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2 results

  • 9 - Molecular Signaling Pathways that Regulate Diapause

  • David L. Denlinger, Ohio State University
  • Book:
    Insect Diapause
    Published online:
    13 January 2022
    Print publication:
    03 February 2022, pp 240-292

  • Summary

    Hormones and downstream components of molecular signaling pathways that dictate entry and exit from diapause vary depending on the stage of diapause. Diapause hormone, a neuropeptide, directs entry into embryonic diapause in the silk moth, but embryonic diapauses in other species appear to be regulated by ecdysteroids or juvenile hormones. Larval and pupal diapauses are commonly initiated by a shutdown in the brain-prothoracic gland axis, reflected in failure of the prothoracic gland to produce ecdysone. Adult diapauses commonly are prompted by a failure of the corpora allata to produce the juvenile hormone needed for reproduction. Insulin signaling is central to diapause, and transcription factors such as FoxO provide a pathway to explain how a single hormone response can lead to the multiple downstream effects elicited by the diapause program. Organ cross talk, epigenetics, and small noncoding RNAs have emerged more recently as important new dimensions in the regulatory scheme of diapause.

  • 9 - Basic science: eggs and ovaries

  • from SECTION 2 - BASIC SCIENCE OF REPRODUCTIVE AGEING
  • Edited by Susan Bewley, William Ledger, University of New South Wales, Sydney, Dimitrios Nikolaou
  • Book:
    Reproductive Ageing
    Published online:
    05 February 2014
    Print publication:
    01 June 2009, pp 89-94

  • Summary

    This chapter presents a discussion between experts on eggs and ovaries. There is no genetic condition in humans which seems to be associated with a long-time rescue of primordial follicles. Sixty seems to be pretty close to the limit, maybe very exceptionally beyond that. Eggs or ovarian tissue can be frozen. The central role that signalling pathway plays in cell growth throughout the body is indisputable, which actually limits what we might be able achieve in an oocyte. But there are molecules that suppress the destruction of FOXO. An aspect is some fascinating data in mice suggest that nutrition has a major impact on the rate at which oocytes are lost from the ovary. Certainly, reproductive lifespan and functional lifespan of the ovary can be prolonged by calorie restriction. Real clock genes operate in oocytes that intrinsically regulate the rate at which the follicles start to grow and become atretic.