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Biomedical subjects

C Owens

Publications and source records attributed to C Owens.

At least 37 records · Page 2Linked to original sources
PubMed1989

The effects of bergapten and sunlight on cutaneous pigmentation.

The effects of bergapten-containing preparations in sunlight-induced skin pigmentation were evaluated. Oil and lotion vehicles with bergapten/UV-B sunscreen or sunscreen alone were applied to the backs of subjects twice weekly for 4 weeks and the subjects were exposed to gradually increasing doses of midday sunlight. The degree of skin darkening was assessed by clinical examination, reflectometry, and light microscopy of skin biopsy specimens. At 5 weeks, 1 week after the last sunlight exposure, the sites treated with either the bergapten/UV-B sunscreen lotion or the lotion vehicle were significantly darker than the sites treated with the sunscreen lotions without bergapten. Oil preparations produced less clearcut results, possibly because of a less potent sunscreen or because the bergapten did not leave the vehicle and absorb into the epidermis. In type I skin, the bergapten/sunscreen and the oil vehicle alone produced the same amount of tanning; both yielded more tanning than the sunscreen in oil by clinical examination. The findings were not confirmed by reflectometry or by light microscopy. Thus, we conclude that bergapten added to a UV-B sunscreen lotion preparation can increase skin pigmentation over the sunscreen alone when one is exposed to sunlight. The bergapten/UV-B sunscreen combination is a potentially useful product since one can develop a psoralen and UV-A-induced tan while being protected from UV-B-induced sunburn by the UV-B sunscreen incorporated into the formulation.

5-Methoxypsoralen↗
PubMed1988

Preclinical Creutzfeldt-Jakob disease discovered at autopsy in a human growth hormone recipient.

An adolescent girl with idiopathic hypothalamic dysfunction and hypopituitarism was treated with human growth hormone between 1969 and 1979, dying of parainfluenza pneumonia 2 months after her last hormone treatment. Although she had no signs of progressive neurologic disease, reexamination of autopsy material revealed a focus of spongiform change and astrogliosis in the corpus striatum. Thus, this growth hormone recipient, who died of intercurrent infection, was unexpectedly found to be in an early, preclinical phase of Creutzfeldt-Jakob disease.

Adolescent↗
PubMed1987

Compression of the optic chiasm due to a lymphoreticular malignancy.

A patient is described who presented with visual loss due to infiltration of the optic chiasm by chronic lymphocytic leukaemia. This case demonstrates intracranial infiltration as a primary presentation of chronic lymphocytic leukaemia without lymphoreticular involvement and, to our knowledge, is the first report of a chiasmal syndrome due to this lymphoproliferative disorder.

Humans↗
PubMed1983

A collaborative study of the measurement of glycosylated haemoglobin by several methods in seven laboratories in the United Kingdom.

A collaborative study compared methods for measuring glycosylated haemoglobin in seven laboratories in the United Kingdom. No satisfactory standard for general use was found. Satisfactory internal quality control systems were in use for each assay which allowed the maintenance of a normal range in each participating laboratory. No satisfactory quality control system suitable for general use could be identified. Costs and convenience of the assays are reported. The technical problems with each type of assay and precautions for their use were identified, such as the need for standardization in incubation times, the practicability of automation of colorimetric assays, and the precision of pH needed for buffers in column separation methods. The relevance of the technical problems to interpretation of measurements is also considered. It is concluded that laboratories measuring glycosylated haemoglobin should maintain a normal range, use 'in-house' quality controls to monitor assay performance and keep clinical colleagues informed of the findings and of any changes in methodology that might affect the interpretation of results.

Autoanalysis↗
PubMed1982

Impact of home blood glucose monitoring on childhood diabetes.

Ninety diabetic children each provided at least one 24-hour blood glucose profile at home using an impregnated filter paper strip. The mean 24-hour blood glucose level correlated significantly with urine control, height velocity, and Hb A1. The correlation coefficient for individual blood glucose values (r = 0.61) and for mean 24-hour blood glucose values (r = 0.73) repeated within 14 days showed an acceptable degree of reproducibility for the blood glucose profiles. Mean 24-hour blood glucose values fell significantly overall (11.4 to 9.8 mmol/l; 205 to 176 mg/100 ml) in 47 children who had repeated profiles more than 2 weeks apart. Unrecognised nocturnal hypoglycaemia (less than 3.0 mmol/l; 54 mg/100 ml) was found in 19% of children on twice-daily Semitard insulin. The study shows that children over age 7 years manage home blood glucose monitoring without difficulty. It shows that the results are reproducible and correlate with other indices of control, and that it provides a practical basis for the improvement of diabetic control.

Blood Glucose↗
PubMed1979

Determination of therapeutic and toxic concentrations of doxepin and loxapine using gas-liquid chromatography with a nitrogen-sensitive detector, and gas chromatography-mass spectrometry of loxapine.

A gas-liquid chromatographic procedure is presented for the determination of therapeutic and toxic serum levels of doxepin and loxapine, using a nitrogen-phosphorus-sensitive detector. Amitriptyline is used as the internal standard. The method is accurate, sensitive and specific with no derivatization required prior to analysis. An advantage of the procedure is the small serum sample size needed for analysis and the selectivity and sensitivity of the detector, with the limit of detection being 3 and 2 microgram/l for doxepin and loxapine, respectively. Nine cases of doxenin and loxapine misuse are presented. Serum doxepin concentrations ranged from 113 to 439 microgram/l, with a loxapine concentration of 192 microgram/l observed in one patient. The presence of the tricyclics was identified and confirmed by gas chromatography-mass spectrometry and the mass spectrum of loxapine is reported.

