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Biomedical subjects

M Conde

Publications and source records attributed to M Conde.

At least 19 recordsLinked to original sources
PubMed1999

Characterization of calcineurin in human neutrophils. Inhibitory effect of hydrogen peroxide on its enzyme activity and on NF-kappaB DNA binding.

We describe here a specific calcineurin activity in neutrophil lysates, which is dependent on Ca2+, inhibited by trifluoroperazine, and insensitive to okadaic acid. Immunoblotting experiments using a specific antiserum recognized both the A and B chains of calcineurin. Neutrophils treated with cyclosporin A or FK 506 showed a dose-dependent inhibition of calcineurin activity. The effect of oxidant compounds on calcineurin activity was also investigated. Neutrophils treated with hydrogen peroxide (H2O2), where catalase was inhibited with aminotriazole, exhibited a specific inhibition of calcineurin activity. However, the addition of reducing agents to neutrophil extracts partially reversed the inhibition caused by H2O2. A similar inhibitory effect of H2O2 on calcineurin activity was observed to occur in isolated lymphocytes. This is the first demonstration that redox agents modulate calcineurin activity in a cellular system. In addition, electrophoretic mobility shift assays revealed that lipopolysaccharide-induced activation of NF-kappaB in human neutrophils is inhibited by cell pretreatment with H2O2 in a dose-dependent manner. These data indicate that calcineurin activity regulates the functional activity of lipopolysaccharide-induced NF-kappaB/Rel proteins in human neutrophils. These data indicate a role of peroxides in the modulation of calcineurin activity and that the H2O2-dependent NF-kappaB inactivation in neutrophils occurs in concert with inhibition of calcineurin.

Calcineurin↗
PubMed1998

[Hepatocellular carcinoma associated to porphyria cutanea tarda and hepatitis C virus infection without cirrhosis].

The molecular basis of porphyria cutanea tarda is defective activity of hepatic uroporphyrinogen decarboxylase. A common characteristic is liver dysfunction than goes from cirrhosis to hepatocellular carcinoma. A high prevalence of hepatitis C virus markers has been demonstrated. We study a patient with PCT and hepatitis C virus markers that finally develops to hepatocellular carcinoma without previous cirrhosis. Previous studies with association of PCT and hepatitis C virus markers, have found liver diseases ranging from cirrhosis to hepatocellular carcinoma. The importance of this study is the absence of cirrhosis.

Carcinoma, Hepatocellular↗
PubMed1998

[The sensorineural component of hearing loss associated with cholesteatoma].

Patients with cholesteatoma often suffer neurosensorial hearing loss with variable bone conduction thresholds. Its origin is debated and has been attributed to the ototoxicity of topical drugs, immune reactions, effects of ototoxic antibiotics applied to the ear, etc. A selected series of 50 patients who underwent surgery for chronic ear disease due to cholesteatoma in our ENT department were studied to evaluate the possible origin of the bone conduction component of hearing loss. Different clinical, audiological, and surgical aspects were analyzed, including cholesteatoma site and extension, age, sex, evolution of the symptoms, pure tone audiometry data, middle ear involvement, the operation performed, and the occurrence of complications. Bone conduction thresholds were reported as pure tone differential thresholds (affected vs non-affected ear). A specific cholesteatoma-related neurosensorial hearing loss was observed that might lead to irreversible hearing loss. Neurosensorial involvement seems to be related mainly to the duration of symptoms, type of surgery, certain specific clinical aspects, and complications.

Adolescent↗
PubMed1997

A newly synthesized molecule derived from ruthenium cation, with antitumour activity, activates NADPH oxidase in human neutrophils.

