Context dependency of the allelopathic effects of Lonicera maackii on seed germination

Allelopathic effects of invasive plants on native flora may be mitigated by the abiotic and biotic environment into which the allelochemicals are released. Lonicera maackii (Amur honeysuckle), an invasive plant of the eastern deciduous forest, suppresses seed germination in laboratory assays. We investigated how L. maackii leachate interacts with abiotic conditions and with the soil microbial community. First, we tested the effects of leaf extract from L. maackii on germination of the native woodland herb, Blephilia hirsuta, under different light and soil conditions. We found that germination of Blephilia hirsuta was reduced by L. maackii extract, but abiotic conditions did not interact with this effect. We also tested the effects of leaf extract on germination of five native woodland species and L. maackii placed in sterile or live soil. There was an overall suppressive effect of L. maackii extract on itself and the other five native species tested. However, L. maackii extract interacted with live soil in ways that differed with the species being tested and, in some cases, changed over time. Our results indicate that allelopathic potential of L. maackii shows context dependency with respect to soil microorganisms and native species identity but not to light conditions or soil type. Our results imply that restoration of invaded areas may require active reintroduction of species sensitive to allelopathy in live soil. Further, laboratory assays of allelopathy should consider the interaction of allelochemicals with biotic and abiotic conditions to more accurately predict the impacts of allelopathy on plant communities.     

Who likes it hot? A global analysis of the climatic,ecological, and evolutionary determinants of warming tolerance in ants

Effects of climate warming on wild populations of organisms are expected to be greatest at higher latitudes, paralleling greater anticipated increases in temperature in these regions. Yet, these expectations assume that populations in different regions are equally susceptible to the effects of warming. This is unlikely to be the case. Here, we develop a series of predictive models for physiological thermal tolerances in ants based on current and future climates. We found that tropical ants have lower warming tolerances, a metric of susceptibility to climate warming, than temperate ants despite greater increases in temperature at higher latitudes. Using climatic, ecological and phylogenetic data, we refine our predictions of which ants (across all regions) were most susceptible to climate warming. We found that ants occupying warmer and more mesic forested habitats at lower elevations are the most physiologically susceptible to deleterious effects of climate warming. Phylogenetic history was also a strong indicator of physiological susceptibility. In short, we find that ants that live in the canopies of hot, tropical forest are the most at risk, globally, from climate warming. Unfortunately this is where many, perhaps most, ant and other species on Earth live.     

A flux capacitor for moth pheromones

In this issue of Chemical Senses, Baker et al. propose a provocative and intriguing explanation for a commonly observed phenomenon in moth chemocommunication. Sex pheromones in moths typically consist of mixtures of long-chain unsaturated compounds in specific ratios. These ratios are correspondingly detected by male moths using separate olfactory sensory neurons for each pheromone component housed singly or multiply in long trichoid sensilla on the antennal surface. These neurons are often present in different proportions, typically with the neuron responding to the highest ratio component present in greatest abundance or with the largest dendritic diameter. In their article, Baker et al. postulate that these physical differences in neuron magnitudes arise to compensate for the higher molecular flux present with the most abundant pheromone components. Such a suggestion raises several questions concerning the physiological and behavioral nature of pheromone communication. Specifically, is the flux in a natural pheromone plume high enough to warrant increased flux detection for the most abundant components? Second, how can changes in neuronal number or size lead to increased flux detection? And finally, how would this increased flux detection be accomplished at molecular, cellular, and ultimately network scales? We address each of these questions and propose future experiments that could offer insight into the stimulating proposition raised by Baker et al.     

Neandertal mobility and large-game hunting: The exploitation of reindeer during the Quina Mousterian at Chez-Pinaud Jonzac (Charente-Maritime, France)

Neandertals were effective hunters of large ungulates throughout their geographic and temporal ranges. Equipped with this knowledge, researchers in paleoanthropology continue to seek insight on the relationships between hunting and subsistence strategies with other components of the Neandertals’ niche, such as mobility, site use, and lithic technology. The Quina Mousterian deposits from the rockshelter site of Chez Pinaud Jonzac (Charente-Maritime, France; hereafter Jonzac) offer an excellent opportunity to pursue these issues. This paper focuses on the extensive and well-preserved skeletal remains of reindeer (Rangifer tarandus) recovered from recent excavations of the site, representing at least 18 individuals that were hunted by Neandertals during the fall through winter. Our zooarchaeological results indicate that all ages of reindeer were hunted but adult individuals predominate. No bias is evident in the comparable frequencies of males and females. These prey were butchered on-site, with abundant evidence of meat filleting and marrow exploitation. In the excavated sample, the absence of hearths and the almost complete lack of burned bones or stones suggest that Neandertals were not using fire to assist with processing the reindeer carcasses. The zooarchaeological results presented here indicate that reindeer were hunted during a restricted window of time when they were seasonally abundant in the local area near Jonzac. Taken together with the lithic industry based on bifacial elements, the evidence is consistent with a pattern of site use by highly mobile hunter-gatherers making frequent, short-term visits. Ongoing research at Jonzac and other Quina Mousterian localities will contribute to a better understanding of Neandertal behavior during cold climate phases.     

