Sodium regulation in the freshwater/land crabHolthuisana transversa

Summary Holthuisana transversa maintains sodium balance at very low external concentrations (7–25 M). This is achieved by the high affinity of the uptake mechanism (K _m=0.18 mM), a low rate of sodium loss (0.17 mol g^–1h^–1) and a large increase in the rate of sodium uptake after depletion. The site of sodium absorption is the gills and extraction of sodium from respired water by sodium-depleted crabs can be as high as 28%. Crabs tolerate direct transfer to 80% sea-water and, following acclimation, the sodium and calcium levels of the haemolymph are maintained above those of the medium while the level of magnesium is significantly lower.     

Adaptations to a terrestrial existence by the robber crab,Birgus latro L.

Summary The activity of carbonic anhydrase (CA), which catalyses the equilibrium CO₂H⁺+HCO ₃ ^- , was investigated in various tissues implicated in the excretion of CO₂ by Birgus latro. Carbonic anhydrase was detected in the water-soluble fraction of gill tissue but also occurred in association with lipids (membrane bound). This is consistent with a CO₂ excretory role and an ion regulation function for the gills. In the lungs (branchial chamber lining) CA activity was found in the membrane bound fraction but was not detected in the soluble fraction, suggesting that the lung CA is not important for ion regulation. The specific CA activity of gill tissue homogenate (A=1.8±0.7·mg^-1) was higher than that measured for lung homogenates (A=0.4±0.2·mg^-1), but when the whole organ was considered the total CA activity in the lungs was not significantly different from total CA activity in the gills. In comparison to aquatic and amphibious crustaceans the specific activity of carbonic anhydrase in the lungs was high (25% cf. gill activity). This CA activity in the lungs could be correlated with significant CO₂ excretion by the lungs. CA may be retained in the branchial tissue as an adjunct to ion reabsorption by the gills.     

Radiorespirometry evidence for the discrimination between 13C-enriched glucose and unlabelled glucose molecules by Paracoccus denitrificans

Paracoccus denitrificans was grown on either unlabelled glucose, [1-13C]glucose or [6-13C]glucose as the sole carbon source for growth. The cells were then incubated with a range of 14C-glucose substrates to compare the 14CO2-evolution rates between cells grown on the glucose and the 13C-labelled glucose. Cells grown on 13C-glucose had significantly faster rates of 14CO2-evolution than those grown on unlabelled glucose. The % yields of 14CO2, per [1-14C]-, [6-14C]- and [U-14C]glucose supplied were also substantially greater than those measured for cells grown on unlabelled glucose. The data indicated that growth of Paracoccus on 13C-enriched glucose substrates resulted in cells with notably different 14C-glucose oxidation metabolism compared to that observed in cells grown on unlabelled glucose.     

The effect of oxygen concentration on the teratogenicity of salicylate, niridazole, cyclophosphamide, and phosphoramide mustard in rat embryos in vitro

Comparisons were made of rat embryos cultured at 5% or 20% oxygen in the presence of salicylate (SAL), cyclophosphamide (CP), niridazole (NDZ), or phosphoramide mustard (PM). Multiple regression analyses were used to compare the effects of drug concentration, oxygen concentration, and the product of drug times oxygen concentration on malformation incidence, viability, and protein content of embryos cultured for 24 hours. Drug concentration significantly affected malformation incidence or severity and protein content (P less than 0.001) for the four drugs tested. Oxygen concentration significantly affected protein content for the four compounds (P less than 0.001) but affected malformation incidence only with NDZ. Furthermore, the interaction of oxygen concentration and drug concentration significantly affected the malformation incidence in the presence of NDZ (P less than 0.001), and protein content (P less than 0.001) and viability (P less than 0.001) in the presence of CP. The pattern of significant effects of the independent variables (drug concentration, oxygen concentration, and drug times oxygen concentration) is consistent with the hypotheses of oxygen-dependent metabolism (or lack of metabolism) of the drugs in question. NDZ, which is thought to be converted to reactive intermediates by an oxygen-inhibited nitroreductase, was more toxic at reduced oxygen tension. CP, which is activated by an oxygen-dependent P-450 system, was more toxic with increased oxygen tension. Significant effects of the independent variables on embryos exposed to SAL or PM were consistent with the effects on control embryos, notably, increased protein content with increased oxygen.     

An EPR study of the lineshape of copper in cytochrome c oxidase.

