Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The C and oxyphil cells of the human thyroid are analyzed in the light of recent advances in cellular biology, cytochemistry, and histopathology. The C cell is present in the normal human thyroid, where its identification is cardinally by means of argyrophilic cytoplasmic granules. The morphology, topography and argyrophilia of C cells are discussed with reference to tumor, cyst, and teratoma formation in the thyroid gland. Oxyphil cells of the thyroid are cytochemically akin to C cells but arise from follicular cells. They occur in the thyroid and other protein-producing organs, but are themselves inefficient producers of proteins and glycoproteins. Speculation is made on their morphological characteristics, and consideration is given to DNA-RNA involvement in the functional and morphological alterations of this follicular cell type.
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PMID:The oxyphil and C cells of the human thyroid gland. A cytochemical and histopathologic review. 5 94

Particles possessing a density of 1.16 g/ml and encapsulating a 70S RNA and a RNA-instructed DNA polymerase (reverse transcriptase) have been prepared from the spleen of a patient with chronic lymphocytic leukemia. These particles have been converted to cores with a density of 1.26 g/ml and containing the enzyme-RNA complex, in complete analogy to the known RNA tumor viruses of avian and murine origin. The reverse transcriptase was purified from the cores by column chromatography to a stage showing a single major protein band of 70,000 daltons in a gel electrophoresis. The enzyme was capable of transcribing heteropolymeric RNA into DNA complements as demonstrated by specific back hybridization to template RNA. The leukemic spleen would appear to represent an important source of this enzyme, as well as other potentially important leukemia-specific reagents.
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PMID:Purification of RNA-instructed DNA polymerase from human leukemic spleens. 5 34

Virions of Moloney murine leukemia virus can synthesize two classes of DNA molecules complementary to their 70S RNA. One class consists of molecules about 200 nucleotides long, which are of limited sequence complexity; these molecules are formed preferentially if the dNTP concentration during the reaction is low. The second class consists of very heterogeneous DNA molecules with weight-average size of about 1,000 nucleotides containing at least 70% of the viral RNA sequences in approximately equal concentration. The longest of these molecules can be 5,000 nucleotides long. This second class of DNA is formed in large amounts only in reactions containing dNTP concentrations of 0.2 mM or higher. In such reactions after 24 h of incubation, at least 35% of the input RNA is represented in DNA copies. The ability to make long, representative DNA transcripts of tumor virus RNA provides a source of excellent probes for molecular hybridization.
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PMID:Synthesis of long, representative DNA copies of the murine RNA tumor virus genome. 5 41

DNA polymerase from RNA tumor viruses ("reverse transcriptase") has been analyzed for activities which have been associated with other DNA polymerases. Homogeneous DNA polymerase from avian myeoblastosis virus catalyzes pyrophosphate exchange and pyrophosphorolysis. Pyrophosphate exchange is dependent on a template and is base-specific. With avian myeloblastosis virus DNA polymerase, ribonucleotide templates are more efficient for synthesis while deoxyribonucleotide templates are more effective for pyrophosphate exchange. Synthesis, pyrophosphate exchange, and pyrophosphorolysis were inhibited by the chelating agent 1,10-phenanthroline, suggesting that enzyme-bound zinc is required for each of these reactions. The pyrophosphate exchange reaction was also demonstrated with the DNA polymerase from a mutant of Rous sarcoma virus that possesses a temperature-sensitive DNA polymerase. The pyrophosphate exchange reaction with the mutant polymerase is temperature-sensitive which demonstrates that pyrophosphate exchange is indeed catalyzed by the viral DNA polymerase and that the same mutation effects both DNA polymerase and pyrophosphatase activity. Unlike Escherichia coli DNA polymerase I, the DNA polymerase from avian myeloblastosis virus fails to degrade polydeoxyribonucleotides or to convert deoxynucleoside triphosphates into monophosphates. This lack of hydrolytic activities in avian myeoblastosis DNA polymerase should facilitate kinetic studies on the mechanism of DNA synthesis by this enzyme.
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PMID:On the fidelity of DNA replication. Enzyme activities associated with DNA polymerases from RNA tumor viruses. 5 14

