Quantitative comparison of anti-fading mounting media for confocal laser scanning microscopy.

Fading is one of the major obstacles to reliable observation in fluorescence microscopy. Using a confocal laser scanning microscope (CLSM) coupled to a computer, we quantitatively measured fading of fluorescence to formulate an equation, evaluated the anti-fading ability of several anti-fading media, and restored the faded images to the original level according to this equation. NIH 3T3 cells were stained with fluorescein isothiocyanate (FITC)-phalloidin, mounted with several commercial and homemade anti-fade media, and observed with CLSM under repeated illumination. With any mounting medium, attenuation of fluorescence intensity at a certain pixel occurred stepwise and the decrease was proportional to the intensity of the previous scan. From these results, we formulated an equation that has three coefficients: anti-fading factor (A), indicating the ability to retard fading; fluorescent intensity at the first scan (EM(1)); and background fluorescence (B). The fluorescent intensity at a certain point following nth scan is given as EM(n) = EM(1) * A ((n-1)). This equation was available for restoring faded images to their original states, even after the image had faded to only 60% of its original intensity.     

Remodelling of cardiomyocyte cytoarchitecture visualized by three-dimensional (3D) confocal microscopy

The break-down and reassembly of myofibrils in long-term cultures of adult rat cardiomyocytes was investigated by a novel combination of confocal laser scanning microscopy and three-dimensional image reconstruction, referred to as FTCS, to visualize the morphological changes these cells undergo in culture. FTCS is discussed as an alternative imaging mode to low-magnification scanning electron microscopy. The three-dimensional shape of the cells are correlated with the assembly state of myofibrils in different stages. Based on immunofluorescence and confocal laser scanning microscopy it was shown that myofibrils are degraded within a few days after plating and that newly assembled myofibrils are predominantly confined to the continuous area in the perinuclear region close to the membrane in contact with the substratum. The localization of myofibrils along the cell's vertical axis has been investigated both by optical sectioning using confocal light microscopy and by physical sectioning following by transmission electron microscopy. Based on the distribution of myofibrillar proteins we propose a model of myofibrillar growth locating the putative assembly sites to a region concentric around the nuclei. We provide evidence that the cell shape is dominated by the myofibrillar apparatus.     

A mercury arc lamp-based multi-color confocal real time imaging system for cellular structure and function

Multi-point scanning confocal microscopy using a Nipkow disk enables the acquisition of fluorescent images with high spatial and temporal resolutions. Like other single-point scanning confocal systems that use Galvano meter mirrors, a commercially available Nipkow spinning disk confocal unit, Yokogawa CSU10, requires lasers as the excitation light source. The choice of fluorescent dyes is strongly restricted, however, because only a limited number of laser lines can be introduced into a single confocal system. To overcome this problem, we developed an illumination system in which light from a mercury arc lamp is scrambled to make homogeneous light by passing it through a multi-mode optical fiber. This illumination system provides incoherent light with continuous wavelengths, enabling the observation of a wide range of fluorophores. Using this optical system, we demonstrate both the high-speed imaging (up to 100 Hz) of intracellular Ca(2+) propagation, and the multi-color imaging of Ca(2+) and PKC-gamma dynamics in living cells.     

Targeted optical injection of gold nanoparticles into single mammalian cells

We present an all optical technique for the targeted delivery of single 100 nm diameter gold nanoparticles into a specified region of the interior of an individual mammalian cell through a combination of optical tweezing and optical injection. The internalisation of the nanoparticle is verified by confocal laser scanning microscopy and confocal laser scanning reflectance microscopy. This represents the first time that nano sized particles have been tweezed and optically injected into mammalian cells using only light, and provides a novel methodology for internalising nanosphere based biosensors within specific intracellular regions of a mammalian cell. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

激光共聚焦显微镜与光学显微镜之比较

激光扫描共聚焦显微镜在活细胞的动态检测、光学切片和三维结构重建等方面较光学显微镜有质的飞跃。本文对激光扫描共聚焦显微镜和光学显微镜进行了比较和讨论,并简单介绍多光子激光扫描显微镜。     

激光扫描共聚焦显微镜荧光探针的选择和应用

激光扫描共聚焦显微镜是检测生物荧光信号的最新技术手段。不仅广泛用于荧光定性、定量测量,还可用于活细胞动态荧光监测、组织细胞断层扫描、三维图象重建、共聚焦图象分析、荧光光漂白恢复、激光显微切割手术等。本文拟就激光扫描共聚焦显微镜常用的检测内容及其相关荧光探针的选择和应用做一简单的介绍。     

Confocal scanning optical microscopy and three-dimensional imaging

Summary— Confocal scanning optical microscopy has significant advantages over conventional fluorescence microscopy: it rejects the out-of-locus light and provides a greater resolution than the wide-field microscope. In laser scanning optical microscopy, the specimen is scanned by a diffraction-limited spot of laser light and the fluorescence emission (or the reflected light) is focused onto a photodetector. The imaged point is then digitized, stored into the memory of a computer and displayed at the appropriate spatial position on a graphic device as a part of a two-dimensional image. Thus, confocal scanning optical microscopy allows accurate non-invasive optical sectioning and further three-dimensional reconstruction of biological specimens. Here we review the recent technological aspects of the principles and uses of the confocal microscope, and we introduce the different methods of three-dimensional imaging.     

