bluuebunny/crossref_metadata_2025 huggingface dataset:
Microtensile strain on the corrosion performance of diamond‐like carbon coating
Authors: Lee Seung‐Hwan , Kim Jung‐Gu , Choi Heon‐Woong , Lee Kwang‐Ryeol
Published: September 2007

Hydrogenated diamond‐like carbon films (a‐C:H DLC) were deposited on STS 304 substrates for the fabrication of vascular stents by means of the r.f. plasma‐assisted chemical vapor deposition technique. This study provides reliable and quantitative data for the assessment of the effect of strain on the corrosion performance of DLC‐coated systems in the simulated body fluid obtained through electrochemical techniques (potentiodynamic polarization test and electrochemical impedance spectroscopy) and surface analysis (scanning electron microscopy). The electrolyte used in this test was 0.89% NaCl solution at pH 7.4 and 37°C. It was found that the corrosion resistance of the plastically deformed DLC coating was insufficient for use as a protective film in a corrosive body environment. This is due to the increase in the delamination area and degradation of the substrate's corrosion properties with increasing tensile deformation. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Cisplatin‐loaded Au–Au2S nanoparticles for potential cancer therapy: Cytotoxicity, in vitro carcinogenicity, and cellular uptake
Authors: Ren Lei , Huang Xiao‐Li , Zhang Bin , Sun Li‐Ping , Zhang Qi‐Qing , Tan Mei‐Chee , Chow Gan‐Moog
Published: September 2007

Cisplatin is one of the most effective cytotoxic agents against cancers. Its usage, however, is limited because of severe resistance and systemic toxicity. A formulation of cisplatin‐loaded Au–Au2S nanoparticles (NPs) with near‐IR (NIR) sensitivity is reported to partly overcome this limitation in this paper. NIR sensitive Au–Au2S NPs were successfully synthesized by the reduction of tetrachloroauric acid (HAuCl4) using sodium sulfide (Na2S), and cisplatin was loaded onto Au–Au2S NPs via a MUA (11‐mercaptoundecanoic acid) layer. To further investigate the biological safety of cisplatin‐loaded Au–Au2S NPs, three different cell lines were used to investigate the acute cytotoxicity and the long‐term potential carcinogenicity in vitro. Cisplatin‐loaded Au–Au2S NPs were also tested for limited hemocompatibility in vitro. Our in vitro short and long‐term data provided preliminary evidence suggesting that cisplatin‐loaded Au–Au2S NPs with NIR sensitivity are nontoxic below the maximum recommended dosage. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Arg‐Gly‐Asp (RGD) peptide conjugated poly(lactic acid)–poly(ethylene oxide) micelle for targeted drug delivery
Authors: Hu Zhiyuan , Luo Fang , Pan Yifeng , Hou Can , Ren Lifeng , Chen Jiji , Wang Jiwei , Zhang Yangde
Published: September 2007

In this study, a new poly(lactic acid)–poly (ethylene oxide)‐Arg‐Gly‐Asp (PLA‐PEO‐RGD) derivative was synthesized, and paclitaxel‐loaded PLA‐PEO‐RGD micelles were prepared by this derivative. The solubility assay showed that micelles mixed with Pluronic F‐68 as surfactant could increase the solubility of this hydrophobic paclitaxel in aqueous solution. The cell‐binding assay showed that PLA‐PEO‐RGD micelle (IC50 = 11.13 ± 1.38 nmol/L) had about 3.6‐fold higher integrin avidity than PLA‐PEO‐RGD conjugates (IC50 = 40.33 ± 3.12 nmol/L). The avidity of micelle was also higher than RGD4C peptide (IC50 = 24.44 ± 1.21 nmol/L). The in vitro drug release profile of drug‐loaded PLA‐PEO‐RGD micelles exhibited initial burst release to 37% ± 2% (w/w) during the first 12 h, and then the release rate became steady in a controlled release manner. Furthermore, treatment of the MDA‐MB‐435 breast cancer cell line with paclitaxel‐loaded PLA‐PEO‐RGD micelles yielded cytotoxicities, with EC50 values of ∼30 μmol/L. The paclitaxel‐loaded PLA‐PEO‐RGD micelles treated group showed the most dramatic tumor reduction in MDA‐MB‐435 tumor‐bearing nude mice, and the final mean tumor load was 31 ± 16 mm3 (mean ± SD; n = 8). 125I‐labeled micelles administration resulted in significant (p < 0.001) higher tumor uptake (2.68% ± 0.14%, ID/g) of PLA‐PEO‐RGD micelles compared to PLA‐PEO micelles (0.84% ± 0.09%, ID/g) after 2.5 h postinjection. Biodistribution study showed the best blood clearance of PLA‐PEO‐RGD micelles after 4.5 h postinjection. The results of this study suggest that paclitaxel‐loaded PLA‐PEO‐RGD micelles based on the specific recognition of αVβ3 integrin represent a potential and powerful target delivery technology. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008
Possible role of calcium on oocyte development after intracytoplasmic sperm injection in quail (Coturnix japonica)
Authors: Mizushima Shusei , Takagi Soichi , Ono Tamao , Atsumi Yusuke , Tsukada Akira , Saito Noboru , Shimada Kiyoshi
Published: September 2007

