Resumen: Siguiendo un enfoque similar al de trabajos como Coe y Helpman (1995) Keller (1997) o Fr... more Resumen: Siguiendo un enfoque similar al de trabajos como Coe y Helpman (1995) Keller (1997) o Frantzen (2000), este estudio estima los efectos de las externalidades tecnológicas internacionales en el crecimiento de la productividad total de los factores (PTF) de diez agregaciones sectoriales de la manufactura de Finlandia, Francia, Italia, Estados Unidos, Canadá y España (únicos países para los que se ha podido reunir información suficientemente desagregada). Para evaluar los efectos se ha contrastado, por un lado, si las economías que importan principalmente de países con un elevado capital tecnológico perciben más externalidades tecnológicas y, por tanto, tienen una PTF sectorial mayor que las que adquieren de países con menores stocks tecnológicos. Y, por otro, se ha contrastado si existe alguna relación entre la mayor apertura de un país y su nivel de PTF, por razones no sólo de difusión tecnológica internacional sino también porque una mayor competencia puede inducir mejoras de eficiencia. Como principales aportaciones efectuadas pueden resaltarse el empleo de los datos sectoriales (desagregados a dos dígitos) más recientes de las bases de datos STAN y ANBERD de la OCDE; la unificación del poder adquisitivo de las monedas de los distintos países mediante los índices de valor unitarios del Groningen Growth and Development Centre, el cálculo de las variables que aproximan los stocks sectoriales de capital físico, la PTF y las externalidades tecnológicas; y, finalmente, la utilización tanto de test de raíces unitarias y cointegración para paneles de datos como de tres estimadores: mínimos cuadrados ordinarios, plenamente modificados y dinámicos. Los resultados empíricos ponen de manifiesto la relevancia de la tecnología foránea como factor impulsor del crecimiento y el papel que desempeña el comercio como vehículo transmisor de la misma. Palabras clave: Productividad total de los factores, transferencia de tecnología, comercio internacional, cointegración, paneles de datos.
Thirty-two commercially produced white, rosé, and red wines from Spain were assayed for genotoxic... more Thirty-two commercially produced white, rosé, and red wines from Spain were assayed for genotoxicity. The Ara forward mutagenicity assay with Salmonella typhimurium served as the test system. All the wines were mutagenic in the absence of mammalian microsomal activation (S9 mix) and/or glycosidase activities with the exception of one rosé wine which gave a clear dose-response relationship, although its mutagenic potency was considered statistically nonsignificant. The mutagenic activity covered nearly a 30-fold range. Compared to white and rosé wines, red wines showed the highest levels of mutagenicity; this wine type included four "very potent" (greater than 3,000 AraR mutants/ml) mutagenic wines. The level of wine mutagenicity did not correlate with either the region or the year of production (vintage). Individual winery methods are suggested as primarily responsible for variations in mutagenic activity. The present study with the Ara test supports the possibility that wine components other than the flavonols quercetin and rutin are the major putative mutagens: (1) white wines, as well as rosé or red wines, were detected as being mutagenic; (2) in no case was activation required for the detection of mutagenicity; (3) mutagen(s) were detected mainly (red wine) when not exclusively (white and rosé wine) in the polar fraction from XAD-2 chromatography. The high sensitivity of the Ara test has allowed the screening of the mutagenicity of a variety of wines with no previous process of extraction or concentration. The comparison of the mutagenic activity of the entire complex mixture to that of its lyophilized residue has revealed a positive synergistic role for ethanol in the mutagenicity of certain wines. Finally, this work suggests that the Ara test is a useful tool for mutagenicity screening in wines. Thus, this test might play an important role in elucidating the genotoxic mechanism of action of alcoholic beverages, and for studying optional production methods to decrease the mutagenicity of commercial wines.
