Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0043346 (xeroderma pigmentosum)
 2,924 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The method of DNA alkaline elution was applied to a study of the formation and resealing of DNA single-strand breaks after irradiation of human fibroblasts with ultraviolet light (UV). The general features of the results were consistent with current concepts of DNA excision repair, in that breaks appeared rapidly after UV, and resealed slowly in normal fibroblasts, whereas breaks did not appear in those cells of patients with xeroderma pigmentosum (XP) that are known to have defects in DNA repair synthesis. The appearance of breaks required a short post-UV incubation, consistent with the expected action of an endonuclease. Cells of the variant form of XP characterized by normal DNA repair synthesis exhibited normal production of breaks after UV, but were slower than normal cells in resealing these breaks. This difference was enhanced by caffeine. A model is proposed to relate this finding with a previously described defect in post-replication repair in these XP variant cells. DNA crosslinking appears to cause an underestimate in the measurement of DNA breakage after UV.
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PMID:DNA single-strand breaks during repair of UV damage in human fibroblasts and abnormalities of repair in xeroderma pigmentosum. 0 51

The author reports on the molecular biological site of action for cancerogenic substances. He shows how UV-radiation may lead to malignomas of the skin in the hereditary disease xeroderma pigmentosum and how ionising rays may cause changes of the DNA, the place of the genetic information. Since the virus genesis of malignant diseases has become more important lately, the author tries to point out the molecular biological connections of an eventual involvement of virus in the development of malignant diseases.
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PMID:[New aspects of tumor genesis (author's transl)]. 3 9

A simple and sensitive technique for detection of strand breaks in DNA has been further developed. The method has been used to follow UV-induced excision-repair in human fibroblasts. It has been possible to study the kinetics of enzymic reactions in intact cells, in which strand breaks in DNA are produced and sealed again. Hydroxyurea, 5-fluorodeoxyuridine and 1-beta-D-arabinofuranosylcytosine, potent inhibitors of DNA synthesis, drastically increased the number of breaks observed during the repair process. This was probably due to a decreased polymerase activity, which will cause the strand breaks formed by endonuclease to remain open longer. The initial rate of strand-break formation did not seem to be influenced by hydroxyurea or araC, and was about 4000 breaks per minute in a diploid genome, at a dose of 20 J/m2. After 5--30 min, depending on the dose of UV, the number of breaks reached a maximum and started to decrease again. Hydroxyurea decreased the rate of polymerization in the sites under repair. However, there was no concomitant reduction of repair-induced incorporation of [3H]thymidine and no reduction of the excision of pyrimidine dimers. It therefore seems that the action of the polymerase was not a rate-limiting event, but rather an earlier step. It is likely that the endonucleolytic activity determined the rate of repair. As a consequence, the endonuclease and polymerase cannot be bound in a permanent complex. Under certain assumptions, the time for repair of a site, i.e. the time from incision to final ligase sealing, can be estimated as between 3 and 10 min. Essentially no breaks were produced in Xeroderma pigmentosum cells belonging to complementation group A, and there was no enhancement by hydroxyurea. Cells from the variant type of Xeroderma pigmentosum behaved like normal cells in this respect.
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PMID:Single-strand breaks in DNA during repair of UV-induced damage in normal human and xeroderma pigmentosum cells as determined by alkaline DNA unwinding and hydroxylapatite chromatography: effects of hydroxyurea, 5-fluorodeoxyuridine and 1-beta-D-arabinofuranosylcytosine on the kinetics of repair. 3 44

The formation of sister chromatid exchanges has been postulated to depend upon the action of DNA repair enzymes. Our experiments with various human cell lines show that the yield of sister chromatid exchanges is within normal limits in both excision-repair-defective and post-replication-repair-defective cells from the autosomal recessive disease, xeroderma pigmentosum. These results indicate that hypotheses invoking known DNA repair processes to acconnt for the recombination of sister chromatids are inadequate and that the exact enzymatic processes are as yet unknown.
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PMID:Sister chromatid exchange in xeroderma pigmentosum cells that are defective in DNA excision repair or post-replication repair. 5 81

The severity of neurological abnormalities in patients with xeroderma pigmentosum has been found to be related to their ability to repair ultraviolet (U.V.)-damaged D.N.A. Patients with the most severe neurological abnormalities have the least effective D.N.A. repair is shown by the decreased colony-forming ability of their U.V.-irradiated fibroblasts. These results suggest that the lack of adequate D.N.A. repair is causally related to the clinical manifestations of a human heredodegenerative nervous system disease.
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PMID:Relation of D.N.A. repair processes to pathological ageing of the nervous system in xeroderma pigmentosum. 5 10

