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Biomedical subjects

W G Thilly

Publications and source records attributed to W G Thilly.

At least 145 records · Page 8Linked to original sources
PubMed1979

Concentration-dependent mutation by alkylating agents in human lymphoblasts and Salmonella typhimurium: N-methyl-N-nitrosourethane and beta-propiolactone.

The toxic and mutagenic effects of the alkylating agents N-methyl-N-nitrosourethane (MNUT) and beta-propiolactone (BPL) were quantitatively measured in human lymphoblasts and Salmonella typhimurium. Forward mutation to 6-thioguanine resistance was measured in the human lymphoblasts, and forward mutation to 8-azaguanine resistance was measured in the bacterial cells after equigenerational (1.5 doubling times) exposures. In both systems, the induced mutant fraction rose linearly as a function of concentration for BPL and was biphasic for MNUT. The responses of the two assay systems to eight alkylating agents were compared. The exposure of the cells to each alkylating agent was calculated as exposure concentration multiplied by the time of exposure, and allowance was made for the decomposition of the alkylating agents during exposure (integral exposure). Human cells were 2.5--13 times more sensitive than was S. typhimurium to the alkylating agents methyl methanesulfonate, ethyl methanesulfonate, propyl methanesulfonate, N-methyl-N'-nitro-N-nitrosoguanidine, methylnitrosourea, and MNUT. S. typhimurium cells were three times more sensitive to butyl methanesulfonate and 25 times more sensitive to BPL than were human cells.

Alkylating Agents↗
PubMed1979

Methylmethacrylate is a mutagen for Salmonella typhimurium.

The long-term effects of exposure to monomeric methylmethacrylate have yet to be established. We have measured the toxicity and mutagenicity of methylmethacrylate for Salmonella typhimurium. At levels of thirty-four millimolar, methylmethacrylate exhibited 28 per cent of the mutagenic activity of an equimolar dose of dimethylnitrosamine. Methylmethacrylate alone exhibited toxicity to the bacteria, but when the methylmethacrylate was incubated with a rat-liver enzyme metabolizing system, mutagenesis was induced. These findings suggest that an intermediate metabolite of methylmethacrylate is mutagenic to Salmonella typhimurium.

Adhesives↗
PubMed1979

Parameters affecting cell growth on reduced charge microcarriers.

The development of the reduced charge microcarrier and cell behavior on carriers of different degrees of DEAE substitution, and under different growth conditions are described. Parameters other than the microcarrier which limit productivity are discussed, and microcarrier growth data for certain cell types are presented.

Animals↗
PubMed1978

Phenotypic lag and mutation to 6-thioguanine resistance in diploid human lymphoblasts.

Mutants of a diploid human lymphoblast line resistant to 6-thioguanine (6TG) appear 6--16 generations after treatment with any of a diverse group of mutagents: methylnitrosourea (MNU), methylnitrosoguanidine (MNNG), ICR-191, 5-bromodeoxyuridine (BUdR). A hypothesis is advanced that expression of the 6-thioguanine-resistant state may require the removal of essentially all pre-existing hypoxanthine--guanine phosphoribosyl transferase (HGPRT) molecules via division, dilution, and protein turnover. Design of protocols for quantitative mutation assays requires attention to this phenomenon.

Bromodeoxyuridine↗
PubMed1978

Quantitative forward mutation assay in Salmonella typhimurium using 8-azaguanine resistance as a genetic marker.

We have developed a quantitative forward mutation assay using Salmonella typhimurium, in which resistance to the purine analog 8-azaguanine is used as a genetic marker. We present the assay protocol, the concentration-dependent toxicity and mutagenicity of five known mutagens (N-methyl-N'-nitro-N-nitrosoguanidine, ICR-191, 9-aminoacridine, dimethylnitrosamine, and benzo[a]pyrene), and reconstruction experiments testing the assay for possible bias. The relative merits of forward versus reverse mutation assays are discussed.

Azaguanine↗
PubMed1978

Relative sensitivities of forward and reverse mutation assays in Salmonella typhimurium.

Forward mutation to 8-azaguanine resistance and reverse mutation to histidine prototrophy were measured in Salmonella typhimurium after treatment with 16 mutagens of both base-substitution and frameshift classes. The two approaches were found to be equisensitive for all 16 mutagens--i.e., induction of significant mutation occurred at similar concentrations in the forward mutation assay and in the most sensitive of the five Ames tester strains.

Animals↗
PubMed1978

Alkyl methane sulfonate mutation of diploid human lymphoblasts and Salmonella typhimurium.

