bluuebunny/crossref_metadata_2025 huggingface dataset:
Is there a change in water proton density associated with functional magnetic resonance imaging?
Authors: Jochimsen Thies H. , Norris David G. , Möller Harald E.
Published: January 2005

In a recent series of studies (see, for example, Stroman et al. Magn Reson Imag 2001; 19:827–831), an increase of water proton density has been suggested to correlate with neuronal activity. Owing to the significant implications of such a mechanism for other functional experiments, the functional signal changes in humans at very short echo times were re‐examined by spin‐echo EPI at 3 T. The results do not confirm the previous hypothesis of a significant increase in extravascular proton density at TE = 0. Instead, an alternative explanation of the effect is offered: The use of a low threshold to identify activated voxels may generate an artificial offset in functional contrast due to the inclusion of false‐positives in the analysis. Magn Reson Med 53:470–473, 2005. © 2005 Wiley‐Liss, Inc.
Ischemia‐induced ADC changes are larger than osmotically‐induced ADC changes in a neonatal rat hippocampus model
Authors: van Pul C. , Jennekens W. , Nicolay K. , Kopinga K. , Wijn P.F.F.
Published: January 2005

Diffusion‐weighted imaging (DWI) is frequently used to diagnose stroke. However, the origin of the observed reduction in the apparent diffusion coefficient (ADC) in the acute phase following ischemia is not well understood. Although cell swelling is considered to play an important role, it is unclear whether this can completely explain the large ADC decrease. We developed a method to induce in neonatal rat hippocampal slices both osmotic perturbations, which lead to cell swelling, and oxygen/glucose deprivation (OGD), which simulates ischemia. A perfusion system was used to provide the hippocampal slices with nutrients and oxygen to maintain slice viability, which was verified with the use of fluorescent dyes (live/dead staining). Upon induction of OGD, the ADC decreased to ∼57% of the initial value within 2 hr. The ADC reduction cannot fully be explained by changes due to cell swelling, since these led only to a maximum decrease of ∼83%. Therefore, in addition to cell swelling, other changes must contribute significantly to the ADC reduction. Magn Reson Med 53:348–355, 2005. © 2005 Wiley‐Liss, Inc.
Measurement and correction of transmitter and receiver induced nonuniformities in vivo
Authors: Wang Jinghua , Qiu Maolin , Yang Qing X. , Smith Michael B. , Constable R. Todd
Published: January 2005

Signal intensity nonuniformities in high field MR imaging limit the ability of MRI to provide quantitative information and can negatively impact diagnostic scan quality. In this paper, a simple method is described for correcting these effects based on in vivo measurement of the transmission field B1+ and reception sensitivity maps. These maps can be obtained in vivo with either gradient echo (GE) or spin echo (SE) imaging sequences, but the SE approach exhibits an advantage over the GE approach for correcting images over a range of flip angles. In a uniform phantom, this approach reduced the ratio of the signal SD to its mean from around 30% before correction to approximately 6% for the SE approach and 9% for the GE approach after correction. The application of the SE approach for correcting intensity nonuniformities is demonstrated in vivo with human brain images obtained using a conventional spin echo sequence at 3.0 T. Furthermore, it is also shown that this in vivo B1+ and reception sensitivity mapping can be performed using segmented echo planar imaging sequences providing acquisition times of less than 2 min. Although the correction presented here is demonstrated with a simultaneous transmit and receive volume coil, it can be extended to the case of separate transmission and reception coils, including surface and phase array coils. Magn Reson Med 53:408–417, 2005. © 2005 Wiley‐Liss, Inc.
Imaging anisotropic and viscous properties of breast tissue by magnetic resonance‐elastography
Authors: Sinkus R. , Tanter M. , Catheline S. , Lorenzen J. , Kuhl C. , Sondermann E. , Fink M.
Published: January 2005

MR‐elastography is a new technique for assessing the viscoelastic properties of tissue. One current focus of elastography is the provision of new physical parameters for improving the specificity in breast cancer diagnosis. This analysis describes a technique to extend the reconstruction to anisotropic elastic properties in terms of a so‐called transversely isotropic model. Viscosity is treated as being isotropic. The particular model chosen for the anisotropy is appealing because it is capable of describing elastic shear anisotropy of parallel fibers. The dependence of the reconstruction on the particular choice of Poisson's ratio is eliminated by extracting the compressional displacement contribution using the Helmholtz–Hodge decomposition. Results are presented for simulations, a polyvinyl alcohol breast phantom, excised beef muscle, and measurements in two patients with breast lesions (invasive ductal carcinoma and fibroadenoma). The results show enhanced anisotropic and viscous properties inside the lesions and an indication for preferred fiber orientation. Magn Reson Med 53:372–387, 2005. © 2005 Wiley‐Liss, Inc.
Detection threshold of single SPIO‐labeled cells with FIESTA
Authors: Heyn Chris , Bowen Chris V. , Rutt Brian K. , Foster Paula J.
Published: January 2005

