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  • 1
    Electronic Resource
    Electronic Resource
    Optical-field calculations for lossy multiple-layer AlxGa1−xN/InxGa1−xN laser diodes (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1196-1203 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical-field profiles in wide-band-gap AlxGa1−xN/InxGa1−xN multiple-quantum well (MQW) separate-confinement heterostructure (SCH) laser diodes (LDs) were calculated using a 2×2 transfer-matrix approach that accommodates complex refractive indices. The refractive indices of AlxGa1−xN and InxGa1−xN were approximated by shifting the refractive index of GaN according to the band-gap energy of the solid solution. Current LDs were analyzed and show reasonable optical confinement. Optimization of the SCH waveguide for a three MQW active region was performed by varying the waveguide and cladding layer thicknesses. For 0.8μm thick Al0.10Ga0.90N cladding layers, waveguides on sapphire and SiC substrates had a maximum confinement factor of ∼3.3%. Layers outside of the waveguide strongly affected the optical field for thin (∼0.4 μm) cladding layer thicknesses and resulted in resonant coupling of the light out of the waveguide. Sapphire substrates were found to enhance light confinement, while SiC substrates were found to reduce optical confinement as the cladding layer thickness is reduced. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368185
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  • 2
    Electronic Resource
    Electronic Resource
    Linear optical properties of a heavily Mg-doped Al0.09Ga0.91N epitaxial layer (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 3188-3190 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The room-temperature absorption coefficient and ordinary refractive index for a ∼0.4-μm-thick p-type wurtzite Al0.09Ga0.91N epitaxial layer were determined via optical transmission measurements. The layer was grown by metal organic chemical vapor deposition and heavily doped (∼5×1019 cm−3) with Mg. Additional measurements of the refractive index by prism coupling to the layer confirmed the transmission results. The low-temperature AlN buffer layer altered the expected interference fringes of the transmission spectrum below the band-gap energy and had to be accounted for in the analysis. The absorption coefficient exhibited band-tail effects and had a reduced slope near band-gap energy as compared to undoped GaN. Using a detailed balance argument, the reduced slope was consistent with the lack of a peak in the continuous-wave photoluminescent emission. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124102
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  • 3
    Electronic Resource
    Electronic Resource
    Ordinary and extraordinary refractive indices for AlxGa1−xN epitaxial layers (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 67-69 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dispersion of the ordinary and extraordinary indices of refraction for wurtzite AlxGa1−xN epitaxial layers with x=0.00, 0.04, 0.08, 0.11, and 0.20 in the range of wavelengths 457〈λ〈980 nm were measured via a prism-coupled waveguide technique. The quantitative accuracy of x is ±10% and the accuracy of the refractive indices is ∼±0.01. The dispersion is found to be well described by a 1st-order Sellmeier dispersion formula. A simple functional form is presented that allows calculation of the refractive indices as functions of x and λ. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124278
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  • 4
    Electronic Resource
    Electronic Resource
    Ki-67 and biological behaviour in meningeal haemangiopericytomas (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science Ltd
    Histopathology 29 (1996), S. 0 
    Details
    ISSN: 1365-2559
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The biological behaviour of meningeal haemangiopericytomas was retrospectively studied using immunohistochemical staining with MIB1, a monoclonal antibody against the Ki-67 antigen, a nuclear protein related to cell proliferation. Paraffin-embedded material from 62 tumours from 40 patients were investigated. The proliferating compartment of the tumours was estimated by evaluating the MIB1 staining index, i.e. the percentage of MIB1 positive nuclei in at least 1000 counted tumour cells in representative areas. The staining index ranged from 1.24% to 39.01%. Statistical analysis revealed no significant correlation between the staining index and recurrence-free survival (χ2 = 0.3922, P = 0.5311). Long-term observation (〉100 months), however, revealed a tendency to longer survival in the group with a staining index less than 5%. According to our results, the MIB1 staining index does not contribute to the accuracy of predicting the clinical outcome of meningeal haemangiopericytomas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2559.1996.d01-479.x
