Chronic brain inflammation and persistent herpes simplex virus 1 thymidine kinase expression in survivors of syngeneic glioma treated by adenovirus-mediated gene therapy: implications for clinical trials.

The long-term consequences of adenovirus-mediated conditional cytotoxic gene therapy for gliomas remain uncharacterized. We report here detection of active brain inflammation 3 months after successful inhibition of syngeneic glioma growth. The inflammatory infiltrate consisted of activated macrophages/microglia and astrocytes, and T lymphocytes positive for leucosyalin, CD3 and CD8, and included secondary demyelination. We detected strong widespread herpes simplex virus 1 thymidine kinase immunoreactivity and vector genomes throughout large areas of the brain. Thus, patient evaluation and the design of clinical trials in ongoing and future gene therapy for brain glioblastoma must address not only tumor-killing efficiency, but also long-term active brain inflammation, loss of myelin fibers and persistent transgene expression.

Quinidine and melittin both decrease the fluidity of liver plasma membranes and both inhibit hormone-stimulated adenylate cyclase activity.

Increasing concentrations of either quinidine or melittin gave a dose-dependent inhibition of both the glucagon- and fluoride-stimulated activities of adenylate cyclase in the liver plasma membranes. At similar concentrations these agents increased the order of liver plasma membranes as detected by a fatty acid ESR probe, doxyl stearic acid. This increase in bilayer order (decrease in 'fluidity') is suggested to explain the inhibitory action of quinidine on adenylate cyclase activity but only in part contributes to the inhibitory action of melittin on adenylate cyclase. Arrhenius plots of fluoride-stimulated activity became non-linear in the presence of either quinidine or melittin, with a single well-defined break occurring at around 12 degrees C in each instance. Arrhenius plots of the glucagon-stimulated activity also exhibited such a novel break at around 12 degrees C when either quinidine or melittin were present as well as exhibiting a break at around 28 degrees C, as was seen in the absence of these ligands. The fatty acid spin probe inserted into liver plasma membranes detected a novel lipid phase separation occurring at around 12 degrees C when either quinidine or melittin was present and showed that the lipid phase separation occurring at around 28 degrees C in native membranes was apparently unaffected by these ligands.

The phase behaviour of dispersions of Bis-Azo PC: photoregulation of bilayer dynamics via lipid photochromism.

A phospholipid, 1,2-bis(4-(n-butyl)phenylazo-4'-phenylbutyroyl)phosphatidylcholine (Bis-Azo PC), has been synthesised and shown to form stable bilayer vesicles. Light-scattering measurements and differential scanning calorimetry show that a dispersion of the lipid has a cooperative phase transition at a similar temperature to that of dipalmitoylphosphatidylcholine, which Bis-Azo PC resembles in overall size. The phase behaviour of Bis-Azo PC has been investigated by fluorescence spectroscopy and using a series of spin-labelled fatty acid probes. Fluorescence measurements using chlorophyll a as probe sense the onset of the cooperative phase transition, but this is not clearly revealed by any of the spin probes tested. Hysteresis in the phase transition is detected both by light scattering measurements and by fluorescence spectroscopy. No transition is observed for a lipid analogue having a palmitic acid chain and a single azo-containing substituent. Bis-Azo PC is reversibly photochromic, isomerising on exposure to ultraviolet light to a photostationary state mixture where cis isomer predominates. Electron microscopy shows that photoisomerisation decreases average vesicle size, and light scattering and calorimetry demonstrate that the cooperative phase transition is abolished. Illumination with visible light establishes a new photostationary state where trans isomer predominates, and the phase transition is restored. The ability to modulate bilayer phase behaviour reversibly has possible application to relaxation studies of bilayer membrane function, and to drug delivery research.

Distribution of 5-doxylstearic acid in the membranes of mammalian cells.

