SEARCH · PubMed Health

Results for “Evolution of cooperation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 883 records · Page 49Linked to original sources

PubMed1999

Prisoner's dilemma in an RNA virus.

The evolution of competitive interactions among viruses was studied in the RNA phage phi6 at high and low multiplicities of infection (that is, at high and low ratios of infecting phage to host cells). At high multiplicities, many phage infect and reproduce in the same host cell, whereas at low multiplicities the viruses reproduce mainly as clones. An unexpected result of this study was that phage grown at high rates of co-infection increased in fitness initially, but then evolved lowered fitness. Here we show that the fitness of the high-multiplicity phage relative to their ancestors generates a pay-off matrix conforming to the prisoner's dilemma strategy of game theory. In this strategy, defection (selfishness) evolves, despite the greater fitness pay-off that would result if all players were to cooperate. Viral cooperation and defection can be defined as, respectively, the manufacturing and sequestering of diffusible (shared) intracellular products. Because the low-multiplicity phage did not evolve lowered fitness, we attribute the evolution of selfishness to the lack of clonal structure and the mixing of unrelated genotypes at high multiplicity.

Bacteriophage phi 6↗

PubMed1996

Network analysis of human Y microsatellite haplotypes.

To investigate the utility of Y chromosome microsatellites for studying human male-lineage evolution, we typed samples from three populations for five tetranucleotide repeats and an Alu insertion polymorphism. We found very high levels of haplotype diversity and evidence that most mutations involve the gain or loss of only one repeat unit, implying that any given microsatellite haplotype may have arisen independently on two or more Y-chromosome lineages. Together, these factors suggest that interpretation of small sample sizes (< 30) will be problematic. By typing a large sample of individuals (n = 174) from one population, East Anglia, we were able to construct a haplotype network. The network exhibits a well-connected core structure of commoner haplotypes. Computer simulations based on this network estimate the convergence time for African and Caucasian groups may be between 1.4 and 1.8 times as long as the convergence of the East Anglian population. Based on our comparison between large and small sample sizes, we suggest that large sample sizes are necessary in order to interpret Y-microsatellite haplotypes, and that a network analysis of the type we describe may prove informative in future studies.

Base Sequence↗

PubMed1999

Intercellular bridges between granulosa cells and the oocyte in the elasmobranch Raya asterias.

In the present ultrastructural study intercellular bridges, connecting somatic granulosa cells to oocyte, have been detected for the first time and their modifications have been followed during Raja oogenesis. Intercellular bridges make their first appearance in small previtellogenic follicles as connecting devices between small cells and the oocyte. Later on, when the follicular epithelium becomes polymorphic and multilayered, for the presence of small, large, and pyriform-like cells, intercellular bridges link the oocyte and the different granulosa cells. Intercellular bridges contain ribosomes, whorl of membranes, mitochondria and vacuoles. Such cytoplasmic components are present also in the cell apex of large and pyriform-like cells thus suggesting, in agreement with other species (Motta et al. J. Exp. Zool., 1996;276:223-241) they may flow toward the oocyte. In this regard the presence of intercellular bridges during the oogenesis of cartilagineous fish may represent a crucial event of the active cooperation between granulosa cells and the oocyte.

Animals↗

PubMed1996

Molecular reconstruction and homology modelling of the catalytic domain of the common ancestor of the haemostatic vitamin-K-dependent serine proteinases.

The vitamin-K-dependent serine proteinases of coagulation have evolved by a process of gene duplication and divergence, acquiring along the way a considerable degree of functional diversity that has equipped them for their different roles in haemostasis. The cDNA sequences encoding the catalytic domains of the early mammalian ancestors of five vitamin-K-dependent factors (factors VII, IX and X, protein C and prothrombin) were reconstructed by employing cDNA sequence data from a range of extant mammals and by using established phylogenies. The cDNA sequence of the putative common ancestor of these early mammalian proteins was then reconstructed from the five sequences by using a deduced phylogeny that was different in a number of respects from those previously proposed. Factor IX is proposed to have branched off early on, followed by protein C and prothrombin and finally factors VII and X. Significant differences in mutation rates were observed between proteins within a species; factor IX exhibited a lower mutation rate than the other proteins, consistent with its early emergence. Differences in mutation rates were also observed between species for a given protein and these exhibited an inverse correlation with generation time. A biophysically plausible structure for the ancestral vitamin-K-dependent factor protein was constructed by comparative methods. Studies of the functional architecture of this model provide new insights into the evolution of protein-binding specificity in this family of proteins.

