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Biomedical subjects

B Mari

Publications and source records attributed to B Mari.

32 records · Page 2Linked to original sources
PubMed1994

Thrombin and thrombin receptor agonist peptide induce early events of T cell activation and synergize with TCR cross-linking for CD69 expression and interleukin 2 production.

Thrombin stimulation of the T leukemic cell line Jurkat induced a transient increase in [Ca2+]i. Proteolytic activity of the enzyme was required for this effect since diisopropyl fluorophosphate-thrombin failed to increase [Ca2+]i. Furthermore, hirudin and anti-thrombin III inhibited the thrombin-induced [Ca2+]i rise in Jurkat T cells. A synthetic thrombin receptor agonist peptide (TRP) of 7 residues (SFLLRNP) was found to be as effective as thrombin for [Ca2+]i mobilization, and both agonists induced Ca2+ release exclusively from internal stores. Thrombin stimulated tyrosine phosphorylation of several proteins of molecular mass 40, 42, 70, 120, and 130 kDa. There was a good correlation between thrombin-induced tyrosine phosphorylation of the latter three proteins and Ca2+ mobilization. Thrombin and TRP also caused translocation of protein kinase C from the cytosol to the plasma membrane. As a likely consequence of these events, thrombin activated the nuclear factor NF-kB. Several cell lines of hematopoietic origin including the leukemic T cell line HPB.ALL and the erythroleukemic cell line K562 were responsive to thrombin, whereas others such as THP1, a myelomonocytic cell line, and BL2, a Burkitt lymphoma were refractory to thrombin or TRP stimulation. The magnitude of the thrombin response in the different cell types paralleled the expression of the thrombin receptor mRNA. We found that activation of Jurkat T cells by a combination of phytohemagglutinin and phorbol 12-myristate 13-acetate led to a dramatic inhibition of thrombin receptor mRNA expression and to a concomitant loss of the thrombin response. Finally, we demonstrate that thrombin and TRP enhanced CD69 expression and interleukin 2 production induced by T cell receptor cross-linking in both Jurkat T cells and peripheral blood lymphocytes. These findings highlight the role of thrombin as a potential regulator of T lymphocyte activation.

Amino Acid Sequence↗
PubMed1994

Induction of tyrosine phosphorylation and T-cell activation by vanadate peroxide, an inhibitor of protein tyrosine phosphatases.

Rapid tyrosine phosphorylation of key cellular proteins is a crucial event in the transduction of activation signals to T-lymphocytes. The regulatory role of protein tyrosine phosphatases (PTPases) in this process was explored by studying the effects of a powerful PTPase inhibitor, vanadate peroxide (pervanadate), on the activation cascade of Jurkat human leukaemic T-cells. Pervanadate induced activation of the tyrosine kinases lck and fyn (4- and 3-fold respectively) and a dramatic increase in tyrosine phosphorylation of cellular proteins, notably phospholipase C gamma 1. After this event, we observed a rise in intracellular Ca2+ concentration, corresponding to an influx. This effect required surface expression of the CD45 PTPase and was not observed in CD45-deficient variants of Jurkat cells. In the CD45-negative variant, the effect of pervanadate on tyrosine phosphorylation was globally decreased and some phosphorylated substrates were specifically missing. Pervanadate also stimulated transcription of the c-fos gene and accumulation of its mRNA as well as several other hallmarks of T-lymphocyte activation such as surface expression of the CD69 antigen and the interleukin 2 receptor alpha-chain (CD25). Pervanadate synergized with signals delivered by T-cell antigen receptor engagement or by a phorbol ester to induce interleukin 2 production. Pervanadate activated NF-kappa B, as shown by an increase in DNA-binding activity of this transcription factor. We thus conclude that PTPases play a crucial role in the negative regulation of signal transduction culminating in T-lymphocyte activation. Moreover, induction of tyrosine phosphorylation appears sufficient per se to initiate a complete activation programme.

