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At least 865 records · Page 48Linked to original sources
PubMed1990

Binding and internalization of ricin labelled with fluorescein isothiocyanate.

The toxic lectin ricin has been covalently labelled with fluorescein isothiocyanate on the enzymatically active A chain. The fluorescein reacted toxin maintains its biological activity. The lateral diffusion coefficient of cell surface bound ricin, studied in two cell lines by fluorescence photobleaching recovery, is D = 1 - 2 x 10(-10) cm2/s. Fluorescence microscopy provides preliminary evidence for secondary endosomes in the cytoplasm.

Animals↗
PubMed1984

Fluorescein conjugates as indicators of subcellular pH. A critical evaluation.

Fluorescein and tetramethylrhodamine conjugates to protein or dextran were used to determine subcellular pH. The pH dependence of fluorescence of fluorescein isothiocyanate (FITC) conjugates could be described by a single proton dissociation (pK'a approximately 6.8). This allowed pH to be derived accurately from spectra using the simple Henderson-Hasslebach equation. FITC and TRITC conjugates were delivered to mouse macrophage lysosomes by pinocytosis. Lysosomal pH was then determined in several different ways. First, by direct matching of the subcellular fluorescence spectrum with calibration spectra obtained in free solution. Secondly, monensin was used to equilibrate internal and extracellular pH. Subcellular pH could then be determined by the relative increase in fluorescence of the FITC conjugate without loss of probe from the lysosomes. This allowed the calibration of pH dependence with the probe in situ. Finally, macrophages were permitted to pinocytose FITC and TRITC dextran conjugates simultaneously. pH could be determined from the ratio of emissions from the two dyes within the lysosomes. Each of these different methods gave a similar value for lysosomal pH (4.8 +/- 0.1).

Animals↗
PubMed1983

The diffusion of fluorescein in the stroma of rabbit cornea.

The diffusion rate and the distribution ratio of fluorescein in the stroma was studied in rabbit cornea. A strip of corneal stroma was mounted in a chamber and fluorescein in a phosphate buffer solution was circulated across the end of the strip for 24 hr. The change in fluorescence intensity was measured along the strip and the diffusion coefficient was calculated using Fick's diffusion equation. The mean coefficient of diffusion was 1.21 +/- 0.24 (+/- S.D.) X 10(-6) cm2/sec at 19 degrees C. The ratio of fluorescence between the stroma and the solution was 1.34 to 1.33 for the concentrations ranging from 0.1 to 10 g/ml.

Animals↗
PubMed1989

Probing the nucleotide-binding site of sarcoplasmic reticulum (Ca2+-Mg2+)-ATPase with anti-fluorescein antibodies.

Antibodies raised against fluorescein were unable to bind to the fluorophore when bound at the nucleotide-binding site of native (Ca2+-Mg2+)-ATPase, as judged by fluorescence quenching assays or competitive ELISAs, but were able to bind when the ATPase was denatured. Indirect ELISAs, in which native and denatured FITC-ATPase were used to coat ELISA plates, were unable to detect the difference in accessibility of the fluorescein bound to the native and denatured ATPase. These results indicate that the nucleotide-binding site is relatively inaccessible in the native structure, even though fluorescence energy transfer studies [(1987) Biochim. Biophys. Acta 897, 207-216] indicate that this site must be close to the surface of the ATPase. In addition the results suggest that the indirect ELISA method may be of limited value in probing the accessibility of epitopes using antibodies.

Animals↗
PubMed1982

Cell sorting using a universally applicable affinity chromatography matrix: solid-phase anti-fluorescein isothiocyanate antibody.

Procedures are described for fractionating cells utilizing a universally applicable cellular affinity chromatography matrix. The affinity matrix consists of immunoabsorption purified goat anti-fluorescein isothiocyanate antibody coupled to large derivatized polyacrylamide beads. This matrix may, in principle, be used to isolate any cell subpopulation provided it has a fluorescein-labeled ligand on its surface. In this report the matrix was used to isolate viable purified fractions of mouse surface Ig-positive cells, Lyt1 cells, and mouse lymphocytes that bind the lectin soybean agglutinin. A preliminary experiment using the anti-FITC beads suggested that this technique can provide a fraction of cells enriched in antigen binding cells. Cell populations isolated by this technique retain their ability to respond to in vitro mitogen stimulation, as well as their ability to be maintained in cell culture following fractionation. Additional experiments using a column consisting of goat anti-rabbit Ig antibody coupled to the same support material are also reported.

Animals↗
PubMed1986

Preparation and properties of antibodies doubly labeled with tritium and fluorescein.

A method was developed to prepare doubly labeled antibodies whereby fluorescein-labeled antibodies were reacted with N-[ethyl-2-3H]ethylmaleimide. This tritiated conjugate exhibited the same immunoreactivity as the non-derivatized fluorescein-labeled antibody. This method provides a marker for immunocytochemical studies which takes advantage of the rapidity of fluorescent tracing combined with the stability and precision of the radioautography technique.

Animals↗
PubMed1991

The effect of fluorescein labels on the affinity of antisera to small haptens.