MRI of superparamagnetic iron oxide (SPIO)‐labeled cells has become a valuable tool for studying the in vivo trafficking of transplanted cells. Cellular detection with MRI is generally considered to be orders of magnitude less sensitive than other techniques, such as positron emission tomography (PET), single photon emission‐computed tomography (SPECT), or optical fluorescence microscopy. However, an analytic description of the detection threshold for single SPIO‐labeled cells and the parameters that govern detection has not been adequately provided. In the present work, the detection threshold for single SPIO‐labeled cells and the effect of resolution and SNR were studied for a balanced steady‐state free precession (SSFP) sequence (3D‐FIESTA). Based on the results from both theoretical and experimental analyses, an expression that predicts the minimum detectable mass of SPIO (mc) required to detect a single cell against a uniform signal background was derived: mc = 5v/(Kfsl · SNR), where v is the voxel volume, SNR is the image signal‐to‐noise ratio, and Kfsl is an empirical constant measured to be 6.2 ± 0.5 × 10−5 μl/pgFe. Using this expression, it was shown that the sensitivity of MRI is not very different from that of PET, requiring femtomole quantities of SPIO iron for detection under typical micro‐imaging conditions (100 μm isotropic resolution, SNR = 60). The results of this work will aid in the design of cellular imaging experiments by defining the lower limit of SPIO labeling required for single cell detection at any given resolution and SNR. Magn Reson Med 53:312–320, 2005. © 2005 Wiley‐Liss, Inc.
Small tip angle three‐dimensional tailored radiofrequency slab‐select pulse for reduced B1 inhomogeneity at 3 T
Authors: Saekho Suwit , Boada Fernando E. , Noll Douglas C. , Stenger V. Andrew
Published: January 2005

This work presents a small tip‐angle 3D tailored RF slab‐select pulse for reducing the B1 field inhomogeneity at 3T. The compensated slice profile was determined from a B1 inhomogeneity map. SNR improvement and degree of artifact reduction were evaluated in a NiCl2 doped phantom and human brains. The technique was found to reduce inhomogeneities as large as 30% of the peak image magnitude in all three spatial directions in the brain using a standard head coil. Magn Reson Med 53:479–484, 2005. © 2005 Wiley‐Liss, Inc.
Echo time optimization for linear combination myelin imaging
Authors: Vidarsson Logi , Conolly Steven M. , Lim Kelvin O. , Gold Garry E. , Pauly John M.
Published: January 2005

A 3‐echo linear combination myelin imaging method is presented. The echo times and weights are chosen such that the signal‐to‐noise ratio (SNR) of myelin–water is maximized, and signals from other white matter components are sufficiently suppressed. Interfering tissue water and cerebrospinal fluid (CSF) signals are much stronger than myelin due to their longer T2 and abundance. By carefully optimizing the echo times a 50‐fold tissue water suppression is achieved along with a 10‐fold CSF suppression. For comparison 4, 5, and 32 echo filters are also designed using the same method. The SNR efficiency of these filters is very similar. The 3‐echo filter design was validated by phantom scans. In addition, multislice in vivo myelin images were acquired from both a healthy volunteer and a multiple sclerosis patient. Total scan time was 5 min. A uniform T2 filter is also designed to pass all white matter species with uniform gain. The myelin–water fraction of the in vivo 3‐echo data set is then measured by dividing the myelin image by the uniformly filtered image. Obtained myelin–water fractions compare well with previous work. Magn Reson Med 53:398–407, 2005. © 2005 Wiley‐Liss, Inc.
Assessing linear time‐invariance in human primary somatosensory cortex with BOLD fMRI using vibrotactile stimuli
Authors: Nangini C. , MacIntosh B.J. , Tam F. , Staines W.R. , Graham S.J.
Published: January 2005

The assumption of linear time‐invariance (LTI) in the human primary somatosensory cortex (SI) is assessed for fMRI signals generated by variable‐duration vibrotactile stimuli. Predictions based on time‐shifted summation (TSS) of responses to 2 s stimuli overestimate observed BOLD signal amplitudes in response to longer‐duration stimuli, in agreement with previous findings in other primary sensory cortices. To interpret these results, we undertook an alternative approach for LTI assessment by characterizing BOLD signals using two biophysical models. The first model assumes that the input stimulus envelope is proportional to neural activity. The second assumes that neural activity exhibits both transient and steady‐state components, consistent with extensive electrophysiological data, and fits the experimental data better. Although nonlinearity remains evident for short stimulus durations, the latter model shows that the TSS procedure to assess LTI overestimates the BOLD signal because the temporal characteristics of neural activity have not been considered adequately. Further research to investigate the BOLD response to time‐varying neural activity is required. Magn Reson Med 53:304–311, 2005. © 2005 Wiley‐Liss, Inc.
Effects of the apparent transverse relaxation time on cerebral blood flow measurements obtained by arterial spin labeling
Authors: St. Lawrence K.S. , Wang J.
Published: January 2005

Previous modeling studies have predicted that a significant fraction of the signal in arterial spin labeling (ASL) experiments originates from labeled water in the capillaries. Provided that the relaxation times in blood and tissue are similar, ASL data can still be analyzed with the conventional one‐compartment Kety model. Such studies have primarily focused on T1 differences and have neglected any differences in transverse relaxation times (T2 and T). This is reasonable for studies at lower fields; however, it may not be valid at higher fields due to the stronger susceptibility effects of deoxygenated blood. In this study a tracer kinetic model was developed that includes T differences between capillary blood and tissue. The model predicts that a reduction in blood T at higher fields will attenuate the capillary contribution to the ASL signal. This in turn causes an underestimation of CBF when ASL data are analyzed with the one‐compartment Kety model. We confirmed this prediction by comparing ASL data collected at 1.5 and 4 T, and at multiple gradient echoes (19, 32, 45, and 58 ms). A decrease in resting‐state CBF with echo time (TE) was observed at 4 T, but not at 1.5 T. These results suggest that at higher fields AST data should be collected using gradient‐echo techniques with short TEs, or with spin‐echo techniques. Furthermore, the sensitivity of the CBF measurements to venous T may affect the interpretation of concurrent ASL/BOLD studies. Magn Reson Med 53:425–433, 2005. © 2005 Wiley‐Liss, Inc.
Mitigation of susceptibility‐induced signal loss in neuroimaging using localized shim coils
Authors: Hsu Jung‐Jiin , Glover Gary H.
Published: January 2005

