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Strong evidence is emerging that mitochondrial permeability transition (MPT) may be important in certain physiological conditions and, above all, in the processes of cell damage and death. Reversible MPT, triggered by inducing agents in the presence of calcium ions, has resulted in the opening of a dynamic multiprotein complex formed in the inner mitochondrial membrane and has caused large-amplitude mitochondrial swelling. In the present work, the exposure of de-energized rat cardiac mitochondria to peripheral benzodiazepine receptor (PBR) ligands (1-(2-chlorophenyl-N-methyl-1-methylpropyl)-3-isoquinolinecarboxamide (PK 11195), 7-chloro-5-(4-chlorophenyl)-1,3-dihydro-1-methyl-2H-1,4-benzodiazepin-2-one (Ro5-4864), and diazepam) produced a dose-dependent and cyclosporin A (CSP)-sensitive loss of absorbance, which was indicative of mitochondrial swelling. By contrast, the addition of a high-affinity central benzodiazepine receptor ligand (clonazepam) was ineffective, even at the highest concentration tested. The ultrastructural changes associated with swelling were similar in mitochondria exposed either to PK 11195 or to calcium. Supporting the apoptotic role of PK 11195-induced swelling, supernatants from mitochondria that had undergone permeability transition caused apoptotic changes in isolated cardiac nuclei. In addition, ultrastructural abnormalities were observed in rat cardiac tissue following in vivo PK 11195 administration, with these abnormalities being prevented by CSP co-administration. These data indicate that PBR ligands induce mitochondrial permeability transition and ultrastructural alterations in isolated cardiac mitochondria as well as in myocardiocytes, suggesting a novel strategy for studying the implication of PBR ligands as apoptosis inducers, through a probable effect on the MPT pore.

Cross sections per equivalent quantum, in the energy range 0.3–1.0 GeV, have been measured for spallation residuals from 51V, 55Mn, natural Fe, and 59Co targets. Mean cross sections per photon have been deduced in this energy range and the data analysed in terms of charge-dispersion curves and mass-yield distributions. The mean cross sections per photon have also been compared with a semiempirical Rudstam's formula. A satisfactorily good agreement has been found with the calculated yields within a factor of two.

The CO2-laser-induced decomposition of cyclohexene has been studied in the presence of SiF4, SF6 and C6F6 as sensitizers. The pressure range investigated is between 10 and 30 Torr at laser fluences between 0.20 and 1.20 J cm−2. At the same time measurements of the IR multiphoton absorption of the three sensitizers were also performed. The results have been analyzed within the framework of a kinetic model based on the assumption that the rate is controlled by vibrational energy transfer from the multiphoton-excited sensitizer molecules to the reactant. Evidence is presented to show that these sensitized reactions proceed under non-equilibrium conditions.

Mean cross sections for the photoproduction of 11C and 7Be from 40Ca targets have been measured using bremsstrahlung beams in the energy range 0·3–1 GeV. The values obtained turned out to be much larger than those expected from a simple spallation mechanism. A fragmentation-like process has therefore been suggested to explain such a discrepancy.

The use of the 19F(γ, n)18F, 27Al(γ, x)24Na, 197Au(γ, n)196Au, and 12C(γ, x)7Be reactions as absolute monitors for high-energy, high-intensity bremsstrahlung beams is discussed. The cross sections per equivalent quantum and the absolute cross sections, in the energy range 300–1000 MeV, are reported for these reactions. 19F(γ, n)18F, 27Al(γ, x)24Na, and 12C(γ, x)7Be reactions are proposed as very simple and suitable systems for monitoring purposes.

Aluminium targets have been irradiated with bremsstrahlung beams at energies between 0·3 GeV and 1GeV and the cross-sections of the photoproduction of 18 F have been measured by activation analysis.

The (γ, n) cross sections per equivalent quantum of 12C, 103Rh, 127I, 197Au and 238U have been measured with a bremsstrahlung beam of maximum energies in the range 1–5.5 GeV. Within the experimental errors of the activation method, no contribution of photons above 1 GeV was found. This result disagrees with some previous measurements at energies below 1 GeV but agrees with the predicted values obtained from simple theoretical estimates.

The use of the ferrous sulfate dosimeter in the energy range of 0.3–1 GeV is proposed. The linearity range of dosimeter and the comparison between its response and that of the Wilson quantameter are described. Approximate G values at 0.3 and 1 GeV have been determined.

The separation of Tellerium 127 and 129 nuclear isomers by paper chromatography is described. The dibutyltelluride, formed from tellurite during isomer transition in a medium of HCl-butyl alcohol, travels with the solvent from whilst the tellurite shows a Rf = 0·60.