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At least 379 records · Page 21Linked to original sources
PubMed2001

A natural matrix (pureed tomato) candidate reference material containing residue concentrations of pesticide chemicals.

NARL (the Australian National Analytical Reference Laboratory) is preparing a pureed tomato reference material spiked with residue concentrations of a range of pesticide chemicals relevant to the Australian horticultural industry. Traceable certified pesticide concentration values will be established using both isotope dilution mass spectrometry primary methods (developed within NARL) and measurements carried out by a number of experienced laboratories. As far as we are aware, there is no other similar CRM available anywhere in the world. The need for such a material is evident from the results of interlaboratory proficiency studies conducted by NARL among Australian and Asia-Pacific residue testing laboratories. Many participants are experiencing difficulties with the analysis of pesticide residues in fruit and vegetables at concentrations of regulatory significance. Chemicals such as methamidophos (an organophosphorus pesticide widely used on tomato crops) are causing particular problems. In a pilot study, a number of units of control (unspiked tomato) and the candidate reference material were prepared and packaged into lacquered steel cans which were sealed and sterilised by immersion in boiling water. Accelerated stability testing of the packaged material was conducted using isochronous measurement. All of the pesticides showed some degree of degradation after 4 weeks of storage at 50 degrees C, and after 168 days of storage at room temperature. However, all appeared to be stable after 168 days of freezer storage. Homogeneity testing involved duplicate test portions taken from every 50th unit of reference material. An experimental protocol was devised with the aim of minimising the analytical variability and assuring the quality of the data generated. There is some degree of inhomogeneity in the prepared material and a small fill trend is also indicated. Potential improvements to the spiking and preparation procedure have been identified and it is planned to prepare a second batch of both control and spiked material for further homogeneity trials and for certification of the pesticide concentrations.

Cold Temperature↗
PubMed2004

Down-regulation of Ku 70 and Ku 80 mRNA expression in transitional cell carcinomas of the urinary bladder related to tumor progression.

DNA-dependent protein kinase (DNA-PK) containing the regulatory subunits Ku 70 and Ku 80 plays a prominent role in the repair of double-stranded DNA breaks by a nonhomologous end-joining pathway maintaining genomic stability. In an attempt to elucidate the significance of the DNA-PK complex for human urothelial carcinogenesis, the expression of Ku 70 and Ku 80 was studied in 71 transitional cell carcinomas (TCC) of the urinary bladder of various grades and stages, and in relation to lifestyle and occupational bladder cancer risk factors. To analyse the mRNA expression of Ku 70 and Ku 80, real-time quantitative reverse transcription-polymerase chain reaction was used and the protein expression assessed by immunohistochemistry. Advanced high-grade, high-stage TCC expressed the mRNA of Ku 70 and Ku 80 at a lower level than superficial low-grade, low-stage carcinomas, suggesting down-regulation of the Ku system to be associated with progression of bladder cancer from a low to a high malignant potential. The protein expression of Ku 70 and Ku 80 was closely related and decreased consistently with increasing grades and stages, paralleling the expression of the mRNA. Among hazardous environmental bladder cancer risk factors, heavy consumption of coffee was associated with a twofold decreased Ku 70 and Ku 80 mRNA expression, whereas tobacco smoke did not substantially affect the activity of the Ku system, except for a trend towards a dose-response relationship in the expression of Ku 70 mRNA. There is some evidence that exposure to polycyclic hydrocarbons, paints and lacquer, and stone dust may modify the expression of Ku 70 mRNA. Although the underlying molecular genetic pathways are not yet clearly understood, our data indicate that down-regulation of the Ku system promotes progression of urothelial carcinogenesis to a more malignant and aggressive clinical behavior, presumably as a result of an impaired capacity for DNA repair.

Antigens, Nuclear↗
PubMed1999

Bilateral macular hemorrhage after laser in situ keratomileusis.

BACKGROUND: This is the first report of a bilateral submacular hemorrhage after LASIK surgery in an extreme myo pic patient. A 31-year-old man underwent bilateral surgery for correction of -16.75+0.75x70 degrees and -16.50+0.50x55 degrees. METHODS: Case report. RESULTS: One day after surgery the patient's uncorrected visual acuity was in the 20/50 range OU and by 17 days after surgery his visual acuity had declined to 20/200 range. Fundus examination showed multifocal subretinal macular and posterior pole hemorrhages. Fluorescein angiography showed some macular lesions compatible with lacquer cracks. CONCLUSIONS: Preoperative and postoperative fundus examination is important to detect this phenomenon. Patients should be informed of this rare complication.

