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At least 631 records · Page 35Linked to original sources
PubMed1992

[Noninvasive metabolic analysis of the diabetic cornea and lens: in vivo measurement].

In vivo measurement of metabolic changes in diabetic cornea and lens were performed using redox fluorometry in nonobese diabetic (NOD) mice. Autofluorescence from reduced pyridine nucleotides (PN) and oxidized flavoproteins (Fp) were measured, and the PN/Fp ratio was used as a tissue metabolism indicator. The PN/Fp ratios were significantly higher in the diabetic corneal endothelium. Morphometric analysis of the corneal endothelium using specular microscopy revealed no significant differences between the two groups. These results indicate that redox fluorometry is able to detect early metabolic changes in the corneal endothelium and lens epithelium, which are induced by diabetes mellitus. Activation of the polyol pathway may be responsible for the change. Corneal epithelia may be less susceptible to diabetic changes than the corneal endothelium and lens epithelium.

Animals↗
PubMed1992

Determining zinc coproporphyrin in maternal plasma--a new method for diagnosing amniotic fluid embolism.

We measured the concentration of zinc coproporphyrin I (ZnCP-I), a characteristic component of meconium, in maternal plasma by fluorometry after HPLC. We obtained plasma samples from 89 women: 35 at weeks 10-40 of normal pregnancy, 41 shortly after normal delivery, 4 from patients with amniotic fluid embolism (AFE), and 9 from non-AFE patients with intra- or postpartum shock caused by genital bleeding. The plasma ZnCP-I concentration was 97 (SD 83, range 38-240) nmol/L in the AFE patients, 11 (SD 9.2) nmol/L in the non-AFE patients, 12 (SD 7.9) nmol/L during normal pregnancy, and 26 (SD 10) nmol/L shortly after normal delivery. We suggest that measuring ZnCP-I in maternal plasma by fluorometry on HPLC is a rapid, noninvasive, and sensitive method for diagnosing AFE and propose 35 nmol/L as the cutoff value for the ZnCP-I concentration in maternal plasma for the diagnosis of AFE.

Adult↗
PubMed2006

[Determination of tetracyclines by a new spectrum technique].

Tetracyclines are light-fluorescence substances, which cannot be detected directly by fluorometry. Herein a new spectrum method was proposed to detect tetracyclines directly by fluorometry. Under optimal conditions, the calibration graph is linear over the range 0.10-9.00 microg x mL(-1) for tetracyclines, and the detection limits of tetracycline, oxytetracycline, chlortetracycline and doxycycline are 0.065, 0.067, 0.068 and 0.070 microg x mL(-2), respectively.

Anti-Bacterial Agents↗
PubMed1990

Methods of theophylline assay and therapeutic monitoring of this drug.

The purpose of this article is to review various analytical methods of monitoring plasma theophylline. This article was investigated by the "Drug Commission" of SFBC (Société Française de Biologie Clinique). The primary objective is to provide the "know-how", particular for this analysis, which allows the choice between various analytical methods available: immunochemical or physiochemical ones. The techniques described are not necessarily the best, they are approved and tested methods which are the most frequently used in routine practice. The proposed immunochemical methods are: absorption spectroscopy methods: Enzyme ImmunoAssay (EIA), Enzyme Multiplied ImmunoAssay Technique (EMIT); Reflectance spectroscopy method: Apoenzyme Reactivation Immunoassay System (ARIS); Fluorometry spectroscopy method: Substrate Labeled FluoroImmunoAssay (SLFIA); Fluorometry spectroscopy on solid base; Polarization fluorescence spectroscopy ImmunoAssay (FPIA); Turbidimetric measurements: Particle Enhanced Turbidimetric Inhibition ImmunoAssay (PETINIA); Nephelometric measurement: Nephelometric Inhibition ImmunoAssay (NIIA). And the proposed physicochemical methods are: High Performance Liquid Chromatography (HPLC), Gas Chromatography (GC). The second objective is a review of pharmacological properties of theophylline, necessary for a good understanding of therapeutic drug monitoring: intestinal resorption, distribution, metabolism and elimination, drug interactions, dose/response relationship, physiopathological variations and proposed "predictive" "theophylline test". The authors conclude that because of the multiplicity of methodologies used in theophylline therapeutic monitoring the choice of one of them is not easy. The best way to compare different techniques available would be the use of a "reference material" for theophylline monitoring and a quality control network between different clinical pharmacological laboratories.

Chromatography, Gas↗
PubMed1990

Time-resolved fluorescence in biospecific assays.

