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Biomedical subjects

E Zeiger

Publications and source records attributed to E Zeiger.

At least 163 records · Page 9Linked to original sources
PubMed1981

Statistical analysis of the Ames Salmonella/microsome test.

A family of statistical models for analysis of Ames Salmonella/microsome test data is constructed that considers mutation and toxicity as competing risks and allows hyper-Poisson variability. These models have a parameter than can be employed as a mutagenic index because it approximates the slope at zero dose of a dose-response curve adjusted for toxicity. A second parameter quantifies plate-to-plate variability and lends itself to the study of factors affecting internal test reproducibility. The detection of aberrant plate counts is also addressed. This methodology is illustrated with data from a Salmonella test.

Animals↗
PubMed1981

Fluorescence Properties of Guard Cell Chloroplasts: EVIDENCE FOR LINEAR ELECTRON TRANSPORT AND LIGHT-HARVESTING PIGMENTS OF PHOTOSYSTEMS I AND II.

The presence of chloroplasts in guard cells from leaf epidermis, coleoptile, flowers, and albino portions of variegated leaves was established by incident fluorescence microscopy, thus confirming the notion that guard cell chloroplasts are remarkably conserved. Room temperature emission spectra from a few chloroplasts in a single guard cell of Vicia faba showed one major peak at around 683 nanometers. Low-temperature (77 K) emission spectra from peels of albino portions of Chlorophytum comosum leaves and from mesophyll chloroplasts of green parts of the same leaves showed major peaks at around 687 and 733 nanometers, peaks usually attributed to photosystem II and photosystem I pigment systems, respectively. Spectra of peels of V. faba leaves showed similar peaks. However, fluorescence microscopy revealed that the Vicia peels, as well as those from Allium cepa and Tulipa sp., were contaminated with non-guard cell chloroplasts which were practically undetectable under bright field illumination. These observations pose restrictions on the use of epidermal peels as a source of isolated guard cell chloroplasts. Studies on the 3-(3,4-dichlorophenyl)-1,1-dimethylurea-sensitive variable fluorescence kinetics of uncontaminated epidermal peels of C. comosum indicated that guard cell chloroplasts operate a normal, photosystem II-dependent, linear electron transport. The above properties in combination with their reported inability to fix CO(2) photosynthetically may render the guard cell chloroplasts optimally suited to supply the reducing and high-energy phosphate equivalents needed to sustain active ion transport during stomatal opening in daylight.

Journal Article↗
PubMed1980

Differential effects of cytochrome P450-inducers on promutagen activation capabilities and enzymatic activities of S-9 from rat liver.

Studies have been conducted to determine aryl hydrocarbon hydroxylase, benzphetamine-N-demethylase, epoxide hydrase and glutathione S-transferase activities and cytochrome P-450 content in the liver 9000xg supernatant fractions from rats treated with either phenobarbital, beta-naphthoflavone, ARoclor 1254 or a combination of phenobarbital and beta-naphthoflavone. The metabolic activation of 2-anthramine, 2-acetylaminofluorene, 3-methylcholanthrene, and benzo(a)pyrene to metabolites that are mutagenic in Salmonella typhimurium TA1535 or TA98 by S-9 from rats treated with these inducers was also determined. The induction of drug metabolizing enzymes in the S-9 from Aroclor or phenobarbital plus beta-naphthoflavone treated animals was very similar. The overall results seem to indicate that a combination treatment of phenobarbital and beta-naphthoflavone can be used as a substitute for Aroclor 1254 as inducer for enzyme activity and for the in vitro activation of promutagens to mutagenic metabolites in Salmonella mutagenesis assay systems.

Animals↗
PubMed1979

Genetic effects of PR toxin in eukaryotic microorganisms.

The genetic activity of PR toxin, a mycotoxin from Penicillium roqueforti, was studied in Saccharomyces cerevisiae and Neurospora crassa. The results show that PR toxin, without enzymic activation, causes gene conversion in S. cerevisiae strains D4 and D7, reverse mutation in S. cerevisiae strain D7 and N. crassa strain N24, and mitotic crossing-over in S. cerevisiae strain D7, In the log phase cells of S. cerevisiae the effects are more pronounced at alkaline than at acid pH. The active site responsible for the genetic activity and toxicity is known. The carbonyl groups appear to play an important role in the biologic activity of this molecule.

