Activity Of Corpora Allata Research Articles

The relative importance of nervous and humoral pathways for control of corpus allatum activity in the adult colorado potato beetle, Leptinotarsa decemlineata (Say)

To elucidate corpus allatum (CA) regulatory mechanisms under the influence of photoperiod and starvation in Leptinotarsa decemlineata, gland activities were measured in vitro by the short-term radiochemical assay. This data was substantiated with juvenile hormone (JH) titer determinations by using a physicochemical method or a radioimmunoassay. Under short-day conditions both neural and humoral factors may be involved in CA inhibition. This was indicated by the temporary activation of short-day glands after denervation in early prediapause and the gradual inhibition of active CA from long-day females implanted into short-day hosts. Studies with farnesenic acid as a precursor indicated that the last two steps in the biosynthetic pathway of JH are also diminished during humoral inhibition of the CA. Transfer of short-day beetles to long-day photoperiod completely activated the CA and this process was independent of CA innervation. Starvation leads to neural inhibition of intact glands but to possible stimulation of the denervated CA, since implanted glands in starved hosts were fully activated irrespective of the photoperiod.

Corpus allatum activity during overlapping cycles of oöcyte growth in adult female Melanoplus sanguinipes

Cycles of oögenesis in Melanoplus sanguinipes overlap to the extent that there are always 2 and occasionally 3 sets of vitellogenic oöcytes in the ovarioles at any one time. Three phases of vitellogenic oöcyte development can be distinguished: (1) An initial 24-hour phase of slow development (1.0–1.2 mm, 0.05–0.10 mm 3). (2) A phase of rapid oöcyte growth (1.2–3.5 mm, 0.1–1.3 mm 3). The duration of this phase is 2 days in the first cycle and 3 days in subsequent cycles. (3) A final phase of rapid oöcyte growth and maturation (3.5–4.5 mm, 1.3–2.8 mm 3). Including the time taken for oviposition the duration of this latter phase is 3 days. Phases 1, 2 and 3 of cycles n + 2, n + 1 and n, respectively, overlap entirely. Activity of the corpora allata was measured using a radio-biosynthetic technique. A period of increased corpus allatum activity coincides with the initial part of phase 2 in each cycle. Each set of oöcytes is, thus, subject to 2 and occasionally 3 peaks of corpus allatum activity during development. Using these data a model of the control of oöcyte development has been devised

Neural influence on corpus allatum activity and egg maturation in starved virgin Periplaneta americana

ABSTRACT. Of sixty‐seven adult female Periplaneta americana (L.) isolated when less than 8h old and kept without food at 25–30°C in LD 12:12, only six produced oothecae during 25–35 days. Growth of the basal oocytes was retarded, and maximal oocyte volume, only one‐third of that in fed virgins, was achieved after about 12 days. By day 14, 60% of the basal oocytes were being resorbed in the starved females, and corpora lutea were usually all that remained beyond day 20. Oocyte growth was potentiated in starved, virgin females by severing either of the two nervi corporis allati 1 (NCA 1), and oothecae were then produced in 45–80% of cases. Sham‐operated controls oviposited in fewer than 27% of the trials. Because oocyte maturation was prevented by extirpating both corpora allata (CA), but not when the glands were replaced, and because the juvenile hormone analogue, ZR 515, was highly effective in causing the starved cockroaches to produce oothecae, the starvation‐induced reproductive failure probably reflects diminished hormone production by the CA. The most likely consequence of severing NCA 1 is de‐repression of juvenile hormone production. The directness of the neural influence was shown by removing the one denervated CA, in which case stimulation of oogenesis was minimal even though the contralateral innervated gland was present. The incidence of ootheca production was not enhanced by transecting the NCA 2, which suggests that the CA of starved cockroaches are not inhibited via this pathway.

