Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “morphological evolution”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 883 records · Page 49Linked to original sources
PubMed1996

Mitochondrial phylogeography of rock-dwelling cichlid fishes reveals evolutionary influence of historical lake level fluctuations of Lake Tanganyika, Africa.

The East African Lakes Tanganyika, Malawi and Victoria each harbour hundreds of endemic invertebrate and vertebrate species. Inferences about the ecological and evolutionary processes responsible for the origin of these species flocks will only be possible when they are made within historical and comparative frameworks. Specifically, the relative importance of intrinsic characteristics and extrinsic factors may offer information about the processes that drive diversification and speciation in these species. We investigated the sequence variation of a segment of the mitochondrial DNA control region of 32 populations representing all four nominal species in the three genera of eretmodine cichlids from Lake Tanganyika. Based on a phylogenetic analysis of these data we attempted to evaluate the importance of major lake level fluctuations on patterns of intralacustrine speciation. The geography of genetic variation reveals a high degree of within-lake endemism among genetically well-separated lineages distributed along the inferred shore lines of three historically intermittent lake basins. Seismic data indicate that extreme lowering of water levels in the Pleistocene caused the single Lake Tanganyika basin to split into three isolated ones. The strong phylogeographic structure of the Eretmodini, and the observation that some closely related populations occur on opposite shores of the lake, agree with this geological scenario. The three-clade-three-basin phylogeographic pattern was repeated twice within this tribe of cichlids. The phylogeographic pattern of eretmodine cichlids suggests that major fluctuations in the level of the lake have been important in shaping their adaptive radiation and speciation. The mitochondrially defined clades are in conflict with the current taxonomy of the group and suggest that there has been convergent evolution in trophic morphology, particularly in the shapes of oral teeth, taxonomically the most diagnostic characters of the three genera.

Age Factors↗
PubMed2001

Late Jurassic salamanders from northern China.

With ten extant families, salamanders (urodeles) are one of the three major groups of modern amphibians (lissamphibians). Extant salamanders are often used as a model system to assess fundamental issues of developmental, morphological and biogeographical evolution. Unfortunately, our understanding of these issues has been hampered by the paucity of fossil evidence available to assess the early history of the group. Here we report the discovery of an extraordinary sample of salamander fossils, some with rare soft-tissue impressions, from the Upper Jurassic of China. With over 500 articulated specimens, this assemblage documents the morphological diversity of early urodeles and includes larvae and adults of both neotenic and metamorphosed taxa. Phylogenetic analysis confirms that these salamanders are primitive, and reveals that all basal salamander clades have Asian distributions. This is compelling evidence for an Asian origin of Recent salamanders, as well as for an extensive and early radiation of several major lineages. These discoveries show that the evolution of salamanders has involved phylogenetic and ecological diversification around a body plan that has remained fundamentally stable for over 150 million years.

Animals↗
PubMed1986

Trophic molecules and evolution of the nervous system.

Although recent work has reemphasized the general importance of ontogeny in evolution, underlying developmental molecular mechanisms are largely undefined. What heritable ontogenetic mechanisms result in the evolution of new morphologies and functions? Such questions are particularly difficult in the nervous system, in which each of 10(11) neurons forms approximately equal to 10(4) specific interconnections. I propose that specific heritable, trophic interactions during development, which determine cell survival and pathway size, form a substrate for neural evolution. This model is based on the observation that neurons are vastly overproduced during ontogeny; neurons, their pathways and connections are dependent on target-derived trophic factors for developmental survival; and co-innervating, functionally and anatomically distinct neural populations compete for common trophic factors for survival. Focusing on sympathetic and sensory neurons, which require the target-derived, trophic protein nerve growth factor at different times for developmental survival, and which innervate common targets, different classes of ontogenetic evolutionary mechanisms may be characterized. Evolution may occur from heritable changes in the structure of trophic gene products or altered timing of expression. Molecular mechanisms underlying heterochrony are thereby described. The model is directly applicable to evolution of the brain and is testable in a variety of situations.

Biological Evolution↗
PubMed1984

Human leukocyte cyclic AMP and cyclic GMP levels during chemotaxis in delayed type hypersensitivity.

