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M Righi

Publications and source records attributed to M Righi.

36 records · Page 2Linked to original sources
PubMed1991

Mouse macrophage clones immortalized by retroviruses are functionally heterogeneous.

Murine macrophage clones were generated from thymus, spleen, brain, and bone marrow by in vitro immortalization with recombinant retroviruses carrying an avian v-myc oncogene. The cloned cell lines express F4/80 molecules, exert phagocytosis, have nonspecific esterase activity, and express class II molecules after interferon gamma activation. The macrophage clones are diploid and their karyotypes have remained stable for greater than 3 years in culture. After the macrophage clones were activated, their pattern of cytokine production was investigated. Functional heterogeneity in cytokine transcription was demonstrated: one of six liposaccharide-activated macrophages was unable to transcribe interleukin 1 alpha, whereas all of the liposaccharide-activated clones were able to transcribe tumor necrosis factor alpha. Interleukin 6 production was detected in three of six clones. The production of nitrite and tumor necrosis factor alpha as effector molecules of cytotoxicity was detected in all clones, thus showing that a single macrophage can exert more than one cytotoxic mechanism. The results indicate that immortalized and cloned macrophages have a differentially regulated expression of cytokine genes, adding further evidence for the existence of functional heterogeneity among cloned macrophages. This heterogeneity seems to derive from differentiation-related mechanisms rather than from external constraints.

Animals↗
PubMed1991

Activation of the M-CSF gene in mouse macrophages immortalized by retroviruses carrying a v-myc oncogene.

We have recently immortalized murine brain macrophages (microglial cells) with a complex of retroviruses (3RV) transducing separately the myc and mil oncogenes. Surprisingly, the immortalized cells harboured an exogenous v-myc oncogene, but no v-mil sequences. The transformed macrophage cell lines grew in vitro without the addition of exogenous growth factors and were also able to grow in vivo in nude mice. In addition, they released oncogenic retroviruses able to immortalize mouse macrophages from primary splenic or thymic cultures. Molecular cloning of the provirus (VN-11) harboured in a microglial clone demonstrated that no cell-derived sequences apart from an avian v-myc gene were transduced by the recombinant retrovirus. When cells were tested for production of myeloid growth factors, they were found to transcribe and synthesize the Macrophage-Colony Stimulating Factor (M-CSF). The correlation between viral infection and activation of the M-CSF gene was tested using a M-CSF dependent cell line from which growth factor independent clones could be readily obtained after infection. The synthesis of M-CSF was detected only in cells expressing the avian v-myc protein. These data support the hypothesis that, in our conditions, macrophages can be immortalized by the expression of v-myc and the concomitant establishment of an autocrine loop triggered by viral infection.

Animals↗
PubMed1990

Cellular sources and effects of tumor necrosis factor-alpha on pituitary cells and in the central nervous system.

Cytokine-mediated communication between the immune system and the nervous system has been shown in the past few years. The precise cellular sources of these molecules in the brain is still a controversial issue. We have thus immortalized primary cell cultures from mouse embryonic brains to analyze cloned cells involved in cytokine production. The cell clones obtained were identified as microglial cells and shown to produce several monokines. Among these, TNF alpha was detected by molecular analysis and cytotoxicity assays and shown to be expressed by microglial cells, after activation with LPS. Surprisingly, the TNF alpha-mediated cytotoxic activity, which was neutralized by specific antisera, was not detected in the cell supernatants but was mediated through cell-to-cell contact. Using antibodies to TNF alpha in FACS analysis, specific cell membrane staining on live microglial cells was shown. The results suggest that in the brain the form of TNF alpha detectable by standard procedures is the cell bound form and not the most common form, secreted TNF alpha. In addition, the effects of recombinant TNF alpha in vitro and in vivo were evaluated. In vitro, rTNF alpha stimulated beta-endorphin, GH, and PRL release from cultured cells prepared from rat anterior pituitary glands. In vivo, the administration of rTNF alpha to rats was able to modify analgesic responses. The concomitant administration of naloxone, an opiate receptor antagonist, or monoclonal anti-IL-1 antibody decreased the analgesic effects induced by rTNF alpha. This indicates that the analgesic effect might not be mediated directly by rTNF alpha but by other mediators, whose action is under the control of TNF alpha.

Animals↗
PubMed1989

Monokine production by microglial cell clones.

