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Results for “evolutionary potentiation”

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PubMed2005

Crocodile attack in Australia: an analysis of its incidence and review of the pathology and management of crocodilian attacks in general.

Crocodilians represent one of the oldest constant animal lineages on the planet, in no small part due to their formidable array of predatory adaptations. As both human and crocodilian populations expand, they increasingly encroach on each others' territories, bringing morbidity and mortality to both populations. In this article, the medical and herpetologic literature pertaining to injuries caused by crocodilians is reviewed, and the patterns of saltwater crocodile attacks in Australia from 1971 to 2004 are analyzed. In this review, we examine the features of crocodilians that contribute to explaining their evolutionary success, as well as the potential hazard they pose to humans. Only by understanding their capabilities is it possible to mitigate the potential threat to life and limb.

Adolescent↗
PubMed1996

Hepatic infarction caused by arterial insufficiency: spectrum and evolution of CT findings.

PURPOSE: To determine the CT imaging appearances of liver infarction due to arterial insufficiency and to attempt to understand reasons for apparent discrepancy of appearance in prior reports. MATERIALS AND METHODS: Thirty-seven CT examinations from 18 patients with proven hepatic infarction were evaluated for character, location, and evolution of lesions by all investigators, with a consensus interpretation. Etiologies of infarction included posttransplant complication (15), laparoscopic cholecystectomy complication (2), and traumatic arterial injury (1). Proof of hepatic infarction was made by hepatectomy (11), biopsy (1), or clinical course compatible with infarction with angiographic (3) or surgical (3) evidence of hepatic arterial abnormality. In patients without histologic proof of infarction, all lesions seen at CT were considered to be due to hepatic infarction, except those meeting the criteria for hemangioma. In 10 patients, serial examinations were available over 2-180 days and a determination of serial changes in specific lesions was made using a similar image analysis. RESULTS: Of 55 lesions identified, 53 could be classified into three shapes--wedge-shaped (18), rounded or oval (26), or irregularly shaped low-attenuation lesions paralleling bile ducts (9). The other two lesions were flat hypodense areas along the posterior aspect of the medial left hepatic lobe. Wedge-shaped lesions were peripherally located; rounded lesions were either peripheral (10) or central (26). The caudate lobe was spared except in one patient. Of 16 serially followed wedge-shaped lesions, four evolved into rounded lesions. No rounded lesions became wedge-shaped. CONCLUSION: Hepatic infarction caused by arterial disease produces a spectrum of CT findings. Prior reported discrepancies in appearance may be due to the small number of cases in each report and the variety of potential imaging appearances,aas well as evolutionary changes.

Adult↗
PubMed2000

The conserved exon method for gene finding.

A new approach to gene finding is introduced called the "Conserved Exon Method" (CEM). It is based on the idea of looking for conserved protein sequences by comparing pairs of DNA sequences, identifying putative exon pairs based on conserved regions and splice junction signals then chaining pairs of putative exons together. It simultaneously predicts gene structures in both human and mouse genomic sequences (or in other pairs of sequences at the appropriate evolutionary distance). Experimental results indicate the potential usefulness of this approach.

Animals↗
PubMed2005

Dispersal, philopatry, and infidelity: dissecting local genetic structure in superb fairy-wrens (Malurus cyaneus).

Dispersal influences evolution, demography, and social characteristics but is generally difficult to study. Here we combine long-term demographic data from an intensively studied population of superb fairy-wrens (Malurus cyaneus) and multivariate spatial autocorrelation analyses of microsatellite genotypes to describe dispersal behavior in this species. The demographic data revealed: (1) sex-biased dispersal: almost all individuals that dispersed into the study area over an eight-year period were female (93%; n = 153); (2) high rates of extragroup infidelity (66% of offspring), which also facilitated local gene dispersal; and (3) skewed lifetime reproductive success in both males and females. These data led to three expectations concerning the patterns of fine-scale genetic structure: (1) little or no spatial genetic autocorrelation among females, (2) positive spatial genetic autocorrelation among males, and (3) a heterogeneous genetic landscape. Global autocorrelation analysis of the genotypes present in the study population confirmed the first two expectations. A novel two-dimensional local autocorrelation analysis confirmed the third and provided new insight into the patterns of genetic structure across the two-dimensional landscape. We highlight the potential of autocorrelation analysis to infer evolutionary processes but also emphasize that genetic patterns in space cannot be fully understood without an appropriate and intensive sampling regime and detailed knowledge of the individuals genotyped.

Animals↗
PubMed1986

Pseudogenes.

