Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A long-term cell culture of human glioblastoma was investigated microscopically, virologically, and biochemically. Reverse transcriptase activity was detected in cultured human glioblastoma cells. 3H uridine was incorporated into particles of buoyant density at 1.07 g/ml (Ficoll) which is equal to that of Oncorna virus particles, but 3H thymidine was not incorporated at all. Furthermore, reverse transcriptase activity was also demonstrated with the particles, suggesting that the cultured human glioblastoma cells were producing type C Oncorna virus. Ultrastructural observations of cell culture of glioblastoma showed type C virus particles in cisternae and culture medium. Budding of the virus was also seen on the surface of the cell. The mean diameter of the particles was approximately 100 nm. Ca. 1.1 nm of spikes protruded from the envelope. Both types of virions were observed, i.e. the doughnut-shaped type form and the solid circular form.
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PMID:Type C particles in culture of human glioblastoma cells. 8 68

Glioblastoma multiforme, representing about 50% of all gliomas, encompasses a group of intrinsic tumours of the brain in later years (age peak around 50 years), the morphological hallmarks of which are an ensemble of variations in tumour cell and tissue structure featuring its biological malignancy. Glioblastoma, while sometimes appearing as a distinct "primary" tumour type, is usually accepted as an extreme manifestation of anaplasia and dedifferentiation of glia, mostly astrocytic. The astrocytic nature of most glioblastomas has been confirmed by ultrastructural studies and progressive differentiation of tumours maintained in organotypic tissue culture. Reproducible experimental models are particularly induced by oncogenic RNA (oncorna) viruses. The cell kinetic parameters are similar to those of other solid malignant tumours except for a comparatively low growth fraction of glioblastoma. The frequent occurrence of giant cells as well as of regressive changes with necrosis and vascular responses are indirect (secondary) indicators of malignancy which coincide with histochemical (enzymatic anisochronia) and biochemical data (lower level of glia specific S100 protein than in differentiated gliomas). Vascular proliferation, a characteristic feature of glioblastoma, may occasionally progress to sarcomatous transformation with development of gliosarcomas (mixed glial-mesenchymal tumours). While dissemination of glioblastoma through the cerebrospinal pathways is not uncommon, extraneural distant metastatic spread is rare, and usually observed after craniotomy. The results of modern neuro-oncology support the pathogenetic view that glioblastoma results from neoplastic transformation of glial elements with continuing dedifferentiation. This transformation can be experimentally induced by various factors including oncogenic DNA (oncorna) viruses by using a reverse transcriptase, while there is indirect evidence for an oncorna-virus information in human glioblastoma. The significance of immunological factors in the pathogenesis of brain tumours and in the course of neoplastic transformation of glia is not yet understood, but both morphological and immunological data are in favour of a cell mediated immunological reaction against tumour-specific antibodies. Since immunological factors and changes in cytokinetics are apparently active after the transformed tumour cells proliferate, all available therapeutic methods, including radiation, chemotherapy, and immunotherapy of glioblastoma only influence the final stages of neoplastic development with clinical manifestation of the tumour. In spite of modern combination and multimodality therapy schemes the prognosis of glioblastoma is still poor.
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PMID:Glioblastoma multiforme: morphology and biology. 21 8

The newer methods of molecular virology, including molecular hybridization and the "simultaneous detection test," were used to examine human brain tumors for evidence of RNA tumor viruses. It was found that they contained 70S RNA and RNA-directed DNA polymerase, both encapsulated in a particle possessing a density of 1.17 g/ml. These particles therefore satisfy the three diagnostic features that characterize the animal RNA tumor viruses. Of 26 of the most malignant (glioblastoma and medullo blastoma) brain tumors examined, 24 (92%) contained these virus-like entities. The possible usefulness of these particles as aids in diagnosis and monitoring therapy is briefly discussed.
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PMID:Molecular evidence for a viral etiology of human CNS tumors. 96 99

