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At least 793 records · Page 44Linked to original sources
PubMed1990

Rapid evolution in response to high-temperature selection.

Temperature is an important environmental factor affecting all organisms, and there is ample evidence from comparative physiology that species and even conspecific populations can adapt genetically to different temperature regimes. But the effect of these adaptations on fitness and the rapidity of their evolution is unknown, as is the extent to which they depend on pre-existing genetic variation rather than new mutations. We have begun a study of the evolutionary adaptation of Escherichia coli to different temperature regimes, taking advantage of the large population sizes and short generation times in experiments on this bacterial species. We report significant improvement in temperature-specific fitness of lines maintained at 42 degrees C for 200 generations (about one month). These changes in fitness are due to selection on de novo mutations and show that some biological systems can evolve rapidly in response to changes in environmental factors such as temperature.

Biological Evolution↗
PubMed1995

Circadian rhythm of body temperature in an ectotherm (Iguana iguana).

Ectothermic animals regulate their body temperatures primarily by behavioral adjustment in relation to the thermal characteristics of the environment. Several studies have shown that some vertebrate ectotherms may show a daily pattern of body temperature selection when given a choice of environmental temperature. The pattern of body temperature selection free-runs when the animals are kept in constant darkness, demonstrating the existence of circadian regulation. To test whether there might also be a low amplitude circadian rhythm of body temperature itself, we examined the pattern of body temperature and locomotor activity of the lizard Iguana iguana held in a constant environmental temperature. Both variables were recorded for 3 days in a light:dark cycle and then for 10 days in constant dim light (0.1 lux). Under these conditions the body temperature of the lizard oscillates with a circadian period as does the locomotor behavior. These results demonstrate for the first time that ectothermic animals may display physiologically generated circadian rhythms of body temperature similar to those recorded in endotherms. In some animals the circadian rhythms of body temperature and locomotor activity showed different free-running periods, demonstrating that the body temperature rhythm was not caused by locomotor activity and suggesting internal desyncronization of the two rhythms.

Animals↗
PubMed1991

The physiology of spacecraft and space suit atmosphere selection.

The majority of the environmental factors which comprise the spacecraft and space suit environments can be controlled at "Earth normal" values, at optimum values, or at other values decided upon by spacecraft designers. Factors which are considered in arriving at control values and control ranges of these parameters include physiological, engineering, operational cost, and safety considerations. Several of the physiological considerations, including hypoxia and hyperoxia, hypercapnia, temperature regulation, and decompression sickness are identified and their impact on spacecraft and space suit atmosphere selection are considered. The past experience in controlling these parameters in U.S. and Soviet spacecraft and space suits and the associated physiological responses are reviewed. Current areas of physiological investigation relating to environmental factors in spacecraft are discussed, particularly decompression sickness which can occur as a result of change in pressure from Earth to spacecraft or spacecraft to space suit. Physiological considerations for long-term lunar or Martian missions will have different impacts on atmosphere selection and may result in the selection of atmospheres different than those currently in use.

Atmospheric Pressure↗
PubMed1997

Selective dopamine neurotoxicity by an industrial chemical: an environmental cause of Parkinson's disease?

While unproved, environmental toxins of industrial and or agricultural origin represent an attractive theory to explain the increasing incidence of degenerative diseases of the nervous system such as Parkinson's disease (PD). We have examined several chemicals utilized in an area of Israel previously demonstrated to contain a statistically greater than average number of people with Parkinson's disease. One of these agents, a light stabilizer employed universally in the production of polyolifins used in plastics, depleted primary mesencephalic cultures of dopamine neurons, and produced a dopamine-specific lesion of the substantia nigra pars compacta when injected stereotactically into the ventral midbrain of adult rats. The observed effects were dose-dependent. These findings represent a potentially significant development in the search for industrial/environmental causes of neurodegenerative disease.

Animals↗
PubMed1994

Structure and expression of a novel, neuronal protein kinase C (PKC1B) from Caenorhabditis elegans. PKC1B is expressed selectively in neurons that receive, transmit, and process environmental signals.

