Developmental toxicity of carbon black oil in mice

BACKGROUND: Carbon black oil (CBO) is a refinery side-stream product used to produce asphalt and other commercial products. CBO contains several classes of hydrocarbons, several of which are known to exhibit systemic and gestational toxicities, making this mixture a candidate for causing reproductive toxicity. METHODS: Swiss-Webster mice were administered CBO (300, 350, 400 mg/kg/day) via oral gavage in a dosage volume of 10 microl/g body weight on gestation days (GD) 6-15. Uterine contents were evaluated on GD 18. RESULTS: Treatment with CBO at all dosage levels resulted in a high frequency of maternal clinical symptoms and a decrease in maternal weight gain. Decreased fetal viability was observed, manifested as a decrease in viable implants and, in a high percentage of treated dams, as early resorption of the entire litter. A significant reduction in fetal weight was also observed. However, neither structural malformations nor developmental delays in ossification were observed in any of the living offspring. To minimize maternal toxicity, the dosage range was lowered (100, 200, 300 mg/kg/day), and the concentration was adjusted such that the volume administered to each dam was decreased by 20%. In this trial, the only maternal effect observed was an increase in maternal liver weight at 200 and 300 mg/kg. The fetal lethality effects observed previously were reduced substantially. Nevertheless, the frequency of resorption among all treatment groups was higher statistically than in controls. CONCLUSIONS: These data support the hypothesis that CBO is reproductively toxic in Swiss-Webster mice at oral doses of >/=100 mg/kg/day.     

Out of Africa and back again: nested cladistic analysis of human Y chromosome variation

We surveyed nine diallelic polymorphic sites on the Y chromosomes of 1,544 individuals from Africa, Asia, Europe, Oceania, and the New World. Phylogenetic analyses of these nine sites resulted in a tree for 10 distinct Y haplotypes with a coalescence time of approximately 150,000 years. The 10 haplotypes were unevenly distributed among human populations: 5 were restricted to a particular continent, 2 were shared between Africa and Europe, 1 was present only in the Old World, and 2 were found in all geographic regions surveyed. The ancestral haplotype was limited to African populations. Random permutation procedures revealed statistically significant patterns of geographical structuring of this paternal genetic variation. The results of a nested cladistic analysis indicated that these geographical associations arose through a combination of processes, including restricted, recurrent gene flow (isolation by distance) and range expansions. We inferred that one of the oldest events in the nested cladistic analysis was a range expansion out of Africa which resulted in the complete replacement of Y chromosomes throughout the Old World, a finding consistent with many versions of the Out of Africa Replacement Model. A second and more recent range expansion brought Asian Y chromosomes back to Africa without replacing the indigenous African male gene pool. Thus, the previously observed high levels of Y chromosomal genetic diversity in Africa may be due in part to bidirectional population movements. Finally, a comparison of our results with those from nested cladistic analyses of human mtDNA and beta-globin data revealed different patterns of inferences for males and females concerning the relative roles of population history (range expansions) and population structure (recurrent gene flow), thereby adding a new sex-specific component to models of human evolution.      

Cellular responses to targeted genomic sequence modification using single-stranded oligonucleotides and zinc-finger nucleases

Single-stranded oligonucleotides (ssODNs) and zinc-finger nucleases (ZFNs) are two approaches that are being pursued to achieve sequence specific genome modification. ZFNs induce high rates of homologous recombination (HR) between the target sequence and a given donor by introducing site-specific genomic double-strand breaks (DSBs). The mode of action that is used by ssODNs remains largely unknown, but may involve genomic integration of the ssODNs. In this work, cellular responses following ssODN and ZFN mediated correction of a genomic reporter gene have been investigated in human cells. Comparison of the cell cycle distribution of corrected cells following ssODN or ZFN exposure, established that ssODN corrected cells were arrested in the late S and G2/M cell cycle phases, while ZFN corrected cells displayed normal cell cycle profiles. We demonstrate that after ssODN mediated gene correction, phosphorylation of the damage sensor protein H2AX could be observed in 5.8% and 29% of the corrected cells, using a single copy and a multi copy reporter, respectively. When using the ZFN strategy in a single copy reporter only 1.5% of the corrected cells were positive for γ-H2AX staining. By direct detection of genomic DSBs we establish that the observed cell cycle arrest following ssODN mediated gene correction could be associated with the presence of unrepaired genomic DSBs. Lastly, we establish that although a mutant cellular mismatch repair (MMR) system as expected enhanced ssODN mediated gene correction, the capacity of the ssODN corrected cells to proliferate was not influenced by the MMR system. In conclusion gene correction by means of the ssODN strategy leads to activation of DNA damage signalling and cell cycle arrest due to formation of unrepaired genomic DSBs in a high proportion of the corrected cells. On the contrary, cells corrected using ZFNs displayed normal cell cycle distribution and lower rates of DNA damage.     

