Thermoacclimatory variations in the activities of enzymes implicated in ion transport in the rainbow trout, salmo gairdneri

Two groups of rainbow trout were acclimated to 20 , 100 , and 18 o C. Plasma sodium, potassium, and chloride levels were determined for both. One group was employed in the estimation of branchial and renal (Na+-K+)-stimulated, (HC0 3-)-stimulated, and CMg++)-dependent ATPase activities, while the other was used in the measurement of carbonic anhydrase activity in the blood, gill and kidney. Assays were conducted using two incubation temperature schemes. One provided for incubation of all preparations at a common temperature of 2S oC, a value equivalent to the upper incipient lethal level for this species. In the other procedure the preparations were incubated at the appropriate acclimation temperature of the sampled fish. Trout were able to maintain plasma sodium and chloride levels essentially constant over the temperature range employed. The different incubation temperature protocols produced different levels of activity, and, in some cases, contrary trends with respect to acclimation temperature. This information was discussed in relation to previous work on gill and kidney. The standing-gradient flow hypothesis was discussed with reference to the structure of the chloride cell, known thermallyinduced changes in ion uptake, and the enzyme activities obtained in this study. Modifications of the model of gill lon uptake suggested by Maetz (1971) were proposed; high and low temperature models resulting. In short, ion transport at the gill at low temperatures appears to involve sodium and chloride 2 uptake by heteroionic exchange mechanisms working in association w.lth ca.rbonlc anhydrase. G.l ll ( Na + -K + ) -ATPase and erythrocyte carbonic anhydrase seem to provide the supplemental uptake required at higher temperatures. It appears that the kidney is prominent in ion transport at low temperatures while the gill is more important at high temperatures. 3 Linear regression analyses involving weight, plasma ion levels, and enzyme activities indicated several trends, the most significant being the interrelationship observed between plasma sodium and chloride. This, and other data obtained in the study was considered in light of the theory that a link exists between plasma sodium and chloride regulatory mechanisms.

Thermoaclimatory variations in the microenvironment of hemoglobin in the rainbow trout, Salmo gairdneri and the carp, Cyprinus carpio

Several inorganic substances (e.g., C£ , Mg , Ca , H ) are potent negative modulators of hemoglobin-oxygen affinity. To evaluate the possibility that potentially adaptive changes in the red cell ionic environment of hemoglobin may take place during acclimation of fishes to increased environmental temperature, hematological status (hemoglobin, hematocrit, red cell numbers, mean erythrocytic volume and hemoglobin content), plasma + + 2+ 2+ and packed red cell electrolyte levels (Na , K , Ca , Mg , C£ ) were evaluated in summer and winter populations of the stenothermal rainbow trout, Salmo gairdneri, following acclimation to 2°, 10°, 18°C, and in a spring population of eurythermal carp, Cyprinus carpio, held at 2°, 16° and 30°C. From these data cell ion concentrations and ion:hemoglobin ratios were estimated. In view of the role of red cell carbonic anhydrase in the reductions of blood C02 tensions and the recruitment of Na and C£~ lost by fishes, a preliminary investigation of thermoacclimatory changes in the activity of this system in rainbow trout erythrocytes was conducted. Few changes in hematological status were encountered following acclimation. There was, however, some evidence of weight-specific differential hematological response in carp. This lead to markedly greater increases in hemoglobin, hematocrit and red cell numbers in smaller rather than in larger specimens at higher temperatures; variations which were 2+ well correlated with changes in plasma Ca . Plasma composition in summer trout was not altered by acclimation. In winter trout plasma Na and K increased at higher temperatures. Carp were characterized by increases in plasma calcium, and reductions in sodium and magnesium under these conditions. Several significant seasonal differences in plasma ion levels were observed in the trout. (n) In trout, only erythrocytic K and K :Hb were altered by acclimation, rising at higher temperatures. In carp Na , Na :Hb, C£~ and C£~:Hb in- 2+ 2+ creased with temperature, while Mg and Mg :Hb declined. Changes in overall ionic composition in carp red cells were consistent with increases in H content. In both species significant reciprocal variations in C£~ 2+ - + and Mg were found. In mammalian systems increases in C£ and H reduce hemoglobin-oxygen affinity by interaction with hemoglobin. Reduction in 2+ 2+ Mg maximizes organophosphate modulator availability by decreasing ATP»Mg complex formation. Thus, the changes observed may be of adaptive value in reducing hemoglobin-oxygen affinity, and facilitating oxygen release to cells at higher temperatures. Trout appear to maintain a high chloridelow magnesium state over the entire thermal tolerance zone. Carp, however, achieved this state only at higher temperatures. In both species mean erythrocytic volume was decreased at higher temperatures and this may facilitate branchial oxygen loading. Since mean erythrocytic volume was inversely related to red cell ion content, it is hypothesized that reductions in cell volume are achieved by export of some unidentified solute or solutes. Variations in the carbonic anhydrase activity that could be attributed to the thermoacclimatory process were quite modest. On the other hand, assays performed at the temperature of acclimation showed a large temperature effect where under in vivo conditions of temperature fish acclimated to higher temperatures might be expected to have higher activities. Furthermore, since hematocrit increased with temperature in these fish, while carbonic anhydrase is present only in the erythrocyte, the whole blood levels of this enzyme are expected to increase and further augment the temperature effect. This, in turn, could aid in the reduction of C02 (111) tension and increase the production of H and HC0~~ used in the active uptake of Na and C£ at higher temperatures.