Although a rise in intracellular calcium concentration of vertebrate oocytes plays a pivotal role for the initiation of fertilization or oocyte activation, no study on this subject has been reported in birds. This study was conducted to study the role of intracellular calcium in relation to fertilization in avian oocytes. First, immediately after a quail oocyte was injected with a sperm, it was treated with strontium chloride as an inducer for intracellular calcium rise at doses of 0, 2.5, 5, 7.5, 10 mM for 4 hr in the culture medium and was followed by 20‐hr culture. Treatment with 5 mM of strontium chloride induced blastodermal development in 24.2% of injected eggs, although no oocytes developed without strontium treatment. Second, quail oocytes were injected with a sperm and 0.1 M calcium chloride or a sperm and saline solution, cultured without calcium for 4 hr and was followed by 20‐hr culture without strontium. The calcium solution induced blastodermal development in 20.5% of the oocytes, although no oocytes developed without calcium treatment. Third, quail oocytes were injected with 1,2‐bis (o‐aminophenoxy) ethane‐N,N,N′,N′‐tetraacetic acid (BAPTA) as a calcium chelator, cultured with strontium (5 mM) for 4 hr followed by 20‐hr culture without strontium. Only one oocyte developed after BAPTA and strontium treatment of 36 oocytes examined. Developmental stages of all the oocytes ranged from IV to VII. These results suggest that intracellular calcium rise may participate in quail oocyte activation and allow fertilization and blastodermal development. J. Exp. Zool. 307A:647–653, 2007. © 2007 Wiley‐Liss, Inc.
Exploring housing subsidies to households in Russia
Authors: Hamilton Ellen , Banerjee Sudeshna Ghosh , Lomaia Maka
Published: September 2007

Since the early 1990s, the Russian government has undertaken a series of reforms intended to change the system from one where housing and communal services (HCSs) were nearly free to one where residents paid the costs of their housing while protecting vulnerable families. Although households payments have increased, subsidies for HCSs remain substantial (about 4 per cent of GDP) and are exceeded only by public spending for pensions. This paper uses newly available data to analyse recipients of the two major housing subsidy programs. We find that neither l'goti (which are not targeted) nor allowances (which are supposed to be targeted) have provided much protection for poorer households from tariff increases. Copyright © 2007 John Wiley & Sons, Ltd.
Increased expression of tyrosine hydroxylase and anomalous neurites in catecholaminergic neurons of ATF‐2 null mice
Authors: Kojima Masayo , Suzuki Takahiro , Maekawa Toshio , Ishii Shunsuke , Sumi‐Ichinose Chiho , Nomura Takahide , Ichinose Hiroshi
Published: September 2007

ATF‐2/CRE‐BP1 was originally identified as a cAMP‐responsive element (CRE) binding protein abundant in the brain. We previously reported that phosphorylation of ATF‐2 increased the expression of tyrosine hydroxylase (TH), which is the rate‐limiting enzyme for catecholamine biosynthesis, directly acting on the CRE in the promoter region of the TH gene in PC12D cells (Suzuki et al. [2002] J. Biol. Chem. 277:40768–40774). To examine the role of ATF‐2 on transcriptional control of the TH gene in the brain, we investigated the TH expression in ATF‐2–/– mice. We found that TH expression was greatly increased in medulla oblongata and locus ceruleus of the ATF‐2‐deficient embryos. Ectopic expression of TH was observed in the raphe magnus nucleus, where serotonergic neural cell bodies are located. Interestingly, A10 dorsal neurons were lost in the embryos of ATF‐2–/– mice. There was no difference in the TH immunoreactivity in the olfactory bulb. The data showed that alteration in TH expression by absence of ATF‐2 gradually declined from caudal to rostral part of the brain. We also found anomalous neurite extension in catecholaminergic neurons of ATF‐2 null mice, i.e., increased dendritic arborization and shortened axons. These data suggest that ATF‐2 plays critical roles for proper expression of the TH gene and for neurite extension of catecholaminergic neurons, possibly through a repressor‐like action. © 2007 Wiley‐Liss, Inc.
Dopamine receptor agonists reverse behavioral abnormalities of α‐synuclein transgenic mouse, a new model of Parkinson's disease
Authors: Wakamatsu Masaki , Iwata Shingo , Funakoshi Takeo , Yoshimoto Makoto
Published: September 2007

Parkinson's disease (PD) is characterized by loss of nigral dopaminergic (DAergic) neurons and presence of Lewy bodies, whose major component is α‐synuclein. We had previously generated transgenic mice termed Syn130m that express truncated human α‐synuclein (amino acid residues 1–130) in DAergic neurons. Syn130m mice showed significant loss of DAergic neurons in the substantia nigra pars compacta. Subsequently, the striatal DA level and spontaneous locomotor activity of the mice were decreased significantly. In the present study, we investigated behavioral responses of Syn130m mice to L‐DOPA and DA receptor agonists. Administration of L‐DOPA dose dependently ameliorated the reduction of spontaneous locomotor activity of Syn130m mice. Similarly, D2 agonists, quinpirole and talipexole, and a D1/D2 agonist, pergolide, were effective against the reduction. Syn130m mice also showed significant reduction in exploratory behavior compared with non‐Tg littermates when they were placed in a novel environment, but this abnormality was ameliorated by treatment with pergolide. These results strongly suggest that the behavioral abnormalities of Syn130m mice were caused by low striatal DA content. On the other hand, the expression of postsynaptic D2‐like receptors (DRD2) in the striatum was not increased in Syn130m mice, although the low striatal DA level is known to induce compensatory expression of DRD2. Because the abnormalities could be rectified by treatment with DA receptor agonists, it is likely that Syn130m mice provide a useful tool to explore therapeutic possibilities for PD as a new animal model of the disease. © 2007 Wiley‐Liss, Inc.
N‐Propanoylmannosamine interferes with O‐GlcNAc modification of the tyrosine 3‐monooxygenase and stimulates dopamine secretion
Authors: Bork Kaya , Kannicht Christoph , Nöhring Sabine , Reutter Werner , Weidemann Wenke , Hart Gerald W. , Horstkorte Rüdiger
Published: September 2007

