bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of the signalling pathways associated with sperm capacitation during epididymal maturation
Authors: Baker Mark A. , Lewis Beverley , Hetherington Louise , Aitken R. John 
Published: February 2003

AbstractAs spermatozoa mature within the epididymis they acquire the potential for capacitation and ultimately fertilization. In biochemical terms, the former is reflected in the progressive activation of a signal transduction pathway characterized by cAMP‐mediated induction of phosphotyrosine expression on the sperm tail. In this study, we have examined the cellular mechanisms controlling this maturational event. Caput epididymal spermatozoa exhibited tyrosine phosphorylation on the sperm head that was largely unresponsive to cAMP and not significantly impaired by removal of extracellular HCO3−. In contrast, caudal epididymal spermatozoa exhibited low levels of phosphorylation on the sperm head, yet responded dramatically to cAMP by phosphorylating a new set of proteins on the sperm tail via mechanisms that were highly dependent on extracellular HCO3−. The impact of extracellular HCO3− depletion on caudal cells was not associated with a significant change in the redox regulation of cAMP but could be fully reversed by buffering the intracellular pH with N‐Tris[Hydroxymethyl]methyl‐3‐amino‐propanesulfonic acid (TAPS). The pattern of tyrosine phosphorylation was also profoundly influenced by the presence or absence of added extracellular calcium. In the presence of this cation, only caudal spermatozoa could respond to increased extracellular cAMP with tyrosine phosphorylation of the sperm tail. However, in calcium‐depleted medium, this difference completely disappeared. Under these conditions, caput and caudal spermatozoa were equally competent to exhibit phosphotyrosine expression on the sperm tail in response to cAMP. These results emphasize the pivotal role played by calcium and HCO3− in modulating the changes in tyrosine phosphorylation observed during epididymal maturation. Mol. Reprod. Dev. 64: 446–457, 2003. © 2003 Wiley‐Liss, Inc.
c‐fos and estrogen receptor gene expression pattern in the rat uterine epithelium during the estrous cycle
Authors: Mendoza‐Rodríguez C. Adriana , Merchant‐Larios Horacio , Segura‐Valdez Maria L. , Moreno‐Mendoza Norma , Cruz María E. , Arteaga‐López Paola , Camacho‐Arroyo Ignacio , Domínguez Roberto , Cerbón Marco 
Published: February 2003

AbstractDifferent studies in ovariectomized estrogen treated animals support the idea that c‐fos plays a role in the proliferation of uterine epithelial cells. However, these studies invite us to reassess the role played by c‐fos in epithelial cell types of the endometrium during the estrous cycle. The present study was undertaken to determine the c‐fos and estrogen receptor (ER) gene expression pattern in the rat uterine epithelium during the estrous cycle in which natural and cyclic changes of steroid hormones occur, and correlate these changes with the proliferation status of this cellular types. Proliferation was assessed during the estrous cycle using bromodeoxyuridine incorporation to DNA. ERα and β proteins were assessed by immunohistochemistry. The regulation of c‐fos gene expression in the uterus of intact animals during the estrous cycle was evaluated using both in situ hybridization and immunohistochemistry. Estradiol (E2) and progesterone (P4) plasma levels were assessed by radioimmunoassay. The results indicated that luminal (LE) and glandular epithelia (GE) presented maximal proliferation during the metestrus (M) and the diestrus (D) days. However, during the proestrus (P) day only LE presented proliferation, and during the estrus (E) day only the stromal cells proliferated. A marked immunostaining for ERα was detected in both LE and GE cells during the early phases of the cycle but diminished on the P and the E day. In contrast, ERβ was undetectable in both epithelia during all stages of the cycle. The highest c‐fos mRNA level was detected in both epithelia on the M day, followed by a significant reduction during the other days of the cycle. The highest protein content was observed on the M and D days, and the minimal value was detected on the E day. The c‐Fos protein level in LE was increased during M and D days, presenting a high correlation with the cellular proliferation pattern of this cell type. In conclusion, the overall results indicate that c‐Fos protein presented a good correlation with uterine epithelial cell proliferation of LE. In the case of GE, the same tendency was observed, although no significant correlation was found. Both in LE and GE, c‐fos mRNA did not strictly correlate with its protein levels. c‐fos seems to have a postranscriptional regulation in uterine epithelial cells during the rat's estrous cycle. Mol. Reprod. Dev. 64: 379–388, 2003. © 2003 Wiley‐Liss, Inc.
Efficient measurement and calculation of MR diffusion anisotropy images using the Platonic variance method
Authors: Akkerman Erik M. 
Published: February 2003

