Showing papers by "University of Buenos Aires published in 1976"

Integral geometry and geometric probability

Abstract: Part I. Integral Geometry in the Plane: 1. Convex sets in the plane 2. Sets of points and Poisson processes in the plane 3. Sets of lines in the plane 4. Pairs of points and pairs of lines 5. Sets of strips in the plane 6. The group of motions in the plane: kinematic density 7. Fundamental formulas of Poincare and Blaschke 8. Lattices of figures Part II. General Integral Geometry: 9. Differential forms and Lie groups 10. Density and measure in homogenous spaces 11. The affine groups 12. The group of motions in En Part III. Integral Geometry in En: 13. Convex sets in En 14. Linear subspaces, convex sets and compact manifolds 15. The kinematic density in En 16. Geometric and statistical applications: stereology Part IV. Integral Geometry in Spaces of Constant Curvature: 17. Noneuclidean integral geometry 18. Crofton's formulas and the kinematic fundamental formula in noneuclidean spaces 19. Integral geometry and foliated spaces: trends in integral geometry.

Role of ubiquinone in the mitochondrial generation of hydrogen peroxide

Abstract: Antimycin-inhibited bovine heart submitochondrial particles generate O2- and H2O2 with succinate as electron donor. H2O2 generation involves the action of the mitochondrial superoxide dismutase, in accordance with the McCord & Fridovich [(1969) j. biol. Chem. 244, 6049-6055] reaction mechanism. Removal of ubiquinone by acetone treatment decreases the ability of mitochondrial preparations to generate O2- and H2O2, whereas supplementation of the depleted membranes with ubiquinone enhances the peroxide-generating activity in the reconstituted membranes. Addition of superoxide dismutase to ubiquinone-reconstituted membranes is essential in order to obtain maximal rates of H2O2 generation since the acetone treatment of the membranes apparently inactivates (or removes) the mitochondrial superoxide dismutase. Parallel measurements of H2O2 production, succinate dehydrogenase and succinate-cytochrome c reductase activities show that peroxide generation by ubiquinone-supplemented membranes is a monotonous function of the reducible ubiquinone content, whereas the other two measured activities reach saturation at relatively low concentrations of reducible quinone. Alkaline treatment of submitochondrial particles causes a significant decrease in succinate dehydrogenase activity and succinate-dependent H2O2 production, which contrasts with the increase of peroxide production by the same particles with NADH as electron donor. Solubilized succinate dehydrogenase generates H2O2 at a much lower rate than the parent submitochondrial particles. It is postulated that ubisemiquinone (and ubiquinol) are chiefly responsible for the succinate-dependent peroxide production by the mitochondrial inner membrane.

A model for describing the water sorption behavior of foods

Abstract: A multilayer adsorption equation, originally developed for physical adsorption on nonuniform surfaces, is used to describe the water sorption behavior of a great variety of foods and food components. Characteristic parameters of the sorption equation, for each of the products tested, were computed. A comparison was made between Halsey's equation and Henderson's classical one. Literature data for 220 food isotherms, comprising 69 different materials, were utilized to compare both equations. It was found that in most cases Halsey's equation has a better fit than Henderson's.

Localization of peroxidase activity in Trypanosoma cruzi microbodies.

Abstract: Electron microscopic observation ofTrypanosoma cruzi epimastigotes reveals the presence of microbody-like structures (microperoxisomes) in which 3,3′-diaminobenzidine (DAB) is peroxidized to electron-opaque material. The role of peroxidase in DAB peroxidation is supported by the enzyme demonstration in disrupted epimastigotes and the microbody-containing cell fractions.

