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 13,001 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The biologic peculiarities of tumors of early life are elucidated. The oncogenic grace period is emphasized, wherein infantile tumors tend to behave in a relatively benign fashion up until 3-6 months of age. A review of the types of congenital malformations associated with the development of neoplasms is presented. These associations appear to be of fundamental importance in developmental pathobiology. They are illustrated by the tendency for neoplasms to develop in anomalous or dysplastic tissues, such as developmental vestiges, undescended testes, dysgenic gonads and certain hamartoses. There is an increased incidence of tumor occurrence in: (1) specific teratologic disorders: aniridia, hemihypertrophy, Beckwith's syndrome, basal cell nevus syndromes and others; (2) cytogenetic abnormalities: Down's syndrome, 13q- syndrome (D-deletion), trisomy 18; (3) chromosomal instability syndromes: Fanconi's anemia, ataxia-telangiectasia, Bloom's syndrome. Finally, many agents, known to be carcinogenic when administered postnatally to animals, are teratogenic in the fetus. A few agents--urethan, alkylnitrosoureas, estrogens--are both teratogenic and carcinogenic when administered to the fetus transplacentally. It is suggested that the timing of intrauterine insult is important in determining whether the effect on the offspring is teratogenic, oncogenic or both. Teratogenesis appears to be the more primitive response. Other theories explaining the concurrence of tumors and anomalies are offered.
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PMID:Neoplasia of early life and its relationships to teratogenesis. 18 28

Skin fibroblasts from normal donors, donors with ataxia-telangiectasia or Fanconi's anemia, and from 1 cancer patient were treated with repeated gamma-radiation at about 16 rads per hour. The remaining division potential of all fibroblasts, except for the Fanconi's anemia cells, was reduced to different extents by radiation. The growth potential of Fanconi's anemia cells was increased in all the irradiated cultures. The increase was 54% in the group that survived the longest. These results were identical to those obtained with fibroblasts from certain species that have a high probability of transformation.
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PMID:Effect of low-dose-rate irradiation on the division potential of cells in vitro. V. Human skin fibroblasts from donors with a high risk of cancer. 22 19

The eldest brother in a sibship of five children died of acute myelogenous leukemia at 10 years of age. The second and third eldest brothers died of hypoplastic anemia at ages five and nine years, respectively. A surviving 6 year old brother, the proband of the study, has abnormalities that suggest a preleukemic state: mild pancytopenia, platelet dysfunction, immunodeficiency, and bone marrow hypoplasia with approximately 18 per cent blast forms. His 17 year old sister has a mild normochromic normocytic anemia. Cytogenetic studies revealed C-group monosomy in the bone marrows of the proband and the third brother (45, XY, -C); band studies demonstrated that a No. 8 chromosome was missing in the proband (45, XY, -8). At least four of the siblings and their father had cerebellar ataxia, and evidence of a small cerebellum at autopsy examination or by computerized axial tomography. The disorder in this family has major features of two autosomal recessive preleukemic diseases, ataxia-telangiectasia and Fanconi's anemia. However, these and other inherited conditions were excluded by clinical or laboratory criteria, and no environmental causes of the familial disorder were found. The constellation of abnormalities in the family may constitute a new genetic syndrome.
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PMID:A family with acute leukemia, hypoplastic anemia and cerebellar ataxia: association with bone marrow C-monosomy. 28 89

Excision repair of damage due to ultraviolet radiation, N-acetoxy-2-acetyl-aminofluorene and a combination of both agents was studied in normal human fibroblasts and various cells from cancer prone patients (ataxia telangiectasia, Fanconi's anemia, Cockayne syndrome and Bloom's syndrome). Three methods giving similar results were used: unscheduled DNA synthesis by radioautography, photolysis of bromodeoxyuridine incorporated into parental DNA during repari, and loss of sites sensitive to an ultraviolet endonuclease. All cell lines were proficient in repair of ultraviolet and acetoxy acetylaminofluorene damage and at saturation doses of both agents repair was additive. We interpret these data as indicating that the rate limiting step in excision repair of ultraviolet and acetoxy acetylaminofluorene is different and that there are different enzyme(s) working on incision of both types of damages.
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PMID:Excision repair in ataxia telangiectasia, Fanconi's anemia, Cockayne syndrome, and Bloom's syndrome after treatment with ultraviolet radiation and N-acetoxy-2-acetylaminofluorene. 73 87

A sensitive new approach for measuring the repair of single strand breaks in DNA induced by low doses of gamma irradiation was tested in cultured fibroblasts from Chinese hamster lung, human afflicted with ataxia telangiectasia or Fanconi's anemia and in normal cells of early and late passages. The assay is based on the increasing rate of strand separation of DNA duplexes in alkali for molecules with increasing numbers of single strand scissions. DNA strand separation is shown to follow the relation, in F = -(1/Mn - const) - tbeta where F is the proportion of double-stranded DNA, detected as S1 nuclease resistant, after alkaline denaturation time, t. Mn is the number-average molecular weight of DNA between single strand breaks. beta less than 1 is an empirically determined constant. The results suggest an increase in the number-average molecular weight between breaks, Mn, with increasing times for repair. The final level attained corresponds to the Mn of control DNA in unirradiated cells. As few as one break introduced into 109 daltons of single-stranded control cell DNA can be detected. The kinetics, requirements and sensitivities of this assay are described.
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PMID:Single strand breakage and repair in eukaryotic DNA as assayed by S1 nuclease. 84 Jun 43

