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Biomedical subjects

J Drouin

Publications and source records attributed to J Drouin.

At least 91 records · Page 5Linked to original sources
PubMed1988

Cloning and expression of the atrial natriuretic factor gene.

Atrial natriuretic factor (ANF) is a 28-amino acid peptide hormone with potent natriuretic, diuretic and vasodilator properties. Isolation and DNA sequence analysis of rat and human cDNA clones revealed that ANF is synthesized from a 126-amino acid precursor which is highly conserved in both species. Southern blot analysis indicated that the ANF gene is present in a single copy per haploid genome. Both human and rat ANF genes were isolated and showed a similar structural organization which consisted of three exons and two introns. The ANF gene was localized to the short arm of human chromosome 1 and mouse chromosome 4. While atria are the major site of expression of the ANF gene in adult heart, other tissues like ventricles, lung, anterior pituitary, hypothalamus and adrenal synthesize ANF albeit to a much lower extent. In ventricles, ANF mRNA levels are 150 times lower than in atria. However, in cardiac hypertrophy or in congestive heart failure, ventricular ANF mRNA and peptide levels are dramatically (100-fold) increased both in animal models and in humans. This suggests that ventricles are a major site of ANF gene expression in certain pathophysiological conditions and that ANF is not an exclusively atrial peptide as was originally thought.

Animals↗
PubMed1988

Residual amounts of glycoprotein Ib concomitant with near-absence of glycoprotein IX in platelets of Bernard-Soulier patients.

A study of the Bernard-Soulier syndrome in two unrelated families using different polyclonal antibodies in a sensitive immunoblot assay showed residual amounts of platelet membrane glycoprotein (GP) lb in the eight homozygotes, as well as the near-absence of GPlb beta and GPIX. The eight heterozygotes studied showed a double band pattern for GPlb and about half the normal level of GPlb beta and GPIX. Therefore, we conclude that the Bernard-Soulier syndrome is heterogeneous and is probably not due to gene deletions.

Bernard-Soulier Syndrome↗
PubMed1987

Thyroid hormone stimulates rat pro-natriodilatin mRNA levels in primary cardiocyte cultures.

Pro-natriodilatin (PND) is the precursor for atrial natriuretic peptide (ANP), a hormone which plays an important role in cardiovascular homeostasis. Since the effects of thyroid hormone (T3) on the cardiovascular and renal systems appear to mimic those elicited by ANP, we studied the effect of T3 on PND gene expression using rat neonatal cardiocytes in primary cultures. Treatment of cardiocytes for 48 h with T3 (5 X 10(-9) M) results in a maximal increase in PND mRNA levels; this increase is two fold in atrial and four fold in ventricular cell cultures. These results taken together with a previous report showing decreased plasma ANP in hypothyroid and increased plasma ANP in hyperthyroid rats suggest that at least some of the cardiovascular and renal effects of T3 may be mediated by a T3-dependent increase in PND gene expression.

Animals↗
PubMed1987

Pro-opiomelanocortin gene: a model for negative regulation of transcription by glucocorticoids.

The gene encoding pro-opiomelanocortin (POMC) offers an interesting model system to study negative control of transcription in eucaryotes. Indeed, glucocorticoid hormones specifically inhibit transcription of the POMC gene in the anterior pituitary. The POMC gene is predominantly expressed in the anterior and intermediate lobes of the pituitary. However, only anterior pituitary POMC transcription is inhibited by glucocorticoids and stimulated by corticotropin-releasing hormone (CRH). Rat POMC promoter sequences required for anterior pituitary-specific expression were localized between positions -480 and -34 base pairs (bp) by DNA-mediated gene transfer into the POMC-expressing tumor cells. AtT-20. These POMC promoter sequences also confer glucocorticoid inhibition of transcription. While two of the six in vitro binding sites for purified glucocorticoid receptor identified in the rat POMC gene are within these sequences, only one is required for glucocorticoid inhibition; this binding site is located at position -63 bp in the promoter and overlaps a putative CCAAT box sequence. The DNA sequence of the POMC -63 bp receptor binding site is homologous to receptor binding sites identified in the glucocorticoid responsive element (GRE) of glucocorticoid-inducible genes. However, DNA sequence divergencies between these sites, in particular within the conserved hexanucleotide sequence 5'-TGTYCT-3', may be involved in their opposite transcriptional activity. Alternatively, binding of the receptor in the promoter proximal region of the POMC gene may inhibit transcription by a hormone-dependent repressor mechanism.

