SEARCH · PubMed Health

Results for “Continuous 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 1,171 records · Page 65Linked to original sources

PubMed2000

Repeated, recent and diverse transfers of a mitochondrial gene to the nucleus in flowering plants.

A central component of the endosymbiotic theory for the bacterial origin of the mitochondrion is that many of its genes were transferred to the nucleus. Most of this transfer occurred early in mitochondrial evolution; functional transfer of mitochondrial genes has ceased in animals. Although mitochondrial gene transfer continues to occur in plants, no comprehensive study of the frequency and timing of transfers during plant evolution has been conducted. Here we report frequent loss (26 times) and transfer to the nucleus of the mitochondrial gene rps10 among 277 diverse angiosperms. Characterization of nuclear rps10 genes from 16 out of 26 loss lineages implies that many independent, RNA-mediated rps10 transfers occurred during recent angiosperm evolution; each of the genes may represent a separate functional gene transfer. Thus, rps10 has been transferred to the nucleus at a surprisingly high rate during angiosperm evolution. The structures of several nuclear rps10 genes reveal diverse mechanisms by which transferred genes become activated, including parasitism of pre-existing nuclear genes for mitochondrial or cytoplasmic proteins, and activation without gain of a mitochondrial targeting sequence.

Amino Acid Sequence↗

PubMed2006

The transformation of spinal curvature into spinal deformity: pathological processes and implications for treatment.

BACKGROUND: This review summarizes what is known about the pathological processes (e.g. structural and functional changes), by which spinal curvatures develop and evolve into spinal deformities. METHODS: Comprehensive review of articles (English language only) published on 'scoliosis,' whose content yielded data on the pathological changes associated with spinal curvatures. Medline, Science Citation Index and other searches yielded > 10,000 titles each of which was surveyed for content related to 'pathology' and related terms such as 'etiology,' 'inheritance,' 'pathomechanism,' 'signs and symptoms.' Additional resources included all books published on 'scoliosis' and available through the Arizona Health Sciences Library, Interlibrary Loan, or through direct contact with the authors or publishers. RESULTS: A lateral curvature of the spine-'scoliosis'-can develop in association with postural imbalance due to genetic defects and injury as well as pain and scarring from trauma or surgery. Irrespective of the factor that triggers its appearance, a sustained postural imbalance can result, over time, in establishment of a state of continuous asymmetric loading relative to the spinal axis. Recent studies support the longstanding hypothesis that spinal deformity results directly from such postural imbalance, irrespective of the primary trigger, because the dynamics of growth within vertebrae are altered by continuous asymmetric mechanical loading. These data suggest that, as long as growth potential remains, evolution of a spinal curvature into a spinal deformity can be prevented by reversing the state of continuous asymmetric loading. CONCLUSION: Spinal curvatures can routinely be diagnosed in early stages, before pathological deformity of the vertebral elements is induced in response to asymmetric loading. Current clinical approaches involve 'watching and waiting' while mild reversible spinal curvatures develop into spinal deformities with potential to cause symptoms throughout life. Research to define patient-specific mechanics of spinal loading may allow quantification of a critical threshold at which curvature establishment and progression become inevitable, and thereby yield strategies to prevent development of spinal deformity.Even within the normal spine there is considerable flexibility with the possibility of producing many types of curves that can be altered during the course of normal movements. To create these curves during normal movement simply requires an imbalance of forces along the spine and, extending this concept a little further, a scoliotic curve is produced simply by a small but sustained imbalance of forces along the spine. In fact I would argue that no matter what you believe to be the cause of AIS, ultimately the problem can be reduced to the production of an imbalance of forces along the spine 1.

Journal Article↗

PubMed2000

Evolution of the perioperative clinical nurse specialist role.

Perioperative nursing roles continue to rapidly change as we enter the twenty-first century. The need for strong leadership skills, expert clinical skills, creative management, ongoing continuing education, and research continues to grow in every department of surgical services. The clinical nurse specialist plays an important role in addressing each of these needs. Great opportunities exist within the field of nursing for perioperative nurses to expand their practice using their creativity, ideas, and skills. Using the clinical nurse specialist in the perioperative setting can foster creativity, stimulate development of new methods based on research, and maximize the delivery of high quality care by the entire OR staff.

Consultants↗

PubMed1998

Evolution of outpatient parenteral antibiotic therapy.

The future will no doubt continue to promote safe, cost-effective therapies such as outpatient intravenous therapy. It is imperative that physicians trained and knowledgeable in the administration of outpatient intravenous antimicrobial drug administration continue to assume responsibility and leadership roles.

