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Biomedical subjects

B Dupuy

Publications and source records attributed to B Dupuy.

At least 55 records · Page 3Linked to original sources
PubMed1991

Control of pilus expression in Neisseria gonorrhoeae as an original system in the family of two-component regulators.

We have previously reported the identification of two genes, pilA and pilB, which act in trans to regulate pilus expression in Neisseria gonorrhoeae. Here we show that PilA and PilB have amino acid sequence similarities with members of the two component 'sensor-regulator' family of proteins. PilB has homology with histidine kinase sensors. Alkaline phosphatase fusions to the predicted sensor and transmitter domains are described. Their PhoA activity and cellular location suggest that PilB is inserted in the cytoplasmic membrane and predict periplasmic and cytoplasmic locations for the sensor and the transmitter domains, respectively. PilA has homology with response regulators in its N-terminal part, and with components of the eukaryotic protein secretory apparatus (SRP 54 and SRP receptor) as well as two Escherichia coli gene products in its C-terminal part. In particular, it contains a putative GTP-binding site. Mini-transposon insertions into different regions of pilA were obtained. The phenotypes and genotypes of these mutants and preliminary biochemical studies of the gene products of two of these mutants lend further support to the hypothesis that PilA is a DNA-binding response regulator and confirm that it participates in an essential function in the bacterium.

Alkaline Phosphatase↗
PubMed1991

Neisseria gonorrhoeae prepilin export studied in Escherichia coli.

The pilE gene of Neisseria gonorrhoeae MS11 and a series of pilE-phoA gene fusions were expressed in Escherichia coli. The PhoA hybrid proteins were shown to be located in the membrane fraction of the cells, and the prepilin product of the pilE gene was shown to be located exclusively in the cytoplasmic membrane. Analysis of the prepilin-PhoA hybrids showed that the first 20 residues of prepilin can function as an efficient export (signal) sequence. This segment of prepilin includes an unbroken sequence of 8 hydrophobic or neutral residues that form the N-terminal half of a 16-residue hydrophobic region of prepilin. Neither prepilin nor the prepilin-PhoA hybrids were processed by E. coli leader peptidase despite the presence of two consensus cleavage sites for this enzyme just after this hydrophobic region. Comparisons of the specific molecular activities of the four prepilin-PhoA hybrids and analysis of their susceptibility to proteolysis by trypsin and proteinase K in spheroplasts allow us to propose two models for the topology of prepilin in the E. coli cytoplasmic membrane. The bulk of the evidence supports the simplest of the two models, in which prepilin is anchored in the membrane solely by the N-terminal hydrophobic domain, with the extreme N terminus facing the cytoplasm and the longer C terminus facing the periplasm.

Alkaline Phosphatase↗
PubMed1991

Rationale for the design of biomaterials and the evaluation of their biocompatibility.

The biocompatibility of a material can be considered as the ideally expectable result of its interactions with living tissues with which it is interfaced. This property determines the ability of devices involving this material in their constitution, to correctly assume their ascribed function; reciprocally a bad fitting, between devices and their intended use, coming from a non-optimized design or from an inappropriate prescription, may alter the original biocompatibility of constitutive materials. Accordingly, the actual biocompatibility of a biomaterial depends upon both its intrinsic properties and the application in which it is involved. Such considerations must be taken into account by specialists who try to design more performant biomaterials, or new assist devices, should they be implantable or not; but they draw also methodological guidelines for the evaluation of the biocompatibility of these biomedical products.

Biocompatible Materials↗
PubMed1991

[Accidental poisoning with podophyllin: a case with study of peripheral nerve].

A 53 year-old veterinary surgeon accidentally ingested 0.8 g of podophyllin. Twelve hours later, he was deeply comatose, with clinical and EMG signs of extensive axonal sensorimotor and autonomic peripheral neuropathy. In addition, transient bone marrow and hepatic toxicity occurred. The coma lasted 2 weeks. Systemic and neurological disturbances started to improve at 3 months post-onset, but the patient died four months later from gastro-intestinal bleeding. Sural nerve biopsy showed loss of myelinated fibers and signs of axonal degeneration with type E teased fibers. The cytoplasm of Schwann and endothelial cells was vacuolated and swelled. Diffuse interstitial aedema was noted. Podophyllin acts as a spindle poison, binds microtubular proteins and inhibits axoplasmic flow.

