Activity Of Corpora Allata Research Articles

Ultrastructural Changes of Corpora Allata during Larval and Pupal Stages in the Silkworm, Bombyx mori

Changes in fine structure of the corpora allata cells were observed through the larval and pupal stages of the silkworm. Basal lamina surrounding the corpora allata cells began to disappear at the beginning of the pupal stage. During this time, the axons in the cytoplasm and the basal lamina were found to reduce in number. Mitochondria changed from a spherical shape into a rod one during the larval-pupal development. Lipid droplets appeared and increased after the 8th day of the 5th instar larvae. Consideration was given to the relationship between these changes and the activity of corpus allatum.

Interendocrine regulation of the corpora allata and prothoracic glands of Manduca sexta

Regulation of the haemolymph titres of ecdysteroids and the juvenile hormones (JH) during larval-pupal development of the tobacco hornworm, Manduca sexta, involves the interendocrine control of the synthesis of each hormone by the other. Temporal relationships between the ecdysteroid titre peaks in the fourth and early fifth larval instar and the increases in corpora allata (CA) activity at these times suggests that ecdysteroids are evoking the increases. Incubation of brain-corpora cardiaca-corpora allata (Br-CC-CA) complexes and isolated CA from these stages with 20-hydroxyecdysone (20-HE) revealed that 20-HE stimulates CA activity and that it does this indirectly via the Br-CC. The resulting increase in the JH titre after the commitment (first) peak in the fifth instar stimulates the fat body to secrete a factor which appears to be the same as a haemolymph stimulatory factor for the prothoracic glands. This moiety acts as a secondary effector that modulates the activity of the prothoracic glands and thus the ecdysteroid titre. These findings together have begun to elucidate the mechanisms by which the principal developmental hormones in the insect interact to regulate postembryonic development.

Disinhibition of oocyte growth in adult, virgin Periplaneta americana by corpus allatum denervation: Age dependency and relatedness to mating

AbstractUnilateral section of the nervi corporis allati I (NCA‐1) of isolated, starved, adult, virgin Periplaneta americana disinhibited oocyte growth during a specific period following their adult emergence. The effect required that the corpus allatum (CA) be free of NCA‐1 innervation for 4 days beyond the time the females were 7–8 days old. The onset of this sensitive period corresponds to when most isolated, starved virgins become sexually receptive. The results suggest that NCA‐1 inhibition of CA activity, initiated about 7 days, is relieved by mating. When done on sexually receptive, starved virgins, unilateral NCA‐1 section was as effective as insemination for stimulating growth and chorionation of the first generation of oocytes. Neural inhibition of juvenile hormone (JH) secretion by the CA may also explain diminished production of oocytes by isolated, fed virgins, for during 30 days following unilateral NCA‐1 section they produced 2.6 to 5 times more oothecae than did controls with a single CA removed or after the sham operation. The number of oothecae deposited by fed virgins was similarly increased after bilateral NCA‐1 section, but to a lesser extent than when the operation was done on fed, inseminated females of the same age.Specificity of the response of the CA to denervation was substantiated by experiments in which the CA were extirpated and reimplanted, by topically applying C16JH, and by experiments in which the nervus corporis cardiaci 1 and 2 on the right or left side were severed.

Control of C-16 juvenile hormone biosynthesis in active corpora allata of female African locusts

Summary Corpora allata from 8-day-old female Locusta migratoria, during the phase of yolk deposition, exhibit high rates of C-16 juvenile hormone (JH) biosynthesis. The effect of different potential factors which may be involved in the regulation of corpora allata activity is reported. The biosynthetic activity of corpora allata was determined by radiochemical assay. In maturing females, no changes in corpora allata activity are detected during one daily cycle. Starvation reduces JH biosynthesis only 3 days after the beginning of the food deprivation. Suppression of the median neurosecretory material by electrocoagulation of the internal cardiaca tract (TCC-I) does not disturb JH biosynthesis whereas the transection of the allata I nerve fibres (NCA-I) or the electrocoagulation of the lateral neurosecretory pericarya results in a rapid decline of JH biosynthesis. These data indicate that the median and lateral allatotropins are different, and that only the lateral neurosecretory material exerts an allatos...

