Synthesis and characterization of Pt(IV) fluorescein conjugates to investigate Pt(IV) intracellular transformations

Pt(IV) anticancer compounds typically operate as prodrugs that are reduced in the hypoxic environment of cancer cells, losing two axial ligands in the process to generate active Pt(II) species. Here we report the synthesis of two fluorescent Pt(IV) prodrugs of cisplatin in order to image and evaluate the Pt(IV) reduction process in simulated and real biological environments. Treatment of the complexes dissolved in PBS buffer with reducing agents typically encountered in cells, glutathione or ascorbate, afforded a 3- to 5-fold fluorescence turn-on owing to reduction and loss of their fluorescein-based axial ligands, which are quenched when bound to platinum. Both Pt(IV) conjugates displayed moderate cytotoxicity against human cancer cell lines, with IC50 values higher than that of cisplatin. Immunoblotting and DNA flow cytometry analyses of one of the complexes, Pt(IV)FL2, revealed that it damages DNA, causes cell cycle arrest in S or G2/M depending on exposure time, and ultimately triggers apoptotic cell death. Fluorescence microscopic studies prove that Pt(IV)FL2 enters cells intact and undergoes reduction intracellularly. The results are best interpreted in terms of a model in which the axial fluorescein ligands are expelled through lysosomes, with the platinum(II) moiety generated in the process binding to genomic DNA, which results in cell death.

Coordinated movements of eukaryotic translation initiation factors eIF1, eIF1A, and eIF5 trigger phosphate release from eIF2 in response to start codon recognition by the ribosomal preinitiation complex

Accurate recognition of the start codon in an mRNA by the eukaryotic translation preinitiation complex (PIC) is essential for proper gene expression. The process is mediated by eukaryotic translation initiation factors (eIFs) in conjunction with the 40 S ribosomal subunit and (initiator) tRNA(i). Here, we provide evidence that the C-terminal tail (CTT) of eIF1A, which we previously implicated in start codon recognition, moves closer to the N-terminal domain of eIF5 when the PIC encounters an AUG codon. Importantly, this movement is coupled to dissociation of eIF1 from the PIC, a critical event in start codon recognition, and is dependent on the scanning enhancer elements in the eIF1A CTT. The data further indicate that eIF1 dissociation must be accompanied by the movement of the eIF1A CTT toward eIF5 in order to trigger release of phosphate from eIF2, which converts the latter to its GDP-bound state. Our results also suggest that release of eIF1 from the PIC and movement of the CTT of eIF1A are triggered by the same event, most likely accommodation of tRNA(i) in the P site of the 40 S subunit driven by base pairing between the start codon in the mRNA and the anticodon in tRNA(i). Finally, we show that the C-terminal domain of eIF5 is responsible for the factor's activity in antagonizing eIF1 binding to the PIC. Together, our data provide a more complete picture of the chain of molecular events that is triggered when the scanning PIC encounters an AUG start codon in the mRNA.

Mucin deficiency causes functional and structural changes of the ocular surface

MUC5AC is the most abundant gel-forming mucin in the ocular system. However, the specific function is unknown. In the present study, a Muc5ac knockout (KO) mouse model was subject to various physiological measurements as compared to its wide-type (WT) control. Interestingly, when KO mice were compared to WT mice, the mean tear break up time (TBUT) values were significantly lower and corneal fluorescein staining scores were significantly higher. But the tear volume was not changed. Despite the lack of Muc5ac expression in the conjunctiva of KO mice, Muc5b expression was significantly increased in these mice. Corneal opacification, varying in location and severity, was found in a few KO mice but not in WT mice. The present results suggest a significant difference in the quality, but not the quantity, of tear fluid in the KO mice compared to WT mice. Dry eye disease is multifactorial and therefore further evaluation of the varying components of the tear film, lacrimal unit and corneal structure of these KO mice may help elucidate the role of mucins in dry eye disease. Because Muc5ac knockout mice have clinical features of dry eye, this mouse model will be extremely useful for further studies regarding the pathophysiology of the ocular surface in dry eye in humans.