The nematode Caenorhabditis elegans provides an advantageous system for investigating the regulation, expression, and functions of protein kinase C (PKC) isoforms. We cloned and characterized cDNAs encoding a novel C. elegans PKC designated PKC1B. The predicted PKC1B polypeptide contains features characteristic of the nPKC subfamily of PKC isoforms. The levels of PKC1B and its cognate mRNA vary over a 7-fold range during C. elegans postembryonic development. PKC1B protein and mRNA are abundant at the earliest larval stage, but their relative concentrations decrease coordinately in late larvae. Embryos, which are enriched in PKC1B mRNA, contain little PKC1B protein. Thus, PKC1B expression is regulated at a translational or post-translational level during early development. Cells engaged in PKC1B gene transcription were identified in transgenic C. elegans that carry the lacZ gene under the regulation of the PKC1B promoter. Staining for beta-galactosidase revealed PKC1B promoter activity exclusively in sensory neurons and interneurons. Immunofluorescence microscopy disclosed that the PKC1B polypeptide is located in the processes (axons and dendrites) and perinuclear regions of approximately 75 neurons that constitute the sensory circuitry of the nematode. The intracellular localization of PKC1B and the enzyme's differential solubility in ionic and nonionic detergents suggest that the kinase is associated with membranes and the cytoskeleton.

Amino Acid Sequence↗
PubMedDate not supplied

Selective approaches to basic neurobehavioral testing of children in environmental health studies.

To identify neurotoxic effects in children living near hazardous waste sites, the Agency for Toxic Substances and Disease Registry (ATSDR) has designed a basic Pediatric Environmental Neurobehavioral Test Battery (PENTB) for children 1 through 16 years of age. It emphasizes tests appropriate to the stages of a child's development. These stages were fundamental factors in selecting tests for the PENTB, which includes both informant- and performance-based assessment procedures. Assessment of children under 4 years of age is restricted to four informant-based instruments, to evaluate as many functions as possible while minimizing testing time and the professional expertise needed in the test setting. The assessment of children 4 through 16 years of age includes 10 performance-based tests to evaluate key functions within the cognitive, motor, and sensory domains analogous to functions affected by neurotoxic chemicals in adults. In all age groups, it is crucial to also assess family, cultural, economic, and other potentially confounding variables.

Child↗
PubMed2006

Use of a nonmedicated dietary supplement correlates with increased prevalence of streptomycin-sulfa-tetracycline-resistant Escherichia coli on a dairy farm.

We examined how a dietary supplement affects the prevalence of antibiotic-resistant Escherichia coli on a dairy farm in Washington State. Between 2001 and 2004 the prevalence of fecal E. coli strains resistant to streptomycin, sulfadiazine, and tetracycline (SSuT strains) declined from 59.2% to 26.1% in the calf population. In 2003 the dairy discontinued use of a dietary supplement, and we hypothesized that the decline in prevalence of SSuT strains was related to this change in management. To test this we established three treatments in which calves received no supplement, the dietary supplement with oxytetracycline, or the dietary supplement without oxytetracycline. Calves receiving either dietary supplement had a significantly higher prevalence of SSuT E. coli than the no-supplement control group (approximately 37% versus 20%, respectively; P = 0.03). Importantly, there was no evidence that oxytetracycline contributed to an increased prevalence of fecal SSuT E. coli. We compared the growth characteristics of SSuT and non-SSuT E. coli in LB broth enriched with either the complete dietary supplement or its individual constituents. Both the complete dietary supplement and its vitamin D component supported a significantly higher cell density of SSuT strains (P = 0.003 and P = 0.001, respectively). The dry milk and vitamin A components of the dietary supplement did not support different cell densities. These results were consistent with selection and maintenance of SSuT E. coli due to environmental components independent of antibiotic selection.

Animals↗
PubMed1989

The development of the ego: biological and environmental specificity in the psychopathological developmental process and the selection and construction of ego defenses.

