bluuebunny/crossref_metadata_2025_split huggingface dataset:
Apoptosis during spermatogenesis in the spotted ray Torpedo marmorata
Authors: Prisco Marina , Liguoro Annamaria , Comitato Raffaella , Cardone Anna , D'Onghia Barbara , Ricchiari Loredana , Angelini Francesco , Andreuccetti Piero 
Published: January 2003

AbstractThis article is a cytological and molecular investigation on the occurrence of apoptosis during spermatogenesis in Torpedo, a cartilaginous fish characterised by a typical cystic testis. Using DNA fragmentation and Bak gene expression, it demonstrated that germ cells undergo apoptosis only at the stages of spermatocyte and spermatid, and degeneration also involves Sertoli but not Leydig cells. In immature cysts, this cellular process probably occurs when the ratio of germ cells to the only Sertoli cell (SC) forming the spermatoblast changes. Apoptosis also takes place in mature cysts after sperm release to eliminate most of the SCs. Few of them, however, become cytoplasts and probably continue secreting androgens so as to control the final events of spermatogenesis, i.e., passage of spermatozoa through the ductus deferentes. Finally, the present investigation demonstrated that, in Torpedo testis, Bak mRNA is expressed during spermatogenesis, thus suggesting that the mitochondrial pathway might be active. This observation in one of the oldest vertebrate classes indicates that, in all vertebrates, the apoptotic process during spermatogenesis is conserved, contributing to testicular homeostasis. Mol. Reprod. Dev. 64: 341–348, 2003. © 2003 Wiley‐Liss, Inc.
Glucose‐ and fructose‐induced dog‐sperm glycogen synthesis shows specific changes in the location of the sperm glycogen deposition
Authors: Palomo Maria J. , FernÁndez‐Novell Josep M. , Peña Alejandro , Guinovart Joan J. , Rigau Teresa , Rodríguez‐Gil Joan E. 
Published: January 2003

AbstractImmunocytochemistry of glycogen deposition in dog sperm from fresh ejaculates showed that 53.7% of the population had glycogen at the midpiece, whereas 27.3% of the whole population accumulated glycogen only in the post‐acrosomal region of the head. A similar distribution was observed when glycogen synthase, the enzyme which controls glycogen deposition, was studied. Incubation of spermatozoa with fructose increases the intracellular glycogen levels in a time‐ and concentration‐dependent manner. Moreover, after incubation with 2 mM fructose for 30 min, 47.3% of the spermatozoa had glycogen located in both the midpiece and post‐acrosomal zone, 25.4% of the population showed the polysaccharide only in the midpiece, and 24.7% of the spermatozoa showed a uniform distribution of glycogen all over the cell. Similar results were observed after incubation with 10‐mM fructose. The distribution of glycogen synthase followed a similar pattern to that of glycogen. Incubation with glucose also induced a time‐ and concentration‐dependent increase of glycogen content, whereas incubation with 2 mM glucose for 30 min showed that the majority of the population (81.2%) had the glycogen distributed throughout either the midpiece or the midpiece and the post‐acrosomal zones together. There were practically no cells with a uniform glycogen distribution. Similar results were obtained after incubation with 10‐mM glucose, whereas glycogen synthase suffered a similar glucose‐induced distribution change. These results indicate that dog‐sperm glycogen metabolism is modulated by changes in the activity of their controlling enzymes and also by changes in the specific location places where glycogen synthesis is produced. Mol. Reprod. Dev. 64: 349–359, 2003. © 2003 Wiley‐Liss, Inc.
Developmental failure of hybrid embryos generated by in vitro fertilization of water buffalo (Bubalus bubalis) oocyte with bovine spermatozoa
Authors: Patil Shekhar , Totey Satish 
Published: January 2003

