Showing papers by "University of Oviedo published in 1983"

In vitro plantlet regeneration through asexual embryogenesis in cotyledonary segments of Corylus avellana L.

Abstract: Cotyledonary nodes of corylus avellana L. excised from young seedlings cultured in K(h) medium for 5 weeks were used to induce embryoid formation. Embryogenesis was achieved in 60% of the explants over two 20-day culture steps in the presence of IBA (5 μM) plus BAP (0.5 μM) and BAP (5 μM) plus IBA (0.5 μM) respectively. Subsequent proliferation was successfully maintained during 5 subcultures on K(h) basal medium and in an unlimited number of subcultures in the presence of BAP (0.5 μM). Plant regeneration (50–55%) was easily achieved by planting into a basal K(h) medium after 10–20 days.

Active filters for static power convertors

Abstract: The need for output filters with static power convertors is well known. The paper presents a different way of solving the problem. A new configuration is therefore proposed, which includes both active and passive components. The advantages of this system are, among others, that it can be used for both AC and DC convertors, especially where very low distortion is needed at the output. A method for calculating the different components is proposed, and practical results obtained from a prototype are given. The possibility of using such filters with variable-frequency convertors is discussed.

Pairing Competition between Identical and Homologous Chromosomes in Rye and Grasshoppers.

Abstract: Meiotic pairing preferences between identical and homologous but not identical chromosomes were analyzed in spontaneous tetraploid/diploid chimeras of three male grasshoppers (Eyprepocnemis plorans) whose chromosome pair 11 were heterozygous for C-banding pattern and in four induced tetraploid/diploid chimaeral rye plants (Secale cereale) heterozygous for telomeric heterochromatin C-bands in chromosomes 1R and 2R. In the grasshoppers, a preference for identical over homologous pairing was observed, whereas in rye both a preference for homologous rather than identical pairing and random pairing between the four chromosomes of the set was found. From the results in rye, it can be deduced that pairing preferences do not depend exclusively on the similarities between chromosomes involved. It is suggested that genotypic or cryptic structural differences between the homologous chromosomes of each pair analyzed might be responsible for the pairing preferences found. This hypothesis can also explain the results obtained in grasshoppers, although the possibility of premeiotic association cannot be excluded in this material.

Aetiological factors in chronic secretory otitis in relation to age

Abstract: The prevelance of chronic secretory otitis media was studied in 5414 children aged 2-12 yr. The maximum incidence of the disease was at the age of 2 yr decreasing progressively to the age of 12, the results fitting a logarithmic curve. Of all the children, 8.7% had chronic otitis media, 0.59% had adhesive otitis and 0.35% chronic suppurative otitis media. The prevalence of secretory otitis was, significantly, related to infections of the upper respiratory tract and to nasal obstruction. The part played by the adenoid was more questionable. Purulent otorrhoea was more frequent in those children with secretory otitis than normal children.

Metaphase I bound arms and crossing over frequency in rye III. Non-chiasmate bonds in desynaptic plants

Abstract: In order to analyze the correspondence between the number of metaphase I bonds and the chiasma frequency of specific chromosome arms in desynaptic plants, two F1 hybrids were backcrossed to the parental inbred lines. The plants obtained were desynaptic. Some of these plants were heterozygous for a prominent telomeric C-band in chromosomes 1R (long arm) and/or 2R (short arm). From the frequency of bound arms at metaphase I and the frequency of recombined chromosomes at anaphase I in the arms considered, estimates of chiasma frequencies have been derived. The results have been compared with those obtained for the F1s between inbred lines from which the desynaptic plants were produced (Giraldez and Orellana, 1979; Orellana and Giraldez, 1981) as well as with those obtained in an open pollinated variety of rye (Orellana and Giraldez, 1981). The excess of anaphase I parental chromosomes found in the desynaptic plants can be explained on the assumption that some of the bonds appearing at metaphase I are achiasmate and a remnant of prophase pairing.

