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Biomedical subjects

J Devaux

Publications and source records attributed to J Devaux.

At least 19 recordsLinked to original sources
PubMed2006

Coupling of the biochemical composition and calorific content of zooplankters with the Microcystis aeruginosa proliferation in a highly eutrophic reservoir.

The impact of the Cyanobacteria Microcystis aeruginosa on zooplankton dynamics was studied in the hypertrophic Villerest Reservoir (France). Samples were collected and their biochemical composition and calorific content examined. Three most abundant zooplankton species in the reservoir were considered: the cladoceran Daphnia longispina and the copepods Cyclops vicinus and Eudiaptomus gracilis. The three species were differently affected by the Microcystis aeruginosa blooms. Daphnia longispina did not seem to suffer from the proliferation of the M. acruginosa, although its biomass decreased concomitantly to the bloom. This collapse would be attributable to the lack of nutritional value of algae. Cyclops vicinus seemed to move away when Microcystis invaded the superficial layers of the reservoir. Because this zooplankter had migratory abilities, it reached the littoral zone where food was available. The energetic costs linked to this migration were clearly pointed out when the species recovered the pelagial zone in early fall. The behaviour of Eudiaptomus gracilis was not clear. This species underwent diapause as M. aeruginosa proliferated. This suggests that Eudiaptomnus gracilis moved away from the pelagial zone over the cyanobacterial blooms. In most cases, the cyanobacterial toxins affected the growth of zooplankton and the potential to use herbivorous zooplankton as a means to combat Microcystis proliferation in the Villerest reservoir seems limited.

Animals↗
PubMed2004

[Ion channels and demyelination: basis of a treatment of experimental autoimmune encephalomyelitis (EAE) by potassium channel blockers].

Voltage-gated potassium channels (Kv channels) are ion channels, openings of which provide an outward flow of potassium ions repolarising the cell. In neurons, Kv channels play a crucial role in action potential repolarisation and in shaping neuronal excitability. In non-excitable cells, such as T lymphocytes, Kv channels and calcium-activated K+ channels (KCa channels) determine the driving force for Ca2+ entry. During T cell activation the calcium entry depolarises the cell and increases the cytosolic calcium concentration, which in return activates Kv and KCa channels. K+ channel opening repolarises the cell and drives the membrane potential to a negative voltage. The roles of Kv channels in nervous and immune systems have been investigated here by means of a rat experimental autoimmune disease of the central nervous system, the experimental autoimmune encephalomyelitis (EAE). EAE is characterised clinically by paralysis, and pathologically by inflammatory cell infiltrations into the brain and the spinal cord. Among the inflammatory cells, T lymphocytes play a major role. Hence, EAE can be adoptively transferred into syngenic animals by the injection of T cells reactive to myelin antigens. During adoptive-EAE, somato-sensory evoked potentials recorded along the spinal tracts decrease in amplitude and axonal propagation is disrupted. We have analysed the consequences of Kv channels blockade by peptidyl toxins on central nerve conduction, on T cell activation and on the time course of EAE. In rat optic nerves, Kv channels have been identified up from postnatal day 1. Their blockade by kaliotoxin (a scorpion toxin) or by dendrotoxin-I (a snake toxin) enlarges the compound action potentials, demonstrating the participation of Kv channels to spike repolarisation. This effect disappears at adult age due to the sequestration of Kv channels under the myelin, in the paranodal regions. During acute demyelination by lysophosphatidyl-choline, the surface area of compound action potential decreased probably because conduction block occurred. Demyelination unmasked Kv channels, which are again accessible to toxins. Their blockade by dendrotoxin-I or kaliotoxin favoured a slow delayed conduction suggesting that those Kv channel blockers exert a neurological benefit during demyelinating diseases. In a T-cell line reactive to myelin basic protein antigen, which is used to adoptively transfer experimental autoimmune encephalomyelitis, Kv1.3 channels are constitutively expressed. Their blockade leads to a pronounced reduction of the T cell proliferative response, cytokine production and Ca2+ influx. In the rat, blockade of Kv1.3 inhibits the delayed type hypersensitivity response to myelin basic protein prevents and treats adoptive experimental autoimmune encephalomyelitis. Blockade of Kv channels alone or in combination with KCa channels improves the symptoms of the disease. These results demonstrate that K+ channel blockers displaying high selectivity are potent immunosuppressive agents with beneficial symptomatic effects in experimental autoimmune encephalomyelitis.

