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D Thomas

Publications and source records attributed to D Thomas.

At least 343 records · Page 19Linked to original sources
PubMed1997

Selective feticide by embolization in twin-twin transfusion syndrome. A report of two cases.

BACKGROUND: The early development of complications in twin-twin transfusion syndrome is a poor prognostic sign. For this reason, new techniques for intrauterine therapy are being developed: invasive options, such as selective feticide of one of the twins, have been reported. CASES: Two cases of twin-twin transfusion syndrome in the late second trimester were treated by selective feticide using vascular embolization to the more severely damaged fetus. In one case the embolized fetus was a hydropic recipient with a normal cotwin; in the other, the donor fetus was affected by bilateral hydrocephalus. These fetuses underwent ultrasound-guided embolization using a bolus of histoacryl injected into the umbilical vein and fetal heart. Both patients went on to deliver healthy singletons in the third trimester. CONCLUSION: In twin-twin transfusion syndrome of early onset, embolization may help one of the twins survive. This technique is neither time-consuming nor expensive and does not require a general anesthetic.

Adult↗
PubMed1997

[Echocardiographic diagnosis of left intraventricular thrombus. A comparative study of 2.5, 3.5 and 5 MHz transducers].

The authors undertook a prospective and comparative echocardiographic study of 2.5, 3.5 and 5 MHz ultrasonic transducers for the detection of left ventricular mural thrombosis in 53 patients with left ventricular dysfunction. Thirty-three patients had advanced ischaemic heart disease following anterior myocardial infarction and 20 had dilated cardiomyopathy with a left ventricular ejection fraction of < or = 40%. Eighty-two per cent of patients had anticoagulant therapy. The diagnosis of thrombosis was based on Asinger's classification. Eleven thrombi were detected, an incidence of 21%. Using the 5 MHz transducer as a reference, the sensitivity of the 3.5 MHz transducer was 100% and much greater than that of the 2.5 MHz transducer (55%) which was associated with 4 false positive results. The specificities were respectively 97 and 86% for the 3.5 and 2.5 MHz transducers. There was no correlation between the apical Doppler flow velocities and the presence of mural thrombosis. Atrial fibrillation was significantly associated with mural thrombosis (p = 0.04). The increased sensitivity associated with transducers of higher frequency is, however, limited by the echogenicity of patients. The introduction of transducers of variable frequencies should facilitate the diagnosis and improve the sensitivity of echocardiography in detecting left ventricular mural thrombosis.

Aged↗
PubMed1997

[Use of abciximab during coronary angioplasty].

The IIb-IIIa glycoprotein is the platelet receptor of fibrinogen and the final common pathway of platelet activation and aggregation. Abciximab is a Fab fragment of the chimeric monoclonal antibody (c7E3) interfering with the glycoprotein receptor. It is the only anti IIb-IIIa currently available, commercialized under the name of Reopro. Preliminary clinical data has been obtained with its use in high risk coronary angioplasty. The EPIC trial showed a 35% relative reduction of the principal combined criterion of judgement of cardiac morbidity and mortality at 1 month, a benefit even greater in acute coronary syndromes (-72%) than in programmed procedures for complex type C lesions (-10%). The incidence of severe bleeding was high (14%). The results of the CAPTURE trial could widen the indications of abciximab to include the period surrounding angioplasty for unstable angina as the use of Reopro in the 24 hours before the procedure significantly reduced the risk of ischaemic events (10.8% versus 16.4%). In programmed angioplasty, the EPILOG trial investigated the effects of adapting the dose of heparin and an infusion of abciximab to body weight early (4th to 6th hour) withdrawal of the arterial introducer without continuing heparin. Using a 70 IU/Kg dosage modulated to algorithms taking into account the ACT, the incidence of bleeding complications was reduced to 1.8%, the same as the control group, and the benefits with regards to ischaemic events were not only maintained but increased (a 56% reduction at 1 months). Utilization of abciximab would be supported by the Cost saving approach of the EPIC trial 3-years follow-up which showed presentation of the initial benefits.

Abciximab↗
PubMed1996

Intracellular acidification mediates the proliferative response of PC12 cells induced by potassium ferricyanide and involves MAP kinase activation.