Isolation of hydrophobic proteins binding amino acids. stereoselectivity of the binding of l-[14c]glutamic acid in cerebral cortex

Abstract: From the total lipid extract of ncrve-ending membranes or the homogenate of cerebral cortex a hydrophobic protein fraction binding L-[14C]glutamic acid was separated by chromatography on Sephadex LH20. This protein could only be partially separated from the [14C]GABA-binding protein and from the lipids that are present in the fraction; however, it was demonstrated that both amino acids bind to different sites. The saturation of the binding showed a high (Kd1= 0.3μM), a medium (Kd, = 5 μM) and a low (Kd, = 55 μM) affinity binding site. The high affinity binding site had a binding capacity of 0.53 nmol/mg of protein and was highly stereoselective for the L-enantiomer. The binding of L-[14C]glutamic acid was not inhibited by GABA, was slightly inhibited by glycine and glutamine and was strongly inhibited in a progressive order by DL-a-methylglutamic acid, L-nuciferine, L-aspartic acid and L-glutamic acid diethyl ester. These results are compared with those previously obtained with the L-glutamic acid-binding protein isolated from crustacean muscle. The stereoselectivity of the binding and the possible role of this protein in synaptic transmission are discussed.

Survey of Argentine Medicinal Plants -Folklore and Phytochemical - Screening. II

Abstract: Argentina has around 500 native medicinal plants, according to the folklore use, plus nearly 200 toxic species. So there are 700 indigenous species suitable to be used in pharmacognostical-pharmacological studies with a high probability of getting active compounds from them. As the Instituto Nacional de Farmacologia y Bromatologia was interested in the medicinal flora to be studied we considered that a catalog of Argentine species with their uses and chemical composition would help in promoting research on them. Nevertheless, as there have been few species exhaustively investigated we screened them for different constituents ( 1,2) (Table I) while surveying the literature for chemical composition and folklore data for medicinal use up to 1972 (Table II)2.

ISOLATION OF HYDROPHOBIC PROTEINS BINDING AMINO ACIDS: l‐ASPARTIC ACID‐BINDING PROTEIN FROM THE RAT CEREBRAL CORTEX

Abstract: — Lyophilized rat cerebral cortex was treated with chloroform-methanol (2:1, v/v), and the extracted hydrophobic proteins (i.e. proteolipids) were separated by column chromatography on Sephadex LH-20. The first peak of protein, eluting with chloroform in the void volume, had high affinity binding for l-[14C]aspartic acid. The saturation of the binding showed three saturable sites with apparent dissociation constants of 0.2 μm, 10 μm and 50 μm. The binding capacities of the three sites were 2.8, 132 and 617 nmol/mg of protein, respectively. There were 8.0 nmol of high affinity binding sites for l-aspartic acid and 1.53 nmol for l-glutamic acid per g of fresh tissue in the cerebral cortex of the rat. Differentiation between binding of l-aspartic and l-glutamic acid was clearly established by cross-binding and competition experiments with agonists and antagonists. It is suggested that the isolated protein fraction may correspond to a synaptic receptor and not to the transport system. It is concluded that in the cerebral cortex there is a separate receptor for l-aspartic acid. This is further support to the possible role of this amino acid as a central excitatory transmitter.

The Distinction between Sequential and Simultaneous Models for Sodium and Potassium Transport

Abstract: Publisher Summary This chapter analyzes the available experimental evidence to see if it can be used to place restrictions on the possible molecular mechanisms of active transport. It is hoped that these restrictions will help to reach the goal of elucidating its mechanism. It concentrates on one particular problem within the general question of the mechanism of active transport—namely, the relation between the inward-facing and the outward-facing, cation-binding sites of the Na pump. The chapter intends to define with precision the concept of cation-binding sites and to characterize the interactions between sites and with cations. It presents a statement of the two alternative explanations that have been proposed to account for the linkage between inner and outer sites: (1) these sites are alternative states of the same set of sites or (2) they are two physically distinct and independent sets of sites that coexist in each transport unit. It is believed that available experimental evidence rather strongly favors the idea of the simultaneous existence of inner and outer cation-binding sites. The chapter undertakes a critical analysis of this evidence. Although structural and biochemical data are taken into account, the main weight of the reasoning is placed on the results of experiments on the kinetics of cation fluxes. The chapter also deals with the biochemical aspects of the Na pump, like with the intermediate steps and the partial reactions of the hydrolysis of ATP catalyzed by this system. It aims to show that the present knowledge of the mechanism of the hydrolysis of ATP by the Na pump is not incompatible with the postulates of simultaneous models for active transport.

