Showing papers by "Instituto Politécnico Nacional published in 1970"
TL;DR: The intraportal injection of an equal volume of isosmotic NaCl did not produce any noticeable change in the feeding behavior of the same dogs and the satiating effect was obtained only when the glucose went directly into the liver and not when distributed throughout the organism.
167 citations
105 citations
TL;DR: Tetramisole caused contraction of Ascaris muscle previously depolarized with high K+ solutions, suggesting that tetram isole can induce a contracture that is independent of membrane depolarization.
Abstract: 1. Tetramisole (100 mug/ml) paralysed live Ascaris in 3 min.2. Tetramisole (10 mug/ml) caused a sustained contraction of the isolated somatic muscles of the worm. This contraction was not blocked by curare nor by piperazine.3. Tetramisole reduced the resting potential of Ascaris muscle from 34+/-4 to 10+/-1 mV.4. Tetramisole caused contraction of Ascaris muscle previously depolarized with high K(+) solutions. This observation suggests that tetramisole can induce a contracture that is independent of membrane depolarization.
95 citations
38 citations
TL;DR: The structural elucidation of roxburghines A–E, new diastereoisomeric indole alkaloids C 31 H 32 N 4 O 2, isolated from the leaves and stems of an Uncaria Sp.
31 citations
TL;DR: By using a combination of subcutaneous and intraventricular injections of [14C]uridine and [3H]methyl‐l‐methionine, maximum incorporation in about 40 min of both radioactive precursors into nuclear RNA from rat brain is obtained.
Abstract: — By using a combination of subcutaneous and intraventricular injections of [14C]uridine and [3H]methyl-l-methionine we have obtained maximum incorporation in about 40 min of both radioactive precursors into nuclear RNA from rat brain. In this nuclear fraction we found at least two different types of RNA that were rapidly labelled. One of them incorporated both [14C]uridine and [3H]methyl groups and seemed to correspond to species of rRNA and their precursors. The other RNA fraction was less methylated or non-methylated and exhibited sedimentation coefficients distributed along a continuous 8–30 % sucrose density gradient. At least part of the latter type of RNA very probably was mRNA, but much of it must conespond to a different RNA similar to that recently described in HeLa cells by Penman, Vesco and Penman (1968).
We also found that labelled 185 and 285 rRNA components began leaving the nucleus for the cytoplasm within 24 to 33 min after the radioactive precursors had been injected, and, in the cytoplasmic fraction, the patterns of incorporation for [14C]uridine and [3H]-methyl groups were similar for the 18S and 28S rRNA components. We estimate that in this fraction of rat brain the 18S rRNA component was 1·4 times more methylated than the 28S component. We also detected a lower sedimentation coefficient for the non- or slightly methylated, species of soluble RNA found in the cytoplasmic fraction.
29 citations
TL;DR: In this article, the chemical behavior of 6-hydroxy-4,5-dihydro-1,2,4 H -oxazines (VI) has been investigated, showing that when two dissymmetric centers are present in VI rapid epimerization can be observed at C-6, probably through the open chain form.
27 citations
TL;DR: Methionine was decomposed by some bacteria which were isolated from soil and it was indicated that the first step in methionine decomposition was its oxidadative deamination to alpha-keto-gamma-methyl mercaptobutyrate by a constitutive amino acid oxidase.
Abstract: Methionine was decomposed by some bacteria which were isolated from soil. The sulfur of the methionine was liberated as methanethiol, and part of this became oxidized to dimethyl disulfide. Detailed studies with one of these cultures, Achromobacter starkeyi, indicated that the first step in methionine decomposition was its oxidadative deamination to alpha-keto-gamma-methyl mercaptobutyrate by a constitutive amino acid oxidase. The following steps were carried out by inducible enzymes, the synthesis of which was inhibited by chloramphenicol. alpha-Keto-gamma-methyl mercaptobutyrate was split producing methanethiol and alpha-keto butyrate which was oxidized to propionate. The metabolism of propionate was similar to that described for animal tissues; the propionate was carboxylated to succinate via methyl malonyl coenzyme A, and the succinate was metabolized through the Krebs cycle.
27 citations
01 Jan 1970
TL;DR: In this paper, the authors analyze the educational policies implemented by the Mexican Government, against the SARS-CoV-2 that causes the disease Covid-19, and which resulted in the period of social isolation.
