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PubMed2002

Grasping primate origins.

The evolutionary history that led to Eocene-and-later primates of modern aspect (Euprimates) has been uncertain. We describe a skeleton of Paleocene plesiadapiform Carpolestes simpsoni that includes most of the skull and many postcranial bones. Phylogenetic analyses indicate that Carpolestidae are closely related to Euprimates. C. simpsoni had long fingers and an opposable hallux with a nail. It lacked orbital convergence and an ankle specialized for leaping. We infer that the ancestor of Euprimates was primitively an arboreal grasper adapted for terminal branch feeding rather than a specialized leaper or visually directed predator.

Animals↗

PubMed1991

[Life and environment: from aquatic animals to terrestrial animals and to man].

Whether animals are vertebrates or invertebrates, the problems raised by the invasion of land are common to all who have succeeded--terrestrial worms, mollusks and crustaceans, arachnids, insects, terrestrial vertebrates. Many physiological traits, although supported by quite different morphological structures, are convergent and related to the environmental characteristics. Thus one is led to put terrestrial animals and aquatic animals belonging to very distantly related phyla, and then suggest an ecophysiological transphyletic division of the animal kingdom.

Animal Population Groups↗

PubMed2000

Long-Term Experimental Evolution in Escherichia coli. VIII. Dynamics of a Balanced Polymorphism.

We describe the short- and long-term dynamics of a phenotypic polymorphism that arose in a population of Escherichia coli while it was serially propagated for almost 20,000 generations in a glucose-limited minimal medium. The two types, designated L and S, differ conspicuously in the size of the colonies they form on agar plates as well as the size of their individual cells, and these differences are heritable. The S type reached a detectable frequency (>1%) at generation 6,000, and it remained above that frequency throughout the subsequent generations. In addition to morphological differences, L and S diverged in important ecological properties. With clones isolated at 18,000 generations, L has a maximal growth rate in fresh medium that is ∼20% higher than that of S. However, experiments with conditioned media demonstrate that L and S secrete one or more metabolites that promote the growth of S but not of L. The death rate of L during stationary phase also increases when S is abundant, which suggests that S may either secrete a metabolite that is toxic to L or remove some factor that enables the survival of L. One-day competition experiments with the clones isolated at generation 18,000 show that their relative fitness is frequency dependent, with each type having an advantage when rare. When these two types are grown together for a period of several weeks, they converge on an equilibrium frequency that is consistent with the 1-d competition experiments. Over the entire 14,000-generation period of coexistence, however, the frequency of the S type fluctuated between approximately 10% and 85%. We offer several hypotheses that may explain the fluctuations in this balanced polymorphism, including the possibility of coevolution between the two types.

Escherichia coli↗

PubMed2006

Stochastic models for mainland-island metapopulations in static and dynamic landscapes.

This paper has three primary aims: to establish an effective means for modelling mainland-island metapopulations inhabiting a dynamic landscape; to investigate the effect of immigration and dynamic changes in habitat on metapopulation patch occupancy dynamics; and to illustrate the implications of our results for decision-making and population management. We first extend the mainland-island metapopulation model of Alonso and McKane [Bull. Math. Biol. 64:913-958, 2002] to incorporate a dynamic landscape. It is shown, for both the static and the dynamic landscape models, that a suitably scaled version of the process converges to a unique deterministic model as the size of the system becomes large. We also establish that, under quite general conditions, the density of occupied patches, and the densities of suitable and occupied patches, for the respective models, have approximate normal distributions. Our results not only provide us with estimates for the means and variances that are valid at all stages in the evolution of the population, but also provide a tool for fitting the models to real metapopulations. We discuss the effect of immigration and habitat dynamics on metapopulations, showing that mainland-like patches heavily influence metapopulation persistence, and we argue for adopting measures to increase connectivity between this large patch and the other island-like patches. We illustrate our results with specific reference to examples of populations of butterfly and the grasshopper Bryodema tuberculata.

