We review the empirical phylogenetic literature on plant diversification, highlighting challenges in separating the effects of speciation and extinction, in specifying diversification mechanisms, and ...in making convincing arguments. In recent discussions of context dependence, key opportunities and landscapes, and indirect effects and lag times, we see a distinct shift away from single-point/single-cause ‘key innovation’ hypotheses toward more nuanced explanations involving multiple interacting causal agents assembled step-wise through a tree. To help crystalize this emerging perspective we introduce the term ‘synnovation’ (a hybrid of ‘synergy’ and ‘innovation’) for an interacting combination of traits with a particular consequence (‘key synnovation’ in the case of increased diversification rate), and the term ‘confluence’ for the sequential coming together of a set of traits (innovations and synnovations), environmental changes, and geographic movements along the branches of a phylogenetic tree. We illustrate these concepts using the radiation of Bromeliaceae. We also highlight the generality of these ideas by considering how rate heterogeneity associated with a confluence relates to the existence of particularly species-poor lineages, or ‘depauperons.’ Many challenges are posed by this re-purposed research framework, including difficulties associated with partial taxon sampling, uncertainty in divergence time estimation, and extinction.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Rates of molecular evolution vary widely between lineages, but quantification of how rates change has proven difficult. Recently proposed estimation procedures have mainly adopted highly parametric ...approaches that model rate evolution explicitly. In this study, a semiparametric smoothing method is developed using penalized likelihood. A saturated model in which every lineage has a separate rate is combined with a roughness penalty that discourages rates from varying too much across a phylogeny. A data-driven cross-validation criterion is then used to determine an optimal level of smoothing. This criterion is based on an estimate of the average prediction error associated with pruning lineages from the tree. The methods are applied to three data sets of six genes across a sample of land plants. Optimally smoothed estimates of absolute rates entailed 2- to 10-fold variation across lineages.
Intercellular calcium (Ca(2+)) waves (ICWs) represent the propagation of increases in intracellular Ca(2+) through a syncytium of cells and appear to be a fundamental mechanism for coordinating ...multicellular responses. ICWs occur in a wide diversity of cells and have been extensively studied in vitro. More recent studies focus on ICWs in vivo. ICWs are triggered by a variety of stimuli and involve the release of Ca(2+) from internal stores. The propagation of ICWs predominately involves cell communication with internal messengers moving via gap junctions or extracellular messengers mediating paracrine signaling. ICWs appear to be important in both normal physiology as well as pathophysiological processes in a variety of organs and tissues including brain, liver, retina, cochlea, and vascular tissue. We review here the mechanisms of initiation and propagation of ICWs, the key intra- and extracellular messengers (inositol 1,4,5-trisphosphate and ATP) mediating ICWs, and the proposed physiological functions of ICWs.
Intercellular calcium (Ca
2+
) waves (ICWs) represent the propagation of increases in intracellular Ca
2+
through a syncytium of cells and appear to be a fundamental mechanism for coordinating ...multicellular responses. ICWs occur in a wide diversity of cells and have been extensively studied in vitro. More recent studies focus on ICWs in vivo. ICWs are triggered by a variety of stimuli and involve the release of Ca
2+
from internal stores. The propagation of ICWs predominately involves cell communication with internal messengers moving via gap junctions or extracellular messengers mediating paracrine signaling. ICWs appear to be important in both normal physiology as well as pathophysiological processes in a variety of organs and tissues including brain, liver, retina, cochlea, and vascular tissue. We review here the mechanisms of initiation and propagation of ICWs, the key intra- and extracellular messengers (inositol 1,4,5-trisphosphate and ATP) mediating ICWs, and the proposed physiological functions of ICWs.
Key points
Airway hyper‐responsiveness in asthma is driven by excessive contraction of airway smooth muscle cells (ASMCs).
Agonist‐induced Ca2+ oscillations underlie this contraction of ASMCs and the ...magnitude of this contraction is proportional to the Ca2+ oscillation frequency.
Sustained contraction and Ca2+ oscillations require an influx of extracellular Ca2+, although the mechanisms and pathways mediating this Ca2+ influx during agonist‐induced ASMC contraction are not well defined.
By inhibiting store‐operated calcium entry (SOCE) or voltage‐gated Ca2+ channels (VGCCs), we show that SOCE, rather than Ca2+ influx via VGCCs, provides the major Ca2+ entry pathway into ASMCs to sustain ASMCs contraction and Ca2+ oscillations.
