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Biomedical subjects

A Martinez

Publications and source records attributed to A Martinez.

At least 19 recordsLinked to original sources
PubMed2007

Spatio-temporal analysis of feature-based attention.

The cortical mechanisms of feature-selective attention to color and motion cues were studied in humans using combined electrophysiological, magnetoencephalographic, and hemodynamic (functional magnetic resonance imaging) measures of brain activity. Subjects viewed a display of random dots that periodically either changed color or moved coherently. When attention was directed to the color change it elicited enhanced neural activity in visual area V4v, previously shown to be specialized for processing color information. In contrast, when dot movement was attended it produced enhanced activity in the motion-specialized area human MT. Parallel recordings of event-related electrophysiological and magnetoencephalographic responses indicated that the attention-related facilitation of neural activity in these specialized cortical areas occurred rapidly, beginning as early as 90-120 ms after stimulus onset. We conclude that selection of an entire feature dimension (motion or color) boosts neural activity in its specialized cortical module much more rapidly than does selection of one feature value from another (e.g., one color from another), as reported in previous electrophysiological studies. By combining methods with high spatial and temporal resolution it is possible to analyze the precise time course of feature-selective processing in specialized cortical areas.

Adult↗
PubMed2006

Ocular haemodynamics in pseudoexfoliative and primary open-angle glaucoma.

OBJECTIVE: To compare the retrobulbar haemodynamic parameters in the ophthalmic artery (OA) and short posterior ciliary arteries (SPCA) in pseudoexfoliative and primary open-angle glaucoma patients. SUBJECTS AND METHODS: Fourty-three eyes from 43 patients with pseudoexfoliative glaucoma (PXE) and 31 eyes from 31 patients with primary open-angle glaucoma (POAG) who met the inclusion/exclusion criteria were included in this prospective cross-sectional study. Colour Doppler imaging measurements, peak systolic velocity (PSV), and end-diastolic velocity (EDV) were assessed in the OA and posterior ciliary arteries (PCA). Pourcelot resistivity indices (RI) were calculated. Visual function was assessed using the 24-2 Swedish Interactive Threshold Algorithm (SITA). The main outcomes of the study were PSV, EDV, and RI in the OA and SPCA. RESULTS: In POAG patients, PSV and EDV were significantly lower in the OA, P=0.003 and P<0.001 respectively, and in the PCA, P=0.003 and P<0.001 respectively, when compared with the PXE group. The RI was significantly higher, P<0.001, in both vessels, in the POAG group. CONCLUSION: The results of this study have found reduced PSV and EDV and increased RI in the retrobulbar vessels of POAG patients when compared with PXE patients.

Aged↗
PubMed2006

Blood-brain distribution of morphine-6-glucuronide in sheep.

BACKGROUND AND PURPOSE: At present there are few data regarding the rate and extent of brain-blood partitioning of the opioid active metabolite of morphine, morphine-6-glucuronide (M6G). In this study the cerebral kinetics of M6G were determined, after a short-term intravenous infusion, in chronically instrumented conscious sheep. EXPERIMENTAL APPROACH: Five sheep received an intravenous infusion of M6G 2.2 mg kg(-1) over a four-minute period. Non-linear mixed-effects analysis, with hybrid physiologically based kinetic models, was used to estimate cerebral kinetics from the arterio-sagittal sinus concentration gradients and cerebral blood flow measurements. KEY RESULTS: A membrane limited model was selected as the final model. The blood-brain equilibration of M6G was relatively slow (time to reach 50% equilibration of the deep compartment 5.8 min), with low membrane permeability (PS, population mean, 2.5 ml min(-1)) from the initial compartment (V1, 13.7 ml) to a small deep distribution volume (V2) of 18.4 ml. There was some between-animal variability (%CV) in the initial distribution volume (29%), but this was not identified for PS or V2. CONCLUSION AND IMPLICATIONS: Pharmacokinetic modelling of M6G showed a delayed equilibration between brain and blood of a nature that is primarily limited by permeability across the blood-brain-barrier, in accordance with its physico-chemical properties.

Animals↗
PubMed2006

Phase-amplitude characterization of a high-repetition-rate quantum dash passively mode-locked laser.

