Showing papers by "University of Barcelona published in 1990"

Preparation and application of the 5-(4-(9-fluorenylmethyloxycarbonyl)aminomethyl-3,5-dimethoxyphenoxy)-valeric acid (PAL) handle for the solid-phase synthesis of C-terminal peptide amides under mild conditions

Abstract: The pure para isomer of title compound (I) was prepared by each of two efficient five-step routes, in overall yields from 52% to 74%. The handle I was coupled into a variety of amino group-containing supports to provide a general starting point for stepwise assembly of peptide chains according to a wide range of chemistries. In particular, protocols based on the base-labile Nα-9-fluorenylmethyloxycarbonyl (Fmoc) group worked well with PAL handle I. A side reaction involving alkylation at tryptophan was elucidated, and conditions were developed to minimize its occurrence. The methodology was demonstrated by syntheses of over a hundred peptides, among which acyl carrier protein (65-74) amide (natural and retro sequences), luteinizing hormone-releasing hormone, adipokinetic hormone, PHI porcine fragment (18-27), and human gastrin-I are highlighted in this report

WHO International Histological Classification of Tumours. Tentative Histological Classification of Salivary Gland Tumours.

Abstract: The principles of the proposed modified WHO Histological Typing of Salivary Gland Tumours are based on the following: 1) The classification of tumours is oriented to the routine work of the practicing surgical pathologists, those who do not see tumours of the salivary glands very often. The inclusion of rare, but clearly defined tumour entities should be helpful to surgical pathologists consulting with clinical specialists. 2) The different types of carcinomas must be distinguished not only by precise histopathological definitions, but also considering differences in prognosis and treatment. For example, the polymorphous low-grade adenocarcinoma and the epithelial-myoepithelial carcinoma are characterized by a relatively good prognosis in contrast to the salivary duct carcinoma. 3) Special points of discussion are: subclassification and grading of carcinomas (e.g. acinic cell carcinoma, mucoepidermoid carcinoma and adenoid cystic carcinoma), the classification of basal cell tumours (basal cell adenoma, basal cell carcinoma, solid type of adenoid cystic carcinoma), malignant tumours in pleomorphic adenomas and the differential diagnosis between primary tumours and metastases.

Leuko-Araiosis on Magnetic Resonance Imaging and Speed of Mental Processing

Abstract: • The clinical significance of white matter abnormalities seen in brain imaging studies, termed leuko-araiosis (LA), still remains uncertain. Leuko-araiosis has been associated with a global decline in cognitive performance, although little is known about the cognitive functions that LA may account for. We present the correlates between LA severity on magnetic resonance imaging and mental deterioration in a selected sample of 41 elderly patients with vascular risk factors. We found that LA was related to performance on tasks measuring the speed of information processing and, in particular, on those that involve complex processes. This impairment can be important in producing reduction in daily living activities as it is in the support to the relationship found with some commonly used behavioral rating scales. Leuko-araiosis is also related to the presence of some primitive reflexes, suggesting that their disinhibition may be due to diffuse corticofugal fibers damage.

Lipoprotein lipase: cellular origin and functional distribution.

Abstract: Lipoprotein lipase (LPL, E.C. 3.3.1.34) is the enzyme responsible for hydrolysis of triacylglycerols in plasma lipoproteins, making the fatty acids available for use by subjacent tissues. LPL is functional at the surface of endothelial cells, but it is not clear which cells synthesize the enzyme and what its distribution is within tissues and vessels. We have searched for specific cell expression of the LPL gene by in situ hybridization using a RNA probe and for the corresponding protein distribution by immunocytochemistry on cryosections of some LPL-producing tissues of guinea pigs. In white and brown adipose tissues, heart and skeletal muscle, and lactating mammary gland, there was positive hybridization for LPL mRNA over all members of the major cell types, indicating that mature and immature adipocytes, muscle cells, and mammary epithelial cells are main sources of LPL. In large vessels, LPL expression was detected in some smooth muscle cells in the media layer. There was no positive hybridization for LPL mRNA over endothelial cells in any of the tissues studied, but there was immunoreaction for LPL protein at endothelial surfaces of all blood vessels. In the kidney, there was strong immunofluorescence at the vascular endothelium, particularly in the glomeruli, but little or no LPL mRNA was detected in the surrounding cells. These observations suggest that in some tissues LPL is synthesized by parenchymal cells and spreads along the vascular mesh. Transfer to the vascular endothelium is, however, not the only route taken by LPL. In the mammary gland most of the enzyme protein appeared to be secreted, partly in association with milk fat droplets.(ABSTRACT TRUNCATED AT 250 WORDS)

Single-breath carbon monoxide diffusing capacity prediction equations from a Mediterranean population.

