Showing papers by "University of Extremadura published in 1986"
TL;DR: It is proposed that under the present experimental conditions the mesenchymal cells are diverted from the death programme by a primary transformation into cartilage by a partial inhibition of interdigital cell death in the proximal zone of the interdigit.
Abstract: In the present work, we have analysed the possible involvement of ectodermal tissue in the control of interdigital mesenchymal cell death. Two types of experiments were performed in the stages previous to the onset of interdigital cell death: (i) removal of the AER of the interdigit; (ii) removal of the dorsal ectoderm of the interdigit. After the operation embryos were sacrificed at 10–12h intervals and the leg buds were studied by whole-mount cartilage staining, vital staining with neutral red and scanning electron microscopy. Between stages 27 and 30, ridge removal caused a local inhibition of the growth of the interdigit. In a high percentage of the cases, ridge removal at these stages was followed 30–40 h later by the formation of ectopic nodules of cartilage in the interdigit. The incidence of ectopic cartilage formation was maximum at stage 29 (60%). In all cases, cell death took place on schedule although the intensity and extent of necrosis appeared diminished in relation to the intensity of inhibition of interdigital growth and to the presence of interdigital cartilages. Ridge removal at stage 31 did not cause inhibition of the growth of the interdigit and ectopic chondrogenesis was only detected in 3 out of 35 operated embryos. Dorsal ectoderm removal from the proximal zone of the interdigit at stage 29 caused the chondrogenesis of the proximal interdigital mesenchyme in 6 out of 18 operated embryos. The pattern of neutral red vital staining was consistent with these results revealing a partial inhibition of interdigital cell death in the proximal zone of the interdigit. It is proposed that under the present experimental conditions the mesenchymal cells are diverted from the death programme by a primary transformation into cartilage.
67 citations
55 citations
54 citations
TL;DR: In this article, a review of the basic formalism involved in the application of nuclear rotational models to the problem of electron scattering from axially symmetric deformed nuclei is made.
52 citations
TL;DR: In this paper, a general method for the synthesis of pyrimidine C -nucleosides involves a one-step reaction of aldohexoses and aldopentoses with barbituric acids.
45 citations
TL;DR: Results indicate that Ap4A is also an activator of the cytosol 5'-nucleotidase from rat liver and concentrations of ATP two orders of magnitude higher are needed to elicit similar effects on the enzyme.
34 citations
TL;DR: In this paper, 1,3,4,6-tetra O -acetyl-2]-3-alkyl(aryl)-thioureido]-2-deoxy-α-d -glucopyranoses were converted in high yield into O -deacetylated thiazoline hydrobromide by hydrogen bromide-promoted cyclisation.
27 citations
TL;DR: A new staining technique with toluidine blue and safranin is described which yields satisfactory results in histological sections of chick embryo tissue fixed in a mixture of glutaraldehyde and formaldehyde and embedded in Spurr's resin.
Abstract: SUMMARY
A new staining technique with toluidine blue and safranin is described which yields satisfactory results in histological sections of chick embryo tissue fixed in a mixture of glutaraldehyde and formaldehyde and embedded in Spurr's resin. In zones of embryonic cell death, this technique allows the blue-staining of dying cell pyknotic nuclei to be clearly distinguished from red-staining healthy cells. The possible factors underlying this differential staining of pyknotic nuclei are discussed.
26 citations
TL;DR: Representative conditional yeast secretory mutants, blocked in transport of secretory and plasma membrane proteins from the endoplasmic reticulum, from the Golgi body and in transportof secretory vesicles, accumulated exoglucanase when incubated at the restrictive temperature (37°C).
Abstract: Representative conditional yeast secretory mutants, blocked in transport of secretory and plasma membrane proteins from the endoplasmic reticulum (sec 18), from the Golgi body (sec 7) and in transport of secretory vesicles (sec 1), accumulated exoglucanase, a constitutive yeast activity, when incubated at the restrictive temperature (37°C). Different proportions of the accumulated activity were released by mutant cells under permissive conditions. The presence or absence of cycloheximide during the secretion period made no differences in the results. More than 90% of the internal activity was bound to membrane in wild type cells. However, only the soluble pool underwent changes during the accumulation or secretion periods. The bulk of secretory invertase accumulated by sec 1 was also soluble. By contrast sec 7 and sec 18 accumulated membrane-bound as well as soluble invertase forms and both were secreted in similar proportions in each mutant. More than 90% of the accumulated invertase was secreted at the permissive temperature in sec 18 cells. That percentage was significantly lower for exoglucanase (<65%). Concomitantly, invertase accumulated by this mutant exited from the cells with a lower half time (t 1/2=150 min). These results may be interpreted assuming that exoglucanase is exported by a passive flow of the soluble pool.
