Chlorophyll a fluorescence induction measured by a fluorometer with a high temperature stressed plant material shows a new K step which is a clear peak due to fast fluorescence rise and subsequent decrease of fluorescence intensity. We focused on an explanation of the decrease of fluorescence after the K step using artificial electron acceptors and donors to photosystem 2 (PS2). Addition of the artificial electron acceptors or donors suppressed the decrease of fluorescence after the K step. We suggest that the decrease mainly reflects (by more than 81 %) an energy loss process in the reaction centre of PS2 which is most probably a nonradiative charge recombination between P680+ (oxidised primary electron donor in PS2) and a negative charge stored on either Pheo- or QA- (reduced primary electron acceptor of PS2 and reduced primary quinone electron acceptor of PS2, respectively). We suggest that the energy loss process is only possible when the inhibition of both the donor and the acceptor sides of PS2 occurs. and D. Lazár, P. Pospíšil, J. Nauš.
F.xcept other functions, surface saccharide residues on trematode larvae are supposed either to be the targets of the intermediate (molluscan) and final host immune systems, or to represent candidates for molecular mimicry. Therefore, changes in surface saccharide patterns during the development of the avian schistosome Trichobilharzia szidati were characterized. Whole parasite larval stages and their tissue sections were examined using FITC-conjugated lectins. Marked surface differences were found among larval stages (miracidia, mother sporocysts, daughter sporocysts, cercariae, schistosomula). Staining by some lectins reflected known ultrastructural changes of the outer tegument. Reaction of lectins with cercarial embryos was almost negative. In case of other developmental stages, binding of at least one member from each carbohydrate-specificity group of lectins (Man/Glc-, GIcNAc-, Gal/GalNAc- and Fuc-specific) occurred. One exception is represented by mother and daughter sporocysts which practically failed to react with Fuc-specific lectins. Besides other lectins which recognized larval surfaces, a-L-fucose-specific lectins (LTA, UEA-I) and (GlcNAcfll —>4)„-spccific WGA bound very strong to certain stages. The comparison of mature intrasporocystic cercariae with those emerged from snails brought the indication that some snail glycosylated molecules adhere to the surface of schistosome larvae or that emerged cercariae express some new carbohydrate epitopes under changed environmental conditions. The result partially supports the theory of parasite mimicry/masking strategies and immune evasion in the host.
This study investigates the identity of hookworms parasitising the Australian sea lion, Neophoca cinerea (Péron), from three colonies in South Australia, Australia. The Australian sea lion is at risk of extinction because its population is small and genetically fragmented. Using morphological and molecular techniques, we describe a single novel species, Uncinaria sanguinis sp. n. (Nematoda: Ancylostomatidae). The new species is most similar to hookworms also parasitic in otariid hosts, Uncinaria lucasi Stiles, 1901 and Uncinaria hamiltoni Baylis, 1933. Comparative morphometrics offered limited utility for distinguishing between species within this genus whilst morphological features and differences in nuclear ribosomal DNA sequences delineated U. sanguinis sp. n. from named congeners. Male specimens of U. sanguinis sp. n. differ from U. lucasi and U. hamiltoni by relatively shorter anterolateral and externodorsal rays, respectively, and from other congeners by the relative lengths and angulations of bursal rays, and in the shape of the spicules. Female specimens of U. sanguinis sp. n. are differentiated from Uncinaria spp. parasitic in terrestrial mammals by differences in vulval anatomy and the larger size of their eggs, although are morphologically indistinguishable from U. lucasi and U. hamiltoni. Molecular techniques clearly delimited U. sanguinis sp. n. as a distinct novel species. Obtaining baseline data on the parasites of wildlife hosts is important for the investigation of disease and the effective implementation and monitoring of conservation management.