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  • 1
    Electronic Resource
    Electronic Resource
    Feed from Sewage, Sewage Sludge as Feed Ingredient for Swine and Poultry (1955)
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 3 (1955), S. 795-796 
    Details
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jf60055a011
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  • 2
    Electronic Resource
    Electronic Resource
    Cytochemical localization of the K+ regulation interface between blood and brain (1977)
    Springer
    Cellular and molecular life sciences 33 (1977), S. 1093-1094 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Phosphatase activity identified with Na+−K+-ATPase was localized at the basal surface of cerebral cortical capillary endothelium by perfusion with a p-nitrophenyl phosphate-strontium medium. The relationship of this to the blood-brain barrier to K+ is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01945990
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  • 3
    Electronic Resource
    Electronic Resource
    Distribution and properties of an adenosine triphosphatase in the tanycyte ependyma of the IIIrd ventricle of the rat (1976)
    Springer
    Histochemistry and cell biology 47 (1976), S. 145-157 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distribution, histochemical properties and ultrastructural localization of adenosine triphosphate (ATP) hydrolyzing enzymes in the tanycyte ependyma of the third ventricle have been studied in female Wistar rats. Using a calcium-cobalt procedure and a lead capture technique, splitting of ATP could be demonstrated in perikarya and processes of tanycytes in the region of the ventromedial nucleus. The reaction showed no dependence on magnesium or sodium ions, did not occur with other monodi-, and tri-phosphates as substrates, and was inhibited by p-chlormercuribenzoate (PCMB) and sodium fluoride, but not by ouabain. With the calciumcobalt method the highest intensity of reaction was found at pH 9.4, whereas the lead method gave optimal results at pH 6–8. At the ultrastructural level, the reaction product was found at the outer surface of the plasma membranes of tanycytes and reached its highest concentrations in the region of the apical microvilli. From the findings it is concluded that splitting of ATP in tanycytes is due to a true ATPase. The enzyme might be involved in an active transport of substances by tanycytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00492562
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  • 4
    Electronic Resource
    Electronic Resource
    The localization and properties of membrane adenosine triphosphatases in the guinea-pig placenta (1979)
    Springer
    Histochemistry and cell biology 61 (1979), S. 157-165 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distribution and properties of cytochemically demonstrable phosphatases in the near-term guinea-pig placenta were examined using a strontium capture technique for sodium- and potassium-dependent adenosine triphosphatase (Na+, K+-ATPase) and a lead capture technique for magnesium-dependent adenosine triphosphatase (Mg2+-ATPase). Localizations with the strontium technique in the presence of an alkaline phosphatase inhibitor were mainly on the syncytiotrophoblast plasma membranes; the reaction was potassium-dependent and ouabain-sensitive. Reaction product using the lead capture method was found on both trophoblast and endothelial cell plasma membranes and was independent of magnesium and insensitive to p-hydroxymercuribenzoate (POHMB), an inhibitor of membrane ATPases. However, a very large proportion of this reaction could be blocked by an alkaline phosphatase inhibitor. It is concluded that the strontium capture technique gave a reliable localization for Na+, K+-ATPase. However, the lead capture method mainly demonstrated alkaline phosphatase, and does not offer a useful approach to specific ATPase studies in this particular system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00496528
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  • 5
    Electronic Resource
    Electronic Resource
    Development of Endothelial Paracellular Clefts and their Tight Junctions in the Pial Microvessels of the Rat (1997)
    Springer
    Journal of neurocytology 26 (1997), S. 567-575 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The microvessels of the pia mater lack an investment with astrocyte processes but nonetheless have a high transendothelial electrical resistance which has caused them to be regarded as part of the blood-brain barrier. This high resistance is known to be acquired in the perinatal period. The aim of our study was to relate the known physiological changes with differentiation of the endothelial paracellular clefts and especially of their tight junctions which provide the basis for the high transendothelial resistance of blood-brain barrier vessels. Tight junctions of endothelial cell paracellular clefts in pial microvessels were examined by transmission electron microscopy using goniometric tilting to reveal and measure membrane separations at tight junctions in fetal, postnatal and adult rats. These tight junctional membrane separations narrowed over the period (E16:6.3 nm, D1:6.4 nm, D7:5.4 nm) and differentiated into two groups by the adult stage: one with a membrane separation of 2.8 nm and the staining characteristics of non-brain endothelial junctions, and the other with no detectable membrane separation and the staining characteristic of blood-brain barrier endothelial junctions. This patchy and incomplete differentiation of pial tight junctions into a blood-brain barrier-like form could result either from non-uniform exposure to inductive signals or to local variation in responsiveness to such agents. Although these changes in junction organization may be related to the known increase in pial transendothelial resistance in the perinatal period, we have not yet identified any sharply defined structural change which coincides with this physiological event.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015438624949
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  • 6
    Electronic Resource
    Electronic Resource
    The role of gap junctions in trophoblastic cell fusion in the guinea-pig placenta (1980)
    Springer
    Cell & tissue research 205 (1980), S. 311-318 
    Details
    ISSN: 1432-0878
    Keywords: Placenta ; Guinea pig ; Trophoblast ; Cell fusion ; Gap junctions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Fusion of cytotrophoblast cells in the guinea-pig placenta occurs at regions of plasma membrane interdigitation where the cells are attached to one another by complex arrays of gap junctions and desmosomes. Fusion begins at the gap junctions, which are lost in this process. The desmosomes play no obvious part in the fusion mechanism and remain after fusion as sites of attachment of syncytiotrophoblast membrane to itself. It is proposed that a major role of gap junctions in placental development is to bring trophoblast plasma membranes into a close relationship which may act as a starting point for cell fusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234689
