Showing papers by "Spanish National Research Council published in 1980"

A specialized type of neuron in the visual cortex of cat: a Golgi and electron microscope study of chandelier cells.

Abstract: The axonal arborization of chandelier cells is characterized by its conspicuous, vertically oriented, bouton aggregates. The efferent synaptic relationships established by these terminal formations were investigated by electron microscopy of Golgi preparations after gold toning and deimpregnation. In all cases examined form layers II and III of cat areas 17 and 18, the terminal formations, here denominated specific terminal portions (stp), make symmetric synapses upon axon initial segments of pyramidal neurons. Some identified stp's were reconstructed from ultrathin serial sections with the aid of a microcomputer-based system, and the number of synaptic contacts established on axon initial segments was evaluated. No evidence was found that parts of the axonal tree other than stp's also engage in synaptic contacts. Specific terminal portions are rather variable in complexity. However, the synaptic contacts they engage in are constant and the complexity of stp's from the same axonal arborization varies. It is, therefore, clear that all stp's are terminal axonal formations of a unique, specialized type of neuron. Computer techniques and conventional Golgi observations were used to study further details of chandelier cell morphology. Axonal plexuses are preferentially, although not exclusively, local and distribute within spheric, ovoid, or disk-shaped spaces In most chandelier cells, the main axonal trunk descends to the white matter, where we have been unable to follow it further.

Effect of ATPase Inhibitors on the Proton Pump of Respiratory-Deficient Yeast

Abstract: Diethylstilbestrol and dicyclohexylcarbodiimide inhibit the ATPase of the plasma membranes and the proton-pumping activity of the cells in a respiratory-deficient mutant of Saccharomyces cerevisiae. The effects of the inhibitors in vivo seem to be specific because neither the proton permeability nor the ATPase levels of the cells are affected. These results indicate that the yeast plasma-membrane ATPase corresponds to the proton pump of the cells. The fact that both inhibitors of the ATPase delay the fall of ATP levels which follows a block of fermentation indicates that ATPase function is one of the major ATP-consuming pathways in yeast. In addition, diethylstilbestrol prevents the fall of ATP levels produced by dinitrophenol, suggesting that this fall was caused by partial dissipation of the proton gradient and consequent stimulation of the proton-pumping ATPase.

Synthesis and mode(s) of action of a new series of imide derivatives of 3-nitro-1,8 naphthalic acid.

Abstract: Four new imide derivatives of 3-nitro-1,8-naphthalic acid have been synthesised. The compounds show strong cytostatic activity against both HeLa and KB cells and are moderately toxic towards both mice and rats (LD50 above 4 mg/kg IP). Two of the most active compounds, M-4212 and M-12210, prevented the development of mouse Ehrlich ascites and rat Yoshida carcinoma. All these drugs block cell growth by inhibiting the synthesis of both DNA and RNA. In particular, both M-4212 and M-12210 raise the melting point of double-stranded DNA.

Catalytic activity of perovskite-type oxides LaMeO3

Abstract: Catalytic activities for CO oxidation of a series of LaMeO3(Me3+=V3+, Cr3+, Mn3+, Fe3+, Co3+, Ni3+) perovskite-type oxides were measured. Maxima for Mn3+ and Co3+ were found. The relation between local symmetry of solid surfaces and chemisorption and catalysis is discussed.

Method for Testing Degree of Infectivity of Rhizobium meliloti Strains.

Abstract: The infectiveness of different strains of Rhizobium meliloti was tested with a technique that uses the addition of tetracycline to the root medium. To stop the infection, the antibiotic was added some time after the inoculation of Medicago sativa plants. A coefficient of infectivity for each strain was calculated according to the number of nodules that appeared with and without the addition of the antibiotic. This method seems useful in infectivity studies and is simpler and easier to perform than the test of competence between strains.

Effects of introduced and indigenous va mycorrhizal fungi on nodulation, growth and nutrition of medicago sativa in phosphate-fixing soils as affected by p fertilizers

Abstract: The legumeMedicago sativa was grown in two phosphate-fixing soils which received soluble or rock phosphate. The effects of the inoculation withGlomus mosseae on plant nutrition and nodulation were studied. The introduced VA fungi became successfully established and improved the degree of infection over level achieved by native endophytes. In all experimental conditions tested, plant dry weight, the total uptake of N and P and nodulation byRhizobium meliloti were increased by mycorrhizal inoculation. The size of the increase was inversely correlated with soluble P content in the soil. Mycorrhization, enhanced by introduction of suitable VA fungi, had similar effects to that of the dose of soluble phosphate tested. Indigenous and native endophytes cooperated in these effects. Results are discussed in terms of reducing the input of soluble P fertilizer to phosphate-fixing soils and the possibility of restoring the phosphate stock using a more rational supply of soluble P, that allows cooperation with VA fungi, or by the use of less soluble and expensive forms of P fertilizers.

