Biomedical subjects

Carlos Martínez

Publications and source records attributed to Carlos Martínez.

13 recordsLinked to original sources

PubMed2006

SOCS up-regulation mobilizes autologous stem cells through CXCR4 blockade.

The chemokine CXCL12 influences self-renewal and differentiation of hematopoietic stem cell precursors in bone marrow by directing them toward specific stromalcell components. CXCL12 up-regulates members of the SOCS family through JAK/STAT activation, a mechanism that attenuates chemokine responses. SOCS expression may thus modulate retention of hematopoietic precursors (Sca-1(+) c-Kit(+)Lin(-) cells) in bone marrow. We show that in bovine growth hormone transgenic mice and in growth hormone-treated mice, SOCS up-regulation correlated with a large number of Sca-1(+) c-Kit(+)Lin(-) cells in blood. Retroviral transduction of SOCSs blocked in vitro migration of Sca-1(+)c-Kit(+)Lin(-) cells, as well as their capacity to reconstitute lethally irradiated mice. Furthermore, in lethally irradiated mice reconstituted with bone marrow infected by a tetracycline-regulated, SOCS-expressing lentiviral vector, doxycycline treatment promoted rapid, extensive precursor mobilization to the periphery. The results indicate that by blocking CXCR4-mediated functions, SOCSs modulate hematopoietic precursor cell retention in bone marrow, and suggest the therapeutic interest of SOCS manipulation in several pathologic situations.

Animals↗

PubMed2006

Opioids trigger alpha 5 beta 1 integrin-mediated monocyte adhesion.

Inflammatory reactions involve a network of chemical and molecular signals that initiate and maintain host response. In inflamed tissue, immune system cells generate opioid peptides that contribute to potent analgesia by acting on specific peripheral sensory neurons. In this study, we show that opioids also modulate immune cell function in vitro and in vivo. By binding to its specific receptor, the opioid receptor-specific ligand DPDPE triggers monocyte adhesion. Integrins have a key role in this process, as adhesion is abrogated in cells treated with specific neutralizing anti-alpha5beta1 integrin mAb. We found that DPDPE-triggered monocyte adhesion requires PI3Kgamma activation and involves Src kinases, the guanine nucleotide exchange factor Vav-1, and the small GTPase Rac1. DPDPE also induces adhesion of pertussis toxin-treated cells, indicating involvement of G proteins other than Gi. These data show that opioids have important implications in regulating leukocyte trafficking, adding a new function to their known effects as immune response modulators.

Animals↗

PubMed2006

G protein-coupled receptor dimerization and signaling.

G protein-coupled receptors are involved in the regulation of many aspects of normal physiology and pathology. Recent research has broadened our view of how the cell transduces ligand binding to cellular responses. It is becoming clear that phenomena that take place both at the cell surface, such as receptor oligomerization, as well as intracellularly, such as interaction between different signaling pathways, have important roles in the response elicited by a ligand. The study of these events requires the combined use of classical biochemical techniques with novel methods that allow analysis of these mechanisms. This chapter gives an overview of both types of techniques, with an emphasis on discussing their main applications and the conclusions that can be drawn in each case.

Calcium↗

PubMed2005

Effect of pulsed estrogen therapy on hemostatic markers in comparison with oral estrogen regimen in postmenopausal women.

BACKGROUND/AIMS: Hormone replacement therapy (HRT) is associated with an increased risk of thromboembolism dependent on the type of HRT; therefore, we compared therapy effects of intranasal with oral estrogens on coagulation and fibrinolysis markers in postmenopausal women. METHODS: A randomized study in which 29 healthy hysterectomized women received intranasal 17beta-estradiol or oral estrogens for 3 months. RESULTS: There were no significant differences in the baseline characteristics between groups. Those women receiving intranasal estradiol showed a mild increment in plasminogen activator inhibitor-1 (PAI-I) (from 6.8 +/- 3.5 to 9.6 +/- 3.9 U/ml, p < 0.01); however, fibrinogen, factor VII-tissue factor complex (VIIa-rTF), antithrombin III (ATIII), protein C (PC) activity, protein S (PS) activity, plasminogen (PLG), and tissue-type plasminogen activator antigen (t-PA) were unchanged. In contrast, oral unopposed estrogens elevated t-PA (from 4.9 +/- 2.9 to 9.6 +/- 5.1 ng/ml, p < 0.01) in parallel with a decrement in PAI-I (from 5.2 +/- 4.0 to 2.7 +/- 1.7 U/ml, p < 0.05) and VIIa-rTF (from 201.2 +/- 181.0 to 140.6 +/- 108.7 mU/ml, p < 0.05). Fibrinogen, ATIII, PC, PS, and PLG were unchanged. CONCLUSIONS: Nasal 17beta-estradiol had no effect on the coagulation markers, except a moderate increment in PAI-1. In contrast, oral estrogens elicited a decrement in both VIIa-rTF and PAI-1; however, those changes did not surpass normal limits.

