Mitochondrial degeneration after organic phosphate poisoning in prosimian primates

Summary The degenerative reaction of mitochondria to tricresylphosphate (TCP) poisoning in spinal ganglion cells of Slow Loris (Nycticebus coucang coucang) were studied with the electron microscope. In neurones of animals treated with TCP, mitochondria display various stages of alterations which confirm mitochondrial involvement in TCP poisoning. The role of degenerated mitochondria in the formation of neuronal lipofuscin is discussed. It is suggested that the lipofuscin granule is a metabolic product inherently related to mitochondrial degeneration, irrespective of the primary cause: ageing or intoxication.Fellow of the Deutscher Akademischer Austauschdienst on study leave from the Medical Faculty, University of SingaporeA grant from the Deutsche Forschungsgemeinschaft (Gl. 28/20) is gratefully acknowledgedThe skilfull technical assistance of Mr. Tajuddin b.M. Ali, Mr. P. Gopal, Mr. R. Dungan and Mrs. C. Weinrichter is gratefully acknowledged     

Schistosoma mansoni: uptake of exogenous hemeproteins by schistosomules grown in vitro

The uptake and fate of the hemeproteins horseradish peroxidase (HRPO) and hemoglobin (Hb) by schistosomules of Schistosoma mansoni maintained in vitro were studied by electron microscopy and cytochemical techniques. After administration of HRPO, reaction product was observed initially in the lumen of the digestive tract, and, after 2 hr of feeding, reaction product was also visible in the cytoplasm of the gastrodermis. There was no evidence of pinocytosis. After administration of Hb, reaction product was observed only in the lumen of the digestive tract. As is found following red blood cell feeding, digestive pigment was formed in the lumen of the gut following Hb feeding. The possible significance of these findings is discussed.     

Similar molecules spatially correlate with lipofuscin and N-retinylidene-N-retinylethanolamine in the mouse but not in the human retinal pigment epithelium

The accumulation of lipofuscin in the retinal pigment epithelium (RPE) has been implicated in the development of age-related macular degeneration (AMD) in humans. The exact composition of lipofuscin is not known but its best characterized component is N-retinylidene-N-retinylethanolamine (A2E), a byproduct of the retinoid visual cycle. Utilizing our recently developed matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI–IMS)-based technique to determine the spatial distribution of A2E, this study compares the relationships of lipofuscin fluorescence and A2E in the murine and human RPE on representative normal tissue. To identify molecules with similar spatial patterns, the images of A2E and lipofuscin were correlated with all the individual images in the MALDI–IMS dataset. In the murine RPE, there was a remarkable correlation between A2E and lipofuscin. In the human RPE, however, minimal correlation was detected. These results were reflected in the marked distinctions between the molecules that spatially correlated with the images of lipofuscin and A2E in the human RPE. While the distribution of murine lipofuscin showed highest similarities with some of the known A2E-adducts, the composition of human lipofuscin was significantly different. These results indicate that A2E metabolism may be altered in the human compared to the murine RPE.     

Pigment architecture of the human telencephalic cortex

Summary Cortical lamination and parcellation of the retrosplenial region in the human brain is evaluated with the aid of frontal serial sections stained for nerve cells (15 m), myelin sheaths (100 m), and lipofuscin granules (800 m).For the most part, the retrosplenial region is buried in the depth of the sulcus corporis callosi covering the posterior parts of the cingulate gyrus. It lies between the supracallosal derivatives of the allocortex (fascia dentata, cornu ammonis, subiculum) and the mature parietal isocortex.The region can be subdivided into five areas. The transitory periallocortical Area ectosplenialis is followed by a richly differentiated proisocortical core displaying extremely externopyramidal, externoteniate, and astriate to unitostriate characteristics. The parvocellular core is averagely poor in pigment (Typus clarus) and rich in myelinated fibres (Typus dives). Minor structural differences allow for its subdivision into a lateral, an intermediate, and a medial retrosplenial field. The accompanying Area parasplenialis is adjacent to the equoteniate parietal isocortex. It is only weakly externopyramidal, externoteniate, and propebistriate. The already homotypical field shows an average pigmentation and myelin content. These structural features permit its classification as a belt area of the retrosplenial core.Supported by grants from the Deutsche Forschungsgemeinschaft     

