Different Exposures (different + exposure)

Distribution by Scientific Domains

Selected Abstracts

Structural properties of trimers and tetramers of ribonuclease A

PROTEIN SCIENCE, Issue 10 2001
Arianna Nenci
Abstract Ribonuclease A aggregates (dimers, trimers, tetramers, pentamers) can be obtained by lyophilization from 40% acetic acid solutions. Each aggregate forms two conformational isomers distinguishable by different basic net charge. The crystal structure of the two dimers has recently been determined; the structure of the higher oligomers is unknown. The results of the study of the two trimeric and tetrameric conformers can be summarized as follows: (1) RNase A trimers and tetramers form by a 3D domain-swapping mechanism. N-terminal and C-terminal types of domain swapping could coexist; (2) the secondary structures of the trimeric and tetrameric conformers do not show significant differences if compared with the secondary structure of monomeric RNase A or its two dimers; (3) a different exposure of tyrosine residues indicates that in the aggregates they have different microenvironments; (4) the two trimeric and tetrameric conformers show different susceptibility to digestion by subtilisin; (5) dimers, trimers, and tetramers of RNase A show unwinding activity on double-helical poly(dA-dT) , poly(dA-dT), that increases as a function of the size of the oligomers; (6) the less basic conformers are more stable than the more basic ones, and a low concentration in solution of trimers and tetramers favors their stability, which is definitely increased by the interaction of the aggregates with poly(dA-dT) , poly(dA-dT); (7) the products of thermal dissociation of the two trimers indicate that their structures co ld be remarkably different. The dissociation products of the two tetramers allow the proposal of two models for their putative structures. [source]

New insight on ,-lactoglobulin binding sites by 1-anilinonaphthalene-8-sulfonate fluorescence decay

PROTEIN SCIENCE, Issue 10 2000
Maddalena Collini
Abstract The fluorescence time decay parameters of the ,-lactoglobulin-1-anilinonaphthalene-8-sulfonate complex have been investigated under physical and chemical perturbations (2 < pH < 8 and added electrolyte 0 < NaCl < 0.5 M) to obtain new insight on the nature of the protein binding interactions. A double exponential decay of the bound probe lifetime has been confirmed by the presence of a longer component, 11 to 14.5 ns, and a shorter component, 2.5 to 3.5 ns. The two lifetimes are ascribed to different binding modes associated also with different exposure to the solvent; in particular, the longer component is attributed to binding inside the hydrophobic beta barrel, while a "surface" site is suggested for the shorter component. A detailed analysis of the lifetime fractional intensities correlates the binding constants with ionic strength and supports the presence of electrostatic effects at both sites. A Debye,Hückel approach, applied to extrapolate the electrostatic free energy contribution vs. pH at vanishing ionic strength, gives interesting clues on the effective charge felt by the ANS ligands in the proximity of each site. In particular, binding is found to parallel the aspartate and glutamate titrations between pH 3 and pH 4.5; the "surface" site mainly responds to the presence of these local titrating charges while the "internal" site more closely follows the overall protein net charge. [source]

Influence of methotrexate exposure on outcome in patients treated with MBVP chemotherapy for primary central nervous system lymphoma

Hélène Blasco
WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT Although treated using the same high-dose methotrexate (HD-MTX)-based multiagent chemotherapy, patients with primary central nervous system lymphoma (PCNSL) have significant differences in outcome. However, little information has been published about factors influencing outcome in PCNSL. As it is known that the pharmacokinetics of MTX vary considerably between subjects leading to different exposure in patients receiving the same dose, it is important to evaluate its role in response to chemotherapy. WHAT THIS STUDY ADDS This study is the first to evaluate the exposure,response relationship in patients treated with MBVP chemotherapy. We found that patients who were early non-responders to MBVP chemotherapy had poor survival, whatever the salvage regimen. Tumour response at early evaluation was not associated with MTX pharmacokinetics and increasing the dose would probably not improve results. AIMS Although the standard treatment for primary central nervous system lymphoma (PCNSL) consists of three cycles of MBVP (methotrexate, BCNU, VP16, methylprednisolone) and radiotherapy, early failure of treatment may require modification of the treatment. However, our understanding of the outcome in such patients and of the factors involved in early failure of treatment is poor. In addition to known prognostic factors, we evaluated the influence of methotrexate (MTX) exposure on the response to MBVP chemotherapy in patients treated for PCNSL after the first two cycles. METHODS We retrospectively analyzed all patients with PCNSL treated with the MBVP regimen over the previous 10 years. Clinical, personal data and known prognostic factors were studied. The parameters of MTX exposure were estimated using a population pharmacokinetic approach with NONMEM. Objective response (OR), overall survival (OS) and failure-free survival (FFS) were evaluated in all patients. RESULTS Thirty-seven patients were studied. We observed lower FFS and OS (0.49 years) in patients who were not able to receive the planned treatment (group 1, n= 12) than in those who received three cycles (8.04 years) (group 2, n= 25). Known prognostic factors were comparable in both groups, but mean dose of MTX and mean AUC tended to be lower in patients who failed prematurely or showed no response after two cycles. CONCLUSIONS We found that patients who were early non-responders to MBVP chemotherapy had poor survival, without major influence of MTX exposure. It is thus probably unlikely that increasing the dose of MTX would improve outcome. [source]