Algorithms↗

PubMedDate not supplied

The effectiveness of the advanced trauma life support system in a mass casualty situation by non-trauma-experienced physicians: Grenada 1983.

Mass casualty is a sporadic event precipitated by natural or man made causes which can be defined as the need for medical care exceeding the ability to provide it. Many literature reports of mass casualty evolutions depict scenes of chaos and confusion, leading to a need for a standardized approach to assessment, triage, and initial resuscitation. Even with the advent of trained emergency medicine specialists to direct these activities, such a framework would seem highly desirable for other participating primary care specialists. Additionally, a uniform system might be particularly useful in the mass casualty situation where international rescue teams converge on one disaster site. Advanced Trauma Life Support (ATLS) is a standardized approach easily adaptable to triage and resuscitation of multiple patients. Its use and effectiveness in mass casualty, however, has not had prior mention in the literature. This paper presents the first reported adaptation of ATLS principles to mass casualty during the invasion of Grenada. The bulk of 76 patients brought to the Primary Casualty Receiving and Treatment Center (PCRTC) were triaged, stabilized, and resuscitated by three PGY-1 trained, non-trauma-experienced physicians. During the primary survey, 8 major life threatening problems were identified and immediately corrected without loss of life. The ATLS system seemed to provide a comfortable framework for these partially trained physicians. Arguments for its adaptation and use as an international system approach are discussed.

Education, Medical, Graduate↗

PubMed1999

Quantitative analysis of receptors for adenosine nucleotides obtained via in vitro selection from a library incorporating a cationic nucleotide analog.

5-(3"-Aminopropynyl)-2'-deoxyuridine (dJ), a modified nucleoside with a side chain carrying a cationic functional group, was incorporated into an oligonucleotide library, which was amplified using the Vent DNA polymerase in a polymerase chain reaction (PCR). When coupled to an in vitro selection procedure, PCR amplification generated receptors that bind ATP. This is the first example of an in vitro selection generating oligonucleotide receptors where the oligonucleotide library has incorporated a cationic nucleotide functionality. The selection yielded functionalized receptors having sequences differing from a motif known to arise in a standard selection experiment using only natural nucleotides. Surprisingly, both the natural and the functionalized motifs convergently evolved to bind not one, but two ATP molecules cooperatively. Likewise, the affinity of the receptors for ATP had converged; in both cases, the receptors are half saturated at the 3 mM concentrations of ATP presented during the selection. The convergence of phenotype suggests that the outcome of this selection experiment was determined by features of the environment during which selection occurs, in particular, a highly loaded affinity resin used in the selection step. Further, the convergence of phenotype suggests that the optimal molecular phenotype has been achieved by both selections for the selection conditions. This interplay between environmental conditions demanding a function of a biopolymer and the ability of the biopolymer to deliver that function is strictly analogous to that observed during natural selection, illustrating the nature of life as a self-sustaining chemical system capable of Darwinian evolution.

Adenine Nucleotides↗

PubMed1999

Diffusion and scaling in escapes from two-degrees-of-freedom Hamiltonian systems.

