Bridge percolation: electrical connectivity of discontinued conducting slabs by metallic nanowires.

The properties of nanostructured networks of conductive materials have been extensively studied under the lens of percolation theory. In this work, we introduce a novel type of local percolation phenomenon used to investigate the conduction properties of a new hybrid material that combines sparse metallic nanowire networks and fractured conducting thin films on flexible substrates. This original concept could potentially lead to the design of a novel composite transparent conducting material. Using a complementary approach including formal analytical derivations, Monte Carlo simulations and electrical circuit representation for the modelling of bridged-percolating nanowire networks, we unveil the key relations between linear crack density, nanowire length and network areal mass density that ensure electrical percolation through the hybrid. The proposed theoretical model provides key insights into the conduction mechanism associated with the original concept of bridge percolation in random nanowire networks.

Striking differences in cellular catalase activity between two DNA repair-deficient diseases: xeroderma pigmentosum and trichothiodystrophy.

Xeroderma pigmentosum (XP) and trichothiodystrophy (TTD) are two recessively transmitted human diseases characterized by DNA repair deficiency. While XP is associated with a very high incidence of cancer on skin exposed to sunlight, TTD is not a cancer-prone disease. Therefore, unrepaired UV-induced DNA lesions do not appear to be enough to give rise to tumors. In order to understand the differences between these two syndromes, we measured catalase activity in cellular extracts, UV irradiated or not, and quantified H2O2 production following in vitro UV irradiation. We confirmed on 21 different XP diploid fibroblast lines that catalase activity was decreased on average by a factor of five as compared to controls, while XP heterozygote lines exhibited intermediary responses. All seven TTD lines we tested were deficient in UV-induced lesion repair and exhibited a high level of catalase activity. However, molecular analysis of catalase transcription showed no difference between normal, XP and TTD cell lines. This was confirmed by Western blots where the amount of catalase subunits was identical in all cell lines studied. Finally, UV irradiation induces five and three times more H2O2 production in XP lines compared with TTD or controls respectively. These striking differences between TTD and XP indicate that UV light, directly or indirectly, together with defective oxidative metabolism may increase the initiation and/or the progression steps in the XP environment compared to TTD. This may partly explain the different tumoral phenotype observed between the two diseases.

[Anti-radical enzymes, oxygenated free radicals and lipoperoxydation in rheumatoid polyarthritis. Effects of treatment with D-penicillamine]. / Enzymes anti-radicalaires, radicaux libres oxygénés et lipoperoxydation dans la polyarthrite rhumatoïde. Effets du traitement par la D-pénicillamine.

Three aspects of the action of oxygenated free radicals were studied in 10 controls and 20 patients with rheumatoid arthritis, 11 not treated and 9 treated with D-penicillamine. Free radical production was evaluated in whole blood, malondialdehyde was measured in plasma, the concentration of antiradicular enzymes (copper and manganese superoxide dismutase, catalase and glutathion peroxydase) in hemolysate, platelets and plasma and copper superoxide dismutase activity in a chloroform erythrocyte extract. Only patients treated with D-penicillamine showed a significant decrease in the concentration of platelet anti-radicular enzymes and plasma manganese superoxide dismutase. The involvement of oxygenated free radicals in the pathophysiology of rheumatoid arthritis and in the mechanism of action of D-penicillamine in this pathology is discussed.

Preparation and characterization of xanthine oxidase-antibody and -hapten conjugates for use in sensitive chemiluminescent immunoassays.

Methods have been developed to label haptens or antibodies with xanthine oxidase for use in chemiluminescent enzyme immunoassays. We have optimised coupling reactions involving the use of heterobifunctional cross-linkers, the introduction of sulfhydryl groups and the utilization of accessible cysteine residues on the native enzyme. The versatility of xanthine oxidase as a label in immunoanalysis was studied in five assay systems, including both competition procedures (TT4 and direct serum estradiol assays) and immunometric assays (TSH, IgE, hCG). In all of the assay systems, the performance of the conjugates was excellent, demonstrating that the chelate enhanced luminometric detection of xanthine oxidase should have a wide potential in many immunoassays.

