Showing papers by "University of Buenos Aires published in 1977"
TL;DR: Evidence for the role of ubiquinone as peroxide generator is provided by the generation of O 2 − and H 2 O 2 during autoxidation of quinols.
837 citations
TL;DR: Theorem 4.7 is similar to a known result which can be found in [10, 11] and as discussed by the authors, and the results proved in this paper will require some familiarity wkh the concepts introduced in [3].
430 citations
TL;DR: It was realized that this assay could be easily interfered by endogenous hydrogen donor of the horseradish peroxidase and by exogenous hydrogen donors in the mitochondrial preparations, and consequently, an alternative method was developed.
Abstract: The development and application of sensitive methods for the determination of hydrogen peroxide led, a few years ago in the laboratories of the Johnson Research Foundation, to the recognition, of intact mitochondria as an effective source of H2O2 (Fig. 1; refs. 1–4). Previous observations by Jensen (5) and by Hinkle et al. (6) had indicated that the mitochondrial respiratory chain was capable of producing H2O2. However, these results were taken with caution, in the sense that they might reflect an artificial activity induced by the ultrasonic or alkaline treatment used in the preparation of the submitochondrial particles. In 1971, Chance and Oshino (1) demonstrated variations in the level of the catalase intermediate of the peroxisomal-mitochondrial fraction of rat liver following the addition of mitochondrial substrates and uncouplers. In the same year, Loschen et al. (2) showed H2O2 formation in pigeon heart mitochondria and its relationship to the mitochondrial metabolic state by using the peroxidase-scopoletin method. It was realized that this assay could be easily interfered by endogenous hydrogen donor of the horseradish peroxidase and by exogenous hydrogen donors in the mitochondrial preparations, and consequently, an alternative method was developed.
415 citations
TL;DR: Independence of the lipid used, current fluctuations vary in amplitude between 1 and 4·10−10, Ω−1, show a strong dependence on the applied voltage, and are selective for cations in the sequence Rb+ > K+ > Na+ > Li+.
97 citations
TL;DR: When supplemented with NADH and NADPH, the mitochondrial, microsomal, and supernatant fractions produced H2O2, the soluble fraction and the mitochondrial membranes being apparently the main generators of H 2O2.
Abstract: Homogenates from T. cruzi epimastigotes produced 3.4 pmoles H2O2/min 106 cells, as detected by the cytochrome c peroxidase assay. Addition of NADH or NADPH increased H2O2 production by a factor of 3 and 5, respectively. When supplemented with NADH and NADPH, the mitochondrial, microsomal, and supernatant fractions produced H2O2, the soluble fraction and the mitochondrial membranes being apparently the main generators of H2O2. The epimastigote homogenates showed cyanide-sensitive superoxide dismutase activity, equivalent to 0.28 μg bovine superoxide dismutase per mg homogenate protein.
76 citations
TL;DR: In this paper, β-lapachone (a 1,2-naphthoquinone derivative) causes ultrastructural and metabolic alterations in Trypanosoma cruzi epimastigotes.
74 citations
TL;DR: The structural parameters and estimated standard deviations (3σ) have been found for (CF 3 O) 2,: r g, (O-O) = 1419 ± 0020 A, r g (C-O), (O)-O-C) = 1399 ± 0009 A; r g(C-F), (F-C-C)-F = 1320 ± 0003 A, ∠(C O-O)-C, O-C), ∠ (C −12° +-12°,
54 citations
TL;DR: Two cases of punctate porokeratosis of Mibelli are presented and other punctate lesions with similar clinical features which should be considered in the differential diagnosis are discussed.
Abstract: Punctate porokeratosis is not usually recognized as a clinical form of porokeratosis of Mibelli. Two cases of punctate porokeratosis are presented. Other punctate lesions with similar clinical features which should be considered in the differential diagnosis are discussed.
43 citations
TL;DR: In this paper, a long exact sequence connecting Amitsur cohomology groups H> n (S R, U) and H n ( S R, Pic) is derived for every faithfully flat commutative R -algebra S.
35 citations
TL;DR: Postherpetic craniofacial neuralgias present a real challenge to neurosurgery and spontaneous sensations closely resemble those arising from areas denervated by other causes, and they can probably be equated with other deafferentation states.
