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At least 1,531 records · Page 85Linked to original sources
PubMed1992

The involucrin gene of Old-World monkeys and other higher primates: synapomorphies and parallelisms resulting from the same gene-altering mechanism.

The involucrin gene of platyrrhines and hominoids contains a segment of 10-codon repeats which were added vectorially at the same site in the coding region. We have now cloned and sequenced the involucrin gene of four cercopithecoid monkeys--two macaques (mulatta and fascicularis) and two Cercopithecus monkeys (aethiops and hamlyni). Each gene contains a similar segment of short repeats; some of these were added in a common anthropoid lineage, others were added in a common catarrhine lineage, and still others were added in a common macaque or Cercopithecus lineage. Repeats added before a lineage diverges become synapomorphies in the sister taxa resulting from the divergence. Repeats added independently in different diverged lineages become parallelisms. The synapomorphies are the result of the action of a targeted duplication mechanism acting in a common ancestral lineage, but the parallelisms are the result of the same duplication mechanism transmitted to successively divergent sublineages and acting independently in each.

Alleles↗
PubMed2001

Phase separation in a homogeneous shear flow: morphology, growth laws, and dynamic scaling.

We numerically investigate the influence of a homogeneous shear flow on the spinodal decomposition of a binary mixture by solving the Cahn-Hilliard equation in a two-dimensional geometry. Several aspects of this much studied problem are clarified. Our numerical data show unambiguously that, in the shear flow, the domains have on average an elliptic shape. The time evolution of the three parameters describing this ellipse is obtained for a wide range of shear rates. For the lowest shear rates investigated, we find the growth laws for the two principal axis R perpendicular (t) approximately const, R parallel (t) approximately t, while the mean orientation of the domains with respect to the flow is inversely proportional to the strain. This implies that when hydrodynamics is neglected, a shear flow does not stop the domain growth process. We also investigate the possibility of dynamic scaling, and show that only a nontrivial form of scaling holds, as predicted by a recent analytical approach to the case of a nonconserved order parameter. We show that a simple physical argument may account for these results.

Journal Article↗
PubMed2001

Analysis of optical pulse propagation with two-by-two (ABCD) matrices.

We review and extend the analogies between Gaussian pulse propagation and Gaussian beam diffraction. In addition to the well-known parallels between pulse dispersion in optical fiber and cw beam diffraction in free space, we review temporal lenses as a way to describe nonlinearities in the propagation equations, and then introduce further concepts that permit the description of pulse evolution in more complicated systems. These include the temporal equivalent of a spherical dielectric interface, which is used by way of example to derive design parameters used in a recent dispersion-managed soliton transmission experiment. This formalism offers a quick, concise, and powerful approach to analyzing a variety of linear and nonlinear pulse propagation phenomena in optical fibers.

Journal Article↗
PubMed1998

Evolution of chronic nitric oxide inhibition hypertension: relationship to renal function.

We conducted longitudinal measurements of blood pressure and renal function in the conscious, chronically catheterized rat before and during acute nitric oxide synthase inhibition (N-nitro-L-arginine methylester [L-NAME], 37 micromol/kg IV) and then chronic administration of oral L-NAME (approximately 37 micromol/kg per 24 hours). These studies specifically investigate the impact on plasma and renal renin as well as volume status during the evolution of this hypertension in rats not subjected to acute experimental stress. Blood pressure progressively increased with chronic administration of L-NAME and reached values greatly above those seen with acute administration of L-NAME. There were parallel increases in renal vascular resistance and development of proteinuria, and glomerular filtration rate began to decline at day 21, coincident with the appearance of renal damage. Twenty-four-hour urinary nitrite and nitrate excretion remained depressed, reflecting reduced nitric oxide synthesis. The plasma renin activity was variable and only increased transiently at 21 days, thus the angiotensin II dependence of this hypertension is not caused by stimulated plasma renin activity. Despite severe hypertension, sodium intake and excretion were unchanged over the 21 days of L-NAME administration. Plasma volume was significantly reduced at days 2 and 12 of L-NAME administration; thus the prolonged plasma volume contraction must result from the acute natriuretic response to the initial acute L-NAME administration.

Animals↗
PubMedDate not supplied

[Territorial experiment: inter-relational evolution of a group of inmates in the course of an extra-institutional working experiment].

