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Biomedical subjects

C Brigati

Publications and source records attributed to C Brigati.

12 recordsLinked to original sources
PubMed2000

Tissue inhibitors of metalloproteases: regulation and biological activities.

A central role in tissue invasion is played by proteases that degrade extracellular matrices; in particular specific metalloproteases (MMPs) have been frequently correlated with the invasive potential of tumor cells and with the angiogenic process. MMPs are tightly regulated by molecules controlling their activation and by specific inhibitors of MMPs, known as the Tissue Inhibitors of MetalloProteases or TIMPs. Four TIMP family members are currently known. An imbalance between MMPs and TIMPs is linked to the degradation of the extracellular matrix associated with several physiologic and pathologic events including angiogenesis, invasion and metastasis. TIMPs are not only the 'guardians' of tissue degradation, they are able to control cell proliferation and cell survival as well. Given the critical role that TIMPs play, it is vital to know how the expression of TIMPs is controlled. Here we review the major biological properties and the molecular regulation of the TIMP expression.

Amino Acid Sequence↗
PubMed1999

A unique carboxy-terminus truncation mutant of the retinoic acid receptor alpha gene associated with a variant marker chromosome in a retinoic acid resistant HL-60 subline.

In order to contribute to the study of the molecular basis of leukemic cellular resistance to the induction of differentiation by all-trans retinoic acid (RA) we have generated and analyzed a mutant, RA-resistant HL-60 cell line. Molecular analysis of the retinoic acid receptor alpha (RARalpha) cDNA disclosed, in one of the two alleles, a novel mutation consisting of a 7-base deletion in the ligand binding domain that includes part of a FokI restriction endonuclease site previously described. As a consequence of this deletion and translational frame-shift, a stop signal is created that truncates the protein at codon 421, disrupting an essential functional component of the receptor. Transducing an epitope tagged RARalpha into the mutant is sufficient to inhibit clonal growth in the presence of RA. Standard cytogenetic analysis, fluorescent in situ hybridization (FISH) and comparative genomic hybridization (CGH) analysis revealed the presence of two RARalpha loci, and showed a composite karyotype with additional abnormalities with respect to the parental line, including a chromosome 8 insertion in a chromosome previously known as marker three.

Alleles↗
PubMed1995

A retinoic acid resistant HL-60 cell clone sensitive to N-(4-hydroxyphenyl) retinamide-mediated clonal growth inhibition.

Among the Retinoic Acid (RA) derivatives, retinamides, and in particular N-(4-hydroxyphenyl) retinamide (4-HPR), are currently being investigated in selected cases of cancer chemoprevention. The cellular target range, however, seems to be limited, as cells of hemopoietic origin are virtually incapable of terminal differentiation upon addition of the compound. We have reconsidered the effect of 4-HPR on HL-60 cells by taking advantage of a mutant clone, generated in our laboratory, unresponsive to RA but highly responsive to dimethylsulfoxide (DMSO). We show here that this clone, upon addition of 4-HPR, although unable of undergoing full differentiation, shows considerable reduction of clonal growth. Moreover, the combination of 4-HPR and RA resulted in a much greater effect than the administration of 4-HPR alone. We suggest that 4-HPR and RA, at least in terms of mediating growth inhibition, may follow different metabolic pathways.

Animals↗
PubMed1994

An improved RT-PCR protocol for the quantitation of human retinoic acid receptor RNA.

A quantitative reverse transcriptase polymerase chain reaction (RT-PCR) system has been developed to calculate the level of expression of human retinoic acid receptors (hRAR) alpha, beta, and gamma. Starting from a single cDNA preparation, the system allows the measurement of the number of molecules of each mRNA receptor. This is made possible by a synthetic internal standard mRNA which is added in known concentrations at the beginning of the reaction. The system is tested in a rhabdomyosarcoma cell line (A-673) where we have measured the upregulation of beta and gamma receptor mRNAs following treatment with retinoic acid.

Base Sequence↗
PubMed1993

An essential yeast gene encoding a TTAGGG repeat-binding protein.

A yeast gene encoding a DNA-binding protein that recognizes the telomeric repeat sequence TTAGGG found in multicellular eukaryotes was identified by screening a lambda gt11 expression library with a radiolabeled TTAGGG multimer. This gene, which we refer to as TBF1 (TTAGGG repeat-binding factor 1), encodes a polypeptide with a predicted molecular mass of 63 kDa. The TBF1 protein, produced in vitro by transcription and translation of the cloned gene, binds to (TTAGGG)n probes and to a yeast telomeric junction sequence that contains two copies of the sequence TTAGGG separated by 5 bp. TBF1 appears to be identical to a previously described yeast TTAGGG-repeat binding activity called TBF alpha. TBF1 produced in vitro yields protein-DNA complexes with (TTAGGG)n probes that have mobilities on native polyacrylamide gels identical to those produced by partially purified TBF alpha from yeast cells. Furthermore, when extracts are prepared from a strain containing a TBF1 gene with an antigen tag, we find that the antigen copurifies with the predominant (TTAGGG)n-binding activity in the extracts. The DNA sequence of TBF1 was determined. The predicted protein sequence suggests that TBF1 may contain a nucleotide-binding domain, but no significant similarities to any other known proteins were identified, nor was an obvious DNA-binding motif apparent. Diploid cells heterozygous for a tbf1::URA3 insertion mutation are viable but upon sporulation give rise to tetrads with only two viable spores, both of which are Ura-, indicating that the TBF1 gene is essential for growth. Possible functions of TBF1 (TFB alpha) are discussed in light of these new results.

