The dark-colour-inducing neurohormone of locusts in relation to an albino mutant of Schistocerca gregaria

In the albino mutant of an Okinawa strain of Locusta migratoria (L.) (Orthoptera: Acrididae), albinism is caused by the absence of the dark‐colour‐inducing neurohormone (DCIN), which is present in the corpora cardiaca (CC) of normally coloured phenotypes. This study tests whether the absence of DCIN is responsible for albinism in an albino mutant of another locust, Schistocerca gregaria (Forsk.) (Orthoptera: Acrididae). This seemed feasible because a single Mendelian unit controls albinism in both species. However, implantation of CC, or injection of an extract of CC, from albino donors of S. gregaria, induce dark coloration in crowded nymph recipients of the Okinawa albino mutant of L. migratoria, as effectively as do implanted CC, or injections of extract of CC, from normal phenotype donors of S. gregaria. Therefore, DCIN is present in the albino mutant of S. gregaria, and consequently, the albinism in this mutant is not caused by its absence. Implantation of CC, or injection of extracts of CC, from albino donors of S. gregaria to conspecific albino nymphs does not induce darkening. Only extremely high doses of synthetic DCIN injected into albino nymphs of S. gregaria are effective, inducing some darkening. The dose to induce such darkening in albino nymphs of S. gregaria is 50 nmol, ≈ 5 × 10⁶ times higher than that (10 femtomol) needed to induce equivalent darkening in nymphs of the Okinawa albinos of L. migratoria. The results are discussed and some possible explanations of the observed effects outlined.     

The levels of ecdysteroids in uninjured and leg-autotomized nymphs of Blattella germanica (L.)

The levels of ecdysteroids in control and leg-autotomized first-instar nymphs of Blattella germanica were determined by radioimmunoassay from hatching to the time of the first ecdysis. Uninjured nymphs showed a distinct release of ecdysteroids half-way through the stadium, and this resulted in the commencement of the moult cycle which formed the cuticle of the second instar. Cockroaches which had legs autotomized at 48 h after hatching (i.e. before the control ecydsteroid release) had their instar duration increased by that time period. Releases of ecdysteroids and events of the moulting cycle were also postponed by the 48 h period. The titre of ecdysteroids in injured animals was double that of controls. Nymphs were also autotomized at 96 h (i.e. after the normal release of ecdysteroids) but no changes in instar duration, ecdysteroid releases, or events of the moult cycle were recorded. The effects of injury, prothoracicotropic hormone activity and ecdysteroid release are discussed.     

Spatial and temporal distribution of pheromone biosynthesis-activating neuropeptide in Helicoverpa (Heliothis) armigera using RIA and in vitro bioassay.

A [3H]-PBAN (pheromone biosynthesis-activating neuropeptide) analog was synthesized, and binding of the radioligand to a specific PBAN-antiserum was achieved. The inhibition of binding of the radioligand by unlabeled PBAN, several PBAN analogs, and other competitors was studied and a specific radio-immunoassay was developed. Using this radioimmunoassay we found PBAN-like immunoreactivity in methanol extracts of hemolymph and neural tissues from females. Higher levels of PBAN-like immunoreactivity in extracts of brain-suboesophageal ganglion complexes, corpora cardiaca, thoracic ganglia, and abdominal ganglia were observed during the 4-5th h scotophase when compared to the PBAN-like immunoactivity levels during the 6-11th h photophase. On the other hand, the concentrations of PBAN-like immunoreactivity, in the terminal abdominal ganglion were higher during the photophase relative to minimal levels observed during the scotophase, indicating an accumulation before the onset of pheromone production. These differences in concentrations of PBAN were also reflected in the stimulation of in vitro pheromone glands, whereby significant stimulations were obtained by scotophase and photophase brain extracts, scotophase thoracic ganglia extracts, and photophase terminal abdominal ganglia extracts. No detectable levels of PBAN were found in hemolymph extracts during the sampling periods.     

Comparison of the Protection against Neuronal Injury by Hypothalamic Peptides and by Dexamethasone

The comparative study has been carried out on hypothalamic neurohormone (proline-rich polypeptides-PRP) and synthetic glucocorticoid dexamethasone (DEX) protective properties at the systemic (i/m) administration. Both background and evoked electrical activity (on n.ischiadicus stimulation) of single neurons in the lumbo-sacral part (laminae II–VI and VII–VIII by Rexed) and field potentials (FP) of spinal cord were recorded during acute experiments on intact spinal rats, subjected to Vipera Raddei (VR) venom intoxication, and chronic spinal cord trauma (hemisection). The action of PRP was characterized by the pronounced activation of the background activity (BA) with adaptive effect, depending on dose and initial level of BA, by results of the statistical analysis. A high effect is received from comparatively small doses. For comparison it was used strong glucocorticoid DEX, possessing single-directed but less expressed excitative action on investigated spinal cord neurons. The initial increase of BA frequency with subsequent depression was the typical symptom of venom influence. A protective effect of preliminary PRP injection is revealed on the succeeding VR venom influence. Use of PRP and DEX causes the increase of reduced activity of neurons on the injury side of animals with spinal cord hemisection. It provides the possibility of the therapeutic utilization. It was revealed considerably more expressed PRP action on neurodegenerative process connected to spinal cord injury (in comparison with DEX). The influence of hormones was compared in identical conditions of experiments on non-injured (control) and injured sides. Taking into consideration revealed protection characteristic of PRP and also the ability of snake venom to stabilize and to prolong its action combined with these preparations, the assumption is made on prospective use of the specified combination in clinical practice.     

