High resolution imaging of ultrafine bubbles in water by Atmospheric SEM-CL

Various analytical methods such as high-resolution observation of ultrafine bubbles in water are required to clarify the mechanisms and interrelationships of various effects brought about by ultrafine bubbles. In this study, we used atmospheric scanning electron microscopy-cathodoluminescence (ASEM-CL) method for observing ultrafine bubbles in water. ASEM can observe samples in water, and the fine electron beam provides high spatial resolution. Furthermore, the gas in the bubble can be estimated from the CL emission spectrum. We have measured characteristics such as bubble size and particle number density. Also, the CL spectra has shown that the ultrafine bubbles contained nitrogen.

A Case of Intraocular Lymphoma Diagnosed by Subretinal Fluid Biopsy

Although intraocular lymphoma (IOL) mainly has have vitreous opacity and subretinal infiltration, its clinical symptoms are diverse. We report a case of IOL that mainly showed exudative retinal detachment in which analysis of IgH gene rearrangement (AIGHR) of the collected subretinal fluid sample was useful for diagnosis. A 77-year-old woman developed decreased left visual acuity for 1 month. She had been treated for dermatomyositis, diabetes mellitus, and right parotid tumor for 3 years. Visual acuity was 0.1 OD and counting fingers OS. Slit-lamp examination showed grade 4 (Emery-Little classification) nuclear cataract in both eyes and keratoprecipitates and tan vitreous opacity in the left eye. Fundoscopy details were unclear except for a vaguely observable optic nerve head due to yellow-brown vitreous opacity, which we judged as an old vitreous hemorrhage. Phacovitrectomy was performed and almost total retinal detachment was found, except for a part of the superior periphery. Since no retinal break was found and a wide range of thin membrane-like tissue was found on the surface of the retina, the surgeon suspected primary IOL and performed unplanned biopsy. The peripheral vitreous was collected as a sample, and then the subretinal fluid was collected through an intentional break to prevent mixing with other fluids. The subretinal strand was gently removed and collected. Cytology showed class III, the IL10/IL6 ratio was low, and AIGHR was positive. Postoperatively, fundus autofluorescence showed no abnormality, no leakage was observed on fluorescein and indocyanine green angiography, and the location of typical infiltration lesions under the retina was unclear. There were no positive findings on systemic examinations and a diagnosis of primary IOL was made. The main symptoms of this case were vitreous opacity and exudative retinal detachment, and AIGHR using subretinal fluid was useful for diagnosis.

High Spatial Resolution Ion Imaging by Focused Electron-Beam Excitation with Nanometric Thin Sensor Substrate

We developed a high spatially-resolved ion-imaging system using focused electron beam excitation. In this system, we designed a nanometric thin sensor substrate to improve spatial resolution. The principle of pH measurement is similar to that of a light-addressable potentiometric sensor (LAPS), however, here the focused electron beam is used as an excitation carrier instead of light. A Nernstian-like pH response with a pH sensitivity of 53.83 mV/pH and linearity of 96.15% was obtained. The spatial resolution of the imaging system was evaluated by applying a photoresist to the sensing surface of the ion-sensor substrate. A spatial resolution of 216 nm was obtained. We achieved a substantially higher spatial resolution than that reported in the LAPS systems.

Quantitative assessment of macular function after surgery for optic disc pit maculopathy: A case report

RATIONALE

We describe a case of optic disc pit maculopathy (ODP-M) in which vitrectomy with juxtapapillary laser (JPL) treatment led to the reattachment of retinoschisis (RS) as well as serous retinal detachment (SRD).

PATIENT CONCERNS

An 80-year-old man complained of distorted vision and decreased visual acuity (VA) in his left eye for 12 months.

DIAGNOSIS

We conducted quantitative functional evaluation on the area of RS and SRD using the Humphrey visual field analyzer. Fundus examination and optical coherence tomography showed SRD and RS in connection with the optic disc. The best-corrected logarithm of the minimum angle of resolution (logMAR) VA was 0.7.

INTERVENTIONS

The patient underwent JPL treatment combined with pars plana vitrectomy. During surgery, posterior vitreous detachment and tamponade were created with sulfur hexafluoride.

