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F Dumas

Publications and source records attributed to F Dumas.

At least 73 records · Page 4Linked to original sources
PubMed1992

A rabbit reticulocyte ubiquitin carrier protein that supports ubiquitin-dependent proteolysis (E214k) is homologous to the yeast DNA repair gene RAD6.

The two isoforms of the 14-kDa ubiquitin carrier protein (E2(14k)) are unique among rabbit E2s in efficiently supporting ubiquitin-protein ligase (E3)-mediated ubiquitination of proteins destined for degradation. To begin determining the structural basis for this property, we have isolated a cDNA encoding the predominant reticulocyte isoform of the E2 from a rabbit skeletal muscle library. The sequence predicts a protein of 152 amino acids with a molecular weight of 17,293. Expression of the cDNA in Escherichia coli and purification of the recombinant protein revealed an E2 with high affinity for E3 and ubiquitin activating enzyme (E1). The latter high affinity interaction appears to be between the ubiquitin charged form of E1 and the uncharged form of E2 and does not result in a stable complex between these two enzymes. The predicted sequence shows regions of strong homology with other sequenced E2s, suggesting that these regions may be involved in binding to E1 and/or in ubiquitin transfer from E1, functions common to all E2s. Surprisingly, the E2(14k)) sequence is markedly more similar to Saccharomyces cerevisiae RAD6 (69% identity) than to its proposed homologs UBC4/UBC5 (38% identity). The sequence is identical to that recently reported for a human 17-kDa E2 which can complement rad6 mutants thereby identifying rabbit E2(14k) as a RAD6 homologue. The biochemical properties of this previously uncharacterized human 17-kDa E2 are now defined and its misassignment as a homologue of rabbit E2(17k) is corrected. Our findings resolve current confusion regarding relationships among E2s and define yeast RAD6, rabbit E2(14k), and the human 17-kDa E2 as a subclass of E2s which biochemically support E3-mediated conjugation and ubiquitin-dependent proteolysis and physiologically play a role in DNA repair.

Amino Acid Sequence↗
PubMed1992

The pro-region of the Kex2 endoprotease of Saccharomyces cerevisiae is removed by self-processing.

We have produced in the baculovirus/insect cells expression system a soluble secreted form of the Saccharomyces cerevisiae Kex2 endoprotease. This secreted enzyme was purified and its NH2-terminal sequence determined. The NH2-terminal sequence started at residue Leu109 of the sequence deduced from the KEX2 gene nucleotide sequence, showing that the Kex2 enzyme is produced as a proenzyme. Residue Leu109 is preceded by a pair of basic amino acid residues (Lys107-Arg108) which is a potential processing site for the Kex2 endopeptidase. Furthermore, expression of an inactive form of this truncated enzyme resulted in the production of a protein with a higher molecular weight. These observations suggest that the pro-region of Kex2 endoprotease is removed by a self-processing event.

Amino Acid Sequence↗
PubMed1992

The predicted amino acid sequence of the spheroidin protein from Amsacta moorei entomopoxvirus: lack of homology between major occlusion body proteins of different poxviruses.

Entomopoxviruses replicate in the cytoplasm of insect cells and characteristically produce occlusion bodies which serve to protect the virion from the environment; the major component of these bodies is a protein called spheroidin. We have previously identified and sequenced the gene encoding the major occlusion body protein of eastern spruce budworm (Choristoneura biennis) entomopoxvirus (CbEPV) and found it to encode a 47K polypeptide which aggregates due to the formation of intermolecular disulphide bonds. In this publication we demonstrate that the insect poxvirus of Amsacta moorei produces spheroidin with a unit Mr of 114.8K. The gene for this protein was cloned and sequenced, and the predicted polypeptide was demonstrated to contain 38 cysteine residues, a leucine zipper for possible protein-protein interactions and 14 potential Asn-linked glycosylation sites. Other than possessing a large number of sulphydryl groups, this protein showed no homology to its analogue found in cells infected with CbEPV. Antibodies directed against occlusion body proteins of the two viruses also failed to cross-react significantly on Western blots. In addition, nucleic acid probes prepared from the two different genes did not cross-hybridize on Southern blots of genomic DNA prepared from the viruses. Finally, the occlusion body proteins from the two insect viruses were compared with the A-type inclusion body protein of cowpox virus. Again, little homology between these proteins was evident, with the exception of a generally high cysteine content and a similarity between their late gene promoters. We conclude that the major occlusion body proteins of different poxviruses possess diverse primary structures, but all are capable of yielding large aggregates through the formation of disulphide bonds.

Amino Acid Sequence↗
PubMed1992

Mechanistic and structural studies on Rhodococcus ATCC 39484 nitrilase.