AbstractThe Platonic variance method produces MR diffusion anisotropy (DA) images with a minimum amount of computational effort. It can be programmed in a self‐contained MR sequence, thus eliminating the need for postprocessing on a separate workstation. The method uses gradient acquisition schemes, based on Platonic solids: the “icosahedric” scheme (N = 6), the “dodecahedric” scheme (N = 10), and combinations thereof. For these schemes the average of the diffusion tensor eigenvalues equals the average of the measured apparent diffusion coefficients (ADCs), and the variance of the eigenvalues equals 5/2 times the variance of the diffusion coefficients. This results in compact expressions for anisotropy measures, directly in terms of the acquired images, i.e., without calculating the eigenvalues or even the tensor elements. The resulting anisotropy images were shown to be identical to the ones traditionally derived. It is expected that this method will considerably promote the routine use of DA imaging. Magn Reson Med 49:599–604, 2003. © 2003 Wiley‐Liss, Inc.
Quantitative measurements of proton spin‐lattice (T1) and spin–spin (T2) relaxation times in the mouse brain at 7.0 T
Authors: Guilfoyle David N. , Dyakin Victor V. , O'Shea Jacqueline , Pell Gaby S. , Helpern Joseph A. 
Published: February 2003

AbstractThe goal of this work is to provide regional T1 and T2 values at a field strength of 7 T for the normal mouse brain at 6 weeks and 1 year old. A novel segmented snapshot FLASH sequence was used to measure T1 in the hippocampus, corpus callosum, and the retrosplenial granular (RSG) cortex; T2 measurements were made in the same regions using a single spin echo sequence repeated at six separate echo times. Both T1 and T2 measurements were validated with phantom measurements. Magn Reson Med 49:576–580, 2003. © 2003 Wiley‐Liss, Inc.
Myocardial triglycerides and systolic function in humans: In vivo evaluation by localized proton spectroscopy and cardiac imaging
Authors: Szczepaniak Lidia S. , Dobbins Robert L. , Metzger Gregory J. , Sartoni‐D'Ambrosia Greta , Arbique Debbie , Vongpatanasin Wanpen , Unger Roger , Victor Ronald G. 
Published: February 2003

AbstractRecent experimental data suggest that adiposity directly damages the heart by promoting ectopic deposition of triglyceride, a process known as myocardial steatosis. The goal of this study was to develop and validate proton magnetic resonance spectroscopy (1H MRS) as an in vivo tool to measure myocardial lipid content. Complementary studies in rat tissue ex vivo and in 15 healthy humans in vivo provided evidence that 1H MRS constitutes a reproducible technique for the measurement of myocardial triglyceride. In myocardial tissue from Zucker rats, the 1H MRS measurement of triglyceride matched that obtained by biochemical measurement (P < 0.001). In human subjects triglyceride was evident in the hearts of even the very lean individuals and was elevated in overweight and obese subjects. Increased myocardial triglyceride content was accompanied by elevated LV mass and suppressed septal wall thickening as measured by cardiac imaging. Magn Reson Med 49:417–423, 2003. © 2003 Wiley‐Liss, Inc.
Detecting stiff masses using strain‐encoded (SENC) imaging
Authors: Osman Nael F. 
Published: February 2003

AbstractA method is proposed for detecting stiff masses using strain‐encoded (SENC) magnetic resonance imaging (MRI). An object of interest is compressed to produce local strain distribution that depends on local elasticity, where intensities correlate with the local through‐imaging‐plane strain component. Because the strain is lower inside a stiff mass than in the surrounding soft tissue, an intensity contrast in the resulting images would enable direct detection of the mass without postprocessing. The technique was validated by a phantom experiment in which a gel phantom with a stiff region was used. The advantages of the proposed method include short imaging time and uncomplicated postprocessing. However, in its current form the technique does not measure elasticity. Magn Reson Med 49:605–608, 2003. © 2003 Wiley‐Liss, Inc.
Quantitative imaging of magnetization transfer using an inversion recovery sequence
Authors: Gochberg Daniel F. , Gore John C. 
Published: February 2003