The Authors analize the interrelational evolution of a group of inmates during an outside working activity, with relation to the resocializing experiences which consider the insertion in the area of individuals subjected to detentive security measures. Such evolution, in relation with the influences of the social enviornment one was associated with, was associated with, was marked by an initial cohesion stage between members (of defensive significance), followed by a gradual research of a personal autonomy, in parallel with the acquisition of a reassuring and stabilized role. The utilization of a social space according to the conventional parameters used in the area (with particular concern towards syndical dynamics and rules), reached at the cost of self-exposure, has confirmed the reached maturity and the self balance in proposing themselves to the others as subjects active in their own resocialization, sharing the acquired social rights. Beside the situation concerning the side of the group in its insertion progress, the Authors take into examination the side of the free community in tis receptivity and availability towards the group members, analizing the interactions with the environment as therapeutical moment.

Humans↗
PubMed2001

Boas, Darwin, science, and anthropology.

This paper presents a new reading of Franz Boas's philosophy of science and his approach to the understanding of culture and behavior. It points out that his approach had important parallels with the worldview of the major figures associated with pragmatism and suggests that a similar perspective can be useful today.

Anthropology↗
PubMed1997

[Impairment of color vision in glaucoma].

The paper presents the historical evolution of knowledge about colour vision impairment in glaucoma, to the point where a peculiar type of chromatic disability has been delineated. Unlike other acquired defects, that of glaucoma implies predominantly the tritan axis, has a precocious onset and parallels the functional deficit of cones. Short-wave cones are predominantly affected. It is useful to associate colour vision tests with PEV and perimetry in investigating glaucoma at early stages.

Color Perception Tests↗
PubMed2003

[Radiotherapy at the Grand Duchy of Luxembourg].

The Centre François Baclesse was created as National Radiotherapy Center in 2000. Oncology Radiotherapy has been developed in Luxembourg in parallel with existing medical and surgical oncology departments. Cancer is a Public Health problem in Luxembourg. More than 1800 new cases of cancer are diagnosed every year, out of wich 70 % will need radiotherapy at the time of the evolution of the disease. Technical platform and Human Resources available at this time are able to deliver high quality treatment. The activity reached a plateau in 2002 with almost 800 patients treated per year, whereas the theorical need for radiation oncology treatment is 1200 patients per year in Luxembourg. A large architectural project will add 2 new linear accelerators and will be finished by 2007-2008. Multidisciplinary oncological network has been developed together with cancer treatment units of 6 luxembourgish hospitals. Clinical Research is one of the missions of the Center. After the achievement of its extension, the Centre François Baclesse will be able to cover the need of the Regional, luxembourgish and cross-boarder patients pool, in line with an European approach in treating cancer.

Humans↗
PubMed1987

Cloning and sequence of rat myoadenylate deaminase cDNA. Evidence for tissue-specific and developmental regulation.

Myoadenylate deaminase is the muscle-specific isoform of AMP deaminase (EC 3.5.4.6), an enzyme which plays a special role in energy metabolism in skeletal muscle. A 2.3-kilobase cDNA encoding this enzyme has been cloned from a lambda gt10 library prepared from rat skeletal muscle using oligonucleotide probes designed from AMP deaminase peptide sequences. This cDNA was sequenced, and the amino acid sequence of this isoform of AMP deaminase was deduced. Sequences homologous to this cDNA are identified in the genome of eukaryotes as diverse as yeast and man. Tissue-specific expression of a 2.5-kilobase AMP deaminase transcript is demonstrated, and the abundance of this transcript as well as the 80-kDa adult, muscle-specific peptide of AMP deaminase increase in parallel during postnatal skeletal muscle development. In the adult animal, the abundance of this transcript and AMP deaminase activity are differentially expressed in various skeletal muscle fiber types. We conclude that AMP deaminase sequences have been highly conserved during evolution, and in mammals there is developmental and tissue-specific control of expression of this gene.

AMP Deaminase↗
PubMedDate not supplied

[The nineteenth century roots of the contemporary biological revolution].

