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Results for “Parallel evolution”

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PubMed2004

The evolution of female preferences for multiple indicators of quality.

In a variety of species, females exhibit preferences for multiple male ornaments. Several hypotheses have been proposed to explain this phenomenon. Which, if any, of these hypotheses is the most plausible in general remains largely unresolved based on the available empirical data. Yet theoretical studies conclude that the evolution of preferences for multiple signals of male quality is unlikely, especially when the use of an additional cue in mate choice strongly increases the overall cost of choice. This would imply that most male courtship characters do not reflect the male's genetic quality but instead evolved through Fisherian sexual selection. However, the existing models focus on ornaments that signal overall genetic quality and do not address the possibility that different ornaments provide information about different aspects of quality. Therefore, we develop a model in which the ornaments act as signals for distinct quality components. When the ornaments provide overlapping information about these quality components, we retrieve the results of earlier models. However, when the ornaments provide independent information, preferences for multiple ornaments may evolve, even when exhibiting multiple preferences is costly. We discuss our results in relation to the multiple-message and redundant-signal hypotheses for ornament diversity and identify parallels between Fisherian and good-genes mechanisms for the evolution of multiple ornaments.

Animal Communication↗

PubMedDate not supplied

Morphometric assessment of nucleolar activity in liver cells during the evolutive pathway of chronic hepatitis C to cirrhosis.

Using a computer-assisted image analysis system, we performed a morphometric study of silver-stained nucleoli of hepatocytes in liver biopsy specimens from hepatitis C virus-positive patients with chronic persistent hepatitis (3 cases), chronic active hepatitis (4 cases), and cirrhosis (4 cases). The number and the total area of nucleoli, the average area of each nucleolus and the nuclear area were determined for each of 100 hepatocytes per case. A continuing increase in the area of both nucleoli and nuclei paralleled a progressive decrease in the number of nucleoli during the evolution of chronic hepatitis C to liver cirrhosis. These findings would indicate that the hepatitis C virus-induced liver damage causes reactive changes in surviving hepatocytes resulting in an increased nucleolar biosynthetic activity rather than in an increment of cell proliferation rate. Therefore, the liver response to hepatitis C virus injury seems to be mainly based on a condition of cell "hypertrophy", whereas we previously showed that a process also of compensatory hyperplasia occurs in chronic hepatitis B, possibly resulting from a different pathogenesis of the viral damage.

Cell Nucleolus↗

PubMedDate not supplied

Climate variability and the energetic pathways of evolution: the origin of endothermy in mammals and birds.

Large-scale climate oscillations in earth's history have influenced the directions of evolution, last but not least, through mass extinction events. This analysis tries to identify some unifying forces behind the course of evolution that favored an increase in organismic complexity and performance, paralleled by an increase in energy turnover, and finally led to endothermy. The analysis builds on the recent concept of oxygen-limited thermal tolerance and on the hypothesis that unifying principles exist in the temperature-dependent biochemical design of the eukaryotic cell in animals. The comparison of extant water-breathing and air-breathing animal species from various climates provides a cause-and-effect understanding of the trade-offs and constraints in thermal adaptation and their energetic consequences. It is hypothesized that the high costs of functional adaptation to fluctuating temperatures, especially in the cold (cold eurythermy), cause an increase in energy turnover and, at the same time, mobility and agility. These costs are associated with elevated mitochondrial capacities at minimized levels of activation enthalpies for proton leakage. Cold eurythermy is seen as a precondition for the survival of evolutionary crises elicited by repeated cooling events during extreme climate fluctuations. The costs of cold eurythermy appear as the single most important reason why metazoan evolution led to life forms with high energy turnover. They also explain why dinosaurs were able to live in subpolar climates. Finally, they give insight into the pathways, benefits, and trade-offs involved in the evolution of constant, elevated body temperature maintained by endothermy. Eurythermy, which encompasses cold tolerance, is thus hypothesized to be the "missing link" between ectothermy and endothermy. Body temperatures between 32 degrees and 42 degrees C in mammals and birds then result from trade-offs between the limiting capacities of ventilation and circulation and the evolutionary trend to maximize performance at the warm end of the thermal tolerance window.

