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At least 1,297 records · Page 72Linked to original sources
PubMed2004

Conformational resemblance between the structures of integrin-activating pentapetides derived from betaig-h3 and RGD peptide analogues in a membrane environment.

The peptides NKDIL and EPDIM, respectively derived from the 2nd and 4th domains of betaig-h3, were fully active in mediating cell adhesion through interactions with alpha3beta1 integrin [Biochem. Biophys. Res. Commun. 294 (2002) 940; J. Biol. Chem. 275 (2000) 30907]. Here, the conformational differences between NKDIL and EPDIM in water and in membrane environments were studied using CD spectroscopy, and their structures in sodium dodecylsulfate micelles were determined by NMR. The two peptides adopt beta-turn structures like RGD peptides, and have more regular structures in micelles than in aqueous buffers. EPDIM shows a distorted type I beta-turn for the PDIM segment in a membrane environment. The structure of NKDIL is similar with the standard type I' beta-turn, but shows large backbone flexibility even in a membrane environment. The conformational change of the 4th repeated domain of betaig-h3 in micelle solutions suggests that the Asp-Ile motif of the 4th fas-1 domain (EPDIM) would be solvent-exposed and could interact with integrin alpha3beta1 in a membrane environment. The present study provides a structural basis of betaig-h3 function and information for the development of integrin-regulating drugs involving the wound healing protein.

Amino Acid Sequence↗
PubMed2004

Sources and transformations of chlorophenols in the natural environment.

The present review updates our knowledge about chlorophenols, their chemical reactions and transformations in the natural environment, as well as factors affecting kinetics and mechanisms of these processes. Effects of pH of the environment and structure of molecules (also the number of chlorine atoms and their position in the molecule) on the behaviour of these compounds in the natural environment are also discussed. In addition, ways of propagation of chlorophenols in the natural environment are presented and discussed on the background of their physical and chemical properties, which influence the propagation rate in the ecosystems.

Animals↗
PubMed2004

Levels and trends of radioactive contaminants in the Greenland environment.

Levels of radioactive contaminants in various Greenland environments have been assessed during 1999-2001. The source of 137Cs, 90Sr and (239,240)Pu in terrestrial and fresh water environments is mainly global fallout. In addition, the Chernobyl accident gave a small contribution of 137Cs. Reindeer and lamb contain the largest observed 137Cs concentrations in the terrestrial environment--up to 80 Bq kg(-1) fresh weight have been observed in reindeer. Due to special environmental conditions, 137Cs is transferred to landlocked Arctic char with extremely high efficiency in South Greenland leading to concentrations up to 100 Bq kg(-1) fresh weight. In these cases very long ecological half-lives are seen. Concentrations of 99Tc, 137Cs and 90Sr in seawater and in marine biota decrease in the order North-East Greenland and the coastal East Greenland current > South-West Greenland > Central West Greenland and North-West Greenland > Irmiger Sea-Faroe Islands. The general large-scale oceanic circulation combined with European coastal discharges and previous contamination of the Arctic Ocean causes this. As the same tendency is seen for the persistent organic pollutants (POPs) DDT and PCB in marine biota, it is suggested that long-distance oceanic transport by coastal currents is a significant pathway also for POPs in the Greenland marine environment. The peak 99Tc discharge from Sellafield 1994-1995 has only been slightly visible in the present survey year 2000. The concentrations are expected to increase in the future, especially in East Greenland. The Bylot Sound at the Thule Airbase (Pituffik) in North-West Greenland was contaminated with plutonium and enriched uranium in a weapons accident in 1968. Biological activity has mixed accident plutonium efficiently into the new sediments resulting in continued high surface sediment concentrations three decades after the accident. Transfer of plutonium to benthic biota is low--and lower than observed in the Irish Sea. This is supposed to be caused by the physico-chemical form of the accident plutonium. A recent study indicates that 'hot particles' hold considerably more plutonium than previously anticipated and that the Bylot Sound sediments may account for the major part of the un-recovered plutonium after the accident, i.e. approximately 3 kg.