The most consistent neurochemical abnormality in Parkinson's disease is degeneration of dopaminergic neurons in the substantia nigra, leading to a reduction of striatal dopamine levels. The rate‐limiting step in the biosynthesis of dopamine, noradrenalin, and adrenalin is catalyzed by tyrosine 3‐monooxygenase (=tyrosine hydroxylase), which catalyzes the formation of L‐DOPA. In earlier studies, we demonstrated that the novel synthetic sialic acid precursor N‐propanoylmannosamine is a potent stimulator of axonal growth and promotes reestablishment of the perforant pathway from layer II of cortical neurons to the outer molecular layer of the dentate gyrus. Here we show that application of N‐propanoylmannosamine leads to increased biosynthesis and secretion of dopamine. This increased biosynthesis of dopamine is due to decreased expression of O‐linked N‐acetylglucosamine on tyrosine 3‐monooxygenase. Intracellular attachment of O‐linked N‐acetylglucosamine to serine and threonine residues hinders phosphorylation, thereby regulating the activity of the proteins concerned. We therefore propose a model in which the application of ManNProp leads to increased phosphorylation and activation of tyrosine 3‐monooxygenase, which in turn leads to an increased synthesis of dopamine. © 2007 Wiley‐Liss, Inc.
Career success and weak paradigms: the role of activity, resiliency, and true scores
Authors: Hollenbeck John R. , Mannor Michael J.
Published: September 2007

Questions have been raised about the significant influence that weak paradigm development has on the careers of individuals struggling to make a life in the field of organization science. Based on the fact that a weak paradigm leads to low levels of agreement about the quality of any manuscript, it has been suggested that the marketplace for ideas is beyond comprehension to even the most talented individuals, and that career outcomes are determined largely by chance events over which people have no control. We re‐examine this argument and the influence of weak paradigms on the reliability of evaluations at the career level of analysis. Using Spearman–Brown Prophecy formula, we show that the reliability of evaluations at the career level is very high, even if one makes very pessimistic assumptions regarding inter‐rater agreement at the manuscript/journal level. Although weak paradigms create high levels of uncertainty on any one single pass through the review system, our results suggest that within 5 years, researchers are likely to be reliability evaluated. This reliability converges on 1.0 under specific conditions that are easily controlled by authors (activity level and resiliency) and editors (forming independent judgments and the use of three reviewers rather than two). Copyright © 2007 John Wiley & Sons, Ltd.
Contribution of olive seed to the phenolic profile and related quality parameters of virgin olive oil
Authors: Luaces Pilar , Romero Carmen , Gutierrez Francisca , Sanz Carlos , Pérez Ana G
Published: September 2007

BACKGROUND: Conflicting results have been reported about the effect of fruit de‐stoning on the virgin olive oil (VOO) phenolic profile. The aim of the present study was to determine whether olive seed plays any role in the synthesis of this oil phenolic fraction.

RESULTS: Increases of around 25% of total phenolic compounds were observed in oils obtained from de‐stoned olive fruits in three main Spanish cultivars. To investigate the involvement of olive seed in determining the phenolic profile of VOO, whole intact olive fruits were added with up to 400% olive stones. Excellent regression coefficients were found in general for the decrease of total phenolic compounds and, particularly, of o‐diphenolics in the resulting oils. On the other hand, it was found that olive seed contains a high level of peroxidase (POX) activity (72.4 U g−1 FW), accounting for more than 98% of total POX activity in the whole fruit. This activity is able to modify VOO phenolics in vitro, similar to the effect of adding stones during VOO extraction.

CONCLUSION: Olive seed plays an important role in determining VOO phenolic profile during the process to obtain an oil that seems to be associated with a high level of POX activity. Copyright © 2007 Society of Chemical Industry
On the possibility of an absolute negative conductivity of diamond at the irradiation by picosecond laser pulse
Authors: Rastunkov V S , Krainov V P
Published: September 2007

We investigate one of the possibilities for production of carriers in diamond resulting in its absolute negative conductivity at low temperatures T ∼ 10 – 30 K. Production and dynamics of electrons and holes in diamond at the irradiation by picosecond laser pulse with the peak laser intensity of 1010 W/cm2 has been considered and compared to each other. Then carriers are cooled due to emission of acoustic phonons. Diamond heating is estimated in focussing region. The conclusion has been made about small local increasing of lattice temperature in the irradiation region. Thus, laser irradiation can produce conditions for possible experimental observation of an absolute negative conductivity of diamond at low temperatures.
Bond strength of an adhesive system irradiated with Nd:YAG laser in dentin treated with Er:YAG laser
Authors: Malta D A M P , Costa M M , Pelino J E P , de Andrade M F , Lizarelli R F Z
Published: September 2007

The purpose of this in vitro study was to verify through micro tensile bond test the bond strength of an adhesive system irradiated with Nd:YAG laser in dentine previously treated with Er:YAG laser. Twenty caries free extracted human third molars were used. The teeth were divided in four experimental groups (n = 5): (G1) control group; (G2) irradiation of the adhesive system with the Nd:YAG laser; (G3) dentin treatment with Er:YAG laser; (G4) dentin treatment with Er:YAG laser followed by the irradiation of the adhesive system with Nd:YAG laser. The Er:YAG laser fluency parameter for the dentin treatment was of 60 J/cm2. The adhesive system was irradiated with the Nd:YAG laser with fluency of 100 J/cm2. Dental restorations were performed with Adper Single Bond 2/Z250. One tooth from each group was prepared for the evaluation of the adhesive interface under SEM and bond failure tests were also performed and evaluated. The statistical analysis showed statistical significant difference between the groups G1 and G3, G1 and G4, G2 and G3, and G2 and G4; and similarity between the groups G1 and G2, and G3 and G4. The adhesive failures were predominant in all the experimental groups. The SEM analysis showed an adhesive interface with features confirming the results of the mechanical tests. The Nd:YAG laser on the adhesive system did not influence the bond strength in dentin treated or not with the Er:YAG laser.
Comparative optical study of thulium-doped YAlO3and GdVO4single crystals
Authors: Li Y F , Wang Y Z , Yao B Q
Published: September 2007

