bluuebunny/crossref_metadata_2025 huggingface dataset:
In vivo gene marking of rhesus macaque long‐term repopulating hematopoietic cells using a VSV‐G pseudotyped versus amphotropic oncoretroviral vector
Authors: Shi Patricia A. , Angioletti Maria De , Donahue Robert E. , Notaro Rosario , Luzzatto Lucio , Dunbar Cynthia E.
Published: March 2004

Background

Gene transfer efficiency into primitive hematopoietic cells may be limited by their expression of surface receptors allowing vector entry. Vectors pseudotyped with the vesicular stomatitis virus (VSV‐G) envelope do not need receptors to enter cells, and therefore may provide superior transduction efficiency.

Methods

Using a competitive repopulation model in the rhesus macaque, we examined in vivo gene marking levels of blood cells transduced with two vectors: (i) a VSV‐G pseudotyped retrovirus and (ii) a conventional amphotropic retrovirus. The VSV‐G vector, containing the human glucose‐6‐phosphate dehydrogenase (G6PD) gene, was constructed for treatment of severe hemolytic anemia caused by G6PD deficiency. Three myeloablated animals were transplanted with peripheral blood CD34+ cells, half of which were transduced with the VSV‐G vector and the other half with the amphotropic vector.

Results

In all animals post‐transplantation, levels of in vivo marking in circulating granulocytes and mononuclear cells were similar: 1% or less with both vectors. In one animal, the human G6PD enzyme transferred by the VSV‐G vector was expressed in erythrocytes, early after transplantation, at a level of 45% of the endogenous rhesus G6PD protein.

Conclusions

In a clinically relevant animal model, we found similar in vivo marking with a VSV‐G pseudotyped and a standard amphotropic oncoretroviral vector. Amphotropic receptor expression may not be a limiting factor in transduction efficiency, but VSV‐G pseudotypes possess other practical advantages that may make them advantageous for clinical use. Copyright © 2004 John Wiley & Sons, Ltd.
Improvement of retroviral vectors by coating with poly(ethylene glycol)‐poly(L‐lysine) block copolymer (PEG‐PLL)
Authors: Katakura Hiromichi , Harada Atsushi , Kataoka Kazunori , Furusho Miki , Tanaka Fumihiro , Wada Hiromi , Ikenaka Kazuhiro
Published: March 2004

Background

Although some cationic reagents, such as polybrene, improve gene transduction in vitro, their use in vivo is prohibited due to their toxicity to the exposed cells. This paper demonstrates that a new cationic reagent, poly(ethylene glycol)‐poly(L‐lysine) block copolymer (PEG‐PLL), improves gene transduction with retroviral vectors without increasing cell toxicity.

Methods

A retroviral vector derived from the Moloney leukemia virus, containing the lacZ gene, was modified with PEG‐PLL prior to transduction into NIH3T3, Lewis lung carcinoma, and primary cultured mouse brain cells. LacZ transduction efficacy was evaluated by counting the number of X‐Gal‐positive cells.

Results

We have demonstrated that PEG‐PLL is able to stably modify the viral particle surface due to the affinity of the PEG moiety to the biomembrane, and neutralizes negative charges by the cationic nature of the poly‐lysine residue. Thus, PEG‐PLL increased the gene transduction efficiency and minimized cell toxicity because free PEG‐PLL was removable by centrifugation. We have shown that PEG‐PLL increased the viral gene transduction efficiency 3‐ to 7‐fold with NIH3T3 or Lewis lung carcinoma cell lines without increasing cytotoxicity. It improved retroviral gene transduction efficacy even against labile cells, such as primary cultured brain cells.

Conclusions

PEG‐PLL is a novel reagent that improves retroviral gene transduction efficacy without increasing cytotoxicity. Copyright © 2004 John Wiley & Sons, Ltd.
Cell‐surface glycosaminoglycans inhibit cation‐mediated gene transfer
Authors: Ruponen Marika , Honkakoski Paavo , Tammi Markku , Urtti Arto
Published: March 2004

Background

Cationic polymers and liposomes are used to wrap DNA into complexes that promote its cellular uptake. The mechanisms of the uptake and the intracellular fate of these complexes are obscure, as are reasons for an unpredictable and sometimes poor efficiency of the transgene expression. Polyanionic glycosaminoglycans (GAGs) on the cell surface interact with the cationic DNA complexes and influence transfection.

Methods

The quantities of heparan sulfate (HS), chondroitin sulfate (CS) and hyaluronan (HA) on the cell surface of mutated Chinese hamster ovary (CHO) cells and manipulated (chlorate, xyloside, chondroitinase ABC or Streptomyces hyaluronidase) smooth muscle cells were correlated with the uptake of four different DNA complexes, and the expression of the transgene.

Results

Two CHO mutants, without cell‐surface HS and CS, showed a 1.5–6‐fold increase in cellular association of DNA, and 3–25‐fold increase of transgene expression, as compared with the wild type. A CHO mutant with a 5.7‐fold increase of cell‐surface CS, but devoid of HS, showed enhanced DNA association, but 20–40% reduction in its expression. The removal of HS, CS, or HA from the cell surface of smooth muscle cells had a minor or insignificant effect on the cell association and transfection of the carriers and only polyethyleneimine showed increased association and expression of the transgene.

