Biomedical subjects

D Martinez

Publications and source records attributed to D Martinez.

At least 19 recordsLinked to original sources

PubMed2006

Trocar site hernia after laparoscopic ventral hernia repair.

BACKGROUND: The incidence of trocar site hernia (TSH) after laparoscopic ventral hernia repair (LVHR) is reported to be low. The present study investigates the associated risk factors, with a view to preventing this complication. METHODS: A retrospective study was made of the incidence of TSH in a personal series of LVHR, recording anthropometric and clinical data on the patients. Risk factors were assessed by bivariate and multivariate analyses. The patients were subjected to clinical and telephone follow-up. RESULTS: In a series of 27 LVHR, the incidence of TSH was 22% (6 patients). The use of meshes larger than 10 x 15 cm for LVHR was the only TSH risk factor to reach statistical significance. Female gender and diabetes showed a higher incidence in the TSH group. CONCLUSIONS: The use of large meshes may be a risk factor for TSH. We believe this to be due to dilatation of the trocar orifice during introduction of the mesh, and also to postoperative retraction of the mesh.

Adult↗

PubMed2006

Six years experience in intracoronary brachytherapy procedures: patient doses from fluoroscopy.

Typical patient dose levels during intracoronary brachytherapy (ICB) procedures using beta sources were determined across a sample of 221 treatments. Dose-area product values, fluoroscopy time and number of frames per procedure, with median values of 62 Gy cm2, 17.0 min and 1493 images, respectively, resulted in a 20% to 50% increase in the values measured for percutaneous transluminal coronary angioplasty procedures in the same medical centre (median values 41 Gy cm2, 14.3 min and 1078 images). Likely reasons for this increase include the additional complexity of ICB, the need for recording and reporting every step of the treatment, getting the essential parameters for the volume determination of the lesion and therapeutic radiation dose calculation and, finally, the learning curve for this kind of procedure. A high concentration skin dose distribution during ICB procedures was measured and in 12% of the patients peak skin doses higher than 1.5 Gy were confirmed. 10 patients were submitted to clinical follow-up and skin injuries were not identified.

Angioplasty, Balloon, Coronary↗

PubMed2006

Risk factors for encephalitis and death from West Nile virus infection.

We conducted a nested case-control study to determine potential risk factors for developing encephalitis from West Nile virus (WNV) infection. Retrospective medical chart reviews were completed for 172 confirmed WNV cases hospitalized in Houston between 2002 and 2004. Of these cases, 113 had encephalitis, including 17 deaths, 47 had meningitis, and 12 were fever cases; 67% were male. Homeless patients were more likely to be hospitalized from WNV compared to the general population. A multiple logistic regression model identified age [odds ratio (OR) 1.1, P<0.001], history of hypertension, including those cases taking hypertension-inducing drugs (OR 2.9, P=0.012), and history of cardiovascular disease (OR 3.5, P=0.061) as independent risk factors for developing encephalitis from WNV infection. After adjusting for age, race/ethnicity (being black) (OR 12.0, P<0.001), chronic renal disease (OR 10.6, P<0.001), hepatitis C virus (OR 23.1, P=0.0013), and immunosuppression (OR 3.9, P=0.033) were identified as risk factors for death from WNV infection.

Adolescent↗

PubMed2006

Mutant p53 protein in serum could be used as a molecular marker in human breast cancer.

