Biomedical subjects

R Applegate

Publications and source records attributed to R Applegate.

4 recordsLinked to original sources

PubMed1998

Generation of third-order spherical and coma aberrations by use of radically symmetrical fourth-order lenses.

We have extended the method of Alvarez [J. Am. Optom. Assoc. 49, 24 (1978)] to generate a variable magnitude of third-order spherical and/or coma aberration by using a combination of fourth-order plates with a magnification system. The technique, based on the crossed-cylinder aberroscope, is used to measure the wave-front aberration generated by the plates. The method has been applied to correct the third-order spherical aberration generated by an artificial eye as well as the coma produced by a progressive addition ophthalmic lens. The simplicity of the method and its relatively low cost make it attractive for partial correction of the aberrations of the eye.

Humans↗

PubMed1985

Is amblyopia spatial frequency or retinal locus specific?

The visual deficit associated with amblyopia is thought to be both spatial frequency and retinal locus dependent. However, most data that have been obtained can be accounted for by either of these factors or by a combination of both. We have tried to distinguish between these three possibilities by measuring contrast sensitivity at different retinal loci using discrete localized patches of grating. For five of nine amblyopes, we find the contrast sensitivity deficit to be constant across the retina for a given spatial frequency. In only two cases were there substantial changes as a function of retinal eccentricity. Therefore, most of our data suggest that the visual deficit in amblyopia is primarily spatial frequency and not retinal locus specific.

Amblyopia↗

PubMed1978

Enolase isozymes in Coho salmon.

1. Analysis of the enolase isozymic distribution has been performed in tissues of the Coho salmon, using electrophoretic separation on cellulose acetate strips followed by localization of enzymatic activity. 2. A total of six electrophoretically distinct forms are seen in Coho salmon in patterns that differ both qualitatively and quantitatively from one tissue to another. 3. The isozymes in skeletal muscle and liver are sufficiently similar to one another that a purification procedure previously developed for trout muscle enolase by Cory & Wold (1966) can be used to partially purify enolase from either of the above-mentioned Coho tissues. The main form of enolase in Coho muscle has an isoelectric point of 7.57. 4. Both liver and skeletal muscle enolases can be reversibly denatured in guanidine HCl and subsequently renatured. Liver enolase appeared to renature somewhat faster than muscle enolase under the same conditions. 5. While polyploidy among salmonids may contribute to the complexity of enolase patterns in fish, the differences in isozymic patterns seen from one tissue to another indicate the presence of distinct, nonallelic genes, probably arising through gene duplication.

Animals↗

PubMedDate not supplied

Accuracy of cardiac output estimation with biplane transesophageal echocardiography.

To evaluate the accuracy of cardiac output measurements with biplane transesophageal Doppler echocardiography, we examined 26 sets of observations in 14 patients using thermodilution technique as the standard. A mitral inflow method by single-plane combined the time-velocity integral of mitral inflow at the mitral annulus with the area of mitral annulus, assuming it to be a circular shape, by use of either the four- or the two-chamber view. With both views, a mitral inflow method by biplane combined the average of time-velocity integral of mitral inflow from the four- and the two-chamber views with the area of mitral annulus, assuming it to be an ellipsoid shape. The correlation coefficients between thermodilution and single-plane method of cardiac output were 0.81 (SEE = 0.72 L/min) and 0.85 (SEE = 0.79 L/min) for the four- and the two-chamber views, respectively. The correlation coefficient with biplane method was 0.93 (SEE = 0.47 L/min). Thus, biplane transesophageal Doppler echocardiography can be used for more accurate estimation of cardiac output.

Aged↗