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J Duchateau

Publications and source records attributed to J Duchateau.

At least 109 records · Page 6Linked to original sources
PubMed1990

Effects of immobilization on contractile properties, recruitment and firing rates of human motor units.

1. The contractile properties, recruitment and firing rates of motor units from the human adductor pollicis and the first dorsal interosseous were studied during voluntary isometric contractions after 6-8 weeks' immobilization of the corresponding limbs. 2. In both muscles, motor units of different force thresholds showed a proportionally identical twitch tension decrease and slowing of their time course after immobilization. 3. When expressed as a percentage of the maximal voluntary contraction, more high-threshold motor units were recorded in disused muscles than in control muscles, but the order of recruitment was maintained. 4. The motor unit firing rate at recruitment was identical in control and disused muscles, but the maximal firing rate decreased in all motor units after immobilization. This decrease of the maximal firing rate was greater in motor units of lower threshold than in those of higher threshold. 5. The results further document motoneuronal plasticity in human muscles of different fibre type composition.

Action Potentials↗
PubMed1990

Modulation of the interleukin 2 receptor by maternal and cord blood serum.

In this report, the potential inhibitive action, of maternal serum (retroplacental and peripheral), and cord blood serum on the expression of the Il2r has been studied. Calf and male serum were used as a control. In order to have an optimal Il2r expression, a previous PHA cellular stimulation was performed. The maternal serum's Il2r inhibitive property was measured during and after the pregnant period. The presence of Il2r on maternal lymphocytes, cord blood cells, and unrelated donor mononuclear cells has been investigated (after a PHA stimulation assay). The downregulated Il2r expression of neoplastic cell line (Hut78 cell line) under the influence of maternal serum has been observed. The examination of the inhibitive action due to maternal serum has suggested that a factor included in the IgG fraction is mainly responsible for the downregulating property concerning the Il2r expression. A possible mechanism for the action of this factor has been studied. Further experiments suggest that the addition of recombinant Il2 during the action of low doses of maternal IgG allows a partial reexpression of the Il2 receptor. However, at physiological concentrations of IgG, the Interleukin 2 receptor downregulation becomes irreversible.

Blood Cells↗
PubMed1990

Modulation of the HLA class II antigen at a molecular level by maternal serum.

The recent immunological literature has described the existence of a retroplacental serum factor being responsible for the downregulation of the MHC Class II antigen expression. In this report, the same property has been found in peripheral maternal serum. The HLA Class II modulating activity is however diminished in the presence of peripheral maternal serum as compared to retroplacental serum suggesting that the IA like inhibiting factor is released at the fetomaternal interface. After a three-day incubation period of unrelated lymphocytes in a maternal serum pool, it was shown that the HLA Dr., the HLA Dp., and more significantly, the HLA Dq. molecules were modulated. When third party lymphocytes were stimulated by Candidine or unrelated mononuclear cells in the presence of retroplacental serum, only the cellular subpopulation belonging to the CD4+ subset showed an HLA Dq. downregulation. The molecular constituents of the MHC Class II antigen expression characterizing cells belonging to other subsets remained unchanged. When the same stimulation assay was performed in the presence of a control medium (nulliparous serum), no changes concerning the MHC Class II molecular constituents were observed. When unrelated mononuclear cells were PHA stimulated in the presence of maternal and nulliparous serums, the HLA Dq. expression of the CD8+ subset showed a significant downregulation in the maternal serum mediated stimulation assay as compared to the control stimulation test. The molecular expression of the HLA Class II antigen related to the other subpopulations (CD4+, CD3+) stimulated by a mitogenic lectin remained unchanged. It is suggested that these molecular MHC Class II modulations are due to a factor included in the maternal IgG reaction. Retroplacental IgG contains the highest concentration of this factor.

Down-Regulation↗
PubMed1989

Muscle fatigue, effects of training and disuse.

The study of muscle fatigue started about a century ago, when it was proposed that the observed decrease in force during prolonged voluntary contractions resulted from changes in central processes which reduced the motor drive. In the middle of this century it was noticed that this loss of force could not be restored by maximal electrical stimulation of the motor nerve, and thus the importance of peripheral mechanisms, located beyond the motoneuron, was emphasized. However, it was not clear which peripheral site was most important in decreasing the muscle mechanical capacity during fatigue. More recently, the comparison between peripheral failures during sustained and intermittent contractions indicated that recorded mechanical changes underwent deterioration which was not closely related to the recorded electrical changes. It was thus proposed that muscle intracellular processes dominate the force decrease during muscle fatigue. This concept has been substantiated by the study of standard fatigue tests performed in control, trained, and disused human muscles, as reviewed in this paper.

