Gräserzüchtung

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Preparation of polypeptide subunits of cytochrome oxidase from Neurospora crassa.

Cytochrome oxidase was purified from Neurospora crassa by ammonium sulfate fractionation in the presence of bile salts. The enzyme preparations contained 10-13 nmol of heme a per mg of protein; no other hemoproteins could be detected. Dodecylsulfate gel electrophoresis resolved the enzyme complex into seven major bands, representing seven polypeptide subunits. A procedure is described that allows the isolation of these enzyme subunits on a large scale starting from a single batch of oxidase preparation. It involves dissociation of the enzyme complex by dodecylsulfate and subsequent separation of the obtained polypeptides by chromatography in the presence of various dodecylsulfate concentrations. Purification of subunits 3, 4, 5, 6 and 7 was achieved by column chromatography using molecular sieves (Sephadex G-100, Bio Gel P-60) and hydroxylapatite. For the purification of subunits 1 and 2 an electrophoretic separation on a preparative polyacrylamide gel was required. The advantages and disadvantages of the separation procedure of the enzyme polypeptides are discussed. As a special point of interest, the conservation of antigenic determinants of the polypeptide chains during the dodecylsulfate treatment is considered.     

Weitere Untersuchung der Ziele der tierischen Handlung

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Ultrastructure of the Cuticle of Loricifera and Demonstration of Chitin using Gold-Labelled Wheat Germ Agglutinin

The pharyngeal and lorical cuticles of adult and larval Loricifera were investigated by transmission electron microscopy. LR White sections of larval and adult Loricifera were labelled with the lectin wheat germ agglutinin (WGA) conjugated to colloidal gold. The pharyngeal cuticle of Nanaloricus mysticus exhibits a multilaminate epicuticle and an amorphous basal layer with osmiophilic fibres. The lorical cuticle consists of an osmiophilic or trilaminate epicuticle, one to three amorphous layer(s), and a basal fibrous layer which is strongly labelled by the lectin-gold conjugate. Chitinase treatment or competitive inhibition with N-, N '-, N "-triacetylchitotriose exclude labelling almost completely, whereas competitive inhibition with N -acetyl-D-glucosamine does not affect labelling intensity. The binding of WGA in connection with competition experiments indicates the presence of chitin in the fibrous layer. In most areas of a section, three amorphous layers extend below the epicuticle of the Nanaloricidae. Only in favourably orientated sections can all three "amorphous" layers be seen to be formed by stacks of lamellae. Modified articulation sites with bundles of osmiophilic longitudinal fibres and an osmiophilic plate (Nanaloricidae only) occur in adult Loricifera, but not in the larval stages. The ultrastructure of the lorical cuticle of the Loricifera resembles that of other Nemathelminthes (= Aschelminthes). The morphology of the articulation sites and the number of lorical plates seem to differ between the Loricifera and Priapulida. Therefore, it is currently not possible to conclude whether the lorica of the Loricifera and Priapulida are homologous structures. © 1997 The Royal Swedish Academy of Sciences. Published by Elsevier Science Ltd.     

Extracellular DNA in aquatic ecosystems may in part be due to phycovirus activity

In a eutrophic lake, a crash of the algal population was followed by a significant increase in the number of virus-like particles (from ca. 1 10⁶ ml^–1 to ca. 26 10⁶ ml^–1), and soon thereafter by an increase of the amount of extracellular DNA (from ca. 20 µg l^–1 to ca. 40 µg l^–1). The same pattern of correlation between decrease of algae and increase of viruses and extracellular DNA could be demonstrated by an in vitro experiment with a Chlorella-virus-system. Lysis of algae by viruses increased both the number of viruses and the amount of DNA in the culture medium. Extracellular DNA mainly consisted of material with a molecular weight below 500 bp.The Chlorella-virus-system is discussed. It could be used as a model-system for studying the dynamics of interaction of viruses and algae in aquatic ecosystems.