Showing papers by "University of Barcelona published in 1986"

La investigación cualitativa

Abstract: Se presenta la conceptualizacion y logica de la investigacion cualitativa, que, por tener rango de cientificidad, implica (y no siempre se cumple) gran rigurosidad descriptiva en el registro, y por su caracter de cualitativa se fundamenta en una recogida de informacion en base a datos categoricos, que, en consecuencia, podran someterse al proceso de categorizacion y a las fases aqui indicadas, siendo despues altamente recomendable proceder a la triangulacion, acrecentando su validez. Si desde su trayectoria historica la investigacion cualitativa ha sufrido diversas vicisitudes, tambien, en consecuencia los estudios de caso unico supeditados a esta metodologia, contemplandose desde una posicion en que el respeto a la espontaneidad en todo lo que envuelve al caso Unico nos imposibilita la replicabilidad y plantea serios problemas a la generalizacion, que debera resolverse mediante la elaboracion de un diseno adecuado.

Lymphocyte doubling time in chronic lymphocytic leukaemia: analysis of its prognostic significance.

Abstract: Summary. In 100 untreated patients with chronic lymphocytic leukaemia (CLL) lymphocyte doubling time (LDT) has been investigated in relationship with clinical stages, bone marrow histological patterns, treatment-free period and survival. Although partially correlated with clinical stages and bone marrow patterns. LDT has a clear prognostic significance by itself: whereas a LDT of 12 or less months identifies a population of patients with poor prognosis, a LDT higher than 12 months is indicative of good prognosis as substantiated by a long treatment-free period and survival. This simple parameter can be useful in the clinical management of CLL patients.

Generalized stochastic integrals and the malliavin calculus

Abstract: The paper first reviews the Skorohod generalized stochastic integral with respect to the Wiener process over some general parameter space T and it's relation to the Malliavin calculus as the adjoint of the Malliavin derivative. Some new results are derived and it is shown that every sufficiently smooth process {ut, t∈T} can be decomposed into the sum of a Malliavin derivative of a Wiener functional, and a process whose generalized integral over T vanishes. Using the results on the generalized integral, the Bismut approach to the Malliavin calculus is generalized by allowing non adapted variations of the Wiener process yielding sufficient conditions for the existence of a density which is considerably weaker than the previously known conditions.

A reduction of order two for infinite-order Lagrangians

Abstract: Given a Lagrangian system depending on the position derivatives of any order, and assuming that certain conditions are satisfied, a second-order differential system is obtained such that its solutions also satisfy the Euler equations derived from the original Lagrangian. A generalization of the singular Lagrangian formalism permits a reduction of order keeping the canonical formalism in sight. Finally, the general results obtained in the first part of the paper are applied to Wheeler-Feynman electrodynamics for two charged point particles up to order 1/${c}^{4}$.

On the optimal station keeping control of halo orbits

Abstract: Techniques for computing and controlling a halo orbit are considered in this paper. It presents a semi-analytical theory for the halo orbits in the Restricted Three Bodies Problem (RTBP), that is valid and amenable to computation to any order. Results are presented up to order 11. The Floquet modes of the monodromy matrix are used to define a local optimal control procedure through the concepts of projection and gain functions.

Selective Aerobic Degradation of Methyl-Substituted Polycyclic Aromatic Hydrocarbons in Petroleum by Pure Microbial Culturest

Abstract: Studies of laboratory degradation of Arabian light crude oil (b.p. < 200°C) by pure cultures of bacterial strains Pseudomonas sp. isolated from tanker ballast waters showed that biodegradation of alkyl-substituted polycyclic aromatic hydrocarbons strongly depends on the number, position, and the type of the substituents. Biodegradation of alkylphenanthrenes and dibenzothiophenes decreased with increasing number of substitutents. Biodegradation of methylphenanthrenes (P), dibenzothiophenes (DBT), pyrenes (Py) and chrysenes (C) showed a pattern similar to that previously observed for the methylnapthalenes; compounds containing unsubstituted α and β adjacent positions were more readily degraded. Thus, 2- and 3-MP, 2- and 3-MDBT, 1-MPy and 2- and 3-MC were shown to be less resistant to degradation within these families. Cycloalkylaromatics, such as partially aromatized steranes, hopanes and 8, 14-secohopanes were generally resistant to degradation by the cultures employed.

