The flow cytometric measurement of DNA distributions of cells has many applications in biomedical research. Phase fractions estimated (calculated) from such distributions are used to study the growth characteristics of various types of cells, particularly when the cells have been exposed to perturbing agents such as chemotherapeutic drugs. For more than 10 years many methods for resolving DNA
This paper is a continuation of parts I (history, methods and cell kinetics) and II (clinical applications and carcinogenesis) published previously (Dolbeare, 1995 Histochem. J. 27, 339, 923). Incorporation of bromodeoxyuridine (BrdUrd) into DNA is used to measure proliferation in normal, diseased and injured tissue and to follow the effect of growth factors. Immunochemical detection of BrdUrd can be used to determine proliferative characteristics of differentiating tissues and to obtain birth dates for actual differentiation events. Studies are also described in which BrdUrd is used to follow the order of DNA replication in specific chromosomes, DNA replication sites in the nucleus and to monitor DNA repair. BrdUrd incorporation has been used as a tool for in situ hybridization experiments.
Mutagenic heterocyclic amines are generated in foods when they are cooked at temperatures over 150 degrees C. These compounds are present from 0.1 to 50 ppb, depending on the food and cooking conditions. These heterocyclic amines are not only present in cooked red meat, fish, and chicken, but are also present at lower levels in baked and fried foods derived from grain. Mutagenicity of fried beef hamburgers cooked at 230 degrees C is 800 +/- 37 TA98 revertants per gram cooked weight. We measured 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MelQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMelQx), and 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) formation at this temperature and found 3.0 +/- 2.0, 1.0 +/- 0.18, and 0.06 +/- 0.03 ng/g, respectively. 2-amino-1-methyl-6-phenylimidaz[4,5-b]pyridine (PhIP) was found at a higher concentration of 9.6 ng/g. In our laboratory we have shown these heterocyclic amines are capable of producing both reverse and forward mutations in Salmonella bacteria and forward mutations in Chinese hamster ovary cells (CHO). We have also been able to show a statistically significant increase in mutations in the pancreas of the "mutamouse" following PhIP exposure. The pancreas also shows relatively high DNA binding compared to other organs in the mouse. The number and type of mutations depend on the repair capacity of the cells for both Salmonella and CHO. In Salmonella the mutations are primarily 2-base deletions when the cells lack uvrB repair, but mutations are more complex (larger deletions and insertions) but lower in frequency when repair is functional.(ABSTRACT TRUNCATED AT 250 WORDS)
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