ALBERT

Description: Many studies have demonstrated linkages between the occurrence of fog and ecophysiological functioning in cloud forests, but few have investigated hydraulic functioning as a determining factor that explains sharp changes in vegetation. The objective of this study was to compare the plant water status during cloud-immersed and non-immersed conditions and hydraulic vulnerability in branches and roots of species across a temperate, mountain fog ecotone. Because cloud forests are often dark, cool and very moist, we expected cloud forest species to have less drought-tolerant characteristics (i.e., lower P e and P 50 —the pressures required to induce a 12 and 50% loss in hydraulic conductivity, respectively) relative to non-cloud forest species in adjacent (lower elevation) forests. Additionally, due to the ability of cloud forest species to absorb cloud-fog water, we predicted greater improvements in hydraulic functioning during fog in cloud forest species relative to non-cloud forest species. Across the cloud forest ecotone, most species measured were very resistant to losses in conductivity with branch P 50 values from –4.5 to –6.0 MPa, hydraulic safety margins ( min – P 50 ) 〉1.5 MPa and low calculated hydraulic conductivity losses. Roots had greater vulnerabilities, with P 50 values ranging from –1.4 to –2.5 MPa, leading to greater predicted losses in conductivity (~20%). Calculated values suggested strong losses of midday leaf hydraulic conductance in three of the four species, supporting the hydraulic segmentation hypothesis. In both cloud forest and hardwood species, s were greater on foggy days than sunny days, demonstrating the importance of fog periods to plant water balance across fog regimes. Thus, frequent fog did not result in systemic changes in hydraulic functioning or vulnerability to embolism across our temperate cloud forest ecotone. Finally, roots functioned with lower hydraulic conductivity than branches, suggesting that they may serve as more sensitive indicators of hydraulic functioning in these mesic, foggy ecosystems.

Description: The metal mining industry faces many large challenges in future years, among which is the increasing need to process low-grade ores as accessible higher grade ores become depleted. This is against a backdrop of increasing global demands for base and precious metals, and rare earth elements. Typically about 99% of solid material hauled to, and ground at, the land surface currently ends up as waste (rock dumps and mineral tailings). Exposure of these to air and water frequently leads to the formation of acidic, metal-contaminated run-off waters, referred to as acid mine drainage, which constitutes a severe threat to the environment. Formation of acid drainage is a natural phenomenon involving various species of lithotrophic (literally ‘rock-eating’) bacteria and archaea, which oxidize reduced forms of iron and/or sulfur. However, other microorganisms that reduce inorganic sulfur compounds can essentially reverse this process. These microorganisms can be applied on industrial scale to precipitate metals from industrial mineral leachates and acid mine drainage streams, resulting in a net improvement in metal recovery, while minimizing the amounts of leachable metals to the tailings storage dams. Here, we advocate that more extensive exploitation of microorganisms in metal mining operations could be an important way to green up the industry, reducing environmental risks and improving the efficiency and the economy of metal recovery.

Description: Arginase deficiency is caused by deficiency of arginase 1 (ARG1), a urea cycle enzyme that converts arginine to ornithine. Clinical features of arginase deficiency include elevated plasma arginine levels, spastic diplegia, intellectual disability, seizures and growth deficiency. Unlike other urea cycle disorders, recurrent hyperammonemia is typically less severe in this disorder. Normalization of plasma arginine levels is the consensus treatment goal, because elevations of arginine and its metabolites are suspected to contribute to the neurologic features. Using data from patients enrolled in a natural history study conducted by the Urea Cycle Disorders Consortium, we found that 97% of plasma arginine levels in subjects with arginase deficiency were above the normal range despite conventional treatment. Recently, arginine-degrading enzymes have been used to deplete arginine as a therapeutic strategy in cancer. We tested whether one of these enzymes, a pegylated human recombinant arginase 1 (AEB1102), reduces plasma arginine in murine models of arginase deficiency. In neonatal and adult mice with arginase deficiency, AEB1102 reduced the plasma arginine after single and repeated doses. However, survival did not improve likely, because this pegylated enzyme does not enter hepatocytes and does not improve hyperammonemia that accounts for lethality. Although murine models required dosing every 48 h, studies in cynomolgus monkeys indicate that less frequent dosing may be possible in patients. Given that elevated plasma arginine rather than hyperammonemia is the major treatment challenge, we propose that AEB1102 may have therapeutic potential as an arginine-reducing agent in patients with arginase deficiency.

