The Effect of Coumarin on Growth, Production of Dry Matter, Protein and Nucleic Acids in Roots of Maize and Wheat and the Interaction of Coumarin with Metabolic Inhibitors

Effects of coumarin on fresh weight, dry matter, protein and nucleic acid content per cell in attached roots of maize and wheat and in whole excised elongation zones of maize were determined. The inhibition in cell length exerted by coumarin did not correspond to an inhibition of the net synthetic capacity. Coumarin treatment increased the cell surface, the production of dry matter and the protein content per cell. The dry matter and the protein content per unit surface was slightly increased or unaffected. The effect of coumann on cell shape seemed to be independent of that on dry matter production and net protein synthesis. The same was found in excised elongation zones. —The net DNA-synthesis per cell was slightly increased in attached roots by coumann treatment, but this effect was probably not correlated with the morphogenetic changes. Inhibition of DNA-synthesis with hydroxyurea did not alter the coumarin induced changes in cell shape. —The net RNA-synthesis per cell was slightly decreased after coumarin treatment, but the net RNA-synthesis per cell and the morphogenetic effects exerted by coumarin were not related with each other. Inhibition of m-RNA-synthesis with actinomycin D did not prevent the effects of coumarin on cell division, cell expansion, dry matter production and net protein synthesis. The same was true for inhibitors of protein synthesis, puromycin and p-fluorophenyl-alanine. The findings are in support of the view that coumarin affects already existing structures or enzymes. —Comparisons between coumarin and the uncouplers, DNP and dicoumarol, showed that the effects of coumarin were not, solely, due to uncoupling. SH-protecting agents, BAL, DTE and glutathione, did, with few exceptions, not reduce the morphogenetic effects of coumarin.     

Imidazo[1,2-b]pyridazines: a potent and selective class of cyclin-dependent kinase inhibitors

Modification of imidazo[1,2-a]pyridine CDK inhibitors lead to identification of less lipophilic imidazo[1,2-b]pyridazine series of CDK inhibitors. Although several equivalent compounds from these two series have similar structure and show similar CDK activity, the SAR of the two series differs significantly. Protein inhibitor structure determination has confirmed differences in binding mode and given some understanding of these differences in SAR. Potent and selective imidazo[1,2-b]pyridazine inhibitors of CDK2 have been identified, which show >1 microM plasma levels following a 2mg/kg oral dose to mice.     

Mitochondrial DNA of the extinct quagga: Relatedness and extent of postmortem change

Sequences are reported for portions of two mitochondrial genes from a domestic horse and a plains zebra and compared to those published for a quagga and a mountain zebra. The extinct quagga and plains zebra sequences are identical at all silent sites, whereas the horse sequence differs from both of them by 11 silent substitutions. Postmortem changes in quagga DNA may account for the two coding substitutions between the quagga and plains zebra sequences. The hypothesis that the closest relative of the quagga is the domestic horse receives no support from these data. From the extent of sequence divergence between horse and zebra mitochondrial DNAs (mtDNAs), as well as from information about the fossil record, we estimate that the mean rate of mtDNA divergence in Equus is similar to that in other mammals, i.e., roughly 2% per million years.     

Sulfur stable isotopes separate producers in marine food-web analysis

Ecological applications of stable isotope analysis rely on different producers having distinct isotopic ratios to trace energy and nutrient transfer to consumers. Carbon (C) and nitrogen (N) are the usual elements analysed. We tested the hypothesis that producers unable to be separated using C and N would be separated by sulphur (S), by reviewing estuarine and marine food web studies using all three elements (total of 836 pairwise comparisons between producers). S had a wider range of values across all producers than C and N (S: 34.4, C: 23.3, N: 18.7), and a higher mean difference among producers (S: 9.3, C: 6.5, N: 3.3). We varied from 1 to 10 the distance producers must be apart to be considered separate. For each of these gap distances, S-separated producers tied on C and N in 40% or more of cases. Comparing the three elements individually, S had fewer tied pairs of producers for any gap distance than C or N. However, S also has higher within-producer variability. Statistical tests on simulated data showed that this higher variability caused S to be less effective than C for analysing differences among mean producer values, yet mixing models showed that S had the smallest confidence intervals around mean estimates of source contributions to consumers. We also examined the spatial and temporal scales over which S isotope signatures of the saltmarsh plant Spartina alterniflora varied. Differences between samples taken within tens of metres were smallest, but between samples hundreds of metres apart were as different as samples thousands of kilometres apart. The time between samples being taken did not influence S signatures. Overall, the use of S is recommended because it has a high probability of distinguishing the contribution of different producers to aquatic food webs. When two elements are employed, the combination of S and C separates more producers than any other combination.     