Human CSF cells in cases of non-neoplastic disease of the central nervous system (CNS) were examined in vitro by 3H-thymidine autoradiography. Immediately after withdrawl by lumbar or ventricular puncture, the CSF was incubated in a sedimentation chamber at 37 degrees C for 1 hr with an admixture of 3H-thymidine at a concentration of 1-2 muCi/ml CSF. In a few cases the CSF withdrawn was incubated in a glass tube in the same condition as in a sedimentation chamber, and the CSF cells were collected by centrifugation. The CSF cells collected were fixed in methanol and the microautoradiographic procedure was performed. Labeled CSF cells were found in 21 cases out of 22. The average labeling index of the total nucleated cells was 0.22% with the highest labeling of 0.74%. Almost all the labeled cells were thought to be medium to large sized lymphocytes and monocytoids. Peripheral blood was examined by a similar method and the results were compared with those of the CSF. It may be noteworthy that thre exist DNA synthesizing cells in the CSF even in a non-neoplastic state of the CNS, although the number is not large.
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PMID:3H-thymidine autoradiography of the CSF cells in cases of non-neoplastic disease. 5 87

In vitro transformation of BHK 21/13 cells by chemical carcinogens is reported. The hamster cells were treated with MCA, BP, 4-NQO and 5-azaCR at various concentration and duration of treatment. The morphological, karyological and growth characteristics of cell lines were investigated. Search for RNA tumor viruses in transformed cells using 3H-uridine labeling, detection of DNA polymerases, electron microscopy investigations failed to detect presence of C-type virus particles.
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PMID:Transformation of BHK 21/13 cells by chemical carcinogens and mutagens. 5 82

1-beta-D-Arabinofuranosylcytosine (cytarabine; ara-C) and 5-azacytidine (5-azaCR), cytosine nucleoside antimetabolites with different mechanisms of action, are both effective in the treatment of human leukemia, and the clinical use of these two agents in combination has been suggested. We have studied the therapeutic effect in L1210 leukemic mice of single i.p. doses of ara-C and 5-azaCR in combination. Therapeutic effects observed depended markedly on the sequence and time interval between the doses of each agent. Antagonism was observed when both agents were administered simultaneously. The optimal therapeutic effect was observed when 5-azaCR was administered after ara-C at a time when tumor DNA synthesis had maximally recovered after the ara-C dose. The dose-interval effect and correlation with recovery of DNA synthesis capacity were also observed in studies in vitro in which the survival of L1210 cells in culture was examined. ara-C was shown to inhibit the incorporation of [4-14C]-5-azaCR-derived radioactivity into DNA of L1210 cells in culture, and the therapeutic effects observed are interpreted in terms of these latter results and the mechanisms of action of the two agents.
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PMID:Combination chemotherapy of L1210 leukemia with 1-beta-D-arabinofuranosylcytosine and 5-azacytidine. 5 29

The interactions between bleomycin and X-ray damage and repair have been examined in rat and human tumor cells. Bleomycin itself indices extensive DNA single-strand breaks but does not appear to inhibit the repair of X-ray-induced DNA single-strand breaks. Quantitative analysis of these interactions is complicated by the retention of active bleomycin within cells that remains capable of further DNA degradation even under the conditions of alkaline sucrose gradient cell lysis. DNA double-strand breaks and/or disruptions of DNA-lipid complexes also occur following bleomycin exposure. X-ray-induced excision repair replication is only minimally influenced by even high concentrations of bleomycin. A small amount of excision repair is demonstrable in nonirradiated cells treated with high concentrations of bleomycin consistent with repair of bleomycin-induced nucleotide damage in cellular DNA by a "cut and patch" repair mechanism. Repair of bleomycin-induced DNA single-strand breaks also occurs. The data indicate that bleomycin and X-ray damage are quite similar both in their induction and repair, but that lesions occur and are repaired independently. The enzymatic mechanisms appear similar in the two cell types despite substantial differences in their sensitivity to bleomycin.
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PMID:Molecular interactions of the combined effects of bleomycin and x-rays on mammalian cell survival. 5 30

