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  • 1
    Publication Date: 2014-06-10
    Description: In humans, the Crumbs homolog-1 ( CRB1 ) gene is mutated in autosomal recessive Leber congenital amaurosis and early-onset retinitis pigmentosa. In mammals, the Crumbs family is composed of: CRB1, CRB2, CRB3A and CRB3B. Recently, we showed that removal of mouse Crb2 from retinal progenitor cells, and consequent removal from Müller glial and photoreceptor cells, results in severe and progressive retinal degeneration with concomitant loss of retinal function that mimics retinitis pigmentosa due to mutations in the CRB1 gene. Here, we studied the effects of cell-type-specific loss of CRB2 from the developing mouse retina using targeted conditional deletion of Crb2 in photoreceptors or Müller cells. We analyzed the consequences of targeted loss of CRB2 in the adult mouse retina using adeno-associated viral vectors encoding Cre recombinase and short hairpin RNA against Crb2. In vivo retinal imaging by means of optical coherence tomography on retinas lacking CRB2 in photoreceptors showed progressive thinning of the photoreceptor layer and cellular mislocalization. Electroretinogram recordings under scotopic conditions showed severe attenuation of the a-wave, confirming the degeneration of photoreceptors. Retinas lacking CRB2 in developing photoreceptors showed early onset of abnormal lamination, whereas retinas lacking CRB2 in developing Müller cells showed late onset retinal disorganization. Our data suggest that in the developing retina, CRB2 has redundant functions in Müller glial cells, while CRB2 has essential functions in photoreceptors. Our data suggest that short-term loss of CRB2 in adult mouse photoreceptors, but not in Müller glial cells, causes sporadic loss of adhesion between photoreceptors and Müller cells.
    Print ISSN: 0964-6906
    Electronic ISSN: 1460-2083
    Topics: Biology , Medicine
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  • 2
    Publication Date: 2012-09-28
    Description: Retinitis pigmentosa (RP) is a group of genetically heterogeneous, severe retinal diseases commonly leading to legal blindness. Mutations in the CNGB1a subunit of the rod cyclic nucleotide-gated (CNG) channel have been found to cause RP in patients. Here, we demonstrate the efficacy of gene therapy as a potential treatment for RP by means of recombinant adeno-associated viral (AAV) vectors in the CNGB1 knockout (CNGB1 –/– ) mouse model. To enable efficient packaging and rod-specific expression of the relatively large CNGB1a cDNA (~4 kb), we used an AAV expression cassette with a short rod-specific promoter and short regulatory elements. After injection of therapeutic AAVs into the subretinal space of 2-week-old CNGB1 –/– mice, we assessed the restoration of the visual system by analyzing (i) CNG channel expression and localization, (ii) retinal function and morphology and (iii) vision-guided behavior. We found that the treatment not only led to expression of full-length CNGB1a, but also restored normal levels of the previously degraded CNGA1 subunit of the rod CNG channel. Both proteins co-localized in rod outer segments and formed regular CNG channel complexes within the treated area of the CNGB1 –/– retina, leading to significant morphological preservation and a delay of retinal degeneration. In the electroretinographic analysis, we also observed restoration of rod-driven light responses. Finally, treated CNGB1 –/– mice performed significantly better than untreated mice in a rod-dependent vision-guided behavior test. In summary, this work provides a proof-of-concept for the treatment of rod channelopathy-associated RP by AAV-mediated gene replacement.
