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Results for “Continuous Evolution”

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PubMed2002

The importance of histopathological and clinical variables in predicting the evolution of colon cancer.

UNLABELLED: It has been a consensus that prognostic factors should always be taken into account before planning treatment in colorectal cancer. AIM: A 5 year prospective study was conducted, in order to assess the importance of several histopathological and clinical prognostic variables in the prediction of evolution in colon cancer. Some of the factors included in the analysis are still subject to dispute by different authors. METHODS: 46 of 53 screened patients qualified to enter the study and underwent a potentially curative resection of the tumor, followed, when necessary, by adjuvant chemotherapy. Univariate and multivariate analyses were carried out in order to identify independent prognostic indicators. The endpoint of the study was considered the recurrence of the tumor or the detection of metastases. RESULTS: 65.2% of the patients had a good evolution during the follow up period. Multivariate survival analysis performed by Cox proportional hazard model identified 3 independent prognostic factors: Dukes stage (p = 0.00002), the grade of differentiation (p = 0.0009) and the weight loss index, representing the weight loss of the patient divided by the number of months when it was actually lost (p = 0.02). Age under 40 years, sex, microscopic aspect of the tumor, tumor location, anemia degree were not identified by our analysis as having prognostic importance. CONCLUSIONS: Histopathological factors continue to be the most valuable source of information regarding the possible evolution of patients with colorectal cancer. Individual clinical symptoms or biological parameters such as erytrocyte sedimentation rate or hemoglobin level are of little or no prognostic value. More research is required relating to the impact of a performance status index (which could include also weight loss index) as another reliable prognostic variable.

Aged↗

PubMed2005

Evolution of eyelid surgery.

Cosmetic rejuvenation of the periorbital area has been an area of continual advancement in surgical knowledge over the past century. It is anticipated that some new currently described advances will be incorporated into continuing practice patterns, with advances in nonsurgical rejuvenation and surgical techniques.

Blepharoplasty↗

PubMed2005

Evolutionary approaches to understanding sleep.

A major controversy over REM sleep's role in memory processing may owe to inadequate allowances for the highly conservative nature of evolutionary adaptations. The controversy hinges on whether NREM sleep, alone, retains primitive memory processing capabilities. The selective pressure for primitive sleep, is thought to have been the need to obviate conflicts between enormous neural processing requirements of complex visual analysis and split-second control of movements, on the one hand, and memory processing, on the other. The most efficient memory processing during mammalian and avian sleep appears to be a two-step process: synapses in individual component circuits of events are reinforced primarily by slow brain waves during NREM sleep, with the reinforced components temporally bound by fast waves, and manifested as dreams, during REM sleep. This dual action could account for partitioning of sleep periods into multiple NREM-REM cycles. It is proposed that in the absence of REM sleep, all needed memory processing can be accomplished by NREM sleep, alone, though less efficiently. Many symptoms of fatal familial insomnia are attributed to subnormal nightly reinforcement of brain circuitry because of almost total loss of sleep, and compensatory responses thereto during waking. During this disorder, sensory circuitry seemingly is spared by virtue of its supernormal reinforcement during almost continuous waking. Contrariwise, sparing of an adult's 'higher faculties' in encephalitis lethargica appears to owe to supernormal circuit reinforcement during almost continuous sleep.

Awareness↗

PubMed1998

Drug concentration heterogeneity facilitates the evolution of drug resistance.

Pathogenic microorganisms use Darwinian processes to circumvent attempts at their control through chemotherapy. In the case of HIV-1 infection, in which drug resistance is a continuing problem, we show that in one-compartment systems, there is a relatively narrow window of drug concentrations that allows evolution of resistant variants. When the system is enlarged to two spatially distinct compartments held at different drug concentrations with transport of virus between them, the range of average drug concentrations that allow evolution of resistance is significantly increased. For high average drug concentrations, resistance is very unlikely to arise without spatial heterogeneity. We argue that a quantitative understanding of the role played by heterogeneity in drug levels and pathogen transport is crucial for attempts to control re-emergent infectious disease.

