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M Dreyfus

Publications and source records attributed to M Dreyfus.

At least 145 records · Page 8Linked to original sources
PubMed1989

Regulatory elements involved in the bidirectional activity of an immunoglobulin promoter.

We show that the promoter from the mouse VH441 heavy-chain immunoglobulin gene, when present on plasmids transiently introduced into myeloma cells, promotes transcription bidirectionally, due to the presence on both strands of TATA-like sequences bracketing the highly conserved decanucleotide element. The two divergent promoters compete for the transcriptional machinery, their relative strength ultimately reflecting the likeness of the two TATA boxes to the consensus sequence. Moreover, their relative activity is also strongly influenced by certain point mutations within the distally located heavy-chain enhancer. The bearing of these results on current concepts of promoter function is discussed.

Animals↗
PubMed1989

[Adenomas of the liver and oral contraception. Clinical and therapeutic aspects apropos of a giant adenoma].

The first cases of benign liver tumors following estroprogestative therapy were described in 1973. Since that time, this relation between cause and effect has been demonstrated. The authors report the case of a giant liver adenoma which developed after 13 years of uninterrupted use of oral contraceptives. The advantage of this disease is not so much its prevalence which is low, but its clinical diagnosis. In fact, failure to recognize this entity may result in dramatic complications such as haemorrhagic rupture of the liver. The therapeutic approaches, whether wait-and-see or aggressive, all present a common objective: permanent discontinuance of estroprogestative drugs.

Adult↗
PubMed1989

Renin-promoter SV40 large T-antigen transgenes induce tumors irrespective of normal cellular expression of renin genes.

Chimeric genes containing the 5'-flanking regions of the mouse renin genes, Ren1 and Ren2, associated with the early region of the simian virus 40 (SV40) were constructed. The two recombinant genes which contain, respectively, 0.45- and 2.5-kb the Ren1 and Ren2 5'-flanking sequences, named Ren1Tag and Ren2Tag, were microinjected into fertilized eggs. Tumors arose after a latency of 5-9 months in mouse lines harboring these hybrid genes except for one, in which a different and earlier pathology was observed (peripheral neuropathies). Most of the pathologies developed by these transgenic mice reflect the tumorigenic spectrum of the SV40 early region gene (choroid plexus, kidney, intestinal tumors, and peripheral neuropathies). None of these tumors arose from renin-producing cells nor produced renin. As suggested by the tumor pathology, the expression of the SV40 large T-antigen did not follow the normal expression of the Ren1 and the Ren2 genes since SV40 large T-antigen mRNA was found in tissues which normally do not express renin.

Animals↗
PubMed1989

[Preanesthetic consultation in pediatrics: experience with the use of drawings].

69 children scheduled for ENT surgery have been asked by the anesthesiologist to draw a picture. A analysis of some of those drawings provides information about the psychological reactions of children facing surgery, determined by their current situation, personality and past history. This simple method proved to be an useful adjunct to the psychological preparation of children to anesthesia and surgery. It contributes to a better relationship between anesthesiologist and child, and to a better knowledge of the reactions of children; it could be used in a more systematic manner.

Anesthesia↗
PubMed1988

What constitutes the signal for the initiation of protein synthesis on Escherichia coli mRNAs?

Small DNA fragments (60 to 80 nucleotides), randomly obtained from a collection of 14 catabolic, biosynthetic or regulatory Escherichia coli genes, have been shot-gun cloned in place of the lacZ ribosome binding site. A total of 47 recombinants showing substantial beta-galactosidase synthesis (at least 1/30th of the wild-type) were isolated, and their newly acquired translational starts were characterized. Of these, 46 were found to carry a ribosome binding site from one of the original genes, and only one, a non-natural start. Moreover, 12 out of the 14 natural starts were found. The two that were not found are the only ones lacking a Shine-Dalgarno element. So, real starts are generally active in the lac mRNA, whereas the many sites (approx. 100 in this gene collection) that carry a Shine-Dalgarno element followed by AUG or GUG but are located in intra- or intergenic regions, or on non-transcribed strands, are inactive. I conclude that: (1) these "false" starts, being strongly discriminated against in the lac message, are presumably also inactive in their original mRNAs; (2) the discriminating information, being portable from one mRNA to another, must be contained within a small DNA region surrounding the starts. Indeed, I further show that it generally lies within a sequence of about 35 nucleotides bracketing real starts; and (3) this information must have a larger effect on initiation than the exact structure of the mRNA, because the discrimination persists despite a complete change of this structure. Previous statistical analysis has shown that real starts differ from false starts in having a non-random sequence composition from nucleotides -20 to +15 with respect to the start. To uncover whether these biases constitute the discriminating information or simply reflect coding constraints, translational starts were randomly searched in eukaryotic, largely non-coding, DNA. These "eukaryotic" starts all have an in-phase AUG or GUG, preceded by a typical Shine-Dalgarno sequence; outside these elements, the initiator region is strikingly rich in A, and poor in C. These biases match those found around real starts, demonstrating that they are indeed part of the initiation signal. Finally, I describe a simple procedure for introducing any DNA fragment in place of the lac operator site on the E. coli chromosome.

