Is the decrease of the total electron energy density a covalence indicator in hydrogen and halogen bonds?

In this work, halogen bonding (XB) and hydrogen bonding (HB) complexes were studied with the aim of analyzing the variation of the total electronic energy density H(r _b ) with the interaction strengthening. The calculations were performed at the MP2/6?311++G(2d,2p) level of approximation. To explain the nature of such interactions, the atoms in molecules theory (AIM) in conjunction with reduced variational space self-consistent field (RVS) energy decomposition analysis were carried out. Based on the local virial theorem, an equation to decompose the total electronic energy density H(r _b ) in two energy densities, (?G(r _b )) and 1/4?²ρ(r _b ), was derived. These energy densities were linked with the RVS interaction energy components. Through the connection between both decomposition schemes, it was possible to conclude that the decrease in H(r _b ) with the interaction strengthening observed in the HB as well as the XB complexes, is mainly due to the increase in the attractive electrostatic part of the interaction energy and in lesser extent to the increase in its covalent character, as is commonly considered.     

Effects of proprioceptive training program on core stability and center of gravity control in sprinters

The purpose of this study was to determinate the effect of a 6-week specific-sprinter proprioceptive training program on core stability and gravity center control in sprinters. Thirty-three athletes (age = 21.82 ± 4.84 years, height = 1.76 ± 0.07 m, weight = 67.82 ± 08.04 kg, body mass index = 21.89 ± 2.37 kg · m(-2)) from sprint disciplines were divided into a control (n = 17) and experimental (n = 16) groups. A 30-minute proprioceptive training program was included in the experimental group training sessions, and it was performed for 6 weeks, 3 times each week. This program included 5 exercises with the BOSU and Swiss ball as unstable training tools that were designed to reproduce different moments of the technique of a sprint race. Stability with eyes open (EO) and eyes closed, postural stability, and gravity center control were assessed before and after the training program. Analyses of covariance (α = 0.05) revealed significant differences in stability in the medial-lateral plane with EO, gravity center control in the right direction and gravity center control in the back direction after the exercise intervention in the experimental athletes. Nevertheless, no other significant differences were demonstrated. A sprinter-specific proprioceptive training program provided postural stability with EO and gravity center control measures improvements, although it is not clear if the effect of training would transfer to the general population.     

Influence of Two Vaccination Campaigns on Genetic Diversity of Invasive Neisseria meningitidis Isolates in Northern Spain (1997–2008)

Background

Neisseria meningitidis diversifies rapidly, due to its high recombination rates. The aim of this study was to analyze the possible impact of two vaccination campaigns (a once-off A/C polysaccharide vaccination campaign in people aged 18 months to 20 years old in 1997, and a meningococcal C conjugate vaccination campaign in children aged ≤6 years old from 2000 to 2008) on diversification of the population of invasive isolates obtained between 1997 and 2008. All of the 461 available isolates were included (2, 319, 123, 11 and 6 belonging to serogroups A, B, C, Y and W-135, respectively).

Methodology/Principal Findings

The isolates were analyzed for diversity using multilocus sequence typing, eBURST and the S.T.A.R.T.2 program. One hundred and seven sequence types (ST) and 20 clonal complexes were obtained. Five different STs (ST11, ST8, ST33, ST1163 and ST3496) included 56.4% of the isolates. With the exception of ST11, all other STs were associated with a specific serogroup. Epidemic circulation of serogroup C ST8 isolates was detected in 1997–1998, as well as epidemic circulation of ST11 isolates (serogroups B and C) in 2002–2004. The epidemic behavior of serogroup B ST11 (ST11_B:2a:P1.5) was similar, although with lesser intensity, to that of ST11 of serogroup C. Although clonality increased during epidemic years, the overall diversity of the meningococcal population did not increase throughout the 12 years of the study.

Conclusion

The overall diversity of the meningococcal population, measured by the frequency of STs and clonal complexes, numbers of alleles, polymorphic sites, and index of association, remained relatively constant throughout the study period, contradicting previous findings by other researchers.     

Aspects of neural plasticity in the central nervous system—VI. Studies of the effects of gangliosides on brain metabolic lesions

The effects of gangliosides have been studied in two models of metabolic insult (insulin-induced hypoglycemia and transient forebrain ischemia) of the central nervous system. In the severe hypoglycemia experiments lactate extracellular fluid levels were evaluated by means of a microdialysis probe implanted in the frontoparietal cortex. Ganglioside GM1, given either peripherally (10 mg/kg, i.p.) or intracerebrally (2 × 10⁻⁴ M, via the microdialysis probe) 2 h before insulin injection, was able to reduce the decay of the perfusate levels of lactate induced by the insulin injection. In the same animal model peripheral, but not central, administration of GM1 reduced the hypoglycemia-induced increase of cerebral blood flow and increased the survival time observed after the insulin injection. In the experiments on transient forebrain ischemia, a GM1 derivative, AGF2 (5 mg/kg/day, i.p.), was administered chronically, starting 5 days before or the day after the ischemic insult. With both treatment schedules a similar protective effect was observed in a neurological test battery and in the step-through latency in a passive avoidance test.     

