bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modifications in cell cycle kinetics and in expression of G1 phase‐regulating proteins in human amniotic cells after exposure to electromagnetic fields and ionizing radiation
Authors: Lange S. , Viergutz T. , Simkó M. 
Published: September 2004

Abstract.  Low‐frequency electromagnetic fields are suspected of being involved in carcinogenesis, particularly in processes that could be related to cancer promotion. Because development of cancer is associated with deregulated cell growth and we previously observed a magnetic field‐induced decrease in DNA synthesis [Lange et al. (2002) Alterations in the cell cycle and in the protein level of cyclin D1p, 21CIP1, and p16INK4a after exposure to 50 HZ. MF in human cells. Radiat. Environ. Biophys.41, 131], this study aims to document the influence of 50 Hz, 1 mT magnetic fields (MF), with or without initial γ‐ionizing radiation (IR), on the following cell proliferation‐relevant parameters in human amniotic fluid cells (AFC): cell cycle distribution, expression of the G1 phase‐regulating proteins Cdk4, cyclin D1, p21CIP1 and p16INK4a, and Cdk4 activity. While IR induced a G1 delay and a dose‐dependent G2 arrest, no discernible changes in cell cycle kinetics were observed due to MF exposure. However, a significant decrease in the protein expression of cyclin D1 and an increase in p21CIP1‐ and p16INK4a‐expression could be detected after exposure to MF alone. IR‐exposure caused an augmentation of p21CIP1‐ and p16INK4a‐ levels as well, but did not alter cyclin D1 expression. A slight diminution of Cdk4 activity was noticed after MF exposure only, indicating that Cdk4 appears not to act as a mediator of MF‐ or IR‐induced changes in the cell cycle of AFC cells. Co‐exposure to MF/IR affected neither cell cycle distribution nor protein expression or kinase activity additionally or synergistically, and therefore MF seems not to modify the mutagenic potency of IR.
Endothelial markers in chronic heart failure: training normalizes exercise‐induced vWF release
Authors: Sabelis L. W. E. , Senden P. J. , Fijnheer R. , De Groot P. G. , Huisveld I. A. , Mosterd W. L. , Zonderland M. L. 
Published: September 2004

AbstractBackground  Chronic heart failure (CHF) is characterized by endothelial dysfunction. Vascular endothelium is important for control of haemostasis and vasoregulation. The aim of the present study was to investigate plasma levels of several endothelial markers and the exercise‐induced changes on these plasma levels in CHF patients. Subsequently, the effect of a 6‐month training programme on these markers is described.Materials and methods  Twenty‐nine male CHF patients (NYHA II/III, age 60 ± 8 year, body mass index 26·7 ± 2·3 kg m−2, left ventricular ejection fraction 26·3–7·2%; mean ± SD) participated. Patients were randomly assigned to a training or control group. Training (26 weeks; combined strength and endurance exercises) was four sessions/week: two sessions supervised and two sessions at home. Before and after intervention, anthropometry, endothelial markers (haemostasis and vasoregulation), maximal workload and peak oxygen uptake were assessed.Results  Physical training positively affected maximal workload. Plasma levels of endothelial markers were not affected by physical training and not related to exercise tolerance. After training, stimulated (maximal exercise) plasma von Willebrand Factor (vWF) release was present, whereas at baseline this release was absent.Conclusion  Physical training led to normalization of the stimulated plasma vWF release. Plasma levels of other endothelial markers were not affected by physical training either at rest or under stimulated (maximal exercise) conditions.
Do gene–environment interactions influence fasting plasma lipids? A study of twins
Authors: Greenfield J. R. , Samaras K. , Jenkins A. B. , Kelly P. J. , Spector T. D. , Campbell L. V. 
Published: September 2004

