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P Pérez

Publications and source records attributed to P Pérez.

At least 19 recordsLinked to original sources
PubMed2006

Philicity indices within the spin-polarized density-functional theory framework.

The electrophilicity index is analyzed within the framework of spin-polarized density-functional theory. In this context, constrained philicities, omega(N) identical with (mu(N))(2)(2eta(NN)), are introduced in order to define the capability of a system to acquire or donate electrons in a process at constant spin number. The spin-philicity/spin-donicity indices, omega(S)(+/-) identical with (mu(S) (+/-))(2)(2eta(SS)), are examined and rationalized here as the philicity of a given system to change its spin-polarization state, as being defined through the spin potential mu(S) and spin hardness eta(SS) for a process at constant number of electrons. The local extension of these indices has been also outlined and numerical results have been discussed on the analysis of the electrophilic nature of some simple carbene systems both in the singlet and triplet states.

Journal Article↗
PubMed2006

Classification and scoring systems in myelodysplastic syndromes: a retrospective analysis of 311 patients.

The main objective of this study was to evaluate the role of the recent World Health Organization (WHO) classification for assessing prognosis in patients with myelodysplastic syndromes (MDS). To this effect, we analyzed the prognostic impact of the WHO and French-American-British (FAB) morphologic classifications and of four different scoring systems in a series of 311 patients with primary MDS diagnosed between October 1990 and June 2001. Both the FAB and WHO classifications identified groups with different prognoses (p<0.0001), those presenting refractory anemia (RA) and refractory anemia with ringed sideroblasts (RARS) showing the best prognosis. The WHO classification subdivided RA into RA with only red cell dysplasia, and refractory cytopenia with multilineage dysplasia (RCMD), and RARS into RARS plus refractory cytopenia with multilineage dysplasia and ringed sideroblast (RCMD-RS). In our population, we have shown that the two subtypes characterized by dysplasia affecting exclusively the erythroid population (RA and RARS) have a better prognosis, with a median survival of 122.2 and 81.9 months, respectively, than those with multilineage dysplasia (RCMD and RCMD-RS) with a median survival of 32.3 and 43.2 months, respectively. There were no significant differences in median survival comparing RA with RAS (p<0.95), or comparing RCMD with RSCMD (p<0.97). Besides, the four scoring systems discriminated our MDS patients in terms of survival, and an increase in prognostic capacity was achieved on adding the score to the morphological classifications. Risk scoring had a greater prognostic impact than the FAB and WHO classifications. Prognostic scoring systems may be an important tool for risk stratification in hematological practice, and add significance to morphological classification. Combined application of the WHO classification and score system is useful for improving the identification of patients with a poorer prognosis. The WHO classification establishes more homogeneous subcategories than the FAB classification and is also able to identify groups with different prognoses.

Adult↗
PubMed2006

Inorganic particles in the skin of inhabitants of volcanic areas of Central America: their possible immunomodulatory influence in leishmaniasis and leprosy.

We have evaluated biopsies from patients with atypical nodular and typical ulcerated lesions of cutaneous leishmaniasis, from leishmanin reactions and skin from normal individuals from Nicaragua, Honduras and Guatemala for the presence of inorganic particles using confocal microscopy with a polarised light source and conventional histopathological techniques. Analysis by semiquantitative confocal microscopy permitted the demonstration of significantly larger numbers of particles in atypical lesions. Silica and aluminium, important components of these particles, were less abundant in particles from normal skin. The histology of these atypical lesions, characterised by 'naked' sarcoidal granulomas with epithelioid differentiation but very few lymphocytes, was very similar to the histological reaction observed after 14 days in persisting inflammation at leishmanin skin test sites. The presence of these unusual lesions in areas of Central American countries characterised by the presence of large amounts of volcanic ash, as well the unexpectedly low prevalence of leprosy in Central America, suggest that environmental factors may contribute significantly to the frequency and clinical manifestations of these infections. Among possible environmental features, the presence of inorganic particles with immunomodulatory properties in the skin may be a significant factor.

Aluminum↗
PubMed2005

Empirical energy-density relationships applied to the analysis of the basicity of strong organic superbases.