Conclusions

The uptake of DNA complexes varies depending on carrier, cell type and amounts of cell‐surface HS, CS, and HA, whereas all GAGs inhibit the transgene expression. This implies that cell‐surface GAGs probably direct complexes into intracellular compartments that do not support transcription. Copyright © 2004 John Wiley & Sons, Ltd.
Enhancement of both cellular and humoral responses to genetic immunization by co‐administration of an antigen‐expressing plasmid and a plasmid encoding the pro‐apoptotic protein Bax
Authors: Kinsey Berma M. , Marcelli Marco , Song Ling , Bhogal Balbir S. , Ittmann Michael , Orson Frank M.
Published: March 2004

Background

Transfecting cells with plasmid DNA encoding the protein Bax causes programmed cell death (apoptosis) and results in the formation of cell fragments (apoptotic bodies). It has been known for some time that when dendritic cells phagocytose apoptotic bodies derived from tumor cells, an immune response to tumor antigens can be generated.

Methods

Gene expression in the skin was evaluated after intradermal injection with plasmids encoding fluorescent proteins. Plasmids encoding foreign antigens were co‐injected intradermally with Bax‐encoding plasmids or control plasmids to elicit both humoral and cytotoxic immunity. Immune responses to the antigens were assessed by ELISA and cytotoxicity assays.

Results

We demonstrate here that injection of a mixture of reporter gene plasmids into the skin results in the expression of both plasmids in the large majority of the transfected cells. It is known that immune responses to multiple antigens can be elicited by co‐injection of separate individual plasmids. When mice were injected with equal quantities of two antigenic plasmids and either the Bax plasmid or a noncoding control plasmid, antibody responses were increased 4–8‐fold in the Bax group. Similarly, cytotoxic T lymphocyte (CTL) responses in the Bax group showed an 80% increase in the number of lytic units per million cells.

Conclusions

This data shows that simply including the apoptosis‐inducing Bax plasmid along with antigen‐expressing plasmids may provide a significant enhancement of immune responses to DNA vaccines. Published in 2004 by John Wiley & Sons, Ltd.
Reduction in mortalin level by its antisense expression causes senescence‐like growth arrest in human immortalized cells
Authors: Wadhwa Renu , Takano Syuichi , Taira Kazunari , Kaul Sunil C.
Published: March 2004

Background

Human normal cells have active p53 and pRB tumor suppressor pathways and undergo telomere shortening at each cell division. When immortalized, these exhibit functional inactivation of one or both tumor suppressor pathways and activation of telomere‐maintaining mechanisms. Regulation of immortalization promoting molecular pathways by other genes is poorly understood and is an essential component of cancer therapeutics. In the present study, we have immortalized human normal cells by functional inactivation of p53 and pRB tumor suppressor proteins and simultaneous activation of telomerase function. We demonstrate that when the expression of mortalin (a member of hsp70 family proteins) was suppressed in such genetically defined immortal cells they underwent a permanent growth arrest.

Methods

WI‐38 cells were transfected with expression plasmids encoding papilloma virus E6 and E7 proteins and a catalytic subunit of human telomerase enzyme. The derivative cells were compromised for p53 and pRB senescence pathways, showed telomerase activity and were immortalized. These cells were transfected with antisense expression plasmid for mortalin. The derivative clones were analyzed for mortalin expression, proliferation and telomerase activity.

Results

WI‐38 cells were immortalized with E6, E7 and the catalytic subunit of human telomerase. The derivative‐immortalized cells when suppressed for mortalin expression underwent senescence‐like growth arrest.

Conclusions

The data demonstrate that suppression of mortalin is sufficient to induce growth arrest in human immortalized cells that have compromised p53 and pRB functions and possess telomerase activity. Copyright © 2004 John Wiley & Sons, Ltd.
Hepatic delivery of particulates in the submicron range by a hydrodynamics‐based procedure: implications for particulate gene delivery systems
Authors: Kobayashi Naoki , Hirata Kazuhiro , Chen Shi , Kawase Atsushi , Nishikawa Makiya , Takakura Yoshinobu
Published: March 2004

Background

A large‐volume intravenous (i.v.) injection of DNA, i.e. a hydrodynamics‐based transfection procedure, is known to be an efficient and liver‐specific method of in vivo gene delivery. However, little is available on an applicable particle size in the procedure.

Methods

We examined the effect of particle size on the hepatic delivery by the hydrodynamics‐based procedure, using fluorescein isothiocyanate labeled polystyrene microspheres (MS) of 50, 200 or 500 nm in diameter. MS were injected intravenously to mice by a conventional (normal) or the hydrodynamics‐based procedure and their degree of hepatic uptake was determined fluorometrically.

Results

For all sizes tested, the two procedures were similar in terms of the apparent degree of hepatic uptake, whereas the intrahepatic localization of MS was apparently different between the procedures as shown by an examination of frozen tissue sections. In mice with gadolinium chloride induced Kupffer cell blockade, the hepatic uptake of MS following the normal procedure was decreased while that of the hydrodynamics‐based procedure was less affected. This phenomenon of enhanced hepatic delivery seemed to be more effective for larger particles. Confocal microscopic observation of hepatocyte suspensions indicated that part of the injected MS‐50 was delivered intracellularly following the hydrodynamics‐based procedure, whereas almost all the observed MS‐200 and MS‐500 were detected in the extracellular compartment or on the surface of the cells. This was supported by the fact that most of the injected MS existed pericellularly around the transgene‐expressing cells.

Conclusions

The hydrodynamics‐based procedure facilitated extravasation and hepatic delivery of MS. Larger MS were more efficiently extravasated and trapped by the liver, whereas intracellular delivery hardly occurred with them. Copyright © 2004 John Wiley & Sons, Ltd.
Dependence of the cellular internalization and transfection efficiency on the structure and physicochemical properties of cationic detergent/DNA/liposomes
Authors: Llères David , Weibel Jean‐Marc , Heissler Denis , Zuber Guy , Duportail Guy , Mély Yves
Published: March 2004

Background

Control of the structure and physicochemical properties of DNA complexed with nonviral vectors is essential for efficient biodistribution and gene delivery to cells. Cationic liposomes interact with DNA giving transfection competent but large and heterogeneous aggregates. On the other hand, cationic detergents condense DNA into small homogeneous but reversible complexes inefficient for transfection.