Adaptation, Physiological↗

PubMed1997

Evolution of repellent tolerances in representative arthropods.

Eight commercial insect repellents were tested against Ornithodoros parkeri (Acari: Argasidae), Dermacentor variabilis (Acari: Ixodidae), Aedes aegypti (Diptera: Culicidae), and Xenopsylla cheopis (Siphonaptera: Pulicidae). Patterns of tolerance to the test materials were distinctive for each test species. Levels of tolerance were coded as character state 0 (sensitive), 1 (intermediate), or 2 (tolerant) and mapped on a cladogram reflecting the accepted classification of the test species. Character state 0 was regarded as primitive, as indicated by the ontology of repellent tolerances in ticks. Aedes aegypti was least evolved and X. cheopis was most evolved in tolerance to repellents. Multiple parallelism of the arachnid and X. cheopis lines occurred in the evolution of the observed tolerances.

Aedes↗

PubMed2002

Origin of plant glycerol transporters by horizontal gene transfer and functional recruitment.

Gene-family evolution mostly relies on gene duplication coupled with functional diversification of gene products. However, other evolutionary mechanisms may also be important in generating protein diversity. The ubiquitous membrane intrinsic protein (MIP) gene family is an excellent model system to search for such alternative evolutionary mechanisms. MIPs are proteins that transport water, glycerol, and small solutes across cell membranes in all living organisms. We reconstructed the molecular phylogeny of MIPs based on amino acid sequence data by using neighbor-joining, maximum-likelihood, and Bayesian methods of phylogenetic inference. The recovered trees show an early and distinct separation of water and glycerol transporters, i.e., aquaporins (AQPs), and aquaglyceroporins. The latter are absent from plants. As expected, gene duplication and functional diversification account for most of the diversity of animal and plant members of the family. However, in contrast to this model, we find that the sister group of plant glycerol transporters are bacterial AQPs. This relationship suggests first that plant glycerol transporters may resulted from a single event of horizontal gene transfer from bacteria, which we have estimated to have occurred approximately 1,200 million years ago, at the origin of plants, and second that bacterial AQPs were likely recruited to transport glycerol in plants because of their absence of aquaglyceroporins. This striking example of adaptive evolution at the molecular level was demonstrated further by finding convergent or parallel replacements at particular amino acid positions related to water- and glycerol-transporting specificity.

Amino Acid Sequence↗

PubMed1996

The echidna Tachyglossus aculeatus combines REM and non-REM aspects in a single sleep state: implications for the evolution of sleep.

Placental and marsupial mammals exist in three states of consciousness: waking, non-REM sleep, and REM sleep. We now report that the echidna Tachyglossus aculeatus, a representative of the earliest branch of mammalian evolution (the monotremes), does not have the pattern of neuronal activity of either of the sleep states seen in nonmonotreme mammals. Echidna sleep was characterized by increased brainstem unit discharge variability, as in REM sleep. However, the discharge rate decreased and the EEG was synchronized, as in non-REM sleep. Our results suggest that REM and non-REM sleep evolved as a differentiation of a single, phylogenetically older sleep state. We hypothesize that the physiological changes that occur during postnatal sleep development parallel certain aspects of the changes that have occurred during the evolution of sleep-waking states in mammals.

Animals↗

PubMed2006

Casting a genetic light on the evolution of eyes.

Light has been exploited for information by organisms through the evolution of photoreceptors and, ultimately, eyes in animals. Only a handful of eye types exist because the physics of light constrains photodetection. In the past few years, genetic tools have revealed several parallel pathways through which light guides behavior and have provided insights into the convergent evolution of eyes. The gene encoding opsin (the primary phototransduction protein) and some developmental genes had very early origins and were recruited repeatedly during eye evolution. Eye lens proteins arose separately and make up a diverse group, many of which were co-opted from other functions. A major challenge now is understanding how newly discovered pathways for processing light evolved and how they collaborate with eyes to harvest information from light.

Animals↗

PubMed2004

Population and group structure of western lowland gorillas (Gorilla gorilla gorilla) at Lokoué, Republic of Congo.