To determine the nature of the mechanism by which certain derived ruthenium (Ru) complexes induce regression in tumour growth, we have investigated the possibility that this mechanism was associated with an increase of superoxide anion (O2-. production by phagocytic cells, which are usually found in tumour nodes. Here we present evidence that a newly synthesized complex, Ru3+-propylene-1, 2-diaminotetra-acetic acid (Ru-PDTA), derived from Ru and the sequestering ligand (PDTA), specifically stimulates O2-. production. This increase was associated with the translocation of cytosolic factors p47(phox) and p67(phox) of NADPH oxidase to the plasma membrane. The Ru-PDTA-complex-dependent O2-. production was abrogated by staurosporine, partially inhibited by diphenylene iodonium, and it was insensitive to pertussis toxin or dibutyryl cyclic AMP pretreatment. An increase of cytosolic Ca2+ levels were also detected in neutrophils treated with the Ru-PDTA complex. Also, Ru-PDTA complex induced the phosphorylation of tyrosine residues of several proteins as assessed by Western blotting. Present data are consistent with the possibility that Ru-PDTA-dependent antitumour effects are due in part to the complex's ability to stimulate the release of toxic oxygen metabolites from phagocytic cells infiltrating tumour masses.

Antineoplastic Agents↗
PubMed1997

The Bamako Initiative in Benin and Guinea: improving the effectiveness of primary health care.

The objective of the health system revitalization undergone in Benin and Guinea since 1986 is to improve the effectiveness of primary health care at the periphery. Second in a series of five, this article presents the results of an analysis of data from the health centres involved in the Bamako Initiative in Benin and Guinea since 1988. Data for the expanded programme of immunization, antenatal care and curative care, form the core of the analysis which confirms the improved effectiveness of primary health care at the peripheral level over a period of six years. The last available national data show a DPT3 immunization coverage of 80% in 1996 in Benin and 73% in 1995 in Guinea. In the Bamako Initiative health centres included in our analysis, the average immunization coverage, as measured by the adequate coverage indicator, increased from 19% to 58% in Benin and from less than 5% to 63% in Guinea between 1989 to 1993. Average antenatal care coverage has increased from 5% in Benin and 3% in Guinea to 43% in Benin and 51% Guinea. Utilization of coverage with curative care has increased from less than 0.05 visit per capita per year to 0.34 in Guinea and from 0.09 visit per capita per year to 0.24 in Benin. Further analysis attempts to uncover the reasons which underlie the different levels of effectiveness obtained in individual health centres. Monitoring and microplanning through a problem-solving approach permit a dynamic process of adaptation of strategies leading to a step by step increase of coverage over time. However, the geographical location of centres represents a constraint in that certain districts in both countries face accessibility problems. Outreach activities are shown to play an especially positive role in Guinea, in improving both immunization and antenatal care coverage.

Benin↗
PubMed1997

Implementation of the Bamako Initiative: strategies in Benin and Guinea.

Two West African countries, Benin and Guinea, have been reorganizing their peripheral health systems since 1986, with the goal of improving access to primary health care (PHC). A comprehensive approach evolve, based on improving effectiveness, optimizing efficiency, ensuring financial variability and promoting equity. These strategies were launched as the Bamako Initiative by the World Health Organization's Regional Assembly in 1987. This is the first in a series of five articles on the Bamako Initiative in Benin and Guinea. The strategies implemented in these two countries are discussed. Subsequent articles discuss the improved health indicators, impact on service costs efficiency, and community empowerment through local cost recovery and equity implications. The health center is the basis for a revitalized primary care system. From here, an integrated minimum health care package is readily accessible to meet basic community health needs. Through the Bamako Initiative program, drugs and other essential resources are always available, regular contract between the community health service providers and communities has increased, and the quality of care has improved while also becoming more efficient. Community health resources are managed locally through joint microplanning and monitoring, involving health personnel and village committees. Community ownership, fostered by local budgeting and decision making, is an essential pillar for the success of the system.

Benin↗
PubMed1997

Nicotinamide inhibits inducible nitric oxide synthase enzyme activity in macrophages by allowing nitric oxide to inhibit its own formation.

Nitric oxide (NO) production by macrophages is mainly regulated by induction of nitric oxide synthase (iNOS) by cytokines and microbial products. Nicotinamide (NIC) inhibits NO production by activated macrophages in a dose dependent manner. NIC also inhibits NOS enzyme activity in extracts from activated macrophages. The inhibition was noncompetitive with L-arginine (Ki 13.37 +/- 4.40 mM, n=3), uncompetitive versus NADPH (Ki 3.06 +/- 0.17 mM, n=3) and tetrahydrobiopterin. Finally, the inhibition by nicotinamide was fully reversed by scavenging NO with hemoglobin. We suggest that NIC acts by allowing NO to inhibit its own formation.

