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Biomedical subjects

C Roy

Publications and source records attributed to C Roy.

At least 37 records · Page 2Linked to original sources
PubMed1994

[In situ fibrinolysis of acute arteriovenous shunt obstructions during hemodialysis].

Several techniques (surgical revision, thrombectomy, ...) have been described for the treatment of thrombosed vascular access (VA) in hemodialysis patients. We propose a technique with local thrombolytic infusion in conjunction with angiography and percutaneous dilatation and/or recanalization. A total of fourteen patients with twenty-two episodes of thrombosed VA was studied. Eleven patients had a Brescia-Cimino fistula and three patients had a graft fistula. We used in 21 cases urokinase (243000 UI +/- 100000 UI) and in 1 case rt-PA (50 mg). Of the 22 VA, 19 issued in an immediate patency and were restored to full function; and whereof 17 remained patent more than 2 weeks. Failures occurred in 3 cases: localized bleeding from previous dialysis puncture sites (1), venous outflow obstruction (1), and resistant venous stenosis (1). There were no infectious complications, and no systemic bleeding complications. We observed one pseudoaneurysm and one humeral asymptomatic thrombo-embolism. Stenoses were the most frequent factor in precipitating thrombosis. We believe that our technique should be the first line of treatment of occluded hemodialysis vascular access.

Adult↗
PubMed1993

Amino acid sequence and thermostability of xylanase A from Schizophyllum commune.

The amino acid sequence (197 residues) of xylanase A from the fungus, Schizophyllum commune, was determined by automated analysis of peptides from proteolytic and acid cleavage. The sequence is similar to two Trichoderma xylanases (approximately 56% identical amino acids), but also shows at least 40% identities with xylanases from Bacillus subtilis, B. pumilus and B. circulans. The conserved regions of the enzyme contain only two glutamic acid residues which implicates their possible involvement in catalysis. The disulfide bond in xylanase A is not conserved in this family. In spite of this, the B. subtilis xylanase was found to be more thermostable than xylanase A.

Amino Acid Sequence↗
PubMed1993

Inhibition of gene transcription by purine rich triplex forming oligodeoxyribonucleotides.

Several oligodeoxynucleotides (ODNs) were designed in order to interact with the purine rich element of the IRE (Interferon Responsive Element) of the 6-16 gene by triplex formation. An ODN of 21 bases, the sequence being identical to that of the purine strand of the IRE (48% G), but in reverse orientation, was able to interact with the IRE (KD: 20 nM). The binding was Mg2+ dependent. The two purine strands of the triplex were oriented antiparallel as confirmed by DNAase I and copper-phenanthroline footprinting experiments. An ODN in which A were replaced by T, also interacted with the same target, but with a lower affinity. Exonuclease III action indicated that the two IRE repeats of the 6-16 promoter interacted with each other through Hoogsteen base pairing, the third strand being parallel to the paired Watson-Crick strand. This led to a potential H-DNA structure which could be destabilized by adding ODNs able to form a triplex structure. 6-16 IRE driven-reporter gene constructs lost their interferon stimulability when co-transfected with triplex forming ODNs. The range of effective ODN concentrations was compatible with the affinity determined when measuring their direct interactions with the DNA.

Base Sequence↗
PubMed1993

Inhibition of the Moloney murine leukemia virus cycle at a post reverse transcriptional step by the netropsin-intercalating hybrid molecule netropsin-oxazolopyridocarbazole.

In a search for new antiretroviral agents acting at the nucleic acid level, two hybrid molecules composed of a bispyrrolecarboxamide chain related to netropsin, linked to the intercalating chromophore oxazolopyridocarbazole, were tested on the cycle of a defective Moloney murine leukemia virus (M.MuLV) derived from the SVX shuttle and expressing resistance to the G418 antibiotic. The drug netropsin-oxazolopyridocarbazole (Net-OPC), which displays a binding preference to duplex DNA containing A + T bases, inhibits the retroviral replicative cycle (IC50 = 4.8 microM). In contrast, the related molecule (bis)pyrollecarboxamide-oxazolopyridocarbazole (Bpc-OPC) devoid of sequence preference as well as the elemental components of Net-OPC, namely OPC, pentyl-OPC and netropsin, displays no significant action on the viral cycle. The estimation of cytosolic viral DNA in infected cells using quantitative polymerase chain reaction suggests that Net-OPC impairs a post retrotranscriptional step of the viral cycle.

3T3 Cells↗
PubMed1993

Characterization of penicillinase-producing strains of Neisseria gonorrhoeae.

