PROTOZOA AS TOXICOLOGIC TOOLS.
Explore the source record for details and available documents.
SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The possible production of carcinogenic polynuclear hydrocarbons in the charcoal broiling of food has been investigated. Fifteen steaks were cooked and the polynuclear compounds were extracted, separated by chromatography, and identified spectrometrically. Many polynuclear hydrocarbons were identified, but no nitrogen heterocyclic compounds were detected. The carcinogen benzo(a)pyrene was present in the average amount of 8 micrograms per kilogram of steak.
When incorporated into a nutrient overlay, the carcinogenic hydrocarbons benzo[a]pyrene and 7,12-dimethylbenz[a]anthracene inhibit plaque formation by herpes virus and vaccinia virus, DNA viruses, but not by Sindbis virus, an RNA virus. These carcinogens also decrease herpes and vaccinia virus yields in liquid medium, without affecting Sindbis virus yields. Four structurally related, but noncarcinogenic polycyclic hydrocarbons, namely benzo[e]pyrene, pyrene, benz[a]anthracene and anthracene, have no inhibitory effect on DNA virus replication. Taken together with the known inhibition of interferon production, these effects on virus growth resemble the action of actinomycin D and hence provide evidence for a selective interaction of these carcinogens with DNA.
The interactions in solution between purine or pyrimidine bases and polybenzenoid aromatic hydrocarbons probably consist in a vertical, stacking-type physical association. By molecular orbital calculations the role of the Van der Waals-London intermolecular forces in these interactions is determined. The electrostatic dipole-dipole forces are negligible, the polarization (or induction) dipole-induced dipole forces are contributory, but most important are the dispersion (or fluctuation) forces. This loose, physical type of interaction should not show any specificity with respect to the carcinogenic activity of the hydrocarbons.
Moulder, James W. (University of Chicago, Chicago, Ill.), Dorothy L. Novosel, and Ilse I. E. Tribby. Changes in mouse pneumonitis agent associated with development of resistance to chlortetracycline. J. Bacteriol. 89:17-22. 1965.-A chlortetracycline-resistant mutant of mouse pneumonitis agent, a member of the psittacosis group of microorganisms, differed in several ways from the susceptible stock from which it had been derived by serial chick-embryo passage in the presence of the antibiotic. It was almost completely resistant to chlortetracycline, had a longer growth cycle, produced many more very large particles, was not neutralized by parent antiserum and vice versa, was 10 times as resistant to d-cycloserine, and was highly lethal to mice when inoculated intracerebrally. These changes probably do not occur independently of one another but are the reflection of some genetically controlled change in the surface structure of the mouse pneumonitis particle which enables the resistant mutant to multiply in the presence of chlortetracycline.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Dietary unsaturated fat is required for maximum induction of the hepatic mixed function oxidases (MFO) responsible for activating carcinogens to forms that may bind covalently to DNA. The aim of this study was to assess the influence of dietary fat type and content on the activities of some enzymes involved in activation and detoxification of the carcinogen benzo[a]pyrene (B[a]P). Modification of these changes by pretreatment with phenobarbital (PB) was also evaluated. Male rats were fed diet devoid of fat or containing 20% corn oil (CO) or 20% menhaden fish oil (MO) for 4 days. PB induced soluble glutathione S-transferase, a detoxifying enzyme, only in rats fed dietary fats. Microsomes from rats fed both types of dietary fat had increased levels of cytochrome P-450 (P-450) and PB induced P-450 only in rats fed these fats. Although ethoxycoumarin O-dealkylase was significantly elevated in the MO group, the induction by PB was not dependent on dietary fat type or level. Dietary fat increased microsome-catalyzed in vitro binding of [3H]-B[a]P to calf thymus DNA, especially in response to PB. Menhaden oil depressed B[a]P hydroxylation and PB treatment depressed this activity to the greatest extent in rats fed this diet. When calculated as B[a]P metabolized per unit of P-450, PB seems to induce a P-450 in fat fed animals having lower affinity and capacity for B[a]P hydroxylation and activation than in rats fed the fat-free diet.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.