Biomedical subjects

P Dubois

Publications and source records attributed to P Dubois.

At least 19 recordsLinked to original sources

PubMed2002

Computed tomography image analysis of the calcaneus in male osteoporosis.

The present study aimed to characterize bone microarchitecture assessed by computed tomography (CT) at the calcaneus in male subjects suffering from osteoporosis. Seventy-nine subjects were assessed (45 with osteoporosis and 34 control subjects matched for age). Osteoporosis was defined according to the World Health Organization classification either at the lumbar spine or at the femoral neck. Thirty-three subjects (73%) had a past history of low-energy fracture mainly represented by vertebral fractures (24/33). Nine axial sections (1 mm in width and 2 mm apart) were selected for each subject. Bone microarchitecture analysis was performed using structural (binary and skeletonized images but also skeletonization from gray levels) and fractal analyses. Bone densitometry by dual-energy X-ray absorptiometry (DXA) at the calcaneus was also performed in 73 cases. Bone mineral density (BMD) was decreased in osteoporotic patients compared with controls both at the lumbar spine and hip and also at the calcaneus (p<0.01). Also 14 microarchitectural features among 25 measured were significantly different between the two groups (p<0.01). The odds ratio for fracture per 1 control group standard deviation decrease were also significant for 13 structural features but also for BMD at the calcaneus. The odds ratios after adjustment for BMD at the calcaneus were significant for the following features (p<0.05): number of valleys, 2.8 (1.2-6.9); trabecular partition, 3.3 (1.3-7.9); apparent trabecular spacing, 1.8 (1.0-3.1); trabecular bone pattern factor, 2.2 (1.1-4.3); Euler number, 3.0 (1.1-8.7); node-to-terminus strut count, 3.3 (1.4-7.8); terminus-to-terminus strut count, 2.9 (1.2-6.9); and fractal dimension, 3.7 (1.5-9.7). Few and weak correlations were found between BMD at the calcaneus measured with DXA and features obtained from CT, suggesting that these two methods give different information about bone status. In conclusion, male osteoporosis is a disease characterized by decreased bone mass but also by microarchitectural deterioration of bone tissue which is partly independent of BMD.

Absorptiometry, Photon↗

PubMed2001

Regeneration of spines and pedicellariae in echinoderms: a review.

Morphogenesis of tissues during regeneration of echinoderm spines and pedicellariae is reviewed. Regeneration of the skeleton is rather well documented while that of associated soft tissues is poorly investigated. In particular, little information is available on the early regeneration stages which follow wound healing. From the available information, it is suggested that regeneration of broken spines proceeds through a morphallactic process of which the organizational information, as well as the involved cells, lies in the stump. In contrast, regeneration of removed spines and pedicellariae may depend on an epimorphic process whose organizational information could be located in the mutable connective tissue that joins the appendage to the main body wall.

Animals↗

PubMed2001

Proteins and saccharides of the sea urchin organic matrix of mineralization: characterization and localization in the spine skeleton.

Properties of the echinoderm skeleton are under biological control, which is exerted in part by the organic matrix embedded in the mineralized part of the skeleton. This organic matrix consists of proteins and glycoproteins whose carbohydrate component is specifically involved in the control mechanisms. The saccharide moiety of the organic matrix of the spines of the echinoid Paracentrotus lividus was characterized using enzyme-linked lectin assays (ELLAs). O-glycoproteins, different types of complex N-glycoproteins, and terminal sialic acids were detected. Sialic acids are known to interact with Ca ions and could play an important role in the mineralization process. Some of the carbohydrate components detected by ELLAs as well as two organic matrix proteins (SM30 and SM50) were localized within different subregions of the spine skeleton using field-emission scanning electron microscopy. The mappings show that some of these components are not homogeneously distributed in the different skeletal subregions. For example, some N-glycoproteins were preferentially located in the putative amorphous subregion of the skeleton, whereas some O-glycoproteins were localized in the subregion where skeletal growth is inhibited. These results suggest that the biological control exerted on the skeletal properties can be partly modulated by local differences in the organic matrix composition.

Animals↗

PubMed2001

Effects of PCBs on reactive oxygen species (ROS) production by the immune cells of Paracentrotus lividus (Echinodermata).