The EPR spectrum of copper in cytochrome c oxidase (EC 1.9.3.1) has been studied between 5 and 220 degreesK, and the spectral parameters have been determined for both forms of EPR-detectable copper by computer simulation methods. Numerical methods have been developed to separate the spectra of intrinsic copper and inactive copper. Evidence is presented to show that inactive copper is probably formed by denaturation. The EPR parameters for intrinsic copper were determined as gx = 1.99, gy = 2.03, gz = 2.185, / Ax(Cu) / = 0.0020 cm-1, / Ay(Cu) / = 0.0025 cm-1, / Az(Cu) / = 0.0030 cm-1. The principal values of the g tensor and the small value of /Az(Cu) / are interpreted in terms of mixing of 3d, 4s, and 4p metal orbitals. A flattened-tetrahedral stereochemistry about Cu2+ with an additional rhombic distrotion is in best agreement with all of the data. The peak-to-peak linewidth is found to be orientation dependent, and is described by a tensor with principal values deltaHx = 45G, deltaHy = 65 G, deltaHz = 85 G. A weak dipolar interaction with a low-spin ferric species stereochemistry for the copper ion is consistent with the electron transport function of the enzyme. Broad EPR signals with a very short spin-lattice relaxation time has been observed near g = 14 and g = 3 at 5 degrees K in oxidized cytochrome oxidase but not in the reduced or denatured enzyme. The possibility that these are due to the "EPR-undetectable" iron and copper is raised.     

CRAVE: a database, middleware and visualization system for phenotype ontologies

MOTIVATION: A major challenge in modern biology is to link genome sequence information to organismal function. In many organisms this is being done by characterizing phenotypes resulting from mutations. Efficiently expressing phenotypic information requires combinatorial use of ontologies. However tools are not currently available to visualize combinations of ontologies. Here we describe CRAVE (Concept Relation Assay Value Explorer), a package allowing storage, active updating and visualization of multiple ontologies. RESULTS: CRAVE is a web-accessible JAVA application that accesses an underlying MySQL database of ontologies via a JAVA persistent middleware layer (Chameleon). This maps the database tables into discrete JAVA classes and creates memory resident, interlinked objects corresponding to the ontology data. These JAVA objects are accessed via calls through the middleware's application programming interface. CRAVE allows simultaneous display and linking of multiple ontologies and searching using Boolean and advanced searches.     

Characterization of a mononuclear copper carboxylate complex: Bis(acetylsalicylato)bis(pyridine)copper(II)

The preparation, spectral properties, and crystal structure of a mononuclear copper(II) complex of acetylsalicylate and pyridine are reported. The complex exists as bis(acetylsalicylato)bis(pyridine)copper(II) both in the solid state and in chloroform solution. The crystal is monoclinic, space group P2₁/n, with a = 17.823(5), b = 10.903(4), c = 6.598(2) Å, β = 95.74(2)°. The final refinement used 1472 observed reflections and gave an R of 0.046. The copper atom is surrounded by four atoms in a trans square planar arrangement with two short CuO distances of 1.949(3) Å and two CuN distances of 2.003(4) Å. Two longer CuO distances of 2.623(3) Å are made with the remaining oxygen atoms of the aspirin carboxylate groups.     

Growth of Paracoccus denitrificans on [2,3-13C]succinate and [1,4-13C]succinate. III. Biosynthetic pathways

The biosynthesis in vivo of a number of amino acids, sugars, and purines in Paracoccus denitrificans grown on either [2,3-13C]succinate or [1,4-13C]succinate was investigated by using gas chromatography-mass spectrometry. The distribution of label in the TCA-cycle-related amino acids indicated that carbon intermediates of energy metabolism were utilized as precursors for the biosynthesis of these amino acids in vivo. The biosynthesis of glycine, serine, phenylalanine and glycerol from labelled succinate in vivo were consistent with phosphoenol pyruvate as an intermediate. A mechanism for the formation of C4, C5 and C6 sugars without the use of fructose-1,6-bisphosphate aldolase (which has not been detected in P. denitrificans) is proposed. The 13C-enrichments of ribose in the bacterium indicate that there are at least three routes of ribose biosynthesis operating during growth on labelled succinate. The probability distribution of labelled purine molecules was successfully predicted for adenine, guanine and adenosine, thus confirming their generally accepted route of biosynthesis in vivo.     

Stable isotope evidence for the localisation of some metabolic pathways in the bacterium Paracoccus denitrificans

Paracoccus denitrificans was grown on [6-13C]-glucose as the sole carbon source for growth and the extracts were fractionated and analysed by gas chromatography-mass spectrometry. The 13C-enrichments of some metabolites indicated that the "hydrolysate pools" of these metabolites were not in isotopic equilibrium with the water soluble "free pools". It was concluded that localisation of some metabolic pathways had occurred in Paracoccus during growth on [6-13C]-glucose.