The recent publication of the human genomic sequence is the most important progress in biology. It originates from four major watersheds between 1860-1865, namely the biological evolution by Darwin in 1858, the Mendel laws of heredity in 1865, the basis of physiology established by Claude Bernard also in 1865, and the discoveries of microbacteria by Louis Pasteur around 1857. Before 1860, biology did not exist as a science. After 1860, the Darwin's theory progressively became a law after the discovery of the DNA polymorphism and that of the mechanisms of genetic mixing. So far the Mendel's laws were confirmed in parallel with the development of molecular genetics after the discovery of DNA structure and genetic code. The discovery of hormones is one example, amongst several on how integrative physiology applies to Claude Bernard's basis. Finally, based on Pasteur's discovery and Pasteur Institutes, microbiology became a tool for molecular biologists.

Biological Evolution↗
PubMedDate not supplied

Characterization of MADS genes in the gymnosperm Gnetum parvifolium and its implication on the evolution of reproductive organs in seed plants.

Gnetales, one of the extant gymnosperm orders, has traditionally been recognized to be most closely related to flowering plants, because the reproductive organ of Gnetales has some morphological characteristics similar to flowering plants. Most recent molecular phylogenetic studies do not support the sister relationship of the Gnetales and flowering plants, but instead support a close relationship between Gnetales and other extant gymnosperms. The MADS genes are transcription factors, some of which are involved in reproductive organ development in flowering plants. To resolve the discrepancy in phylogenetic inferences, and to provide insights into the evolution of reproductive organs in seed plants, four MADS genes (GpMADS1-4) were cloned from Gnetum parvifolium. GpMADS2 is likely to be a pseudogene and the other three genes were characterized. A MADS gene tree based on partial amino acid sequences showed that GpMADS3 is included in the AGL6 group, but the other two genes do not cluster with any previously reported MADS gene. The three GpMADS genes were expressed during the early stage of ovule development in the differentiating nucellus and three envelopes. A comparison of MADS gene expression among conifers, Gnetum, and flowering plants suggests that the comparable reproductive organs in Gnetum and flowering plants evolved in parallel, and is likely to support the homology between the ovule-ovuliferous scale complex of conifers and the Gnetum ovules, including the three envelopes.

Amino Acid Sequence↗
PubMed2004

A time series of evolution in action: a latitudinal cline in wing size in South American Drosophila subobscura.

Drosophila subobscura is geographically widespread in the Old World. Around the late 1970s, it was accidentally introduced into both South and North America, where it spread rapidly over broad latitudinal ranges. This invading species offers opportunities to study the speed and predictability of trait evolution on a geographic scale. One trait of special interest is body size, which shows a strong and positive latitudinal cline in many Drosophila species, including Old World D. subobscura. Surveys made about a decade after the invasion found no evidence of a size cline in either North or South America. However, a survey made in North America about two decades after the invasion showed that a conspicuous size cline had evolved and (for females) was coincident with that for Old World flies. We have now conducted parallel studies on 10 populations (13 degrees of latitude) of flies, collected in Chile in spring 1999. After rearing flies in the laboratory for several generations, we measured wing sizes and compared geographic patterns (versus latitude or temperature) for flies on all three continents. South American females have now evolved a significant latitudinal size cline that is similar in slope to that of Old World and of North American flies. Rates of evolution (haldanes) for females are among the highest ever measured for quantitative traits. In contrast, the size cline is positive but not significant for South or North American males. At any given latitude, South American flies of both sexes are relatively large; this in part reflects the relatively cool climate of coastal Chile. Interestingly, the sections of the wing that generate the size cline for females differ among all three continents. Thus, although the evolution of overall wing size is predictable on a geographic scale (at least for females), the evolution of size of particular wing components is decidedly not.

Animals↗
PubMed2002

Karyomorphology of Taiwanese Begonia (Begoniaceae): taxonomic implications.

