Improved organic matter biodegradation through pulsed H2 injections during in situ biomethanation.

During in situ biomethanation, microbial communities can convert complex Organic Matter (OM) and H2 into CH4. OM biodegradation was compared between Anaerobic Digestion (AD) and in situ biomethanation, in semi-continuous processes, using two inocula from the digester (D) and the post-digester (PoD) of an AD plant. The impact of H2 on OM degradation was assessed using a fractionation method. Operational parameters included 20 days of hydraulic retention time and 1.5 gVS.L-1.d-1 of organic loading rate. During in situ biomethanation, 485 NmL of H2 were injected for each feeding (3 times a week). Maximum organic COD removal was 0.6 gCOD in AD control and at least 1.6 gCOD for in situ biomethanation. Therefore, COD removal was 2.5 times higher with H2 injections. These results bring out the potential of H2 injections during AD, not only for CO2 consumption but also for better OM degradation.

Archaeal community composition as key driver of H2 consumption rates at the start-up of the biomethanation process.

The performance of hydrogen consumption by various inocula derived from mesophilic anaerobic digestion plants was evaluated under ex situ biomethanation. A panel of 11 mesophilic inocula was operated at a concentration of 15 gVS.L-1 at a temperature of 35 °C in batch system with two successive injections of H2:CO2 (4:1 mol:mol). Hydrogen consumption and methane production rates were monitored from 44 h to 72 h. Hydrogen consumption kinetics varies significantly based on the inoculum origin, with no accumulation of volatile fatty acids. Microbial community analyses revealed that microbial indicators such as the increase in Methanosarcina sp. abundance and the increase of the Archaea/Bacteria ratio were associated to high initial hydrogen consumption rates. The improvement in the hydrogen consumption rate between the two injections was correlated with the enrichment in hydrogenotrophic methanogens. This work provides new insights into the early response of microbial communities to hydrogen injection and on the microbial structures that may favor their adaptation to the biomethanation process.

Cardiovascular effects of lepadiformine, an alkaloid isolated from the ascidians Clavelina lepadiformis (Müller) and C. moluccensis (Sluiter).

The effects of lepadiformine, a natural marine alkaloid isolated from the ascidians Clavelina lepadiformis (Müller) and C. moluccensis (Sluiter), were studied in vivo by arterial blood pressure (aBP) recordings and electrocardiograms (ECG) in anaesthetised rats and in situ by peripheral vascular pressure recordings on perfused rabbit ear. Transmembrane resting (RP) and action (AP) potentials were also recorded by intracellular microelectrodes on electrically stimulated left ventricular papillary muscle and spontaneously beating atrium isolated from rat and frog hearts, respectively. Intravenous injection of lepadiformine (6mg/kg) produced marked bradycardia and a lengthening of ECG intervals as well as a transient decrease of aBP, which rapidly returned to normal. The decrease of aBP may have been related to a vasoconstrictor effect observed in the perfused ear experiment. Lepadiformine did not alter RP, but significantly lengthened the repolarising phase of AP in rat papillary muscle and frog atrium. Lepadiformine also mimicked the effect of Ba(2+) (0.2mM) on the rat AP repolarising phase. Moreover, the lengthening of the AP in frog atrium induced by lepadiformine still developed after the delayed outward K(+) current (I(K)) was blocked by tetraethylammonium (10mM). These observations suggest that lepadiformine-induced lengthening of AP duration was not due to a decrease of I(K), but may reasonably be attributed to a reduction of the inward rectifying K(+) current (I(K1)). This blockade of I(K1) could account for the cardiovascular effects of lepadiformine in vivo and in vitro and suggests that lepadiformine has antiarrhythmic properties.

Analgesic and antiinflammatory activities of an extract from Parkia biglobosa used in traditional medicine in the Ivory Coast.

In the Ivory coast, Parkia biglobosa (Mimosaceae) is used in traditional medicine as an analgesic drug, especially against dental pain. Of the three extracts obtained from the plant bark, the hexane fraction was studied to determine its analgesic and/or antiinflammatory activities. The results show that this extract possesses a marked analgesic activity when evaluated with the abdominal writhing test in mice, but, like paracetamol, was ineffective with the hot-plate method, a feature suggesting a peripheral mechanism of action. This activity was accompanied by an antiinflammatory effect, somewhat weaker than the analgesic one.