Parasite regulation of host insect metamorphosis: a new form of regulation in pseudoparasitized larvae of Trichoplusia ni.

When eggs of Trichoplusia ni (lepidoptera) are stung by a parasitic wasp, Chelonus sp., the developing host larvae precociously initiate metamorphosis ten days later. Precocious initiation of metamorphosis occurs even in 'pseudoparasitized' stung hosts which contain no living parasites at the time of symptoms of host regulation by the parasite. In feeding, penultimate instar, pseudoparasitized hosts, the corpora allata activity, hemolymph juvenile hormone esterase activity, in vivo rates of juvenile hormone metabolism and changes in hemolymph protein composition all follow the pattern of the normal last instar. This and other evidence suggests the entire developmental pattern of the last larval instar is precociously expressed in penultimate instar, pseudoparasitized hosts. The cause of precocious expression of the developmental program leading to metamorphosis is a significant decrease in the critical size parameter that, in normal larvae, signals attainment of the last instar. The induction, in preultimate instar larvae, of the entire feeding stage developmental program leading to metamorphic commitment, using either biochemical, surgical or parasitic experimental probes, has not been previously reported. The results have important implications for the study of host-parasite endocrine interaction, of normal insect metamorphosis and even of human puberty.

Juvenile hormone and reproduction in crickets, Gryllus bimaculatus De Geer: corpus allatum activity (in vitro) in females during adult life cycle

ABSTRACT. Incubation conditions were established for a short‐term radiochemical assay of spontaneous juvenile hormone (JH) biosynthesis in vitro by corpora allata from adult female Gryllus bimaculatus. The only JH synthesized was shown by HPLC to be JH III. A further incubation product, predominantly extracted from the corpora allata, was thought to be the JH III precursor, methyl farnesoate. In adult females reared at a constant temperature of 27°C the synthetic activities of the corpora allata‐corpora cardiaca complexes in vitro increase from almost zero to a high peak value 4 days after the imaginal moult. Thereafter the activity decreases to varying intermediate levels, but always lower than the first maximum. Two days after the first peak in corpus allatum activity, ovarian fresh weight increases dramatically and the first oviposition occurs 2 days later.Topical application of JH III to females reared at 20°C, which usually have a low fecundity, causes a dose‐dependent stimulation of egg production and oviposition.

Juvenile hormone and reproduction in the cricket. II. Effect of rearing temperature on corpus allatum activity (in vitro) in adult females

In the Mediterranean field cricket,Gryllus bimaculatus, reproduction is controlled by temperature and the corpus allatum (CA) hormone JH III. In CA of females reared at 24°∶12°C(16∶8 h) (high reproduction rate) a first peak in JH III synthesis is reached about 4 days earlier than in those of 20°C females (low reproduction rate). Furthermore, in 20°C animals CA activity is low during the entire oviposition period, whereas at 24°∶12°C high CA activity is found during this period of adult life. The results indicate a stimulation of CA activity and reproduction by thermoperiods around a constant low temperature.

Brain-mediated 20-hydroxyecdysone regulation of juvenile hormone synthesis by the corpora allata of the tobacco hornworm, Manduca sexta

In the latter part of the last larval instar (Days 6–7) of Manduca sexta an increase in the hemolymph titer of juvenile hormone (JH) occurs which is involved in directing the pharate pupal development elicited by the large increase in the ecdysteroid titer on Days 7–8 of the instar. A time course analysis on Days 3–4 of the instar of both the first hemolymph ecdysteroid titer peak, which is responsible for wandering behavior and pupal commitment, and of the capacity of the corpora allata (CA) to synthesize JH I and III in vitro revealed a temporal correlation between the increasing ecdysteroid titer and a following increase in CA activity. The temporal arrangement of these increases suggested that ecdysteroids, i.e., 20-hydroxyecdysone, may elicit the increase in CA activity which contributes to the second increase in the JH titer during the latter part of the instar. Regulation of the CA by 20-hydroxyecdysone was investigated in vitro by assessing the effect of this ecdysteroid on JH I and III synthesis by CA incubated either as a complex with the brain-corpora cardiaca or as isolated glands. Dose-response analyses revealed that 20-hydroxyecdysone indeed had a stimulatory effect on JH synthesis by the CA, but only when the glands were complexed with the brain-corpora cardiaca. The effective concentration of 20-hydroxyecdysone was the same as the hemolymph concentration of the hormone at this time. Thus it appears that the increase in CA activity between Days 5 and 7 of the last larval instar is elicited in response to the commitment peak of 20-hydroxyecdysone, acting indirectly via the braincorpora cardiaca. These results constitute the first direct demonstration of interhormonal regulation between the ecdysteroids and juvenile hormones in an insect, and suggest that these hormones act to regulate postembryonic development not only at the level of the target tissue but by regulating the synthesis of the hormones by the endocrine glands themselves.