Abstract: Because of unanswered questions about prediction equations for the single-breath carbon monoxide diffusing capacity (DlCO) and as part of a larger collaborative project, standardized DlCO measurements were carried out in a selected sample of 361 healthy nonsmoking volunteers (194 men and 167 women) living in the Barcelona metropolitan area (Spain). Except for the test FiO2 (0.18), the study essentially followed the American Thoracic Society (ATS) and European Community for Coal and Steel (ECCS) recommendations for standardizing the methodology of measuring DlCO. Prediction equations for ages 20 through 70 were calculated separately for both sexes. Simple linear equations using age, height, and body weight as independent variables predicted the DlCO indices (DlCO, Va, and Dl/Va) as well as more complex equations. In addition, a complete analysis of the residuals (predicted measured values) showed that the assumptions of the multiple regression analysis (independence, homoscedasticity and Gaussian distribut...

Factors influencing carbon fixation and water use by Mediterranean sclerophyll shrubs during summer drought

Abstract: Mediterranean sclerophyll shrubs respond to seasonal drought by adjusting the amount of leaf area exposed and by reducing gas exchange via stomatal closure mechanisms. The degree to which each of these modifications can influence plant carbon and water balances under typical mediterranean-type climate conditions is examined. Leaf area changes are assessed in the context of a canopy structure and light microclimate model. Shifts in physiological response are examined with a mechanistically-based model of C3 leaf gas exchange that simulates progressive reduction of maximum photosynthesis and transpiration rates and increasingly strong midday stomatal closure over the course of drought. The results demonstrate that midday stomatal closure may effectively contribute to drought avoidance, increase water use efficiency, and strongly alter physiological efficiency in the conversion of intercepted light energy to photoproducts. Physiological adjustments lead to larger reductions in water use than occur when comparing leaf area index 3.5 to 1.5, extremes found for natural stands of sclerophyll shrubs in the California chaparral. Reductions in leaf area have the strongest effect on resource capture and use during non-water-stressed periods and the least effect under extreme drought conditions, while shifts in physiological response lead to large savings of water and efficient water use under extreme stress. An important model parameter termed GFAC (proportionality factor expressing the relation of conductance [g] to net photosynthesis rate) is utilized, which changes in response to the integrated water stress experimence of shrubs and alters the degree to which stomata may open for a given rate of carbon fixation. We attempt to interpret this parameter in terms of physiological mechanisms known to modify control of leaf gas exchange during drought. The analysis helps visualize means by which canopy gas exchange behavior may be coupled to physiological changes occurring in the root environment during soil drying.

Down's syndrome and Alzheimer's disease: dendritic spine counts in the hippocampus.

Abstract: Samples of the hippocampus of four patients with Down's syndrome [two men aged 35 and 36 years with no evidence of Alzheimer's disease (AD) and two patients aged 47 and 55 years with associated AD] were obtained at post mortem and processed according to the rapid Golgi method. A significant reduction in the number of dendritic spines (DS) was found in the apical (middle, distal and oblique segments) and basilar (thick and thin segments) dendritic arbors of CA1 and CA2–3 pyramidal neurons in patients with Down's syndrome and no AD when compared to age-matched controls. An additional decrease of DS in every segment occurred in Down's patients with associated AD when compared to agematched controls and Down's patients with no AD. In Down's syndrome (either associated or not to AD) thin basilar dendrites were the most severely involved; in AD patients CA1 pyramids were more severely affected than pyramidal neurons of the CA2–3 subfield.

Anticipative calculus for the Poisson process based on the Fock space

Abstract: © Springer-Verlag, Berlin Heidelberg New York, 1990, tous droits réservés. L’accès aux archives du séminaire de probabilités (Strasbourg) (http://portail. mathdoc.fr/SemProba/) implique l’accord avec les conditions générales d’utilisation (http://www.numdam.org/conditions). Toute utilisation commerciale ou impression systématique est constitutive d’une infraction pénale. Toute copie ou impression de ce fichier doit contenir la présente mention de copyright.

