Chemotaxis is not a special case of haptotaxis

Summary Serum peptides containing classical anaphylatoxin (CAT) produce marked chemotactic orientation of human neutrophil granulocytes without modifying cell attachment to the substratum. Furthermore gradients of adhesion produced with gammaglobulins fail to induce morphological orientation of neutrophils. The results suggest that chemotaxis is not a special case of haptotaxis.The excellent technical assistance of Miss M. Schuster, Mrs A. Damschen and Mr M. Arnold is gratefully acknowledged. This work was supported by the Swiss National Science Foundation and the Sandoz-Stiftung zur Förderung der Medizinisch-Biologischen Forschung.     

Ecological long-term effects of cultigens becoming feral and of naturalization of non-native species

Transgenic cultigens may become feral as we know of some non-transgenic cultigens. The article explains two basic ways how cultigens become feral: through hybridization with a closely related wild plant and through revert to the wild-type. A long list of examples of cultigens becoming feral in Central Europe is presented. The process of becoming feral is compared to the naturalization of non-native species (Exotic Species Model). Ecological long-term effects of both cultigens becoming feral and non-native species being naturalized are discussed with special regard to the predictability of such events. The ecological aspects discussed in the article are as significant for transgenic cultigens as for non-transgenic cultigens.     

Maternal vitamin A restriction alters biochemical development of the brain in rats

Summary The biochemical development of the fetal brain in relation to maternal vitamin A restriction was studied in rats. The vitamin A status of pregnant rats was varied by supplying low, medium and adequate amounts (6, 40, and 100 g retinol/day/kg body weight, respectively) of vitamin A during pregnancy and suckling. The maternal vitamin A restriction caused an altered brain development in terms of tissue weight, DNA, RNA and protein levels, and biosynthesis of DNA and protein from [³H]-thymidine and [³H]-leucine, respectively. A dose-dependent effect of maternal vitamin A restriction on the metabolism of DNA, RNA and protein was noticed in the developing fetal brain of rats.     

Effects of polysorbates and Cremophor EL on vascular responses in rat aorta

The effects of Tween 20, Tween 80, and Cremophor EL, surface active agents which are used for dispersion of water-insoluble substances, on vascular responsiveness were investigated using rat aortic rings. In high concentrations all these agents produced persistent contractions in aortic rings independent of the presence of endothelium. These contractions were not influenced by inhibitors of known endogenous contractile mediators. Incubation with these agents caused a concentration-dependent inhibition of the endothelium-dependent relaxant responses to acetylcholine in intact precontracted aortic rings. Endothelium-independent relaxations produced by sodium nitroprusside were not inhibited, but rather potentiated in the presence of Tween 80 (10^–1 ml/l). On the other hand, Tween 80 inhibited the contractile effects of 5-hydroxytryptamine, phenylephrine, and bradykinin significantly. The data suggests that these substances affect both endothelial cells and vascular smooth muscle.     

Further evidence for the existence of a bottleneck in the metabolism of Saccharomyces cerevisiae

The growth physiology of Saccharomyces cerevisiae strains H1022 and Whi2+ has been studied in aerobic batch and continuous (chemostat) cultures. Results from the measurement of biomass and medium components (off-line) together with oxygen, carbon dioxide and heat measurements (on-line) have been used in an attempt to explore the existence of 'overflow' or 'bottleneck' metabolism as opposed to catabolite repression (Crabtree effect) in these strains. Chemostat experiments indicated that specific oxygen uptake rate (qO2) was linearly related to the dilution rate (D) at values below the critical dilution rate (D crit), becoming constant above D crit, which is in agreement with the bottleneck theory. However, batch culture experiments indicated negligible oxygen consumption during the initial glucose growth phase, the culture exhibiting purely anaerobic metabolism. The bottleneck theory would propose that qO2 has a constant (maximum) value under these conditions. The results presented here suggest that while the bottleneck theory can be adequately used to describe chemostat growth of S. cerevisiae, some other control mechanism must be operating under conditions of high glucose concentrations, such as those initially prevailing in the batch culture experiments.     

济南城市化进程中的交通问题及对策研究

在分析城市化对交通影响的基础上，着重讨论了济南市目前城市交通问题的现状及深层次的原因，并提出了相应的建议。