Scanning Microphotolysis: Three-Dimensional Diffusion Measurement and Optical Single-Transporter Recording

Scanning microphotolysis (SCAMP) is a combination of fluorescence microphotolysis and confocal laser scanning microscopy. A laser scanning microscope is equipped with an optical switch able to modulate the power or/and wavelength of the laser beam in less than a microsecond while a dedicated computer program is employed to precisely coordinate scanning process and laser beam modulation. By these means it becomes possible to vary the power or/and wavelength of the laser beam during scanning at a precision of one resolution element. Patterns of almost arbitrary design can be written into the object by photolysis, e.g., photobleaching or photoactivation. The dissipation of the photolysis pattern by diffusion or other types of molecular transport can be followed at confocal resolution and used to characterize the transport process. SCAMP can be employed in conjunction with single-photon or multiphoton excitation. Furthermore, it can be easily installed on virtually any confocal laser scanning microscope. We summarize at first the conceptual and practical basis of SCAMP. Then, two novel applications are discussed: (i) measurements of translational diffusion coefficients in truly three-dimensional systems at diffraction-limited resolution, and (ii) optical recording of single transporters in membrane patches.     

Three-dimensional organization of ribosomal DNA in interphase nuclei ofPisum sativum by in situ hybridization and optical tomography

The three-dimensional (3D) organization of rDNA-containing chromatin was studied in structurally well preserved, interphase nuclei ofPisum sativum root tips by in situ hybridization using a biotinylated cDNA probe to the 18, 5.8 and 25 S rDNA sequences. The probe was detected by immunofluorescence and optical section images recorded either by video imaging or by using a confocal laser scanning microscope. Detailed 3D reconstructions were made of 12 nucleoli by projection of confocal optical sections. The probe labelled four perinucleolar heterochromatin sites, one pair 1.0–2.1 µm in diameter and the other 0.5–1.0 µm diameter. It also labelled intranucleolar structures including 300–500 nm spots emanating from the perinucleolar sites into the body of the nucleolus. The intranucleolar labelled structures emanating from the perinucleolar sites lay in discrete domains. Medium power observations of 22 fields of cells (6–30 cells per field) were made by optical sectioning using a video camera and computer deblurring. The arrangement of the perinucleolar sites was modelled in each cell and the arrangements examined for nonrandomness. The sites tended to be spaced out around the nucleolar periphery approximating a regular tetrahedral arrangement as if to minimize clustering and the large sites appeared to lie in a plane perpendicular to the root axis. Cells with multiple nucleoli did not have any preferred distribution of sites between nucleoli. These observations are discussed in terms of current models of rDNA organization.     

Principles and practices of laser scanning confocal microscopy

The laser scanning confocal microscope (LSCM) is an essential tool for many biomedical imaging applications at the level of the light microscope. The basic principles of confocal microscopy and the evolution of the LSCM into today's sophisticated instruments are outlined. The major imaging modes of the LSCM are introduced including single optical sections, multiple wavelength images, three-dimensional reconstructions, and living cell and tissue sequences. Practical aspects of specimen preparation, image collection, and image presentation are included along with a primer on troubleshooting the LSCM for the novice.     

Three-dimensional visualization and quantitative analysis of cervical cell nuclei with confocal laser scanning microscopy

OBJECTIVE: To develop a method for the acquisition and processing of 3-dimensional images based on confocal laser scanning microscopy for the purpose of 3-dimensional visualization and quantitative analysis of cell nuclei. STUDY DESIGN: A contour-based surface rendering method was used, and volume rendering was implemented according to the basic volume rendering pipeline. To extract quantitative features, a 3-dimensional labeling method based on slice information was used. After applying the labeling algorithm, the measurements for 3-dimensional quantitative analysis of nuclei were extracted: nuclear volume, surface area and spherical shape factor. We compared the 3-dimensional features of normal and abnormal cervical cell nuclei. RESULTS: Comparison of the size of 3-dimensional cervical cell nuclei between normal and abnormal revealed a statistically significant difference. The proposed method could overcome the limitation inherent in 2-dimensional analysis and could become a way of improving the accuracy and reproducibility of quantification of cell nuclei. CONCLUSION: Three-dimensional visualization and quantification of cell nuclei provide valuable medical information that can lead to a more objective diagnosis.     

