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Preimplantation Genetic Testing of Aneuploidies (PGT-A)
Published in Carlos Simón, Carmen Rubio, Handbook of Genetic Diagnostic Technologies in Reproductive Medicine, 2022
Daniela N. Bakalova, Darren K. Griffin, Maria E. Póo, Alan R. Thornhill
FISH on preimplantation embryos was clinically introduced in the early 90s using X and Y chromosome probes to identify families at risk of transmitting sex-linked disorders, followed by early PGT-A protocols screening for sporadic aneuploidy of common chromosomes associated with live-birth defects. Soon after, chromosomes 16 and 22 were also included, both of which are commonly seen in first trimester pregnancy loss. Preliminary data obtained from these more comprehensive protocols demonstrated a doubling in implantation rates, albeit showing no notable increase in pregnancy rates [45]. However, these must be applied over multiple rounds of hybridization, and assume that the morphology and integrity of the single nucleus sample remain sufficient for accurate and consistent chromosomal analysis. Subsequent hybridization to allow for expanded screening of all 23 pairs of chromosomes proved especially challenging due to overlapping signals, probe failures, and nuclear organization [8]. The combination of these limitations (as well as study-specific deleterious effects of embryo biopsy) provides a convincing argument why randomized control trials (RCTs) conducted in the early 2000s did not demonstrate an improvement in live-birth rates using cleavage-stage biopsy and FISH, and thus led to more general and lasting concerns surrounding the clinical application of PGT-A [44,45].
The Dorsal Vagal Complex Forms a Sensory-Motor Lattice: The Circuitry of Gastrointestinal Reflexes
Published in Sue Ritter, Robert C. Ritter, Charles D. Barnes, Neuroanatomy and Physiology of Abdominal Vagal Afferents, 2020
T.L. Powley, H.-R. Berthoud, E.A. Fox, W. Laughton
The presupposition that any topography in the dmnX would be organized as a chain of transverse subnuclei arrayed along a longitudinal axis seems to have developed from at least three independent ideas and/or sets of observations. First, the dmnX has long been recognized as a condensation of cells in the more extensive general visceral efferent column that includes the rostral salivatory nuclei associated with the glossopharyngeal and facial nerves.4,14,39,58 In early attempts to map the dmnX, there seems to have been a widely held, if tacit, extrapolation from this internuclear organization to an internuclear plan: i.e., if the general visceral efferent column is organized into specialized compartments along the neuroaxis, then it would be reasonable to expect further compartmentalization along the same axis. The equally tenable (or equally tenuous, depending on point of view) extrapolation that the pervasive columnar organization of the medulla (e.g., general visceral motor, special somatic motor, etc.) might be replicated at the intranuclear level was apparently overlooked.
Preimplantation Genetic Testing for Aneuploidies: Where We Are and Where We're Going
Published in Darren K. Griffin, Gary L. Harton, Preimplantation Genetic Testing, 2020
Andrea Victor, Cagri Ogur, Alan Thornhill, Darren K. Griffin
FISH is still occasionally used for chromosomal screening of human embryos in certain clinics, but it has largely been replaced by genome-wide molecular techniques. Though it continues to be used in instances of inherited structural rearrangements where breakpoints cannot be adequately diagnosed using PCR-based methods (see PGT-SR in Chapter 4), it is mostly relegated to research practices in IVF and PGT in the investigation of nuclear organization and mosaicism [54].
Ultrastructural effects of nerve growth factor and betamethasone on nerve regeneration after experimental nerve injury
Published in Ultrastructural Pathology, 2020
Leman Sencar, Mustafa Güven, Dilek Şaker, Tuğçe Sapmaz, Abdullah Tuli, Sait Polat
Although some of the myelinated nerve fibers revealed slight myelin sheath alterations, mild vacuolization of Schwann cell cytoplasm, and a few number of empty vacuol-like spaces between axon and myelin sheath, most of the nerve fibers showed normal axonal structure and myelin sheath Lamellar arrangement. The nerve fibers generally appeared quite mature in size and shape with a thick myelin sheath. Furthermore, the Schwann cells exhibited normal nuclear organization and cytoplasmic structures in most areas. Also, a few number of the macrophages were seen among the nerve fibers with lipid droplets and membranous whorl-like structures in its cytoplasm. Moreover, the unmyelinated nerve fibers also showed normal ultrastructure in general (Figure 5a and Figure 5b)
Dioxin and endometriosis: a new possible relation based on epigenetic theory
Published in Gynecological Endocrinology, 2020
Pierluigi Giampaolino, Luigi Della Corte, Virginia Foreste, Fabio Barra, Simone Ferrero, Giuseppe Bifulco
Besides the well-known dioxin’s pathway of action, several papers are focusing on the role of epigenetic mechanisms, according to which xenobiotics are able of altering the biology of organs, tissues and cells [50,51]. Essentially, epigenetic mechanisms represent a way through which the genome responds to the environment, and the effect can lead to permanent changes in gene expression until affecting the phenotypes or cause disease. Nonetheless, the effects depend on a complex interaction between the individual genetic profile and epigenetic modulations [52,53]. The epigenetics effects are reversible and don’t involve alterations in the DNA sequence; the most common mechanisms are DNA methylation, histone modifications and ncRNAs that can affect transcript stability, DNA folding, nucleosome positioning, chromatin compaction, and nuclear organization with the final results of determining if a gene can be expressed or silenced [54–57]. Different mechanisms of AhR-dependent histone modification, DNA methylation, and ncRNAs regulation mechanisms have been described for dioxin. These new acknowledge seem to match with the new theory of the epigenetic pathogenesis of endometriosis. As Konickx et al. [21] reported in a recent article, the development of endometriosis lesions are linked to a series of additional transmissible genetic and epigenetic incidents that occurs in a cell, which may vary from endometrial to stem cells. The most common epigenetic change studies in endometriosis include DNA methylation, histone modification as well as RNA transcriptional changes.
Research progress on therapeutic targeting of quiescent cancer cells
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2019
Jinhua Zhang, Jing Si, Lu Gan, Cuixia Di, Yi Xie, Chao Sun, Hongyan Li, Menghuan Guo, Hong Zhang
The majority of cells from both unicellular to multicellular organisms spend part of their lifetime in quiescence, a temporary nonproliferating state [17]. As a single-cell eukaryote, yeast presents an excellent model organism to investigate cell division and quiescence [18,19]. The advantage of studying quiescence in free-living, unicellular organisms is the lack of intervention or genetic manipulation required to track transition in or out of the quiescent state [20]. S-adenosylmethionine synthetase (Sam1), a family of SHK gene products, is implicated in cell growth and proliferation as well as maintenance and termination of the G0 phase in fission yeast [19]. Meanwhile, ssd1 and the cell wall integrity pathway promote entry, maintenance, and recovery from the quiescent state in budding yeast [20]. To date, studies on Saccharomyces cerevisiae are broadly responsible for demonstrating the functional importance of nuclear organization. Previous research has shown that following carbon source exhaustion, the silencing factor Sir3 drives the telomeres of G0 cells to form a discrete, large cluster (hyper-cluster) at the center of the nucleus, resulting in spatial reorganization of the genome that favors long-term survival during quiescence. Notably, ROS produced by mitochondrial activity commit cells to form a telomere hypercluster upon starvation and sustain longevity of G0 cells [21].