Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “FLUORESCEINS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,027 records · Page 57Linked to original sources
PubMed1999

Accurate measurement of avidin and streptavidin in crude biofluids with a new, optimized biotin-fluorescein conjugate.

A new biotin-fluorescein conjugate with an ethylene diamine spacer was found to be the first fluorescent biotin derivative which truly mimicked d-biotin in terms of high affinity, fast association, and non-cooperative binding to avidin and streptavidin tetramers. These exceptional properties were attributed to the small size/length of the new ligand since all larger/longer biotin derivatives are known for their mutual steric hindrance and anti-cooperative binding in 4:1 complexes with avidin and streptavidin tetramers. Specific binding of the new biotin-fluorescein conjugate towards avidin and streptavidin was accompanied by 84-88% quenching of ligand fluorescence. In the accompanying study this effect was used for rapid estimation of avidin and streptavidin in a new 'single tube assay'. In the present study the strong quenching effect was utilized to accurately monitor stoichiometric titration of biotin-binding sites in samples with >/=200 pM avidin or streptavidin. The concentration was calculated from the consumption of fluorescent ligand up to the distinct breakpoint in the fluorescence titration profile which was marked by the abrupt appearance of strongly fluorescent ligands which were in excess. Due to this protocol the assay was not perturbed by background fluorescence or coloration in the unknown samples. The new fluorescence titration assay is particularly suited for quick checks on short notice because getting started only means to thaw an aliquot of a standardized stock solution of fluorescent ligand. No calibration is required for the individual assay and the ligand stock solution needs to be restandardized once per week (or once per year) when stored at -25 degrees C (or at -70 degrees C, respectively).

Avidin↗
PubMed1998

Fluorescein blue, light-assisted capsulorhexis for mature or hypermature cataract.

This technique is for use in eyes with mature or hypermature cataract resulting in lack of fundus reflex during capsulorhexis. Fluorescein staining is performed before the capsulorhexis is made. A blue filter in the coaxial light accentuates the remaining rim of bright blue fluorescence and aids in exact formation of the anterior opening. Seven eyes with a postoperative visual acuity of light perception had surgery using this technique. Visual acuity ranged from 20/200 to 20/20 up to 3 months postoperatively. No untoward reaction to the fluorescein was observed; however, the long ultrasound exposure for very hard nuclei (up to 4 minutes) caused corneal edema in two eyes. This technique is regularly used in all eyes with insufficient fundus reflex caused by lens opacity or vitreous disease.

Capsulorhexis↗
PubMed1996

Evaluation of pedicled skin flap viability by pH, temperature and fluorescein: an experimental study.

In order to test methods of predicting skin flap viability, a skin flap model in Sprague-Dawley rats was established. As criteria for studying skin flap survival, we compared measurement of skin pH, temperature, as well as fluorescence photography and computer aided digital morphometry (CADM). Ninety male Sprague-Dawley rats were divided into three groups in which pedicles were clamped for 10, 15, or 20 h. A standardized bipedicled skin flap was prepared, maintained by the epigastric artery, vein and nerve. All flaps were sutured back in place immediately after clamping. We found that postoperative prediction of flap survival based solely upon external appearance was impossible until the 2nd postoperative day. Changes in pH were not statistically significant in the prediction of vital or necrotic flaps. The temperature measurements showed, that in the event of viability the decrease in flap temperature versus the reference temperature (rectal temperature) was significant (P < 0.0094 in Group II, 15 h of ischaemia) or at least a tendency to significance (P < 0.059 in Group III, 10 h of ischaemia) bigger than in the event of partial or total flap necrosis. The photographic documentation using fluorescein showed that all coloured areas survived. Group I (20 h) showed predominantly total flap necrosis. Most flaps in Group III (10 h) exhibited a small necrotic area at the tip. In Group II (15 h) no typical staining pattern could be observed. Furthermore, computer aided digital morphometry demonstrated a decrease of the necrotic area by 7% between the 2nd and 4th postoperative day in Groups II and III. The method which gave the most exact prediction about viability was the fluorescein staining of the flaps via the tail vein.

Animals↗
PubMed2001

Neutral liposome-mediated delivery process of fluorescein-modified oligonucleotides in cultured human keratinocytes.