Amino Acid Sequence↗

PubMed1981

Instability and reiteration of DNA sequences within the vaccinia virus genome.

The sequence arrangement within the nontranscribed portion of the inverted terminal repetition of the vaccinia virus genome exists in quasi-stable and unstable forms that are not distinguishable on the basis of viral infectivity. The unstable forms, which composed about 20% of a serially passaged stock of virus, were recognized by terminal heterogeneity on restriction endonuclease analysis. Instead of a single terminal fragment from each end of the genome, an array of eight or more fragments differing in size by 1650-base-pair increments was detected. This feature was not eliminated by repeated plaque purification, indicating that the population of DNA molecules with various numbers of reiterations can rapidly evolve from the DNA of a single virus particle. However, at each successive round of plaque purification, about 20% of the unstable isolates revert back to the more stable form. Stable forms are characterized by the presence of a set of 13-17 tandem 70-base-pair repeats on each side of a 435-base-pair intervening sequence near both ends of the genome. In contrast, the unstable forms possess sets of tandem repeats and intervening sequences that alternate many times in series. The transition between the two genomic forms and the evolution of the unstable form appear to be mediated by recombinational events.

Base Sequence↗

PubMed2003

Competitive fates of bacterial social parasites: persistence and self-induced extinction of Myxococcus xanthus cheaters.

Cooperative biological systems are susceptible to disruption by cheating. Using the social bacterium Myxococcus xanthus, we have tested the short-term competitive fates of mixed cheater and wild-type strains over multiple cycles of cooperative development. Cheater/wild-type mixes underwent several cycles of starvation-induced multicellular development followed by spore germination and vegetative population growth. The population sizes of cheater and wild-type strains in each pairwise mixture were measured at the end of each developmental phase and each growth phase. Cheater genotypes showed several distinct competitive fates, including cheater persistence at high frequencies with little effect on total population dynamics, cheater persistence after major disruption of total population dynamics, self-extinction of cheaters with wild-type survival, and total population extinction. Our results empirically demonstrate that social exploitation can destabilize a cooperative biological system and increase the risk of local extinction events.

Biological Evolution↗

PubMed1996

Developing patient and family education programs for a transplant center.

Patient and family education is an important component of the organ transplant programs at the University of Nebraska Medical Center. The Medical Center is in the process of planning a new transplant center which will employ the family-centered, educationally-intensive cooperative care concept. This approach was chosen as the model for the delivery of care at the Lied Transplant Center because it emphasizes efficient, effective clinical care by requiring active participation by the family or essential other, thereby better preparing both the patient and the family for the transition to home and to the community. This article presents the evolution of patient education in our transplant programs, discusses the educational needs of transplant patients across the continuum of care, provides insight into the process of planning educational programs for the new center and provides a sample module for teaching which is based on the Cooperative Care concept.

Curriculum↗

PubMed2025

Origin and evolution of mitochondrial inner membrane composition.

Unique membrane architectures and lipid building blocks underlie the metabolic and non-metabolic functions of mitochondria. During eukaryogenesis, mitochondria likely arose from an alphaproteobacterial symbiont of an Asgard archaea-related host cell. Subsequently, mitochondria evolved inner membrane folds known as cristae alongside a specialized lipid composition supported by metabolic and transport machinery. Advancements in phylogenetic methods and genomic and metagenomic data have suggested potential origins for cristae-shaping protein complexes, such as the mitochondrial contact site and cristae-organizing system (MICOS). MICOS protein homologs function in the formation of cristae-like intracytoplasmic membranes (ICMs) in diverse extant alphaproteobacteria. The machinery responsible for synthesizing key mitochondrial phospholipids - which cooperate with cristae-shaping proteins to establish inner membrane architecture - could have also evolved from a bacterial ancestor, but its origins have been less explored. In this Review, we examine the current understanding of mitochondrial membrane evolution, highlighting distinctions between prokaryotic and eukaryotic mitochondrial-specific proteins and lipids and their differing roles in shaping cristae and ICM architecture, and propose a model explaining the concurrent specialization of the mitochondrial lipidome and inner membrane structure in eukaryogenesis. We discuss how advancements across a range of disciplines are shedding light on how multiple membrane components co-evolved to support the central functions of eukaryotic mitochondria.