Animals↗
PubMed2005

238Pu and 239+240Pu inventory and distribution through the lower Rhone valley terrestrial environment (Southern France).

Because of atmospheric global fallout due to thermonuclear tests performed between 1945 and 1980 and to the American SNAP 9A satellite explosion in 1964, plutonium's long-lived alpha emitter isotopes ((238)Pu, (239)Pu and (240)Pu) can be found everywhere in the environment. In the soils of the lower Rhone valley, over a surface area of approximately 11,000 km(2), existing results allow estimation of the total inventory resulting from this origin of 551 GBq as regards these radionuclides. The Marcoule Nuclear Reprocessing Plant (NRP) has been releasing (238)Pu and (239+240)Pu into the environment for over 40 years in the region and is as such a second likely source for Pu input. This article gives a global review of plutonium distribution in this particular region. It is shown that releases from Marcoule, although accounting for less than 2% of the total Pu inputs into the terrestrial environment, are responsible for localised and measurable Pu enrichments close to the facility (+2.8 GBq), and in the Rhone delta where sediments from the river settled during the past floods (+0.1 GBq). Irrigating with water from the Rhone River also allowed the transfer of approximately 3.8 GBq of (238)Pu and (239+240)Pu to the soils for the whole 1960-1998 period. These inputs, distributed over wide irrigated surface areas, do not induce significant increases of soil Pu-activity levels. In a second section, this study confirms that most of the plutonium existing in the terrestrial environment is accumulated in the soil. Less than 0.1% of the activities exist currently in the plant compartments, and the flows exported by agricultural productions are very low, although we are interested here in a French region where agriculture prevails.

Air Pollutants, Radioactive↗
PubMed2005

Review of evidence: are endocrine-disrupting chemicals in the aquatic environment impacting fish populations?

In this paper, evidence from the current literature is presented that addresses either of two questions: 1) do EDCs in the aquatic environment have the potential to impact the reproductive health and survival of various fish species, and 2) are EDCs in the aquatic environment actually impacting the reproductive health and sustainability of indigenous populations of fish? Overall, data from laboratory experiments support the hypothesis that EDCs in the aquatic environment can impact the reproductive health of various fish species, but evidence that EDCs in the aquatic environment are actually impacting the reproductive health and sustainability of indigenous fish populations is less convincing. The scarcity of evidence linking impacts of environmental EDCs with changes in reproductive success of indigenous fish populations may reflect a critical need for a dependable method or indicator to assess reproduction of fish in situ. In addition, more studies that investigate whether fish populations routinely exposed to EDCs in situ are experiencing changes in population structure are needed. Linking endocrine disruption and reproductive impairment with an ecologically relevant impact on the sustainability of real fish populations remains, with few exceptions, an open challenge.

Animals↗
PubMed2004

The political environment of HIV: lessons from a comparison of Uganda and South Africa.

Considerable interest has arisen in the role of governance or political commitment in determining the success or failure of HIV/AIDS policies in sub-Saharan Africa. During the 1990s, Uganda and South Africa both faced dramatic HIV/AIDS epidemics and also saw transformations to new political systems. However, their responses to the disease differed in many ways. This paper compares and contrasts the ways in which policy environments, particularly government structures, can impede or expedite implementation of effective HIV prevention. Four elements of these environments are discussed--the role of political leadership, the existing bureaucratic system, the health care infrastructure, and the roles assigned to non-state actors. Two common international strategies for HIV prevention, syndromic management of sexually transmitted infections and sexual behaviour change interventions, are examined in relation to these elements in Uganda and South Africa during the mid-to-late 1990s. During this period, Uganda's political system succeeded in promoting behaviour change interventions, while South Africa was more successful in syndromic management efforts. Interactions between the four elements of the policy environment were found to be conducive to such results. These elements are relatively static features of the socio-political environments, so lessons can be drawn for current HIV/AIDS policy, both in these two countries and for a wider audience addressing the epidemic.