Application of a long-term enhanced xanthine oxidase-induced luminescence in solid-phase immunoassays.

The use of xanthine oxidase (XO) as a label in immunoanalysis has not been previously reported. This can be explained by the difficulties encountered in XO assays (poor sensitivity and versatility) and the competitive inhibition of the enzyme by allopurinol, a widely used hypouricemic agent. We demonstrate here that both difficulties can be circumvented. (i) The XO-dependent luminescent signal related to the oxidation of luminol is dramatically enhanced in the presence of iron-EDTA complex and sodium perborate in alkaline buffer. The mechanism of this enhancement is consistent with an O2-driven Fenton reaction, leading to the production of highly reactive OH radical. (ii) Residual inhibition of solid-phase bound XO by serum allopurinol and its metabolites is spontaneously reversible and can be prevented by the presence of folic acid or azahypoxanthine in the incubation buffer. With these two problems solved, XO can be classified as a choice label in immunoanalysis with the following properties: (i) high detection sensitivity (3 amol label), (ii) long-term luminescent signal (several days), (iii) versatile preparation and stability of conjugates, and (iv) long-term stability of the luminescence reagent. As an example of application, some data concerning total IgE and direct 17 beta-estradiol assays are described. Several other luminescent immunoassays of large and small molecules have been developed using XO conjugates as tracer (free and total T4, ultrasensitive thyroid stimulating hormone, CA 19.9, prolactin, hCG, specific IgE, anti-toxoplasma, and anti-chlamydia IgG), thus proving that XO can be classified as a universal label.

T4 and ultrasensitive TSH immunoassays using luminescent enhanced xanthine oxidase assay.

The use of xanthine oxidase in immunoanalysis has never been reported. We describe here a procedure in which the xanthine oxidase dependent luminescence of luminol is enhanced in the presence of Fe-EDTA complex, providing an highly sensitive assay (3 amol of enzyme) and a long-term signal. This specific amplification has been applied to T4 and ultrasensitive TSH solid phase immunoassays, with T4-XO and anti-TSH monoclonal antibody-XO conjugates as tracers. The performances of these assays are at least equivalent to those obtained with iodinated tracers, using the same solid phases and the same calibrators. The major advantages of these immunoassays are: (1) the long-term signal which can be repeatedly recorded over several days, (2) the high detection sensitivity, (3) the long-term stability of the luminescence reagent and (4) the stability of the conjugates.

[Assay of erythrocyte, platelet and serum superoxide dismutase, glutathione peroxidase and catalase in rheumatoid polyarthritis]. / Dosage de la superoxyde dismutase, de la glutathion peroxydase et de la catalase érythrocytaire, plaquettaire et sérique au cours de la polyarthrite rhumatoïde.

The authors present a study of superoxide dismutase, catalase and glutathione peroxidase in hemolysis product, platelets and serum of 23 patients with rheumatoid polyarthritis and 11 healthy subjects. The nature of the treatment enables to divide the 23 patients into 3 groups: group I (8 cases): no treatment; Group II (7 cases): steroid therapy alone; group III (8 cases): basic treatment associated (3 cases) or not (5 cases) to steroid therapy. Statistical analysis shows no significant difference, whatever the environment and the treatment contemplated. The significance of these results is discussed and compared with literature data concerning only enzymatic activities and not the blood levels as in the present study.

[Toxicity of oxygen and (Cu) superoxide dismutase and (Mn) superoxide dismutase in newborn infants with respiratory distress. Preliminary results]. / Toxicité de l'oxygène et taux de surenoxyde dismutase (Cu) et de surenoxyde dismutase (Mn) chez le nouveau-né en détresse respiratoire. Résultats préliminaires.

Twelve premature newborns mechanically ventilated with high FiO2 for hyaline membrane disease were tested for SOD contents during their first two weeks of life. CuSOD and MnSOD were measured in plasma, platelets and red cells using a radioimmunology method. No correlation was found between FiO2 levels neither with CuSOD and MnSOD contents. Furthermore no correlation was found between the SOD contents, at birth, and the constitution of bronchopulmonary dysplasia (BPD). Our results don't prove any relationship between lack of SOD and BPD. BPD pathogeny is certainly plurifactorial. Other protecting systems against O2 toxicity are also known to play an important role.

