Ultrastructural analysis of the dorsal body gland of the terrestrial snail Megalobulimus abbreviatus (Becquaert, 1948) / Análise ultraestrutural da glândula corpo dorsal do caracol terrestre Megalobulimus abbreviatus (Becquaert, 1948)

The ultrastructure of the reproductive gland, dorsal body (DB), of Megalobulimus abbreviatus was analysed. Electron microscope immunohistochemistry was used to detect FMRFamide-like peptides in the nerve endings within this gland. Nerve backfilling was used in an attempt to identify the neurons involved in this innervation. In M. abbreviatus, the DB has a uniform appearance throughout their supraesophageal and subesophageal portions. Dorsal body cells have several features in common with steroid-secreting gland cells, such as the presence of many lipid droplets, numerous mitochondria with tubular cristae and a developed smooth endoplasmic reticulum cisternae. Throughout the DB in M. abbreviatus numerous axonal endings were seen to be in contact with the DB cells exhibiting a synaptic-like structure. The axon terminals contained numerous electron-dense and scanty electron-lucid vesicles. In addition, the DB nerve endings exhibited FMRFamide immunoreactive vesicles. Injection of neural tracer into the DB yielded retrograde labelling of neurons in the metacerebrum lobe of the cerebral ganglia and in the parietal ganglia of the subesophageal ganglia complex. The possibility that some of these retrograde-labelled neurons might be FMRFamide-like neurons that may represent a neural control to the DB in M. abbreviatus is discussed.

Foi analisada a ultraestrutura da glândula reprodutiva corpo dorsal (CD) de Megalobulimus abbreviatus. Imunoistoquímica para microscopia eletrônica foi utilizada para detectar peptídeos relacionados ao tetrapeptídeo FMRFamida nas terminações axonais existentes nessa glândula. Foi utilizada marcação neuronal retrógada com o intuito de localizar os neurônios envolvidos nesta inervação. O CD de M. abbreviatus possui um aspecto uniforme em toda sua extensão, tanto na porção supraesofágica como subesofágica. As células do CD possuem várias características de glândulas esteroidogênicas, tais como a presença de inúmeras gotículas lipídicas, numerosas mitocôndrias com cristas tubulares e cisternas bem desenvolvidas de retículo endoplasmático liso. Por toda a extensão do CD de M. abbreviatus foram encontradas numerosas terminações axonais fazendo contatos estruturalmente semelhantes a sinapses com as células do CD. As terminações axonais continham grande número de vesículas eletrodensas e esparsas vesículas eletrolúcidas. As terminações axonais no CD apresentavam vesículas com conteúdo imunorreativo à FMRFamida. A injeção de traçador neural no CD resultou em marcação retrógrada de neurônios no metacérebro dos gânglios cerebrais e nos gânglios parietais do complexo ganglionar subesofágico de M. abbreviatus. É discutida a possibilidade de que estes neurônios identificados por marcação retrógrada possam representar a via de controle neural do CD de M. abbreviatus, cujo mediador químico seria um neuropeptídeo relacionado à FMRFamida.

Fmrfamide-like immunoreactive midgut endocrine cells in different castes of the bee Melipona quadrifasciata anthidioides (apidae; meliponini)

FMRFamide-like immunoreactive cells have been identified in almost all insect species studied. However, the functions of this peptide are still unknown, although several studies have suggested that FMRFamide may play a role in controlling peristalsis, digestion, development and reproduction in insects. Differences in the number, morphology, and distribution of FMRFamide-like cells have been observed among insects. Social bees are characterized by the presence of well-defined castes, each with a different behavior, energy demand and nutrient consumption. In this work, we used immunofluorescence to assess the number, morphology,and distribution of FMRFamide-like immunoreactive cells in different castes of the bee Melipona quadrifasciata anthidioides. These immunoreactive cells were observed only in the posterior region of the midgut, whereas FMRFamide-immunoreactive nerve fibers were more abundant in the fore-and hind-midgut boudary . However, htere were no differences in the number and distribution of FMRFamide-like cells among the castes. This localization of immunoreactivity may indicate that the nervous system controls the passage of food through the cardiac and pyloric valves, while the passge of food through the midgut is controlled by midgut endocrine cells. The number, morphology and distribution of midgut FMRFamide-like cells were not influencend by behavior, feeding habits, cast, or sex in this species.

Peripheral nerve connections influence the appearance of neurosecretary material in neural sheath of ventral ganglion of the fly Sarcophaga bullata: an immunocytochemical study.

This study examined the role of the brain and peripheral connections with the target organs in the appearance of neurosecretary material within the dorsal neural sheath of the ventral ganglion of the fly S. bullata. Specifically, the accumulation of the neuropeptide FMRFamide (the neurosecretary material) was examined by immunocytochemistry. Immunoreactions were performed on: (1) a normal intact ventral ganglion, (2) an isolated ventral ganglion that was cultured in vivo, and (3) a ventral ganglion that was isolated by transection from the brain, but retained its peripheral nerve connections. The results demonstrate that (a) the neurons of the ganglia survive and exhibit FMRFamide immune reaction independent of their peripheral connections, and (b) the accumulation of neuropeptide in the dorsal neural sheath is controlled by intact peripheral nerve connections with the ganglion. It is suggested that in the absence of their peripheral connections, the axons of FMRFamide immunoreactive neurons fail to invade the neural sheath resulting in the accumulation of neurosecretary material.

Effect of neuropeptide FMRFamide on immobile behavior in rats.

In the forced swimming induced immobility test, neuropeptide FMRFamide (5-20 micrograms) administered via the intracerebroventricular (icv) route, prolonged immobilization period in rats. On the other hand, immunoneutralization of endogenous FMRFamide by its antiserum (1 microliter, icv) significantly reduced the duration of immobility. Intraperitoneal administration of amitriptyline (3 mg/kg), imipramine (5 mg/kg), fluoxetine (5 mg/kg) or amphetamine (0.5 mg/kg) attenuated FMRFamide-induced prolongation of immobility. Biochemical studies indicated that FMRFamide treatment had significant effects on rat brain monoamines. FMRFamide significantly lowered the brain levels of 5-hydroxytryptamine and norepinephrine in the doses that prolonged the immobility. These results that FMRFamide prolongs the duration of immobility, perhaps by modulating the release of neurotransmitters like 5-hydroxytryptamine and/or norepinephrine.

Stimulation of gastric acid secretion by central administration of FMRFamide in rats.

The possible role of centrally administered tetrapeptide FMRFamide (Phe-Met-Arg-Phe-NH2) on gastric acid secretion in pylorus ligated rats was investigated. Intracerebroventricularly administered FMRFamide stimulated the gastric acid secretion in a dose-dependent manner. This stimulatory effect was abolished by vagotomy and atropine pretreatment. The presence of FMRFamide in rat brain and the ability of FMRFamide to stimulate gastric acid secretion suggest that FMRFamide plays a physiological role in brain modulation of gastric acid secretion.