During a 17-month study at the Lokoué clearing in Odzala National Park, Republic of Congo, we identified 377 western lowland gorillas. This population included 31 solitary males, 37 breeding groups, and eight nonbreeding groups. Its age- and sex-class structure was similar to those observed at two other clearings in the same forest block. However, the size of breeding groups varied with site (either clearing or forest sites). At Lokoué, breeding groups (mean size: 8.2 gorillas; range: 3-15) included a single silverback male and, on average, 3.2 adult females. Nonbreeding groups (mean size: 5.5; range: 2-15) were devoid of adult females. Five of the nonbreeding groups were composed predominantly of blackbacks, subadult males, and juveniles, and thus fit the definition of all-male groups previously observed in mountain gorillas. Our study confirms that 1) one-male breeding groups are the norm in western gorillas, and 2) all-male groups occur in this species. Despite frequent changes in members due to migrations of the males, the persistence of these all-male groups indicates that they may play an important role in the life of migrating males. Variations in population structure, and group composition and type among gorilla populations are discussed. However, a further understanding of the evolution of group-living in gorillas requires detailed ecological studies conducted in parallel with studies of the population structure and dynamics of these groups.

Age Factors↗

PubMed1996

Myocardial markers of injury. Evolution and insights.

Knowledge of the pathophysiology of ischemic heart disease has advanced in parallel with awareness of the significant limitations inherent in clinical assessment. Biochemical assays, long established as the most reliable means of detecting myocardial injury, have improved significantly. Creatine kinase MB, now optimally measured by the newer mass monoclonal antibody assays, and also measurement of the cardiac troponins objectively identify adverse prognosis. Cardiac troponin I appears to have significant advantages over other markers and may become the assay of choice. This is attributable to the confirmation of cardiospecificity claims regarding this marker. These assays permit increased appreciation of the continuous spectrum of ischemic myocardial injury, earlier diagnosis, refinement of the clinical assessment of risk, and evaluation of alternative treatment regimens. Reassessment of the incorporation of biochemical indicators for thrombolytic therapy can be anticipated. This paper integrates the clinical and biochemical literature in reviewing these concepts.

Biomarkers↗

PubMedDate not supplied

[Evolution of serum cholesterol and cholesterol lipoprotein fraction levels in the neonatal period].

A parallel study of serum lipoproteins was carried out in 2 groups of neonates fed either humanized milk (HM) or breast milk (BM): 1. Mean levels at birth were higher than those reported in the literature; this may be due to peripheral venous blood drawings rather than cord-blood. 2. There was a larger increase in total cholesterol (TC) levels in children fed with BM at 10 days of life. 3. The significant correlation (r = 0.55; p less than 0.02) between TC and HDL cholesterol at 10 days in children fed with BM was not found in children fed with HM. These findings suggest 2 questions: 1. Even though it is rich in cholesterol, BM may have a better protective effect against atheroma; from a preventive point of view, is it necessary to check only the daily cholesterol intakes? 2. Since BM is a model for nutritionists, is it justified to reduce the cholesterol level in HM?

Animals↗

PubMed2005

Genome sequence of Blochmannia pennsylvanicus indicates parallel evolutionary trends among bacterial mutualists of insects.

The distinct lifestyle of obligately intracellular bacteria can alter fundamental forces that drive and constrain genome change. In this study, sequencing the 792-kb genome of Blochmannia pennsylvanicus, an obligate endosymbiont of Camponotus pennsylvanicus, enabled us to trace evolutionary changes that occurred in the context of a bacterial-ant association. Comparison to the genome of Blochmannia floridanus reveals differential loss of genes involved in cofactor biosynthesis, the composition and structure of the cell wall and membrane, gene regulation, and DNA replication. However, the two Blochmannia species show complete conservation in the order and strand orientation of shared genes. This finding of extreme stasis in genome architecture, also reported previously for the aphid endosymbiont Buchnera, suggests that genome stability characterizes long-term bacterial mutualists of insects and constrains their evolutionary potential. Genome-wide analyses of protein divergences reveal 10- to 50-fold faster amino acid substitution rates in Blochmannia compared to related bacteria. Despite these varying features of genome evolution, a striking correlation in the relative divergences of proteins indicates parallel functional constraints on gene functions across ecologically distinct bacterial groups. Furthermore, the increased rates of amino acid substitution and gene loss in Blochmannia have occurred in a lineage-specific fashion, which may reflect life history differences of their ant hosts.

