Factors reducing the superoxide dismutase activity of the liver of rats with Pliss lymphosarcoma

The procedures for isolation and purification of Cu/Zn superoxide dismutase (SOD) from small amounts of rat liver at different stages of Pliss lymphosarcoma growth were developed. Two stages of tumour growth were distinguished. At the first stage (4-5th day after reinoculation) the intensity of optical (680 nm) and EPR spectra of SOD was decreased, on the average, to 30%, while at the second stage--by 40% at 680 nm and by 32%, at 260 nm. The intensity of the EPR spectra was also diminished by 40% as compared to the control. It was assumed that at initial stages of tumour growth the decrease of the SOD activity is mainly due to the reduction of enzyme Cu, while at the second stage--to the decrease of the protein content. In all probability, the observed changes are induced by the activation of lipid peroxidation involving active O2 species. The second stage is associated with the superoxide-induced impairment of the function of nucleic acids involved in protein biosynthesis.     

N-acetyltransferase activity during growth of the transplantable Pliss lymphosarcoma and during pregnancy in rats

Study of the distribution of female noninbred rats according to N-acetyltransferase activity has permitted the conclusion to be derived that the animals may have a "slow", "intermediate" and "fast" phenotype of acetylation. It was discovered that the rate of N-acetyltransferase activity increased 1.5-2-fold on days 12 and 15 after transplantation of Pliss's lymphosarcoma. The time course of changes in N-acetyltransferase activity was characterized by individual features. The pattern of changes in N-acetyltransferase activity in pregnancy was dependent on the initial acetylation phenotype: in animals with a "slow" and "intermediate" phenotype of acetylation, the activity ascended by the 21st day of pregnancy, whereas in animals with a "fast" phenotype of acetylation, it declined.     

Metabolic activity of microorganisms in evaporites

Crystalline salt is generally considered so hostile to most forms of life that it has been used for centuries as a preservative. Here, we present evidence that prokaryotes inhabiting a natural evaporite crust of halite and gypsum are metabolically active while inside the evaporite for at least 10 months. In situ measurements demonstrated that some of these "endoevaporitic" microorganisms (probably the cyanobacterium Synechococcus Nageli) fixed carbon and nitrogen. Denitrification was not observed. Our results quantified the slow microbial activity that can occur in salt crystals. Implications of this study include the possibility that microorganisms found in ancient evaporite deposits may have been part of an evaporite community.     

Metabolic activity of permafrost bacteria below the freezing point

Metabolic activity was measured in the laboratory at temperatures between 5 and -20 degrees C on the basis of incorporation of (14)C-labeled acetate into lipids by samples of a natural population of bacteria from Siberian permafrost (permanently frozen soil). Incorporation followed a sigmoidal pattern similar to growth curves. At all temperatures, the log phase was followed, within 200 to 350 days, by a stationary phase, which was monitored until the 550th day of activity. The minimum doubling times ranged from 1 day (5 degrees C) to 20 days (-10 degrees C) to ca. 160 days (-20 degrees C). The curves reached the stationary phase at different levels, depending on the incubation temperature. We suggest that the stationary phase, which is generally considered to be reached when the availability of nutrients becomes limiting, was brought on under our conditions by the formation of diffusion barriers in the thin layers of unfrozen water known to be present in permafrost soils, the thickness of which depends on temperature.     

Metabolic activity of phagocytes in experimental sporotrichosis

Phagocytosis plays an important role as a protective mechanism against infections, since polymorphonuclear leukocytes (PMN) and macrophages are the first cellular lines opposed to agressive microorganisms. In patients with sporotrichosis a diminished capability of killing engulfed yeast by their PMN has been described, but the origin of this deficiency remains unknown.In this work, partial aspects of the oxidative metabolism of PMN leukocytes and peritoneal macrophages of mongolian gerbils experimentally infected with sporotrichosis were studied. For this purpose the nitroblue tetrazolium (NBT) test as described by Baehner and Nathan (1) and myeloperoxidase activity measured according to Kaplow's method were utilized.The PMN and macrophages of mongolian gerbils infected with sporotrichosis showed increased reduction of NBT when compared with the phagocytic cells of normal ones, as is usually observed in most infections. Myeloperoxidase activity was diminished in both PMN and macrophages, but this diminution was statistically significant only in PMN leukocytes. These results show that part of the oxidative mechanisms of phagocytic cells can be impaired in experimental sporotrichosis, and could be correlated with the diminished fungicidal activity of PMN leukocytes obtained from patients infected with sporotrichosis.     

Metabolic activation of pesticides with proestrogenic activity

The role of metabolism in the estrogenic activity of chlorinated hydrocarbon pesticides was examined. Whether the estrogenic activity in technical grade preparations of the pesticide methoxychlor is due to methoxychlor or to contaminants was also investigated. Identified compounds in technical methoxychlor were examined by an in vitro method to determine whether they are estrogens or proestrogens. This method showed that purified methoxychlor and MDDE, an olefinic derivative of methoxychlor, are proestrogens and that monohydroxymethoxychlor and monohydroxy-MDDE are estrogens. Thus, the estrogenic activity in technical methoxychlor is due to both methoxychlor and contaminants. MDDE is an in vivo metabolite of methoxychlor, and the mono- and bishydroxy derivatives of methoxychlor and MDDE are metabolites of methoxychlor and MDDE, respectively. These metabolites exhibited in vitro estrogenic activity in the following order of potency: bis-OH-MDDE greater than bis-OH-methoxychlor greater than mono-OH-MDDE greater than mono-OH-methoxychlor. A similar order of potency was observed in vivo, demonstrating that metabolites of methoxychlor are potent estrogens. In addition to phenolic products, hepatic monooxygenases metabolize methoxychlor and MDDE to reactive intermediates that bind covalently to microsomal proteins. Further studies are needed to determine the factors controlling the two pathways of methoxychlor metabolism and determine whether covalent binding is associated with cellular and organ toxicity.     

Metabolic and pharmacokinetic activity of the isolated sheep bronchial circulation

We sought to determine bronchial vascular metabolic and pharmacokinetic activity toward benzoyl-Phe-Ala-Pro (BPAP), ADP, adenosine, and prostaglandin E2 (PGE2) by developing an isolated sheep bronchial circulation preparation. We measured mean transit time (t), uptake, and metabolism by injecting 3H-labeled substrates with [14C]sucrose into the bronchial artery of sheep lungs stripped clean of parenchymal tissue. After [3H]BPAP the t for 3H was the same as for 14C. Thirty-six percent of the injected BPAP was converted to metabolite ([3H]benzoyl-Phe) in a single pass. An inhibitor of angiotensin-converting enzyme, SQ 20,881, depressed BPAP metabolism by 50%, while perfusion of the bronchial circulation with glutaraldehyde reduced metabolism to a basal level. After [3H]ADP the t for 3H was again the same as for 14C. 3H recovery after 40 pmol [3H]ADP was less (58%) than after 400 nmol [3H]ADP (79%). Twenty-two percent of the injected radioactivity emerged in the effluent as metabolites of ADP for either dose. Adenosine and PGE2 uptake was negligible, and most of the recovered radioactivity in each case was unchanged substrate. This study suggests that the bronchial circulation is pharmacokinetically and metabolically active with respect to vasoactive mediators like angiotensin I, bradykinin, and adenine nucleotides, and that the enzymes responsible for this metabolic activity line the vascular lumen.