Animals↗
PubMed1997

[Deafness secondary to lumbar puncture].

INTRODUCTION AND OBJECTIVE: Disorders of hearing have been described in patients who have undergone lumbar puncture. The lower frequencies are most affected, temporarily and with spontaneous recovery in most cases. It would seem that the cochlea aqueduct (AC) (an anatomical structure found in the internal ear) is the part involved in the pathogenesis of this infrequent complication. The object of this paper is to review the different hypothesis put forward by various authors on the subject, emphasizing the one which seems most probable. At the same time, we offer a new vision of this little known and often forgotten anatomical structure of the internal ear. The anatomy and physiology of the AC is considered, studying the part played by the labyrinth fluid when the patient undergoes an operation involving the cerebro-spinal fluid (CSF) or the subarachnoid space. CONCLUSIONS: Whenever this technique is to be used, it is essential to obtain a clinical history to find out whether the patient has, or has had, any problems of hearing, and if so of what type. All patients should be warned of the possibility of deafness, in most cases temporary, and if the patient has hydrops endolymphaticus (syndrome of Ménière) of the high risk of worsening his hearing threshold. We therefore recommend precise evaluation of the use of this technique.

Audiometry↗
PubMed1996

Enhancement of Antigen-specific functional responses by neutrophils from allergic patients.

It has been demonstrated that neutrophils from healthy donors or from patients with inflammatory disorders can bind immunoglobulin (Ig) E proteins through binding to Mac-2/epsilon bp. Functional responses to allergens were assessed by measuring the respiratory burst and intracellular Ca2+ levels, and binding of allergens to neutrophils was assessed by flow cytometry analysis and fluorescence microscopy. In this article, we demonstrate that neutrophils sensitized to specific allergens (from allergic patients), but not from healthy donors, are sensitive to allergens of the same type as those that produce clinical allergic symptoms. The activation of neutrophils was analyzed by the induction of a respiratory burst that was detected with luminol-dependent chemiluminescence. Intracellular Ca2+ levels increased parallel to those of the inducing allergens. In addition, the specific binding of allergens on the cell surface was revealed by flow cytometry and allergen-FITC-labeled staining analyses. The present data suggest a restricted recognition of allergen by sensitive neutrophils, probably associated with the specific binding of the allergen to its corresponding IgE molecule, which is bound to the Mac-2/epsilon bp structure. These findings demonstrate a functional role of allergen-associated neutrophils during the allergic state.

Allergens↗
PubMed1996

Anti-CD69 antibodies enhance phorbol-dependent glucose metabolism and Ca2+ levels in human thymocytes. Antagonist effect of cyclosporin A.

The human activation antigen CD69 is an early inducible surface glycoprotein acquired by T cells in the thymus at the stage of positive selection and during activation of mature lymphoid cells both in vivo and in vitro. We have studied the regulatory influence of CD69 activation pathway on the glycolytic process and transduction signals of thymocytes. Treatment of human thymocytes with different anti-CD69 monoclonal antibodies (mAbs), in the presence of submitogenic doses of phorbol ester, produced an enhanced release of lactate without significant alterations in Fru 2,6-P2 levels or phosphofructokinase-2 (PFK-2) and pyruvate kinase activities. A small increase in phosphofructokinase-1 (PFK-1) activity was also detected. Furthermore, anti-CD69 mAb increased the glucose detritiation from [2-3H] and [3-3H]glucose, thus indicating an enhanced flux through hexokinase and PFK-1 steps. In addition, de novo synthesis of diacylglycerol and intracellular Ca2+ levels increased after anti-CD69 mAb treatment. The stimulatory effects of anti-CD69 mAb on both glycolysis and Ca2+ levels were inhibited by cyclosporin A. Because CD69 molecules are present in certain subset populations of immature thymocytes, the ability of anti-CD69 mAb to stimulate the glycolysis, the synthesis of diacylglycerol and the intracellular Ca2+ levels suggest that the activation signals delivered through CD69 molecules could play a role in the thymus cells maturation.

