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Biomedical subjects

A Prieto

Publications and source records attributed to A Prieto.

At least 55 records · Page 3Linked to original sources
PubMed1999

Stimulus correlation and adaptive motion detection using spiking neurons.

Stimulus correlation and adaptive movement detection, among other tasks can be performed with VLSI general-purpose neurons that have controllable steady and transient responses. This paper presents experimental results of simple neural primitives based on the CMOS neuron approach described in [11]. Stimulus correlation experiments illustrate the well defined behavior of the CMOS approach. This basic primitive is used to implement motion detectors with adaptive capabilities that enable it to work efficiently in a wide velocity range.

Action Potentials↗
PubMed1999

A new measurement of noise immunity and generalization ability for MLPs.

This paper shows a quantitative relation between the regularization techniques, the generalization ability, and the sensitivity of the Multilayer Perceptron (MLP) to input noise. Although many studies about these topics have been presented, in most cases only one of the problems is addressed, and only experimentally obtained evidence is provided to illustrate some kind of correlation between generalization, noise immunity and the use of regularization techniques to obtain a set of weights after training that provides the corresponding MLP with generalization ability and noise immunity. Here, a new measurement of noise immunity for a MLP is presented. This measurement, which is termed Mean Squared Sensitivity (MSS), explicitly evaluates the Mean Squared Error (MSE) degradation of a MLP when it is perturbed by input noise, and can be computed from the statistical sensitivities (previously proposed) of the output neurons. The MSS provides an accurate evaluation of the MLP performance loss when its inputs are perturbed by noise and can also be considered a measurement of the smoothness of the error surface with respect to the inputs. Thus, as the MSS can be used to evaluate the noise immunity or the generalization ability, it gives a criterion to select among different weight configurations that present a similar MSE after training.

Models, Neurological↗
PubMed1999

Regulatory effects of cytokines and cyclosporine A on peripheral blood mononuclear cells from stable multiple sclerosis patients.

The proliferative response (PR) of peripheral blood mononuclear cells (PBMC) to lectins such as phytohemaglutinin (PHA), anti-CD3 monoclonal antibodies such as OKT-3 or phorbol esters such as tetradecanoyl-phorbol 13-acetate (TPA) was investigated in 18 stable multiple sclerosis (MS) patients (9 untreated and 9 treated patients) and 10 healthy controls. PBMC from untreated MS patients showed a significantly higher PR to PHA than healthy controls. The PR of PHA, anti-CD3 or TPA stimulated PBMC from treated patients was lower than that from untreated MS patients. Mitogen stimulated PBMC from untreated patients shown both increased sensitivity to the stimulatory effect of IL-2 and increased resistance to the inhibitory effect of IL-10 and IFN-alpha. The addition of IL-2 increased the PR in PHA-stimulated PBMC from untreated MS patients, but not in those from treated MS patients and healthy controls. Mitogen stimulated cells from untreated patients were more resistant to the inhibitory effect of IL-10 and IFN-alpha than PBMC from either treated MS patients or healthy controls. Cyclosporine A (CsA) inhibited the PR and the expression of activation antigens induced by PHA in PBMC from the three groups of subjects. This inhibitory effect of CsA have was enhanced by the addition of IFN-alpha.

Adult↗
PubMed1999

Abnormal functional behavior of peripheral blood mononuclear cells from Hashimoto's disease patients. Immunomodulatory effects of cyclosporin A.

In vitro studies of activation and proliferation induced by mitogens in the presence of Cyclosporin A (CsA) and or cytokines were carried out to determine the effects of CsA and cytokines on mitogen activated peripheral blood mononuclear cells (PBMC) from thirteen Hashimoto's disease patients (HP) and ten healthy controls. The proliferative response (PR) of PBMC from HP to mitogens at 7 days of culture was higher than in controls. Interleukin 2 (IL-2) addition significantly increased the PR in phytohemagglutinin-stimulated PBMC from HP, but not in controls. CsA inhibited in a dose dependent manner the PR, as well as the expression of activation antigens induced by mitogens in both groups of subjects, but PBMC from HP were sensitive to CsA at lower doses than those that were effective on PBMC from controls. Both IL-2 or IL-4 overcame the inhibitory effect of CsA on PBMC from HP and controls. Conversely, IL-10 or IFN-alpha addition increases the inhibitory effect of CsA on the PR of PBMC from both HP and controls. We conclude that PBMC from Hashimoto's disease patients shown an abnormal pattern of PR that is associated to increased PR to mitogens and higher sensitivity to immunomodulatory effects of IL-2 and CsA.

