[Histiomonocytic reticulosis with rapidly fatal evolution (1 year and a half) despite continued corticotherapy and a rather reassuring histopathology].
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Biological Evolution↗
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Apneic diffusion oxygenation and continuous flow apneic ventilation. A review.
Evolution of life coincides with the most rapid rate of rise in atmospheric oxygen concentration during Devonian time. Oxygen is essential for life, but at the same time is a cellular poison if present in tensions considerably higher than those the particular cellular milieu has become adapted to. Animals exposed to low oxygen tensions breathe continuously, e.g. most species of fish obtain their oxygen from a continuous flow of water at low oxygen tensions. Evolution from water to land breathing generally is associated with intermittent breathing, mass movement of gas in one direction, i.e. inhalation and exhalation. Intermittent breathing is part of this evolutionary process and reduces the inspired oxygen tension from 150 mmHg (19.95 kPa) to approximately 100 mmHg (13.3 kPa) at the alveolar blood interface. Perhaps evolution from continuous ventilation to intermittent breathing may be protecting the body against the high atmospheric oxygen tension. Therefore, it is not surprising that mammals can have adequate oxygen uptake with apneic diffusion oxygenation (ADO) and continuous flow apneic ventilation (CFAV). Mechanical ventilation classic techniques, i.e. intermittent positive-pressure ventilation and continuous positive-pressure ventilation, employ ventilatory frequencies close to the resting breathing rate of the adult. Utilizing low-compression patient circuits has made mechanical ventilation with higher frequencies possible. 60 to 400 breaths per min is used for high-frequency positive-pressure ventilation and high-frequency jet ventilation, and up to 40 Hz is used for high-frequency oscillation (HFO). The two extremes of artificial ventilation - ADO, i.e. supply of O2 by continuous flow, and HFO, i.e. supply of O2 by oscillatory changes - both primarily involve diffusion, even though convection (also secondary to cardiac oscillations) obviously is important in the process of gas exchange. Some recent experimental findings favor continued development and evaluation of CFAV as an additional alternative to artificial ventilation.
Animals↗
Evolution of salamander life cycles: a major-effect quantitative trait locus contributes to discrete and continuous variation for metamorphic timing.
The evolution of alternate modes of development may occur through genetic changes in metamorphic timing. This hypothesis was examined by crossing salamanders that express alternate developmental modes: metamorphosis vs. paedomorphosis. Three strains were used in the crossing design: Ambystoma tigrinum tigrinum (Att; metamorph), wild-caught A. mexicanum (Am; paedomorph), and laboratory Am (paedomorph). Att/Am hybrids were created for each Am strain and then backcrossed to their respective Am line. Previous studies have shown that a dominant allele from Att (met(Att)) and a recessive allele from lab Am (met(lab)) results in metamorphosis in Att/Am hybrids, and met(Att)/met(lab) and met(lab)/met(lab) backcross genotypes are strongly associated with metamorphosis and paedomorphosis, respectively. We typed a molecular marker (contig325) linked to met and found that met(Att)/met(lab) and met(Att)/met(wild) were associated with metamorphosis in 99% of the cases examined. However, the frequency of paedomorphosis was 4.5 times higher for met(lab)/met(lab) than for met(wild)/met(wild). We also found that met(Att)/met(wild) and met(wild)/met(wild) genotypes discriminated distributions of early and late metamorphosing individuals. Two forms of phenotypic variation are contributed by met: continuous variation of metamorphic age and expression of discrete, alternate morphs. We suggest that the evolution of paedomorphosis is associated with genetic changes that delay metamorphic timing in biphasic life cycles.
Age Factors↗
Experimental radiotherapy: a brief history.
Studies of the effects of ionizing radiation on tumors and normal tissues began within weeks of Roentgen's discovery of X rays, and are continuing today. The evolution of these studies reflects both the changing philosophy and sociology of science and the continuing application of new technologies and new knowledge from a diverse range of scientific fields to address the important problem of improving the treatment of cancer. This brief history reviews the evolution of "experimental radiotherapy" over the past century and describes how the development of new technologies and new experimental models influenced this field of study. In addition, it describes critical points at which studies in radiation biology and cancer biology had an impact on research throughout the biomedical sciences.
Animals↗
[Molecular basis of symbiogenic evolution: from free-living bacteria towards organelles].
