The relationship of immunology to carcinogenesis.
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Animals↗
SEARCH · PubMed Health
Results for “Experimental evolution”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
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Behavioral evolution. The evolution of the golden rule.
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Altruism↗
Social and developmental biology of the myxobacteria.
Myxobacteria are soil bacteria whose unusually social behavior distinguishes them from other groups of procaryotes. Perhaps the most remarkable aspect of their social behavior occurs during development, when tens of thousands of cells aggregate and form a colorful fruiting body. Inside the fruiting body the vegetative cells convert into dormant, resistant myxospores. However, myxobacterial social behavior is not restricted to the developmental cycle, and three other social behaviors have been described. Vegetative cells have a multigene social motility system in which cell-cell contact is essential for gliding in multicellular swarms. Cell growth on protein is cooperative in that the growth rate increases with the cell density. Rippling is a periodic behavior in which the cells align themselves in ridges and move in waves. These social behaviors indicate that myxobacterial colonies are not merely collections of individual cells but are societies in which cell behavior is synchronized by cell-cell interactions. The molecular basis of these social behaviors is becoming clear through the use of a combination of behavioral, biochemical, and genetic experimental approaches.
Base Sequence↗
Mucosal damage mediated by clostridial toxin in experimental clindamycin-associated colitis.
A toxin produced by Clostridium difficile has been implicated in the pathogenesis of antibiotic-associated colitis in humans and experimental animals. This study was undertaken in order to define the sequential evolution of caecal mucosal lesions in the hamster and to relate those lesions directly to the clostridial toxin. Sterile filtrates from a culture of C. difficile and from caecal contents of clindamycin-treated hamsters were studied with respect to their effects on the caecal mucosa and on cultured cell monolayers. The toxic filtrates both produced cellular swelling in vitro, and appeared to have a similar cytotoxic effect on caecal epithelial cells in vivo. Cellular damage was followed by extensive epithelial desquamation and the evolution of an acute pseudomembranous typhlitis. The pathogenetic sequence produced by the filtrates was identical with that previously described after direct clindamycin treatment. These findings demonstrate that intraluminal clostridial toxin can mediate development of the characteristic antibiotic-associated mucosal lesions.
Animals↗
Now and then, the history of parenteral fluid administration.
The use of blood and intravenous fluid therapy is now considered routine therapy. The level of sophistication that we now perceive as standard has resulted from centuries of legends, religious beliefs, pseudo-science, non-scientific supposition, experimentation and error. The purpose of this article is to review the evolution of parenteral fluid and transfusion therapy through history. Data were collected via online search through the medical literature (ovid-medline), historical journals, medical history books as well as visits to historical medical libraries. We express our appreciation and gratitude to the hundreds of scientists whose work has allowed us to practice medicine, as we know it.
Blood Transfusion↗
The emergence of evolutionary and community ecology as experimental sciences.
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Adaptation, Biological↗
Necatoriasis: treatment and developmental therapeutics.
Two hookworm parasites, Necator americanus and Ancylostoma duodenale, infect approximately one billion people worldwide. These hookworms are one of the leading causes of iron-deficiency anaemia especially in children, resulting directly from intestinal capillary blood loss following the feeding activities of fourth-stage (L(4)) larva and adult worms. If ignored, human hookworm infections can retard growth and the intellectual development of children. Another clinical manifestation often associated with hookworm infections is cutaneous larva migrans (CLM). It is a well recognised, usually self-limiting condition caused by the infectious larvae of nematodes, especially Ancylostoma spp. CLM is characterised by skin eruption and represents a clinical description rather than a definitive diagnosis. Of the hookworm parasites, the dog and cat worm A. braziliense and A. caninum are the most common nematodes causing CLM, although many other species have also been implicated. The major subject of this review article will be discussion of the evolution of therapies and treatment of human necatoriasis and the development of experimental infections with N. americanus. Difference in the clinical efficacy of mebendazole and albendazole will be discussed along with drug resistance of N. americanus.
Ancylostomiasis↗
Calcium instabilities in mammalian cardiomyocyte networks.
The degeneration of a regular heart rhythm into fibrillation (a chaotic or chaos-like sequence) can proceed via several classical routes described by nonlinear dynamics: period-doubling, quasiperiodicity, or intermittency. In this study, we experimentally examine one aspect of cardiac excitation dynamics, the long-term evolution of intracellular calcium signals in cultured cardiomyocyte networks subjected to increasingly faster pacing rates via field stimulation. In this spatially extended system, we observed alternans and higher-order periodicities, extra beats, and skipped beats or blocks. Calcium instabilities evolved nonmonotonically with the prevalence of phase-locking or Wenckebach rhythm, low-frequency magnitude modulations (signature of quasiperiodicity), and switches between patterns with occasional bursts (signature of intermittency), but period-doubling bifurcations were rare. Six ventricular-fibrillation-resembling episodes were pace-induced, for which significantly higher complexity was confirmed by approximate entropy calculations. The progressive destabilization of the heart rhythm by coexistent frequencies, seen in this study, can be related to theoretically predicted competition of control variables (voltage and calcium) at the single-cell level, or to competition of excitation and recovery at the cell network level. Optical maps of the response revealed multiple local spatiotemporal patterns, and the emergence of longer-period global rhythms as a result of wavebreak-induced reentries.