Base Sequence↗
PubMed1988

The build-up of the thrombospondin extracellular matrix. An apparent dependence on synthesis and on preformed fibrillar matrix.

Thrombospondin (TSP) is a multifunctional protein synthesized by several cell types in culture, among them endothelial cells, and incorporated into the extracellular matrix (ECM) of these cells. In vitro it has been detected in most interstitial spaces, and its presence has been suggested to be developmentally controlled. With the aim of elucidating the role of TSP in the extracellular matrix, we studied the build-up of this protein in the matrix as a function of cell type density and age in culture. The development of the TSP matrix was compared to that of fibronectin (FN) and of von Willebrand Factor (VWF) in the same cultures using our monoclonal anti-TSP antibody B7-3 and monospecific anti-FN or anti-VWF antibodies. In cultures of bovine aortic endothelial cells (BAEC) we observed that both the pattern and distribution of TSP in the matrix changed with cell density and time in culture; it started as a completely amorphous dense layer of protein when the cells were sparse and changed to well organized fibrils when the cells had been confluent for a while. The first appearance of the fibrillar arrays of TSP coincides perfectly with that of the FN fibers; extracellular VWF also was first detected at this point. From this time in culture, there was an increasing coincidence of the TSP with the FN and the VWF matrices suggesting the formation of a complex multicomponent structure of the fibrillar network.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1987

Isolation of DNA-protein complexes based on streptavidin and biotin interaction.

We describe a method for the purification of proteins binding to specific DNA sites based on the strong interaction between streptavidin and biotin. We tested the efficiency of this method using the Escherichia coli lactose operon operator-repressor system. dUTP coupled to biotin is incorporated into a DNA fragment containing the lactose operator. A crude E. coli extract is first incubated with the biotinylated fragment and the reaction mixture is filtered on a streptavidin-agarose column. Proteins retained on the column are either eluted alone by high salt or isopropyl beta-D-thiogalactoside, or as a complex with the DNA site by enzymatic digestion of the DNA. We thus obtained a 3400-fold enrichment of the repressor complexed to the operator in one step. The method is simple and makes use of commercially available reagents. The large concentration of biotin-binding sites of the streptavidin-agarose matrix (0.1 mumol/ml packed gel) provides a very high capacity for the concentration and purification of large amounts of proteins. The advantage of this method for the detection and purification of other DNA-binding proteins is discussed.

Bacterial Proteins↗
PubMed1987

The conserved decanucleotide from the immunoglobulin heavy chain promoter induces a very high transcriptional activity in B-cells when introduced into an heterologous promoter.

A conserved decanucleotide (ATGCAAATNA) is present 45-60 nucleotides upstream from the transcription startpoint in all immunoglobulin heavy chain promoters (VH promoters). We have introduced this decanucleotide (cd sequence) at a similar position into the upstream flanking sequence of the mouse Renin-1 gene. This gene is only transcribed in highly specialized tissues, and the fragment used here (-449 to +30 with respect to the main transcription startpoint) has little promoter activity in fibroblastic or myeloma cell lines, even if coupled to a functional enhancer. In contrast, after insertion of the decanucleotide, this fragment, while still inactive in non-lymphoid cells, becomes a potent promoter in B-cells when associated with SV40 or immunoglobulin heavy chain enhancer. In all respects, the engineered fragment behaves like an authentic VH promoter isolated in this laboratory, except that it is even more active in B-cells. Deletion experiments show that all renin sequences are dispensable for the activity of the chimaeric promoter, except probably for the renin TATA box which defines the precise transcription startpoint. We conclude that the decanucleotide is sufficient to activate a promoter in B-cells but not in non-B-cells, and therefore that no other element is needed to account for the B-cell specificity of the VH promoter. In addition, our results suggest that the lack of activity of the renin promoter in non cognate cells is not due to the binding of a repressor.

