P. Glees

Electron microscopical studies of the synapse in the developing chick spinal cord

SummaryA search for synaptic strutures in the developing spinal cord of the chick has been made with the help of the electron microscope. We used as criteria of identification the presence of a) a thickening of neuronal membrane in contact with one another b) mitochondria and c) a type of vesicle usually associated with synapses. Structures fulfilling some of these requirements apear at the five day incubation stage and are clearly present at the ten day stage. Fully matured axosomatic and axo-dendritic synapses of both types appear at 16–18 days.

Ultrastructural analysis of individual layers in the lateral geniculate body of the monkey

Summary1.The cellular and synaptic pattern of the lateral geniculate body of the monkey has been studied electronmicroscopically by using microdissected portions from individual layers. For general orientation and comparison the Golgi technique has been utilised extensively.2.This technique revealed four different types of neuron whose distribution differs in the various layers. The first type has 3–4 stem dendrites, which possess tiny side branches or appendages. The second type is smaller and has 8–10 stem dendrites. The third type is a Golgi type II cell with very long dendrites with bushy terminal arborisations. The fourth type are very small neurons and it is difficult to separate them from glial cells with certainty.3.The synaptic organisation has been examined in great detail, in particular the different composition of the glomeruli in different layers. Seven components of a glomerulus have been found whose individual contributions vary in different layers. These components are: main axon, main dendrite, peripheral axons, peripheral dendrites, dendritic and axonal thorns and glia lamellae.4.In addition to this synaptic pattern a further interesting synapse has been found, an axo-axonal type in contact with the initial segment of a large axon of a geniculate cell.Zusammenfassung1.Der zelluläre Aufbau und die synaptische Organisation einzelner Schichten des Corpus geniculatum laterale des Affen wurde mit der Golgi-Technik und elektronenmikroskopisch untersucht. Die kleinen Gewebsstücke aus verschiedenen Regionen einer bestimmten Schicht wurden für die Elektronenmikroskopie durch Mikrosektion nach vorheriger Anfärbung des ganzen Geniculatum präpariert.2.In Golgipräparaten lassen sich vier Neuronenarten unterscheiden, deren quantitative Verteilung in den Schichten verschieden ist. Die erste Art besitzt 3–4 Stammdendriten, die noch winzigste Seitenäste tragen. Die zweite Art ist kleiner und hat 8–10 Stammdendriten. Die dritte Art entspricht der Golgi-Zelle II. Ihre Stammdendriten sind sehr lang und mit dichten Endverzweigungen ausgestattet. Die vierte Zellart wird von kleinen, glia-ähnlichen Zellen gebildet. Diese lichtmikroskopischen Befunde sind für die elektronenmikroskopische Auswertung wertvoll.3.Die synaptische Organisation ist elektronenmikroskopisch analysiert worden, insbesondere die Zusammensetzung der Glomeruli. Sieben verschiedene neuronale und gliöse Fortsätze tragen dazu bei, aber ihre mengenmäßige Beteiligung ist für die einzelnen Schichten unterschiedlich. Diese Fortsätze setzen sich wie folgt zusammen: Ein Hauptaxon, ein Hauptdendrit, peripher gelegene kleinere Axone, peripher gelegene Dendriten, dornenartige Fortsätze der Dendriten und der Axone, Glialamellen.4.Eine weitere Synapsenart von besonderem Interesse zeigte sich in einer axo-axonalen Art, deren postsynaptische Teile von dem Initialsegment des efferenten Axons einer Geniculatumzelle gebildet werden.

Accumulation of lipofuscin in the myocardium of senile guinea pigs: Dissolution and removal of lipofuscin following dimethylaminoethyl p-chlorophenoxyacetate administration. An electron microscopic study

Abstract Ultrastructural investigations of the left ventricular myocardium of senile guinea pigs revealed marked accumulation of lipofuscin pigment. Dimethylaminoethyl p-chlorophenoxyacetate administration (daily 80 mg/kg of body weight i.m.) to guinea pigs for 30–90 days, caused dissolution as well as marked reduction in the size of the pigment. Pigment residuals were carried by phagocytic cells to the capillary wall and discharged into the lumen. These pigment alterations and their mode of transport were not found in the control group of guinea pigs.