Fruit-set of unpollinated ovaries of Pisum sativum L. : Influence of vegetative parts.

Abstract: The influence of removing the apical shoot and different leaves above and below the flower on the fruit-set of unpollinated pea ovaries (Pisum sativum L. cv. Alaska) has been studied. Unpollinated ovaries were induced to set and develop either by topping or by removing certain developing leaves of the shoot. Topping had a maximum effect when carried out before or on the day of anthesis, and up to four consecutive ovaries were induced to set in the same plant. The inhibition of fruit-set was due to the developing leaves and not to the apex. The third leaf above the first flower, which had a simultaneous development to the ovary, had the stronger inhibitory effect on parthenocarpic fruit-set. The application of different plant-growth regulators (indoleacetic acid, naphthylacetic acid, 2,4-dichlorophenoxyacetic acid, gibberellic acid, benzyladenine and abscisic acid) did not mimic the negative effect of the shoot.

Identification and geochemical significance of long chain acyclic isoprenoid hydrocarbons in crude oils

Abstract: A series of acyclic isoprenoid hydrocarbons with head-to-tail, tail-to-tail and head-to-head linkages are present as important components in petroleum. This paper presents some evidence for the occurrence of the extended series beyond the C40 isomers described to date. Thus, the regular head-to-tail homologs up to C45 have been identified, as well as a new C21C39 series, exhibiting methyl branches in the positions 3, 7, 11, 15,… of the molecule, which could derive from homologue members of the head-to-head series higher than C40. To reinforce the mass spectrometric identification of these compounds their gas chromatographic behaviour has been examined and retention indices of individual members compared with those predicted by retention increments. The relative abundance of the above series and the internal distribution of structural isomers in oils and rock extracts are considered as valuable parameters in correlation studies. Such distributions are geochemically significant from the standpoint of the origin and maturation of the sedimentary organic matter. Recent progress in the knowledge of the lipid composition of archaebacteria provides a definite argument for a substantial contribution of bacterial cell-wall lipids to petrogenesis.

A linear-potential model for quark confinement

Abstract: Under the assumption that quarks are confined, in a first approximation, by a relativistic linear potentialV(r)=1/2 (1+β)(V0+λr), several properties of low-lying baryons have been calculated. Corrections to the mass spectrum have also been calculated, by taking the one-gluon exchange into consideration.

Effects of boron on nitrogen metabolism and sugar levels of sugar beet

Abstract: The effects of deficient and toxic levels of boron on various aspects of nitrogen metabolism in sugar beet are studied. Plant analysis shows a nitrate ion accumulation, a decrease in the activity of the nitrate reductase enzyme and a lower molybdenum absorption.

Plantlet formation from embryonic tissue of chestnut grown in vitro

Abstract: Development of axillary shoots was induced when isolated embryonic axes of chestnut (Castanea sativa Mill.) were cultured on a defined medium containing 6-benzyl-aminopurine (BAP). The optimal concentrations of BAP were determined for development of axillary shoots from both embryonic axes and subcultured shoots. After shoot multiplication a great number of shoots have been maintained sequentially without significant change in the proliferative rate for one year. Limited rooting has been obtained with excised shoots. Indole-3-butyric acid (IBA) at 2 mg/l was used to induce root primordia. After 8 days of treatment the plantlets were transferred to an auxin-free medium for root development.

Manganese superoxide dismutase from a higher plant : Purification of a new Mn-containing enzyme.

Abstract: A manganese-containing superoxide dismutase (EC 1.15.1.1) was purified to homogeneity from a higher plant for the first time. The enzyme was isolated fromPisum sativum leaf extracts by thermal fractionation, ammonium sulfate salting out, ion-exchange and gel-filtration column chromatography, and preparative polyacrylamide gel electrophoresis. Pure manganese superoxide dismutase had a specific activity of about 3,000 U mg-1 and was purified 215-fold, with a yield of 1.2 mg enzyme per kg whole leaf. The manganese superoxide dismutase had a molecular weight of 94,000 and contained one g-atom of Mn per mol of enzyme. No iron and copper were detected. Activity reconstitution experiments with the pure enzyme ruled out the possibility of a manganese loss during the purification procedure. The stability of manganese superoxide dismutase at-20°C, 4°C, 25°C, 50°C, and 60°C was studied, and the enzyme was found more labile at high temperatures than bacterial manganese superoxide dismutases and iron superoxide dismutases from an algal and bacterial origin.