Antibodies, Monoclonal↗
PubMed1996

Streptozotocin-induced diabetes increases fructose 2,6-biphosphate levels and glucose metabolism in thymus lymphocytes.

Acute effect of streptozotocin-induced diabetes on several parameters of glucose metabolism was investigated in thymus lymphocytes (thymocytes). The cells from diabetics rats accumulated in vitro about 2-fold more fructose 2,6-bisphosphate (Fru-2, 6-P2) in the presence of increasing glucose concentration than cells from normal rats. An increased production of lactate was also observed. Phosphofructokinase-1 (PFK-1) and phosphofructokinase-2 (PFK-2) activities were enhanced in cells from diabetic rats compared with those from normal rats. [U-14C]glucose incorporation into glycogen was also increased in cells from diabetic rats and the 14CO2 liberation was lesser than in cells from normal animals. From these data it may be concluded that the response of thymocytes to streptozotocin-induced diabetes is similar to that observed in other extrahepatic tissues.

Animals↗
PubMed1996

Protection from nicotinamide inhibition of interleukin-1 beta-induced RIN cell nitric oxide formation is associated with induction of MnSOD enzyme activity.

We have studied the long-term effects of nicotinamide (NIC) on the synthesis of NO by insulin producing cells. NIC delays the formation of nitrite by interleukin (IL)-1 beta-(IL-1, 25 U/ml)-stimulated RINm5F cells, and previous exposure of cells to IL-1 for 15 h prevents this effect. The delay is associated with a lack of cytokine-induced inducible nitric oxide synthase (iNOS) enzyme activity in cell extracts. NIC (20 mM) inhibits NO synthase (NOS) activity in extracts from cells incubated with IL-1 for 6 h and 24 h, and oxyhemoglobin counteracts this inhibition. Hence, NIC could scavenge O2- and allow NO to inhibit the enzyme. The NO donor SIN-1 inhibits in a concentration-dependent manner iNOS activity, and the effect is potentiated by NIC. In intact cells, protection from NIC is associated with IL-1-induced expression of MnSOD activity, and reversible blockade of iNOS expression with pyrrolidine dithiocarbamate counteracts the NIC effect. We conclude that O2- plays a role in preventing NO inhibition of iNOS. The loss of this action coincides with the induction of MnSOD enzyme activity. In addition, the stimulation by NIC of IL-1-induced nitrite production in pyrrolidine dithiocarbamate-treated cells is a novel action that should be considered when the drug is proposed as potential agent for the prevention of insulin-dependent diabetes mellitus.

Animals↗
PubMed1996

Respiratory burst is decreased by human hyperlipemic serum in rat peritoneal macrophages.

The effect of hyperlipemic human serum on superoxide anion (O2-) production by rat peritoneal macrophages was investigated. Phorbol myristate acetate (PMA)-stimulated O2- production was inhibited when cells were preincubated with hyperlipemic human serum. This inhibition was specifically carried out by a lipid fraction and was dependent on both cholesterol and triglyceride serum levels. This inhibitory effect was not exerted by a direct effect on NADPH-oxidase activity, nor by a putative superoxide dismutase activity present in the serum. With human neutrophils, we observed a decreased mobility of the cytosolic factor p47-phox to the membrane during the activation process, caused by hyperlipemic serum. We did not find any effect of hyperlipemic serum on NO2- production by cultured rat macrophages. These results suggest that a pathological increase of circulating plasma lipids may be associated with an impaired inflamatory capacity of macrophages.

Animals↗
PubMed1996

Thrombin-stimulated phospholipase C activity is inhibited without visible delay by a rapid increase in the cyclic GMP levels induced by sodium nitroprusside.

