Demonstration of the correlation of the degree of synthesis and 4-aminobutyric acid levels in the central nervous system; effect of repeated convulsive seizures

GABA turnover rates have been determined in 15 brain areas in five inbred strains of Mice or sublines (DBA/2J, C57/6J, Swiss Rb1, Swiss Rb2, Swiss Rb3). GABA turnover rates and levels are correlated (2 P less than 0.05). After repeated seizures (twice a day for 15 days), induced by an acoustic stimulus in Swiss Rb1 Mice selected for audiogenic seizures, this correlation is no longer observed.     

The effect of hexose monophosphate shunt inhibitors on adenohypophyseal and ceruloplasmin reactions to oestrogen.

Oestradiol benzoate, as an aqueous microcrystal suspension, was administered i.m. to rats in doses of 1 mg twice a week; it induced adenohypophyseal hyperplasia and an increase of the thyroxine-binding capacity of the adenohypophyseal proteins in vitro and raised the blood ceruloplasmin level. The simultaneous administration of a hexose monophosphate shunt inhibitor--6-aminonicotinamide (200 microgram/rat/day in food) or oxythiamine (8 mg/rat/day in food)--did not modify the reaction of the adenohypophysis; the hexose monophosphate shunt thus probably does not play a significant role in the adenohypophyseal reaction to oestrogens. By themselves, both inhibitors raised the blood ceruloplasmin level and their effect summated with that of oestradiol. The mechanism of action of the inhibitors is not known, but a nonspecific stress effect leading to an increase in the ceruloplasmin level as an "acute phase protein" is considered to be the most likely.     

Critical Reactions in Fluorobenzoic Acid Degradation by Pseudomonas sp. B13

3-Chlorobenzoate-grown cells of Pseudomonas sp. B13 readily cometabolized monofluorobenzoates. A catabolic pathway for the isomeric fluorobenzoates is proposed on the basis of key metabolites isolated. Only 4-fluorobenzoate was utilized and totally degraded after a short period of adaptation. The isoenzymes for total degradation of chlorocatechols, being found during growth with 3-chlorobenzoate or 4-chlorophenol, were not induced in the presence of fluorobenzoates. Correspondingly, only the ordinary enzymes of the benzoate pathway were detected in 4-fluorobenzoate-grown cells. Ring cleavage of 3-fluorocatechol was recognized as a critical step in 3-fluorobenzoate degradation. 2-Fluoro-cis,cis-muconic acid was identified as a dead-end metabolite from 2- and 3-fluorobenzoate catabolism. During 2-fluorobenzoate cometabolism, fluoride is eliminated by the initial dioxygenation.     

Synthese der lunularsäure

A ten-step synthesis of lunularic acid, starting from phenyl β-chloropropionate is described. Detailed spectroscopic data are given for lunularic     

Fluorescence induction in whole leaves: Differentiation between the two leaf sides and adaptation to different light regimes

In a variety of plants, the induction kinetics of chlorophyll fluorescence vary substantially depending on whether measured on the upper or lower side of the same leaf. The responses are comparable to those of plants grown under sun and shade conditions. Leaf morphology appears not to be the primary cause of the differences since inversion of the leaves can lead to reversed fluorescence responses. Fluorescence induction was analyzed in control and inverted leaves, and in one case, in chloroplasts from sun and shade leaves. It is concluded from the data that the major differences between the chloroplasts of the upper and lower leaf side reflect ionic and thylakoidmembrane conformational factors, rather than structural differences. Mg²⁺ flux probably plays a significant role in the adjustment of the thylakoid membrane to high or low light conditions.     

A quantitative fluorometric assay for detection and characterization of Fc receptors

A new quantitative fluorometric binding assay that uses fluoresceinated aggregated IgG is proposed for the study of Fc receptors. The method was compared with a radiolabeling binding assay on three well characterized murine cell lines (38C-13, EL4, and BW). The apparent association constant of the binding and the amount of aggregated IgG bound per cell at saturation were calculated. The fluorometric assay enables the detection of 5 X 10(-10) M bound aggregated IgG. Inhibition studies with monomeric IgG, reduced and alkylated aggregated IgG, and aggregated F(ab')2 fragments of IgG confirmed the specificity of the assay. Staphylococcal protein A inhibited the binding of the aggregated IgG to Fc receptors.     

