The karyotype of Nothoscordum arenarium Herter (Gilliesioideae, Alliaceae): A populational and cytomolecular analysis

The genus Nothoscordum Kunth comprises approximately 20 species native to South America. Karyologically, the genus is remarkable for its large chromosomes and Robertsonian translocations. Variation in chromosome number has been recorded in a few polyploid species and it is unknown among diploids. This study presents the chromosome number and morphology of 53 individuals of seven populations of N. arenarium Herter (2n = 10). In addition, karyotype analyses after C-banding, staining with CMA and DAPI, and in situ hybridization with 5S and 45S rDNA probes were performed in six individuals from one population. All individuals exhibited 2n = 10 (6M + 4A), except for one tetraploid (2n = 20, 12M + 8A) and one triploid (2n = 15, 9M + 6A) plant. C-banding revealed the presence of CMA(+) /DAPI (-) heterochromatin in the short arm and in the proximal region of the long arm of all acrocentric chromosomes. The 45S rDNA sites co-localized with the CMA (+) regions of the acrocentrics short arms, while the 5S rDNA probe only hybridized with the subterminal region of a pair of metacentric chromosomes. A change in the pattern of CMA bands and rDNA sites was observed in only one individual bearing a reciprocal translocation involving the long arm of a metacentric and the long arm of an acrocentric chromosome. These data suggest that, despite isolated cases of polyploidy and translocation, the karyotype of N. arenarium is very stable and the karyotypic instability described for other species may be associated with their polyploid condition.     

Black Yeast Biota in the Mangrove, in Search of the Origin of the Lethargic Crab Disease (LCD)

Knowledge of natural ecology is essential for a better understanding of pathogenicity and opportunism in black yeast-like fungi. Although etiological agents of diseases caused by these fungi are supposed to originate from the environment, their isolation from nature is difficult. This is probably due to their oligotrophic nature, low competitive ability, and, overall, insufficient data on their natural habitat. We obtained environmental samples from mangrove areas where mortalities by lethargic crab disease (LCD) are reported and areas without disease recorded. Isolation of chaetothyrialean black yeasts and relatives was performed using a highly selective protocol. Species-specific primers were used to determine if these isolates represented Exophiala cancerae or Fonsecaea brasiliensis, two proven agents of LCD, in order to test hypotheses about the origin of the disease. Isolates, identified by morphology as Fonsecaea- or Exophiala-like, were tested specific diagnostic markers for the fungi associated with LCD. Although several black fungi were isolated, the main causative agent of the LCD, E. cancerae, was not found. Molecular markers for F. brasiliensis revealed 10 positive bands for isolates from biofilms on mangrove leaves, branches, and aerial roots, of which four were confirmed by ITS sequencing. The absence of E. cancerae in environmental samples suggests that the species is dependent on the crab, as a genuine pathogen, different from F. brasiliensis, which is probably not dependent on the host species, U. cordatus. However, we did not attempt isolation from the marine water, which may represent the pathway of dispersion of the black yeast species between neighbor mangroves.     

Brain changes in BDNF and S100B induced by ketogenic diets in Wistar rats

AimsWe investigated the effects of ketogenic diet (KD) on levels of tumor necrosis factor alpha (TNF-α, a classical pro-inflammatory cytokine), BDNF (brain-derived neurotrophic factor, commonly associated with synaptic plasticity), and S100B, an astrocyte neurotrophic cytokine involved in metabolism regulation.Main methodsYoung Wistar rats were fed during 8 weeks with control diet or two KD, containing different proportions of omega 6 and omega 3 polyunsaturated fatty acids. Contents of TNF-α, BDNF and S100B were measured by ELISA in two brain regions (hippocampus and striatum) as well as blood serum and cerebrospinal fluid.Key findingsOur data suggest that KD was able to reduce the levels of BDNF in the striatum (but not in hippocampus) and S100B in the cerebrospinal fluid of rats. These alterations were not affected by the proportion of polyunsaturated fatty acids offered. No changes in S100B content were observed in serum or analyzed brain regions. Basal TNF-α content was not affected by KD.SignificanceThese findings reinforce the importance of this diet as an inductor of alterations in the brain, and such changes might contribute to the understanding of the effects (and side effects) of KD in brain disorders.     