In the absence of nucleotide excision repair, the additional deficiency of the DNA alkyltransfera... more In the absence of nucleotide excision repair, the additional deficiency of the DNA alkyltransferase (ATase) encoded by the constitutive ogt gene of Escherichia coli caused a marked increment in mutation induction by N-propyl-N-nitrosourea (PNU). Irrespective of the presence or the absence of the Ogt ATase, little mutagenic response was detected in Uvr+ bacteria in the concentration range 0-8 mM PNU, indicating that most premutagenic DNA lesions induced at these concentrations are efficiently recognized and repaired by the nucleotide excision repair system. Some increased susceptibility to mutagenesis by PNU was detected in Uvr- Ogt+ bacteria, but the Uvr- Ogt- double mutant exhibited much higher sensitivity. These data suggest that the Ogt ATase can replace to a great extent the repair capacity of the (A)BC excinuclease. Forward mutations induced by 6 mM PNU within the initial part of the lacl gene were recovered from Uvr+ Ogt-, Uvr- Ogt+, and Uvr- Ogt- bacteria. A total of 439 independent mutations were characterized by DNA sequence analysis. The PNU-induced spectra were dominated by G:C-->A:T transitions, consistent with the major role of the O6-alkylguanine miscoding lesion in mutagenesis by alkylating agents. Specific sites for G:C-->A:T transitions were recovered more or less frequently in one genetic background versus the others, giving statistically significant differences among the spectra (P < 10(-6)). We examined the influence of DNA repair by (A)BC excinuclease and Ogt ATase on the 5'-flanking base and DNA-strand associated with the PNU-induced G:C-->A:T transitions. Preferences different from those previously reported for the ethylating (ENU) and methylating (MNU) analogs were detected. We indicate that these differences might be caused by the PNU possibility of giving iso-propyl adducts, in addition to the expected n-propyl adducts, and by possible preferences in the initial distribution of these lesions as well as in their repair by the (A)BC excinuclease and the Ogt ATase of E. coli.
Forward mutations induced by 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) in the lacl gene... more Forward mutations induced by 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) in the lacl gene of Escherichia coli were recovered from bacteria proficient (Ogt+ Ada+) and deficient (Ogt- Ada-) in O6-alkylguanine-DNA alkyltransferase activity. A CCNU dose of 1 mM was selected for DNA sequence analysis. A total of 245 induced mutations were characterized. The mutations were almost exclusively (95%) GC-->AT transitions, indicating that CCNU-induced mutations arose in bacteria primarily from misreplication of O6-chloroethylguanine, in total agreement with results obtained for monofunctional alkylating agents. The distribution of CCNU-induced GC-->AT mutations was significantly altered by the presence of DNA alkyltransferase activity (P = 0.01). In the Ogt+ Ada+ mutational spectrum, guanines flanked on both sides by A:T base-pairs were on average 2.8 times more likely to mutate than those flanked by G:C base-pairs on at least one side. This bias disappeared in the Ogt- Ada- genetic background, thereby providing evidence that O6-chloroethylated guanines adjacent to G:C base-pairs are better targets for bacterial alkyltransferase than those not adjacent to G:C base-pairs. We recently reported a similar bias for ethyl methanesulfonate, strengthening the idea that CCNU is acting as a simple ethylating compound. In summary, this paper presents for the first time evidence that DNA repair by O6-alkylguanine-DNA alkyltransferases plays a major role in removing lesions responsible for GC-->AT transitions induced by CCNU, influencing their ultimate distribution with respect to sequence context.