AbstractThe developmental potential of inter‐species hybrid embryos produced by in vitro fertilization of in vitro matured buffalo oocytes with bovine spermatozoa was studied with a view to investigate pre‐implantation embryo development and its gross morphology, early embryonic gene expression, and embryonic genome activation. Fertilization events with both buffalo and cattle spermatozoa were almost similar. Overall fertilization rate with cattle spermatozoa was 78.4% was not significantly different from that of buffalo spermatozoa (80.2%). Initial cleavage rate between buffalo and hybrid embryo was also similar, and there was no significant difference in their developmental rate till 8‐cell stage (26.0 ± 4.1 vs. 24.3 ± 4.8). However, only 5.3% of hybrid embryos developed into blastocyst stage compared to 21.7% in buffalo. mRNA phenotyping of insulin‐like growth factor family (Insulin, insulin receptor, IGF‐I, IGF‐I receptor, IGF‐II, and IGF‐II receptor) and glucose transporter isoforms (GLUT‐I, II, III, IV) in hybrid embryos clearly showed that these molecules were not expressed after 8‐cell stage onward. Similarly, as observed in buffalo embryos, incorporation of 35S‐methionine and 3H‐uridine could not be observed in hybrid embryos from 8‐cell stage onward. This suggests that the maternal‐zygotic genome activation did not occur in hybrid embryos. Differential staining also showed that the blastomere stopped dividing after 8‐cell stage. Collectively, these parameters clearly showed that there was developmental failure of hybrid embryos. Mol. Reprod. Dev. 64: 360–368, 2003. © 2003 Wiley‐Liss, Inc.
Improved perfusion‐weighted MRI by a novel double inversion with proximal labeling of both tagged and control acquisitions
Authors: Jahng Geon‐Ho , Zhu Xiao‐Ping , Matson Gerald B. , Weiner Michael W. , Schuff Norbert 
Published: January 2003

AbstractA novel pulsed arterial spin labeling (PASL) technique for multislice perfusion‐weighted imaging is proposed that compensates for magnetization transfer (MT) effects without sacrificing tag efficiency, and balances transient magnetic field effects (eddy currents) induced by pulsed field gradients. Improved compensation for MT is demonstrated using a phantom. Improvement in perfusion measurement was compared to other PASL techniques by acquiring perfusion images from 13 healthy volunteers (nine women and four men; age range 29–64 years; mean age 45 ± 14 years) and second‐order image texture analysis. The main improvements with the new method were significantly higher image contrast, higher mean signal intensity, and better signal uniformity across slices. In conclusion, this new PASL method should provide improved accuracy in measuring brain perfusion. Magn Reson Med 49:307–314, 2003. © 2003 Wiley‐Liss, Inc.
In vivo time‐resolved quantitative motion mapping of the murine myocardium with phase contrast MRI
Authors: Streif Jörg U.G. , Herold Volker , Szimtenings Michael , Lanz Titus E. , Nahrendorf Matthias , Wiesmann Frank , Rommel Eberhard , Haase Axel 
Published: January 2003

AbstractMyocardial motion of healthy mice and mice with myocardial infarction was assessed in vivo by phase contrast (PC) cine MRI. The imaging module was a segmented fast low angle shot (FLASH) sequence with velocity compensation in all three gradient directions. To accomplish additional motion encoding, the spin phase was prepared using bipolar gradient pulses, which resulted in a linear dependence between the voxel velocity and spin phase. This method provided accurate quantification of the velocity magnitude and direction of the murine myocardium at a spatial resolution of 234 μm and a temporal resolution of about 10 ms. The acquisition was EKG‐gated and the mice were anesthetized by inhalation of 1.5–4.0 vol.% isoflurane at 1.5 l/min oxygen flow. To validate the MRI measurements, an experiment with a calibrated rotating phantom was performed. Deviations between MR velocity measurements and optical assessment by a light detector were lower than 1.6%. During our study, myocardial motion velocities between 0.4 cm/s and 1.7 cm/s were determined for the healthy murine myocardium across the heart cycle. Areas with myocardial infarction were clearly segmented and showed a motion velocity which was significantly reduced. In conclusion, the method is an accurate technique for the assessment of murine myocardial motion in vivo. Magn Reson Med 49:315–321, 2003. © 2003 Wiley‐Liss, Inc.
Dynamic MRI reveals that the magnitude of the ischemia‐related enhancement in skeletal muscle is age‐dependent
Authors: Sbarbati Andrea , Marzola Pasquina , Nicolato Elena , Farace Paolo , Asperio Roberto M. , Lunati Ernesto , Fabene Paolo F. , Marzioni Daniela , Castellucci Mario , Capogrossi Maurizio C. , Osculati Francesco 
Published: January 2003

