Principles of self-generation and self-maintenance

Living systems are characterized as self-generating and self-maintaining systems. This type of characterization allows integration of a wide variety of detailed knowledge in biology.The paper clarifies general notions such as processes, systems, and interactions. Basic properties of self-generating systems, i.e. systems which produce their own parts and hence themselves, are discussed and exemplified. This makes possible a clear distinction between living beings and ordinary machines. Stronger conditions are summarized under the concept of self-maintenance as an almost unique character of living systems. Finally, we discuss the far-reaching consequences that the principles of self-generation and self-maintenance have for the organization, structure, function, and evolution of single- and multi-cellular organisms.     

Über die Entstehung dorsaler Blattschläuche beiAnthurium scherzerianum Schott

Ohne ZusammenfassungMit 12 Textabbildungen.     

Learning capabilities enhanced in harsh environments: a common garden approach

Previous studies have suggested that the ability to inhabit harsh environments may be linked to advanced learning traits. However, it is not clear if individuals express such traits as a consequence of experiencing challenging environments or if these traits are inherited. To assess the influence of differential selection pressures on variation in aspects of cognition, we used a common garden approach to examine the response to novelty and problem-solving abilities of two populations of black-capped chickadees (Poecile atricapillus). These populations originated from the latitudinal extremes of the species''s range, where we had previously demonstrated significant differences in memory and brain morphology in a multi-population study. We found that birds from the harsh northern population, where selection for cognitive abilities is expected to be high, significantly outperformed conspecifics from the mild southern population. Our results imply differences in cognitive abilities that may be inherited, as individuals from both populations were raised in and had experienced identical environmental conditions from 10 days of age. Although our data suggest an effect independent of experience, we cannot rule out maternal effects or experiences within the nest prior to day 10 with our design. Nevertheless, our results support the idea that environmental severity may be an important factor in shaping certain aspects of cognition.     

Insulin-mimetic anti-insulin receptor monoclonal antibodies stimulate receptor kinase activity in intact cells.

In the present studies, nine different monoclonal antibodies to the extracellular domain of the insulin receptor were tested in three different cell types for their ability to stimulate the intrinsic tyrosine kinase activity of the receptor. Previous studies had suggested that several of these monoclonal antibodies stimulate biological responses without stimulating the intrinsic tyrosine kinase activity of the receptor (Hawley, D. M., Maddux, B. A., Patel, R. G., Wong, K. Y., Manula, P. W., Firestone, G. L., Brunetti, A., Verspohl, E., and Goldfine, I. D. (1989) J. Biol. Chem. 264, 2438-2444 and Soos, M. A., O'Brien, R. M., Brindle, N. P. J., Stigter, J. M., Okamoto, A. K., Whittaker, J., and Siddle, K. (1989) Proc. Natl. Acad. Sci. U. S. A. 86, 5217-5221). In the present study, a more sensitive assay was utilized, and these same monoclonal antibodies, when added to intact cells, were found to stimulate the phosphotransferase activity of the receptor. This increase in activity was reversed by phosphatase treatment of the receptor. In contrast, monoclonal antibodies which had no insulin-mimetic activities did not stimulate the receptor's kinase activity. In addition, Western blot analyses of lysates with anti-phosphotyrosine antibodies showed that insulin-mimetic, but not non-insulin-mimetic antibodies, stimulated tyrosine phosphorylation of the receptor as well as an endogenous substrate (phosphoprotein Mr = 160,000). Finally, these antibodies were found to stimulate the tyrosine phosphorylation of another endogenous substrate of the insulin receptor kinase, the type I phosphatidylinositol kinase. These studies support the hypothesis that monoclonal antibodies, like insulin, stimulate biological responses via their ability to stimulate the tyrosine kinase activity of the receptor.