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Stasis
Kinds of Stasis Selected AbstractsMoment of Stasis: The Successful Failure of a Constitution for EuropeEUROPEAN LAW JOURNAL, Issue 3 2009Andreas Philippopoulos-Mihalopoulos The 2005 French and Dutch negative votes on the Constitution open up a space of conceptualisation, not only of Europe's relation to its demos, but significantly to its failures. Through a critical analysis of mainly Niklas Luhmann's systems theory, the article proposes taking a distance from traditional constitutional dogmatics that are no longer capable of dealing with the paradox of contemporary society, and more specifically with the eventual resurgence of the European project as one of absence and stasis: the two terms are used to explain the need, on the one hand, to maintain the ,absent community' of Europe, and, on the other, to start realising that any conceptualisation of the European project will now have to take place in that space of instability and contingency revealed by the constitutional failure. The relation between law and politics, the location of a constitution, the distinction between social and normative legitimacy, the connection between European identity and demos, and the concept of continuity between constitutional text and context are revisited in an attempt to trace the constitutional failure as the constitutional moment par excellence. [source] Gastric Stasis Occurs in Spontaneous, Visually Induced, and Interictal MigraineHEADACHE, Issue 10 2007Sheena Aurora MD Objective., To evaluate and compare gastric motility and emptying during spontaneous migraine to previous observations from induced migraine. Blackground., We have previously demonstrated a delay in gastric emptying both during the interictal period and during an induced migraine. A limitation noted in these studies was whether there are differences gastrointestinally during a visually induced migraine compared to spontaneous migraines. To address this, 9 additional studies have been performed to ascertain if there is a similar delay during spontaneous migraine Methods., Gastric scintigraphy using a standard meal was performed in 3 subjects during 3 periods: spontaneous migraine, induced migraine, and interictal period. Results., On average, the time to half emptying was delayed during spontaneous migraine (124 minutes), during induced migraine (182 minutes), and during the interictal period migraine (243 minutes) compared to normative values established at our center (112 minutes). On average, similar gastric slowing was seen in all 3 groups when the percentage of nuclear material remaining in the stomach at 2 hours was measured. Conclusions., This study provides additional evidence of gastric stasis in migraineurs interictally during induced and spontaneous migraine. [source] Gastric Stasis in Migraine: More Than Just a Paroxysmal Abnormality During a Migraine AttackHEADACHE, Issue 1 2006Objective.,The aim of this article is to evaluate gastric motility and emptying in the ictal and interictal period in migraine. Background.,Nausea is a predominant symptom of migraine and the basis of it is thought to be gastric stasis. Objective methods to establish this are however lacking. We utilized gastric scintigraphy studies to determine gastric motility in the ictal and interictal period of migraine. Methods.,Ten migraine subjects were compared to equal number of age and sex matched controls. Gastric scintigraphy using a standard meal was performed in all control subjects once and in all 10 migraine subjects in the interictal period and nine studies were performed in the ictal period migraine. Results.,The time to half emptying was delayed in migraine ictally (78%) and interictal period (80%) using normative data at this institution. Gastric stasis was less pronounced ictally (149.9 minutes) compared to interictal period (188.8 minutes). There was a significant delay compared to nonmigrainous controls (migraine 188.8 minutes vs normal controls 111.8 minutes; P < .05). These data were replicated in percentage of radioactive material remaining in the stomach at 2 hours. Conclusions.,Contrary to previous belief, this study has demonstrated that migraineurs suffer from gastric stasis both during and outside an acute migraine attack. This may suggest that migraineurs may have an abnormal autonomic function compared to nonmigrainous controls. The potential role of this in pathophysiology of migraine is discussed and avenues for further investigations are explored. [source] Balancing Theory versus Fact, Stasis versus Change: A Look at Some Introductions to International RelationsINTERNATIONAL STUDIES PERSPECTIVES, Issue 1 2004Andrew J. Enterline Do dramatic events in international relations (IR) signal fundamental changes in political behavior? How do international relations texts address change, and what are the implications of textbook design for the way that we teach undergraduate introductions to the field? This article provides an initial inquiry into these questions by surveying a sample of five international relations texts. Rather than seek to pick the best book, the article examines the methods by which the textbook authors balance theory versus facts, as well as stasis versus change, in formulating introductory frameworks. This analysis is motivated by way of a general comparison of the sample texts with Organski's (1958) text, World Politics. Finally, the author discusses the strengths and weaknesses of different balancing strategies, and the implications of these strategies for teaching introductions to international relations. [source] An In-Vivo Analysis of Capillary Stasis and Endothelial Apoptosis in a Model of HypertensionMICROCIRCULATION, Issue 8 2007Edward D. Tran ABSTRACT Objective: Recent evidence suggests endothelial apoptosis may be a mechanism for capillary rarefaction in hypertensives. The objective of this study was to examine the early phase of endothelial apoptosis and capillary