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Biomedical subjects

J García

Publications and source records attributed to J García.

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

Coronary endothelial dysfunction as a predictor of intimal thickening in the long term after heart transplantation.

OBJECTIVES: The mechanisms of cardiac allograft vasculopathy and its predisposing factors are multifactorial and as yet not well established. To determine the influence of endothelial dysfunction on the development of intimal thickening, we prospectively analyzed the vasomotor response to acetylcholine and nitroglycerin, as well as other donor and recipient variables. Findings were correlated with the coronary intimal thickness, which was evaluated by means of intravascular ultrasonography. METHODS: Nineteen patients who had undergone heart transplantation 4.89 +/- 2.35 years previously and who had angiographically normal coronary arteries were included. Endothelial function was analyzed by quantitative coronary analysis of the vasomotor response of the left anterior descending artery to acetylcholine. An intimal thickness index, reflecting the percentage of intima obstructing the coronary lumen, was calculated. RESULTS: Nine (47%) patients showed endothelial dysfunction, and the remaining 10 (53%) patients had a normal response. Four (44%) of 9 patients with a weight gain of greater than 20% after the operation showed endothelial dysfunction compared with none of the 10 patients with normal responses (P <.04). The severity of the intimal thickness correlated with the years after transplant (r = 0.45, P <.05). Patients with endothelial dysfunction had more intimal thickening than those without (32% +/- 17% vs 17% +/- 12%, respectively; P <.05). Furthermore, the degree of intimal thickening correlated with the magnitude of the vasomotor response to acetylcholine (r = -0.60, P =.006). No relationship was found between intimal thickness and the vasodilatory response to nitroglycerin. As independent variables for intimal thickness, multivariate analysis detected the magnitude of the response to acetylcholine (P =.0005), years after transplant (P =.01), and ischemic time (P =.03). CONCLUSIONS: Cardiac allograft vasculopathy is a multifactorial disease the severity of which increases over time. Endothelial dysfunction is a predictive factor of intimal thickening severity. Predisposing factors that provoke endothelial injury, such as perioperative ischemic time and obesity, may contribute to the development of allograft vasculopathy.

Acetylcholine↗
PubMed2001

Acute cellulitis: an unusual manifestation of meningococcal disease.

We describe 2 patients who both developed cellulitis due to Neisseria meningitidis and review 8 other cases reported since 1966. Female patients outnumbered male patients by 8 to 2, and there were 5 children and 5 adults. Four cases were caused by the serogroup C meningococcus, 2 cases by serogroup B and 2 others by serogroup Y (the nature of the meningococcal group was not available in 2 cases). Diverse medical underlying conditions were present in 4 of the adult patients. The periorbital region (in all 5 children), limb (in 3 adults), neck (in 1 adult) and face and neck (in 1 adult) were the locations of the meningococcal cellulitis. In all 10 patients, a favorable clinical response to the antibiotic therapy was documented and no relapses occurred. These cases indicate that N. meningitidis should be considered as a causative agent of cellulitis in the appropriate clinical setting, particularly in children with signs of periorbital infection or adults with underlying diseases.

Acute Disease↗
PubMed2001

Two-dimensional optical wavelet decomposition with white-light illumination by wavelength multiplexing.

We present a novel method for achieving in real time a two-dimensional optical wavelet decomposition with white-light illumination. The underlying idea of the suggested method is wavelength multiplexing. The information in the different wavelet components of an input object is transmitted simultaneously in different wavelengths and summed incoherently at the output plane. Experimental results show the utility of the new proposed method.

Journal Article↗
PubMed2001

Differential effect of gabapentin on neuronal and muscle calcium currents.