Action Potentials↗
Conserved functions of yeast genes support the duplication, degeneration and complementation model for gene duplication.
Gene duplication is often cited as a potential mechanism for the evolution of new traits, but this hypothesis has not been thoroughly tested experimentally. A classical model of gene duplication states that after gene duplication one copy of the gene preserves the ancestral function, while the other copy is free to evolve a new function. In an alternative duplication, divergence, and complementation model, duplicated genes are preserved because each copy of the gene loses some, but not all, of its functions through degenerating mutations. This results in the degenerating mutations in one gene being complemented by the other and vice versa. These two models make very different predictions about the function of the preduplication orthologs in closely related species. These predictions have been tested here for several duplicated yeast genes that appeared to be the leading candidates to fit the classical model. Surprisingly, the results show that duplicated genes are maintained because each copy carries out a subset of the conserved functions that were already present in the preduplication gene. Therefore, the results are not consistent with the classical model, but instead fit the duplication, divergence, and complementation model.
Gene Duplication↗
Neonatal treatment with fluoxetine reduces depressive behavior induced by forced swim in adult rats.
Serotonin plays a role at the pathophysiology of depression in humans and in experimental models. The present study investigated the depressive behavior and the weigh evolution in adult rats (60 days) treated from the 1st to the 21st postnatal day with fluoxetine, a selective serotonin reuptake inhibitor (10 mg/kg, sc, daily). The depressive behavior was induced by the forced swim test (FST). The animals were submitted to two sessions of FST: 1st session for 15 min and the 2nd session 24h later, for 5 min. During the 2nd session the Latency of the Attempt of Escape (LAE) and Behavioral Immobility (BI) were appraised. The Fluoxetine group when compared to the Control group, showed an increase in LAE and a decrease in BI. The neonatal administration of fluoxetine reduced the depressive behavior in adult rats, possibly by increase in the brain serotonergic activity. This alteration can be associated to process of neuroadaptation.
Animals↗
Fracture mechanics of cortical bone tissue: a hierarchical perspective.
The performance of bone tissue in the presence of flaws is a highly remarkable one. Bone tissue is the outcome of an adaptive evolutionary process; thus, insight into the mechanisms by which it fails would provide valuable information not only for development of mechanically superior biomimetic materials but also for development of treatment modalities to prevent debilitating bone fractures. Clinically, fractures of skeletal organs occur as a result of aging, disease, overuse, and trauma. Fracture mechanics, a sub-discipline of solid mechanics that investigates the performance of cracked materials, has been employed extensively in characterizing the mechanisms by which bone tissue fractures. At present the fracture mechanisms at the macroscale are better characterized than at the microscale. On the other hand, a mechanistic understanding of damage evolution at the submicroscopic scale is largely limited to postulations with little experimental insight. The challenge of skeletal fragility will be dealt with more efficiently with deeper understanding of the fracture process at each hierarchical size scale. The most recent review on this subject matter was a decade ago, and there have been numerous developments in the fracture mechanics of bone since then. This review recaps the existing literature with an emphasis on the hierarchical nature of the fracture process in bone, entailing the supramolecular, microscopic, and macroscopic scales.
Animals↗
[The decision to treat based on epidemiological methodology: the paradigm of hypercholesterolemia].
The author reviews the epidemiological methods, both non experimental and experimental, founding evidence-based medicine. As an example, he reviews the evolution of the scientific knowledge about the relationship between hypercholesterolemia and coronary heart disease and about the determinants of the serum cholesterol concentration. Epidemiology studies the causal chain between exposure and event (sickness) and proposes, within the framework of primary and secondary prevention of coronary heart disease, interventions to interrupt the causal chain at a given level.
Causality↗
Parasitic infections. Treatment and developmental therapeutics. 1. Necatoriasis.