Fiber autoradiograms prepared from radioactive DNA of diploid skin fibroblasts and lymphocytes from normal adult humans show patterns of replication of chromosomal DNA that are closely similar to those from other mammalian cells. The rate of replication fork movement is 0.64 micrometer/min and 0.42 micrometer/min for fibroblasts and lymphocytes respectively. In both types of cells, replication units show a median length of about 70 micrometer. Replication proceeds bidirectionally from a central origin in most units and adjacents units initiate synthesis synchronously. In skin fibroblasts from individuals with Fanconi's anemia or ataxia telangiectasia, the autoradiographic patterns of DNA replication are the same as in controls. This suggests that S phase DNA synthesis is normal in these disorders.
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PMID:Human DNA replication: fiber autoradiographic analysis of diploid cells from normal adults and from Fanconi's anemia and ataxia telangiectasia. 88 Nov 96

The familial occurrence of head and neck cancers supports the role of heredity in this disease group. The roles of environmental and genetic factors are difficult to separate. There are several well-characterized entities, however, that are associated with risk and prognosis of head and neck cancer, including Lynch-II syndrome, Bloom syndrome, Fanconi's anemia, xeroderma pigmentosum, ataxia telangiectasia, and Li-Fraumeni syndrome. Mutagen-induced chromosomal damage is associated with an increased risk of multiple primary neoplasms and upper aerodigestive tract cancers. A possible reduction of genotoxicity, mediated by micronutrients, was demonstrated in vitro. Sister chromatid exchanges and micronuclei are useful exposure and disease markers. Metabolic changes (acetylation, DBQ phenotype, and the AH locus polymorphism) have been found to be associated with cancer of the upper aerodigestive tract. Most associations between histocompatibility antigens and solid tumors are relatively weak, probably because of the masking effects of environmental factors. Infections by HPV, EBV, and HSV have a causative or predisposing role in several types of head and neck cancer. Amplification and rearrangement of oncogenes may also play a role in carcinogenesis, and oncogene amplification may be associated with aggressive tumor behavior and unfavorable clinical prognosis. Ploidy of tumors seems to be an important determinant of survival and response to therapy.
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PMID:Hereditary and environmental factors associated with risk and progression of head and neck cancer. 140 93

Normal human fibroblast (i.e., GM2936B, GM2907A, and IMR-90) and cancer-prone human fibroblast (i.e., Fanconi's anemia, Bloom's syndrome, and Ataxia telangiectasia) cells demonstrated the induction of intracellular and extracellular levels of tissue-type plasminogen activator (t-PA) at 6 and 12 hr, respectively, following ionizing radiation. Induced t-PA enzymatic activities following ionizing radiation were blocked by actinomycin D treatments. t-PA enzymatic activities were induced over 14-fold in Ataxia telangiectasia cells, over 9-fold in Bloom's syndrome cells, and over 6-fold in Fanconi's anemia cells, as compared to normal human fibroblasts. Similarly, the induction of t-PA mRNA levels in cancer-prone cells were between 5- to 10-fold higher than those observed in normal cells following equitoxic doses of ionizing radiation. Temporal induction of t-PA mRNA levels for normal and cancer-prone human cells were consistent with quantifiable enzymatic activities. The elevated induction of an intracellular protease (i.e., t-PA) in cancer-prone human cells is reminiscent of an "SOS"-like response observed in yeast and bacteria.
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PMID:Enhanced induction of tissue-type plasminogen activator in normal human cells compared to cancer-prone cells following ionizing radiation. 144 36

Since all organisms are continuously exposed to exogenous and endogenous DNA damaging agents, mechanisms of repair of DNA lesions are necessary to maintain the integrity of the genome. Studies of the cellular defects in human inherited diseases with deficiencies in DNA repair have given new insights into these processes. Nucleotide excision repair is an important DNA repair pathway in which several types of DNA lesions are removed by a multi-step enzymatic process. This repair mechanism is deficient in the rare disease xeroderma pigmentosum (XP), which results in extreme sensitivity to ultraviolet light (UV) and development of UV-induced skin tumors at an early age. There are several genetic complementation groups of XP. The genes that are mutated in some of the XP complementation groups have been cloned and the functions of the encoded proteins are being characterised. Several types of DNA lesions are removed more rapidly from active genes than from other regions of DNA. This preferential repair of active genes is deficient in Cockayne's syndrome, which is characterised by developmental abnormalities and UV-sensitivity but no marked increase in cancer incidence. Other syndromes associated with increased sensitivity to certain DNA damaging agents where no defect in DNA repair has been defined include Fanconi's anemia (sensitivity to DNA cross-linking agents), hereditary dysplastic nevus syndrome (sensitivity to UV) and ataxia-telangiectasia (sensitivity to ionizing radiation).
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PMID:Inherited defects in DNA repair and susceptibility to DNA-damaging agents. 147 Nov 67

The CT and MRI appearances of 5 patients with Cockayne's syndrome, 5 with ataxia telangiectasia and 1 with Fanconi's anaemia are reported. These conditions, together with Bloom's syndrome and xeroderma pigmentosum are regarded as disorders of DNA repair. Characteristic CT and MRI features of Cockayne's syndrome include generalised atrophy, calcification in basal ganglia and dentate nuclei and white matter low density. Neuroradiological findings in the other DNA repair disorders are nonspecific.
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PMID:Cranial CT and MRI in diseases with DNA repair defects. 160 8


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