Persistent organochlorine pesticides detected in blood and tissue samples of vultures from different localities in South Africa

Gaschromatography was used to establish the presence of quantifiable residues of 14 persistent chlorinated hydrocarbon pollutants in whole blood, clotted blood, heart, kidney, liver and muscle samples obtained from individual African whitebacked (Pseudogyps africanus), Cape griffon (Gyps coprotheres) and Lappetfaced (Torgos tracheliotos) vultures from different localities in South Africa. The levels of pesticides measured in whole blood samples of live specimens were compared between nestlings from two natural breeding colonies, adults from a wildlife area and birds held in captivity. Statistically significant (P<0.05) differences between populations were detected in geometric means calculated for γ-BHC (lindane), α(cis)-chlordane and α-endosulfan. Five of the organochlorine contaminants displayed significant variations between concentrations detected in the clotted blood, organs and muscles excised from vulture carcasses. This includes residues of γ-BHC, α-chlordane, dieldrin, β-endosulfan and heptachlor epoxide. Values of the respective biocides measured in vulture samples were generally low in comparison to results documented for a number of avian species. Although no threat is posed by any of the organochloride pesticides, continual monitoring of especially breeding colonies is recommended. Furthermore, the suitability of African whitebacked vulture nestlings as basic bioindicators is highly advocated.     

POLLEN PERFORMANCE AND SEX-RATIO EVOLUTION IN A DIOECIOUS PLANT

There has been a proliferation of studies, in a variety of taxa, that have detected sex-linked or cytoplasmic genes that enhance their own transmission via sex-ratio distortion. One of the most important parameters influencing the dynamics of these elements is the magnitude of their transmission advantage. In many systems, the mechanism of sex-ratio distortion is to abort X- or Y-bearing gametes. With this mechanism, the transmission advantage associated with sex-ratio distortion is diminished when the production of male gametes limits offspring production or when competition among the gametes of different males is intense. In this study, we analyzed the outcome of pollen competition between males that produced different sex ratios in the dioecious plant, Silene alba, and estimated how the sex-ratio bias influenced the transmission properties of the sex chromosomes. We varied the intensity of pollen competition by controlling the quantity of pollen used in crosses and used a combination of single-male pollinations and pollen mixtures to evaluate the effects of multiple paternity. Paternity in pollen mixtures was estimated using allozymes. Sex-ratio bias was directly influenced by the quantity of pollen, but the magnitude of this effect was small. The relative performance of pollen from different males varied substantially, especially when there was multiple paternity. Specifically, males with biased sex ratios sired far fewer offspring of either sex in pollen mixtures. In crosses involving single males, however, these “sex-ratio” males produced the same number of offspring as other males, so the female bias caused a significant transmission advantage for X-linked genes. X-linked genes could enhance their transmission via sex-ratio distortion in Silene populations, but the magnitude of this transmission advantage will depend on the ecological circumstances that influence the opportunity for multiple paternity.     

Potential long-acting contraceptive agents: esters of testosterone with alkoxy- and halogeno-substituted carboxylic acids

The chemical synthesis and physical data of several new esters of testosterone (17 beta-hydroxyandrost-4-en-3-one), which contain either a halogeno or an alkoxy substituent in the acid chain, are reported.     

Thermodynamics of transfer ribonucleic acids: the effect of sodium on the thermal unfolding of yeast tRNAPhe.

The thermal unfolding of yeast phenylalanine-specific tRNA (tRNA^Phe) has been calorimetrically investigated at several salt concentrations in the absence of magnesium. Application of the deconvolution theory of macromolecular conformational transitions allows calculation of the thermodynamic parameters of unfolding. It is demonstrated that the unfolding of tRNA^Phe occurs in a sequential fashion and that four separate transitions or five macromolecular thermodynamic states exist in the temperature range 8–72°C under the experimental conditions of these studies (0.067–0.52M Na⁺). The enthalpy and entropy changes between states and the relative population of each state as a function of temperature and salt concentration have been obtained. Sodium stabilizes the low-temperature conformations of tRNA^Phe. The increase in the melting temperatures of each transition is shown to be linearly dependent on the logarithm of sodium concentration. These results allow calculation of the “phase” diagram for the transitions as a function of salt concentration.     

Contributions of phenylalanine 335 to ligand recognition by human surfactant protein D: ring interactions with SP-D ligands

Surfactant protein D (SP-D) is an innate immune effector that contributes to antimicrobial host defense and immune regulation. Interactions of SP-D with microorganisms and organic antigens involve binding of glycoconjugates to the C-type lectin carbohydrate recognition domain (CRD). A trimeric fusion protein encoding the human neck+CRD bound to the aromatic glycoside p-nitrophenyl-alpha-D-maltoside with nearly a log-fold higher affinity than maltose, the prototypical competitor. Maltotriose, which has the same linkage pattern as the maltoside, bound with intermediate affinity. Site-directed substitution of leucine for phenylalanine 335 (Phe-335) decreased affinities for the maltoside and maltotriose without significantly altering the affinity for maltose or glucose, and substitution of tyrosine or tryptophan for leucine restored preferential binding to maltotriose and the maltoside. A mutant with alanine at this position failed to bind to mannan or maltose-substituted solid supports. Crystallographic analysis of the human neck+CRD complexed with maltotriose or p-nitrophenyl-maltoside showed stacking of the terminal glucose or nitrophenyl ring with the aromatic ring of Phe-335. Our studies indicate that Phe-335, which is evolutionarily conserved in all known SP-Ds, plays important, if not critical, roles in SP-D function.     