Correction of magnetic field distortions is essential for obtaining accurate brain blood‐oxygen‐level‐dependent functional magnetic resonance imaging (fMRI) activation maps. The present work introduces an active shimming method that utilizes the magnetic field generated by resistive shim coils placed in the mouth to locally homogenize the magnetic field in the inferior portion of the frontal lobe, where the field is most seriously distorted. The shimming field can be optimized in situ patient by patient for the region of interest of the scanner operator's choice. The method at 1.5 T is shown to be effective in reducing field inhomogeneity and in recovery of fMRI signal. For example, in a region of interest approximately of 149 cm3, a coil of simple geometry can reduce the root mean square of the magnetic field by more than 50% and the recovered signal increases the extent of activation detected in a breath‐holding fMRI experiment. Magn Reson Med 53:243–248, 2005. © 2005 Wiley‐Liss, Inc.
MR spectroscopic evidence for glial increase but not for neuro‐axonal damage in MS normal‐appearing white matter
Authors: Vrenken H. , Barkhof F. , Uitdehaag B.M.J. , Castelijns J.A. , Polman C.H. , Pouwels P.J.W.
Published: January 2005

Quantitative single‐voxel, short echo‐time (TE) MR spectroscopy (MRS) was used to determine metabolite concentrations in the cerebral normal‐appearing white matter (NAWM) of 76 patients with multiple sclerosis (MS), and the WM of 25 controls. In NAWM of all MS disease types (primary progressive, relapsing‐remitting, and secondary progressive), the concentration ratio of total N‐acetyl‐aspartate (tNAA)/total creatine (tCr) was decreased compared to controls. Remarkably, this was entirely due to an increase of tCr in MS patients, whereas there was no difference in tNAA. Separate quantification of the two tNAA components yielded no significant difference in NAA (N‐acetyl‐aspartate), while the concentration of NAAG (N‐acetyl‐aspartyl‐glutamate) was slightly—but significantly—elevated in MS patients. Myo‐inositol (Ins) was strongly increased in MS patients, and choline‐containing compounds (Cho) were mildly increased. There were no metabolite differences between disease types, and no correlations with disability scores. The results are supported by measures of spectral quality, which were identical for patients and controls. In conclusion, MS NAWM containing very little perilesional tissue is characterized by increased glial cell numbers (increase of Ins and tCr) without evidence of axonal dysfunction (normal NAA). Further studies should elucidate the mechanism underlying increased NAAG in MS NAWM. Magn Reson Med 53:256–266, 2005. © 2005 Wiley‐Liss, Inc.
Muruganandham et al. In Vivo Tumor Lactate Relaxation Measurements by Selective Multiple‐Quantum‐Coherence (Sel‐MQC) Transfer, Magn Reson Med 2004;52:902‐906
Authors: Muruganandham Manickam
Published: January 2005

The original article to which this Erratum refers was published in Magnetic Resonance in Medicine (2004) 52(4) 902–906.
Dynamic contrast‐enhanced MRI in normal and abnormal prostate tissues as defined by biopsy, MRI, and 3D MRSI
Authors: Noworolski S.M. , Henry R.G. , Vigneron D.B. , Kurhanewicz J.
Published: January 2005

This study characterized dynamic contrast‐enhanced (DCE) MRI of prostate tissues: cancerous peripheral zone (PZ), normal PZ, stromal benign prostatic hyperplasia (BPH), and glandular BPH. MRI, MRSI, and DCE MRI were performed on 25 patients. Tissues were identified with MRI, MRSI, and (when available) biopsy results. Motion between MRI and DCE MRI, and within DCE MRI was assessed and manually corrected. To assess tissue and patient effects, native T1's were measured in 12 of 25 patients, and DCE MRI results were normalized to muscle enhancement. Regions of cancer had a higher peak enhancement (P < 0.006), faster enhancement rate (P < 0.0008), and faster washout slope (P < 0.05) than normal PZ tissues. Stromal BPH had the fastest enhancement rate (P < 0.003) of all tissues and tended to have the greatest enhancement. Intersequence motion averaged 2.6 mm and reached 7.9 mm. Motion within DCE MRI was generally minimal (<2 pixels), but one case showed a large shift that would have confounded the results. Native T1's were similar across the prostatic tissues. Interpatient variability in DCE MRI was only partially reduced by normalization to muscle. DCE MRI of the prostate discriminated PZ cancer from normal PZ tissues and predominantly stromal and glandular BPH. Magn Reson Med 53:249–255, 2005. © 2005 Wiley‐Liss, Inc.
Stochastic modeling for computational warranty analysis
Authors: Wortman M.A. , Elkins Debra A.
Published: January 2005

We examine two key stochastic processes of interest for warranty modeling: (1) remaining total warranty coverage time exposure and (2) warranty load (total items under warranty at time t). Integral equations suitable for numerical computation are developed to yield probability law for these warranty measures. These two warranty measures permit warranty managers to better understand time‐dependent warranty behavior, and thus better manage warranty cash reserves. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005.
Validation and advantages of FAWSETS perfusion measurements in skeletal muscle
Authors: Marro Kenneth I. , Hyyti Outi M. , Vincent Michelle A. , Kushmerick Martin J.
Published: January 2005