The impact of four PCB congeners: 3,3',4,4'-tetrachlorobiphenyl (IUPAC congener #77), 3,3',4,4',5-pentachlorobiphenyl (IUPAC #126), 2,2',4,4',5,5'-hexachlorobiphenyl (IUPAC #153) and 3,3',4,4',5,5'-hexachlorobiphenyl (IUPAC #169) was investigated on the reactive oxygen species (ROS) production by coelomocytes of the echinoid Paracentrotus lividus, an important species in marine benthic ecosystems. PCBs were found to increase ROS production and to delay the time of peak production. These effects were stronger on bacteria-stimulated cells and were congener-specific: coplanar congeners (#77, 126 and 169) had more effect than the non-coplanar PCB #153. Among coplanar congeners, PCB #169 showed dose-dependent effects whereas PCB #77 and 126 were more toxic at high and low doses, respectively. The relative immunotoxicity of the different PCB congeners is discussed in the light of their structural properties and biological affinities.

Animals↗

PubMed2001

Mechanisms and kinetics of thermal degradation of poly(epsilon-caprolactone).

Thermogravimetric analysis (TGA) simultaneously coupled with mass spectrometry (MS) and Fourier transform infrared spectrometry (FTIR) was developed as an original technique to study the thermal modification/degradation of poly(epsilon-caprolactone) (PCL) through in depth analysis of the evolved gas. Perfectly well-defined PCL samples with controlled end groups, predictable molecular weight, and narrow molecular weight distribution were synthesized by living "coordination-insertion" ring-opening polymerization of epsilon-caprolactone initiated by aluminum triisopropoxide. TGA analyses carried out on purified PCL samples, deprived from any residual catalyst or monomer, highlighted a two-step thermal degradation. Evolved gas analysis by both MS and FTIR showed that the first process implies a statistical rupture of the polyester chains via ester pyrolysis reaction. The produced gases were identified as H(2)O, CO(2), and 5-hexenoic acid. The second step leads to the formation of epsilon-caprolactone (cyclic monomer) as result of an unzipping depolymerization process. The influence of parameters such as polyester molecular weight, nature of the PCL end groups, and presence of catalytic residues as well as the type of purge gas were investigated. The activation energy of the thermal degradation was also studied.

Chromatography, Gel↗

PubMed2001

Cold-adapted beta-galactosidase from the Antarctic psychrophile Pseudoalteromonas haloplanktis.

The beta-galactosidase from the Antarctic gram-negative bacterium Pseudoalteromonas haloplanktis TAE 79 was purified to homogeneity. The nucleotide sequence and the NH(2)-terminal amino acid sequence of the purified enzyme indicate that the beta-galactosidase subunit is composed of 1,038 amino acids with a calculated M(r) of 118,068. This beta-galactosidase shares structural properties with Escherichia coli beta-galactosidase (comparable subunit mass, 51% amino sequence identity, conservation of amino acid residues involved in catalysis, similar optimal pH value, and requirement for divalent metal ions) but is characterized by a higher catalytic efficiency on synthetic and natural substrates and by a shift of apparent optimum activity toward low temperatures and lower thermal stability. The enzyme also differs by a higher pI (7.8) and by specific thermodynamic activation parameters. P. haloplanktis beta-galactosidase was expressed in E. coli, and the recombinant enzyme displays properties identical to those of the wild-type enzyme. Heat-induced unfolding monitored by intrinsic fluorescence spectroscopy showed lower melting point values for both P. haloplanktis wild-type and recombinant beta-galactosidase compared to the mesophilic enzyme. Assays of lactose hydrolysis in milk demonstrate that P. haloplanktis beta-galactosidase can outperform the current commercial beta-galactosidase from Kluyveromyces marxianus var. lactis, suggesting that the cold-adapted beta-galactosidase could be used to hydrolyze lactose in dairy products processed in refrigerated plants.

Adaptation, Physiological↗

PubMed2001

[Right ventricular migration of a stent after endovascular treatment of a superior vena cava syndrome].

The authors report a case of migration of a Palmaz stent used for treatment of a patient with a malignant superior vena caval syndrome. Transoesophageal echocardiography showed the metallic device in the tricuspid subvalvular apparatus. Several attempts to recover the stent percutaneously failed. This case illustrates a rare but serious complication of endovascular stenting: migration of the material. Although it is often possible to reposition the stent by radiological interventional techniques, when the stent is located in the right ventricle, the procedure is more difficult and usually fails. Transoesophageal echocardiography enables accurate localisation of the material with respect to the surrounding cardiac structures, especially the tricuspid valve.

Adult↗

PubMed2000

Ultrastructure of sea urchin calcified tissues after high-pressure freezing and freeze substitution.

