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Biomedical subjects

R Cathcart

Publications and source records attributed to R Cathcart.

10 recordsLinked to original sources
PubMed2004

A prospective, single-blind, randomized controlled trial of petroleum jelly/Vaseline for recurrent paediatric epistaxis.

The aim of the study was to determine if petroleum jelly was an effective treatment for paediatric epistaxis. A single-blind, prospective, randomized controlled trial was undertaken in an otolaryngology outpatient clinic of a paediatric hospital from March 2001 to March 2002. A total of 105 children referred with recurrent epistaxis were randomized into the study, 52 into the treatment arm and 53 into the control arm. Children in the treatment arm applied Vaseline twice a day bilaterally for 4 weeks and were monitored for any bleeds for the next 4 weeks. Children in the control arm were simply given an 8-week appointment and the number of bleeds were monitored for the 4 weeks prior to their appointment. The outcome measure was the proportion of children in each group without nosebleeds in the preceding 4 weeks. Both groups were equally distributed in age, duration of symptoms and duration of each bleed. Fourteen of 51 (27.5%) patients of the treatment arm and 18 of 53 (34%) of the control arm did not bleed in the 4 weeks before review (chi-square test, P = 0.472). It can be concluded that Vaseline alone confers no benefit over simple observation in recurrent childhood epistaxis.

Adolescent↗
PubMed1992

A new approach to template purification for sequencing applications using paramagnetic particles.

A new method using traditional hybridization methodology, coupled with the new magnetic particle technology, has been developed for DNA purification, specifically for sequencing applications. The method is similar to the reverse hybridization blot system; however, a specific oligonucleotide probe was attached to the paramagnetic particle instead of a sheet membrane. The target DNA containing the complementary sequence of the probe hybridizes to the probe that is attached to the bead and is then magnetically removed from solution, washed and collected. This system eliminates the need of organic extractions and precipitation/concentration steps. The entire hybridization-purification system can be done in a 1.5-ml microcentrifuge tube making the method ideal for automation. M13 phage clones were purified with this method, both by manual means and by using the CATALYST 800 Molecular Biology LabStation fitted with a prototype magnetic station, and then sequenced. DNA sequencing results obtained with this system were reproducible and gave excellent length of read with low background.

Base Sequence↗
PubMed1990

Automation of specific human gene detection.

An instrument/chemistry system is described that automates a new chemical procedure functionally equivalent to Southern blotting. A fluorescence gel scanner that detects migrating DNA fragments in real-time analyzes the samples produced by a prototype liquid-handling instrument that automates a solution-phase hybridization/solid-phase capture chemistry for DNA analysis. The combination of this chemistry, the gel scanner, and robotic automation eliminates the tedium encountered in traditional manual methods for specific gene detection and reduces analysis time from days to hours. Restriction fragment lengths are measured with high precision by comparison with in-lane standards to minimize effects attributable to migration anomalies. The utility of this automated system is demonstrated by executing a clinical research application involving hybridization to a multi-copy repeat sequence on the Y chromosome and its detection.

Automation↗
PubMed1987

High-performance liquid chromatographic analysis of oligodeoxyribonucleotide base composition.

A significantly improved method for base composition analysis of synthetic oligodeoxyribonucleotides is presented. This highly accurate and sensitive method used enzymatic digestion followed by high-resolution HPLC of the nucleosides to determine the empirical base composition of the parent compound. The enzymatic digestion reaction is quantitative and is not blocked by modified bases, thus allowing the degree of base deprotection and chemical modification to be assessed. Digestion data are presented for oligodeoxyribonucleotides which range from 18 to 150 bases in length with excellent agreement of experimental and theoretical composition. The method is also applicable to high-molecular-weight genomic DNA.

Alkaline Phosphatase↗
PubMed1984

Thymine glycol and thymidine glycol in human and rat urine: a possible assay for oxidative DNA damage.

Thymine glycol is a DNA damage product of ionizing radiation and other oxidative mutagens. In an attempt to find a noninvasive assay for oxidative DNA damage in individuals, we have developed an HPLC assay for free thymine glycol and thymidine glycol in urine. Our results indicate that humans excrete about 32 nmol of the two glycols per day. Rats, which have a higher specific metabolic rate and a shorter life span, excrete about 15 times more thymine glycol plus thymidine glycol per kg of body weight than do humans. We present evidence that thymine glycol and thymidine glycol are likely to be derived from repair of oxidized DNA, rather than from alternative sources such as the diet or bacterial flora. This noninvasive assay of DNA oxidation products may allow the direct testing of current theories which relate oxidative metabolism to the processes of aging and cancer in man.

Animals↗
PubMed1983

Detection of picomole levels of hydroperoxides using a fluorescent dichlorofluorescein assay.

A highly sensitive fluorometric method for the quantitation of cholesterol, lipid, and other hydroperoxides at the picomole level is described. The method is based on the oxidation of dichlorofluoroscin to the fluorescent dichlorofluoroscein by hydroperoxide and hematin under mild conditions. A 1:1 stoichiometry is observed between the hydroperoxide added and the dichlorofluoroscein produced. Since endoperoxides (e.g., PGH2) do not react in the assay, they do not interfere in the determination of lipid hydroperoxides.

Fluoresceins↗
PubMed1981

Uric acid provides an antioxidant defense in humans against oxidant- and radical-caused aging and cancer: a hypothesis.

During primate evolution, a major factor in lengthening life-span and decreasing age-specific cancer rates may have been improved protective mechanisms against oxygen radicals. We propose that one of these protective systems is plasma uric acid, the level of which increased markedly during primate evolution as a consequence of a series of mutations. Uric acid is a powerful antioxidant and is a scavenger of singlet oxygen and radicals. We show that, at physiological concentrations, urate reduces the oxo-heme oxidant formed by peroxide reaction with hemoglobin, protects erythrocyte ghosts against lipid peroxidation, and protects erythrocytes from peroxidative damage leading to lysis. Urate is about as effective an antioxidant as ascorbate in these experiments. Urate is much more easily oxidized than deoxynucleosides by singlet oxygen and is destroyed by hydroxyl radicals at a comparable rate. The plasma urate levels in humans (about 300 microM) is considerably higher than the ascorbate level, making it one of the major antioxidants in humans. Previous work on urate reported in the literature supports our experiments and interpretations, although the findings were not discussed in a physiological context.

Adult↗