blood flow in the spontaneously hypertensive rat (SHR) and the normotensive Wistar-Kyoto (WKY) rat. Methods: Since hypertension in SHR is dependent on glucocorticoids, the animals were treated with dexamethasone (DEX), by intraperitoneal injection and then by superfusion on exposed mesentery. Selected capillaries were continuously observed. Annexin V and propidium iodide were used to detect apoptosis. Results: Without central pressure reduction, permanent capillary stasis was initiated by the entrapment of leukocytes at the location of an endothelial cell that had platelets attached to it. Apoptosis of the endothelial cell was followed by apoptosis in other endothelial cells of the obstructed capillary. The incidence of stasis and total cell death in WKY+DEX were higher than WKY, whereas there were no differences between SHR+DEX and SHR. Blockade of the lectin domain of L-selectin or a platelet membrane adhesion molecule (glycoprotein IIb/IIIa) blocked the development of stasis. Conclusions: Glucocorticoid facilitates cell death and microvessel stasis. Immobilized platelets and leukocytes play a central role in capillary stasis, which leads to progression of endothelial apoptosis. [source] Geographies of Architecture: The Multiple Lives of BuildingsGEOGRAPHY COMPASS (ELECTRONIC), Issue 5 2010Peter Kraftl Arguably, cultural geography began with the study of architectural forms. The first half of this article traces the geographical study of buildings as a relatively small but significant sub-field of cultural geography. It summarises three approaches that characterise this work. First, the study of everyday, vernacular buildings, found especially (but not exclusively) in North American cultural geography. Second, radical critiques of the political,economic imperatives that are built into particular architectural forms such as the skyscraper and the related interpretation of buildings as signs, symbols or referents for dominant socio-cultural discourses or moralities. Third, what can broadly (but not unproblematically) be termed non-representational or ,critical' methods that stress practice, materiality and affect. The second half of the article highlights the productive connections between these three approaches. It stresses that recent research on the geographies of architecture has adopted elements of each approach to make a number of contributions to the study of cultural geography. Two key themes are considered: movement/stasis; the politics of architectural design and practice. Consideration of these themes anticipates a conclusion with some broad suggestions for future geographical research on architecture. [source] Prostaglandin I2 sensory input into the enteric nervous system during distension-induced colonic chloride secretion in rat colonACTA PHYSIOLOGICA, Issue 3 2010J. D. Schulzke Abstract Aim:, Intestinal pressure differences or experimental distension induce ion secretion via the enteric nervous system, the sensorial origin of which is only poorly understood. This study aimed to investigate sensorial inputs and the role of afferent and interneurones in mechanically activated submucosal secretory reflex circuits. Methods:, Distension-induced rheogenic chloride secretion was measured as increase in short-circuit current 10 min after distension (,ISC10; distension parameters ± 100 ,L, 2 Hz, 20 s) in partially stripped rat distal colon in the Ussing-chamber in vitro. PGE2 and PGI2 were measured by radioimmunoassay. Results:, ,ISC10 was 2.0 ± 0.2 ,mol h,1 cm,2 and could be attenuated by lobeline, mecamylamine and dimethylphenylpiperazine, indicating an influence of nicotinergic interneurones. Additionally, a contribution of afferent neurones was indicated from the short-term potentiation of ,ISC10 by capsaicin (1 ,m). As evidence for its initial event, indomethacin (1 ,m) inhibited distension-induced secretion and the release of PGI2 was directly detected after distension. Furthermore, serotoninergic mediation was confirmed by granisetron (100 ,m) which was functionally localized distally to PGI2 in this reflex circuit, as granisetron inhibited an iloprost-induced ISC, while indomethacin did not affect serotonin-activated ion secretion. Conclusions:, Distension-induced active electrogenic chloride secretion in rat colon is mediated by a neuronal reflex circuit which includes afferent neurones and nicotinergic interneurones. It is initiated by distension-induced PGI2 release from subepithelial cells triggering this reflex via serotoninergic 5-HT3 receptor transmission. Functionally, this mechanism may help to protect against intestinal stasis but could also contribute to luminal fluid loss, e.g. during intestinal obstruction. [source] From genomes to morphology: a view from amphioxusACTA ZOOLOGICA, Issue 1 2010Peter W. H. Holland Abstract Holland, P.W.H. 2010. From genomes to morphology: a view from amphioxus. ,Acta Zoologica (Stockholm) 91: 81,86 As complete genome sequences are determined from an ever-increasing number of animal species, new opportunities are arising for comparative biology. For zoologists interested in the evolution of shape and form, however, there is a problem. The link between genome sequence and morphology is not direct and is obfuscated by complex and evolving genetic pathways, even when conserved regulatory genes are considered. Nonetheless, a large-scale comparison of genome sequences between extant chordates reveals an intriguing parallel between genotypic and phenotypic evolution. Tunicates have highly altered genomes, with loss of ancestral genes and shuffled genetic arrangements, while vertebrate genomes are also derived through gene loss and genome duplication. The recently sequenced amphioxus genome, in contrast, reveals much greater stasis on the cephalochordate lineage, in parallel to a less derived body plan. The opportunities and challenges for relating genome evolution to morphological evolution are discussed. [source] Past and present potential distribution of