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  • Quantitative electron microscopy  (5)
  • Tannic acid  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Regulation of neurosecretory activity in the freshwater pulmonate Lymnaea stagnalis (L.) (1973)
    Springer
    Cell & tissue research 146 (1973), S. 177-205 
    Details
    ISSN: 1432-0878
    Keywords: Neurosecretory activity ; Lymnaea stagnalis ; Transplantation ; Osmoregulation ; Quantitative electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The neurosecretory Dark Green Cells (DGC) in the pleural and parietal ganglia of the freshwater pulmonate Lymnaea stagnalis are involved in osmoregulation, producing a diuretic hormone. The secretory activity of these cells is dependent on the osmolarity of the environment. In order to investigate whether the regulation of this activity is under nervous control, two experiments were carried out in which the right pleural and parietal ganglion complex (PPC) was transplanted into acceptor snails. The light and electron microscopic observations in the first experiment—transplantation of the PPC into control snails, kept under normal conditions—indicate that degeneration in transplants occurs only during the first week of transplantation and is mainly restricted to neuronal processes of non-neurosecretory cells (non-NSC) of which the cell bodies are located outside the PPC. Degenerated nervous elements are eliminated by phagocytozing amoebocytes and glial cells. Degeneration of neurosecretory elements was only very seldom observed. Like most non-NSC, the DGC and the three other neurosecretory cell (NSC) types in the right parietal ganglion show a normal morphology. Moreover, up to at least 6 weeks after transplantation the NSC remain capable of synthesizing, transporting and releasing their neurosecretory material (NSM). Apparently these processes can proceed in the absence of nervous input from outside the PPC. After 3 and 6 weeks of transplantation outgrowth was noted of both non-NSC and NSC axons. In the second experiment groups of acceptor snails were exposed during one week to different environmental osmolarities. Thereafter the NSC activities of the transplanted DGC and of the DGC in the acceptor's own nervous system were determined by quantitative light and electron microscopy. The following observations apply to both transplanted and acceptor DGC. Compared with the control condition (tap water) exposure of snails to demineralized water leads to a significant increase in nuclear and cytoplasmic volumes and in the extent of the granular endoplasmic reticulum (GER) and the Golgi apparatus. Moreover, the activity of the Golgi apparatus is strongly enhanced. In the DGC axon endings located in the pleuroparietal connective the release of NSM is raised markedly above control level. Conversely, exposure to a 0.08 M NaCl solution (hypertonic to the blood) reduces the secretory activity of the DGC, as is obvious from the decrease of nuclear and cytoplasmic volumes, the smaller extent of the GER and of the Golgi apparatus and the lower Golgi activity. The number of cytosomes is increased dramatically, which accounts for the breakdown of elementary granules and of other cytoplasmic constituents. The NSM of the DGC is partly broken down in the axon endings by lysosomal action. Its release takes place at a low rate. Since these changes in neurosecretory activity occur in a similar fashion in transplanted and in acceptor DGC it is concluded that the response of the DGC to environmental osmolarity is not regulated via nervous pathways to the PPC. The only significant difference between transplanted and acceptor DGC concerns the higher number of clear vesicles in the DGC axon endings of transplants. Some explanations for this phenomenon are discussed. Possible mechanisms of regulation of DGC neurosecretory activity are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00307346
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  • 2
    Electronic Resource
    Electronic Resource
    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 (1976)
    Springer
    Cell & tissue research 174 (1976), S. 201-219 
    Details
    ISSN: 1432-0878
    Keywords: Neurosecretion ; Lymnaea stagnalis ; Neuron isolation ; Culture ; Quantitative electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222159
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  • 3
    Electronic Resource
    Electronic Resource
    Regulation of neurosecretory activity in the freshwater pulmonate Lymnaea stagnalis (L.) with particular reference to the role of the eyes (1975)
    Springer
    Cell & tissue research 160 (1975), S. 291-314 
    Details
    ISSN: 1432-0878