Gas chromatography-mass spectroscopy analysis of juvenile hormone released by insect corpora allata

Corpora allata incubated in appropriate medium release several compounds including juvenile hormones. Juvenile hormones ( 14C labeled or unlabeled) were extracted with hexane and directly analyzed by gas chromatography-mass spectroscopy. This method allowed the qualitative and quantitative analysis of total released juvenile hormone. It could also be used as a routine assay for evaluation of corpus allatum activity. Data obtained by this method were compared to those obtained by radiochemical assay.

Rapid in vitro activation of corpora allata by extracted locust brain allatotropic factor

AbstractBrains of young (newly emerged) adult female locusts (Locusta migratoria migratorioides) and of mature (> 9 days old) locusts contain an extractable allatotropic factor, soluble in 100% methanol and in distilled water. This factor stimulates juvenile hormone III (JH III) synthesis and release from corpora allata (CA) that have been excised from donor locusts and then incubated with (radiolabeled methyl)‐methionine in vitro in its presence. In addition to JH III, which is the major product synthesized by the CA, other hexanesoluble, radiolabeled compounds–‐more polar than JH III–‐are also released when CA are incubated in vitro. The activation of CA by the allatotropic factor is rapid and quickly declines when the factor is removed from the medium. Corpora allata excised from young females are marginally active and can be activated by brain allatotropic factor to less of an extent than CA of mature locusts. The content of allatotropic factor in brains of mature locusts is higher than that ascertained in brains of young females. Allatotropic factor is also present in the corpora cardiaca.

Endocrine events during pre-diapause and non-diapause larval-pupal development of the tobacco hornworm, Manduca sexta

The haemolymph ecdysteroid titre and in vitro capacities of prothoracic glands and corpora allata to synthesize ecdysone and juvenile hormone, respectively, during the last-larval instar of diapause-destined (short-day) and non-diapause-destined (long-day) Manduca sexta were investigated. In general, the ecdysteroid titres for both populations of larvae were the same and exhibited the two peaks characteristic of the haemolymph titre during this developmental stage in Manduca. The only difference in the titre occurred between day 7 plus 12 h and day 7 plus 20 h, when the short-day larval titre did not decrease as quickly as the long-day titre. The in vitro synthesis of ecdysone by prothoracic glands of short- and long-day larvae during the pharate pupal phase of the instar were also essentially the same. Activity fluctuated at times which would support the idea that ecdysone synthesis by the glands is a major contributing factor to the changes in the haemolymph ecdysteroid titre. There was one subtle difference in prothoracic gland activity between the two populations, occurring on day 7 plus 2 h. By day 7 plus 10 h, however, rates of ecdysone synthesis by the short- and long-day glands were comparable. This elevated activity of the short-day glands occurred just prior to the period the haemolymph ecdysteroid titre remained elevated in these larvae. The capacities of corpora allata to synthesize juvenile hormone I and III in vitro were not markedly different in long- and short-day last-instar larvae. At the time of prothoracicotropic hormone release in the early pupa, activity of corpora allata from short- and long-day reared animals was low and also essentially the same. There were a few differences in the levels of synthesis at isolated times, but they were not consistent for both homologues. Overall, there are no compelling differences in the fluctuations of ecdysteroids and juvenile hormones between diapause-destined and non-diapause-destined Manduca larvae. Since these hormones do not appear to play any obviously significant role in the induction of pupal diapause in this insect, the photoperiodic induction of diapause in Manduca appears to be a predominantly brain-centred phenomenon not involving endocrine effectors.

