Components of the lactoperoxidase system were measured during incubation in Isosensitest broth, with enzymatic (glucose oxidase, GO) or chemical (sodium carbonate peroxyhydrate, SCP) means to generate H2O2. When low levels of thiocyanate (SCN-) were used in the GO system, H2O2 was detected and lactoperoxidase (LP) was inactivated when SCN- was depleted. With 10-fold higher SCN-, LP remained active and H2O2 was not detectable. The oxidation product of the LP reaction, most likely hypothiocyanite, was present in low concentrations. When SCP was used for the immediate generation of H2O2 in a system employing low SCN-, half the LP activity was lost within minutes but thereafter it remained stable. Low concentrations of oxidation product were measured and H2O2 was not detected during the course of the experiment. At high SCN- levels, relatively high concentrations of oxidation product were produced immediately, with H2O2 undetectable. The results suggest that the final product of the LP reaction depends on the method of H2O2 generation and the relative proportions of the substrates. Antibacterial activity of the two LPS was tested against an enterotoxigenic strain of Escherichia coli. Both systems showed bactericidal activity within 4 h incubation at 37 degrees C.

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The decomposition of the oxalateprecursors Y2(C204)3.4BaC204 . (6 + n)CuCgO4 . xH20 for the synthesis of high Tc superconductors and the individual Y-, Ba-, Cu-oxalate components is investigated by DTA and by TGA coupled with FTIR. INTRODUCTIONA common route for the preparation of the YBa2Cu3076 superconductor is the solid state reaction of physically mixed oxides or carbonates. Several disadvantages of this method have been mentioned such as inhomogeneities at atomic level (1) resulting in long calcination and sintering times. Therefore several other techniques have been checked for the synthesis of high Tc superconductors. One of these methods is the thermal treatment of coprecipitated oxalates (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)). An important difficulty in this method is the control of the stoichiometric ratio of the metalions, because, due to side reactions, the metalion ratio in solution is not necessarily the one found in the precipitate. In a previous publication (12) we reported a method by which it is possible to obtain a simultaneous precipitation of the metal ions in any desired ratio; the method has been succesfully used for the preparation of YBa2Cu307 (12), YBa2Cu3,507.5 (13) and YBa2Cu408 (13).

The lactoperoxidase-thiocyanate-hydrogen peroxide (LP) system inhibited the growth of enterotoxigenic Eschrrzchia coli strains responsible for scouring in neonatal and post-weaning piglets. An enzymatic system for hydrogen peroxide generation (glucose oxidase, GO; 0.1 U/ml) and a chemical source (sodium carbonate peroxyhydrate, SCP; 90 mg/l) were used in the LP system to test 19 strains in a 6-h growth assay at 37°C. Only three strains were highly sensitive to the LP/GO system, while all exhibited significant growth inhibition with the LP/SCP system. Hydrogen peroxide alone had less effect than the complete system. The bactericidal activity of the LP/GO system towards a previously resistant strain was greatly increased by increasing the level of glucose oxidase in the system by three-or five-fold. US. Copyright ClearanceCenter Code Statement: 0931 -1793/92/39O7-0537$02.50/0 538 GRIEVE, DIONYSIUS and Vos examined the in d u o antibacterial activity of the LP system towards enterotoxigenic strains of porcine E. Cali isolated from cases of neonatal and post-weaning scours. The effects of two exogenous sources of hydrogen peroxide, a glucose/glucose oxidase H202generating system and a chemical system (sodium carbonate peroxyhydrate, SCP) on the antibacterial activity of the LP system were also studied. Material and Methods Bacteria and Culture ConditionsEnterotoxigenic Escherichia coli (ETEC) strains were isolated from cases of neonatal and postweaning scours in piglets. Eight isolates (PEC 1-8) were obtained from the Regional Veterinary Laboratory (Wagga Wagga, NSW, Australia) and were kindly provided by Dr. PAT BLACKALL (Animal Research Institute, Brisbane, Q., Australia). Eleven isolates were kindly provided by Dr. TONY FAHY (Regional Veterinary Laboratory, Bendigo, Vic., Australia).Each isolate, on receival at the laboratory, was allocated a laboratory reference number (PEC 1 -19), regenerated in Isosensitest broth (Oxoid Limited, Basingstoke, Hampshire, England), and inoculated and grown overnight on peptone-yeast extract (PYE) agar slants at 37°C. PYE agar