Calcium channels modulate cell function by controlling Ca(2+) influx. A main component of these proteins is the alpha 2/delta subunit. Nevertheless, how this subunit regulates channel activity in situ is unclear. Gabapentin (GBP), an analgesic and anti-epileptic agent with an unknown mechanism of action, specifically binds to the alpha 2/delta subunit. Using the patch clamp technique, we tested the effects of GBP on Ca(2+) currents from dorsal root ganglion (DRG) cells, the mediators of pain perception, to determine how GBP binding modifies channel activity. In DRGs, GBP significantly reduced whole cell Ca(2+) current amplitude at positive membrane potentials when a pulse preceded the test pulses or when cells were stimulated with a train of pulses. In control cells, neither prepulse depolarization nor pulse trains reduced Ca(2+) currents at positive potentials. GBP did not reduce the low-voltage activated Ca(2+) current under any experimental condition. Similar to DRG cells, GBP attenuated Ca(2+) current in skeletal myotubes at positive membrane potentials in the presence of a depolarizing prepulse. However, GBP did not significantly alter Ca(2+) currents in cardiac myocytes. Reverse transcription-polymerase chain reaction was used to confirm expression of the alpha 2/delta subunit in these cells. Each cell type expressed multiple isoforms of alpha 2/delta. Muscle cells showed a more variable expression of alpha 2/delta subunits than did DRG cells. Our results suggest a possible participation of the alpha 2/delta subunit in the action of GBP. Our data also indicate that GBP inhibits Ca(2+) channels in a use- and voltage-dependent manner at a therapeutically relevant concentration.

Acetates↗
PubMed2001

Faecal bacteria and bacteriophage inactivation in a full-scale UV disinfection system used for wastewater reclamation.

A study was carried out to compare the inactivation of faecal bacteria and one type of bacteriophage in a full-scale UV disinfection system. The system is part of a water reclamation facility for effluent reuse in golf course and agricultural irrigation. Influent and effluent samples were taken over two sampling periods (three consecutive days in July and one day in August), with three different UV doses applied each day (ranging from 10 to 40 mW.s/cm2 and 20 to 80 mW.s/cm2 in July and August, respectively). Effluent samples were also taken from a chlorine disinfection channel (5 mg Cl2/L dose) operating in parallel to the UV system. Total coliforms (TC), faecal coliforms (FC), faecal streptoccoci (FS) and somatic coliphages (SC) were measured in each sample. F-specific RNA bacteriophages and bacteriophages of Bacteroides fragilis were also measured one day in July. The decay ratio observed for all the microorganisms was similar when UV doses applied were low (July), ranging from 1.15 to 1.25 log-units. This suggests that bacterial indicators may be suitable for virus inactivation control when low UV doses are applied; however, such low doses are inadequate to achieve effluent quality requirements for unrestricted irrigation. At higher UV doses (August), decay ratios for TC and FC were 3.1 and 2.8 log-units respectively, indicating that they were more susceptible to UV exposure than SC and FS, with decay ratios of 2.6 and 1.0 log-units, respectively. Nevertheless, these higher doses were also inadequate to achieve water quality requirements for unrestricted irrigation. The decay ratio of SC during chlorine disinfection was clearly lower than that of the other microorganisms. Bacteriophages of Bacteroides fragilis were more resistant to UV disinfection than SC and F-specific RNA. In fact, bacteriophages of Bacteroides fragilis were not affected during UV exposure. A UV dose ranging from 40 to 80 mW.s/cm2 marks the borderline beyond which inactivation rates of SC are clearly lower than those of bacterial indicators.

Bacteria↗
PubMed2001

[Usefulness of the statistical bulletin of deaths to identify extrahospital deaths in the context of a myocardial infarction population registry].