Absorption and emission spectra of Tm3+in YAlO3and GdVO4single crystals are reported and analyzed. Lifetimes of1G4(22 μs)3F4(5.1 ms) states in YAlO3and1G4(16 μs)3F4(2.3 ms) states in GdVO4are measured, Fluorescence decay curves of blue and infrared emissions are also been given. In addition, widely tunable laser performances of Tm:YAlO3and Tm:GdVO4lasers are demonstrated.
Density functional theory of the trapped Fermi gas in the unitary regime
Authors: van Zyl B P , Hutchinson D A W
Published: September 2007

We investigate a density-functional theory (DFT) approach for an unpolarized trapped dilute Fermi gas in the unitary limit. A reformulation of the recent work of T. Papenbrock [1] in the language of fractional exclusion statistics allows us to obtain an estimate of the universal factor, ξ3D, in three dimensions (3D), in addition to providing a systematic treatment of finite-N corrections. We show that in 3D, finite-N corrections lead to unphysical values for ξ3D, thereby suggesting that a simple DFT applied to a small number of particles may not be suitable in 3D. We then perform an analogous calculation for the two-dimensional (2D) system in the infinite-scattering length regime, and obtain a value of ξ2D=1. Owing to the unique properties of the Thomas-Fermi energy density-functional in 2D our result, in contrast to 3D, is exact and therefore requires no finite-N corrections.
Micellization Kinetics of a Novel Multi‐Responsive Double Hydrophilic Diblock Copolymer Studied by Stopped‐Flow pH and Temperature Jump
Authors: Zhang Yanfeng , Wu Tao , Liu Shiyong
Published: September 2007

Double hydrophilic diblock copolymer, poly(N‐isopropylacrylamide)‐block‐poly(2‐diethylamino ethyl methacrylate) (PNIPAM‐b‐PDEA), was synthesized via reversible addition‐fragmentation chain transfer (RAFT) polymerization. Containing the well‐known thermo‐responsive PNIPAM block and pH‐responsive PDEA block, this novel diblock copolymer exhibits intriguing “schizophrenic” micellization behavior in aqueous solution, forming PDEA‐core micelles at alkaline pH and room temperature, and PNIPAM‐core micelles at acidic pH and elevated temperatures. The kinetics of the pH‐ and thermo‐responsive micellization processes were studied in detail using a stopped‐flow apparatus equipped with a newly developed millisecond temperature jump (mT‐jump) accessory. Upon a pH jump from 4 to 12 at 25 °C, the early stages of relaxation curves monitoring the formation PDEA‐core micelles can be well‐fitted using a double‐exponential function, leading to two characteristic relaxation time constants, τ1 and τ2. As τ2 decreases with increasing polymer concentration, the slow process is thus expected to proceed via micelle fusion/fission mechanism, approaching the final equilibrium state. Upon a temperature jump from 20 to 45 °C at pH 4, the relaxation curves monitoring the formation PNIPAM‐core micelles can also be well‐fitted using a double‐exponential function. The fast process (τ1) is associated with the quick association of unimers into a large amount of small micelles and the formation of quasi‐equilibrium micelles. τ2 is almost independent of polymer concentration, suggesting that unimer insertion/expulsion is the main mechanism for the slow process. The protonated PDEA corona of quasi‐equilibrium micelles renders the micelle fusion/fission mechanism less favorable due to electrostatic repulsion.

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Influence of the Composition on Crystal Phase and Thermal Behavior of trans‐1,4‐Butadiene/Isoprene Copolymers
Authors: Bertini Fabio , Canetti Maurizio , Ricci Giovanni
Published: September 2007

Butadiene/isoprene copolymers were prepared using the catalyst system V(acac)3‐MAO. The structure of the comonomers is trans‐1,4 and the butadiene and isoprene units are statistically distributed along the polymer chain. The attitude of the butadiene sequences to crystallize in the monoclinic form and to evolve in the hexagonal form is preserved in the copolymer for a certain range of composition. The temperature interval between the two endothermic events is progressively reduced by increasing the isoprene content. The monoclinic/hexagonal transition produces a considerable increase in the lamellar thickness of the polymers. Thermal degradation of the copolymers is influenced by the composition and takes place in two different stages: a series of cyclization and cross‐linking reactions occur before the decomposition step.

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Local sentences and Mahlo cardinals
Authors: Finkel Olivier , Todorcevic Stevo
Published: September 2007

Local sentences were introduced by Ressayre in [6] who proved certain remarkable stretching theorems establishing the equivalence between the existence of finite models for these sentences and the existence of some infinite well ordered models. Two of these stretching theorems were only proved under certain large cardinal axioms but the question of their exact (consistency) strength was left open in [4]. Here we solve this problem, using a combinatorial result of J. H. Schmerl [7]. In fact, we show that the stretching principles are equivalent to the existence of n ‐Mahlo cardinals for appropriate integers n. This is done by proving first that for every integer n, there is a local sentence φn having well ordered models of order type τ, for every infinite ordinal τ > ω which is not an n ‐Mahlo cardinal. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Conserving involution in residuated structures
Authors: Hsieh Ai‐ni , Raftery James G.
Published: September 2007

This paper establishes several algebraic embedding theorems, each of which asserts that a certain kind of residuated structure can be embedded into a richer one. In almost all cases, the original structure has a compatible involution, which must be preserved by the embedding. The results, in conjunction with previous findings, yieldseparativeaxiomatizations of thededucibility relationsof various substructural formal systems having double negation and contraposition axioms. The separation theorems go somewhat further than earlier ones in the literature, which either treated fewer subsignatures or focussed on the conservation of theorems only. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pairwise disjoint eight‐shaped curves in hybrid planes
Authors: Costantini Camillo
Published: September 2007