Administration, Intranasal↗

PubMed2005

Comparison between logistic regression and neural networks to predict death in patients with suspected sepsis in the emergency room.

INTRODUCTION: Neural networks are new methodological tools based on nonlinear models. They appear to be better at prediction and classification in biological systems than do traditional strategies such as logistic regression. This paper provides a practical example that contrasts both approaches within the setting of suspected sepsis in the emergency room. METHODS: The study population comprised patients with suspected bacterial infection as their main diagnosis for admission to the emergency room at two University-based hospitals. Mortality within the first 28 days from admission was predicted using logistic regression with the following variables: age, immunosuppressive systemic disease, general systemic disease, Shock Index, temperature, respiratory rate, Glasgow Coma Scale score, leucocyte counts, platelet counts and creatinine. Also, with the same input and output variables, a probabilistic neural network was trained with an adaptive genetic algorithm. The network had three neurone layers: 10 neurones in the input layer, 368 in the hidden layer and two in the output layer. Calibration was measured using the Hosmer-Lemeshow goodness-of-fit test and discrimination was determined using receiver operating characteristic curves. RESULTS: A total of 533 patients were recruited and overall 28-day mortality was 19%. The factors chosen by logistic regression (with their score in parentheses) were as follows: immunosuppressive systemic disease or general systemic disease (2), respiratory rate 24-33 breaths/min (1), respiratory rate > or = 34 breaths/min (3), Glasgow Come Scale score < or = 12 (3), Shock Index > or = 1.5 (2) and temperature < 38 degrees C (2). The network included all variables and there were no significant differences in predictive ability between the approaches. The areas under the receiver operating characteristic curves were 0.7517 and 0.8782 for the logistic model and the neural network, respectively (P = 0.037). CONCLUSION: A predictive model would be an extremely useful tool in the setting of suspected sepsis in the emergency room. It could serve both as a guideline in medical decision-making and as a simple way to select or stratify patients in clinical research. Our proposed model and the specific development method -- either logistic regression or neural networks -- must be evaluated and validated in an independent population.

Adolescent↗

PubMed2005

Transdermal estradiol does not impair hemostatic biomarkers in postmenopausal women.

OBJECTIVE: To evaluate the effect of transdermal estradiol therapy (ET) on coagulation and fibrinolysis markers in postmenopausal women. METHODS: Prospective open trial study in 59 healthy hysterectomized postmenopausal women. Thirty women received transdermal ET (50 microg per day) during 3 months and 29 women formed the untreated arm. RESULTS: Baseline factor VII-tissue factor complex (VIIa-rTF), fibrinogen and plasminogen activator inhibitor-1 (PAI-1) levels decreased significantly (P < 0.01) after therapy. In contrast, tissue-type plasminogen activator antigen (t-PA) levels increased significantly (P < 0.01). After ET, there was no difference in protein C activity (PC), protein S activity (PS), plasminogen (PLG), and antithrombin III (ATIII) levels. None of participants reported thromboembolic events. CONCLUSION: ET elicited a decrement in blood biomarkers implicated in coagulation activation which in turn seemed to improve fibrinolytic activity. These results suggest that transdermal route does not impair thrombotic risk.

Administration, Cutaneous↗

PubMed2005

MLH1 and MSH2 mutations in Colombian families with hereditary nonpolyposis colorectal cancer (Lynch syndrome)--description of four novel mutations.