OUTCOMES

After surgery, SRD (and subsequently RS) gradually reduced and had completely disappeared at 31 months. VA gradually improved and was 0.0 (logMAR) at 28 months. The analysis of the mean macular thickness of the central 3-mm diameter showed that the macula thickness recovered to 300 μm at 17 months postoperatively. Retinal sensitivity began to improve at 24 months postoperatively and had increased at 48 months postoperatively.

LESSONS

In conclusion, vitrectomy with JPL treatment for ODP-M had a favorable anatomical outcome as well as a long-term functional outcome. These findings provide useful information for clinicians who are planning a therapeutic strategy, including the choice of surgical procedure for ODP-M.

Depth structure analysis by surface scanning in near-field microscopes

High-resolution imaging of the surfaces of samples can be performed using near-field optical microscopes by scanning a small light spot; however, structures located deep beneath cannot be observed because the light spot spreads in three directions. In this study, we propose an observation technique for near-field optical microscopes that can obtain depth information within the resolution of the diffraction limit of light by analyzing interference patterns formed with divergent incident light and scattered light from a sample. We analyze depth structures by evaluating correlation coefficients between observed interference patterns and calculated reference patterns. Our technique can observe both high-resolution surface images and the diffraction-limited three-dimensional structure by scanning a near-field light source on a single plane.

Enhanced Surface Plasmon Resonance Wavelength Shifts by Molecular Electronic Absorption in Far- and Deep-Ultraviolet Regions

In this study, surface plasmon resonance (SPR) wavelength shifts due to molecular electronic absorptions in the far-ultraviolet (FUV, < 200 nm) and deep-ultraviolet (DUV, < 300 nm) regions were investigated by attenuated total reflectance (ATR) spectroscopy. Due to the strong absorption in the DUV region, N,N-dimethylformamide (DMF) significantly increased the SPR wavelength shift of Al film. On the other hand, no such shift enhancement was observed in the visible region for Au film because DMF does not have absorbance compared to non-absorbing materials such as water and alcohols. The enhanced SPR wavelength shift, caused by the overlap between SPR and molecular resonance wavelengths in FUV-DUV region, is expected to result in high sensitivity for resonant materials.

Ultrashort laser based two-photon phase-resolved fluorescence lifetime measurement method

This paper presents a two-photon phase-resolved fluorescence-lifetime measurement method based on the use of an ultrashort pulse laser. The proposed method also involves the use of a lock-in amplifier to control the phase difference between the reference and fluorescence signals, thereby facilitating the use of an alternative method for determining fluorescence lifetimes. Verification of the fluorescence lifetimes as measured in this study was performed using rhodamine B and a cellular thermoprobe as samples. In this study, we assume that the fluorescence decay was monoexponential in all cases. Rhodamine B was observed to exhibit an average fluorescence lifetime of 2.15 ns, whereas a temperature sensitivity of 1.39 ns C^-1 over a temperature range of 33.79-37.2 °C was demonstrated for the cellular thermoprobe. These results validate the feasibility of the proposed method for accurate measurement of fluorescence lifetimes using a simple laser configuration.

Visualization of ultraviolet absorption distribution beyond the diffraction limit of light by electron-beam excitation-assisted optical microscope

We demonstrated that the high spatial resolution absorption contrast imaging of the crystal of vitamin B9 has absorption at ultraviolet wavelengths. The absorption wavelength matches with the wavelength of the emission of the fluorescent thin film of an electron-beam excitation-assisted (EXA) optical microscope. The fine crystal structure was imaged beyond the optical diffraction limit. The image contrast corresponded with the thickness of the crystal. The illumination light is absorbed with the vitamin B9 crystal and the intensity of the transmitted light depends on the thickness of the vitamin B9 crystal. The EXA optical microscope is useful for analysis of growth of a crystal, bioimaging and so on.

