Egg-laying hormone

Egg-laying hormone (ELH), ISINQDLK AI TDMLLTEQIR ERQRYLADLR3 QRL LEKa, a 36-peptide amide from Aplysia California. ELH is synthesized by the bag cell neurons, and acts as a hormone facilitating expulsion of the egg string, and as a neurotransmitter on cells of the abdominal ganglion [A. Y. Chiu et al., Proc. Natl. Acad. Sci. USA 1979, 76, 6656 R. H. Scheller et al.. Cell 1983, 32, 7]. 

Interaction of vitamin D and its metaboUtes with sex hormones has been demonstrated, particularly ia birds ia which the egg-laying functions combine calcium needs and reproductive activity. The metaboUtes of vitamin D behave as hormones. As such, they play an active role ia the endocrine system, along with other hormones, to maintain the various body functions. Several biological influences of metaboUtes of vitamin D have been studied, including effects related to cancer (193—197), skin diseases (198—201), immunomodulatory effects (202,203), and Alzheimer s disease (204—206) (Fig. 9). 

To provide for these demands, intestinal calcium absorption is increased and medullary bone is resorbed Medullary bone is the storage system for calcium used by the bird during its reproductive phase of life It is woven bone having little structural capability and forms in response to a direct action by estradiol and testosterone on bone These two sex hormones are released as the female bird approaches maturity accounting for the initiation of medullary bone formation Egglaying birds have high levels of the renal 25-OH-D3-l-hydroxylase activity as compared to males or non-egg-laying mature females In-... 

Frogs are primed and injected with hormone to induce egg laying as described previously (Kay and Peng, 1991). Eggs are dejellied in 2% (w/v) cysteine, pH 7.8, and those that are clearly necrotic (loss of pigmentation and marbling ) are removed with a pasteur pipet. 

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