Studies on 125I-labeled proteins in rat plasma using an air-driven ultracentrifuge: protein-protein interactions and nonideality

The molecular weights of a number of ¹²⁵I-labeled plasma proteins have been determined from an analysis of their sedimentation equilibrium behavior in an air-driven ultracentrifuge. The values obtained agree well with results obtained by other methods. Molecular weights obtained for ¹²⁵I-labeled bovine serum albumin and the rat serum proteins albumin, α₁-acid glycoprotein, and major acute-phase α₁-protein were unaffected by the addition of 7% rat plasma. Direct evidence for protein-protein interactions was obtained for mixtures of ¹²⁵I-labeled rat α₁-acid glycoprotein and the plant lectin concanavalin A and for mixtures of ¹²⁵I-labeled protein A from Staphylococcus aureus and 7% rat plasma. Interactions of a different type were observed when the sedimentation equilibrium profiles of ¹²⁵I-labeled proteins were determined in concentrated solutions of other proteins. Under these conditions the effects of molecular exclusion or nonideality became significant and low estimates were obtained for the molecular weights of the labeled proteins. Analysis of the data obtained for ¹²⁵I-labeled bovine serum albumin in concentrated solutions of bovine serum albumin (20–80 mg/ ml) yielded nonideality coefficients in good agreement with literature values. Analysis of the behavior of ¹²⁵I-labeled rat serum albumin, transferrin, and α₁-acid glycoprotein yielded nonideality coefficients and hence activities of these proteins in undiluted rat plasma.     

Activation of Fc gamma RII induces tyrosine phosphorylation of multiple proteins including Fc gamma RII.

Platelets provide a useful system for studying Fc gamma receptor-mediated signaling events because these cells express only a single class of Fc gamma receptors and because platelet aggregation and secretion can be activated through Fc gamma receptor stimulation. We report here that stimulation of platelets by cross-linking antibodies to Fc gamma RII or by treatment with an anti-CD9 monoclonal antibody, which acts through Fc gamma RII, causes an induction of tyrosine phosphorylation of multiple platelet proteins. Although the profile of tyrosine-phosphorylated proteins induced by stimulation of this Fc receptor was similar to that induced by thrombin, an additional 40-kDa phosphorylated protein was also detected. This protein co-migrated with Fc gamma RII and was immunoprecipitated with a monoclonal antibody to Fc gamma RII. In addition, after the cross-linking of Fc gamma RII in HEL cells or in COS-1 cells transfected with Fc gamma RII cDNA, the 40-kDa protein immunoprecipitated with anti-Fc gamma RII was also phosphorylated on tyrosine. These data strongly suggest that Fc gamma RII itself is a substrate for a tyrosine kinase(s) activated when Fc gamma RII is stimulated. Fc gamma RII was phosphorylated by the Src protein in vitro, suggesting that this kinase may be responsible for phosphorylation of Fc gamma RII in vivo. These studies establish that activation of platelets and human erythroleukemia cells through Fc gamma RII and CD9 involves an induction of tyrosine phosphorylation of multiple proteins including Fc gamma RII itself and suggest that these phosphorylation events may be involved in Fc gamma RII-mediated cell signaling.     

Reconstitution of a physical complex between the N-formyl chemotactic peptide receptor and G protein. Inhibition by pertussis toxin-catalyzed ADP ribosylation.

Photoaffinity-labeled N-formyl chemotactic peptide receptors from human neutrophils solubilized in octyl glucoside exhibit two forms upon sucrose density gradient sedimentation, with apparent sedimentation coefficients of approximately 4 and 7 S. The 7 S form can be converted to the 4 S form by guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) with an EC50 of approximately 20 nM, suggesting that the 7 S form may represent a physical complex of the receptor with endogenous G protein (Jesaitis, A. J., Tolley, J. O., Bokoch, G. M., and Allen, R. A. (1989) J. Cell Biol. 109, 2783-2790). To probe the nature of the 7 S form, we reconstituted the 7 S form from the 4 S form by adding purified G protein. The 4 S form, obtained by solubilizing GTP gamma S-treated neutrophil plasma membranes, was incubated with purified (greater than 95%) Gi protein from bovine brain (containing both Gi alpha 1 and Gi alpha 2) or with neutrophil G protein (Gn), and formation of the 7 S complex was analyzed on sucrose density gradients. The EC50 of 7 S complex formation induced by the two G proteins was 70 +/- 25 and 170 +/- 40 nM for Gn and Gi, respectively. No complexation was measurable when bovine transducin (Gt) was used up to 30 times the EC50 for Gn. The EC50 for Gi was the same for receptors, obtained from formyl peptide-stimulated or unstimulated cells. The addition of 10 microM GTP gamma S to the reconstituted 7 S complex caused a complete revision of the receptor to the 4 S form, and anti-Gi peptide antisera immunosedimented the 7 S form. ADP-ribosylation of Gi prevented formation of the 7 S form even at 20 times the concentration of unribosylated Gi normally used to attain 50% conversion to the 7 S form. These observations suggest that the 7 S species is a physical complex containing N-formyl chemotactic peptide receptor and G protein.