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  • Articles  (4)
  • Citrate synthase  (2)
  • Human  (2)
  • Biology  (4)
  • Geography
  • 1
    Electronic Resource
    Electronic Resource
    Elastic fibres are an essential component of human placental stem villous stroma and an integrated part of the perivascular contractile sheath (1995)
    Springer
    Cell & tissue research 283 (1995), S. 133-141 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Elastic fibres ; Placental stem villi ; Extravascular smooth muscle cells ; Adhesion plaques ; Talin immunoreactivity ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The stroma of human placental stem villi is believed to consist only of reticular and collagen fibres. In the present study we were able to show for the first time by light (orcein staining) and electron microscopy large amounts of elastic fibres in the stem villous stroma. Electron microscopically, homogeneous elastin was found alone or in association with microfibrils. In addition, microfibrils were observed forming long bands. These three structures, generally known to form elastic connective tissue, were seen in close connection with placental extravascular smooth muscle cells, which belong to the perivascular contractile sheath (PVCS) of stem villi. Elastin was associated with these smooth muscle cells and connected to collagen fibres via microfibrils. Collagen fibres were additionally interconnected by spike-like structures. Extravascular smooth muscle cells revealed numerous adhesion plaques which occupied conspicuously long cytoplasmic faces of the plasma membrane. In cryostat sections, immunoreactivity of talin, an attachment protein of adhesion plaques linking intracellular α-actin filaments with extracellular fibronectin, was detected in extravascular and vascular (media) smooth muscle cells. The arrangement of placental extravascular smooth muscle cells, elastic and collagen fibres suggests a functional myofibroelastic unit within the PVCS, which surrounds the large foetal blood vessels possibly contributing to elasticity and supporting tensile and/or contracting forces within the stem villi.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050521
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular anatomy of the perivascular sheath in human placental stem villi: the contractile apparatus and its association to the extracellular matrix (1997)
    Springer
    Cell & tissue research 290 (1997), S. 601-607 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Placental stem villi ; Perivascular contractile sheath ; Molecules of adhesion plaques ; Extracellular matrix molecules ; Immunocytochemistry ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. In previous studies, we have shown that smooth muscle cells and myofibroblast subpopulations of the perivascular stem villous sheath of the human placenta contain focal adhesion plaques and talin immunoreactivity. The close association of these cells to elastic and collagen fibres have led to the assumption of a functional myofibroelastic unit within the perivascular stem villous sheath. Interactions between the extracellular matrix and smooth muscle cells depend on a variety of structural protein assemblies. In the present study, we examined, by immunocytochemistry, whether the molecular assembly of extracellular matrix proteins and molecules of focal adhesions, known to be essential for signal transduction in smooth muscle cells, are also found in smooth muscle cells of the perivascular stem villous sheath of the human placenta. Vascular and extravascular smooth muscle cells were immunoreactive for α-actinin, vinculin, paxillin and tensin, the integrin chains α1 and β1, and the basement membrane components laminin and heparan/-chondroitin sulfate proteoglycan perlecan. pp125FAK did not react. In the extracellular matrix of blood vessel walls and the perivascular stem villous sheath, we found immunoreactivity of fibronectin and collagen types I, VI and undulin (collagen type XIV). From our data we conclude that within the perivascular stem villous sheath, there exists a system of signal transduction molecules, indicating a cross talk between the smooth muscle cells of this sheath and their surrounding extracellular matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050965
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  • 3
    Electronic Resource
    Electronic Resource
    Ecophysiological studies on citrate-synthase: (I) enzyme regulation of selected crustaceans with regard to temperature adaptation (1995)
    Springer
    Journal of comparative physiology 165 (1995), S. 46-55 
    Details
    ISSN: 1432-136X
    Keywords: Citrate synthase ; Enzyme characteristics ; Temperature adaptation ; Isopod crustacea ; Euphausiid crustacea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The characteristics and properties chromatographically purified citrate synthase from the euphausiids Euphausia superba (Antarctica) and Meganyctiphanes norvegica (Scandinavian Kattegat and Mediterranean Sea) and from the isopods Serolis polita (Antarctica) and Idotea baltica (Baltic Sea) were used to elucidate biochemical mechanisms of temperature adaptation. Additionally, maintenance experiments were carried out on the euphausiids to determine mechanisms of short term acclimation. Temperature optima (between 37 and 45°C) were unrelated to genotypic cold adaptation, but the activation energy of the Antarctic krill E. superba (10.9 kJ · mol-1) was only a quarter of that in other species (41.8–45.1 kJ · mol-1). The minima of apparent Michaelis constants (total range: 4–20 μmol · 1-1 oxaloacetate; 7–45 μmol · 1-1 acetyl-coenzyme A) showed no relation to natural conditions, and no distinct pH optimum occurred at ambient temperatures. In contrast, apparent Michaelis constants and specific enzyme activities were related to maintenance temperatures in M. norvegica, but not in E. superba. The differences between M. norvegica and E. superba can be interpreted as adaptations to the changes in ambient temperature with regard to the respective steno- and eurythermic tolerances of these crustaceans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264685
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  • 4
    Electronic Resource
    Electronic Resource
    Ecophysiological studies on citrate synthase: (II) enzyme regulation of selected crustaceans with regard to life-style and the climatic zone (1995)
    Springer
    Journal of comparative physiology 165 (1995), S. 56-61 
    Details
    ISSN: 1432-136X
    Keywords: Citrate synthase ; Enzyme regulation ; Temperature adaptation ; ATP inhibition ; Crustacea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Citrate synthase is a regulatory enzyme of the energy metabolism pathway controlling the citric acid cycle. It was studied in order to determine modes of enzyme regulation with regard to the life-style of the investigated species. Citrate synthase from crustaceans with different life-styles were compared: the pelagic euphausiids Euphausia superba from the Antarctic and Meganyctiphanes norvegica from the Scandinavian Kattegat and the Mediterranean were compared to the benthic isopods Serolis polita from the Antarctic and Idotea baltica from the Baltic. Citrate synthase was partly purified chromatographically and the influence of adenosine 5′-triphosphate on enzyme activity was examined. Mechanisms of inhibition and inhibitor constants were determined. Two different mechanisms of enzyme regulation by ATP were found. Citrate synthase from isopods was only competitively inhibited, while citrate synthase from euphausiids showed not only competitive inhibition but also activation by low concentrations of ATP. This activation is equivalent to the reversed methanism of uncompetitive inhibition. The ecophysiological relevances of the coupling of these mechanisms are discussed. The degree of competitive inhibition was different in the two groups of investigated crustaceans. Inhibitor constants were similar within the euphausiids but not in isopods, which showed higher or lower inhibition depending on the climatic zone: the colder the ambient temperature the lower the ATP inhibition. A possible mechanism of temperature adaptation through effects of varying inhibition constants is concluded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264686
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    Paper (German National Licenses)
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