Chromosomes↗
PubMed1979

Effects of the hepatic S9 fraction from aroclor-1254-treated rats on the mutagenicity of benzo[alpha]pyrene and 2-aminoanthracene in the Salmonella/microsome assay.

The mutagenicity of benzo[alpha]pyrene and 2-aminoanthracene for Salmonella typhimurium TA98 in the plate-incorporation test was studied using liver S9 from untreated and aroclor-1254-treated rats. The induction of liver S9 protein, arylhydrocarbon hydroxylase (AHH), and cytochrome P448/450 was followed with time. There was no change in protein concentrations with induction; AHH and cytochrome levels were increased at 1, 3, 5 and 7 days post Aroclor treatment. Benzo[alpha]pyrene mutagenicity was enhanced with Aroclor treatment while 2-aminoanthracene mutagenicity was depressed. The benzo[alpha]pyrene mutagenicity showed a positive correlation with the levels of AHH and cytochrome on the plate; 2-aminoanthracene showed a negative correlation with activity in induced samples.

Animals↗
PubMed1979

The intrasanguineous host-mediated assay procedure distribution and retention of yeast in the mouse.

A study of the factors that could affect a method to detect mutations in cells recovered from different organs after intravenous injection in mice, was performed by using the D4 strain of Saccharomyces cerevisiae. The recovery of the yeast cells 5 min to 3 days after injection in the host animal was investigated. The circulation, distribution and localization of the cells were determined, and histopathologic analysis was performed in order to detect possible interactions between the mice and the microorganisms. We found that the yeast cells were trapped primarily in the capillaries of the organs; 3 days after injection no cells were found outside of the tissue-blood vessels. The spontaneous gene-conversion frequency of the yeast cells recovered at different times after injection was increased, but this increase was not time-dependent.

Animals↗
PubMed1979

Genetic toxicity of procarbazine in bacteria and yeast.

Procarbazine [N-isopropyl-alpha-(2-methylhydrazino)-p-toluamide hydrochloride] is used to treat Hodgkin's disease. This compound was tested in vitro without and with S10 fraction from mice liver (microsomal assay) using Saccharomyces cerevisiae strain D7, Salmonella typhimurium (strains TA98, TA100, TA1535) and in vivo in Swiss albino mice (host-mediated assay) using D7. Procarbazine, without S10 fraction, is highly toxic and induced mitotic crossover, gene conversion, and reverse mutation in D7. It had a toxic effect on all the Salmonella strains; but did not induce reverse mutations at the histidine loci. Procarbazine, with S10 fraction, was less toxic and did not induce genetic effects in yeast or Salmonella. In the host-mediated assay, no genetic effects were seen.

Drug Evaluation, Preclinical↗
PubMed1979

Blue light-induced, intrinsic vacuolar fluorescence in onion guard cells.

Guard cells of onion irradiated with broad-band blue light display a green intrinsic fluorescence. The fluorescence has been found in eleven species of Allium, but it has not been observed in any other monocot or dicot examined. The fluorescence occurs only in guard cells and is absent in neighbouring epidermal cells. During development it is first apparent in guard mother cells soon after the asymmetric division. Microscopic observation reveals that the fluorescence is associated with the vacuole and examination of vacuoles isolated from guard cell protoplasts suggests that it may be localized on the tonoplast. Microspectrophotometric analysis of single cells reveals an emission peak at around 520 nm. Our results are consistent with the view that this blue light receptor is a flavin or flavoprotein and that it might be related to the blue light-enhanced stomatal opening observed in onion.

Fluorescence↗
PubMed1979

Mutagenic activity of chemical carcinogens and related compounds in the intraperitoneal host-mediated assay.

The mutagenic activities of 79 carcinogens, noncarcinogens, and structurally related compounds toward Salmonella typhimurium strains TA1530, TA1535, and TA1538 and toward Saccharomyces cerevisiae D3 were investigated in the intraperitoneal host-mediated assay. Fewer than half of the carcinogens were mutagenic toward the Salmonella strains. The insensitivity of the system was most marked with the aromatic amine and polycyclic hydrocarbon procarcinogens. Under the test conditions, fewer than 10% of the carcinogens showed clear mutagenic activity toward S. cerevisiae D3. However, none of the noncarcinogens was significantly mutagenic toward either S. typhimurium or S. cerevisiae D3. Overall, the intraperitoneal host-mediated assay does not seem suitable for routine preliminary screening of large numbers of potential carcinogens. The median lethal doses to mice of 46 compounds were determined.

