Early Postnatal Ages Research Articles

Catecholamine concentration in the developing rat brain after gamma-hydroxybutyric acid.

The effect of the GABA receptor agonist gamma-hydroxybutyric acid (GHBA) on brain catecholamine concentration was investigated in 1 to 28 day old rats. The infant rats were given GHBA in various doses (375--1500 mg/kg) and the effects on whole brain or regional brain concentration of dopamine (DA) and noradrenaline (NA) were measured. Brain DA concentration increased in a dose-dependent way already from two days of postnatal age. In the regional brain study of the 14- and 28-day-old animals the increase in DA concentration was found to be almost exclusively located in the striatal region. Generally, no changes in NA concentration were found in the whole brain or various brain regions at any of the ages after GHBA. It is concluded that the inhibitory striatal-nigral neurons, utilizing GABA as a transmitter, are functionally developed during early postnatal age.

Organization of developing precruciate corticostriate projections in kittens

We used silver impregnation and autoradiographic tracing methods to map the topographical distribution of precruciate corticostriate projections in kittens. These studies provided neuroatomical support for earlier physiological studies which showed that these pathways are well developed at early postnatal ages.

Developmental susceptibilities of rabbits to various biological activities of bacterial endotoxin.

The developmental plaarmacology of endotoxin (Escherichia coli UKT-b) inthe rabbit was studied. When newborn rabbits were kept at a high ambient temperatureat which its basal metabolism was considered minimal, a small but definite febrile responsewas observed to endotoxin administered intravenously (0.5 pg/kg), subcutaneously (l pg/kg)or intracisternally (0.1 ng/kg). At room temperature (25C), such a significant febrileresponse was not observed. The febrile response increased in magnitude with the advancein age. Susceptibilities to the lethal effect of intravenous or intracisternal endotoxin werehigh in rabbits from the lst to 3rd day of life. They decreased over a period from the 7thto 21st day of life. Thereafter, tltey increased with the advance in age. Neither skinreaction nor shock by endotoxin was observed in rabbits under 21 days of age. Theseresults suggested that the receptor-effector mechanisms to endotoxin might be developedfairly in the CNS, but very poorly in the peripheral organs of rabbits in the early postnatal age.

Immunological Distinction between Neurofilament and Glial Fibrillary Acidic Proteins by Mouse Antisera and Their Immunohistological Characterization (Part 2 of 2)

Antisera were raised in mice to the presumed protein subunits of the two types of 100 Ǻ filaments in nervous tissue, glial fibrillary acidic (GFA) protein and neurofilament (NF) protein. These antisera detect a pronounced antigenic distinction between these two proteins. Antiserum to GFA protein reacts only with astroglial cells and is therefore similar to antisera prepared in rabbits. Mouse antiserum to NF protein reacts with neurons and their processes known to be rich in 100 Ǻ filaments. Postsynaptic densities do not detectably react with anti-NF antiserum when assayed by the indirect immunoperoxidase method and studied at the electron microscopic level. The two antisera do not react with actin, myosin or tubulin containing non-neural or neural tissues. During development of the mouse nervous system, NF protein is immunohistologically detectable at embryonic day 13 (the earliest stage tested). GFA protein is not detectable with this method during embryonal development but becomes apparent only at early postnatal ages. In several species (rabbit, rat, chicken, fish, turtle, and frog) anti-NF protein antiserum only reacts with neurons, and anti-GFA protein antiserum stains glia exclusively. On the surface of trypsin-dissociated, single live cerebellar cells from 7-day-old mice, each antiserum detects antigenic specificities which are cross-reactive with its corresponding antigen.

Immunological Distinction between Neurofilament and Glial Fibrillary Acidic Proteins by Mouse Antisera and Their Immunohistological Characterization (Part 1 of 2)

Antisera were raised in mice to the presumed protein subunits of the two types of 100 A filaments in nervous tissue, glial fibrillary acidic (GFA) protein and neurofilament (NF) protein. These antisera detect a pronounced antigenic distinction between these two proteins. Antiserum to GFA protein reacts only with astroglial cells and is therefore similar to antisera prepared in rabbits. Mouse antiserum to NF protein reacts with neurons and their processes known to be rich in 100 A filaments. Postsynaptic densities do not detectably react with anti-NF antiserum when assayed by the indirect immunoperoxidase method and studied at the electron microscopic level. The two antisera do not react with actin, myosin oe nervous system, NF protein is immunohistologically detectable at embryonic day 13 (the earliest stage tested). GFA protein is not detectable with this method during embryonal development but becomes apparent only at early postnatal ages. In several species (rabbit, rat, chicken, fish, turtle, and frog) anti-NF protein antiserum only reacts with neurons, and anti-GFA protein antiserum stains glia exclusively. On the surface of trypsin-dissociated, single liver cerebellar cells from 7-day-old mice, each antiserum detects antigenic specificities which are cross-reactive with its corresponding antigen.