Anti-HIV Agents↗

PubMed1987

Evolution of a nursing center.

The collaborative spirit that characterized the project period resulted in continuation of the nursing center after the expiration of the contract. The town purchased the modular unit and provides ongoing maintenance, housekeeping services, and utilities. A secretary is funded through a program providing employment for older adults. The University provides the salary for one full-time certified NP to manage the center, and students and faculty together provide care and continue the services of the center. An advisory committee composed of representatives from the town, senior center, and university oversees the ongoing activities of the center. Although the center has evolved from a small room to a fully equipped modular unit, the purpose of providing high-quality nursing care through education, practice, and research remains the same.

Aged↗

PubMedDate not supplied

[A continuously revised problem: the treatment of stenosis of the male urethra].

This paper outlines the evolution experienced in the treatment of male urethral stenosis over the last 25 years, based on self experience and the review of relevant literature. Criteria justifying such evolution are illustrated including explanations and criticism of techniques from the primitive urethral "dilatation" to endoprothesis. Special emphasis is laid on the importance of pre-operative diagnosis and the need for adequate urethrographic examination which, very often, the urologist himself should perform in order to avoid interpretation mistakes and lamentable surprises during surgery. Finally, in view of all the above, a strategy of practical actuation is outlined.

Humans↗

PubMed1994

AANA Journal course: update for nurse anesthetists--outcome measures in anesthesiology: are we going in the right direction?

Anesthesia care appears to be a remarkably safe enterprise. Improvements in the "safety" of the process can be attributed to technological, pharmacological, cognitive, and behavioral factors. One yardstick by which we measure the impact of change is by the study of outcomes. This installment of the AANA Journal course deals with the issue of "safety" and the role that outcome studies play in quantifying its evolution.

Anesthesia↗

PubMed1996

The evolution of aminoglycoside therapy: a single daily dose.

After five decades of clinical use, aminoglycosides continue to be important antibiotics in the management of gram-negative infections. However, antimicrobial therapy with gentamicin, tobramycin, amikacin and netilmicin has been complicated by the risk of nephrotoxicity and ototoxicity. Considerable research has been conducted to determine the optimal aminoglycoside dosing method that will produce maximum efficacy with minimal toxicity. Experimental data and clinical experience suggest that aminoglycoside regimens modified from standard dosing (every eight to 12 hours) to once-daily dosing may provide improved clinical outcomes, with reduced toxicity and cost of therapy. Gentamicin, tobramycin and netilmicin may be administered in single daily dosages ranging from 4 to 7 mg per kg, and amikacin may be given in a dosage of 15 to 20 mg per kg once daily.

Aminoglycosides↗

PubMed1996

[Measles and pregnancy. Evolution and management].

Measles is a highly infectious disease. In Mexico, nevertheless the postvaccine era, continue being an endemic disease. It has been described that measles increase the maternal mortality, because pregnant women have a more severe clinical course of the disease; measles also has negative repercussion on pregnancy, increasing the frequency of premature labor. We report two pregnant women complicated with measles, both of them had a clinical course of the disease and they didn't have obstetric or neonatal complications.

Adult↗

PubMed2000

Taxon sampling, correlated evolution, and independent contrasts.

