Carbamyl phosphate synthesis in Bacillus subtilis

In vitro and "in situ" assays have been developed to test the carbamyl phosphate synthetase (CPSase) activity of a series of pyrimidine-requiring mutants of Bacillus subtilis. The enzyme has been shown to be highly unstable, and was successfully extracted only in the presence of 10% glycerol and 1 mM dithiothreitol (Cleland's reagent). It loses activity rapidly when sonicated or when treated with lysozyme. Genetic studies, using mutants, indicate that B. subtilis may possess two CPSases. This possibility and its physiological consequences were probed enzymatically. CPSase activity has been shown to undergo inhibition by both uridine triphosphate and dihydroorotate; activation has been demonstrated in response to phosphoribosyl pyrophosphate (PRPP) and (to a lesser extent) ornithine.     

The reactions of octaethylporphyrin and its iron (II) and iron (III) complexes with free radicals

The reactions of dilute solutions of octaethylporphyrin and its iron (II) and iron (III) complexes with methyl, 2-cyanopropyl, t-butoxy, and benzoyloxy radicals are described. The results are summarized: (i) The reactivity of the porphyrin and its high-spin iron (II) and iron (III) complexes toward alkyl and t-butoxy radicals stands in the order: Fe^II > Fe^III ? free porphyrin. For benzoyloxy radicals the order is Fe^II > Porp > Fe^III. (ii) The exclusive path of reaction of high-spin iron (II) porphyrin with radicals is the rapid reduction of the radical and generation of an iron (III) porphyrin. The dominant path of reaction of high-spin iron (III) porphyrin with alkyl and (presumably) t-butoxy radicals is a rapid axial inner sphere reduction of the porphyrin. An axial ligand of iron is transferred to the radical. (iv) The reaction of benzoyloxy radicals with high or low-spin iron (III) porphyrins occurs primarily at the meso position. With the low-spin dipyridyl complex in pyridine the attendant reduction to iron (II) can be observed spectrally. Methyl radicals also reduce this complex by adding to the meso position. (v) The reaction of a radical with either an iron (II) or an iron (III) porphyrin results in the generation of the other valence state of iron and consequently oxidation and reduction products emanating from both iron species are obtained. (vi) No evidence for an iron (IV) is intermediate is apparent. (vii) Iron (II) porphyrins in solvents that impart either spin state are easily oxidized by diacyl peroxides. The occurrence of both axial and peripheral redox reactions with the iron complexes supports an underlying premise of a recent theory of hemeprotein reactivity. The relevance of the work to bioelectron transfer and heme catabolism is noted.     

Interactions of Standard Antibody with Australia Antigens in Au Ag-Ab Radioimmunoassay

Human antisera against Australia (Au) antigen have been characterized by liquid-phase radioimmunoassay (RIA) for their precipitation of (125)I-labeled Au antigen. The end-point dilutions of sera (anti-Au) which precipitated 50% of (125)I-Au antigen by RIA correlated well with complement fixation titers but had a much wider range, indicating a greater precision and perhaps a better sensitivity of assay. Anti-Au serum diluted to precipitate 50% of (125)I-labeled Au antigen was used as standard antibody in RIA tests to detect either inhibition or enhancement of the reaction by preincubated mixtures of Au antigen and antibody specimens. Without free Au antigen or antibody in the resultant mixtures there was no inhibition or enhancement; the mixtures presumably contained immunoreactively equivalent proportions of Au antigen and antibody. RIA data for diagnostic specimens indicated an end-point sensitivity which was proportional to the dilution of the standard anti-Au sera used in the test. High concentrations of the standard antibody permitted detectable inhibition of (125)I-Au antigen precipitation at lower antigen specimen concentrations. Similarly, low concentrations of the standard antibody permitted detectable enhancement of (125)I-Au antigen precipitation at lower antibody specimen concentrations. Omitting the standard antibody altogether resulted in a more sensitive RIA for Au antibody in test sera.     

