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Biomedical subjects

S David

Publications and source records attributed to S David.

At least 91 records · Page 5Linked to original sources
PubMed1997

Alternative pathway complement activation induces proinflammatory activity in human proximal tubular epithelial cells.

BACKGROUND: Proximal tubular epithelial cells express a surface C3-convertase activity which induces C fixation and insertion of the C5b-9 membrane attack complex (MAC) into the cell plasma membrane. The physiopathological consequences of this phenomenon are unknown. METHODS: The effect of C fixation on the production of inflammatory mediators by human proximal tubular epithelial cells in culture was explored. RESULTS: Proximal tubular epithelial cells incubated with a sublytic amount of normal human serum as a source of C, but not with heat-inactivated human serum, showed a time-dependent calcium influx and a concomitant release of 14C-arachidonic acid (14C-AA). Eicosanoid synthesis following the arachidonic acid mobilization was studied as prostaglandin E2 release. Mg2+/EGTA, which did not prevent C activation by the C3-convertase, and p-bromodiphenacyl bromide a phospholipase A2-inhibitor, inhibited mobilization of 14C-AA. These results suggest the activation of an extracellular Ca(2+)-dependent, phospholipase A2. Complement fixation was associated with the synthesis of proinflammatory cytokines such as IL-6 and TNF-alpha. Experiments with C6-deficient sera indicated that the release of 14C-AA and the production of cytokines were dependent on the insertion of the terminal components of complement in the plasma membrane. Indeed, the reconstitution of normal haemolytic activity of C6-deficient sera with purified C6 restored also the release of 14C-AA and the production of cytokines. CONCLUSIONS: In vitro complement activation on the proximal tubular cell surface triggers the generation of proinflammatory mediators, which may potentially contribute to the pathogenesis of tubulointerstitial injury.

Arachidonic Acid↗
PubMed1997

Evaluation of Interventions for Prevention of Back, Neck, and Shoulder Disorders in Three Occupational Groups.

An epidemiologic study was carried out in order to evaluate the effects of prevention programs at the workplace aimed at reducing back, neck, and shoulder morbidity among active workers. The intervention group included 275 workers in three occupational subgroups: hospital workers, warehouse workers, and office workers. The control group included 250 workers as comparable as possible to the intervention group. Comparisons were made, according to one-year changes in morbidity scores, for low back, upper back, neck, and shoulder disorders separately. An overall measure was also used. The one-year change in the overall measure was significantly different between the intervention group and the control group, indicating a positive effect of the prevention programs. Positive effects were stronger for some sites of pain and some occupational groups.

Journal Article↗
PubMed1997

In vitro and in vivo biocompatibility of substituted cellulose and synthetic membranes.

Regenerated cellulosic membranes are held as bioincompatible due to their high complement - and leukopenia - inducing properties. Adherence of polymorphonuclear neutrophils and monocyte purified from normal human blood to the three membranes were evaluated in an in vitro recirculation circuit in the presence or absence of fresh, autologous plasma after recirculation in an in vitro circuit using minimodules with each of the three membranes. In in vivo studies, 9 patients were treated with conventional haemodialysis for 2 weeks with each membrane and 1 week for wash-out using haemodialysers with the following surface: 1.95 m2 for benzyl-cellulose, 1.8 m2 for acetate-cellulose and low-flux polysulfone. Measurement of leukopenia, plasma C3a des Arg and elastase-alpha1 proteinase inhibitor complex levels as well as urea, creatinine, phosphate and uric acid clearances was performed. Plasma-free neutrophils adhered maximally to acetate-cellulose (65% remaining in the circulation), while there was no significant difference between low-flux polysulfone and benzyl-cellulose (80% circulating neutrophils, at 15 min, p<0.001 vs acetate cellulose). In the presence of fresh plasma, as source of complement, the differences between acetate cellulose vs polysulfone and benzyl-cellulose were even more evident, suggesting the role of complement-activated products in neutrophil adherence. A similar trend was observed for monocyte adherence with the three membranes in the absence or presence of plasma. In vivo studies showed that the nadir of leukopenia was at 15 and 30 min with acetate-cellulose (79%) and benzyl-cellulose (50%) (p<0.05 acetate- vs benzyl-cellulose) and at 15 min with polysulfone (24%) (p<0.01 vs acetate- and benzyl-cellulose). Plasma C3a des Arg levels arose to 2037 +/- 120 ng/ml, 1216 + 434 ng/ml and 46 +/- 55 ng/ml with acetate-, benzyl-cellulose and polysulfone, respectively. No pre- vs post-dialysis increase in the intracellular content of TNF-alpha was detected with any of three membranes. Clearance values of urea, creatinine and uric acid were superimposable for all the three membranes. However, benzyl cellulose had a significantly higher clearance for phosphorus (normalized for surface area) (p<0.01 vs acetate-cellulose, 0.001 vs polysulfone). These results implicate that synthetic modification of the cellulose polymer as for the benzyl-cellulose significantly reduces the in vitro adherence, delays the in vivo activation of "classic" biocompatibility parameters and notably improves the removal of inorganic phosphorus.

