Time sequential single photon emission computed tomography (SPECT) studies using thallium-201 were performed in 25 patients with brain tumours to evaluate the kinetics of thallium in the tumour and the biological malignancy grade preoperatively. After acquisition and reconstruction of SPECT data from 1 min post injection to 48 h (1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 15-20 min, followed by 4-6, 24 and 48 h), the thallium uptake ratio in the tumour versus the homologous contralateral area of the brain was calculated and compared with findings of X-ray CT, magnetic resonance imaging, cerebral angiography and histological investigations. Early uptake of thallium in tumours was related to tumour vascularity and the disruption of the blood-brain barrier. High and rapid uptake and slow reduction of thallium indicated a hypervascular malignant tumour; however, high and rapid uptake but rapid reduction of thallium indicated a hypervascular benign tumour, such as meningioma. Hypovascular and benign tumours tended to show low uptake and slow reduction of thallium. Long-lasting retention or uptake of thallium indicates tumour malignancy.

The ultrastructural localization of glucose-6 dehydrogenase (G6PD) activity has been investigated using a copper ferrocyanide method in the rat liver cells by immersion fixation and freeze substitution fixation by using glutaraldehyde. After immersion in 2% glutaraldehyde fixative for 30min at 4•Ž, the site of reaction products, copper ferrocyanide, were on the cytoplasm close to the r-ER in hepatic parenchymal cells of rat. These findings were ascertained by several control experiments and X-ray microanalysis. After the metal contact quenching at-196•Ž, freeze substitution fixation, 2% glutaraldehyde in aceton for 3 days at-80•Ž, was performed. The reaction products were not observed on the cytoplasm close to the r-ER, but also on the cytoplasm near the r-ER. It is suggested that freeze substitution fixation were useful to elucidate the ultrastructural sites of soluble enzyme. study of basic FGF related to the development of capillaries in the bovine retina. Hitoshi ISHIGOOKA (1) and Takashi KITAOKA (2)