bluuebunny/crossref_metadata_2025_split huggingface dataset:
Different measures of smoking exposure and mammographic density in postmenopausal Norwegian women: a cross-sectional study
Authors: Bremnes Yngve , Ursin Giske , Bjurstam Nils , Gram Inger T 
Published: October 2007

Abstract
Background
Recent cohort studies have suggested an increased risk of breast cancer with long duration of smoking, and with smoking initiation before first birth. Cigarette smoking may have both carcinogenic effects and antiestrogenic effects on the breast tissue. We decided to examine the relationship between different measures of smoking exposure and mammographic density.

Methods
Lifetime smoking history was collected through interview and questionnaires among 907 postmenopausal participants in the Tromsø Mammography and Breast Cancer study. The mammograms were obtained from the governmental Norwegian Breast Cancer Screening Program. Mammograms were classified according to the percentage and absolute mammographic densities using a previously validated computer-assisted method.

Results
Sixty-five percent of the women reported having ever smoked cigarettes, while 34% were current smokers. After adjustment for age, age at first birth, parity, age at menopause, postmenopausal hormone therapy use, and body mass index, smoking was inversely associated with both measures of mammographic density (both trends P < 0.01). Both current smokers and former smokers had significantly lower adjusted mean percentage mammographic density compared with never smokers (P = 0.003 and P = 0.006, respectively). An inverse dose–response relationship with mammographic density was found between both the number of cigarettes and the number of pack-years smoked among current smokers. Current smokers who smoked 11 cigarettes or more daily had a 3.7% absolute (36% relative difference) lower percentage mammographic density compared with current smokers who smoked seven cigarettes or less daily (P = 0.008). When former smokers were stratified according to time since smoking cessation, we found that women who had stopped smoking less than 24 years ago had a significantly lower mean percentage mammographic density compared with never smokers (P < 0.001).

Conclusion
We found modest inverse dose–response associations between numbers of cigarettes and of pack-years smoked and both measures of mammographic density among current smokers. Former smokers who had stopped smoking less than 24 years ago also had a statistically significantly lower mean percentage mammographic density when compared with never smokers. These findings are consistent with an antiestrogenic effect of cigarette smoking on the breast tissue.
Impaired thymic selection in mice expressing altered levels of the SLP-76 adaptor protein
Authors: Ramsey Kimberley , Luckashenak Nancy , Koretzky Gary A , Clements James L 
Published: October 2007

AbstractIntracellular signaling initiated by ligation of the TCR influences cell fate at multiple points during the lifespan of a T cell. This is especially evident during thymic selection, where the nature of TCR-dependent signaling helps to establish a MHC-restricted, self-tolerant T cell repertoire. The Src homology 2 domain-containing leukocyte-specific phosphoprotein of 76 kDa (SLP-76) adaptor protein is a required intermediate in multiple signaling pathways triggered by TCR engagement, several of which have been implicated in dictating the outcome of thymic selection (e.g., intracellular calcium flux and activation of ERK family MAPKs). To determine if thymocyte maturation and selection at later stages of development are sensitive to perturbations in SLP-76 levels, we analyzed these crucial events using several transgenic (Tg) lines of mice expressing altered levels of SLP-76 in the thymus. In Tg mice expressing low levels of SLP-76 in preselection thymocytes, the CD4:CD8 ratio in the thymus and spleen was skewed in a manner consistent with impaired selection and/or maturation of CD4+ thymocytes. Low SLP-76 expression also correlated with reduced CD5 expression on immature thymocytes, consistent with reduced TCR signaling potential. In contrast, reconstitution of SLP-76 at higher levels resulted in normal thymic CD5 expression and CD4:CD8 ratios in the thymus and periphery. It is curious that thymic deletion of TCR-Tg (HY) thymocytes was markedly impaired in both lines of Tg-reconstituted SLP-76−/− mice. Studies using chimeric mice indicate that the defect in deletion of HY+ thymocytes is intrinsic to the developing thymocyte, suggesting that maintenance of sufficient SLP-76 expression from the endogenous locus is a key element in the selection process.
Management of L-Dopa related hyperhomocysteinemia: catechol-O-methyltransferase (COMT) inhibitors or B vitamins? Results from a review
Authors: Zoccolella Stefano , Iliceto Giovanni , deMari Michele , Livrea Paolo , Lamberti Paolo 
Published: October 2007