Aged↗
PubMed1996

Myelin-associated glycoprotein inhibits neurite/axon growth and causes growth cone collapse.

We have previously shown that myelin-associated glycoprotein (MAG) inhibits neurite growth from a neuronal cell line. In this study we show that 60% of axonal growth cones of postnatal day 1 hippocampal neurons collapsed when they encountered polystyrene beads coated with recombinant MAG (rMAG). Such collapse was not observed with denatured rMAG. Neurite growth from rat embryonic hippocampal and neonatal cerebellar neurons was also inhibited about 80% on tissue culture substrates coated with rMAG. To investigate further the inhibitory activity of MAG in myelin, we purified myelin from MAG-deficient mice and separated octylglucoside extracts of myelin by diethylaminoethyl (DEAE) ion-exchange chromatography. Although there was no significant difference in neurite growth on myelin purified from MAG-/- and MAG+/+ mice, differences were observed in the fractionated material. The major inhibitory peak that is associated with MAG in normal mice was significantly reduced in MAG-deficient mice. These results suggest that although MAG contributes significantly to axon growth inhibition associated with myelin, its lack in MAG-deficient mice is masked by other non-MAG inhibitors. Axon regeneration in these mice was also examined after thoracic lesions of the corticospinal tracts. A very small number of anterogradely labeled axons extended up to 13.2 mm past the lesion in MAG-/- mice. Although there is some enhancement of axon generation, the poor growth after spinal cord injury in MAG-/- mice may be due to the presence of other non-MAG inhibitors. The in vitro studies, however, provide the first evidence that MAG modulates growth cone behavior and inhibits neurite growth by causing growth cone collapse.

Animals↗
PubMed1996

Topical glucocorticoids modulate the lesion interface after cerebral cortical stab wounds in adult rats.

A lesion interface, consisting of a glia limitans lined by a laminin-rich basal lamina and leptomeningeal cells, forms within 2-3 weeks after penetrating wounds to the adult mammalian central nervous system (CNS). This interface prevents the growth of axons across the lesion. We have examined the effects of topically applied steroids on the formation of such an interface after stab wounds to the adult rat cerebral cortex. Immediately after lesioning, the surface of cortex in the region of the wound was treated with a topical application of either 0.1% halcinonide or 0.05% betamethasone dipropionate or their respective placebos. Cryostat sections through the lesioned area were obtained 3 weeks later and assessed by immunofluorescence. Steroid treatment attenuated all components of the lesion. The continuous anti-laminin labeling along the lesion in untreated rats became patchy after steroid treatment. The number of leptomeningeal cells that infiltrated into the wound was reduced in the laminin-negative regions in steroid-treated rats. In addition, astrocytic processes in the laminin-negative regions after steroid treatment were loosely arranged, compared with the tightly packed parallel processes forming the glia limitans in laminin-positive regions in controls. The mechanism of steroid-mediated attenuation of the lesion interface was examined in vitro. Betamethasone but not halcinonide reduced laminin secretion slightly in leptomeningeal cell cultures, but both steroids reduced cell proliferation. These results suggest that steroids modulate the formation of the lesion interface after CNS injury, at least in part by decreasing leptomeningeal cell proliferation. Such modulation of the lesion interface by steroids or other agents may permit the growth of axons across the lesion site and thus could enhance the overall degree of axon regeneration if other factors such as neurotrophic support and neutralization of axon growth inhibitory molecules are optimized.

Animals↗
PubMed1996

The lactose transporter in Leuconostoc lactis is a new member of the LacS subfamily of galactoside-pentose-hexuronide translocators.