Spatial resolution and cathodoluminescence intensity dependence on acceleration voltage in electron beam excitation assisted optical microscopy using Y2O3:Eu3+ film

This study presents relationship between acceleration voltage and spatial resolution of electron-beam assisted (EXA) optical microscope. The nanometric illumination light sources of the present EXA microscope was red-emitting cathodoluminescence (CL) in the Y₂O₃:Eu³⁺ thin film excited by focused electron beam. Our experimental results demonstrated that the spatial resolutions of the EXA microscope were higher as the acceleration voltage was higher. We managed to make images of the scattered gold particles with approximately 90 nm-resolutions at the voltages higher than 20 kV. The dependence of the spatial resolution on the acceleration voltage was explained by the distribution of simulated electron scattering trajectories in the luminescent thin film.

Cell structure imaging with bright and homogeneous nanometric light source

Label-free optical nano-imaging of dendritic structures and intracellular granules in biological cells is demonstrated using a bright and homogeneous nanometric light source. The optical nanometric light source is excited using a focused electron beam. A zinc oxide (ZnO) luminescent thin film was fabricated by atomic layer deposition (ALD) to produce the nanoscale light source. The ZnO film formed by ALD emitted the bright, homogeneous light, unlike that deposited by another method. The dendritic structures of label-free macrophage receptor with collagenous structure-expressing CHO cells were clearly visualized below the diffraction limit. The inner fiber structure was observed with 120 nm spatial resolution. Because the bright homogeneous emission from the ZnO film suppresses the background noise, the signal-to-noise ratio (SNR) for the imaging results was greater than 10. The ALD method helps achieve an electron beam excitation assisted microscope with high spatial resolution and high SNR.

Direct optical measurements of far- and deep-ultraviolet surface plasmon resonance with different refractive indices

The surface plasmon resonance (SPR) of Al thin films was investigated by varying the refractive index of the environment near the films in the far-ultraviolet (FUV, 120-200 nm) and deep-ultraviolet (DUV, 200-300 nm) regions. An original FUV-DUV spectrometer that adopts an attenuated total reflectance (ATR) system was used. The measurable wavelength range was down to the 180 nm, and the environment near the Al surface could be controlled. The resultant spectra enabled the dispersion relationship of Al-SPR in the FUV and DUV regions to be obtained. In the presence of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) on the Al film, the angle and wavelength of the SPR became larger and longer, respectively, compared to those in air. These shifts correspond well with the results of simulations performed using Fresnel equations.

Label-free cellular structure imaging with 82 nm lateral resolution using an electron-beam excitation-assisted optical microscope

We present label-free and high spatial-resolution imaging for specific cellular structures using an electron-beam excitation-assisted optical microscope (EXA microscope). Images of the actin filament and mitochondria of stained HeLa cells, obtained by fluorescence and EXA microscopy, were compared to identify cellular structures. Based on these results, we demonstrated the feasibility of identifying label-free cellular structures at a spatial resolution of 82 nm. Using numerical analysis, we calculated the imaging depth region and determined the spot size of a cathodoluminescent (CL) light source to be 83 nm at the membrane surface.

Expression of Two Classes of Pax6 Transcripts in Reprogramming Retinal Pigment Epithelium Cells of the Adult Newt

The adult newt has the remarkable ability to regenerate a functional retina from retinal pigment epithelium (RPE) cells, even when the neural retina (NR) is completely lost from the eye. In this system, RPE cells are reprogrammed into a unique state of multipotent cells, named RPESCs, in an early phase of retinal regeneration. However, the signals that trigger reprogramming remain unknown. Here, to approach this issue we focused on Pax6, a transcription factor known to be expressed in RPESCs. We first identified four classes (v1, v2, v3 and v4) of Pax6 variants in the eye of adult newt, Cynops pyrrhogaster. These variants were expressed in most tissues of the intact eye in different combinations but not in the RPE, choroid or sclera. On the basis of this information, we investigated the expression of Pax6 in RPE cells after the NR was removed from the eye by surgery (retinectomy), and found that two classes (v1 and v2) of Pax6 variants were newly expressed in RPE cells 10 days after retinectomy, both in vivo and in vitro (RLEC system). In the RLEC system, we found that Pax6 expression is mediated through a pathway separate from the MEK-ERK pathway, which is required for cell cycle re-entry of RPE cells. These results predict the existence of a pathway that may be of fundamental importance to a better understanding of the reprogramming of RPE cells in vivo.

