The spatial variation of the refractive index in biological cells

Beuthan, J.; Minet, Olaf; Helfmann, Jürgen; Herrig, M; Müller, G.

doi:10.1088/0031-9155/41/3/002

Cited by 282 publications

(218 citation statements)

References 13 publications

(15 reference statements)

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“…(2) Perturbations were added randomly up to 5% of the cell's width 15 in order to simulate the uneven boundaries and undulations of the cells. (3) We also added random perturbations to the cell's refractive indices and its extracellular vicinity 26 , on a scale of 1 mm and 5-15% of the local refractive index difference between the cell and its surrounding (see Methods). The results of the simulations are robust ( Supplementary Fig.…”

Section: Resultsmentioning

confidence: 99%

“…This may result from small density fluctuations in the cells, within the path of light. These short-scale fluctuations 26 generate Rayleigh scattering of the far blue wavelengths, which cannot be simulated in the framework of beam propagation methods (BPM). It should be noted that guinea pig retina contains rods with visual pigment absorbing maximally at 500 nm and two types of cones; a shortwavelength cone (S-cone) with maximal absorption at 400 nm and a medium-wavelength cone (M-cone) with peak absorption at 530 nm (ref.…”

Section: Resultsmentioning

confidence: 99%

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Müller cells separate between wavelengths to improve day vision with minimal effect upon night vision

et al. 2014

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Vision starts with the absorption of light by the retinal photoreceptors-cones and rods. However, due to the 'inverted' structure of the retina, the incident light must propagate through reflecting and scattering cellular layers before reaching the photoreceptors. It has been recently suggested that Müller cells function as optical fibres in the retina, transferring light illuminating the retinal surface onto the cone photoreceptors. Here we show that Müller cells are wavelength-dependent wave-guides, concentrating the green-red part of the visible spectrum onto cones and allowing the blue-purple part to leak onto nearby rods. This phenomenon is observed in the isolated retina and explained by a computational model, for the guinea pig and the human parafoveal retina. Therefore, light propagation by Müller cells through the retina can be considered as an integral part of the first step in the visual process, increasing photon absorption by cones while minimally affecting rod-mediated vision.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Müller cells separate between wavelengths to improve day vision with minimal effect upon night vision

et al. 2014

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“…2. Choosing the optical index close to that in typical cells [4] as n=1.4, the averaged velocity of ultrasound in vacuole is obtained from (1) as 1.60 ± 0.10 µm/ns. Note that the sound velocity in water at this temperature of 22°C is equal to 1.49 µm/ns [5] which is different from the experimental value in vacuole.…”

Section: Results In Depth Resolution and Sensitivity To Adhesionmentioning

confidence: 99%

In Vitro picosecond ultrasonics in a single cell

Rossignol¹,

Chigarev²,

Ducousso³

et al. 2008

Applied Physics Letters

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The picosecond ultrasonic technique is applied for the non-invasive evaluation of sound velocity at a submicron scale in living onion cells. Velocity and attenuation of hypersound in cells are measured by a femtosecond laser pump-probe technique. A nanometric co-polymer layer deposited between the cell and the substrate has been used to improve the photoacoustic signal. Comparison of the measured signals with the photoacoustic responses calculated according to thermoelastic generation mechanism and reflectometric detection shows high sensitivity to the cell adhesion on substrate. Measurements achieved in different vegetal cells illustrate the sensitivity of the technique. In addition to single cell imaging with the high lateral resolution provided by optics (ie ≈1µm), the sensitivity of the measurements to cell compressibility suggests promising perspectives in the field of biology

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“…The full resolution of high-NA oil-immersion objectives cannot be achieved with cells attached to the other side of a cover glass. The index of refraction of cytoplasm ranges from 1.358 to 1.374 (14), and that of lipid is $1.48 (16). While greater than water, these indices are below the 1.515 index of refraction of the cover glass and the matching immersion oil.…”

Section: Discussionmentioning

confidence: 99%

Digital differential interference contrast autofocus for high‐resolution oil‐immersion microscopy

et al. 2008

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Continued advances in cellular fluorescent biosensors enable studying intracellular protein dynamics in individual, living cells. Autofocus is valuable in such studies to compensate for temperature drift, uneven substrate over multiple fields of view, and cell growth during long-term high-resolution time-lapse studies of hours to days. Observing cellular dynamics with the highest possible resolution and sensitivity motivates the use of high numerical aperture (NA) oil-immersion objectives, and control of fluorescence exposure to minimize phototoxicity. To limit phototoxicity, to maximize light throughput of the objective for biosensor studies, and because phase contrast is distorted by the meniscus in microtiter plates, we studied autofocus in differential interference contrast (DIC) microscopy with a 603 1.45 NA oil objective after removing the analyzer from the fluorescent light path. Based on a study of the experimental DIC modulation transfer function, we designed a new bandpass digital filter for measuring image sharpness. Repeated tests of DIC autofocus with this digital filter on 225 fieldsof-view resulted in a precision of 8.6 nm (standard deviation). Autofocus trials on specimens with thicknesses from 9.47 to 33.20 lm, controlled by cell plating density, showed that autofocus precision was independent of specimen thickness. The results demonstrated that the selected spatial frequencies enabled very high-precision autofocus for high NA DIC automated microscopy, thereby potentially removing the problems of meniscus distortion in phase contrast imaging of microtiter plates and rendering the toxicity of additional fluorescence exposure unnecessary. ' International Society for Advancement of CytometryKey terms autofocus; image cytometry; lab automation; differential interference contrast; modulation transfer function IMAGE cytometry enables multidimensional measurements on cell populations during studies in chemical genomics and intervention by drugs, RNAis, and cDNAs. Obtaining an in-depth understanding of the heterogeneous responses across cell populations in these studies has motivated high-resolution time-lapse measurements of subcellular dynamics in living cells (1). Heterogeneity even in clonal cell culture populations motivates scanning multiple fields of view (FOVs), while heterogeneity is even greater in other populations, e.g., differentiating embryonic stem cell colonies. High-resolution, time-lapse image acquisition on multiple FOVs requires high-precision autofocus (small depths of field) with immersion objectives.The challenge of designing high-performance autofocus increases as the depth of field shrinks proportionally with numerical aperture (NA 2 ). The smaller depths of field make it increasingly difficult to maintain focus during time-lapse image acquisition as objective NA is increased. The challenge is compounded in extended timelapse studies, where cell growth, ambient temperature fluctuations, and other microscope instabilities have in some cases necessitated manual focu...

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The spatial variation of the refractive index in biological cells

Cited by 282 publications

References 13 publications

Müller cells separate between wavelengths to improve day vision with minimal effect upon night vision

Müller cells separate between wavelengths to improve day vision with minimal effect upon night vision

In Vitro picosecond ultrasonics in a single cell

Digital differential interference contrast autofocus for high‐resolution oil‐immersion microscopy

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