Methods

In order to combine the favorable features of both vectors, ternary complexes were prepared by adding cationic liposomes to plasmid DNA condensed by cationic detergents. The structure and physicochemical properties of these complexes were investigated by electron microscopy, quasi‐elastic light scattering, gel electrophoresis and fluorescence techniques. These data were then correlated with the transfection efficiency and intracellular trafficking of the ternary complexes determined by luciferase gene expression and confocal microscopy, respectively.

Results

The ternary complexes were found to form small, homogeneous, globular, stable and positively charged particles with a highly dense and packed lamellar internal structure differing from the multilamellar structure $(L_{\alpha}^{C})$ of the corresponding lipoplexes. In the presence of serum, the ternary complexes were more efficiently internalized into cells, less toxic and showed 20‐fold higher transfection efficiency than lipoplexes.

Conclusions

This study showed that small, monodisperse and highly stable complexes could be obtained by precompaction of DNA with cetyltrimethylammonium bromide, followed by addition of cationic lipids. The higher efficiency of the ternary complexes with respect to their corresponding lipoplexes was related to their internal structure which prevents their dissociation by serum proteins and allows efficient internalization in the target cells. Copyright © 2004 John Wiley & Sons, Ltd.
In vivo measurement of T1ρ dispersion in the human brain at 1.5 tesla
Authors: Borthakur Arijitt , Wheaton Andrew J. , Gougoutas Alexander J. , Akella Sarma V.S. , Regatte Ravinder R. , Charagundla Sridhar R. , Reddy Ravinder
Published: March 2004

Purpose

To measure T1ρ relaxation times and T1ρ dispersion in the human brain in vivo.

Materials and Methods

Magnetic resonance imaging (MRI) was performed on a 1.5‐T GE Signa clinical scanner using the standard GE head coil. A fast spin‐echo (FSE)‐based T1ρ‐weighted MR pulse sequence was employed to obtain images from five healthy male volunteers. Optimal imaging parameters were determined while considering both the objective of the study and the guarantee that radio‐frequency (RF) power deposition during MR did not exceed Food and Drug Administration (FDA)‐mandated safety levels.

Results

T1ρ‐weighted MR images showed excellent contrast between different brain tissues. These images were less blurred than corresponding T2‐weighted images obtained with similar contrast, especially in regions between brain parenchyma and cerebrospinal fluid (CSF). Average T1ρ values for white matter (WM), gray matter (GM), and CSF were 85 ± 3, 99 ± 1, and 637 ± 78 msec, respectively, at a spin‐locking field of 500 Hz. T1ρ is 30% higher in the parenchyma and 78% higher in CSF compared to the corresponding T2 values. T1ρ dispersion was observed between spin‐locking frequencies 0 and 500 Hz.

Conclusion

T1ρ‐weighted MRI provides images of the brain with superb contrast and detail. T1ρ values measured in the different brain tissues will serve as useful baseline values for analysis of T1ρ changes associated with pathology. J. Magn. Reson. Imaging 2004;19:403–409. © 2004 Wiley‐Liss, Inc.
Four‐dimensional magnetic resonance velocity mapping of blood flow patterns in the aorta in patients with atherosclerotic coronary artery disease compared to age‐matched normal subjects
Authors: Bogren Hugo G. , Buonocore Michael H. , Valente Richard J.
Published: March 2004

Purpose

To test the hypothesis that age and atherosclerotic coronary artery disease (CAD) may influence aortic blood flow patterns.

Materials and Methods

A total of 21 patients with CAD, 37–86 years old, were studied, together with 20 age‐matched normal subjects. Time‐resolved, three‐direction velocity data over an entire volume were obtained with sequential single‐slice two‐dimensional cardiac‐gated magnetic resonance (MR) velocity‐encoded phase‐contrast sequences.

Results

In both normal subjects and CAD patients, the time it took for particles to travel from aortic valve to descending aorta was significantly longer in the elderly age group than in the younger (37–46 years old). This time was significantly longer in patients than in normal subjects. Systolic velocities were significantly higher in young normal subjects than in elderly normal subjects, and significantly lower in CAD patients than in age‐matched normal subjects. Retrograde velocity was higher in CAD patients than in normal subjects, and higher in elderly CAD patients than in young.

Conclusion

CAD patients have abnormal blood flow patterns in the aorta compared with age‐matched normal subjects, especially young patients ages 37–46. The aging process has a similar effect on blood flow patterns as atherosclerosis. Ascending aorta flow is chaotic in some very elderly normal subjects and in CAD patients of all ages. Chaotic aortic flow may result in reduced blood flow into the coronary arteries. J. Magn. Reson. Imaging 2004;19:417–427. © 2004 Wiley‐Liss, Inc.
Stability of real‐time MR temperature mapping in healthy and diseased human liver
Authors: Weidensteiner Claudia , Kerioui Noureddine , Quesson Bruno , de Senneville Baudoin Denis , Trillaud Hervé , Moonen Chrit T.W.
Published: March 2004

Purpose

To determine the stability and quality of MR temperature mapping using the proton resonance frequency (PRF) method in the liver of hepatic tumor patients.