Multi-modal imaging of HeLa cells using a luminescent ZnS:Mn/NaGdF4:Yb:Er nanocomposite with enhanced upconversion red emission

ZnS:Mn/NaGdF₄:Yb:Er nanocomposite was synthesized using a single-step hot injection method and then applied in the downconversion and upconversion optical imaging of living HeLa cells.

Intensity distribution analysis of cathodoluminescence using the energy loss distribution of electrons

We present an intensity distribution analysis of cathodoluminescence (CL) excited with a focused electron beam in a luminescent thin film. The energy loss distribution is applied to the developed analysis method in order to determine the arrangement of the dipole locations along the path of the electron traveling in the film. Propagating light emitted from each dipole is analyzed with the finite-difference time-domain (FDTD) method. CL distribution near the film surface is evaluated as a nanometric light source. It is found that a light source with 30 nm widths is generated in the film by the focused electron beam. We also discuss the accuracy of the developed analysis method by comparison with experimental results. The analysis results are brought into good agreement with the experimental results by introducing the energy loss distribution.

Cell culture on hydrophilicity-controlled silicon nitride surfaces

Cell culture on silicon nitride membranes is required for atmospheric scanning electron microscopy, electron beam excitation assisted optical microscopy, and various biological sensors. Cell adhesion to silicon nitride membranes is typically weak, and cell proliferation is limited. We increased the adhesion force and proliferation of cultured HeLa cells by controlling the surface hydrophilicity of silicon nitride membranes. We covalently coupled carboxyl groups on silicon nitride membranes, and measured the contact angles of water droplets on the surfaces to evaluate the hydrophilicity. We cultured HeLa cells on the coated membranes and evaluated stretch of the cell. Cell migration and confluence were observed on the coated silicon nitride films. We also demonstrated preliminary observation result with direct electron beam excitation-assisted optical microscope.

Carboxylic monolayer formation for observation of intracellular structures in HeLa cells with direct electron beam excitation-assisted fluorescence microscopy

Intracellular structures of HeLa cells are observed using a direct electron beam excitation-assisted fluorescence (D-EXA) microscope. In this microscope, a silicon nitride membrane is used as a culture plate, which typically has a low biocompatibility between the sample and the silicon nitride surface to prevent the HeLa cells from adhering strongly to the surface. In this work, the surface of silicon nitride is modified to allow strong cell attachment, which enables high-resolution observation of intracellular structures and an increased signal-to-noise ratio. In addition, the penetration depth of the electron beam is evaluated using Monte Carlo simulations. We can conclude from the results of the observations and simulations that the surface modification technique is promising for the observation of intracellular structures using the D-EXA microscope.

Fabrication of bright and thin Zn₂SiO₄ luminescent film for electron beam excitation-assisted optical microscope

We fabricated a bright and thin Zn₂SiO₄ luminescent film to serve as a nanometric light source for high-spatial-resolution optical microscopy based on electron beam excitation. The Zn₂SiO₄ luminescent thin film was fabricated by annealing a ZnO film on a Si₃N₄ substrate at 1000 °C in N₂. The annealed film emitted bright cathodoluminescence compared with the as-deposited film. The film is promising for nano-imaging with electron beam excitation-assisted optical microscopy. We evaluated the spatial resolution of a microscope developed using this Zn₂SiO₄ luminescent thin film. This is the first report of the investigation and application of ZnO/Si₃N₄ annealed at a high temperature (1000 °C). The fabricated Zn₂SiO₄ film is expected to enable high-frame-rate dynamic observation with ultra-high resolution using our electron beam excitation-assisted optical microscopy.

High-resolution, label-free imaging of living cells with direct electron-beam-excitation-assisted optical microscopy

High spatial resolution microscope is desired for deep understanding of cellular functions, in order to develop medical technologies. We demonstrate high-resolution imaging of un-labelled organelles in living cells, in which live cells on a 50 nm thick silicon nitride membrane are imaged by autofluorescence excited with a focused electron beam through the membrane. Electron beam excitation enables ultrahigh spatial resolution imaging of organelles, such as mitochondria, nuclei, and various granules. Since the autofluorescence spectra represent molecular species, this microscopy allows fast and detailed investigations of cellular status in living cells.

