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Results for “systematic evolution”

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PubMed1992

Evolution of behavioral attractors with learning: nonequilibrium phase transitions.

Learning a bimanual coordination task (synchronization to a visually specified phasing relation) was studied as a dynamical process over 5 days of practicing a required phasing pattern. Systematic probes of the attractor layout of the 5 Ss' coordination dynamics (expressed through a collective variable, relative phase) were conducted before, during, and after practice. Depending on the relationship between the initial coordination dynamics (so-called intrinsic dynamics) and the pattern to be learned (termed behavioral information, which acts as an attractor of the coordination dynamics toward the required phasing), qualitative changes in the phase diagram occurred with learning, accompanied by quantitative evidence for loss of stability (phase transitions). Such effects persisted beyond 1 week. The nature of change due to learning (e.g., abrupt vs. gradual) is shown to arise from the cooperative or competitive interplay between behavioral information and the intrinsic dynamics.

Adult↗

PubMed1994

The influence of mortality trials on the evolution of clinical practice.

Clinical practice is complex and is influenced by a number of factors such as time since medical qualification, opportunities for further education and peer review, as well as trial results and marketing. Systematic audit and peer review are powerful tools that are being used increasingly. When aided by the intelligent, but not Draconian, use of financial carrots they are an effective means of changing practice. Positive trials, such as those of thrombolytic therapy, have rapidly resulted in the widespread use of such treatment. Negative trials, for example those involving anti-arrhythmic prophylaxis after myocardial infarction or the use of calcium antagonists in patients with impaired left ventricular function, have also correctly resulted in an appropriate change in practice. Advertising does not always reflect best clinical practice and could lead to under-promotion of older but more useful drugs. Peer review and audit are probably the best available methods for promoting good clinical practice.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2006

Diagnostic value and prognostic implications of serum procalcitonin after cardiac surgery: a systematic review of the literature.

INTRODUCTION: Systemic inflammatory response syndrome is common after surgery, and it can be difficult to discriminate between infection and inflammation. We performed a review of the literature with the aims of describing the evolution of serum procalcitonin (PCT) levels after uncomplicated cardiac surgery, characterising the role of PCT as a tool in discriminating infection, identifying the relation between PCT, organ failure, and severity of sepsis syndromes, and assessing the possible role of PCT in detection of postoperative complications and mortality. METHODS: We performed a search on MEDLINE using the keyword 'procalcitonin' crossed with 'cardiac surgery,' 'heart,' 'postoperative,' and 'transplantation.' Our search was limited to human studies published between January 1990 and June 2006. RESULTS: Uncomplicated cardiac surgery induces a postoperative increase in serum PCT levels. Peak PCT levels are reached within 24 hours postoperatively and return to normal levels within the first week. This increase seems to be dependent on the surgical procedure and on intraoperative events. Although PCT values reported in infected patients are generally higher than in non-infected patients after cardiac surgery, the cutoff point for discriminating infection ranges from 1 to 5 ng/ml, and the dynamics of PCT levels over time may be more important than absolute values. PCT is superior to C-reactive protein in discriminating infections in this setting. PCT levels are higher with increased severity of sepsis and the presence of organ dysfunction/failure and in patients with a poor outcome or in those who develop postoperative complications. PCT levels typically remain unchanged after acute rejection but increase markedly after bacterial and fungal infections. Systemic infections are associated with greater PCT elevation than is local infection. Viral infections are difficult to identify based on PCT measurements. CONCLUSION: The dynamics of PCT levels, rather than absolute values, could be important in identifying patients with infectious complications after cardiac surgery. PCT is useful in differentiating acute graft rejection after heart and/or lung transplantation from bacterial and fungal infections. Further studies are needed to define cutoff points and to incorporate PCT levels in useful prediction models.

Biomarkers↗

PubMed2006

The pattern and timing of diversification of Philippine endemic rodents: evidence from mitochondrial and nuclear gene sequences.