Lysosomes in iron metabolism,ageing and apoptosis

The lysosomal compartment is essential for a variety of cellular functions, including the normal turnover of most long-lived proteins and all organelles. The compartment consists of numerous acidic vesicles (pH ∼4 to 5) that constantly fuse and divide. It receives a large number of hydrolases (∼50) from the trans-Golgi network, and substrates from both the cells’ outside (heterophagy) and inside (autophagy). Many macromolecules contain iron that gives rise to an iron-rich environment in lysosomes that recently have degraded such macromolecules. Iron-rich lysosomes are sensitive to oxidative stress, while ‘resting’ lysosomes, which have not recently participated in autophagic events, are not. The magnitude of oxidative stress determines the degree of lysosomal destabilization and, consequently, whether arrested growth, reparative autophagy, apoptosis, or necrosis will follow. Heterophagy is the first step in the process by which immunocompetent cells modify antigens and produce antibodies, while exocytosis of lysosomal enzymes may promote tumor invasion, angiogenesis, and metastasis. Apart from being an essential turnover process, autophagy is also a mechanism by which cells will be able to sustain temporary starvation and rid themselves of intracellular organisms that have invaded, although some pathogens have evolved mechanisms to prevent their destruction. Mutated lysosomal enzymes are the underlying cause of a number of lysosomal storage diseases involving the accumulation of materials that would be the substrate for the corresponding hydrolases, were they not defective. The normal, low-level diffusion of hydrogen peroxide into iron-rich lysosomes causes the slow formation of lipofuscin in long-lived postmitotic cells, where it occupies a substantial part of the lysosomal compartment at the end of the life span. This seems to result in the diversion of newly produced lysosomal enzymes away from autophagosomes, leading to the accumulation of malfunctioning mitochondria and proteins with consequent cellular dysfunction. If autophagy were a perfect turnover process, postmitotic ageing and several age-related neurodegenerative diseases would, perhaps, not take place.     

Lipofuscin Accumulation in Cultured Retinal Pigment Epithelial Cells Causes Enhanced Sensitivity to Blue Light Irradiation

Lipofuscin accumulates with age within secondary lysosomes of retinal pigment epithelial (RPE) cells of humans and many animals. The autofluorescent lipofuscin pigment has an excitation maximum within the range of visible blue light, while it is emitting in the yellow-orange area. This physico-chemical property of the pigment indicates that it may have a photo-oxidative capacity and, consequently, then should destabilize lysosomal membranes of blue-light exposed RPE. To test this hypothesis, being of relevance to the understanding of age-related macular degeneration, cultures of heavily lipofuscin-loaded RPE cells were blue-light–irradiated and compared with respect to lysosomal stability and cell viability to relevant controls. To rapidly convert primary cultures of RPE, obtained from neonatal rabbits, into aged, lipofuscin-loaded cells, they were allowed to phagocytize artificial lipofuscin that was prepared from outer segments of bovine rods and cones. Following blue-light irradiation, lysosomal membrane stability was measured by vital staining with the lysosomotropic weak base, and metachromatic fluorochrome, acridine orange (AO). Quantifying red (high AO concentration within intact lysosomes with preserved proton gradient over their membranes) and green fluorescence (low AO concentration in nuclei, damaged lysosomes with decreased or lost proton gradients, and in the cytosol) allowed an estimation of the lysosomal membrane stability after blue-light irradiation. Cellular viability was estimated with the delayed trypan blue dye exclusion test. Lipofuscin-loaded blue-light–exposed RPE cells showed a considerably enhanced loss of both lysosomal stability and viability when compared to control cells. It is concluded that the accumulation of lipofuscin within secondary lysosomes of RPE sensitizes these cells to blue light by inducing photo-oxidative alterations of their lysosomal membranes resulting in a presumed leakage of lysosomal contents to the cytosol with ensuing cellular degeneration of apoptotic type. The suggested mechanism may have bearings on the development of age-related macular degeneration. © 1997 Elsevier Science Inc.     