Abstract: Postherpetic craniofacial neuralgias present a real challenge to neurosurgery. Facial involvement occurs in about 15~ of all postherpetic neuralgias (Stookey and Ransohoff 1959), making this site second only in frequency to the trunk. Although any portion of the head or face can be involved (Engstr6m and Wohlfart 1949), the most commonly affected area is the territory served by the ophthalmic division of the fifth nerve (Tatlow 1952). Postherpetic painful phenomena have certain peculiar characteristics (Noordenbos 1959, 1972). They do not occur in cases of shingles without sensory loss. There is no exception to this. However, they do not occur in all cases with sensory loss, but only in a few of them. Nevertheless, the dysaesthesiae are more intense as the sensory loss is greater. These spontaneous sensations closely resemble those arising from areas denervated by other causes, and they can probably be equated with other deafferentation states. Therefore, further attempts at interruption of the primary afferent neuron at any level are unlikely to be successful. Indeed, this is the common experience (Stookey and Ransohoff 1959, White and Sweet 1969). Nevertheless, they sometimes remove the hyperaesthesia or the hyperpathia (Hit&co& and Schvarcz 1972), but on the other hand they can intensify the deep ba&ground pain. This also holds true for postherpetic neuralgia in other places (Schvarcz 1976). Curiously enough, more central atta&s on mesencephalic, diencephalic, or telencephalic structures have also been disappointing (Cassinari and Pagni 1969, White and Sweet 1969).
32 citations
TL;DR: Mitochondria obtained from nonfatty livers of male rats fed alcohol for 4 months showed reduced contents of cy tochromes a-a3 and b and decreased activity of cytochrome oxidase and mitochondrial H2O2 production, suggesting chronic interference of ethanol with the synthesis of protein may result in lowered values of components of the electron transport chain and thus in interference with mitochondrial properties.
TL;DR: In this paper, experimental and theoretical work on mass transfer to gauzes was carried out and the experimental data of this and other works were correlated as j/Z vs Re and j.E/(D/d)13 vs Ret′, parameters obtained from the theoretical models, which showed to improve the correlation of data with respect to usual empirical relationships.
TL;DR: Dialysed cell-free extracts from Trypanosoma cruzi contained ADP-linked phosphoenolpyruvate carboxykinase, which is probably the main CO 2 -fixing enzyme in T. cruzi, as in some invertebrates which are also able to ferment glucose with production of succinate.
Abstract: 1. 1. Dialysed cell-free extracts from Trypanosoma cruzi contained ADP-linked phosphoenolpyruvate carboxykinase (EC 4.1.1.49) and NADP-linked malic enzyme (EC 1.1.1.40). Pyruvate carboxylase (EC 6.4.1.1), phosphoenolpyruvate carboxylase (EC 4.1.1.31) and phosphoenolpyruvate carboxytransphosphorylase (EC 4.1.1.30) were not detected. 2. 2. The carboxylating activity of phosphoenolpyruvate carboxykinase was 6-fold greater than that of malic enzyme, when assayed at their optimal pH value (about 6.2). 3. 3. Phosphoenolpyruvate carboxykinase is probably the main CO 2 -fixing enzyme in T. cruzi , as in some invertebrates which are also able to ferment glucose with production of succinate.
TL;DR: The response to N-ethylmaleimide of the ATPase and phosphatase activites stimulated by K+ or Na+ in the presence of Ca2+ parallels that of the Ca2-dependent activities, suggesting that theCa2+-ATPase system possesses sites at which monovalent cations bind to increase its activity.
Abstract: In human red cell membranes the sensitivity to N-ethylmaleimide of Ca2+-dependent ATPase and phosphatase activities is at least ten times larger than the sensitivity to N-ethylmaleimide of (Na+ + K+)-ATPase and K+-activated phosphatase activities. All activities are partially protected against N-ethylmaleimide by ATP but not by inorganic phosphate or by p-nitrophenylphosphate. (ii) Protection by ATP of (Na+ + K+)-ATPase is impeded by either Na+ or K+ whereas only K+ impedes protection by ATP of K+-activated phosphatase. On the other hand, Na+ or K+ slightly protects Ca2+-dependent activities against N-ethylmaleimide, this effect being independent of ATP. (iii) The sensitivity to N-ethylmaleimide of Ca2+-dependent ATPase and phosphatase activities is markedly enhanced by low concentrations of Ca2+. This effect is half-maximal at less than 1 micron Ca2+ and does not require ATP, which suggests that sites with high affinity for Ca2+ exist in the Ca2+-ATPase in the absence of ATP. (IV) Under all conditions tested the response to N-ethylmaleimide of the ATPase and phosphatase activities stimulated by K+ or Na+ in the presence of Ca2+ parallels that of the Ca2+-dependent activities, suggesting that the Ca2+-ATPase system possesses sites at which monovalent cations bind to increase its activity.
