Catalase Activity and Post-anoxic Injury in Monocotyledonous Species

Three anoxia-intolerant species, Glyceria maxima, Juncus effusus and Iris germanica (var. Quechei), and three anoxia-tolerant species Schoenoplectus lacustris, Acorus calamus and Iris pseudacorus were chosen for investigation. Rhizomes of anoxia-intolerant species show increased catalase activities when returned to air after periods of prolonged anoxia. Levels of catalase remained fairly constant in anoxia-tolerant species under the same conditions. In the anoxia intolerant G. maxima, the post-anoxic increase in catalase activity was reduced by circulating the anaerobic atmosphere. This treatment also reduced the ethanol content of the tissue under incubation, and increased the survival of the rhizomes as seen in their ability to resume growth in the post-anoxic phase. Exposure of anaerobic G. maxima rhizomes to ethanol vapour increased post-anoxic levels of catalase activity and when this produced a 5-fold increase always resulted in death of the rhizomes. Acetaldehyde vapour applied in the same way gave rise to increases in catalase activity followed by rapid death of the rhizomes. It is suggested that post-anoxic oxidation of anaerobically accumulated ethanol may result in a surge of acetaldehyde production, which could exert a toxic effect on the recovering tissues. The possible role of catalase in an ethanol-oxidation reaction, which is well documented in animals, is discussed in the light of the association between the natural accumulation of large concentrations of ethanol and subsequent post-anoxic death in some plant tissue

Anchor cell signaling and vulval precursor cell positioning establish a reproducible spatial context during C. elegans vulval induction

How cells coordinate their spatial positioning through intercellular signaling events is poorly understood. Here we address this topic using Caenorhabditis elegans vulval patterning during which hypodermal vulval precursor cells (VPCs) adopt distinct cell fates determined by their relative positions to the gonadal anchor cell (AC). LIN-3/EGF signaling by the AC induces the central VPC, P6.p, to adopt a 1° vulval fate. Exact alignment of AC and VPCs is thus critical for correct fate patterning, yet, as we show here, the initial AC-VPC positioning is both highly variable and asymmetric among individuals, with AC and P6.p only becoming aligned at the early L3 stage. Cell ablations and mutant analysis indicate that VPCs, most prominently 1° cells, move towards the AC. We identify AC-released LIN-3/EGF as a major attractive signal, which therefore plays a dual role in vulval patterning (cell alignment and fate induction). Additionally, compromising Wnt pathway components also induces AC-VPC alignment errors, with loss of posterior Wnt signaling increasing stochastic vulval centering on P5.p. Our results illustrate how intercellular signaling reduces initial spatial variability in cell positioning to generate reproducible interactions across tissues

An investigation of some of the resistance aspects of the catamaran hull

This thesis document was issued under the authority of another institution, not NPS. At the time it was written, a copy was added to the NPS Library collection for reasons not now known. It has been included in the digital archive for its historical value to NPS. Not believed to be a CIVINS (Civilian Institutions) title.A symmetrical hull catamaran with dimensions 1n line with current proposed submarine rescue vessels was designed and tested at several hull spacings in order to determine the effect of separation on resistance. A single hull was tested to assess the relative increase in resistance or interference compared to the infinite separation represented by the single hull results. In general, it was found that the resistance decrease with increasing separations and for certain speeds and separations favorable interference was observed which made the overall resistance slightly less than twice the single hull results. A comparison with the submarine rescue vessels, a Taylor expansion and a comparable single hull ship is made where in the case of the latter the catamaran demonstrates its superiority at speed length ratios greater than 1.2. The effect of trim for the proposed design is also evaluated, resulting in decreased resistance with trim by the stern. A possible method employing the use of a single model to predict the resistance of a catamaran was tested with promising results.http://www.archive.org/details/investigationofs00braeLieutenant, United States Nav

Evaluation des activités d’information et de sensibilisation du Programme Cantonal Tabac Tessinois (PCT1) : rapport final

Le programme cantonal tabac 2015-2018 du canton du Tessin a pour but de consolider la dénormalisation de la consommation de tabac au sein de la population tessinoise. Parmi les projets qui composent ce programme, le PCT1 a pour objectif principal de produire et de diffuser différents supports d’information et d’assurer une présence sur le terrain afin de sensibiliser la population aux risques liés à la consommation de tabac. Objectifs de la phase finale de l’évaluation: La phase finale de cette évaluation poursuivait les trois objectifs principaux suivants : 1) mesurer l’atteinte des objectifs du PCT1 en matière de couverture, de diffusion de connaissances et d’impact sur les attitudes en lien avec le tabagisme et sa prévention au sein de la population tessinoise ; 2) identifier les pratiques exemplaires en matière de communication à large échelle de message de prévention du tabagisme ; 3) mieux comprendre les processus à l’oeuvre dans le pilotage et la mise en oeuvre du PCT1

The genetic basis of natural variation in C. elegans telomere length [preprint]

Telomeres are involved in the maintenance of chromosomes and the prevention of genome instability. Despite this central importance, significant variation in telomere length has been observed in a variety of organisms. The genetic determinants of telomere-length variation and their effects on organismal fitness are largely unexplored. Here, we describe natural variation in telomere length across the Caenorhabditis elegans species. We identify a large-effect variant that contributes to differences in telomere length. The variant alters the conserved oligosaccharide/oligonucleotide-binding fold of POT-2, a homolog of a human telomere-capping shelterin complex subunit. Mutations within this domain likely reduce the ability of POT-2 to bind telomeric DNA, thereby increasing telomere length. We find that telomere-length variation does not correlate with offspring production or longevity in C. elegans wild isolates, suggesting that naturally long telomeres play a limited role in modifying fitness phenotypes in C. elegans

