16β-Hydroxycholestanol als biogenetische vorstufe der steroidsapogenine

It has been shown that 5,6-³H,16β-hydroxycholestanol is used in the biogenesis of the steroid sapogenins, tigogenin and gitogenin, by plants of Digitalis lanata but not for the formation of tomatidine by Solanum lycopersicum.     

A method for characterization and fractionation of deoxyribonucleic acid by continuous turbidimetry of cetyltrimethylammonium-DNA precipitates

Cetyltrimethylammonium-DNA from solutions containing 1 m NaCl may be precipitated by continuously lowering the NaCl concentration. By monitoring the increasing turbidity of the reaction mixture at 600 nm as a function of dilution, a curve of apparent absorbance versus volume of diluting solution (or decreasing salt concentration) is obtained. Evaluation of these curves allows (a) an estimation of DNA concentration even in the presence of components absorbing at 260 nm; (b) analysis of the molecular weight distribution of DNA samples; (c) separation of native DNA, RNA and proteins on an analytical or preparative level; (d) optimization of yield and purity by simple procedures even with considerable excess of RNA; (e) characterization at the analytical level and partial, eventually complete separation of doublestranded from single-stranded DNA.The controlled fractionation of protein, DNA, and RNA is the basis of a preparation procedure for DNA from practically all biological objects, yielding products of high quality.     

Scanning electron microscopy of Drosophila embryogenesis: 1. The structure of the egg envelopes and the formation of the cellular blastoderm

As part of a series of detailed observations on embryogenesis in Drosophila, the protective coverings of the egg and surface changes in the embryo prior to gastrulation have been studied with the SEM. Four specializations of the chorion are described: the plastron, micropylar cone, operculum, and the posterior thickening. After removal of the protective coverings the surface changes during development can be observed. During the first eight synchronous nuclear divisions a dense array of thin microprojections covers the whole embryo. After the ninth division between 373 and 408 nuclei reach the surface and become located in cytoplasmic projections. From counts of the number of surface bulges during the syncytial blastema stages, it was established that 13 synchronous divisions take place producing between 5600 and 6500 surface nuclei. During formation of the cellular blastoderm, the location of the prospective cells becomes obscured by a dense pattern of microprojections from each cell. However, with the completion of the blastoderm, the surfaces of the cells become smooth and the cell outlines distinct. The usefulness of the SEM in developmental studies is discussed.     

Ein Fall von zweikieligem adossiertem Vorblatt beiSwertia perennis L

Ohne Zusammenfassung     

Die bodenfauna des greifswalder boddens. Ein beitrag zur ökologie der brackwasserfauna

Ohne Zusammenfassung     

Die Wirkung von Licht auf den Transport von 2-[14C]Abscisinsäure in Bohnenwurzelsegmenten

Summary Light promotes the acropetal movement of 2-[¹⁴C]ABA through root segments of Phaseolus coccineus L. The promotion occurs only when the segments are irradited during the transport period. Red light and blue light are as effective as white light. There is no significant promotion when the segments are irradiated with green light or when they are kept in darkness during the transport period after preceding light treatment. Light has no effect on basipetal ABA-transport.

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Abkürzungen ABA Abscisinsäure - D Dunkel - GA Gibberellinsäure - IAA Indolessigsäure - L Licht - PPO Diphenyloxazol