Showing papers by "University of Barcelona published in 1976"

Nonabsorbing atomic coherences by coherent two-photon transitions in a three-level optical pumping

Abstract: A three-level system, with two ground state levels and an excited level, irradiated by two classical monocromatic light fields is theoretically considered. In the steady-state a ground state coherence appears via coherent two-proton transitions which originates a destructive interference between the two optical excitations. The phenomenon constitute a transversal optical pumping mechanism which shows a Doppler-free resonance behaviour when the mode frequency separation matches the ground state splitting.

Prognostic value of spontaneous hyponatremia in cirrhosis with ascites.

Abstract: Spontaneous hyponatremia in cirrhosis with ascites is generally considered to be due to an impaired renal ability to excrete free water, to be a contraindication of diuretics, and to be a bad prognostic sign. These concepts are reviewed in this paper. 55 cirrhotics with ascites were divided into three groups. Group I consisted of 13 patients with hyponatremia and very low free-water clearance (\(C_{H_2 O} \), 0.07±0.26 ml/min). These patients also had poor renal function: low inulin clearance (CINU, 40.6±25.9 ml/min) and paraamino-hippurate clearance (CPAH, 383±275 ml/min). Group II consisted of 8 patients who also had hyponatremia.\(C_{H_2 O} \), CINU, and CPAH in these patients were fairly high: 5.85±1.53 ml/min, 85.7±26.2 ml/min, and 651±294 ml/min. These values are similar to those of the 34 patients without hyponatremia who make up Group III: (6.37±4.27 ml/min, 94.7±33.1 ml/min, and 598±199 ml/min). Hyponatremia in Group I could be related to the impaired free-water clearance. The mechanism of hyponatremia in Group II patients is not clear. Patients with hyponatremia and low CINU and CPAH had a negative response to diuretics and a poor prognosis. Patients with hyponatremia but with relatively good renal function had a good prognosis, similar to Group III patients. They responded to diuretics with no worsening of their hyponatremia.

Mitosis in the intact and regenerating planarian Dugesia mediterranea n.sp. I. Mitotic studies during growth, feeding and starvation

Abstract: Planarian neoblasts, the only cell type in this organism endowed with mitotic power, decrease in density as total body volume, total cell number, and length increase. Studies on mitosis show that the neoblast mitotic rate is a function of body length, being lower as the organism increases in length. The cephalo-caudal distribution of mitotic figures in animals of different sizes shows a change towards a more even distribution of mitosis jointly with a mitotic increase in the caudal regions as length increases. However, in the sagittal and dorso-ventral axes, the distribution of mitosis is always nonuniform, probably due to the uneven distribution of parenchymal tissue along them. The pharynx of animals in all size groups examined shows no mitotic figures except some near its base. This may suggest for this organ a proximal type of growth with some cell migration. Feeding elicits a very rapid increase in mitosis which lasts for almost a week, whereas long periods of starvation do not cause a significant increase or decrease in the basal mitotic rate. All these results stress the need of looking at the planarian neoblast mainly as a stem or replacement cell of most differentiated cell types and not as a mere “regeneration cell.” The implications of the results obtained for the mechanisms of growth and shrinkage are discussed.

Mitosis in the intact and regenerating planarian Dugesia mediterranea n.sp. II. Mitotic studies during regeneration, and a possible mechanism of blastema formation

Abstract: In planarian regeneration mitosis occurs in both anterior and posterior blastemas. The mitotic increase is visible as early as one hour after amputation, reaches a rapid first maximum at 5–12 hours, a relative minimum at 24–30 hours, and a higher and longer second maximum at two to four days depending on body size, level of amputation, and on whether blastema is anterior or posterior. The spatial dynamics of mitosis show a rapid and high mitotic increase in the distal regions but not in the proximal regions. Later, the proliferative zone shifts in sucessive mitotic waves to more proximal regions, paralleling the formation of the head ganglia and nerve cords. These results do not agree with theories of blastema formation through neoblast migration or through cell dedifferentiation, in as much as the local proliferation of neoblasts encountered is sufficiently high and early to account for the number of blastema cells found during period of regeneration. Therefore, we suggest that blastema formation during planarian regeneration occurs mainly through local neoblast proliferation. These results and the data obtained on regeneration rates enable us to suggest that nervous tissue may be one of the factors responsible for the differing mitotic increases found. Since neoblasts are the only planarian cells capable of mitosis, we suggest that neoblast proliferation could be under nervous tissue control through some stimulatory substance (s) released from the nerve terminals. The implications of this hypothesis for the maintenance of axial polarity are also discussed.

