Magnetic labeling of activated microglia in experimental gliomas.
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Microglia, as intrinsic immunoeffector cells of the central nervous system (CNS), play a very sensitive, crucial role in the response to almost any brain pathology where they are activated to a phagocytic state. Based on the characteristic features of activated microglia, we investigated whether these cells can be visualized with magnetic resonance imaging (MRI) using ultrasmall superparamagnetic iron oxides (USPIOs). The hypothesis of this study was that MR microglia visualization could not only reveal the extent of the tumor, but also allow for assessing the status of immunologic defense. Using USPIOs in cell culture experiments and in a rat glioma model, we showed that microglia can be labeled magnetically. Labeled microglia are detected by confocal microscopy within and around tumors in a typical border-like pattern. Quantitative in vitro studies revealed that microglia internalize amounts of USPIOs that are significantly higher than those incorporated by tumor cells and astrocytes. Labeled microglia can be detected and quantified with MRI in cell phantoms, and the extent of the tumor can be seen in glioma-bearing rats in vivo. We conclude that magnetic labeling of microglia provides a potential tool for MRI of gliomas, which reflects tumor morphology precisely. Furthermore, the results suggest that MRI may yield functional data on the immunologic reaction of the CNS. (+info)
Characterization of focal hepatic lesions with SPIO-enhanced MRI.
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AIM: To evaluate the value of superparamagnetic iron oxide (SPIO) enhanced MRI in characterizing focal hepatic lesions. METHODS: Forty-three patients (32 men,11 women, mean age 51 years, age range 25-74 years) with previously identified focal hepatic lesions were enrolled into this study. All the patients underwent plain, Gd-DTPA enhanced MRI and the SPIO enhanced MRI 1-7 d later. The surgico-pathologic diagnosis was aestablished in 31 cases and the diagnosis in other 12 cases was made on the basis of clinical findings and biochemical tests. The signal changes of lesions were analyzed and the CNRs of lesion-to-liver were measured before and after SPIO enhancement. The data were analyzed by paired t test. RESULTS: Focal hepatic lesions included primary hepatocellular carcinoma (HCC,n=22), hemangioma (n=5), cyst (n=4), metastases (n=5), cirrhotic nodule (n=4), focal nodular hyperplasia (FNH, n=5) and other miscellaneous lesions (n=6). After SPIO enhancement HCC demonstrated iso- or slight hyperintensity on T1WI and moderate hyperintersity on T2WI, hemangioma showed moderate hyperintensity on T1WI and obvious hyperintensity on T2WI, the SI of cyst had no change either on T1WI or on T2WI, cirrhotic nodules revealed iso-intensity on T2WI, and the SI of FNH decreased significantly on T2WI. No specific manifestations were found in the other 6 miscellaneous lesions after SPIO enhancement. CONCLUSION: SPIO enhanced-MRI can improve the characterization confidence for diagnosis of focal hepatic lesions. (+info)
Desulfovibrio magneticus sp. nov., a novel sulfate-reducing bacterium that produces intracellular single-domain-sized magnetite particles.
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A novel type of dissimilatory sulfate-reducing bacterium, designated strain RS-1T, capable of producing intracellular magnetite particles (magnetosomes) was isolated from freshwater sulfide-rich sediments. Phylogenetic analysis based on 16S rDNA sequences revealed that RS-1T is a member of the genus Desulfovibrio. Its closest known relative is Desulfovibrio burkinensis (sequence similarity of 98.7%). Strain RS-1T contains desulfoviridin, c-type cytochromes and, unlike other Desulfovibrio spp., it possesses menaquinone MK-7(H2) instead of MK-6 or MK-6(H2). Strain RS-1T is also unique compared with other members of Desulfovibrio in its ability to synthesize intracellular magnetite particles. A novel species, Desulfovibrio magneticus sp. nov., is proposed for RS-1T (= ATCC 700980T = DSM 13731T), a sulfate-reducing magnetotactic bacterium. (+info)
In vivo detection of acute rat renal allograft rejection by MRI with USPIO particles.
