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PubMed1991

Evolutionary implications of primate endogenous retroviruses.

Endogenous DNA sequences related to retroviruses are probably present in all primates. By using approaches based on the polymerase chain reaction, two separate studies have revealed the evolutionary history of some of these sequences. In the first study, a retrovirus-like reverse transcriptase (RT) sequence homologous to that of Baboon endogenous virus (BaEV) has been identified in both Old World monkeys and African apes, but not in humans or Asian apes. This RT sequence is highly conserved at the amino acid level, but not the nucleotide level, in the baboon, African green monkey, Java macaque, chimpanzee, and gorilla. The patterns of nucleotide substitution indicate functional conservation and suggest that this RT sequence was present in the primate germline before apes and Old World monkeys diverged about 30 million years ago. In the second study, a comparison of endogenous proviral DNAs and their adjacent sequences has been used to analyze the evolutionary history of three previously reported human endogenous retroviruses, HERV-E(4.14), HERV-R(3), and HERV-Ia. It is shown that these retroviruses have also been resident in the primate line since before the ape-Old World monkey divergence. The implications of the presence of functionally conserved RT genes in the germlines of primates, and the potential for using integration sites as tools for analyzing phylogenetic relationships among primates and their retroviruses, are discussed.

Amino Acid Sequence↗
PubMedDate not supplied

Immune privilege in the eye: an evolutionary adaptation.

The purpose of this study was to determine whether immune privilege exists in the eye of goldfish and to explore from an evolutionary point of view the relationship between the immunological and neurobiological microenvironments in the eye. Neural retinal or scale allografts and autografts were implanted into the vitreous cavity or the anterior chamber of goldfish eyes. Histological examinations were conducted to determine the fate of these grafts. In order to detect donor-specific immune suppression induced by intraocular retinal allografts, scale allografts obtained from the same donors were subsequently implanted orthotopically and evaluated. Neural retinal allografts implanted intraocularly were rapidly rejected by postimplantation day 8. In contrast, neural retinal autografts survived well within the eye with no inflammation. Prior intraocular allografts, either scale or retinal grafts, did not prevent rejection of subsequent scale allografts nor did they induce down-regulation of systemic immunity. Thus, immune privilege does not exist in the goldfish eye, implying that immune privilege in the eye (or central nervous system) may be an evolutionary adaptation acquired by higher vertebrates. Considering that the capacity for neural regeneration in the central nervous system diminishes during evolution, the hypothesis that immune privilege and neural regeneration may be mutually exclusive properties is addressed.

Animals↗
PubMed1995

Evolutionary history of the ligand-gated ion-channel superfamily of receptors.

The fast-acting ligand-gated ion channels (LGICs) constitute a group that encompasses nicotinic ACh, 5-HT3, GABAA and glycine receptors. Undoubtedly, they all share a common evolutionary ancestor, and the group can therefore be considered to be a gene superfamily. Because the members of the superfamily are all receptors, it is reasonable to suppose that their common ancestor must also have been some type of receptor, and because the receptors are made of similar subunits, the ancestor was probably homo-oligomeric. Although we failed to find a group of proteins that are related evolutionarily to this superfamily, the analysis of the evolutionary relationships within the superfamily is possible and can give rise to information about the evolution of the structure and function of present-day receptors and indeed of the nervous system itself.

Animals↗
PubMed1985

Evolutionary conservation of ribosomal protein mRNA sequences: application for expansion of corresponding cDNA and gene libraries.

Cloned cDNAs, containing ribosomal protein sequences from mouse (five cDNAs) or Xenopus laevis (six cDNAs), were used to estimate the evolutionary conservation, from insects to mammals, of the corresponding mRNA sequences. Northern blot analysis reveals a variable degree of homology between these sequences in different eukaryotes. Thus, among the ribosomal protein cDNA clones utilized, some exhibit complete, others partial, and a few no interphyla cross-hybridization. Melting profile analysis was employed to quantitate this homology. It is proposed that for expansion of eukaryotic ribosomal cDNA and gene libraries, one can exploit the interspecies homology of the corresponding sequences. However, the diverse evolutionary conservation of individual ribosomal protein gene sequences should be taken into account.

Animals↗
PubMed1989

Evolutionary immunobiology.

Identifying the evolutionary origin of inducible, specific immune recognition represents a major objective in developmental immunology. In order to address this issue from an overall phylogenetic perspective, major studies of cellular and humoral immune function are being undertaken using lower vertebrate and invertebrate models. Here, C. Reinisch and G. Litman discuss the application of new technologies, particularly molecular genetic approaches, that is providing important new insights into the genetic mechanisms that have influenced the evolutionary diversification of immunological function.

