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PubMed1977

Humoral and cellular immune response during the growth of an SV40 induced tumour in hamsters.

Hamster fibroblasts transformed in vivo by the SV40 virus (TSV5Cl2) induce tumours when injected into adult hamsters and antibodies present in sera of tumour-bearing animals are used to demonstrate the presence of the antigens specific for the viral transformation. These tumours are a very useful tool in studying the evolution of the immune response during the tumour growth. A systematic histological examination of the spleen, thymus and lymph nodes was undertaken and the results thus obtained were correlated with a parallel study of the cells of the peritumoral region, the thymus and the spleen by immunofluorescence using antisera of different specificities. We were able to show that the plasma cells which make up the early peritumoral reaction and the lymphoblasts found later in spleen and thymus both synthesize antibodies directed against virus induced antigens. Circulating antibody directed against the same antigens is first detected at/or about the time that the peritumoral plasma cell reaction disappears and increases progressively as tumour weight increases.

Animals↗

PubMed1995

The cold-shock response in bacteria.

The 'cold shock' response that occurs when exponentially growing Escherichia coli at 37 degrees C are transferred to 10 degrees C leads to the cesation of most protein synthesis, however, about 14 'cold shock' proteins continue to be made. These 'cold shock' proteins facilitate growth at low temperatures. Central to the regulation of this switch in gene expression is the 200 fold induction in the relative rate of synthesis of a small cold-shock protein only 70 amino acids in length, known as CS7.4. There is a remarkable conservation through evolution of the primary sequence found in this small cold shock protein and that of a nucleic acid binding domain within the Y-box family of eukaryotic gene regulatory proteins. Parallel studies on CS7.4 and the Y-box proteins have elucidated both molecular mechanisms regulating the cold shock response and a novel site for the regulation of eukaryotic gene expression.

Amino Acid Sequence↗

PubMed2002

The evolution of embryo size in angiosperms and other seed plants: implications for the evolution of seed dormancy.

Seed dormancy plays an important role in germination ecology and seed plant evolution. Morphological seed dormancy is caused by an underdeveloped embryo that must mature prior to germination. It has been suggested that the presence of an underdeveloped embryo is plesiomorphic among seed plants and that parallel directional change in embryo morphology has occurred separately in gymnosperms and in angiosperms. We test these hypotheses using original data on embryo morphology of key basal taxa, a published dataset, and the generalized least squares (GLS) method of ancestral character state reconstruction. Reconstructions for embryo to seed ratio (E:S) using family means for 179 families showed that E:S has increased between the ancestral angiosperm and almost all extant angiosperm taxa. Species in the rosid clade have particularly large embryos relative to the angiosperm ancestor. Results for the gymnosperms show a similar but smaller increase. There were no statistically significant differences in E:S between basal taxa and any derived group due to extremely large standard errors produced by GLS models. However, differences between reconstructed values for the angiosperm ancestor and more highly nested nodes are large and these results are robust to topological and branch-length manipulations. Our analysis supports the idea that the underdeveloped embryo is primitive among seed plants and that there has been a directional change in E:S within both angiosperms and gymnosperms. Our analysis suggests that dormancy enforced by an underdeveloped embryo is plesiomorphic among angiosperms and that nondormancy and other dormancy types probably evolved within the angiosperms. The shift in E:S was likely a heterochronic change, and has important implications for the life history of seed plants.

Biological Evolution↗

PubMed2001

Feather mites (Acari: Astigmata): ecology, behavior, and evolution.

Birds host many lineages of symbiotic mites, but the greatest diversity is shown by the three superfamilies of astigmatan feather mites: Analgoidea, Pterolichoidea, and Freyanoidea. Members of this diphyletic grouping have colonized all parts of the avian integument from their ancestral nidicolous habitat. Whereas some clearly feed on feather pith or skin, acting as parasites, other feather mites are paraphages and consume feather oils without causing structural damage. Sexual dimorphism in feather mites is often extreme, and little is known of the function of many elaborate male structures. Abundance and location of vane-dwelling mites is affected by season, temperature, light, humidity, and host body condition. Because transmission between hosts usually depends on host body contact, it is unsurprising that feather mite phylogeny often parallels host phylogeny; however, recent cladistic analyses have also found evidence of host-jumping and "missing the boat" in several mite lineages.

