The ultrastructure of the sinus gland of Carcinus maenas (Crustacea: Decapoda)

Summary The sinus gland of Carcinus maenas consists of the swollen axonal endings of the neurosecretory cells of the major ganglia and acts as a storage release centre for the membrane bound neurosecretory material. These neurosecretory granules fall into five different types based on size and electron density. Their contents are released by exocytosis of the primary granules or smaller units budded from the primary granules.I thank Professor E. Naylor for his constant advice and Professor E. W. Knight-Jones, Department of Zoology, University College, Swansea, for the provision of laboratory facilities. I am grateful to the Science Research Council for the financial support. Finally, I thank the Electron Microscope Unit, Southampton General Hospital, where the work was completed.     

Appearance and innervation of CHH-producing cells in the eyestalk of the crayfish Astacus leptodactylus examined after tracing with Lucifer Yellow

Summary By injection of the fluorescent dye Lucifer Yellow into individual Crustacean Hyperglycemic Hormone (CHH)-producing cells, the shape of these neurosecretory cells in the eyestalk of the crayfish Astacus leptodactylus can be traced. A highly fluorescent perikaryon gives rise to an axon that can be followed by the fluorescent label to the neurohemal region, the sinus gland. The proximal part of that axon sends out extensive branches into the neuropil of the medulla terminalis. Electron-microscopic investigations reveal synaptic input to these axonal ramifications.     

Tracing of neurosecretory neurons in crayfish optic ganglia by cobalt iontophoresis

Summary The axonal connections between the medulla terminalis ganglionic X-organ (MTGXO) and the sinus gland are traced by iontophoretic application of cobalt dye to the neurosecretory system in the eyestalks of the crayfish, Orconectes limosus. The MTGXO consists of about 15 large perikarya, forming a distinct subgroup of neurosecretory cells in the medulla terminalis and giving rise to a prominent fibre bundle. Additional axons reaching the sinus gland from the medulla interna, the medulla externa and the optic nerve are less conspicuous.Supported by a grant from the Deutsche Forschungsgemeinschaft (SFB 87, Projekt A 3).Part of the work has been presented at the 9th Conference of European Comparative Endocrinologists in Giessen, August 1977Thanks are due to Dr. H.G. Wolff of the Universität Köln for his advice during the initial stage of this work     

Relationship between Rous sarcoma virus production in golden hamster cells and the cell cycle]

The axon terminals of neurosecretory cells, containing elementary granules of neurosecretory materials, have been described on the basis of light and electron microscopy. No allochthonous neurosecretory elements were found in the sinus gland. The discharge of the granules from some terminals of the sinus gland occur with the changed salinity of the environment. There is a great difference in the structure of the sinus gland when salinity is changed. The structure of the sinus gland and its modification under experimental conditions indicate a possibility of neurohormonal regulation of the hydromineral balance.     

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.     

Anatomy and ultrastructure of the salivary gland in the thorax of the honeybee worker,Apis mellifera (Insecta,Hymenoptera)

Summary The thoracic salivary gland of the worker honeybee was investigated by dissection, light microscopy, scanning electron microscopy, and transmission electron microscopy. The glands are paired and each lateral half consists of two parts, a smaller external and a larger internal lobe. The lobes are composed of densely packed secretory tubes and ducts, the tubes of which often show ramifications. A reservoir is packed within the anterior medial part of the gland. The secretory tubes are composed of two types of cells, secretory cells, which are most frequent, and parietal cells. Secretory cells are characterized by a basal labyrinth, abundant rough endoplasmic reticulum, dark secretory vesicles, light vesicles of different sizes, and apical microvilli. Parietal cells are smaller and have a characteristically lobed nucleus and no secretory vesicles. Between the cells there are intercellular canaliculi. In the center of each tube there is an extracellular space with a central cuticular channel. The abundance of rough endoplasmic reticulum and the rare occurrence of smooth endoplasmic reticulum implies a saliva with proteins but rarely with pheromones. Between the secretory tubes there are frequently neuronal profiles which are partly in contact with the secretory cells. Thus a nervous control of this gland is, in contrast to previous investigations, clearly demonstrated. The axonal endings contain dark neurosecretory vesicles as well as light synaptic vesicles. Large parts of the glands are surrounded by a thin tissue sheath which has a smooth surface towards the secretory tubes and shows irregular protrusions towards the outer side. This sheath is considered to be a tracheal air sac, and due to its large extension is probably of importance for the hemolymph flow in the thorax.     