Adult↗
PubMed1993

Oxidative turnover increases the rate constant and extent of intramolecular electron transfer in the multicopper enzymes, ascorbate oxidase and laccase.

Using laser flash photolysis of lumiflavin/EDTA solutions containing ascorbate oxidase, we find that the rate constant for intramolecular electron transfer varies from one enzyme preparation to another and is generally a more sensitive measure of the state of the active site than are steady-state assays. Thus, type I copper is initially reduced in a second-order reaction followed by first-order reoxidation by the type II-III trinuclear copper center. The observed rate constant for this intramolecular process in presumably native enzyme is 160 s-1 at pH 7, whereas an enzyme preparation which had less than 20% activity had a rate constant of 2.6 s-1. Other samples of relatively active enzyme showed biphasic intramolecular kinetics intermediate between the above values. The inactive enzyme sample could be reactivated by dialysis against ascorbate or by treatment with ferricyanide, resulting in a corresponding increase in the intramolecular rate constant for type I copper reoxidation to a value comparable to that of native enzyme. Using this same methodology, we have determined that the type I copper in Japanese lacquer tree laccase is reoxidized by the type II-III trinuclear copper center in a first-order (intramolecular) process with rate constants of 1 s-1 at pH 7.0 and 4.9 s-1 at pH 6.0, values which are approximately two orders of magnitude smaller than for ascorbate oxidase. The intramolecular rate constant and enzyme activity for laccase also increased, but only by a factor of 2-6, when the enzyme was treated with ascorbate or ferricyanide, respectively. We further found that intramolecular electron transfer in laccase was completely inhibited by fluoride ion, in contrast to ascorbate oxidase which is unaffected by this ion. These differences in behavior for these two very similar enzymes are rather remarkable, when it is considered that the distance between copper atoms is constrained by the location of the protein-derived copper ligands in the three-dimensional structure, and that the redox potentials of the enzymes are similar. Our results may be interpreted in terms of an interconversion between active and inactive enzyme in which there is a rearrangement of the type II-III trinuclear copper center, resulting in a lowering of the redox potential and a block in electron transfer. Turnover restores the active enzyme conformation.(ABSTRACT TRUNCATED AT 400 WORDS)

Ascorbate Oxidase↗
PubMed1978

Steady-state kinetics of laccasse from Rhus vernicifera.

The steady-state kinetics of laccasse (monophenol, dihydroxyphenylalanine: oxygen oxidoreductase, EC 1.14.18.1) from the lacquer tree Rhus vernicifera is investigated using the respirograph method to produce Lineweaver-Burk plots of oxygen consumption rate against oxygen concentration. A ping-pong mechanisms is established. The kinetic constants obtained according to the model is in close agreement with the corresponding values obtained from earlier studies on the transient reactions between the reduced enzyme and oxygen (Andréasson, L.E., Brändén, R. and Reinhammar, B. (1976) Biochim. Biophys. Acta 438, 370--379) and between the oxidized enzyme and reducing substrates (Andréasson, L.E. and Reinhammar, B. (1976) Biochim. Biophys. Acta 445, 579--597).

Catechol Oxidase↗
PubMed1989

Tooth crazing associated with threaded pins: a three-dimensional model.

A model for observing the three-dimensional pattern of cracking associated with placement of self-threading retentive pins was developed. Four sizes of self-threading pins were placed in extracted posterior tooth samples. The pins were subsequently removed and the samples coated with butyl acetate lacquer except for the pin channel orifice. Samples were immersed in dye solution followed by a demineralization and dehydration process. Samples were placed in methyl salicylate until cleared. Cleared samples were examined for dye penetration into the pin channel and communication with the pulp chamber. Comparisons were made of the patterns created by the four sizes of retentive pins. Results showed that more extensive cracks occurred with the larger size pins and that crack communication with the pulp chamber occurred more frequently with the larger pins.

Acetates↗
PubMed1990

Chamber testing of organic emission from building and furnishing materials.

The equipment and the procedure employed for the qualitative and quantitative determination of the volatile organic compounds emitted from samples of building and furnishing materials are described. The equipment includes two small test chambers (0.45 m3), with accurately controlled temperature, relative humidity and air flow rate, and instrumentation for sampling and analysis (Tenax tubes, GC-FID and GC-MS). To find quasi-steady-state emission conditions, the procedure includes the determination of the time profiles of the organic compounds concentration, which develop after the introduction of the samples into the chamber. A best-fitting, double exponential equation is used for this purpose. The procedure has been applied to three materials: particle board with carpet; gypsum board with wallpaper; and plywood with polyurethane lacquer, for which the steady-state emission factors (mg m-2 h-1) of several compounds are given. Many other compounds were identified, but were not quantified. Some comments are given on the health significance of the compounds emitted from the materials when used indoors.

