Über die durch Licht bedingte «Missweisung» bei den Tänzen im Bienenstock

Summary Bees are able to indicate direction to their hive comrades by means of a waggling dance of 2 kinds: in the horizontal plane with regard to the sun they point directly towards the goal by a waggling walk using the same angle to the sun as they took in their flight. Inside the dark hive in the vertical honey-comb, they transpose the angle between goal and sun to the field of gravity, whereby the sun's direction is shown by a waggling walk upwards, and the angle to the right or left of the sun's position is given by a dance-direction in the corresponding angle to the right or left of the zenith.If a piece of blue sky is made visible in an observation hive to the bees which are dancing in orientation by gravity, they recognise the position of the sun by this polarisation sample, and the effort to orientate themselves directly by the sun (as in the horizontal plane) comes into conflict with the orientation by gravity. The result is a dance direction which corresponds remarkably well with the halving of the angle between what the dance direction should have been by gravity and what it should have been by light orientation (Figure 1). This is also true when the bee is orientating itself by polarised sky light over its back, while the sun is at the other side of the honey-comb under its front (Figure 2), a situation which does not occur during flight but which is important for its dance in the swarm. The bees receiving the information compensate the deviation of the angle determined by light, and fly to the right goal.As the sun itself, as well as the piece of blue sky, was made visible to the dancers, its influence dominated and they orientated themselves by its light (Figure 3).     

Adipocyte extracellular matrix composition, dynamics and role in obesity

The central role of the adipose tissue in lipid metabolism places specific demands on the cell structure of adipocytes. The protein composition and dynamics of the extracellular matrix (ECM) is of crucial importance for the functioning of those cells. Adipogenesis is a bi-phasic process in which the ECM develops from a fibrillar to a laminar structure as cells move from the commitment phase to the growth phase characterized by storage of vast amounts of triglycerides. Mature adipocytes appear to spend a lot of energy on the maintenance of the ECM. ECM remodeling is mediated by a balanced complement of constructive and destructive enzymes together with their enhancers and inhibitors. ECM remodeling is an energy costing process regulated by insulin, by the energy metabolism, and by mechanical forces. In the obese, overgrowth of adipocytes may lead to instability of the ECM, possibly mediated by hypoxia.     

Autophagy and other vacuolar protein degradation mechanisms.

Autophagic degradation of cytoplasm (including protein, RNA etc.) is a non-selective bulk process, as indicated by ultrastructural evidence and by the similarity in autophagic sequestration rates of various cytosolic enzymes with different half-lives. The initial autophagic sequestration step, performed by a poorly-characterized organelle called a phagophore, is subject to feedback inhibition by purines and amino acids, the effect of the latter being potentiated by insulin and antagonized by glucagon. Epinephrine and other adrenergic agonists inhibit autophagic sequestration through a prazosin-sensitive alpha 1-adrenergic mechanism. The sequestration is also inhibited by cAMP and by protein phosphorylation as indicated by the effects of cyclic nucleotide analogues, phosphodiesterase inhibitors and okadaic acid. Asparagine specifically inhibits autophagic-lysosomal fusion without having any significant effects on autophagic sequestration, on intralysosomal degradation or on the endocytic pathway. Autophaged material that accumulates in prelysosomal vacuoles in the presence of asparagine is accessible to endocytosed enzymes, revealing the existence of an amphifunctional organelle, the amphisome. Evidence from several cell types suggests that endocytosis may be coupled to autophagy to a variable extent, and that the amphisome may play a central role as a collecting station for material destined for lysosomal degradation. Protein degradation can also take place in a 'salvage compartment' closely associated with the endoplasmic reticulum (ER). In this compartment unassembled protein chains are degraded by uncharacterized proteinases, while resident proteins return to the ER and assembled secretory and membrane proteins proceed through the Golgi apparatus. In the trans-Golgi network some proteins are proteolytically processed by Ca(2+)-dependent proteinases; furthermore, this compartment sorts proteins to lysosomes, various membrane domains, endosomes or secretory vesicles/granules. Processing of both endogenous and exogenous proteins can occur in endosomes, which may play a particularly important role in antigen processing and presentation. Proteins in endosomes or secretory compartments can either be exocytosed, or channeled to lysosomes for degradation. The switch mechanisms which decide between these options are subject to bioregulation by external agents (hormones and growth factors), and may play an important role in the control of protein uptake and secretion.     

