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The Biosphere
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Primitive single-celled organisms, particularly bacteria, undergo asexual reproduction, in which a cell simply splits to form two cells. Humans and most other multicell organisms undergo sexual reproduction, requiring that male sperm cells fertilize female egg cells to produce cells capable of dividing and producing new individuals.
Introduction to Anatomy and Physiology
Published in Reginald L. Campbell, Roland E. Langford, Terry L. McArthur, Fundamentals of Hazardous Materials Incidents, 2020
Reginald L. Campbell, Roland E. Langford, Terry L. McArthur
Male sex cells, called sperm, are formed in the male gonads, the testes. The process of sperm formation is called spermatogenesis. These cells begin their development from precursor cells, which are formed at the edges of the testes. These precursor cells contain 46 chromosomes. They divide by a process called mitosis or cell division whereby identical daughter cells result from a splitting of the parent cell. As the population of cells increases, the cells move to the center of the testes where they become mature sperm following the last two stages of meiosis and end with only 23 chromosomes. These sperm look like small tadpoles, having a rounded or arrow-shaped head and a long tail.
Perception, Planning, and Scoping, Problem Formulation, and Hazard Identification
Published in Ted W. Simon, Environmental Risk Assessment, 2019
In this paper, two groups of young men, one group exposed to 2,3,7,8-tetrachlorodibenzodioxin (TCDD) as boys and the other not exposed, were examined for reproductive parameters, including sperm concentration. It is important to note that the WHO manual provides the normal range of sperm concentration as 15,000,000–213,000,000 per ml. The group of 71 exposed individuals had a geometric mean (GM) value of 53,600,000 and the control group of 82 individuals had a geometric mean of 72,500,000. The geometric standard deviations (GSDs) were 2.46 and 2.29 respectively. Please note that both samples were in the normal range. Statistical analysis of semen concentrations is most often conducted in logarithmic space, which is why the GM and GSD values are provided.
Why human germline genome editing is incompatible with equality in an inclusive society
Published in The New Bioethics, 2021
Genome editing procedures through the deliberate modification of targeted DNA sequences in living cells are increasingly being considered in the treatment of a number of genetic disorders in already existing human beings (Cong et al. 2013). But genome editing could also be used in assisted reproduction to genetically modify sperm or egg cells, or their precursors, as well as very early embryos. This would generally result in all the cells of a future individual, including his or her reproductive cells, being genetically modified. Heritable germline changes could thus be developed in which there is an intentional modification of the genetic heritage of the person being brought into existence and all his or her possible descendants.
Mixture analysis of associations between exposure to low levels of multiple metals and semen quality and sperm DNA integrity
Published in Journal of Environmental Science and Health, Part A, 2022
Hueiwang Anna Jeng, Sinjini Sikdar, Yeou-Lih Huang, Chih-Hon Pan
The characteristics of the 93 participants are shown in Table 1. The participants had an average of 40 years old and had an average BMI of 25.2. About 52% of the participants had at least a high school degree; about 54% were smokers, and about 40% were drinkers, who drink alcohol more than 4 time a week. More than 97% of individuals have healthy sperm count greater than 20 × 106/mL. 18.8% of the subjects had asthenospermia, which percentage of motile sperm <40%. Urinary metals were detected in all samples. The summary statistics (median, 25th percentile, and 75th percentile) of the urinary metal levels of the subjects are shown in Table 2.