High resolution fluorescent bio-imaging with electron beam excitation

We have developed electron beam excitation assisted (EXA) optical microscope[1-3], and demonstrated its resolution higher than 50 nm. In the microscope, a light source in a few nanometers size is excited by focused electron beam in a luminescent film. The microscope makes it possible to observe dynamic behavior of living biological specimens in various surroundings, such as air or liquids. Scan speed of the nanometric light source is faster than that in conventional near-field scanning optical microscopes. The microscope enables to observe optical constants such as absorption, refractive index, polarization, and their dynamic behavior on a nanometric scale. The microscope opens new microscopy applications in nano-technology and nano-science.Figure 1(a) shows schematic diagram of the proposed EXA microscope. An electron beam is focused on a luminescent film. A specimen is put on the luminescent film directly. The inset in Fig. 1(a) shows magnified image of the luminescent film and the specimen. Nanometric light source is excited in the luminescent film by the focused electron beam. The nanometric light source illuminates the specimen, and the scattered or transmitted radiation is detected with a photomultiplier tube (PMT). The light source is scanned by scanning of the focused electron beam in order to construct on image. Figure 1(b) shows a luminescence image of the cells acquired with the EXA microscope, and Fig. 1(c) shows a phase contrast microscope image. Cells were observed in culture solution without any treatments, such as fixation and drying. The shape of each cell was clearly recognized and some bright spots were observed in cells. We believe that the bright spots indicated with arrows were auto-fluorescence of intracellular granules and light- grey regions were auto-fluorescence of cell membranes. It is clearly demonstrated that the EXA microscope is useful tool for observation of living biological cells in physiological conditions.jmicro;63/suppl_1/i16/DFU090F1F1DFU090F1Fig. 1.(a) Optical setup of EXA microscpe, and observation results of of living MARCO-expressing CHO cells with (b) EXA microscope and (c) phase contrast microscope. We proposed the EXA microscope as a technique with high spatial resolution beyond the diffraction limit of light. A spatial resolution greater than 100 nm was achieved for the EXA microscope and the dynamic behavior of moving nanoparticles in water was observed by time lapse imaging. We also demonstrated luminescence image of living cells in culture solution without any treatments.

A transcriptome for the study of early processes of retinal regeneration in the adult newt, Cynops pyrrhogaster

Retinal regeneration in the adult newt is a useful system to uncover essential mechanisms underlying the regeneration of body parts of this animal as well as to find clues to treat retinal disorders such as proliferative vitreoretinopathy. Here, to facilitate the study of early processes of retinal regeneration, we provide a de novo assembly transcriptome and inferred proteome of the Japanese fire bellied newt (Cynops pyrrhogaster), which was obtained from eyeball samples of day 0-14 after surgical removal of the lens and neural retina. This transcriptome (237,120 in silico transcripts) contains most information of cDNAs/ESTs which has been reported in newts (C. pyrrhogaster, Pleurodeles waltl and Notophthalmus viridescence) thus far. On the other hand, de novo assembly transcriptomes reported lately for N. viridescence only covered 16-31% of this transcriptome, suggesting that most constituents of this transcriptome are specific to the regenerating eye tissues of C. pyrrhogaster. A total of 87,102 in silico transcripts of this transcriptome were functionally annotated. Coding sequence prediction in combination with functional annotation revealed that 76,968 in silico transcripts encode protein/peptides recorded in public databases so far, whereas 17,316 might be unique. qPCR and Sanger sequencing demonstrated that this transcriptome contains much information pertaining to genes that are regulated in association with cell reprogramming, cell-cycle re-entry/proliferation, and tissue patterning in an early phase of retinal regeneration. This data also provides important insight for further investigations addressing cellular mechanisms and molecular networks underlying retinal regeneration as well as differences between retinal regeneration and disorders. This transcriptome can be applied to ensuing comprehensive gene screening steps, providing candidate genes, regardless of whether annotated or unique, to uncover essential mechanisms underlying early processes of retinal regeneration.