Differentiation of L-aspartate and L-glutamate high-affinity binding sites in a protein fraction isolated from rat cerebral cortex.

Abstract: THE possibility that L-glutamate and L-aspartate are excitatory transmitters in the CNS is supported by neurochemical and neurophysiological evidence1. The problems of identifying particular synapses that are excited by one or the other of these dicarboxylic amino acids, and distinguishing between the two receptors are, however, more difficult. At the recent International Meeting of Neurochemistry (September 1975) Graham summarised some of the evidence favouring distinct functions for the two amino acids, concentrating on the possible transmitter role of L-aspartate. For example, a higher content of this amino acid is found in the ventral than in the dorsal grey matter of the spinal cord2, aortic occlusion leads to loss of aspartate content and degeneration of small neurones3, reduction in aspartate content is seen in the spinal cord after section of dorsal roots4 and in the olfactory cortex after olfactory bulbectomy5, which also decreases glutamate. Renshaw cells are slightly more sensitive to the ionotophoretic administration of L-aspartate while the reverse is true of interneurones of the dorsal spinal horn6. It is possible that L-glutamate and L-aspartate, being flexible molecules, fold or unfold and could interact with either receptor and McCulloch et al.7 accordingly used kainate, a conformational restricted analogue of glutamic acid, which would be unlikely to fold to occupy the aspartate receptor, and N-methyl-D-aspartate, which would be too small to interact with the glutamate receptor (Fig. 1). The difference in sensitivity between the two groups of neurones to these agonists was much greater: the Renshaw cells were much more sensitive to N-methyl-D-aspartate and the dorsal interneurones to kainate7.

Cell-mediated immune response in head and neck cancer patients.

Abstract: The immune reactivity of 100 head and neck cancer patients was studied by means of DNCB, candidine, blastic transformation with PHA, and lymphocyte counts. DNCB reactivity was strong in only 21% of the population and was found impaired in patients with advanced primitive tumors, with more than one primitive tumor, and in patients after radiation. Candidine reactivity was impaired in bigger primitive tumors, positive nodes, and advanced stages, as well as in postradiation patients. Blastic transformation was significantly worse in patients over 70 years and tended to be lower in patients with more than one primitive tumor. Good blastic transformation was also lowered in postradiation patients.

Retinal alterations induced by continuous light in immature rats. I. Fine structure and electroretinography.

Abstract: Immature albino rats were exposed to continuous illumination for 5–93 days and the light induced ultrastructural and electroretinographic changes were studied. Another group was exposed to continuous light for 7–9 days and then kept in complete darkness, or in cyclic light-dark up to 90 days.

Early skeletal effect of alkali therapy upon the osteomalacia of renal tubular acidosis.

Abstract: The administration of alkaline agents to a 16-year-old girl with severe renal tubular acidosis and osteomalacia caused an almost immediate rise of the urinary excretion of total hydroxyproline. The increment of the dyalizable fraction predominated over the nondyalizable component. Gradually serum phosphate and serum alkaline phosphatase increased whereas urinary calcium and magnesium and phosphate clearance declined. Serum PTH remained elevated throughout. We suggest that the correction of the metabolic acidosis might increase the transport of phosphate and calcium across the functional bone membrane leading to a rapid deposition of lime salts in the uncalcified matrix with a concomitant increase in bone collagen turnover.

Biosynthesis of uroporphyrinogens from porphobilinogen: mechanism and the nature of the process.

