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Biomedical subjects

C Lacroix

Publications and source records attributed to C Lacroix.

At least 73 records · Page 4Linked to original sources
PubMed2000

Transgenic mice carrying large human genomic sequences with expanded CTG repeat mimic closely the DM CTG repeat intergenerational and somatic instability.

Myotonic dystrophy (DM) is caused by a CTG repeat expansion in the 3'UTR of the DM protein kinase (DMPK) gene. A very high level of instability is observed through successive generations and the size of the repeat is generally correlated with the severity of the disease and with age at onset. Furthermore, tissues from DM patients exhibit somatic mosaicism that increases with age. We generated transgenic mice carrying large human genomic sequences with 20, 55 or >300 CTG, cloned from patients from the same affected DM family. Using large human flanking sequences and a large amplification, we demonstrate that the intergenerational CTG repeat instability is reproduced in mice, with a strong bias towards expansions and with the same sex- and size-dependent characteristics as in humans. Moreover, a high level of instability, increasing with age, can be observed in tissues and in sperm. Although we did not observe dramatic expansions (or 'big jumps' over several hundred CTG repeats) as in congenital forms of DM, our model carrying >300 CTG is the first to show instability so close to the human DM situation. Our three models carrying different sizes of CTG repeat provide insight on the different factors modulating the CTG repeat instability.

3' Untranslated Regions↗
PubMed2000

Comparison of simple neural networks and nonlinear regression models for descriptive modeling of Lactobacillus helveticus growth in pH-controlled batch cultures.

A set of 20 Lactobacillus helveticus growth curves was obtained from pH-controlled batch cultures with different pH setpoints, whey permeate and yeast extract concentrations. To find the best descriptive model of the biomass concentration versus time (y = X(t)) growth curve, fitting results of a large number of models were compared with statistical and approximate methods. Models studied included simple neural networks, reparameterized Logistic, Gompertz, Richards, Schnute, Weibull, and Morgan-Mercier-Flodin models, Amrane-Prigent model, and four new models based on autonomous growth functions. Simple neural networks with only four weights were good descriptive models of the growth curves and fitting qualities were similar to those of the best existing four-parameter models, such as the Logistic model. However, meaningful parameters had to be calculated numerically and use of simple neural networks yielded no distinctive advantages over other models. A new five-parameter model, based on an autonomous growth function, yielded the best fitting results, even when the number of model parameters was accounted for in the comparisons. However, the maximum specific growth rate was not always well estimated. Therefore the five-parameter Richards model was chosen as the best descriptive model of the growth curve.

Journal Article↗
PubMed2000

The course and prognostic factors of familial amyloid polyneuropathy after liver transplantation.

Familial amyloid polyneuropathy (FAP) associated with mutations of the transthyretin (TTR) gene is the most common type of FAP, a devastating disease causing death within 10 years after the first symptoms. Because most of the amyloidogenic mutated TTR is secreted by the liver, transplantation is widely used to treat these patients, but long-term quantitative evaluation of the effects of liver transplantation on the progression of the neuropathy are not available. We have treated 45 patients with symptomatic TTR-FAP, including 43 with the Met30 TTR gene mutation, and report on the results of periodic evaluation of markers of neuropathy in 25 of them, who have been followed for more than 2 years after liver transplantation (mean follow-up 4 years). The overall survival rates at 1 and 5 years were 82 and 60%, respectively. Urinary incontinence and a low Norris score at liver transplantation were associated with poorer outcome. The motor score stabilized in seven of 11 patients (64%) with mild sensorimotor neuropathy (walking unaided) and in two of the eight patients (25%) with severe sensorimotor deficit (walking with aid) at liver transplantation. In five other patients, deterioration of motor deficit occurred only within the first year after liver transplantation, but was progressive after this interval in two patients. None of the six patients with pure sensory neuropathy developed motor loss and superficial sensory loss remained unchanged. Two years after liver transplantation, the rate of myelinated axon loss in nerve biopsy specimens was markedly lower in seven transplanted patients (0.9/mm(2) of endoneurial area/month) than in non-transplanted patients (70/mm(2) of endoneurial area/month). Symptoms of dysautonomia and quantitated cardiocirculatory autonomic tests remained unchanged. In all patients, serum mutated TTR decreased to 2.5% of pre-liver transplantation values and remained at this level during follow-up. We presently recommend liver transplantation in FAP patients at onset of first symptoms and exclusion of those with a Norris score below 55 and/or with urinary incontinence.

Action Potentials↗
PubMed2000

MICs of mutacin B-Ny266, nisin A, vancomycin, and oxacillin against bacterial pathogens.

