Identification and Phytotoxicity of 3-methylthiopropanoic and Trans-3-methylthiopropenoic Acids Produced in Culture by Xanthomonas campestris pv. vitians

Two phytotoxic metabolites were isolated from culture filtrates of Xanthomonas campestris pv, vitians , the causal agent of lettuce leaf spots and headrot. The two compounds were identified as 3-methylthiopropanoic (1) and trans-3-methylthiopropenoic (2) acids by chemical and spectroscopic methods. Toxic effects of the two compounds on leaf tissues and protoplasts of lettuce and cabbage were investigated. Solutions of 1 and 2 induced chlorosis and necrosis on lettuce leaves at minimum concentrations of 300 and 50 μg/ml, respectively. Infiltration in cabbage leaves did not produce any symptoms. The LD₅₀ values for 1 and 2 against lettuce protoplasts were 15 and 16 μg/ml, respectively. Activity of the two metabolites against cabbage protoplasts was very low (LD₅₀ > 500 μg/ml).     

Ribosomal DNA variation in the grasshopper, Dichroplus elongatus.

We report an RFLP analysis of ribosomal DNA variation in natural populations of the grasshopper, Dichroplus elongatus, previously analyzed for mitochondrial DNA variation. DNA samples were digested with five restriction enzymes, BamHI, EcoRI, HindIII, PstI, and XbaI. BamHI was the only enzyme that showed no variation. The remaining enzymes showed fragment size variation at both intra- and interpopulation levels. Stepwise regression analysis revealed that the average number of length variants per individual is significantly associated with altitude. Moreover, the same analysis indicated that the frequency of some restriction variants exhibits a significant regression on both geographic and climatic variables. The intra- and interpopulation variability of rDNA was analysed by Lynch's and Hedrick's similarity indices using presence or absence of a fragment and band intensities, respectively. The corresponding neighbour-joining (N-J) trees based on Lynch's and Hedrick's genetic distances resulted in similar topologies. However, these trees were not in agreement with the N-J dendrogram obtained from mtDNA data previously reported by Clemente et al. (2000). The disagreement between mtDNA and rDNA phenograms along with the observed correlation between rDNA variability and geographical and climatic variables suggest some form of selection, besides genetic drift and migration, is involved in the pattern of rDNA variation.     

Siderophore synthesis in Klebsiella pneumoniae and Shigella sonnei during iron deficiency.

Klebsiella pneumoniae 298/53 and Shigella sonnei 43-GG9 exhibited restricted growth and enterochelin synthesis only under iron-deficient conditions. S. sonnei also produced an unidentified secondary hydroxamate siderophore.     

Natural-killer-stimulatory effect of combined low-dose interleukin-2 and interferon β in hairy-cell leukemia patients

The association of low doses of interleukin-2 (IL-2; 5 IU/ml) and interferon (IFN; 10 IU/ml) induced an additive or synergic stimulatory effect on natural killer (NK) activity (32%) in peripheral blood samples from hairy-cell leukemia patients, both those with active disease and those in remission. The synergic NK stimulatory effect was more commonly found in samples from patients with active disease, while the additive effect was more frequent in the patients in remission. The IL-2/IFN combination provoked a nonadditive nonsynergic NK-stimulatory effect in a further 19.8% samples. The targets of the IL-2/IFN combination were typical NK cells, as shown by the fact that there was increased cytotoxicity (synergic, additive or nonadditive nonsynergic) against the K562, but not the Daudi cell line in peripheral blood mononuclear cell samples treated with the combination of the two cytokines. When CD16⁺/CD56⁺ or CD57⁺/CD16⁺/CD56⁺ cells were removed, the NK-stimulatory effect was lost. The fact that the NK-cell-enhancing activity of the IL-2/IFN combination was reduced when Percoll fractions 2 and 3 were used, but still persisted in 66% of tests, may have been due to cytotoxicity being higher in the untreated fractions 2 and 3 than in the untreated unfractionated samples. One of the factors responsible for the NK-stimulatory effect appears to be the capacity of the IL-2/IFN combination to trigger an increase in IFN synthesis. If similar experiments give like results in samples from patients suffering from other B-cell lymphoproliferative, or HIV-associated disorders, all of which are characterized by a deficiency in NK activity, it should be possible to use low-dose IL-2/IFN to treat these disorders and, perhaps, residual neoplastic disease without exposing the patient to undue toxicity. Further, by testing other combinations one should be able to identify the lowest IL-2 and IFN doses that would effectively boost the additive or synergic effect in a greater number of cases.     

Scale-up of virus-like particles production: effects of sparging, agitation and bioreactor scale on cell growth, infection kinetics and productivity

The baculovirus-insect cells expression system was used for the production of self-forming Porcine parvovirus (PPV) like particles (virus-like particles, VLPs) in serum-free medium. At 2l bioreactor scale an efficient production was achieved by infecting the culture at a concentration of 1.5 x 10(6)cells/ml using a low multiplicity of infection of 0.05 pfu per cell. In a continuous bioreactor, it was shown that the uninfected insect cells were not sensitive to local shear stress values up to 2.25 N/m2 at high Reynolds numbers (1.5 x 10(4)) in sparging conditions. Uninfected insect cells can be grown at scaled-up bioreactor at high agitation and sparging rates as long as vortex formation is avoided and bubble entrapment is minimized. An efficient process scale-up to 25 l bioreactor was made using constant shear stress criteria for scale-up. The kinetics of baculovirus infection at low multiplicity of infection, either at different cell concentration or at different scales, are very reproducible, despite the different turbulence conditions present in the bioreactor milieu. The results suggest that the infection kinetics is controlled by the rate of baculovirus-cell receptor attachment and is independent of the bioreactor hydrodynamic conditions. Furthermore, the achieved specific and volumetric productivities were higher at the 25 l scale when compared to the smaller scale bioreactor. Different rates of cell lysis after infection were observed and seem to fully explain both the shift in optimal harvest time and the increase in cell specific productivity. The results emphasize the importance of integrated strategies and engineering concepts in process development at bioreactor stage with the baculovirus insect cell system.     

