Bafilomycin A1 is a potassium ionophore that impairs mitochondrial functions

Novel activities of bafilomycin A1, a macrolide antibiotic known as an inhibitor of V-ATPases, were discovered. Bafilomycin A1 induced uptake of potassium ions by energized mitochondria and caused mitochondrial swelling, loss of membrane potential, uncoupling of oxidative phosphorylation, inhibition of the maximal respiration rates, and induced pyridine nucleotide oxidation. The mitochondrial effects provoked by nanomolar concentrations of bafilomycin A1 were connected to its activity as a potent, K⁺-specific ionophore. The K⁺ ionophoric activity of bafilomycin A1 was observed also in black lipid membranes, indicating that it was an inherent property of the bafilomycin A1 molecule. It was found that bafilomycin A1 is a K⁺ carrier but not a channel former. Bafilomycin A1 is the first and currently unique macrolide antibiotic with K⁺ ionophoric properties. The novel properties of bafilomycin A1 may explain some of the biological effects of this plecomacrolide antibiotic, independent of V-ATPase inhibition.     

A quantitative model for linking Na+/Ca2+ exchanger to SERCA during refilling of the sarcoplasmic reticulum to sustain [Ca2+] oscillations in vascular smooth muscle

We have developed a quantitative model for the creation of cytoplasmic Ca²⁺ gradients near the inner surface of the plasma membrane (PM). In particular we simulated the refilling of the sarcoplasmic reticulum (SR) via PM–SR junctions during asynchronous [Ca²⁺]_i oscillations in smooth muscle cells of the rabbit inferior vena cava. We have combined confocal microscopy data on the [Ca²⁺]_i oscillations, force transduction data from cell contraction studies and electron microscopic images to build a basis for computational simulations that model the transport of calcium ions from Na⁺/Ca²⁺ exchangers (NCX) on the PM to sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase (SERCA) pumps on the SR as a three-dimensional random walk through the PM–SR junctional cytoplasmic spaces. Electron microscopic ultrastructural images of the smooth muscle cells were elaborated with software algorithms to produce a very clear and dimensionally accurate picture of the PM–SR junctions. From this study, we conclude that it is plausible and possible for enough Ca²⁺ to pass through the PM–SR junctions to replete the SR during the regenerative Ca²⁺ release, which underlies agonist induced asynchronous Ca²⁺ oscillations in vascular smooth muscle.     

Noninvasive Estimation of Black Bear Abundance Incorporating Genotyping Errors and Harvested Bear

ABSTRACT Estimating black bear (Ursus americanus) population size is a difficult but important requirement when justifying harvest quotas and managing populations. Advancements in genetic techniques provide a means to identify individual bears using DNA contained in tissue and hair samples, thereby permitting estimates of population abundance based on established mark-capture-recapture methodology. We expand on previous noninvasive population-estimation work by geographically extending sampling areas (36,848 km²) to include the entire Northern Lower Peninsula (NLP) of Michigan, USA. We selected sampling locations randomly within biologically relevant bear habitat and used barbed wire hair snares to collect hair samples. Unlike previous noninvasive studies, we used tissue samples from harvested bears as an additional sampling occasion to increase recapture probabilities. We developed subsampling protocols to account for both spatial and temporal variance in sample distribution and variation in sample quality using recently published quality control protocols using 5 microsatellite loci. We quantified genotyping errors using samples from harvested bears and estimated abundance using statistical models that accounted for genotyping error. We estimated the population of yearling and adult black bears in the NLP to be 1,882 bears (95% CI = 1,389-2,551 bears). The derived population estimate with a 15% coefficient of variation was used by wildlife managers to examine the sustainability of harvest over a large geographic area.     

West Nile Virus Exposure in Black Bears of Northeastern Wisconsin

ABSTRACT Knowledge of the distribution and pathology of West Nile virus (WNV) in black bears is a necessary tool that allows wildlife managers to implement a management plan, set harvest quotas, and relocate nuisance bears. We studied the presence and significance of WNV titers in free-roaming black bears (Ursus americanus) in northeastern Wisconsin between February 2003 and March 2005. Serum neutralizing antibodies to WNV, with confirmation by plaque-reduction neutralization test to both WNV and Saint Louis encephalitis, identified exposure in 13 of 74 (17.6%) bears. This compares with a 6% infection rate in black bears in Virginia and 22% in European brown bears (Ursus arctos). Pathologic effects from exposure to WNV were not seen in any of the black bears studied.     

