Effect of lithium on brain aconitase activity

Résumé Nous avons déterminé l'activité spécifique de l'aconitase cérébrale des souris après une période de 108 jours de traitement avec du lithium (Li₂CO₃). Une inhibition significative de l'enzyme à été observée. D'autre part, nous n'avons trouvé in vitro aucun effet du Li₂CO₃ sur l'aconitase cérébrale.

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R. R. A. was supported by a research grant from the Conselho Nacional de Pesquisas (National Research Council of Brasil).     

Luffariellolide,an anti-inflammatory sesterterpene from the marine spongeLuffariella sp.

Summary Luffariellolide (2) is a sesterterpene from the Palauan spongeLuffariella sp. that has useful anti-inflammatory properties. In contrast with the irreversible action of manoalide (1) on phospholipase A₂, luffariellolide (2) is a slightly less potent but partially reversible PLA₂ inhibitor.30 December 1986Acknowledgment We thank Edward Luedtke, Elise Clason and Ellen Snideman for performing some of the assays reported above. The sponge was identified by Dr. Klaus Rützler, Smithsonian Institution, Washington, D.C. The research was supported by grants from Allergan Pharmaceuticals and the California Sea Grant College Program (Projects R/MP-30 and R/MP-31).     

The influence of lithium on serum ceruloplasmin

Summary Serum ceruloplasmin oxidase activity did not change in mice treated orally for 120 days with Li₂CO₃ (0.58 mEq/kg/day). After a single i.p. injection of LiCl (20 mEq/kg), a significant activation of ceruloplasmin was observed.R. R. A. is working with a research grant from the Conselho Nacional de Pesquisas (National Research Council of Brasil).     

Effects of CO2 exposure on distribution of various forms of iron and copper in guinea-pig tissues

Summary The effects on iron and copper distribution and metabolism of exposure to high levels of CO₂ were studied in the guinea-pig. Mature, male animals were placed in an atmosphere of 15% CO₂, 21% O₂ (balance N₂), and sacrificed from 1 h to 1 week thereafter. Total iron and copper concentrations of blood, liver, spleen and bone, as well as concentrations of heme and ferritin iron, were measured together with blood hematocrit, reticulocytes, plasma hemoglobin, plasma ceruloplasmin and copper concentrations. The results show clearly that rapid and sustained red cell damage or hemolysis ensued several h from the start of CO₂ treatment. This resulted in loss of iron and copper from the blood, an influx of both elements into liver, spleen and bone, and a rise in plasma ceruloplasmin. Influx of iron into liver and spleen caused an accumulation of ferritin, the main site for iron storage in cells. Following the effect on red cells, there was an accumulation of heme iron, and a decreased hematocrit, best explained by a depressed activity of the reticuloendothelial and erythropoietic systems. A period of adaptation succeeded these events, in which all blood parameters and most tissue values returned to normal, despite the continuing presence of high CO₂. The only changes not reversed were the elevations in liver, spleen and bone iron stores. These remained high, with a net accumulation of >2 mg iron, or 3–4 times more than originally present. The results indicate that at least in the guinea-pig, high CO₂ exposure results in red cell damage and other events leading to an accumulation of additional iron in the body; also, that iron accumulated as ferritin and hemosiderin in liver and spleen may not be readily available to restore blood hemoglobin concentrations on an acute basis.Acknowledgments. We gratefully acknowledge the technical assistance of Joan R. Moor and Lakshmi Vulimiri with these studies, and the support of Grants No. 17249 and HL22410 from the U.S. Public Health Service.     

The influence of N2-fixation on the carbon balance of leguminous plants

Biological dinitrogen fixation by legume-rhizobia symbiosis is very important both from the economic and from the ecological point of view. Theoretically, the reduction of the N₂-molecule to ammonia requires at least 16 ATP and 1.5 mg C per mg N fixed (N_fix). These values are difficult to determine in situ as this necessitates the determination of that part of root respiration which drives N₂-fixation. New approaches to such determinations and the results obtained are described. The values vary, depending on the plant species studied, the developmental stage of the plants and the genetic variability of macro- (and micro-?) symbionts. The values range between 1.5 and 4 mg C/mg N_fix. In some species (e.g.Vicia faba L. cv. Fribo), the apparent CO₂ assimilation is enhanced in order to meet this high energy need. In others (e.g.Pisum sativum L. cv. Grapis), root growth is restricted. Physiological criteria are discussed which allow an early diagnosis of the energetic efficiency of various combinations of macro-and microsymbionts as a basis for a selection in plant breeding.     

