Physiologically based pharmacokinetic modeling of perfluoroalkyl substances in the human body

Currently, there are limited data on the levels of perfluoroalkyl substances other than perfluorooctane sulfonic acid and perfluorooctanoic acid in the human body. Most of this information has been extracted from biological monitoring of plasma while the occurrence of perfluoroalkyl substances in other human tissues is rarely studied. The objective of the present study was to develop a physiologically based pharmacokinetic model to assess the concentration of perfluoroalkyl substances in human tissues, based on an existing model previously validated for perfluorooctane sulfonic acid and perfluorooctanoic acid. Experimental data on concentrations of perfluoroalkyl substances in human tissues from individuals in Tarragona County (Catalonia, Spain) were used to estimate the values of some distribution and elimination parameters needed for the simulation. No significant correlations were found between these parameters and the chain lengths. The model was finally validated for five perfluoroalkyl substances.     

Cloning and expression analysis of geosmin synthase gene from Aphanizomenon gracile北大核心CSCD

Geosmin is a secondary metabolite responsible for earthy odors. The occurrence of geosmin has great impact on the quality of water environment. The gene essential for geosmin biosynthesis have been identified in several species. But little is known about the mechanism of geosmin synthesis in Aphanizomenon gracile. This study attempted to clone the gene involved in geosmin biosynthesis of Aphanizomenon gracile a nd a nalyze t he geosmin production u nder d ifferent e nvironments. T he high-efficiency thermal asymmetric interlaced PCR (hiTAIL-PCR) was used to amplify the full-length of geosmin synthase gene from Aphanizomenon gracile (WH-1). Real time PCR (RT-PCR) was applied to quantify the geosmin production in different light and temperature. As a result, geo, a geosmin synthase gene from Aphanizomenon gracile (WH-1) was cloned by hiTAIL-PCR. The full-length open reading frame (ORF) of geo was 2 262 bp, coding for a protein of 753 amino acids. Meanwhile, WH-1 was treated with different environment conditions and mRNA expression levels of geo were quantified by RT-PCR. It was found that low temperature (15 °C), high light intensity (35 μmol m-2 s-1) and continuous light illumination were beneficial to the expression of geo. The successful amplification of geosmin synthase gene verified that hiTAIL-PCR is an effective and simple procedure of low cost. The result provides fundamental knowledge on the monitoring and prevention for odorants.     

Effects of soil nematodes communities on litter decomposition in urban forest of Dalian北大核心CSCD

In order to further expound the effect of soil nematodes on litter decomposition in urban forest, this study investigated the responses of soil nematodes communities to litter decomposition by litterbags technology at different mesh sizes in Dalian National Forest Park. Soil nematodes community composition, decomposition rate of litter and nutrient release were also analyzed. It found a total of 4 418 nematodes from 39 genera. Higher relative density of soil nematodes was found in the bags with 0.1 mm mesh size (1.55 individuals and 7.34 orders per g of dry litter) compared to the bags with 0.02 mm mesh size (0.21 individuals and 0.49 orders per g of dry litter). There were very few soil nematodes in the 0.02 mm litter bags. Thus we regarded that soil nematodes only affected the 0.1 mm litter bags. The mass loss rates as well as C and P release rates was higher in litter bags with 0.1 mm mesh size than in those with 0.02 mm mesh size, indicating a significant influence of soil nematodes on mass loss and nutrient release. The contribution of soil nematodes to the litter mass loss was about 24%. The effect of soil nematodes on the nutrient release rates differed among elements. The soil nematodes had a bigger influence on the release rate of N than that of other elements, whereas the influence on K release rate was the lowest. The results showed that soil nematodes communities has a significant effect on the litter decomposition and nutrient release of the forest litter in Dalian city, especially promoting the mass loss rates and N release rates.     