Mécanismes de recuit dans le silicium implanté par faisceau d’ion caractérisés par nanocalorimétrie

Nous présenterons le procédé de fabrication, la caractérisation, ainsi qu’un modèle numérique permettant l’optimisation d’un nouveau dispositif permettant d’effectuer des mesures de nanocalorimétrie sur un échantillon de silicium monocristallin. Ce dernier possède entre autre des propriétés thermiques nous permettant d’effectuer des mesures à des températures supérieures à 900 C, avec une résolution meilleure que 16 C. Ceci nous a permis d’étudier la dynamique des défauts induits par implantation ionique dans le silicium monocristallin. Deux comportements différents sont observés dans la germination de la phase amorphe induite par implantation à 10 et 80 keV. Ces résultats ont été confrontés à des simulations Monte-Carlo basées sur le modèle des paires lacunesinterstitiels. La comparaison entre les simulations et les mesures expérimentales ont montré que ce modèle est incomplet car il ne reproduit qualitativement que certaines caractéristiques observées expérimentalement. Des mesures réalisées à partir de -110 C dans le silicium monocristallin et amorphisé implanté avec des ions légers, ont mis en évidence des différences claires entre la relaxation dans le silicium amorphe et le recuit des défauts dans le silicium monocristallin. Deux processus à des énergies d’activation de 0.48 et 0.6 eV ont été observés pour les implantations réalisées dans le silicium monocristallin tandis qu’un relâchement de chaleur uniforme ne révélant qu’un spectre continu d’énergie d’activation a été observé dans le silicium amorphe.

Défauts et diffusion dans le silicium amorphe

Nous avons observé une augmentation ‘’transient’’du taux de cristallisation interfacique de l’a-Si lorsqu’on réimplante du Si à proximité de l’interface amorphe/cristal. Après amorphisation et traitement thermique à 650°C pendant 5s de la couche a-Si crée par implantation ionique, une partie a été réimplantée. Les défauts produits par auto-réimplantation à 0.7MeV se trouvent à (302±9) nm de l’interface initiale. Cela nous a permis d’étudier d’avantage la variation initiale de la vitesse SPE (Épitaxie en phase solide). Avec des recuit identiques de 4h à 500°C, nous avons déterminé les positions successives des interfaces et en déduit les taux de cristallisation SPE. La cristallisation débute à l’interface et continue graduellement vers la surface. Après le premier recuit, (252±11) nm s’est recristallisé dans la zone réimplantée soit un avancement SPE de 1.26x10^18at./cm2. Cette valeur est environ 1.50 fois plus importante que celle dans l’état relaxé. Nous suggérons que la présence de défauts à proximité de l’interface a stimulé la vitesse initiale. Avec le nombre de recuit, l’écart entre les vitesses diminue, les deux régions se cristallisent presque à la même vitesse. Les mesures Raman prises avant le SPE et après chaque recuit ont permis de quantifier l’état de relaxation de l’a-Si et le transfert de l’état dé-relaxé à relaxé.

Characterization of radio frequency plasma using Langmuir probe and optical emission spectroscopy

The radio frequency plasma generated during the sputtering of Indium Tin Oxide target using Argon was analyzed by Langmuir probe and optical-emission spectroscopy. The basic plasma parameters such as electron temperature and ion density were evaluated. These studies were carried out by varying the RF power from 20 to 50 W. A linear increase in ion density and an exponential decrease in electron temperature with rf power were observed. The measured plasma parameters were then correlated with the properties of ITO thin films deposited under similar plasma conditions.

