Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Minor: Evolution”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 631 records · Page 35Linked to original sources
PubMed1992

Chromosomal genotypes (evolutionary lines) of Salmonella berta.

The copy number and location of the insertion sequence IS200, a mobile DNA element, was established across a collection of Salmonella berta. All strains contained one common site, assumed to be present in the evolutionary ancestor of this serovar. With one exception, all strains, including recent outbreak isolates from the UK and sporadic isolates of world-wide distribution, were representatives of a single genotypic clone which carried three common IS200 insertion sites. This clone has acquired diverse combinations of plasmids, reflecting its actual or recent distribution and host. A single isolate, belonging to a second, minor genotypic clone was characterised by two IS200 insertion sites.

Animals↗
PubMed1985

[Coma in full-term newborn infants following acute fetal distress: electro-clinical evolution].

Twenty full term infants who had birth asphyxia were studied. These infants were in a comatose state for 4 to 15 days and at least 3 EEG recordings were performed during this period. Six infants recovered without sequelae and in 2 cases there were minor abnormalities. In 7 cases there were major deficits (follow-up: 1 to 9 years) and 5 infants died within 15 days. Abnormal movements were observed in all the babies. Thirteen infants had EEG documented seizures (intermittent in 5 cases and status epilepticus in 8 cases). The prognosis was not correlated with the time of onset or duration of the coma, the time of onset or type of abnormal movements, nor with the presence of intermittent or continuous electrographic seizure activity. The initial tracing on the first day is the most significant prognostic factor. On subsequent days, an inactive EEG always indicated a poor prognosis. An improvement in the EEG on the 2nd on the 3rd day may not correlate with a favourable outcome since 3 such cases had a poor outcome. The clinical and EEG findings during therapy and the value of high levels of anticonvulsant therapy are discussed.

Coma↗
PubMed1997

[Ultrasonic diagnosis of nodal lesions of the axillary-jugular lymphatic plexus and their evolution].

Axillary lymph nodes of three levels may be adequately differentiated on the basis of the TNM classification by application of layer-by-layer tomographic examination of axillary fossa and thoracic and clavicular-thoracic triangles in the axillary cavity. Echographs show musculus thoracis minor as a distinct point of reference. Topographic features of deep lateral cervical lymph nodes may be used in anatomical identification of internal jugular nodes, transverse cervical artery, accessory nerve and suprajugular lymph nodes. In cases of multiple involvement of lymph nodes, their shape (chain or cluster) may be identified. It can be shown Whether lymph flows are in series, collateral centripetal, collateral centrifugal (recirculatory) or run parallel in metastatic areas. Varying patterns of lymph flow through collateral pathways formed in the axillary-jugular lymph plexus are responsible for the variety of patterns of lesion clusters in the lymph nodes system.

Axilla↗
PubMed1994

Evolution of antigen drift/switching: continuously evading pathogens.

Following infection to a host, some pathogens repeatedly alter their antigen expression, and thereby escape the immune defense (antigen drift/switching). This paper examines the evolutionarily stable mutation rate of pathogens which maximizes the stationary pathogen density in a host. Assumptions are: (i) most mutations are deleterious but a minor fraction, p, of mutations can contribute to the alternation of antigenic property of the pathogen; and. (ii) potential antigen types can be indexed in a one-dimensional lattice (the stepping-stone model). The model reveals that: (a) if the mutation rate is higher than a threshold mu(c) = R0/(1-p), where R0 is the per capita growth rate of pathogen before the immune system is activated, pathogens cannot maintain themselves because too many progeny are lost by lethal mutations; (b) if the mutation rate lies between zero and mu(c), the system converges to a traveling wave of antigen variants with a constant wave speed; (c) the evolutionarily stable mutation rate microESS is unexpectedly high: more than 0.25 per genome per replication even if most mutations are lethal. Hence more than a fourth of progeny are born defective in the evolutionarily stable state; (d) the microESS is even higher if multiple infections by pathogens are common. The paper also studies the evolutionarily stable mutation rate if every mutant antigen belongs to a different type (the infinite allele model), and the evolution of antigen switching between a finite number of antigen variants stored in the pathogen genome.

Alleles↗
PubMed1984

[Prognostic value of the neurodevelopmental status in the first year of life in children with increased perinatal risk].

