Vulnerability, livelihood assets and institutional dynamics in the management of wetlands in Lake Victoria watershed basin

This paper uses data from 600 households in the Lake Victoria watershed in Tanzania, Kenya, and Uganda to analyze the effects of vulnerabilities and shocks on the management and exploitation of wetlands within the context of agricultural activities and high poverty levels. A multinomial logit model is used to determine variables that influence the perception of wetlands degradation, while a tobit model is used to establish the determinants of willingness to pay for wetland conservation and the imputed value of wetland product extracts. The model results show that although the perception of wetland degradation is modest, it is influenced by attributes of social capital. Variables such as floods, diseases and droughts significantly influence the households’ willingness to pay for wetland conservation. Land size and ownership, education level and household size all influence households’ likelihood to actively engage in wetland resource exploitation and willingness to pay for its conservation. The implications of these results hinge on measures that would moderate the effects of shocks, mobilize collective action, and improve physical infrastructure within the context of sustainable wetland resource use.     

Docking of Antizyme to Ornithine Decarboxylase and Antizyme Inhibitor using Experimental Mutant and Double-Mutant Cycle Data

Antizyme (Az) is a highly conserved key regulatory protein bearing a major role in regulating polyamine levels in the cell. It has the ability to bind and inhibit ornithine decarboxylase (ODC), targeting it for degradation. Az inhibitor (AzI) impairs the activity of Az. In this study, we mapped the binding sites of ODC and AzI on Az using Ala scan mutagenesis and generated models of the two complexes by constrained computational docking. In order to scan a large number of mutants in a short time, we developed a workflow combining high-throughput mutagenesis, small-scale parallel partial purification of His-tagged proteins and their immobilization on a tris-nitrilotriacetic-acid-coated surface plasmon resonance chip. This combination of techniques resulted in a significant reduction in time for production and measurement of large numbers of mutant proteins. The data-driven docking results suggest that both proteins occupy the same binding site on Az, with Az binding within a large groove in AzI and ODC. However, single-mutant data provide information concerning the location of the binding sites only, not on their relative orientations. Therefore, we generated a large number of double-mutant cycles between residues on Az and ODC and used the resulting interaction energies to restrict docking. The model of the complex is well defined and accounts for the mutant data generated here, and previously determined biochemical data for this system. Insights on the structure and function of the complexes, as well as general aspects of the method, are discussed.     

On a Reproductive Stage-Structured Model for the Population Dynamics of the Malaria Vector

A reproductive stage-structured deterministic differential equation model for the population dynamics of the human malaria vector is derived and analysed. The model captures the gonotrophic and behavioural life characteristics of the female Anopheles sp. mosquito and takes into consideration the fact that for the purposes of reproduction, the female Anopheles sp. mosquito must visit and bite humans (or animals) to harvest necessary proteins from blood that it needs for the development of its eggs. Focusing on mosquitoes that feed exclusively on humans, our results indicate the existence of a threshold parameter, the vectorial reproduction number, whose size increases with increasing number of gonotrophic cycles, and is also affected by the female mosquito’s birth rate, its attraction and visitation rate to human residences, and its contact rate with humans. A stability analysis of the model indicates that the mosquito can establish itself in the environment if and only if the value of the vectorial reproduction number exceeds unity and that mosquito eradication is possible if the vectorial reproduction number is less than unity, since, then, the trivial steady state which always exist is unique and is globally and asymptotically stable. When a persistent vector population steady state exists, it is locally and asymptotically stable for a range of reproduction numbers, but can also be driven to instability via a Hopf bifurcation as the reproduction number increases further away from unity. The model derivation identifies and characterizes control parameters relating to activities such as human-mosquito contact and the mosquito’s survival chances between blood meals and egg laying. Our results show that the total mosquito population size increases with increasing number of gonotrophic cycles. Therefore understanding the fundamental aspects of the mosquito’s behaviour provides a pathway for the study of human-mosquito contact and mosquito population control. Control of the mosquito population densities would ultimately lead to malaria control.     

Tolerance of β-diketone hydrolases as representatives of the crotonase superfamily towards organic solvents

Crotonase superfamily enzymes catalyze a wide variety of reactions, including hydrolytic C–C bond cleavage in symmetrical β‐diketones by 6‐oxo camphor hydrolase (OCH) from Rhodococcus sp. The organic solvent tolerance and temperature stability of OCH and its structurally related ortholog Anabaena β‐diketone hydrolase have been investigated. Both enzymes showed excellent tolerance toward organic solvents; for instance, even in the presence of 80% (v/v) THF or dioxane, OCH was still active. In most solvent mixtures, except methanol, the stereospecificity was conserved (>99% e.e. of product), hence neither the type of solvent nor its concentration appeared to have an effect on the stereoselectivity of the enzyme. Attempts to correlate the observed activities with log P, functional solvent group or denaturing capacity (DC) of the solvent were only successful in the case of DC for water miscible solvents. This study represents the first investigation of organic solvent stability for members of the crotonase superfamily. Biotechnol. Bioeng. 2011;108: 2815–2822. © 2011 Wiley Periodicals, Inc.     