This work attempted to derive a quantitative relationship between mutagenicity and carcinogenicit... more This work attempted to derive a quantitative relationship between mutagenicity and carcinogenicity by examining the association between mutagenic potency in the Ara test of Salmonella typhimurium and carcinogenic potency in rodents. Mutagenesis was monitored by selecting forward mutations to L-arabinose resistance. Lethality was measured at equivalent experimental conditions to those of mutant yield by using a mixed population of a pair of isogenic strains distinguished by their differential nutritional requirements. The study was carried out with a group of 11 direct-acting monofunctional alkylating agents, which failed to show any quantitative correlation in the histidine reverse-mutation test. Our data suggest that the mutagenic efficiency of the compounds is directly proportional to the magnitude of the maximum yield of L-arabinose resistance mutants and inversely proportional to the dose and the number of lethal hits at which the maximum yield occurs. A highly significant correlation (r10 = 0.86, P less than 0.01) was found between the mutagenic efficiencies of the compounds in the Ara test and their carcinogenic potencies in rodents, expressed as TD50 ('tumor dose' 50) values. The result suggests that the Ara forward-mutation test of S. typhimurium might be capable of reflecting the relative potency of animal carcinogens, at least when confined to particular chemical classes. A more generic and definitive conclusion about the predictive value of the Ara test would require this analysis to be extended to other types of genotoxic carcinogens.
ha generado una segunda generación de modelos para ofrecer una respuesta a las paradojas empírica... more ha generado una segunda generación de modelos para ofrecer una respuesta a las paradojas empíricas surgidas con referencia a la primera generación. Estos modelos se desarrollan en torno a dos propuestas teóricas: la teoría de crecimiento semi-endógeno y la teoría del crecimiento completamente endógeno con supuestos disímiles respecto al principal factor impulsor del crecimiento económico: el progreso técnico. En esta investigación, por primera vez, se analiza la validez de las citadas teorías en un contexto sectorial, aplicando los más modernos test y procedimientos de estimación econométrica para el tratamiento de series temporales de datos de panel.
Este trabajo, partiendo de las recientes teorías de crecimiento, pretende poner de manifiesto la ... more Este trabajo, partiendo de las recientes teorías de crecimiento, pretende poner de manifiesto la importancia y diversidad del impacto del capital tecnológico en la producción de los distintos sectores industriales. Para conseguir este propósito, se ha formado un panel con datos de nueve países de la Unión Europea durante el período 1975-1992, a partir del cual se ha estimado para doce agregaciones sectoriales una función de producción ampliada. Entre las principales aportaciones del estudio, cabe señalar la adopción de un enfoque sectorial en la estimación de un modelo con datos de España y de otros ocho países de la Unión Europea y la utilización de contrastes de raíces unitarias y de cointegración para validar las estimaciones realizadas mediante las técnicas de datos de panel, tratando de evitar, de esta forma, la posibilidad de que las regresiones sean espúreas. Los resultados confirman que, para la mayoría de los sectores manufactureros, es preciso ampliar la función de producción tradicional e introducir el capital tecnológico, variable cuya contribución al crecimiento de la producción difiere ostensiblemente de unos sectores a otros.
Mutation Research Fundamental and Molecular Mechanisms of Mutagenesis, Jul 31, 1989
A simple method is described for the determination of the lethal effects of chemicals assayed wit... more A simple method is described for the determination of the lethal effects of chemicals assayed with the zarabinose resistance test of Salmonella typhimurium. The method uses a mixed culture of 2 isogenic bacterial strains which are distinguished on the basis of their different nutritional requirements: sensitivity or resistance to L-arabinose, auxotrophy or prototrophy to histidine and leucine. BA13 (the mutation indicator strain) is the strain for routine screening of mutagens and allows the selection of forward mutation from Larabinose sensitivity to t-arabinose resistance. BALl3 (the survival indicator strain) is a derivative of BA13. Both bacterial strains are found to be equally sensitive to the lethal effects of mutagens. The method described permits the measurement of cell survival at the same high cell concentration as used in the measurement of the mutant yield and in the same type of minimal medium with z-arabinose and glycerol, except for the histidine supplement in the mutant plates or the leucine in the survival plates.
