Biosynthesis of ferredoxin in Chlamydomonas reinhardii

The selective action of the antibiotics chloramphenicol and cycloheximide on the synthesis of ferredoxin in liquid cultures of Chlamydomonas reinhardii was studied. Highly specific antibodies raised against Chlamydomonas ferredoxin were used to determine the in vivo synthesis of apoferredoxin and conversion into native protein. The results indicate that 80S ribosomes are involved in the synthesis. Chlamydomonas cells growing in the absence of iron did not synthesize immunologically detectable amounts of ferredoxin. We suggest that this is based upon feed-back inhibition of apoferredoxin synthesis at the translational level.Abbreviations CAP chloramphenicol - CHI cycloheximide - IgG Immunoglobulin G - PBS 140.4 mM NaCl. 9 mM Na₂HPO₄, 1.3 mM NaH₂PO₄ (pH 74) - SDS sodium dodecvl sulphate - Fd Ferredoxin - apoFd Apoferredoxin - CM-Fd Scarboxymethylated Fd - TCA-Fd Fd treated with trichloroacetic acid     

Properties of the selenium-containing moiety of nicotinic acid hydroxylase from Clostridium barkeri

The nicotinic acid hydroxylase from Clostridium barkeri is a selenoenzyme, as evidenced by the copurification of selenium with enzyme activity. This conclusion is supported by data showing a 23-fold increase in nicotinic acid hydroxylase activity when C. barkeri was cultured in media supplemented with selenium. A labile, selenium-containing compound was released from the native protein by treatment with either chaotropic agents and heat or by heating alone. A stable selenium compound was formed when the enzyme was alkylated prior to denaturation. This compound had the same chromatographic properties as dialykyl selenide in a number of systems. The formation of dialkyl selenide upon alkylation is not consistent with the selenium moiety being selenocysteine. Thus, nicotinic acid hydroxylase represents a new type of selenoenzyme.     

Auranofin affects early events in human polymorphonuclear neutrophil activation by receptor-mediated stimuli

Auranofin, a new oral antirheumatic gold compound, in concentrations achieved therapeutically, inhibits neutrophil phagocytosis, chemotaxis, chemiluminescence, reduction of cytochrome c, and release of lysosomal enzymes. To further characterize the mechanism by which auranofin affects neutrophils, we studied the effects of auranofin on unstimulated properties and functions of neutrophils as well as on rapidly stimulated functions. When examined by electron microscopy, 4 micrograms/ml of auranofin significantly decreased the number of visualized centriole-associated microtubules in resting cells. Furthermore, auranofin inhibited neutrophil spreading on glass and caused a decrease in negative surface charge (electrophoretic mobility). In addition, auranofin inhibited several fmet-leu-phe-stimulated responses such as shape change, increases in centriole-associated microtubules, decreases in surface charge, and elicited membrane potential changes (di-O-C5(3) dye response). Auranofin (1 micrograms/ml) inhibited fmet-leu-phe-stimulated superoxide and hydrogen peroxide production by 80% (p less than 0.05), and also increased the affinity of receptors for fmet-leu-phe (from Ka 0.035 to Ka 0.48, p less than 0.001). Auranofin also affected neutrophil responses to phorbol myristic acetate (PMA). The total amount of PMA-stimulated superoxide production was suppressed by as little as 0.4 micrograms/ml of auranofin, but the lag time for activation was shortened by low concentrations of auranofin (0.5 to 1 microgram/ml). Four micrograms per milliliter of auranofin suppressed the decrease in surface charge induced by PMA. However, auranofin did not influence superoxide production elicited by the ionophore A23187. The results indicate that auranofin affects the earliest detected responses in neutrophil activation by certain receptor-mediated stimuli.     

Inositol- and Galactose-Binding Lectins of Chicken Brain Fractions Enriched with Glial Cells

Galactose- and inositol-binding proteins with lectin activity (GL-GAL and GL-I, respectively) were isolated from membranes enriched with cells of chicken brain fractions. Both lectins are glycoproteins of molecular mass 13.5 and 11.5 kDa, respectively; they show a high affinity to EDTA (GL-I) and EGTA (GL-GAL, GL-I), which indicates an important role of Ca⁺² in molecular organization of these lectins. In brain glial cells of chick embryos, unlike adult chickens, a soluble form of lectins has been revealed; it is easily extracted with 2 mM EDTA and shows sensitivity to L-lactose, D-galactose, and N-acetyl-D-galactosamine. It is suggested that in the course of embryonal and postembryonal development of the chicken brain, a transformation and qualitative changes of the lectin spectrum occur due to a change of function of glial cells.     

Determination of plasma leukotrienes in antigen-induced bronchoconstrictive guinea pigs.

Convenient extraction and radioimmunoassay methods for measurement of leukotrienes C4 and D4 (LTC4 and LTD4) in biological fluids are described. LTC4 or LTD4 in plasma was extracted with acetonitrile, and the extract was washed with dichloromethane then adjusted to pH 3.5 or 6.0, respectively. Each leukotriene was partially purified by using a C18-bonded silica cartridge and quantitated by radioimmunoassay. Amounts of LTC4 and LTD4 in the range of 0.025-1.6 ng could be assayed in plasma. This procedure was employed to examine the increase in plasma LTC4 (0.249 +/- 0.036 ng/ml) and LTD4 (1.399 +/- 0.235 ng/ml) of guinea pigs during intravenous challenge-induced anaphylactic bronchoconstriction, and the suppression of the increase of bronchoconstriction and leukotrienes by the administration of 5-lipoxygenase inhibitors such as E6080 (6-hydroxy-2-(4-sulfamoylbenzyl-amino)- 4,5,7-trimethylbenzothiazole hydrochloride), AA861 (2,3,5-trimethyl-6-(12-hydroxy-5,10-dodecadiynyl)-1,4-benzoquinone ) and phenidone. On the other hand, LTC4 and LTD4 were not detected in plasma after an inhaled challenge, though significant bronchoconstriction was provoked. It was concluded that the present study validates a new technique for quantitating plasma leukotrienes on the basis of pH and a suitable method for evaluating the pharmacological efficacy of 5-lipoxygenase inhibitors.