bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of meso‐Coumarin‐Conjugated Porphyrins and Investigation of Their Luminescence Properties
Authors: Lin Weiying , Long Lingliang , Feng Jianbo , Wang Bin , Guo Cancheng 
Published: July 2007

AbstractA series of meso‐coumarin‐conjugated porphyrins 1a–e were designed and synthesized. Condensation of 4‐chloroacetoacetate ethyl ester with m‐cresol or resorcin afforded 4‐chloromethylcoumarins, which were then hydrolyzed to give coumarin alcohols, followed by oxidation to provide coumarin aldehydes. The reaction of coumarin aldehydes with pyrrole under Adler or Lindsey conditions afforded the meso‐coumarin‐conjugated porphyrins 1a–e. Their UV/Vis absorption spectra and photoluminescent spectra were recorded both in dilute THF solution and as solid films. Analysis of the luminescence spectra indicate that the energy transfer from the coumarin substituents to the porphyrin core for 1a–e is more efficient in solid film than in solution, and the energy transfer from the coumarin substituent to the porphyrin core for 1d and 1e is more efficient than that of 1a, 1b and 1c in solid film. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Synthesis and Reactivity of 23‐tert‐Butyl‐ and 23‐Phenyltetraarylazuliporphyrins: an Analysis of the Effect of Bulky Substituents on Oxidative Ring Contractions to Benzocarbaporphyrins
Authors: El‐Beck Jessica A. , Lash Timothy D. 
Published: July 2007

Abstract6‐tert‐Butyl‐ and 6‐phenylazulene reacted with pyrrole and benzaldehyde in a molar ratio of 1:3:4 in the presence of BF3·Et2O in chloroform, followed by oxidation with DDQ, to give 23‐substituted tetraphenylazuliporphyrins in 15–20 % yield. Slightly higher yields of the related meso‐tetrakis(4‐chlorophenyl)azuliporphyrins were obtained using 4‐chlorobenzaldehyde. The presence of an electron‐donating tert‐butyl substituent increased the diatropic character of the azuliporphyrin system as determined by the proton NMR chemical shifts for the internal CH resonance, while intermediary results were noted for 23‐phenylazuliporphyrins. Addition of TFA afforded dications with increased aromatic ring currents, but electron‐donating substituents (tBu > Ph) again produced a larger upfield shift for the internal CH signal due to stabilization of the tropylium character that is required so that the system can attain carbaporphyrin‐type aromaticity. The substituted azuliporphyrins reacted with nickel(II) acetate or palladium(II) acetate to give the corresponding organometallic derivatives. In addition, oxidations with tBuOOH and KOH afforded benzocarbaporphyrin products in approximately 50 % yield. The presence of tert‐butyl or phenyl substituents did not block these oxidative ring contraction processes, and the rate of reaction was slightly increased compared to 23‐unsubstituted azuliporphyrins. The major products were 22‐tert‐butyl or phenyl‐substituted benzocarbaporphyrins and minor products with an additional formyl substituent were also isolated. These products are consistent with an initial nucleophilic addition occurring at the position adjacent to the R group on the azulene ring. Detailed mechanisms are proposed to explain these observations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
The power of two‐locus affected sib‐pair linkage analysis to detect interacting disease loci
Authors: Hallgrímsdóttir Ingileif B. , Speed Terence P. 
Published: July 2007

