Neural factors in the regulation of oxygen consumption rhythm in the tissues of the scorpion, Heterometrus fulvipes (C. Koch)

Circadian variation in the effect of cephalothoracic nerve mass (CTNM) extract and blood of the oxygen consumption of the isolated hepatopancreas of the scorpion, Heterometrus fulvipes, was studied. Both CTNM extract and blood from 2000 animal cause maximum increase in oxygen consumption. Another maximum increase was also noted at 0800. It is inferred that a chemical factor from the CTNM is responsible for the observed changes in oxygen consumption of hepatopancreas.     

Ultrastructural studies on the secretory cycle of the neurosecretory cells and the formation of herring bodies in the paraventricular nucleus of the rat

Summary The ultrastructure of the neurosecretory cells in the paraventricular nucleus of the normal male rat was studied by electron microscopy during various functional states. Four morphologically distinct types of neurosecretory cells were observed. It appears that they do not represent different classes of cells but different phases of secretory activity of a single cell type. The perikarya of the neurosecretory cells show a definite cycle of formation and transportation of secretory granules. We have designated the phases of this cycle as: (1) phase of synthesis, (2) phase of granule production, (3) phase of granule storage and (4) phase of granule transport. The neurosecretory granules appear to be moved in bulk into the axons, forming a large axonal swelling filled with granules as a result of one cycle in the neurosecretory process. Thus it may be postulated that a secretory cycle in the perikaryon of the neurosecretory cell seems to result in the formation of a Herring body in its axon, and that its content is then conveyed to the posterior pituitary.     

Firing activity of "diapause hormone" producing cells in the male silkmoth,Bombyx mori

Diapause hormone (DH) originally identified to be a factor originating from neurosecretory cells in the suboesophageal ganglion acts on developing ovaries to produce diapause eggs in a female silkmoth, Bombyx mori. A male silkmoth has homologous neurosecretory cells, but little is known of the physiological nature of the cells and actions of their products. We examined the long-term firing activity of putative DH-producing neurosecretory cells and hormonal activity of their products in male pupae that had been experienced different environmental regimens for diapause induction. Firing activity patterns of male labial cells strongly depended on diapause types of pupae: cells in a diapause-type male were active throughout the pupal period, whereas the same cells in a non-diapause-type male were usually inactive during the early two-thirds of the pupal period. A male pupa with electrically active labial cells could induce diapause eggs in a female pupa connected parabiotically to that male. The firing activity of male neurosecretory cells and hormonal action of their products are qualitatively the same as in the female previously examined. We suggest that there is no evident sexual dimorphism in the physiological and biochemical nature of neurosecretory cells producing DH and the amidated peptide DH has different functions in a male.     

An ultrastructural in vitro study on the regulation of neurosecretory activity in the freshwater snail Lymnaea stagnalis (L.) with particular reference to Caudo-dorsal cells

The neurosecretory Caudo-Dorsal Cells (CDC) in the cerebral ganglia of the freshwater pulmonate snail Lymnaea stagnalis produce an ovulation stimulating hormone. Previously it has been shown that neuronal and non-neuronal inputs are involved in the regulation of their activity. The degree of autonomy of these cells has been investigated by studying with morphometric methods the ultrastructure of CDC maintained in vitro. CDC of isolated cerebral ganglia which were cultured for 7 days show a considerable rate of synthesis, transport and release of neurohormone. Apparently these processes can proceed in the absence of neuronal and hormonal inputs from outside the cerebral ganglia. Completely isolated CDC, however, do not show neurosecretory activity in vitro; active Golgi zones, indicating the formation of neurosecretory elementary granules, are absent from such cells. Isolation does not seem to affect general cell functions such as protein synthesis and respiration. It is suggested that a neuronal input, originating within the cerebral ganglia, is necessary for the stimulation of CDC neurosecretory activity. Techniques are described for the isolation and culture of neurosecretory cells of L. stagnalis.     