SOCE may therefore serve as a potential target for new bronchodilators to reduce airway hyper‐responsiveness in asthma.
Asthma is characterized by airway hyper‐responsiveness: the excessive contraction of airway smooth muscle. The extent of this airway contraction is proportional to the frequency of Ca2+ oscillations within airway smooth muscle cells (ASMCs). Sustained Ca2+ oscillations require a Ca2+ influx to replenish Ca2+ losses across the plasma membrane. Our previous studies implied store‐operated calcium entry (SOCE) as the major pathway for this Ca2+ influx. In the present study, we explore this hypothesis, by examining the effects of SOCE inhibitors (GSK7975A and GSK5498A) as well as L‐type voltage‐gated Ca2+ channel inhibitors (nifedipine and nimodipine) on airway contraction and Ca2+ oscillations and SOCE‐mediated Ca2+ influx in ASMCs within mouse precision‐cut lung slices. We found that both GSK7975A and GSK5498A were able to fully relax methacholine‐induced airway contraction by abolishing the Ca2+ oscillations, in a manner similar to that observed in zero extracellular Ca2+ (Ca2+e). In addition, GSK7975A and GSK5498A inhibited increases in intracellular Ca2+ (Ca2+i) in ASMCs with depleted Ca2+‐stores in response to increased Ca2+e, demonstrating a response consistent with the inhibition of SOCE. However, GSK7975A and GSK5498A did not reduce Ca2+ release via IP3 receptors stimulated with IP3 released from caged‐IP3. By contrast, nifedipine and nimodipine only partially reduced airway contraction, Ca2+ oscillation frequency and SOCE‐mediated Ca2+ influx. These data suggest that SOCE is the major Ca2+ influx pathway for ASMCs with respect to sustaining agonist‐induced airway contraction and the underlying Ca2+ oscillations. The mechanisms of SOCE may therefore form novel targets for new bronchodilators.
Key points
Airway hyper‐responsiveness in asthma is driven by excessive contraction of airway smooth muscle cells (ASMCs).
Agonist‐induced Ca2+ oscillations underlie this contraction of ASMCs and the magnitude of this contraction is proportional to the Ca2+ oscillation frequency.
Sustained contraction and Ca2+ oscillations require an influx of extracellular Ca2+, although the mechanisms and pathways mediating this Ca2+ influx during agonist‐induced ASMC contraction are not well defined.
By inhibiting store‐operated calcium entry (SOCE) or voltage‐gated Ca2+ channels (VGCCs), we show that SOCE, rather than Ca2+ influx via VGCCs, provides the major Ca2+ entry pathway into ASMCs to sustain ASMCs contraction and Ca2+ oscillations.
SOCE may therefore serve as a potential target for new bronchodilators to reduce airway hyper‐responsiveness in asthma.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Estimating divergence times and rates of substitution from sequence data is plagued by the problem of rate variation between lineages. R8s version 1.5 is a program which uses parametric, ...nonparametric and semiparametric methods to relax the assumption of constant rates of evolution to obtain better estimates of rates and times. Unlike most programs for rate inference or phylogenetics, r8s permits users to convert results to absolute rates and ages by constraining one or more node times to be fixed, minimum or maximum ages (using fossil or other evidence). Version 1.5 uses truncated Newton nonlinear optimization code with bound constraints, offering superior performance over previous versions. Results: Availability: The linux executable, C source code, sample data sets and user manual are available free at http://ginger.ucdavis.edu/r8s. Contact: mjsanderson@ucdavis.edu
Abstract The development of therapeutic approaches to treat lung disease requires an understanding of both the normal and disease physiology of the lung. Although traditional experimental approaches ...only address either organ or cellular physiology, the use of lung slice preparations provides a unique approach to investigate integrated physiology that links the cellular and organ responses. Living lung slices are robust and can be prepared from a variety of species, including humans, and they retain many aspects of the cellular and structural organization of the lung. Functional portions of intrapulmonary airways, arterioles and veins are present within the alveoli parenchyma. The dynamics of macroscopic changes of contraction and relaxation associated with the airways and vessels are readily observed with conventional low-magnification microscopy. The microscopic changes associated with cellular events, that determine the macroscopic responses, can be observed with confocal or two-photon microscopy. To investigate disease processes, lung slices can either be prepared from animal models of disease or animals exposed to disease invoking conditions. Alternatively, the lung slices themselves can be experimentally manipulated. Because of the ability to observe changes in cell physiology and how these responses manifest themselves at the level of the organ, lung slices have become a standard tool for the investigation of lung disease.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Fluorescence microscopy Sanderson, Michael J; Smith, Ian; Parker, Ian ...