Zur Pigmentarchitektonik der Großhirnrinde des Menschen

Zusammenfassung Mit Hilfe einer neu entwickelten Methode zur Darstellung von Neurolipofuscinen werden die am Aufbau des Subiculum beteiligten Zellschichten elektiv hervorgehoben. Da sich die Methode auf die Darstellung nur einer Cytoplasmakomponente beschränkt, werden Unterschiede zwischen den verschiedenen Nervenzelltypen stärker betont als im Nisslbild. Weiterhin lassen sich bis zu 800 dicke Schnitte verwenden die — unter dem Stereomikroskop betrachtet — die Verfolgung und Grenzbestimmung der einzelnen Zellschichten außerordentlich erleichtern.Im Pigmentbild stellt sich das Subiculum nicht als eine Übergangsrinde zwischen dem Cornu ammonis und den entorhinalen Feldern dar, sondern erscheint als eine eigene Region innerhalb der Ammonsformation mit kennzeichnenden Zellschichten, die in den benachbarten Feldern nicht vorkommen. Diese eigenständigen Schichten werden durch unmittelbar aufeinanderfolgende Lagen großer und mittelgroßer Pyramidenzellen gebildet (Lamina pyramidalis externa und interna subiculi). In den großen Subiculumneuronen des äußeren Blattes finden sich neben Pigmentanhäufungen im apikalen Cytoplasma vor allem bemerkenswerte Lipofuscinkonzentrationen in den mittleren Abschnitten der Spitzendendriten, ein Verteilungsmuster, das im Zentralnervensystem des Menschen nur selten angetroffen wird. Die Neurone der Lamina interna speichern demgegenüber das Lipofuscin nur im Zelleib.Die beiden eigenständigen Subiculumschichten werden durch das Eindringen fremder Zellschichten aus der Umgebung ergänzt. Zellwolken aus dem Praesubiculum schieben sich in der Lamina zonalis weit in den Subiculumbereich vor. Außerdem wird ein Randabschnitt des Subiculum von Abkömmlingen der inneren Hauptschicht aus der Regio entorhinalis unterlagert (Pri- und Pri-). Vom Sektor CA I (h₁) her schieben sich Ammonspyramiden über die Lamina pyramidalis externa subiculi.Alle Schichten verändern kontinuierlich ihre Breite, so daß die Zusammensetzung der Rinde örtlich großen Veränderungen unterworfen ist und kein Punkt innerhalb dieser Region einem anderen gleicht.Das Subiculum des Menschen besteht aus einem langgestreckten flügelförmigen Areal zwischen Cornu ammonis und Regio entorhinalis, bzw. praesubicularis, und einem schalenförmigen Abschnitt im Gyrus uncinatus. Beide sind an ihrem rostromedialen Pol miteinander verbunden. In diesem Areal grenzen wir mit Hilfe der Pigmentarchitektonik acht Felder gegeneinander ab.Im Bereich des sechsschichtigen s _med.oral. werden die beiden eigenständigen Zellblätter von Zellwolken und -platten aus dem Praesubiculum und den Schichten Pri- und Pri- aus der Regio entorhinalis zangenartig eingefaßt. Die Zahl der Schichten wird in s _med.caud. durch das Verschwinden der entorhinalen Zellamellen reduziert. Das seitliche Feld ist dadurch gekennzeichnet, daß Neurone des Cornu ammonis in wechselnder Breite die Lamina pyramidalis externa subiculi überdecken. Da die äußere Schicht der großen Subiculumneurone nicht so weit nach lateral reicht wie die innere Schicht, läßt sich ein großflächiges vierschichtiges Zentralfeld (s _lat.centr. ) von einem schmalen dreischichtigen Randstreifen (s _lat.marg. ) unterscheiden.Im Gyrus uncinatus wiederholen sich die genannten Felder in leicht abgewandelter Form. Dementsprechend findet sich ein mediales Feld (s _g.u.med. ) mit Praesubiculuminseln und Pri- und ein laterales Areal (s _{g.u.lat.centr.,marg.} ) mit CA-I-Neuronen. In Richtung auf den Limbus Giacomini ist eine weitere weniger hoch differenzierte vierschichtige Randzone entwickelt (s _g.u.dors. ), die aus Zellmaterial des Gyrus intralimbicus und des Subiculum besteht.