Abstract: This paper is the result of a qualitative research with theoretical-analytical support that aims to analyze the educational policies implemented by the Mexican Government, against the SARS-CoV-2 that causes the disease Covid-19, and which resulted in the period of social isolation. In particular, the documents and communications issued by the Secretariat of Public Education for basic education will be analyzed; as well as the effects of virtual platforms and digital resources available for the continuity of classes from home. It is concluded that there is a poor culture in Information and Communication Technologies on the part of the school population, that there are deficiencies in connectivity and availability of technology applicable to education, and that it is necessary to reconsider the current curriculum for basic education, as well as teaching practices, in order to focus on new educational models capable of facing not only a crisis like the current one, generated by the Covid-19 pandemic, but also as viable options for training for life, for citizenship and solidarity.
25 citations
TL;DR: In this article, the authors measured the time annihilation spectra of positrons in solid and liquid NaCl, KCl, and CsCl at temperatures between 295 and 1223, where the positron can be captured by a lattice defect.
Abstract: The time annihilation spectra of positrons were measured in solid and liquid NaCl, KCl, and CsCl at temperatures between 295 and 1223\ifmmode^\circ\else\textdegree\fi{}K. An abrupt change of the spectral shapes is observed at melting. It was possible to show that the so-called $A$-center model, which is based on the assumption that the positron can be captured by a lattice defect, can account for this effect. In the framework of the $A$-center model, an effective electron number has been calculated which increases when passing from LiCl to CsCl.
24 citations
TL;DR: In this article, a new C 19 H 18 O 8 metabolite from a strain of Penicillium funiculosum Thom was shown to be 2- trans -propenyl-3-hydroxy-5-(2′-carbomethoxy-4′,6′-dimethoxybenzoyl-)4-pyrone.
TL;DR: It is suggested that a reduction in the degree of ordered structure of the water molecules at the interphase brings about a correlated increment in lipid mobility which seems to be related to an increased cell permeability (reduction in cell hydrophobicity).
TL;DR: In this paper, the presence of C3H6 in the gas phase influences the MoO3 bond at the surface, and the infrared spectra of the sample after acrolein adsorption also reveal the presence strongly and weakly adsorbed species.
TL;DR: It could be inferred that a normal rate of phospholipid (phosphoinositides) biosynthesis is necessary to have a normal arsenate uptake and that inositide accumulation impairs both the mechanism responsible for the uptake and accumulation of arsenate and the rate of lipid biosynthesis.
Abstract: In studying the possibility that phosphoinositides which formed complexes with arsenic were involved in the arsenate transport system of yeasts, a comparative study of the phospholipid composition and metabolism was carried out both in Saccharomyces carslbergensis and in its arsenate-adapted variant, which showed a deficient inflow of arsenate. It was found that the lipid composition of the two organisms was quite similar, the main classes of phospholipids being phosphatidylcholine, phosphatidylethanolamine, and phosphoinositides. The only difference was a 1.5- to 2-fold increase in the proportion of inositides in the arsenate-adapted cells. When the transport of arsenate became inactivated in the nonadapted yeasts after a 30- to 60-min exposure to 10−2m arsenate, an increment of inositides of 29 to 50% over the original level was also detected. A study of the incorporation of radioactivity from uniformly labeled 14C-maltose and from 32P-orthophosphate (32Pi) demonstrated a decreased rate of lipid biosynthesis in the arsenate-adapted cells as compared to the normal nonadapted ones. The turnover of the phosphate in phospholipids demonstrated no turnover in phosphatidylcholine and phosphatidylethanolamine, and a slow turnover in phosphoinositides. It could be inferred that a normal rate of phospholipid (phosphoinositides) biosynthesis is necessary to have a normal arsenate uptake and that inositide accumulation impairs both the mechanism responsible for the uptake and accumulation of arsenate and the rate of lipid biosynthesis. No differences were found in the deoxyribonucleic acid or protein content of the two types of cells. Also, the arsenate-adapted cells, once freed of external arsenate, showed an increased uptake of 32Pi from low external concentrations of phosphate (10−6 to 10−8m, 10-fold over that observed in AsS cells). These results are indicative of independent behavior in phosphate and arsenate transport systems.
TL;DR: In this article, the relativistic equations of motion for elastic continua have been studied in the context of a new formulation called "asynchronous" to distinguish it from the usual synchronous formulation of the relativism dynamics for extended bodies.
Abstract: The answer is yes, if we consider the mean accelerations of the rod’s points. Namely, the acceleration of the application point of the external force only depends on the rod’s mass and the force’s magnitude. Consequently the other points of the rod accelerate differently according to their positions in order to set up Lorentz contraction. In Sect.1 the problem is solved kinematically, considering that the rod’s motion is rigid if the external force is constant and assuming that the motion of the application point of the external force is hyperbolic. In Sect.2 the above assumption then proves to be in agreement with the relativistic equations of motion for elastic continua. Moreover, by these equations, the acceleration of the application of the external force turns out to be given, in any instantaneous rest system of inertia, byF/m0, whereF is the force’s magnitude andm0 the rod’s proper mass. In Sect.3 the problem is studied also by the equations recently proposed by Cavalleri and Salgarelli in the context of a new formulation called « asynchronous », to distinguish it from the usual « synchronous » formulation of the relativistic dynamics for extended bodies. By the asynchronous equations, the hyperbolic motion for the rod can be immediately deduced. The problem studied can interest models of extended particles, « pushed or pulled » by exchanges of real and virtual photons, mesons, gravitons.
