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1.
We present here an improvement to the analysis of oxygen evolution with four sigma coefficients (4-S) by computing z, the sum of the S-state probabilities, which was introduced earlier (Delrieu and Rosengard 1987, Biochim Biophys Acta 892: 163–171). We demonstrate that z is equal to the ratio of two consecutive Mean Y (the estimation of the steady state oxygen production based on local properties) found by three sigma analysis. The quantity z is useful for computing double-hits, and for showing the inactivation/activation processes of PS II complexes. Three sigma analysis assumes z=1 exactly; since this is not verified, it is argued that four sigma analysis is closer to the real workings of the water oxidizing complex. Oxygen evolution can then be interpreted in the frame of a modified Kok's model where the sum of the probabilities equals z. We therefore suggest that the closer fitting of four sigma analysis to oxygen production data is not simply due to an extra, unnecessary variable, but to the fact that PS II complexes can be inactivated and reactivated under flashing light. Finally, in order to facilitate the use of four sigma analysis, a computer program is made available upon request. 相似文献
2.
Radovan Borojević 《Helgoland Marine Research》1967,15(1-4):116-119
Résumé 1. Les travaux deSarà (1953) et deBurton (1963) ont remis en question la valeur systématique des caractères morphologiques dans la classification des Eponges Calcaires, et ont proposé de considérer de nombreuses formes connues comme des variétés individuelles et régionales d'espèces très plastiques et variables. Nous avons essayé de préciser, par l'observation directe en plongée libre, la distribution et les préférences écologiques des Calcaires, de définir ainsi les limites naturelles de leurs populations, et d'étudier ensuite la variabilité des caractères morphologiques à l'intérieur de ces populations.2. Nous exposons ici l'exemple des espèces des genresClathrina etAscandra, étudiées en Adriatique, dans les régions de Marseille et de Roscoff. Leur distribution est en rapport direct et très précis avec l'exposition aux vagues et à la lumière, à tel point que sur une surface réduite plusieurs espèces se succèdent et se remplacent en fonction de l'exposition de l'endroit. Dans la règion de Roscoff cette distribution est plus large ce qui est dû aux effets des marées, mais les zones écologique préférentielles pour les espèces deClathrina ont pu être établies en fonction de l'importance de l'apport des sédiments par les eaux côtières.3. La possibilité de définir des populations dont la distribution est très précisemment délimitée malgré une coexistence dans un espace réduit, et qui ne sont pas réliées par les formes transitoires, permet d'éliminer l'hypothèse de la cospécificité de ces populations. Elle permet également d'établir les variations morphologiques possibles au sein d'une espèce, de retenir les caractères significatifs pour la classification, et finalement de distinguer les espèces qui se ressemblent morphologiquement. Dans le cas d'animaux qui, commeClathrina, possèdent très peu de caractères utilisables en systématique, c'est la seule façon de résoudre les problèmes de leur taxonomie.
The importance of research on the ecological distribution for the taxonomy of calcareous sponges
The particular difficulties of the taxonomy of calcareous sponges are due to their great plasticity and their capacity for adaptation which obscure the natural limits of species. An attempt was made to define the natural populations of the Mediterranean species of the generaClathrina andAscandra through a study of their ecological distributions. The populations not connected by the transitory forms were defined by their ecological preferences, and, as they are found in a close cohabitation, were treated as having the specific values. The variability of different morphological features is discussed, the features significant for taxonomy are pointed out and the morphologically close species are defined.相似文献
3.
Alvaro N. A. Monteiro Radovan Borojevic 《In vitro cellular & developmental biology. Animal》1995,31(2):149-155
Summary Liver connective tissue cells (LCTC) isolated from patients with fibrotic livers have morphological and biochemical characteristics
of myofibroblasts. We have examined the proliferation of LCTC derived from normal livers and from livers with fibrosis of
different etiologies, as well as proliferation of skin fibroblasts. We have compared proliferation rates in the presence of
fresh human serum and heat-inactivated serum. While skin fibroblast and LCTC from normal liver showed no difference, proliferation
of LCTC from fibrotic livers was markedly decreased in the presence of heat-inactivated serum. We demonstrate that the native
complement component C1 is a factor involved in the induction of DNA synthesis and proliferation of LCTC isolated from fibrotic
livers. We propose that native C1, acting probably in cooperation with other growth factors, is involved in the expansion
of connective tissue cells during the development of liver fibrosis. 相似文献
4.
5.
