Energy-dependent accumulation of iron by isolated rat liver mitochondria. III. Submitochondrial localization of the iron accumulated

Isolated rat liver mitochondria accumulate iron partly by an energy-dependent and partly by an energy-independent mechanism (Romslo, I. and Flatmark, T. (1973) Biochim. Biophys. Acta 305, 29–40). When the iron-loaded mitochondria were disrupted mechanically and the mitochondrial subfractions isolated by density gradient centrifugation, the iron accumulated by the energy-dependent mechanism was recovered mainly in the soluble matrix and intermembrane space (approx. 50% of the total activity) and the inner membrane (approx. 30%). A negligible contribution to the total iron content of the soluble fraction by intermembrane space was revealed by the preparation of ‘mitoplasts’. On the other hand, most of the energy-independent iron accumulation was confined to the outer and inner membranes (approx. 35% of the total activity in each).     

Feinstruktur intrazellular wachsenderCuscuta-Hyphen

Zusammenfassung Es wird die Feinstruktur derCuscuta-Hyphen vor dem Anschluß an ein Wirtsleitelement beschrieben. Diese sog. Such-Hyphe, die durch einen besonders dichten und organellenreichen Protoplasten gekennzeichnet ist, durchstößt beim intrazellularen Wachstum die Wirtswand und stülpt den Wirtsprotoplasten handschuhfingerartig ein. Die Hyphenspitze ist stets von einer eigenen Wand umgeben. Diese wird häufig von Plasmafäden durchzogen, die Parasitenund Wirtszelle direkt verbinden. Diese — erstmals elektronenoptisch nachgewiesenen —Außenwandplasmodesmen werden in basalen, älteren Hyphenbereichen durch eine von der Wirtszelle ausgeschiedene Wand sekundär verschlossen. Auf Unterschiede dieser Plasmastrukturen gegenüber den Ektodesmen in den Epidermisaußenwänden wird hingewiesen sowie ihre Entstehung diskutiert.

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Fine structure of intracellular growingCuscuta-hyphae

Summary The fine structure of parasiticCuscuta-hyphae that has not yet a contact to the conducting tissue of the host has been studied. The so called searching hyphae are characterized by rich protoplasts with many organells. When intracellular growing they push through the host wall and keep surrounded by the plasmalemma of the host protoplasts. The tip of the hypha always has its own wall, that is penetrated sometimes by numerous plasmatic filaments, directly connecting the protoplast of the parasit with that of the host cell. These plasmodesmata of the outer wall, the ultrastructures of which are described for the first time, are shut lateron by a following wall apposition of the host cell against the hypha. The origin of these plasmodesmata of the outer wall and the differences to the so-called ectodesmata in outer walls of the epidermis are discussed.

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Teilabdruck einer Diss. d. Mathem.-Naturwiss. Fakultät der Universität Bonn. Das vollständige Exemplar kann an obiger Stelle eingesehen werden.

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Mein Dank gilt meinem verehrten Lehrer Herrn Prof. Dr. W.Schumacher. Ganz besonders danke ich Herrn Doz. Dr. R.Kollmann für alle wertvollen Diskussionen und seine jederzeitige Hilfe.     

Diffusion models for the dispersal of insects near an attractive center

From a general point of view we discuss various models for the dispersal of insects that are attracted towards a point by some mechanism. The basic model is a diffusion with drift towards the attractive center. It is shown that most quantities of interest in the model can be found explicitly when the drift is inversely proportional to the distance from the center. Experiments to test the models are proposed, and the results of one such experiment are summarized.     

On the occurrence of antimicrobial substances in the course of composting of municipal garbage

Summary Various extracts obtained from different phases of composting municipal garbage were tested for their effect on the growth of Bacillus megaterium and a mixed bacterial population. The results showed that antimicrobial substances are present in the fresh garbage. Their biocidal efficiency decreases during the rotting process and no new antimicrobial substances are produced during rotting. The evolution of heat as well as a certain kind of detoxication is important for the sanitation of garbage by the composting process.Extract from the Dissertation I. in der Schmitten, Giessen 1979     

Strukturelle Grundlagen des Parasitismus beiOrobanche

Zusammenfassung Innerhalb des Haustoriums vonOrobanche werden zur Assimilatleitung besondere Zellen ausgebildet. Diese zeigen viele Merkmale der typischen Siebelement-Differenzierung: Tonoplastenverlust, Kernverlust, Veränderung der Plastiden und Mitochondrien. Während der Entwicklung der haustorialen Siebröhren bleiben die Ribosomen jedoch in großer Dichte vorübergehend erhalten. Dieses Zwischenstadium der Siebelemententwicklung wird von uns als Übergangssiebelement bezeichnet. Erst mit der Desintegration der Ribosomen treten die typischen Plasmafilamente angiospermer Siebröhren auf, die Plasmodesmen werden zu Siebporen erweitert. Charakteristisch für die haustorialen Siebelemente ist ein glattes zisternales, wandständiges ER, das um so stärker ausgebildet ist, je näher die Parasitenzelle an der Wirtssiebröhre liegt.Ein direkter Anschluß dieser umdifferenzierten Zellen an die Wirtssiebröhren wird jedoch nicht beobachtet. Stets ist zwischen den Leitelementen beider Organismen mindestens eine Kontaktzelle ausgebildet, die einen normalen, wenngleich besonders dicht strukturierten Protoplasten zeigt. Es werden keine plasmatischen Verbindungen zwischenOrobanche und ihrem Wirt gefunden.Die Befunde anOrobanche werden mit denjenigen an anderen parasitischen Pflanzen verglichen.

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Structural features of parasitism ofOrobanche II. The differentiation of assimilate conducting elements within the haustorium

Summary Within the haustorium ofOrobanche special assimilate conducting cells are developed. These cells show many typical features of sieve element differentiation: disintegration of tonoplast and nucleus, structural changes of plastids and mitochondria. The ribosomes however persist in high quantity in the developing sieve element. We call this intermediate stage of sieve element differentiation transition-sieve element. Only after disappearance of ribosomes the typical plasmatic filaments of angiosperm sieve tubes appear and plasmodesmata dilate to sieve pores. A smooth surfaced ER adjacent to the wall, is specific for haustorial sieve elements. The closer the parasitic cell lies to the host sieve tube, the better ER is developed. However a direct contact of this specialized cell to the host sieve tube was not observed. There is always a particular contact cell, showing a normal protoplast of high density. No plasmatic connections betweenOrobanche and its host are detected. These findings onOrobanche are compared with those on other parasitic plants.

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Wir danken FrauChristl Glockmann für ihre verantwortungsvolle Mitarbeit. Die Untersuchungen wurden durch Mittel der Deutschen Forschungsgemeinschaft gefördert.     

Filament formation in vitro of a sieve tube protein from Cucurbita maxima and Cucurbita pepo

Summary Phloem proteins of the sieve tube exudate from Cucurbita maxima Duch. and Cucurbita pepo L. were investigated as to their filament forming ability in vitro. From the two main proteins (116000 dalton, 30000 dalton) only the 116000 dalton protein was found to form reversibly distinct filaments of 6–7 nm diameter upon removal of SH-protecting agents from the buffer, whereas the 30000 dalton protein was precipitated as amorphous material under these conditions. The protein filaments were similar to the filaments ocurring within the sieve tube cells in vivo.Abbreviations SDS sodium dodecyl sulfate - TCA trichloroacetic acid