Concentration-dependent spin broadening of ESR spectra of the nitroxide 5-doxylstearic acid has been used to evaluate the distribution of 5-doxylstearic acid in the membranes of intact mouse thymus-bone marrow (TB) and Chinese hamster ovary (CHO) cells. TB cells, CHO cells, erythrocytes, and isolated plasma membranes from CHO cells were labelled with 5-doxylstearic acid and the peak to peak linewidths of the central line of the resulting ESR spectra were measured. The measured line widths were linearly dependent on the amount of 5-doxylstearic acid incorporated into the sample over the range of 0-0.18 mol nitroxide per mol lipid. In erythrocytes, the relationship between linewidths approximated a linear function at lower concentrations of 5-doxylstearic acid, up to 0.07 mol nitroxide per mol lipid. The amount of broadening of the central line for a given amount of 5-doxylstearic acid was far less for intact cells than for either erythrocytes or plasma membrane, indicating that the 5-doxylstearic acid samples a much larger lipid pool in the intact cells. With the broad assumption that the mobility of the 5-doxylstearic acid is similar in different membranes, the size of the lipid pool sampled by 5-doxylstearic acid is approximately equal to the total cellular lipid in intact cells. If a given concentration of 5-doxylstearic acid sampled only the plasma membrane of TB or CHO cells, we would expect to see a linewidth corresponding to a 12-20-fold greater local concentration of 5-doxylstearic acid than was observed, since the plasma membranes of CHO and TB cells represent only 5-8 percent of the total cellular lipid. Therefore, the 5-doxylstearic acid must distribute into most or all cellular membranes of intact cells and is not localized in the plasma membrane alone.

Dimethylnitrosamine inhibits the glucagon-stimulated adenylate cyclase activity of rat liver plasma membranes and decreases plasma membrane fluidity.

The effect of the hepatocarcinogen dimethylnitrosamine on rat liver plasma membrane adenylate cyclase activity and lipid fluidity was assessed. Glucagon-stimulated adenylate cyclase activity exhibited a complex response to increasing concentrations of dimethylnitrosamine, whereas fluoride-stimulated adenylate cyclase activity was progressively inhibited. Maximal inhibitory effects were observed at a concentration of 15 mM in both cases. The activity of detergent-solubilized adenylate cyclase was unaffected by dimethylnitrosamine. ESR analysis using a fatty acid spin probe showed that dimethylnitrosamine produced a marked, dose-dependent reduction in the fluidity of the plasma membrane with a maximal effect occurring at 20 mM. Dimethylnitrosamine also elevated the temperature at which the lipid phase separation occurred in rat liver plasma membranes, from 28 degrees C to 31 degrees C. The non-carcinogenic but structurally similar compound, dimethylamine hydrochloride neither inhibited adenylate cyclase nor decreased plasma membrane fluidity. It is suggested that the decrease in membrane fluidity, induced by dimethylnitrosamine, via its effects on membrane fluidity, could influence plasma membrane function and cellular regulation.

Free radicals and food irradiation.

Ionizing radiation can be used to control insect and microbial infestation of foodstuffs, inhibit sprouting, delay ripening and reduce the dangers from food-poisoning bacteria. Irradiation produces free radicals, most of which decay rapidly, although some are more persistent. These latter radicals can be detected and characterized by electron spin resonance (ESR). In bone and other calcified tissues, the radiation-induced radicals are distinguishable from naturally occurring radicals, and their stability makes them ideal for radiation dosimetry. The radicals induced in plant material, such as seeds and dried spices, are generally indistinguishable from the endogenous radicals and decay over a period of days or weeks. However, in many of these materials, a radiation-specific radical can be detected at low concentration, thereby permitting identification of irradiated samples, although precluding accurate dosimetry. ESR, although not universally applicable, currently provides the most specific method for the detection of irradiated food.

Evidence for free radical generation after primary percutaneous transluminal coronary angioplasty recanalization in acute myocardial infarction.

