Exopolysaccharides produced by the symbiotic nitrogen-fixing bacteria of leguminosae

The process of biological nitrogen fixation (BNF), performed by symbiotic nitrogen fixing bacteria with legume species, commonly known as α and β rhizobia, provides high sustainability for the ecosystems. Its management as a biotechnology is well succeeded for improving crop yields. A remarkable example of this success is the inoculation of Brazilian soybeans with Bradyrhizobium strains. Rhizobia produce a wide diversity of chemical structures of exopolysaccharides (EPS). Although the role of EPS is relatively well studied in the process of BNF, their economic and environmental potential is not yet explored. These EPS are mostly species-specific heteropolysaccharides, which can vary according to the composition of sugars, their linkages in a single subunit, the repeating unit size and the degree of polymerization. Studies have showed that the EPS produced by rhizobia play an important role in the invasion process, infection threads formation, bacteroid and nodule development and plant defense response. These EPS also confer protection to these bacteria when exposed to environmental stresses. In general, strains of rhizobia that produce greater amounts of EPS are more tolerant to adverse conditions when compared with strains that produce less. Moreover, it is known that the EPS produced by microorganisms are widely used in various industrial activities. These compounds, also called biopolymers, provide a valid alternative for the commonly used in food industry through the development of products with identical properties or with better rheological characteristics, which can be used for new applications. The microbial EPS are also able to increase the adhesion of soil particles favoring the mechanical stability of aggregates, increasing levels of water retention and air flows in this environment. Due to the importance of EPS, in this review we discuss the role of these compounds in the process of BNF, in the adaptation of rhizobia to environmental stresses and in the process of soil aggregation. The possible applications of these biopolymers in industry are also discussed.

The experience of transplantation for patients and their significant ones: A difficult encounter of two worlds

Objectives This paper reports on a longitudinal qualitative study exploring concerns of 60 patients before and after transplantation. Methods Semi-structured interviews were conducted without time constraints in a protected space out of the hospital. Qualitative analysis was performed. Results Prior to transplantation, all patients talked freely about negative feelings, stigmatisation, being misunderstood by others, loneliness and culpability caused by increasing physical dependency or abandoned roles. They mentioned alternative ways to cope (magic, spirituality), and even expressed their right to let go. In a subset of 13 patients, significant ones allowed themselves in the interview, or were integrated on the request of the patients. In this modified setting, two illness-worlds were confronted. If common themes were mentioned (e.g., modified life plans, restricted space, physical and psychological barriers), they were experienced differently. Fear of transplantation or guilt towards the donors was overtly expressed, often for the first time. Mutual hiding of anxiety in order to protect loved ones or to prevent loss of control was disclosed. The significant ones talked about accumulated stress and exhaustion related to the physical degradation of the patient, fear of the unpredictable evolution of illness and financial problems, and stressed their difficulty to adapt adequately to the fluctuating state of the patient. After transplantation, other themes emerged, where difficulty in disclosure was observed: intensive care and near death experiences, being a transplanted person, debt to the donor and his/her family, fear of rejection. Conclusions With the self-imposed strategy of hiding concerns to protect one another, a discrepancy between two illness-worlds was created. When concerns were confronted during the interviews, a new mutual understanding emerged. Patients and their families stated the need for sharing concerns in the course of illness.

Influence of pressure and radio frequency power on deposition rate and structural properties of hydrogenated amorphous silicon thin films prepared by plasma deposition

The influence of radio frequency (rf) power and pressure on deposition rate and structural properties of hydrogenated amorphous silicon (a-Si:H) thin films, prepared by rf glow discharge decomposition of silane, have been studied by phase modulated ellipsometry and Fourier transform infrared spectroscopy. It has been found two pressure regions separated by a threshold value around 20 Pa where the deposition rate increases suddenly. This behavior is more marked as rf power rises and reflects the transition between two rf discharges regimes. The best quality films have been obtained at low pressure and at low rf power but with deposition rates below 0.2 nm/s. In the high pressure region, the enhancement of deposition rate as rf power increases first gives rise to a reduction of film density and an increase of content of hydrogen bonded in polyhydride form because of plasma polymerization reactions. Further rise of rf power leads to a decrease of polyhydride bonding and the material density remains unchanged, thus allowing the growth of a-Si:H films at deposition rates above 1 nm/s without any important detriment of material quality. This overcoming of deposition rate limitation has been ascribed to the beneficial effects of ion bombardment on the a-Si:H growing surface by enhancing the surface mobility of adsorbed reactive species and by eliminating hydrogen bonded in polyhydride configurations.