AMP Analogs: Their Function in the Activation of Glycogen Phosphorylase b

Abstract: A series of AMP analogs has been selected in order to better understand the structural requirements (a) for the efficient binding of the activator molecule at the correct site on phosphorylase b from rabbit skeletal muscle and (b) for the activation which is observed. Two types of activation are known, according to Black and Wang [J. Biol. Chem. 243, 5892-5898 (1968)]: either a cooperative response with respect to the activator concentration (like the one which is obtained for AMP itself) or a non-cooperative response observed in the case of IMP. It is shown that the 5'-phosphate moiety is absolutely required for the analog to bind at the correct site (adenine or adenosine bind at another enzymic site), and that the free enthalpy, delta G, corresponding to the association process varies in a complex manner with respect to the substitution of the different positions of the AMP molecule. Moreover, the differences delta G (analog) - delta G (AMP) = delta G obtained for two types of substitution separately do not add up to the same energy difference as the one obtained when the two substitutions are made simultaneously on the AMP molecule. It appears that all the mononucleotides which have been tested up to now may be divided into two classes. Class I (AMP class) is characterized, apart from a strong activation, by the following features: (a) one molecule of analog expels two molecules of bound glucose 6-phosphate as it binds on the enzyme; (b) bound analog protects slowly one crucial cysteinyl residue against attack by 5,5'-dithio-bis(2-nitrobenzoic acid) at 4 degrees C; (c) association of two molecules of dimer is strengthened at 4 degrees C in the presence of the analog. Class II (IMP class) is associated with a weak activation and with the following set of properties: (a) a single molecule of bound glucose 6-phosphate is released as the first molecule of analog binds on the dimer; (b) two slowly reacting cysteinyl residues per subunit are immediately protected against 5,5'-dithio-bis(2-nitrobenzoic acid) by the binding of the analog at 4 degrees C; (c) the analog dissociates the low amount of tetramer which is present at 4 degrees C in the absence of AMP into two molecules of dimer. These results are discussed according to a plausible scheme of transconformations taking place in glycogen phosphorylase b, a model which has been derived earlier by relaxation studies.

Crystallization kinetics of a Se–Ge–Sb alloy glass

Abstract: The glass-forming ability of a Se0.615Ge0.154Sb0.231 alloy is analysed by computing the critical cooling rate and the time-temperature-transformation curve, at various temperatures. The calculation is based on some experimentally determined portions of the time-temperature-transformation curve, from which the rate of increase of viscosity with falling temperature below the melting point is deduced, using classical crystallization kinetics treatment.

El lago de Montcortés, descripción de un ciclo anual.

Abstract: Este trabajo presenta los primeros resultados obtenidos despues de un primer ciclo anual de estudio del lago de Montcortes y tiene el interes de poder establecer comparaciones con el lago de Banyoles, otro lago carstico de caracteristicas bastante distintas y muy bien estudiado con anterioridad (PLANAS, 1 973; M I RACLE, 1 976). Ha sido ventajoso poder integrar en un solo equipo el esfuerzo de especialistas en disciplinas muy distintas (hidrografia , plancton, bacteriologia). A pesar de ello, algunos apartados no han podido ser todavia elaborados en su totalidad (recuentos de fitoplancton, por ejemplo) y esperamos que el avance del trabajo realizado sirva para acometer en un futuro inmediato la resolucion de una serie de problemas que han ido surgiendo y para la que este primer ciclo puede constituir el marco idoneo. La informacion existente anteriormente sobre la biologia del lago era muy limitada.

Hereditary hemolytic anemia with erythrocyte pyrimidine 5'-nucleotidase deficiency in Spain. Clinical, biological and familial studies.

Abstract: We report a hereditary hemolytic anemia associated with a severe erythrocyte pyrimidine 5′-nucleotidase deficiency in a Spanish family of five members in which the parents are first cousins. Both parents exhibited decreased nucleotidase activity without clinical or hematologic abnormalities. Two children (a male and a female) showed severe pyrimidine 5′-nucleotidase deficiency with hemolytic anemia. The remaining child (a male) showed no signs of the disease. The findings strongly suggest an autosomal recessive mode of inheritance in this enzymopathy. This seems to be the first report of pyrimidine 5′ nucleotidase deficiency in Spain.

Ribosome-lamellae complex in chronic lymphatic leukaemia.

Abstract: The Ribosome Lamellae Complex (RLC) was found in two out of 35 patients with Chronic Lymphatic Leukaemia (CLL). The proportion of lymphocytes bearing RLC was very small (4% in the first case and less than 0.5% in the second case). The significance of this type of inclusion is discussed and the possible relationship to the circular profiles of endoplasmic reticulum is emphasized.