Mitochondrial Membranes↗

PubMed1997

The quality evolution in managed care organizations: shifting the focus to community health.

Community demand for high-quality, cost-effective health care is forcing many new changes for managed care organizations (MCOs). Competition among MCOs often prevents cooperative and comprehensive approaches to the enhancement of the health status of the community. MCOs are beginning to measure quality based on the health of enrolled populations, and communities are seeking communitywide quality of care indicators. To cope with the demands of capitated health care, MCOs need to shift their focus to managing the health status of specific community populations. Strategies for managing the health status of populations include community assessments, collaboration among competing players, and a focus on consumer health information.

Community Health Planning↗

PubMed2004

Linkage of the beta-like omega-globin gene to alpha-like globin genes in an Australian marsupial supports the chromosome duplication model for separation of globin gene clusters.

The structure, function, and evolutionary history of globin genes have been the subject of extensive investigation over a period of more than 40 years, yet new globin genes with highly specialized functions are still being discovered and much remains uncertain about their evolutionary history. Here we investigate the molecular evolution of the beta-globin gene family in a marsupial species, the tammar wallaby, Macropus eugenii. We report the complete DNA sequences of two beta-like globin genes and show by phylogenetic analyses that one of these genes is orthologous to embryonically expressed epsilon-globin genes of marsupials and eutherians and the other is orthologous to adult expressed beta-globin genes of marsupials and eutherians. We show that the tammar wallaby contains a third functional beta-like globin gene, omega-globin, which forms part of the alpha-globin gene cluster. The position of omega-globin on the 3' side of the alpha-globin cluster and its ancient phylogenetic history fit the criteria, originally proposed by Jeffreys et al. (1980), of a "fossil" beta-globin gene and suggest that an ancient chromosome or genome duplication preceded the evolution of unlinked clusters of alpha- and beta-globin genes in mammals and avians. In eutherian mammals, such as humans and mice, omega-globin has been silenced or translocated away from the alpha-globin locus, while in marsupials omega-globin is coordinately expressed with the adult alpha-globin gene just prior to birth to produce a functional hemoglobin (alpha2 omega2).

Amino Acid Sequence↗

PubMed2005

Still waiting for the toll?

Multicellular organisms including invertebrates and vertebrates live in various habitats that may be aquatic or terrestrial where they are constantly exposed to deleterious pathogens. These include viruses, bacteria, fungi, and parasites. They have evolved various immunodefense mechanisms that may protect them from infection by these microorganisms. These include cellular and humoral responses and the level of differentiation of the response parallels the evolutionary development of the species. The first line of innate immunity in earthworms is the body wall that prevents the entrance of microbes into the coelomic cavity that contains fluid in which there are numerous leukocyte effectors of immune responses. When this first barrier is broken, a series of host responses is set into motion activating the leukocytes and the coelomic fluid. The responses are classified as innate, natural, non-specific, non-anticipatory, non-clonal (germ line) in contrast to the vertebrate capacity that is considered adaptive, induced, specific, anticipatory and clonal (somatic). Specific memory is associated with the vertebrate response and there is information that the innate response of invertebrates may under certain conditions possess specific memory. The invertebrate system when challenged affects phagocytosis, encapsulation, agglutination, opsonization, clotting and lysis. At least two major leukocytes, small and large mediate lytic reactions against several tumor cell targets. Destruction of tumor cells in vitro shows that phagocytosis and natural killer cell responses are distinct properties of these leukocytes. This has prompted newer searches for immune function and regulation in other systems. The innate immune system of the earthworm has been analyzed for more than 40 years with every aspect examined. However, there are no known entire sequences of the earthworm as exists in these other invertebrates. Because the earthworm lives in soil and has been utilized as a successful monitor for pollution, there are studies that reveal up and down regulation of responses in the immune system after exposure to a variety of environmental pollutants. Moreover, there are partial sequences that appear in earthworms after exposure to environmental pollutants such as cadmium and copper. There are now attempts to define the AHR receptor crucial for intracellular signaling after exposure to pollutants, but without linking the signals to changes in the immune system. There are several pathways for signal transduction, including JAK/STAT, TOLL, TRAF PIP3, known in invertebrates and vertebrates. For resistance to pathogens, conserved signal transduction components are required and these include a Toll/IL-1 receptor domain adaptor protein that functions upstream of a conserved p38 MAP kinase pathway. This pathway may be an ancestral innate immune signaling pathway found in a putative common ancestor of nematodes, arthropods and even vertebrates. It could also help us to link pollution, innate immunity and transduction in earthworms.

