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Biomedical subjects

R B Setlow

Publications and source records attributed to R B Setlow.

At least 73 records · Page 4Linked to original sources
PubMed1980

DNA excision repair in human cells treated with ultraviolet radiation and 7,12-dimethylbenz[a]anthracene 5,6-oxide.

Excision repair was measured in normal human and xeroderma pigmentosum group C cells treated with 7,12-dimethylbenz[a]-anthracene 5,6-oxide and with ultraviolet radiation by the techniques of unscheduled DNA synthesis, repair replication, a modification of bromodeoxyuridine photolysis employing the dye Hoechst 33258 and 365 nm radiation, and endonuclease-sensitive sites assay. Radioautography and repair replication showed that in normal cells the magnitude of repair after a saturation dose of epoxide (approx. 10 microM) to be 0.1-0.2 that after a saturating ultraviolet dose (20 J/m2 at 254), though survival data showed that both doses gave nearly similar killings. Repair was of the long-patch type and repair kinetics after the epoxide treatment were similar to ultraviolet. After a combined treatment with both agents, unscheduled synthesis in normal cells was more than additive, although, considering the experimental errors, these data and those of repair replication are consistent with additivity. The epoxide did not inhibit loss of sites sensitive to the ultraviolet endonuclease. However, after a combined treatment to xeroderma pigmentosum cells there was appreciably less unscheduled synthesis than for the sum of both treatments and the epoxide inhibited the loss of nuclease-sensitive sites. We interpret the data to indicate that there are different rate-limiting steps in the removal of the ultraviolet and the epoxide damages, and that the residual repair activity in xeroderma pigmentosum cells is accomplished by different, not just fewer, enzymes than in normal cells.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1980

Dna repair pathways.

Our knowledge about DNA repair mechanisms in mammalian cells is reviewed. Ways of measuring excision repair are summarized, and various modes of excision repair are described in terms of mechanisms that yield patch sizes of 0, 1, and few (short patch), and many (long patch) bases. The biological and molecular ways of measuring the effects of replication on a damaged template are presented, as are various models of postreplication repair.

Animals↗
PubMed1980

DNA excision in repair proficient and deficient human cells treated with a combination of ultraviolet radiation and acridine mustard (ICR-170) or 4-nitroquinoline 1-oxide.

Excision repair was measured in normal human and xeroderma pigmentosum group C fibroblasts treated with ultraviolet radiation and the carcinogens acridine mustard (ICR-170) or 4-nitroquinoline 1-oxide (4NQO) by the techniques of unscheduled synthesis, photolysis of bromodeoxyuridine incorporated into parental DNA during repair, and assays of sites sensitive to ultraviolet (UV)-endonuclease. Doses of ICR-170 and 4NQO, low enough not to inhibit unscheduled DNA synthesis (UDS), caused damage to DNA that was repaired by a long patch type mechanism and the rates of UDS decreased rapidly in the first 12 h after treatment. Repair after a combined action of UV plus ICR-170 or UV plus 4NQO was additive in normal cells and no inhibition of loss of endonuclease sensitive sites was detected. In xeroderma pigmentosum (XP) C cells there was less repair after UV plus ICR-170 than after each treatment separately; whereas there was an additive effect after UV plus 4NQO and no inhibition of loss of endonuclease sensitive sites. The results indicate that in normal human fibroblasts there are different rate limiting steps for removal of chemical and physical damages from DNA and that XP cells have a different repair system for ICR-170, not just a lower level, than normal cells. Possibly the same long patch repair system works on 4NQO damage in both normal and XP cells.

4-Nitroquinoline-1-oxide↗
PubMed1980

DNA repair after ultraviolet irradiation of ICR 2A frog cells. Pyrimidine dimers are long acting blocks to nascent DNA synthesis.

The ability of ICR 2A frog cells to repair DNA damage induced by ultraviolet irradiation was examined. These cells are capable of photoreactivation but are nearly totally deficient in excision repair. They have the ability to convert the small molecule weight DNA made after irradiation into large molecules but do not show an enhancement in this process when the UV dose is delivered in two separate exposures separated by a 3- or 24-h incubation. Total DNA synthesis is depressed and low molecular weight DNA continues to be synthesized during pulse-labeling as long as 48 h after irradiation. The effects of pyrimidine dimer removal through exposure of UV irradiated cells to photoreactivating light indicate that dimers act as the critical lesions blocking DNA synthesis.

Animals↗
PubMed1980

Postreplication repair in three murine melanomas, a mammary carcinoma, and a normal mouse lung fibroblast line.

Repair of ultraviolet light-induced damage to DNA was studied in three melanoma lines, a mammary carcinoma line, EMT6, and a normal lung fibroblast line, MLF, all from the mouse. The melanomas were B16CL4, a gamma-ray-resistant clonal line derived from B16; S91H-, an auxotrophic line derived from Cloudman S91; and HP, a freshly isolated line from s.c. grown Harding-Passey melanoma. The melanomas and MFL were found to perform minimal excision repair and photoreactivation. Postreplication repair, on the other hand, was an active process in all five of the lines. All three melanomas exhibited postreplication repair rates that were about twice that of MLF. The freshly isolated HP line evolved during subcultivation, and its postreplication repair rate dropped after 3 months to a rate comparable to EMT6, which was 1.5 times that of MLF. The results suggest that postreplication repair is an important process in melanomas and may be related to radiation response.

