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1.
Werner E.C. Muller Jürgen Conrad Rudolf K. Zahn Renate Steffen Gerhard Uhlenbruck Isabel Miller 《Differentiation; research in biological diversity》1984,26(1-3):30-35
Abstract. The Hexactinellida sponge Aphrocallistes vastus contains a soluble aggregation factor (AF) whose purification has been described in this communication. It is characterized by a S°20.w value of 37 and a buoyant density of 1.45 g/cm3 . The AF is a glycoporteinaceous particle composed of three major protein species; no core structure could be visualized. In the presence of Ca2+ , the AF causes secondary aggregation of single cells. The aggregation process is temperature, pH, and ionic strength independent within a broad range. Evidence is presented indicating that two (or more) AF molecules are required for the establishment of a stable cell: cell interaction. In contrast to the AFs from demosponges, the hexactinellid AF functions species-unspecifically. 相似文献
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Zusammenfassung Die bemerkenswerte Sternbildung von Agrobacterium luteum Stamm A61 (Moll et al., 1967; Ahrens, 1968) ist auf polare Fimbrien zurückzuführen, die um die Sternaggregate ausgebreitet sind. Es wird angenommen, daß sich Schwärmzellen an den Fimbrien verfangen und durch Kontraktion rasch zum Stern gezogen werden. Nach elektronenoptischen Präparaten sind die Fimbrien bis zu 10,5 lang und können die beobachtete Sternbildung gut erklären. Agrobacterium luteum Stamm B14 besitzt ebenfalls lange polare Fimbrien. Beide Stämme tragen peritriche Geißeln, deren Struktur sich deutlich von den dünnen und unregelmäßigen Fimbrien unterscheidet.
The function of fimbriae in the peculiar star formation of Agrobacterium luteum
Summary The remarkable way of star formation in Agrobacterium luteum strain A61 (Moll et al., 1967; Ahrens, 1968) was found to be due to polar fimbriae which are spread around the star-shaped aggregates. It is assumed that swarmers adhere to the fimbriae and, by contraction, are swiftly pulled towards the star. As seen in electron microscopic preparations, the fimbriae are up to 10,5 long and may well explain the star formation observed. Agrobacterium luteum strain B 14 also possesses long polar fimbriae. Both strains have peritrichous flagella, the structure of which being clearly distinct from the delicate and irregular fimbriae.相似文献
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The high-affinity uptake system of phosphatelimited cyanobacterium Anacystis nidulans [Synechococcus leopoliensis (Raciborski) Komarek] is characterized by a threshold value below which uptake cannot occur. Here it is shown that, if phosphate-limited cyanobacteria are challenged with a short pulse of high phosphate concentration that appreciably exceeds this threshold value, the uptake system undergoes an adaptive response, leading to the attainment of new kinetic properties and a new threshold value. These new properties are maintained for several hours after the pulse. A notable characteristic of this new state is a wide linear dependence of the uptake rate on the external phosphate potential that is a function of the driving force of the uptake process. According to theoretical arguments it is shown that this “linear operation mode” can be explained by the simultaneous operation of several uptake systems with different, staggered threshold values and kinetic properties. Moreover, the new linear uptake properties, in turn, reflect the prehistory of phosphate supply experienced by the population. The consequences of this result with regard to environmental fluctuations of the phosphate concentration in lakes are discussed. 相似文献
6.
Renate Kostrzewa und Achim Kostrzewa 《Journal of Ornithology》1997,138(1):73-82
Zusammenfassung In einer zeitgleichen Untersuchung über 10 Jahre (1985–94) wird die Brutbiologie des Turmfalken in 17 Gebieten Deutschlands verglichen. Insgesamt 3017 Brutpaare mit 11 423 Jungen sind untersucht worden (Tab. 1). Der Bruterfolg in den einzelnen Gebieten ist für jedes Gebiet spezifisch. Er schwankt in den unterschiedlichen Gebieten und Jahren um bis zu 4 Juv/+BP, in jedem Gebiet für sich betrachtet maximal bis 2,5 Juv/+BP. Bedeutung hat insbesondere der Einfluß des Brutplatztyps: Geschützte Brutplätze (in Gebäuden und Kästen) haben höheren Bruterfolg 4 Juv/+BP als offene Brutplätze (Baumnester, Körbe), in denen 4 Juv/+BP ausfliegen. Die Gründe hierfür werden diskutiert.
