Showing papers by "University of Buenos Aires published in 1972"
TL;DR: In this paper, nine methylated flavonols isolated from Larrea cuneifolia Cav. collected in Argentina have been fully characterized using UV, MS and NMR spectral data, all of which were identified as methyl ethers of quercetin and kaempferol.
105 citations
TL;DR: It is suggested that the fast-reassociating chromosomal DNA (as detected by AO in centromeric heterochromatin and interphase chromocenters), represents repetitive DNA.
Abstract: A cytological technique based on heat denaturation of in situ chromosomal DNA followed by differential reassociation and staining with acridine orange was developed. Mouse nuclei and chromosomes in fixed cytological preparations show a red-orange fluorescence after thermal DNA denaturation (2–4 minutes at 100° C), and fluoresce green if denaturation is followed by a total DNA reassociation (two minutes or more at 65–66°C). — A reassociation time between a few and 60–90 seconds demonstrates the centromeric heterochromatin of chromosomes (which sometimes aggregate in the form of clusters) and the interphase chromocenters in green, the chromosomal arms fluorescing red-orange. Under the same conditions, the Y chromosome presents a pale green or yellow-green fluorescence along its chromatids, but its centromeric region fluoresces weakly. — The interpretation is suggested that the fast-reassociating chromosomal DNA (as detected by AO in centromeric heterochromatin and interphase chromocenters), represents repetitive DNA.
63 citations
TL;DR: New histophysiological data are presented here suggesting a regulatory participation of type “B” fibers in gonadotropic and prolactin cell activities, and a brief summary of the anatomy of the hypothalamo-hypophysial relationships in the lungfish Lepidosiren paradoxa is presented.
58 citations
TL;DR: It is suggested that 3‐mercaptopropionic acid induces in the cerebellum an imbalance among the amino acids involved in the excitation‐inhibition mechanisms.
Abstract: — The effect of the convulsant, 3-mercaptopropionic acid (MP) on the content of free amino acids and on the activity of some enzymes related to their metabolism was studied in the rat cerebellum. A decrease in the activity of glutamate decarboxylase (EC 4.1.1.15) and in the level of GABA was found; at the same time, the activity of GABA-aminotransferase (EC 2.6.1.19) was increased. These changes coincided with a profound alteration of the morphology of the Purkinje cells which was related to the dose of MP. These findings, plus some changes in the content of other free amino acids and the activities of related enzymes, suggest that 3-mercaptopropionic acid induces in the cerebellum an imbalance among the amino acids involved in the excitation-inhibition mechanisms.
56 citations
TL;DR: Da die Aktivität der Pinealdrüse bei weiblichen Ratten mit dem Cyklus wechselt, wurde die Wirkung von Oe tradiol und Progesteron auf ihre AktivistitäT bei kastrierten weiblyen Ratten untersucht.
Abstract: Da die Aktivitat der Pinealdruse bei weiblichen Ratten mit dem Cyklus wechselt, wurde die Wirkung von Oe tradiol und Progesteron auf ihre Aktivitat bei kastrierten weiblichen Ratten untersucht. Oestradiol bewirkte Gewichtsabnahme und Funktionssteigerung, wahrend Progesteron die Pinealis-Aktivitat herabsetzte.
46 citations
TL;DR: This chapter argues that the so called isolated nerve endings (INE) provide a means of studying the properties of the synaptic region of the neuron in vitro, and is able to carry many of the functions that have been previously recognized in brain slices.
Abstract: Publisher Summary The isolation of the nerve endings has simplified the problem of tackling the complex structural and biochemical organization of the brain by allowing direct study of this most important part of the neuronal circuitry. This chapter argues that the so called isolated nerve endings (INE) provide a means of studying the properties of the synaptic region of the neuron in vitro . These isolated particles, surrounded by a membrane, are able to carry many of the functions that have been previously recognized in brain slices. In the process of chemical transmission, it is generally thought that transport of monovalent and divalent ions takes place at the synaptic region and that some of these ions are involved in the release of the transmitters. The isolated nerve endings provide a direct approach in learning about the sequence of reactions involved in the entrance of precursors, the synthesis of transmitters, and the triggering mechanisms involved in the release of the transmitters at the arrival of the nerve impulse. Another fundamental line of research opened by these isolation studies concerns the binding of drugs that may act at receptor sites localized in the postsynaptic membrane. The isolation of INE provides neurobiologists the possibility of exploring the most important part of the neuron where transmission of electrochemical signals and probably other fundamental functions of the nervous tissues take place.
