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Results for “Continuous Evolution”

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At least 1,459 records · Page 81Linked to original sources

PubMed1998

Give us this day our daily germs.

Modern vaccinations, fear of germs and obsession with hygiene are depriving the immune system of the information input upon which it is dependent. This fails to maintain the correct cytokine balance and fine-tune T-cell regulation, and may lead to increased incidences of allergies and autoimmune diseases. If humans continue to deprive their immune systems of the input to which evolution has adapted it, it may be necessary to devise ways of replacing it artificially.

Adult↗

PubMed2003

Gastrointestinal hemorrhage: is the surgeon obsolete?

The management of GI hemorrhage has undergone tremendous evolution in recent decades. Once commonly managed by surgeons, the almost continuous introduction of new technologies and pharmacotherapies has dramatically improved clinicians' ability to identify and control sources of bleeding without surgery. Although a gastroenterologist can successfully manage most cases of GI hemorrhage endoscopically, surgical consultation remains an important consideration for the emergency physician in selected cases.

Blood Transfusion↗

PubMed1998

The genetic effects of environmental lead.

This article reviews the effects of lead on genetic systems in the context of lead's various other toxic effects and its abundance and distribution in the environment. Lead is perhaps the longest used and best recognized toxic environmental chemical, yet it continued be used recklessly until only very recently. Lead is thus a lesson in the limitations and strengths of science, human conscience and common sense. Lead has been tested and found to be capable of eliciting a positive response in an extraordinarily wide range of biological and biochemical tests; among them tests for enzyme inhibition, fidelity of DNA synthesis, mutation, chromosome aberrations, cancer and birth defects. It reacts or complexes with many biomolecules and adversely affects the reproductive, nervous, gastrointestinal, immune, renal, cardiovascular, skeletal, muscular and hematopoietic systems as well as developmental processes. It is likely that lead is a selective agent that continues to act on and influence the genetic structure and future evolution of exposed plant and animal populations.

Animals↗

PubMed2003

Epileptogenesis, ictogenesis and the design of future antiepileptic drugs.

There is still no medical cure for epilepsy. Clinical epileptology is in need of a "paradigm shift" when it comes to the continuing development of therapeutics. An important first step in this conceptual evolution is differentiating between the notions of ictogenesis and epileptogenesis. All traditional therapeutics are anti-ictogenic, not antiepileptogenic. The future of antiepileptic drug development lies in the discovery of antiepileptogenics. Just as aspirin is not the drug of choice for meningitis, an anticonvulsant is not the drug of choice for epilepsy. Drug design for epilepsy needs to discover a penicillin, not more aspirins.

Anticonvulsants↗

PubMed2006

Multi-scale approach continuously relating the microstructure and the macroscopic mechanical properties of plaster pastes during their settings.

A new multi-scale experimental approach is proposed to continuously relate the microstructure and the macroscopic mechanical properties of plaster pastes during their settings. (1)H NMR relaxometry is used to follow continuously and not destructively, the degree of hydration and the microstructure evolution during the setting and hardening of plaster paste. Transmission of shear and compressional ultrasonic velocities enable the determination of macroscopic mechanical properties of the material during the setting. On the basis of similar behaviors of Young's modulus and NMR-population of confined water as function of the degree of hydration, we conclude that NMR gives a better understanding of the evolution of the microstructure at the origin of a better control of the macroscopic mechanical properties.

Journal Article↗

PubMed2004

Endovascular graft limb occlusion.

Endovascular aneurysm repair (EVAR) has undergone a tremendous evolution in the nearly 15 years since it was first described. Continual refinement of the technology and techniques associated with EVAR and the respectable short-term results of this procedure led the United States Food and Drug Administration to approve several devices for the endovascular treatment of abdominal aortic aneurysm (AAA). There has been a corresponding rapid dissemination of this technology throughout the vascular surgery community in the United States. Availability and critical analysis of mid- and long-term follow-up data on the increasing number of patients who have undergone EVAR has begun to raise questions about the long-term durability and effectiveness of EVAR. Numerous complications of EVAR are now recognized and well described in the literature. One of these is graft limb dysfunction. Graft limb occlusion occurs in a significant number of patients and it is imperative that physicians who perform EVAR have a thorough understanding of this condition. There are a variety of factors that predispose patients to development of graft limb occlusion. These factors can be classified as either anatomic or graft-related. When patients present with graft limb occlusion, endovascular treatment is usually possible and it is highly effective. Some cases require traditional surgical treatment. Prevention of graft limb occlusion is of paramount importance. It can only be achieved with an aggressive search for graft limb compromise and liberal use of angioplasty and/or stenting at the time of graft implantation.

