Stream nitrate variations explained by ground water head fluctuations in a pyrite-bearing aquifer.

In the context of agricultural nitrogen excesses in northwestern France, pyrite-bearing weathered schist aquifers represent important hydrological compartments due to their capacity to eliminate nitrate (NO3-). Under oxygen-free conditions, nitrate is reduced simultaneously with the oxidation of pyrite leading to the release of sulfate (SO4/2-). The aim of the present study is to identify the hydrological conditions under which the weathered schist ground water influences the stream water chemistry, leading to a decrease in NO3- concentration. We measured the ground water head on a small catchment over weathered schist, near the bank and under the streambed, and analyzed the chemical composition of the ground water as well as the stream water on both seasonal and storm-event timescales. Using SO4/2- as a tracer of the weathered schist ground water, we showed that ground water inflow caused a decrease of NO3- concentration in the stream during the autumn as well as during storm events in spring and summer. In summer, the NO3- concentration was controlled by the sources of the stream, and in winter by the shallow ground water inflow. The effect of the weathered schist ground water on the NO3- depletion remained relatively limited in time. This effect persisted into late autumn as long as the NO3(-) -rich shallow ground water did not feed the stream. The duration and intensity of the effect would be extended by decreasing the shallow ground water inflow, which depends on climate as well as the presence of landscape features such as hedges and buffer zones.

[Outcome of operated transposition of the great vessels]. / Devenir des transpositions des gros vaisseaux opérées.

The object of this report is to describe the long-term outcome of patients operated for transposition of the great vessels. Understanding what we mean by transposition of the great vessels, the surgical options with their advantages, limitations and complications, helps the cardiologist decide on the mode of follow-up, the investigations and even the reoperations that these patients may need. The authors review the results of the literature and their experience over the years with children and adults with congenital heart disease. Although considerable progress has been made in the management of a condition considered to be constantly and often rapidly fatal, most of the procedures which allow patients to have a normal or quasi-normal quality of life have not resolved all the problems and require maintenance of long-term follow-up.

Linear insertion of atrioventricular valves without septal defect: a new anatomical landmark for Down's syndrome?

Our objective was to explore whether minor anatomical abnormalities of the septal insertion of tricuspid and mitral valves could be a feature of trisomy 21 in fetuses with an otherwise normal heart. Postmortem examinations were performed in 41 fetuses affected by Down's syndrome and in 52 controls. Adjoining the standard postmortem procedure, an apex-to-base section of the crux of the heart was made on a plane corresponding to the sonographic four-chamber view. This allowed gross and histological examination of the hinge points of tricuspid and mitral leaflets, showing the usual apical displacement of the tricuspid valve in all controls. Of 41 fetuses affected by Down's syndrome, 18 had a structural heart defect. Of the 23 Down syndrome fetuses without a patent heart defect, 16 (i.e., 69% of those considered as having 'normal hearts') had nevertheless a linear insertion of atrioventricular valves at autopsy. Prospective clinical studies are required to evaluate if these postmortem findings can be transposed to the clinical setting of 2nd-trimester sonographic screening.

In vitro and in vivo effects of glucocorticoids on gene transfer to skeletal muscle.

As a pharmacological approach to potentially improve gene transfer efficiency into skeletal muscle cells, glucocorticoids were shown here to allow efficient transfection of cultured and mouse human myoblasts, human pulmonary A549 cells, but not dog myoblasts, independently of the transfection protocol, the reporter gene and the transcription promoter employed. Transduction with adenovirus was also increased by dexamethasone. Pretreatment of cells 48 h prior to transfection was most effective and was shown to be concentration-dependent. This effect is mediated by binding to the glucocorticoid receptor, but not by glucocorticoid responsive elements present in the vectors. The acute dexamethasone effect could be due to increased plasmid entry into the cells as suggested by Southern blot, whereas the sustained increase of luciferase activity in dexamethasone-treated cultures may be related to intracellular mechanisms following cell entry. In mice in vivo, a similar increase of luciferase activity upon glucocorticoid treatment was found.