The karyomorphology of all 14 species of Taiwanese Begonia was investigated to elucidate their chromosome features and chromosomal evolution. Among all species investigated, differences in chromosome features are found in: (1) chromosome number 2 n = 22, 26, 36, 38, 52, 60, 64, 82, and (2) frequencies of chromosomes with secondary, tertiary, and/or small constrictions of polyploids, ranging from 23% to 63%, which is higher than the expected value of about 9%. It is suggested that after polyploidization from the diploid species (i.e., 2 n = 22 and frequencies of chromosomes with secondary, tertiary, and/or small constrictions of polyploids of about 9%), chromosome translocations occurred, followed by a decrease in chromosome number, and subsequently stabilized genomes were formed in various species in Taiwan. The karyomorphological evidence also suggested that the chromosome morphology has evolved in parallel in the begonias belonging to different sections in Taiwan. The variation in chromosomal features is more complex than the variation in floral and fruit morphologies. Karyomorphological data also supports the recognition of five new species in Taiwan: Begonia bouffordii, B. chuyunshanensis, B. pinglinensis, B. tengchiana, and B. wutaiana. Based on detailed karyomorphological analyses, the taxonomic implications, speciation, and chromosomal evolution in Taiwanese Begoniaare discussed.

Journal Article↗
PubMed1979

DNA and RNA from uninfected vertebrate cells contain nucleotide sequences related to the putative transforming gene of avian myelocytomatosis virus.

The avian carcinoma virus MC29 (MC29V) contains a sequence of approximately 1,500 nucleotides which may represent a gene responsible for tumorigenesis by MC29V. We present evidence that MC29V has acquired this nucleotide sequence from the DNA of its host. The host sequence which has been incorporated by MC29V is transcribed into RNA in uninfected chicken cells and thus probably encodes a cellular gene. We have prepared radioactive DNA complementary to the putative MC29V transforming gene (cDNA(mc) (29)) and have found that sequences homologous to cDNA(mc) (29) are present in the genomes of several uninfected vertebrate species. The DNA of chicken, the natural host for MC29V, contains at least 90% of the sequences represented by cDNA(mc) (29). DNAs from other animals show significant but decreasing amounts of complementarity to cDNA(mc) (29) in accordance with their evolutionary divergence from chickens; the thermal stabilities of duplexes formed between cDNA(mc) (29) and avian DNAs also reflect phylogenetic divergence. Sequences complementary to cDNA(mc) (29) are transcribed into approximately 10 copies per cell of polyadenylated RNA in uninfected chicken fibroblasts. Thus, the vertebrate homolog of cDNA(mc) (29) may be a gene which has been conserved throughout vertebrate evolution and which served as a progenitor for the putative transforming gene of MC29V. Recent experiments suggest that the putative transforming gene of avian erythroblastosis virus, like that of MC29V, may have arisen by incorporation of a host gene (Stehelin et al., personal communication). These findings for avian erythroblastosis virus and MC29V closely parallel previous results, suggesting a host origin for src (D. H. Spector, B. Baker, H. E. Varmus, and J. M. Bishop, Cell 13:381-386, 1978; D. H. Spector, K. Smith, T. Padgett, P. McCombe, D. Roulland-Dussoix, C. Moscovici, H. E. Varmus, and J. M. Bishop, Cell 13:371-379, 1978; D. H. Spector, H. E. Varmus, and J. M. Bishop, Proc. Natl. Acad. Sci. U.S.A. 75:4102-4106, 1978; D. Stehelin, H. E. Varmus, J. M. Bishop, and P. K. Vogt, Nature [London] 260:170-173, 1976), the gene responsible for tumorigenesis by avian sarcoma virus. Avian sarcoma virus, avian erythroblastosis virus, and MC29V, however, induce distinctly different spectra of tumors within their host. The putative transforming genes of these viruses share no detectable homology, although sequences homologous to all three types of putative transforming genes occur and are highly conserved in the genomes of several vertebrate species. These data suggest that evolution of oncogenic retroviruses has frequently involved a mechanism whereby incorporation and perhaps modification of different host genes provides each virus with the ability to induce its characteristic tumors.

Alpharetrovirus↗
PubMed2005

Germline and somatic diversification of immune recognition elements in Metazoa.

