Local enrichment with homopolymeric (dA/dT) DNA in genomes of some lower dipterans and Drosophila melanogaster

An investigation into the chromosomal localization of homopolymeric dA/dT was carried out with species of the genera Rhynchosciara, Chironomus, Drosophila and several other taxa. In situ hybridisation probing mitotic and polytene chromosomes with RNA homopolymers was performed, followed by immunological detection of the DNA/RNA hybrid. Use of this method allowed us to assess specific regions of some dipteran genomes, where the signal was generally, but not always, located in heterochromatic regions. Human and Drosophila chromosome regions known to contain dA/dT runs of up to 153 bp were devoid of consistent labelling. The stability of the rA/dT hybrid formed in situ was in agreement with the T(m) for long rA/dT hybrid complexes, suggesting that the method used in this work is able to identify unusually long homopolymeric dA/dT tracts.     

The chromosomes of Rhynchosciara baschanti (Diptera: Sciaridae): molecular cytogenetic comparisons with taxa in the americana-like group.

Polytene chromosome analysis is presented for Rhynchosciara baschanti, a species belonging to the americana-like group of Rhynchosciara. R. baschanti chromosomes show morphological differences in centromeric and telomeric regions compared to two other members within the group, R. americana and R. hollaenderi. In addition, fixed band and autosomal inversion differences were noted. Physical mapping data showed synteny among the taxa under study for DNA puffs and single-copy or histone gene probes, whereas rDNA and poly-(r)A probes showed different diagnostic patterns. The activity of developmentally active genes and the pattern of thymidine incorporation into DNA puff sites of R. baschanti are consistent with those found in the two previously studied species, except for lower levels of expression at some of these sites. These results suggest that differential duplication of specific DNA sequences, in particular repetitive and homopolymeric DNA, has played a role in the chromosomal evolution of these Rhynchosciara species. Inversions and band dimorphisms have also occurred, but the processes leading to their maintenance and fixation appear to have been slow, since these three species are in general chromosomally monomorphic.     

Gustatory stimulation of a homeotic mutant appendage,Antennapedia, inDrosophila melanogaster

Summary The proboscis extension response was used to prove the leg identity of chemosensory neurons in the homeotic appendage of theDrosophila mutantAntennapedia (Antp ^73b). The data suggest that the homeotic appendage, which is morphologically characterized as a mesothoracic leg, corresponds to a mesothoracic leg as well when considering its gustatory responsiveness (Figs. 1A, B; 3A, B). The neuronal pathway which might mediate the reflex between homeotic chemoreceptors and motor neurons responsible for the proboscis extension is discussed.     

Synergistic interaction between vitamin E and the bile pigments bilirubin and biliverdin

The oxidation of soybean phosphatidylcholine (PC) liposomes initiated with a lipid-soluble azo compound within the liposomal membranes has been studied in the absence and presence of membrane-bound vitamin E and water-soluble bile pigments. In the absence of vitamin E, lipid peroxidation proceeded linearly and without delay. Low micromolar amounts of bilirubin ditaurine (BR-DT, a model compound of conjugated bilirubin) or biliverdin (BV) inhibited the oxidation of PC significantly and in a concentration-dependent way. In contrast, neither taurine, ascorbic acid nor reduced glutathione inhibited significantly under these conditions. Both bile pigments were consumed during their protective action. Vitamin E incorporated into the liposomal membranes suppressed the oxidation initially almost completely, thereby producing an induction period. In the combined presence of vitamin E and either of the two bile pigments at 10 microM each, this induction period was increased by at least 200%. In contrast, when 10 microM vitamin E was combined with an equimolar concentration of reduced glutathione, the induction period increased by only about 30%. BR-DT and BV both spared the consumption of vitamin E during the oxidation of PC liposomes. These results demonstrate that conjugated bilirubin and BV located in the aqueous phase can directly scavenge lipid radicals to some extent. Furthermore, both bile pigments can act synergistically with membrane-bound vitamin E to prevent lipid peroxidation initiated in the lipid phase, most likely through regeneration of the vitamin from its chromanoxyl radical.     

Plasmatische Untersuchungen an dürreempfindlichen und dürreresistenten Sorten landwirtschaftlicher Kulturpflanzen

Ohne ZusammenfassungMit 3 Textabbildungen.Zweite Mitteilung der Untersuchungen über die physiologischen Grundlagen der Dürreresistenz des Botanischen Instituts der Technischen Hochschule Darmstadt. Dem Deutschen Forschungsrat und der Deutschen Forschungsgemeinschaft danken wir für die Bereitstellung von Mitteln und die Gewährung eines Stipendiums. 1. Mitteilung:H. Schmidt: Plasmazustand und Wasserhaushalt beiLamium maculatum. Protoplasma33, 25 (1939).     