Materials and Methods

The standard deviation (SD) of a series of temperature maps was determined in 30 patients (21 patients with cirrhotic livers with carcinoma, and nine patients with noncirrhotic livers with metastasis or angioma) and in five volunteers at normal body temperature under free breathing. A respiratory‐gated segmented echo‐planar imaging (EPI) sequence (three slices in one expiration phase) was performed with sensitivity encoding (SENSE) acceleration on a 1.5 T scanner. Motion‐corrupted images were identified by calculation of the cross‐correlation coefficient, and discarded.

Results

A T2* range of 10–33 msec was found, with especially low values in advanced cirrhotic livers. The mean temperature SD in patients was 2.3°C (range = 1.5–5.0°C). The stability in healthy livers was slightly better than that in cirrhotic livers, and it was higher in the right liver than in the left liver. The gating failed in 4% of the images when the respiratory cycle was irregular, leading to motion artifacts and errors in the temperature maps.

Conclusion

The achieved temperature stability and image quality makes real‐time quantitative monitoring of thermal ablation of liver tumors feasible on a clinical scanner. J. Magn. Reson. Imaging 2004;19:438–446. © 2004 Wiley‐Liss, Inc.
Analytical error propagation in diffusion anisotropy calculations
Authors: Poonawalla Aziz Hatim , Zhou Xiaohong Joe
Published: March 2004

Purpose

To develop an analytical formalism describing how noise and selection of diffusion‐weighting scheme propagate through the diffusion tensor imaging (DTI) computational chain into variances of the diffusion tensor elements, and errors in the relative anisotropy (RA) and fractional anisotropy (FA) indices.

Materials and Methods

Singular‐value decomposition (SVD) was used to determine the tensor variances, with diffusion‐weighting scheme and measurement noise incorporated into the design matrix. Anisotropy errors were then derived using propagation of error. To illustrate the applications of the model, 12 data sets were acquired from each human subject, over a range of b‐values (500–2500 seconds/mm2) and diffusion‐weighting gradient directions (N = 6–55). The mean RA and FA values and their respective errors were calculated within a region of interest (ROI) in the splenium. The RA and FA errors as a function of b‐value and N were evaluated, and a number of diffusion‐weighting schemes were assessed based on a new metric, sum of diffusion tensor variances.

Results

When the acquisition time was held constant, the sum of the diffusion tensor variances decreased as N increased. The same trend was also observed for several diffusion‐weighting schemes with constant condition number when noise in the diffusion‐weighted (DW) images was assumed unity. Errors in both FA and RA increased with b‐value and decreased with N. The FA error in the splenium was approximately threefold smaller than RA error, irrespective of b‐value or N.

Conclusion

The condition number may not adequately characterize the noise sensitivity for a given diffusion‐weighting scheme. Signal averaging may not be as effective as increasing N, especially when N is small (e.g., N < 13). Due to its smaller error, FA is preferred over RA for quantitative DTI applications. J. Magn. Reson. Imaging 2004;19:489–498. © 2004 Wiley‐Liss, Inc.
Volumetric interpolated contrast‐enhanced MRA for the diagnosis of pulmonary embolism in an ex vivo system
Authors: Biederer Jürgen , Liess Carsten , Charalambous Nikolas , Heller Martin
Published: March 2004

Purpose

To implement a three‐dimensional gradient‐recalled echo (GRE) volumetric interpolated breath‐hold examination (VIBE) sequence for pulmonary contrast‐enhanced MRA (CE‐MRA) in an experimental setup.

Materials and Methods

Eight porcine lungs were intubated, inflated inside a chest phantom, and examined at 1.5 T during slow perfusion (2–300 mL/minute). Three‐dimensional‐MRA was performed with and without contrast agent using three‐dimensional‐GRE (VIBE) with TR/TE = 4.5/1.9 msec, TA = 23 seconds, FOV = 390 mm, FA = 12°/30°, as well as a standard three‐dimensional‐GRE sequence and T2 fast spin‐echo (FSE) sequences. Four of the eight lungs were embolized with autologous blood clots. By consensus readings, two observers evaluated the detectability of peripheral vessels, signal intensity over vessels and lung, and visualization of emboli. Digital subtraction angiograms served as a control to document vessel patency.

Results

Prior to contrast administration, three‐dimensional‐VIBE/12° yielded the best results for lung parenchyma signal and visualization of small vessels (third‐order, P < 0.01); however, no emboli were detected (due to lack of contrast). After administration of contrast agent, three‐dimensional‐GRE (VIBE) at FA = 30° provided significantly better results (fifth‐order branches, documentation of subsegmental occlusions [fourth order], P < 0.01). T2‐FSE images documented water uptake into the lungs. Digitally subtracted angiography (DSA) confirmed the patency of seventh‐order branches.

Conclusion

This ex vivo study confirms the potential advantages of using a dual MR investigation for pulmonary embolism, combining three‐dimensional‐GRE (VIBE) at FA = 12° to image lung parenchyma and at FA = 30° for CE‐MRA. J. Magn. Reson. Imaging 2004;19:428–437. © 2004 Wiley‐Liss, Inc.
Parallel and nonparallel simultaneous multislice black‐blood double inversion recovery techniques for vessel wall imaging
Authors: Itskovich Vitalii V. , Mani Venkatesh , Mizsei Gabor , Aguinaldo Juan Gilberto S. , Samber Daniel D. , Macaluso Frank , Wisdom Paul , Fayad Zahi A.
Published: March 2004

Purpose

To reduce long examination times of black‐blood vessel wall imaging by acquiring multiple slices simultaneously and by using parallel acquisition techniques.

