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Principles behind Magnetic Resonance Imaging (MRI)
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Hence, it is very convenient to view the matrix into which signal values are placed, as a mathematical space spanned by the kx and ky axes (Figure 32.14b–c). In general terms, the desired image properties, in terms of, for example, field of view and spatial resolution, require sufficient amounts of signal data to be collected, with appropriate sampling density and sampling window, and the signal sampling strategy is elegantly illustrated with the k-space formalism. The signal sampling track in k-space is often referred to as the trajectory. For a conventional GRE, SE or IR sequence, k-space is, as indicated above, covered ‘line by line’ over the different phase-encoding steps, and, in the standard case, a N×N signal data matrix in k-space (m-1) results in a N×N image matrix (m) after inverse Fourier transform (Figure 32.15).
Biochemical Markers in Ophthalmology
Published in Ching-Yu Cheng, Tien Yin Wong, Ophthalmic Epidemiology, 2022
Abdus Samad Ansari, Pirro G. Hysi
DNA methylation (DNAm) is an attachment of a methyl group to the cytosine residue in the DNA. Somewhat reductively, we distinguish three separate molecular mechanisms involved in DNAm. The first, mediated primarily by DNMT3A and DNMT3B enzymes [79], methylates cytosine residues in previously unmethylated DNA. This process is of particular importance during early developmental stages and germline cell differentiation. This process causes cells to gradually lose their embryonic pluripotency and acquire methylation profiles that are characteristic of a specific line, organ, and tissue, distinct from other cell lines and tissues. Pluripotency and loss thereof, during cell differentiation processes, is controlled by not yet fully understood mechanisms and involves a small number of transcription factors. Among those, four transcription factors (Oct3/4, Sox2, Klf4, and Myc), the so-called Yamanaka factors [80], appear to act as master regulators. Tissue specificity arising since the earliest embryonic stages is a main feature of DNAm and is conserved across the different species [81].
Dynamics of Immunoglobulin and T-cell Receptor Genes Recombinations During Lymphocyte Development
Published in Gérard Chaouat, The Immunology of the Fetus, 2020
Daniele Primi, Evelyne Jouvin-Marche, Raphael A. Clynes, Jean-Pierre Marolleau, Carine Gris, Kenneth B. Marcu, Pierre-André Cazenave
To better analyze this possibility, we subcloned this line and studied both CTβ and JH rearrangements. Figure 6 shows that in six out of the eight subclones analyzed, secondary rearrangements at the JH locus have occurred. Interestingly, some of these secondary recombinations are of one type only, suggesting that this phenomenon is not a random event, but rather that it represents a highly regulated event that probably results from a preprogrammed molecular cascade. Two out of the eight subclones have also rearranged CTβ2 on both chromosomes with consequent deletion of both CTβ1 alleles (Figure 7). Thus, M8T cells appear to be competent not only to differentiate along the T-cell lineage but also to further recombine immunoglobulin loci. In order to further define the differentiation potential of these cells, we cultured M8T clones for 48 h in the presence of the B-cell mitogen LPS. At the end of the incubation time, all clones were tested for the expression of a surface marker that has been shown to be selectively expressed on pre-B-cells. Surprisingly, one of these clones, M8T3S, could be induced by LPS to express the BP3 marker. Taken together, these findings strongly suggest that M8T line can differentiate along both the T- and B-cell lineage, depending on the nature of exogenous signals. This line, therefore, represents a valuable tool for dissecting the molecular events that lead to the differentiation of a specific lineage.
In vitro study of the mechanism of intraneuronal β-amyloid aggregation in Alzheimer’s disease
Published in Archives of Physiology and Biochemistry, 2022
Shahad Alsunusi, Taha A. Kumosani, Charles G. Glabe, Etimad A. Huwait, Said S. Moselhy
Cell line culture has been widely used to examine the intraneuronal aggregation of amyloidogenic proteins, such as huntingtin, alpha-synuclein and tau (Gouras et al.2000). The common approach for studying intracellular protein aggregation is the regulated expression of a green fluorescent protein (GFP)-tagged amyloidogenic protein in a specific cell line derived from a transplantable rat PC12 cell (Walsh et al.2002). This type of cell line has a wide range of uses, from understanding disease mechanisms (Goedert 1999) to identifying for drugs that inhibit aggregation (Frost et al.2009). They have used the ecdysone-inducible PC12 cell expression system to express amyloid precursor protein C-terminal fragment C99 (APP-CTF99) and amyloid precursor protein intracellular domain (AICD) constructs in PC12 cells that contain GFP fused to the carboxyl terminus of amyloid precursor protein C-terminal fragment (APP-CTF). For APP-CTF99 and AICD, expression leads to the formation of intracellular aggregates or “inclusion bodies” in a concentration and time-dependent fashion as previously published (Arrasate et al.2004).
Psychiatric Nurses’ Lived Experiences of Workplace Violence in Acute Care Psychiatric Units in Western Canada
Published in Issues in Mental Health Nursing, 2022
Bridget J. Hiebert, W. Dean Care, Sonia A. Udod, Candice M. Waddell
Colaizzi’s (1978) distinctive seven-step process for data analysis was utilized to assist in identifying and creating thematic representations of the study participants’ experience (Morrow et al., 2015). This included: 1) becoming familiar with transcribed data through immersion and reading to identify primary ideas; 2) generating initial codes in the transcription by reviewing line by line; 3) searching for and identifying categories; 4) reviewing categories to identify relationships between categories and subcategories; 5) naming and defining categories and sub-categories; 6) producing the final report from the analysis; and lastly, 7) validation of the findings was sought from the study participants by emailing these findings to each participant for them to compare the primary researcher’s descriptive results with their experiences (Morrow et al., 2015).
Liquid biopsy in head and neck squamous cell carcinoma: circulating tumor cells, circulating tumor DNA, and exosomes
Published in Expert Review of Molecular Diagnostics, 2020
Wen-Ying Yang, Lin-Fei Feng, Xiang Meng, Ran Chen, Wen-Hua Xu, Jun Hou, Tao Xu, Lei Zhang
de Jesus et al. [85] evaluated methylated ctDNA both in tumor tissue and paired plasma of OPSCC patients by ddPCR. Methylated ctDNA was positive in 73.3% (11/15) and negative in 5/5 paired plasma samples: 7 cases with CCNA1, 2 cases with TIMP3, 1 case in CDH8, and 1case in DAPK. The concordance of the test results in both sample types was 80%. Posttreatment plasma with a high level of this methylated ctDNA can predict the recurrence. It has been demonstrated that the activity of LINE-1 has an association with global DNA hypomethylation, genomic instability, and tumor development [86]. Furthermore, the increased level of hypomethylation of LINE-1 was observed in tumor tissues of OPSCC with recurrence [87]. Several studies also have shown that 5-hmC can actively intermediate DNA demethylation [88]. A recent study also investigated LINE-1 hypomethylation levels have predictive value in patient prognosis. HNSCC patients had higher LINE-1 hypomethylation levels and a decrease of 5-hmC in plasma [89].