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At least 1,333 records · Page 74Linked to original sources
PubMed1986

Progress of bleomycin-induced lung fibrosis in rabbits.

Progression of lung fibrosis induced in rabbits by intratracheal bleomycin (BLM, 10 mg/kg) was monitored by biochemical and morphological measurements. These indicated that the evolution of fibrosis in the rabbit was slower than in other experimental animals. Histology revealed cellular and fibrocellular lesions 4 weeks after BLM. At 8 weeks these lesions still predominated, indicating continuing active disease accompanied by a progression to fibrosis. The gradual progression of the response was reflected in alterations in lung composition. Changes in lung content of collagen, protein and DNA were evident at 8 weeks after BLM, at which time concentration (micrograms/mg dry weight) of collagen and protein were also elevated (P less than 0.05). Plasma angiotensin converting enzyme (ACE), a marker of endothelial injury, decreased 1 week after BLM (P less than 0.01) and then returned to normal, indicating that endothelial injury does not parallel the fibrotic response. In summary, the continuing active inflammation and slow progress of fibrosis induced by i.t. BLM in the rabbit suggests that this model has advantages over others for the serial study of the cellular and biochemical evolution of lung fibrosis.

Animals↗
PubMed1983

Light Stimulation of Ethylene Release from Leaves of Gomphrena globosa L.

The effect of light and CO(2) on both the endogenous and 1-aminocyclopropane-1-carboxylic acid (ACC)-dependent ethylene evolution from metabolically active detached leaves and leaf discs of Gomphrena globosa L. is reported. Treatment with varying concentrations of ACC did not appear to inhibit photosynthesis, respiration, or stomatal behavior. In all treatments, more ethylene was released into a closed flask from ACC-treated tissue, but the pattern of ethylene release with respect to light/dark/CO(2) treatments was the same.Leaf tissue in the light with a source of CO(2) sufficient to maintain photosynthesis always generates 3 to 4 times more ethylene than tissue in the dark. Conversely, the lowest rate of ethylene release occurs when leaf tissue is illuminated and photosynthetic activity depletes the CO(2) to the compensation point. Ethylene release in the dark is also stimulated by CO(2) either added to the flask as bicarbonate or generated by dark respiration. Ethylene release increases dramatically and in parallel with photosynthesis at increasing light intensities in this C(4) plant. Ethylene release appears dependent on CO(2) both in the light and in the dark. Therefore, it is suggested that the important factor regulating the evolution of ethylene gas from leaves of Gomphrena may be CO(2) metabolism rather than light per se.

Journal Article↗
PubMedDate not supplied

[R. Goldschmidt and J. Huxley: creative parallelisms].

The comparative analysis of scientific heritage of Richard Goldschmidt and Julian Huxley shows convincingly the resemblance of these two scientists' views over the core problems of evolutionary theory, genetics and development biology. They both contributed to developing a triad "genetics--development--evolution". The problem of a relative growth of animals was the central point in both Goldschmidt's and Huxley's works. Huxley developed a formula of the allometric growth (law of constant differential growth) while Goldschmidt was the first to draw up the broad interpretation of the consequences of that phenomenon. Both scientists belonged to initiators of development genetics and used the "non-morganian" genetics in their efforts of solving problems of macroevolution. Goldschmidt tended toward an idea of an important role of macromutation in the process of macroevolution, though Huxley adhered to more moderate views. But at the same time the concept of preadaptive mutations proposed by Huxley was close to Goldschmidt's idea of macromutants. It is shown that both scientists analyzed profoundly the changes in early stages of embryogenesis in respect to macroevolution. It is not likely to be reasonable to oppose firmly Goldschmidt's saltationism to the evolutionary synthesis of Huxley. They developed the larger biological problems in a similar way, and undoubtedly their works in the field helped to enrich the development of the views over genetics and evolution. The open-minded analysis of Goldschmidt's and Huxley's concepts leads to creating modern and up-to-date views over the theory of evolution where seemingly incompatible things go together rather well and supplement each other. Evo-Devo rediscovered Goldshmidt's Biology and Huxley's Synthesis.

Animals↗
PubMed1986

Temporal scaling of molecular evolution in primates and other mammals.