Materials and Methods

DIR‐rapid acquisition with relaxation enhancement (;RARE) techniques imaging up to 10 simultaneous slices per acquisition with single and multiple 180°‐reinversion pulses were developed. A slab‐selective reinversion multislice DIR‐RARE sequence incorporating generalized autocalibrating partially parallel acquisitions (GRAPPA) imaging was implemented. Four‐channel and eight‐channel carotid coils were built to test these sequences. A total of 11 subjects were studied. Contrast‐to‐noise ratio (CNR) and signal‐to‐noise ratio (SNR) efficiency factor (SEF, SNR/unit time/slice) were measured from aortic images of three healthy subjects to determine optimal MR parameters. The DIR–RARE‐GRAPPA sequence was run on aortas and carotid arteries of the five remaining healthy subjects and three atherosclerotic patients with optimal parameters (acquisition times 12–21 seconds).

Results

SEFs of slab‐selective protocols were significantly higher than those of slice‐selective protocols, and SEFs of DIR‐RARE‐GRAPPA protocols were significantly higher than corresponding non‐GRAPPA protocols (P < 0.05). CNR was not significantly different for all imaging protocols. The DIR‐RARE‐GRAPPA multislice sequence showed 8.35‐fold time improvement vs. single–slice DIR‐2RARE sequence.

Conclusion

Future MRI atherosclerotic plaque studies can be performed in substantially shorter times using these methods. J. Magn. Reson. Imaging 2004;19:459–467. © 2004 Wiley‐Liss, Inc.
Water diffusion in a rat glioma during ganciclovir‐thymidine kinase gene therapy‐induced programmed cell death in vivo: Correlation with cell density
Authors: Valonen Piia K. , Lehtimäki Kimmo K. , Väisänen Tuula H. , Kettunen Mikko I. , Gröhn Olli H.J. , Ylä‐Herttuala Seppo , Kauppinen Risto A.
Published: March 2004

Purpose

To study the characteristics of diffusion magnetic resonance imaging (MRI) contrast in a rat brain BT4C glioma during progression of ganciclovir (GCV)‐thymidine kinase gene therapy‐induced programmed cell death (PCD) in vivo.

Materials and Methods

The trace of the diffusion tensor (Dav = 1/3Trace
equation image
), T2, and spin density were determined by MRI and the apparent diffusion coefficient (ADC) of water by diffusion nuclear MR (NMR) spectroscopy using largely varying b values and diffusion times (tD) at 4.7 T. Cell count and apoptotic cells were quantified by histological means.

Results

Decline in cell count was strongly associated with increase in both Dav and T2. Spin density ratio between tumor and contralateral parietal cortex increased with a very similar time course as Dav and T2, indicating net water gain into the eradicating tumor. Diffusion spectroscopy showed a nonmonoexponential signal decay at all tD values ranging from 14–192 msec. During PCD, the ADC of the component yielding fast diffusion coefficient (D1), as acquired with tD ≥ 47 msec, increased with kinetics similar to those of Dav (tD = 4.8 msec). The fractional size of D1 increased by 10% to 15% throughout the entire tD range. Apparent water residence time of the slow diffusion component, D2, shortened from a value of 38.3 ± 1.7 msec on day 0 to 33.4 ± 0.5 msec by day 8.

Conclusion

The present results show that reduced cell density and increased water content, leading to altered water microenvironment, are associated with increased water diffusion coefficient in eradicating gliomas as a result of PCD. J. Magn. Reson. Imaging 2004;19:389–396. © 2004 Wiley‐Liss, Inc.
A novel method for analysis of TOMROP data
Authors: Pickup Stephen , Wood Andrew K.W. , Kundel Harold L.
Published: March 2004

Purpose

To develop an efficient method for extracting maps of the corrected T1 from images generated using the T One by Multiple Read Out Pulses (TOMROP) sequence.

Materials and Methods

An expression is developed for the true T1 in terms of the parameters from a three‐parameter fit of the TOMROP data. Solutions of gadodiamide in normal saline with concentrations of 0.0, 0.06, 0.11, 0.23, 0.46, and 0.91 mM were prepared and T1 measurements were performed using both the inversion recovery (IR) and the TOMROP methods. The TOMROP data were analyzed using the proposed technique and the results compared to those from the IR measurements.

Results

The T1 estimates generated from the TOMROP data using the proposed method were consistent with the IR results. However, systematic errors were observed in the T1 estimates when the repetition time was not sufficient for full recovery of axial magnetization. Relaxation times determined using the proposed method were within 1% of the spectroscopiclly determined values for T1 values in the range of 0.28–2.8 seconds when a suitable delay was employed.

Conclusion

The proposed method of analysis was found to yield accurate T1 estimates when the assumptions used in the analysis were not violated. J. Magn. Reson. Imaging 2004;19:508–512. © 2004 Wiley‐Liss, Inc.
MRI of bone tumors: Fast STIR imaging as a substitute for T1‐weighted contrast‐enhanced fat‐suppressed spin‐echo imaging
Authors: Tokuda Osamu , Hayashi Noriko , Matsunaga Naofumi
Published: March 2004

Purpose

To compare the usefulness of short inversion recovery (STIR) and T1‐weighted, contrast‐enhanced, fat‐suppressed (T1W‐CEFS) sequences for the evaluation of bone tumors.

Materials and Methods

Eighteen patients with 19 bone tumors who underwent both STIR and T1W‐CEFS imaging were evaluated. The tumors were categorized in pairs as follows: bone marrow and soft‐tissue components, benign and malignant tumors, and tumors with and without mineralization. The signal difference‐to‐noise ratio (SDNR), signal‐to‐noise ratio (SNR), and tumor volume were calculated in each group. An additional qualitative analysis was performed by means of the ratings of imaging contrast.

