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Biomedical subjects

M Lacour

Publications and source records attributed to M Lacour.

At least 55 records · Page 3Linked to original sources
PubMed1994

cAMP up-regulates IL-4 and IL-5 production from activated CD4+ T cells while decreasing IL-2 release and NF-AT induction.

Seven days after activation with concanavalin A and irradiated spleen cells, murine CD4+ T cells were re-stimulated with ionomycin and phorbol 12-myristate 13-acetate (PMA). IL-2 and IL-4 were determined in the supernatant. When cholera toxin, forskolin together with phosphodiesterase inhibitors or dibutyryl-cAMP were added at the time of re-stimulation, a dose-dependent increase of IL-4 and IL-5 release was noted. IL-2 was down-regulated as reported before. The up-regulation of IL-4 and the down-regulation of IL-2 correlated with an increase of IL-4 mRNA and a decrease of IL-2 mRNA as determined by semi-quantitative reverse transcriptase polymerase chain reaction. Similar results were found with prostaglandin E2 using PMA and ionomycin or plate-bound anti-CD3 antibody as re-stimulants. These results suggest that, in activated CD4+ T cells, cAMP-elevating agents induce a switch of lymphokine production towards a Th2-like phenotype through regulation at the transcriptional level. This is supported by the fact that complex formation between a synthetic nuclear factor of activated T cells (NF-AT) binding site from the IL-2 promoter and nuclear extracts was decreased when cholera toxin was added to re-activated CD4+ T cells, suggesting that cholera toxin and cAMP down-regulate IL-2 expression via decreased NF-AT binding. Finally, since IL-4 has been reported to amplify IL-4 release from activated CD4+ T cells, the autoinduction of IL-4 may very well function via cAMP.

Animals↗
PubMed1994

[Fundamental elements of maxillofacial orthodontics in the treatment of sagittal maxillo-mandibular disproportions].

The entire cephalometric parameters and specially the alveolar inclinations have to be taken into account, while treating skeletal sagittal discrepancies. In fact, they are either compensatory and should be kept as, or aggravating the basal bone discrepancies, manifesting a neuro-muscular imbalance and complicating remarkably the prognosis. In order to maintain the morphological results, the anatomical corrections have to take into account the neuro-muscular balance concerning position, function and tonicity. That is the concept which provides satisfactory surgical, orthopedic and natural results. We think that the goals of these treatments should not be limited to esthetic or standardized criteria. They have to be achieved in respect to this functional concept and absolutely adapted to each patient.

Cephalometry↗
PubMed1993

Thrombocytopenia in a case of neonatal mumps infection: evidence for further clinical presentations.

We report a rare case of congenital mumps infection in a newborn girl. Her mother developed bilateral parotitis beginning the day of the delivery. The child was subsequently severely ill and suffered from fever, splenomegaly and thrombocytopenia, however, without parotitis nor pancreatic involvement. Both mother and child recovered well with symptomatic treatment. A review of the literature shows that clinical mumps is rare and usually benign in neonates. However, severe respiratory distress may occur. The recent appearance of mumps outbreaks in adolescents and young adults calls for a reinforcement of mumps vaccination and should prompt an immunological assessment of pregnant women after exposure.

Adult↗
PubMed1993

Recovery of head postural control following unilateral vestibular neurectomy in the cat. Neck muscle activity and neuronal correlates in Deiters' nuclei.

Recovery of head postural control after unilateral vestibular neurectomy was investigated in the alert cat by chronically recording the spontaneous neck muscle EMG activity from splenius capitis on both sides and the vestibulocollic reflexes evoked during roll and pitch tilts. Neuronal correlates occurring within the lateral (Deiters) vestibular nuclei (LVN) were also recorded during the time-course of recovery. During the acute phase (1-2 weeks), the cats exhibited strong imbalance in spontaneous neck muscle activity, characterized by increased muscular tone in the ipsilateral splenius capitis muscle and hypoactivity in the contralateral one. At the same time, the mean resting activity of Deiters' neurons strongly decreased on the deafferented side, while a slight but significant decrease was observed on the intact side. Vestibulocollic reflexes were totally lacking during the acute phase, whatever the direction and the amplitude of tilt. Recovery developed in the following weeks, leading to complete rebalance of spontaneous EMG activity as well as near to normal static vestibulocollic reflexes 5 weeks after the lesion. However, compensation remained sub-normal during roll tilts while overcompensation was found during pitch tilts, suggesting that the intact labyrinth would play a leader role in the recovery process but that bilateral cooperation of the two labyrinths is required for proper head postural control. Five weeks are also needed for a partial rebalancing of resting activity between both LVN. These results indicate that changes in neck muscle activity observed in the acute cats and that recovery found in the compensated animals could result from modifications in neural networks controlling neck musculature, such as the LVN.

Animals↗
PubMed1992

H-2-linked control of the Yaa gene-induced acceleration of lupus-like autoimmune disease in BXSB mice.