Este trabajo, partiendo de las recientes teorías de crecimiento, pretende poner de manifiesto la ... more Este trabajo, partiendo de las recientes teorías de crecimiento, pretende poner de manifiesto la importancia y diversidad del impacto del capital tecnológico en la producción de los distintos sectores industriales. Para conseguir este propósito, se ha formado un panel con datos de nueve países de la Unión Europea durante el período 1975-1992, a partir del cual se ha estimado para doce agregaciones sectoriales una función de producción ampliada. Entre las principales aportaciones del estudio, cabe señalar la adopción de un enfoque sectorial en la estimación de un modelo con datos de España y de otros ocho países de la Unión Europea y la utilización de contrastes de raíces unitarias y de cointegración para validar las estimaciones realizadas mediante las técnicas de datos de panel, tratando de evitar, de esta forma, la posibilidad de que las regresiones sean espúreas. Los resultados confirman que, para la mayoría de los sectores manufactureros, es preciso ampliar la función de producción tradicional e introducir el capital tecnológico, variable cuya contribución al crecimiento de la producción difiere ostensiblemente de unos sectores a otros.
A forward and a reverse mutation assay designed to detect environmental mutagens have been compar... more A forward and a reverse mutation assay designed to detect environmental mutagens have been compared in Salmonella typhimurium. The forward mutation assay scored resistance to L-arabinose and the reverse assay, reversion of histidine auxotrophy. Eighteen chemicals of different structural groups, aDl known to be mutagenic in the histidine reverse assay, were applied to strains carrying the genetic markers needed to perform both mutation assays. The mutagenicity of each chemical was determined by both plate and liquid tests. The plate test counted absolute numbers of surviving mutants and the liquid test separately measured survival and frequency of mutants among the survivors. All the chemicals used were found to be mutagenic in both mutation assays. The response of the L-arabinose assay was equal to or larger than the response of the histidine assay in the case of 16 chemicals. The two other compounds, 2-nitrofluorene and sodium azide, were detected more efficiently by the histidine assay. Sodium azide, a non-carcinogenic compound, is a potent mutagen in the histidine assay, but very weak in the L-arabinose assay.
Siguiendo un enfoque similar al de trabajos como Coe y Helpman (1995) Keller (1997) o Frantzen (2... more Siguiendo un enfoque similar al de trabajos como Coe y Helpman (1995) Keller (1997) o Frantzen (2000), este estudio estima los efectos de las externalidades tecnológicas internacionales en el crecimiento de la productividad total de los factores (PTF) de diez agregaciones sectoriales de la manufactura de Finlandia, Francia, Italia, Estados Unidos, Canadá y España (únicos países para los que se
Mutation Research/Environmental Mutagenesis and Related Subjects, 1985
Strain TA102 of S. typhimurium is a new histidine-requiring mutant, particularly suited to the de... more Strain TA102 of S. typhimurium is a new histidine-requiring mutant, particularly suited to the detection of oxidative mutagens acting at A. T base pairs. 10 oxidizing chemicals, previously tested in strain TA102, were used to evaluate the mutagenic sensitivity of the L-arabinose forward mutation assay of S. typhimurium with respect to those types of mutagens. The mutagenicity of each compound was determined by liquid test, measuring both the frequency of mutants among the survivors and the absolute number of mutants growing in selective plates with traces of D-glucose. Strain BA13 with a wild-type lipopolysaccharide barrier was used as compared to the deep rough derivative strain BA9. The chemicals studied were: bleomycin, t-butyl hydroperoxide, chromium trioxide, cumene hydroperoxide, formaldehyde, glyoxal, glutaraldehyde, hydrogen peroxide, paraquat, and phenylhydrazine. Additionally, ultrasonic oscillation was used as a presumable non-mutagenic lethal control treatment. The L-arabinose forward mutation assay detected the mutagenic activity of all the chemicals under study with a high degree of sensitivity, including paraquat which is unable to revert strain TA102. Positive responses were obtained at doses equivalent to or 10 times lower than the doses detected by strain TA102. The results support the idea that the L-arabinose forward mutation assay could replace the set of specific tester strains used by the histidine reverse mutation assay in general screening for genetic toxins. Bacterial mutation assays are commonly used in the detection of genetic toxins present in our environment since they are rapid, inexpensive, technically simple and sensitive (Hollstein et al., 1979). A popular reverse mutation assay has been developed in Salmonella typhimurium by Ames et al.