We apply a novel phase-amplitude characterization method to a one-section quantum dash-based passively mode-locked laser at a 42.2 GHz repetition rate. The method relies on the measurement of the spectral phase of the longitudinal modes by the successive analysis of the correlation signal of a group of three adjacent modes. It provides both the temporal shape of the intensity and the phase of the emitted signal. A pulse of 1.5 ps of width is measured, and a pedestal is exhibited. Extinction ratio limitation is explained by investigating the origin of this pedestal. The accuracy of the method is estimated by comparing the measured autocorrelation signal and the calculated one from the phase analysis.

Journal Article↗
PubMed2006

Distributed Bragg reflector fiber laser fabricated by femtosecond laser inscription.

A femtosecond laser inscription technique is proposed for the fabrication of a fiber grating laser directly into a nonphotosensitive gain fiber. A distributed Bragg reflector fiber grating laser is realized in a conventional, untreated Er:Yb-codoped fiber as an illustration. Robust, single-mode, single-polarization laser operation at temperatures in excess of 600 degrees C is further achieved without compromising performance. A nonlinear, thermally induced wavelength shift is also observed at elevated temperatures.

Journal Article↗
PubMed2006

Control of neuronal branching by the death receptor CD95 (Fas/Apo-1).

The CD95 (Apo-1/Fas)/CD95 ligand (CD95L) system is best characterized as a trigger of apoptosis. Nevertheless, despite broad expression of CD95L and CD95 in the developing brain, absence of functional CD95 (lpr mice) or CD95L (gld mice) does not alter neuronal numbers. Here, we report that in embryonic hippocampal and cortical neurons in vivo and in vitro CD95L does not induce apoptosis. Triggering of CD95 in cultured immature neurons substantially increases neurite branches by promoting their formation. The branching increase occurs in a caspase-independent and death domain-dependent manner and is paralleled by an increase in the nonphosphorylated form of Tau. Most importantly, lpr and gld mutants exhibit a reduced number of dendritic branches in vivo at the time when synapse formation takes place. These data reveal a novel function for the CD95 system and add to the picture of guidance molecules in the developing brain.

Animals↗
PubMed2006

Bone remodelling after total hip arthroplasty using an uncemented anatomic femoral stem: a three-year prospective study using bone densitometry.

PURPOSE: To evaluate the clinical, radiological, and densitometric changes in the bone-remodelling patterns of femoral stems aligned in neutral, valgus, or varus positions. METHODS: Between February and October 2000, 70 patients underwent unilateral total hip arthroplasty for primary osteoarthritis using an uncemented Anatomique Benoist Girard (ABG) II stem. 69 patients (30 males and 39 females) with a mean age of 59 years (range, 38-76 years) and a mean body weight of 79.3 kg (range, 29-110 kg) completed 3 years' follow-up on bone remodelling. The clinical, radiological, and densitometric changes of the neutral, valgus, and varus groups were evaluated, and the difference in bone-remodelling patterns between the 3 groups was analysed. RESULTS: 54 patients had neutrally placed stems, while varus and valgus malalignment occurred in 6 and 9 patients, respectively. Clinical and radiological evaluations were very similar among the 3 groups. Only densitometry could detect traceable changes resulting from the differing biomechanics of the neutral, varus, and valgus stem alignments. CONCLUSION: The ABG II stem design made moderate errors in alignment biomechanically tolerable. Alignment defects had no clinical consequences and resulted in minimal differences in bone remodelling.

Absorptiometry, Photon↗
PubMed2006

Oxidative stress markers in plasma and urine of prepubertal patients with type 1 diabetes mellitus.

Markers of oxidative stress were studied in plasma and urine of prepubertal patients with type 1 diabetes mellitus (DM1) with less than 5 years of disease (n = 27). The results were compared to healthy, age- and sex-matched control children (n = 27). Oxidative stress parameters evaluated included advanced oxidation protein products (AOPP), total peroxyl radical-trapping antioxidant parameter (TRAP), and F2-isoprostanes (8-epi-prostaglandin-F2: 8-isoPGF2alpha). No statistically significant differences were found for any of the oxidative stress markers assessed between patients with DM1 and controls. In addition, weight, height, and routine metabolic tests, including creatininemia and cholesterol levels, were similar between the groups. The lack of significant differences between healthy controls and patients with DM1 suggests that treatment is able to counteract the increase in free radical production.

Antioxidants↗
PubMed2005

PADI4 polymorphisms are not associated with rheumatoid arthritis in the Spanish population.

