Localization of a putative ClC chloride channel in spinach chloroplasts

Seven genes seem to encode for putative ClC chloride channels (AtClC-a to AtClC-g) in Arabidopsis thaliana. Their function and localization is still largely unknown. AtClC-f shares considerable sequence similarity with putative ClC channel proteins from Synechocystis, considered to represent the precursor of chloroplasts. We show by biochemical and mass spectrometry analysis that ClC-f is located in the outer envelope membrane of spinach chloroplasts. Consistent with the plastidial localization of ClC-f, p-chlorophenoxy-acetic acid (CPA) reduces photosynthetic activity and the protein is expressed in etioplasts and chloroplasts but not in root tissue. These findings may represent a step toward the molecular identification of ion channel activities in chloroplast membranes.     

Alkaline chitosan solutions

Rigid and transparent hydrogels were obtained upon pouring chitosan salt solutions into saturated ammonium hydrogen carbonate. Incubation at 20 degrees C for 5 days yielded chitosan carbamate ammonium salt, Chit-NHCO(2)(-)NH(4)(+) a chemical species that either by hydrolysis or by thermal treatment decomposed to restore chitosan in free amine form. Chitosans of different degrees of acetylation, molecular sizes and origins (squid and crustaceans) were used as hydrochloride, acetate, glycolate, citrate and lactate salts. Their hydrogels obtained in ammonium hydrogen carbonate yielded chitosan solutions at pH values as high as 9.6, from which microspheres of regenerated chitosans were obtained upon spray-drying. These materials had a modest degree of crystallinity depending on the partial acylation that took place at the sprayer temperature (168 degrees C). Citrate could cross-link chitosan and impart insolubility to the microspheres. Chloride on the contrary permitted to prepare microspheres of chitosan in free amine form. By the NH(4)HCO(3) treatment, the cationicity of chitosan could be reversibly masked in view of mixing chitosan with alginate in equimolar ratio without coacervation. The clear and poorly viscous solutions of mixed chitosan carbamate and alginate were spray-dried at 115 degrees C to manufacture chitosan-alginate microspheres having prevailing diameter approx 2 micron.     

Prevalence of coccidia parasites (Protozoa) in red squirrels ( Sciurus vulgaris): effects of host phenotype and environmental factors

We investigated the relative importance of environmental factors versus host phenotype in determining parasite prevalence in Eurasian red squirrels ( Sciurus vulgaris). One hundred and forty-three fecal samples of 116 different squirrels collected in 2000 and 2001 from five study areas in the Italian Alps, were examined for intestinal protozoans. Two species of Eimeria were present with a medium to high prevalence in both years and in all areas, while two other species were rare, occurring only in some areas and not in all years. Cryptosporidium parvum had a high prevalence in the two study areas of the Western Alps, while in the three areas of the Central Alps it was recorded only once. The prevalence of Eimeria sciurorum and C. parvum fluctuated in parallel with squirrel density, suggesting a possible correlation between the presence of these protozoans and host density. A gender effect on E. sciurorum prevalence at low density could be explained by different space use patterns and social organization of males and females. C. parvum occurred more frequently in young squirrels, suggesting an acquired immunity in adults, but age-related susceptibility was not found for eimerian species. The coccidian community was more similar within than between regions, and study area and year were key parameters in predicting coccidia infection. There was no evidence of competition between coccidian species, but one positive interaction between E. sciurorum and E. andrewsi was observed. Our results suggest that the effects of geographic region, area features, and year effects probably related to fluctuations in host population density, were more important than individual phenotypic host characteristics in structuring the coccidian assemblage and determining levels of parasite prevalence in red squirrel populations.     

