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PubMed1988

Ultrastructure of the spermatozoon of Lepidogalaxias salamandroides and its phylogenetic significance.

The spermatozoon of Lepidogalaxias salamandroides possesses an acrosome (putative), one or two perforatoria (putative) but no nine-triplet centrioles. Two elongated mitochondria (12 micron long) are situated in parallel between the nucleus (20 micron long) and the axoneme (53 micron long). The above features are unique among other teleosts with internal fertilization. The presence of an "acrosome" in this primitive teleost supports the hypothesis that this structure has been secondarily lost in teleosts during evolution. The uncertainty of phylogenetic placement of this fish is reflected by its unique sperm ultrastructure.

Acrosome↗
PubMed2004

Biological space experiments for the simulation of Martian conditions: UV radiation and Martian soil analogues.

The survivability of resistant terrestrial microbes, bacterial spores of Bacillus subtilis, was investigated in the BIOPAN facility of the European Space Agency onboard of Russian Earth-orbiting FOTON satellites (BIOPAN I -III missions). The spores were exposed to different subsets of the extreme environmental parameters in space (vacuum, extraterrestrial solar UV, shielding by protecting materials like artificial meteorites). The results of the three space experiments confirmed the deleterious effects of extraterrestrial solar UV radiation which, in contrast to the UV radiation reaching the surface of the Earth, also contains the very energy-rich, short wavelength UVB and UVC radiation. Thin layers of clay, rock or meteorite material were shown to be only successful in UV-shielding, if they are in direct contact with the spores. On Mars the UV radiation climate is similar to that of the early Earth before the development of a protective ozone layer in the atmosphere by the appearance of the first aerobic photosynthetic bacteria. The interference of Martian soil components and the intense and nearly unfiltered Martian solar UV radiation with spores of B. subtilis will be tested with a new BIOPAN experiment, MARSTOX. Different types of Mars soil analogues will be used to determine on one hand their potential toxicity alone or in combination with solar UV (phototoxicity) and on the other hand their UV protection capability. Two sets of samples will be placed under different cut-off filters used to simulate the UV radiation climate of Mars and Earth. After exposure in space the survival of and mutation induction in the spores will be analyzed at the DLR, together with parallel samples from the corresponding ground control experiment performed in the laboratory. This experiment will provide new insights into the principal limits of life and its adaptation to environmental extremes on Earth or other planets which and will also have implications for the potential for the evolution and distribution of life.

Bacillus subtilis↗
PubMed1996

Evidence for a double-helical structure for modular polyketide synthases.

Modular polyketide synthases are multienzymes responsible for the biosynthesis of a large number of clinically important natural products. They contain multiple sets, or modules, of enzymatic activities, distributed between a few giant multienzymes and there is one module for every successive cycle of polyketide chain extension. We show here that each multienzyme in a typical modular polyketide synthase forms a (possibly helical) parallel dimer, and that each pair of identical modules interacts closely across the dimer interface. Such an arrangement would allow identical modules to share active sites for chain extension, and thus to function independently of flanking modules, which would have important implications both for mechanisms of evolution of polyketide synthases and for their future genetic engineering.

Amino Acid Sequence↗
PubMed1988

Structure of a full-length cDNA clone for the prepro alpha 2(I) chain of human type I procollagen. Comparison with the chicken gene confirms unusual patterns of gene conservation.

A cDNA clone from a human placental library was found to consist of an essentially full-length cDNA of 4.6 kb for the prepro alpha 2(I) chain of type I procollagen. Nucleotide sequencing of the 5'-end of the cDNA provided a sequence of 1617 nucleotide residues and codons for 539 amino acid residues not previously defined. Comparison of the complete structure of the prepro alpha 2(I) cDNA with previously reported sequences for the chicken pro alpha 2(I) gene indicated that 83% of 1366 total amino acid residues were conserved. In the alpha-chain domain 84% of 1014 amino acid residues were conserved. Also, there was conservation of the previously noted preference for U and C in the third position of codons for glycine, proline and alanine. One major difference between the human and the chicken prepro alpha 2(I) chain was that the human chain contained 21 fewer proline residues, an observation that probably explains why the triple helix of human type I procollagen unfolds at temperatures that are 1-2 degrees C lower. In parallel experiments, sequencing of intron-exon boundaries for nine exons of genomic subclones confirmed and extended previous observations that the pro alpha 2(I) gene, like other genes from fibrillar collagens, has an unusual 54-base pattern of exon sizes that is highly conserved through evolution.