Animals↗
PubMed1987

Regulated expression of the Ren-2 gene in transgenic mice derived from parental strains carrying only the Ren-1 gene.

The Ren-2 gene encoding the mouse submaxillary gland (SMG) renin was microinjected into the pronuclei of fertilized eggs from mice carrying only the Ren-1 gene. In addition to the whole transcription unit, the injected DNA contained 2.5 and 3 kb of upstream and downstream flanking sequences, respectively. Three independent transgenic mice lines were obtained; two of them had integrated one copy of the Ren-2 gene, the last one had integrated five and eleven copies at two independent sites. Independently of the number of Ren-2 copies integrated, the pattern of Ren-2 gene expression in all the transgenic mice was identical to that observed in wild-type animals in which Ren-1 and Ren-2 are closely linked on chromosome 1. In particular, the exogenous Ren-2 gene was only transcribed in the kidney and in the SMG. In the kidney, Ren-1 and Ren-2 mRNAs were present at a comparable level, whereas in the SMG Ren-2 mRNA was at least 100-fold more abundant than Ren-1 mRNA. Moreover, Ren-2 expression in the SMG was positively regulated by androgens. Only one difference between transgenic mice and wild-type mice carrying the Ren-2 gene has been observed: the basal level of Ren-2 transcription in the SMG of transgenic females was lower than in two-gene strain females. Androgen treatment of transgenic females induced SMG renin mRNA to a level identical to that of transgenic males. This suggests that the basal level of SMG renin mRNA is dependent upon cis-acting elements which are not present in the microinjected fragment.

Animals↗
PubMed1987

[Trophoblastic tumor of placental location or trophoblastic pseudotumor. Apropos of 2 cases. Review of the literature].

Two cases of trophoblastic tumor of placental site are reported, less than 30 such lesions being listed in the published literature. Identification of this tumor from among other trophoblastic lesions is facilitated by immunohistochemical and electron microscopy technics, and demonstration of histoprognostic and biologic criteria improves assessment of evolutory potential of this type of tumor and allows adaptation of therapy. Treatment at the localized stage requires early diagnosis and wide surgical excision, results of chemotherapy in metastatic forms being, inversely than with choriocarcinoma, very deceiving.

Adult↗
PubMed1987

[Idiopathic autoimmune thrombopenic purpura and pregnancy].

Immune thrombocytopenic purpura can no longer be considered as incompatible with pregnancy provided that close surveillance is undertaken. However, the main risk (a possible intracranial hemorrhage) persists in the newborn when severe thrombocytopenia due to the placental transfer of maternal IgG has occurred. None of the maternal parameters is predictive of the fetal thrombocytopenia or of its magnitude. A platelet count on fetal blood obtained by in utero or scalp sampling allows the choice between vaginal delivery or cesarean section, to limit the risk of intracranial bleeding. In most cases i.v. IgG infusion allows rapid correction of severe thrombocytopenia in the newborn.

Autoimmune Diseases↗
PubMed1986

Prothrombin Clamart: prothrombin variant with defective Arg 320-IIe cleavage by factor Xa.

