Contrasting heterozygosity‐fitness correlations across life in a long‐lived seabird

Selection is a central force underlying evolutionary change and can vary in strength and direction, for example across time and space. The fitness consequences of individual genetic diversity have often been investigated by testing for multilocus heterozygosity‐fitness correlations (HFCs), but few studies have been able to assess HFCs across life stages and in both sexes. Here, we test for HFCs using a 26‐year longitudinal individual‐based data set from a large population of a long‐lived seabird (the common tern, Sterna hirundo), where 7,974 chicks and breeders of known age were genotyped at 15 microsatellite loci and sampled for life‐history traits over the complete life cycle. Heterozygosity was not correlated with fledging or post‐fledging prospecting probabilities, but was positively correlated with recruitment probability. For breeders, annual survival was not correlated with heterozygosity, but annual fledgling production was negatively correlated with heterozygosity in males and highest in intermediately heterozygous females. The contrasting HFCs among life stages and sexes indicate differential selective processes and emphasize the importance of assessing fitness consequences of traits over complete life histories.     

Thrombospondin-1 inhibits nitric oxide signaling via CD36 by inhibiting myristic acid uptake

Although CD36 is generally recognized to be an inhibitory signaling receptor for thrombospondin-1 (TSP1), the molecular mechanism for transduction of this signal remains unclear. Based on evidence that myristic acid and TSP1 each modulate endothelial cell nitric oxide signaling in a CD36-dependent manner, we examined the ability of TSP1 to modulate the fatty acid translocase activity of CD36. TSP1 and a CD36 antibody that mimics the activity of TSP1 inhibited myristate uptake. Recombinant TSP1 type 1 repeats were weakly inhibitory, but an anti-angiogenic peptide derived from this domain potently inhibited myristate uptake. This peptide also inhibited membrane translocation of the myristoylated CD36 signaling target Fyn and activation of Src family kinases. Myristate uptake stimulated cGMP synthesis via endothelial nitric-oxide synthase and soluble guanylyl cyclase. CD36 ligands blocked myristate-stimulated cGMP accumulation in proportion to their ability to inhibit myristate uptake. TSP1 also inhibited myristate-stimulated cGMP synthesis by engaging its receptor CD47. Myristate stimulated endothelial and vascular smooth muscle cell adhesion on type I collagen via the NO/cGMP pathway, and CD36 ligands that inhibit myristate uptake blocked this response. Therefore, the fatty acid translocase activity of CD36 elicits proangiogenic signaling in vascular cells, and TSP1 inhibits this response by simultaneously inhibiting fatty acid uptake via CD36 and downstream cGMP signaling via CD47.     

The status and conservation of the Cape Gannet Morus capensis

The Cape Gannet Morus capensis is one of several seabird species endemic to the Benguela upwelling ecosystem (BUS) but whose population has recently decreased, leading to an unfavourable IUCN Red List assessment. Application of ‘JARA’ (‘Just Another Red-List Assessment,’ a Bayesian state-space tool used for IUCN Red List assessments) to updated information on the areas occupied by Cape Gannets and the nest densities of breeding birds at their six colonies, suggested that the species should be classified as Vulnerable. However, the rate of decrease of Cape Gannets in their most-recent generation exceeded that of the previous generation, primarily as a result of large decreases at Bird Island, Lambert’s Bay, and Malgas Island, off South Africa’s west coast (the western part of their range). Since the 1960s, there has been an ongoing redistribution of the species from northwest to southeast around southern Africa, and ～70% of the population now occurs on the south coast of South Africa, at Bird Island in Algoa Bay, on the eastern border of the BUS. Recruitment rather than adult survival may be limiting the present population; however, information on the seabird’s demographic parameters and mortality in fisheries is lacking for colonies in the northern part of the BUS. Presently, major threats to Cape Gannet include: substantially decreased availability of their preferred prey in the west; heavy mortalities of eggs, chicks and fledglings at and around colonies, inflicted by Cape Fur Seals Arctocephalus pusillus and other seabirds; substantial disturbance at colonies caused by Cape Fur Seals attacking adult gannets ashore; oiling; and disease.     