OBJECTIVES: The presence of anti-citrullinated peptide antibodies is the most specific serological marker known of rheumatoid arthritis (RA). The PADI4 gene, encoding a haematopoietic isoform of the peptidylarginine deiminase citrullinating enzyme, has recently been associated with susceptibility to RA in the Japanese population. A subsequent UK report could not confirm this association, and a later French study also yielded a negative result. Given this discrepancy and the importance of antibodies against citrullinated peptides in the early course of the disease, we performed a replication study. METHODS: Three hundred and fifty-four Spanish RA patients and 498 Spanish controls were recruited from two Madrid hospitals. The padi4_104 and padi4_94 single-nucleotide polymorphisms (SNP) were analysed by TaqMan assays. RESULTS: Similarly to what was described in the British and French population, the less frequent allele of this SNP was not associated with the disease (genotype TT, 16.1% in RA patients vs 14.3% in controls; P = 0.46, odds ratio 1.15, 95% confidence interval 0.78-1.71). A confirmatory negative result was obtained on analysing another SNP in the same gene, padi4_94, in 248 RA patients and 394 controls. CONCLUSIONS: The results of our group and from the British and French studies strongly suggest that polymorphisms of the PADI4 gene do not play a role in susceptibility to RA in European populations.

Adult↗
PubMed2005

A neonatal diagnosis of congenital chronic inflammatory demyelinating polyneuropathy.

We report a female infant noticed by her mother to have reduced movements of her right wrist and left foot at birth. This female presented to the Accident and Emergency Department of Queen Elizabeth Hospital, London, UK, aged 6 weeks, with significant weakness of her right wrist and left foot. Her clinical history also revealed sudden diminution in fetal movements 2 weeks before delivery, consistent with neuropathology in utero and neuromuscular deficit in the immediate postnatal period. An initial examination revealed generalized hypotonia, areflexia, and paucity of movements. Electrophysiological studies suggested demyelinating polyneuropathy; sural nerve biopsy confirmed a diagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP). With the results and the pre- and postnatal clinical history, we believe this to be the first reported individual with congenital CIDP confirmed in the neonatal period. We describe the treatment and outcome up to the age of six years.

Anti-Inflammatory Agents↗
PubMed2005

Long-term outcome of allogeneic PBSC transplantation in pediatric patients with hematological malignancies: a report of the Spanish Working Party for Blood and Marrow Transplantation in Children (GETMON) and the Spanish Group for Allogeneic Peripheral Blood Transplantation (GETH).

We analyzed the clinical outcome in 90 children undergoing allogeneic PBSC transplantation from HLA-identical relative for leukemia. GvHD prophylaxis was CsA+ methotrexate in 50 and CsA+/-steroids in 40. Median CD34+ cells infused were 6 x 10(6)/kg (range, 1.4-32). Median follow-up was 60 months (range, 6-115). CI of transplant-related mortality (TRM) was 18.4+/-4%. On multivariate analysis, high Lansky score (>80) at transplantation was associated with lower TRM (HR, 0.9; P<0.0002). Relapse incidence (RI) was 33.6+/-6%. On multivariate analysis, high Lansky score at transplantation and cGvHD were associated with lower RI (HR, 0.04; P<0.0005 and HR, 0.23; P<0.03, respectively). Disease-free survival (DFS) was 57.8+/-5%. Disease status at transplantation (HR, 0.33; P<0.02), steroid treatment at day +90 (HR, 5.61; P<0.005) and cGvHD (HR, 0.23; P<0.005) had a significant impact on DFS in multivariate analysis. CI of cGvHD was 63.7+/-7%. Patients with cGvHD had better DFS (65+/-5%) because of lower RI (15.7+/-6%) and similar TRM (27.4+/-4%). These data suggest acceptable long-term outcomes after allogeneic PBSC transplantation in children despite the high incidence of cGvHD. These patients had a lower risk of relapse and a better DFS.

Adolescent↗
PubMed2005

Evaluation of new external quality assessment guidelines involving random blinded rechecking of acid-fast bacilli smears in a pilot project setting in Mexico.