A Selective Sweep on a Deleterious Mutation in CPT1A in Arctic Populations

Arctic populations live in an environment characterized by extreme cold and the absence of plant foods for much of the year and are likely to have undergone genetic adaptations to these environmental conditions in the time they have been living there. Genome-wide selection scans based on genotype data from native Siberians have previously highlighted a 3 Mb chromosome 11 region containing 79 protein-coding genes as the strongest candidates for positive selection in Northeast Siberians. However, it was not possible to determine which of the genes might be driving the selection signal. Here, using whole-genome high-coverage sequence data, we identified the most likely causative variant as a nonsynonymous G>A transition (rs80356779; c.1436C>T [p.Pro479Leu] on the reverse strand) in CPT1A, a key regulator of mitochondrial long-chain fatty-acid oxidation. Remarkably, the derived allele is associated with hypoketotic hypoglycemia and high infant mortality yet occurs at high frequency in Canadian and Greenland Inuits and was also found at 68% frequency in our Northeast Siberian sample. We provide evidence of one of the strongest selective sweeps reported in humans; this sweep has driven this variant to high frequency in circum-Arctic populations within the last 6–23 ka despite associated deleterious consequences, possibly as a result of the selective advantage it originally provided to either a high-fat diet or a cold environment.     

Macrocyclic inhibitors of the malarial aspartic proteases plasmepsin I, II, and IV

The first macrocyclic inhibitor of the Plasmodium falciparum aspartic proteases plasmepsin I, II, and IV with considerable selectivity over the human aspartic protease cathepsin D has been identified. A series of macrocyclic compounds were designed and synthesized. Cyclizations were accomplished using ring-closing metathesis with the second generation Grubbs catalyst. These compounds contain either a 13-membered or a 16-membered macrocycle and incorporate a 1,2-dihydroxyethylene as transition state mimicking unit. The binding mode of this new class of compounds was predicted with automated docking and molecular dynamics simulations, with an estimation of the binding affinities through the linear interaction energy (LIE) method.     

Energy Intensities and Carbon Dioxide Emissions in a Social Accounting Matrix Model of the Andalusian Economy

The aim of this article is to calculate energy intensity and carbon dioxide (CO₂) emissions in Andalusia, the largest and most populated region of Spain. Energy intensities for five energy commodities used in production activities are calculated using a social accounting matrix (SAM) model with three alternative scenarios, each utilizing differing closure rules. More interestingly, by using 2005 data and updating the values of exogenous accounts, the article also provides estimates of CO₂ emissions ten years out from the 1995 base year. Finally, counterfactual experiments are performed to quantify the overall reduction in direct energy coefficients that would have made it possible to maintain constant production‐sector emissions from 1995 to 2005. The results indicate that there is a strong interdependence among energy sectors and the most intensive energy users; they also indicate the importance of induced effects when factor accounts and private consumption are endogenous. The estimates obtained concerning CO₂ emissions are close to official estimates, both from 1995 and 2005. The counterfactual experiments indicate that a 26.5% cut in the size of direct energy requirements would have made it possible to maintain constant emissions. They also indicate that efforts to curtail emissions should be focused on improving efficiency in coal extraction and combustion and oil refining.     

Growth, water relations and photosynthesis of seedlings and resprouts after fire

Seasonal patterns of growth, water relations, photosynthesis and leaf characteristics were compared between obligate seeders (Cistus monspeliensis and Cistus ladanifer) and resprouters (Arbutus unedo and Pistacia lentiscus) from the first to the second year after fire. We hypothesized that seedlings would be more water-limited than resprouts due to their shallower root systems. Regarding water use strategies, Cistus species are drought semi-deciduous and A. unedo and P. lentiscus are evergreen sclerophylls, therefore, comparisons were based on the relative deviation from mature conspecific plants. Seedlings and resprouts had higher shoot elongation and leaf production than mature plants, and over an extended period. Differences from mature plants were larger in resprouts, with two-fold transpiration, leaf conductance and photosynthesis in late spring/early summer. Seedlings of C. monspeliensis exhibited higher transpiration and leaf conductance than mature plants, while those of C. ladanifer only exhibited higher water potential. Growth increments and ameliorated water relations and photosynthesis after fire were attributed to an increase in water and nutrient availability. The small differences in water relations and photosynthesis between seedlings and mature conspecifics are in accordance with the prediction of seedlings experiencing higher water limitation than resprouts. We attribute these results to differences in root systems: resprouters benefited from an increase in root/shoot ratios and the presence of deep roots whereas Cistus seedlings relied on very shallow roots, which cannot provide assess to deep water during summer. Nevertheless, seedlings did not show evidence of experiencing a more severe water limitation than mature conspecifics, which we attributed to the presence of efficient mechanisms of avoiding and tolerating water stress. The results are discussed in relation to post-fire demography of seeders and resprouters in Mediterranean communities.