---

Summary By means of a newly developed method demonstrating neurolipofuscines the cellular layers constituting the subiculum are stained selectively. Since this method is confined to the demonstration of one cytoplasmic component, differences between various types of neurons show up more clearly than in Nisslpreparations. In addition up to 800 thick sections can be used which—if viewed at under the stereomicroscope—facilitate the recognition and identification of borders of cortical cellular layers.Pigmentarchitecturally the subiculum does not appear as a transitory zone between ammonsformation and entorhinal areas, but represents an own region within the ammonsformation with characteristic cellular layers which are absent in neighbouring fields. These autochthonous layers are constituted by large and medium sized pyramidal cells (lamina pyramidalis externa and interna subiculi), which lie closely together. In the large subicular neurons of the outer lamina beside pigment accumulations in the apical cytoplasm, above all remarkable concentrations of lipofuscin in the middle parts of the apical dendrites are to be found. This pattern of distribution is only rarely to be encountered in the central nervous system of man. The neurons of the lamina interna on the contrary store their lipofuscin in the perikaryon.The two autochthonous subicular layers are completed by the invasion of foreign cellular layers from the surrounding fields. Cell islands from the praesubiculum penetrate far into the lamina zonalis of the subiculum. Further on a marginal part of the subiculum is underlain by derivatives of the inner principal layer of the regio entorhinalis (Pri- and Pri-). Ammonspyramids from CA I (h₁) overlie the lamina pyramidalis externa subiculi.All layers change continuously their width, so that the appearance of the cortex is submitted to extensive local alterations.The subiculum of man consists of an elongated wingshaped area between cornu ammonis and regio entorhinalis, or praesubiculum respectively, and a cupshaped part in the gyrus uncinatus. Both are connected at their rostromedial poles. In this region on the basis of the pigmentarchitecture eight areas are to be separated.In the six-layered s _med.oral. the two autochthonous cellular layers are embraced by cell-clouds and -plates from the praesubiculum and the layers Pri- and Pri- from the regio entorhinalis. The number of the layers in the s _med.caud. is reduced by the disappearance of the entorhinal laminae. The lateral field is characterised by the fact that the lamina pyramidalis externa subiculi is covered in various extent by neurons of the cornu ammonis. Since the outer layer of the large subiculum neurons does not extend so far laterally as the inner layer, a large four-layered central field (s _lat.centr. ) can be distinguished from a narrow three-layered marginal strip (s _lat.marg. ).In the gyrus uncinatus the same fields can be found, however in a slightly modified form. Thus a medial field (s _g.u.med. ) with presubicular islands and Pri- and a lateral area (s _{g.u.lat.centr.,marg.} ) with CA I neurons are to be detected. In the direction of the limbus Giacomini a further less highly differentiated four-layered marginal area (s _g.u.dors. ) is developed which consists of material of the gyrus intralimbicus and the subiculum.

Mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft.     

The effect of dietary antioxidants on lipofuscin accumulation in the crustacean brain

Lipofuscin accumulation is associated with ageing at the subcellular level. A strong correlation between lipofuscin and age has been found in crustaceans using histological techniques. This association has been proposed as the basis for a methodology to age crustaceans and in some cases lipofuscin levels were found to be better correlated with age than size. The experiment presented here was designed to test the potential effect of diet, in particular dietary antioxidants, on lipofuscin accumulation and age estimation.The shrimp, Penaeus japonicus, was reared in an aquaculture facility and fed commercial pellets with modified vitamins C and E contents. One group was fed with levels of vitamins C and E of 1000 and 150 mg/kg, respectively, and another group with 2500 and 5000 mg/kg, respectively. The experiment started when the shrimp were 19 weeks old. Samples were obtained at this point and at ages 33 and 43 weeks. Lipofuscin was measured in the nerve cords (antennal neuropils and oesophageal connectives) in an area adjacent to the brain.Dietary antioxidants significantly affected lipofuscin levels. High vitamin content in the diet resulted in lower percentage of the observed area covered with lipofuscin, lower lipofuscin granule density and lower average granule size. Gender had no effect on any of these variables and granule size did not significantly change within each treatment. Lipofuscin area and granule density increased with age in both vitamin treatments.These results suggest that age estimation using lipofuscin indices may be biased when: (1) wild populations are dispersed over diverse environments; (2) the age estimation of wild individuals is based on the results obtained using laboratory-reared individuals.     