Abstract: The enzymic self-polymerization of prophobilinogen gives rise to the cyclic tetrapyrroles uroporphyrinogen III and uroporphyrinogen I. The former is the precursor of all the natural porphyrins and chlorins. The formation of uroporphyrinogen III is catalysed by a dual enzymic system, porphobilinogen deaminase and uroporphyrinogen III cosynthase. Deaminase polymerizes four porphobilinogen units on the enzymic surface, without liberation of free intermediates into the reaction medium, and forms uroporphyrinogen I. Cosynthase enters into association with the deaminase, and acts as a 'specifier protein' of the latter, changing the mode of porphobilinogen condensation on the enzymic surface. The association is independent of the presence of substrate. While deaminase catalyses the head-to-tail condensation of the porphobilinogen units, the association deaminase-cosynthase catalyses the head-to-head condensation of the same units. As a result different enzyme-bound dipyrrylmethanes are formed form the beginning of the process, and this can be demonstrated by using synthetic dipyrrylmethanes and tripyrranes.

Antibody‐dependent cell‐mediated cytotoxicity in rheumatoid arthritis. Effect of rheumatoid serum fractions on normal lymphocytes

Abstract: Reduced antibody-dependent cell-mediated cytotoxicity (ADCC) was demonstrated in lymphocytes of patients with rheumatoid arthritis (RA). Rheumatoid factor (RF) positive sera inhibited ADCC of normal lymphocytes by reacting both with effector and target cells (sensitized chicken red blood cells). These sera were fractionated by specific adsorption or gradient ultracentrifugation, and isolated RF or RF negative fractions were tested for their ability to inhibit ADCC by reacting with normal human lymphocytes or target cells. RF was ineffective on normal lymphocytes but it strongly inhibited the reaction by interaction with target cells. IgG RF negative fractions of certain sera were inhibitory by direct interaction with effector cells.

Detection of immunologically active zones in equine growth hormone.

Abstract: Peptide fragments, obtained from equine growth hormone by cyanogen bromide cleavage and further chemical treatment, were isolated and identified. Their immunological reactivities were tested by hemagglutination and complement fixation methods using rabbit antisera against native hormone. Antigenic determinants were detected in the fragments comprising amino acid sequences 5–72 and 73–123, this last one being predominant. Fragment 124–178 had very low reactivity. Nitration of peptide 73–123 did not modify its immunological properties, but oxidation diminished them. Comparison of the antigenicity of equine growth hormone fragment 73–123 with that of the homologous ovine growth hormone fragment 86–123 lent support to the hypothesis that at least one antigenic determinant area in the horse hormone fragment is dependent on sequence 86–123.