Repeated copulation and testes enlargement in Macrotermes michaelseni

ABSTRACT. The minimal copulation frequency of the reproductives of Macrotermes michaelseni (Sjöstedt) was investigated by removing the king from incipient laboratory colonies and from mature field colonies. Laboratory females stopped producing fertile eggs 56–154 days, and physogastric queens from field colonies less than 13 days after the removal of the king. Compared with young laboratory male reproductives, kings from mature field colonies are reported to have enormously enlarged testes, larger corpora allata (CA) and a higher juvenile hormone (JH) titre. However, JH application to young males did not increase the volume of the testes. The testes volumes only increased if the males were kept with additional workers or if their incipient colonies were allowed to grow continuously under unrestricted space conditions. These males also had bigger CA, and the soil in their midgut was replaced by food from the workers. It is concluded that in a growing colony the king is differently fed by the increasing number of workers and that trophic change in combination with higher CA activity induce enlargement of the testes. These enlarged testes are able to produce the sperm to fertilize the large number of eggs laid by a physogastric queen.

Juvenile hormone synthesis in vitro by larval and pupal corpora allata of Manduca sexta

The synthesis of juvenile hormone I (JH I) and juvenile hormone III (JH III) in vitro by isolated corpora allata (CA) and brain-corpora cardiaca-corpora allata complexes (BR-CC-CA) from fourth and fifth instar larvae and pupae of Manduca sexta was assessed by JH I and JH III radioimmunoassays of incubation medium. Fluctuations in synthesis occurred at specific stages during larval-pupal development. These fluctuations temporally approximated those of previously determined hemolymph titers of JH I and III for this developmental period, except for the synthesis of JH III during the prepupal period, when the JH III hemolymph titer was negligible but JH HI synthesis in vitro increased to the highest rate observed. The overall agreement between CA activity and the JH hemolymph titers suggests that the in vitro system supports physiological gland activity and that changes in biosynthesis contribute significantly to changes in the titers. A comparison of JH I and JH III synthesis by isolated CA with that by BR-CC-CA suggests that the BR-CC can differentially modulate the synthesis of these two homologs. The significance of these findings with regard to the possible endocrine function of JH III and the proposed neuroendocrine control of the CA is discussed.

Activity of corpora allata, endocrine balance and reproduction in female Labidura riparia (Dermaptera).

The reproductive activity of Labidura riparia females involves, after a 5-day maturation stage, a regular alternation of ovarian cycles and egg-care stages averaging 10 days each. Vitellogenesis is characterized by an increase in the size of the corpora allata (CA) where structured SER bodies appear, and by a rise of juvenile hormone (JH III) content in the hemolymph which is followed by an increase in the level of ecdysteroids. During the egg-care periods, the CA are inactive; structured bodies generate autophagic vacuoles, the titer of JHs and later that of ecdysteroids in the hemolymph decreases and remains stationary. Ovariectomy causes hypertrophy and hyperactivity of the CA for about two months. Subsequently, the titer of JH decreases and old females may display parental behaviour; the level of ecdysteroids falls and remains unchanged. After cauterization of the pars intercerebralis (PI) of the protocerebrum, the ovarian activity stops, the ovary shrinks, the JHs rapidly disappear but ecdysteroids remain at the same or even higher levels than those of normal females of the same age. On the basis of these data, we postulate the existence of a center located in the PI, inhibiting the production of ecdysteroids, and of a stimulating center located outside this area. The PI also exhibits an allatotropic function.

Intrinsic differences in juvenile hormone synthetic ability between corpora allata of males and females of the cockroach Diploptera punctata

To study the basis for differences in juvenile hormone (JH) synthesis exhibited by corpora allata (CA) of males and females of the cockroach Diploptera punctata, the activity of male and female CA is compared after implantation into allatectomized adult females. Implanted male CA are able to support complete oocyte development, but at a reduced rate. Measurement of juvenile hormone biosynthesis by implanted CA with an in vitro radiochemical assay shows that implanted male CA synthesize JH at much lower rates than those of implanted female CA. The fact that male CA are smaller than female CA accounts in part for their lesser synthetic ability.