Amino Acid Sequence↗
PubMed2000

Nucleotide bias causes a genomewide bias in the amino acid composition of proteins.

We analyzed the nucleotide contents of several completely sequenced genomes, and we show that nucleotide bias can have a dramatic effect on the amino acid composition of the encoded proteins. By surveying the genes in 21 completely sequenced eubacterial and archaeal genomes, along with the entire Saccharomyces cerevisiae genome and two Plasmodium falciparum chromosomes, we show that biased DNA encodes biased proteins on a genomewide scale. The predicted bias affects virtually all genes within the genome, and it could be clearly seen even when we limited the analysis to sets of homologous gene sequences. Parallel patterns of compositional bias were found within the archaea and the eubacteria. We also found a positive correlation between the degree of amino acid bias and the magnitude of protein sequence divergence. We conclude that mutational bias can have a major effect on the molecular evolution of proteins. These results could have important implications for the interpretation of protein-based molecular phylogenies and for the inference of functional protein adaptation from comparative sequence data.

Amino Acids↗
PubMedDate not supplied

[Autonomic dysfunction in acute inflammatory demyelinating polyneuropathy].

Acute inflammatory demyelinating polyneuropathy (AIDP) is an autoimmune process that is characterized by progressive weakness, mild sensory changes and autonomic dysfunction. It is a rare disorder, afflicting about 1 person in 100,000. Yet, since the decline in the number of polio cases, it represents the most common cause of acute neuromuscular paralysis. AIDP is thought to arise as a result of the production of antibody to bacterial Campylobacter jejuni, sugar-containing surface antigen(s) that, due to molecular mimicry, cross-react with the myelin sheath and the axons of nerve cells. Antibody and/or cell mediated immune reactions are believed to produce degeneration of the nerve or interruption of neurotransmission. Autonomic dysfunction include: transient hypertension or, less often, hypotension, sinus tachycardia, bradycardia, urinary retention who usually improves in parallel with motor and sensory function. Our purpose was to study the disturbances of autonomic function of the patients with acute idiopathic demyelinating polyneuropathy. We had studied 36 patients with AIDP admitted in I-st Clinic of Neurology, Iassy, between 1998 and 2002. Analyzing the evolution of these autonomic disturbances we observed the early onset together with motor symptoms, tachycardia and tachypnea was more persistent and a real vital risk factor.

Adult↗
PubMed1985

[Organization of the Escherichia coli genome].

A review of literature data reveals that for the last years, the molecular biology techniques have been of an increasing use in the study of the Escherichia coli genome, having supplemented the standard genetic mapping. For the proper understanding of the Escherichia coli genome organization, recombinational events occurring in the course of evolution should be considered. The bacterial genome seems to carry traces of both "long-term" evolution, possibly responsible for appearance of the bacterial cell itself, and "current" evolution, consisting mainly of periodic genome entering by new plasmid-originated genes. It is supposed that in the process of stabilization within a genome, every new gene undergoes a stage of the "transgene", that is the gene situated in a transposon on the chromosome. In parallel with integration of new genes into the genome, some genes deleting should also take place. The formation of deletions could occur by unequal crossing over in segments of direct homologous repeats which seem to be ordinarily revealed in the experimental study of the tandem gene duplications.

Chromosome Mapping↗
PubMed1997

Prediction of clinical course in patients with idiopathic erythrocytosis by endogenous erythroid colony assay but not by serum erythropoietin levels.

We studied the in vitro culture growth of bone marrow and blood erythroid progenitors and serum erythropoietin (EPO) levels by radioimmunoassay in 24 patients with idiopathic erythrocytosis (IE). All patients had an increased red blood cell (RBC) mass and lacked a cause of secondary polycythemia, but did not fulfill the diagnostic criteria of polycythemia vera (PV). Marrow and blood cultures were obtained simultaneously; the results of endogenous (EPO-independent) erythroid colony (EEC) growth were parallel in both cultures. EECs were present in five patients, all of them developed PV 3 to 48 months later. The EEC number did not correlate with the time to the progression of PV. In contrast, none of the 19 EEC-negative patients had PV evolution during a median follow-up period of 38 months. Three of the five IE patients in whom EECs formed displayed vascular complications during their clinical course compared with three of 19 patients who did not have EEC. The serum EPO levels were variable: low in five, normal in 14, and high in five patients. Serial measurements of serum EPO levels in three of five patients who had high initial levels showed persistently elevated values; the underlying cause of the increased EPO production could not be defined during a follow-up period of more than 36 months. Of the five patients who subsequently developed PV, two had low serum EPO levels and three had normal values at initial evaluation. Serum EPO levels did not correlate with the occurrence of thrombotic complications. Our results show that serum EPO levels have limited value in determining the underlying cause of IE and cannot predict the clinical course of patients with IE, whereas the assessment of EEC in bone marrow or blood can identify IE patients who will have PV evolution.