Anti-Bacterial Agents↗

PubMed2005

Evolution of nuclearly encoded mitochondrial genes in Metazoa.

All Metazoan nuclear genomes underwent a continuous process of both complete and partial genetic material gain and loss. The forces modulating these events are also subject to the strict interaction between nuclear and mitochondrial (mt) genome. In this context we investigate the evolution of nuclear genes encoding proteins which target the mitochondrion, with a particular attention to genes involved in oxidative phosphorylation (OXPHOS), one of the most ancient and conserved functions. To examine thoroughly the evolutionary strategies that preserve OXPHOS and coordinate the two cellular genomes, a comparative analysis has been carried out for 78 OXPHOS gene families in several Metazoa (insects, tunicates, fishes and mammals). We demonstrate that the duplication rate of OXPHOS genes increases passing from invertebrates to vertebrates consistently with the total increase in genome size, but all species are prone to negatively select OXPHOS duplicates compared to the general trend of nuclear gene families. These results are consistent with the 'balance hypothesis' and, at least in insects, the expression of duplicate genes is low and strongly testis-biased.

Animals↗

PubMed1989

Increased Tolerance to Photoinhibitory Light in Paraquat-Resistant Conyza bonariensis Measured by Photoacoustic Spectroscopy and CO(2)-Fixation.

Tolerance to photoinhibition was compared between a paraquat-resistant and a sensitive biotype of Conyza bonariensis (L.). Cronq. Photoinhibitory damage was measured as a decrease in oxygen evolution or energy storage using photoacoustic spectroscopy, or as a decrease of (14)CO(2)-fixation. Prior to exposure to high fluence rates, both biotypes had similar quantum yields of oxygen evolution and energy storage. After exposure to high intensity light, the resistant biotype continued to evolve oxygen and to store energy with a high quantum yield while both energy storage and oxygen evolution were severely reduced in the sensitive biotype. CO(2)-fixation was less rapidly inhibited in the resistant biotype compared to the sensitive one. The data show that the paraquat resistant biotype with its high constitutive levels of the chloroplast localized enzymes of the oxygen detoxification pathway, is also partially protected from photoinhibition. This supports the theory that an enhanced radical scavenging system can give temporary protection against photooxidative damage from a variety of sources.

Journal Article↗

PubMed2006

E-cadherin, laminin and collagen IV expression in the evolution from dysplasia to oral squamous cell carcinoma.

OBJECTIVES: Study the loss or reduction of the cellular adhesion mediated for E-cadherin in oral leukoplakias, oral squamous cell carcinomas and metastatic nodules. Study the loss of continuity of the laminin and collagen IV expression in the epithelial basal membrane from the biological development of the oral leukoplakias and oral carcinomas. MATERIAL AND METHOD: we have studied 124 samples of patient pays leukoplakias and oral carcinomas with diverse diagnosis that embrace from normal epithelium (13 samples), mild dysplasias (2), moderate dysplasias (12), in situ carcinomas (13), microinvasive carcinomas (11) oral squamous cell carcinomas (64 samples) and metastatic nodules (9). 7 blocks of tissue microarrays were built with needle of 2mm and was carried out a study by means of immunohistochemical technique for E-cadherin (clone 36, Biogenex), Laminin (078P, Biogenex) and Collagen IV (PHM12, Biogenex). RESULTS: In Mild and Moderate Dysplasias the results present loss of E-cadherin, Laminin, and Collagen IV (20%) expression. in situ and microinvasive carcinomas, the results presented loss of E-cadherin expression (73%), and loss in Laminin and Collagen IV expression (57%). In the squamous cell carcinomas , we find E-cadherin underexpression (90%) and discontinuity in the Basal Membrane. (70%). All the metastatic nodules presented loss of E-cadherin expression and discontinuity in Laminin and Collagen IV expression. CONCLUSIONS: The loss of E-cadherin expression is increased when increasing the dysplasia grade of lesions. The loss of continuity in the laminin and Collagen IV expression follow a parallel evolution from dysplasias to metastatic nodules. The underexpression of the three markers has been significant in the evolution of the oral lesions.

Adult↗

PubMedDate not supplied

Haemostatic changes in systemic inflammatory response syndrome during continuous renal replacement therapy.

