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  • 1
    Electronic Resource
    Electronic Resource
    Involvement of preoptic-anterior hypothalamic GABA neurons in the regulation of pituitary LH and prolactin release (1983)
    Springer
    Experimental brain research 52 (1983), S. 356-362 
    Details
    ISSN: 1432-1106
    Keywords: Preoptic ; anterior hypothalamic area ; GABA ; Muscimol ; Norepinephrine turnover ; LH ; Prolactin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of intraventricular injections of the highly specific gamma-amino-butyric acid (GABA) agonist muscimol (5 nmol/animal) on blood LH and prolactin levels were measured in ovariectomized (ovx) and in ovx estrogen-progesterone (OEP) primed rats. While the drug stimulated pituitary prolactin release in both experimental groups, pituitary LH release was significantly inhibited in the ovx animals. Muscimol was without any effect on LH levels in ovx-OEP primed rats. Bilateral implantation of tubes containing a muscimol-mannitol mixture into the medial preoptic/ anterior hypothalamic (MPO/AH) area abolished pulsatile LH release whereas blood prolactin values were elevated. The intraventricular injection of GABA (8 μmol) also reduced LH and increased prolactin levels in the blood. Measurements of catecholamine turnover rates in the MPO/AH and in the mediobasal hypothalamus (MBH) yielded reduced preoptic but unchanged hypothalamic norepinephrine (NE) and stimulated hypothalamic dopamine (DA) turnover. In view of the well known stimulatory involvement of the NE system in the mechanism of pulsatile LH release and the inhibitory effect of GABA and its agonist muscimol on pulsatile LH release, it is suggested that GABA inhibits NE release in the MPO/AH by the mechanism of presynaptic inhibition. The observation that muscimol is unable to suppress LH release in vox OEP-primed rats may indicate that those estrogen receptive neurons in the MPO/AH which mediate the negative feedback action of the steroid may use GABA as neurotransmitter and that they are the neurons which inhibit NE release. The inhibitory effect of locally implanted muscimol into the MPO/AH also supports this hypothesis. The facilitatory action of this implanted GABAergic drug on prolactin release points to the involvement of control mechanisms for the regulation of prolactin secretion which reside in the MPO/ AH. The stimulatory effect of intraventricularly injected GABA on hypothalamic DA turnover makes it likely that other than dopaminergic mechanisms are involved in mediating the stimulatory effect of GABA on prolactin release.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238029
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  • 2
    Electronic Resource
    Electronic Resource
    Micronodular endocrine cell hyperplasia in hypergastrinaemia: Evidence of morphological heterogeneity
    Amsterdam : Elsevier
    Regulatory Peptides 40 (1992), S. 191 
    Details
    ISSN: 0167-0115
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0167-0115(92)90300-J
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  • 3
    Electronic Resource
    Electronic Resource
    Regulatory peptides (glucagon, somatostatin, substance P, and VIP) in the brain and gastrointestinal tract of Ambystoma mexicanum
    Amsterdam : Elsevier
    General and Comparative Endocrinology 58 (1985), S. 150-158 
    Details
    ISSN: 0016-6480
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0016-6480(85)90148-0
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  • 4
    Electronic Resource
    Electronic Resource
    Observations on blood flow related electrical impedance changes in rigid tubes (1976)
    Springer
    Pflügers Archiv 366 (1976), S. 289-291 
    Details
    ISSN: 1432-2013
    Keywords: impedance cardiography ; pulsatile blood flow ; erythrocyte orientation ; electrical conductivity of blood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Mammalian blood in pulsatile flow through a rigid tube has been shown to be anisotropic with regard to its electrical conductivity. When flow increases there is a rise in conductivity in the longitudinal and a fall in the radial direction. These changes are caused by flow-dependent variations in the orientation of the disk-shaped erythrocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00585894
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  • 5
    Electronic Resource
    Electronic Resource
    Origin of the impedance cardiogram investigated in the dog by exchange transfusion with a stroma-free haemoglobin solution (1977)
    Springer
    Pflügers Archiv 368 (1977), S. 169-171 
    Details
    ISSN: 1432-2013
    Keywords: impedance cardiography ; electrical conductivity of blood ; stroma-free haemoglobin solution ; thoracic electrical impedance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In an anaesthetized dog an exchange transfusion was carried out with stroma-free haemoglobin solution. The total circulating blood volume was kept constant. The heart-synchronous changes in the thoracic electrical impedance (Z o ) were measured before and after the exchange transfusion.Z o consists of a parallel connection of a tissue impedance (Z t ) and a blood impedance (Z b ). With the aid of this model forZ o the relative variations inZ b (ΔZ b /Z b ) were calculated from the relative variations inZ o (ΔZ o /Z o ). The marked decrease of ΔZ b /Z b during the experiment can only be explained by the fact that apart from the heart-synchronous changes in vascular volume the impedance changes are also caused by flow-dependent changes in the electrical conductivity of blood caused by variations in orientation of the erythrocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01063473
