Defects in the experimental design of radioisotopic studies on the insect nerve cord

Effect of metabolic inhibition on sodium ion exchange in the ventral nerve cord of Melanoplus differentialis

“…In the present study, component is defined as a single exponential ; however, after the subtraction of all six components from the original desaturation curve, it was found that some residual radioactivity still remained in the majority of desaturation curves. The resolution of the remainder of the desaturation curves into further components is hindered by the difficulty of taking accurate samples in time periods of less than 5 set (Weidler et al, 1971). Using the graphical method, we found that six components are always demonstrable ; their half-times were analyzed statistically and presented in Table 1.…”

“…The decline in radioactivity of individual nerve cords during the washout period was analyzed by the graphical method (see Solomon, 1960;Weidler et al, 1971). In this method, the components are subtracted from the original desaturation curve by beginning with the asymptote of the desaturation curve itself, which is the component having the longest half-time.…”

“…Although the commonly used compartmental methods of kinetic analysis were employed in these studies (Treherne, 1965;Weidler & Diecke, 1970a, b), it was recently shown that there were certain defects in the experimental design of these radioisotopic studies, and that the resulting component analysis was faulty (Weidler et al, 1971). However, despite these defects it is clear that active Na+ absorption occurs in the nerve cords of C. morosus and D. fmorata because total uptake values are not dependent on the methods of component analysis.…”

“…To test this hypothesis, we utilized the revised experimental design for radioisotopic studies on the insect nerve cord described by Weidler et al (1971). , 1970a, b;Weidler et al, 1971); therefore only deviations from previous methods will be described in detail. Adult female Melanqplus differentialis, which were used in the present study, were collected from the Missouri River Valley near Omaha, Nebraska, and maintained in the laboratory on a diet of bluegrass.…”

Ultrastructural study of the neural fat-body system in the cockroach Periplaneta americana

“…In a more recent study, it was demonstrated that in adult male P. americana the neural fat body occupies approximately 22% of the total nerve cord volume (Weidler et al, 1971). The present work deals with the ultrastructure of the fat body adhering to the ventral nerve cord of P. americana.…”