Ultrastructure of neurosecretory cells in the frontal ganglion of the tobacco hornworm, Manduca sexta(L)

Ultrastructural evidence is presented to indicate the synthesis, storage, and packaging of neurosecretory material in the frontal ganglion of Mandaca sera. Two morphologically distinct stages in the development of NSG were observed in the NSC. The immature granule contains granular electron dense material and arises from dilations of the rough endoplasmic reticulum. In diapause pupae the immature granules accumulate, whereas in developing larvae and pupae, they fuse with the proximal face of the Golgi apparatus. The mature granule contains opaque electron dense material and is seen in close association with the distal cisternae of the Golgi apparatus in developing pupae and larvae. The mature granules presumably contain the material from the immature granules which has been chemically altered and condensed by the Golgi apparatus and probably represent the mature NSG.The second process in neurosecretory cells of developing larvae is cyclic and the various stages are described. A comparison of neurosecretion in photoperiodically induced diapause and developing (non-diapause) larvae and pupae is presented.     

Further observations on the B-type neurosecretory cells in the thoracic ganglion of the crab, Potamon magnum magnum (Pretzman).

Only four types of the secretory neurones were observed in the thoracic ganglion of the fresh water crab, Potamon magnum magnum (Pretzman). These cells are classified as A, A', B and C types. Our results also confirmed that the B and B' types of cells (BAID et al. 1968) are one and the same type, the B cells. The B cells are of two forms, with and without the axons. They clearly showed sequential histological patterns pointing out to their phases. The secretory material is discharged either through the periphery or through the axon and periphery both. The vacuoles were observed in both the forms of the B cells. The remarkable sign of the activity of the nuclear membrane especially at the beginning of the secretory cycle and the appearance of the first secretory granules around the nucleus strongly support the vital role of the nucleus in the initiation of the secretory cycle.     

Histochemical observations on the giant neurosecretory cells of the thoracic ganglion of the adult and juvenile crabs, Potamon magnum magnum (Pretzman).

The giant neurosecretory cells in the thoracic ganglion of the adult and juvenile crab, Potamon magnum magnum (Pretzman) were histochemically investigated. The secretion is mainly proteinaceous in nature, containing considerable amounts of acid mucosubstances, sulphate esters, lipids and a little carbohydrate but no glycogen. The detailed nature of proteinaceous neurosecretory material in the adult crab was further tested. It appears that the neurosecretory material of these cells contains moderate amounts of sulfhydryl groups and few of disulphide bonds. No trace of tyrosine could be observed. The neurosecretory granules were associated with considerable amounts of cytoplasmic RNA. In general, stronger reactions were obtained in summer and winter than in other seasons.     

Ultrastructure of neurosecretory cells of the hypothalamic supraoptic nucleus in white rats following painful stress and during aging

The ultrastructural organization of neurosecretory cells (NSC) belonging to the hypothalamic supraoptic nucleus was investigated in young rats following periods of painful stress differing in duration (of 2 and 20 min). Intact young rats of similar age and others at late stages of development (24–27 months old) served as controls. Short- and longer-acting painful stress was found to intensify and inhibit the functional activity of NSC respectively. Complex ultrastructural changes in the NSC of young rats following protracted painful stress is compared with the ultrastructural organizational pattern in several NSC of aging rats. Findings would imply that aging occurs in rats following prolonged painful stress, resulting from functional hypersecretion and depletion.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 3, pp. 389–395, May–June, 1989.     

Distribution and ultrastructure of neurosecretory cells in the cerebral ganglion of the earthworm

Neurosecretory (Nsy) cells within the cerebral ganglion of Lumbricus terrestris were classified ultrastructurally. The Nsy cells within the subesophageal ganglion, nerve cord ganglion, and the peripheral nervous system were also examined. A comparative survey of Nsy cells of four other species of oligochaetes, Eisenia feotida, octolasion cyaneum, Dendrobeona subrubicunda, and Allolophora longa, was also carried out. Seven cell types (A1, A2, A3, A4, A5, C, and SEF), distinguished by special cytological and ultrastructural features, were found within the cerebral ganglion. Distribution of these cells inside and outside the cerebral ganglion was studied in detail by light and electron microscopy. The nerve terminals of each cell type were followed into the neuropile region. Exocytosis from cell bodies appears to be the main release mechanism for the Nsy granules, whereas small Nsy vesicles are released through synapses in the neuropile. Peripheral fibers of some cell types (A1, A2, and A3) extend through the capsule to the pericapsular epithelium. It is possible that Nsy cells secrete hormones from their cell bodies and peripheral processes and that their centrally directed axons release modulators/transmitters within the neuropile.     

The neurosecretory cells of the brain and suboesophageal ganglion of Chironomus riparius

The neurosecretory cells of the supra- and suboesophageal ganglia of young, unmated, adult male midges, Chironomus riparius, have been examined by both light and electron microscopy. The 5 cell types recognized have been placed in three major categories on the basis of their ultrastructural characteristics:—α₁ cells, of which there are 8 in each medial neurosecretory cell (MNC) group and 3 in each group of ventral neurosecretory cells (VNC), contain electron-dense granules, 150 to 200 nm in diameter; α₂ cells containing irregular, electron-dense granules, 70 to 120 nm in diameter comprise the remaining 3 cells in each VNC group and the 2 or 3 cells in each outer neurosecretory cell (ONC) group; α₃ cells, of which there are 1 or 2 on each side of the midline in the ventral cortex of the sub-oesophageal ganglion (SNC₂), contain electron-lucent, spherical granules, 70 to 120 nm in diameter. The β cells contain spherical or ellipsoidal, electron-lucent granules, 80 to 100 nm in diameter, and make up the lateral neurosecretory cell (LNC) groups, each of three or four cells. The γ cells contain both spherical and flattened, electron-dense granules, 130 to 160 nm in diameter and 150 to 250 by 70 to 150 nm in size respectively, only 1 cell of this category being found in each half of the suboesophageal ganglion in the dorsal cortex (SNC₁). Axons from the MNC and VNC form the nervi corporis cardiaci I (NCCI) and those of the LNC and ONC, the nervi corporis cardiaci II (NCCII). Those of the SNC₁ appear to enter the wall of the stomodaeum but axons of the SNC₂ could not be traced.     

