Ultrastructure of the protocerebral neurosecretory cells of larval Galleria mellonella, in situ and after culture of the brain in vitro

Three major groups of neurosecretory cells are described in the larval brain of Galleria mellonella at two different times during the last larval instar and in larval brains after 72 hr of culture in vitro. The medial group in vivo consists of four distinct neurosecretory cell types, based on characteristic size and morphology, while the posterior and lateral groups each contain a single distinct type of neurosecretory cell. Morphological differences between the same neurosecretory cells at the different times during the last instar are most apparent in the lateral L-1 cells and in the medial M-2 cells, where pleiomorphism is particularly evident in the size, density and accumulations of neurosecretory granules. The only neurosecretory cells in which apparent synthesis of neurosecretory granules is still observed after culture of the brain in vitro are the medial M-2 cells. The other neurosecretory cell types show no accumulation of neurosecretory granules nor new synthesis of neurosecretory material, but are similar to neurosecretory cells in the brain in vivo in all other respects. The morphology of the neurosecretory cells in the larval brain in vivo and in vitro is discussed in relation to their appearance at the light microscopic level and to a known neurohormonal function of the brain which is maintained during 72 hr in vitro.     

鲫鱼尾部神经分泌系统显微和亚显微结构的季节性变化

鲫鱼尾部神经分泌系统的神经分泌细胞和它的轴突中可观察到各种不同电子密度的颗粒。在性腺各个不同的发育阶段,该系统的分泌物具有累积、充满、释放和恢复这样一种周期性变化,由此说明鲫鱼的尾部神经分泌系统和它的生殖有关。     

Etude histologique,histochimique et ultrastructurale de la pars intercerebralis chez Locusta migratoria L. (Orthoptere)

Summary A histological, histochemical and ultrastrucutral study of the pars intercerebralis (PI) has been made in Locusta migratoria. The acellular neural lamella is made up of an elastic tissue and collagen fibrils. The cells of the perilemma contain numerous lysosome structures and lipid granules.Three different types of neurosecretory cells (NSC A, B and C) have been distinguished in the PI associated with giant neurons.The cells termed A and B seem not to have an activity cycle during the two last larval instars. At the moment of sexual maturity the NSC A show an important accumulation of neurosecretory material and their number increases at the expense of the NSC B. The NSC A, which are characterized by a highly developped endoplasmic reticulum, contain numerous secretory granules which appear to be individualized in the Golgi complex in three different ways. The NSC B, with a reduced endoplasmic reticulum and an almost quiescent Golgi complex, contain abundant lysosome structures and more seldom some neurosecretory granules. In fact, the study of the fine structure shows different intermediate types, linking in a continuous way typical A cells and typical B cells. NSC A and NSC B might correspond to two opposed stages of secretory activity of one single cell type: the A cell representing the activity stage and the B cell the quiescent stage.NSC C show an accumulation of their neurosecretory products in relation to metamorphosis and sexual maturity. Ultrastructural evidence confirms their neurosecretory activity.A mode of regulating neurosecretion in NSC A and B by internal catabolism of the secretion and formation of lysosome like structures is discussed in the present paper.The giant neurons, which are surrounded by a glial envelope (trophospongium), contain several dense granules originated from Golgi complex.     

Sequence of ultrastructural changes induced by activation in the posterior neurosecretory cells in the brain of Rhodnius prolixus with special reference to the role of lysosomes.

The posterior neurosecretory cell (PNC) group in the brain of Rhodnius prolixus is composed of five ultrastructurally identical cells. The PNC were examined in the unfed fifth instar and at seven stages (from 15 min to 14 days) after activation was initiated by feeding. Each stage examined revealed successive changes in morphology which can be related to the synthesis, maturation, storage and transport of neurosecretory material. It is suggested, in particular, that the lysosomal system (dense bodies and multivesicular bodies) may play a role in the maturation of the secretory granules.     