Animals↗

PubMed2003

A tale of two polymers: new insights into helical filaments.

Many proteins function as helical polymers within the cell. Two intensively studied examples are eukaryotic actin and bacterial RecA, which belong to two different protein superfamilies. However, most other members of these superfamilies do not polymerize into helical filaments. General features of polymorphism, cooperativity and allostery that emerge from studies of eukaryotic actin and bacterial RecA raise more general issues about how conserved these filamentous structures have been during evolution.

Actins↗

PubMed1998

Ascertainment bias cannot entirely account for human microsatellites being longer than their chimpanzee homologues.

A large majority of human microsatellite markers are longer than their homologues in chimpanzees, suggesting that more expansion mutations have occurred in the lineage leading to humans. However, such a length difference has also been explained as arising from the selection of unusually long microsatellites as genetic markers. In order to resolve this controversy and to establish the true source of the observed length differences, we have now conducted the necessary reciprocal study. We have compared the lengths of size-selected markers cloned from chimpanzees between this species and humans. We find that of 19 markers which were informative and polymorphic in both species, 13 are longer in humans. This result is incompatible with ascertainment bias being the sole explanation for the inter-specific length differences. We estimate that dinucleotide repeat microsatellites are an average of 3.2 repeat units longer in humans than in chimpanzees, implying a mutational bias in favour of microsatellite expansions and a higher average genome-wide microsatellite mutation rate in the human lineage.

Animals↗

PubMed1996

Conserved sequence motifs, alignment, and secondary structure for the third domain of animal 12S rRNA.

Secondary structure models are an important step for aligning sequences, understanding probabilities of nucleotide substitutions, and evaluating the reliability of phylogenetic reconstructions. A set of conserved sequence motifs is derived from comparative sequence analysis of 184 invertebrate and vertebrate taxa (including many taxa from the same genera, families, and orders) with reference to a secondary structure model for domain III of animal mitochondrial small subunit (12S) ribosomal RNA. A template is presented to assist with secondary structure drawing. Our model is similar to previous models but is more specific to mitochondrial DNA, fitting both invertebrate and vertebrate groups, including taxa with markedly different nucleotide compositions. The second half of the domain III sequence can be difficult to align precisely, even when secondary structure information is considered. This is especially true for comparisons of anciently diverged taxa, but well-conserved motifs assist in determining biologically meaningful alignments. Patterns of conservation and variability in both paired and unpaired regions make differential phylogenetic weighting in terms of "stems" and "loops" unsatisfactory. We emphasize looking carefully at the sequence data before and during analyses, and advocate the use of conserved motifs and other secondary structure information for assessing sequencing fidelity.

Animals↗

PubMed2002

A Gondwanan origin of passerine birds supported by DNA sequences of the endemic New Zealand wrens.