p53 wild-type is a tumor suppressor gene involved in DNA gene transcription or DNA repair mechanisms. When damage to DNA is unrepairable, p53 induces programmed cell death (apoptosis). The mutant p53 gene is the most frequent molecular alteration in human cancer, including breast cancer. Here, we analyzed the genetic alterations in p53 oncogene expression in 55 patients with breast cancer at different stages and in 8 normal women. We measured by ELISA assay the serum levels of p53 mutant protein and p53 antibodies. Immunohistochemistry and RT-PCR using specific p53 primers as well as mutation detection by DNA sequencing were also evaluated in breast tumor tissue. Serological p53 antibody analysis detected 0/8 (0%), 0/4 (0%) and 9/55 (16.36%) positive cases in normal women, in patients with benign breast disease and in breast carcinoma, respectively. We found positive p53 mutant in the sera of 0/8 (0.0%) normal women, 0/4 (0%) with benign breast disease and 29/55 (52.72%) with breast carcinoma. Immunohistochemistry evaluation was positive in 29/55 (52.73%) with mammary carcinoma and 0/4 (0%) with benign breast disease. A very good correlation between p53 mutant protein detected in serum and p53 accumulation by immunohistochemistry (83.3% positive in both assays) was found in this study. These data suggest that detection of mutated p53 could be a useful serological marker for diagnostic purposes.

Adult↗

PubMed2005

Role of endogenous channels in red blood cells response to their exposure to the pore forming toxin Sticholysin II.

Sticholysin II (St II) is a highly hemolytic cytolysin isolated from the sea anemone Stichodactyla heliantus. The toxin hemolytic action takes place through the formation of channels that provoke an electrolyte unbalance leading to osmotic shock. The lytic event must involve the exchange of electrolytes and the entrance of water, leading to red blood cell disruption. These processes can occur through St II pores and/or the endogenous red blood cells transporters. In order to evaluate the contribution of these channels to water, anion and cation transport, we have measured the hemolysis and K+ efflux rates in the presence of several specific inhibitors. The results obtained in the presence of Hg, an AQP1 blocker, indicate that water transport through these channels is not essential for the occurrence of the lytic process induced by St II. The data also support a partial role of K+ and anion transporters. In particular, they are compatible with a preferential K+ efflux though the K(+)/Cl- co-transport as a response to the promoted swelling. Furthermore, they suggest that chloride influx, a process that can regulate both K+ efflux and lysis, is partially mediated by the endogenous cell transporters, in particular, band-3 anion exchange system being relevant at early stages of the lytic process.

Animals↗

PubMed2005

Grain morphology and trapping effects on electron transport in dye-sensitized nanocrystalline solar cells.

We have examined the combined effects of grain morphology and electron trapping on the transient response of photoelectrons moving through the TiO2 grains in a dye-sensitized nanocrystalline solar cell using a multi-time-scale random walk Monte Carlo model. Our use of a multi-time-scale approach enables us to simulate transport for electrons moving through spherical connected grains in a three-dimensional (3D) voided network and look at the effect of the size of interparticle boundaries on carrier dynamics. We can also address similar times to those over which measurements are taken, namely, 0.1 ms. These times are long because of deep traps in the TiO2 grains. The grains have 2-fold connectivity in one dimension (linear chains) or 4-fold or 6-fold connectivity in three dimensions and traps with an exponential distribution of energies. Photoelectrons are generated by a light pulse of short duration. The spatial distribution of the photogenerated electron density from this pulse either has a uniform profile or is peaked on the electrolyte side. We show that the constrictions at the grain necks slow the electrons, making trapping more likely and hence further delaying their passage to the extracting electrode. By comparing our results for 4-fold and 6-fold coordinated particles on a cubic lattice with 2-fold coordinated particles on linear chains, we show that transport is slowed in the former case due to the additional paths available to the electrons in the 3D network. We also find that the charge and current transients cannot be fit to an analytical solution of the continuum equations with an effective diffusion coefficient even at long times. Therefore, caution must be exercised when attempting to fit experimental transient data with an effective diffusion coefficient.

Journal Article↗

PubMed2004

Analysis of Ehrlichia ruminantium-specific T1/T2 responses during vaccination with a protective killed vaccine and challenge of goats.