Cold Spring Harbor protocols,
2014-Oct-01, Volume:
2014, Issue:
10
Journal Article
Open access
Fluorescence microscopy is a major tool with which to monitor cell physiology. Although the concepts of fluorescence and its optical separation using filters remain similar, microscope design varies ...with the aim of increasing image contrast and spatial resolution. The basics of wide-field microscopy are outlined to emphasize the selection, advantages, and correct use of laser scanning confocal microscopy, two-photon microscopy, scanning disk confocal microscopy, total internal reflection, and super-resolution microscopy. In addition, the principles of how these microscopes form images are reviewed to appreciate their capabilities, limitations, and constraints for operation.
The inositol trisphosphate receptor (Formula: see text) is one of the most important cellular components responsible for oscillations in the cytoplasmic calcium concentration. Over the past decade, ...two major questions about the Formula: see text have arisen. Firstly, how best should the Formula: see text be modeled? In other words, what fundamental properties of the Formula: see text allow it to perform its function, and what are their quantitative properties? Secondly, although calcium oscillations are caused by the stochastic opening and closing of small numbers of Formula: see text, is it possible for a deterministic model to be a reliable predictor of calcium behavior? Here, we answer these two questions, using airway smooth muscle cells (ASMC) as a specific example. Firstly, we show that periodic calcium waves in ASMC, as well as the statistics of calcium puffs in other cell types, can be quantitatively reproduced by a two-state model of the Formula: see text, and thus the behavior of the Formula: see text is essentially determined by its modal structure. The structure within each mode is irrelevant for function. Secondly, we show that, although calcium waves in ASMC are generated by a stochastic mechanism, Formula: see text stochasticity is not essential for a qualitative prediction of how oscillation frequency depends on model parameters, and thus deterministic Formula: see text models demonstrate the same level of predictive capability as do stochastic models. We conclude that, firstly, calcium dynamics can be accurately modeled using simplified Formula: see text models, and, secondly, to obtain qualitative predictions of how oscillation frequency depends on parameters it is sufficient to use a deterministic model.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Background and Purpose
While selective, bitter tasting, TAS2R agonists can relax agonist‐contracted airway smooth muscle (ASM), their mechanism of action is unclear. However, ASM contraction is ...regulated by Ca2+ signalling and Ca2+ sensitivity. We have therefore investigated how the TAS2R10 agonists chloroquine, quinine and denotonium regulate contractile agonist‐induced Ca2+ signalling and sensitivity.
Experimental Approach
Airways in mouse lung slices were contracted with either methacholine (MCh) or 5HT and bronchodilation assessed using phase‐contrast microscopy. Ca2+ signalling was measured with 2‐photon fluorescence microscopy of ASM cells loaded with Oregon Green, a Ca2+‐sensitive indicator (with or without caged‐IP3). Effects on Ca2+ sensitivity were assessed on lung slices treated with caffeine and ryanodine to permeabilize ASM cells to Ca2+.
Key Results
The TAS2R10 agonists dilated airways constricted by either MCh or 5HT, accompanied by inhibition of agonist‐induced Ca2+ oscillations. However, in non‐contracted airways, TAS2R10 agonists, at concentrations that maximally dilated constricted airways, did not evoke Ca2+ signals in ASM cells. Ca2+ increases mediated by the photolysis of caged‐IP3 were also attenuated by chloroquine, quinine and denotonium. In Ca2+‐permeabilized ASM cells, the TAS2R10 agonists dilated MCh‐ and 5HT‐constricted airways.
Conclusions and Implications
TAS2R10 agonists reversed bronchoconstriction by inhibiting agonist‐induced Ca2+ oscillations while simultaneously reducing the Ca2+ sensitivity of ASM cells. Reduction of Ca2+ oscillations may be due to inhibition of Ca2+ release through IP3 receptors. Further characterization of bronchodilatory TAS2R agonists may lead to the development of novel therapies for the treatment of bronchoconstrictive conditions.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
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