Secreted and intracellular phospholipases A2 inhibition by 1-decyl 2-octyl-glycerophosphocholine in rat peritoneal macrophages.

Compounds able to inhibit phospholipases A2 can be considered as potential anti-inflammatory drugs. In this respect, the inhibitory effect of the phospholipid analogue 1-decyl 2-octyl-rac-glycero-3-phosphocholine (decyloctyl-GPC) added to the culture medium of rat peritoneal macrophages stimulated with ionophore A23187 was determined. (a) The substrate of phospholipase A2 1-octadecanoyl 2-[14C]eicosatetraenoyl-sn-glycero-3-phosphocholine ([14C]20:4-GPC) was added to the culture medium. In macrophages + extracellular fluids, its hydrolysis at the 2-position, produced [14C]non-phosphorous lipids which reached 12% of the dose at 0.14 microM, 73% at 0.9 and > 90% at 1.6 microM; in experiments where macrophages and extracellular fluids were analyzed separately, decyloctyl-GPC initially added at 4 microM, significantly inhibited the release of [14C]fatty acids and the eicosanoid synthesis, demonstrating its ability to inhibit secreted and/or intracellular phospholipases A2. (b) Extracellular fluids were separated from the macrophages and incubated with [14C]20:4-GPC: 48% of the dose was hydrolyzed by extracellular fluid-associated secreted phospholipase A2 and decyloctyl-GPC at 3 microM, reduced this hydrolysis by 50%. (c) [3H]arachidonic acid ([3H]20:4) was added to the culture medium and was esterified in the macrophage membrane phospholipids. Activation of intracellular phospholipase A2 induced the release of [3H] fatty acids and eicosanoid synthesis. These releases were inhibited by 50% with decyloctyl-GPC added at 4 microM. (d) [3H]20:4 and [14C]20:4-GPC were added to the culture medium of the macrophages. [3H] and [14C] fatty acids and eicosanoids were released in macrophages or extracellular fluids. They were significantly reduced by the phospholipid analogue added at 4 microM. It is concluded that secreted and intracellular phospholipases A2 were both inhibited by decyloctyl-GPC which extensively reduced the 20:4 release from exogenous and membrane phospholipids and therefore eicosanoid synthesis.

Synthesis and anti-inflammatory activity of polyazaheterocyclic derivatives of 6-amino-2,4-lutidine and their precursors.

Derivatives of N-(4,6-pyridin-2-yl)arylcarboxamides resulting from the integration of the amidic function into 4H-1,2,4-triazole, triazol-3(2H)-one and 1H-tetrazole rings were evaluated as potential anti-inflammatory compounds. The level of activity decreased as compared to carboxamides, nevertheless their precursors and notably the corresponding amidrazones exhibited potent activity; amidrazone 21, whose ID50 was 34.4 mg.kg-1 in the rat paw edema test, was selected for further investigation. These heteroarylcarboxamide derivatives could represent an interesting alternative to classical non-steroidal anti-inflammatories in so far as they partly act by inhibition of tumor necrosis factor-alpha production.

Involvement of alpha2-adrenergic mechanisms in experimental analgesic and anti-inflammatory activities of a benzamide derivative.

Several non-steroidal anti-inflammatory drugs of the N-pyridinyl-benzamide series that produce experimental peripheral and central anti-inflammatory effects possess a dopaminomimetic component and inhibit eicosanoid synthesis without acting directly on the enzymes classically involved in this process. We compared the anti-inflammatory and analgesic activities of one of the most active benzamide derivatives with those of clonidine. Rat paw and brain edemas were inhibited by these two agents, whereas different methods showed that yohimbine counteracted this effect and the analgesia it induced. The involvement of an alpha2-adrenergic and/or serotoninergic components in these activities is considered, without excluding the possibility that the mechanism of action is in part due to inhibition of prostaglandin synthesis.

Effect of clonidine on experimental brain edema in the rat.

