bluuebunny/crossref_metadata_2025 huggingface dataset:
Secreted apolipoprotein E reduces macrophage‐mediated LDL oxidation in an isoform‐dependent way
Authors: Mabile Laurence , Lefebvre Chantal , Lavigne Jacques , Boulet Lucie , Davignon Jean , Lussier‐Cacan Suzanne , Bernier Lise
Published: October 2003

As an inflammatory cell, the macrophage produces various oxidizing agents, such as free radical species. These can modify LDL as a secondary effect and doing so may favor atherogenic processes. Any molecule able to counteract these reactions would be of much benefit, especially if secreted by the macrophage itself at the lesion site. Such is the case for apolipoprotein E (apoE), which has been shown to exert antioxidant properties in some studies, mostly in relation to Alzheimer's disease. In this study, we assessed the antioxidant potential of the various isoforms of apoE (E2, E3, and E4) using a metal‐induced LDL oxidation system with exogenous recombinant apoE and an in vitro model of macrophage‐mediated LDL oxidation. We found that all three isoforms had an antioxidant capacity. However, whereas apoE2 was the most protective isoform in the cell‐free system, the opposite was observed in apoE‐transfected J774 macrophages. In the latter model, cellular cholesterol efflux was found to be more important with apoE2, possibly explaining the larger quantity of oxidative indices observed in the medium. It is proposed that the antioxidant property of apoE results from a balance between direct apoE antioxidant capacities, such as the ability to trap free radicals, and potentially pro‐oxidative indirect events associated with cholesterol efflux from cells. Our observations add to the therapeutic potential of apoE. However, they also suggest the need for more experiments in order to achieve careful selection of the apoE isoform to be targeted, especially in the perspective of apoE transgene use. © 2003 Wiley‐Liss, Inc.
Temperature interpolation at a large scale: test on a small area in Svalbard
Authors: Joly D. , Nilsen L. , Fury R. , Elvebakk A. , Brossard T.
Published: October 2003

A major environmental concern regarding the Arctic is how global change effects can influence vegetation and ecosystems. The amount of summer warmth is the single most important variable for biological processes in the Arctic, and the one that is most likely to be affected by climate change. A major task is to establish how temperature conditions are modified at a very high spatial resolution.

In order to build up scenarios that are as relevant as possible concerning vegetation development, the key point is to know how the spatial distribution of temperature varies and can be related to different environment factors at different spatial scales. A method is suggested for modelling the temperature distribution at a high resolution (2 × 2 m2) and with high accuracy. In step one, a polynomial equation is established for modelling the distribution of temperature values measured in the field at low spatial resolution (1 × 1 km2), with latitude and longitude defining the general trend surface of the temperature distribution. In step two, residue values from the previous step are explained by environment factors stored as numerical information layers in a geographical information system. These environmental data are derived from a high‐resolution digital elevation model and from a digitized infrared aerial photograph. Finally, the combination of these kilometric and micro‐scale models make it possible to restore the thermic field of the study area and to represent it through different maps at a very fine‐grained resolution. The method is tested on two glacier forefields in Svalbard, covering an area of 8 km2. Copyright © 2003 Royal Meteorological Society
Thermal field over Tibetan Plateau and Indian summer monsoon rainfall
Authors: Bansod Sanjay D. , Yin Zhi‐Yong , Lin Zhenyao , Zhang Xueqin
Published: October 2003

The interannual variability of the temperature anomalies over the Tibetan Plateau (25–45 °N, 75–105 °E) is examined in relation to the Indian summer monsoon rainfall (ISMR: June to September total rainfall). For this purpose, the temperature anomaly data of the central‐eastern Tibetan Plateau is divided into three regions using principal component analysis and the ISMR data for the period 1957–89 have been used. It is found that the January temperature anomaly of Region 2 has a significant negative relationship (r = −0.67) with the ISMR of the subsequent season. This region is located over the northeastern part of the Tibetan Plateau, mostly in Qinghai province, including the Bayan Harr Mountain range and the Qaidam Basin. This relationship is consistent and robust during the period of analysis and can be used to predict the strength of the Indian summer monsoon in the subsequent season. It was found that the January temperature anomaly in this region was associated with a persistent winter circulation pattern over the Eurasian continent during January through to March. Finally, the variation patterns of the temperature anomalies in all three regions over the central‐eastern Tibetan Plateau during extreme years of the ISMR are examined. It is concluded that the January temperature anomaly over the northeastern Tibetan Plateau can be useful in forecasting the drought and flood conditions over India, especially in predicting the monsoon rainfall over the areas lying along the monsoon trough. Copyright © 2003 Royal Meteorological Society
Relations between sea‐surface temperature and crop yields in Argentina
Authors: Travasso M. I. , Magrin G. O. , Rodríguez G. R.
Published: October 2003

The El Niño–southern oscillation phenomenon (ENSO) is one of the principal sources of interannual climatic variability. In Argentina, the ENSO signal is evident both in climate and crop yields. As ENSO phases (El Niño, La Niña, Neutral) can actually be predicted several months before their occurrence, the use of ENSO‐based climate forecasts as tools to assist farmers in decision making has recently been proposed. However, the use of ENSO‐phases could be insufficient for planning in the agricultural sector due to the signal interannual intra‐phase variability. Moreover, the observed spatial variability in the ENSO signal suggests the existence of other factors that influence the local climate and crop responses in the region. Looking for alternative indicators of climate variability other than ENSO phases, monthly sea‐surface temperature (SST) anomalies from the equatorial Pacific and the South Atlantic Oceans were related to maize and wheat yield anomalies in the main crop‐producing zone of the Pampas region. In general, yield anomalies were better correlated with SST anomalies occurring in the months prior to sowing. This indicator could be a useful tool to ascertain what range of yields could be expected with sufficient anticipation so as to modify crop management decisions. Copyright © 2003 Royal Meteorological Society
The teleconnections between the extreme phases of the southern oscillation and precipitation patterns over Turkey
Authors: Çaǧatay Karabörk M. , Kahya Ercan
Published: October 2003

