Shear and the Melting of DNA: An Especially Sensitive Portion of the Escherichia coli Genome

The melting point of DNA is shown to be a function of shear stress. The higher the molecular weight of the DNA, the further its melting point is lowered by a given shear rate. During lysis of E. coli, a part of the DNA is especially shear sensitive, so that its melting curve in the presence of shear shows a low-melting region prior to the main transition. Lysis and dilution of the cell contents destroys the extra shear sensitivity, perhaps because the DNA dissociates from the cell membrane or from some other large subcellular structure. Such a structure would impart increased shear sensitivity to the associated region of the genome.     

Quantitative und qualitative elektronenmikroskopische Untersuchungen zur Struktur des Leberläppchens normaler Ratten

Zusammenfassung Untersucht wurden zufällig ausgewählte Leberstückchen normaler Wistarratten. 25 lückenlose Übersichten von periportalen und zentralen Arealen des Leberläppchens, die aus 2564 elektronenmikroskopischen Einzelaufnahmen (Vergrößerung 4600 x) zusammengesetzt waren, wurden bei einer Gesamtvergrößerung von 53000 x mit Hilfe eines Liniengitters nach der Methode. von Loud quantitativ ausgewertet.Die mittlere Cytoplasmafläche eines Hepatocyten, der im Läppchenzentrum liegt, ist größer als diejenige einer in der Peripherie des Läppchens gelegenen Leberzelle, die Zahl der Anschnitte von Mitochondrien pro Cytoplasmafläche im Zentrum geringfügig größer als in der Peripherie. Die Zahl der Lysosomen pro Cytoplasmafläche ist in der Peripherie des Lobulus dreimal höher als in seinem Zentrum.Der Flächenanteil der Mitochondrienanschnitte an der Cytoplasmafläche im Zentrum beträgt 12,3%, im periportalen Bereich 19,3%. Die mittlere Fläche eines Mitochondrienanschnittes ist im periportalen Gebiet doppelt so groß wie im Zentrum, die Membranprofildichte in Mitochondrien periportaler Zellen ist um etwa ein Drittel größer.Schüsselförmige und schlegeloder hantelförmige Mitochondrien mit parallel zur Längsachse ausgerichteten inneren Membranen wurden nur im Zentrum des Leberläppchens gefunden. Dasselbe gilt für Plasmaprotusionen der Hepatocyten in den Disseschen Raum. Glykogenablagerungen sind gleichmäßig über den Lobulus verteilt, auffallend ist jedoch die ungleichmäßige Verteilung auf die einzelnen Zellen.Die quantitativen Daten werden mit histochemischen Befunden und biochemisch ermittelten Enzymaktivitäten verglichen. Die morphologischen Beobachtungen werden im Zusammenhang mit ähnlichen Befunden, die an pathologisch veränderten Lebern erhoben wurden, diskutiert.

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Structure of the hepatic lobule of the rat

Summary Small randomly chosen pieces of liver tissue of normal Wistar rats were investigated with the electron microscope. 25 survey pictures, consisting of 2564 individual micrographs, were analyzed quantitatively at a final magnification of 53,000 x by a linear scanning method as described by Loud.The average area of cytoplasm is larger in the centrolobular than in the periportal area. The number of mitochondria per unit of cytoplasmic area was roughly the same throughout a liver lobule. However, in the periportal zone the mitochondria were about two times larger than in the center and displayed a 30% higher membrane profile concentration. It was found that the total mitochondrial area per unit of cytoplasm was 12,3% in the centrolobular region as compared to 19,3% in the periportal zone. The number of lysosomes per unit of cytoplasmic area was about three times higher in the periportal than in the centrolobular zone.Cup- and dumbbell-shaped mitochondria with densely packed and longitudinally arranged internal membranes were only found in the centrolobular area. Irregular protrusions of the liver cell into the space of Disse were also found exclusively in this area. The amount of glycogen varied considerably from cell to cell but no significant difference in this respect could be seen between the two zones of the liver lobule.The quantitative findings are discussed with reference to available bio- and histochemical data. The morphological observations are compared with similar observations made on pathologically altered liver cells.

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

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Carotenoids and carotenoid metabolism in Carcinus maenas (Crustacea: Decapoda)

The carotenoid pigments of the hepatopancreas, ovaries and epidermis of Carcinus maenas were investigated. The following pigments were identified: β-carotene, δ-carotene, echinenone, isocryptoxanthin, canthaxanthin, lutein, zeaxanthin, flavoxanthin and astacene.
The relative abundance of these pigments in the three tissues and the presence of possible hydroxy and keto intermediates suggest the metabolism of astaxanthin from β-carotene. The metabolic pathway in Carcinus is discussed in relation to recent studies on other invertebrates.     

Carotenoids and carotenoid metabolism in Carcinus maenas (Crustacea: Decapoda)

The carotenoid pigments of the hepatopancreas, ovaries and epidermis of Carcinus maenas were investigated. The following pigments were identified: β-carotene, δ-carotene, echinenone, isocryptoxanthin, canthaxanthin, lutein, zeaxanthin, flavoxanthin and astacene.
The relative abundance of these pigments in the three tissues and the presence of possible hydroxy and keto intermediates suggest the metabolism of astaxanthin from β-carotene. The metabolic pathway in Carcinus is discussed in relation to recent studies on other invertebrates.     

The Growth and Toxin Production of Clostridium botulinum Type E in Certain Vacuum Packed Fish

The growth and toxin production of Clostridium botulinum type E in various types of vacuum packed fish products was tested, with particular reference to the time/temperature relationship of storage. Toxin production was most rapid in herring although smoking retarded its development. With as small an inoculum as 10² spores/pack, fresh herring became toxic after storage for 15 days at 5°. Irradiation of three species of fish after inoculation with Cl. botulinum type E showed that spores surviving radiation germinated and produced toxin more rapidly than an equivalent concentration of spores in nonirradiated fish.     

Genetic transformation of apple (Malus pumila Mill.) using a disarmed Ti-binary vector

The disamed Ti-binary vector pBIN 6 in Agrobacterium tumefaciens has been used in leaf disc transfomations to produce transgenic apple (Malus pumila Mill.) plants with a nomal phenotype except for a somewhat reduced capacity to root. The presence of the genes for nopaline synthase and neomycin phosphotrans ferase (conferring kanamycin resistance), inserted into the host genome by the vector, was confirmed by Southern blot analysis, the detection of nopaline synthase activity and rooting in the presence of the antibiotic.The nopaline synthase gene continued to be expressed in glasshouse-grown plants several months after removal from in vitro growth conditions.