Effect of pH on preferential antibacterial-activity of ethylenediaminetetraacetic acid (EDTA)]

Ethylenediaminetetraacetic acid (EDTA), a chelating agent, was examined for the antibacterial activity against 15 species of bacteria by treating with a 10mM solution at pH adjusted to 5.0, 7.0 or 9.0. All bacterial species tested were classified into three groups; tentatively named the pH5 EDTA-sensitive group comprising Vibrio cholerae and Staphylococcus aureus, the pH9 EDTA-sensitive group comprising Escherichia coli and Pseudomonas aeruginosa and the EDTA-nonsensitive group comprising Proteus mirabilis. The EDTA-sensitivity grouping may be used as a tool for preferential decontamination of certain bacteria in live edible fishes, although further experiments are needed to characterize more strains and also species of bacteria.     

Antigenic analysis of Clostridium chauvoei flagella with protective and non-protective monoclonal antibodies.

Five monoclonal antibodies (mAbs) directed against the flagellin of Clostridium chauvoei were used to analyse the structural and antigenic characteristics on the bacterial flagellar surface. Immune electron microscopy showed that three protective mAbs recognized the surfaced-exposed epitopes on the flagellar filament of this bacteria. In contrast, two non-protective mAbs recognized internal epitopes of the flagellar filament. These findings have been confirmed by ELISA using mAbs absorbed with whole cells of C. chauvoei possessing flagella. Competitive binding assays showed that protective mAbs indicated reciprocal competition, while each of the non-protective mAbs had topographically distinct epitopes. Moreover, immunoblotting analysis with cyanogen-bromide-cleaved flagellin showed that protective mAbs may preferentially recognize conformational epitopes, whilst one of the non-protective mAbs may recognize a linear and conformation-independent epitope in the flagellin of C. chauvoei.     

Occurrence of tributyltin-tolerant bacteria in tributyltin- or cadmium-containing seawater.

Tributyltin chloride (TBTCl)-tolerant bacteria accounted for 90% of the flora in natural seawater to which TBTCl was added. These tolerant bacteria were insensitive to 250 nmol of TBTCl per disc, and all were Vibrio species. Total counts of viable bacteria did not decrease upon storage of the TBTCl-treated seawater, indicating that enrichment of tolerant strains took place. Addition of CdSO4 to seawater resulted in the occurrence of TBTCl-tolerant bacteria as well as Cd-tolerant bacteria, suggesting some correlation of Cd tolerance and TBTCl tolerance.     

ATP-dependent strontium uptake by basolateral membrane vesicles from rat renal cortex in the absence or presence of calcium

ATP-dependent Sr²⁺ transport was examined in vitro using basolateral membrane (BLM) vesicles isolated from rat renal cortex to clarify the discrimination mechanisms between strontium (Sr) and calcium (Ca) in renal tubules during reabsorption. ATP-dependent Sr²⁺ uptake and Ca²⁺ uptake were observed in renal BLM vesicles and were inhibited by vanadate. Hill plots indicate similar kinetic behavior for Ca²⁺ and Sr²⁺ uptake. The apparentK _m andV _max of ATP-dependent Sr²⁺ uptake were both higher than those for Ca²⁺ uptake. ATP-dependent Sr²⁺ uptake by BLM vesicles diminished in the presence of 0.1 μM Ca²⁺ and was more markedly inhibited by 1 μM Ca²⁺. Hill plots of Sr²⁺ uptake data with and without 0.1 μM Ca²⁺ showed that the cooperative behavior of Sr²⁺ uptake was not changed by Ca²⁺. In the presence of 0.1 μM Ca²⁺, the affinity of the transport system for Sr²⁺ and the velocity of Sr²⁺ uptake in the BLM were both decreased. However, the rate of Ca²⁺ uptake was not diminished by Sr²⁺ concentrations of <1.6 μM. These results suggest that Ca²⁺ is preferentially transported in the renal cortex BLM when Ca²⁺ and Sr²⁺ are present at the same time.     

Alterations in cardiac contractile proteins due to oxygen free radicals.

In view of the potential role of free radicals in the genesis of cardiac abnormalities under different pathophysiological conditions and the importance of contractile proteins in determining heart function, this study was undertaken to examine the effects of oxygen free radicals on the rat heart myofibrils. Xanthine plus xanthine oxidase (X + XO) which is known to generate superoxide anions (O2-) and hydrogen peroxide (H2O2), an activated species of oxygen, was found to decrease Ca(2+)-stimulated ATPase activity, increase Mg(2+)-ATPase activity and reduce sulfhydryl (SH) group contents in myofibrils; these effects were completely prevented by superoxide dismutase (SOD) plus catalase (CAT). Both H2O2 and hypochlorous acid (HOCl), an oxidant, produced actions on cardiac myofibrils similar to those observed by X + XO. The effects of H2O2 and HOCl were prevented by CAT and L-methionine, respectively. N-ethylmaleimide (NEM) and 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), inhibitors of SH groups, also produced effects similar to those seen with X + XO. Dithiothreitol (DTT), a well known sulfhydryl-reducing agent, prevented the actions of X + XO, H2O2, HOCl, NEM and DTNB. These results suggest that marked changes in myofibrillar ATPase activities by different species of oxygen free radicals may be mediated by the oxidation of SH groups.     