Ethanol from cellulose

Summary An excess of organic waste, containing up to 60% cellulose and hemicellulose is produced worldwide. The conversion of this cellulosic material to ethanol is discussed: The two-step process consisting of a hydrolysis step to glucose and the subsequent fermentation by yeasts; and the one-step process, a fermentation of the cellulose by the anaerobic thermophileClostridium thermocellum, or by a thermophilic, anaerobic, defined mixed culture. The use of the latter seems to be very feasible., To achieve an economic process, it is suggested to combine this approach with a thermophilic fermentation of the effluent and/or stillage obtained to produce methane.Acknowledgment. Part of this work was supported by Energy and Research Development Administration contract number EY-76-509-0888-M003, and by the Deutsche Forschungsgemeinschaft.     

Inhibition of rat liver transglutaminase by nucleotides

Summary Tissue-type transglutaminase (TGase) was purified from rat liver, and the effects of nucleotides on its activity were examined. The enzyme activity is inhibited by ATP in a concentration-dependent way, with complete inhibition by 3 mM ATP. Partially-purified TGase from human brain was inhibited by ATP in a manner similar to that observed with the rat liver enzyme. This suggests that the inhibition is a common phenomenon for tissue-type TGase in all species and tissues. The inhibition is reversible since full activity is restored by lowering the ATP concentration. CTP has a TGase-inhibitory potency equivalent to that of ATP, whereas GTP and UTP possess about 50% of the inhibitory activity of ATP. ADP inhibits TGase activity to the same extent as ATP, but AMP causes much less inhibition, and there is no inhibition by adenosine or adenine. The inhibition by ATP is insensitive to ionic strength and is non-competitive with the substrate putrescine. Since ATP levels in cells are of mM order, these results suggest that TGase activity is controlled by ATP in vivo.     

Nitric oxide biosynthesis, nitric oxide synthase inhibitors and arginase competition for L-arginine utilization

Nitric oxide (NO) is a recently discovered mediator produced by mammalian cells. It plays a key role in neurotransmission, control of blood pressure, and cellular defense mechanisms. Nitric oxide synthases (NOSs) catalyze the oxidation of L-arginine to NO and L-citrulline. NOSs are unique enzymes in that they possess on the same polypeptidic chain a reductase domain and an oxygenase domain closely related to cytochrome P450s. NO and superoxide formation as well as NOS stability are finely regulated by Ca²⁺/calmodulin interactions, by the cofactor tetrahydrobiopterin, and by substrate availability. Strong interactions between the L-arginine-metabolizing enzymes are clearly demonstrated by competition between NOSs and arginases for L-arginine utilization, and by potent inhibition of arginase activity by N^ω-hydroxy-L-arginine, an intermediate in the L-arginine to NO pathway.     

Pluralism and objectivity: Exposing and breaking a circle

The paper argues that Helen Longino’s pluralism implies circularity as it claims a preferably high number of qualified contributions to any scientific discussion that aims for objectivity, but does not regard the question who or what sets and employs the standards that rule the decision who is qualified to contribute and who is not. Therefore, objectivity is premised for a process that is to generate that very objectivity. Philip Kitcher’s ideal of democratization of science seems only to bypass the problem by introducing ideal deliberators tutored by appropriate experts, as for the implementation of this ideal the deliberators and experts, again, would have to be appointed by someone. However, Kitcher’s approach is based on a Rawlsian egalitarism and in this sense calls for political intrusion which could be based on case-by-case decisions. This offers a solution. I will illuminate the problem by some examples from climatology and demonstrate how Kitcher’s approach can help to tackle the problem by a final case study of pluralism in the Intergovernmental Panel on Climate Change.     

Das beim Gefrieren von Gelen entstehende Eis

Summary Highly swollen gels which contain, in addition to a large amount of solvent, a spatial network formed by chains of a high polymer, show an abnormal lowering of the freezing point. This is caused by the fact that the network prevents the formation of macroscopically undisturbed crystals.If, in the course of freezing at this lower temperature, a conglomerate of microcrystals were created corresponding in size to the width of the network, one should be able to observe a broadening of the X-ray interference lines. Experiments have shown that no measurable broadening takes place.This is explained by the assumption that a crystal which is prevented from growing in the normal way by the surrounding filaments of the gel, when cooled to a suitably low temperature grows crystallites with a small cross-section corresponding to the mesh size. The crystallites thus formed are orientated in a crystallographically exact manner toward their supporting crystal and parallel to each other. Therefore, when reaching the necessary height, they unite to larger, ordered crystalline regions which incorporate the polymeric filaments. This explains the observed sharpness of the X-ray interferences as well as the observation that, upon heating of a frozen gel, the melting does not occur at the same low temperature as the freezing, but closer to the melting point of macroscopic ice.     

