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Prenatal Diagnosis and Screening for Aneuploidy
Published in Vincenzo Berghella, Obstetric Evidence Based Guidelines, 2022
Sarah Harris, Angie Jelin, Neeta Vora
In 1942, Dr. Harry Klinefelter described males who had enlarged breasts, sparse facial and body hair, small testes, and azoospermia. By the late 1950s these findings were associated initially with an extra Barr body, and later the extra X chromosome was identified with the karyotype 47,XXY.
General Biological Aspects of Oncogenesis
Published in Pimentel Enrique, Oncogenes, 2020
The X sex chromatin, also called Barr body, may be observed in more than 30% of the interphase nuclei of most cells containing two or more X chromosomes and consequently, in mammals it is found only in somatic cells of the female. In general, the number of Barr bodies in a given cell is equal to the number of X chromosomes minus one, the latter corresponding to the actively transcribing X chromosome. The inactivation of X chromosomes to form Barr bodies is apparently associated with a process of hypermethylation of DNA sequences,17 which determines an almost complete transcriptional silence of the whole X chromosome. Barr bodies are difficult to visualize in neoplastic cells due to the aforementioned increase in the heterochromatin fraction and other morphological changes occurring in the nucleus, but there is evidence that their number and/or structure may be abnormal at least in some types of cancer cells whereas no changes are observed in benign tumors.18,20 However, no correlation exists between the incidence of Barr bodies in malignant tumors and different prognostic factors like the spread and histological grading of the tumor.21 The measurement of X-linked enzymatic activities in female teratocarcinoma cells, which are malignant cells containing two X chromosomes, give conflictive results as to whether only one or both X chromosomes are active in the tumor cells.22,23
Genetic counselling in Mendelian disorders
Published in Angus Clarke, Alex Murray, Julian Sampson, Harper's Practical Genetic Counselling, 2019
The terms ‘dominant’ and ‘recessive’ must be used with caution in X-linked disease, because a high degree of variability is seen in disease expression in the heterozygous female. The factors that lead to a heterozygous variant of an autosomal gene manifesting in the phenotype – that is, that make it dominant or recessive – may still apply to loci on the X chromosome but, in addition, there are also the effects of the random nature of X-chromosome inactivation (Mary Lyon's hypothesis). This process applies to a large majority of the loci on the X chromosome in the human female. One of the two X chromosomes is randomly inactivated in each cell in the early embryo and becomes visible cytogenetically as the ‘sex chromatin’ or ‘Barr body’ under the nuclear membrane. Because the clonal descendants of each cell retain the same inactivated X chromosome, it follows that a female heterozygous for an X-linked disorder or trait will be mosaic, with two populations of cells, one of which has the ‘normal’ and the other the ‘abnormal’ X chromosome functioning.
Review of Ilana Löwy, Imperfect Pregnancies: A History of Birth Defects & Prenatal Diagnosis
Published in The American Journal of Bioethics, 2019
Chapter 5 traces the history of the sex chromosome aneuploidies Turner and Klinefelter syndromes. Prior to the correlation of these syndromes with aneuploidy of the sex chromosomes, they were assumed to be conditions of sex inversion, with individuals with Klinefelter syndrome presumed to be biological women (due to Barr body presence) and individuals with Turner syndrome biological men (due to Barr body absence). Women receiving amniocentesis to diagnose Down, Edwards, or Patau syndromes in the 1960s were sometimes confronted with the diagnosis of a sex chromosome aneuploidy, diagnoses for which little data existed on the outcomes of children with these conditions. The remainder of the chapter discusses modern detection and understanding of these syndromes, including the differences between the current state of prenatal detection of the two conditions (i.e., Turner syndrome is often diagnosed via ultrasound; Klinefelter syndrome as an incidental finding in the evaluation of Down syndrome risk).
Self-Control Strength and Mindfulness in Physical Exercise Performance: Does a Short Mindfulness Induction Compensate for the Detrimental Ego Depletion Effect?
Published in Journal of Applied Sport Psychology, 2019
Eva Stocker, Chris Englert, Roland Seiler
The institutional ethics committee approved the study, and all participants provided written informed consent before participating. Participants had to attend the study twice (Week 1 and Week 2), whereby the two measurements were separated by exactly 7 days. As a dependent variable, we used an isometric plank exercise as physical exercise performance (e.g., Ede, Sullivan, & Feltz, 2017) because, based on previous research, we assumed that this exercise requires the inhibition of the impulse or desire to quit, as the task becomes exhausting and painful over time. This means that the participants have to override or inhibit their predominant tendency to interrupt this self-control task to remain in this plank position (Hofmann, Schmeichel, & Baddeley, 2012). In line with the current literature (Bray, Martin Ginis, Hicks, & Woodgate, 2008; Englert, 2016; Graham et al., 2014; Hagger et al., 2010), we assumed that temporary reductions in self-control strength (ego depletion) would result in poorer physical exercise performance compared to a control group with temporarily available self-control strength. For the physical exercise performance, participants were told to remain in a proper plank position—a task with which they were familiar from previous sport classes—for as long and as correctly as they could (e.g., Ede et al., 2017). Participants received instruction about the criterion applied for correct position. The examiners were trained to apply a strict cutoff criterion when the plank position was no longer being held properly. Stop criterion were as follows: The correct position was not held anymore, participants’ loin left the installed bar, body-fully-extended was abandoned, head left the wall. If the form was beginning to break, the examiner told the participant to end the exercise, and the time was stopped. Performance in the plank exercise was measured as the time (in seconds) that the participants successfully performed the plank. To this end, physical performance was videotaped, and a certified fitness expert—blinded to the experimental conditions—subsequently rated the plank positions and the time spent in the proper position. We preliminary tested the applicability of this novel physical exercise task (N = 10). The results of this pilot study showed that, on a descriptive level, there was a stronger decrease in plank performance from the first baseline trial (T1) to T2 in the depletion group (n = 5; T1: M = 125.05, SD = 36.83; T2: M = 101.63, SD = 21.31), compared to the nondepletion group (n = 5; T1: M = 121.35, SD = 47.16; T2: M = 106.01, SD = 43.40). Based on these descriptive findings and the application of similar physical exercise tasks in previous research (Dorris, Power, & Kenefick, 2012), we view this task as a valid measure of self-control. In the current study, we assessed performance in the plank exercise twice: at the beginning of the experiment as a baseline measurement (T1) and after the self-control manipulation (T2).