Description: Water transport from soils to the atmosphere is critical for plant growth and survival. However, we have a limited understanding about many portions of the whole-tree hydraulic pathway, because the vast majority of published information is on terminal branches. Our understanding of mature tree trunk hydraulic physiology, in particular, is limited. The hydraulic vulnerability segmentation hypothesis (HVSH) stipulates that distal portions of the plant (leaves, branches and roots) should be more vulnerable to embolism than trunks, which are nonredundant organs that require a massive carbon investment. In the current study, we compared vulnerability to loss of hydraulic function, leaf and xylem water potentials and the resulting hydraulic safety margins (in relation to the water potential causing 50% loss of hydraulic conductivity) in leaves, branches, trunks and roots of four angiosperms and four conifer tree species. Across all species, our results supported strongly the HVSH as leaves and roots were less resistant to embolism than branches or trunks. However, branches were consistently more resistant to embolism than any other portion of the plant, including trunks. Also, calculated whole-tree vulnerability to hydraulic dysfunction was much greater than vulnerability in branches. This was due to hydraulic dysfunction in roots and leaves at less negative water potentials than those causing branch or trunk dysfunction. Leaves and roots had narrow or negative hydraulic safety margins, but trunks and branches maintained positive safety margins. By using branch-based hydraulic information as a proxy for entire plants, much research has potentially overestimated embolism resistance, and possibly drought tolerance, for many species. This study highlights the necessity to reconsider past conclusions made about plant resistance to drought based on branch xylem only. This study also highlights the necessity for more research of whole-plant hydraulic physiology to better understand strategies of plant drought tolerance and the critical control points within the hydraulic pathway.

Description: Aims To determine if an experimentally applied anomalous weather year could have effects on species composition and community structure that would carry over into the following year. Methods We conducted a field experiment applying two levels of temperature (ambient and +4°C) and two levels of precipitation (ambient and doubled) and followed cover of plant species during the treatment year and one post-treatment year. Data analysis included ordination analysis, examination of species frequency distributions and comparison of cover of functional groups and individual species. Important Findings A drought during the summer and fall of the treatment year resulted in significant differences in community structure between the 2 years. C 3 and winter annual species were depressed in the spring of the second year following the dry autumn. Species richness and legume cover increased in the second, wetter, year. Treatments caused no overall differences in community structure but did alter the dominance hierarchy of species among treatments as well as years. Warming decreased relative cover of winter annuals and early spring-flowering species but increased other annuals. Warming and double precipitation together increased cover of C 4 perennial graminoids. In particular, the warming and precipitation treatments both increased the abundance of Andropogon gerardii , not individually altering the dominance hierarchy but together nearly doubling the relative cover of A.gerardii , making it the most abundant species in the combined treatment, while the cover of Bromus arvensis , the former dominant, decreased by 25%. The following year, Andropogon relative cover increased further in the former warmed plots, becoming dominant in both the formerly warmed and warmed plus double precipitation treatments. The year following treatments also saw an increase in relative cover of summer-blooming species in the formerly warmed plots and differences among the former treatments in species richness of functional groups. If the effects of one anomalous year on plant abundance can carry over into the following year, several warm years could have a significant impact on plant community structure.

Description: Aims Seedlings are vulnerable to many kinds of fatal abiotic and biotic agents, and examining the causes of seedling dynamics can help understand mechanisms of species coexistence. To disentangle the relative importance of neighborhood densities, habitat factors and phylogenetic relatedness on focal seedling survival, we monitored the survival of 5306 seedlings of 104 species 〉15 months. We address the following questions: (i) How do neighborhood densities, habitat variables and phylogenetic relatedness affect seedling survival? What is the relative importance of conspecific densities, habitat variables and phylogenetic relatedness to seedling survival? (ii) Does the importance of the neighborhood densities, habitat variables and phylogenetic relatedness vary among growth forms, leaf habits or dispersal modes? Specially, does the conspecific negative density dependence inhibit tree and deciduous seedlings more compared with shrub and evergreen species? Does density dependence affect the wind and animal-dispersed species equally? Methods We established 135 census stations to monitor seedling dynamics in a 25-ha subtropical forest plot in central China. Conspecific and heterospecific seedling density in the 1-m 2 seedling plot and adult basal area within a 20-m radius provided neighborhood density variables. Mean elevation, convexity and aspect of every 5- x 5-m grid with seedling plots were used to quantify habitat characteristics. We calculated the relative average phylodiversity between focal seedling and heterospecific neighbors to quantify the species relatedness in the neighborhood. Eight candidate generalized linear mixed models with binominal error distribution were used to compare the relative importance of these variables to seedling survival. Akaike’s information criteria were used to identify the most parsimonious models. Important Findings At the community level, both the neighborhood densities and phylogenetic relatedness were important to seedling survival. We found negative effects of increasing conspecific seedlings, which suggested the existence of species-specific density-dependent mortality. Phylodiversity of heterospecific neighbors was negatively related to survival of focal seedlings, indicating similar habitat preference shared among phylogenetically closely related species may drive seedling survival. The relative importance of neighborhood densities, habitat variables and phylogenetic relatedness varied among ecological guilds. Conspecific densities had significant negative effect for deciduous and wind-dispersed species, and marginally significant for tree seedlings 〉10cm tall and animal-dispersed species. Habitat variables had limited effects on seedling survival, and only elevation was related to the survival of evergreen species in the best-fit model. We conclude that both negative density-dependent mortality and habitat preference reflected by the phylogenetic relatedness shape the species coexistence at seedling stage in this forest.