Biochemical effects of cadmium, salinity and temperature on the catabolism of proteins and purines in oreochromis mossambicus (Peters)

In the present investigation, three important stressors: cadmium ion (Cd++), salinity and temperature were selected to study their effects on protein and purine catabolism of O. mossambicus. Cadmium (Cd) is a biologically nonessential metal that can be toxic to aquatic animals. Cadmium is a trace element which is a common constituent of industrial effluents. It is a non-nutrient metal and toxic to fish even at low concentrations. Cadmium ions accumulate in sensitive organs like gills, liver, and kidney of fish in an unregulated manner . Thus; the toxic effects of cadmium are related to changes in natural physiological and biochemical processes in organism. The mechanics of osmoregulation (i.e. total solute and water regulation) are reasonably well understood (Evans, 1984, 1993), and most researchers agree that salinities that differ from the internal osmotic concentration of the fish must impose energetic regulatory costs for active ion transport. There is limited information on protein and purine catabolism of euryhaline fish during salinity adaptation. Within a range of non-lethal temperatures, fishes are generally able to cope with gradual temperature changes that are common in natural systems. However, rapid increases or decreases in ambient temperature may result in sub lethal physiological and behavioral responses. The catabolic pathways of proteins and purines are important biochemical processes. The results obtained signifies that O. mossambicus when exposed to different levels of cadmium ion, salinity and temperature show great variation in the catabolism of proteins and purines. The organism is trying to attain homeostasis in the presence of stressors by increasing or decreasing the activity of certain enzymes. The present study revealed that the protein and purine catabolism in O. mossambicus is sensitive to environmental stressors.

Natural resources, redistribution and Human capital formation

How do resource booms affect human capital accumulation? We exploit time and spatial variation generated by the commodity boom across local governments in Peru to measure the effect of natural resources on human capital formation. We explore the effect of both mining production and tax revenues on test scores, finding a substantial and statistically significant effect for the latter. Transfers to local governments from mining tax revenues are linked to an increase in math test scores of around 0.23 standard deviations. We find that the hiring of permanent teachers as well as the increases in parental employment and improvements in health outcomes of adults and children are plausible mechanisms for such large effect on learning. These findings suggest that redistributive policies could facilitate the accumulation of human capital in resource abundant developing countries as a way to avoid the natural resources curse.

Linking molecular and population stress responses in Daphnia magna exposed to cadmium

DNA microarrays can be used to measure environmental stress responses. If they are to be predictive of environmental impact, we need to determine if altered gene expression translates into negative impacts on individuals and populations. A large cDNA microarray (14000 spots) was created to measure molecular stress responses to cadmium in Daphnia magna,the most widely used aquatic indicator species, and relate responses to population growth rate (pgr). We used the array to detect differences in the transcription of genes in juvenile D. magna (24 h old) after 24 h exposure to a control and three cadmium concentrations (6, 20, and 37 mu g Cd2+ L-1). Stress responses at the population level were estimated following a further 8 days exposure. Pgr was approximately linear negative with increasing cadmium concentration over this range. The microarray profile of gene expression in response to acute cadmium exposure begins to provide an overview of the molecular responses of D. magna, especially in relation to growth and development. Of the responding genes, 29% were involved with metabolism including carbohydrate, fat and peptide metabolism, and energy production, 31% were involved with transcription/translation, while 40% of responding genes were associated with cellular processes like growth and moulting, ion transport, and general stress responses (which included oxidative stress). Our production and application of a large Daphnia magna microarray has shown that measured gene responses can be logically linked to the impact of a toxicant such as cadmium on somatic growth and development, and consequently pgr.

Extraction behavior of the synergistic system 2,6-bis-(benzoxazolyl)-4-dodecyloxylpyridine and 2-bromodecanoic acid using Am and Eu as radioactive tracers

In this study, the extraction properties of a synergistic system consisting of 2,6-bis-(benzoxazolyl)-4-dodecyloxylpyridine (BODO) and 2-bromodecanoic acid (HA) in tert-butyl benzene (TBB) have been investigated as a function of ionic strength by varying the nitrate ion and perchlorate ion concentrations. The influence of the hydrogen ion concentration has also been investigated. Distribution ratios between 0.03-12 and 0.003-0.8 have been found for Am(III) and Eu(HI), respectively, but there were no attempts to maximize these values. It has been shown that the distribution ratios decrease with increasing amounts of ClO4-, NO3-, and H+. The mechanisms, however, by which the decrease occurs, are different. In the case of increasing perchlorate ion concentration, the decrease in extraction is linear in a log-log plot of the distribution ratio vs. the ionic strength, while in the nitrate case the complexation between nitrate and Am or Eu increases at high nitrate ion concentrations and thereby decreases the distribution ratio in a non-linearway. The decrease in extraction could be caused by changes in activity coefficients that can be explained with specific ion interaction theory (SIT); shielding of the metal ions, and by nitrate complexation with Am and Eu as competing mechanism at high ionic strengths. The separation factor between Am and Eu reaches a maximum at similar to1 M nitrate ion concentration. Thereafter the values decrease with increasing nitrate ion concentrations.

