Inhibition of chlortetracycline activity by magnesium ions.

Up to 50% of the antimicrobial activity of chlortetracycline (CTC) can be inhibited by the presence of MgSO4 in microbiological turbidimetric assays. From 50 to 200 mM MgSO4 inhibited CTC activity, and the relationship between CTC inhibition and MgSO4 concentration is linear. The possible mechanism of this inhibition and its potential implication are discussed.

[Antioxidant stabilization of the antifoaming agents used in the fermentation process]. / Stabilizatsiia penogasitelei, ispol'zuemykh v protsesse fermentatsii, antiokisliteliami.

Oils used as antifoaming agents in fermentation are subjected to oxidation to form various products, such as aldehydes, carboxylic acids, peroxides, etc. The negative effect of such products on biosynthesis of chlortetracycline by strains VUA 84 and Iz 22/VUPL of Str. aureofaciens was recorded. The level of the oil oxidation was characterized by the contents of peroxides and epihydrinaldehydes. The Kreiss qualitative test was modified for quantitative estimation of epihydrinalydehydes. The oil antifoaming agents characterized by the routine parameters used in determination of oil quality, such as acid number, saponification number and iodine number. In the control experiments lard and soybeen oil were oxidized by air at a temperature of 100 degrees C without an antioxidant (2,6-ditetrabutyl-4-methylphenol). The oil antifoaming agents such as soybeen oil and lard were tested in biosynthesis of chlortetracycline carried out in flasks and pilot plant 750 1 apparatus. Antioxidant 4K, an alkylphenol antioxidant, in a 2% concentration proved to be effective for prevention of oxidation and nontoxic for the culture.

[Tetracycline inactivation by magnesium sulfate in testing for microbial contamination by the membrane filtration method]. / Inaktivatsiia tetratsiklinov sernokislym magniem pri ispytanii mikrobnoi obsemenennosti metodom membrannoi fil'tratsii

It was shown that the residual amounts of tetracyclines adsorbed on membrane filters may be inactivated by addition of 2M magnesium sulphate solution to the agar for placing the filters after filtration. The antibiotic inactivation increases the possibilities of the test for antibiotic sensitivity of the microflora present in the drugs and may be used in determination of microbial dissmination of non-injection tetracyclines.

Inhibition of the oxidation of glutamate and isocitrate in liver mitochondria at a specific NADP+-reducing site.

The cation-complexing carboxylic-acid antibiotic X-537A, at concentrations far below that required for ionophorous activity, selectively inhibits the oxidation of glutamate and isocitrate by liver mitochondria in steady-state 3. The site of inhibition has been localized specifically at the reduction of NADP(+). Glutamate and isocitrate dehydrogenases, the oxidation of NAD(+)-dependent substrates, pyridine nucleotide transhydrogenations, and the respiratory chain between NADH (or NADPH) and O(2) are unaffected by the antibiotic X-537A. Kinetic evidence, i.e., competition between chlorotetracycline (a fluorescence probe for membrane-bound bivalent cation) and X-537A, indicates that the NADP(+)-reducing, antibiotic-sensitive site is most probably associated with the inner mitochondrial membrane.