Fluid flow along venous adventitia in rabbits: is it a potential drainage system complementary to vascular circulations?

Background

Our previous research and other studies with radiotracers showed evidence of a centripetal drainage pathway, separate from blood or lymphatic vessels, that can be visualized when a small amount of low molecular weight tracer is injected subcutaneously into a given region on skin of humans. In order to further characterize this interesting biological phenomenon, animal experiments are designed to elucidate histological and physiologic characteristics of these visualized pathways.

Methods

Multiple tracers are injected subcutaneously into an acupuncture point of KI3 to visualize centripetal pathways by magnetic resonance imaging or fluorescein photography in 85 healthy rabbits. The pathways are compared with venography and indirect lymphangiography. Fluid flow through the pathways is observed by methods of altering their hydrated state, hydrolyzing by different collagenases, and histology is elucidated by optical, fluorescein and electron microscopy.

Results

Histological and magnetic imaging examinations of these visualized pathways show they consist of perivenous loose connective tissues. As evidenced by examinations of tracers’ uptake, they appear to function as a draining pathway for free interstitial fluid. Fluorescein sodium from KI3 is found in the pathways of hind limbs and segments of the small intestines, partial pulmonary veins and results in pericardial effusion, suggesting systematical involvement of this perivenous pathway. The hydraulic conductivity of these pathways can be compromised by the collapse of their fiber-rich beds hydrolyzed by either of collagenase type I, III, IV or V.

Conclusions

The identification of pathways comprising perivenous loose connective tissues with a high hydraulic conductivity draining interstitial fluid in hind limbs of a mammal suggests a potential drainage system complementary to vascular circulations. These findings may provide new insights into a systematically distributed collagenous connective tissue with a circulatory function and their potential relevance to the nature of acupuncture meridians.

Is the use of topical fluorescein helpful for management of CSF leakage?

OBJECTIVES/HYPOTHESIS

We aimed to evaluate the effectiveness of topical intranasal fluorescence application together with high-resolution computed tomography and magnetic resonance imaging and/or magnetic resonance cisternography for the preoperative diagnosis of cerebrospinal fluid (CSF) leakage and for intraoperative localization of CSF fistulas. We also assessed postoperative recurrence.

STUDY DESIGN

Descriptive study.

METHODS

Twenty-four cases underwent endonasal endoscopic repair for CSF leakage. Following intranasal topical application of fluorescein 10% to the middle turbinate-cribriform plate region and anterior wall of the sphenoid sinus, a color change of the fluorescein from yellow-brown to green was accepted as evidence of CSF leakage. A nasoseptal flap, collagen matrix, or fascia lata and septal cartilage graft were used for reconstruction of the CSF fistula.

RESULTS

The use of topical fluorescein application was helpful in diagnosing CSF rhinorrhea preoperatively and locating the CSF fistula intraoperatively. One case had both ethmoid roof and sphenoid sinus defects, and this case underwent a second operation for closure of the sphenoid defect. All CSF leakages were successfully repaired by endoscopic endonasal surgery using a nasoseptal flap.

CONCLUSIONS

Cases with traumatic CSF leakage pose a higher risk of meningitis than the cases with spontaneous CSF leakage. Topical application of fluorescein is highly specific and sensitive in identifying preoperative, intraoperative, and postoperative CSF leakage. It is a simple, quick, and sensitive technique. The surgeon should be vigilant for multiple defects.

Gene transfer using micellar nanovectors inhibits choroidal neovascularization in vivo

PURPOSE

Age-related macular degeneration caused by choroidal neovascularization (CNV) remains difficult to be treated despite the recent advent of several treatment options. In this study, we investigated the in vivo angiogenic control by intravenous injection of polyion complex (PIC) micelle encapsulating plasmid DNA (pDNA) using a mice CNV model.