AbstractThis study was designed to evaluate the influence of age on the dynamic contrast‐enhanced MRI of ischemic tissue. A well‐established model of peripheral arterial insufficiency (i.e., the rat hindlimb ischemia after removal of femoral artery) in different age groups (i.e., young, presenescent, and senescent rats) was studied. The analysis of the MR signal demonstrated a marked accumulation of a contrast agent (Gd‐DTPA) in the ischemic leg (ischemia‐related enhancement, IRE). IRE was an age‐related event: 4‐month‐old rats showed a strong IRE while 12‐month‐old rats and 20‐month old rats showed a significantly reduced IRE in comparison to young animals. Histological analysis of the ischemic muscles revealed that there was no evidence of significant necrosis of the muscle tissue but only a weak interstitial fibrosis; CD31‐immunostaining revealed a preserved microcirculatory bed. Magn Reson Med 49:386–390, 2003. © 2003 Wiley‐Liss, Inc.
Detection of eye movements from fMRI data
Authors: Beauchamp Michael S. 
Published: January 2003

AbstractAwake humans make eye movements with amplitudes and frequencies that depend on behavioral state and task. This poses two problems for functional magnetic resonance imaging (fMRI) studies that compare brain activity across tasks. First, motion of the eye in the orbit increases the variance of the MR signal in adjacent regions of the orbitofrontal cortex, hampering activation detection. Second, eye movements are associated with activity in a distributed network of brain areas, confounding comparisons of task activation. Direct measurement of eye movements in the scanner bore is possible with expensive and technically demanding equipment. A method is described that detects eye movements directly from MR data without the use of additional equipment. Changes in the MR time series from the vitreous of the eye were observed that correlated with eye movements, as measured directly with an infrared pupil tracking system. In each of 10 subjects, the variance of the MR time series from the eye vitreous was greater when the subject made eye movements than when the subject fixated centrally (average standard deviation (SD) 99.7 vs. 75.6, P = 0.001). The assessment of eye movements directly from fMRI data may be especially useful for retrospective and meta‐analyses. Magn Reson Med 49:376–380, 2003. Published 2003 Wiley‐Liss, Inc.
Visualization of myocardial microstructure using high‐resolution T imaging at high magnetic field
Authors: Köhler Sascha , Hiller Karl‐Heinz , Waller Christiane , Jakob Peter M. , Bauer Wolfgang R. , Haase Axel 
Published: January 2003

AbstractThe analysis of myocardial microstructure in vivo is important for the determination of myocardial contractility and function. The purpose of the present study was to demonstrate that high‐resolution T imaging has the potential to visualize the microstructure of beating, isolated rat hearts. To perform T imaging, a multiple gradient‐echo sequence was implemented on an 11.75 Tesla microscopy system. An in‐plane resolution of 78 μm and a slice thickness of 250 μm were achieved in 24 min. In comparison to histological sections, the T maps showed an excellent spatial correspondence to the myocardial fiber structure. To demonstrate the utility of this technique, morphologic alterations in myocardial microstructure were investigated in hearts with chronic myocardial infarction. Scar tissue and the extent of the infarcted region were clearly visualized and quantified using high‐resolution T imaging. Magn Reson Med 49:371–375, 2003. © 2003 Wiley‐Liss, Inc.
Renal and systemic pH imaging by contrast‐enhanced MRI
Authors: Raghunand Natarajan , Howison Christine , Sherry A. Dean , Zhang Shanrong , Gillies Robert J. 
Published: January 2003

AbstractPerturbations of renal and systemic pH accompany diseases of the kidney, such as renal tubular acidosis, and the ability to image tissue pH would be helpful to assess the extent and severity of such conditions. A dual‐contrast‐agent strategy using two gadolinium agents, the pH‐insensitive GdDOTP5− and the pH‐sensitive GdDOTA‐4AmP5−, has been developed to generate pH maps by MRI. The renal pharmacokinetics of the structurally dissimilar pH‐insensitive contrast agents GdDTPA2− and GdDOTP5− were found to be similar. On that basis, and on the basis of similarity of structure and charge, the renal pharmacokinetics of GdDOTP5− and GdDOTA‐4AmP5− were assumed to be identical. Dynamic T1‐weighted images of mice were acquired for 1 hr each following boluses of GdDOTP5− and GdDOTA‐4AmP5−. The time‐varying apparent concentration of GdDOTP5− and the time‐varying enhancement in longitudinal relaxation rate following GdDOTA‐4AmP5− were calculated for each pixel and used to compute pH images of the kidneys and surrounding tissues. MRI pH maps of control mice show acidic regions corresponding to the renal papilla, calyx, and ureter. Pretreatment of mice with the carbonic anhydrase inhibitor acetazolamide resulted in systemic metabolic acidosis and accompanying urine alkalinization that was readily detected by this dual‐contrast‐agent approach. Magn Reson Med 49:249–257, 2003. © 2003 Wiley‐Liss, Inc.
Resolution enhancement in lung 1H imaging using parallel imaging methods
Authors: Heidemann R.M. , Griswold M.A. , Kiefer B. , Nittka M. , Wang J. , Jellus V. , Jakob P.M. 
Published: January 2003