Brain neurosecretory cell and ecdysiotropin activity of the non-diapausing,pre-diapausing and diapausing southwestern corn borer, Diatraea grandiosella Dyar

The location and number of brain neurosecretory cells were studied in the larval southwestern corn borer. One posterior, two median and two lateral groups of paraldehyde-fuchsin positive cells were found in each cerebral hemisphere.Implantation of brain parts containing different groups of neurosecretory cells revealed that the median neurosecretory cells contained higher ecdysiotropic activity than the other cell groups. In vitro culture of ecdysial gland with brain or brain-parts extract showed also that the median neurosecretory cells contained much higher ecdysiotropic activity than other neurosecretory cells. To estimate the ecdysiotropic activity of pre-diapausing 6th instar larvae, their brain or brain extract was incubated in culture medium containing an ecdysial gland from a day-4 last-instar non-diapausing larva. Data showed that the ecdysiotropic activity in the pre-diapausing larvae was far lower than in non-diapausing and diapausing larvae.     

Rhythmic firing activity of median neurosecretory cells of the subesophageal ganglion and its coordination with periodically occurring abdominal movements in the tenebrionid [corrected] beetle, Zophobas atratus [corrected

An immunocytochemical study using an FXPRLamide antiserum revealed three clusters of neurosecretory cells along the midline of the subesophageal ganglion of the tenebrionid [corrected] beetle, Zophobas atratus [corrected] Firing activity of five pairs of neurosecretory cells in the mandibular and maxillary clusters was recorded from an axonal tract of the cells throughout the entire pupal period. The population of neurosecretory cells became active during the middle and late pupal periods, and they usually discharged clusters of action potentials at an interval of 30-90 min. The ultradian activity rhythm of the cells in Z. atratus [corrected] was related to a periodic discharge of electrical activity in developing flight muscles, as has been observed in the homologous cells in the silkmoth, Bombyx mori. Furthermore, the rhythmic activity of the neurosecretory cells in the mealworm was closely synchronized with periodically occurring rhythmic abdominal movements that caused extracardiac hemocoelic pulsations, which facilitate hemolymph circulation and exchange of respiratory gases. The results suggest that the secretory products of the neurosecretory cells may activate and/or orchestrate physiological mechanisms supporting morphogenesis during metamorphosis.     

Cholinesterases in the hypothalamo-hypophysial neurosecretory system of the White-crowned Sparrow,Zonotrichia leucophrys gambelii

Summary The distribution of cholinesterases in hypothalamo-hypophysial neurosecretory system of the White-crowned Sparrow has been examined histochemically. The perikarya of the neurosecretory cells of the paraventricular and supraoptic nuclei have a high acetylcholinesterase activity. Acetylcholinesterase activity also occurs in the cells of the infundibular nucleus. The proximal parts of the axons of the cells of the neurosecretory and infundibular nuclei have strong acetylcholinesterase activity and weak non-specific cholinesterase activity. In the median eminence, the activity of acetylcholinesterase is strongest in the palisade layer. In the pars nervosa, there is definite, although weak, acetylcholinesterase activity.This investigation was supported by grants from the National Institutes of Health to Professor Farner (B-1353) and to Dr. Kobayashi (A-3678).     

A comparative analysis of the effect of an analog of vasopressin on functionally different neurons in the grape snail

Application of desglycine-argininvasopressin (DG-AVP) differently influenced different types of cells of snail isolated central nervous system. In neurosecretory cells an increase of spontaneous impulse activity took place and, as a rule, bursts of impulses appeared, most often of synaptic origin, excluding PPa1 neurones and one of the neurosecretory cells of the left parietal ganglion. The increase of the bursts activity in these cells was based on the increase of the amplitude of membrane potential waves. Under the influence of neurosecretory cells system activation, EPSPs frequency and amplitude in secondary-sensory neurones increased, which led to a greater probability of the action potentials appearance. At prolonged action the spontaneous EPSPs in these cells began to group in bursts. Excitability and membrane resistance of these cells remained unchanged. DG-AVP had no influence on primary-sensory neurones and motoneurones.     