Molecular clocks are routinely tested for linearity using a relative rate test and routinely calibrated against the geological time scale using a single or average paleontologically determined time of divergence between living taxa. The relative rate test is a test of parallel rate equality, not a test of rate constancy. Temporal scaling provides a test of rates, where scaling coefficients of 1.0 (isochrony) represent stochastic rate constancy. The fossil record of primates and other mammals is now known in sufficient detail to provide several independent divergence times for major taxonomic groups. Molecular difference should scale negatively or isochronically (scaling coefficients less than 1.0) with divergence time: where two or more divergence times are available, molecular difference appears to scale positively (scaling coefficient greater than 1.0). A minimum of four divergence times are required for adequate statistical power in testing the linear model: scaling is significantly nonlinear and positive in six of 11 published investigations meeting this criterion. All groups studied show some slowdown in rates of molecular change over Cenozoic time. The break from constant or increasing rates during the Mesozoic to decreasing rates during the Cenozoic appears to coincide with extraordinary diversification of placental mammals at the beginning of this era. High rates of selectively neutral molecular change may be concentrated in such discrete events of evolutionary diversification.

Amino Acid Sequence↗
PubMed2005

Ecological context of the evolution of self-pollination in Clarkia xantiana: population size, plant communities, and reproductive assurance.

The repeated evolutionary transition from outcrossing to self-pollination in flowering plants has been suggested to occur because selfing provides reproductive assurance. Reports from biogeographical and ecological surveys indicate that selfing taxa are often associated with stressful and ephemeral environments, situations in which plant abundance is low (e.g., Baker's law) and with novel plant communities, however experimental tests of ecological hypotheses are few. In this study, we examined the ecological context of selection on mating system traits (herkogamy and protandry) in a California annual, Clarkia xantiana, where natural selfing populations differ from outcrossing populations in that they are often of small size or low density and occur mainly outside the range of pollinator-sharing congeners. We constructed artificial populations of plants with broad genetic variation in floral traits and manipulated two ecological factors, plant population size, and the presence versus absence of pollinator-sharing congeners, in the center of the geographic range of outcrossing populations. We found evidence for context-dependent selection on herkogamy and protandry via female fitness in which reduced traits, which promote autonomous selfing, were favored in small populations isolated from congeners whereas selection was comparatively weak in large populations or when congeners were present. In small, isolated populations, the fertility of plants with low herkogamy or protandry was elevated by 66% and 58%, respectively, compared to those with high herkogamy or protandry. The presence of pollinator-sharing congeners augmented bee visitation rates to C. xantiana flowers by 47% for all bees and by 93% for pollen specialists. By facilitating pollinator visitation, congeners mitigated selection on mating system traits in small populations, where outcross mating success is often low (the Allee effect). We also found support for the hypothesis that pollinator availability directly influenced variation in the strength of selection on herkogamy among populations. The striking parallels between our experimental results and patterns of variation in ecological factors across the geographic range of outcrossing and selfing populations suggest that reproductive assurance may play a central role in directing mating system evolution in C. xantiana.

Analysis of Variance↗
PubMed1993

The costs of reproduction and dietary restriction: parallels between insects and mammals.

Dietary restriction increases life span in mammals. This essay connects the dietary restriction response to evolutionary life history theory and experiments related to it. Evolutionary biologists have shown mathematically that aging is an inevitable consequence of age-specific natural selection acting on species with somata separate from germ lines. Empirical tests of this prediction currently point to its general validity. Two specific genetic mechanisms are known which could underlie the evolution of aging under these conditions: age-specificity of gene effects and antagonistic pleiotropy between early and late ages. The antagonistic pleiotropy theory assumes that some genes with beneficial effects on early life fitness will have deleterious effects upon fitness in later life. Experimental work in insects, particularly selection experiments in Drosophila melanogaster, has tested these ideas. The negative genetic correlation between longevity and reproductive effort produced by selection has been shown to be paralleled, in some cases, by environmental manipulation. Thus the increase in life span caused by dietary restriction might be explained as an incidental consequence of lower reproductive effort. This response also could have been an adaptation that enhanced fitness in some species that faced uncertain food supplies, a condition that may have evolved independently in a wide variety of taxa. Several schools of research, besides that of the evolutionary biologists concerned with genetic correlations, have produced corroborations of this hypothesis in insects and mammals: the gerontological work on life span extension, reproductive physiologists concerned with factors that affect fertility, and various life history studies.