Synaptic organization of the molecular and the outer granular layer in the motor cortex in the white mouse during postnatal development. A Golgi- and electronmicroscopical study

SummaryThe motor cortex of white mice has been studied from the first postnatal day up to an age of three weeks electronmicroscopically and with the Golgi method. Special attention has been paid to the dendritic organization in the molecular and outer granular layers. The following observations were made:1.Branching of the apical dendrites of neurons of the second layer occur already from the third day, whereas the basal dendrites start branching only at the end of the first week.2.The deeper laying cells of the second layer mature at an earlier stage than the more superficial cells.3.Immediately after birth, the first axodendritic synapses are found on the large stem dendrites. Their spines develop by the end of the first postnatal week. The spines of the apical dendrites develop before those of the basal ones.4.Axosomatic synapses are found on the cell bodies of the external granular layer in the second postnatal week.5.The development of the apical dendrites from the deeper layers (III–V) is an important factor in the maturation of the external layers. These dendrites have acquired their final number of spines by the end of the second week.6.During their development the dendrites of the third to fifth layer show intimate contact by mutual indentation. The cells of the second layer complete their maturation by the end of the third week.ZusammenfassungDer motorische Cortex von weißen Mäusen wurde vom ersten Tag nach der Geburt bis zum Alter von 3 Wochen mit Hilfe der Golgi-Methode und elektronen-mikroskopisch untersucht. Besonderes Interesse galt seiner dendritischen Organisation in Molekularis und äußerer Körnerschicht.Die apikalen Dendriten der Nervenzellen der II. Schicht verzweigen sich nach dem 3. Tag, die basalen Dendriten am Ende der 1. Woche.Die tiefgelegenen Zellen der zweiten Schicht reifen früher als die mehr oberflächlich liegenden Zellen. Die ersten axodendritischen Synapsen findet man unmittelbar nach der Geburt an den großen Stammdendriten. Ihre Dornen entwickeln sich am Ende der ersten postnatalen Woche. Die synaptischen Dornen der apikalen Dendriten entwickeln sich früher als jene der basalen.Die axosomatischen Synapsen finden sich an den Zellen der äußeren Körnerschicht im Laufe der 2. Woche. Einen wichtigen Faktor in der Ausreifung der beiden oberen Schichten stellt die Entwicklung der apikalen Dendriten der unteren Schichten (III–V) dar. Diese Dendriten entwickeln ihren endgültigen Dornenbesatz am Ende der 2. Woche.Die Dendriten der Schichten III–IV verzahnen sich im Laufe der Entwicklung eng miteinander. Ihre Ausreifung entspricht am Ende der 3. Woche den Verhältnissen bei der erwachsenen Maus.

Terminal degeneration in the lateral geniculate body of the monkey; An electron-microscope study

Summary1.The degeneration of optic terminals in the lateral geniculate body (LGB) has been studied in 16 monkeys after enucleation of one eye. In contrast to the results of our previous studies with the ligth-microscope, electronmicroscopical studies of normal and degenerated LGB now reveal complex synaptic structures, many of them arranged in synaptic islands.2.The presence of bulbous enlargement of synapses, the functional portion of terminals, occuring during the process of degeneration, previously reported, is confirmed. They are considered to be due to a marked fibrillisation of the cytoplasm.3.Other clear signs of synaptic degeneration besides the enlargement are the disappearance of synaptic vesicles and an irregular disintegration of the intersynaptic connecting (“cementing”) substance.4.Reactive neuroglia produce a complex of enveloped synaptic and myelin débris, penetrating normal neighbouring layers. Great care must be taken in interpreting late stages of degeneration.

The differentiation of endoplasmatic reticulum in developing neurons of the chick spinal cord

Summary1.We have failed in the early stages of development to separate neuroblasts from glioblasts with the means of electronmicroscopy. All cells forming the wall of the neural groove or tube have the same cytological structure seen in other primitive somatic cells.2.Some identification is possible around the 7th day of incubation when synaptic differentiation permits the recognition of neuroblasts.3.Neurons are characterised by a continuous and prolonged formation of granular ER which eventually becomes organized in parallel cisterns around the 14th–16th days when typical Nissl bodies can be recognized.