Site selectivity and reactivity in some strong organic super bases RN=C(NR(2))R, containing several possible sites for protonation, have been analyzed qualitatively in terms of global and local chemical reactivity descriptors defined in the context of conceptual density functional theory. On the basis of the condensed-to-site Fukui function values, the protonation site is predicted to be located at the imino nitrogen. Linear relationships between global energy-dependent quantities and the variation of the Fukui function (or the local softness) at the protonation site have been also found. These linear relationships can be interpreted within a local HSAB rule framework, as observed for instance for the gas-phase basicity of alkylamines and gas-phase acidity of alcohols and thioalcohols. This work extends the range of applicability of reactivity models developed for the treatment of substituent effects based on empirical energy-density Hammett-like relationships.

Models, Chemical↗
PubMed2005

Basal lamina disorganisation of the acini and ducts of labial salivary glands from patients with Sjogren's syndrome: association with mononuclear cell infiltration.

OBJECTIVE: To study the expression of laminin and type IV collagen as biomarkers of the organisation of the basal lamina of acini and ducts in labial salivary glands from patients with Sjögren's syndrome, and to relate this organisation to inflammatory cell invasion of acini and ducts. METHODS: Immunohistochemistry for laminin and type IV collagen was undertaken on sections of labial salivary glands from 30 patients with Sjögren's syndrome, 10 control subjects, and 24 controls with chronic sialoadenitis. Immunohistochemistry reaction, alterations to cell morphology, and the presence of inflammatory cells in acini and ducts were evaluated and scored using a semiquantitative method. RESULTS: Changes in the expression of laminin and type IV collagen in the basal lamina of acini and ducts of labial salivary glands from patients with Sjögren's syndrome were more pronounced than in labial salivary glands from control groups. A remarkable characteristic was the disorganisation of the basal lamina in the labial salivary glands in Sjögren's syndrome. The pattern of immunoreactivity of the basal lamina of other structures (for example, blood vessels) did not change. In Sjögren's syndrome, invasion of cytotoxic T lymphocytes was only observed in acini and ducts which had a disorganised basal lamina. CONCLUSIONS: The high state of disorganisation of the basal lamina of acini and ducts could allow invasion of cytotoxic T lymphocytes in Sjögren's syndrome, contributing to cell death and ductal hyperplasia.

Adult↗
PubMed2005

Fructan synthesis is inhibited by phosphate in warm-grown, but not in cold-treated, excised barley leaves.

The inhibition of fructan accumulation by phosphate was investigated in warm-grown and cold-treated barley (Hordeum vulgare) plants. Detached leaves were incubated in water or phosphate for 24 h under lighting or in darkness. Fructosyltransferase, sucrose phosphate synthase (SPS) and cytosolic fructose-1,6-bisphosphatase (FBPase) activities were subsequently analysed, as well as the content of carbohydrates, hexose-phosphates, phosphate, amino acids and protein. In warm-grown leaves, phosphate decreased fructan accumulation and total carbon in carbohydrates and did not affect protein content. Phosphate increased hexose-phosphates, phosphate and amino acids. Fructosyltransferase and FBPase activities were not affected by phosphate feeding, while SPS activity was inhibited by phosphate in incubations in both light and darkness. In cold-treated leaves, which before incubation had higher SPS activities than warm-grown leaves, phosphate had no inhibitory effect on fructan accumulation, carbohydrate content or total C in carbohydrates. The activities of SPS and FBPase were unaffected by phosphate. The results indicate that phosphate decreases fructan accumulation through an inhibition of SPS whenever this activity is not high before a rise in phosphate content.

Amino Acids↗
PubMed2005

[Infectious complications after epidural analgesia to control pain after abdominal surgery].

Epidural abscess as a complication of spinal analgesia is rare, but because of its potential clinical implications it must always be watched for in patients who have undergone epidural procedures. The case we report is of interest because of the long latency period between removal of the catheter and the onset of clinical signs and because of the rarity of the pathogen implicated in forming the abscess (Candida albicans).

Ampulla of Vater↗
PubMed2004

Action of different monoterpenic compounds against Anisakis simplex s.l. L3 larvae.

Different natural monoterpenes (geraniol, citronellol, citral, carvacrol, cuminaldehyde and eugenol) are studied in vitro against Anisakis simplex s.l. L3 larvae, employing perillaldehyde as a reference substance. Final concentrations used were: 12.50, 6.25 and 3.12 microg/ml for each of the tested products. The parameters average survival, survival 50 and maximum survival were determined at 4, 8, 24 and 48 hours after the start of the experiment. All tested products, except eugenol, were active at the highest concentration (12.50 microg/ml). The damage caused to A. simplex s.l. L3 was by examining histological sections. The antioxidant activity of the tested products by DPPH free radical scavenging does not appear to be associated with their larvicide activity against A. simplex s.l. L3.