METHODS

The transfection efficiency of the PIC micelle was investigated using the laser-induced CNV in eight-week-old male C57 BJ/6 mice. Firstly, each mouse received intravenous injection of micelle encapsulating pDNA of Yellow Fluorescent Protein (pYFP) on days 1,3 and 5. The expression of YFP was analyzed using fluorescein microscopy and western blotting analysis. In the next experiments, each mouse received intravenous injection of micelle encapsulating pDNA of soluble Fms-like tyrosine kinase-1 (psFlt-1) 1,3 and 5 days after the induction of CNV and the CNV lesion was analyzed by choroidal flatmounts on day 7.

RESULTS

Fluorescein microscopy and western blotting analysis revealed that the expression of YFP was confirmed in the CNV area after injection of the PIC micelle, but the expression was not detected neither in mice that received naked pDNA nor those without CNV. Furthermore, the CNV area in the mice that received intravenous injection of the psFlt-1-encapsulated PIC micelle was significantly reduced by 65% compared to that in control mice (p<0.01).

CONCLUSIONS

Transfection of sFlt-1 with the PIC micelle by intravenous injection to mice CNV models showed significant inhibition of CNV. The current results revealed the significant potential of nonviral gene therapy for regulation of CNV using the PIC micelle encapsulating pDNA.

Micelle nanoparticles for FRET-based ratiometric sensing of mercury ions in water, biological fluids and living cells

A fluorescence resonance energy transfer (FRET) based ratiometric sensing system for mercury ions is built in nano-sized core/corona micelles formed by a poly(ethylene oxide)-b-polystyrene diblock copolymer. For this system, a hydrophobic fluorescein derivative (FLS-C12), which serves as the energy transfer donor, is incorporated into the micelle core during the micelle formation; and a spirolactam-rhodamine derivative (RhB-CS) as a probe for mercury ions is located at the micelle core/corona interface. An efficient ring-opening reaction of RhB-CS induced by mercury ions generates the long-wavelength rhodamine B fluorophore which can act as the energy acceptor, affording the micelle nanoparticles the water-dispersible FRET-based ratiometric detection system for mercury ions, with a detection limit of 0.1 µM in water. The donor and the probe fluorophores, with their structure being appropriately modified, can strongly bind (non-covalently) to the specific sites of the micelles and form a stable ratiometric sensor in water and in some biological fluids. In addition, with the water-soluble and biocompatible poly(ethylene oxide) (PEO) as the corona of the micelles, the nano-sized sensing system can readily permeate through cell membrane and detect intracellular Hg(2+) level changes.

Ocular manifestation of rheumatoid arthritis-different forms and frequency

Rheumatoid arthritis (RA) is a systemic inflammatory disease associated with a number of extra-articular organ manifestations. Ocular manifestations involved with RA are keratoconjunctivitis sicca, episcleritis, scleritis , corneal changes, and retinal vasculitus. The etiopathogenesis of this autoimmune disorder is still unknown. Aim of our study was to present different ocular manifestations of RA and their frequency. We have examined 691 patient with the diagnoses of RA. All examined patients were in I or II stage of the disease according to criteria of The American College of Rheumatology. Ophthalmological exam obtained: visual acuity by Snellen sings, biomicroscopy of anterior segment, Schirmer test, tear break-up time (BUT), applanation tonometry and indirect ophthalmoscopy. In all patients with retinal vasculitis fotofundus and in indicated cases fluorescein angiography was preformed. The most common manifestation of ocular involvement was keratoconjunctivitis sicca. Episcleritis was diagnosed in 5.06% patients with RA, while scleritis was present in 2.06% of patients. Diffuse scleritis was present in one patient, while nodular was present in 13 patients. There were no patients with posterior or necrotizing scleritis among examined patients. Sclerosing keratitis was diagnosed in 11 female patients. It is characterized with peripheral thickening and opacification of the stroma adjacent to the site of inflammation. Posterior scleritis or scleromalacia of cornea was not present in our patients, because all of them were in I or II stage of disease. Retinal vasculitis was present in three patients, two male and one female patient (0.45%). Ocular manifestation was present in 27.2% of patients. Women were more affected.

