Millimeter-wave breast cancer imaging by means of a dual-step approach combining radar and tomographic techniques: preliminary results.

Breast cancer is one of the most diagnosed forms of cancer among women worldwide. However, the survival rate is very high when the tumor is diagnosed early. The search for diagnostic techniques increasingly able to detect lesions of the order of a few millimeters and to overcome the limitations of current diagnostic techniques (e.g., the X-ray mammography, currently used as standard for screening campaigns) is always active. Among the main emerging techniques, microwave and millimeter-wave imaging systems have been proposed, using either radar or tomographic approaches. In this paper, a novel dual-step millimeter-wave imaging which combines the advantages of tomographic and radar approaches is proposed. The goal of this work is to reconstruct the dielectric profile of suspicious regions by exploiting the morphological information from the radar maps as a priori information within quantitative tomographic techniques. Promising preliminary dielectric reconstruction results against simulated data are shown in both single- and dual-target scenarios, in which high-density healthy and tumor tissues are present. The reconstruction results were compared to the dielectric characteristics of human breast exvivo tissues used in the simulated models. The proposed dual-step approach allows to distinguish the nature of the targets also in the most challenging case represented by the co-presence of high-density healthy tissues and a malignant lesion, thus paving the way for a deeper investigation of this approach in experimental scenarios. Clinical Relevance-The proposed dual-step approach in the millimeter-wave regime allows to improve the reliability of the diagnostic technique, increasing its specificity.

Effect of vitamin E on characteristics of liver mitochondrial fractions from cold-exposed rats.

In cold exposed rats, it is known that vitamin E induces an increase in the respiration of the whole mitochondrial population isolated from liver. To obtain information on the effects of cold exposure and vitamin E treatment on the dynamics of mitochondrial population, we determined characteristics of rat liver mitochondrial fractions, resolved at 1,000 (M(1)), 3,000 (M(3)), and 10,000 g (M(10)). We found that cold exposure increased the liver content of total mitochondrial proteins irrespective of vitamin E treatment. Conversely, protein distribution among the mitochondrial subpopulations was differentially affected by cold and antioxidant integration. In a cold environment, the M(1) fraction, characterized by the highest O(2) consumption and H(2)O(2) production rates, underwent a remarkable protein content reduction, which was attenuated by vitamin E. These changes were dependent on the opposite effects of the two treatments on mitochondrial oxidative damage and susceptibility to swelling. The proteins of the other fractions, in which the above effects were lower, underwent smaller (M(3)) or no change (M(10)) in the treatment groups. The cold also led to an increase in O(2) consumption of the M(1) fraction which was accentuated by vitamin E treatment. This phenomenon and the vitamin-induced recovery of the M(1) proteins supply an explanation of the previously reported increase in the respiration of the whole mitochondrial population induced by vitamin E in the liver from cold exposed rats.

Effect of vitamin E administration on response to ischaemia-reperfusion of hearts from cold-exposed rats.

In both 3,5,3-triiodothyronine (T(3))-induced hyperthyroidism and cold-induced functional hyperthyroidism, the heart displays an increased susceptibility to oxidative challenge in vitro. Hearts from T(3)-treated rats also exhibit an increased susceptibility to ischaemia-reperfusion, a condition that raises free radical production. The present study was designed to establish whether cold-exposed rats exhibit an increased cardiac susceptibility to ischaemia-reperfusion which can be attenuated by vitamin E. The following four groups of animals were used: C, control rats (n = 8, temperature 24°C); C+VE, vitamin E-treated rats (n = 8, temperature 24°C); CE, cold-exposed rats (n = 8, temperature 4°C); and CE+VE, cold-exposed vitamin E-treated rats (n = 8, temperature 4°C). Langendorff preparations from these animals were submitted to 20 min ischaemia followed by 25 min reperfusion. At the end of the ischaemia-reperfusion protocol, homogenates and mitochondria were prepared and used for analytical procedures. With respect to control hearts, cold hearts showed a lower inotropic recovery and a higher oxidative stress, as inferred by higher levels of oxidized proteins and lipids and lower reduced glutathione levels. These changes were prevented when cold rats were treated with vitamin E. Evidence was also obtained that mitochondria are involved in the tissue derangement of cold hearts. Indeed, they display a faster production of reactive oxygen species, which causes mitochondrial oxidative damage and functional decline that parallel the tissue dysfunction. Moreover, vitamin E-linked improvement of tissue function was associated with a lower oxidative damage and a restored function of mitochondria. Finally, the mitochondrial population composition and Ca(2+)-induced swelling data indicate that the decline in mitochondrial function is in part due to a decrease in the amount of the highly functional heavy mitochondria linked to their higher susceptibility to oxidative damage and swelling. In conclusion, our work shows that vitamin E treatment attenuates harmful side-effects of the cardiac response to cold, such as oxidative damage and susceptibility to oxidants, thus preserving mitochondrial function and tissue recovery from ischaemia-reperfusion.