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  • 6
    Electronic Resource
    Electronic Resource
    Somatostatin cells in rat antral mucosa: qualitative and quantitative ultrastructural analyses in different states of gastric acid secretion (1991)
    Springer
    Histochemistry and cell biology 95 (1991), S. 373-382 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the gastrointestinal tract somatostatin is localized in endocrine cells and in neurons. The antral somatostatin (D-) cell shares features of both cell types. The activity of the antral D-cell is regulated by intragastric pH. Therefore different states of gastric acidity were induced experimentally in order to study D-cell morphology at the electron microscopical level. The morphological findings were related to measurements of plasma and tissue concentrations of the peptide. The D-cell is characterized by extensive membrane interdigitations with neighbouring cells. Changes in the activity of antral D-cells are reflected by an increase in cytoplasmic secretory granule density and a shift of secretory granules towards basal cell processes. Direct endocrine cell contacts at the level of the perikarya were rarely observed. The intracellular distribution of secretory granules suggests that cell communication is more likely to take place at the level of the strongly immunoreactive cytoplasmic processes. No evidence for endocrine or exocrine (luminar) secretion was observed morphologically. This is in agreement with the concept of paracrine secretion of the antral D-cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00266965
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  • 7
    Electronic Resource
    Electronic Resource
    Light and electron microscopical immunocytochemical localization of pancreastatin-like immunoreactivity in porcine tissues (1990)
    Springer
    Histochemistry and cell biology 93 (1990), S. 369-380 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Pancreastatin is a 49 amino acid comprising peptide isolated from porcine pancreas that is derived by proteolytic processing from chromogranin A. Using an antibody against the synthetic C-terminal fragment pancreastatin (33–49), we examined the light and electron microscopical immunocytochemical localization of this peptide in porcine tissues. Pancreastatin-like immunoreactivity (PLI) was found in pancreatic somatostatin-, insulin- and glucagon cells in varying intensities; pancreatic polypeptide cells were always negative. At the electron microscopical (EM) level the immunoreactivity was confined to the electron dense core of the secretory granules in the case of somatostatin and insulin cells or to the less electron dense “halo” of the glucagon granules. In the antrum PLI positive cells represented gastrin (G), somatostatin (D) and enterochromaffin (EC) cells, in the duodenum in addition to EC- and G-cells a small number of PLI positive cells showed a positive immunoreaction for glucagon-like peptide (GLP) I and secretin in serial sections. Both norepinephrine and epinephrine containing cells of the adrenal medulla exhibited a strong reaction for PLI. In the pituitary several cell populations stained with varying intensities, including gonadotrophs and thyrotrophs. PLI is present in a distinct and characteristic subpopulation of neuroendocrine cells in various organs. The subcellular localization may indicate a function in the granular concentration, packaging and storage of peptides and amines in the brain-gut endocrine system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00315853
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  • 8
    Electronic Resource
    Electronic Resource
    Electron-microscopical evidence for heterogeneity of micronodular argyrophil cell growth in man (1998)
    Springer
    Cell & tissue research 292 (1998), S. 91-99 
    Details
    ISSN: 1432-0878
    Keywords: Key words Argyrophil cells ; Chronic gastritis ; Gastrinoma/Zollinger-Ellison syndrome ; Hypergastrinaemia ; Neuroendocrine complexes ; Pernicious anaemia ; Proton pump inhibitors ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Hypergastrinaemia-associated changes of non-antral argyrophil cells in man are of increasing interest, because of the development of potent inhibitors of gastric acid secretion. Using an antibody against chromogranin A, we identified micronodular endocrine cell hyperplasia of the oxyntic mucosa in gastric biopsy specimens of patients with hypergastrinaemia of different backgrounds. Consecutive ultrathin sections were examined at the electron-microscopical level. Endocrine cell types within the (extraepithelial) micronodules closely resembled those in the adjacent mucosa. Micronodules were classified into two groups. The first group was composed of endocrine cells only and predominated in patients with drug-induced hypergastrinaemia and/or chronic gastritis, and in a gastrinoma/MEN I patient. The second group represented “neuroendocrine complexes”, showing a close intermingling of non-myelinated nerve fibres with endocrine cells, and was found predominantly in pernicious anaemia. Micronodular argyrophil cell growth in man is therefore heterogeneous and depends on the background of the hypergastrinaemia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410051038
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