Climatic links between monthly precipitation in Turkey and the El Niño and La Niña events using the empirical methodology of Ropelewski and Halpert are investigated. Coherent and significant precipitation responses to both the extreme phases of the southern oscillation (SO) are found in two core regions, namely western Anatolia (WA) and eastern Anatolia (EA). The geographical extent of the two regions, together with a defined signal season for each tropical event, are identified. For WA, the April–July wet period during El Niño events is the season when the teleconnection is strong and consistent. For EA, the February–June wet period during El Niño events is found to be the signal season having high rates of coherence and consistency. The occurrence of the signal season (the dry period of April–October) during La Niña events appears to be less significant in EA according to the hypergeometric model. Moreover, the annual cycle analysis implies somewhat of a modulation of regional precipitation in the WA and EA regions during the relevant signal season. From other perspectives, correlation results of seasonal precipitation and seasonal SO index values confirm the implied teleconnections, and the powers of line spectra corresponding to the El Niño occurrences supply some indications. The final aim of this work is to show some guidance for quantification of the SO‐related precipitation teleconnections for the core regions by examining shifts in precipitation amounts at various percentiles as a function of the SO extremes. Overall, the results of this investigation are in good agreement with previous relevant studies (especially global‐scale type) that try to understand complex global circulation dynamics. In conclusion, mid‐latitude precipitation responses to the extreme phases of the SO are detectable in the climate of Turkey. Copyright © 2003 Royal Meteorological Society
Carbon dioxide and water vapour flux densities over a grassland area in the Netherlands
Authors: Jacobs Adrie F. G. , Heusinkveld Bert G. , Holtslag Albert A. M.
Published: October 2003

Measurements of carbon dioxide and water vapour flux densities were carried out for a grassland area in the centre of the Netherlands during a 12 month continuous experiment using the eddy‐covariance technique. Lolium perenne and Poa trivialis mainly dominated the vegetation of the area. The leaf area index (LAI) of the grassland varied between 2.5 and 3.4, depending on the mowing scheme at the site. Fluxes are also calculated by using a canopy model in which the canopy resistance is related to the assimilation rate (A–gs model). The calculated evapotranspiration fluxes agree within 7% of the measured fluxes (R2 = 0.93;SEE = 23 W m−2). The calculated net carbon dioxide fluxes agree within 12% of the measured fluxes (R2 = 0.79;SEE = 0.16 mg m−2s−1). The net carbon dioxide fluxes consist of two opposite components: the uptake via assimilation and release via soil and plant respiration. It appears that nearly the whole year round the assimilation term dominates, which means an accumulation of carbon dioxide if no other exchange processes are present. For 2002 a net carbon uptake was found of 6.8 tonnes ha−1. Copyright © 2003 Royal Meteorological Society
Comparative analysis of spatial and seasonal variability: Austrian precipitation during the 20th century
Authors: Matulla Christoph , Penlap Edouard K. , Haas Patrick , Formayer Herbert
Published: October 2003

The purpose of this investigation is to demonstrate the usability of objective methods to study the variability of precipitation and hence to contribute to a better understanding of spatial and seasonal variability of Austria's precipitation climate during the 20th century.

This will be achieved by regionalizing the intra‐annual variability of seasonal precipitation distributions during three non‐overlapping 33 year samples (1901–33, 1934–66, 1967–99). Monthly precipitation totals were extracted at 31 Austrian stations from a homogenized long‐term climate dataset provided by the Austrian weather service. Three statistical techniques, namely cluster analysis (CLA), rotated empirical orthogonal functions (REOFs) and an unsupervised learning procedure of artificial neural networks (ANNs), were utilized to find homogeneous precipitation regions.

The results of summer (June, July, August (JJA)) and winter (December, January, February (DJF)) seasons are presented. The resulting homogeneous precipitation regions depend on season, period and method in this order. Hence, differences introduced by using different methods are small compared with those inferred by investigating different episodes and especially with those related to the seasons.

During winter, three homogeneous precipitation regions are found, independent from the period considered. These regions can be assigned to different airflows dominating Austria's climate and triggering precipitation events during the cold season. The situation during summer is more complicated. Thus, at least four clusters are necessary to record the circumstances, which are caused by spatially inhomogeneous convective events such as thunderstorms. Copyright © 2003 Royal Meteorological Society
Winter snow anomaly and atmospheric circulation in Mongolia
Authors: Morinaga Yuki , Tian Shao‐Fen , Shinoda Masato
Published: October 2003

An observational study was conducted of winter snow anomaly in Mongolia and the associated atmospheric circulation. Monthly data of snow depth and temperature at 23 Mongolian stations from 1940 to 1992 were used for a statistical analysis. The Mongolian snow amount is fairly large in the northern mountainous regions and decreases to the south. On average, there is a substantial seasonal increase in snow depth during November and December. The deepest snow occurs in January, with an average depth of 3.4 cm averaged for all 23 stations. The correlation coefficients for November and December between the snow depth and temperature are significant and negative over wide areas.

