http://science.sciencemag.org/content/sci/171/3973/757.full.pdf

Allelochemics: Chemical Interactions between Species

Tropical blackwater rivers, animals, and mast fruiting by the Dipterocarpaceae

Publisher Summary
This chapter briefly discusses hormonal control of diapause. Diapause is an arrest in development accompanied by a major shutdown in metabolic activity. The evolution of diapause is arguably one of the most critical events bolstering the success of insects. The capacity to periodically shut down development has enabled insects and their arthropod relatives to invade environments that are seasonally hostile. Indeed, very few environments permit continuous insect development. Even in the tropics, where temperatures throughout the year may be compatible with ectotherm development, seasonal patterns of rainfall drive cycles of plant growth that favor insects with the ability to periodically become dormant. Unlike a simple quiescence that is an immediate response to an unfavorable environmental condition, diapause is a genetically programmed response that occurs at a specific stage for each species. Sometimes, the insect will enter diapause at this particular stage in each generation regardless of the environmental conditions it receives—a developmental program referred to as obligatory diapause. Much more frequently, the decision to enter diapause is determined by environmental factors, usually day length, received by that individual or its mother at an earlier developmental stage. This is referred to as facultative diapause.

10 – Hormonal Control of Diapause

7 – The Role of Ecdysteroids in Reproduction

Experimental circular dichroic (CD) spectra of three proteins have been combined with estimates of the content of peptide-chain structural modes obtained from x-ray diffraction studies of the same proteins. Solution of the simultaneous equations at a series of wavelengths permits the construction of a CD spectrum for each of three structural modes: α-helix, β-structure, and the so-called “random”. The CD spectra thus obtained are compared with those obtained from polypeptide models. The α-helical spectra from the two approaches are nearly congruent, the β-structure spectra are in fair agreement, and the third forms agree qualitatively, but are substantially different quantitatively. Comparisons are made between the present approach and earlier approaches to interpreting protein CD spectra. Certain advantages of the present approach are indicated.

https://www.pnas.org/content/pnas/68/5/969.full.pdf

A New Basis for Interpreting the Circular Dichroic Spectra of Proteins

1. Ecdysone is in a highly dynamic state after its injection or its secretion by the ring-gland of Sarcophaga peregrina. Hormonal activity is rapidly destroyed by an inactivating mechanism which is present in the tissues but not in the blood.2. Inactivation is blocked by low temperatures or anaerobic conditions—a finding that implicates chemical and, more particularly, oxidative reactions. The mechanism in question could be demonstrated in larval fragments but not in crude or fractionated homogenates.3. When injected into mature larvae, 1 µg of α-ecdysone loses 50% of its activity in 1 hour and 98% in 8 hours. Lower doses show even briefer "half-lives."4. The rapid inactivation of ecdysone can account for its low titer in both the blood and tissues. Thus at the "critical period" for puparium formation, the entire larva contains only 2.5 nanograms, corresponding to only 7% of a Sarcophaga unit.5. The evidence points to the accumulation, not of the hormone itself, but the covert biochemical and biophysical ...

Dynamics of ecdysone secretion and action in the fleshfly sarcophaga peregrina

https://www.pnas.org/content/pnas/58/3/981.full.pdf

ECDYSONE AND ECDYSONE ANALOGUES: THEIR ASSAY ON THE FLESHFLY Sarcophaga peregrina.

1. The phytoecdysone, cyasterone, is twice as active as authentic α-ecdysone when injected into mature larvae of the fleshfly, Sarcophaga peregrina. It is 25 times as active as α-ecdysone when injected into diapausing pupae of the silkworm, Samia cynthia.2. By the biological assay of hormone extracted from injected animals, it was possible to approximate the half-inactivation times of the endocrine activities provoked by the injection of α-ecdysone or cyasterone.3. In the fly larva the half-inactivation time was about 1 hour for α-ecdysone and about 3-4 hours for cyasterone. Therefore, cyasterone's resistance to inactivation can fully account for its 2-fold greater activity in the larval fly.4. In diapausing silkworm pupae the half-inactivation time was about 6 hours for α-ecdysone and 32 hours for cyasterone. Consequently, cyasterone's 5-fold greater stability can only partially account for its 25-fold greater activity in the pupal silkworm.5. The residual difference must be due to other presently unknow...

Tetsuya Ohtaki

Papers

Dynamics of ecdysone secretion and action in the fleshfly sarcophaga peregrina

ECDYSONE AND ECDYSONE ANALOGUES: THEIR ASSAY ON THE FLESHFLY Sarcophaga peregrina.

INACTIVATION OF α-ECDYSONE AND CYASTERONE BY LARVAE OF THE FLESHFLY, SARCOPHAGA PEREGRINA, AND PUPAE OF THE SILKWORM, SAMIA CYNTHIA