    Print ISSN: 0964-6906
    Electronic ISSN: 1460-2083
    Topics: Biology , Medicine
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  • 3
    Publication Date: 2013-03-23
    Description: Equipartition arguments provide an easy way to find a characteristic scale for the magnetic field from radio emission by assuming that the energy densities in cosmic rays and magnetic fields are the same. Yet most of the cosmic ray content in star-forming galaxies is in protons, which are invisible in radio emission. Therefore, the argument needs assumptions about the proton spectrum, typically that of a constant proton/electron ratio. In some environments, particularly starburst galaxies, the reasoning behind these assumptions does not necessarily hold: secondary pionic positrons and electrons may be responsible for most of the radio emission, and strong energy losses can alter the proton/electron ratio. We derive an equipartition expression that should work in a hadronic loss-dominated environment like starburst galaxies. Surprisingly, despite the radically different assumptions from the classical equipartition formula, numerically the results for starburst magnetic fields are similar. We explain this fortuitous coincidence using the energetics of secondary production and energy loss times. We show that these processes cause the proton/electron ratio to be ~100 for GHz-emitting electrons in starbursts.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 4
  • 5
    ISSN: 1432-072X
    Keywords: Endoglucanase ; Exoglucanase ; Cellulomonas fimi ; Divergent promoter ; Broad-host range
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cartridge was constructed which contained the divergent tet promoters of transposon Tn10 between an exoglucanase gene (cex) and an endoglucanase gene (cenA) of Cellulomonas fimi. When carried in a broad-host-range vector, the cartridge gave expression of cex and cenA in Escherichia coli, Rhodobacter capsulatus and Klebsiella pneumoniae.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 103 (1972), S. 482-491 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung In Au-diffundierten, Phosphor-dotierten Si-Scheiben wurden durch Transmissionselektronenmikroskopie feine Ausscheidungsteilchen beobachtet, von denen angenommen wurde, daß sie aus einer Au−P-Verbindung bestehen. Um die für eine Identifizierung dieser Ausscheidung mittels Elektronenbeugung notwendigen Daten der Kristallstruktur zu eihalten, wurde eine geringe Menge von Au2P3-Einkristallen durch eine Gasphasentransportreaktion der Elemente hergestellt. Die erhaltenen Kristalle wurden chemisch und durch Röntgenbeugung untersucht. Weiters wurden Aussagen über die Morphologie und die Stabilität der Au2P3-Kristalle erhalten.
    Notes: Abstract Fine precipitate particles assumed to consist of a Au−P compound were observed by transmission electron microscopy in Au-diffused phosphorus-doped Si-wafers. To obtain crystal structure data required for an electron diffraction identification of this precipitate, a small amount of Au2P3 single crystals was grown from the elements by a vapor transport method and analyzed by chemical and X-ray diffraction methods. In addition, information on the morphology and stability of Au2P3 crystals was obtained.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 9 (1972), S. 122-130 
    ISSN: 1432-0827
    Keywords: Tetracycline ; Development ; Calcification ; Statolith ; Nematocysts ; Aurelia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé L'effet de la tétracycline HCl sur la synthèse de statolithes de sulfate de calcium chezAurelia a été étudié. La tétracycline inhibe la synthèse de statolithes et nématocystes à un stade précoce de strobilation. La tétracycline, cependant, n'est pas incorporée dans les statolithes ou nématocystes en formation. Comme la tétracycline ne se combine pas avec le calcium des statolithes de sulfate de calcium dihydraté d'Aurelia, l'explication des effets d'inhibition sur la différenciation de statolithes et nématocystes ne semble pas liée avec un facteur en rapport avec l'incorporation. Des étudesin vitro de quatre systèmes inorganiques de calcium et de tétracycline montrent que le sulfate de calcium dihydraté (gypse) n'incorpore pas la tétracycline: il en est de même de son équivalent isostructural, le phosphate de calcium hydrogéné dihydraté (brushite). Le carbonate de calcium et le phosphate de calcium (apatite) incorpore la tétracycline. L'explication des différences de comportement du calcium peut être liée à la structure cristalline des composés respectifs, et, en particulier, au fait que l'ion Ca est prêt ou non à réagir avec la tétracycline.
    Abstract: Zusammenfassung Es wird über die Wirkung von Tetracyclinchlorhydrat auf die Synthese von Calciumsulfat-Statolithen beiAurelia berichtet. Wird das Tetracyclin in einem Frühstadium der Strobilation verabreicht, so hemmt es die Synthese der Statolithen und der Nematocysten. Das Tetracyclin wird jedoch nicht in die sich bildenden Statolithen oder Nematocysten eingebaut. Da sich das Tetracyclin nicht mit dem Calcium der Calciumsulfatdihydrat-Statolithen derAurelia verbindet, so kann dessen Hemmwirkung auf die Statolithen und die sich differenzierenden Nematocysten offenbar nicht mit einem einbaubedingten Faktor erklärt werden. Untersuchunge, die in vitro mit vier verschiedenen anorganischen Calciumsalzen und Tetracyclin ausgeführt wurden, zeigten, daß weder Calciumsulfatdihydrat (Gips), noch dessen isotrukturelles Aequivalent Calciumhydrogenphosphatdihydrat (Bruschit) Tetracyclin einbauen. Dagegen inkorporieren Calciumcarbonat und Calciumphosphat (Apatit) das Tetracyclin. Die Erklärung für dieses unterschiedliche Verhalten der Calciumsalze findet sich in der Kristallstruktur der betreffenden Verbindungen, d.h. es hängt davon ab, ob das Calciumion ür die Reaktion mit Tetracyclin leicht verfügbar ist.
