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E L Palacios-Prü

Publications and source records attributed to E L Palacios-Prü.

13 recordsLinked to original sources
PubMed2000

Levels of amino acid neurotransmitters during mouse olfactory bulb neurogenesis and in histotypic olfactory bulb cultures.

The developmental changes in the levels of amino acid neurotransmitters were analyzed by high pressure liquid chromatography during mouse olfactory bulb neurogenesis, from embryonic day (E)13 until the young adult age, between postnatal days (P)30 and P40. During the embryonic period, high levels of glutamate, aspartate and GABA were observed, with the values of GABA about 2-fold higher than those of glutamate and aspartate. At P0, the production of these neurotransmitters experienced birth stress as shown by a significant 2-fold reduction in their levels. During the first two postnatal weeks, a progressive increase in the glutamate content was detected diminishing slightly in the adult stage. The aspartate concentrations showed a maximal value at P3 and then decreased gradually until the second postnatal week; in the young adult age, its concentration was comparable with that of glutamate. The postnatal GABA contents increased progressively from birth to maturity, showing maximal levels at P3, P11 and in the adult. Throughout the studied developmental period, the concentration of glycine remained relatively low. With regard to taurine, very low concentrations were detected during the prenatal period but after birth, the taurine content gradually increased with age, and in the adult animal, its concentration was comparable with those of GABA and glutamate. Our data demonstrate the predominance of GABA and glutamate during olfactory bulb synaptogenesis, however, in the adult animal, both glutamate and aspartate exert the same influence in the excitatory synaptic transmission; in the adult inhibitory synaptic transmission, taurine appears to play an important neuromodulatory or neurotransmitter role as that of GABA. To determine the intrinsic neurotransmitter production, primary histotypic olfactory bulb cultures were prepared from mice at P10. The comparative analysis of in vitro neurotransmitter contents with those in in situ adult animal showed higher levels of endogenously produced glutamate, glycine and GABA in the olfactory bulb than the extrinsic ones coming from olfactory nerve axons and higher olfactory brain centers. On the other hand, most of aspartate and taurine neurotransmitters apparently come from extrinsically located neurons.

Age Factors↗
PubMed1999

Levels of amino acid neurotransmitters during mouse cerebellar neurogenesis and in histotypic cerebellar cultures.

The variation in the levels of excitatory (glutamate and aspartate) and inhibitory (GABA, glycine and taurine) neurotransmitters during neurogenesis in mouse cerebellum, from embryonic day (E) 15 until the young adult stage, was analyzed by high-pressure liquid chromatography. Between E15 and E21, high contents of GABA, glutamate and aspartate were detected, with the GABA levels approximately 2- to 3-fold higher than those of glutamate and aspartate. After birth, the levels of GABA remained high during the first 2 postnatal weeks and then reached a plateau comparable to adult values by the third week. The levels of glutamate and aspartate increased gradually from birth to the young adult stage, showing peak values at postnatal days (P) 3 and P11. Glycine and taurine were present at relatively low concentrations during the prenatal period, then rose significantly by about 4-fold after birth; their levels decreased by the end of the first postnatal week but increased gradually thereafter until reaching adult values by the third week. To determine the endogenous neurotransmitter production in the cerebellar cortex, primary histotypic cerebellar cultures prepared at P10 were analyzed and the in vitro transmitter contents were compared with the adult in situ values. The cultures showed about the same levels of glutamate and aspartate; however, their concentrations were lower by half than in vivo, suggesting that both play an equally important role in the excitatory neurotransmission of the cerebellar cortex internal circuitry pathways and that in mature cerebellum, about 50% of the excitatory synaptic inputs derive from the afferent climbing and mossy fibers. The in vitro GABA and glycine contents were comparable with the in vivo levels, whereas the taurine concentrations were about 5-fold lower in vitro than in vivo. These findings indicate that most of the GABA and glycine transmitters are produced intrinsically while a high proportion of taurine in the cerebellum comes from extracerebellar afferents. This study provides data on the changing levels of the amino acid neurotransmitters in developing mouse cerebellum and the relative proportions of neurotransmitter contents that are produced by intrinsic neurons in contrast to those derived from extrinsic afferent fibers.