AbstractIn recent years, L-Dopa treatment has been indicated as an acquired cause of hyperhomocysteinemia (HHcy). The mechanism underlying L-Dopa-related HHcy is the O-methylation of the drug catalyzed by the enzyme catechol-O-methyltransferase (COMT). Folate and cobalamin status also influences the effects of L-Dopa on plasma homocysteine (Hcy) levels. Although clinical correlations of HHcy in Parkinson's disease still remain uncertain, management of elevated plasma Hcy levels has been advocated, due to multiple cytotoxic effects of Hcy on neurons. This review summarizes data available in the literature concerning the two main therapeutic approaches to L-Dopa-related HHcy (use of COMT inhibitors or B vitamins diet supplementation).Clin Chem Lab Med 2007;45:1607–13.
Quantitative profiling of folate and one-carbon metabolism in large-scale epidemiological studies by mass spectrometry
Authors: Ueland Per Magne , Midttun Øivind , Windelberg Amrei , Svardal Asbjørn , Skålevik Rita , Hustad Steinar 
Published: October 2007

AbstractClin Chem Lab Med 2007;45:1737–45.
Metabolic regulatory properties of S-adenosylmethionine and S-adenosylhomocysteine
Authors: Finkelstein James D. 
Published: October 2007

AbstractIn mammalian liver, two intersecting pathways, remethylation and transsulfuration, compete for homocysteine that has been formed from methionine. Remethylation of homocysteine, employing either methyltetrahydrofolate or betaine as the methyl donor, forms a methionine cycle that functions to conserve methionine. In contrast, the transsulfuration sequence – cystathionine synthase and cystathionase – serves to irreversibly catabolize the homocysteine while synthesizing cysteine. The rate of homocysteine formation and its distribution between these two pathways are the sites for metabolic regulation and coordination. The mechanisms for regulation include both the tissue content and the kinetic properties of the component enzymes as well as the concentrations of their substrates and other metabolic effectors. Adenosylmethionine and adenosylhomocysteine are important regulatory metabolites and may use one or more mechanisms to affect the enzymes. Adenosylmethionine is a positive effector of its own synthesis, cystathionine synthase and glycine methyltransferase but impairs both homocysteine methylases. Thus, the concentration of adenosylmethionine may be self-regulatory in mammalian liver. By means of other enzymatic mechanisms, the hepatic concentration of adenosylhomocysteine, an index of homocysteine accumulation, is also self-regulated. These considerations pertain primarily to liver, which has the unique capacity to synthesize more adenosylmethionine in the presence of excess methionine. However, there are organ-specific patterns of methionine metabolism and its regulation. All tissues possess the methionine cycle with methyltetrahydrofolate as the methyl donor but only liver, kidney, pancreas, intestine and brain also contain the transsulfuration pathway. The limitation of adenosylmethionine concentrations may make adenosylhomocysteine a more significant metabolic regulator in extrahepatic tissues. However, estimates of regulatory changes based on determinations of the plasma concentrations of the two metabolites are of limited value and must be used with caution. In addition, the recent description of “cystathionine (CBS) domains” in proteins not involved with methionine metabolism raises the possibility that abnormal concentrations of the adenosyl metabolites may impact on other metabolic pathways.Clin Chem Lab Med 2007;45:1694–9.
Measuring the Repassivation Potential of Alloy 22 Using the Potentiodynamic-Galvanostatic-Potentiostatic Method
Authors: Evans Kenneth J. , Rebak Raul B. 
Published: October 2007

Abstract
Traditionally, the susceptibility of Alloy 22 (N06022) to suffer crevice corrosion has been measured using the Cyclic Potentiodynamic Polarization (CPP) technique (ASTM G 61). When the alloy is not very susceptible to crevice corrosion, the values of repassivation potential obtained using the CPP technique are not highly reproducible. To circumvent the large uncertainty in the values of the repassivation potential by the CPP method, the repassivation potential of Alloy 22 may be measured using a slower method that combines sequentially potentiodynamic, galvanostatic, and potentiostatic treatments (this method is called the Tsujikawa-Hisamatsu Electrochemical or THE method). In the THE method the anodic charge is applied to the specimen in a more controlled manner, which avoids driving the alloy to transpassivity and therefore results in more reproducible repassivation potential values. Results using THE method under various testing conditions are presented. A new standard has been prepared for ASTM balloting for the THE method. The round robin matrix results are also discussed.
Optimal Dosing of Piperacillin‐Tazobactam for the Treatment of Pseudomonas aeruginosa Infections: Prolonged or Continuous Infusion?
Authors: Kim Aryun , Sutherland Christina A. , Kuti Joseph L. , Nicolau David P. 
Published: October 2007

