Dioxygen affinity in heme proteins investigated by computer simulation

We present an investigation of the molecular basis of the modulation of oxygen affinity in heme proteins using computer simulation. QM-MM calculations are applied to explore distal and proximal effects on O(2) binding to the heme, while classical molecular dynamics simulations are employed to investigate ligand migration across the polypeptide to the active site. Trends in binding energies and in the kinetic constants are illustrated through a number of selected examples highlighting the virtues and the limitations of the applied methodologies. These examples cover a wide range of O(2)-affinities, and include: the truncated-N and truncated-O hemoglobins from Mycobacterium tuberculosis, the mammalian muscular O(2) storage protein: myoglobin, the hemoglobin from the parasitic nematode Ascaris lumbricoides, the oxygen transporter in the root of leguminous plants: leghemoglobin, the Cerebratulus lacteus nerve tissue hemoglobin, and the Alcaligenes xyloxidans cytochrome c'.     

Motor Axon Pathfinding

Motor neurons are functionally related, but represent a diverse collection of cells that show strict preferences for specific axon pathways during embryonic development. In this article, we describe the ligands and receptors that guide motor axons as they extend toward their peripheral muscle targets. Motor neurons share similar guidance molecules with many other neuronal types, thus one challenge in the field of axon guidance has been to understand how the vast complexity of brain connections can be established with a relatively small number of factors. In the context of motor guidance, we highlight some of the temporal and spatial mechanisms used to optimize the fidelity of pathfinding and increase the functional diversity of the signaling proteins.Motor neurons residing in the brain stem and spinal cord extend axons into the periphery and are the final relay cells for locomotor commands. These cells are among the longest projection neurons in the body and their axons follow stereotypical pathways during embryogenesis to synapse with muscle and sympathetic/parasympathetic targets. Cellular studies of motor axon navigation in developing chick and zebrafish embryos have shown that motor neurons located at different rostrocaudal positions show specific preferences for axonal pathways (see Landmesser 2001; Lewis and Eisen 2003 for reviews). This early cellular research laid the foundation for molecular studies of motor axon guidance by establishing the concept that motor neurons are in fact a diverse cell population. The molecular studies covered in this article have sought to identify genetic differences between motor neurons and to characterize the signaling pathways that underlie the specificity of motor axon targeting.     

Guiding the Selection of Processing Additives for Increasing the Efficiency of Bulk Heterojunction Polymeric Solar Cells

In bulk heterojunction (BHJ) polymeric organic solar cells (OSCs), the use of processing additives in the material formulation has emerged as a promising, cost‐effective, and widely applicable method for optimizing the phase separation between the donor (D) and acceptor (A) materials, thus increasing their efficiency. So far, however, there has been no systematic approach for identifying suitable processing additives for a given D:A system. A method based on the Hansen solubility parameters (HSPs) is proposed for guiding the selection of processing additives for a given D:A combination. The method is applied to the archetypical poly(3‐hexylthiophene) (P3HT) and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) system. The HSPs of these materials are determined and used to define a set of numerical criteria that need to be satisfied by a processing additive in order for it to be effective in realizing a higher efficiency OSC. Applying the selection criteria results in the identification of three novel processing additives. OSCs made of these formulations demonstrate an increase in their short‐circuit current density (J_SC) and power conversion efficiency (PCE). These results demonstrate the efficiency of these novel processing additives and show that the HSPs represent a useful tool to determine and explore new types of processing additives for BHJ‐OSCs.     