Relative effects of nocturnal vs diurnal pollinators and distance on gene flow in small Silene alba populations

Silene alba exists in natural metapopulations throughout its range and is visited by a suite of both diurnal and nocturnal pollinators. Pollen-mediated gene flow may help reduce genetic isolation of subpopulations. Here, we compared the relative effects of nocturnal vs diurnal pollinators on pollen-mediated gene flow in subpopulations separated by two distance treatments. We established populations consisting of genetically marked individuals in an old field in Tennessee (USA). Electrophoretic examination of seedlings produced by plants exposed to nocturnal, diurnal and control pollinator treatments and separated by either 20 or 80 m allowed us to directly measure pollen-mediated gene flow. Gene flow was more common between populations separated by only 20 m. Nocturnal pollinators were responsible for most gene flow between populations, regardless of distance. Diurnal pollinators played only a small role in pollen-mediated gene flow. The results suggest that nocturnal pollinators are better than diurnal pollinators at moving pollen between small S. alba subpopulations. However, their effectiveness declines as the distance between subpopulations increases, making them relatively ineffective at moving genes between isolated subpopulations.     

Microbial communities and fecal indicator bacteria associated with Cladophora mats on beach sites along Lake Michigan shores

A high biomasses of Cladophora, a filamentous green alga, is found mainly during the summer along the shores of Lake Michigan. In this study, the abundance and persistence of the fecal indicator bacterium Escherichia coli and sulfate-reducing bacteria (SRB) on Cladophora mats collected at Lake Michigan beaches were evaluated using both culture-based and molecular analyses. Additionally, 16S rRNA gene cloning and sequencing were used to examine the bacterial community composition. Overall, E. coli was detected in all 63 samples obtained from 11 sites, and the average levels at most beaches ranged from 2,700 CFU/100 g (wet weight) of Cladophora to 7,500 CFU/100 g of Cladophora. However, three beaches were found to have site average E. coli densities of 12,800, 21,130, and 27,950 CFU/100 g of Cladophora. The E. coli levels in the lake water collected at the same time from these three sites were less than the recommended U.S. Environmental Protection Agency limit, 235 CFU/100 ml. E. coli also persisted on Cladophora mats in microcosms at room temperature for more than 7 days, and in some experiments it persisted for as long as 28 days. The SRB densities on Cladophora mats were relatively high, ranging from 4.4x10(6) cells/g (6.64 log CFU/g) to 5.73x10(6) cells/g (6.76 log CFU/g) and accounting for between 20% and 27% of the total bacterial counts. Partial sequences of the 16S rRNA gene clones revealed a phylogenetically diverse community, in which the Cytophaga-Flavobacterium-Bacteroides cluster and the low-G+C-content gram-positive bacteria were the dominant organisms, accounting for 40% and 12.8%, respectively, of the total clone library. These results further reveal the potential public health and ecological significance of Cladophora mats that are commonly found along the shoreline of Lake Michigan, especially with regard to the potential to harbor microorganisms associated with fecal pollution and odor-causing bacteria.     

Hematology, serum chemistry, and serology of Galápagos penguins (Spheniscus mendiculus) in the Galápagos Islands, Ecuador

The Galápagos penguin (Spheniscus mendiculus) is an endangered species endemic to the Galápagos Islands, Ecuador. In 2003 and 2004, 195 penguins from 13 colonies on the islands of Isabela and Fernandina in the Galápagos archipelago were examined. Genetic sexing of 157 penguins revealed 62 females and 95 males. Hematology consisted of packed cell volume (n = 134), white blood cell differentials (n = 83), and hemoparasite blood smear evaluation (n = 114). Microfilariae were detected in 22% (25/114) of the blood smears. Female penguins had significantly higher eosinophil counts than males. Serum chemistry on 83 penguins revealed no significant differences between males and females. Birds were seronegative to avian paramyxovirus type 1-3, avian influenza virus, infectious bursal disease virus, Marek's disease virus (herpes), reovirus, avian encephalomyelitis virus, and avian adenovirus type 1 and 2 (n = 75), as well as to West Nile virus (n = 87), and Venezuelan, western and eastern equine encephalitis viruses (n = 26). Seventy-five of 84 (89%) penguins had antibodies to Chlamydophila psittaci but chlamydial DNA was not detected via polymerase chain reaction in samples from 30 birds.