Peptide antibiotics, particularly lantibiotics, are good candidates for replacing antibiotics to which bacteria have become resistant. In order to compare two such lantibiotics with two antibiotics, the MICs of nisin A, mutacin B-Ny266, vancomycin, and oxacillin against various bacterial pathogens were determined. The results indicate that nisin A and mutacin B-Ny266 are as active as vancomycin and oxacillin against most of the strains tested. Furthermore, mutacin B-Ny266 remains active against strains that are resistant to nisin A, oxacillin, or vancomycin. The wide spectrum of activity of mutacin B-Ny266, its low MICs against bacterial pathogens, and its activity against bacteria resistant to other inhibitors support the development of this substance for therapeutic use.

Anti-Bacterial Agents↗
PubMed2000

Simultaneous immunofluorescent detection of coentrapped cells in gel beads.

An immunofluorescent method involving double color labeling and confocal microscopy was reported to specifically detect lactic acid bacteria and probiotic cells coimmobilized in gels beads. The method described is rapid (4 h) and sensitive and may be useful for studying cell dynamics during mixed-culture starter production using immobilized cells in gel beads. Microscopic observations were perfectly correlated to cell counts obtained using a sandwich enzyme-linked immunosorbent assay.

Bifidobacterium↗
PubMed2000

Fungal contamination of food in hematology units.

The prevalence of thermotolerant fungi on non-heat-sterilizable food was determined. Aspergillus spp. were noted in 100% of pepper and regular tea samples, 12 to 66% of fruits, 27% of herbal teas, and 20% of freeze-dried soup samples. All soft cheese samples were contaminated by Geotrichum and yeast (Candida norvegensis) but Candida albicans was never identified.

Aspergillus↗
PubMed2000

Modeling of pH and acidity for industrial cheese production.

A three-layer feedforward neural network was successfully used to model and predict the pH of cheese curd at various stages during the cheese-making process. An extended database, containing more than 1800 vats over 3 yr of production of Cheddar cheese with eight different starters, from a large cheese plant was used for model development and parameter estimation. Neural network models were developed with inputs selected among 33 quantitative and qualitative process variables for final pH of cheese, pH at cutting, and acidity at whey drawing-off and at pressing. In all cases, very high correlation coefficients, ranging from 0.853 to 0.926, were obtained with the validation data. A sensitivity analysis of neural network models allowed the relative importance of each input process variable to be identified. The sensitivity analysis in conjunction with a priori knowledge permitted a significant reduction in the size of the model input vector. A neural network model using only nine input process variables was able to predict the final pH of cheese with the same accuracy as for the complete model with 33 original input variables. This significant decrease in the size of neural networks is important for applications of process control in cheese manufacturing.

Biotechnology↗
PubMed2000

Peripheral neuropathy with hypomyelination, chronic intestinal pseudo-obstruction and deafness: a developmental "neural crest syndrome" related to a SOX10 mutation.

We describe the case of a girl with an unusual congenital phenotype, combining peculiar peripheral nerve lesions with hypomyelination, chronic intestinal pseudoobstruction, and deafness. She was found to have a de novo heterozygous frameshift mutation in the gene encoding the SOX10 transcription factor. The likely role of SOX10 in determining the fate of Schwann cells during early embryogenesis may explain the peripheral nervous system developmental disorder observed in this patient.

Amino Acid Sequence↗
PubMed1999

Persistent mitochondrial dysfunction and perinatal exposure to antiretroviral nucleoside analogues.

BACKGROUND: Zidovudine is commonly administered during pregnancy to prevent mother-to-child HIV-1 transmission. We investigated mitochondrial toxic effects in children exposed to zidovudine in utero and after birth. METHODS: We analysed observations of a trial of tolerance of combined zidovudine and lamivudine and preliminary results of a continuing retrospective analysis of clinical and biological symptoms of mitochondrial dysfunction in children born to HIV-1-infected women in France. Mitochondrial dysfunction was studied by spectrophotometry and polarography of respiratory-chain complexes in various tissues. FINDINGS: Eight children had mitochondrial dysfunction. Five, of whom two died, presented with delayed neurological symptoms and three were symptom-free but had severe biological or neurological abnormalities. Four of these children had been exposed to combined zidovudine and lamivudine, and four to zidovudine alone. No child was infected with HIV-1. All children had abnormally low absolute or relative activities of respiratory-chain complexes I, IV, or both months or years after the end of antiretroviral treatment. No mutation currently associated with constitutional disease was detected in any patient. INTERPRETATION: Our findings support the hypothesis of a link between mitochondrial dysfunction and the perinatal administration of prophylactic nucleoside analogues. Current recommendations for zidovudine monotherapy should however be maintained. Further assessment of the toxic effects of these drugs is required.