Molecular mechanisms of the bacteria evolution are addressed in the context of the theory of symbiogenic origin of eukaryotic cells. In the evolution of symbiotic bacteria two strategies are implemented: (a) combinative, resulted in the formation of symbiotic (sym) gene systems from the genes previously involved in the autonomous life (facultative and ecologically obligatory symbioses); (b) reductive, related to the loss of genes for the autonomous life (genetically obligatory symbioses). Both strategies are based on the increase in genomic plasticity leading: (a) during combinative evolution--to the segregation of sym gene systems into the special plasmids or "islands" (the genome size and complexity increase); (b) during the reductive evolution--to the losses of many metabolic pathways (genome size decreases). These processes are continued during the evolution of mitochondria, hydrogenosomes and plastids in which many genes for the transcription and translation were lost, while the genomes of organelles and nuclei recombined. These reorganizations are related to the peculiarities of the bacteria population dynamics within the symbiotic systems. The bacteria which combine the abilities for symbiotic and autonomous lifestyles are characterized by ecotypic polymorphism (stable coexistence of symbiotic and asymbiotic genotypes). A key role in their evolution is implemented by horizontal transfer of sym genes that in combination with different forms of natural selection (individual, frequency-dependent and group selection) are responsible for the combinative evolution of bacteria genome. In the populations of obligatory symbionts, the genetic drift and group selection dominate that ensure bacteria genome reduction, loss of their biological identity and transformation into organelles.
Bacteria↗
The modern evolution of mechanical ventilation.
Continuous mechanical ventilation used for life support is accepted as standard practice in nearly every hospital in the United States today. The history of the evolution of techniques that we take virtually for granted today is fascinating. This article recounts some of the highlights in the development of modern-day mechanical ventilators, with emphasis on the past 25 years.
Forecasting↗
Antiquity of Homo sapiens in China.
Ten years ago a well-preserved skull of an early form of Homo sapiens was unearthed from Pleistocene cave deposits at the Jinniushan site in China. Here we present electron-spin resonance (ESR) and uranium-series dates from five fossil animal teeth collected from the hominid locality. The minimum ESR ages (195-165 kyr) are about 50 kyr younger than the uranium-series dates. Taken together, the results suggest an age of about 200 kyr or older for the Jinniushan skull, making it among the oldest H. sapiens material found in China, and almost as old as some of the latest Chinese H. erectus. This raises the possibility of the coexistence of the two species in China. The morphology of the skull suggests a strong local component of evolution, consonant with the 'multi-regional continuity' model of the evolution of H. sapiens.
Animals↗
Carbon dioxide evolution during the cell cycle of the fission yeast Schizosaccharomyces pombe.
The rate of CO2 evolution was measured in synchronous cultures of the fission yeast Schizosaccharomyces pombe growing in a minimal medium. The rate of CO2 evolution was found to double sharply at about the time of nuclear division (0.75 of the way through the cell cycle). For the remainder of the cell cycle the rate remained constant. Addition of inhibitors of DNA synthesis or nuclear division did not affect the pattern of CO2 evolution in synchronous cultures. Similarly, in an induced synchronous culture, in which DNA synthesis, nuclear division and cell division--but not growth, were synchronized, CO2 evolution showed a continuous pattern and not the step-wise increase associated with the normal synchronous cultures. When S. pombe was grown in a complete medium, the evolution of CO2 in a synchronous cultures was shown to increase in a continuous manner but at a rate faster than the growth of the culture.
Ascomycota↗
The Relationship between H(2) Evolution and Acetylene Reduction in Pisum sativum-Rhizobium leguminosarum Symbioses Differing in Uptake Hydrogenase Activity.
Peas (Pisum sativum L.) were inoculated with strains of Rhizobium leguminosarum having different levels of uptake hydrogenase (Hup) activity and were grown in sterile Leonard jars under controlled conditions. Rates of H(2) evolution and acetylene reduction were determined for intact nodulated roots at intervals after the onset of darkness or after removal of the shoots. Hup activity was estimated using treatment plants or equivalent plants from the growth chamber, by measuring the uptake of H(2) or (3)H(2) in the presence of acetylene. In all cases, the rate of H(2) evolution was a continuous function of the rate of acetylene reduction. In symbioses with no demonstrable Hup activity, H(2) evolution increased in direct proportion to acetylene reduction and the slopes were similar with the Hup(-) strains NA502 and 128C79. Hup activity was similar in strains 128C30 and 128C52 but significantly lower in strain 128C54. With these strains, the slopes of the H(2) evolution versus acetylene reduction curves initially increased with acetylene reduction, but became constant and similar to those for the Hup(-) strains at high rates of acetylene reduction. On these parallel portions of the curves, the decreases in H(2) evolution by Hup(+) strains were similar in magnitude to their H(2)-saturated rates of Hup activity. The curvilinear relationship between H(2) evolution and acetylene reduction for a representative Hup(+) strain (128C52) was the same, regardless of the experimental conditions used to vary the nitrogenase activity.