Accidents↗
PubMed1991

[In vitro study of the cytotoxicity of inflammation mediators secreted around microencapsulated cells].

One of the implantation problems in immunoprotected living cells is the appearance of local inflammatory phenomena around microcapsules. Some of the mediators released in such pathophysiological conditions were tested. A toxic action of compounds such as elastase, collagenase was evidenced. Interleukins 1 and 2 revealed no cytotoxicity within the test limits on the experimental cellular model chosen. These results underline the importance of inflammatory mediators released by adjacent cells of the implant.

Animals↗
PubMed1991

[Accuracy and reproducibility of Nidek's photokeratoanalyser].

We studied the accuracy and reproducibility of the keratoscope PKS 1,000 and keratoanalyser PKA 1,000 (Nidek laboratory). When calibrated steel balls are studied without any precaution, the system is unreliable. The photokeratoscope and the keratoanalyser provide good results only if they are used with care. To use the system, we propose the following schedule. Firstly, take a photograph of a steel ball, then set this picture under the video camera and vary the illumination until the accuracy remains unchanged during repeated calibration. With homogenous and constant illumination, the accuracy is about 0.5 diopter.

Cornea↗
PubMed1990

Biocompatibility of polyacrylamide microcapsules implanted in peritoneal cavity or spleen of the rat. Effect on various inflammatory reactions in vitro.

The biocompatibility of polyacrylamide microcapsules was investigated by implanting microcapsules in the peritoneal cavity or the spleen of rats. The capsules were retrieved every four weeks for twenty weeks. They remained isolated and free in the peritoneal cavity, but led to a slight inflammatory reaction in the spleen. These results were confirmed, in vitro, by determinations of chemiluminescence and interleukin I levels, and by evaluation of attachment and growth of human fibroblasts. The microcapsules did not enhance these inflammatory reactions, and they were a poor support for cellular proliferation.

Acrylic Resins↗
PubMed1989

[Neurologic forms of Lyme disease. 12 cases].

Twelve cases of Lyme's disease with neurological complications are reported. Seven patients had meningoradiculitis of the Garin-Bujadoux-Bannwarth type, with facial palsy in 2 cases. In 1 case the radiculitis involved only the cauda equina. Two more patients had meningomyelitis. Of the remaining 3, 1 had subacute inflammatory polyneuritis with albumino-cytologic dissociation, 1 had probable dorsal epiduritis, and the last one developed parkinsonism and communicating hydrocephalus after an otherwise classical meningoradiculitis. Three patients recalled a tick bite but only one a cutaneous eruption. No arthritis or cardiac involvement were observed. In 2 cases the CSF contained pseudo-neoplastic cells. Severe pain was a prominent feature in most cases. Pain consistently and rapidly improved on high-dose intravenous penicillin, while other signs or symptoms (e.g. paresthesias or fatigue) often lasted several months. Parkinsonism and hydrocephalus were not influenced by penicillin, and both required specific therapy. Isolated neurological (both central and peripheral) involvement is not unusual in Lyme's disease and may give rise to a wide range of signs and symptoms. This diagnosis is to be considered even when other features of Borrelia burgdorferi infection are lacking.

Adult↗
PubMed1988

In situ polymerization of a microencapsulating medium round living cells.

A new process for microencapsulating living cells is described. Pancreatic islet cells in solution in agarose were extruded from a syringe into a paraffin-oil-containing medium. A rigid interface around each bead was produced when the agarose gelled. A polymerizable mixture of monomers containing 30% of acrylamide and 1.5% of bisacrylamide was then added to these beads. Polymerization was initiated by a photochemical process using riboflavin as a photosensitizer, which enabled use of oxygenated solutions. As other polymerizations initiated by an oxido-reduction reaction, this method did not require heating, and could thus be carried out at ambient temperature. The oil phase near the agarose beads effectively prevented any rise in temperature, and also led to formation of an acrylamide concentration gradient in the aqueous phase, which reduced the potential cytotoxicity of the reaction. Radioimmunoassay of insulin liberated from encapsulated islets of Langerhans demonstrated a good viability of the cells.

