Involvement of reactive oxygen species in the microsomal S-oxidation of thiobenzamide

Summary Superoxide dismutase, catalase and methional proved capable of inhibiting the microsomal oxidation of thiobenzamide, which is most probably catalyzed by the flavin-containing monooxygenase. This indicates that excited oxygen species (e. g.·O ₂ ^– , H₂O₂, ·OH) are involved in the catalytic cycle of this enzymatic reaction. CO, which inhibits the cytochrome P-450-dependent oxygen radical formation, had no effect on the oxidation reaction, suggesting that the source of the reactive oxygen species is not the microsomal mixed-function oxidase.     

Relations du « métabolisme respiratoire » des bactéries et du type de bactériophage avec l'activité de substances antiphages

Summary Quantitative determination of bacteriolysis with different T_1–7-phages confirms earlier observations that with substances inhibiting the action of T₁-phage the normal respiratory metabolism of the protected bacteria is quantitatively restored in every detail.With T₂-phage, showing a different respiratory course of bacteriolysis, no effect is obtained with the same substance, either on the respiration of the bacteria or on the typical course of respiration during bacteriolysis. The action of the phage inhibiting substance against T₁-phage is therefore an effect of definite specificity.     

Proliferationen der Fischepidermis nach der Einwirkung von inhibitoren des glykolytischen Energiestoffwechsels

Summary When fluoride-ions or monoiodoacetate is added to the ambient medium, there occur in fish larvae after 12 h, and in eels after 24 h, in some places, solid epidermal proliferations. The effect of glycolysis inhibitors on epidermal mitotic activity might be due to an impairment of energy metabolism as it is nullified by a simultaneous application of inorganic diphosphate or by doubled O₂ partial pressure of 320 mm Hg.     

Modulation of dopaminergic transmission by alpha-noradrenergic agonists and antagonists: Evidence for antidopaminergic properties of some alpha antagonists

Summary The effects on dopamine (DA) metabolism, on³H-spiperone binding and on amphetamine-induced stereotypies of a variety of drugs with different actions on alpha₁-and alpha₂-noradrenergic (NA) receptors have been investigated.The preferential alpha₂-antagonists yohimbine, rauwolscine, piperoxane and esproquin as well as the preferential alpha₁-antagonists corynanthine and WB4101 increased homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in the rat striatum, mesolimbic area, and cortex. Prazosine and clonidine tended to reduce HVA and DOPAC. The preferential alpha₂-antagonists, tolazoline and RX-781094A, had no measurable effects on DA metabolism even at high doses.Those compounds which in comparable doses increased DA metabolism inhibited³H-spiperone binding in the hippocampus. The effects in the striatum and cortex were smaller and did not show a relation to those in hippocampus or on DA metabolism. Only the yohimbine alkaloids antagonized amphetamine-induced stereotypies.The results suggest that the effects on DA metabolism at least of yohimbine, rauwolscine, and corynanthine are related to their intrinsic antidopaminergic properties. The same might be true, although with a lesser degree of certainty, for piperoxane, esproquin, and WB4101.Since many of the tested compounds possessing alpha-antagonistic properties interacted with the DA system, a close molecular relationship between alpha-noradrenergic and DA receptors might be anticipated. The preference of these compounds for the hippocampal subtype of DA receptors might indicate a particular role of the latter in the regulation of DA metabolism. On the other hand, the antagonism against haloperidol's enhancing effect on DA metabolism by clonidine suggests a modulatory NA influence on DA transmission. The observation that clonidine reduced the effects of yohimbine and piperoxane to a lesser degree than that of haloperidol, is in agreement with this notion.Part of this work has been presented at the 13th Meeting of the Union of Swiss Societies of Experimental Biology, Lausanne, March 26/27. 1981 (for abstract see Waldmeier and Bischoff, 1981).     