Small haptens such as methylamphetamine (MW 149) cannot, on their own, induce an immune response. It is also unlikely that they fill the binding site of any antibody that recognises them. Under such circumstances any attached label might be expected to enter the area of the binding site and exert an influence on overall binding. To investigate the possible influence of the label on binding, a range of fluorescein-labelled derivatives, differing in bridge length, were prepared. Antiserum binding of these labelled derivatives was then compared to that of the unlabelled drug. Evidence is presented which suggests that, with small haptens, the closeness of the fluorescein molecule can markedly influence antibody binding. Significant differences were found in titre, sensitivity, and assay kinetics. These overall effects appear to be brought about by the change in affinity of the antibody for the labelled hapten.

Amphetamines↗
PubMed1995

Preparation and characterization of fluorescein-labeled plasma membrane vesicles from transfected Chinese hamster ovary cells.

Plasma membrane vesicles have been used to study a wide variety of biological events including the nature of receptor-ligand interactions and the physiology of molecular transport across membranes. Plasma membrane vesicles were chemically induced from an adherent Chinese hamster ovary cell line expressing recombinant glycophorin A, a well-studied intrinsic membrane protein of the red blood cell. They were also prepared from Chinese hamster ovary cells in suspension culture. Biochemical and immunological assays demonstrated the equivalence of glycophorin A on cell membranes and vesicles. The transfected Chinese hamster ovary cell membrane was also labeled with a highly aliphatic fluorescent cell linker. Vesicles produced by the fluorescein-labeled cells demonstrated bright surface staining of the plasma membrane. They too expressed glycophorin A biochemically and immunologically indistinguishable from cellular-based glycophorin A. Plasma membrane vesicles are non-adherent in culture and stably retain the fluorescent probe in the cell membrane. Fluorescein-labeled vesicles will be particularly useful for studying cellular interactions in which both constituents of a receptor-ligand pair are expressed on adherent cell lines. Unlabeled vesicles may also prove to be useful as soluble immunoadsorbants in both the clinical laboratory and basic science research settings.

Animals↗
PubMed1993

Light-emitting properties of recombinant semi-synthetic aequorins and recombinant fluorescein-conjugated aequorin for measuring cellular calcium.

15 kinds of recombinant semi-synthetic aequorins and a recombinant fluorescein-conjugated aequorin were prepared and their properties in Ca(2+)-triggered luminescence were studied. The semi-synthetic aequorins showed a wide range of Ca(2+)-sensitivity. The luminescence intensity of a high-sensitivity type (hcp-aequorin) was greater than 10(4)-times that of a low-sensitivity type (n-aequorin) at pCa 6.0-6.5. The fluorescein-conjugated aequorin exhibited fluorescence in addition to the Ca(2+)-triggered luminescence, thus it can be used to visualize the diffusion and distribution of aequorin in cells. The data obtained, particularly the Ca(2+)-sensitivity curves, are useful in selecting a suitable semi-synthetic aequorin for an experiment.

Aequorin↗
PubMed2007

In vivo fluorescein staining of SI-30NB silicone intraocular lens.

We report a case of a 48-year-old pseudophakic woman who presented 3 weeks after Heidelberg retinal angiography using intravenous sodium fluorescein 2%. Bilateral retinal vasculitis with severe retinal ischemia and extensive capillary dropouts had been diagnosed. Anterior segment examination revealed green staining on the silicone optic of the 3-piece SI-30NB intraocular lens (IOL) (AMO), with no cell or flare in the aqueous humor. The anterior and posterior capsules were not stained. The patient did not report dark vision, double vision, or altered color vision. The anterior and posterior IOL surfaces demonstrated an autofluorescence at the time of fundus photography, which persisted to the 6-week examination although there were no symptoms. This is suggestive of deposits of sodium fluorescein on the IOL surface following angiography.

Female↗
PubMed2007

Segmentation of blood vessels from red-free and fluorescein retinal images.

The morphology of the retinal blood vessels can be an important indicator for diseases like diabetes, hypertension and retinopathy of prematurity (ROP). Thus, the measurement of changes in morphology of arterioles and venules can be of diagnostic value. Here we present a method to automatically segment retinal blood vessels based upon multiscale feature extraction. This method overcomes the problem of variations in contrast inherent in these images by using the first and second spatial derivatives of the intensity image that gives information about vessel topology. This approach also enables the detection of blood vessels of different widths, lengths and orientations. The local maxima over scales of the magnitude of the gradient and the maximum principal curvature of the Hessian tensor are used in a multiple pass region growing procedure. The growth progressively segments the blood vessels using feature information together with spatial information. The algorithm is tested on red-free and fluorescein retinal images, taken from two local and two public databases. Comparison with first public database yields values of 75.05% true positive rate (TPR) and 4.38% false positive rate (FPR). Second database values are of 72.46% TPR and 3.45% FPR. Our results on both public databases were comparable in performance with other authors. However, we conclude that these values are not sensitive enough so as to evaluate the performance of vessel geometry detection. Therefore we propose a new approach that uses measurements of vessel diameters and branching angles as a validation criterion to compare our segmented images with those hand segmented from public databases. Comparisons made between both hand segmented images from public databases showed a large inter-subject variability on geometric values. A last evaluation was made comparing vessel geometric values obtained from our segmented images between red-free and fluorescein paired images with the latter as the "ground truth". Our results demonstrated that borders found by our method are less biased and follow more consistently the border of the vessel and therefore they yield more confident geometric values.