Study Objective. To compare conventional intermittent dosing regimens of piperacillin‐tazobactam with prolonged and continuous infusions to determine the optimal dosing scheme against a local Pseudomonas aeruginosa population.Design. Pharmacodynamic Monte Carlo simulation model.Data Source. Microbiologic data from 470 consecutive nonduplicate P. aeruginosa isolates collected from a single institution over 6 months in 2006.Patients. Five thousand simulated surgical patients and patients with neutropenia.Measurements and Main Results. We simulated serum concentration‐time profiles at steady state for several piperacillin‐tazobactam dosing regimens, including intermittent, prolonged, and continuous infusions. The probability of achieving 50% free time above the MIC against 470 P. aeruginosa isolates was calculated. The cumulative fractions of response for the intermittent‐infusion regimens were 74.7% (3.375 g every 6 hrs), 79.9% (4.5 g every 6 hrs), and 85.6% (3.375 g every 4 hrs). For prolonged‐infusion regimens, the cumulative fractions of response were 83.3% (3.375 g every 8 hrs, 4‐hr infusion), 87.1% (4.5 g every 8 hrs, 4‐hr infusion), and 89.6% (4.5 g every 6 hrs, 3‐hr infusion). For continuous‐infusion regimens, the cumulative fractions of response were 82.3% (10.125 g), 86.5% (13.5 g), 89.2% (18 g), 90.0% (20.25 g), and 90.6% (22.5 g).Conclusion. Both prolonged‐ and continuous‐infusion strategies improved the pharmacodynamics of piperacillin‐tazobactam over those of traditional 30‐minute intermittent‐infusion regimens. Prolonged‐ and continuous‐infusion regimens that contained the same daily doses of piperacillin had similar likelihoods of bactericidal exposure. Thus, the selection of dosing strategy depends on the availability of intravenous access versus the convenience of once‐daily administration.
Creation of Engineered Human Embryonic Stem Cell Lines Using phiC31 Integrase
Authors: Thyagarajan Bhaskar , Liu Ying , Shin Soojung , Lakshmipathy Uma , Scheyhing Kelly , Xue Haipeng , Ellerström Catharina , Strehl Raimund , Hyllner Johan , Rao Mahendra S. , Chesnut Jonathan D. 
Published: October 2007

Abstract
It has previously been shown that the phage-derived phiC31 integrase can efficiently target native pseudo-attachment sites in the genome of various species in cultured cells, as well as in vivo. To demonstrate its utility in human embryonic stem cells (hESC), we have created hESC-derived clones containing expression constructs. Variant human embryonic stem cell lines BG01v and SA002 were used to derive lines expressing a green fluorescent protein (GFP) marker under control of either the human Oct4 promoter or the EF1α promoter. Stable clones were selected by antibiotic resistance and further characterized. The frequency of integration suggested candidate hot spots in the genome, which were mapped using a plasmid rescue strategy. The pseudo-attP profile in hESC differed from those reported earlier in differentiated cells. Clones derived using this method retained the ability to differentiate into all three germ layers, and fidelity of expression of GFP was verified in differentiation assays. GFP expression driven by the Oct4 promoter recapitulated endogenous Oct4 expression, whereas persistent stable expression of GFP expression driven by the EF1α promoter was seen. Our results demonstrate the utility of phiC31 integrase to target pseudo-attP sites in hESC and show that integrase-mediated site-specific integration can efficiently create stably expressing engineered human embryonic stem cell clones.
Disclosure of potential conflicts of interest is found at the end of this article.
Retinoic Acid and Bone Morphogenetic Protein Signaling Synergize to Efficiently Direct Epithelial Differentiation of Human Embryonic Stem Cells
Authors: Metallo Christian M. , Ji Lin , de Pablo Juan J. , Palecek Sean P. 
Published: October 2007