[Concentrations of superoxide dismutase (copper and manganese), catalase and glutathione peroxidase in red cells, platelets and plasma in patients with rheumatoid polyarthritis]. / Concentration en superoxyde dismutase (cuivre et manganèse), catalase et glutathion peroxydase dans les hématies, les plaquettes et le plasma de sujets atteints de polyarthrite rhumatoïde.

Antioxidant enzymes assays (CuZnSOD, MnSOD, catalase glutathione peroxidase) have been performed by radioimmunoassay in erythrocytes, platelets and plasma of rheumatoid polyarthritis patients. No difference has been shown as compared with control subjects whatever the therapy or the length of time for which the patients have been affected. If a deficiency in antioxidant enzymes is related to the destruction of joint tissues by free radicals, it cannot be detected in blood tissue elements.

Anti-inflammatory activity of superoxide dismutases: inhibition of adriamycin induced edema in rats.

Various superoxide dismutases from different sources, containing Cu, Mn or Fe at the active centre, have been examined with respect to anti-inflammatory activity in a model using adriamycin-induced edema in rats. Very large differences in efficiency are observed, the most active being E. coli Mn-SOD and bovine Cu-SOD. The Fe-SOD from E. coli is active whereas P. leiognathi Fe-SOD is not. Human Mn-SOD shows no significant activity and homologous rat Cu-SOD is totally inactive. Yeast Cu-SOD shows pro-inflammatory properties. Anti-inflammatory activity is not a function of molecular weight or circulation life-time.

Immunoreactive SOD-1 in amniotic fluid, amniotic cells and fibroblasts from trisomy 21 fetus.

Copper superoxide dismutase (Cu-SOD or SOD-1) was measured by radioimmunoassay (RIA) in amniotic cells and fluid as well as in fetal trisomy 21 fibroblasts. The significant increase of the SOD-1 activity observed in amniotic cells and fetal trisomy 21 fibroblasts demonstrates the early physiopathogenic expression of the supernumerary chromosome 21 in affected patients.

Effects of the 1,5-benzodiazepine clobazam on pituitary hormones in the male rat.

The aim of this study is to evaluate the effects of the acute and subchronic administration of the benzodiazepine clobazam (20 mg/kg orally) on the plasma levels of the pituitary hormones (prolactin, FSH and LH) in the male rat. This 1.5 benzodiazepine did not induce any variation of the hormone levels either after acute or subchronic administration. These negative data are discussed as compared to the effects of other benzodiazepines of GABA and GABA receptor agonists and antagonists on the pituitary hormone levels according to particular experimental conditions.

Pharmacokinetic and anti-inflammatory properties in the rat of superoxide dismutases (Cu SODs and Mn SOD) from various species.

The comparison of the anti-inflammatory properties (carrageenan paw edema in the rat) of exogenous Cu SODs from various species and human Mn SOD administered at doses corresponding to clinical schedules, shows that human and bovine Cu SOD are fully active, whereas rat Cu SOD and Mn SOD are inefficient. This difference does not correspond to the similarity of pharmacokinetic properties (blood levels, subcellar location in kidney cortex) of the Cu proteins or to the increased circulating life time of Mn SOD. The pharmacological activity of exogenous SOD is limited to heterologous Cu SODs in the rat. A similar problem may occur in man. The true mechanism of action of Cu SOD remains to be elucidated.

Immunoreactive copper-zinc superoxide-dismutase (SOD-1) in mosaic trisomy 21 and normal subjects.

Copper-zinc superoxide-dismutase (SOD-1) (E.C. 1.15.11) levels were measured in 9 children with mosaic trisomy 21 as identified by R, H, G-banding technics. Radioimmunoassay of erythrocytes and fibroblasts did not demonstrate any significant correlation between levels of SOD-1 and percentage of trisomic 21 cells in the two target cell populations studied.

[Neuroendocrine effects of a sodium valproate and diazepam combination in the male rat]. / Effets neuroendocriniens de l'association valproate de sodium diazépam chez le rat mâle.