Acidosis, Lactic↗
PubMed1999

Reinnervation of denervated lumbar ventral roots and their target muscle by thoracic spinal motoneurons via an implanted nerve autograft in adult rats after spinal cord injury.

Intraspinally implanting a nerve autograft (NAG) to promote axonal regeneration toward periphery was investigated as a surgical treatment for spinal cord injury in adult rats. Fifteen animals underwent a left hemisection of the spinal cord at T12 level and an intradural section of all ipsilateral lumbar ventral roots. In repaired animals (n = 9), the electrophysiologically selected left L3 and L4 lumbar ventral roots supplying the quadriceps muscle were anastomosed to a NAG. The NAG was taken from the right peroneal nerve and then ventrolaterally implanted into the cord at a level 7 mm rostral to the hemisection. In the control group (n = 6), sectioned lumbar ventral roots were left unrepaired. Nine months later, the animals were assessed with clinical, electrophysiological, and histological examinations. Muscle action potential and motor evoked potential were obtained from the denervated/reinnervated quadriceps in all repaired animals, with a mean amplitude of 918.3+/-328.9 microV and 215.8+/-39.7 microV, respectively. Horseradish peroxidase retrograde labeling from the denervated/repaired lumbar ventral roots, performed in five repaired animals, showed that the mean of labeled neurons, ipsilaterally located in the thoracic ventral horn near the implantation site, was 145.8+/-111.7. Histological analysis showed numerous myelinated axons in the NAG and denervated/repaired lumbar ventral roots of all repaired animals. The study of neuromuscular junctions furthermore confirmed numerous newly formed endplates appearing in the denervated/reinnervated quadriceps. These changes were absent in the control animals. These data indicate that the rostral thoracic spinal motoneurons can innervate the caudal denervated/repaired lumbar ventral roots and the target quadriceps via an implanted NAG, thereby inducing some functional recovery in adult rats after lower thoracic spinal cord injury.

Action Potentials↗
PubMed1999

Digoxigenin-labeled probe for rapid identification of nisinogenic Lactococcus lactis strains.

From the nisZ gene sequence, a non-radioactive digoxigenin-labeled DNA probe, was tested for detection of nisin-producing strains using polymerase chain reaction amplification. The digoxigenin-labeled DNA probe clearly discriminated between nisin-producing and non-producing strains with a high degree of sensitivity and specificity. By agarose gel electrophoresis, 1.4 ng of nisin DNA was detected using the digoxigenin-labeled DNA probe compared with 11 ng using direct polymerase chain reaction amplification. A colony hybridization method using digoxigenin-labeled DNA to selectively detect nisinogenic bacteria showed that the nis-probe was specific and did not react with any other non-bacteriocinogenic and non-nisinogenic strains.

DNA Probes↗
PubMed1999

The Roussy-Lévy family: from the original description to the gene.

In 1926, Roussy and Lévy described a large family whose members manifested an early onset dominantly inherited gait ataxia, pes cavus, and areflexia, which was eventually associated with distal muscle atrophy, postural tremor, and minor sensory loss. Slow nerve conduction and demyelination of nerve fibers with onion bulb formations in nerve biopsy specimens led to the Roussy-Lévy syndrome (RLS) being considered a variant of demyelinating Charcot-Marie-Tooth disease (CMT-1). In the present article, we report on the long-term follow-up, on nerve biopsy findings, and on the underlying molecular genetic defect in members of the original family studied by Roussy and Lévy. All patients were able to walk during their seventh decade of life. Morphologically, a chronic demyelinating neuropathy with the remarkable aspects of a focally hypertrophic myelin sheath and major loss of myelinated fibers was observed in nerve biopsy specimens of 3 members of this family. Molecular genetic testing identified a previously unknown heterozygous missense point mutation which yielded an Asn131Lys substitution in the extracellular domain of the myelin protein zero (P0). These findings show that the Roussy-Lévy family belongs to the CMT-1B subtype and has original morphological and genetic features.

Aged↗
PubMed1999

Long-term mechanical and biological stability of an immobilized cell reactor for continuous mixed-strain mesophilic lactic starter production in whey permeate

The aim of this study was to characterize the biological and rheological stability of continuous immobilized cell fermentation for the production of mixed-strain mesophilic starters. Three strains of Lactococcus were immobilized separately in kappa-carrageenan-locust bean gum gel beads. Continuous fermentation was carried out in a 1 L pH-controlled stirred tank reactor, operated at 30 degrees C, pH = 6.2, and D = 2 h(-)(1) in whey permeate medium supplemented with yeast extract (1.5%) and 0.1 M KCl and inoculated with 30% (v/v) bead inoculum (strain ratio 1:1:1). The continuous mixed-strain immobilized cell fermentation demonstrated a high biological stability, and no strain became dominant or was eliminated during the 52 day fermentation. The total and specific free cell populations showed high time stability. All immobilized populations, except MD, were unchanged, but a cross contamination of gel beads initially immobilizing a pure culture occurred, leading to a redistribution of immobilized population in individual beads. After initial modifications of bead rheological properties during colonization batches, the beads demonstrated a high mechanical stability, even with reduced KCl supplementation of the broth medium, in the range 0.1-0 M. This work emphasizes the potential of immobilized cell technology for producing mixed lactic starters in continuous fermentation.