Aging↗
PubMed1998

Evolution of satellite DNAs from the genus Palorus--experimental evidence for the "library" hypothesis.

Satellite DNA profiles have been characterized in the congeneric species Palorus ratzeburgii, Palorus subdepressus, Palorus genalis, and Palorus ficicola (Coleoptera, Insecta), each of which contains a single, A + T-rich satellite DNA comprising a considerable portion of the genome (20%-40%). These satellites exhibit insignificant mutual sequence similarity. Using PCR assay, it has been shown that all four sequences are present in each of the tested Palorus species: one of them is amplified into a high copy number or a major satellite, while the three others are in the form of low-copy-number repeats estimated to make up approximately 0.05% of the genome. Each of the four satellites is interspecifically high conserved concerning the sequence, monomer length, and tandem repeat organization. Major, as well as low-copy-number, satellites are colocalized in the regions of pericentromeric heterochromatin on all chromosomes of the complement. The low-copy-number satellites are dispersed between the large arrays of the major satellite over the whole heterochromatic block. Our results explain satellite DNA evolution, confirming the hypothesis that related species share a "library" of conserved satellite sequences, some of which could be amplified into a major satellite. Due to the evolutionary dynamics of satellite DNAs, the content of the "library" is variable; the elimination of some sequences parallels the creation of the new ones. Quantitative changes in satellite DNAs, induced by occasional amplification of satellite repeat from the "library", could possibly occur in the course of the speciation process, thus forming a species-specific profile of satellite DNAs.

Animals↗
PubMedDate not supplied

Network theory of aging.

Evolution theory indicates that investment in mechanisms of somatic maintenance and repair is likely to be limited, suggesting that aging may result from the accumulation of unrepaired somatic defects. An important corollary of this hypothesis is that multiple mechanisms of aging operate in parallel. We describe a recently developed "network theory of aging" that integrates the contributions of defective mitochondria, aberrant proteins, and free radicals in the aging process and that includes the protective effects of antioxidant enzymes and proteolytic scavengers. Possibilities for further extension of the theory and its role in prediction and simulation of experimental results are discussed.

Aging↗
PubMed1997

Characterization and expression of two chicken cDNAs encoding ubiquitin fused to ribosomal proteins of 52 and 80 amino acids.

We have determined the complete nucleotide sequence of two chicken cDNAs, Ub-t52 and Ub-t80, encoding ubiquitin fused to ribosomal proteins of 52 and 80 amino acids. The deduced amino acid sequences of the ribosomal proteins are identical or very similar to the homologous human and rat proteins and to the corresponding proteins of other species. Unexpectedly, the ubiquitin moiety of the Ub-t52 protein showed two amino acid substitutions: serine-20 has been replaced by asparagine and serine-57 by alanine. Ubiquitin is a protein strongly conserved during evolution, with no changes in sequence previously reported in vertebrates. Ub-t52 and Ub-t80 are highly expressed in early embryogenesis and during postmitotic stages of spermatogenesis, in parallel with the expression of the polyubiquitin gene UbII. Whereas the 5' untranslated regions (5'UTRs) of the chicken polyubiquitin mRNAs showed marked differences in mature testes in relation to somatic tissues, no differences were observed in the 5'UTRs of the ubiquitin-ribosomal protein mRNAs. These mRNAs possess a 5'-terminal oligopyrimidine tract that could be used as a mechanism to postpone translation during postmitotic stages of spermatogenesis, as has been proposed in quiescent cells.

Alanine↗
PubMed1998

DAP-2, the Drosophila homolog of transcription factor AP-2.

Transcription factor AP-2 is essential for craniofacial, nervous system, and limb development in the mouse. We report here the cloning and expression pattern analysis of DAP-2, the Drosophila homolog of AP-2 family genes. DAP-2 is expressed in discrete regions of procephalic neuroectoderm, the brain, ventral nerve cord, and maxillary segment during Drosophila embryogenesis, and in the brain, optic lobes, ventral nerve cord, antenno-maxillary complex, and antennal and leg imaginal disks in third instar larvae. Protein sequence conservation and parallels between the embryonic expression patterns of DAP-2 and mammal ian AP-2 family genes indicate that transcription factor AP-2 has been structurally and functionally conserved during metazoan evolution.

