Disruption of Nongenomic Steroid Actions on Gametes and Serotonergic Pathways Controlling Reproductive Neuroendocrine Function by Environmental Chemicals
Rajesh K. Naz in Endocrine Disruptors, 2004
Moreover, inhibitors of transcription did not prevent 17,20β-P-induced final OM in teleosts, which supports the concept that the action of the MIS is nongenomic [77]. The finding that increases in cyclic AMP levels by pharmacological agents block MIS stimulation of OM in vitro also suggests that the action of the MIS is nongenomic and instead involves a second messenger signal transduction pathway [77]. A decrease in cyclic AMP is required for MIS induction of final oocyte maturation in rainbow trout and spotted seatrout, which is mediated by activation of a pertussis toxin-sensitive inhibitory G-protein in the signal transduction pathway across the oocyte plasma membrane to the cytoplasm [77, 83]. A cytoplasmic factor, named maturation-promoting factor, composed of cdc 2 kinase and cyclin B, is formed and is the intracellular mediator of OM [77].
Regulation of Cell Functions
Enrique Pimentel in Handbook of Growth Factors, 2017
Cyclin is an acidic nuclear protein of 36 kDa that is involved in the control of DNA synthesis and cell proliferation. It was first detected in fertilized sea urchin eggs and clam oocytes and was found later also to be present in higher eukaryotes.250,251 Cyclin is identical with the protein called proliferating cell nuclear antigen (PCNA).252-254 In embryonic Xenopus laevis cells, cyclin expression occurs in the period of the cycle dedicated to DNA synthesis, and it has been suggested that cyclin may be a useful marker of cells engaged in S phase and could be an alternative to thymidine labeling.255 However, in HeLa cells, cyclin was found to be present in constant amounts during the cycle and its synthesis is not tightly linked to DNA synthesis.256 Notwithstanding, the amount of cyclin that binds to chromatin increases in HeLa cells to a maximum during the peak of the S phase of the cycle. Studies on frog eggs showed that cyclin synthesis can induce mitosis and allows the progression from mitosis to the next interphase.257 The activation of a specific protein, the maturation promoting factor (MPF), induces cells to enter mitosis and meiosis, and cyclin is directly required for the generation of MPF.258 Injection of a human antibody against cyclin into unfertilized Xenopus eggs results in inhibition of DNA replication.259 It may be concluded that cyclin plays a pivotal role in the control of mitosis. In addition, cyclin may be involved in DNA repair, as shown by UV irradiation of quiescent cultured human fibroblasts.260 The cellular action of cyclin is exerted through its association with the protein kinase cdc2 in the form of the MPF complex, which is required for G2 to M transition during the cell cycle.
Boron, Manganese, Molybdenum, Nickel, Silicon and Vanadium
Judy A. Driskell, Ira Wolinsky in Sports Nutrition, 2005
Two hypotheses have been advanced for the biochemical function of boron in higher animals. These hypotheses accommodate a large and varied response to boron deprivation and the known biochemistry of boron. One hypothesis is that boron has a role in cell membrane function or stability such that it influences the cell response to hormones, transmembrane signaling, or transmembrane movement of regulatory cations or anions.11 The hypothesis is supported by the recent identification of a bacterial quorum-sensing signal molecule that is a furanosyl borate diester.8 Quorum sensing is the cell-to-cell communication in bacteria that is accomplished through the exchange of extracellular signaling molecules called autoinducers. The boron autoinducer (AI-2) has been proposed to be a universal signal for inter-species communication among bacteria. AI-2 is synthesized from adenosylmethionine, which supplies the 2′-3′-cis-diol of a ribose moiety that binds boron well. Another group of biomolecules that contain ribose moieties, the diadenosine phosphates, have been characterized as novel boron binders.13 Diadenosine phosphates function as signal nucleotides. Another study supporting the membrane role for boron was that determining the effect of boron on frog egg development. Culturing stage 1 and stage 2 oocytes from boron-adequate frogs in medium containing progesterone resulted in successful maturation to stage 5 or 6 oocytes. In contrast, oocytes from boron-deprived frogs did not respond to progesterone and did not mature in vitro. Further study of the maturation process14 revealed that the boron-deprived oocytes were capable of producing progesterone and the maturation-promoting factor (involved in binding progesterone to its receptor on the plasma membrane) and responding to this factor. It was hypothesized that the impaired maturation process was caused by progesterone’s not being bound efficiently to the membrane receptor because of changes in its structural homology.