Algorithms↗
PubMed1984

Kinetics of interaction of N epsilon-fluorescein isothiocyanate-lysine-23-cobra alpha-toxin with the acetylcholine receptor.

We have studied the kinetics of N epsilon-fluorescein isothiocyanate-lysine-23 cobra alpha-toxin (FITC-toxin) binding to the membrane-associated acetylcholine receptor from the Torpedo californica electric organ. The fluorescent toxin not only enabled us to monitor the binding reaction continuously but also to examine simultaneously the enhancement of ligand fluorescence and the increase in steady state polarization of fluorescence associated with binding of the alpha-toxin. Over the range of concentrations employed, both parameters yielded identical kinetic constants, suggesting that the enhancement of fluorescence of fluorescein and its immobilization are occurring in the same time frame. Both an initial rate analysis and the integrated rate expression showed association to be a simple, reversible bimolecular process. The apparent second-order association rate constant derived from the integrated rate analysis was constant within a factor of 2 over a 40-fold concentration range (6.7 +/- 1.7 X 10(3) M-1 S-1). The unimolecular dissociation rate constant was found to be 3.3 +/- 0.5 X 10(-5) S-1.

Animals↗
PubMedDate not supplied

Retinal vasculitis revealed by fluorescein angiography in patients with inflammatory bowel disease.

Fluorescein angiography was performed to examine retinal vascular abnormalities in five consecutive patients with inflammatory bowel disease seen during the 2 years from April 1995 to March 1997, in a university hospital. All patients showed dye leakage from retinal capillaries in the peripheral fundi of both eyes. Other ocular findings included iritis in both eyes of two patients and clinically significant macular edema in the unilateral eye of one patient. This study indicates that subclinical retinal vasculitis, revealed only by fluorescein angiography, is present in patients with inflammatory bowel disease.

Adult↗
PubMed1986

Iontophoresis of fluorescein into the posterior segment of the rabbit eye.

Iontophoresis of appreciable quantities of fluorescein into the vitreous body of the rabbit results from the use of a high electrical current density over a limited area of the globe. This is achieved by passing current through the fluorescein when it is held against the region of the ora serrata in a tube less than 1 mm in diameter. The retina is destroyed over a corresponding area when the current enters the eye. An electrode is described which is held to the eye by suction and could be practical for clinical applications.

Animals↗
PubMed1990

Assessment of tear drainage after canalicular obstruction using fluorescein dye disappearance.

Assessment of tear drainage impairment after monocanalicular obstruction can be difficult. The authors used fluorescein dye disappearance to evaluate tear drainage after experimental obstruction of upper, lower, neither, or both canaliculi in 20 subjects. Marked impairment was noted in all subjects when both canaliculi were occluded (P less than 0.004). Monocanalicular obstruction (either upper or lower) generally resulted in minimal or no impairment, though 10% of subjects showed marked impairment. Fluorescein dye disappearance proved a reliable, rapid method for assessing tear drainage and detecting lacrimal obstruction.

Fluorescein↗
PubMed1984

Fixed-tissue binding of fluorescein-conjugated concanavalin A to malignant melanomas versus nevi.

Concanavalin A (con A) is a plant-derived lectin that has the capability of agglutinating malignant cells in vitro. We studied the binding of fluorescein isothiocyanate-conjugated con A to formalin-fixed, paraffin-embedded malignant melanomas and nevocellular nevi. Both malignant melanoma cells and nevus cells emitted partial or circumferential, cytoplasmic rim, apple green fluorescence. There was no demonstrable difference between fluorescence distribution or intensity between the two groups. Control, unstained tissue specimens yielded a brilliant nuclear and nucleolar yellow-green autofluorescence, which is peculiar to melanoma cells and rare to absent in nevus cells. Fluorescein isothiocyanate-conjugated con A provided no clear differentiation between malignant melanomas and nevocellular nevi in fixed tissue. However, characteristic melanoma cell autofluorescence may prove to be of benefit for differentiating malignant melanocytic from benign nevocytic lesions.

Binding Sites↗
PubMed1999

Fatal anaphylactic shock during a fluorescein angiography.

The Authors describe an extremely rare fatal case (sixth case in the literature) of anaphylactic shock following a fluorescein angiography. This is the first report in which the diagnosis of anaphylactic reaction to the dye was made through laboratory analyses. The diagnosis of fatal shock due to sodium fluorescein was made based on clinical, laboratory and immunohistochemical data. Mast-cell tryptase was dosed in serum and a pulmonary immunohistochemical evaluation was performed. Tryptase, a neutral protease of human mast-cells is a potentially important indicator of mast-cell involvement in anaphylactic events.

Aged↗