This paper suggests that differences in early sensory processing, integration, and differentiation, contribute, in highly specific ways, to characteristics of the ego, deficits in ego functions, and the ego's tendency to employ certain defenses (when certain pathogenic environmental experiences are present). Specifically (1) auditory-verbal-affective vulnerabilities may be associated with disorders of thought and obsessive-compulsive patterns, especially when coupled with environments that tend to confuse affective meanings at behavioral-gestural and symbolic levels; (2) visual-spatial-affective vulnerabilities may be associated with disorders of affect regulation and hysterical patterns, especially when coupled with environments that lack empathy and/or limit setting; (3) spatial, motor movement (vestibular) vulnerabilities may be associated with phobic and/or counterphobic tendencies. The author contends that these hypotheses are sufficiently specific and testable to lead to new research opportunities.

Child↗
PubMed1987

Modification of muscle proteins IEF patterns in a fish Lebistes reticulatus, related to diet, immunization and genetic selection.

The effects of some environmental and genetic factors on the isoelectric focusing (IEF) patterns of muscle proteins from a fish Lebistes reticulatus (Cyprinodonts) were investigated. Of two diets applied the restricted one resulted in a loss of bands in the IEF patterns of the treated fishes muscle homogenate. Instead immunization gave an increase in both number and intensity of IEF bands in (4.0-6.0; 7.0-7.9) pH ranges which are typical of immunoglobulins. Lastly IEF patterns from random and assortative mating animals were compared, resulting in loss of IEF-bands in the inbred lines. Results showed that IEF of muscle proteins could be an excellent method to evaluate the response by fish phenotypes to environmental or genetic factors.

Animals↗
PubMed2003

Music agnosia and auditory agnosia. Dissociations in stroke patients.

A review and an experimental study were carried out in search of dissociations between the recognition of music (music agnosia) and that of environmental sounds (auditory agnosia) in stroke patients. The review focused on 45 adequately studied cases published since 1883. The experimental study consisted of administering standard tests of music and environmental sound recognition to 40 unselected patients with unilateral stroke. Among case reports, music was selectively impaired more frequently than environmental sounds, whereas the reverse occurred in the experimental study. In this, right hemisphere lesions tended either to disrupt the apperception of environmental sounds, sparing music entirely, or to disrupt both environmental sounds and melody, sparing rhythm, whereas left hemisphere lesions tended to spare melody and to disrupt rhythm, either selectively or in association with the semantic identification of environmental sounds.

Adult↗
PubMed1999

Multiple environmental factors regulate the expression of the carbohydrate-selective OprB porin of Pseudomonas aeruginosa.

In response to low extracellular glucose concentration, Pseudomonas aeruginosa induces the expression of the outer membrane carbohydrate-selective OprB porin. The promoter region of the oprB gene was cloned into a lacZ transcriptional fusion vector, and the construct was mobilized into P. aeruginosa OprB-deficient strain, WW100, to evaluate additional environmental factors that influence OprB porin gene expression. Growth temperature, pH of the growth medium, salicylate concentration, and carbohydrate source were found to differentially influence porin expression. This expression pattern was compared to those of whole-cell [14C]glucose uptake under conditions of high osmolarity, ionicity, variable pH, growth temperatures, and carbohydrate source. These studies revealed that the high-affinity glucose transport genes are down-regulated by salicylic acid, differentially regulated by pH and temperature, and are specifically responsive to exogenous glucose induction.

ATP-Binding Cassette Transporters↗
PubMed2001

The hormetic zone: an ecological and evolutionary perspective based upon habitat characteristics and fitness selection.