The accelerated development of lupus-like autoimmune disease in male BXSB mice (H-2b, I-E-) is associated to the presence of a mutant gene, designated Yaa, located on their Y chromosome. To investigate whether the H-2b haplotype and/or the lack of expression of I-E molecules play any role in the Yaa-linked acceleration of autoimmune disease, an I-E+ BXSB.H-2d congenic strain was created by backcross procedures. We compared the development of autoimmune disease in the novel BXSB.H-2d (I-E+) strain to that of BXSB.H-2b (I-E-) and BXSB.H-2b/d (I-E+) heterozygous mice. Male BXSB.H-2d (I-E+) mice exhibited only a limited production of autoantibodies and a lower incidence of glomerulonephritis with a markedly prolonged survival rate, which were essentially identical to those of female BXSB mice of both-H-2b and H-2d haplotypes. However, BXSB.H-2b/d (I-E+) heterozygous males developed an accelerated disease comparable to that of conventional BXSB.H-2b (I-E-) male mice. These results indicate that the expression of I-E molecules and consequent clonal deletion or anergy of I-E reactive T cells does not appear to be responsible for the prevention of accelerated autoimmune disease in BXSB.H-2d (I-E+) male mice. The finding that the Yaa gene-induced acceleration of lupus-like autoimmune disease is modulated by gene(s) within or closely linked to the H-2 complex underlines the crucial role of the major histocompatibility complex and the polygenetic nature of autoimmune disease in BXSB mice.

Animals↗
PubMed1992

Functional coupling of the stabilizing eye and head reflexes during horizontal and vertical linear motion in the cat.

The otolith contribution and otolith-visual interaction in eye and head stabilization were investigated in alert cats submitted to sinusoidal linear accelerations in three defined directions of space: up-down (Z motion), left-right (Y motion), and forward-back (X motion). Otolith stimulation alone was performed in total darkness with stimulus frequency varying from 0.05 to 1.39 Hz at a constant half peak-to-peak amplitude of 0.145 m (corresponding acceleration range 0.0014-1.13 g). Optokinetic stimuli were provided by sinusoidally moving a pseudorandom visual pattern in the Z and Y directions, using a similar half peak-to-peak amplitude (0.145 m, i.e., 16.1 degrees) in the 0.025-1.39 Hz frequency domain (corresponding velocity range 2.5 degrees-141 degrees/s). Congruent otolith-visual interaction (costimulation, CS) was produced by moving the cat in front of the earth-stationary visual pattern, while conflicting interaction was obtained by suppressing all visual motion cues during linear motion (visual stabilization method, VS, with cat and visual pattern moving together, in phase). Electromyographic (EMG) activity of antagonist neck extensor (splenius capitis) and flexor (longus capitis) muscles as well as horizontal and vertical eye movements (electro-oculography, EOG) were recorded in these different experimental conditions. Results showed that otolith-neck (ONR) and otolith-ocular (OOR) responses were produced during pure otolith stimulation with relatively weak stimuli (0.036 g) in all directions tested. Both EMG and EOG response gain slightly increased, while response phase lead decreased (with respect to stimulus velocity) as stimulus frequency increased in the range 0.25-1.39 Hz. Otolith contribution to compensatory eye and neck responses increased with stimulus frequency, leading to EMG and EOG responses, which oppose the imposed displacement more and more. But the otolith system alone remained unable to produce perfect compensatory responses, even at the highest frequency tested. In contrast, optokinetic stimuli in the Z and Y directions evoked consistent and compensatory eye movement responses (OKR) in a lower frequency range (0.025-0.25 Hz). Increasing stimulus frequency induced strong gain reduction and phase lag. Oculo-neck coupling or eye-head synergy was found during optokinetic stimulation in the Z and Y directions. It was characterized by bilateral activation of neck extensors and flexors during upward and downward eye movements, respectively, and by ipsilateral activation of neck muscles during horizontal eye movements. These visually-induced neck responses seemed related to eye velocity signals. Dynamic properties of neck and eye responses were significantly improved when both inputs were combined (CS).(ABSTRACT TRUNCATED AT 400 WORDS)

Acceleration↗
PubMed1991

Selective autoantibody production by Yaa+ B cells in autoimmune Yaa(+)-Yaa- bone marrow chimeric mice.

The accelerated autoimmune syndrome observed in BXSB/MpJ male mice is associated with the presence on the Y chromosome of an as yet unidentified mutant gene, designated Y chromosome-linked autoimmune acceleration (Yaa). To study the mechanisms by which the Yaa gene accelerates and/or induces the production of autoantibodies, we have developed double-congenic bone marrow chimeras containing B cells from autoimmune males carrying the Yaa gene, and from nonautoimmune male or female mice lacking it and differing by the Igh allotype. The analysis of the allotype of total immunoglobulins and anti-DNA antibodies in Yaa+ male-normal female (Yaa-) chimeric mice revealed that the selective activation of B cells from autoimmune Yaa+ male mice was responsible for the hypergammaglobulinemia and autoantibody production. This phenomenon was not due to an anti-HY interaction between female T helper cells and male B cells, because first, Yaa+ B cells were selectively stimulated to produce autoantibodies in Yaa+ male-Yaa- male chimeric mice; and second, normal male and female chimeras failed to develop an autoimmune syndrome. In addition, the fact that both B cell populations in Yaa(+)-Yaa- chimeras similarly responded to a foreign antigen, human IgG, argues against the possibility that the selective activation of Yaa+ B cells may be due to their hyper-responsiveness to T helper signals. We propose that a cognate interaction of T helper cells with Yaa+ B cells, because of possible T cell recognition of a Yaa-related molecule expressed on Yaa+ B cells, may be responsible for the acceleration and/or induction of autoantibodies in BXSB/MpJ mice.

