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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2701-2703 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A GaN pyramid grown selectively on a (111)Si substrate with a patterned dot structure of a SiO2 mask, by metalorganic vapor phase epitaxy using AlGaN as an intermediate layer, was characterized by transmission electron microscopy. The dot pattern has an array of 5.0-μm-diameter window openings with a 10 μm period. The density of threading dislocations observed in the window region decreased gradually with increasing distance from the interface. This was mainly due to the dislocation reaction and bending of threading dislocations for the first 2 μm region from the interface and for the upper region, respectively. Dominantly observed defects in the lateral-growth part were dislocations parallel to the interface. An amorphous layer was formed at the interface in the window region. Nitride particles were observed at the interface in the mask region. © 2000 American Institute of Physics.
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 955-957 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using transmission electron microscopy, we have characterized defect structures in laterally overgrown GaN crystals, grown directly on SiO2 stripe-patterned (111)Si substrates by metalorganic vapor phase epitaxy using AlGaN as an intermediate layer. The width and the period of the stripe windows were nominally 1 and 2 μm, respectively. The average threading dislocation density for a completely coalesced 2-μm-thick GaN crystal obtained on the [112¯]-oriented stripe-patterned substrate was ∼2×109 cm−2. The reduction in threading dislocation density is a consequence of the lateral growth and dislocation reactions at the coalesced front of the mask. On the other hand, valleys and pits tend to remain on the mask during the growth on the [11¯0]-oriented stripe-patterned substrate. Cracks were present in both crystals. © 2001 American Institute of Physics.
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  • 3
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  To investigate the relationship between the gap junction protein connexin 43 and the glucose transporter GLUT1, their localization was visualized by double-immunofluorescence microscopy using frozen sections as well as immunogold staining of ultrathin frozen sections. In pigmented epithelial cells, most of the GLUT1 was localized along the plasma membrane facing the blood vessels, whereas in non-pigmented epithelial cells, it was present along the plasma membrane facing the aqueous humor. Connexin 43 was abundant in the ciliary body and localized mainly in the gap junctions connecting the pigmented and non-pigmented epithelial cells. Localization of GLUT1 and connexin 43 in the blood-aqueous barrier suggests that GLUT1, connexin 43, and GLUT1 disposed in this order could be a machinery responsible for the transport of glucose across the blood-aqueous barrier.
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  • 4
    ISSN: 1432-0878
    Keywords: α-Subunit ; Pituitary glycoprotein hormone ; PRL cell ; Pars distalis ; Colocalization ; Immunocytochemistry ; Bullfrog, Rana catesbeiana (Anura)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Our recent finding that the number of immunoreactive α-subunit cells was invariably greater than the total number of immunoreactive gonadotropin (GTH) and thyrotropin (TSH) cells in the bullfrog (Rana catesbeiana) pituitary gland raises the possibility that the α-subunit also exists in pituitary cells other than GTH and TSH cells. The present study demonstrates that there are a considerable number of immunoreactive prolactin (PRL) cells that are also stained with antibody against the α-subunit when adjacent sections are immunocytochemically examined. Neither immunoreactive growth hormone nor adrenocorticotropin cells are stained with the antibody against the α-subunit. The specificity of the antibody against the α-subunit and of that against PRL was demonstrated by preabsorption test, non-competitive binding test, and immunoblot analysis. Double-immunolabeling with gold particles of different sizes for the α-subunit and PRL revealed that most of the immunolabeled PRL-secretory granules are also labeled with the α-subunit antibody. The gold particles indicating the presence of the α-subunit were mostly found in the peripheral zone of the secretory granules.
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  • 5
    ISSN: 1432-0878
    Keywords: Key words: Glucose transporter ; GLUT1 ; Connexin 26 ; Gap junctions ; Placenta ; Syncytiotrophoblast ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Interhemal membrane in the rat placenta is composed of three trophoblastic layers and endothelial cells. GLUT1, an isoform of the facilitated-diffusion glucose transporter, is abundant in the cells of the placental barrier, i.e., syncytiotrophoblastic layers I and II. GLUT1 is localized at the plasma membranes of the maternal-blood side of syncytiotrophoblastic layer I, and of the fetal-blood side of syncytiotrophoblastic layer II. Double-immunofluorescence microscopy has shown that connexin 26 is present between these GLUT1-positive sites, i.e., between syncytiotrophoblastic layers I and II. Immunogold electron microscopy has revealed that connexin 26 is localized in the gap junctions connecting the two layers. Connexin 26 in these layers therefore makes them functionally a single syncytial layer for the transfer of small molecules such as glucose in the rat placental barrier. These results suggest that glucose transfer in the rat placental barrier is carried out as follows: GLUT1 is used for the entry of glucose into the cytoplasm of syncytiotrophoblastic layer I, connexin 26 for the transfer of glucose from syncytiotrophoblastic layer I to syncytiotrophoblastic layer II, and GLUT1 for the exit of glucose to the fetal circulation.
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  • 6
    ISSN: 1432-0878
    Keywords: Key words Water channel protein ; Aquaporin ; AQP5 ; Rat ; Salivary glands ; Immunolocalization ; Secretory stimulation ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Aquaporin-5 (AQP5) is a water channel protein and is considered to play an important role in water movement across the plasma membrane. We raised anti-AQP5 antibody and examined the localization of AQP5 protein in rat salivary and lacrimal glands by immunofluorescence microscopy. AQP5 was found in secretory acinar cells of submandibular, parotid, and sublingual glands, where it was restricted to apical membranes including intercellular secretory canaliculi. In the submandibular gland, abundant AQP5 was also found additionally at the apical membrane of intercalated duct cells. Upon stimulation by isoproterenol, apical staining for AQP5 in parotid acinar cells tended to appear as clusters of dots. These results suggest that AQP5 is one of the candidate molecules responsible for the water movement in the salivary glands.