Potassium ferricyanide is known to elicit cell growth and mitogenesis in various cells by stimulating a transplasma membrane electron-transport system. When serum-starved PC12 cells were treated with potassium ferricyanide, stimulation of mitogenesis was evidenced by enhanced DNA synthesis, as well as by increased cell numbers. Intracellular pH (pH(i)) of PC12 cells was measured at 37 degrees C by microfluorimetric analysis of 2',7'-bis-(2-carboxyethyl)-5(and -6)-carboxyfluorescein (BCECF). The resting pH(i) of unstimulated cells was 7.52 (external pH 7.40). Addition of potassium ferricyanide (100 microM) decreased pH(i) by about 0.25 pH units. Lowering pH(i) to a similar extent, either by decreasing external pH (pH(o)) or by adding a weak acid, also elicited a mitogenic response, indicating that intracellular acidification by itself has growth factor-mimicking, mitogenic effects. Nerve growth factor (NGF) or basic fibroblast growth factor (bFGF) triggered proliferation without changes in pH(i). The mitogenic treatments eliciting intracellular acidification did not activate protein kinase C (PKC) but stimulated the p42/p44 mitogen-activated protein (MAP) kinase. Our results indicate that 2 distinct mitogenic pathways are active in PC12 cells: the first is independent of pH(i) and involves activation of the PKC pathway and the second requires a permissive pH(i) value around 7.25 and involves activation of the p42/p44 MAP kinase pathway.

Animals↗
PubMed1996

Molecular cloning and characterization of an insect aquaporin functional comparison with aquaporin 1.

We previously described the structural organization of P25, a member of the major-intrinsic-protein family found in the digestive tract of homopteran sap-sucking insects [Beuron, F., Le Cahérec, F., Guillam, M. T., Cavalier, A., Garret, A., Tassan, J. P., Delamarche, C., Schultz, P., Mallouh, V., Rolland, J. P., Hubert, J.F., Gouranton, J. & Thomas, D. (1995) J. Biol. Chem. 270, 17414-17422]. We demonstrated, by means of introducing P25 tetramers into the membranes of Xenopus oocytes, that this protein exhibits functional properties similar to those of aquaporin 1, the archetypal water channel [Le Cahérec, F., Bron, P., Verbavatz, J. M., Garret, A., Morel, G., Cavalier, A., Bonnec, G., Thomas, D., Gouranton, J. & Hubert, J.F. (1996) J. Cell Sci. 109, 1285-1295]. In the present work, we cloned a full-length cDNA from a Cicadella viridis library with an open reading frame of 765 bp that encoded a 26-kDa protein whose sequence was 43, 40, 36 and 36% identical to aquaporins 1, 2, z and tonoplast intrinsic protein gamma, respectively. Translation of the corresponding RNA in Xenopus oocytes generated a polypeptide that was specifically recognized by polyclonal antibodies raised against native P25. Expression of the protein in Xenopus oocyte membranes was assessed by immunocytochemistry and led to a 15-fold increase of osmotic membrane water permeability. This increase was inhibited by HgCl2. The permeability had an Arrhenius activation energy of 11.7 kJ/mol. We called this protein Cicadella aquaporin (AQPcic). The oocytes expressing Cicadella aquaporin were less sensitive to HgCl2 than oocytes expressing aquaporin 1. In the Xenopus oocyte system, Cicadella aquaporin failed to transport glycerol, urea and ions. It exhibited permeabilities to ethylene glycol and formamide similar to those measured for aquaporin 1 under the same conditions.

Amino Acid Sequence↗
PubMed1996

AREVA: multicenter randomized comparison of low-dose versus standard-dose anticoagulation in patients with mechanical prosthetic heart valves.