Adult↗
PubMed2003

Male-biased transmission of deleterious mutations to the progeny in Arabidopsis thaliana.

The extent and cause of male-biased mutation rates, the higher number of mutations in sperm than in eggs, is currently an active and controversial subject. Recent evidence indicates that this male (sperm) bias not only occurs in animals but also in plants. The higher mutation rate in plant sperm was inferred from rates of evolution of neutral DNA regions, and the results were confined to the mitochondria and chloroplasts of gymnosperms. However, the relative transmission rates of deleterious mutations, which have substantial evolutionary consequences, have rarely been studied. Here, an investigation is described by using the hermaphroditic self-compatible flowering plant Arabidopsis thaliana, in which we artificially increased the rate of mutation in pollen (i.e., sperm donor) and maternal (i.e., egg donor) parents, by using two kinds of UV irradiation in parallel and separate experiments, and assessed the deleterious effects on fitness of the F(2) generation. The results show that more deleterious induced mutations are transmitted to the progeny by a sperm than by an egg. These findings provide the first experimental evidence that more deleterious mutations are inherited from sperm than from an egg in any organism. Possible causes underlying this male bias are discussed.

Arabidopsis↗
PubMed2003

Cell death in the unicellular chlorophyte Dunaliella tertiolecta. A hypothesis on the evolution of apoptosis in higher plants and metazoans.

Apoptosis is essential for normal growth and development of multicellular organisms, including metazoans and higher plants. Although cell death processes have been reported in unicellular organisms, key elements of apoptotic pathways have not been identified. Here, we show that when placed in darkness, the unicellular chlorophyte alga Dunaliella tertiolecta undergoes a form of cell death reminiscent of apoptosis in metazoans. Many morphological criteria of apoptotic cell death were met, including an increase in chromatin margination, degradation of the nucleus, and DNA fragmentation. Biochemical assays of the activities of cell death-associated proteases, caspases, measured using highly specific fluorogenic substrates, increased with time in darkness and paralleled the morphological changes. The caspase-like activities were inhibited by caspase-specific inhibitors. Antibodies raised against mammalian caspases cross-reacted with specific proteins in the alga. The pattern of expression of these immunologically reactive proteins was correlated with the onset of cell death. The occurrence of key components of apoptosis, and particularly a caspase-mediated cell death cascade in a relatively ancient linage of eukaryotic photoautotrophs, argues against current theories that cell death evolved in multicellular organisms. We hypothesize that key elements of cell death pathways were transferred to the nuclear genome of early eukaryotes through ancient viral infections in the Precambrian Ocean before the evolution of multicellular organisms and were subsequently appropriated in both metazoan and higher plant lineages.

Algal Proteins↗
PubMed1997

The interphotoreceptor retinoid binding protein gene in therian mammals: implications for higher level relationships and evidence for loss of function in the marsupial mole.

The subclass Theria of Mammalia includes marsupials (infraclass Metatheria) and placentals (infraclass Eutheria). Within each group, interordinal relationships remain unclear. One limitation of many studies is incomplete ordinal representation. Here, we analyze DNA sequences for part of exon 1 of the interphotoreceptor retinoid binding protein gene, including 10 that are newly reported, for representatives of all therian orders. Among placentals, the most robust clades are Cetartiodactyla, Paenungulata, and an expanded African clade that includes paenungulates, tubulidentates, and macroscelideans. Anagalida, Archonta, Altungulata, Hyracoidea + Perissodactyla, Ungulata, and the "flying primate" hypothesis are rejected by statistical tests. Among marsupials, the most robust clade includes all orders except Didelphimorphia. The phylogenetic placement of the monito del monte and the marsupial mole remains unclear. However, the marsupial mole sequence contains three frameshift indels and numerous stop codons in all three reading frames. Given that the interphotoreceptor retinoid binding protein gene is a single-copy gene that functions in the visual cycle and that the marsupial mole is blind with degenerate eyes, this finding suggests that phenotypic degeneration of the eyes is accompanied by parallel changes at the molecular level as a result of relaxed selective constraints.