Phylogenetic position of the AmericanTimarcha Latr. (Coleoptera, Chrysomelidae) based on chromosomal data

Abstract: The chromosomal analysis ofT. intricata Hald. has shown a diploid complement of 44 chromosomes, the highest number found inTimarcha and clearly different from those of the taxa previously studied. This complement favours a derivative origin of theAmericanotimarcha subgenus from a hypothetical ancestral species of 20 chromosomes. The implications of this karyotype are also discussed with some morphological, biogeographical and ecological points of view and observations.

Necropsy and ultrastructural findings in histiocytic medullary reticulosis.

Abstract: SUMMARY In a case of histiocytic medullary reticulosis with protracted course and necrotic skin lesions, histological study revealed infiltration of the fat tissue by atypical rcticulohistiocytic cells, areas of asso-ciated fat necrosis and vascular lesions. Autophagocytosis (phagocytosis of erythrocytes, erythroblasts, platelets, lymphoid cells, and nuclear debris) was found in biopsy specimens of the subcutaneous in-filtrates, lymph nodes, and bone marrow, and in necropsy specimens of skin, iliac mesenteric lymph nodes, bone marrow, liver, spleen, and suprarenal glands. Electron microscopy of various viscera showed abnormal histiocytic cells containing multiple phagocytosed erythrocytes and other blood cells in different stages of destruction and digestion. Multi-membranous bodies also were present. Defective lysosomal degradation of intracytoplasmatic ceroids in this condition is postulated.

[Contribution to study of Ixodidae (Acarina, Ixodoidea) in Cantabric Mountains (Spain) (author's transl)].

Abstract: Cinq especes d’Ixodidae parasites des micromammiferes ont ete identifiees dans le Nord-Ouest de l’Espagne, plus particulierement dans les Monts CantabriquesParmi ces especes, les auteurs soulignent la presence d’Ixodes acuminatus (Neumann, 1901) et d’Ixodes trianguliceps (Birula, 1895) qui, a leur connaissance, n’ont jamais ete signales dans la Peninsule Iberique

Quasi-light-cone frame and approximate galilean symmetries

Abstract: By introducing a modification in the light-cone co-ordinate frame (ordinary and Bell and Ruegg’s), an approximate Galilean symmetry appears which leads to the calculation of higher-order terms in the nonrelativistic limit of the Dirac and Klein-Gordon equations (i.e. the Schrodinger-Pauli equations).

Gyromagnetic ratio and galilean symmetries in the light-cone formulation

Abstract: The Galilean symmetries of the light-cone formulation of the wave equations are further exploited. The formulation in this frame of the Dirac, Bargmann-Wigner, Proca and Rarita-Schwinger equations is seen to give the Galilean invariant field equations of Levy-Leblond, and Hagen and Hurley. In the cases studied here, the two possible ways in which the symmetry of the LCF can be used,i.e. either obtaining first the Galilean invariant free equations from the relativistic ones in the LCF and introducing the minimal coupling there, or, as in the preceding paper, working with relativistic equations in the interacting case and using the Galilean symmetries of the LCF at the end of the calculations, give the same result, provided that the Galilean theory is the 6s + 1 minimal one. Otherwise, the first way proves to be the right one in order to get the usual resultg(s)=1/s for the gyromagnetic ratio. In fact the equations of Proca and Rarita-Schwinger, which do not give minimal Galilean theories, produce anomalous results forg(s) when they are treated in the second way. A general method is developed in order to get the good field variables in the LCF for every spin. A difference between the light-cone approach and that of the usual nonrelativistic limit of the relativistic theories is seen to be the fact that the first gives only the pure nonrelativistic structure (i.e. just the lowest-order term) of the theory.

Contribución al conocimiento de la flora y distribución de los mixomicetes en el Mediterráneo occidental. - III. Sureste de España: Murcia

Abstract: During 1977-78, 139 collections of Myxomicetes were made in the Provincia of Murcia by the authors and coUaborators of the Dpt. of Botany (Murcia). The resulting list of 43 species is commented from distribution and phytosociologic points of wiew. Identity of Arcyria anmdifera Tonend is confirmed, and a completad description, based in Murcian material, is included. We point up the importance of dead fallen cladodia of Opuntia ficus-indica as media rich in fruiting Myxomycetes.

Ultrastructural study of binucleation in cells of the rat adrenal glomerular zone after a prolonged low-sodium diet

Abstract: Binucleate cells have been found in the glomerular zone of the adrenal cortex in rats subjected to low-sodium diets By considering the various possibilities for their production, both the findings of nuclei in process of constriction and nuclei identical in form, confronted and smaller in size than those of neighbour cells, are in agreement with an amitotic nuclear division as the possible mechanism for the formation of these cells