The improvements brought by high-pressure freezing/freeze substitution fixation methods to the ultrastructural preservation of echinoderm mineralized tissues are investigated in developing pedicellariae and teeth of the echinoid Paracentrotus lividus. Three freeze substitution (FS) protocols were tested: one in the presence of osmium tetroxide, one in the presence of uranyl acetate, and the last in the presence of gallic acid. FS in the presence of osmium tetroxide significantly improved cell ultrastructure preservation and should especially be used for ultrastructural studies involving vesicles and the Golgi apparatus. With all protocols, multivesicular bodies, suggested to contain Ca(2+), were evident for the first time in skeleton-forming cells. FS in the presence of gallic acid allowed us to confirm the structured and insoluble character of a part of the organic matrix of mineralization in the calcification sites of the tooth, an observation which modifies the current understanding of biomineralization control in echinoderms.

Animals↗

PubMed2000

Mimicking a conformational B cell epitope of the heat shock protein PfHsp70-1 antigen of Plasmodium falciparum using a multiple antigenic peptide.

The Pf72/Hsp70-1 antigen is a major target in the naturally acquired immunity against Plasmodium falciparum malaria. We carried out an extensive analysis of the responses to several epitopes on the least conserved C-terminal domain, according to the mode of sensitization: malaria infection or immunization with different immunogens. We found significant differences in the panel of B-cell epitopes recognized by animal models including primates, and by humans sensitized by natural infection. We focused the analysis on one epitope that is unique to Plasmodium species. It is specifically recognized by a monoclonal antibody that mediates the killing of infected hepatocytes in vitro. We produced a polymeric multiple antigenic peptide (MAP) form of this sequence, which enabled us to identify a new B-cell epitope not detected by ELISA with linear peptides. The polymer was strongly recognized by sera from monkeys or humans sensitized by natural infection, whereas the monomer was not. We modelled the three-dimensional structure of the Pf72/Hsp70-1 sequence, using known Escherischia coli DnaK structures as a template. This predicted that the corresponding region would form a loop in the native antigen. The results presented here suggest that the MAP strategy is also particularly useful as a means of obtaining suitable synthetic models for conformation-dependent epitopes.

Amino Acid Sequence↗

PubMed2000

In vivo comparison between computed tomography and magnetic resonance image analysis of the distal radius in the assessment of osteoporosis.

In a prospective case-control cross-sectional study, we investigated the usefulness of both computed tomography (CT) and magnetic resonance (MR) image analysis of the distal radius for distinguishing a small sample of fractured osteoporotic women from control women regardless of bone mineral density. The study population included 12 subjects who were divided into two groups according to their bone status. The first group consisted of six women with at least one vertebral fracture occurring in the absence of high-energy trauma, and the second group consisted of six women without disease affecting bone mass or bone metabolism. Cross-sectional and coronal slices were obtained from both CT and MR systems. For CT images, the slice thickness was 1000 jim and the plane resolution was approx 200 jim x 200 jim. MR images were obtained from a 1.5-T imager with a two-dimensional spin-echo Ti-weighted sequence leading to a slice thickness of 2000 jim and a plane resolution of 195 jim x 195 jim. Bone texture analysis was performed using fractal and structural methods leading to the measurement of 23 features. Most of the structural variables derived from histomorphometric parameters and were measured after segmentation from a binary or a skeletonized image. Bone densitometry was measured by dual-energy X-ray absorptiometry both at the lumbar spine and the nondominant femoral neck. On cross-sectional slices, 12 variables, mainly obtained from structural analysis, were significantly different between the two groups for CT images (p < 0.05) against two variables only for MR images (p < 0.05). The number of variables statistically different between the two groups was significantly higher for CT images compared with MR images (p = 0.003). In the same way, odds ratios for fracture per 1 control group standard deviation decrease were significant for 10 variables on CT images, whereas, in contrast, none of the variables measured on MRI images led to significant odds ratios. The results obtained for the two methods on coronal slices were poorer without a difference between either CT or MR images in terms of discrimination between fracture and nonfracture subjects. In conclusion, this study suggests that bone texture analysis obtained from CT compared with MRI offers a best discrimination between controls and osteoporotic patients, probably the result to the spatial resolution. which is better for CT than for MR images.

Absorptiometry, Photon↗

PubMed2000

Does high-resolution computed tomography image analysis of the distal radius provide information independent of bone mass?