This work discusses the strengths, limitations and validity of a novel arterial spin labeling technique when used specifically to measure perfusion in limb skeletal muscle. The technique, flow‐driven arterial water stimulation with elimination of tissue signal (FAWSETS), offers several advantages over existing arterial spin labeling techniques. The primary goal of this study was to determine the perfusion signal response to changes in net hind limb flow that were independently verifiable. The range of perfusate flow was relevant to skeletal muscle during mild to moderate exercise. Localized, single voxel measurements were acquired from a 5 mm‐thick slice in the isolated perfused rat hind limb at variable net flow rates. The results show that the perfusion signal is linearly proportional to net hind limb flow with a correlation coefficient of 0.974 (p = 0.0013). FAWSETS is especially well suited for studies of skeletal muscle perfusion, where it eliminates the need to compensate for magnetization transfer and arterial transit time effects. A conceptual discussion of the basic principles underlying these advantages is presented. Copyright © 2005 John Wiley & Sons, Ltd.
Sputum induction in children with difficult asthma: Safety, feasibility, and inflammatory cell pattern
Authors: Lex Christiane , Payne Donald N.R. , Zacharasiewicz Angela , Li Albert M. , Wilson Nicola M. , Hansel Trevor T. , Bush Andrew
Published: January 2005

Difficult childhood asthma is defined by persistent symptoms despite maximal conventional therapy. We aimed to establish a safe method of sputum induction for these children and to study cytology and the relationship to exhaled nitric oxide (eNO). Sputum induction was performed in 38/40 children (aged 6–16 years) with difficult asthma, using 3.5% saline for four 5‐min periods after bronchodilator pretreatment. Two children were excluded from sputum induction because postbronchodilator forced expired volume in 1 sec (FEV1) was <65% predicted. Seven of 38 children had symptoms (dyspnea and wheezing) during induction; of these, 3 experienced a fall in FEV1 of >20% from postbronchodilator FEV1, readily reversed with salbutamol. Sputum induction was successful in 28/38 children, with a higher success rate in children ≥ 12 years than in younger children (87% vs. 50%, P = 0.02). Only 9/28 had abnormal sputum cytology; of these, 6 had predominant sputum eosinophilia (>2.5% eosinophils, ≤54% neutrophils), while 3 had sputum neutrophilia (≤2.5% eosinophils, >54% neutrophils). Of 23 children with elevated eNO values, only 6 had sputum eosinophilia. In conclusion, sputum induction can be used to assess airway inflammation in children with difficult asthma, but abnormal sputum cytology is only present in a minority. Raised nitric oxide is only poorly predictive of sputum eosinophilia in these children. Pediatr Pulmonol. 2005; 39:318–324. © 2005 Wiley‐Liss, Inc.
Thrombophilia in children with cystic fibrosis
Authors: Balfour‐Lynn I.M. , Malbon K. , Burman J.F. , Davidson S.J.
Published: January 2005

In some children with cystic fibrosis (CF), percutaneous long lines occlude sooner than expected (due to thrombophlebitis or thrombosis), and many have a totally implantable venous access device (TIVAD), a recognized complication of which is thrombosis. This complication is more likely if the child has an underlying thrombotic tendency, which may be enhanced in the presence of inflammatory lung disease. There are no reports of an identified association of heritable thrombophilia with CF, although individual cases have been recognized. Our aim was to determine the incidence of thrombophilia in children with CF. In a tertiary pediatric CF center, blood was screened for thrombophilia at annual review, and retested if abnormal. A thrombotic abnormality was found in 41/204 (20%) patients. These included activated protein C resistance (10/204, 5%) with a prevalence similar to that expected, but the following abnormalities had an increased prevalence: antithrombin deficiency (2/204, 1%), protein S deficiency (11/204, 5%), protein C deficiency (8/204, 4%), and lupus anticoagulant (18/204, 9%). There were no differences found in those with thrombophilia for the following parameters: age, gender, genotype, lung function, presence of Pseudomonas aeruginosa, prothrombin time, serum IgE, aspergillus‐specific IgE, liver function, and blood inflammatory markers. Fifteen children had TIVADs, 4 of whom had evidence of thrombophilia. In conclusion, a significant proportion of patients had a thrombophilic abnormality. We recommend that thrombophilia screening be performed prior to insertion of a TIVAD, and also in those with a history of venous thrombosis, blocked TIVADs, or recurring problems with long lines. Pediatr Pulmonol. 2005; 39:306–310. © 2005 Wiley‐Liss, Inc.
Exercise‐induced respiratory symptoms are poor predictors of bronchoconstriction
Authors: De Baets Frans , Bodart Eddy , Dramaix‐Wilmet Michèle , Van Daele Sabine , de Bilderling Georges , Masset Sophie , Vermeire Paul , Michel Olivier
Published: January 2005

