Showing papers by "University of Extremadura published in 1988"

Debrisoquin oxidation polymorphism in a Spanish population.

Abstract: The capacity for debrisoquin metabolism was determined in 377 healthy Spanish volunteers by measuring the amount of debrisoquin and its main metabolite, 4-hydroxydebrisoquin, in urine after an oral dose of debrisoquin. Debrisoquin oxidation was polymorphic, with 25 subjects (6.6%) phenotyped as poor metabolizers whereas 352 subjects (93.4%) were classified as extensive metabolizers. The metabolic ratio between debrisoquin and 4-hydroxydebrisoquin (percent of dose) in 6-hour urine samples ranged from 0.03 in extensive metabolizers to 93.5 in poor metabolizers. The proportion of poor metabolizers found is in the range observed in other white populations studied. Clinical Pharmacology and Therapeutics (1988) 44, 74–76; doi:10.1038/clpt.1988.115

Cell death in the ventral region of the neural retina during the early development of the chick embryo eye

Abstract: The present study deals with morphologic and quantitative changes that take place in the area of cell death in the ventral part of the presumptive retinal wall of the chick embryo. These changes were followed from the optic vesicle stage until the first optic fiber fascicles leave the neural retina. Our results show that both the volume occupied by the area of cell death and the density of its pyknotic fragments undergo considerable variation during the period between Hamburger and Hamilton's (1951) stages 12 to 20. In the optic vesicle stages, cell death in the ventral wall of the vesicle was observed in 50 to 75% of the embryos studied. During stages 14 and 15, this zone was seen in more than 90%. By the time invagination of the optic cup was complete, the ventral retinal zone of cell death had disappeared entirely in a large proportion of embryos; in all others, it shrank significantly both in volume and density of pyknotic fragments. In stage 19, when the first optic fiber fascicles begin to emerge from the retina, a dramatic increase occurs in the number of pyknotic fragments in the posterior pole of the retina. The appearance of dying cells, in a region shortly to be traversed by developing ganglion cell axons, supports the hypothesis that cell death processes are apparently somehow related to the creation of a suitable environment for the emergence of fibers toward the optic stalk. Densities of mitotic and interphasic cells as well as the mitotic index were determined in both the retinal zone of cell death and in areas devoid of dead cells. In all developmental stages analyzed, the mitotic index was notably lower in the former than in non-necrotic zones, suggesting that cell proliferation is partially inhibited in retinal areas of cell death.

Microhardness and Fracture Toughness Anisotropy in Cubic Zirconium Oxide Single Crystals

Abstract: Vickers and Knoop indentation tests have been used to study the fracture and deformation characteristics of 9.4-mol%-Y2O3-stabilized ZrO2 single crystals. Kc is anisotropic, with values of 1.9 and 1.1 MPa·m1/2 for radial cracks propagating along (100) and (110), respectively. The toughness for these two orientations was also determined using the single-edge notched-beam geometry, and yielded values of 1.9 and 1.5 MPa·m1/2.

Cell death in suboptic necrotic centers of chick embryo diencephalon and their topographic relationship with the earliest optic fiber fascicles.

Abstract: The structural features of suboptic necrotic centers (SONCs) in the floor of the chick embryo diencephalon were studied. These necrotic areas were observed lateral to the prospective zone of the optic chiasm through developmental stages 14 to 24. The relationship between SONCs and the earliest optic fiber fascicles also was studied in an attempt to determine the possible significance of these cell death areas in the mechanism of optic pathway development. In SONCs, healthy neuroepithelial cells contain primary lysosomes and phagocytose fragments of dead cells. Discrete regions within the cytoplasm of some cells show electron-transparent vacuoles in contact with dense contents of ruptured lytic bodies. The cytoplasm of dying cells and dead cell fragments are notably electron dense, with numerous secondary lysosomes and electron-transparent vacuoles. These observations are interpreted on the assumption that after autophagic processes, condensation and fragmentation take place in dying cells of the SONCs. In the ventricular lumen adjacent to the SONCs, numerous more or less spherical bodies are observed that appear to be shed from the tip of the cells constituting the SONCs. Three different types of intraventricular bodies can be distinguished: loose, moderately dense, and highly dense. The first type appears to originate from apical portions of cells that undergo autolytic processes. Moderately dense fragments are interpreted as originating from dying cells in which the cytoplasm is undergoing condensation. Finally, highly dense intraventricular bodies appear to be fragments of dead cells that are shed into the ventricular lumen. SONCs separate the prospective area of the optic chiasm from lateral regions of the diencephalic floor. Extracellular spaces are poorly developed within the wall of the SONCs, whereas the neuroepithelium of the presumptive optic chiasm and regions located rostral and caudal to SONCs show abundant and extensive extracellular spaces. These are bounded by long marginal processes of neuroepithelial cells. Sagittal sections of embryonic heads at stages 22–24 reveal optic fiber fascicles penetrating the SONCs asymmetrically, as they are found only in its caudal half. These observations suggest that the SONCs function as doorways made of compact neuroepithelium, to be traversed by the earliest optic fibers before they reach the middle zone of the floor of the diencephalon through which they travel to the contralateral optic tract within large extracellular spaces.