Cultured peripheral blood leukocytes from a woman (patient HL23) with acute myelogenous leukemia produced type-C RNA tumor viruses (HL23V). The viruses were analyzed by molecular hybridization experiments after transmission to five secondary cell culture lines. Using the criteria of molecular hybridization, we concluded that all of the transmitted virus isolates have nucleotide sequences related to the genome of simian sarcoma virus (SiSV). In addition, in agreement with data reported elsewhere, some of the transmitted viruses also have nucleotide sequences related to those of the baboon endogenous virus (BaEV). We also used molecular hybridization to ascertain whether both viruses could have originated from the patient HL23. Utilizing [3H] cDNA complementary to RNA from the separated BaEV-related component of HL23V and hybridizing this cDNA to DNA from tissues of the patient, we detected sequences related to BaEV in DNA obtained from the patient's spleen. These BaEV DNA sequences were also detectable when 125I-labeled RNA from BaEV was used as a probe. In agreement with earlier results, however, no SiSV-related sequences were detectable in the DNA of her tissues. Cytoplasmic viral-like particles, which had a buoyant density of 1.15-1.2 g/ml and were capable of synthesizing cDNA in association with a 35S RNA in vitro, were also found in the patient's fresh uncultured leukemic blood cells. cDNA synthesized by the cytoplasmic particles contained some sequences that hybridized to RNA from SiSV and, in addition, some that hybridized to RNA from BaEV. The cDNA also hybridized significantly to DNA isolated from the spleen of patient HL23 and to cytoplasmic RNA from the patient's leukocytes. These molecular hybridization results with nucleic acids obtained from the fresh blood cells of the patient, combined with the repeated isolation of similar viruses from different blood and bone marrow samples from the same patient, suggest that the virus come directly from the leukemic cell samples. The finding of BaEV-related DNA proviral sequences in the spleen of the patient strongly supports this interpretation. The failure so far to find a complete SiSV-related provirus is perplexing, but could be attributable to the existence of such a provirus in DNA of only a small population of cells in most leukemic patient.
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PMID:Primate type-C virus nucleic acid sequences (woolly monkey and baboon types) in tissues from a patient with acute myelogenous leukemia and in viruses isolated from cultured cells of the same patient. 5 61

Several human prostatic tissues have been examined for possible particles and associated DNA polymerizing activity generally associated with the C-type RNA tumor virus family. Partially purified tissue extracts, when centrifuged to equilibrium in sucrose gradients, yield fractions which contain actinomycin D resistant, endogenous DNA polymerase activity; this activity bands at a density of 1.15-1.18 gm/cm3. Further analysis of the endogenous products by sucrose gradient sedimentation suggested the presence of high molecular weight RNA:DNA hybrids generally felt to be indicative of a faithful copy of a lengthy stretch of viral specific RNA. However, most of the DNA products synthesized in these endogenous reactions sedimented in much lower molecular weight regions of these sucrose gradients. Clearly, the relative distributions of "high" and "low" molecular weight products could critically depend on the nuclease content of the subcellular fraction under study, and the prostate may be relatively enriched in nucleases. Further, oligo (dT) stimulated the endogenous DNA polymerase activity contained in these extracts, and omission of one of the DNA precursor nucleotides depressed it. Thus, it seems unlikely that terminal transferase activity, rather than genuine DNA polymerization, was being measured primarily. Because of the spectrum of molecular weight classes formed by these DNA:RNA hybrids, as well as their apparent presence in normal prostatic tissue, we find it difficult to ascribe their presence with certainty either to the presence of typical C-type RNA viruses or to the exclusive behavior of the neoplastic prostatic tissue. Thus, our studies lend support to the growing evidence for functions similar to those of C-type RNA viruses being relatively widespread in human tissues without the apparent necessity for a possible etiologic role in neoplastic production (Strand and August, 1974; Sherr et al., 1974). At the same time, our current studies emphasize the need for caution in drawing conclusions from results utilizing probes generally felt quite useful in scoring for presence of virus in lower animals at least in the human prostate.
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PMID:RNA tumor virus-like activities in human solid tissues: endogenous RNA:DNA polymerase activities in the prostate. 5 36


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