Several experimental brain edema models are currently available for drug evaluation. Brain edemas are essentially vasogenic and/or cytotoxic, and eicosanoids are involved in the development of these edemas. Thus, a new model developed in our laboratory, which was obtained by phospholipase A2 intracerebral injection was used to study the antiinflammatory effect of clonidine. The copper wire edema model was chosen as reference. Edemas were evaluated by determining the swelling and Na+ and K+ tissue concentrations of each hemisphere. Drugs were administered intraperitoneally. Dexamethasone was the only drug to inhibit copper wire-induced edema, whereas indomethacin and clonidine as well as dexamethasone exhibited marked antiedematous activity in our model. The effect of clonidine, which could be inhibited by prior administration of yohimbine, suggests that central alpha 2-adrenergic stimulation is involved in reducing experimental brain edema.

Prenatal diagnosis of Niemann-Pick type C disease: current strategy from an experience of 37 pregnancies at risk.

Thirty-seven pregnancies at risk for Niemann-Pick type C disease were monitored by study of cultured amniotic fluid cells (8 cases) or chorionic villus cells (29 cases) in 23 couples over the period 1984-91. An early protocol combined determination of sphingomyelinase activity with electron microscopy. The current strategy, based on the demonstration of specific abnormalities in intracellular processing of exogenous cholesterol, combines the study of the early phase (first 6 h) of LDL-induced cholesteryl ester formation and the histochemical evaluation (filipin staining after 24 h of LDL uptake) of the LDL-induced accumulation of unesterified cholesterol. Thirteen fetuses were predicted to be affected. Confirmation of the diagnosis was made by study of cholesterol processing in fetal skin fibroblast cultures and/or by demonstration of a characteristic lipid storage in fetal liver, already present at 14 w gestation. Definition of the biochemical phenotype (classical, variant, or intermediate) of the index case, with regard to cholesterol-processing abnormalities, is an absolute prerequisite to adequate genetic counseling in a given family. Prenatal diagnosis has now proved a safe procedure in the predominant (approximately 85%) group of families with the classical phenotype.

Type C Niemann-Pick disease: spectrum of phenotypic variation in disruption of intracellular LDL-derived cholesterol processing.

To investigate biochemical heterogeneity within Niemann-Pick type C disease (NPC), the two most characteristic abnormalities, namely (1) kinetics of LDL-stimulated cholesteryl ester formation and (2) intravesicular accumulation of LDL-derived unesterified cholesterol, evaluated by histochemical filipin staining, were studied in cultured skin fibroblasts from a population of 125 NPC patients. Profound alterations (esterification rates less than 10% of normal, very numerous and intensely fluorescent cholesterol-filipin granules) were demonstrated in 86% of the cases, depicting the 'classical' NPC phenotype. The remaining cell lines showed a graded less severe impairment and more transient delay in the induction of LDL-mediated cholesteryl esterification, along with an attenuated accumulation of unesterified cholesterol. In particular, cells from a small group (7%) of patients, which have been individualized as representative of a 'variant' phenotype, showed only slight alterations of esterification, restricted to the early phase of LDL uptake and undistinguishable from those in heterozygotes. In these cells, an abnormal cytochemical distribution of LDL-derived cholesterol, although moderate, was still evident provided rigorous experimental conditions were followed. A third, less clearly individualized group (7%), differing from the classical phenotype mostly by higher rates of cholesteryl ester formation, has been designated as an 'intermediary' phenotype to reflect a more difficult diagnosis of such patients. These findings have an important bearing with regard to diagnosis and genetic counselling, although the significance of such a phenotypic variation in terms of genetic heterogeneity has still to be demonstrated. A given biochemical phenotype was however a constant observation within a family (14 pairs of siblings tested so far). The unique feature of LDL-cholesterol processing alterations in NPC has been further established from comparative studies in Wolman disease and I-cell disease, showing normal or different intracellular distribution of unesterified LDL-derived cholesterol in the latter disorders. Correlation between biochemical and clinical NPC phenotypes was only partial, but a correlation between the severity of alterations in cholesterol processing and sphingomyelin catabolism could be established.

Bistramide A, a new toxin from the urochordata Lissoclinum bistratum Sluiter: isolation and preliminary characterization.