Ten nickel-allergic patients and six healthy control subjects participated in a study of the morphology, kinetics and evolution of the cAMP and cGMP concentrations of migrated leukocytes, using an improved skin chamber technique. Also studied was the effect of nickel exposure in the chamber medium during development of an eczematous reaction in the nickel-allergic patients. Nickel exposure had a specific effect on the morphology, from the 24th hour to the end of the 48 h observation period, with a significant increase in the percentages of basophils, eosinophils and lymphocytes and a decrease of neutrophils. A significantly increased leukocyte migration rate (LMR) was observed from the 27th to 39th hour in six of the allergic patients exposed to nickel. There were no specific permanent changes in cAMP and cGMP concentrations during nickel exposure. The control chambers of the allergic patients and healthy controls had identical leukocyte morphology, LMR and leukocyte concentrations of cAMP and cGMP. However, no correlations were found between LMR, cAMP and cGMP in the eczema patients throughout the observation period.

Adult↗
PubMed1999

Phylogeny of the arachnid order Opiliones (Arthropoda) inferred from a combined approach of complete 18S and partial 28S ribosomal DNA sequences and morphology.

The phylogenetic relationships among the main evolutionary lines of the arachnid order Opiliones were investigated by means of molecular (complete 18S rDNA and the D3 region of the 28S rDNA genes) and morphological data sets. Equally and differentially weighted parsimony analyses of independent and combined data sets provide evidence for the monophyly of the Opiliones. In all the analyses, the internal relationships of the group coincide in the monophyly of the following main groups: Cyphophthalmi, Eupnoi Palpatores, Dyspnoi Palpatores, and Laniatores. The Cyphophthalmi are monophyletic and sister to a clade that includes all the remaining opilionid taxa (=Phalangida). Within the Phalangida the most supported hypothesis suggests that Palpatores are paraphyletic, as follows: (Eupnoi (Dyspnoi + Laniatores)), but the alternative hypothesis (Laniatores (Eupnoi + Dyspnoi)) is more parsimonious in some molecular data analyses. Relationships within the four main clades are also addressed. Evolution of some morphological characters is discussed, and plesiomorphic states of these characters are evaluated using molecular data outgroup polarization. Finally, Martens' hypothesis of opilionid evolution is assessed in relation to our results.

Animals↗
PubMed2005

Insight into the phylogeny of African Clariidae (Teleostei, Siluriformes): implications for their body shape evolution, biogeography, and taxonomy.

The phylogenetic relationships among Clariidae species (Teleostei, Siluriformes) were assessed using 563 nucleotides of the cytochrome b mitochondrial gene. We included 32 Clariidae species representative of seven genera in our analysis. Hetropneustes fossilis (Heteropneustidae) and Clarotes laticeps (Claroteidae) were used as outgroups. The molecular data identified two evolutionary lineages that correspond on one hand to African species and on the other hand to Asian species. Morphological and osteological evolution in Clariidae did not follow an orthogenetic series. Species with robust body, strong ossified head, and large adipose fin were not ancestral ones and eel-like species were not phylogenetically related and represent independent adaptation to life in mud. Adaptation to life in deep water occurred two times independently in lake Tanganyika (with Dinotopterus cunningtoni) and in Lake Malawi (with Bathyclarias species). Molecular dating using a molecular clock of 1% divergence per million years and a comparison with fossils records allowed an estimate of the timing of cladogenesis within the species studied. The Clariidae family originated in Asia 50 MY ago but contemporary African and Asian studied species originated from a common ancestor that was present on the Arabian plate about 15 MY ago. Systematic implications of these results are also discussed.

Africa↗
PubMed1997

[AMEBIOSIS]

This is a short review of the infection and disease caused by Entamoeba histolytica. The morphology of the evolutive stages and the life cycle of the parasite is described, including biochemical and immunological data.The intestinal and extraintestinal forms of this disease are briefly characterized as well as the diagnosis by images and laboratory. Differentiation between E. histolytica and E. dispar (known as nonpathogenic E. histolytica) with similar morphology is crucial for individual or mass treatment.This treatment is dealing with the better known drugs and their recommended dosis. The infection by E. histolytica/E. dispar is widely distributed in Peru with variable rates of prevalence (1 to 28%), according with the applied methodology, and the studied population. Recently, the presence of both amoebas has been confirmed by biochemical characterization, and their real prevalence must be determined. The profilaxis and control of this parasitism is based in avoiding fecalism. Sanitary education, environmental sanitation, and mass treatment of risk groups would be the most important measures against ameblasis.