A principal component analysis was applied to interannual anomalies of January snow depth. The first mode (PC1) reveals widespread loadings of the same sign, and the second mode (PC2) shows a northeast–southwest dipole pattern. A correlation analysis was employed to examine relationships between PC1, PC2 and the preceding atmospheric circulation modes derived from a principal component analysis of the Northern Hemisphere 500 hPa geopotential heights. The PC1 time series for January is highly correlated with the North Atlantic oscillation for November, and the PC2 time series is significantly correlated with the Eurasian pattern for December. These relationships will provide a potential basis for long‐range forecasts of mid‐winter anomalous snow that leads to a significant loss of livestock (so‐called white dzud) in Mongolia. Copyright © 2003 Royal Meteorological Society
Comparative genomic hybridization of estrogen‐induced ectopic uterine‐like stem cell neoplasms in the hamster kidney: Nonrandom chromosomal alterations
Authors: Papa Dan , Li Sara Antonia , Li Jonathan J.
Published: October 2003

Karyotype and comparative genomic hybridization (CGH) analyses were performed to identify nonrandom/consistent chromosomal alterations in solely estrogen (E)‐induced primary ectopic uterine‐like stem cell tumors in the kidney (EULTK) of the Syrian hamster, using a criterion of ≥20% frequency for nonrandom occurrence. Employing this criterion, EULTK karyotype analysis showed consistent gains in chromosomes 3, 6, 11, 14, 16, 20, and 21. Consistent trisomies were seen in all of these nonrandomly gained chromosomes. Only chromosomes 3 and 6 exhibited appreciable tetrasomies. Chromosome losses were observed consistently in chromosomes 7, 12, 17, and 19. Employing the same criterion, CGH analysis of primary EULTKs showed nonrandom amplified sequences at 1pa1–a4, 2cen–pter, 3pa1–a4, 6qb2–b4, 20qa1–a4, 21qa1–a2, Xqa3–qter and regional consistent losses at 1qc1‐qter, 2qb1–c1, 3qa2–a7, 11qb5‐qter, 15qa2–a5, 18qa2–a4, and 21pa. Moreover, 88% of the EULTKs examined exhibited amplification of the 6qb2–b4 region, where c‐myc resides. The data presented lend credence to the supposition that chromosomal instability (CIN) is elicited by the upstream overexpression and subsequent amplification of c‐myc by Es in multipotential interstitial uterine stem cells present in the kidney, thus leading to neoplastic development. © 2003 Wiley‐Liss, Inc.
Cell growth inhibition by all‐trans retinoic acid in SKBR‐3 breast cancer cells: Involvement of protein kinase Cα and extracellular signal‐regulated kinase mitogen‐activated protein kinase
Authors: Nakagawa Shino , Fujii Teruhiko , Yokoyama Goro , Kazanietz Marcelo G. , Yamana Hideaki , Shirouzu Kazuo
Published: October 2003

All‐trans retinoic acid (ATRA), a synthetic derivative of vitamin A, inhibits the growth of breast cancer cells. To elucidate the mechanism by which ATRA causes cell growth inhibition, we examined changes in cell cycle and intracellular signaling pathways, focusing on protein kinase C (PKC) and mitogen‐activated protein kinase (MAPK). Using the estrogen receptor‐negative, retinoid receptor–positive breast cancer cell line SKRB‐3, we found that treatment with ATRA significantly decreased the expression of PKCα, as well as reducing ERK MAPK phosphorylation. ATRA treatment leads to dephosphorylation of Rb, and consequently to G1 arrest. Marked changes in the expression of cyclins (particularly cyclins A and E) were observed in SKBR‐3 cells treated with ATRA. Using a series of pharmacological and molecular approaches, we found evidence that ATRA‐induced SKBR‐3 cell growth inhibition involves the deregulation of the PKCα‐MAPK pathway. These data suggest that retinoids interfered with signal transduction pathways that are crucial for cell cycle progression, and highlight the complexities of the biological effects of retinoid derivatives. © 2003 Wiley‐Liss, Inc.
Reduced transcription of the RB2/p130 gene in human lung cancer
Authors: Xue Jun Hu , Gemma Akihiko , Hosoya Yoko , Matsuda Kuniko , Nara Michiya , Hosomi Yukio , Okano Tetsuya , Kurimoto Futoshi , Seike Masahiro , Takenaka Kiyoshi , Yoshimura Akinobu , Toyota Minoru , Kudoh Shoji
Published: October 2003

