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Biomedical subjects

F Bayard

Publications and source records attributed to F Bayard.

At least 55 records · Page 3Linked to original sources
PubMed1996

Ligands of the antiestrogen-binding site are able to inhibit virion production of human immunodeficiency virus 1-infected lymphocytes.

Since the discovery of human immunodeficiency retrovirus, the drug arsenal against retrovirus has rapidly increased. Concomitantly, new challenges in the therapy of acquired immune deficiency syndrome have arisen, including drug toxicities, drug resistance, and the development of various cancers as effective therapies prolong survival. Tamoxifen, a nonsteroidal antiestrogen with a low incidence of side effects, is widely used in cancer therapy; it is known to exert pleiotropic activities by binding essentially to the estrogen receptor and other unidentified proteins. In the present work, quantification of the p24 core protein of human immunodeficiency virus 1 produced by infected lymphocytes shows an inhibitory effect of tamoxifen on virion production. Moreover, we assume that this effect is not mediated by the estrogen receptor because antiestrogen ligands interacting with the antiestrogen-binding site exhibit efficacy related to their affinity for this site, although specific antiestrogens of the estrogen receptor are ineffective.

Antiviral Agents↗
PubMed1996

Vascular endothelial growth factor and retinal neovascularisation: a new therapeutic approach for diabetic retinopathy.

Since the pioneer work of Michaelson in 1947 reporting that retinal ischemia induces the release of soluble angiogenic compounds, numerous studies have been conducted to identify the molecular structure of such messengers. In the early 1980s, the deciphering of angiogenic factor-signaling pathways and their description in the retina focused attention on growth factors. Vascular endothelial growth factor, the major candidate identified in 1992, induces in vivo angiogenesis and vascular permeability. Its expression is enhanced in vitro by hypoxia and hypoglycaemia; and its immunoreactivity is increased in diabetic patients. A decrease in its bioavailability reduces the intensity of neovascularization.

Animals↗
PubMed1995

Inhibition of fibroblast growth factor 2 expression by antisense RNA induced a loss of the transformed phenotype in a human hepatoma cell line.

Fibroblast growth factor 2 (FGF-2 or basic FGF) is associated with the cell-transformed phenotype. To clarify the function of FGF-2 in the malignancy of tumor cells, we designed experiments to express antisense RNA in a hepatoma cell line. Using FGF-2 mRNA, alternative initiations of translation at one AUG and three CUG start codons led to the synthesis of four isoforms. SK-Hep1 cells, which naturally produce the four FGF-2 proteins, were stably transfected with expression vectors that generate antisense RNAs targeted against different sites of human FGF-2 mRNA. A variable decrease of all of the isoforms of FGF-2 synthesis was observed compared with the control: the strongest inhibition was obtained with the smaller antisense targeted against AUG codon. Our results clearly demonstrated that inhibition of FGF-2 expression led to a loss of anchorage independence in soft agar. This effect was not reversed by adding exogenous FGF-2, indicating that an intracrine process of FGF-2 probably is involved in the phenotypic changes of SK-Hep1 cells. Furthermore, the inhibition of FGF-2 synthesis was correlated with a loss of tumorigenicity in nude mice. These results clearly argue for a key role of endogenous FGF-2 in transformation and tumorigenesis of the hepatoma cell line used in this study.

Animals↗
PubMed1995

Oestrogen synthesis, oestrogen metabolism and functional oestrogen receptors in bovine aortic endothelial cells.

In order to investigate the mechanisms by which oestrogenic hormones influence the vascular system, we have studied their metabolism and the functioning of oestrogen receptors in bovine aortic endothelial cells from primo-secondary cultures, a widely studied model of vascular pathophysiology. We have demonstrated the enzymic activity of oestradiol-17 beta-hydroxysteroid dehydrogenase, 17-ketoreductase and aromatase in these cells. Immunocytochemical analyses, using two different monoclonal antibodies that recognize epitopes in the A/B domain of the oestrogen receptor, showed that this molecule has a predominantly cytoplasmic localization even after the addition of oestrogen to the culture medium. We showed that the hormone-receptor complexes were functional by demonstrating their transactivating ability in transfection experiments using the luciferase gene reporter and an oestrogen-responsive element transcriptional enhancer, although the amplitude of the response was in the range of only 140-150%: this was not a consequence of the presence of a specific limiting factor, but instead might be related to the peculiar subcellular localization of the oestrogen receptor.

Animals↗
PubMed1995

Localization of mRNA coding for the three subtypes of atrial natriuretic factor (ANF) receptors in rat anterior pituitary gland cells.