Resumen: Siguiendo un enfoque similar al de trabajos como Coe y Helpman (1995) Keller (1997) o Fr... more Resumen: Siguiendo un enfoque similar al de trabajos como Coe y Helpman (1995) Keller (1997) o Frantzen (2000), este estudio estima los efectos de las externalidades tecnológicas internacionales en el crecimiento de la productividad total de los factores (PTF) de diez agregaciones sectoriales de la manufactura de Finlandia, Francia, Italia, Estados Unidos, Canadá y España (únicos países para los que se ha podido reunir información suficientemente desagregada). Para evaluar los efectos se ha contrastado, por un lado, si las economías que importan principalmente de países con un elevado capital tecnológico perciben más externalidades tecnológicas y, por tanto, tienen una PTF sectorial mayor que las que adquieren de países con menores stocks tecnológicos. Y, por otro, se ha contrastado si existe alguna relación entre la mayor apertura de un país y su nivel de PTF, por razones no sólo de difusión tecnológica internacional sino también porque una mayor competencia puede inducir mejoras de eficiencia. Como principales aportaciones efectuadas pueden resaltarse el empleo de los datos sectoriales (desagregados a dos dígitos) más recientes de las bases de datos STAN y ANBERD de la OCDE; la unificación del poder adquisitivo de las monedas de los distintos países mediante los índices de valor unitarios del Groningen Growth and Development Centre, el cálculo de las variables que aproximan los stocks sectoriales de capital físico, la PTF y las externalidades tecnológicas; y, finalmente, la utilización tanto de test de raíces unitarias y cointegración para paneles de datos como de tres estimadores: mínimos cuadrados ordinarios, plenamente modificados y dinámicos. Los resultados empíricos ponen de manifiesto la relevancia de la tecnología foránea como factor impulsor del crecimiento y el papel que desempeña el comercio como vehículo transmisor de la misma. Palabras clave: Productividad total de los factores, transferencia de tecnología, comercio internacional, cointegración, paneles de datos.
Thirty-two commercially produced white, rosé, and red wines from Spain were assayed for genotoxic... more Thirty-two commercially produced white, rosé, and red wines from Spain were assayed for genotoxicity. The Ara forward mutagenicity assay with Salmonella typhimurium served as the test system. All the wines were mutagenic in the absence of mammalian microsomal activation (S9 mix) and/or glycosidase activities with the exception of one rosé wine which gave a clear dose-response relationship, although its mutagenic potency was considered statistically nonsignificant. The mutagenic activity covered nearly a 30-fold range. Compared to white and rosé wines, red wines showed the highest levels of mutagenicity; this wine type included four "very potent" (greater than 3,000 AraR mutants/ml) mutagenic wines. The level of wine mutagenicity did not correlate with either the region or the year of production (vintage). Individual winery methods are suggested as primarily responsible for variations in mutagenic activity. The present study with the Ara test supports the possibility that wine components other than the flavonols quercetin and rutin are the major putative mutagens: (1) white wines, as well as rosé or red wines, were detected as being mutagenic; (2) in no case was activation required for the detection of mutagenicity; (3) mutagen(s) were detected mainly (red wine) when not exclusively (white and rosé wine) in the polar fraction from XAD-2 chromatography. The high sensitivity of the Ara test has allowed the screening of the mutagenicity of a variety of wines with no previous process of extraction or concentration. The comparison of the mutagenic activity of the entire complex mixture to that of its lyophilized residue has revealed a positive synergistic role for ethanol in the mutagenicity of certain wines. Finally, this work suggests that the Ara test is a useful tool for mutagenicity screening in wines. Thus, this test might play an important role in elucidating the genotoxic mechanism of action of alcoholic beverages, and for studying optional production methods to decrease the mutagenicity of commercial wines.