Journal Article↗
PubMed2000

Differentiation and the polymorphic nature of the Y chromosomes revealed by repetitive sequences in the dioecious plant, Rumex acetosa.

The dioecious plant Rumex acetosa has a multiple sex chromosome system: females are 2n = XX + 12, males are 2n = XY1Y2 + 12, and the two Y chromosomes are heterochromatic. A DNA sequence abounded in the mare genome was isolated and analyzed. The sequence (RAE180) was a 180-bp-long tandemly arranged repetitive sequence, distributed in chromosomes Y1 and Y2, and two pairs of autosomes. Both Y chromosomes contained large amounts of RAE180 and the sequence formed many DAPI bands, while, on the two pairs of autosomes, RAE180 did not form DAPI bands. The internal structure and morphological changes of the Y chromosomes were analyzed by FISH, using RAE180 and the Y-chromosome-specific sequence RAYSI as probes. The pattern of the FISH signals caused by the accumulation of RAE180 and RAYSI suggested the structural change in the Y chromosomes during the process of sex chromosome evolution, and the morphological change in the Y chromosomes was explained by reciprocal translocation and inversion.

Chromosome Inversion↗
PubMed2006

Incompetent great saphenous veins treated with endovenous 1,320-nm laser: results for 71 legs and morphologic evolvement study.

BACKGROUND: Endovenous lasers with various wavelengths have been utilized with good outcomes in treating leg varicose veins. The natural history and evolution of treated veins after endovenous procedures, however, have seldom been addressed. OBJECTIVE: This study determines the efficacy vein ablation and serial venous morphologic evolution of incompetent great saphenous veins (GSVs) after endovenous 1,320-nm laser treatment. METHODS: Fifty patients with symptomatic varicose veins secondary to GSV insufficiency treated with 1,320-nm endovenous laser ablation were enrolled. The treated varicose veins in each limb were mapped and sized before laser treatment. Vein wall diameters were measured with duplex ultrasound at follow-up visits. RESULTS: Seventy-one limbs in 50 patients were enrolled. During the mean 13.1-month follow-up, closure of GSVs was observed in 94% of limbs (67/71). Vein diameters at 3 cm below saphenofemoral junction level were reduced to 81% at 2 days, 75% at 1 month, 48% at 3 months, and 39% at 5 months. Average mean duration for treated GSVs to narrow as fibrotic cords (internal diameter,<2.5 mm) was 5.8 months. CONCLUSION: The endovenous 1,320-nm laser ablation procedures have excellent efficacy in treating incompetent GSVs. This excellent shrinkage behavior may be the basis for nice long-term results of patients treated with 1,320-nm Cooltouch endovenous laser.

Adult↗
PubMed1977

Ultrastructural study of methionine sulfoximine-induced Alzheimer type II astrocytosis.

An ultrastructural study of cerebral cortex was performed in rats during the preictal period following the administration of the convulsant methionine sulfoximine (MSO). The morphologic changes were restricted to astrocytes and consisted of cytoplasmic enlargement, mitochondrial and rough endoplasmic reticulum proliferation, accumulation of glycogen, development of cisternal and saccular smooth endoplasmic reticulum, nuclear chromatin clumping, and hydropic degenerative changes. These findings resemble those seen in experimental ammonia encephalopathy, suggesting an important role of ammonia in the evolution of these morphologic changes. The findings, moreover, suggest that the primary effect of MSO is on astrocytes and that abnormalities in astrocytes may play a role in the development of MSO-induced seizures.

Alzheimer Disease↗
PubMed2006

Phosphorylation and cleavage of presenilin-associated rhomboid-like protein (PARL) promotes changes in mitochondrial morphology.

