Studies on the neurosecretory system and retrocerebral endocrine glands of Nezara viridula Linn. (Heteroptera: Pentatomidae)

The neurosecretory system and retrocerebral endocrine glands of Nezara viridula Linn. have been described on the basis of in situ preparations and histological sections employing the paraldehyde fuchsin (PF) and performic acid-victoria blue (PAVB) techniques. In the brain of N. viridula, there are two medial groups–each consisting of five neurosecretory cells which belong to A-type. The lateral neurosecretory cells are absent. The axons of the two groups of medial neurosecretory cells (MNC) compose the two bundles of neurosecretory pathways (NSP) that decussate in the anterodorsal part of the protocerebrum. The two pathways, after the cross-over, run deep into the protocerebrum and deutocerebrum and emerge as NCC-I from the tritocerebrum. The nervi corporis cardiaci-I (NCC-I) of each side which are heavily loaded with NSM terminate in the aorta wall. Thus, the neurosecretory material (NSM), elaborated in the medial neurosecretory cells of the brain, is stored in the aortic wall and nervi corporis cardiaci-I (NCC-I). The NCC-II are very short nerves that originate from the tritocerebrum and terminate in the corpora cardiaca (CC) of their side. Below the aorta, but dorsal to the oesophagus, lie two oval or spherical corpora cardiaca. A corpus allatum (CA) lies posterior to the corpora cardiaca (CC). The corpora cardiaca do not contain NSM; only the intrinsic secretion of their cells has been occasionally observed which stains orange or green with PF staining method. The corpus allatum sometimes exhibits PF positive granules of cerebral origin. A new connection between the corpus allatum and aorta has been recorded. The suboesophageal ganglion contains two neurosecretory cells of A-type which, in structure and staining behaviour, are similar to the medial neurosecretory cells of the brain. The course and termination of axons of suboesophageal ganglion neurosecretory cells, and the storage organ for the secretion of these cells have been reported. It is suggested that the aortic wall and NCC-I axons function as neurohaemal organ for cerebral and suboesophageal secretions.     

Glucagon-like and insulin-like hormones of the insect neurosecretory system.

Aqueous extracts of corpus cardiacum-corpus allatum complexes of the adult tobacco hornworm Manduca sexta produced both glycogenolysis and hypoglycaemia when injected into the larval form of the same species. Application of specific radioimmuno assays to similar extracts showed also that these gland complexes contain both glucagon-like and insulin-like peptides. Further, the partially purified immunoreactive peptides had the expected biological activities. The former decreased the glycogen content of the fatbody and the latter the circulating trehalose levels in recipient animals. These results suggest the existence of hormones in these invertebrates having both biological and structural similarities to vertebrate insulin and glucagon.     

Plasticity in the hypothalamic magnocellular neurosecretory system

Over the past decade or so, plasticity has emerged as an important, quantifiable property of the mammalian hypothalamic magnocellular neurosecretory system. This plasticity has turned out to be genuinely related to normal function in the sense that it is a set of responses to physiological stimulation rather than only the sequelae of insult or injury, and it is generally completely reversible. This latter property, of course, distinguishes it further from the plasticity observed after injury. Four features of this magnocellular system that have been shown to display predictable and reversible intercellular plasticity are reviewed: the relationships between neurons and their associated astrocytic glia at various levels (dendritic somatic and terminal) of the magnocellular elements; the extent of terminal and glial contact with the basement lamina in the neurohypophysis; the type and possible efficacy of synaptic input, and the extent of electrotonic coupling among the magnocellular neurons.     

Ultrastructural changes of the hypothalamo-hypophysial neurosecretory system in the magnesium deficient rats.

A magnesium deficient diet caused transient but marked degenerative changes in the rat hypothalamo-hypophysial neurosecretory system which strongly resembled in many ultrastructural respects those induced by a prolonged administration of aldosterone as previously reported by us. The possible mechanism for this selective alteration in the neurosecretory neurons has been briefly discussed with regard to aldosterone secretion.     

The neurosecretory system of the adult Calliphora erythrocephala

Summary The histology of the corpus cardiacum (c. card.) and the hypocerebral ganglion of Calliphora has been described from sections mainly stained with paraldehyde-fuchsin (PAF) and counterstained with Halmi's mixture. Concurrently the nervous connections of these organs with the neurosecretory system and the stomatogastric nervous system were studied.Neurosecretory material from the medial neurosecretory cells of the brain (m.n.c.) could be traced through the cardiac-recurrent nerve, and passing through the c. card. it was seen to be abundantly present in the wall of the aorta and the two pairs of nerves leaving the c. card.-hypocerebral ganglion complex posteriorly, i.e. the aortic and the oesophageal nerves. However, in some old, fed flies a considerable amount of neurosecretory material was also observed in anastomosing branches of the cardiac-recurrent nerve inside the c. card. Thus storage of neurosecretory material originating in the m.n.c. may take place both in the aorta wall and in the c. card. This observation is relevant to the interpretation of previous experiments of E. Thomsen (1952).The c. card. cells proper (the c.n.c.) were not stained by the PAF, although they are known to be neurosecretory.This work was supported by grants from the Carlsberg Foundation. I am grateful to Professor C. Overgaard Nielsen for laboratory facilities.     

Brain stem innervation of the caudal neurosecretory system

Summary The innervation of the caudal neurosecretory system of Poecilia sphenops (black molly) was studied by use of the retrograde horseradish peroxidase (HRP) method. The structure of the caudal neurosecretory system in this species was well suited for application of HRP procedures. Acrylamide/HRP gel implants were placed in the nucleus of the caudal neurosecretory system. Two neuronal groups which contained HRP filled cells were found in the brain stem. Bilateral projections originate from the dorsal tegmentum of the midbrain and the reticular nucleus of the medulla.Supported by PHS 5429-19-4 and BNS 8206452The authors wish to thank Drs. R. Parsons, S. Freedman and J. Wells for reading this report and A. Angel for photographic assistance