Exercise‐induced asthma (EIA) is a possible cause of poor physical performance in children. No data are available on the value of respiratory symptoms to discriminate children with bad physical fitness from children with EIA. We evaluated respiratory symptoms in school‐age children during and after exercise in relation to EIA. The population of 149 primary schools (849 classes with 15,241 children) was enrolled in the study. EIB was assessed using the 6‐min free‐running‐test (6MFRT) in 15,241 children. At the end or at premature arrest of the 6MFRT, signs reported by the children and clinical symptoms observed by supervising physicians were recorded. Peak flow measurements were obtained before and 5 and 10 min after the 6MFRT, a decrease of 15% or more being defined as significant. The 6MFRT was positive in 7.4% of primary schoolchildren. Girls were more likely to have a positive test than boys (8.5% vs. 6.4%,P < 0.001), and children living in urban areas more than those living in rural areas (8.9% vs. 7.0%,P < 0.01). Premature arrest was seen in 3.5% (i.e., n = 353) of the children. The main reasons for premature arrest were dyspnea and chest pain. Among them, only 21% had a positive 6MFRT, while 89% with a positive 6MFRT could terminate the test. Premature arrest, breathlessness, chest tightness, wheezing, and cough had a positive predictive value to detect a EIA of 21.9%, 20.8%, 36.4%, 41.2%, and 28.3%, respectively, and a sensitivity of 10.8%, 29.5%, 14.9%, 4.8%, and 13.0%, respectively. In conclusion, EIA was detected in 7.4% of schoolchildren. A slightly higher incidence was observed in girls and children from an urban area. Neither premature arrest nor clinical signs and symptoms were good predictors of EIA in primary schoolchildren. Pediatr Pulmonol. 2005; 39:301–305. © 2005 Wiley‐Liss, Inc.
Neonatal chest wall suspension splint: A novel and noninvasive method for support of lung volume
Authors: Miller Thomas L. , Palmer Charles , Shaffer Thomas H. , Wolfson Marla R.
Published: January 2005

Surfactant and musculoskeletal immaturity results in lower compliance of the lung relative to the chest wall, with clinical manifestations of low lung volume, marked chest wall retractions (CWR), and thoracoabdominal asynchrony. Inspiratory efforts are dissipated on distorting the chest wall inward rather than recruiting lung volumes. The current study tests the hypothesis that a novel neonatal chest wall suspension splint (SP), designed to provide stability to the compliant chest wall, would reduce inspiratory chest wall retractions and improve lung volumes. Nine preterm infants (29 ± 1 SE weeks of gestation; 1.59 ± 0.27 SE kg study weight) were studied at 16 ± 5 SE days of life at baseline (BL) and following application of the front plate (FP) and the full SP (Hug n Snug™ Neonatal Chest Splint, Respironics, Inc.). Phase angle of thoracoabdominal motion, CWR, functional residual capacity (FRC), and pulmonary function were evaluated during spontaneous breathing. Compared to BL, there was a significant decrease in anterior CWR (2.21 ± 0.91 SE vs. 0.25 ± 0.09 SE mm; P < 0.05), an increase in FRC (16.6 ± 2.8 SE vs. 27.8 ± 5.5 SE ml/kg; P < 0.05) and tidal volume (4.8 ± 1.5 SE vs. 7.3 ± 1.4 SE ml/kg; P < 0.05), minimal effect on pulmonary compliance (1.98 ± 0.50 SE vs. 1.72 ± 0.30 SE ml/cmH2O/kg), and a trend for a decrease in phase angle (128.4 ± 10.9 SE vs. 111.8 ± 19.3 SE) with the application of the splint. FRC correlated inversely with severity of CWR across all conditions (P < 0.05, r = −0.68). Phase angle was directly correlated to anterior CWR (r = 0.72; P < 0.05) and correlated inversely with FRC (P < 0.005; r = −0.56). We speculate that by improving CW stability, the use of this splint may reduce the energetic requirements of breathing and, potentially, the need for more invasive ventilatory support in the neonate. Pediatr Pulmonol. © 2005 Wiley‐Liss, Inc.
Full potential calculation of structural, elastic and electronic properties of BaZrO3 and SrZrO3
Authors: Terki R. , Feraoun H. , Bertrand G. , Aourag H.
Published: January 2005

Ab initio calculations have been performed on the structural and electronic properties of perovskite‐type compounds BaZrO3 and SrZrO3 ceramics. The Kohn–Sham equations were solved by applying the full‐potential linearized augmented‐plane‐wave (FP‐LAPW) method. In this approach, the generalized gradient approximation was used for the exchange‐correlation potential. The ground state properties such as lattice parameter, elastic constants, bulk modulus and its pressure derivative were calculated and the results are compared with previous calculations and experimental data when available. The SrZrO3 perovskite should exhibit higher hardness and stiffness than BaZrO3. Furthermore, the electronic structure calculations show that these materials are weakly ionic and exhibit indirect and wide band gaps, which are typical of insulators. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A molecular dynamics study on liquid 1‐octanol. Part 3. Evaluating octanol/water partition coefficients of novel thrombin inhibitors via free‐energy perturbations
Authors: Fernandes De Oliveira César Augusto , Werneck Guimarães Cristiano Ruch , De Mello Heloisa , Echevarria Aurea , De Alencastro Ricardo Bicca
Published: January 2005

Thrombin inhibition is an important strategy for the treatment of thrombotic and embolic disorders. Despite high in vitro affinity for the enzyme, synthetic thrombin inhibitors have limited oral bioavailability due to low intestinal permeability. In a previous work, we obtained the following order for thrombin binding by using molecular dynamics (MD) simulations and the finite difference thermodynamic integration (FDTI) method: p‐(2‐oxo‐1‐propyl)benzamidine (POPBz) > p‐ethylbenzamidine (PEBz) > p‐(1‐propyl)benzamidine (PPBz) > p‐methylbenzamidine (PMBz) > benzamidine (Bz). As the octanol/water partition coefficient (log Po/w) is a thermodynamic property that may be related to drug transfer across biological membranes, we now turn our attention to the calculation by the FDTI method of relative log Po/w for the benzamidine derivatives. To examine the reliability of the method, log Po/w values for Bz and PMBz were determined experimentally. Experimental log Po/w of −1.02 and −0.89 were obtained for Bz and PMBz, and theoretical log Po/w of −0.12, −0.01, and −1.00 were obtained for PEBz, PPBz, and POPBz. Thus, we improved the hydrophobicity of Bz by adding the methyl, ethyl, propyl, and 2‐oxo‐propyl groups, but further substitutions should be conducted to raise log Po/w above zero and into a region where reasonable oral absorption might be expected. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Simultaneous determination of zidovudine and lamivudine from rat tissues by liquid chromatography/tandem mass spectrometry
Authors: Alnouti Yazen , Lewis Summer R. , White Catherine A. , Bartlett Michael G.
Published: January 2005