La voie du pentose phosphate dans le métabolisme du glucose et son interaction avec la glutathion-réductase dans les noyaux de foie de rat

Summary Rat liver nuclei, isolated in sucrose medium, convert carbon-1 of glucose-6-phosphate to CO₂ via the 6-phosphogluconic acid oxidative pathway. Conversion of glucose-1-¹⁴C to¹⁴CO₂ by the cytoplasmic fraction is greatly inhibited by nuclei. In the presence of low concentrations of NADP, the CO₂ formed by nuclei is markedly increased by the addition of GSSG.     

The CO2-binding capacity of rat brain tissuein vivo

Zusammenfassung 73 Ratten wurden hyperventiliert und mit Gasgemischen verschiedener CO₂-Gehalte (0–12%) während 30–180 min beatmet (arteriellerP _{CO 2} 12–107 Torr). Die Versuchstiere wurdenin situ eingefroren und der CO₂-Gehalt des Gehirngewebes mit eigener Methode bestimmt. Dissoziationskurve und Pufferkapazität des Gehirngewebes für CO₂ in vivo werden mitgeteilt.     

The response of Ca-mediated action potentials and contractile activity in mammalian ventricular myocardium towards alkalosis

Summary Alkalosis (pH 7.8) produced by reduction of CO₂ concentration augmented both upstroke velocity of Ca action potentials and isometric contractile force of mammalian heart muscle. If the increase of pH to 7.8 was achieved by a raise of HCO₃ concentration (with simultaneous reduction of CO₂ concentration), the positive inotropic response was not accompanied by an augmented Ca current. Obviously, the well-known positive inotropic effect of alkalosis does not only depend upon the enhancement of transmembrane Ca influx during excitation, but can be mediated alone by affecting intracellular Ca movements as well.     

The rate of incorporation of gaseous14CO2 into brain tissue constituents

Zusammenfassung Die¹⁴CO₂-Fixation verschiedener Fraktionen des Rattengehirnes wurde untersucht. Die Ratten wurden 15–120 min in gasförmigem¹⁴CO₂ exponiert und in flüssigem N₂ gefroren. Nach 15, 30, 60 und 120 min waren 9, 17, 21 und 35% vom Gesamt-¹⁴CO₂ in der Gehirnsubstanz organisch gebunden. Der grösste Teil des organischen¹⁴CO₂ fand sich in säurelöslicher Fraktion, während ein kleinerer Teil (etwa 10%) aus der Proteinfraktion isoliert werden konnte.     

Veränderungen des Glucoseabbaus in Kaninchenaorten unter dem Einfluss von Biguaniden

Summary The influence of biguanides on glucoseoxidation was studied in intima-preparations of rabbit aortae. With high doses (500 µg/ml) an inhibition of CO₂-formation predominantly from position C-1 of glucose was found. With 4 µg/ml there was no significant change of CO₂-for-mation from glucose.     

Einfluss einiger lipophiler Lösungsmittel in gasförmigem Zustand auf die CO2-fixierung durch Luzerne

Summary Vapourized organic solvents such as: diethyl ether, methylene chloride, carbon disulfide, benzene, and n-octane have an inhibiting effect on CO₂ fixation in alfalfa leaves (Medicago sativa). One exception is CS₂ which stimulates overall fixation up to 10 vol%. Beyond 10 vol% it inhibits overall CO₂ fixation like the other solvents, but stimulates the formation ofl-alanine as the major remaining fixation product. Proportionality exists between water insolubility of the organic solvents and their inhibiting effect on CO₂ fixation.     