We introduce a suitable notion of eight‐shaped curve in the product S × ℝ of a Suslin line S for the real line ℝ, and we prove that if S is dense in itself, then every collection of pairwise disjoint eight‐shaped curves in S × ℝ is countable. This parallels a folklore result which holds for the real plane. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Categorical abstract algebraic logic: The categorical Suszko operator
Authors: Voutsadakis George
Published: September 2007

Czelakowski introduced the Suszko operator as a basis for the development of a hierarchy of non‐protoalgebraic logics, paralleling the well‐known abstract algebraic hierarchy of protoalgebraic logics based on the Leibniz operator of Blok and Pigozzi. The scope of the theory of the Leibniz operator was recently extended to cover the case of, the so‐called, protoalgebraic π‐institutions. In the present work, following the lead of Czelakowski, an attempt is made at lifting parts of the theory of the Suszko operator to the π‐institution framework. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Erratum: Analysis of a FitzHugh–Nagumo–Rall model of a neuronal network Math. Meth. Appl. Sci. 2007 (DOI: 10.1002/mma.880)
Authors: Cardanobile Stefano , Mugnolo Delio
Published: September 2007

The above article (DOI: 10.1002/mma.880) was published online on 25 May 2007. An error was subsequently identified. Proposition 5.3.3 should read as follows:

(3) If pj ≡ 0 and γi = 0 for all j = 1, …, m and i = 1, …, n, then there exist initial conditions […]

The print publication will incorporate the amendment identified by this erratum notice.
1H and 13C NMR assignments for five anthraquinones from the mangrove endophytic fungus Halorosellinia sp. (No. 1403)
Authors: Xia Xue‐Kui , Huang Hua‐Rong , She Zhi‐Gang , Shao Chang‐Lun , Liu Fan , Cai Xiao‐Ling , Vrijmoed L. L. P. , Lin Yong‐Cheng
Published: September 2007

We report the unambiguous assignments of the 1H and 13C NMR spectra of two new natural products, namely, 1,4,5,6,7,9‐hexahydroxy‐2‐methoxy‐7‐methyl‐5β,9β,8aβ, 6α,10aα‐hexahydroanthracen‐10 (10aH)‐one (1) and 1,4,6‐trihydroxy‐2‐methoxy‐7‐methylanthracene‐9, 10‐dione (2), together with three known anthraquinones. These compounds were all isolated from the marine endophytic fungus No. 1403 collected from the South China Sea. Compounds 3 and 4 were isolated from the marine fungus for the first time. The structures were elucidated by the spectroscopic methods 1D and 2D NMR including COSY, HMQC, HMBC and NOE, and HREIMS. In our cytotoxicity assays, compound 5 showed cytotoxicity toward KB and KBv‐200 cells with IC50 of 1.40 and 2.58 µg/ml, respectively. In addition, the plausible biogenic relationship of compounds 1, 2, 3 and 4 is discussed. Copyright © 2007 John Wiley & Sons, Ltd.
Analysis of signal‐to‐noise behavior in Cartesian continuous sampling sequences: Predictions and experimental validation of opportunities for improved image SNR
Authors: Bookwalter Candice A. , Griswold Mark A. , Sunshine Jeffrey L. , Duerk Jeffrey L.
Published: September 2007

Image signal‐to‐noise ratio (SNR) limits many MRI applications. Here we propose a method to improve SNR based on continuous sampling (CS) during each TR without significant increases in acquisition time. The general concept of CS is defined here as sampling the NMR signal immediately after slice excitation including ramp times, both the dephase and rephase lobes, the phase‐encoding (PE) gradient application, and the slice refocusing gradient. This study analyzes several cases of CS and demonstrates a specific case where sampling occurs during an isolated and balanced readout gradient in order to increase SNR in a rectilinear Cartesian sequence without significantly increasing overall acquisition time. The noise correlation consequences of rectilinear CS are mathematically derived and proven through simulation. The SNR improvement of up to ∼40% measured in both phantom and asymptomatic human volunteer images is comparable to theoretical prediction of increased SNR proportional to the increase in the square root of the sampling time. Magn Reson Med 58:819–824, 2007. © 2007 Wiley‐Liss, Inc.
Spectral quality control in motion‐corrupted single‐voxel J‐difference editing scans: An interleaved navigator approach
Authors: Bhattacharyya P.K. , Lowe M.J. , Phillips M.D.
Published: September 2007

Motion has an adverse effect on spectral quality and needs to be properly identified in MR spectroscopy (MRS) scans. Spectral subtraction‐based techniques like J‐difference editing are prone to be affected more by subject motion where motion can result in false peaks or inefficient subtraction of peaks. Introducing a water signal‐based interleaved navigator scan in the MEGA point‐resolved spectroscopy (MEGA‐PRESS) sequence and acquiring data on a shot‐by‐shot basis, subject motion inside a scanner was tracked and motion‐corrupted data were identified and excluded from the dataset. Performing a γ‐aminobutyric acid (GABA) editing scan at the occipital cortex, it was possible to retrieve a properly edited GABA spectrum from a dataset otherwise to be discarded due to motion. This study demonstrates the importance of independent motion assessment in J‐difference editing. Magn Reson Med 58:808–812, 2007. © 2007 Wiley‐Liss, Inc.
Impact of incidental magnetization transfer effects on inversion‐recovery sequences that use a fast spin‐echo readout
Authors: Meara Simon J.P. , Barker Gareth J.
Published: September 2007