The effects of chronic administration of sodium valproate (200 mg/Kg/d i.p.) and diazepam (5 mg/Kg/d i.m.) alone or in association on the plasma levels of the pituitary hormones (prolactin, FSH and LH) were studied in the m ale rat. Sodium valproate increases prolactin plasma levels. This effect is antagonized by diazepam. Both molecules do not affect FSH levels, whereas they increase LH levels when given alone or in association. This pharmacological data state precisely the hypothalamohypophysiotropic effects of valproate and diazepam during its association.

[Effects of the acute and chronic administration of clobazam on plasma prolactin and gonadotrophins in the male rat]. / Effets de l'administration aiguë et chronique de clobazam sur la prolactine et les gonadotrophines plasmatiques chez le rat mâle.

The effects of the acute or chronic administration of clobazam (20 mg/kg per os) on the plasma levels of the main anterior pituitary hormones (prolactin, FSH and LH) were studied in the male rat. This 1,5 benzodiazepine did not induce any modification of the hormones levels either after acute or chronic administration. These negative data are discussed as compared to the effects of other benzodiazepines or GABA and GABAmimetic drugs on the pituitary hormones levels according to particular experimental conditions.

Variation of superoxide dismutase levels in fetal calf serum.

The results of cytogenetic studies and of other experiments based on tissue-culture systems may be influenced by various components of tissue-culture medium and by variations among batches of fetal calf serum used for supplementation of the media. Negative results may be obtained in breakage studies as a consequence of medium components with a protective effect [6]. Attention has been drawn to differences in growth pattern [8] and mitotic indices [11] in lymphocyte cultures set up with different culture media. Variations in the incidence of sister-chromatid exchanges according to differences in media [7] and sera [5] have also been observed. It has been suggested [9] that the failure of some laboratories to detect increases in sister-chromatid exchanges after treatment with the tumor promoter phorbol-myristate-acetate (PMA) may be due to high concentrations of the free-radical-scavenging enzyme superoxide dismutase (SOD) in the sera used and that heat inactivation of the sera may be responsible for these differences. In the following, we report that considerable variation in the SOD content exists between batches of fetal calf serum, up to levels with anticlastogenic effect.

Immunoreactive Cu-SOD and Mn-SOD in lymphocytes sub-populations from normal and trisomy 21 subjects according to age.

Copper and manganese superoxide dismutases (Cu-SOD and Mn-SOD) were measured by radioimmunoassay in B and T lymphocytes and macrophages, in patients with trisomy 21 and in matched controls. In the controls, Cu-SOD was present in greater amounts than Mn-SOD and there were quantitative differences in the distribution in the three cellular sub-populations. In trisomy 21, levels of Cu-SOD were raised, with no change in levels of Mn-SOD, supporting the theory of a gene dosage effect. There were significant positive and negative correlations between age and Cu-SOD levels in controls, and a correlation approaching significance for Mn-SOD. In trisomy 21, there was no correlation between age and Cu-SOD levels, and the only significant correlation for Mn-SOD was for B lymphocytes.

[Neuroendocrine effects of the chronic administration of carbamazepine in male and female rats]. / Effets neuroendocriniens de l'administration chronique de carbamazépine chez le rat male et femelle.

Relationships between epilepsy, antiepileptic drugs and neuroendocrinological events justify the study of an eventual influence of antiepileptic drugs of the regulation mechanisms of ovulation. Thus carbamazepine effects on the oestrus cycle of female rats and on FSH, LH and PRL serum levels has been studied. Carbamazepine was given orally once daily for 21 consecutive days to Wistar AF SPF female (exhibiting regular 4 days cycles) and male rats: three doses were used: 100, 10 and 5 mg per kg bodyweight. Oestrous cycle was studied by daily vaginal smears. Our data show that carbamazepine do not significantly modify the evolution of oestrous cycle nor FSH, LH or PRL serum levels. These results agree with those of literature even if literature data have been obtained with a single administration in man. Finally our data confirm also a previous work on oestrous cycle effects of perinatal exposure to carbamazepine in the female rat.