Effect of some culture conditions on the production of indole-3-acetic acid and a gibberellin-like substance by Azotobacter vinelandii

Ethyl acetate extracts of concentrated culture supernatants were studied using thin-layer and paper chromatography in four solvent systems and Avena, Lactuca, and Hordeum bioassays. Indole-3-acetic acid (IAA) was synthesized between 3 and 6 days of incubation and remained maximal at 8 × 10−8 M from 7 to 40 days. A possible precursor, tentatively identified as 3-indoleacetamide (IAM), was present during the early period of IAA production. Relatively more IAA was produced in shaking than in stationary culture and in nitrogen-free than in ammonium-containing medium.A gibberellin-like substance which had some similarity to GA3 was detected but could not be reproducibly demonstrated. It occurred in 18- and 40-day-old cultures at a concentration of 3 × 10−3 μg GA3-equivalent/ml but was never seen in cultures of 12 days or less.

Similarities in the action patterns of exopolygalacturonate lyase and pectinesterase from Clostridium multifermentans

Exopolygalacturonate lyase and pectinesterase from Clostridium multifermentans were assayed simultaneously in the same reaction mixture which contained a highly esterified pectin, polymethyl polygalacturonic acid methyl glycoside. Lyase is specific for unesterified galacturonide residues and cannot degrade this substrate in the absence of the esterase. The rate for esterase was twice the rate for lyase throughout the entire course of the combined reaction. Thus, the molar ratio of the two enzyme activities was the same since the product of the lyase is an unsaturated digalacturonic acid containing two free carboxyl groups. Since clostridial exopolygalacturonate lyase is known to degrade polygalacturonate in a linear manner beginning from the reducing ends of polygalacturonate chains, it was apparent that clostridial pectinesterase must hydrolyze methyl groups in highly esterified pectins with an action pattern similar to that of the lyase. Otherwise it would be impossible for the two enzyme rates to have corresponded on the basis of a 2:1 ratio.

Metabolism of 75Se-selenite by human whole blood in vitro

When 75Se, as selenite, is added to human blood it is rapidly taken up by the cells (50–70% within 1–2 min) and is then released into the plasma so that most of the radioactivity is in the plasma by 15–20 min. Uptake is inhibited by 10−3 M cyanide. The release of radioactivity from the cells is inhibited by 10−3 M para-chloromercuribenzoate and by 10−3 M iodoacetamide, although these agents do not affect uptake. Azide and 2,4-dinitrophenol (at 10−3 M) do not affect either process. Large quantities of sulfite, sulfate, and selenate (1000 times as much S or Se as 75Se) do not affect uptake or release, but large amounts of selenite (1000 times) inhibit release. The release rate follows first-order kinetics and increases with temperature. 75Se released from cells is bound by a plasma protein but can be removed from the protein by treatment with cysteine. Studies suggest that the released selenium is in an altered form or state, although this product has not been characterized. A hypothetical pathway for the metabolism of selenium is presented to account for the observations.

Modification of the two-way gastrostomy tube for vagotomy and pyloroplasty

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Studies in Mineral Metabolism : III. Calcium and the Kidney: Experimental II

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Studies in Mineral Metabolism : II. Calcium and the Kidney: Experimental I

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Congenital Absence of the Fibula with Associated Deformity of the Femur

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Congenital Absence of Ulna with Associated Deformity of Radius

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