Description: The value of big old fat fecund female fish (BOFFFFs) in fostering stock productivity and stability has long been underappreciated by conventional fisheries science and management, although Hjort (1914) indirectly alluded to the importance of maternal effects. Compared with smaller mature females, BOFFFFs in a broad variety of marine and freshwater teleosts produce far more and often larger eggs that may develop into larvae that grow faster and withstand starvation better. As (if not more) importantly, BOFFFFs in batch-spawning species tend to have earlier and longer spawning seasons and may spawn in different locations than smaller females. Such features indicate that BOFFFFs are major agents of bet-hedging strategies that help to ensure individual reproductive success in environments that vary tremendously in time and space. Even if all else were equal, BOFFFFs can outlive periods that are unfavourable for successful reproduction and be ready to spawn profusely and enhance recruitment when favourable conditions return (the storage effect). Fishing differentially removes BOFFFFs, typically resulting in severe truncation of the size and age structure of the population. In the worst cases, fishing mortality acts as a powerful selective agent that inhibits reversal of size and age truncation, even if fishing intensity is later reduced. Age truncation is now known to destabilize fished populations, increasing their susceptibility to collapse. Although some fisheries models are beginning to incorporate maternal and other old-growth effects, most continue to treat all spawning-stock biomass as identical: many small young females are assumed to contribute the same to stock productivity as an equivalent mass of BOFFFFs. A growing body of knowledge dictates that fisheries productivity and stability would be enhanced if management conserved old-growth age structure in fished stocks, be it by limiting exploitation rates, by implementing slot limits, or by establishing marine reserves, which are now known to seed surrounding fished areas via larval dispersal. Networks of marine reserves are likely to be the most effective means of ensuring that pockets of old-growth age structure survive throughout the geographic range of demersal species.

Description: Slit3 is a large molecule with multiple domains and belongs to axon guidance families. To date, the biological functions of Slit3 are still largely unknown. Our recent study demonstrated that the N-terminal fragment of Slit3 is a novel angiogenic factor. In this study, we examined the biological function of the C-terminal fragment of human Slit3 (HSCF). The HSCF showed a high-affinity binding to heparin. The binding appeared to be heparin/heparan sulfate-specific and depends on the size, the degree of sulfation, the presence of N- and 6- O -sulfates and carboxyl moiety of the polysaccharide. Functional studies observed that HSCF inhibited antithrombin binding to heparin and neutralized the antifactor IIa and Xa activities of heparin and the antifactor IIa activity of low-molecular-weight heparin (LMWH). Thromboelastography analysis observed that HSCF reversed heparin's anticoagulation in global plasma coagulation. Taken together, these observations demonstrate that HSCF is a novel heparin-binding protein that potently neutralizes heparin's anticoagulation activity. This study reveals a potential for HSCF to be developed as a new antidote to treat overdosing of both heparin and LMWH in clinical applications.

Description: Growth media have been developed to facilitate the enrichment and isolation of acidophilic and acid-tolerant sulfate-reducing bacteria (aSRB) from environmental and industrial samples, and to allow their cultivation in vitro . The main features of the ‘standard’ solid and liquid devised media are as follows: (i) use of glycerol rather than an aliphatic acid as electron donor; (ii) inclusion of stoichiometric concentrations of zinc ions to both buffer pH and to convert potentially harmful hydrogen sulphide produced by the aSRB to insoluble zinc sulphide; (iii) inclusion of Acidocella aromatica (an heterotrophic acidophile that does not metabolize glycerol or yeast extract) in the gel underlayer of double layered (overlay) solid media, to remove acetic acid produced by aSRB that incompletely oxidize glycerol and also aliphatic acids (mostly pyruvic) released by acid hydrolysis of the gelling agent used (agarose). Colonies of aSRB are readily distinguished from those of other anaerobes due to their deposition and accumulation of metal sulphide precipitates. Data presented illustrate the effectiveness of the overlay solid media described for isolating aSRB from acidic anaerobic sediments and low pH sulfidogenic bioreactors.