Die cucurbitacine in Bryonia alba und Bryonia dioica

The cucurbitacins in roots of Bryonia dioica and B. alba have been investigated. Both species contain the cucurbitacins E, B, I, D, J, K and L, the dihydrocucurbitacins E and B, and tetrahydrocucurbitacin I. The detection of certain cucurbitacin aglycones depends upon the date of harvest, the duration of storage and the methods used for extraction.     

Ultrastructure of the prothoracic gland cells of the last instar of Galleria mellonella in relation to the state of development

The prothoracic glands of the last instar of Galleria mellonella undergo characteristic alterations of their cellular fine structure closely related to cellular activity. During progressive secretory activity of the gland cells there are extensive plasmalemmal infoldings and formation of a pronounced lacunar system. Mitochondria of the active cell phase are characterized by a specific increase in size and paler colour of the matrix. In contrast to the alterations, nuclei, ER and Golgi cisterns do not undergo any submicroscopic changes during the different phases of cellular activity. The relationship between the substructural phenomena and the specific phases of cellular activity are discussed.     

Single-Stranded Annealing Induced by Re-Initiation of Replication Origins Provides a Novel and Efficient Mechanism for Generating Copy Number Expansion via Non-Allelic Homologous Recombination

Copy number expansions such as amplifications and duplications contribute to human phenotypic variation, promote molecular diversification during evolution, and drive the initiation and/or progression of various cancers. The mechanisms underlying these copy number changes are still incompletely understood, however. We recently demonstrated that transient, limited re-replication from a single origin in Saccharomyces cerevisiae efficiently induces segmental amplification of the re-replicated region. Structural analyses of such re-replication induced gene amplifications (RRIGA) suggested that RRIGA could provide a new mechanism for generating copy number variation by non-allelic homologous recombination (NAHR). Here we elucidate this new mechanism and provide insight into why it is so efficient. We establish that sequence homology is both necessary and sufficient for repetitive elements to participate in RRIGA and show that their recombination occurs by a single-strand annealing (SSA) mechanism. We also find that re-replication forks are prone to breakage, accounting for the widespread DNA damage associated with deregulation of replication proteins. These breaks appear to stimulate NAHR between re-replicated repeat sequences flanking a re-initiating replication origin. Our results support a RRIGA model where the expansion of a re-replication bubble beyond flanking homologous sequences followed by breakage at both forks in trans provides an ideal structural context for SSA–mediated NAHR to form a head-to-tail duplication. Given the remarkable efficiency of RRIGA, we suggest it may be an unappreciated contributor to copy number expansions in both disease and evolution.     

The effects of lime and superphosphate on manganese toxicity in steam-sterilized soil

Summary The effects of liming and superphosphate application on the manganese nutrition of lettuce were studied in factorial experiments. A fairly acid silt loam of the Hamble series, which on steam-sterilization released considerable amounts of manganese in readily available forms, was used in the investigation.Manganese toxicity in lettuce was prevented by liming to increase the pH of the soil. The amounts of water-soluble, exchangeable and total active manganese present in the soil, and the manganese content of lettuce plants, decreased with increasing soil pH; easily reducible soil manganese increased with increasing soil pH.The effect of added superphosphate depended on the pH of the untreated soil. When the soil had a high pH, application of phosphate invariably decreased the pH and increased the manganese uptake. In acid soil supplying excessive amounts of manganese, application of phosphate reduced the manganese content of the plants; the pH of the soil was either unchanged or slightly increased by the treatment.Correlations were calculated between soil pH, various fractions of soil manganese, and the manganese content and yield of lettuce.From a comparison of plants grown in soil and sand culture it was concluded that the presence of a further toxic factor in the soil was probable.The results are discussed in relation to those obtained by other investigators.     

Studies on the Assembly Characteristics of Large Subunit Ribosomal Proteins in S. cerevisae

During the assembly process of ribosomal subunits, their structural components, the ribosomal RNAs (rRNAs) and the ribosomal proteins (r-proteins) have to join together in a highly dynamic and defined manner to enable the efficient formation of functional ribosomes. In this work, the assembly of large ribosomal subunit (LSU) r-proteins from the eukaryote S. cerevisiae was systematically investigated. Groups of LSU r-proteins with specific assembly characteristics were detected by comparing the protein composition of affinity purified early, middle, late or mature LSU (precursor) particles by semi-quantitative mass spectrometry. The impact of yeast LSU r-proteins rpL25, rpL2, rpL43, and rpL21 on the composition of intermediate to late nuclear LSU precursors was analyzed in more detail. Effects of these proteins on the assembly states of other r-proteins and on the transient LSU precursor association of several ribosome biogenesis factors, including Nog2, Rsa4 and Nop53, are discussed.     

Compensation of large motion sensor displacements during long recordings of limb movements

In motion capture applications using electromagnetic tracking systems the process of anatomical calibration associates the technical frames of sensors attached to the skin with the human anatomy. Joint centers and axes are determined relative to these frames. A change of orientation of the sensor relative to the skin renders this calibration faulty. This sensitivity regarding sensor displacement can turn out to be a serious problem with movement recordings of several minutes duration. We propose the “dislocation distance” as a novel method to quantify sensor displacement and to detect gradual and sudden changes of sensor orientation. Furthermore a method to define a so called fixed technical frame is proposed as a robust reference frame which can adapt to a new sensor orientation on the skin. The proposed methods are applied to quantify the effects of sensor displacement of 120 upper and lower limb movement recordings of newborns revealing the need for a method to compensate for sensor displacement. The reliability of the fixed technical frame is quantified and it is shown that trend and dispersion of the dislocation distance can be significantly reduced. A working example illustrates the consequences of sensor displacement on derived angle time series and how they are avoided using the fixed technical frame.     

The lysolipid sphingosine modulates pyrophosphatase activity in tonoplast vesicles and isolated vacuoles from a heterotrophic cell suspension culture of Chenopodium rubrum

The proton pumping activity of the tonoplast (vacuolar membrane) H⁺-ATPase and H⁺-pyrophosphatase (H⁺-PPase) has been studied on a tonoplast-enriched microsomal fraction and on intact vacuoles isolated from a heterotrophic cell suspension culture of Chenopodium rubrum L. in the presence of the lysosphingolipids D-sphingosine, psychosine (galactosylsphingosine) and lysosulfatide (sulfogalactosyl-sphingosine). Sphingosine strongly stimulates (K_a= 0.16 μ M ) the PPase activity, assayed both as ΔpH formation across the tonoplast vesicle membrane, and as reversible clamp current measured by the whole-vacuolar mode of the patch-clamp technique. Psychosine showed a minor, and lysosulfatide no stimulatory effect. No effect upon the ATPase activity has been observed. No sphingosine-induced change could be observed in the affinity of the PPase for its substrate (apparent K_m= 10 μ M MgPPi). We tentatively conclude that sphingosine, which is known as a potent inhibitor of the protein kinase C in animal cells, may be a regulator of the plant vacuolar PPase.