Biomedical subjects

Jean Lebacq

Publications and source records attributed to Jean Lebacq.

6 recordsLinked to original sources

PubMed2004

Effect of muscle creatine content manipulation on contractile properties in mouse muscles.

The effects of muscle creatine manipulation on contractile properties in oxidative and glycolytic muscles were evaluated. Whereas control mice (NMRi; n = 12) received normal chow (5 g daily), three experimental groups were created by adding creatine monohydrate (CR group; 5%, 1 week; n = 13); beta-guanidinoproprionic acid, an inhibitor of cellular creatine uptake (beta-GPA group; 1%, 2 weeks; n = 12); or CR following beta-GPA (beta-GPA+CR group; n = 11). Total creatine (TCr) and the contractile properties of incubated soleus and extensor digitorum longus (EDL) muscles were determined. For the soleus, compared with control, TCr increased in the CR group (+25%), decreased in beta-GPA group (-50%), and remained stable in the beta-GPA+CR group, whereas, for the EDL, TCr was similar in the CR, and lower in the beta-GPA (-40%) and beta-GPA+CR (-15%) groups. None of the experimental groups (CR, beta-GPA, or beta-GPA+CR) showed changes in peak tension (P(peak)), time to peak tension, or relaxation in soleus or EDL during twitch or tetanic stimulation. For the soleus, fatigue reduced P(peak) to approximately 60% of initial P(peak); 5 min of recovery restored P(peak) to values approximately 15% higher in CR than in controls. P(peak) recovery was not affected by beta-GPA or beta-GPA+CR in the soleus or any treatment in the EDL. Thus, peak tension recovery is enhanced by creatine intake in oxidative but not glycolytic muscles. This may be implicated in the beneficial action of creatine loading.

Adenosine Triphosphate↗

PubMed2004

Effect of creatine supplementation on skeletal muscle of mdx mice.

Dystrophic mice (mdx) and their controls (C57/Bl10) were fed for 1 month with a diet with or without creatine (Cr) enrichment. Cr supplementation reduced mass (by 19%, P < 0.01) and mean fiber surface (by 25%, P < 0.05) of fast-twitch mdx muscles. In both strains, tetanic tension increased slightly (9.2%) without reaching statistical significance (P = 0.08), and relaxation time increased by 16% (P < 0.001). However, Cr had no protective effect on the other hallmarks of dystrophy such as susceptibility to eccentric contractions; large numbers of centrally nucleated fibers in tibialis anterior; and elevated total calcium content, which increased by 85% (P = 0.008) in gastrocnemius mdx muscles. In conclusion, Cr may be a positive intervention for improving function of dystrophic muscle.

Animals↗

PubMed2004

Basic protocol for transepithelial nasal potential difference measurements.

Transepithelial nasal potential difference (NPD) measurements assess ion conductance in the upper respiratory epithelium. NPD is useful in assisting in the diagnosis of classical and atypical cystic fibrosis (CF) and of cystic fibrosis transmembrane regulator (CFTR)-related disorders, as well as for monitoring the effect of pharmacological agents and gene transfer approaches to correct the abnormalities of ion transport in CF. The article summarizes the objectives and the principle of NPD measurements, describes a hands-on protocol of the procedure and provides quality control measures, practical hints and troubleshooting.

Clinical Protocols↗

PubMed2003

Beneficial effects of creatine supplementation in dystrophic patients.

The effect of creatine (Cr) supplementation on muscle function and body composition of 12 boys with Duchenne muscular dystrophy and three with Becker dystrophy was evaluated by a randomized double-blind cross-over study (3 g Cr or maltodextrin daily for 3 months, with wash-out period of 2 months). After placebo, no change was observed in maximal voluntary contraction (MVC) and resistance to fatigue, whereas total joint stiffness (TJS) was increased by approximately 25% (P < 0.05). The patients receiving Cr did not show any change in TJS, improved MVC by 15% (P = 0.02), and almost doubled their resistance to fatigue (P < 0.001). In patients still independent of a wheelchair (n = 5), bone mineral density increased by 3% (P < 0.05), and urinary excretion of collagen type I cross-linking N-telopeptide declined to about one third (P < 0.001) after Cr. No adverse effect was observed. Thus, Cr may provide some symptomatic benefit in these patients.

Administration, Oral↗

PubMed2003

Modified method to measure nasal potential difference.

Nasal potential difference (NPD) measurements have been proposed to assess defective ion transport in cystic fibrosis (CF). Implementing it routinely is, however, difficult. Therefore, a modified method based on nasal instillation in supine position at reduced flow rate was tested to evaluate its ability to discriminate CF from non-CF subjects. Classical and modified methods were compared in nine healthy subjects and there were no statistical differences. Following the new method, 97 tests were performed on 74 subjects divided in three cohorts: 21 CF patients and two control groups consisting of 19 patients with other pulmonary diseases and 34 healthy subjects. Twenty five children were enrolled in this study. Maximal NPD in CF patients (-44.9 +/- 2.5 mV) was significantly different from that obtained in control groups (-18.1 +/- 1.6 and -17.2 +/- 1.1 mV). Depolarization after amiloride also discriminated CF patients (25.9 +/- 1.4 mV) from control groups (10.5 +/- 0.9 and 8.1 +/- 0.7 mV). Marked repolarization following isoprenaline plus amiloride in low chloride solution was seen in control groups (-15.7 +/- 1.1 and -15.3 +/- 1.1 mV). We conclude that the modified method represents a simplified and equally effective approach to discriminate CF patients from non-CF subjects. Moreover, this method presents practical advantages for the patients related to hygiene and convenience, favoring its application in small children.

Adolescent↗

PubMed2002

Role of IGF-I and IGFBPs in the changes of mass and phenotype induced in rat soleus muscle by clenbuterol.

Clenbuterol induces hypertrophy and a slow-to-fast phenotype change in skeletal muscle, but the signaling mechanisms remain unclear. We hypothesized that clenbuterol could act via local expression of insulin-like growth factor I (IGF-I). Administration of clenbuterol to 3-mo-old female Wistar rats resulted in a 10 and 13% increase of soleus muscle mass after 3 and 9 days, respectively, reaching 16% after 4 wk. When associated with triiodothyronine, clenbuterol induced a dramatic slow-to-fast phenotype change. In parallel, clenbuterol administration induced in soleus muscle a fivefold increase in IGF-I mRNA levels associated with an eightfold increase in IGF-binding protein (IGFBP)-4 and a fivefold increase of IGFBP-5 mRNA levels on day 3. This increased IGF-I gene expression was associated with an increase in muscle IGF-I content, already detected on day 1 and persisting until day 5 without increase in serum IGF-I concentrations. These data show that muscle hypertrophy induced by clenbuterol is associated with a local increase in muscle IGF-I content. They suggest that clenbuterol-induced muscle hypertrophy could be mediated by local production of IGF-I.

Adrenergic beta-Agonists↗