Mesoporous silica nanotubes coated with multilayered polyelectrolytes for pH-controlled drug release

Two kinds of inorganic/organic hybrid composites based on mesoporous silica nanotubes (MSNTs) and pH-responsive polyelectrolytes have been developed as pH-controlled drug delivery systems via the layer by layer self-assembly technique. One system was based on alternatively loading poly(allylamine hydrochloride) and sodium poly(styrene sulfonate) onto as-prepared MSNTs to load and release the positively charged drug doxorubicin. The other system was synthesized by alternately coating sodium alginate and chitosan onto amine-functionalized MSNTs, which were used as vehicles for the loading and release of the negatively charged model drug sodium fluorescein. Controlled release of the drug molecules from these delivery systems was achieved by changing the pH value of the release medium. The results of in vitro cell cytotoxicity assays indicated that the cell killing efficacy of the loaded doxorubicin against human fibrosarcoma (HT-1080) and human breast adenocarcinoma (MCF-7) cells was pH dependent. Thus, these hybrid composites could be potentially applicable as pH-controlled drug delivery systems.

Vasoconstrictive Effects of Sodium Fluorescein on Retinal Vessels Is Increased by Light Exposure

PURPOSE

To determine whether clinically relevant doses of sodium fluorescein produce changes in vascular tone in retinal arterioles and veins and whether any such effects were light dependent.

METHODS

Segments of porcine retinal arterioles and veins were dissected, cannulated, and perfused and their outer diameter monitored during intraluminal application of increasing doses (10(-10) to 10 (-3) g/ml) of sodium fluorescein under either brightly lit (350 lux) or dimly lit (4 lux) conditions. The significance of any induced change in vessel diameter was assessed in relation to the initial vessel diameter.

RESULTS

At the higher light level, sodium fluorescein produced a significant dose-dependent contraction in porcine retinal arterioles and veins with a threshold of 10 (-5) g/ml and 10 (-9) g/ml sodium fluorescein, respectively. At the maximal dose tested (10(-3) g/ml), vessel diameter was reduced to approximately 85% of the initial vessel diameter in retinal arterioles and veins. Under dimly lit conditions, the vasoconstrictive effect of sodium fluorescein was still evident but the constriction was significantly smaller (p < 0.05) in both arteries and veins, reaching approximately 91% and 93%, respectively.

CONCLUSIONS

Sodium fluorescein induced light-dependent vasoconstrictive effects on the retinal vasculature of the pig. Should a similar effect be present in human retinal vessels, then reduced illumination level may limit the vasoconstrictive effects of sodium fluorescein when used in routine ophthalmic examinations.

Intravenous application of fluorescein for confocal laser scanning microscopy: evaluation of contrast dynamics and image quality with increasing injection-to-imaging time

BACKGROUND

Confocal laser scanning microscopy (CLSM) is reported to be a promising tool for in vivo histopathology during an endoscopy. The most commonly used fluorophore is fluorescein sodium given intravenously. However, so far, there are no objective data on contrast dynamics and image quality over time after injection of the substance.

OBJECTIVE

We aimed to investigate the ideal time period for the best CLSM imaging when using fluorescein sodium.

DESIGN

The proximal stomachs of 4 anesthetized pigs were examined via standard endoscopes with a portable confocal miniprobe. After injection of 1% fluorescein intravenously (0.1 mL/kg body weight), consecutive sequences were recorded after 1, 2, 3, 5, 8, 20, 30, 40, 50, and 60 minutes. After the procedure, histograms, which represented signal intensity of 20 images (at respective time points), were analyzed from representative regions of interest (ROI). The mean (standard deviation [SD]) pixel value of the pixel values in the ROI were noted. A signal-to-noise ratio (SNR), defined as the ratio between the mean and the SD, was calculated. In addition, 5 images per time period were put into a random order and then blindly evaluated by 2 endoscopists.