the Iberian Abies species: a phytogeographic approach using fossil pollen data and species distribution modelsDIVERSITY AND DISTRIBUTIONS, Issue 2 2010Francisca Alba-Sánchez Abstract Aim, Quaternary palaeopalynological records collected throughout the Iberian Peninsula and species distribution models (SDMs) were integrated to gain a better understanding of the historical biogeography of the Iberian Abies species (i.e. Abies pinsapo and Abies alba). We hypothesize that SDMs and Abies palaeorecords are closely correlated, assuming a certain stasis in climatic and topographic ecological niche dimensions. In addition, the modelling results were used to assign the fossil records to A. alba or A. pinsapo, to identify environmental variables affecting their distribution, and to evaluate the ecological segregation between the two taxa. Location, The Iberian Peninsula. Methods, For the estimation of past Abies distributions, a hindcasting process was used. Abies pinsapo and A. alba were modelled individually, first calibrating the model for their current distributions in relation to the present climate, and then projecting it into the past,the last glacial maximum (LGM) and the Middle Holocene periods,in relation to palaeoclimate simulations. The resulting models were compared with Iberian-wide fossil pollen records to detect areas of overlap. Results, The overlap observed between past Abies refugia,inferred from fossil pollen records,and the SDMs helped to construct the Quaternary distribution of the Iberian Abies species. SDMs yielded two well-differentiated potential distributions: A. pinsapo throughout the Baetic mountain Range and A. alba along the Pyrenees and Cantabrian Range. These results propose that the two taxa remained isolated throughout the Quaternary, indicating a significant geographical and ecological segregation. In addition, no significant differences were detected comparing the three projections (present-day, Mid-Holocene and LGM), suggesting a relative climate stasis in the refuge areas during the Quaternary. Main conclusions, Our results confirm that SDM projections can provide a useful complement to palaeoecological studies, offering a less subjective and spatially explicit hypothesis concerning past geographic patterns of Iberian Abies species. The integration of ecological-niche characteristics from known occurrences of Abies species in conjunction with palaeoecological studies could constitute a suitable tool to define appropriate areas in which to focus proactive conservation strategies. [source] Ecological fitting by phenotypically flexible genotypes: implications for species associations, community assembly and evolutionECOLOGY LETTERS, Issue 11 2008Salvatore J. Agosta Abstract Ecological fitting is the process whereby organisms colonize and persist in novel environments, use novel resources or form novel associations with other species as a result of the suites of traits that they carry at the time they encounter the novel condition. This paper has four major aims. First, we review the original concept of ecological fitting and relate it to the concept of exaptation and current ideas on the positive role of phenotypic plasticity in evolution. Second, we propose phenotypic plasticity, correlated trait evolution and phylogenetic conservatism as specific mechanisms behind ecological fitting. Third, we attempt to operationalize the concept of ecological fitting by providing explicit definitions for terms. From these definitions, we propose a simple conceptual model of ecological fitting. Using this model, we demonstrate the differences and similarities between ecological fitting and ecological resource tracking and illustrate the process in the context of species colonizing new areas and forming novel associations with other species. Finally, we discuss how ecological fitting can be both a precursor to evolutionary diversity or maintainer of evolutionary stasis, depending on conditions. We conclude that ecological fitting is an important concept for understanding topics ranging from the assembly of ecological communities and species associations, to biological invasions, to the evolution of biodiversity. [source] THIS ARTICLE HAS BEEN RETRACTED Tn5530 from Burkholderia cepacia strain 2a encodes a chloride channel protein essential for the catabolism of 2,4-dichlorophenoxyacetic acidENVIRONMENTAL MICROBIOLOGY, Issue 1 2007Antonio Sebastianelli Summary Chloride channel proteins (ClC) are found in living systems where they transport chloride ions across cell membranes. Recently, the structure/function of two prokaryotic ClC has been determined but little is known about the role of these proteins in the microbial metabolism of chlorinated compounds. Here we show that transposon Tn5530 from Burkholderia cepacia strain 2a encodes a ClC protein (BcClC) which is responsible for expelling Cl, ions generated during the catabolism of 2,4-dichlorophenoxyacetic acid (a chlorinated herbicide). We found that BcClC has the ability to transport Cl, ions across reconstituted proteoliposome membranes. We created two mutants in which the intrachannel glutamate residue of the protein, known to be responsible for opening and closing the channel (i.e. gating), was changed in order to create constitutively open and closed forms. We observed that cells carrying the closed-channel protein accumulated Cl, ions intracellularly leading to a decrease in intracellular pH, cell stasis and death. Further, we established that BcClC has the same gating mechanism as that reported for the ClC protein from Salmonella typhimurium. Our results show that the physiological role of ClC is to maintain cellular homeostasis which can be impaired by the catabolism of chlorinated compounds. [source] Lymphoscintigraphy of draught horses with chronic progressive lymphoedemaEQUINE VETERINARY JOURNAL, Issue 2 2006H. E. V. De Cock Summary Reasons for performing study: Early diagnosis of chronic progressive lymphoedema (CPL) may result in more