Ehrlichia ruminantium is an obligate intracellular bacterium that causes heartwater in ruminants and for which T-cell-mediated immunity is believed to play an important role in protection. To better characterize protective cellular immunity, E. ruminantium-specific IFN-gamma and IL-4 recall responses in major T-cell subsets were analysed by flow cytometry during immunization of goats with a killed vaccine and following a virulent challenge. The killed vaccine elicited both CD8+ and CD4+ subsets to produce cytoplasmic IFN-gamma in the absence of IL-4, thus indicating a biased T1 response. The relative capacity of CD8+ T-cells to produce IFN-gamma was significantly higher than CD4+ T-cells but the final contribution of both subsets was comparable. Circulating ER-specific CD4 and CD8 effectors substantially decreased in numbers after the booster injection and could not be detected in most animals during challenge, which warrants further investigation in immune compartments other than blood. Since IFN-gamma inhibits the growth of the pathogen in target cells, the information provided in this study on E. ruminantium-specific T1 responses will be valuable to develop cellular tools for the identification of potential protective antigens.

Animals↗

PubMed2003

Age-dependent synuclein pathology following traumatic brain injury in mice.

Synucleins (Syn), a family of synaptic proteins, includes alpha-Syn, which plays a pivotal role in Parkinson's disease and related neurodegenerative diseases (synucleinopathies) by forming distinct brain pathologies (Lewy bodies and neurites). Since traumatic brain injury (TBI) is a poorly understood risk factor for Parkinson's disease, we examined the effects of TBI in the young and aged mouse brain on alpha-, beta-, and gamma-Syn. Immunohistochemical analysis showed that brains from sham-injured young and aged mice had normal alpha- and beta-Syn immunoreactivity (IR) in neuropil of cortex, striatum, and hippocampus with little or no gamma-Syn IR. At 1 week post TBI, the aged mouse brain showed a transient increase of alpha- and beta-Syn IR in the neuropil as well as an induction of gamma-Syn IR in subcortical axons. This was associated with strong labeling of striatal axon bundles by antibodies to altered or nitrated epitopes in alpha-Syn as well as by antibodies to inducible nitric oxide synthase. However, these TBI-induced changes disappeared by 16 weeks post TBI, and altered Syn IR was not seen in young mice subjected to TBI nor in alpha-Syn knockout mice while Western blots confirmed that TBI induced transient alterations of alpha-Syn in the mouse brains. This model of age-dependent TBI-induced transient alterations in alpha-Syn provides an opportunity to examine possible links between TBI and mechanisms of disease in synucleinopathies.

Aging↗

PubMed2003

Effects of sodium dodecyl sulfate on the conformation and hemolytic activity of St I and St II, two isotoxins purified from Stichodactyla helianthus.

The effect of sodium dodecyl sulfate (SDS) upon the conformation and hemolytic activity of St I and St II strongly depends on its concentration. At relatively low surfactant concentrations (ca. 0.5-5mM range) the surfactant leads to the formation of aggregates, as suggested by the turbidity observed even at relatively low (micromolar range) protein concentrations. In this surfactant range, the proteins show an increase in intrinsic fluorescence intensity and reduced quenching by acrylamide, with an almost total loss of its hemolytic activity. At higher surfactant concentrations the protein adducts disaggregates. This produces a decrease in fluorescence intensity, increase in quenching efficiency by acrylamide, loss of the native tertiary conformation (as reported by the near UV-CD spectra), and increase in alpha-helix content (as evidenced by the far UV-CD spectra). However, and in spite of these substantial changes, the toxins partially recover their hemolytic activity. The reasons for this recovering of the activity at high surfactant concentrations is discussed.

Animals↗

PubMed2002

Cerebral venous thrombosis, intraventricular haemorrhage and white matter lesions in a preterm newborn with factor V (Leiden) mutation.

We report a preterm newborn who presented extensive cerebral vein thrombosis on MRI but no abnormal neurological signs. The baby underwent MRI as germinal-matrix intraventricular haemorrhage was revealed by a routine ultrasound brain scan performed on day 16; earlier ultrasound scans (day 2, 7, 12) were all normal. Cerebral vein thrombosis was diagnosed at the first MRI scan together with abnormal restriction in diffusion weighted imaging in the frontal white matter parenchyma. Bilateral microcavitations with a linear pattern of distribution reflecting the distribution of medullary veins developed a week later in the same white matter areas where abnormal diffusion weighted imaging was formerly noted. The baby was later found to be heterozygous for factor V Leiden.