Methylxanthine inhibition of neurosecretion in the brain and corpus cardiacum of Cecropia

The fine-structure of the median neurosecretory cells and corpora cardiaca of the Cecropia silkmoth during the first 7 days after transfer from cold conditions to room temperature was compared to that of similar animals whose development was arrested with aminophylline. The major difference observed was the failure of the intrinsic secretory cells of the corpus cardiacum to degenerate in the arrested animals. This failure to degenerate coincides with the expected period of brain hormone release. After long periods of arrest, the medial neurosecretory cells and their axons became distended with neurosecretory granules. The significance of these observations in the initiation of adult development is discussed.     

Daily changes of neurosecretory type-II cell structure of Pieris larvae entrained by short and long days

The neurosecretory type-II cell (NS-II cell) group of each brain hemisphere consists of three kinds of cells: two small cells, six large ones, and two others having characteristic vacuolated endoplasmic reticulum (ER).Ultrastructural changes of large NS-II cells were observed through the fifth instar and diurnally when short-day and long-day larvae were compared. There were little differences between short-day and long-day larvae in cell structures on corresponding developmental days except for daily changes, but remarkable changes were observed every day through the instar. A secretory cycle through the instar was supposed being based on the ultrastructural changes in NS-II cells: reduced secretory activity on the first day, formation of organelles necessary for the synthesis of secretory materials throughout the instar on the second day, active synthesis and secretion of secretory material during the middle stage (third-fourth day), and reversion to a reduced level of cell activity after the cessation of feeding.In short-day larvae on the third to fourth day, NS-II cells contained large aggregates of secretory granules during the day except for the time of 13 hr after the onset of photophase when a decrease of secretory granules occurred. In long-day larvae, only a small amount of secretory granules was observed at 8 and 13 hr after the onset. Rough ER changed daily paralleling with the quantitative change of the secretory granules.Based on these differences of daily changes in NS-II cell activity between short-day and long-day larvae, it was concluded that photoperiodic time measurement of diapause induction depends on the daily secretory cycle entrained by the photoperiods during the larval stage.     

Cytological aspects of different nerve cell somata in the buccal ganglia of Helix pomatia L.

In early September most of the neurons of the buccal ganglia of Helix pomatia contain neurosecretory material as membrane bound granules. There is only one, in exceptional cases 2 types of granules per cell. This suggests that different types of granules do not change into one another, and that each granule type contains a different secretory product. One granule type contains PAF-positive neurosecretory material, another one catecholamines, but most of the granules cannot be associated with special substances. The identified giant neurons B1-B4 contain granules in less density than the smaller neurons. B1 and B2 resemble each other in their granule type, whereas both B3 and B4 differ from B1 and B2.     

Neurosecretory cells in Dysdercus similis (Hemiptera)

The neurosecretory cells of Dysdercus similis have been described. "A", "B", "C" and "D" types of neurosecretory cells are present. The "A" type of cells of the pars-intercerebralis show cyclical secretion. When these cells show secretory activity during one to three days of emergence, they have scattered granules. The cells are seen packed with clumps of neurosecretory material when they are not secreting, and this is interpreted as a storage stage. The axons of these cells supply the corpora cardiaca and some neurosecretory material also reaches the corpus allatum. The release of this neurosecretory material can be correlated both with moulting in the young stages and later with reproduction in the adults.     