The effects of juvenile hormone, 20-hydroxyecdysone and precocene II on activity of corpora allata and the mode of negative-feedback regulation of these glands in the adult Colorado potato beetle

When the titre of juvenile hormone III in female Leptinotarsa decemlineata was elevated by the implantation of supernumerary corpora allata or by the injection of the hormone, the rate of endogenous hormone production by the host glands was significantly restrained, as determined by the short-term in vitro radiochemical assay. From denervation studies, it is suggested that during phases of elevated juvenile hormone titre, the corpus allatum activity is regulated via humoral as well as neural factors requiring intact nerve connections. Restrainment of gland activity appears to be mainly via the neural pathway. Isolated corpora allata were not influenced by 10 −5 M juvenile hormone III added to the incubation medium in vitro. Studies with farnesenic acid revealed that the final two enzymatic steps in the biosynthetic pathway of juvenile hormone are also diminished during prolonged neural inhibition of the corpora allata. 20-Hydroxyecdysone and precocene II had no apparent effect on the corpus allatum activity of Leptinotarsa decemlineata.

The mode of regulation of the corpus allatum activity during starvation in adult females of the Colorado potato beetle, Leptinotarsa decemlineata (Say)

When two-day-old female Leptinotarsa decemlineata were starved, their corpus allatum activity, as measured by the radiochemical in vitro assay, was significantly reduced after 24 hr. Such a reduction was not observed when the nerve connections between the central nervous system and the retrocerebral complex were severed and the beetles starved up to 5 days. In some experiments, the rate of juvenile hormone biosynthesis in vitro, was substantiated by measurement of the juvenile hormone titre in the haemolymph by physico-chemical methods. It is concluded that intact nervous connections between the central nervous system and the corpora allata are essential for restraining the juvenile hormone biosynthesis during the initial stages of starvation. Corpora allata from 1-day starved insects were considerably stimulated in vitro by farnesenic acid indicating that juvenile hormone synthesis is controlled enzymatically at a stage prior to the final two steps in the pathway. However, on day 5 of starvation, rate-limitation may occur after formation of this intermediate, since farnesenic acid stimulation was much less at this time. Corpora allata of adult females newly emerged from the soil were activated within 4 hr regardless of feeding.

Improved assay conditions for measurement of corpus allatum activity in vitro in the adult Colorado potato beetle, Leptinotarsa decemlineata

Assay conditions for the short-term, radiochemical, in vitro determination of the spontaneous rate of juvenile biosynthesis by isolated corpora allata from Leptinotarsa decemlineata have been further improved, permitting the measurement of juvenile hormone biosynthesis by individual pairs of corpora allata. The final incubation product has been identified as juvenile hormone III with the aid of High-performance liquid chromatography (HPLC) and juvenile hormone esterase degradation. Using the new assay conditions, the activities of adult corpora allata during maturation were found to be significantly higher in reproductive, long-day animals than in pre-diapause, short-day beetles. During diapause no activity was detectable, whereas corpora allata from post-diapause beetles were reactivated totally after 5 days. Simultaneous determination of the in vitro rates of juvenile hormone biosynthesis and corpus allatum volumes revealed no clear correlation although the results suggest that the volume may be indicative of the maximal capacity for juvenile hormone production. Corpora allata from a population of beetles did not display any synchronous diurnal rhythmicity.

Effect of the photoperiod on corpus allatum activity in vitro in the beetle,Pterostichus nigrita F

In the carabid beetlePterostichus nigrita reproduction is controlled by photoperiods and the corpus allatum hormone. Corpora allata were incubated in vitro and the release of juvenile hormone was quantified. Short-day conditions induced low activity of the corpora allata; long days, after short-day treatment, stimulate high corpus allatum activity, while long days alone have no effect.

Increased juvenile hormone synthesis and decreased fertility in aging Schistocerca gregaria

The fertility of aging Schistocerca gregaria females of both solitary and gregarious phases is markedly reduced in comparison with that of young females. Examination of eggs (from both young and aging females) maintained in vitro revealed that the decreased fertility of aging females of both phases could be attributed to a decrease in viability of eggs. This, in turn, was found to be in large part due to an increase in the proportion of embryos showing inhibited development. The proportion of inhibited embryos, in pods from young and old females, respectively, increased from 5 to 42% for gregarious animals and from 3 to 38% for solitary animals. Inhibition was found to occur at all stages from blastokinesis to ecdysis of the provisional cuticle. These morphogenetic aberrations were very similar to those obtained after treatment of S. gregaria eggs with exogenous juvenile hormone (JH). Investigation of the JH synthetic activity of corpora allata from aging females of each phase revealed a marked increase in the rates of JH synthesis in comparison with those of young females of the same phase. Furthermore, injection of JH into young females increased the proportion of embryos showing inhibited development from 7% (in control females) to 30% (in JH-treated females). These results suggest a possible correlation between reduced viability of eggs and high rates of JH synthesis in aging S. gregaria of both phases.