AbstractHuman embryonic stem cells (hESCs) can differentiate to various somatic lineages, including stratified squamous epithelia, although the molecular mechanisms of epithelial specification from hESCs currently remain undefined. Here, we demonstrate a novel, stage-specific effect of retinoic acid (RA) on epithelial differentiation of hESCs. RA strongly upregulated expression of keratin 18 and the transcription factor p63, which is involved in epidermal morphogenesis and ectodermal specification, while repressing early neural marker transcription. RA-induced hESCs efficiently differentiated to keratin 14-expressing epithelial cells, although this effect was dependent upon on the context of bone morphogenetic protein signaling. Furthermore, these hESC-derived keratinocytes could be subcultured to obtain relatively pure keratinocyte populations that retained the capacity to terminally differentiate. These findings suggest that RA plays an important role in epithelial differentiation of hESCs.Disclosure of potential conflicts of interest is found at the end of this article.
Competitive Mobilization of Phosphate and Arsenate Associated with Goethite by Root Activity
Authors: Vetterlein Doris , Szegedi Krisztian , Ackermann Juliane , Mattusch Jürgen , Neue Heinz‐Ulrich , Tanneberg Hartmut , Jahn Reinhold 
Published: October 2007

AbstractArsenate (AsV) is the predominant form of arsenic in soils under aerobic conditions and competes with the major plant nutrient phosphorus (P) in the form of phosphate (PV) not only for sorption sites on mineral surfaces in soil but also for root membrane transporters. Plants have evolved several mechanisms for the mobilization of PV in soils in response to P deficiency, such as the release of organic anions and protons. The aim of the present study was to test whether these mechanisms result in a simultaneous mobilization of arsenate and what would be the consequences for As transfer from soil to plant. The compartment system approach with Zea mays as model crop was chosen as an experimental setup. The system is equipped with micro suction cups and allowed us to investigate processes occurring in the vicinity of roots. As a case study, an artificial quartz substrate with well defined soil physical properties was fertilized, spiked with AsV, and amended with increasing amounts of goethite (0, 1, and 4 g kg−1 in treatments G‐0, G‐1, and G‐4, respectively). The addition of goethite alleviated the AsV‐induced growth reduction and reduced AsV transfer from the substrate to the plant but induced P deficiency at the same time. When low amounts of goethite (1 g kg−1) were added, plants mobilized PV but not AsV, which might be related to differences in surface complexation reported for PV and AsV No mobilization of PV or AsV was observed with the addition of higher amounts of goethite, probably because of decreasing competition between organic anions, PV, and AsV for binding sites.
Influence of Different Organic Amendments on the Degradation, Metabolism, and Adsorption of Terbuthylazine
Authors: Dolaptsoglou Christina , Karpouzas Dimitrios G. , Menkissoglu‐Spiroudi Urania , Eleftherohorinos Ilias , Voudrias Evangelos A. 
Published: October 2007

AbstractThe behavior of the herbicide terbuthylazine (TA) was studied in a clay loam soil after the addition of different organic amendments (OAs). Addition of poultry compost (PC) and urban sewage sludge (USS) retarded degradation of TA with half‐life values of 60.3 and 73.7 d, respectively. In contrast, addition of corn straw (CS) did not significantly alter the degradation of TA (half‐life 55.5 d) compared with its degradation in nonamended soils (half‐life 57.3 d). Sterilization of amended and nonamended soils resulted in a partial inhibition of TA degradation, indicating that biotic and abiotic processes are involved in TA degradation in soil. Degradation of TA led to the formation of desethyl‐terbuthylazine, which was detected in low amounts (<8% of the initially applied TA) in all soils. Adsorption of TA was relatively low, with Kd values ranging from 2.31 L kg‐1 in the nonamended soil to 3.93 L kg‐1 in the soil amended with USS. In general, Kd values increased with increasing soil organic carbon content. The dissolved organic matter extracted from the OAs did not appear to interact with the pesticide or the soil surfaces, suggesting that it would not probably facilitate herbicide transport. Desorption studies indicated a slight hysteresis of TA desorption in the amended soils compared with TA desorption in the nonamended soil, which was entirely reversible. These findings might have practical implications for the environmental fate of TA in agricultural soils, where the studied OAs are commonly used.
Vertical Distribution of Phosphorus in Agricultural Drainage Ditch Soils
Authors: Vaughan Robert E. , Needelman Brian A. , Kleinman Peter J.A. , Allen Arthur L. 
Published: October 2007