Twenty-three penicillinase-producing strains of Neisseria gonorrhoeae were characterized. All strains showed hybridization with a TEM-1 probe and production of a TEM-1 type beta-lactamase (pI 5.4) on isoelectric focusing. Eight strains also showed a beta-lactamase band of pI 5.5. The penicillin MICs for the strains producing only TEM-1 were in the range 4-16 micrograms/ml; MICs of the strains with the additional pI 5.5 band were > or = 128 micrograms/ml for seven strains and 4 micrograms/ml for an arginine-hypoxanthine dependent strain. The association of the high MICs with the presence of the pI 5.5 band was statistically significant. The pI 5.5 band could represent a new beta-lactamase type or a TEM-1 mutant.

Isoelectric Point↗
PubMed1993

Instrument development in the measurement of unsupported arm exercise endurance in normal adult subjects.

Many daily activities, from basic grooming to employment tasks, require adequate unsupported arm endurance (UAE). We developed an electromechanical device to measure UAE endurance. The purpose of this study was to standardize the instrument for two rates of arm motion, moderate and slow, in 18 normal adult subjects (FEVI = 3.7L +/- .78, FVC = 4.2L +/- .74, FEV1/FVC = 1.1 +/- .08). Exercise endurance limits, and the following metabolic, ventilatory, and sensation responses were determined at rest prior to exercise and at end-exercise limits for both rates of UAE:minute ventilation (Ve), tidal volume (VT), respiratory rate (RR), duty cycle (Ti/Ttot), oxygen uptake (VO2), carbon dioxide production (VCO2), inspiratory flow (VT/Ti), heart rate (HR), and visual analog scale measurements (VAS) of dyspnea (D), respiratory effort (RE), and arm fatigue (AF). Significance increases from baseline rest were shown at the endurance limits for both rates of UAE in: VO2, VCO2, Ve, VT, RR, VT/Ti, HR, VAS-D, VAS-RE, and VAS-AF. There were no changes in Ti/Ttot and SaO2 with UAE. Peak VO2, RR, Ve, VT/Ti, and VAS-D with moderate exercise were significantly greater than slow UAE; and there was a trend increase in peak HR for moderate as opposed to slow rate UAE. Despite these differences, the endurance time between the two rates of UAE were similar. These data provide standards against which UAE in COPD can be evaluated.

Adult↗
PubMed1993

Gap junctions formed of connexin43 are found between smooth muscle cells of human corpus cavernosum.

Despite sparse autonomic innervation, the smooth muscle cells of the corpus cavernosum relax and contract synchronously to achieve penile erection and flaccidity. As with other smooth muscle cell types, the excitation process in the corpora is presumably propagated through gap junctions to allow the diffusion of current-carrying ions and second messenger molecules from cell to cell. Using both molecular and immunocytochemical techniques, we have identified gap junctions between human corporal smooth muscle cells in situ and in culture. Northern analyses demonstrated that corporal smooth muscle cells express the gap junction protein connexin43, but not connexin26 mRNA. Immunoblots showed the presence of connexin43 isoforms, whereas connexin32 was not detected. Immunocytochemical studies in cultured cells identified prominent connexin43 immunoreactive puncta between cells, as well as within the cytoplasm. In addition, gap junction membranes both in situ and in culture were labelled in thin section by anti-connexin43 antibodies using the immunogold technique. We conclude that the presence and distribution of gap junctions in this sparsely innervated tissue may provide an important mechanism of intercellular communication among the smooth muscle cells, and thus play a major role in coordinating tissue contraction and relaxation.

Blotting, Northern↗
PubMed1993

Lipoprotein abnormalities associated with cholesteryl ester transfer activity in cystic fibrosis patients: the role of essential fatty acid deficiency.

The purpose of this study was to elucidate the roles of lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP) in the lipoprotein derangement of cystic fibrosis (CF) patients with respect to their essential fatty acid (EFA) status. Triglyceride enrichment and cholesteryl ester (CE) depletion were observed in the lipoproteins of 22 CF patients. The abnormal chemical composition was more severe in 12 EFA-deficient (EFAD) than in 10 EFA-sufficient (EFAS) patients. Expressed in nmol.L-1.h-1, LCAT activity was higher (P < 0.05) in both EFAS (mean +/- SE, 92.7 +/- 1.9) and EFAD (108.8 +/- 3.0) patients than in control subjects (65.2 +/- 0.9). An equal CE transfer was recorded in the lipoprotein-deficient serum, as a source of CETP activity, in all groups studied by using normal exogenous low-density lipoprotein (LDL) and high-density lipoprotein (HDL). However, in contrast to the maximal amount of CE transferred from endogenous HDL to endogenous apolipoprotein B (apo B) in control subjects, a reduction in CETP activity was seen in CF patients and more pronounced in the EFAD group. These findings indicate that impaired lipoprotein composition may have marked effects on the transfer of CE between HDL and apo B in EFAD CF patients.