Acrylamides↗
PubMed1988

Neural activity from the acutely infected HSV-1 rabbit cornea.

Herpes simplex virus type 1 (HSV-1) infections of the human cornea are often accompanied by abnormal sensations. In this study, a combination of physiological and structural methods was used to examine the innervation of the corneas of rabbits with HSV-1 lesions of varying severity. Degeneration of the plexiform neural layer adjacent to dendritic lesions and surrounding normal neurology provided a basis for the limited physiological changes. Extensive degeneration of the corneal innervation at all levels occurred within the anesthetic area of the geographic lesion. Abnormal physiological activity characterized by hyperexcitability and loss of stimulus specificity were included in the physiological profile. Collateral sprouts seen in the geographic lesion were suggested as an anatomical substrate for the abnormal neural activity. Thus, the neural changes could be associated with the severity of HSV-1 lesions.

Action Potentials↗
PubMed1988

[Preservation of the functional integrity of cellular material after cell microencapsulation by polymerization].

A new process for microencapsulating living cells is described. A cross linked network was polymerized using acrylamide and bisacrylamide monomers round agarose-embedded cells in an hydrophobic medium. The reaction was initiated by excitation of Vit. B2 under visible irradiation. The absence of toxic effect was evaluated from the insulin secretion of encapsulated islets of Langerhans.

Animals↗
PubMed1987

Use of the glucose clamp technique for confirmation of insulinoma autonomous hyperinsulinism.

The diagnosis of insulinoma on the basis of persistent hypoglycemia requires further confirmation. The insulin suppression test has been used to support this diagnosis prior to surgical intervention. In this study the euglycemic clamp technique was used to compare five control volunteers with four hypoglycemic patients with suspected insulinoma. Insulin was infused over successive two-hour periods at 2, 4, and 8 mU/kg/min. Plasma glucose levels were clamped at 80 mg/dL (4.4 mmol/L) using an artificial pancreas. High insulin levels were measured in all subjects, ranging from 225 +/- 30 microU/mL (1614 +/- 215 pmol/L) to 1018 +/- 239 microU/mL (7304 +/- 1714 pmol/L). Levels of C peptide fell to 0.1 ng/mL (0.028 nmol/L) in control subjects but remained at high levels in the patients. Insulinoma was confirmed on laparotomy in all four patients. In two patients tested after removal of the tumor the results were found to have returned to normal.

Adenoma, Islet Cell↗
PubMed1987

[Hemodynamic study of obstructive lesions of the internal carotid artery: value of coupled measurement of regional cerebral blood flow and volume].

A study of 130 patients having presented either a transient ischemic attack or a completed stroke, or admitted for an asymptomatic carotid stenosis, allowed the following investigations: CT-scan, doppler, angiography, measurement of the regional cerebral blood flow (rCBF) by the study of 133Xe clearance (Novocerebrograph (R)), and measurement of the regional cerebral blood volume (rCBV) made by gamma emission tomography after autotransfusion of 99m Tc-labeled erythrocytes with an Elscint Apex 415 ECT (R) camera. Our aim was to look in which case a rCBF and/or a rCBV interhemispheric asymmetry was observed, by comparing the previous hemodynamic parameters with clinical, CT-scan and angiographic data. Although a rCBF and/or a rCBV asymmetry appeared more often among patients presenting with infarction than among those of the asymptomatic category, this does not seem specific for any clinical grade. The same statement applies to the comparison between hemodynamic parameters and CT data. The arterial lesions were classified in 4 groups: no stenosis (12 cases), uni or bilateral moderate carotid stenosis (40 cases), unilateral severe carotid stenosis or occlusion (65 cases), bilateral carotid severe stenosis or occlusion (13 cases). We observed a rCBF asymmetry among some patients in the 4 groups, although this was more frequent among the two latter groups. Nevertheless no case of a rCBV asymmetry was observed in the 2 first groups. Such an asymmetry was present in 31 percent of the patients belonging to the two latter groups. In patients of the third group the asymmetry was always due to a relative increase of rCBV beyond the carotid lesion.(ABSTRACT TRUNCATED AT 250 WORDS)

Arterial Occlusive Diseases↗
PubMed1986

Hemodynamic study of internal carotid artery stenosis and occlusion: value of combined isotopic measurements of regional cerebral blood flow and blood volume.