Two cases of human intoxication caused by the lyophilized powder of Lissoclinum bistratum Sluiter, a New Caledonian ascidian, are reported. The symptoms observed were caused by a substance designated bistramide A (C40H68N2O8) of hitherto unknown chemical structure. Preliminary toxicological investigations indicate that bistramide A may effect the central nervous system, leading to paresthesia and loss of muscle tone. A progressive decrease in cardiac rhythm was also observed in animals. Bistramide A (1.4 x 10(-6) M) did not alter the resting potential of frog heart and skeletal muscle but reduced the amplitude and duration of cardiac action potential and prolonged the interval between action potentials. Bistramide A also has a marked cytotoxic effect on cancer cells KB (IC50 = 4.5 x 10(-8) M) and P 388 (IC50 = 2.0 x 10(-8) M) and on normal endothelial cells (IC50 = 2.2 x 10(-8) M). However, it has not been possible to relate the cytotoxic property to the symptoms of intoxication. Bistramide A may originate from the urochordate itself or from symbiotic algae.

[Effects of an anti-inflammatory agent of benzamide structure, dexamethasone and indomethacin on experimental cerebral edema induced by phospholipase 2 in rats]. / Effets d'un anti-inflammatoire à structure benzamide, de la déxaméthasone et de l'indométacine sur l'oedème cérébral expérimental à la phospholipase A2 chez le rat.

Only a few molecules show any efficacy against brain edema. Different methods such as brain copper-wire implantation or arachidonic acid injection are used in the research of active drugs. A new model, involving injection of phospholipase A2, is described. The effect of an anti-inflammatory compound, N-(4,6-dimethyl 2-pyridinyl) benzamide, was evaluated on the three different experimental brain edemas mentioned above; dexamethasone and indomethacin were used as reference drugs. The studied molecule is, like dexamethasone, active on the three brain edema models. It has no direct inhibitory effect on phospholipase A2, cannot block cyclooxygenase activity but does reduce prostaglandin biosynthesis. Other factors, such as dopaminergic and alpha 2-adrenergic agonist activities, could also interfere.

Biochemical studies in Niemann-Pick disease. III. In vitro and in vivo assays of sphingomyelin degradation in cultured skin fibroblasts and amniotic fluid cells for the diagnosis of the various forms of the disease.

Sphingomyelinase activities were assayed in vitro in cultured skin fibroblasts of 61 patients with Niemann-Pick disease (NPD). Residual activities found in type A and B were 1% and 4%, respectively, of the mean control values, i.e. significantly higher in type B. In 27 cases with NPD type C, the mean activity was 42% of that in controls, with residual activities ranging from 15% up to normal. Fifteen pregnancies at risk for NPD type A and B were monitored; 4 affected foetuses were found. The uptake of exogenously added radiolabelled sphingomyelin by cultured cells and metabolism of the choline moiety of this lipid were studied in 35 patients with NPD and 14 controls. No difference of uptake between normal and mutant cells was observed. Normally, 77 +/- 5% of the radioactivity taken up was converted to phosphatidylcholine after 18 h incubation, compared to 5 +/- 2% (n = 7) in NPD type A. A substantially greater hydrolysis (31 +/- 12%; n = 8) occurred in NPD type B, and the test allowed complete discrimination between these two types. In NPD type C, 16 patients showed an abnormally low rate of intracellular sphingomyelin degradation (48 +/- 5%) while 4 others were not distinguishable from controls. There was a correlation (r = 0.76) between the results of the in vitro and in vivo assays, but also between the severity of the clinical symptoms and the impairment in sphingomyelin degradation. For the diagnosis of NPD type C, the in vivo test gave more reproducible and more clearcut results than the in vitro assay.

[Effect of dibutyryl cyclic AMP on cerebral energy charge and electrocorticographic activity in rats under asphyxic hypoxia]. / Influence du dibutyryl-AMP cyclique sur la charge énergétique cérébrale et sur l'activité électrocorticographique chez le rat sous hypoxie asphyxique.

In Rats anesthetized with pentobarbital and submitted to brief asphyxic episodes, intracerebroventricular administration of dibutyryl cyclic AMP inhibits the decrease of energy charge, delays the disappearance of electrocorticographic activity (E Co G) and shortens the recovery time of E Co G.