Oxidative stress in cold-induced hyperthyroid state.

Exposure of homeothermic animals to low environmental temperature is associated with oxidative stress in several body tissues. Because cold exposure induces a condition of functional hyperthyroidism, the observation that tissue oxidative stress also happens in experimental hyperthyroidism, induced by 3,5,3'-triiodothyronine (T(3)) treatment, suggests that this hormone is responsible for the oxidative damage found in tissues from cold-exposed animals. Examination of T(3)-responsive tissues, such as brown adipose tissue (BAT) and liver, shows that changes in factors favoring oxidative modifications are similar in experimental and functional hyperthyroidism. However, differences are also apparent, likely due to the action of physiological regulators, such as noradrenaline and thyroxine, whose levels are different in cold-exposed and T(3)-treated animals. To date, there is evidence that biochemical changes underlying the thermogenic response to cold as well as those leading to oxidative stress require a synergism between T(3)- and noradrenaline-generated signals. Conversely, available results suggest that thyroxine (T(4)) supplies a direct contribution to cold-induced BAT oxidative damage, but contributes to the liver response only as a T(3) precursor.

Vitamin E attenuates cold-induced rat liver oxidative damage reducing H2O2 mitochondrial release.

Vitamin E is a major chain-breaking antioxidant which is able to reduce liver oxidative damage without modifying aerobic capacity in T(3)-treated rats. We investigated whether vitamin E has similar effects in hyperthyroid state induced by cold exposure. Cold exposure increased aerobic capacity and O(2) consumption in homogenates and mitochondria and tissue mitochondrial protein content. Vitamin E did not modify aerobic capacity and mitochondrial protein content of cold liver, but increased ADP-stimulated respiration of liver preparations. Succinate-supported H(2)O(2) release rates were increased by cold during basal and stimulated respiration, whereas the pyruvate/malate-supported ones increased only during basal respiration. Vitamin administration to cold-exposed rats decreased H(2)O(2) release rates with both substrates during basal respiration. This effect reduced ROS flow from mitochondria to cytosol, limiting liver oxidative damage. Cold exposure also increased mitochondrial capacity to remove H(2)O(2), which was reduced by vitamin treatment, showing that the antioxidant also lowers H(2)O(2) production rate. The different effects of cold exposure and vitamin treatment on H(2)O(2) generation were also found in the presence of respiration inhibitors. Although this can suggest that the cold and vitamin induce opposite changes in mitochondrial content of autoxidizable electron carriers, it is likely that vitamin effect is due to its capacity to scavenge superoxide radical. Finally, vitamin E reduced mitochondrial oxidative damage and susceptibility to oxidants, and prevented Ca(2+)-induced swelling elicited by cold. In the whole, our results suggest that vitamin E is able to maintain aerobic capacity and attenuate oxidative stress of hepatic tissue in cold-exposed rats modifying mitochondrial population characteristics.

Free radical involvement in doxorubicin-induced electrophysiological alterations in rat papillary muscle fibres.

