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The molecular tilt azimuth in domains of a condensed phase in monolayers of 1-monopalmytoyl-rac-glycerol at the air/water interface exhibits a regular star texture. Lateral-force microscopy has been used to investigate the friction behavior of a monolayer that has been transferred onto a silicon substrate. The condensed domains revealed strong friction anisotropies and asymmetries. The angular dependence of these properties correlates well with the tilt azimuth of the alkyl tails in the monolayer.

N-isopropyl-p-[125I]iodoamphetamine (125I-IMP) binding to crude synaptosomal membranes of rat brain was saturable and pharmacologically displacable. Scatchard analysis of binding data revealed an apparent dissociation constant, KDof 56.2±5.2 $mUM, and the estimated maximum number of binding sites, Bmaxof 7.5±1.1 nmoles mg-1protein; and competition studies demonstrated structure activity relationships among structural analogues of arylalkylamines. These findings suggest that the retention mechanism of IMP in the brain is probably associated with saturable binding of IMP to extreme high-density, relatively low-affinity binding sites rather than any of the well-known amine receptors.

123I-labelled 15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) myocardial single photon emission computed tomography (SPECT) was performed in 17 patients with hypertrophic cardiomyopathy, and was compared with 201Tl exercise stress myocardial perfusion SPECT images. Fourteen patients showed asymmetrical hypertrophy, and three demonstrated apical hypertrophy. SPECT was performed 20 min and 3 h after injection of 111 MBq 123I-BMIPP at rest. Exercise stress 201Tl SPECT was performed at 10 min and 3 h after injection and was compared with BMIPP imaging. In 13 patients BMIPP accumulation in the hypertrophied area in the 20 min image was lower than that of 3 h 201Tl uptake. Interestingly, six patients demonstrated 201Tl redistribution in the region where the uncoupling of BMIPP uptake at 20 min and 201Tl accumulation at 3 h after exercise was observed. These findings suggest that impaired fatty acid metabolism or utilization in hypertrophic myocardium and ischaemia or impaired coronary flow reserve may be one of the causes of the abnormality of fatty acid accumulation.

Triplet energy migration in poly[(9-phenanthrylmethyl methacrylate)-co-(methyl methacrylate)] films has been investigated by phosphorescence spectroscopy. Phosphorescence spectra from triplet trap sites were slightly shifted toward the low-energy side with a rise in temperature. The energy migration rates in these systems are complicated, since the trap sites have various energy levels depending on the amplitude of interaction energies. The kinetic analysis was made on the basis of Bässler's model in which the site energies have a Gaussian distribution. The fitting procedure well reproduced the phosphorescence decay data in the temperature range 15−100 K, indicating that the concentration of the supertrap increased steeply with the motion of the matrix polymer.

The rates of intramolecular triplet energy transfer from carbazole (Cz) to naphthalene (Np) chromophore for the bichromophoric compounds with a flexible alkyl spacer, Cz−(CH2)n−Np, n = 4−12, doped in poly(methyl methacrylate) matrixes were measured by phosphorescence spectroscopy and laser flash photolysis. The results were interpreted in terms of a model that allows a distribution of donor−acceptor distances for a given spacer length by using Dexter's equation. This model provided the transfer rate for all the compounds tested, and the comparative study with experimental results indicated that the “through-space” mechanism mainly governs the intramolecular triplet−triplet energy transfer in flexible spacer compounds. The temperature dependence of the rates of triplet energy transfer was also investigated.

In an effort to develop new, clinically useful 99Tcm-diaminodithiol (99Tcm-DADT) complexes for the evaluation of regional cerebral perfusion, basic diaminodithiols (DADT-TM, DADT-HM and DADT-MHM) and three diaminodithiol ligands functionalized with p-iodophenethyl (DADT-IPE), N-ethyl-p-fluorophenethyl amine (DADT-EFPE) or N-ethyl-p-iodophenethyl amine (DADT-EIPE), whose chemical structures are analogous to N-isopropyl-p-iodoamphetamine (IMP), were synthesized, labelled with 99Tcmand evaluated comparatively in experimental animals. In addition, the relationships between the chemical properties of the derivatives and their brain uptake and retention were investigated. The results were: (1) Isomeric configuration of 99Tcm-DADT complexes has an influence on uptake and retention in the rat brain. (2) In basic 99Tcm-DADT complexes, a correlation exists between initial brain uptake and lipophilicity, but in 99Tcm-DADT complexes containing a chemical structure similar to that of IMP, no correlation exists. (3) 99Tcm-DADT-IPE has relatively high uptake and long retention in the rat brain.

Highresolution threeheaded single photon emission computed tomography SPET equipped with fanbeam collimators was applied to myocardial perfusion imaging in infants aged from 1 to 11 months n5. A tabletop designed specifically for infants was fixed on the SPET couch to reduce the radius of camera rotation to 13.2 cm. Significant improvement in resolution was achieved with the fanbeam collimators compared to parallelhole highresolution collimators. With the administration of approximately 37 MBq 2644 MBq 201T1, 5 min acquisition time was possible for SPET imaging, which provided good image quality in all patients. Thus, a smaller administration dose is possible within a practical short acquisition time, Highresolution fanbeam SPET imaging can be a routine diagnostic method for heart disease in newborn babies and infants.

