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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of environmental contamination and toxicology 58 (1997), S. 8 -15 
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2048
    Keywords: Polyamine ; Ribulose-1,5-bisphosphate carboxylase/oxygenase (large subunit) ; Thylakoid membrane (stabilization) ; Thylakoid protein (D1, D2, cytochrome f)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Monocotyledonous leaves subjected to osmotica used for protoplast isolation accumulate a massive amount of putrescine (Put), lose chlorophyll and senesce rapidly. Treatment with spermidine (Spd) or spermine (Spm) prevents the loss of chlorophyll, indicating preservation of the thylakoid membranes at the site of the chlorophyll-protein complexes. Using several recently produced antibody probes, the effects on the stabilization of thylakoid membranes of applying either difluoromethylarginine (DFMA), a specific inhibitor of putrescine synthesis via arginine decarboxylase, or the polyamines Spd, Spm, or diaminopropane (Dap) to osmotically shocked oat leaves (Avena sativa L.) have been investigated. High protein levels were maintained in thylakoid membranes of leaf tissue incubated in the dark in the presence of 0.6 M sorbitol when pretreated with DFMA. After 48 h incubation, the level of the thylakoid protein D1, at the core of photosystem II, was higher in the DFMA-pretreated leaves as was the stromal protein ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco; as indicated by the level of large subunits). Applications of Spd, Spm or Dap were effective in retarding the loss of D1, D2 and cytochrome f from the thylakoid membranes as well as Rubisco large subunits and chlorophyll from the leaf tissue. The effects of polyamine applications may be mediated through Dap since most of the added Spd or Spm was converted to Dap within 6 h. The possible mechanisms of action of polyamine applications and DFMA-pretreatment on stabilizing the composition of the thylakoid membrane are also discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular histology 14 (1982), S. 943-947 
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A cytochemical study on the endothelium of the hypodermic lymphatic capillaries of the green lizard,Lacerta hispanica, has been carried out. The dialysed iron method produced a homogeneous precipitate on the surface of the endothelial cells and on the inside of the endocytic vesicles. The periodic acid-thiocarbohydrazide-silver proteinate, low pH phosphotungstic acid and high iron diamine techniques gave negative results. The carbohydrates in the capillaries thus seem to be glycosaminoglycans with carboxyl groups. The possible role of these glycosaminoglycans in the formation of the endocytic vesicles is discussed.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1435-1803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary In the anulus fibrosus and it's surrounding at the base of the atrioventricular valves and in the adjacent myocardium arise already in youth foci with histolytic oedemas, which turn to amorph collagen and hyalin scars. A part of these scars calcifies, but mostly after the 50th year of age. — As there is scarcely any histologically normal heart valve, as well there is no anatomically optimal anulus fibrosus with normal surrounding. At the base of the small leaflet of the mitral valve such scars are more frequent and greater and they arise earlier than at the tricuspidal valve. Apparently the mechanical load is the main reason for the oedema and the degenerative alterations of the connective tissue; they are in a broader sense “a traumatic consequence” of the load. Clinically the scars lead from a certain size on to disturbations of valve function, they favorite the formation of extravalvular insufficiencies of the atrioventricular valves and can be accompanied by murmurs. If they can cause a heart block, couldn't be descisively clarified. Radiologically such calcified scars can project themselves into the branches of Rr. circumflexi, especially of the R. circumflexus sinister. In differential diagnosis they must be separated from the calcified foci of the coronary arteries, from myocardial calcifications as well as from the constrictive pericarditis with calcification. These degenerative alterations with loss of the fibrous structure of collagen may be a reason for seam insufficiency, as it may arise after implantation of artificial heart valves.
    Notes: Zusammenfassung Im Anulus fibrosus und seiner Umgebung, also in der Basis der Segelklappen und im angrenzenden Myokard, entstehen schon bei Jugendlichen Herde mit histolytischem Ödem, die in amorphe, kollagene und hyaline Narbenherde übergehen. Ein Teil dieser Herde verkalkt, meistens allerdings erst jenseits des 50. Lebensjahres.—Wie es kaum einmal eine histologisch normale Herzklappe gibt, so auch keinen anatomisch optimalen Anulus fibrosus mit normaler Umgebung. In der Basis des kleinen Segels der Mitralklappe sind solche Herde häufiger und größer, enstehen auch früher als an der Trikuspidalklappe. Anscheinend ist die mechanische Belastung die Hauptursache des Ödems und der degenerative Veränderungen des Bindegewebes; sie sind also im weiteren Sinne Belastungsfolge. Die Herde führen von einer gewissen Größe an klinisch zu Störungen der Klappenfunktion; sie begünstigen die Entstehung extravalvulärer Insuffizienzen der Segelklappen und können mit Geräuschen einhergehen. Ob sie zu einem Herzblock führen können, war nicht eindeutig zu klären. Röntgenologisch können sich solche Kalkherde in den Verlauf der Rr. circumflexi, besonders des R. circumflexus sinister, projizieren. Sie müssen differentialdiagnostisch von verkalkten koronarsklerotischen Herden. Herzmuskelverkalkungen sowie von der verkalkten Perikarditis abgegrenzt werden. Diese degenerativen Veränderungen mit Verlust der Faserstruktur des Kollagens können eine Ursache der Nahtinsuffizienz sein, wie sie nach Implantation künstlicher Klappen auftreten kann.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Plant growth regulation 12 (1993), S. 331-340 
    ISSN: 1573-5087