Quantitative analysis of riparian herbaceous community in Liaohe River Conservation Area and its tributaries北大核心CSCD

Research on community characteristics of riparian herbs is an important scientific basis of riparian vegetation rehabilitation. This study aimed to investigate the species diversity and quantitative characteristics of riparian herbs in Liaohe River Conservation Area and its tributaries. Herbaceous communities were investigated by sample line method. Group average clustering analysis and detrended correspondence analysis (DCA) were used to find the major environmental factors affecting the distribution pattern of riparian herbaceous communities. The result showed altogether 154 herbaceous species, belonging to 40 families and 96 genera. The riparian herbaceous species diversity was found to be correlated to river slope, sinuosity and stream order, being lower in rivers of mountain area than in rivers of plain area, and higher in tributaries than in Liaohe River Conservation Area. Clustering analysis classified the herbaceous communities into 23 types, being dominated by hygrophytes including communities of Echinochloa crusgalli, Oenanthe javanica, Polygonum hydropiper, Murdannia keisak, Artemisia selengensis, Scirpus triqueter, Heleocharis soloniensis, Pycreus sanguinolentus, Cyperus fuscus, Phragmites australis, Polygonum amphibium, Carex diandra + Artemisia selengensis and Carex diandra + Rorippa islandica. Correlation analysis between DCA ordination axes and environmental factors showed that the altitude, river slope, sinuosity and stream level were the major environmental factors affecting the distribution pattern of herbaceous communities in the riparian zone of Liaohe River Conservation Area and its tributaries. The results of CCA showed that the contribution ratio of stream level was the highest, followed by altitude and slope, with sinuosity the last. The results suggested that riparian herbaceous characteristics are affected by the comprehensive force of altitude, river slope, sinuosity and stream order, and that Calamagrostis epigeios, Triarrhena sacchariflora and Phragmites australis are suitable species for riparian vegetation rehabilitation.     

Microbial communities biostimulated by ethanol during uranium (VI) bioremediation in contaminated sediment as shown by stable isotope probing

Stable isotope probing (SIP) was used to identify microbes stimulated by ethanol addition in microcosms containing two sediments collected from the bioremediation test zone at the US Department of Energy Oak Ridge site, TN, USA. One sample was highly bioreduced with ethanol while another was less reduced. Microcosms with the respective sediments were amended with ¹³C labeled ethanol and incubated for 7 days for SIP. Ethanol was rapidly converted to acetate within 24 h accompanied with the reduction of nitrate and sulfate. The accumulation of acetate persisted beyond the 7 d period. Aqueous U did not decline in the microcosm with the reduced sediment due to desorption of U but continuously declined in the less reduced sample. Microbial growth and concomitant ¹³C-DNA production was detected when ethanol was exhausted and abundant acetate had accumulated in both microcosms. This coincided with U(VI) reduction in the less reduced sample. ¹³C originating from ethanol was ultimately utilized for growth, either directly or indirectly, by the dominant microbial community members within 7 days of incubation. The microbial community was comprised predominantly of known denitrifiers, sulfate-reducing bacteria and iron (III) reducing bacteria including Desulfovibrio, Sphingomonas, Ferribacterium, Rhodanobacter, Geothrix, Thiobacillus and others, including the known U(VI)-reducing bacteria Acidovorax, Anaeromyxobacter, Desulfovibrio, Geobacter and Desulfosporosinus. The findings suggest that ethanol biostimulates the U(VI)-reducing microbial community by first serving as an electron donor for nitrate, sulfate, iron (III) and U(VI) reduction, and acetate which then functions as electron donor for U(VI) reduction and carbon source for microbial growth.     

No evidence for genetic differentiation between Antarctic limpet Nacella concinna morphotypes

The extent to which genetic divergence can occur in the absence of physical barriers to gene flow is currently one of the most controversial topics in evolutionary biology, with implications for our understanding of speciation, phenotypic plasticity and adaptive potential. This is illustrated by a recent study reporting a surprising pattern of genetic differentiation between intertidal and subtidal morphotypes of the broadcast-spawning Antarctic limpet Nacella concinna. To explore this further, we collected almost 400 Antarctic limpets from four depths (intertidal, 6, 15 and 25 m) at Adelaide island, Antarctica, and conducted a combined morphometric and genetic analysis using 168 polymorphic amplified fragment length polymorphism (AFLP) loci. Morphological analysis revealed not only pronounced differences between the two morphotypes, but also a continuous cline in shell shape from the intertidal zone down to 25 m depth, suggesting that the distinction between the morphotypes may be artificial. Moreover, genetic analysis using both F _st and a Bayesian analogue found no evidence for differentiation either between the two morphotypes or by depth, and a Bayesian cluster analysis did not detect any cryptic genetic structure. Our findings lend support to the notion that limpets can be phenotypically highly plastic, although further studies are required to determine unequivocally whether there is any genetic basis to the observed variation in shell morphology.     