A simple liquid chromatography/tandem mass spectrometry (LC/MS/MS) method has been developed and validated for the simultaneous determination of zidovudine (AZT) and lamivudine (3TC) in rat plasma, amniotic fluid, placental, and fetal tissues. Samples were processed by acetonitrile precipitation. Chromatography was performed using a C18 column (5 μm, 150 × 3.9 mm i.d). The mobile phase consisted of 30% methanol and 7.5 mM ammonium acetate (pH 6.5). The method was validated in the range of 0.05–25 μg/mL for both 3TC and AZT in the four biological matrices. Finally, the method was applied to a study involving fetal transport following co‐administration of these compounds at a dose of 25 mg/kg each in a pregnant rat. Copyright © 2005 John Wiley & Sons, Ltd.
Weak solutions to a nonlinear variational wave equation with general data
Authors: Zhang Ping , Zheng Yuxi
Published: January 2005

We establish the existence of global weak solutions to the initial value problem for a nonlinear variational wave equation

u_{tt}−c(u)(c(u)u_{x})_{x} = 0

with general initial data

(u(0)\text{,}u_{t}(0)) = (u_{0}\text{,}u_{1}) \in W^{1\text{,}2} \times L^{2}

under the assumptions that the wave speed

c(u)

satisfies

c^{′}( \cdot )⩾0

and

c^{′}(u_{0}( \cdot )) > 0

. Moreover, we obtain high regularity for the spatial derivative

\partial _{x}u

of the wave amplitude

u

away from where

c^{′}(u) = 0

. This equation arises from studies in nematic liquid crystals, long waves on a dipole chain, and a few other fields. We use Young measure method in the setting of

L^{p}

spaces and method of renormalization to overcome the difficulty that oscillations in a sequence of approximations get amplified by the quadratic growth term of the equation. We use a high space-time estimate for

\partial _{x}u

to handle possible concentrations. This result improves our earlier existence result for initial data in the space

W^{1\text{,}\infty } \times L^{\infty }

to the natural space

W^{1\text{,}2} \times L^{2}

.

Nous prouvons l'éxistence de solutions faibles globales pour le problème de Cauchy concernant une équation des ondes non variationnelles

u_{tt}−c(u)(c(u)u_{x})_{x} = 0

avec des conditions initiales générales

(u(0)\text{,}u_{t}(0)) = (u_{0}\text{,}u_{1}) \in W^{1\text{,}2} \times L^{2}

sous l'hypothèse que la vitesse d'onde

c(u)

vérifie

c^{′}( \cdot )⩾0

et

c^{′}(u_{0}( \cdot )) > 0

. De plus, nous obtenons une régularité élevée pour la dérivée spatiale

\partial _{x}u

de l'amplitude

u

de l'onde loin de la zone où

c^{′}(u) = 0

. Cette équation intervient dans l'étude des crystaux liquides nématiques, d'ondes longues dans des chaînes dipolaires et de quelques autres domaines. Nous utilisons la méthode des mesures de Young dans le contexte d'espaces

L^{p}

et la méthode de renormalisation pour résoudre la difficulté de l'amplification par les termes à croissance quadratique de l'équation, des oscillations d'une suite d'approximations. Nous nous servons d'une estimée d'ordre élevé en espace et en temps pour

\partial _{x}u

afin de traiter les concentrations éventuelles. Ce résultat étend nos résultats d'éxistence antérieurs pour des données initiales dans l'espace

W^{1\text{,}\infty } \times L^{\infty }

au cas naturel de l'espace

W^{1\text{,}2} \times L^{2}

.
Production of transgenetic sugarbeet (Beta vulgaris L.) plants resistant to phosphinothricin
Authors: Kishchenko E.M. , Komarnitskii I.K. , Kuchuk N.V.
Published: January 2005

A method of Agrobacterium‐mediated genetic transformation of sugarbeet (Beta vulgaris L.) with vacuum infiltration has been developed. Aseptic 3‐weeks old etiolated seedlings of two diploid O‐type sugarbeet lines (KS3 and KS7) have been used for genetic transformation. Transgenic sugarbeet plants carrying the reporter β‐glucuronidase gene have been selected for their resistance to glufosinate ammonium herbicide. Integration of transgenes into sugarbeet genome was confirmed with GUS assay and PCR using primers for bar and gusA genes.
Intracellular redistribution of heme in rat liver under oxidative stress: the role of heme synthesis*
Authors: Kaliman Pavel A. , Barannik Tatyana , Strel'chenko Ekaterina , Inshina Natalya , Sokol Oxana
Published: January 2005