[Congenital heart disease and nuchal translucency with normal karyotype. Report of 3 cases]. / Cardiopathie congénitale et clarté nucale avec caryotype normal. A propos de 3 cas.

We report three pregnancies where enlarged nuchal translucency was discovered at the first trimester transvaginal ultrasound examination; congenital heart disease developed later. Two cases of hypoplastic left heart were diagnosed prenatally at the mid-trimester sonographic examination. The pregnancies were terminated. In the third case, a supravalvular pulmonary stenosis was discovered on the second day of life. Further investigations demonstrated a mutation on the elastin locus, thus confirming the diagnosis of Williams-Beuren syndrome. The role of nuchal translucency as a risk marker for congenital heart disease is discussed.

Up to 100-fold increase of apparent gene expression in the presence of Epstein-Barr virus oriP sequences and EBNA1: implications of the nuclear import of plasmids.

A 100-fold increase in luciferase activity was observed in 293 cells, stably expressing Epstein-Barr nuclear antigen 1 (EBNA1; 293-EBNA1 cells), that had been transiently transfected with plasmids carrying Epstein-Barr virus (EBV) oriP sequences. This increase was observed in comparison to reporter gene activity obtained after transfection with a plasmid carrying no oriP sequences. The luciferase gene on these plasmids was under the control of either the cytomegalovirus immediate-early 1 gene enhancer-promoter (CMV IE1) or the Rous sarcoma virus promoter. The increase of reporter gene activity was not due to plasmid replication, since a similar enhancement was observed in the presence of aphidicolin, an inhibitor of replicative DNA synthesis, or after deletion of the dyad symmetry (DS) element within oriP. Luciferase production was not increased in the presence of only the DS element. Microinjection of plasmids carrying the CMV IE1 promoter-driven luciferase gene with or without oriP sequences into the nuclei of 293-EBNA1 cells resulted in a 17-fold increase in luciferase activity. Cytoplasmic injection of these plasmids led to an enhancement of luciferase activity of up to 100-fold. This difference in the factor of activation after nuclear or cytoplasmic injection could be ascribed to increased transport of plasmids carrying oriP from the cytoplasm to the nucleus in the presence of EBNA1. These data suggest the possibility of substantially increasing the apparent expression of a gene under the control of a strong constitutive promoter in the presence of oriP sequences and EBNA1. This improvement in expression is due to intranuclear enhancement of gene expression. oriP-specific transport of plasmid DNA from the cytoplasm of 293-EBNA1 cells to the nucleus seems to contribute to the observed effect.

[Microdeletion of the chromosome 22q11 in children: apropos of a series of 49 patients]. / La microdélétion du chromosome 22q11 chez l'enfant: à propos d'une série de 49 patients.

UNLABELLED: Most of the children with Di George syndrome and 60% of patients with velocardiofacial syndrome exhibit a microdeletion within chromosome 22q11. The phenotypic expression of this chromosomal abnormality is highly variable. PATIENTS: Forty-nine children, 0 to 15 years of age, were demonstrated as carriers of a 22q11 microdeletion. The main referral diagnoses were: Di George syndrome (19 cases), velocardiofacial syndrome (14 cases); congenital heart defect with dysmorphism (9 cases); hypoparathyroidism (2 cases). The microdeletion was detected by fluorescent in situ hybridization with probes specific of the 22q11 region. RESULTS: Facial dysmorphism was the only constant feature. A congenital heart defect was present in 84% of cases. Significant hypocalcemia was documented in 51% of cases and thymic hypo or agenesis in 83%. Significant immune deficiency was documented in nine cases. The most frequent associated defects were urinary tract malformations (8 cases). A cleft palate was present in height enfants but velopharyngeal insufficiency was almost constant. Two-thirds of children had psychomotor delay, and five children exhibited behavioral problems. Of the 35 couples of parents tested, eight mothers were found to be carriers of the deletion. CONCLUSION: For the pediatrician, it is essential to know the variability of the clinical picture. The long-term prognosis is conditioned by the possibility of mental retardation and learning disabilities. Parents should be tested for the presence of the deletion. The occurrence of the microdeletion in asymptomatic relatives raises difficult problems in genetic counselling.