Adult↗
PubMed1979

Interrelations between serum gastrin levels, gastric emptying and acid output before and after proximal gastric vagotomy and truncal vagotomy and antrectomy.

In a prospective study of proximal gastric vagotomy and truncal vagotomy and antrectomy measurements were made, before and after operation, of acid output, gastrin output and gastric emptying of a solid and a liquid meat extract meal. No relationships were demonstrable between acid output and gastrin output. Truncal vagotomy and antrectomy (TVA) produced rapid early emptying of both meals combined with gross prolongation of the overall emptying of the solid meal. Truncal vagotomy and antrectomy reduced the intergrated gastrin output after either meal. Proximal gastric vagotomy (PGV) produced rapid early emptying of the liquid meal with no alteration in the early emptying of the solid meal; however, overall solid meal emptying was delayed. Proximal gastric vagotomy increased basal, peak and integrated gastrin output. In preoperative patients slow solid meal emptying was associated with higher gastrin output but after PGV the reverse was found, the slowest emptiers having the lowest gastrin output. These findings do not support the contention that a pyloroplasty should be added to PGV to reduce the hypergastrinaemia produced by the operation.

Clinical Trials as Topic↗
PubMed1979

Gastrin and the ultrastructure of G cells in the fasting rat.

The effect of fasting on serum and antral gastrin concentrations and G cell ultrastructure in the rat has been examined using a radioimmunoassay and quantitative electron microscopy. Serum gastrin levels in fasting animals were markedly reduced and there was also a significant decrease in antral gastrin concentrations after 48 hours and 72 hours of fasting. This was associated with a significant fall in the granule content and cytloplasmic volume of individual G cells, at its greatest by 48 hours. A relative absence of electron dense granules in the Golgi zones of cells from animals fasted for 72 hours suggested a paucity of newly formed granules, but fasting produced no detectable change in the electron density of the granule population taken as a whole. The results indicate that, during fasting, release and then synthesis of gastrin is inhibited, so that granule stores and cell size diminish. The correlation between the granule content of G cells and the antral content of gastrin suggests that hormone release occurs by exocytosis, rather than by any change in the content of individual granules.

Animals↗
PubMed1979

Disopyramide determination by gas chromatography, liquid chromatography, and gas chromatography--mass spectrometry.

Disopyramide is determined in serum by gas chromatography with a nitrogen-selective detector, by liquid chromatography, and by gas chromatography--mass spectrometry. Comparable results are obtained with the three techniques, with a within-run and between-run precision of 5 to 10% (coefficient of variation). Least-squares analysis of data on patients' sera, analyzed first by gas chromatography (y) and then liquid chromatography (x), gave a slope of 1.12; y-intercept, -0.31; standard error of estimate, 0.46; and correlation coefficient, 0.94. Comparison of patients' sera by gas chromatography (y) and then by gas chromatography--mass spectrometry (x) gave a slope of 0.94; y-intercept, 0.42; standard error of estimate, 0.38; and correlation coefficient, 0.97. Interferences observed when using one technique--for example, gas chromatography--can be eliminated by analyzing the sample extract with one of the other techniques.

Chromatography, Gas↗
PubMed1979

Gas-chromatographic determination of disopyramide in serum, with use of a nitrogen-selective detector.

In this procedure for disopyramide in serum, the drug is extracted into n-heptane/isobutanol (96/4 by vol), then back-extracted into 1 mol/L H2SO4. The acidic solution is made basic with sodium hydroxide, extracted with diethyl ether, and the extract evaporated. The residue is redissolved in ethanol and analyzed by gas-chromatography, with use of a nitrogen-selective detector. p-Chlorodisopyramide is used as internal standard. Concentration and instrument response for serum extracts are linearly related from 1 to 5 mg/L, the slope being 0.61, the y-intercept -0.10, the standard error of estimate 0.01, and the correlation coefficient 0.99. Within-run precision was 6 and 4% for 3 and 5 mg/L concentrations, respectively, with a between-run precision of 7% at the 3 mg/L concentration. Diazepam interferes, but procainamide, chlordiazepoxide, quinidine, lidocaine, propranolol, sulfanilamide, and many other basic drugs do not.

Chromatography, Gas↗
PubMed1978

A modified sensitive spectrofluorometric method for the determination of propranolol in serum.

A modification of the spectrofluorometric propranolol procedure of Shand and associates and Ambler and colleagues is presented. A 3-ml volume of propranolol in serum is made basic with sodium hydroxide and extracted with 1.5% isoamyl alcohol in n-heptane. The drug is back-extracted into a mixture of 0.01 M citric acid in 50% ethylene glycol and measured spectrofluorometrically with the use of 299 nm for excitation and 352 nm for emission. Excellent linearity is observed in the 25--200 ng/ml range. The effects of sodium hydroxide, citric acid, and ethylene glycol concentration on the procedure were investigated. Ethylene glycol--citric acid in water is a better back-extracting mixture from the organic phase than hydrochloric acid. Using pentyl acetate as the extracting solvent instead of isoamyl alcohol in n-heptane did not change significantly the amount of the drug extracted. Other extracting solvents investigated did not increase sensitivity. At high citric acid concentrations a decrease in fluorescence intensity was observed at 350 nm. Interferences from other drugs using this procedure were investigated. Quinidine, methaqualone, and procainamide interfere at therapeutic levels.

Citrates↗