This study searched for mutations in the MLH1 and MSH2 genes in 23 unrelated Colombian families with suspected hereditary nonpolyposis colorectal cancer (HNPCC). The families were grouped according to the fulfillment of the Amsterdam II criteria or the Bethesda guidelines. We screened all probands by single-strand conformational polymorphism (SSCP) and direct DNA sequencing. Eleven families fulfilled the Amsterdam criteria II and 12 families the Bethesda guidelines. Germline mutations were detected in 11 families, which corresponds to a mutation detection rate of 48%. When only families fulfilling the Amsterdam II criteria were analyzed, the mutation detection rate rose to 82%. Only 8% of the mutation detection rate was found in families following the Bethesda guidelines. Three mutations were shared by two different families, which corresponds to a total of eight different mutations, seven of them found in the MLH1 gene and one in the MSH2 gene. We have identified four mutations that have not been previously reported to the International Collaborative Group of HNPCC. Three of these are pathogenic, a single base substitution (C > T) at codon 640, exon 17, a G deletion at codon 619, exon 16 and in the MLH1 gene and a two-nucleotide deletion (TG) at codon 184, exon 3 in the MSH2. Also, an unclassified variant, a substitution (C > G) at the codon 141, exon 5 of the MLH1, was detected.

Adaptor Proteins, Signal Transducing↗

PubMed2005

[Detection mutations in the DNA mismatch repair genes of hMLH1 and hMSH2 genes in Colombian families with suspicion of hereditary non-polyposis colorectal carcinoma (Lynch syndrome)].

INTRODUCTION: Colorectal cancer (CRC) is the second highest cause of cancer mortality in developed countries. In Colombia, CRC ranks fifth as a cause of cancer death. Approximately 75% of CRC appear to be spontaneous and 25% are familial, with 5% of the latter clearly hereditary. Of these, hereditary non-polyposis colorectal carcinoma (HNPCC)-or Lynch syndrome is the most important. OBJECTIVE: Herein, the two most important genes involved in Lynch syndrome, the hMLH1 and hMSH2 were analyzed for presence of mutations. MATERIALS AND METHODS: Seventeen Colombian families that fulfilled the Amsterdam II criteria or Bethesda guidelines for Lynch syndrome were selected. The of 35 exons of hMLH1 and hMSH2 genes were screened by SSCP and those with electrophoretic variants were sequenced. RESULTS: Eight germinal mutations were detected, corresponding to a 47% detection mutation rate. Six of the eight mutations have previously been reported. These consisted of the following mutations: a single base substitution at the donor splicing site of exon 9, a single base substitution (A>G) at codon 755 of the exon 17, and another single base substitution (G>A) at codon 681 of exon 18. The two novel mutations consisted of a single base substitution (C>T) at codon 640 of exon 17 of the hMLH1 gene and a two-nucleotide deletion (TG) at codon 184 of exon 3 of hMSH2 gene. In addition, two families were observed with a polymorphism in the intron 13 (G>A) nt 1558+14, of hMLH1 gene. CONCLUSIONS: This study represented the first survey for detecting mutations associated with Lynch syndrome in Colombia, and is intended to lead to the establishment of a management and prevention program.

Adaptor Proteins, Signal Transducing↗

PubMed2003

Structure and molecular interactions of a unique antitumor antibody specific for N-glycolyl GM3.

N-glycolyl GM3 ganglioside is an attractive target antigen for cancer immunotherapy, because this epitope is a molecular marker of certain tumor cells and not expressed in normal human tissues. The murine monoclonal antibody 14F7 specifically recognizes N-glycolyl GM3 and shows no cross-reactivity with the abundant N-acetyl GM3 ganglioside, a close structural homologue of N-glycolyl GM3. Here, we report the crystal structure of the 14F7 Fab fragment at 2.5 A resolution and its molecular model with the saccharide moiety of N-glycolyl GM3, NeuGcalpha3Galbeta4Glcbeta. Fab 14F7 contains a very long CDR H3 loop, which divides the antigen-binding site of this antibody into two subsites. In the docking model, the saccharide ligand is bound to one of these subsites, formed solely by heavy chain residues. The discriminative feature of N-glycolyl GM3 versus N-acetyl GM3, its hydroxymethyl group, is positioned in a hydrophilic cavity, forming hydrogen bonds with the carboxyl group of Asp H52, the indole NH of Trp H33 and the hydroxyl group of Tyr H50. For the hydrophobic methyl group of N-acetyl GM3, this environment would not be favorable, explaining why the antibody specifically recognizes N-glycolyl GM3, but not N-acetyl GM3. Mutation of Asp H52 to hydrophobic residues of similar size completely abolished binding. Our model of the antibodycarbohydrate complex is consistent with binding data for several tested glycolipids as well as for a variety of 14F7 mutants with replaced VL domains.