Journal Article↗
Evolution of R5 and X4 human immunodeficiency virus type 1 gag sequences in vivo: evidence for recombination.
Human immunodeficiency virus type 1 (HIV-1) infection is in general established by CCR5-utilizing (R5) virus variants, which persist throughout the course of infection. R5 HIV-1 variants evolve into CXCR4-utilizing (X4) HIV-1 variants in approximately half of the infected individuals. We have previously observed an ongoing genetic evolution with a continuous divergence of envelope gp120 sequences of coexisting R5 and X4 virus variants over time. Here, we studied evolution of gag p17 sequences in two patients who developed X4 variants in the course of infection. In contrast to the envelope gp120 sequences, gag p17 sequences of R5 and X4 virus populations intermingled in phylogenetic trees and did not diverge from each other over time. Statistical evaluation using the Shimodaira-Hasegawa test indicated that the different genomic regions evolved along different topologies, supporting the hypothesis of recombination. Therefore, our data imply that recombination between R5 and X4 HIV-1 variants occurs in vivo.
Cell Line↗
Theoretical analysis of mutation-adaptive evolutionary algorithms.
Adaptive evolutionary algorithms require a more sophisticated modeling than their static-parameter counterparts. Taking into account the current population is not enough when implementing parameter-adaptation rules based on success rates (evolution strategies) or on premature convergence (genetic algorithms). Instead of Markov chains, we use random systems with complete connections - accounting for a complete, rather than recent, history of the algorithm's evolution. Under the new paradigm, we analyze the convergence of several mutation-adaptive algorithms: a binary genetic algorithm, the 1/5 success rule evolution strategy, a continuous, respectively a dynamic (1+1) evolutionary algorithm.
Algorithms↗
Phylogenetic analysis of the N8 neuraminidase gene of influenza A viruses.
Phylogenetic analysis of the N8 neuraminidase (NA) genes from 18 influenza A viruses, representing equine and avian hosts in different geographic locations, revealed three major lineages: (i) currently circulating equine 2 viruses; (ii) avian viruses isolated in the Eurasian region, including A/Equine/Jilin/1/89, a recent avian-like N8 isolate found in horses in China; and (iii) avian viruses isolated in North America. Comparison of mutation rates indicated that avian N8 genes have evolved more slowly than their equine counterparts. That is, in both avian lineages, 72% of the nucleotide changes were silent in the terminal branches of the phylogenetic tree, whereas in equine 2 viruses, 59% of the nucleotide changes were silent. This suggests greater selective pressure on the NA gene from the mammalian immune system, leading to progressive evolution. Alternatively, the slower mutation rate for avian N8 genes could reflect a selective advantage gained from a longer, continuous span of evolution. The shape of the phylogenetic tree, the evolutionary rate, and the calculated date of origin for the N8 equine 2 virus lineage were comparable to findings for the equine 2 virus hemagglutinin (HA) gene (Bean et al., J. Virol. 66, 1129-1138, 1992). This suggests that both viral membrane glycoproteins of equine 2 viruses have evolved together and have been subjected to similar levels of selective pressure. Several amino acid residues were found to differ among the three host-specific lineages, but they may not be involved in host restriction of the NA, as they are shared by EQ/Jilin/1/89 and viruses of avian origin. The present findings complement detailed structural information on the N2 and N9 subtypes and should prove valuable in understanding future X-ray diffraction studies of N8 crystals.
Amino Acid Sequence↗
International perspectives on antiretroviral resistance. Nonnucleoside reverse transcriptase inhibitor resistance.
Although understanding of nonnucleoside reverse transcriptase inhibitor (NNRTI) resistance is less clearly established than that of other classes of antiretroviral drugs, certain facts have been established. The treatment-associated genetic mutation profiles of the available NNRTIs have been mapped, and resistance has been found to develop rapidly after initiation of NNRTI therapy. Despite the chemical diversity of the NNRTIs, cross-resistance among agents of this class is nearly universal. Although the viral replicative capacity ("fitness") of NNRTI-induced viral variants has not been extensively studied, available data suggest that NNRTI-selected mutations confer little damage to viral fitness, and thus a single point mutation produces a strain that is both resistant and fit. Furthermore, with continued therapy, viral evolution persists, creating species with greater numbers of mutations and higher level phenotypic resistance. Taken together, these facts suggest that continued use of NNRTIs after emergence of resistance will produce variants of complex mutational patterns that limit future treatment options, and, therefore, strong consideration should be given to discontinuing NNRTIs after virologic failure is confirmed. This article describes the scientific literature establishing the efficacy and limitations of NNRTI therapy and attempts to define a role for this class of drug in the long-term treatment of HIV-1 disease.