Aortic Aneurysm, Abdominal↗

PubMed1985

Anomalous origin of the right pulmonary artery from the ascending aorta: successful surgical repair.

A case of isolated anomalous origin of the right pulmonary artery from the ascending aorta with severe pulmonary hypertension is reported. Surgical repair was achieved by anastomosis of the anomalous vessel to the pulmonary artery trunk using a continuous absorbable suture. Special emphasis is laid on the favorable postoperative evolution of the pulmonary hypertensive disease following the successful repair. The poor natural history of this uncommon congenital defect if untreated makes early corrective surgery imperative.

Adult↗

PubMed1998

Loss of social behaviors by myxococcus xanthus during evolution in an unstructured habitat.

Social behaviors are often targets of natural selection among higher organisms, but quantifying the effects of such selection is difficult. We have used the bacterium Myxococcus xanthus as a model system for studying the evolution of social interactions. Changes in the social behaviors of 12 M. xanthus populations were quantified after 1,000 generations of evolution in a liquid habitat, in which interactions among individuals were continually hindered by shaking and low cell densities. Derived lineages were compared with their ancestors with respect to maximum growth rate, motility rates on hard and soft agar, fruiting body formation ability, and sporulation frequency during starvation. Improved performance in the liquid selective regime among evolved lines was usually associated with significant reductions in all of the major social behaviors of M. xanthus. Maintenance of functional social behaviors is apparently detrimental to fitness under asocial growth conditions.

Journal Article↗

PubMed2000

Molecular epidemiology: recent advances and future directions.

In 1982 we proposed the concept and a framework for implementing molecular cancer epidemiology. Here, we review progress during the past 17 years in validating and applying this approach to cancer prevention. There have been major advances, notably in the understanding of environment-susceptibility interactions in human cancer. However, a review of major findings to date reveals several urgent research needs to keep pace with the rapid evolution in knowledge of mechanisms in carcinogenesis. Although much valuable progress continues to be made in the study of carcinogens that cause direct DNA damage and are mutagenic, exogenous and endogenous carcinogens can also act by altering gene expression, cell proliferation and differentiation. The mechanisms include aberrant DNA methylation, oxidative damage, effects on metabolism of nitrogen oxide and nitrites, activation of receptors and transcription factors, cyclins and other cell cycle proteins. Sensitive, validated biomarkers are needed to detect these mechanisms in small numbers of cells, tissues or fluids. There is also increasing recognition that individual risk from carcinogen exposure varies as a function of both inherited and acquired factors. Recent advances in genomics, microassay technologies and informatics hold promise for rapid identification of polymorphic variants or changes in expression of genes influencing both response and susceptibility to carcinogens. Another emerging area of molecular epidemiology concerns the role of nutrition and specific dietary factors (including studies on antioxidants, energy metabolism, insulin and various growth factors) and the modulating effect of genetic polymorphisms. Finally, molecular epidemiology has enormous potential in cancer prevention through the early identification of 'at risk' populations and the rapid assessment of intervention efficacy. Its success in fully reaching this potential will depend on the application of validated biomarkers, with adherence to sound epidemiologic and ethical principles.

Carcinogens↗

PubMed1995

Regulation of photosynthesis in interior spruce during water stress: changes in gas exchange and chlorophyll fluorescence.

Photosynthetic response to water stress was analyzed in 1-year-old interior spruce (Picea glauca (Moench) Voss x P. engelmanni Parry hybrid complex) seedlings and emblings produced from somatic embryogenesis. Carbon dioxide uptake, oxygen evolution and chlorophyll fluorescence at 20 degrees C were monitored as predawn shoot water potential (Psi) decreased. Concurrently with stomatal closure, carbon assimilation declined rapidly as Psi decreased to -1.0 MPa. Oxygen evolution at 10,000 micro l CO(2) l(-1) declined continuously as Psi decreased to -1.6 MPa. At photon flux densities (PFD) above 50 micro mol m(-2) s(-1), photochemical efficiency of photosystem (PS) II observed during actinic light exposure (Phi(II), calculated as DeltaF/F(m)') decreased as Psi decreased. At the same PFDs, photochemical quenching (q(P)) declined with decreasing Psi and nonphotochemical quenching (q(N)) increased steadily. At PFDs below 50 micro mol m(-2) s(-1), major decreases in q(N) were not observed until Psi decreased below -1.6 MPa. We identified three phases of photosynthetic response to progressive water stress in interior spruce: a pronounced decline in gas exchange, subsequent photoprotective changes in chlorophyll fluorescence as primary photochemistry was down-regulated, and a decline in photochemical efficiency of dark-adapted needles.