This paper summarizes an investigation of the statistical properties of orbits escaping from three different two-degrees-of-freedom Hamiltonian systems which exhibit global stochasticity. Each time-independent H=H(0)+ varepsilon H('), with H(0) an integrable Hamiltonian and varepsilon H(') a nonintegrable correction, not necessarily small. Despite possessing very different symmetries, ensembles of orbits in all three potentials exhibit similar behavior. For varepsilon below a critical varepsilon (0), escapes are impossible energetically. For somewhat higher values, escape is allowed energetically but still many orbits never escape. The escape probability P computed for an arbitrary orbit ensemble decays toward zero exponentially. At or near a critical value varepsilon (1)> varepsilon (0) there is a rather abrupt qualitative change in behavior. Above varepsilon (1), P typically exhibits (1) an initial rapid evolution toward a nonzero P(0)( varepsilon ), the value of which is independent of the detailed choice of initial conditions, followed by (2) a much slower subsequent decay toward zero which, in at least one case, is well fit by a power law P(t) proportional, variant t(-&mgr;), with &mgr; approximately 0.35-0.40. In all three cases, P(0) and the time T required to converge toward P(0) scale as powers of varepsilon - varepsilon (1), i.e., P(0) proportional, variant ( varepsilon - varepsilon (1))(alpha) and T proportional, variant ( varepsilon - varepsilon (1))(beta), and T also scales in the linear size r of the region sampled for initial conditions, i.e., T proportional, variant r(-delta). To within statistical uncertainties, the best fit values of the critical exponents alpha, beta, and delta appear to be the same for all three potentials, namely alpha approximately 0.5, beta approximately 0.4, and delta approximately 0.1, and satisfy alpha-beta-delta approximately 0. The transitional behavior observed near varepsilon (1) is attributed to the breakdown of some especially significant KAM tori or cantori. The power law behavior at late times is interpreted as reflecting intrinsic diffusion of chaotic orbits through cantori surrounding islands of regular orbits. (c) 1999 American Institute of Physics.

Journal Article↗

PubMed1996

Evolution of ophthalmic and electrophysiological findings in identical twin sisters with the carbohydrate deficient glycoprotein syndrome type 1 over a period of 14 years.

AIMS: To evaluate the evolution of ocular and electroretinographic findings in identical twin sisters with the carbohydrate deficient glycoprotein (CDG) syndrome over a period of 14 years. METHODS: Both girls underwent a clinical ophthalmic examination with funduscopy and an electrophysiological assessment with recording of flash electroretinogram (FERG) at the age of 4 years and 18 years RESULTS: On ophthalmic examination at the age of 4 years an alternating convergent squint and a saccadic pursuit was diagnosed. In both, vision was 6/9 bilaterally. Fundus examination showed normal optic discs, narrow blood vessels, and a mild irregular pigmentation in the periphery. In one girl the FERG showed a recognisable a, b1, and b2-wave with reduced amplitude to less than 40% of the normal. In the other girl the reduction in amplitude was still more obvious, but for the white flash a small b1-wave was still present. At the age of 18 vision had remained 6/9 in both eyes. Funduscopy showed pink optic discs, moderately narrowed blood vessels, and bony spicule pigmentary deposits in the mid periphery. The adapto ERG, performed in identical conditions at 18 years of age, showed a completely extinguished trace for both eyes. CONCLUSIONS: Despite progressive deterioration of ERG findings good central vision was preserved over 14 years.

Congenital Disorders of Glycosylation↗

PubMed2006

Personality disorder as harmful dysfunction: DSM'S cultural deviance criterion reconsidered.

The DSM's general criteria for personality disorder (PD) attempt to define PD versus nondisordered personality conditions. If dimensionalization of PD occurs in the DSM-V (perhaps, it is suggested, with PD diagnosis moved to Axis I and overall personality assessment in Axis II, thus separating diagnosis from case formulation), general criteria likely will still be needed to prevent massive false positives. In this article, one of the general criteria, the cultural deviance requirement (CDR), is examined from the perspective of the evolution-based harmful-dysfunction analysis of disorder. The CDR is often assumed to express value relativity of harm in diagnosis, but cultural values are a designed feature of human social functioning that influence personality formation. The CDR is thus argued to be an indicator of whether an individual's personality organization is due to an evolutionary dysfunction. Value relativity and evolutionary analysis thus converge.

Comorbidity↗

PubMed2006

[Multisite validation study of questionnaire assessing out-patient satisfaction with care questionnaire in ambulatory chemotherapy or radiotherapy treatment].