Action Potentials↗
PubMed1989

Immunomodulation with thymopentin: in vitro studies.

Immunomodulation is interpreted as a temporary alert in a certain part of the immune system. The activation of immune competent cells is presented as a possible basic mechanism of this phenomenon. In the absence of a primary stimulus, immunomodulation remains physiologically silent, but it results in a modified immune response if the corresponding targets are being stimulated. For practical reasons it is suggested that distinctions be made between preventive and regulative immunomodulation. The PWM-induced IgG production of PBMCs was used as a model for the demonstration of the modulatory effect of thymopentin in vitro. Depending on the concentration of thymopentin used in the cultures, this pentapeptide can either stimulate or inhibit the induced IgG production. It also influences PGE2 production and catabolism in the cultures stimulated with PWM. Indomethacin abolishes the modulatory effect of thymopentin on IgG production in this model. It is suggested that the possibility of interactions between an immune modulator and therapeutic approaches which can influence the proportions or functions of the corresponding target cells be considered.

Adjuvants, Immunologic↗
PubMed1989

Arterial infection following renal transplantation: successful management using transperineal femorofemoral crossover graft.

Infection of a vascular prosthesis or an arterial receptor site is one of the most challenging situations for the vascular surgeon. In some instances the standard extraanatomic routes to bypass infected areas cannot be used. Two cases of arterial infection following renal transplantation are presented. An infrascrotal perineal approach for a femorofemoral bypass was used to achieve revascularization of a threatened limb.

Adult↗
PubMed1989

Effect of inhaled endotoxin on bronchial reactivity in asthmatic and normal subjects.

Endotoxins are released from the membrane of Gram-negative bacteria present in the environment and in oral and nasal cavities. They are proinflammatory substances that could participate in bronchial obstruction and hyperreactivity in asthmatic patients. This hypothesis was tested by using bronchial challenge tests with inhaled lipopolysaccharides (LPS) from Escherichia coli 026:B6 (22.2-micrograms total dose) followed by a histamine nonspecific challenge test and compared with a placebo procedure, in which the diluent was substituted for the LPS solution. In doing so we showed that LPS induces a slight but significant (P less than 0.01) bronchial obstruction (measured as forced expiratory volume in 1 s) in asthmatics (n = 8) but not in normal subjects (n = 6). The histamine hyperresponsiveness, expressed as the dosage of histamine necessary to decrease the bronchial specific conductance by 50%, was increased 5 h after LPS inhalation in asthmatics (P less than 0.05) but not in normal subjects. This effect of LPS on bronchial obstruction and hyperresponsiveness was observed in extrinsic (n = 6) as well as in intrinsic (n = 2) asthma.

Administration, Inhalation↗
PubMed1989

Functional modifications of the CD4+ and the CD8+ subset due to maternal serum.

Numerous experiments have been performed to try to explain the successful gestation of the semiallogeneic mammalian fetus in the immuno-competent mother. A popular hypothesis is that localized intra uterine suppression mediates the immune response and contributes directly to the survival of the fetus. Suppressive factors synthesized at the fetomaternal interface may be transported by the bloodstream and be found in the retroplacental and peripheral blood circulation. In this report we aim to study these modulating factors by exposing a proteinaceous antigen (Candidine or human mono nuclear cells) to unrelated human lymphocytes in the presence of a pool of maternal serum, retroplacental (MAT SR) or peripheral (MAT SP), or to a pool of male or calf serum (MALS or CS). A significant downregulation of the candidine mediated lymphocytic stimulation was observed in the case of the maternal serum. In order to further characterize this inhibition, a quantitative evaluation of the expression of the CD4 and CD8 positive subpopulations was performed. A selective inhibition of the CD4 positive subset was observed. In the PHA stimulation assay in the presence of maternal serum there was an inhibition of the thymidine uptake of unrelated lymphocytes. When studying the different subsets which were stimulated in the presence of maternal serum and control media it was shown that the CD4 positive subpopulation remained unchanged while there was a slight inhibition of the CD8 positive subset in the first case (maternal serum treated). The same CD4 positive inhibitive property of maternal serum was observed when a neoplastic cell line (HUT cells) was used as target for candidine in a stimulation test. This CD4 inhibited expression remained constant as long as the maternal serum was renewed. Maternal lymphocytes however remained resistant to the inhibitive action of maternal serum and did not show any change in their CD4 and CD8 positive subpopulation. By investigating the different blood components, it was shown that the suppressive factor was included in the IgG fraction and synthesized at the placental level. Appearing quite early during the gestation (at the 5-6th week), this factor was vanishing 2 weeks after the delivery.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1989

Maternal immune status against beta-lactoglobulin and cow milk allergy in the infant.

