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Biomedical subjects

R S Day

Publications and source records attributed to R S Day.

At least 73 records · Page 4Linked to original sources
PubMed1984

Relationship of DNA repair phenotypes of human fibroblast and tumor strains to killing by N-methyl-N'-nitro-N-nitrosoguanidine.

Two DNA repair assays were used to group human cells. (a) The first assay, survival of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-treated adenovirus infecting cellular monolayers, was previously used to define the Mer phenotype of the strain. Strains that supported the growth of MNNG-treated viruses as well as did human fibroblasts were "Mer+"; those that gave rise to clearly less virus survival were "Mer-." (b) The second assay, data from which are presented in this paper, was that of post-MNNG colony-forming ability, and defined the Rem phenotype of the strain. Strains having post-MNNG colony-forming ability like that of human fibroblasts were "Rem+"; more sensitive strains were "Rem-". In all, 22 human cell strains were analyzed for their post-MNNG colony-forming ability. The most resistant strains (eight Mer+ Rem+ strains) had an average inactivation slope of 0.32 "lethal hit"/microM and were those fully able to repair O6-methylguanine (O6mGua) produced in their DNA by a 5 microM dose of MNNG. The most sensitive strains (9 Mer- Rem- strains) had an average inactivation slope of 7.0 "lethal hits"/microM, and were strains that failed to repair O6mGua. Five strains of intermediate sensitivity (Mer+ Rem-) had an average inactivation slope of 0.93 "lethal hit"/microM and were able to repair some labeled O6mGua produced by a 5 microM dose of labeled MNNG, but they repaired significantly less labeled O6mGua if pretreated with unlabeled MNNG. Representative strains from each group were treated with MNNG and assayed for ability: (a) to perform DNA repair synthesis (and DNA repair replication); (b) to support the growth of MNNG-treated adenoviruses; and (c) to restore control levels of tertiary structure to their DNA as assayed by nucleoid sedimentation. The results support the hypothesis that a lesion (both produced by agents that produce O6mGua and repaired by cell strains that repair O6mGua, but not by those that do not) is a lesion lethal to Mer- Rem- strains. This lesion may also initiate induction of excess DNA repair synthesis, the relaxed conformation of nucleoids, the reduced ability to repair MNNG-treated adenovirus, and sister chromatid exchanges as well.

Adenoviridae↗
PubMed1984

Sensitivity of human cell strains having different abilities to repair O6-methylguanine in DNA to inactivation by alkylating agents including chloroethylnitrosoureas.

In order to investigate the mechanisms of cellular damage by alkylating agents, human fibroblasts and tumor cell strains having different sensitivities to killing by N-methyl-N'-nitro-N-nitrosoguanidine [and different abilities to repair O6-methylguanine ( O6mGua ) in their DNA] were treated with other alkylating agents. Methyl methanesulfonate, 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), 1-(2-hydroxyethyl)-3-(2-chloroethyl)-3-nitrosourea, and N-ethyl-N'-nitro-N-nitrosoguanidine gave rise to sensitivity differences, but the differences were less than those observed with N-methyl-N'-nitro-N-nitrosoguanidine. After treatment with UV light, the strains showed similar survival. The data show that the DNA repair mechanism(s) responsible for the differential survival of the strains after N-methyl-N'-nitro-N-nitrosoguanidine treatment probably play(s) a role in repairing DNA damage produced by methyl methanesulfonate, N-ethyl-N'-nitro-N-nitrosoguanidine, BCNU, and 1-(2-hydroxyethyl)-3-(2-chloroethyl)-3-nitrosourea but not that produced by UV. Furthermore, the results support the idea that a breakdown product of BCNU, that does not cause damage repairable by O6mGua repair mechanisms, contributes to the lethal effects due to BCNU-produced DNA-damage that is repairable by O6mGua repair mechanisms. The survival data, along with nucleoid sedimentation and adenovirus host-cell reactivation data, are consistent with the hypothesis that the lesion(s) lethal to tumor cells defective in O6mGua DNA repair are lesions in which DNA oxygen atoms are alkylated.