Reduced expression of the retinoblastoma gene (RB)2/p130 protein, as well as mutation of exons 19, 20, 21, and 22 of the same gene, has been reported in primary lung cancer. However, it has been suggested by other investigators that mutational inactivation and loss of the RB2/p130 gene and protein, respectively, are rare events in lung cancer. In order to determine the contribution and mechanisms of RB2/p130 gene inactivation to lung cancer development and progression, we quantified RB2/p130 mRNA expression levels in a range of human lung cancer cell lines (n = 13) by real‐time reverse transcription (RT)‐polymerase chain reaction (PCR) analysis. In comparison to normal lung tissue, reduced transcription of the RB2/p130 gene was found in all small cell lung cancer cell lines examined, along with six out of the eight nonsmall cell lung cancers tested, most of which had inactivation of RB/p16 pathway. On the basis of Western blot analysis, the expression of RB2/p130 protein was consistent with RNA expression levels in all lung cancer cell lines examined. In addition, the mutational status of the RB2/p130 gene (specifically, exons 19, 20, 21, and 22) was determined in 30 primary lung cancers (from patients with distant metastasis) and 30 lung cancer cell lines by PCR‐single strand conformation polymorphism (SSCP) analysis and direct DNA sequencing. There was no evidence of somatic mutations within the RB2/p130 gene in the 60 lung cancer samples (both cell lines and tumors) assessed, including the 11 lung cancer cell lines that displayed reduced expression of the gene. Furthermore, hypermethylation of the RB2/p130 promoter was not found in any of the above‐mentioned 11 cell lines, as determined by a DNA methylation assay, combined bisulfite restriction analysis (COBRA). The results of the present study suggest that the reduced RB2/p130 expression seen in lung cancer may be in part transcriptionally mediated, albeit not likely via a mechanism involving hypermethylation of the RB2/p130 promoter. The observed reduction in RB2/p130 gene expression may be due to histone deacetylation, altered mRNA stability, and/or other forms of transcriptional regulation. © 2003 Wiley‐Liss, Inc.
Ultimate intrinsic signal‐to‐noise ratio for parallel MRI: Electromagnetic field considerations
Authors: Ohliger Michael A. , Grant Aaron K. , Sodickson Daniel K.
Published: October 2003

A method is described for establishing an upper bound on the spatial encoding capabilities of coil arrays in parallel MRI. Ultimate intrinsic signal‐to‐noise ratio (SNR), independent of any particular conductor arrangement, is calculated by expressing arbitrary coil sensitivities in terms of a complete set of basis functions that satisfy Maxwell's equations within the sample and performing parallel imaging reconstructions using these basis functions. The dependence of the ultimate intrinsic SNR on a variety of experimental conditions is explored and a physically intuitive explanation for the observed behavior is provided based on a comparison between the electromagnetic wavelength and the distance between aliasing points. Imaging at high field strength, with correspondingly short wavelength, is shown to offer advantages for parallel imaging beyond those already expected due to the larger available spin polarization. One‐dimensional undersampling of k‐space yields a steep drop in attainable SNR for more than a 5‐fold reduction of scan time, while 2D undersampling permits access to much higher degrees of acceleration. Increased tissue conductivity decreases baseline SNR, but improves parallel imaging performance. A procedure is also provided for generating the optimal coil sensitivity pattern for a given acceleration, which will serve as a useful guide for future coil designs. Magn Reson Med 50:1018–1030, 2003. © 2003 Wiley‐Liss, Inc.
In vivo monitoring of hepatic oxygenation changes in chronically ethanol‐treated rats by functional magnetic resonance imaging
Authors: Foley Lesley M. , Picot Paul , Thompson R. Terry , Yau Melissa J. , Brauer Manfred
Published: October 2003

In this study, functional magnetic resonance imaging (fMRI) was used to evaluate in vivo hepatic oxygenation changes in chronically ethanol (CE)‐treated and pair‐fed (PF) control rats. Male Wistar rats were pair‐fed an all‐liquid diet containing 36% of total calories as either ethanol or dextrin‐maltose for 8 weeks. The rats were initially examined under normoxic conditions, and then subjected to 100% oxygen (hyperoxia), 10% oxygen (hypoxia), 5% carbon dioxide (hypercapnia), or an acute dose of ethanol (1.4 g/kg bw intraperitoneally). A T2‐weighted spin‐echo sequence, which may be more selective for sinusoidal (capillary bed) changes, was performed before, during, and after the four challenges. During hyperoxia, both the CE and PF rats showed a statistically significant increase in signal intensity (22% ± 5% and 48% ± 6%, respectively, P < 0.05) relative to normoxia, while hypoxic challenge decreased the signal intensity (9% ± 4%, p>0.05 and 15% ± 3%, P < 0.05, respectively). The hypercapnic challenge, which causes vasodilation, resulted in a small increase in signal intensity in CE‐fed rats (5% ± 3%, P > 0.05) and a significant increase in the PF rats (15% ± 4%, P < 0.05), again consistent with expected changes in deoxyhemoglobin. With all three physiological challenges, the degree of change was less in CE rats compared to PF controls. An acute dose of ethanol that causes vasodilation also increased signal intensity, with no significant difference between the two groups. The signal intensity changes seen with fMRI were highly correlated with pulse oximeter readings (r2 = 0.95; P < 0.05). In conclusion, fMRI was shown to be a good noninvasive indicator of tissue deoxyhemoglobin changes in the liver. In addition, fMRI was able to detect subtle, early effects of CE administration (manifested as an impaired ability of the liver to respond adequately to oxygenation challenges), consistent with microvascular dysfunction. Magn Reson Med 50:976–983, 2003. © 2003 Wiley‐Liss, Inc.
Characterization and propagation of uncertainty in diffusion‐weighted MR imaging
Authors: Behrens T.E.J. , Woolrich M.W. , Jenkinson M. , Johansen‐Berg H. , Nunes R.G. , Clare S. , Matthews P.M. , Brady J.M. , Smith S.M.
Published: October 2003

A fully probabilistic framework is presented for estimating local probability density functions on parameters of interest in a model of diffusion. This technique is applied to the estimation of parameters in the diffusion tensor model, and also to a simple partial volume model of diffusion. In both cases the parameters of interest include parameters defining local fiber direction. A technique is then presented for using these density functions to estimate global connectivity (i.e., the probability of the existence of a connection through the data field, between any two distant points), allowing for the quantification of belief in tractography results. This technique is then applied to the estimation of the cortical connectivity of the human thalamus. The resulting connectivity distributions correspond well with predictions from invasive tracer methods in nonhuman primate. Magn Reson Med 50:1077–1088, 2003. © 2003 Wiley‐Liss, Inc.
k‐t BLAST and k‐t SENSE: Dynamic MRI with high frame rate exploiting spatiotemporal correlations
Authors: Tsao Jeffrey , Boesiger Peter , Pruessmann Klaas P.
Published: October 2003