Results

The mean SDNRs of all bone marrow components and bone marrow components without mineralization were significantly higher on fast STIR images than on T1W‐CEFS images (P < 0.05). There was no significant difference in the mean SDNR and SNR of the other group (surrounding soft tissue components, bone marrow components with mineralization, benign and malignant lesions) between fast STIR images and T1W‐CEFS images. The mean volume of the tumors was significantly higher with STIR than with the T1W‐CEFS sequence (P < 0.05).

Conclusion

The STIR sequence should be used instead of T1W‐CEFS imaging for the evaluation of bone tumors. J. Magn. Reson. Imaging 2004;19:475–481. © 2004 Wiley‐Liss, Inc.
Correction of spatial distortion in EPI due to inhomogeneous static magnetic fields using the reversed gradient method
Authors: Morgan Paul S. , Bowtell Richard W. , McIntyre Dominick J.O. , Worthington Brian S.
Published: March 2004

Purpose

To derive and implement a method for correcting spatial distortion caused by in vivo inhomogeneous static magnetic fields in echo‐planar imaging (EPI).

Materials and Methods

The reversed gradient method, which was initially devised to correct distortion in images generated by spin‐warp MRI, was adapted to correct distortion in EP images. This method provides point‐by‐point correction of distortion throughout the image. EP images, acquired with a 3 T MRI system, of a phantom and a volunteer's head were used to test the correction method.

Results

Good correction was observed in all cases. Spatial distortion in the uncorrected images ranged up to 4 pixels (12 mm) and was corrected successfully.

Conclusion

The correction was improved by the application of a nonlinear interpolation scheme. The correction requires that two EP images be acquired at each slice position. This increases the acquisition time, but an improved signal‐to‐noise ratio (SNR) is seen in the corrected image. The local SNR gain decreases with increasing distortion. In many EPI acquisition schemes, multiple images are averaged at each slice position to increase the SNR; in such cases the reversed gradient correction method can be applied with no increase in acquisition duration. J. Magn. Reson. Imaging 2004;19:499–507. © 2004 Wiley‐Liss, Inc.
Metabolites of an orally active antimicrobial prodrug, 2,5‐bis(4‐amidinophenyl)furan‐bis‐O‐methylamidoxime, identified by liquid chromatography/tandem mass spectrometry
Authors: Zhou Lian , Thakker Dhiren R. , Voyksner Robert D. , Anbazhagan Mariappan , Boykin David W. , Hall James E. , Tidwell Richard R.
Published: March 2004

DB75 (2,5‐bis(4‐amidinophenyl)furan) is a promising antimicrobial agent against African trypanosomiasis and Pneumocystis carinii pneumonia. However, it suffers from poor oral activity in rodent models for both infections. In contrast, a novel prodrug of DB75, 2,5‐bis(4‐amidinophenyl)furan‐bis‐O‐methylamidoxime (DB289), has excellent oral activity. DB289 is currently undergoing clinical investigation as a candidate drug to treat primary stage African trypanosomiasis and Pneumocystis carinii pneumonia. In this study, metabolites of DB289 formed after incubation with freshly isolated rat hepatocytes were characterized using liquid chromatography/ion trap mass spectrometry. Administration of DB289 and octadeuterated DB289 in a 1 : 1 mixture greatly facilitated metabolite identification by providing isotope patterns with twin ions separated by 8 m/z units in the ratio 1 : 1, in the extracted ion chromatograms of molecular ions and in the product ion mass spectra of metabolites. Ten metabolites were identified. Series of O‐demethylations and N‐dehydroxylations led to the metabolic activation of DB289 to DB75 with the production of four intermediate phase I metabolites. Phase II glucuronidation and sulfation led to the formation of four glucuronide and one sulfate metabolites. Copyright © 2004 John Wiley & Sons, Ltd.
Peak capacity of ion mobility mass spectrometry: the utility of varying drift gas polarizability for the separation of tryptic peptides
Authors: Ruotolo Brandon T. , McLean John A. , Gillig Kent J. , Russell David H.
Published: March 2004

Ion mobility mass spectrometry (IM‐MS) peptide mass mapping experiments were performed using a variety of drift gases (He, N2, Ar and CH4). The drift gases studied cover a range of polarizabilities ((0.2–2.6) × 10−24 cm3) and the peak capacities obtained for tryptic peptides in each gas are compared. Although the different gases exhibit similar peak capacities (5430 (Ar) to 7580 (N2)) in some cases separation selectivity presumably based on peptide conformers (or conformer populations), is observed. For example the drift time profiles observed for some tryptic peptide ions from aldolase (rabbit muscle) show a dependence on drift gas. The transmission of high‐mass ions (m/z > 2000) is also influenced by increased scattering cross‐section of the more massive drift gases. Consequently the practical peak capacity for IM‐MS separation cannot be assumed to be solely a function of resolution and the ability of a gas to distribute signals in two‐dimensional space; rather, peak capacity estimates must account for the transmission losses experienced for peptide ions as the drift gas mass increases. Copyright © 2004 John Wiley & Sons, Ltd.
Mass spectrometry of 1,3‐ and 1,5‐dicaffeoylquinic acids
Authors: Schram Karl , Miketova Petra , Slanina Jiri , Humpa Otakar , Taborska Eva
Published: March 2004

Samples of 1,3‐ (1) and 1,5‐dicaffeoylquinic acid (2) and their hexaacetate derivatives were examined using positive and negative electrospray ionization mass spectrometry and tandem mass spectrometry. Differences in the various spectra allow the discrimination of each of the isomers. Specific losses in the spectra of 2 also permit the identification of the site of substitution of one of the caffeic acid moieties as being at the 5‐position. The spectra of 3,5‐ (3) and 4,5‐dicaffeoylquinic (4) acids and their hexaacetate derivatives were compared with those of 1 and 2 and their derivatives, and differences in ion abundances or the presence/absence of specific ions can be used to identify uniquely each of the compounds. Copyright © 2004 John Wiley & Sons, Ltd.
Observation of self‐ion–molecule reactions during collisionally activated dissociation in an ion‐trap mass spectrometer
Authors: Wu Hui‐Fen , Chen Chien‐Hung , Wu Meng‐Ting
Published: March 2004