Cerebral Veins↗

PubMed2002

IFN-gamma as an indicator of successful immunization of goats vaccinated with a killed Cowdria ruminantium vaccine.

Cowdria ruminantium-induced production of IFN-gamma was measured by ELISA on a weekly basis during the course of vaccination with killed organisms emulsified in ISA50. Upon challenge, all (3/3) vaccinated animals that gave the lowest IFN-gamma response died of peracute cowdriosis. On the other hand, only one of three animals showing high IFN-gamma responses to vaccination died, but with a delay of 4 days in comparison with naïve controls. Thus, there seems to be a threshold level of IFN-gamma below which the probability for vaccinated animals to survive a lethal challenge is very low. During challenge, a much lower, but still physiologically meaningful production of IFN-gamma was detected using the 24-hour whole blood assay on day 5 after infection in animals controlling the infection. In contrast, IFN-gamma production was absent or negligible in naïve and vaccinated animals that died within 8-10 days after infection. Although these results need to be validated on a larger number of animals, they strongly suggest that IFN-gamma is a useful indicator of protective immunity in animals immunized with killed COWDRIA:

Animals↗

PubMed2002

Cowdria ruminantium antigens of around 15 kDa are potent inducers of IFN-gamma.

Cellular responses induced in two Creole goats by vaccination with killed Cowdria ruminantium (Cowdria) were confirmed by IFN-gamma production and interleukin-2 receptor (IL-2R) expression. Both CD4+ and CD8+ but not WC1+ T cells showed a substantial increase in cell surface expression of IL-2R molecules in response to whole Cowdria lysate. Cowdria (Welgevonden strain) proteins were fractionated using continuous-flow electrophoresis and tested for their ability to induce IFN-gamma production by PBMC collected three weeks after the first inoculation and one week after the booster injection. Pooled fractions of around 15, 22, and 24 kDa were found to induce significant IFN-gamma production in both vaccinated animals on one of the two occasions. Antigens of around 15 kDa induced substantially higher IFN-gamma production than any other fractions in both animals. These pilot experiments pave the way towards the identification of proteins/genes that have potential for the development of a recombinant vaccine against heartwater.

Animals↗

PubMed2002

Magnetic resonance imaging of the infant brain: anatomical characteristics and clinical significance of punctate lesions.

OBJECTIVE: To describe the magnetic resonance imaging (MRI) characteristics of punctate brain lesions in neonates (number, appearance, distribution, and association with other brain abnormalities) and to relate them to neurodevelopmental outcome. METHODS: A retrospective analysis was performed of 110 MRI brain scans from 92 infants admitted in 1998 to the neonatal intensive care unit. Results of routine neurodevelopmental follow up (1998-2001) in those infants with punctate brain lesions were analysed. RESULTS: Punctate lesions were observed in 15/50 preterm and 2/42 term infants. In the preterm group, the number of lesions was < 3 in 20%, 3-10 in 27%, and > 10 in 53%. In 14/15 the lesions were linearly organised and located in the centrum semiovale. Other brain abnormalities were absent or minor--that is, "isolated" punctate lesions--in 8/15 and major in 7/15. In the term group, punctate lesions were organised in clusters and no other brain abnormalities were observed. Isolated punctate lesions were observed in 10/17 infants, and a normal neurodevelopmental outcome was seen in 9/10 (mean follow up 29.5 months). One infant showed a slight delay in language development. In the infants with associated brain lesions (7/17, mean follow up 27.5 months), outcome was normal in only two subjects. CONCLUSIONS: Punctate lesions are predominantly seen in preterm infants, are usually linearly organised, and border the lateral ventricles. Isolated punctate lesions may imply a good prognosis, because most of these subjects have a normal neurodevelopmental outcome so far.