AbstractIt has been shown that two‐locus linkage analysis can, for some two‐locus disease models, be used to detect effects at disease loci that do not reach significance in a genome scan. However, few examples exist where two‐locus linkage has been successfully used to map genes. We study the possible gain in power of affected sib‐pair nonparametric two‐locus linkage analysis for two‐locus models which fulfil the two‐locus triangle constraints. Using a new parameterization of the two‐locus joint identity‐by‐descent sharing probabilities we can, for fixed marginal sharing at both of two unlinked disease loci, derive a two‐locus distribution such that the power of a two‐locus analysis is maximized. In a simulation study we look at two test statistics, the two‐locus maximum likelihood score and the correlation between nonparametric linkage scores, and study power as a function of marginal sharing. We show that in a best‐case scenario two‐locus linkage can have considerable power to detect pairs of interacting loci if there is a moderate increase in allele sharing at one of the two loci, even if there is a very small increase in allele sharing at the other locus. But we also show that the power to detect interacting loci in a two‐locus analysis decreases as the marginal sharing at the two loci decreases and for any distribution with a small increase in allele sharing at both loci the power of a two‐locus analysis is always low. Genet. Epidemiol. 2007. © 2007 Wiley‐Liss, Inc.
Multiple cascade effects of oxidative stress on astroglia
Authors: Bond Cherie E. , Greenfield Susan A. 
Published: July 2007

AbstractMany neurodegenerative diseases share common underlying features, most prominent of which are dysregulation of calcium homeostasis and reactive astrogliosis, ultimately triggered by oxidative stress. Interestingly, an additional feature of the early response to stress conditions is the upregulation and release of acetylcholinesterase (AChE). This study therefore investigates the link between oxidative stress, calcium influx, gene expression, protein synthesis, and AChE release. We report that, in astroglia and in an immortalized cell line, GH4‐hα7, acute oxidative stress causes influx of extracellular calcium through L‐type voltage‐gated calcium channels (L‐VGCC), followed by increased release of AChE into the extracellular medium. Moreover, rapid and sustained changes in mRNA expression of AChE, L‐VGCC, and melastatin‐like transient receptor potential 2 (TRPM2) accompany profound suppression of global protein synthesis. Application of L‐VGCC blockers selectively reduces stress‐induced calcium influx and AChE release, mitigates changes in gene expression, and facilitates recovery from protein synthesis suppression. Although glia exhibit greater sensitivity in their responses, the results are comparable in astroglia and GH4‐hα7 cells, and suggest a generalized and integrated cellular response to stress conditions that characterizes changes observed in neurodegeneration. © 2007 Wiley‐Liss, Inc.
A lipidomic analysis of nonalcoholic fatty liver disease
Authors: Puri Puneet , Baillie Rebecca A. , Wiest Michelle M. , Mirshahi Faridoddin , Choudhury Jayanta , Cheung Onpan , Sargeant Carol , Contos Melissa J. , Sanyal Arun J. 
Published: July 2007

Abstract

The spectrum of nonalcoholic fatty liver disease (NAFLD) includes a nonalcoholic fatty liver (NAFL) and nonalcoholic steatohepatitis (NASH). The specific types and amounts of lipids that accumulate in NAFLD are not fully defined. The free fatty acid (FFA), diacylglycerol (DAG), triacylglycerol (TAG), free cholesterol (FC), cholesterol ester, and phospholipid contents in normal livers were quantified and compared to those of NAFL and NASH, and the distribution of fatty acids within these classes was compared across these groups. Hepatic lipids were quantified by capillary gas chromatography. The mean (nmol/g of tissue) DAG (normal/NAFL/NASH: 1922 versus 4947 versus 3304) and TAG (13,609 versus 128,585 versus 104,036) increased significantly in NAFLD, but FFA remained unaltered (5533 versus 5929 versus 6115). There was a stepwise increase in the mean TAG/DAG ratio from normal livers to NAFL to NASH (7 versus 26 versus 31,

P

< 0.001). There was also a similar stepwise increment in hepatic FC (7539 versus 10,383 versus 12,863,

P

< 0.05 for NASH). The total phosphatidylcholine (PC) decreased in both NAFL and NASH. The FC/PC ratio increased progressively (0.34 versus 0.69 versus 0.71,

P

< 0.008 for both). Although the levels for linoleic acid (18:2n-6) and α-linolenic acid (18:3n-3) remained unaltered, there was a decrease in arachidonic acid (20:4n-6) in FFA, TAG, and PC (

P

< 0.05 for all) in NASH. Eicosapentanoic acid (20:5n-3) and docosahexanoic acid (22:6n-3) were decreased in TAG in NASH. The n-6:n-3 FFA ratio increased in NASH (

P

< 0.05).