The effect of N-acetylcysteine on the antitumor activity of ifosfamide

Ifosfamide-induced nephrotoxicity is a serious adverse effect in children undergoing chemotherapy. Our previous cell and rodent models have shown that the antioxidant N-acetylcysteine (NAC), used extensively as an antidote for acetaminophen poisoning, protects renal tubular cells from ifosfamide-induced nephrotoxicity at a clinically relevant concentration. For the use of NAC to be clinically relevant in preventing ifosfamide nephrotoxicity, we must ensure there is no effect of NAC on the antitumor activity of ifosfamide. Common pediatric tumors that are sensitive to ifosfamide, human neuroblastoma SK-N-BE(2) and rhabdomyosarcoma RD114-B cells, received either no pretreatment or pretreatment with 400 μmol/L of NAC, followed by concurrent treatment with NAC and either ifosfamide or the active agent ifosfamide mustard. Ifosfamide mustard significantly decreased the growth of both cancer cell lines in a dose-dependent manner (p < 0.001). The different combined treatments of NAC alone, sodium 2-mercaptoethanesulfonate alone, or NAC plus sodium 2-mercaptoethanesulfonate did not significantly interfere with the tumor cytotoxic effect of ifosfamide mustard. These observations suggest that NAC may improve the risk/benefit ratio of ifosfamide by decreasing ifosfamide-induced nephrotoxicity without interfering with its antitumor effect in cancer cells clinically treated with ifosfamide.     

Reconstructing Mid-Pleistocene paleovegetation and paleoclimate in the Golan Heights using the δ(13)C values of modern vegetation and soil organic carbon of paleosols

The Golan Heights borders the Upper Jordan Valley on its eastern side and likely served as a prime foraging area for hominin groups that inhabited the Upper Jordan Valley during the Mid-Pleistocene. This study tests the hypothesis that Mid-Pleistocene climate in the Golan region was similar to that of the present day. Carbon isotope composition of present day plant communities and soil organic carbon from the Golan were compared to those of paleosols from Nahal Orvim to reconstruct Mid-Pleistocene paleoclimatic conditions. After correcting the paleosol values for recent changes in atmospheric carbon isotope values and potential biodegradation, the isotopic results show a strong similarity to those of present day local plants and soils. These results indicate that during the Mid-Pleistocene, the Golan was dominated by C₃ vegetation, shared similar climatic conditions with the present day, and displayed long-term environmental stability. The span of time of paleosol formation is unknown and might cover multiple climatic episodes; thus, although short climatic fluctuations may have occurred, their impact was not substantial enough to be detected in the Nahal Orvim paleosols. This study concludes that the Golan slopes provided hominins and large grazers with a reliable and highly nutritious foraging area that complemented the Jordan Valley riparian ecosystem.     

Informing and influencing the interface between biodiversity science and biodiversity policy in South Africa

South Africa, as a megadiverse country (±21 700 vascular plants, 4800 vertebrates and 68 900 invertebrates described), is presently engaged with an extended, modified Global Strategy for Plant Conservation (GSPC). The country is fortunate in having a strong tradition of systematics research and, inter alia, houses several million preserved plant specimens (±1 million databased and georeferenced), allowing taxonomists and conservationists to track both the occurrence and distribution of indigenous and naturalized plant species. These rich local resources have been extensively drawn upon to deliver, with varying degrees of success, the 16 outcome-oriented GSPC 2010 Targets. The National Environmental Management: Biodiversity Act (NEMBA, 2004), the National Biodiversity Strategy and Action Plan (NBSAP) and the National Biodiversity Framework (NBF) have provided a robust legislative, enabling and policy framework for making operational and advancing GSPC-related efforts. However, within an emerging economy, the conservation of biodiversity has competed for government resources with housing, sanitation, primary education, basic health care and crime prevention, delivery of which translates to the currency of politicians: votes. A key challenge identified by local (and global) biodiversity scientists for the current GSPC phase is broad-scale advocacy, communicating the changing state of nature, and the inter-relatedness of biodiversity and human well-being. The nature of meeting this challenge is explored.     

Isolation by environment

The interactions between organisms and their environments can shape distributions of spatial genetic variation, resulting in patterns of isolation by environment (IBE) in which genetic and environmental distances are positively correlated, independent of geographic distance. IBE represents one of the most important patterns that results from the ways in which landscape heterogeneity influences gene flow and population connectivity, but it has only recently been examined in studies of ecological and landscape genetics. Nevertheless, the study of IBE presents valuable opportunities to investigate how spatial heterogeneity in ecological processes, agents of selection and environmental variables contributes to genetic divergence in nature. New and increasingly sophisticated studies of IBE in natural systems are poised to make significant contributions to our understanding of the role of ecology in genetic divergence and of modes of differentiation both within and between species. Here, we describe the underlying ecological processes that can generate patterns of IBE, examine its implications for a wide variety of disciplines and outline several areas of future research that can answer pressing questions about the ecological basis of genetic diversity.