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Biomedical subjects

M Lafontaine

Publications and source records attributed to M Lafontaine.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1989

Risk of lung, larynx, pharynx and buccal cavity cancers among carbon electrode manufacturing workers.

Among workers employed in factories producing carbon graphite products the risk of cancer due to exposure to polycyclic aromatic hydrocarbons was estimated. In one cohort (plant A), a cancer incidence study was carried out; the number of cases were not significantly increased for lung cancers [7 cases, standardized incidence ratio (SIR) 79] or for cancers of the upper respiratory and alimentary tract (10 cases, SIR 103). In another cohort (plant B), a mortality study was carried out; neither the mortality from lung cancer [13 deaths, standardized mortality ratio (SMR) 118] nor that from upper respiratory and alimentary tract cancers (10 deaths, SMR 125) was significantly higher than expected. Within each cohort, a case-referent study was carried out. In plant A the odds ratios were high but nonsignificant for lung cancers (odds ratio 3.42) and upper respiratory and alimentary tract cancers (odds ratio 2.19) and they showed a nonsignificant relationship with duration of exposure. In plant B, the odds ratios were low for every cancer site.

Carbon↗
PubMed1989

[Initial dislocation of the patella; which treatment?].

Twenty patients, victims of a first luxation of the patella, were the object of a retrospective study. They were all subjected to arthroscopic examination during which, in 7 of the patients, the liquid injected under pressure massively escaped into the subcutaneous layer of the medial side of the knee. The patients were divided into 2 groups according to the integrity of the capsule of their knees. Group I consisted of 7 patients, group II of 13 patients. The treatments, the majority of which were conservative, were quite varied, but the post-traumatic functional recuperation was much slower and more variable for the group I patients. These patients presented more significant tissue lesions which certainly contributed to the functional prognosis of the traumatized joint. Seventy two percent of the patients, equally distributed between the 2 groups, presented trochleo-patellar dysplasia. With the exception of age, different clinical parameters (sex, circumstances of the accident, clinical examination) and radiological criteria (external displacement of the patella, detached bony fragment at the interior border of the patella, value of the patellar and trochlear angles, patella alta) did not permit a distinction between the two groups. Because of our results and those in the existing literature we recommend arthroscopy, which is the only examination capable of establishing a complete picture of the lesions and which, in addition, permits rising of the joint and sometimes allows extraction of free osteo-cartilaginous fragments. The younger patients may then benefit from immediate functional reeducation. For older patients, where the tissue lesions are more important, conservative treatment is associated with a slower and sometimes variable functional recuperation. It remains to be determined, whether surgical treatment, adapted to each case, would permit us to obtain better results more rapidly.

Adolescent↗
PubMed1989

[Instability of fractures of the lower end of the radius: apropos of a series of 167 cases].

One-hundred-sixty-seven consecutive cases of distal radius fracture have been treated in our department from October 1985 until November 1987. All cases were rated according to anatomical criteria defined on the first radiogram. These criteria were the presence of a dorsal tilt greater than 20 degrees, dorsal comminution, intra-articular radiocarpal involvement, an associated fracture of the ulna and comminution of the distal radius. Age greater than 60 years was also considered as a factor in determining severity. With regard to fractures treated conservatively (from which comminuted fractures were excluded), a strong correlation was found between the sum of these factors and the risk of secondary displacement. This complication occurs despite a satisfactory initial reduction. Although the surgically treated cases were more severe, significantly better radiological results were observed following surgical management. This mode of classification of distal radius fractures is helpful for determining prognosis and evaluating the risk of secondary displacement and in the course, should help in the selection, perhaps earlier of the most appropriate treatment.

Adolescent↗
PubMed1988

Human thymic dendritic cells. Characterization, isolation and functional assays.

