Localization of concanavalin-A binding sites inTetrahymena by scanning electron microscopy

Summary Binding sites of concanavalin-A were detected inTetrahymena on the body ciliature, while the cell membrane itself and the oral ciliature failed to bind the lectine.Supported by the Scientific Research Council, Ministry of Health, Hungary 1-01-0302-02-1/Cs.     

EGF receptor induction and insulin-EGF overlap in Tetrahymena

Offspring generations of Tetrahymena pretreated (imprinted) with insulin showed a greater binding capacity for the hormone than offspring of untreated ones. The epidermal growth factor (EGF) imprinted for insulin to a greater degree than insulin itself, and vice versa: insulin imprinted for EGF more efficiently than EGF itself. These phenomena can be explained by the overlap of insulin and EGF on one another's receptors in Tetrahymena.     

Presence of benzodiazepine binding sites (receptors) and amplification thereof by imprinting in Tetrahymena

Live Tetrahymena cells bound 3H-diazepam specifically, as demonstrated by autoradiographic evidence of displacement of about 25% of labeled diazepam in the presence of a 1000-fold amount of cold diazepam. The 3H-diazepam bound to membrane preparations isolated from untreated (control) cells was not displaced by cold diazepam, whereas cells involved in primary interaction (imprinting) with diazepam showed amplification and specificity of diazepam binding in both in vivo (cell suspension) and in vitro (pellicle) systems, as well as displacement of bound label in the presence of 1000-fold cold diazepam. It appears that diazepam induced imprinting and, consequently, also the formation of specific receptors in Tetrahymena.     

Changes of blood glucose during anaphylaxis in pertussis sensitized rats

Zusammenfassung Nachweis, dass der Blutzuckerspiegel von mitBordetella pertussis vorbehandelten Ratten durch anaphylactischen Schock wesentlich vermindert ist, obwohl er in nicht vorbehandelten Tieren unverändert blieb.     

Effect of thymectomy on immune response in adult rats

Zusammenfassung Röntgenbestrahlung thymectomi-sierter Ratten ergab eine abgeschwachte Immunreaktion. Für eine Immunreaktion adulter Tiere scheint jedoch der Thymus nicht notwendig zu sein. In Abhängigkeit von Zeit und Alter der Tiere zeigten sich Unterschiede in der Stärke der Immunreaktion.     

Why do hormone receptors arise?

Conclusions In view of the foregoing considerations, it appears that the receptor-hormone relationship is, by origin, essentially a cell-environment (chemical) relationship which influences cell behavior. With the development of multicellularity, the interests of the single (individual) cell became subordinated to those of the cell population (community), and the cell-environment relationship became modified inasmuch as receptor activity became integrated into the functional program of the entire organism. Accordingly, the open program of the individual cell, which involved continuous dynamic changes of the membrane receptors under the influence of the signal molecules, was superseded by a closed program for the given receptor, which gave rise to a chemical memory of the cell. With multicellularity the cellular functions have become integrated into an almost entirely predetermined program in which the quality and operation of the receptors are encoded to maintain the system of regulation, and impart differentiating features to given types of target cells which distinguish them from others, and delimit the response potentials of the species. A limited openness of the pre-programed system exists in the early stage of ontogenesis, and accounts for certain individual variations within the limited potentials of the species.The answer to the question posed in the title of this paper is therefore the following: the hormone receptors arise because the external environment of the individual cell is transformed at the multicellular level to an internal environment, in which the random variety of environmental molecules is replaced by a predetermined set of ligands (signal molecules). Under these conditions the randomlypresented membrane patterns capable of signal reception are transformed to encoded receptor structures which execute a programed function of the closed system, but nevertheless preserve some primordial traits, which can explain many surprising observations in the field of receptor physiology.The Editors wish to thank Professor G. Csaba for having designed and coordinated this review.     

Absence of effects of Sir2 overexpression on lifespan in C. elegans and Drosophila

Overexpression of sirtuins (NAD(+)-dependent protein deacetylases) has been reported to increase lifespan in budding yeast (Saccharomyces cerevisiae), Caenorhabditis elegans and Drosophila melanogaster. Studies of the effects of genes on ageing are vulnerable to confounding effects of genetic background. Here we re-examined the reported effects of sirtuin overexpression on ageing and found that standardization of genetic background and the use of appropriate controls abolished the apparent effects in both C. elegans and Drosophila. In C. elegans, outcrossing of a line with high-level sir-2.1 overexpression abrogated the longevity increase, but did not abrogate sir-2.1 overexpression. Instead, longevity co-segregated with a second-site mutation affecting sensory neurons. Outcrossing of a line with low-copy-number sir-2.1 overexpression also abrogated longevity. A Drosophila strain with ubiquitous overexpression of dSir2 using the UAS-GAL4 system was long-lived relative to wild-type controls, as previously reported, but was not long-lived relative to the appropriate transgenic controls, and nor was a new line with stronger overexpression of dSir2. These findings underscore the importance of controlling for genetic background and for the mutagenic effects of transgene insertions in studies of genetic effects on lifespan. The life-extending effect of dietary restriction on ageing in Drosophila has also been reported to be dSir2 dependent. We found that dietary restriction increased fly lifespan independently of dSir2. Our findings do not rule out a role for sirtuins in determination of metazoan lifespan, but they do cast doubt on the robustness of the previously reported effects of sirtuins on lifespan in C. elegans and Drosophila.