Sobre el concepto de orden jurídico

Abstract: An idea widely recognized and accepted by jurists is that legal norms form an order, The concept of legal order requires, consequently, an analysis based on the notion used by jurists. In this paper, legislative and not customary norms are taken into account. Two terminological explanations should be made at this point: (1) norms rather than propositions about norms are discussed, and (2) “legal norm” should be interpreted in its broadest sense, that is, statements that form part of legal texts, whether they be normative or not. The intuitive notion of legal order can be said to consist of eight theses: I. It is the totality of valid norms according to a criterion of validity. II. It is a set of norms. III. It is a system of norms. IV. Its norms are created and derogated by acts of will. V. It is subject to changes in time. VI. The changes affect its content but not its identity. VII. Its content is, in principle, determinable at all times. VIII. In each State there is one and only one legal order. Although these theses are intuitively acceptable, it is not easy to mold them into one coherent theory, since several of them are contradictory (III and IV with VII and VIII) . Theses I and II are acceptable, although incomplete, definitions of “legal order” which could be made more precise. With regard to III, “system” is understood to be a deductive system —a set of sentences which contains all its logical consequences— and a distinction is made, therefore, between norms that are expressly formulated and those that are derived. Theses IV and V are acceptable almost without doubt, especially as they refer to positive law. Thesis VI, accepted by almost all jurists, is, nevertheless, incompatible with II. If a legal order is a set, it cannot change without losing its identity since the identity of a set depends on that of its elements. The solution would be to recognize two concepts of legal order covered by the same expression, or to submit that “legal order” designates a sequence of sets, and that only a modification of the identification criteria would make it lose its identity. The article deals with the alleged contradictions of III and IV with VII and VIII, presenting first the problem that if VII is false, then VIII is also false because the latter is a consequence of the former. For this reason, the notion of “promulgation of norms” is explained. It is shown, by means of an example, that the promulgation adds not only a promulgated norm, but also its logical consequences as well as the derivable of the union of such norms with the system. This promulgation is always univocal because it produces a definite normative system. In the explanation of the notion of “derogation of norms”, mention is made of the derogation of the formulation of a norm, which eliminates not a norm but a redundant formula. Exemplification is also given of the derogation of a formulated norm. Here also not only the norm but also all its consequences are derogated, and it is univocal: it leads to another definite system. Finally, the derogation of a derived norm is discussed, and it is shown, with examples, that it is possible that this derogation may lead to a plurality of alternative systems. This shows that creation and derogation are not symmetrical since the latter can produce a logical indetermination of the system, that is, the situation in which various alternative systems appear. With this, the falseness of VII is proved, and therefore VI and VIII become problematic. If III and IV are accepted, thesis VII must be rejected. In Section 4, the logical defects of legal systems are dealt with, as are logical indetermination, gaps, and contradictions, with mention made to some aspects of these problems. Regarding the gaps, some of the ideas contained in the authors’ book, Normative Systems, are put forth. Later, a definition of “normative contradiction” is offered, with recognition of the fact that it is difficult to satisfy the formal point of view and intuitions at the same time. It is contended that two norms are contradictory when the fulfilment of one of them excludes, for logical reasons, the fulfilment of the other. Logical indetermination has, at the same time, the same practical consequences, although its origin is different. Logic alone cannot solve any of these problems, but it allows that they be made known and permits the examination of certain legal concepts whose analysis has practical application. [Summary by Javier Esquivel]

Potassium-Activated Phosphatase

Abstract: The existence of a phosphatase activated by K in piasma membranes was first demonstrated by Judah et al. (1962). These authors showed that human red blood cell (RBC) membranes, incubated at neutral pH and in the presence of Mg, are capable of accelerating the hydrolysis of P -nitrophenylphosphate (P-NPP), the rate of hydrolysis in Mg-containing media being almost doubled by K. The activating effect of K required Mg since the activity in the absence of the divalent cation was shown to be very low and insensitive to K. A distinctive property of the enzyme was that 10−4 M ouabain abolished the activating effect of K, leaving unaltered the activity in the absence of the monovalent cation. The report of Judah et al. (1962) was followed by many others describing activities with characteristics similar to that from human RBCs in membrane preparations from tissues as diverse as brain (Ahmed and Judah, 1964; Fujita et al., 1965; Israel and Titus, 1966; Yoshida et al., 1966; Nagai et al., 1966), kidney (Ahmed and Judah, 1964; Bader and Sen, 1966; Nagai et al., 1966), gastric mucosa (Forte et al., 1967), intestinal epithelia (Boyd et al., 1968), liver (Ahmed and Judah, 1964; Nagai et al., 1966), and smooth muscle (Ahmed and Judah, 1964). The distribution and some kinetic parameters of K-activated phosphatase in different tissues are summarized in Table 1.