We propose a model of the intracellular delivery process in which fluorescein-labeled natural oligonucleotides (F-DNA) are transferred into the nuclei of cultured human keratinocytes. By encapsulation in neutral multilamellar lecithin liposomes, the F-DNA appeared to be protected against intracellular interactions with cellular materials and nuclease attacks in the cytoplasm during the process. The intracellular behavior of F-DNA and fluorescent phospholipid-labeled liposomes was observed by means of fluorescence analysis. Results showed that: F-DNA encapsulated in neutral multilamellar liposomes reached the cellular nuclei more efficiently than either free F-DNA, or F-DNA in unilamellar liposomes; the liposomal membranes appeared to be left in the cytoplasm. The reaction of F-DNA with complementary DNA was suggested by a rapid quenching of the fluorescence in the nucleus. In addition, the fluorescence decrease was evidently suppressed in the cytoplasm, indicating a protective effect of the neutral multilamellar liposomes against the interaction of F-DNA with cytoplasmic materials. The application of these findings to 'photo'-antisense studies has been discussed, where suppression of a gene expression is attempted by using oligonucleotide-attached fluorescein with the aid of a photo-induced covalent binding property.

Binding Sites↗
PubMed2004

A three-dimensional flow control concept for single-cell experiments on a microchip. 2. Fluorescein diacetate metabolism and calcium mobilization in a single yeast cell as stimulated by glucose and pH changes.

Using a three-dimensional flow control concept to manipulate and retain a single yeast cell in a microchip, we were able to study the kinetics of intracellular metabolism and calcium mobilization at the single-cell level, as stimulated by glucose and pH changes. As a model study, the fluorogenic substrate fluorescein diacetate (FDA) was chosen to study how the intracellular carboxylesterase metabolize it. A single yeast cell was first cultured in the microchip. Thereafter, under a constant concentration of FDA, influx of FDA into the yeast cell occurred and FDA was hydrolyzed or metabolized. It was found that changes in both pH and glucose stimulated the FDA metabolism in a yeast cell, and the stimuli can elicit multiple responses from the cell. Since it was carried out within the microchip, the whole experiment on one single yeast cell could last for as long as 10 h. The dormant cell, budding cell, and pretreated budding cell (in low-pH buffer) of yeast resulted in different responses. Experimental data provided details on the FDA metabolism at the single-cell level and revealed strong correlations between FDA metabolism and calcium mobilization. Furthermore, efflux of the FDA metabolite fluorescein could start spontaneously if there was glucose in the medium. The experiments on a single cell were of the "human cell conservation" style because the cell responded to the reagent changes implemented by the human researcher. A mathematical model was also developed to study the influx-hydrolysis-efflux processes of the FDA metabolism using single-cell fluorescent data. These long overdue single-cell experiments are now rendered possible using the three-dimensional flow control in the microchip.

Calcium↗
PubMed2005

Fluorescein-labeled beta-lactamase mutant for high-throughput screening of bacterial beta-lactamases against beta-lactam antibiotics.

The increasing emergence of new bacterial beta-lactamases that can efficiently hydrolyze beta-lactam antibiotics to clinically inactive carboxylic acids has created an intractable problem in the treatment of bacterial infections, and it is highly desirable to develop a useful tool that can rapidly screen bacteria for beta-lactamases against a variety of antibiotic candidates in a high-throughput manner. This paper describes the use of a fluorescein-labeled beta-lactamase mutant (E166Cf) as a convenient fluorescent tool to screen beta-lactamases, including the Bacillus cereus beta-lactamase I (PenPC), B. cereus beta-lactamase II, Bacillus licheniformis PenP, Escherichia coli TEM-1, and Enterobacter cloacae P99 against various beta-lactam antibiotics (penicillin G, penicillin V, ampicillin, cefuroxime, cefoxitin, moxalactam, cephaloridine), using a 96-well microplate reader. The E166Cf mutant was constructed by replacing Glu166 on the flexible Omega-loop, which is close to the enzyme's active site, with a cysteine residue on a class A beta-lactamase (B. cereus PenPC) and subsequently labeling the mutant with thiol-reactive fluorescein-5-maleimide. Such modifications significantly impaired the hydrolytic activity of the E166Cf mutant compared to that of the wild-type enzyme. The fluorescence intensity of the E166Cf mutant increases in the presence of beta-lactam antibiotics. For antibiotics that are resistant to hydrolysis by the E166Cf mutant (cefuroxime, cefoxitin, moxalactam), the fluorescence signal slowly increases until it reaches a plateau. For antibiotics that can be slowly hydrolyzed by the E166Cf mutant (penicillin G, penicillin V, ampicillin), the fluorescence signal rapidly increases to the plateau and then declines after a prolonged incubation. The E166Cf mutant retains its characteristic pattern of fluorescence signals in the presence of both bacterial beta-lactamases and beta-lactamase-resistant antibiotics. In contrast, in the presence of both bacterial beta-lactamases and beta-lactamase-sensitive antibiotics, the fluorescence signals of the E166Cf mutant were decreased. The fluorescence signals from the E166Cf mutant allow an unambiguous differentiation of beta-lactamase-resistant antibiotics from beta-lactamase-sensitive ones in the screening of bacterial beta-lactamases against a panel of antibiotic candidates. This simple method may provide an alternative tool in choosing potent beta-lactam antibiotics for treatment of bacterial infections.