INTRODUCTION AND AIMS: This paper aimed to study the usefulness of the Statistical Bulletin of Deaths (SBD) for identifying extrahospital deaths due to acute coronary ischaemia, and to determine the most efficient strategy in the selection of death causes that appear in the SBD, which are the most efficient for the identification. METHODS: Those extrahospital deaths, which, among the causes of death, recorded a diagnostic code indicating that they might have been caused by coronary ischaemia, were included. To study the usefulness of the death certificate we calculated the sensitivity and the positive predictive value of cardiac ischaemia. To determine the most efficient strategy for selecting causes of death we compared two selection strategies: the first, using only the basic cause of death; and the second using all the causes appearing in the SBD. RESULTS: Of the 395 SBD selected, 161 were classed as acute heart attacks. In those SBD in which cardiac ischaemic disease was given as the basic cause of death, we obtained a sensitivity of 82.6% (CI 95%: 75.9-88.1) and a positive predictive value of 72.7% (CI 95%: 65.6-79). The most efficient strategy in SBD selection proved to be the investigation of death certificates in which cardiac ischaemia appeared as one of all the causes of death, and death certificates in which the basic cause of death was coded as diabetes mellitus, essential arterial hypertension, hypertensive heart disease, cardiac dysrhythmia, and cardiac insufficiency. CONCLUSIONS: The information provided by death certificates for extrahospital deaths due to coronary ischaemia is reliable. A sensitive and efficient SBD selection strategy is proposed for the detection of cases.

Adult↗
PubMed2000

Usefulness of unipolar electrograms to detect isthmus block after radiofrequency ablation of typical atrial flutter.

BACKGROUND: RS morphology of the unipolar electrogram is associated with propagation of the wave front through the exploring electrode, whereas positive uniphasic (R) unipolar electrograms are characteristic of the end of activation. METHODS AND RESULTS: Unipolar electrograms were recorded in 45 consecutive patients with atrial flutter who were undergoing radiofrequency ablation (RFA). Bidirectional cavotricuspid isthmus (CTI) block was achieved in 44 patients. The unipolar electrogram obtained before RFA at the low anterolateral right atrium during coronary sinus pacing changed from RS, rS, or QS to R or Rs in all patients after clockwise CTI block was obtained. The morphology of unipolar electrograms recorded close to the coronary sinus during pacing from the low anterolateral right atrium changed from RS or rS to R or Rs in all but 4 patients after counterclockwise CTI block. In the patient in whom CTI block was not achieved, the RS morphology of the unipolar electrogram remained unchanged. In 18 patients, the results of the RFA were assessed with only the unipolar electrogram. The unipolar electrogram correctly predicted 100% and 89% of the cases of clockwise and counterclockwise CTI block, respectively. CONCLUSIONS: The creation of CTI block is associated with an easily detectable loss of negative components and development of an R or Rs pattern of the unipolar electrogram recorded close to the ablation line while pacing at the opposite side of the CTI.

Aged↗
PubMed2000

Resonant "forbidden" reflections in magnetite.

Resonant x-ray scattering was used to investigate electronic fluctuations of the octahedral iron atoms in magnetite. We measured the (002) and (006) "forbidden" x-ray diffraction reflections permitted by the anisotropy of the iron anomalous scattering factor. The energy and azimuthal angle dependencies of these reflections, and the polarization analysis, are shown and discussed. The results clearly show p and d iron empty states ordering in magnetite at room temperature. Moreover, the octahedral iron atoms are electronically equivalent in a time scale lower than 10(-16) sec. Therefore, magnetite should be considered as an itinerant magnet and not as a fluctuating mixed valence material.

Journal Article↗
PubMed2000

Vaccination against Taenia solium cysticercosis in underfed rustic pigs of México: roles of age, genetic background and antibody response.

Vaccination of pigs of mixed genetic make-up, raised as rustically as done in rural Mexico, resulted in effective protection to experimental challenge against Taenia solium cysticercosis. Maximum protection was achieved if pigs were immunized at 70 days of age. There was large variation of viable parasite load within vaccinated pigs and controls, which is suggestive of significant genetic factors influencing susceptibility, besides immunization. Our results strengthen the advisability of pig vaccination for control of T. solium cysticercosis, since it lowers the number of viable cysticerci capable of transforming into tapeworms.

Age Factors↗
PubMed2000

Efficient transduction of human hematopoietic repopulating cells generating stable engraftment of transgene-expressing cells in NOD/SCID mice.