Radiochemical assays of corpus allatum activity in adult female cockroaches following ovariectomy in the last nymphal instar

Surgical removal of the ovaries from nymphalPeriplaneta americana results in lower than normal corpus allatum activity in the adult insect and an apparent absence of the manifestly cyclic pattern of juvenile hormone biosynthesis found in intact mated females. The results suggest that the presence of synchronously developing ovaries is necessary for the attainment of normal synthetic activity in the corpus allatum of this species.

Effects of starvation and feeding upon corpus allatum activity and oöcyte growth in adult female Periplaneta americana

Direct radiochemical determinations of juvenile hormone (JH) biosynthesis by corpora allata (CA) isolated from starved and re-fed Periplanteta americana have been employed to elucidate the humoral mechanisms involved in the modulation of reproductive activity in response to food availability. When starvation was initiated in mature adult females at the time of formation of an oötheca the next oötheca was normally deposited 5 to 6 days later, a delay of 2–3 days, and a third oötheca was formed by only 50% of starved females. The terminal oöcytes in the remaining females were either resorbed or maintained in an arrested state. Ovarian development had effectively ceased after 2 weeks of starvation but recommenced within 3 days of re-feeding. The CA of most starved females exhibited 2 activity cycles following food withdrawal. The first peak occurred on day 1 of the starvation period and was coincident with the timing for fed controls. The second peak was delayed by about 2 days and the activity of the CA then declined to the extent that glands from animals starved for more than 11 days were completely inactive. Feeding, after 10 or 16 days starvation, resulted in a resumption of CA activity which was detectable in some animals within 24 hr, and very high rates of JH biosynthesis were found 4 or 5 days later. The results suggest that P. americana can readily and efficiently modulate egg production in response to food supply, and that control is effected through alterations in JH production by the CA. The use of farnesenic acid as a biochemical probe indicates that CA inactivity after long periods of starvation does not arise because malnutrition has caused complete metabolic shut-down in the glands, and that JH biosynthesis is basically modulated at a control point prior to the last two enzymic stages in the pathway.

Inhibitory regulation of corpus allatum activity in mosquitoes

In order to determine whether juvenile hormone (JH) in mosquitoes is regulated by ovarian inhibitory feedback, we implanted JH-sensitive pupal ovaries into adult mosquitoes and observed subsequent ovarian maturation. Removal or destruction of resting-stage ovaries (previously JH-stimulated) resulted in JH-stimulated development of implanted pupal ovaries. Ablation experiments demonstrated the ovary-corpus allatum sequence of maturation, and application of exogenous hormone analogs confirmed that development of implanted pupal ovaries is JH-dependent. Incidental observations indicated that ovaries of preapolytic pupae produce a hormone that causes more mature ovaries to degenerate. We concluded that corpus allatum activity in Aedes aegypti is regulated by ovarian feedback inhibition.

Chronological and ultrastructural observations on the activities of the embryonic corpus allatum in Carausius morosus BR. (Phasmida : lonchodidae)

Ultrastructural analysis of the vesicular corpus allatum (CA) has been carried out in the embryos of the phasmid, Carausius, according to stage chronology. Special attention was paid to the relations between microvilli and intra-cavitary secretions of the CA cells, then to the differentiation of mitochondria and granular endoplasmic reticulum in these cells. Between dorsal closure of the embryo and eclosion of the young larva, the CA appears to carry out only one program of “exocrine”, i.e. cuticle reminiscent, secretion. This program is late with respect to the production of the 2nd embryonic cuticle by gnathal hypoderm. Its atypical and abortive execution is accompanied by the disappearance of glycogen heaps and lipid droplets accumulated in the CA cells. Two similar phases of processes that could be ascribed to “endocrine” activity of the embryonic CA were discovered. The first one coincides with the completion of dorsal closure in the prothoracic region of the embryo, at stages VI 7-VI 8. The second one occurs simultaneously with the darkening of the mandibular base at a much later stage, namely VII. Both are best characterized by the appearance of dilated intercellular spaces between lateral and baso-lateral membranes of the CA cells, into which cellular protrusions containing clustered mitochondria intertwine. The matrices of the mitochondria tend to lose their electron density, mostly at stage VII 3. After each of the 2 phases, the dilated intercellular spaces appear to collapse rather rapidly and their fluid is very likely discharged into embryonic haemolymph. However, this “endocrine” motion does not settle the questions whether the liquid emission occurs simultaneously with a juvenile hormone discharge or is a necessary carrier for the latter. Regarding the granular endoplasmic reticulum, 2 very similar sequences of its evolution were discovered in the CA cells. Both sequences coincide in part with the former described phases of presumed endocrine activity, but at the present time their actual meaning cannot be determined.