Patient satisfaction is now recognised as an important quality of care outcome which is particularly relevant in oncology. Adapted from the EORTC In-Patsat32, the Out-Patsat35 is a 35-item satisfaction with care questionnaire measuring cancer outpatients' perception of hospital doctors and nurses, as well as aspects of care organisation and services. This study assessed the psychometric properties of this scale. Patients undergoing ambulatory chemotherapy (CT) or radiotherapy (RT) in 7 cancer centres in France were invited to complete at home the Out-Patsat35 as well as EORTC QLQ-C30 for psychometric testing. Of 416 eligible patients recruited, 96% returned the questionnaire. Most patients (71% in CT; 69% in RT) completed this scale within 15 minutes and the mean rate of item omission was only 4.4%. Confirmatory analyses revealed good convergent validity and excellent internal consistency, although some subscales within the Out-Patsat35 were relatively highly correlated. Items and subscales of the Out-Patsat35 and of the QLQ-C30 were not significantly correlated, underlying that the two questionnaires are assessing quite distinct concepts. The subscales of the Out-Patsat35 were not related to age, gender and education, suggesting a cultural evolution in French cancer patients towards a greater homogeneity in their opinion toward care. This study supports the acceptability to patients, and the psychometric properties of the EORTC Out-Patsat35 questionnaire.

Ambulatory Care↗

PubMed1998

Who will standardise the standardisers: an analysis of the evolution of the standards-making process.

For many years, there have been a number of different bodies producing standards--formal standards bodies, collaborative organisations and industrial consortia. Each process has its own advantages and disadvantages. More recently, there have been considerable efforts made to bring these processes together and to optimise the standards-making process for the benefit of standards-makers, industry and the end-user. This paper describes the various means by which standards are currently produced, examines their advantages and disadvantages and discusses how they are converging. It also indicates the likely results of this convergence.

Computer Communication Networks↗

PubMed2003

Relationships and origin of endemic Lake Baikal gastropods (Caenogastropoda: Rissooidea) based on mitochondrial DNA sequences.

The phylogenetic relationships and the origin of two groups of rissooid freshwater snails endemic to Lake Baikal were investigated using partial mitochondrial COI, 12S rDNA, and 16S rDNA sequences. The Baikalian Benedictiinae proved to be closely related to the Lithoglyphinae. According to a molecular clock estimate the two groups diverged in the Paleogene. The Benedictiinae might have evolved autochthonously in precursors of Lake Baikal. The Baikalian Baicaliidae are probably most closely related to the Amnicolidae and the Bithyniidae. These groups diverged at the latest during the Cretaceous. Thus the origin of the Baicaliidae predates the origin of the Baikal rift zone. The Baicaliidae evolved probably in other Central Asian freshwater reservoirs. However, the radiation of the extant Baicaliidae only started in the Neogene and might have occurred autochthonously in Lake Baikal. The conchological similarity of the Baicaliidae and the Pyrgulidae is due to convergence. The Pyrgulidae diverged from the common stem lineage of the other hydrobiid families at the latest in the Jurassic. The Bithyniidae is derived from hydrobiids and is related to the Amnicolidae.

Animals↗

PubMed2001

Evolutionary attempts at 4 eyes in vertebrates.