Remodeling of mitochondria is a dynamic process coordinated by fusion and fission of the inner and outer membranes of the organelle, mediated by a set of conserved proteins. In metazoans, the molecular mechanism behind mitochondrial morphology has been recruited to govern novel functions, such as development, calcium signaling, and apoptosis, which suggests that novel mechanisms should exist to regulate the conserved membrane fusion/fission machinery. Here we show that phosphorylation and cleavage of the vertebrate-specific Pbeta domain of the mammalian presenilin-associated rhomboid-like (PARL) protease can influence mitochondrial morphology. Phosphorylation of three residues embedded in this domain, Ser-65, Thr-69, and Ser-70, impair a cleavage at position Ser(77)-Ala(78) that is required to initiate PARL-induced mitochondrial fragmentation. Our findings reveal that PARL phosphorylation and cleavage impact mitochondrial dynamics, providing a blueprint to study the molecular evolution of mitochondrial morphology.

Amino Acid Sequence↗
PubMed1982

Functional morphology of beta cells in the area centralis of the cat's retina: a model for the evolution of central retinal specializations.

The dendritic morphology of beta cells in and around the area centralis of the retinae of normally pigmented and Siamese cats is described. Individual central beta cells in the Siamese cat do not differ morphologically from central beta cells in normally pigmented cats, and in both groups of animals, there is a clear morphological continuity between central and peripheral beta cells. On the basis of systematic patterns of beta cell dendritic orientation, ther area centralis of the normal cat can be divided into a central region, approximately 200 micrometers in diameter, and a pericentral region, approximately 1,400 micrometers in diameter. In the central region, nearly all beta cells have a single large primary dendrite which descends perpendicular to the plane of inner plexiform layer, and gives rise to a dendritic tree which is vertically aligned with the cell's soma. In the pericentral region, the single primary dendrite of most cells descends obliquely through the inner plexiform layer and gives rise to a dendritic tree which is displaced laterally from the position of the soma. For most of the cells the trajectory of the dendrite is systematically related to the location of the cell relative to the area centralis such that the somas are displaced away from its center, presumably in order to minimize the thickness of the ganglion cell layer in the high acuity region. Many beta cells outside the pericentral region also have oriented single primary dendrites, but their orientation seems fairly random with respect to the location of the area centralis. In the Siamese area centralis, this systematic pattern of beta cell dendritic orientation is markedly reduced, suggesting that the pattern is under genetic control. On the basis of these observations, a model for the evolution of the area centralis and fovea is presented which involves selection for systematic for systematic patterns of dendritic orientation in regions of high ganglion cell density.

Animals↗
PubMed1988

Frequency-dependent selection, metrical characters and molecular evolution.

Computer models of selection acting on a quantitative character show that a combination of frequency-dependent and stabilizing selection can maintain many polymorphisms among the genes that determine the character. The models also show that the random order of mutations can give rise to selectively driven stochastic effects that are sometimes more important than random genetic drift. They suggest simple explanations for patterns of divergence between populations and species, and for apparent discrepancies between the rates of morphological and molecular evolution. They point towards a selective theory of 'molecular clocks'.

Animals↗
PubMedDate not supplied

[Early cirrhosis, an early modality of the evolution of acute hepatitis. The clinico-biological, immunological and morphological aspects].

A group of 12 patients with recent acute hepatitis (8/86 with HVB and 4/22 with alcoholic hepatitis) had a rapid evolution (under 2 years) towards hepatic cirrhosis (early H.C.). The clinical-biological, immunological and morphological study made evident several characteristics, which became predictive markers of the early cirrhotic evolution of acute hepatitis. Clinically, a persistence of dyspeptic disorders and appearance of several systemic manifestations is noticed. Biologically, the maintenance of some increased transmainases, variable bilirubinemia and decrease of serinemia. Immunologically, the transfer of IgM towards increased IgM, the decrease of the total T lymphocyte and of T1 substrate, the increase of the active B and T lymphocyte. The morphologic exploration is decisive for specification of the diagnosis in the early hepatic cirrhosis.

Acute Disease↗
PubMed1989

[Radiographic course of inverted osteochondral graft using the Regnauld technic in the surgical treatment of hallux valgus].