Neurosecretory cells in the optic lobe of two aquatic coleopteran species,Dineutes indicus aube and Cybister rugulosus redt

In each optic lobe and optic peduncle of two aquatic beetles viz. Dineutes indicus and Cybister rugulosus the neurosecretory cells are observed with the help of various histochemical techniques. These cells are arranged to form a discrete group. A group in the optic lobe of both species contains about 25 to 30 neurosecretory cells. On the basis of staining properties the neurosecretory cells are classified into A and B types. These cells stain with chrome haematoxylin-phloxine and paraldehyde fuchsin, but do not stain with azan. Histochemically, the neurosecretory material is positive for proteins and shows a negative reaction for 1,2-glycols. The cells show variations in RNA contents in correlation with the state of secretory activity. Axons of the neurosecretory cell group of the optic lobe are observed directed to the optic peduncle. The axonal tract from neurosecretory cells in the optic peduncle runs towards the lateral margin of the brain.     

Structural re-evaluation of the neurosecretory system in the crayfish eyestalk

Summary The topography of the neurosecretory system in the decapod eyestalk has not been precisely delineated with light microscopy. Cobalt iontophoresis and electron microscopy have proved useful in clarifying the microstructure of this system. The sinus gland (sg) of the crayfish eyestalk consists of aggregated axon terminals which end at or near the blood space, lontophoresing cobalt back through the cut base of the sinus glands reveals proximal cell bodies in the eyestalk only in the X organ (Xo) region. Electron microscopy demonstrates that axons from about 115 neurosecretory cell bodies in the Xo form the Xo-sg tract. Intermingled with these Xo somata are smaller non-neurosecretory cell bodies which do not send axons into the sinus gland. One of these exhibits catecholamine fluorescence. Backfilling also reveals a second group of fibres which run from the brain along the optic tract and into the sinus gland. These brain-sg fibres are smaller in diameter than Xo-sg axons and lack neurosecretory vesicles. From these fibres collaterals extend into the eyestalk neuropil, especially in the proximity of the visual elements. The possible function of these non-neurosecretory processes within the sinus gland is discussed.This work was supported by a National Research Council of Canada grant     

Histochemistry and ultrastructure of the albumen gland duct of the prosobranch gastropod Pomacea paludosa

Summary

The albumen gland duct passes through the base of the albumen gland. It consists of a single layer of cells composed of ciliated and secretory cells. Sulfated and non-sulfated acid mucopolysaccharides are secreted by the cells of the albumen gland duct. Cell resembling neurosecretory cells are also found between the ciliated and secretory cells. The secretion products probably contribute to the formation of the albumen layer which surrounds the fertilized egg.     

锯缘青蟹窦腺显微和超微结构研究

借助光学和电子显微镜观察据缘青蟹（Ｓｃｙｌｌａ ｓｅｒｒａｔａ）窦腺的形态结构。窦腺位于眼柄视神经节内髓背侧近外髓处。窦腺呈羹状;腺体壁山神经分泌细胞的末梢和神经胶质细胞组成。神经末梢内充满了电子致密的神经分泌颗粒。根据颗粒的大小、形态及电子致密度等特征,可以区分出４种类型的神经末梢。一些末梢中的多形性颗粒可能是由Ⅱ型末梢中的颗粒转变而成的。一些现象表明,神经分泌物质可以通过胞吐作用或一种类似“顶浆分泌”的方式释放,从而说明神经激素的释放可能是多途径的．     

Dynamics, following axotomy, of the A1 and A2 median protocerebral neurosecretory cells of the African locust. I. Histophysiological study

In the African locust, the secretory dynamics of the A1 and A2 median protocerebral neurosecretory cells (M-NSC) is evaluated by the product content and the gonadotropic action of these cells. The axotomy of the A1 and A2 M-NSC disturbes their secretory dynamics. The axonal regeneration, if it leads to a reconnexion with the corpora cardiaca (CC), restores a normal secretory dynamics of the M-NSC. Without reconnexion to the CC, the nervi corpori cardiaci interni (NCCI) do note regenerate or regenerate to form new nerve endings. In these cases, the secretory dynamics of the M-NSC remains more or less inhibited specially that of the A2 M-NSC which can be completely suppressed. A functional state of the A2 M-NSC could be necessary for the beginning of the vitellogenesis. In the CC, separated from the regenerating M-NSC, the A1 and A2 neurosecretory products are transformed into large globules which became intensively basophil before disappearance.     

