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Biomedical subjects

M Lacroix

Publications and source records attributed to M Lacroix.

At least 37 records · Page 2Linked to original sources
PubMed2002

Personalized biomechanical modeling of Boston brace treatment in idiopathic scoliosis.

The aim of this study was to describe how the Boston brace modify the scoliotic curvatures using a finite element (FE) model and experimental measurements. The experimental protocol, applied on 12 scoliotic girls, was composed of the pressure measurement at the brace-torso interface followed by two radiographic acquisitions of the patient's torso with and without brace. A 3D FE model of the trunk was built for each unbraced patient. The brace treatment was represented by two different modeling approaches: 1) using equivalent forces calculated from the measured pressures; 2) by an explicit personalized FE model of the brace (hexahedral elements) and its interface with the torso (contact elements). In the first model, measured brace forces less than 40N and up to 113N induced respectively less than 21% and up to 87% of real correction. Thoracic forces induced the main correction, affecting partially both lumbar and thoracic curves, in agreement with the literature. In the second model, the brace closing reduced the curves up to 35% of real correction. Contact reaction forces (16-79N) were similar to real brace forces (11-72N). The results suggested that other mechanisms than brace pads contribute to the equilibrium of the patients. Postural control by the muscular system remains a problem to address in a future study. The second model represented more realistically the load transfer from the brace to the spine than external forces application. With such model, it is expected to predict the effect of a brace before its design and manufacturing, and also to improve its design.

Adolescent↗
PubMed2001

Gamma-ray crosslinking of poly(3-hydroxyoctanoate-co-undecenoate).

The gamma-ray crosslinking of films made of poly(3-hydroxyoctanoate) containing undecenoate moieties (up to 33 mole%) were studied. X-ray diffraction, thermal analysis, dynamic mechanical analysis (DMA), solid state nuclear magnetic resonance (NMR) spectroscopy and degree of crosslinking (swelling analysis) as a function of irradiation dose were evaluated for treatments in air or in N(2) atmosphere. After uncrosslinked material was isolated by CHCl(3) extraction, solid state NMR data suggested that only a small percentage of the double bonds took part in the formation of irradiation crosslinks. Crosslinking in N(2) was more efficient than in air and a 20 kGy dose was sufficient for optimal crosslinking. The X-ray diffraction patterns of the polymer films were unaffected by moderate irradiation. The use of sodium hypochlorite to isolate poly(3-hydroxyoctanoate-co-undecenoate) samples resulted in partial chlorination of the double bonds and considerable depolymerization.

Biocompatible Materials↗
PubMed2001

Combined effect of antimicrobial coating and gamma irradiation on shelf life extension of pre-cooked shrimp (Penaeus spp.).

The present study was conducted to evaluate the combined effect of low-dose gamma irradiation and antimicrobial coating on the shelf life of pre-cooked shrimp (Penaeus spp.). Antimicrobial coatings were obtained by incorporating various concentrations of thyme oil and trans-cinnamaldehyde in coating formulations prepared from soy or whey protein isolates. Coated shrimps were stored at 4 +/- 1 degrees C under aerobic conditions and were periodically evaluated for aerobic plate counts (APCs) and Pseudomonas putida. Sensory evaluations were performed for appearance, odor, and taste using a hedonic test. Results showed that gamma irradiation and coating treatments had synergistic effects (p < or = 0.05) in reducing the APCs and P. putida with at least a 12-day extension of shelf life. Without irradiation, the inhibitory effects of the coating solutions were closely related to the concentration of thyme oil and trans-cinnamaldehyde. No detrimental effects of gamma irradiation on organoleptic parameters (appearance, odor, and taste) were observed. However, incorporation of thyme oil and trans-cinnamaldehyde reduced the acceptability scores for taste and odor.

Animals↗
PubMed2001

Interleukins-6 and -11 expression in primary breast cancer and subsequent development of bone metastases.

Breast cancers frequently metastasize to bone where they often cause extensive tumor-induced osteoclast-mediated osteolysis. Interleukin-6 (IL-6) and IL-11 are two cytokines exhibiting osteolytic properties through their potent stimulation of osteoclast formation. We investigated the expression of IL-6 and IL-11 in 99 invasive primary breast tumors by immunohistochemistry and in situ hybridization, respectively. We examined their potential as predictive factors for further development of bone metastases. 52/90 (57%) of tumor samples showed IL-6 cytoplasmic immunostaining. There was no significant association between IL-6 status and any of the classical prognostic factors. 15/89 (17%) of the tumor samples expressed IL-11 mRNA. A positive IL-11 mRNA status was associated with a low tumor grade (P=0.05). Tumors expressing IL-11 mRNA had a statistically significant (P=0.002) higher rate of bone metastases occurrence (12/15, 80%) than IL-11 negative tumors (27/74, 37%). Such association was not found for IL-6. Our findings demonstrate for the first time IL-11 gene expression in some primary invasive breast tumors and suggest the potential of this cytokine as possible biological predictive factor for the development of bone metastases.