36 citations
TL;DR: The results suggest that this special proteolipid, when added to the artificial membranes, induces a "chemical excitability" toward cholinergic ligands.
Abstract: Previous studies have shown that a special proteolipid extract from the electric organ of Electrophorus showed high affinity binding for acetylcholine and other cholinergic agents. This proteolipid has now been incorporated into ultrathin lipidic membranes, and the membrane resistance was studied. The resistance decreased from 7.27 ± 0.82 x 105 ohm cm2 in the control membrane to 1.83 x 105 ohm cm2 with addition of 72 µg/ml proteolipid. The decrease in resistance followed a potential function of order four with the proteolipid concentration in the membrane-forming solution. The presence of this proteolipid determined some type of cationic selectivity which was not observed in the control. At a critical point of proteolipid concentration the conductance spontaneously fluctuated between two levels. The membrane current jumped from one state to another by way of single discrete steps, reminiscent of those obtained with the excitatory inducing material or the macrocyclic antibiotics. In membranes containing another proteolipid having no cholinergic binding properties, the increase in conductance was smaller, and had a linear function with the concentration. In this case the "flip flop" fluctuation and the cationic selectivity were not observed. The membranes containing the cholinergic proteolipid reacted to the addition of acetylcholine by a rapid and transient increase in conductance that was considerably reduced or abolished by a previous application of d-tubocurarine. These membranes also interacted with other cholinergic agents, such as gallamine triethiodide, hexamethonium, and α-bungarotoxin. These results suggest that this special proteolipid, when added to the artificial membranes, induces a "chemical excitability" toward cholinergic ligands.
36 citations
TL;DR: The saturation curve of the binding in Peak 1 suggests that this proteolipid contains two groups of sites with different dissociation constants, and the possibility that Peak 1 of proteolIPid represents the adrenergic receptor of the spleen capsule is discussed.
35 citations
TL;DR: The incorporation of [3H]thymidine into nuclear DNA of rat brain progressively increased from birth until the 8th postnatal day and it was lowest in the adult brain and the greatest difference in the rate of protein synthesis between 8‐ and 1‐day‐old brain occurred in the nuclear proteins, especially those associated with DNA.
Abstract: —The incorporation of [3H]thymidine into nuclear DNA of rat brain progressively increased from birth until the 8th postnatal day and it was lowest in the adult brain. When isolated nuclei from brain cells were separated into a neuronal- and a glial-rich fraction (composed of glial and neuroblast nuclei in young animals), the specific radioactivity of the DNA was higher in the glial-rich fraction at all ages investigated. The incorporation of [3H]leucine into proteins of rat brain was considerably higher in the 8-than in the 1-day-old rat. The greatest difference in the rate of protein synthesis between 8- and 1-day-old brain occurred in the nuclear proteins, especially those associated with DNA. There was an accumulation of protein and RNA in nuclei from brain cells from birth to the 8th postnatal day. The increased content of proteins occurred primarily in the fraction soluble in buffered saline (nuclear sap).
35 citations
TL;DR: In the infected mice, the endotoxin-detoxifying ability of the spleen was found to be impaired, and Infected mice had an increasing susceptibility to the lethal effect of endotoxin.
Abstract: SYNOPSIS
Mice (Rockland strain) infected with Trypanosoma cruzi strain Tulahuen were treated with Escherichia coli endotoxin before, simultaneously with, and after inoculation of the parasites. The peak parasitemias of endotoxin-treated mice were higher than those of nontreated infected animals, regardless of the time of endotoxin administration. Peak parasitemias occurred at the same time in infected nontreated mice as in animals given endotoxin before or simultaneously with the trypanosomes. If endotoxin was administered 24 hr after the infection, a delay in the peak parasitemia was noted. Changes in the survival time were not observed unless endotoxin was given 24 hr postinfection. Infected mice had an increasing susceptibility to the lethal effect of endotoxin. The LD50 of endotoxin decreased from 675 μg for normal mice to 230, 92, and 18 μg for infected animals 1, 3, and 8 days after the infection, respectively. In the infected mice, the endotoxin-detoxifying ability of the spleen was found to be impaired.
31 citations
TL;DR: A new group of enzymes was isolated from wheat germ and rat liver which oxidized the pyrrole ring of indoles affording o -formamidophenacyl derivatives, and were named pyrrolooxygenases, which had an absolute requirement for oxygen and an exogenous reducing agent.
