Dative modification, with the base moiety being the preferred target. However
Dative modification, with the base moiety being the preferred target. However, in most cases, damaged DNA can be efficiently repaired by several PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/25957400 systems according to the double stranded nature of DNA. Since unrepaired bases are mutagenic, cells carrying them must also be eliminated. The physiological relevance of antioxidative/redox systems in male reproductive tract has been overviewed recently [3] and, hence, are only briefly mentioned here. The emphasis of this review is on systems in female reproductive organs under physiological and pathological conditions and viewpoint is extended to fertilization and early embryonal development.III, catalyzes the formation of NO from arginine and oxygen using NADPH as an electron donor. Among NO derived from the three isoforms of NOS, NO from nNOS (NOS I) appears to function as a neurotransmitter. NO generated from endothelial NOS (NOS III) is involved in vascular relaxation. NOS III expression is increased by luteinizing hormone (LH) surge or human chorionic gonadotropin (hCG). NOS III may also be involved in oocyte maturation and the ovulatory process as described below. The expression of inducible NOS (NOS II) is induced by many stimuli, including inflammatory cytokines. Since a certain fraction of NO is converted to harmful RNOS, such as peroxynitrite by reaction with ROS, nitrosative stress occurs simultaneously with ROS generation. NOS II is also commonly a matter of concern in reproductive organs under pathological conditions because it produces large amounts of NO in response to inflammatory and other stimuli. Malondialdehyde and 4-hydroxy-2-nonenal C.I. 75535 chemical information levels are increased under conditions of oxidative stress and are still toxic because they carry aldehyde group. Carbonyl compounds are produced under hyperglycemic conditions, in addition to oxidative and nitrosative stress, and increase during the aging process. Amino acid residues in proteins are also subject to oxidative modification and are converted into carbonyl containing compounds. Since carbonyl compounds are also reactive toward thiols and amino groups and cause carbonyl stress [7], detoxification by reduction constitutes another pivotal system.Origin of oxidative, nitrosative, and carbonyl stressROS are generated via various reactions in the body. Some ROS are produced by non-enzymatic reactions, for example via the Fenton reaction in the presence of transient metal ions [1]. Biological reactions, such as electron transfer and oxygenase reactions that utilize oxygen molecules as the substrate, also generate large amounts of ROS. Since the mitochondrial respiratory chain is the main oxygenconsuming system in cells, the majority of ROS are produced from this system under physiological conditions. The generation of ROS becomes excessive under conditions of elevated metabolism and pathological conditions and is matter of special concern. The following are wellknown enzymatic systems that generate ROS. Xanthine dehydrogenase, an enzyme involved in purine metabolism, is converted to xanthine oxidase that generates superoxide under ischemic conditions in cardiovascular systems [4]. Cyclooxygenase, which catalyzes the initial oxidation step in the conversion from arachidonate to prostanoids and is induced under inflammatory conditions, also generates ROS [5]. The generation of ROS by the P450 system is important during the metabolic process of steroid hormone synthesis from cholesterol in endocrine organs, such as the ovary and testis. Pro.