Showing papers by "University of Buenos Aires published in 1968"

The neurotubular system of the axon and the origin of granulated and non-granulated vesicles in regenerating nerves.

Abstract: Electronmicroscope observations have been made on compressed sciatic nerves and preganglionic afferents to the superior cervical ganglia of rats. After 6 hours, the proximal regenerating stumps of both myelinated and unmyelinated axons become filled with enlarged neurotubules and vesicles. Granulated vesicles of 750–900 A, having a dense core become abundant in all types of regenerating axons and they increase in number after 24 hours. The vesicular material is formed by dilatation and pinching off from neurotubules. The existence of a neurotubular system within the axon, connected with the Golgi complex at the perikaryon and involved in the formation of vesicles, is postulated. The presence of granulated vesicles in all types of regenerating axons and nerve terminals is discussed in relation with their possible functional significance. The distal stumps of compressed sciatic nerves show, after 6 hours, a considerable increase in membranous material within the axoplasm mainly represented by multivesicular and lamellar bodies. This reaction, which is interpreted as being autolytic, is compared with the regenerative reaction of the proximal stump.

Lipids and proteolipids in isolated subcellular membranes of rat brain cortex.

Abstract: — The cerebral cortex of the rat was submitted to an extensive cell fractionation schedule and in the various fractions, protein, proteolipid protein, total phospholipids, cholesterol, galactolipids, plasmalogens, and gangliosides were determined. With increasing purification the different isolated membranous structures: i.e. myelin, nerve ending membranes, synaptic vesicles, mitochondria, and microsomes, show a definite biochemical specialization reflected in their lipid composition. The presence of gangliosides in some nerve ending membranes is confirmed, and the possible functional role of these acid glyco-lipids is discussed. The importance of proteolipids as structural components of membranes is recognized. The richness of these compounds in myelin is confirmed and a special localization in the nerve ending membranes is indicated. Analysis of the molar ratios of the different lipids and proteins in the isolated membranes demonstrates that each one has a specific pattern of molecular organization. This pattern is discussed in relation to the macromolecular structures revealed by electronmicroscopy and some of the molecular models postulated for cell membranes.

Isolation of Ammonia‐oxidizing Autotrophic Bacteria

Abstract: SUMMARY Procedures are described for isolating ammonia-oxidizing autotrophic bacteria in pure culture, using solid media made from purified agar and appropriate micromanipulations.

Action of reserpine on the osmium tetroxide zinc iodide reactive site of synaptic vesicles in the pineal nerves of the rat.

Abstract: The technique of Champy-Maillet was used to stain pineal nerves in an electron microscopic study Synaptic vesicles appear as a negative image of that revealed with osmium tetroxide They are totally stained and 34% of the total vesicles show a paler core, with a mean diameter of 280 A Reactive granules with a mean diameter of 255 A, were observed with the histochemical technique of Wood for catechol and indoleamines These reactive granules may correspond to the clear cores revealed with the osmium tetroxide-zinc iodide technique and the dense cores visualized with osmium tetroxide alone These results seem to indicate that the osmium tetroxide-zinc iodide technique stains a component present in the synaptic vesicles which is not catechol or indoleamine

The effect of castration upon the ultrastructure of the rat hypothalamus. I. Supraoptic and paraventricular nuclei.

Abstract: The neurosecretory hypothalamic nuclei and the inner zone of the median eminence of castrated rats were studied under the electron microscope. After one month of castration all the neurosecretory neurons of both nuclei show signs of hyperactivity characterized by dilated cisternae of the endoplasmic reticulum containing a macromolecular filamentous material and an increase in the number of ribosomes. After six months of castration, some neurosecretory neurons show an increased number of neurotubules and larger lysosomes than in the controls. Other neurons show a very significant hypertrophy of the endoplasmic reticulum, with large amounts of intracisternal filamentous material. These cells have few neurosecretory granules and in the adjacent synapses the number of granulated vesicles is increased. In the supraoptic nucleus there are two kinds of neurosecretory axons: the clear ones, which are similar to those that appear in control animals and the dark ones, which have smaller elementary granules. In the inner zone of the median eminence the axons show an increase in the number of neurosecretory granules with respect to the controls. After supplementary administration of sexual hormones, all the modifications produced by castration disappear. The ultrastructural changes observed in the neurosecretory nuclei after castration are discussed in relation to those previously described in the neurohypophysis under the same experimental conditions. A feedback regulatory action of sex hormones on hypothalamic neurosecretory neurons is postulated.

The ultrastructural changes in the neurohypophysis after destruction of the paraventricular nuclei in normal and castrated rats.