    Keywords: polyamines ; putrescine ; spermidine ; spermine ; ethylene ; ACC ; RNA ; DNA ; protein synthesis ; enzyme activities ; membranes ; free radicals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Suggested roles for polyamine function, and the evidence for these functions, is reviewed. These include membrane stabilization, free radical scavenging, effects on DNA, RNA and protein synthesis, effects on the activities of RNase, protease and other enzymes, the interaction with ethylene biosynthesis, and effects on second messengers. It is concluded that in addition to interacting with plant hormones, polyamines are able to modulate plant development through a fundamental mechanism(s) common to all living organisms.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Basic research in cardiology 43 (1964), S. 235-249 
    ISSN: 1435-1803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Zusammenfassung 1. Stenosen — arteriosklerotische oder luische — der aortalen Koronarostien bilden eine Barriere für den Einstrom des Blutes in die Koronararterien. — Zentrale Ostiumbarrieren—. 2. Die Äste der Koronarstämme können bei leichter und schwerer Arteriosklerose Stenosen haben, die den Blutzustrom von den Stämmen zu den Ästen vermindern. Ostiumatresien schneiden die Äste vom Blutstrom des Stammes ab. — Periphere Ostiumbarrieren—. 3. Ostiumbarrieren können symptomlos bleiben oder aber zu einer lokalen Blutverteilungsstörung mit Nekrosen und Narben in ihrem Versorgungsgebeit führen. Wenn viele Ostiumbarrieren vorhanden sind, kann sogar das Bild einer Koronarinsuffizienz auftreten. 4. Ostiumbarrieren können durch Kollateralen und Anastomosen umgangen werden. 5. Ostiumbarrieren führen gelegentlich zum Umbau der Gefäßarchitektur. 6. Ostiumbarrieren können sicherlich für flüchtige pectanginöse Beschwerden, manchmal sogar für einen Herztod, besonders bei leichter Koronarsklerose, verantwortlich sein.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-0878
    Keywords: Mucous cells ; Small intestine ; Gastrointestinal system ; Lizard ; Lacertilia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An ultrastructural study of the mucous cells of the intestinal epithelium of four lacertilian species (Lacerta lepida, Lacerta hispanica, Psammodromus algirus and Acanthodactylus erythrurus) is here reported. Two types of mucous cells have been found in these species: common mucous cells and granular mucous cells. Immature and mature forms of both types have been observed. The common mucous cells or typical goblet cells have the same characteristics in all four species. The granules of the granular mucous cells of the two species of Lacerta are similar but differ from those of the other two species.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The histology of the ovotestis was studied by light and electron microscopy in two nudibranch gastropod species. While in Hypselodoris tricolor the ovotestis is intimately associated with the digestive gland tissue, the large gonadal mass of Godiva banyulensis is placed freely in the haemocoele. This fact results in great histological differences between both species.As is common among Mollusca, the immature yolk granule in Hypselodoris and Godiva presumably originates from membrane-rich cytoplasmic inclusions, which we have termed dense multivesicular bodies. Such inclusions consist of an outer membrane enclosing membrane remnants and a granular, electron-dense material. These elements are accumulated and mixed in the center of the dense multivesicular body and could be actually transformed into the paracrystalline core of the immature yolk granule, the cortex of which is made up of part of the central accumulation materials that have not spread into the crystal. During vitellogenesis, some mitochondria are subjected to a process of transformation affecting mainly their inner membrane (including mitochondrial cristae) and matrix. However, the conversion of modified mitochondria into yolk precursors, as reported for other gastropod species, could not be determined with absolute certainty on the basis of our observations on static material.The mature yolk granule consists of a central paracrystalline core, similar in structure to that of the immature yolk granule, and a peripheral membranous cortex, which seems to spread centripetally, thus permitting the crystal to grow. The cortical material consumed in synthesizing the central core appears to be restored by addition of degenerative mitochondria to the yolk granule surface.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0570-0833
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Publication Date: 2014-03-22
    Description: Genetic recombination associated with sexual reproduction increases the efficiency of natural selection by reducing the strength of Hill–Robertson interference. Such interference can be caused either by selective sweeps of positively selected alleles or by background selection (BGS) against deleterious mutations. Its consequences can be studied by comparing patterns of molecular evolution and variation in genomic regions with different rates of crossing over. We carried out a comprehensive study of the benefits of recombination in Drosophila melanogaster , both by contrasting five independent genomic regions that lack crossing over with the rest of the genome and by comparing regions with different rates of crossing over, using data on DNA sequence polymorphisms from an African population that is geographically close to the putatively ancestral population for the species, and on sequence divergence from a related species. We observed reductions in sequence diversity in noncrossover (NC) regions that are inconsistent with the effects of hard selective sweeps in the absence of recombination. Overall, the observed patterns suggest that the recombination rate experienced by a gene is positively related to an increase in the efficiency of both positive and purifying selection. The results are consistent with a BGS model with interference among selected sites in NC regions, and joint effects of BGS, selective sweeps, and a past population expansion on variability in regions of the genome that experience crossing over. In such crossover regions, the X chromosome exhibits a higher rate of adaptive protein sequence evolution than the autosomes, implying a Faster-X effect.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
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