01 Jan 1970
TL;DR: In this paper, an artigo analisa a evolucao do conceito de equidade and as suas implicacoes na agenda e definicao das politicas publicas de educacao.
Abstract: O artigo analisa a evolucao do conceito de equidade e as suas implicacoes na agenda e definicao das politicas publicas de educacao. Analisa-se tambem a relacao da equidade em educacao com os resultados escolares, salientando designadamente dois indicadores de acesso e de sucesso. Neste quadro, estuda-se a respetiva evolucao no sistema escolar portugues, nos ultimos 50 anos, concluindo pela progressao das condicoes de equidade, expressa na melhoria continuada dos dois indicadores, ainda que de forma mais constante na dimensao do acesso do que na do sucesso escolar.
TL;DR: In this paper, a series of 2,4 and 2,6-dinitrophenyl- and 2.4-dinternaphthyl- aryl ethers were studied and the existence of preferred conformations was shown.
Abstract: PMR studies of a series of 2,4- and 2,6- dinitrophenyl- and 2,4-dinitronaphthyl- aryl ethers strongly indicate the existence of preferred conformations. Extensive conjugation of the ether linkage with the dinitro ring, resulting in their coplanarity, is an important stereochemical influence. In the ensuing skew conformation the dinitro ring is positioned in such a way that the 6-substituent is proximal to the other ring. In the case of the 2,4-dinitrophenyl ethers (1) this is the 6-proton, which shows the expected shielding due to the ring current in the other ring. In the 2,6-dinitrophenyl-(2) and 2,4-dinitronaphthyl-(3) ethers, this is a nitro group, twisted out of coplanarity to fit over the other ring, whose magnetic anisotropy is reflected in the shielding experienced by the 6′-protons. When there is a 2′-substituent
present the ring which bears it twists in such a way as to bring the 6′-proton closer to the proximal nitro-group, explaining the greater shielding observed in these cases. Variable temperature studies provided further evidence in favor of these conformations since no significant changes were observed from −55° to + 155°, even for compounds with four substituents flanking the ether linkage. Nevertheless, the compounds studied here are not frozen in these conformations, but probably inter-convert via concerted rotation with others.
TL;DR: In this article, the authors show that burst noise is an intermittent large-scale recombination; its rate of occurrence depends on mechanical stresses, and that dislocations acting as large scale recombination centres explain the burst-noise characteristics.
Abstract: Several experiments show that burst noise is an intermittent large-scale recombination; its rate of occurrence depends on mechanical stresses Moving dislocations acting as large-scale recombination centres explain the burst-noise characteristics From experiment, the cause of dislocation motion seems to be momentum transfer from the emitter current
TL;DR: Evidence for location of the enzyme outside the cell membrane is as follows: maltose was hydrolyzed in conditions which prevented its penetration, the total amount of enzyme was higher in purified cell walls than in the cytoplasm and most of the α-glucosidase was released by a lytic enzyme which converted germinated spores into spheroplasts.
TL;DR: The steady potential changes which develops together with spreading depression of the cat sensoriomotor cortex were recorded at several cortical depths and related with concomitant modifications in cell firing rates.
Abstract: The steady potential changes which develops together with spreading depression of the cat sensoriomotor cortex were recorded at several cortical depths and related with concomitant modifications in cell firing rates.
In most cases, it was found that the slow negative wave which spreads on the cortical surface does not invade the deep cortical layers. In these cases only a slow positive wave was recorded at the deep layers.
At each layer the cell firing rates modification of PT and non-identified neurons consisted of an initial acceleration followed by a depression. The deeper the recorded cells, the more prolonged the acceleration and shorter lasting the depression. At layers invaded by the slow negative wave, acceleration occurred during a part or all the temporal course of such wave. At layers not invaded by the slow negative wave, acceleration occurred coinciding with the slow positive wave.
Acceleration of cell firing is believed to result from an adequate “local” active or “remote” passive depolarization of the cortical cells. Depression could result from excessive depolarization of the cortical cells. Depression could result from excessive depolarization of cortical neurons and presynaptic fibers.