Amino Acid Sequence↗

PubMed2005

Virus evolution: fitting lifestyles to a T.

The structure of a double-stranded RNA virus outer shell has revealed unexpected similarities with virions of positive-strand RNA viruses. These similarities intersect with emerging parallels in RNA replication to create intriguing evolutionary possibilities.

Biological Evolution↗

PubMed2005

Observation of magnetic ripple and nanowidth domains in a layered ferromagnet.

We investigated ferromagnetic domain structures on nanometer to micrometer scale for single crystals of a layered ferromagnet, La(2-2x)Sr(1+2x)Mn2O7 (0.32 < or = x < or = 0.40), as functions of x and temperature by means of Lorentz electron microscopy. We have succeeded in observing the evolution of magnetic ripple structure, dynamically, related to a spin reorientation transition where the magnetization direction switches between parallel and perpendicular to the layers. Our high-resolution magnetic domain imaging revealed that the ripple state is characterized by the evolution of magnetic nanowidth domains.

Journal Article↗

PubMed2003

Description and interpretation of adaptive evolution of Escherichia coli K-12 MG1655 by using a genome-scale in silico metabolic model.

Genome-scale in silico metabolic networks of Escherichia coli have been reconstructed. By using a constraint-based in silico model of a reconstructed network, the range of phenotypes exhibited by E. coli under different growth conditions can be computed, and optimal growth phenotypes can be predicted. We hypothesized that the end point of adaptive evolution of E. coli could be accurately described a priori by our in silico model since adaptive evolution should lead to an optimal phenotype. Adaptive evolution of E. coli during prolonged exponential growth was performed with M9 minimal medium supplemented with 2 g of alpha-ketoglutarate per liter, 2 g of lactate per liter, or 2 g of pyruvate per liter at both 30 and 37 degrees C, which produced seven distinct strains. The growth rates, substrate uptake rates, oxygen uptake rates, by-product secretion patterns, and growth rates on alternative substrates were measured for each strain as a function of evolutionary time. Three major conclusions were drawn from the experimental results. First, adaptive evolution leads to a phenotype characterized by maximized growth rates that may not correspond to the highest biomass yield. Second, metabolic phenotypes resulting from adaptive evolution can be described and predicted computationally. Third, adaptive evolution on a single substrate leads to changes in growth characteristics on other substrates that could signify parallel or opposing growth objectives. Together, the results show that genome-scale in silico metabolic models can describe the end point of adaptive evolution a priori and can be used to gain insight into the adaptive evolutionary process for E. coli.

Adaptation, Physiological↗

PubMed2004

Ecological correlates and evolutionary divergence in the skull of turtles: a geometric morphometric assessment.

Resource use and phylogeny are often correlated with morphological variation. Moreover, because biological shapes are often complex and evolve depending on several internal constraints, they must be assessed using integrative methods. We analyzed the morphological variation of the turtle skull in the context of an adaptive radiation. Our focus are turtles of the superfamily Testudinoidea, which are remarkably diverse, both in number of species and in ecology. In this study, we depict morphological variation in the turtle skull in three dimensions with respect to diet, phylogeny, and habitat using modern geometric morphometrics. Our study revealed that morphological specialization was related to both diet and habitat. Morphological variation is decomposed in regard of both resource use (habitat and diet) and phylogeny. Feeding mode depending on environment was suggested as a key factor determining morphological evolution and diversification of turtle skulls. Diet (especially durophagy) leads to parallel morphologies in different clades. Phylogeny seemed to constrain only localized features of the skull and remained of minor influence, because overall morphotypes, closely correlated with ecological factors, occurred in both clades. In conclusion, the adaptive radiation of the Testudinoidea is revealed to demonstrate a clear relationship between the skull shape and life style.

