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V Barbu

Publications and source records attributed to V Barbu.

At least 19 recordsLinked to original sources
PubMed1992

Processing and characterization of the low density lipoprotein receptor in the human colonic carcinoma cell subclone HT29-18: a potential pathway for delivering therapeutic drugs and genes.

Low density lipoprotein (LDL) processing has been investigated in the subcloned human colonic carcinoma cell line HT29-18. LDL binding at 4 degrees C was a saturable process in relation to time and LDL concentration. The Kd for LDL binding was 11 micrograms/ml. ApoE-free HDL3 or acetylated LDL did not significantly compete with 125I-LDL binding, up to 500 micrograms/ml. 125I-LDL binding was decreased by 70% in HT29-18 cells preincubated for 24 hours in culture medium containing 100 micrograms/ml unlabelled LDL. Ligand blotting studies performed on HT29-18 homogenates using colloidal gold labelled LDL indicated the presence of one autoradiographic band corresponding to an apparent molecular weight of 130 kDa, which is consistent with the previously reported molecular weight of the LDL receptor in human fibroblasts. At 37 degrees C, 125I-LDL was actively internalized by HT29-18 cells and lysosomal degradation occurred as demonstrated by the inhibitory effect of chloroquine. LDL uptake and degradation by HT29-18 cells also resulted in a marked decrease in endogenous sterol synthesis. These data demonstrate that the HT29-18 human cancerous intestinal cells are able to specifically bind and internalize LDL, and that LDL processing results in down-regulation of sterol biosynthesis. Thus, intestinal epithelial cells possess specific LDL receptors that can be exploited to accomplish drug delivery and gene transfer via the receptor-mediated endocytosis pathway.

Colonic Neoplasms↗
PubMed1992

Detection of BCR/ABL translocation by polymerase chain reaction in leukemic progenitor cells (ALL-CFU) from patients with acute lymphoblastic leukemia (ALL).

In about 30% of cases, BCR/ABL transcripts are present in freshly isolated mononuclear cells from the bone marrow of patients with acute lymphoblastic leukemia (ALL) using the polymerase chain reaction (PCR) technique. We applied PCR to investigate the leukemic nature of ALL colony-forming unit (ALL-CFU) colonies grown in a clonogenic assay using a double feeder system. The high sensitivity of PCR enables us to detect 1 leukemic cell among 10(5) normal cells. Several controls were taken to assess contamination. In this report we studied three patients with ALL. In all of them, BCR/ABL transcripts were detected at initial diagnosis. We showed that the PCR technique could identify the leukemic nature of ALL-CFU progenitors. In addition, we demonstrated the nonleukemic nature of granulocyte-macrophage colony-forming unit (CFU-GM) and erythroid burst-forming unit (BFU-E) colonies using the same analysis. We conclude that the PCR technique is of great value in the identification of leukemic clones whenever specific molecular markers are present.

Autoradiography↗
PubMed1991

Serum-free liquid marrow culture in patients with acute lymphoblastic leukaemia: a potential application to purge marrow for autologous transplantation.

We have previously established a serum-free (SF) culture medium, which supports normal haemopoietic progenitor cell growth for at least 4 weeks as does conventional serum dependent (SD) medium. In the present study, we investigated the efficacy of such a defined SF liquid medium which sustained in vitro residual normal haemopoietic proliferation of marrow derived from ALL patients and which was detrimental for the leukaemic population. Evidence for a potential selective effect of SF culture was obtained by a leukaemic progenitor cell assay (ALL-CFU) and the detection of the bcr/abl translocation by polymerase chain reaction (PCR). In 13 experiments including 12 patients, morphological blast cells and ALL-CFU were dramatically reduced within 3 weeks of incubation in both SF and SD cultures. Likewise, in 5/5 experiments in SD and 2/5 experiments in SF conditions, leukaemic cells expressing the bcr/abl fusion gene disappeared within 3-4 weeks. In contrast, the absolute numbers of supernatant cells harvested weekly from SF and SD cultures were similar. No difference in CFU-GM production was detected for the two culture systems. Erythropoiesis in SF medium exhibited a slower decline than that found in SD. These results indicate that liquid marrow culture may selectively deplete leukaemic lymphoblastic cells and enable repopulation by residual normal haemopoietic cells. This technique may be useful to purge leukaemic cells for clinical autologous bone marrow transplantation in patients with ALL.

Adolescent↗
PubMed1991

Clinical value of PCR in diagnosis and follow-up of leukaemia and lymphoma: report of the third Workshop of the Molecular Biology/BMT study group.

The proceedings of the third workshop of the molecular biology/bone marrow transplantation (BMT) study group held in January 1991 in Verona, Italy. This workshop was convened to review progress in the application of molecular techniques to the diagnosis and follow-up of patients with chronic myeloid leukaemia (CML) as well as other haematologic malignancies. The results of polymerase chainreaction studies in 157 CML patients 1-90 months post BMT suggest that leukaemia is frequently detectable for the first 12 months but rarely detected thereafter except in patients known to have a high risk of relapse. In the acute leukaemias and lymphomas there is a rapidly increasing number of leukaemia-specific as well as clone-specific molecular markers now available for the detection of minimal disease. It may be possible to coordinate multi-center prospective studies to investigate the role of these markers in the diagnosis and follow-up of haematologic malignancies.

