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Biomedical subjects

G B Rossi

Publications and source records attributed to G B Rossi.

At least 73 records · Page 4Linked to original sources
PubMed1987

Recovery of HIV-related retroviruses from Italian patients with AIDS or AIDS-related complex and from asymptomatic at-risk individuals.

Human retroviruses have been detected in supernatants of cultures of Ficoll-enriched lymphocytes from peripheral blood, lymph nodes and bone marrow of (a) 32 out of 42 patients with Acquired Immunodeficiency Syndrome (AIDS), (b) 34 out of 64 patients with AIDS-related Complex (ARC), (c) 9 out of 18 asymptomatic children born from Human Immunodeficiency Virus (HIV) seropositive mothers, and (d) 9 out of 28 asymptomatic drug abusers or hemophiliacs. Virus detection was monitored by assaying culture supernatants for the presence of Mg++-dependent reverse transcriptase (R.T.) activity. A number of these virus-positive sups were passaged repeatedly in cultures of phytohemagglutinin-stimulated and Interleukin-2 (IL-2) treated fresh lymphocytes from healthy blood donors. Occasionally, multiple samples were obtained at varying time intervals from the same patient and consistently yielded detectable retroviral activity. Several isolates were characterized as closely related if not identical to HIV, HTLV-IIIB strain, since cells from either patients' own lymphocyte cultures or subcultures infected with passaged virus were stained in an indirect immunofluorescent assay with both patients sera and monoclonal antibody against p24 antigen of the HTLV-IIIB strain. Representative isolates, grown on fresh lymphocytes of healthy donors and metabolically labelled with 35S-cysteine, were also analyzed in a radioimmunoprecipitation assay (RIPA) against patients' sera to define their antigenic pattern, which was widely superimposable to that obtained with HTLV-IIIB-infected H9 cells. DNA from lymphocytes infected with 2 representative isolates were Southern-blotted and probed with an insert from a plasmid containing the entire genome of the HTLV-IIIB strain. The hybridization patterns were comparable with those obtained with DNA from H9-infected cells.

AIDS-Related Complex↗
PubMed1986

Interferon production in L929 cells under impaired translational conditions: comparison of rates of interferon, actin, Newcastle disease and encephalomyocarditis viruses mRNAs initiation of protein synthesis.

The pattern of Interferon (IFN) production in virus-infected cells has been compared with the rate of bulk cellular protein synthesis, on one hand, and with the synthesis of representative cell and virus proteins such as actin, the gamma and the NP proteins of encephalomyocarditis (EMC) and Newcastle Disease (NDV) viruses, on the other hand. This was investigated under conditions of impaired protein synthesis such as i) high osmolarity media, ii) a virus-induced shut-off, and iii) in cells exposed to relatively low doses of cycloheximide (CXM), which slow elongation of protein chain and thus favour the translation of low-affinity messenger RNAs (mRNAs). In each instance IFN production was compared with 35S-methionine incorporation into TCA-precipitable materials and into SDS-polyacrylamide gel-analysed proteins. Data obtained from each of the experimental approaches all indicate that IFN production and cellular protein synthesis are modified in a closely related fashion suggesting that their mRNAs share a similar degree of affinity for ribosomes. Conversely, two mRNAs coding for representative EMC and NDV virus proteins exhibit, respectively, the highest and the lowest affinity for ribosomes as compared to actin mRNA.

Actins↗
PubMed1986

Natural resistance in mice against Friend leukemia cells. I. Studies with in vitro passaged interferon-sensitive and interferon-resistant cell clones.

Anti-lymphoma natural resistance (NR) has been detected in DBA/2 mice inoculated intravenously (iv) with syngeneic Friend leukemia cells (FLC). Interferon-sensitive 745 or interferon-resistant 3Cl-8 clones, passaged in vitro and exhibiting "low" tumorigenicity in syngeneic DBA/2 mice, were used. NR, measured as rapid clearance of radiolabeled cells from lung and liver of recipient mice, was age-dependent, was boosted by host pretreatment with polyinosinic-polycytidylic (poly I:C) acid or Friend leukemia virus, and was decreased by mice pretreatment with cyclophosphamide or i-carrageenan. Treatment of "target" FLC with interferon suppressed the susceptibility of 745 FLC, but not that of 3Cl-8 FLC to host's NR. These data suggest that the "low" in vivo tumorigenicity of in vitro passaged FLC is, at least in part, due to host's NR directed against target structures associated with leukemia cells.