Robustness issues in structural equation modeling: a review of recent developments

Abstract: In structural equation modeling the statistician needs assumptions inorder (1) to guarantee that the estimates are consistent for the parameters of interest, and (2) to evaluate precision of the estimates and significance level of test statistics. With respect to purpose (1), the typical type of analyses (ML and WLS) are robust against violation of distributional assumptions; i.e., estimates remain consistent or any type of WLS analysis and distribution of z. (It should be noted, however, that (1) is sensitive to structural misspecification.) A typical assumption used for purpose (2), is the assumption that the vector z of observable follows a multivariate normal distribution. In relation to purpose (2), distributional misspecification may have consequences for efficiency, as well as power of test statistics (see Satorra, 1989a); that is, some estimation methods may bemore precise than others for a given specific distribution of z. For instance, ADF-WLS is asymptotically optimal under a variety of distributions of z, while the asymptotic optimality of NT-WLS may be lost when the data is non-normal Violation of a distributional assumption may have consequences for purpose (2). However, recent theory, such as the one described in Sections 7 and 8, showes that asymptotic variances of estimates and asympttic null distributions of test statistics derived under the normality assumption may be correct even when z is non-normal provided certain model conditions hold (the conditions of Theorem 1). That is, in a specific application with z non-normally distributed, the assumption that z is normal play the role of a “working device” that facilitates calculation of the correct distribution of statistics of interest. This corresponds to what in Section 7 and 8 has been called asymptotic robustness. For most of the models considered in practice, replacing the assyumption uncorrelation for the assumption of independence implised reaching the properties of asymptotic robustness; in that case, in order to evaluate the asymptotic behavior of statistics of interest, a NT form for Γ produces correct results even for non-normal data. This robustness result applies regardless of the type of fitting criterion used. Distinction between “uncorrelation’ and ‘independence’ becomes crucial when dealing with the asymptotic robustness issue. Statistical independence among variables of the model guarantee that the distribution of statistics of interest are asymptotically distribution-free of the non-normal variables; thus a NT form for Γ applies. As an example of where such distinction is apparent, consider a simple regression model with a heteroskedastic disturbance term. Here the disturbance term is uncorrelated with the regressor, but the variance varies with the value of the regressor. For a study showing that ADF-WLS protects against heteroskedasticity of erros, while ML wil generally fail, see Mooijaart and Satorra (1987). In regresion analysis the usual method for detecting heteroskedasticity is by looking at residual plots. Presumably, alsi in structural equation modeling, the need to distinguish between uncorrelation and independence will force the researcher to go back to the row data in order to do a similar type of “residuals’ inspection. In concluding, an importance consideration is to compute sampling variability for estimates and test statistics using appropriate formulae, without requiring that the estimation procedure be the ‘best’ in some sense. We have seen that such computations can be carried out correctly using the wrong assumptions with respect to the distribution of the vector of observable variables, provided some additional model conditions hold. Roughly speaking, such additional model conditions amount to strengthen the usual assumption of uncorrelation among some random constituents of the model to the assumption of stochastic independecen.

Patterns of Lipid Content and Stratification in the Blubber of Fin Whales (Balaenoptera physalus)

Abstract: The lipid content and layering structure of the blubber of 82 fin whales ( Balaenoptera physalus ) caught off Spain were studied in relation to individual biological attributes. The lipid content of the external blubber stratum is stable and shows no apparent variation with age, reproductive status, or day of capture in either sex. This indicates that this stratum does not play a significant role in the dynamics of fat storage in fin whales. The internal stratum, in contrast, is variable, clearly reflecting the nutritive reserves of individuals. The mid-stratum is a transition between the external and internal layers. Reproductive categories are discriminated best by the mean of the values of the three layers than by any of them used independently. For this reason, this mean is proposed as the best index of condition for fin whales. Reproductive status is the main factor determining variation in lipid content of blubber in females, but is meaningless in males. Ranking of blubber fatness for the reproductive categories is: pregnant females > males = immature females > resting females > lactating females. These dissimilarities are explained by the energetic, migrational, and physiological characteristics of the different population components. In males, lipid content of blubber decreased significantly with age, whereas in immature females it increased with age. In both sexes, lipid reserves accrued from early May until mid-August, but tended to decrease afterwards, following variations in food availability. The nutritive condition of lactating females improved during late lactation probably because of increasing food consumption and decreasing energetic demands of suckling young.