Adolescent↗
PubMed1993

A survey of beta-lactamases from 618 isolates of Klebsiella spp.

beta-Lactamases from 618 isolates of Klebsiella spp. (487 Klebsiella pneumoniae and 131 Klebsiella oxytoca) were identified by analytical isoelectric focusing. The strains were consecutive isolates from 618 different patients in five hospital centres between 1980 and 1984. Most of the chromosomal beta-lactamases from the K. pneumoniae isolates had a pI of 7.1, and most of the K. oxytoca isolates had chromosomal beta-lactamases of pIs 7.8, 5.3 and 5.5. Plasmid-mediated beta-lactamases were produced by 91.8% of K. pneumoniae isolates and 9.9% of K. oxytoca isolates. The beta-lactamase types identified most frequently were SHV-1 in the former species, and TEM-1 in the latter species. Of the K. pneumoniae isolates, 101 produced both of these plasmid-mediated beta-lactamases, while one strain produced an extended-spectrum SHV-like beta-lactamase. Of the 131 K. oxytoca isolates, 20 were hyper-producers of chromosomal beta-lactamase. The susceptibility of this genus to beta-lactam antibiotics is controlled almost exclusively by beta-lactamases, the production of which may differ from one strain to another; thus the empirical therapeutic use of beta-lactam antibiotics is not recommended for this genus.

Chromosomes, Bacterial↗
PubMed1993

Gap junctions modulate tissue contractility and alpha 1 adrenergic agonist efficacy in isolated rat aorta.

Immunocytochemical analysis, using antibodies directed against connexin43, revealed abundant gap junctions between smooth muscle cells in intact aorta from Fischer 344 rats. Therefore, the authors evaluated the potential contribution of these intercellular junctions to contractile responses elicited by alpha 1 adrenergic receptor activation in rat aortic rings. Preincubation with the selective junctional uncoupling agent heptanol (200 microM) diminished the magnitude of contractions induced by the low-efficacy partial agonist oxymetazoline (1-3 microM) by 50.6 +/- 4.5% (P < .01; n = 16 rings from 16 rats) but had no effect on equivalent contractions induced by the high-efficacy agonist phenylephrine (0.1 microM; n = 16 rings from 16 animals). Reduced phenylephrine contractility was observed at higher heptanol concentrations (500 microM). However, neither 200 nor 500 microM heptanol altered the magnitude of contractions elicited by 60 mM KCl, indicating that tissue contractility per se was unaffected by heptanol. In calcium-free solution, the magnitude of the phasic contraction induced by phenylephrine was three-fold greater than the magnitude of the oxymetazoline-induced phasic contraction (P < .001) but the phasic responses to both agonists were unaffected by the same heptanol concentrations that significantly diminished their steady-state responses. Because heptanol, at the concentrations used, has selective pharmacological actions on gap junctions, these studies provide additional support for a role of gap junctions in the maintenance and modulation of vasomotor tone. In rat aorta, junctional transfer of alpha 1 adrenergic-receptor activated second-messenger molecules appears to be an important modulator of tissue contractility and agonist efficacy.

Adrenergic alpha-Agonists↗
PubMed1993

[Magnetic resonance imaging of seminal vesicles. Normal and pathological aspects].

We have studied the normal and pathological aspects of seminal vesicles by MRI with body coil by correlation between imaging and pathologic findings after radical surgery of 63 patients with urogenital carcinoma. On normal T2 weighted sequence, the ampulla of the was deferens visible in 71% of cases exhibited a nodular low signal intensity. Seminal vesicles demonstrated an hypersignal in 79%, a low signal intensity in 19% and an heterogeneous signal intensity in 2%. Overall accuracy for the diagnosis of invasion was 77%. MRI was not efficient for bladder carcinoma (sensitivity: 1; specificity: 82%) but it was always gross infiltration (superior to 5 mm) than for prostatic carcinoma (sensitivity: 40%; specificity: 67%). The numerous false positives (15 cases) were related to hypointense normal (8 cases) or fibrous (6 cases) seminal vesicles and one case of atrophy. The false negatives were related to small invasion. Only, the negative predictive value was good value (overall NPV: 96%; bladder carcinoma NPV: 1; prostatic carcinoma NPV: 89%). A normal bilateral hypersignal of seminal vesicles permit to eliminate a gross invasion.

Aged↗
PubMed1993

[The urinary tract in pregnancy].

Pregnancy is associated with morphologic alterations of the urinary tract, of which physiological ureterohydronephrosis is the most common. Acute pyelonephritis and obstruction by stones are the two most frequent urinary tract diseases of pregnancy. Medical imaging aims at differentiating physiological ureterohydronephrosis from obstruction and at detecting infections. Ultrasonography plays a central role. Limited roentgenographic investigations can be performed during the second and third trimester. Magnetic resonance imaging can be expected to gain more widespread use in the near future.

Diagnosis, Differential↗