Entwicklung und Bau der Doppelspermien bei den DytiscidenAcilius sulcatus L.,Dytiscus marginalis L. undHydaticus transversalis Pont. (Coleoptera)

Zusammenfassung BeiAcilius sulcatus undDytiscus marginalis wurde die Spermiogenese bis zu den reifen Doppelspermien, beiHydaticus transversalis wurden nur die reifen Doppelspermien untersucht. Die Konjugation der Spermien dieser Arten erfolgt als letzter Schritt erst im distalen Teil des Hodenausführungsganges. Voraussetzungen für ihr Zustandekommen sind sowohl lokale Differenzierungen der Spermienmembran, alsauch spezifische polysaccharidhaltige Beläge, von denen nach dem Aussehen sowie nach Zeitpunkt und Ort ihres Auftretens vier unterschieden werden können, die teils schon im Zystenlumen, teils erst nach Eindringen des Spermienvorderendes in tiefe Fächer der Zystenwandzellen gebildet werden. Die mit allen Belägen versehenen Einzelspermien treten zusammen mit abgeschnürten Resten der Zystenwandzellen in den Ausführungsgang ein, dessen Epithel die Plasmareste der Zystenwandzellen phagozytiert. Die Beläge der Spermien sind nach der Konjugation verändert. Damit muß als letzte Bedingung für das Zustandekommen des Aneinanderhaftens noch eine Reaktion im Ausführungsgang stattfinden. Weiterhin wurde die Entwicklung des als microtubular border beschriebenen Strukturelements im Schwanz verfolgt und als centriole adjunct identifiziert, welches sich aus Kernmaterial herleitet und zu einem Geißelbegleitkörper modifiziert hat. Schließlich wird auf anscheinend regelmäßige und in zeitlich abgestimmter Folge auftretende Beziehungen des Endomembransystems zu den sich differenzierenden Strukturen der Spermatide hingewiesen.

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Development and structure of the conjugate sperm of the dytiscidaeAcilius sulcatus L.,Dytiscus marginalis L. andHydaticus transversalis pont. (Coleoptera)

Summary Spermiogenesis and structure of the double sperm have been investigated inAcilius sulcatus andDytiscus marginalis whereas only mature double sperm have been studied inHydaticus transversalis. The conjugation of the sperm in these species is accomplished as a last step in the distal part of the vas deferens. Preconditions for the pairing are local differentiations of the sperm membrane in combination with specific layers of polysaccharids. According to their aspect as well as the chronological order and place of their appearance four such layers can be discerned. These are formed in part still in the lumen of the cyst, in part not earlier than after the anterior ends of the sperm have deeply entered into recesses of the surrounding cyst wall cells. Single sperm supplied with all layers and cytoplasmic remnants pinched off from the cyst wall cells enter the vas deferens where the cytoplasmic remainders are phagocytised by its epithelial cells. The layers of the sperm are transformed after conjugation. Thus as a last precondition for the occurrance of pairing a reaction in the vas deferens must take place. Furthermore, the development of the structural element of the tail described as microtubular border has been traced and identified as a centriole adjunct derived from nuclear material and modified to a body accompanying the flagellum. Finally, it is pointed out that apparently regular relationships in temporally correlated sequence exist between the endomembranous system and differentiating structures of the spermatid.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.

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För die rasterelektronenmikroskopischen Aufnahmen der Abb. 9 danke ich Frau L. Schulz, Homburg, verbindlichst. Die Teilbilder 16g u. h konnten mit einem Siemens Elmiskop 102 aufgenommen werden. För die Anfertigung dieser Aufnahmen bin ich Frau Dr. C. Weichan, Berlin, zu Dank verpflichtet.     

A special class of nonlinear interactions in the visual system of the fly

Flies can detect a small object in front of a randomly contrasted background if the object undergoes small motions. The effect was investigated in fixed flying flies under open-loop conditions. The results suggest that nonlinear inhibitory interactions underly this elementary case of figure-ground discrimination.     

Esterase-D polymorphism in Assam by cellulose acetate electrophoresis

Summary With the help of a simplifed and quick method, cellulose acetate electrophoresis, the phenotypes of esterase D were determined in an Assamese population. The gene frequencies of Es D¹ were 0.7263 and 0.2737 for Es D².

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Zusammenfassung In einer Stichprobe aus Assam wurde mit Hilfe einer einfachen und schnellen Methode, der Cellulose-Acetat-Elektrophorese, die Bestimmung der Esterase D-Phänotypen durchgeführt. Die Genfrequenzen wurden für Es D¹ zu 0,.7263 und für Es D² zu 0.2737 bestimmt.

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Supported by the Deutsche Forschungsgemeinschaft, the Stiftung VW and the Fonds der Chemischen Industries.     