AbstractA new imaging method has been developed for quantitatively measuring magnetization transfer (MT). It uses a simple inversion recovery sequence, although one with very short (milliseconds) inversion times, and thus can be implemented on clinical imaging systems with little modification to existing pulse sequences. The sequence requires an inversion pulse with a length much longer than T2m (typically 10 μs) and much shorter than T2f (typically tens of ms) and 1/kmf (typically tens of ms), where T2m and T2f are the transverse relaxation times of the immobile macromolecular and free water protons, respectively, and kmf is the rate of MT between these populations. The resultant NMR signal is sensitive to MT when this inversion pulse affects the mobile and immobile proton pools to different degrees and by appropriate analysis of the signals obtained for different inversion times, quantitative information can be derived on the macromolecular content and exchange rates within the sample. The method has been used in conjunction with echo planar imaging to produce maps of the spatial distribution of the macromolecular content and MT rate in cross‐linked bovine serum albumin. Comparisons between this method and other quantitative MT techniques are discussed. Magn Reson Med 49:501–505, 2003. © 2003 Wiley‐Liss, Inc.
Macrophage labeling by SPIO as an early marker of allograft chronic rejection in a rat model of kidney transplantation
Authors: Beckmann N. , Cannet C. , Fringeli‐Tanner M. , Baumann D. , Pally C. , Bruns C. , Zerwes H.‐G. , Andriambeloson E. , Bigaud M. 
Published: February 2003

AbstractAnatomical and functional information (renography, perfusion) was obtained by MRI in a life‐supporting transplantation model, in which Lewis rats received kidneys from Fisher 344 donors. Renography and perfusion analyses were carried out with Gd‐DOTA and small particles of iron oxide (SPIO), respectively. Starting 12 weeks posttransplantation, images from grafts of untreated recipients exhibited distinctive signal attenuation in the cortex. Animals treated with cyclosporin (Sandimmune Neoral; Novartis Pharma, Basel, Switzerland) to prevent acute rejection showed a signal attenuation in the cortex at 33 weeks posttransplantation, while kidneys from rats treated additionally with everolimus (Certican; Novartis), a rapamycin derivative, had no changes in anatomical appearance. A significant negative correlation was found between the MRI cortical signal intensity and the histologically determined iron content in macrophages located in the cortex. Renography revealed a significantly reduced functionality of the kidneys of untreated controls 33 weeks after transplantation, while no significant changes in perfusion were observed in any group of rats. These results suggest the feasibility, by labeling macrophages with SPIO, of detecting signs of graft rejection significantly earlier than when changes in function occur. Monitoring early changes associated with chronic rejection can have an impact in preclinical studies by shortening the duration of the experimental period and by facilitating the investigation of novel immunomodulatory therapies for transplantation. Magn Reson Med 49:459–467, 2003. © 2003 Wiley‐Liss, Inc.
SMASH navigators
Authors: Bydder M. , Atkinson D. , Larkman D.J. , Hill D.L.G. , Hajnal J.V. 
Published: February 2003

AbstractThe additional data acquired when using multiple receiver coils is commonly used to improve SNR or reduce acquisition times. It may also be used to remove image artifacts by selectively replacing corrupt data. In the present study, a correction scheme is presented based on simultaneous acquisition of spatial harmonics (SMASH) that enables detection and correction of motion artifacts caused by 2D translations. Newly measured data is compared with predictions from previously measured data by making negative and positive spatial harmonics. Differences are attributed to motion occurring in the interval between the acquisition of separate phase encode lines and correction parameters are determined. Two types of rigid body motion are considered: 1) object and coil array move, and 2) object only moves, since each causes different phase errors in k‐space. Simulation, phantom, and volunteer experiments demonstrate the validity of the technique. Magn Reson Med 49:493–500, 2003. © 2003 Wiley‐Liss, Inc.
Delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC) in early knee osteoarthritis
Authors: Tiderius Carl Johan , Olsson Lars E. , Leander Peter , Ekberg Olle , Dahlberg Leif 
Published: February 2003