Line-Scanning Microscopy for Time-Gated and Spectrally Resolved Fluorescence Imaging

Laser-scanning fluorescence microscopy for efficient acquisition of time-gated and spectrally resolved fluorescence images was developed based on line illumination of the laser beam and detection of the fluorescence image through a slit. In this optical arrangement, the fluorescence image was obtained by scanning only one axis perpendicular to the excitation line, and the acquisition time was significantly reduced compared with conventional laser-scanning confocal microscopy. A multidimensional fluorescence dataset consisting of fluorescence intensities as a function of x-position, y-position, fluorescence wavelength, and delay time after photoexcitation was analyzed and decomposed based on the parallel factor analysis model. The performance of the line-scanning microscopy was examined by applying it to the analysis of one of the plant defense responses, accumulation of antimicrobial compounds of phytoalexin in oat (Avena sativa), induced by the elicitor treatment.     

Assessing Confocal Microscopy Systems for Purchase

Confocal laser scanning microscopy now has so many functions and applications that choosing a new multiuser confocal laser microscopy system can be a daunting task, particularly for a first-time buyer and new users of confocal microscopy. How does one determine which features are most appropriate for any particular laboratory, application, or imaging environment? Each confocal microscopy system has its own individual advantages and limitations, which ultimately defines its market niche. Here, we describe the features that differentiate the four confocal microscopy systems we assessed. The decisive factors in choosing a confocal microscopy system for our anatomical laboratory were user-friendly software for on-line acquisition and off-line processing; the working distances of objective lenses; applicability for a multiuser environment; interactions with company representatives; and turnaround times for questions, service, and accessories.     

用激光扫描共聚焦显微镜观察雪松花粉和花粉管

为更直观地观察和显示花粉和花粉管中细胞结构及其细胞核的状态与行为。雪松花粉和花粉管经卡诺液固定,分别以埃氏苏木精、曙红、Hoechst 33243单染和曙红-Hoechst 33342双染后,用冬青油整体透明,在激光扫描共聚焦显微镜下观察。4种染色法观察效果不同;以曙红-Hoechst 33342双染的样品观察效果最佳,在紫外光激发下清晰地显示出细胞核,在488 nm激光激发下不仅能清晰看到花粉和花粉管壁结构,且能分辨管细胞、柄细胞及体细胞的结构特点和空间位置关系。建立了一种快速简便的适于在激光扫描共聚焦显微镜下观察花粉和花粉管中成员细胞结构及其细胞核的状态、行为的制片技术;激光扫描共聚焦显微镜具有独特的共轭成像装置、连续光学扫描、图像三维重组和多通道检测等功能,极好地展示了雪松花粉和花粉管的结构特点,相比于传统的光学显微镜和荧光显微镜,其观察到的图像更清晰、更直观、更具立体感。     

共聚焦荧光镜检术揭示大蒜鳞片细胞间期核中的F肌动蛋白网络

采用免疫荧光和荧光分子探针技术与共聚焦激光扫描显微镜观察相结合,对大蒜（Ａｌｌｉｕｍ ｓａｔｉｖｕｍ Ｌ．）鳞片细胞间期核中是否存在Ｆ肌动蛋白进行了研究。结果表明,以兔抗肌动蛋折抗体为一抗、ＦＴＴＧ－羊抗兔ＩｇＧ抗体为二抗进行免疫荧光标记实验,在荧光镜下观察到蒜瓣薄壁组织的细胞核及表皮细胞核均发出明亮的黄绿色荧光经共聚焦激光扫描显微镜进一步检查,整个细胞核呈黄绿色荧光,说明其中含有肌动蛋白。经ＴＲ     

Changes in volume,surface area,and frequency of nuclear pores on the vegetative nucleus of tobacco pollen in fresh,hydrated, and activated conditions

The vegetative nucleus (VN) of Nicotiana tabacum L. has been qualitatively and quantitatively studied in fresh, hydrated, and activated pollen. Techniques included the use of optical sectioning by confocal scanning laser microscopy to obtain volume and surface area measurements, and stereoscopic pairs; and freeze-etch electron microscopy to estimate the frequency of nuclear pores per m² in the vegetative nucleus. Several morphological changes were observed to occur in pollen grain nuclei during the early processes of tube growth. In freshly dehisced pollen grain, the vegetative and generative nuclei were side by side, but following hydration and activation of the grain, the elongated generative nucleus became partially surrounded by the vegetative nucleus. It was found that during hydration, the surface area of the vegetative nucleus increased and there was a decrease in the frequency of nuclear pores. The calculated total number of pores remained similar. After activation and pollen-tube growth, the vegetative nucleus retained the same surface area as in the hydrated state but the frequency of nuclear pores decreased; therefore, the calculated total number of pores was significantly lowered. When considered alongside complementary biochemical data, these morphological results indicate that RNA production in the vegetative nucleus decreases following germination.Abbreviations VN vegetative nucleus (nuclei) - GN generativenucleus - GC generative cell - CSLM confocal scanning laser microscope We acknowledge research support by the Biotechnology Action Programm of the Commission of European Communities, and CNR for the fellowship awarded to Dr. Wagner. We would also like to thank Mrs. C. Faleri for the expert technical help.     