Cytological study on Sertoli cells and their interactions with germ cells during annual reproductive cycle in turtle

Sertoli cells (SCs) play a central role in the development of germ cells within functional testes and exhibit varying morphology during spermatogenesis. This present study investigated the seasonal morphological changes in SCs in the reproductive cycle of Pelodiscus sinensis by light microscopy, transmission electron microscopy (TEM), and immunohistochemistry. During hibernation period with the quiescent of spermatogenesis, several autophagosomes were observed inside the SCs, the processes of which retracted. In early spermatogenesis, when the germ cells started to proliferate, the SCs contained numerous lipid droplets instead of autophagosomes. In late spermatogenesis, the SCs processes became very thin and contacted several round/elongated spermatids in pockets. At this time, abundant endoplasmic reticulum and numerous mitochondria were present in the SCs. The organization of the tight junctions and the adherens junctions between the SCs and germ cells also changed during the reproductive cycle. Moreover, SCs were involved in the formation of cytoplasmic bridges, phagophores, and exosome secretions during spermatogenesis. Tubulobulbar complexes (TBC) were also developed by SCs around the nucleus of the spermatid at the time of spermiation. Strong, positive expression of vimentin was noted on the SCs during late spermatogenesis compared with the hibernation stage and the early stage of spermatogenesis. These data provide clear cytological evidence about the seasonal changes in SCs, corresponding with their different roles in germ cells within the Chinese soft‐shelled turtle Pelodiscus sinensis.     

Ultrastructure of the neurosecretory cells of the anterior commissural nucleus of the hypothalamus in rats

The ultrastructure of neurosecretory cells of the anterior commissural nucleus of rat hypothalamus is similar to that of the supraoptic nucleus and of the "magnocellular" part of the paraventricular nucleus. The only difference is a less expressed granular endoplasmatic reticulum and a smaller diameter of elementary neurosecretory granules (80-150 nm in diameter). Such elementary granules are characteristic of neurosecretory terminals located in the external zone of the median eminence. It is suggested that neurosecretory cells of the anterior commissural nucleus project to this neurohemal region.     

Ultrastructure of the hypothalamic neurosecretory system of the dog

Summary The hypothalamic neurosecretory system of normal dogs was studied by light and electron microscopy after perfusion-fixation. In the supraoptic nucleus most neurons are loaded with elementary neurosecretory granules having a content of low electron density. Neurons with less neurosecretory material and signs of enhanced synthetic activity, as recognized by the changes in the endoplasmic reticulum, were also observed.The vesiculated neurons ofJewell were studied under the electron microscope and various stages of development were described. It was postulated that they originate by a localized process of cytoplasmic cytolysis which ends in the formation of a large aqueous intracellular cavity limited by a plasma membrane. The possible significance of these vesiculated neurones is discussed. Some few myelinated neurosecretory axons are found in the supraoptic nucleus.The neurons of the paraventricular nucleus are smaller and contain less neurosecretory material. This is abundant and very pale in the axons. The median eminence consists of an inner zone, mainly occupied by the neurosecretory axons of the hypothalamic-neurohypophysial tracts, and an outer zone in which some neurosecretory axons end on the capillary of the portal system. This outer zone contains numerous axons with the axoplasm rich in neurofilaments and some containing granulated and non-granulated synaptic vesicles. Some neurons with granulated vesicles were observed in this region. The adrenergic nature of these neurons and axons is postulated.The infundibular process of the neurohypophysis shows small axons with discrete amounts of elementary granules and vesicles of synaptic type at the endings. Some enlarged axons having, in addition, large polymorphic bodies are observed and related to the Herring bodies.The size and morphology of the granules are analyzed along the entire hypothalamic-neurohypophysial system. The changes in diameter and electron density are related to the maturation of the granules and the possible significance of such evolution.Supported by grants from the Consejo Nacional de Investigaciones Cientificas y Técnicas and by the Air Force Office of Scientific Research (AF-AFOSR 963-66).     

Ultrastructure of neurosecretory cells in the pars intercerebralis of Rhodnius prolixus (Hemiptera).

Six neuron types are distinguished in the pars intercerebralis of the starved fifth instar of Rhodnius prolixus. All neuron types contain electron dense secretory granules derived from Golgi complexes which are of characteristic size and morphology in each type. The neuron types are not thought to represent stages in a secretory cycle. The variety of neuron types described is related to that revealed by staining sections of the same cells with paraldehyde fuchsin. Active synthesis of neurosecretory granules continues throughout starvation and the lysosomal system appears to be involved in the continual degradation of secretory granules. Some of the variations in granule morphology observed may be a consequence of granule fusion and the importance of cytoplasmic events in the development of neurosecretory granules is discussed.     

Light- and electron-microscopic observations of the spinal ganglion cells of mice

Under the light microscope, large and small types of spinal ganglion cells can be seen in the mouse. Among those of the small type bipolar cells are observed. By electron microscopy, the cells of the large type have a low electron density and those of the small type a high electron density. Bipolar cells continue to be observed among the latter. The cells of the spinal ganglia contain different cellular apparatus in enormous quantity. There are four kinds of lysosomes in the GERL, i.e. the coated vesicles, dense bodies, multivesicular bodies and autophagic vacuoles.