Alkylating Agents↗
PubMed1983

Delayed onset of overt porphyria cutanea tarda in a patient on long-term haemodialysis. A case report.

After 7 years on haemodialysis, a 37-year-old anephric man developed cutaneous lesions of the hands, arms and face, shown by skin biopsy to be compatible with porphyria cutanea tarda (PCT) (symptomatic porphyria). Elevated levels of plasma uroporphyrin and 7-COOH porphyrin were detected alongside a predominant isocoproporphyrin fraction in the faeces by means of quantitative thin-layer chromatography, confirming the diagnosis of overt PCT. The plasma uroporphyrin did not pass into the dialysate, even after chloroquine therapy. There was no evidence of hereditary PCT, chronic liver disease or iron overload, although the patient had a history of excessive alcohol consumption. The overt PCT developed after 8 months of home dialysis using softened water with high aluminium concentrations and subsided clinically and biochemically when the softened water was replaced by deionized water.

Adult↗
PubMed1983

Repair of O6-methylguanine in DNA by demethylation is lacking in Mer- human tumor cell strains.

The ability of extracts of human tumor cells to demethylate O6-methylguanine (O6-MeG) in DNA was assayed using the synthetic DNA polymer poly(dC,dG,m6dG). Cell strains proficient in repair of O6-MeG in vivo (Mer+ phenotype) contained a methyltransferase activity while repair deficient cells (Mer- phenotype) had little or no activity. Mixing extracts of different Mer- strains did not result in the appearance of the activity. Extracts of Mer- cells did not inhibit the activity in extracts of Mer+ cells. Both Mer+ and Mer- strains contained methylnitrosourea-damage-specific endonuclease activity. The data suggest that the Mer- strains are deficient in methyltransferase and that this is the fundamental reason for their hypersensitivity to the cytotoxic effects of DNA alkylation. The activity was partially purified from a Mer+ colon carcinoma cell strain. Its kinetics parallel the repair of O6-MeG in DNA in vivo and suggest that the activity is inactivated during repair of DNA.

DNA Repair↗
PubMed1983

A biochemical defect in the repair of alkylated DNA in cells from an immunodeficient patient (46BR).

The fibroblast cell strain 46BR, derived from an immunodeficient individual, is hypersensitive to the lethal effects of a variety of DNA-damaging agents, this effect being particularly marked for monofunctional methylating agents. After u.v. irradiation 46BR cells show normal unscheduled DNA synthesis, daughter strand repair, and recovery of DNA and RNA synthesis. The inhibition of DNA replicative synthesis by u.v. is slightly less than that of normal cells. After gamma-irradiation the rejoining of strand breaks is normal as are the kinetics of replicative DNA synthesis. Following treatment with dimethylsulphate, replicative DNA synthesis is affected in a similar way to normal cells, unscheduled DNA synthesis may be increased relative to normal cells, but more strand breaks persist in 46BR than in normal cells. In addition 46BR cells are hypersensitive to the toxic effects of 3-aminobenzamide, an inhibitor of ADP-ribosyl transferase. This enzyme is involved in the ligation step of repair of alkylation damage. A hypothesis is presented suggesting that 46BR may be defective in DNA ligase I.

Benzamides↗
PubMed1982

Differential effects of hydroxyurea on the survival of UV- and MNNG-treated adenovirus 5.

The effects of hydroxyurea on plaque formation by UV-irradiated and MNNG-treated adenovirus 5 were investigated. Hydroxyurea blocked the recovery of UV-irradiated viruses in all cases studied, but the effect was less when fibroblasts from a patient with xeroderma pigmentosum were used. This fact supports the notion that hydroxyurea blocks excision repair of UV-produced damage. The recovery of MNNG-treated viruses was not blocked by hydroxyurea when viruses were used to infect normal human fibroblasts, but was blocked if the cell strain used as viral host were deficient in repair of O6-methylguanine. To account for these data, we propose that hydroxyurea blocks repair in which DNA polymerases play a role, but does not block repair in which DNA polymerases are not required.