Separation of Ba-137m from Cs-137 using new ion exchanger Na-2(H2O)(4)(H3O)[Al(OH)(6)Mo6O18]

A new polyoxometalate of chemical formula, Na-2(H2O)(4)(H3O)[Al(OH)(6)Mo6O18] (1) containing Anderson type large anion has been synthesized and characterized by single-crystal X-ray structure determination and IR spectroscopic studies. The crystal of 1 is triclinic, spacegroup P-1 with cell dimensions, a = 6.365(9) angstrom, b = 10.37(1) angstrom, c = 10.44(1) angstrom and alpha = 65.41(1), beta = 77.18(1), gamma = 86.58(1) and Z = 1. The compound 1 behaves as an ion exchanger and is stable in thermal, radiation and chemical environments. Radiochemical separation of the short-lived daughter Ba-137m (t(1/2) = 2.50 min) from its long-lived parent Cs-137 using this newly designed and synthesized ion exchanger has been developed.

Effects of calcium chloride and sodium hexametaphosphate on certain chemical and physical properties of soymilk

Soymilks with sodium hexametaphosphate (SHMP) (0% to 1.2%) and calcium chloride (12.50, 18.75, and 25.00 mM Ca),were analyzed for total Ca, Ca ion concentration, pH, kinematic viscosity, particle diameter, and sediment after pasteurization. Higher added Ca led to significant (P <= 0.05) increases in Ca ion concentration and significant (P <= 0.05) decreases in pH. At certain levels of SHMP, higher concentrations of added Ca significantly increased (P <= 0.05) kinematic viscosity, particle diameter, and sediment. Increasing SHMP concentration reduced Ca ion concentration, particle diameter, and dry sediment content, but reduced kinematic viscosity of samples (P <= 0.05). Adding SHMP up to 0.7% influenced pH of soymilk in different ways, depending on the level of Ca addition. When the pH of Ca-fortified soymilk was adjusted to a higher level, ionic Ca decreased as pH increased. Ihere was a negative linear relationship between the logarithm of ionic Ca concentration and the adjusted pH of the soymilk. Ionic Ca appeared to be a good indicator of thermally induced sediment formation, with little sediment being produced if ionic Ca was maintained below 0.4 mM.

Recovery of lactoferrin and lactoperoxidase from sweet whey using colloidal gas aphrons (CGAs) generated from an anionic surfactant, AOT

The recovery of lactoferrin and lactoperoxidase from sweet whey was studied using colloidal gas aphrons (CGAs), which are surfactant-stabilized microbubbles (10-100 mum). CGAs are generated by intense stirring (8000 rpm for 10 min) of the anionic surfactant AOT (sodium bis-2-ethylhexyl sulfosuccinate). A volume of CGAs (10-30 mL) is mixed with a given volume of whey (1 - 10 mL), and the mixture is allowed to separate into two phases: the aphron (top) phase and the liquid (bottom) phase. Each of the phases is analyzed by SDS-PAGE and surfactant colorimetric assay. A statistical experimental design has been developed to assess the effect of different process parameters including pH, ionic strength, the concentration of surfactant in the CGAs generating solution, the volume of CGAs and the volume of whey on separation efficiency. As expected pH, ionic strength and the volume of whey (i.e. the amount of total protein in the starting material) are the main factors influencing the partitioning of the Lf(.)Lp fraction into the aphron phase. Moreover, it has been demonstrated that best separation performance was achieved at pH = 4 and ionic strength = 0.1 mol/L i.e., with conditions favoring electrostatic interactions between target proteins and CGAs (recovery was 90% and the concentration of lactoferrin and lactoperoxidase in the aphron phase was 25 times higher than that in the liquid phase), whereas conditions favoring hydrophobic interactions (pH close to pI and high ionic strength) led to lower performance. However, under these conditions, as confirmed by zeta potential measurements, the adsorption of both target proteins and contaminant proteins is favored. Thus, low selectivity is achieved at all of the studied conditions. These results confirm the initial hypothesis that CGAs act as ion exchangers and that the selectivity of the process can be manipulated by changing main operating parameters such as type of surfactant, pH and ionic strength.