On the use of AM1 and MNDO wave functions to compute accurate electrostatic charges

Abstract: A new strategy to evaluate accurate electrostatic charges from semiempirical wave functions is reported. The rigorous quantum mechanical molecular electrostatic potentials computed from both MNDO and AM1 wave functions are fitted to the point-charge molecular electrostatic potential to obtain the electrostatic charges. The reliability of this strategy is tested by comparing the semiempirical electrostatic charges for 21 molecules with the semiempirical Mulliken charges and with the ab initio STO-3G and 6-31G* electrostatic charges. The ability of the dipoles derived from the semiempirical electrostatic and Mulliken charges as well as from the SCF charge distributions to reproduce the ab initio 6-31G* electrostatic dipoles and the gas phase experimental values is determined. The statistical analysis clearly point out the goodness of the semiempirical electrostatic charges, specially when the MNDO method is used. The excellent relationships found between the MNDO and 6-31G* electrostatic charges permit to define a scaling factor which allows to accurately reproduce the 6-31G* electrostatic charge distribution as well as the experimental dipoles from the semiempirical electrostatic charges.

Spectral analysis of 49 years of rainfall rate and relation to fade dynamics

Abstract: The nature of the rainfall rate R(t) as a transient random process is presented in the context of microwave attenuation and fade dynamics. Using 49 years of data recorded in Barcelona, the spectral densities of energy and power and the autocorrelation function are presented, together with their analytical model. Examples for specific rain events are also presented. Several regimes covering a wide range of intensities have been investigated, and it is found that the spectral densities all exhibit a similar form which is independent of the average regime of R considered. This leads to a mean frequency and a spectral width which appear to be universal constants and independent of the regime. Similar features are found for the autocorrelation function. The mathematical models and numerical values found are compared to the Maseng-Bakken model (1981) proposed in earlier work of fade dynamics, and the agreement is good. The method is proposed for modeling the denormalized autocorrelation, and hence the spectrum, using only the measured average rainfall rate during a period of interest. Finally, the average number of crossings per unit of time is modeled and compared to the experimental results, and the agreement is satisfactory. >

Isotype distribution of anticardiolipin antibodies in systemic lupus erythematosus: prospective analysis of a series of 100 patients.

Abstract: A prospective study of IgG and IgM isotypes of anticardiolipin antibodies (aCL) in a series of 100 patients with systemic lupus erythematosus was carried out. To determine the normal range of both isotype titres a group of 100 normal control serum samples was studied and a log-normal distribution of IgG and IgM isotypes was found. The IgG anticardiolipin antibody serum was regarded as positive if a binding index greater than 2.85 (SD 3.77) was detected and a binding index greater than 4.07 (3.90) was defined as positive for IgM anticardiolipin antibody. Twenty four patients were positive for IgG aCL, 20 for IgM aCL, and 36 for IgG or IgM aCL, or both. IgG aCL were found to have a significant association with thrombosis and thrombocytopenia, and IgM aCL with haemolytic anaemia and neutropenia. Specificity and predictive value for these clinical manifestations increased at moderate and high anticardiolipin antibody titres. In addition, a significant association was found between aCL and the presence of lupus anticoagulant. Identification of these differences in the anticardiolipin antibody isotype associations may improve the clinical usefulness of these tests, and this study confirms the good specificity and predictive value of the anticardiolipin antibody titre for these clinical manifestations.

Hepatitis C virus infection in patients with nonalcoholic chronic liver disease.

Abstract: Study Objective:To determine the prevalence and meaning of antibodies to the hepatitis C virus (HCV) in patients with nonalcoholic chronic liver diseases. Design:Cross-sectional study. Set...