Animals↗
PubMed1990

Evolutionary implications of a new bypass activation pathway of the complement system.

The classical pathway of complement activation is a highly specific and amplifiable effector system responding to recognition of foreign antigens by antibody. It comprises a group of well characterized proteins in mammalian plasma. There are many similarities with the alternative pathway of complement activation, which suggests that they have a common evolutionary origin. Both pathways have homologous components, use related activation and regulatory mechanisms, result in the release of the anaphylatoxins C3a and C5a, and deposit C3b onto activating surfaces. This fixed C3b then becomes the focus of further immune reactions, involving either the lytic complement components or C3b receptors on effector cells. Phylogenetic data indicate that the alternative pathway is the older, and that the classical pathway evolved from it. Here Timothy Farries and colleagues review this evolutionary process and present a possible sequence of events that is suggested by recent functional data from their laboratory.

Animals↗
PubMed1993

A silent mutation in HLA-DPB1*0101 and its evolutionary implications.

A novel HLA-DPB1 allele (DPB1*/A6) has been identified in West Africa, and the occurrence of the recently reported allele DPB1*4001 (DPB1*BRI-5) in Negroid populations has been confirmed DPB1*WA6 differs from DPB1*0101 by a silent nucleotide exchange at codon position 43 only. It constitutes, thereby, a link to DPB1*1101, *1501, and *2601 and suggests and evolutionary relationship with these alleles. Carrying the same silent mutation, DPB1*1101, *1501, and *2601 may, by recombinations, have evolved from DPB1*WA6. An apparently older evolutionary branch arose directly from DPB1*0101 and comprises the closely related alleles DPB1*2701 and DPB1*4001 reported only from individuals of African descent.

Alleles↗
PubMed1987

A computer model of evolutionary optimization.

Molecular evolution is viewed as a typical combinatorial optimization problem. We analyse a chemical reaction model which considers RNA replication including correct copying and point mutations together with hydrolytic degradation and the dilution flux of a flow reactor. The corresponding stochastic reaction network is implemented on a computer in order to investigate some basic features of evolutionary optimization dynamics. Characteristic features of real molecular systems are mimicked by folding binary sequences into unknotted two-dimensional structures. Selective values are derived from these molecular 'phenotypes' by an evaluation procedure which assigns numerical values to different elements of the secondary structure. The fitness function obtained thereby contains nontrivial long-range interactions which are typical for real systems. The fitness landscape also reveals quite involved and bizarre local topologies which we consider also representative of polynucleotide replication in actually occurring systems. Optimization operates on an ensemble of sequences via mutation and natural selection. The strategy observed in the simulation experiments is fairly general and resembles closely a heuristic widely applied in operations research areas. Despite the relative smallness of the system--we study 2000 molecules of chain length v = 70 in a typical simulation experiment--features typical for the evolution of real populations are observed as there are error thresholds for replication, evolutionary steps and quasistationary sequence distributions. The relative importance of selectively neutral or almost neutral variants is discussed quantitatively. Four characteristic ensemble properties, entropy of the distribution, ensemble correlation, mean Hamming distance and diversity of the population, are computed and checked for their sensitivity in recording major optimization events during the simulation.

Base Sequence↗
PubMed1981

Ernst Haeckel's concept of an evolutionary origin of life.

In 1865/66 E. Haeckel for the first time suggested an evolutionary sequence in order to explain the origin of the first living cell. Haeckel's concept is compared with modern theories of the origin of life. It is evident that Haeckel has not as yet received the credit that he deserves for his evolutionary concept.

Biological Evolution↗
PubMed1986

Phenylalanyl-tRNA synthetases as an example for comparative and evolutionary aspects of aminoacyl-tRNA synthetases.

Aminoacyl-tRNA synthetases are indispensable components of protein synthesis in all three lines of evolutionary descent, eubacteria, archaebacteria and eukaryotes. Furthermore they are also present in the translational apparatus of the semi-autonomous organelles, mitochondria and chloroplasts, of the eukaryotic cell. Therefore aminoacyl-tRNA synthetases are appropriate objects for comparative molecular biology in order to obtain a comprehensive picture of the evolution of the translational process. The analysis of the phenylalanyl-tRNA synthetase in a large variety of organisms and organelles in this respect is the most advanced. In addition to comparison of quaternary structure, analysis includes functional aspects of accuracy mechanisms (proofreading) and comparison of structural features by means of substrate analogs. Evolutionary relationships are furthermore elucidated using the immunological approach and heterologous aminoacylation.