Zur Pigmentarchitektonik der Großhirnrinde des Menschen

Zusammenfassung Mit Hilfe einer neu entwickelten Methode zur Darstellung der Neurolipofuscine werden die am Aufbau der Regio entorhinalis beteiligten Zellschichten elektiv hervorgehoben. Bei einem solchen Vorgehen werden die Unterschiede zwischen den einzelnen Zellarten stärker betont als im Nisslbild, weil nur eine Cytoplasmakomponente dargestellt wird. Diese Beschränkung erlaubt zugleich die Verwendung sehr dicker Schnitte (bis zu 800 ), die — aufgehellt — unter dem Stereomikroskop analysiert werden. Auf diese Weise lassen sich Verfugungen aneinandergrenzender Rindenregionen und Kantenbildungen einzelner Rindenschichten sicher erfassen.Die Schichten des Allocortex unterscheiden sich im Pigmentbild deutlich von denen des Isocortex. Sie gehen nicht kontinuierlich ineinander über. Die Rinde der Regio entorhinalis läßt sich in eine Lamina principalis externa (Pre) und eine Lamina principalis interna (Pri) gliedern. Die äußere und innere Hauptschicht sind meist durch einen zellarmen Faserstreifen (Lamina dissecans) voneinander getrennt. Beide Schichten lassen sich weiter unterteilen (Pre- Pre-, Pre-, Pri-, Pri-, Pri-).In der Regio entorhinalis des Menschen werden 16 Felder pigmentarchitektonisch voneinander unterschieden. Davon bestehen 11 Felder ausschließlich aus allocorticalen Schichten, während die restlichen Areae, welche den Übergang zum Isocortex bilden, aus einer wechselnden Zahl allo- und isocorticaler Zellschichten zusammengesetzt sind.Im Bereich des Gyrus parahippocampalis lassen sich 7 rein allocorticale Felder voneinander abgrenzen. Die Areae gruppieren sich ringartig mit stufenweise abnehmender Organisationshöhe um ein hoch differenziertes Zentrum, das im oralen und lateralen Bezirk der Regio entorhinalis liegt. Das kennzeichnende Merkmal für die zentralen Felder ist eine Aufspaltung von Pri- in drei Schichten (Pri-, Pri-, Pri-). In dem Feld e _{centr. lat.} sind alle drei Unterschichten der Lamina principalis externa enthalten, während in e _{centr. med.} Pre- fehlt. Die angrenzenden Felder mit einheitlichem Pri- lassen sich wieder in Arae mit Pre- (e _{interpol.lat.} , e _caud. ) und ein Gebiet ohne Pre- (e _{interpol. med.} ) gliedern. In den rostralen und medialen Abschnitten verschmelzen Pri- und Pri- zu einer einheitlichen Zellschicht und bilden damit das Feld e _oral. . An der Grenze zum Gyrus ambiens in Nähe des Sulcus rhinencephali inferior findet sich ein schmaler Rindenstreifen, in dem die Schichten der Lamina principalis externa nur mangelhaft ausgebildet sind. Diese limitrophe Zone setzt sich nach caudal in das Grenzfeld zum Praesubiculum (e _{marg. caud.} ) fort.Eine ähnliche areale Gradation wie im Gyrus parahippocampalis findet sich auch unter den vier Feldern des Gyrus ambiens. Das am höchsten organisierte Feld (ga _centr. ) liegt im caudalen und medialen Abschnitt und ist durch eine dreischichtige Lamina principalis interna und eine deutliche Lamina cellularis profunda ausgezeichnet. Im angrenzenden Feld ga _lat. ist Pri- stark reduziert. In ga _oral. findet sich nur eine einschichtige Lamina principalis interna. Der Grenzstreifen zum Mandelkernkomplex (e _{marg. oral.} ) besteht nur aus Teilen der äußeren Hauptschicht.Der breite Übergangsbereich von den rein allocorticalen Feldern der Regio entorhinalis bis zum Isocortex wird in vier Areae unterteilt, in denen allo- und isocorticale Schichten fugenartig ineinandergreifen. Die Stufungen ergeben sich dadurch, daß die einzelnen Zellamellen unterschiedlich weit vordringen. Eine modifizierte äußere Körnerschicht reicht bis in das Feld e _{trans. med.} ; zugleich wird Pre- in tiefer gelegene Rindenschichten verlagert. An der Grenze zu e _{trans. intermed.} endet Pre-. Die Spindelzellschicht beteiligt sich als ein weiteres isocorticales Element am Aufbau des intermediären Übergangsfeldes. Die seitlichen Kanten von Pre- und Pri- bilden die lineare Grenze zum lateralen Übergangsfeld, e _{trans. lat.} , dessen Struktur durch das Hinzutreten einer äußeren und inneren Pyramidenschicht bereits weitgehend dem Isocortex gleicht. Im Feld e _{trans. caud.} findet sich sowohl die Spindelzellschicht als auch Pre-. Es bildet damit eine Stufung zwischen dem medialen und intermediären Übergangsfeld, die jedoch nur im caudalen Abschnitt der Regio entorhinalis am Übergang zum Praesubiculum vorhanden ist.