This paper describes the formation of protonated molecules ([M + H]+) and adduct ions by self‐ion–molecule reactions (SIMR) during collisionally activated decomposition (CAD) of methyne addition ions ([M + CH]+) produced from chemical ionization (CI) or SIMR in both an external and internal source ion‐trap mass spectrometer (ITMS). The CAD results for the methyne addition ions of dopamine produced from both SIMR and dimethyl ether CI undertaken in the external and internal source ITMS were compared in order to prove the occurrence of SIMR during CAD processes. Compared with the external source ITMS, the internal source ITMS is much more easily applicable to this type of reaction owing to the large population of neutral analytes present in the trap. Copyright © 2004 John Wiley & Sons, Ltd.
Alternative approaches for the detection of various phospholipid classes by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Estrada Rosendo , Yappert M. Cecilia
Published: March 2004

The detection of phospholipids (PLs) by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry was demonstrated nearly a decade ago. However, its use as a conventional tool for PL analysis has been hindered by ambiguities in peak assignments caused by spectral overlaps and difficulties in the detection of some PL classes when analytes with positively charged head groups, such as sphingomyelins (SMs) and phosphatidylcholines (PCs) are present. In this work, either a strong cation‐exchange resin or CsCl crystals were added directly to the PL samples to reduce spectral complexity and enhance sensitivity. The quantitative exchange resulted in virtually only protonated or Cs+ adducts. To alleviate difficulties in the detection and identification of PL classes with ionization efficiencies lower than those of SMs and PCs, improvements in the sensitivity of negative‐ion mass spectra were sought. For this purpose, several neutral and basic matrices were tried. Among them, p‐nitroaniline (PNA) proved to be an advantageous alternative to the use of 2,5‐dihydroxybenzoic acid (DHB), the most commonly used matrix in PL analysis. Because of its lower acidity, PNA increased the relative amount of deprotonated species and improved the sensitivity of negative‐ion mass spectra. It was possible to confirm peak assignments for PL classes that normally give weak signals when DHB is used. Noteworthy is the detection (in both positive and negative modes) and conclusive identification of species in natural mixtures of phosphatidylethanolamines (PEs) and PE plasmalogens (PEps). PNA allowed the identification of PEs and PEps even in mixtures containing SMs and PCs. Although some cations related to PCs and PEs overlapped in positive‐ion spectra, these interferences were eliminated in the negative mode as only the deprotonated forms of PEs and PEps were detectable and those of SMs and PCs were absent owing to their neutrality. Copyright © 2004 John Wiley & Sons, Ltd.
Simple and sensitive liquid chromatographic quantitative analysis of the novel marine anticancer drug Yondelis™ (ET‐743, trabectedin) in human plasma using column switching and tandem mass spectrometric detection
Authors: Stokvis E. , Rosing H. , López‐Lázaro L. , Beijnen J. H.
Published: March 2004

The development of a simple and sensitive assay for the quantitative analysis of the marine anticancer agent Yondelis (ET‐743, trabectedin) in human plasma using liquid chromatography (LC) with column switching and tandem mass spectrometric (MS/MS) detection is described. After protein precipitation with methanol, diluted extracts were injected on to a small LC column (10 × 3.0 mm i.d.) for on‐line concentration and further clean‐up of the sample. Next, the analyte and deuterated internal standard were back‐flushed on to an analytical column for separation and subsequent detection in an API 2000 triple‐quadrupole mass spectrometer. The lower limit of quantitation was 0.05 ng mL−1 using 100 µl of plasma with a linear dynamic range up to 2.5 ng ml−1. Validation of the method was performed according to the most recent FDA guidelines for bioanalytical method validation. The time needed for off‐line sample preparation has been reduced 10‐fold compared with an existing LC/MS/MS method for ET‐743 in human plasma, employing a labor‐intensive solid‐phase extraction procedure for sample pretreatment. The proposed column switching method was successfully applied in phase II clinical trials with Yondelis and pharmacokinetic monitoring. Copyright © 2004 John Wiley & Sons, Ltd.
Application of liquid chromatography‐ion trap mass spectrometry to the characterization of the 16‐membered ring macrolide josamycin propionate
Authors: Govaerts Cindy , Chepkwony Hezekiah Kibet , Van Schepdael Ann , Adams Erwin , Roets Eugène , Hoogmartens Jos
Published: March 2004

Coupled liquid chromatography and ion trap mass spectrometry (LC/MS) was used for the characterization of the semi‐synthetic 16‐membered ring macrolide josamycin propionate. On‐line identification of impurities in this antibiotic complex was performed with an ion trap mass spectrometer without recourse to time‐consuming isolation and purification procedures. Ion trap mass spectrometry is ideally suited to identification of impurities because it provides MSn capability, enabling multiple stages of mass spectrometry to obtain the maximum amount of structural information for a given molecule. The ion trap was used with an electrospray ionization source operated in the positive ion mode or with an atmospheric pressure chemical ionization source operated in the negative ion mode. The identity of the unknown compounds was deduced using the MS/MS and MSn collision‐induced dissociation spectra of reference substances or structural analogs as interpretative templates, combined with knowledge about the nature of functional group fragmentation behavior. Given the importance attached to the identification of impurities of unknown identity in pharmaceutical substances, this study is useful for companies producing josamycin propionate. The knowledge of the fragmentation behavior is also of importance in further research on other 16‐membered macrolides. Copyright © 2004 John Wiley & Sons, Ltd.
Modelling PBG devices to DWDM filters design
Authors: Giorgio Agostino , Pasqua Decio , Gina Perri Anna
Published: March 2004

The fibre optic transmission systems require a bandwidth of about 25 THz in telecommunications networks, for which it is necessary to resort to dense wavelength division multiplexing (DWDM) systems. These systems need optical filters to broadcast selectively or not in a given wavelength band.

