Ecdysteroids are present in the blood of wild passerine birds.

Ecdysteroids (arthropod molting hormones) play an important role in the development and sexual maturation of arthropods, and they have been shown to have anabolic and "energizing" effect in higher vertebrates. The aim of this study was to assess ecdysteroid diversity, levels according to bird species and months, as well as to observe the molting status of hard ticks (Acari: Ixodidae) infesting the birds. Therefore, blood samples and ticks were collected from 245 birds (244 songbirds and a quail). Mass spectrometric analyses showed that 15 ecdysteroids were regularly present in the blood samples. Molting hormones biologically most active in insects (including 20-hydroxyecdysone [20E], 2deoxy-20E, ajugasterone C and dacryhainansterone) reached different levels of concentration according to bird species and season. Similarly to ecdysteroids, the seasonal presence of affected, apolytic ticks peaked in July and August. In conclusion, this study demonstrates the presence of a broad range and high concentrations of ecdysteroids in the blood stream of wild-living passerine birds. These biologically active, anabolic compounds might possibly contribute to the known high metabolic rate of songbirds.

Hemolymph ecdysteroids during the last three molt cycles of the blue crab, Callinectes sapidus: quantitative and qualitative analyses and regulation.

The profiles of circulating ecdysteroids during the three molt cycles prior to adulthood were monitored from the juvenile blue crab, Callinectes sapidus. Ecdysteroid patterns are remarkably similar in terms of peak concentrations ranging between 210-330 ng/ml hemolymph. Analysis of hemolymph at late premolt stage revealed six different types of ecdysteroids with ponasterone A (PoA) and 20-OH ecdysone (20-OH E) as the major forms. This ecdysteroid profile was consistent in all three molt cycles. Bilateral eyestalk ablation (EA) is a procedure that removes inhibitory neurohormones including crustacean hyperglycemic hormone (CHH) and molt-inhibiting hormone (MIH) and often results in precocious molting in crustaceans. However, the inhibitory roles of these neuropeptides in vivo have not yet been tested in C. sapidus. We determined the regulatory roles of CHH and MIH in the circulating ecdysteroid from ablated animals through daily injection. A daily administration of purified native CHH and MIH at physiological concentration maintained intermolt levels of ecdysteroids in the EA animals. This suggests that Y organs (YO) require a brief exposure to CHH and MIH in order to maintain the low level of ecdysteroids. Compared to intact animals, the EA crabs did not exhibit the level of peak ecdysteroids, and the major ecdysteroid turned out to be 20-OH E, not PoA. These results further underscore the important actions of MIH and CHH in ecdysteroidogenesis, as they not only inhibit, but also control the composition of output of the YO activity.

Cytophysiological correlations between prothoracic gland activity and hemolymph ecdysteroid concentrations in Rhodnius prolixus during the fifth larval instar: further studies in normal and decapitated larvae.

Hemolymph ecdysteroid titers in fifth instar larvae of Rhodnius prolixus were determined by radioimmunoassay, and their prothoracic glands were excised and examined by electron microscopy. During the last larval instar, the titer of ecdysteroid increased between the head-critical period until Day 13, at which time the peak titer was 3100 pg 20-hydroxyecdysone equivalents/microliter. The activation of secretory cells at the time of the second period of prothoracicotropic hormone release was correlated with the development of major cellular organelles. The smooth endoplasmic reticulum first appeared at the head-critical period and then proliferated in close relation to the increase in ecdysteroid titer until Day 13, after which time it disappeared. Mitochondria expand and develop tubular cristae. They are closely associated with the smooth endoplasmic reticulum. When insects were decapitated, hemolymph ecdysteroid titer remained below 10 pg/microliter and the prothoracic gland cells failed to develop smooth endoplasmic reticulum. We conclude that in the prothoracic gland cells as well as other steroidogenic tissues the smooth endoplasmic reticulum in association with mitochondria is involved in ecdysone biosynthesis.

Patterns of serum ecdysteroids during induced and uninduced proecdysis in the fiddler crab, Uca pugilator.