13 citations
TL;DR: In this paper, a DDHF calculation of the momentum distribution of the Wigner transform and the nuclear density is presented, and the volume, surface, and higher order contributions to the momentum distributions are given.
8 citations
TL;DR: Formulas and recursion relations for the expectation values of the operators {1-exp[-a(r-${r}_{e}$${)]\mathrm{}}}^{n}$ are derived for a rotating Morse oscillator.
Abstract: In this paper formulas and recursion relations for the expectation values of the operators {1-exp[-a(r-${r}_{e}$${)]\mathrm{}}}^{n}$, (r-${r}_{e}$${)}^{n}$, exp[-a(r-${r}_{e}$${)]}^{n}$, and (r-${r}_{e}$){exp[-a(r-${r}_{e}$${)]\mathrm{}}}^{n}$ are derived for a rotating Morse oscillator. These equations can be used to calculate the diagonal (v=v', J=J') and off-diagonal (v\ensuremath{
e}v', J\ensuremath{
e}J') matrix elements. Asymptotic approximations for the diagonal elements of the (r-${r}_{e}$${)}^{n}$ operator, 〈vJ\ensuremath{\Vert}(r-${r}_{e}$)\ensuremath{\Vert}vJ〉 and 〈vJ\ensuremath{\Vert}(r-${r}_{e}$${)}^{2}$\ensuremath{\Vert}vJ〉, are also obtained.
TL;DR: The composition and arrangement of the cytoskeletal elements of the endothelium of the semilunar valves have been studied in the embryonic chick heart during the stages 30 to 38 and a possible linkage with differences in the local characteristics of the blood flow is discussed.
Abstract: The composition and arrangement of the cytoskeletal elements of the endothelium of the semilunar valves have been studied in the embryonic chick heart during the stages 30 to 38. Microtubules, vimentin intermediate filaments and actin microfilaments were constant components of the valvular endothelial cells in the studied stages. Scanning electron microscopy after Triton-X-100 extraction revealed significant differences in the tridimensional arrangement of the cytoskeleton in the course of valve development. In the ventricular face of the cusps the cytoskeletal elements displayed a progressive longitudinal alignment, while in the arterial face of the cusps the cytoskeleton maintained the appearance of a network. Transmission electron microscopy revealed that these differences were especially prominent for vimentin intermediate filaments, although a similar tendency was also observed for microtubules. Microfilaments were scarce in the endothelial cells of both faces of the cusps, and the stress fibers typical of the endothelial cells of the adult valves were not observed in the embryonic material. The significance of these results in valve morphogenesis and histogensis and a possible linkage with differences in the local characteristics of the blood flow are discussed.
TL;DR: In this article, six Pd(II) and Au(III) complexes of 4-glycopyranosylamino-5-nitroso-6-oxo-pyrimidine derivatives were prepared.
Abstract: Six Pd(II) and Au(III) complexes of 4-glycopyranosylamino-5-nitroso-6-oxo-pyrimidine derivatives were prepared. On the basis of their1H-NMR and IR spectra, it has been found that the coordination sites are the 5-nitroso and the 6-oxo substituents. Likewise, the thermal behaviour of the complexes has also been studied.
28 Jun 1986
TL;DR: Miguel Angel Melon estudia en este articulo la repercusion de la expansion demografica and del avance agrario en la Extremadura dieciochesca en la obstaculizaron de la trashumancia, especialmente de la camerana as mentioned in this paper.
Abstract: Miguel Angel Melon estudia en este articulo la repercusion de la expansion demografica y del avance agrario en la Extremadura dieciochesca en la obstaculizaron de la trashumancia, especialmente de la camerana. El articulo completa el anterior al aportar causas externas al fenomeno de la crisis de cameros con abundante documentacion, a la vez que ratifica el crecimiento y la fuerza del movimiento de la lucha por la tierra en Caceres y su comarca.
TL;DR: In this paper, the authors found that the cloning of the rpoB and rpoC genes in a high copy number vector in E. coli increased the amount of the encoded gene products, the β and β′ subunits of RNA polymerase.
Abstract: The cloning of the rpoB and rpoC genes in a high copy number vector in E. coli increased the amount of the encoded gene products, the β and β′ subunits of RNA polymerase. However, this unexpectedly caused a 30–50% decrease in RNA synthetic activity which alternatively induced a reduction of growth rate and enlargement of cell size, and decreased the DNA replication time. The results can be explained by autogenous regulation of the RNA polymerase genes by the ββ′ subunits. A relation between the decrease in number of transcription units and the observed higher rate of movement of DNA replication forks is discussed.