TL;DR: Palaeomagnetic data for the Cretaceous Pirgua Subgroup from 14 different time units of basalts and red beds exposed in the north-western part of Argentina (25° 45′ S 65° 50′ W) are given in this article.
Abstract: Palaeomagnetic data for the Cretaceous Pirgua Subgroup from 14 different time units of basalts and red beds exposed in the north-western part of Argentina (25° 45′ S 65° 50′ W) are given.
After cleaning all the units show normally polarized magnetic remanence and yield a palaeomagnetic pole at 222° E 85° S (dΦ= 7°, dχ= 10°).
The palaeomagnetic poles for the Pirgua Subgroup (Early to Late Cretaceous, 114–77 Myr), for the Vulcanitas Cerro Rumipalla Formation (Early Cretaceous,<118 Myr, Valencio & Vilas) and for the Pocos de Caldas Alkaline Complex (Late Cretaceous, 75 Myr, Opdyke & McDonald) form a ‘time-group’ reflecting a quasi-static interval (mean pole position, 220° E 85° S, α95= 6°) and define a westward polar wander in Early Cretaceous time for South America.
Comparison of the positions of the Cretaceous palaeomagnetic poles for South America with those for Africa suggests that the separation of South America and Africa occurred in late Early Cretaceous time, after the effusion of the Serra Geral basalts.
The K-Ar ages of basalts of the Pirgua Subgroup (114 ± 5; 98 ± 1 and 77 ± 1 Myr) fix points of reference for three periods of normal polarity within the Cretaceous palaeomagnetic polarity column.
TL;DR: The Smith-Hallam model has been used to combine palaeomagnetic data from the Gondwana continents for the Late Palaeozoic and Mesozoic of South America as discussed by the authors.
TL;DR: The application of percutaneous and stereotactic techniques to the spinal cord has opened an exciting new field, which has provided a unique opportunity to study the functional organization of the spinomedullary region.
Abstract: The application of percutaneous and stereotactic techniques to the spinal cord has opened an exciting new field, which has provided a unique opportunity to study—with therapeutic purposes—the functional organization of the spinomedullary region.
TL;DR: The kinetics of l -[ 14 C]leucine transport as a function of amino acid concentration indicate the existence of two apparently distinct transport systems, namely, one with high affinity and low transport activity (System A) and the other with low affinity and high transport activity(System B).
TL;DR: Oxygen consumption in mitochondria and nerve endings isolated from rat cerebral cortex was studied after the administration of the convulsant 3-mercaptopropionic acid and it was found that the respiratory rate of these fractions was higher than in the controls.
TL;DR: The rapid rate of Ca release reported in this article may serve as a model of the rapid Ca relase from sarcoplasmic reticulum, in vivo, which triggers muscle contraction, since it occurs by effect of physiological agents.
TL;DR: Morphologically detectable glial differentiation began by the end of this week, and during the third week almost every neuronal element, including the axonic fascicles, became associated with glial cells showing astrocytic features.
Abstract: Dissociation and reaggregation cultures from different portions of the chick embryo neural tube were made, and the resulting aggregates were fixed for electron microscopy after 1, 5, 8, 14, 16 and 22 days in vitro. All cultures (pure aggregates of telencephalon, optic lobe or neural retina, and combined aggregates made from mixtures of optic lobe plus neural retina or optic lobe plus telencephalon) show a common timing of neuronal and glial morphological differentiation. During the first week in vitro, some cells developed neuronal characteristics in the absence of morphological evidence of glial differentiation. Numerous axonic processes usually formed fascicles with all the fibers running parallel to each other. Axonic growth cones were abundant and a few immature synapses were also present. The second week in culture was characterized by the disappearance of growth cones and the increase in number and morphological maturation of synapses. Morphologically detectable glial differentiation began by the end of this week, and during the third week almost every neuronal element, including the axonic fascicles, became associated with glial cells showing astrocytic features.
TL;DR: A small collection of marine fossils from three localities of the Taiguati and San Telmo(?) formations (Machareti Group) in southern subandean Bolivia (Parapeti River and Serrania de Balapuca) contains Leuipustula leuis Maxwell, Limipecten cf. L. burnettensrs Maxwell, Cyþrieardinia(?) boliuiana sp. nov'' Stutchburia sp., Myonia sp., and Mourlonia balaþucense sp nov.