Der Einfluss von 2-Deoxy-D-glucose auf die Substratoxydation in Ascites-Tumorzellen

Summary The effect of the glycolytic inhibitor 2-deoxy-D-glucose on the oxidation of¹⁴C-labelled substrates of the tricarboxylic acid cycle was investigated in ascites carcinoma cells of the mouse. In the presence of high concentrations of glucose, deoxyglucose stimulates the oxidation of pyruvate C-2 and C-3 to CO₂, but not the oxidation of succinate C-1,4 to CO₂. While deoxyglucose causes, in the absence of glucose, an inhibition of the oxidation of exogenous palmitate C-1 to CO₂, it causes, in the presence of glucose, a stimulation of the palmitate oxidation. There is a possible correlation between the effect of deoxyglucose on the intracellular ATP metabolism and the effect of deoxyglucose on the palmitate oxidation.     

Hypoxia in the regulation of neural stem cells

In aerobic organisms, oxygen is a critical factor in tissue and organ morphogenesis from embryonic development throughout post-natal life, as it regulates various intracellular pathways involved in cellular metabolism, proliferation, survival and fate. In the mammalian central nervous system, oxygen plays a critical role in regulating the growth and differentiation state of neural stem cells (NSCs), multipotent neuronal precursor cells that reside in a particular microenvironment called the neural stem cell niche and that, under certain physiological and pathological conditions, differentiate into fully functional mature neurons, even in adults. In both experimental and clinical settings, oxygen is one of the main factors influencing NSCs. In particular, the physiological condition of mild hypoxia (2.5–5.0% O₂) typical of neural tissues promotes NSC self-renewal; it also favors the success of engraftment when in vitro-expanded NSCs are transplanted into brain of experimental animals. In this review, we analyze how O₂ and specifically hypoxia impact on NSC self-renewal, differentiation, maturation, and homing in various in vitro and in vivo settings, including cerebral ischemia, so as to define the O₂ conditions for successful cell replacement therapy in the treatment of brain injury and neurodegenerative diseases.     

The response of human skeletal muscle tissue to hypoxia

Hypoxia refers to environmental or clinical settings that potentially threaten tissue oxygen homeostasis. One unique aspect of skeletal muscle is that, in addition to hypoxia, oxygen balance in this tissue may be further compromised when exercise is superimposed on hypoxia. This review focuses on the cellular and molecular responses of human skeletal muscle to acute and chronic hypoxia, with emphasis on physical exercise and training. Based on published work, it is suggested that hypoxia does not appear to promote angiogenesis or to greatly alter oxidative enzymes in skeletal muscle at rest. Although the HIF-1 pathway in skeletal muscle is still poorly documented, emerging evidence suggests that muscle HIF-1 signaling is only activated to a minor degree by hypoxia. On the other hand, combining hypoxia with exercise appears to improve some aspects of muscle O₂ transport and/or metabolism.     

Über die Wirkung von Prostaglandin E1 auf den Ca-Haushalt isolierter Meerschweinchenherzen

Summary The stimulatory effect of PGE₁ on different functions of isolated guinea-pig hearts (Langendorff method, Tyrode solution) was coupled with an increase in the rate of⁴⁵Ca uptake from the perfusion medium. The total myocardial Ca content and the amount of exchangeable cellular Ca were not affected. This action of PGE₁ on the myocardial Ca metabolism seems to be related to the positive inotropic action of PGE₁ and can most probably be explained by an increase in the membrane permeability to Ca ions (similar to the action of epinephrine).     

Role of the ubiquitin–proteasome system in the regulation of P2Y13 receptor expression: impact on hepatic HDL uptake

