Showing papers by "Instituto Politécnico Nacional published in 1978"
TL;DR: The isolation of functional chitosomes from five widely diverse genera, representing five major fungal groups and three distinct developmental forms, suggests that the chitOSomes are a ubiquitous component of the cytoplasmic mechanism that conveys chitin synthetase to the sites of microfibril assembly at the surface of fungal cells.
158 citations
123 citations
TL;DR: It is suggested that the reduction in transepithelial Na-free solutions is caused by increased cytoplasmic calcium levels, and during the action of metabolic inhibitors, Ca efflux from the epithelium was increased markedly.
Abstract: Exposure of frog skins to Na-free solutions on the basal border causes a reduction in transepithelial Na transport. Since Na-free solutions produce an increase in cell Ca concentration in some cell types, we have explored whether such increase plays a role in their inhibitory effects on transepithelial transport. Measurements of 45 Ca uptake in isolated epithelia showed that Na-free solutions caused a threefold stimulation of Ca uptake; nearly all the increased uptake occurred through the basal border. The reduction in transepithelial Na transport caused by Na-free solutions was absent when Ca was also eliminated from the basal solution. These findings suggest that the reduction in transepithelial Na-free solutions is caused by increased cytoplasmic calcium levels. We also found that during the action of metabolic inhibitors, Ca efflux from the epithelium was increased markedly. Since such as increase in efflux is probably due to increased (Ca) in the cytoplasm, we suggest that the reduced epithelial Na permeability observed during metabolic inhibition may be due to increased cytoplasmic calcium.
103 citations
TL;DR: In this paper, a new class of selective catalysts for the allylic oxidation of butene to butadiene and propylene to acrolein was proposed. Butadiene is a single chemical compound.
43 citations
TL;DR: In this article, β-glucan synthetase from S. cerevisiae was studied and shown to be competitively inhibited by UDP (Ki=0.12mm), EDTA and hydroxyquinoline were inhibitory.
Abstract: Properties of β-glucan synthetase from S. cerevisiae were studied. The enzyme exhibited optimal activity at pH 6.7 and 24 C. Km for UDP-glucose was 0.12mm. Addition of Mg++ or Mn++ stimulated its activity by 60% and 21% respectively. High concentrations of EDTA and hydroxyquinoline were inhibitory. Glucan synthetase was fully active in cell-free extracts. Small concentrations of trypsin or subtilopeptidase A from Bacillus subtilis, caused only a slight increase in glucosyl transferase activity, but larger concentrations destroyed β-glucan synthetase. Acid proteases were neither stimulatory nordestructive. Thus it seemsunlikelythat β-glucan synthetase exists in a zymogen form. Glucan synthetase was unstable. It was inactivated more rapidly at 28 C than at 0 C. The presence of substrate, β-glucan or the protease inhibitors PMSF, Antipain or Pepstatin A did not protect β-glucan synthetase from inactivation. Glucan synthetase was not stimulated by addition of cellobiose or β-glucans. The synthesis of β-glucans was competitively inhibited by UDP (Ki=0.45mm). Glucono-δ-lactone, a known inhibitor of β-glucosidases was a strong non-competitive inhibitor of β-glucan synthetase.
36 citations
TL;DR: The spectral characteristics of rhodopsin in the organic phase were similar to those of native rhodopin in disc membranes.