Licht- und elektronenmikroskopische Untersuchung des Corpus cardiacum der Eintagsfliege Ephemera danica Müll. (Ephemeroptera: Ephemeridae) während der Metamorphose*

Kaiser, H. 1980. Licht- und elektronenmikroskopische Untersuchung des Corpus cardiacum des Eintagsfliege Ephemera danica Müll. (Ephemeroptera: Ephemeridae) während der Metamorphose. [Light- and electron microscopic investigation on the corpus cardiacum in the mayfly Ephemera danica Müll. (Ephemeroptera: Ephemeridae) during metamorphosis.] (Zoologisches Institut der Universität Basel, Schweiz.) — Acta zool. (Stockh.) 61(2): 93–103. The corpus cardiacum (cc) of Ephemera danica is an unpaired organ in the dorsal wall of the aorta. During the last four instars there has been no significant change in the volume of the cc of the males. In the females, however, the cc enlarges in the final nymphal instar due to a thickening of the organ. Owing to a shortening prior to the subimaginal moult the volume has diminished in the subimagines and imagines. In the electron microscope different types of axons and secretory granules could be observed. The type a axons contain electron opaque granules with a mean diameter of 125 nm. The granules in the axons of type b are smaller (mean diameter 85 nm) and are more or less electron opaque, and the type c axons are filled with less electron opaque secretory droplets with mean diameters of 170 nm. In the fourth type of axons (d) the granules are approximately the same size as those of the type a but are more irregular in shape. In addition to the different axons two cell types—interstitial and secretory cells—are described, and the probable mechanism of the release of neurosecretory material is discussed. During metamorphosis only minor changes were apparent at the ultrastructural level.     

Neurosecretion in the scorpion Heterometrus swammerdami

Gross morphology, staining characteristics and mapping of the diversity of the neurosecretory cell types in the brain and subesophageal ganglion of the scorpion Heterometrus swammerdami are reported. Special neurosecretory cell groups whose product is stainable with orange-G, acid fuchsin and Heidenhain's hematoxylin are present in the brain. In many of the living isolated neurosecretory cells, the secretory material appears luminous when viewed with dark ground illumination and granular when observed with phase contrast microscope. In the subesophageal ganglion the metameric arrangement of neurosecretory cells is distinct. Neurosecretory product accumulating in specific regions of subesophageal ganglion, and its axonal transport into the dorsal nerves and their termination in cephalic blood vessels apparently representing a storage and release organ of neurosecretion is reported.     

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.     

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.     

Neurosecretory cells in the central nervous system of the adult blowfly, Phormia regina Meigen (Diptera: Calliphoridae)

• 1 Neurosecretary cells in the central nervous system of the adult blowfly, Phormia regina Meig., have been examined histologically using the parparaldehyde-fuchsin and Gomori's staining method. Six groups of the neurosecretory cells occur in each hemisphere of the brain, the medial, frontal, lateral A, lateral B, posterior I and posterior II groups. In the subesophageal ganglion, four B-cells and two A-cells are present. In the thoracico-abdominal ganglion, ten A-cells are found in the thoracic region and a total of about 50 A- and B-cells in the hind part of the abdominal region.
• 2 A comparison with the neurosecretory system of two other species of blowfly, Calliphora erythrocephala Meig., Sarcophaga bullata Parker, and the housefly, Musca domestica L., showed similar arrangements and grouping.
• 3 Neurosecretory granules have been observed along the axons originating from the medial neurosecretory cells of the brain, and the thoracico-abdominal ganglion. The granules originating from the medial groups can be traced directly to the corpus cardiacum from which they move to the aorta, crop duct and cardia through axons.
• 4 There is with advancing age a gradual increase in the size of cell bodies and nuclei of the median neurosecretory cells in both females and males of Phormia regina, and also a decrease in stainable granules. This increase in size is dependent on nutrition, with no increase in water alone, a slight increase on sugar, and a maximum increase on sugar and liver. Corresponding increases in size occur in the ovaries in connection with feeding the same substances.

     

The neurosecretory system of the eyestalk of Carcinus maenas (Crustacea: Decapoda)

The optic ganglia neurosecretory cells of male and female Carcinus maenas during intermoult are distinguishable into six types based on size, location, appearance and method of secretory material release from the perikaryon. Release occurs via the sinus gland and also, in one case, directly into blood capillaries among the neurosecretory cells themselves. The sinus gland consists of axonal extensions of the neurosecretory cells; no secretory granules are produced there and nuclei observed between the axonal endings are those of ill-defined glial cells.     