Protection Against Snake Venom-Induced Neuronal Injury by the New Hypothalamic Neurohormone

The action of PRP is characterized by the pronounced activation of the background activity (BA) of the brain spinal cord, and the degree of the activity depends on BA initial level. The typical peculiarity of Vipera raddei venom influence is the initial increase in frequency of BA with subsequent depression. A preliminary injection of PRP has a protective effect at subsequent influence of venom. In animals with hemisection the PRP increases the decreased activity of neurons on injury side. Taking into consideration the protective peculiarities of PRP in the relationship to snake venom and the possibility of the latter to stabilize and prolong the action of drugs (in the case of PRP) combined with them, it is supposed that the mentioned use of the combination in clinical practice will be perspective. The data obtained testify the PRP to be a neuroprotector against many toxic compounds formed in organism (glutamate, ceramid, beta-amyloid neurotoxisity, etc.). Investigations in this aspect are still in the process.     

Evidence for both humoral and neural regulation of sex pheromone biosynthesis in Spodoptera littoralis

Selected tissues presumably involved in the control of sex pheromone production were analyzed by ELISA for the presence of PBAN-like immunoreactivity (PBAN-IR) in Spodoptera littoralis. The temporal distribution pattern of PBAN-IR in the hemolymph is similar to that of pheromone production in the gland. On the other hand, analysis of the retrocerebral complex, brain-subesophageal ganglion complex, and terminal abdominal ganglion (TAG) revealed similar PBAN-IR levels in both photophase and scotophase periods. Pheromonotropic activity exhibited by both hemolymph and TAG, as determined by a modified in vitro bioassay, agrees with the results of the immunochemical analyses. Severing the ventral nerve cord anterior to the TAG impaired normal sex pheromone production by second-scotophase females. These results are discussed in the context of how sex pheromone biosynthesis is regulated by PBAN in S. littoralis. © 1996 Wiley-Liss, Inc.     

Production of antibodies to Manduca sexta cerebral neurosecretory cells

Understanding the neuroendocrine regulation of insect development depends upon having antibody probes to the neurohormones involved, which are usually present at trace levels, making antibody generation difficult. This report describes a simple method for producing antibodies specific to cerebral neurosecretory cells (NSC) of the tobacco hornworm, Manduca sexta, and to the neurohormone(s) they produce. The method involves the isolation of only a few hundred NSC somata (～ 0.3 μg of protein) that serve as the immunogen. The cerebral NSC used were the L-NSC III, the prothoracicotropes, that produce the prothoracicotropic hormone (PTTH), the principal neuroendocrine effector of insect molting and metamorphosis. A PTTH-containing extract of microsurgically isolated somata of the L-NSC III was injected intraperitoneally into a Balb/c mouse. The antiserum produced specifically immunostained the L-NSC III in wholemounts of brains from different developmental stages. This antiserum also contained antibodies directed against PTTH, as shown by its ability to inhibit the neurohormone's biological activity in an in vitro prothoracic gland bioassay. Such antiserum can be used to investigate the ontogeny and phylogeny of NSCs. With the hybridoma technique, monoclonal antibodies to individual NSC proteins (PTTH) could be obtained, circumventing the need to purify them for antibody production. This method should be applicable to comparable neurosecretory cell systems in other insect species.     

Involvement of neurohormone in regulation of oxygen consumption in the marine gastropod,Onchidium verruculatum

Ablation of whole central nervous system (CNS) or pleurovisceral (PV) ganglia significantly inhibited O₂ uptake, after 4 hr through 24 hr of the operation over sham controls. Replacement of PV in PV-less animals restored their metabolic rates to the normal level. O₂ consumption of normal animals is significantly augmented by the macerates of CNS and PV, but not by cerebral and pleural ganglia, and body muscles. Reserpine was ineffective in lowering the O₂ uptake of PV-removed animals unlike in normal, intact individuals. The possible implication of a neurohormone originating from PV ganglia controlling whole body O₂ consumption, is discussed.     

Effect of the brain and corpus cardiacum on egg production in Rhodnius prolixus

Using total egg production corrected for size of blood meal as an index of the activity of the corpus allatum (CA), the effects of various surgical manipulations of the neuroendocrine system have been examined. Isolation of the CA from its nervous connections increases egg production well beyond that of a normal insect, thus confirming that the CA is at least partly controlled by inhibitory nerves from the brain. Removal of the corpora cardiaca (CC) reduces the level of this increased egg production, and decapitation anterior to the CC results in a level of egg production that is greater than that found in females decapitated between the CA and CC. Implanting a CC together with a CA into a decapitated female results in a higher egg production than implanting a CA alone. These results demonstrate that an allatotropic influence is exerted by the CC. Experiments designed to examine the role of the brain were inconclusive and did not eliminate the possibility that the allatotropin from the CC originated in the brain.     

Neurohormonal regulation of calcium in the cell

Neurohormone C (NC) is a glycopeptide isolated from bovine hypothalamus, which inhibits Ca-calmodulin (CaM)-dependent cAMP and cGMP phosphodiesterase (PDE) and is a regulator of Ca in the cell. Distribution of [⁴⁵Ca]CaCl₂ in the mitochondria and reticulum (SR) of heart and brain mitochondria and changes of Ca-binding proteins in these organelles under NC influence have been studied in the myocardium before and after isoproterenol-induced necrosis. Intraperitoneal administration of 80–100 mU of PDE inhibitory activity of NC to rats did not cause any noticeable changes in the protein content of intracellular organelles, but altered the affinity of certain proteins to⁴⁵Ca²⁺. This property of NC was especially noticable after isoproterenol necrosis. Necrotic injury of the myocardium induced Ca²⁺ storage in the mitochondria and SR of brain, and decreased the Ca²⁺ concentration in myocardial mitochondria. NC injection to the animals with necrosis was followed by Ca²⁺ release from all the studied organelles.