Fitness varies nonlinearly with environmental variables such as temperature, water availability, and nutrition, with maximum fitness at intermediate levels between more stressful extremes. For environmental agents that are highly toxic at exposures that substantially exceed background levels, fitness is maximized at concentrations near zero--a phenomenon often referred to as hormesis. Two main components are suggested: (1) background hormesis, which derives from the direct adaptation of organisms to their habitats; and (2) stress-derived hormonesis, which derives from metabolic reserves that are maintained as an adaptation to environmental stresses through evolutionary time. These reserves provide protection from lesser correlated stresses. This article discusses illustrative examples, including ethanol and ionizing radiation, aimed at placing hormesis into an ecological and evolutionary context. A unifying approach comes from fitness-stress continua that underlie responses to abiotic variables, whereby selection for maximum metabolic efficiency and hence fitness in adaptation to habitats in nature underlies hormetic zones. Within this reductionist model, more specific metabolic mechanisms to explain hormesis are beginning to emerge, depending upon the agent and the taxon in question. Some limited research possibilities based upon this evolutionary perspective are indicated.

Adaptation, Physiological↗
PubMed2003

Have environmental mutagens caused oncomutations in people?

Age-specific cancer rates show large historical increases that indict environmental risk factors. But these environmental factors did not necessarily act by increasing oncomutation rates. Mathematical analyses suggest selective effects on pre-existing oncomutants. The widely held hypothesis that environmental chemicals induce a substantial fraction of human point mutations has not been supported by observation. Direct measurement of the kinds and numbers of point mutations in human tissues have, in fact, found no clear relationship with exposure to environmental agents, save for sunlight in the skin. Alternative hypotheses that point mutations arise primarily as errors during turnover of undamaged DNA and that environmental conditions select rather than induce oncomutants seem to better explain the facts of environmental carcinogenesis in humans.

Carcinogens, Environmental↗
PubMed1994

Heredity and age-related macular degeneration. Observations in monozygotic twins.

OBJECTIVE: To determine the concordance of age-related macular degenerative changes in monozygotic twins. PATIENTS: Between 1984 and 1993, we examined a total of nine pairs of monozygotic twins with substantial age-related macular degenerative changes in at least one member of the pair, ranging from extensive large drusen to advanced atrophic and/or disciform scarring. Eight pairs were female and one pair was male. Ages ranged from 62 to 88 years. Monozygosity was confirmed by genetic testing in each of the seven twin pairs on whom it was performed. RESULTS: In eight of the nine twin pairs, the fundus appearance and the incidence of visual impairment were similar. In the ninth pair, one twin had advanced exudative age-related macular degeneration with vision loss in one eye, while the other had large, confluent drusen and good visual function in both eyes. Environmental factor, including diet, geographic background, and medical history, were essentially similar in the twin pairs. CONCLUSION: Although selection factors and similar environmental influences might impact our findings, the markedly similar incidence of macular degenerative changes in these monozygotic twins suggests that a substantial genetic component may exist in a potentially large proportion of patients with age-related macular degeneration. Further studies are warranted to define this hereditary influence.

Aged↗
PubMed1997

Selection of marker-free transgenic plants using the isopentenyl transferase gene.

We have developed a new plant vector system for repeated transformation (called MAT for multi-auto-transformation) in which a chimeric ipt gene, inserted into the transposable element Ac, is used as a selectable marker for transformation. Selectable marker genes conferring antibiotic or herbicide resistance, used to introduce economically valuable genes into crop plants, have three major problems: (i) the selective agents have negative effects on proliferation and differentiation of plant cells; (ii) there is uncertainty regarding the environmental impact of many selectable marker genes; (iii) it is difficult to perform recurrent transformations using the same selectable marker to pyramid desirable genes. The MAT vector system containing the ipt gene and the Ac element is designed to overcome these difficulties. When tobacco leaf segments were transformed and selected, subsequent excision of the modified Ac produced marker-free transgenic tobacco plants without sexual crosses or seed production. In addition, the chimeric ipt gene could be visually used as a selectable marker for transformation of hybrid aspen (Populus sieboldii x Populus grandidentata). The chimeric ipt gene, therefore, is an attractive alternative to the most widely used selectable marker genes. The MAT vector system provides a promising way to shorten breeding time for genetically engineered crops. This method could be particularly valuable for fruit and forest trees, for which long generation times are a more significant barrier to breeding and genetic analysis.

Journal Article↗