Pseudogenes are DNA sequences that bear significant homology to functional genes, yet they lack promoter sequences for their transcription or contain other mutations that preclude formation of a functional product. They appear to be a common feature of many eukaryotic genomes. Pseudogenes were first described among the 5S RNA genes of Xenopus; subsequently, they have been found for a wide range of genes, including globins, snRNAs, immunoglobulins, tubulins, and metallothionein. Some pseudogenes, like those of the beta-globins, lie within the gene cluster of their functional counterparts; they may simply have arisen by accumulation of mutations in a duplicated nonselected gene. Other pseudogenes appear to have arisen by a very different process. Characteristically, they are dispersed in the genome, lack introns, and have oligoA tracts at their 3' ends. Their structure suggests an origin from mRNAs through reverse transcription and integration into the genome. Pseudogenes have no known function. They may represent dead-end byproducts of normal cellular and evolutionary processes, yet they are also potential starting points from which new genes might evolve.

Animals↗
PubMedDate not supplied

Ethological models in research into the neural mechanisms of short-term memory.

Rats are protected against intake of toxic diets by specific evolutionary prepared behavioral adaptations. Intake of potentially dangerous novel food is reduced by neophobia. The taste signal is stored for several hours in a short-term memory file from which it gradually emerges in form of a permanent gustatory engram labeled as safe, when there are no adverse effects of feeding, or as aversive, when visceral symptoms of poisoning appear in the critical post-ingestion interval. The experimental evidence reviewed indicates that positive labeling (manifested by attenuation of neophobia) requires intact higher brain functions whereas the aversive experience (manifested by conditioned taste aversion) is recorded even under deep coma. The biological significance of the different neural mechanisms underlying the above forms of gustatory-visceral associations is discussed.

Animals↗
PubMed1997

Protein model representation and construction.

Crystallographic studies play a major role in current efforts towards protein structure determination. However, despite recent advances in computational tools for molecular modeling and graphics, the task of constructing a protein model from crystallographic data remains complex and time-consuming, requiring extensive expert intervention. This paper describes an approach to automating the process of model construction, where a model is represented as an annotated trace (or partial trace) of the three-dimensional backbone of the structure. Potential models are generated using an evolutionary algorithm, which incorporates multiple fitness functions tailored to different structural levels in the protein. Preliminary experimental results, which demonstrate the viability of the approach, are reported.

Algorithms↗
PubMed1990

Common fragile sites in man and three closely related primate species.

The expression of common fragile sites was studied in peripheral lymphocytes of man, gorilla, chimpanzee, and orangutan after induction with aphidicolin, methotrexate, or fluorodeoxyuridine. As far as the chromosomal localization is concerned, it appears that many of these sites have been highly conserved during primate evolution. However, differences were found in the relative expression of certain sites. In all four species, mapping of approximately 500 lesions disclosed the most breakage-prone common fragile sites, at which about 90% of all induced aberrations were localized. Comparison of chromosome regions involved in evolutionary changes to fragile sites in the four primate species revealed 30 sites that were located at or close to the same chromosomal band. However, no correlation was found between the relative expression of a certain common fragile site in vitro and a potential involvement of this chromosomal site in evolutionary changes.

Animals↗
PubMed2004

Evolution and the American social sciences: An evolutionary social scientist's view.

American social scientists rarely ever use evolutionary concepts to explain behavior, despite the potential of such concepts to elucidate major social problems. I argue that this observation can be understood as the product of three influences: an ideologically narrowed political liberalism; a fear of ''Social Darwinism'' as a scientific idea, rather than a scientific apostasy; and a widely believed criticism of evolutionary thinking as deterministic, reductionistic, and Panglossian. I ask what is to be done to encourage social scientists to learn and to apply evolutionary lessons. I answer with four solutions. First, evolutionary social scientists should more effectively educate their non-evolutionary students and colleagues. Second, they should publicize, even popularize, accessible refutations of perennially misleading criticisms. Third, they should more credibly assure skeptics that evolutionary theory not only keeps the ''social'' in social science but better explains social behavior than can any individual-level theory, such as rational-choice theory. Fourth, they should recall that biology took generations to become Darwinian, and they must understand that the social sciences may take as long to become evolutionary.

Journal Article↗
PubMed2002

Changes to acoustic communication systems in human-altered environments.

Animal communication systems have become closely tuned to local habitat conditions as populations have adjusted to different long-term environmental pressures. However, many habitats are now rapidly changing because of anthropogenic modification. Maintenance of effective communication systems in greatly altered environments will depend on communicative responses on both evolutionary and ontogenetic time scales. Consideration of potential acoustic challenges caused by human-generated habitat modification has important implications for basic research and conservation biology. First, the observed signal structure of individuals in altered environments may not match the normally hypothesized call structure. Second, species that either possess little ability to adapt quickly on an evolutionary time scale or have little plasticity in their communicative systems may be unable to respond to large anthropogenic alterations in their acoustic environment.

Animal Communication↗
PubMed2004

Menopause: why does fertility end before life?