Multislice MR images obtained using a fast spin‐echo (FSE) readout are strongly affected by magnetization transfer (MT) effects, which will cause a decrease in the observed longitudinal relaxation times for tissues with a large bound water component. This is pertinent for FSE‐based inversion‐recovery (IR) sequences, as it would be expected to cause a change in the required inversion times. Furthermore, the effect will be greater as the number of slices that are acquired within the repetition time (TR) is increased. A pseudo‐3D IR‐FSE sequence was used to obtain images of a phantom consisting of thermally crosslinked bovine serum albumin. It was found that increasing the number of slabs acquired per TR period led to a decrease in the inversion time that maximally suppressed the signal from the MT phantom; this was not the case for water. This has important consequences for any IR imaging sequence that uses an FSE readout. Magn Reson Med 58:825–829, 2007. © 2007 Wiley‐Liss, Inc.
Selective parity RARE imaging
Authors: Norris David G.
Published: September 2007

This work describes a novel method for rapid acquisition with relaxation enhancement (RARE)/fast spin‐echo (FSE) imaging that removes the constraint of compliance with the Carr‐Purcell‐Meiboom‐Gill (CPMG) condition. In a multiecho sequence, echoes with either odd or even parities are acquired. The refocusing angles are chosen using a recursive algorithm, so that the signal amplitude satisfies a predetermined modulation function. In the examples given in this article an exponential decay to a plateau is used. At each echo the echo parity that gives the desired signal amplitude for the minimum refocusing angle is selected. It is further shown that in the presence of an initial magnetization having an arbitrary phase distribution, the complex conjugate of the signal of one echo parity has to be taken and its k‐space coordinates reversed. T‐weighted images are presented and initial applications to diffusion‐weighted imaging (DWI) and functional imaging shown. Magn Reson Med 58:643–649, 2007. © 2007 Wiley‐Liss, Inc.
MR diffusion tensor imaging study of postinfarct myocardium structural remodeling in a porcine model
Authors: Wu Ed X. , Wu Yin , Nicholls John M. , Wang Jie , Liao Songyan , Zhu Shuguang , Lau Chu‐Pak , Tse Hung‐Fat
Published: September 2007

This study aimed to investigate postinfarct left ventricular (LV) fiber structural alterations by ex vivo diffusion tensor imaging (DTI) in a porcine heart model. In vivo cardiac MR imaging was first performed to measure ventricular function in six adult pigs with septal infarction near apex induced by the LAD ligation 13 weeks earlier. Hearts were then excised from the infarct pigs (n = 6) and six intact controls (n = 6) and fixed in formalin. High‐resolution DTI was employed to examine changes in fractional anisotropy (FA), apparent diffusion coefficient (ADC), and transmural helix angle distribution in the infarct, adjacent and remote regions as compared to the sham regions in the controls. FA values were found to decrease in the infarct and differ between the adjacent and remote regions. ADC increase in the infarct region was substantial, while changes in the adjacent and remote regions were insignificant. Structurally, the double‐helix myocardial structure shifted toward more left‐handed around the infarcted myocardium. Accordingly, the histological analysis revealed clear fiber structural degradation in the adjacent region. These findings confirmed the subtle alterations in the myocardial fiber quality and structure not only in the infarcted but also in the surrounding noninfarcted myocardium or borderzone. Magn Reson Med 58:687–695, 2007. © 2007 Wiley‐Liss, Inc.
Assessment of metabolite quantitation reproducibility in serial 3D‐1H‐MR spectroscopic imaging of human brain using stereotactic repositioning
Authors: Langer Deanna L. , Rakaric Peter , Kirilova Anna , Jaffray David A. , Damyanovich Andrei Z.
Published: September 2007

Intrasubject reproducibility of metabolite quantitation in three‐dimensional proton magnetic resonance spectroscopic imaging (3D‐MRSI) was investigated in 10 healthy volunteers over five separate sessions using two echo times (TEs): 144 and 30 ms. The use of a Gill‐Thomas‐Cosman (GTC) stereotactic head frame enabled precise subject repositioning and immobilization. Metabolite levels from each voxel in the volume of interest (VOI) were quantified using the Linear Combination of Model spectra (LCModel) analysis algorithm, and coefficients of variation (CVs) were calculated. Standard error estimates (%SD or Cramer‐Rao lower bounds) generated by LCModel were used as a confidence filter. The 95% confidence interval (CI) was found for each metabolite, providing an indication of the normal fluctuation expected for 3D‐MRSI. In vivo, median CVs at the %SD ≤ 20 level were found to be (%CV for TE = 144 and 30 ms, respectively): N‐acetyl‐aspartate plus N‐acetyl‐aspartyl‐glutamate (NAA): 10.2% and 13.5%; creatine plus phosphocreatine (Cr), 14.4% and 21.7%; and choline‐containing compounds (Cho), 15.2% and 18.4%. Relaxing the statistical filtering criteria to %SD ≤ 30 increased median CVs by less than 5% and permitted in vivo quantitation reproducibility to be evaluated for glutamine plus glutamate (Glx) and myoinositol (Ins) for TE = 30 ms, yielding CVs of 24.0% and 21.0%, respectively. Magn Reson Med 58:666–673, 2007. © 2007 Wiley‐Liss, Inc.
Cardiac and respiratory self‐gated cine MRI in the mouse: Comparison between radial and rectilinear techniques at 7T
Authors: Hiba Bassem , Richard Nathalie , Thibault Hélène , Janier Marc
Published: September 2007

