PubMed Health⌕ Search

Biomedical subjects

M Lafontaine

Publications and source records attributed to M Lafontaine.

At least 19 recordsLinked to original sources
PubMed2000

Inhalation study on exposure to bitumen fumes. Part 1: Development and validation of the equipment.

Bitumen fumes emitted during road paving or roofing contain polycyclic aromatic hydrocarbons (PAHs). Experimental studies have been previously performed to test the carcinogenic potency of bitumen fumes. Some of them have been criticised either on the grounds that the fume condensates were not representative of fumes to which humans are exposed or because the fumes were never characterised in terms of particle size and poorly in terms of composition and concentration in the chambers. For a nose-only inhalation study, we have evaluated the ability of a new fume generation system to deliver stable and reproducible atmospheres of bitumen fumes to an inhalation chamber and investigated the representativity of the fumes generated at a concentration level of 5 mg/m3. The fume generator comprises: (1) an insulated 20 l heated kettle (200 degrees C for bitumen); (2) an insulated inlet pipe with a needle valve to adjust the flow of the test compound from the kettle; (3) a fume generation chamber equipped with a series of interchangeable channels of different width. The fume concentration in the exposure chamber can be controlled by changing the channel width or by restricting the evaporation surface with aluminium foil, and/or by changing the flow rate. Samples of the atmosphere in the chamber were collected and analysed for quantitative determination of total particulate matter (TPM), soluble matter, benzo[a]pyrene (B[a]P) content of the fumes and other PAHs, and evaluation of the particle size distribution. The representativeness of the fumes has been tested by comparison with fumes generated in the Shell small-scale fume rig, which was previously validated against field fumes collected during paving operations. Evaporative losses from the filters during sampling, transport and storage have been also assessed. At 5 mg/m3 TPM, the agreement between laboratories was quite good for the TPM analyses and was good for the soluble matter and B[a]P. Evaporative losses may lead to underestimation of the true exposure level in the inhalation chambers but the use of an XAD-2 cartridge backup is one approach to partially recover losses which occur on the filter. The particle size distributions are somewhat different from those reported for fumes associated with roofing and indoor mastic laying works, in that we found more than 85% of particles to be smaller than 1 micron, compared with 40% particles in the previous analyses. In conclusion, this equipment allows reproducible generation of fumes at the 5 mg/m3 TPM that are fairly representative of those produced in the field with the same bitumen.

Equipment Design↗
PubMed2000

Inhalation study on exposure to bitumen fumes. Part 2: Analytical results at two exposure levels.

During the hot application of bitumen-containing materials, e.g. in road paving or roofing, fumes are emitted that contain traces of polycyclic aromatic compounds (PACs). Although worker's exposure to these fumes is low, it might lead to health problems. For studying DNA adduct formation as a consequence of inhalation of bitumen fumes we developed and validated an inhalation system (a dynamic fume generator plus a nose only inhalation chamber). This paper presents and discusses the analytical results from the different laboratories involved in this study on the fumes sampled in the inhalation chamber during three series of experiments where the animals were exposed to fumes at the 5 mg/m3 and 50 mg/m3 level, coming from bitumen heated at 200 degrees C and, as a positive control, fumes from coal tar, heated to 110 degrees C at the 5 mg/m3 level. The following parameters were controlled: temperatures at different key places in the generator; humidity of the chamber; the bitumen or coal tar flow rate; and Total Particulate Matter (TPM). Analyses were performed for Benzene Soluble Matter (BSM), the EPA polycyclic aromatic hydrocarbon (PAH) mixture and for a number of heteroatom-containing PACs. The data show that the coal tar fumes produced at 110 degrees C were very volatile and that most of the differences in particulate matter found between the laboratories can be attributed to evaporative losses. The bitumen fumes boil 25-50 degrees C higher and contain higher boiling compounds. A comparison is made between the PAC exposure profiles for bitumen experiments aimed at 5 and 50 mg/m3. Although the same molecules are found in both fumes their proportion is dramatically different. This effect is largest with the 2- and 3-ring PACs, the ratio of the concentrations found in the 50 mg/m3 TPM concentration to that in the 5 mg/m3 experiment gradually declines from 5500 for acenaphthene to 500 for pyrene, for the 5-ring PACs this ratio is 20-30. As function of their vapour pressure, the ratios of the concentrations of the hetero PACs follow the same trend as that of the 16 EPA PAHs and are of the same order of magnitude. In conclusion, for the compounds investigated, the equipment delivers a fume atmosphere in a reproducible manner. The 50 mg/m3 bitumen fumes are not representatives of field fumes. The reason for these quantitative differences is unclear and further work would be needed to clarify this. Nevertheless it was felt that these fumes at 50 mg/m3 might be a useful tool for qualitative detection of DNA adducts in an animal exposure study.