OBJECTIVE: This work was designed to determine whether the doxorubicin-induced changes in heart electrical activity are due to increased free radical production and membrane oxidative damage. METHODS: Four groups of rats (60 days old) were used. One group was untreated and the others were treated with doxorubicin (DXR), DXR and vitamin E, and DXR and N-acetylcysteine (NAC), respectively. DXR was administered by single i.p. injection (20 mg/kg b.wt.). Vitamin E was administered by ten daily i.m. injections (100 mg/kg), while NAC (100 mg/kg) was injected i.p. 1 h before and 7 h after DXR. The effectiveness of the drug in inducing oxidative stress in different tissues and of the antioxidants in offering protection was established by determining antioxidant capacity, susceptibility to oxidative stress, and lipid peroxidation in heart, liver, and blood. The drug effect on heart electrical activity was determined by measuring the heart rate in vivo and action potential configuration in papillary muscle fibres in vitro. Heart lipid peroxidation and electrical activity were also examined in both vitamin E and NAC-treated rats. RESULTS: DXR treatment decreased antioxidant capacity and increased lipid peroxidation and susceptibility to oxidative stress in heart and blood, but not in liver. DXR administration to rats treated with antioxidants did not produce significant changes in antioxidant capacity and susceptibility to oxidative stress even in heart and blood. Furthermore, lipid peroxidation in heart and liver from DXR- and vitamin E-treated rats, and in liver from DXR- and NAC-treated rats was lower than in untreated controls. DXR treatment also increased the duration of ventricular action potentials in untreated rats, but not in antioxidant-treated rats. The treatment of control animals with the antioxidants affected lipid peroxidation, but not cardiac electrical activity. CONCLUSIONS: The protection offered by antioxidants against electrophysiological alterations indicates a free radical involvement in such alterations. In contrast, although electrical modifications are associated with increased peroxidative processes and both are prevented by the antioxidants, it is not yet clear whether a causative relationship exists between them.

Effect of thyroid state on enzymatic and non-enzymatic processes in H2O2 removal by liver mitochondria of male rats.

We investigated thyroid state effect on capacity of rat liver mitochondria to remove exogenously produced H2O2, determining their ability to decrease fluorescence generated by an H2O2 detector system. The rate of H2O2 removal by both non respiring and respiring mitochondria was increased by hyperthyroidism and decreased by hypothyroidism. However, the rate was higher in the presence of respiratory substrates, in particular pyruvate/malate, indicating a respiration-dependent process. Generally, the changes in H2O2 removal rates mirrored those in H2O2 release rates excluding the possibility that endogenous and exogenous H2O2 competed for the removing system. Pharmacological inhibition revealed thyroid state-linked differences in antioxidant enzyme contribution to H2O2 removal which were consistent with those in antioxidant system activities. The H2O2 removal was only in part due to enzymatic systems and that imputable to non-enzymatic processes was higher in hyperthyroid and lower in hypothyroid mitochondria. The levels of cytochrome c and the light emissions, due to luminol oxidation catalyzed by cytochrome/H2O2, exhibited similar changes with thyroid state supporting the idea that non-enzymatic scavenging was mainly due to hemoprotein action, which produces hydroxyl radicals. Further support was obtained showing that the whole antioxidant capacity, which provides an evaluation of capacity of the systems, different from cytochromes, assigned to H2O2 scavenging, was lower in hyperthyroid than in hypothyroid state. In conclusion, our results show that mitochondria from hyperthyroid liver have a high capacity for H2O2 removal, which, however, leading in great part to more reactive oxygen species, results harmful for such organelles.

Cold-induced hyperthyroidism produces oxidative damage in rat tissues and increases susceptibility to oxidants.