Dynamic autofluorescence imaging of intracellular components inside living cells using direct electron beam excitation

We developed a high-resolution fluorescence microscope in which fluorescent materials are directly excited using a focused electron beam. Electron beam excitation enables detailed observations on the nanometer scale. Real-time live-cell observation is also possible using a thin film to separate the environment under study from the vacuum region required for electron beam propagation. In this study, we demonstrated observation of cellular components by autofluorescence excited with a focused electron beam and performed dynamic observations of intracellular granules. Since autofluorescence is associated with endogenous substances in cells, this microscope can also be used to investigate the intrinsic properties of organelles.

Multi-color imaging of fluorescent nanodiamonds in living HeLa cells using direct electron-beam excitation

Multi-color, high spatial resolution imaging of fluorescent nanodiamonds (FNDs) in living HeLa cells has been performed with a direct electron-beam excitation-assisted fluorescence (D-EXA) microscope. In this technique, fluorescent materials are directly excited with a focused electron beam and the resulting cathodoluminescence (CL) is detected with nanoscale resolution. Green- and red-light-emitting FNDs were employed for two-color imaging, which were observed simultaneously in the cells with high spatial resolution. This technique could be applied generally for multi-color immunostaining to reveal various cell functions.

Fluorescence enhancement with deep-ultraviolet surface plasmon excitation

We report the experimental demonstration of fluorescence enhancement in fluorescent thin film using surface plasmon excitation in deep-ultraviolet (deep-UV) region. Surface plasmon resonance in deep-UV is excited on aluminum thin film in the Kretschmann-Raether geometry. Considering the oxidation thickness of aluminum, the experimentally measured incident angle dependence of reflectance show good agreement with Fresnel theory. Surface plasmon resonance was excited at the incident angle of 49 degrees for 266 nm p-polarized excitation light on the film of 18 nm-thick aluminum with 6.5 nm-thick alumina. Fluorescence of CdS quantum dots coated on this aluminum film was enhanced to 18-fold in intensity by the surface plasmon excitation.

Intracellular calcium ion concentration measurement using a phase-modulation fluorescence lifetime method with compensation for phase shift due to the presence of proteins

The calcium ion concentration in cells was measured by a phase-modulation fluorescence lifetime method with compensation for proteins. A high-accuracy measurement of the calcium ion concentration is best realized by fluorescence lifetime measurements, because the fluorescence lifetime is independent of the fluorescence intensity. The fluorescence intensity is easily varied by the scattering of excitation and emission light in cells, photobleaching, the concentration of fluorochromes, and wavelength dispersion of optical elements. A phase-modulation fluorescence lifetime measurement, however, provides high accuracy and precision, and can measure not only the calcium ion concentration, but also other ion concentrations, such as that of magnesium, sodium, and potassium. We have examined the phase-modulation fluorescence lifetime shift using protein compensation in cells, and have measured the calcium ion concentration in cells stimulated with bradykinin.

Dynamic and high-resolution live cell imaging by direct electron beam excitation

We propose a direct electron-beam excitation assisted optical microscope with a resolution of a few tens of nanometers and it can be applied for observation of dynamic movements of nanoparticles in liquid. The technique is also useful for live cell imaging under physiological conditions as well as observation of colloidal solution, microcrystal growth in solutions, etc. In the microscope, fluorescent materials are directly excited with a focused electron beam. The direct excitation with an electron beam yields high spatial resolution since the electron beam can be focused to a few tens of nanometers in the specimens. In order to demonstrate the potential of our proposed microscope, we observed the movements of fluorescent nanoparticles, which can be used for labelling specimens, in a water-based solution. We also demonstrated an observation result of living CHO cells.