Atrial Natriuretic Factor (ANF) action is mediated by highly selective and specific receptors. Three subtypes have been characterized and cloned: ANF receptor-A, -B and -C. These subtypes are all expressed in the anterior pituitary of the rat. In the present study, the mRNA for each subtype was detected by in situ hybridization. The amounts of ANFR-A and -B mRNA were found to be similar, and to be twice that of ANFR-C mRNA. At the ultrastructural level, the three types of ANFR mRNA were expressed in three anterior pituitary cell types, namely lactotrophs, corticotrophs, and gonadotrophs, identified by their hormonal content. No signal was revealed in somatotrophs or thyrotrophs. The different forms of mRNA were similar in terms of subcellular localization: in the cytoplasmic matrix and the nuclear euchromatin. These data indicate that the anterior pituitary is an important target tissue for ANF action.

Animals↗
PubMed1995

Alternative translation of human fibroblast growth factor 2 mRNA occurs by internal entry of ribosomes.

Alternative initiations of translation of the human fibroblast growth factor 2 (FGF-2) mRNA, at three CUG start codons and one AUG start codon, result in the synthesis of four isoforms of FGF-2. This process has important consequences on the fate of FGF-2: the CUG-initiated products are nuclear and their constitutive expression is able to induce cell immortalization, whereas the AUG-initiated product, mostly cytoplasmic, can generate cell transformation. Thus, the different isoforms probably have distinct targets in the cell. We show here that translation initiation of the FGF-2 mRNA breaks the rule of the cap-dependent ribosome scanning mechanism. First, translation of the FGF-2 mRNA was shown to be cap independent in vitro. This cap-independent translation required a sequence located between nucleotides (nt) 192 and 256 from the 5' end of the 318-nt-long 5' untranslated region. Second, expression of bicistronic vectors in COS-7 cells indicated that the FGF-2 mRNA is translated through a process of internal ribosome entry mediated by the mRNA leader sequence. By introducing additional AUG codons into the RNA leader sequence, we localized an internal ribosome entry site to between nt 154 and 318 of the 5' untranslated region, just upstream of the first CUG. The presence of an internal ribosome entry site in the FGF-2 mRNA suggests that the process of internal translation initiation, by controlling the expression of a growth factor, could have a crucial role in the control of cell proliferation and differentiation.

Animals↗
PubMed1995

Estrogen synthesis, estrogen metabolism, and functional estrogen receptors in rat arterial smooth muscle cells in culture.

To investigate the mechanisms by which estrogen hormones influence the vascular system, the metabolism of these hormones and the functionality of estrogen receptors were characterized in rat aortic smooth muscle cells from secondary cultures, a widely studied model of vascular biology. Aromatase, estradiol-17 beta-hydroxysteroid dehydrogenase and 17-ketoreductase enzyme activities were demonstrated in these cells. The presence of functional estrogen receptor could also be demonstrated by estrogen-induced transactivating ability in transfection experiments using the luciferase gene reporter and an estrogen responsive element as transcriptional enhancer although the amplitude of the response was only in the range of 140 to 150%. Immunocytochemical analyses, using monoclonal antibodies that recognize epitopes in the A/B domain of the molecule, showed a predominant cytoplasmic localization of these estrogen receptors, even after estrogen addition to the culture medium. Western blot analysis using antibodies that recognize epitopes in the A/B or F domain gave a mol wt of 67,000. Analysis of the estrogen receptor messenger RNA showed that there was no deletion of the proto-signals for nuclear accumulation. The aromatase and dehydrogenase activity results, coupled with the estrogen receptor immunological, RNA analysis, and transfection data strongly support the contention that rat aortic smooth muscle cells are estrogen target cells. This in vitro model is convenient for studying the mechanisms of action of estrogen hormones that seem very peculiar in this cell population.

17-Hydroxysteroid Dehydrogenases↗
PubMed1995

The impact of continuous subcutaneous infusion of octreotide on gallstone formation in acromegalic patients.

Treatment of acromegaly with intermittent sc injections of octreotide is associated with an increased incidence of cholelithiasis. We investigated the incidence of gallstone formation, the occurrence of gallbladder disease, and the response of gallstones to ursodeoxycholic acid in 30 acromegalic patients who were treated with a continuous sc infusion of octreotide at doses between 200 and 800 micrograms/day for 3-70 months. Of the 30 patients, 28 had pretretment ultrasonography of the biliary tree performed, and all had frequent follow-ups. Nine patients underwent pre- and posttreatment bile sampling. No patient treated for less than 6 months and 18.5% of patients treated for more than 6 months developed new gallstones. No patient developed symptomatic cholelithiasis while receiving octreotide therapy. Of six patients who developed gallstones, four were treated with ursodeoxycholic acid, which dissolved all gallstones. One patient with gallstones experienced an episode of biliary colic when octreotide was withdrawn; however, no cholecystitis was found at subsequent cholecystectomy. Bile sampling showed that 8 (75%) of the 12 patients who were assessed demonstrated microcrystals, whereas in 3 (50%) of 6 patients who were closely analyzed thereafter, microcrystals disappeared once octreotide therapy was stopped. Our results show that continuous sc infusion octreotide therapy increases the incidence of cholelithiasis over normal values, as is the case with intermittent sc injections. Although higher octreotide levels are sustained with continuous sc infusion, this is not associated with an increased risk of gallstone formation compared with intermittent sc octreotide therapy.