Relationships between photosynthetic capacity and leaf structure in several shade plants

Abstract: Leaf structure, photosynthetic characteristics and related physiological parameters have been studied in three ornamental shade species: Fatsia japonica, Cissus rhombifolia (relatively lighttolerant plants), and Philodendron scandens (obligate shade plant). Species were grown in a shadehouse. Maximum photosynthetic photon flux density was 470 ,umol m-2 s-'. Net rate of CO2 uptake at light saturation (maximum Pn) in Fatsia was 6.90 ? 1.27 umol m-2 s-'. In Cissus and Philodendron values were about 30% and 63% less respectively, than those measured in Fatsia. The nitrogen content, relative dry wt, specific leaf dry wt (SLDW), chlorophyll a/b ratio, and nitrogen to chlorophyll ratio were lower in Philodendron. However, leaf thickness in Philodendron (296 ? 17 ,um) was about 54% and 160% higher, respectively, than in Fatsia and Cissus, and the ratio between mesophyll cell area and leaf surface area (Ames/A) was nearly similar in the three species. However Philodendron exhibited a percentage of palisade parenchyma about three times lower than that observed in the two other species. The chloroplast number per mm of cell wall in transverse sections (chloroplast density) in the palisade parenchyma was fairly constant (about 65), irrespective of species. The "chloroplast density" in the spongy parenchyma of Philodendron was about 53% and 63%, respectively, of Fatsia and Cissus values. In Fatsia and Cissus chloroplast ultrastructure seems to change gradually and continuously from sun to shade type with the depth from the adaxial to abaxial surface. Special emphasis was given in order to determine the structural parameters best correlated with maximum Pn between the different species. In this way chloroplast number in transverse sections (chloroplast number) and the ratio between chloroplast area and leaf surface area (Achl/A) were the parameters best correlated with maximum Pn, and stomatal frequency was also a good determinant of maximum Pn. However, leaf thickness, SLDW, and even Ames/A ratio were weakly correlated with maximum Pn. THE POTENTIAL LEAF photosynthetic capacity, expressed on a leaf surface area basis, is determined by the intrinsic cell physiological capacity and also by a structural component: the quantity and arrangement of the cellular material per unit leaf area (Nobel and Longstreth, 1981; Longstreth, Bolaiios and Goddard, 1985). The internal area of mesophyll cells per unit leaf area (Ames/A) is a basic parameter when we study the relationships between leaf structure and photosynthetic capacity, at ambient CO2 and 02 levels (Nobel, Zaragoza and Smith, 1975; Nobel, 1976). An increase in the ratio Ames/A would increase the surface area available for diffusive ' Received for publication 5 February 1986; revision accepted 9 June 1986. We thank Professor A. Caballero for critically reading the manuscript and X. Martinez for shadehouse maintenance. We are very grateful for "Servei de Microscopia Electronica de la Universitat de Barcelona" for technical assistance, and especially to Drs. R. BargaIl6 and J. Lopez. This work has been partially supported by the "CIRIT" of the "Generalitat de Catalunya," Spain. transfer of CO2 in the liquid phase (Nobel et al., 1975; Nobel, 1976). However diffusive transfer of CO2 in the liquid phase only seems to impose a small limitation to photosynthesis in C3 plants (Raven and Glidewell, 1981; Farquhar and Sharkey, 1982). However, this ratio seems valid if it makes it possible to quantify differences in the amount of photosynthetic tissue per unit leaf area (Longstreth et al., 1985). For any given species, especially sun species, light-saturated photosynthetic rate on a leaf surface area basis is closely and positively correlated with Ames/A (Nobel et al., 1975; Nobel, 1976, 1980; Longstreth, Hartsock and Nobel, 1981; Oquist, Brunes and Hallgren, 1982). It seems, however, that the relationship between photosynthetic rate and Ames/A is considerably poorer for other species (Bunce et al., 1977; Chabot and Chabot, 1977; Jurik, Chabot and Chabot, 1979). On the other hand, there is no indication that Ames/A ratio is a major determinant of photosynthetic rate, at light saturation, between different species (Bjorkman, 1981).

Heterogeneous localization of some purine enzymes in subcellular fractions of rat brain and cerebellum.

Abstract: The activity of guanine deaminase (GAH, E.C.3.5.4.3) was lower in rat cerebellum soluble and microsomal fractions than in rat brain subfractions. Adenosine deaminase (ADA, E.C.3.5.4.4) activity was released in higher proportion than guanine deaminase, purine nucleoside phosphorylase (PNP, E.C.2.1.2.4), 5'-nucleotidase (5'N, E.C.3.1.3.5), and lactate (LDH, E.C. 1.1.1.27) and malate (MDH, E.C. 1.1.1.37) dehydrogenase in press-juices of rat brain. Furthermore, nerve ending-derived fractions (synaptosomes and synaptic vesicles) showed an enrichment of adenosine deaminase and also of 5'-nucleotidase. The action of deoxycholate over the subfractions did not increase the activity of either enzyme. The contrary occurred with the remaining enzymes studied. Thus, it is possible that one set of enzymes are located on the surface of the particulate vesicles, whereas another set are located inside these vesicles, suggesting a compartmentation of purine catabolic enzymes in different areas of the central nervous system.