Clinical and molecular study of DiGeorge sequence.

DiGeorge sequence (DGS) is a developmental field defect of the third and fourth pharyngeal pouches. The cardinal features of the syndrome are hypo- or aplasia of the thymus and parathyroids, congenital heart defect of the conotruncal type and characteristic facial dysmorphism. Such a pattern of malformations has been associated with various conditions but it is now well established that most cases of DGS are due to haplo-insufficiency of the chromosome 22q11 region. We report here a series of 16 patients, including a familial case. Minimal criteria for inclusion in this series were two or more of the following features: conotruncal heart defect, hypocalcaemia, hypoplastic/absent thymus and typical facial dysmorphism. Molecular analysis with specific probes of the 22q11 region was conducted in all patients according to two methods, fluorescent in situ hybridization and DNA dosage analysis. A deletion was found at the molecular level in all patients. We emphasize the fact that clinical analysis remains an important step of the diagnosis. The implication of these molecular techniques on diagnosis, prognosis and genetic counselling of DGS are discussed.

Amphibian oocytes and sphere organelles: are the U snRNA genes amplified?

The sphere organelles (spheres) of Xenopus and other amphibian oocytes are known to contain small nuclear ribonucleoprotein particles (snRNPs) and have been suggested to play a role in snRNP complex assembly. Coupled with the similarities that exist between spheres and nucleoli and the quantitative and kinetic aspects of snRNA synthesis in the Xenopus oocyte, we have investigated whether or not the U snRNA encoding genes are amplified in Xenopus oogenesis, the spheres being possible sites for the location of such extrachromosomal gene copies. By applying a number of quantitative nucleic acid hybridization procedures to both total and fractionated oocyte and somatic DNA, employing both homologous and heterologous U snRNA gene probes and suitable amplification and non-amplification control probes, we show that the U snRNA genes do not undergo any major amplification in Xenopus oogenesis. Therefore, the analogy between the sphere organelles and nucleoli appears to be limited. The role of the spheres and their relationship to other snRNP containing structures, specifically B snurposomes, and the sphere organizer loci remains obscure.

Transferrin-polycation-mediated introduction of DNA into human leukemic cells: stimulation by agents that affect the survival of transfected DNA or modulate transferrin receptor levels.

We have subverted a receptor-mediated endocytosis event to transport genes into human leukemic cells. By coupling the natural iron-delivery protein transferrin to the DNA-binding polycations polylysine or protamine, we have created protein conjugates that bind nucleic acids and carry them into the cell during the normal transferrin cycle [Wagner, E., Zenke, M., Cotten, M., Beug, H. & Birnstiel, M. L. (1990) Proc. Natl. Acad. Sci. USA 87, 3410-3414]. We demonstrate here that this procedure is useful for a human leukemic cell line. We enhanced the rate of gene delivery by (i) increasing the transferrin receptor density through treatment of the cells with the cell-permeable iron chelator desferrioxamine, (ii) interfering with the synthesis of heme with succinyl acetone treatment, or (iii) stimulating the degradation of heme with cobalt chloride treatment. Consistent with gene delivery as an endocytosis event, we show that the subsequent expression in K-562 cells of a gene included in the transported DNA depends upon the cellular presence of the lysosomotropic agent chloroquine. By contrast, monensin blocks "transferrinfection," as does incubation of the cells at 18 degrees C.

GATC sequences, DNA nicks and the MutH function in Escherichia coli mismatch repair.