Action Potentials↗
PubMed2003

Interfacial layer characterization in dental composite.

Nowadays, dental resins find increasing use by practitioners. However, photopolymerization of such resins is limited to a so-called 'depth of cure'. To face this problem, dentists superimpose resin layers of limited depth. This technique raises the problem of the quality of interlayer. This paper aims at screening different cases of adhesion at the interface. Shear strength of such interfacial layers is tested in shear mode in various conditions (with or without an oxygen-inhibited layer, or contaminated by saliva or water). Unexpectedly, the presence of an oxygen-inhibition on the first layer, as assessed using micro-Raman spectroscopy, induces higher shear strength. In this case, a cohesive break occurs while an adhesive one is observed in all the other cases.

Composite Resins↗
PubMed2002

Food web structure in the recently flooded Sep Reservoir as inferred from phytoplankton population dynamics and living microbial biomass.

Phytoplankton dynamics, bacterial standing stocks and living microbial biomass (derived from ATP measurements, 0.7-200 mm size class) were examined in 1996 in the newly flooded (1995) Sep Reservoir ('Massif Central,' France), for evidence of the importance of the microbial food web relative to the traditional food chain. Phosphate concentrations were low, N:P ratios were high, and phosphate losses converted into carbon accounted for <50% of phytoplankton biomass and production, indicating that P was limiting phytoplankton development during the study. The observed low availability of P contrasts with the high release of "directly" assimilable P often reported in newly flooded reservoirs, suggesting that factors determining nutrient dynamics in such ecosystems are complex. The phosphate availability, but also the water column stability, seemed to be among the major factors determining phytoplankton dynamics, as (i) large-size phytoplankton species were prominent during the period of increasing water column stability, whereas small-size species dominated phytoplankton assemblages during the period of decreasing stability, and (ii) a Dinobryon divergens bloom occurred during a period when inorganic P was undetectable, coinciding with the lowest values of bacterial standing stocks. Indication of grazing limitation of bacterial populations by the mixotrophic chrysophyte D. divergens (in late spring) and by other potential grazers (mainly rotifers in summer) seemed to be confirmed by the Model II or functional slopes of the bacterial vs phytoplankton regressions, which were always <0.63. Phytoplankton biomass was not correlated with phosphorus sources and its contribution was remarkably low relative to the living microbial biomass which, in contrast, was positively correlated with total phosphorus in summer. We conclude that planktonic microheterotrophs are strongly implicated in the phosphorus dynamics in the Sep Reservoir, and thus support the idea that an important amount of matter and energy flows through the "microbial loop" and food web, shortly after the flooding of a reservoir.

Bacteria↗
PubMed2002

Raman scattering determination of the depth of cure of light-activated composites: influence of different clinically relevant parameters.

The purpose of this research was to determine the depth of cure of light-activated composites in relation with different clinically relevant parameters. A Raman spectroscopic method has been used. The measurement of cure is made on a relative basis by comparing the vibration band of the residual unpolymerized methacrylate C=C bond at 1640 cm-1 against the aromatic C=C stretching band at 1610 cm-1 used as an internal standard. The information gained draw attention to the importance of light transmission during the exposure. The influence of sample's thickness on the depth of cure is illustrated by a second order polynomial regression. The shade and translucency of the resin composite also modify the light transmission and thus have a significant influence on the degree of conversion. Moreover the light-source intensity and the distance from the curing tip are important parameters of influence. A significant reduction of the depth of cure is observed for all sample thickness of resin composite tested when using a light device with an intensity of 300 mW cm-2 as well as using a distance from the curing tip higher than 20 mm.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2001

Selective blocking of voltage-gated K+ channels improves experimental autoimmune encephalomyelitis and inhibits T cell activation.