Aging↗
PubMed1998

Levels of monoamine and amino acid neurotransmitters in the developing male mouse hypothalamus and in histotypic hypothalamic cultures.

The variation in the levels of the monoamine and amino acid neurotransmitters was studied during the period of neurogenesis in male mouse hypothalamus, from embryonic day 15 until the age of young adult. The results shown in this study demonstrate that the monoamines appear early in the fetal brain and that the maximum expression of the catecholaminergic system, particularly that of dopamine, occurs during the late neonatal period or mouse infancy, when the role played by the catecholamines on the maturation of the neurosecretory systems is more significant. In relation to the amino acid neurotransmitters, glutamate and taurine seem to be the principal transmitters of the hypothalamus since their concentrations were about five-tenfold higher than the levels of glycine and GABA. Both amino acids had the same pattern of variation during development, showing elevated values during the prenatal, late neonatal and early pubertal period. Increased concentrations of the inhibitory neurotransmitter GABA were observed on the day before birth, at the end of the neonatal period and throughout the prepubertal period, suggesting that the influence of GABA on hypothalamic neurogenesis increases by the time when the hypothalamic nuclei have reached maturity and the local circuits have been established. To determine the intrinsic neurotransmitter production, primary hypothalamic histotypic cultures prepared from mice at postnatal days 8-10 were analyzed for their content of neurotransmitters. The in vitro analysis revealed that the hypothalamic neurons intrinsically produce dopamine, glutamate, taurine and glycine in homologable amounts with those of young adult animals. The comparative analysis also showed that about 50% of the GABA content and less than 5% of the hypothalamic epinephrine level are locally produced, while serotonin comes mainly from extrinsically located neurons.

Animals↗
PubMed1998

Hypothalamic synaptogenesis and its relationship with the maturation of hormonal secretion.

1. Information obtained during the last decade has demonstrated that hypothalamic neurons release a wide variety of neuroactive substances, such as neurotransmitters, mostly monoamines and amino acids, and neuromodulators such as the peptides vasopressin (AVP) and oxytocin (OXT) and hypophysial releasing hormones. 2. Synapse formation between hypothalamic neurons was followed at different times within a given nucleus and among different nuclei during development of the mouse hypothalamus. 3. The amounts of various neurotransmitters and hormones were determined at various stages of development. 4. A correlation is presented of the biochemical and ultrastructural features and their functional implications during maturation.

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PubMed1995

Existence of a putative specific postsynaptic density protein produced during Purkinje cell spine maturation.

This study identified a 140 kDa polypeptide as a putative specific component of Purkinje cell spines' postsynaptic densities and which began to appear during the critical period of cerebellar cortex synaptogenesis. Mouse cerebellar cortices at postnatal days 5, 7, 9, 11, 15 and young adult, between days 30 and 40, were used to purify subcellular fractions of synaptosomes, synaptic membranes and postsynaptic densities. The purity of the subcellular fractions was assessed by electron microscopy and the protein composition of the different fractions was characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Polypeptides of apparent molecular weights of 25, 26, 27, 30, 33, 37, 43, 45, 52, 64, 74, 85, 94, 110, 125, 130, 165 and 174 kDa were found in the synaptosomal fractions of all the ages studied, even before the critical period of synaptogenesis, at postnatal day 7, when the postsynaptic densities were still nonexistent, indicating that the polypeptides are nonspecific constituents of these structures. On the other hand, a 140 kDa polypeptide was detected in the postsynaptic density fractions at postnatal day 11, immediately after postsynaptic structures began to appear, suggesting the possibility that this protein is a specific component of the cerebellar cortex postsynaptic densities. The 140 kDa polypeptide was electroeluted from the gel and analysed for its amino acid composition by reverse-phase high-pressure liquid chromatography. The analysis showed that this protein has a high content of nonpolar amino acid residues, such as leucine, isoleucine, glycine, phenylalanine and valine. A hypothetical model relative to the participation of the 140 kDa protein in the molecular organization of the postsynaptic density is suggested which may contribute to the understanding of the role played by this structure in synaptic function.

