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Biomedical subjects

K Brauer

Publications and source records attributed to K Brauer.

At least 109 records · Page 6Linked to original sources
PubMed1978

Phylogenetical changes and functional specializations in the dorsal lateral geniculate nucleus (dLGN) of mammals.

Depending on their visual specialization and their place in the zoological system the mammalian species show some peculiarities in the morphology of the dorsal lateral geniculate nucleus (dLGN). The lamination of dLGN can be find in mammals with a highly developed visual system and a proportionally big part of ipsilaterally projecting retinogeniculate fibres. Number and sequence of ipsi- and contralaterally innervated laminae varies between species of different taxonomical categories. Hence these features depend on phylogenetical trends which could traced back to the beginning of the "mammalian radiation" in the cretaceous period and the earliest tertiary. Ancestral conditions may be found in mammals with an unlaminated dLGN and a medially located ipsilaterally innervated part. It may be registrated that a cytoarchitectonical separation of laminae (concerning the ipsi- and contralateral innervation) is the secondary step after fibre anatomical separation. The most primitive status may be realized in mammals having a zone of mixed ipsi- and contralateral fibre input. Some conclusions are made with regard to the suitability of lab mammals for generalization of results in the dLGN morphology.

Animals↗
PubMed1978

[Axon-like glial extensions in the pars ventralis of the corpus geniculatum laterale (CGLv) of the albino rat].

In sections of the Corpus geniculatum laterale, pars ventralis (CGLv) of adult albino rats impregnated according to Golgi-Kopsch, structures are visible very similar to long unbranched axons with large boutons en passage. Within the CGLv these axon-like structures can be followed parallel to the optic tract. Generally they take a ventro-dorsal, exceptionally a dorso-ventral course. As well in Golgi-Kopsch material as in sections in which glial cells are specifically impregnated the described structures could be traced to cells mainly located subpial in the Tractus opticus. Within the optic tract these axon-like structures change their appearance looking similar as the numerous other processes originating from these cells too. These other processes take a course right-angled to the optic fibers and in general they don't bear axon-like structures as described. In our opinion based also on investigations of Nissl-stained sections the origination cells represent a specialized type of astroglia of until now unknown function.

Afferent Pathways↗
PubMed1977

[Spine density of lamina V pyramidal cells in the visual cortex of laboratory rats after lengthy dark exposure].

1. The spine density was investigated at the apical dendrites of lamina-V-pyramidal cells in the visual cortex of rats following dark rearing for 250 days. 2. There are no significant differences in the average spine density between rats reared in darkness and normal conditions. 3. The results are discussed in view of the significant differences found after dark rearing for 50 days. It is assumed that these present results are caused by a delay in spine development in younger animals, which is compensated in the adult stage.

Animals↗
PubMed1977

[Investigations on the basal dendritic tree of lamina-V-pyramidal cells in the visual cortex of rats after destruction of the lateral geniculate body and after dark raising (author's transl)].

The basal dendritic trees of the lamina-V-pyramidal cells of rats were investigated after 1th unilateral destruction of the dorsal lateral geniculate body (Cgld) 2nd dark raising I. Animals with destroyed Cgld. Comparing the data of free dendritic terminations (FDE), branching points (VZP), number of segments (AdD) and length of segments (LdD) no significant differences have been remarked between--controls of the same litter (non-influenced side),--influenced sides of animals of the same litter. A significant difference between the ipsi- and contralateral hemispheres of animals with unilateral geniculate destruction. II. Dark raised animals There were no significant differences between dark raised animals, their controls and between dark raised animals and controls. The causes of postoperative changings have been discussed. Mainly retrograde degeneration effects may be responsible for the ascertained differences.

Animals↗
PubMed1976

[Electron microscopic and light microscopic studies of optical and cortical afferents in the lateral geniculate body, pars dorsalis, of albino rats with special attention to synaptic organization].

1. In the CGLd of the albino rat there are to be found two forms of retinal terminals in electronmicroscopic investigations, they are identical with 2a and 2b terminals described formerly in Golgi-preparations. 2. The small 2b terminals are situated previously in the extraglomerular neuropil, which is identical with the terminal part of P-neuron dendrites. They establish asymmetric GRAYtype I contacts with dendrites and spines of the relay-cell-dendrites. 3. The large 2a terminals form filamentous contacts with the smooth surfaces of the dendrites of the stem-and branching-zones. Synaptic contacts (GRAY I) are established with the grape-like appendages in the branching zone of P-neuron dendrites. 4. In the glomeruli of the CGLd there are three main components, which are the nerve endings of large optic axons, the interneuron dendritic terminals and the relay-cell-dendrites. They are surrounded by astrocytic processes. 5. In the extra-glomerular neuropil there are numerous small nerve endings, they form GRAY type I contacts with relay-cell-dendrites and their spines. They are partly identical with the type I endings in Golgi-preparations (cortical terminals). 6. After the eye enucleation and ablation of the visual cortex the type 2a and 2b and type 1 terminals degenerate. There are two forms of degeneration, the light and the dark one. 7. After eye enucleation two forms of degenerations in the degenerating retinal axons occur, which are the "watery" and the "dense" form. Besides the astrocytes the oligodendrocytes remove the destroyed particles. 8. The ultrastructural characteristics of the interneuronal dendritic terminals and their possible funktion are discussed. 9. There is added a table of the synonyma of CGLd structures.