effective interventions and provide a basis for further investigation of whether early diagnosis could be used as a means of eliminating potential genetic influences by cessation of breeding from affected individuals. Hypothesis: Lymphoscintigraphy may be useful in draught horses to differentiate early lesions of CPL from other conditions in the pastern region. Methods: Forelimbs of 2 normal and 5 CPL-affected draught horses were evaluated with lymphoscintigraphy. Results: Lymphoscintigraphy showed clearly the presence of interstitial fluid stasis and delayed lymphatic drainage in the affected extremities of diseased animals in contrast to normal animals of these breeds. The rate of decreased clearance of a particulate radiopharmaceutical from the tissues was related positively to the severity of clinical signs. Conclusions and potential relevance: Our findings support the hypothesis that lymph stasis is probably responsible for the progressive swelling and concurrent skin lesions observed in association with CPL in draught horses. Lymphoscintigraphy should also prove useful in diagnosis of CPL in draught horses, even in the mild stages of the disease; such early diagnosis may result in more effective intervention. [source] Moment of Stasis: The Successful Failure of a Constitution for EuropeEUROPEAN LAW JOURNAL, Issue 3 2009Andreas Philippopoulos-Mihalopoulos The 2005 French and Dutch negative votes on the Constitution open up a space of conceptualisation, not only of Europe's relation to its demos, but significantly to its failures. Through a critical analysis of mainly Niklas Luhmann's systems theory, the article proposes taking a distance from traditional constitutional dogmatics that are no longer capable of dealing with the paradox of contemporary society, and more specifically with the eventual resurgence of the European project as one of absence and stasis: the two terms are used to explain the need, on the one hand, to maintain the ,absent community' of Europe, and, on the other, to start realising that any conceptualisation of the European project will now have to take place in that space of instability and contingency revealed by the constitutional failure. The relation between law and politics, the location of a constitution, the distinction between social and normative legitimacy, the connection between European identity and demos, and the concept of continuity between constitutional text and context are revisited in an attempt to trace the constitutional failure as the constitutional moment par excellence. [source] EVOLUTIONARY CONSTRAINT AND ECOLOGICAL CONSEQUENCESEVOLUTION, Issue 7 2010Douglas J. Futuyma One of the most important shifts in evolutionary biology in the past 50 years is an increased recognition of sluggish evolution and failures to adapt, which seem paradoxical in view of abundant genetic variation and many instances of rapid local adaptation. I review hypotheses of evolutionary constraint (or restraint), and suggest that although constraints on individual characters or character complexes may often reside in the structure or paucity of genetic variation, organism-wide stasis, as described by paleontologists, might better be explained by a hypothesis of ephemeral divergence, according to which the spatial or temporal divergence of populations is often short-lived because of interbreeding with nondivergent populations. Among the many consequences of acknowledging evolutionary constraints, community ecology is being transformed as it takes into account phylogenetic niche conservatism and the strong imprint of deep history. [source] GRADUAL VERSUS PUNCTUATED EQUILIBRIUM EVOLUTION IN THE TURKANA BASIN MOLLUSCS: EVOLUTIONARY EVENTS OR BIOLOGICAL INVASIONS?EVOLUTION, Issue 3 2008Bert Van Bocxlaer A running controversy in evolutionary thought was Eldredge and Gould's punctuated equilibrium model, which proposes long periods of morphological stasis interspersed with rapid bursts of dramatic evolutionary change. One of the earliest and most iconic pieces of research in support of punctuated equilibrium is the work of Williamson on the Plio-Pleistocene molluscs of the Turkana Basin. Williamson claimed to have found firm evidence for three episodes of rapid evolutionary change separated by long periods of stasis in a high-resolution sequence. Most of the discussions following this report centered on the topics of (eco)phenotypy versus genotypy and the possible presence of preservational and temporal artifacts. The debate proved inconclusive, leaving Williamson's reports as one of the empirical foundations of the paradigm of punctuated equilibrium. Here we conclusively show Williamson's original interpretations to be highly flawed. The supposed rapid bursts of punctuated evolutionary change represent artifacts resulting from the invasion of extrabasinal faunal elements in the Turkana palaeolakes during wet phases well known from elsewhere in Africa. [source] PHYLOGEOGRAPHIC STRUCTURE AND CRYPTIC SPECIATION IN THE TRANS-ANTARCTIC MOSS PYRRHOBRYUM MNIOIDESEVOLUTION, Issue 2 2003Stuart F. McDaniel Abstract Many bryophyte species have distributions that span multiple continents. The hypotheses historically advanced to explain such distributions rely on either long-distance spore dispersal or slow rates of morphological evolution following ancient continental vicariance events. We use phylogenetic analyses of DNA sequence variation at three chloroplast loci (atpB-rbcL spacer, rps4 gene, and trnL intron and 3,spacer) to examine these two hypotheses in the trans-Antarctic moss Pyrrhobryum mnioides. We find: (1) reciprocal monophyly of Australasian and South American populations, indicating a lack of intercontinental dispersal; (2) shared haplotypes between Australia and New Zealand, suggesting recent or ongoing migration across the Tasman Sea; and (3) reciprocal monophyly among Patagonian and neotropical populations, suggesting no recent migration along the Andes. These results corroborate