Fluorescent lanthanide chelates and their detection using time-resolved fluorometry for in vitro as well as for microscopic bio-specific assays are reviewed, with reference to other fluorescent dyes and labelling materials. The minimum detectable dose of labelled components and the theoretical ultimate sensitivities of immunoassays and DNA-assays are discussed and compared with experimental results. It is concluded that the time-resolved fluorometry provides a high sensitivity labelling method in immunoassays, and a sensitivity comparable to phosphorus-32 in DNA hybridization assays. It is also concluded that lanthanide chelates are a potential alternative for organic fluorescent dyes in microscopy and that they are most useful in multiparameter assays. The combination of organic fluorescent dyes and lanthanide chelates provides the highest separation efficiency between two assay parameters.

DNA Probes↗
PubMedDate not supplied

Comparison of two immunochemical methods with thin-layer chromatographic methods for determination of aflatoxins.

Three different methods were compared for the determination of total flatoxins in corn and peanuts naturally contaminated with aflatoxins and in corn, peanuts, cottonseed, peanut butter, and poultry feed spiked with aflatoxins B1, B2, and G1. The 3 methods were an enzyme-linked immunosorbent assay (ELISA) screening test; a monoclonal antibody-affinity column-solid-phase separation method; and the AOAC official thin-layer chromatography (TLC) methods for all except poultry feed, for which Shannon's TLC method for mixed feed was used. The ELISA test is designed to provide only positive results for total aflatoxins at greater than or equal to 20 ng/g or negative results at less than 20 ng/g. The affinity column separation is coupled with either bromination solution fluorometry to estimate total aflatoxins or liquid chromatography (LC) to quantitate individual aflatoxins. Fluorodensitometry was used to determine aflatoxins in commodities analyzed by the TLC methods. The LC and TLC results were in good agreement for all the analyses. The results for the affinity column using bromination solution fluorometry were similar except those for cottonseed, which were about 60% higher. The ELISA screening method correctly identified naturally contaminated corn and peanut positive samples. No false positives were found for controls. The correct response for spiked corn, raw peanuts, peanut butter, and cottonseed at greater than or equal to 20 ng aflatoxins/g was about 90%. The correct response for spiked poultry feed at greater than or equal to 20 ng aflatoxins/g was about 50%.

Aflatoxins↗
PubMed1989

[Modification of the determination of lipid peroxidation products in a reaction with thiobarbituric acid].

The aim of the study was to choose the optimal conditions for spectrophotometry of the blood serum lipid peroxidation (LPO) products by the thiobarbituric acid (TBA) test. LPO products have been measured in trichloroacetic acid filtrate and in lipoprotein sediment by spectrophotometry and fluorometry. The optimal conditions for spectrophotometry of TBA-active LPO products are as follows: the proteins are sedimented with 20% solution of phosphotungstic acid, stabilizing the pH values in 1.3-1.5 range; the incubation temperature is 99-100 degrees C; the optic density of the aqueous extract is measured spectrophotometrically at wavelengths 535 and 580 nm. The suggested method permits spectrophotometry of LPO products without additional extraction with butanol, and its results are compatible with those of fluorometry. The coefficient of convergence variations is 3.42%, the repeatability factor 3.31%.

Humans↗
PubMed1989

[A method of suturing of dilated cardial veins in patients with portal hypertension].

Ultrasonic fluorometry used in 22 patients with portal hypertension facilitates the detection, marking the venous trunks of the cardia with inflammatory alterations of the mucosa. Intraoperative control of surgical treatment with the help of ultrasonic fluorometry allows operations to be performed more radically and to considerably reduce the intraoperative blood loss.

Cardia↗
PubMed1979

New fluorometric analysis for mandelic and phenylglyoxylic acids in urine as an index to styrene exposure.

I describe a new fluorometric method for determination of mandelic and phenylglyoxylic acids in urine, the fluorometry being preceded by extraction into ether and thin-layer chromatography. The chromatographically separated acids were quantitated after conversion to stable highly fluorescent derivatives by treatment with concentrated sulfuric acid. This method proves to be more precise, accurate, and reproducible than the existing colorimetric method. The limit of detection is 2 microgram of either acid per milliliter of urine with a CV of less than 15%. The standard curve for either acid is essentially linear from 2 to 100 microgram/mL of urine, with a correlation coefficient (r) of 0.97. No satisfactory correlation was obtained between the concentrations of either acid metabolite as measured in rat urine by fluorometry and colorimetry. The present method is considered suitable for routine biological monitoring of persons exposed to both high and low concentrations of styrene.