Animals↗
PubMed1976

[Studies on the spine density in lamina V pyramidal cells of the visual cortex in young and subadult rats after dark-rearing and destruction of the dorsal nucleus in the lateral geniculate body].

1. Dark reared 50 days old rats have a significantly diminuished number of spines at the apical dendrite of the lamina-V-pyramidal cells in the visual cortex. 2. Likewise we could ascertain a significant diminution of spines after destroying the upsilateral Cgld. The topistical distribution of spine density differs in both investigated series. 3. The spine diminution at the apical dendrites of lamina-V-pyramidal cells differs in this way: pyramidal cells with thick apical dendrites show a weaker spine diminution than the pyramidal cells with thin apical dendrites. 4. Some topistical problems concerning specific afferents in the visual cortex are discussed.

Age Factors↗
PubMed1976

[Role of interneurons in the lateral corpus geniculatum in mammals].

1. This paper presents a summary of the morphological characteristics of I-neurons in the Cgld of mammals. These neurons consist of smaller somata and less dendrites being longer than the P-neurons. In all species investigated until now a short branched axon has been found. The dendritic structures show postsynaptic as well as presynaptic characteristics. 2. The innervation of I-neurons is not cleared up sufficiently. Besides retinal and cortical afferents, recurrent collaterals of P-neurons can be taken into account. Physiologists and morphologists give priority to retinal terminals. 3. The presynaptic dendrites of I-neurons are connected in triads with retinal terminals an P-neuron dendrites. Morphological and physiological findings open up the possibility of triads acting as "quasi interneurons" (HAMORI et al. 1974) and make the tonical activity change into the phasical one. 4. The endings of I-neuron axons being constantly presynaptic, synapse perferably at the somata of P-neurons and act presumably as inhibitors of P-neurons in the margin of a retinal input zone (surroundinhibition). In this connection quantitative considerations are carried out. 5. The morphological specializations of I-neurons are discussed in connection with their supposed physiological properties.

Animals↗
PubMed1975

[Columnar organization of pyramidal cells of the visual cortex in the albino rat].

1. The arrangement of the pyramidal cells of the visual cortex has been investigated by light and electron microscopy in 36 albino rats. 2. It was shown, that the apical dendrites form bundles. The number of dendrites per bundle is about 5 in the lower lamina Vb and 7.5 in the upper lamina Va, the diameter of bundles is about 25.7 mum. The average distance between the centers of bundles is 76,4 mum, and between the peripheries 53.1 mum. 3. The results are compared with physiological and morphological findings. It was shown, that there is an agreement of diameter of bundles und their lateral branching dendrites with diameters of columns of cells and of terminal branchings of specific afferents. 4. The morphological results are graphically reconstructed.

Animals↗
PubMed1975

[Relais cells and afferent axons in the dorsal part of the lateral geniculate body in the albino rat under geometrical aspects].

1. The average volumes of dendritic domaines of relay neurons (P-neurons) were calculated and the quantitative relations to the neuronal elements situated in this area were investigated. Likewise we carried out measurements and calculations at the terminal parts of afferent axons, to find a conception concerning possible contacts between axons and P-neurons considering quantitative aspects. 2. The dendrites of one P-neuron are distributed in an area of about 0,008 mum3. In this area there are located somata of at least 120 other P-neurons and dendrites of altogether about 900 P-neurons. 3. The type-1-axons (cortical afferents) run almost linearly in the longitudinal system of the CGLd. Traversing a distance adequate to the diameter of a P-neuron (250 mum) the dendrites of 150 to 170 P-neurons may cross the course of one axon. At this distance the axon, however, has just set up about 50 boutons, thus synaptic contacts may be established with one third at most of the existing cells. A type-1-axon that is bifurcating in the entrance area into the CGLd is altogether of about 2000 mum in length and is able to develop about 420 presynaptic profiles. 4. The type-2-axons (retinal afferents) show a distinct terminal branching zone. The Golgi-Kopsch impregnated terminals of type-2a-axons are distributed in a space of 147000 mum3 capacity, the corresponding terminals of type-2b-axons in a space of 443000 mum3. The type-2a-axons having an average number of 23 boutons, may contact the dendritic branching zones of 25 P-neurons. There is a good reason to assume that type-2b-axons are in contact also with terminal dendritic parts of P-neurons. Thus the number of P-cells, which spread their dendrites into the terminal branching zone of one type-2b-axon may amount to 540. The average number of boutons of one type-2b-terminal, however, is only about 160. This means that synaptic contacts may be developed to the P-neurons-dendrites not exceeding 30% of them. 5. Various aspects of divergence of axon terminals in the albino rat's CGLd are discussed.

Animals↗
PubMed1974

[Light and electron microscope investigation of axons and dendrites in the pars dorsalis of the corpus geniculatum laterale of the albino rat].

1. The neuronal elements of the GLD of the albinorat were investigated by Golgi-Kopsch and Golgi-Rapid methods. Furthermore the terminals of the tractus opticus were investigated by electron microscopy after eye enucleation. 2. The thalamo-cortical relay neurons have dendritic protrusions. These spine-like protrusions are to be found in the terminal parts of the dendrites. In contrast to spines in the pyramidal cells there is no thickening of the terminal part. Few relay cells have grape-like appendages in their branching zone. Only the initial segments of the axons of the P-neurons are visible. There is no evidence of recurrent collaterals. 3. The Golgi-type-2-neurons (interneurons, I-neurons) have less dendrites than the P neurons, but they are longer...

Animals↗