The evolution of lignified xylem allowed for the efficient transport of water under tension, but also exposed the vascular network to the risk of gas emboli and the spread of gas between xylem ...conduits, thus impeding sap transport to the leaves. A well‐known hypothesis proposes that the safety of xylem (its ability to resist embolism formation and spread) should trade off against xylem efficiency (its capacity to transport water). We tested this safety–efficiency hypothesis in branch xylem across 335 angiosperm and 89 gymnosperm species. Safety was considered at three levels: the xylem water potentials where 12%, 50% and 88% of maximal conductivity are lost. Although correlations between safety and efficiency were weak (r² < 0.086), no species had high efficiency and high safety, supporting the idea for a safety–efficiency tradeoff. However, many species had low efficiency and low safety. Species with low efficiency and low safety were weakly associated (r² < 0.02 in most cases) with higher wood density, lower leaf‐ to sapwood‐area and shorter stature. There appears to be no persuasive explanation for the considerable number of species with both low efficiency and low safety. These species represent a real challenge for understanding the evolution of xylem.
1. Shrubs in fire prone chaparral communities have evolved different life history types in response to fire. A key to understanding the evolution of life history type differences is to understand how ...physiological traits are linked to differences in life history type. Vascular adaptations are important for delivering an efficient and stable water supply to evergreen chaparral shrub leaves. This study tested for a link between vascular physiology and life history type in chaparral shrubs. 2. Chaparral shrub species along the south-western coast of North America survive wildfire by three different life histories. Non-sprouters are killed by fire and re-establish exclusively through germination of fire-stimulated seeds, facultative sprouters re-establish by a combination of vegetative sprouting and fire-stimulated seeds, and obligate sprouters re-establish exclusively by vegetative sprouting because their seeds do not survive fire. Non-sprouters and facultative sprouters establish seedlings in the open canopy post fire environment, whereas obligate sprouters establish seedlings in the shady understory of the mature chaparral canopy. 3. Seedlings of nine species (Rhamnaceae) representing three each of the different life history types were grown in deep containers in a common garden under treatments of sun and shade. Hydraulic conductance was measured using a high-pressure flow meter for all organs, and a vacuum technique was used to measure conductance of fine and woody roots. We predicted that non-sprouters would exhibit greater hydraulic efficiency than the sprouting species, and that facultative sprouters would be more efficient than the shade tolerant obligate sprouters. 4. Non-sprouters had the greatest hydraulic conductance per unit leaf and sapwood area at the whole seedling level, whereas facultative and obligate sprouters were not different. Comparing hydraulic conductance across major organs (from fine roots to leaves) showed that the hydraulic system was well coordinated. At the whole seedling level, the root system was more of a bottleneck than the shoot system. This pattern was consistent with high resistance extraxylary pathways in roots and differences in root architecture. 5. The greater hydraulic efficiency of the non-sprouter life history type is attributed to its post-fire pioneering habit and may partially explain the relatively high speciation in the non-sprouters. Lower hydraulic efficiency is associated with a sprouting life history and greater shade tolerance. The seedling root systems represent a hydraulic bottleneck that may place roots under especially intense selection.
Xylem safety and efficiency were analyzed for stems of evergreen shrubs that inhabit fynbos communities in the Mediterranean-type climate region of South Africa. We hypothesized that species with ...different life history types would differ in xylem function on account of their different regeneration niches. Comparisons were made among postfire nonsprouters, facultative sprouters, obligate sprouters, and opportunists. Measurements included xylem resistance to water stress–induced cavitation (xylem safety) and xylem-specific hydraulic conductivity (xylem efficiency) at a dry site and at a wetter site. Life history types differed in hydraulic traits: xylem safety was greater in life history types with disturbance-dependent recruitment. By contrast, water stress resistance was lowest in postfire obligate resprouters that recruit seedlings during fire-free intervals in the litter layer of shady microsites. Among life history types, greater xylem safety came at the cost of reduced hydraulic efficiency. This pattern was also observed between field sites, with most taxa from the drier site having greater levels of cavitation resistance and lower levels of xylem-specific hydraulic conductivity than taxa from the wetter site. We conclude that xylem traits are linked to differences in life history types in fynbos species.