Animals↗

PubMed2003

Enhanced antitumor immunity in mice deficient in CD69.

We investigated the in vivo role of CD69 by analyzing the susceptibility of CD69-/- mice to tumors. CD69-/- mice challenged with MHC class I- tumors (RMA-S and RM-1) showed greatly reduced tumor growth and prolonged survival compared with wild-type (WT) mice. The enhanced anti-tumor response was NK cell and T lymphocyte-mediated, and was due, at least in part, to an increase in local lymphocytes. Resistance of CD69-/- mice to MHC class I- tumor growth was also associated with increased production of the chemokine MCP-1, diminished TGF-beta production, and decreased lymphocyte apoptosis. Moreover, the in vivo blockade of TGF-beta in WT mice resulted in enhanced anti-tumor response. In addition, CD69 engagement induced NK and T cell production of TGF-beta, directly linking CD69 signaling to TGF-beta regulation. Furthermore, anti-CD69 antibody treatment in WT mice induced a specific down-regulation in CD69 expression that resulted in augmented anti-tumor response. These data unmask a novel role for CD69 as a negative regulator of anti-tumor responses and show the possibility of a novel approach for the therapy of tumors.

Animals↗

PubMed2003

Chemokines integrate JAK/STAT and G-protein pathways during chemotaxis and calcium flux responses.

The JAK/STAT (Janus kinase / signaling transducer and activator of transcription) signaling pathway is implicated in converting stationary epithelial cells to migratory cells. In mammals, migratory responses are activated by chemoattractant proteins, including chemokines. We found that by binding to seven-transmembrane G-protein-coupled receptors, chemokines activate the JAK/STAT pathway to trigger chemotactic responses. We show that chemokine-mediated JAK/STAT activation is critical for G-protein induction and for phospholipase C-beta dependent Ca(2+) flux; in addition, pharmacological inhibition of JAK or mutation of the JAK kinase domain causes defects in both responses. Furthermore, G alpha(i) association with the receptor is dependent on JAK activation, and the chemokine-mediated Ca(2+) flux that requires phospholipase C-beta activity takes place downstream of JAK kinases. The chemokines thus employ a mechanism that links heterologous signaling pathways--G proteins and tyrosine kinases--in a network that may be essential for mediating their pleiotropic responses.

Calcium↗

PubMed2003

Thrombin generation in platelet-poor plasma is normal in patients with hereditary mucocutaneous haemorrhages.

Mild hereditary bleeding disorders presenting with mucocutaneous haemorrhages are usually difficult to diagnose. We measured thrombin generation in platelet-poor plasma (TG-PPP) in 206 patients with a clinically unequivocal bleeding tendency: 45 with von Willebrand disease (vWD), 49 with platelet aggregation/secretion defects (PASD), 10 with a combination of both and 102 who did not fit the diagnostic criteria for any known haemostatic disorder. TG-PPP was not significantly different from controls in all patient groups, indicating that an abnormality in the plasmatic clotting system is unlikely to contribute to the bleeding in patients with type 1 vWD and PASD. In patients with undiagnosed mild hereditary bleeding disorders, there must be other mechanisms which explain the abnormal haemorrhagic tendency, most likely as yet unrecognized defects in platelet-vessel wall interaction. As a next step we plan to investigate thrombin generation in PRP.

Adolescent↗

PubMed2003

Amikacin alters auditory brainstem conduction time in newborns.

The purpose of this paper was to describe whether there are some relationships between amikacin serum levels and central conduction time in brainstem auditory evoked potentials (BAEP) within therapeutic range levels in newborns as index of drug toxicity in brainstem auditory centers in neonatally exposed infants. We performed a cross-sectional study to compare BAEP from 35 infants under amikacin administration and 24 control infants; both examinations were blinded to investigators. Bivariate and partial correlations were calculated between amikacin and BAEP measurements in treated infants. Amikacin determinations were within therapeutic levels. No clinical alterations in BAEP were found and no differences between amikacin-treated and control infants were found. Significant positive Pearson correlation between latency of I-III interwaves interval and amikacin Cmin serum levels was found and was present when calculations were controlled by partial correlations for gestational age at birth and Apgar score at 5 min. The findings suggest that increased amikacin levels in newborns are related to increased latencies in I-III interwave interval in infants, which may be an early index of brainstem effects of subclinical neurotoxicity of amikacin.

Amikacin↗