Immunocytochemical localization of peptidergic neurons and neurosecretory cells in the neuro-endocrine system of the Colorado potato beetle with antisera to vertebrate regulatory peptides.

A large number of antisera to regulatory vertebrate peptides was tested immunocytochemically on the nervous system of the Colorado potato beetle to further characterize the peptidergic cells of the neuro-endocrine system and to reveal cells participating in endocrine control mechanisms. Neurons, neurosecretory cells, axons and axon terminals were revealed by antisera to ACTH, gastrin, CCK, alpha-endorphin, beta-endorphin, gamma 1-MSH, insulin, motilin, human calcitonin, growth hormone, somatostatin, CRF, ovine prolactin and rat prolactin. Together with previously described results these findings demonstrate that at least 19 different peptidergic cell types are present in the Colorado potato beetle. Several of these cell types are identical with the known neurosecretory cells, while others have not been identified before. The functions of the immunoreactive neurons are as yet unclear, although in two cases the localization of these cells gives some clues. Thus the lateral neurosecretory cells, which are immunoreactive with antisera to beta-endorphin and ovine prolactin, may regulate corpus allatum activity, whereas a CRF immunoreactive substance seems to be used as neurotransmitter by antennal receptors. These immunocytochemical findings do not imply that the immunoreactive substances are evolutionarily related to the vertebrate peptides to which the antisera were raised. It is postulated that if the part of the substance recognized by a certain antiserum is functionally important for the insect, which should be so if the insect peptide is evolutionarily related to its vertebrate homologue, the antiserum should reveal homologous cells in different insect species. The consequence of this hypothesis is, that if an antiserum does not reveal homologous neurons in different insect species, the immunologically demonstrated substance is probably of little physiological importance, and will not be related evolutionarily to the vertebrate analogue. The positive immunocytochemical results in the Colorado potato beetle are discussed in relation to these considerations.

Adaptation of a radiochemical assay for juvenile hormone biosynthesis to study caste differentiation in a primitive termite

A radiochemical assay measuring juvenile hormone synthesis by corpora allata incubated in vitro was adapted for use with the termite Zootermopsis angusticollis. Corpora allata from 3–4-day old virgin female neotenic reproductives were used in these studies because this caste showed the highest rates of juvenile hormone synthesis (0.6 pmol h−1 per pair corpora allata). Juvenile hormone-III synthesis was linear for up to 6 h over the range of concentrations of labelled l-methionine from 27–280 μM. Rates of juvenile hormone synthesis were stimulated up to 10-fold in a dose-dependent manner by the addition of farnesoic acid to the incubation medium. However, the relatively high concentration of 120 μM farnesoic acid reduced the rates of juvenile hormone synthesis. The radiochemical assay was used to determine rates of juvenile hormone synthesis in vitro by corpora allata from larvae with a queen and king vs orphaned larvae. The presence of reproductives resulted in a suppression of larval corpus allatum activity relative to orphaned controls.

Neural control of the corpus allatum in the Colorado potato beetle, Leptinotarsa decemlineata: An electron microscope study utilizing the in vitro tannic acid Ringer incubation method

The release of material from neurosecretory synapses in the corpora allata of the Colorado potato beetle, Leptinotarsa decemlineata was visualised by an electron microscope procedure which involved tissue incubation in tannic acid. Using morphometry, the frequency of exocytosis phenomena was quantified in beetles kept under two different photoregimes. The number of exocytosis phenomena in the neurosecretory synapses in the corpora allata of beetles kept under short days was significantly higher than that of beetles reared under long-day conditions. In addition, the corpus allatum gland cells appeared to be more richly innervated by neurosecretory synapses under short-day than under long-day conditions. Previous studies using the in vitro radiochemical assay showed that the corpus allatum activity of short-day beetles is at least partly restrained by neurally mediated factors. The present morphological data strongly imply that this corpus allatum inhibitory substance is released from the neurosecretory synapses.