Concentration dependence of mutation in equigenerational exposures to methyl, ethyl, propyl, and butyl methanesulfonates has been determined in diploid human lymphoblasts and Salmonella typhimurium. Forward mutation was measured at the hypoxanthine guanine phosphoribosyltransferase locus in human lymphoblasts and at the putative guanine phosphoribosyltransferase locus in S. typhimurium. Reverse mutation at the his G46 locus was also measured in S. typhimurium. This analysis and previous reports support the conclusion that S. typhimurium and mammalian cells are essentially equisensitive to the mutagenic effects of ethyl methanesulfonate when concentration and exposure time are taken into account. Comparison of forward and reverse mutation assays in S. typhimurium reveals no important differences in sensitivities for the four compounds studied.

Animals↗
PubMed1977

Comparative mutagenicity of ICR-191 to S. typhimurium and diploid human lymphoblasts.

Concentration-dependent mutagenicity of ICR-191 has been measured in Salmonella typhimurium strain TA98 and in a diploid human cell line. In both cell systems, approximately equigenerational exposure produced mutation linearly related to concentration in the lower range of ICR-191 concentrations tested. Saturation behavior was observed in the human cell assay but not in the bacterial assay. However, a 25-fold greater concentration of ICR-191 was required to induce a significant rise in the mutant fraction in the S. typhimurium assay than in the human cell assay. These differences may be linked to the differences in the biochemical events required for mutation or in the time of exposure to ICR-191.

Acridines↗
PubMed1977

Microcarrier cell culture: new methods for research-scale application.

A positive-charge-carrying, dextran microsphere has been developed which serves as an excellent surface for the attachment and growth of anchorage-dependent cells in microcarrier culture. With standard cell culture media, saturation cell concentrations in excess of 4 X 10(6) cells/ml are routinely obtained for secondary chicken embryo fibroblasts or normal diploid human fibroblasts. The use of microcarriers reduces the time, expense, and apparatus complexity required for the routine propagation of anchorage-dependent cells.

Cells, Cultured↗
PubMed1977

Chemical mutation in human lymphoblasts.

We have developed a facile and reliable assay for mutation by chemicals and other mutagenic agents induced in the hgprt locus of diploid human lymphoblasts. We discuss here the detailed protocol and summarize the experiments, reported elsewhere, in which we tested the method for possible systemic bias. The concentration dependence of mutation for methylnitronitrosoguanidine, methylnitrosourea, ICR-191, and bromodeoxyuridine are also summarized to demonstrate the responsiveness of the new system to alkylating agents, an intercalating agent, and a base analog, respectively.

Alkylating Agents↗
PubMed1977

Nucleic acid content of HeLa S3 cells during the cell cycle: variations between cycles.

The process of continuous resynchronization with excess thymidine provides sufficient cell material for accurate chemical determination of DNA and RNA in HeLa S3 cells at hourly intervals during the cell cycle. Total DNA is constant during the non-S phase portion of the cell cycle but varies widely among cycles of synchronous growth. Total cellular RNA content increases linearly in the G1 phase and accelerates to a higher linear rate of accumulation, which remains constant during most of the S and G2 phases. The ratios of early and late cycle rates of RNA accumulation are not constant among cycles.

Cell Division↗
PubMed1977

Virus production with a newly developed microcarrier system.

Primary cell cultures as well as established lines have been grown on a recently developed microcarrier configuration that overcomes the problem of toxicity attendant on earlier developments in this technology. Virus yields from these cells propagated on the new microcarriers have been measured. Microcarrier-grown cells, when compared to roller-bottle-grown cells, gave virus yields on a per-cell basis that varied from slightly greater with the Sindbis virus-Chinese hamster ovary cells and polio-WI-38 combinations to approximately one-third with Moloney murine leukemia virus-Cl-1 mouse cells and vesicular stomatitis virus-chicken embryo fibroblasts. Yields ranged from 8.0 X 10(7) to 3.6 X 10(8) cells per 100-ml microcarrier culture and from 3.7 X 10(7) to 4.1 X 20(8) cells per roller-bottle culture. Secondary chicken embryo fibroblast yields were approximately four times as great in microcarrier cultures as in standard roller-bottle cultures, per unit volume of medium consumed. In spite of the reduced virus yields per cell seen in some instances, the greater cellular productivity of microcarrier cultures appears to hold great promise for large-scale virus production. Optimizing microcarrier conditions for specific cell-virus systems should result in improved yields.

Cell Division↗