Analysis of non-heme iron in arachidonate 12-lipoxygenase of porcine leukocytes

Arachidonate 12-lipoxygenase of porcine leukocytes, which was purified to homogeneity by immunoaffinity chromatography, was analyzed for iron content by atomic absorption spectrophotometry. The enzyme contained 0.70 +/- 0.09 g atom of iron per mol of enzyme (mean +/- S.D., n = 4). Inorganic iron, which was added to the enzyme solution as an internal standard, was recovered in almost 100% yield. Among various iron chelators tested, only 2,2'-dipyridyl at 1 mM inactivated the enzyme by 87%, but the enzyme was not reactivated by the addition of excess ferrous or ferric iron.     

Primary structure of two linker chains of the extracellular hemoglobin from the polychaete Tylorrhynchus heterochaetus

Two types of linker subunits (linkers 1 and 2) of the extracellular hemoglobin of Tylorrhynchus heterochaetus have been isolated as disulfide-linked homodimers by C18 reverse-phase chromatography. These subunits constituted 6 and 13%, respectively, of total protein area on the chromatogram. The complete amino acid sequences of linkers 1 and 2 were determined by automated Edman sequencing of the peptides derived by digestions with lysyl endopeptidase, trypsin, chymotrypsin, Staphylococcus aureus V8 protease, pepsin, and endoproteinase Asp-N. The linker 1 consisted of 253 amino acid residues (the calculated molecular mass, 28,200 Da), while the linker 2 consisted of 236 residues (26,316 Da). The two chains showed 27% sequence identity. The amino acid sequences of Tylorrhynchus linkers 1 and 2 also showed 23-27% homology with the recently determined sequence of a linker chain of Lamellibrachia hemoglobin (Suzuki, T., Takagi, T., and Ohta, S. (1990) J. Biol. Chem. 265, 1551-1555). In the three linker chains, half-cystine residues were highly conserved; 8 out of 13 residues are identical, suggesting that such residues would contribute to the formation of intrachain disulfide bonds essential for the protein folding of the linker polypeptides. Based on the exact molecular masses of the linker and the heme-containing subunits, the molar ratios estimated for the subunits and the minimum molecular weights per 1 mol of heme, a model is proposed for the subunit structure of the Tylorrhynchus hemoglobin, consisting of 216 polypeptide chains, 192 heme-containing chains, and 24 linker chains.     

Molecular cloning and expression of human arachidonate 12-lipoxygenase

The cDNA for a 12-lipoxygenase was isolated from cDNA library of human erythroleukemia cells. The cDNA had an open reading frame encoding 663 amino acids with a calculated molecular weight of 75,513. The deduced amino acid sequence of human 12-lipoxygenase exhibited 41.5%, 65.3% and 65.4% identity with human 5-lipoxygenase, human 15-lipoxygenase and porcine 12-lipoxygenase, respectively. Blot hybridization analysis of RNA from human erythroleukemia cells demonstrated a single species (3.1 kb) of mRNA with the cDNA probe for 12-lipoxygenase of these cells, but not with the cDNA for porcine leukocyte enzyme. The cytosol of Escherichia coli transformed with a recombinant pUC19 plasmid oxygenated the position 12 of arachidonic acid.     

Induction of angiogenesis in chick yolk-sac membrane by polyamines and its inhibition by tissue inhibitors of metalloproteinases (TIMP and TIMP-2).

Treatment of yolk-sac membranes of 4-day-old chick embryos with spermine or spermidine resulted in angiogenesis in the membranes. The angiogenic activity of spermine was stronger than that of spermidine. Putrescine, polylysine and histamine did not induce angiogenesis in the membranes. Administration of putrescine, spermidine and spermine increased their respective levels in yolk-sac membranes, but no interconversion of these amines was observed. The increases in spermidine and spermine levels in yolk-sac membranes preceded induction of angiogenesis. The angiogenesis induced by spermine was inhibited by tissue inhibitors of metalloproteinases, that is, TIMP and TIMP-2. These findings suggest that spermine and spermidine are angiogenesis factors in yolk-sac membranes of chick embryos and that matrix metalloproteinases represented by collagenase are involved in their action.