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71.
A technique is presented that is useful for selecting conditional-lethal mutants of mycoplasma cells and viruses. The method is based on growing mycoplasma on Millipore filters. Mutants can be isolated directly from filters seeded with mycoplasma. The filters can be transferred from condition to condition, acting as its own “master” and “replica” template. Virus mutants from the non-lytic Mycoplasma Group L1 and L2 viruses can also be picked from filters seeded with infected cells. This method is analogous to classical “replica plating” which is not a practical technique for mycoplasmas. 相似文献
72.
Some effects of aphidicolin have been investigated in relationship to dose, in a permanent cell line, JU56. Inhibition of semi-conservative DNA synthesis occurred at concentrations greater than 3 X 10(-7) M. In this respect the cells were about as sensitive as L1210 and HeLa cells, and more than 10-fold more sensitive than PHA-stimulated human peripheral blood leucocytes. Delay of progress of cells through G2 occurred at concentrations which inhibited synthesis to about 2% of control levels. Chromatid aberrations appeared in cells at concentrations which decreased synthesis to 5%. Synergism with X-rays in the production of chromatid aberrations occurred at doses which reduced semi-conservative synthesis to 40% of control levels. Isochromatid aberrations appeared in cells continuously exposed to aphidicolin in G2 at concentrations which reduced synthesis to 5% of control units. 相似文献
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74.
H. A. Boger P. Mannangatti D. J. Samuvel A. J. Saylor T. S. Bender J. F. McGinty A. M. Fortress V. Zaman P. Huang L. D. Middaugh P. K. Randall L. D. Jayanthi B. Rohrer K. L. Helke A.‐C. Granholm S. Ramamoorthy 《Genes, Brain & Behavior》2011,10(2):186-198
Brain‐derived neurotrophic factor (BDNF) is critical in synaptic plasticity and in the survival and function of midbrain dopamine neurons. In this study, we assessed the effects of a partial genetic deletion of BDNF on motor function and dopamine (DA) neurotransmitter measures by comparing Bdnf+/? with wildtype mice (WT) at different ages. Bdnf+/? and WT mice had similar body weights until 12 months of age; however, at 21 months, Bdnf+/? mice were significantly heavier than WT mice. Horizontal and vertical motor activity was reduced for Bdnf+/? compared to WT mice, but was not influenced by age. Performance on an accelerating rotarod declined with age for both genotypes and was exacerbated for Bdnf+/? mice. Body weight did not correlate with any of the three behavioral measures studied. Dopamine neurotransmitter markers indicated no genotypic difference in striatal tyrosine hydroxylase, DA transporter (DAT) or vesicular monoamine transporter 2 (VMAT2) immunoreactivity at any age. However, DA transport via DAT (starting at 12 months) and VMAT2 (starting at 3 months) as well as KCl‐stimulated DA release were reduced in Bdnf+/? mice and declined with age suggesting an increasingly important role for BDNF in the release and uptake of DA with the aging process. These findings suggest that a BDNF expression deficit becomes more critical to dopaminergic dynamics and related behavioral activities with increasing age. 相似文献
75.
Kwek Yan Chong Richard T. Corlett Darren C. J. Yeo Hugh T. W. Tan 《Biological invasions》2011,13(7):1571-1577
Worldwide spread and establishment of alien plant species continues to accelerate and damage ecological and agricultural systems.
Early warning and prevention of high-risk introductions is the most cost-effective approach to minimise losses while maximising
benefits, and the Australian Weed Risk Assessment (A-WRA) system has been the most well-developed and successful predictive
scheme. However, any system would be limited if the results or scores were confined to the locality of assessment. We compiled
A-WRA scores conducted in four tropical to sub-tropical regions and tested the accuracy of these scores for predicting naturalisations
for a separate well-documented, equatorial, exotic flora where weed risk assessments have never been conducted. Receiver Operating
Characteristic (ROC) curves reflect high accuracies of predictions, comparable to those in other studies. No significant differences
in accuracy were found between each regional subset and the compiled set of scores. Our results show that A-WRA scores assessed
at one locality can be used for others of similar climate, increasing the utility of every species’ assessment. A global database
of A-WRA scores would enable rapid local decision-making in border controls on imported plant species. A growing record of
species assessments would also facilitate monitoring evolutionary and ecological aspects of invasive species. 相似文献
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78.