RESULTS

A total of 560 histograms from selected ROIs were analyzed. The SNR decreased significantly after 8 minutes, with the lowest values being reached after 30 minutes. Subjective evaluation of still images also demonstrated a continuous decrease, with the lowest image quality after 30 minutes. A slight increase of image quality after 40 minutes occurred because of extramucosal leakage of fluorescein, with fluorophore deposits in the crypt orifices.

CONCLUSIONS

In the pig model, fluorescein-based CLSM of the GI tract delivered the best contrast and image quality within the first 8 minutes after injection of the fluorophore. These data might facilitate standardization of the procedure for research purposes but may also help when applying this new technology in a daily routine manner.

The mystery of cotton-wool spots - a review of recent and historical descriptions

PURPOSE

Cotton-wool spots (CWSs) lie superficially as opaque swellings in the retina, with occurring as acute lesions. The occurrence of CWSs is a sign of serious vascular damage.

METHODS

CWSs can usually be diagnosed by ophthalmoscopy. In the literature, there are reports of examinations by fluorescein angiography, visual fields, or optical coherence tomography (OCT).

RESULTS

CWSs are non-specific, as they can occur in different diseases involving the retinal vascular system. CWSs are localized accumulations of axoplasmic debris within adjacent bundles of ganglion cell axons. They occur after arteriolar occlusion at the borders of large ischemic areas, and should not be regarded as retinal fiber layer infarcts (McLeod). The "principal constituent of the CWS" are cytoid bodies. Microaneurysms may be present at the edge of some CWSs in different diseases with retinal ischemia. The presence of many CWSs may be a significant predictor for the development of rubeosis iridis, for instance in a patient with central retinal vein occlusion. CWSs have disappeared in weeks or occasionally a few months in hypertensive patients. However, in diabetic patients, they may persist for as long as one or two years. CWSs have been the most frequent ocular findings in patients with Aids. Aids patients show a strong correlation between CWSs and multiple opportunistic infections. Aids patients with CWSs have shown a poorer prognosis compared to those without CWSs. Leukocyte counts were found to be significantly lower, and the proportion of patients with significant weight loss was greater among Aids patients who revealed CWSs.

CONCLUSION

CWSs delineate ischemic retina, which is attributed to obstruction of axoplasmic transport. Ischemia is the essential factor in the development of CWSs. Early detection of a CWS is necessary to evaluate a hitherto occult systemic disease with a vascular component.

Neuroinvasion of fluorescein-positive monocytes in acute simian immunodeficiency virus infection

Monocytes and macrophages play a central role in the pathogenesis of human immunodeficiency virus (HIV)-associated dementia. They represent prominent targets for HIV infection and are thought to facilitate viral neuroinvasion and neuroinflammatory processes. However, many aspects regarding monocyte brain recruitment in HIV infection remain undefined. The nonhuman primate model of AIDS is uniquely suited for examination of the role of monocytes in the pathogenesis of AIDS-associated encephalitis. Nevertheless, an approach to monitor cell migration from peripheral blood into the central nervous system (CNS) in primates had been lacking. Here, upon autologous transfer of fluorescein dye-labeled leukocytes, we demonstrate the trafficking of dye-positive monocytes into the choroid plexus stromata and perivascular spaces in the cerebra of rhesus macaques acutely infected with simian immunodeficiency virus between days 12 and 14 postinfection (p.i.). Dye-positive cells that had migrated expressed the monocyte activation marker CD16 and the macrophage marker CD68. Monocyte neuroinvasion coincided with the presence of the virus in brain tissue and cerebrospinal fluid and with the induction of the proinflammatory mediators CXCL9/MIG and CCL2/MCP-1 in the CNS. Prior to neuroinfiltration, plasma viral load levels peaked on day 11 p.i. Furthermore, the numbers of peripheral blood monocytes rapidly increased between days 4 and 8 p.i., and circulating monocytes exhibited increased functional capacity to produce CCL2/MCP-1. Our findings demonstrate acute monocyte brain infiltration in an animal model of AIDS. Such studies facilitate future examinations of the migratory profile of CNS-homing monocytes, the role of monocytes in virus import into the brain, and the disruption of blood-cerebrospinal fluid and blood-brain barrier functions in primates.