Abstract: The extraction of rhodopsin-phospholipid complexes into lipid solvents is described. Two general procedures were developed: (i) the extraction of detergent-solubilized rhodopsin which involved: (a) solubilization of rhodopsin from bovine retinal rod disc membranes in detergent solutions; (b) partial removal of detergent from solubilized rhodopsin; (c) recombination with a defined lipid mixture by sonication of lipid and protein in salt media; and (d) sequential extraction into organic solvents. (ii) The direct transfer of rhodopsin from purified retinal rod disc membranes into apolar solvents which involved: (a) resuspension of membranes in hexane containing phospholipids; (b) sonication; (c) charge neutralization with salts; and (d) sequential extraction into organic solvents. The extraction yield was dependent on several parameters such as: phospholipid to rhodopsin ratio, sonication, type of solvent, and others. The composition of the extracts regarding the molar ratio of phospholipid, detergent, and rhodopsin varied according to the extraction protocol. The spectral characteristics of rhodopsin in the organic phase were similar to those of native rhodopsin in disc membranes. The capacity to regenerate the characteristic dark absorbance maximum at ∼485 nm after incubation of dark chromophore (9-cis retinal) with bleached rhodopsin was preserved to about 70%. The general applicability of these techniques in functional reconstitution studies of membrane systems is considered.
33 citations
TL;DR: Observations indicate that H (or D) bonding between the solvent and the protein as well as the strength of the hydrophobic interactions within the enzyme as determined by the solvent are of central importance in determining the overall activity of F 1 and the stability of the enzyme to denaturing conditions.
32 citations
TL;DR: A soluble protein inhibitor of chitin synthetase (UDP-2-acetamindo- 2-deoxy-D-glucose:chitin 4-beta- acetamidodeoxyglucosyltransferase, EC 2.4.1.16) was isolated from the cytoplasm of Mucor rouxii and Presumably, the inhibitor forms part of the regulatory mechanism ofChitin synthesis in the cell.
28 citations
TL;DR: Das ungesattigte Carbinol (I) liefert bei der Oxidation mit Peroxydisulfat in Gegenwart von Silber(I)-Ionen wie Lepidin (III) sowie Saure unter Angriff auf den Heteroaromaten und Cyclisierung die Reaktionsprodukte (IV) und (V).
28 citations
TL;DR: In this article, a submarine pipeline is conceived as a slender beam, subjected to vertical loads and undergoing “small” deflections, contrasted without friction by a supporting rigid profile, and the relevant contact (unilateral constraint) problem is formulated in approximate, algebraic terms on the basis of discrete models, allowing for the presence of a significant given tension force.
27 citations
TL;DR: A new highly oxidized coumarin was isolated from the roots of Perezia multiflora and its structure was elucidated as 3,4,8-trimethoxy-6-hydroxy-5-formyl-2 H -1-benzopyran-2-one.
TL;DR: In this article, the role of surface acidic properties on isomerization and extensive oxidation reactions was investigated in the presence and absence of steam in the feed, and strong analogies within the series of the investigated catalysts were observed.
TL;DR: In this paper, the authors analyzed available potency estimates for 35 pairs of enantiomeric arylcarboxylic acids with auxin activity (flax-root-growth inhibition test) and revealed extensive correlations between the activity of the more potent and less potent isomers, as well as between the log of the ratio of potencies and the log potency when structurally similar analogs are compared.
TL;DR: DNA content was determined by means of diphenylamine reaction in trophozoites of exponentially growing, axenized Entamoeba histolytica, finding small variations in DNA content may be due to (i) slight changes in ploidy, (ii) genomic heterogeneity, or (iii) differences in the degree of synchrony of the cultures.
TL;DR: Evidence suggesting two types of mechanisms, changes in surface potential and the level of cell Ca, are suggested to determine the rate of transepithelial Na transport is described in greater detail.
Abstract: An attempt to define the main categories of regulatory mechanisms of transepithelial sodium transport across tight epithelia is presented.
TL;DR: CdTeMoO6 has been obtained by solid state reactions of CdMoO4 with orth.TeO2 at 425°C, with tetr. TeO2 with H6TeO6 at 490°C as mentioned in this paper.
TL;DR: The paper deals with the evaluation and stochastic modelling of an overall pollution index for the region of interest, namely the integral of the daily dosage over the region (dosage area product or DAP) and a stationary autoregressive Stochastic model is proposed in order to describe the fluctuations of the series.
