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PubMed2006

Self-recognition in an Asian elephant.

Considered an indicator of self-awareness, mirror self-recognition (MSR) has long seemed limited to humans and apes. In both phylogeny and human ontogeny, MSR is thought to correlate with higher forms of empathy and altruistic behavior. Apart from humans and apes, dolphins and elephants are also known for such capacities. After the recent discovery of MSR in dolphins (Tursiops truncatus), elephants thus were the next logical candidate species. We exposed three Asian elephants (Elephas maximus) to a large mirror to investigate their responses. Animals that possess MSR typically progress through four stages of behavior when facing a mirror: (i) social responses, (ii) physical inspection (e.g., looking behind the mirror), (iii) repetitive mirror-testing behavior, and (iv) realization of seeing themselves. Visible marks and invisible sham-marks were applied to the elephants' heads to test whether they would pass the litmus "mark test" for MSR in which an individual spontaneously uses a mirror to touch an otherwise imperceptible mark on its own body. Here, we report a successful MSR elephant study and report striking parallels in the progression of responses to mirrors among apes, dolphins, and elephants. These parallels suggest convergent cognitive evolution most likely related to complex sociality and cooperation.

Animals↗
PubMed1984

tau, a repeated DNA sequence in yeast.

We have found a 371-base-pair (bp) repeated DNA element, tau, in Saccharomyces cerevisiae. The ends of tau are composed of a 5-bp inverted repeat, similar in sequence to those reported for the Ty, sigma, copia, and spleen necrosis virus elements. These inverted repeats are flanked by 5-bp direct repeats of a target sequence that occurs only once in an allele that lacks the tau element. This overall structure is characteristic of transposable elements. Like sigma, tau elements have been found (in both orientations) closely associated with tRNA genes (409 and 198 bp from the 5' end, respectively). It is noteworthy that one representative of tau was isolated in a concentric insertion of tau, delta, and sigma.

Base Composition↗
PubMed1995

Polymorphic variation in the human protein C (PROC) gene promoter can influence transcriptional efficiency in vitro.

The haplotype frequencies of two closely linked diallelic polymorphisms in the protein C(PROC) gene promoter were determined in the British population. In principle, differences in transcription efficiency between PROC promoter haplotypes could represent an additional risk factor in determining whether or not an individual already predisposed to venous thrombosis will come to clinical attention. In order to explore this postulate, transient transfection of human hepatoma cells with PROC promoter-luciferase reporter gene constructs was performed in vitro. In HepG2 cells, the T.....A haplotype exhibited at least a two-fold higher transcription efficiency than the C.....G haplotype. A sample of British protein C deficiency patients with recurrent venous thrombosis was then allelotyped by a combination of oligonucleotide discriminant hybridization and DNA sequencing. The frequency of the low expressing C.....G haplotype was found to be slightly yet not significantly higher in these patients (0.43) than in controls (0.35).

Base Sequence↗
PubMed1997

Molecular cloning of quail thyroid-stimulating hormone (TSH) beta subunit.

Thyroid-stimulating hormone (TSH) beta subunit cDNA was obtained from Japanese quail (Coturnix japonica) by PCR and its nucleotide sequence was determined. The cDNA encodes a putative signal peptide and a mature protein consisting of 20 and 114 amino acids, respectively. The amino acid sequence of quail TSHbeta subunit shows homologies of 67-69% in mammalian species, 58% in amphibian and 43-49% in teleost fish. Comparison of the amino acid sequence with TSHbeta subunits of other species reveals some differences in several regions responsible for its biological functions and characteristic features of the avian TSHbeta subunit, suggesting that the functional domains have diverged cooperatively between the hormone and its receptor during evolution.

Amino Acid Sequence↗
PubMed2004

Diminishing returns in social evolution: the not-so-tragic commons.

