The environmental contaminant DDE fails to influence the outcome of sexual differentiation in the marine turtle Chelonia mydas.

In many turtles, the temperature experienced during the middle of egg incubation determines the sex of the offspring. The implication of steroid sex hormones as the proximate trigger for sex determination opens the possibility that endocrine-disrupting contaminants may also influence the outcome of sexual differentiation. In this study we investigate the potential effects of DDE (a common DDT metabolite) on sexual differentiation of Chelonia mydas (green sea turtle). Four clutches of eggs collected from Heron Island, Queensland, Australia, were treated with DDE at the beginning of the thermosensitive period for sexual determination. An incubation temperature of 28 degrees C or less produces male hatchlings in this species, whereas 30 degrees C or more produces female hatchlings. Dosed eggs were consequently incubated at two temperatures (27.6 degrees C and 30.4 degrees C) on the upper and lower boundaries of the sex determination threshold for this species. DDE, ranging from 3.3 to 66.5 microg, was dissolved in 5, 10, and 25 microl ethanol and applied to eggshells above the embryo. Less than 2.5 ng/g DDE was present in eggs prior to dosing. Approximately 34% of the applied DDE was absorbed in the eggs, but only approximately 8% of applied DDE was found in embryos. Thus, treated eggs, corrected for background DDE, had up to 543 ng/g DDE. The sex ratio at these doses did not differ from what would be expected on consideration of temperature alone. Incubation time, hatching success, incidence of body deformities, hatching size, and weight were also within the limits of healthy developed hatchlings. This indicates that the eggs of C. mydas in the wild with concentrations of DDE less than 543 ng/g should produce hatchlings with relatively high hatching success, survival rate, and normally differentiated gonads

Estimation of 123I-IMP arterial blood activity from dynamic planar imaging of the chest using a graph plot method for the quantification of regional cerebral blood flow

Purpose: I-123 labeled N-isopropyl-p-iodoamphetamine(123I-IMP) is used for measurement of regional cerebral blood flow(rCBF). A continuous or single arterial blood sampling(ABS) is necessary to estimate an integral of arterial input function(AIF) for the measurement of rCBF by using a microsphere model analysis. Therefore, the method to measure rCBF without any blood sampling is desired. The aim of this study was to establish the method to estimate the AIF from the time-activity curve of the lungs after the injection of 123I-IMP using a regression analysis for the measurement of rCBF without any blood sampling. Materials and methods: Thirty-seven prospective studies in 10 consecutive patients were enrolled. A chest planar dynamic imaging for 3 minutes and continuous ABS for 5 minutes after a bolus injection of 167MBq 123I-IMP were performed in all studies. Data from the chest imaging were analyzed in comparison with ABS data(AIF(5)) in the first 10 studies, and an equation for estimation yielding accurate AIF(5) from the total counts cleared from the lungs during 5 minutes after injection of 123I-IMP(TCL(5)) was derived. The validity of the proposed method was evaluated in the subsequent 27 studies.Results: A good correlation was obtained between the AIF and TCL by regression analysis in the first 10 studies(r=0.94, p<0.001). An equation for the estimation of AIF by the regression analysis in the first 10 studies was defined as follows, estimated AIF=2146.7336 +4.1735xTCL(5). In the subsequent 27 studies, a good linear correlation was obtained between measured AIF(5) and estimated AIF(5) by using the equation(r=0.79, p<0.001). Conclusion: AIF(5) can be accurately estimated from the TCL(5). Therefore, estimated AIF(5) can be used for the measurement of rCBF instead of ABS data