Base Sequence↗
PubMed1994

High levels of functional endopeptidase 24.11 (CD10) activity on human thymocytes: preferential expression on immature subsets.

Although it is now well established that cells of the immune system express most of the exopeptidases described so far, little information is available concerning the identification and the characterization of the peptidases associated with the surface of human thymocytes. In the present study we have focused on CD10 expression on thymocytes using both FACS and enzymatic analysis. Unfractionated intact human thymocytes were shown to express significant levels of CD10-specific enzymatic activity, as assessed by the hydrolysis of the neutral endopeptidase (NEP) substrate Suc-Ala-Ala-Phe-pNA and of D-Ala2-Leu-enkephalin, a typical NEP substrate. CD10 activity was abolished by specific NEP inhibitors, including thiorphan, retrothiorphan and phosphoramidon. Moreover, high performance liquid chromatography (HPLC) analysis showed that intact thymocytes and purified NEP hydrolysed thymopentin, a thymic factor known to induce the maturation of prothymocytes into thymocytes. Finally, CD 10/NEP was preferentially associated with CD3- CD3low and immature CD4- CD8- thymocytes. The data demonstrate for the first time that human thymocytes express functional NEP and suggest a role for this enzyme in the maturation of human thymocytes.

CD3 Complex↗
PubMed1993

Differential expression of adenosine A1 and A2 receptors in preadipocytes and adipocytes.

Multiple physiological functions have been described to be affected by adenosine in numerous cell types. A comparative study of the expression of adenosine receptors has been performed in preadipocytes and adipocytes from rat epididymal fat pad. The results show that, in agreement with its well known antilipolytic effect, adenosine induces a negative modulation of adenylate cyclase via the A1 receptor present in adipocytes. By contrast, the A2 receptor subtype, which is positively coupled to adenylate cyclase, is herein demonstrated to be only expressed in adipose precursor cells. This expression allows, in chemically defined medium, the adenosine analogue NECA, by means of its ability to elevate cAMP concentration, to potentiate differentiation. These findings emphasize the role that adenosine might play as a bimodal regulatory extracellular signal in adipose tissue development.

Adenosine↗
PubMed1993

Characterization and purification of T lymphocyte aminopeptidase B: a putative marker of T cell activation.

We have previously described that human T lymphocytes express membrane-associated peptidase activities (Mari et al., EMBO J., 1992, 11:3875). We show in this report that intact Jurkat T cells readily cleaved H-Arg-paranitroanilide, an aminopeptidase B (AP-B) substrate. The identification of the hydrolyzing activity as AP-B was confirmed by its sensitivity to both arphamenine B and bestatin in the nanomolar range. Significant AP-B activity was released in the supernatant upon incubation of intact T lymphocytes at 37 degrees C. However, AP-B activity was found mainly in the cytosolic fraction of Jurkat T cells. Cytosolic T cell AP-B was purified to homogeneity and exhibited a molecular mass of 72 kDa. Purified AP-B cleaved N-terminal basic amino acid-containing peptides such as thymopentin (H-Arg-Lys-Asp-Val-Tyr-OH), indicating that it might play a role in the regulation of the concentration of important soluble mediators of T cell activation. A rabbit polyclonal antibody was shown to recognize AP-B as assessed by both immunoprecipitation and Western blot experiments. Finally, we found that AP-B was up-regulated during activation of normal and leukemic T lymphocytes.

Aminopeptidases↗
PubMed1993

Development of a single dilution ELISA to detect antibody to Dermatophilus congolensis in goat and cattle sera.