Journal Article↗

PubMed1985

Metronidazole inhibition of hydrogen production in vivo in drug-sensitive and resistant strains of Trichomonas vaginalis.

H2 production by the human protozoan parasite Trichomonas vaginalis was monitored continuously under a mobile gas phase using a membrane-inlet mass spectrometer. Simultaneous and continuous measurement of dissolved H2, O2 and CO2 indicated that H2 evolution was inhibited at levels of O2 (less than 0.25 microM) undetectable by the technique, whereas CO2 production was stimulated. Respiration was not stimulated by admitting H2 to the gas phase. Metronidazole inhibited both H2 and CO2 production. Values of K1 for inhibition of H2 formation in strain ATCC 30001 (metronidazole sensitive) of 0.16 mM and in strain 85 (metronidazole resistant) of 1.0 mM were obtained. These data suggest that metronidazole not only competes with protons as electron acceptor but that the drug itself or a product of reduction actively inhibits some hydrogenosomal enzyme or electron carrier involved in H2 production. Under these conditions metronidazole inhibition leads to irreversible loss of cell motility.

Carbon Dioxide↗

PubMed2001

Dynamics of coarsening foams: accelerated and self-limiting drainage.

The evolution of a foam is determined by drainage flow of the continuous (liquid) phase and coarsening (aging) of the dispersed phase (gas bubbles). Free-drainage experiments with slow- and fast-coarsening gases show markedly different dynamics and elucidate the importance of the coupling of the two effects. Strong coarsening leads to drainage times that are shorter (accelerated drainage) and independent of the initial liquid content (self-limiting drainage). A model incorporating the physics of both drainage and diffusive coarsening shows quantitative agreement with experiment.

Journal Article↗

PubMed1971

Effect of exposure to subfreezing temperatures on ethylene evolution and leaf abscission in citrus.

Citrus leaves exposed to subfreezing temperatures evolved ethylene at rates between 0.1 and 38.3 microliters per kilogram fresh weight per hour whereas untreated leaves evolved between 0.01 and 0.50 microliter per kilogram fresh weight per hour. Leaves not injured by freezing temperatures did not abscise, and ethylene evolution was near normal after 2 days. Freeze-injured leaves continued evolving high ethylene levels 4 or 5 days subsequent to freeze injury, and many of the freeze-killed leaves abscised. Supportive evidence suggested freeze-induced ethylene was involved in freeze-induced leaf abscission; whereas freeze-inhibited abscission was not due to a lack of ethylene but injury to other metabolic systems necessary for abscission.

Journal Article↗

PubMedDate not supplied

Evolution of migraine after a 10-year follow-up.

OBJECTIVE: To assess the evolution of headaches in a workplace cohort over a 10-year period. BACKGROUND: Migraine headaches are associated with significant handicap in everyday activities and poor quality of life. The prevalence of migraine shows a bell-shaped age distribution with a peak during the third and fourth decades. However, there is little longitudinal data available on the natural history of this condition. A prospective health survey undertaken in a large workplace cohort since 1989 provides an opportunity to assess the evolution of migraine and other headache syndromes over a 10-year period. METHODS: A sample of 2500 subjects who reported regular headaches was chosen at random from those with headache identified in a cohort of 46,244 employees of the French national power company aged between 35 and 50 years in 1989 participating in a yearly health survey. In 1993, all subjects were sent a headache questionnaire to complete and return. In 2003, an identical questionnaire was sent to all subjects who had returned exploitable data in 1993. Headache diagnosis was assigned retrospectively using the International Headache Society (IHS) criteria to migraine (IHS categories 1.1 and 1.2), migrainous disorder (IHS category 1.7), or other episodic headaches. RESULTS: Of 2500 subjects sampled, 2051 (82%) returned exploitable data for the first questionnaire in 1993. In 2003, 1250 (61%) of these provided a second data set. In 1993, 623 (30.4%) of subjects fulfilled diagnostic criteria for migraine. However, only 37% of these retained the diagnosis 10 years later. In contrast, the proportion of subjects with other forms of episodic headache rose from 23.7% to 31.6%. In 2003, 9.5% of the sample were headache-free. Retention or acquisition of a diagnosis of migraine was more common in women than in men, and age was associated with evolution to a less severe headache syndrome. In those subjects who continued to have headaches, frequency and severity were lower at the second assessment. CONCLUSIONS: Only a minority of subjects diagnosed with migraine or migrainous disorder retain the diagnosis 10 years later, with most subjects evolving to a less disabling headache type.