Adult↗
PubMed2001

Assembly and enzymatic properties of the catalytic domain of human complement protease C1r.

The catalytic properties of C1r, the protease that mediates activation of the C1 complex of complement, are mediated by its C-terminal region, comprising two complement control protein (CCP) modules followed by a serine protease (SP) domain. Baculovirus-mediated expression was used to produce fragments containing the SP domain and either 2 CCP modules (CCP1/2-SP) or only the second CCP module (CCP2-SP). In each case, the wild-type species and two mutants stabilized in the proenzyme form by mutations at the cleavage site (R446Q) or at the active site serine residue (S637A), were produced. Both wild-type fragments were recovered as two-chain, activated proteases, whereas all mutants retained a single-chain, proenzyme structure, providing the first experimental evidence that C1r activation is an autolytic process. As shown by sedimentation velocity analysis, all CCP1/2-SP fragments were dimers (5.5-5.6 S), and all CCP2-SP fragments were monomers (3.2-3.4 S). Thus, CCP1 is essential to the assembly of the dimer, but formation of a stable dimer is not a prerequisite for self-activation. Activation of the R446Q mutants could be achieved by extrinsic cleavage by thermolysin, which cleaved the CCP2-SP species more efficiently than the CCP1/2-SP species and yielded enzymes with C1s-cleaving activities similar to their active wild-type counterparts. C1r and its activated fragments all cleaved C1s, with relative efficiencies in the order C1r < CCP1/2-SP < CCP2-SP, indicating that CCP1 is not involved in C1s recognition.

Binding Sites↗
PubMed2001

[Isolated pancreatic neck rupture].

AIM OF THE STUDY: Through four cases of pancreatic neck rupture, the study aim was to emphasize the advantages of an early laparotomy when there is a doubt about a canal disruption and the risks of a later surgical management. PATIENTS AND RESULTS: Four patients were operated on for a neck disruption of the pancreas due to blunt trauma. Two patients underwent laparotomy in the first 48 hours after a radiological exploration and underwent a left pancreatectomy with spleen preservation. There were no associated injuries, no lesions of acute pancreatitis. The two other patients were, at first, medically treated and developed an acute pancreatitis with pseudocyst. They underwent laparotomy, 7 and 10 days after the trauma because of pain and hyperthermia, and a conservative treatment by cystojejunostomy was performed in difficult conditions because of the acute pancreatitis. A late pancreatic pseudocyst (4 and 6 months) occurred in two patients. CONCLUSION: When pancreatic trauma occurs, an exploration with echography, scanner, endoscopic retrograde cholangiopancreatography or magnetic resonance cholangiopancreatography can suggest a neck disruption and a canal rupture. When the canal is safe, a drainage close to the pancreas is sufficient. When the rupture of the canal is suspected or proved, an early laparotomy is necessary in order to investigate the pancreas and to perform the appropriate procedure. This surgery is easier before the occurrence of pseudocyst and acute pancreatitis.

Adolescent↗
PubMed2001

Combined effect of ascorbic acid and gamma irradiation on microbial and sensorial characteristics of beef patties during refrigerated storage.

The present study was undertaken to evaluate the effect of ascorbic acid concentrations (0.03 to 0.5%) and irradiation doses (0.5 to 4 kGy) on microbial growth, color coordinates (L, a, and b), and sensory characteristics (taste and odor) of beef patties during storage at 4 +/- 1 degrees C. Ascorbic acid was also compared to citric acid at a similar pH value in order to differentiate the effects of ascorbic acid from those of pH reduction. Results showed significant reduction (p< or = 0.05) of aerobic plate counts (APCs) and total coliforms, and a significant interaction (p< or = 0.05) between ascorbic acid and irradiation dose was observed. The irradiation treatment had detrimental effects on redness, yellowness, and hue angle values of meat. However, incorporation of ascorbic acid into the meat before irradiation resulted in significant (p< or = 0.05) stabilization of color parameters. The color improvement obtained with ascorbic acid was not related to the pH reduction. Also, no significant detrimental effect on taste or odor was found in irradiated samples containing ascorbic acid.

Animals↗
PubMed2001

Mechanical and barrier properties of cross-linked soy and whey protein based films.