Surfaces and interfacial water: evidence that hydrophilic surfaces have long-range impact

It is generally thought that the impact of surfaces on the contiguous aqueous phase extends to a distance of no more than a few water-molecule layers. Older studies, on the other hand, suggest a more extensive impact. We report here that colloidal and molecular solutes suspended in aqueous solution are profoundly and extensively excluded from the vicinity of various hydrophilic surfaces. The width of the solute-free zone is typically several hundred microns. Such large exclusion zones were observed in the vicinity of many types of surface including artificial and natural hydrogels, biological tissues, hydrophilic polymers, monolayers, and ion-exchange beads, as well as with a variety of solutes. Using microscopic observations, as well as measurements of electrical potential and UV-Vis absorption-spectra, infrared imaging, and NMR imaging, we find that the solute-free zone is a physically distinct and less mobile phase of water that can co-exist indefinitely with the contiguous solute-containing phase. The extensiveness of this modified zone is impressive, and carries broad implication for surface-molecule interactions in many realms, including cellular recognition, biomaterial-surface antifouling, bioseparation technologies, and other areas of biology, physics and chemistry.

Evidence of ball-and-chain transport of ferric enterobactin through FepA

The Escherichia coli iron transporter, FepA, has a globular N terminus that resides within a transmembrane beta-barrel formed by its C terminus. We engineered 25 cysteine substitution mutations at different locations in FepA and modified their sulfhydryl side chains with fluorescein maleimide in live cells. The reactivity of the Cys residues changed, sometimes dramatically, during the transport of ferric enterobactin, the natural ligand of FepA. Patterns of Cys susceptibility reflected energy- and TonB-dependent motion in the receptor protein. During transport, a residue on the normally buried surface of the N-domain was labeled by fluorescein maleimide in the periplasm, providing evidence that the transport process involves expulsion of the globular domain from the beta-barrel. Porin deficiency much reduced the fluoresceination of this site, confirming the periplasmic labeling route. These data support the previously proposed, but never demonstrated, ball-and-chain theory of membrane transport. Functional complementation between a separately expressed N terminus and C-terminal beta-barrel domain confirmed the feasibility of this mechanism.

Fluorescence study of DNA binding and bending by EcoRI DNA methyltransferase

We have applied fluorescence anisotropy and fluorescence resonance energy transfer (FRET) techniques to study the interaction between EcoRI DNA methyltransferase (M.EcoRI) and its target DNA in solution. Upon binding with M.EcoRI, the dsDNA containing GAATTC bends to flip out the second adenine for methylation. The binding affinity of M.EcoRI to two dsDNA fragments (20 and 38 bp) was studied with fluorescence anisotropy. Their binding constants at different temperatures from 20 to 40 degrees C were obtained, and the thermodynamic parameters of binding were derived. The results showed that M.EcoRI had a higher binding affinity to the short dsDNA strand than to the long one, and its binding to DNA was primarily entropy-driven. By labeling the 5' ends of the 20-bp dsDNA with two fluorescent dyes, fluorescein (FAM) and tetramethylrhodamine (TMR), we were able to monitor the enhanced TMR fluorescence in the presence of M.EcoRI. The end-to-end distance of the dsDNA determined from the FRET efficiency was changed from 72.4 to 63.4 A, and the DNA bending angle was estimated as 57.8 degrees .