The protective effect of high density lipoproteins (HDL) against atherosclerosis is mainly attributed to their capacity to transport excess cholesterol from peripheral tissues back to the liver for further elimination into the bile, a process called reverse cholesterol transport (RCT). Recently, the importance of the P2Y₁₃ receptor (P2Y₁₃-R) was highlighted in HDL metabolism since HDL uptake by the liver was decreased in P2Y₁₃-R deficient mice, which translated into impaired RCT. Here, we investigated for the first time the molecular mechanisms regulating cell surface expression of P2Y₁₃-R. When transiently expressed, P2Y₁₃-R was mainly detected in the endoplasmic reticulum (ER) and strongly subjected to proteasome degradation while its homologous P2Y₁₂ receptor (P2Y₁₂-R) was efficiently targeted to the plasma membrane. We observed an inverse correlation between cell surface expression and ubiquitination level of P2Y₁₃-R in the ER, suggesting a close link between ubiquitination of P2Y₁₃-R and its efficient targeting to the plasma membrane. The C-terminus tail exchange between P2Y₁₃-R and P2Y₁₂-R strongly restored plasma membrane expression of P2Y₁₃-R, suggesting the involvement of the intra-cytoplasmic tail of P2Y₁₃-R in expression defect. Accordingly, proteasomal inhibition increased plasma membrane expression of functionally active P2Y₁₃-R in hepatocytes, and consequently stimulated P2Y₁₃-R-mediated HDL endocytosis. Importantly, proteasomal inhibition strongly potentiated HDL hepatic uptake (>200 %) in wild-type but not in P2Y₁₃-R-deficient mice, thus reinforcing the role of P2Y₁₃-R expression in regulating HDL metabolism. Therefore, specific inhibition of the ubiquitin–proteasome system might be a novel powerful HDL therapy to enhance P2Y₁₃-R expression and consequently promote the overall RCT.     

Möglicher Einfluß chemischer Gleichgewichte auf Viskosität und Relaxationszeit im Erdinnern

Summary A thermodynamic consideration shows that SiO₂ may be reduced to Si by hydrogen at the temperatures present in the earth's interior. The reaction can be expected to involve a rapid change of viscosity with depth inside the earth, required for the explanation of the seismic discontinuity at 2,900 km.     

Bromocriptine/SKF38393 ameliorates islet dysfunction in the diabetic (db/db) mouse

Dysfunction of pancreatic islets plays a crucial role in the etiology of type II diabetes. Chronic hyperglycaemia or hyperlipidaemia may impair islet function. Previous studies by our laboratory have demonstrated that dopaminergic agonists ameliorated hyperglycaemia and hyperlipidaemia in obese and diabetic rodents. In the present study, we investigated the effect of a treatment with the dopamine D₂ /D₁ receptor agonists (bromocriptine/SKF38393, BC/SKF) on islet dysfunction in db/db mice. Our results show that a 2-week BC/SKF treatment markedly reduced hyperglycaemia and hyperlipidaemia, and significantly improved islet dysfunction demonstrated by an increase of secretagogue-stimulated insulin release from islets of db/db mice to levels observed in islets from lean mice. There was also a fourfold increase of insulin content in the pancreas of BC/SKF-treated db/db mice compared with that in untreated controls. The effect of BC/SKF on islet function cannot be mimicked in pair-fed animals. BC/SKF had no direct stimulatory effect on islet insulin secretion, suggesting BC/SKF treatment improved islet function via an indirect mechanism. This treatment markedly improved the abnormally elevated daily levels of corticosterone, blood glucose and plasma lipids, supporting the view that BC/SKF may affect the neuroendocrine system that in turn regulates peripheral metabolism and thereby improves islet function. Received 3 April 1998; accepted 27 April 1998     

Kondensationsprodukte von Oxyketonen und Aminoketonen mit 2,4,5-Triamino-6-oxy-pyrimidin

Summary By condensing 2:4:5-triamino-6-hydroxy-pyrimidine with dihydroxyacetone (diacetate), diaminoacetone or acetone-1,3-di (p-formylaminobenzoic acid) not the expected 8- or 9-oxymethyl resp. -aminomethyl-pteridines but 8-or 9-methyl-pteridines were obtained. With p-tolyl-d-isoglucosamine not a tetrahydroxybutyl-pteridine but a trihydroxybutyl-pteridine was formed. For an explanation of these results it is supposed that from the dihydro-pteridines formed at first by intramolecular splitting off of H₂O or R·NH₂ aromatization takes place.     