Adjuvants, Immunologic↗
PubMed1999

Defective proliferative response of T lymphocytes from patients with inactive systemic lupus erythematosus.

OBJECTIVE: To further define the pattern of alterations in the activation and apoptosis of T lymphocytes in patients with inactive systemic lupus erythematosus (SLE) through analysis of a large series of individuals. METHODS: We isolated CD2+ peripheral blood lymphocytes (PBL) from 41 patients with inactive SLE and analyzed their proliferative and apoptotic responses to polyclonal activation. RESULTS: In 19 of 41 (47%) patients, a low proliferative response to polyclonal mitogens was found. This defective response was inversely associated with an increased apoptotic response and increased expression of CD95 and CD45RO antigens. CONCLUSION: We found that 2 groups of patients with inactive disease can be defined according to the functional behavior of their T lymphocytes, as defined by the proliferative and apoptotic responses to mitogenic signals.

Adolescent↗
PubMed1998

Altered pattern of cytokine production by peripheral blood CD2+ cells from B chronic lymphocytic leukemia patients.

To determine if activation-induced cytokine production is altered in CD2+ lymphocytes from B-CLL patients, cytokine levels were determined by ELISA in supernatants of PHA-stimulated cultures of CD2+ cells from 33 B-CLL patients and 22 healthy controls. The production of Interferon gamma (IFN-gamma) and Tumor Necrosis Factor (TNF-alpha) by mitogen-activated CD2+ lymphocytes from B-CLL patients was higher than that found in healthy controls, while no differences were found in TNF-beta production. IFN-gamma and TNF-alpha levels determined at 72 h in PHA-stimulated CD2+ cell cultures from B-CLL patients statistically correlated with the percentages of CD3+CD45RO+ and CD3-CD56+ lymphocytes, respectively. Although there were differences in the production kinetics of interleukins (ILs) 2 and 4 between B-CLL patients and the healthy controls, no differences were found at the time when the levels of both interleukins peak. The production of both IFN-gamma and IL-4 by PHA-stimulated CD2+ lymphocytes from non-smouldering B-CLL patients was significantly higher than that from smouldering B-CLL patients while no significant differences were found in the production of IL-2, TNF-alpha, and TNF-beta between the two B-CLL patient groups. These data suggest that functional alterations in the production of cytokines by CD2+ cells from B-CLL patients could help to explain the expansion of leukemic cells in B-CLL patients.

Adult↗
PubMed1998

Cyclosporin A-induced hydrogen peroxide synthesis by cultured human mesangial cells is blocked by exogenous antioxidants.

Cyclosporin A (CsA) is the immunosupressor most widely used in transplanted patients for preventing organ rejection, but it has some toxic side effects in vascular beds and kidney. The purpose of this work was to study if H2O2, a reactive oxygen species, is involved in the CsA-induced toxic effects on kidney in vitro. Human mesangial cells (HMC) in culture were incubated in presence of CsA (10[-5]-10[-8]M) and H2O2 was measured by flow cytometry. The specificity of the probe used in this method was demonstrated as fluorescence was not detected when superoxide anion generated through a Xanthine-Xanthine oxidase system was present, but fluorescence was noted when H2O2 was present in the incubation medium, both directly and after addition of superoxide dismutase to the medium thus promoting H2O2 synthesis. CsA induced a significant dose and time-response increased H2O2 synthesis by cultured HMC. This increase appeared 5 min after CsA addition, being maximal between 15-45 min at CsA concentration of 10(-7)M. When HMC were preincubated with antioxidants as vitamin E or selenium, the CsA-induced H2O2 production was partially blocked. In addition, selenium also induced an increased activity of glutathion peroxidase in HMC after 24 hours of incubation, suggesting that it exerted its H2O2 scavenging action through the modulation of the activity of this enzyme.

Antioxidants↗
PubMed1998

Role of the new azoles in the treatment of fungal osteoarticular infections.