The histories of the immune systems of Metazoa during evolution are envisaged like as many adaptations to the continuous diversification of immune receptors and effectors genes under the pressure of changing environments. A basic diversity of potential immune receptor genes existed in primitive Metazoa. Their subsequent recruitment into immunity, their diversification revolving around the conservation of signaling cascades was paralleled by cell specialization and the introduction of regulatory networks. Polymorphism, duplication and somatic mechanisms of diversification affected independently and still affect different gene families in many phyla, creating a greater variety of immune system exhibiting sometimes little homology but much analogy to one another. Diversity and multiplicity of receptors was generated by duplication and creation of multigene families. Independently in several phyla further diversity is created somatically by alternate splicing, somatic mutation, gene conversion and gene rearrangement. In several instances combinatorial usage of polypeptide chains or genes segments increases the repertoire of the recognition structures. Metazoa had to adapt to the conditions generated by this diversity: the control of expression of multiple genes and the risk of autoimmunity.

Adaptation, Physiological↗
PubMedDate not supplied

Fire fly luciferin as antioxidant and light emitter: the evolution of insect bioluminescence.

Insects are the main group with luminescent species among terrestrial animals. In this paper, we report that fire fly luciferin is endowed with antioxidant properties against oxidative and nitrosative stress. The luciferin reduces linoleate peroxidation in acellular tests and increases the viability of mammalian cells exposed to the oxidant tert-butyl hydroperoxide. Dehydrorhodamine-based tests indicate that fire fly luciferin also scavenges peroxynitrite, whereas parallel tests on cells showed a marked protection of cells subjected to the peroxynitrite generator SIN-1. Together, these results suggest that fire fly luciferin's antioxidant properties could help photocytes coping with the hyperoxidant conditions to which they are submitted during luminous emissions. These data could also suggest that the evolutionary foundation of the bioluminescent system could have been the luciferin, and not the luciferase, first serving as a scavenger of oxidants toxic to the cells, then as a light emitting substrate for luciferase precursors. Similarities with the evolutionary scenario proposed for marine bioluminescent organisms relying on coelenterazine suggest that the surprisingly high success rate observed in the independent emergence of bioluminescent animals could reflect the ease of transformation of antioxidant mechanisms into light-producing systems.

Animals↗
PubMed2006

Conservation and evolution of gene coexpression networks in human and chimpanzee brains.

Comparisons of gene expression between human and non-human primate brains have identified hundreds of differentially expressed genes, yet translating these lists into key functional distinctions between species has proved difficult. Here we provide a more integrated view of human brain evolution by examining the large-scale organization of gene coexpression networks in human and chimpanzee brains. We identify modules of coexpressed genes that correspond to discrete brain regions and quantify their conservation between the species. Module conservation in cerebral cortex is significantly weaker than module conservation in subcortical brain regions, revealing a striking gradient that parallels known evolutionary hierarchies. We introduce a method for identifying species-specific network connections and demonstrate how differential network connectivity can be used to identify key drivers of evolutionary change. By integrating our results with comparative genomic sequence data and estimates of protein sequence divergence rates, we confirm a number of network predictions and validate these findings. Our results provide insights into the molecular bases of primate brain organization and demonstrate the general utility of weighted gene coexpression network analysis.

Animals↗
PubMed1999

Molecular evolution of a tandemly repeated trnF(GAA) gene in the chloroplast genomes of Microseris (Asteraceae) and the use of structural mutations in phylogenetic analyses.

We sequenced the first ca. 900 bp of the 5'-trnL(UAA)-trnV(UAC)/ndhJ region of the chloroplast DNA of different Microseris accessions in order to resolve homoplasious length variation detected in the trnL(UAA)-trnF(GAA) region. We found two to four tandemly repeated trnF genes in the species of Microseris (Asteraceae, Lactuceae) and two in their sister genus Uropappus. Sequences indicated nonhomologous transitions between two, three, and four trnF genes in different Microseris taxa. Independent origins of similar trnF copy numbers were inferred from a chloroplast phylogeny of Microseris. The taxa involved grow on separate continents, supporting parallel origins of similar length variants. The changes in trnF copy numbers were best explained by interchromosomal recombination with unequal crossing over. The 5' copies of the repeats showed the highest sequence conservation, suggesting that these copies are likely to be functional trnF genes, whereas the other ones probably represent pseudogenes. Our results show that length polymorphisms accumulate once a duplicated sequence has become incorporated. Due to parallel gains of similar trnF copy numbers, homoplasious length variation was introduced into the data matrix. The data demonstrate that length polymorphisms cannot be used as indicators for phylogenetic distance unless they can be analyzed at the sequence level.

Base Sequence↗