Independent contrasts are widely used to incorporate phylogenetic information into studies of continuous traits, particularly analyses of evolutionary trait correlations, but the effects of taxon sampling on these analyses have received little attention. In this paper, simulations were used to investigate the effects of taxon sampling patterns and alternative branch length assignments on the statistical performance of correlation coefficients and sign tests; "full-tree" analyses based on contrasts at all nodes and "paired-comparisons" based only on contrasts of terminal taxon pairs were also compared. The simulations showed that random samples, with respect to the traits under consideration, provide statistically robust estimates of trait correlations. However, exact significance tests are highly dependent on appropriate branch length information; equal branch lengths maintain lower Type I error than alternative topological approaches, and adjusted critical values of the independent contrast correlation coefficient are provided for use with equal branch lengths. Nonrandom samples, with respect to univariate or bivariate trait distributions, introduce discrepancies between interspecific and phylogenetically structured analyses and bias estimates of underlying evolutionary correlations. Examples of nonrandom sampling processes may include community assembly processes, convergent evolution under local adaptive pressures, selection of a nonrandom sample of species from a habitat or life-history group, or investigator bias. Correlation analyses based on species pairs comparisons, while ignoring deeper relationships, entail significant loss of statistical power and as a result provide a conservative test of trait associations. Paired comparisons in which species differ by a large amount in one trait, a method introduced in comparative plant ecology, have appropriate Type I error rates and high statistical power, but do not correctly estimate the magnitude of trait correlations. Sign tests, based on full-tree or paired-comparison approaches, are highly reliable across a wide range of sampling scenarios, in terms of Type I error rates, but have very low power. These results provide guidance for selecting species and applying comparative methods to optimize the performance of statistical tests of trait associations.

Biological Evolution↗

PubMed1996

Recent influenza B viruses in Europe: a phylogenetic analysis.

BACKGROUND: Influenza B virus evolution is currently in a unique situation having two cocirculating main lineages B/Yamagata/16/88 (YM/88)-like and B/Victoria/2/87 (VI/87)-like viruses. Continuation of this bifurcation would mean development towards distinct forms resembling the HA subtypes of influenza A viruses. OBJECTIVE: We wanted to examine both intraepidemic heterogeneity and recent evolution in these two lineages. The initial purpose was to determine the geographic distribution of the two sublineages of the VI/87-like viruses in Europe in 1989-1990 under circumstances of low epidemic activity. Due to the outbreaks of YM/88-like viruses since 1991, the study was extended to contain the evolution of these viruses and their genetic relationship with the vaccine strains of that time. STUDY DESIGN: The HA1 gene sequences of 33 influenza B strains isolated in ten European countries since 1989 were determined and compared with those available through databases or personal contacts. RESULTS: The two main lineages, YM/88-like and VI/87-like viruses, both continued to circulate. In both lineages, changes in the potential glycosylation sites were observed. Two sublineages of the VI/87 lineage cocirculated during the 1989-1990 season with somewhat different geographic distributions. A high degree of intraepidemic heterogeneity was observed, as well as examples of conserved nucleotide sequences. CONCLUSIONS: It is important to follow the evolution and circulation of VI/87-like viruses. Current vaccines give poor or no protection against VI/87-like viruses in immunologically unprimed children or even in primed adults (Levandowski et al., 1991, Pyhala et al., 1994). Changes in the potential glycosylation pattern in the latest virus isolates of both main lineages have occurred and it is interesting to see the significance of these changes to viral evolution.

Journal Article↗

PubMed1988

Effects of continuous low dose-rate irradiation: computer simulations.

The effects of continuous low dose-rate irradiation are studied with a computer model that incorporates cell kinetics and the accumulation and repair of radiation damage. This theoretical approach independently explores the effects on survival curves of a phase block, inherited damage and proliferation by dying cells. The computer model is a Monte Carlo simulation which follows the evolution in time of the family trees of a growing cell population under continuous irradiation. The model uses as input the measured phase-specific survival curves for acute exposures and the cell kinetic parameters to generate survival curves for continuous low dose-rate irradiations. Cell survival curves for Chinese hamster lung cells (V79) for dose rates ranging from 15 to 500 cGy/h have been generated using various model assumptions. The model shows that for these cells a G2 block will maximize cell killing for an optimum dose rate near 75 cGy/h. The effect on survival curves of inherited damage, as well as that of the proliferation by dying cells, is shown to increase monotonically with decreasing dose rates, and to be quite large at low dose rates.