In this work, we investigated whether cold exposure-induced hyperthyroidism increases oxidative damage and susceptibility to oxidants of rat liver, heart and skeletal muscle. All tissues exhibited gradual increases in hydroperoxide and protein-bound carbonyl levels. Glutathione peroxidase activity increased in all tissues after 2 days and further increased in the muscle after 10 days of cold exposure. Liver glutathione reductase activity increased after 10 days of cold exposure, while heart and muscle activities were not modified. Vitamin E levels were not affected by cold, while coenzyme Q9 and coenzyme Q10 levels decreased in heart and muscle after 2-day cold exposure and were not further modified after 10 days. Liver coenzyme Q9 levels increased after 2 days whereas coenzyme Q10 levels increased after 10 days in the cold. The whole antioxidant capacity was lowered, while parameters positively correlated with susceptibility to oxidants were increased by cold. Lipid fatty acid composition was modified in all tissues. In particular, fatty acid unsaturation degree increased in heart and muscle. Cytochrome oxidase activity increased, suggesting an increased content of hemoproteins, which are able to generate .OH radical. This view was supported by the observation that the tissue susceptibility to H(2)O(2) treatment, which is strongly correlated to iron-ligand content, increased after cold exposure. In this frame, it is apparent that the increase in oxidative capacity, necessary for homeotherm survival in low temperature environments, has potential harmful effects, because it results in increased susceptibility to oxidative challenge.

(Imidazolylphenyl)pyrrol-2-one inhibitors of cardiac cAMP phosphodiesterase.

Seven 3-alkyl-4-aryl-1,5-dihydro-2H-pyrrol-2-ones were prepared as potential inhibitors of cardiac cAMP phosphodiesterase (PDE). The design of these compounds made use of rolipram, a known inhibitor of the brain cAMP PDE isozyme, as a lead structure and was guided by a model which describes the features required for potent inhibition of the cardiac isozyme. Syntheses for the new compounds are described, together with the results of theoretical and crystallographic studies aimed toward ascertaining their three-dimensional structures. The activities of these compounds as inhibitors of the cardiac and brain cAMP PDE isozymes and their positive inotropic activity in ferret papillary muscle are also reported. Selected compounds were further examined in an in vivo hemodynamic model. One compound 1,5-dihydro-4-[4-(1H-imidazol-1- yl)phenyl]-3-methyl-2H-pyrrol-2-one, was identified as a potent and selective positive inotropic agent and inhibitor of cardiac cAMP PDE.

Synthesis and cardiac electrophysiological activity of N-substituted-4-(1H-imidazol-1-yl)benzamides--new selective class III agents.

The synthesis and cardiac electrophysiological activity of 18 N-substituted imidazolylbenzamides or benzene-sulfonamides are described. Compounds 6a,d,f-k and 11 exhibited potency in the in vitro Purkinje fiber assay comparable to that of N-[2-(diethylamino)ethyl]-4- [(methylsulfonyl)amino]benzamide (1, sematilide), a potent selective class III agent which is undergoing clinical trials. These data indicate that the 1H-imidazol-1-yl moiety is a viable replacement for the methylsulfonylamino group for producing class III electrophysiological activity in the N-substituted benzamide series. N-[2-(Diethylamino)ethyl]-4-(1H-imidazol-1-yl)benzamide dihydrochloride (6a) was further studied in two in vivo models of reentrant arrhythmias and showed potency and efficacy comparable to those of 1.

Heteroaryl-fused 2-phenylisothiazolone inhibitors of cartilage breakdown.

The synthesis, biological evaluation, and structure-activity relationships of a series of N-phenyl heteroaryl-fused isothiazolones are described. These isothiazolones have been shown to exhibit potent, dose-dependent inhibition of IL-1 beta-induced breakdown of proteoglycan in a cartilage organ culture assay. This effect is likely due to inhibition of MMP activation and a consequent reduction in MMP activity following IL-1 beta stimulation. Thus these compounds potentially represent simple, non-peptidic disease-modifying agents for the treatment of arthritic diseases. To examine the effects of structure on in vitro activity, three general features of the molecules were varied, substituents on the pendant N-phenyl group, the position of ring fusion to the isothiazolone, and substituents on the fused ring peri to the isothiazolone sulfur.