Animals↗
PubMedDate not supplied

Identification of fluorescein-5'-isothiocyanate-modification sites in proteins by electrospray-ionization mass spectrometry.

Model peptides and proteins, such as hen eggwhite lysozyme, have been modified with fluorescein-5'-isothiocyanate (FITC) to yield the corresponding fluorescein-thiocarbamoyl (FTC) conjugates (N, N'-disubstituted thiourea and dithiourethane adducts). The extent of FITC incorporation, i.e., number of modified residues, has been identified by direct molecular weight determination using matrix-assisted laser desorption-ionization and electrospray-ionization mass spectrometry (MALDI-MS; ESI-MS). A specific fragmentation by cleavage of the FTC moiety from modified residues occurs by nozzle-skimmer dissociation in ESI mass spectra at increased declustering potential. This fragmentation pathway is easily obtained and renders ESI-MS an efficient tool for the characterization of FITC-modified proteins, and identification of modification sites in FTC-peptide mixtures.

Animals↗
PubMed1995

Intestinal fatty acid binding protein: folding of fluorescein-modified proteins.

The rat intestinal fatty acid binding protein is an almost all beta-sheet protein that encloses a large interior cavity into which the fatty acid ligand binds. The protein contains neither cysteine nor proline. In a previous report, six site-directed mutants were obtained, each having a single cysteine residue [Jiang, N., & Frieden, C., (1993) Biochemistry 32, 11015-11021] either in a turn or pointed into the cavity. In this report, each mutant has been unfolded in denaturant and modified with 5-iodoacetamido-fluorescein to introduce a large, bulky, and fluorescent group into the protein at a known position. In all cases, fluorescence changes indicated that the modified protein refolded, and circular dichroism measurements suggested that the refolded protein appeared to be mostly beta-sheet. Denaturation curves suggest that for two mutants intermediate structures exist at denaturant concentrations well below the midpoint of the unfolding curve. For each modified, folded protein, one- and two-dimensional 1H NMR spectra were accumulated and compared to the unmodified and wild-type proteins. While the spectra for the modified proteins showed a number of changes in chemical shifts, they were also consistent with folded proteins on the basis of the degree of chemical shift dispersion. Of the six modified mutant proteins, two appear to have the fluorescein group located in the cavity, but only one of these did not bind fatty acid. The remaining modified proteins are capable of ligand binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Labeling the (Ca(2+)-Mg2+)-ATPase of sarcoplasmic reticulum at Glu-439 with 5-(bromomethyl)fluorescein.

The (Ca(2+)-Mg2+)-ATPase of skeletal muscle sarcoplasmic reticulum was labeled with 5-(bromomethyl)fluorescein. A stoichiometry of one label per ATPase molecule was found, which was unaffected by the presence of ATP. Labeling resulted in a 60% decrease in ATPase activity. Sequencing identified the labeled residue as Glu-439. The fluorescence emission spectrum of the labeled ATPase was unaffected by the addition of Ca2+ or vanadate or by phosphorylation with either Pi or ATP. Measurement of the pK of the bound fluorescein and observation of quenching by KI were consistent with a relatively exposed location for the fluorophore. Measurements of fluorescence energy transfer located the position of Glu-439 relative to Lys-515 and Cys-344 and relative to the membrane surface. None of these distances changed in binding Ca2+ or vanadate.

Amino Acid Sequence↗
PubMed1998

Evidence for hydrophobic interaction between galanin and the GalR1 galanin receptor and GalR1-mediated ligand internalization: fluorescent probing with a fluorescein-galanin.