In animal models, oxygen-derived free radicals have been found to be important mediators of reperfusion injury to ischemic but viable myocardium. However, in humans, there is no direct evidence of free radical production after the restoration of coronary artery patency in acute myocardial infarction. The purpose of this study was to quantitate and assess the time course of free radical production in coronary venous outflow in patients with acute myocardial infarction undergoing successful recanalization of the infarct-related artery by primary percutaneous transluminal coronary angioplasty (PTCA). Primary PTCA was performed in 17 patients with acute myocardial infarction of < 6 hours duration. Direct free radical production was assessed by coronary venous effluent blood sampling before PTCA and at timed intervals up to 24 hours (or 48 hours in 6 patients) after recanalization. All samples were added to the spin trapping agent alpha-phenyl N-tert butyl nitrone and analyzed by electron paramagnetic resonance spectroscopy. Vessel patency resulted in a sharp increase in free radical signal. Relative to the level before PTCA, the changes reached statistical significance after only 15 minutes (p < 0.05). Peak signals were observed between 1 1/2 and 3 1/2 hours (p < 0.001), then declined up to 5 hours. A second increase in signal level was detected between 18 and 24 hours despite no angiographic evidence of reocclusion. A gradual decline was observed after 24 hours. These findings provide the first direct and quantitative evidence of free radical production in the immediate postrecanalization phase after thrombotic occlusion of a major coronary artery in humans.

Singlet oxygen and superoxide characteristics of a series of novel asymmetric photosensitizers.

The singlet oxygen quantum yields and superoxide quantum yields for a series of novel compounds based on an asymmetrical protoporphyrin molecule have been examined. Electron spin resonance was used to measure superoxide yield and time resolved luminescence for singlet oxygen. A comparison between these results and previously published cell survival data was carried out. A broad association was found between singlet oxygen quantum yield and clonogenic cell kill.

Free radical production from normal and adriamycin-treated rat cardiac sarcosomes.

The production of hydroxyl radicals in rat myocardial sarcosomes treated with adriamycin was demonstrated by the electron spin resonance technique of spin trapping. Using the spin trapping agent 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), the formation of a hydroxyl radical spin adduct was observed in adriamycin-treated rat heart sarcosomes with NADPH as co-factor. Oxygen, NADPH and sarcosomal protein were absolute requirements for hydroxyl radical production. Hydroxyl radical spin adduct formation was not inhibited by the metal ion chelators diethylenetriaminepenta-acetic acid (DETAPAC) or desferrioxamine, or by addition of superoxide dismutase but could be inhibited by addition of catalase and high concentration of the hydroxyl radical scavengers mannitol and N-acetylcysteine. Hydroxyl radical production in adriamycin-treated rat myocardial sarcosomes appears to arise from the reductive metabolism of adriamycin by an NADPH-dependent quinone reductase--NADPH: cytochrome P450 reductase; the reduced quinone (semiquinone) reduces oxygen to hydrogen peroxide, probably via superoxide, although this was not detected. The hydrogen peroxide appears to react directly with adriamycin semiquinone, although involvement of traces of iron in a Fenton type of reaction cannot be excluded. From the observations it is suggested that adriamycin-induced cardiotoxicity is an oxidative pathology arising from intracellular generation of relatively high levels of hydroxyl radicals.

Free radical formation from anthracycline antitumour agents and model systems--I. Model naphthoquinones and anthraquinones.

Several naphthoquinones and anthraquinones were chosen as simple models of the anthracycline drugs and their semiquinone radical anions were generated by various methods. With the exception of 1,4-naphthoquinone, all of the quinones studied gave radicals that were highly reactive with oxygen, but which, in its absence, were stable over a limited pH range. The radicals were studied using electron spin resonance (ESR) spectroscopy and an examination was made of the effect on the distribution of the unpaired electron, of introducing various groups into the conjugated ring system. Hydroxyl groups capable of participating in strong intramolecular hydrogen bonding with neighbouring carbonyl groups had a marked influence on electron distribution and reduced the effects of intermolecular hydrogen bonding of the radicals with solvent molecules.

Forskolin and ethanol both perturb the structure of liver plasma membranes and activate adenylate cyclase activity.