The 22 genera and 64 species of rodents (Muridae: Murinae) distributed in the Philippine Islands provide a unique opportunity to study patterns and processes of diversification in island systems. Over 90% of these rodent species are endemic to the archipelago, but the relative importance of dispersal from the mainland, dispersal within the archipelago, and in situ differentiation as explanations of this diversity remains unclear, as no phylogenetic hypothesis for these species and relevant mainland forms is currently available. Here we report the results of phylogenetic analyses of the endemic Philippine murines and a wide sampling of murine diversity from outside the archipelago, based on the mitochondrial cytochrome b gene and the nuclear-encoded IRBP exon 1. Analysis of our combined gene data set consistently identified five clades comprising endemic Philippine genera, suggesting multiple invasions of the archipelago. Molecular dating analyses using parametric and semiparametric methods suggest that colonization occurred in at least two stages, one ca. 15 Mya, and another 8 to 12 million years later, consistent with the previous recognition of "Old" and "New" endemic rodent faunas. Ancestral area analysis suggests that the Old Endemics invaded landmasses that are now part of the island of Luzon, whereas the three New Endemic clades may have colonized through either Mindanao, Luzon, or both. Further, our results suggest that most of the diversification of Philippine murines took place within the archipelago. Despite heterogeneity between nuclear and mitochondrial genes in most model parameters, combined analysis of the two data sets using both parsimony and likelihood increased phylogenetic resolution; however, the effect of data combination on support for resolved nodes was method dependent. In contrast, our results suggest that combination of mitochondrial and nuclear data to estimate relatively ancient divergence times can severely compromise those estimates, even when specific methods that account for rate heterogeneity among genes are employed. [Biogeography; divergence date estimation; mitochondrial DNA; molecular systematics; Murinae; nuclear exon; Philippines; phylogeny.].

Animals↗

PubMed2006

Molecular evidence for multiple polyploidization and lineage recombination in the Chrysanthemum indicum polyploid complex (Asteraceae).

The Chrysanthemum indicum polyploid complex comprises morphologically differentiated diploids, tetraploids and hybrids between C. indicum and C. lavandulifolium. The relationships between species and cytotypes within this complex remain poorly understood. Random amplified polymorphic DNAs (RAPDs), intersimple sequence repeats (ISSRs) and chloroplast SSR markers were used to elucidate the genetic diversity and relationships of the C. indicum polyploid complex. Molecular analysis of three diploid and nine tetraploid populations provided strong evidence for recurrent origins and lineage recombination in the C. indicum polyploid complex. The high similarity in molecular marker profiles and cpDNA haplotypes between the diploids and tetraploids distributed in the Shen-Nong-Jia Mountain area of China suggested an autopolyploid origin of the tetraploids, while the tetraploids from other populations may have originated via allopolyploidization. Lineage recombination was revealed by the extensive sharing of chloroplast haplotypes and genetic markers among the tetraploid populations with different origins. Multiple differentiation and hybridization/polyploidization cycles have led to an evolutionary reticulation in the C. indicum polyploid complex, and resulted in the difficulties in systematic classification.

China↗

PubMed2002

Molecular phylogeny of a cosmopolitan group of woodpeckers (genus Picoides) gased on COI and cyt b mitochondrial gene sequences.

Picoides is the largest genus of woodpeckers and member species are found on most major land masses. Current systematic arrangement of this group, based on morphological, behavioral, and plumage characters, suggests that New World species evolved from a single invasion by a Eurasian common ancestor and that all New World species form a monophyletic group. No clear link has ever been established between the relationships of Old World and New World species other than to infer that the most primitive species is Eurasian. This study employs DNA sequences for two protein-coding mitochondrial genes, cytochrome oxidase I and cytochrome b, to reconstruct phylogenetic relationships among all New World species and several Eurasian representatives of the genus Picoides. A well-resolved mitochondrial gene tree is in direct conflict with proposed species relationships based on nongenetic characters; monophyly among New World species is rejected, the evolution of New World species likely resulted from as many as three independent Eurasian invasions, and Picoides is paraphyletic with two other woodpecker genera, Veniliornis and Dendropicos. These results strongly suggest that this large, cosmopolitan genus is in need of systematic revision in order to reflect evolutionary history.