Animals↗
PubMed1991

Lack of anti-DNA precursors in lambda chain-bearing B lymphocytes in (NZB x NZW)F1 mice. Evidence for the contribution of V kappa genes to anti-DNA specificity.

We have analyzed by the limiting dilution assay on spleen cells from (NZB x NZW)F1 hybrid mice the repertoire of lipopolysaccharide-responsive murine kappa- and lambda 1-secreting B cells committed to the production of anti-DNA autoantibodies to determine the contribution of the heavy and light chains to anti-DNA specificities. Our results demonstrated that anti-DNA precursors were predominantly found in the kappa-secreting B cell population, but not in lambda 1-secreting B cells, while anti-hapten, dinitrophenyl, and anti-tetanus toxoid activities were distributed fairly well in both populations of B cells. This suggests that the V kappa gene segments are critically involved in the generation of anti-DNA specificities, and that at least at the germ-line gene level, the heavy chain V region genes by themselves are not able to confer the anti-DNA autoreactivity.

Animals↗
PubMed1991

Osteoarticular infections due to Kingella kingae in children.

By the description of two cases of osteoarticular infections due to Kingella kingae in two young children we wish to draw the attention of clinicians to invasive infections due to this micro-organism. Since its biological characterization in 1976, K. kingae has been increasingly reported as a human pathogen. Most common presentations are endocarditis, bacteraemia, septic arthritis, osteomyelitis and spondylodiscitis. Interestingly, osteorticular involvement is largely predominant in previously healthy children. From the literature, we reviewed 51 cases of K. kingae bone and joint infections, representing 23 cases of septic arthritis, 17 of osteomyelitis and 11 spondylodiscitis. Of the cases 88% occurred in children below 5 years of age and in all cases only one bone or joint was involved. An underlying disorder could be found in only 4 patients. Since these infections have a favourable outcome with intravenous antibiotic treatment, proper isolation and identification of K. kingae is essential.

Arthritis, Infectious↗
PubMed1991

Plasticity mechanisms in vestibular compensation in the cat are improved by an extract of Ginkgo biloba (EGb 761).

The effects of administration of an extract of Ginkgo biloba (EGb 761) on vestibular compensation was studied in unilateral vestibular neurectomized cats. This experimental model of CNS plasticity was investigated by using behavioral tests (postural disorders compensation, locomotor balance recovery), electrophysiological (spontaneous and evoked neck muscle activity) and neurophysiological (spontaneous firing rate recovery of deafferented vestibular cells) recordings, and immunocytochemical methods (synaptic loss and synaptic reoccupation within the deafferented vestibular nuclei). In all experiments, EGb 761 was administered over 30 days at daily doses of 50 mg/kg IP. The results showed a faster recovery in the EGb-treated group of cats as compared to an untreated control group. EGb administration strongly accelerated postural and locomotor balance recovery. Concomitantly, spontaneous neck muscle activity, vestibulo-collic reflexes and spontaneous firing rate of vestibular units located on the lesioned side were restored earlier. Morphological correlates characterized by a more rapid synaptic reoccupation were found in the deafferented medial vestibular nucleus by means of immunoreactive labelling using an antibody against a synaptic vesicle-associated protein (synaptophysin), but they displayed a longer time-constant in comparison with the behavioral and neurophysiological data. These results clearly demonstrate that EGb 761 acts on recovery mechanisms considered as key processes in vestibular compensation. They suggest that this substance would possess neurotrophic and/or neuritogenic properties improving functional recovery after CNS injury.

Animals↗
PubMed1991

Spray-induced frostbite in a child: a new hazard with novel aerosol propellants.

A case of deep frostbite occurred in an 8.5-year-old child. The lesion was due to the improper use of a toilet air freshener and was severe enough to require a skin graft. The propellants contained in the spray were propane and butane. We measured the temperature of this aerosol during spraying (-40 degrees) in comparison with an ethyl chloride spray (-3 degrees) widely used for local skin anesthesia. This difference is mainly due to the much lower evaporation temperature of propane (-42.2 degrees) and butane (-0.6 degrees) compared with ethyl chloride (12.5 degrees). This child aimed the spray directly toward his skin, thus producing a deep frostbite. We wish to draw the attention of clinicians to this potential hazard with new propellants, since they should soon replace chlorohydrofluorocarbons throughout the world for ecologic reasons.

Aerosol Propellants↗