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Genetics and exercise: an introduction
Published in Adam P. Sharples, James P. Morton, Henning Wackerhage, Molecular Exercise Physiology, 2022
Claude Bouchard, Henning Wackerhage
It is important to understand the distinction between germ cells and somatic cells. Male and female germ cells, sperm and oocyte, respectively, are termed gametes. A mature germ cell has only 22 autosomes plus one sex chromosome (i.e. 23 chromosomes in total) in its nucleus instead of the full complement of 46 chromosomes seen in somatic cells (i.e. body cells or non-germ cells). A germ cell containing 23 chromosomes is said to be “haploid”, whereas normal somatic cells contain a “diploid” set of chromosomes. When a haploid sperm and a haploid oocyte fuse, they form a diploid, fertilized oocyte, termed zygote, which is the first cell of the new organism. It has 2 × 22 autosomes plus either two X chromosomes (XX, a female) or an X and a Y (XY, a male) chromosome.
Chromosome Pairing and Fertility in Polyploids
Published in Christopher B. Gillies, Fertility and Chromosome Pairing: Recent Studies in Plants and Animals, 2020
Polyploidy is the presence in cells or tissues of an organism of three or more copies of the basic set of chromosomes (the haploid genome). Occasional polyploid cells occur in many types of tissues in both plants and animals. Many important crop plants are polyploid, and polyploidy has undoubtedly been important in the evolution of many plants and probably some animals. More than one third of angiosperms are polyploid1 and 70 to 80% may have polyploidy in their ancestry. In contrast, polyploidy in sexually reproducing animals is rare. The usual explanation advanced is that polyploidy would disturb the sex chromosome balance, leading to intersexes,2,3 but this is not always the case. Nevertheless, approximately 10% of human zygotes are polyploid, although most spontaneously abort and the rare liveborns do not survive long.4,5 Sexually reproducing polyploid species do occur naturally among the amphibia6,8 and fish,9,10 but polyploidy in animals is often associated with parthenogenic reproduction, e.g., amphibia, fish, reptiles,11 nematodes,12,13 earthworms,14 and insects.15
Cell structure, function and adaptation
Published in C. Simon Herrington, Muir's Textbook of Pathology, 2020
Mitosis results in daughter cells being produced, each containing the full complement of DNA (46 chromosomes, diploid) (Figure 2.4), whereas in meiosis the DNA content of a cell is halved, and cells become haploid (Figure 2.5). Diploidy is achieved when two haploid cells combine, usually an egg (ovum) and a sperm. Although disturbance in the cell cycle is widely recognized to be important in the pathogenesis of cancer, an understanding of how cell proliferation is controlled is also needed to fully appreciate processes such as wound healing (see Chapter 3) and atherosclerosis (see Chapter 7). Classically, the cycle is divided into four states: gap 1 (G1), synthesis (S), gap 2 (G2), and mitosis (M), with an additional fifth state, gap 0 (G0), which is a non-cycling, resting state (Figure 2.6).
A comprehensive clinical guide for Pneumocystis jirovecii pneumonia: a missing therapeutic target in HIV-uninfected patients
Published in Expert Review of Respiratory Medicine, 2022
Ahmad R. Alsayed, Abdullah Al-Dulaimi, Mohammad Alkhatib, Mohammed Al Maqbali, Mohammad A. A Al-Najjar, Mamoon M.D. Al-Rshaidat
Light microscopic and ultrastructural analyses of materials derived from animals and humans have helped to understand the life cycle of Pneumocystis. The trophic form and the cyst are the two distinct life cycle forms for Pneumocystis organisms. A plasma membrane, rather than a rigid cell wall, surrounds the trophic form is asymmetrical in shape. The trophic forms have a single haploid nucleus and no rigid cell wall structure [34]. The cyst is larger than the trophic form, with up to eight intracystic bodies. Cyst nuclei are diploid, tetraploid, or octaploid. Excystment is the rupture of a mature cyst containing eight intracystic bodies of the nucleus, releasing them as new trophic forms. The rigid Pneumocystis cyst wall is composed of β-glucan, a complex branching polysaccharide containing glycoprotein A/major surface glycoprotein, chitins, and additional surface-expressed proteins. The cyst wall provides rigidity, support, and defense against the host’s environment. According to research, interactions between cyst walls and lung cells can also stimulate the host’s innate immune system [35].
Neuropsychological and Social Characteristics of a 7 Year Old Child with Hypomelanosis of Ito Followed for 11 Years
Published in Developmental Neuropsychology, 2022
George P. Prigatano, Alexandra Novak, Vinodh Narayanan
This child was born prematurely at 34 weeks gestation, weighing 4 lb 11 oz. Apart from requiring phototherapy for hyperbilirubinemia, his neonatal history was unremarkable. He had a mild delay in his development. He walked at 17 months and started using words at 2.5–3 years. Early evaluation by genetics led to the diagnosis of Hypomelanosis of Ito (based on regions of skin hypopigmentation). MRI of the brain, cervical spine, and thoracic spine were normal; lumbar spine MRI showed conus medullaris at L2-L3 level. When he was four years of age, he underwent a skin biopsy for a mosaic chromosome study of his fibroblasts. Of 100 cells counted, 28 had an extra entire haploid set of chromosomes (triploidy) while the remaining 72 cells were normal: 69,XXY [28]/46,XY [72]. The report called attention to four prior reports in the literature of cases of HI associated with diploid/triploid mosaicism.
Strictly selected Mono- and non-pronuclear blastocysts could result in appreciable clinical outcomes in IVF cycles
Published in Human Fertility, 2022
Lei Fu, Dapeng Chu, Wenhui Zhou, Yuan Li
Fertilization abnormality is a common problem in assisted reproductive technology. According to our data, nearly half of the cycles contained 1PN zygotes. The ratio was even higher for 0PN zygotes (Table 1). The appearance of non-2PN zygotes upon fertilization check can be related to asynchronous PN formation, premature breakdown or formation delay of PN, failure of sperm head decondensation and oocyte activation failure (Basile et al., 2013; Feenan & Herbert 2006; Flaherty et al., 1995; Munné et al., 1993; Payne et al., 1997; Rosenbusch, 2014). Some researchers do not advocate the use of non-2PN-derived embryos (Noyes et al., 2008; Reichman et al., 2010; Yan et al., 2010). However, it is a waste to discard these embryos directly because some of them were normal diploid (Bradley et al., 2017; Destouni et al., 2018; Lim & Lee, 2019; Staessen et al., 1993; Staessen & van Steirteghem, 1997; Yan et al., 2010; Yao et al., 2016), and haploidy also exists in 2PN-derived embryos (Noyes et al., 2008; Yao et al., 2016). Although the case of live birth is not unique (Bradley et al., 2017; Dasig et al., 2004; Hondo et al., 2019; Itoi et al., 2015; Li et al., 2015; 2020; Si et al., 2019), the application of non-2PN-derived embryos was not widespread.