experimental work suggesting that spore features may be critical determinants of species range. We use the mid-Miocene development of the Atacama Desert, 14 million years ago, to calibrate a molecular clock for the tree. The age of the trans-Antarctic disjunction is estimated to be 80 million years ago, consistent with Gondwanan vicariance, making it among the most ancient documented cases of cryptic speciation. These data are in accord with niche conservatism, but whether the morphological stasis is a product of stabilizing selection or phylogenetic constraint is unknown. [source] ECOLOGICAL BISTABILITY AND EVOLUTIONARY REVERSALS UNDER ASYMMETRICAL COMPETITIONEVOLUTION, Issue 6 2002Fabio Dercole Abstract How does the process of life-history evolution interplay with population dynamics? Almost all models that have addressed this question assume that any combination of phenotypic traits uniquely determine the ecological population state. Here we show that if multiple ecological equilibria can exist, the evolution of a trait that relates to competitive performance can undergo adaptive reversals that drive cyclic alternation between population equilibria. The occurrence of evolutionary reversals requires neither environmentally driven changes in selective forces nor the coevolution of interactions with other species. The mechanism inducing evolutionary reversals is twofold. First, there exist phenotypes near which mutants can invade and yet fail to become fixed; although these mutants are eventually eliminated, their transitory growth causes the resident population to switch to an alternative ecological equilibrium. Second, asymmetrical competition causes the direction of selection to revert between high and low density. When ecological conditions for evolutionary reversals are not satisfied, the population evolves toward a steady state of either low or high abundance, depending on the degree of competitive asymmetry and environmental parameters. A sharp evolutionary transition between evolutionary stasis and evolutionary reversals and cycling can occur in response to a smooth change in ecological parameters, and this may have implications for our understanding of size-abundance patterns. [source] Isolation of a Carnobacterium maltaromaticum- like bacterium from systemically infected lake whitefish (Coregonus clupeaformis)FEMS MICROBIOLOGY LETTERS, Issue 1 2008Thomas P. Loch Abstract Herein we report on the first isolation of a Carnobacterium maltaromaticum -like bacterium from kidneys and swim bladders of lake whitefish (Coregonus clupeaformis) caught from Lakes Michigan and Huron, Michigan. Isolates were Gram-positive, nonmotile, facultatively anaerobic, asporogenous rods that did not produce catalase, cytochrome oxidase, or H2S, and did not grow on acetate agar. Except for carbohydrate fermentation, many phenotypic characteristics of lake whitefish isolates coincided with those of C. maltaromaticum, the causative agent of pseudokidney disease. Partial sequencing of 16S and 23S rRNA genes, as well as the piscicolin 126 precursor gene, yielded 97% and 98% nucleotide matches with C. maltaromaticum, respectively (accession numbers EU546836 and EU546837; EU643471). Phylogenetic analyses showed that lake whitefish isolates of this study are highly related, yet not fully identical to C. maltaromaticum. The presence of the C. maltaromaticum -like bacterium was associated with splenomegaly, renal and splenic congestion, and thickening of the swim bladder wall with accumulation of a mucoid exudate. Examination of stained tissue sections revealed renal and splenic congestion, vacuolation and bile stasis within the liver, and hyperplasia within the epithelial lining of the swim bladder. The concurrent presence of pathological changes and the C. maltaromaticum -like bacteria suggests that this bacterium is pathogenic to lake whitefish. [source] Evolution on ecological time-scalesFUNCTIONAL ECOLOGY, Issue 3 2007S. P. CARROLL Summary 1Ecologically significant evolutionary change, occurring over tens of generations or fewer, is now widely documented in nature. These findings counter the long-standing assumption that ecological and evolutionary processes occur on different time-scales, and thus that the study of ecological processes can safely assume evolutionary stasis. Recognition that substantial evolution occurs on ecological time-scales dissolves this dichotomy and provides new opportunities for integrative approaches to pressing questions in many fields of biology. 2The goals of this special feature are twofold: to consider the factors that influence evolution on ecological time-scales , phenotypic plasticity, maternal effects, sexual selection, and gene flow , and to assess the consequences of such evolution , for population persistence, speciation, community dynamics, and ecosystem function. 3The role of evolution in ecological processes is expected to be largest for traits that change most quickly and for traits that most strongly influence ecological interactions. Understanding this fine-scale interplay of ecological and evolutionary factors will require a new class of eco-evolutionary dynamic modelling. 4Contemporary evolution occurs in a wide diversity of ecological contexts, but appears to be especially common in response to anthropogenic changes in selection and population structure. Evolutionary biology may thus offer substantial insight to many conservation issues arising from global change. 