Heat-inactivated peroxidases and the role of calcium abstraction as a cause of their enhanced lipid oxidation activity: potential effects on the flavour quality of heat-processed vegetables

Cationic swede and anionic turnip peroxidases were partially purified by ion-exchange and gel-filtration chromatography, respectively. Heat treatment of these enzymes and of a commercial high purity horseradish peroxidase (HRP) caused a loss of enzyme activity and a corresponding increase in linoleic acid hydroperoxide formation activity. The hydroperoxide levels in model systems increased only in the early stages of the oxidation reaction and then declined as degradation became more significant. The presence of a dialysed blend of cooked swede markedly lowered the hydroperoxide level formed. Analysis of volatile compounds formed showed that hexanal predominated in a buffer system and in a blend of cooked turnip. In dialysed blends of cooked swede, hexanol was the primary volatile compound generated. After inactivation under mild conditions in the presence of EDTA, the peroxidases showed hydroperoxide formation activity and patterns of volatile compounds from linoleic acid that were similar to those found on heat-inactivation. This suggested that calcium abstraction from the peroxidases was critical for the enhancement of lipid oxidation activity. (C) 2002 Elsevier Science Ltd. All rights reserved.

Gene transcription in Daphnia magna: effects of acute exposure to a carbamate insecticide and an acetanilide herbicide.

Daphnia magna is a key invertebrate in the freshwater environment and is used widely as a model in ecotoxicological measurements and risk assessment. Understanding the genomic responses of D. magna to chemical challenges will be of value to regulatory authorities worldwide. Here we exposed D. magna to the insecticide methomyl and the herbicide propanil to compare phenotypic effects with changes in mRNA expression levels. Both pesticides are found in drainage ditches and surface water bodies standing adjacent to crops. Methomyl, a carbamate insecticide widely used in agriculture, inhibits acetylcholinesterase, a key enzyme in nerve transmission. Propanil, an acetanilide herbicide, is used to control grass and broad-leaf weeds. The phenotypic effects of single doses of each chemical were evaluated using a standard immobilisation assay. Immobilisation was linked to global mRNA expression levels using the previously estimated 48h-EC(1)s, followed by hybridization to a cDNA microarray with more than 13,000 redundant cDNA clones representing >5000 unique genes. Following exposure to methomyl and propanil, differential expression was found for 624 and 551 cDNAs, respectively (one-way ANOVA with Bonferroni correction, Pand up-regulation was prevalent for both test chemicals. Both pesticides promoted transcriptional changes in energy metabolism (e.g., mitochondrial proteins, ATP synthesis-related proteins), moulting (e.g., chitin-binding proteins, cuticular proteins) and protein biosynthesis (e.g., ribosomal proteins, transcription factors). Methomyl induced the transcription of genes involved in specific processes such as ion homeostasis and xenobiotic metabolism. Propanil highly promoted haemoglobin synthesis and up-regulated genes specifically related to defence mechanisms (e.g., innate immunity response systems) and neuronal pathways. Pesticide-specific toxic responses were found but there is little evidence for transcriptional responses purely restricted to genes associated with the pesticide target site or mechanism of toxicity.

Synthesis and X-ray crystal structure of the copper(I) dicarboxylic acid complex [Cu(η1-bdoaH)(PPh3)3] (bdoaH2 = benzene-1,2- dioxyacetic acid)

The copper(II) complex [Cu(bdoa)(H2O)2] (bdoaH2 = benzene-1,2-dioxyacetic acid) reacts with triphenylphosphine (1:4 mol ratio) to give the colourless copper(I) complex [Cu(η1-bdoaH)(PPh3)3] (1) in good yield. The X-ray crystal structure of the complex shows the copper atom at the centre of a distorted tetrahedron, and is ligated by the phosphorus atoms of the three triphenylphosphines and one carboxylate oxygen atom of the bdoaH− ligand. Significant intermolecular hydrogen-bonding exists between the pendant carboxylate OH function of one molecule and the uncoordinated “ketonic” oxygen of a neighbouring molecule. Complex 1 is non-conducting in chloroform but ionizes readily in acetonitrile. The cyclic voltammogram of an acetonitrile solution of 1 shows a single irreversible anodic peak for the oxidation of the PPh3 ligands and the copper(I) centre, and a single irreversible cathodic peak for the reduction of the bdoaH− ion. IR and mass spectral data for 1 are given.