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  • 7
    ISSN: 1432-0878
    Keywords: Key words: Prohormone convertase ; PC1 ; PC2 ; Pituitary gland ; Corticotrope cell ; Melanotrope cell ; Immunocytochemistry ; Rana catesbeiana ; Buto japonicus ; Xeriopus laevis ; Rana brevipoda ; Buergeria japonica (Anura)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Specific antisera against mammalian prohormone convertases PC1 and PC2 have been used to examine, light-immunocytochemically, the distribution of these enzymes in the pituitary gland of five different species of anuran amphibians (Rana catesbeiana, Bufo japonicus formosus, Xenopus laevis, Rana brevipoda porosa, and Buergeria japonica). A differential pattern of immunoreactivity of PC1 and PC2 was found among these species. Only PC1 was found in the corticotrope cells of the pars distalis in R. catesbeiana, B. japonicus formosus, and X. laevis. Only PC2 was observed in these cells in B. japonica, whereas both PC1 and PC2 were present in these cells in R. brevipoda porosa. PC2 immunoreactivity was always observed in melanotrope cells in the pars intermedia of all of the species, but it coexisted with PC1 immunoreactivity only in R. catesbeiana and X. laevis. The nerve fibers and terminals in the pars nervosa in all of the species were intensely immunopositive with both PC1 and PC2 antibodies. Immunoelectron microscopy on B. japonicus formosus and B. japonica, by means of double-labeling with gold particles of different sizes, revealed that almost all the adrenocorticotropin-positive secretory granules in the corticotrope cells and α-melanophore-stimulating-hormone-positive secretory granules in the melanotrope cells were also labeled with either PC1 or PC2 antibodies. This study suggests that PC1 and PC2 are involved in the intracellular proteolytic cleavage of proopiomelanocortin in amphibian pituitary glands, a situation similar to that proposed for mammals.
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  • 8
    ISSN: 1432-0878
    Keywords: Pituitary ; Gonadotrophs ; LHβ ; FSHβ ; Immunohistochemistry ; Rana japonica (Anura)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Immunohistochemical localization of lutropin β (LHβ) and follitropin β (FSHβ) in the pituitary gland of the frog Rana japonica was studied by the peroxidase-anti-peroxidase method and the two-face, double-labeling method with different-sized gold particles at the light-and electron-microscopic levels, respectively, using monoclonal antibodies against bullfrog LHβ and FSHβ. Light-microscopic immunohistochemistry indicated that approximately 66.0% of all the gonadotrophs in the pituitary contained both LHβ and FSHβ, whereas 33.4% of gonadotrophs contained only LHβ, and 0.6% contained only FSHβ. The staining intensity of LHβ and FSHβ varied from cell to cell. The gonadotrophs were classified into four types (Types I–IV) in terms of their ultrastructural and immunolabeling characteristics. Moreover, several secretory granule types were recognized according to differences in their shape and electron density. In all the cell types, both LHβ and FSHβ were often seen in the same secretory granules, but the proportion of granules bearing both hormones ranged from 5.5% in Type I to 32.7% in Type IV. Most secretory granules in Types I and II were immunolabeled with LHβ alone, whereas a small number of granules were immunolabeled with FSHβ alone. More immunolabeled FSHβ granules were present in Types III and IV than in Types I and II.
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  • 9
    ISSN: 1432-0878
    Keywords: Key words: Pituitary ; Gonadotrophs ; LHβ ; FSHβ ; Immunohistochemistry ; Rana japonica (Anura)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Immunohistochemical localization of lutropin β (LHβ) and follitropin β (FSHβ) in the pituitary gland of the frog Rana japonica was studied by the peroxidase-anti-peroxidase method and the two-face, double-labeling method with different-sized gold particles at the light- and electron-microscopic levels, respectively, using monoclonal antibodies against bullfrog LHβ and FSHβ. Light-microscopic immunohistochemistry indicated that approximately 66.0% of all the gonadotrophs in the pituitary contained both LHβ and FSHβ, whereas 33.4% of gonadotrophs contained only LHβ, and 0.6% contained only FSHβ. The staining intensity of LHβ and FSHβ varied from cell to cell. The gonadotrophs were classified into four types (Types I-IV) in terms of their ultrastructural and immunolabeling characteristics. Moreover, several secretory granule types were recognized according to differences in their shape and electron density. In all the cell types, both LHβ and FSHβ were often seen in the same secretory granules, but the proportion of granules bearing both hormones ranged from 5.5% in Type I to 32.7% in Type IV. Most secretory granules in Types I and II were immunolabeled with LHβ alone, whereas a small number of granules were immunolabeled with FSHβ alone. More immunolabeled FSHβ granules were present in Types III and IV than in Types I and II.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 240 (1985), S. 271-276 
    ISSN: 1432-0878
    Keywords: Pituitary ; Castration ; Gonadotropes ; Mitosis ; Testosterone replacement ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The proliferation of gonadotropes in the anterior pituitary of the castrated male rat was examined immunohistochemically after colchicine treatment. The results show a more than 10-fold increase in mitotic frequency in gonadotropes 1 or 2 weeks after castration, as compared with controls. This result explains the increase in the population of immunoreactive LH cells in castrated male rats. The gonadotropes decreased significantly 1 month after castration. The mitotic activity of gonadotropes was almost completely suppressed in castrates implanted with a silastic tube filled with testosterone.
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