5Recent studies suggest that fluctuating selection and associated periods of contemporary evolution are the norm rather than exception throughout the history of life on earth. The consequences of contemporary evolution for population dynamics and ecological interactions are likely ubiquitous in time and space. [source] History of marine biodiversityGEOLOGICAL JOURNAL, Issue 3-4 2001Peter M. Sheehan Abstract During the Phanerozoic, three steps of increasing diversity each had a unique Evolutionary Fauna (EF). During each EF, there were geologically long intervals of community stasis referred to as Ecological Evolutionary Units (EEUs). These intervals were characterized by communities composed of incumbent faunas that dominated particular habitats. Niches that were already occupied by incumbents were seldom invaded by new taxa, and the resilience of the incumbents to new competitors resulted in the long interval stasis. Most EEUs were terminated by extinction events that were caused by severe disruptions of the physical environment such as glaciations and extraterrestrial impacts. During mass extinctions many niches were vacated when incumbents were eliminated. Mass extinctions were followed by recovery intervals lasting on the order of 5 million years during which many surviving clades evolved adaptations which allowed them to move into vacated niches. New incumbents were established during these recovery intervals, and the next EEU began. In many ways, the recovery intervals resemble times when organisms invaded previously unoccupied ecospace, such as the emergence of life on land or the progressive filling of previously unoccupied habitats such as deep-burrowing and high epifaunal tiers that were colonized during the Palaeozoic. The recognition of long intervals of ecological stasis and the importance of physical disruptions in clearing incumbents is forcing revision of the traditional evolutionary viewpoint. The idea that most evolutionary change was accomplished very gradually by competition between organisms and by becoming better adapted to a relatively stable environment is being replaced by a recognition that major morphological and synecological changes tend to occur very rapidly and at times when there are few established competitors. Copyright © 2001 John Wiley & Sons, Ltd. [source] Global change and carnivore body size: data are stasisGLOBAL ECOLOGY, Issue 2 2009Shai Meiri ABSTRACT Aim, Global warming and other anthropogenic changes to the environment affect many aspects of biology and have often been invoked as causing body size changes in vertebrates. Here we examine a diverse set of carnivore populations in search of patterns in body size change that could reflect global warming (in accord with Bergmann's rule). Location, Global. Methods, We used > 4400 specimens representing 22 carnivore species in 52 populations collected over the last few decades to examine whether size changed with collection date when geography and sex are accounted for. We then examined several factors related to global warming, body mass, diet, and the attributes of the different datasets, to see whether they affect the standardized slope (,) of the size versus time regression. Results, Six of 52 populations we examined show a significant effect of year of collection on body size at the 0.05 probability level. The response of size to global warming does not reflect spatial patterns of size variation, nor do diet or body mass affect tendency of populations to change in body size. Size changes are no more pronounced in populations that have been sampled more recently. However, change, where it occurs, is rapid. Main conclusions, There may be a tendency in the literature to report only cases where recent changes are prevalent. Although in our data only a minority of populations show body size changes, we may see changes accelerating in the future in response to more drastic climatic changes and other anthropogenic changes. [source] Reconstructing the demise of Tethyan plants: climate-driven range dynamics of Laurus since the PlioceneGLOBAL ECOLOGY, Issue 6 2008Francisco Rodríguez-Sánchez ABSTRACT Aim Climate changes are thought to be responsible for the retreat and eventual extinction of subtropical lauroid species that covered much of Europe and North Africa during the Palaeogene and early Neogene; little is known, however, of the spatial and temporal patterns of this demise. Herein we calibrate ecological niche models to assess the climatic requirements of Laurus L. (Lauraceae), an emblematic relic from the Tethyan subtropical flora, subsequently using these models to infer how the range dynamics of Laurus were affected by Plio-Pleistocene climate changes. We also provide predictions of likely range changes resulting from future climatic scenarios. Location The Mediterranean Basin and Macaronesian islands (Canaries, Madeira, Azores). Methods We used a maximum-entropy algorithm (Maxent) to model the relationship between climate and Laurus distribution over time. The models were fitted both to the present and to the middle Pliocene, based on fossil records. We employed climatic reconstructions for the mid-Pliocene (3 Ma), the Last Glacial Maximum (21 ka) and a CO2 -doubling future scenario to project putative species distribution in each period. We validated the model projections with Laurus fossil and present occurrences. Results Laurus preferentially occupied warm and moist areas with low seasonality, showing a marked stasis of its climatic niche. Models fitted to Pliocene conditions successfully predicted the current species distribution. Large suitable areas existed during the Pliocene, which were strongly reduced during the Pleistocene, but humid refugia within the Mediterranean Basin and Macaronesian islands enabled long-term persistence. Future climate conditions are likely to re-open areas suitable for colonization north of the current range. Main conclusions The climatic requirements of Laurus remained virtually unchanged over the last 3 Myr. This marked niche conservatism imposed largely deterministic range dynamics driven by climate conditions. This species's relatively high drought tolerance might account for the survival of Laurus in continental Europe throughout the Quaternary whilst other Lauraceae became extinct. Climatic scenarios for the end of this century would favour an expansion of the species's range towards northern latitudes, while severely limiting southern populations due to increased water stress. [source] Gastric