Chromosome Replication in Salmonella typhimurium

The replication of the Salmonella typhimurium chromosome was studied. As with E. coli 15T(-), replication was sequential. After amino acid starvation, replication proceeded from a unique and heritable region of the chromosome. 5-Bromouracil, when substituted for thymine, did not disturb the sequence of replication nor did it initiate extra replication cycles. By labeling the origin and the terminus of the chromosome with (3)H- and (14)C-thymine, respectively, it was possible to determine that the rate of chain elongation decreases as the growth rate decreases. No gap in the replication cycle could be observed.     

Zur Morphologie und Phylogenie der Schizorhynchia (Turbellaria,Kalyptorhynchia)

The proboscis organs of 21 species of Schizorhynchia represent new characters. The meaning of apomorph characters of the proboscis organ and of certain parts of the genital apparatus is discussed. In the phylogenetic system the position of the four families of Schizorhynchia is considered.

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Gefördert durch eine Sachbeihilfe der Deutschen Forschungsgemeinschaft im Schwerpunktprogramm Litoralforschung — Abwassereinflüsse in Küstennahe.     

Feinstrukturen der Mikrokörper (Microbodies) des proximalen Nierentubulus

Zusammenfassung Die Feinstrukturen der Mikrokörper des Nierenepithels werden beschrieben und mit denjenigen der Leber-Mikrokörper verglichen. Als besondere Charakteristika der Nieren-Mikrokörper sind eine (nicht kristalline) nucleoide Verdichtung und eigentümliche stabförmige Ausstülpungen (Stäbe) anzusehen. Die Stäbe stellen unterschiedlich lange Zylinder mit einem Durchmesser von 100 nm dar. Im Inneren findet sich eine unmittelbar der Membran anliegende, ring- oder spiralförmig angeordnete, granuläre Struktur (Granula-Durchmesser 50 Å), die in Stablängsschnitten eine Querstreifung vortäuscht. Es wird eine in Phasen ablaufende Bildung der Mikrokörper-Stäbe angenommen: ein in der Matrix entstandener Granula-Zylinder hebt sich aus dem Mikrokörper heraus, wobei die Mikrokörper-Membran entsprechend vorgebuchtet wird, und wächst schließlich zu einem eigenständigen, allseits membranumzogenen Stab aus. Die Möglichkeit, daß die Stäbe von Mikrokörpern abgestoßen werden, wird diskutiert. — Die Segregation von Mikrokörpern in Vakuolen wird nicht als aktive Beteiligung an lytischen Prozessen, sondern als autophagischer Vorgang gedeutet.

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Fine structure of microbodies in proximal tubular epithelium of the kidney

Summary Ultrastructural observations on microbodies in normal proximal tubule cells of the rat kidney are described and compared with microbodies of hepatic parenchymal cells. After fixation in osmium tetroxide with phosphate buffer the special features of the renal microbodies are the non-crystalline nucleoid and protrusions (rods) extending from the main body. These rods are cylindrical in shape having a diameter about 100 nm and are of varying lengths. Inside the limiting membrane are ring- or spiral-like ordered profiles consisting of granules (about 50 Å in diameter) which often appeared as a row of parallel linear densities arranged at approximately right angles to the long axis of the rod. It can be demonstrated that the parallel linear pattern depends on the projection of the granules in the photographic plane. — The findings suggest that the cylindrical structures of granules are formed in the peripheral matrix of microbodies; in a second phase they are lifted outside, in part enveloped with the membrane of the microbody; in this situation, the protrusions are formed. This form of creation would explain the characteristic excentrical (tangential) relation between protrusions and the main body. The observation that rods are often seen apparently isolated in the cytoplasm without visible connection with a microbody is only discussed hypothetically, because of the plane of sectioning. — Microbodies and rods can be identified in cytosegresomes. These investigations were interpreted as an autophagic degradation and not as an active role of the enzymes of microbodies in digestive mechanisms.

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Herrn Prof. Dr. Helmut Ruska zum 60. Geburtstag gewidmet.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.

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Herrn Doz. Dr. W. Thoenes danke ich für wertvolle Hinweise und für die kritische Durchsicht des Manuskriptes.     

Zum Bewegungssehen des Mehlkäfers Tenebrio molitor

Summary The locomotory turns of the beetle Tenebrio molitor were recorded from free walking animals which were held in stationary position and orientation by means of a tread compensator. Striped patterns revolved around an animal elicit optomotor responses which undergo an inversion at smaller stripe widths. The position of the inversion point characterizes the resolving power of the motion detectors, and corresponds to a 6.5° average angle between the optical axes of interacting elements in the motion detecting device. This indirectly determined value is consistent with the anatomically measured 7° average angle between the axes of neighbouring ommatidia in the Tenebrio compound eye.     

Segregation of Deoxyribonucleic Acid in Bacteria: Association of the Segregating Unit with the Cell Envelope

Cells of the gram-positive organism Lactobacillus acidophilus R-26 were labeled with ³H-thymine to measure the segregation of radioactive deoxyribonucleic acid (DNA) into daugher cells. Such cells were found to contain 8 conserved units of DNA which would correspond to two replicating chromosomes per cell. Fluorescent antibody (FA) against this organism was used to demonstrate that portions of the cell surface (2 to 4 units per cell) were conserved during growth and division. The permanent association of DNA with these conserved cell surface units was measured by combining autoradiography with FA techniques. DNA synthesized immediately before FA labeling was not associated with the fluorescent cell surface, whereas DNA synthesized a generation previously was. The results are consistent with a model in which DNA becomes permanently fixed to the cell surface when it is first used as a template.     