Histological studies of the neurosecretory and retrocerebral complex of the water beetle,Hydrophilus olivaceus Fabr. (Insecta,Coleoptera)

The neurosecretory cells (NSC) in the breeding phases show gigantic sized droplets. NSC show two peaks of activity in females at midnight and at 9 A.M., while a single peak occurs in males between midnight and 3 A.M. Light has a triggering effect on the neurosecretory release. The corpus cardiacum is the main neurohaemal organ. It has a nerve core formed by the nervi corpus cardiacum I and II, which is surrounded by the glandular region. Intrinsic secretory chromophilic cells and chromophobic cells occur randomly. Aorta is probably not a storage-release centre. The corpora allata are lobulated structures, showing cyclical activity which is correlated with egg-maturation. No neurosecretory material occurs in allatum.     

Interactions of the ring gland, overies, and juvenile hormone with brain neurosecretory cells in Musca domestica.

The staining intensity (median neurosecretory cell index) of the median neurosecretory cells (MNC) in Musca domestica increased as oögenesis progressed from stages 2 to 10. The amount of neurosecretory material within the MNC was dependent upon the presence of ovaries with developing or mature follicles. Ovariectomized flies had a median neurosecretory index that was 50 per cent less than that of control flies with mature eggs. In addition, we found that ring gland removal decreased the staining frequency of three different neurosecretory cell groups; increased staining frequency in another; increased the amount of neurosecretory material within the MNC fibre tract; increased the cytoplasmic area of types A and A′ MNC. Furthermore, neither the juvenile hormone analogue nor the ring gland had a direct effect on the median neurosecretory cell index but did influence neurosecretory activity indirectly by activating the ovaries. We hypothesize that an ovarian hormone—the oöstatic hormone—regulates either the release from or synthesis of neurosecretory material within the MNC.     

Histology, histochemistry, and ultrastructure of neurosecretory cells in the optic lobe of the cockroach, Periplaneta americana

In the region of the distal optic chiasma of each optic lobe of Periplaneta americana, there is a group of about 120 monopolar neurosecretory cells. These cells do not stain with paraldehyde fuchsin but remain acidophilic after oxidation. They stain red or sometimes indigo with the azan technique. Histochemically, the neurosecretory material is positive for protein and the amino acids tryptophan and arginine but negative for 1, 2-glycols and strongly acidic groups. At the ultrastructural level, the cytoplasm of the cells contain many elementary neurosecretory granules 100 to 170 nm in dia. The cells also contain well-developed Golgi bodies and endoplasmic retieulum. The axons from these cells run toward the interior of the optic lobe. In this region, axons containing dense granules (mean diameter 70 nm) and synaptic vesicles synapse onto the axons from the neurosecretory cells. The neurosecretory axons then cross over to the anterior side of the optic lobe and run towards the brain. The function of these neurosecretory cells is unknown, but they may be involved with photoperiodically controlled activity rhythms.     

Effect of apoptotic proteins on function of rat vasopressin-and dopaminergic hypothalamic neurons

To study character of effect of apoptotic signal proteins on activities of neurosecretory cells and neurons of rat hypothalamus, pharmacological inhibitors of proapoptotic protein p53 Pifithrin-α and antiapoptotic protein Bcl-2 HA14-1 were injected into hypothalamus. Activation of vasopressinergic neurosecretory cells at administration of the blocker Bcl-2 HA14-1 was shown: there were observed an increase of vasopressin mRNA in neurons of hypothalamic supraoptical and paraventricular nuclei, a decrease of the immunoreactive vasopressin content in posterior pituitary, and reduction of diuresis. Inactivation of p53 inhibited release of vasopressin from hypothalamus cell bodies, which is indicated by an elevated content of immunoreactive vasopressin in neurosecretory cell bodies with its unchanged synthesis, a decrease of the neurohormone content in the posterior pituitary, and an increase of diuresis rate. Activation of vasopressinergic neurons of the suprachiasmatic nucleus was also shown. Administration of the blocker of Bcl-2 has been revealed to decrease functional activity both of dopaminergic neurons (zona incerta) and of dopaminergic neurosecretory cells (arcuate nucleus), in which a decrease of the tyrosine hydroxylase content was observed. The p53 inactivation also led to a decrease of activity of dopaminergic neurosecretory cells of arcuate nucleus, whereas activity of the neurons of zona incerta did not change. Thus, it has been shown that a change of the apoptotic protein content in vasopressinergic and dopaminergic neurons and neurosecretory cells leads to a change of their functional activity, the character and possibly mechanisms of effects of apoptotic proteins on activities of vasopressin-and dopaminergic cells being different.     