Solute-solvent interactions. Adaptation of the cavity size as a function of the basis set

Abstract: This work puts forward the adaptation of the molecular cavity size in the bosom of a solvent, useful in the SCF-LCAO-MO treatment of the solute-solvent interactions following the continuum model and taking into account the basis set used and the electronic characteristics of the solute

Differential inhibition of the initiation of DNA replication in stringent and relaxed strains of Escherichia coli

Abstract: Starvation for isoleucine inhibits chromosome, minichromosome and pBR322 DNA replication in a stringent strain of E. coli, but does not do so in a relaxed mutant. Starvation for other amino acids inhibits either chromosome and minichromosome replication in both strains. From these results we conclude that oriC and pBR322 replication are stringently regulated and that isoleucine seems not to be essential for the protein synthesis required at the initiation of oriC replication. Deprivation of isoleucine in a Rel− strain gives rise to amplification of minichromosome and pBR322 with a better yield of the latter plasmid than that following treatment with chloramphenicol.

A preliminary report on a quantum-mechanical model for the energetics of a solute at the surface separating two immiscible liquid phases

Abstract: Le modele considere ici est a relier a l'evaluation de la variation de l'energie libre lors du passage d'un solute d'un solvant dans un deuxieme. Application aux alcanes, alcool et amines-n primaires, les solvants etant l'eau et p-xylene

Investidura de armas de los reyes españoles en los siglos XII y XIII

Abstract: Este trabajo quiere ser una primera aproximacion a uno de los temas mas apasionantes para la simbologia politica medieval: la investidura de armas del rey en la Espana cristiana de los siglos XII y XIII. El tema tiene todas las dificultades propias de los estudios de simbologia, que se acrecientan cuando se trata de simbologia politica y mas aun cuando se interfieren —como en este caso— conceptos caballerescos. Precisa entonces de unos planteamientos muy amplios que atiendan, por una parte, a la evolucion pluriforme del acto de investidura, y por otra, al contexto sociopolitico en el que esta se produce, a fin de captar los matices y circunstancias que inciden en su significado.

Radiocesium concentration in migratory birds wintering in Spain after the Chernobyl accident.

Abstract: Levels of TXCs and TUCs resulting from the Chernobyl nuclear accident were studied in 195 birds that winter in two regions of Spain. Only five of the 12 species examined were contaminated. The average values for TXCs vary between 1.6 and 41 Bq kg-1 fresh. In particular, the contamination for song-thrushes (Turdus philomelos) are compared between the regions of Extremadura and Valencia, 350 km east of Extremadura at the same latitude. The results show that the contamination of birds wintering in Spain decreases from east to west. The whole-body dose commitment for humans consuming these contaminated birds was calculated. The values are well below the established ICRP guideline.

Preparation of New Glycoheptofurano[2,1-d]Imidazolidine-2-Thiones., Isomerizations to Acyclic-Sugar C-Nucleoside Analogues of Imidazole

Abstract: 1-Methyl- and 1-aryl-(1,2-dideoxy-D-glyofurano)[2,1-d]-imidazolidine-2-thiones having the configurations β-D-glycero-L-gluco (4), β-D-glycero-D-ido (5—8), α-D glycerol-D-galacto (9—10) and β-D-glycero-D-talo (11, 12) are prepared by reaction of 2-amino-2-deoxy-aldoses with methyl and aryl isothiocyanates. 1-Aryl-(1,2-dideoxy–β-D-glycero-L-gluco-heptofurano)[2,1-d]imidazolidine-2-thiones (1—3) have been converted into 1-aryl-4-(D-galacto-pentitol-1-yl)-4-imidazo-line-2-thiones (24—26) by acid catalysed isomerization.