Orally active isoxazoline glycoprotein IIb/IIIa antagonists with extended duration of action.

Modification of the alpha-carbamate substituent of isoxazoline GPIIb/IIIa (alphaIIb beta3) antagonist DMP 754 (7) led to a series of alpha-sulfonamide and alpha-sulfamide diaminopropionate isoxazolinylacetamides which were found to be potent inhibitors of in vitro platelet aggregation. Aryl- and heteroaryl-alpha-sulfonamide groups, in conjunction with (5R)-isoxazoline (2S)-diaminopropionate stereochemistry, were found to impart a pronounced duration of antiplatelet effect in dogs, potentially due to high affinity for unactivated platelets. Isoxazolylsulfonamide 34b (DMP 802), a highly selective GPIIb/IIIa antagonist, demonstrated a prolonged duration of action after iv and po dosing and high affinity for resting and activated platelets. The prolonged antiplatelet profile of DMP 802 in dogs and the high affinity of DMP 802 for human platelets may be predictive of clinical utility as a once-daily antiplatelet agent.

Discovery of an orally active series of isoxazoline glycoprotein IIb/IIIa antagonists.

Using isoxazoline XR299 (1a) as a starting point for the design of highly potent, long-duration GPIIb/IIIa antagonists, the effect of placing lipophilic substituents at positions alpha and beta to the carboxylate moiety was evaluated. Of the compounds studied, it was found that the n-butyl carbamate 24u exhibited superior potency and duration of ex vivo antiplatelet effects in dogs. Replacement of the benzamidin-4-yl moiety with alternative basic groups, elimination of the isoxazoline stereocenter, and reversal of the orientation of the isoxazoline ring resulted in lowered potency and/or duration of action.

Effect of thyroid state on lipid peroxidation, antioxidant defences, and susceptibility to oxidative stress in rat tissues.

The effects of altered thyroid states on lipid peroxidation, antioxidant capacity, and susceptibility to oxidative stress of rat tissues were examined. Hypothyroidism was induced by administering methimazole in drinking water for 15 days. Hyperthyroidism was elicited by a 10-day treatment of hypothyroid rats with tri-iodothyronine (10 micrograms/100 g body weight). In tissues of hypothyroid rats the lipid peroxidation was not modified, whereas in hyperthyroid rats lipid peroxidation increased in liver and heart but not in skeletal muscle. The glutathione peroxidase activity increased significantly in heart and muscle of hypothyroid rats and in muscle of hyperthyroid rats. The glutathione reductase activity was not modified in tissues of hypothyroid and hyperthyroid rats. In both rat groups the whole antioxidant capacity of tissues decreased, but significantly only in liver and heart. The results obtained studying the response to oxidative stress in vitro indicated that the susceptibility to oxidative challenge was increased in all tissues of hyperthyroid rats and in heart and muscle of hypothyroid animals. These results are explainable in terms of tissue variations in haemoprotein content and/or of antioxidant capacity. Since it has been reported that hypothyroidism offers in vivo protection against free radical damage, we suggest that such an effect could be due to greater effectiveness of cellular defence systems different from antioxidant ones.

Antioxidant-sensitive shortening of ventricular action potential in hyperthyroid rats is independent of lipid peroxidation.