Adaptation, Physiological↗

PubMed2006

Drosophila flies in "Evolution Canyon" as a model for incipient sympatric speciation.

The genetic basis of population divergence leading to adaptive radiation and speciation is a major unresolved problem of evolutionary biology. Molecular elucidation of "speciation genes" advanced recently, yet it remains without clear identification of the gene complexes participating in reproductive isolation between natural populations, particularly, in sympatry. Genetic divergence was discovered between Drosophila melanogaster populations inhabiting ecologically contrasting, opposite slopes in "Evolution Canyon" (EC), Mt. Carmel, Israel. Interslope migration of flies is easy and verified. Nevertheless, significant interslope D. melanogaster population divergence was established at EC involving habitat choice, mate choice, thermal and drought tolerances, adaptive genes, and mobile elements. Parallel patterns of stress tolerance, habitat choice, and mate choice were demonstrated in Drosophila simulans at EC, although on a smaller scale. However, some tests for interslope genetic differentiation in Drosophila, derived from the opposite EC slopes, gave somewhat controversial results. Here we present new empirical data on interslope genetic divergence of Drosophila at EC, and summarize previous supporting and controversial results. We suggest that Drosophila populations at EC represent a rare example, demonstrating how selection overrides migration, and propose an ad hoc ecological model of incipient sympatric divergence.

Adaptation, Biological↗

PubMed1998

Critical reexamination of palynological characters used to delimit Asclepiadaceae in comparison to the molecular phylogeny obtained from plastid matK sequences.

The family Asclepiadaceae (Dicotyledones) was created by Brown in 1810 by splitting in two the family Apocynaceae of Jussieu established in 1789. The morphological characters used to make this distinction were mainly palynological, such as presence of tetrads or pollinia and number and orientation of pollinia. Those characters, still used in higher taxonomic delimitation (families, subfamilies, and tribes), are here critically reexamined and compared to a molecular phylogeny obtained with one of the more variable plastid genes (matK) of 46 species in the order Gentianales. In this molecular phylogeny, Asclepiadaceae form a monophyletic group derived from within Apocynaceae. Each of the subfamilies of Asclepiadaceae is monophyletic and based on reliable palynological characters, but palynological characters are not useful to delimit tribes of the subfamily Asclepiadoideae. Based on the molecular data, these tribes have undergone parallelisms in several reproductive traits.

Base Sequence↗

PubMed1992

Skilled reaching in rats and humans: evidence for parallel development or homology.

Forelimb reaching by the rat is used as a paradigm for the experimental study of neural control, plasticity, and recovery of function after injury, in the expectation that results are generalizable to humans. The present study was done to compare rat to human reaching movements. The movements of both species were videorecorded and subjected to frame-by-frame analysis using Cartesian (spatial and velocity) and Eshkol-Wachman Movement Notation (EWMN) systems. The component movements of reaching, their sequence and velocity profiles, and their topography were similar in the two species. Both species also displayed more supination and lengthened grasping times when reaching for small as opposed to large objects. Both rats and humans moved the limb medially using the upper arm to aim it when they were required to reach through an aperture but in a free reaching test only rats continued to aim the limb. Human movements were characterized by greater blending of movement components, more variability, and independent digit use. Arguments are presented that the similarities and differences in rat and human reaching are not trivially accounted for by limb and task similarities. The many similarities in the movements of the two species provide evidence for at least parallel development or perhaps even homology.

Adult↗

PubMed2004

Functional divergence of duplicated genes formed by polyploidy during Arabidopsis evolution.

To study the evolutionary effects of polyploidy on plant gene functions, we analyzed functional genomics data for a large number of duplicated gene pairs formed by ancient polyploidy events in Arabidopsis thaliana. Genes retained in duplicate are not distributed evenly among Gene Ontology or Munich Information Center for Protein Sequences functional categories, which indicates a nonrandom process of gene loss. Genes involved in signal transduction and transcription have been preferentially retained, and those involved in DNA repair have been preferentially lost. Although the two members of each gene pair must originally have had identical transcription profiles, less than half of the pairs formed by the most recent polyploidy event still retain significantly correlated profiles. We identified several cases where groups of duplicated gene pairs have diverged in concert, forming two parallel networks, each containing one member of each gene pair. In these cases, the expression of each gene is strongly correlated with the other nonhomologous genes in its network but poorly correlated with its paralog in the other network. We also find that the rate of protein sequence evolution has been significantly asymmetric in >20% of duplicate pairs. Together, these results suggest that functional diversification of the surviving duplicated genes is a major feature of the long-term evolution of polyploids.

