Author(s): Wirestam R, Salford LG, Thomsen C, Brockstedt S, Persson BR,
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Abstract Gradient-echo pulse sequences with velocity-encoding gradients of 22.5-25 mT/m, were used for brain-motion and CSF-flow studies. To reduce motion artifacts, a phase-correction technique based on navigator echoes was evaluated. Three patients with right-sided parietal tumours were investigated; one astrocytoma grade III-IV, one astrocytoma grade I-II and one benign meningioma. In healthy volunteers, a maximal brain-tissue velocity of (0.94 +/- 0.26) mm/s (mean +/- 1SD) was observed, which is consistent with previously presented results. The phase correction was proven useful for reduction of artifacts due to external head movements in modulus and phase images, without loss of phase information related to internal motion. The tissue velocity within the astrocytomas was low during the entire cardiac cycle. An abnormally high rostral velocity component was, however, observed in the brain tissue frontal to the astrocytomas. In all patients, an abnormal CSF flow pattern was observed. The study of brain motion may provide further understanding of the effects of tumours and other pathological conditions in the brain. When considering intracranial motion as a source of error in diffusion/perfusion MRI, the present study suggests that a pathology can alter the properties of brain motion and CSF flow considerably, leading to a more complex impact on diffusion/perfusion images.
This article was published in Magn Reson Imaging
and referenced in Journal of Bioengineering & Biomedical Science
- Yosef Yarden
Classically, the 3âuntranslated region (3âUTR) is that region in eukaryotic protein-coding genes from the translation termination codon to the polyA signal. It is transcribed as an integral part of the mRNA encoded by the gene. However, there exists another kind of RNA, which consists of the 3âUTR alone, without all other elements in mRNA such as 5âUTR and coding region. The importance of independent 3âUTR RNA (referred as I3âUTR) was prompted by results of artificially introducing such RNA species into malignant mammalian cells. Since 1991, we found that the middle part of the 3âUTR of the human nuclear factor for interleukin-6 (NF-IL6) or C/EBP gene exerted tumor suppression effect in vivo. Our subsequent studies showed that transfection of C/EBP 3âUTR led to down-regulation of several genes favorable for malignancy and to up-regulation of some genes favorable for phenotypic reversion. Also, it was shown that the sequences near the termini of the C/EBP 3âUTR were important for its tumor suppression activity. Then, the C/EBP 3âUTR was found to directly inhibit the phosphorylation activity of protein kinase CPKC in SMMC-7721, a hepatocarcinoma cell line. Recently, an AU-rich region in the C/EBP 3âUTR was found also to be responsible for its tumor suppression. Recently we have also found evidence that the independent C/EBP 3âUTR RNA is actually exists in human tissues, such as fetal liver and heart, pregnant uterus, senescent fibroblasts etc. Through 1990âs to 2000âs, world scientists found several 3âUTR RNAs that functioned as artificial independent RNAs in cancer cells and resulted in tumor suppression. Interestingly, majority of genes for these RNAs have promoter-like structures in their 3âUTR regions, although the existence of their transcribed products as independent 3âUTR RNAs is still to be confirmed. Our studies indicate that the independent 3âUTR RNA is a novel non-coding RNA species whose function should be the regulation not of the expression of their original mRNA, but of some essential life activities of the cell as a whole.
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