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  • Electron microscopy  (4)
  • Fos  (4)
  • Springer  (8)
  • American Chemical Society (ACS)
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  • Springer  (8)
  • American Chemical Society (ACS)
Years
  • 1
    ISSN: 1432-0827
    Keywords: Parathyroid hormone ; Osteoclasts ; Electron microscopy ; Morphometry ; Metaphysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The effects of parathyroid hormone (PTH) on the size of the osteoclasts, nuclei, ruffled borders, and clear zones in long bones of thyroparathyroidectomized (TPTX) rats were quantitated as a function of time. These data were compared with the number of osteoclasts in the bone and with plasma calcium levels. A significant increase in the average size of the ruffled borders was demonstrated 30 min after injection of 50 U of purified bovine PTH, and of the clear zones 30–90 min after PTH. This was followed at 90 min by an increase in the average size of the cells. The sizes of ruffled borders and clear zones dropped sharply to control levels after 6 h, whereas the size of the cells remained elevated up to 12 h and returned to control values at 24 h. Plasma calcium levels were increased, but not significantly, between 30 min and 6 h. An increase in the number of osteoclasts was significant after 12 h. Removal of the parathyroid glands did not diminish the normal activity of osteoclasts. In animals with intact glands injection of 50 U of PTH did not cause a significant change in cell size or resorbing apparatus. It is concluded that PTH acts to rapidly stimulate the bone resorptive activity of osteoclasts and to cause a delayed increase in their number.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 106 (1970), S. 309-321 
    ISSN: 1432-0878
    Keywords: Red nucleus ; Substantia nigra ; Neuroglia ; Pericytes ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The morphology of perivascular and perineuronal cells in the substantia nigra and red nucleus was studied in Nissl, silver carbonate, and electron microscopic preparations. In light microscopic preparations of the red nucleus and substantia nigra oligodendrocytes and astrocytes are located adjacent to blood vessels and nerve cells. Pericytes are also found adjacent to blood vessels. Scattered perineuronal oligodendrocytes and astrocytes are present in the magnocellular portion of the red nucleus and in the substantia nigra, whereas a distinguishing morphological feature of the parvocellular portion of the red nucleus is the clustering of perineuronal oligodendrocytes around a single neuron. In the present electron micrographs of the red nucleus and substantia nigra oligodendrocytes are separated from the vascular basement membrane (basal lamina) by astrocyte processes and therefore are not truly perivascular. Pericytes are easily identified by the basement membrane which encompasses their cell bodies and processes. Characteristic of the neuropil in the red nucleus are astrocytic processes that approximate dendrites. In contrast, astrocytic processes in the substantia nigra rarely contact dendrites which are covered by a mosaic of synaptic endings. A “third type of neuroglial element” is also present in the neuropil of the substantia nigra and the red nucleus.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 134 (1972), S. 529-538 
    ISSN: 1432-0878
    Keywords: Calyx cells ; Nasonia vitripennis ; Effects of host deprivation ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. The changes in the ultrastructure of the cells of the calyx in the female reproductive system of Nasonia vitripennis are described during a period extending from a condition when host puparia are readily available to a condition of prolonged host deprivation. 2. In conditions when host puparia are available, the calyx cells resemble typical secretory cells with rough endoplasmic reticulum, Golgi complex and mitochondria. After periods of host deprivation the calyx cells increase in size, the organelles change and become reorientated and cytolysomes appear producing a configuration of cells undergoing autophagy. 3. When host puparia become available again, the cells show an ability to recover and recommence production of secretory droplets.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 153 (1974), S. 497-515 
    ISSN: 1432-0878
    Keywords: Arcuate nucleus ; Hypothalamus ; Sexual cycle ; Ribbon-rolls ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Changes in subcellular structures of arcuate neurons correlated in a consistent way with stages of the estrous cycle of the rat. Associated with the rough endoplasmic reticulum short ribbons of moderately electron dense material appeared at metestrus and circular or elliptical bodies termed “ribbon-rolls” at diestrus and proestrus. Although present in proestrus, the ribbon-rolls were smaller at this stage. In a few neurons in diestrous females and in ovariectomized animals one to seven months before perfusion multiple large ribbon-rolls occupied much of the cytoplasm. Also, frequency of dense granules and lysosomes increased in diestrus. The significance of the ribbon-rolls and changes in other structures during the estrous cycle are discussed.