TL;DR: The in vitro response of human peripheral lymphocytes to Trypanosoma (Schizotrypanum) cruzi antigens and to phytohemagglutinin was used to study the role of cellular immunity in Chagas disease.
Abstract: The in vitro response of human peripheral lymphocytes to Trypanosoma (Schizotrypanum) cruzi antigens and to phytohemagglutinin was used to study the role of cellular immunity in Chagas disease (American trypanosomiasis). Solubilized T. cruzi antigens elicited 5 to 30% transformed cells in 5-day cultures of lymphocytes from adults chronically infected with T. cruzi. No major difference was noted between the response of 22 asymptomatic individuals and of 3 patients with chagasic cardiopathy. No correlation was found between degree of lymphocytic transformation and serum antibody titer. Lymphocytes from 15 normal controls yielded no significant transformation. Intradermal tests provoked a local delayed hypersensitivity reaction in infected individuals only, as evaluated clinically and histologically. The response to phytohemagglutinin of lymphocytes from chronically infected individuals was identical with that of normal controls.
TL;DR: The kinetics of the reaction is similar to that followed by immune lysis of sensitized sheep erythrocytes, as is the concentration of divalent cations required for optimal lysis, the occurrence of cell membrane uptake of the complement components C3 and C4, and the development of characteristic ultrastructural modifications on the cell membrane.
Abstract: Studies were performed on the mechanism of immune lysis of culture forms of Trypanosoma (Schizotrypanum) cruzi. Antibody-mediated lysis is caused by complement, which is activated via the classical pathway. The properdin system is not required. The kinetics of the reaction is similar to that followed by immune lysis of sensitized sheep erythrocytes, as is the concentration of divalent cations required for optimal lysis (0.15 mm Ca2+ and 0.5 mm Mg2+), the occurrence of cell membrane uptake of the complement components C3 and C4, and the development of characteristic ultrastructural modifications on the cell membrane.
TL;DR: The chemical study of ovine growth hormone has reached a point in the laboratory where it is possible to express its complete amino acid sequence by a unique combination of tryptic, chymotryptic and peptic peptides, plus information mentioned before.
TL;DR: The findings of renin, angiotensins I and I1 and converting enzyme in the central nervous system of the rat and the dog are important clues to account for the local formation of the polypeptide.
Abstract: ANGIOTENSIN 1 seems to modify adrenergic function via a neurogenic mechanism, and is the only hormone that has been demonstrated to increase transmitter release (HUGHES and ROTH, 1971). Furthermore, angiotensin I1 can also accelerate the synthesis of norepinephrine in various sympathetically innervated tissues (BOADLE, H U ~ H E S and R m , 1969). Recently this polypeptide has been postulated to be a mediator of a variety of physiological mechanisms involving the central nervous system, such as the release of antidiuretic hormone ( M o m etal., 1971), the excitation of supraoptic neurosecretory cells (NICOLL and BARKER, 1971), and the control of drinking behaviour (FITZSIMONS and SXMONS, 1969). Moreover, the polypeptide has a central pressor effect mediated by the sympathetic nervous system (SMOOKLER et at., 1966). However, it is known that angiotensin I1 does not have a ready access to the brain (VOLICER and Lorn, 1970). The findings of renin (FISCHER-FERRARO et al., 1971 ; GANTEN et al., 1971b), angiotensins I and I1 (FISCHER-FERRARO et al., 1971; GOLDSTEIN et al., 1970; GANTEN et al., 1971~) and converting enzyme (ROTH, WEITZMAN and PIQUELOUD, 1969) in the central nervous system of the rat and the dog are important clues to account for the local formation of the polypeptide. However, no definitive evidence has been advanced to characterize angiotensin I1 as a neurotransmitter. In any case, some mechanism is required for terminating the pharmacological actions of the polypeptide in the central nervous system. We decided to search in the brain tissue of the rat and the dog for the presence of enzymes capable of specifically inactivating angiontensin 11. We followed the isolation procedure described for hog kidney angiotensinase C (YANG et al., 1970) with the use of fresh brains from Wistar rats and mongrel dogs.
TL;DR: The hypothesis that acetylcholine affects the turnover of phosphatidylinositol during the transmission process is favoured, as it was found that the enzyme was essentially particle bound with the higher concentration in the cholinergic nerve-ending membranes, following the distribution of acetyl Choline.
TL;DR: It is concluded that the cholinergic proteolipid extracted with organic solvents is similar to the protein-α-bungarotoxin complex separated by the use of strong detergents.