Animals↗
PubMed2000

Polycyclic aromatic hydrocarbon exposure in an artificial shooting target factory: assessment of 1-hydroxypyrene urinary excretion as a biological indicator of exposure.

Five representative workers and two external observers were monitored by personal air and urinary 1-hydroxypyrene (PyOH) sampling for a four-shift working week in an artificial shooting target factory. The targets (clay pigeons), are made from petroleum pitch and molded at 190 degrees C. No respiratory protective mask was worn. Atmospheric concentrations of pyrene and benzo (a) pyrene (BaP) ranged from 0.66 to 5.05 microg/m(3) and 0.037 to 0.270 microg/m(3) respectively with a mean pyrene/BaP ratio of about 20 and a correlation r = 0.51. Maximum PyOH urinary excretion ranged from 1.84 to 10.9 micromol/molCreat. This occurred at the postshift for the observers but often appeared later for workers: up to 10.75 h for the person with the apparently highest dermal exposure. The apparent PyOH excretion half lives ranged from 1.9 to 12.5 h with an arithmetic mean of 6.1 h. All these data were confirmed by additional measurements taken over a weekend after the postshift. The correlation between atmospheric pyrene and urinary PyOH concentrations (increase over the shift) was poor (r = 0.37). It improve greatly (r = 0.74) if the amount of pyrene inhaled over the shift and the corresponding amount of PyOH excreted were considered. The ratio of urinary excreted PyOH to the pyrene inhaled dose (with assumed retention of 100%), ranged from 0.18 to 0.70 (arithmetic mean = 0.34). This suggests that the respiratory tract is the main entrance route for pyrene (apart from the worker who handled crude targets without gloves).

Air Pollutants, Occupational↗
PubMed1998

Automated column-switching high-performance liquid chromatography for the determination of aflatoxin M1.

An extractionless method for determining aflatoxin M1 (AFM1), a major metabolite of aflatoxin B1 (AFB1), in human urine was developed. The biological fluid is injected directly into the chromatographic system after simple dilution and centrifugation. A pre-column, packed with a cation-exchange phase and coupled on-line to a column-switching liquid chromatography (LC) system, is used for sample pre-treatment and concentration. The analytes are non-selectively desorbed with the LC eluent and cleaned by means of a column-switching procedure. Pre-treatment and analysis were performed within 40 min. Average AFMI recovery reached 97% in the 10-100 ng/l range of urine. The detection limit of AFM1 in urine and milk was 2.5 ng/l for 1 ml of injected sample. A comparison with an immunoaffinity column clean-up and LC method was performed. The method was applied to determine AFM1 in the urine of AFB1 gavaged rats, and in the urine of both potentially exposed and supposedly unexposed workers. The method was also extended to milk.

Aflatoxin M1↗
PubMed1998

Characterization of the cytotoxic factor(s) released from thymic dendritic cells upon human immunodeficiency virus type 1 infection.