Aging↗
PubMed1995

Development of the neurogliohemal complex in the mouse neurohypophysis.

The mouse neurohypophysis was studied at different ages of development in order to analyse the ultrastructural changes that lead to the maturation of the neurogliohemal complex and to determine the existence of permeability between the blood capillaries and the neurohypophysial channels. In all the studies ages, two groups of 5 animals each were intravenously injected with different tracer solutions: to one group, 10 microliters of cationized ferritin were used and to the other, 10 microliters of ferrous fumarate were applied. For the ultrastructural studies the tissue samples were processed using the conventional techniques for electron microscopy. At day 17 of prenatal age, some hypothalamic axons (10 axonic profiles/20 microns2) were already seen within the neurohypophysis, increasing threefold (26 to 30 axonic profiles/20 microns2) at prenatal day 19. In these axons terminals, the first neurosecretory vesicles began to appear. At this early age, the glial cells formed few prolongations. Between postnatal days 1 and 9, numerous axon terminals containing dense neurosecretory vesicles composed the neuropile areas. After day 9, there was a broadening of the intercellular space, which we have termed as neurohypophysial channels; these were actually expansions of the existing extracellular space in the neurohypophysis. Between days 9 and 21, the population of axon terminals showing a higher density of neurosecretory vesicles continued to increase in number. Some of these axon terminals were separated by irregular neurohypophysial channels. The glial cells showed scarce cytoplasm and formed numerous lamellar prolongations, which became increasingly finer surrounding bundles of individual axons.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1992

Release of neurotransmitters and neurosecretory substances during in vitro maturation of mouse hypothalamic cultures.

The maturation of the neurosecretory activity of a hypothalamic nerve cell population grown in vitro, prepared from 10-day-old mice and cultured for 6 days, has been demonstrated in the present report. A low-molecular weight polypeptide of 30-kD was found to be released into the culture media during the 6-day period of incubation, as analyzed by SDS-polyacrylamide gel electrophoresis. Comparative electrophoresis of the in situ hypothalamic, neurohypophysis and cerebral cortex homogenates revealed the presence of a 30-kD protein component in both the hypothalamus and neurohypophysis but not in the cerebral cortex. The release of the 30-kD polypeptide into the incubation media indicates an expression of the neurosecretory activity of the peptidergic neurons of the hypothalamus during in vitro maturation. On the other hand, high pressure liquid chromatography with electrochemical detection showed appreciable quantities of released dopamine (DA), epinephrine and serotonin (5-HT) in the incubation media in which the neurons were allowed to differentiate. There was a steady release of DA during the 6-day incubation period, varying from 0.21 +/- 0.02 to 0.49 +/- 0.05 ng/mg protein. The epinephrine level increased progressively from day 1 to 6 of culture, from 3.73 +/- 0.57 to 12.08 +/- 1.81 ng/mg protein, respectively. The measured 5-HT level was 0.07 +/- 0.001 on day 2 and increased to 0.38 +/- 0.05 ng/mg protein on day 6 of culture. These data demonstrate the functional maturation of catecholaminergic, serotoninergic and peptidergic neurons in these rotary histotypic cultures of the mouse hypothalamus.

Animals↗
PubMed1991

In vitro hypothalamic neurogenesis: morphological maturation of mouse hypothalamic cultures and in vitro versus in situ biochemical analysis.

