The reviev concerns-the newer asptzt.as of plant cell wall construction and modification, including the structure and biosynthesis of basic components during the cell growth and differentiation, as well as their breakdown. The special interest is given to the enzymes incorporated into the cell wall and their specific activity in the biosynthesis and degradation processes, but also in the transfer of glycosyl fragments (blocks), which is connected with its thickening, softening, constructing the channels a.o. New aspects of lignification and specialisation of particular wall fragments, playing various functions, such as fruit ripening, dropping down leaves, fruits and flowers, breaking the dormancy, and others, are also presented.

Amphotericin B delays the onset of clinical symptoms in hamsters infected with scrapie agent strain 263K. Here we show that accumulation of a scrapie-specific isoform of the prion protein (PrP-res) and agent replication were delayed early in amphotericin B-treated animals. By 8 weeks postinfection, only untreated animals exhibited clinical symptoms of scrapie infection whereas PrP-res levels and titers were similar in treated and untreated animals. This suggests that although PrP-res accumulation and agent replication are linked, they are not the sole factors required for the onset of clinical disease.

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P~trescine-l,4-'~C was fed to the excised root cultures of Datura metel L., and the alkaloids subsequently isolated. These consisted of hyoscyamine, hyoscine, and a base of undetermined constitution designated as alkaloid X. All three bases were radioactive. Degradation of the hyoscyamine revealed that ca. 8% of the radioactivity was present in the tropic acid moiety, but that all the radioactivity of the tropine moiety was located in the pyrrolidine ring. The implications of these results are discussed. INTRODUCTIOK

No abstract