Video-rate scanning two-photon excitation fluorescence microscopy and ratio imaging with cameleons

A video-rate (30 frames/s) scanning two-photon excitation microscope has been successfully tested. The microscope, based on a Nikon RCM 8000, incorporates a femtosecond pulsed laser with wavelength tunable from 690 to 1050 nm, prechirper optics for laser pulse-width compression, resonant galvanometer for video-rate point scanning, and a pair of nonconfocal detectors for fast emission ratioing. An increase in fluorescent emission of 1.75-fold is consistently obtained with the use of the prechirper optics. The nonconfocal detectors provide another 2.25-fold increase in detection efficiency. Ratio imaging and optical sectioning can therefore be performed more efficiently without confocal optics. Faster frame rates, at 60, 120, and 240 frames/s, can be achieved with proportionally reduced scan lines per frame. Useful two-photon images can be acquired at video rate with a laser power as low as 2.7 mW at specimen with the genetically modified green fluorescent proteins. Preliminary results obtained using this system confirm that the yellow "cameleons" exhibit similar optical properties as under one-photon excitation conditions. Dynamic two-photon images of cardiac myocytes and ratio images of yellow cameleon-2.1, -3.1, and -3.1nu are also presented.

Digital imaging in transmission electron microscopy

The digital revolution currently under way, as evidenced by the rapid development of the Internet and the world-wide-web technologies, is undoubtedly impacting the field of transmission electron microscopy (TEM). Digital imaging systems based on charge-coupled device (CCD) technologies, with pixel array size up to 2 k x 2 k at the present and increasing, are available for TEM applications and offer many attractions. Is it time to phase out film cameras on TEMs and close the darkrooms for good? This paper reviews digital imaging technologies for TEM at different voltages, and contrasts the performance of digital imaging systems with that of TEM film. The performance characteristics of CCD-based digital imaging systems, as well as methods for assessing them, are discussed. Other approaches to digital imaging are also briefly reviewed.

High-sensitivity lens-coupled slow-scan CCD camera for transmission electron microscopy

A lens-coupled slow-scan CCD camera has been built for transmission electron microscopy (TEM) applications. In this design, a leaded glass window, which is coated with a 20 microns layer of red P20 phosphor, is mounted on the bottom of the microscope. A lens assembly and mirror prism, located outside the microscope vacuum below the leaded glass, relays the image onto a back-thinned 1kx1k charge-coupled device (CCD) detector. This CCD is electronically cooled to below -30 degrees C during operation. It is found that X-ray irradiation, generally found to be annoying in fiber-optically coupled CCD cameras, is completely eliminated by this configuration. The collection efficiency of this system, although not as high as some of the fiber-optically coupled CCD cameras, is high enough to achieve single-electron sensitivity under a high-gain mode.

ASIC-based event-driven 2D digital electron counter for TEM imaging

A two-dimensional application specific integrated circuit (ASIC) based detector, designed for X-ray protein crystallography, has been tested to determine its suitability as a direct electron detector for TEM imaging in the voltage range of 20-400 keV. Several markedly different properties of this device distinguish it from the charge coupled device (CCD) detectors: (1) the ASIC detector can be used directly under electron bombardment in the voltage range stated above, therefore requiring no scintillator screen; (2) each active pixel of the device is an electron counter and generates digital output independently; (3) the readout of the device is frameless and event driven; (4) the device can be operated at the room temperature and is nearly noise free; and (5) the counting dynamic range of the device is virtually unlimited. It appears that an imaging system based on this type of device would be ideal for low-dose TEM imaging and online diffraction observation and recording, as well as more conventional imaging, providing the many advantages of direct digital readout for almost all applications.

Effect of cadmium exposure on the histopathology of cerebral cortex in juvenile mice

