Neocarzinostatin chromophore: Presence of a highly strained ether ring and its reaction with mercaptan and sodium borohydride

Spectroscopic evidence suggests the presence of a highly strained ether ring (Fig. 1) (possibly an epoxide) in the C₁₂-subunit of the previously determined partial structure $\text{2a}$ (Fig. 2) of the major neocarzinostatin chromophore (NCS-Chrom $\text{A}$) which completes assignment of all the oxygens in the molecule. The main product from mercaptan treatment suggests opening of the ether ring involving the addition of one molecule of mercaptan as well as reduction of the C₁₂-substructure, whereas a parallel two-step reduction occurs on NaBH₄ treatment. Both reactions occur with rearrangement of the C₁₂-substructure and the implication for the mechanism of action of NCS-Chrom $\text{A}$ in DNA strand scission activity is discussed. The evidence suggests a downward revision of the molecular formula for NCS-Chrom $\text{A}$ as well as minor components $\text{B}$ and $\text{C}$ by two protons.     

Modifikationen des DNS-Gehalts in Zuckerrübenzellen

Summary In epidermal cells of the cytoledons of sugar beets, Beta vulgaris L., the DNA content per cell can be increased 2–4 fold by means of compensatory growth and other measures of better nutrition, by application of stronger light, or by addition of more moisture to the soil. It decreases with deviations from the optimal growth temperature (22° C) and after lack of nitrogen in the nutritive solution. Differences in DNA content, representing mainly differences in the level of endopolyploidy, result in corresponding differences in the number of plastids in the cells.     

Mechanism of α Factor Biosynthesis in Saccharomyces cerevisiae

The biosynthesis of alpha factor, a mating-type-specific regulatory oligopeptide which is secreted by Saccharomyces cerevisiae cells of alpha mating type, was studied. In batch cultures only small amounts of the peptide were synthesized during the exponential growth phase. During the stationary phase, alpha factor was produced at a constant rate and accumulated in the culture medium. Inhibition of translation in wild-type cells by cycloheximide, or in mutant strains under conditions which blocked protein or ribonucleic acid (RNA) synthesis completely inhibited the production of alpha factor. These results indicate that the factor is produced by ribosomal translation of a specific messenger RNA and not by an extraribosomal mechanism of peptide synthesis.     

Some functional properties of hemoglobin Leiden

Hemoglobin Leiden, a human mutant that contains a deletion of a glutamic residue at position 6 or 7 (A3 or A4) of the #x03B2; chains, has a slightly higher oxygen affinity in 0.1 M Phosphate, a normal Bohr effect but an abnormal response to 2,3 diphosphoglycerate and inositol hexaphosphate. Hb Leiden participates to the same extent as does Hb A in gelation with deoxy Hb S.     

Intracerebral distribution pattern of radioactive morphine and morphine-like drugs after intraventricular and intrathecal injection

Summary The intracerebral distribution patterns of ¹⁴C-morphine, ³H-dihydromorphine, and ³H-fentanyl after intraventricular injection were studied autoradiographically in rats and rabbits. The extent of permeation into the ventricular wall was measured at different times after injection. The hydrophilic morphine and dihydromorphine could be demonstrated within the tissue up to 4 hours. They seemed to be retained within the gray matter and hindered in crossing fiber bundles. On the other hand, the lipophilic fentanyl was quickly removed from the brain but remained relatively longer demonstrable within the white matter. Also, after intrathecal injection of ¹⁴C-morphine a time dependent spread from the injection site was observed. The use of autoradiography in pharmacological experiments as described was found advantageous. Thus, it is possible to correlate directly, the time course of the pharmacological effect and the respective distribution pattern of the drug applied. This may lead to better information about the probable sites of drug action.     

Nachweis einer Pupillenreaktion im Auge der Schmeißfliege

Zusammenfassung Elektronenoptische Untersuchungen mit der Gefrierätzmethode an Augen der Normalform von Calliphora erythrocephala (Meig.) ergeben, daß im dunkeladaptierten Zustand die Rhabdomere 1–6 in den Retinulazellen dicht von Vesikeln umgeben sind, die wahrscheinlich durch Pinocytose an den Mikrovilli der Rhabdomere entstehen. Diese Bläschen fehlen im helladaptierten Zustand nahezu völlig. Die optische Dichte des umgebenden Mediums der lichtleitenden Rhabdomere wird dadurch im Dunkel-Auge herabgesetzt, was mit Hilfe der Becke-Methode im Lichtmikroskop festgestellt werden konnte.Physikalische Berechnungen mit den Gleichungen der geometrischen Optik ergeben, daß durch diese Brechzahländerung in den Sinneszellen im dunkeladaptierten Auge der physiologisch wirksame Lichtfluß in den Rhabdomeren l–6 im grünen Spektralbereich um etwa 30% erhöht werden kann.