Cyclic nucleotide levels in the perfused rat heart subjected to hypoxia

Summary Isolated rat hearts were subjected to hypoxic perfusion on a recirculating Langendorff apparatus. Following a 30-min-period of aerobic stabilization the hearts were perfused for 30 min with media equilibrated with 84% N₂, 12% O₂ and 4% CO₂. At the end of the hypoxic period myocardial concentrations of cyclic AMP and cyclic GMP were determined by radioimmunoassay. Exposure to hypoxia resulted in a significant increase in cyclic AMP (p<0.01) and a decrease in cyclic GMP (p<0.05) as compared to hearts perfused for 60 min with media gassed with 96% O₂, 4% CO₂.Acknowledgment. We gratefully acknowledge the excellent technical assistance provided by Mrs Inger O. Boggs and Miss Patricia C. Hannigan. This work was supported in part by U. S. Public Health Service grant HL 14661 from the National Heart and Lung Institute, and by a grant from the Central Ohio Heart Chapter.     

Manometrische Regelung kontinuierlicher Gärungen durch das Gärungs-CO2

Summary Using CO₂ in manometric control of continuous cultures (Sacch. cer.), the cultures were maintained constant ir intensity of metabolism in respect to CO₂-production. The small fermentors (50 ml) are useful for investigations in metabolism under various conditions at a steady state.     

Plant aquaporin selectivity: where transport assays, computer simulations and physiology meet

Plants contain a large number of aquaporins with different selectivity. These channels generally conduct water, but some additionally conduct NH₃, CO₂ and/or H₂O₂. The experimental evidence and molecular basis for the transport of a given solute, the validation with molecular dynamics simulations and the physiological impact of the selectivity are reviewed here. The aromatic/arginine (ar/R) constriction is most important for solute selection, but the exact pore requirements for efficient conduction of small solutes remain difficult to predict. Yeast growth assays are valuable for screening substrate selectivity and are explicitly shown for hydrogen peroxide and methylamine, a transport analog of ammonia. Independent assays need to address the relevance of different substrates for each channel in its physiological context. This is emphasized by the fact that several plant NIP channels, which conduct several solutes, are specifically involved in the transport of metalloids, such as silicic acid, arsenite, or boric acid in planta.     

Carbon dioxide sensitivity of pulmonary receptors in the frog

Summary Pulmonary mechano-receptors have been found in the frog lung that are sensitive to CO₂ concentrations in the lungs and airways comparable to the physiological levels recorded in frogs. These results support the suggestion that a pulmonary receptor with distinct mechano- and chemosensitive properties may represent the functional precursor of the more specialized pulmonary receptor types which have evolved in birds and mammals.Supported by grants from N. R. C. C. and the Presidents Fund, University of British Columbia.     

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.     

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.     

Effect of blood pH on anionic ferritin transport through rat aortic endothelium

Summary Acute lowering of blood pH between 7.4 and 6.9 in rats by ventilation with 10 or 20% CO₂ does not increase the passage of ferritin molecules across the aortic endothelium. These results do not rule out alteration of endothelial permeability to anionic macromolecules in local circulatory disturbances when blood pH drops to levels much lower than 6.9.Supported by The Medical Research Council of Canada grant No. MA-5958.Dr J.R. Fraser was a recipient of a Summer Research Scholarship from McGill University during the completion of this study.The authors thank Colin Bier for the statistical analysis.     

The mechanics of breathing in respiratory acidosis

Zusammenfassung Nachweis, dass Inhalation von Luftgemisch mit 10% CO₂ bei wachen Kaninchen eine bronchiale Konstriktion verursacht, wenn die Lungendehnung selbst von niedrigem Blut pH begleitet ist. Erhöhung von CO₂ allein erschlafft die Bronchien und unterdrückt teilweise die Bronchienkontraktion, was mit dem niedrigen Blut pH zusammenhängt.     

Enrichment of CO2 and magnesium in early stages of biomineralization

Summary Simultaneous topochemical analyses of calcium, magnesium, carbonate (as CO₂) and phosphorus in a mineralizing collagen rich system (turkey tibia tendon) showed a strong enrichment of Mg and CO₂ in the prestages of biomineralization.We thank the Deutsche Forschungsgemeinschaft for support and Mr E. Kalthoff for assistance.