Alkylating Agents↗
PubMed1978

The mutagenicity of heterocyclic N-nitrosamines for Salmonella typhimurium.

14 carcinogenic and noncarcinogenic heterocyclic N-nitrosamines were evaluated for mutagenicity to Salmonella typhimurium TA-1535, which responds to mutagens inducing base-pair substitutions. Both suspension and plate tests were used, with mouse and rat liver in vitro metabolic activation systems. All carcinogenic nitrosamines showed a positive response in at least one test system, as did the noncarcinogens. In general, the mutagenic responses obtained with mouse liver were equal to, or greater than, the responses obtained with rat liver in both the suspension and plate tests. Although it is difficult to make quantitative comparisons between plate and suspension tests, both systems appeared to be responsive to the same dose ranges for the individual nitrosamines.

Animals↗
PubMed1976

Protocols for the dominant lethal test, host-mediated assay, and in vivo cytogenetic test used in the food and drug administration's review of substances in the gras (generally recognized as safe) list.

Protocols are described for the dominant lethal and in vivo cytogenetics test in rats and the host-mediated assay, using Salmonella typhimurium and Saccharomyces cerevisiae in mice, as used by the Food and Drug Administration in its mutagenicity review of substances from the generally recognized as safe (GRAS) list. In addition proctolols are described for in vitro mutagenicity tests with S. typhimurium and S. cerevisiae and for statistical treatment for evaluation of data from dominant lethal tests.

Animals↗
PubMed1976

Production of guard cell protoplasts from onion and tobacco.

Guard cell protoplasts (GCP) from young cotyledons of onion and tobacco were isolated in culture microchambers where optimal isolating and culture conditions could be determined in situ. The digestion course was quantified by following under polarized light the loss of.retardation of the birefringent cellulose of the guard cells. The assay showed that driselase has a 5-fold higher cellulytic activity than cellulysin. Driselase is, however, harmful to the GCP. Calcofluor staining was less adequate for establishing digestion courses because it increases sharply after exposing guard cells to cellulysin.Osmotic conditions were crucial for GCP survival. Onion guard cells fragment in the presence of strong plasmolyticum (>0.45 m) indicating cytoplasmic connections between neighboring guard cells and/or cytoplasmic attachments to the wall. Tobacco guard cells plasmolyzed with 0.7 m mannitol revealed several areas of strong attachment to the wall which resulted in severe damage to the cells. Healthy tobacco GCP are obtained by an initial digestion with 4% (w/v) cellulysin in 0.23 m mannitol for 2 to 3 hours followed by an increase in the osmoticum to 0.7 m to stabilize the forming protoplasts.Onion GCP were obtained by digesting paradermal slices with 4% (w/v) cellulysin in 0.23 m mannitol. Protoplasts can be osmotically released by replacing the enzyme solution with 0.23 m mannitol at early stages of digestion. They are also available after prolonged digestion (6-12 hours). Paradermal slices also yield mesophyll and epidermal cell protoplasts but they can be selectively washed away if a pure preparation of GCP is desired. Onion GCP have been kept alive in a simple culture solution for up to 10 days.

Journal Article↗
PubMed1975

Dietary modifications affecting the mutagenicity of N-nitroso compounds in the host-mediated assay.

The effects of various dietary modifications on the mutagenicity of dimethylnitrosamine (DMNA), N-nitrosomorpholine, and N-methyl-N-nitrosourea for Salmonella typhimurium his G-46 in the host-mediated assay were studied. The diets used were:chow, complete semisynthetic, protein-free, and all-casein, in addition to a 24-hr starvation regimen. The mutagenicity of DMNA and N-nitrosomorpholine, which require metabolic activation for their biological activity, was depressed by the complete semisynthetic diet, as compared to the mutagenicity in mice fed the chow diet. DMNA mutagenicity was depressed by the protein-free diet and enhanced by pure casein as compared with the complete semisynthetic diet. N-Nitrosomorpholine mutagenicity was enhanced by starvation, but results with mice fed the protein-free and all-casein diets were ambiguous. N-Methyl-N-nitrosourea, which does not require metabolic activation for its biological activities, responded in an opposite manner to that of DMNA; its mutagenicity was enhanced by the complete semisynthetic and protein-free diets, but was depressed by the all-casein diet.

Animals↗