Arabidopsis↗

PubMed1990

[Injuries of the upper end of the tibia in children. With the exclusion of fractures of the tibial shaft].

We review 58 cases of proximal tibial fractures in children. Their evolution and prognostic depend on the localisation. The intra epiphyseal fractures have a good prognostic if care is taken in reduction of the great deplacement fractures: as well as the epiphyseal plate fractures. The upper anterior tibial apophysis fractures have been reduced and screwed without any genu recurvatum sequellae. Severe growth disorder may follow proximal tibial contusions without parallelism regarding to them. Among the iatrogenic causes of these contusions, the trans-tibial pine traction may induce a genu recurvatum even far from the tibial tubercle: so we must avoid this method. The proximal metaphyseal tibial fractures and the valgus deformity following them represents a high difficult treatment. This deformity often recurs after osteotomy (with the risks of the operation). Anyway the tibia valga disappears spontaneously. Its evolution shows that it has a double origin: the fracture displacement then the medial overgrowth epiphyseal plate. The first cause can be treatment actually in order to limit the final valgus by closed reduction with anesthesia.

Adolescent↗

PubMed1996

Two genes encode highly similar chloroplastic NADP-malic enzymes in Flaveria. Implications for the evolution of C4 photosynthesis.

To gain an understanding of the molecular events underlying the evolution of C4 photosynthesis, we have undertaken as detailed study of the NADP-malic enzyme gene family in C4 and C3 species of Flaveria. Three genomic clones form the C4 species Flaveria bidentis were characterized and found to encode two highly similar chloroplastic forms of NADP-malic enzyme, termed ME1 and ME2. Genomic southern blotting with gene-specific probes showed that both Me1 and Me2 are found in Flaveria trinervia (C4) and Flaveria pringlei (C3) as well as in F. bidentis. Northern blots demonstrated that Me1 expression in leaves parallels the degree of C4 photosynthesis in seven Flaveria species. Furthermore, whereas Me2 was expressed at a low level in both roots and leaves of F. bidentis, Me1 expression was seen only in leaves and was light-regulated. We discuss these results in the context of the evolution of C4 photosynthesis in Flaveria.

Base Sequence↗

PubMedDate not supplied

[Evolutionary aspects of hair polymorphism].

Polymorphism of hair was considered in terms of their origin in mammalian evolution. Vibrissae significantly differ from hairs by the structure. Apparently, they originated from mechanoreceptors of Cotylosauria and developed only in the Theriodontia-Cynodontia-Panthotheria-Theria lineage (Metatheria, Eutheria). No vibrissa developed in the lineage of Theriodontia-Cynodontia-Prototheria (Multituberculata, Triconodonta, Monotremata), where mechanoreceptors or glandular structures of amphibian ancestors transformed into electro- and mechanoreceptors. Hairs originated in these lineages in parallel from keratin epidermis in correlation with the establishment of homeothermy but independently of vibrissae. Wide and active adaptive radiation provided for a strong differentiation of hairs largely similar in different taxa. Spines originated by heterochrony of hair generations.

Animals↗

PubMed2006

Controlled synthesis of high-quality PbS star-shaped dendrites, multipods, truncated nanocubes, and nanocubes and their shape evolution process.

Well-defined single-crystalline PbS nano- and microstructures including dendrites, multipods, truncated nanocubes, and nanocubes were synthesized in high yield by a simple solution route. Novel star-shaped PbS dendrites with six symmetric arms along the 100 direction, each of which shows one trunk (long axis) and four branches (short axes), have been achieved using Pb(AC)2 and thioacetamide (TAA) as precursors, under the molar ratio Pb(AC)2/TAA = 2/1, at initial reaction temperature 80 degrees C, refluxing for 30 min at 100 degrees C, in the presence of cetyltrimethylammonium bromine (CTAB). The "nanorods" in each branch are parallel to each other in the same plane and are perpendicular to the trunk. The truncated nanocubes mainly bounded by the {100} plane were prepared under a different Pb(AC)2/TAA molar ratio, at initial reaction temperature 40 degrees C, refluxing for 12 h at 100 degrees C. Based on the systematic studies on their shape evolution, a possible growth mechanism of these PbS nano- and microstructures was proposed. The shapes of PbS nanocrystals with face-centered cubic (fcc) structure are mainly determined by the ratio (R) between the growth rates along the (100) and (111) directions. The Pb(AC)2/TAA molar ratio and the initial reaction temperature influence the growth ratio R in the formation of PbS nuclei at an early stage, which results in the final morphology of PbS nanocrystals. Under the current experimental conditions, we can control the PbS shape evolution by simply tuning the molar ratio, the initial reaction temperature, and the period of reaction. Based on the systematic studies on the shape evolution, this approach is expected to be employed for the control-shaped synthesis of other fcc structural semiconductor nanomaterials. The photoluminescence properties were investigated and the prepared nano- and microstructures displayed a very strong luminescence around 600-650 nm at room temperature.