ECG‐gated cardiac MRI in the mouse is hindered by many technical difficulties in ECG signal recording inside high magnetic field scanners. The present study proposes a robust rectilinear method of acquiring cardiac and respiratory self‐gated cine images in mouse hearts. In this approach, a motion‐synchronization MR signal is collected in the center of k‐space simultaneously with imaging data in each readout of a nontriggered rectilinear acquisition. This signal is then used for both cardiac and respiratory retrospective gating before cine image reconstruction. The value of this approach for overcoming ECG‐gating failure was demonstrated by performing cardiac imaging in eight mice with myocardial infarction. Comparison with an auto‐gated radial k‐space sampling technique, previously reported for cardiac applications in the mouse, found the rectilinear strategy more robust, thanks to a more reliable self‐gating signal, while the radial strategy was less sensitive to motion and flow artifacts. Magn Reson Med 58:745–753, 2007. © 2007 Wiley‐Liss, Inc.
Parallel MRI reconstruction using variance partitioning regularization
Authors: Lin Fa‐Hsuan , Wang Fu‐Nien , Ahlfors Seppo P. , Hämäläinen Matti S. , Belliveau John W.
Published: September 2007

Multiple receivers can be utilized to enhance the spatiotemporal resolution of MRI by employing the parallel imaging technique. Previously, we have reported the L‐curve Tikhonov regularization technique to mitigate noise amplification resulting from the geometrical correlations between channels in a coil array. Nevertheless, one major disadvantage of regularized image reconstruction is lengthy computational time in regularization parameter estimation. At a fixed noise level, L‐curve regularization parameter estimation was also found not to be robust across repetitive measurements, particularly for low signal‐to‐noise ratio (SNR) acquisitions. Here we report a computationally efficient and robust method to estimate the regularization parameter by partitioning the variance of the noise‐whitened encoding matrix based on the estimated SNR of the aliased pixel set in parallel MRI data. The proposed Variance Partitioning Regularization (VPR) method can improve computational efficiency by 2–5‐fold, depending on image matrix sizes and acceleration rates. Our anatomical and functional MRI results show that the VPR method can be applied to both static and dynamic MRI experiments to suppress noise amplification in parallel MRI reconstructions for improved image quality. Magn Reson Med 58:735–744, 2007. © 2007 Wiley‐Liss, Inc.
Variable slew‐rate spiral design: Theory and application to peak B1 amplitude reduction in 2D RF pulse design
Authors: Xu Dan , King Kevin F. , Liang Zhi‐Pei
Published: September 2007

A new class of spiral trajectories called variable slew‐rate spirals is proposed. The governing differential equations for a variable slew‐rate spiral are derived, and both numeric and analytic solutions to the equations are given. The primary application of variable slew‐rate spirals is peak B1 amplitude reduction in 2D RF pulse design. The reduction of peak B1 amplitude is achieved by changing the gradient slew‐rate profile, and gradient amplitude and slew‐rate constraints are inherently satisfied by the design of variable slew‐rate spiral gradient waveforms. A design example of 2D RF pulses is given, which shows that under the same hardware constraints the RF pulse using a properly chosen variable slew‐rate spiral trajectory can be much shorter than that using a conventional constant slew‐rate spiral trajectory, thus having greater immunity to resonance frequency offsets. Magn Reson Med 58:835–842, 2007. © 2007 Wiley‐Liss, Inc.
Suitability of T1Gd as the “dGEMRIC index” at 1.5T and 3.0T
Authors: Williams Ashley , Mikulis Brandon , Krishnan Nitya , Gray Martha , McKenzie Charlie , Burstein Deborah
Published: September 2007

Delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC) is based on the theory that Gd‐DTPA2− will distribute in inverse relation to cartilage glycosaminoglycan (GAG). T1Gd (T1 after penetration of a 0.2 mmol/kg dose of Gd‐DTPA2−) has been used as the dGEMRIC index, although (1/T1Gd–1/T1o) should be more representative of Gd‐DTPA2− concentration (where T1o = T1 before contrast). T1o and T1Gd were measured in 20 volunteers at both 1.5T and 3T and the correlation between the metrics of T1Gd and (1/T1Gd–1/T1o) was calculated. There was a high correlation coefficient between the two metrics at both field strengths, with R = 0.94, 0.93, and 0.90 for central medial femur, posterior medial femur, and medial tibia, respectively, at 1.5T and 0.87, 0.94, 0.96 at 3T. In all cases P < 0.0001. Therefore, these data suggest that, for native cartilage, the current practice of measuring T1Gd (but not also T1o) is adequate at both 1.5T and 3T. Magn Reson Med 58:830–834, 2007. © 2007 Wiley‐Liss, Inc.
Magnetic nanoparticle labeling of mesenchymal stem cells without transfection agent: Cellular behavior and capability of detection with clinical 1.5 T magnetic resonance at the single cell level
Authors: Hsiao Jong‐Kai , Tai Ming‐Fong , Chu Hung‐Hao , Chen Shin‐Tai , Li Hung , Lai Dar‐Ming , Hsieh Sung‐Tsang , Wang Jaw‐Lin , Liu Hon‐Man
Published: September 2007

The purpose of this work was to evaluate the efficacy of labeling human mesenchymal stem cells (hMSCs) by ionic superparamagnetic iron oxide (SPIO) without a transfection agent and verifying its capability to be detected with clinical 1.5 T magnetic resonance (MR) at the single‐cell level. Human hMSCs were incubated for 24 h with an ionic SPIO, Ferucarbotran. The labeling efficiency of hMSCs was determined by iron content measurement spectrophotometrically, and the influence of labeling on cell behavior was ascertained by examination of cell viability using the trypan blue exclusion method, cell proliferation analysis using MTT (3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay, mitochondrial membrane potential (MMP) change, differentiation capacity, and reactive oxygen species (ROS) production measured by dichlorofluorescein diacetate (DCFDA) fluorescent probe. Labeled hMSCs were scanned under 1.5 T MRI with three‐dimensional (3D) and two‐dimensional (2D) T2‐weighted gradient echo (GRE) pulse sequences. Human hMSC labeling without transfection agent was efficient. The iron content in hMSCs was 23.4 pg Fe/cell. No significant change was found in viability, proliferation, MMP change, ROS production, or differentiation capacity. About 45.2% of the hMSCs could be detected using 1.5 T MRI at the single cell level with 3D GRE and four repetitions. Magn Reson Med 58:717–724, 2007. © 2007 Wiley‐Liss, Inc.
Spin‐echo MRI underestimates functional changes in microvascular cerebral blood plasma volume using exogenous contrast agent
Authors: Mandeville Joseph B. , Leite Francisca P. , Marota John J.A.
Published: September 2007

