- Title
- Physiological and pathological aspects of sperm metabolism
- Creator
- Gibb, Zamira; Aitken, Robert John
- Relation
- The Sperm Cell: Production, Maturation, Fertilization, Regeneration p. 109-125
- Publisher Link
- http://dx.doi.org/10.1017/9781316411124.009
- Publisher
- Cambridge University Press
- Resource Type
- book chapter
- Date
- 2017
- Description
- Spermatozoa are highly specialized cells, playing the vital roles of paternal DNA delivery and activation of the oocyte following fertilization. The site of sperm deposition (in the vagina or uterus in the mammal) is physically removed from the site of fertilization (the oviduct), and while a proportion of sperm transport is facilitated by uterine contractions (in mammals), the spermatozoa must in themselves be sufficiently motile to traverse the uterotubal junction and ultimately locate a single cell, the oocyte. In addition, during their sojourn within the female tract, spermatozoa must undergo a maturation process called capacitation in order to attain the competence to recognize the egg and then engage in a complex cascade of cell–cell interactions in order to achieve union of the gametes at fertilization. This process involves extensive remodelling of the sperm plasma membrane as well as the induction of hyperactivated motility and, as such, is a highly energy-dependent process. The process of spermatogenesis requires extensive remodelling of a conventional spherical cell to become one of the most highly specialized and morphologically differentiated cells in the body. During this transformation, the DNA in the sperm nucleus reaches the physical limits of compaction to achieve a quasicrystalline state. This extreme compaction requires the removal or resorption of most of the cytoplasm, at the same time removing the majority of the organelles (such as the endoplasmic reticulum, ribosomes and Golgi apparatus) that are intimately involved in the regulation of metabolism in somatic cells. The result of this extensive remodelling is that spermatozoa are left translationally and transcriptionally silent, as well as relatively depleted of intracellular enzymes and energy reserves such as fat droplets, yolk granules and glycogen. For this reason, spermatozoa are heavily dependent on their immediate extracellular environment for the energy substrates that drive metabolism, as well as a variety of specialized enzymatic activities that would normally be conducted intracellularly. For example, in somatic cells, the array of enzymes and low-molecular-mass scavengers involved in mediating protection against oxidative stress is housed intracellularly, largely within the cytoplasmic space. Spermatozoa, on the other hand, largely depend upon the epididymal and seminal plasmas to provide the richest and most diverse combination of antioxidants in the body, including several that are unique to the male reproductive tract. In much the same way that economies trade using a currency rather than a barter system, biological systems have all evolved their own unique ‘currencies’ for the exchange of energy.The most important of these currencies is adenosine 5’-triphosphate (ATP), which provides the metabolic energy to drive activities in all living cells.
- Description
- 2nd ed.
- Subject
- sperm metabolism; sperm; spermatozoa; DNA; spermatogenesis
- Identifier
- http://hdl.handle.net/1959.13/1387803
- Identifier
- uon:32666
- Identifier
- ISBN:9781316411124
- Language
- eng
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