Despite increasing use of cell-based assays in high-throughput screening (HTS) and lead optimization, one challenge is the adequate supply of high-quality cells expressing the target of interest. To ...this end, cell lines stably expressing targets are often established, maintained, and scaled up by cell culture. These steps require large investments of time and resources. Moreover, significant variability invariably occurs in cell yield, viability, expression levels, and target activities. In particular, stable expression of targets such as transient receptor potential A1 (TRPA1) causes toxicity, cell line degeneration, and loss of functional activity. Therefore, in an effort to identify TRPA1 antagonists, the authors used large-scale transiently transfected (LSTT) cells, enabling rapid establishment of assays suitable for HTS. LSTT cells, which could- be stored frozen for a long period of time (e.g., at least 42 weeks), retained TRPA1 protein expression and could be easily revived to produce robust and consistent signals in calcium influx and electrophysiological assays. Using cells from a single transfection, a chemical library of 700,000 compounds was screened, and TRPA1 antagonists were identified. The use of LSTT circumvented issues associated with stable TRPA1 expression, increased flexibility and consistency, and greatly reduced labor and cost. This approach will also be applicable to other pharmaceutical targets.
A review of the epidemiologic aspects of the New World leishmaniases, including their known geographic distribution, etiologic agents, zoonotic reservoirs, and insect vectors, based on biological and ...molecular characterization of Leishmania isolates is presented. Data summarized in this paper on parasite taxonomy and geographic distribution come from our studies of greater than 1,000 New World Leishmania isolates identified by species-specific monoclonal antibodies using an indirect radioimmune binding assay and from scientific literature.
Introduction Treatment completion is the cornerstone of tuberculosis (TB) control strategy globally. Although the majority of reported TB cases in the U.S. have documented treatment completion, ...individuals diagnosed while incarcerated are less likely to have documentation of whether or not they completed treatment. This study assessed trends and correlates of no documented treatment completion among individuals incarcerated at diagnosis. Methods U.S. National TB Surveillance System (1999–2011) data on cases eligible for treatment completion were analyzed during 2014–2015. Treatment outcomes and trends in no documented completion were assessed by incarceration status. Multivariable logistic regression identified correlates of no documented completion among people incarcerated at diagnosis. Results A lower proportion of individuals incarcerated at diagnosis had documented TB treatment completion than non-incarcerated individuals (75.6% vs 93.7%), and a higher proportion were lost to follow-up (10.7% vs 2.2%) or moved (9.4% vs 2.3%) during treatment ( p <0.001). The 1999–2011 trend in no documented completion significantly increased among those incarcerated at diagnosis and declined among non-incarcerated individuals. Being foreign born was the strongest correlate of no documented completion among people incarcerated at diagnosis (AOR=2.86, 95% CI= 2.35, 3.49). Social risk factors for TB (e.g., homelessness, substance abuse), although common among incarcerated individuals, did not emerge as correlates of no documented completion. Conclusions People diagnosed with TB disease at U.S. correctional facilities, especially the foreign born, require enhanced strategies for documenting TB treatment completion. Strengthened collaboration between correctional and public health agencies could improve continuity of care among released inmates.
Characterization of Leishmania colombiensis sp.n. is presented, which on the basis of biological and molecular criteria, appears to be a new member of the L. braziliensis complex. A total of nine ...isolates of the new parasite were made in Colombia and Panama between 1980 and 1986: two from human cases of cutaneous leishmaniasis, six from phlebotomine sand flies, and one from a sloth. Although most closely related to L. lainsoni, L. colombiensis sp.n. is clearly distinguishable from other members of the genus by its reactivity with monoclonal antibodies, isoenzyme electrophoresis, and restriction endonuclease fragment patterns of kinetoplast DNA (k-DNA).
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