In the absence of nucleotide excision repair, the additional deficiency of the DNA alkyltransfera... more In the absence of nucleotide excision repair, the additional deficiency of the DNA alkyltransferase (ATase) encoded by the constitutive ogt gene of Escherichia coli caused a marked increment in mutation induction by N-propyl-N-nitrosourea (PNU). Irrespective of the presence or the absence of the Ogt ATase, little mutagenic response was detected in Uvr+ bacteria in the concentration range 0-8 mM PNU, indicating that most premutagenic DNA lesions induced at these concentrations are efficiently recognized and repaired by the nucleotide excision repair system. Some increased susceptibility to mutagenesis by PNU was detected in Uvr- Ogt+ bacteria, but the Uvr- Ogt- double mutant exhibited much higher sensitivity. These data suggest that the Ogt ATase can replace to a great extent the repair capacity of the (A)BC excinuclease. Forward mutations induced by 6 mM PNU within the initial part of the lacl gene were recovered from Uvr+ Ogt-, Uvr- Ogt+, and Uvr- Ogt- bacteria. A total of 439 independent mutations were characterized by DNA sequence analysis. The PNU-induced spectra were dominated by G:C-->A:T transitions, consistent with the major role of the O6-alkylguanine miscoding lesion in mutagenesis by alkylating agents. Specific sites for G:C-->A:T transitions were recovered more or less frequently in one genetic background versus the others, giving statistically significant differences among the spectra (P < 10(-6)). We examined the influence of DNA repair by (A)BC excinuclease and Ogt ATase on the 5'-flanking base and DNA-strand associated with the PNU-induced G:C-->A:T transitions. Preferences different from those previously reported for the ethylating (ENU) and methylating (MNU) analogs were detected. We indicate that these differences might be caused by the PNU possibility of giving iso-propyl adducts, in addition to the expected n-propyl adducts, and by possible preferences in the initial distribution of these lesions as well as in their repair by the (A)BC excinuclease and the Ogt ATase of E. coli.
Forward mutations induced by 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) in the lacl gene... more Forward mutations induced by 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) in the lacl gene of Escherichia coli were recovered from bacteria proficient (Ogt+ Ada+) and deficient (Ogt- Ada-) in O6-alkylguanine-DNA alkyltransferase activity. A CCNU dose of 1 mM was selected for DNA sequence analysis. A total of 245 induced mutations were characterized. The mutations were almost exclusively (95%) GC-->AT transitions, indicating that CCNU-induced mutations arose in bacteria primarily from misreplication of O6-chloroethylguanine, in total agreement with results obtained for monofunctional alkylating agents. The distribution of CCNU-induced GC-->AT mutations was significantly altered by the presence of DNA alkyltransferase activity (P = 0.01). In the Ogt+ Ada+ mutational spectrum, guanines flanked on both sides by A:T base-pairs were on average 2.8 times more likely to mutate than those flanked by G:C base-pairs on at least one side. This bias disappeared in the Ogt- Ada- genetic background, thereby providing evidence that O6-chloroethylated guanines adjacent to G:C base-pairs are better targets for bacterial alkyltransferase than those not adjacent to G:C base-pairs. We recently reported a similar bias for ethyl methanesulfonate, strengthening the idea that CCNU is acting as a simple ethylating compound. In summary, this paper presents for the first time evidence that DNA repair by O6-alkylguanine-DNA alkyltransferases plays a major role in removing lesions responsible for GC-->AT transitions induced by CCNU, influencing their ultimate distribution with respect to sequence context.