Clinical exome sequencing identifies novel compound heterozygous mutations of the WEE2 gene in primary infertile women with fertilization failure
Published in Gynecological Endocrinology, 2021
Ancong Wang, Shan Huang, Min Liu, Baosong Wang, Fengxia Wu, Dongyi Zhu, Xiangyu Zhao
The mature oocyte is arrested at the second meiotic metaphase (MII) and must undergo MII exit in order to be fertilized. Fertilization results in a series of rapid and transient increases in intracellular calcium concentration. These Ca2+ signals drive cell cycle recovery by inactivating the maturation promoting factor (MPF), which is regulated by the inhibitory phosphorylation of cdc2. Cdc2 is a kinase family catalyzed by WEE2 protein [7]. It is found that WEE2 protein encoded by WEE2 gene belongs to WEE kinase protein family, which comes from maternal origin and preserved among different species. Studies on some oocytes of mammals have shown that WEE2 is involved in GV phase quiescence, MII, and prokaryote formation [8–11]. Recently, studies reported that primary infertility in several women with fertilization failure was caused by mutations of the WEE2 gene [12–18].
Human oocyte cryopreservation: revised evidence for practice
Published in Human Fertility, 2023
Virginia N. Bolton, Catherine Hayden, Michele Robinson, Dima Abdo, Angela Pericleous-Smith
It has been suggested that warmed oocytes should be incubated in culture medium to allow repolymerisation of the meiotic spindle (ACE and BFS, Cutting et al., 2009) before insemination using ICSI. With respect to the timing of ICSI following warming, it has been suggested that ICSI should be carried out within 1 hour of warming to avoid any potentially deleterious effects of in vitro aging (Iussig et al., 2019). Thawed slow frozen oocytes allowed to age in vitro show reduced levels of maturation-promoting factor (MPF) after 1 hour in culture (Bromfield et al., 2009). Since MPF is critical in the preservation of spindle integrity, it has been suggested that as for slow frozen oocytes, the duration of culture of vitrified oocytes between warming and ICSI should be limited to 1h to prevent potential loss in the organisation of the meiotic spindle (Iussig et al., 2019).
Genetic analysis of embryo in a human case of spontaneous oocyte activation: a case report
Published in Gynecological Endocrinology, 2020
Yuanyuan Ye, Na Li, Xiaohong Yan, Rongfeng Wu, Weidong Zhou, Ling Cheng, Youzhu Li
Oocyte maturation plays an important role for the oocyte to attain competence for successful fertilization and subsequent embryonic development. In this case, the unexpected occurrence of the maternal pronucleus before ICSI indicated a failure in meiotic arrest at metaphase II. Oocytes from nearly all mammals arrest at metaphase II before fertilization. The kind of arrest is due to an activity that has been termed cytostatic factor (CSF), which maintains arrest through preventing loss in maturation promoting factor (MPF) [9]. MPF phosphorylation by inhibitory proteins keeps an inactive pre-MPF state [10]. Besides, in mammalian oocytes, meiotic arrest is regulated by high intracellular cAMP levels, that is, decrease in cAMP levels will lead to meiotic resumption [1,2].
Related Knowledge Centers
- G2 Phase
- Phosphatase
- Threonine
- Oocyte
- Meiosis
- Mitosis
- Cell Cycle
- Cyclin-Dependent Kinase 1
- Adenosine Triphosphate
- Serine