Abstract: In normal and castrated rats an electrolytic lesion of 1–1.5 mm in diameter was placed in the hypothalamus using bilateral electrodes. Such a lesion destroyed both paraventricular nuclei and surrounding tissue. The electron microscope study of the neurohypophysis revealed that about 1/5 of the neurosecretory axons and terminals degenerated. In the castrated rats, the “clear” axons described in a previous paper (Zambrano andDe Robebtis, 1968), were those that underwent degeneration. This finding supports our previous assumption that such axons belong to the paraventricular system. The sequence of the ultrastructural changes occurring in the degenerating axons and terminals is described. Special features were the early lysis of the neurotubules, the breakage of the membrane of the elementary granules and of the axolemma. Disrupted axonic material was observed in the interstitial tissue. The degeneration of the “clear” axons from the paraventricular system is discussed in relation to their possible oxytocinergic nature. An early cellular reaction was found in the perivascular microglial type of cell. These increased in number and underwent ultrastructural changes indicative of active phagocytosis and pinocytosis. Both the protoplasmatic and the fibrous pituicytes did not participate in the removal of the degenerating axons. This was apparently done by extracellular digestion and engulfment by microglial cells.

Shovel-Shaped Incisors in a Northwestern Argentine Population

Abstract: The prevalence and the inheritance of shovel-shaped incisors were studied in children from northwestern Argentine provinces. One hundred percent of the deciduous and permanent incisors were shovel shaped, and a high frequency of the S-gene in the permanent dentition was found. These findings demonstrate a strong Mongoloid genetic component in this population.

Ultrastructure of transitional epithelium of man.

Abstract: Blocks of human normal renal pelvis and ureter obtained at the time of surgery were fixed in glutaraldehyde and osmium with or without ruthenium red, for electron microscopic observations. The transitional epithelium is arranged in three cell layers: basal, intermediate and superficial. All epithelial cells show numerous microvilli and contain the characteristic vesicles of transitional epithelium, bundles of cytoplasmic filaments, microtubules and numerous free ribosomes. The epithelial extracellular compartment is notably large and appears as an intricate, tridimensional network of canaliculi and cisternae which are wider in the intermediate and superficial layers and in which microvilli and cytoplasmic folds of vicinal cells are often attached or interdigitated. At these sites there are desmosomes. The surface of all transitional epithelial cells is covered by a fibrillar mucous coat which is more developed at the plasmalemma of the free border of luminal cells in which microvilli are also seen. Ruthenium red stains selectively the plasmalemma and the mucous coat of the free surface of the epithelium, indicating the presence of an acid polysaccharide. With this technic (Luft, 1965), it is observed, radiating from the plasmalemma, branching filaments which measure 100 A in diameter forming a zone of varying density which is about 400 mμ wide and which corresponds, at the light microscopic level, to the luminal border of the transitional epithelial cells in which a sialomucin has been identified. The slender filaments have a beaded appearance. At the free border, superficial cells are attached by functional complexes in which tight junctions seal the epithelial intercellular space, which is opened at the level of the basement membrane where only desmosomes are observed. The ultrastructure of human transitional epithelium of urinary tract resembles the duct cells of the salt gland of certain marine birds (Fawcett, 1962) and the amphibian epidermis (Farquhar and Palade, 1965) in which there are active processes of transport. The mucous surface coat, selectively stained by the ruthenium red, contains a sialomucin (Monis and Dorfman, 1965, 1967). The ultrastructure and histochemistry of the mucous fluffy coat of man transitional epithelium and the observations of Porter and Tamm (1955), on the ultrastructure of preparations of the Tamm and Horsfall mucoprotein (1952) are bases for suggesting that transitional epithelium of urinary tract of man is the site of biosynthesis of certain urinary mucoids. Present investigations are directed to obtain evidence to substantiate this hypothesis.

Ultrastructure of the peptidergic and monoaminergic neurons in the hypothalamic neurosecretory system of anuran batracians.

Abstract: In the toad Bufo arenarumHensel the following regions of the hypothalamic — neurohypophyseal system were studied under the electronmicroscope: preoptic and paraventricular nuclei, median eminence and infundibular process of the neurohypophysis.

Ultrastructural changes of the neurohypophysis of the rat after castration.

Abstract: The infundibular processes of the neurohypophysis of male and female rats were studied after different periods of castration. After seven days an increase in neurosecretory granules was observed. Two types of neurosecretory nerve endings were identified: dark ones, with dense neurosecretory elementary granules of 1600 A, and clear ones, with lighter neurosecretory granules of 1800 A. Protoplasmatic pituicytes showed a large increase in lipid granules together with a general hypertrophy. After one week of castration but with hormonal therapy the protoplasmatic pituicytes appeared normal or even showed less lipid granules than in the controls.

Ultrastructure of neurons in the arcuate nucleus of the rat.