The effects of substances able to reduce peroxidative processes on thyroid hormone-induced electrophysiological changes in ventricular muscle fibres were examined. For this study, 60 day old euthyroid and hyperthyroid rats were used. One group of hyperthyroid rats was untreated and the others were treated with vitamin E, N-acetylcysteine, and cholesterol, respectively. Hyperthyroidism was elicited by 10 day treatment with daily i.p. injections of triiodothyronine (10 microg/100 g body weight). Vitamin E and N-acetylcysteine were administered for 10 days by daily i.m. injections (20 mg/100 g body weight) and daily i.p. injections (100 mg/100 g body weight), respectively. Cholesterol was administered by cholesterol-supplemented diet (4%) from day 30. Hyperthyroidism induced a decrease in the whole antioxidant capacity and an increase in both lipid peroxidation and susceptibility to oxidative stress. Vitamin E and N-acetylcysteine administration to hyperthyroid rats led to reduction in lipid peroxidation and susceptibility to oxidative stress and to increase in antioxidant level, while the diet addition of cholesterol decreased lipid peroxidation but did not modify the other parameters. The hyperthyroid state was also associated with a decrease in the duration of the ventricular action potential recorded in vitro. The vitamin E and N-acetylcysteine administration attenuated the thyroid hormone-induced changes in action potential duration, which was however, significantly different from that of the euthyroid rats. In contrast, cholesterol supplementation did not modify the electrical activity of hyperthyroid heart. These results demonstrate that the triiodothyronine effects on ventricular electrophysiological properties are mediated, at least in part, through a membrane modification involving a free radical mechanism. Moreover, they indicate that the antioxidant-sensitive shortening of action potential duration induced by thyroid hormone is likely independent of enhanced peroxidative processes in sarcolemmal membrane.

Role of nitric oxide in the reperfusion induced injury in hyperthyroid rat hearts.

We recently reported that hyperthyroidism affects the heart response to ischemia/reperfusion. A significant tachycardia during reperfusion was associated with an increase in the oxidative stress of hearts from T3-treated animals. In the present study we checked the possible role of nitric oxide (NO) in this major stress induced by the hyperthyroid state. We compared the functional recovery from ischemia/reperfusion of Langendorff preparations from euthyroid (E) and hyperthyroid (H, ten daily intraperitoneal injections of T3, 10 microg/100 g body weight) rats, in the presence and in the absence of 0.2 mM Nomega-nitro-L-arginine (L-NNA). At the end of the ischemia/reperfusion protocol (10 min preischemic perfusion, 20 min global ischemia, 30 min reperfusion) lipid peroxidation, antioxidant capacity (CA) and susceptibility to in vitro oxidative stress were determined on heart homogenates. The main effect of hyperthyroidism on the reperfusion functional response was confirmed to be a strong tachycardic response (154% recovery at 25 min reperfusion) accompanied by a low recovery in both left ventricular diastolic pressure (LVDP) and left ventricular dP/dtmax. This functional response was associated with a reduction in CA and an increase in both lipid peroxidation and susceptibility to oxidative stress. Perfusion of hearts with L-NNA per se had small but significant negative chronotropic and positive inotropic effects on preischemic performance of euthyroid rat hearts only. More importantly, L-NNA perfusion completely blocked the reperfusion tachycardic response in the hyperthyroid rats. Concomitantly, myocardium oxidative state (lipid peroxidation, CA and in vitro susceptibility to oxidative stress) of L-NNA perfused hearts was similar to that of E animals. These results suggest that the higher reperfusion-induced injury occurring in hyperthyroid animals is associated with overproduction of nitric oxide.

Effect of vitamin E on the response to ischemia-reperfusion of Langendorff heart preparations from hyperthyroid rats.

Hyperthyroidism has been reported to decrease heart antioxidant capacity and increase its susceptibility to in vitro oxidative stress. This may affect the heart response to ischemia-reperfusion, a condition that increases free radical production. We compared the functional recovery from in vitro ischemia-reperfusion (Langendorff) of hearts from euthyroid (E), hyperthyroid (H, ten daily intraperitoneal injections of T3, 10 microg/100g body weight), vitamin E-treated (VE, ten daily intramuscular injections, 20 mg/100g body weight) and hyperthyroid vitamin E-treated (HVE) rats. We also determined lipid peroxidation, tissue antioxidant capacity and the tissue capability to face an oxidative stress in vitro. A significant tachycardia was displayed during reperfusion following 20 min ischemia by the hyperthyroid hearts, together with a low recovery of left ventricular developed pressure (LVDP) and left ventricular dP/dt(max). When H hearts were paced at 300 beats/min, the functional recovery (LVDP and dP/dt(max)) was close to 100% and significantly higher than in E paced hearts. At the end of the ischemia-reperfusion protocol, myocardium antioxidant capacity was significantly lower, whereas lipid peroxidation and the susceptibility to in vitro oxidative stress were higher in the T3 treated (H) than in euthyroid rats. The in vitro tachycardic response, the reduction in the antioxidant capacity and the increase in lipid peroxidation were prevented by treatment of hyperthyroid rats with vitamin E (HVE). These results suggest that the tachycardic response to reperfusion following chronic T3 pretreatment was associated with the reduced capability of the heart to face oxidative stresses in hyperthyroidism.

