Polyamine depletion increases cellular ribonucleotide levels

Summary Depletion of the putrescine and spermidine content of Ehrlich ascites tumor cells by -difluoromethylornithine (DFMO) treatment results in at least a 1500-fold increase in the decarboxylated S-adenosylmethionine (deSAM) content. The accumulation of this adenine nucleoside occurs because of the absence of putrescine and spermidine to act as aminopropyl group acceptors in the spermidine and spermine synthase reactions and because of an increase in S-adenosylmethionine decarboxylase activity. The fact that the synthesis of deSAM continues in DFMO-treated cells makes the pathway an adenine trap. This prompted a study of the adenine nucleotide pools. High-performance liquid chromatographic analysis showed that the total adenine nucleotide pool increased, rather than decreased, as a result of DFMO treatment; the major contributors to the increase being ATP and ADP, which increased 2.6 and 1.9 times, respectively. The cellular content of other ribonucleotides increased as well, particularly that of UTP and CTP. When putrescine was added together with DFMO, the increases in cellular ribonucleotide contents were prevented, showing that they were indeed caused by polyamine depletion.     

Species- and age-dependent sensitivity to ozone in young plants of pea,wheat and spinach: Effects on acyl lipid and pigment content and metabolism

Acyl lipids and pigments were analyzed in young plants of garden pea, spring wheat and spinach exposed to < 5 or 65 nl l^?1 ozone 12 h per day for 6 days. In one set of experiments, the plants were exposed to ¹⁴CO₂ for 2 h 3 days prior to ozone exposure. The plants responded differently to the moderately enhanced level of ozone used Spinach was not at all sensitive while in both pea and wheat, leaves of different ages differed in ozone sensitivity. In pea, ozone sensitivity increased with leaf age. In the second and third oldest leaves, the amounts of galactolipids per leaf area and the proportions of 18:3 of the total lipid extract and of phosphatidylglycerol decreased. In the second oldest leaf, ozone also caused a decreased proportion of 18:3 of monogalactosyldiacylglycerol. In the fourth oldest leaf, lipid composition and galactolipid unsaturation was unaffected, but ozone caused decreased leaf expansion resulting in increased acyl lipid content per leaf area. In both the first and second leaves of wheat, ozone fumigation caused a marked decrease in the content of monogalactosyldiacylglycerol and in the first leaf, the contents of phosphatidylcholine and phosphatidylethanolamine increased. The proportion of 18:3 in phosphatidylcholine was larger in ozone-fumigated than in control plants, while the reverse applied for phosphatidylglycerol. In the oldest sampled leaves of pea and wheat, ozone caused an increase in the radioactivity associated with β-carotene, indicating increased turnover. Thus, while spinach was unaffected, in both pea and wheat ozone caused a decrease in the proportion of chloroplast membrane lipids to non-chloroplast membrane lipids in older leaves while younger leaves were less sensitive.     

Effects of the mixotrophic flagellate Ochromonas sp. on colony formation in Microcystis aeruginosa

The aim of this study was to investigate the interactions between the cyanobacteria (Microcystis aeruginosa) and the potential grazer (Ochromonas sp.) with regard to colony formation. Two kinds of treatments were carried out: (i) In the dialyse experiment Microcystis aeruginosa and Ochromonas sp. were physically separated by a dialyse tubing. (ii) In the contact experiment interactions between Microcystis aeruginosa, heterotrophic bacteria and Ochromonas sp. in different concentrations were investigated. In one treatment where the predator Ochromonas sp. came in direct contact with Microcystis, aggregates were formed.In the contact experiment, there were some interactions between the predator Ochromonas sp. and the two groups of prey, Microcystis aeruginosa and heterotrophic bacteria. When exposed to a low initial Ochromonas sp. concentration, Microcystis aeruginosa decreased and then remained stable in concentration. Ochromonas sp. switched to feed on heterotrophic bacteria and increased. At a high initial Ochromonas sp. concentration Microcystis was grazed down.     