Adaptation, Physiological↗

PubMed2000

Geometric phases for mixed states in interferometry.

We provide a physical prescription based on interferometry for introducing the total phase of a mixed state undergoing unitary evolution, which has been an elusive concept in the past. We define the parallel transport condition that provides a connection form for obtaining the geometric phase for mixed states. The expression for the geometric phase for mixed state reduces to well known formulas in the pure state case when a system undergoes noncyclic and unitary quantum evolution.

Journal Article↗

PubMed1976

Synaptogenesis in the ventromedial hypothalamus of the prenatal mouse.

Mouse embryos from day 13 to day 19 of gestation (E13 through E19) were removed by Caesarean section and their brains were prepared for electron microscopy. Coronal sections were examined in three planes through the ventromedial hypothalamus: anterior, the level at which the optic tracts pass posterolaterally to become partially enclosed in the major brain mass; middle, the level at which the floor of the third ventricle begins to widen and flatten; posterior, the level at which the most anterior infundibulum appears. Three types of junctional complexes were examined. Close junctions are identified as straight, parallel areas of two apposed membranes which appear more electron-dense than immediately adjacent regions. The membranes are separated by a clearly visible cleft. Unlike synapses, no clear synaptic vesicles are found in either of the adjacent profiles unless randomly distributed and accompanied by ribosomes or glycogen. Close junctions are seen most frequently on day E15, then decrease in number through E19. Their participation in synaptogenesis is discussed from temporal, morphological, distributional and quantitative perspectives and is provisionally rejected. Immature synapses show only the minimal membrane specialization found in close junctions, but vesicles are present, ribosomes absent in at least one of the adjacent cytoplasms. Their appearance peaks on E17-E18, paralleling and slightly preceding that of the mature synapses. Their evolution from close junctions has only weak temporal support. Mature synapses display the cytoplasmic densities which immature synapses lack. They attain their greatest prenatal numbers on E18, then decrease in number on E19. The conclusion is advanced that synaptogenesis does--or at least can--occur without the prior appearance of avesicular regions of increased membrane density.

Animals↗

PubMed1989

Histomorphometry of bone marrow biopsies in primary osteomyelofibrosis/-sclerosis (agnogenic myeloid metaplasia)--correlations between clinical and morphological features.

Histomorphometry was performed on representative trephine biopsies of the bone marrow on admission of 50 patients (21 male, 29 female - age 67 years) with so-called primary osteomyelofibrosis/-sclerosis (OMF) not preceded by any other subtype of chronic myeloproliferative disorders. This study was firstly aimed at testing correlations between histological features (amount of haematopoiesis, cytological aspects of megakaryocytes, density of reticulin and collagen fibres and degree of osteosclerosis) and laboratory data, as well as spleen size and duration of relevant prediagnostic symptoms. Secondly, we concentrated on a discrimination of OMF patients into two subgroups according to bone marrow morphology and clinical variables. Statistical evaluation of histomorphometric variables and haematological findings disclosed that there was a progressive fibro-osteosclerotic process in the evolution of disease features. Increase in medullary fibrosis was significantly paralleled by an abnormal or pleomorphic megakaryopoiesis in the bone marrow: there was an increase in irregularity of perimeters for megakaryocytes and naked nuclei combined with smaller sizes of these elements including the nuclei. Additionally, there was a greater number of pycnotic bare nuclei. A number of morphometric features (density of fibres, degree of osteosclerosis, amount of haematopoiesis) were associated with corresponding clinical data (spleen size, length of preclinical history). By consideration of a set of basic histomorphometric variables our cohort of 50 patients could be divided into an early hyperplastic subtype with no or minimal medullary reticulin and another group with conspicuous fibrotic and osteosclerotic alterations of the bone marrow. It was noticeable that we found no significant correlation between amount of haematopoiesis or marrow cellularity with splenomegaly. This result suggests that splenic haematopoiesis (myeloid metaplasia) may represent an autonomous or neoplastic process and not only compensation for a failing fibro-osteosclerotic bone marrow.

Aged↗