Treatment of Skin and Soft Tissue Infections with Cefadroxil, a New Oral Cephalosporin

Abstract: Oral cefadroxil in doses of 0-6-1-8 g per day given on twice or three times daily schedules was effective in the treatment of thirty-six patients with infections such as abscesses, carbuncles, cellulitis, furunculosis and impetigo. Staphylococcus aureus strains and beta-haemolytic streptococci, alone or in combination, were cultured from lesions before treatment. In vitro studies with test discs showed that all the organisms were sensitive to cefadroxil, but twenty-three of twenty-nine S aureus strains and one of the seven streptococci strains were resistant to penicillin G. Pre- and post-treatment laboratory tests of renal, hepatic and haematopoietic functions produced no evidence of drug toxicity. The cefadroxil dosage effective in this study is lower than that recommended for currently available oral cephalosporins, which must be given on a four times daily schedule.

Morphological changes induced by -SH reagents in rod photoreceptor outer segments.

Abstract: Rat retinas were treated in vitro with -SH reagents and “stained” with zinc iodide-osmium tetroxide (ZIO). Dithioerythritol (DTE), an -S-S-reducing agent, increased the electron opaque deposits observed after ZIO staining in the intraand extradiskal spaces of the rods. N-ethyl-maleimide (NEM), an -SH blocking agent, applied directly or after DTE, blocks the ZIO reaction. Furthermore, after treatment with NEM, distorted tubular and vesicular structures are substituted for the stacks of disks. These results strongly suggest that ZIO reacts with -SH groups in rod outer segments. They also indicate that SH-groups play an important role in the structural organization of rod outer segments.

Muscarinic receptors and the ACh stimulated phosphatidylinositol effect in the CNS

Abstract: A LARGE variety of cells undergo a marked increase in turnover of PI under the influence of different physiological and pharmacological stimuli (For reviews, see LAPETINA & MICHELL. 1973; MICHELL. 1975). The features in common of the so-called PI effect are: (1) it is probably mediated by receptor sites at the cell surface and (2) it involves only the phosphorylinositol moiety of PI. In the CNS. ACh was found to stimulate the PI turnover of brain slices (HOKIN & HOKIN, 1955, 1958), homogenates (HOKIN & HOKIN, 1958; REDMAN & HOKIN, 1964) and of fractions enriched in nerve endings (i.e. synaptosomes) (DURRELL & SODD, 1966; YAGIHARA & HAWTHORNE. 1972: SCHACHT & AGRANOFF. 1973). The PI effect was also found in electrically stimulated brain slices (PUMPHREY, 1969) and synaptosome beds (BLEASDALE & HAWTHORNE, 1974). It is well known that the CNS has both muscarinic and nicotinic receptor sites (For a review, see DE ROBERTIS, 1975); thus the PI effect stimulated by ACh could be mediated by one or the other type of receptors. Scattered observations favor the view that the muscarinic receptors are related to the metabolism of PI. In particulate fractions HOKIN & HOKIN (1958) found that the PI effect, was blocked by atropine and SCHACHT & AGRANOFF (1973), in a synaptosomal fraction, observed that the ACh stimulation was insensitive to d-tubocurarine. To investigate this problem further, in addition of using appropriate cholinergic agonists and antagonists, an approach would be that of taking into consideration the regional distribution of both types of receptors in the CNS. For example, while in the entire mouse brain the cholinergic receptor sites are almost equally divided between nicotinic and muscarinic (SCHLEIFER & ELDEFRAWI, 1974). in the n. caudatus there is a predominance of muscarinic binding sites (HILEY & BURGEN, 1974; YAMAMURA et al., 1974). Recently SARACENO & DE ROBERTIS (1976) found that the cholinergic receptor proteolipid protein isolated by affinity chromatography from bovine caudate nucleus probably contained 907, muscarinic sites and only l0g; nicotinic. In this paper we have taken advantage of the regional distribution of receptors by using the bovine caudate nucleus as an essentially muscarinic tissue, in comparison with the rat cerebral cortex in which there is a mixture of the two types of receptor sites. With this approach and the use of appropriate cholinergic blocking agents we have reached the conclusion that the PI effect, stimulated by ACh in the CNS is mediated only by muscarinic receptors.