Variability of measurements was reduced with the computer-assisted perimeter method compared with the diameter method, which suggests that changes in volume can be detected more accurately with the perimeter method. The differences between these techniques seem large enough to have an impact on grading the response to therapy.

The aim of this study was to examine basal ganglia volumes and regional cerebral blood flow in asymptomatic subjects at-risk for Huntington's disease who had undergone genetic testing. We determined which measures were the best 'markers' for the presence of the mutation and for the onset of symptoms. Twenty subjects who were Huntington's disease gene mutation-positive and 24 Huntington's disease gene mutation-negative participants, all of whom had a parent with genetically confirmed Huntington's disease, and were therefore 50% at-risk for inheriting the Huntington's disease gene mutation, were included in the study. To evaluate basal ganglia structure and function, MRI and single photon emission computed tomography (SPECT) were used. Quantitative measures of regional volumes and relative measures of regional perfusion were calculated. SPECT and MRI scans were co-registered so that MRI anatomy could be used accurately to place SPECT regions. Estimated years-to-onset in the mutation-positive subjects was calculated based on a regression formula that included gene (CAG)(n) repeat length and parental age of onset. Changes in imaging measures in relation to estimated years-to-onset were assessed. The imaging measure that was most affected in mutation-positive subjects was putamen volume. This was also the measure that correlated most strongly with approaching onset. In subjects >/=7 years from estimated onset age, the putamen volume measures were similar to those of the mutation-negative subjects. However, in subjects 90% discrimination from both the far-from-onset and the mutation-negative subjects. Caudate volume and bicaudate ratio also showed a significant decline in the close-to-onset subjects, although to a lesser degree than putamen volume reductions. Furthermore, SPECT basal ganglia perfusion deficits were observed in mutation-positive subjects. Imaging markers of neuropathological decline preceding clinical onset are important for assessing the effects of treatments aimed at slowing the course of Huntington's disease. The current study suggests that quantitative assessment of basal ganglia may provide a means to track early signs of decline in individuals with the Huntington's disease gene mutation prior to clinical onset.

The principal objective of the research reported here was to determine whether a plant's periodic growth oscillations, called circumnutations, would persist in the absence of a significant gravitational or inertial force. The definitive experiment was made possible by access to the condition of protracted near weightlessness in an earth satellite. The experiment, performed during the first flight of Spacelab on the National Aeronautics and Space Administration shuttle, Columbia, in November and December, 1983, tested a biophysical model, proposed in 1967, that might account for circumnutation as a gravity-dependent growth response. However, circumnutations were observed in microgravity. They continued for many hours without stimulation by a significant g-force. Therefore, neither a gravitational nor an inertial g-force was an absolute requirement for initation or continuation of circumnutation. On average, circumnutation was significantly more vigorous in satellite orbit than on earth-based clinostats. Therefore, at least for sunflower (Helianthus annuus L.) circumnutation, clinostatting is not the functional equivalent of weightlessness.

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