BACKGROUND: Endothelial damage and hemostatic imbalance play an important role in the evolution of the Systemic Inflammatory Response Syndrome (SIRS) into the Multiple Organ Dysfunction Syndrome (MODS). In Acute Renal Failure associated with SIRS, different types of Continuous Renal Replacement Therapies (CRRT) may give non-renal benefits by modifying the levels of some factors related to those disturbances. METHODS: Forty patients with SIRS-associated ARF were randomised to receive either continuous venovenous hemofiltration (CVVH) or continuous venovenous hemodiafiltration (CVVHDF) for the first 24 h. Afterwards the CRRT method was reversed. The group treated with CVVH moved to CVVHDF and that treated with CVVHDF to CVVH for the next 24 h. Plasma levels of: von Willebrand Factor (vWF), thrombomodulin, plasminogen activity inhibitor type 1 (PAI-1: antigen and activity), tissue type plasminogen activator (t-PA: antigen), prothrombin fragment 1+2 (F1+2) and thrombin-antithrombin complexes (TAT) were measured previously to CRRT (base-line), and after 24 and 48 hours of therapy. Multivariate ANOVA was the statistical method used. RESULTS: In the MANOVA study a significant decrease in PAI-1 activity during the treatment procedure was observed (horizontality p <0.05). PAI-1 antigen showed a tendency to decrease although without statististical significance. There were no significantly different changes in the other factors analysed during either CRRT (parallelism p >0.05). At the base-line point, all the factors were higher than normal values in healthy adults. CONCLUSIONS: The present study suggests that CRRT, in patients with SIRS, may promote a decrease in PAI-1 and consequently, a better outcome. There were no differences between the CVVH and the CVVHDF methods regarding the factors analysed. The present data confirms that there is an important endothelial and hemostatic dysfunction in SIRS from the early phases.

Acute Kidney Injury↗

PubMed1982

Ascorbate as a substrate for photoproduction of hydrogen by photosystem I of chloroplasts.

The photoproduction of hydrogen by 2-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU)-inhibited chloroplasts from ascorbate under anaerobic conditions was studied in the pH range 5.0 to 7.5 using methyl viologen (MV), N,N,N',N'-tetramethyl-P-phenylenediamine (TMPD), and excess hydrogenase from Desulfovibrio desulfuricans. (a) At neutral and basic pHs, the photoreduction of MV, which reacted back with photoxidized ascorbate (dehydroascorbate [DHASC]), and the rates of H(2) photoproduction were very low. The slow H(2) photoproduction was explained by the reversible reduction of MV by the photoproduced H(2) (catalyzed by hydrogenase) and its reoxidation by DHASC resulting in H(2) uptake. (b) At pH 5.2, relatively high initial rates of H(2) photoproduction were obtained, which were comparable to the rates of O(2) consumption at pH 5.2 by photosystem I (catalyzed by photoreduced MV). However, accumulation of photoreduced MV under anaerobic conditions was not detected. In the presence of high concentrations of protons, the H(2) uptake by DHASC was very slow because the equilibrium concentration of H(2)-reduced MV was very small, thus allowing H(2) evolution mediated by photoreduced MV to compete with the back reaction with DHASC. (c) The continuous accumulation of DHASC, which was generated together with H(2), gradually slowed the H(2) evolution until it stopped after about 3 hours. At high concentrations, DHASC was able to compete with the coupling of photoreduced MV to hydrogenase and H(2) evolution. (d) Dithiothreitol (DTT) reduced the DHASC and consequently competed with the back reaction of the photoreduced and H(2)-reduced MV with DHASC. DTT thus prolonged the time period of H(2) photoproduction from ascorbate and abolished the dependence of its rate on pH in the range of 5.2 to 7.5 (e) A study of H(2) uptake by chemically oxidized ascorbate (in the dark) showed that MV and hydrogenase were both required to catalyze electron transfer from H(2) to DHASC. TMPD prevented this H(2) consumption by DHASC (in a chloroplast reaction mixture containing MV and hydrogenase). Illumination restored the H(2) uptake presumably by generating reduced MV which activated the hydrogenase.

Journal Article↗

PubMedDate not supplied

Redefining continuing education delivery.