The gene encoding the lactose transport protein (lacS) of Leuconostoc lactis NZ6009 has been cloned from its native lactose plasmid, pNZ63, by functional complementation of lactose permease-deficient Escherichia coli mutants. Nucleotide sequence analysis revealed an open reading frame with the capacity to encode a protein of 639 amino acids which had limited but significant identity to the lactose transport carriers (LacS) of Streptococcus thermophilus (34.5%) and Lactobacillus bulgaricus (35.6%). This similarity was present both in the amino-terminal hydrophobic carrier domain, which is homologous to the E. coli melibiose transporter, and in the carboxy-terminal enzyme IIA-like regulatory domain. The flanking regions of DNA surrounding lacS were also sequenced. Preceding the lacS gene was a small open reading frame in the same orientation encoding a deduced 95-amino-acid protein with a sequence similar to the amino-terminal portion of beta-galactosidase I from Bacillus stearothermophilus. The lacS gene was separated from the downstream beta-galactosidase genes (lacLM) by 2 kb of DNA containing an IS3-like insertion sequence, which is a novel arrangement for lac genes in comparison with that in other lactic acid bacteria. The lacS gene was cloned in an E. coli-Streptococcus shuttle vector and was expressed both in a lacS deletion derivative of S. thermophilus and in a pNZ63-cured strain, L. lactis NZ6091. The role of the LacS protein was confirmed by uptake assays in which substantial uptake of radiolabeled lactose or galactose was observed with L. lactis or S. thermophilus plasmids harboring an intact lacS gene. Furthermore, galactose uptake was observed in NZ6091, suggesting the presence of at least one more transport system for galactose in L. lactis.

Amino Acid Sequence↗
PubMed1996

Work conditions and mental health among prison staff in France.

OBJECTIVES: A cross-sectional epidemiologic survey was conducted among prison staff in France to investigate the relationships between work conditions and mental health. METHODS: The sample included men and women 20 to 64 years of age belonging to all categories of prison personnel (prison guards, administrative staff, socioeducational workers, technicians, health care workers, and managers). A postal self-administered questionnaire was used to assess sociodemographic factors, work conditions, and physical and mental disorders. Multiple logistic regression analyses were conducted to determine the effects of work conditions and social relationships on the mental health of prison staff. RESULTS: The results presented in this report only concern depressive symptomatology (measured by the French version of the Center for Epidemiologic Studies Depression Scale), anxiety (measured by the state version of the State-Trait Anxiety Inventory), and sleep disorders. The percentage of mental disorders was higher among prison staff than that determined for other occupational samples. Guards comprised the prison staff least affected by these symptoms. CONCLUSIONS: The results show that, in our sample, the factors concerning the subjective evaluation of work conditions and social support were more closely related to mental disorders than work conditions. In addition, seniority was associated with depressive symptoms and anxiety among the men.

Adult↗
PubMed1996

[Working conditions, living conditions and physical health problems declared among penitentiary administration personnel in France].

A cross-sectional epidemiological survey was conducted among prison staff in France to investigate the relationships between working conditions and health. The sample included men and women 20 to 64 years old belonging to all categories of prison personnel: prison guards, administrative staff, socioeducational workers, technicians, health care workers, and managers (n = 4587, response rate 45.7%). A mailed self-administered questionnaire was used to assess sociodemographic characteristics, working conditions, and physical and mental disorders. Multiple logistic regression analyses were conducted to determine the effects of working conditions and social relationships on health of prison staff. However, the results reported here only concern 17 health disorders: body mass index, sick leave, medication use, accidents, digestive disorders, lower extremities and back disorders, hypertension, hemorrhoids, arthritis, skin disorders, urinary infections, chronic bronchitis, cholesterol, gastric ulcer, respiratory infections, ocular disorders. The living non professional conditions mostly associated with health disorders were financial difficulties (OR: 1.9 for digestive disorders, 1.8 for gastric ulcer, 1.7 for medication use) and irregularity of meals (OR = 1.5 for digestive disorders, and hypertension). In the occupational environment, the factors most associated with health disorders are seniority (OR = 4.2 for arthritis, 2.3 for cholesterol) and constraints (OR = 1.7 for lower extremities disorders). In spite of some limits associated to this kind of study, relationships between occupational and non occupational factors and physical health conditions were observed; the results also pointed out the protective role of the social relationships for health conditions.

Administrative Personnel↗
PubMed1996

Microleakage of CAD-CAM porcelain restorations.

PURPOSE: To evaluate the microleakage of CAD-CAM porcelain inlay restorations cemented with four different dual cure resin cements. MATERIALS AND METHODS: Thirty human extracted caries-free molar teeth were prepared with a Class II MOD cavity design. One proximal box ended on enamel and the other on root surface dentin. The teeth were divided into six groups of five samples each. Two groups were restored with a direct placement composite resin to serve as a control. The other four groups were restored with CAD/CAM-generated ceramic inlays that were cemented with four dual cure resin cements. All specimens were thermocycled. Microleakage of the restorations was assessed by dye penetration. RESULTS: Compared to direct placement resin composite which demonstrated an excellent enamel marginal seal, CAD/CAM-generated porcelain inlays produced excellent marginal seals at both the enamel and dentin interfaces.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1996

Non Hodgkins lymphoma of ethmoidal sinus with rhinoorbital myiasis.