Stable Mycoplasma Antigen Preparations for Indirect Hemagglutination Tests

In immunological studies of mycoplasmas, the use of glutaraldehyde for the fixative makes it possible to use erythrocytes from commercially available defibrinated sheep blood. It eliminates the necessity of having to screen blood from individual sheep to obtain a suitable source of erythrocytes, as when employing tannic acid for fixation and sensitization. The chemical bonding of soluble mycoplasma proteins to glutaraladehyde-fixed sheep erythrocytes by bis-diazotized 3,3'dimethoxy derivative, benzidine, yields preparations that are satisfactory antigens for performing the indirect hemagglutination test by the microtiter technique. The antigenic preparations are satisfactory for use after storage at 4 or -10 C for many months. Incorporation of 5% glycerine in the final suspending milieu makes it possible to obtain uniform suspensions of the fixed and sensitized sheep erythrocytes after freezing and after repeated freezing and thawing. Proteins from Mycoplasma arthritidis and M. hominis have been coupled to glutaraldehyde-fixed erythrocytes by diazotization. The last mentioned preparation detected the presence of antibodies in titers greater than 1:10 in 37% of 237 pregnant women whose ages ranged between 20 and 30 years. There was no correlation between the presence of specific antibodies in the blood and the isolation of M. hominis from the cervical canal.     

Density-labelling evidence for the phytochrome-mediated activation of phenylalanine ammonia-lyase in mustard cotyledons

When dark-grown mustard seedlings are irradiated with far-red light the level of phenylalanine ammonia-lyase (EC 4.3.1.5) activity increases. After ²H₂ O treatment phynlalanine amonia-lyase from seedlings irradiated with far-red light is density-labelled to a lesser extent than enzyme from dark-grown tissue. Theoretical arguments are advanced and data presented which show that this result cannot be explained in terms of an increase in de novo synthesis of phenylalanine ammonia-lyase and that the increase most likely involves activation of existing enzyme.     

Rapid detection of hypoxanthine-guanine phosphoribosyltransferase on cellogel

Zusammenfassung 541 Serumproben von nichtverwandten Deutschen aus dem Kölner Raum wurden auf ihre Pt- und C3-Typen untersucht. Bei 537 Seren fand sich eine Überein-stimmung der Pt A-Typen mit den C3 F-Typen, der Pt AB-Typen mit den C3 FS-Typen und der Pt B-Typen mit C3 S-Typen. Die C3-Varianten F0.65S, F0.6S, F0.5S wurden als Pt AB bestimmt, die C3-Variante F0.55S wurde als Pt B bestimmt. Die Frage der Vergleichbarkeit der Systeme sowie die Untersuchungsmethoden werden diskutiert.

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Comparative studies on posttransferrin (Pt) and C3 in the polymorphism of the third component of human complement

Summary Sera of 541 unrelated Germans from the Cologne area were examined for their Pt and C3 types. There was correspondence between Pt A and C3 F, Pt AB and C3 FS, and Pt B and C3 S in 537 sera. C3 variants F0.65S, F0.6S, F0.5S were determined as Pt AB, C3 F0.55S was determined as Pt B. The question of possible identity and the methods used are discussed.

     

Contrasting effect of hemodialysis and peritoneal dialysis on the inhibition of in vitro calcification by uremic serum

Our findings support the earlier observation of Yendt, Connor and Howard that uremic serum inhibits the calcification of rachitic rat cartilage in vitro. We also confirmed their studies showing that this inhibition is not the consequence of increased levels of serum magnesium or blood urea. In addition, we have shown that aqueous solutions of creatinine and uric acid in concentrations up to 20 mg./100 ml. do not cause any inhibition.Hemodialysis of uremic patients does not change the inhibitory activity of their blood. In contrast, after 24 hours of peritoneal dialysis, the blood of most patients does not inhibit calcification.The inhibitory activity of uremic serum, observed in vitro, may be important in the pathogenesis of osteomalacia in patients with renal failure. Failure of hemodialysis to alter this activity may contribute to the progression of renal osteodystrophy in patients on maintenance hemodialysis.     

Cellular differentiation of heterospory inSelaginella

Summary Selaginella pilijera consistently displays two rows of microsporangia and two rows of megasporangia. It is therefore possible to detect in longitudinal sections of strobili at least three significant differences in development between both types of sporangia prior to meiosis: size of young sporangia, abortion or development of sporocytes based an RNA staining, and presence or absence of callose walls around sporocytes. The functional significance of these differences is discussed in relation to the heterosporous habit and higher plant sporogenesis.