TL;DR: The reaction between (benzene)(1,3-cyclohexadiene)ruthenium(0) and acetylenes RCCR under UV irradiation yields complexes of the formula (C 6 R 6 ) 2 Ru or (c 6 H 6 )(C 6R 6 )Ru, depending on the acetylene used as mentioned in this paper.
TL;DR: In this article, a second order pion-carbon optical potential in momentum space was constructed and used to calculate cross sections for energies between 40 and 280 MeV, and the sensitivity of the results to the use of different relativistic propagators for the pion was studied.
TL;DR: In this paper, the authors deal with the calculation of the intensities of Raman active fundamental vibrations of methane and its isotopical derivatives by the electrooptical theory of valence and with the "least squares" refinement of a set of Electrooptical parameters from the experimental data.
TL;DR: In this paper, a new equation relating the Ps formation I(o-Ps) to the inhibitor concentration was deduced, which allows to advance some predictions, inter alia the behaviour of the positronium inhibition in solvent mixtures can be inferred.
TL;DR: A follow up was made of the technics used to evaluate interdisciplinary classes in automotive manufacturing engineering, based in a method proposed by the Instituto Politecnico Nacional (IPN).
Abstract: At the present article a follow up was made of the technics used to evaluate interdisciplinary classes in automotive manufacturing engineering, based in a method proposed by the Instituto Politecnico Nacional (IPN) The method is related to the evaluation through competency-based learning, although is not a new method worldwide, in the engineering education specifically in Mexico is gaining popularity The evaluation method of the IPN is center in the flexibility, the continuous education, and the professional formation of the student by working in a lab of manufacturing processes The conducted follow up of the method deals with the performance of students working in small teams, and the way the students are evaluated using equipment The results were obtained through observation, and analysis of the methods used to evaluate, and making comparisons with the method of competency based learning proposed by the IPN
TL;DR: Synthesis of chitin inMucor rouxii was studied comparatively in whole cells, spheroplasts, toluene-treated cells, and cell-free extracts in order to determine the cellular location and regulation of Chitin synthetase.
Abstract: Synthesis of chitin inMucor rouxii was studied comparatively in whole cells, spheroplasts, toluene-treated cells, and cell-free extracts in order to determine the cellular location and regulation of chitin synthetase. Our data indicated that most of the enzyme is located inside the permeability barrier of the cell in the form of an inactive precursor. Apparently the enzyme and its destroying factor (protease?) are located in separate compartments of the cell. The role of proteases as the natural activating factors was questioned.
TL;DR: Psilocybe aztecorum is a Gram-positive bacterium of the phytochemical group related to “silicon-like” deposits found in the fruit bodies of flies and other animals.
Abstract: Based upon data obtained from a study of the type as well as from Heim's and Singer and Smith's descriptions and from several fresh specimens collected by the author, Psilocybe aztecorum is here em...
TL;DR: The benzotriazolides of N-methacryloylglycine, Nmethacetyl-e-aminocaproic acid, and 4methacidoxybenzoic acid have been prepared and polymerized.
Abstract: The benzotriazolides of N-methacryloylglycine, N-methacrylolyl-e-aminocaproic acid, and 4-methacryloxybenzoic acid, have been prepared and polymerized. The exchange reactions of the resulting polymers with amines, alcohols, and phenol have been studied.
TL;DR: In this paper, a general theory for the analysis of the direct problem of the statics and dynamics for a large class of systems of rigid bodies is proposed, known as homokinetic ball joints.
TL;DR: The possibility of two different conformations of the enzyme can be “frozen” by any of the compounds tested, “isolating” the enzyme from any subsequent physical change of the membrane due to temperature.
TL;DR: In this article, the superconducting critical temperature T c is lowered irreversibly, until an annealing temperature T t is reached at which the overlay film fractures because of the occurrence of the abnormal-to-ordinary structure transformation.
TL;DR: A correlation discovered between the sweetness of D and the bitterness of L -aminoacids suggests the possible existence of corresponding taste receptors with enantiomeric active sites, and possible explanations for the reported taste characteristics of various other substances.