Factors responsible for the initiation of a second oöcyte maturation cycle in the ovoviviparous cockroach Nauphoeta cinerea

The factors responsible for the initiation of a second oöcyte maturation cycle were investigated by measuring oöcyte growth, vitellogenin titre, and corpus allatum activity after injection of juvenile hormone and/or removal of the egg-case from pregnant females and by performing ovary and corpus allatum transplant experiments. Egg-case removal in late pregnancy results in immediate oöcyte growth, whereas in early pregnancy oöcyte growth is resumed only after a lapse of time, even after injection of juvenile hormone. This, however, induces an immediate increase in the haemolymph vitellogenin titre. A single injection of 2 or 10 μg of juvenile hormone II first stimulates some oöcyte growth after this lapse of time and later activates the corpora allata, which in turn leads to completion of oöcyte maturation. A repeat injection of 10 μg stimulates continuous oöcyte growth without activating the corpora allata. In the presence of an egg case, activation of the corpora allata is suppressed, even after injection of 2 μg of juvenile hormone III, and the oöcytes do not grow. Injection of higher doses stimulates oöcyte growth and leads to expulsion of the egg case in up to 95% of the females. This, however, is not a direct consequence of the increase in size of the ovaries. Ovary transplant experiment show that in young pregnant females the second generation of oöcyte is not yet competent for growth and that ovaries which are competent can mature in young pregnant females, treated with juvenile hormone, whose egg case has been removed. The results are summarized in a model demonstrating the various factors involved in regulating corpus allatum activity in oöcyte maturation and pregnancy and after application of juvenile hormone. We prepose that the corpus allatum activating effect of exogenous juvenile hormone is mediated by the growing oöcyte and that this activation can be suppressed by the continuous presence of exogenous juvenile hormone.

Regulation of the corpora allata in the black mutant of Manduca sexta

Regulation of corpus allatum activity in the black mutant strain of Manduca sexta was studied in vivo and in vitro. Allatectomy, denervation, and implantation studies demonstrated that black mutant corpus allatum activity remains low in both wild-type and black mutant host larvae. Attempts to distinguish humoral control mechanisms versus mechanisms dependent on intact allatal nerves indicated that intact allatal nerves were not required for the reduced black mutant corpus allatum activity in vivo. Incubation of corpora allata, using [1- 14C]propionate as a juvenile hormone biosynthetic precursor and haemolymph as culture medium, confirmed that black mutant corpora allata are suppressed by a factor(s) in the haemolymph. Under identical conditions wild-type corpora allata were unaffected. Finally, the lowered black mutant corpus allatum activity in haemolymph in vitro correlates with the lowered juvenile hormone titre in black mutant larvae.

Effects of food and water availability, and of NCA-1 section, upon juvenile hormone biosynthesis and oöcyte development in adult female Periplaneta americana

The combined stimuli from feeding, drinking, mating and crowding are required for the highest rates of oöcyte development in maturing adult female Periplaneta americana. A graded series of “sexually suppressed” females can be produced by withholding one or more of these stimuli, and this stepwise retardation of ovarian development appears to be achieved by a progressive increase in corpus allatum restrain. It seems that all of these environmental cues are centrally integrated such that juvenile hormone-dependent processes can proceed at an appropriate pace. Water availability is evidently the most important factor. Water-deprived females are sexually unreceptive, and are found to have very low rates of juvenile hormone biosynthesis and ovarian development. This holds true even when they are provided with food. In contrast, 75% of starved females are sexually receptive if allowed free access to drinking water. At the same time they have enhanced corpus allatum activity, and show significant oöcyte growth. The mode of regulation of corpus allatum function in adult female P. americana appears to be significantly different to the model proposed for the cockroaches Leucophaea maderae and Diploptera punctata. Allatotropic signals may be more important than inhibitory signals in the former species. The glands continue to be moderately active in fed, mated female P. americana after NCA-1 section (although a major peak of corpus allatum activity is not obvious), and the rate of oöcyte development is not greatly reduced. However, NCA-1 mediated inhibition of juvenile hormone biosynthesis is less readily demonstrated. We could observe no enhancement of corpus allatum activity nor stimulation of oöcyte growth after unilateral NCA-1 section when the operation was performed on starved virgins, and the same result was found after bilateral NCA-1 section when starvation or virginity were separately enforced. A slight stimulation of juvenile hormone biosynthesis, together with a small increase in oöcyte development, could only be demonstrated after both NCA-1 were cut in starved virgins. We conclude that neurally mediated corpus allatum inhibition in has yet to be adequately verified, and that the available evidence does not contradict the theory that juvenile hormone biosynthesis in adult females could be regulated predominantly by chemicals released into the haemolymph.