Zoogeographic, palaeontological and biochemical data support a Southern Hemisphere origin for passerine birds, while accumulating molecular data suggest that most extant avian orders originated in the mid-Late Cretaceous. We obtained DNA sequence data from the nuclear c-myc and RAG-1 genes of the major passerine groups and here we demonstrate that the endemic New Zealand wrens (Acanthisittidae) are the sister taxon to all other extant passerines, supporting a Gondwanan origin and early radiation of passerines. We propose that (i) the acanthisittids were isolated when New Zealand separated from Gondwana (ca. 82-85 Myr ago), (ii) suboscines, in turn, were derived from an ancestral lineage that inhabited western Gondwana, and (iii) the ancestors of the oscines (songbirds) were subsequently isolated by the separation of Australia from Antarctica. The later spread of passerines into the Northern Hemisphere reflects the northward migration of these former Gondwanan elements.

Animals↗

PubMed2001

Paramyxovirus accessory proteins as interferon antagonists.

A new role of the Paramyxovirus accessory proteins has been uncovered. The P gene of the subfamily Paramyxovirinae encodes accessory proteins including the V and/or C protein by means of pseudotemplated nucleotide addition (RNA editing) or by overlapping open reading frame. The Respirovirus (Sendai virus and human parainfluenza virus (hPIV)3) and Rubulavirus (simian virus (SV)5, SV41, mumps virus and hPIV2) circumvent the interferon (IFN) response by inhibiting IFN signaling. The responsible genes were mapped to the C gene for SeV and the V gene for rubulaviruses. On the other hand, wild type measles viruses isolated from clinical specimens suppress production of IFN, although responsible viral factors remain to be identified. Both human and bovine respiratory syncytial viruses (RSVs) counteract the antiviral effect of IFN with inhibiting neither IFN signaling nor IFN production. Bovine RSV NS1 and NS2 proteins cooperatively antagonize the antiviral effect of IFN. Studies on the molecular mechanism by which viruses circumvent the host IFN response will not only illustrate co-evolution of virus strategies of immune evasion but also provide basic information useful for engineering novel antiviral drugs as well as recombinant live vaccine.

Base Sequence↗

PubMed2003

An evolutionary model of carcinogenesis.

A quantitative model of carcinogenesis based on methods from population biology and game theory demonstrates normal cells in vivo occupy a ridge-shaped maximum in a well-defined tissue fitness landscape, a novel configuration that allows cooperative coexistence of multiple cellular populations. This state, although necessary for development of functioning multicellular organisms, is subject to invasion by fitter, mutant phenotypes permitting somatic evolution of cancer. The model demonstrates carcinogenesis is an emergent phenomenon requiring a sequence of evolutionary steps as cellular proliferation follows successful adaptation to varying environmental constraints. In the initial development of preneoplastic lesions, cellular proliferation is controlled exclusively by interactions with other cells, the extracellular matrix, and soluble or insoluble growth factors so that gain of function mutations in oncogenes, loss of function mutations in tumor suppressor genes, and disruption of normal senescence pathways will permit clonal expansion. This provides explicit selection mechanisms for the mutations depicted in the classical Fearon-Vogelstein model of colorectal carcinogenesis. The model demonstrates neoplastic cellular proliferation can also be promoted by alterations in the somatic landscape that reduce inhibitory signals produced by the normal cells and extracellular matrix. This is consistent with experimental evidence for a strong microenvironmental influence in tumorigenesis independent of genomic changes in the neoplastic populations. However, we find that these changes alone produce only self-limited neoplastic growth because cellular crowding alters system dynamics so that proliferation is dependent on substrate availability. Consequent cellular competition for critical nutrients results in Darwinian selection pressures favoring phenotypes that increase substrate delivery (e.g., angiogenesis) or uptake (e.g., amplify membrane transporters). These previously unknown substrate dynamics in the later stages of carcinogenesis provide a mechanism for evolution of cellular properties typically found in invasive cancers including the angiogenic and glycolytic phenotypes.

Animals↗

PubMed1987

[Morphologico-functional study of the locomotor system of penguins as a principle of the general motor model of "underwater flight." III].

Based on some ideas about the evolution of the underwater flight of penguins (part I) and morphological data obtained by dissection of 26 individuals (part II), a survey is developed about the cooperation and interaction of the components of the muscle apparatus and some ethological peculiarities of Penguins are explained by their anatomical basis. The knowledge of the mechanics of the shoulder joint will be useful for comparative anatomical studies of specimens of recent and fossil birds.

Animals↗