A challenge for evolutionary theory is to understand how cooperation can occur in the presence of competition and cheating, a problem known as the tragedy of commons. Here I examine how varying the fitness returns from reproductive competition or cooperation affects the negative impact of competition on a social group. Varying linear returns does not affect the impact of competition. However, diminishing returns, where additional investments in either competition or cooperation give smaller and smaller rewards, reduce the effects of competition on the group. I show that diminishing returns are common in many systems, including social vertebrates, microbes, social insects and mutualisms among species. This suggests that the tragedy of the commons is not so tragic and that the disruptive effects of competition upon social life will often be minor.

Animals↗
PubMed2005

Time dependency of molecular rate estimates and systematic overestimation of recent divergence times.

Studies of molecular evolutionary rates have yielded a wide range of rate estimates for various genes and taxa. Recent studies based on population-level and pedigree data have produced remarkably high estimates of mutation rate, which strongly contrast with substitution rates inferred in phylogenetic (species-level) studies. Using Bayesian analysis with a relaxed-clock model, we estimated rates for three groups of mitochondrial data: avian protein-coding genes, primate protein-coding genes, and primate d-loop sequences. In all three cases, we found a measurable transition between the high, short-term (< 1-2 Myr) mutation rate and the low, long-term substitution rate. The relationship between the age of the calibration and the rate of change can be described by a vertically translated exponential decay curve, which may be used for correcting molecular date estimates. The phylogenetic substitution rates in mitochondria are approximately 0.5% per million years for avian protein-coding sequences and 1.5% per million years for primate protein-coding and d-loop sequences. Further analyses showed that purifying selection offers the most convincing explanation for the observed relationship between the estimated rate and the depth of the calibration. We rule out the possibility that it is a spurious result arising from sequence errors, and find it unlikely that the apparent decline in rates over time is caused by mutational saturation. Using a rate curve estimated from the d-loop data, several dates for last common ancestors were calculated: modern humans and Neandertals (354 ka; 222-705 ka), Neandertals (108 ka; 70-156 ka), and modern humans (76 ka; 47-110 ka). If the rate curve for a particular taxonomic group can be accurately estimated, it can be a useful tool for correcting divergence date estimates by taking the rate decay into account. Our results show that it is invalid to extrapolate molecular rates of change across different evolutionary timescales, which has important consequences for studies of populations, domestication, conservation genetics, and human evolution.

Animals↗
PubMed2007

Understanding the recent evolution of the human genome: insights from human-chimpanzee genome comparisons.

The sequencing of the chimpanzee genome and the comparison with its human counterpart have begun to reveal the spectrum of genetic changes that has accompanied human evolution. In addition to gross karyotypic rearrangements such as the fusion that formed human chromosome 2 and the human-specific pericentric inversions of chromosomes 1 and 18, there is considerable submicroscopic structural variation involving deletions, duplications, and inversions. Lineage-specific segmental duplications, detected by array comparative genomic hybridization and direct sequence comparison, have made a very significant contribution to this structural divergence, which is at least three-fold greater than that due to nucleotide substitutions. Since structural genomic changes may have given rise to irreversible functional differences between the diverging species, their detailed analysis could help to identify the biological processes that have accompanied speciation. To this end, interspecies comparisons have revealed numerous human-specific gains and losses of genes as well as changes in gene expression. The very considerable structural diversity (polymorphism) evident within both lineages has, however, hampered the analysis of the structural divergence between the human and chimpanzee genomes. The concomitant evaluation of genetic divergence and diversity at the nucleotide level has nevertheless served to identify many genes that have evolved under positive selection and may thus have been involved in the development of human lineage-specific traits. Genes that display signs of weak negative selection have also been identified and could represent candidate loci for complex genomic disorders. Here, we review recent progress in comparing the human and chimpanzee genomes and discuss how the differences detected have improved our understanding of the evolution of the human genome.

Animals↗
PubMed1993

The probability of permanence.

Numerical experiments suggest that cooperation is a very rare phenomenon in autocatalytic networks with more than about five interacting species. There is strong evidence that the probability for cooperative behavior in random networks decreases at least exponentially and at most as an2 with the number n of interacting species. The evolution of larger persistent networks by subsequent incorporation of additional species into a cooperative network is shown to be even less probable. This leads to the conclusion that hypercycle-type interactions alone are not sufficient to maintain the genetic information of more than a few interacting species in a pure RNA world.