Magnetic quantification of urban pollution sources in atmospheric particulate matter

S. Spassov
SUMMARY A new method is presented for fast quantification of urban pollution sources in atmospheric particulate matter (PM). The remanent magnetization of PM samples collected in Switzerland at sites with different exposures to pollution sources is analysed. The coercivity distribution of each sample is calculated from detailed demagnetization curves of anhysteretic remanent magnetization (ARM) and is modelled using a linear combination of appropriate functions which represent the contribution of different sources of magnetic minerals to the total magnetization. Two magnetic components, C1 and C2, are identified in all samples. The low-coercivity component C1 predominates in less polluted sites, whereas the concentration of the higher-coercivity component C2 is large in urban areas. The same sites were monitored independently by Hüglin using detailed chemical analysis and a quantitative source attribution of the PM. His results are compared with the magnetic component analysis. The absolute and relative magnetic contributions of component C2 correlate very well with absolute and relative mass contributions of exhaust emissions, respectively. Traffic is the most important PM pollution source in Switzerland: it includes exhaust emissions and abrasion products released by vehicle brakes. Component C2 and traffic-related PM sources correlate well, which is encouraging for the implementation of non-destructive magnetic methods as an economic alternative to chemical analysis when mapping urban dust pollution. [source]

Long-term investigations of the snow cover in a subalpine semi-forested catchment

Manfred Stähli
Abstract To improve spring runoff forecasts from subalpine catchments, detailed spatial simulations of the snow cover in this landscape is obligatory. For more than 30 years, the Swiss Federal Research Institute WSL has been conducting extensive snow cover observations in the subalpine watershed Alptal (central Switzerland). This paper summarizes the conclusions from past snow studies in the Alptal valley and presents an analysis of 14 snow courses located at different exposures and altitudes, partly in open areas and partly in forest. The long-term performance of a physically based numerical snow,vegetation,atmosphere model (COUP) was tested with these snow-course measurements. One single parameter set with meteorological input variables corrected to the prevailing local conditions resulted in a convincing snow water equivalent (SWE) simulation at most sites and for various winters with a wide range of snow conditions. The snow interception approach used in this study was able to explain the forest effect on the SWE as observed on paired snow courses. Finally, we demonstrated for a meadow and a forest site that a successful simulation of the snowpack yields appropriate melt rates. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Devaluation Expectations and the Stock Market: a new measure and an application to Mexico 1994/95

Torbjörn Becker
Abstract This paper develops a market-based measure of devaluation expectations derived from the relative stock market performance of companies with different exposures of current and future profits to exchange-rate changes. The measure can be viewed as a complement to measures of devaluation expectations based on interest-rate-parity conditions, survey data or macroeconomic models. Some of the benefits of the measure are that data are available on a timely basis and that the stock market has traditionally been free of central bank intervention. As an illustration, we examine the Mexican devaluation of 1994. Contrary to what might have been expected given the alleged peso overvaluation, high-net-exporting firms outperformed the market beginning in late 1993. This pattern is, on the other hand, consistent with forward-looking stock prices that assigned an increasing probability to a devaluation benefiting exporting firms. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Effects of different exposures of hyperbaric oxygen on ligament healing in rats

Yoshimasa Ishii
Hyperbaric oxygen (HBO) is a method of augmenting, intermittently, oxygen availability to tissues. We examined the effect of three different HBO exposures on the healing of experimentally induced ligament lacerations in the right hind limb of 44 male Wistar rats. Animals were divided into four groups after ligament injury: (a) control group, animals breathed room air at 1 ATA (atmosphere absolute) in a hyperbaric chamber for 60 min; (b) HBO treatment at 1.5 ATA for 30 min once a day, (c) HBO treatment at 2 ATA for 30 min once a day, (d) 2 ATA for 60 min once a day. At 14 days post-ligament injury, we compared the ligaments of the four treatment groups for gross appearance, histology and expression of pro-,(I) mRNA by northern hybridization. Our results indicate that HBO was effective in promoting ligament healing compared to control (p < 0.01). Of these three exposures, HBO at 2 ATA for 60 min was the most effective, resulting in enhanced extra-cellular matrix deposition as measured by collagen synthesis. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source]