We previously demonstrated that infection of primary human thymic dendritic cells (DCs) with laboratory strains of HIV leads to the release of soluble factor(s) which induced thymocyte killing. In the present paper, we extend the characterization of this process. Our results reveal that primary HIV-1 isolates are similarly able to induce the production of cytotoxic factor(s) from thymic DCs and that the release of such factor(s) is dependent on viral infection. Interestingly, we observed that CD4+ and CD8+ purified thymocyte subsets, and activated PBMCs are susceptible to the cytotoxic activity, whereas freshly isolated resting PBMCs are resistant to this effect. Cycloheximide treatment prevents the killing of thymocytes exposed to HIV-infected DC supernatant, revealing that this form of cell death is an active biological process requiring protein synthesis. Finally, our data suggest that FasL and TNF alpha could both participate in the killing process. These in vitro observations provide a plausible model, whereby HIV-infected DCs can play a role in vivo in the induction of uninfected thymocyte killing.

Animals↗
PubMed1997

Human thymic dendritic cells.

ABSTRACT Human thymic dendritic cells (DC) represent a member of the bone marrow-derived dendritic cell family. They have a dendritic shape and are found in small numbers mainly at the corticomedullary border and in medullary regions of the thymus. Human thymic DC were isolated by density gradient separation, followed by treatment with CD2, CD7, CD1, and CD11b mAb and immunobeads magnetic separation. The resulting population contains 60-75% brightly HLA-DR+ cells which present the morphological characteristics of DC observed in situ. Extensive phenotypic analysis confirmed that they are of mesenchymal origin and that some express CD11a and CD54 molecules. Freshly isolated DC do not stain with a wide variety of anti-T-B and -monocyte or -macrophage mAb. However, they acquire the CD1 molecule after a few days in culture. By using a cell sorter we obtained 90-95% of purified human thymic DC. Functional studies have shown that human thymic DC are potent activators in mixed lymphocyte reactions, act as accessory cells in mitogenic thymocyte proliferation, increase the thymocyte proliferative response to a toxin signal, and produce IL-1. They also formed spontaneous physical associations with thymocytes, which raises questions about the implication of DC in differentiation and/or maturation processes of thymocytes.

Dendritic Cells↗
PubMed1997

[False aneurysm of the knee after arthroscopy].

Pseudoaneurysm of the inferomedial genicular artery is a rare complication of arthroscopy. We report one case after arthroscopy ans medialisation of the anterior tibial tuberosity. Exploration and excision were performed.

Aged↗
PubMed1995

[Mortality due to bronchopulmonary cancers in workers of 2 foundries].

A mortality study was carried out in two factories producing stainless steel in order to assess lung cancer risk among workers employed in coke oven, blast and open hearth furnaces, foundry, electric furnace, hot and cold rolling mills and pickling areas. Occupational exposures of interest were chromium compounds, nickel compounds, polycyclic aromatic hydrocarbons (PAH), silica and asbestos. All male workers having at least one year of employment between 01.01.1960 and 31.12.1990 were followed up for mortality. The vital status was assessed from birth place registries. Complete job histories since date of first employment were abstracted from the company files. The smoking habits of 50% of the cohort members were known from medical records. The observed number of deaths (obs) were compared with the expected ones based on regional rates with adjustment for age, sex and calendar time (Standardized Mortality Ratio, SMR). The cohorts included 6324 (factory 1) and 5270 (factory 2) workers. The overall mortality did not differ markedly from that expected in both factories: SMR = 0.95 (obs = 1540, p = 0.05) in factory 1 and SMR = 1.06 (obs = 916, non-significant) in factory 2. SMRs for lung cancer did not differ from unity, respectively 0.99 (obs = 105) and 1.00 (obs = 54), in whole cohorts. Non-significant lung cancer excesses were observed among workers of some workshops where exposures of interest might have occurred: coke oven (SMR = 2.04), blast furnace (SMR = 1.36), open hearth furnace (SMR = 1.75), hot rolling mills (SMR = 1.29). These processes, however, are no longer involved in the study factories. Furthermore, no lung cancer excess was observed among workers employed in current workshops: electric furnaces and cold rolling mills.

Adult↗
PubMed1992

The human thymic dendritic cell phenotype and its modification in culture.