Networked buffering: a basic mechanism for distributed robustness in complex adaptive systems

A generic mechanism - networked buffering - is proposed for the generation of robust traits in complex systems. It requires two basic conditions to be satisfied: 1) agents are versatile enough to perform more than one single functional role within a system and 2) agents are degenerate, i.e. there exists partial overlap in the functional capabilities of agents. Given these prerequisites, degenerate systems can readily produce a distributed systemic response to local perturbations. Reciprocally, excess resources related to a single function can indirectly support multiple unrelated functions within a degenerate system. In models of genome:proteome mappings for which localized decision-making and modularity of genetic functions are assumed, we verify that such distributed compensatory effects cause enhanced robustness of system traits. The conditions needed for networked buffering to occur are neither demanding nor rare, supporting the conjecture that degeneracy may fundamentally underpin distributed robustness within several biotic and abiotic systems. For instance, networked buffering offers new insights into systems engineering and planning activities that occur under high uncertainty. It may also help explain recent developments in understanding the origins of resilience within complex ecosystems. \ud \u

Bias and Evolution of the Mutationally Accessible Phenotypic Space in a Developmental System

Genetic and developmental architecture may bias the mutationally available phenotypic spectrum. Although such asymmetries in the introduction of variation may influence possible evolutionary trajectories, we lack quantitative characterization of biases in mutationally inducible phenotypic variation, their genotype-dependence, and their underlying molecular and developmental causes. Here we quantify the mutationally accessible phenotypic spectrum of the vulval developmental system using mutation accumulation (MA) lines derived from four wild isolates of the nematodes Caenorhabditis elegans and C. briggsae. The results confirm that on average, spontaneous mutations degrade developmental precision, with MA lines showing a low, yet consistently increased, proportion of developmental defects and variants. This result indicates strong purifying selection acting to maintain an invariant vulval phenotype. Both developmental system and genotype significantly bias the spectrum of mutationally inducible phenotypic variants. First, irrespective of genotype, there is a developmental bias, such that certain phenotypic variants are commonly induced by MA, while others are very rarely or never induced. Second, we found that both the degree and spectrum of mutationally accessible phenotypic variation are genotype-dependent. Overall, C. briggsae MA lines exhibited a two-fold higher decline in precision than the C. elegans MA lines. Moreover, the propensity to generate specific developmental variants depended on the genetic background. We show that such genotype-specific developmental biases are likely due to cryptic quantitative variation in activities of underlying molecular cascades. This analysis allowed us to identify the mutationally most sensitive elements of the vulval developmental system, which may indicate axes of potential evolutionary variation. Consistent with this scenario, we found that evolutionary trends in the vulval system concern the phenotypic characters that are most easily affected by mutation. This study provides an empirical assessment of developmental bias and the evolution of mutationally accessible phenotypes and supports the notion that such bias may influence the directions of evolutionary change

The Genetic Basis of Natural Variation in Caenorhabditis elegans Telomere Length

Telomeres are involved in the maintenance of chromosomes and the prevention of genome instability. Despite this central importance, significant variation in telomere length has been observed in a variety of organisms. The genetic determinants of telomere-length variation and their effects on organismal fitness are largely unexplored. Here, we describe natural variation in telomere length across the Caenorhabditis elegans species. We identify a large-effect variant that contributes to differences in telomere length. The variant alters the conserved oligonucleotide/oligosaccharide-binding fold of protection of telomeres 2 (POT-2), a homolog of a human telomere-capping shelterin complex subunit. Mutations within this domain likely reduce the ability of POT-2 to bind telomeric DNA, thereby increasing telomere length. We find that telomere-length variation does not correlate with offspring production or longevity in C. elegans wild isolates, suggesting that naturally long telomeres play a limited role in modifying fitness phenotypes in C. elegans

Legal determinants of external finance revisited : the inverse relationship between investor protection and societal well-being

This paper investigates relationships between corporate governance traditions and quality of life as measured by a number of widely reported indicators. It provides an empirical analysis of indicators of societal health in developed economies using a classification based on legal traditions. Arguably the most widely cited work in the corporate governance literature has been the collection of papers by La Porta et al. which has shown, inter alia, statistically significant relationships between legal traditions and various proxies for investor protection. We show statistically significant relationships between legal traditions and various proxies for societal health. Our comparative evidence suggests that the interests of investors may not be congruent with the interests of wider society, and that the criteria for judging the effectiveness of approaches to corporate governance should not be restricted to financial metrics

Life-Cycle Switching and Coexistence of Species with No Niche Differentiation

The increasing evidence of coexistence of cryptic species with no recognized niche differentiation has called attention to mechanisms reducing competition that are not based on niche-differentiation. Only sex-based mechanisms have been shown to create the negative feedback needed for stable coexistence of competitors with completely overlapping niches. Here we show that density-dependent sexual and diapause investment can mediate coexistence of facultative sexual species having identical niches. We modelled the dynamics of two competing cyclical parthenogens with species-specific density-dependent sexual and diapause investment and either equal or different competitive abilities. We show that investment in sexual reproduction creates an opportunity for other species to invade and become established. This may happen even if the invading species is an inferior competitor. Our results suggests a previously unnoticed mechanism for species coexistence and can be extended to other facultative sexual species and species investing in diapause where similar density-dependent life-history switches could act to promote coexistence