Some Properties of Heat-Resistant and Heat-Sensitive Strains of Clostridium perfringens I. Heat Resistance and Toxigenicity

Heat resistance at 100 C (D-values), sporulating ratios, toxigenicity for mice, and lecithinase activity (as micrograms per milliliter of enzyme, ascertained by the lecithovitellin reaction) were determined for four strains of Clostridium perfringens. A definite inverse relationship between thermal resistance and toxigenicity was found. The D-values ranged from 17.6 for the most heat-resistant strain to 0.3 for the strain possessing the least heat resistance, with corresponding lecithinase activities from 25 to 133 mug/ml of enzyme. The sporulating ratios did not differ greatly between the strains. The heat stability of the toxin was greater at 100 C than at 75 C. There was a noticeable difference between the heat stabilities of the toxin in the culture fluids of the heat-sensitive and heat-resistant strains at pH 7.0 when the toxic filtrates were held at 100 C. At a holding temperature of 75 C, a similar but lesser difference was observed at pH 5.5. Heat resistance and lecithinase activity did not change when a substrain of the least heat-resistant parent strain was obtained through heat selection by a single transfer, or when the most heat-resistant strain was transferred serially 12 times.     

Uraninschwellen des Protoplasmas der BraunalgeStypocaulon scoparium

Ohne Zusammenfassung     

Mikropinozytose im Zentralnervensystem

Zusammenfassung An durch Perfusion mit Glutaraldehyd fixierten Rattengehirnen wurde das Erscheinungsbild der Mikropinozytose in Elementen der Meso- und Neuroglia sowie an den Perikarya und synaptischen Endformationen der Nervenzellen elektronenmikroskopisch dargestellt.Die bei der Mikropinozytose von der Zellmembran invaginierten Caveolen und Tubuli können einfache Verzweigungen zeigen. Ihre Oberfläche und die der mikropinozytotischen Bläschen zeigen an der gegen das Zytoplasma gerichteten Membranseite einen Stachelsaum. Diese Membrandifferenzierung dürfte mit der Resorption besonderer, zum Teil makromolekularer Substanzen zusammenhängen.Im Bereich großer Synapsen, z.B. in den Moosfasertelodendren der Glomerula cerebellaria oder in der Zona glomerulosa des Bulbus olfactorius sind mikropinozytotische Invaginationen und Bläschen sehr häufig. Möglicherweise übernehmen sie von den postsynaptischen Dendriten, die dünne Zytoplasmaprotrusionen in die Invaginationen hineinsenden, Stoffe. Es wird vermutet, daß es sich hierbei um inaktivierte Transmittersubstanz handelt, die auf diesem Wege dem präsynaptischen Abschnitt wieder zugeführt wird. Die zurückresorbierten Abbauprodukte der Transmittersubstanz werden in einem präsynaptischen Golgi-Komplex resynthetisiert und in synaptischen Bläschen angereichert. Dieses morphologische Bild ergänzt die biochemische Hypothese eines Acetylcholin-Kreislaufes im Bereich von Nervenendigungen.Entsprechende mikropinozytotische Erscheinungen wurden in caudalen Abdominalganglien von Leucophaea maderae beobachtet. Es wird angenommen, daß die Mikropinozytose ein allgemein verbreiteter Resorptionsmechanismus im Zentralnervensystem ist.Herrn Prof. Dr. F. Wassermann zum 80. Geburtstag gewidmet.Mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft.     

The effect of iron chelate fertilization of poplar upon CO2-uptake,leaf size,and content of leaf pigments and iron

Summary Potted poplars (strainsmarilandica, serotina andFlachslanden ofPopulus euramericana) which developed iron-deficiency symptoms (chlorosis of upper leaves, winter die-back of leader, flushing of lateral buds) were treated with a soil application of iron chelate to study the effect of iron nutrition upon CO₂-uptake, iron and pigment content of leaves, and leaf size of a tree species. Foliar content of each iron, chlorophyll, -carotene, lutein, and violaxanthin was significantly increased by the treatment. Chlorophyll b proved to be particularly sensitive to iron supply and the Q^a/b was also significantly altered.CO₂-uptake increased in fertilized and non-fertilized leaves with increasing light up to 40,000 Lux, but fertilized leaves assimilated more CO₂ than non-fertilized leaves, especially at light intensities from 5,000 Lux upwards. The assimilatory number was decreased by the iron application since larger amounts of chlorophyll were present in fertilized leaves. If CO₂-uptake was based upon an area unit basis the fertilizer effect became distinct even at 500 Lux. Thus CO₂-uptake is a quick, valuable measure of fertilizer responses.In severe cases, iron deficiency also affects leaf size and thus indirectly reduces photosynthetic activity. A chelate application during the growing season will not affect the size of leaves already formed but may considerably increase the size of leaves formed subsequent to the treatment.