The osteocartilaginous bone graft, conceived by Regnauld for surgical treatment of hallux valgus, is to-day widely known and practised. We have preferably employed the so called "inverted graft", while Regnauld, in his recent monography, defines it less satisfactory than the "cork" or "hat" shaped grafts. Therefore, we have observed the radiological evolution of our inverted grafts, to evaluate the possible differences of their "rootage" in comparison to the cork grafts, studied by Valenti in 1976. Some possible causes of the infrequent failures of this grafting are also examined and discussed. We conclude that the osteocartilaginous graft evolution do not show radiological differences referable to the graft morphology and that unfavourable evolution, when is present, concern at first the articular (cartilaginous) side of the graft, being independent of failed rootage or aseptic necrosis of the bony side.

Bone Transplantation↗
PubMed2005

Flower development and evolution: gene duplication, diversification and redeployment.

Gene duplication and diversification can provide the raw material for the evolution of new morphologies. In plants, the numbers of MADS-box genes have multiplied considerably, resulting in a plethora of these transcriptional regulators in the angiosperms (flowering plants). MADS-box genes have been implicated in the regulation of a variety of flower developmental processes; therefore, understanding the functional consequences of duplication and diversification in this gene family can shed light on the evolution of different floral forms. Recent functional analyses of MADS-box gene lineages have demonstrated that in various instances these genes have swapped roles, acquired novel roles, or retained ancestral roles. These studies underscore the idea that gene function cannot be extrapolated from structural orthology.

Evolution, Molecular↗
PubMed1989

Age-related changes in the density and morphology of plaques and neurofibrillary tangles in Down syndrome brain.

Fifteen cases of Down syndrome between age 25-59 years were examined neuropathologically. A variety of histological methods were used to identify plaques and neurofibrillary tangles (NFT). All cases had some plaques or NFT, but their density was generally not high before the age of 40 years. Plaques and NFT tended to appear at about the same time although in somewhat different cortical areas. Changes appeared first in the dentate gyrus, subiculum, entorhinal and association neocortex. The stages in the evolution of plaque morphology were quantitated in the dentate gyrus. The earliest change was the extracellular accumulation of fibrillar material with the histological characteristics of amyloid. In the second stage there was an exuberant neuritic reaction with swollen processes that contained little or no paired helical filaments (PHF). Stage 1 and 2 plaques were seen predominantly between ages 25-38 years, and were not obviously associated with blood vessels or glial cells. In the third stage of plaque formation neurites appeared to degenerate, contained more PHF, and surrounded a compact core of amyloid. Stage 3 plaques were never very numerous, and were seen only between ages 48-55 years. Stage 4 plaques consisted of a cloud of silver-positive debris. They appeared to be the final stage and were the predominant morphological type in the dentate gyrus after age 48 years. Amyloid angiopathy was present only after age 48, and was a prominent finding in only three cases.

Adult↗
PubMed2002

Evolution of ejaculates: patterns of phenotypic and genotypic variation and condition dependence in sperm competition traits.

Sperm competition is widely recognized as a potent force in evolution, influencing male behavior, morphology, and physiology. Recent game theory analyses have examined how sperm competition can influence the evolution of ejaculate expenditure by males and the morphology of sperm contained within ejaculates. Theoretical analyses rest on the assumption that there is sufficient genetic variance in traits important in sperm competition to allow evolving populations to move to the evolutionarily stable equilibrium. Moreover, patterns of genotypic variation can provide valuable insight into the nature of selection currently acting on traits. However, our knowledge of genetic variance underlying traits important in sperm competition is limited. Here we examine patterns of phenotypic and genotypic variation in four sperm competition traits in the dung beetle Onthophagus taurus. Testis weight, ejaculate volume, and copula duration were found to have high coefficients of additive genetic variation (CV(A)S), which is characteristic of fitness traits and traits subject to sexual selection. Heritabilities were high, and there was some evidence for Y-linked inheritance in testis weight. In contrast, sperm length had a low CV(A), which is characteristic of traits subject to stabilizing selection. Nevertheless, there was little residual variance so that the heritability of sperm length exceeded 1.0. Such a pattern is consistent with Y-linked inheritance in sperm length. Interestingly, we found that testis weight and sperm length were genetically correlated with heritable male condition. This finding holds important implications for potential indirect benefits associated with the evolution of polyandry.

Animals↗