Inhibition of sugar uptake by ascorbic acid in Escherichia coli

The uptake of glucose by the glucose phosphotransferase system in Escherichia coli was inhibited greater than 90% by ascorbate. The uptake of the nonmetabolizable analog of glucose, methyl-alpha-glucoside, was also inhibited to the same extent, confirming that it was the transport process that was sensitive to ascorbate. Similarly, it was the transport function of mannose phosphotransferase for which mannose and nonmetabolizable 2-deoxyglucose were substrates that was partially inhibited by ascorbate. Other phosphotransferase systems, including those for the uptake of sorbitol, fructose and N-acetylglucosamine, but not mannitol, were also inhibited to varying degrees by ascorbate. The inhibitory effect on the phosphotransferase systems was reversible, required the active oxidation of ascorbate, was sensitive to the presence of free-radical scavengers, and was insensitive to uncouplers. Because ascorbate was not taken up by E. coli, it was concluded that the active inhibitory species was the ascorbate free radical and that it was interacting reversibly with a membrane component, possibly the different enzyme IIB components of the phosphotransferase systems. Ascorbate also inhibited other transport systems causing a slight reduction in the passive diffusion of glycerol, a 50% inhibition of the shock-sensitive uptake of maltose, and a complete inhibition of the proton-symport uptake of lactose. Radical scavengers had little or no effect on the inhibition of these systems.     

Surface-charge related actions of polylysine on thylakoid membranes

Polycation binding to the negatively charged surface of chloroplast thylakoid membranes is known to cause an inhibition of photosystem I activity. It also interferes with the cation-dependent rearrangement of chlorophyll proteins in the thylakoid membrane. It was shown that added anions prevented or reversed the inhibition of photosystem I by polylysine without decreasing its binding to the membranes. Anions also caused a change in the interaction of the chlorophyll proteins in polylysine-treated thylakoids as indicated by an increase in the relative fluorescence intensity from photosystem II. In both cases, the relative effectiveness of the anions tested depended on their valence; for example, the tetravalent species Fe(CN)₆^4t- was effective at a concentration at least 2 orders of magnitude lower than the divalent species SO₄^2?. These results suggest that anions act by screening the positive charge of the polylysine-coated membrane surface. Measurements of the response of the anionic fluorescent probe 1-anilinonapthalene-8-sulfonate to an addition of anions to polylysine-treated thylakoids supported this contention. It was concluded that the action of polylysine on photosystem I and on the chlorophyll proteins is mediated by changes of the electrical properties of the thylakoid membrane and may not involve a direct binding of the polycation to the affected membrane proteins.     

Embryo transfer in water buffalo (Bubalus bubalis)

A normal, live 35-kg water buffalo bull calf was born 300 days after it was nonsurgically collected as a 7-day blastocyst from a water buffalo donor and transferred nonsurgically to an unrelated water buffalo recipient. The development of estrus synchronization, superovulation and estrus detection methods in water buffalo are described.     

Determination of Root Exudates in a Steril Continuous Flow Culture. II. Short-Term and Long-Term Variations of Exudation Intensity

The exudate production of alfalfa under the conditions of the sterile flow culture was quantitatively measured. In the first 40 days 3.10⁻³ μmoles amino-N, 2.5 μequivalents of organic acids and approximately 10⁻⁴ μmoles of reducing sugars were liberated per plant and per day into the percolating nutrient solution. The amino acid concentration in the outflow varies according to a daily periodicity. The exudation of a colored substance also shows daily periodical variations. This pattern is different from the pattern of the amino acid exudation, however, and directly coupled to shoot illumination. Short-term 2,4-dinitrophenol additions to the nutrient lower the liberation of amino acids into the percolating solution.     

Deutungsversuch zur Nahrungsaufnahme eines schnabelverletzten Austernfischers(Haematopus ostralegus)

Zusammenfassung Eine MitteilungFlints über die Nahrungsaufnahme eines schnabelverletzten Austernfischers (Gefangenschaftsvogel) gab Anlaß zu einigen Gedanken darüber, welche angeborenen Verhaltensweisen dem Vogel bei der Erfindung seiner neuen Methode von Nutzen gewesen sein können. — So wird das Aufspießen von Brocken in der Futterschüssel mit dem Erbeuten von Muscheln und Krabben durch Aufspießen verglichen und das Herausschleudern des Bissens als Versuch gedeutet, einen Fremdkörper loszuwerden. Das beachtliche Hinstoßen des Brockens zu einer Rinne im Käfigboden wird als Surrogat für einen im Freileben vorkommenden zielgerichteten Nahrungstransport angesehen und im schließlichen Versenken des überstehenden Schnabelteils in der Rinne zum Fassen der Nahrung wird das normale Nahrungsstochern der Art erblickt. — Es wird eine Hypothese zur mutmaßlichen Entstehung der verblüffenden Umorientierung entwickelt.

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Summary A short note byFlint about the feeding habits of an Oystercatcher(Haematopus ostralegus) in captivity with only three quarters of his under bill gave reason for reflections which of the innate motor patterns of the species might have helped the bird in finding its new method. — At first a morsel of food in the tray is stabbed with the upper bill. This is compared with the stabbing of mussels and crabs. The morsel is then flung out of the tray in the way of getting rid of annoying matter. After this the bit is pushed along the floor towards a slit and right across it. This remarkable performance seems to be a substitute for an oriented food transport directed to a special place occurring under full scope conditions. The sinking of the beak into the cleft in order to seize the food at last may be identical with the usual probing for worms. — A conjecture is given as to how this bewildering reorganization of feeding habits might have come into being.

     

Zur Elektronenmikroskopie der Kerneinschlüsse im menschlichen Nebenhodenepithel

Zusammenfassung Es werden verschiedene Typen von Einschlußkörperchen im Karyoplasma der Epithelzellen des menschlichen Nebenhodenepithels beschrieben. Die verschieden strukturierten Kerninklusionen werden als eine Differenzierungsreihe aufgefaßt. Sie beginnt mit kleinen rundlichen Körperchen aus feinfädigem Material und führt über die Ausbildung von Anhäufungen dichter homogener Kugeln zu großen Vakuolen wechselnden Inhaltes.

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Summary Different types of inclusion bodies are described in the karyoplasm of the epithelial cells of the human epididymis. The structural differences between these inclusions are interpreted as being indicative of consecutive stages in the process of their formation. Thus small, spherical bodies consisting of a fine fibrous material are believed to be the initial stages in the formation of the inclusion bodies whereas the dense, homogenous globules are thought to represent a later stage. Large vacuoles containing different materials are regarded as the final stage in this process of differentiation.

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Herrn Professor Dr. W. Bargmann zum 60. Geburtstag gewidmet.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

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