Post-proteasomal and proteasome-independent generation of MHC class I ligands

Peptide ligands presented by MHC class I molecules are produced by intracellular proteolysis, which often involves multiple steps. Initial antigen degradation seems to rely almost invariably on the proteasome, although tripeptidyl peptidase II (TPP II) and insulin-degrading enzyme (IDE) may be able to substitute for the proteasome in rare cases. Recent evidence suggests that the net effect of cytosolic aminopeptidases is destruction of potential class I ligands, although a positive role in selected cases has been documented. This may apply particularly to the trimming of long precursors by TPP II. In contrast, trimming of ligand precursors in the endoplasmic reticulum is essential for the generation of suitable peptides and has a substantial impact on the repertoire of ligands presented. Trimming by the ER aminopeptidase (ERAP) enzymes most likely acts on free precursors and is adapted to the needs of class I molecules by way of a molecular ruler mechanism. Trimming by ERAP enzymes also occurs for cross-presented ligands, which can alternatively be processed in a special endosomal compartment by insulin-regulated aminopeptidase.     

Kinetic analysis and simulation of glucose transport in plasma membrane vesicles of glucose-repressed and derepressed Saccharomyces cerevisiae cells

In this study experimental data on the kinetic parameters investigated by other authors 1-5, 11 together with own data on plasma membrane vesicles, have been subjected to a computer simulation based on the equations describing facilitated diffusion. The simulation led to an ideal fit describing the above data. From this it can be concluded that glucose is transported by facilitated diffusion, and not by active transport as was postulated by Van Steveninck 14,15. The simulation method also demonstrates that the fast sampling technique used by these authors 1-5, 11 underestimated the fluxes. Thus, the parameters given do not contribute to the understand of glucose transport under different metabolic conditions. The K value of plasma membrane vesicles prepared from glucose-repressed cells is around 7 mM. Derepression, particularly by galactose, causes a highly significant increase in affinity as shown by a decrease in the K value to 2 mM. The highest affinity was measured in a triple kinaseless mutant grown on glycerol with a K value of 1 mM. It seems, therefore, that the kinetic parameters derived from initial uptake rates of glucose in intact cells 1-5, 11 using single flux analysis, such as Eadie-Hofstee- or Lineweaver-Burk-plots, are in error.     

Léon Rosenfeld and the challenge of the vanishing momentum in quantum electrodynamics

Léon Rosenfeld published in 1930 the first systematic Hamiltonian approach to Lagrangian models that possess a local gauge symmetry. The application of this formalism to theories with local internal symmetries, such as electromagnetism in interaction with charged matter fields, is valid and complete, and predates by two decades the work by Dirac and Bergmann. Although he provided a group-theoretical justification for gauge fixing procedures that had just been implemented in the first expositions of quantum electrodynamics by Heisenberg and Pauli, and also by Fermi, his contribution went largely unnoticed. This lack of impact seems to be related to a generalized disenchantment with second quantization in the 1930s and 1940s.     

Zeitbedarf der Längsteilung von miteinander verzwirnten Fadenmolekülen

Summary The time requirement is treated for a longitudinal fission by Brownian movement of a very long particle consisting of two or more filaments twisted a great number of times round each other to form a double spiral. It is shown that a comparatively swift disintegration is obtained by partial rotation or torsion round the axis of the spiral, resulting in a loosing of the spiral structure and subsequent separation of the constituents by translational Brownian movement. The time required to separate a double spiral consisting of about 900 turns of a height of 3.4 × 10⁻⁷ cm and a radius of 10⁻⁷ cm, thus having a length of 3 × 10⁻⁴ cm being realized approximately by deoxyribonucleic acid is found by this mechanism to be about 50 to 80 s. The time required to undo the same spiral by unwrapping it turn by turn would be about 150 days. The result of the considerations is related to observations published byAlexander andSteacy on deoxyribonucleic acid. An additional remark stresses the importance of stereochemical asymmetry for the practicability of the mechanism and therefore the importance of optical activity for the time requirement of such disintegrations or transformations of high polymer material occurring in living organisms.      

Fourth World Conference on Women: the Namibian perspective

This consideration of some of the issues raised at the Fourth World Conference on Women (WCW) from a Namibian perspective begins by mentioning the pernicious nature of domestic violence and briefly summarizing some of the main points raised at a 1994 symposium on domestic violence. The discussion continues by noting that Namibia's report for the WCW reaffirms that it is crucial for women to be involved in the decision-making process at all levels. Next, the paper notes that traditional male attributes of strength are losing their importance in a world that values mental alertness, intuition, and traditional female qualities of love and service. This has led to a call for a transformation of society supported by the education of women and their economic empowerment. The essay ends by defining an empowered person as possessing a belief in the ability of human intervention to change the world, a sense of self-worth, a sense of the self as a viable agent of change, and a notion of what constitutes a better life.     