β3-Adrenergic eNOS stimulation in left ventricular murine myocardium

This study investigates mechanisms underlying β3-adrenergic activation of the endothelial nitric oxide synthase (eNOS) in myocardial tissue of wild-type (WT) and β3-adrenoceptor knockout (β3-KNO) mice, in the absence and presence of BRL 37344 (BRL), the preferential β3-adrenoceptor selective agonist. Nitric oxide (NO)-liberation was measured after the application of BRL (10 µmol/L), using fluorescence dye diaminofluorescein (DAF), in left ventricular cardiac preparations. Phosphorylation of eNOSSer1177, eNOSThr495, eNOSSer114, and eNOS translocation, and alterations of 8-isoprostaglandin F2α (a parameter for reactive oxygen radical generation), after application of BRL (10 µmol/L), were studied using immunohistochemical stainings in isolated, electrically stimulated (1 Hz) right atrial (RA) and left ventricular (LV) myocardium. An increased NO release after BRL application (10 µmol/L) was observed in the RA and LV myocardial tissue of WT mice, but not in β3-KNO mice. This NO liberation in WT mice was paralleled by an increased eNOSSer1177, but not eNOSThr495, phosphorylation. A cytosolic eNOS translocation was observed after the application of BRL (10 µmol/L) only in the RA myocardial tissue of WT mice. A BRL (10 µmol/L)-dependent increase in eNOSSer114 phosphorylation was observed only in the LV myocardial tissue of WT mice; this was paralleled by an increase in 8-isoprostaglandin F2α. In murine myocardium, 3 β3-adrenoceptor-dependent activation pathways for eNOS exist (i.e., a translocation and phosphorylation of eNOSSer1177 and eNOSSer114). These pathways are used in a regional-dependent manner. β3-adrenergic oxygen-derived free radical production might be important in situations of enhanced β3-adrenoceptor activation, as has been described in human heart failure.

Effects of topical anaesthetics and fluorescein on the real-time PCR used for the diagnosis of Herpesviruses and Acanthamoeba keratitis

BACKGROUND

The early microbiological diagnosis of corneal infections may prevent the condition from worsening.

AIM

To study the potential interferences of oxybuprocain and fluorescein solutions used by ophthalmologists on the performances of the real-time polymerase chain reaction (PCR) carried out as routine test for diagnosis of keratitis.

METHODS

Quantified suspensions of Herpes simplex virus (HSV1), Varicella zoster virus (VZV), Cytomegalovirus (CMV) and Acanthamoeba with and without oxybuprocain or fluorescein added before DNA extraction were tested by real-time PCR.

RESULTS

The capacities of the real-time PCR to detect HSV, VZV, CMV and Acanthamoeba were reduced by oxybuprocain and fluorescein. Both products diluted to 1/16 reduced the PCR detection capacities for more than 2 logs (DNA copies/sample).

CONCLUSIONS

The simultaneous introduction of fluorescein or topical anaesthetics into the tubes containing the specimens to be tested by PCR may lead to false negative results. Because corneal specimens for microbiological diagnosis of keratitis are obtained after topical administration of anaesthetics and corneal staining with fluorescein, ophthalmologists should be aware to rinse the eye surface intensively with appropriate eye solutions to minimise the risks of misdiagnosis.

Agar plate freezing assay for the in situ selection of transformed ice nucleating bacteria

An agar plate freezing assay is described based on the incorporation of fluorescein dye in agar medium. Upon addition of fluorescein the medium becomes transparent. This facilitates the monitoring of the ice nucleation event in vivo and the subsequent in situ selection of transformed ice nucleating bacteria. In comparison with known assays for the screening of transformants, the proposed assay is very accurate and reproducible. It may be applied in environmental samples screening for ice nucleating organisms, or in cDNA or genomic libraries for identifying novel ice nucleation genes. It may also prove useful in comparative studies of the ice nucleation activity, e.g. in directed evolution experiments involving ice nucleation genes.