Breeding success of the KestrelFalco tinnunculus in Germany: results 1985–1994
We compare breeding biology and success of 17 Kestrel subpopulations in Germany in 1985–1994. A total sample of 3,017 breeding attemps and 11,423 fledged young were analyzed by our study group. Breeding success was not parallel over years and study areas; differences were up to four fledged young per successful pair, area and year. Within areas the differences reached 2,5 fledged young per successful pair. The most striking result was the influence of nesting site on breeding success. Clutches in sheltered sites in buildings or in nest boxes always reached mean values above 4 fledged young per successful pair, open nest sites like crow nests, however, were most clearly below this value.相似文献
7.
Renate Lüllmann-Rauch 《Histochemistry and cell biology》1982,76(1):71-87
Summary Tilorone, an agent with antiviral and antitumor activities, has previously been reported to produce clear cytoplasmic vacuoles in many cell types of the rat. The present study on rat spleen was planned to investigate the ultrastructural and histochemical features of the tilorone-induced vacuoles occurring in sinus endothelium, trabecular smooth muscle cells, and macrophages of the red pulp. Evidence was obtained that the vacuoles represent lysosomes overloaded with acid glycosaminoglycans (aGAG). The main purpose of the present study was to overcome the technical difficulties of preserving the intralysosomal storage materials which were highly water-soluble and non-fixable by aldehyde fixatives. Preservation, at least for the light microscopical level, was achieved by freeze drying and by means of cationic dyes which served also to characterize the storage materials on the basis of their acidities. Tissue slices were used to determine the critical MgCl2 concentration necessary to abolish Alcian blue staining; cartilage and mast cells served as references. For the storage material in sinus endothelium, the critical MgCl2 concentration was found to be >0.7 M, as compared to >0.5 M for cartilage and >0.9 M for mast cells. The storage materials in trabecular cells and macrophages were slightly less acidic than cartilagineous matrix and more heterogeneous than that in sinus endothelium. Ultrastructurally, positive staining with high iron diamine (HID) confirmed the presence of aGAG within the tilorone-induced vacuoles. 相似文献
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Renate L. E. P. Reniers Laura Murphy Ashleigh Lin Sandra Para Bartolomé Stephen J. Wood 《PloS one》2016,11(4)
This study investigated the influence of personality characteristics and gender on adolescents’ perception of risk and their risk-taking behaviour. Male and female participants (157 females: 116 males, aged 13–20) completed self-report measures on risk perception, risk-taking and personality. Male participants perceived behaviours as less risky, reportedly took more risks, were less sensitive to negative outcomes and less socially anxious than female participants. Path analysis identified a model in which age, behavioural inhibition and impulsiveness directly influenced risk perception, while age, social anxiety, impulsiveness, sensitivity to reward, behavioural inhibition and risk perception itself were directly or indirectly associated with risk-taking behaviour. Age and behavioural inhibition had direct relationships with social anxiety, and reward sensitivity was associated with impulsiveness. The model was representative for the whole sample and male and female groups separately. The observed relationship between age and social anxiety and the influence this may have on risk-taking behaviour could be key for reducing adolescent risk-taking behaviour. Even though adolescents may understand the riskiness of their behaviour and estimate their vulnerability to risk at a similar level to adults, factors such as anxiety regarding social situations, sensitivity to reward and impulsiveness may exert their influence and make these individuals prone to taking risks. If these associations are proven causal, these factors are, and will continue to be, important targets in prevention and intervention efforts. 相似文献