Cytokines have been suggested to act as intermediates between the immune and the central nervous system, but little is known about the type of cells synthesizing them in the brain. We have immortalized with oncogenic retroviruses primary brain cell cultures from mouse embryos and have generated clones of microglial cells that have been characterized. Three of the clones studied produce interleukin 1 (IL 1); IL 6 and tumor necrosis factor-alpha as assessed by biological assays and by Northern blot analysis. Our data raise the question on the role of these cytokines in the brain and suggest that early resident microglial cells might play an important role in development processes and in the adult brain.

Animals↗
PubMed1989

Generation of new oncogenic murine retroviruses by cotransfection of cloned AKR and MH2 proviruses.

We have obtained a set of oncogenic recombinant retroviruses, the 3RV complex, by cotransfecting murine fibroblasts (SC-1 cells) with plasmids containing the cloned genomes of the avian MH2 and murine AKR viruses. The transfected culture (TAM-2) was shown to release murine transforming viruses by means of reverse transcription and focus formation assays. Analysis of TAM-2 intracellular RNA revealed new transcripts hybridizing with the oncogenes myc and mil and cross-hybridizing with an AKR probe. The biological activity of the 3RV complex was tested for the induction of murine macrophage proliferation in the absence of exogenous growth factors, a property described as the result of mil and myc cooperativity. Cell-free supernatants from 3RV transformed fibroblasts were indeed able to induce the proliferation of macrophage-like cells from murine bone marrow and spleen primary cultures. Such cultures were capable of continuous growth and showed independence from exogenous myeloid growth factors. The cells expressed antigenic markers and functional properties specific of the monocytic-macrophage lineage. These results suggest that transfection-induced recombination could be a novel way to generate biologically active recombinant retroviruses.

Animals↗
PubMed1985

Rearrangement and expression of the antigen receptor alpha, beta and gamma genes in suppressor antigen-specific T cell lines.

The rearrangement and transcription of the antigen receptor alpha, beta and gamma genes were investigated in murine antigen-specific suppressor T cell lines, to establish whether the suppressor T cell subset expresses the same antigen receptor transcripts previously found in helper and cytotoxic T lymphocytes. The genomic organization of the alpha, beta and gamma chain loci was investigated using probes representative of the entire gene or fragments from variable, joining and constant regions. The present results show that in functional suppressor T cells the three antigen receptor genes are all rearranged. The beta gene is expressed in all the tested cell lines, while the expression of the alpha and gamma genes is variable. In one cell line (LH8) alpha and gamma genes are not efficiently transcribed; in the other cell line (LA41) the gamma mRNA is found in amounts similar to beta mRNA, whereas the alpha gene is expressed at low levels. These data suggest that in suppressor T cells no direct correlation exists between the expression of alpha, beta and gamma antigen receptor genes and the effector function.

Animals↗
PubMed1984

The second oncogene mil of avian retrovirus MH2 is related to the src gene family.

The nucleotide sequence of a PstI fragment prepared from a cloned MH2 virus genome, pMH2-Hd, has been deduced using chemical and enzymatic methods. This fragment, 1862 nucleotides in length, starts with the gag gene, encodes the v-mil sequence and stops within the v-myc gene. This sequence shows that the v-mil gene is fused to the gag gene giving rise to a fused polyprotein of 98 000 daltons: 515 amino acids at the amino terminus would correspond to p10, p19, p27 and part of p12 determinants, 347 amino acids at the carboxy terminus correspond to the v-mil specific sequence. The mil protein shares homology with a number of onc proteins such as src, fes, fms, mos, yes, fps and erbB, as well as with the catalytic chain of the cAMP-dependent protein kinase. This PstI fragment also encodes the beginning of the myc gene which was integrated in MH2 along with the 3' end of the preceding intron placing an acceptor splice site in front of the used open reading frame. As deduced from the sequence, the MH2 myc protein is not identical to the MC29 myc protein. It differs at its amino terminus, which contains little or no gag determinants, depending on the ATG used to initiate translation.

Amino Acid Sequence↗
PubMed1984

Ultrastructural and biochemical evidence that the L929 cell retrovirus lacks the env gene translation product.