Circadian rhythms in enzymatic activity of rat liver arginase and glucose 6-phosphate dehydrogenase.

Abstract: The circadian rhythms of glucose 6-phosphate dehydrogenase (G6PD) and of arginase activities and total protein content have been studied in the livers of 24-h fasted rats. Both G6PD and arginase activities reach a maximum at night and a minimum during the light period. On the other hand, the total protein level was maximal during the light period while it decreased to its lowest level during the dark period. These results are in agreement with the existence of a lipogenesis-lipolysis circadian rhythm in the rat, since the higher G6PD activity at night provides the necessary NADPH for lipid biosynthesis. The increase in arginase activity is also in agreement with an increase in amino-acid catabolism, probably as a source of energy and metabolic intermediates.

Initiation of glucan synthesis in yeast

Abstract: Fractions of the glucan synthesized in vitro by glucan synthase preparations obtained by mechanical breakage of whole cells of Sacchromyces cerevisiae and Candida albicans were solubilized by sodium dodecyl sulphate (SDS). Part of this material migrated in denaturing electrophoresis at the level of a Coomassie Blue-stained area. In addition, it was solubilized by both an exoglucanase and papain. These results suggest that some yeast glucan is built, associated with a protein.

The effects of removal of the root tip on lateral root distribution in adventitious roots of anion

Abstract: SUMMARY Distribution patterns of lateral roots (LRs) were analysed in intact (control) and decapitated adventitious roots (ARs) of Allium cepa L. Removal of the root tip caused: (1) The cessation of elongation of the AR. (2) An increase in the number of LRs per cm which developed on the AR. (3) Changes in the distribution of LRs along the mother root One aspect of the distribution modified by the decapitation was the suppression of an apical zone without LRs which was observed immediately behind the apex in intact roots. In decapitated ones by contrast accumulation of LRs was enhanced in this zone. Moreover, decapitation appeared responsible for successive LRs opposite the same xylem pole developing nearer each other than in intact roots. (4) Changes in the frequency and location of clumps of LRs. In decapitated roots 21.6%, of the total number of LRs were clumped. In intact ARs this figure was only 13.5%. Moreover, intact roots showed a tendency to LR clumping preferentially in their basal zone In contrast, clumps of LRs were noted indistinctly in both basal and distal zones of decapitated ARs. I his fact implies that removal of the root tip enhances the natural tendency toward clumping of LRs, chiefly in distal zones of the AR. Other aspects of the pattern remain unchanged after removing the root apex. Hence in decapitated as well as intact ARs there were two neighbouring xylem poles opposite which large number of LRs were produced, whereas the remaining ones were considerably less prolific. A further aspect which was not altered by the decapitation was the significantly high frequency of formation of neighbour LRs opposite adjacent xylem poles.

Heat stress in the presence of low RNA polymerase activity increases chromosome copy number in Escherichia coli

Abstract: A temperature shift-up accompanied by a reduction in RNA polymerase activity in Escherichia coli causes an increased rate of initiation leading to a 1.7- to 2.2-fold increase in chromosome copy number. A temperature shift-up without a reduction in polymerase activity induces only a transient non-scheduled initiation of chromosome replication caused by heat shock with no detectable effect on chromosome copy number.

Direct procedure for the determination of the number of replication forks and the reinitiation fraction in bacteria

Abstract: A direct method for calculating the average number of replication forks per chromosome in an exponentially growing bacterial culture and the fraction of reinitiation after an inductive treatment of the initiation step is presented. This method has allowed the development of REPLICON, a computer program designed for the resolution of the algorithm and simulation of the bacterial chromosome replication. Using REPLICON the following parameters can be obtained: average number of replication forks per chromosome, time required for the complete replication cycle, average amount of DNA per nucleotide, gene frequency of any chromosomal locus and reinitiation fraction. The use of this analysis also permits the determination of the uni- or bidirectionality of replication.

Dominance Relationships in Female Groups of Red Deer: Seasonal Changes

Abstract: A study is made on agonistic interactions and dominance relationships in female groups of wild i'ed deer (Cervus elaphus L.), in terms of age-sex classes, and comparing the periods before and after the rut. A decrease in interaction rates and the arising of reversals was found from pre-breeding to post-breeding. Seasonal changes are discussed in relation to availability of resources and development of individuals.