Zur temperaturregelung des menschlichen Körpers

the control-loop of human body-temperature is treated as a distributed-parameter-system. The equations of heat-balance are formulated, admitting discontinuities of parameters. Using two succeeding integral-transformations and an expansion with eigenfunctions, an analytical solution is found for the closed control-loop. Regarding the stationary as well as the dynamical behaviour, the mathematical results are on the whole compatible with experimental results.     

Das Sediment des Kummerower Sees. Untersuchungen des Chemismus und der Diatomeenflora

The Sediment of Lake Kummerow. Investigations on the Chemism and the Diatom Flora The paper deals with the distribution of chemical parameters and of diatoms in the deposits of the eutrophic Lake Kummerow (GDR), produced during about the last 3500 years. The sediment consists of a calcareous gyttja with a very low content of sand and clay. The results indicate a relatively constant trophic state of the lake in former times and an increased production within the last five centuries. Stephanodiscus astraea and its variety minutula is by far the most constant diatom species; in the uppermost parts of the sediment small sized planctonic taxa are increasing, in the main Stephanodiscus hantzschii var. pusillus, Melosira granulata var. angustissima, Asterionella formosa and Synedra acus var. angustissima and var. radians.     

Evolutionary transition pathways for changing peptide ligand specificity and structure

We identified evolutionary pathways for the inter- conversion of three sequentially and structurally unrelated peptides, GATPEDLNQKL, GLYEWGGARI and FDKEWNLIEQN, binding to the same site of the hypervariable region of the anti-p24 (HIV-1) monoclonal antibody CB4-1. Conversion of these peptides into each other could be achieved in nine or 10 single amino acid substitution steps without loss of antibody binding. Such pathways were identified by analyzing all 7 620 480 pathways connecting 2560 different peptides, and testing them for CB4-1 binding. The binding modes of intermediate peptides of selected optimal pathways were characterized using complete sets of substitution analogs, revealing that a number of sequential substitutions accumulated without changing the pattern of key interacting residues. At a distinct step, however, one single amino acid exchange induces a sudden change in the binding mode, indicating a flip in specificity and conformation. Our data represent a model of how different specificities, structures and functions might evolve in protein-protein recognition.     

Subcellular localization of EGFR in esophageal carcinoma cell lines

Background: The EGF receptor is a therapeutic target in cancer cells, whereby mutations of EGFR and/or signalling members act as predictive markers. EGFR however also exhibits dynamic changes of subcellular localization, leading to STAT5 complex formation, nuclear translocation and induction of Aurora-A expression in squamous cancer cells. We previously described high EGFR and Aurora-A expression in esophageal cancer cells. Here, we investigated subcellular localization of EGFR and STAT5 in esophageal cancer cells. Results: Quantitative immunofluorescence analyses of four esophageal cancer cell lines reflecting esophageal squamous cell carcinomas (ESCC) and esophageal adenocarcinomas (EAC) revealed that the subcellular localization of EGFR was shifted from a membranous to cytoplasmic localization upon EGF-stimulation in OE21 (ESCC) cells. Thereby, EGFR in part co-localized with E-Cadherin. In parallel, phosphorylated STAT5-Tyr694 appeared to increase in the nucleus and to decrease at the cell membrane. In three additional cell lines, EGFR was only marginally (Kyse-410/ESCC; OE19/EAC) and weakly (OE33, EAC) detectable at the cell membrane. Partial co-localization of EGFR and E-Cadherin occurred in OE33 cells. Post EGF-stimulation, EGFR was detected in the cytoplasm, resembling endosomal compartments. Furthermore, OE19 and OE33 exhibited nuclear STAT5-Tyr694 phosphorylation upon EGF-stimulation. None of the four cell lines showed nuclear EGFR expression and localization. Conclusion: In contrast to other (squamous) cancer cells, activation of EGFR in esophageal squamous cancer cells does not result in nuclear translocation of EGFR. Still, the subcellular localization of EGFR may influence STAT5-associated signaling pathways in esophageal cancer cells and hence possibly also the responses to ErbB, respective EGFR-targeted therapies.     

Sequencing of pools of nucleic acids on oligonucleotide arrays

In sequencing-by-hybridization methods, the nucleotide sequence of a nucleic acid is reconstructed by overlapping oligonucleotides capable of hybridizing with the nucleic acid. In their present form, the methods are hardly suitable for sequencing of long nucleic acid molecules because of the occurrence of non-unique overlaps between the oligonucleotides, and similarly to the conventional sequencing methods, it is necessary to obtain an individual molecule. In the method described here, most ambiguities in reconstruction of a sequence from the constituent oligonucleotides are eliminated by preparing on oligonucleotide arrays and separate surveying of the nucleic acid nested partials. This enables longer nucleic acids to be sequenced, and results in a high redundancy of the input data allowing most hybridization errors to be eliminated by algorithmic means. Furthermore, large pools of nucleic acid strands can be sequenced directly, without isolating individual strands.