Menopause is associated with an ultimate cessation of child-bearing potential. Medical research on menopause focuses mostly on the underlying physiological changes associated with menopause. By contrast, evolutionary biologists are interested in understanding why women lose their potential to reproduce before the end of their lives. Evolution by natural selection predicts that the behaviors that we observe today are products of generations of selection on the genes that govern those behaviors. Since one would expect an individual reproducing throughout its life to produce more offspring than an individual stopping early, one would seldom expect genes for menopause to be selected for during our evolutionary past. This article discusses how menopause and prolonged lifespan might be explained by evolutionary theory, and highlights some angles for future research.

Aging↗
PubMed2003

Ecological and evolutionary opportunities of apomixis: insights from Taraxacum and Chondrilla.

The ecological and evolutionary opportunities of apomixis in the short and the long term are considered, based on two closely related apomictic genera: Taraxacum (dandelion) and Chondrilla (skeleton weed). In both genera apomicts have a wider geographical distribution than sexuals, illustrating the short-term ecological success of apomixis. Allozymes and DNA markers indicate that apomictic populations are highly polyclonal. In Taraxacum, clonal diversity can be generated by rare hybridization between sexuals and apomicts, the latter acting as pollen donors. Less extensive clonal diversity is generated by mutations within clonal lineages. Clonal diversity may be maintained by frequency-dependent selection, caused by biological interactions (e.g. competitors and pathogens). Some clones are geographically widespread and probably represent phenotypically plastic 'general-purpose genotypes'. The long-term evolutionary success of apomictic clones may be limited by lack of adaptive potential and the accumulation of deleterious mutations. Although apomictic clones may be considered as 'evolutionary dead ends', the genes controlling apomixis can escape from degeneration and extinction via pollen in crosses between sexuals and apomicts. In this way, apomixis genes are transferred to a new genetic background, potentially adaptive and cleansed from linked deleterious mutations. Consequently, apomixis genes can be much older than the clones they are currently contained in. The close phylogenetic relationship between Taraxacum and Chondrilla and the similarity of their apomixis mechanisms suggest that apomixis in these two genera could be of common ancestry.

Asteraceae↗
PubMed2025

Experimental Test of Evolutionary Safety of a CRISPR-Cas9 Gene-Drive Element.

CRISPR-Cas9 gene drives (CCGDs) are powerful tools for genetic control of wild populations, with applications from disease eradication to species conservation. However, Cas9 alone and in a complex with gRNA can cause double-stranded DNA breaks at off-target sites, which could increase the mutational load and lead to unintended loss-of-heterozygosity (LOH) events. These undesired effects raise potential concerns about the long-term evolutionary safety of CCGDs, but the magnitude of these effects is unknown. To measure how the presence of a CCGD or a Cas9 alone in the genome affects the rates of LOH events and de novo mutations, we carried out a mutation accumulation experiment in yeast Saccharomyces cerevisiae. We found no detectable effects on the genome-wide rates of mutations or LOH events. Our power calculations suggest that CCGD or Cas9 affect these rates by less than 30%, which is much less than natural variation for these traits in yeast. A more detailed examination shows that CCGD or Cas9 may alter the lengths and genomic distributions of LOH events, but the statistical support for these effects is weak. Thus, our results demonstrate that CCGDs impose at most a weak additional mutational burden in the yeast model. Although mutagenic effects of gene drives need to be further evaluated in other systems, our results add credence to the proposition that the evolutionary risks posed by well designed gene drives are likely acceptable.

Journal Article↗
PubMed2005

Evolutionary mechanisms acting on proteinase inhibitor variability.

The interaction of proteinase inhibitors produced, in most cases, by host organisms and the invasive proteinases of pathogens or parasites or the dietary proteinases of predators, results in an evolutionary 'arms race' of rapid and ongoing change in both interacting proteins. The importance of these interactions in pathogenicity and predation is indicated by the high level and diversity of observable evolutionary activity that has been found. At the initial level of evolutionary change, recruitment of other functional protein-folding families has occurred, with the more recent evolution of one class of proteinase inhibitor from another, using the same mechanism and proteinase contact residues. The combination of different inhibitor domains into a single molecule is also observed. The basis from which variation is possible is shown by the high rate of retention of gene duplication events and by the associated process of inhibitory domain multiplication. At this level of reorganization, mutually exclusive splicing is also observed. Finally, the major mechanism by which variation is achieved rapidly is hypervariation of contact residues, an almost ubiquitous feature of proteinase inhibitors. The diversity of evolutionary mechanisms in a single class of proteins is unlikely to be common, because few systems are under similar pressure to create variation. Proteinase inhibitors are therefore a potential model system in which to study basic evolutionary process such as functional diversification.

Amino Acid Sequence↗
PubMed2003

Helicobacter pylori flagellins have very low intrinsic activity to stimulate human gastric epithelial cells via TLR5.

