PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “systematic evolution”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16Linked to original sources
PubMed2005

The prevalence of rheumatic diseases in the elderly in developed countries and its evolution over time.

OBJECTIVES: This study aims at evaluating the prevalence of rheumatic diseases in the elderly and its evolution over time. METHODS: We present a systematic international literature review of the prevalence of rheumatic diseases in the elderly and its evolution over time. RESULTS: The estimated current prevalence of rheumatic diseases among people aged 65 and more varies between 41% and 53%, and is similar to estimated prevalence rates in studies performed before 1990 (35-55%). The prevalence is high and seems to increase rapidly with age. Furthermore, women suffer more frequently from rheumatic diseases than men. CONCLUSION: The selected studies included a large range of methods, making comparisons difficult. However, estimates of the prevalence of rheumatic diseases in the elderly appear to be homogeneous in different countries and stable since 1980.

Age Factors↗
PubMed2001

Progression of dysarthria and dysphagia in postmortem-confirmed parkinsonian disorders.

BACKGROUND: Dysarthria and dysphagia are known to occur in parkinsonian syndromes such as Parkinson disease (PD), dementia with Lewy bodies (DLB), corticobasal degeneration (CBD), multiple system atrophy (MSA), and progressive supranuclear palsy (PSP). Differences in the evolution of these symptoms have not been studied systematically in postmortem-confirmed cases. OBJECTIVE: To study differences in the evolution of dysarthria and dysphagia in postmortem-confirmed parkinsonian disorders. PATIENTS AND METHODS: Eighty-three pathologically confirmed cases (PD, n = 17; MSA, n = 15; DLB, n = 14; PSP, n = 24; and CBD, n = 13) formed the basis for a multicenter clinicopathological study organized by the National Institute of Neurological Disorders and Stroke, Bethesda, Md. Cases with enough clinicopathological documentation for the purpose of the study were selected from research and neuropathological files of 7 medical centers in 4 countries (Austria, France, England, and the United States). RESULTS: Median dysarthria latencies were short in PSP and MSA (24 months each), intermediate in CBD and DLB (40 and 42 months), and long in PD (84 months). Median dysphagia latencies were intermediate in PSP (42 months), DLB (43 months), CBD (64 months), and MSA (67 months), and long in PD (130 months). Dysarthria or dysphagia within 1 year of disease onset was a distinguishing feature for atypical parkinsonian disorders (APDs) (specificity, 100%) but failed to further distinguish among the APDs. Survival time after onset of a complaint of dysphagia was similar in PD, MSA, and PSP (15 to 24 months, P =.7) and latency to a complaint of dysphagia was highly correlated with total survival time (rho = 0.88; P<.001) in all disorders. CONCLUSIONS: Latency to onset of dysarthria and dysphagia clearly differentiated PD from the APDs, but did not help distinguish different APDs. Survival after onset of dysphagia was similarly poor among all parkinsonian disorders. Evaluation and adequate treatment of patients with PD who complain of dysphagia might prevent or delay complications such as aspiration pneumonia, which in turn may improve quality of life and increase survival time.

Aged↗
PubMed2003

Intimate evolution of proteins. Proteome atomic content correlates with genome base composition.

Discerning the significant relations that exist within and among genome sequences is a major step toward the modeling of biopolymer evolution. Here we report the systematic analysis of the atomic composition of proteins encoded by organisms representative of each kingdoms. Protein atomic contents are shown to vary largely among species, the larger variations being observed for the main architectural component of proteins, the carbon atom. These variations apply to the bulk proteins as well as to subsets of ortholog proteins. A pronounced correlation between proteome carbon content and genome base composition is further evidenced, with high G+C genome content being related to low protein carbon content. The generation of random proteomes and the examination of the canonical genetic code provide arguments for the hypothesis that natural selection might have driven genome base composition.

Animals↗
PubMed2002

Can mutation or fixation biases explain the allele frequency distribution of human single nucleotide polymorphisms (SNPs)?