BACKGROUND: Moderate anticoagulation may be proposed to reduce the risk of hemorrhage for certain patients with a mechanical prosthesis, but the consequences for risk of thromboembolism are debated. METHODS AND RESULTS: The purpose of the AREVA trial was to compare moderate oral anticoagulation (international normalized ratio [INR] of 2.0 to 3.0) with the usual regimen (INR of 3.0 to 4.5) after a single-valve replacement with a mechanical prosthesis, either Omnicarbon or St Jude. Patients included were between 18 and 75 years old, in sinus rhythm, and with a left atrial diameter < or = 50 mm on the time-motion echocardiogram. Patients were randomized for INR after surgery. From 1991 to 1994, 433 patients underwent valve replacement (aortic, 414; mitral, 19) with 353 St Jude and 80 Omnicarbon prostheses; 380 patients were randomized for INR: 188 for INR 2.0 to 3.0 and 192 for INR 3.0 to 4.5. Mean follow-up was 2.2 years (1 to 4 years). Analysis of 18001 INR samples showed that the mean of the median of INR was 2.74 +/- 0.35 in the 2.0 to 3.0 group and 3.21 +/- 0.33 in the 3.0 to 4.5 group (P < .0001). Thromboembolic events, as assessed from clinical data and CT brain scans, occurred in 10 patients in the 2.0 to 3.0 INR group and 9 patients in the 3.0 to 4.5 INR group (P = .78). Hemorrhagic events occurred in 34 patients in the 2.0 to 3.0 INR group and 56 patients in the 3.0 to 4.5 INR group (P < .01), with 13 and 19 major hemorrhagic events, respectively (P = .29). CONCLUSIONS: In selected patients with mechanical prostheses, moderate anticoagulation prevents thromboembolic events as effectively as conventional anticoagulation and reduces the incidence of hemorrhagic events.

Administration, Oral↗
PubMed1996

The study of methionine uptake in Saccharomyces cerevisiae reveals a new family of amino acid permeases.

The screening of mutants resistant to the oxidized analogues of methionine (methionine sulphoxide and ethionine sulphoxide) allowed the characterisation of a yeast mutant strain lacking the high affinity methionine permease and defining a new locus that was called MUP1. The study of MUP1 mutants showed that methionine is transported into yeast cells by three different permeases, a high affinity and two low affinity permeases. The MUP1 gene was cloned and was shown to encode an integral membrane protein with 13 putative membrane-spanning regions. Database comparisons revealed that the yeast genome contains an ORF whose product is highly similar to the MUP1 protein. This protein is shown here to encode very low affinity methionine permease and the corresponding gene was thus called MUP3. It has previously been suggested that the amino acid permeases from yeast all belong to a single family of highly similar proteins. The two methionine permeases encoded by genes MUP1 and MUP3 are only distantly related to this family and thus define a new family of amino acid transporters.

Amino Acid Transport Systems↗
PubMed1996

Parasympathetic activity in Friedrich's ataxia.

We compared 19 patients with Friedreich's ataxia, a progressive hereditary neuromuscular disorder, with 19 healthy age-matched subjects. During nighttime, patients had shorter mean RR and decreased heart rate variability parameters related to parasympathetic activity than healthy subjects, whereas no difference occurred during daytime.

Adult↗
PubMed1996

Regulation of inositol trisphosphate-induced membrane currents in Xenopus oocytes by a Jurkat cell calcium influx factor.