Different drugs that elevate the cGMP levels inhibit the agonist-induced platelet activation. The mechanisms of action of cGMP probably include inhibition of both phospholipase C and the increase in intracellular Ca2+ concentration, and these effects seem to be mediated by cGMP-dependent protein kinases. However, in most studies, cells were preincubated with nitrovasodilators before stimulation. The effect of the preincubation with sodium nitroprusside before stimulation or the simultaneous addition of sodium nitroprusside and thrombin has been compared. The simultaneous addition of sodium nitroprusside and thrombin was able to inhibit without any significant delay the platelet aggregation. This rapid effect was correlated with an inhibition of both the maximum increase in intracellular Ca2+ concentration and the phospholipase C activity. Also, the simultaneous addition of sodium nitroprusside and thrombin clearly accelerated the decline in the Ca2+ signal, which was not observed in platelets preincubated with sodium nitroprusside. The rapid inhibition induced by sodium nitroprusside was correlated with a rapid and significant increase in the cGMP levels and reversed when platelets were pretreated with methylene blue. The inhibitor of cAMP-dependent protein kinase Rp-8-(4-chlorophenylthio)-adenosine-3',5'-cyclic monophosphorothioate was able to abolish nearly completely the inhibitory effect induced by sodium nitroprusside independent of the protocol used. Thus, the rapid inhibition induced by sodium nitroprusside seems to be induced by a rapid phosphorylation-dependent mechanism. In addition, both cGMP- and cAMP-dependent protein kinase seem to be involved; however, the cAMP-dependent protein kinase seems to be more important.

Calcium↗
PubMed1995

Decrease in free-radical production with age in rat peritoneal macrophages.

The respiratory-burst reaction has been studied in rat peritoneal macrophages of different ages (3, 12 and 24 months) using phorbol 12-myristate 13-acetate (PMA) to stimulate NADPH oxidase. Production of O2-. and H2O2 decreased with age (about 50 and 75% respectively); however, no difference in NADPH oxidase activity was found. NO. production was also reduced with age (40%). Furthermore, a progressive and significant decrease in the pentose phosphate flux was detected as a function of age in control and PMA-stimulated macrophages. The NADPH/NADP+ ratio decreased with age in control and PMA-stimulated macrophages. Glucose uptake was lower in middle-aged (12 months) and old (24 months) animals but no differences were found between these groups.

Aging↗
PubMed1995

Effect of thimerosal and other sulfhydryl reagents on calcium permeability in thymus lymphocytes.

We have studied the effects of thimerosal, a mercurial compound extensively used as a preservative, as well as other sulfhydryl reagents (e.g. p-hydroxymercurybenzoate, hydrogen peroxide, bromophenacyl bromide, and mercuric chloride) on Ca2+ homeostasis and the redox status of sulfhydryl groups in thymus lymphocytes. They all induced an increase in [Ca2+]i which was blocked with dithiothreitol, suggesting that they act via the oxidation or blockade of sulfhydryl groups. [Ca2+]i increase could be directly related to the effect of the different reagents on cellular protein sulfhydryl content. Experiments with ethidium bromide indicate that the observed rise in [Ca2+]i was not due to a non-specific increase in membrane permeability. Thimerosal differs from the other agents studied in its oxidative properties, which is probably linked to the production of a potent reductor molecule, thiosalicylic acid, which may modulate its oxidative capacity.

Animals↗
PubMed1995

Modulation of phorbol ester-induced respiratory burst by vanadate, genistein, and phenylarsine oxide in mouse macrophages.

The effect of the inhibitors of tyrosine phosphatase (vanadate and phenylarsine oxide) and of an inhibitor of tyrosine kinase (genistein) on O2.- production in mouse peritoneal macrophages was examined. Vanadate and phenylarsine oxide produced a dose-dependent inhibition of phorbol myristate acetate (PMA)-induced O2.- production, whereas genistein potentiated O2.- production triggered by phorbol ester. Vanadate had no effect on the respiratory burst in human neutrophils challenged with fMLP, in agreement with previously published data on human intact neutrophils. It did not alter reduced nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase activity in membrane preparations of mouse peritoneal macrophages. These data suggest that the phosphorylation of protein(s) in tyrosine residues blocked the PMA-dependent respiratory burst in mouse macrophages.

Animals↗