AbstractBackground  The aims of this study were to determine the influence of smoking, alcohol consumption, physical activity and hormone replacement therapy (HRT) on lipids, independently of genetic factors, and to detect whether gene–environment interactions influence these associations.Materials and methods  Fasting plasma total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides, apolipoproteins AI and B and lipoprotein(a) were measured in 685 female twins (96 monozygotic, 230 dizygotic pairs and 33 singletons).Results  Smokers had higher triglyceride and lower HDL cholesterol levels than never‐smokers (P < 0·001). After controlling for genetic influences, smoking accounted for 0·35 mmol L−1 and 0·22 mmol L−1 differences in triglyceride and HDL cholesterol levels, respectively (P < 0·005), remaining significant after excluding alcohol‐discordant twin pairs. In a gene–environment interaction analysis, the association between smoking and triglycerides was exaggerated in subjects at high genetic risk of hypertriglyceridaemia (interaction P = 0·04). All levels of alcohol consumption were associated with higher HDL cholesterol levels than abstinence, but only moderate alcohol consumers had lower LDL cholesterol and triglyceride levels. In monozygotic twins concordant for smoking, an alcohol intake > 10 units week−1 accounted for a 0·32 mmol L−1 difference in LDL cholesterol, independently of genetic effects (P = 0·04). In postmenopausal women, those using HRT had 0·54 mmol L−1 lower LDL cholesterol and 0·21 µmol L−1 lower lipoprotein(a) levels than nonusers (P < 0·001 and P = 0·04, respectively); these differences were attenuated after accounting for genetic effects in monozygotic twins. Although physically active subjects had higher levels of HDL cholesterol than nonactive subjects, this was nonsignificant after adjusting for genetic factors.Conclusions  Smoking‐induced aberrations in HDL cholesterol and triglycerides and alcohol‐related differences in LDL cholesterol were independent of genetic influences. The association between smoking and hypertriglyceridaemia was accentuated in high genetic risk individuals.
Precocious puberty at an endocrine centre in Jordan
Authors: Taher B. M. , Ajlouni H. K. , Hamamy H. A. , Shegem N. S. , Madanat A. Y. , Ajlouni K. M. 
Published: September 2004

AbstractBackground  Data from developed countries about precocious puberty are abundant; data from developing countries are limited. Causes are different, and diagnostic and treatment possibilities are very expensive. The present study aimed to display the spectrum of initial presentation and aetiology among children with precocious puberty and to assess any association between th e clinical features and the underlying cause of the condition.Patients and method  Forty‐three girls and seven boys with precocious puberty were diagnosed at the Endocrine Clinic of Jordan University Hospital and at The National Center for Diabetes, Endocrinology and Genetics, Amman, Jordan, between the 1984 and 2003.Results  Mean age for the girls with precocious puberty was 4·1 years ± 2·5 SD and for the boys was 2·4 years ± 1·9 SD. Among the girls, 21% presented with breast development only, 9% with pubic hair appearance only and 70% with multiple signs. All the boys presented with pubic hair appearance and enlarged genitalia. Organic causes for precocious puberty were detected in 42% of the girls and in all the boys. Idiopathic precocious puberty was more common among the girls presenting with breast development only (89%) compared with those presenting with multiple presenting signs (50%), and also was more common among girls presenting between 6 and 8 years (82%) than among those presenting < 6 years of age (42%). Congenital adrenal hyperplasia was diagnosed in four boys and four girls, and hypothyroidism in three girls.Conclusion  Precocious puberty in the girls was usually of idiopathic origin when it presented with breast development only and at age older than 6 years. Congenital adrenal hyperplasia and hypothyroidism could represent important causes for precocious puberty in our community.
Resistance and resilience of stream insect communities to repeated hydrologic disturbances after a wildfire
Authors: Vieira Nicole K. M. , Clements William H. , Guevara Lynette S. , Jacobs Brian F. 
Published: September 2004