Revealing the F_actin Networks in Interphase Nuclei of Garlic Clove Cells by Confocal Fluorescence Microscopy

The interphase nuclei of parenchyma cells and epidermal cells of garlic (Allium sativum L.) clove were labelled with rabbit anti-actin antibody and FITC-conjugated goat anti-rabbit IgG antibody. The authors observed results with fluorescence microscopy and confocal laser scanning microscopy. The nuclei showed prominent green-yellow fluorescence, indicating the presence of actin in the nuclei. Fluorescence examination with TRITC-phalloidin showed distinctive red fluorescence in the nuclei, indicating that F-actin is present in the nuclei. Confocal laser scanning microscopy indicated the presence of F-actin containing network structures in the nuclei, but the network structures were absent and the nuclei still showed red fluorescence when the cells were treated with cytochalasin D before fixation; the red fluorescence in the nuclei was hard to be observed when the cells were treated with unlabelled phalloidin before the cells were stained with TRITC-phalloidin. These results indicate that F-actin is in the nuclei and forms network structures in the nuclei of garlic cells.     

人膀胱癌细胞纤维肌动蛋白共聚焦激光扫描显微镜观察

探讨膀胱癌细胞纤维肌动蛋白（F－actin)的空间结构。采用共聚焦激光扫描显微镜光学切片技术结合异硫酸氢荧光素－鬼笔环肽（FITC－phalloidin)标记纤维肌动蛋白和碘化丙啶（PI）和标记核酸的荧光探针双重标记技术对膀胱癌细胞纤维肌动蛋白进行形态学观察,结果可见膀胱癌细胞内纤维肌动蛋白微丝形态完整,成细束或细丝状,平行排列地整个细胞或细胞突起,在胞质边缘处较密集。     

Visualization of silver-enhanced reaction products from protein- and immuno-colloidal gold probes by laser scanning confocal microscopy in leflection mode

We have employed a laser scanning confocal microscope in reflection mode to directly and indirectly visualize sites of deposition of silver-enhanced reaction products from colloidal gold probes. A direct approach was used for the localization of alpha-fetoprotein receptors in human myoblasts by incubating primary cultures with an alpha-fetoprotein-gold conjugate. For an indirect approach, cultured CEM cells, derived from a human T-lymphoma cell line, were incubated with a mouse monoclonal antibody to mature T-cells, followed by a gold-labelled antibody to mouse immunglobulins. Multiple optical sections of each sample were collected by reflection laser scanning confocal microscopy and combined into three-dimensional renderings. A (non-confocal) transmission image was generated of each field for comparative purposes. The increasing use of reflection laser scanning confocal microscopy combined with colloidal gold conjugates as biological markes will probably be of considerable advantage in cytochemical analysis.     

The effect of sodium tetrathionate stabilization on the distribution of three nuclear matrix proteins in human K562 erythroleukemia cells

Using both conventional fluorescence and confocal laser scanning microscopy we have investigated wheter or not stabilization of isolated human erythroleukemic nuclei with sodium tetrathionate can maintain in the nuclear matrix the same spatial distribution of three polypeptides (M_r 160 kDa and 125 kDa, previously shown to be components of the internal nuclear matrix plus the 180-kDa nucleolar isoform of DNA topoisomerase II) as seen in permeabilized cells. The incubation of isolated nuclei in the presence of 2 mM sodium tetrathionate was performed at 0° C or 37° C. The matrix fraction retained 20–40% of nuclear protein, depending on the temperature at which the chemical stabilization was executed. Western blot analysis revealed that the proteins studied were completely retained in the high-salt resistant matrix. Indirect immunofluorescence experiments showed that the distribution of the three antigens in the final matrix closely resembled that detected in permeabilized cells, particularly when the stabilization was performed at 37° C. This conclusion was also strengthened by analysis of cells, isolated nuclei and the nuclear matrix by means of confocal laser scanning microscopy. We conclude that sodium tetrathionate stabilization of isolated nuclei does not alter the spatial distribution of some nuclear matrix proteins.