Aging exacerbates negative remodeling and impairs endothelial regeneration after balloon injury

Many older patients, because of their high prevalence of coronary artery disease, are candidates for percutaneous coronary interventions (PCI), but the effects of vascular aging on restenosis after PCI are not yet well understood. Balloon injury to the right carotid artery was performed in adult and old rats. Vascular smooth muscle cell (VSMC) proliferation, apoptotic cell death, together with Akt induction, telomerase activity, p27kip1, and endothelial nitric oxide synthase (eNOS) expression was assessed in isolated arteries. Neointima hyperplasia and vascular remodeling along with endothelial cell regeneration were also measured after balloon injury. Arteries isolated from old rats exhibited a significant reduction of VSMC proliferation and an increase in apoptotic death after balloon injury when compared with adult rats. In the vascular wall of adult rats, balloon dilation induced Akt phosphorylation, and this was barely present in old rats. In arteries from old rats, Akt-modulated cell cycle check points like telomerase activity and p27kip1 expression were decreased and increased, respectively, compared with adults. After balloon injury, old rats showed a significant reduction of neointima formation and an increased vascular negative remodeling compared with adults. These results were coupled by a marked delay in endothelial regeneration in aged rats, partially mediated by a decreased eNOS expression and phosphorylation. Interestingly, chronic administration of L-arginine prevented negative remodeling and improved reendothelialization after balloon injury in aged animals. A decreased neointimal proliferation, an impaired endothelial regeneration, and an increase in vascular remodeling after balloon injury were observed in aged animals. The molecular mechanisms underlying these responses seem to be a reduced Akt and eNOS activity.     

Determinants of Affiliative Interactions between Adult Males and Lactating Females in Pigtail Macaques (Macaca nemestrina nemestrina)

In some species of Cercopithecine primates, unrelated adult males and females maintain affiliative relationships ('friendships') that are apparently unrelated to mating or parental care. This study investigated the occurrence of friendships in a captive group of pigtail macaques, and some of their possible determinants. Study subjects were six adult males and 15 adult females with their newborn infants. Females were focally observed for 2 h every week during the first 12 wk of lactation. With the exception of the fourth-ranking male, adult males showed little interest in initiating affiliative interactions with lactating females and their infants. Most episodes of contact and grooming were initiated by high-ranking females and directed to the alpha male. Because female grooming was not generally reciprocated by the alpha male, it is likely that females benefited from associating with him in terms of agonistic support or protection. Genetic data on paternity determination indicated that the fourth-ranking male, who displayed high levels of affiliation towards mother-infant dyads, sired most of the infants born in the group in the year prior to this study. Thus, whereas females may be interested in associating with males to obtain their support, some males may affiliate with females as a consequence of their previous mating relationships with them or to increase the chances of future mating success. Taken together, however, the findings of this study provide little evidence that adult males and lactating females maintain strong reciprocal bonds that may qualify as friendships.     

Road exposure and the detectability of birds in field surveys

Road ecology, the study of the impacts of roads and their traffic on wildlife, including birds, is a rapidly growing field, with research showing effects on local avian population densities up to several kilometres from a road. However, in most studies, the effects of roads on the detectability of birds by surveyors are not accounted for. This could be a significant source of error in estimates of the impacts of roads on birds and could also affect other studies of bird populations. Using road density, traffic volume and bird count data from across Great Britain, we assess the relationships between roads and detectability of a range of bird species. Of 51 species analysed, the detectability of 36 was significantly associated with road exposure, in most cases inversely. Across the range of road exposure recorded for each species, the mean positive change in detectability was 52% and the mean negative change was 36%, with the strongest negative associations found in smaller-bodied species and those for which aural cues are more important in detection. These associations between road exposure and detectability could be caused by a reduction in surveyors’ abilities to hear birds or by changes in birds’ behaviour, making them harder or easier to detect. We suggest that future studies of the impacts of roads on populations of birds or other taxa, and other studies using survey data from road-exposed areas, should account for the potential impacts of roads on detectability.     