An abnormal prothrombin has been detected in a 23 yr-old healthy female and her mother. Both patients appeared to be heterozygous for the abnormality, plasma prothrombin being 50% of normal using the usual one stage assay, but normal when measured either by using Echis carinatus venom or by immunoassay. No abnormality in the immunoelectrophoretic pattern was observed. Prothrombin isolation on DEAE Sephadex failed to separate the abnormal population (prothrombin Clamart) from the normal one. The rates of prothrombin activation by factor Xa, in the presence or absence of phospholipids and/or factor Va, were determined by measuring the production of both clotting and amidolytic activities. The thrombin generation rate from prothrombin isolated from the propositus plasma was 50% slower than normal whatever the method of measurement and the composition of the activation mixture. Analysis of the final activation products by SDS polyacrylamide gel electrophoresis revealed that equal amounts of prethrombin 2 and thrombin had been formed. Prethrombin 2 Clamart was shown to be resistant to proteolysis upon further incubation with factor Xa, whereas it was readily converted to thrombin by Echis carinatus venom. Prothrombin Clamart appears to be characterized by an impairment of Arg 320-IIe cleavage by factor Xa.

Adult↗
PubMed1986

Analysis of promoter and enhancer cell type specificities and the regulation of immunoglobulin gene expression.

We have analysed the properties of IgH promoter (VH) and enhancer (Ig) regions which were used to drive the expression of the chloramphenicol acetyl transferase (CAT) gene (cat) in recombinant plasmids. We observe little synergistic effect between the VH promoter and Ig enhancer on cat gene expression in our constructs. Replacing the VH promoter by the thymidine kinase (TK) promoter does not affect the enhancer-mediated B-cell-specific expression of the cat gene. However, replacement of the VH promoter by the mouse renin gene promoter, which is not normally expressed in B cells, completely abolishes cat gene expression in cells of this lineage. When the Ig enhancer is replaced by the SV40 enhancer (SV), CAT activity is restricted to B cells. The VH promoter is as efficient as the TK promoter in a preB cell line. Extending the size of the VH promoter fragment to include sequences between 126 to 639 bp upstream from the transcription start point results in an eight-fold decrease in CAT activity. In this situation, the tissue specificity of the promoter cat fusion is maintained. Among the various combinations tested here, the association of the TK promoter and the Ig enhancer expresses the cat gene most efficiently. The implications of these observations are discussed.

Acetyltransferases↗
PubMed1986

[Autoimmune thrombopenia and pregnancy. Value of counting scalp platelets].

Fetuses of mothers who have auto-immune thrombocytopenia are at risk in utero of having transitory thrombocytopenia. There is no maternal biological test that can predict the numbers of platelets in the fetus. This count of platelet numbers can be estimated from taking fetal blood from the scalp at the onset of labour, and if the count is less than 50 X 10(9) per litre a caesarean operation is indicated. The authors report a series of 23 pregnancies where the mother had auto-immune thrombocytopenia and where fetal scalp blood sampling was indicated. This series has been compared with a previous series of 14 pregnancies where scalp sampling was not carried out. There was no case of severe fetal thrombocytopenia after scalp sampling was carried out and where the best way of delivery could be predicted early enough in each case. The ease of taking the sample and the safety and reliability of it for estimating the degree of thrombocytopenia in the fetus and thus deciding the method of delivery makes us believe that this method should be used more frequently in cases of maternal thrombocytopenia that appear late in pregnancy.

Autoimmune Diseases↗
PubMed1985

Point mutations that affect translation initiation in the Escherichia coli gal E gene.

This paper describes the selection and characterization of several mutations in the Escherichia coli galactose operon that affect translation initiation of the galE gene but are located outside of the Shine-Dalgarno sequence and the initiator codon. One mutation lies in the gal promoter region and shifts transcription initiation from the galP1 to the galP2 promoter. This results in a gal messenger that is five nucleotides longer and that is translated threefold more efficiently in vivo. This accords with previous observations from in vitro experiments which showed that the longer gal messenger was better translated (Queen & Rosenberg, 1981). The other mutations that affect galE translation are located in the coding sequence immediately downstream from the initiator codon. In contrast to the promoter mutation, these cause alterations in galE expression only when the gene carries a mutated initiator codon or Shine-Dalgarno sequence and have no effect on the wild-type galE gene. These findings are discussed with respect to our present knowledge of translation initiation mechanisms.

Base Sequence↗
PubMed1985

Intravenous immunoglobulin for neonatal isoimmune thrombocytopenia.

An infant with severe, isoimmune thrombocytopenia secondary to maternal anti-Pla 1 immunisation was treated successfully by intravenous gammaglobulin (400 mg/kg per day for five days). This treatment compared with Pla 1 negative platelet transfusions is discussed.

Blood Platelets↗