Animals↗

PubMed1999

Homoplasy, homology and the problem of 'sameness' in biology.

The reality of evolution requires some concept of 'sameness'. That which evolves changes its state to some degree, however minute or grand, although parts remain 'the same'. Yet homology, our word for sameness, while universal in the sense of being necessarily true, can only ever be partial with respect to features that change. Determining what is equivalent to what among taxa, and from what something has evolved, remain real problems, but the word homology is not helpful in these problematic contexts. Henning saw this clearly when he coined new terms with technical meanings for phylogenetic studies. Analysis in phylogenetic systematics remains contentious and relatively subjective, especially as new information accumulates or as one changes one's mind about characters. This pragmatic decision making should not be called homology assessment. Homology as a concept anticipated evolution. Homology dates to pre-evolutionary times and represents late 18th and early 19th century idealism. Our attempts to recycle words in science leads to difficulty, and we should eschew giving precise modern definitions to terms that originally arose in entirely different contexts. Rather than continue to refine our homology concept we should focus on issues that have high relevance to modern evolutionary biology, in particular homoplasy--derived similarity--whose biological bases require elucidation.

Adaptation, Biological↗

PubMed2006

Site-specific nucleation and growth kinetics in hierarchical nanosyntheses of branched ZnO crystallites.

Here we report a site-specific sequential nucleation and growth route to the systematic building of hierarchical, complex, and oriented ZnO micro/nanostructures in solution nanosynthesis. Structures and morphologies of the products were confirmed by results from X-ray diffraction and scanning electron microscopy studies. The organic structure-directing agents (SDAs), diaminopropane and citrate, are found to play different roles in controlling the evolution of these new morphologies. Through the selective adsorptions of SDAs on different crystal facets of the primary ZnO rods, we have alternated the hierarchical growth of secondary and tertiary new complex nanostructures. Roles of the SDA concentration, nucleation time, and growth kinetics in the solution hierarchical ZnO nanosyntheses have all been systematically investigated.

Journal Article↗

PubMed2005

Molecular insights into human brain evolution.

Rapidly advancing knowledge of genome structure and sequence enables new means for the analysis of specific DNA changes associated with the differences between the human brain and that of other mammals. Recent studies implicate evolutionary changes in messenger RNA and protein expression levels, as well as DNA changes that alter amino acid sequences. We can anticipate having a systematic catalogue of DNA changes in the lineage leading to humans, but an ongoing challenge will be relating these changes to the anatomical and functional differences between our brain and that of our ancient and more recent ancestors.

Animals↗

PubMed1997

Host-specific driving force in human immunodeficiency virus type 1 evolution in vivo.

To investigate the process of human immunodeficiency virus type 1 (HIV-1) evolution in vivo, a total of 179 HIV-1 V3 sequences derived from cell-free plasma were determined from serial samples in three epidemiologically linked individuals (one infected blood donor and two transfusion recipients) over a maximum period of 8 years. A systematic analysis of pairwise comparisons of intrapatient sequences, both within and between each sample time point, revealed a preponderance and accumulation of nonsynonymous rather than synonymous substitutions in the V3 loop and flanking regions as they diverged over time. This strongly argues for the dominant role that positive selection for amino acid change plays in governing the pattern and process of HIV-1 env V3 evolution in vivo and nullifies hypotheses of purely neutral or mutation-driven evolution or completely chance events. In addition, different rates of evolution of HIV-1 were observed in these three different individuals infected with the same viral strain, suggesting that the degree of positive pressure for HIV-1 amino acid change is host dependent. Finally, the observed similar rate of accumulation in divergence within and between infected individuals suggests that the process of genetic divergence in the HIV epidemic proceeds regardless of host-to-host transmission events, i.e., that transmission does not reset the evolutionary clock.