Summary1. Wildfires are often followed by severe, sediment‐laden floods in burned catchments. In this study, we documented resistance and resilience of stream insect communities to repeated postfire flash floods in a ‘burned stream’. We employed a before‐after‐control‐impact (BACI) design, where communities in comparable reaches of a burned stream and a reference stream were sampled from 2 years before, to 6 years after, a crown wildfire in north‐central New Mexico.2. The first 100‐year flood following the 1996 Dome wildfire reduced total insect density and taxon richness to near zero in the burned stream. Despite showing low resistance, density returned rapidly to prefire levels because of colonisation by simuliids, chironomids and the mayfly Baetis tricaudatus. In general, taxa that were generalist feeders (collectors) with strong larval dispersal dominated communities in early postfire years with repeated, moderate flash floods.3. Taxon richness and community composition were less resilient to postfire hydrologic disturbances. Taxon richness did not recover until floods dampened 4 years after the fire. Despite hydrologic recovery, composition in the burned stream still differed from prefire and reference stream compositions after 6 years postfire. A unique assemblage, dominated by taxa with strong larval or adult dispersal, was established after flash floods abated. Specialist feeders (shredders and grazers) that were common in prefire years were reduced or absent in the postfire assemblage.4. Community succession in the burned stream was explained by the interaction between species traits, geographic barriers to colonisation and hydrologic conditions after the fire. Comparable changes in insect density, taxon richness, community composition and trait representation were not found in the reference stream, providing strong evidence that repeated postfire flash floods shaped community responses in the burned stream.
Contradictory results from different methods for measuring direction of insect flight
Authors: Macneale Kate H. , Peckarsky Barbara L. , Likens Gene E. 
Published: September 2004

Summary1. Stream ecologists have been puzzled by the apparent paradox that invertebrate populations persist in headwater streams despite the high frequency with which individuals drift downstream. To resolve this ‘drift paradox’, directions and distances of both larval and adult movement must be identified. Using over 50 interception traps in combination with results from several mark–capture experiments using 15N as a label, we tested the assumption that interception traps accurately represent the ultimate direction of adult insect flight.2. In several streams in the Hubbard Brook Experimental Forest, 76% of 15N‐labelled stoneflies (Leuctra ferruginea) had flown upstream from where they emerged to where they were captured. In contrast, over 60% of stoneflies were flying downstream when captured, i.e. on the upstream side of an interception trap.3. The instantaneous direction, as indicated by the side of the interception trap on which they were captured, indicated the ultimate flight direction for fewer than 1/3 of the individuals captured. Thus, such traps did not accurately reflect the ultimate flight patterns of individuals, as indicated by mark–capture data.4. Conclusions drawn from interception trap counts regarding the direction of movement and the distribution and persistence of populations may need to be re‐evaluated. We suggest that better tracking methods, including mass mark–capture studies using stable isotopes, be used to evaluate the potentially complex patterns of adult insect movement and the consequences of that movement for individuals and populations.
A deep maximum of green sulphur bacteria (‘Chlorochromatium aggregatum’) in a strongly stratified reservoir
Authors: Chapin Bridgett R. K. , DeNoyelles Frank , Graham David W. , Smith Val H. 
Published: September 2004