Animals↗
PubMed1994

Characterization of photodynamic actions of rose bengal on cultured cells.

PURPOSE: The authors have previously reported successful photodynamic occlusion of corneal blood vessels using intravenous rose bengal and argon green laser irradiation. To explore the action mechanism of this novel technique of photothrombosis, they examined the photodynamic effect of rose bengal on cultured fibroblasts, smooth muscle cells, and vascular endothelium--the cellular components of blood vessels. METHODS: Five types of cells were exposed to different concentrations of rose bengal and argon green laser irradiation. The irradiated cell areas were analyzed by fluorescence microscopy and fluorometry. Various potential quenchers and proteins were tested for their modulation of the photodynamic action. RESULTS: Upon irradiation with 16 W/cm2 of argon green laser light in conjunction with rose bengal concentrations extending above 1 x 10(-4) M, all cultured cell types showed a dose-dependent photobiologic effect characterized by constriction and detachment of the laser-irradiated cell region from the rest of the cell monolayer. In addition, there was dye photobleaching and development of a blue shift of the fluorescence excitation and emission maxima in the irradiated cell areas. Binding of rose bengal to intracellular components was demonstrated by fluorescence microscopy and by fluorometry showing a red shift of the excitation maximum compared to the maximum in solution. This binding was a prerequisite for expression of the described photobiologic effect, because polymer-conjugated rose bengal (Sensitox II) failed to reproduce it. The addition of native or heat-inactivated bovine serum albumin or catalase decreased this photobiologic effect also owing to dye binding, as indicated by G-75 Sephadex gel filtration chromatography. CONCLUSION: These results indicate that the specific photobiologic effect of monolayer contraction, which simulates the vasoconstriction seen during photothrombosis under argon green irradiation, appears to be caused by the photochemical interaction of rose bengal bound with intracellular components.

Animals↗
PubMed1994

Biochemical and biophysical properties of recombinant human interphotoreceptor retinoid binding protein.

PURPOSE: Interphotoreceptor retinoid-binding protein (IRBP) binds and transports retinoids and fatty acids in the interphotoreceptor space (IPS). To understand the relationship between the protein structure and its functions requires bulk quantities of human IRBP. The authors sought to produce recombinant human IRBP (rhIRBP), a perfect duplicate in amino acid sequence of the authentic human protein. This material could serve as a supply of the protein and later could be used to make mutants of the protein. The goals of the present study were to produce human IRBP in an expression system and to examine some of its biochemical properties. METHODS: A cDNA encoding human IRBP was cloned into the transplacement vector, pVL1392, and the plasmid was recombined with linearized baculovirus on cotransfection into Sf9 cells. Viruses containing the human IRBP cDNA were identified by polymerase chain reaction analysis. IRBP was secreted from virus-infected insect cells. rhIRBP was purified from cell medium and was examined by chromatography, N-terminal protein sequencing, immunologic techniques, and fluorometry. Eyecup and retina washes of human donor eyes provided a source of authentic human IRBP (IPS-IRBP). RESULTS: rhIRBP and IPS-IRBP exhibit similar elution profiles on concanavalin A, ion-exchange, and size exclusion chromatography. rhIRBP contains a five-amino-acid propeptide at the N-terminus as deduced from the cDNA sequence. Retinol binding of rhIRBP has been characterized by fluorometric titration. The dissociation constant is approximately 1.04 microM, close to that reported for bovine IRBP. By scanning fluorometry, the emission and excitation maxima are 479 nm and 339 nm, respectively. CONCLUSIONS: The baculovirus system provides an excellent method to produce and secrete human IRBP. The recombinant protein can be readily purified from cell culture medium. Its behavior in chromatography and in binding studies suggests that the recombinant protein is virtually identical to the authentic protein. This validates its use in place of IRBP from human donor eyes. Small, but significant, differences in biochemical properties in comparing human and bovine material highlight the significance of studying the human protein.

Amino Acid Sequence↗
PubMed1994

Amyloid fibril formation in gelsolin-derived amyloidosis. Definition of the amyloidogenic region and evidence of accelerated amyloid formation of mutant Asn-187 and Tyr-187 gelsolin peptides.