LCV, a murine retrovirus released by L929 mouse cell fibroblasts, is non-infectious when inoculated into SC-1, mink, D-17 or Vero cells. Ultrastructural examination by thin sectioning, freeze-etching or negative staining revealed the absence, on the viral envelope, of the radially disposed spikes. Polyacrylamide gel electrophoresis of radiolabelled viral components showed the absence of the glycosylated protein gp70 as well as of the p15E cleavage product of the polyprotein precursor gPr90env. The premature loss of the gp70 molecule from LCV to the culture medium was ruled out since no peak of D-[14C]glucosamine-labelled glycoprotein was detected by affinity chromatography or immunoprecipitation of concentrated medium. The ultrastructural and biochemical results all supported the hypothesis that the absence of infectivity was due to the lack of gp70 glycoprotein in the envelope of LCV. A possible block at a translational or post-translational level was also investigated by immunofluorescence studies with antisera directed against ecotropic or xenotropic gp70; Moloney murine leukaemia virus-infected or NZB cells were used as positive controls for eco- or xenotropic viruses respectively. The absence of fluorescent stain in L929 cells further supported these results and suggested that LCV and the L929 parental cell line lack the uncleaved precursor and the final product of the env gene translation process.

Animals↗
PubMed1983

Two different types of transcription for the myelocytomatosis viruses MH2 and CMII.

The four avian defective leukemia retroviruses (DLVs) MC29, CMII, MH2 and OK10 all transform primarily macrophages in an in vitro bone marrow transformation assay, and contain specific nucleotide sequences closely related to the myc gene of MC29. These viruses were thought to express their oncogenic potential through a gag-myc fusion polyprotein, since fusion polyproteins were found in all tested cells transformed by MC29. We show here that MH2 virus does not conform to this model. Whereas MC29 produces only one mRNA detectable by RNA blotting in productively transformed cells, we reported recently that OK10 induced the synthesis of two myc-containing mRNAs, the smaller species being a spliced mRNA and a possible candidate for a transforming protein lacking gag determinants. However, the studies with OK10 were ambiguous because this virus produced also, in infected cells, a fusion protein containing gag, pol and myc determinants. We have therefore investigated the transcription pattern of the two other members of this group of viruses, namely CMII and MH2. Our results show that CMII resembles MC29 whereas MH2 produces, as OK10, two mRNAs containing myc-related sequences. However, unlike OK10, the MH2 fusion protein of 100 kd described previously cannot contain myc determinants and thus is likely to produce from its subgenomic mRNA a v-myc protein-lacking gag determinants. We thus conclude that the product of the v-myc oncogene is transforming with (MC29) or without (MH2) its fusion to gag determinants and that the multiple oncogenic spectrum is not basically affected since MH2 and MC29 both transform macrophages, fibroblasts and epithelial cells.

Avian Leukosis Virus↗
PubMed1983

The human DNA locus related to the oncogene myb of avian myeloblastosis virus (AMV): molecular cloning and structural characterization.

Chicken and human cell DNA contains sequences homologous to the avian myeloblastosis virus oncogene, v-myb. These cellular sequences, c-myb (human) and c-myb (chicken), were isolated from libraries of human or chicken cell DNA fragments, generated by partial digestion with the restriction enzymes AluI and HaeIII, and compared. The chicken c-myb locus isolated from two distinct overlapping recombinant phages, contained five contiguous EcoRI fragments of 5.4, 1.1, 2.1, 2.2 and 9 kbp, accounting for all the bands seen with a v-myb probe in a complete EcoRI digest of chicken cellular DNA. Likewise, the screening of the human library yielded a recombinant phage hybridizing with the v-myb specific probe, that contained five EcoRI fragments of 2.8, 2.6, 2.0, 1.2 and 5.0 kbp (the last ending with an artificial EcoRI site, due to the construction of the library) belonging to the c-myb (human) locus. Probes using the EcoRI chicken DNA cloned fragments revealed corresponding contiguous EcoRI fragments in the human clone. Subsequent analyses of cellular polyadenylated mRNA extracted from human and chicken cells allowed the identification of single RNA species of 3.8 and 4.0 kb, respectively, as the representative transcripts of the c-myb locus in the two species. Thus, c-myb appears as a single locus in man and chicken, conserved with a similar structure in the two distantly related species. Our preparation of a specific human c-myb probe with an increased sensitivity on DNA/RNA blots should facilitate analyses concerning this gene in human normal or tumour cells or tissues.

Animals↗
PubMed1983

Molecular cloning of the avian acute transforming retrovirus MH2 reveals a novel cell-derived sequence (v-mil) in addition to the myc oncogene.