DNA synthesis in isolated mitochondria: effect of thyroidectomy and of triiodothyronine administration in vivo.

The incorporation was studied of labelled deoxy-ribonucleosides triphosphates into acid-insoluble material by isolated liver mitochondria, obtained from either normal young male rats, or thyroidectomized at weaning, or thyroidectomized and then treated with triiodothyronine (T3). The incorporation extents in normal animals decreased with the age starting from the weaning until the 210th day. Thyroidectomy reduced the incorporation extent to about 70% of the values observed in normal animals. During the T3 treatment of thyroidectomized rats a sharp increase of incorporation was observed one day after the first administration, followed by a decrease from the 1st to the 3rd day; successively the incorporation extent remained unchanged until the 12th day. Finally, evidence was provided that T3 doses used were thyreomimetic and definitely lower than the thyreotoxic ones.

Effect of thyroidectomy and in vivo administration of triiodothyronine on DNA synthesis in isolated mitochondria.

The experimental conditions were studied which allow hormonal levels to affect the incorporation of labelled deoxyribonucleosides triphosphates (dNTP's) into mitochondrial DNA by isolated liver mitochondria, obtained either from thyroidectomized young male rats (T) or from animals of the same age thyroidectomized and then treated with triiodothyronine (T + T3). It was demonstrated that: (a) extramitochondrial DNA, on which extramitochondrial DNA polymerase may act, was absent; (b) the permeability to dNTP's, the thymidine kinase activity, the energy supply, and the nuclease activities were unaffected by hormonal conditions; (c) the bacterial contaminations contribute for only 1% to incorporation. The characterization of incorporation product showed that: (a) such product was indeed DNA, as it was DNase-degradable for about 90%; (b) the labelled DNA was indeed mitochondrial DNA, as a 10 minutes preincubation with acriflavine or ethydium bromide (Eth. Br.) inhibited the synthesis by 90%.

Modifications of antioxidant capacity and heart electrical activity induced by hydroperoxide in normal and vitamin E-fed rats.

Wistar rats, fed control or vitamin E-supplemented diet, were subjected to oxidative stress by a ten day treatment with daily intraperitoneal dose of tert-butyl hydroperoxide (TBHP) (0.1 mumol/100 g body weight). The effectiveness of both diet and hydroperoxide treatment was established by determining the antioxidant capacity of blood, liver, and heart with an enhanced luminescence method. While the diet addition of vitamin E increased the antioxidant capacity of all the tissues in treated and untreated animals, the hydroperoxide treatment failed to decrease liver antioxidant capacity in control diet fed animals. The effect of the reiterated production of free radicals on electrophysiological properties of myocardium was determined by studying the heart rate in vivo and the time course of the surface electrical activity in papillary muscle fibers in vitro. In vivo, a significant tachycardia was found only in TBHP-treated, normal diet fed rats. The duration of action potential, recorded in Krebs' solution at 26 degrees C, was not affected by diet in untreated animals but was modified by hydroperoxide treatment in a diet-dependent way: shortened in normal diet-fed rats and lengthened in vitamin E-supplemented diet-fed rats. On the basis of analogies with the results of electrophysiological recordings on different preparations subjected to oxidative stress in vitro, we suggest that the changes of action potential duration might depend on relative levels of added pro-oxidant and cell antioxidants.