TL;DR: Cacalol (Ia), cacalone (Ic) and decompostin (II) were isolated from the roots of Cacalia ampullacea as discussed by the authors. But the extraction of C. decomposita gave known compounds and the new acetal V, which appears to be an artifact of isolation.
TL;DR: In this paper, the authors show the perception of teachers, administrators and managers on the Competency Based Educational Model in Polytechnic´s Universities in Mexico ten years after its implementation, through a data collection with faculty and staff of these universities, was held a qualitative study relied on data Grounded Theory, obtaining a series of concept maps, that with the Atlas ti program, it was the basis for carrying out an analysis that would enable the perception on an educational model that is itself their daily work.
Abstract: El presente articulo muestra la percepcion del profesorado, personal administrativo y directivo sobre el Modelo Educativo Basado en Competencias en las Universidades Politecnicas en Mexico a diez anos de su implementacion; mediante una recoleccion de datos con docentes y administrativos de estas universidades, se llevo a cabo un estudio cualitativo de datos apoyado en la Teoria Fundamentada, obteniendo una serie de mapas conceptuales, que con el programa Atlas ti, fueron base para llevar a cabo un analisis que permitiera conocer la percepcion del personal docente y administrativo respecto de un modelo educativo, que es en si su quehacer diario. El articulo muestra un conjunto de conceptos que se obtuvieron de las vivencias de los participantes y que se plasman como una base para proponer en estudios futuros un modelo de gestion por competencias para las Universidades Politecnicas en Mexico. This article shows the perception of teachers, administrators and managers on the Competency Based Educational Model in Polytechnic´s Universities in Mexico ten years after its implementation, through a data collection with faculty and staff of these universities, was held a qualitative study relied on data Grounded Theory, obtaining a series of concept maps, that with the Atlas ti program, it was the basis for carrying out an analysis that would enable the perception of faculty and staff on an educational model that is itself their daily work. The article shows a set of concepts that were derived from the experiences of the participants and which are reflected as a basis for future studies to propose a model of competence management to Polytechnic´s Universities in Mexico.
TL;DR: In this article, the thermal decomposition of polyvinylidene chloride homopolymer (PVDC) was studied at temperatures between 140 and 180°. And the reaction is of zero order with respect to PVDC, at least over a wide range of conversion.
TL;DR: There is a net movement of potassium out of the bladder in metamorphosed terrestrial axolotl animals, and differences in bladder urine sodium concentration between larval animals and meetamorphosed aquatic animals were not significant.
TL;DR: Both problems of asymptotic aggregation of an ergodic Markov chain are approached from a topological point of view and solutions are given in terms of signal-flow graph techniques.
Abstract: This paper deals with two problems of asymptotic aggregation of an ergodic Markov chain. The first is concerned with the determination of an aggregated Markov chain, the asymptotic probabilities of which are just equal to conditional asymptotic probabilities defined on the original Markov chain. The second one relates to the determination of an aggregated chain, the asymptotic probabilities of which are equal to the asymptotic probabilities of the elements of a given state partition. Both problems are approached from a topological point of view and solutions are given in terms of signal-flow graph techniques. Comments about the main computational features of the method are also included.
01 Jan 1970
TL;DR: In this paper, the authors present the results of a qualitative study carried out about dropping out in four technological/agricultural high schools in Mexico, based on qualitative interviews with principals, teachers, counselors, students, and young people who dropped out of school.
Abstract: This article presents the results of a qualitative study carried out about dropping out in four technological/agricultural high schools in Mexico. The research was based on qualitative interviews with principals, teachers, counselors, students, and young people who dropped out of school. The main reason is no longer economic, thanks to the scholarship policy, but failing grades. Failure is associated with academic deficits, absenteeism and lack of interest. Its reasons are also associated with family problems, a lack of economic resources, parental disinterest in their children’s education, health issues and teenage pregnancy. Conclusions discuss the policy of flexibilization of accreditation criteria.
TL;DR: The photodynamic inactivation of native or denatured transforming deoxyribonucleic acid (DNA) from Haemophilus influenzae is described and the guanine content of photoinactivated native DNA at neutral pH was less than untreated DNA.
Abstract: The photodynamic inactivation of native or denatured transforming deoxyribonucleic acid (DNA) from Haemophilus influenzae is described. The inactivation at the same pH was higher for denatured than native DNA. At acidic pH, the inactivation both for native and denatured DNA was faster than at alkaline pH. The guanine content of photoinactivated native DNA at neutral pH was less than untreated DNA. The inactivation of biological activity was more extensive than the alteration of guanine. The absorption spectrum of photoinactivated native or denatured DNA was only slightly different than the control DNA at the different experimental conditions.