TL;DR: In this paper, a spectrophotometric study of isophthaldihydroxamic acid with Co(II) showed that a complex of stoichiometry 1:1 (Co:R) is formed.
TL;DR: The development of a suitable osmotic stabilizer now indicates thatSaccharomyces cerevisiae HMSF‐176 accumulates exoglucanase activity, and another ER‐blocked mutant behaved in a similar way.
TL;DR: Observations reported here are evidence of a "cleaning-role", for the removal of cell debris, when there is endocrine disfunction.
Abstract: Effects of septic shock by repeated inoculations with Escherichia coli on the ultrastructure of the folliculo-stellate cells and cavities of the adenohypophysis of the chicken were investigated in order to determine the function of these cavities. The principal morphological modifications were dilation of the Golgi apparatus, endoplasmic reticulum and autophagic vacuoles, and necrosis phenomena in the stellate cells. The follicular cavities showed dilation, and there was heterogeneous dense material and granular elements in the follicular lumen. Based on results reported in the literature, the observations reported here are evidence of a "cleaning-role", for the removal of cell debris, when there is endocrine disfunction.
TL;DR: Both pAp extracted from liver and that obtained from a commercial source showed the same pattern of hydrolysis by alkaline phosphatase, i.e., more 5'-AMP than 2'-AMP was obtained as an intermediate of the reaction.
TL;DR: In this article, the absorption of carbon dioxide by aqueous glycerine solutions in a column containing a string of spheres and cylinders was studied and the Reynolds number was varied between 5 and 560.
Abstract: The absorption of carbon dioxide by aqueous glycerine solutions in a column containing a string of spheres and cylinders has been studied. The Reynolds number was varied between 5 and 560. Using a model based on Higbie's penetration theory, modified to fit the characteristics of this absorber, the number of surface renewals that takes place in the column has been evaluated and correlated with the operating variables that can influence it. The liquid viscosity has no influence on the surface renewal which depends mainly on the liquid rate.
On a etudie l'absorption du dioxyde de carbone par des solutions aqueuses de glycerine dans une colonne contenant un garnissage de spheres et de cylindres pour un nombre de Reynolds compris entre 5 et 560. Le nombre de renouvellements de surface dans la colonne a ete estime en utilisant un modele base sur la theorie de la penetration de Higbie modifie afin de representer les caracteristiques de l'absorbeur. Ce nombre a ete correle avec les variables de fonctionnement pouvant l'influencer. La viscosite du liquide n'a aucune influence sur le renouvellement de surface qui depend essentiellement du debit du liquide.
TL;DR: An efficient computer-aided method (ANSWICAP) is presented for determining the transfer function in ideal switched capacitor networks with n-phases.
Abstract: An efficient computer-aided method (ANSWICAP) is presented for determining the transfer function in ideal switched capacitor networks with n-phases. The rational function representing the transfer function may be obtained symbolically as a function of z and of as many capacitors and gains of the circuit as are desired. Application of the method takes the input signal to be a sampled data signal, and that the network to be periodically switched.
TL;DR: The dependence of the absorption and fluorescence spectra of 1-hydroxy-2-carboxy-anthraquinone on pH and Hammett acidity have been studied and its ground state and lowest excited singlet-state dissociation constants have been determined.
TL;DR: In this paper, six 5-acetyl-4-β-d -glycopyranosylaminopyrimidine derivatives and their acetylated sugar homologues have been characterized by elemental analysis, IR and 1 H-NMR spectroscopy.
TL;DR: In this article, 2-Pyrilideniminobenzohydroxamic acid (PIBHA) has been synthesized by the reaction of o-aminobenzhydroxam acid and pyridine-2-carbaldehyde.
Abstract: 2-Pyrilideniminobenzohydroxamic acid (PIBHA) has been synthesized by the reaction ofo-aminobenzohydroxamic acid and pyridine-2-carbaldehyde. Its solubility in several solvents, spectral characteristics andpKa values are reported. Its reactivity with inorganic ions, in aqueous media and by extraction with chloroform, isoamyl alcohol, toluene, and a toluenic solution of trioctylmethylammonium chloride (Adogen 464) has been investigated. ThepK values corresponding to the formation constants of the complexes formed between PIBHA and Cd(II), Mn(II), Co(II), Ni(II) and Cu(II) in ethanol-water medium are also reported.