Arachidonic acid signaling is involved in the mechanism of imidazoline-induced K<Subscript>ATP</Subscript> channel-independent stimulation of insulin secretion

The mechanism by which the novel, pure glucose-dependent insulinotropic, imidazoline derivative BL11282 promotes insulin secretion in pancreatic islets has been investigated. The roles of K_ATP channels, α₂-adrenoreceptors, the I₁-receptor-phosphatidylcholine-specific phospholipase (PC-PLC) pathway and arachidonic acid signaling in BL11282 potentiation of insulin secretion in pancreatic islets were studied. Using SUR1^(-/-) deficient mice, the previous notion that the insulinotropic activity of BL11282 is not related to its interaction with K_ATP channels was confirmed. Insulinotropic activity of BL11282 was not related to its effect on α₂-adrenoreceptors, I₁-imidazoline receptors or PC-PLC. BL11282 significantly increased [³H]arachidonic acid production. This effect was abolished in the presence of the iPLA₂ inhibitor, bromoenol lactone. The data suggest that potentiation of glucose-induced insulin release by BL11282, which is independent of concomitant changes in cytoplasmic free Ca²⁺ concentration, involves release of arachidonic acid by iPLA₂ and its metabolism to epoxyeicosatrienoic acids through the cytochrome P-450 pathway. Received 5 July 2007; received after revision 18 September 2007; accepted 20 September 2007     

Diabetes alters drug metabolism-in vivo studies in a streptozotozin-diabetic rat model

Summary The influence of experimental streptozotozin-induced diabetes on hepatic drug metabolism in vivo has been studied in rats, using¹⁴CO₂-exhalation after¹⁴C-aminopyrine injection. Male diabetic rats showed a decreased (–18%), females an increased (+19%)¹⁴CO₂-exhalation compared to controls, indicating altered hepatic drug metabolism due to diabetes.     

Action de l'eau oxygénée sur un anaérobie strict

Summary A quantitative study on the action of H₂O₂ uponCl. saccharobutyricum shows that the primary action is produced upon a first substance X, very likely an enzyme, following a mechanism such as one equivalent of oxygen gives a reversible combination, and two equivalents an irreversible combination.     

Sur les relations entre la production d'hexosamines et d'hydroxyproline de la part de fibroblastes cultivés in vitro dans différentes concentrations d'O2

Summary Studies and comparison of the hexosamine and hydroxyprolin production by fibroblasts cultivated in vitro at different oxygen concentrations. The results show that the highest hexosamine production occurs at a low oxygen concentration (5%). The highest hydroxyprolin production occurs at 20% O₂; this oxygen concentration is considered as an hyperoxic one for fibroblasts cultivated in vitro. Besides it has been ascertained that the highest sulphated MPS production occurs between 5 and 20% oxygen without any significant variation.     

The action of the peptidoleukotriene LTD4 on intracellular calcium in rat mesangial cells

The dose-dependent effect of CGP 45715A on the LTD₄-induced Ca²⁺ response of glomerular mesangial cells has been studied. Our results demonstrate that the LTD₄-dependent increase in the cytosolic Ca²⁺ concentration primarily involves an InsP₃-mediated release of Ca²⁺ from intracellular storage sites and to a minor extent an enhanced influx of Ca²⁺ through receptor-operated Ca²⁺ channels located in the plasma membrane. The action of CGP 45715A on the Ca²⁺ response is an inhibitory one and is convincingly explained by a displacement of LTD₄ from its receptor site(s). The contractile effect of LTD₄ on pulmonary smooth muscle is proposed to be mainly caused by a receptor-mediated hydrolysis of phosphatidylinositol-4,5-bisphosphate.     