Amino Acyl-tRNA Synthetases↗
PubMed1989

Evolutionary learning and hierarchical Markov systems.

The observation is made that various forms of evolutionary learning systems and classical evolutionary processes can be formally described as hierarchical systems of Markov processes. This leads to a simplification of issues such as convergence criteria and limiting behavior of such systems. The hierarchical structures in question are derived from the notion of rules and meta-rules for moving on graphs studied previously.

Biological Evolution↗
PubMed1992

The uncertainty principle as an evolutionary engine.

Heisenberg's uncertainty principle in quantum mechanics underlies the genesis of evolutionary variability. When the uncertainty principle is coupled with the incontrovertible principle of the conservation of energy and material resources, there appears an uncertainty relationship between local fluctuations in the quantities to be conserved on a global scale and the rate of their local variation. Since the local fluctuations are accompanied by the non-vanishing rate of variation because of the uncertainty relationship, they generate subsequent fluctuations. Generativity latent in the uncertainty relationship is non-random and ubiquitous all through various evolutionary stages from abiotic synthesis of monomers and polymers up to the emergence of behavior-induced variability of organisms.

Amino Acid Sequence↗
PubMed1985

Climacteric in women: an evolutionary defect?

This is a theoretical paper. Climacteric in women has two basic consequences: (i) Sterility, which is interpreted here as a positive feature, because it protects the older woman from the hardships of pregnancy. (ii) Hormonal deficiency, which is interpreted here as a negative feature, because it leads to deleterious changes in various parts of the body. Can these negative features be regarded as evolutionary defects? The answer is no, if the following points are considered. Through human innovations, women's natural lifespan of less than 30 years has been extended to almost 80 years. Had the lifespan not been manipulated, most women would not reach climacteric, which normally does not begin before the fourth decade of life. When interpreting climacteric as a phenomenon precipitated by man rather then by Nature, it follows that the negative features of climacteric should not be regarded as evolutionary defects.

Adult↗
PubMed1995

Evidence for an evolutionary relationship among type-II restriction endonucleases.

Type-II restriction-modification (R-M) systems comprise two enzymes, a DNA methyltransferase (MTase) and a restriction endonuclease (ENase), each of which specifically interact with the same 4-8 bp sequence. All type-II MTases share several amino acid (aa) sequence motifs, which makes an evolutionary relatedness among these enzymes probable. The type-II ENases, in contrast, except for some homologous isoschizomers, do not share significant aa sequence similarity. Therefore, ENases in general have been considered unrelated. Here we show that in addition to the analysis of the genotype (aa sequence), a comparison of the phenotype (recognition sequence) of these enzymes can provide independent information regarding evolutionary relationships, and thereby, help to analyze the significance of weak aa sequence similarities. Multistep Monte-Carlo analyses were employed to demonstrate that the recognition sequences of those ENases, which were found to be related by a progressive multiple aa sequence alignment, are more similar to each other than would be expected by chance. This analysis supports the notion that not only type-II MTases, but also type-II ENases did not arise independently in evolution, but rather evolved from one or a few primordial DNA-modifying and DNA-cleaving enzymes, respectively.

Amino Acid Sequence↗
PubMedDate not supplied

Systematic anatomy of Erythroxylum P. Browne: practical and evolutionary implications for the cultivated cocas.