    Keywords: Neurosecretory activity rhythms ; Lymnaea stagnalis ; Synapses ; Cell synchrony ; Quantitative electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The process of neurosecretion in the Caudo-Dorsal Cells (CDC) of the freshwater snail Lymnaea stagnalis, which produce an ovulation hormone, shows a diurnal rhythmicity. Synthesis, transport and release of the neurosecretory material (NSM) is high during the evening and the early night and low during the rest of the day, while storage of NSM mainly occurs during the daytime. In the present study the role of the eyes in the regulation of the CDC-rhythm was investigated. During a 24-hr period, at time intervals of 6 hrs, cerebral ganglia, which contain CDC, of blinded and control snails (5 per group) were fixed and the CDC were studied with quantitative electron microscopical methods. The CDC of the controls showed a distinct diurnal rhythmicity. Blinding, on the other hand, clearly affected this rhythmicity. The results indicate that after blinding the circadian CDC-rhythms of individual snails are no longer synchronous with each other (“interanimal desynchronization”). It is suggested that the rhythm of CDC neurosecretory activity is synchronized by the natural light/dark cycle via the eyes. The information from the eyes probably reaches the CDC via a nervous pathway. True synapses and three types of synapse-like structures were found on the CDC. Their role in the regulation of CDC-activity is discussed. The effect of blinding is specific for the CDC; blinding does not influence the diurnal rhythmicity of another type of cerebral neurosecretory cells, the Light Green Cells (LGC). The CDC within a cluster act synchronously. This synchrony does not depend upon the presence of the eyes. Some structures which may be involved in establishing this synchrony, such as subsurface cisterns, desmosome-like structures and “specific release sites”, are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222041
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  • 4
    Electronic Resource
    Electronic Resource
    Morphometric in vitro analysis of the control of the activity of the neurosecretory dark green cells in the freshwater snail Lymnaea stagnalis (L.) (1976)
    Springer
    Cell & tissue research 174 (1976), S. 221-231 
    Details
    ISSN: 1432-0878
    Keywords: Neurosecretion ; Lymnaea stagnalis ; Osmoregulation ; In vitro ; Quantitative electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The neurosecretory Dark Green Cells (DGC) in the pleural and parietal ganglia of the freshwater snail Lymnaea stagnalis seem to be involved in osmoregulation. Previous experiments have indicated that changes of the osmolality of the environment induce activity changes of the DGC. Furthermore, it was shown that information on environmental osmolality reaches the DGC via the blood. In the present study right pleural and parietal ganglion complexes were cultured for 3 days in vitro under different osmotic conditions. Quantitative electron microscopy revealed that, compared with the control osmolality (130 mOsm/kg H2O), osmolalities of 160 and 190 mOsm/kg H2O caused a reduced synthesis and an increased storage of neurohormone in the DGC. Apparently, the activity of the DGC depended on the osmotic pressure of the medium. It is proposed that in vivo the osmotic pressure of the blood (which is related to the osmolality of the environment) regulates DGC activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222160
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  • 5
    Electronic Resource
    Electronic Resource
    Neuronal and non-neuronal control of the neurosecretory Caudo-Dorsal cells of the freshwater snail Lymnaea stagnalis (L.) (1976)
    Springer
    Cell & tissue research 168 (1976), S. 11-31 
    Details
    ISSN: 1432-0878
    Keywords: Neurosecretion ; Regulatory input ; Lymnaea stagnalis ; Synapse degeneration ; Quantitative electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The cerebral ganglia of the freshwater snail Lymnaea stagnalis contain two clusters of neurosecretory Caudo-Dorsal Cells (CDC). These cells produce a neurohormone which stimulates ovulation. Ganglion transplantation and quantitative electron microscopy show that neuronal isolation of the cerebral ganglia complex (CCC) results in an activation of the CDC. It was, therefore, concluded that the CDC are controlled by an inhibitory neuronal input originating outside the cerebral ganglia. Ultrastructural studies on synaptic degeneration in the CCC suggest that this input reaches the CDC via a special type of synapse-like structure, the type C-SLS. Furthermore, transplantation of CCC into acceptor snails leads to a reduced release and an increased intracellular breakdown of neurohormone in the CDC of the nervous system of the acceptors. It is supposed that these phenomena are caused by the release of an (unknown) factor from the transplanted CCC. Special attention was given to the formation and degradation of a peculiar type of neurohormone granule, the large electron dense granule. The physiological significance of the neuronal and non-neuronal control mechanisms which regulate CDC activity is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00219720
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  • 6
    Electronic Resource
    Electronic Resource
    Light- and electron-microscopic immunocytochemistry of a molluscan insulin-related peptide in the central nervous system of Planorbarius corneus (1992)
    Springer
    Cell & tissue research 267 (1992), S. 473-481 
    Details
    ISSN: 1432-0878