Alkynes↗
Evolution of ageing.
Explaining why ageing occurs is a solution to the longstanding enigma of the role of senescence in nature. Even after half a century of progress, this solution continues to unfold. Evolution theory argues strongly against programmed ageing, suggesting instead that organisms are programmed for survival, not death. In the current view, ageing results from the twin principles that (i) the force of natural selection declines with age, and (ii) longevity requires investments in somatic maintenance and repair that must compete against investments in growth, reproduction and activities that might enhance fitness. In addition to explaining why ageing occurs, the evolutionary theory also provides insight into the mechanisms underlying the complex cellular and molecular changes that contribute to senescence, as well as an array of testable predictions. Some of the most interesting current problems are to understand how the genetic factors influencing ageing and longevity are predicted to respond to fluctuating environments, such as temporary periods of famine, as well as to other kinds of spatial and/or temporal heterogeneity. Rapid progress in human genomics raises the prospect of greatly increasing our knowledge of the determinants of human longevity. To make progress in understanding the role and evolution of genetic and non-genetic factors in human longevity, we need more detailed theoretical studies of how intra-population variables, such as socio-economic status, influence the selection forces that shape the life history.
Aged↗
[Anxiety disorders: an issue for public health?].
The enhancement of mental health is becoming an increasingly important public health issue. Anxiety disorders are the most common mental problems. In light of the scope of the problem, public health has the mandate to continuously monitor the evolution of these disorders and to ensure that the health care system serves the population appropriately, in terms of service availability, accessibility, continuity and effectiveness. Moreover, public health ensures that prevention and promotion programs are put in place to contend with risk factors and encourage individuals to adopt habits that promote good mental health. This article describes public health interventions in relation to anxiety disorders in Montreal.
Anxiety Disorders↗
The evolution of renal osteodystrophy in patients undergoing continuous ambulatory peritoneal dialysis (CAPD).
Since the introduction of continuous ambulatory peritoneal dialysis by Popovich et al [1] and the subsequent modification of the technique by Oreopoulos et al [2], an increasing number of patients with end-stage renal disease are maintained on this new treatment modality. To date, there has not been any report of the effect of CAPD on the evolution of renal osteodystrophy which is one of the major complications of chronic renal failure. In this report we will present the results of our radiological and biochemical studies of renal osteodystrophy in 28 patients who have been on CAPD from 6 to 23 months.
Adult↗
Evolution of promoter sequences: elements of a canonical promoter for prespore genes of Dictyostelium.
An attempt is made to define a minimal prespore promoter which contains all elements essential for correct regulation of expression of a prespore gene. The prespore genes of Dictyostelium are coregulated during development. Most begin transcription at the same early stage, and activity of all is restricted to prespore tissue during the later slug stage. Sequences 5' to the coding sequences of eight prespore genes were searched for all elements proposed to control transcription and for new elements. The meaningfulness of occurrences of elements and pairs of elements in prespore promoters was evaluated by comparison with frequencies of occurrences in promoters of other, nonprespore genes. These comparisons resulted in definition of a canonical prespore promoter, a stretch of about 200 nucleotides containing at least one of each of three elements. Certain limitations were found on the spacing of elements. Orientation of elements with respect to each other appeared unrestricted. All elements often occurred in multiple copies. This structure suggests that individual copies of each element are not conserved during evolution, but instead continually appear and disappear.
Animals↗
[What do we control in mammaplasty for hypertrophic and/or ptotic breasts?].
A retrospective view on the history of mammaplasties for hypertrophic and/or ptotic breasts, shows its evolutive sense, in which we attempted to describe the main stages, avoiding to make a long "catalog". The first period (the longest) was marked by progresses concerning the control of vascular security of the areola and the nipple. That stage was essential by the fact it permitted to liberate the attention of surgeons for other questions: those concerning the shape of the breast, means of fixity and the long term evolution, quality and length of scars... In the continuity of this long evolution, each one of the authors presents a personal reflexion about the elements of control (and of course their limits!), developing some concepts as: the supra-medical pedicle for the vascular security, the advantage of the association mammaplasty and breast implant in the long term evolution and attentive post operative care to improve the quality of the scar (J.Ohana); the usefulness of a geometrical methodology-in which the importance of parameters as congruence and base of mammary gland conservation ("BAMACO") for shortening the scar without compromising the quality of the operated breast is demonstrated and with a relatively good stability of correction of the ptosis (-58% after 2 years) (R. Selinger).
Breast↗