Search PubMed⌕ Search

Biomedical subjects

R W Brown

Publications and source records attributed to R W Brown.

At least 163 records · Page 9Linked to original sources
PubMed1969

Effect of propranolol on exercise tolerance of patients with atrial fibrillation.

Six patients with atrial fibrillation who were taking digitalis were exercised before and after 30 mg. of propranolol twice daily. Though there was a lower pulse rate at rest and on exercise in all patients, three suffered deterioration of exercise tolerance. It is concluded that propranolol does not improve the exercise tolerance of patients with atrial fibrillation whose resting ventricular rate is controlled with digitalis.

Adult↗
PubMed1966

Color of cultures of Staphylococcus epidermidis determined by spectral reflectance colorimetry.

Brown, Richard W. (National Animal Disease Laboratory, Ames, Iowa). Color of cultures of Staphylococcus epidermidis determined by spectral reflectance colorimetry. J. Bacteriol. 91:911-918. 1966.-A colorimeter with a reflectance attachment was used to study pigment production by Staphylococcus epidermidis strains grown on a medium containing Trypticase Soy Agar (BBL) and cream. The color of each culture was first characterized by reflectance colorimetry for dominant wavelength, purity, and luminous reflectance (Y) and was then classified visually into 1 of 10 color grades. There was not complete agreement in grading colors by the two methods, inasmuch as cultures that were considered more pigmented in relation to other cultures by the reflectance method were sometimes graded visually as less pigmented, and vice versa. Nevertheless, when the cultures were visually graded as being more pigmented, there was a concomitant increase in the average values of dominant wavelength and purity with a decrease in Y for the cultures in each higher grade. Thus, the nonpigmented cultures had the lowest dominant wavelength and purity values but the highest Y (brightness) values, whereas the most pigmented cultures had the highest dominant wavelength and purity values, but the lowest Y values. These results indicated that the cultures did not produce pigments of different hues (greenish-yellow, yellow, yellowish-orange) each with high, medium, and low degrees of purity and brightness. The value (1 - z), where the chromaticity coordinate z = Z/(X + Y + Z), was found to be proportional to the purity value. An inverse relationship between the tristimulus Z and purity values was also demonstrated. All cultures tested by the reflectance method were also classified according to the type of spectral absorption curve obtained with pigments extracted from the cultures with methanol. A comparison of these methods indicated that determining the type of spectral absorption curve would be better for differentiating strains of S. epidermidis, whereas the use of the reflectance method would be better for determining differences of pigment production within strains.

Color↗