Aging↗
PubMed1986

2',5'-Oligoadenylate synthetase-uninducible alpha/beta-interferon-resistant Friend cells develop an antiviral state when permeabilized with lysolecithin and treated with 2',5'-oligoadenylate oligomers.

Variant sublines of Friend erythroleukemia cells (FLC) that do not respond to alpha/beta-interferon (IFN-alpha/beta) by developing an antiviral state but respond partially to IFN-gamma with an induced antiviral state, lack the ability to induce the 2',5'-oligoadenylate (2-5A) synthetase pathway. Exposure of wild-type and variant cells to exogenous 2-5A oligomers made permeable with lysolecithin resulted in 50-70% inhibition of protein synthesis. Further, the replication of vesicular stomatitis virus in IFN-resistant 2-5A synthetase-deficient FLC exposed to 2-5A trimer was inhibited to the same extent as in wild-type cells. Last, a significant cleavage of ribosomal RNA was observed in samples of total RNAs extracted from variant and wild-type permeabilized FLC, but only if they were exposed to 2-5A. These data are compatible with the conclusion that (i) the activation of the 2-5A-dependent endoribonuclease is not impaired in the variant cells, and (ii) the uninducibility of 2-5A synthetase can be bypassed by exogenously introducing its products, which leads to the establishment of a bona fide antiviral state.

2',5'-Oligoadenylate Synthetase↗
PubMed1986

Immunohistochemical demonstration of p24 HTLV III major core protein in different cell types within lymph nodes from patients with lymphadenopathy syndrome (LAS).

The p24 protein is the major core protein of LAV/HTLV III which is the putative agent of the lymphadenopathy syndrome. By the use of an anti-p24 monoclonal antibody we have studied the presence of LAV/HTLV III infected cells in 20 lymph nodes obtained from lymphadenopathy syndrome patients: 14 lymph nodes were characterized by prominent follicular hyperplasia consistent with the early phase of the syndrome and six lymph nodes presented marked regressive changes. Cells positive for p24 were detected in 8/14 lymph nodes with hyperplastic changes and in 1/6 lymph nodes with regressive changes. Positive cells were most often located in germinal centres and were mainly characterized by a lymphoid morphology. However, immunoreactivity for p24 protein was also occasionally observed in some histiocytic-like cells and in high endothelial cells of post-capillary venules, suggesting that these 'accessory cells' also play a role in the early phases of the lymphadenopathy syndrome.

Adult↗
PubMed1986

Proliferative response and oncogene expression induced by epidermal growth factor in EL2 rat fibroblasts.

Extensive evidence supports a two-step model for the control of fibroblast growth, which includes first the action of a competence factor (e.g., platelet-derived growth factor) followed by the stimulus of a progression factor (e.g., epidermal growth factor [EGF]). We investigated whether this model may be applied to the euploid EL2 fibroblast line recently isolated from rat embryos (E. Liboi, M. Caruso, and C. Basilico, Mol. Cell. Biol. 4:2925-2928, 1984). Our results clearly show that EGF alone leads EL2 cells to proliferate in serum-free conditions at a rate corresponding to 50 to 60% of that observed in the presence of 10% calf serum. It is of interest that, when resting EL2 cells were exposed to EGF, transcription of both c-myc and c-fos was markedly induced. Altogether, these observations suggest that, in contrast with the model of fibroblast growth mentioned above, EL2 cells require the presence of a single growth factor (EGF) for induction of DNA synthesis, and the expression of myc and fos proto-oncogenes may represent an obligatory step in the pathway of commitment of EL2 cells to proliferation. In addition, we showed that EGF may induce EL2 cells to acquire some properties of transformed cells, such as growth in agar and loss of contact inhibition. This suggests that the particular response to EGF of the EL2 line may be strictly connected with the expression of a transformed phenotype.