Necator americanus is a nematode hookworm of the family Ancylostomatidae, subfamily Necatorinae. This nematode parasite, which is distinguished by two chitinous cutting plates in the buccal cavity and fused male copulatory spicules, is the causative agent of necatoriasis, a hookworm disease prevalent in the Americas as well as in the tropical regions of Africa, southern Asia, and Polynesia. The adult parasites attached to the villi of the small intestines will suck blood causing abdominal discomfort, diarrhea and cramps, anorexia, wight loss, and in advanced disease, hypochromic microcytic anemia. Hookworm infections in man, especially in children, are one of the leading causes of iron-deficiency anemia resulting directly from intestinal capillary blood loss following the feeding activities of fourth-stage (L4) larva and adult worms. Another clinical manifestation often associated with hookworm infections is cutaneous larva migrans (CLM). It is a well recognized, usually self-limiting condition caused by the infectious larvae of nematodes. CLM is characterized by skin eruption and represents a clinical description rather than a definitive diagnosis. Of the hookworm parasites, the dog and cat worm Ancylostoma braziliense is the most common causing CLM, although many other species have been implicated. The major subject of this review article will be discussion of the evolution of therapies and treatment of human necatoriasis and the development of experimental infections with N. americanus. Difference in the clinical efficacies of mebendazole and albendazole will be discussed along with drug resistance of N. americanus.
Albendazole↗
[Information program applied to the temporal study of pathological processes in animal populations].
WinEpi Tasas 2.0 is a new, globally accessible computer program, which has been developed as a research tool for the epidemiological study of the pathological processes which affect animal populations. This new version of the program, based on the experimental version, WinEpi Tasas 1.0, enables users to study the distribution and evolution of diseases in affected populations, over time. This information, combined with data on spatial distribution, is of fundamental importance for the establishment of appropriate control strategies and health policies. Such disease control measures are of particular significance in the current context of emerging and re-emerging diseases. The program can be run in either English or Spanish.
Animal Diseases↗
Theoretical foundation, goals, and methodology of a new science--biospherics
Scientific endeavor is motivated by mankind's needs, desires, and inherent nature to explore. The history of scientific revolutions involves paradigmatic breakthroughs that uncover previously unknown perspectives by which a phenomenon can be viewed. In this issue a noted scientist, Nickolai Pechurkin, gives a seminal brief on the theoretical foundation, goals, and methodology leading to a new science--biospherics. While biospherics has so far eluded a simple definition, it is not something taken from "whole cloth." Biospherics has many antecedents, but most noticeably arises from the global scale research and theory associated with the technological advances of the Space-Age. The Space-Age also created the need for totally closed life-support systems which involve experimentation with artificial biospheres.
Biological Evolution↗
The paradox of human goodness.
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Altruism↗
A phylogenetic foundation for comparative mammalian genomics.
A major effort is being undertaken to sequence an array of mammalian genomes. Coincidentally, the evolutionary relationships of the 18 presently recognized orders of placental mammals are only just being resolved. In this work we construct and analyse the largest alignments of amino acid sequence data to date. Our findings allow us to set up a series of superordinal groups (clades) to act as prior hypotheses for further testing. Important findings include strong evidence for a clade of Euarchonta+Glires (=Supraprimates) comprised of primates, flying lemurs, tree shrews, lagomorphs and rodents. In addition, there is good evidence for a clade of all placental mammals except Xenarthra and Afrotheria (=Boreotheria) and for the previously recognised clades Laurasiatheria, Scrotifera, Fereuungulata, Ferae, Afrotheria, Euarchonta, Glires, and Eulipotyphla. Accordingly, a revised classification of the placental mammals is put forward. Using this and molecular divergence-time methods, the ages of the superordinal splits are estimated. While results are strongly consistent with the earliest superordinal divergences all being >65 mybp (Cretaceous period), they suffer from greater uncertainty than presently appreciated. The early primate split of tarsiers from the anthropoid lineage at ~55 mybp is seen to be an especially informative fossil calibration point. A statistical framework for testing clades using SINE data is presented and reveals significant support for the tarsier/anthropoid clade, as well as the clades Cetruminantia and Whippomorpha. Results also underline our thesis that while sequence analysis can help set up hypothesised clades, SINEs obtainable from sequencing 1-2 MB regions of placental genomes are essential to testing them. In contrast, derivations suggest that empirical Bayesian methods for sequence data may not be robust estimators of clades. Our findings, including the study of genes such as TP53, make a good case for the tree shrew as a closer relative of primates than rodents, while also showing a slower rate of evolution in key cell cycle genes. Tree shrews are consequently high value experimental animals and a strong candidate for a genome sequencing initiative.
Animals↗
Artificial life and speciation, a case study: heterochromatin and speciation in the Microtus savii Group (Rodentia-Arvicolinae).
Artificial life is a tool which is used for simulation of peculiar cases of evolutionary events. The main characteristic of artificial life is that with this technique it is possible to simulate for a high number of generations the evolution of a population of individuals. Each individual is characterised by a small number of parameters, but each individual has its own evolutive story. So far it is possible to simulate the evolution of a population of some thousands specimens, for a high number of generations. The realistic aspect of the simulation is that each specimen is taken individually. In our opinion this instrument is very useful to simulate the evolution of the hybrids barrier during speciation. For this reason it is applied to a peculiar case of speciation, that of the Savi pine vole (Microtus savii) whose experimental data were recently investigated.
Animals↗
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