Intracellular pool of Streptomyces spores: amino acids, nucleosides, adenine nucleotide levels and energy charge

Abstract: We have previously reported that Streptomyces antibioticus spores incorporate [ 3 H]uridine and [ 3 H]leucine into RNA and protein, respectively, during incubation of spores in distilled water. These macromolecule biosynthetic processes must require the presence of a source of RNA and protein precursors in the dormant spore and energy able to supply the energetic requirements this biosynthesis demands. The former may be originated either in the existence of a pool of free amino acids and nucleotides, nucleosides or bases, or in the activity of degradative enzymes acting on RNA and protein species. The latter may arise from the utilization of some reserve polymers of the dormant spore and in the presence of quickly mobilized high-energy compounds, i.e. ATP. To obtain some answers to these questions and because there is a lack of information about the intracellular pool of Streptomyces spores, we have analysed the amino acid and nucleic acid presursor pools, the adenine nucleotide levels and energy charge of Streptomyces spores. This communication gives a description of this intracellular pool

Transient responses of yeast continuous cultures to qualitative changes in the nutrient supply. Induction and repression of the galactose pathway enzymes

Abstract: Induction and repression kinetics of alphagalactosidase, galactose uptake system and Leloir pathway enzymes were studied in chemostat cultures by changing the medium feed from glucose (11 mM) to glucose and galactose (11 mM; 17 mM respectively) in the induction experiments; and from galactose (11 mM) or (111 mM) to galactose plus glucose (83 mM) in the repression experiments

Zeta potential and the effect of coagulants on coal slurries.

Abstract: Etude experimentale de l'influence d'ions Al 3+ et Fe 3+ , du pH et de la concentration en solide sur le potentiel zeta de suspensions diluees de particules de charbon. Presentation de microphotographies d'agregats obtenus par coagulation. Conclusions relatives au mecanisme de la coagulation

Características físicas y alterabilidad de la piedra de villamayor (Salamanca)

Abstract: Physical properties of Villamayor sandstone (Salamanca), and especially porosity, water absorption and capillary flow through rock are studied in relation to its lithological characteristics. Laboratory weatherability tests (wetting-drying, freezing-thawing, and salt crystallisation) shows the susceptibility to destructive effects of frost and humidity fluctuations, and provides estimated data about the potential durability of this building stone.

La industria asturiana en la segunda mitad del siglo XIX: de la industrializacion a la expansion hullera

Abstract: El ministro de Marina, Luis Maria Salazar, habia enviado, en los primeros meses de 1829, a Gregorio G. Azaola —director de las Fundaciones Estatales de Lierganas y la Cavada— a Paris y Belgica para ponerse en contacto con los productores de hierro europeos, puesPocos meses despues, el industrial belga Adolphe Lesoinne recorre el norte de Espana, conducido por Azaola, tratando de encontrar un lugar adecuado para la industria del hierro, siguiendo «le vif desir du ministre Salazar de voir l'industrie metallurgique et la fabrication des armes de guerre s'installer en Espagne».

Structure du rhabdome de l'oeil nauplien adulte d'artemia (anostraca)

Abstract: The rhabdom of the adult nauplius eye of Artemia is distributed as a spacial net near the pigment cups Each retinula cell has proximal rhabdomeric surfaces, which constitute a ring around the cell or just one cellular side, and which intermingle with those of neighbouring cells to form a closed rhabdom of a structure not comparable to that of ommatidia The whole is irregular and aleatory By one of its poles the rhabdom is in contact with the space between the retinula cells and the pigment cup and progressively becomes more slender by the opposite pole and reaches different levels It is sometimes possible to find a rhabdomic portion isolated from the rest

Diffusion coefficients of some derivatives in dinonyl phthalate by gas-liquid chromatography

Abstract: Liquid diffusivities of furan, 2-methyl furan, 2,5-dimethyl furan, tetrahydrofuran, 2-methyl tetrahydrofuran and 2,5-dimethyl tetrahydrofuran in dinonyl phthalate are reported at several temperatures. Measurements were made by gas-liquid chromatography using glass beads coated with dinonyl phthalate as stationary phase. Mass transfer resistances in the gas and the liquid phase for the chromatographic separation are also reported.

Una nota sobre la cuantificacion de la incertidumbre correspondiente a las utilidades

Abstract: In a previous paper we have studied the relevant analogies between the variance, applied to compound scheme of probability and utility, and the measure which we had defined to evaluate the unquietness for such a compound scheme.