Search PubMed⌕ Search

Biomedical subjects

C Vincent

Publications and source records attributed to C Vincent.

At least 73 records · Page 4Linked to original sources
PubMed2001

Performance of two ELISAs for antifilaggrin autoantibodies, using either affinity purified or deiminated recombinant human filaggrin, in the diagnosis of rheumatoid arthritis.

OBJECTIVE: To develop a standardisable enzyme linked immunosorbent assay (ELISA), using human filaggrin, for detection of antifilaggrin autoantibodies in rheumatoid arthritis (RA). To compare the diagnostic performance of the ELISA with those of reference tests: "antikeratin antibodies" ("AKA"), and antibodies to human epidermis filaggrin detected by immunoblotting (AhFA-IB). METHODS: Two ELISAs were developed using either affinity purified neutral-acidic human epidermis filaggrin (AhFA-ELISA-pur) or a recombinant human filaggrin deiminated in vitro (AhFA-ELISA-rec) as immunosorbent. Antifilaggrin autoantibodies were assayed in 714 serum samples from patients with well characterised rheumatic diseases, including 241 RA and 473 other rheumatic diseases, using the two ELISAs. "AKA" and AhFA-IB tests were carried out in the same series of patients. The diagnostic performance of the four tests was compared and their relationships analysed. RESULTS: The titres of "AKA", AhFA-IB, and the AhFA-ELISAs correlated strongly with each other. The diagnostic sensitivity of the AhFA-ELISA-rec, which was better than that of AhFA-ELISA-pur, was 0.52 for a specificity of 0.95. This performance was similar to those of "AKA" or AhFA-IB. However, combining AhFA-ELISA-rec with AhFA-IB led to a diagnostic sensitivity of 0.55 for a specificity of 0.99. CONCLUSION: A simple and easily standardisable ELISA for detection of antifilaggrin autoantibodies was developed and validated on a large series of patients using a citrullinated recombinant human filaggrin. The diagnostic performance of the test was similar to that of the "AKA" and AhFA-IB. Nevertheless, combining the AhFA-ELISA-rec with one of the other tests clearly enhanced the performance.

Adolescent↗
PubMed2001

[Regionalization of rehabilitation services. Survey of users of a Quebec center].

OBJECTIVE: To understand the situation of and difficulties encountered by users of a supraregional rehabilitation institute when they are transferred from the institute to facilities in their own regions, and to discover how they address these difficulties. DESIGN: Qualitative descriptive study. SETTING: Regions in Quebec served by a physical rehabilitation institute (Institut de réadaptation en déficience physique de Québec). PARTICIPANTS: Thirty-nine people who used services at the institute and then sought rehabilitation in their own regions. METHOD: Telephone survey using a validated questionnaire with both open-ended and closed questions. MAIN FINDINGS: About 69% of users had difficulty obtaining adequate follow up in their regions; the regions lacked professionals with expertise; more efficient methods of communication are required; and physicians' role in providing continuity of care needs to be recognized. CONCLUSION: Providing continuity of care on a regional basis is a formidable challenge for the entire health and social services network, but ways of meeting this challenge are within reach.

Adolescent↗
PubMed2001

[The monaural pseudo-stereophonic hearing aid (BAHA) in unilateral total deafness: a study of 29 patients].

For many years, unilateral total deafness has been considered a minor handicap which does not require the fitting of a hearing aid. If the condition did give a major problem, the usual recommendation for this type of hearing loss was a CROS system which, in addition to problems of function and aesthetics, gave poor results. Faced with increasing demands from these patients, and given the good performance of bone conduction implants (BAHA), we decided to try to implant these devices on the deaf side, which allowed, by way of transcranial conduction, stimulation of the functioning ear and the re-establishment of a certain degree of stereophonic hearing. This study of 29 patients who were tested by stereophonic audiometry pre- and post-implantation shows that this type of aiding is beneficial, with improvement of the threshold of intelligibility against background noise of between 5 and 15 dB during Hirsch's test, correction of the "dead angle" on the deaf side, and improvement in localisation of sound in space. From the functional point of view, 88% of patients were satisfied with their aid, which they wore for 8 or 9 hours per day, and had a marked improvement in their hearing performance under various conditions which had proved very difficult for them before they were fitted with the aid. These results all demonstrate the effectiveness of the implant used in this way. The fact that sounds are received on the totally deaf side goes a long way towards establishing satisfactory hearing. True stereophonic hearing could not be established in any of the cases, because this requires input from two ears. It is for this reason that we have termed this type of aid as monaural pseudo-stereophonic.