Inactivity induces increases in abdominal fat.

Previously, inducing inactivity for 53 h after 21 days of voluntary running resulted in a 25 and 48% increase in epididymal and omental fat pad weights, respectively, while rats continued to eat more than a group that never had access to a running wheel (J Physiol 565: 911-925, 2005). We wanted to test the hypothesis that inactivity, independent of excessive caloric intake, could induce an increase in fat pad mass. Twenty-one-day-old rats were given access to voluntary running wheels for 42-43 days so that they were running approximately 9 km/day in the last week of running, after which wheels were locked for 5, 53, or 173 h (WL5, WL53, WL173) before the rats were killed. During the 53 and 173 h of inactivity, one group of animals was pair fed (PF) to match sedentary controls, whereas the other continued to eat ad libitum (AL). Epididymal and retroperitoneal fat masses were significantly increased in the WL173-PF vs. the WL5 group, whereas epididymal, perirenal, and retroperitoneal fat masses were all significantly increased in the WL173-AL group compared with the WL5 group. Additionally, hyperplasia, and not hypertrophy, of the epididymal fat mass was responsible for the increase at WL173-AL as demonstrated by a significant increase in cell number vs. WL5, with no change in cell diameter or volume. Thus two important findings have been elucidated: 1) increases in measured abdominal fat masses occur in both AL and PF groups at WL173, and 2) adipocyte expansion via hyperplasia occurred with an ad libitum diet following cessation of voluntary running.     

The economics of producing sustainable aviation fuel: a regional case study in Queensland,Australia

The airline industry has a strong interest in developing sustainable aviation fuels, in order to reduce their exposure to increasing oil prices and cost liability for greenhouse gas emissions. The feasibility and cost of producing sustainable biomass‐based jet fuels at a sufficient scale to materially address these issues is an enormous challenge. This paper builds directly on the biophysical study by H.T. Murphy, D.A. O'Connell, R.J. Raison, A.C. Warden, T.H. Booth, A. Herr, A.L. Braid, D.F. Crawford, J.A. Hayward, T. Javonovic, J.G. McIvor, M.H. O'Connor, M.L. Poole, D. Prestwidge, N. Raisbeck‐Brown & L. Rye, In review, which examined a 25 year scale‐up strategy to produce 5% of projected jet fuel demand in Australia in 2020 (470 mL) in the Fitzroy region of Queensland, Australia. The strategy was based on the use of a mixed ligno‐cellulosic biomass feedstock and assumed, for the sake of exploring and quantifying the scenario, a simplified two‐step conversion process – conversion of biomass to crude bio‐oil within the region, and upgrade to jet fuel at a central Brisbane facility. This paper provides details on the costs of production in this scenario, focusing on two different strategies for biomass utilization, and two types of novel small–medium scale conversion technologies. The cost analyses have taken into account technology learning curves, different economies of scale and key cost sensitivities. The cost of biomass‐based jet fuels is estimated to be between 0.70 and 1.90 The airline industry has a strong interest in developing sustainable aviation fuels, in order to reduce their exposure to increasing oil prices and cost liability for greenhouse gas emissions. The feasibility and cost of producing sustainable biomass‐based jet fuels at a sufficient scale to materially address these issues is an enormous challenge. This paper builds directly on the biophysical study by H.T. Murphy, D.A. O'Connell, R.J. Raison, A.C. Warden, T.H. Booth, A. Herr, A.L. Braid, D.F. Crawford, J.A. Hayward, T. Javonovic, J.G. McIvor, M.H. O'Connor, M.L. Poole, D. Prestwidge, N. Raisbeck‐Brown & L. Rye, In review, which examined a 25 year scale‐up strategy to produce 5% of projected jet fuel demand in Australia in 2020 (470 mL) in the Fitzroy region of Queensland, Australia. The strategy was based on the use of a mixed ligno‐cellulosic biomass feedstock and assumed, for the sake of exploring and quantifying the scenario, a simplified two‐step conversion process – conversion of biomass to crude bio‐oil within the region, and upgrade to jet fuel at a central Brisbane facility. This paper provides details on the costs of production in this scenario, focusing on two different strategies for biomass utilization, and two types of novel small–medium scale conversion technologies. The cost analyses have taken into account technology learning curves, different economies of scale and key cost sensitivities. The cost of biomass‐based jet fuels is estimated to be between 0.70 and 1.90 $ L^?1 when the efficiency of conversion of biomass to biocrude and subsequently to aviation fuel is varied by ±10% of published values, with an average value of 1.10 $ L^?1. This is within the range of the projected 2035 conventional jet fuel price of 1.50 $ L^?1. Therefore, biomass‐based jet fuel has the potential to contribute to supply of Australia's jet fuel needs in the future.     