Animals↗
PubMed1980

Modulation by caffeine of enhanced postreplication repair in mammalian cells treated with N-acetoxy-acetylaminofluorene.

As shown previously, newly synthesized DNA from Chinese hamster, excision proficient and excision deficient xeroderma pigmentosum (XP) cells treated with split doses of N-acetoxy-acetylaminofluorene (AAAF) or ultraviolet radiation (uv) is larger in size than DNA from cells treated with only the single dose. In this report we determined the effects of caffeine, an inhibitor of postreplication repair, upon enhancement of repair by a split dose treatment with AAAF. Caffeine was added to cells either immediately following the first or the second dose of AAAF and the size of newly synthesized DNA was determined by alkaline sucrose gradient sedimentation. Results showed that: (a) the DNA from V79 and XP cells incubated with caffeine between the first and second dose of AAAF was smaller in size than DNA from cells not incubated with caffeine; (b) caffeine exhibited a lesser effect when added after the second dose during the pulse-chase; and (c) caffeine has little effect upon daughter DNA of normal human cells treated with single or split doses of AAAF. These data indicate that caffeine interferes with the enhancement of postreplication repair in V79 and XP cells treated with AAAF.

2-Acetylaminofluorene↗
PubMed1979

UV-endonuclease from calf thymus with specificity toward pyrimidine dimers in DNA.

We describe the partial purification of an endonuclease from calf thymus that nicks phage PM2 DNA irradiated with UV doses producing only a few pyrimidine dimers per molecule. It has much less activity on DNA that has been subjected to enzymatic photoreactivation after UV irradiation. The calf thymus endonuclease is different from other mammalian UV-endonucleases so far described in that it seems to be dimer specific. The enzyme is stimulated by Mg2+ and is inactive in the presence of EDTA. It binds to UV-irradiated DNA-Sepharose from which it is released by low concentrations of KCl. Gel filtration data indicate that the endonuclease may belong to a high molecular weight protein or protein complex. The enzyme is very labile and freezing increases its lability.

Animals↗
PubMed1979

Repair of ultraviolet light damage to the DNA of cultured human epidermal keratinocytes and fibroblasts.

Pure cultures of dermal fibroblasts and epidermal keratinocytes have been obtained from a single biopsy of newborn foreskin. The cells were labeled, exposed to several doses of UV light, and allowed to repair in the dark for 16 hr. The number of pyrimidine dimers before and after repair was assessed by measuring the numbers of sites in the DNA sensitive to a specific UV endonuclease. At all doses used, the extent of repair was similar in the cultured keratinocytes and cultured fibroblasts.

Cells, Cultured↗
PubMed1979

Migration of intraperitoneally injected thyroid cells in the Amazon molly, Poecilia formosa.

We have previously reported the development of an extensive invasive growth of the thyroid gland of the gynogenetic teleost, Poecilia formosa (the Amazon molly), following i.p. injection of UV- or gamma-irradiated thyroid cells. This result was surprising by comparison with mammalian work, in which the thyroid is rarely the site for tumor metastases, but the anatomy of the circulation of fish is different from mammals, and in fish the gills and thyroid gland would be among the first tissues in which injected cells might be arrested. Techniques using a fluorescent dye, 125I membrane label, or [3H]thymidine label were used to follow the distribution of i.p. injected cells in the Amazon molly. Fish sampled as soon as 30 min after injection had some labeled cells dispersed in the connective tissue around the ventral aorta and in the bases of the gills, and by 1 to 4 hr large numbers of cells had moved into the thyroid region. A few cells still persisted there 200 hr later. Experiments on the distribution of heat-killed cells indicated that the initial distribution of the cells was largely governed by mechanical factors. Injected cells would appear to be disseminated in fish by mechanisms similar to those in mammals.

Animals↗
PubMed1979

DNA repair in xeroderma pigmentosum cells treated with combinations of ultraviolet radiation and N-acetoxy-2-acetylaminofluorene.

We used three techniques to examine excision repair in human cells treated with ultraviolet radiation, N-acetoxy-2-acetylaminofluorene, and a combination of the two. The three techniques gave similar results. Two types of human cells were used: (a) excision repair proficient (normal human fibroblasts and xeroderma pigmentosum variants); and (b) excision repair deficient (xeroderma pigmentosum C, D, and E). Saturation doses were determined and used for combined treatments with both agents. We observed two patterns of repair: (a) in repair-proficient cells total repair was additive; and (b) in repair-deficient cells total repair was much less than additive (usually less than that repair was much less than additive (usually less than that observed for separate treatments) and N-acetoxy-2-acetylaminofluorene inhibited excision of pyrimidine dimers. We conclude that, in the first group of cells, pathways for repair of ultraviolet radiation- and N-acetoxy-2-acetylaminofluorene-induced lesions are not identical and, in the second group of cells, there is an inhibitory effect exerted by major or minor products of each agent on the repair enzyme(s) of the other.

Acetoxyacetylaminofluorene↗