BACKGROUND: We have recently shown that the actin-modulating cytoskeletal and plasma protein gelsolin is involved in the pathogenesis of familial amyloidosis of Finnish type. To define the amyloidogenic region(s) in gelsolin and clarify the mechanisms involved in amyloid formation, we tested the amyloidogenicity of synthetic gelsolin peptide analogues. EXPERIMENTAL DESIGN: The in vitro amyloid fibril formation was studied using 22 synthetic peptides 7 to 30 residues long having sequence homology with wild-type or mutant gelsolins. Amyloid formation was monitored by Congo-red staining and polarization microscopy of the peptide aggregates, by negative staining electron microscopy, and by quantitative fluorometry with thioflavine T. RESULTS: Ultrastructurally, amyloid-like fibrils were formed from the mutant Asn-187 and Tyr-187 gelsolin peptides corresponding to the naturally occurring missense mutations found in familial gelsolin amyloidosis syndromes, as well as from a gelsolin peptide having a Val-187 substitution. The shortest peptide tested that was capable of forming amyloid-like fibrils was 9-residue mutant Asn-187 peptide. The corresponding wild-type peptide did not form amyloid. Quantitative fluorometry at the emission maximum 482 nm revealed highly accelerated amyloid fibril formation of the mutant Asn-187, Tyr-187 and Val-187 peptides as compared with the corresponding wild-type peptides. CONCLUSIONS: We have defined the amyloidogenic region of gelsolin to a 9-residue sequence in the highly conserved repetitive motif B and showed that residue 187 represents a critical site where a substitution of an amino acid with a charged side chain (Asp) with an amino acid with an uncharged (Asn) or hydrophobic side chain (Tyr, Val) creates a conformation that is highly amyloidogenic thus providing an explanation for the amyloidogenicity of the Asn-187 and Tyr-187 gelsolin variants.

Amino Acid Sequence↗
PubMed1996

First-order kinetic model of Alzheimer's beta-amyloid fibril extension in vitro.

Recently, several studies have proposed models describing the mechanisms of Alzheimer's beta-amyloid fibril formation in vitro. However, these models are somewhat controversial and no exact kinetic analyses measuring the polymerization velocity as an indicator of the reaction, have thus far been available. We first formed beta-amyloid fibrils from a synthetic peptide, beta-amyloid(1-40), and determined the optimum conditions for quantitative fluorometry of these beta-amyloid fibrils with thioflavine T. Optimum fluorescence measurements of beta-amyloid fibrils were obtained at the excitation and emission wavelengths of 446 and 490 nm, respectively, with the reaction mixture containing 5 microM thioflavine T and 50 mM of glycine-NaOH buffer, pH 8.5. We then focused our study on the extension phase of beta-amyloid fibril formation in vitro. When beta-amyloid fibrils were incubated with monomeric beta-amyloid(1-40) in conditions where de novo seed formation does not occur, the extension of beta-amyloid fibrils was observed with electron microscopy. Quantitative fluorometry revealed that: (a) extension of amyloid fibrils proceeded by a pseudo-first-order exponential increase as measured by the fluorescence of thioflavine T; (b) the rate of extension was maximum around pH 7.5, and was dependent on the incubation temperature. Between 20 and 37 degrees C, good linearity was observed between the common logarithm of the initial rate and the reciprocal of the absolute temperature; (c) the rate of polymerization was found to be proportional to the product of beta-amyloid fibrils number concentration and the beta-amyloid(1-40) concentration; (d) the net rate of extension was the sum of the rates of polymerization and depolymerization. These results show that beta-amyloid fibril formation can be explained by a first-order kinetic model: i.e., the extension of beta-amyloid fibrils proceeds via the consecutive association of beta-amyloid(1-40) onto the ends of existing fibrils.

Alzheimer Disease↗
PubMedDate not supplied

Application of immunoaffinity columns to mycotoxin analysis.

Immunoaffinity columns (IACs) are widely used for cleanup and isolation of mycotoxins extracted from foods and biological fluids, particularly aflatoxins, ochratoxin A, and fumonisins. The columns are prepared by binding antibodies specific for a given mycotoxin to a specially activated solid-phase support and packing the support suspended in aqueous buffer solution into a cartridge. The mycotoxin in the extract or fluid binds to the antibody, impurities are removed with water or aqueous solution, and then the mycotoxin is desorbed with a miscible solvent such as methanol. Further separation can be performed with IAC, followed by liquid chromatographic (LC) quantitation, either off-line or on-line in an automated system, or by fluorometry. IACs have been used by laboratories that developed the antibodies but are also available commercially for aflatoxins, ochratoxin A, fumonisins, zearalenone, and deoxynivalenol. Among commercial IACs, Aflatest P is used as the cleanup step in an LC method and in a solution fluorometry method for corn, peanuts, and peanut butter that was adopted as an AOAC INTERNATIONAL Official Method after evaluation by an international collaborative study. As part of a fluorometer-based test kit, aflatest P was further certified by the AOAC Research Institute to measure total aflatoxins in 10 grains and grain products. IACs can concentrate the analyte from a large amount of sample, allowing detection limits at low parts-per-trillion levels in some cases (e.g., for aflatoxin M1 and ochratoxin A in liquid food matrixes). Regeneration of IACs for reuse in aflatoxin, ochratoxin A, fumonisin, and zearalenone analyses has been investigated.