Animals↗

PubMed1991

Enhancement by chloride ions of photoactivation of oxygen evolution in manganese-depleted photosystem II membranes.

The Mn cluster that catalyzes photosynthetic oxygen evolution was removed from the photosystem II (PSII) complex by treating PSII membranes with 1.0 mM NH2OH with concomitant inactivation of oxygen evolution. The cluster was reconstituted by incubating the treated membranes with 1.0 mM Mn2+, 20 mM Ca2+, 10 microM 2,6-dichlorophenolindophenol, and Cl- under illumination with continuous or flashing light to restore the oxygen-evolving capacity. This light-dependent activation (photoactivation) of oxygen evolution did not occur to a significant extent at 3 mM Cl-, but markedly accelerated at higher Cl- concentrations without showing a saturation phenomenon even at 1 M Cl-. At 10 mM Cl- only about 10% of the oxygen-evolving activity before NH2OH treatment was restored by 5-min illumination with continuous light, whereas at 600 mM Cl- about 60% of the original activity was recovered. This acceleration resulted from at least two different actions of Cl-: (1) stabilization of the intermediate state involved in the photoactivation process and (2) increase in the quantum yield of photoactivation. The stabilization of the intermediate was saturated at about 150 mM Cl-, whereas the increase in yield did not show saturation. The Cl(-)-induced increase in quantum yield did not involve any changes in the affinity of either Mn2+ binding or Ca2+ binding for photoactivation, but was rather ascribed to a protective effect of Cl- against inhibition of photoactivation by high concentrations of Mn2+. We also found that removal of the extrinsic 33-kDa protein from the PSII complex increased the Cl- requirement for photoactivation.

Binding Sites↗

PubMedDate not supplied

[The origin and evolution of parasitism on terrestrial vertebrates in insects, mites, and ticks].

Coexistence of terrestrial vertebrates and arthropods has been continuing over 200 million years; various forms of parasitism originated independently in various groups of arthropods during this period. The association of Acari and insects with nests and shelters of their hosts (nidicoly) played the main role in the origin of parasitism in these major groups of arthropods. The primary step in the evolution of parasitism was the permanent habitation in nests and borrows of mammals and birds in Mesozoic era. The second step was a substitution of various forms of schizophagy by the regular feeding on products of vital activity and dead parts of host body. The next step was the feeding on various body parts of vertebrate hosts, namely skin, hair, feathers, external excreta, and drops of blood. The final step was the development of the ability to damage skin and suck out the blood of vertebrates. In some taxa of astigmatid mites the parasitism on birds originated from phoresy: hypopi (heteromorphous deutonymphs) obtained the ability to absorb the liquid nutrients from hair follicles and subcutaneous tissues through the cuticle. The development of haematophagous feeding on mammals in several families of Diptera was the second way of the origin of parasitism. Highly mobile dipterans with the piercing-sucking or licking mouthparts were able to change easily from the accidental puncturing of the host skin or licking of the blood, pus, and mucus to the obligatory haematophagy. The evolution of some arthropod taxa did not went beyond a primary domination of spatial relations, as in many astigmatid mites, or trophic relations in the form of micropredatory, as in the haematophagous Diptera.

Animals↗

PubMedDate not supplied

The selfish karyotype. An analysis of the biological basis of morals.

An analysis is made of the kin-selection/group-selection debate on the issue of the biological basis of morals. The kin-selection view sees altruism, and morals in the case of humans, as resting solely on genetic factors; in fact, on this view, evolution itself is to take place only through genetic change -- a position which cannot be reconciled with our knowledge that species evolution involves karyotypic change. Morality is thought to stem from a particular gene which at one time was completely absent from the human population but which later entered and spread through it. On the generally accepted conception of kin selection, this 'altruistic' gene is to be responsible not only for apparently altruistic behaviour towards near relatives, but also for parental care. Thus this view, among other things, has the absurd consequence that there was a period directly after humans first came into existence during which we did not care for our young. In contrast, the group-selection view, as developed here, sees morality as stemming from the species' karyotype, and to be passed on karyotypically from species to species through evolution. As suggested by Darwin, morality is thus derived from our social instincts, and is fundamentally directed to members of one's tribe or community, not to members of one's family. In keeping with this perspective, it is suggested here that the biological basis of morals does not concern the continuation of each individual's gene line, but the continuing existence of the individual's community, and thus, indirectly, the survival of the human species, through supporting the continuing instantiation of its karyotype.

