Median Neurosecretory Cells Research Articles

Studies on the initiation of growth and moulting in Locusta migratoria migratorioides R. & F.—III. The role of the frontal ganglion

A brief review is given of some of the functions hitherto attributed to the frontal ganglion. An account is given of its gross anatomy and histology. The posterior and anterior pharyngeal nerves have been traced to the surface of the gut. The posterior pharyngeal nerves end on the anterior surface of the pharynx in two groups of three sensory organs dorso-lateral to the midline. Histologically these cells resemble the stretch receptors figured by Finlayson and Lowenstein, and this functions is provisionally accepted for them. Further studies were made on the effect of removal of the frontal ganglion at different times during the instar on the growth and moulting of the locust. Animals in which the frontal ganglion had been removed at 0, 12, and 24 hr showed a slight increase in weight and then remained constant until they died; they showed no sign of new cuticle formation at autopsy. Removal at 33 hr resulted in no increase in weight but at autopsy new cuticle formation was found under the old. The locusts did not attempt to ecdyse. Removal at 72 hr resulted in the loss of weight following the operation not being recovered, whereas at 96 hr the animals lost weight until they died some 61 hr later. In both the latter cases new cuticle under the old was found at autopsy. Those 96 hr old had made some attempt to ecdyse but they were unsuccessful due to wound adhesions. Cutting the frontal connectives had the same effect as the removal of the frontal ganglion. For unknown reasons it was always accompanied with a far higher mortality than the seemingly more severe operation of the removal of the frontal ganglion. Cutting one frontal connective had no adverse effect on the further growth and moulting of the locusts. The separation of the frontal ganglion from the surface of the foregut, which involved the cutting of the anterior and posterior pharyngeal nerves, resulted in the complete cessation of growth and moulting in the locust. Comparisons were made of the oxygen consumption of normal, starved, and frontal ganglionectomized insects. No significant difference was found between the operated and the normal locusts in oxygen consumption expressed as mm 3/mg. Starved insects showed a significant drop in oxygen consumption. In time the oxygen consumption of operated insects remained constant. It is concluded that the frontal ganglion forms a link in the passage of nervous impulses originating from the stretch receptors of the pharynx and passing via the posterior pharyngeal nerves, frontal ganglion, and frontal connectives to the brain where they may influence the medial neurosecretory cells, and possibly also via the recurrent nerve and hypocerebral ganglion to the corpora cardiaca.

Influence of Neurosecretory Cells and of Corpus Allatum On Intestinal Protease Activity in the Adult Calliphora Erythrocephala Meig

ABSTRACT The protease activity of the adult Calliphora female measured on the first 5 days after emergence was found to be highly influenced by the diet, the activity of females fed on sugar, water and meat (meat-flies) being much higher than that of females fed only on sugar and water (sugar-flies). The development of the enzyme(s) was found to be controlled by the medial neurosecretory cells (m.n.c.), the mean protease activity of females deprived of their m.n.c. only amounting to one-quarter to one-third of the maximum values for the meat-flies. Implantation of corpora cardiaca-allata (presumably containing m.n.c. hormone) into females without m.n.c. raised the protease activity of these significantly, showing that the influence of the implanted organs must be hormonal. The corpus allatum was found to have a certain, if minor, effect on the protease activity. It is concluded that in Calliphora the eating of meat exerts its effect on the production of protease mainly indirectly by causing liberation of m.n.c. hormone into the blood. As proteases are themselves proteins, the effect of the m.n.c. hormone on the production of proteolytic enzymes by the gut cells must be regarded as an effect on the specific protein synthesis of these cells. There is some evidence that the m.n.c. hormone might be involved in the regulation of protein synthesis in general.

BEHAVIORAL ASPECTS OF PROTEIN INGESTION BY THE BLOWFLY PHORMIA REGINA MEIGEN

There is a difference in the pattern of protein feeding by the two sexes of the blowfly Phormia regina Meigen. Males, whether mated or not, gradually increase their intake from the time of emergence until the fourth to eighth day. There after little protein is taken. The pattern is similar for virgin females, but the volume ingested is greater. Mated females increase their protein intake after each batch of eggs is laid. If females are denied protein at times when the intake would normally be great, they show a decided preference for protein over carbohydrate in a choice situation. Choice is mediated by the contact chemoreceptors; odor is not a factor. The peak in protein ingestion that occurs after emergence is not altered by removal of the ovaries, corpus allatum, or medial neurosecretory cells. Subsequent peaks are abolished by any procedure that prevents egg development. Changes in feeding behavior are correlated with changes in protein levels which in turn are related to hormonal and reproductive cyc...

The Relationships Between Nutrition, Hormones and Reproduction in the Blowfly Calliphora Erythrocephala (Meig.)

ABSTRACT A study has been made of the effects of removal of ovaries, copora allata (c.a.) and median neurosecretory cells (m.n.c.) upon the selection by female blowflies of carbohydrate (sugar in water) or ‘protein’ (Mannite in milk). Extirpation of the ovaries resulted in high carbohydrate-low protein selection and in hypertrophy of the c.a. Extirpation of the c.a. resulted in low carbohydrate selection. Extirpation of both ovaries and c.a. resulted in low carbohydrate selection. These and other results suggest that selection is independent of direct ovarian control, but that the ovaries influence selection in that they utilize the ingested foods and thus bring about the succession of feeding cycles. The c.a., whose volume (activity?) changes cyclically during each cycle of reproduction, appears to control the fluctuations in carbohydrate consumption. The m.n.c. seem to be necessary for the ingestion of ‘protein’ and for the activity of the c.a. Reproductive cycles tend to overlap. The succeeding cycle in a gravid female must be taken into consideration when events are being related to reproduction.