Stratigraphic and environmental implications of a large ice-wedge cast at Tjæreborg, Denmark

Else Kolstrup
Abstract Exceptionally large ice-wedge casts and composite-wedge casts occur together with involutions (cryoturbations) in a gravel pit near Tjæreborg, western Jutland. The filling reveals distinctly different, vertically-orientated sedimentary units, suggesting discrete events. Variations in wedge structure and infill between the different exposures suggest differences with alternating pools and drier conditions over the former wedges. In an attempt to date and correlate crack development a perusal of local glacial history is given and optically-stimulated-luminescence (OSL) dates are presented. A review of Saalian and early Weichselian wedge casts and deep involutions in other areas in northwest Europe is provided for correlation. It is suggested that the cracking in Tjæreborg took place during the Saale or/and early Weichselian. The existence of such old wedges shows that the present land surface has probably existed since the Saalian, leaving the ground available for cracking and infilling during succeeding periods of permafrost. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Insecticidal activity of 23 essential oils and their major compounds against adult Lipaphis pseudobrassicae (Davis) (Aphididae: Homoptera)

Blair J Sampson
Abstract Essential oils from 23 species of plants comprising 14 genera and 4 plant families were obtained by Clevenger-type water distillation. The major compounds in these essential oils were identified with GC-MS and their insecticidal activity against adult turnip aphids, Lipaphis pseudobrassicae (Davis), tested with dosage-mortality bioassays. We examined mortality only for viviparous adults because sizeable aphid populations on crucifer (Brassicaceae) hosts are largely produced by these wingless, parthenogenic females. Twenty-two of the oils were directly applied to aphid females in randomized blocks at concentrations of 0.0, 1.0, 2.5, 5.0 and 10.0 mg ml,1. Essential oils mixed with a non-toxic emulsifying agent, dimethyl sulfoxide (DMSO), more easily penetrated the waxy insect cuticle. Probit analysis and LC50 at three different exposures showed aphids were quickly incapacitated and killed by aliphatic aldehydes, phenols and monocyclic terpenes contained in Bifora and Satureja oils and at applied concentrations as low as 0.3 to 1.0 mg ml,1. Only enough Pimpinella isaurica oil and its three phenylpropanoid fractions were available for testing at a single concentration of 10 mg ml,1. We could not spare any additional P. isaurica oil for testing at other concentrations. Phenylpropanoids isolated from P. isaurica oil when recombined or left naturally blended in the oil were highly bioactive against L. pseudobrassicae at 10 mg ml,1. Copyright © 2005 Society of Chemical Industry [source]

Leg length and age of puberty among men and women from a developing population: The Guangzhou Biobank Cohort study

C.M. Schooling
Objectives: Leg length and relative leg length are considered to be reliable markers of prepubertal living conditions. Cessation of leg growth, driven by estrogen, occurs earlier in puberty in girls than boys. We hypothesized that leg length and relative leg length, as sitting height to leg ratio, might have sex-specific associations with age of puberty. Methods: We used multivariable linear regression in 10,046 older (,50 years) Chinese from the Guangzhou Biobank Cohort Study (Phase 3) to examine the associations of recalled age of puberty (women: age of menarche, and men: mean age of first nocturnal emission, voice breaking, and first pubic hair) with subischeal leg length, sitting height to leg ratio, and sitting height. Results: Leg length and sitting height to leg ratio had different associations with age of puberty in men and women (P -values for interaction <0.001), but sitting height did not. Per year earlier puberty, legs were longer among men by 0.09 cm (95% confidence interval (CI) 0.01,0.18) and shorter among women by ,0.16 cm (95% CI ,0.20 to ,0.12). Further adjustment for age, hip size (as a marker of buttock fat), and several markers of childhood conditions did not obviate the difference in association by sex. Conclusions: Adult leg length and relative leg length (sitting height to leg ratio) may be biomarkers of different exposures in men and women, with corresponding implications for their interpretation as a biomarker of early life exposures. Am. J. Hum. Biol. 22:683,687, 2010. © 2010Wiley-Liss, Inc. [source]

Zoospores of Three Arctic Laminariales Under Different UV Radiation and Temperature Conditions: Exceptional Spectral Absorbance Properties and Lack of Phlorotannin Induction