Altruism↗

PubMed2004

[Analysis of the fixation of discrete genetic structures by means of an integral model of evolution in a Mendelian one-locus population of diploid organisms].

An integral model of the evolution of a Mendelian one-locus population of diploid organisms with continual allele diversity developing under density-limiting conditions or without density limitation has been proposed and analyzed. The model was used to study the mechanism of the appearance of discrete genetic structures, i.e., the fixation of a limited number of alleles. Local resistance of the resultant genetic distributions to homogeneous equiprobable mutations has been demonstrated.

Alleles↗

PubMed2026

Emergence of two novel HIV-1 Circulating Recombinant Forms (CRF190_0708 and CRF191_0708): molecular characterization and clinical insights from a five-year study in Yunnan, China.

BACKGROUND: To characterize HIV-1 molecular epidemiology and identify novel circulating recombinant forms (CRFs) among antiretroviral therapy (ART)-naïve heterosexuals in Yunnan, China, and evaluate their clinical impact. METHODS: This study examined 636 HIV-1 pol sequences to analyze genetic diversity, pretreatment drug resistance (PDR), and transmission networks. Near full-length genomes were obtained to identify and characterize novel recombinants, with their evolutionary history inferred by Bayesian analysis. Co-receptor tropism was predicted, and the five-year clinical outcomes (including immune reconstitution and virologic response) of patients infected with the novel CRFs were compared. RESULTS: The most prevalent type identified was CRF08_BC, accounting for 50.16% of cases. The prevalence of drug resistance was 5.97% (38/636), with the K103N mutation being the most common. An analysis of transmission networks revealed that 52.2% (272/521) of clusters were associated with CRF07_BC and CRF08_BC. Two novel second-generation CRFs were identified: CRF190_0708, with an estimated time to the most recent common ancestor (tMRCA) of 1998.9, and CRF191_0708, with a more recent tMRCA ranging from 2009.5 to 2011.6. During the five-year follow-up period, viral rebound was observed in 7 patients in the CRF190_0708 group and in 1 patient in the CRF191_0708 group. Drug-resistance mutations (M184V and K103N) were detected in a subset of rebound cases in the CRF190_0708 group. CONCLUSIONS: This study identifies two novel HIV-1 recombinants, CRF190_0708 and CRF191_0708, highlighting ongoing viral evolution in Yunnan. Preliminary findings suggest possible clinical differences, warranting further investigation. Continued molecular surveillance is needed. TRIAL REGISTRATION: The clinical study was registered at ClinicalTrials.gov under the identifier NCT03852849. The date of registration was March 22, 2019.

Adult↗

PubMed2000

[The multifood allergy syndrome].

Multiple food intolerance in infants and young children is increasingly diagnosed. More than 40% of infants less than 1 y.o. could be affected. The syndrome is characterized by the seriousness of atopic dermatitis (SCORAD > 50), by enterocolitis or failure to thrive or various associations of symptoms that may change over time. The evolution is long-lasting. Common food allergens are milk, egg, soy, wheat, but other ones can be implicated. The diagnosis is established by standardized oral challenges. Multiple etiopathogenic factors are involved: atopy, gastro-enteritis induced intestinal hyperpermeability, precocity of food diversification, breast-feeding continued after the onset of symptoms. Amino-acid based formulas have changed the evolution.

Allergens↗