Bone Marrow Transplantation↗
PubMed1990

Immortalization and neoplastic transformation of fetal rat intestinal epithelial cells: morphological and cytogenetic analysis, (proto)oncogene expression and effect of gamma-interferon on cell growth.

The permanent SLC-11 and -41 intestinal epithelial cells respectively immortalized by the E1A and large T oncogenes and their clonal derivatives showed a cytogenetic heterogeneity characterized by a near diploidy in SLC-11 and -12 cells and a generalized polyploidy in SLC-41 and -44 cells. Persistence of chromosome translocations and trisomy 3 were observed. The expression of the E1A oncogene in immortalized SLC-11 cells is associated with a strong repression of c-fos transcription during the exponential growth, as compared to the resting phase or to control rat fetal intestinal epithelial cells. The transcription of c-myc was also reduced in SLC-11 cells, especially in confluent cells. A complex relationship between the levels and size of the c-fos, c-myc mRNAs and the expression of the E1A oncogene was therefore observed in SLC-11 cells. Immortalized SLC-11 and -41 cells showed a remarkable growth inhibition in response to recombinant rat gamma-IFN. Neoplastic transformation by activated human Ha-ras in SLC-12T and -44 T cells confer resistance to the antigrowth effects of IFN. The combination of culture conditions using defined medium, membrane matrix (laminin, collagen, proteoglycans) and intestinal mesenchyme revealed the persistence of the undifferentiated phenotype of the E1A, large T-immortalized and Ha-ras-transformed SLC cells in vitro or in the nude mice. In association with the intestinal chick endoderm, SLC-11 cells possess some inductive properties on the differentiation of villi projections arising from the chick endoderm in vivo. In contrast, SLC-41 cells were induced to differentiate in enterocyte-like cells by the intestinal chick mesenchyme. The immortalized and Ha-ras-transformed SLC cells therefore constitute new models in the sequential analysis of the molecular and genetic mechanisms involved in the proliferation, differentiation and oncogene-mediated neoplastic transformation in gut. Further attempts in SLC cell differentiation have to be accomplished using chemical inducers for prolonged periods of time, or by transfection of intestinal epithelial cells using temperature- or glucocorticoid-inducible vectors.

Animals↗
PubMed1990

Application of serum-free liquid bone marrow cultures to bone marrow purging for autologous bone marrow transplantation in acute lymphoblastic leukemia.

We have previously established a serum-free (SF) culture medium which allows normal haematopoietic progenitor cells to be maintained for at least 4 weeks as in the conventional serum dependent SD) medium. In the present study we investigated the efficiency of the SF liquid system to sustain normal residual haemopoiesis to the detriment of the leukemic population in patients with ALL. Probes for a potential selective effect were brought through leukemic progenitor cell assay (CFU-ALL) and the polymerase chain reaction (PCR) study of the bcr/abl translocation. In 13 experiments done in 12 patients, morphological blast cells and the ALL-CFU were dramatically reduced within 3 weeks of incubation in both SF and SD cultures. In 5/5 experiments in SD conditions and 2/5 experiments in SF conditions, leukemic cells expressing the bcr/abl fusion gene also disappeared within the same period. There was no difference in the CFU-GM production between SF and SD mediums. Erythropoiesis exhibited a slower decline in conditions SF, compared to the conditions SD. These results indicate that the liquid marrow culture may selectively deplete the leukemic lymphoblastic cells and enable repopulation by residual normal hemopoietic cells. It may be useful to purge leukemic cells for clinical autologous bone marrow transplantation in patients with ALL.

Bone Marrow Cells↗
PubMed1990

Mevalonate deprivation alters the induction of fos and myc by growth factors.

Besides cholesterol, mevalonate is the precursor of several isoprenoid compounds including the farnesyl moiety of isoprenylated proteins. Inhibition of mevalonate biosynthesis leads to a growth arrest that can be relieved by addition of mevalonate, but not of cholesterol. To get a better understanding of the mechanisms underlying this growth inhibition, we have investigated whether mevalonate derivatives are implicated in the early response to growth factors. Our results show that pretreatment of quiescent human fibroblasts with mevinolin, an HMG CoA reductase inhibitor, partially suppresses fos and myc mRNA accumulation in response to serum stimulation. This effect of mevalonate deprivation appears to be on the transcriptional regulation of fos and does not depend upon the nature of the initial events of signal transduction, since the same phenomenon was observed following EGF and TPA stimulation.

Blotting, Northern↗
PubMed1989

Human placental microvilli as a source of antigen for the preparation of a polyclonal antibody directed against the LDL receptor.