Beta-lactoglobulin (BLG) is probably the major cow milk antigen. Serum levels of anti-BLG antibodies were determined prospectively in mothers. The results were analyzed according to the existence of allergic manifestations in infants during the first months of life. Mothers of babies who developed allergy had statistically lower IgG anti-BLG concentrations than mothers of infants who presented no symptoms (P less than .001). Together with IgE umbilical cord blood screening, determine maternal IgG anti-BLG concentrations can more clearly define the allergic risk in the infant.

Adult↗
PubMed1989

[Immunopathologic mechanisms associated with granulomas and odontogenic cysts: a general review].

The authors make a general survey of the immunopathological mechanisms involved in odontogenic cysts and granulomas. The dental pulp and the sound periapical tissues contain neither inflammatory nor immunoglobin-producing cells. Dental decay associated with bacterial aggression of the dental pulp and periapical tissues might induce a nonspecific inflammation which subsequently becomes more specific. Immunoglobulins are present in fluid aspirates from odontogenic cysts and granulomas. Several investigations have pointed out nonspecific inflammatory mediators (including the C3 complement components), T lymphocytes (helpers and suppressors), B lymphocytes, protein S-100 + cells (Langerhans cells). The presence of immunoglobulins, immunocompetent cells and C3 complement components confirms that all constituents of both humoral and cell-mediated immunological reactions might play an essential role in the pathogenesis of osteolysis.

Humans↗
PubMed1989

[Comparison of the effect of 2 methods of histamine administration on the bronchomotor response in asthmatics].

Bronchial provocation tests are useful for the detection of subclinical bronchial hyper-reactivity. Their standardisation is vital, in particular the method of administration of the bronchoconstrictor agent. Our study compares two systems of histamine delivery: an aerosol propellant with freons and a jet nebuliser linked to a dosimeter. Ten allergic asthmatics underwent bronchial provocation by each of these two systems at 8 days interval. The forced expired volume in one second FEV1 (VEMS) and specific conductance (sGAW) were measured during both tests. The dose of histamine inducing a reduction of VEMS of 20% (PD VEMS) or of sGAW of 40% (PD sGAW) was calculated. The comparison of the two methods showed a lower threshold of sensitivity when histamine was administered by dosimetry whether it was in terms of PD 20 VEMS (p less than 0.01) or PD 40 sGAW (p less than 0.05). The threshold of sensitivity expressed as PD 20 VEMS and PD 40 sGAW are superimposable by the dosimetric technique but on the other hand, using the aerosol dosage method, the threshold of sensitivity expressed in PD 40 sGAW is significantly lower than that for PD 20 VEMS (p less than 0.02). The 2 differences of bronchial response as a function of the method of administration of histamine could be explained by a better bronchial penetration, accompanied by a more central depot of the drug when histamine is administered by dosimetry.

Adult↗
PubMed1989

Decrease of motoneuron excitability during stretching of the human soleus.

Changes of motoneuron (MN) excitability was studied during the basic modalities of slow or static stretching of the human soleus muscle (Sol). Tendon (T) and Hofmann (H) reflexes were recorded during slow passive (assisted) stretching (SS). The H response was analysed in SS, in SS preceded by a maximal isometric contraction of the muscle or contraction-relaxation (CR) and during stretching of the muscle by contracting the antagonistic muscle (AC). The maximal joint mobilization during SS, CR and AC appears to be closely related to the decrease of the H response. It is suggested that the joint mobilization during slow stretching is closely controlled by the level of inhibition of the MN pool excitability, which lasts only as long as the stretching manoeuvre is maintained.

Adult↗
PubMed1989

Peripheral changes during muscle fatigue and their adaptation to training and disuse.

Muscle fatigue has been studied in the human adductor pollicis during electrically evoked (30 Hz) contractions. The peripheral electrical and mechanical changes were compared during sustained (60s) and intermittent (sixty ls) contractions separated by 2.0, 1.0 and 0.5s intervals. The results indicate that the mechanical failure is not closely related to the electrical changes and it is proposed that intracellular processes dominate the force deterioration during fatigue. This point of view is discussed on the basis of data recorded from control, trained and disused muscles, during standard fatigue tests.

Adaptation, Physiological↗
PubMed1988

Muscle stretching and motoneuron excitability.