Adult↗

PubMed2001

Ongoing horizontal and vertical transmission of virulence genes and papA alleles among Escherichia coli blood isolates from patients with diverse-source bacteremia.

The phylogenetic distributions of multiple putative virulence factors (VFs) and papA (P fimbrial structural subunit) alleles among 182 Escherichia coli blood isolates from patients with diverse-source bacteremia were defined. Phylogenetic correspondence among these strains, the E. coli Reference (ECOR) collection, and other collections of extraintestinal pathogenic E. coli (ExPEC) was assessed. Although among the 182 bacteremia isolates phylogenetic group B2 predominated, exhibited the greatest concentration of individual VFs, and contained the largest number of familiar virulent clones, other phylogenetic groups exhibited greater concentrations of certain VFs than did group B2 and included several additional virulent clones. Certain of the newly detected VF genes, e.g., fyuA (yersiniabactin; 76%) and focG (F1C fimbriae; 25%), were as prevalent or more prevalent than their more familiar traditional counterparts, e.g., iut (aerobactin; 57%) and sfaS (S fimbriae; 14%), thus possibly offering additional useful targets for preventive interventions. Considerable diversity of VF profiles was observed at every level within the phylogenetic tree, including even within individual lineages. This suggested that many different pathways can lead to extraintestinal virulence in E. coli and that the evolution of ExPEC, which involves extensive horizontal transmission of VFs and continuous remodeling of pathogenicity-associated islands, is a highly active, ongoing process.

Adult↗

PubMed1998

Emerging tobacco hazards in China: 2. Early mortality results from a prospective study.

OBJECTIVE: To monitor the evolving epidemic of mortality from tobacco in China following the large increase in male cigarette use in recent decades. DESIGN: Prospective study of smoking and mortality starting with 224 500 interviewees who should eventually be followed for some decades. SETTING: 45 nationally representative small urban or rural areas distributed across China. SUBJECTS: Male population aged 40 or over in 1991, of whom about 80% were interviewed about smoking, drinking, and medical history. MAIN OUTCOME MEASURE: Cause specific mortality, initially to 1995 but later to continue, with smoker versus non-smoker risk ratios standardised for area, age, and use of alcohol. RESULTS: 74% were smokers (73% current, only 1% former), but few of this generation would have smoked substantial numbers of cigarettes since early adult life. Overall mortality is increased among smokers (risk ratio 1.19; 95% confidence interval 1.13 to 1.25, P<0.0001). Almost all the increased mortality involved neoplastic, respiratory, or vascular disease. The overall risk ratios currently associated with smoking are less extreme in rural areas (1.26, 1.12, or 1.02 respectively for smokers who started before age 20, at 20-24, or at older ages) than in urban areas (1.73, 1.40, or 1.16 respectively). CONCLUSION: This prospective study and the accompanying retrospective study show that by 1990 smoking was already causing about 12% of Chinese male mortality in middle age. This proportion is predicted to rise to about 33% by 2030. Long term continuation of the prospective study (with periodic resurveys) can monitor the evolution of this epidemic.

Adult↗

PubMed2003

Long-term follow-up of childhood-onset hypopituitarism in patients with the PROP-1 gene mutation.

OBJECTIVE: The PROP-1 gene mutation is a rare disorder leading to combined pituitary hormone deficiencies over time. The aim was to analyze the clinical picture of 40 years of an almost untreated PROP-1 gene mutation. METHODS: We describe the clinical and hormonal data of 2 brothers from childhood to adulthood as well as imaging procedures (MRI of the pituitary gland, bone mineral density by QCT and DPX). The PROP-1 gene mutation (301-302delAG) was confirmed by DNA sequencing. RESULTS: Although long-standing untreated hypopituitarism was present, there was normal physical and professional activity. Bone mineral density was low only in 1 patient. Adrenocortical deficiency occurred late at 45 and 39 years. CONCLUSIONS: The biological evolution of the PROP-1 gene mutation illustrates the importance of continuous care for these patients. Hormonal deficiencies do not necessarily lead to the same phenotype as is obvious in differences of bone age and bone mineral density.

Adolescent↗

PubMed2006

Novel strategies in joint replacement.

As the need for hip and knee replacement continues to increase, technical and material changes have allowed a dramatic evolution in the way that degenerative, inflammatory and traumatic arthritis are managed. Advances include new bearing surfaces which should have greater longevity, minimal incision joint replacement, computer guidance and partial joint resurfacing for younger patients. These advances and their implications are discussed.

Arthritis↗