Dynamic images of natural objects exhibit significant correlations in k‐space and time. Thus, it is feasible to acquire only a reduced amount of data and recover the missing portion afterwards. This leads to an improved temporal resolution, or an improved spatial resolution for a given amount of acquisition. Based on this approach, two methods were developed to significantly improve the performance of dynamic imaging, named k‐t BLAST (Broad‐use Linear Acquisition Speed‐up Technique) and k‐t SENSE (SENSitivity Encoding) for use with a single or multiple receiver coils, respectively. Signal correlations were learned from a small set of training data and the missing data were recovered using all available information in a consistent and integral manner. The general theory of k‐t BLAST and k‐t SENSE is applicable to arbitrary k‐space trajectories, time‐varying coil sensitivities, and under‐ and overdetermined reconstruction problems. Examples from ungated cardiac imaging demonstrate a 4‐fold acceleration (voxel size 2.42 × 2.52 mm2, 38.4 fps) with either one or six receiver coils. k‐t BLAST and k‐t SENSE are applicable to many areas, especially those exhibiting quasiperiodic motion, such as imaging of the heart, the lungs, the abdomen, and the brain under periodic stimulation. Magn Reson Med 50:1031–1042, 2003. © 2003 Wiley‐Liss, Inc.
Regional atrophy in the brain of lissencephalic mouse lemur primates: Measurement by automatic histogram‐based segmentation of MR images
Authors: Dhenain Marc , Chenu Evelyne , Hisley Calvin K. , Aujard Fabienne , Volk Andreas
Published: October 2003

Age‐related regional cerebral atrophy was evaluated in a small lissencephalic primate, model of cerebral aging. Twelve mouse lemurs (Microcebus murinus), ages 1.9–10.9 years (maximum life span: 12 years), were studied. 3D inversion‐recovery fast spin‐echo MR images (isotropic resolution = 234 μm) were recorded at 4.7 T with a surface coil actively decoupled from the transmitting birdcage probe. The surface coil‐related sensitivity gradient was corrected by normalization with images from an agar and NaCl phantom. An automatic statistical segmentation technique based on a classification‐maximization algorithm was tested on digital phantoms that mimicked the brain and applied to the 3D brain images. Segmented 3D maps that displayed gray matter, white matter, and cerebro‐spinal fluid (CSF) voxels were computed. The ventricles and peri‐encephalic spaces were categorized into 14 regions, defined on brain atlases on the basis of cytoarchitectural and anatomical criteria. The volume of CSF voxels belonging to each of these regions was calculated as an index of regional atrophy. Dilation of the mammillary fossa was an early event in the aging process. CSF accumulation within the occipital, parieto‐temporal, temporal, and frontal ventral peri‐encephalic spaces was particularly marked in the oldest animals that also displayed ophthalmologic alterations. Magn Reson Med 50:984–992, 2003. © 2003 Wiley‐Liss, Inc.
Proton HR‐MAS spectroscopy and quantitative pathologic analysis of MRI/3D‐MRSI‐targeted postsurgical prostate tissues
Authors: Swanson Mark G. , Vigneron Daniel B. , Tabatabai Z. Laura , Males Ryan G. , Schmitt Lars , Carroll Peter R. , James Joyce K. , Hurd Ralph E. , Kurhanewicz John
Published: October 2003

Proton high‐resolution magic angle spinning (1H HR‐MAS) NMR spectroscopy and quantitative histopathology were performed on the same 54 MRI/3D‐MRSI‐targeted postsurgical prostate tissue samples. Presurgical MRI/3D‐MRSI targeted healthy and malignant prostate tissues with an accuracy of 81%. Even in the presence of substantial tissue heterogeneity, distinct 1H HR‐MAS spectral patterns were observed for different benign tissue types and prostate cancer. Specifically, healthy glandular tissue was discriminated from prostate cancer based on significantly higher levels of citrate (P = 0.04) and polyamines (P = 0.01), and lower (P = 0.02) levels of the choline‐containing compounds choline, phosphocholine (PC), and glycerophosphocholine (GPC). Predominantly stromal tissue lacked both citrate and polyamines, but demonstrated significantly (P = 0.01) lower levels of choline compounds than cancer. In addition, taurine, myo‐inositol, and scyllo‐inositol were all higher in prostate cancer vs. healthy glandular and stromal tissues. Among cancer samples, larger increases in choline, and decreases in citrate and polyamines (P = 0.05) were observed with more aggressive cancers, and a MIB‐1 labeling index correlated (r = 0.62, P = 0.01) with elevated choline. The elucidation of spectral patterns associated with mixtures of different prostate tissue types and cancer grades, and the inclusion of new metabolic markers for prostate cancer may significantly improve the clinical interpretation of in vivo prostate MRSI data. Magn Reson Med 50:944–954, 2003. © 2003 Wiley‐Liss, Inc.
Radial alternating TE sequence for faster fat suppression
Authors: Flask Chris A. , Dale Brian , Lewin Jonathan S. , Duerk Jeffrey L.
Published: October 2003