In order to extend our study of human thymic dendritic cells (DC) we have purified DC by density gradient separation followed by treatment with CD1 and CD2 mAb and antibody-coated immunobeads. The resulting population contains 60 to 75% brightly HLA-DR+ cells. Morphological and functional studies demonstrate that these cells share the common characteristics of dendritic cells. Extensive phenotypic analysis of the purified DC has been made using a panel of mAb. Cytofluorometric assays with mAb reactive with common leucocyte antigen confirm that the brightly HLA-DR+ cells are of mesenchymal origin. Thymic DC express HLA-DQ and HLA-class I antigens. They are also positive for the expression of CD45RA molecules and some express the ICAM-1 and the LFA-1 molecules. DC do not stain with a wide variety of anti-T, -B, and -monocyte or -M phi mAb and lack Fc gamma RIII, CR2, and CR3. Freshly isolated DC failed to stain with OKT6 mAb; however, they progressively acquire the CD1 molecule after a few days culture. The acquisition of CD1 molecule is selective since CD4, CD2, and HLA-ABC molecules are not upregulated under the same conditions. From phenotypic results, it was therefore possible to sort brightly HLA-DR+ or -DQ+ cells and so obtain greater than 90 to 95% purified human thymic DC. Such homogeneous DC populations are obviously of great interest for the study of thymic DC functions.

Antigens, CD↗
PubMed1991

Internal ribosome-binding site directs expression of parathyroid hormone analogue (8-84) in Escherichia coli.

Expression of the human parathyroid hormone (PTH) gene in E. coli yielded intact PTH and PTH-(8-84). To determine if PTH-(8-84) is the result of a competing translation initiated from methionine codon-8 or degradation of the intact PTH, twelve new gene constructs with or without an internal ribosome-binding site (iRBS) in the PTH-(1-5) region were prepared via substitution with degenerate codons. Expression of constructs without iRBS produced only intact PTH. Constructs with weak iRBS, including one that resembles the cDNA sequence, yielded PTH-(8-84) as a minor product. In contrast, constructs with strong iRBS produced predominantly or exclusively this shorter analogue.

Binding Sites↗
PubMed1991

Pigmented villonodular synovitis of the hip. A case report and review of the literature.

A 73-year-old patient, whose hip was completely destroyed by pigmented villonodular synovitis, was successfully treated by a total prosthetic replacement of this articulation. The etiopathogenesis of the illness is uncertain. Its' localization in the hip is, fortunately, a rare occurrence. It can be responsible for frequently extensive articular destruction which is even more dramatic when it affects young patients, whose average age is 35. Only early diagnosis permits conservative surgical treatment: total synovectomy associated with curettage of the foyers of osteolysis and their filling with bone grafts. If the destructive lesions are too extensive, an arthrodesis or replacement arthroplasty are proposed.

Aged↗
PubMed1991

IL-1 production by human thymic dendritic cells: studies on the interrelation with DC accessory function.

Thymic dendritic cells (DC) have been proposed to play a critical role in the generation of immunocompetent T lymphocytes. Since IL-1 is widely considered to be an important second signal in T cell stimulation, we have studied the ability of isolated human thymic DC to produce IL-1. Using the EL4/CTLL conversion assay standardized with recombinant IL-1 beta (rIL-1 beta), we demonstrate that upon LPS-stimulation thymic DC produce small amounts of IL-1 as compared to peripheral blood monocytes (PBM). In contrast with PBM, DC IL-1 production is not influenced by indomethacin. IL-1 activity was detected in the supernatants of DC cultures from all thymuses tested, although quantitative variability was noted among individual thymic donors. The specificity of the active factor was confirmed by neutralization assays with anti-IL-1 beta mAb. On the other hand, we demonstrate that rIL-1 beta cannot substitute for nor amplify the accessory function of thymic DC and that anti-IL-1 beta mAb fails to block the DC accessory function. Thus we conclude that IL-1 beta might not be a major factor for the efficient DC accessory function toward mature thymocytes recently demonstrated in our laboratory. Of interest, IL-1 beta was also detected in the supernatants of DC-thymocyte cocultures in the absence of mitogenic factor, suggesting that thymocyte contacts can constitute a sufficient signal to induce DC to produce IL-1. These observations indicate that human thymic DC represent an intrathymic source of IL-1 whose role in thymocyte proliferation or maturation remains to be understood.

