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The observed decrease in the striatal dopamine transporter density in JNCL offers a rational basis for a trial of dopaminergic drugs in this disease.

Leptin is a peptide hormone produced by adipocytes which provides a negative feedback signal to control the amount of body fat. The action of leptin on food intake and weight loss is thought to be mediated by interaction with its hypothalamic receptor. We examined the biodistribution and brain uptake of radioiodinated leptin (123I-leptin) by dynamic gamma imaging in six anaesthetized New Zealand white rabbits. Leptin uptake was seen in the brain, lungs, liver and kidneys. In the brain, increase in radioactivity as a function of time was seen in the choroid plexus area. The choroid plexus to brain radioactivity ratio (CP/BR) was used as the target to background ratio. The CP/BR ratio increased up to approximately 40-60 min, after which a steady state in CP/BR was achieved. The steady state uptake ratio was higher in the rabbits that had fasted for only 6-8 h before the experiment (CP/BR approximately 2.5) than in those that had fasted for 25-27 h before the experiment (CP/BR approximately 1.8). Thus, leptin uptake in vivo occurs in the choroid plexus region of the brain and in the lungs, kidney and the liver. The uptake of leptin in the choroid plexus appears to be saturable, as indicated by the achieved steady state in the CP/BR radioactivity curve 40-60 min following 123I-leptin injection. The lower steady state CP/BR after prolonged fasting may be the result of the downregulation of leptin receptors in the choroid plexus.

Summanr Low-density lipoprotein (LDL) uptake in gliomas was studied to find out if LDL has potential as a drug camrer of boron. especially for boron neutron capture therapy. Single photon emission tomography (SPET) was performed 2 h and 20 h after intravenous injection of autologous 9"9Tc-labelled LDL in four patients with untreated and five patients with recurrent glioma. 9'Tc-LDL uptake was compared with the uptake of 9'Tc-labelled human serum albumin (HSA). an established blood pool marker. The intra-and peritumoral distributions of radioactivity in the SPET images were not identical for radiolabelled LDL and HSA. The mean LDL tumour to brain ratio, determined from transversal SPET slices at 20 h post injection. was 1.5 in untreated and 2.2 in recurrent gliomas; the corresponding ratios for HSA were 1.6 and 3.4. The brain to blood ratio remained constant at 2 h and 20 h in both types of tumours. These data are not consistent with highly selective, homogeneous uptake of LDL in gliomas. However, the different tumoral distribution and rate of uptake of 9Tc-LDL, as compared with 9'Tc-HSA, indicate that the uptake of LDL is different from that of HSA and that further studies on the mechanism of LDL uptake in glioma are warranted.Keywords: brain neoplasm; glioma; radionucides: 'Tc-albumin: 'Tc-LDL Brain tumours, about half of which are gliomas, are among the ten most common human tumours (Fogeiholm et al., 1984; Cancer Society of Finland, 1992). More than half of the gliomas are malignant with a median survival time of about I year (Kalijo et al., 1991). In recent decades there has been no significant improvement in survival of patients with malignant glioma in spite of efforts to improve conventional treatments and to develop new ones. Boron neutron capture therapy (BNCT) is a relatively new binary therapy utilising low-energy neutrons and the neutron capture reaction of boron (Barth and Soloway, 1992). Gliomas have been treated with BNCI and are still the main target of research in this field (Barth and Soloway, 1992). BNCT requires sufficiently high and selective uptake of boron in the tumour tissue. The boronated agent mainly used in BNCT has been watersoluble borocaptate (BSH). The tumour to brain (T:Br) boron concentration ratios obtained with BSH have been rather low and are apparently dependent on blood flow (Dewit et al., 1990;Barth and Soloway, 1992;Haritz et al., 1994). Low-density lipoprotein (LDL), the main cholesterol carrier in blood, has been suggested as a more selective vehicle for boron since growing tumour tissue requires cholesterol for cell membrane synthesis (Kahl and Callaway,. 1989;Laster et al., 1991;Vitols, 1991).LDL is carried into the cell by a receptor-mediated mechanism (Brown and Goldstein, 1986). Leukaemic cells, lung cancers, brain tumours and glioma cell lines have LDL receptors (Murakami et al., 1990;Rudling et al., 1990;Vitols et al., 1990Vitols et al., , 1992 and LDL has been used for drug delivery in ovarian cancer therapy trials (Gal et al., 1981; Filipowska et al., 1992)....