Journal Article↗
PubMed1999

Production and utilization of polyclonal antibodies against nisin in an ELISA and for immuno-location of nisin in producing and sensitive bacterial strains.

Specific nisin polyclonal antibodies (PAb) were produced in rabbits using nisin Z produced by Lactococcus lactis subsp. lactis biovar diacetylactis UL 719. Antisera were obtained from white female New Zealand rabbits that were first immunized with a nisin Z-keyhole limpet haemocyanin conjugate and boosted with free nisin Z. Nisin-specific PAb were purified by affinity chromatography with a yield of 15 mg specific antinisin 100 ml-1 serum. The detection limit of the ELISA test for nisin Z was 0.75 ng ml-1 in buffer but was 1.7 and 3.5 ng ml-1 in milk and complex media broth spiked (5, 10, 20 microg ml-1) with nisin Z, respectively. In nisin Z-spiked samples, the average concentration was between 90 and 107% of actual added amount. In contrast, when the bioassay (microtitration method) was used, only 50-63% of nisin Z biological activity could be detected. In addition, the affinity-purified nisin PAb, antirabbit IgG gold conjugate and transmission electron microscopy were successfully used to locate nisin Z on producing cells and to observe its bactericidal effects against sensitive cells.

Animals↗
PubMed1999

Fatal case of dichloromethane poisoning.

A 47-year-old man was found dead in a factory where dichloromethane (DCM) tanks were stocked. He was making an inventory of the annual stock of DCM contained in several tanks (5- to 8000-L capacity) by transferring the solvent into an additional tank with the help of compressed air. During this operation, one of the tanks overflowed and the man, who was not wearing any protection, was intoxicated. Autopsy showed digestive, suprarenal, and liver bleeding. Blood was also found in the trachea. DCM was identified by headspace gas chromatography-mass spectrometry (GC-MS). A headspace gas chromatography-flame ionization detection technique (GC-HS-FID) optimized for quantitation in biological fluids, organs and viscera was established at autopsy. The following concentrations of DCM were found: blood (150 mg/L), urine (2.0 mg/L), gastric content (5.6 mg/L), brain (122 mg/kg), fat (99 mg/kg), liver (44 mg/kg), lung (20 mg/kg), and kidney (15 mg/kg). A study of the storage stability of DCM was carried out on these samples. Ethanol production was measured in some organs. The results are discussed in light of the rarity of existing literature.

Fatal Outcome↗
PubMed1999

Calcium-regulating hormones, bone mineral content, breaking load and trabecular remodeling are altered in growing pigs fed calcium-deficient diets.

Studies on calcium nutrition in appropriate large animal models can be directly relevant to humans. We have examined the effect of dietary Ca deficiency on various bone and bone-related variables, including plasma markers, histomorphometry, mineral content and breaking strength in pigs. Three groups of eight 38-d-old female pigs were fed adequate (0.9%; control), low (0.4%; LCa) or very low (0.1%; VLCa) Ca diets for 32 d. Plasma Ca significantly decreased over time only in the VLCa-deficient pigs. The concentrations of the parathyroid hormones (PTH) and calcitriol increased as Ca deficiency developed, and the plasma PTH and calcitriol levels varied inversely with dietary Ca. The total bone ash contents, bending moments, trabecular bone volume and the mineral apposition rate all decreased as the calcium intake decreased. The osteoclast surface areas were greater than those of controls in both Ca-deficient groups, whereas the osteoblast surface areas were greater only in the VLCa group. The plasma osteoblast-related markers (alkaline phosphatase, carboxy-terminal propeptide of type I procollagen and osteocalcin) were either greater or unaffected in the Ca-deficient pigs. The results indicate that deficient bone mineralization combined with an increased bone resorption led to bone loss and fragility. The differences in the changes in bone cells (number and activity) between LCa and VLCa groups might be due to differences (time and extent) of circulating PTH and calcitriol. The defective mineralization in both Ca-depleted groups resulted mainly from the lack of Ca because their osteoblast activity was either maintained or stimulated. The results also underline the progressive sensitivity of pigs to Ca supply and the usefulness of this model.

Animals↗