The effect of plant secondary metabolites on the interplay between the internal and external environments of marsupial folivores

Most woody plants contain a diverse array of plant secondary metabolites (PSMs) that deter vertebrate herbivores. However, mammalian folivores have evolved a complex of physiological and behavioural strategies to counter these compounds, leading to the development of an “evolutionary arms race”. Marsupial folivores are ideal models to investigate the role of PSMs in the interaction between the external foraging environment and the digestive physiology of mammalian herbivores, as we have a very strong understanding of the diversity and modes of action of PSMs in Eucalyptus, as well as the mechanisms by which animals overcome the effects of these compounds. Studies of marsupial folivores have benefited from the facts that: these herbivores subsist on relatively poor quality diets; they include feeding types from specialist species such as the koala, to generalists; and life history factors such as maternal investment in reproduction can be measured more easily than in eutherians. Here, we describe patterns of spatial variation in the types and distributions of plant secondary metabolites in Australian forests and discuss how this variation influences foraging behaviour, habitat selection and life history strategies in arboreal, folivorous marsupials. We also provide a summary of our understanding of the mechanisms by which marsupials detect and regulate their intake of toxic compounds. While our examples are drawn largely from studies of the interaction between marsupials and Eucalyptus, this knowledge is applicable to advancing our understanding of interactions in plant–mammal systems more broadly. We also identify and discuss key areas that should be the focus of future research.     

Persistence models for mark-recapture

The stable of models available for analyzing mark-recapture data (Otis et al. Wild Momogr 66:135, 1978) includes those having behavioral characteristics, time variation, heterogeneity, along with combinations of those characteristics. This paper proposes use of a series of models based on the persistence model of Ramsey and Usner (Biometrics 59:331–339, 2003). We show that persistence can be modeled in combination with behavior and with time variation. We apply the persistence model to situations in which capture occasions are not equally-spaced in time. Two case studies illustrate the use of these extended persistence models.     

Digit ratio (2D:4D) and dominance rank in female rhesus macaques (Macaca mulatta)

Female rhesus macaques exhibit matrilineal dominance structures, and high dominance rank confers fitness benefits across a lifetime and across generations. Rank effects are “inherited” through social processes that are well understood; however, biological mechanisms that might impact these processes are not well known. Recently, it has been shown that prenatal androgens appear to be implicated in supporting dominance rank hierarchies in some mammals. In humans, interindividual differences in the second (index) to fourth (ring) digit ratio (2D:4D) have been linked indirectly to variation in prenatal androgens, with low 2D:4D in both sexes associated with higher inferred prenatal androgen effects. 2D:4D has also been related to dominant social behavior and has been shown to co-vary with social systems across nonhuman primate species. Here, we investigate how 2D:4D co-varies with socially inherited dominance rank in female rhesus macaques. Low 2D:4D was associated with higher-ranking females, while higher 2D:4D was associated with lower-ranking females. Similar relationships were also shown between ranked families within matrilines. This is the first study to show such a relationship between 2D:4D and dominance rank in a nonhuman primate and suggests that prenatal androgen effects could be involved in the maintenance of dominance rank in female cercopithecine primates.     

Estimation of age at maturation and growth of Atlantic green turtles (Chelonia mydas) using skeletochronology

Despite the vast amount of research on threatened and endangered green turtle populations, some uncertainty regarding stage durations, growth rates, and age at maturation remains. We used skeletochronology to address this gap in knowledge for green turtle populations in the North Atlantic Ocean that use coastal waters along the southeastern U.S. as developmental habitat. Oceanic stage duration was estimated at 1–7 years ( [`(\textX)] \overline{\text{X}}  = 3 years). Several growth models, including von Bertalanffy, logistic, Gompertz, and power functions were evaluated for describing sex-specific length-at-age data. Ages at maturation estimated using mean size at nesting for females from each genetic sub-population contributing juveniles to this neritic foraging area were 44 years (Florida), 42.5 years (Costa Rica), and 42 years (Mexico), which were higher than previously reported ages. This implies that nesting populations comprising primarily individuals utilizing foraging grounds in the southeastern U.S. may take longer to recover than previously estimated.