Animals↗
PubMed2004

Role of histone tails in the conformation and interactions of nucleosome core particles.

The goal of this work was to test the role of the histone tails in the emergence of attractive interactions between nucleosomes above a critical salt concentration that corresponds to the complete tail extension outside the nucleosome [Mangenot, S., et al (2002) Biophys. J. 82, 345-356; Mangenot, S., et al (2002) Eur. Phys. J. E 7, 221-231]. Small angle X-ray scattering experiments were performed in parallel with intact and trypsin tail-deleted nucleosomes with 146 +/- 3 bp DNA. We varied the monovalent salt concentration from 10 to 300 monovalent salt concentration and followed the evolution of (i) the second virial coefficient that characterizes the interactions between particles and (ii) the conformation of the particle. The attractive interactions do not emerge in the absence of the tails, which validates the proposed hypothesis.

Animals↗
PubMed2001

A bizarre predatory dinosaur from the Late Cretaceous of Madagascar.

Here we report the discovery of a small-bodied (approximately 1.8 m) predatory dinosaur from the Late Cretaceous (Maastrichtian) of Madagascar. Masiakasaurus knopfleri, gen. et sp. nov., represented by several skull elements and much of the postcranial skeleton, is unique in being the only known theropod with a highly procumbent and distinctly heterodont lower dentition. Such a derived dental morphology is otherwise unknown among dinosaurs. Numerous skeletal characteristics indicate that Masiakasaurus is a member of Abelisauroidea, an enigmatic clade of Gondwanan theropods. Previously, small-bodied abelisauroids were known only from Argentina. The occurrence of Masiakasaurus on Madagascar suggests that small-bodied abelisauroids, like their larger-bodied counterparts, were more cosmopolitan, radiating throughout much of Gondwana and paralleling the diversification of small coelurosaur theropods in Laurasia.

Animals↗
PubMed2005

Tectonic implications of Mars crustal magnetism.

Mars currently has no global magnetic field of internal origin but must have had one in the past, when the crust acquired intense magnetization, presumably by cooling in the presence of an Earth-like magnetic field (thermoremanent magnetization). A new map of the magnetic field of Mars, compiled by using measurements acquired at an approximately 400-km mapping altitude by the Mars Global Surveyor spacecraft, is presented here. The increased spatial resolution and sensitivity of this map provide new insight into the origin and evolution of the Mars crust. Variations in the crustal magnetic field appear in association with major faults, some previously identified in imagery and topography (Cerberus Rupes and Valles Marineris). Two parallel great faults are identified in Terra Meridiani by offset magnetic field contours. They appear similar to transform faults that occur in oceanic crust on Earth, and support the notion that the Mars crust formed during an early era of plate tectonics.

Journal Article↗
PubMed2002

Physical interaction between GATA-5 and hepatocyte nuclear factor-1alpha results in synergistic activation of the human lactase-phlorizin hydrolase promoter.

GATA-4, -5, and -6 zinc finger and hepatocyte nuclear factor-1alpha (HNF-1alpha) homeodomain transcription factors are expressed in the intestinal epithelium and synergistically activate the promoter of intestinal genes. Here, we demonstrate that GATA-5 and HNF-1alpha physically associate both in vivo and in vitro and that this interaction is necessary for cooperative activation of the lactase-phlorizin hydrolase promoter. Furthermore, physical association is mediated by the C-terminal zinc finger of GATA factors and the homeodomain of HNF-1alpha. Deletion of HNF-1alpha activation domains or interruption of HNF-1-binding sites in the lactase-phlorizin hydrolase promoter resulted in a complete loss of cooperativity, whereas deletion of GATA-5 activation domains or interruption of GATA-binding sites resulted in a reduction, but not an elimination, of cooperativity. We hypothesize that GATA/HNF-1alpha cooperativity is mediated by HNF-1alpha through its activation domains, which are oriented for high levels of activation through binding to DNA and physical association with GATA factors. These data suggest a paradigm whereby intestine-specific gene expression is regulated by unique interactions among tissue-restricted transcription factors coexpressed in the intestine. Parallel mechanisms in other tissues as well as in Drosophila suggest that zinc finger/homeodomain interactions are an efficient pathway of cooperative activation of gene transcription that has been conserved throughout evolution.