Sterilized biofilms based on soy protein isolate (SPI, S system) and a 1:1 mixture of SPI and whey protein isolate (WPI, SW system) were achieved through the formation of cross-links by means of gamma-irradiation combined with thermal treatments. The effect of the incorporation of carboxymethylcellulose (CMC) and poly(vinyl alcohol) was also examined. gamma-Irradiation combined with thermal treatment improved significantly the mechanical properties, namely, puncture strength and puncture deformation, for all types of films. Irradiated formulations that contain CMC behave more similarly as elastomers. CMC showed also significant improvements of the barrier properties, namely, water vapor permeability, for irradiated films of the S system and for non-irradiated films of the SW system.

Carboxymethylcellulose Sodium↗
PubMed2001

Estrogen receptor analysis in primary breast tumors by ligand-binding assay, immunocytochemical assay, and northern blot: a comparison.

Estrogen receptor (ER) status is an important parameter in breast cancer management. In this study, ER protein contents established by two conventional techniques were confronted to ER mRNA level, to analyze whether the latter may be introduced in routine assay. Eighty-seven breast tumor samples were examined. ER amounts were determined by ligand-binding assay (LBA) and by computer-assisted immunocytochemical assay (ICA), ER mRNA was analysed and quantified by northern blot. Seventy-seven percent of tumor samples examined were positive for ER mRNA and they all expressed the 6.7-kb receptor signal. No trace of small-sized ER mRNA variants was detected in any sample. Following akaike information criterion (AIC) discriminant analysis, a simple linear correlation was found between ER mRNA levels and ER amounts provided by LBA. This was not observed when either mRNA or LBA values were compared to ICA values. These latter were found to rapidly reach a plateau at increasing mRNA or LBA values. In conclusion, our data points to the linear correlation between ER amounts determined in breast tumors at both protein and mRNA levels by quantitative methods; they also indicate that the semi-quantitative computer-associated ICA may complement rather than replace these quantitative methods.

Adult↗
PubMed2001

Regulation of acute cortisol synthesis by cAMP-dependent protein kinase and protein kinase C in a teleost species, the rainbow trout (Oncorhynchus mykiss).

The effects of cAMP-dependent protein kinase (PKA) and protein kinase C (PKC) on acute ACTH-stimulated cortisol secretion were assessed using a specific PKA inhibitor (H-89) and a PKC activator (phorbol 12-myristate 13-acetate, PMA) in dispersed head kidney cells of rainbow trout (Oncorhynchus mykiss). To investigate the sites of action of both PKA and PKC, pregnenolone (a cortisol precursor stemmed from the rate limiting step in cortisol synthesis) and 25-OH-cholesterol (an exogenous substrate that bypasses the rate limiting step) were used as substrates, with and without ACTH stimulation. Inhibition of PKA decreased ACTH-stimulated cortisol secretion while activation of PKC had the same effect, demonstrating that PKA stimulates and PKC inhibits cortisol synthesis. Inhibition of PKA and activation of PKC had no significant effect on pregnenolone-stimulated cortisol synthesis, indicating that both PKA and PKC act upstream from the pregnenolone step. Inhibition of PKA and activation of PKC had no significant effect on basal cortisol secretion in the presence of 25-OH-cholesterol, suggesting that PKA and PKC exert their effects on the mitochondrial cholesterol translocation step. This study provided evidence for the stimulatory role of PKA and the inhibitory role of PKC in the signalling pathways leading to cortisol synthesis in teleosts.

Adrenocorticotropic Hormone↗
PubMed2001

A multivariate analysis of 416 patients with glioblastoma multiforme: prognosis, extent of resection, and survival.

OBJECT: The extent of tumor resection that should be undertaken in patients with glioblastoma multiforme (GBM) remains controversial. The purpose of this study was to identify significant independent predictors of survival in these patients and to determine whether the extent of resection was associated with increased survival time. METHODS: The authors retrospectively analyzed 416 consecutive patients with histologically proven GBM who underwent tumor resection at the authors' institution between June 1993 and June 1999. Volumetric data and other tumor characteristics identified on magnetic resonance (MR) imaging were collected prospectively. CONCLUSIONS: Five independent predictors of survival were identified: age, Karnofsky Performance Scale (KPS) score, extent of resection, and the degree of necrosis and enhancement on preoperative MR imaging studies. A significant survival advantage was associated with resection of 98% or more of the tumor volume (median survival 13 months, 95% confidence interval [CI] 11.4-14.6 months), compared with 8.8 months (95% CI 7.4-10.2 months; p < 0.0001) for resections of less than 98%. Using an outcome scale ranging from 0 to 5 based on age, KPS score, and tumor necrosis on MR imaging, we observed significantly longer survival in patients with lower scores (1-3) who underwent aggressive resections, and a trend toward slightly longer survival was found in patients with higher scores (4-5). Gross-total tumor resection is associated with longer survival in patients with GBM, especially when other predictive variables are favorable.

Adult↗
PubMed2000

Estrogen receptor of primary breast cancers: evidence for intracellular proteolysis.