Journal Article↗

PubMedDate not supplied

[Molecular evolution of AdoMet synthetase by DNA recombination with a novel separate-mixing method].

We describe a new approach to in vitro DNA recombination termed Separate-Mixing method in this study. The reaction process of this method consists of two stages: at the first stage the reaction was implemented in two parallel teams, which generated random recombination by template-switching of growing polynucleotides from primers in the presence of unidirectional single-stranded DNA fragments used as templates, and then both teams were mixed together for further extension and recombination of DNA sequences at the second stage. Because of the particular strategy, the reaction process was also accompanied by the other two processes of DNA shuffling and StEP simultaneously. Two AdoMet synthetase genes sam2 from Saccharomyces cerevisiae and metK from Escherichia coli, which have only 56% homology on the DNA level were used for recombination with Separate-Mixing method. DNA recombination was available after a single round of reaction. With sequencing of 10 randomly selected recombinants, no unshuffled parental clone was found, and also no unexpected insertion, deletion or rearrangement was detected. An evolved gene sam' was obtained after screen and selection, which could obviously increase the accumulation of AdoMet in S. cerevisiae.

Directed Molecular Evolution↗

PubMed1990

Hypervariability of intronic simple (gt)n(ga)m repeats in HLA-DRB genes.

We have investigated the extent of DNA variability in intronic simple (gt)n(ga)m repeat sequences and correlated this to sequence polymorphisms in the flanking exon 2 of HLA-DRB genes. The polymerase chain reaction (PCR) was used to amplify a DNA fragment containing exon 2 and the repeat region of intron 2. The PCR products were separated on sequencing gels in order to demonstrate length hypervariability of the (gt)n(ga)m repeats. In a parallel experiment, the PCR products were cloned and sequenced (each exon 2 plus adjacent simple repeats) to characterize the simple repeats in relation to the HLA-DRB sequences. In a panel of 25 DRB1, DRB4, and DRB5 alleles new sequences were not detected. Restriction fragment length polymorphism (RFLP) subtyping of serologically defined haplotypes corresponds to translated DNA sequences in 85% of the cases, the exceptions involving unusual DR/DQ combinations. Many identical DRB1 alleles can be distinguished on the basis of their adjacent simple repeats. We found group-specific organization of the repeats: the DRw52 supergroup repeats differ from those of DRB1*0101, DRB4*0101, and DRB5*0101 alleles and from those of pseudogenes. Finally, we amplified baboon DNA and found a DRB allele with extensive similarity to DRB1 sequences of the DRw52 supergroup. The simple repeat of the baboon gene, however, resembles that of human pseudogenes. In addition to further subtyping, the parallel study of polymorphic protein and hypervariable DNA alleles may allow conclusions to be drawn on the relationships between the DRB genes and perhaps also on the theory of trans-species evolution.

Amino Acid Sequence↗

PubMed1988

Cytoplasmic and mitochondrial arginine kinases in Drosophila: evidence for a single gene.

Mitochondrial and cytoplasmic isozymes of arginine kinase have been identified in Drosophila melanogaster. On the basis of their immunological similarity, parallel dosage responses, and cosegregation of electrophoretic mobility differences, it is concluded that both isozymes are the product of a single gene. The consequences of this in relation to the regulation and evolution of this unusual gene-enzyme system are discussed. It is inferred that the origin of the phosphagen shuttle must predate the divergence of invertebrates and vertebrates.