Amino Acid Sequence↗

PubMed2006

Shape evolution and size-controllable synthesis of Cu2O octahedra and their morphology-dependent photocatalytic properties.

Octahedral Cu(2)O crystals with tunable edge length were synthesized by reducing copper hydroxide with hydrazine without using any surfactant. Systematic experiments were carried out to investigate the factors which impact on the morphology and size of the products. The molar ratios of the reagents (NH(3):Cu(2+) and OH(-):Cu(2+)) determined the morphology and size of the corresponding products via affecting the coordination between NH(3) and Cu(2+). It is demonstrated that the ratio of growth rate along 111 versus 100 was varied by adjusting the molar ratio of NH(3) to Cu(2+), thus Cu(2)O crystals with different morphologies such as spheres, cubelike, and octahedra were obtained. The edge lengths of octahedra can be easily tuned from 130 to 600 nm by adjusting the molar ratio of OH(-) to Cu(2+). It is an effective and facile method for the controlled synthesis of octahedral Cu(2)O. The obtained octahedral Cu(2)O particles show improved ability on adsorption and photodegradation of methyl orange compared with cubic Cu(2)O particles.

Journal Article↗

PubMed1984

Genesis and evolution of behavioral disorders: from infancy to early adult life.

The New York Longitudinal Study has followed the behavioral development of 133 subjects from early infancy to early adult life. Special attention has been given to the systematic clinical evaluation and follow-up of all subjects presenting any evidence of behavior disorder. The authors present incidence and outcome data, define the concept of temperament, and briefly discuss conceptual issues and empirical findings. They found the "goodness of fit" (consonance between the individual and the environment) concept useful in tracing developmental sequences. The authors summarize quantitative analyses identifying significant group correlations between antecedent variables and early adult outcome and suggest a tentative classification of the idiosyncratic factors also evident in the clinical course of individual subjects, with case illustrations.

Adaptation, Psychological↗

PubMedDate not supplied

[Old problems of new bacterial systematics].

This review analyzes the situation that arose after the existence of adaptive mutations had been proven. Manifold acceleration of the mutation process and intragenome rearrangements in nondividing cells demonstrates the inapplicability of the theory of neutral evolution to bacteria, the lack of isochronism between the evolution of individual macromolecules and the organism as a whole, and thus, the invalidity of using rRNA homologies as markers of the position of the organism in the phylogenetic tree and in the taxonomic system.

Bacteria↗

PubMed2004

Pinpointing the source of a lunar meteorite: implications for the evolution of the Moon.

The lunar meteorite Sayh al Uhaymir 169 consists of an impact melt breccia extremely enriched with potassium, rare earth elements, and phosphorus [thorium, 32.7 parts per million (ppm); uranium, 8.6 ppm; potassium oxide, 0.54 weight percent], and adherent regolith. The isotope systematics of the meteorite record four lunar impact events at 3909 +/- 13 million years ago (Ma), approximately 2800 Ma, approximately 200 Ma, and <0.34 Ma, and collision with Earth sometime after 9.7 +/- 1.3 thousand years ago. With these data, we can link the impact-melt breccia to Imbrium and pinpoint the source region of the meteorite to the Lalande impact crater.

Crystallization↗

PubMed2005

Reconstructing the evolutionary history of the Lorisidae using morphological, molecular, and geological data.