The postnatal development of the caudate nucleus: a golgi and electron microscopic study of kittens

This study used light and electron microscopy to describe changes in the synaptic organization of developing caudate nucleus and to quantitate postnatal synaptogenesis in this region. Observation at the light microscopic level focus on the perinatal period and suggest an early maturation of spiny interneurons of the caudate nucleus. Golgi impregnation of these cells at early postnatal ages (birth to 7 days) reveals 3-5 primary dendrites which radiate from the cell body and extend for distances of 8-16 micron before branching. Secondary dendritic branches contain spines and extend, with further branching, for additional distances of 60-160 micron. The dendritic fields of neighboring caudate neurons overlap and the axons which arise from these cells course and branch within the dendritic fields. Examination of perinatal caudate neuropil (birth to 5 days) by electron microscopy reveals an extensive and well-developed axodendritic connectivity. Axonal profiles form multiple synapses en passant along single dendrites and dendritic spines or on several adjacent dendritic branches. At these ages, terminals contain few synaptic vesicles and synaptic junctions are slightly asymmetrical. By the fifteenth postnatal day, boutons are filled with vesicles, junctional complexes are distinctly asymmetrical, and axondendritic connectivity has been modified by the increase of dendritic spines and branchlets. Thus, the basic pattern underlying the organization of synapses in the mature caudate nucleus, is established within the first week postpartum and subsequent changes are primarily quantitative.

Neuron-glia relationship during granule cell migration in developing cerebellar cortex. A Golgi and electronmicroscopic study in Macacus Rhesus.

AbstractThe cytology of the postmitotic migratory granule cell and its relationship to Bergmann glial processes was examined with Golgi staining and electron microscopy in the three cardinal planes in the developing cerebellar cortex of Macacus rhesus at various late fetal and early postnatal ages. After final mitosis the granule cell body transforms from a nearly round shape in the superficial zone of the external granular layer to a horizontal bipolar form with elongated processes oriented longitudinally to the folium, at the outer border of the molecular layer. Another descending process develops, and the cell soma becomes a pyramid flattened in the plane longitudinal to the folium. The nucleus moves into the descending process and the cell soma assumes a vertically oriented spindle shape while migrating among previously formed parallel fibers deeper in the molecular layer, and finally attains a round shape again when it lies deep to the Purkinje cell layer. During these transformations, the cell cytoplasm becomes more voluminous and contains a prominent Golgi apparatus, numerous free ribosomes, mitochondria, multivesicular and dense bodies, and fascicles of microtubules Longitudinally oriented microtubules concentrated in the vertical leading process disappear by the time the cell soma enters the granular layer. The slender trailing process loss most of its cytoplasmic organelles, acquires microtubules and together with the horizontal processes forms the characteristic T‐shaped axon. The axon forms synapses with Purkinje and stellate cell dendrites at a time when other granule cells are still migrating among them.During the entire course of their migration across the molecular layer, granule cells are directly apposed to vertically oriented Bergmann fibers belonging to the Golgi epithelial cells. The sequence of developmental stages indicates that Golgi epithelial cells are a type of protoplasmic astrocyte. The Bergmann fibers were present at all stages examined, and their constant apposition to granule cells suggests a role in the lartter's migration. Numerous electronluscent beady enlargements are seen along the fiber except at sites were the surface is in contact with migrating cells; probably these enlargements change position as the granule cells pass along the Bergmann fiber. Lamellate expansions also project from the main shaft of the glial fiber and envelop the synaptic sites on spines of Purkinje cell dendrites. These expansions seem more durable, and the young neuron appears to avoid collision with them by sprialling around the glial shaft during its descent to the granular layer. The neuron‐glia relationship apparently provides the necessary conditions for the migration of the young granule cell. Especially at late developmental stages when the molecular layer is more than 250 μ wide and is densely packed with highly oriented cell processes that have already established synaptic connections.

Persistent Changes in Vaginal Epithelium in Mice Induced by Short-Term Treatment with Estrogen Beginning at Different Early Postnatal Ages

Persistent Changes in Vaginal Epithelium in Mice Induced by Short-Term Treatment with Estrogen Beginning at Different Early Postnatal Ages