OBJECTIVES: To analyze the usefulness of the new azoles for the treatment of fungal osteoarticular infections, and to report three cases of fungal knee arthritis treated with fluconazole in our unit. METHODS: The medical literature was reviewed for all cases of osteoarticular infection caused by fungi and treated with fluconazole or itraconazole registered in the MedLine Silver Platter database from 1972 to 1997. RESULTS: The total number of patients included in this review was 56; 19 were treated with fluconazole and 37 with itraconazole. The most frequent causative agents implicated were fungi of the genuses Candida and Aspergillus. There were eight therapeutic failures, and there were no statistically different findings among the patients in terms of their health status. Adverse effects were unusual. CONCLUSIONS: Controlled studies are necessary to establish the true role of the new azole drugs in the treatment of fungal osteoarticular infections, but they seem to be a promising therapeutic option.

Adult↗
PubMed1998

Nonpigmenting fixed drug eruption due to pseudoephedrine.

BACKGROUND: The nonpigmenting fixed drug eruption is a distinctive drug reaction characterized by large, tender and symmetric erythematous plaques that disappear with no residual pigmentation. METHODS: A case of a non-pigmenting fixed drug eruption due to pseudoephedrine is reported. RESULT: The reappearance of typical lesions at the same sites after oral challenge with 60 mg pseudoephedrine together with the absence of pigmentation confirm the diagnosis. CONCLUSION: A new case of proven nonpigmenting fixed drug eruption to pseudoephedrine is described.

Adult↗
PubMed1998

Immune function in aged women is improved by ingestion of vitamins C and E.

We have investigated the effects of supplementation of the diet with the antioxidant vitamins C and E on several functions of the immune response of aged women. Ten healthy women and 20 women (72 +/- 6 years old) suffering two diseases often associated with age (10 with major depression disorders, MDD, and 10 with coronary heart disease, CHD) were administered 1 g of vitamin C and 200 mg of vitamin E daily for 16 weeks. Blood samples were collected before and after treatment for measurement of several immunological functions, namely proliferative response of lymphocytes to the mitogen phytohemagglutinin (20 mg/L) and phagocytic functions of polymorphonuclear (PMN) neutrophils, i.e., adherence to vascular endothelium, chemotaxis, phagocytosis of latex beads, and superoxide anion production. In addition, we also determined the levels of serum cortisol and lipid peroxides. Intake of vitamins resulted in a significant increase in the lymphoproliferative capacity and in the phagocytic functions of PMN neutrophils as well as in a significant decrease of serum levels of lipid peroxides and cortisol, both in the healthy aged women and in the aged women with MDD or CHD. These findings suggest an important role of antioxidant supplementation in the improvement of immune function in aged females as well as in the prevention and treatment of specific diseases associated with age that are quite prevalent in the developed countries.

Aged↗
PubMed1997

Studies on the structure and the solution conformation of an acidic extracellular polysaccharide isolated from Bradyrhizobium.

The structure of an acidic extracellular polysaccharide isolated from Bradyrhizobium (Chamaecytisus proliferus) has been elucidated by hydrolysis, methylation analysis, and 1D and 2D 1H- and 13C-NMR spectroscopy of the complete polysaccharide. The NMR spectrum showed that microheterogeneity was present due to the minor existence of a variety of O-acetyl groups. Thus, a deacetylated sample was prepared by alkaline treatment which was then fully analysed. The deacetylated polysaccharide has the following sequence: -->3)-[alpha-D-Galp-(1-->6)-alpha-D-Glcp-(1-->3)-beta-D-Glcp-(1-->3)- alpha-D-GalpA-(1-->3)-alpha-D-Manp-(1--> The sample is partially O-methylated at position 4 of the alpha-D-Galp-(1-->6) unit. In addition, the same moiety of the native sample is also partially and heterogeneously O-acetylated. The conformational features of the deacetylated sample have been evaluated by molecular mechanics and dynamics calculations and NOE spectroscopy. The results indicate that the polysaccharide may adopt a variety of three dimensional shapes, and that there is a fair agreement between the NMR-derived distances and those provided by the calculations

Carbohydrate Conformation↗
PubMed1997

Structure of complex cell wall polysaccharides isolated from Trichoderma and Hypocrea species.