In an attempt to develop efficient procedures of human hematopoietic gene therapy, retrovirally transduced CD34(+) cord blood cells were transplanted into NOD/SCID mice to evaluate the repopulating potential of transduced grafts. Samples were prestimulated on Retronectin-coated dishes and infected with gibbon ape leukemia virus (GALV)-pseudotyped FMEV vectors encoding the enhanced green fluorescent protein (EGFP). Periodic analyses of bone marrow (BM) from transplanted recipients revealed a sustained engraftment of human hematopoietic cells expressing the EGFP transgene. On average, 33.6% of human CD45(+) cells expressed the transgene 90 to 120 days after transplantation. Moreover, 11.9% of total NOD/SCID BM consisted of human CD45(+) cells expressing the EGFP transgene at this time. The transplantation of purified EGFP(+) cells increased the proportion of CD45(+) cells positive for EGFP expression to 57. 7% at 90 to 120 days after transplantation. At this time, 18.9% and 4.3% of NOD/SCID BM consisted of CD45(+)/EGFP(+) and CD34(+)/EGFP(+) cells, respectively. Interestingly, the transplantation of EGFP(-) cells purified at 24 hours after infection also generated a significant engraftment of CD45(+)/EGFP(+) and CD34(+)/EGFP(+) cells, suggesting that a number of transduced repopulating cells did not express the transgene at that time. Molecular analysis of NOD/SCID BM confirmed the high levels of engraftment of human transduced cells deduced from FACS analysis. Finally, the analysis of the provirus insertion sites by conventional Southern blotting indicated that the human hematopoiesis in the NOD/SCID BM was predominantly oligoclonal.

Animals↗
PubMed2000

Amino terminal peptides of the ring infected erythrocyte surface antigen of Plasmodium falciparum bind specifically to erythrocytes.

The Ring-Infected Erythrocyte Surface Antigen (Pf155/RESA) sequence was chemically synthesized in fifty four 20-mer sequential peptides, covering the entire protein, each of which was tested in erythrocyte binding assays. Peptides 6671 and 6673, corresponding to residues 141-160 and 181-200, respectively, presented a high specific binding activity to erythrocytes with affinity constants of 190 nM and 105 nM respectively. Their binding was sensitive to previous enzymatic treatment of erythrocytes. A region of peptide 6673 has been identified, very recently, as a B-cell epitope, target of neutralizing antibodies (Siddique AB, Iqbal J, Ahlborg N, Wâhlin FB, Perlmann P, Berzins K. Antibodies to nonrepeat sequences of antigen Pf155/RESA of Plasmodium falciparum inhibit parasite growth in vitro. Parasitol Res 1998;84:485-91). The critical residues for erythrocyte binding for peptide 6671 (MTDVNRYRYSNNYEAIPHIS) and for peptide 6673 (LGRSGGDIIKKMQTLWDEIM) were recognized. Based on these data, the presence of five functional regions of RESA is postulated.

Amino Acid Sequence↗
PubMed2000

Mutations affecting mRNA splicing are the most common molecular defects in patients with neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) is one of the most common inherited disorders in humans and is caused by mutations in the NF1 gene. To date, the majority of the reported NF1 mutations are predicted to result in protein truncation, but very few studies have correlated the causative NF1 mutation with its effect at the mRNA level. We have applied a whole NF1 cDNA screening methodology to the study of 80 unrelated NF1 patients and have identified 44 different mutations, 32 being novel, in 52 of these patients. Mutations were detected in 87% of the familial cases, but in 51% of the sporadic ones. At least 15 of the 80 NF1 patients (19%) had recurrent mutations. The study shows that in 50% of the patients in whom the mutations were identified, these resulted in splicing alterations. Most of the splicing mutations did not involve the conserved AG/GT dinucleotides of the splice sites. One frameshift, two nonsense and two missense mutations were also responsible for alterations in mRNA splicing. The location and type of mutation within the NF1 gene, and its putative effect at the protein level, do not indicate any relationship to any specific clinical feature of NF1. The high proportion of aberrant spliced transcripts detected in NF1 patients stresses the importance of studying mutations at both the genomic and RNA level. It is possible that part of the clinical variability in NF1 could be due to mutations affecting mRNA splicing, which is the most common molecular defect in NF1.

Adult↗