Simulation of MscL gating in a bilayer under stress

The initial stages of the gating of the mechanoselective channel of large conductance from Mycobacterium tuberculosis have been studied in atomic detail using molecular dynamics simulation techniques. A truncated form of the protein complex embedded in a palmitoyloleoylphosphatidylcholine lipid bilayer and surrounded by explicit water was simulated under different pressure conditions to mimic the effects of tension and compression within the membrane on the protein. As a direct result of lateral tension being applied to the membrane, an increase in the tilt of a subset of the transmembrane helices was observed. This in turn led to the enlargement of the pore and the disruption of the hydrophobic gate consisting of residues Ile-14 and Val-21. The simulations suggest that opening occurs in a sequential staged process. Such a mechanism could explain the partial opening or staged conductance observed in patch-clamp experiments using related large conductance mechanosensitive channel complexes.     

Asymmetric synthesis with immobilized yeast in organic solvents: equilibrium conversion and effect of reactant partitioning on whole cell biocatalysis

A newly isolated strain of the yeast Saccharomyces cerevisiae is investigated for the biocatalytic reduction of ketones and the oxidation of alcohols in organic solvents. The yeast cells are immobilized by entrapment within calcium alginate beads and are found to possess the ability to stereoselectively reduce prochiral ketones and oxidize chiral alcohols to equilibrium conversions. The effect of reactant partitioning on the initial rate of the reactions is also investigated. The observed initial rates are found to vary inversely with reactant partitioning between the organic solvent and the biocatalyst beads. A kinetic model is developed to describe the initial reaction rate of hexanone reduction as a function of substrate concentration within the alginate beads.     

The relationship between congenital heart disease and cancer in Swedish children: A population-based cohort study

BackgroundBirth defects have been consistently associated with elevated childhood cancer risks; however, the relationship between congenital heart disease (CHD) and childhood cancer remains conflicting. Considering the increasing patient population with CHD after improvements in their life expectancies, insights into this relationship are particularly compelling. Thus, we aimed to determine the relationship between CHD and cancer in Swedish children.Methods and findingsAll individuals registered in the Swedish Medical Birth Register (MBR) between 1973 and 2014 were included in this population–based cohort study (n = 4,178,722). Individuals with CHD (n = 66,892) were identified from the MBR and National Patient Register, whereas cancer diagnoses were retrieved from the Swedish Cancer Register. The relationship between CHD and childhood cancer (<20 years at diagnosis) was evaluated using Cox proportional hazards regression models. We observed increased risks of cancer overall, leukemia, lymphoma, and hepatoblastoma in children with CHD, but after adjustment for Down syndrome, only the increased lymphoma (hazard ratio (HR) = 1.64, 95% confidence interval (CI) 1.11 to 2.44) and hepatoblastoma (HR = 3.94, 95% CI 1.83 to 8.47) risk remained. However, when restricting to CHD diagnoses from the MBR only, i.e., those diagnosed around birth, the risk for childhood cancer overall (HR = 1.45, 95% CI 1.23 to 1.71) and leukemia (HR = 1.41, 95% CI 1.08 to 1.84) was more pronounced, even after controlling for Down syndrome. Finally, a substantially elevated lymphoma risk (HR = 8.13, 95% CI 4.06 to 16.30) was observed in children with complex CHD. Limitations of the study include the National Patient Register not being nationwide until 1987, in addition to the rareness of the conditions under study providing limited power for analyses on the rarer cancer subtypes.ConclusionsWe found associations between CHD and childhood lymphomas and hepatoblastomas not explained by a diagnosis of Down syndrome. Stronger associations were observed in complex CHD.

Christina-Evmorfia Kampitsi and colleagues investigate the relationship between congenital heart disease and cancer in Swedish children.     

Localization of the gene-richest and the gene-poorest isochores in the interphase nuclei of mammals and birds

At a resolution of 850 bands, human chromosomes comprise two subsets of bands, the GC-richest H3⁺ and the GC-poorest L1⁺ bands, accounting for about 17 and 26%, respectively, of all bands. The former are a subset of the R bands and the latter are a subset of the G bands. These bands showed the highest and the lowest gene densities, respectively, as well as a number of other distinct features. Here we report that human and chicken interphase nuclei are characterized by the following features. (1) The gene-richest/GC-richest chromosomal regions are predominantly distributed in internal locations, whereas the gene-poorest/GC-poorest DNA regions are close to the nuclear envelope. (2) The interphase chromosomes seem to be characterized by a polar arrangement, because the gene-richest/GC-richest bands and the gene-poorest/GC-poorest bands are predominantly located in the distal and proximal regions, respectively, of chromosomes, and because interphase chromosomes are extremely long. While this polar arrangement is evident in the larger chromosomes, it is not displayed by the chicken microchromosomes and by some small human chromosomes, namely by chromosomes that are almost only composed by GC-rich or by GC-poor DNA. (3) The gene-richest chromosomal regions display a much more spread-out conformation compared to the gene-poorest regions in human nuclei. This finding has interesting implications for the formation of GC-rich isochores of warm-blooded vertebrates.     