Rhodococcus ATCC 39484 produced a nitrilase when induced with isovaleronitrile. The enzyme was obtainable pure in milligram amounts, had a subunit Mr of 40 kDa, and demonstrated a substrate-induced activation related to aggregation of subunits to form a 560-kDa complex. The enzyme had a broad substrate specificity, had a pH optimum of 7.5, was stable up to 40 degrees C, and had one disulfide bridge and two free cysteine residues, one of which appeared to be catalytically essential. The N-terminal sequence was determined and found to have 78.3% homology, in a 23-residue overlap, with Klebsiella ozaenae nitrilase. The enzyme was inhibited competitively by benzylamine and benzaldehyde and irreversibly by benzyl bromide. However, benzyl bromide was shown to be nonspecific, causing multiple alkylation. Acid quenching of enzyme-substrate mixtures allowed for the detection of covalent enzyme-substrate complexes using mass spectrometry. The covalent intermediate is suggested to be either a thioimidate or an acylenzyme and a reaction mechanism consistent with this observation and also the inhibitor results is proposed. The rate of breakdown of the covalent intermediates was found to be rate limiting even for substrates with undetectable rates of hydrolysis or those with very slow rates of intermediate formation. For phenylacetonitrile, a poor substrate, in addition to acid, approximately 2% of the product was the corresponding amide. This result suggests that a tetrahedral intermediate is formed which, for selected substrates, can break down anomalously to produce amide in place of the normal acid product. Under the conditions used in this study all other substrates tested were converted to acid.

Amino Acid Sequence↗
PubMed1991

[Possible sexual transmission of hepatitis C virus].

The development of hepatitis C virus (HCV) serology has made it possible to identify high-risk populations. The predominant mode of contamination is parenteral, but the relative frequency of the so-called sporadic hepatitis C cannot be explained in this way, and this raises the question of possible sexual contamination. The risk of HCV being transmitted by sexual intercourse has been studied in 30 couples, each with one infected partner. Among the 30 HCV seropositive subjects, 18 were followed up for chronic hepatitis and 2 for haemophilia; 10 were recruited in sessions of blood donation. The other 30 partners were tested for HCV seropositivity and investigated for other possible risk factors by means of a questionnaire. Three of them had antibodies to HCV, but only one, whose partner had chronic hepatitis, showed no other source of contamination. The prevalence of HCV positivity was 3.3 percent overall and 5.5 percent in the chronic hepatitis group. Thus, the risk of HCV heterosexual contamination is low when compared with that of the other sexually transmitted diseases. However, the prevalence of HCV in this population seems to be 5 to 10 times higher on average than in the general population.

Adult↗
PubMed1991

HPr polymorphism in oral streptococci is caused by the partial removal of the N-terminal methionine.

HPr is a small phosphocarrier protein of the bacterial phosphoenolpyruvate:sugar phosphotransferase system involved in the transport and phosphorylation of sugars. It has recently been reported that streptococci possess two forms of HPr having identical biochemical properties. In this communication, we show by N-terminal amino-acid sequencing and by ion-spray mass spectroscopy that these two forms differ by the presence or the absence of the N-terminal methionine.

Amino Acid Sequence↗
PubMed1991

Pharmacokinetics and protein binding of cefpiramide in patients with alcoholic cirrhosis.

The pharmacokinetics of cefpiramide, a new cephalosporin, were investigated after a single 1 gm intravenous injection in 11 patients with alcoholic cirrhosis and compared with those of 11 healthy subjects. In patients with cirrhosis the plasma elimination half-life was three times longer than that in normal subjects. The total plasma clearance was decreased significantly (p less than 0.001): 12.3 +/- 6.5 ml/min in patients and 25.6 +/- 4.6 ml/min in healthy volunteers, respectively. The urinary excretion of unchanged drug (percent of intravenous dose) for patients (69.8% +/- 29.9%) was statistically higher (p less than 0.01) than that for subjects (16.2% +/- 3.9%). The renal elimination became increasingly important with hepatic impairment. Protein binding of cefpiramide was reduced significantly in the group with cirrhosis. The average unbound fraction was 10.4% +/- 9.5% in patients with cirrhosis and 1.9% +/- 0.3% in normal subjects (p less than 0.01). Because the rate of elimination from plasma in patients is slower, the dosage regimen of cefpiramide would probably be modified in cirrhosis.

Adult↗
PubMed1991

Effects of a single session of prolonged plantarflexor stretch on muscle activations during gait in spastic cerebral palsy.

Activations of the triceps surae (TS) and tibialis anterior (TA) muscles during gait were studied in children with spastic cerebral palsy (CP) immediately before and after 30 min of standing on a tilt-table with the ankle dorsiflexed to stretch the TS in the experimental group (n = 8) or after a rest period in the control group (n = 11). The EMG activity from the TS and TA was recorded concomitantly with electronic footswitch signals by a computer. Video records were made of the sagittal gait movements. Effects of PMS were determined by comparing change scores for selected spatiotemporal and muscle activation parameters between the groups. The change scores defined for the muscle activations were: a post-test/pre-test ratio of the EMG activity in specific segments of the gait cycle and a locomotor spasticity index. PMS did not significantly (p greater than 0.05) affect any of the spatiotemporal parameters nor did it alter any of the TS and most of the TA activation parameters or the SI indexes for the TS and TA. Only the TA post/pre activation ratio for the 0-16% segment of the gait cycle was smaller (p less than 0.01), indicating a decrease in TA activation post-PMS.