Unique oxidative mechanisms for the reactive nitrogen oxide species, nitroxyl anion

The nitroxyl anion (NO-) is a highly reactive molecule that may be involved in pathophysiological actions associated with increased formation of reactive nitrogen oxide species. Angeli's salt (Na2N2O3; AS) is a NO- donor that has been shown to exert marked cytotoxicity. However, its decomposition intermediates have not been well characterized. In this study, the chemical reactivity of AS was examined and compared with that of peroxynitrite (ONOO-) and NO/N2O3. Under aerobic conditions, AS and ONOO- exhibited similar and considerably higher affinities for dihydrorhodamine (DHR) than NO/N2O3. Quenching of DHR oxidation by azide and nitrosation of diaminonaphthalene were exclusively observed with NO/N2O3. Additional comparison of ONOO- and AS chemistry demonstrated that ONOO- was a far more potent one-electron oxidant and nitrating agent of hydroxyphenylacetic acid than was AS. However, AS was more effective at hydroxylating benzoic acid than was ONOO-. Taken together, these data indicate that neither NO/N2O3 nor ONOO- is an intermediate of AS decomposition. Evaluation of the stoichiometry of AS decomposition and O2 consumption revealed a 1:1 molar ratio. Indeed, oxidation of DHR mediated by AS proved to be oxygen-dependent. Analysis of the end products of AS decomposition demonstrated formation of NO2- and NO3- in approximately stoichiometric ratios. Several mechanisms are proposed for O2 adduct formation followed by decomposition to NO3- or by oxidation of an HN2O3- molecule to form NO2-. Given that the cytotoxicity of AS is far greater than that of either NO/N2O3 or NO + O2, this study provides important new insights into the implications of the potential endogenous formation of NO- under inflammatory conditions in vivo.     

Nitroxyl anion regulation of the NMDA receptor

Nitric oxide (NO) is an important regulator of NMDA channel function in the CNS. Recent findings suggest that nitroxyl anion (NO(-)) may also be generated by nitric oxide synthase, which catalyzes production of NO. Using recombinant NMDA receptors (NMDA-r) transfected into human embryonic kidney cells, our data demonstrate that the nitroxyl anion donor, Angeli's salt (AS; Na(2)N(2)O(3)) dramatically blocked glycine-independent desensitization in NMDA-r containing NR1-NR2A subunits. AS did not affect glycine-dependent desensitization, calcium dependent inactivation or glutamate affinity for the NMDA-r. This effect could be mimicked by treatment with DPTA, a metal chelator and was not evident under hypoxic conditions. In contrast, receptors containing the NR1-NR2B subunits demonstrated an approximate 25% reduction in whole cell currents in the presence of AS with no apparent change in desensitization. Our data suggest that the regulation of NMDA-r function by nitroxyl anion is distinctly different from NO and may result in different cellular outcomes compared with NO.     

Analysis of the neuroprotective effects of various nitric oxide donor compounds in murine mixed cortical cell culture

Nitric oxide (NO) has been implicated in both the pathogenesis of and protection from NMDA receptor-mediated neuronal injury. This apparent paradox has been attributed to alternate redox states of nitrogen monoxide, whereby, depending on the redox milieu, nitrogen monoxide can be neuroprotective via nitrosation chemistry or react with superoxide to form secondary toxic species. In our murine mixed cortical cell culture system, the NONOate-type NO donors diethylamine/NO complex sodium (Dea/NO), (Z)-[N-(3-ammoniopropyl)-N-(n-propyl)amino]diazen-1-ium++ +-1,2-diolate (Papa/NO), and spermine/NO complex sodium (Sper/NO), as well as the S-nitrosothiols S-nitroso-L-glutathione (GSNO) and S-nitroso-N-acetyl-D,L-penicillamine (SNAP) (NO+ equivalents), decreased NMDA-induced neuronal injury in a concentration-dependent manner. 8-Bromo-cyclic GMP did not mimic the inhibitory effects of the donors, suggesting that the neuroprotection was not the result of NO-stimulated neuronal cyclic GMP production. Furthermore, neuronal injury induced by exposure of cultures to H2O2 was not altered by the presence of Dea/NO, indicating the absence of a direct antioxidant effect. NONOates did, however, reduce NMDA-stimulated uptake of 45Ca2+, whereas high potassium-induced 45Ca2+ accumulation, a measurement of entry via voltage-gated calcium channels, was unaffected. The parallel reduction of 45Ca2+ accumulation and NMDA neurotoxicity by NONOates mimicked that seen with an NMDA receptor antagonist. Electrochemical measurements of NO via an NO-sensitive electrode demonstrated that neuroprotective concentrations of all donors produced appreciable amounts of NO over the 5-min time frame. Determination of the formation of NO+ equivalents, as assessed by N-nitrosation of 2,3-diaminonaphthylene, revealed little or no observable N-nitrosation by Sper/NO, GSNO, and SNAP with significant N-nitrosation observed by Papa/NO and Dea/NO. However, addition of ascorbate (400 microM) effectively prevented the nitrosation of 2,3-diaminonaphthylene produced by Dea/NO and Papa/NO without altering their neuroprotective properties or their effects on 45Ca2+ accumulation. Present results indicate that the intrinsic NO/NO+ characteristics of NO donor compounds may not be a good predictor of their ability to inhibit NMDA receptor-mediated neurotoxicity at the cellular level.     