Cadmium, a heavy metal, is a toxic environmental and industrial pollutant. Exposure to cadmium can lead to the toxic effects in a variety of tissues, also including the brain. The present study investigated the effect of cadmium exposure on the histopathology of cerebral cortex in juvenile mice. Juvenile mice were randomly divided into control, low (1.87 mg/kg), medium (3.74 mg/kg), and high (7.48 mg/kg) dose groups. After cadmium exposure by drinking water for 10 days, the cerebral cortex was obtained for histopathology studies. The medium and high dose of cadmium, rather than low dose, could induce the histopathology alterations of cerebral cortex in a dose-dependent manner. In the high-dose group, microstructure significantly showed pia mater encephali divorcing from cerebral cortex layer, serious hyperemia of blood capillary in pia mater encephali and cerebral cortex, broadening vessel peripheral clearance, a large number of eosinophil leukocyte infiltrating around blood vessel, vacuolar degeneration in part granule cells, and obviously increasing apoptotic cells. Ultrastructure obviously displayed marginalized heterochromatin, incomplete or fused nuclear membranes, broadened perinuclear space, ambiguous mitochondria cristae, decreased synaptic cleft, and fused presynaptic and postsynaptic membrane. Our results revealed that cadmium at the middle and high dose could induce obvious microstructure and ultrastructure alterations of cerebral cortex in juvenile mice, which may be one important mechanism of cadmium neurotoxicity.

In vivo calcineurin crystals formed using the baculovirus expression system

Calcineurin is a heterodimeric phosphatase involved in the signal transduction of antigen-activated T cells. Coexpression of its two subunits, the regulatory subunit from human and the catalytic subunit from Neurospora crassa in cultured insect cells using the baculovirus expression system results in the formation of very large crystals in the cytoplasm. The crystals are formed initially in vesicles, but their subsequent growth appears to be uninhibited and continues without the need of an enclosing membrane until the host cell lyses. Although these in vivo crystals are low in population, ranging only 0-3 per cell, they are extremely large, over 10 mu m in some cases. Biochemical assays confirm their calcineurin origin, with the regulatory subunit incorporated being myristoylated, although both the myristoylated and unmyristoylated forms are expressed. The lattice structure of the in vivo crystals, with a spacing of 5.5 nm, is preserved with the regular electron microscopic (EM) specimen preparation procedure.

Telemicroscopy

The feasibility of operating an electron microscope from a remote location using a high-speed computer network has been investigated. A 400 kV electron microscope was modified so that most microscope parameters and stage movement (x, y, z and tilt), can be controlled by a local host computer. The host computer also controls acquisition of digital images from the microscope from either a TV or a slow-scan CCD camera. A computer located at a remote site may send commands to the host computer via a fiber optic network to receive digital images and information concerning the status of microscope. Such a system has been demonstrated at the SIGGRAPH 1992 conference in Chicago and the Supercomputing 92 conference in Minneapolis, where we remotely collected three-dimensional image data sets using the electron microscope in San Diego. This approach, referred to as "telemicroscopy", promises to make possible live microscopy teleconferencing and thereby increase the accessibility and effective usage of the limited number of specialized microscopy resources.

Optimization of thin-foil based phosphor screens for CCD imaging in TEM in the voltage range of 80-400 kV

The voltage dependence characteristics of thin-foil based phosphor screens in the thickness range of approximately 10-60 microns are examined for CCD imaging in transmission electron microscopy (TEM) in the voltage range of 80-400 kV. The brightest screen is obtained with a P20 layer of about 12 microns at 80 kV, and a thicker screen lowers both the screen brightness and resolution. The thickness of the brightest screen is higher at higher voltage, but other considerations for a practical CCD imaging system suggest that the P20 layer should not be greater than approximately 18 microns for the voltage range stated above.

Performance of thin foil scintillating screen for transmission electron microscopy

Scintillating screens made by coating a thin metal foil with a layer of phosphor appear to be attractive for transmission electron microscopy applications. We report here the brightness and resolution in the voltage range of 100-400 kV of such a screen made of a 10 microns layer of P20 phosphor on a 2 microns Al foil. Both brightness and resolution are superior to that of a screen made by coating a glass plate with a similar layer of phosphor. An exciting property of such a device is that its resolution improves slightly at higher voltages. This, combined with its excellent resistivity to radiation damage and stability under the electron beam, makes it a good candidate for high-voltage applications.