Antigen-Presenting Cells↗
PubMed1990

Accessory function of human thymic dendritic cells in Con A-induced proliferation of autologous thymocyte subsets.

Human thymic dendritic cells (DC) have previously been shown to be intimately associated with thymocytes in situ and in culture. We report that thymic DC express LFA-3 and ICAM-1 adhesion molecules and may spontaneously associate with autologous thymocytes within mitogen-independent clusters. Moreover, the accessory activity of isolated human thymic DC was investigated in Con A-stimulation assays. By proliferation experiments, measured as [3H]TdR incorporation, we demonstrated that irradiated thymic DC strongly increase the mitogen-induced activation of autologous PBL as well as of unfractionated thymocytes. More interestingly, in coculture assays performed with purified thymocyte subsets, we have found that thymic DC greatly enhance the Con A proliferation of CD1- CD3bright thymocytes whereas the accessory activity toward the CD1+ CD3- thymocytes was very weak. Inhibition experiments demonstrated that the DC accessory activity is inhibited by anti-DR-related and anti-IL-2R mAb. However, blocking assays with anti-CD11b, anti-CD11c, anti-LFA-3, and anti-ICAM1 mAb showed that the accessory function obtained is similar to that with untreated cultures. We conclude that isolated human thymic DC may present potent DR- and IL-2-dependent accessory activity mainly directed toward the CD1- CD3bright thymocyte subpopulation, suggesting that thymic DC may be involved in the in vivo proliferation of mature thymocytes.

Antigen-Presenting Cells↗
PubMed1990

[Radiography profile in forced plantar flexion for studying unsteady feet].

We have studied the interest of an original radiological incidence ("Plantar hyperflexion") allowing to demonstrate a possible hyperlaxity of medio-tarsal joints. We discovered a significant difference of mobility between patients with unstable feet and the control group. The existence of a medio-tarsal hyperlaxity should be taken into account before starting any treatment.

Foot↗
PubMed1989

Human thymic dendritic cell-thymocyte association: ultrastructural cell phenotype analysis.

In rodent thymus, associations between dendritic cells (DC) and thymocytes have been suggested to be implicated in differentiation and/or maturation processes. In this study, we report intimate associations formed between human thymic DC and thymocytes in culture and we analyze their ultrastructural cell phenotype. Observations by phase contrast microscopy showed that DC present long and thin dendrites and bind many thymocytes. Transmission (TEM) and scanning electron microscopy (SEM) revealed that both cellular populations were in close connection and tight membrane contact could be observed. The phenotype of DC and attached thymocytes was characterized with a series of monoclonal antibodies by protein A-gold TEM and SEM immunolabelings. Quantitative evaluation of immunolabeling (number of gold granules/microns of cellular membrane) suggests the presence of two subpopulations of CD1+ thymic DC (strong and weak), whereas this discrepancy is not observed in DR+ and CD4+ DC populations. On the other hand, the majority of thymocytes bound to DC strongly express the CD1, CD4, CD8 and CD2 antigens and weakly the CD3 antigen, indicating that they represent double-positive immature thymocytes. Uniform distribution of DC and thymocytes membrane antigens was confirmed with a backscattered SEM study. This morphological and immunolabeling TEM and SEM analysis demonstrates that human thymic DC may form associations with CD4+CD8+CD3weak thymocytes and raises questions about their physiological relationship.

Antigens, CD1↗
PubMed1989

Stability assessment of distal radius fractures.

A total of 112 consecutive cases of fractures of the distal radius managed conservatively were graded according to radiological criteria using the first radiograph. These criteria, as well as age over 60 years, were considered as gravity factors. A strong correlation was found between these criteria and the risk of secondary displacement, despite a correct initial reduction.

Adolescent↗