A solid phase immunosorbent assay to detect antibodies to Dermatophilus congolensis in ruminant sera was developed to be used as a single dilution ELISA in large epidemiological surveys. Optimal conditions for the test are described. The use of blocking proteins to reduce non specific binding was necessary. Non fat dry cow milk and fetal calf serum were the only two efficient blocking agents out of six tested. Comparison of 4 antigenic fractions obtained after sonication and differential centrifugations of D. congolensis cultures showed that cell-wall (CW) or membrane (M) enriched preparations were more specific than a crude extract (CR) or a soluble (S) antigen. Whole spores and filaments performed poorly as antigens. The best sensitivity and specificity of the ELISA were obtained when the cut-off point of positivity was fixed at mean absorbance of negative sera + 2.58 sd. The specificity was then 97.6% either with M or CR antigen. The sensitivity was improved from 93.4% with CR to 98.2% with M antigen. Threshold values for a positive test varied between the 3 geographical areas tested. CW and M were also the most efficient antigens for discerning between serotypes of D. congolensis. The precision of the test was evaluated with CR antigen and expressed in residual expressed in residual coefficient of variation (CV). The precision was CV = 5.1% when each serum was titrated in duplicate and the antibody levels were expressed in absorbances. The expression of antibody levels in arbitrary standard units estimated from calibration curves reduced the precision (CV = 13.8%). Several methods were tested to decrease between plate variability but these did not greatly improve the reproducibility since it was shown that the main source of variation was within the plate.

Actinomycetales↗
PubMed1993

Epidemiological studies on dermatophilosis in the Caribbean.

Dermatophilosis is one of the most important diseases of domestic ruminants in the Caribbean islands where the clinical disease has been shown to be associated with the presence of the tick Amblyomma variegatum. Seroepidemiological studies were conducted to clarify the epidemiology of the disease in the region with a particular attention paid to the role of A. variegatum. A bank of 1300 cattle sera from the Lesser Antilles was screened by ELISA for the presence of antibodies to Dermatophilus congolensis. It appeared that seropositive animals do exist in islands non infested by A. variegatum and where dermatophilosis is never or seldom seen. Moreover, there was no significant difference in prevalence of seropositive animals between tick-infested and non infested areas of Martinique and Saint Lucia, 2 islands partly infested by the tick, and where dermatophilosis is only seen in tick-infested areas. Prevalence was low in small islands with a dry climate. This confirms experimental data showing that A. variegatum is not necessary for the transmission of D. congolensis which is widespread in most of the islands. High concentrations of prostaglandin E2 (between 151 and 377 ng/ml) and prostacyclin (between 124 and 134 ng/ml) found in the saliva of females A. variegatum strongly suggest that the tick could favour the development of the lesions through an immunomodulating activity of its saliva. However, despite some success in reproducing dermatophilosis on goats simultaneously infested with adult A. variegatum and scarified with Dermatophilus, no difference was observed between naturally resistant Creole cattle and very susceptible Brahman animals using the same model. The lesions of dermatophilosis remained very mild on animals of both breeds.(ABSTRACT TRUNCATED AT 250 WORDS)

Actinomycetales Infections↗
PubMed1992

Jurkat T cells express a functional neutral endopeptidase activity (CALLA) involved in T cell activation.

We have characterized a T lymphocyte endopeptidase activity that hydrolyses succinyl-alanine-alanine-phenylalanine-paranitroanilide (Suc-Ala-Ala-Phe-pNa). Hydrolysis of this substrate by intact Jurkat T cells was markedly enhanced when exogenous aminopeptidase N was added to the incubation medium. It thus appears that the release of paranitroaniline from Suc-Ala-Ala-Phe-pNA results from the combination of two distinct enzymatic activities: (i) an endopeptidase activity that cleaves the substrate at the alanyl bond and (ii) an aminopeptidase activity that ultimately cleaves the phenylalanyl bond. This cleavage was further confirmed by HPLC analysis. Specific endopeptidase 24.11 inhibitors were shown to inhibit the endopeptidase activity. These features are reminiscent of the characteristics of neutral endopeptidase (NEP, also known as endopeptidase 24.11, CALLA or CD10). Anti-CD10 monoclonal antibodies (mAbs) recognized the CD10+ B cell line Raji, but not Jurkat cells as assessed by FACS analysis. This is probably due to a lack of sensitivity of this method, the level of NEP activity in Jurkat T cells being 3-5% of that measured in B cell lines. Anti-CD10 mAbs immunoprecipitated endopeptidase 24.11 activities in both Jurkat T cells and Raji B cells, demonstrating that T lymphocytes express a CALLA-related endopeptidase. We also demonstrate that T and B cell endopeptidases have the same molecular weight, that T cells express less functional CALLA mRNA than B cells and that there are at least two shorter transcripts (1.8 and 0.8 kb) in both T and B cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1990