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  • 7
    Electronic Resource
    Electronic Resource
    Interendothelial junctions of cardiac capillaries in rats: their structure and permeability properties (1988)
    Springer
    Cell & tissue research 252 (1988), S. 57-66 
    Details
    ISSN: 1432-0878
    Keywords: Heart ; Endothelium ; Tracer studies ; Junctional structures ; Permeability ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The isolated perfused heart model was used to examine the structure of rat cardiac capillaries and their permeability to macromolecules of various sizes. Haemoglobin (diameter 6.4 nm) and catalase (10.4 nm) did not cross the endothelium but remained on the luminal side. Cytochrome C (3 nm) and horseradish peroxidase (6 nm) both crossed the endothelium to the subendothelial space and filled the caveolae on the abluminal side as well as the entire length of the lateral intercellular spaces. The membranes of the endothelial cells are separated by an intercellular gap of mean width 18.2 nm. At one or more zonular regions within each lateral intercellular space the two membranes approach each other more closely and frequently appear to fuse. However, tilting the specimen shows that, in these regions, there is a gap of mean width 5.4 nm (in lanthanum- and tannic acid-treated tissue, 3.8 nm in ferrocyanide-treated tissue) between the membranes. We conclude that these narrow regions sieve macromolecules on the basis of size although other factors may determine their permeability properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213826
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  • 8
    Electronic Resource
    Electronic Resource
    Structural features and quantitative age-dependent changes in the intervascular barrier of the guinea-pig haemochorial placenta (1977)
    Springer
    Cell & tissue research 184 (1977), S. 507-516 
    Details
    ISSN: 1432-0878
    Keywords: Placenta ; Guinea-pig ; Transport ; Syncytiotrophoblast ; Endothelium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The haemomonochorial placenta of the guinea-pig undergoes several quantitative changes between the 49th and 64th days of gestation, all of which are in such a direction as to increase the efficiency of transplacental transport. The fetal vessels become larger, the maternal vessels increase in surface area by proliferation of microvilli, and the effective mean distance between the two vessel sets decreases. The magnitude of these changes suggests that the efficiency of transport of hydrophilic solutes across the maternal-fetal interface could double, although changes in the number of permeation sites per unit area may modify this relationship. The presence of open intercellular spaces and fenestrations in the fetal endothelium suggests that this layer may not be a major permeability barrier in the guinea-pig, but may create an unstirred layer of extracellular fluid between endothelium and syncytiotrophoblast.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220974
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  • 9
    Electronic Resource
    Electronic Resource
    Ultrastructural study of the permeability of the guinea-pig placenta to horseradish peroxidase (1981)
    Springer
    Cell & tissue research 219 (1981), S. 637-647 
    Details
    ISSN: 1432-0878
    Keywords: Placenta ; Guinea pig ; Syncytiotrophoblast ; Endothelium ; Horseradish peroxidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Horseradish peroxidase (HRP) was used to study macromolecule permeation into the guinea-pig placenta perfused in situ. When tissue culture medium 199 (TC 199) was used as fetal-side perfusate, the tracer reaction product was found only lining the fetal endothelium. When a longer period of perfusion with HRP in TC 199 was used, a small amount of reaction product was found in the subendothelial space and syncytiotrophoblastic vesicles, but not in maternal lacunae. In similar experiments using a Krebs bicarbonate Ringer (KRBG) as perfusate the tracer was found (i) lining the fetal endothelium, (ii) in the lateral intercellular spaces of the endothelium, (iii) in the subendothelial space, and (iv) in the maternal lacunae. It is therefore evident that the vehicle influenced the permeability of the guinea-pig placenta to horseradish peroxidase. As other studies have shown that perfusion of the fetal side with salt solution increases pore size, the results with TC 199 are regarded as more representative of the situation in the intact animal. It is therefore suggested that the fetal endothelium of the guinea-pig placenta may be largely impermeable to molecules of the size of horseradish peroxidase (4 nm) or larger.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00210001
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  • 10
    Electronic Resource
    Electronic Resource
    Permeability of the foetal capillary endothelium of the guinea-pig placenta to haem proteins of various molecular sizes (1982)
    Springer
    Cell & tissue research 223 (1982), S. 165-178 
    Details
    ISSN: 1432-0878
    Keywords: Placenta ; Guinea-pig ; Maternal/foetal exchange ; Capillary permeability ; Trophoblast ; Endothelium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Haem proteins of different molecular sizes were perfused into the foetal circulation of the guinea-pig placenta to study the permeability of the foetal endothelium. The smallest molecules tested, microperoxidase (ae 1.0 nm) and cytochrome C (ae 1.5 nm), readily penetrated the endothelium; tracer-reaction product was found in the subendothelial space of the capillaries. However, there was no uptake of these two tracers into the syncytiotrophoblast layer of the placenta. An intermediate-sized molecule, myoglobin (ae 1.7 nm), produced only a weak reaction product in the subendothelial space even when perfused at high concentration. The largest molecule tested, haemoglobin (ae 2.8 nm), did not penetrate the foetal endothelium at any of the concentrations employed. The foetal capillary endothelium thus provided a barrier to protein penetration from the foetal circulation, dependent on molecular size. There was evidence that the site of this barrier was located in the lateral intercellular spaces between the endothelial cells. The syncytiotrophoblast of this haemomonochorial placenta provided an almost absolute barrier to protein penetration from the foetal circulation. As other workers have described maternal-to-foetal transmission of proteins across this layer in the guinea-pig, a working hypothesis of the role of endothelium and syncytiotrophoblast in maternal/foetal protein exchange is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00221507
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