Acoustic Stimulation↗
PubMed2000

Relationship between exopolysaccharide production and protein-tyrosine phosphorylation in gram-negative bacteria.

The phosphorylation of proteins at tyrosine residues is known to play a key role in the control of numerous fundamental processes in animal systems. In contrast, the biological significance of protein-tyrosine phosphorylation in bacteria, which has only been recognised recently, is still unclear. Here, we have analysed the role in Escherichia coli cells of an autophosphorylating protein-tyrosine kinase, Wzc, and a phosphotyrosine-protein phosphatase, Wzb, by performing knock-out experiments on the corresponding genes, wzc and wzb, and looking at the metabolic consequences induced. The results demonstrate that the phosphorylation of Wzc, as regulated by Wzb, is directly connected with the production of a particular capsular polysaccharide, colanic acid. Thus, when Wzc is phosphorylated on tyrosine, no colanic acid is synthesised by bacteria, but when dephosphorylated by Wzb, colanic acid is produced. This process is rather specific to the pair of proteins Wzc/Wzb. Indeed, a much lesser effect, if any, on colanic acid synthesis is observed when knock-out experiments are performed on another pair of genes, etk and etp, which also encode respectively a protein-tyrosine kinase, Etk, and a phosphotyrosine-protein phosphatase, Etp, in E. coli. In addition, the analysis of the phosphorylation reaction at the molecular level reveals differences between Gram-negative and Gram-positive bacteria, namely in the number of protein components required for this reaction to occur.

Amino Acid Sequence↗
PubMed2000

Effect of various essential oils on Callosobruchus maculatus (F.) (Coleoptera: Bruchidae).

Essential oils were extracted from four West African plant species [Tagetes minuta (Family Compositae), Hyptis suaveolens (Family Labiatae), white basil Ocimum canum (Family Labiatae), and sweet basil O. basilicum (Family Labiatae)] by steam distillation. The oil of the pepper Piper guineense (Family Piperaceae), was extracted from the fruits by hydro distillation and ethanol extraction. Mixed essential oil and total ethanol extract was used. Kaolin powder (clay) was mixed (aromatized) with these different oils. Cowpea weevils were reared on chickpeas and newly emerged males and females were deposited on uninfested seeds. Bioassays, i.e. fumigation with pure essential oils and aromatized kaolin powders, were carried out on adults and eggs. Twenty four hours after fumigation, 99 and 0% adult mortality were observed, respectively, as the result of treatments with Ocimum basilicum and the control. The application of powders aromatized with the same oils to weevil pairs resulted in a complete lack of oviposition, whereas 31, 56 and 76 eggs were laid in the controls after 24, 48 and 72 h, respectively. Application of aromatized powders did not have a significant effect on egg hatching (50 out of 110 with O. canum, 100 out of 115 with O. basilicum and 100 out of 130 in the control sample) but did have a significant impact on adult emergence: 0% for the two treatments compared with 100% in the controls. Our results suggest that plants of the genus Ocimum can be used as an alternative to synthetic insecticides.

Journal Article↗
PubMed2000

The disruption of adherens junctions is associated with a decrease of E-cadherin phosphorylation by protein kinase CK2.

The down-regulation of E-cadherin is a common event in carcinogenesis. Phosphorylation/dephosphorylation is one posttranscriptional process which may regulate intercellular junctions. Here we show that in okadaic acid-treated keratinocytes, E-cadherin expression is shifted from the membrane to the cytoplasm, preventing cells from forming aggregates. These changes of E-cadherin localization and function are associated with a decrease in its phosphorylation state. The decrease in E-cadherin phosphorylation was essentially detected in okadaic acid-treated cell lysates isolated from 0.5% Triton-soluble fraction and not in the Triton-insoluble fraction linked to the cytoskeleton, suggesting a role of E-cadherin phosphorylation in cell-cell interactions. E-cadherin was markedly phosphorylated by CK2, either the purified recombinant enzyme or the endogenous enzyme. Using specific CK2 inhibitors such as heparin and 5, 6-dichloro-1-beta-d-ribofuranosylbenzimidazole, endogenous CK2 was confirmed as the main enzyme phosphorylating E-cadherin. The decrease in E-cadherin phosphorylation by endogenous CK2 was not restored by the addition of purified CK2, confirming that it is not due to a defect in CK2 expression or to its reduced activity, but rather to the incapacity of CK2 to phosphorylate E-cadherin. The co-immunoprecipitation and colocalization of E-cadherin and CK2 suggests that CK2 may play a critical role in the maintenance of epidermis cohesion.