Cross-Cultural Comparison↗
PubMed2005

The influence of neighborhood environment on the incidence of childhood asthma: a multilevel approach.

Some ecological analyses suggest an influence of neighborhood environment on asthma outcomes. However, no previous study has applied a multilevel approach to assess an ecological effect of neighborhood environment on the incidence of childhood asthma accounting for individual risk factors. This study assessed the influence of neighborhood and individual-level factors on the incidence of childhood asthma among all children born in Rochester, Minnesota, between 1976 and 1979. We identified asthmatics among all children born in Rochester, between 1976 and 1983. We applied a multilevel survival model with the frailty term to assess the effects of neighborhood characteristics, such as mean family income per census tract (n = 16) from the 1980 census report and the status of whether a census tract faces intersections with major highways or railroads, on asthma incidence. The relative risks (RR) of neighborhood socioeconomic status (SES), the status of whether census tracts face intersections with highways or railroads and the variance of random effect of census tracts were calculated adjusting individual-level covariates for asthma, including gender, birth weight, mother's age at birth and parental educational level at birth. We found that the RR of developing asthma among children living in census tracts facing intersections with highways or railroads was 1.6 (95% CI: 1.1-2.2) compared to those who lived in census tracts not facing intersections, adjusting individual- and neighborhood-level covariates. The variance of the frailty term attributable to census tracts was small (0.0085) and was modified (from 0.004 to 0.0085, 112% change) by adding neighborhood covariates. The overall effects of individual-level factors on asthma incidence were independent of neighborhood environment. The influence of neighborhood environment on childhood asthma in a non-inner-city setting, like Rochester, Minnesota, was small to modest. Incorporating pertinent neighborhood-level covariates into multilevel models needs to be considered in assessing the random effect of clusters.

Asthma↗
PubMed2006

Advantage of storage in a fluctuating environment.

We will elaborate the evolutionary course of an ecosystem consisting of a population in a chemostat environment with periodically fluctuating nutrient supply. The organisms that make up the population consist of structural biomass and energy storage compartments. In a constant chemostat environment a species without energy storage always out-competes a species with energy reserves. This hinders evolution of species with storage from those without storage. Using the adaptive dynamics approach for non-equilibrium ecological systems we will show that in a fluctuating environment there are multiple stable evolutionary singular strategies (ss's): one for a species without, and one for a species with energy storage. The evolutionary end-point depends on the initial evolutionary state. We will formulate the invasion fitness in terms of Floquet multipliers for the oscillating non-autonomous system. Bifurcation theory is used to study points where due to evolutionary development by mutational steps, the long-term dynamics of the ecological system changes qualitatively. To that end, at the ecological time scale, the trait value at which invasion of a mutant into a resident population becomes possible can be calculated using numerical bifurcation analysis where the trait is used as the free parameter, because it is just a bifurcation point. In a constant environment there is a unique stable equilibrium for one species following the "competitive exclusion" principle. In contrast, due to the oscillatory dynamics on the ecological time scale two species may coexist. That is, non-equilibrium dynamics enhances biodiversity. However, we will show that this coexistence is not stable on the evolutionary time scale and always one single species survives.

Adaptation, Physiological↗
PubMed2005

Design of functional simulation of renal cancer in virtual reality environments.

