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1.
The properties of the pH 4.0 endonuclease from adenovirus-type-2-infected KB cells were determined. The enzyme has a molecular weight of approximately 40000. Its pH optimum is at pH 4.0, it is not inhibited by ethylenediaminetetraacetate (EDTA), and it is active at temperatures up to 60 degree C. The enzyme cleaves adenovirus DNA in a stepwise manner. The limit digestion product has a molecular weight of 120000-200000. There is evidence that the cleavage reaction proceeds via an initial single-strand nick. Under the conditions tested the endonuclease did not seem to reveal a high degree of specificity as to the recognition of cleavage sites, or else the sites recognized occurred very frequently. 相似文献
2.
D W Reif V M Samokyszyn D M Miller S D Aust 《Archives of biochemistry and biophysics》1989,269(2):407-414
The diabetogenic action of alloxan is believed to involve oxygen free radicals and iron. Incubation of glutathione (GSH) and alloxan with rat liver ferritin resulted in release of ferrous iron as assayed by spectrophotometric detection of ferrous-bathophenanthroline complex formation. Neither GSH nor alloxan alone mediated iron release from ferritin. Superoxide dismutase (SOD) and catalase did not affect initial rates of iron release whereas ceruloplasmin was an effective inhibitor of iron release. The reaction of GSH with alloxan resulted in the formation of the alloxan radical which was detected by ESR spectroscopy and by following the increase in absorbance at 310nm. In both instances, the addition of ferritin resulted in diminished alloxan radical detection. Incubation of GSH, alloxan, and ferritin with phospholipid liposomes also resulted in lipid peroxidation. Lipid peroxidation did not occur in the absence of ferritin. The rates of lipid peroxidation were not affected by the addition of SOD or catalase, but were inhibited by ceruloplasmin. These results suggest that the alloxan radical releases iron from ferritin and indicates that ferritin iron may be involved in alloxan-promoted lipid peroxidation. 相似文献
3.
4.
Wolf-Ernst Reif 《Journal of the history of biology》1986,19(1):79-130
Summary Six schools of thought can be detected in the development of evolutionary theory in German paleontology between 1859 and World War II. Most paleontologists were hardly affected in their research by Darwin's Origin of Species. The traditionalists (School 1) accepted evolution within lower taxa (genera and families) but not for organisms in general. They also rejected Darwin's theory of selection. The early Darwinians (School 2) accepted Darwin's theory of transmutation and theory of selection as axioms and applied them fruitfully to the fossil record, thereby laying the foundation for the new research areas of phylogeny and paleo-biology. The enthusiasm of the early Darwinians faded when the fossil record and the problems of its interpretion became more widely known. The pluralists of the turn of the century (School 3) invented and adopted a wealth of hypothetical mechanisms in order to explain individual features of the fossil record. They failed, however, to provide one coherent theory. Dissatisfaction with this situation led to adoption of a dogmatic neo-Lamarckism (School 4), which was regarded as a coherent theory providing a fruitful research program. The rejection of the Lamarckian mechanism early in this century left paleontologists with only one kind of evolutionary mechanism: inner causes.Like many neo-Lamarckians several orthogeneticists (School 5) were highly interested in adaptation and did not see any contradiction between the inner causes of evolution and adaptation. The dominance of stratigraphical research programs in paleontology led in the 1930s and 1940s to a decrease in interest in adaptation. Stratigraphical records of taxa were accepted as meaningful in the context of evolutionary theory. Orthogenesis and the new concepts of saltation and cyclicism were amalgamated into one theory: typostrophism (School 6). This theory dominated German paleontology for decades after the war and only recently has the synthetic theory been seriously considered.Evolution was never very intensively discussed in German paleontology in the hundred years after Darwin's book. Most information used here comes from textbooks or from papers given on special occasions. It has been impossible to summarize how members of one school defended their views or discussed the ideas of competing schools. 相似文献
5.
Wolf -Ernst Reif 《Pal?ontologische Zeitschrift》1983,57(1-2):7-20
Hilgendorf’s (1866) publication on the phylogenyof Planorbis multiformis from Steinheim, Swabian Mountains, is one of the most important contributions of paleontology to early Darwinism. At the same time it helped to lay the foundation for paleontological phylogenetics. Hilgendorf’s unpublished dissertation of 1863, the newly rediscovered collection to his dissertation and the document-file ofHilgendorf’s graduation from Tübingen University help to trace back the origin of Hilgendorf’s ideas.Hilgendorf’s collection contains the oldest phylogenetic tree, which is known so far. 相似文献
6.
7.