Animals↗
PubMed1985

Establishment of the antiviral state in alpha, beta-interferon-resistant Friend cells treated with gamma-interferon. Induction of 67-kilodalton protein kinase activity in absence of detectable 2-5A synthetase.

Treatment with murine gamma-interferon (IFN) preparations of variant sublines of Friend leukemia cells resistant to the alpha, beta IFN-induced antiviral state (Affabris, E., Jemma, C., and Rossi, G.B. (1982) Virology 120, 441-452; Affabris, E., Romeo, G., Belardelli, F., Jemma, C., Mechti, N., Gresser, I., and Rossi, G. B. (1983) Virology 125, 508-512) results in the establishment of a bona fide antiviral state. In fact, gamma IFN preparations are able to induce a dose-dependent reduction of endogenous virus release and of vesicular stomatitis or encephalomyocarditis viruses yields (up to 1.5 log). Under these experimental conditions, no inducible 2-5A synthetase activity is detectable in cell extracts. The 67-kDa protein kinase, uninducible by treatment with alpha, beta IFN (up to 13,000 units/ml), is instead induced upon treatment with gamma IFN at a similar rate of activity as in wild-type Friend leukemia cells, both when assayed in solution and after immobilization on poly(rI) X poly(rC)-agarose.

2',5'-Oligoadenylate Synthetase↗
PubMed1985

Induction and/or selective retention of proteins in mammalian cells exposed to cycloheximide.

Exposure of a number of murine and human cell lines to low graded doses of cycloheximide (CXM) results in a pattern of protein synthesis consisting of enhanced and induced species. These can be divided into two main classes according to molecular weight (20-40 and 70-120 Kd), similar to what has been described for other agents that modify the physiological conditions of growth. In addition, the pronounced synthesis of a hitherto unreported 50-Kd protein species has been consistently observed in all lines tested. Simultaneous exposure of cells to CXM and actinomycin D results in suppressing synthesis of some but not all protein species observed, indicating that control mechanisms at both transcriptional and posttranscriptional levels may be operative in this system.

Animals↗
PubMed1984

Role of interferon and 2',5'-oligoadenylate synthetase in erythroid differentiation of Friend leukemia cells. Studies with interferon-sensitive and -resistant variants.

It has been suggested that the interferon (IFN)-induced 2',5'-oligoadenylate (2-5A) synthetase, which polymerizes ATP into a series of 2',5'-linked oligomers with the general formula pppA(2'p5'A)n, plays a general role in cell growth and terminal differentiation. For instance, an increase in 2-5A synthetase activity has been described during dimethyl sulfoxide (Me2SO)-induced erythroid differentiation of Friend leukemia cells (FLC). 2-5A synthetase has been measured in two Friend leukemia cell sublines by various techniques including a radioimmunoassay of its products which would detect 10(-16) mol of 2-5A cores. Although cells of both sublines fully differentiate (as measured by benzidine staining), only in one subline was there an increase in 2-5A synthetase activity upon treatment with Me2SO. Hexamethylenebisacetamide, another potent agent of differentiation in this system, did not increase 2-5A synthetase activity in either of these two sublines. An IFN-resistant FLC variant differentiated normally upon treatment with Me2SO or hexamethylenebisacetamide while it was noninducible for 2-5A synthetase activity by exogenous IFN or by the inducers themselves. A similar situation has been observed with regard to the level of phosphorylation of the IFN-induced Mr = 67,000 protein band. In addition, treatment of IFN-sensitive and resistant FLC sublines with mouse alpha beta IFN antiserum did not affect differentiation. Even though we have duplicated previous findings on the increase of 2-5A synthetase activity in Me2SO-induced FLC, the lack of any such increase with other inducers or other sublines indicates that there is no causal relationship between the enzyme activation and FLC differentiation.

2',5'-Oligoadenylate Synthetase↗