Both forskolin and ethanol elicit the activation of basal and ligand-stimulated adenylate cyclase activities in rat liver plasma membranes. Ethanol is most potent at activating the fluoride- and glucagon-stimulated activities whilst having little effect on basal activity. In contrast forskolin exerts its greatest effect on basal activity. Over the concentration range that ethanol activates adenylate cyclase, it also increases bilayer fluidity as indicated by a decrease in the values of the order parameters for an incorporated fatty acid spin probe. At high concentrations forskolin does increase bilayer fluidity. However, it only begins to do so at concentrations above those where forskolin has already exerted its maximal effect in activating adenylate cyclase. Forskolin can still activate, albeit to a reduced extent, detergent-solubilized adenylate cyclase whereas ethanol cannot. Forskolin elicits a pronounced rise in hepatocyte intracellular cyclic AMP concentrations, whereas ethanol does not. Both forskolin and ethanol reduce the temperature of onset of the lipid phase separation occurring in rat liver plasma membranes. This is detected in Arrhenius plots of both glucagon-stimulated adenylate cyclase activity and order parameters of an incorporated fatty acid spin probe, where we find that forskolin is particularly potent in decreasing the temperature at which this lipid phase separation occurs. Our results are consistent with the notion that forskolin exerts its effect on adenylate cyclase primarily by a direct action on the catalytic unit of the enzyme. However, as forskolin is a potent perturber of the organisation of the lipid bilayer it is possible that this could modulate its effect on adenylate cyclase and might be expected to affect the activity of other membrane enzymes.

Fatal anaphylaxis in systemic mastocytosis.

A 42-year-old woman died after an episode of anaphylaxis associated with a raised serum histamine level. A diagnosis of systemic mastocytosis was established, with lymphadenopathy and hepatosplenomegaly, not associated with the usually pre-existing skin lesions of urticaria pigmentosa.

An assessment of whole blood impedance aggregometry using blood from normal subjects and haemodialysis patients.

Impedance aggregometry allows the measurement of platelet responses in whole blood as well as in PRP. The variability of haematocrit values encountered when applying this technique to haemodialysis patients prompted an investigation of the effects of red cells on platelet aggregation in whole blood. Collagen induced aggregation was measured in both PRP and whole blood from haemodialysis patients and healthy controls. Platelets from haemodialysis patients were less aggregable than those from the controls when tested in PRP, but more aggregable when tested in whole blood. Blood samples with a range of haematocrit values were prepared by mixing PRP and autologous red cells, and used to study the effect of haematocrit on platelet aggregation. In blood from control subjects aggregation rate was reduced by rising haematocrit but no reduction of maximum aggregation occurred until haematocrit exceeded 40%. In contrast uraemic platelets showed increased responses in the presence of red cells. In a limited cross over study no significant difference was found in the effect on platelet aggregation of washed erythrocytes from uraemic and non-uraemic donors. It is concluded that red cell presence influences platelet aggregation by complex mechanisms during impedance aggregometry and that this effect must be considered when interpreting results.

Anthralin-derived transients--II. Formation of the radical by spontaneous fragmentation of both singlet and triplet states of the 10,10'-dehydrodimer: radical pair multiplicity effects.

The singlet and triplet states of the anthralin (1,8-dihydroxy-9-anthrone) dehydrodimer have been produced selectively in benzene via pulsed laser excitation and pulse radiolysis respectively. The lifetime of S1 is less than or equal to 30 ps, that of T1 short but unspecified. Both states fragment spontaneously to yield a pair of anthralin radicals. The singlet radical pair predominantly undergoes geminate recombination within the solvent cage. In contrast, the corresponding triplet radical pair undergoes essentially exclusive cage escape to give the anthralin free radical (lambda max 370, 490 and 720 nm) which recombines under normal diffusive conditions. Both recombination processes lead, at least in part, to one or more species which have been assigned as tautomeric forms of the original dimer. The anthralin free radical in benzene is insensitive to the vitamin E model 6-hydroxy-2,2,5,7,8-pentamethylchroman and reacts only slowly with oxygen.

An ESR spin label study of childhood kidney tumours.