TL;DR: The aim of this work was to study the possible role of GGT in placental transfer of amino acids and to observe that the blood flow to rat uterine horns is proportional to the number of foetuses contained in the mother.
Abstract: The possibility that the y-glutamyl cycle functions as an amino acid transport system (Meister, 1973) is still an open question. Evidence against a direct role for yglutamyltransferase (GGT) (EC 2.3.2.2.) in amino acid transport in renal brush-border membrane vesicles has been offered (Hsu et al., 1984). However, we reported that GGT is involved in amino acid uptake by mammary gland in vivo (Viiia et al., 1981, 1983). The aim of this work was to study the possible role of GGT in placental transfer of amino acids. We recently developed a method to measure placental transfer of metabolites (Lasuncion et al., 1983) and have used it to study the effect of starvation (Palacin et al, 1985a) and diabetes (Herrera et al., 1985) on the placental transfer of substrates. It basically consists of the infusion through the left uterine artery of tracer amounts of I4C-labelled metabolites dissolved in physiological saline. Thus, the left uterine horn receives the tracer directly, whereas it reaches the right horn after dilution and metabolism in the mother. Twenty-day-pregnant Wistar rats were anaesthetized with pentobarbital and then 1 ml of 0.9% NaCl (controls) or 1 ml of 0.9% NaCl containing 5 mg of acivicin (AT. 125, Upjohn, Kalamazoo, U.S.A.) was injected. After 30 min we opened the abdominal cavity and infused 10 pCi of ~-[U-'~C]alanine through the left uterine artery. Foetuses from both uterine horns were processed separately. GGT activity was measured as described by Tate & Meister (1974) and alanine as described by Williamson (1974). E. Herrera, J. Lorenzo, M. A. Lasuncion & M. Palacin (personal communication) observed that the blood flow to rat uterine horns is proportional to the number of foetuses contained in the
TL;DR: In this article, it was shown that for certain sequence spaces 4, a Mackey space a can be found satisfying the following condition: if F is any infinite-dimensional Banach space with Schauder basis, for every 0-neighborhood U in E, there exists an absolutely convex 0-nighbors V in V such that ffv is norm-isomorphic to F.
Abstract: If E is the nuclear space s of rapidly decreasing sequences and F is any infinitedimensional Banach space with Schauder basis, then for every 0-neighborhood U in E there exists an absolutely convex 0-neighborhood Vc U in E such that /~v is norm-isomorphic to F (see [6]). This result of Saxon was improved later on by Valdivia [8] proving its validity when E is an arbitrary nuclear space and F any infinite-dimensional separable Banach space. In the present paper we bring up these results into the context of 2-nuclearity. Namely, we will prove that for certain sequence spaces 4, a Mackey space a can be found satisfying the following condition: If F is any infinite-dimensional Banach space with Schauder basis, for every 0-neighborhood U in othere is an absolutely convex 0-neighborhood V in osuch that ffv is norm-isomorphic to F. As a consequence we prove an embedding theorem of k-nuclear spaces into some product of any given infinite-dimensional Banach space with Schauder basis. This research, supported by the University of Extremadura, was carried out during the author's visit to the University of Kaiserslautern (F.R.G.).
TL;DR: The results indicate: the reduction by morphine of tritium release from both kinds of vessels is through a mechanism unrelated to opiate receptors, and the noradrenaline release elicited by morphine could be due in part to inhibition of its reuptake.
Abstract: 1. 1. Morphine reduced the [ 3 H]noradrenaline uptake in cat cerebral and femoral arteries and induced a dose-dependent tritium release from these vessels prelabelled with this amine, which was diminished in Ca 2+ -free medium. 2. 2. The opioid decreased the radioactivity release induced by electrical field simulation as well as its potentiation by tetraethylamonium. These effects were unaffected by naloxone. 3. 3. These results indicate: (a) the reduction by morphine of tritium release from both kinds of vessels is through a mechanism unrelated to opiate receptors, and (b) the noradrenaline release elicited by morphine could be due in part to inhibition of its reuptake.
TL;DR: The phosphorylation and dephosphorylation of proteins are characterized and the methylation of protein carboxyl groups is linked to the control of behaviour and to signal transduction in both prokaryotes and eukaryotes.
Abstract: Reversible covalent modifications of proteins play an important role in cellular function. The phosphorylation and dephosphorylation of proteins are perhaps the best characterized examples. Recently, another class of covalent modification, the methylation of protein carboxyl groups, has been linked to the control of behaviour and to signal transduction in both prokaryotes and eukaryotes27,23.