Abstract: A small collection of marine fossils from three localities of the Taiguati and San Telmo(?) formations (Machareti Group) in southern subandean Bolivia (Parapeti River and Serrania de Balapuca) contains Leuipustula leais Maxwell, Limipecten cf. L. burnettensrs Maxwell, Cyþrieardinia(?) boliuiana sp. nov'' Stutchburia sp., Myonia sp. and Mourlonia balaþucense sp. nov. The presence of Leuiþustula leuis and the probable affinities of associated species indicate a Late Carboniferous (Namurian-Westphalian) age for the fauna, its Gondwanic nature and link with similar assemblages from the Precordillera of Argentina and eastern Australia. This conclusion aflects the prevailing paleogeographic interpretation of the area.
TL;DR: The immunological properties of a synthetic human growth hormone fragment comprising the amino acids 73 through 128 and of the homologous natural horse growth hormones fragment formed by amino acids73 through 123, have been comparatively studied.
Abstract: The immunological properties of a synthetic human growth hormone fragment comprising the amino acids 73 through 128 and of the homologous natural horse growth hormone fragment formed by amino acids 73 through 123, have been comparatively studied.
Antisera obtained in rabbits inoculated with the native human hormone or with the fragments, were used. By hemagglutination experiments both fragments have the same reactivity toward the anti-human growth hormone serum, but complement fixation curves detect the existence of at least two populations of antibodies presumably originated against the sequence 73–128 of human growth hormone. Of these, only one of the corresponding antigenic areas is present in the homologous region of equine growth hormone. The known cross-reactivity detected between both hormones is thus partially explained.
In the antiserum against the horse growth hormone fragment there is a very low level of antibodies reacting with native horse hormone.
01 Jan 1977
TL;DR: Facial central pain is usually difficult to manage and stereotactic trigeminal nucleotomy is a valuable procedure, but there is still a group of supra-caudalis origin, which is resistant to current techniques and paraqueductal lesions offer an attractive approach.
Abstract: Facial central pain is usually difficult to manage. Although stereotactic trigeminal nucleotomy is a valuable procedure, there is still a group of supra-caudalis origin, which is resistant to current techniques. For them, paraqueductal lesions offer an attractive approach.
TL;DR: The distribution of radioactivity in the tissues of the rat has been established after the administration of radioactive bovine growth hormone preparations and tissue radioactivity distribution curves obtained belong to two different categories: in kidney, liver and spleen there is an early concentration which attains a maximum in 15 minutes after the injection of the hormone, and rapidly declines.
Abstract: The distribution of radioactivity in the tissues of the rat has been established after the administration of radioactive bovine growth hormone preparations.
TL;DR: An NMR spectroscopic method for the determination of mixtures of trimethoprim and sulfamethoxazole is described, and the results were compared to those obtained using the BP procedure.
TL;DR: A postoperative staging system, amenable to computer analysis, that can be retrospectively applied to a large series of invasive squamous cell carcinomas of the vulva is presented and could, in time, provide answers to many questions concerning invasive squamy cell carcinoma of the Vulva.
TL;DR: The immunological properties, as measured in this work, are practically unmodified, even in completely trinitrophenylated equine growth hormone.
TL;DR: Phospholipase C increases the sensitivity of the phosphatase to N-ethylmaleimide but has little effect on the kinetic parameters relating the phosph atase activity to substrate and cofactors, suggesting that no extensive structural disarrangement of the Ca2+-ATPase system has occurred after incubation with phospholipases C.
Abstract: Treatment of human red cell membranes with pure phospholipase A2 results in a progressive inactivation of both Ca2+-dependent and (Ca2++K+)-dependent ATPase and phosphatase activities. When phospholipase C replaces phospholipase A2, Ca2+-dependent ATPase activity and Ca2+-dependent phosphorylation of red cell membranes are lost, while Ca2+-dependent phosphatase activity is enhanced and its apparent affinity for Ca2+ is increased about 20-fold. Activation of Ca2+-dependent phosphatase following phospholipase C treatment was not observed in sarcoplasmic reticulum preparation. Phospholipase C increases the sensitivity of the phosphatase to N-ethylmaleimide but has little effect on the kinetic parameters relating the phosphatase activity to substrate and cofactors, suggesting that no extensive structural disarrangement of the Ca2+-ATPase system has occurred after incubation with phospholipase C.
TL;DR: Porphobilinogen oxygenase from wheat germ was purified and was found to be a cationic protein containing 8 mol of nonheme iron and 8–10 mol of labile sulfide per mole of enzyme.