Maurice E. Levasseur Jean-Claude Morissette Radovan Popovic Paul J. Harrison 《Journal of phycology》1990,26(3):479-484
The effects of long term exposure to suboptimal growth temperature on the photosynthetic apparatus of Dunaliella tertiolecta Butcher were investigated using carbon fixation rate versus irradiance curves and the variable fluorescence induction method. Carbon fixation rates per unite chlorophyll a at saturating (pBm) and subsaturating (αB) irradiances were 55% and 39% lower, respectively, at 12° C than at 20° C. Chlorophyll a quotas and the spectrally averaged in vivo absorption cross section normalized to chlorophyll a (a*) were not significantly different at these two temperatures. Analysis of the fluorescence kinetics revealed 1) no significant variations of the amount of PSII photoactive reaction centers per unit chlorophyll a, 2) a 14% decrease of the PSII quantum yield(+) and 3) a 29% decrease of the energy transfer efficiency between the light harvesting chlorophyll a pigment bed and the PSII reaction centers. The decrease in energy transfer efficiency between the antennae and the PSII reaction centers at 12° C was interpreted as a mechanism to avoid photoinhibition. 相似文献
6.
Tissue expansion in soft-tissue reconstruction 总被引:18,自引:0,他引:18
C Radovan 《Plastic and reconstructive surgery》1984,74(4):482-492
Tissue expansion in soft-tissue reconstruction is described. The main principle is to develop donor tissue by expansion adjacent to the defect. Such a donor flap is doubled in size by intermittent injections of normal saline into the expander. After sharing the expanded flap for reconstruction, the donor site is well preserved, while the defect is reconstructed with contiguous tissue of similar texture, color, thickness, and sensation. There is minimal scar formation. Over 130 patients were reconstructed with expanded flaps. The average time of flap development was 3 to 6 weeks. 相似文献
7.
8.
Gabriela Seydlová Radovan Fišer Radomír Čabala Petr Kozlík Jaroslava Svobodová Miroslav Pátek 《生物化学与生物物理学报:生物膜》2013
Surfactin is a cyclic lipopeptide antibiotic that disturbs the integrity of the cytoplasmic membrane. In this study, the role of membrane lipids in the adaptation and possible surfactin tolerance of the surfactin producer Bacillus subtilis ATCC 21332 was investigated. During a 1-day cultivation, the phospholipids of the cell membrane were analyzed at the selected time points, which covered both the early and late stationary phases of growth, when surfactin concentration in the medium gradually rose from 2 to 84 μmol·l− 1. During this time period, the phospholipid composition of the surfactin producer's membrane (Sf+) was compared to that of its non-producing mutant (Sf−). Substantial modifications of the polar head group region in response to the presence of surfactin were found, while the fatty acid content remained unaffected. Simultaneously with surfactin production, a progressive accumulation up to 22% of the stress phospholipid cardiolipin was determined in the Sf+ membrane, whereas the proportion of phosphatidylethanolamine remained constant. At 24 h, cardiolipin was found to be the second major phospholipid of the membrane. In parallel, the Laurdan generalized polarization reported an increasing rigidity of the lipid bilayer. We concluded that an enhanced level of cardiolipin is responsible for the membrane rigidification that hinders the fluidizing effect of surfactin. At the same time cardiolipin, due to its negative charge, may also prevent the surfactin-membrane interaction or surfactin pore formation activity. 相似文献
9.
10.
Spurny R Abdoulrahman K Janda L Rünzler D Köhler G Castañón MJ Wiche G 《The Journal of biological chemistry》2007,282(11):8175-8187
As an intermediate filament (IF)-based cytolinker protein, plectin plays a key role in the maintenance of cellular cytoarchitecture and serves at the same time as a scaffolding platform for signaling cascades. Consisting of six structural repeats (R1-6) and harboring binding sites for different IF proteins and proteins involved in signaling, the plectin C-terminal domain is of strategic functional importance. Depending on the species, it contains at least 13 cysteines, 4 of which reside in the R5 domain. To investigate the structural and biological functions of R5 cysteines, we used cysteine-to-serine mutagenesis and spectroscopic, biochemical, and functional analyses. Urea-induced unfolding experiments indicated that wild-type R5 in the oxidized, disulfide bond-mediated conformation was more stable than its cysteine-free mutant derivative. The binding affinity of R5 for vimentin was significantly higher, however, when the protein was in the reduced, more relaxed conformation. Of the four R5 cysteines, one (Cys4) was particularly reactive as reflected by its ability to form disulfide bridges with R5 Cys1 and to serve as a target for nitrosylation in vitro. Using immortalized endothelial cell cultures from mice, we show that endogenous plectin is nitrosylated in vivo, and we found that NO donor-induced IF collapse proceeds dramatically faster in plectin-deficient compared with wild-type cells. Our data suggest an antagonistic role of plectin in nitrosylation (oxidative stress)-mediated alterations of IF cytoarchitecture and a possible role of R5 Cys4 as a regulatory switch. 相似文献