Pilot study of the association of the DDAH2 -449G polymorphism with asymmetric dimethylarginine and hemodynamic shock in pediatric sepsis

Background

Genetic variability in the regulation of the nitric oxide (NO) pathway may influence hemodynamic changes in pediatric sepsis. We sought to determine whether functional polymorphisms in DDAH2, which metabolizes the NO synthase inhibitor asymmetric dimethylarginine (ADMA), are associated with susceptibility to sepsis, plasma ADMA, distinct hemodynamic states, and vasopressor requirements in pediatric septic shock.

Methodology/Principal Findings

In a prospective study, blood and buccal swabs were obtained from 82 patients ≤18 years (29 with severe sepsis/septic shock plus 27 febrile and 26 healthy controls). Plasma ADMA was measured using tandem mass spectrometry. DDAH2 gene was partially sequenced to determine the −871 6g/7g insertion/deletion and −449G/C single nucleotide polymorphisms. Shock type (“warm” versus “cold”) was characterized by clinical assessment. The −871 7g allele was more common in septic (17%) then febrile (4%) and healthy (8%) patients, though this was not significant after controlling for sex and race (p = 0.96). ADMA did not differ between −871 6g/7g genotypes. While genotype frequencies also did not vary between groups for the −449G/C SNP (p = 0.75), septic patients with at least one −449G allele had lower ADMA (median, IQR 0.36, 0.30–0.41 µmol/L) than patients with the −449CC genotype (0.55, 0.49–0.64 µmol/L, p = 0.008) and exhibited a higher incidence of “cold” shock (45% versus 0%, p = 0.01). However, after controlling for race, the association with shock type became non-significant (p = 0.32). Neither polymorphism was associated with inotrope score or vasoactive infusion duration.

Conclusions/Significance

The −449G polymorphism in the DDAH2 gene was associated with both low plasma ADMA and an increased likelihood of presenting with “cold” shock in pediatric sepsis, but not with vasopressor requirement. Race, however, was an important confounder. These results support and justify the need for larger studies in racially homogenous populations to further examine whether genotypic differences in NO metabolism contribute to phenotypic variability in sepsis pathophysiology.     

Long-term organ culture of mouse mammary gland

Summary A method for maintaining mouse mammary gland in organ culture for periods of at least 30 days is described. Strips of the number four mammary glands were cultured in individual tubes while fully submerged in Medium 199 supplemented with insulin, aldosterone, ovine prolactin and bovine growth hormone. Exchange processes were aided by slowly rotating the tubes during culture. Mammary tissue from midpregnant BALB/c and virgin GR/A mice was induced to undergo lobulo-alveolar development, secrete and remain differentiated and metabolically active for the period of culture. Cells of both the ductal and alveolar epithelium continued to synthesize DNA and divide. The submerged roller-tube culture allows the use of larger pieces of tissue than can be accommodated in static culture, and the technique may prove applicable to the culture of a variety of tissues.     

Nucleic acid aptamers for target validation and therapeutic applications.

In the simplest view, aptamers can be thought of as nucleic acid analogs to antibodies. They are able to bind specifically to proteins, and, in many cases, that binding leads to a modulation of protein activity. New aptamers are rapidly generated through the SELEX (Systematic Evolution of Ligands by Exponential enrichment) process and have a very high target affinity and specificity (picomoles to nanomoles). Furthermore, aptamers composed of modified nucleotides have a long in vivo half-life (hours to days), are nontoxic and nonimmunogenic, and are easily produced using standard nucleic acid synthesis methods. These properties make aptamers ideal for target validation and as a new class of therapeutics. As a target validation tool, aptamers provide important information that complements that provided by other methods. For example, siRNA is widely used to demonstrate that protein knock-out in a cellular assay can lead to a biological effect. Aptamers extend that information by showing that the dose-dependent modulation of protein activity can be used to derive a therapeutic benefit. That is, aptamers can be used to demonstrate that the protein is a good target for drug development. As a new class of therapeutics, aptamers bridge the gap between small molecules and biologics. Like biologics, biologically active aptamers are rapidly discovered, have no class-specific toxicity, and are adept at disrupting protein-protein interaction. Like small molecules, aptamers can be rationally engineered and optimized, are nonimmunogenic, and are produced by scalable chemical procedures at moderate cost. As such, aptamers are emerging as an important source of new therapeutic molecules.