PURPOSE: To understand and compare the optical, histological, and ecological differences among 4 vertebrate species that have had evolutionary attempts toward 4 eyes. METHODS: An evolutionary attempt at 4 eyes in defined as the duplication or one or more structures integral to the refraction or interpretation of the visible spectrum for that animal. We reviewed and compared the known optics, histology, and ecology of each of these vertebrate species with attempts at 4 eyes including Anableps anableps, Dialomnus fuscus, Mnierpes macrocephalus, and Bathylychnops exilis. These animals have developed portions of ancillary eyes that have diverged from the primary globe in 3 different patterns. At least 1 specimen of each of those vertebrate species known to have 4 eyes was examined histologically and compared to the animal's ecology and current cladistic relationship. RESULTS: A anabteps has 2 distinct optical systems in each eye: an upper one for aerial vision and a lower system for aquatic vision. These systems feature separate retinae and an asymmetric lens to achieve focus in the aerial and aquatic vision, but only 1 optic nerve per eye. The visual system is split horizontally to function optimally in a "prone" position in the water. D fuscus is a terrestrial feeder and has a vertically (almost perpendicular to the long axis of the fish) divided cornea using pigment and a condensation of collagen as the divider, a single pupil, and a divided retina. The split cornea allows for the fish to remain vertical with 1 cornea in air and 1 cornea in water. M macrocephalus is probably closely related to D fuscus with a similar split cornea. B exilis is a mesopelagic inhabitant living at approximately 200 to 1,000 m and has an ancillary globe that "buds" off the primary globe. This secondary globe is directed inferiorly toward the ocean floor as compared to the primary globe, which is directed 35 degrees superiorly from the horizontal. Adult species of B exilis have 2 additional scleral bodies suspected to be lenses. If so, these structures would be capable of focusing light from the inferior field onto the superior retina, presumably adding to the panoramic inferior visual field. There are other mesopelagic species, including Styleophorus chordatus, Opisthoproctus grimaldii, Scopelarchus gantheri (or guentheri), Dolichopteryx binocularis, Benthalbella infans, and Evermannella indica, that have other unusual ocular mechanisms, such as retinal diverticulae and lens pads capable of reflection, but do not meet the definition of multiple eyes, as defined for purposes of this work. CONCLUSIONS: D fuscus and M macrocephalus are terrestrial feeders requiring aquatic and aerial vision, and hence have a split cornea for this purpose, and they probably use their anterior corneae for terrestrial vision. A anableps swims at the surface with combined aerial and aquatic vision for feeding and protection from predators. B exilis is a mesopelagic feeder requiring a binocular visual field in the horizontal meridian and above, and simultaneously is a bottom scavenger using an ancillary globe and perhaps scleral lenses for recognition of bioluminescent detritus. Although 2 of these models are related (D fuscus and M macrocephalus), these 4 fish represent 3 separate, distinct, and unrelated convergent evolutionary attempts toward 4 eyes in vertebrates satisfying the ecological needs of each. The 3 different models are unrelated evolutionarily and are found in 3 separate orders.

Animals↗

PubMed2006

Evolution of funnel-revolver flowers and ornithophily in nasa (loasaceae).

Floral morphology, distribution, and flower visitors for 60 taxa of Nasa are investigated and compared to molecular trees inferred both from a combined marker analysis (ITS1 and trnL (UAA)) and from a single marker (ITS1). Flowers conform to two different floral types: Firstly, "tilt-revolver flowers", with spreading to reflexed, white to yellow petals and small, brightly coloured floral scales contrasting with the petals and firmly enclosing the nectar (Saccatae and Carunculatae); secondly, "funnel-revolver flowers", with half-erect to erect, orange to red petals and floral scales not contrasting with the petals, or enclosed in the corolla, and nectar freely accessible by funnel-shaped floral scales ( Alatae, Grandiflorae, and N. venezuelensis species group). Phylogenetic analysis shows that "tilt-revolver flowers" represent the plesiomorphic condition by outgroup comparison. The two groups with tilt-revolver flowers in Nasa are not monophyletic ( Saccatae are paraphyletic, Carunculatae are polyphyletic). Most Saccatae fall into two monophyletic assemblages, the N. poissoniana species group and the N. triphylla species group. The remainder of Saccatae group either with Grandiflorae ( N. insignis species group) or with Alatae ( N. laxa species group). The clades retrieved in the molecular analysis contradict the traditional classification, but are congruent with vegetative morphology, details of the flower morphology, and biogeography. "Funnel-revolver flowers" represent the derived condition, but molecular data suggest a convergent development (at least twice independently), since the corresponding species do not constitute a monophyletic group. "Tilt-revolver flowers" are visited and pollinated by bees (especially Colletidae), whereas "funnel-revolver flowers" are mostly visited by hummingbirds. The transition from melittophily to ornithophily may have been the license for the colonization of, and the diversification in, both cloud forest and high Andean habitats.