Circular heteroduplex DNAs of bacteriophage phi X174 have been constructed carrying either a G:T (Eam+/Eam3) or a G:A (Bam+/Bam16) mismatch and containing either two, one or no GATC sequences. Mismatches were efficiently repaired in wild-type Escherichia coli transfected with phi X174 heteroduplexes only when two unmethylated GATC sequences were present in phi X174 DNA. The requirements for GATC sequences in substrate DNA and for the E. coli MutH function in E. coli mismatch repair can be alleviated by the presence of a persistent nick (transfection with nicked heteroduplex DNA in ligase temperature-sensitive mutant at 40 degrees C). A persistent nick in the GATC sequence is as effective in stimulating mutL- and mutS-dependent mismatch repair as a nick distant from the GATC sequence and from the mismatch. These observations suggest that the MutH protein participates in methyl-directed mismatch repair by recognizing unmethylated DNA GATC sequences and/or stimulating the nicking of unmethylated strands.

GATC sequence and mismatch repair in Escherichia coli.

The Escherichia coli mismatch repair system greatly improves DNA replication fidelity by repairing single mispaired and unpaired bases in newly synthesized DNA strands. Transient undermethylation of the GATC sequences makes the newly synthesized strands susceptible to mismatch repair enzymes. The role of unmethylated GATC sequences in mismatch repair was tested in transfection experiments with heteroduplex DNA of phage phi 174 without any GATC sequence or with two GATC sequences, containing in addition either a G:T mismatch (Eam+/Eam3) or a G:A mismatch (Bam+/Bam16). It appears that only DNA containing GATC sequences is subject to efficient mismatch repair dependent on E. coli mutH, mutL, mutS and mutU genes; however, also in the absence of GATC sequence some mut-dependent mismatch repair can be observed. These observations suggest that the mismatch repair enzymes recognize both the mismatch and the unmethylated GATC sequence in DNA over long distances. The presence of GATC sequence(s) in the substrate appears to be required for full mismatch repair activity and not only for its strand specificity according to the GATC methylation state.

Processing of mispaired and unpaired bases in heteroduplex DNA in E. coli.

Bacteriophage lambda and phi X 174 DNAs, carrying sequenced mutations, have been used to construct in vitro defined species of heteroduplex DNA. Such heteroduplex DNAs were introduced by transfection, as single copies, into E. coli host cells. The progeny of individual heteroduplex molecules from each infective center was analyzed. The effect of the presence of GATC sequences (phi X 174 system) and of their methylation (lambda system) was tested. The following conclusions can be drawn: some mismatched base pairs trigger the process of mismatch repair, causing a localized strand-to-strand information transfer in heteroduplex DNA: transition mismatches G:T and A:C are efficiently repaired, whereas the six transversion mismatches are not always readily recognized and/or repaired. The recognition of transversion mismatches appears to depend on the neighbouring nucleotide sequence; single unpaired bases (frameshift mutation "mismatches") are recognized and repaired, some equally efficiently on both strands (longer and shorter), some more efficiently on the shorter (-1) strand; large non-homologies (about 800 bases) are not repaired by the Mut H, L, S, U system, but some other process repairs the non-homology with a relatively low efficiency; full methylation of GATC sequences inhibits mismatch repair on the methylated strand: this is the chemical basis of strand discrimination (old/new) in mismatch correction; unmethylated GATC sequences appear to improve mismatch repair of a G:T mismatch in phi X 174 DNA, but there may be some residual mismatch repair in GATC-free phi X 174, at least for some mismatches.(ABSTRACT TRUNCATED AT 250 WORDS)

[Behçet's disease in a 2-year-old girl]. / Maladie de Behçet chez une fillette de 2 ans.

The authors report a case of gangrenous stomatitis with lingual and anal ulcers and pericarditis in a 2-year-old girl. They propose the diagnosis of Behçet's syndrome for this patient despite the absence of uveitis.