Impairment of energy metabolism in hippocampus of rats subjected to chemically-induced hyperhomocysteinemia

Homocystinuria is an inherited metabolic disease biochemically characterized by tissue accumulation of homocysteine (Hcy). Mental retardation, ischemia and other neurological features, whose mechanisms are still obscure are common symptoms in homocystinuric patients. In this work, we investigated the effect of Hcy administration in Wistar rats on some parameters of energy metabolism in the hippocampus, a cerebral structure directly involved with cognition. The parameters utilized were 14CO2 production, glucose uptake, lactate release and the activities of succinate dehydrogenase and cytochrome c oxidase (COX). Chronic hyperhomocysteinemia was induced by subcutaneous administration of Hcy twice a day from the 6th to the 28th day of life in doses previously determined in our laboratory. Control rats received saline in the same volumes. Rats were killed 12 h after the last injection. Results showed that Hcy administration significantly diminished 14CO2 production and glucose uptake, as well as succinate dehydrogenase and COX activities. It is suggested that impairment of brain energy metabolism may be related to the neurological symptoms present in homocystinuric patients.     

Spatial and temporal variation in Nothofagus pumilio growth at tree line along its latitudinal range (35°40'–55° S) in the Chilean Andes

Aim To identify the dominant spatial and temporal patterns of Nothofagus pumilio radial growth over its entire latitudinal range in Chile, and to find how these patterns relate to temperature and precipitation variation from instrumental records. Location This study comprises 48 tree line or high elevation N. pumilio sites in the Chilean Andes between 35° 36′ and 55° S. Nothofagus pumilio is a deciduous tree species that dominates the upper tree line of the Chilean and Argentinean Andes in this latitudinal range. Methods At each of the sampled sites, two cores from 15 to 40 living trees were collected using increment borers. Cores were processed, tree rings were measured and cross‐dated, using standard dendrochronological procedures. Radii from nearby sites were grouped into 13 study regions. A composite tree‐ring width chronology was developed for each region in order to capture and integrate the common growth patterns. For the identification of the dominant patterns of growth, as well as temperature and precipitation variation, we used principal components (PCs) analysis. Correlation analysis was used for the study of the relationship of N. pumilio tree‐ring growth with temperature and precipitation records. Results Nothofagus pumilio tree line elevation is 1600 m in the northernmost region and gradually decreases to 400 m in the southernmost region. Despite local differences along the transect, the decrease in tree line elevation is fairly constant, averaging c. 60 m per degree of latitude (111 km). Tree growth at the northernmost regions shows a positive correlation with annual precipitation (PC1‐prec) and negative correlation with mean annual temperature (PC2‐temp), under a Mediterranean‐type climate where water availability is a major limiting factor. Conversely, tree growth is positively correlated with mean annual temperature (PC1‐temp) in the southern portion of the gradient, under a relatively cooler climate with little seasonality in precipitation. Main conclusions Our findings indicate that temperature has a spatially larger control of N. pumilio growth than precipitation, as indicated by a significant (P < 0.05) either positive or negative correlation of tree growth and PC1‐temp and/or PC2‐temp for nine of the 13 regional chronologies (69.2% of the total), whereas precipitation is significantly correlated with only two chronologies (15.4% of the total). Temporal patterns of N. pumilio tree growth reflected in PC1‐growth for the period between 1778 and 1996 indicate an increasing trend with above the mean values after 1963, showing high loadings in the southern part of the gradient. This trend may be explained by a well‐documented increase in temperature in southern Patagonia. Ongoing and future research on N. pumilio growth patterns and their relationship to climate covering the Chilean and Argentinean Andes will improve the understanding of long‐term climate fluctuations of the last three to four centuries, and their relationship to global change at a wide range of spatial and temporal scales.     

Race to the Future: Integrating 21st Century Skills into Science Instruction

Race to the Future is an exciting and dynamic activity modeled after the reality television show The Amazing Race. It exemplifies how 21st century skills can be incorporated into core subject instruction and at the same time positively enhance student engagement. In this activity, students work quickly and cooperatively with their teammates and use 21st century skills to successfully decipher five clues related to science content. We have used this activity with excellent results with different groups of students (middle school, high school, and university students), for different purposes (ice-breaker, team-building, course assessment, and evaluation), and in broad curriculum areas (science and math). However, the activity is especially powerful when introduced during the first day or week of class. The meaningful and enjoyable student collaboration, the upbeat class environment, and the enhanced student engagement achieved at the conclusion of this challenging activity set an optimal teaching and learning environment for the entire quarter/semester.     

Quinazolinecarboline alkaloid evodiamine as scaffold for targeting topoisomerase I and sirtuins

This paper reports the synthesis of a series of evodiamine derivatives. We assayed the ability to inhibit cell growth on three human tumour cell lines (H460, MCF-7 and HepG2) and we evaluated the capacity to interfere with the catalytic activity of topoisomerase I both by the relaxation assay and the occurrence of the cleavable complex. Moreover, whose effect on sirtuins 1, 2 and 3 was investigated. Finally, molecular docking analyses were performed in an attempt to rationalize the biological results.