Animals↗
PubMed2004

[Endovascular resolution of iliac artery pseudoaneurysm in a transplanted patient].

A 58-year-old patient with end-stage idiopatic renal disease underwent kidney transplantation from a cadaveric donor. Approximately one year after the transplant he complained of abdominal pain and presented a pulsating mass in his right pelvic region. Dupplex study and arteriography were performed and showed a large pseudoaneurysm arising from the right common iliac artery. We report the case in which a covered stent placement and an embolization of the right internal iliac artery solved the problem with successful clinical and radiological results.

Aneurysm, False↗
PubMed2003

H-bonded N-heterocyclic base-pair phototautomerizational potential barrier and mechanism: The 7-azaindole dimer.

A theoretical analysis of the double proton transfer (PT) in a hydrogen-bonded N-heterocyclic base pair is presented. The calculated (time-dependent density functional theory) double PT barrier calculated for the concerted process of the 7-azaindole C(2h) dimer in the first excited singlet electronic state S(1) conforms well to the kinetic data and the photophysical evidence reported in this article. The calculated PT energy barrier of 4.8 kcal/mol height, and the corresponding zero point energy value, yield for the S(1) state an activation energy barrier of 0.3 kcal/mol. This finding implies that the double PT concerted process is almost barrierless, confirming previous experiments. Upon N-H deuteration of the 7-azaindole dimer, the theoretical excited-state activation energy for the double deuterium transfer is determined to be 1.4 kcal/mol, in agreement with experiment, which in low-temperature spectroscopy is shown to negate excited-state double-deuteron transfer.

Journal Article↗
PubMed2002

[Nasal polyposis: postoperative long term results (5 years) after endoscopic sinus surgery].

The purpose of this study is to evaluate the results after endoscopic sinus surgery in cases of nasal polyposis. We include 54 patients with diffuse nasal polyposis suffering from nasal obstruction. An endoscopic sinus surgery under general anesthesia with excision of the polyposis was performed. There were no complications. The patients were followed closely and treated with local and systemic steroids. After 5 years, the 75% of these patients were free of nasal symptoms and in the 67% the mucosa appeared normal. We also review the influence of some factors (ASA triad, anosmia, allergy...) in the recurrence of the disease.

Adult↗
PubMed2002

Effect of bile on the lipid composition and surface properties of bifidobacteria.

AIM: The changes produced on the bacterial surface of Bifidobacteria cells when they are grown in bile were compared with those provoked by bile added to bacteria grown in the absence of bile. METHODS AND RESULTS: The adhesive properties, the zeta potential and the lipid composition of Bifidobacterial strains, isolated from human faeces and grown in MRS medium, were determined. Bacteria grown in MRS with bile showed a loss of adherence and autoaggregation in correlation with a decrease in the surface hydrophobicity in comparison to those grown in MRS without bile, concomitant with the absence of two glycolipids, the increase of sugar content and minor changes in fatty acid composition. The surface changes caused by bile shock on bacteria grown in bile-free medium were much less pronounced and, in addition, no effect on the lipid composition was apparent. CONCLUSIONS: The comparison of the results indicates that bile action on surface properties is related to metabolic changes. SIGNIFICANCE AND IMPACT OF THE STUDY: Long-term exposure of bacteria to bile may cause metabolic changes affecting their adhesive properties irreversibly. This may be taken as a criterion to define the probiotic properties of different strains.

Bacterial Adhesion↗
PubMed2001

Altered skin development and impaired proliferative and inflammatory responses in transgenic mice overexpressing the glucocorticoid receptor.