OBJECTIVES: The preoperative planning of partial nephrectomy can be facilitated by the ability to view the tumor and surrounding tissue in three-dimensional (3D) virtual reality (VR). A technique to convert Digital Imaging and Communications in Medicine computed tomography scan data into a fully 3D VR environment was developed. The model can be transferred to a personal computer, allowing the surgeon to view the 3D model in the operating room. METHODS: Computed tomography data from a patient with multifocal renal masses was converted into a 3D polygonal mesh using Amira running on a desktop personal computer with Windows XP Professional. A Silicon Graphics Monster Onyx2 running the Linux operating system was used to view the 3D stereo model in the VR environments: either the CAVE or a specialized desk called the Immersadesk. An application to view and interact with the model on a desktop personal computer was written in C++. RESULTS: A 3D model of the kidney, the multiple tumors, and the associated systems was created. The model could be viewed and manipulated in a true VR environment and on a desktop personal computer. CONCLUSIONS: This project completed two major goals. First, a 3D model of a kidney containing multiple masses was created and viewed in a VR environment. Second, an interface to display the model on a desktop personal computer in the operating room was created. This is the first step in bringing VR technology to the operating room to assist the surgeon directly.

Aged↗
PubMed2000

The safety climate and its relationship to safety practices, safety of the work environment and occupational accidents in eight wood-processing companies.

Employees continuously observe their work environment and the actions of their fellow workers and superiors, and they use such observations as a basis for the creation of cognitive models associated with safety. These models regulate their actions in the workplace and thus have an influence on safety. This study attempts to define the structure of the safety climate as perceived by workers and the correlations between the safety climate, on the one hand, and the safety practices of the company, the safety level of the work environment and occupational accidents on the other. The variables used in this study were the same as those employed in two previous Finnish safety climate studies carried out in the plywood industry, shipyards, the forestry industry, building construction and stevedoring. The safety climate was measured by means of a questionnaire. Workers from four sawmills, two plywood factories and two parquet plants participated. The total number of participants was 508 in 1990 and 548 in 1993. The variables formed four factors, whose contents and reliabilities closely resembled the results obtained in the earlier studies. These results indicate that the structure of the safety climate among Finnish workers is quite stable. The safety climate correlated both with the safety level of the work environment and with the safety practices of the company, but the correlation between the safety climate and the safety of the work environment was stronger. This result differs from those of the previous studies, in which the safety climate was defined specifically in terms of an individual's perceptions of the safety practices of the company and of the behavior of other employees. The two safety climate factors that described a company's attitudes to safety and its safety precautions correlated with the accident rates. The better the safety climate of the company was, the lower was the accident rate. Four companies with an accident rate below the average for the wood-processing industry had a better safety climate than four similar companies with an accident rate above the average.

Accidents, Occupational↗
PubMed2003

Quality management and the work environment: an empirical investigation in a public sector organization.

The integration of quality management initiatives, particularly total quality management (TQM), and ergonomics has received increasing attention from scholars and practitioners. Above all, the question of how TQM programs relate to ergonomic aspects of organizational design and culture is at the center of this discussion. This study examines how elements of a "typical", Deming-inspired, TQM program in the public sector interact with the work environment. Elements of the TQM program were defined and measured using the Malcom Baldridge Award criteria. The specific elements examined were "Management Support of Quality", "Information and Analysis", "Human Resources", "Processes and Quality Results", and "Customer Focus and Satisfaction". The relationship between these TQM elements and the work environment were defined through five separate hypotheses. The work environment was described by the constructs "Supervisor Support", "Task Clarity", "Task Orientation", and "Innovation". Data were obtained through survey questionnaires administered to employees of four departments in a municipal government organization. Results supported three of the hypotheses, but produced some unanticipated outcomes with regard to the other two. Namely, "Management Support of Quality" was significantly related to "Supervisor Support", "Task Orientation", "Task Clarity" and "Innovation"; "Human Resources" was significantly related to "Supervisor Support"; "Processes and Quality Results" was significantly related to "Task Orientation" and "Innovation". Contrary to predicted "Information and Analysis" was negatively related to "Innovation", and "Customer Focus" was unrelated to any of the outcome variables. The relationships between these TQM elements and work environment dimensions are discussed. Implications for TQM and ergonomic practice are analyzed, and directions for future research proposed.

Empirical Research↗
PubMed2001

Dissociations between the effects of intra-accumbens administration of amphetamine and exposure to a novel environment on accumbens dopamine and cortical acetylcholine release.