Conclusions:

NAFLD is associated with numerous changes in the lipid composition of the liver. The potential implications are discussed. (HEPATOLOGY 2007.)
Role of the coagulation system in acetaminophen-induced hepatotoxicity in mice
Authors: Ganey Patricia E. , Luyendyk James P. , Newport Sandra W. , Eagle Theresa M. , Maddox Jane F. , Mackman Nigel , Roth Robert A. 
Published: July 2007

Abstract

Acetaminophen (

N-acetyl
-
p

-aminophenol [APAP]) is one of the leading causes of acute liver failure, and APAP hepatotoxicity is associated with coagulopathy in humans. We tested the hypothesis that activation of the coagulation system and downstream protease-activated receptor (PAR)-1 signaling contribute to APAP-induced liver injury. Fasted C57BL/J6 mice were treated with either saline or APAP (400 mg/kg intraperitoneally) and were euthanized 0.5-24 hours later. Hepatotoxicity and coagulation system activation occurred by 2 hours after administration of APAP. Treatment with APAP also caused a rapid and transient increase in liver procoagulant activity. In addition, significant deposition of fibrin was observed in the liver by 2 hours, and the concentration of plasminogen activator inhibitor-1 in plasma increased between 2 and 6 hours. Pretreatment with heparin attenuated the APAP-induced activation of the coagulation system and hepatocellular injury and diminished hepatic fibrin deposition at 6 hours. Loss of hepatocellular glutathione was similar in APAP-treated mice pretreated with saline or heparin, suggesting that heparin did not diminish bioactivation of APAP. In mice deficient in tissue factor, the principal cellular activator of coagulation, APAP-induced liver injury, activation of coagulation, and hepatic fibrin deposition were reduced at 6 hours. Formation of the tissue factor–factor VIIa complex leads to the generation of thrombin that can activate cells through cleavage of PAR-1. Mice lacking PAR-1 developed less injury and hepatic fibrin deposits at 6 hours in response to APAP than control mice.

Conclusion:

Activation of the coagulation system and PAR-1 signaling contribute significantly to APAP-induced liver injury. (HEPATOLOGY 2007.)
Hepatitis B virus DNA prediction rules for hepatitis B e antigen–negative chronic hepatitis B
Authors: Feld Jordan J. , Ayers Melissa , El-Ashry Dahlia , Mazzulli Tony , Tellier Raymond , Heathcote Jenny E. 
Published: July 2007

Abstract

After hepatitis B e antigen (HBeAg) seroconversion, hepatitis B may become inactive or progress to HBeAg-negative hepatitis with persistent or intermittent alanine aminotransferase (ALT) elevation. The aim of this study was to prospectively identify factors predictive of the clinical course in HBeAg-negative chronic hepatitis B (CHB). Patients were stratified by ALT and HBeAg status and followed every 3 months for up to 5 years. Kaplan-Meier and Cox regression analysis using the change from normal ALT to elevated ALT as endpoints were performed to determine factors associated with ALT elevation/normalization. Seventy-four HBeAg-negative and 32 HBeAg-positive patients were prospectively evaluated. For HBeAg-negative patients, hepatitis B virus (HBV) DNA was predictive of future ALT. Only 1 patient with normal ALT and an HBV DNA value lower than 10,000 copies/mL developed an elevated ALT within the subsequent year, whereas 67% with an HBV DNA value greater than 100,000 copies/mL had a rise in ALT above normal within 1 year. Patients with a previous history of ALT elevation and longer follow-up at all levels of HBV DNA were more likely to experience ALT elevations. For HBeAg-negative patients with elevated ALT and all HBeAg-positive patients, HBV DNA did not predict future ALT. Other viral and host factors were not predictive of future ALT.