Air Pollutants↗
PubMed1982

Measurement of strain rate behaviour in complete mandibular dentures.

A major cause of fracture in complete lower dentures is due to the denture falling onto a hard floor. Impact failure has never been investigated in complete dentures and in a material which is strain rate dependent, a knowledge of the maximum strain and strain rate at failure is essential if laboratory tests are to evaluate materials in a realistic manner. The work described includes brittle lacquer studies to establish the strain pattern which occurs when a denture is dropped from a height of 1 metre. This was used to orientate strain gauges and experimental dentures were then hit by a specially constructed ram driven at known velocities by a spring, whilst the strain was recorded on a storage oscilloscope. Photographs of the stored wave form were then used to establish the results at ram velocities equal to that of a denture falling 1 metre. Maximum strains were achieved of 11 x 10(3) microstrain and strain rates of 1.04 x 10(3) microstrain/ms. Laboratory impact machines for testing denture materials should therefore be designed to achieve these figures.

Dental Materials↗
PubMed1987

Wire electrodes for chronic single unit recording of dopamine cells in substantia nigra pars compacta of awake rats.

Stainless steel wire electrodes of varying sizes and coated with different insulating materials were tested in order to find a flexible fine wire which would allow the recording of small cells in deep structures of the brain in unrestrained, awake rats. Our main interest is to record from cells of substantia nigra pars compacta during locomotion. We found that stress relieved 18 micron stainless steel wire doubly insulated with lacquer and Parylene C provided the impedance, physical size, and flexibility needed to record single units during intense motor behavior.

Animals↗
PubMed1988

A combined recording and microiontophoresis technique for input-output analysis of single neurons in the mammalian CNS.

A method is described for producing electrolytically sharpened and lacquer-insulated steel microelectrodes and for their attachment to a multibarrel micropipet assembly by light-curing bonding compound. This electrode complex is specially designed for recordings from deep brain structures. It permits the analysis of the input signals to and the output signals from a single neuron recorded simultaneously from an extracellular electrode position, termed juxtacellular recording. Furthermore it provides the ability to manipulate pharmacologically the input-output ratio expressed by the neuron under varying sequences of natural stimulation.

Action Potentials↗
PubMed1990

Drug-induced, photosensitive, erythema multiforme-like eruption: possible role for cell adhesion molecules in a flare induced by Rhus dermatitis.

Drug-induced, photosensitive erythema multiforme has not been reported, although drugs and sunlight are listed among precipitating factors in erythema multiforme. We describe a case of a drug-induced erythema multiforme-like eruption in a photodistribution that was reproduced by clinical challenge with the drug and sunlight. On contact with Rhus verniciflua, the Japanese lacquer tree, the patient had a flare of the eruption, which was limited to the areas previously exposed to sun. Immunohistochemical studies suggested that the keratinocytes in the skin that retain teh photoactivated substances may facilitate epidermal invasion of lymphocytes by persistent expression of intercellular adhesion molecule-1.

Adult↗
PubMed2004

Macular hemorrhage after laser in situ keratomileusis (LASIK) with femtosecond laser flap creation.

PURPOSE: To report the first case of macular hemorrhage following laser in situ keratomileusis (LASIK) with femtosecond laser flap creation. DESIGN: Observational case report. METHODS: A 36-year-old woman underwent uncomplicated, bilateral, simultaneous LASIK procedures for correction of moderate myopia (-5.00 diopters OD and -6.00 diopters OS). LASIK flap creation was performed using the IntraLase femtosecond laser. RESULTS: On postoperative day 1, the patient's uncorrected and best-corrected visual acuities were 20/20 OD and 20/40 OS. A dilated fundoscopic examination revealed a one-third disk diameter macular hemorrhage OS. An intravenous fluorescein angoiogram ruled out the presence of predisposing macular pathology. Two months after LASIK, the macular hemorrhage had cleared, and 6 months later, the BCVA improved to 20/25 OS. CONCLUSIONS: Macular hemorrhage may occur after LASIK, even in the absence of previously identified risk factors, such as high myopia, pre-existing choroidal neovasculaization, lacquer cracks, and sudden changes in intraocular pressure associated with microkeratome-assisted flap creation.