SETTING: Laboratories in Mexico that support the national tuberculosis (TB) control program have been involved in an acid-fast bacilli (AFB) microscopy external quality assurance program which includes rechecking 100% of smears identified as AFB-positive by the local laboratories and 10% of smears identified as AFB-negative. Very few errors have been detected in Mexico using non-random selection and unblinded rechecking of the slides. OBJECTIVE: To evaluate the results from a 1-year pilot program involving blinded rechecking of randomly selected AFB slides from local TB laboratories in two Mexican states and determine its feasibility for future implementation. DESIGN: To reduce potential bias, laboratory staff from the National TB Laboratory, Institute for Epidemiological Diagnosis and Reference (InDRE), performed quarterly statistical sampling of AFB smears and on-site evaluations in local laboratories in each state. AFB smears were rechecked at the respective state laboratories with discordant results resolved at InDRE. RESULTS: A significantly greater percentage of errors was detected on the randomly selected, blinded AFB smears than on the non-randomly selected, unblinded smears. CONCLUSION: Random blinded rechecking provides more accurate estimates of AFB microscopy results, resulting in improved diagnosis and monitoring of treatment response.

Bacteriological Techniques↗
PubMed2004

Adipose tissue gene expression in obese subjects during low-fat and high-fat hypocaloric diets.

AIMS/HYPOTHESIS: Adaptation to energy restriction is associated with changes in gene expression in adipose tissue. However, it is unknown to what extent these changes are dependent on the energy restriction as such or on the macronutrient composition of the diet. METHODS: We determined the levels of transcripts for 38 genes that are expressed in adipose tissue and encode transcription factors, enzymes, transporters and receptors known to play critical roles in the regulation of adipogenesis, mitochondrial respiration, and lipid and carbohydrate metabolism. Two groups of 25 obese subjects following 10-week hypocaloric diet programmes with either 20-25 or 40-45% of total energy derived from fat were investigated. Levels of mRNA were measured by performing real-time RT-PCR on subcutaneous fat samples obtained from the subjects before and after the diets. RESULTS: The two groups of subjects lost 7 kg over the duration of the diets. Ten genes were regulated by energy restriction; however, none of the genes showed a significantly different response to the diets. Levels of peroxisome proliferator-activated receptor gamma co-activator 1alpha mRNA were increased, while the expression of the genes encoding leptin, osteonectin, phosphodiesterase 3B, hormone-sensitive lipase, receptor A for natriuretic peptide, fatty acid translocase, lipoprotein lipase, uncoupling protein 2 and peroxisome proliferator-activated receptor gamma was decreased. Clustering analysis revealed new potential coregulation of genes. For example, the expression of the genes encoding the adiponectin receptors may be regulated by liver X receptor alpha. CONCLUSIONS/INTERPRETATION: In accordance with the comparable loss of fat mass produced by the two diets, this study shows that energy restriction and/or weight loss rather than the ratio of fat: carbohydrate in a low-energy diet is of importance in modifying the expression of genes in the human adipose tissue.

Adipose Tissue↗
PubMed2004

Msx1 expression in the adult mouse brain: characterization of populations of beta-galactosidase-positive cells in the hippocampus and fimbria.

We have analyzed Msx1 expression in the mature mouse brain using in situ hybridization and beta-galactosidase activity in Msx1(nLacZ) mice. The study revealed that Msx1 is strongly expressed in the circumventricular organs, such as the subcommissural organ and choroid plexus, and in some epithelia, such as that of the dorsal, but not the ventral part of the third ventricle. Immunohistochemical analysis revealed that the Msx1-expressing cells of the hippocampus and fimbria are astrocytes, oligodendrocytes or immature oligodendrocytes. In contrast, no co-expression was detected in these structures using several neuronal markers. These results were confirmed, using transmission electron microscopy, by the presence of 5-bromo-3-indolyl-beta-D-galactopyranosideprecipitates in astrocytes and oligodendrocytes in both sites. Moreover, using an anti-glial fibrillary acidic protein antibody (GFAP), our study reveals two populations of astrocytes in the adult hippocampus and other areas, such as the fimbria, namely Msx1+/GFAP+ and Msx1-/GFAP+. Beta-galactosidase activity was also observed in endothelial cells of hippocampal fissure blood vessels. We also observed co-localization of polysialic acid neural cell adhesion molecule, a marker of the polysialylated form of the neural cell adhesion molecule, in Msx1-expressing cells in the fimbria. These cells may be precursors of glial cells and originate from the epithelium of the fimbria. The present study indicates, in the mature mouse brain, that Msx1 may be linked to secretory activity in circumventricular organs, and to glial proliferation and differentiation in the hippocampus and fimbria, and presumably also in other cerebral areas. We suggest that Msx1 could be associated with brain homeostasis and blood-brain barrier function.

Aging↗