Heme distribution in subcellular fractions of rat liver was studied first hours under the action of several agents causing oxidative stress in vivo. Total and post‐mitochondrial heme content in liver was found to depend on both the level of hemolysis products in blood and agent's capacity to modify heme and hemoproteins. The increase of activity of 5‐aminolevulinate synthase (ALAS) and/or heme accumulation in mitochondria was accompanied by increase of tryptophan‐2,3‐dioxygenase (TDO) heme saturation. Membrane stabilisation by tocopherol or prevention of early ALAS induction by cycloheximide prevented both mitochondrial heme accumulation and increase of TDO heme saturation. Modification of heme fully prevented the alterations of total heme content even under severe hemolysis as well as the increase of TDO heme saturation if no increase of heme synthesis occurred. Thus heme synthesis can greatly contribute to heme intracellular redistribution under oxidative stress.
Bacterial multidrug resistance unrelated to multidrug exporters: cell biology insight
Authors: Cherepenko Yelena , Hovorun Dmytro M.
Published: January 2005

Multidrug resistance (MDR) revealed in malignant cell lines was firstly attributed to the activity of multidrug exporters pumping drugs out of the cell. However, mutagenised Escherichia coli develop extraordinary numerous mutants resistant to target inhibitor and we have shown that with mutations mapped around the entire genome most of the mutants were multiple‐resistant. In case of one such mutant studied MDR was shown as a sum of individual resistances due to mutations resulted in target and ligand sequestration and induced simultaneously in tightly linked, cassette‐like genes. An explanation of local mutagenesis efficiency and the nature of sequestration process is proposed. A cassette‐like organization of genes responsible for chemoresistance emergence could promote the local intensity of mutagenesis by a cassette facing the intracellular space and flux and contacting unlike other genes mutagen the first. Target and ligand sequestration could result from clogging the intracellular flux due to cytoplasm geometry alteration attributable to disorder—order transition in natively unfolded proteins affected with mutation.
Transfer of transformed chloroplasts from Nicotiana tabacum to the Lycium barbarum plants
Authors: Sytnik Ekaterina , Komarnytsky Igor , Gleba Yuri , Kuchuk Nikolay
Published: January 2005

Plastid transformation is an attractive technology for obtaining crop plants with new useful characteristics and for fundamental researches of plastid functioning and nuclear—plastid interaction. The aim of our experiments was to obtain plants with Lycium barbarum nucleus and transformed Nicotiana tabacum plastids. Plastome of previously engineered transplastomic tobacco plants contains reporter uidA gene and selective aadA gene that confers resistance to antibiotics spectinomycin and streptomycin. Asymmetric somatic hybridization was performed for transferring transformed tobacco plastids from transplastomic tobacco plants into recipient L. barbarum wild type plants. Hybrid L. barbarum plants containing transformed tobacco plastome with active aadA and uidA genes were obtained as a result of the experiments. The work shows the possibility of obtaining transplastomic plants by transferring the transformed plastids to remote species by using somatic hybridization technology. The developed technique is especially effective for obtaining transplastomic plants that have low regeneration and transformation ability.
An assessment of Greenland walrus populations
Authors: Witting Lars , Born Erik W.
Published: January 2005

Recent abundance estimates were combined with historical catches and an age- and sex-structured population dynamic model to perform Bayesian assessments of the walrus (Odobenus rosmarus) populations in West Greenland, the North Water in northern Baffin Bay, and East Greenland. The model assumed density-regulated dynamics and pre-harvest populations in population-dynamical equilibrium. It projected the populations under the influence of the catches to estimate the historical trajectories and the current population status. It was found that the West Greenland and North Water populations have been heavily exploited during the last century with the current abundance being at best only a few per cent of the historical abundance. Apparently these populations are still being exploited above sustainable level. The East Greenland population was heavily exploited after 1889 and during the first half of the 20th century and was depleted to approximately 50% of pristine population size in 1933. After protective measures were introduced in the 1950s this population has increased to a current level close to the abundance in 1889, and the present exploitation appears to be sustainable.
Using fish-processing time to carry out acoustic surveys from commercial vessels
Authors: O'Driscoll Richard L. , Macaulay Gavin J.
Published: January 2005

In some fisheries large factory freezer trawlers have periods of down time as the catch is processed. By utilizing this time, scientific acoustic surveys can be carried out between commercial-fishing operations without compromising fishing success. Examples are presented from three acoustic surveys for hoki (Macruronus novaezelandiae) in New Zealand waters during 2002 and 2003 conducted from a commercial vessel fitted with a scientifically calibrated SIMRAD ES-60 echosounder. These surveys confirmed the presence of a new spawning area for hoki and provided biomass estimates from known fishing grounds. The approach described works well for small-scale acoustic surveys adjacent to areas of high catch rates and is cost-effective because the vessel “pays for itself” by fishing commercially. The major limitation is that the boundaries of the survey area are determined by the time available during processing, which is related to the size of the catch and the time required to search for a suitable location for the next commercial trawl. In the New Zealand hoki surveys, processing time was typically 3–8 h, which was sufficient to carry out about 10–70 km of acoustic transects. Acoustic research was also limited to periods of relatively good conditions by the use of a hull-mounted transducer.
Effects of preceding birth intervals on neonatal, infant and under‐five years mortality and nutritional status in developing countries: evidence from the demographic and health surveys
Authors: Rutstein S.O.
Published: January 2005

Objective

This paper examines the association between birth intervals and infant and child mortality and nutritional status.

Methods

Repeated analysis of retrospective survey data from the Demographic and Health Surveys (DHS) program from 17 developing countries collected between 1990 and 1997 were used to examine these relationships. The key independent variable is the length of the preceding birth interval measured as the number of months between the birth of the child under study (index child) and the immediately preceding birth to the mother, if any. Both bivariate and multivariate designs were employed. Several child and mother‐specific variables were used in the multivariate analyses in order to control for potential bias from confounding factors. Adjusted odds ratios were calculated to estimate relative risk.