Animals↗

PubMed1993

On the formulation and computer implementation of an age-dependent two-sex demographic model.

A two-sex age-dependent demographic model is formulated within the framework of a stochastic population process, including both time-homogeneous and time-inhomogeneous laws of evolution. An outline of the parametric components of the system, which expedite computer implementation and experimentation, is also given. New features of the model include a component for couple formation, using the class of Farlie-Morgenstern bivariate distributions to accommodate age preferences in selecting marriage partners, a component for couple dissolution due to separation or divorce, and an outline of techniques for initializing a two-sex projection given scanty information. For the case of time-homogeneous laws of evolution, stability properties of two-sex models that are analogs of those for one-sex models are difficult to prove mathematically due to nonlinearities. But computer experiments in this case suggest that these properties continue to hold for two-sex models for such widely used demographic indicators as period crude birth rates, period rates of natural increase, and period age distributions, which converge to constant forms in long-term projections. The values of the stable crude birth rate, rate of natural increase, and quantiles of the stable age distribution differ markedly among projections that differ only in selected values of parameters governing couple formation and dissolution. Such experimental results demonstrate that two-sex models are not merely intellectual curiosities but exist in their own right and lead to insights not attainable in simpler one-sex formulations.

Age Factors↗

PubMedDate not supplied

A genetic algorithm based on prepotency evolution using chaotic initiation used for network training.

The concept of "prepotency" is introduced in evolution algorithm. The logistic mapping as a simple and powerful device in the chaos theory is combined with the newly proposed prepotency evolution (PE) algorithm to formulate a new genetic algorithm. PE with a population initialized by chaotic numbers is applied to the multiple-layer feed-forward ANN training (PECNN). The logistic mapping ensures the PE starts each time from different initial population never used before. The newly designed PE operator partially includes the crossover and mutation operations implicitly. The proposed algorithm has a higher convergence speed comparing to the conventional GA. During the PE operation the distances between members would become smaller and smaller until all members turning to be almost identical with the potential best minimum being found. It does not waste searching time surrounding the testing minima like the conventional GA and not show symptoms of overfitting to the training set samples. The combination of logistic mapping and PE used in ANN training makes PECNN be able to test lots of minima rapidly and effectively. This greatly enlarges the opportunity to find the global minimum. The proposed algorithm has been testified by prediction of the frequency data of tetrahedral vibration modes (nu(1) and nu(2)) of tetrahalide MX(4)(n) ions. The results obtained by the proposed PECNN compared favorably with those of the conventional chemometric method PLS regression.

Journal Article↗

PubMed2003

Involvement of the INK4a/Arf gene locus in senescence.

The INK4a/ARF locus encodes two proteins whose expression limits cellular proliferation. Whilst the biochemical activities of the two proteins appear very different, they both converge on regulating the retinoblastoma and p53 tumour suppressor pathways. Neither protein is required for normal development, but lack of either predisposes to the development of malignancy. Both proteins have also been implicated in the establishment of senescence states in response to a variety of stresses, signalling imbalances and telomere shortening. The INK4a/Arf regulatory circuits appear to be partially redundant and show evidence of rapid evolution. Especially intriguing are the large number of biological differences documented between mice and man. We review here the brief history of INK4a/Arf and explore possible links with organismal aging and the evolution of longevity.

Animals↗

PubMed2000

The approach of a neuron population firing rate to a new equilibrium: an exact theoretical result.

The response of a noninteracting population of identical neurons to a step change in steady synaptic input can be analytically calculated exactly from the dynamical equation that describes the population's evolution in time. Here, for model integrate-and-fire neurons that undergo a fixed finite upward shift in voltage in response to each synaptic event, we compare the theoretical prediction with the result of a direct simulation of 90,000 model neurons. The degree of agreement supports the applicability of the population dynamics equation. The theoretical prediction is in the form of a series. Convergence is rapid, so that the full result is well approximated by a few terms.

Algorithms↗