The structure of fungal polysaccharides isolated from the cell wall of Trichoderma reesei, T. koningii, and Hypocrea psychrophila, have been investigated by means of chemical analyses and 1D and 2D NMR spectroscopy. The polysaccharides have an irregular structure, idealized as follows: [formula: see text] The proportions of the different side chains vary from a species to another, being n above some three times larger in H. psychrophila than in T. reesei or T. koningii.

Carbohydrate Conformation↗
PubMed1997

Structural elucidation of acidic fungal polysaccharides isolated from the cell-wall of genera Cylindrocladium and Calonectria.

The structure of acidic fungal polysaccharides, isolated from the cell wall of Cylindrocladium and Calonectria species, has been investigated by chemical analysis, methylation and reductive cleavage analyses, and 1D and 2D 1H and 13C NMR spectroscopy. The polysaccharides have an idealized repeating unit: [formula: see text] linked to a small mannan core (< 5%), with n = 3 for Cylindrocladium penicilloides and C. quinqueseptatum and n = 5 for Calonectria theae, C. crotalariae, and C. colhounii.

Carbohydrate Sequence↗
PubMed1997

Characteristics of thoracic duct lymph in multiple organ dysfunction syndrome.

OBJECTIVE: To investigate the presence of endotoxin, bacteria, and potential humoral and cellular mediators in thoracic duct lymph and peripheral blood in patients with severe refractory multiple organ dysfunction. DESIGN: Convenience sample. SETTING: General intensive care unit of a university hospital. PATIENTS: Two men and 2 women were studied after a mean of 7.25 days (range, 6-9 days) of multiple organ dysfunction syndrome. The primary injury was thoracic in 1 patient and abdominal in 3 patients. INTERVENTION: The thoracic duct was cannulated with a 7F catheter and samples of lymph and peripheral blood were obtained. MAIN OUTCOME MEASURES: Simultaneous lymph and serum levels of lipopolysaccharide, tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6, and activation markers on T lymphocytes. RESULTS: Lipopolysaccharide and cytokine levels were low in lymph and serum, except for a mean lymph-to-serum ratio of 53.4 for interleukin-1 beta. There was phenotypical evidence of intense polyclonal T-lymphocyte activation in both lymph and peripheral blood with increased lymph-to-peripheral blood ratios. Increased percentages in lymph of CD45RA + CD45RO + lymphocytes were observed. In 1 patient, Proteus mirabilis grew simultaneously in lymph, pancreatic necrosis fluid, and a central venous catheter tip. All simultaneous blood cultures were negative. CONCLUSIONS: Our results provide evidence of the participation of the gut-associated lymphatic tissue in the pathogenesis of the multiple organ dysfunction syndrome, suggesting that T-cell activation and cytokine production occur at the gut level. Future studies are needed to confirm and extend our findings.

Female↗
PubMed1997

Morphological variants of leukemic cells in B chronic lymphocytic leukemia are associated with different T cell and NK cell abnormalities.

B chronic lymphocytic leukemia (B-CLL) is a heterogeneous disease. The different morphological variants of leukemic B cells appear to define different clinical groups of patients. Several abnormalities have been found in T lymphocytes and natural killer (NK) cells from B-CLL patients. We have investigated the phenotypic and functional characteristics of purified CD2+ cells from B-CLL patients at Binet's stage A and classified according to the neoplastic B lymphocyte morphology criteria: 32 patients with typical B-CLL and 12 patients with atypical B-CLL. Forty-three age and sex matched healthy controls were also studied. In fresh purified CD2+ cells from typical B-CLL patients, percentages of CD4+, CD4+CD45RA+, CD8+CD45RA+ T lymphocytes and CD3-CD56+ (NK) cells were significantly higher than those found in atypical B-CLL patients. However, in DC2+ cells from typical B-CLL patients, percentages of CD3+, CD3+DR+, CD8+, CD4+CD45RO+, and CD3+CD56+ cells were significantly lower than those found in atypical B-CLL patients. Increased percentage of NK cells was only found in typical B-CLL patients. The proliferative response and the production of interleukin (IL)-2 and IL-4 by phytohemagglutinin (PHA) stimulated CD2+ cells were significantly higher in typical B-CLL patients than in atypical B-CLL patients. We concluded that different patterns of phenotypic and functional alterations in the T lymphocytes and NK cells of B-CLL patients are found in patients with typical or atypical B-CLL defined according to the morphology of the leukemic cells.

Adult↗