Just as technology is transforming the delivery of education, the Internet and advanced telecommunication applications are changing the "face" of CE and the connotation of "lifelong learning." As late as the mid-1980s, a discussion of computer applications in nursing CE focused on the "timely" transition to microcomputers as tools for the enhancement of managerial tasks for increased productivity. Even as recently as 1990, there seemed to be "time" for those providers who were "slower to adopt innovation" to "catch up." Now, the CE provider who does not integrate the microcomputer and advanced telecommunications as an integral component of their delivery modalities may be outsourced rapidly by an educational or commercial competitive unit that is able to utilize the communication medium, mergers and partnerships, enterprise, and individual lifestyle and learning patterns that will epitomize the CE unit of the 21st century. As with the "re-engineering" of nursing education, the "re-engineered" delivery modalities of evolving CE entity might now best be conceptualized on a continuum from the traditional mode that time and place dependent to a mode of synchronous and asynchronous data and advanced telecommunication. Delivery methods will need to be selected according to the target populations, content, and situation. The health-care educational provider may discover, as in other industries, that a combination of distance and residential offerings will be the most successful medium for the delivery of CE to the progressively more "information and technologically savvy" lifelong learner of the 21st century. In addressing the dramatic effects of the information technology era on the refocused multimedia/interactive delivery method for student education, educators amply quoted Bob Dylan's phrase of the 1960s, "The times, they are a-changing." And so, we see that the times are also changing at an astronomical rate for the health-care educational provider as well as the individual health-care worker consumer. A number of national and world-wide trends are propelling rapid changes in the delivery modalities and types of emerging providers for health-care CE. Examples of these advanced telecommunications applications of CE opportunities for health-care personnel are becoming more prevalent in the literature and the pattern of CE marketing, and delivery evolution can be seen readily on the Internet. Continued program success and viability will belong to the individuals and organizations who are able to conceptualize and envision the positive transformations and opportunities that can occur from the evolving paradigm of education for the lifelong learner of the 21st century.

Computer Communication Networks↗

PubMed1997

Fragmented and scrambled mitochondrial ribosomal RNA coding regions among green algae: a model for their origin and evolution.

Mitochondrial ribosomal RNA coding regions in the only three green algal taxa investigated to date are fundamentally different in that they are continuous in Prototheca wickerhamii, but highly fragmented and scrambled in Chlamydomonas reinhardtii and Chlamydomonas eugametos. To gain more insight into the mode of evolution of fragmented and scrambled mitochondrial ribosomal RNA (rRNA) genes within the green algal group, this work (1) provides additional information on fragmentation patterns of mitochondrial small- and large-subunit (SSU and LSU) rRNAs that strongly supports the concept of a gradual increase in the extent of discontinuity of mitochondrial rRNAs among chlorophycean green algae and (2) reports the first example of fragmented and scrambled mitochondrial LSU rRNA coding regions in a green algal taxon outside the Chlamydomonas group. The present study (1) suggests that the scrambling of the mitochondrial rRNA coding regions may have occurred early in the evolution of fragmented and scrambled mitochondrial rRNA genes within the chlorophycean green algal group, most likely in parallel with the fragmentation events, (2) proposes recombination as a possible mechanism involved in the evolution of these mitochondrial rRNA genes, and (3) presents a hypothetical pathway for converting continuous mitochondrial rRNA genes into the highly fragmented and scrambled rRNA coding regions of Chlamydomonas through a series of recombinatorial events between short repeated sequences.

Animals↗

PubMed2004

Origins of introns based on the definition of exon modules and their conserved interfaces.

Central to the unraveling of the early evolution of the genome is the origin and role of introns. The evolution of the genome can be characterized by a continuous expansion of functional modules that occurs without the interruption of existing processes. The design-by-contract methodology of software development offers a modular approach to design that seeks to increase flexibility by focusing on the design of constant interfaces between functional modules. Here, it is shown that design-by-contract can offer a framework for genome evolution. The definition of an ancient exon module with identical splice sites leads to a relatively simple sequence of events that explains the role of introns, intron phase differences and the evolution of multi-exon proteins in an RNA world. An interaction of the experimentally defined six-nucleotide splicing consensus sequence together with a limited number of primitive ribozymes can account for a rapid creation of protein diversity.

Animals↗

PubMed1983

Selection and evolution in macromolecular systems.

The notion of a quasi-species represents the ensemble of macromolecular sequences derived by the mechanism of mutation and replication from a single wild type. In Eigen (1971) and Eigen & Schuster (1979), the deterministic evolution of this ensemble under constant environmental conditions is given in terms of continuous models which describe the dynamics of the distribution of polynucleotides. This paper starts from a discrete model of macromolecular evolution and introduces the notion of a genealogy in order to study the dynamics of the quasi-species in constant and variable environments. We introduce, in terms of these genealogies, the notions of entropy and adaptive value of a quasi-species and the notion of capacity of the environment. We discuss the significance of these indices as measures of selective value and we analyse the conditions under which these measures coincide with the growth rate of the quasi-species.

Base Sequence↗

PubMed2006

Source-sink dynamics of virulence evolution.