A Neurosecretory System in the Brain of the Lancelet, Branchiostoma lanceolatum

Ultrastructural and histochemical studies indicate a neurosecretory system exists in the lancelet brain with basal properties resembling a primitive hypothalamic system. A nucleus of secreting neurons, containing peptide granules (115 nm), is prominent in the dorsal walls of the brain. The axons establish contacts with the ventral brain surface, probably releasing their secretory product out of the brain. The neurons are innervated by dopaminergic "boutons en passant" often very active with a high number of electron translucent vesicles as well as dense-core vesicles (90 nm). Ventrally located cellbodies containing what are probably secretory peptide granules (110 nm) establish contacts with their basal processes on the ventral brain surface.     

Ultrastructure of retrocerebral complex of the earwig, Euborellia annulipes, and rôle of aorta as a neurohaemal organ

The ultrastructure of the retrocerebral endocrine-aortal complex of the earwig, Euborellia annulipes has been studied. The space between the inner and outer stromal layers of the aorta is occupied by numerous axon terminals and pre-terminals containing large electron dense granules (NS-I) of approximately 100 to 220 nm and a few axon terminals having small granules (NS-II) of approximately 40 to 90 nm; the former appear to belong to medial neurosecretory A-cells, and the latter to the B-cells of the brain. The corpora cardiaca consist of intrinsic cells with mitochondria and multivesicular bodies. Granules of type NS-II and NS-III are observed in the axon terminals and pre-terminals in the corpora cardiaca. The NS-II are identical to those found in the aorta and are probably the secretions of the lateral B-cells. Granules of type NS-III are 40 to 120 nm and electron dense, and are intrinsic in origin. Similar granules occur in the intrinsic cells of the corpora cardiaca. E M studies have confirmed the rôle of the aorta as a neurohaemal organ for the medial neurosecretory cells, and the corpora cardiaca for the lateral neurosecretory cells of the brain. The corpora cardiaca also act as a reservoir for the intrinsic secretion. The corpus allatum is a solid body consisting of parenchymal cells with prominent nuclei, mitochondria, and endoplasmic reticulum. In between its cells are occasional glial cells and also neurosecretory as well as non-neurosecretory axons. The gland is devoid of A-cell NSM.     

Cytochemical ultrastructural study of the glycoproteins in the rat hypothalamo-post-pituitary complex]

The results obtained with various methods applied to the cytochemical detection of carbohydrates at an ultrastructural level, confirm the existence of glycoproteins in neurosecretory material in the neurohypophysis as well as in the hypothalamic magnocellular nuclei. This glycoproteic component, however, is not present in all the secretory granules and, according to their cytochemical behaviour, it is possible to distinguish two types of neurosecretory fibres: one where all the granules respond negatively; the other where most of the granules are reactive. The existence of two types of neurons corresponding to these two fibres cannot yet be asserted, but seems very likely, perhaps connected with the hormonal duality of the magnocellular nuclei. The reactions are also positive on the Golgi apparatus, in accordance with its function in glycoprotein synthesis. But the difference of reactivity between the Golgi cisternae and the neurosecretory product suggests that glycoprotein synthesis is still going on in the neurosecretory granules outside the Golgi area.     

Morphometric and electron microscopic studies of the secretory granules of neurosecretory cells of the supraoptic and paraventricular nuclei of white rats and mice]

The morphometrical and electron microscopic analysis of secretory granules in the perikaryons of neurosecretory cells of the supraoptic and paraventricular nuclei in male rats and mice has shown than in the cells of these nuclei in both species of animals there occur secretory granules of the same kind and size. Therefore this method fails to determine which of them contain oxytocin and which of them contain vasorpressin. The neurosecretory granules located in the Golgi apparatus zone are of a less size and have more osmiophilic cnetral material than the granules localized on the periphery which mainly have granular central material and are of a greater size. The distinctions in the size and type of secretory granules are associated with certain stages of their "maturation". Granular particles appear to be "swallen", more active forms of storing neurohormones. The presence of larger granular particles in the supraoptic nucleus of mice allows to suggest greater reactivity of this nucleus than in rats which is likely to be associated with a higher ability of mice, as compared with rats, to adaptate to disturbances in water-salt metabolism.     