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  • 5
    Electronic Resource
    Electronic Resource
    Rab3 Proteins and SNAP-25, Essential Components of the Exocytosis Machinery in Conventional Synapses, are Absent from Ribbon Synapses of the Mouse Retina (1996)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 8 (1996), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: GTP-binding rab proteins, present in synaptic vesicles and endocrine secretory granules, have been shown to be involved in the control of regulated exocytosis. We found rab3 proteins in immunoblots of diverse areas of the mouse central nervous system (spinal cord, olfactory bulb, hippocampus, cerebellum and neocortex). Immunohistochemical observations at light- and electron-microscopical levels in the hippocampus and other areas revealed rab3 proteins in virtually all synaptic fields and terminals of the areas investigated. In the retina, rab3A immunoreactivity was confined to the inner and outer plexiform layers. Ultrastructural examination revealed that rab3A was present in conventional terminals in the inner plexiform layer and in horizontal cell processes of the outer plexiform layer. In contrast ribbon synapses, which play a key role in transferring information from the photoreceptor cells to the central nervous system, were immunonegative. We also tested whether other proteins of the rab3 family are present in ribbon synapses. However, using an antibody recognizing rab3B and rab3C in addition to rab3A, we found no immunoreactivity in these synapses. Interestingly, we observed also no immunoreactivity for synaptosomal-associated protein 25 (SNAP-25) in ribbon synapses, but conventional synapses and horizontal cell processes were heavily stained. Our data show that the known rab3 and SNAP-25 isoforms, which are components of the secretory apparatus of conventional synapses, are absent from ribbon synapses of the retina. Our observations suggest different mechanisms of transmitter exocytosis in conventional and ribbon terminals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1996.tb01177.x
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  • 6
    Electronic Resource
    Electronic Resource
    The Expression of Connexins during Growth and Development of Skeletal Elements in the Dog (2005)
    Berlin, Germany : Blackwell Verlag GmbH
    Anatomia, histologia, embryologia 34 (2005), S. 0 
    Details
    ISSN: 1439-0264
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Efficient and well-regulated intercellular communication is essential to organize the activities of the different cell populations involved during growth and concomitant structural maturation of the skeleton. For direct cell-cell communication gap junctions composed of connexins (Cx) are present. So far 21 Cx types have been identified in mammals, which differ in molecular permeability as well as tissue expression pattern. To characterize the Cx distribution in the developing canine skeleton, samples from humerus, scapula and lumbar vertebrae of Beagle dogs aged 1.5, 3, 4.5 months and 1.5 years were fixed in Bouin's solution, decalcified with 25% EDTA and embedded in paraffin wax. Using immunohistochemistry and in situ hybridization, the expression of Cx 26, 30, 31, 32, 43, and 45 was studied in bone tissue plus associated epiphyseal and growth plate cartilage. Of all bone cells, osteoblasts showed the largest Cx expression repertoire: they were positive for Cx 26, 30, 32 and 43. After transformation into bone lining cells Cx43 expression was lost while in osteocytes only Cx 26 and 32 was detected. A wide variety of Cx reactions was also found in osteoclasts: Cx 26, 30, 32, and 43. In contrast, chondrocytes showed a much more restricted Cx expression pattern. Positive reactions were only seen in hypertrophic chondrocytes of epiphyseal cartilage (Cx 26, 31, 32) and in the proliferative (Cx32) and hypertrophic zone (Cx 26 and 32) of growth plate cartilage. Additionally, Cx31 was strongly expressed in the cellular layer of the periosteum covering areas of intensive bone modelling in the puppies. Age- and microlocation-dependent variations in expression and/or staining intensity were also observed in the other Cx types. These results demonstrated that canine bone cells are capable of synthesizing a wide variety of Cx types during skeletal development, thus propagating different cellular signals via gap junctions in a differentially regulated and requirement orientated manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1439-0264.2005.00669_106.x