Adolescent↗
PubMed1990

[Treatment of gallbladder lithiasis by piezoelectric extracorporeal lithotripsy].

We report the results of extracorporeal piezoelectric lithotripsy of gallbladder stones, using the EDAP LT 01 device, in 60 patients treated without anaesthesia or analgesia. Fragmentation was satisfactory (i.e. with fragments less than 5 mm wide) in 31 patients (52 per cent) after multiple sessions (mean: 1.6). The satisfactory fragmentation rate was higher in patients with stones smaller than 20 mm (63 vs 8 per cent; P less than 0.01) and not different in patients with solitary or multiple stones (53 vs 50 per cent). After bile acid dissolution treatment during 3, 6 and 12 months, the stone-free rates were 23, 41 and 64 per cent respectively, and significantly better at 3 and 6 months in patients with satisfactory fragmentation (42 vs 4 per cent; P less than 0.05, and 71 vs 9 per cent; P less than 0.01). Fourteen patients (23 per cent) reported biliary colic, but only one required cholecystectomy. No severe complication was observed. Piezoelectric lithotripsy is safe, requires short hospitalization and gives interesting results when the stones are less than 20 mm wide.

Adult↗
PubMed1990

Effects of prolonged muscle stretch on reflex and voluntary muscle activations in children with spastic cerebral palsy.

We studied the short term effects of a single session of prolonged muscle stretch (PMS) on reflex and voluntary muscle activations in 22 children with spastic cerebral palsy (CP) assigned to an experimental (n = 12) and a control group (n = 10). Children of the experimental group underwent PMS of the triceps surae (TS) by standing with the feet dorsiflexed on a tilt-table for 30 min, whereas children of the control group were kept at rest. The effects were determined by measuring the associated changes in torque and in electromyographic (EMG) activity of the TS and tibialis anterior (TA) muscles during both passive ankle movements and maximal static voluntary contractions. The results indicate that PMS led to reduced spasticity in ankle muscles as demonstrated by the significant reductions (p less than 0.05) of the neuromuscular responses (torque and EMG) to passive movement. These inhibitory effects lasted up to 35 min after cessation of PMS. In addition, the capacity to voluntarily activate the plantar flexors was significantly (p less than 0.05) increased post-PMS, but the capacity to activate the dorsiflexors was apparently not affected. These findings suggest that repeated sessions of PMS may have beneficial effects in the management of spasticity in children with CP.

Cerebral Palsy↗
PubMed1990

[Evaluation of decontamination procedures used at digestive endoscopy units in Gironde].

Decontamination procedures used for endoscopes were noted in 23 digestive endoscopy units, public and private, in the department of Gironde and compared to recommended procedures. Serial, bacteriological samples were obtained from one esogastroscope and one colonoscope in each unit, after upper endoscopy and colonoscopy diagnostic procedures at the end of the endoscopy session. Six units of 23 used complete decontamination procedures. In the 17 other units, principal errors of decontamination procedures were: inadequate cleaning of internal channel of scopes (12 units) and lack of utilization of glutaraldehyde between each endoscopy (8 units). Bacteriological samples were negative in 11/12 endoscopes after a complete decontamination procedure and in 8/39 after an inadequate procedure (p less than 0.01). Complete procedures are efficacious but not used often enough. Information and changes in endoscopic practices are necessary in digestive endoscopy units.

Bacterial Infections↗
PubMed1989

[Tissue effects of extracorporeal lithotripsy on a model of experimental biliary calculi in dogs].

Extracorporeal shock waves represent a new method to treat gallstones. This study was designed to evaluate: 1) the effectiveness of a recently available lithotripter (EDAP LT 01) for gallstone fragmentation; 2) adverse tissue reactions after treatment; 3) the optimum conditions for use of this apparatus in man. A human cholesterol stone was surgically implanted into the gallbladder of ten 20-25 kg mongrel dogs. One dog was used as a control. The other nine animals were divided into three groups (A, B and C). Two 60 min sessions of lithotripsy were carried out twice a week. Sonographic and CT examinations were performed 9 and 16 days after operation. The animals were killed 21 days after operation. Satisfactory fragmentation was obtained in 4 of the 9 animals, and in 2 dogs no stone fragments were detected. Fragments were found in the common bile duct in 5 dogs. In 2 animals a pathologic aspect of the papilla of Vater was observed. Marked hematoma was observed in the animals treated at 5 and 10 pulses/sec. In 5 cases, hematoma was observed in the gallbladder and in one case the gallbladder was ruptured. Hematoma was also noted in the hepatic vascular bed in 3 animals. Except for microscopic hemorrhagic lesions observed at the base of the right lung, no lesions were detected in any other organ. Shock waves produced by the EDAP LT 01 are effective for fragmentation of gallstones. However, in view of the tissue reactions observed at the higher pulse rates, the pulse rate should not exceed 2.5 pulses/s for use in man.

Animals↗