Conclusion:

HBeAg-negative CHB has a fluctuating course. HBV DNA values lower than 10,000 copies/mL predict persistently normal ALT for at least 1 year. Patients with HBV DNA values between 10,000 and 100,000 copies/mL can safely be followed at 6 monthly intervals, whereas HBV DNA values greater than 100,000 copies/mL are highly predictive of future ALT elevation and should prompt regular follow-up. (HEPATOLOGY 2007.)
Analysis of suspended sediment yields after low impact forest harvesting
Authors: Hotta Norifumi , Kayama Toshiya , Suzuki Masakazu 
Published: July 2007

AbstractDisturbances to forest catchments have profound effects on the environment of headwater streams and have an impact on suspended sediment (SS) management. Forest harvesting is a dominant factor in increasing SS yields. Road construction, skidder activity and ploughing associated with harvesting cause serious soil disturbance that results in SS increases. However, few studies have shown whether harvesting itself increases SS yields. This study examined how harvesting influenced SS yields in a steep forested area. During harvesting, soil surface disturbance was prevented as much as possible by using skyline logging treatments and piling branches and leaves at selected locations in the watershed. Using these methods, the representative SS rating curve did not change significantly after harvesting. The results also show that the characteristics of SS transport were related to the SS source area, and reveal that the riparian zone/stream bank was a dominant SS source area at the study site. Annual SS yields did not increase despite increasing annual water yields after harvesting. The limited water capacity of the soil at the study site likely led to only slight differences in pre‐ and post‐harvest water discharge from heavy rainfall events. Most SS was transported during heavy rainfall events, and increases in SS yields were not detected after harvesting. We concluded that it is possible to prevent post‐harvest SS increases by performing careful, low‐impact harvesting procedures. Copyright © 2007 John Wiley & Sons, Ltd.
Electronic structure, chemical bonding, and geometry of pure and Sr‐doped CaCO3
Authors: Stashans Arvids , Chamba Gaston , Pinto Henry 
Published: July 2007

AbstractThe electronic structure, chemical bonding, geometry, and effects produced by Sr‐doping in CaCO3 have been studied on the basis of density‐functional theory using the VASP simulation package and molecular‐orbital theory utilizing the CLUSTERD computer code. Two calcium carbonate structures which occur naturally in anhydrous crystalline forms, calcite and aragonite, were considered in the present investigation. The obtained diagrams of density of states show similar patterns for both materials. The spatial structures are computed and analyzed in comparison to the available experimental data. The electronic properties and atomic displacements because of the trace element Sr‐incorporation are discussed in a comparative manner for the two crystalline structures. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008
Effects of a gonadotropin‐releasing hormone antagonist on gonadotropin levels in masu salmon and sockeye salmon
Authors: Amano Masafumi , Ikuta Kazumasa , Kitamura Shoji 
Published: July 2007

AbstractThe salmon gonadotropin‐releasing hormone (sGnRH) is considered to be involved in gonadal maturation via gonadotropin (GTH) secretion in salmonid fishes. However, there is no direct evidence for endogenous sGnRH‐stimulated GTH secretion in salmonids. In this study, to clarify whether endogenous sGnRH stimulates GTH secretion, we examined the effects of the mammalian GnRH (mGnRH) antagonist [Ac‐Δ3‐Pro1, 4FD‐Phe2, D‐Trp3,6]‐mGnRH on luteinizing hormone (LH) levels in 0‐year‐old masu salmon Oncorhynchus masou and sockeye salmon Oncorhynchus nerka. First, the effects of the GnRH antagonist on LH release were examined in 0‐year‐old precocious male masu salmon. GnRH antagonist treatment for 3 hr significantly inhibited an increase in plasma LH levels that was artificially induced by exogenous sGnRH administration, indicating that the GnRH antagonist is effective in inhibiting LH release from the pituitary. Subsequently, we examined the effect of the GnRH antagonist on LH synthesis in 0‐year‐old immature sockeye salmon that were pretreated with exogenous testosterone for 42 days to increase the pituitary LH contents; the testosterone treatment did not affect the plasma LH levels. GnRH antagonist treatment slightly but significantly inhibited an increase in the testosterone‐stimulated pituitary LH content levels. However, no significant differences in the plasma LH levels were observed between the GnRH antagonist‐treated and control groups. These results suggest that endogenous sGnRH is involved in LH secretion in salmonid fishes. J. Exp. Zool. 307A:535–541, 2007. © 2007 Wiley‐Liss, Inc.
Structural and transfection properties of amine‐substituted gemini surfactant‐based nanoparticles
Authors: Wettig Shawn D. , Badea Ildiko , Donkuru McDonald , Verrall Ronald E. , Foldvari Marianna 
Published: July 2007