To understand the evolution of genetic diversity within species--bacterial and others--we must dissect the first steps of genetic adaptation to novel habitats, particularly habitats that are suboptimal for sustained growth where there is strong selection for adaptive changes. Here, we present the view that bacterial human pathogens represent an excellent model for understanding the molecular mechanisms of the adaptation of a species to alternative habitats. In particular, bacterial pathogens allow us to develop analytical methods to detect genetic adaptation using an evolutionary 'source-sink' model, with which the evolution of bacterial pathogens can be seen from the angle of continuous switching between permanent (source) and transient (sink) habitats. The source-sink model provides a conceptual framework for understanding the population dynamics and molecular mechanisms of virulence evolution.

Adaptation, Biological↗

PubMed1989

Allergy to pollen grains from Amaranthaceae and Chenopodiaceae in Cordoba, Spain. Annual and daily variation of pollen concentration.

We have studied the annual and daily variation of pollen grains from Amaranthaceae and Chenopodiaceae for 3 consecutive years. Samples of pollen grains from both families, which make a stenopalynologic group, were collected by the volumetric method with the aid of a Burkard spore-trap. These pollen grains were found to occur in the atmosphere of the city of Córdoba virtually throughout the year, although their presence was continual only between April and October with maximum concentrations detected in the summer months. We have also studied the daily variation of pollen concentration, which peaked between 10 AM and 3 PM. In order to determine the incidence of pollinotic patients sensitive to pollen grains from Chenopodium, we reviewed 1000 clinical records available in the Allergy Unit and found 8.42% to be allergic. On evaluation of the time evolution of the symptoms we found that most patients continued to show them until September each year.

Air Pollution↗

PubMed2003

Creationism and intelligent design.

Creationism, the rejection of evolution in favor of supernatural design, comes in many varieties besides the common young-earth Genesis version. Creationist attacks on science education have been evolving in the last few years through the alliance of different varieties. Instead of calls to teach "creation science," one now finds lobbying for "intelligent design" (ID). Guided by the Discovery Institute's "Wedge strategy," the ID movement aims to overturn evolution and what it sees as a pernicious materialist worldview and to renew a theistic foundation to Western culture, in which human beings are recognized as being created in the image of God. Common ID arguments involving scientific naturalism, "irreducible complexity," "complex specified information," and "icons of evolution," have been thoroughly examined and refuted. Nevertheless, from Kansas to Ohio to the U.S. Congress, ID continues lobbying to teach the controversy, and scientists need to be ready to defend good evolution education.

Biological Evolution↗

PubMed1984

[Hepatotoxicity of isaxonine phosphate: 4 cases of severe subacute hepatitis].

Isaxonine phosphate is known to induce acute hepatitis which in most cases is reversible after withdrawal of the drug. The authors describe 4 new cases of hepatitis which differ from those previously reported by their evolutive and pathological features. In 3 cases, the outcome was fatal within a delay of 15-40 days despite discontinuation of the drug, and was associated with hepatic encephalopathy and ascites. In the 4 cases plasma concentration of alanine- and aspartate-aminotransferases were initially increased (up to 33 X upper normal range) and decreased to normal values in 2 cases. Plasma bilirubin levels were also elevated at first and continued to increase during the first 15 days of evolution. Pathological examination of the liver showed mild necrosis, sometimes with a piecemeal or a bridging aspect, marked fibrosis infiltrated with mononuclear and neutrophil polymorphonuclear cells and a conspicuous biliary neogenesis. In these particular cases of hepatitis due to isaxonine phosphate, occurrence in women, increased serum immunoglobulin levels, presence of autoantibodies, clinical and pathological aspects resembling those observed in iproniazid hepatitis may be suggestive of an immunological, or even autoimmune, mechanism.

Acute Disease↗

PubMed2003

Streamer initiation in atmospheric pressure gas discharges by direct particle simulation.

A two-dimensional particle code that simulates electrical breakdown of gases by modeling avalanche evolution from the initial ion-electron pair up to the development of a streamer is presented. Trajectories of individual particles are followed, the self-field is included consistently and collision processes are accurately modeled using experimentally determined cross sections. It is emphasized that the tadpolelike structure of well-formed streamer heads is present throughout the avalanche phase, and that the transition to the self-similar evolution characteristic of the streamer phase merely reflects the continued development of this structure. The importance of this for conventional fluid simulations of streamers, where the initial conditions for the streamer are taken to be a structureless Gaussian concentration of neutral plasma with significant density, is discussed. In the (realistic) situation where several avalanches are present simultaneously the large self-fields that rapidly develop lead to a strong interaction between them, in accord with the standard "cartoon" of streamer evolution.

Journal Article↗