Multiple colonization of Madagascar and Socotra by colubrid snakes: evidence from nuclear and mitochondrial gene phylogenies

Colubrid snakes form a speciose group of unclarified phylogeny. Their almost cosmopolitan distribution could be interpreted as a product of plate-tectonic vicariance. We used sequences of the nuclear c-mos, the mitochondrial cytochrome b and the 16S rRNA genes in 41 taxa to elucidate the relationships between the endemic colubrid genera found in Madagascar and in the Socotra archipelago. The well-resolved trees indicate multiple origins of both the Malagasy and the Socotran taxa. The Malagasy genus Mimophis was nested within the Psammophiinae, and the Socotran Hemerophis was closely related to Old World representatives of the former genus Coluber. The remaining 14 genera of Malagasy colubrids formed a monophyletic sister group of the Socotran Ditypophis (together forming the Pseudoxyrhophiinae). Molecular-clock estimates place the divergence of Malagasy and Socotran colubrids from their non-insular sister groups into a time-frame between the Eocene and Miocene. Over-seas rafting is the most likely hypothesis for the origin of at least the Malagasy taxa. The discovery of a large monophyletic clade of colubrids endemic to Madagascar indicates a need for taxonomic changes. The relationship of this radiation to the Socotran Ditypophis highlights the potential of the Indian Ocean islands to act as an evolutionary reservoir for lineages that have become extinct in Africa and Asia.     

Chemical composition and biological activity of the essential oils of Senecio aegyptius var. discoideus Boiss

The essential oil of Senecio aegyptius var. discoideus flowers, leaves, stems and roots were isolated by hydrodistillation. Analysis of the oils by capillary GLC and GLC-mass spectrometry were performed and 34 out of 37 compounds were identified. The main component was isolated and characterized as 1,10-epoxyfuranoeremophilane using a combination of GLC, GLC-MS, and NMR analyses. The oils of flowers, leaves and stems were rich in monoterpene hydrocarbons while the root oil mainly contains furanoeremophilanes. Flower and leaf volatile oils showed significant level of antifungal activity against C. albicans, moderate effect against Gram positive bacteria, however, it has weak activity against Gram negative bacteria. The isolated sesquiterpene (1,10-epoxyfuranoeremophilane) exhibited substantial inhibitory activity against Gram negative bacteria.     

Identification of brain ecto-apyrase as a phosphoprotein

The divalent cation requirements of NOS activity in bovine retina homogenate supernatant were investigated. Supernatants were assayed under standard conditions (in mM: EDTA 0.45, Ca²⁺ 0.25, Mg²⁺ 4.0). In order to investigate the enzyme's dependence on divalent cations, the tissue homogenate was depleted of di- and trivalent cations by passing it over a cation-exchange column (Chelex 100). Surprisingly, NOS activity was 50-100% higher in this preparation. However, addition of either EDTA (33 M) or EGTA (1 mM) almost fully inhibited NOS activity, suggesting a requirement for residual divalent metal cation(s). Phenanthroline or iminodiacetic acid at low concentrations had little effect on activity, suggesting no requirement for Fe²⁺, Zn²⁺ or Cu²⁺. Ca²⁺ had a moderate stimulatory effect, with an optimum activity around 0.01 mM. Mg²⁺ or Mn²⁺ had little effect at concentrations < 0.25 mM. However, in the presence of EDTA, Mn²⁺ or Ca²⁺ markedly stimulated NOS activity with the optimum at 0.1 mM. At high concentrations (> 0.1-0.2 mM), all divalent cations tested (Ba²⁺, Zn²⁺, Co²⁺, Mn²⁺, Mg²⁺, Ca²⁺), as well as La³⁺, dose-dependently inhibited NOS activity. We propose that retinal NOS requires low concentrations of naturally occurring divalent metal ions, most probably Ca²⁺, for optimal activity and is inhibited by high di- and trivalent metal concentrations, probably by competition with Ca²⁺.