Stasis Occurs in Spontaneous, Visually Induced, and Interictal MigraineHEADACHE, Issue 10 2007Sheena Aurora MD Objective., To evaluate and compare gastric motility and emptying during spontaneous migraine to previous observations from induced migraine. Blackground., We have previously demonstrated a delay in gastric emptying both during the interictal period and during an induced migraine. A limitation noted in these studies was whether there are differences gastrointestinally during a visually induced migraine compared to spontaneous migraines. To address this, 9 additional studies have been performed to ascertain if there is a similar delay during spontaneous migraine Methods., Gastric scintigraphy using a standard meal was performed in 3 subjects during 3 periods: spontaneous migraine, induced migraine, and interictal period. Results., On average, the time to half emptying was delayed during spontaneous migraine (124 minutes), during induced migraine (182 minutes), and during the interictal period migraine (243 minutes) compared to normative values established at our center (112 minutes). On average, similar gastric slowing was seen in all 3 groups when the percentage of nuclear material remaining in the stomach at 2 hours was measured. Conclusions., This study provides additional evidence of gastric stasis in migraineurs interictally during induced and spontaneous migraine. [source] Gastric Stasis in Migraine: More Than Just a Paroxysmal Abnormality During a Migraine AttackHEADACHE, Issue 1 2006Objective.,The aim of this article is to evaluate gastric motility and emptying in the ictal and interictal period in migraine. Background.,Nausea is a predominant symptom of migraine and the basis of it is thought to be gastric stasis. Objective methods to establish this are however lacking. We utilized gastric scintigraphy studies to determine gastric motility in the ictal and interictal period of migraine. Methods.,Ten migraine subjects were compared to equal number of age and sex matched controls. Gastric scintigraphy using a standard meal was performed in all control subjects once and in all 10 migraine subjects in the interictal period and nine studies were performed in the ictal period migraine. Results.,The time to half emptying was delayed in migraine ictally (78%) and interictal period (80%) using normative data at this institution. Gastric stasis was less pronounced ictally (149.9 minutes) compared to interictal period (188.8 minutes). There was a significant delay compared to nonmigrainous controls (migraine 188.8 minutes vs normal controls 111.8 minutes; P < .05). These data were replicated in percentage of radioactive material remaining in the stomach at 2 hours. Conclusions.,Contrary to previous belief, this study has demonstrated that migraineurs suffer from gastric stasis both during and outside an acute migraine attack. This may suggest that migraineurs may have an abnormal autonomic function compared to nonmigrainous controls. The potential role of this in pathophysiology of migraine is discussed and avenues for further investigations are explored. [source] Do head lice spread in swimming pools?INTERNATIONAL JOURNAL OF DERMATOLOGY, Issue 11 2007Deon Canyon PhD, MACTM, MMCAA This study investigated the potential for head lice transmission in swimming pools using an in vitro experiment and a field trial. In the former study, head lice were submerged for 20 min in aqueous solutions at 25 ± 1 °C: deionized water, sea water, salt solutions (30, 60, 120 and 240 g/l), and chlorinated water (0.2, 2 and 5 mg/l). In all trials, lice located on cut hairs became immobile and did not respond to physical prodding. After entering stasis, no movement was observed until after rescue from submersion and a brief recovery period (0,1 min). Upon recovery, all lice fed and no mortality was observed within the next 4 h. In the field trial, four naturally infected individuals swam in a chlorinated pool for 30 min. No loss of lice or head to head transfer was observed. These results indicated that although head lice survive immersion, head lice transmission is unlikely to occur via the water of swimming pools. [source] Venous stasis and routine hematologic testingINTERNATIONAL JOURNAL OF LABORATORY HEMATOLOGY, Issue 5 2006G. LIPPI Summary Prolonged venous stasis, as generated by a long tourniquet placement, produces spurious variations in several measurable analytes. To verify to what extent venous stasis influences routine hematologic testing, we assessed routine hematologic parameters, including hemoglobin, hematocrit, red blood cell count (RBC), main cell hemoglobin (MHC), main cell volume (MCV), platelet count (PLT), main platelet volume (MPV), white blood cell count (WBC) and WBC differential on the Advia 120 automated hematology analyzer in 30 healthy volunteers, either without venous stasis (no stasis) or after application of a 60 mmHg standardized external pressure by a sphygmomanometer, for 1 (1-min stasis) and 3 min (3-min stasis). Although the overall correlation between measures was globally acceptable, the mean values for paired samples were significantly different in all parameters tested, except MCV, MHC, PLT, MPV, eosinophils, basophils and large unstained cells after 1-min stasis and all parameters except MCV, MHC, MPV and basophils after 3-min venous stasis. As expected RBC, hemoglobin and hematocrit displayed a significant trend towards increase, whereas WBC and the WBC subpopulations were decreased. Difference between measurements by Bland and Altman plots exceeded the current analytical quality specifications for desirable bias for WBC, RBC, hemoglobin, hematocrit, lymphocytes and monocytes in samples collected after either 1- and 3-min stasis. These results provide clear evidence that venous stasis during venipuncture might produce spurious and clinically meaningful biases in the measurement of several hematologic parameters, prompting further considerations on the usefulness of adopting appropriate