China
Africa
Explore chapters and articles related to this topic
Evidence for a Thymus-Pineal Axis
Published in Nate F. Cardarelli, The Thymus in Health and Senescence, 2019
The gonadotropic activity of JH affects the oocytes. These have three major growth phases: previtellogenesis, vitellogenesis, and chorionation. Vitellogenesis is inhibited by a low molecular weight polypeptide antigonadotropic hormone AG.219–221 JH directs transcription for vitellogenin, the predominant yolk protein precursor made in the fat body.220
Sexual dimorphism in ultradian and 24h rhythms in plasma levels of growth hormone in Indian walking catfish, Clarias batrachus
Published in Chronobiology International, 2021
Raj Naresh Gopal, Dhanananajay Kumar, Vinay Kumar Singh, Atanu Kumar Pati, Bechan Lal
In fish, GH has been further reported to influence gametogenesis (Kajimura et al. 2004), gonadal steroidogenesis (Singh et al. 1988), vitellogenesis (Björnsson et al. 1994; Mosconi et al. 2002), and oocyte maturation (Sarang and Lal 2005). A previous report (Peng and Peter 1997) revealed that GH secretion is controlled by several metabolic and reproductive hormones. These metabolites, sex steroids, thyroid hormones, and neuroendocrine secretions interact and coordinate together to regulate GH secretion and maintain its rhythmicity (Peng and Peter 1997). In catfish, in-vivo injection of sGnRH, testosterone, and morphine caused a significant increase in plasma GH secretion. Whereas, 5-hydroxy tryptophan resulted in lowered GH levels in a dose-dependent manner (Lal and Singh 2005), indicating the role of several internal metabolic factors in regulating GH plasma production. Therefore, based on the published literature, we infer that such apparent 24 h variation in plasma GH in catfish seems to have physiological roles. For instance, GH may regulate gonadal and somatic growth and may affect reproductive processes in catfish. In female catfish, GH shows different effects on somatic growth and ovarian development. The differential effect of GH was observed to depend on the season and on the time during the 24 h of its administration (Singh and Lal 2008). Similarly, in male catfish, GH caused enhanced testicular steroidogenic and spermatogenic activities. This increase further shows dependence on photoperiod and water temperature (Gopal et al. 2014).
Impact of paternal transmission of gamma radiation on reproduction, oogenesis, and spermatogenesis of the housefly, Musca domestica L. (Diptera: Muscidae)
Published in International Journal of Radiation Biology, 2021
Regarding the radiation impact on the ovarian development, results obtained exhibit signs of degenerative process in the vitellogenic region, weakness/distortion of the ovarian sheath and vacuolation. Appearance of degenerated nurse cells, damage and lysis of oocytes, shrinkage of the nucleus, and disappearance of nucleus with condensed chromatin was also noticed. These changes are considered a deviation from the normal developmental pattern and indicate the impact of radiation on the vitellogenin synthesis process. Vitellogenesis inhibition is considered the main reason that induces such abnormal alterations in the development of female reproductive organs (Nair et al. 1967; Degrugillier and Leopold 1973; Shoman 1994). Additionally, radiation interferes with females’ reproductive cell division causing atrophy of the ovaries (Walder and Calkins 1992).
Nanoformulations and their mode of action in insects: a review of biological interactions
Published in Drug and Chemical Toxicology, 2021
Kiran Shahzad, Farkhanda Manzoor
NPs possessing a negative charge can be distributed through the body and may persist in ovaries in treated female larvae even after metamorphosis (Phanse et al.2015). Exposure to NMs in feed reduced female fertility by disrupting oogenesis and causing defects in the ovary which negatively impacts egg laying capabilities (Chen et al.2015, Raj et al.2017a, Wu and Uskoković 2017) while AgNPs were observed to disturb pupation and emergence as well the ratio of male/female in Chironomus riparius adults (Nair et al.2011). Likewise, fecundity was reduced while larval period and pupation were prolonged in C. maculatus after treatment with Bt-ZnO NPs (Malaikozhundan et al.2017). In contrast, Blattella germanica nymphs exposed to aerosolized AuNPs reached adulthood earlier, but the viability of ootheca was decreased which the authors theorized could be due to stress from ingesting AuNPs. The stress could direct energy away from juvenile hormone synthesis thereby downgrading vitellogenesis. While the nymphs did not accumulate a significant amount of gold, the gold content was found to be 12.7 ± 9.4 μg/g within adults (Small et al.2016). In male Agrius convolvuli, titanium dioxide NPs (TiO2-NPs) or ZnO-NPs lowered sperm bundles and decreased the weight of testis while becoming internalized in the vacuoles via phagocytosis (Pompa et al.2011, Kubo-Irie et al.2015). They may also restrict development and decrease germline stem cells by increasing ROS activity in the testis (Ong et al.2016).