Computational Modeling of Open-Irrigated Electrodes for Radiofrequency Cardiac Ablation Including Blood Motion-Saline Flow Interaction

Radiofrequency catheter ablation (RFCA) is a routine treatment for cardiac arrhythmias. During RFCA, the electrode-tissue interface temperature should be kept below 80°C to avoid thrombus formation. Open-irrigated electrodes facilitate power delivery while keeping low temperatures around the catheter. No computational model of an open-irrigated electrode in endocardial RFCA accounting for both the saline irrigation flow and the blood motion in the cardiac chamber has been proposed yet. We present the first computational model including both effects at once. The model has been validated against existing experimental results. Computational results showed that the surface lesion width and blood temperature are affected by both the electrode design and the irrigation flow rate. Smaller surface lesion widths and blood temperatures are obtained with higher irrigation flow rate, while the lesion depth is not affected by changing the irrigation flow rate. Larger lesions are obtained with increasing power and the electrode-tissue contact. Also, larger lesions are obtained when electrode is placed horizontally. Overall, the computational findings are in close agreement with previous experimental results providing an excellent tool for future catheter research.     

Leishmania mexicana glycerol-3-phosphate dehydrogenase showed conformational changes upon binding a bi-substrate adduct

Certain pathogenic trypanosomatids are highly dependent on glycolysis for ATP production, and hence their glycolytic enzymes, including glycerol-3-phosphate dehydrogenase (GPDH), are considered attractive drug targets. The ternary complex structure of Leishmania mexicana GPDH (LmGPDH) with dihydroxyacetone phosphate (DHAP) and NAD(+) was determined to 1.9A resolution as a further step towards understanding this enzyme's mode of action. When compared with the apo and binary complex structures, the ternary complex structure shows an 11 degrees hinge-bending motion of the C-terminal domain with respect to the N-terminal domain. In addition, residues in the C-terminal domain involved in catalysis or substrates binding show significant movements and a previously invisible five-residue loop region becomes well ordered and participates in NAD(+) binding. Unexpectedly, DHAP and NAD(+) appear to form a covalent bond, producing an adduct in the active site of LmGPDH. Modeling a ternary complex glycerol 3-phosphate (G3P) and NAD(+) with LmGPDH identified ten active site residues that are highly conserved among all GPDHs. Two lysine residues, Lys125 and Lys210, that are presumed to be critical in catalysis, were mutated resulting in greatly reduced catalytic activity. Comparison with other structurally related enzymes found by the program DALI suggested Lys210 as a key catalytic residue, which is located on a structurally conserved alpha-helix. From the results of site-directed mutagenesis, molecular modeling and comparison with related dehydrogenases, a catalytic mechanism of LmGPDH and a possible evolutionary scenario of this group of dehydrogenases are proposed.     

Socioeconomic Factors and All Cause and Cause-Specific Mortality among Older People in Latin America,India, and China: A Population-Based Cohort Study

Background

Even in low and middle income countries most deaths occur in older adults. In Europe, the effects of better education and home ownership upon mortality seem to persist into old age, but these effects may not generalise to LMICs. Reliable data on causes and determinants of mortality are lacking.

Methods and Findings

The vital status of 12,373 people aged 65 y and over was determined 3–5 y after baseline survey in sites in Latin America, India, and China. We report crude and standardised mortality rates, standardized mortality ratios comparing mortality experience with that in the United States, and estimated associations with socioeconomic factors using Cox''s proportional hazards regression. Cause-specific mortality fractions were estimated using the InterVA algorithm. Crude mortality rates varied from 27.3 to 70.0 per 1,000 person-years, a 3-fold variation persisting after standardisation for demographic and economic factors. Compared with the US, mortality was much higher in urban India and rural China, much lower in Peru, Venezuela, and urban Mexico, and similar in other sites. Mortality rates were higher among men, and increased with age. Adjusting for these effects, it was found that education, occupational attainment, assets, and pension receipt were all inversely associated with mortality, and food insecurity positively associated. Mutually adjusted, only education remained protective (pooled hazard ratio 0.93, 95% CI 0.89–0.98). Most deaths occurred at home, but, except in India, most individuals received medical attention during their final illness. Chronic diseases were the main causes of death, together with tuberculosis and liver disease, with stroke the leading cause in nearly all sites.

Conclusions

Education seems to have an important latent effect on mortality into late life. However, compositional differences in socioeconomic position do not explain differences in mortality between sites. Social protection for older people, and the effectiveness of health systems in preventing and treating chronic disease, may be as important as economic and human development. Please see later in the article for the Editors'' Summary