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  • 1
    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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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular charge as a determinant of macromolecule permeability across the fetal capillary endothelium of the guinea-pig placenta (1983)
    Springer
    Cell & tissue research 229 (1983), S. 365-377 
    Details
    ISSN: 1432-0878
    Keywords: Placenta ; Guinea pig ; Capillary permeability ; Endothelium ; Maternal/fetal exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effect of molecular charge on the permeability to macromolecules of the fetal capillary endothelium of the guinea-pig placenta has been investigated. In a series of experiments four horseradish peroxidase (HRP) isoenzymes with different isoelectric points were perfused through the fetal circulations of guinea-pig placentae, which were then prepared for ultracytochemical localization of peroxidase activity. It was found that the two anionic HRP tracers did not penetrate the endothelial cell layer of the fetal capillaries. By contrast, both cationic HRP tracers did penetrate; reaction product was found in the subendothelial space underlying the endothelial cell layer. The route of transendothelial penetration was via the lateral intercellular spaces (LIS) between endothelial cells. In further experiments cationic and anionic ferritins were perfused. Cationic ferritins were found apparently bound in clusters to the luminal surface of the endothelial cell layer in the luminal ends of the LIS whereas very few anionic ferritin molecules were present. We conclude that molecular charge is an important determinant of macromolecule permeability through the fetal capillary endothelium of the guinea-pig placenta and may be related to the presence of anionic sites on the luminal plasma membrane of the endothelial cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00214979
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    Paper (German National Licenses)
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  • 3
    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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    Paper (German National Licenses)
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  • 4
    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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    Paper (German National Licenses)
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