The assessment of the intracranial hemodynamic consequences of obstructive lesions of the carotid artery by measuring resting rCBF is inadequate because cerebral blood flow may remain constant in spite of significant drops in the intraluminal pressure due to autoregulation. Moreover, flow may be permanently decreased following cerebral infarction, even if the arterial anatomical conditions have resumed their normal state because of the decreased metabolic demand of an infarcted area. Measurement of the regional cerebral blood volume (rCBV) helps with the hemodynamic assessment of these conditions, since there is a linear and inverse relationship between intraarterial pressure and intracranial blood volume. In 24 patients exhibiting various carotid and ischemic brain lesions we studied both rCBF and rCBV. The latter is a comparative measure between hemispheres obtained by single photon emission tomography after autotransfusion of 99m Technetium labeled erythrocytes. There was no correlation between rCBF and clinical status, CT scan or arterial lesions. There was no correlation between rCBV and clinical status or CT scan. There was, however, an interesting correlation between rCBV and the severity of the arterial lesion. The rCBV was symmetrical in all patients with normal or moderately stenotic carotid arteries before and after operation. In some patients with severe unilateral stenosis or occlusion, there was a significant relative increase of rCBV in the hemisphere downstream from the lesion, which disappeared after surgery (endarterectomy or extra-intracranial bypass). In some patients with severe and bilateral carotid lesions, we noted an asymmetry in rCBV that disappeared after a unilateral operation. Other patients with similar lesions develop asymmetry only after an operation that resulted in a relative increase in rCBV in the hemisphere supplied by the non-operated artery. In conclusion analysis of these results suggests that in this series of patients, rCBV modifications were the consequence of cerebral autoregulation distal to the arterial lesions and provided satisfactory assessment of hemodynamic improvement after surgical repair.

Adult↗
PubMed1985

[Neuropathies caused by thalidomide].

Symptoms and signs in four patients with thalidomide-induced neuropathy developing during treatment of discoid lupus were limited for long period to distal paresthesiae with altered sensory conduction velocities. Semi-thin biopsy specimens of the distal sural nerve showed depopulation of myelinized fibers, mainly affecting those of large caliber, and signs of axonal degeneration. Study of dissociated fibers showed a high proportion of E fibers. Morphometry confirmed the axonal lesion. Ultrastructural examination demonstrated anomalies of axons of amyelinic fibers (vacuoles, lamellar figures) and of Schwann cells (stacked cytoplasmic prolongations), together with numerous collagen pockets, all non-specific lesions. The disease course was slow, with disappearance of sensory symptoms in a few weeks in 3 of the 4 cases and normal clinical findings in one of the four patients one year after cessation of treatment. Definite correlations between the dose administered and the severity of the neuropathy could not be established. The still poorly understood mechanism of action is discussed.

Acute Disease↗
PubMed1984

[Peripheral nerves in a case of lead neuropathy].

A patient developed lead neuropathy with an asymmetrical distal weakness of the four limbs and sensory signs. Tap water contained high amounts of lead and biopsy confirmed the intoxication. The electromyogram was altered from the onset of the disorder and was still abnormal one year after treatment with EDTA, which however brought frank improvement. Biopsies were taken from nerves of the upper and lower limbs. Examination of teased nerve fibers showed the predominance of fibers of small diameter and segmental demyelinization with signs of remyelination in the lower limbs. Semi-thin sections demonstrated depopulation of large myelinated fibers, regeneration clusters and Schwann cells with globular nuclei. Electron microscopy showed myelin sheath alterations and neuritic lesions, some hyperactive Schwann cells. Main alterations were seen in basal membranes of Schwann cells of unmyelinated fibers and endoneuronal capillaries. Such alterations to our knowledge have never been reported in human peripheral lead neuropathy, but have been described after experimental intoxication. These findings together with recent experimental studies allow a discussion about the site of entry of lead into the nerve and about its site of action on the various constituents of the peripheral nerve.

Adult↗