Abstract: In the arcuate nucleus of the normal rat there are two types of neurons. One of them is characterized by a dense cytoplasmic matrix, dilated endoplasmic reticulum cisternae and well developed Golgi complexes; the other cell type by a paler overall appearance. In both of them granulated vesicles of about 1000 A in diameter with a core of variable density are present. The frequent association between these vesicles and the Golgi complex suggests that they are formed in relation to this organoid. The presence of lysosomes and multivesicular bodies and their close relationship with granulated vesicles is analyzed. The neuropil of the nucleus is constituted by axons, dendrites and glial processes. The majority of the axon profiles and nerve endings contain a mixed population of clear and granulated vesicles, the latter having a diameter ranging between 600 to 1300 A. The finding of granulated vesicles in arcuate neurons is discussed in relation with the known monoamine content of them and the dopaminergic nature of the fibers that form the tuberoinfundibular tract. It is suggested that these granulated vesicles contain primary monoamines.

Degeneration in the parvocellular portion of the lateral geniculate nucleus of the Cebus monkey. A light and electron microscope study.

Abstract: The synaptology of the Cebus lateral geniculate nucleus (LGN) was studied after varying (3–15 days) periods of survival following unilateral and bilateral eye enucleations. Part of the material was processed with the Glees and Nauta techniques for light microscopy while the rest was processed for electron microscope observation. The study revealed a variety of degenerated terminals in the parvocellular portion of the LGN and allowed the differentiation of the retinal from the extraretinal terminals. The most frequent synaptic type of retinal origin is a glomerular large central terminal (up to 20 μ long) which makes axodendritic and axoaxonic synaptic contacts with geniculate dendrites and peripheral small terminals. Simple axodendritic and axosomatic terminals of retinal and extraretinal origin were also found. The early changes affecting the geniculate neurons and astrocytes during the degenerative process are described.

The arcuate complex of the female rat during the sexual cycle. An electron microscopic study.

Abstract: The arcuate complex, comprising the nucleus and the outer zone of the median eminence, was studied under the electron microscope during the whole sexual cycle of the female rat. The content of granulated vesicles in neurons and terminals was minimal at estrus, rose during diestrus and reached maximal levels during the morning of proestrus. In the afternoon of proestrus the number of granulated vesicles suddenly decreased and lysosomes seemed to become activated similar changes were found in the nerve endings of the outer zone of the median eminence. These cyclic changes observed in the arcuate complex are discussed in relation to the knowledge on the histophysiology of this region of the hypothalamus and specially to the probable regulatory effect of monoamines on the secretion of gonadotrophins.

Ultrastructure of cells and synapses in the parvocellular portion of the cebus monkey lateral geniculate nucleus.

Abstract: The ultrastructural study of the Cebus lateral geniculate nucleus shows the existence of a complex synaptic organization in which several synaptic types are recognized: a) axosomatic; b) simple axodendritic; c) glomeruli. Three main synaptic contacts were found in the glomeruli: 1. axodendritic 1, between central terminals and primary and secondary dendrites; 2. axodendritic 2, between peripheral terminals and dendrites and 3. axoaxonic, between central and peripheral terminals. At the axoaxonic junctions, the central are presynaptic to the peripheral terminals. Elliptical vesicles fill the peripheral terminals. These findings are discussed in relation with a) previous results of other authors in primates and cats; b) previous neurophysiological and pharmacological evidences for the existence of chemical synapses in the lateral geniculate nucleus; c) the possible functions of axoaxonic synapses.

Carboxylase Levels and Carbon Dioxide Fixation in Baker's Yeast

Abstract: Levels of pyruvate carboxylase (PC), phosphopyruvate carboxylase (PEPC), and malate dehydrogenase (decarboxylating) were compared in wild-type bakers' yeast (I), a cytoplasmic-respiratory mutant (II), a biotin-deficient wild-type yeast (III), and a biotin-deficient respiratory mutant (IV). PC activities were greatly reduced in III and IV, whereas PEPC was reduced in II and IV. Malate dehydrogenase (decarboxylating) could not be detected in any of the yeasts. With yeast I growing on glucose as the sole carbon source, PEPC decreased to negligible levels during the logarithmic phase of growth (glucose repression effect), whereas PC increased. Both enzymes reverted to their original levels during the stationary phase, when glucose in the medium was exhausted. In agreement with the leading role of PC for CO(2) assimilation, the rates of (14)CO(2) fixation in yeasts I and II were approximately equal and were much higher than that in yeast IV. With I and II, most of the (14)C was distributed similarly in oxalacetate derivatives; with yeast IV, most of (14)C appeared in a compound apparently unrelated to CO(2) fixation via C(4)-dicarboxylic acids.

Role of pituirary in the thyroid hypertrophy of pinealectomized rats.

Abstract: Epiphysektomie bei verschiedenen Gruppen weiblicher Ratten ergab Zunahme des Schilddrusengewichtes. Diese war postoperativ in der ersten Woche besonders stark und perennierte wahrend 7 Wochen der Experimentdauer. Entsprechende Gewichtszunahme der Schilddruse resultiert auch nach Epiphysektomie bei hypophysenlosen Tieren.