Cadherins↗
PubMed2000

Immune response of the hibiscus mealybug, Maconellicoccus hirsutus Green (Homoptera: Pseudococcidae), to oviposition of the parasitoid Anagyrus kamali Moursi (Hymenoptera: Encyrtidae).

Anagyrus kamali Moursi has been recently introduced into the Caribbean as a biological agent against the hibiscus mealybug, Maconellicoccus hirsutus Green. This host has a cellular defense reaction that involves encapsulation and melanization of the endoparasitoid egg. The impact of this immune response on the parasitoid progeny was assessed, as well as the response of the parasitoid countermeasures to overcome it. Under laboratory conditions, significant differences in the immune response were found for different developmental stages of M. hirsutus. The intensity of the immune response varied between second instar, third instar and adult mealybugs. After 30 h, the level of encapsulation was the highest for eggs oviposited in adults: 58% of eggs were encapsulated, followed by third (32%) and second (4%) instars. Three days after oviposition 23, 44 and 86% of the parasitoid eggs oviposited, respectively, in adult, third and second instars were not encapsulated. The unencapsulated parasitoid eggs could hatch and continue their development. Adult mealybugs required 30 h to encapsulate 50% of the eggs, whereas in second and third instars, 50% level encapsulation was never reached. Superparasitism had a saturating effect on the immune system; reduced levels of encapsulation occurred when more than 10 eggs were oviposited in a single mealybug. Wasp larvae were never encapsulated by M. hirsutus.

Journal Article↗
PubMed2000

In vitro evaluation of the sensitization potential of weak contact allergens using langerhans-like dendritic cells and autologous T cells.

Contact hypersensitivity is a major public health concern in most industrial countries, which is why predictive tests which could identify potential allergens are needed. We have established an in vitro approach for the detection of primary immune response. This model uses Langerhans-like dendritic cells (LLDC) derived from cord blood progenitors and autologous T lymphocytes, isolated from the same blood sample. Treatment of day 12-14 LLDC, with strong haptens trinitrobenzene sulfonic acid (TNP), fluorescein isothiocyanate (FITC) or Bandrowski's base (BB), results in the proliferation of T lymphocytes, whereas weak allergens and irritants, such as sodium dodecyl sulfate (SDS) are ineffective. The use of immature (day 8) LLDC and the addition of a 48 h stage of incubation after hapten contact, result in phenotypic maturation of LLDC in addition to lymphocyte activation in all the cultures with strong haptens. The 48 h stage of incubation, results in sensitization and in some cases the induction of T cell proliferation to citronellal (1/8), coumarine (1/8) and to a prohapten p-phenylenediamine (pPDA; 2/8). The phenotype of DC after 48 h of contact with a strong hapten, becomes that of mature DC (CD83(+), CD86(+) and HLA-DR(++)). With fragrance molecules, weak haptens and prohaptens, a comparable phenotype is observed only when T lymphocytes are activated. These data suggest that the unresponsiveness observed with weak haptens, may be the consequence on an incomplete maturation of LLDC.

Allergens↗
PubMed2000

Langerin, a novel C-type lectin specific to Langerhans cells, is an endocytic receptor that induces the formation of Birbeck granules.

We have identified a type II Ca2+-dependent lectin displaying mannose-binding specificity, exclusively expressed by Langerhans cells (LC), and named Langerin. LC are uniquely characterized by Birbeck granules (BG), which are organelles consisting of superimposed and zippered membranes. Here, we have shown that Langerin is constitutively associated with BG and that antibody to Langerin is internalized into these structures. Remarkably, transfection of Langerin cDNA into fibroblasts created a compact network of membrane structures with typical features of BG. Langerin is thus a potent inducer of membrane superimposition and zippering leading to BG formation. Our data suggest that induction of BG is a consequence of the antigen-capture function of Langerin, allowing routing into these organelles and providing access to a nonclassical antigen-processing pathway.