Among 503 high-risk newborns followed-up systematically in a prospective study up to 5 years of age, abnormalities of the development of posture, of maturation of tone and of psychomotor development were diagnosed at the age of 6 months in 70 children (13.9%) who form the study group. Among the other 433 high-risk newborns who presented a normal psychomotor development at the age of 6 months, 73 were selected at random and form the control group. In the study group, 59% of the children had a development which became normal during the second year of life (transitory disorders), 21% had persistent minor neurological abnormalities at the age of 5 years, and 20% evolved towards cerebral palsy and/or mental retardation. In the control group, 97.3% of the children remained normal and 2.7% presented minor neurological abnormalities at 5 years. Three parameters are important to estimate the prognosis of the children in the study group. These are: the presence of neurological disorders during the neonatal period, the type of neurodevelopmental abnormalities diagnosed at the age of 6 months, and the evolution of these abnormalities during the second semester of life. Among the 14 major handicaps, 13 were found in children who presented neurological neonatal disorders and 12 appeared in children who had an abnormality of muscular tonus associated with cognitive and social retardation at the age of 6 months. 52% of the children, whose status had not been "normalized" at 12 months, had a major handicap at 5 years. However, a hypertonia predominating in the lower limbs and observed at 6 months has a good prognosis; it disappears during the second year of life in 81.2% of cases (transitory disorders) and is associated with persistent minor neurological abnormalities in 18.8% of cases.--This study gives useful information for the establishment of an early prognosis and a rational management of the high-risk newborn children who present neurodevelopmental abnormalities during their first year of life.

Cerebral Palsy↗
PubMed1993

Diversity within natural populations of eastern equine encephalomyelitis virus.

We evaluated genetic and phenotypic diversity within natural populations of the alphavirus, Eastern equine encephalomyelitis (EEE) virus. RNA fingerprinting revealed that most populations within infected hosts (unpassaged isolates) contained a consensus genotype along with minority genotypes differing in one to three T1-resistant oligonucleotides. Mutation frequencies appeared to be similar to those reported for other RNA viruses, suggesting that the slow rate of EEE virus evolution is not limited by fidelity of genome replication. Within a given year, genetic diversity was generally greater among geographically distant isolates than among those from the same transmission focus, suggesting that dispersal among EEE viruses in North America is not complete annually. Two of three bird isolates from Maryland and New York contained relatively distantly related genotypes, differing in 15-19 oligonucleotides. A 1985 mosquito isolate from Maryland contained stable, small plaque variants which comprised the majority of that population. These small plaque variants differed by up to eight T1-resistant oligonucleotides when compared with their large plaque counterparts. Temperature sensitive virus was not detected in six unpassaged mosquito isolates from Maryland and New York.

Amino Acid Sequence↗
PubMed1984

Role of chemotherapy in the treatment of lung cancer: evolving strategies for non-small cell histologies.

Lung cancer treatment has been considered to have made little progress except for advances in small cell carcinoma. For other histologies an attitude of nihilism has prevailed principally because of lack of effective systemic therapy and of no persuasive evidence that results could be improved by combined modality treatment. On the other hand, favorable results from surgery are confined to a small percent of all patients with this disease. This review emphasizes possibilities for progress in evolving new therapeutic strategies. Although improvement over other systemic therapies is modest, cisplatin-containing regimens yield more consistent response rates and apparent survival advantage relative to single agents. Immediate progression occurs in the minority of patients. In addition, regimens combining cisplatin with vinca alkaloids have no substantial deleterious effects on the lung, marrow or esophagus to aggravate radiation-induced complications. These features encourage the evolution of strategies which begin with chemotherapy and then use consolidation with radiation therapy. Clinical trials using these and newer strategies must be instituted if progress is to occur in the treatment of non-small cell histologies at all stages.

Adenocarcinoma↗
PubMed2002

Division of labour influences the rate of ageing in weaver ant workers.

The evolutionary theory of ageing predicts that the timing of senescence has been primarily shaped by the extrinsic mortality rate, which causes selection intensity to decline over time. One difficulty in testing the evolutionary theory of ageing is that extrinsic mortality risk is often confounded with body size and fecundity, which may also directly affect lifespan. Social insects with a pronounced division of labour between worker castes provide a unique opportunity to study the direct effect of extrinsic mortality on the evolution of ageing rates independently of body size, reproductive effort and genetic configuration. In the weaver ant, Oecophylla smaragdina, the major (large) workers perform the risky tasks outside the nest, while the minor (small) workers stay within the highly protected arboreal nest. Hence, this pronounced division of labour is associated with high differences in extrinsic mortality risks. The evolutionary theory of ageing predicts that the minor workers should have a longer intrinsic lifespan than the major workers. In line with this prediction, we found that in a protected environment the minor workers lived significantly longer than the major workers did. Hence, the ageing rate appears to have been moulded by variation in the extrinsic mortality rate independently of size, reproductive effort and genetic configuration.

Aging↗
PubMed2000

One sequence, two ribozymes: implications for the emergence of new ribozyme folds.