Glucocorticoid-induced differentiation of primary cultured bone marrow mesenchymal cells into adipocytes is antagonized by exogenous Runx2

Long-term clinical use of glucocorticoids often causes the serious side effect of non-traumatic avascular osteonecrosis. The aim of this study was to examine the effects and mechanisms of a glucocorticoid, dexamethasone (Dex), on differentiation of primary cultured rat bone marrow mesenchymal cells (BMCs). We also tried to block the inhibitory effects of Dex on osteoblast differentiation. Adipocyte markers (peroxisome proliferator-activated receptorgamma-2 and aP2) were increased in response to Dex treatment in a dose- and time-dependent manner, while osteoblastic markers [Runx2, COL 1, osterix, alkaline phosphatase (ALP) and OC] were down-regulated, consistent with ALP and osteocalcin promoter activity. To validate the effects of Runx2 on the expression of osteogenesis and adipocyte genes, pCMV/Flag-Runx2 was transfected into BMCs, and relevant markers were detected after 10(-7) M Dex treatment for 48 h. The results indicated that Dex treatment induced adipogenic differentiation and suppressed proliferation. No significant difference was detected in expressions of these genes between Runx2-transfected cells and Dex-treated BMCs. These data suggest that Dex primarily induced adipocyte differentiation of BMCs. Exogenous Runx2 can antagonize the effect of Dex on osteoblast differentiation.

Multiport-readout frame-transfer 5 megapixel CCD imaging system for TEM applications

A multiport-readout, frame-transfer charge-coupled device (CCD) digital imaging system has been successfully developed and tested for intermediate-high-voltage electron microscopy (IVEM) applications up to 400 keV. The system employs a back-thinned CCD with 2560 x 1960 pixels and a pixel size of 24 microm x 24 microm. In the current implementation, four of the eight on-chip readout ports are used in parallel each operating at a pixel rate of 1- or 2-MHz so that the entire CCD array can be read out in as short as 0.6 s. The frame-transfer readout functions as an electronic shutter which permits the rapid transfer of charges in the active pixels to four masked buffers where the charges are readout and digitized while the active area of the CCD is integrating the next frame. With a thin film-based phosphor screen and a high-performance lens relay, the system has a conversion factor of 2.1 digital units per incident electron at 400 keV, and a modulation transfer function value of 14% at the Nyquist frequency.

Construction of Cu(I)-Organic Frameworks with Effective Sorption Behavior for Iodine and Congo Red

The assembly of a tetradentate pyridine-derived ligand with CuX has afforded two isostructural Cu(I)-organic frameworks [Cu₂X₂(TBD)·DMF]_n (X = Cl for 1 and Br for 2) in this work. Structural analysis indicates that the compounds feature hybrid layered architectures, and the three-dimensional supramolecular frameworks are finally fabricated through the alternative stacking of adjacent layers wherein large open channels are simultaneously constructed. The chemical stability has been studied showing the excellent skeleton maintenance of the prepared solids in various solvents and even in water. Moreover, the iodine and dye sorption performance for compound 1 has been further tested. The Cu(I)-based metal-organic framework exhibits outstanding sorption and separation abilities on the targeted species, which could be considered as a promising adsorbent with high efficiency and selectivity.

Stereoscopy by tilted illumination in transmission electron microscopy

We describe a new technique for stereoscopic observation in transmission electron microscopy, employing tilted illumination. A triple-hole objective aperture is used so that the bright beam can pass through with or without tilt. Stereo views can be acquired by tilting the illumination such that the bright beam passes through a pair of symmetrically arranged apertures alternately. The advantages of this technique as compared to the commonly used method of single-axis tilt are: (i) greater speed, potentially at or close to video rate so that live 3D observation is possible; (ii) elimination of specimen movement associated with stage tilt; and (iii) perspective views corresponding to multiple tilting axes which can be realized by installing more aperture-holes and choosing their positions properly. The main limitation is that the angle of tilt is limited by the extent to which the astigmatism, introduced by beam tilt, can be compensated by the objective lens stigmators.

Long-Term Efficacy of Maintenance Therapy for Multiple Myeloma: A Quantitative Synthesis of 22 Randomized Controlled Trials