Kaliotoxin (KTX), a blocker of voltage-gated potassium channels (Kv), is highly selective for Kv1.1 and Kv1.3. First, Kv1.3 is expressed by T lymphocytes. Blockers of Kv1.3 inhibit T lymphocyte activation. Second, Kv1.1 is found in paranodal regions of axons in the central nervous system. Kv blockers improve the impaired neuronal conduction of demyelinated axons in vitro and potentiate the synaptic transmission. Therefore, we investigated the therapeutic properties of KTX via its immunosuppressive and symptomatic neurological effects, using experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis. The T line cells used to induce adoptive EAE were myelin basic protein (MBP)-specific, constitutively contained mRNA for Kv1.3. and expressed Kv1.3. These channels were shown to be blocked by KTX. Activation is a crucial step for MBP T cells to become encephalitogenic. The addition of KTX during Ag-T cell activation led to a great reduction in the MBP T cell proliferative response, in the production of IL-2 and TNF, and in Ca(2+) influx. Furthermore, the addition of KTX during T cell activation in vitro led a decreased encephalitogenicity of MBP T cells. Moreover, KTX injected into Lewis rats impaired T cell function such as the delayed-type hypersensitivity. Lastly, the administration of this blocker of neuronal and lymphocyte channels to Lewis rats improved the symptoms of EAE. We conclude that KTX is a potent immunosuppressive agent with beneficial effects on the neurological symptoms of EAE.

Adoptive Transfer↗
PubMed1999

The micro-Raman spectroscopy, a useful tool to determine the degree of conversion of light-activated composite resins.

Light-activated composites are now among the most popular dental restorative materials. Nevertheless, concerns exist about the so-called depth of cure. Infrared spectroscopy (FTIR) has traditionally been used to quantify this problem by evaluating the degree of conversion of dental resins. However, Raman scattering provides an alternate method. This article describes the advantages and the limitations of micro-Raman spectroscopy, as compared to FTIR and other techniques, for calculating the local degree of conversion and the depth of cure of light-cured composites.

Biocompatible Materials↗
PubMed1991

Can we predict the mating pattern of Drosophila females from the sperm length distribution in males?

In order to test the validity of the prediction of the mating pattern of females from the sperm length distribution in males, three species of Drosophila were analysed. Males in the three species are equally polygynous but females differ in the level of polyandry. A 'low recurrence polyandry' is observed in the sperm dimorphic species D. affinis while a 'high recurrence polyandry' is observed in the sperm monomorphic species D. latifasciaeformis and D. littoralis. These results are consistent with the hypothesis proposed previously that sperm dimorphism in males can only be maintained by a selective alternative in females (i.e. facultative female polygamy), whereas a stricter mating system (e.g. 'obligatory' polyandry) should only result in sperm monomorphism irrespective of the absolute value of sperm length.

Animals↗
PubMed1991

Comparative kinetics of short and long sperm in sperm dimorphic Drosophila species.

All species of the Drosophila obscura group exhibit within-ejaculate sperm length dimorphism. The present work is a contribution to the understanding of sperm competition through a comparative study of sperm kinetic parameters in four of these species. Videomicrographic observations at 200 frames per second of sperm from males and females, out of the storage organ, prior or after storage were made. Drosophila sperm display both major and minor waves. The former is analysed by measuring coiling diameter (micron) and the latter by recording both beat frequency (s-1) and wave propagation velocity (micron.s-1). Results show that the 'behaviour' of short and long spermatozoa noticeably differ: short sperm kinetics remains unaltered after storage while both major and minor waves of long spermatozoa are markedly modified. Thus, evidence is provided here of a sort of "differential activation" which is assumed to result in different survival abilities of short and long sperm within the storage organ of females.

Animals↗
PubMed1987

Severe erosive lichen planus and polycythemia vera in an adolescent.

Erosive lichen planus developed in a 12-year-old adolescent also presenting polycythemia vera (Vaquez' disease). Though a casual association cannot be excluded, the rarity of the two diseases in children suggests a pathogenetic link, possibly involving an abnormal hematologic stem cell line.

Biopsy↗
PubMed1985

Study of the 78A1 isolate of Moloney murine sarcoma virus. I. Molecular cloning and characterization.