One of the most abiding controversies in evolutionary biology concerns the role of neutral processes in molecular evolution. A main focus of the debate has been the evolution of isochores, the strong and systematic variation of base composition in mammalian genomes. One set of hypotheses argue that regions of similar GC are owing to localised mutational biases coupled with neutral evolution. The alternatives point to either selection or biased gene conversion as mechanisms to preferentially remove A or T bases, favouring G and C instead. Using a novel method, we compare models including such fixation biases to models based on mutation bias alone, under the assumption that non-coding, non-repetitive human DNA is at compositional equilibrium. While failing to fully explain the allele frequency distributions of recent single nucleotide polymorphism data, we show that the data are best fitted if the mutation bias is assumed to be constant across the genome, while fixation bias varies with GC content. We also attempt to estimate the strength of fixation bias, which increases linearly with increasing GC. Our approximation suggests that this force exists within the necessary parameter range: it is not so weak as to be drowned by random drift, but not so strong as to lead to exclusive use of G and C alone. Together these results demonstrate that mutation bias fails to explain the evolution of isochores, and suggest that either selection or biased gene conversion are involved.

Alleles↗
PubMed1996

Time-resolved line shape studies of Nd : YAG laser-induced microplasmas arising from gold surfaces.

A systematic study of the time evolution of the line shape of radiation emitted by a gold plasma and an exact line intensity calculation was carried out. The emission of the hot and dense plasma produced by a Q-switched Nd:YAG laser in atmospheric air was measured by a time-gated optical multichannel analyzer. Asymmetric Lorentz-type profile equations were tested for two gold lines (406.51, 389.79 nm) as a function of time. A strong broadening, asymmetry and shift is observable up to 800-1000 ns after the laser pulse. Spectral profiles of the delayed (with 0.8-1.0 micros) and time-integrated (gate time of 2.5 micros) measurements were found to be well represented by a symmetric Lorentz-type curve.

Journal Article↗
PubMed2005

First sequenced mitochondrial genome from the phylum Acanthocephala (Leptorhynchoides thecatus) and its phylogenetic position within Metazoa.

The complete sequence of the mitochondrial genome of Leptorhynchoides thecatus (Acanthocephala) was determined, and a phylogenetic analysis was carried out to determine its placement within Metazoa. The genome is circular, 13,888 bp, and contains at least 36 of the 37 genes typically found in animal mitochondrial genomes. The genes for the large and small ribosomal RNA subunits are shorter than those of most metazoans, and the structures of most of the tRNA genes are atypical. There are two significant noncoding regions (377 and 294 bp), which are the best candidates for a control region; however, these regions do not appear similar to any of the control regions of other animals studied to date. The amino acid and nucleotide sequences of the protein coding genes of L. thecatus and 25 other metazoan taxa were used in both maximum likelihood and maximum parsimony phylogenetic analyses. Results indicate that among taxa with available mitochondrial genome sequences, Platyhelminthes is the closest relative to L. thecatus, which together are the sister taxon of Nematoda; however, long branches and/or base composition bias could be responsible for this result. The monophyly of Ecdysozoa, molting organisms, was not supported by any of the analyses. This study represents the first mitochondrial genome of an acanthocephalan to be sequenced and will allow further studies of systematics, population genetics, and genome evolution.

Acanthocephala↗
PubMed2026

Paralogous evolution of the ITS2 region in Xiphophorus.

Ribosomal ITS2 is widely used in phylogenetic studies, yet its multigene organization and potential paralogy can obscure true species relationships. This proof-of-concept study investigates whether ITS2 sequences derived from long-read genomic data in multiple Xiphophorus species primarily reflect orthologous history or are shaped by ancient and local duplications. Phylogenetic analyses reveal two major, reciprocally mirroring ITS2 clades that represent long-standing paralogous rDNA lineages rather than simple allelic variants. The two paralogons show strong asymmetry in copy retention and loss for the majority of the species analyzed in this study. Exceptionally some other species are confined to one paralogon group and exhibit alternating ITS2 variants consistent with persistent ancestral polymorphism. A striking copy number imbalance in X. variatus, combined with its phylogenetic incongruence relative to the established species tree, is best explained by historical rDNA introgression followed by biased concerted evolution that nearly erased one paralogous copy. Despite incomplete homogenization, heterogeneous evolutionary rates, and occasional long-branch artifacts, the recovered paralog-specific topologies largely recapitulate the accepted Xiphophorus species phylogeny, indicating that ITS2 retains a robust organismal signal while also recording episodes of introgression and differential paralog evolution. These results demonstrate that explicit recognition of ITS2 paralogs can both improve phylogenetic interpretation and open avenues for future sequence-structure-based analyses of rDNA evolution and genus-level systematics in Xiphophorus.

Gene duplication↗
PubMedDate not supplied

Interpersonal relationships in isolation and confinement: long-term bed rest in head-down tilt position.