Animals↗

PubMed1991

Evolution of immunoreactivity of monoclonal antibodies H222 and/or D547 used in the detection of breast cancer estrogen receptors. Varying reactivity of receptor isoforms.

From 1984 to 1990, human breast cancer estrogen receptors have been measured both by a radioligand assay (RLA[3H]estradiol) and by an enzyme immunoassay (Abbott ER-EIA kit). The ratio EIA/RLA results increased continuously from 1.04 (1984) to 1.87 (1990), and this evolution was consistent with the last trial of the E.O.R.T.C. receptor study group (Trial 1989-II, EIA/RLA = 2.5). Dilution studies of cytosols with the current ER-EIA kits showed an important parallelism defect of the standard curve, the final result of cytosols (fmol/mg protein) obtained from the upper part of the curve (between 100 and 500 fmol/ml) being 1.5 to 2 times higher than the results obtained from readings of the lower part of the standard curve (between 0 and 50 fmol/ml). Chromatographic experiments were carried out during 1986 and the measures of binding sites by RLA and of immunoreactive sites by EIA on chromatographic fractions were compared. Identical results were obtained with EIA and RLA, either on polymeric forms of the estrogen receptor, or on monomeric forms obtained after dissociation by 0.4 M KCl. The same experiments performed during 1990 showed that, in the chromatographic fractions, the concentration of immunoreactive sites was twice as large as that of ligand-binding sites, detected by tritiated estradiol. Furthermore, the detection of polymeric and monomeric receptor isoforms by monoclonal antibodies varied, and was increased by the presence of KCl (0.4 M) and/or bovine serum albumin (BSA) (1 mg/ml) in the cytosol. These findings showed that the large differences between enzyme immunoassay and ligand-binding assay results currently observed were due to differential reactivity of monoclonal antibodies for the estrogen receptor standard provided in the ER-EIA kits and for the estrogen receptor present in cytosols from human breast cancers, suggesting modifications of immunoreactivity of the monoclonal antibodies actually provided in the ER-EIA kits.

Antibodies, Monoclonal↗

PubMed2003

Retroids in archaea: phylogeny and lateral origins.

Until recently, none of the diverse elements bearing reverse transcriptase (retroids) have been known from Archaea. However, in the recently published genomes of the acetate-utilizing archaeal methanogens, Methanosarcina acetivorans and M. mazei, several open reading frames (ORFs) are annotated as reverse transcriptase (RT). These annotations led us to the characterization of a retron and 13 retrointrons, including three twintrons, clustered at seven loci of the M. acetivorans genome, and four retrointrons at two loci of the M. mazei genome. Based on a phylogeny of the RT ORFs, we infer four lateral gene transfers (LGT) of these retroids from Bacteria to Archaea and of retrointron mobility within the Archaea genomes. Our phylogenetic analysis also identifies several novel retrons from GenBank in the bacterial groups Firmicutes, Fusobacteria, Cyanobacteria and beta-Proteobacteria, as well as in M. acetivorans. The discovery of retrointrons in Archaea as a consequence of LGT from Bacteria suggests that they did not originate in the progenote and parallels the "mitochondrial seed" theory of the origin of spliceosomes. Extending the known phylogenetic distribution of retroids to Archaea is consistent with the view that they have played a significant role in evolution of genomes throughout the tree of life.

Archaea↗

PubMed1997

Two novel gene orders and the role of light-strand replication in rearrangement of the vertebrate mitochondrial genome.

Two novel mitochondrial gene arrangements are identified in an agamid lizard and a ranid frog. Statistical tests incorporating phylogeny indicate a link between novel vertebrate mitochondrial gene orders and movement of the origin of light-strand replication. A mechanism involving errors in light-strand replication and tandem duplication of genes is proposed for rearrangement of vertebrate mitochondrial genes. A second mechanism involving small direct repeats also is identified. These mechanisms implicate gene order as a reliable phylogenetic character. Shifts in gene order define major lineages without evidence of parallelism or reversal. The loss of the origin of light-strand replication from its typical vertebrate position evolves in parallel and, therefore, is a less reliable phylogenetic character. Gene junctions also evolve in parallel. Sequencing across multigenic regions, in particular transfer RNA genes, should be a major focus of future systematic studies to locate novel gene orders and to provide a better understanding of the evolution of the vertebrate mitochondrial genome.

Amino Acid Sequence↗