Animals↗
PubMed1987

Combined intraommaya methotrexate, cytosine arabinoside, hydrocortisone and thio-TEPA for meningeal involvement by malignancies.

Twenty-three adult patients with meningeal involvement by a variety of malignancies were treated with the intra-Ommaya combination of methotrexate, hydrocortisone, cytosine arabinoside, and thio-TEPA. Whole brain irradiation was also administered to most patients who had not previously received it. Most patients demonstrated improvement of cerebrospinal fluid parameters, but only 50% of the patients experienced neurological improvement. Patients who did not receive cranial irradiation and performance status 4 patients were less likely to respond than were patients who did receive cranial irradiation as part of their treatment and patients who were performance status 0-3. Four patients developed possible and 2 patients developed probable or definite serious neurological complications. Another 4 patients developed less severe, reversible neurological toxicity. It is possible (but still uncertain) that this regimen is more toxic than other less intensive regimens, and further studies should be undertaken cautiously.

Adult↗
PubMed1987

A program for the graphic representation and manipulation of DNA sequences.

We have developed a program for the graphic representation and manipulation of DNA sequences. The program (named CARTE from the French for 'map') is intended as a tool in the planning and analysis of recombinant DNA experiments. DNA sequences are represented as standard restriction maps, using any desired combination of restriction enzymes. Features of interest, such as promoters or coding sequences, can be highlighted. The sequence can be manipulated to mimic cloning, using deletions, insertions or replacements at specified sites. This process is facilitated by the simultaneous display of a graphic map of the entire sequence, a detailed picture of the work in progress, and a menu of functions.

Base Sequence↗
PubMed1987

Tissue-specific activity of the pro-opiomelanocortin gene promoter.

The pro-opiomelanocortin (POMC) gene is specifically expressed in corticotroph cells of the anterior pituitary. To define the POMC promoter sequences responsible for tissue-specific expression, we assessed POMC promoter activity by gene transfer into POMC-expressing pituitary tumor cells (AtT-20) and fibroblast L cells. The rat POMC promoter was only efficiently utilized and correctly transcribed in AtT-20 cells. 5'-End deletion analysis revealed two promoter regions required for activity in AtT-20 cells. When tested by fusion to a heterologous promoter, DNA fragments corresponding to both regions exhibited tissue-specific activity, suggesting the presence of at least two tissue-specific DNA sequence elements within the promoter. In summary, POMC promoter sequences from -480 to -34 base pairs appear sufficient to mimic the specificity of anterior pituitary expression.

Animals↗
PubMed1987

Tissue-specific regulation of pituitary proopiomelanocortin gene transcription by corticotropin-releasing hormone, 3',5'-cyclic adenosine monophosphate, and glucocorticoids.

The release of pituitary hormones derived from POMC is under multihormonal and tissue-specific control in the anterior and intermediate lobes of the pituitary where the same single-copy POMC gene is expressed. In order to assess the tissue-specificity of POMC regulation at the gene level, we have previously shown that glucocorticoids inhibit POMC gene transcription in the anterior but not in the intermediate pituitary. In the present work, we have investigated the role of corticotropin-releasing hormone (CRH) and cAMP in the differential regulation of anterior and intermediate pituitary POMC gene transcription. Using pituitary cells in primary culture and nuclear run-on transcription assays, we found that cAMP increases POMC gene transcription rate to the same extent in both anterior and intermediate pituitary cells while CRH only increases anterior pituitary POMC transcription rate. This observation contrasts with the stimulation of ACTH and alpha MSH release from anterior and intermediate pituitary cells, respectively, by both CRH and cAMP. In the anterior pituitary, both CRH and cAMP stimulated as well as basal POMC transcription rates are inhibited by glucocorticoids. In the anterior pituitary, both CRH stimulation and glucocorticoid inhibition of POMC transcription are rapid and do not require de novo protein synthesis. Thus, we report that transcription of the POMC gene is differentially regulated by CRH, cAMP, and glucocorticoids in anterior and intermediate pituitary tissues, in much the same way as the control of POMC processing and release.