Acromegaly↗
PubMed1995

Intramuscular injections of slow-release lanreotide (BIM 23014) in acromegalic patients previously treated with continuous subcutaneous infusion of octreotide (SMS 201-995).

Nine acromegalic patients (five females and four males), mean age 50 +/- 4 years, presented macroadenomas (N = 7), microadenoma (N = 1) or normal computed tomography scans (N = 1). Patients were treated with continuous subcutaneous infusion of octreotide (range 200-600 micrograms/day). Following a washout period of 7 days, the patients were injected im with 30 mg slow-release lanreotide every 10 days for the first month and then twice monthly. In case of elevated growth hormone (GH) levels at 3 months, the patients were injected every 10 days for the next three months. Plasma GH and insulin-like growth factor I (IGH-I) decreased in all patients during octreotide treatment. After 6 months of octreotide treatment, seven patients were considered as well controlled (mean 8 h GH < 5 micrograms/l, IGF-I normal) whereas in two patients the mean 8-h GH and/or IGF-I levels remained increased. Serum GH and IGH-I increased after octreotide withdrawal. In one patient, serum GH and IGF-I increased during slow-release lanreotide administration and injections were stopped after 45 days. After 3 months of lanreotide, three patients were well controlled while in five patients GH or IGF-I levels were not normalized. At 6 months, five patients were injected twice monthly and three patients had one injection every 10 days. Six patients were well controlled and in two patients the mean 8-h GH level remained increased. The pituitary tumor volume decreased by 20-30% in two patients during octreotide, as well as in one other during slow-release lanreotide therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Acromegaly↗
PubMed1995

[Differential effect of estrogens in target tissues].

Using ER 1D5 new antibody it is shown that the estrogen receptor has an extra-nuclear localisation in vascular cells. This work exhibits, moreover, that the polymorphism of the estrogen receptor is in part regulated at the translation step.

Animals↗
PubMed1995

Expression of basic fibroblast growth factor (bFGF) and FGF-receptors in human leukemic cells.

Recent reports have suggested that basic fibroblast growth factor (bFGF) could play a permissive role in hematopoiesis, in combination with specific colony-stimulating factors. We investigated the expression of bFGF and FGF-receptors (FGF-Rs) in leukemic cell lines of various hematopoietic lineages. Three protein isoforms of bFGF of approximately 18, 22 and 24 kDa were detected in the myeloid cell line K562, but not in myelomonocytic or lymphoid (T or B) cell lines. In vitro-induced differentiation of K562 cells did not change the pattern of expression of the different bFGF isoforms. Accordingly, the mRNA of bFGF was found expressed in K562, but not in other leukemic lines tested, as assayed by reverse transcript amplification (RT-PCR). Using the same technique, we searched for the presence of high affinity FGF-Rs on these cells: in eight out of ten cell lines tested, mRNA for at least one FGF-R among FGF-R1, FGF-R3 or FGF-R4 was expressed, whereas FGF-R2 was never detected. We found that two cell lines were responsive to bFGF in different biological assays: (i) in K562 myeloid cells induced to differentiate by hemin, preincubation with bFGF and heparin increased cell viability and decreased hemin-induced DNA fragmentation, without affecting erythroid differentiation; and (ii) in U937 monocytic cells, the production of plasminogen activator was increased by bFGF or aFGF in combination with heparin. Binding experiments with 125I-bFGF (up to 200 pM) in the presence of heparin revealed high affinity receptors on the K562 and U937 cell lines (1177 +/- 440 and 392 +/- 184 sites/cell, Kd = 61.7 +/- 8.6 and 43.1 +/- 13.5 pM, respectively). Thus our results strongly suggest that cells of hematopoietic origin could express functional FGF-receptors.

Base Sequence↗
PubMed1994

Detection of vascular endothelial growth factor messenger RNA and vascular endothelial growth factor-like activity in proliferative diabetic retinopathy.