Ecology↗
PubMed2003

Parallel changes in gene expression after 20,000 generations of evolution in Escherichiacoli.

Twelve populations of Escherichia coli, derived from a common ancestor, evolved in a glucose-limited medium for 20,000 generations. Here we use DNA expression arrays to examine whether gene-expression profiles in two populations evolved in parallel, which would indicate adaptation, and to gain insight into the mechanisms underlying their adaptation. We compared the expression profile of the ancestor to that of clones sampled from both populations after 20,000 generations. The expression of 59 genes had changed significantly in both populations. Remarkably, all 59 were changed in the same direction relative to the ancestor. Many of these genes were members of the cAMP-cAMP receptor protein (CRP) and guanosine tetraphosphate (ppGpp) regulons. Sequencing of several genes controlling the effectors of these regulons found a nonsynonymous mutation in spoT in one population. Moving this mutation into the ancestral background showed that it increased fitness and produced many of the expression changes manifest after 20,000 generations. The same mutation had no effect on fitness when introduced into the other evolved population, indicating that a mutation of similar effect was present already. Our study demonstrates the utility of expression arrays for addressing evolutionary issues including the quantitative measurement of parallel evolution in independent lineages and the identification of beneficial mutations.

Biological Evolution↗
PubMed2006

The evolution of adaptive immune systems.

A clonally diverse anticipatory repertoire in which each lymphocyte bears a unique antigen receptor is the central feature of the adaptive immune system that evolved in our vertebrate ancestors. The survival advantage gained through adding this type of adaptive immune system to a pre-existing innate immune system led to the evolution of alternative ways for lymphocytes to generate diverse antigen receptors for use in recognizing and repelling pathogen invaders. All jawed vertebrates assemble their antigen-receptor genes through recombinatorial rearrangement of different immunoglobulin or T cell receptor gene segments. The surviving jawless vertebrates, lampreys and hagfish, instead solved the receptor diversification problem by the recombinatorial assembly of leucine-rich-repeat genetic modules to encode variable lymphocyte receptors. The convergent evolution of these remarkably different adaptive immune systems involved innovative genetic modification of innate-immune-system components.

Animals↗
PubMed1989

Cytosine methylation and the fate of CpG dinucleotides in vertebrate genomes.

The dinucleotide CpG is a "hotspot" for mutation in the human genome as a result of (1) the modification of the 5' cytosine by cellular DNA methyltransferases and (2) the consequent high frequency of spontaneous deamination of 5-methyl cytosine (5mC) to thymidine. DNA methylation thus contributes significantly, albeit indirectly, to the incidence of human genetic disease. We have attempted to estimate for the first time the in vivo rate of deamination of 5mC from the measured rate of 5mC deamination in vitro and the known error frequency of the cellular G/T mismatch-repair system. The accuracy and utility of this estimate (md) was then assessed by comparison with clinical data, and an improved estimate of md (1.66 X 10(-16) s-1) was derived. Comparison of the CpG mutation rates exhibited by globin gene and pseudogene sequences from human, chimpanzee and macaque provided further estimates of md, all of which were consistent with the first. Use of this value in a mathematical model then permitted the estimation of the length of time required to produce the level of "CpG suppression" currently found in the "bulk DNA" of vertebrate genomes. This time span, approximately 450 million years, corresponds closely to the estimated time since the emergence and adaptive radiation of the vertebrates and thus coincides with the probable advent of heavily methylated genomes. An accurate estimate of the 5mC deamination rate is important not only for clinical medicine but also for studies of gene evolution. Our data suggest both that patterns of vertebrate gene methylation may be comparatively stable over relatively long periods of evolutionary time, and that the rate of CpG deamination can, under certain limited conditions, serve as a "molecular clock".

Animals↗
PubMed1992

The future for healthcare capital investments.

