Über den Flavonoidstoffwechsel während der Samenkeimung

Es wurde das Flavonoidmuster ruhender Samen und 8 bis 10 Tage alter Keimlinge von 18 Pflanzenarten unterschiedlicher taxonomischer Einheiten verglichen. Als allgemeines Ergebnis kann festgestellt werden: In den meisten Samen und in allen Keimlingen liegen neben Zimtsäuren (und Derivaten) Flavonoide, hauptsächlich Quercetin- und Kämpferolglykoside, in unterschiedlicher Anzahl und Menge vor. Das “Ruhemuster” unterscheidet sich allgemein von der Pigmentausstattung junger Keimlinge. Drei typische Gruppen von Pflanzen wurden gefunden, deren Pigmentgehalt und -muster während der Samenkeimung charakteristisch verändert wird.     

Pupariation in flies: A tool for monitoring effects of drugs,venoms, and other neurotoxic compounds

A complex Sarcophaga bullata pupariation assay was used to evaluate the neurotropic effects of several drugs, venoms, and insecticides. The assay consists of tests for (1) immediate effects on the intact larva, (2) effects on ligated (ie, isolated from the central nervous system) larval abdomens, (3) morphogenetic effects on the puparium, and (4) effects on stereotyped pupariation behavior. The latter are monitored barographically by recording changes in hemocoelic pressure. Of 62 compounds screened, 18 showed morphogenetic activity at a threshold dose of 5 μg or less, 11 at a dose of 50 μg, four at a dose of 100 μg, and 29 showed no morphogenetic activity. From a comparison of the putative pharmacological actions of the tested compounds with their morphogenetic effects, certain generalizations can be made: Agents that paralyze neuromuscular systems at the peripheral level (eg, tetrodotoxin), or suppress or modify basic motor patterns centrally (eg, veratrine sulphate), cause retention of larval morphological characters in the puparium. Compounds that stimulate convulsive contractions of segmental musculature (mostly cholinergic drugs like eserine sulphate, nicotine, organophosphate insecticides) cause retention of larval segmentation on longitudinally contracted puparia. Five compounds (venom of the scorpion, Leirus quinquestriatus, pyrethrins, protoveratrine A, and kainic and quisqualic acids) stimulate musculature of the denervated abdomen. Barographic monitoring of changes in pupariation behavior appears to be a most sensitive and informative test. It reveals great differences in the ways in which compounds producing seemingly identical morphogenetic effects affect and modify behavior, thus making pharmacological classification more accurate.     

Proofreading exonuclease on a tether: the complex between the E. coli DNA polymerase III subunits α, ε, θ and β reveals a highly flexible arrangement of the proofreading domain

A complex of the three (αεθ) core subunits and the β₂ sliding clamp is responsible for DNA synthesis by Pol III, the Escherichia coli chromosomal DNA replicase. The 1.7 Å crystal structure of a complex between the PHP domain of α (polymerase) and the C-terminal segment of ε (proofreading exonuclease) subunits shows that ε is attached to α at a site far from the polymerase active site. Both α and ε contain clamp-binding motifs (CBMs) that interact simultaneously with β₂ in the polymerization mode of DNA replication by Pol III. Strengthening of both CBMs enables isolation of stable αεθ:β₂ complexes. Nuclear magnetic resonance experiments with reconstituted αεθ:β₂ demonstrate retention of high mobility of a segment of 22 residues in the linker that connects the exonuclease domain of ε with its α-binding segment. In spite of this, small-angle X-ray scattering data show that the isolated complex with strengthened CBMs has a compact, but still flexible, structure. Photo-crosslinking with p-benzoyl-L-phenylalanine incorporated at different sites in the α-PHP domain confirm the conformational variability of the tether. Structural models of the αεθ:β₂ replicase complex with primer-template DNA combine all available structural data.     

Structural characteristics of marsupial brood pouches of the antarctic sea urchins Abatus nimrodi and Abatus shackletoni (Echinoidea: Spatangoida)

Marsupial spines, tubercles, and pedicellariae of the antarctic brooding spatangoids Abatus nimrodi and Abatus shackletoni have been examined by scanning electron microscopy. Individual brood pouches of A. nimrodi may hold up to 28 embryos and juveniles and those of A. shackletoni may hold up to 38 lecithotrophic embryos and juveniles. Juveniles can be divided into (a) those with early development of external elements and a mean size of 2.0 and 1.6 mm, respectively, and (b) those equipped with fully developed external elements and a mean length of 4.3 and 2.8 mm, respectively. Mean diameters of aboral brood pouch openings of A. nimrodi and A. shackletoni were 6.5 and 4.1 mm, respectively. Brood pouches contain tall, distally enlarged spines, and smaller, layered cover-spines, which form a protective arch over the marsupia. There are also slender brood-pouch-bottom spines, which have an extremely thickened spinal epidermis. A. nimrodi has mainly bidentate, but also triand quadrodentate pedicellariae. A. shackletoni has two forms of tridentate, rostrate, and globiferous pedicellariae. In A. shackletoni, marsupial spine density is significantly lower than in A. nimrodi. These differences may be related to distinct sediment characteristics in their respective habitats. © 1993 Wiley-Liss, Inc.