AbstractResolution in 1H lung imaging is limited mainly by the acquisition time. Today, half‐Fourier acquisition single‐shot turbo spin‐echo (HASTE) sequences, with short echo time (TE) and short interecho spacing (Tinter) have found increased use in lung imaging. In this study, a HASTE sequence was used in combination with a partially parallel acquisition (PPA) strategy to increase the spatial resolution in single‐shot 1H lung imaging. To investigate the benefits of using a combination of single‐shot sequences and PPA, five healthy volunteers were examined. Compared to conventional imaging methods, substantially increased resolution is obtained using the PPA approach. Representative in vivo 1H lung images acquired with a HASTE sequence in combination with the generalized autocalibrating partially parallel acquisition (GRAPPA) method, up to an acceleration factor of three, are presented. Magn Reson Med 49:391–394, 2003. © 2003 Wiley‐Liss, Inc.
Is TrueFISP a gradient‐echo or a spin‐echo sequence?
Authors: Scheffler Klaus , Hennig Jürgen 
Published: January 2003

AbstractIt is commonly accepted that TrueFISP (balanced FFE, FIESTA) belongs to the class of gradient‐echo (GRE) sequences. GRE sequences are sensitive to dephasing effects of the transverse magnetization between the excitation pulse and echo acquisition, and phase coherence is only established directly after and before excitation pulses. However, an analysis of the phase evolution of transverse magnetization in a TrueFISP experiment shows very close similarities to the echo formation of a spin‐echo (SE) experiment. If dephasing between excitation pulses is below ±π, TrueFISP exhibits a nearly complete refocusing of transverse magnetization at TE = TR/2. Only signals acquired before and after TR/2 show an additional T sensitivity. Magn Reson Med 49:395–397, 2003. © 2003 Wiley‐Liss, Inc.
Theoretical and experimental evaluation of detached endcaps for 3 T birdcage coils
Authors: Alecci Marcello , Collins Christopher M. , Wilson James , Liu Wanzhan , Smith Michael B. , Jezzard Peter 
Published: January 2003

AbstractThe use of detached endcaps for 3 T birdcage coils was investigated both theoretically and experimentally. Finite difference time domain analysis, along with workbench and MRI techniques, were used to map the radiofrequency (RF) B1 distribution along the coil axis with and without an endcap. Without an endcap the measured B1 value at the service end of the birdcage was only 45% of the value at the coil's center. This was improved to 85% with a detached endcap of maximum achievable diameter (375 mm), positioned 4 mm from the RF shield. The B1 field distribution on the patient side of the coil was unaffected by the presence of the endcap. The dependence of the B1 distribution as a function of endcap diameter was also investigated. Surprisingly, simulations and experiments show that there is an optimum ratio of endcap‐to‐birdcage coil diameter (≈1.08) that gives the best B1 homogeneity. In the human head the optimized endcap, positioned 16 mm from the RF shield, improves the MRI signal amplitude from 55% to 85% of maximum toward the service end. This novel endcap design is easy to implement with existing birdcage coils, and could prove useful when flexibility in access to the RF coil is required. Magn Reson Med 49:363–370, 2003. © 2003 Wiley‐Liss, Inc.
Simulations of thermal tissue coagulation and their value for the planning and monitoring of laser‐induced interstitial thermotherapy (LITT)
Authors: Puccini Silvia , Bär Nils‐Karsten , Bublat Martin , Kahn Thomas , Busse Harald 
Published: January 2003

