Lime treatment and its effects on the chemistry and biota of hardwater eutrophic lakes

1. The main focus of this study was to investigate the effects of single and multiple moderate doses of lime (slaked lime, Ca(OH)₂, and/or calcite, CaCO₃) on eutrophic hardwater lakes. This information would contribute to strategies to manage phytoplankton and macrophyte biomass in eutrophic lakes.
2. Water chemistry and biota were monitored for up to 7 years after initial lime treatment and results were compared with reference systems.
3. Complementary studies investigated the effect of lime on macrophytes in ponds, irrigation canals and microcosm experiments.
4. When water pH was kept within its natural range (≤ 10), single and multiple lime applications to lakes and ponds controlled macrophyte biomass, without negatively affecting invertebrate communities.
5. Single lime treatments at moderate dosages of lakes and ponds resulted in variable and mostly temporary changes in chlorophyll a (chl a ) and phosphorus (P) concentration. Although sediment P release was reduced in single-dose lakes during the first winter following treatment, reductions appeared temporary.
6. Multiple treatments of lakes and ponds were effective at reducing both chl a and P concentrations over longer periods. Mean winter P release rate was also reduced after initial treatment.
7. In laboratory studies, sediment cores were incubated with eight different treatments to assess P release. Redox-sensitive treatments were no more effective at lowering total P concentration in overlying water than some redox-insensitive treatments. Lime reduced total P concentrations, but was not as effective as treatments with alum.
8. The use of lime in managing macrophyte and phytoplankton biomass in shallow, hardwater lakes and ponds may be preferable over other treatments, because lime is economical and non-toxic as long as pH is kept within a natural range.     

Ultraviolet-Stimulated KHCO(3) Efflux from Rose Cells: Regulation of Cytoplasmic pH

Suspension-cultured cells of Rosa damascena that have been irradiated with ultraviolet light (254 nanometers, 2.1 × 10⁴ joules per square meter) rapidly lose K⁺ and HCO₃⁻ ions to the medium. If the HCO₃⁻ is derived from respiratory CO₂ inside the cell, then loss of HCO₃⁻ should be accompanied by an acidification of the cytoplasm. Estimates of the pH of control and ultraviolet-irradiated cells by ³¹P-nuclear magnetic resonance spectroscopy indicated that, following irradiation, the pH of both cytoplasm and vacuole dropped by 0.2 to 0.3 units. This change was not as great as was predicted from the observed HCO₃⁻ loss. Analysis of nitrogenous compounds in the cell suggested that reduction of nitrate and synthesis of γ-aminobutyric acid absorbed some of the protons formed by the synthesis and dissociation of bicarbonate.     

Introduced cats Felis catus eating a continental fauna: inventory and traits of Australian mammal species killed

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Ruffling of metalloporphyrins bound to IsdG and IsdI, two heme-degrading enzymes in Staphylococcus aureus

IsdG and IsdI are paralogous proteins that are intracellular components of a complex heme uptake system in Staphylococcus aureus. IsdG and IsdI were shown previously to reductively degrade hemin. Crystal structures of the apoproteins show that these proteins belong to a newly identified heme degradation family distinct from canonical eukaryotic and prokaryotic heme oxygenases. Here we report the crystal structures of an inactive N7A variant of IsdG in complex with Fe(3+)-protoporphyrin IX (IsdG-hemin) and of IsdI in complex with cobalt protoporphyrin IX (IsdI-CoPPIX) to 1.8 A or better resolution. These structures show that the metalloporphyrins are buried into similar deep clefts such that the propionic acids form salt bridges to two Arg residues. His(77) (IsdG) or His(76) (IsdI), a critical residue required for activity, is coordinated to the Fe(3+) or Co(3+) atoms, respectively. The bound porphyrin rings form extensive steric interactions in the binding cleft such that the rings are highly distorted from the plane. This distortion is best described as ruffled and places the beta- and delta-meso carbons proximal to the distal oxygen-binding site. In the IsdG-hemin structure, Fe(3+) is pentacoordinate, and the distal side is occluded by the side chain of Ile(55). However, in the structure of IsdI-CoPPIX, the distal side of the CoPPIX accommodates a chloride ion in a cavity formed through a conformational change in Ile(55). The chloride ion participates in a hydrogen bond to the side chain amide of Asn(6). Together the structures suggest a reaction mechanism in which a reactive peroxide intermediate proceeds with nucleophilic oxidation at the beta- or delta-meso carbon of the hemin.     

A role for inositol hexakisphosphate in the maintenance of basal resistance to plant pathogens

Phytic acid (myo-inositol hexakisphosphate, InsP6) is an important phosphate store and signal molecule in plants. However, low-phytate plants are being developed to minimize the negative health effects of dietary InsP6 and pollution caused by undigested InsP6 in animal waste. InsP6 levels were diminished in transgenic potato plants constitutively expressing an antisense gene sequence for myo-inositol 3-phosphate synthase (IPS, catalysing the first step in InsP6 biosynthesis) or Escherichia coli polyphosphate kinase. These plants were less resistant to the avirulent pathogen potato virus Y and the virulent pathogen tobacco mosaic virus (TMV). In Arabidopsis thaliana, mutation of the gene for the enzyme catalysing the final step of InsP6 biosynthesis (InsP5 2-kinase) also diminished InsP6 levels and enhanced susceptibility to TMV and to virulent and avirulent strains of the bacterial pathogen Pseudomonas syringae. Arabidopsis thaliana has three IPS genes (AtIPS1-3). Mutant atips2 plants were depleted in InsP6 and were hypersusceptible to TMV, turnip mosaic virus, cucumber mosaic virus and cauliflower mosaic virus as well as to the fungus Botrytis cinerea and to P. syringae. Mutant atips2 and atipk1 plants were as hypersusceptible to infection as plants unable to accumulate salicylic acid (SA) but their increased susceptibility was not due to reduced levels of SA. In contrast, mutant atips1 plants, which were also depleted in InsP6, were not compromised in resistance to pathogens, suggesting that a specific pool of InsP6 regulates defence against phytopathogens.     