AbstractDelayed contrast‐enhanced MRI of cartilage (dGEMRIC) is a noninvasive technique to study cartilage glycosaminoglycan (GAG) content in vivo. This study evaluates dGEMRIC in patients with preradiographic degenerative cartilage changes. Seventeen knees in 15 patients (age 35–70) with arthroscopically verified cartilage changes (softening and fibrillations) in the medial or lateral femoral compartment, knee pain, and normal weight‐bearing radiography were included. MRI (1.5 T) was performed precontrast and at 1.5 and 3 hr after an intravenous injection of Gd‐DTPA2−at 0.3 mmol/kg body weight.T1measurements were made in regions of interest in medial and lateral femoral cartilage using sets of five turbo inversion recovery images. Precontrast,R1(R1= 1/T1, 1/s) was slightly lower in diseased compared to reference compartment, indicating increased hydration (P= 0.01). Postcontrast,R1was higher in diseased than in reference compartment at 1.5 hr, 3.45 ± 0.90 and 2.64 ± 0.58 (mean ± SD), respectively (P< 0.01), as well as at 3 hr, 2.94 ± 0.60 and 2.50 ± 0.37, respectively (P= 0.01). The washout of the contrast medium was faster in diseased cartilage as shown by a higherR1at 1.5 than at 3 hr in the diseased but not in the reference compartment. In conclusion, dGEMRIC can identify GAG loss in early stage cartilage disease with a higher sensitivity at 1.5 than 3 hr. Magn Reson Med 49:488–492, 2003. © 2003 Wiley‐Liss, Inc.
In vivo detection of a pH‐sensitive nitroxide in the rat stomach by low‐field ESR‐based techniques
Authors: Foster Margaret A. , Grigor'ev Igor A. , Lurie David J. , Khramtsov Valery V. , McCallum Stephen , Panagiotelis Ioannis , Hutchison James M.S. , Koptioug Andrei , Nicholson Ian 
Published: February 2003

AbstractA study was made of the in vivo detectability of a pH‐sensitive, imidazolidine spin probe, and the efficacy of low‐frequency electron spin resonance (ESR)‐based techniques for pH measurement in vitro and in vivo in rats. The techniques used were longitudinally‐detected ESR (LODESR) and field‐cycled dynamic nuclear polarization (FC‐DNP) for in vitro and in vivo measurements, and radiofrequency (RF)‐ and X‐band ESR for comparisons in vitro. The spin probe was hexamethyl imidazolidine (HMI) with a pK of 4.6. All techniques detected HMI. Detection by FC‐DNP implies coupling between the free radical and solvent water spins. Separations between the three spectral lines of the nitroxide radical, relative to measurement frequency, were consistent with theory. The overall spectrum width from unprotonated HMI (pH > pK) was greater than that from protonated agent (pH < pK). This was observed in vitro and in vivo. Longer‐term studies showed that HMI is detectable and has the same spectral width (i.e., is at the same pH) up to 2 hr after gavage into the stomach, although the magnitude of the signal decreases rapidly during the first hour. These findings demonstrate the suitability of LODESR and FC‐DNP for monitoring HMI and measuring pH in vivo. These techniques would be useful for monitoring disease and drug pharmacology in the living system. Magn Reson Med 49:558–567, 2003. © 2003 Wiley‐Liss, Inc.
Mechanism of magnetization transfer during on‐resonance water saturation. A new approach to detect mobile proteins, peptides, and lipids
Authors: van Zijl Peter C.M. , Zhou Jinyuan , Mori Noriko , Payen Jean‐Francois , Wilson David , Mori Susumu 
Published: February 2003

AbstractThe mechanism of magnetization transfer (MT) between water and components of the proton spectrum was studied ex vivo in a perfused cell system and in vivo in the rat brain (n = 5). Water was selectively labeled and spectral buildup consequential to transfer of longitudinal magnetization was followed as a function of time. At short mixing time (Tm), nitrogen‐bound solvent‐exchangeable protons were observed, predominantly assigned to amide groups of proteins and peptides. At longer Tm, intramolecular nuclear Overhauser enhancement (NOE) was observed in the aliphatic proton region, leading to a mobile‐macromolecule‐weighted spectrum that resembles typical protein spectra described in the literature. This effect on the proton spectrum is distinct from that of classical off‐resonance MT, which has been shown to be due to the immobile solid‐like proton pool. When studying a solution of major brain metabolites under physiological concentrations and conditions (pH), no transfer effects were observed, in line with expectations based on reduced NOE effects in rapidly tumbling molecules and the fast proton exchange rates of amino, amine, SH, and OH groups. The spectral intensities of the amide protons may serve as indicators for pH and cellular levels of mobile proteins and peptides, while the aliphatic components are representative of several types of mobile macromolecules, including proteins, peptides, and lipids. Magn Reson Med 49:440–449, 2003. © 2003 Wiley‐Liss, Inc.
A correlative measure for processing multiangle diffusion‐weighted images
Authors: Pipe James G. , Farthing Victoria G. 
Published: February 2003