AbstractMRI information is widely used for the monitoring of thermal therapies, such as laser‐induced interstitial thermotherapy (LITT). However, a detailed knowledge about the relationship between time/temperature exposure and resulting tissue thermal damage is needed to estimate the lesion extent. The aims of this work were to model the thermal response of laser‐irradiated tissue and to assess the value of Monte Carlo simulation (MCS) for tumor therapy planning and monitoring. MCS yielded true 3D distributions of laser‐induced temperature and thermal damage. These results were compared with 2D MR thermometry data from in vitro experiments performed on animal liver tissue over an ordinary range of laser powers (10–25 W) and irradiation times (5–25 min). Clinical reference data were available from MR‐guided liver LITT procedures. MCS correctly predicted the shape of temperature and damage distributions. The quantitative agreement between simulated and measured lesion diameters was within 10% and 15% for the in vitro and in vivo cases, respectively. The simulated 53°C isotherm best estimated the boundary of the final thermal damage (6% variance). This study shows that MCS of interstitial laser coagulation provides unique information that can be of use in the empirical correlation of temperature with thermal damage, and can assist greatly in thermal treatment planning and monitoring. Magn Reson Med 49:351–362, 2003. © 2003 Wiley‐Liss, Inc.
Characterization of aortic root atherosclerosis in ApoE knockout mice: High‐resolution in vivo and ex vivo MRM with histological correlation
Authors: Itskovich V.V. , Choudhury R.P. , Aguinaldo J.G.S. , Fallon J.T. , Omerhodzic S. , Fisher E.A. , Fayad Z.A. 
Published: January 2003

AbstractIn vivo, cardiac‐gated, black‐blood, and ex vivo magnetic resonance microscopy (MRM) images of the aortic root, and histopathology data were obtained from 12 transgenic and wild‐type (WT) mice. MRM was performed using a black‐blood imaging spin‐echo sequence with upstream and downstream in‐flow saturation pulses to obtain aortic root images in three contrast techniques: proton density‐weighted (PDW), T1‐ (T1W), and T2‐weighted (T2W). Aortic wall thickness and area were measured and correlated with histopathology data (R > 0.90). Ex vivo lesion components (lipid core, fibrous tissue, and cell tissue) were identified and characterized by differing image contrast in PDW, T1W, and T2W MRM, and by histopathology. The differences between WT and transgenic mice for maximal wall thickness and area were statistically significant (P < 0.05). This study demonstrates the feasibility of in vivo murine aortic root lesion assessment and ex vivo plaque characterization by MRM. Magn Reson Med 49:381–385, 2003. © 2003 Wiley‐Liss, Inc.
Myocardial tagging with SSFP
Authors: Herzka Daniel A. , Guttman Michael A. , McVeigh Elliot R. 
Published: January 2003

AbstractThis work presents the first implementation of myocardial tagging with refocused steady‐state free precession (SSFP) and magnetization preparation. The combination of myocardial tagging (a noninvasive method for quantitative measurement of regional and global cardiac function) with the high tissue signal‐to‐noise ratio (SNR) obtained with SSFP is shown to yield improvements in terms of the myocardium–tag contrast‐to‐noise ratio (CNR) and tag persistence when compared to the current standard fast gradient‐echo (FGRE) tagging protocol. Myocardium–tag CNR and tag persistence were studied using numerical simulations as well as phantom and human experiments. Both quantities were found to decrease with increasing imaging flip angle (α) due to an increased tag decay rate and a decrease in myocardial steady‐state signal. However, higher α yielded better blood–myocardium contrast, indicating that optimal α is dependent on the application: higher α for better blood–myocardium boundary visualization, and lower α for better tag persistence. SSFP tagging provided the same myocardium–tag CNR as FGRE tagging when acquired at four times the bandwidth and better tag– and blood–myocardium CNRs than FGRE tagging when acquired at equal or twice the receiver bandwidth (RBW). The increased acquisition efficiency of SSFP allowed decreases in breath‐hold duration, or increases in temporal resolution, as compared to FGRE. Magn Reson Med 49:329–340, 2003. Published 2003 Wiley‐Liss, Inc.
Directional correlation characterization and classification of white matter tracts
Authors: Sun Shu‐Wei , Song Sheng‐Kwei , Hong Chung‐Yi , Chu Woei C. , Chang Chen 
Published: January 2003

AbstractTo study the architectural characteristics of white matter (WM) tracts, the directional correlation (DC), defined as the inner product of the major eigenvector of adjacent pixels, was used as a quantitative index to investigate directional similarity in WM tracts. A region‐growing algorithm was employed to propagate an area from a seed point as a function of the DC threshold (DCt) to critically evaluate the directional properties of WM tracts. As the DCt was increased, more pixels were excluded from the propagated region as their DC fell below the DCt, and neighboring WM tracts could be distinguished as the area decreased. Taking the DC into account, a systematic classification routine for WM tracts was devised and tested on a mouse brain in vivo. The results show that individual WM tracts possess a high degree of directional similarity, and, by careful choice of the DCt value, the proposed classification algorithm can recognize all possible WM tracts in a given data set. Magn Reson Med 49:271–275, 2003. © 2003 Wiley‐Liss, Inc.