Comparative study of the molecular Electrostatic potential obtained from different wavefunctions. Reliability of the semiempirical MNDO wavefunction

Abstract: A systematic analysis of the molecular electrostatic potential (MEP) is presented. This study has been performed with a twofold purpose: first, to study the MEP dependence with regard to the quality of the basis set used to compute the ab initio SCF wavefunction and second, to develop and to assess a new strategy for computing isoelectrostatic potential maps using the semiempirical MNDO wavefunction. The only differences between this procedure and the ab initio SCF MEP computation lie in the freezing of the inner electrons and in the origin of the first-order density matrix. The statistical analysis of MEPs computed for a large number of molecules from MNDO wavefunction and ab initio SCF wavefunctions obtained using STO-3G, 4-31G, 6-31G, 4-31G*, 6-31G*, and 6-31G** basis sets points out the ability of any wavefunction to reproduce the general topological characteristics of the MEP surfaces. Nevertheless, split-valence basis sets including polarization functions are necessary to obtain accurate MEP minimum energy values. MNDO wavefunction tends to overestimate the MEP minima depth by a constant factor and shows an excellent ability to reflect the relative variation of MEP minima energies derived from a rather sophisticated (6-31G*) basis set, lacking of the shortcomings detected in the semiempirical CNDO approximation.

Biochemical and histochemical adaptation to sprint training in young athletes

Abstract: The purpose of the present study was to investigate the effects of 8 months of a specific and controlled sprint training programme on three groups of young athletes (two groups of males and one of females). Biopsies of vastus lateralis were taken before and after the period of training. The type percentage and diameter of the fibres, as well as the glycogen content and the activities of the enzymes of glycogen metabolism (glycogen synthase and glycogen phosphorylase), glycolysis (phosphofructokinase, pyruvate kinase, aldolase and lactate dehydrogenase), oxidative metabolism (succinate de-hydrogenase) and creatine kinase and aminotransferases were studied. The results show an increase in the percentage of type I fibres and an increase in the diameter of both fibre types. A significant increase was also observed in glycogen content, and in the activities of glycogen synthase, glycogen phosphorylase, phosphofructokinase, pyruvate kinase, succinate dehydrogenase, aspartate aminotransferase and alanine aminotransferase. We conclude that a long period of sprint training induces a biochemical muscle adaptation to anaerobic exercise. This metabolic adaptation is followed by a morphological adaptation, although this is probably not as specific as the biochemical one.

Prevention of early aortocoronary bypass occlusion by low-dose aspirin and dipyridamole. Grupo Español para el Seguimiento del Injerto Coronario (GESIC)

Abstract: To analyze the efficacy of low-dose aspirin in preventing early aortocoronary vein graft occlusion, 1,112 consecutive patients were enrolled in a multicenter, randomized, double-blind, placebo-controlled trial comparing 50 mg t.i.d. aspirin, 50 mg aspirin plus 75 mg t.i.d. dipyridamole, and placebo. All patients received 100 mg q.i.d. dipyridamole for 48 hours before surgery, and assigned treatment was started 7 hours after surgery. Vein graft angiography was performed in 927 patients (83%) within 28 days of surgery (mean, 10 days). Aspirin plus dipyridamole significantly (p = 0.017) reduced the occlusion rate of distal anastomoses from 18% (placebo) to 12.9%. Occlusion rate in the aspirin group was 14%, which approached statistical significance (p = 0.058). Furthermore, only aspirin plus dipyridamole reduced (p = 0.01) the number of patients with occluded grafts (placebo, 33%; aspirin, 27.1%; aspirin plus dipyridamole, 24.3%). Mediastinal drainage was slightly higher (p = 0.04) in the aspirin plus dipyridamole group (713 +/- 456 ml) than in the other two groups (placebo, 670 +/- 437 ml; aspirin, 629 +/- 337 ml), but hospital mortality (average, 4.6%) and early reoperation (average, 3.9%) rates were similar among the three groups. Thus, low-dose aspirin plus dipyridamole safely improves early saphenous vein aortocoronary graft patency; this effect is an added benefit to a preoperative regimen of dipyridamole.

A distance based regression model for prediction with mixed data

Abstract: A multiple regression method based on distance analysis and metric scaling is proposed and studied. This method allow us to predict a continuous response variable from several explanatory variables, is compatible with the general linear model and is found to be useful when the predictor variables are both continuous and categorical. Real data examples are given to illustrate the results obtained.