Robert D. Phemister

Visually evoked EEG potentials of beagles irradiated in utero

Abstract This experiment investigated a non-destructive, non-invasive method for detecting long-term functional alterations in the visual system of beagles irradiated in utero . Ipsilateral and contralateral summed visual evoked potentials (SVEP) to monocular photic stimuli were recorded from the scalp and dura of the cerebral cortex of normal, young adult beagles and beagles irradiated in utero of a similar age. The latency of the initial peak of the SVEP was the parameter for comparing the two groups. The effect of light intensity on the latency of the SVEP was also studied. In spite of demonstrable morphologic damage in the retinas of the irradiated group, no significant difference in the initial peak latency was found between the irradiated and the control group. General features of the SVEP that were found to be significant are (1) latency decreased with increasing light intensity; (2) latency of the ipsilateral response was longer than the contralateral.

Counting renal corpuscles in tissue sections.

SummaryTwo stereologic methods of counting renal corpuscles in tissue sections were evaluated. Weibel’s stereologic method was found to be an accurate and efficient means of determining the number of corpuscles in normal and diseased kidneys. Weibel’s method was preferred over the stereologic method of Elias and Hennig because the former is independent of tissue section thickness and is sensitive to variation in corpuscular size. A modification of Weibel’s method eliminated the need for an additional point-counting procedure to determine the volumetric fraction of corpuscles in a kidney. The modification made use of previously completed measurements to calculate the area fraction of corpuscles and then substituted this value for the volumetric fraction of renal corpuscles.