    Notes: Abstract The effect of tetracycline HCl on synthesis of calcium sulphate statoliths inAurelia is reported. Tetracycline inhibits synthesis of statoliths and nematocysts when administered at an early stage of strobilation. The tetracycline, however, is not incorporated into the developing statoliths or nematocysts. As the tetracycline does not combine with the calcium of the calcium sulfate dihydrate statoliths ofAurelia, an explanation for its inhibitory effects on statoliths and nematocyst differentiation apparently does not rest with an incorporation-related factor. In vitro studies of four inorganic calcium systems and tetracycline revealed that calcium sulfate dihydrate (gypsum) did not incorporate tetracycline nor did its isostructural equivalent, calcium hydrogen phosphate dihydrate (brushite). Calcium carbonate and calcium phosphate (apatite) did incorporate tetracycline. The explanation for these different behaviors of calcium can be found in the crystal structure of the respective compounds, namely, whether or not the Ca ion is readily available to react with tetracycline.
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  • 8
    ISSN: 1617-4623
    Keywords: Key words Cell wall proteins ; Chlamydomonas reinhardtii ; Gamete-specific genes ; Gene expression patterns ; Hydroxyproline-rich glycoproteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gametic differentiation in Chlamydomonas reinhardtii is a two-step process, which is controlled by the sequential action of the two extrinsic signals, nitrogen starvation and blue light. The gamete-specific genes GAS28 and GAS29 are expressed in the late phase of gametogenesis. Their light-induced expression is restricted to cells that have completed the first, nitrogen starvation-activated, phase of differentiation. A comparison of the two genes revealed striking similarities as well as differences. Their most prominent shared feature is an extended sequence homology of over 90% in their 5′-untranslated regions, suggesting a role in translational regulation. GAS28 and GAS29 both encode hydroxyproline-rich proteins (HRGPs) of very similar sizes that exhibit typical features of volvocalean cell wall constituents. GAS28 shows a high degree of homology with the Volvox pherophorin gene family, suggesting a relationship between these genes.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 10 (1954), S. 14-15 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Es wird gezeigt, dass die Hyperkonjugation einen entscheidenden Einfluss auf den Siedepunkt der einfach ungesättigten aliphatischen Kohlenwasserstoffe hat. Dieser Zusammenhang wird durch vergrösserte Elektronendelokalisierung in Molekülen, die Hyperkonjugation aufweisen, theoretisch verständlich. Ein grösseres Ausmass der Elektronendelokalisierung führt zu stärkerer Kohäsion und dadurch zu erhöhten Siedepunkten. Die neue Gesetzmässigkeit ergänzt ohne Widerspruch die bekannten Hückelschen Siedepunktsregeln und erklärt Beobachtungen, die aus keiner der bisher aufgestellten Regeln ableitbar waren. Es ist zu erwarten, dass analoge Zusammenhänge in anderen Gruppen von organischen Verbindungen aufgewiesen werden können.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Physics and chemistry of minerals 27 (2000), S. 665-678 
    ISSN: 1432-2021
    Keywords: Key words Amber ; Rumantite ; Succinite ; Pyrolysis ; Gas chromatography ; Mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  Romanian amber (rumanite) has been considered to be a separate species of fossil resin for more than a century. While earlier investigators held it to be very similar to succinite (Baltic amber), modern scholars have assigned it a distinctly different botanical origin. We have found that almost all of the constituents of the ether-soluble fractions of 13 specimens of authentic rumanite identified by gas chromatography–mass spectrometry have previously been reported in the soluble fraction of succinite, including succinic acid and its monoterpene esters. Additionally and significantly, the soluble fraction of rumanite contains a number defunctionalized compounds that do not preexist in succinite, but that are produced by pyrolysis of whole succinite or of its insoluble polymeric fraction. Simultaneous methylation pyrolysis–gas chromatography–mass spectrometry of the polymeric fraction of seven of the rumanite specimens yielded further copious amounts of dimethyl succinate, a number of diterpene resin acid methyl esters, and additional defunctionalized compounds known to be pyrolysis products of succinite. The evidence shows conclusively that the botanical origin of rumanite is not distinct from that of succinite. Rather, rumanite is a succinite that has suffered partial thermal degradation in the course of the folding of the Oligocene Kliwa sandstone formation in which it is most commonly found.
    Type of Medium: Electronic Resource
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