Base Sequence↗
PubMed1985

Evolutionary change of restriction cleavage sites and phylogenetic inference for man and apes.

A mathematical theory for the evolutionary change of restriction endonuclease cleavage sites is developed, and the probabilities of various types of restriction-site changes are evaluated. A computer simulation is also conducted to study properties of the evolutionary change of restriction sites. These studies indicate that parsimony methods of constructing phylogenetic trees often make erroneous inferences about evolutionary changes of restriction sites unless the number of nucleotide substitutions per site is less than 0.01 for all branches of the tree. This introduces a systematic error in estimating the number of mutational changes for each branch and, consequently, in constructing phylogenetic trees. Therefore, parsimony methods should be used only in cases where nucleotide sequences are closely related. Reexamination of Ferris et al.'s data on restriction-site differences of mitochondrial DNAs does not support Templeton's conclusions regarding the phylogenetic tree for man and apes and the molecular clock hypothesis. Templeton's claim that Nei and Li's method of estimating the number of nucleotide substitutions per site is seriously affected by parallel losses and loss-gains of restriction sites is also unsupported.

Animals↗
PubMed1986

Macronodular adrenal hyperplasia with hypothalamic-pituitary-adrenal suppression by ultra-high-dose dexamethasone: regression following hypophysectomy.

Cushing's syndrome associated with macronodular adrenal hyperplasia (MAH) may present with high-dose dexamethasone (dex) nonsuppressible hypercortisolemia. This has been interpreted as suggesting a primary adrenal disorder, leading to recommendations for curative adrenalectomy in these cases. The present case of MAH demonstrates high urinary and serum cortisol levels, sufficiently suppressed only by ultra-high-dose (32 mg/day X 2 day) dex, with parallel reduction of plasma adrenocorticotrophin noted as well. Subsequent clinical cure by transsphenoidal hypophysectomy and identification of a pituitary adenoma confirmed the secondary nature of adrenal cortical hypersecretion. The conceptual evolution of macronodules and altered feedback dynamics of the hypothalamo-pituitary-adrenal axis in MAH are briefly discussed.

Adrenal Gland Diseases↗
PubMed1988

Lipid-related barriers and gradients in the epidermis.

The stratum corneum, once regarded as a degenerate, inconsequential tissue, is now respected as a structurally heterogeneous and metabolically active tissue. The segregation of lipids into intercellular domains, and the shift in composition from a mixture of polar lipids and neutral lipids to sphingolipids and neutral lipids have important implications for both barrier function and desquamation. Metabolic studies demonstrate the capacity of epidermis to synthesize lipids, the relative autonomy of such synthesis from extracutaneous influences, and the regulation of epidermal lipogenesis by local barrier requirements. Abundant lipid biosynthesis appears to occur in the stratum granulosum, consistent with the rapid recovery of barrier function following solvent treatment. Whereas nonpolar lipids, including sterol esters and hydrocarbons, provide a superficial barrier, sphingolipids and free sterols provide a more profound barrier. In parallel with the synthesis of lipids for barrier function, hydrolysis of phospholipids, glycolipids, and cholesterol sulfate occurs in the outer epidermis leading to a more hydrophobic lipid mixture with the evolution of broad membrane bilayers that may regulate both transcutaneous water loss and desquamation.

Animals↗
PubMed2004

Evolutionary ecology of the prezygotic stage.

The life cycles of sexually reproducing animals and flowering plants begin with male and female gametes and their fusion to form a zygote. Selection at this earliest stage is crucial for offspring quality and raises similar evolutionary issues, yet zoology and botany use dissimilar approaches. There are striking parallels in the role of prezygotic competition for sexual selection on males, cryptic female choice, sexual conflict, and against selfish genetic elements and genetic incompatibility. In both groups, understanding the evolution of sex-specific and reproductive traits will require an appreciation of the effects of prezygotic competition on fitness.

Animals↗