This work attempted to derive a quantitative relationship between mutagenicity and carcinogenicit... more This work attempted to derive a quantitative relationship between mutagenicity and carcinogenicity by examining the association between mutagenic potency in the Ara test of Salmonella typhimurium and carcinogenic potency in rodents. Mutagenesis was monitored by selecting forward mutations to L-arabinose resistance. Lethality was measured at equivalent experimental conditions to those of mutant yield by using a mixed population of a pair of isogenic strains distinguished by their differential nutritional requirements. The study was carried out with a group of 11 direct-acting monofunctional alkylating agents, which failed to show any quantitative correlation in the histidine reverse-mutation test. Our data suggest that the mutagenic efficiency of the compounds is directly proportional to the magnitude of the maximum yield of L-arabinose resistance mutants and inversely proportional to the dose and the number of lethal hits at which the maximum yield occurs. A highly significant correlation (r10 = 0.86, P less than 0.01) was found between the mutagenic efficiencies of the compounds in the Ara test and their carcinogenic potencies in rodents, expressed as TD50 ('tumor dose' 50) values. The result suggests that the Ara forward-mutation test of S. typhimurium might be capable of reflecting the relative potency of animal carcinogens, at least when confined to particular chemical classes. A more generic and definitive conclusion about the predictive value of the Ara test would require this analysis to be extended to other types of genotoxic carcinogens.
ha generado una segunda generación de modelos para ofrecer una respuesta a las paradojas empírica... more ha generado una segunda generación de modelos para ofrecer una respuesta a las paradojas empíricas surgidas con referencia a la primera generación. Estos modelos se desarrollan en torno a dos propuestas teóricas: la teoría de crecimiento semi-endógeno y la teoría del crecimiento completamente endógeno con supuestos disímiles respecto al principal factor impulsor del crecimiento económico: el progreso técnico. En esta investigación, por primera vez, se analiza la validez de las citadas teorías en un contexto sectorial, aplicando los más modernos test y procedimientos de estimación econométrica para el tratamiento de series temporales de datos de panel.
Este trabajo, partiendo de las recientes teorías de crecimiento, pretende poner de manifiesto la ... more Este trabajo, partiendo de las recientes teorías de crecimiento, pretende poner de manifiesto la importancia y diversidad del impacto del capital tecnológico en la producción de los distintos sectores industriales. Para conseguir este propósito, se ha formado un panel con datos de nueve países de la Unión Europea durante el período 1975-1992, a partir del cual se ha estimado para doce agregaciones sectoriales una función de producción ampliada. Entre las principales aportaciones del estudio, cabe señalar la adopción de un enfoque sectorial en la estimación de un modelo con datos de España y de otros ocho países de la Unión Europea y la utilización de contrastes de raíces unitarias y de cointegración para validar las estimaciones realizadas mediante las técnicas de datos de panel, tratando de evitar, de esta forma, la posibilidad de que las regresiones sean espúreas. Los resultados confirman que, para la mayoría de los sectores manufactureros, es preciso ampliar la función de producción tradicional e introducir el capital tecnológico, variable cuya contribución al crecimiento de la producción difiere ostensiblemente de unos sectores a otros.
Mutation Research Fundamental and Molecular Mechanisms of Mutagenesis, Jul 31, 1989
A simple method is described for the determination of the lethal effects of chemicals assayed wit... more A simple method is described for the determination of the lethal effects of chemicals assayed with the zarabinose resistance test of Salmonella typhimurium. The method uses a mixed culture of 2 isogenic bacterial strains which are distinguished on the basis of their different nutritional requirements: sensitivity or resistance to L-arabinose, auxotrophy or prototrophy to histidine and leucine. BA13 (the mutation indicator strain) is the strain for routine screening of mutagens and allows the selection of forward mutation from Larabinose sensitivity to t-arabinose resistance. BALl3 (the survival indicator strain) is a derivative of BA13. Both bacterial strains are found to be equally sensitive to the lethal effects of mutagens. The method described permits the measurement of cell survival at the same high cell concentration as used in the measurement of the mutant yield and in the same type of minimal medium with z-arabinose and glycerol, except for the histidine supplement in the mutant plates or the leucine in the survival plates.
