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91.
Robert O. Hussa Roland A. Pattillo 《In vitro cellular & developmental biology. Plant》1980,16(7):585-590
Summary The BeWo line of trophoblastic cells, maintained in continuous culture since 1966, was employed to investigate the phenomenon
of gonadotropin α-subunit predominance that exists in several cell lines. The secretion of complete human chorionic gonadotropin
(hCG) relative to α-subunit was compared in several different BeWo sublines, all of which were derived from BeWo stock roller
tube colonies. In all of the BeWo sublines, secretion of hCG originally exceeded secretion of α-subunit. With time in culture,
however, there was a marked decline in production of hCG/hCGβ, but not in α-subunit. Thus it appears that the production of
hCGβ by BeWo choriocarcinoma cells is more labile than the production of the α-subunit. 相似文献
92.
Beate Ackermann-Schmidt Roland Süssmuth Franz Lingens 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1982,699(2)
The mutagen 1,1′-hexamethylene-bis[(5-p-chlorophenyl)-biguanide] reacts at 37°C with guanosine and guanine to yield xanthosine or xanthine and oxidizes cysteine to cystine. After treatment of a guanosine-labelled DNA sample from Escherichia coli with the mutagen xanthine could be detected as a reaction product. At a slow rate the mutagen is hydrolysed spontaneously yielding urea, 1,6-hexanediol and 4-chloroaniline. The reaction mechanisms both of the hydrolysis and of the reaction with cysteine and guanosine are discussed. 相似文献
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96.
The reversibility of the binding of ionophores to the thylakoid membrane is studied. While gramicidin binds practically irreversibly, valinomycin and nonactin bind reversibly, however, only a small fraction (about 1 %) of the membrane-bound valinomycin or nonactin is active in ion transport. The current-voltage relationship is evaluated under these circumstances. We have found that it is practically linear. This together with the relationship between current and ion concentration agrees qualitatively with the results reported for bimolecular lipid membranes, which contain a large fraction of negatively charged lipids. For the ionophores, valinomycin and nonactin, the binding equilibria (K ≈ 104) and the turnover numbers (≈ 3 · 104/s) are evaluated for their action on the thylakoid membrane. Possible reasons for the inactivity of the majority of membrane-bound ionophore molecules are discussed. 相似文献
97.
Robert Belmaker Helmut Beckmann Frederick Goodwin Dennis Murphy William Pollin Monte Buchsbaum Richard Wyatt Roland Ciaranello Friedhelm Lamprecht 《Life sciences》1975,16(2):273-279
The activity of dopamine-B-hydroxylase in blood has recently been demonstrated to be under genetic control and to correlate closely with urinary catecholamine excretion. The results of the present study did not demonstrate any relationship between a major catecholamine metabolite in urine, 3-methoxy-4-hydroxy phenylglycol, and dopamine-B-hydroxylase activity in plasma, monoamine oxidase activity in platelets, or monoamine oxidase activity in plasma. Differences in the origin of urinary catecholamines and urinary 3-methoxy-4-hydroxy phenyglycol may be responsible for these divergent results. 相似文献
98.
Changes in lectin-induced deoxyribonucleic acid synthesis in cultures of chick-embryo fibroblasts at various stages of development
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Concanavalin A and Robinia pseudoacacia lectin decreased [(3)H]thymidine incorporation into acid-insoluble material of fibroblasts cultured from 6-10-day chick embryos. In contrast, these lectins stimulated [(3)H]thymidine incorporation in cells from 16-day embryos. These effects are due to neither [(3)H]thymidine permeability modification nor toxicity of the lectins. The specificity of lectin action was proved by blocking experiments with alpha-methyl mannopyranoside and with anti-(Robinia lectin) serum. 相似文献
99.
Harshad S. Ugamraj Kevin Dang Laure-Hlne Ouisse Benjamin Buelow Eduardo N. Chini Giulia Castello James Allison Starlynn C Clarke Laura M. Davison Roland Buelow Rong Deng Suhasini Iyer Ute Schellenberger Sankar N. Manika Shipra Bijpuria Astrid Musnier Anne Poupon Maria Cristina Cuturi Wim van Schooten Pranjali Dalvi 《MABS-AUSTIN》2022,14(1)
100.
Hlne Chabas Viktor Müller Sebastian Bonhoeffer Roland R. Regoes 《PLoS computational biology》2022,18(7)
Bacteria have adaptive immunity against viruses (phages) in the form of CRISPR-Cas immune systems. Currently, 6 types of CRISPR-Cas systems are known and the molecular study of three of these has revealed important molecular differences. It is unknown if and how these molecular differences change the outcome of phage infection and the evolutionary pressure the CRISPR-Cas systems faces. To determine the importance of these molecular differences, we model a phage outbreak entering a population defending exclusively with a type I/II or a type III CRISPR-Cas system. We show that for type III CRISPR-Cas systems, rapid phage extinction is driven by the probability to acquire at least one resistance spacer. However, for type I/II CRISPR-Cas systems, rapid phage extinction is characterized by an a threshold-like behaviour: any acquisition probability below this threshold leads to phage survival whereas any acquisition probability above it, results in phage extinction. We also show that in the absence of autoimmunity, high acquisition rates evolve. However, when CRISPR-Cas systems are prone to autoimmunity, intermediate levels of acquisition are optimal during a phage outbreak. As we predict an optimal probability of spacer acquisition 2 factors of magnitude above the one that has been measured, we discuss the origin of such a discrepancy. Finally, we show that in a biologically relevant parameter range, a type III CRISPR-Cas system can outcompete a type I/II CRISPR-Cas system with a slightly higher probability of acquisition. 相似文献