Fluorescence anisotropy and FRET studies of G-quadruplex formation in presence of different cations

Results of the steady-state fluorescence, anisotropy and FRET measurements of G-quadruplex formation in the presence of selected cations (Li(+), Na(+), K(+), NEt(4)(+) and Mg(2+)) are reported. Three different fluorescent oligonucleotides with human telomeric sequence labeled with fluorescein (FAM) and tetramethylrhodamine (TAMRA) were investigated: a dual-labeled 21-mer denoted as PSO (Potassium Sensing Oligonucleotide) and two 5'- and 3'- single-labeled probes, FAM-21 and 21-TAMRA, respectively. The fluorescence signal of FAM-21 increased significantly for all systems and the fluorescence enhancement was comparable in magnitude for monovalent cations but it was more pronounced for Mg(2+) cation. This phenomenon was attributed to the protolytic equilibria of FAM affected by the variation in ionic strength. On the other hand, fluorescence of TAMRA was enhanced selectively by Na(I) cation that was explained by the dequenching of TAMRA emission originated from the peculiarity of the basket-type structure of Na(I)-quadruplex. Anisotropy of FAM-21 (but not 21-TAMRA) appeared to be sensitive to the G-quadruplex formation, showing significant increase with an increase in cation concentration and indicating some restrictions in rotational depolarization of FAM. FRET experiments revealed that all tested cations caused quenching of FAM fluorescence in PSO, but only Na(+) and K(+) ions produced sensitized emission of TAMRA acceptor. Higher FRET efficiency observed in the presence of sodium ion was attributed to the specific spectral factor and steric interactions in the basket-type Na(I)-quadruplex.

Solving an enigma: Arterial pole development in the zebrafish heart

It is a widely held belief that the arterial pole of the zebrafish heart is unusual among models of comparative cardiogenesis. This is based, in part, on the report that the bulbus arteriosus undergoes a striated-to-smooth muscle phenotypic transition during development. An implication of this is that the zebrafish, a model almost ubiquitously accepted in other fields of comparative biology, may be poorly suited to the study of conotruncal abnormalities in human disease. However, while the use of atrioventricular-specific molecular markers has allowed extensive characterization of the development of the atrium and ventricle, the lack of any bulbus-specific markers has meant that this region of the zebrafish heart is poorly characterized and quite possibly misunderstood. We have discovered that the fluorescent nitric oxide indicator 4,5-diaminofluorescein diacetate (DAF-2DA) specifically labels the bulbus arteriosus throughout development from approximately 48 h post-fertilization. Therefore, using DAF-2DA and an immunohistochemical approach, we attempted to further characterize the development of the bulbus. We have concluded that no such phenotypic transition occurs, that contrary to current thinking, aspects of zebrafish arterial pole development are evolutionarily conserved, and that the bulbus should not be considered a chamber, being more akin to the arterial trunk(s) of higher vertebrates.

Automated change analysis from fluorescein angiograms for monitoring wet macular degeneration

Detection and analysis of changes from retinal images is important in clinical practice, quantitative scoring of clinical trials, computer-assisted reading centers, and in medical research. This paper presents a fully-automated approach for robust detection and classification of changes in longitudinal time-series of fluorescein angiograms (FA). The changes of interest here are related to the development of choroidal neo-vascularization (CNV) in wet macular degeneration. Specifically, the changes in CNV regions as well as the retinal pigment epithelium (RPE) hypertrophic regions are detected and analyzed to study the progression of disease and effect of treatment. Retinal features including the vasculature, vessel branching/crossover locations, optic disk and location of the fovea are first segmented automatically. The images are then registered to sub-pixel accuracy using a 12-dimensional mapping that accounts for the unknown retinal curvature and camera parameters. Spatial variations in illumination are removed using a surface fitting algorithm that exploits the segmentations of the various features. The changes are identified in the regions of interest and a Bayesian classifier is used to classify the changes into clinically significant classes. The automated change analysis algorithms were found to have a success rate of 83%