    Keywords: Cerebral ganglia ; Neurohormones ; Molluscan insulin-related peptide ; Immunocytochemistry ; Tannic acid ; Planorbarius corneus (Mollusca)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Two groups of cerebral dorsal cells of the pulmonate snail Planorbarius corneus stain positively with antisera raised against synthetic fragments of the B- and C-chain of the molluscan pro-insulin-related prohormone, proMIP-I, of another pulmonate snail, Lymnaea stagnalis. At the light-microscopic level the somata of the dorsal cells and their axons and neurohemal axon terminals in the periphery of the paired median lip nerves are immunoreactive with both antisera. Furthermore, the canopy cells in the lateral lobes of the cerebral ganglia are positive. In addition, MIPB-immunoreactive neurons are found in most other ganglia of the central nervous system. At the ultrastructural level, pale and dark secretory granules are found in somata and axon terminals of the dorsal cells. Dark granules are about 4 times as immunoreactive to both antisera as pale granules. Release of anti-MIPB- and anti-MIPC-immunopositive contents of the secretory granules by exocytosis is apparent in material treated according to the tannic acid method. It is concluded that the dorsal and canopy cells synthesize a molluscan insulin-related peptide that is packed in the cell body into secretory granules and that is subsequently transported to the neurohemal axon terminals and released into the hemolymph by exocytosis. Thus, MIP seems to act as a neurohormone on peripheral targets. On the basis of the analogy between the dorsal cells and the MIP-producing cells in L. stagnalis, it is proposed that the dorsal cells of P. corneus are involved in the control of body growth and associated processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319369
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  • 7
    Electronic Resource
    Electronic Resource
    Immuno-electron microscopy of sorting and release of neuropeptides in Lymnaea stagnalis (1991)
    Springer
    Cell & tissue research 264 (1991), S. 185-195 
    Details
    ISSN: 1432-0878
    Keywords: Caudodorsal cells ; Processing ; Differential storage ; Exocytosis ; Immuno-electron microscopy ; Tannic acid ; Lymnaea stagnalis (Mollusca)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The cerebral caudodorsal cells of the pulmonate snail Lymnaea stagnalis control egg laying and egglaying behavior by releasing various peptides derived from two precursors. The biosynthesis, storage, intracellular breakdown and release of three caudodorsal cell peptides were studied by means of immuno-electron microscopy using antisera raised to fragments of these peptides: (1) Caudodorsal Cell Hormone-I (CDCH-I; derived from precursor I), (2) Caudodorsal Cell Hormone-II (CDCH-II; from precursor II), and (3) α-Caudodorsal Cell Peptide (α CDCP; from both precursors). After affinity purification of the antisera, the specificity of the sera was confirmed with dotting immunobinding assays. From the ultrastructural immunocytochemical data it has been concluded that the precursor molecules are cleaved at the level of the Golgi apparatus after which the C-terminal parts (containing α CDCP) and N-terminal parts (containing CDCH-I or CDCH-II) are sorted and preferentially packaged into large electron-dense granules (MD 150 nm), respectively. Very probably, the content of the large electron-dense granules is degraded within the cell body. The immunoreactivity of the secretory granules increases during discharge from the Golgi apparatus, indicating further processing. At least a portion of the secretory granules contains all three peptides, as shown by double and triple immunopositive stainings whereas other granules appear to contain only one or two of these peptides. The caudodorsal cells release multiple peptides via exocytosis from neurohemal axon terminals into the hemolymph and from blindly ending axon collaterals into the intercellular space of the cerebral commissure (nonsynaptic release).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00305737
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  • 8
    Electronic Resource
    Electronic Resource
    Ultrastructural analysis of peptide-hormone release by exocytosis (1980)
    Springer
    Cell & tissue research 207 (1980), S. 267-275 
    Details
    ISSN: 1432-0878
    Keywords: Exocytosis of secretory peptides ; Tannic acid ; L. stagnalis ; Locust corpora cardiaca ; Rat pituitary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The release of neuropeptides and other proteinaceous hormones by exocytosis was studied in some detail by means of tannic acid in combination with glutaraldehyde (TAGO-method). This method strongly enhances the electron density of extracellular proteins including exocytosed secretory products, and therefore facilitates visualization of the release process in qualitative and quantitative respects. This study included a variety of neurosecretory cell types in the CNS of the freshwater snail L. stagnalis, the storage and glandular lobes of the corpora cardiaca of the locust L. migratoria, and the posterior pituitary of the rat. In addition, peptide secreting cells in the anterior pituitary were examined. The cytochemical specificity of the TAGO-method as well as the significance of “frozen” contents of exocytosing secretory granules in mammotrophs and somatotrophs of the rat is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237811
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