Hospitals have entered into a new era of capital planning. A number of factors will influence hospital buying behavior now that the Medicare capital regulations are being implemented. As purchasing responsibility for additional departments is continually folded into hospitals' central purchasing function there will be increased opportunities for group contracts. As resources shrink and demand for services increases, GPOs will be relied upon for their expertise and financial finesse. The emphasis will be on boosting the use of group contracts among existing members, rather then seeking additional members in a shrinking hospital market. Through effective purchasing, it is generally recognized that a hospital can recover and keep, at best, 5-10 percent of the cost of all purchased goods and services. Group purchasing organizations need to develop better strategies of cooperation with vendors, distributors and hospitals to help providers control capital costs. In this challenging environment, GPOs will aggressively target markets other than acute care as the source of their future growth, just as healthcare facilities are branching out. To accommodate changing needs, the strongest GPOs will continue their evolution into structures more like alliances, offering an array of other cooperative and support programs beyond the purchase of goods and services.

Capital Expenditures↗
PubMed1984

Serological and partial molecular characterization of a Thy-1 homolog in tunicates.

The occurrence of a Thy-1 homolog in the tissues of the advanced invertebrate group of tunicates has been investigated by using two monoclonal antibodies specific to rodent Thy-1.1 determinants and a heterologous anti-rat Thy-1 antiserum. In cellular and soluble-phase radioimmunoassays for Thy-1 using intact hemocytes, tissue extracts and hemolymph, membrane-bound and soluble Thy-1.1 cross-reacting determinants have been detected. Immunoprecipitation experiments with hemocyte deoxycholate extracts and hemolymph, labeled with 125I by lactoperoxidase/chloramine T and with NaB3H4 by galactose oxidase, established the association of the Thy-1.1 cross-reacting determinants with a single glycoprotein of apparent m.w. estimated at 27 000 in hemocytes and 22 500 in hemolymph by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The significance of this finding is discussed in relation to the phylogenetic emergence of the Thy-1 molecule during evolution.

Animals↗
PubMed2002

Neuronal differentiation and synapse formation occur in space and time with fractal dimension.

The analysis of a set of experimental data obtained by an independent team of researchers confirms that neuronal differentiation or synapse formation do occur in time and space with fractal dimension. The interacting cells create first a dynamic system with its own attractor, (i.e., a fragment of time and space where the dynamic processes occur and where no further evolution of the system is possible at all owing to the action of the intrasystemic forces unless some extrasystemic forces act upon it). This attractor is then modified in the active manner by the differentiating cells until the system attains a degenerated stationary state and differentiation ends. The fractal structure of the system is also lost in the course of tumor progression. Our data indicate that the cellular system can attain the degenerated stationary state, leaving the attractor with a fractal dimension directly or undergoing diversification into many attractors and going through the areas of deterministic chaos. Since evolution of the cellular system is driven by the cooperative dynamic processes, as reflected by the changes of the mean fractal dimension between the intervals of the Gompertzian curve, it is likely that cells differentiate into neurons and create synapses with a conjugated probability and non-Gaussian distribution rather than with the classical probability and the Gaussian distribution. These findings can help to optimize features of artificial neural networks. They also define a simple in vitro biological model for biophysical and biochemical studies on natural neural networks.

Cell Differentiation↗
PubMed1983

T-lymphocyte and B-lymphocyte dichotomy in anuran amphibians: I. T-lymphocyte proportions, distribution and ontogeny, as measured by E-rosetting, nylon wool adherence, postmetamorphic thymectomy, and non-specific esterase staining.

We used sheep erythrocyte (SRBC) E-rosetting, nylon wool fractionation thymectomy and nonspecific esterase staining to assess T-lymphocyte characteristics in Rana pipiens during various developmental stages. T-lymphocytes appear in the spleens of premetamorphic tadpoles. We found significant levels of lymphocytes classifiable as T-cells in the peripheral blood of adults, but fewer numbers of T-cells in the thymus, jugular bodies, spleen, pronephros, mesonephros, liver and bone marrow. In addition, thymectomized Xenopus laevis showed a sharp decrease in T-cells as evidenced by E-rosetting, ANAE stain and nylon wool fractionation. The presence of T-lymphocytes in anuran amphibians and the existence of a receptor for SRBC on a population of these cells, suggest conservation of T-cells during evolution.

Age Factors↗