Der Einfluß des Centrophenoxins auf das Alterspigment in Satellitenzellen und Neuronen der Spinalganglien seniler Ratten

SummaryThe appearance and distribution of old age pigment in the neurons and satellite cells of the cervical spinal ganglions of senile rats were examined light- and electronmicroscopically after the rats had been treated for 4, 5, 8, 11 and 13 weeks with centrophenoxine. Untreated rats of the same age were also examined. Light microscopic examination of PAS-stained material revealed a decrease in the amount of old age pigment present in the neurones after eight or more weeks treatment. In the E.M. sections vacuolization of the pigment granules in the satellite cells could already be observed after four weeks treatment. After 8 weeks similar changes could be seen in the neurones, as well as a disintegration of the large accumulations of pigment in the perikarion type A neurones. The changes increased with length of treatment and led to a decrease in the total amount of pigment present. The possible causes of these changes and the probable route for the removal of old age pigment from nerve cells are discussed.ZusammenfassungAufbau und Vorkommen des Alterspigmentes in Neuronen und Satellitenzellen der cervicalen Spinalganglien seniler Ratten wurde licht- und elektronenmikroskopisch nach 4-, 5-, 8-, 11- und 13 wöchiger Centrophenoxinbehandlung untersucht und mit dem in gleichaltrigen Kontrolltieren verglichen. Lichtmikroskopisch fand sich am PAS-gefärbten Material eine Verminderung des Alterspigmentes nach 8 wöchiger und längerer Behandlungsdauer. Elektronenmikroskopisch ließen sich bereits nach 4 wöchiger Centrophenoxinbehandlung vacuolige Veränderungen an den Pigmentkörpern der Satellitenzellen feststellen. Gleichartige Veränderungen zeigten sich nach 8 wöchiger Behandlung auch an den Pigmenten der Nervenzellen. Gleichzeitig fanden sich die Pigmentkonglomerate in den Typ A-Neuronen in einem Zustand der Disintegration. Die Veränderungen nahmen mit der Dauer der Behandlung zu und führten zu einer Verminderung der Pigmentkörper. Die möglichen Ursachen der Veränderung bzw. Verminderung der Pigmentkörper werden diskutiert und der Weg eines etwaigen Abtransportes der Alterspigmente aus den Nervenzellen erörtert.

The effects of dimethylaminoethyl p-chlorophenoxyacetate on spinal ganglia neurons and satellite cells in culture. Mitochondrial changes in the aging neurons. An electron microscope study.

Abstract The formation and distribution of old age pigment in neurons and satellite cells of spinal ganglia in culture were studied electronmicroscopically, following daily application of the cultures, for 2–3 weeks, with dimethylaminoethyl p -chlorophenoxyacetate and compared with cultures of the same age. The relationship of the aging pigment to the mitochondria has been re-investigated. In the EM sections a fading out as well as conspicuous vacuolation of the pigment could be observed at the beginning of drug application. This was followed by disintegration and replacement of the pigment by fine osmiophilic granules leading to a diminution in the total amount of pigment present. Cytoplasmic processes and satellite cells transported the pigment to the interneural space. Further removal of the pigment occurred by means of phagocytes and proliferating endothelial cells of residual capillaries. The possible mitochondrial genesis of age pigment is discussed.

Early cytological differentiation in the cerebral hemisphere of mice

Summary1. The parietal region of the telencephalic vesicle of mice embryos and newborn mice has been studied electronmicroscopically. Special attention has been paid to developing glia cells. 2. In early stages it is impossible to differentiate neuroblasts from glioblasts. 3. Late pre-natal stages allow a recognition of glioblasts on account of their ultrastructure, as the overall structure of the nucleus and the cytoplasm of a glioblast has a greater electron-density than that of a neuroblast. 4. Glioblasts have a lobulated nucleus at this stage (20th day i.u.) while neuroblasts possess an ovoid nucleus. The quantity of endoplasmic reticulum and of the number of ribosomes is relatively greater in neuroblasts than in glioblasts.

Dissolution and removal of neuronal lipofuscin following dimethylaminoethyl p-chlorophenoxyacetate administration to guinea pigs

SummaryDimethylaminoethyl p-chlorophenoxy acetate (80 mg/kg body weight) was administered (i. m.) to guinea pigs for 30 to 56 days. Electron microscopic examination of the hippocampus, mid-brain reticular formation and the area postrema revealed marked diminution in the electron density of the pigment granules and vacuolization. This type of lipofuscin was detected in some phagocytic cells and in the capillary endothelium. Conspicuous vacuolization of the capillary wall was discernible. These changes were not observed in the “control group” of animals.