Helicobacter pylori is a flagellated chronic pathogen, which colonizes the gastric mucus and mucosal cell surfaces. Flagella and motility are essential for the survival of this bacterium in the stomach environment. Flagellins of several bacterial species are potent activators of the human innate immune system by binding to TOLL-like receptor 5 (TLR5). The possible role of the two H. pylori flagellins FlaA and FlaB in stimulation of the innate immune system and induction of IL-8 release by human gastric epithelial cells was investigated in this study. Transcription and expression of TLR5 in three different human gastric epithelial cell lines was demonstrated. Salmonella enterica serovar Typhimurium FliC flagellin was able to activate human gastric epithelial cells. TLR5 transcription was modulated by H. pylori infection. However, both H. pylori flagellins appeared to possess no immunostimulatory potential on human gastric cells via TLR5, despite their extensive amino acid homology to stimulating flagellins of other bacterial species. The evolutionary development of such unique flagellins of low activating potential is proposed to be a novel mechanism of H. pylori to preserve the essential function of its flagella during chronic colonization of the stomach and to evade the deleterious host immune responses.

Cell Line↗
PubMed1998

Sex differences in perceived controllability of mate value: an evolutionary perspective.

Men and women value different characteristics in potential partners. It was hypothesized that women feel they have less control over traits relevant to their desirability than men feel they have over traits related to male desirability. In Study 1, undergraduates (N = 150) completed questionnaires measuring (a) the importance they attributed to 64 characteristics when choosing a mate and (b) their perceived control over these traits. Men selected partners on the basis of traits that are relatively uncontrollable (e.g., youth, attractiveness), whereas women selected partners on the basis of traits that are more controllable (e.g., status, industriousness; d = 1.75). In Study 2, these findings were replicated in an older, representative community sample (N = 301; d = 1.03). Greater uncontrollability of traits relevant to female mate value may place women at elevated risk for negative affect, depression, low self-esteem, and body dissatisfaction.

Adult↗
PubMed2026

Genome-wide cyclin gene evolution in Arabidopsis and Brassica reveals polyploidization-driven duplication and flowering-time associations.

Cyclin genes are plant cell cycle regulators that play essential roles in growth, development, and reproduction. However, the evolutionary dynamics and genomic organization of cyclin genes across the Brassicaceae family remain poorly understood, particularly in the context of allotetraploid genome evolution. Here, we investigated the diversity, expansion mechanisms, and potential functional diversification of cyclin genes across ten Brassicaceae genomes, including four Arabidopsis and six Brassica species. A total of 1087 cyclin genes representing 23 cyclin types were identified. Comparative genomic analyses revealed that cyclin gene expansion was strongly influenced by polyploidization in Brassica species, with 1845 duplication events involving 1063 genes. Whole-genome duplication was the predominant mechanism driving expansion, while both inter- and intra-genomic duplications contributed to gene retention in tetraploid Brassica species, with the highest duplication frequency observed in Brassica juncea. Across genomes, 120 physical gene clusters were identified, including homogeneous and heterogeneous types. Ortholog analysis between progenitor and allotetraploid species identified 852 orthologous pairs involving 366 genes, indicating extensive conservation following allotetraploid formation. Phylogenetic analysis resolved cyclins into three major clades, while expression-based clustering in Brassica napus grouped genes into four major clusters, suggesting functional diversification. Integration of pan-genomic and flowering-time QTL analyses further identified two cyclin genes, Bna21cycA2 and Bna113cycD4, which contain amino acid polymorphisms and represent putative candidate variations potentially associated with flowering-time variation across multiple genomes. These findings provide new insights into the evolutionary expansion, retention, and potential functional divergence of cyclin genes in Brassicaceae and highlight candidate loci for future functional studies and crop improvement.

Evolution, Molecular↗
PubMed2002

Ecological and evolutionary validity: comments on Johnson-Laird, Legrenzi, Girotto, Legrenzi, and Caverni's (1999) mental-model theory of extensional reasoning.

The mental-model account of naive probabilistic reasoning by P. N. Johnson-Laird, P. Legrenzi, V. Girotto, M. S. Legrenzi, and J.-P. Caverni (1999) provides an opportunity to clarify several similarities and differences between it and ecological rationality (frequentist) accounts. First, ambiguities in the meaning of Bayesian reasoning can lead to disagreements and inappropriate arguments. Second, 2 conflated effects of using natural frequencies are noticed but not actually tested separately because of an artificial dissociation of frequency representations and natural sampling. Third, similarities are noted between the subset principle and the principle of natural sampling. Finally, some potentially misleading portrayals of the role of evolutionary factors in psychology are corrected. Mental-model theory, rather than better explaining probabilistic reasoning, may be able to use frequency representations as a key element in clarifying its own ambiguous constructs.

Bayes Theorem↗