Mill-Hill-2 virus (MH2) proviral DNA was cloned from a transformed non-producer cell culture (MH2QB2) through insertion of randomly cut high mol. wt. cellular DNA in the lambdoid vector L47.1. Restriction analysis of a suitable recombinant phage by Southern DNA blotting and hybridization with different probes allowed us to characterize the genetic organization of the provirus and to identify a novel MH2-specific sequence of at least 1.1kbp. Such a sequence, for which we propose the name v-mil, from MilI-Hill-2 virus, is not homologous to v-myc, the previously described oncogene of MH2, nor to avian leukaemia virus-related sequences. Evidence is presented here that v-mil has a cellular counterpart (c-mil) phylogenetically conserved in birds and mammals, including man, and expressed as a single RNA species at least in some tissues. MH2 virus might thus be regarded, like avian erythroblastosis virus or E26, as another example of retroviruses having recombined with more than one cellular gene.

Journal Article↗
PubMed1983

Identification by monoclonal antibodies of a new epitope in the glycoprotein complex of Sindbis virus.

Monoclonal antibodies against a deletion mutant of Sindbis virus were produced and characterized in order to determine the fine mapping and functional activities of single viral epitopes. All monoclonal antibodies so far tested showed a certain degree of reciprocal competition and were directed against an antigenic determinant which was present only on the undissociated complex of the E1 and E2 glycoproteins. A biological assay measuring viral haemagglutination showed no decrease in the titre of viral samples preincubated with monoclonal antibodies. Conversely, a reduction in viral infectivity was demonstrated, particularly with two of these antibodies. The results suggest that the antibodies which we characterized seem to recognize a new epitope which is represented on both glycoproteins on the surface of this mutant of Sindbis virus.

Animals↗
PubMedDate not supplied

Short-term versus long-term antimicrobial prophylaxis in oncologic head and neck surgery.

BACKGROUND: Although antimicrobial prophylaxis is mandatory in major clean-contaminated oncologic surgery of the head and neck, both the choice of specific antimicrobial compounds and the treatment duration are still discussed. METHODS: A prospective, randomized trial was carried out to compare efficacy and tolerability of clindamycin-cefonicid administered for 1 day versus 3 days in reducing the rate of wound and systemic infections. The following potential risk factors for surgical wound infection were evaluated: type of surgery, stage of disease, preoperative tracheostomy, preoperative radiotherapy, and diabetes mellitus. RESULTS: One-hundred sixty-two patients were evaluable; 81 received 1-day chemoprophylaxis, while the remaining 81 were treated according to the 3-day schedule. During the first 20 days after surgery, wound infections occurred in 2 (2.5%) and 3(3.7%) patients, respectively, in the 1-day and 3-day treatment groups, so that no significant difference was found among the two evaluated chemoprophylaxis schedules. CONCLUSION: A 3-day schedule did not prove useful in preventing wound and systemic infections. All presumed risk factors were not associated with an increased rate of wound infections, although preoperative radiotherapy was associated with a greater severity of infections and a higher risk of late wound complications.

Adult↗
PubMedDate not supplied

Blood pressure measurement in haemodialysis patients.

Several studies suggest that the 24 hour ambulatory blood pressure monitoring (ABPM) predicts left ventricular hypertrophy more accurately than conventional blood pressure measurement (CBPM) with mercury sphygmomanometer. We estimated the left ventricular mass by M-mode echocardiography in 58 patients on regular haemodialysis treatment during the midweek haemodialysis (HD) interval. ABPM was recorded during the 24 hours preceding the dialysis session and the average of values were compared with the average of the 13 pre HD CBPM recorded by nurses during the month preceding the echocardiography study. The two types of BP measurements correlated significantly with each other, (systolic BP r = 0.62; p < 0.001 and diastolic BP r = 0.74; p < 0.001). The correlation of left ventricular mass with pre-HD systolic BP was stronger (r = 0.54; p < 0.001) than with 24h-systolic BP (r = 0.33; p < 0.01). The overall accuracy of prediction was also similar (68% for pre HD-CBPM; 67% for 24h-ABPM). Measurements of diastolic BP did not correlate significantly with LVM. Our data suggest that 24h-ABPM does not offer any advantage over pre HD-CBPM in predicting left ventricular hypertrophy in HD patients.

Aged↗
PubMedDate not supplied

Modulation of cytokine expression by cAMP analogs in myc-immortalized microglial cell lines.

Expression of cytokines can be modulated by cAMP in macrophages or in primary microglial cultures. Similar to what is observed in normal conditions, treatment of immortal microglial cell lines with dibutyryl-cAMP blocked the accumulation of TNF alpha transcripts induced by lipopolysaccharide, whereas activation of Interleukin-1 alpha (IL-1 alpha) remained unaffected. Immortalized cell lines can therefore be regarded as a valid model to test the immune responsiveness of microglial cells in the presence of neuro-endocrine agents modulating cAMP levels.

Animals↗