Major aspects of lorisid phylogeny and systematics remain unresolved, despite several studies (involving morphology, histology, karyology, immunology, and DNA sequencing) aimed at elucidating them. Our study is the first to investigate the evolution of this enigmatic group using molecular and morphological data for all four well-established genera: Arctocebus, Loris, Nycticebus, and Perodicticus. Data sets consisting of 386 bp of 12S rRNA, 535 bp of 16S rRNA, and 36 craniodental characters were analyzed separately and in combination, using maximum parsimony and maximum likelihood. Outgroups, consisting of two galagid taxa (Otolemur and Galagoides) and a lemuroid (Microcebus), were also varied. The morphological data set yielded a paraphyletic lorisid clade with the robust Nycticebus and Perodicticus grouped as sister taxa, and the galagids allied with Arctocebus. All molecular analyses maximum parsimony (MP) or maximum likelihood (ML) which included Microcebus as an outgroup rendered a paraphyletic lorisid clade, with one exception: the 12S + 16S data set analyzed with ML. The position of the galagids in these paraphyletic topologies was inconsistent, however, and bootstrap values were low. Exclusion of Microcebus generated a monophyletic Lorisidae with Asian and African subclades; bootstrap values for all three clades in the total evidence tree were over 90%. We estimated mean genetic distances for lemuroids vs. lorisoids, lorisids vs. galagids, and Asian vs. African lorisids as a guide to relative divergence times. We present information regarding a temporary land bridge that linked the two now widely separated regions inhabited by lorisids that may explain their distribution. Finally, we make taxonomic recommendations based on our results.

Animals↗

PubMed2007

Genetic transformation of Arabidopsis lyrata: specific expression of the green fluorescent protein (GFP) in pistil tissues.

Arabidopsis thaliana has become widely used as a model system for plant biology. Recent phylogenetic studies led to a severe revision of the systematic relationships across species of the Brassicaceae family. This provided an opportunity to examine close relatives of A. thaliana and to study the function and molecular evolution of genes that play roles in ecology and speciation. In this context, developing tools to genetically transform "non-model plants" appears as a major issue to ascertain gene function. Here, we report a method to transform A. lyrata, one of the closest relatives of A. thaliana.

Arabidopsis↗

PubMed2006

Age dependent and cellular origin (stem versus progenitor) of a selected group of spontaneous brain tumors in humans.

The origin of spontaneous human brain tumors has been recently debated as originating from a stem rather than a progenitor cell. Based on the statistical distribution of a selected group of primary brain tumors, and on the clonality and field theory for cancer growth, we propose as plausible the contribution of progenitor cells in the origin of the most common brain tumors such as, pediatric, mixed (glial and neuronal), and the aggressive glioblastoma multiforme in adults. Operationally, stem cell is defined as having a renewal probability of p=1, a progenitor 0<p<1, and a terminally differentiated cell as p=0. The space-time field location (microenvironment, cell-cell interactions...) and mitotic potential of a cell limits the distinguishability between stem and progenitors, due to the interconvertibility of these states via the process of retrodifferentiation (dedifferentiation). If excessively iterated retrodifferentiation of a mitotically competent cell prompts such a cell to organize programs that are atypical vis-à-vis the standard ones. Regarding specifically malignant cells, aperiodic cycles of dedifferentiation favour emergence of subclonal populations whose anachronistic evolution might become idiosyncratically resistant to therapies previously efficient against the initial tumoral mass. Unfortunately the "ab initio" identification of such subclonal "drifters" is impaired by systematic uncertainties as quali-quantified in appendix.

Aging↗

PubMed1972

The histological diagnosis of chronic gastritis in fibreoptic gastroscope biopsy specimens.

The advent of the fibreoptic gastroscope with biopsy facilities has provided the means of obtaining biopsy specimens under direct vision from any part of the stomach. This creates new opportunities for the study of chronic gastritis, and, in particular, its evolution, topographical location, and causal relationships. On the basis of an experience with more than 2,500 biopsy specimens we have outlined a method for their systematic examination and have proposed a classification of chronic gastritis. This classification includes the type of mucosa, the type and stage of activity of the gastritis, and the presence and type of metaplasia. The classification is sufficiently flexible to allow within it quantitative assessment of individual histological features.

Biopsy↗