The Intrahepatic distribution of radioactivity after the per-rectal administration of 201TI-chloride and/or 99Tcm-pertechnetate was investigated in 177 studies in 149 patients with no liver disease or diffuse liver disease and compared with that of 99Tcm-stannous (99Tcm-Sn) colloid scintigrams. The patients were classified into two groups: distribution of intrahepatic radioactivity of 201Tl and/or 99Tcm-pertechnetate scintigrams similar to (homogeneous) or different from (heterogeneous) that of 99Tcm-Sn-colloid scintigrams. The heterogeneous group was divided into three subgroups: increased radioactivity of the right lobe (right dominant pattern), increased radioactivity of the left lobe (left dominant pattern) and uneven distribution of radioactivity in both lobes (uneven pattern). Of the 80 patients in whom the studies were performed in the supine position at rest, 14 (17.5) showed a heterogeneous pattern (8 right dominant, 4 left dominant, 2 uneven) and 66 (82.5) a homogeneous pattern. In the 97 patients allowed free body movement, 6 (6.2) showed a heterogeneous (1 right dominant, 5 left dominant) and 91 (93.8) a homogeneous pattern. A significant difference in the incidence of heterogeneous distribution between the resting and free body movement groups was found (P<0.05). One patient with a left dominant pattern after free body movement with 201Tl showed a right dominant pattern at rest in the 99Tcm-pertechnetate study. It is concluded that a heterogeneous intrahepatic distribution of inferior mesenteric vein blood is sometimes observed and that the distribution of portal vein blood flow seems to be affected by the patient's positioning and free body movement.

Among a group of patients (n=15) with acute coronary syndrome, the results of using two new myocardial radiopharmaceuticals - 123l-labelled 15-(p-iodo-phenyl)-3,R,S-methylpentadecanoic acid (BMIPP) and 123l-meta-iodobenzyl guanidine (MIBG) - were compared with dual 201Tl/99Tcm-pyrophosphate (Tl-PYP) imaging using single photon emission tomography (SPET). Defect scores were evaluated on a segment-by-segment basis for a total of 270 segments. For the 201Tl, BMIPP, and early and delayed MIBG studies, the mean (± S.D.) sums of defect scores were 9 ± 8, 18 ± 9, 22 ± 12 and 29 ± 9, respectively, revealing significantly higher scores for BMIPP and MIBG than 201Tl (P0.005). This was the case irrespective of various functional conditions, such as successful recanalization, failure of coronary angioplasty or restenosis. The culprit coronary artery was best identified using BMIPP, while MIBG SPET showed the most extensive defects. Normal perfusion with decreased BMIPP and MIBG uptake was frequently observed and associated with hypokinesis. 123I-BMIPP and MIBG are more sensitive for the detection of damaged myocardium, and the difference between perfusion and metabolism seems to reflect myocardial stunning.

Abstract: Carrier-free99mTcO4– eluated from clinical99Mo/99mTc generators was examined to determine its specific activity. The observed specific activity was found to be always lower than the calculated value based on the99Mo–99mTc–99Tc decay scheme data. These results could be explained in terms of existence of excess Tc loaded onto generator column.

The triplet energy migration and transfer in Langmuir−Blodgett films prepared by the copolymers of octadecyl methacrylate with 2-(9-carbazolyl)ethyl methacrylate and (4-bromo-1-naphthyl)methyl methacrylate were measured and simulated by the Monte Carlo method. At a high donor density (1.3 × 10^-6 mol/m²), the triplet energy transfer takes place by a dynamic process, i.e., a few steps of energy migration among carbazole (donor) chromophores, and followed by energy transfer to bromonaphthalene (acceptor). By solving the differential equations relevant to the energy migration and energy transfer on a two-dimensional square lattice of 31 × 31 = 961 lattice points, we successfully simulated the time evolution of the triplet energy quenching. The calculated quenching efficiencies were in agreement with the experimental values observed in the LB film of poly(octadecyl methacrylate) containing both the donor and acceptor moieties.

Triplet energy migration in poly[(9-phenanthrylmethyl methacrylate)-co-(methyl methacrylate)] films has been investigated by time-resolved phosphorescence spectroscopy in the temperature range 15−100 K. Phosphorescence spectra from triplet trap sites were slightly shifted toward the low-energy side with the elapse of time. The spectral shift was simulated by the Monte Carlo method. The simulation reproduced experimental data, which allowed estimation of the dispersity of the site energies. Due to homogeneous broadening, the distribution function became broader with the increase of temperature.

To investigate the utility of neuroreceptor imaging in ischaemic cerebrovascular disorders, dual-tracer autoradiography using 99Tcm-hexamethylpropyleneamine oxime (HMPAO) for the evaluation of cerebral blood flow and 125I-iomazenil for the evaluation of central-type benzodiazepine receptor density was performed in experimental brain ischaemia created by occlusion of the unilateral middle cerebral artery of the rat. In the acute phase of ischaemia, 125I-iomazenil accumulation showed less of a decrease than 99Tcm-HMPAO in the cerebral cortex of the lateral convexity and in the lateral segment of the caudate putamen in the lesioned cerebral hemisphere. In the sub-acute phase, both 125I-iomazenil and 99Tcm-HMPAO accumulation increased in the lesion compared with the acute phase. A large accumulation of 99Tcm-HMPAO and 125I-iomazenil in the lesion was considered to be due to luxury perfusion and penetration of 125I-iomazenil hydrophilic metabolites from the blood into the brain tissue through the altered blood-brain barrier. In the chronic phase, 125I-iomazenil accumulation showed a more marked decrease than 99Tcm-HMPAO in the lesion. Moreover, the ipsilateral thalamus, which is remote from the lesion, revealed decreased 125I-iomazenil accumulation despite normal 99Tcm-HMPAO accumulation. Since the central-type benzodiazepine receptors are principally located not on the glial cells but on the neurons, the receptor density may exhibit a change that parallels the neuron density. These results suggest that central-type benzodiazepine receptor imaging is useful for the evaluation of neuronal damage when used in conjunction with brain perfusion imaging in ischaemic cerebrovascular disorders, except in the sub-acute phase.