AbstractBackgroundIncreases in DNA transfection efficiencies for non‐viral vectors can be achieved through rational design of novel cationic building blocks. Based on previous results examining DNA condensation by polyamines, novel gemini surfactants have been designed that incorporate aza or imino substituents within the spacer group in order to increase interactions with DNA and potentially improve their DNA transfection ability.MethodsTransfection efficiencies and cell toxicity of gemini nanoparticles constructed from plasmid DNA, gemini surfactant, and a neutral lipid were measured in COS7 cells using a luciferase assay. Structural properties of nanoparticles were examined by using circular dichroism, particle size, zeta potential, and small‐angle X‐ray scattering (SAXS) measurements.ResultsThe incorporation of aza and imino substituents within the spacer group was observed to enhance the transfection ability of gemini surfactants. Incorporation of an imino group in the structure of the 1,9‐bis(dodecyl)‐1,1,9,9‐tetramethyl‐5‐imino‐1,9‐nonanediammonium dibromide surfactant (12‐7NH‐12) resulted in a statistically significant (p < 0.01) 9‐fold increase in transfection compared to an unsubstituted gemini surfactant and a 3‐fold increase compared to the corresponding aza‐substituted compound. A pH‐dependent transition in size and zeta potential was observed to occur at pH 5.5 for complexes formed from the 12‐7NH‐12 compound. SAXS results show weakly ordered structures and the presence of multiple phases.ConclusionsThe incorporation of a pH‐active imino group within the spacer of the gemini surfactant results in a significant increase in transfection efficiency that can be related to both pH‐induced changes in nanoparticle structure and the formation of multiple phases that more readily allow for membrane fusion that may facilitate DNA release. Copyright © 2007 John Wiley & Sons, Ltd.
Quantitative assessment of ventricular function using three‐dimensional SSFP magnetic resonance angiography
Authors: Greil Gerald F. , Boettger Thomas , Germann Sabrina , Klumpp Bernhard , Baltes Christof , Kozerke Sebastian , Bialkowski Anja , Urschitz Michael S. , Miller Stephan , Wolf Ivo , Meinzer Hans‐Peter , Sieverding Ludger 
Published: July 2007

