Linear dichroism and orientational studies of carotenoid Langmuir-Blodgett films

The linear dichroism of single monolayers of lutein, zeaxanthin and a mixture of lutein and synthetic phosphatidylcholine has been measured. The angle of orientation of the carotenoid molecules was found to lie between 45° and 51° relative to the plane of the solid support. Although the adsorbed monolayers were mostly in a monomeric state, microscopic observations, as well as the II-A isotherms, indicated the existence of crystalline islets. The results have been interpreted in connection with Haidinger's polarization brushes.     

Balance between anionic and cationic extracellular peroxidase activities in Sedum album leaves after ozone exposure. Analysis by high-performance liquid chromatography

Peroxidase activity was assayed with different electron donors (guaiacol, ascorbate, syringaldazine) in the intercellular fluid of Sedum album L. leaves after ozone exposure. Anionic and cationic peroxidases were separated and purified by high performance ion-exchange and gel permeation chromatography. Both isoperoxidases were tested as regards their molecular weight and apparent kinetic constants with different substrates. Ascorbate peroxidase activity was rapidly stimulated after ozone exposure, whereas syringaldazine peroxidase activity reached its maximum 24 h later. Increases in ascorbate and syringaldazine peroxidase activities occurred simultaneously with increases in cationic and anionic peroxidase activities, respectively. Apparent K_m values indicate a high affinity of cationic peroxidases for ascorbate and of anionic peroxidases for syringaldazine. The metabolic role of this balance between cationic and anionic peroxidases after ozone exposure is discussed.     

A burst of CO2 from photosynthesizing leaves after a temperature decrease under constant light conditions

A transient CO₂ burst from seedlings of some plant species was observed after a rapid temperature decrease. The magnitude of the CO₂ release depended on initial temperature, oxygen concentration and light intensity. To obtain a maximal value of CO₂ release, the temperature had to decrease by more than 8°C. The phenomenon was detected only in the light, and was confined to C₃ species. It was inhibited by low oxygen concentration, indicating its possible connection with photorespiration.     

Methanogenesis in an Upflow Anaerobic Sludge Blanket Reactor at pH 6 on an Acetate-Propionate Mixture

High-rate anaerobic digestion can be applied in upflow anaerobic sludge blanket reactors for the treatment of various wastewaters. In upflow anaerobic sludge blanket reactors, sludge retention time is increased by a natural immobilization mechanism (viz. the formation of a granular type of sludge). When this sludge is cultivated on acid-containing wastewater, the granules mainly consist of an acetoclastic methanogen resembling Methanothrix soehngenii. This organism grows either in rods or in long filaments. Attempts to cultivate a stable sludge consisting predominantly of Methanosarcina sp. on an acetate-propionate mixture as substrate by lowering the pH from 7.5 during the start-up to approximately 6 failed. After 140 days of continuous operation of the reactor a filamentous organism resembling Methanothrix soehngenii prevailed in the sludge. The specific methanogenic activity of this sludge on acetate-propionate was optimal at pH 6.6 to 6.8 and 7.0 to 7.2, respectively.     

Sodium arsenite enhances the cytotoxicity, clastogenicity, and 6-thioguanine-resistant mutagenicity of ultraviolet light in Chinese hamster ovary cells

Cytotoxicity, chromosome aberrations, and mutations to 6-thioguanine resistance were synergistically increased by incubating the ultraviolet light (UV)-irradiated Chinese hamster ovary (CHO) cells in medium containing sodium arsenite. However, the frequencies of sister-chromatid exchanges and mutations to ouabain resistance induced by UV were not synergistically increased by sodium arsenite. The synergistic effect of sodium arsenite on UV-induced chromosome aberrations varied with cell-harvesting time and decreased with increasing time intervals between UV and sodium arsenite treatments.     

Requirement for the action of endogenous ethylene during germination of non-dormant seeds of Amaranthus caudatus

The role of endogenous ethylene during germination of non-dormant seeds of Amaranthus caudatus L. was investigated. The seeds readily germinated in water and darkness at 24°C. Application of ethylene or of its precursor I-aminocyclopropane-I-carboxylic acid (ACC) slightly increased the rate of germination. Both compounds effectively antagonized osmotic inhibition by polyethyleneglycol. Application of aminoethoxyvinylglycine (AVG) reduced ethylene production by 90% but did not inhibit germination. However, germination was inhibited by 2,5-norbornadiene, a competitive inhibitor of ethylene action. This inhibition was counteracted by ethylene, ethephon or ACC and enforced by AVG. It is concluded that the action of endogenous ethylene is an indispensable factor during germination of non-dormant seeds of A. caudatus. Ethylene action is required from the start of imbibition on. In water, low levels of endogenous ethylene are sufficient for this action. PEG increased the ethylene requirement considerably.     

Detection of sugar-binding proteins in membrane-depleted nuclei

Nuclear sugar-binding proteins were detected in membrane-depleted nuclei isolated from hamster BHK cells and mouse L 1210 leukemia cells by means of fluorescein-labelled neoglycoproteins. In fluorescence microscopy, the fluorescence was seen throughout the nucleus but was generally brighter over the nucleoli than over the rest of the nucleus. Flow cytofluorometry analysis demonstrated the presence of nuclear sugar-binding proteins for synthetic glycoproteins associated with different sugar residues. Among the nine neoglycoproteins used, four neoglycoproteins (namely alpha-rhamnosylated, alpha-glucosylated, N-acetyl-beta-glucosaminylated and alpha-mannosylated-6P-serum albumin) strongly labelled nuclei. Various controls strongly argue for the specificity of the nuclear labelling. The possibility that some of the sugar-binding proteins might correspond to endogenous nuclear lectins is considered.