We aimed to quantitatively synthesize data from randomized controlled trials (RCTs) concerning maintenance for multiple myeloma (MM). We searched electronic literature databases and conference proceedings to identify relevant RCTs. We selected eligible RCTs using predefined selection criteria. We conducted meta-analysis comparing maintenance containing new agents and conventional maintenance, and subgroup analysis by transplantation status and mainstay agent as well. We performed trial sequential analysis (TSA) to determine adequacy of sample size for overall and subgroup meta-analyses. We performed network meta-analysis (NMA) to compare and rank included regimens. A total of 22 RCTs involving 9,968 MM patients and 15 regimens were included, the overall quality of which was adequate. Significant heterogeneity was detected for progression-free survival (PFS) but not overall survival (OS). Meta-analyses showed that maintenance containing new agents significantly improved PFS but not OS [PFS: Hazard Ratio (HR) = 0.59, 95% Confidence Interval (CI) = 0.54 to 0.64; OS: HR = 0.93, 95% CI = 0.87 to 1.00], compared with controls. Subgroup analyses revealed lenalidomide (Len)-based therapies better than thalidomide-based ones (HR = 0.50 and 0.66, respectively; P = 0.001). NMA revealed that most of the maintenance regimens containing new agents were significantly better than simple observation in terms of PFS but not OS. Len single agent was the most effective, considering PFS and OS both. We concluded that conventional maintenance has very limited effect. Maintenance containing new agents is highly effective in improving PFS, but has very limited effect on OS. Maintenance with Len may have the largest survival benefits. Emerging strategies may further change the landscape of maintenance of MM.

Microstructure and Ultrastructure Alterations in the Pallium of Immature Mice Exposed to Cadmium

The aim of this study was to investigate microstructure and ultrastructure alterations in the pallium of immature mice exposed to cadmium. Forty immature mice were randomly divided into control, 1/100 LD₅₀ (1.87 mg/kg, low), 1/50 LD₅₀ (3.74 mg/kg, medium), and 1/25 LD₅₀ (7.48 mg/kg, high) dose groups. After oral cadmium exposure for 40 days, the pallium of mice was obtained for microstructure and ultrastructure studies. The results showed that both microstructure and ultrastructure alterations of the pallium were observed in all treated mice and the most obvious alterations were in the high dose group. Microstructural analysis showed seriously congested capillary in the pia mater of the pallium in the high cadmium group. Meanwhile, vacuolar degenerate or karyopyknosis presented in some neurocytes, capillary quantity, and the number of apoptotic cells increased, some neurocytes became hypertrophy, the pia mater separated from the cortex, and local hemorrhage and accompanied inflammatory cell infiltration were also observed. Ultrastructural analysis showed that rough endoplasmic reticulum was expanded, heterochromatin marginalized, perinuclear space distinctly broadened, swelling and vacuolization mitochondria appeared, synapse was swelling, presynaptic and postsynaptic membranes presented fusion, and most of mitochondrial cristae were ambiguous. The results indicated that cadmium exposure for 40 days induced dose-dependent microstructure and ultrastructure alterations in pallium of immature mice.

Conditions for electron tomographic data acquisition

The conventional algorithms employed in electron microscope tomography require that the series of images obtained from different orientations of the specimen each represent a parallel orthographic projection under uniform magnification. Electron microscope optics can produce distortions in images that may affect the accuracy of a tomographic reconstruction. These distortions result in images with differential rotation and magnification of regions of a thick or highly tilted specimen located at different distances with respect to the plane of focus. The distortions increase in magnitude and may significantly affect the accuracy of the tomographic data when images are acquired under current center misalignment or non-eucentric positioning of the specimen. An additional source of error can be introduced if the condenser lenses are adjusted to compensate for the intensity attenuation due to the increased beam path length as the specimen is tilted. The change in beam crossover position due to adjustment of the condensers alters the beam divergence and may introduce systematic changes in magnification over the tilt series. The process of alignment of the tilt series will propagate these errors to more central regions of the image. In most cases, with proper consideration, it is possible to minimize these errors to levels where they will have negligible effects on the resolution of the tomographic reconstruction.

[Reversion of eye position after surgical correction of exotropia]

The authors analysed the reversion of eye position in 62 postoperative patients of concomitant exotropia. The results indicated the presence of a correlation with the preoperative condition of binocular vision, the type of strabismus, and the age of patient. The authors opened that the amplitude of surgical correction should depend on these factors, and prudence should be exercised in recommending surgical intervention for mild intermittent exotropia in children.

[Orientation growth of osteocyte in the bone harvest chamber]

OBJECTIVE

To study orientation remodeling without stress in bone harvest chamber.