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  • 5
    ISSN: 1573-3904
    Keywords: Peptide drug ; Peptide delivery ; Leucine zipper ; Anticancer drugs ; Transcription factors ; Jun ; Fos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Various members of the bZip and bHLH-Zip families of eukaryotic transcription factors, including Jun, Fos, and Myc, have been identified as oncoproteins; mutation or deregulated expression of these proteins leads to certain types of cancer. These proteins can only bind to their cognate DNA enhancer sites following homodimerization, or heterodimerization with another family member, via their leucine zipper domain. Thus, a novel anticancer strategy would be to inhibit dimerization of these proteins, thereby blocking their DNA binding and transactivation functions. In this paper we show that it is possible to rationally design leucine zipper peptides that bind with high affinity to the leucine zipper dimerization domains of c-Jun and c-Fos, thus preventing the formation of functional c-Jun homodimers and c-Jun:c-Fos heterodimers; we refer to such peptides as superzippers (SZs). In vivo, c-Jun:SZ and c-Fos:SZ heterodimers should be nonfunctional as they lack one of the two basic domains that are essential for DNA binding. While the transport of a peptidic agent into cells often poses a severe obstacle to its therapeutic use, we show that a 46-residue leucine zipper peptide can be transported into HeLa cells by coupling it to a 17-residue carrier peptide from the Antennapedia homeodomain, thus paving the way for detailed studies of the therapeutic potential of superzipper peptides.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    International journal of peptide research and therapeutics 6 (1999), S. 381-390 
    ISSN: 1573-3904
    Keywords: coiled coil ; dimerisation affinity ; dimerisation specificity ; Fos ; Jun ; leucine zipper ; protein-protein interactions ; superzipper peptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Dimerisation of leucine zippers results from the parallel association of α-helices to form a coiled coil. Coiled coils comprise a heptad repeat, denoted as (abcdefg) n , where residues at positionsa andd are hydrophobic and constitute the core of the dimer interface. Charged amino acids at thee andg positions of the coiled coil are thought to be the major influence on dimerisation specificity through the formation of attractive and repulsive interhelical electrostatic interactions. However, the variability ofa-position residues in leucine zipper transcription factors prompted us to investigate their influence on dimerisation specificity. We demonstrate that mutation of a single interfaciala-position Ala residue to either Val, Ile or Leu significantly alters the homo- and heterodimerisation specificities of the leucine zipper domain from the c-Jun transcription factor. These results illustrate the importance ofa-position residues in controlling leucine zipper dimerisation specificity in addition to providing substantial contributions to dimer stability.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    International journal of peptide research and therapeutics 6 (1999), S. 381-390 
    ISSN: 1573-3904
    Keywords: coiled coil ; dimerisation affinity ; dimerisation specificity ; Fos ; Jun ; leucine zipper ; protein–protein interactions ; superzipper peptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Dimerisation of leucine zippers results from the parallel association of α-helices to form a coiled coil. Coiled coils comprise a heptad repeat, denoted as (abcdefg)n, where residues at positions a and d are hydrophobic and constitute the core of the dimer interface. Charged amino acids at the e and g positions of the coiled coil are thought to be the major influence on dimerisation specificity through the formation of attractive and repulsive interhelical electrostatic interactions. However, the variability of a-position residues in leucine zipper transcription factors prompted us to investigate their influence on dimerisation specificity. We demonstrate that mutation of a single interfacial a-position Ala residue to either Val, Ile or Leu significantly alters the homo- and heterodimerisation specificities of the leucine zipper domain from the c-Jun transcription factor. These results illustrate the importance of a-position residues in controlling leucine zipper dimerisation specificity in addition to providing substantial contributions to dimer stability.
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  • 8
    ISSN: 1573-3904
    Keywords: Peptide drug ; Peptide delivery ; Leucine zipper ; Anticancer drugs ; Transcription factors ; Jun ; Fos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Various members of the bZip and bHLH-Zip families of eukaryotic transcription factors,including Jun, Fos, and Myc, have been identified as oncoproteins; mutation or deregulatedexpression of these proteins leads to certain types of cancer. These proteins can only bind totheir cognate DNA enhancer sites following homodimerization, or heterodimerization withanother family member, via their leucine zipper domain. Thus, a novel anticancer strategywould be to inhibit dimerization of these proteins, thereby blocking their DNA binding andtransactivation functions. In this paper we show that it is possible to rationally design leucinezipper peptides that bind with high affinity to the leucine zipper dimerization domains of c-Jun and c-Fos, thus preventing the formation of functional c-Jun homodimers and c-Jun:c-Fosheterodimers; we refer to such peptides as superzippers (SZs). In vivo, c-Jun:SZ and c-Fos:SZheterodimers should be nonfunctional as they lack one of the two basic domains that areessential for DNA binding. While the transport of a peptidic agent into cells often poses asevere obstacle to its therapeutic use, we show that a 46-residue leucine zipper peptide canbe transported into HeLa cells by coupling it to a 17-residue carrier peptide from theAntennapedia homeodomain, thus paving the way for detailed studies of the therapeuticpotential of superzipper peptides.
    Type of Medium: Electronic Resource
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