AbstractPurposeTo evaluate three‐dimensional (3D), free‐breathing, steady‐state free precession (SSFP) magnetic resonance angiography (MRA) for volumetric assessment of ventricular function.Materials and MethodsIn 18 subjects (mean age = 21.5 years) 3D datasets of the heart and great vessels were acquired using an ECG‐triggered, free‐breathing SSFP technique with a T2‐preparation prepulse. Data were acquired during end‐systole (ES) and end‐diastole (ED) for assessment of stroke volumes (SVs). Through‐plane flow measurements of the great arteries were performed as well as 2D‐cine SSFP imaging for comparison. For image analysis of the 3D SSFP datasets a simplex mesh model was used. Papillary muscles were excluded from ventricular volumes using thresholds. Intra‐ and interobserver variability (Bland‐Altman analysis) and correlations (Pearson's coefficient) between volumetric and flow measurements were assessed.ResultsES and ED datasets were acquired successfully in all subjects. The best correlation was observed between flow vs. 3D SSFP SV for the LV (r = 0.85, mean difference = −1.0 mL) and the RV (r = 0.89, mean difference = −2.2 mL) with high intra‐ (LV: r = 0.93; RV: r = 0.94) and interobserver (LV: r = 0.91; RV: r = 0.93) reproducibility.Conclusion3D SSFP datasets combined with semiautomatic segmentation algorithms allow highly accurate and reproducible assessment of left (LV) and right ventricular (RV) SVs in free‐breathing subjects. J. Magn. Reson. Imaging 2007;26:288–295. © 2007 Wiley‐Liss, Inc.
SAR and temperature: Simulations and comparison to regulatory limits for MRI
Authors: Wang Zhangwei , Lin James C. , Mao Weihua , Liu Wanzhan , Smith Michael B. , Collins Christopher M. 
Published: July 2007

AbstractPurposeTo present and discuss numerical calculations of the specific absorption rate (SAR) and temperature in comparison to regulatory limits. While it is possible to monitor whole‐body or whole‐head average SAR and/or core body temperature during MRI in practice, this is not generally true for local SAR values or local temperatures throughout the body. While methods of calculation for SAR and temperature are constantly being refined, methods for interpreting results of these calculations in light of regulatory limits also warrant discussion.Materials and MethodsNumerical calculations of SAR and temperature for the human head in a volume coil for MRI at several different frequencies are presented.ResultsJust as the field pattern changes with the frequency, so do the temperature distribution and the ratio of maximum local SAR (in 1‐g or 10‐g regions) to whole‐head average SAR. In all of the cases studied here this ratio is far greater than that in the regulatory limits, indicating that existing limits on local SAR will be exceeded before limits on whole‐body or whole‐head average SAR are reached.ConclusionCalculations indicate that both SAR and temperature distributions vary greatly with B1 field frequency, that temperature distributions do not always correlate well with SAR distributions, and that regulatory limits on local temperature may not be exceeded as readily as those on local SAR. J. Magn. Reson. Imaging 2007;26:437–441. © 2007 Wiley‐Liss, Inc.
Evaluation of optimal echo time for 1H‐spectroscopic imaging of brain tumors at 3 Tesla
Authors: Hattingen Elke , Pilatus Ulrich , Franz Kea , Zanella Friedhelm E. , Lanfermann Heinrich 
Published: July 2007

AbstractPurposeTo compare the spectral quality of short echo time (TE) MR spectroscopic imaging (MRSI, TE = 30 msec) with long‐TE MRSI (TE = 144 msec) at 3 Tesla in normal brain and tumor tissue.Materials and MethodsSpectroscopic imaging (chemical‐shift imaging (CSI)) data of 32 patients with histopathological confirmed brain lesions were acquired at 3 Tesla (3T) using TEs of 30 msec and 144 msec. Tumor‐relevant metabolites (trimethylamine (TMA), creatine compounds (tCr), and N‐acetylated compounds (tNAA)) were analyzed with LCModel software, which applies prior knowledge by performing a frequency domain fit using a linear combination of model spectra.ResultsShort‐TE spectra provided up to twice the signal‐to‐noise ratio (SNR) compared to TE = 144 msec. The estimated fitting error was improved up to 30% for TMA and tCr, but was slightly reduced (10%) for tNAA. Quantification in terms of absolute concentrations was consistent at both TEs.ConclusionSince other metabolites observable at TE < 30 msec may be of diagnostic relevance, short‐TE MRSI should be the preferred method at 3T for the evaluation of focal lesions in brain tissue; however, TE = 144 msec can serve as an option for MRS in regions with potential baseline problems. J. Magn. Reson. Imaging 2007;26:427–431. © 2007 Wiley‐Liss, Inc.