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A Grafe

Publications and source records attributed to A Grafe.

At least 19 recordsLinked to original sources
PubMed1983

Criteria for the standardization of Salmonella mutagenicity tests: results of a collaborative study. IV. Relationship between the number of his- bacteria plated and number of his+ revertants scored in the Salmonella mutagenicity test.

Five laboratories participated in a joint ring study to investigate the role of bacterial cell number in the Salmonella mutagenicity test. A strictly standardized protocol, using sodium azide and TA 1535, was developed and employed to test the mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) with different dilutions of Salmonella typhimurium TA-100 and TA-1535 cultures. All laboratories detected the mutagenic activity of sodium azide with only a 2-fold variation of test results. For MNNG the interlaboratory variation was approximately 5-fold. Decreasing numbers of test bacteria employed resulted in lower numbers of MNNG-induced revertants in all laboratories. The number of preexisting revertants decreased in direct proportion to the reduced cell content, whereas the number of spontaneous revertants was not as greatly affected. A critical amount of test bacteria was required in order to obtain numbers of induced revertants which were equal to twice the number of spontaneous revertants. Two evaluation parameters which may be employed to describe the mutagenicity of a compound are compared.

Animals↗
PubMed1981

A European collaborative study of the Ames assay. I. Results and general interpretation.

Results are presented of a collaborative study between 19 European laboratories on the variability of the Ames test. Examples are shown of various methods that are generally used to evaluate an Ames test without reference to a specific statistical model: the number of revertants per plate, mutation factors (increase over the spontaneous value) and determination of the doubling concentration. Considerable variations between test results occurred, between laboratories as well as within laboratories. Partly this was due to different interpretations of the guidelines given, as these allowed some flexibility. The results were also influenced by other factors, some of which are perhaps not yet generally recognized. Apart from the level and quality of the S9 preparations, the most important factor might be the number and physiological condition of the cells plated. When the results from all experiments were considered together, 60-80% of the test results were found within the half- to two-fold range of the overall median. This might be considered satisfactory for a study not using rigidly standardized test conditions. From the experience with the present study, several recommendations are given for the design and performance of future collaborative studies.

Europe↗
PubMed1978

Nucleus anomaly test in Chinese hamster and in rat after treatment with isoniazid.

Nucleus anomaly test in Chinese hamsters and in rats treated with isoniazid (INH) was carried out according to a standard protocol in two different laboratories. These comprised both short-term studies, in which the tests were performed on animals killed 6, 12, 24, 36, or 48 h after the second of two consecutive doses of 5, 25, or 125 mg/kg INH given at an interval of 24 h, and long-term studies in animals treated with 25 mg/kg INH thrice weekly for 12 weeks. As a rule, each group consisted of at least four animals, and 1000 cells from each animal were examined. In one of the laboratories, a slight, but statistically significant increase in the incidence of nuclear anomalies was observed in two experiments on animals sacrificed 24 h after treatment; in the majority of cases, however, the investigations yielded negative results. Two out of three long-term studies revealed a slight, but statistically significant increase in the incidence of nuclear anomalies.

Animals↗
PubMed1978

Chromosome analysis of bone marrow in mammals after treatment with isoniazid.

Cytogenetic investigations in bone marrow from animals treated with isoniazid (INH) were performed in seven different laboratories according to a standard protocol. The experiments were carried out in the Chinese hamster, the mouse, and the rat. In short-term studies INH was administered twice at an interval of 24 h in doses of 5, 25, and 125 mg/kg, and the animals were sacrificed 6, 12, 24, and 48 h after the second dose. In long-term studies doses of 25 and 125 mg/kg were administered thrice weekly for 12 weeks. As a rule, each group consisted of at least four animals, and 100 metaphases per animal were counted. Statistical analysis of the data showed that the incidence of chromosomal aberrations including gaps lay in the critical range for two groups in one laboratory and was significantly higher than in the control in three groups in another of the seven laboratories. From the results of both the short-term and the long-term studies in all laboratories, however, it may be concluded, that isoniazid does not induce gross chromosomal aberrations.

Animals↗
PubMed1977

Small numbers in mutagenicity tests.

Experimental control material for statistical analysis of the results of the micronuclei test in the mouse (NMRI strain) and the Chinese hamster and for the host-mediated assay in the mouse (NMRI strain) using auxotrophic bacterial strains are presented. The binomial distribution of the micronuclei makes it possible to analyse the sample size according to the formula of Cochran and Cox (1957). For the host-mediated assay, the experimental principles are given which make it possible to evaluate the results obtained even with a weakly mutagenic, unknown substance. Critical points in comparative tests are not only the methodological questions, but also pharmacokinetic problems of the substance being tested which can only be clarified in the species used for the mutagenicity test. If this is ignored then even experimentally based findings can only be recorded as speculations.

Animals↗
PubMed1977

Testing the mutagenic potency of chemical substances in a linear host-mediated assay (LIHMA).

Instead of comparing "mutation frequencies" as used in the conventional host-mediated assay (HMA), a modified concept of measuring mutagenic potency is introduced by using a number of time intervals for taking samples. Regression analysis methods can then be applied to the numbers of mutant bacteria (reversions). Not only the mutagenic but also an additional antibacterial potency of a compound can be detected and estimated in the sam assay. It is demonstrated that interference of (undetected) antibacterial activity with the mutagenic activity may lead to misclassification of a substance concening its mutagenicity in the conventional HMA. This kind of erroneous assessment will be avoided by the LIHMA. Another advantage of the LIHMA over the conventiona HMA is that regression analysis also allows estimation of the sensitivity and reliability of the assay. The calculative procedure may be programmed on desk computers and is then most suitable for laboratories where large numbers of substances have to be examined routinely. A numerical is given using results obtained with nitrosoguanidine.

Bacteriological Techniques↗
PubMed1975

Testing the mutagenic potency of chemical substances in a linear host-mediated assay. I. Experimental microbiological basis.

By the use of the mutagenic substance hydrazine sulphate it is shown that the currently used single determination method for determining point mutations in host-mediated assays with calculation of mutation frequencies can lead to erroneous results. The microbiological basis for a linear-method is presented in which the population growth of the auxotrophic and substance-induced mutants used int he test can be described mathematically during their logarithmic growth phase with regression lines.

Animals↗