Dissociation of urease in acetate buffer of pH 3.5 with retention of the enzymatic activity

Riassunto Le molecole dell'urease (peso molecolare 480,000, coefficiente di sedimentazione 18,6 S) si dividono a metà quando trattate con tampone acetato, 0,1M, pH 3,5. Inizialmente, l'attività enzimatica è 40% di quella al pH 7 (tampone fosfato, 0,34M) e la dissociazione è riversibile. Prolungata esposizione al pH 3,5 causa una lenta denaturazione, con perdita dell'attività e dell'abilità di ricostituirsi.

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This work was supported by grant No. GM 13,900 and by Career Development Award No. 5K3 GM 13,489 (to G. G.) from the National Institutes of Health.     

A series solution of theLane-Emden equation of index 5

Zusammenfassung Weitere Untersuchungen über Lösungen derLane-Emden-Gleichung in der Nähe des kritischen Punktes (vgl. Experientia23, 697, 1967).     

Inhibition sélective des «vraies» et «pseudo»-cholinestérases du rectus de grenouille

Summary The hydrolysis of acetylcholine chloride (0.01M) by frog's rectus extracts, is inhibited by low concentrations of 3318 CT (CI-50 3.2×10^–7) and high concentrations of D.F.P. (CI-50 1.3×10^–5). Inversely, the hydrolysis of butyrylcholine perchlorate is inhibited by low concentrations of D.F.P. (CI-50 3×10^–9) and high concentrations of 3318 CT (CI-50 3×10^–4). Both are inhibited by similar concentrations of neostigmine (CI-50 1.1×10^–7 and 1.5×10^–7). Frog's rectus thus contains true and pseudo-cholinesterases. The inhibitions produced by D.F.P. added to the muscle itself (and not the extract) correlates well with the potentiation of the corresponding ester. Sensitization to AcCh and to BuCh appears to be specifically related to the inhibition of Ac ChE for the former ester, of XChE for the second one.     

Activité tuberculostatique de thiouréesortho- etméta-substituées

Summary A large number of substituted thioureas and related compounds, the molecular structure of which diverges more or less from that of the classical 4-4-disubstituted thiocarbanilides, have been tested forin-vitro tuberculostatic activity; many of them have proved effective at a concentration of 10^–5.     

Elektrophysiologische Untersuchungen an der Seitenlinie vonXenopus laevis

Summary Electrophysiological recording of the spontaneous activity from a single group of lateral sense organs on the abdomen ofXenopus laevis results in a more or less regular series of large spikes, either all of the same height or of two different sizes (each group is innervated by two large lateralis fibres). Mechanical stimulation of such a group may cause a rise or a fall of spontaneous impulse frequency. There is evidence for a two-directional sensitivity of the same unit (nerve fibre) from a single group, out of the middle as well as out of the dorsal lateral line.     

Effect of mutagens on the content of nucleic acids in wheat

Zusammenfassung Eine vergleichende Untersuchung über die Wirkung von Röntgenstrahlen auf ruhende Weizensamen und Weizenkeimlinge und von Senföl auf den Gehalt von DNA. und RNA. in Spross und Wurzel von Keimlingen verschiedenen Alters wurde ausgeführt.