This study describes a steady‐state sequence that uses a radial k‐space trajectory and alternating echo times (TEs) between even and odd k‐space views. The sequence generated a single data set that was used to reconstruct images with inherent fat suppression. This fat suppression results from the fat phase variation in alternate echoes giving rise to cancellation in the central portion of k‐space. This new fat‐suppression method provides inherent fat suppression in half the acquisition time relative to the radial two‐point Dixon method. The improvement in k‐space sampling efficiency is demonstrated in phantom and clinical images, and through measured point‐spread functions (PSFs). As a result, the radial alternating TE sequence offers improved temporal resolution over a radial version of the two‐point Dixon sequence by requiring fewer total projections to obtain the same effective resolution in water‐based tissues. Magn Reson Med 50:1095–1099, 2003. © 2003 Wiley‐Liss, Inc.
Development of a tissue‐equivalent MRI phantom using carrageenan gel
Authors: Yoshimura Koichi , Kato Hirokazu , Kuroda Masahiro , Yoshida Atsushi , Hanamoto Katsumi , Tanaka Akio , Tsunoda Masatoshi , Kanazawa Susumu , Shibuya Koichi , Kawasaki Shoji , Hiraki Yoshio
Published: October 2003

A new tissue‐equivalent MRI phantom based on carrageenan gel was developed. Carrageenan gel is an ideal solidifying agent for making large, strong phantoms in a wide variety of shapes. GdCl3 was added as a T1 modifier and agarose as a T2 modifier. The relaxation times of a very large number of samples were estimated using 1.5‐T clinical MRI equipment. The developed phantom was found to have a T1 value of 202–1904 ms and a T2 value of 38–423 ms when the GdCl3 concentration was varied from 0–140 μmol/kg and the agarose concentration was varied from 0–1.6% in a carrageenan concentration that was fixed at 3%. The range of measured relaxation times covered those of all types of human tissue. Empirical formulas linking the relaxation time with the concentration of the modifier were established to enable the accurate and easy calculation of the modifier concentration needed to achieve the required relaxation times. This enables the creation of a phantom having an arbitrary combination of T1 and T2 values and which is capable of retaining its shape. Magn Reson Med 50:1011–1017, 2003. © 2003 Wiley‐Liss, Inc.
MR spectroscopy of muscle and brain in guanidinoacetate methyltransferase (GAMT)‐deficient mice: Validation of an animal model to study creatine deficiency
Authors: Renema W. Klaas Jan , Schmidt Andreas , van Asten Jack J.A. , Oerlemans Frank , Ullrich Kurt , Wieringa Bé , Isbrandt Dirk , Heerschap Arend
Published: October 2003

As a model for guanidinoacetate methyltransferase (GAMT) deficiency in humans, a gene knockout mouse model was generated. Here we report on several metabolic abnormalities in these mice, observed by in vivo and in vitro MR spectroscopy. In 1H MR spectra of brain and hindleg muscle a clearly reduced signal of creatine (Cr) was observed in GAMT‐deficient (GAMT–/–) animals. Analysis of the 1H MR spectra of GAMT–/– brain indicated little or no increase of a signal for guanidinoacetate (Gua). In proton MR spectra of muscle, a broad signal of low intensity was observed for Gua. However, substantial Gua accumulation in intact muscle tissue was unequivocally confirmed in high‐resolution magic angle spinning spectra, in which the Gua signal was resolved as one clear sharp singlet. In 31P MR analysis of brain and hindleg muscle a strongly reduced phosphocreatine (PCr) content was shown. In addition, a signal of phosphorylated Gua at 0.5 ppm upfield of PCr was observed, with much higher intensity in muscle than in brain. This signal decreased when ischemia was applied to the muscle and recovered after ischemia was released. Overall, the in vivo 31P and 1H MR spectroscopy of GAMT–/– mice is similar to that of human GAMT deficiency. This opens up new avenues for the fundamental study of tissue‐type dependence of creatine synthesis and transport and for diagnostic and therapeutic aspects of creatine deficiencies in humans. Magn Reson Med 50:936–943, 2003. © 2003 Wiley‐Liss, Inc.
Optimization of diffusion measurements using Cramer‐Rao lower bound theory and its application to articular cartilage
Authors: Brihuega‐Moreno Oscar , Heese Frank P. , Hall Laurance D.
Published: October 2003

A novel approach to optimized diffusion measurements by minimizing the Cramer‐Rao lower bound (CRLB) with respect to the b‐values used for diffusion measurement was investigated. The applicability of the CRLB to these measurements is shown by the close agreement between the CRLB prediction and the actual precision obtained from experimental results. Where studies using a propagation‐of‐errors approach have restricted the optimization of the diffusion measurement to two b‐values and to specific diffusion coefficient values, the CRLB approach sets no bounds on the number of b‐values and is applicable to any system. The optimal number of b‐values depends on the ratio of the maximum and minimum diffusion coefficients in the sample (the Dratio) and on the number of acquisitions. For a Dratio above 6.8 the optimal number of b‐values increases to three; at a Dratio of 21.8 it increases to four. The optimized sampling schemes for ADC measurements in a variety of representative tissues found in the human body are given. For cartilage the optimal five‐point acquisition scheme requires one measurement at a b‐value of 0 and four at 1036 sec mm−2, whereas brain requires one at 0, three at 660, and one at 1987 sec mm−2. Magn Reson Med 50:1069–1076, 2003. © 2003 Wiley‐Liss, Inc.
Dixon techniques in spiral trajectories with off‐resonance correction: A new approach for fat signal suppression without spatial‐spectral RF pulses
Authors: Moriguchi Hisamoto , Lewin Jonathan S. , Duerk Jeffrey L.
Published: October 2003