Previous research has demonstrated an interaction between the effects of amphetamine and exposure to a novel environment on the activity of neurons in the nucleus accumbens. Given a model in which these accumbens efferents gate the excitability of basal forebrain cholinergic corticopetal neurons, the administration of intra-accumbens amphetamine was hypothesized to potentiate the increase in cortical acetylcholine produced by introduction to a novel environment. Dual probe microdialysis revealed no synergistic interactions between exposure to a novel environment and amphetamine on nucleus accumbens dopamine or cortical acetylcholine efflux. This finding indicates that exposure to a novel environment failed to recruit the telencephalic activation of the nucleus accumbens presumably necessary to reveal modulatory effects of accumbens dopaminergic transmission on cortical acetylcholine release.

Acetylcholine↗
PubMed2002

The clinical learning environment and supervision by staff nurses: developing the instrument.

The aims of this study were (1) to describe students' perceptions of the clinical learning environment and clinical supervision and (2) to develop an evaluation scale by using the empirical results of this study. The data were collected using the Clinical Learning Environment and Supervision instrument (CLES). The instrument was based on the literature review of earlier studies. The derived instrument was tested empirically in a study involving nurse students (N=416) from four nursing colleges in Finland. The results demonstrated that the method of supervision, the number of separate supervision sessions and the psychological content of supervisory contact within a positive ward atmosphere are the most important variables in the students' clinical learning. The results also suggest that ward managers can create the conditions of a positive ward culture and a positive attitude towards students and their learning needs. The construct validity of the instrument was analysed by using exploratory factor analysis. The analysis indicated that the most important factor in the students' clinical learning is the supervisory relationship. The two most important factors constituting a 'good' clinical learning environment are the management style of the ward manager and the premises of nursing on the ward. The results of the factor analysis support the theoretical construction of the clinical learning environment modelled by earlier empirical studies.

Education, Nursing↗
PubMed2000

Juvenile hormone titers, juvenile hormone biosynthesis, ovarian development and social environment in Bombus terrestris.

The effects of the social environment and age on juvenile hormone (JH) and reproduction were investigated by measuring ovarian development, hemolymph levels of JH III, and rates of JH biosynthesis from the same individual bumble bees (Bombus terrestris). Differences in social environment were associated with differences in rates of JH biosynthesis, JH titer and ovarian development. Young queenless workers had a higher rate of JH biosynthesis, JH titer and ovarian development than queenright (QR) workers of similar age. Dominant workers in QR colonies had a higher rate of JH biosynthesis, JH titer and ovarian development than low ranked workers of similar size. There was a positive correlation between JH titer and ovarian development, but no correlation between rate of JH biosynthesis and ovarian development or between JH biosynthesis and JH titer. Both JH titer and rate of JH biosynthesis increased with age from emergence to 3 days of age, but 6-day-old workers, egg-laying workers, and actively reproducing queens had high JH titers and highly developed ovaries but low rates of JH biosynthesis. These results show that reproduction in B. terrestris is strongly affected by the social environment and the influence of the environment on reproduction is mediated by JH. Our data also indicate that the rate of JH biosynthesis measured in vitro is not a reliable indicator of JH titer or ovarian development in B. terrestris; possible reasons are discussed.

Journal Article↗
PubMed1997

Effect of the environment on fetal skin wound healing.