This study aimed to investigate the usefulness of computed tomography (CT) image analysis of the distal radius for comparing two groups of postmenopausal women matched for age and bone mineral density at both the lumbar spine and femoral neck. The first one consisted of 16 women with at least one vertebral fracture and the second consisted also of 16 women without disease affecting bone mass or bone metabolism. Eight slices were selected in each patient: four consecutive coronal slices and four consecutive axial slices. Bone texture analysis was performed using structural methods leading to the measurement of 24 features. Most of the structural variables derived from histomorphometric parameters and were measured after segmentation from a binary or a skeletonized image. Nine variables were significantly different between the two groups on axial slices: valley number, valley surface area, apparent bone volume/tissue volume (BV/TV), apparent trabecular separation, apparent trabecular number, trabecular bone pattern factor, trabecular skeletal length, node count, and node-to-node strut count. Also four variables were significantly different between osteoporotic women and controls on coronal slices: apparent BV/TV, trabecular partition, node-to-node strut count, and terminus-to-terminus strut count. In conclusion this study suggests that bone texture analysis could yield additional data on bone mass for explaining bone strength and therefore could be used for improving the prediction of fracture risk.

Absorptiometry, Photon↗

PubMed1999

Cellular and antibody responses to the Plasmodium falciparum heat shock protein Pf72/HSP70 during and after acute malaria in individuals from an endemic area of Brazil.

Proliferative and antibody responses to three synthetic peptides corresponding to Pf72/ HSP70 were followed-up in acute malaria patients from an endemic area of Brazil. In vitro lymphocyte responsiveness to all peptides was relatively low and short-lived and there was a considerable variation in the frequency and magnitude of the individual lymphoproliferative response to the peptides at different periods after the onset of infection. Although 96% of the patients had IgG antibodies to crude Plasmodium falciparum asexual blood stage antigens, specific IgG antibody responses to the peptides varied from 12.5 to 40% according to the tested peptides. No significant difference was observed in the proliferative or antibody responses to the peptides between individuals that remained parasitemic after treatment and those that recovered from malaria infection. The different frequencies of proliferative responses in peripheral blood T cells on different occasions after the onset of their infection show that, in order to be informative, evaluation of the in vitro cellular immune response to peptides requires longitudinal studies in which each individual is tested repeatedly.

Acute Disease↗

PubMed1999

Image analysis of the distal radius trabecular network using computed tomography.

Bone texture analysis might provide information about bone structure in a noninvasive manner. In a prospective case-control cross-sectional study we investigated the value of computed tomography (CT) image analysis of the distal radius in the assessment of osteoporosis. Twenty patients suffering from postmenopausal osteoporosis were studied and compared with 21 age-matched controls. Eight slices were selected in each patient: four consecutive coronal slices and four consecutive cross-sectional slices. Bone texture analysis was performed using statistical, fractal and structural methods leading to the measurement of 32 features. Structural variables derived from histomorphometric parameters were measured after segmentation from a binary or a skeletonized image. Bone mineral density was measured by dual-energy X-ray absorptiometry both at the lumbar spine and the femoral neck. Eight of the 9 statistical features were significantly different in osteoporotic women as compared with controls (coronal slices, p < 0. 05). Seven structural variables were statistically different between the two groups on coronal slices (p < 0.05): valley surface area, bone volume/tissue volume, trabecular partition, Euler's number, trabecular bone pattern factor, node-to-node strut count and terminus-to-terminus strut count. The most significant results on coronal slices (p < 0.01) concerned 4 structural features: trabecular partition, Euler's number, trabecular bone pattern factor and terminus-to-terminus strut count. Three features were statistically different (p < 0.01) between the two groups on cross-sectional slices (skeletonization from gray levels). A few features yielded by texture analysis were correlated with both lumbar spine and femoral neck bone mineral density, but the level of these correlations was weak (r < 0.5). In conclusion, CT image analysis of the distal radius is a useful tool for characterizing bone texture alterations in osteoporotic women. These findings are in keeping with microarchitectural osteoporosis-related changes diagnosed on bone biopsies.

Aged↗

PubMed1999

Direct qualitative and quantitative characterization of a radiosensitizer, 5-iodo-2'-deoxyuridine within biodegradable polymeric microspheres by FT-Raman spectroscopy.