Results

For neonatal mortality and infant mortality, the risk of dying decreases with increasing birth interval lengths up to 36 months, at which point the risk plateaus. For child mortality, the analysis indicates that the longer the birth interval, the lower the risk, even for intervals of 48 months or more. The relationship between chronic malnutrition and birth spacing is statistically significant in 6 of the 14 surveys with anthropometric data and between general malnutrition and birth spacing in 5 surveys. However, there is a clear pattern of increasing chronic and general undernutrition as the birth interval is shorter, as indicated by the averages of the adjusted odds ratios for all 14 countries.

Conclusion

Considering both the increased risk of mortality and undernutrition for a birth earlier than 36 months and the great number of births that occur with such short intervals, the author recommends that mothers space births at least 36 months. However, the tendency for increased risk of neonatal mortality for births with intervals of 60 or more months leads the author to conclude that the optimal birth interval is between 36 and 59 months. This information can be used by health care providers to counsel women on the benefits of birth spacing.
The HDL2/HDL3 ratio in menopause
Authors: Ushiroyama T. , Sakuma K. , Ikeda A. , Ueki M.
Published: January 2005

Objectives

The influence of the menopause on the HDL2/HDL3 ratio was assessed in association with hypertriglyceridemia.

Methods

Fasting blood samples were collected from 607 patients. Commercially available enzymatic methods were used for determination of TG, and total HDL‐C. HDL2 and HDL3 were measured by ultracentrifugation.

Results

The HDL2/HDL3 ratio had a strong negative correlation with TG (r=−0.272, P<0.0001 and r=‐0.314, P<0.0001) in both pre‐ and postmenopausal women. No significant differences were observed in HDL2, HDL3, and HDL2/HDL3 ratio between pre‐ and postmenopausal women without hypertriglyceridemia. Postmenopausal women had a significantly higher HDL2/HDL3 ratio than premenopausal women with hypertriglyceridemia.

Conclusions

These results indicate that menopausal status not only increases plasma LDL‐cholesterol and triglyceride levels, but also increases the HDL2/HDL3 ratio when associated with elevation of plasma triglyceride levels. These changes may increase the risk for CHD due to enlargement of the lipid pool.
Histoplasmosis Infection Presenting as an Isolated Subcutaneous Periarticular Upper Limb Swelling in the Immunosuppressed Patient
Authors: SMITH G. D. , SHATFORD R. A. D.
Published: January 2005

Atypical mycobacterial and fungal infections may occur in immunosuppressed patients. The impaired host response can make the clinical presentation atypical. Blood and tissue cultures may be negative in the acute phase of the illness, which can lead to a delay in diagnosis. In those patients with AIDS or other underlying immunosuppressive conditions, histoplasmosis cannot always be eradicated, but treatment that achieves chronic suppression may be adequate to maintain functional capacity. This report describes two immunosuppressed patients who presented with isolated subcutaneous histoplasmosis infection around the wrist.
Ultrasound stimulation of tendon cell proliferation and upregulation of proliferating cell nuclear antigen
Authors: Tsai Wen‐Chung , Hsu Chih‐Chin , Tang Fuk‐Tan , Chou Shih‐Wei , Chen Ying‐Jen , Pang Jong‐Hwei S.
Published: January 2005

Therapeutic ultrasound has been widely used in sports‐related tendon injuries. However, previous research has not examined the molecular mechanism of this therapeutic effect on tendon cell proliferation. This study was designed to determine the in vitro effect of ultrasound on the proliferation of tendon cells intrinsic to rat Achilles tendon. Furthermore, the existence of a correlation between this effect and the expression of the proliferating cell nuclear antigen (PCNA) was also examined. Using cultured tendon cells, cell viability was evaluated by MTT assay. The expression of PCNA protein in cells was evaluated by immunocytochemistry. The mRNA expression of PCNA was determined by reverse transcniption‐polymerase chain reaction (RT‐PCR). A dose‐dependent increase in the cellularity of tendon cells by either, pulsed or continuous mode ultrasound was demonstrated by MTT assay (p = 0.044 for the pulsed mode; p = 0.004 for the continuous mode). Ten minutes of treatment achieved maximum cellularity compared to 5 min of treatment time (p = 0.010 for pulsed ultrasound; p = 0.004 for continuous ultrasound). Immunocyto‐chemical staining revealed that ultrasound treated tendon cells were stained more strongly for PCNA than were control cells. Upregulation of PCNA at the mRNA level was also confirmed by RT‐PCR. In conclusion, ultrasound stimulates tendon cell proliferation in a process that is probably mediated by the upregulation of PCNA. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.
Markedness conflation in Optimality Theory
Authors: de Lacy Paul
Published: January 2005

Markedness distinctions can be ignored. For example, in some languages stress avoids central vowels, and falls on high peripheral vowels, yet in the Uralic language Nganasan central and high peripheral vowels are treated in the same way: stress avoids both types equally. Such ‘conflation’ of markedness categories is not only language-specific, but also phenomenon-specific. In contrast, dominance relations in markedness hierarchies are universal; e.g. stress never seeks out a central vowel when a high peripheral vowel is available. This article argues that both language-specific conflation and universal markedness relations can be expressed in Optimality Theory. Constraints that refer to a markedness hierarchy must be freely rankable and mention a contiguous range of the hierarchy, including the most marked element. The empirical focus is sonority-driven stress in Nganasan and Kiriwina. In addition, Prince & Smolensky's (1993) fixed ranking theory of markedness hierarchies is shown to be unable to produce the full range of attested conflations.