Polyclonal antibodies were prepared by immunization of rabbits with partially purified LDL receptor obtained from human placental microvilli. The antiserum reacted with membranes from human placental microvilli and human fibroblasts, as assessed by immunobinding studies. It also reacted with purified LDL receptors of both origins. The antiserum markedly inhibited 125I-labeled LDL binding to cultured human fibroblasts.

Antibody Formation↗
PubMed1988

Cholesterol prevents the teratogenic action of AY 9944: importance of the timing of cholesterol supplementation to rats.

These studies were conducted to determine whether dietary cholesterol supplementation could prevent fetal malformations induced by the amphipathic drug AY 9944, which is well known as a cholesterol biosynthesis inhibitor, and to investigate whether the plasma maternal sterol level and the nature of the sterols found in treated Wistar rats could explain this prevention. Pituitary agenesis was the most constant element of holoprosencephaly when AY 9944 was administered on d 4 of gestation at two dosages, 50 or 75 mg/kg. The rate of malformed fetuses was dose related. A strong negative correlation was established between maternal plasma sterol levels on d 10 of gestation (day of pituitary gland formation) and the rate of fetal anomalies (r = -0.97, P less than 0.01). Supplementation of AY 9944-treated rats with cholesterol had an obvious preventive action on fetal malformations. When cholesterol was added to the diet the same day as AY 9944 treatment and maintained until d 15, the prevention of malformations was almost complete. When the supplementation was initiated later, the prevention of anomalies decreased. The nature of plasma maternal sterols shows that the cholesterol supplementation modifies significantly the ratio of cholesterol to 7-dehydrocholesterol in treated rats. Therefore, maternal plasma sterol perturbations may play a role in the teratogenic action of AY 9944.

Abnormalities, Drug-Induced↗
PubMed1987

Effect of AY 9944 and chlorpromazine on Concanavalin A-induced stimulation of human lymphocytes.

Amphiphilic molecules AY 9944 and chlorpromazine (CPZ) inhibited DNA synthesis in Concanavalin A-stimulated lymphocytes in a dose-dependent manner. While AY 9944 strongly decreased 7-dehydrocholesterol conversion to cholesterol, CPZ did not significantly affect this reaction. Moreover, the inhibitory effect of AY 9944 and CPZ on DNA synthesis took place in the presence of cholesterol in the culture medium. These findings suggest that the mechanism of inhibition of DNA synthesis by AY 9944 or CPZ is not related to endogenous cholesterol synthesis or exogenous cholesterol supply. Results are discussed in relation to the amphiphilic properties of AY 9944 and CPZ and to the interaction of these drugs with membranes or other intracellular targets such as calmodulin.

Autoradiography↗
PubMed1984

Effects of AY 9944 on low density lipoprotein metabolism in cultured human fibroblasts.

Treatment of cultured human fibroblasts with the hypocholesterolemic drug AY 9944 resulted in a marked increase in low density lipoprotein internalization and degradation for concentrations up to 5 X 10(-6)M. Low density lipoprotein binding was less affected. Concentrations above 5 X 10(-6)M resulted in a relative decrease in low density lipoprotein degradation, whereas binding and internalization plateaued. The stimulation of low density lipoprotein internalization took place within the first hours of incubation of cells with the drug, which suggests a direct effect on the cell membrane. Such phenomenon could account at least partially for the hypocholesterolemic effect of the drug, besides its inhibitory effect on 7-dehydrocholesterol reductase.

Cell Line↗
PubMed1984

Phosphate depletion decrease mitogen-mediated stimulation of phospholipid synthesis in human peripheral lymphocytes.

Concanavalin A-mediated stimulation of 32P-phosphate incorporation into phospholipids of human peripheral lymphocytes is comparatively studied in normal and phosphate-depleted media. In the phosphate-depleted medium, 2 hours after the start of cell activation, the stimulation sharply decreases for phosphatidylinositol (6.5-fold) and for phosphatidylcholine (in the latter case, the stimulation is even replaced by a slight inhibition of the incorporation). These results must be related to the rate-limiting effect of inorganic phosphate on ATP formation and thus on phospholipid synthesis, an effect which may be particularly pronounced when there is both phosphate depletion and cell activation.

Humans↗
PubMed1984

Teratogenic effect of AY 9944 in rats: importance of the day of administration and maternal plasma cholesterol level.

An inhibitor of cholesterol synthesis, AY 9944 (trans-1,4-bis(2-chlorobenzylaminomethyl) cyclohexane dihydrochloride) is teratogenic. A single dose of AY 9944 (50 mg/kg or 75 mg/kg) given to Wistar pregnant rats on the second, fourth, sixth, seventh, or eighth day of gestation induced malformations such as holoprosencephaly. They were often limited to isolated pituitary agenesis. The highest percentage of holoprosencephalic fetuses was found when AY 9944 was given on the fourth day of gestation. Whatever the dose and the day of administration, the lower the maternal plasma cholesterol level, the more frequent were holoprosencephalic fetuses. Therefore, it is suggested that the decrease in maternal plasma cholesterol level is at least one of the factors provoking holoprosencephaly.

Abnormalities, Drug-Induced↗