated real-time observations of structures that were previously too faint to see
by the naked eye. Indeed, weak contrast variations composing an image are more
easily detected by the video camera owing to its linear response to light intensity.
While this fact was known since the invention of the video camera in the 1940s, the
better resolution and historical success of photography cemented the latter as the
dogma in microscopic documentation. It would not be until 1975 for this view to
change [36], and another 6 years before the first implementations of this analogue
contrast enhancement [37, 38].
The improvement in analogue contrast immediately precipitated a new problem
of how to remove unwanted background signals such as speckle originating from
uneven illumination or the presence of dust, etc. By digitizing the analogue video
signal, these problems could be readily tackled because the live video signal could
undergo in-line digital processing including static image subtraction, averaging and
differential subtraction [39, 40]. This technique was referred to as digital contrast
enhancement, and along with its analogue cousin, would collectively become known
as video-enhanced microscopy [41, 42] and often paired with DIC imaging. Following its introduction in the early 1980s, video-enhanced microscopy quickly led to
a flurry of efforts to explore previously hidden aspects of cellular architecture and
function, including the network structure of cellular microtubules and actin filaments,
or transport of particles and vesicles in and around the cell [43–47].
Following these demonstrations, the video-enhanced microscopy of the late 1980s
and early 1990 quickly advanced efforts to monitor intracellular dynamics of specific proteins in living cells through introduction of sub-hundred nanometer colloidal
particles. Michael Sheetz and colleagues pioneered this microscopy under the
moniker Nanovid-microscopy (nanometer video-enhanced microscopy) and investigated in vitro mobility assays on microtubules, receptor-mediated endocytosis and
single-protein diffusion in the plasma membrane of cells [48–53]—a body of work
that serves as the foundation for single-particle tracking microscopy. In the latter half
of the 1990s to early 2000s, Akihiro Kusumi and colleagues would use this technique to advance the study of single-protein diffusion in the plasma membrane of
cells [54, 55].
It is worth noting that the challenge of detecting and analyzing micro- and submicroscopic particulates were also confronted in the field of aerosol science, dating
from the period of the 1970s. Whilst employing intensity-based detection, in 1982
Pettit and Peterson [56] introduced an interferometric scheme derived from the Jamin
interferometer to detect the phase shift induced by microscopic particles upon the
incident illuminating beam. By using phase a better estimate of the particle size was