Development of in vitro toxicity tests with cultures of freshly isolated rat hepatocytes

Summary Freshly isolated and cultured hepatocytes were analyzed by two-parameter flow cytometry. The combined analysis of DNA and cellular protein content allowed the contribution of ploidy classes and of subpopulations within a ploidy class to be defined. Analysis of hepatocytes during exposure to dimethylsulfoxide (DMSO), phenobarbital (PB), low oxygen tension (5% O₂) or fetal calf serum (FCS), provided insight into the dynamic response of individual ploidy classes as a function of culture time. By analogy with the age-dependent ploidy shifts in vivo, hepatocyte-cultures shift towards adult animals during exposure to DMSO and towards young animals when cultured at low pO₂ (4% O₂). FCS and phenobarbital disturb this constitutive ploidy balance. FCS increased the 2 N cell population, where stem cells probably respond to the proliferative stimuli provided by growth factors in the serum. Phenobarbital affects the liver-specific 4 N hepatocytes, which agrees with effects seen in liver after exposure in vivo. It is suggested that drug-induced pathological alterations in ploidy in hepatocyte cultures could serve as indicators of compounds, such as liver tumor promoters, which interfere with cell differentiation in liver. The heterotypic cell-cell interaction of freshly isolated hepatocytes with isolated, in vitro cultured, rat liver epithelial cells in co-cultures proved to be a valuable concept in toxicity testing: aldrin epoxidase, an enzyme system involved in xenobiotic metabolism, was stabilized for more than two weeks. After exposure to the three chemicals, 2-acetylaminofluoren, procarbazine and cyproterone-acetate, a preferential toxicity for each compound and cell population was established. Thus heterotypic cell cultures can considerably increase the amount of information available from in vitro studies.The final concept, combining monitoring of cellular DNA (ploidy) and protein content in hepatocyte cultures during and after exposure to a given test compound at tissue oxygen tension with the heterotypic cell-cell interaction, would create a more in vivo-like culture system. This would enhance the predictability of hepatocyte cultures and contribute to a more widespread use of the test system and as a result help to reduce the number of whole-animal tests.     

Effet de l'oxygène et deO-(β-hydroxyaethyl)-rutosidea sur (HR)1 l'artère mésentérique de l'embryon de poulet expantée in vitro

Summary The effect of oxygen and of the semisynthetic flavonoidO-(-hydroxyaethyl)-rutosidea (HR) on the mesenteric artery of chicken embryo explanted in vitro has been studied. The protective effect of HR on the explants appears in anoxic (N₂) and hypoxic (2% O₂) atmosphere, but only during the first 24h of culture. In hyperoxic atmosphere (97% O₂) only after 3 days of culture HR has a protective action on the explants against the toxic effects of oxygen.

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Zyma S.A., Nyon.

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Ces recherches ont été faites grâce à un subside du Fonds National suisse de la Recherche scientifique et de la Fondation E. Barell.     

Antibacterial effect of 2-hydroxy-N-(3,4-dimethyl-5-isoxazolyl)-1,4-naphthoquinone-4-imine onStaphylococcus aureus

The mechanism by which a new naphthoquinone derivative, the 2-hydroxy-N-(3,4-dimethyl-5-isoxazolyl)-1,4-naphthoquinone-4-imine (INQI-E) has antibacterial effect againstStaphylococcus aureus was studied. The interaction of INQI-E with the bacteria was followed by absorption spectroscopy at 323 and 490 nm. The absorption band of INQI-E at 490 nm undergoes a hypochromic shift with a decrease of intensity. This effect was found to be reversible by oxygenation during the first hours of incubation. The participation of an oxidation-reduction process related to the respiratory chain was demonstrated by oxygen consumption. An increase in O₂ uptake and inhibition ofS. aureus growth was observed. Experiments with three inhibitors of the respiratory chain demonstrated that the pathway induced by INQI-E was antimycin-resistant and KCN- and salicylhydroxamic acid (SHAM)-sensitive, which suggests that INQI-E is capable of diverting the normal electron flow to an alternate superoxide-producing route. On the other hand, experiments with Tiron, a specific scavenger of superoxide, hindered the effect of INQI-E againstS. aureus, indicating that the inhibitory growth effect of this quinone-imine is mainly due to the production of the cytotoxic superoxide radical.