The functional interactions of a Jurkat cell-derived calcium influx factor (CIF) with Ins(1,4,5)P3 were examined by microinjection and voltage-clamp recording of current responses in Xenopus oocytes. CIF, which stimulates Ca2+ entry directly on microinjection, was active at dilutions at which it had no direct effect by augmenting both initial rapid Ins(1,4,5)P3-mediated Ca2+ discharge-activated currents and later sustained Ca2+ entry-activated currents. Augmented initial membrane currents were 3-5-fold greater in peak amplitude than currents evoked by injection of the same dose of Ins(1,4,5)P3 alone. The augmented initial response was not decreased by removal of extracellular Ca2+, suggesting that there is potentiation of Ins(1,4,5)P3-mediated discharge from intracellular Ca2+ stores. However, the augmentation of Ins(1,4,5)P3-mediated discharge cannot be due to an enhanced production of endogenous Ins(1,4,5)P3 because maximal Ins(1,4,5)P3-activated currents saturate (approx. 500 nA) with supramaximal levels of Ins(1,4,5)P3 (10-50 microM). Depletion of Ca2+ stores, by pretreatment with thapsigargin or by prior injection with the Ins(1,4,5)P3 receptor antagonist heparin, abolished membrane currents elicited by Ins(1,4,5)P3/CIF co-injection, further suggesting that the Ins(1,4,5)P3 receptor was the target for the initial-current potentiating actions of CIF. In this regard, CIF also induced augmented initial currents with co-injection of either Ins(2,4,5)P3 or Ins(1,3,4,5)P4. The augmentation of Ins(1,4,5)P3-mediated currents by CIF was bell-shaped with regard to Ins(1,4,5)P3 concentration, reminiscent of the regulatory influence of Ca2+ on Ins(1,4,5)P3 responses. Co-injection of Ins(1,4,5)P3 and CIF also augmented (2-3-fold) later current responses arising from sustained Ca2+ entry. The augmented late-current responses were not due to enhanced Ca2+ store depletion because supramaximal levels of Ins(1,4,5)P3 (50 microM) or injection of the poorly metabolized Ins(1,4,5)P3 analogue, Ins(2,4,5)P3, cannot activate the same magnitude of Ca(2+)-entry-dependent currents. These results suggest that CIF at low levels interacts with Ins(1,4,5)P3 to sensitize two pathways of Ca2+ signalling: initial discharge and later Ca2+ entry. Thus under physiological conditions CIF might be more potent as a co-messenger than as a direct Ca2+ entry signal and might provide a novel type of direct feedback regulation between the stores-activated influx pathway and the Ins(1,4,5)P3 receptor. Moreover these results suggest that CIF modulation of the receptor for Ins(1,4,5)P3 may underlie control of both augmentation of discharge and Ca2+ entry, as has been predicted from the conformational coupling model of Ca2+ entry.

Animals↗
PubMed1996

Identification of lysine residues required for signal-induced ubiquitination and degradation of I kappa B-alpha in vivo.

Activation of transcription factor NF-kappaB involves signal-induced degradation of the protein inhibitor IkappaB-alpha and release of NF-kappaB which translocates to the nucleus where it influences transcription of responsive genes. Although multiple regions of IkappaB-alpha are involved in this process, the N-terminal region of the protein has been identified as a regulatory region that is required for signal induced phosphorylation and degradation. The sensitivity of IkappaB-alpha degradation to peptide aldehydes which inhibit components of the proteasome and the detection of ubiquitinated forms of IkappaB-alpha indicate that IkappaB-alpha is degraded by the ubiquitin-proteasome pathway. To identify lysine residues that represent the sites of ubiquitin addition, a series of lysine to arginine mutations were introduced into IkappaB-alpha and the mutant proteins tested for their ability to function in vivo. Exposure of COS7 cells, cotransfected with IkappaB-alpha and a TNF-responsive NF-kappaB reporter gene, resulted in stimulation of reporter activity as a consequence of IkappaB-alpha degradation. In contrast, this effect was drastically reduced when an IkappaKB-alpha mutant carrying serine to alanine changes at amino-acids, 32 and 36, which blocks both signal-induced phosphorylation and ubiquitin conjugation of the protein, was co-transfected with the reporter gene. Likewise, a mutant form of IkappaB-alpha containing lysine to arginine changes at positions 21 and 22 (K21R, K22R) severely reduces TNF-induced activation of the NF-kappaB-dependent reporter gene. Examination of the metabolism of mutant IkappaB-alpha molecules reveals that, while the K21R, K22R mutant inhibits the DNA-binding activity of NF-kappaB and undergoes signal induced phosphorylation, it is neither ubiquitinated nor degraded in response to TNF. Thus, it is likely that after signal-induced phosphorylation Of IkappaB-alpha on serine residues 32 and 36, lysine residues 21 and 22 are major sites of ubiquitin ligation which target the protein for rapid degradation by the proteasome.

Amino Acid Sequence↗
PubMed1996

Cloning and expression in Escherichia coli of the OGG1 gene of Saccharomyces cerevisiae, which codes for a DNA glycosylase that excises 7,8-dihydro-8-oxoguanine and 2,6-diamino-4-hydroxy-5-N-methylformamidopyrimidine.