Galanin is a neuropeptide that activates specific receptors to modulate several physiological functions including food intake, nociception, and learning and memory. The molecular nature of the interaction between galanin and its receptors and the fate of the galanin/receptor complex after the binding event are not understood. A fluorescein-N-galanin (F-Gal) was generated to measure the interaction between galanin and rat GalR1 galanin receptor (rGalR1) and rGalR1-mediated ligand internalization using flow cytometry in transfected Chinese hamster ovary (CHO) cells. Like galanin, F-Gal bound rGalR1 with high affinity and stimulated intracellular signaling events. Fluorescence quenching by soluble KI of rGalR1-bound F-Gal revealed a highly protected environment around the fluorescein, suggesting that the N-terminal portion of galanin, which constitutes the binding site of galanin for the receptor, binds to a protected hydrophobic binding pocket within the receptor. Exposure to F-Gal stimulated rapid (t1/2 approximately 10 min) and extensive (78%) internalization of surface F-Gal into rGalR1/CHO cells at 37 degreesC but not at 0 degreesC. In addition, the internalization did not occur in parental CHO cells at either 0 or 37 degreesC and was inhibited by addition of 0.25 M sucrose in the medium, indicating a GalR1-mediated energy-requiring endocytic process. These results revealed a hydrophobic interaction between galanin and the GalR1 receptor, which is in contrast to those of other G protein-coupled receptors that mainly require hydrophilic interaction with their peptide ligands near or outside the plasma membrane surface, and illustrated that the initial binding interaction is followed by rapid cellular internalization of the agonist/GalR1 complex.

Animals↗
PubMed2006

Direct nitric oxide detection in aqueous solution by copper(II) fluorescein complexes.

A series of FL(n) (n = 1-5) ligands, where FL(n) is a fluorescein modified with a functionalized 8-aminoquinoline group as a copper-binding moiety, were synthesized, and the chemical and photophysical properties of the free ligands and their copper complexes were investigated. UV-visible spectroscopy revealed a 1:1 binding stoichiometry for the Cu(II) complexes of FL(1), FL(3), and FL(5) in pH 7.0 buffered aqueous solutions. The reactions of FL(2) or FL(4) with CuCl(2), however, appear to produce a mixture of 1:1 and 1:2 complexes, as suggested by Job's plots. These binding modes were modeled by the synthesis and X-ray crystal structure determination of Cu(II) complexes of 2-[(quinolin-8-ylamino)methyl]phenol (modL), employed as a surrogate of the FL(n) ligand family. Two kinds of crystals, [Cu(modL)(2)](BF(4))(2) and [Cu(2)(modL')(2)(CH(3)OH)](BF(4))(2) (modL' = 2-[(quinolin-8-ylamino)methyl]phenolate), were obtained. The structures suggest that one oxygen and two nitrogen atoms of the FL(n) ligands most likely bind to Cu(II). Introduction of nitric oxide (NO) to pH 7.0 buffered aqueous solutions of Cu(FL(n)) (1 microM CuCl(2) and 1 microM FL(n)) at 37 degrees C induces an increase in fluorescence. The fluorescence response of Cu(FL(n)) to NO is direct and specific, which is a significant improvement over commercially available small molecule-based probes that are capable of detecting NO only indirectly. The NO-triggered fluorescence increase of Cu(FL(5)) occurs by reduction of Cu(II) to Cu(I) with concomitant dissociation of the N-nitrosated fluorophore ligand from copper. Spectroscopic and product analyses of the reaction of the FL(5) copper complex with NO indicated that the N-nitrosated fluorescein ligand (FL(5)-NO) is the species responsible for fluorescence turn-on. Density functional theory (DFT) calculations of FL(5) versus FL(5)-NO reveal how N-nitrosation of the fluorophore ligand brings about the fluorescence increase. The copper-based probes described in the present work form the basis for real-time detection of nitric oxide production in living cells.

Aminoquinolines↗
PubMed2001

Development and validation of an improved oxygen radical absorbance capacity assay using fluorescein as the fluorescent probe.