Actins↗
PubMed1987

Unusual proopiomelanocortin ribonucleic acids in extrapituitary tissues: intronless transcripts in testes and long poly(A) tails in hypothalamus.

The POMC gene is predominantly expressed in the pituitary gland; it is also expressed in various extrapituitary tissues. While POMC mRNAs of similar size (approximately equal to 1000 nucleotides) are present in the anterior and neurointermediate lobes of the pituitary, other POMC-expressing tissues contain POMC mRNAs of different sizes. Longer POMC mRNAs are observed in the hypothalamus. Using S1 nuclease mapping and mRNA deadenylation by RNase H, we have shown that these large hypothalamic POMC mRNAs have longer poly(A) tails than pituitary POMC transcripts but contain the same transcripted sequences. In contrast, the testes contain POMC transcripts which are smaller than pituitary POMC mRNA. RNase and S1 nuclease mapping analyses suggest that these short transcripts do not contain sequences transcribed from pituitary exons 1 and 2. Indeed, as revealed by primer-extension experiments, these transcripts appear to initiate within exon 3 sequences of the POMC gene. The heterogeneous 5'-ends of these short testicular transcripts map into the NH2-terminal portion of the precursor in the region encoding gamma MSH; if ever translated, these transcripts would produce a form of POMC that would be truncated at the NH2-terminus and therefore would be devoid of any signal peptide sequence. Interestingly, the sequence of the short testicular transcripts corresponds to that of the mouse POMC pseudogene, suggesting that this POMC pseudogene may have derived from genomic integration of testicular transcripts via a cDNA intermediate.

Animals↗
PubMed1986

Characterization of reticulofibroblastoid colonies (CFU-RF) derived from bone marrow and long-term marrow culture monolayers.

The maintenance of hemopoietic precursors in long-term liquid bone marrow cultures (LTBMC) is associated with the presence of an adherent stromal layer composed of heterogeneous cell populations. We have used a culture assay to promote the growth of one of its cellular components and characterize its properties. Freshly obtained bone marrow cells and cells derived from the adherent layer of LTBMC were grown in methylcellulose-clotted plasma in the presence of phytohemagglutinin-stimulated leukocyte-conditioned medium (PHA-LCM), hydrocortisone (HC), and citrated normal human plasma. Both sources contained cells (CFU-RF) that gave rise to colonies of cells with a reticulofibroblastoid appearance. In the presence of HC, most colonies contained lipid-laden cells. Colonies could be further propagated as adherent layers when transferred into liquid cultures. These cells produced laminin, fibronectin, and collagen types I, III, IV, and V. They were negative for Von Willebrand factor VIII. The ability to synthesize laminin and collagen type IV distinguished these cells from a population of previously described bone marrow fibroblasts (CFU-F). The relationship of CFU-RF to hemopoietic precursors was investigated using patients with chronic myeloid leukemia and bone marrow transplant recipients. Cells within CFU-RF-derived colonies were uniformly negative for the Philadelphia chromosome, thus making it unlikely that they belonged to the malignant hemopoietic clone. CFU-RF-derived colonies in bone marrow transplant recipients were found to be exclusively of host origin. Both observations support the view that CFU-RF is not part of the repertoire of hemopoietic stem cells.

Antigens↗
PubMed1986

Glucocorticoid inhibition of transcription from episomal proopiomelanocortin gene promoter.

Glucocorticoid hormones alter transcription of specific genes. Glucocorticoid-stimulated genes have been especially useful in unraveling molecular events responsible for positive gene regulation in mammals. The gene encoding proopiomelanocortin (POMC), which is under feedback inhibition by glucocorticoids, provides a model system to study negative gene regulation. Using an episomal bovine papilloma virus vector, we now demonstrate that a 769-base-pair fragment containing the rat POMC promoter is sufficient to confer glucocorticoid inhibition. Transcription from the episomal POMC promoter starts at the same site and is inhibited by glucocorticoids to the same extent as POMC transcription in the anterior pituitary. Glucocorticoid inhibition is specific for POMC transcripts; neither bovine papilloma virus nor cellular actin mRNAs are affected by glucocorticoids. Thus, the episomal bovine papilloma virus/POMC system can be used to study the relationship between negative regulation of POMC transcription and chromatin structure.

