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31.
Summary Labeling cells with bromodeoxyuridine (BrdU) permits the differentiation of mitoses of the first, second, and third generation after the addition of BrdU. The term second mitoses is used for those cells which have incorporated BrdU for two-S-phases and which exhibit sister chromatid differentiation (SCD). However, SCD can also be obtained if the cell was in S-phase at the time of BrdU-addition and had already replicated part of its DNA. Such cells with incomplete BrdU-substitution in the first S-phase can only be differentiated from completely substituted ones by the quality of the SCD and are usually also grouped as second mitoses in the evaluation of experiments. Due to the heterogeneity of the evaluated second mitoses, the determination of proliferation delay and the incidence of sister chromatid exchange-induction can depend on the time of chromosome preparation. 相似文献
32.
Summary The introduced reindeer of South Georgia have had a serious impact on the vegetation throughout the range of three populations on the island. Exclosure experiments in areas where the reindeer were introduced have resulted in a dramatic change in the composition of the protected vegetation. Poa flabellata (the major winter food) and Acaena magellanica (a major summer food) have recovered to their former status inside the exclosures, while Deschampsia antarctia and the introduced grass Poa annua tolerate grazing and trampling and have spread over the grazed areas. Festuca contracta and Rostkovia magellanica are not eaten by the reindeer. Trampling has resulted in a high proportion of bare soil and peat in sites freely accessible to reindeer. However, the changes in the vegetation have not had such a significant effect on the associated invertebrate fauna. Thus in grazed and protected areas the faunistic composition is qualitatively similar, although there are quantitative differences, and some of the trends can probably be attributed to the presence of the reindeer. Compared with reindeer-free areas, the abundance of the perimylopid beetle Hydromedion sparsutum (a major primary decomposer) is reduced. The frequency of their egg parasite Notomymar aptenosoma (Hymenoptera, Mymaridae) increases. Consequently the ratio of perimylopoids to mymarids found in pitfall traps shifts from 1:0.01 (ungrazed areas) to 1:0.54 (grazed areas). Also the frequency of sciarids was found to be higher in reindeer areas. The larvae of these probably introduced gnats do not play a role in the natural terrestrial ecosystem of South Georgia, but in reindeer areas they appear to establish larger populations because they are able to live deeper in the soil and in hardened substrates. There is also a shift in the ratio between Collembola (major prey) to spiders from 1:1.3 (ungrazed areas) to 1:0.82 (grazed areas), for animals collected in pitfall traps. This may be a result of the trampling effect of the reindeer. 相似文献
33.
Changes in erythropoiesis due to radiation or chemotherapy as studied by flow cytometric determination of peripheral blood reticulocytes 总被引:1,自引:0,他引:1
H J Tanke P H van Vianen F M Emiliani I Neuteboom N de Vogel A D Tates E A de Bruijn A T van Oosterom 《Histochemistry》1986,84(4-6):544-548
Flow cytometric determination of time dependent changes of numbers of reticulocytes in peripheral blood were investigated as a parameter for changes in erythropoiesis induced by radiation- or chemotherapy. Rats irradiated or treated with drugs (such as e.g. cyclophosphamide 100 mg/kg, vincristin 0.2 mg/kg, or mitomycin C 1.0 mg/kg) showed clear changes in erythropoietic activity. Reticulocyte numbers decreased rapidly until day 3-4 after treatment; this period was followed by a gradual increase and normal control values were seen at day 8-11. Radiation effects of doses as low 0.5 Gy could be detected in such a way. Similar studies were performed with patients with ovarian tumors treated with cis-platinum, a drug that may cause non-immune haemolysis. During prolonged treatment some patients showed increasing numbers of reticulocytes, measured at the first day of each hospitalization period, whereas leucocyte and platelet counts stayed more or less constant. Increasing numbers of reticulocytes generally indicates stimulation of erythropoietic activity of the bone marrow (due to increased blood loss); in this study increasing numbers often preceeded a decrease in hemoglobin values later on. Flow cytometric analysis of reticulocytes is therefore a potentially useful tool to detect changes in erythropoiesis, and considered more sensitive for the early recognition of patients that develop anemia, than hemoglobin measurements only. 相似文献
34.
Summary In normal diploid fibroblasts of the mouse, 3T3-, SV-3T3-, and Meth A-cells, the chromosome replication patterns were studied by a bromodeoxyuridine (BrdU)-labelling technique. SV-3T3 is a subline of 3T3 transformed by SV 40 and Meth A is a permanent cell line from Balb c transformed by methylcholanthrene. The use of 1 h thymidine pulses permits high resolution of the S-phase after partial synchronization of the cells at G1/S in an otherwise BrdU-substituted S-phase. It could be shown that the autosomal heterochromatin of the mouse (Mus musculus) starts replication during the early S-phase (R-band replication), continues while R-band chromatin finishes, and still replicates when G-band chromatin starts. The heterochromatin finishes before the majority of G-bands have been replicated. There is no fundamental difference in the course of chromosome replication between the different cell lines studied here. It is concluded that there are no obligate changes in the course of the S-phase linked to the process of transformation. 相似文献
35.
A low molecular weight fraction (Mr = 500-1500) was isolated by membrane and gel filtration from rat embryonic brain extract. This fraction was shown to stimulate collagen production in muscle cultures. Procollagen, intermediate collagenous proteins, and collagens of types I, III, and V were identified by analysis on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and DEAE- and Cm-cellulose chromatography and by selective degradation by pepsin, bacterial collagenase, and cyanogen bromide. Immunofluorescent staining with antisera to collagen types I, III, IV, and V of muscle cultures treated with the collagen-inducing factor revealed a large increase in staining compared to control cultures and a distinct pattern of staining on the surface of the treated myotubes. 相似文献
36.
As a consequence of polyploidization, the carp is endowed with three genetic loci coding for LDH in most tissues (and additional ones in liver). However, each such duplicated gene may not be functionally essential for the organism and could be eliminated. In a population survey, an electrophoretic polymorphism was detected which may best be interpreted by the assumption of a null allele, which is apparently not subject to selective pressure. Thus this originally duplicated gene would have diverged in the course of evolution without the origin of differences in function, so that one or the other of the genes is dispensable. 相似文献
37.
Dielectric properties of hemoglobin and myoglobin. I. Influence of solvent and particle size on the dielectric dispersion 总被引:2,自引:0,他引:2
Dielectric dispersion measurements with aqueous solutions of hemoglobin and myoglobin have been performed in the frequency range from 100 kcps to 15 Mcps. The influence of preparation, particle size, and solvent conditions was studied. The results are analyzed in terms of an orientational polarization mechanism. 相似文献
38.
39.
Ohne ZusammenfassungTeile dieser Arbeit wurden von Fräulein M. Kurth im Rahmen ihrer medizinischen Doktordissertation erarbeitet.Die Untersuchungen der Verfasser zum Mutationsproblem werden durch die Deutsche Forschungsgemeinschaft gefördert. 相似文献
40.