Enzymes metabolizing dimethylamine, trimethylamine and trimethylamine N-oxide in the yeast Sporopachydermia cereana grown on amines as sole nitrogen source

Abstract Sporopachydermia cereana , an ascosporogenous yeast, grew on dimethylamine, trimethylamine or trimethylamine N -oxide as sole nitrogen sources and produced mono-oxygenases for dimethylamine and trimethylamine that were significantly more stable than the corresponding enzymes found in Candida utilis . No trimethylamine mono-oxygenase activity was found in S. cereana grown on dimethylamine. In cells grown on trimethylamine N -oxide (but not on the other nitrogen sources), evidence for an enzyme metabolizing the N -oxide, possibly an aldolase, but more probably a reductase was obtained. All these activities showed a similar requirement for the presence of FAD or FMN in the extract buffer during isolation to retain activity. Amine mono-oxygenase activities showed a similar sensitivity to inhibitors, including proadifen hydrochloride and carbon monoxide as the corresponding enzymes in C. utilis . The trimethylamine N -oxide-dependent oxidation of NADH was more sensitive to inhibition by EDTA, N -ethylmaleimide and β-phenylethylamine than the mono-oxygenases, and less sensitive to KCN, and activity was significantly higher with NADPH than was observed with the 2 mono-oxygenases.     

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.     

Stochastic models for cell kinetics

A survey is given of branching process type methods in cell kinetics. Some results are given that allow circadian rhythm and do not require complete independence between cells. Some more classical results on balanced exponential growth are given and some comments are made on flow microfluorometry.     

The role of microtubules in vessel member differentiation inColeus

Summary The role of microtubules in tracheary element formation in cultured stem segments ofColeus has been investigated through the use of the antimicrotubule drug, colchicine. Colchicine treatment of the cultured stem segments produced a dual effect on xylem differentiation. If applied at the time of stem segment isolation or shortly thereafter, wound vessel member formation is almost completely blocked. However, if colchicine is applied after the third day of culture, it does not inhibit differentiation, but instead large numbers of xylem elements are formed which have highly deformed secondary walls. Both effects are related to colchicine's specific affinity for microtubules. In the first case it is shown that colchicine blocks mitosis, presumably by destroying the spindle apparatus, and thus inhibits divisions which are prerequisite for the initiation of xylem differentiation. While, if colchicine is applied after the necessary preparative divisions have taken place, it destroys specifically the cortical microtubules associated with the developing bands of secondary wall, thus causing aberrant wall deposition.Light and electron microscopic analysis of drug-treated cells reveals that the secondary wall becomes smeared over the surface of the primary wall and does not retain the discrete banded pattern characteristic of secondary thickenings in untreated cells. Examination of colchicine-treated secondary walls in KMnO₄ fixed material shows that in the absence of microtubules the cellulose microfibrils lose their normal parallel orientation and are deposited in swirls and curved configurations, and often lie at sharp angles to the axis of the secondary wall band. Microtubules, thus, appear to play a major role in defining the pattern of secondary wall deposition and in directing the orientation of the cellulose microfibrils of the wall. Factors in addition to microtubules also act in controlling the secondary wall pattern, since we observe that even in the absence of microtubules secondary thickenings of two adjacent xylem elements are deposited directly opposite one another across the common primary wall.     

New observations on the bioluminescence of echinoderms

Bioluminescence has been observed in two species of Ophiuroidea, six species of Asteroidea, nine species of Holothuroidea and two species of Crinoidea. The luminescent responses are described and the intensities and time courses of the responses of some species are given.
Histological investigations have indicated possible luminous cells in the Holothuroidea, but the results in other classes remain equivocal. Preliminary analyses of the chemistry of bioluminescence indicate that a similar system may be responsible for bioluminescence in all four classes, although the visible manifestations of the system vary considerably.     

Inhibition of transport systems in cultured rat hepatoma cells by colcemid and ethanol

The transport of uridine, hypoxanthine, and choline in cultures of Novikoff rat hepatoma cells is competitively inhibited by colcemid with apparent K_i values of 135, 60, and 250 μM respectively, whereas the transport of 2-deoxy-D-glucose is not affected. Ethanol at high concentrations inhibits the transport of all four substrates in an apparent competitive manner.     

Intermittent Chemotherapy for Tuberculosis in an Urban Community

A regimen designed for effective foolproof antituberculosis treatment, acceptable on a routine basis, was applied to all patients newly diagnosed at the Chest Clinic, Hammersmith Hospital, in 1963, 1964, and 1965. During the first three months of treatment patients received daily (six days a week) streptomycin 0.75 g. plus isoniazid 300 mg. plus sodium para-aminosalicylate (P.A.S.) 12 g. The P.A.S. was usually stopped when bacterial sensitivity reports made this possible. For a further 15 months streptomycin 1 g. plus isoniazid 600 mg. was given on three alternate days each week to complete a total of 18 months'' treatment.Of the total of 140 patients (66% sputum-positive) 112 (80%) completed the planned 18 months with intermittent streptomycin plus isoniazid and a further eight completed treatment on alternative regimens (a total of 85%). The equivalent figures for one year are 88% and 94%. Excellent clinical and radiological results, together with sputum conversion, were achieved in 138 of the 140 patients (99%). Only two patients were lost from surveillance, because of failure to co-operate, before quiescence was obtained.It is concluded that the total efficiency of supervised intermittent treatment is greater than that of unsupervised daily regimens. Since 100% arrest of tuberculosis is possible with co-operative patients, less should not be accepted in developed countries.