The long-term bed-rest was organized by ESA and CNES, in order to simulate the physiological effects of weightlessness: eight volunteers had to stay 42 days in bed, in a head down tilt position (-6 degrees). There were two subjects in a room, they could not be alone and it was difficult for them to have their own personal space and intimacy. In these circumstances, as in outer space, interpersonal relationships were of prime importance. This situation enabled us, through systematic observation, to analyze the evolution of the relational behavior in dyads, and to quote some social indicators of adaptation. Results show significant withdrawal, and the time spent alone was marked by the emergence, during the experiment, of specific preferential activities. Behavioral contagion was observed in each dyad (people engaged in the same activities at the same time), except in the one case of abandon. Moreover, the highest rates of inactivity and withdrawal were noted in this case. Verbal indicators were useful to comment these results and showed that, for all the dyads, one of the two subjects always played a regulating role by expressing a very positive perception of the situation. These results emphasize the importance of psycho-sociological factors in isolation and confinement. Thus, it appears that different modalities of interpersonal relationships, and not only verbal interactions, play a significant role in adaptation to stress situations.

Adaptation, Psychological↗
PubMed2001

Phylogenetic systematics turns over a new leaf.

Long restricted to the domain of molecular systematics and studies of molecular evolution, likelihood methods are now being used in analyses of discrete morphological data, specifically to estimate ancestral character states and for tests of character correlation. Biologists are beginning to apply likelihood models within a Bayesian statistical framework, which promises not only to provide answers that evolutionary biologists desire, but also to make practical the application of more realistic evolutionary models.

Journal Article↗
PubMed1997

A historical review of selected nursing and medical literature on urinary incontinence between 1850 and 1976.

The nursing and medical literature on urinary incontinence from 1850 to 1976 was reviewed to provide a historic perspective on care patterns before the current surge in interest in this common condition. Relevant nursing and medical journals and a number of textbooks from both fields were systematically examined to document the evolution of treatments and practices regarding urinary incontinence. Throughout the article, findings are examined in light of the broader historical context to reveal how and why practices were favored or disfavored at given times during the years under investigation. As expected, attitudes, values, and practices in the field reflected the state of knowledge and beliefs commonly held by nurses, physicians, and the general population.

Attitude of Health Personnel↗
PubMed2004

Shape and stability of self-assembled surface domains.

The shapes of two-dimensional (2D) nanostructures on surfaces are determined by their boundary energies as well as by long-range elastic, electrostatic or magnetic interactions. Although it is well known that long-range interactions can give rise to shape bifurcation-an abrupt change in shape symmetry at a critical size-a general description of the evolution of shape with size, systematically incorporating both the azimuthal dependence of the boundary energy and long-range interactions, has been lacking. Here we show that unconstrained shape relaxation, including previously ignored boundary curvature, leads to a novel, continuous shape change from convex at small size to concave at large size. In addition to demonstrating a method to quantitatively determine the azimuthal dependence of the boundary energy, we show that the energy gain associated with boundary curvature relaxation is a key factor in stabilizing surface nanostructures. For 7 x 7 domains on Si(111), boundary curvature reduces the formation free-energy by up to 50%.

Materials Testing↗
PubMed2001

Oxymonads are closely related to the excavate taxon Trimastix.

Despite intensive study in recent years, large-scale eukaryote phylogeny remains poorly resolved. This is particularly problematic among the groups considered to be potential early branches. In many recent systematic schemes for early eukaryotic evolution, the amitochondriate protists oxymonads and Trimastix have figured prominently, having been suggested as members of many of the putative deep-branching higher taxa. However, they have never before been proposed as close relatives of each other. We amplified, cloned, and sequenced small-subunit ribosomal RNA genes from the oxymonad Pyrsonympha and from several Trimastix isolates. Rigorous phylogenetic analyses indicate that these two protist groups are sister taxa and are not clearly related to any currently established eukaryotic lineages. This surprising result has important implications for our understanding of cellular evolution and high-level eukaryotic phylogeny. Given that Trimastix contains small, electron-dense bodies strongly suspected to be derived mitochondria, this study constitutes the best evidence to date that oxymonads are not primitively amitochondriate. Instead, Trimastix and oxymonads may be useful organisms for investigations into the evolution of the secondary amitochondriate condition. All higher taxa involving either oxymonads or Trimastix may require modification or abandonment. Affected groups include four contemporary taxa given the rank of phylum (Metamonada, Loukozoa, Trichozoa, Percolozoa), and the informal excavate taxa. A new "phylum-level" taxon may be warranted for oxymonads and Trimastix.