Spiral imaging has recently gained acceptance in MR applications requiring rapid data acquisition. One of the main disadvantages of spiral imaging, however, is blurring artifacts that result from off‐resonance effects. Spatial‐spectral (SPSP) pulses are commonly used to suppress those spins that are chemically shifted from water and lead to off‐resonance artifacts. However, SPSP pulses may produce nonuniform fat signal suppression or unwanted water signal suppression when applied in the presence of B0 field inhomogeneities. Dixon techniques have been developed as methods for water–fat signal decomposition in rectilinear sampling schemes since they can produce unequivocal water–fat signal decomposition even in the presence of B0 inhomogeneities. This article demonstrates that three‐point and two‐point Dixon techniques can be extended to conventional spiral and variable‐density spiral data acquisitions for unambiguous water–fat decomposition with off‐resonance blurring correction. In the spiral three‐point Dixon technique, water–fat signal decomposition and image deblurring are performed based on the frequency maps that are directly derived from the acquired images. In the spiral two‐point Dixon technique, several predetermined frequencies are tested to create a frequency map. The newly proposed techniques can achieve more effective and more uniform fat signal suppression when compared to the conventional spiral acquisition method with SPSP pulses. Magn Reson Med 50: 915–924, 2003. © 2003 Wiley‐Liss, Inc.
Flow effects in balanced steady state free precession imaging
Authors: Markl M. , Alley M.T. , Elkins C.J. , Pelc N.J.
Published: October 2003

An analysis of the effect of flow on 2D fully balanced steady state free precession (SSFP) imaging is presented. Transient and steady‐state SSFP signal intensities in the presence of steady and pulsatile flow were simulated using a matrix formalism based on the Bloch equations. Various through‐plane flow waveforms and rates were modeled numerically considering factors such as the excitation slice profile and both in‐ and out‐flow effects. Phantom measurements in an experimental setup that allowed the assessment of SSFP signal properties as a function of frequency offset and flow rate demonstrated that the computer simulations provided a suitable description of the effects of flow in SSFP imaging. A volunteer scan was performed to provide in vivo validations. For accurate modeling of SSFP signal intensities it is crucial to include effects such as imperfect slice profiles and, more importantly, “out‐of‐slice” contributions to the signal. Both simulations and experiments show that there can be considerably large—frequency offset dependent—signal contributions from flowing spins that have already left the imaging slice but still add to the SSFP signal. Although spins leaving the slice do not experience additional RF‐excitation, gradient activity is not confined to the region of excitations and the balanced nature of the SSFP imaging gradients allows “out‐of‐slice” transverse magnetization to contribute to the total SSFP signal, effectively by broadening the slice thickness for flowing spins. This results in a frequency dependence of in‐flow related signal enhancement and flow artifacts. Magn Reson Med 50:892–903, 2003. © 2003 Wiley‐Liss, Inc.
Degenerate mode birdcage volume coil for sensitivity‐encoded imaging
Authors: Lin Fa‐Hsuan , Kwong Kenneth K. , Huang Ing‐Jye , Belliveau John W. , Wald Lawrence L.
Published: October 2003

A volume birdcage coil for accelerated image encoding with parallel acquisition methods such as SENSE is demonstrated. The coil is degenerately tuned with both the standard homogeneous mode and the first gradient mode of the birdcage coil resonant at the Larmor frequency. Conventional and antisymmetric coupling structures allow imaging from each of these modes simultaneously. The coil for SENSE‐type reconstruction with acceleration factors of up to 2‐fold is demonstrated. The spatial distribution of the added noise from the SENSE reconstruction (g‐factor map) due to geometrical arrangement of the two‐channel system is estimated. The spatially averaged g‐factors were found to be 1.21, 1.36, and 1.55 for 1.3, 1.6, and 2‐fold accelerations, respectively. The system was demonstrated in vivo using accelerated and nonaccelerated anatomical brain images at 1.5 T. The maximal 2‐fold acceleration in this dual‐mode degenerate birdcage coil offers the potential to extend SENSE‐type image reconstruction methods to applications demanding uniform whole brain coverage. Magn Reson Med 50:1107–1111, 2003. © 2003 Wiley‐Liss, Inc.
Inflow effect correction in fast gradient‐echo perfusion imaging
Authors: Ivancevic Marko K. , Zimine Ivan , Montet Xavier , Hyacinthe Jean‐Noel , Lazeyras François , Foxall David , Vallée Jean‐Paul
Published: October 2003

The purposes of this study were to assess the extent of the inflow effect on signal intensity (SI) for fast gradient‐recalled‐echo (GRE) sequences used to observe first‐pass perfusion, and to develop and validate a correction method for this effect. A phantom experiment with a flow apparatus was performed to determine SI as a function of Gd‐DTPA concentration for various velocities. Subsequently a flow‐sensitive calibration method was developed, and validated on bolus injections into an open‐circuit flow apparatus and in vivo. It is shown that calibration methods based on static phantoms are not appropriate for accurate signal‐to‐concentration conversion in images affected by high flow. The flow‐corrected calibration method presented here can be used to improve the accuracy and robustness of the arterial input function (AIF) determination for tissue perfusion quantification using MRI and contrast media. Magn Reson Med 50:885–891, 2003. © 2003 Wiley‐Liss, Inc.
Optimized gradient pulse for use with EPI employing active acoustic control
Authors: Chapman B. L. W. , Haywood B. , Mansfield P.
Published: October 2003

