How do temperature,dissolved organic matter and nutrients influence the response of Leptodiaptomus ashlandi to UV radiation in a subalpine lake?

1. Ultraviolet radiation (UV) is an important stressor for zooplankton in alpine lake ecosystems. Multiple environmental variables such as dissolved organic matter (DOM), temperature and nutrient availability may alter how UV affects zooplankton. 2. We conducted a week‐long experiment manipulating UV, nutrients and DOM in enclosures suspended at the surface of cold and warm alpine lakes to determine the interactive effects of these variables on ovigerous Leptodiaptomus ashlandi (Marsh, 1893), a calanoid copepod. 3. UV had a negative effect on nauplii and gravid females at the colder temperature and at low, ambient DOM levels, but had no effect at the warmer temperature or when DOM was added. At the warmer temperature, fewer nauplii were produced in the +nutrient compared to ?nutrient treatment. Adult survival was not affected by UV or any other experimental variable. 4. These results demonstrate that the extent of the impact of UV radiation on zooplankton in alpine systems is altered by other environmental variables, and that these effects may not be apparent from experiments that look only at the survival of adult organisms that are better defended against UV.     

Photoprotective compounds in weakly and strongly pigmented copepods and co-occurring cladocerans

1. The prevalence of mycosporine‐like amino acids (MAAs) – a group of potential ultraviolet (UV)‐photoprotective compounds – was surveyed across 11 species of freshwater copepods from 20 lakes of varying ultraviolet radiation (UVR) transparency in North America, New Zealand and Argentina. Co‐occurring cladocerans were also analysed (seven species from 12 lakes). Many of the calanoid copepod populations were red with carotenoid pigmentation, allowing comparison of MAA and carotenoid accumulation as photoprotective strategies. 2. In two Pennsylvania (U.S.A.) lakes, MAA and carotenoid contents were followed during the early spring to mid‐summer period of lake warming. A pronounced seasonal pattern of higher carotenoid/low MAA content in spring, shifting to low carotenoid/higher MAA content in summer, was observed in calanoids from the more UV transparent lake. 3. All copepod samples contained MAAs. Visibly red calanoids, especially southern Hemisphere Boeckella, often had moderate to high concentrations (2.5–11 μg MAA mg^?1 dw), but low concentrations (0.04–1 μg MAA mg^?1 dw) in some N. American red calanoids show that high carotenoid pigmentation (e.g. 5–10 μg carotenoid mg^?1 dw) does not necessarily imply high MAA content. 4. No cladoceran sample had more than trace amounts of MAAs (<0.05 μg mg^?1 dw). Therefore, MAA accumulation does not seem to be a photoprotective strategy utilized by Daphnia (five species from nine lakes) or other cladocerans. 5. Seven identifiable MAAs were widely distributed among both calanoids and cyclopoids. Shinorine was ubiquitous and was usually the most abundant MAA in N. American samples. In contrast, porphyra‐334 was the predominant MAA in the southern Hemisphere Boeckella. 6. Copepods from higher UVR lakes tended to have a higher MAA content, but this relationship was statistically weak overall and taxon‐specific when found.     

Nematode‐specific PCR primers for the 18S small subunit rRNA gene

A set of polymerase chain reaction primers were designed, which amplify a c. 1 kb fragment of the 18S ribosomal DNA gene, and are specific to the phylum Nematoda. These have proven useful in isolating nematode genes from samples mixed with other biological material, particularly with application to DNA barcoding. Optimal reaction conditions are described. These primers have successfully amplified the correct fragment from a wide phylogenetic range of nematodes, and have so far generated no sequences from any other organismal group.     

Is life history a barrier to dispersal? Contrasting patterns of genetic differentiation along an oceanographically complex coast

Extreme variation in early life‐history strategies is considered a moderately good predictor of genetic subdivision and hence dispersal for a range of marine species. In reality, however, a good deal of population differentiation must reflect historical effects, more subtle variation in life histories, and, particularly, the interaction of larvae with oceanographic processes. Using a combination of allozyme and microsatellite markers, we show that the large‐scale genetic structure of populations of three species (direct and planktonically developing cushion stars and a planktonic developing sea anemone that is also asexually viviparous) varies consistently, in line with the predicted capacity for dispersal within three geographic regions. We detected high levels of genetic subdivision for the direct developing cushion star (F_ST = 0.6), low levels for the planktonically developing cushion star (F_ST = 0.009), and intermediate levels for the sexual/asexual sea anmone (F_ST = 0.19). These patterns are exhibited despite the highly variable patterns of current movement and the presence of biogeographic barriers. Our results suggest that, although there is large scale genetic differentiation for two species, patterns of population connectivity are remarkably consistent within major regions and do not reflect variation in major oceanographic processes or genetic discontinuity coincident with biogeographic boundaries. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 106–116.     

PALLIATIVE CARE, PUBLIC HEALTH AND JUSTICE: SETTING PRIORITIES IN RESOURCE POOR COUNTRIES

Many countries have not considered palliative care a public health problem. With limited resources, disease-oriented therapies and prevention measures take priority. In this paper, I intend to describe the moral framework for considering palliative care as a public health priority in resource-poor countries. A distributive theory of justice for health care should consider integrative palliative care as morally required as it contributes to improving normal functioning and preserving opportunities for the individual. For patients requiring terminal care , we are guided less by principles of justice and more by the duty to relieve suffering and society's commitment to protecting the professional's obligation to uphold principles of beneficence, compassion and non-abandonment. A fair deliberation process is necessary to allow these strong moral commitments to serve as reasons when setting priorities in resource poor countries.     