Summary1. Fine‐scale physical and chemical gradients and deep photosynthetic microbial populations were assessed to provide an initial characterisation of a small, thermally stratified reservoir (Cross Reservoir, Kansas, U.S.A.) and its deep chlorophyll maxima (DCM). Factors were identified that may affect vertical positioning of subepilimnetic photosynthetic sulphur bacteria (PSB) in lakes.2. Results indicate that Cross Reservoir is a mesotrophic, dimictic lake with large subepilimnetic chlorophyll maxima containing dense layers of PSB. Characteristics of the deep PSB community of Cross Reservoir strongly correlate with both light and nutrient gradients.3. The deep bacterial community mostly contained single‐celled and aggregating green sulphur bacteria, specifically free‐livingChlorobium limicolaand the conspicuous motile ectosymbiotic consortium known as ‘Chlorochromatium aggregatum’. The bacteria were within the anaerobic hypolimnion, beneath a metalimnetic plate ofCryptomonasspp. and within very low sulphide and light conditions [mean of 67 μgS L−1and 0.05% photosynthetically active radiation (PAR)]. Pigment concentrations and fluorescence trends indicate that the bacteria made up a larger proportion of the DCM biomass than did phytoplankton in 1996.4. Cross Reservoir shares characteristics with natural lakes world‐wide that also include a deep PSB community containing dense layers of ‘C. aggregatum’. Correlation analyses indicate that PSB community positioning and density are related to light, sulphide supply, redox potentials and pH. A 2‐factor principal components analysis (PCA) and other data trends supported these interpretations and indicated that PSB are sensitive to the thermal stability of the water column, are nitrogen limited and regulated more by sulphide or sulphide to light ratios than local levels of light. The sensitivity of these deep photosynthetic bacteria to environmental gradients, and their significance to some aquatic systems, demonstrate their potential as indicators of environmental disturbance.
Dissolved organic matter in small streams along a gradient from discontinuous to continuous permafrost
Authors: Kawahigashi Masayuki , Kaiser Klaus , Kalbitz Karsten , Rodionov Andrej , Guggenberger Georg 
Published: September 2004

AbstractThe Yenisei river passes every type of permafrost regime, from south to north, being characterized by increasing continuity of the permafrost and by decreasing thickness of the active layer. We used that situation to test the hypothesis that amounts and properties of dissolved organic matter (DOM) in small streams draining forested catchments respond to different permafrost regimes. Water samples were taken from eight tributaries along the Yenisei between 67°30′N and 65°49′N latitude. The samples were analysed for dissolved organic carbon (DOC) and nitrogen (DON) and DOM was characterized by its chemical composition (XAD‐8 fractionation, sugars, lignin phenols, amino acids, protein, UV and fluorescence spectroscopy), and its biodegradability. Most properties of the tributary waters varied depending on latitude. The higher the latitude, the higher were DOC, DON and the proportion of the hydrophobic fraction of DOC. The contribution of hexoses and pentoses to DOC were higher in southern tributaries; on the other hand, phenolic compounds were more abundant in northern tributaries. Mineralizable DOC ranged between 4% and 28% of total DOC. DOM in northern tributaries was significantly (P<0.05) less biodegradable than that in southern tributaries reflecting the differences in the chemical properties of DOM. Our results suggest that the differences in DOM properties are mainly attributed to differences of permafrost regime, affecting depth of active layer, soil organic matter accumulation and vegetation. Soil organic matter and vegetation determine the amount and composition of DOM produced in the catchments while the depth of the active layer likely controls the quantity and quality of DOM exported to streams. Sorptive interactions of DOM with the soil mineral phase typically increase with depth. The results imply that a northern shift of discontinuous permafrost likely will change in the long term the input of DOM into the Yenisei and thus probably into the Kara Sea.
Dynamics of carbon stocks in soils and detritus across chronosequences of different forest types in the Pacific Northwest, USA
Authors: Sun Osbert J. , Campbell John , Law Beverly E. , Wolf Vernon 
Published: September 2004

AbstractWe investigated variation in carbon stock in soils and detritus (forest floor and woody debris) in chronosequences that represent the range of forest types in the US Pacific Northwest. Stands range in age from <13 to >600 years. Soil carbon, to a depth of 100 cm, was highest in coastal Sitka spruce/western hemlock forests (36±10 kg C m−2) and lowest in semiarid ponderosa pine forests (7±10 kg C m−2). Forests distributed across the Cascade Mountains had intermediate values between 10 and 25 kg C m−2. Soil carbon stocks were best described as a linear function of net primary productivity (r2=0.52), annual precipitation (r2=0.51), and a power function of forest floor mean residence time (r2=0.67). The highest rates of soil and detritus carbon turnover were recorded on mesic sites of Douglas‐fir/western hemlock forests in the Cascade Mountains with lower rates in wetter and drier habitats, similar to the pattern of site productivity. The relative contribution of soil and detritus carbon to total ecosystem carbon decreased as a negative exponential function of stand age to a value of ∼35% between 150 and 200 years across the forest types. These age‐dependent trends in the portioning of carbon between biomass and necromass were not different among forest types. Model estimates of soil carbon storage based on decomposition of legacy carbon and carbon accumulation following stand‐replacing disturbance showed that soil carbon storage reached an asymptote between 150 and 200 years, which has significant implications to modeling carbon dynamics of the temperate coniferous forests following a stand‐replacing disturbance.
Neighbour identity modifies effects of elevated temperature on plant performance in the High Arctic
Authors: Dormann Carsten F. , Van Der Wal René , Woodin Sarah J. 
Published: September 2004