Alcuni Aspetti Citologici Dell'Endosperma di Phaseolus Coccineus L.

Abstract

Some cytological aspects of Phaseolus coccineus L. endosperm. — Cytological observations were made on the endosperm of Phaseolus coccineus, in a limited stage of development of the seed, using different dyes and labelling with ³H-thymidine and ³H-uridine. The results seem to indicate that, contrary to suspensor cells, in the endosperm of Phaseolus, at least in the considered stage, extra DNA synthesis is not present. Chromosomes in these nuclei, however, undergo several endoreduplication cycles. Nucleoli may be either one or more in a cell, and show a characteristic structure. They are often eccentric in the nucleus and extrusions of nucleolar content in the nucleoplasm or cytoplasm are seen. An apparent alternate activity of RNA synthesis in the nucleoli of the suspensor and in those of endosperm cells is discussed.     

The major shifts of human duplicated genes

Since many gene duplications in the human genome are ancient duplications going back to the origin of vertebrates, the question may be asked about the fate of such duplicated genes at the compositional genome transitions that occurred between cold- and warm-blooded vertebrates. Indeed, at that transition, about half of the (GC-poor) genes of cold-blooded vertebrates (the genes of the gene-dense "ancestral genome core") underwent a GC enrichment to become the genes of the "genome core" of warm-blooded vertebrates. Since the compositional distribution of the human duplicated genes investigated (1111 pairs) mimics the general distribution of human genes (about 50% GC(3)-poor and 50% GC(3)-rich genes, the border being at 60% GC(3)), we considered two possibilities, namely that the compositional transition affected either (i) about half of the copies on a random basis, or (ii) preferentially only one copy of the duplicated genes. The two possibilities could be distinguished if each copy is put into one of two subsets according to its GC(3) level. Indeed, in the first case, the two distributions would be similar, whereas in the second case, the two distributions would be different, one copy having maintained the ancestral GC-poor composition, and one copy having undergone the compositional change. Using this approach, we could show that, by far and large, one copy of the duplicated genes preferentially underwent the GC enrichment. This result implies that this copy, which had possibly acquired a different function and/or regulation, was preferentially translocated into the gene-dense compartment of the genome, the "ancestral genome core", namely the "gene space" which underwent the compositional transition at the emergence of warm-blooded vertebrates.     

Immobilized pH gradients for isoelectric focusing. III. Preparative separations in highly diluted gels

A further improvement on the preparative aspects of immobilized pH gradients (IPG) (J. Biochem. Biophys. Methods (1983) 8, 135–172) is described, based on the use of soft (highly diluted) polyacrylamide gels. While in conventional IPGs in 5%T gels an upper load limit of 40–45 mg protein/ml gel volume is found, in 2.5%T gels, containing the same amount of Immobiline, as much as 90 mg protein/ml gel can be applied, without overloading effects. This is an extraordinary amount of material to ba carried by a gel phase, and renders IPG by far the leading technique in any electrophoretic fractionation. A new, two-step casting technique, based on the formation of a %T step and a pH plateau around the application trench, is described. A new method for electrophoretic protein recovery from IPG gel strips, based on embedding on low-gelling agarose (37°C), is reported. The physico-chemical properties of highly diluted gels, in relation to their protein loading ability, are evaluated and discussed. It is recommended that diluted gels (e.g. 3.5%T) be used also in analytical runs, since sharper protein zones are obtained, due to the increased charge density on the polymer coil.