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Evidence for a longitudinal pupil in the blowfly eye from studies with light and electron microscopes

Summary Eyes of the wild-type blowfly, Calliphora erythrocephala (Meig.), were investigated by using freeze-etching and the light microscope. In the dark-adapted eye a layer of vesicles 1 m thick borders on the rhabdomeres in sense cells Nos. 1 to 6. These vesicles may arise by pinocytosis at the bases of the rhabdomeric microvilli and decrease the optical density of the sense cell medium adjacent to the rhabdomeres. In the light-adapted sense cells only a few vesicles could be seen. No differences could be observed to exist between the two states of adaptation in the retinular cells Nos. 7 and 8 and in the axial retinular space.Calculations based on geometrical optics show that when rhabdomeres Nos. 1 to 6 are in the dark-adapted state they can transmit about 1.3 times more light energy than when they are in the light-adapted state. The results show the existence of a light-induced pupil reaction correlated to ultrastructural changes in the photoreceptor cells of the blowfly eye.

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Der Deutschen Forschungsgemeinschaft danke ich für die Gewährung eines Ausbildungsstipendiums.     

Die Rolle der Fimbrien bei der eigenartigen Sternbildung von Agrobacterium luteum

Zusammenfassung Die bemerkenswerte Sternbildung von Agrobacterium luteum Stamm A61 (Moll et al., 1967; Ahrens, 1968) ist auf polare Fimbrien zurückzuführen, die um die Sternaggregate ausgebreitet sind. Es wird angenommen, daß sich Schwärmzellen an den Fimbrien verfangen und durch Kontraktion rasch zum Stern gezogen werden. Nach elektronenoptischen Präparaten sind die Fimbrien bis zu 10,5 lang und können die beobachtete Sternbildung gut erklären. Agrobacterium luteum Stamm B14 besitzt ebenfalls lange polare Fimbrien. Beide Stämme tragen peritriche Geißeln, deren Struktur sich deutlich von den dünnen und unregelmäßigen Fimbrien unterscheidet.

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The function of fimbriae in the peculiar star formation of Agrobacterium luteum

Summary The remarkable way of star formation in Agrobacterium luteum strain A61 (Moll et al., 1967; Ahrens, 1968) was found to be due to polar fimbriae which are spread around the star-shaped aggregates. It is assumed that swarmers adhere to the fimbriae and, by contraction, are swiftly pulled towards the star. As seen in electron microscopic preparations, the fimbriae are up to 10,5 long and may well explain the star formation observed. Agrobacterium luteum strain B 14 also possesses long polar fimbriae. Both strains have peritrichous flagella, the structure of which being clearly distinct from the delicate and irregular fimbriae.

     

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.     

Genetics and physiology of colicin-tolerant mutants of Escherichia coli

A series of colicin-tolerant (tol) mutants of Escherichia coli K-12, which adsorbed colicins but were not killed by them, were isolated and studied genetically and physiologically. Three major classes of mutants were found: tol II, tolerant to colicins A, E1, E2, E3, and K; tol III, tolerant to A, E2, E3, and K; and tol VIII, tolerant to E1 only. The sites of tol II and tol III mutations mapped near the gal region (gene order: tol-gal-bio) and were cotransduced with gal by P1. In heterozygous diploids, tol(+) was dominant over tol; tol II and tol III gave full complementation. All the tol mutations that mapped near gal rendered the bacteria more fragile during growth and hypersensitive to deoxycholate and to ethylenediaminetetraacetic acid. The tol VIII mutation mapped between str and his. These mutants were extremely sensitive to deoxycholate and were also hypersensitive to methylene blue, acridines, and various other compounds. The sensitivity is attributed to increased uptake due to selective alteration of the permeability barrier. The colicin-tolerant mutations are interpreted as affecting some components of the cytoplasmic membrane which mediate between the adsorbed colicin molecules and the target sites of their biochemical effects in the bacterial cell.     

HuminsÄure und PermeabilitÄt

Ohne Zusammenfassung