We have broadly defined the DNA regions regulating esterase6 activity in
several life stages and tissue types of D. melanogaster using P-
element-mediated transformation of constructs that contain the esterase6
coding region and deletions or substitutions in 5' or 3' flanking DNA.
Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and
the primary sequences regulating its activity lie between -171 and -25 bp
relative to the translation initiation site: deletion of these sequences
decrease activity approximately 20-fold. Hemolymph activity is also
modulated by four other DNA regions, three of which lie 5' and one of which
lies 3' of the coding region. Of these, two have positive and two have
negative effects, each of approximately twofold. Esterase6 activity is
present also in two male reproductive tract tissues; the ejaculatory bulb,
which is another ancestral activity site, and the ejaculatory duct, which
is a recently acquired site within the melanogaster species subgroup.
Activities in these tissues are at least in part independently regulated:
activity in the ejaculatory bulb is conferred by sequences between -273 and
-172 bp (threefold decrease when deleted), while activity in the
ejaculatory duct is conferred by more distal sequences between -844 and
-614 bp (fourfold decrease when deleted). The reproductive tract activity
is further modulated by two additional DNA regions, one in 5' DNA (-613 to
-284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to
+2731 bp; threefold decrease when deleted) that probably overlaps the
adjacent esteraseP gene. Collating these data with previous studies
suggests that expression of EST6 in the ancestral sites is mainly regulated
by conserved proximal sequences while more variable distal sequences
regulate expression in the acquired ejaculatory duct site.
相似文献
8.
David Storch Jaroslav Koleček Petr Keil Zdeněk Vermouzek Petr Voříšek Jiří Reif 《Diversity & distributions》2023,29(4):572-585
Aim
Despite the complexity of population dynamics, most studies concerning current changes in bird populations reduce the trajectory of population change to a linear trend. This may hide more complex patterns reflecting responses of bird populations to changing anthropogenic pressures. Here, we address this complexity by means of multivariate analysis and attribute different components of bird population dynamics to different potential drivers.Location
Czech Republic.Methods
We used data on population trajectories (1982–2019) of 111 common breeding bird species, decomposed them into independent components by means of the principal component analysis (PCA), and related these components to multiple potential drivers comprising climate, land use change and species' life histories.Results
The first two ordination axes explained substantial proportion of variability of population dynamics (42.0 and 12.5% of variation in PC1 and PC2 respectively). The first axis captured linear population trend. Species with increasing populations were characterized mostly by long lifespan and warmer climatic niches. The effect of habitat was less pronounced but still significant, with negative trends being typical for farmland birds, while positive trends characterized birds of deciduous forests. The second axis captured the contrast between hump-shaped and U-shaped population trajectories and was even more strongly associated with species traits. Species migrating longer distances and species with narrower temperature niches revealed hump-shaped population trends, so that their populations mostly increased before 2000 and then declined. These patterns are supported by the trends of total abundances of respective ecological groups.Main Conclusion
Although habitat transformation apparently drives population trajectories in some species groups, climate change and associated species traits represent crucial drivers of complex population dynamics of central European birds. Decomposing population dynamics into separate components brings unique insights into non-trivial patterns of population change and their drivers, and may potentially indicate changes in the regime of anthropogenic effects on biodiversity. 相似文献9.
C Möller G Weber MM Dreyfuss 《Journal of industrial microbiology & biotechnology》1996,17(5-6):359-372
Intraspecific variation among 84 isolates of the anamorphic fungusChaunopycnis alba from 26 different geographical locations was analyzed by investigating optimal growth temperatures, differences in the production of secondary metabolites and presence or absence of the cyclosporin synthetase gene. The genetic diversity was assessed using random amplified polymorphic DNA (RAPD). Analysis of these data showed high genetic, metabolic and physiological diversity within this species. Isolates from the Antarctic represented the most homogeneous group withinC. alba and together with isolates from the Arctic these polar strains differed from alpine, temperate and tropical strains by low optimal growth temperatures and by low production of secondary metabolites. Isolates from tropical climes were characterized by high optimal growth temperatures and by the production of comparatively diverse metabolite spectra. Most of the isolates that were similar in the combination of their physiological and metabolic characters were also genetically related. Isolates from different geographical origins did not show many similarities, with the exception of the cyclosporin A-producing isolates, and large diversity could be observed even within a single habitat. This leads us to the suggestion that for pharmaceutical screening programs samples should be collected from a diversity of different geographical and climatic locations. For the selection of strains for screening the RAPD assay seems to be the most powerful tool. It reflected the highest intraspecific diversity and the results corresponded well with the other characteristics. 相似文献