A chymotryptic-type serine protease is required for IL-2 production by Jurkat T cells.

Interleukin-2 (IL-2) production by activated Jurkat T cells was markedly delayed when these cells were treated with low concentrations of the chymotryptic-type protease inhibitor N-alpha-p-tosyl-L-phenylalanine chloromethylketone (TPCK). This increased lag time observed in the presence of TPCK directly correlates with the interaction of the inhibitor with a unique 42,000 molecular weight (MW) serine protease, which can be labelled with [3H]DFP, and was not due to an intracellular accumulation of a non-mature form of IL-2 nor to a non-specific inhibition of overall protein synthesis. The results presented in this report indicate that a 42,000 MW chymotryptic-like serine protease is required for IL-2 production by activated Jurkat T cells.

Cell Line↗
PubMed1989

[Postoperative lymph node scintigraphy in patients with malignant melanoma].

Completeness of regional lymph node dissection was controlled in 23 patients with melanoma malignum. For that purpose 3--6 weeks after block-dissection lymph node scintigraphy was performed, by administration of intercostal and interdigital radiopharmacutical. Blockdissection was considered as complete, when neither after intercostal, nor after interdigital administration, any lymph nodes were delineated. On the basis of investigations until now, postoperative lymph node scintigraphy proves to be suitable, held to be a non-invasive method for controlling completeness of blockdissection.

Adult↗
PubMed1988

[Scintigraphic studies of the lymph nodes in patients with melanoma following lymph node excision].

We report on 20 patients suffering from malignant melanoma, who had undergone regional lymph node dissection. In order to make certain that all the lymph nodes had been completely removed, we performed lymphoscintigraphy 3 to 6 weeks after block dissection with the help of a radiopharmacon intercostally or interdigitally applied. We judged the removal to be complete, if neither intercostal nor interdigital application led to any evidence of regional lymph nodes. On the basis of our experiences so far, we consider postoperative lymphoscintigraphy a suitable non-invasive method to check the completeness of block dissection.

Adult↗
PubMed1981

[Unguis incarnatus syndrome (author's transl)].

Authors establish the occurrence of unguis incarnatus syndrome of Steigleder and Stober-Münster in 114 patients with ingrowing nails. Disturbed carbohydrate metabolism deserves particular attention.

Acromegaly↗
PubMedDate not supplied

Screening of human bladder carcinomas for the presence of Ha-ras codon 12 mutation.

Contradictory results were obtained from previous studies aiming at defining the frequency of Ha-ras codon 12 mutations in bladder tumors. Differences in the sensitivities of the methods used could account for this discrepancy. In this study, we reevaluated the frequency of Ha-ras codon 12 mutations in a series of 87 human bladder tumors using a combination of two different methods. The first was derived from the protocol of Ooi et al and consisted in a one-step allele-specific polymerase chain reaction using mismatched primers in two separate PCR. This method is very rapid and highly sensitive, detecting the presence of minor populations (less than 10%) of mutant alleles. The second strategy consisted in screening all tumors using natural restriction fragment length polymorphism (RFLP) analysis. The two methods were in complete concordance and enabled us to show that only one out of 87 primary bladder carcinomas (1%) exhibited the mutation, in accordance with previous studies. These results strongly suggest that, even if minor cell populations overexpress codon 12 Ha-ras mutation, the analysis of this mutation cannot be used to screen potentially invasive transitional cell tumors of the bladder.

Base Sequence↗