Animals↗
PubMed2003

Structural changes of hexamethylenetetramine and undecanedioic acid co-crystal (HMT-C11) as a function of the temperature.

HMT-C11 belongs to the family of adducts formed by the co-crystallization of N(4)(CH(2))(6) molecules (hexamethylenetetramine or HMT) and aliphatic dicarboxylic acids HOOC(CH(2))(n - 2)COOH with 5 </= n </= 13 (Cn). The adducts exhibit a layered structure in which the packing between HMT and Cn is determined by strong hydrogen bonds. The compounds in this family studied so far present thermotropic structural phase transitions and, depending on the chain length, disordered, twinned and modulated phases. The structure refinement of HMT-C11 based on X-ray diffraction experiments indicates three distinct phases from the melting point down to liquid nitrogen temperature: phase I is not crystalline; phase II is disordered (stacking fault) and its average structure is described in space group Bmmb; phase III is partially disordered and its symmetry is P2(1)/c. The systematic study of the structure evolution of phase III upon cooling revealed that the disorder has a dynamic character (anharmonicity). The main structural change observed from 293 K down to 93 K is the increase of the tilting angle of the C11 chains relative to the layer plane and the rotation of the HMT molecules. Both HMT and C11 behave like rigid bodies in the temperature range investigated. The quality of the refinements leads to a conclusive model for the O-H.N hydrogen bonds linking HMT and C11.

Journal Article↗
PubMedDate not supplied

[Instrument for the evaluation of the adult patients' ability for self-care--CADEM].

This study develops a tool to facilitate the determination of adult patients selfcare ability aiming at promoting clear and objective communication. The tool developed, called CADEM, establishes levels to determine patient's categorization according to their need of nursing care. It has been-considered that CADEM is a valid tool and can help in planning nursing care, and also to register the patients' evolution through its continued and systematic use, therefore helping to justify necessary changes in Nursing care planning.

Activities of Daily Living↗
PubMed2000

Emerging distance degree programs.

The variation in program focus and style is examined in this column, which also identifies resources for evaluation. The integration of Web-based or other distance modality materials to conventional courses, and the expansion of traditional universities to include a virtual campus, should proceed with caution and systematic evaluation. It is an evolution that offers both rewards and pitfalls, but requires more rigorous examination. This article provides information about pedagogical issues and additional distance-education master's degree programs. Some are new, while others are established.

Education, Distance↗
PubMed1992

[Gene pool and gene geography of the USSR population].

Gene pool and gene geography are discussed from the point of view of their conceptual history beginning from the original concept of A.S. Serebrovskiĭ (1928). Difference between the present-day gene geography and gene geography of gene pool is accentuated: the former only represents a portion of the latter. Historical and territorial integrity of the USSR population gene pool, in conjunction with its huge diversity, is the main problem being analysed by various means of computerized genetic cartography. Coupled with the gene frequency mapping, following methods were also used: mapping of average heterozygosity, of interpopulation differentiation, of principal component scores and mapping of geographical trend for each mapped genetic parameter. The work is based on 100 allelic genes and haplotypes from 30 independent loci studied on the average in 225 local populations. Statistical analysis of gene geographical maps is based on 3975 nodes of regular cartographic net for the USSR territory. The wind rose of systematic changes in the USSR gene pool has three main geographic orientations: W-E, SW-NE and S-N. At the same time, there are only two main systematic forces of gene pool evolution: the force of social history with predominant W-E orientation and the force of natural history with predominant S-N orientation of their actions. The heterozygosity level of gene pool declines strictly in accordance with the resultant in the SW-NE direction.

Alleles↗
PubMedDate not supplied

[Role of oxygen in the vital activity of aerobic organisms].

New experimental data that underlie construction of an adaptive-metabolic conception as to curative effect of hyperbaric oxygenation are systematized in the aspect of evolution. Oxygen under high pressure (300 kPa, 60 min) exerts a specific effect on functions of redox and antiredox systems and nonspecific effect determining adaptation mechanisms of functional (regulatory, effector), metabolic (bioenergy, detoxication, biosynthetic) and morphogenetic (cellular and intracellular regeneration) types at different (hyper-, normo- and hypobiotic) levels of vital activity as dependent on the metabolic activity of the functional structures under pathology conditions.

Adaptation, Physiological↗