The use of cyprinodont fish, Aphanius fasciatus, as a sentinel organism to detect complex genotoxic mixtures in the coastal lagoon ecosystem

In the present work we aimed to standardise the alkaline comet assay with erythrocytes of the cyprinodont, Mediterranean Killifish, Aphanius fasciatus. The aims of the study were to explore the suitability of this fish to assess biomarkers of genotoxic effects and as a sentinel organism to detect complex genotoxic mixtures in coastal lagoon ecosystems. Following proper optimisation, the application and effectiveness of the comet assay in erythrocytes of A. fasciatus were tested by measuring the tail DNA (%) induced by (a) in vivo exposure of individual fish to X-rays (dose, 3Gy) and (b) following in vitro challenge of erythrocytes with restriction endonucleases Fok-I and Eco-RI, which selectively induce double-strand breaks with cohesive and blunt termini, respectively. Furthermore, in order to evaluate whether circulating fish blood contained actively proliferating cells that could influence the extent of DNA damage in control (untreated) fish, we measured the number of "comets" positive for 5-bromo-2'-deoxyuridine (BrdU) by the use of anti-BrdU antibody and immuno-histochemical methods. Both treatments (i.e. with X-rays and restriction endonucleases) induced statistically significant increases in tail DNA (%) values compared with the relevant untreated controls, indicating the effectiveness of the comet assay in the erythrocytes of A. fasciatus to detect different types of DNA lesions. Results from anti-BrdU antibody labelling of erythrocytes indicated a very low percentage (5%) of "comets" positive for BrdU. Following optimisation and validation of the assay under laboratory conditions, fish were collected in the Orbetello lagoon (Tuscany, Italy), considered to be a significantly polluted site. The results showed statistically significant increases for tail DNA (%) compared with corresponding values observed in erythrocytes of fish caught in the unpolluted reference site "Saline di Tarquinia". The effects of physico-chemical parameters of the water (i.e., salinity, pH and oxygen content) did not significantly influence the induction of DNA damage. These results indicate that the comet assay provides a reliable parameter and that A. fasciatus is a promising "sentinel organism" to detect the genotoxic impact of complex mixtures in coastal lagoon ecosystems.     

Maternal Anxiety in Rhesus Macaques (Macaca mulatta)

Visual monitoring and scratching were used as behavioral indicators of maternal and social anxiety in small captive groups of rhesus macaques. Young infants were especially at risk from other group members during the first weeks of locomotion away from their mothers. Mothers received aggression from other individuals irrespective of their infants' presence or absence. The rate at which mothers scratched themselves increased significantly when their infants moved away from them and when the infants approached or were approached by individuals who frequently harassed them. The rate of maternal scratching and the rate of glancing at the infant and at other individuals when the infant was away decreased as infants grew older and became less vulnerable to harassment. In contrast, the rate of maternal scratching and visual monitoring of other individuals when the infant was in contact remained stable across the first 12 wk of lactation. The rate of maternal scratching increased when the mother-infant pair was in spatial proximity to the adult male or higher ranking adult females. Although visual monitoring and scratching showed a similar sensitivity to social variables, it is speculated that they might reflect different components of anxiety, namely, anticipation of danger and uncertainty due to motivational conflict. The results of this investigation indicate that a macaque mother's emotional reactivity to a perceived danger for herself and her infant can be measured quite accurately using the rates of visual monitoring and scratching and that the latter represent reliable tools to investigate the emotional correlates of maternal behavior in nonhuman primates.     

Metabolic profiling of rhizomes of native populations of the strictly endemic Croatian species Iris adriatica

Iris adriatica Trinajsti? ex Miti? (Iridaceae L.) is a strictly endemic taxon from Croatia. It is a rhizomatous dwarf plant from the I. pumila complex with a distribution area limited to the Croatian part of the Mediterranean area, mainly central Dalmatia. The genus Iris is known for its richness in isoflavonoids which also play a significant role in chemotaxonomy and biological activity. Hence, in the current study, different plant batches of I. adriatica collected in early spring of 2016 were analysed for their phytochemical profiles and qualitatively compared. UHPLC-PDA-ESI-MS analyses of methanolic rhizome extracts were performed. Altogether, 36 compounds, representing isoflavonoids (including 6,7-methylendioxy derivatives), benzophenones and xanthones were found as aglycones or in glycosidically bound form to be the main constituent groups of I. adriatica rhizomes. Qualitative results were identical between different batches of plant material from collection sites in central Dalmatia, they differed only in quantity. For some phenolic compounds of I. adriatica, chemotaxonomic relevance was detected.