Ruth Müller
Phlorotannins have often been considered to act as UV-protective compounds in zoospores of brown algae. However, only the absorption characteristics of zoospores under UV exposure have been determined and no data are available on the actual content of phlorotannins or on temperature,UV interactions. Therefore, we determined the absorbance spectra and the phlorotannin contents in zoospore suspensions of three Arctic species (Saccharina latissima, Laminaria digitata, Alaria esculenta), and in the media surrounding zoospores after exposure to different radiation (400,700, 320,700, 295,700 nm) and temperature (2,18°C) conditions for 8 h. Absorption typical of phlorotannins with a maximum at 276 nm was monitored in zoospore suspensions as well as in the media surrounding zoospores, but the results depended strongly on radiation treatments and on zoospore densities. Surprisingly, the content of UV-absorbing phlorotannins subsequent to different exposures did not change in any of the three species. The observed exceptional absorption properties could, therefore, not be related to phlorotannin contents. These findings are discussed in light of a strong phlorotannin investment from sporophytes during spore release and a minor UV-protective role of phlorotannins for zoospores of Arctic kelp species. [source]

The influence of sociodemographic characteristics on agreement between self-reports and expert exposure assessments,

Grace Sembajwe ScD
Abstract Background Often in exposure assessment for epidemiology, there are no highly accurate exposure data and different measurement methods are considered. The objective of this study was to use various statistical techniques to explore agreement between individual reports and expert ratings of workplace exposures in several industries and investigate the sociodemographic influences on this agreement. Methods A cohort of 1,282 employees at 4 industries/14 worksites answered questions on workplace physical, chemical, and psychosocial exposures over the past 12 months. Occupational hygienists constructed job exposure matrices (JEMs) based on worksite walkthrough exposure evaluations. Worker self-reports were compared with the JEMs using multivariable analyses to explore discord. Results There was poor agreement between the self-reported and expert exposure assessments, but there was evidence that agreement was modified by sociodemographic characteristics. Several characteristics including gender, age, race/ethnicity, hourly wage and nativity strongly affected the degree of discord between self-reports and expert raters across a wide array of different exposures. Conclusions Agreement between exposure assessment tools may be affected by sociodemographic characteristics. This study is cross-sectional and therefore, a snapshot of potential exposures in the workplace. Nevertheless, future studies should take into account the social contexts within which workplace exposures occur. Am. J. Ind. Med. 53:1019,1031, 2010. © 2010 Wiley-Liss, Inc. [source]

Attributable fractions for partitioning risk and evaluating disease prevention: a practical guide

Geir E. Eide
Abstract Introduction:, The attributable fraction (AF) is used for quantifying the fraction of diseased ascribable to one or more exposures. The methodology and software for its estimation has undergone a considerable development during the last decades. Objectives:, To introduce methods for: (i) apportioning excess risk to multiple exposures, groups of exposures and subpopulations; (ii) graphical description; and (iii) survival data. Results:, Adjusted, sequential and average AFs are reasonable measures obtainable with standard software. The latter two both sum up to the combined AF for a set of exposures. The average AFs are independent of the exposures' ordering. For an ordered, preventive strategy, scaled sample space cubes illustrate the effects on the risk of disease from stepwise exposure removal. Pie charts illustrate the portions of the total risk ascribed to different exposures or risk-profiles. Attributable hazard fraction, AF before time t, and AF within study incorporate time to disease and interventions. Conclusions:, The practice of crude calculations of AFs in epidemiology should be abandoned. Further development of methods for AFs with survival data and possibly linking it to causal modelling is of interest. Please cite this paper as: Eide GE. Attributable fractions for partitioning risk and evaluating disease prevention: a practical guide. The Clinical Respiratory Journal 2008; 2: 92,103. [source]

Equivalent Pharmacokinetics of Mycophenolate Mofetil in African-American and Caucasian Male and Female Stable Renal Allograft Recipients

Mark D. Pescovitz
African-American (AA) renal transplant recipients require higher doses of mycophenolate mofetil (MMF) than Caucasians. A hypothesized pharmacokinetic (PK) difference was tested in stable renal transplant recipients. Whole blood was collected before, and 20, 40 and 75 min, and 2, 3, 4, 6, 8 and 12 h after the MMF dose. Mycophenolic acid (MPA) and its glucuronide metabolite (MPAG) were analyzed using HPLC. Analysis of variance was performed for the primary end-points of dose-adjusted PK parameters AUC0,12 and Cmax of MPA using log-transformed values. Differences between races and genders were estimated: 90% confidence intervals (CI) were calculated. Back-transformation gave estimates of the race and gender ratio and their CI. Equivalence of the groups was determined if the 90% confidence limits were included in the interval (0.80, 1.25). The calculated PK parameters were comparable among the four subgroups (Caucasian, AA, Male, Female). The 90% CIs for the ratio of dose-adjusted AUC0,12 of MPA between races were between 89.7 and 112.9%. There were no race, gender or race-by-gender effects (p-values = 0.196) nor differences between diabetics and nondiabetics. This study demonstrates that dosing requirement for MMF in AA and Caucasians is unlikely to be related to different exposures to MPA. [source]