AbstractPedological processes such as gleization and organic matter accumulation may affect the vertical distribution of P within agricultural drainage ditch soils. The objective of this study was to assess the vertical distribution of P as a function of horizonation in ditch soils at the University of Maryland Eastern Shore Research Farm in Princess Anne, Maryland. Twenty‐one profiles were sampled from 10 agricultural ditches ranging in length from 225 to 550 m. Horizon samples were analyzed for total P; water‐extractable P; Mehlich‐3 P; acid ammonium oxalate‐extractable P, Fe, and Al (Pox, Feox, Alox); pH; and organic C (n = 126). Total P ranged from 27 to 4882 mg kg−1, Pox from 4 to 4631 mg kg−1, Mehlich‐3 P from 2 to 401 mg kg−1, and water‐extractable P from 0 to 17 mg kg−1 Soil‐forming processes that result in differences between horizons had a strong relationship with various P fractions and P sorption capacity. Fibric organic horizons at the ditch soil surface had the greatest mean Pox, Feox, and Alox concentrations of any horizon class. Gleyed A horizons had a mean Feox concentrations 2.6 times lower than dark A horizons and were significantly lower in total P and Pox Variation in P due to organic matter accumulation and gleization provide critical insight into short‐ and long‐term dynamics of P in ditch soils and should be accounted for when applying ditch management practices.
Fungal Inoculum Properties: Extracellular Enzyme Expression and Pentachlorophenol Removal by New Zealand Trametes Species in Contaminated Field Soils
Authors: Ford Christopher I. , Walter Monika , Northcott Grant L. , Di Hong J. , Cameron Keith C. , Trower Tania 
Published: October 2007

AbstractThis study was conducted to improve the ability of indigenous New Zealand white‐rot fungi to remove pentachlorophenol (PCP) from contaminated field soil. The effects of different bioaugmentation conditions on PCP removal and extracellular enzyme expression were measured in the laboratory. The conditions were fungal growth substrate and co‐substrate composition, culture age, and Tween 80 addition to the contaminated soil. The fungi used were Trametes versicolor isolate HR131 and Trametes sp. isolate HR577. Maximum PCP removal was 70% after 7 wk from a 1043 mg kg−1 PCP‐contaminated soil inoculated with an 11‐d‐old fungal culture of T. versicolor isolate HR131. There was minimal production of undesirable pentachloroanisole by the fungi. Tween 80 addition had no affect on PCP removal. Poplar sawdust was more suitable as a fungal growth substrate and a co‐substrate amendment for PCP removal and extracellular enzyme expression than the locally available pine and fir sawdust. Pentachlorophenol removal was not necessarily correlated with extracellular enzyme expression. The research results demonstrate that PCP biodegradation was affected by inoculum culture age, by the presence of a co‐substrate amendment, and by growth substrate composition after white‐rot fungal bioaugmentation into PCP‐contaminated field soils.
Hydrology of Small Field Plots Used to Study Phosphorus Runoff under Simulated Rainfall
Authors: Srinivasan M. S. , Kleinman P. J. A. , Sharpley A. N. , Buob T. , Gburek W. J. 
Published: October 2007

AbstractUse of small plots and rainfall simulators to extrapolate trends in runoff water quality requires careful consideration of hydrologic process represented under such conditions. A modified version of the National Phosphorus Runoff Project (NPRP) protocol was used to assess the hydrology of paired 1 × 2 m plots established on two soils with contrasting hydrologic properties (somewhat poorly drained vs. well drained). Rain simulations (60 mm h−1) were conducted to generate 30 min of runoff. For the somewhat poorly drained soil, simulations were conducted in October and May to contrast dry conditions typically targeted by NPRP protocols with wet conditions generally associated with natural runoff. For the well‐drained soil, only dry conditions (October) were evaluated. Under dry antecedent moisture conditions, an average of 64 mm of rainfall was applied to the somewhat poorly drained soil to generate 30 min of runoff, as opposed to 96 mm to the well‐drained soil. At an extreme, differences in rainfall were equivalent to a 50‐yr rainfall‐return period. An absence of detectable spatial trends in surface soil moisture suggests uniformity of runoff processes within the plots. No differences in applied rainfall were evident between wet and dry antecedent conditions for the somewhat poorly drained soil. However, significant differences in runoff generation processes were observed in dissolved P concentrations between wet and dry conditions. As natural runoff from the somewhat poorly drained soil is largely under wet antecedent conditions, this study highlights the need for care in interpreting findings from generalized protocols that favor infiltration‐excess runoff mechanisms.