Inhibition of rat liver transglutaminase by nucleotides.

Tissue-type transglutaminase (TGase) was purified from rat liver, and the effects of nucleotides on its activity were examined. The enzyme activity is inhibited by ATP in a concentration-dependent way, with complete inhibition by 3 mM ATP. Partially-purified TGase from human brain was inhibited by ATP in a manner similar to that observed with the rat liver enzyme. This suggests that the inhibition is a common phenomenon for tissue-type TGase in all species and tissues. The inhibition is reversible since full activity is restored by lowering the ATP concentration. CTP has a TGase-inhibitory potency equivalent to that of ATP, whereas GTP and UTP possess about 50% of the inhibitory activity of ATP. ADP inhibits TGase activity to the same extent as ATP, but AMP causes much less inhibition, and there is no inhibition by adenosine or adenine. The inhibition by ATP is insensitive to ionic strength and is non-competitive with the substrate putrescine. Since ATP levels in cells are of mM order, these results suggest that TGase activity is controlled by ATP in vivo.     

Effects and duration of resistance acquired by rabbits on feeding and egg laying in Ixodes ricinus L.

Rabbits gradually developed a resistance against Ixodes ricinus ticks as a result of sequential experimental infestations. The resistance was characterized by an increase duration of feeding, by ticks engorging to a smaller extent and by reduced egg production. Once established, the immunity persisted for at least 9 months. Changes in the titre of circulating anti-I. ricinus antibodies was measured by indirect immunofluorescence.     

基于控制图的教学质量评价方法

本文提出了一种利用统计控制图对教学质量进行评估的方法.首先建立了一个教师教学质量评估结果与学生期望等级的回归模型.其次,利用教师教学质量评估分数（区段平均数）的两倍标准差控制图与回归模型的残差控制图来辨别成绩的好坏.但需注意,个体成绩在两个图中都处于控制限以外的情况无法用期望等级来解释.     

量子密钥分发中波长相关攻击安全性研究

本文主要解决在现实条件下,量子密钥分发系统中光纤分束器的波长相关特性引起的测量基矢选择不随机的安全性问题,通过分析分束器波长相关性引起的误码粒子分布偏差的大小,理论推算实际系统中可提炼的最终安全码的下限,从而较好地解决了存在被动基矢选择的波长相关性漏洞的安全性问题,给出了类似安全性攻击方案的一个解决方法.     

'On Going Up in the World': Nation,Region and the Land Elevation Debate in Sweden

The aim of the article is to analyse the relationship between Quaternary geology, the idea of land elevation, nationalism and regionalism in Scandinavia, with special regard to the contribution of Swedish geologists at the end of the nineteenth century. From a scientific point of view, the idea of land elevation was connected to the acceptance of the glaciation theory and the elevation theory of Thomas F. Jamieson, but analysed in a wider cultural context it is possible to understand both the professionalization of Quaternary geology and the new theory of shore-line displacement as expressions of Swedish cultural nationalism. As a complement to the specific cultural history, the Quaternary geology enterprise was a way of constituting a unique natural history of the nation. One of the new theories that developed in this process was that of the Highest Marine Border, a complex concept established by the distinguished geologist Gerard De Geer at the end of the 1880s in order to defend the theory of land elevation, which was threatened by the work of Eduard Suess. The line was considered to be a geographical border that both expressed the elevation pattern and sharply divided Sweden into one part that had been covered by water during the post-glacial period and another part that had not. The study continues by looking more closely at the construction of the border in the north of Sweden. Through an account of a subsequent scientific dispute between De Geer and the geologist Arvid Gustaf Hogbom it is clear that the concept of the Highest Marine Border was shaped not only by nationalism but also by regionalism.     

A semi-automatic computerized analysis of tracks of ciliates

Summary The behavior of Protozoa can be studied by using the ethogram as a conceptual tool capable of giving an almost complete picture of the motor biology of these microorganisms. A new semi-automatic, computerized method for drawing ethograms is described here: it allows a time-saving of about 70%, in comparison with the similar manual procedure. Microorganism movements are photographed by a Pentax LX camera from the screen of a TV monitor, connected to the stereomicroscope by a TV camera, and resolved into single images using a stroboscopic apparatus. The pictorial data are introduced into the computer by means of a digitizing tablet, and the track analysis is performed semi-automatically. The measurements recorded are then processed using a commercial statistics package in order to obtain a general view of the quantitative parameters of each ethogram.