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After immersion of seashore and inland mosses in artificial seawater, their extracellular, exchangeable and intracellular cations were analysed. Levels of extracellular and exchangeable Na and Mg in both inland and seashore mosses increase. In the intracellular fraction of inland species there was a rapid loss of K and an accompanying net uptake of Na by a slower, possibly active, process, K loss from inland mosses occurred in seawater concentrations exceeding 50% whereas seashore species withstood concentrations of seawater up to 200% with little change. Treatment of the seashore moss, Grimmia maritima, with NaCl at the concentration in seawater produced almost complete loss of intracellular K. This effect was greatly alleviated by Ca, partially by Mg and was nullified when Na was accompanied by both Ca and K. When Grimmia spp, were supplied with seawater solutions containing a range of Ca concentrations, G. pulvinata showed stimulation of net uptake of Na and reduced net loss of K with increasing Ca concentration whereas G. maritima showed inhibition of net uptake of Na and increased net uptake of K. The ability of seashore mosses to withstand immersion in seawater without undergoing large changes in intracellular cation content may reflect greater K specificity of the monovalent cation uptake carriers than in the inland species studied. [ABSTRACT FROM AUTHOR]

A study has been made over a range of temperatures at 20 MHz and 35 MHz of the spin relaxation rates of water protons in aqueous solutions of ethylene glycol bis-(aminoethyl)-tetra-acetic acid containing Gd(III) and Eu(II) ions. The results suggest that the dominant relaxation process arises from rotation of the solvated complexes. Relaxation enhancement has been observed for Gd(III) in the presence of lysozyme and values of ∊*, Kd and tc have been determined An application of these results to obtain distances of substrate analogues from the active site of this and other enzymes is discussed. [ABSTRACT FROM AUTHOR]

Cations of monohydropteridine radicals have been obtained in solution and investigated by electron spin resonance. The hyperfine pattern of these signals as well as that of previously described trihydropteridine radical cations has been computed to agreement with experiment. The first mentioned radicals are shown to have 5,8-H2Pter+-structure, whereas the latter are 5,6,7,8-H4Pter+. Substitutions in the pyrimidine part of the system (positions 1-4) do not affect the spin distribution essentially in any case. In monohydropteridine the unpaired electron is delocalized over the whole pyrazine part of the system (positions 5-8), whereas in trihydropteridines it is mainly confined to N(5) and possibly to the bridge carbons. The biochemical implications of pteridine radicals are discussed. While two-electron oxido-reduction, implying 7,8-dihydropteridine, is thermodynamically irreverssible, one-electron oxido-reduction appears to be intermediate in the systems Pter/5,8-H2Pter on the one hand, and 6,7-H2Pter/H4Pter on the other hand, thus permitting rapid electron transfer. Hence, it is reasonable to assume that trihydropteridine radicals might be of biological importance, though clearly not as the strongly acidic cations described here, but maybe in the stabilized form of metal complexes. In this context, existence, stability and eventual biological importance of the various dihydropteridine isomers is discussed. [ABSTRACT FROM AUTHOR]

B. subtilis Gln-tRNA formation, in vitro, involves the initial acceptance of glutamic acid by tRNAGln to form a missense Glu-tRNGln intermediate which is converted to Gln-tRNA by a subsequent amidation step, catalyzed by a specific amido-transferase, and requiring divalent cations, ATP, and L-glutamine or L-asparagine as amide donor. This reaction is associated with stoichiometric cleavage of glutamine and ATP to yield glutamic acid and Pi, respectively. Amidation proceeds via the formation of an activated intermediate which is shown to be γ-phospho-Glu-tRNAGln (P-γ-Glu-tRNAGln). P-γ-Glu-tRNAGln, bound to amido-transfcrase, is detected following incubation in the absence of amide donor. Subsequent addition of L-glutamine to the system leads to the rapid toss of the phosphate moiety from the intermediate concomitantly with the formation of Gln-tRNA, which is released from the enzyme. Consequences of the pathway, if it is duplicated in vivo, are the separation of the synthesis of glutamine destined for protein from that of free glutamine and, further, the coupling of the synthesis of the ammo acid with that, of protein. These implications are discussed with regard to their bearing on possible functions of the pathway. [ABSTRACT FROM AUTHOR]

The effect of sodium and potassium chlorides on glucose uptake by Dendryphiella sauna after growth in glucose-tryptone media of varying cation composition has been studied. The results are explicable in terms of the previous findings on the relationship between glucose uptake and the potassium and sodium content of the mycelium. Other experiments on the effects of potassium and sodium chlorides separately and sodium and calcium chlorides together on growth in a range of glucose concentrations have provided evidence that cations can also influence glucose utilization by providing a source of osmotic pressure within the hyphae alternative to organic solutes. [ABSTRACT FROM AUTHOR]

The present paper is a report on qualitative and quantitative investigations ou the bottom fauna of brooks in the forest district of North Sweden. The work was carried out during the summers of 1952 and 1953 in the vicinity of Bodträskfors. The characteristic physiographical features of the brooks arc: low pH (5.1-5.3), low degree of hardness (0.7 D-degrees). high concentration of iron cations (l.8-3.0 mg/I). A special character of these brooks is the complete absence of a ≫cold stenothermic part ≪. Ecologically all the brooks belong to the Central European ≫ grayling region ≪ because of the wide temperature amplitude. in general the insect fauna consists of boreo-alpine species but in addition endemic high-boreal species are also present. The quantity of bottom fauna increases below the lakes, Furthermore, maximum colonization was caused by the regulations taking place for purposes of timber-floating. Below lakes Trichopteran larvae dominated, on the other hand Simulium larvae attained high density in the cleaned brooks. The brooks cleaned in 1952 show an almost pure colonization by Simulium larvae while those cleaned in 1951 in addition to a dense population of Simulium show increased numbers of rheophilous Trichopteran larvae. The qualitative and quantitative survey of the bottom fauna of the river Spikselån from station 1 (cleaned 1948) shows a gradual transition to Trichopteran larvae. When regulation (cleaning) of a river takes place the velocity of the current increases thus improving the conditions for rheophilous species. Special situations may occur below lakes. The occurrence of Neureclipsis bimaculata and Hydropsyche angustipennis (Trichoptera) is clearly dependent on the variation in current strength. The following current-water biocenoses could be distinguished: 1. Marshy brooks: Biological and physiographical characteristics: low pH, dense vegetation of diatoms (Tabellaria,), low density of Chironomidae and Odonata, 2. Lake-outlet biocenosis. Biological and physiographical characteristics: narrow temperature variations. Because of the variation of the current the species composition varies: Weak current: Neureclipsis himaculata; Spongillidae; Baetidae. Strong current: Hydropsyche angustipennis; Rhyacophila nubila; Simuliidae, Spongillidae. 3. Submerse plant biocenosis. Biological and physiographical characteristics: Wide temperature variation, high O2 content. In strong current: Fontinalis sp. In weak current: Batrachospermum vagum. Typical fauna: Chitonophora aronii; Ephemerella ignita; Paraleptophlebia tumida; Coleoptera; Hydracarina. 4. Rubble biocenosis. Biological and physiographical characteristics: Wide temperature variation; high O2 content, no submerse plants. Typical fauna: Heptagenia dalacarlica; Baetis vernus, Baetis sp.; rarely Coleoptera; Hydracarina. [ABSTRACT FROM AUTHOR]