Cellular and volumetric changes in relation to the activity cycle in the corpora allata of Diploptera punctata

In the corpora allata (CA) of the viviparous cockroach, Diploptera punctata, a cycle of juvenile hormone (JH) synthesis during ovarian maturation can be correlated with cyclical changes in CA volumes and cell numbers. Uptake of [ 3H]-thymidine occurs in nuclei of CA cells during periods of increase in cell number. Both members of a pair of CA maintain symmetry of volume, cell number and rate of JH synthesis. After a cycle of CA activity, the CA can be transplanted to a young, allatectomized female, where they support a second wave of oöcyte development.

Neuroendocrine regulation of corpus allatum activity in Manduca sexta : Sequential neurohormonal and nervous inhibition in the last-instar larva

The inactivation of corpora allata (CA) in the last-instar larva of the tobacco hornworm Manduca sexta was studied using in vivo assay methods that test the capacity of the glands to induce an extra larval molt. Results indicate that the CA are inactivated by a two-step process. In the first step, a neurohormonal inhibition occurs by day 1 after ecdysis, resulting in a decrease in the ability of the glands to respond to allatotropin. The inhibitory hormone appears to be secreted by the medial neurosecretory cells in the brain and remains in the hemolymph only for a short period of <2 days. The second step of inactivation occurs by day 3; it is neurally mediated and essentially terminates juvenile hormone secretion. Neither the neurohormonal nor the neural inhibition is reversible under the conditions used in our larval assays. The timing of the two stages of inhibition coincides with the two periods of reduction in hemolymph juvenile hormone titer; this suggests that the regulation of corpus allatum activity plays an important role in reducing the juvenile hormone titer during the last larval instar-a prerequisite for the transformation of the larva into the pupa.

The activity of corpora allata in dominant and subordinated females of the waspPolistes gallicus

In females ofPolistes gallicus the activity of corpora allata (CA) was determined volumetrically as well as radiochemically using the in vitro assay for juvenile hormone (JH). The results we have compared with the ovarian activity. During the period of egg maturation after overwintering the volume of CA is well correlated with the synthetic activity. But in overwintering females and in ovariectomized females we have observed very large glands which produced only little amounts of JH like the small glands of parasitized wasps. In all dominant females the CA we have found to be larger and more active than in subordinated females indicating that changes in the endocrine activity may be a primary result of social hierarchy.

Neural Inhibition of Corpus Allatum Activity during Metamorphos of Periplaneta americana1: a Reassessment

All last instars with a severed nervus corporis allati 1 (NCA 1) underwent a supernumerary molt, as did 80–85% of those with one corpus allatum (CA) removed. The sham operation caused an extra molt by 60–85% of the nymphs, but those that were totally allatectomized usually metamorphosed. Apparently, juvenile hormone production by the CA was enhanced or sustained following surgery. The NCA 1 and nervus corporis allati 2 (NCA 2) supplying the right CA were cut immediately after removing the opposite gland. Only supernumerary nymphal molts resulted, suggesting that neither of these nerves provides stimuli necessary for CA activity. Furthermore, the incidence of additional nymphal instars after severing NCA 2 to the remaining gland resembled that obtained after removing the left CA, so NCA 2 does not seem to constitute an important inhibitory pathway. Because CA activity fostered by cutting NCA 1 is neither as site-specific nor as direct as reported previously, it may not reflect the removal of an inhibitory innervation.