Innovative use of an automated horse walker when breaking in young horses

There is an inherent element of risk associated with "backing" and riding the previously unbroken horse. If training proceeds too quickly, conflict behaviors may result from the simultaneous application of too many cues. Automated horse walkers (AHW) facilitate the exercising of several horses concurrently at walk or trot for warm-up, cool-down, fitness programs, and rehabilitation purposes. The objective of this study was to investigate if backing the horse within the AHW was an appropriate training method. Ten horses (3-year-olds) took part in this study. They began training within the AHW with a simple bridle and protective boots. A handler subsequently long-reined the horses within the AHW when they wore rollers, side reins, and a saddle. When considered appropriate, the handler went from jumping beside the horse to lying over the saddle to sitting astride the horse within the AHW. The horses habituated to this innovative approach quickly without evidence of conflict behavior. The handler rode the horses from the AHW after approximately 4 riding episodes of this innovative training system.     

Birth of a biome: insights into the assembly and maintenance of the Australian arid zone biota

The integration of phylogenetics, phylogeography and palaeoenvironmental studies is providing major insights into the historical forces that have shaped the Earth's biomes. Yet our present view is biased towards arctic and temperate/tropical forest regions, with very little focus on the extensive arid regions of the planet. The Australian arid zone is one of the largest desert landform systems in the world, with a unique, diverse and relatively well-studied biota. With foci on palaeoenvironmental and molecular data, we here review what is known about the assembly and maintenance of this biome in the context of its physical history, and in comparison with other mesic biomes. Aridification of Australia began in the Mid-Miocene, around 15 million years, but fully arid landforms in central Australia appeared much later, around 1-4 million years. Dated molecular phylogenies of diverse taxa show the deepest divergences of arid-adapted taxa from the Mid-Miocene, consistent with the onset of desiccation. There is evidence of arid-adapted taxa evolving from mesic-adapted ancestors, and also of speciation within the arid zone. There is no evidence for an increase in speciation rate during the Pleistocene, and most arid-zone species lineages date to the Pliocene or earlier. The last 0.8 million years have seen major fluctuations of the arid zone, with large areas covered by mobile sand dunes during glacial maxima. Some large, vagile taxa show patterns of recent expansion and migration throughout the arid zone, in parallel with the ice sheet-imposed range shifts in Northern Hemisphere taxa. Yet other taxa show high lineage diversity and strong phylogeographical structure, indicating persistence in multiple localised refugia over several glacial maxima. Similar to the Northern Hemisphere, Pleistocene range shifts have produced suture zones, creating the opportunity for diversification and speciation through hybridisation, polyploidy and parthenogenesis. This review highlights the opportunities that development of arid conditions provides for rapid and diverse evolutionary radiations, and re-enforces the emerging view that Pleistocene environmental change can have diverse impacts on genetic structure and diversity in different biomes. There is a clear need for more detailed and targeted phylogeographical studies of Australia's arid biota and we suggest a framework and a set of a priori hypotheses by which to proceed.     

Comparative genomic assessment of Multi-Locus Sequence Typing: rapid accumulation of genomic heterogeneity among clonal isolates of <Emphasis Type="Italic">Campylobacter jejuni</Emphasis>

Background  

Multi-Locus Sequence Typing (MLST) has emerged as a leading molecular typing method owing to its high ability to discriminate among bacterial isolates, the relative ease with which data acquisition and analysis can be standardized, and the high portability of the resulting sequence data. While MLST has been successfully applied to the study of the population structure for a number of different bacterial species, it has also provided compelling evidence for high rates of recombination in some species. We have analyzed a set of Campylobacter jejuni strains using MLST and Comparative Genomic Hybridization (CGH) on a full-genome microarray in order to determine whether recombination and high levels of genomic mosaicism adversely affect the inference of strain relationships based on the analysis of a restricted number of genetic loci.     

Macrophage colony stimulating factor prevents NMDA-induced neuronal death in hippocampal organotypic cultures

Macrophage colony stimulating factor (M-CSF) and its receptor are up-regulated in the brain in Alzheimer's disease (AD), in transgenic mouse models for AD, and experimental models for traumatic and ischemic brain injury. M-CSF induces activation and proliferation of microglial cells and expression of proinflammatory cytokines. We examined the role of M-CSF in excitotoxic neuronal cell death in organotypic hippocampal cultures. NMDA treatment induced neuronal apoptosis and caspase-3 activation in organotypic hippocampal cultures, whereas treatment with M-CSF protected hippocampal neurons from NMDA-induced apoptosis. Caspase-3 activation was inhibited by M-CSF treatment to the same degree as with the caspase inhibitor Z-VAD-FMK. These results suggest that M-CSF has neuroprotective properties through inhibition of caspase-3 that could promote neuronal survival after excitotoxic insult. The role of M-CSF in neurological disease should be reevaluated as a microglial activator with potentially neuroprotective effects.