While most functional MRI studies using exogenous contrast agent employ gradient‐echo (GE) signal, spin echo (SE) imaging would represent an attractive alternative if its detection power were more comparable with GE imaging. This study demonstrates that SE methods systematically underestimate functional changes in microvascular cerebral blood plasma volume (CBV), so that SE detection power in brain tissue cannot match that provided by GE signal. Empirically, the in vivo response of SE‐CBV was about 40% smaller than that of GE‐CBV in rat brain at low basal values of CBV, a result that is consistent with physics predictions under the simplifying assumption of uniform vessel dilation. However, increasing values of basal CBV were associated with monotonically increasing mean vessel sizes and monotonically decreasing GE to SE ratios of functional changes in CBV (fCBV). This result suggests the presence of large but weakly reactive conduit vessels at high basal values of CBV. Hence, we conclude that GE imaging is the method of choice for functional MRI (fMRI) using exogenous contrast agent in most cases, although SE methods may represent a more spatially linear representation of underlying neural activity that becomes most apparent in regions with high basal CBV, such as the cortical surface. Magn Reson Med 58:769–776, 2007. © 2007 Wiley‐Liss, Inc.
Dynamic contrast‐enhanced myocardial perfusion MRI accelerated with k‐t sense
Authors: Plein Sven , Ryf Salome , Schwitter Juerg , Radjenovic Aleksandra , Boesiger Peter , Kozerke Sebastian
Published: September 2007

In the k‐t sensitivity encoding (k‐t SENSE) method spatiotemporal data correlations are exploited to accelerate data acquisition in dynamic MRI studies. The present study demonstrates the feasibility of applying k‐t SENSE to contrast‐enhanced myocardial perfusion MRI and using the speed‐up to increase spatial resolution. At a net acceleration factor of 3.9 (k‐t factor of 5 with 11 training profiles) accurate representations of dynamic signal intensity (SI) changes were achieved in computer simulations. In vivo, 5× k‐t SENSE was compared with 2× SENSE (identical acquisition parameters except for in‐plane spatial resolution = 1.48 × 1.48 mm2 vs. 2.64 × 2.64 mm2, respectively). In 10 volunteers no differences in myocardial SI profiles were found (relative peak enhancement = 151% vs. 149.7%, maximal upslope = 12.9%/s vs. 13.3%/s for 2× SENSE and 5× k‐t SENSE, respectively, all P > 0.05). Overall image quality was similar, but endocardial dark rim artifacts were reduced with k‐t SENSE. Signal‐to‐noise ratio (SNR) in the myocardium was greater with 5× k‐t SENSE by a factor of 1.36 ± 0.23 at peak contrast enhancement with the relative yield decreasing with increasing dynamics in the object in accordance to theory. Higher nominal acceleration factors of up to 10‐fold were shown to be feasible in computer simulations and in vivo. Magn Reson Med 58:777–785, 2007. © 2007 Wiley‐Liss, Inc.
MRI detection of paramagnetic chemical exchange effects in mice kidneys in vivo
Authors: Vinogradov Elena , He Huamei , Lubag Angelo , Balschi James A. , Sherry A. Dean , Lenkinski Robert E.
Published: September 2007

In this report, the On resonance PARamagnetic CHemical Exchange Effects (OPARACHEE) method was implemented in vivo using WALTZ‐16* as a preparation pulse with a standard spin echo sequence to detect the accumulation and clearance of the TmDOTA‐4AmC− in mouse kidney. The performance of the technique in vivo is described in terms of the magnitude of the contrast effect versus the bolus agent concentration and signal‐to‐noise ratio (SNR) levels. The lowest injected concentration of TmDOTA‐4AmC−, 200 μL of a 2‐mM stock solution (corresponds to ∼0.2 mM agent in plasma), reduced the total water signal in the kidney papilla by 45% 3 min after the a bolus injection. The results show that the OPARACHEE methodology employing low‐amplitude RF trains can detect paramagnetic exchanging agents in vivo. Magn Reson Med 58:650–655, 2007. © 2007 Wiley‐Liss, Inc.
RASER: A new ultrafast magnetic resonance imaging method
Authors: Chamberlain Ryan , Park Jang‐Yeon , Corum Curt , Yacoub Essa , Ugurbil Kamil , Jack Clifford R. , Garwood Michael
Published: September 2007

A new MRI method is described to acquire a T2‐weighted image from a single slice in a single shot. The technique is based on rapid acquisition by sequential excitation and refocusing (RASER). RASER avoids relaxation‐related blurring because the magnetization is sequentially refocused in a manner that effectively creates a series of spin echoes with a constant echo time. RASER uses the quadratic phase produced by a frequency‐swept chirp pulse to time‐encode one dimension of the image. In another implementation the pulse can be used to excite multiple slices with phase‐encoding and frequency‐encoding in the other two dimensions. The RASER imaging sequence is presented along with single‐shot and multislice images, and is compared to conventional spin‐echo and echo‐planar imaging sequences. A theoretical and empirical analysis of the spatial resolution is presented, and factors in choosing the spatial resolution for different applications are discussed. RASER produces high‐quality single‐shot images that are expected to be advantageous for a wide range of applications. Magn Reson Med 58:794–799, 2007. © 2007 Wiley‐Liss, Inc.