Space Use and Habitat Selection by Female Louisiana Black Bears in the Tensas River Basin of Louisiana

Abstract: Studies of space use and habitat selection of endangered species are useful for identifying factors that influence fitness of individuals and viability of populations. However, there is a lack of published information regarding these behaviors for the federally threatened Louisiana black bear (Ursus americanus luteolus). We documented space use and habitat selection for 28 female black bears in 2 subpopulations of the Tensas River Basin population in northeast Louisiana, USA. The Tensas subpopulation inhabits a relatively large (>300-km²) contiguous area of bottomland hardwood forest, whereas the Deltic subpopulation exists mainly in 2 small (<7-km²) forested patches surrounded by an agricultural matrix. Females on Deltic maintained smaller seasonal and annual home ranges than females on Tensas (all P < 0.04), except for females with cubs during spring. On Tensas, females with cubs maintained smaller home ranges than females without cubs during spring (P = 0.01), but we did not detect this difference on Deltic or in other seasons. Females on Tensas and Deltic exhibited differences in habitat selection when establishing home ranges and within home ranges (P < 0.001). Deltic females selected mature bottomland hardwood forests and avoided agricultural habitats at both spatial scales. Tensas females selected a mixture of swamps, mature and regenerating forests, and exhibited variation in selection across scale, season, and reproductive status. We suggest that differences in space use and habitat selection between Tensas and Deltic are at least partially due to habitat differences at the landscape (i.e., amount of forested habitat) and patch (i.e., food availability) scales. Our results contribute to the understanding of factors that influence space use and habitat selection by black bears and provide specific information on habitat types selected by Louisiana black bears to agencies involved in habitat protection and restoration for this threatened subspecies.     

无量山大寨子黑长臂猿(Nomascus concolor jingdongensis)种群生存力

据2003年9月至2005年9月,对云南中部无量山大寨子黑长臂猿种群（5个群体）进行了观察,获得了群体大小、配偶体制、繁殖间隔、环境容纳量、死亡率、灾害的发生频率等种群参数,并结合近缘种的一些相关数据,利用旋涡模型（Vortex 914）,对无量山大寨子地区黑长臂猿亚种群的动态进行了模拟分析。结果显示：大寨子亚种群是一个具有很强的潜在繁殖力的种群,如果没有偷猎,亚种群在100a之内不会灭绝,并且能迅速达到环境容纳量。但是每年如果有1只成年雄性和1只成年雌性被猎杀,该种群将会在第78年灭绝,且灭绝概率为100%。不同程度的死亡率对种群影响不大,但高死亡率显著延缓了种群到达环境容纳量的时间。环境容纳量对种群遗传多样性损失具有重要的影响,在没有猎杀的情况下,种群的长期存活需要一个较大的环境容纳量。因此,在黑长臂猿受到严格保护、且栖息地主要在保护区内的今天,严密监控火灾的发生,限制牲畜进入林区等人为干扰的影响,保护好黑长臂猿栖息地是首要工作之一。但如果能使其栖息地周围的森林植被得到恢复,增加其栖息范围,将有利于该地区黑长臂猿的发展。     

北京十渡自然保护区越冬黑鹳的种群生态调查

为了解黑鹳在北京地区越冬的生态特点,于2004年1月至2007年3月采用直接观察法对北京市拒马河自然保护区越冬黑鹳的数量、栖息地选择和取食规律进行了观察。结果表明拒马河流域已成为北京地区越冬黑鹳稳定的栖息地,种群数量超过20只。越冬聚群从11月开始,分群时间为次年2月。取食地相对集中,取食活动在越冬初期以上午和中午为主,中期以下午为主,末期则分为早晚两个时段。干旱和人为活动导致的适宜取食地减少是影响黑鹳生存的主要因素。     

An Overview of the Development,Status, and Application of Equilibrium Partitioning Sediment Benchmarks for PAH Mixtures

This article provides an overview of the development, theoretical basis, regulatory status, and application of the U.S. Environmental Protection Agency's (USEPA's) Equilibrium Partitioning Sediment Benchmarks (ESBs) for PAH mixtures. ESBs are compared to other sediment quality guidelines (SQGs) for PAHs. Data that examine the ability of the ESB approach to predict toxic effects to invertebrates are discussed. A USEPA draft methodology for the development of site-specific ESBs that takes into account the limited bioavailability of PAHs at certain sites is discussed. Research is presented that compares the ability of ESBs and site-specific ESBs to predict the toxicity of sediments collected from manufactured gas plants (MGPs). Site-specific ESBs that accounted for adsorption of PAHs onto black carbon were better predictors of the toxicity of sediments from MGP sites than ESBs that did not account for adsorption to black carbon.     

Activation of quiescent infections by postharvest pathogens during transition from the biotrophic to the necrotrophic stage

The evolution of bacterial pathogens from nonpathogenic ancestors is marked principally by the acquisition of virulence gene clusters on plasmids and pathogenicity islands via horizontal gene transfer. The flip side of this evolutionary force is the equally important adaptation of the newly minted pathogen to its new host niche. Pathoadaptive mutations take the form of modification of gene expression such that the pathogen is better fit to survive within the new niche. This mini-review describes the concept of pathoadaptation by loss of gene function. In this process, genes that are no longer compatible with the novel lifestyle of the pathogen are selectively inactivated either by point mutation, insertion, or deletion. These genes are called 'antivirulence genes'. Selective pressure sometimes leads to the deletion of large regions of the genome that contain antivirulence genes generating 'black holes' in the pathogen genome. Inactivation of antivirulence genes leads to a pathogen that is highly adapted to its host niche. Identification of antivirulence genes for a particular pathogen can lead to a better understanding of how it became a pathogen and the types of genetic traits that need to be silenced in order for the pathogen to colonize its new host niche successfully.