METHODS

The bone harvest chamber (BHC) methodology is adopted in this study. Five female Japanese white rabbits were allowed unrestricted activity. The bone harvest chamber was a cylindrical Ti implant body with a transverse 1 mm wide canal for bone ingrowths. Retrieval of the contents of the canal was allowed with minimal disturbance to the surrounding bone or outer cylinder. After bone harvest chambers were implanted into the tibia of rabbits for 8 weeks, the chambers were considered to be osseointegrated with the bone. After harvested, the tissue were fixed and decalcified, then embedded in paraffin. Each rabbit was put into surgical operation 4 times for 4 stages: vacant for the first time; the tissue were cut into longitudinal sections at the second and third stages; harvesting tissues were cut into transverse sections at the fourth stage. Directional analysis: the standard deviation of the orientation of cell nucleus in each section was used as statistics, the difference between longitudinal section and transverse section were analyzed.

RESULTS

Of the tissue into bone harvest chamber, directionality of cells arranged was more significantly on longitudinal section than on transverse section and there was statistical ignificecne.

CONCLUSION

Under the no-stress circumstance of BHC bone remodeling showed directivity. Stress is not the direct leading signal about bone reconstitution. The structure of BHC might be related to orientation remodeling, which suggests that the relationship between orientation and stress is mediated by blood vessel. The effect of stress may be to affect vessel distributing in some orietation.

Performance characteristics of radioluminescent fiber optics as electron scintillators

Terbium-activated radioluminescent fiber-optic face plates have been studied for their suitability as electron scintillators. The energy conversion efficiency of such material is determined to be about 2.5% in the electron energy range of 100-400 keV tested. The resolution is approximately 40 microns at electron energy of 100 keV, as measured by the rise width of an edge. The main advantage of such a device is the potential simplification of CCD camera designs, since it functions both as a scintillator as well as a light guide so that it can be coupled direct to a CCD detector.

Interpretation of genotype-environment-sowing date/plant density interaction in sorghum [Sorghum bicolor (L.) Moench] in early mature regions of China

Sorghum [Sorghum bicolor (L.) Moench] is an important crop for food security in semiarid and arid regions due to its high tolerance to abiotic and biotic stresses and its good performance in marginal lands with relatively low fertility. To deeply understand the interrelationship among sorghum genotype, environment, sowing dates, and densities in the spring sowing early maturing (SSEM) areas of China, and to provide a basis for specifying scientific and reasonable cultural practices, a two-year field experiment was conducted with six popular varieties at six locations. Combined ANOVA showed that the yield difference between years was significant (P<0.05); the yield differences among locations, varieties, sowing dates, and densities were all highly significant (P<0.01). The variety effect was mainly influenced by location, year, sowing dates and their interactions. The sowing effect was mainly influenced by the location, year, variety and their interactions The plant density effect was significantly influenced by location and location-year interaction. Of the contributions of various test factors to yield variance, the location was the largest one (38.18%), followed by variety (12.31%), sowing date (1.53%), density (0.54%), and year (0.09%), with all these single factors accounting for 52.65%. The total contribution of all two-factor interactions accounted for 14.24%, among which the greatest contributor was location-hybrid interaction (8.07%). The total contribution of all three-factor interactions accounted for 14.58%, of which year-location-hybrid interaction was the largest contributor (9.02%). Sowing dates significantly affected model of sorghum growth and development, especially during the late period. The key climatic factors affecting yield were different among the six locations. Weather factors during the grain filling stages contributed much more than those during the early stage to grain yield. Mid-maturing varieties are recommended other than early maturing varieties for the SSEM areas even when late sowing occurs. Sowing as early as possible is recommended for areas with very short frost-free period (Harbin, Tongliao, and Datong). Proper delayed sowing is recommended for areas with a relative long frost-free period (Gongzhuling, Baicheng and Zhangjiakou). This research will provide a conducive reference for sorghum production in similar areas.

High-power top-hat pulses from a Yb master oscillator power amplifier for efficient optical parametric amplifier pumping

We demonstrate shaping of high-energy broadband Yb amplifier pulses for the generation of a (sub)picosecond top-hat temporal pulse profile that significantly improves pumping efficiency of an optical parametric amplifier (OPA). Phase-only modulation is applied by an acousto-optic programmable dispersion filter. This simple scheme is scalable to a high average power due to a relatively broad bandwidth of the Yb:CaF(2) gain medium used in the amplifier that supports a sub-150-fs transform-limited pulse duration. Additionally we show that OPA seeding with supercontinuum remains possible because top-hat-shaped pulses passed through a glass block recompress to ≈200 fs with minimum satellite production.