Response of foundation macrophytes to near‐natural simulated marine heatwaves

Marine heatwaves have been observed worldwide and are expected to increase in both frequency and intensity due to climate change. Such events may cause ecosystem reconfigurations arising from species range contraction or redistribution, with ecological, economic and social implications. Macrophytes such as the brown seaweed Fucus vesiculosus and the seagrass Zostera marina are foundation species in many coastal ecosystems of the temperate northern hemisphere. Hence, their response to extreme events can potentially determine the fate of associated ecosystems. Macrophyte functioning is intimately linked to the maintenance of photosynthesis, growth and reproduction, and resistance against pathogens, epibionts and grazers. We investigated morphological, physiological, pathological and chemical defence responses of western Baltic Sea F. vesiculosus and Z. marina populations to simulated near‐natural marine heatwaves. Along with (a) the control, which constituted no heatwave but natural stochastic temperature variability (0HW), two treatments were applied: (b) two late‐spring heatwaves (June, July) followed by a summer heatwave (August; 3HW) and (c) a summer heatwave only (1HW). The 3HW treatment was applied to test whether preconditioning events can modulate the potential sensitivity to the summer heatwave. Despite the variety of responses measured in both species, only Z. marina growth was impaired by the accumulative heat stress imposed by the 3HW treatment. Photosynthetic rate, however, remained high after the last heatwave indicating potential for recovery. Only epibacterial abundance was significantly affected in F. vesiculosus. Hence both macrophytes, and in particular F. vesiculosus, seem to be fairly tolerant to short‐term marine heatwaves at least at the intensities applied in this experiment (up to 5°C above mean temperature over a period of 9 days). This may partly be due to the fact that F. vesiculosus grows in a highly variable environment, and may have a high phenotypic plasticity.     

Untersuchungen über Umdeterminierung von Fragmenten des Seeigeleies durch chemische Agentien

Ohne Zusammenfassung     

Investigating alginate production and carbon utilization in Pseudomonas fluorescens SBW25 using mass spectrometry-based metabolic profiling

Metabolic profiling of Pseudomonas fluorescens SBW25 and various mutants derived thereof was performed to explore how the bacterium adapt to changes in carbon source and upon induction of alginate synthesis. The experiments were performed at steady-state conditions in nitrogen-limited chemostats using either fructose or glycerol as carbon source. Carbon source consumption was up-regulated in the alginate producing mutant with inactivated anti-sigma factor MucA. The mucA- mutants (also non-alginate producing mucA- control strains) had a higher dry weight yield on carbon source implying a change in carbon and energy metabolism due to the inactivation of the anti-sigma factor MucA. Both LC–MS/MS and GC–MS methods were used for quantitative metabolic profiling, and major reorganization of primary metabolite pools in both an alginate producing and a carbon source dependent manner was observed. Generally, larger changes were observed among the phosphorylated glycolytic metabolites, the pentose phosphate pathway metabolites and the nucleotide pool than among amino acids and citric acid cycle compounds. The most significant observation at the metabolite level was the significantly reduced energy charge of the mucA- mutants (both alginate producing and non-producing control strains) compared to the wild type strain. This reduction was caused more by a strong increase in the AMP pool than changes in the ATP and ADP pools. The alginate-producing mucA- mutant had a slightly increased GTP pool, while the GDP and GMP pools were strongly increased compared to non-producing mucA- strains and to the wild type. Thus, whilst changes in the adenosine phosphate nucleotide pool are attributed to the mucA inactivation, adjustments in the guanosine phosphate nucleotide pool are consequences of the GTP-dependent alginate production induced by the mucA inactivation. This metabolic profiling study provides new insight into carbon and energy metabolism of the alginate producer P. fluorescens.     