MEK-ERK and heparin-susceptible signaling pathways are involved in cell-cycle entry of the wound edge retinal pigment epithelium cells in the adult newt

The onset mechanism of proliferation in mitotically quiescent retinal pigment epithelium (RPE) cells is still obscure in humans and newts, although it can be a clinical target for manipulating both retinal diseases and regeneration. To address this issue, we investigated factors or signaling pathways involved in the first cell-cycle entry of RPE cells upon retinal injury using a newt retina-less eye-cup culture system in which the cells around the wound edge of the RPE exclusively enter the cell cycle. We found that MEK-ERK signaling is necessary for their cell-cycle entry, and signaling pathways whose activities can be modulated by heparin, such as Wnt-, Shh-, and thrombin-mediated pathways, are capable of regulating the cell-cycle entry. Furthermore, we found that the cells inside the RPE have low proliferation competence even in the presence of serum, suggesting inversely that a loss of cell-to-cell contact would allow the cells to enter the cell cycle.

Plasmonic nanofocusing using a metal-coated axicon prism

We propose an excitation method for the localization of photons at the apex of a metal coated axicon prism. The cone angle of the prism and the metallic film thickness are designed to match the excitation conditions for surface plasmons. The plasmons propagate along the sides of the prism and converge at its apex. The resulting nanofocusing was investigated by simulating the intensity distributions around the apex of the prism using a finite-difference time-domain algorithm. For incident radial polarization, a localized and field enhanced spot is generated by the constructive interference of surface plasmons.

Electron beam excitation assisted optical microscope with ultra-high resolution

We propose electron beam excitation assisted optical microscope, and demonstrated its resolution higher than 50 nm. In the microscope, a light source in a few nanometers size is excited by focused electron beam in a luminescent film. The microscope makes it possible to observe dynamic behavior of living biological specimens in various surroundings, such as air or liquids. Scan speed of the nanometric light source is faster than that in conventional near-field scanning optical microscopes. The microscope enables to observe optical constants such as absorption, refractive index, polarization, and their dynamic behavior on a nanometric scale. The microscope opens new microscopy applications in nano-technology and nano-science.

Musashi-1, an RNA-binding protein, is indispensable for survival of photoreceptors

Musashi-1 (Msi1), an RNA-binding protein (RBP), has been postulated to play important roles in the maintenance of the stem-cell state, differentiation, and tumorigenesis. However, the expression and function of Msi1 in differentiated cells remain obscure. Here we show that Msi1 is expressed in mature photoreceptors and retinal pigment epithelium (RPE) cells, and is indispensable for the survival of photoreceptors. We found in the adult newt eye that Msi1 is expressed in all photoreceptors and RPE cells as well as in the retinal stem/progenitor cells in the ciliary marginal zone (CMZ). We found in the analyses of the newt normal and regenerating retinas that the expression profiles of the Msi1 transcripts and protein isoforms in the photoreceptors are different from those in the retinal stem/progenitor cells. Furthermore, we found that all photoreceptors and RPE cells of the adult mice also express Msi1, and that Msi1 knockout (Msi1-KO) results in degeneration of photoreceptors and a lack of a visual cycle protein RPE65 in the microvilli of RPE cells. Taken together, our current results demonstrate that the expression of Msi1 in mature photoreceptors and RPE cells is evolutionarily conserved, and that Msi1 bears essential functions for vision. Considering such an Msi1-KO phenotype in the retina, it is now reasonable to address whether defects of the Msi1 functions are responsible for inherited retinal diseases. Studying the regulation of Msi1 and the target RNAs of Msi1 in photoreceptors and RPE cells might contribute to fundamental and clinical studies of retinal degeneration.

Three-dimensional imaging analysis of confocal and conventional polarization microscopes by use of Mie scattering theory

We present a three-dimensional imaging analysis of confocal and conventional polarization microscopes by using the extended Mie scattering theory. In the analysis, we calculate the images of a Mie particle whose diameter is comparable with the wavelength of confocal and conventional microscopes. It was found that, when we observe a Mie particle, polarization confocal microscopy is not affected by the polarization distortion that is due to focusing with high-numerical-aperture lenses and does not produce pseudopeaks in the images in comparison with conventional polarization microscopy. The three-dimensional resolution of the polarization microscope and the verification of the proposed analysis method are also discussed.