DNA single-strand breakage by bleomycin treatment of cultured mammalian cells was demonstrated by the method of alkaline elution. Elution patterns from treated L1210 cells indicated that part of the DNA was extensively broken while the remainder was affected to a lesser degree. This biphasic effect, which was less prominent in human fibroblasts, may reflect a selective sensitivity either of part of the cell population or of part of the DNA within individual cells. In both cell types, the DNA damage was at least partially repaired upon incubation of the cells after removal of drug. Bleomycin did not inhibit the rejoining of X-ray-induced single-strand breaks. The production and repair of DNA single-strand breaks after bleomycin treatment were the same in normal human and xeroderma pigmentosum fibroblasts, indicating that these events do not require the excision endonuclease that appears to be defective in these ultraviolet light-sensitive xeroderma cells.
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PMID:Single-strand scission and repair of DNA in mammalian cells by bleomycin. 6 Jan 74

Peripheral blood lymphocytes from four patients with ataxia telangiectasia (AT), an inherited disorder showing, among other features, radiosensitivity and a high frequency of cancers, were shown to be cytogenetically more sensitive to bleomycin than were lymphocytes from both normal individuals and a single patient with xeroderma pigmentosum. With cell survival techniques, a biphasic dose-response curve was seen for both normal and AT fibroblasts, although the AT cells showed a much lower survival. The increased sensitivity to bleomycin in AT cells might be expected since it is a radiomimetic drug, but more importantly the known action of bleomycin in producing DNA strand scission suggests that AT cells might be defective in rejoining a proportion of DNA strand breaks.
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PMID:Unusual sensitivity of ataxia telangiectasia cells to bleomycin. 8 79

The pathogenesis of the lupus erythematosus results from co-operation of three principles: (1) genetical disposition, (2) increased reactivity of the immune system, (3) different exogenic influences. The genetical disposition is confirmed by family investigations, metabolic disorders and immune anomalies as well as by parallels to animal models. The reaction manner of the immune system is genetically determined. Exogenic factors influence the immune system (behaviour) either as starter or by modifying the genetical material. The most striking humoral immune phenomenon is an immense number of (auto-)antibodies. Investigations of xeroderma pigmentosum as well as with DNA of different antigenity have shown that an increase of the antigenicity is unlikely for this phenomenon. In the serum of patients there were established and partially characterized factors (mitogens, granulocytic adherence-factor) for increasing the immune reactivity. The increase of such factors may be the sequence of a T-suppressor cell-defect. Like-wise no interdigitating cells in systemic lupus erythematosus have been found, cells which may be responsible for the terminal differentiation of T-lymphocytes. The mode of action of exogenic factors is represented and discussed with the example of the UV provocation.
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PMID:[New studies on the pathogenesis of lupus erythematosus]. 9 93

DNA excision repair was measured in cultured human fibroblasts after single or dual treatments with ultraviolet radiation, 4-nitroquinoline 1-oxide, or N-acetoxy-2-acetylaminofluorene. Three approaches were used to monitor repair: unscheduled DNA synthesis, measured by autoradiography; repair replication, measured by the incorporation of a density-labeled DNA precursor into repaired regions; and excision of ultraviolet endonuclease-sensitive sites. When a single repair- saturating dose of one of the three carcinogens was administered, little stimulation of unscheduled DNA synthesis or repair replication could be observed by additional treatment with one of the other carcinogens. In no instance was total additivity of repair observed. These observations were confirmed by showing that the excision of endonuclease-sensitive sites produced by ultraviolet damage (i.e., pyrimidine dimers) was inhibited by exposure to 4-nitroquinoline 1-oxide and N-acetoxy-2-acetylaminofluorene. The data indicate that the repair of lesions induced by these substances may have common rate-limiting steps, a conclusion previously indicated by the repair deficiency in xeroderma pigmentosum cells in which a single mutation eliminates the repair of damage caused by each of these agents.
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PMID:Overlapping pathways for repair of damage from ultraviolet light and chemical carcinogens in human fibroblasts. 10 94

The replication of chromosomal DNA in a series of abnormal human cell cultures has been studied by means of DNA-fiber autoradiography. In lymphocytes with trisomy 21, in fibroblasts of 45,X;47,XXX;49,XXXXY; and 49,XXXXX chromosomal constitution, and in fibroblasts from a patient with xeroderma pigmentosum (De Sanctis-Cacchione syndrome), the rate of DNA replication does not differ from that in normal cells, varying in a single fork from 0.2 to 1.0 micrometer/min with a mean of about 0.6 micrometer/min. In fibroblasts with trisomy 7 the rate of DNA replication is greater, varying from 0.3 to 1.2 micrometer/min with a mean of about 0.8 micrometer/min. The sizes of replication units in all cells examined are from 80 to 500 micrometer with a mean of about 200-300 micrometer.
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PMID:Replication of chromosomal DNA in cultured abnormal human cells. 14 57


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