The isolated membranes of cells from normal kidneys, foetal kidneys, Wilms' tumours, and bone-metastasizing renal tumours of childhood (BMRTC) have been examined by electron spin resonance, using the lipophilic spin label 5-doxyl stearic acid. No differences in membrane rigidity were detected between normal kidney cells and Wilms' tumour cells, over the temperature range 5 to 40 degrees C. The membranes of foetal kidney cells showed no significant difference at physiological temperatures, but were more rigid than the membranes of normal kidney cells at lower temperatures. In contrast, BMRTC cells showed lower membrane rigidity than normal kidney cells at all temperatures studied, BMRTC cells, unlike normal kidney and Wilms' tumour cells, lack surface fibronectin, but addition of fibronectin to BMRTC cell membranes, in suspension, had no detectable effect on their rigidity.

The transfer of strontium-90 and caesium-137 to milk in a dairy herd grazing near a major nuclear installation.

A field investigation of the transfer of artificially produced radionuclides in the pasture--cow--milk pathway has been made at a farm close to the nuclear fuel reprocessing installation at Sellafield on the north-west coast of England. This paper reports results from analyses of samples collected during 1981, reports transfers coefficients for 90Sr and 137Cs from various types of feed to milk, and discusses factors that affect the transfer of these radionuclides. It is shown that during 1981 a large proportion of the 90Sr and 137Cs consumed by cattle grazing near Sellafield was derived from activity deposited in previous years. Transfer coefficients to milk, Fm, have been derived which are within the ranges of those observed in tracer and fallout studies. There are significant seasonal changes in transfer. For 90Sr, values of Fm between 9 X 10(-4)d 1(-1) and 4 X 10(-3)d 1(-1) have been obtained. It is concluded that this large range arises because daily intakes of 90Sr by the herd during the winter months are lower (by a factor of about 3) than intakes during the summer months and that the concentration of 90Sr in milk is not in equilibrium with intake, that is, the concentration of 90Sr in milk is maintained both by recent intakes and by remobilisation of activity that has been accumulated in bone from earlier intakes. For 137Cs, values of Fm between 3 X 10(-3)d 1(-1) and 9 X 10(-3)d 1(-1) have been obtained. It is concluded that this range most probably occurs because during the summer months, when the cows are grazing, a substantial proportion of the 137Cs intake is associated with soil on the surface of herbage and that, in this form, the 137Cs is less available for uptake from the digestive tract of the cows.

The measurement of radiocaesium in sheep by an in vivo technique.

This paper discusses the use of a large sodium iodide detector to determine gamma-ray emitting radionuclides in living animals, and in particular the application of the technique to investigations that have followed the Chernobyl reactor accident. A series of experiments to validate the technique is presented. The detector and its associated electronics and data collection equipment are sufficiently robust for use in the field, and ancillary equipment to immobilize subjects such as sheep and cattle are readily available. Although the in vivo procedure underestimates activity concentrations in muscle tissue compared to results from samples obtained post mortem, the advantage is that the same animal can be measured repeatedly and reproducibly.

Plutonium and Cs-137 in autopsy tissues in Great Britain.

Tissues removed at autopsy from members of the general public contain significantly higher concentrations of plutonium and 137Cs in west Cumbrians than in people from three other regions of Great Britain. Several autopsy cases from Cumbria showed unusually high values of plutonium. Subsequently it was found that the subjects had been former employees of British Nuclear Fuels.

Use of ESR for the detection of irradiated dates (Phoenix dactylifera L.).

One variety (Aple) of Libyan dry dates (Phoenix dactylifera L.) was irradiated in a 60Co source to absorbed doses of 0.8, 1.0, 1.5 and 2.0 kGy. Unirradiated date stone contains a radical with a single line g = 2.0045, feature A. Irradiation to a dose of 2.0 kGy (the recommended dose for fruits in U.K.) induces the formation of additional radicals with signals g = 1.9895 and 2.0159, feature C. The single line having g = 2.0045 decays in both unirradiated and irradiated samples whereas the additional signals g = 1.9895 and 2.0159 remain almost unchanged over a period of time 15 months stored at room temperature and 4 degrees C.