An improved method of oxygen radical absorbance capacity (ORAC) assay has been developed and validated using fluorescein (3',6'-dihydroxyspiro[isobenzofuran-1[3H],9'[9H]-xanthen]-3-one) as the fluorescent probe. Our results demonstrate that fluorescein (FL) is superior to B-phycoerythrin. The oxidized FL products induced by peroxyl radical were identified by LC/MS, and the reaction mechanism was determined to follow a classic hydrogen atom transfer mechanism. In addition, methodological and mechanistic comparison of ORAC(FL) with other widely used methods was discussed. It is concluded that, unlike other popular methods, the improved ORAC(FL) assay provides a direct measure of hydrophilic chain-breaking antioxidant capacity against peroxyl radical.

Antioxidants↗
PubMed2003

Syntheses of regioisomerically pure 5- or 6-halogenated fluoresceins.

Three routes to regioisomerically pure 5- and 6-iodofluoresceins or 5- and 6-bromofluoresceins are described. The first, shown in Scheme 1, involves diazotization/iodination of the corresponding aminofluoresceins. In the second approach (Scheme 2) a mixture of regioisomeric fluoresceins was prepared, and the 5-bromo isomers were isolated as the ring closed diacetates 9b and 11 by fractional crystallization. Scheme 3 shows an approach to sulfonic acid derivatives 3 and 4 of 5-iodofluorescein. This is the most convenient procedure of the three, and it is particularly useful as sulfofluoresceins have more favorable water solubility characteristics than fluoresceins that lack the sulfonic acid group.

Fluoresceins↗
PubMed1992

Adsorption of fluorescein dyes on albumin microspheres.

The surface characteristics of bovine and egg albumin microspheres were examined using four anionic dyes; sodium fluorescein, eosin, erythrosin, rose bengal, and the cationic dye rhodamine B. The adsorption isotherms of the dyes on unloaded albumin microspheres exhibited Langmuir behavior for dilute solutions of rose bengal, erythrosin, and eosin, suggesting monolayer formation in the initial stages of the sorption process. The adsorption capacity of the microspheres for the dyes (k2) and the affinity constants of the dyes for the microspheres (k1) were found to depend on both the polarizability and the hydrophobic properties of the dye, presumably reflecting the heterogeneous character of the microsphere surface. Further, the extent of sorption at higher dye concentrations was found to depend on the ability of the dye to form stable aggregates inside the microspheres and on environmental long-range forces acting at these sites. At both low and high dye concentrations, the amount adsorbed to the microsphere surface increased with increasing hydrophobicity of the dyes. The lowest adsorption was observed for the nonsubstituted dye fluorescein, whereas the most hydrophobic dye used, rose bengal, was completely adsorbed onto the microsphere surface. The data suggest that the bovine albumin microsphere surfaces are highly hydrophobic and less porous than egg albumin microsphere surfaces.

Adsorption↗
PubMedDate not supplied

Enhanced detection of malignant glioma xenograft by fluorescein-human serum albumin conjugate.

OBJECT: During the surgical resection of malignant gliomas, it is important to make clear the border zone between the tumor tissue and normal brain tissue. For this purpose, we conjugated fluorescein and human serum albumin (FLS-HSA) and compared its effectiveness against that of fluorescein-sodium (FLS-Na) alone in detecting human glioma xenografts in SCID mice through a fluorescence microscope. METHODS: We made FLS-HSA conjugate using carbodiimide as a linking reagent. SCID mice, with U251MG cells transplanted subcutaneously, were prepared as tumor models. The animals were sacrificed 15, 30, 60, 180, 360, or 720 min after the intravenous administration of either the FLS-HSA conjugate or FLS-Na alone (n = 3). Fluorescence images were taken with a digital camera, and the brightness of the tumor and that of the peripheral tissue in each image were quantified. In the group of tumor-bearing mice that received FLS-Na, the fluorescence of tumor tissue disappeared 60 min after the reagent was administered, and there was no significant difference in brightness between the tumor and peripheral tissue at any time point. On the other hand, injection of FLS-HSA revealed relative tumor-selective brightness and sufficient contrast between the tumor and surrounding tissue 60 and 360 min after administration. CONCLUSION: FLS-HSA has the advantages of specificity and persistence of fluorescence over FLS-Na for the purpose of identifying glioma nodules in xenogenic subcutaneous tumor transplantation models.

Animals↗
PubMed2002

Analysis of mean retinal transit time from fluorescein angiography in human eyes: normal values and reproducibility.

