Use of confocal microscopy to investigate cell structure and function.
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UNLABELLED: We have investigated trafficking of two negative regulators of growth hormone receptor (GHR) signaling: a human, truncated receptor, GHR1-279, and a GH antagonist, B2036. Fluorescent-labeled growth hormone (GH) was rapidly internalized by the full-length GHR, with >80% of the hormone internalized within 5 min of exposure to GH. In contrast, <5% of labeled GH was internalized by cells expressing truncated GHR1-279. Using another truncated receptor, GHR1-317 fused to enhanced green fluorescent protein (EGFP), we have exploited fluorescence energy transfer to monitor the trafficking of ligand-receptor complexes. The data confirmed that internalization of this truncated receptor is very inefficient. It was possible to visualize the truncated GHR1-317-EGFP packaged in the endoplasmic reticulum, its rapid movement in membrane bound vesicles to the Golgi apparatus, and subsequent transport to the cell membrane. The GH antagonist, B2036, blocked Jak2-Stat5-mediated GHR signaling but was internalized with a similar time course to native GH. THE RESULTS: 1) demonstrate the rapid internalization of GH when studied under physiological conditions; 2) confirm the hypothesis that internalization of cytoplasmic domain truncated human GHRs is very inefficient, which explains their dominant negative action; and 3) show that the antagonist action of B2036 is independent of receptor internalization.
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Some of the most extensively used fluorophores for multicolour fluorescence labelling of tissue, such as Lucifer yellow, fluorescein, Cyanine-3.18 and rhodamine, all have the disadvantage of being difficult to separate spectrally due to their broad and overlapping emission spectra. With the intensity-modulated multiple-beam scanning (IMS) technique, cross-talk between labels can be reduced to a fraction of that seen using conventional excitation and detection technique. Thus, cross-talk to the 'red' channel decreased with about one order of magnitude for the 'green' fluorophores Lucifer yellow and FITC. For the tested 'red' fluorophores, the amount of cross-talk to the green channel was reduced by 60-90%.
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PURPOSE: : To describe the deposition rate of tamoxifen in the cornea and observe its impact on the cornea with confocal microscopy. METHODS: : Forty-four eyes of 22 women receiving tamoxifen at a dosage of 20 mg/day for at least 6 months for the adjuvant treatment of breast cancer and 30 eyes of 15 healthy age-matched women were examined for corneal drug deposition by slitlamp after pupil dilation. Ultrasound pachymetry, specular microscopy, in vivo confocal microscopy, and Schirmer tear test were also performed in all patients. RESULTS: : The mean duration of tamoxifen intake was 21.6 +/- 7.9 months (range, 13-44 months), and the mean cumulative dose was 12.9 +/- 4.7 g (range, 7.8-26.4 g). Drug depositions in the inferior paracentral cornea were identified in 32 (72%) eyes at pupil-dilated slitlamp examination. There were no significant differences between eyes with keratopathy, those without keratopathy, and control eyes in regard to the mean Schirmer test scores, mean central corneal thickness, mean endothelial cell count, mean basal epithelium cell density, mean anterior and posterior stromal keratocyte density, and mean endothelial cell density (P > 0.05). No pathologic alteration of structure was observed with in vivo confocal microscopy at any corneal level in patients receiving tamoxifen. CONCLUSIONS: : Low-dose tamoxifen use was associated with corneal depositions in 72% of patients. Slitlamp examination performed with pupil dilation was helpful in detection of subtle tamoxifen-related deposits. Amelioration of in vivo confocal microscopy systems may be helpful in accurate imaging of the paracentral and peripheral cornea.
Traditional methods for anatomical and morphometric studies of cochlear tissues have relied upon either microdissection of the organ of Corti or the generation of serial sections of the cochlea. Such methods are time-consuming, disruptive to three-dimensional relationships and often restrict sampling to very limited numbers of cells. We have found that cells and tissue components of the cochlear duct may be labelled by fluorescent markers within intact cochleae, which are then embedded in epoxy resin for subsequent viewing by fluorescent microscopy methods. This approach allows imaging through thick optical volumes with preservation of three-dimensional relationships. Unlike sectioned tissue, alignment of the sample relative to the focal axis may be easily corrected by re-orientation of the optical volume with common image processing software. Fluorescently labelled cochleae embedded in epoxy can be viewed by most fluorescent microscopy methods including laser scanning confocal microscopy, multi-photon confocal microscopy and widefield epi-fluorescence microscopy with deconvolution. Furthermore, semi-thin sections made from these preparations are compatible with traditional histological stains, as well as allowing brightly labelled epi-fluorescent images.
To identify features of posterior polymorphous dystrophy (PPMD) by in vivo confocal microscopy, the corneas of a female patient with PPMD were exam ned using slit-lamp biomicroscopy and slit-scanning in vivo confocal microscopy. Characteristic endothelial vesicular and band lesions were seen clinically and easily identified using in vivo confocal microscopy. However endothelial pleomorphism, an increased density and reflectance of posterior stromal keratocytes, and prominence of corneal nerves were also delineated. In vivo confocal microscopy enhances clinicopathological diagnosis and follow up of corneal dystrophies with subtle clinical presentations, such as PPMD.
Because it provides much higher magnification and better optical sectioning than a slit-lamp biomicroscope, confocal microscopy is ideally suited for clinical imaging of the cornea. One important clinical application of confocal microscopy has been the early detection and diagnosis of a number of infectious conditions, including infection with Acanthamoeba and microsporidium species, fungal keratitis, and contact lens-associated bacterial keratitis. Confocal microscopy has also been used for temporal evaluation of corneal wound healing following refractive surgery and penetrating keratoplasty. With the development of the new technique of quantitative confocal microscopy through-focusing, confocal microscopy can be used to measure epithelial, stromal, and corneal thickness accurately and reproducibly in human patients. Furthermore, conofocal microscopy through-focusing can be used to determine the initial photoablation depth, changes in epithelial, stromal, and corneal thickness, and subepithelial haze following photorefractive keratectomy.