Eyestalk-intact and eyestalkless fiddler crabs, Uca pugilator, have similar temporal patterns of circulating serum ecdysteroids during proecdysis. Both groups of animals showed two distinct transient peaks of radioimmunoassay (RIA)-active ecdysteroids. Peak 1 occurred 3 weeks prior to ecdysis and preceded the onset of rapid proecdysial limb bud growth. Peak 2 was a larger peak that occurred a few days prior to ecdysis. Thin-layer chromatography profiles of the two peaks showed at least seven RIA-active compounds common to both peaks. The relative abundance of these compounds differed between the two peaks. The role of the eyestalks in control of circulating ecdysteroids was limited to maintenance of intermolt conditions. During proecdysis, the control of circulating ecdysteroid levels was located outside of the eyestalks. There was no correlation between limb bud growth rates and serum ecdysteroid levels during proecdysis.

Metabolism of injected [3H]ecdysone in male Sarcophaga bullata (Diptera).

Within 30 min after injection, [3H]ecdysone was rapidly partially metabolized to ecdysterone and other ecdysteroids. After 8 hr most (99%) of the tritiated material had disappeared from the hemolymph. In testes, the predominant ecdysteroid appeared to be ecdysterone but no accumulation occurred. Comparison of the dynamics of the ecdysone metabolism in abdomens and head-thorax sections showed that in the head-thorax ecdysterone was the major component, whereas in abdomens the major metabolites were highly polar products (HPP). However, the total amount of label was nearly the same in both parts. Two groups of HPP have been isolated from the abdomen fractions without testes: HPP B and HPP C. Only HPP B could be hydrolyzed by enzymes and seemed at least to contain glucuronides, beta-glucosides, and sulfate conjugates. After 4 hr most of the tritiated ecdysteroids were found in the fecal material. No male-specific metabolites have been discovered.

The nucleolus during epidermal development in an insect.

The fifth stadium of Calpodes has two phases of epidermal cell development corresponding to preparation for intermoult and for moult syntheses. Both phases begin with a period of elevated RNA synthesis and the elaboration of a multilobed nucleolus. The apparent number of nucleoli changes from about two to eight and back to two again within the few hours of elevated RNA synthesis. The nucleolar changes are preceded by elevated titres of haemolymph ecdysteroid. During the two periods of activity, alveoli in the matrix of the nucleoli contain particles believed to be ribosomal precursors. The staining properties of these granules differ according to size in a way that suggests a developmental sequence. Mature granules are about 20 nm in diameter and do not stain with bismuth. They are found at the periphery of the nucleolus, in the nucleoplasm, at the approaches to and within the nucleopores. Perichromatin granules, believed to be m-RNA precursor packages, are up to 60 nm in diameter, do stain with bismuth and are found at the periphery of chromatin, in nucleoplasm and distorted at the approaches to the nuclear pores to fit within the central channel. During these periods of heightened activity the nuclear envelope contains microvesicles that may be free or attached to either nuclear or cytoplasmic surfaces. The structure is appropriate for the microvesicular transnuclear envelope movement of molecules such as the ecdysteroid believed to initiate the nuclear changes.

Cockroach molting. II. The nature of regeneration-induced delay of molting hormone secretion.

1. The amount of regenerating limb tissue does not control the length of molting delay in cockroaches; rather, a programmed delay associated with each autotomy level and segment allows an appropriate delay for accomplishing the necessary regeneration. 2. Delay of molting is accomplished by inhibiting ecdysiotropin release. 3. Each regenerating limb produces a delay independent of other regenerating limbs. 4. Single and simultaneous double autotomies can be used to obtain substantially increased synchrony of the molting cycle of a wide variety of cockroach species. 5. The signal to delay molting is transmitted to the brain along the ventral nerve cord and requires the stereotyped sensory input associated with autotomy to initiate it. 6. There are two phases of ecdysone titer increase during the molting cycle of cockroaches. An early transitory or gradual increase is associated with the regeneration critical period, while a later major peak is associated with apolysis. The major ecdysone peak was shown to be delayed during leg regeneration.