Marcelo F. Tognelli Agustín M. Abba J. Benjamín Bender Viviana P. Seitz 《Biodiversity and Conservation》2011,20(1):141-151
In this study, we combine species distribution models with a reserve selection approach to assess the degree of representation
of xenarthrans in the existing protected area network of Argentina, and to identify conservation priority areas that may help
expand the current system. Species distribution models were developed from species’ occurrence records using a maximum entropy
algorithm. Maps of species distributions were produced for 15 of the 16 species currently present in the country. To assess
the performance of the existing protected area network in representing all modeled species, and to identify priority areas
to expand the current reserve system, we used the software Zonation. Overall, all species modeled are represented in the existing
protected area network. However, the percentage of their ranges covered by protected areas is very low (average = 6.7%; range = 1.7–17.6%).
To represent at least 5% of the distribution of each species, 8.8% of the country’s area would be needed, and species with
restricted ranges have the greatest increase in representation in this scenario. When 10% of the country is set aside for
conservation, species representation increases considerably, again favoring range-restricted species. Most of the areas identified
as conservation priorities are under strong anthropogenic pressures, including deforestation, agricultural expansion, and
hunting. Our analysis provides a preliminary assessment of conservation priorities for the xenarthrans of Argentina, and we
hope will serve as guideline to focus future conservation assessments at more refined scales. 相似文献
79.
Rene M. van der Zande Michelle Achlatis Dorothea Bender‐Champ Andreas Kubicek Sophie Dove Ove Hoegh‐Guldberg 《Global Change Biology》2020,26(4):2203-2219
Despite recent efforts to curtail greenhouse gas emissions, current global emission trajectories are still following the business‐as‐usual representative concentration pathway (RCP) 8.5 emission pathway. The resulting ocean warming and acidification have transformative impacts on coral reef ecosystems, detrimentally affecting coral physiology and health, and these impacts are predicted to worsen in the near future. In this study, we kept fragments of the symbiotic corals Acropora intermedia (thermally sensitive) and Porites lobata (thermally tolerant) for 7 weeks under an orthogonal design of predicted end‐of‐century RCP8.5 conditions for temperature and pCO2 (3.5°C and 570 ppm above present‐day, respectively) to unravel how temperature and acidification, individually or interactively, influence metabolic and physiological performance. Our results pinpoint thermal stress as the dominant driver of deteriorating health in both species because of its propensity to destabilize coral–dinoflagellate symbiosis (bleaching). Acidification had no influence on metabolism but had a significant negative effect on skeleton growth, particularly when photosynthesis was absent such as in bleached corals or under dark conditions. Total loss of photosynthesis after bleaching caused an exhaustion of protein and lipid stores and collapse of calcification that ultimately led to A. intermedia mortality. Despite complete loss of symbionts from its tissue, P. lobata maintained small amounts of photosynthesis and experienced a weaker decline in lipid and protein reserves that presumably contributed to higher survival of this species. Our results indicate that ocean warming and acidification under business‐as‐usual CO2 emission scenarios will likely extirpate thermally sensitive coral species before the end of the century, while slowing the recovery of more thermally tolerant species from increasingly severe mass coral bleaching and mortality. This could ultimately lead to the gradual disappearance of tropical coral reefs globally, and a shift on surviving reefs to only the most resilient coral species. 相似文献
80.
Ross L. Goldingay Darren G. Quin Orlando Talamo Janice Mentiplay‐Smith 《Ecological Management & Restoration》2020,21(2):131-142
Habitat preferences need to be understood if species are to be adequately managed or conserved. Habitat preferences are presumed to reflect requirements for food, shelter and breeding, as well as interactions with predators and competitors. However, one or more of these requirements may dominate. Tree‐cavity‐dependent wildlife species are one example where shelter or breeding site requirements may dominate. We installed 120 nest boxes across 40 sites to target the vulnerable Brush‐tailed Phascogale (Phascogale tapoatafa) and the non‐threatened Sugar Glider (Petaurus breviceps). The provision of shelter sites where few of quality are available may enable better resolution of habitat preferences. Over three years, we observed the Brush‐tailed Phascogale at 17 sites, whereas the Sugar Glider was observed at 39 sites. We tested four broad hypotheses (H1–H4) relating to habitat that may influence occupancy by these species. There was no influence of hollow (cavity) abundance (H1) on either species suggesting our nest boxes had satisfied their shelter requirements. There was no influence of habitat structure (canopy and tree proximity) (H2) immediately around the nest box trees. We found no influence of distance to the forest edge (H3). Variables at and away from the nest box site that appear to reflect foraging substrates (H4) were influential on the Brush‐tailed Phascogale. Sugar Glider occupancy was only influenced by a single variable at the nest box site. The lack of influence of any other variables is consistent with the very high occupancy observed, suggesting most of the forest habitat is suitable when shelter sites are available. We found no evidence that the Sugar Glider reduced site use by the Brush‐tailed Phascogale. 相似文献