Aflatoxins↗
PubMed1992

Biochemical abnormalities in vitreous of humans with proliferative diabetic retinopathy.

Vitreous changes in diabetes can exacerbate proliferative diabetic retinopathy. These changes may be due to the effects of diabetes on vitreous collagen. Vitreous samples from 19 patients with proliferative diabetic retinopathy and 23 patients without diabetes were analyzed for collagen crosslinks, as well as for the early glycation products, glucitolyllysine and glucitolylhydroxylysine. Fluorometry was performed to measure advanced glycation end products. Vitreous collagen derived from diabetic patients was found to have significantly higher levels of the crosslink dihydroxylysinonorleucine (3.15 vs 1.24 mol/mol collagen, P<.01) than that of control subjects. Early glycation products were elevated in diabetic vitreous (1.65 vs 0.54 mol/mol collagen, P<.05). Levels of advanced glycation end products were 20 times higher in diabetic vitreous compared with the vitreous of controls. These diabetes-induced alterations of human vitreous may be of particular importance given the role of vitreous in proliferative diabetic retinopathy and vision loss.

Adult↗
PubMed1985

Comparative assessment of blood flow to canine island flaps.

Fluorometric quantification of dye delivery, laser Doppler flowmetry, and transcutaneous measurement of tissue oxygen level were evaluated in canine island flaps subjected to vascular occlusion. Each technique readily identified the clamping insult. Relative fluorescein delivery to the flap (compared with a reference area) decreased from 66% before clamping to almost zero during clamping. Laser Doppler readings rapidly declined from an average of 230 to an average of 31 mV. Oxygen readings rapidly declined from 57 to 1 mm Hg. Laser Doppler flowmetry and transcutaneous oxygen monitoring seem best suited for continuous monitoring of trends at a single site. Fluorometry is more precise and can be used to monitor multiple sites. One should weigh the benefits of this technique against the need for dye injection.

Animals↗
PubMed1999

Development and evaluation of a competitive time-resolved immunofluorometric assay for the estrogen-regulated protein pS2.

We have developed a competitive assay to measure the estrogen-regulated protein pS2. A monoclonal pS2 antibody (mAb) and a biotinylated pS2 peptide are used, with time-resolved fluorometry as a detection technique. The assay has a detection limit of 16 ng/mL and is precise (within-run and day-to-day Cvs 3-12%). We used this assay to determine steroid hormone activity of six steroids in cell culture, both in terms of time course and dose response. pS2 concentrations in the tissue culture supernatant of the BT-474 breast carcinoma cell line were significantly higher when estradiol was the stimulating steroid. There was a significant time course and dose response observed for estradiol, but not for the other steroids. The availability of a sensitive, reliable, and convenient method for quantifying pS2 will allow for many research applications including the screening of natural and synthetic compounds for putative estrogenic activity.

Aldosterone↗
PubMedDate not supplied

Molecular recognition by natural macrocycles. I. d-tubocurarine as a host molecule for organic anions.

The binding of 8-anilino-1-naphthalenesulfonate and 15 anions of substituted benzoic, aliphatic dicarboxylic, and N-acetyl-alpha-amino acids to a macrocyclic alkaloid d-tubocurarine in aqueous solution has been studied by fluorometry, conductometry, and 1H NMR. The binding constants vary from ca. 50 to 3300 M-1 depending on the guest structure, charge and hydrophobicity. The results of fluorescence and NMR studies show that the host-guest complexation of the anions of aromatic acids involves the formation of a salt bridge between the quaternary nitrogen of the alkaloid and the anionic group of the guest as well as hydrophobic/Van der Waals interactions between the guest and host aromatic moieties. The binding of dianions of aliphatic dicarboxylic acids most probably is purely electrostatic. In general, d-tubocurarine possesses binding ability comparable to that of synthetic cyclophanes. It binds enantiospecifically anions of N-acetyl-alpha-amino acids and discriminates between positional isomers of anions of hydroxy and carboxy substituted benzoic acids.

Anions↗