Este trabajo, partiendo de las recientes teorías de crecimiento, pretende poner de manifiesto la ... more Este trabajo, partiendo de las recientes teorías de crecimiento, pretende poner de manifiesto la importancia y diversidad del impacto del capital tecnológico en la producción de los distintos sectores industriales. Para conseguir este propósito, se ha formado un panel con datos de nueve países de la Unión Europea durante el período 1975-1992, a partir del cual se ha estimado para doce agregaciones sectoriales una función de producción ampliada. Entre las principales aportaciones del estudio, cabe señalar la adopción de un enfoque sectorial en la estimación de un modelo con datos de España y de otros ocho países de la Unión Europea y la utilización de contrastes de raíces unitarias y de cointegración para validar las estimaciones realizadas mediante las técnicas de datos de panel, tratando de evitar, de esta forma, la posibilidad de que las regresiones sean espúreas. Los resultados confirman que, para la mayoría de los sectores manufactureros, es preciso ampliar la función de producción tradicional e introducir el capital tecnológico, variable cuya contribución al crecimiento de la producción difiere ostensiblemente de unos sectores a otros.
A forward and a reverse mutation assay designed to detect environmental mutagens have been compar... more A forward and a reverse mutation assay designed to detect environmental mutagens have been compared in Salmonella typhimurium. The forward mutation assay scored resistance to L-arabinose and the reverse assay, reversion of histidine auxotrophy. Eighteen chemicals of different structural groups, aDl known to be mutagenic in the histidine reverse assay, were applied to strains carrying the genetic markers needed to perform both mutation assays. The mutagenicity of each chemical was determined by both plate and liquid tests. The plate test counted absolute numbers of surviving mutants and the liquid test separately measured survival and frequency of mutants among the survivors. All the chemicals used were found to be mutagenic in both mutation assays. The response of the L-arabinose assay was equal to or larger than the response of the histidine assay in the case of 16 chemicals. The two other compounds, 2-nitrofluorene and sodium azide, were detected more efficiently by the histidine assay. Sodium azide, a non-carcinogenic compound, is a potent mutagen in the histidine assay, but very weak in the L-arabinose assay.
Siguiendo un enfoque similar al de trabajos como Coe y Helpman (1995) Keller (1997) o Frantzen (2... more Siguiendo un enfoque similar al de trabajos como Coe y Helpman (1995) Keller (1997) o Frantzen (2000), este estudio estima los efectos de las externalidades tecnológicas internacionales en el crecimiento de la productividad total de los factores (PTF) de diez agregaciones sectoriales de la manufactura de Finlandia, Francia, Italia, Estados Unidos, Canadá y España (únicos países para los que se
Mutation Research/Environmental Mutagenesis and Related Subjects, 1985
Strain TA102 of S. typhimurium is a new histidine-requiring mutant, particularly suited to the de... more Strain TA102 of S. typhimurium is a new histidine-requiring mutant, particularly suited to the detection of oxidative mutagens acting at A. T base pairs. 10 oxidizing chemicals, previously tested in strain TA102, were used to evaluate the mutagenic sensitivity of the L-arabinose forward mutation assay of S. typhimurium with respect to those types of mutagens. The mutagenicity of each compound was determined by liquid test, measuring both the frequency of mutants among the survivors and the absolute number of mutants growing in selective plates with traces of D-glucose. Strain BA13 with a wild-type lipopolysaccharide barrier was used as compared to the deep rough derivative strain BA9. The chemicals studied were: bleomycin, t-butyl hydroperoxide, chromium trioxide, cumene hydroperoxide, formaldehyde, glyoxal, glutaraldehyde, hydrogen peroxide, paraquat, and phenylhydrazine. Additionally, ultrasonic oscillation was used as a presumable non-mutagenic lethal control treatment. The L-arabinose forward mutation assay detected the mutagenic activity of all the chemicals under study with a high degree of sensitivity, including paraquat which is unable to revert strain TA102. Positive responses were obtained at doses equivalent to or 10 times lower than the doses detected by strain TA102. The results support the idea that the L-arabinose forward mutation assay could replace the set of specific tester strains used by the histidine reverse mutation assay in general screening for genetic toxins. Bacterial mutation assays are commonly used in the detection of genetic toxins present in our environment since they are rapid, inexpensive, technically simple and sensitive (Hollstein et al., 1979). A popular reverse mutation assay has been developed in Salmonella typhimurium by Ames et al.
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