Preliminary study of the pantropical Erythroxylaceae indicates that anatomical features can provide valuable insight into the generic, infra-generic and specific affinities of unidentified specimens. Combinations of qualitative and quantitative anatomical data are most reliable when considered in conjunction with relevant ecological and plant morphological data. Extreme caution is advised in such taxonomic applications due to the intergrading patterns of anatomical variation exhibited within the family. Careful consideration must be given to the potential influence on anatomy of factors such as plant age, habit, leaf morphology and environmental conditions. Although a few species of Erythroxylum are identifiable solely on the basis of unique wood anatomical features, the majority of species can be identified only through a combination of morphological and vegetative anatomical features. Closely related species and species of similar habitats are often very similar in their wood and leaf structure. Anatomical differences are more subtle among the cultivated cocas and their closest neotropical relatives than among most taxa of Erythroxylaceae. A typological concept of foliar venation patterns among the cultivated cocas permits the varietal identification of isolated coca leaves. Several neotropical relatives of the cultivated cocas represent potential adulterants in commercial samples of coca leaf as a result of their striking similarity to genuine coca in leaf form, venation and anatomy. Due to the broad and overlapping range of leaf structural variation exhibited among the cultivated cocas and their nearest relatives, identifications of isolated leaves or leaf fragments are ill-advised in the absence of relevant ecological data. Patterns of wood and leaf anatomical variation within the Erythroxylaceae are most readily explicable as the result of evolutionary diversification in plant habit, leaf size, form and relative duration. Significant correlations among wood and leaf structure reveal various "adaptive strategies" among species of Erythroxylaceae. Redundant patterns of structural evolution, evident among the different species and genera of Erythroxylaceae, help to elucidate the probable evolutionary origins of the cultivated cocas. Comparative anatomical data support the hypothesis that Bolivian coca (E. coca) represents the most primitive of the cultivated cocas. The Colombian and Trujillo varieties of coca (E. novogranatense) appear to have been derived from a Bolivian-like ancestral coca as a result of long-term cultivation, geographic isolation and human selection for increased flavor, palatability and drought resistance.

Coca↗
PubMed1988

Life table tests of evolutionary theories of senescence.

The phenomenon of senescence requires both evolutionary and proximate explanations. The most widely accepted evolutionary explanation for senescence is that it never gets exposed to natural selection because environmental hazards kill all individuals before the age at which senescence causes decreased fitness. If this explanation is sufficient, wild populations should not demonstrate senescence, and their mortality rates should therefore remain constant during adult life, except when environmental causes of mortality have recently decreased. The alternative explanation for the persistence of the genes that cause senescence is that they have been selected for because they have pleiotropic effects that are beneficial early in life when the force of selection is strongest. Where this is the case, mortality rates should increase with age in wild populations. A method is described for using life table data to calculate an estimate of the intensity of selection acting on senescence in wild populations. This method is applied to a variety of life tables. The results suggest that pleiotropic genes may be important causes of senescence in some populations, but not in others. This has implications for research on the proximate mechanisms of senescence.

Aging↗
PubMed1988

Evolutionary origin of cardiac malformations.

The author has proposed in previous publications that isolated cardiac malformations have an evolutionary origin. This is partly supported by the fact that isolated cardiac malformations found in humans occur also in other placental mammals as well as in birds. External gross examination of the heart in just over 5,000 birds was carried out during a 3 year period. Anomalies included one instance of duplicate hearts, two specimens in which no heart could be identified and in a fourth, a yellow-rumped warbler, the heart lay in the neck outside of the thoracic cavity. Published reports of similar occurrences of an ectopically placed heart concern birds, cattle and humans. The fact that various species of both placental mammals and birds show evidence of heritability for heart defects, and that these species cannot interbreed, combined with the fact that birds and mammals have many similar malformations, points to either a common external causative factor or a common origin. Genes that code the malformed heart must be transmitted with that part of the genetic makeup common to all birds and mammals. Malformations caused by teratogens produce widespread organ injury to a potentially normal embryo whereas the evolutionary malformation is an organ-specific anomaly in an otherwise normal mammal or bird and occurs in widely separated species. The implications of this theory are important for parents of children with an isolated congenital heart defect who may have ingested one or another drug or chemical or have been exposed to toxins or infectious agents before or after conception of the affected offspring.

Animals↗
PubMed1990

The evolutionary watershed of susceptibility to gonococcal infection.

Gonococci do not cause genital infection in any convenient experimental animal, but all too easily cause genital infection in humans. To determine the 'evolutionary watershed' of gonococcal infections (the point on the evolutionary tree at which susceptibility to gonococcal infection begins) we extended previous studies of the interaction of gonococci with animal oviduct mucosa to include chimpanzees and baboons. Gonococci attached to, damaged, and invaded the oviduct (fallopian tube) mucosa of chimpanzees (which are apes) but not the oviduct mucosa of baboons (which are monkeys). Thus, the pattern of gonococcal infection in chimpanzees was identical to that in humans, whereas the pattern in baboons was like that in other animals. These studies indicate that the point in evolution at which susceptibility to gonococcal infection commences is between baboons and chimpanzees (or between monkeys and apes). Susceptibility to gonococcal disease appears to require the presence on genital epithelial cells of receptors for gonococcal ligands such as pili, receptors for gonococcal lipopolysaccharide, or both. The physiological role of these receptors may be to interact with more useful, as yet unidentified molecules.

Animals↗