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  • 7
    Electronic Resource
    Electronic Resource
    The Gap Junctional Protein Connexin(Cx)43 in Testicular Cancer: its Loss Marks Progession from Carcinoma In Situ to Invasive Germ Cell Tumour (2005)
    Berlin, Germany : Blackwell Verlag GmbH
    Anatomia, histologia, embryologia 34 (2005), S. 0 
    Details
    ISSN: 1439-0264
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Carcinoma-in-situ (CIS) of the testis is known to be the pre-invasive stage of most human germ cell tumours (seminoma and non-seminoma), but the mechanisms leading to an increased pubertal proliferation of CIS cells after a long latency and to progression of CIS to an invasive malignancy are still not known. Additionally, CIS and seminoma have also been reported in equine testis (Veeramachaneni and Sawyer, 1998). The gap junctional protein and tumour suppressor gene connexin(cx)43 represents the predominant cx in human, canine and rodent testis so far and it is expected to play a key role for the regulation of both proliferation and differentiation of germ cells (spermatogonia and spermatocytes), and its gene- and protein-expression pattern is typical for the pubertal terminal differentiation of somatic Sertoli cells. Using cDNA-microarray analysis, in-situ hybridization (ISH), RT-PCR from tissue homogenate and semi-quantitative RT-PCR from well defined microdissected tubules with normal spermatogenesis, CIS, intratubular seminoma (ISe) and from seminoma cells from invasive seminoma we found a downregulation of cx43 starting in intratubular CIS, leading to a complete loss in most invasive seminoma cells. This indicates that regulation of cx43 expression takes place at transcriptional level confirming and expanding earlier studies of protein expression (Brehm et al., 2002). This reduction of cx43-expression suggests that an early intratubular derangement in cx43-gene expression and disruption of inter-cellular communication between Sertoli cells and/or Sertoli cells and pre-invasive tumour cells via cx43-gap junctions may play a role in the proliferation of CIS cells and seminoma cells and in the progression phase of testicular seminoma development.References  Veeramachaneni, D. N., and H. R.Sawyer, 1998: Carcinoma in situ and seminoma in equine testis. APMIS 106, 183–185.Brehm R., A. Marks, R. Rey, S. Kliesch, M. Bergmann and K. Steger, 2002: Altered expression of connexins 26 and 43 in Sertoli cells in seminiferous tubules infiltrated with carcinoma-in-situ or seminoma. J. Pathol. 197, 647–653.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1439-0264.2005.00669_16.x
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  • 8
    Electronic Resource
    Electronic Resource
    Die Riesenaxonneuropathie Eine Kasuistik (1996)
    Springer
    Der Pathologe 17 (1996), S. 213-218 
    Details
    ISSN: 1432-1963
    Keywords: Schlüsselwörter Riesenaxonale Neuropathie ; Mikrofilamentallagerung ; Key words Giant axonal neuropathy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary We report a sporadic case of giant axonal neuropathy (GAN) starting in a 5-year-old boy with gait disturbance. At the age of 10 years he showed signs of a sensomotoric polyneuropathy and central neurological symptoms: intention tremor, nystagmus and visual disturbance. The boy also had curly hair. Sural nerve biopsy showed many giant axons with accumulation of microfilaments, which were also found in cytoplasma of Schwann cells, endothelial cells and fibrocytes. Similar changes were detected in endothelial cells of a muscle biopsy, which additionally displayed neurogenic atrophy and target fibers. Immunohistochemically, desmin, vimentin, heat shock protein 70, and ubiquitin were not detectable in giant axons, which, however, contained neurofilament protein 68, 200 and β -tubulin. Our case shows that careful ultrastructural examination of a muscle biopsy may point to the diagnosis of GAN.