Active coping toward predatory stress is associated with lower corticosterone and progesterone plasma levels and decreased methylation in the medial amygdala vasopressin system

An active coping style displayed under stress – which involves proactive investigatory responses toward environmental threats – has been associated with reduced vulnerability to psychiatric illness. However, the neurobiological determinants of coping styles are not well understood. When rats are exposed to a naturalistic stressor (cat fur) in a group, some individuals in the group show robust active investigation of the stimulus while others show a passive response involving retreat, immobility and close aggregation with conspecifics. Here we explored endocrine and epigenetic correlates of these contrasting coping styles. Male Wistar rats (n = 48) were exposed to cat fur in groups of 4 and the passive and active responders were identified and assessed for endocrine and epigenetic differences. Three days after the final cat fur exposure, active responders had substantially lower plasma levels of corticosterone and progesterone than passive responders. Plasma and testicular testosterone levels did not differ between active and passive responders. Active responders had markedly less methylation of the AVP CGCG promoter region located at base 4970 in the posterodorsal region of the medial amygdala but did not differ in the methylation status of the CCGG sequence located at base 2243. This is in agreement with prior research suggesting that AVP and progesterone act in opposition within the medial amygdala to modulate stress-related behaviors. The present study reports striking endocrine and epigenetic differences between active and passive responders, providing insight into potential systems involved in the manifestation of differing coping styles.     

Probing the Structure of the Mechanosensitive Channel of Small Conductance in Lipid Bilayers with Pulsed Electron-Electron Double Resonance

Mechanosensitive channel proteins are important safety valves against osmotic shock in bacteria, and are involved in sensing touch and sound waves in higher organisms. The mechanosensitive channel of small conductance (MscS) has been extensively studied. Pulsed electron-electron double resonance (PELDOR or DEER) of detergent-solubilized protein confirms that as seen in the crystal structure, the outer ring of transmembrane helices do not pack against the pore-forming helices, creating an apparent void. The relevance of this void to the functional form of MscS in the bilayer is the subject of debate. Here, we report PELDOR measurements of MscS reconstituted into two lipid bilayer systems: nanodiscs and bicelles. The distance measurements from multiple mutants derived from the PELDOR data are consistent with the detergent-solution arrangement of the protein. We conclude, therefore, that the relative positioning of the transmembrane helices is preserved in mimics of the cell bilayer, and that the apparent voids are not an artifact of detergent solution but a property of the protein that will have to be accounted for in any molecular mechanism of gating.     

The Role of Currents and Waves in the Dispersal of Submersed Angiosperm Seeds and Seedlings

We tested the hypothesis that currents, waves, and sediment grain size affect the dispersal of seeds and seedlings of the submersed angiosperms Ruppia maritima, Potamogeton perfoliatus and Stuckenia pectinata. Seed settling velocities and initiation of motion of seeds and seedlings and distance transported were quantified on four sediment types under a range of currents and waves in a flume. The rapid settling velocities of R. maritima and S. pectinata seeds and the increased settling velocity of P. perfoliatus in currents above 8 cm/second suggest that primary dispersal of these species is localized to the general area colonized by their parents. Once settled within a bed, seeds are exposed to weak currents and waves, and are likely to be subject to sediment deposition which may further limit dispersal. In contrast, in restoration projects, the absence of vegetation is likely to make seeds more vulnerable to grazing and transport, and may contribute to the lack of plant establishment. If seeds germinate without being buried, they are susceptible to secondary dispersal at relatively low current velocities and small wave heights due to the drag exerted on the cotyledon. Sand grains tend to stick to the seed coat and rootlet of P. perfoliatus seedlings, perhaps a mechanism to reduce the chances of being displaced following germination. These data reveal the close links between sediment, water flow, and submersed angiosperm seedling establishment; these parameters should be considered when using seeds for restoration of submersed angiosperms.     

The Restoration of Phytophagous Beetles in Species‐Rich Chalk Grasslands

This study focuses on the restoration of chalk grasslands over a 6‐year period and tests the efficacy of two management practices, hay spreading and soil disturbance, in promoting this process for phytophagous beetles. Restoration success for the beetles, measured as similarity to target species–rich chalk grassland, was not found to be influenced by either management practice. In contrast, restoration success for the plants did increase in response to hay spreading management. Although the presence of suitable host plants was considered to dictate the earliest point at which phytophagous beetles could successfully colonized, few beetle species colonized as soon as their host plants became established. Morphological characteristics and feeding habits of 27 phytophagous beetle species were therefore tested to identify factors that limited their colonization and persistence. The lag time between host plant establishment and colonization was greatest for flightless beetles. Beetles with foliage‐feeding larvae both colonized at slower rates than seed‐, stem‐, or root‐feeding species and persisted within the swards for shorter periods. Although the use of hay spreading may benefit plant communities during chalk grassland restoration, it did not directly benefit phytophagous beetles. Without techniques for overcoming colonization limitation for invertebrate taxa, short‐term success of restoration may be limited to the plants only.