Animals↗
PubMed1985

Structure of the rat pro-opiomelanocortin (POMC) gene.

The gene encoding pro-opiomelanocortin (POMC) presents unique regulatory features. In particular, glucocorticoids inhibit transcription of the POMC gene in the anterior pituitary, but not in the intermediate pituitary. In order to study the mechanism leading to transcriptional inhibition of POMC by glucocorticoid and the interaction of the glucocorticoid receptor complex with specific DNA sequences along the POMC gene, we have cloned the rat POMC gene and determined its structure. The gene is composed of three exons and appears to be present at a single copy per haploid genome. Besides the usual regulatory signals like 'TATA' and 'CCAAT' boxes, the upstream region contains sequences homologous to known enhancer sequences and to the glucocorticoid receptor binding site observed in glucocorticoid-responsive genes.

Animals↗
PubMed1985

The gene for rat atrial natriuretic factor.

Atrial natriuretic factor (ANF), a peptide hormone recently isolated from heart atria, appears to play an important role in the regulation of extracellular fluid volume and blood pressure. Indeed, natural and synthetic ANF rapidly and markedly stimulate natriuresis and diuresis and produce smooth muscle relaxation. Consistent with the hypothesis that ANF is a novel hormone, it was recently shown that ANF is present in circulation, and high affinity membrane receptors specific for ANF have been described in renal, vascular, and adrenal tissues. These important biological activities suggest that conditions like hypertension could be associated with defective ANF gene expression. We and others have shown by cDNA cloning that ANF is part of a larger precursor, pro-natriodilatin (PND). We now describe the isolation and structural analysis of the rat PND gene. Southern blot analysis of rat genomic DNA suggests the presence of a single PND gene per haploid genome. The PND coding sequences are interrupted by two short introns. A long alternating purine-pyrimidine tract (GT)9GATG(GT)27 is found 111 base pairs downstream of the polyadenylation site; such sequences could adopt Z-DNA configuration and they have been associated with sequences that appear very active in intergenic recombination. Comparison of the rat and human PND genomic sequences shows highest homology in 5'-flanking as well as in coding sequences. The rat PND gene will be a useful model to study the physiology and pathology of this important regulator of the cardiovascular system.

Animals↗
PubMed1985

Plasmodium falciparum malaria mimicking autoimmune hemolytic anemia during pregnancy.

A 30-year-old woman contracted Plasmodium falciparum malaria in the first trimester of her pregnancy while taking chloroquine for malaria prophylaxis. Her illness was characterized by hemolytic anemia with IgG1 coating of the surface of the erythrocytes and IgG3 in her serum. The hemolysis subsided following treatment of the malaria infection early in the third trimester. She delivered at term an infant who had hypoplasia of the right tibia and fibula and absence of the fifth ray of the right foot. The hemolytic process was attributed to the malaria infection, and the birth defect may have been related to the antimalarial therapy in the first trimester of pregnancy.

Abnormalities, Drug-Induced↗
PubMed1985

Opposite regulation of pro-opiomelanocortin gene transcription by glucocorticoids and CRH.

Pro-opiomelanocortin (POMC) is the pituitary precursor for adrenocorticotropin (ACTH), beta-endorphin, beta-lipotropin and the melanotropins. The level of ACTH secretion from the anterior pituitary is largely determined by the competing action of the stimulatory hypothalamic hormone, corticoliberin (corticotropin-releasing hormone, CRH), and the inhibitory effect of glucocorticoids. We now demonstrate that these two hormones, glucocorticoids and CRH, also inhibit and stimulate, respectively, the transcription rate of the POMC gene as measured by nuclear run-on transcription assays. Indeed, we show both by in vivo treatment and with rat anterior pituitary cells in primary culture that glucocorticoids inhibit within 30 min transcription of the POMC gene. Similarly, we find that CRH stimulates POMC gene transcription within 15 min. CRH and glucocorticoids can compete with each other to set the rate of POMC transcription. Our results indicate that CRH and glucocorticoids regulate anterior pituitary POMC gene transcription in addition to their well-documented role in the control of POMC peptide release.

Animals↗