Ultrastructure of the dental epithelium and odontoblasts during enameloid matrix deposition in cichlid teeth

Teleost enameloid matrix has been proposed to be an ectodermal, mesodermal, or joint ectodermal-mesodermal product. To determine its origin we examined the ultrastructure of the inner dental epithelium (IDE), odontoblasts, enameloid, and dentin matrices of cichlid tooth buds at the stage of enameloid formation. © Alan R. Liss, Inc. Columnar IDE cells had apical and basal terminal webs and contained organelles associated with protein synthesis, including elongated secretory granules containing fibrillar material having cross-striations with 60-nm periodicity. The morphology of IDE secretory granules was typical of procollagen granules observed in a large variety of ectodermal and mesodermal cells synthesizing collagen. In contrast, the paucity of secretory granules within three odontoblast types indicates that these cells probably do not synthesize enameloid matrix. These observations are consistent with the idea that the bulk of the enameloid matrix is itself an ectodermal collagen synthesized and secreted by IDE cells.     

Ultrastructural Analysis of the Neuroendocrine Apparatus of Oncopeltus fasciatus (Heteroptera)

• 1 In Oncopeltus fasciatus, the A-cells of the pars intercerebralis and their tracts are stainable in situ with the performic acid-victoria blue (PAVB) method. The axons from these cells, after traversing the corpus cardiacum, terminate in the anterior part of the aorta which thus serves as the neurohemal organ.
• 2 Ultrastructurally, four types of secretory neurons are distinguishable in the pars intercerebralis region: pic-I with granules measuring 1000–3000 Å in diameter; pic-II with granules of irregular size and shape, the elongate ones showing mean dimensions of 2400 × 1400 Å; pic-III with less electron-dense granules measuring 1000–2700 Å in diameter; pic-IV, present not only in the pars intercerebralis but also in adjacent regions of the brain, with variable proportions of granules measuring 700–1800 A and dense-cored vesicles measuring 1000–2400 Å.
• 3 The nervi corporis cardiaci contain at least three types of neurosecretory axons, based on granule content, presumably representing pic-I, pic-II and pic-III neurons.
• 4 The wall of the aorta contains endings of at least three distinct types, again representing pic-I, pic-II and pic-III neurons, and thus provides the neurohemal site for these three types of protocerebral neurosecretory cells. Axons of pic-IV neurons appear to enter the cerebral neuropil.
• 5 The corpus cardiacum is composed of two types of parenchymal secretory cells, with electron-dense granules measuring 1300–3000 Å and 1000–2300 Å in diameter, respectively. The corpus cardiacum also contains interstitial cells and some axons of extrinsic origin, with and without granules.
• 6 The corpus allatum may be paired or median, and receives a small number of at least two types of axons. The corpora allata of some reproducing females show a large number of PAVB-stainable inclusions which appear to be modified cytoplasmic organelles, but are definitely not neurosecretory material.
• 7 The hypocerebral ganglion is composed of two types of secretory-appearing neurons and glial cells. The two neuronal types contain secretory granules, 1000–3000 Å and 900–2100 Å in diameter, respectively. Axons of the recurrent nerve also may contain occasional granules.
• 8 In this heteropteran insect, the two principal functions of the corpus cardiacum appear to be spatially separated: the neurohemal function is subserved by the aortic wall, which permits release of material into both the aortic lumen and the hemocoel, and the intrinsic endocrine function is possessed by the parenchymal cells.