Changes in the hypothalamo-hyophyseal neurosceretory system of mammals following pituitary stalk transection and hypophysectomy]

Hypophysectomy and pituitary stalk section result in dramatic morpho-functional changes in all parts of mammalian hypothalamo-hypophyseal neurosecretory system. Reorganization of the hypophyseal stalk consists of several interconnected but differing in time processes. Simultaneously with the developing traumatic changes (degeneration of the sectioned neurosecretory fibers, secretory disorders) proliferation of pituicytes with characteristic phagocytic activity is observed. A little bit later, intensive mitotic division of endothelial cells and capillary formation piercing the stalk periphery begins. At the same time, a new way for blood outflow from the capillaries of the primary portal plexus into the synuses of the brain pias is restored. Degenerated neurosecretory fibers are gradually substituted by regenerating fibers forming a dense network in heavily vascularizated stalk parts. As differentiation of endothelial cells and regeneration of neurosecretory fibers procede, axovasal contacts are gradually forming. At that time the hypophyseal stalk begins functioning as a neurohumoral organ but morpho-functionally less perfect than the posterior hypophyseal lobule. In the median eminence of the operated animals, unlike the intact ones, neurosecrete is accumulating around the capillaries of the portal plexus. Mechanical damage of neurosecretory fibers during the operation results in degeneration of a greater number of neurosecretory cells in the supraoptical and paraventricular nuclei. Preserved cells have an increased functional activity because of neurohormonal deficiency in the organism. As a result of the structural changes mentioned, diabetes mellitus develops, subsiding gradually with time course.     

Morphofunctional basis of neurosecretory cell plasticity

Mass accumulation and storage of neurosecretory products are typical only for nonapeptidergic elements, as it has been shown by our study of the structure and function in neurosecretory cells of different nature. All liberinergic, statinergic and monoaminergic neurosecretory cells keep constancy in the state of high functional activity of extrusive processes at normal conditions. Morpho-functional features of these elements principally differ from those of nonapeptidergic neurosecretory cells, which are characterized by remarkable secretory cycles. The extremely large size of elementary secretory granules, maximum development of the Herring bodies, various modes of secretion, secretory and extrusive cycles in neurosecretory function, and massive accumulation of neurosecretory granules occurring in neurosecretory terminals finally, all these characters are considered to be the primary features of a high plasticity of the nonapeptidergic neurosecretory cell. A high reactivity of nonapeptidergic neurosecretory cells has been demonstrated here by the quantitative ultrastructural research of the dynamics of functional activity of neurosecretory terminals at both experimental and physiological stressful states. The highest plasticity of nonapeptidergic neurosecretory cells compared to all other neurosecretory cell types may be provided by their ability to restore the initial law level of functional activity, referred to as "functional reversion".     

Effect of apoptosis proteins on function of vasopressin- and dopaminergic hypothalamic neurons

To study character of effect of apoptosis signal proteins on activities of neurosecretory cells and neurons of rat hypothalamus, pharmacologic inhibitors of proapoptotic protein p53 Pifithrin-alpha and antiapoptotic protein Bcl-2 HA14-1 were injected into the hypothalamus. Activation of vasopressinergic neurosecretory cells at administration of the blocker Bcl-2 HA14-1 was shown: there were observed an increase of vasopressin mRNA in neurons of hypothalamus supraoptical and paraventricular nuclei, a decrease of the immunoreactive vasopressin content in posterior pituitary, and reduction of diuresis. Inactivation of p53 inhibited release of vasopressin from hypothalamus cell bodies, which is indicated by an elevated content of immunoreactive vasopressin in neurosecretory cell bodies with its unchanged synthesis, a decrease of the neurohormone content in the posterior pituitary, and an increase of diuresis rate. Activation of vasopressinergic neurons of the suprachiasmatic nucleus was also shown. Administration of the blocker Bcl-2 has been revealed to decrease functional activity both of dopaminergic neurons (Zona Incerta) and of dopaminergic neurosecretory cells (arcuate nucleus), in which a decrease of the tyrosine hydroxylase content was observed. The p53 inactivation also led to a decrease of activity of dopaminergic neurosecretory cells of arcuate nucleus, whereas activity of the proteins Zone Incerta did not change. Thus, it has been shown that a change of the apoptotic protein content in vasopressinergic and dopaminergic neurons and neurosecretory cells leads to a change of their functional activity, the character and possibly mechanisms of effects of apoptotic proteins on activities of vasopressin- and dopaminergic cells being different.     