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BACKGROUND: Magnetic resonance imaging (MRI) for non-invasively detecting renal rejection was developed by monitoring the accumulation of macrophages labeled with dextran-coated ultrasmall superparamagnetic iron oxide (USPIO) particles at the rat renal allografts during acute rejection. METHODS: Five groups of male rats with DA-->BN renal allografts and one group with BN-->BN renal isografts were investigated by MRI before, immediately after, and 24 hr after intravenous infusion with different doses of USPIO particles. All infusions were done on post-operative day 4. MRI experiments were carried out in a 4.7-Tesla instrument using a gradient echo sequence. RESULTS: MR signal intensity (MRSI) of the cortex was found to decrease with higher dosages of USPIO particles. In the absence of USPIO infusion, a decrease in MRSI was seen in the medulla region, presumably due to hemorrhage associated with renal graft rejection, while no significant change was observed in the cortex. The optimal dose of USPIO particles for visualizing rejection-associated changes in our rat kidney model appears to be 6 mg Fe/kg body weight. Iron staining results correlated with the MRSI data, indicating that the signal reduction in the MR images was due to the presence of iron. Immunohistochemical results indicated that USPIO particles were mostly taken up by infiltrating macrophages in the rejecting grafts. CONCLUSIONS: Our results suggest that MRI with intravenous administration of dextran-coated USPIO particles appears to be a valuable and promising tool that can be used as a non-invasive and sensitive method to detect graft rejection in renal transplantation. (+info)
Chromium isotopes and the fate of hexavalent chromium in the environment.
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Measurements of chromium (Cr) stable-isotope fractionation in laboratory experiments and natural waters show that lighter isotopes reacted preferentially during Cr(VI) reduction by magnetite and sediments. The 53Cr/52Cr ratio of the product was 3.4 +/- 0.1 per mil less than that of the reactant. 53Cr/52Cr shifts in water samples indicate the extent of reduction, a critical process that renders toxic Cr(VI) in the environment immobile and less toxic. (+info)
Comparison of two superparamagnetic viral-sized iron oxide particles ferumoxides and ferumoxtran-10 with a gadolinium chelate in imaging intracranial tumors.
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BACKGROUND AND PURPOSE: Ultrasmall superparamagnetic iron oxide particles result in shortening of T1 and T2 relaxation time constants and can be used as MR contrast agents. We tested four hypotheses by evaluating MR images of intracranial tumors after infusion of two iron oxide agents in comparison with a gadolinium chelate: 1) Ferumoxtran in contrast to ferumoxides can be used as an intravenous MR contrast agent in intracranial tumors; 2) ferumoxtran enhancement, albeit delayed, is similar to gadolinium enhancement; 3) ferumoxtran-enhanced MR images in contrast to gadolinium-enhanced MR images may be compared with histologic specimens showing the cellular location of iron oxide particles; 4) ferumoxtran can serve as a model for viral vector delivery. METHODS: In 20 patients, ferumoxides and ferumoxtran were intravenously administered at recommended clinical doses. MR imaging was performed 30 minutes and 4 hours after ferumoxides infusion (n = 3), whereas ferumoxtran-enhanced MR imaging (n = 17) was performed 6 and 24 hours after infusion in the first five patients and 24 hours after infusion in the remaining 12. MR sequences were spin-echo (SE) T1-weighted, fast SE T2- and proton density-weighted, gradient-recalled-echo T2*-weighted, and, in four cases, echo-planar T2-weighted sequences. Representative regions of interest were chosen on pre- and postcontrast images to compare each sequence and signal intensity. RESULTS: Despite some degree of gadolinium enhancement in all tumors, no significant T1 or T2 signal intensity changes were seen after ferumoxides administration at either examination time. Fifteen of 17 patients given ferumoxtrans had T1 and/or T2 shortening consistent with iron penetration into tumor. Histologic examination revealed minimal iron staining of the tumor with strong staining at the periphery of the tumors. CONCLUSION: 1) Ferumoxtran can be used as an intravenous MR contrast agent in intracranial tumors, mostly malignant tumors. 2) Enhancement with ferumoxtran is comparable to but more variable than that with the gadolinium chelate. 3) Histologic examination showed a distribution of ferumoxtran particles similar to that on MR images, but at histology the cellular uptake was primarily by parenchymal cells at the tumor margin. 4) Ferumoxtran may be used as a model for viral vector delivery in malignant brain tumors. (+info)
Ferumoxtran-10, a superparamagnetic iron oxide as a magnetic resonance enhancement agent for imaging lymph nodes: a phase 2 dose study.