Iodinated oestradiol-labeled oestrogen receptor (ER) isoforms devoid of amino-terminal ABC domains represent about two-thirds of the whole receptor population detected in cytosol samples from human breast cancers. This high frequency could not be ascribed to the expression of truncated mRNAs, or to the proteolysis of the native ER peptide at the time of homogenization or assay, suggesting an intracellular proteolysis. Free amino-terminal and ligand-binding domains maintained together within oligomeric structure(s); increase of ionic strength separated them. The amino-terminal region was consistently detected in the cell nucleus by specific immunohistochemistry leading to the concept of a potential intranuclear association between ER cleavage products and/or other regulatory proteins.

Adsorption↗
PubMed2000

[Occurrence of Enterobius vermicularis in children hospitalized at a central hospital].

The aim of the study was to determine the prevalence of EV among hospitalized children and to estimate if abdominal pain is related to EV-infestation. A perianal tape-test for identification of eggs of EV was done on 186 children, aged 1-17, hospitalized in the period 8.3.1996 to 31.12.1997. The children were separated into two groups: 123 children with abdominal pain, and 63 children with symptoms thought not to be related to EV (trauma, testicular retention and hernia). Clinical data were collected from case records. Altogether 40 children (22%) were infested with EV. Among 111 children aged 5-12 the prevalence was 32 (29%). No association was found between abdominal pain and infestation with EV. In conclusion, EV is a common disease among hospitalized children. According to this study there is no indication for routine perianal tape-test of children hospitalized for abdominal pain.

Abdominal Pain↗
PubMed2000

Young children with Velo-Cardio-Facial syndrome (CATCH-22). Psychological and language phenotypes.

This is the first clinical description of a detailed psychological, speech, and language phenotype of four young children (< 5 years) with Velo-Cardio-Facial syndrome (VCFS) due to a deletion on chromosome 22 (22q11.2). The reported elevated risk of developing schizophrenia or bipolar disorder in adolescence for individuals with this chromosomal deletion led us to examine the psychiatric and cognitive status of young children with VCFS. Our observations suggest a phenotype comprised of a borderline to mildly retarded level of intellectual functioning, a language delay, a general deficit in social initiation, difficulties with attention/concentration, and a perturbed train of thought.

Child, Preschool↗
PubMed2000

Development of biodegradable films from whey proteins by cross-linking and entrapment in cellulose.

When cross-linked by heating or by gamma-irradiation and entrapped in cellulose, whey proteins can generate insoluble biofilms with good mechanical properties and high resistance to attack by proteolytic enzymes. Interchain cross-linking of proteins generated an increase in the puncture strength, and a decrease in water vapor permeability. Gelatin was added in film formulation as a stabilizer to improve the puncture strength and film appearance. The structure of the biofilms was also analyzed. SDS-PAGE revealed that heating and gamma-irradiation produce an increase of the molecular weight of the cross-linked protein. Size exclusion chromatography showed a molecular mass of 40 kDa for un-cross-linked whey proteins, whereas for the soluble fractions of the cross-linked proteins, molecular distributions were between 600 and 3800 kDa for the heated proteins and between 1000 and 2000 kDa for gamma-irradiated proteins. No major alteration of the structural conformation of the proteins was observed by FTIR for biofilms obtained after heat treatment, whereas gamma-irradiation induced some modifications in the protein structure. X-ray diffraction analysis suggests that cross-linking by gamma-irradiation seems to modify the conformation of proteins, which became more ordered and more stable.

Biodegradation, Environmental↗
PubMed2000

Effect of gamma-irradiation on phenylalanine ammonia-lyase activity, total phenolic content, and respiration of mushrooms (Agaricus bisporus).

Ionizing treatments were applied at 0.5 kGy, 1.5 kGy, and 2.5 kGy to edible mature mushrooms (Agaricus bisporus, albidus) in order to assess the effect of the gamma-irradiation on some biochemical parameters. Irradiation at doses of 1.5 kGy and 2.5 kGy reduced significantly (p < or = 0.05) the rate of respiration of the mushrooms, compared to that of samples irradiated at 0.5 kGy and nonirradiated control samples (C). Ionizing treatments increased significantly (p < or = 0.05) the phenylalanine ammonia-lyase (PAL) activity and total phenols concentration between days 1 and 4. From days 3-4, to the end of the storage period (day 12), both PAL activity and total phenols in the irradiated samples (I) collapsed to lower values. In contrast, the activity of polyphenol oxidase (PPO) increased until days 7, 9, and 12 for samples treated at 0.5, 1, and 2 kGy, respectively. Color measurements showed a loss of whiteness (L value) during storage. After day 4, however, the effectiveness of gamma-irradiation became apparent, and highest L values were obtained for I only.

Agaricus↗