Physical and biological gradients in a submarine cave on the Western Mediterranean coast (north-east Spain)

Abstract: Submarine caves are semi-closed subsystems within the marine littoral ecosystem. One of the most striking features is the progressive reduction of the number of phyla, species, and biomass towards the interior of such a cave. The decrease in biomass has been explained as the result of low exchange rates of the water inside the caves which limit the supply of oxygen and food particles from the exterior. Many authors have proposed that this reduced exchange rate is associated with the occurrence of marked gradients in temperature, salinity, oxygen and light. Measurement of faunal abundance of a cave in the littoral zone of the Medes Islands (Catalonia, north-east Spain) made between June 1983 and July 1984, revealed a zonation similar to that in other Mediterranean caves. Animal biomass decreased from 260 g ash-free dry weight m-2 at the entrance to 80 g ash-free dry weight m-2 at the end of the cave (50 m from the mouth). A special technique for remote water-sampling was developed to avoid problems due to turbulence caused by divers in this semi-closed system. This involved the installation of a series of plastic tubes at different points along the axis of the cave. The water was brought to the surface using a battery-powered electric pump. The reliability of this method was verified by comparing the results with samples collected directly by divers. Sampling both in winter and summer showed no longitudinal gradients for temperature, salinity, oxygen, chlorophylla and the number and volume of suspended particles. These results suggest that there is a constant circulation within the cave which guarantees water-exchange. The decrease in biomass cannot be explained by physico-chemical gradients due to insufficient exchange with the external system. On a finer scale, however, along the walls of the cave there may exist boundary layers that are not affected by the general circulation. This could account for the observed decrease in the biomass of benthic organisms.

Tuberculosis-associated hemophagocytic syndrome. A systemic process.

Abstract: Virus-associated hemophagocytic syndrome has been recently identified as a benign, reactive histiocytic proliferation distinct from Rappaport's malignant hystiocytosis. Other etiologic agents, including different bacteria, have also been identified. Three autopsy cases of hemophagocytic syndrome associated to acute tuberculous sepsis are presented. Benign histiocytic proliferation with striking hemophagocytosis was present in a disseminated, multisystemic pattern in all three cases. A relationship between systemic histiocytic proliferation and an anergic status in these patients is suggested.

Evaluation of a commercial β-glucuronidase test for the rapid and economical identification of Escherichia coli

Abstract: A commercial beta-glucuronidase (beta-GUR) test for the rapid and economical identification of Escherichia coli was evaluated. A total of 762 clinical strains and 228 environmental isolates were studied. More than 95% of the E. coli strains were found to be beta-GUR positive. Thirty-one clinical isolates of Shigella sonnei, 10 of Enterobacter cloacae, eight of Enterobacter aerogenes, nine of Citrobacter freundii and one of Salmonella enteritidis also gave positive results. The enzyme beta-GUR was also detected in two environmental strains of E. cloacae and one C. freundii. A comparative study between the beta-GUR test and the conventional identification system was carried out in 233 consecutive isolates of lactose positive enterobacteria. Agreement was observed in 223 cases and 190 E. coli strains were correctly identified using this test. Discrepancies were found in 10 cases: nine E. coli were beta-GUR negative and one C. freundii was beta-GUR positive. Escherichia coli was the only species positive for both beta-GUR and indole tests. This procedure permits a rapid, easy, precise and inexpensive identification of E. coli. beta-GUR positive Enterobacter strains have not previously been described.

Stimulation of cellular proliferation and differentiation in the intact and regenerating planarian Dugesia(G) tigrina by the neuropeptide substance P.

Abstract: The neuropeptide substance P (SP) is shown to be a potent mitogen for intact and regenerating planarians. At nanomolar concentrations, SP markedly enhances cellular proliferation causing an increase in the mitotic index and in the number of blastema cells. Moreover, albeit to a lower extent, SP enhances cellular differentiation as shown by the increases in eye and pharynx length in regenerating organisms. On the basis of these observations, we hypothesize that SP may be one of the postulated growth factors necessary for the stimulation of proliferation, and to a lesser extent differentiation of cells in intact and regenerating planarians.