Skin wound healing has been shown to be a different process in the fetus than in the adult animal. Some of these differences have been attributed to the unique fetal environment (i.e., amniotic fluid). The aim of the present study is to compare fetal skin healing in intraamniotic and extraamniotic wounds. A fetal rabbit model has been used in which three types of skin wounds were induced on 23-day-old fetuses in contact with either amniotic fluid or maternal peritoneal fluid. The wounds consisted of a sutured skin incision, a nonsutured incision, and an electrocautery burn. Seven days later all wounds were examined mechanically (scar resistance), biochemically (collagen and noncollagen protein concentration), and histologically. Biochemical and growth factor studies of both environments, the amniotic and the peritoneal fluids, were also conducted. The results showed excellent healing by first intention and absence of healing by second intention in both environments, greater scar resistance in the intraperitoneally positioned fetal wounds, and a higher concentration of insulin-like growth factor-1 (IGF-1) in the peritoneal fluid than in the amniotic fluid. It can be concluded that fetal skin wounds in contact with peritoneal fluid show the same healing pattern as in the natural fetal environment (amniotic fluid). The higher concentration of IGF-1 in the peritoneal fluid suggests that this growth factor, through its relationship with the growth hormone, plays a role in increasing the scar resistance of fetal skin wounds in contact with maternal peritoneal fluid.

Amniotic Fluid↗
PubMed1998

Role of the prenatal environment in the development of obesity.

Establishing that prenatal life is a critical or sensitive period for the development of obesity may focus basic research and clinical prevention efforts on this period. This review summarizes evidence that the intrauterine environment influences the risk of later obesity and considers the mechanisms by which this may occur. The association between birth weight and adult weight suggests that there are enduring effects of the intrauterine environment on later obesity risk. We examine whether the maternal factors of diabetes, obesity, and pregnancy weight gain alter the intrauterine environment and thereby increase the risk of later obesity in the offspring. Of these maternal factors, evidence is strongest for the role of maternal diabetes. No single mechanism explains how these maternal factors could change the intrauterine environment to increase obesity risk. However, all potential mechanisms involve an altered transfer of metabolic substrates between mother and fetus, which may influence the developing structure or function of the organs involved in energy metabolism.

Adult↗
PubMed1998

Epidermal growth factor receptor-mediated expression of NF-kappaB transcription factor in osteoblastic MC3T3-E1 cells cultured under a low-calcium environment.

We examined the effect of a low calcium environment on DNA-protein binding reaction activity of the transcription factor, NF-kappaB in osteoblastic MC3T3-E1 cells, using an electrophoretic mobility shift assay. Binding sites for the NF-kappaB sequence in DNA in nuclear protein in MC3T3-E1 cells are present. This DNA-protein binding reaction activity increased in MC3T3-E1 cells with EGF treatment, compared with those with no treatment. When MC3T3-E1 cells were placed in a low calcium environment, DNA-protein binding reaction activity seemed to decrease. This suggests that the phosphorylation of IkappaB is less active in a low calcium environment as compared with that in a normal calcium environment, because the activation of NF-kappaB is required for the dissociation of the cytoplasmic heterodimer after the phosphorylation of IkappaB. From these facts, it was suggested that gene transcription factor NF-kappaB is intimately associated with inhibitory bone formation in osteoblastic cells.

Animals↗
PubMed2002

Trace organic compounds in the marine environment.

Trace organic chemicals include a range of compounds which, due to a combination of their physico-chemical properties and toxicological implications, have been described as a serious threat to the biotic environment. A global treaty to regulate the manufacture and release of some of the most persistent trace chemicals has been promulgated and signed. The marine environment is an important sink for many trace chemicals, some of which accumulate in the marine food chain and in particular in marine mammals. With respect to the global distribution of trace organic chemicals, the levels of organohalogen compounds in the Southern Hemisphere are comparatively lower for a given environmental compartment and latitude compared to the Northern Hemisphere. A debate is currently evolving about the toxicity of alternative halogen substitutions such as bromine instead of chlorine and also of mixed halogen substitution. Recently a series of potentially natural bioaccumulative and persistent organohalogen chemicals have been found in marine mammals and turtles at levels in excess of those of anthropogenic trace organochlorines including PCBs and DDE. Little is known about the sources, behaviour and effects of natural trace organic chemicals. This manuscript presents an overview on the occurrence of trace organic chemicals in different compartments of the aquatic environment. Important knowledge gaps with regards to trace chemicals in the marine environment are presented.

Animals↗