A new very promising technology for these applications is the photonic crystals with forbidden bandgap (photonic bandgap (PBG)).

In this paper, we propose a model of PBG devices to design DWDM filters on PBG materials. Copyright © 2004 John Wiley & Sons, Ltd.
SSOR preconditioned GMRES for the FEM analysis of waveguide discontinuities with anisotropic dielectric
Authors: Chen R. S. , Ping X. W. , Wang D. X. , K. N. Yung Edward
Published: March 2004

The anisotropic media and active properties of the perfectly matched layer (PML) absorbers significantly deteriorate the finite element method (FEM) system condition and as a result, convergence of the iterative solver is substantially slowed down. To address this issue, the symmetric successive over‐relaxation (SSOR) preconditioning scheme is applied to the generalized minimal residual (GMRES) for solving a large sparse and non‐symmetric system of linear equations resulting from the analysis of ferrite waveguide device by use of edge‐based FEM. Consequently, this preconditioned GMRES (PGMRES) approach can reach convergence ten times faster than GMRES for the typical structures. Copyright © 2004 John Wiley & Sons, Ltd.
The crosstalk characteristics of different PCB layouts with multiconductor transmission line
Authors: Ding C. H. , Wu S. D. , Chou J. H.
Published: March 2004

A simple method of moment numerical scheme is adopted to study the crosstalk characteristics of printed circuit board. Both strip lines and microstrips PCB configurations are investigated. The results indicate that with the ground plane closer to the signal line, the crosstalk voltages can be reduced. Furthermore, the non‐synchronization due to difference in mode velocities can also be reduced. Copyright © 2004 John Wiley & Sons, Ltd.
Numerical approach to field fluctuations and spectral lineshape in InGaAsP laser diodes
Authors: Ahmed Moustafa
Published: March 2004

This paper reports on a numerical approach to model the field fluctuations, spectral lineshape and linewidth in semiconductor lasers. The approach is based on numerical solution of the laser rate equations augmented by Langevin noise sources that account for fluctuations in the lasing field. The paper newly examines contributions of intensity and frequency noises to the spectral characteristics of the lineshape and its linewidth over a wide range of injection current. The model is applied to InGaAsP lasers emitting in a wavelength of 1.5 μm as the most representative light sources in optical communication systems. Accuracy of approximated models of calculating linewidth from low‐frequency components of the frequency noise is checked. Effect of non‐linear gain suppression on the lineshape is also explored. The spectral lineshape promotes and the linewidth decreases as the laser is injected far from the near‐threshold region. The lineshape changes mainly with changes in the frequency noise spectrum while the linewidth is sensitive to variation in the low‐frequency levels of both intensity and frequency noises. Copyright © 2004 John Wiley & Sons, Ltd.
Time‐domain simulation of power transients in Raman fibre amplifiers
Authors: Karásek M. , Kaňka J. , Honzátko P. , Peterka P.
Published: March 2004

We study power transients in Raman fibre amplifiers (RFA). Transients are defined as the output signal power response to abrupt change in the number of signal channels at the input to the RFA (channel addition/removal). The simulations are based on application of a large signal numerical model which incorporates time variation effects, downstream propagation of multiple signals, upstream propagation of pump and both downstream and upstream propagation of amplified spontaneous emission (ASE). System of coupled non‐linear differential equations describing the propagation of the signal, pump and ASE waves along the RFA and their evolution in time represents a two‐boundary value problem. Due to the backward propagating ASE and counter‐directional pumping, an iterative forward and backward solution of propagation equations must be used in order to achieve a steady‐state distribution of signals, pumps, and ASE powers along the RFA. We have used either the fourth‐order Runge–Kutta routine, or an alternative average power analysis (APA) approach to obtain the steady‐state optical power distribution along the fibre. Direct integration is used to obtain time evolution of optical powers as a response to channel addition/removal. Stability of the numerical solution depends on the relation of discretization steps in space and time. Gain locking of the RFA via electronic feedforward pump control derived from a monitoring channel output power has been introduced in the model to study the possibility of suppressing the surviving channel power fluctuations. Copyright © 2004 John Wiley & Sons, Ltd.
Inhibition of patulin production by Penicillium expansum cultured with neem (Azadirachta indica) leaf extracts
Authors: Aparecida Galerani Mossini Simone , De Oliveira Kesia Pires , Kemmelmeier Carlos
Published: April 2004

Aqueous extract of the leaves of neem [Azadirachta indica A. Juss (Meliaceae)] was tested in vitro for antifungal activity against Penicillium expansum. Patulin production was inhibited during cultivation, when concentrations higher than 50 mg/ml of neem leaf extract was added to the culture medium. Analyses of mycotoxin production were performed by TLC

Abbreviations used: TLC, Thin layer chromatography; HPLC, High‐performance liquid chromatography; UEM, Universidade Estadual de Maringá [State University of Maringá]; IAPAR, Instituto Agrônomico do Paraná [Agronomy Institute of Paraná].

and HPLC. Fungal growth and colony characteristics, in the presence of the extract, were investigated and compared with extract‐free cultures. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)