OBJECTIVE: To evaluate three different techniques to quantify retinal blood flow transit times in normal human eyes from fluorescein angiograms. SUBJECTS AND METHODS: Fluorescein angiograms were recorded on two different occasions in 18 normal individuals with a scanning laser ophthalmoscope. The angiograms were digitized (5 frames per second) and the images were aligned. Mean transit times (MTT) were analysed with a newly developed technique based on an impulse-response analysis (MTTIR) and again with the conventional technique (MTTSLOPE). Arterio-venous passage times (AVP) were also calculated. RESULTS: At the first determination, mean values (SD) for MTTIR, MTTSLOPE, and AVP were 3.22 (0.78), 4.88 (1.86), and 1.46 (0.57) seconds, respectively. Detection of an increase of 25% with a power of 80% requires groups of 12, 86 and 17 individuals for the three techniques, respectively. CONCLUSIONS: Mean transit time is a well-defined physiological parameter. The technique based on impulse-response analysis allows for analysis of even badly defined dye curves. We found this technique to be superior to the conventional technique in terms of reproducibility.

Adult↗
PubMed2000

Plasma elimination of cholyl-lysyl-fluorescein (CLF): a pilot study in patients with liver cirrhosis.

BACKGROUND: Cholyl-lysyl-fluorescein (CLF) is a fluorescein-labelled bile acid whose biological behaviour closely resembles that of naturally occurring cholyl glycine. AIM: The aim of this study was to analyze the CLF plasma elimination in patients with liver cirrhosis. METHODS: A dose of CLF at 0.02 mg/kg b.w. was administered i.v. in 26 patients with liver cirrhosis and 9 healthy volunteers. Blood samples were collected before injection and then at 10 min intervals over 60 min. Plasma fluorescence was measured by a luminescence spectrometer and residual fluorescence over the time of the study was compared in each group. Routine liver function tests (rLFTs) were performed before each injection. RESULTS: Plasma elimination of CLF was significantly impaired in patients with cirrhosis compared to healthy subjects with p values <0.0001 at each analyzed time point. CLF test showed 100% sensitivity for liver cirrhosis when residual fluorescence was measured 30, 40, 50 and 60 min after injection. Routine LFTs showed 85% sensitivity for bilirubin, 84% for total bile acids, 69% for aspartate aminotransferase 62% for albumin and 50% for alkaline phosphatase. CLF elimination measured 60 min after injection correlated with Child-Pugh score (r=0.3945; p<0.05) and albumin (rs=0.6451; p<0.001). No adverse reaction or side effects of CLF were observed. CONCLUSIONS: CLF test clearly distinguished between the two analyzed groups and was more sensitive than routine liver function tests. The test appears safe, simple to perform and analyze and after validation in larger cohorts of patients may have the potential to become a useful dynamic test of liver function.

Adult↗
PubMed1988

Patterns of blood flow in episcleral vessels studied by low-dose fluorescein videoangiography.

The blood supply of the ocular anterior segment arises from a saggittal arterial ring composed of the long posterior ciliary arteries, the muscular and anterior ciliary arteries and perforating scleral arteries. This ring supplies coronal arterial circles within and outside the globe. Low dose anterior segment fluorescein videoangiography demonstrates arterial and venous flow, recording its characteristics and direction. Videoangiograms were performed at low and high magnification in 15 normal subjects. Episcleral arteries and veins were distinguishable by the presence or absence of pulsatile flow and by their fluorescence intensity. Arteries usually perfused earlier than veins, and with higher flow velocity. Twenty-five of 40 arteries flowed away from scleral perforations close to the limbus. All 8 veins drained away from the limbus. The communication between two arteries may be demonstrated by a static, pulsating column of non-fluoresceinated blood. This sign arose at a point of scleral perforation, at the junction between muscular and anterior ciliary arteries and in the episcleral anterior circle. It supports the concept of arterial shunting, both in the saggittal plane and in the superficial coronal circle. Perforating scleral arteries lay anterior to the episcleral arterial circle in superior angiograms and posterior to it in inferior studies. Vessels that had been characterised by videoangiography were identified in stereo colour photographs of angiographic fields. Arteries were best distinguished from veins by their high tortuosity and thick walls. Using these photographic characteristics, the distribution of arteries and veins over the rectus muscles was surveyed in 13 subjects. The incidence of arteries is lowest over the lateral rectus muscle. Veins were concentrated in the vertical meridian and were absent over lateral rectus in 8 subjects. Five intra-operative videoangiograms are reported. Retraction of conjunctiva facilitated imaging of the episcleral vessels and demonstrated arterial communication through a shared capillary bed.

Adult↗