Adult↗
PubMed2006

Sensitive gas chromatographic-mass spectrometric method for the determination of phthalate esters, alkylphenols, bisphenol A and their chlorinated derivatives in wastewater samples.

Phthalate esters, alkylphenols, bisphenol A and their chlorinated derivatives are the suspected endocrine disrupters or mutagens. These compounds, commonly called endocrine disrupter chemicals (EDCs), are widely used as plastic additives, lacquers, resins, or surfactants and can be usually found in environmental samples, namely wastewaters. An accurate and reproducible gas chromatographic-mass spectrometric (GC-MS) method is proposed to measure these compounds in wastewater samples of Granada city (Spain). A solid-phase extraction with LiChrolut RP-18 cartridges was carried out and the elution was performed with a diethyl ether/methanol mixture. After isolation, solvent was removed and a silylation step was carried out using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA). Phthalate esters and silylated compounds were identified and quantified by GC-MS using a ZB-5 MS column. Bisphenol F was used as a surrogate. Quantification limits found were between 20 ng L(-1) for 4-nonylphenol and 400 ng L(-1) for benzylbutyl phthalate while inter and intra-day variability was under 5% in all cases. Recoveries for spiked samples were over 95% and under 105%. The method was validated using standard addition calibration and recovery assays.

Benzhydryl Compounds↗
PubMed2006

Cost-effectiveness of diagnostic tests for toenail onychomycosis: a repeated-measure, single-blinded, cross-sectional evaluation of 7 diagnostic tests.

OBJECTIVE: Our purpose was to estimate and compare the cost-effectiveness of the most commonly used diagnostic tests for onychomycosis: potassium hydroxide preparation (KOH), interpreted both by a dermatologist (KOH-CLINIC) and a laboratory technician (KOH-LAB); KOH with dimethyl sulfoxide (KOH-DMSO) and with chlorazol black E (KOH-CBE), interpreted by a dermatologist; culture using dermatophyte test medium, culture with Mycobiotic and Inhibitory Mold Agar (Cx); and histopathologic analysis using periodic acid-Schiff stain (PAS). METHODS: This was a repeated-measure, blinded, cross-sectional study conducted at the Minneapolis Veterans Affairs Medical Center. Inclusion criteria included: at least one toenail with 25% or more clinical disease, which was defined as subungual debris with onycholysis and/or onychauxis. Exclusion criteria included other nail dystrophies, use of oral antifungal medication for 2 months or longer within the past year, or topical ciclopirox lacquer within 6 weeks of enrollment. The main outcome measure was the cost-effectiveness (Medicare and non-Medicare costs) of 7 diagnostic tests. Sensitivity (at least 3 positive tests) was the unit of effectiveness. RESULTS: Two hundred four participants were enrolled; their average age was 69.5 years and 95.5% were male. PAS was the most sensitive test (98.8%); it was statistically significantly more sensitive than all other diagnostic tests except KOH-CBE (94.3%). Dermatophye test medium was the least sensitive test (57.3%). KOH-CBE was statistically significantly more cost effective than any other test, with the exception of KOH-CLINIC and KOH-LAB. PAS was the least cost effective. LIMITATIONS: Test specificities were not evaluated. CONCLUSION: KOH-CBE should be the test of choice for practitioners confident in interpreting KOH preparations because of its combination of high sensitivity and cost-effectiveness.

Aged↗
PubMed2005

Leaching of copper, chromium and arsenic from treated vineyard posts in Marlborough, New Zealand.

There have been conflicting reports as to the extent that copper-chromium-arsenic (CCA) treatments leach from timber. In New Zealand, vineyards utilise CCA-treated posts at a rate of 579 posts per hectare. This represents a potential CCA burden on the soil of 12, 21, and 17 kg/ha, respectively, for the three elements. Given a replacement rate of 4% per year, the use of CCA-treated posts may result in an accumulation of these elements in the soil, possibly leading to groundwater contamination. We undertook a general survey to determine the extent of CCA leaching from treated vineyard posts. Treated Pinus radiata posts were sampled at six sites around the Marlborough region of New Zealand to represent a range of post ages and soil types. For each post, above- and belowground wood samples were taken. As well, the soil adjacent to the post was sampled at a 50 mm horizontal and 100 mm vertical distances from the post. The belowground wood samples of the posts had significantly lower CCA concentrations than the aboveground portions, which were not significantly different from new posts. This indicates leaching. Soils surrounding the posts had significantly higher CCA concentrations than control soils. Higher CCA concentrations were measured under the posts than laterally. Some 25% of the samples exceeded 100 mg/kg As, the Australian National Environment Protection Council (ANEPC) guideline level for As in agricultural soil, and 10% exceeded 100 mg/kg Cr, the ANEPC limit for chromium. At one site, we found a significant positive correlation between post age and CCA-leaching. The CCA issue could be eliminated by using alternative posts, such as steel, concrete, or untreated woods such as Eucalyptus or beech. Alternatively, CCA-treated posts could, for example, be lacquered or otherwise protected, to reduce the rate of CCA leaching.