Animals↗
PubMed1994

Molecular analysis of archael flagellins: similarity to the type IV pilin-transport superfamily widespread in bacteria.

Ultrastructural, biochemical and genetic evidence has shown that the flagella and flagellin proteins from members of the archaea are distinct from their bacterial counterparts. The most important evidence is the sequence dissimilarity between archael and bacterial flagellins. We report here similarity between archael flagellins and members of the bacterial type IV pilin-transport superfamily. In addition to sequence similarity, the archael flagellins and the type IV pilin-transport superfamily share an unusual signal sequence cleavage site and may have functional parallels. This relationship has important implications for the assembly and biogenesis of archael flagella.

Amino Acid Sequence↗
PubMed2006

Frequency of RNA-RNA interaction in a model of the RNA World.

The RNA World model for prebiotic evolution posits the selection of catalytic/template RNAs from random populations. The mechanisms by which these random populations could be generated de novo are unclear. Non-enzymatic and RNA-catalyzed nucleic acid polymerizations are poorly processive, which means that the resulting short-chain RNA population could contain only limited diversity. Nonreciprocal recombination of smaller RNAs provides an alternative mechanism for the assembly of larger species with concomitantly greater structural diversity; however, the frequency of any specific recombination event in a random RNA population is limited by the low probability of an encounter between any two given molecules. This low probability could be overcome if the molecules capable of productive recombination were redundant, with many nonhomologous but functionally equivalent RNAs being present in a random population. Here we report fluctuation experiments to estimate the redundancy of the set of RNAs in a population of random sequences that are capable of non-Watson-Crick interaction with another RNA. Parallel SELEX experiments showed that at least one in 10(6) random 20-mers binds to the P5.1 stem-loop of Bacillus subtilis RNase P RNA with affinities equal to that of its naturally occurring partner. This high frequency predicts that a single RNA in an RNA World would encounter multiple interacting RNAs within its lifetime, supporting recombination as a plausible mechanism for prebiotic RNA evolution. The large number of equivalent species implies that the selection of any single interacting species in the RNA World would be a contingent event, i.e., one resulting from historical accident.

Bacillus subtilis↗
PubMed1987

Optimization by stimulating molecular evolution.

Based on the analogy between mathematical optimization and molecular evolution and on Eigen's quasi-species model of molecular evolution, an evolutionary algorithm for combinatorial optimization has been developed. This algorithm consists of a versatile variation scheme and an innovative decision rule, the essence of which lies in a radical revision of the conventional philosophy of optimization: A number of configurations of variables with better values, instead of only a single best configuration, are selected as starting points for the next iteration. As a result the search proceeds in parallel along a number of routes and is unlikely to get trapped in local optima. An important innovation of the algorithm is introduction of a constraint to let the starting points always keep a certain distance from each other so that the search is able to cover a larger region of space effectively. The main advantage of the algorithm is that it has more chances to find the global optimum and as many local optima as possible in a single run. This has been demonstrated in preliminary computational experiments.

Algorithms↗
PubMed1977

Immune status of mice tolerant of living cells. III. Presence and evolution of cells cytotoxic to the tolerated strain.

Spleen cells from CBA mice neonatally rendered highly tolerant to A/Jax (keeping a skin graft in perfect shape for more than 1 year and without detectable hemagglutinating or cytotoxic antibodies) contain cells cytotoxic for YAC 222 (A/Jax) in Cr release assay. The degree of the cytotoxicity depends on the age of the mouse, following a curve lower than, but parallel to, the one followed by the cytotoxicity of cells from CBA rendered immune by injecting them with A/Jax cells 1 week previously. The maximum of the cytotoxicity curve is reached during the 9th and 10th weeks. Normal CBA cells themselves are moderately cytotoxic to YAC 222. This "natural" cytotoxicity, significantly less intense and presumably directed against Moloney virus-related determinants, does not follow the same time pattern. The cytotoxic indices from both immune and tolerant cell populations are significantly reduced by CBA and anti-A/Jax immune serum. The tested sera of the tolerant mice did not contain hemagglutinating or in vitro-blocking antibodies in the Cr release assay (only the sera from unsuccessfully treated mice, having rejected their skin grafts, had some degree of blocking activity). However (and in agreement with previous experiments), these sera often contained synergistic hemagglutinins and in vivo enhancing properties of A/Jax tumors (Sal) grafted on CBA recipients.