Amino Acid Sequence↗
PubMed2000

In the rheumatoid pannus, anti-filaggrin autoantibodies are produced by local plasma cells and constitute a higher proportion of IgG than in synovial fluid and serum.

IgG anti-filaggrin autoantibodies (AFA) are the most specific serological markers of rheumatoid arthritis (RA). They include the so-called 'anti-keratin antibodies' (AKA) and anti-perinuclear factor (APF), and recognize human epidermal filaggrin and other (pro)filaggrin-related proteins of various epithelial tissues. In this study we demonstrate that AFA are produced in rheumatoid synovial joints. In 31 RA patients, AFA levels were assayed at equal IgG concentrations in paired synovial fluids (SF) and sera. AFA titre-like values determined by indirect immunofluorescence and immunoblotting and AFA concentrations determined by ELISA were non-significantly different in serum and SF, clearly indicating that AFA are not concentrated in SF. In contrast, we demonstrated that AFA are enriched in RA synovial membranes, since the ELISA-determined AFA in low ionic-strength extracts of synovial tissue from four RA patients represented a 7.5-fold higher proportion of total IgG than in paired sera. When small synovial tissue explants from RA patients were cultured for a period of 5 weeks, the profile of IgG and AFA released in the culture supernatants was first consistent with passive diffusion of the tissue-infiltrating IgG (including AFA) over the first day of culture, then with a de novo synthesis of IgG and AFA. Therefore, AFA-secreting plasma cells are present in the synovial tissue of RA patients and AFA can represent a significant proportion of the IgG secreted within the rheumatoid pannus.

Arthritis, Rheumatoid↗
PubMed2000

Langerhans-like dendritic cells generated from cord blood progenitors internalize pollen allergens by macropinocytosis, and part of the molecules are processed and can activate autologous naive T lymphocytes.

BACKGROUND: The safety and efficacy of sublingual immunotherapy have been demonstrated in moderate allergic asthma and seasonal rhinitis. However, not much is known about the precise mechanism of action of the allergen when it crosses the oral mucosa. OBJECTIVE: To define this mechanism, we investigated the role of Langerhans' cells in the capture and internalization of allergens. METHODS: We generated dendritic cells in vitro with the phenotypic characteristics of Langerhans-like dendritic cells (LLDCs) from cord blood CD34(+) progenitors. We used two recombinant major allergens: Bet v 1 and Phl p 1 labeled with FITC. RESULTS: Internalization of allergens and control proteins was dose- and time-dependent and related to the immature state of the cells. LLDCs internalized allergens with a high efficiency in comparison with control molecules. Allergens were only internalized by macropinocytosis, as demonstrated by the use of various inhibitors. Addition of intracellular pH-modifying molecules indicated that only a part of the allergens was accumulated in acidic vesicles, whereas the majority remained in other cytoplasmic structures. Pulse-chase experiments calculated a half-life of 4 hours, suggesting that part of the molecules were not metabolized in the lysosome. Allergen internalization by LLDCs might be followed by processing in some experiments, as demonstrated by activation of autologous T lymphocytes in 4 of 9 experiments. CONCLUSION: These elements showed that Langerhans' cells present in mucosa might play an active role in immune responses to allergens.

Allergens↗
PubMed2000

Children at risk for asthma: home allergen levels, lymphocyte proliferation, and wheeze.

BACKGROUND: Allergic asthma is a common childhood disease. Although T-lymphocyte activation plays a critical role in allergic asthma, the environmental factors promoting lymphocyte activation in children are not well defined. OBJECTIVE: In a cohort of children at risk for asthma (n = 114), we determined whether the levels of cockroach (Bla g 1 or 2), house dust mite (Der f 1), and cat allergen (Fel d 1) in the home during infancy was associated with subsequent allergen-specific lymphocyte proliferation in later life. METHODS: Dust samples from multiple sites in the home were collected at 3 months of age and were measured for allergen levels. Serial questionnaires were applied. At a median age of 2 years, PBMCs were isolated and lymphocyte proliferation to the home allergens and PHA was determined. RESULTS: Increased lymphocyte proliferative responses to Bla g 2 were associated with higher home levels of Bla g 1 or 2 (P for trend with kitchen Bla g levels =.011), in analyses adjusting for cold in the past week. Proliferative responses to Der f 1 were higher in homes with family room levels of Der f 1 > or =10 microg/g dust than in homes with Der f 1 <2 microg/g, but differences were not significant in analyses adjusting for cold (P =. 15). Repeated wheeze in the first 2 years of life was associated with increased allergen-specific and PHA proliferative responses. CONCLUSION: Early-life cockroach allergen exposure at 3 months of age predicts allergen-specific lymphocyte proliferative responses at a median of 2 years of age.