Brain Diseases↗

PubMed2001

Regulation of beta-catenin structure and activity by tyrosine phosphorylation.

beta-Catenin plays a dual role as a key effector in the regulation of adherens junctions and as a transcriptional coactivator. Phosphorylation of Tyr-654, a residue placed in the last armadillo repeat of beta-catenin, decreases its binding to E-cadherin. We show here that phosphorylation of Tyr-654 also stimulates the association of beta-catenin to the basal transcription factor TATA-binding protein. The structural bases of these different affinities were investigated. Our results indicate that the beta-catenin C-terminal tail interacts with the armadillo repeat domain, hindering the association of the armadillo region to the TATA-binding protein or to E-cadherin. Phosphorylation of beta-catenin Tyr-654 decreases armadillo-C-terminal tail association, uncovering the last armadillo repeats. In a C-terminal-depleted beta-catenin, the presence of a negative charge at Tyr-654 does not affect the interaction of the TATA-binding protein to the armadillo domain. However, in the case of E-cadherin, the establishment of ion pairs dominates its association with beta-catenin, and its binding is greatly dependent on the absence of a negative charge at Tyr-654. Thus, phosphorylation of Tyr-654 blocks the Ecadherin-beta-catenin interaction, even though the steric hindrance of the C-tail is no longer present. These results explain how phosphorylation of beta-catenin in Tyr-654 modifies the tertiary structure of this protein and the interaction with its different partners.

Cytoskeletal Proteins↗

PubMed2001

Intermolecular (1)H[(19)F] NOEs in studies of fluoroalcohol-induced conformations of peptides and proteins.

Mixtures of fluorinated alcohols and water can selectively stabilize certain secondary structures of peptides and proteins. Such mixtures may also be of use in solubilizing hydrophobic or membrane-bound proteins. We show that intermolecular dipolar interactions between the fluorine nuclei of such solvents and the protons of a dissolved protein lead to readily detected (1)H[(19)F] nuclear Overhauser effects. These NOEs can potentially provide information about solvent exposure of particular groups as well as indicate the formation of long-lived fluoroalcohol-solute complexes. Results obtained with HEW lysozyme in solutions containing trifluoroethanol illustrate these possibilities.

Hydrogen Bonding↗

PubMed2001

Subcellular localization of Dp71 dystrophin isoforms in cultured hippocampal neurons and forebrain astrocytes.

It has been suggested that the absence or altered structure of Dp71, a C-terminal dystrophin gene encoded protein, is responsible for mental alterations observed in about 30% of Duchenne muscular dystrophy patients. Most of these patients have premature translational termination or point mutations at the C-terminal domain of this gene. In brain, Dp71 is the major protein product of the dystrophin gene. To determine the function of Dp71 isoforms in this organ, it is important to document their presence and intracellular localization in brain cells. Extracts from cultured hippocampal neurons and forebrain astrocytes and 5F3 and Dys 2 monoclonal antibodies were thus used for western blots. In these conditions, two Dp71 isoforms spliced or not at exon 78 were detected in both cells (Dp71f and Dp71d, respectively). By immunocytochemistry, we mapped Dp71f and Dp71d in the Golgi complex (GC) and in neuronal nuclei. Only Dp71d was found in cytoplasmic neurofilaments. In astrocytes, these isoforms were detected in the GC. These cell localization data suggest that these Dp71 isoforms may have different functions in the same cell or organelle, as well as in the two different cells analyzed.

Animals↗

PubMed2001

Effects of lipid composition on membrane permeabilization by sticholysin I and II, two cytolysins of the sea anemone Stichodactyla helianthus.