Neurosecretory centers from the eyestalk of Siriella armata M. Edw. (Crustacea: Mysidacea): ultrastructural variations during normal and experimentally inhibited molt cycle

Summary The ultrastructure of the medulla interna-medulla externa X-organ (MI-ME Xo)-sinus gland (SG) complex in the eyestalk of Siriella armata is described during the normal and the experimentally inhibited molt cycle. In the normal SG, four types of neurosecretory axon terminals, each containing distinguishable neurosecretory granules, can be described. Thus, type-2 granules are synthesized by G1 neurons forming the MI-ME Xo. The cell bodies and axonal endings of these cells in the sinus gland have been examined at the following molt stages: intermolt (stage C4), premolt (D0 and D2), and postmolt (A1, A2 and B). Changes in ultrastructure of the G1 cells have been monitored and correlated to inhibitions of the molt-and reproductive cycle produced by electrocauterization of the MI-ME Xo. The results obtained suggest that the neurosecretion from the G1 cells exerts a positive influence on molt and brood preparation. The occurrence of a distal group of G1 cells whose axons terminate at a different site from the SG suggests that the neural factors of the MI-ME Xo are diverse and control different physiological activities.     

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.     

Fine structure of the neurohemal sinus gland of the shore crab,Carcinus maenas,and immuno-electron-microscopic identification of neurosecretory endings according to their neuropeptide contents

Summary The sinus gland of the shore crab, Carcinus maenas, is a compact assembly of interdigitating neurosecretory axon endings abutting upon the thin basal lamina of a central hemolymph lacuna. Four types of axon endings are distinguishable by the size distribution, shape, electron density and core structure of their neurosecretory granules. One additional type of axon ending is characterized by electron-lucent vacuoles and vesicles. The axon profiles are surrounded by astrocyte-like glial cells. Various fixations followed by epoxy- or Lowicrylembedding were compared in order to optimize the preservation of the fine structure of the granule types and the antigenicity of their peptide hormone contents. By use of specific rabbit antisera, the crustacean hyperglycemic, molt-inhibiting, pigment-dispersing, and red-pigment-concentrating hormones were assigned to the four distinct granule types which showed no overlap of immunostaining. Epi-polarization microscopy and ultrathin section analysis of immunogold-stained Lowicrylembedded specimens revealed that immunoreactivity to Leu-enkephalin and proctolin is co-localized with moltinhibiting hormone immunoreactivity in the same type of granule. The size and core structure of the immunocytochemically identified granule types vary little with the different pretreatments but, in some cases, to a statistically significant extent. The present results are compared with those from earlier studies of sinus glands in different crustaceans. The methods of granule identification used in this study supplement the classical approach in granule typing; they are easier to perform and more reliable for the analysis of release phenomena in identified secretory neurons supplying the neurohemal sinus gland.     

The Cerebral Neurosecretory System,Secretory End-Foot System and Infracerebral Gland—a Probable Neuroendocrine Complex in Nephtys (Annelida; Polychaeta)

Abstract The brain of Nephtys contains four neurosecretory cell types with distinctive cytoplasmic inclusions, a cells are located uniquely in a single pair of ganglionic nuclei and b cells are represented by a single pair of cells, whereas c cells and d cells have a scattered distribution. Their axons form two types of secretory release structure. First, possible axon collaterals synapse upon slender “dentritic twigs” in the core of the brain. Secondly, two tracts descend to the brain floor to form a “neurosecretory neuropile” (or storage and release complex) in contact with the inner surface of the brain capsule. Other neurosecretory fibres penetrate through the capsule, branch extensively, and terminate in contact with its ventral surface in close association with the “infracerebral gland”. The gland is derived from the pericapsular epithelium and exhibits signs of specialization for glandular function. In contrast to certain other polychaetes, it does not contain secretory neuron perikarya. The secretory end-foot system is poorly developed. Its terminals are located adjacent to the neurosecretory neuropile, which they encircle. The cell bodies are probably represented by four e cells which, like the terminals, contain many mitochondria.     

Studies of the neurohaemal organ (sinus gland) of the portunid crab Portunus sanguinolentus (Herbst) (Brachyura). 1. Morphology and histology in relation to moulting

The morphological and histological characters of the neurohaemal organ (sinus gland) of Portunus sanguinolentus are described in detail. The sinus gland lies on the dorsal surface of the optic ganglia, opposite the medulla interna. Histological techniques showed the presence of three tinctorially different secretory granules in the sinus gland. The predominant type of secretory material is basophilic and occurs as large granules, while two types of acidophilic material occur near the basement membrane. Cyclic changes in the relative amounts of acidophilic and basophilic material in correlation to moulting are also discussed. Allochthonous cells present in the sinus gland are identified.     