---

Pigmentarchitecture of the human cortex cerebriI. Regio entorhinalis

Summary By means of a newly developed method demonstrating neurolipofuscines the cellular layers constituting the regio entorhinalis are stained selectively. The differences between the individual cell types show up more clearly than in ordinary Nissl-preparations since by the new technique only one cytoplasmic component is stained. This limitation allows at the same time to use rather thick sections (up to 800 ), which — after clearing — are studied under the stereoscopic microscope. Thus indentations of neighbouring regions of the cortex and the edgelike formations of individual cortical layers can be demonstrated with certainty.The pigmentarchitecture of the allocortical layers differs clearly from that of the isocortex. The layers of the allocortex are not continuous with those of the isocortex. Within the regio entorhinalis the cortex can be divided into a lamina principalis externa (Pre) and a lamina principalis interna (Pri), which are separated by a narrow zone of fibers (lamina dissecans). The two main layers can be further subdivided (Pre-, Pre-, Pre-, Pri-, Pri-, Pri-).In the regio entorhinalis of man 16 areas can be distinguished by their pigmentarchitecture. 11 of these areas consist exclusively of allocortical layers, whereas the other areas which form the transitory part to the isocortex consist of various numbers of allo- and isocortical layers.In the region of the gyrus parahippocampalis 7 purely allocortical areas can be separated from each other. These areas are grouped in gradually decreasing levels of organisation round a highly differentiated center, which lies in oral and lateral parts of the regio entorhinalis. The characteristic feature of the central areas is a splitting of Pri- into three layers (Pri-, Pri-. Pri-). The area: e _{centr. lat.} contains all three sublayers of the lamina principalis externa, whereas in e _{centr. med.} Pre- is lacking. The neighbouring areas with uniform (not subdivided) Pri- can again be separated in areas with Pre- (e _{interpol. lat.} , e _caud. ) and a field without Pre- (e _{interpol. med.} ). In the rostral and medial parts Pri- and Pri- fuse forming an uniform cellular layer constituting the area: e _oral. . At the border of the gyrus ambiens near the sulcus rhinencephali inferior a narrow strip of cortex is to be found, in which the layers of the lamina principalis externa are only poorly developed. This limitrophic zone continues caudally into the border area to the praesubiculum (e _marg.caud. ).A similar areal gradation as in the gyrus parahippocampalis can be found in the four fields of the gyrus ambiens. The area with the highest organisation (ga _centr. ) is situated in the caudal and medial part of the gyrus ambiens and is characterised by a three layered lamina principalis interna and a clearly recognisable lamina cellularis profunda. In the neighbouring field ga _lat . Pri- is considerably reduced. In ga _oral. only an one layered lamina principalis interna is to be found. The border field to the amygdala (e _marg.oral. ) consists only of parts of the lamina principalis externa.The broad transitory region from the exclusively allocortical fields of the regio entorhinalis to the isocortex can be subdivided into four areas, in which allo- and isocortical layers meet in a zone of mutual indentations. The subdivision of the area is based on the different distances of penetration of the individual cellular layers. A modified lamina granularis externa extends into the field e _{trans. med.} ; at the same time Pre- is translocated into deeper cortical regions. At the border to e _{trans. intermed.} Pre- terminates. The lamina multiformis (VI) takes part as a further isocortical element in the construction of the area: e _{trans. intermed.} . The lateral edges of Pre- and Pri- form the linear border to the lateral transitory area (e _{trans. lat.} ), the structure of which resembles considerably that of the isocortex by additional appearance of a lamina pyramidalis externa and interna. In the area e _{trans. caud.} a lamina multiformis as well as the cellular layer Pre- is to be found, thus constituting a gradation between e _{trans. med.} and e _{trans. intermed.} , which, however, is present only in the caudal portions of the regio entorhinalis at the border to the praesubiculum.

Mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Neuronal types in the lateral geniculate nucleus of man

Summary Nerve cell types of the lateral geniculate body of man were investigated with the use of a transparent Golgi technique that allows study of not only the cell processes but also the pigment deposits. Three types of neurons have been distinguished:Type-I neurons are medium-to large-sized multipolar nerve cells with radiating dendrites. Dendritic excrescences can often be encountered close to the main branching points. Type-I neurons comprise a variety of forms and have a wide range of dendritic features. Since all intermediate forms can be encountered as well, it appears inadequate to subdivide this neuronal type. One pole of the cell body contains numerous large vacuolated lipofuscin granules, which stain weakly with aldehyde fuchsin.Type-II and type-III neurons are small cells with few, sparsely branching and extended dendrites devoid of spines. In Golgi preparations they cannot be distinguished from each other. Pigment preparations reveal that the majority of these cells contains small and intensely stained lipofuscin granules within their cell bodies (type II), whereas a small number of them remains devoid of any pigment (type III). Intermediate forms do not occur.