Monoamine oxidase in the hypothalamo-hypophysial region of the teleosts,Anguilla japonica and Oryzias latipes

Summary Distribution of monoamine oxidase (MAO) was histochemically examined in the hypothalamo-hypophysial region of the eel (Anguilla japonica) and the medaka (Oryzias latipes) with a modified Glenner's tryptamine-tetrazolium method. The hypothalamic neurosecretory cells showed very weak MAO activity in their perikarya. MAO-positive fibers were present in close contact with the neurosecretory cells, suggesting that monoaminergic fibers participate in the control of neurosecretory cell activity. The nucleus lateralis tuberis (NLT) contained cells exhibiting strong MAO activity. These cells must be monoaminergic neurons.In the anterior region of the neurohypophysis of both eel and medaka, two bundles of MAO-positive fibers originating from the NLT proceed down along each side of the third ventricle into the pars distalis. This suggests that monoaminergic neurons of the NLT are involved in the release of hormones from the pars distalis. In addition to these tracts, numerous MAO-positive fibers proceed backward from the post-optic area and end around the blood capillaries located between the neurohypophysis and the pars intermedia in both species.I wish to express my gratitude to Prof. H. Kobayashi for his valuable advice during the course of this study. I am indebted to Prof. S. Uchida, Ocean Research Institute, University of Tokyo, for supplying the eels.     

Retinal illumination produces synaptic inhibition of a neurosecretory organ in the crayfish,pacifastacus leniusculus (Dana)

We have identified a cluster of neurosecretory cells in the crayfish eyestalk that possess dendrites in the second optic neuropil (Medulla) and project axons to the first optic neuropil (Lamina). Illumination of the ipsilateral retina produces a synaptic inhibition of these cells that is mimicked by iontophoresis of gamma-aminobutyric acid within the medullary neuropil. The neurosecretory nature of the cells, the efferent projection of their axons, and the strong inhibition of their spiking activity upon retinal illumination suggest that they may be involved in the feedback control of dark adaptation and/or circadian changes in visual sensitivity.     

A Neurosecretory Phenomenon in Some Cerebral Nervous Cells of the Land Snail

Some cerebral neurosecretory cells of the land snail Helix aspersa maxima have been studied using light microscopy combined with image analysis. The amount of neurosecretion varies during the course of the day, displaying a peak at 22:00 GMT. This peak is in phasis with the maxima of the locomotor and food-intake activities recorded by means of a video apparatus.     

Ontogenetic Development of the Caudal Neurosecretory System in the Chum Salmon, Oncorhynchus keta, with Regard to Its Ultrastructural Changes and with Relation to Neuropeptide Y-immunoreactive Fibers

The ontogeny of the caudal neurosecretory cells (Dahlgren cells) in the caudal spinal cord of the chum salmon, Oncorhynchus keta, was examined by conventional electron microscopy and with immunohistochemistry for urotensins (U) and neuropeptide Y (NPY). The precursors of the Dahlgren cells first appeared as agranular ovoid cells in the caudal region of the neural tube of 40-day-old embryos about one week before hatching. The occurrence of cytoplasmic granules in the immature Dahlgren cells became evident by the 14th day after hatching. At this moment, the U-positive reaction was merely demonstrated in some of the granules. Close association of NPY-positive fibers with the caudal neurosecretory structures was recognizable in 1-month-old larvae. Thus, it is apparent that the salmon Dahlgren cells start their secretory activity (production of the secretory granules) in early larval stages and that, thereafter, NPYergic afferent innervation of the caudal neurosecretory system becomes evident.