Micron-scale plasma membrane curvature is recognized by the septin cytoskeleton

Cells change shape in response to diverse environmental and developmental conditions, creating topologies with micron-scale features. Although individual proteins can sense nanometer-scale membrane curvature, it is unclear if a cell could also use nanometer-scale components to sense micron-scale contours, such as the cytokinetic furrow and base of neuronal branches. Septins are filament-forming proteins that serve as signaling platforms and are frequently associated with areas of the plasma membrane where there is micron-scale curvature, including the cytokinetic furrow and the base of cell protrusions. We report here that fungal and human septins are able to distinguish between different degrees of micron-scale curvature in cells. By preparing supported lipid bilayers on beads of different curvature, we reconstitute and measure the intrinsic septin curvature preference. We conclude that micron-scale curvature recognition is a fundamental property of the septin cytoskeleton that provides the cell with a mechanism to know its local shape.     

Diastereoselectivity in scalemic tartrate/titanium epoxidations

Nonlinearity in the diastereoselectivity of epoxidation of allylic alcohols with mixtures of titanium isopropoxide, tertbutyl hydroperoxide, and diethyl tartrate was observed. Racemic and enantiomerically pure alcohols E-2-methyl-4-hexen-3-ol and E-1-methoxy-5-(O-tertbutyldimethylsilyloxy)-2-penten-4-ol were prepared. Epoxidation reactions were carried out with Ti(OPri)4 and ButOOH accompanied by diethyl tartrate of varying enantiomeric purity. The simplest explanation of these results is that a dimeric epoxidation reagent is involved, with significantly different reactivity for the homochiral and racemic forms.     

A distinct pathway remodels mitochondrial cristae and mobilizes cytochrome c during apoptosis.

The mechanism during apoptosis by which cytochrome c is rapidly and completely released in the absence of mitochondrial swelling is uncertain. Here, we show that two distinct pathways are involved. One mediates release of cytochrome c across the outer mitochondrial membrane, and another, characterized in this study, is responsible for the redistribution of cytochrome c stored in intramitochondrial cristae. We have found that the "BH3-only" molecule tBID induces a striking remodeling of mitochondrial structure with mobilization of the cytochrome c stores (approximately 85%) in cristae. This reorganization does not require tBID's BH3 domain and is independent of BAK, but is inhibited by CsA. During this process, individual cristae become fused and the junctions between the cristae and the intermembrane space are opened.     

The glycine max xylem sap and apoplast proteome

Molecular signaling interactions in the plant apoplast are important for defense and developmental responses. We examined the soybean proteome of the apoplastic conduit of root-to-shoot communication, the xylem stream, using gel electrophoresis combined with two types of tandem mass spectrometry. We examined soybeans for the presence of a Bradyrhizobium japonicum-induced, long distance developmental signal that controls autoregulation of nodulation (AON) to determine if xylem proteins (XPs) were involved directly or indirectly in AON. The xylem and apoplast fluids collected in hypocotyl, epicotyl, and stem tissue contained a highly similar set of secreted proteins. The XPs were different from those secreted from imbibing seed implying they play important basic roles in xylem function. The XPs of wild-type and nts1007 plants were indistinguishable irrespective of plant age, inoculation status, or time after inoculation suggesting that none was directly involved in AON. XPs were continuously loaded into the xylem stream, as they were present even 28 h after shoot decapitation. These results were consistent with semiquantitative RT-PCR studies that examined the expression of genes corresponding to the XPs under inoculated or uninoculated conditions. Monitoring the expression of XP genes by RT-PCR showed that four possessed root biased expression. This suggested that the corresponding protein products could be produced in roots and travel long distances to shoots. Of these, a species of lipid transfer protein is a candidate for a water-soluble, long-distance signal-carrier due to the presence of hydrophobic clefts that bind known plant signals in vitro. Two soybean XPs identified in this study, lipid transfer protein and Kunitz trypsin inhibitor (KTI), have known roles in plant signaling.