An infectious proviral clone of the human immunodeficiency virus (HIV) was microinjected into the cell nucleus in six cell lines derived from caprine, ovine, bovine, or human solid tissue to study the utility of this method in effecting viral gene expression in nonlymphoid cells. Immunofluorescence assays for HIV demonstrated viral gene expression in only 5% of cells (100-200 cells per line) 24-48 h after microinjection; however, no reverse transcriptase activity was detectable, presumably due to a low level of virus release in this limited number of cells. Therefore, to indirectly assess infectious virus release, microinjected cells were cocultured with human T4 antigen-positive lymphocytes (H9) sensitive to HIV infection. Syncytia formation, electron microscopy, reverse transcriptase activity, and radioimmunoassay for HIV p24 were used to monitor viral gene expression in cocultures. HIV was efficiently recovered by cocultivating H9 with microinjected cells 48 h after microinjection, regardless of the tissue type or species of origin. H9 syncytia were visualized in some cocultures as early as day 5 but were readily apparent in all experiments on days 7-10. Syncytia induction in H9 was the earliest and most reliable indicator of infectious virus release. A recombinant construct containing a subgenomic envelope gene derived from the proviral clone of HIV was microinjected into human glioblastoma cells. Twenty-four to 48 h after manipulation, 5-20% of microinjected cells were found by immunofluorescence assay to express low levels of a putative gp120. These results suggest a possible approach to producing virus-free HIV envelope antigens in mammalian cells and may be relevant to subunit vaccine development.
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PMID:Microinjection and expression of an infectious proviral clone and subgenomic envelope construct of a human immunodeficiency virus. 283 71

We have previously shown that neoplastic cells of human breast cancers, leukemias, lymphomas, and sarcomas contain particles similar to the viruses that have been established as etiologic agents of these diseases in mice. The present paper concerns tumors of the central nervous system for which no suitable animal model or corresponding virus exists. Nevertheless, using the simultaneous detection test, we showed that human brain tumors contain 70S RNA and RNA-directed DNA polymerase encapsulated in a particulate component possessing a density of 1.17 g/ml. These particles satisfy the three diagnostic criteria that characterize RNA tumor viruses of animals. 24 Out of 26 (92%) of the most malignant (glioblastoma and medulloblastoma) brain tumors examined contained these virus-like entities.
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PMID:Particles with RNA of high molecular weight and RNA-directed DNA polymerase in human brain tumors. 412 27

Expression of nitric oxide synthase (NOS) was studied in nine human neuroblastoma and two human glioblastoma cell lines. Neuronal NOS (n-NOS) mRNA of approximately 10 kb was detected in four of the nine neuroblastoma cell lines by northern blot analysis using human n-NOS cDNA as a probe. Expression of the n-NOS mRNA was also detected in another neuroblastoma cell line in a subsequent reverse transcriptase polymerase chain reaction (RT-PCR) study, but no n-NOS mRNA expression was observed in the other four neuroblastoma cell lines or in the glioblastoma cell lines. The level of NOS activity correlated well with that of n-NOS mRNA expression in neuroblastoma cell lines expressing n-NOS mRNA. Western blot analysis showed that the n-NOS expressed in neuroblastoma cells was a 160-kDa protein reacted with anti-n-NOS antibody. By using the RT-PCR method, a short n-NOS (n-NOS-2) mRNA with a 315-bp inframe deletion from the entire n-NOS (n-NOS-1) mRNA was detected in the human neuroblastoma cells. The structural diversity of human n-NOS mRNA was demonstrated for the first time.
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PMID:Expression of two types of nitric oxide synthase mRNA in human neuroblastoma cell lines. 751 42

Molecular processes resulting in the malignant transformation from low- to high-grade astrocytoma remain poorly understood. Using reverse transcriptase PCR, we identified a gene that is differentially expressed in normal brain and low-grade astrocytoma compared to glioblastoma tissues. This gene is identical to human beta 2-chimaerin, which encodes a 468-amino acid GTPase-activating protein for p21rac. The gene was localized to human chromosome 7p15.3 by fluorescence in situ hybridization mapping. Human beta 2-chimaerin is expressed in a variety of human tissues, with the highest expression level detected in human brain and pancreas. RNase protection assays indicated that the expression level of this gene is high in all the normal brain and low-grade astrocytoma samples tested compared to malignant gliomas. The down-regulation of beta 2-chimaerin expression in the high-grade gliomas suggests that decreased expression of this gene may be a feature of progression in the development of malignant glioma.
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PMID:Identification and characterization of human beta 2-chimaerin: association with malignant transformation in astrocytoma. 761 86