A patient with primary non-hodgkins lymphoma of the paranasal sinuses presenting as rhinoorbital myiasis is reported. The myiasis causing species was identified as Chrysomia bezziana Villeneuve. This case demonstrates the extreme destruction caused by myiasis and the inadequacy of therapeutic options available in such patients.

Ethmoid Sinus↗
PubMed1995

Laminin overrides the inhibitory effects of peripheral nervous system and central nervous system myelin-derived inhibitors of neurite growth.

Axon growth inhibitory proteins associated with central nervous system (CNS) myelin are responsible in part for the absence of long distance axon regeneration in the adult mammalian CNS. We have recently reported that myelin-associated glycoprotein (MAG), which is also present in peripheral nerves, is a potent inhibitor of neurite growth. This was surprising given the robust regenerative capacity of peripheral nerves. We now provide evidence that myelin purified from peripheral nerve also has neurite growth inhibitory activity. However, this activity can be masked by laminin, which is a constituent of the Schwann cell basal lamina. We also report that laminin, which is largely absent from the normal adult mammalian CNS, when added to purified CNS myelin, can override the neurite growth inhibitory activity in CNS myelin. These results have important implications for the development of strategies to foster axon regeneration in the adult mammalian CNS where multiple growth inhibitors exist.

Animals↗
PubMed1995

Characterization of plasmid-encoded citrate permease (citP) genes from Leuconostoc species reveals high sequence conservation with the Lactococcus lactis citP gene.

The citrate permease determinant (citP) in several Leuconostoc strains was demonstrated to be plasmid encoded by curing experiments and hybridization studies with a DNA fragment containing the citP gene from Lactococcus lactis subsp. lactis biovar diacetylactis NCDO176. Cloning and nucleotide sequence analysis of Leuconostoc lactis NZ6070 citP revealed almost complete identity to lactococcal citP.

Amino Acid Sequence↗
PubMed1995

Synthesis of pyrroloquinoline quinone in vivo and in vitro and detection of an intermediate in the biosynthetic pathway.

In Klebsiella pneumoniae, six genes, constituting the pqqABCDEF operon, which are required for the synthesis of the cofactor pyrroloquinoline quinone (PQQ) have been identified. The role of each of these K. pneumoniae Pqq proteins was examined by expression of the cloned pqq genes in Escherichia coli, which cannot synthesize PQQ. All six pqq genes were required for PQQ biosynthesis and excretion into the medium in sufficient amounts to allow growth of E. coli on glucose via the PQQ-dependent glucose dehydrogenase. Mutants lacking the PqqB or PqqF protein synthesized small amounts of PQQ, however. PQQ synthesis was also studied in cell extracts. Extracts made from cells containing all Pqq proteins contained PQQ. Lack of each of the Pqq proteins except PqqB resulted in the absence of PQQ. Extracts lacking PqqB synthesized PQQ slowly. Complementation studies with extracts containing different Pqq proteins showed that an extract lacking PqqC synthesized an intermediate which was also detected in the culture medium of pqqC mutants. It is proposed that PqqC catalyzes the last step in PQQ biosynthesis. Studies with cells lacking PqqB suggest that the same intermediate might be accumulated in these mutants. By using pqq-lacZ protein fusions, it was shown that the expression of the putative precursor of PQQ, the small PqqA polypeptide, was much higher than that of the other Pqq proteins. Synthesis of PQQ most likely requires molecular oxygen, since PQQ was not synthesized under anaerobic conditions, although the pqq genes were expressed.

Aerobiosis↗
PubMed1995

Enamel matrix proteins and ameloblast biology.

The paper reviews the changes in ameloblast ultrastructure, concomitant with the changes in its functions across the major stages of amelogenesis. It describes the mechanisms associated with the major events in biosynthesis and degradation of the major enamel proteins (amelogenins and tuftelin/enamelins) and with the presecretory and postsecretory mechanisms leading to the heterogeneity of these extracellular matrix proteins. The gene structure, chromosomal localization, protein, primary structure and possible function, and the involvement of the different proteins in X-linked (amelogenin) and possibly in autosomally linked (tuftelin) amelogenesis imperfecta, the most common hereditary disease of enamel, are also discussed.

Ameloblasts↗