AbstractA simple metric for the shared diffusion anisotropy between two voxels is proposed. The metric has large values when the diffusion is highly anisotropic in both voxels and oriented in the same direction. This metric can be used in several ways, three of which are illustrated in this article. First, the metric can be used to rapidly calculate a fractional anisotropy measure using an arbitrary number of measured diffusion values. Second, a simple way to exploit the metric for filtering DWI data with neighboring voxels with similar diffusion characteristics is shown. Third, the metric can be used to create color images that reflect tract orientation. Magn Reson Med 49:536–542, 2003. © 2003 Wiley‐Liss, Inc.
Comparison of the return‐to‐the‐origin probability and the apparent diffusion coefficient of water as indicators of necrosis in RIF‐1 tumors
Authors: Helmer Karl G. , Meiler Michael R. , Sotak Christopher H. , Petruccelli Joseph D. 
Published: February 2003

AbstractTwo model‐independent measures of diffusion, the apparent diffusion coefficient (ADC) and return‐to‐the‐origin probability enhancement (R) were compared for their ability to detect tissue necrosis in RIF‐1 murine tumors. Both reflect the degree of restriction experienced by the endogenous water molecules; however, the ADC is calculated from the initial linear slope of the diffusion attenuation curve, while R is calculated from data that includes the non‐monoexponential part of the curve. In spectroscopic studies (n = 9), neither the ADC nor R showed a strong correlation with tumor volume. In imaging studies (n = 14), ADC, R, and T2 were calculated on a pixel‐by‐pixel basis. There, the mean ADC and mean R for the entire imaging slice showed reasonable correlation with necrotic tumor fraction (r2 = 0.679 and −0.665, respectively). The mean T2 value yielded a poor correlation (r2 = 0.436). Regions‐of‐interest were chosen from areas identified as either necrotic or viable and the resulting sets of ADC and R‐values were subjected to discriminant analysis to determine the identification error rate. The error was greater for R than for the ADC (P < 0.001). Therefore, in this application, the use of the non‐monoexponential part of the diffusion attenuation curve does not provide additional identification power. Magn Reson Med 49:468–478, 2003. © 2003 Wiley‐Liss, Inc.
Functional magnetic resonance imaging of the human brain based on signal enhancement by extravascular protons (SEEP fMRI)
Authors: Stroman P.W. , Tomanek B. , Krause V. , Frankenstein U.N. , Malisza K.L. 
Published: February 2003

AbstractFunctional magnetic resonance imaging (fMRI) studies of the human brain were carried out at 3 Tesla to investigate an fMRI contrast mechanism that does not arise from the blood oxygen‐level dependent (BOLD) effect. This contrast mechanism, signal enhancement by extravascular protons (SEEP), involves only proton‐density changes and was recently demonstrated to contribute to fMRI signal changes in the spinal cord. In the present study it is hypothesized that SEEP fMRI can be used to identify areas of neuronal activity in the brain with as much sensitivity and precision as can be achieved with BOLD fMRI. A detailed analysis of the areas of activity, signal intensity time courses, and the contrast‐to‐noise ratio (CNR), is also presented and compared with the BOLD fMRI results. Experiments were carried out with subjects performing a simple finger‐touching task, or observing an alternating checkerboard pattern. Data were acquired using a conventional BOLD fMRI method (gradient‐echo (GE) EPI, TE = 30 ms), a conventional method with reduced BOLD sensitivity (GE‐EPI, TE = 12 ms), and SEEP fMRI (spin‐echo (SE) EPI, TE = 22 ms). The results of this study demonstrate that SEEP fMRI may provide better spatial localization of areas of neuronal activity, and a higher CNR than conventional BOLD fMRI, and has the added benefit of lower sensitivity to field inhomogeneities. Magn Reson Med 49:433–439, 2003. © 2003 Wiley‐Liss, Inc.