AbstractCompetition among plants in extreme environments such as the High Arctic has often been described as unimportant, or even nonexistent; environmental factors are thought to overrule any negative plant–plant interactions. However, few studies have actually addressed this question experimentally in the Arctic, and those that did found only little evidence for competition. Such species interactions will presumably become more important in the future, as Global Climate Change takes effect on terrestrial ecosystems. We investigated plant–plant interactions in the High Arctic, following the growth of Luzula confusa and Salix polaris in pure and mixed stands, and under elevated‐temperature treatment over 2 years. To understand the mechanisms of competition, a parallel experiment was undertaken in phytotrons, manipulating competition, temperature and nutrient availability. Our findings indicate that competition is acting in the natural vegetation, and that climatic warming will alter the balance of interactions in favour of the dwarf shrub S. polaris. The phytotron experiment suggested that the mechanism is a higher responsiveness of Salix to nutrient availability, which increased under warming in the field. While Luzula showed a positive response to higher temperature in the lab, its performance in mixed stands in the field was actually reduced by warming, indicating a competitive repression of growth by Salix. The growth of Salix was also reduced by the presence of Luzula, but it was still able to profit from warming. Our findings suggest that climatic warming will result in greater shrub dominance of High Arctic tundra, but we also conjecture that grazing could reverse the situation to a graminoid‐dominated tundra. These two divergent scenarios would have different implications for ecosystem feedbacks to climatic change.
Estimates of CO2 uptake and release among European forests based on eddy covariance data
Authors: Van Dijk Albert I. J. M. , (HAN) Dolman A. J. 
Published: September 2004

AbstractThe net ecosystem exchange (NEE) of forests represents the balance of gross primary productivity (GPP) and respiration (R). Methods to estimate these two components from eddy covariance flux measurements are usually based on a functional relationship between respiration and temperature that is calibrated for night‐time (respiration) fluxes and subsequently extrapolated using daytime temperature measurements. However, respiration fluxes originate from different parts of the ecosystem, each of which experiences its own course of temperature. Moreover, if the temperature–respiration function is fitted to combined data from different stages of biological development or seasons, a spurious temperature effect may be included that will lead to overestimation of the direct effect of temperature and therefore to overestimates of daytime respiration. We used the EUROFLUX eddy covariance data set for 15 European forests and pooled data per site, month and for conditions of low and sufficient soil moisture, respectively. We found that using air temperature (measured above the canopy) rather than soil temperature (measured 5 cm below the surface) yielded the most reliable and consistent exponential (Q10) temperature–respiration relationship. A fundamental difference in air temperature‐based Q10 values for different sites, times of year or soil moisture conditions could not be established; all were in the range 1.6–2.5. However, base respiration (R0, i.e. respiration rate scaled to 0°C) did vary significantly among sites and over the course of the year, with increased base respiration rates during the growing season. We used the overall mean Q10 of 2.0 to estimate annual GPP and R. Testing suggested that the uncertainty in total GPP and R associated with the method of separation was generally well within 15%. For the sites investigated, we found a positive relationship between GPP and R, indicating that there is a latitudinal trend in NEE because the absolute decrease in GPP towards the pole is greater than in R.