Sticholysin I and II (St I and St II), two basic cytolysins purified from the Caribbean sea anemone Stichodactyla helianthus, efficiently permeabilize lipid vesicles by forming pores in their membranes. A general characteristic of these toxins is their preference for membranes containing sphingomyelin (SM). As a consequence, vesicles formed by equimolar mixtures of SM with phosphatidylcholine (PC) are very good targets for St I and II. To better characterize the lipid dependence of the cytolysin-membrane interaction, we have now evaluated the effect of including different lipids in the composition of the vesicles. We observed that at low doses of either St I or St II vesicles composed of SM and phosphatidic acid (PA) were permeabilized faster and to a higher extent than vesicles of PC and SM. As in the case of PC/SM mixtures, permeabilization was optimal when the molar ratio of PA/SM was ~1. The preference for membranes containing PA was confirmed by inhibition experiments in which the hemolytic activity of St I was diminished by pre-incubation with vesicles of different composition. The inclusion of even small proportions of PA into PC/SM LUVs led to a marked increase in calcein release caused by both St I and St II, reaching maximal effect at ~5 mol % of PA. Inclusion of other negatively charged lipids (phosphatidylserine (PS), phosphatidylglycerol (PG), phosphatidylinositol (PI), or cardiolipin (CL)), all at 5 mol %, also elicited an increase in calcein release, the potency being in the order CL approximately PA >> PG approximately PI approximately PS. However, some boosting effect was also obtained, including the zwitterionic lipid phosphatidylethanolamine (PE) or even, albeit to a lesser extent, the positively charged lipid stearylamine (SA). This indicated that the effect was not mediated by electrostatic interactions between the cytolysin and the negative surface of the vesicles. In fact, increasing the ionic strength of the medium had only a small inhibitory effect on the interaction, but this was actually larger with uncharged vesicles than with negatively charged vesicles. A study of the fluidity of the different vesicles, probed by the environment-sensitive fluorescent dye diphenylhexatriene (DPH), showed that toxin activity was also not correlated to the average membrane fluidity. It is suggested that the insertion of the toxin channel could imply the formation in the bilayer of a nonlamellar structure, a toroidal lipid pore. In this case, the presence of lipids favoring a nonlamellar phase, in particular PA and CL, strong inducers of negative curvature in the bilayer, could help in the formation of the pore. This possibility is confirmed by the fact that the formation of toxin pores strongly promotes the rate of transbilayer movement of lipid molecules, which indicates local disruption of the lamellar structure.

Animals↗

PubMed2001

Effect of pH on the conformation, interaction with membranes and hemolytic activity of sticholysin II, a pore forming cytolysin from the sea anemone Stichodactyla helianthus.

Sticholysin II (St II) is a pore forming cytolysin obtained from the sea anemone Stichodactyla helianthus. Incubation of diluted St II solutions at different pHs (ranging from 2.0 to 12) slightly changes the secondary structure of the protein. These changes are particularly manifested at high pH. Similarly, the intrinsic fluorescence of the protein indicates a progressive opening of the protein structure when the pH increases from acidic (2.0) to basic (12). These modifications are only partially reversible and do not produce any significant increase in the small capacity of the protein to bind hydrophobic dyes (ANS or Prodan). Experiments carried out with model membranes show a reduced capacity of binding to egg phosphatidyl choline:sphingomyelin (1:1) liposomes both at low (2.3) and high (11.5) pH. Preincubation of the protein in the 2. 5-9.0 pH range does not modify its hemolytic activity, measured in human red blood cells at pH 7.4. On the other hand, preincubation at pH 11.5 drastically reduces the hemolytic activity of the toxin. This strong reduction takes place without measurable modification of the toxin ability to be adsorbed to the red blood cell surface. This indicates that preincubation at high pH irreversibly reduces the capacity of the toxin to form pores without a significant decrease in its binding capacity. The present results suggest that at pH > or = 10 St II experiences irreversible conformational changes that notably reduce its biological activity. This reduced biological activity is associated with a partial defolding of the protein, which seems to contradict what is expected in terms of a molten globule formalism.

Animals↗