The significance of free ecdysteroids in the haemolymph of adult cockroaches

The existence of ecdysteroids in the haemolymph of adult Periplaneta americana has been demonstrated for the first time. It appears that 20-hydroxyecdysone is responsible for most of the observed RIA activity. There is a relatively high titre (28.7 ± 3.7 ng/ml) in females immediately after adult emergence, a decrease over the next 5 days, and a new peak (20.3 ± 4.1 ng/ml) towards the end of the first gonotrophic cycle. The post-emergence peak is also apparent in males, and the titre similarly falls over the next few days. However, the subsequent increase does not occur and the second peak is evidently lacking. The female-specific peak can be abolished by surgical removal of the ovaries, and its appearance is similarly prevented when ovarian development is precluded by allatectomy. The evidence suggests that the ovaries are a major source of haemolymph ecdysteroids in adult females of this species. It remains to be seen whether the female-specific peak is merely the result of an inconsequential leakage from developing oöcytes, or is indeed the secretion of a true hormone with a specific function, possibly the suppression of corpus allatum activity at the time of chorion formation. Certainly, we find no evidence for any involvement of haemolymph ecdysteroids in the suppression of juvenile hormone biosynthesis which accompanies enforced virginity or prolonged starvation in P. americana. The significance of these results is discussed both in relation to other titre determinations and to the evolution of corpus allatum regulation in the Blattaria, with additional comments concerning the humoral environment that prevails when certain juvenile hormone-dependent genes are expressed in the adult female.

Control of corpus allatum activity inDiploptera punctata: roles of the pars intercerebralis and pars lateralis

Control of the corpora allata (CA) ofDiploptera punctata is maintained by at least 2 factors. The glands are directly inhibited by an allatostatin arriving at the CA via the nervi corporis cardiaci I (NCC I). Destruction of the putative source (median neurosecretory cells, MNC) of the allatostatin by radio-frequency (RF) cautery relieved the inhibition imposed on the CA of virgin females, and the glands became active. Similarly, destruction of the lateral neurosecretory cells (LNC) also relieved the inhibition. We propose that the LNC stimulated the MNC to release allatostatin. RF-cautery did not result in the activation of CA of pregnant or ovariectomized females. Activation of the CA may therefore require not only absence of the inhibitory factor but also the presence of a stimulatory one (perhaps from the ovary).

Ovarian stimulation of juvenile hormone biosynthesis in the viviparous cockroach, Diploptera punctata

A direct radiochemical assay for juvenile hormone (JH) biosynthesis by the corpora allata (CA) showed that the cyclic changes in biosynthesis associated with the gonadotrophic cycle were abolished in the absence of ovaries whether or not the CA were innervated. In ovariectomized animals denervated CA synthesized JH at slightly higher rates than did innervated CA. However, the low rates of JH synthesis in ovariectomized females were sufficient to result in accumulation of vitellogenin in the hemolymph to levels twice those of normal females. Implantation of one ovary 1 week after ovariectomy resulted in a cycle of JH biosynthesis qualitatively similar to that observed during a normal gonadotrophic cycle. Implantation of one ovariole did not result in a detectable cycle of JH biosynthesis whereas normal rates of JH synthesis were observed after implantation of three or six ovarioles. Implantation of four ovaries resulted in a cycle of CA activity more attenuated than that observed in the presence of one ovary. Nonetheless all four ovaries sequestered a normal quantity of vitellin.