Establishment and Early Growth of Willow at Different Levels of Weed Competition and Nitrogen Fertilization

To evaluate the effects of weed competition and nitrogen fertilization on the early growth performance of willow, cuttings of the clone Tora (Salix schwerinii x S. viminalis) were planted in buckets together with model weeds (spring barley or white mustard) sown 15, 26, and 30 days after willow planting. The buckets were fertilized with 30 or 90 kg N ha^?1. Willow with weeds sown after 15 days produced less biomass and smaller leaf area and had a lower maximum shoot height compared to willow planted without weeds and willow with weeds sown after 26 or 30 days. Fertilization with 90 kg N ha^?1 gave higher willow biomass production in willow with weeds sown after 26 or 30 days. Type of model weed had no effect on willow performance. Weed biomass and maximum shoot height were higher in weeds planted without willows compared to the willow-weed mixtures. A high nitrogen level gave more weed biomass when planted without willows and in the willow-weed mixture with weeds sown after 15 days. We conclude that for the given high density of willow, competition from weeds emerging soon after willow planting had strong effect on early production. Furthermore, if there is a risk of weed infestation, fertilization should be delayed.     

DNA content as a prognostic marker of oral lichen planus with a risk of cancer development

OBJECTIVE: To assess the presence of aneuploidy in oral lichen planus (OLP) and its usefulness as a prognostic marker. STUDY DESIGN: Eighty-one formalin-fixed, paraffin-embedded biopsy samples taken from atrophic-erosive OLP from 70 patients were studied. Approximately 150 random nuclei in basal and/or parabasal epithelia were analyzed with static cytometry. RESULTS: Aneuploidy was detected in 41% of samples. OLPs with ulcerations or location in the tongue had significantly higher values, respectively, for the 2.5c exceeding rate (ER) (p<0.001 and 0.001) and proliferation index (PI) (p = 0.012 and 0.013) than did lesions without ulcerations or at other locations. 2.5c ER was significantly higher in dysplastic OLP lesions (p < 0.001), and the significant value (p = 0.001)for 2.5c ER discriminating DNA aneuploidy was 15.3%. In multivariate analysis only the G2/M ER (G2/MER) was a significant independent predictor of developing cancer in OLP (OR 2.349, 95% CI 1.39-3.97, p = 0.001). CONCLUSION: Ulcerated atrophic-erosive OLPs of the tongue and with dysplasia are at increased risk of cancer development. 2.5c ER, PI and G2/MER might be useful in prognosticating the increased risk of malignancy in OLP.     

Proteasomal activity modulates TGF-ss signaling in a gene-specific manner

Myosin heavy chain kinase A (MHCK A) modulates myosin II filament assembly in the amoeba Dictyostelium discoideum. MHCK A localization in vivo is dynamically regulated during chemotaxis, phagocytosis, and other polarized cell motility events, with preferential recruitment into anterior filamentous actin (F-actin)-rich structures. The current work reveals that an amino-terminal segment of MHCK A, previously identified as forming a coiled-coil, mediates anterior localization. MHCK A co-sediments with F-actin, and deletion of the amino-terminal domain eliminated actin binding. These results indicate that the anterior localization of MHCK A is mediated via direct binding to F-actin, and reveal the presence of an actin-binding function not previously detected by primary sequence evaluation of the coiled-coil domain.     

Effects of Cutting Length,Orientation and Planting Depth on Early Willow Shoot Establishment

To assess the effects of different planting systems on early performance (survival, shoot emergence time, number of shoots, maximum shoot height and biomass shoot production) of willow, cuttings of varying lengths were planted horizontally at different depths and compared with vertically planted cuttings. Cutting lengths of (i) 25–200 cm and (ii) 7–21 cm were studied in a field experiment and in a box experiment, respectively. Shorter cuttings planted deeper had a lower survival rate and emerged a few days later compared to longer cuttings planted shallower. The performance was considerably higher at the apical part of the cuttings, regardless of cutting length. Longer cuttings planted shallow had a higher performance. Vertically planted cuttings produced more biomass and shoots per length unit than horizontally planted cuttings. We conclude that planting systems based on the use of longer horizontally planted cuttings would probably lead to an uneven establishment and gaps in the stand caused by apical dominance. Also, to achieve the same performance, the need of planting material would be considerably higher compared to systems with vertically planted cuttings. To obtain a fast and more even early establishment of willows, we recommend the use of vertically planted cuttings with a length of at least 20 cm. If cuttings are planted horizontally, they should not be planted deeper than 5 cm.