The 78A1 isolate of Moloney murine sarcoma virus (78A1 Mo-MuSV) was cloned from a genomic library obtained from virus producer rat cells, in the lambda vector L47. Among the recombinants hybridizing with a probe specific for the v-mos sequences, we recovered a recombinant which contained leukaemia virus (MuLV) sequences and was able to transform both mouse and rat cells in transfection experiments. The cloned provirus could be rescued by both Mo-MuLV ecotropic and amphotropic viruses in mouse cells, but only with the amphotropic helper virus in rat cells. Comparative restriction mapping indicates that the 78A1 provirus is 200 bp longer than the HT1 provirus. The difference lies in the gag-pol junction region of Mo-MuSV. Other minor differences were found in the gag region, whereas the restriction patterns of the 3' parts of the proviruses were identical.

Animals↗
PubMed1983

[Stewart-Treves syndrome. 2 cases with an ultrastructural study].

The authors present an ultrastructural study of two cases of Stewart-Treves syndrome in elderly women. Under light microscopy, the dermal and hypodermal proliferations showed vascular features which were more clearly preceptible in the second case than in the first. Ultrastructural studies showed, in the first case, clefts containing erythrocytes and surrounded by neoplastic cells which were linked by zonulae adherentes. A rudimentary form of basal membrane was also noted, with an exterior lining of pericyte-like cells. In the second case, typical capillary vessels were bordered by endothelial cells containing a few pinocytotic vesicles and microfilaments, in contact by zonulae adherentes. The walls of these vessels consisted of a clearly defined membrane lined with pericytes, and constituting, in some areas, an anastomotic network due to the swelling of the endothelial cells. Ultrastructural study suggests an angiosarcomatous origin of these lesions. Finally, the article includes a review of the literature.

Aged↗
PubMed1983

Characterization of viral RNA in cells transformed by various isolates of Moloney murine sarcoma virus.

Intracellular polyadenylated viral RNA from cells infected by five different isolates of Moloney murine sarcoma virus (Mo-MuSV) was analysed by gel transfer hybridization. Genomic sizes of 4.6 kilobases (kb) for the ml-MuSV isolate, 5.2 kb for the m3- and 124-MuSV, 6.1 kb for the HTl-MuSV and 6.7 kb for the 78-Al-MuSV were determined. With the exception of the ml strain, subgenomic RNA species were found in cells infected by the various isolates. However, no common subgenomic RNA containing v-mos sequences could be characterized. Each transformed cell line expressed a different set of viral RNA species in terms of size and structure.

Animals↗
PubMed1983

Small bowel deposition of crystals associated with the use of clofazimine (Lamprene) in the treatment of prurigo nodularis.

A 46-year-old woman with widespread prurigo nodularis was treated with 300 mg clofazimine a day for six months. Ten months after stopping the drug she complained of weight loss and gastrointestinal side effects which were shortly improved by a gluten-free diet, but relapsed one year later. At laparotomy, all tissues were stained bright orange-yellow, and histological examination showed crystals deposited in the chorion of intestinal villi and in the mesenteric lymph nodes.

Clofazimine↗
PubMed1982

[Hormonotherapy in acute, idiopathic hirsutism, and seborrheic alopecia (author's transl)].

It has been established that, through skin responds to circulating androgens, it can also produce androgens from precursors. Therapy can address either of the two following physiopathological steps: the secretory step can be countered by replacement or suppressive therapy which is now fairly well mastered; the target-organ step opens new possibilities concerning receptor abnormalities and receptor control. The medical literature was reviewed for data on hormonal therapy for women with acne, idiopathic hirsutism and seborrheic alopecia, three conditions which are usually only partially improved by cosmetic treatment.

Acne Vulgaris↗
PubMed1982

Characterization of a large genomic size Moloney murine sarcoma virus produced by a transformed rat cell line.

A rat cell line (78A1) transformed by the Moloney murine sarcoma virus-Moloney murine leukaemia virus (Mo-MuSV-MuLV) complex was found to produce a sarcoma virus different from the isolates previously described. Analysis of intracellular RNA of the 78A1 cell line by electrophoresis on agarose gel, and hybridization with DNA probes specific to M1-Mo-MuSV and v-mosMo sequences revealed a size of 6.7 kilobases (kb) for the RNA of this sarcoma virus. This genome is larger than those of m1, m3, HT1 and 124 isolates and slightly smaller than the myeloproliferative sarcoma virus genome (7.0 kb).

Animals↗