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BACKGROUND AND PURPOSE: Dextran-coated ultrasmall superparamagnetic iron oxide ferumoxtran-10 (Combidex) is used in reticuloendothelial MR imaging. Our purpose was to determine the optimal dose and imaging time for lymph node evaluation. MATERIALS: Twenty-four healthy volunteers underwent neck MR imaging before and 6, 12, 24, and 36 hours after receiving 1.1, 1.7, 2.6, or 3.4 mg Fe/kg ferumoxtran-10. Vital signs, serum and urine levels, and adverse events were monitored. Qualitative nodal architecture, size, and signal-intensity changes were assessed on T1-, T2-, and T2*-weighted (fast field-echo 25 degrees or 80 degrees flip angle [FFE-25 or FFE-80]) images. Region-of-interest intensities were measured quantitatively. RESULTS: Consistently strong enhancement in normal nodes was found with 24- and 36-hour T2- and T2*-weighted imaging after 2.6 and 3.4 mg Fe/kg doses. No serious adverse events occurred. With 2.6 mg Fe/kg, unblinded (vs blinded) specificities at 24 and 36 hours, respectively, were 100% and 100% (vs 88% and 88%) with T2-weighted, 96% and 96% (vs 73% and 85%) with FFE-25, and 100% and 92% (vs 85% and 88%) with FFE-80 sequences. With 3.4 mg Fe/kg, unblinded (vs blinded) specificities at 24 and 36 hours, respectively, were 89% and 79% (vs 75% and 75%) with T2-weighted, 84% and 79% (vs 95% and 100%) with FFE-25, and 95% and 79% (vs 95% and 80%) with FFE-80 sequences. CONCLUSION: Ferumoxtran-10 nodal imaging appears to be effective and safe. Signal intensity and specificity for normal nodes were best 24 or 36 hours after 2.6 and 3.4 mg Fe/kg doses. Nodal conspicuity was best with T2- and T2*-weighted sequences. (+info)
Optimal pulse sequence for ferumoxides-enhanced MR imaging used in the detection of hepatocellular carcinoma: a comparative study using seven pulse sequences.
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OBJECTIVE: To identify the optimal pulse sequence for ferumoxides-enhanced magnetic resonance (MR) imaging in the detection of hepatocelluar carcinomas (HCCs). MATERIALS AND METHODS: Sixteen patients with 25 HCCs underwent MR imaging following intravenous infusion of ferumoxides. All MR studies were performed on a 1.5-T MR system, using a phased-array coil. Ferumoxides (Feridex IV) at a dose of 15 micromol/Kg was slowly infused intravenously, and axial images of seven sequences were obtained 30 minutes after the end of infusion. The MR protocol included fast spin-echo (FSE) with two echo times (TR3333-8571/TE18 and 90-117), singleshot FSE (SSFSE) with two echo times (TRinfinity/TE39 and 98), T2*-weighted gradient- recalled acquisition in the steady state (GRASS) (TR216/TE20), T2*-weighted fast multiplanar GRASS (FMPGR) (TR130/TE8.4-9.5), and T2*-weighted fast multiplanar spoiled GRASS (FMPSPGR) (TR130/TE8.4-9.5). Contrast-to-noise ratios (CNRs) of HCCs determined during the imaging sequences formed the basis of quantitative analysis, and images were qualitatively assessed in terms of lesion conspicuity and image artifacts. The diagnostic accuracy of all sequences was assessed using receiver operating characteristic (ROC) analysis. RESULTS: Quantitative analysis revealed that the CNRs of T2*-weighted FMPGR and T2*-weighted FMPSPGR were significantly higher than those of the other sequences, while qualitative analysis showed that image artifacts were prominent at T2*-weighted GRASS imaging. Lesion conspicuity was statistically significantly less clear at SSFSE imaging. In term of lesion detection, T2*-weighted FMPGR, T2*- weighted FMPSPGR, and proton density FSE imaging were statistically superior to the others. CONCLUSION: T2*-weighted FMPGR, T2*- weighted FMPSPGR, and proton density FSE appear to be the optimal pulse sequences for ferumoxidesenhanced MR imaging in the detection of HCCs. (+info)