We describe a single RNA sequence that can assume either of two ribozyme folds and catalyze the two respective reactions. The two ribozyme folds share no evolutionary history and are completely different, with no base pairs (and probably no hydrogen bonds) in common. Minor variants of this sequence are highly active for one or the other reaction, and can be accessed from prototype ribozymes through a series of neutral mutations. Thus, in the course of evolution, new RNA folds could arise from preexisting folds, without the need to carry inactive intermediate sequences. This raises the possibility that biological RNAs having no structural or functional similarity might share a common ancestry. Furthermore, functional and structural divergence might, in some cases, precede rather than follow gene duplication.

Base Sequence↗
PubMed2006

An evolutionary concept of polycystic ovarian disease: does evolution favour reproductive success over survival?

Polycystic ovarian disease (PCOD) is currently considered as possibly the most frequent cause of female infertility. It is also closely associated with syndrome XX, which, in turn, is closely linked with premature and excessive mortality. Considering these adverse effects on reproductive success and human survival, the evolutionary survival of PCOD, itself considered by many to be a genetically transmitted condition, would, on first glance, appear surprising, since evolution usually discriminates against both of these traits. However, an analysis of some recently reported characteristics of the condition calls for the reconsideration of PCOD as a condition which, from an evolutionary viewpoint, favours decreased reproductive success. Indeed, the reported observations that patients with PCOD will resume spontaneous ovulation with even relatively minor weight loss, and experience later menopause than controls, suggests exactly the opposite. Under an evolutionary concept, PCOD can thus be seen as a 'fertility storage condition' which in fact favours human reproductive success and allows the human species to maintain fertility even during adverse environmental circumstances, such as famines.

Anovulation↗
PubMed2006

A system for studying evolution of life-like virtual organisms.

BACKGROUND: Fitness landscapes, the dependences of fitness on the genotype, are of critical importance for the evolution of living beings. Unfortunately, fitness landscapes that are relevant to the evolution of complex biological functions are very poorly known. As a result, the existing theory of evolution is mostly based on postulated fitness landscapes, which diminishes its usefulness. Attempts to deduce fitness landscapes from models of actual biological processes led, so far, to only limited success. RESULTS: We present a model system for studying the evolution of biological function, which makes it possible to attribute fitness to genotypes in a natural way. The system mimics a very simple cell and takes into account the basic properties of gene regulation and enzyme kinetics. A virtual cell contains only two small molecules, an organic nutrient A and an energy carrier X, and proteins of five types--two transcription factors, two enzymes, and a membrane transporter. The metabolism of the cell consists of importing A from the environment and utilizing it in order to produce X and an unspecified end product. The genome may carry an arbitrary number of genes, each one encoding a protein of one of the five types. Both major mutations that affect whole genes and minor mutations that affect individual characteristics of genes are possible. Fitness is determined by the ability of the cell to maintain homeostasis when its environment changes. The system has been implemented as a computer program, and several numerical experiments have been performed on it. Evolution of the virtual cells usually involves a rapid initial increase of fitness, which eventually slows down, until a fitness plateau is reached. The origin of a wide variety of genetic networks is routinely observed in independent experiments performed under the same conditions. These networks can have different, including very high, levels of complexity and often include large numbers of non-essential genes. CONCLUSION: The described system displays a rich repertoire of biologically sensible behaviors and, thus, can be useful for investigating a number of unresolved issues in evolutionary biology, including evolution of complexity, modularity and redundancy, as well as for studying the general properties of genotype-to-fitness maps. REVIEWERS: This article was reviewed by Drs. Eugene Koonin, Shamil Sunyaev and Arcady Mushegian.

Journal Article↗
PubMed2003

Evolution in Saccharomyces cerevisiae: identification of mutations increasing fitness in laboratory populations.

Since the publication of the complete sequence of the genome of Saccharomyces cerevisiae, a number of comprehensive investigations have been initiated to gain insight into cellular function. The focus of these studies has been to identify genes essential for survival in specific environments or those that when mutated cause gross phenotypic defects in growth. Here we describe Ty1-based mutational approaches designed to identify genes, which when mutated generate evolutionarily significant phenotypes causing small but positive increments on fitness. As expected, Ty1 mutations with a positive fitness effect were in the minority. However, mutations in two loci, one inactivating FAR3 and one upstream of CYR1, identified in evolving populations, were shown to have small but significantly positive fitness effects.

Amino Acid Sequence↗
PubMed1993

Evolution of the Drosophila melanogaster-sigma virus system in natural populations from Languedoc (southern France).