Post-Anthesis Economy of Carbon in a Cultivar of Cowpea

Budgets for transfer of carbon from individual leaves and othersource organs to fruits and nodulated roots were constructedfor stages of the post-flowering development of symbiotically-dependentcowpea (Vigna unguiculata L. Walp. cv. Vita 3-Rhizobium strainCB756). Exportable surpluses of carbon from sources, assessedfrom net exchanges of CO₂ and changes in carbon content, wereallocated to sink organs in proportion to carbon consumption(growth and respiration) and the ability of each sink organto attract assimilates from the sources, as demonstrated by¹⁴C-feeding. The first 10 d after flowering showed high sinkactivity by roots, stem and petioles, low consumption by fruits,with the upper three trifoliate blossom leaves providing thebulk of the required assimilates. The next 10 d showed a sharpdecline in photosynthesis of the leaf subtending the oldestfruit followed by similar declines in leaves at the other fruitingnodes. All leaflets at fruiting nodes abscised during the final10 d period, while the two lower leaves, not subtending fruits,remained green and supplied most of the carbon required by developingfruits and roots. Throughout fruiting all currently-active sourcessupplied all sinks, with only slight evidence of blossom leavesspecializing in nourishing their subtended fruits. Of the carbontranslocated from leaves during fruiting 32% came from the topmostleaf, 28% from the leaf below this, 16% from the next leaf,and the remaining 24% from the lowest three leaves. Some 80%of the fruit's total intake of carbon came from leaves, therest from mobilization of stored carbon (partly sugars and starch)fromother vegetative parts. Key words: Carbon, Translocation, Cowpea     

Symbiotic Performance of Supernoclulating Soybean (Glycine max (L.) Merrill) Mutants during Development on Different Nitrogen Regimes

Growth and symbiotic performance of soybean (Glycine max (L.)Merrill) cv. Bragg and three of its induced nodulation mutants(nod49, non-nodulating; ntsl 116, intermediate supernodulator;nts1007, extreme supernodulator) were compared throughout developmentunder different nitrogen regimes (0, 2, 5 and 10 mol nitratem^–3). Nitrogen fixation was assessed using ¹⁵N-isotopedilution and xylem sap analysis for ureide content. Both techniquesconfirmed a complete lack of N₂ fixation activity in nod49.Plant reliance on nitrogen fixation by the other genotypes wasdependent on the nitrate regime and the developmental stage.The ntsl007 and ntsl 116 mutants fixed more nitrogen than theparent cultivar in the presence of 10 mol m^–3 nitratein the nutrient solution, but higher input of symbioticallyderived nitrogen was still insufficient to offset the amountof nitrogen removed in the harvested seed. However, the mutantsutilized less nitrate for growth than Bragg. Comparison of estimatesof N₂ fixation derived from the ¹⁵N-dilution technique withthose based on relative ureide content of xylem sap indicatedthat the latter offered a simple and reliable procedure forevaluating the symbiotic performance of supernodulating plants. Key words: ¹⁵N-isotope dilution, supernodulation, ureides     

Effects of Grain Development and Thermal History on Grain Maturation and Seed Vigour of Pennisetum americanum

Studies were made of the viability and vigour of seeds of pearlmillet (Pennisetum americanum) harvested at different stagesof grain development and from different controlled-temperatureenvironments. Seed viability and vigour of the next generationwere dependent on the extent of grain development at harvest.Where grain had developed for only one-third of the potentialgrain-filling period before harvest, seed viability and vigourwere greatly reduced. Harvest at or after the middle of grain-fillingdid not reduce seed viability or vigour. The temperature atwhich the grains had developed did not affect seed viability,but grains that had developed at 21/16 °C (day/night) producedseedlings of greater height and dry weight than those from grainswhich had developed at higher temperatures.     

Normal and Mutant Glycine Transfer RNAs

THE glycine-specific tRNAs of E. coli can be grouped into three subspecies which are separated by chromatography on benzoylated DEAE cellulose (BDC): tRNA^Gly₁ (GGG), tRNA^Gly₂ (GGA/G) and tRNA^Gly₃ (GGU/C)^1,2. The tRNA^Gly₁ and tRNA^Gly₂ are specified by the genes, glyU and glyT, respectively, which have been located at 55 and 77 minutes on the E. coli chromosome. Suppressors of tryptophan A gene (trpA) missense mutations and partial diploid strains have been used extensively to characterize the glycine tRNA structural genes (Table 1)^1–3. A common property of these suppressor mutations is that the altered tRNA^Gly is no longer aminoacylated at the normal rate by the glycyl tRNA synthetase (GRS). When ordinary loading conditions are used virtually none of the suppressor tRNA species are amino-acylated. These studies have shown that single gene copies are normally present at the glyT and glyU loci.     

The 5S and 5.8S Ribosomal RNA Sequences of Tetrahymena thermophila and T. pyriformis1

The nucleotide sequences of the 5S rRNAs of Tetrahymena thermophila and two strains of T. pyriformis have been determined to be identical. The 5.8S rRNA sequences have also been determined; these sequences correct several errors in an earlier report. The 5.8S rRNAs of the two species differ at a single position. The sequencing results indicate that the species are of recent common ancestry. Molecular evidence that has been interpreted in the past as suggestive of an ancient divergence has been reviewed and found to be consistent with a T. pyriformis complex radiation beginning approximately 30–40 million years ago.