OBJECTIVE: To study the involvement of eight angiogenic growth factors that have been identified so far in the literature, especially vascular endothelial growth factor, in proliferative diabetic retinopathy. METHODS: Samples of neovascular membranes were obtained from diabetic patients; these samples, excised at vitrectomy, were used to study the expression of messenger RNA of the angiogenic factors by using the method of the reverse transcription-polymerase chain reaction. Vitreous aspirates that were taken from diabetic and control patients were used to quantify vascular endothelial growth factor-like activity with a competitive radioreceptor assay. RESULTS: Of the eight angiogenic factors studied, vascular endothelial growth factor was the only one that was always expressed in the samples of neovascular membranes. Furthermore, vascular endothelial growth factor receptor-binding activity was greater in vitreous aspirates that were obtained from diabetic patients than in samples that were taken from control patients (P < .01). CONCLUSION: Vascular endothelial growth factor seems to be an appropriate candidate for mediating retinal diabetic neovascularization.

Adolescent↗
PubMed1994

Regulations of vasculatropin/vascular endothelial growth factor bioavailability.

Angiogenesis is a key step in organ development and remodelling during embryogenesis or tissue regeneration. Some pathological events such as tumor growth or diabetic retinopathy also lead to angiogenesis formation. Several molecules have already been identified as promoting angiogenesis in vivo. We have recently purified a new angiogenic growth factor. Its unique specificity for vascular endothelial cells led us to provisionally name it vasculotropin (VAS) or vascular endothelial growth factor (VEGF) or vascular permeability factor (VPF). In vitro, despite a moderate action on proliferation, VAS/VEGF strongly stimulates cell migration. In vivo, VAS/VEGF is a potent inducer of angiogenesis and vascular permeability. Its central role in angiogenesis is emphasized by the observation that its immunoneutralization prevents tumor progression.

Animals↗
PubMed1994

Regulation of natriuretic peptide receptor A and B expression by transforming growth factor-beta 1 in cultured aortic smooth muscle cells.

Two types of natriuretic peptide receptors (NPR-A and NPR-B) are membrane guanylate cyclases whose relative expression varies in different tissues. Because natriuretic peptides have been shown to inhibit aortic smooth muscle proliferation, we investigated the regulation of NPR-A and NPR-B in these cells under different proliferative conditions. NPR subtype mRNA levels were measured by our newly developed quantitative reverse transcription-polymerase chain reaction assay using mutated NPR-A and NPR-B cRNA as internal standards. The functional impact of their expression was determined by atrial natriuretic peptide (ANP)- and C-type natriuretic peptide (CNP)-induced stimulation of cyclic GMP production. In the intact aorta, NPR-B mRNA levels were found to be 10-fold higher than those of NPR-A. This dominance was further amplified (1000-fold) in long-term cultures (10 to 15 passages) of aortic smooth muscle cells (ASMC). Higher cyclic GMP production with CNP than with ANP was observed in cultured ASMC from Wistar-Kyoto (WKY) rats. Similar stimulation by the two agonists was noted in spontaneously hypertensive rat (SHR) cells, paralleled by a 10-fold increase in NPR-A mRNA levels and ANP stimulation of cyclic GMP in hypertensive cells. The present study also evaluated NPR-A and NPR-B mRNA control by transforming growth factor-beta 1 (TGF-beta 1), an important regulator of cell proliferation that is overexpressed in SHR ASMC. TGF-beta 1 decreased both NPR-A and NPR-B mRNA levels with a predominant effect in SHR cells at high cell density.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Characterization of the membranous antiestrogen binding protein: I. Partial purification of the protein in its active state.

We previously demonstrated that, in addition to the estrogen receptor, the Antiestrogen Binding Site (ABS) is also a potent mediator of the antitumorous activity of the clinical drug tamoxifen. Because of report discrepancies in the binding parameters of rat liver ABS we first attempted to improve binding study conditions. In this way buffer, protein concentration, methodology for bound/free ligand separation and phospholipidic ratio were determined. This work was used to evaluate the Stoke radius (4.4 S) and isoelectric point (pH = 6.6) of the protein in its native state. These studies constituted the obligatory transition from rat liver to pure ABS protein.

Animals↗
PubMed1994

Characterization of the membranous antiestrogen binding protein: II. Purification to homogeneity.

Our knowledge of the biological role of the antiestrogen binding site ABS in the antitumoral activity of tamoxifen, will be increased with the determination of its coding gene sequence. To this end our team has for some time attempted to purify this membranous protein. In this work we report the purification to homogeneity of ABS from rat liver in a six step succession. Specific photolabeling with a tritiated photoprobe, solubilization of rat liver microsomes, chromatofocusing of the labeled proteins, preparative electrophoresis on polyacrylamide gel, and two consecutive high performance liquid chromatography separations on C4 hydrophobic resin produced 2.5 micrograms of pure ABS by silver stain analysis of SDS-PAGE. The NH2-terminal residue of the protein appears to be blocked, which hinders the Edman degradation method for obtention of the whole protein sequence.

Animals↗