Glucocorticoids (GCs) are potent inhibitors of epidermal proliferation and effective anti-inflammatory compounds, which make them the drug of choice for a wide range of inflammatory and hyperproliferative skin disorders. GC action is mediated via the glucocorticoid receptor (GR). To study the role of GR in skin development and the molecular mechanisms underlying its action, we generated transgenic mice overexpressing GR in epidermis and other stratified epithelia, under the control of the keratin K5 promoter. Newborn mice show altered skin development, manifested as variable-sized skin lesions that range from epidermal hypoplasia and underdeveloped dysplastic hair follicles to a complete absence of this tissue. In the most affected individuals, skin was absent at the cranial and umbilical regions, and the vibrissae and eyebrows appear scarce, short, and curly. In addition, as a consequence of transgene expression in other ectodermally derived epithelia, K5-GR mice exhibited further abnormalities that strikingly resemble the clinical findings in patients with ectodermal dysplasia, which includes aplasia cutis congenita. In adult transgenic skin, topical application of the tumor promoter TPA did not elicit hyperplasia or transcriptional induction of several proinflammatory cytokines. This anti-inflammatory role of GR was due at least in part to interference with NF-kB, leading to a strong reduction in the kB-binding activity without altering the transcriptional levels of the inhibitor IkBa.

Animals↗
PubMed2001

The Aspergillus nidulans carnitine carrier encoded by the acuH gene is exclusively located in the mitochondria.

The location of the Aspergillus nidulans carnitine/acyl-carnitine carrier (ACUH) was studied. ACUH with a His-tag at its N-terminus was over-expressed in Escherichia coli and purified by Ni(2+) affinity chromatography. The purified protein was utilised to raise polyclonal antibodies which were characterised by Western blotting. For localisation studies A. nidulans T1 strain, that contains the acuH gene under control of the strong promoter alcA(p), was derived. Results obtained demonstrate the exclusively mitochondrial localisation of ACUH and therefore exclude the targeting of the acuH gene product to the peroxisomal membrane.

Antibodies↗
PubMed2001

Solvent effects on electrophilicity.

Continuum solvent effect on the electrophilicity index recently proposed by Parr and co-workers (Parr, R. G.; von Szentpaly, L.; Liu, S. J. Am. Chem. Soc. 1999, 121, 1922) is discussed in detail. Solvent effect is introduced using the self-consistent isodensity polarized continuum model (SCI-PCM). A linear relationship is found between the change in electrophilicity index and the solvation energy as represented in the frame of the reaction field theory. The effect of a polarizable environment on the global electrophilicity is examined for a series of 18 well-known electrophiles presenting a wide diversity in structure and bonding properties. It is found that solvation enhances the electrophilicity power of neutral electrophilic ligands but attenuates this power in charged and ionic electrophiles.

Journal Article↗
PubMed2001

A novel mutation within the extracellular domain of TrkA causes constitutive receptor activation.

The TrkA NGF receptor extracellular region contains three leucine repeats flanked by cysteine clusters and two immunoglobulin-like domains that are required for specific ligand binding. Deletion of the immunoglobulin-like domains abolishes NGF binding and causes ligand independent activation of the receptor. Here we report a specific mutation that increases the binding affinity of the TrkA receptor for NGF. A change of proline 203 to alanine (P203A) in the linker region between the leucine repeats and the first Ig-like domain increased NGF binding by decreasing the ligand rate of dissociation. This mutated receptor was appropriately expressed on the cell surface and promoted ligand-independent neurite outgrowth in PC12nnr5 cells. The mutant receptor was capable of spontaneous dimerization and was constitutively phosphorylated in the absence of ligand. Moreover, expression of TrkA-P203A receptor in fibroblasts induced DNA synthesis and transformation and generated tumours in nude mice. These data suggest that domains outside of the immunoglobulin-like structure contribute to ligand binding and constitutive activation of Trk receptors.

Amino Acid Substitution↗
PubMed2001

Fine-needle aspiration cytology of Kikuchi's lymphadenitis: a report of ten cases.

The purpose of this study was to evaluate the cytologic features of Kikuchi's lymphadenitis (KL). Smears from 10 patients with histologically proven KL were reviewed. In all cases, fine-needle aspiration (FNA) was performed prior to biopsy. To assess the validity of morphologic recognition, a blinded study, including smears from non-Hodgkin's lymphomas, nonspecific, and mycobacterial lymphadenitis was performed. At least 5 cases showed characteristic cytologic findings that permitted their specific recognition. A polymorphous lymphoid population with abundant karyorrhectic debris and histiocytes, many of which showed a small size and eccentrically placed, crescent nuclei, were characteristic features of KL. The remaining 5 cases failed to show typical findings and were indistinguishable from other nonspecific, reactive lymphadenopathies. When typical cytologic findings are present in an adequate clinical context (cervical nodes in young patients), a precise diagnosis is possible, avoiding unnecessary biopsies.

Adult↗