Air Pollution, Indoor↗
PubMed2000

Correlation between Ki-67 index and some clinical aspects of acoustic neuromas (vestibular schwannomas).

Evaluation of the proliferation activity of neuromas has a practical meaning when there are doubts about the complete resection of the tumor. Evaluation of the clinical aspects connected with increased proliferation activity may have a much broader application. The aim of this study was to correlate selected clinical and radiologic aspects of vestibular schwannomas with the results of the Ki-67 index. The studied group included 23 males and 20 females. Unilateral neuromas were stated in 38 cases (mean age, 52.2 years) and bilateral tumors in 5 cases (mean age, 44.2 years). The immunohistochemical tests (Ki-67) were performed on the specimens preserved in formalin and stored in paraffin. The Ki-67 index was estimated in a semiquantitative study. The mean value of Ki-67 index was 1.86%. In case of unilateral neuromas (n = 38), the average Ki-67 index was 1.74%. In 5 cases of bilateral tumors, the index amounted to 2.79% (P = 0.278). No significant correlation was found by comparing the value of the Ki-67 index with the age of patients (P = 0.410: r = 0.128). Significant differences in the value of the Ki-67 index were noted in the sub-groups of tumors that were evaluated radiologically as growing and stable. The mean value of Ki-67 index was 3.17% in the first subgroup; in stable neuromas, it was significantly lower, amounting to 1.11% (P = 0.020). Such results may confirm that the growth rate of vestibular schwannomas varies and may explain the difficulties in estimating the growth of neuromas on the basis of clinical aspects only.

Adolescent↗
PubMed2000

Antifilaggrin autoantibodies in early rheumatoid arthritis.

OBJECTIVE: To study antifilaggrin autoantibodies in patients with early rheumatoid arthritis. METHODS: Antifilaggrin autoantibodies were detected by immunoblotting (AFA) and by indirect immunofluorescence ('AKA') in sera from 112 patients with early RA. RESULTS: At baseline, 'AKA' were detected in 29% and AFA in 32% of sera, whereas after 12 months, they were present in 23% and 26% of sera, respectively. Significant associations between 'AKA', AFA, and rheumatoid factor were found. 'AKA' and AFA titres were significantly higher in patients with susceptibility alleles. No clear relation was observed between 'AKA', AFA, and disease activity but radiological progression tended to be more pronounced in patients having antifilaggrin autoantibodies. CONCLUSIONS: Antifilaggrin autoantibodies, being present in about one third of all new cases of RA, may have a value in early diagnosis. The present data suggest that these autoantibodies also may be a marker of disease severity.

Adult↗
PubMed2000

Effects of five insecticides used in apple orchards on Hyaliodes vitripennis (Say) (Hemiptera: Miridae).

Azinphos-methyl, carbaryl, dimethoate, phosmet and phosalone were used in apple orchards to manage apple aphid, apple maggot, woolly apple aphid and leaf eating caterpillars. Among the five insecticides evaluated, dimethoate, carbaryl and azinphosmethyl were the most toxic to the nymphs and adults of Hyaliodes vitripennis (Say) from two regions. Phosalone was the least toxic. Nymphs were more resistant than the adults. While the LC50 for dimethoate was 130 ppm for nymphs, it was 3 ppm for adults from St. Jean-Baptiste-de-Rouville. There were also significant differences in the level of resistance between the two regions where the H. vitripennis were collected. At St. Alexandre the LC50 for phosalone on nymphs was 19,250 ppm whereas, at St. Jean-Baptiste-de-Rouville it was 160,000 ppm.

Agriculture↗