An analysis of natural populations of Drosophila melanogaster in a southern French region (Languedoc) was started in 1983, concerning two non Mendelian systems: the P-M system of transposable elements and the sigma virus. This virus is not contagious, but only transmitted through gametes; it is usually present in a minority of individuals in natural populations. The first data collected revealed unexpectedly clear and fast-evolving phenomena; they also gave evidence of some interesting correlations between the two systems. This paper presents all the results gathered from 1983 to 1991 in the Drosophila-sigma system. Striking correlations were observed for three interconnected parameters: frequency of infected flies, frequency of an allele of the fly giving resistance to the virus, and adaptation of the virus to this allele. This adaptation consisted of a qualitative step (change of viral type) followed by quantitative variation (better adaptation to the allele). This analysis also showed, firstly, that the evolution of natural populations differs completely in Languedoc from the rest of France; secondly, that three geographical zones where selective forces worked differently persisted over time in Languedoc.

Adaptation, Physiological↗
PubMed2004

New aspects on lanosterol 14alpha-demethylase and cytochrome P450 evolution: lanosterol/cycloartenol diversification and lateral transfer.

Sterol 14alpha-demethylase (CYP51) is a member of the cytochrome P450 superfamily, widely found in animals, fungi, and plants but present in few prokaryotic groups. CYP51 is currently believed to be the ancestral cytochrome P450 that has been transferred from prokaryotes to eukaryotic kingdoms. We propose an alternate view of CYP51 evolution that has an impact on understanding the evolution of the entire CYP superfamily. Two hundred forty-nine bacterial and four archaeal CYP sequences have been aligned and a bacterial CYP tree designed, showing a separation of two branches. Prokaryotic CYP51s cluster to the minor branch, together with other eukaryote-like CYPs. Mycobacterial and methylococcal CYP51s cluster together (100% bootstrap probability), while Streptomyces CYP51 remains on a distant branch. A CYP51 phylogenetic tree has been constructed from 44 sequences resulting in a ((plant, bacteria),(animal, fungi)) topology (100% bootstrap probability). This is in accordance with the lanosterol/cycloartenol diversification of sterol biosynthesis. The lanosterol branch (nonphotosynthetic lineage) follows the previously proposed topology of animal and fungal orthologues (100% bootstrap probability), while plant and D. discoideum CYP51s belong to the cycloartenol branch (photosynthetic lineage), all in accordance with biochemical data. Bacterial CYP51s cluster within the cycloartenol branch (69% bootstrap probability), which is indicative of a lateral gene transfer of a plant CYP51 to the methylococcal/mycobacterial progenitor, suggesting further that bacterial CYP51s are not the oldest CYP genes. Lateral gene transfer is likely far more important than hitherto thought in the development of the diversified CYP superfamily. Consequently, bacterial CYPs may represent a mixture of genes with prokaryotic and eukaryotic origin.

Bacteria↗
PubMed2005

Ductal breast carcinoma develops through different patterns of chromosomal evolution.

In a previous study that used comparative genomic hybridization (CGH) to analyze 43 ductal breast carcinomas selected for hyperdiploidy, we proposed the existence of two distinct pathways of chromosomal evolution. In the present study, in which we reassessed our cytogenetic findings on 158 ductal breast carcinomas selected for having a modal number of chromosomes of fewer than 60, we confirmed the existence of two subtypes of tumors. Along with the great majority of tumors (142 of 158) that evolved through structural rearrangements with no or very few whole-chromosome gains, we found that a minor subset (16 of 158) evolved through progressive gains of whole chromosomes with no or only a few associated rearrangements. In this article, we describe the karyotypes of these 16 tumors together with data from CGH, which was performed for 10 of them. Chromosomes 5, 7, 8, and 20 were the most frequently gained. Our findings support the evidence of a new pathway of chromosomal evolution in a small subset of ductal breast carcinomas characterized by numerical chromosome aberrations.

Aged↗
PubMed1998

First case of mother-to-infant HIV type 1 group O transmission and evolution of C2V3 sequences in the infected child. French HIV Pediatric Cohort Study Group.

We report the first case of mother-to-infant transmission and follow-up for an HIV-1 group O virus from Cameroon. Isolates were obtained from the mother at delivery and from the child at birth and when 16 and 30 months old. We analyzed the viral evolution within mother and child by examining 51 sequences spanning C2V3 regions of the viral envelope gene. The mother carried two genotypes, v1 and v2. The genotype v1 was dominant in the child at birth, and persisted as a minor genotype at age 30 months. The genotype v2 was absent in the child sequences. The variability of the nucleotide sequences of the isolates from the child increased with age from 0.8 to 6%, and a novel genotype (v3) appeared at age 30 months. The nonsynonymous-to-synonymous mutation ratio increased with the age of the child, from 0.75 at birth to 1.86 at 30 months, indicating a high rate of fixation of amino acid changes in the child. The overall pattern was similar to that reported by Ganeshan et al. (J Virol 1997;71:663-677) for group M viruses infecting child with a slow-developing form of the disease.

Acquired Immunodeficiency Syndrome↗