The c-myb protooncogene plays a major role in regulating the process of in vitro and in vivo hematopoiesis via its activity as transcriptional regulator in hematopoietic progenitor cells. Since the bone marrow microenvironment appears to regulate in vivo hematopoiesis by maintaining the growth of multipotent progenitors via secretion of specific cytokines, we asked whether c-myb is also required for the proliferation of and/or cytokine production by stromal cells that generate fibroblast-like colonies (fibroblast colony-forming units [CFU-F]). Using the reverse transcriptase polymerase chain reaction technique, we detected low levels of c-myb mRNA transcripts in human normal bone marrow fibroblasts. Treatment of these cells with c-myb antisense oligodeoxynucleotides caused downregulation of c-myb expression, decreased in the number of marrow CFU-F colonies (approximately 54% inhibition) and in the cell number within residual colonies (approximately 80%), and downregulation of granulocyte/macrophage colony-stimulating factor (GM-CSF) and stem cell factor (SCF) mRNA expression. Transfection of T98G glioblastoma cells, in which expression of c-myb, GM-CSF, and SCF mRNAs is undetectable or barely detectable, with a plasmid containing a full-length c-myb cDNA under the control of the SV40 promoter induced the expression of biologically active SCF and GM-CSF in these cells. Regulation of GM-CSF expression by c-myb was due in part to transactivation of the GM-CSF promoter. These results indicate that, in addition to regulating hematopoietic cell proliferation, c-myb is also required for proliferation of and cytokines synthesis by bone marrow fibroblasts.
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PMID:Regulation of proliferation and cytokine expression of bone marrow fibroblasts: role of c-myb. 768 94

Interleukin 10 (IL-10) was initially discovered on the basis of its ability to suppress cytokine synthesis. Additionally, it can exert immunosuppressive effects on a variety of cell types. Because patients with malignant gliomas present with a general impairment of the immune system, we investigated IL-10 expression in the glioma tissue. Because expression of IL-10 and IL-6 is associated in hematopoietic cells and IL-6 can act as an autocrine growth stimulator for glioblastoma cell lines, we looked in addition for a relationship between IL-10 and IL-6 expression. Using a quantitative reverse transcriptase polymerase chain reaction, IL-10 and IL-6 mRNA levels were determined in 37 glial tumors of different grades including 2 recurrencies, 3 specimens from normal brain tissue, and 3 glioblastoma cell lines. Expression of IL-10 mRNA was demonstrable in all tumors as well as in normal brain. High grade tumors and recurrent cases expressed significantly higher amounts of IL-10-specific mRNA compared with low grade tumors, whereas 2 of 3 cell lines showed only weak constitutive expression, mRNA for IL-6 was found in 86.5% of all gliomas with a correlation concerning the expression levels for both cytokines in 69% of gliomas. We suggest that IL-10 may contribute to the progression of astrocytomas by suppressing the patient's immune response, whereas IL-6 provides an additional growth advantage.
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PMID:Messenger RNA expression of the immunosuppressive cytokine IL-10 in human gliomas. 785 43

Expression of CD44 and of specific splice-variants of CD44 has been causally related to metastatic behaviour in a variety of carcinomas and lymphomas. To elucidate whether, in principle, similar splice-variants could be involved in glioma cell invasion we examined the expression of CD44 and its splice-variants in a series of 38 primary human brain tumors (28 astrocytomas, WHO grade I-III and 10 glioblastomas, WHO grade IV) and in cell lines derived from 9 glioblastomas. All brain tumors examined showed strong immunoreactivity for an N-terminal epitope present on all CD44 isoforms known. Using a polyclonal antiserum raised against the complete sequence encoded by variant exons v3 to v10, CD44 splice-variants could be detected irrespective of the grade of malignancy in many of the tumor samples at a low level and often restricted to only a few clustered tumor cells. Thus, the N-terminal epitope probably indicates the presence of the smallest and most ubiquitous isoform CD44s. Interestingly, all glioblastomas expressed CD44 variants whereas expression in astrocytomas WHO grade I, II, and III could only be detected in about half of the tumor samples. Using reverse transcriptase-PCR we were able to detect different CD44 splice-variants in the glioblastoma cell lines and in cultured primary astrocytic cells. Glioblastoma cells analyzed by flow cytometry showed the expected binding capacity for hyaluronic acid which could be increased twofold after pretreatment with hyaluronidase. The results presented show that there is low expression of CD44 variants in human tumors of astrocytic origin. Expression of CD44 and its splice-variants could contribute to the migration capacity of neoplastic astrocytes, and may be considered as a target for new diagnostic and therapeutic approaches in the clinical management of brain tumors.
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PMID:Expression of variant CD44 epitopes in human astrocytic brain tumors. 875 Jan 82


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