preventive measures for minimizing such influences. [source] Extracorporeal shock wave lithotripsy produces a lower stone-free rate in patients with stones and renal cystsINTERNATIONAL JOURNAL OF UROLOGY, Issue 1 2002CHARALAMBOS DELIVELIOTIS Abstract Background: Renal cysts have a space-occupying effect and therefore can distort the pelvicalyceal anatomy. This distortion often produces abnormalities in normal urinary drainage. In the same way, it may effect the ability of the kidneys to become stone free after extracorporeal shock wave lithotripsy (ESWL). The purpose of the current study is to evaluate the effect of renal cysts on the outcome of ESWL. Methods: We studied 15 patients who had renal stones and coexistent renal cysts. Four patients had polycystic disease, five patients had multiple cysts and six patients has solitary ones. All cysts produced a distortion to the calyceal system of the kidneys, a fact confirmed by intravenous urography (IVU) and computed tomography (CT). All patients underwent ESWL and their stone-free status was evaluated 1 month later by ultrasound and plain kidney ureter bladder (KUB) X-ray. Results: We had a total 60% (9/15) stone-free patients in our study group and a stone fragmentation rate of 100%. Patients with more cysts had lower stone-free rates. Patients with polycystic kidneys had a 25% (1/4) stone-free rate, while patients with multiple cysts and solitary cysts had, 60% (3/5) and 83.3% (5/6), respectively. These results are lower than the rates reported in patients without renal cysts. Conclusions: We believe that renal cysts may interfere with the passage of stone fragments, due to the impediment of drainage and urinary stasis from the stretching and distortion of the calyceal system by the renal cysts. [source] Balancing Theory versus Fact, Stasis versus Change: A Look at Some Introductions to International RelationsINTERNATIONAL STUDIES PERSPECTIVES, Issue 1 2004Andrew J. Enterline Do dramatic events in international relations (IR) signal fundamental changes in political behavior? How do international relations texts address change, and what are the implications of textbook design for the way that we teach undergraduate introductions to the field? This article provides an initial inquiry into these questions by surveying a sample of five international relations texts. Rather than seek to pick the best book, the article examines the methods by which the textbook authors balance theory versus facts, as well as stasis versus change, in formulating introductory frameworks. This analysis is motivated by way of a general comparison of the sample texts with Organski's (1958) text, World Politics. Finally, the author discusses the strengths and weaknesses of different balancing strategies, and the implications of these strategies for teaching introductions to international relations. [source] Evolution, origin and age of lineages in the Californian and Mediterranean florasJOURNAL OF BIOGEOGRAPHY, Issue 7 2009David D. Ackerly Abstract This paper addresses some of the conceptual issues involved in the analysis of the age and origin of mediterranean-climate plant taxa, paying particular attention to three topics: (1) the importance of an explicit time frame in the definition of biogeographical origins, (2) the distinction between the age of traits and the age of taxa, and (3) the idea of mediterranean-type ecosystems as environmental islands. (1) In California, recent analyses demonstrate that the diversity of species derived from different biogeographical origins is significantly correlated with temperature and precipitation gradients. These patterns support the hypothesis that niche conservatism is an important factor structuring modern diversity gradients. However, depending on how far back in time one looks, a species may be assigned to different origins; future discussions of biogeographical origins need to address the appropriate time frame for analysis. (2) Past research has demonstrated distinctive trait syndromes among woody plants of the Mediterranean, Chile, California and Mexico, and proposed that the syndromes are associated with lineages of different age in these floras. Reanalysis of individual traits demonstrates greater variability among regions than previously reported. The classification of plants into ,old' and ,new' genera is re-evaluated, and it is suggested that greater attention be paid to the age of traits, rather than to the age of taxa, especially at an arbitrary rank such as genus. (3) The idea of mediterranean-climate regions as ,climatic islands' is examined. Space,time diagrams of climate enable one to view the emergence of distinctive climatic regions in a continental context. The terms ,synclimatic' and ,anticlimatic' are proposed, referring to migration routes that parallel climate contours in space and time versus those that cross contours (including the case of geographic stasis in the face of climate change), respectively. Mediterranean-climate regions have served as important case studies in plant ecology and evolution, and merit continued close examination in the light of continued advances in phylogenetics and palaeoecology. [source] Esophageal Hematoma Complicating Catheter Ablation for Atrial FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2 2009REBECCA McCALL B.V.C.Des Significant injury to the esophagus during ablation for atrial fibrillation is rare but may be devastating. Esophageal fistulas and injury to branches of the vagus nerve resulting in gastric stasis have previously been described. In this case report, we describe another type of esophageal injury associated with catheter ablation for atrial fibrillation. The patient experienced chest pain and vomiting on recovery from anesthesia. Echocardiography and computerized tomography were used to identify a large esophageal hematoma. The hematoma was treated conservatively and the patient recovered fully after several weeks. [source] | |||||||||||||||||||||||||||||||||||||