Amino Acid Sequence↗
PubMed1992

Regulation of plasma retinol binding protein secretion in human HepG2 cells.

Retinol binding protein (RBP) is the plasma transport protein of retinol. Mobilization of RBP from the liver stores is stimulated by retinol. During vitamin A deficiency, RBP secretion is specifically inhibited while its rate of biosynthesis is unaffected. As a consequence, RBP, as apoprotein, accumulates inside the endoplasmic reticulum (ER) of the hepatocyte, and a new elevated steady-state concentration is reached. We have studied the role of degradation on the regulation of RBP metabolism in retinol deficient HepG2 cells and determined the intracellular site where RBP degradation takes place. Pulse-chase experiments show that RBP half-life is ca.9 h in retinol-depleted cells. RBP degradation is slow and is insensitive to the treatment with NH4Cl, which inactivates lysosomal proteases and to the drug brefeldin A, which prevents protein export from the ER. The data obtained suggest that RBP degradation occurs, at least in part, in a pre-Golgi compartment. 2-Mercaptoethanol, at millimolar concentration, induces RBP secretion, suggesting a possible role for sulfhydryl-mediated apo-RBP retention by resident ER proteins.

Carcinoma, Hepatocellular↗
PubMed1986

Inhibition of in vitro alloreactivity by cyclosporin A: evidence for an inter-individual variation in sensitivity.

Cyclosporin A (CyA) is the immunosuppressive treatment of choice in preventing allograft rejection and graft-versus-host disease. However, clinical trials indicate that there may exist inter-individual variations in sensitivity to the drug. We have approached this issue by studying CyA-mediated inhibition of in vitro alloreactions, as measured by mixed lymphocyte reactions (MLR) and cell-mediated lympholysis (CML), using mouse and human normal spleen cells. The differences between individuals in the CyA concentration required for 50% inhibition of the human alloreactions were twentyfold for the MLR and fortyfold for the CML. Moreover, the CML appeared to be inhibited at lower doses of the drug. No correlation was found between inhibitory doses and variables such as the magnitude of the response, age, or human leukocyte antigen phenotype. When the same experiments were performed with mouse spleen cells, no differences were observed among eight inbred strains. The lack of demonstrable individual sensitivity of mice in relation to humans is discussed.

Animals↗
PubMed1985

CPH-86, a highly purified podophyllotoxin, efficiently suppresses in vivo and in vitro immune responses.

Podophyllotoxin, a component of the plant resin Podophyllin, has been used as a clinical drug for many years. Recently it has been highly purified under the denomination of CPH-86. We here demonstrate that extremely low doses of the compound efficiently inhibit antibody responses to SRBC and prolong allogeneic skin graft survival in mice. In vitro immune reactions, such as mitogen and alloantigen induced proliferation and development of cytotoxic T cells, are also suppressed in a dose dependent manner. This effect does not seem to be due to direct cellular toxicity or to a shift in the kinetic pattern of the responses.

Animals↗
PubMed1984

Altered expression of B lymphocyte surface immunoglobulins in minimal change nephrotic syndrome and focal glomerulosclerosis.

In 20 patients with nephrotic syndrome (10 minimal change glomerulonephritis, MCN; 10 focal glomerulosclerosis, FGS) the peripheral blood lymphocytes showed a statistically significant increase in IgG-bearing cells (SIgG-C) in comparison with 30 patients with other histological types of primary glomerulonephritis with and without nephrotic syndrome (14 and 16, respectively). In the same MCN and FGS patients the serum IgG levels were slightly decreased. Furthermore, 5 cases of MCN in sustained remission for 1 year after steroid therapy showed normalization of the SIgG-C and the serum IgG levels. The possible significance of these phenomena in the pathogenesis of the hypo-IgG-globulinemia in MCN and FGS is discussed.

Adolescent↗
PubMed1983

Minimal change glomerulonephritis and focal glomerulosclerosis markers and 'in vitro' activity of peripheral blood mononuclear cell.

Serum concentrations of IgG, IgA and IgM and PBMC were investigated in 11 prevalently adult patients with idiopathic glomerulonephritis, five minimal change glomerulonephritis (MCGN) and six focal glomerulosclerosis (FGS) and nephrotic syndrome. Among the peripheral blood mononuclear cells (PBMC) E rosette forming cells (T-cells), surface immunoglobulin bearing cells (B-cells), and T-cells with IgG Fc receptor (T gamma) were determined. In the culture supernatants of PBMC stimulated with PWM, the concentration of secreted IgG, IgA and IgM was determined by a solid phase immunofluorescence assay. After stimulation with PWM and PHA, the 3H-TdR uptake from PBMC was evaluated. In patients only the serum values of IgG were found significantly decreased. No difference was observed between patients and healthy age and sex matched controls, in percentage and absolute number of T and B-cells, whereas an increased number of T gamma was present in patients. In these patients after stimulation with PWM the production of IgG and IgA, but not IgM, and the 3H-TdR incorporation, were significantly lower than in healthy controls. These results suggest an imbalance in the cellular co-operation or an intrinsic B-cell defect in the synthesis or secretion of Ig in MCGN and FGS.

Adolescent↗