    Notes: Zusammenfassung Wir berichten über einen sporadischen Fall von Riesenaxonneuropathie (RAN), die bei einem 5 jährigen Jungen mit einer progredienten Gangstörung begann. Auffällig waren außerdem stumpfe, gekräuselte Haare. Im Alter von 10 Jahren bestanden eine sensomotorische Polyneuropathie und zentral-neurologische Symptome: Visusminderung, sakkadierte Blickfolge und Intentionstremor. Die Biopsie des N. suralis bestätigt das Vorliegen einer Neuropathie und zeigt viele Risenaxone mit ultrastruktureller Anhäufung von Mikrofilamenten. Diese sind auch im Zytoplasma der Schwann-Zellen, Endothelzellen und Fibrozyten zu erkennen. Auch intramuskuläre Endothelzellen enthalten gleichartige Veränderungen; darüber hinaus ist im Muskel ein neurogenes Gewebsbild ausgebildet. Immunhistochemisch exprimieren die Axone Neurofilamentprotein 200 und 68 sowie β -Tubulin, jedoch weder Desmin, Vimentin, Heat-shock-Protein 70 oder Ubiquitin. Der Fall illustriert, daß die ultrastrukturelle Untersuchung einer Muskelbiopsie diagnostische Hinweise für eine RAN liefern kann.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002920050158
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  • 9
    Electronic Resource
    Electronic Resource
    Different variants of frontotemporal dementia: a neuropathological and immunohistochemical study (1996)
    Springer
    Acta neuropathologica 92 (1996), S. 170-179 
    Details
    ISSN: 1432-0533
    Keywords: Key words Frontotemporal dementia ; Dementia of ; frontal lobe type ; Pick’s disease ; Motor neuron disease ; with dementia ; Pick bodies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Histological and immunohistochemical findings in 20 cases of frontotemporal dementias – 8 cases of dementia of frontal lobe type (DFT), 7 cases of Pick’s disease (PD), and 5 cases of motor neuron disease with dementia (MND/D) – are presented. Common features of all three syndromes were: frontotemporal atrophy, involvement of subcortical nuclei, and swollen chromatolytic cells. Ubiquitin (Ub)-positive and tau-negative inclusions in cortical, hippocampal, and motor neurons were found in MND/D and DFT cases, suggesting a common pathogenesis of MND/D and DFT. MND/D showed the same cytoskeletal alterations in motor nuclei as MND without dementia: Bunina bodies and skein-like, Ub-positive inclusions. DFT differed from PD in the preponderance of histopathological changes in upper cortical layers, the sparseness of chromatolytic cells, and the absence of tau-positive Pick bodies (PBs). There were, however, two transitional cases showing Pick-type histology but no PBs, thus linking DFT and PD. PBs expressed chromogranin B and secretoneurin strongly, but chromogranin A only weakly. They were negative for the 70-kDa heat-shock protein, metallothionein, and glutathione-S-transferase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004010050505
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  • 10
    Electronic Resource
    Electronic Resource
    Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL): a morphological study of a German family (1996)
    Springer
    Acta neuropathologica 92 (1996), S. 341-350 
    Details
    ISSN: 1432-0533
    Keywords: Key words Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) ; Hereditary multi-infarct dementia ; Skin biopsy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is characterized clinically by recurrent cerebral infarcts, subcortical dementia and pseudobulbar palsy, and morphologically by a granular degeneration of cerebral and, to a lesser degree, extracerebral blood vessels. We present morphological findings in a further German family affected by CADASIL. The index case showed the typical periodic acid-Schiff-positive granular degeneration of vascular smooth muscle cells (VSMC) in cerebral vessels, which did not react with antibodies against various immunoglobulins or complement factors. Ultrastructurally, granular osmiophilic material (GOM) covered the VSMC in different cerebral regions as well as in extracerebral organs (muscle, nerve, skin, small and large intestine, liver, kidney and heart). Skin biopsy samples from other family members of the last two generations also revealed GOM irrespective of the clinical symptomatology (CADASIL, migraine only or asymptomatic). Patients in the third generation had higher amounts of GOM in skin vessels than did asymptomatic or migraine patients in the fourth generation. We conclude that skin biopsy is a useful and less-invasive screening method for the differential diagnosis of CADASIL.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004010050528
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