The concept of active acoustic control was recently introduced by Mansfield and Haywood (MAGMA 2000:10:147–151) to ameliorate the problem of acoustic noise from MRI, particularly that from high‐speed EPI. A 30 dB reduction in noise was previously achieved with the use of acoustic control operating at spot frequencies within a narrow band. In this work, a new acoustic gradient pulse is introduced that comprises an oscillating gradient of finite duration, incorporating a combination of frequencies within this band designed for use as the switched read gradient in echo‐planar imaging (EPI). Employing this pulse with active acoustic control results in a reduction of acoustic noise by 50 dB. Magn Reson Med 50:931–935, 2003. © 2003 Wiley‐Liss, Inc.
Predegenerated peripheral nerve graft with and without methylprednisolone administration after traumatic spinal cord injury in adult rats
Authors: Salgado‐Ceballos Hermelinda , Grijalva Israel , Guizar‐Sahagun Gabriel , Espitia Ana Laura , Martínez Angelina , Feria‐Velasco Alfredo
Published: October 2003

Traumatic spinal cord injury (TSCI) produces paralysis by destruction of axons and demyelination of surviving fibers. Using methylprednisolone (MP) as neuroprotector and a predegenerated peripheral nerve (PPN) graft as regenerative strategy, 83 rats with TSCI were divided into non‐grafted, fresh peripheral nerve (FPN) and PPN grafted groups with and without MP administration. Myelination index (MI), number of axons, myelinated fibers, and axon collaterals were assessed 21 h, 7 days, 2, and 4 months after TSCI. Animals with PPN grafts showed more axons and myelinated fibers than animals with FPN grafts, while the latter showed the highest number of axon collaterals. When MP was used, collateral emission was decreased in all treated groups. However, PPN graft plus MP group had the best MI and highest number of axons and myelinated fibers. Combination of one neuroprotective with a regenerative strategy is a good therapeutic option, although new combinations should be further explored.
Neuroprotective effect of Alpinia oxyphylla extract against glutamate‐induced apoptosis in cultured mouse cortical neurons
Authors: Yu Xinyu , Ceballos Yongqui Wang , Zhao Hong , Xu Zhongqui
Published: October 2003

Glutamate‐induced neuronal apoptosis plays an important role in neurodegenerative disorders. In the process of screening for naturally occurring substances with neuroprotective effects against glutamate exitotoxicity, we have discovered that the extract from Alpinia oxyphylla, a traditional Chinese medicinal herb, exhibited significant neuroprotective activity against glutamate exitotoxicity in cultured cortical neurons. The present study was designed to investigate the protective effect of Alpinia oxyphylla extract against glutamate‐induced neuronal apoptosis in primary cultured mouse cortical neurons. After exposure of the neurons to glutamate (30 μM), apoptotic cell death was observed as evidenced by alteration of neuronal morphology, DNA fragmentation on agarose gel and flow cytometric analysis. Co‐treatment of the neurons with Alpinia oxyphylla extract (80–240 μg/ml) in the presence of glutamate significantly elevated the cell viability, reduced the number of apoptotic cells and decreased the intensity of glutamate‐induced DNA fragmentation. The results suggest the neuroprotective potential of Alpinia oxyphylla against glutamate‐induced neuronal apoptosis.
Effects of caffeic acid phenethyl ester against doxorubicin‐induced neuronal oxidant injury
Authors: Fadillioglu Ersin , Erdogan Hasan , Iraz Mustafa , Yagmurca Murat
Published: October 2003

Oxygen‐derived free radicals have been implicated in the pathogenesis of doxorubicin‐induced toxicities. The aim of this study was to investigate the effects of caffeic acid phenethyl ester (CAPE), an antioxidant agent, on doxorubicin‐induced neuronal oxidative injury in rats. The rats were treated with CAPE (10μmol/kg/day i.p.) or saline starting 2 days before a single dose of doxorubicin (20 mg/kg i.p.) or saline. Ten days after the first experiments, the brain was excised to analyze the activities of antioxidant enzymes and levels of malondialdehyde (MDA) and nitric oxide (NO). Doxorubicin alone resulted in higher MDA level in brain tissue than the other groups. The activity of catalase was higher in doxorubicin plus CAPE group than doxorubicin group. There were no significant differences in NO level, glutathione peroxidase (GSH‐Px) and superoxide dismutase activities between the groups. There were negative correlations between GSG‐Px activity and MDA level in both doxorubicin and doxorubicin plus CAPE groups. It can be concluded that doxorubicin induced oxidant injury can be prevented by CAPE treatment through its antioxidant properties in rat brain.
Comparative neurochemistry of the avian forebrain and striatum: a microdialysis study
Authors: Karakuyu Dilek , Diekamp Bettina , Güntürkün Onur
Published: October 2003

The mammalian and avian striatum are homologous structures, while the mammalian prefrontal cortex (PFC) and the avian neostriatum caudolaterale (NCL) represent functionally equivalent, possibly homoplastic structures. We used brain microdialysis to study basal levels and release mechanisms of dopamine (DA) and serotonin (5‐HT) in the pigeons' forebrain to be able to compare the biochemical characteristics between these structures and different species. Basal DA levels in the pigeons' NCL were different from those in the rats' PFC, but were similar in the striatum. This was converse for 5‐HT. As in mammals, perfusion with artificial cerebrospinal fluid (aCSF) with elevated potassium significantly increased DA levels, whereas calcium‐free aCSF decreased the DA efflux. In summary, the avian and mammalian forebrains show a complex pattern of neurochemical similarities and differences. These data suggest that absolute and relative concentrations of modulatory systems may change considerably over evolutionary time, while basic biochemical mechanismsm stay unaltered.