Two-dimensional gel electrophoresis of neurosecretory polypeptides in crustacean eyestalk

Summary A knowledge of the precise location of neurosecretory cell bodies is a prerequisite for studying the synthesis and subsequent processing of neurosecretory polypeptides stored in axon terminals comprising the sinus gland of the crustacean eyestalk. Structural data establish that the X organ in the medulla terminalis ganglion (mtXo) of the crayfish eyestalk represents 90–95% of the cell bodies actively synthesizing neurosecretory vesicles stored in the neurohemal sinus gland (Fig. 4). These cell bodies transport rather than accumulate neurosecretory vesicles as judged by light and electron microscopy suggesting that neurohormone precursors, but not subsequently stored products, might be found there. Two-dimensional electrophoresis of sinus gland and mtXo homogenates support this hypothesis. In crayfish, lobster and blue crab, stained two-dimensional gels display a number of sinus gland-specific polypeptides whose high concentrations and low molecular weights are consistent with stored neurosecretory material (Table 1). These neuropeptides are not detected in mtXo homogenates or in non-neurosecretory neural tissue with Coomassie Blue staining. By decreasing the porosity of the second dimension, the two-dimensional gel technique has proven useful in determining the molecular weights of a variety of neurosecretory polypeptides stored in the sinus gland. The crayfish and lobster store several polypeptides of ca. 7,000 Dalton. The blue crab stores two 7,000, two 13,000 and three 20,000 Dalton sinus gland polypeptides detected in stained gels.Following a 4 h incubation in³H-labelled amino acids, predominantly labelled 19,000–21,000 Dalton polypeptides are detected in crayfish mtXo homogenates by 2-D gel autoradiography (Fig. 12). Concomitantly, three labelled polypeptides (4,000–10,000 Dalton) appear in the sinus gland (Fig. 13), suggesting that they are cleaved from 19,000–21,000 Dalton molecules. This study is the first to examine neurosecretory precursors and their putative cleavage products in the Crustacea.Abbreviations mtXo medulla terminalis X organ - NEPHGE non-equilibrium pH gradient electrophoresis - PAF paraldehyde fuchsin - SDS sodium dodecylsulfate     

Immunohistochemical Identification of Hyperglycemic Hormone- and Molt-Inhibiting Hormone-Producing Cells in the Eyestalk of the Kuruma Prawn, Penaeus japonicus

This study deals with the localization of crustacean hyperglycemic hormone (CHH, Pej-SGPIII) and molt-inhibiting hormone (MIH, Pej-SGP-IV) in the eyestalk of the kuruma prawn Penaeus japonicus using immunohistochemistry. High-titer and highly specific antisera were raised in rabbits against synthetic Pej-SGP-III C-terminal peptide (Glu-Glu-His-Met-Ala-Ala-Met-Gln-Thr-Val-NH2) and Pej-SGP-IV C-terminal peptide (Val-Trp-Ile-Ser-Ile-Leu-Asn-Ala-Gly-Gln-OH), both of which were conjugated with bovine serum albumin by a cross linker. Eyestalks were removed from mature male prawns at the intermolt stage of the molting cycle and fixed in Bouin's solution. Serial sections stained immunohistochemically showed that neurosecretory cells of Pej-SGP-III and Pej-SGP-IV were located in the same cluster of the medulla terminalis ganglionic X-organ (MTGX), and that three kinds of neurosecretory cells, which were stained with anti-PejSGP-III antiserum and/or anti-Pej-SGP-IV antiserum were present. The number of neurosecretory cells which stained with both antisera was much fewer than that of neurosecretory cells which stained with one of the antisera only. The axon and axon terminals in the sinus gland were also stained and the staining density of the sinus gland was always deeper than that of the neurosecretory cells.     

Posttranslational isomerization of a neuropeptide in crustacean neurosecretory cells studied by ultrastructural immunocytochemistry

Isomerization of the third amino acid residue (a phenylalanine) of crustacean hyperglycemic hormone (CHH) has been previously reported to occur as a late step of hormone precursor maturation in a few neurosecretory cells in the X-organ-sinus gland complex of the crayfish Orconectes limosus. In the present report, using conformation-specific antisera combined with immunogold labeling, we have studied, at the ultrastructural level, the distribution of L- and D-CHH immunoreactivity in CHH-secreting cells of the crayfish Astacus leptodactylus. Two CHH-secreting cell populations were observed, the first one (L-cells), the most numerous, exhibited only labeling for L-CHH. In the second one (D-cells), four secretory granule populations were distinguished according to their labeling: unlabeled, either L- or D- exclusively or both L- and D-granules. Labeling quantification by image analysis in D-cells showed a marked increase in D-labeling from the cell body to the axon terminal. However some L- and mixed granules remain in axon terminals. Our results demonstrate that Phe3 isomerization of CHH occurs within the secretory granules of specialized neurosecretory cells and progresses as the granules migrate along the axonal tract. The observation that not all the CHH synthesized is isomerized, and the great variability in the proportion of L- and D-immunoreactivity in granules in every cell region may suggest an heterogeneous distribution of the putative enzyme involved in Phe3 isomerization, a peptide isomerase, within the secretory pathway.