The phenotypic analysis of human thymic dentritic cells (DC) in culture and in purified suspensions has been studied with light and electron microscopic (EM) immunolabelling techniques. Using a series of monoclonal antibodies (mAb) and a protein A-gold technique, we demonstrated that DR- and T6-positive cultured DC strongly bind the 9.3F10 mAb, an anti-DR-related antibody produced against human blood DC, and weakly express the T4 antigen, a membrane marker shared by Langerhan's cells (LC). On the other hand, thymic-cultured DC are negative for the other T-cell and monocyte-macrophage antigens. These results support the hypothesis that human thymic DC may be related to blood DC and epidermal LC. Moreover DC, unlike thymic macrophages, do not phagocytose latex particles, opsonized sheep red blood cells (SRBC) or Candida albicans. An efficient two-step technique of isolation, using a Percoll density gradient followed by an indirect panning technique, yields a purified (70-80%) thymic DC population, OKIa1-, 9.3F10- and OKT6-positive and esterase-negative. Immunolabelling and electron microscopy confirm that these isolated DC present similar phenotypic and ultrastructural features to human thymic DC in situ and in culture. Purified DC, used as stimulator cells in mixed leucocyte reaction (MLR), induce stronger proliferative responses than peripheral blood monocytes used as a control; blocking assays with OKIa1 mAb plus complement greatly reduced this stimulatory potency. These functional assays demonstrate that we obtained a purified typical DC population that can be used in immunological functional studies to elucidate the specific role of DC in human thymus.

Antigens, Surface↗
PubMed1986

Demonstration of OKT6 antigen on human thymic dendritic cells in culture.

In situ, two types of dendritic cells (DCs) have been characterized in more detail: the interdigitating DCs of peripheral lymphoid tissues and the epidermal Langerhans cells. In order to characterize human thymic DCs, normal human thymus specimens were obtained from children undergoing cardiovascular surgery. In culture, DCs could be easily differentiated from macrophages and epithelial cells by their long fine processes, irregular nucleus, and dark, membrane-bound granules. By immunoelectron microscopy, using the protein A-gold and the avidin-biotinperoxidase complex techniques, cultured DCs were strongly labeled with anti-Ia and anti-OKT6 monoclonal antibodies. These results demonstrate that the phenotype of thymic DCs is similar to that of epidermal Langerhans cells and suggest that they may belong to the same cellular lineage.

Antibodies, Monoclonal↗
PubMed1984

Roles of gastrin release and neural reflexes during the gastric phase of acid secretion in dogs.

The acid secretion from the main stomachs and from denervated Heidenhain pouches in response to peptone meals infused in the stomach was determined in 4 dogs. When expressed as percent of the maximal acid response to histamine, the acid secretion from the innervated and from the denervated fundic mucosa was similar, but the response from the Heidenhain pouch was larger when expressed as percent of the maximal response to pentagastrin. These studies indicate that, under the conditions used, short (gastrogastric) and long (vagovagal) reflexes during the gastric phase, are of minor importance in inducing the acid response to the meal.

Animals↗
PubMed1984

[Interactions between secretin and somatostatin on acid secretion and gastric emptying in dogs].

Secretin and somatostatin are two peptides released by H+ ions. The fact that blood levels of these peptides increase during the postprandial period makes them the most probable candidates for gastric acid secretion retrocontrol . The aim of our study was to determine whether a potentiation of inhibitory effects exists when the two peptides are administered simultaneously. Seven dogs were provided with a gastric fistula. Gastric acid secretion was stimulated by intragastric infusion of a bactopeptone solution or by pentagastrin (1 microgram X kg-1 X h-1). Acid outputs and gastric emptying rates were measured at regular intervals. The tests were repeated during intravenous infusion of secretin (0.125 micrograms X kg-1 X h-1), somatostatin (0.2 micrograms X kg-1 X h-1) or both peptides together at the same doses. Both secretin and somatostatin inhibited acid secretion and gastric emptying. The inhibition was not greater when both peptides were administered together. Under the conditions used, no potentiation or additive effects between the two peptides were observed on gastric acid secretion or gastric emptying.

Animals↗