Neurosecretion in the Brain of the Larva of the Sheep Blowfly, Lucilia caesar

ABSTRACT Six groups of neurosecretory cells were identified in the brain of the mature larva of Lucilia caesar. Five of these groups belonged to the category of medial neurosecretory cells and one to that of lateral neurosecretory cells. The groups differ in position, cell size, staining characteristics, and sequence of activity. It is apparent that only some of the groups are concerned with the process of thoracic gland activation, though all function during metamorphosis. At least one group, not concerned in thoracic gland activation in the non-diapause larva, is continually active during diapause.

Neurosecretion and intestinal proteinase activity in an insect, Calliphora erythrocephala Meig.

SOME years ago it was suggested that the medial neurosecretory cells of the brain of Calliphora erythrocephala in some way influence protein metabolism, and especially the synthesis of protein. This hypothesis was based on the fact that in females deprived of these cells, the ovaries, accessory glands, corpora allata and œnocytes, organs which normally increase considerably in size during the early period of adult life, developed to a limited extent only although the flies were given an adequate diet of meat, sugar and water1,2. Furthermore, in flies fed on sugar and water only, but no meat, the organs mentioned were very nearly the same size as in females deprived of their medial neurosecretory cells. Therefore it seemed likely that in the absence of the hormone from the medial neurosecretory cells for some unknown reason the fly was unable to utilize the ingested meat. Observations proved that the flies did in fact eat some of the meat offered to them.

The neurosecretory system of the fruit flyChjætodacus Cucurbitæ coq.

1. The neurosecretory system of the adult Chaetodacus Cucurbitae (Trypetidae: Diptera) consists of the cerebral, thoracic and abdominal centres of secretory neurons. 2. The cerebral neurosecretory centres consist of the median and lateral neurosecretory cells of the pars intercerebralis. The cells show characteristic tintorial properties when stained in chrome-haematoxylinphloxin and in Azan, recalling the nature of similar cells in other insects. 3. The axons of the median cerebral neurosecretory cells are fairly long, and the nervi corporis cardiaci and corpus cardiacum show granules similar to those observed in the cytoplasm and axons of the cells. 4. The thoracic ganglion shows a more conspicuous set of neuro-secretory cells. They consist of an anterior, lateral anterior, lateral posterior and posterior cell clusters, which in the first three are paired. 5. The single abdominal ganglion contains a few neurosecretory cells also showing characteristic tintorial properties. 6. The nerve emerging from the abdominal ganglion and going to the gut shows blue granules traceable from the neurosecretory cells at the posterior end of the ganglion. 7. Phase contrast observations of the cells show that the neurosecretory cells of the fly have a general structure with prominent cytoplasmic products in the form of dark granules and large and small spheroids and globules. 8. Measurements of the thoracic neurosecretory cells, which forms the larger cells of the system, have been given.

On the Yellow Pigments Found in the Viscera in Cases of Arsenical Poisoning

<h3>Abstract</h3> Appropriate nutritional intake is essential for organismal survival. In holometabolous insects such as <i>Drosophila melanogaster</i>, the quality and quantity of food ingested as larvae determines adult size and fecundity. Here we have identified a subset of dopaminergic neurons (THD’) that maintain the larval motivation to feed. Dopamine release from these neurons requires the ER Ca²⁺ sensor STIM. Larvae with loss of STIM stop feeding, whereas expression of STIM in THD’ neurons rescues feeding, growth and viability of STIM null mutants. Moreover STIM is essential for maintaining excitability and release of dopamine from THD’ neurons. Optogenetic stimulation of THD’ neurons identified connectivity to neuropeptidergic cells, including median neuro secretory cells that secrete insulin-like peptides. Loss of STIM in THD’ cells alters the developmental profile of specific insulin-like peptides including ilp3. Loss of ilp3 partially rescues STIM null mutants and inappropriate expression of ilp3 in larvae affects development and growth. In summary we have identified a novel STIM-dependent dopamine-ILP circuit that regulates developmental changes in larval feeding behaviour. <h3>Author summary</h3> The ability to feed appropriately when hungry is an essential feature for organismal survival and is under complex neuronal control. An array of neurotransmitters and neuropeptides integrate external and internal signalling cues to initiate, maintain and terminate feeding. In adult vertebrates and invertebrates dopamine serves as a reward cue for motor actions, including feeding. Larvae of holometabolous insects, including <i>Drosophila melanogaster</i>, feed and grow constantly followed by gradual cessation of feeding, once sufficient growth is achieved for transition to the next stages of development. Here we identified a subset of larval dopaminergic neurons in <i>Drosophila melanogaster</i>, activity in which maintains continuous feeding in larvae. By analysis of a null mutant we show that these neurons require the Stromal Interaction Molecule (STIM) an ER Ca²⁺ sensor, to maintain excitability. In turn they modulate activity of certain neuropeptidergic cells. Among these are the median neurosecretory cells (MNSc) that synthesize and secrete insulin-like peptides including ilp3. The identified dopaminergic neurons dysregulate the normal pattern of larval ilp3 expression leading to premature cessation of feeding and growth. Overall, our study identified a simple dopamine-insulin feeding circuit whose manipulation could be useful for model organism studies related to feeding disorders, obesity and diabetes.