Adenoviruses, Human↗
PubMed1982

Porphyrins in renal transplantation.

The porphyrin status of 38 renal transplant patients was investigated using a sensitive thin-layer chromatographic assay. Abnormalities of porphyrin synthesis observed in patients on hemodialysis were generally reversed on receipt of a transplant with sustained good renal function. Urinary coproporphyrin levels and the creatinine clearance appeared directly related in both individual cases and generally, substantiating the theory that coproporphyrin is of renal origin. The pre- and postoperative porphyrin status of a unique patient with variegate porphyria who received a successful renal transplant implies that the excess urinary porphyrins and precursors excreted in the acute porphyrias are also of mainly renal, as opposed to hepatic origin. Furthermore, the posttransplant overproduction of porphyrins by a kidney from a normal donor suggests the existence of an endogenous porphyrogenic agent in the circulation of patients with acute porphyria.

Adult↗
PubMed1982

Severe cutaneous porphyria in a 12-year-old boy: hepatoerythropoietic or symptomatic porphyria?

Deforming cutaneous porphyria developed in a 12-year-old boy; the severity of his skin disease resolved spontaneously as he grew older. The clinical and biochemical aspects of this case clearly fit the descriptions in the medical literature of both hepatoerythropoietic porphyria (HEP) and infantile symptomatic porphyria (SP). Further porphyrin analyses indicated that our patient suffered from infantile SP. The lack of unquestionably unique features diagnostic for HEP raises strong doubts that it exists as a separate disease entity substantially different from infantile SP.

Child↗
PubMed1981

Human tumor strains defective in the repair of alkylated DNA fail to regenerate rapidly-sedimenting nucleoids after N-methyl-N'-nitro-N-nitrosoguanidine treatment.

Upon treatment with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), human cell strains characterized as either proficient or defective both in repair of alkylation-damaged DNA and in supporting the growth of MNNG-treated adenovirus (Mer+ and Mer- phenotypes (1,2)), all underwent a rapid relaxation of nucleoid DNA, as judged by sedimentation in 15--30% neutral sucrose gradients. DNA in the repair-proficient Mer+ strains (normal fibroblast and tumor) was restored to the rapidly-sedimenting (control) form within 2--4 h after the removal of MNNG. In contrast, nucleoid DNA of the repair-deficient Mer- tumor strains remained slowly-sedimenting even after 48 h of incubation. The delayed recovery of Mer- nucleoid DNA was specific for MNNG damage, since after u.v. irradiation, to which Mer+ and Mer- strains are equally resistant (2), all cell lines tested underwent DNA relaxation within the first hour after irradiation (3 J/m2) and regenerated rapidly-sedimenting nucleoids within 4--6 h of repair incubation.

Cell Line↗
PubMed1981

MNNG-pretreatment of a human kidney carcinoma cell strain decreases its ability to repair MNNG-treated adenovirus 5.

When treated with 4-32 micro M N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), monolayers of the A498 human kidney carcinoma cell strain were less able to support plaquing by MNNG-treated adenovirus 5 than were control monolayers that received no MNNG. However, non-treated and MNNG-treated monolayers were equally able to support plaquing by adenovirus that was not treated with MNNG. Both N-ethyl-N'-nitro-N-nitroguanidine and N-methyl-N-nitrosourea (but neither u.v. nor methyl methanesulfonate) treatment of A498 monolayers caused the depressed survival of MNNG-treated adenoviruses, also indicating specificity of phenomenon. When cells infected by MNNG-treated adenovirus were treated with MNNG for 1 h as a function of post-infection time, the MNNG-depressed viral survival, observed early after infection, decreased, and was unobservable 12 h post-infection, suggesting that repair of MNNG-damaged viruses had occurred over that time period.

Adenoviruses, Human↗