TL;DR: The results suggest that the observed effects of MA on the ion permeability of the red cell are caused by its combination with amino groups of cell membrane proteins.
Abstract: Maleic anhydride (MA) has been shown to react specifically and rapidly with amino groups of proteins; the maleyl amino groups are negatively charged and completely stable at neutral pH. Treatment of human red cells with this reagent results in a significant increase in K+ permeability which is associated with a much smaller increase in Na+ permeability. Opposite effects are observed on anion permeability, the SO 4 −− and Cl− permeability being decreased to an approximately similar extent upon treatment with MA.
TL;DR: The results described in this paper on the lipolyric action of bovine growth hormone (BGH) bound to large Sepharose beads suggests that this hormone may also exert its effect through interaction with the plasma membrane of its target cells.
TL;DR: In this paper, three peptide alkaloids have been isolated from Discaria longispina, including frangulanine, discarine A (II) and discarine B (III).
TL;DR: It is proposed that both isomers originate by different pathways from the start of the polymerization and that the dipyrrylmethane 5 resulting from the formal head-to-head condensation of two units of porphobilinogen is a first intermediate of the enzymatic system involved in uroporphyrinogen polymerization.
TL;DR: Urea accumulates markedly in the tissues during aestivation but ammonia does not, probably due at least mainly, to a decrease in ammonia formation.
Abstract: 1. 1. Lepidosiren paradoxa, kept in water, either fed or unfed, excretes up to 38 per cent its nitrogenous waste as urea. 2. 2. d -Arginine is hydrolyzed by liver homogenates but l -arginine and guanidinic compounds are not. 3. 3. Urea is synthesized in the liver from bicarbonate and ammonia in a process that requires acetylglutamic acid and is inhibited by citrulline but not by arginine. 4. 4. Synthesis of urea via a uricolytic pathway is barely detectable and does not increase in aestivated animals. 5. 5. Urea accumulates markedly in the tissues during aestivation but ammonia does not, probably due at least mainly, to a decrease in ammonia formation.
TL;DR: In this paper, the Arrhenius parameters for the intramolecular hydrogen abstractions have been derived; the dependence of these parameters on the carbon-hydrogen bond dissociation energy is discussed.
TL;DR: The existence of a new enzyme present in plants and animals which efficiently oxidizes porphobil inogen transforming it into 5-oxo-porphobilinogen 2, a product which is not transformed into porphyrins any longer is described.
TL;DR: It was found that with the exception of the sperm-immobilizing test, which was positive in some animals, no detectable anti-spermatic antibodies of complement-fixing or precipiting types appeared in this immunologic response.
Abstract: Unilateral thermal orchitis was induced in adult guinea pigs by intratesticular infiltration with boiling saline. The immunologic response and lesions which developed in the contralateral gland were studied. It was found that: (1) With the exception of the sperm-immobilizing test, which was positive in some animals, no detectable anti-spermatic antibodies of complement-fixing or precipiting types appeared. (2) Delayed hypersensitivity, as revealed by skin test, was present. (3) Lesions similar to those of allergic orchitis appeared in the contralateral gonad and corresponding epididymis. (4) No evident difference was observable in this immunologic response when injured animals were in addition injected with complete Freund's adjuvant.
TL;DR: It is concluded that although rat liver mitochondria can acquire part of their own provision of phosphatidyl choline by transference from microsomes, all organelles and specially mitochondria, can independently synthesize this phospholipid.
TL;DR: The changes of cerebrosides, gangliosides, phospholipids, cholesterol, and proteolipid protein were studied throughout early postnatal maturation of the cerebral cortex and cerebellum of the rat to establish a relation with chemical and histological events taking place through maturation.
TL;DR: Apical plugs were produced by compressing radicular pulp and dentin chips in 157 molars from rats and materials that contained corticoids showed a good periapical response, slight cementum necrosis, and narrowing of the foramen in many instances.
Abstract: Apical plugs were produced by compressing radicular pulp and dentin chips in 157 molars from rats. Root canal fillings were performed with 15 different materials. After seven days, tissue reaction with all materials was favorable. After 30 and 90 days, materials that contained corticoids showed a good periapical response, slight cementum necrosis, and narrowing of the foramen in many instances.
TL;DR: Kinetic studies of the labelling of different nuclear and microsomal RNA species confirm that neonatal thyroidectomy reduced the transcriptional activity of nuclei, and suggest that it may also be responsible for alterations in post-transcriptional regulatory mechanisms.