A spontaneous mutator strain of Escherichia coli (fpg mutY) was used to clone the OGG1 gene of Saccharomyces cerevisiae, which encodes a DNA glycosylase activity that excises 7,8-dihydro-8-oxoguanine (8-OxoG). E. coli (fpg mutY) was transformed by a yeast DNA library, and clones that showed a reduced spontaneous mutagenesis were selected. The antimutator activity was associated with pYSB10, an 11-kbp recombinant plasmid. Cell-free extracts of E. coli (fpg mutY) harboring pYSB10 possess an enzymatic activity that cleaves a 34-mer oligonucleotide containing a single 8-oxoG opposite a cytosine (8-OxoG/C). The yeast DNA fragment of 1.7 kbp that suppresses spontaneous mutagenesis and overproduces the 8-OxoG/C cleavage activity was sequenced and mapped to chromosome XIII. DNA sequencing identified an open reading frame, designated OGG1, which encodes a protein of 376 amino acids with a molecular mass of 43 kDa. The OGG1 gene was inserted in plasmid pUC19, yielding pYSB110. E. coli (fpg) harboring pYSB110 was used to purify the Ogg1 protein of S. cerevisiae to apparent homogeneity. The Ogg1 protein possesses a DNA glycosylase activity that releases 8-OxoG and 2,6-diamino-4-hydroxy-5-N-methylformamidopyrimidine. The Ogg1 protein preferentially incises DNA that contains 8-OxoG opposite cytosine (8-OxoG/C) or thymine (8-OxoG/T). In contrast, Ogg1 protein does not incise the duplex where an adenine is placed opposite 8-OxoG (8-OxoG/A). The mechanism of strand cleavage by Ogg1 protein is probably due to the excision of 8-OxoG followed by a beta-elimination at the resulting apurinic/apyrimidinic site.

Amino Acid Sequence↗
PubMed1996

Stability of plasmid pHV1431 in free and immobilized cell cultures. Effect of temperature.

The segregational and structural stability of pHV1431 has been examined in Bacillus subtilis grown at 30 and 37 degrees C in continuous cultures without selection pressure. Immediately after appearance of plasmid-free cells in the reactor, a competition was observed between bacteria that favored plasmid-free cells because of the faster growth. A stronger instability was found at 30 degrees C compared to that at 37 degrees C. At 30 degrees C after 50 hours of culture, 2% of the cells carried the plasmid, whereas at 37 degrees C this percentage was reached after 130 hours. In both cases, no structural instability was observed. To improve the stability, the recombinant Bacillus subtilis (pHV1431) was immobilized in kappa-carrageenan gel beads. In comparison to free cell systems, a higher cell concentration was obtained. Moreover, the plasmid was maintained stable for longer periods; after 150 hours of culture 40% of cells in the reactor still carried the plasmid at both temperatures.

Bacillus subtilis↗
PubMed1996

A heteromeric complex containing the centromere binding factor 1 and two basic leucine zipper factors, Met4 and Met28, mediates the transcription activation of yeast sulfur metabolism.

Transcription activation of sulfur metabolism in yeast is dependent on two DNA binding factors, the centromere binding factor 1 (Cbf1) and Met4. While the role of Met4 was clearly established by showing that it acts as a transcription activator, the precise function in transcription of the multi-functional factor Cbf1 remains more elusive. We report here the identification of a new transcription factor Met28 which participates in the regulation of sulfur metabolism. Cloning and sequencing of MET28 revealed that it encodes a new member of the basic leucine zipper DNA binding factor family. We also demonstrate that Met28 possesses no intrinsic transcription activation capabilities. Studies of the DNA binding characteristics of Met28 led us to identify in gel mobility assays a heteromeric complex containing Cbf1, Met4 and Met28. We further demonstrated that the presence of Cbf1 and Met4 stimulates the binding of Met28 to DNA. 'Two-hybrid' studies allowed us to carry out preliminary investigations on the binary protein-protein interactions involved in the formation of the Cbf1-Met4-Met28 complex. Our results give evidence that the leucine zippers of Met4 and Met28, along with the basic helix-loop-helix domain of Cbf1, provide the protein surfaces mediating these interactions. All these results suggest that the multi-functional factor Cbf1 functions in transcription activation by tethering specific activating factors to the DNA.

Amino Acid Sequence↗