The morphological and biochemical changes that occur during in vitro neurogenesis of the mouse hypothalamus were studied in rotary cultures prepared from mice between 4 and 16 days of postnatal age. After 6 days of in vitro growth, histotypic cultures with a high degree of morphological differentiation were obtained in cultures prepared from 8- to 10-day-old mice. Before day 8, the cultures showed immature neurons, while after day 12 most of them exhibited an undesired number of degenerated cells. Light-microscopic, Golgi and ultrastructural studies clearly showed the stages of development of the neurosecretory cells in culture. The particular organization of the hypothalamic cells in these cultures can be homologized to its equivalent region in vivo, as demonstrated by their morphological similarities as well as by the fact that the majority of the neurons orient their axons toward the external part of the culture in order to release the neurosecretory material outside the in vitro grown neuronal population, as is the case in situ since hypothalamic neurons release their neurosecretory products at the vascular system. Biochemical parameters such as DNA, RNA and protein contents were determined during the period of in situ development used for the preparation of histotypic cultures and compared to the biochemical changes that occurred during in vitro maturation. The changes in the in vitro DNA and protein contents showed the same variation pattern as in situ. The DNA/protein and RNA/protein ratios also had comparable characteristics, having peak values at days 10 and 16 in situ and in the histotypic cultures prepared from 10-day-old mice. These studies have demonstrated the correlation between the in vitro biochemical and morphological development and the significance of the critical period during hypothalamic neurogenesis for successful organotypic preparations.

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PubMed1983

In vitro and in situ formation of neuron-glia junctions.

The formation of neuron-glia junctions during neurogenesis has been considered as an error of the neuronal specificity mechanism or as a consequence of the artificial conditions when observed in central nervous system tissue culture. We report the demonstration of the regular existence of synaptic-like junctions in tissue cultures prepared from different regions of chick central nervous system as well as the occurrence of such intercellular contacts in the cerebellum of adult and normal frogs. The formation of neuron-glia junctions in tissue culture during normal neurogenesis and their presence in adult frogs seem to indicate that those types of neuron-glia relationships are not a simple biologic error. Rather, we propose that they may represent a primitive, but normal neuron-glia interaction.

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PubMed1982

In vitro development of chick hypothalamic neurosecretory cells.

The in vitro maturation of chick hypothalamic neurosecretory cells has been studied by the Golgi method and electron microscopy. Rotary cultures prepared from chick embryos aged 6, 8 and 10 days of development fail to assemble histotypic cultures; however, cultures prepared from older embryos, i.e. 12, 14 and 16 days of development, progressively exhibited more neurosecretory characteristics. It is interesting to point out that cultures prepared from 12-, 14- and 16-day-old chick embryos form complex surfaces composed of patches of glioepithelial cells alternating with zones containing neurosecretory nerve endings partially surrounded by glial processes. This particular distribution of the nerve endings seems to indicate that cytotypic hypothalamic neurons in rotary cultures deliver their products to the incubation medium; this interpretation is further reinforced by the observed exocytosis of the neurosecretory material within the external neuropile of histotypic cultures. Details of the neurosecretory cell maturation are given in the text.

Animals↗
PubMed1981

Synaptogenetic mechanisms during chick cerebellar cortex development.

Chick embryo cerebellar cortex development was analyzed in an attempt to visualize the fine ultrastructural changed involved in cortical synaptogenesis. Three major stages of synapses formation were detected during days 13 to 18 of maturation: intermembranous adherence, cytoplasmic recognition, and definitive synaptic formation period. The more primitive morphological event indicative of synaptic onset was the occurrence of external plaques; these plaques must have a negative charge since they accumulated cationized electron-dense tracers. These plaques favor the adhesions between parallel fibers and Purkinje cell dendrites. Once axonal and dendritic membranes adhered to form an adhesion contact, the dendritic half of this contact forms a pinocytic vesicle that incorporates part of the membrane of the axonic half of the contact. This particular pinosome delivers its content to different cytoplasmic organelles including the nucleus. At day 15 Purkinje cells significantly increase the number of dendritic-forming pinocytic vesicles; this phenomenon means that during this day a large amount of parallel fiber membrane is passed into the Purkinje cell cytoplasm. From day 15 to 16 postsynaptic densities begin to appear; ribosomes associated to these structures seem to be the origin of a progressively accumulated amorphous material composing the rare primitive postsynaptic densities. Some other morphological details related to these processes are given in the text.

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