Age Factors↗
PubMed2001

Development of a kinematic coordination pattern in toddler locomotion: planar covariation.

The purpose of this study is to analyze the coordination patterns of the elevation angles of lower limb segments following the onset of unsupported walking in children and to look for the existence of a planar covariation rule as previously described in adult human locomotion. The kinematic patterns of locomotion were recorded in 21 children (11-144 months of age) and 19 adults. In 4 children we monitored the very first unsupported steps. The extent to which the covariation of thigh, shank, and foot angles was constrained on a plane in 3D space was assessed by means of orthogonal regression and statistically quantified by means of principal component analysis. The orientation of the covariation plane of the children was compared with the mean value of the adults' plane. Trunk stability with respect to the vertical was assessed in both the frontal (roll) and sagittal (pitch) planes. The evolution with walking experience of the plane orientation and trunk oscillations demonstrated biexponential profiles with a relatively fast time constant (< 6 months after the onset of unsupported locomotion) followed by a much slower progression toward adult values. The initial fast changes of these walking parameters did not parallel the slow, monotonic maturation of anthropometric parameters. The early emergence of the covariation plane orientation and its correlation with trunk vertical stability reflect the dynamic integration of postural equilibrium and forward propulsion in a gravity-centered frame. The results support the view that the planar covariation reflects a coordinated, centrally controlled behavior, in addition to biomechanical constraints. The refinement of the planar covariation while morphological variables drastically change as the child grows implies a continuous update of the neural command.

Aging↗
PubMed2005

Restriction-refeeding of calories and protein induces changes to slow wave and paradoxical sleep that parallel changes in body lipid and protein levels in rats.

Recent data have suggested that the activity of various brain nuclei is modulated during sleep. In this context, we developed the idea that sleep may participate in adapting brain responsiveness to feeding, so as to tune the control of peripheral energy metabolism. In order to characterize the nature of a possible link between sleep and peripheral energy metabolism, we have investigated the relationship between sleep parameters [wakefulness (W), slow wave sleep (SWS), paradoxical sleep (PS)] and the intensity of peripheral lipid and protein deposition processes. To achieve this, by manipulating the amount and quality of food available to rats, we induced states of energy or protein depletion/repletion which would specifically affect lean or fat body mass, which was quantified by an analysis of body composition. In parallel, using a permanently implanted cortical electrode, we measured electroencephalogram signals (EEG) to quantify the time spent in W, SWS and PS. Analysis of EEG changes in relation to the changes induced in body composition, showed that (1) the amount of sleep (PS and SWS) followed the evolution of energy supply levels, and (2) the time spent in PS relative to SWS varied to a considerable degree (14-23.5%) and followed the same trend as the ratio of lean body mass to fat mass. These results suggest the possible existence of quantitative and qualitative interactions between sleep quality and the anabolic and catabolic processes of peripheral fat and protein deposition.

Adaptation, Physiological↗
PubMed1997

Comparative aspects on nitric oxide in brain and its role as a cerebral vasodilator.

Histological studies have detected nitric oxide (NO) synthase in the central nervous system of all vertebrates examined, from lampreys to mammals. However, there are still very few comparative physiological studies on the function of NO synthase in the brain of non-mammalian vertebrates. So far, we know that acetylcholine can cause an NO-dependent increase in brain blood flow in turtles and some fish species (crucian carp and rainbow trout), whereas some other fishes appear to lack such a mechanism. Hypercapnia can induce NO-dependent cerebral vasodilation in mammals, but such a mechanism appears to be lacking in the ectothermic vertebrates examined. The number of species studied needs to be expanded before we can draw any firm conclusions about the origin of NO-dependent brain blood flow regulation: if it has evolved more than once or if it has been occasionally lost during evolution. We conclude that NO synthase may be present in all vertebrate brains but that its functions can vary, as judged from its role in cerebral blood flow regulation. The diversity of functions that NO has proven to have within the mammalian brain is likely to be paralleled by the same degree of diversity of function between vertebrate groups.

Animals↗