Biological, clinical and population relevance of 95 loci for blood lipids.

Plasma concentrations of total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol and triglycerides are among the most important risk factors for coronary artery disease (CAD) and are targets for therapeutic intervention. We screened the genome for common variants associated with plasma lipids in >100,000 individuals of European ancestry. Here we report 95 significantly associated loci (P < 5 x 10(-8)), with 59 showing genome-wide significant association with lipid traits for the first time. The newly reported associations include single nucleotide polymorphisms (SNPs) near known lipid regulators (for example, CYP7A1, NPC1L1 and SCARB1) as well as in scores of loci not previously implicated in lipoprotein metabolism. The 95 loci contribute not only to normal variation in lipid traits but also to extreme lipid phenotypes and have an impact on lipid traits in three non-European populations (East Asians, South Asians and African Americans). Our results identify several novel loci associated with plasma lipids that are also associated with CAD. Finally, we validated three of the novel genes-GALNT2, PPP1R3B and TTC39B-with experiments in mouse models. Taken together, our findings provide the foundation to develop a broader biological understanding of lipoprotein metabolism and to identify new therapeutic opportunities for the prevention of CAD.

Diabetes mellitus and vascular lesions.

Cardiovascular complications represent by far the most severe manifestations of diabetes mellitus. Treatment aimed at stopping progression of vascular lesions may fall short if initiated when the disease becomes clinically evident. Therefore, identification of the earliest vascular disfunctions may offer the best opportunity to interfere with pathogenic mechanisms and avoid progression of diabetic vasculopathy. In this report, we present a few mechanisms that alter hemodynamic and metabolic homeostasis in the course of diabetes mellitus. Endothelial function with special emphasis on nitric oxide and oxidative stress, advanced glycation end products, and the renin angiotensin system are briefly discussed. New pharmacological agents that may favorably influence these parameters are presently undergoing clinical trials. However, tight control of plasma glucose and cardiovascular risk factors represent the cornerstone of the treatment in diabetes to slow progression of vascular disease.

Hundreds of variants clustered in genomic loci and biological pathways affect human height.

Most common human traits and diseases have a polygenic pattern of inheritance: DNA sequence variants at many genetic loci influence the phenotype. Genome-wide association (GWA) studies have identified more than 600 variants associated with human traits, but these typically explain small fractions of phenotypic variation, raising questions about the use of further studies. Here, using 183,727 individuals, we show that hundreds of genetic variants, in at least 180 loci, influence adult height, a highly heritable and classic polygenic trait. The large number of loci reveals patterns with important implications for genetic studies of common human diseases and traits. First, the 180 loci are not random, but instead are enriched for genes that are connected in biological pathways (P = 0.016) and that underlie skeletal growth defects (P < 0.001). Second, the likely causal gene is often located near the most strongly associated variant: in 13 of 21 loci containing a known skeletal growth gene, that gene was closest to the associated variant. Third, at least 19 loci have multiple independently associated variants, suggesting that allelic heterogeneity is a frequent feature of polygenic traits, that comprehensive explorations of already-discovered loci should discover additional variants and that an appreciable fraction of associated loci may have been identified. Fourth, associated variants are enriched for likely functional effects on genes, being over-represented among variants that alter amino-acid structure of proteins and expression levels of nearby genes. Our data explain approximately 10% of the phenotypic variation in height, and we estimate that unidentified common variants of similar effect sizes would increase this figure to approximately 16% of phenotypic variation (approximately 20% of heritable variation). Although additional approaches are needed to dissect the genetic architecture of polygenic human traits fully, our findings indicate that GWA studies can identify large numbers of loci that implicate biologically relevant genes and pathways.