Agriculture↗
PubMed2005

Styrene and ethylene glycol have a synergetic effect on lipid peroxidation that is better protected than repaired by CoQ10.

Previous study of a group of 22 workers occupationally exposed to styrene, ethylene glycol and their mixture at a paint and lacquer industry indicated significantly elevated concentration of malondialdehyde with 4-hydroxynonenal (MDA+4-HNE) in the blood plasma, successfully decreased with coenzyme Q10 (CoQ10) supplementation. The aim of present study is to evaluate whether the exposure to styrene or/and ethylene glycol could be responsible for the increase in MDA level. The mechanism of a single solvent action and the mixture was examined, specially whether it is connected with hydroxyl radical (*OH) generation. It was also investigated whether coenzyme Q10 could be considered as a protective (given before the solvents) or repairing (given after the solvents) agent in oxidative stress caused by the solvents. The results indicate that ethylene glycol nor styrene increase MDA and *OH, but as a mixture give synergetic interaction, elevating MDA and *OH concentration to a statistically significant extent. Coenzyme Q10 at a dose of 3.0 microg/ml only protects, but does not repair increased lipid peroxidation caused by ethylene glycol with styrene. In order to obtain both a protective and repairing effect, a concentration of 12.0 microg/ml CoQ is needed.

Coenzymes↗
PubMed2005

Biotic and abiotic degradation behaviour of ethylene glycol monomethyl ether (EGME).

Glycol ethers are widely used in many processes in the chemical industry. Their high water solubility means they are used as solvents for different purposes (e.g. lacquers and varnishes). Since glycol ethers are known to produce toxic metabolites such as the teratogenic methoxyacetic acid during biodegradation, the biological treatment of glycol ethers can be hazardous. However, using oxidizing agents like hydrogen peroxide could be a feasible option for treating wastewater containing glycol ether. In this study, both-, biodegradation and abiotic oxidation experiments with ethylene glycol monomethyl ether (EGME) as contaminant were performed. The biodegradation experiments were conducted with a synthetic model wastewater containing 15 wt% NaCl and 5000 mgl(-1) of EGME. While experiments with the fungus Aspergillus versicolor resulted in the exhaustive biotic degradation of EGME, the toxic metabolite methoxyacetic acid (MAA) was produced as a 'dead end' product. Sodium hydroxide was added to adjust the decreasing pH caused by the production of MAA. In abiotic degradation experiments with EGME, other degradation products--organic acids and toxic aldehydes, e.g. methoxy acetaldehyde (MALD)--were detected. It must be taken into account that EGME and its biotic and abiotic degradation products are usually not analysed in routine wastewater measurements owing to their physical properties.

Acetaldehyde↗
PubMed1997

Macular complications associated with posterior staphyloma.

PURPOSE: To report macular abnormalities associated with posterior staphyloma in eyes with myopia. METHODS: In a retrospective study, we surveyed 116 eyes of 58 patients with myopic refractions. Myopic fundus abnormalities are related to clinically quantified posterior staphyloma formation. RESULTS: A posterior staphyloma was present in 88 (75.9%) of 116 eyes with myopic refractions of -3 diopters or more. Best-corrected visual acuity was decreased among eyes in all staphyloma grades. Eyes with the shallowest staphyloma depth (grade 1) displayed the largest drop in visual acuity as well as the greatest frequency of choroidal neovascular membranes and hemorrhages. A linear relationship was observed between staphyloma grade and conus formation (P = .001), retinal pigment epithelial defects (P = .0001), lacquer cracks (P = .0001), and chorioretinal atrophy (P = .001). All these variables were increased in staphylomatous eyes. A significant difference in means by staphyloma grade was observed for myopic refractive error (P = .001), axial length (P = .001), and best-corrected visual acuity (logMAR, P = .0001). CONCLUSIONS: There was an unexpected high frequency of choroidal neovascular membranes, hemorrhage, and poor best-corrected visual acuity in the lower staphyloma categories. This suggests that the development of a choroidal neovascular membrane requires relative preservation of the choriocapillaris as present in eyes with less advanced stages of posterior staphyloma formation.

Adolescent↗