Change of motoneuron excitability has been studied during the three basic modalities of slow or static stretching of the human soleus muscle. Tendon (T) and Hoffmann (H) reflexes were analyzed during static stretching (SS). The H response was compared in SS, in SS preceded by a maximal isometric contraction of the muscle or contraction-relaxation (CR) and during stretching of the muscle by contracting the antagonistic muscles (AC). During progressive dorsiflexion of the foot there is a significant difference (p less than 0.05) between T and H reflexes during SS, although the amplitude of direct motor (M) response, evoked by a maximal stimulation of the motor nerve, is not changed. The maximal joint mobilization during SS, CR and AC modalities appears to be closely related to the decrease in the H response during stretching. This decrease is significantly (p less than 0.05) smaller in SS than in AC or CR. In this last method, the duration of the maximal isometric contraction does not affect the results. In these three basic stretching procedures, the H reflex quickly recovers as soon as the manoeuvre is interrupted. It is suggested that changes in muscle motoneuron pool excitability closely control joint mobilization during slow or static stretching. The inhibition of the motoneurons observed during SS, CR and AC modalities is limited to the duration of the stretching manoeuvre.

Adult↗
PubMed1988

Innervation of the rectus abdominis muscle: implications for rectus flaps.

The usefulness of leaving lateral strips of the rectus abdominis muscle in place during a transverse rectus abdominis musculocutaneous (TRAM) flap procedure is questioned. Since textbooks do not agree on the course of the intercostal nerves in the rectus fascia and no precise description is given of the exact site of penetration of the nerves in the rectus muscle, six fresh cadavers were dissected. It has been observed that the nerves enter the deep face of the muscle in its middle portion. Lateral parts of the muscle are consequently denervated during a transverse rectus abdominis musculocutaneous flap, which preserves them. This has been confirmed by CT scan of the abdominal wall in 10 patients 2 to 37 months after a transverse rectus abdominis musculocutaneous flap. In these patients, a progressive fibrosis and disappearance of the remaining muscle could be demonstrated. It is concluded that a partial taking of the rectus abdominis muscle does not preserve its muscular function.

Abdominal Muscles↗
PubMed1988

Polymeric and monomeric IgA response in serum and milk after parenteral cholera and oral typhoid vaccination.

The effect of vaccinating lactating Pakistani mothers with a combination of live oral typhoid vaccine and parenteral inactivated cholera vaccine on specific milk and serum IgA antibodies in both monomeric (m) and polymeric (p) forms was analysed. IgA antibody titres peaked for both antigenic specificities 2 weeks after the first dose of vaccine. 82 +/- 7% of anti-Vibrio cholerae and 72 +/- 17% of anti-Salmonella typhi IgA were in the polymeric form. These serum pIgA antibodies were mainly dimeric IgA, not complexed with the secretory component. They disappeared more rapidly from serum than mIgA antibodies. Anti-V. cholerae IgA responses were parallel in serum and milk samples, whereas anti-S. typhi responses were dissociated. In milk, IgA antibodies were secretory IgA for both antigenic specificities, being probably of local origin in the mammary gland. Our results indicate that both oral and parenteral vaccinations can induce pIgA antibodies in serum and secretions, confirming that the presence of pIgA in serum does not necessarily reflect an immune stimulation only at the mucosal level.

Administration, Oral↗
PubMed1988

IgA immune response patterns to gliadin in serum.

The incidence, titer and molecular size of anti-gliadin (GL) IgA were analyzed in sera from children with celiac disease (CD, n = 66), hospitalized control children (n = 64) and children with other malabsorption disorders (n = 103). Anti-GL IgA was assessed by solid-phase radioimmunoassay, and its molecular size was analyzed by sucrose density gradient ultracentrifugation. The median anti-GL IgA titer was significantly higher in untreated CD than in the other groups, with some overlap. Whereas 57% of anti-GL IgA were polymeric IgA (pIgA) in acute CD, only 17% were pIgA in children with other malabsorption disorders. These anti-GL pIgA consisted mainly of dimers with in some children, a low proportion of anti-GL secretory IgA (SIgA). A large proportion of anti-GL pIgA was associated with high total serum IgA. After the onset of a gluten-free diet (GFD), anti-GL pIgA disappeared more quickly from serum than mIgA. During the gluten challenge test, anti-GL IgA comprised 20% pIgA when they reappeared in serum, but 59% pIgA at the end of the test. The presence of anti-GL pIgA in serum seems related to chronic exposure to gluten of CD patients with a flat intestinal mucosa. These serum pIgA antibodies could result from a spillover from the intestinal mucosal synthesis into the circulation.

Antibodies, Anti-Idiotypic↗