Non-destructive qualitative and quantitative characterization of a radiosensitizer, 5-iodo-2'-deoxyuridine (IdUrd), incorporated within injectable microspheres of a biodegradable polymer, poly(D,L-lactide-co-glycolide) (PLGA), was performed using Fourier transform (FT) Raman spectroscopy. Raman spectra of IdUrd, free and entrapped in microspheres, were recorded under fluorescence-free conditions, described and assigned. For the Raman bands of the PLGA microspheres, assignments with preferential localization of the corresponding vibrations at lactic or glycolic units were proposed. No evidence for drug-polymer interactions in microspheres was found. This allowed the FT-Raman spectra to be used for the quantification of the IdUrd content in the samples. For the microspheres with IdUrd loadings varying from 2 to 27% of the total weight, the methodology used provided good reproducibility and precision (1%). Within the sensitivity of the technique, samples exposed to sterilization doses (27 kGy) of gamma-radiation did not exhibit marked changes in the drug structure.

Humans↗

PubMed1999

Ultrastructural localization of proteins involved in sea urchin biomineralization.

Three skeletal tissues of the adult echinoid Paracentrotus lividus (the pedicellaria primordium, the test, and the tooth) were immunolabeled with three sera raised against the total mineralization organic matrix and two specific matrix proteins (SM30 and SM50) from the embryo of the echinoid Strongylocentrotus purpuratus. Two conventional chemical fixation protocols and two high-pressure freezing/freeze-substitution protocols were tested. One conventional protocol is recommended for its good preservation of the ultrastructure, and one high-pressure freezing/freeze-substitution protocol is recommended for its good retention of antigenicity. Immunolabeling was obtained in the three adult tissues. It was confined to the active skeleton-forming cells and to the structured organic matrix. The results indicate that the matrix proteins follow the classical routes of secretory protein assembly and export and suggest that SM30 and SM50 are a part of the tridimensional network formed by the organic matrix before the onset of mineralization. They show that the genetic program of part of skeletogenesis is conserved among different calcification models and developmental stages.

Animals↗

PubMed1999

Particle counting immunoassay for urinary cotinine. Comparison with chromatography, enzyme-linked immunoassay and fluorescence polarization immunoassay.

Urinary cotinine was measured according to its inhibitory activity on the agglutination of cotinine-coated latex particles by anti-cotinine antibodies, the agglutination being measured by optical counting of the remaining non-agglutinated particles (particle counting, PaC). The detection limit was 0.03 microgram/ml and the practical range extended from 0.03 to 3.9 micrograms/ml. The correlation results of 320 urine samples with those of high pressure liquid chromatography, enzyme-linked (Coti-Tracq EIA, Serex Inc., Maywood, NJ, USA), and fluorescence polarization immunoassay (TDX instrument, Abbott, Abbott Park, IL, USA) were r = 0.90, r = 0.69, r = 0.87, respectively, whereas the correlation coefficients between the assays other than particle counting ranged from 0.62 to 0.88. PaC does not require any separation step and can thus be easily automated.

Chromatography, High Pressure Liquid↗

PubMed1999

Serial measurement of calcaneal pitch during midstance.

Although emerging evidence suggests a causal relationship between arch structure and musculoskeletal injury, few investigations have adequately assessed arch function during gait. In this study, digitized videofluoroscopy was used to evaluate the sagittal plane motion of the calcaneus during gait. Nine female subjects requiring diagnostic foot radiographs underwent videofluoroscopy. The calcaneal inclination angle, arch height ratio, and tarsal index were digitally analyzed for all radiographic images. Calcaneal pitch was correlated to both the arch height ratio and the tarsal index. Repeated measures analysis of variance helped to identify a significant reduction in the mean calcaneal pitch during the midstance and early propulsive periods of gait. These findings suggest that although calcaneal pitch may be used as an indicator of rearfoot position, biomechanical classification of foot types based on radiographs may result in erroneous conclusions concerning foot function.

Adult↗

PubMed1999

[Intermittent claudication in a young patient. A case of isolated fibromuscular dysplasia of the external iliac artery].

Effort-linked intermittent claudication of arterial origin in sportsmen is often attributed to endofibrosis of the external iliac artery. Some knowledge of possible differential diagnoses, in particular the fibrodysplasia, is of importance regarding the therapy involved. Angioplasty treatment of external iliac endofibrosis may be controversial. However, the same does not apply to fibrodysplasia angioplasty, particularly if the latter is accomplished by inserting an endoprothesis. A case of fibromuscular dysplasia of external iliac artery in a 37 year old woman, treated with endoluminal angioplasty and stent, is reported.

Adult↗