Separation and Characterization of Cholesteryl Oxo- and Hydroxy-Linoleate Isolated from Human Atherosclerotic Plaque

In previous work we demonstrated that up to 30 % of cholesteryl linoleate in homogenates of advanced human plaque samples is present in oxidized forms. Here we show that the material from plaque hexane extracts which co-elutes with cholesteryl hydroxylinoleate on reversed phase HPLC (Anal Biochem 1993;213:79), is composed of several isomers of cholesteryl hydroxy- and cholesteryl oxo-octadecadienoate. Enzymatic hydrolysis and measurement of liberated cholesterol and disappearance of the esters revealed that almost all of the material consisted of unoxidized cholesterol esterified to oxidized derivatives of octadeca-dienoate. Semi-preparative reversed-phase HPLC was used to obtain sufficient quantities of this co-eluting material to undertake normal phase HPLC separation of these components. The nature of such separated and isolated compounds was identified, by co-chromatography with authentic standards, UV spectroscopy and chemical ionization and electron impact mass spectrometry, as cholesteryl hydroxy- and cholesteryl oxo-octadecadienoate. These oxidized fatty acids have been observed previously in plaque, in agreement with our new unambiguous demonstration of their presence as cholesteryl esters. The application of the methods described for the separation of the various forms of oxidized cholesteryl octadecadienoate may aid mechanistic studies of in vitro and in vivo lipoprotein lipid oxidation.     

A field study of the effects of elevated CO2 and plant species diversity on ecosystem-level gas exchange in a planted calcareous grassland

The relationship between plant species diversity and ecosystem CO₂ and water vapour fluxes was investigated for planted calcareous grassland communities composed of 5, 12, or 32 species assembled from the native plant species pool. These diversity manipulations were done in factorial combination with a CO₂ enrichment experiment in order to investigate the degree to which ecosystem responses to elevated CO₂ are altered by a loss of plant diversity. Ecosystem CO₂ and H₂O fluxes were measured over several 24-h periods during the 1994 and 1995 growing seasons. Ecosystem CO₂ assimilation on a ground area basis decreased with decreasing plant diversity in the first year and this was related to a decline in above-ground plant biomass. In the second year, however, CO₂ assimilation was not affected by diversity, and this corresponded to the disappearance of a diversity effect on above-ground biomass. Irrespective of diversity treatment, CO₂ assimilation on a ground area basis was linearly related to peak above-ground biomass in both years. Elevated CO₂ significantly increased ecosystem CO₂ assimilation in both years with no interaction between diversity and CO₂ treatment, and no corresponding increase in above-ground biomass. There were no significant effects of diversity on water vapour flux, which was measured only in the second year. There were indications of a small CO₂ effect on water vapour flux (3–9% lower at elevated CO₂ depending on the light level). Our findings suggest that decreasing plant species diversity may substantially decrease ecosystem CO₂ assimilation during the establishment of such planted calcareous grassland communities, but also suggest that this effect may not persist. In addition, we find no evidence that plant species diversity alters the response of ecosystem CO₂ assimilation to elevated CO₂.     

Effect of vitamin E on aortic lipid oxidation and intimal proliferation after arterial injury in cholesterol-fed rabbits.

Oxidized low-density lipoproteins (LDL) are implicated in atherosclerosis. However, large-scale intervention studies designed to test whether antioxidants, such as vitamin E, can ameliorate cardiovascular disease have generated ambivalent results. This may relate to the fact that the mechanism whereby lipid oxidation is initiated in vivo is unknown and the lack of direct evidence for a deficiency of antioxidants in atherosclerotic lesions. Further, there is little evidence to suggest that vitamin E acts as an antioxidant for lipid peroxidation in vivo. Here we tested the antioxidant effect of dietary vitamin E (alpha-tocopherol) supplementation on intimal proliferation and lipid oxidation in balloon-injured, hypercholesterolemic rabbits. alpha-Tocopherol supplementation increased vascular content of alpha-tocopherol over 30-fold compared to nonsupplemented and alpha-tocopherol-deficient chows. Balloon injury resulted in oxidized lipid deposition in the aorta. Maximum levels of primary lipid oxidation products, measured as hydroperoxides of esterified lipid (LOOH) and oxidized linoleate (HODE), were 0.22 and 1.10 nmol/mg, representing 0.21 and 0.39% of the precursor molecule, respectively. Secondary lipid oxidation products, measured as oxysterols, were maximal at 5.60 nmol/mg or 1.48% of the precursor compound. Vascular HODE and oxysterols were significantly reduced by vitamin E supplementation. However, the intima/media ratio of aortic vessels increased with vitamin E supplementation, suggesting that the antioxidant promoted intimal proliferation. Thus, the study demonstrates a dissociation of aortic lipid oxidation and lesion development, and suggests that vitamin E does not prevent lesion development in this animal model.