The relationship between the cell time available for repair and the effectiveness of a damaging treatment in provoking the formation of sister-chromatid exchanges

Abstract: The effectiveness of a given dosage of visible light in inducing increased yields of SCEs was studied in Allium cepa L. meristems. Cells were first grown for one cycle time in the presence of BrdUrd and then irradiated at different times throughout the second cell cycle. The effectiveness of this treatment in provoking the formation of SCEs increases the closer the irradiation time is to the beginning of the S phase, and then decreases rapidly as cells progress through the S period. The largest increase in SCEs is obtained when irradiation coincides with early S phase. These results strongly suggest that SCEs arise at the time of DNA replication due to the presence of unrepaired lesions. Since repair appears to be a time-dependent process, the shorter the interval between damage induction and DNA replication, the greater the number of lesions that remain unrepaired, and as a consequence, the higher the effectiveness of the damaging treatment in provoking the formation of SCEs.

New aspects of the microhardness of ultraoriented polyethylene

Abstract: The influence of extrusion conditions on the microhardness of ultradrawn polyethylene (PE) has been investigated. The micromechanical behaviour of ultradrawn PE fibres can be defined in terms of a creep constant and a microhardness value (MH) at 0.1 min, relating to the size of indentation under load rather than to the residual dimension. The PE strands show, in addition, a conspicuous anisotropic shape of the indentation pattern (MH ‖>MH ⊥) which involves a local elastic recovery of the material parallel to the fibre axis. The hardening of the fibres in the parallel and perpendicular direction to the fibre axis is an increasing function of both extrusion temperature and extrusion pressure and can be explained in terms of a simultaneous improvement in the strength and the lateral packing of fibrils and microfibrils in fibre direction. For extrusion temperatures (T e) greater than 134° C the microhardness shows, however, a decrease which is thought to be related to the molecular relaxation occurring in the vicinity of the melting point. In the range of extrusion temperatures (90 to 137° C) and extrusion pressures (0.24 to 0.5 GPa) investigated, the hardness anisotropy on the fibre surface, ΔMH, is a unique increasing function of draw ratio λ. It is completely independent of both the extrusion temperature and pressure. ΔMH in the core of cleaved fibres shows a constant value which is independent of λ and equals the extrapolated value at the surface for the maximum attainable value of λ. The results can be satisfactorily explained if one considers the existing morphological differences between the outer sheath and the inner core of the fibres.

Specific binding of kainic acid to purified subcellular fractions from rat brain.

Abstract: The subcellular distribution of kainic acid (KA) binding sites in rat brain has been studied using a microcentrifugation assay. KA did not bind to myelin or brain cytosol and had few or no binding sites in the nuclear fraction. However, it bound to microsomal components (K d =128–136 nM; 2.5–4.8 pmol/mg protein), purified synaptic plasma membranes (SPM) (K d =45–71 nM; 5.8–6.5 pmol/mg), and purified cell-body and intraterminal mitochondria (K d =11–31 nM; 0.4–1.1 pmol/mg). Bound KA could be totally displaced byl-glutamate orl-aspartate, but several putative antagonists of these amino acids (nuciferin, compound HA-966, 2-amino-4-phosphonobutyrate, and 2-amino-3-phosphonoproprionate) failed to displace KA or did so at very high concentrations (≥4 mM). Glutamic acid diethyl ester (GDEE) andd,l-α-aminoadipate (α-AA) were more effective (IC50, 0.2–0.8 mM) and showed differential effects in their capacity to displace KA bound to the various subcellular fractions. Thus, GDEE only displaced 40–60% of the KA bound by SPM or mitochondria and did not prevent the binding of KA to microsomes. α-AA, on the other hand, was more effective in preventing the binding of KA at high concentrations and displaced between 80 and 100% of the drug. Both compounds showed biphasic curves of KA displacement from synaptic plasma membranes and mitochondria. The overall results indicate the presence of multiple binding sites for KA in brain cells and suggest that KA does not act exclusively at synaptic glutamate receptors. The mechanism of KA action is most likely quite complex, and the drug probably acts at multiple binding sites affecting a number of processes.