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M Frotscher

Publications and source records attributed to M Frotscher.

211 records · Page 12Linked to original sources
PubMed1978

[Relationship between the environment and pyramidal neuron differentiation in the hippocampus (CA 1) of the rat. Differentiation of apical lateral and basal dendrites].

A total of 60 newborn Wistar-rats was divided into three groups, each of which was exposed to a different environmental situation. The first group was reared in complete darkness while the second one was subjected to permanent noise. The third group (controls) was reared under normal laboratory conditions. The animals of all three groups were sacrificed on postnatal day 15 and prepared according to the Golgi-Kopsch technique. Apical oblique dendrites and basal dendrites of hippocampal pyramidal cells (CA 1 region) were ranked in a centrifugal ordering system for measurements of dendritic length and for spine counts. In the successive dendritic orders as well as in the dendritic field (all branches of a dendrite arising from the cell body or main apical shaft) no statistically significant differences between the groups were found with regard to dendritic length. The spine counts, however, revealed significant changes. In the dark reared group, the number of spines on oblique dendrites as well as on basal dendrites is significantly decreased in comparison with the controls. On the contrary, animals subjected to permanent noise exhibit significantly more spines on oblique and basal dendrites when compared with the controls (mean number of spines in the apical dendritic field: controls 30.1 +/- 26.9, dark reared animals 17l1 +/- 15.4 (-43.2%), animals subjected to noise 36.4 +/- 31.4 (+ 20.9%); basal dendritic field: controls 82.2 +/- 70.1, dark reared animals 47.3 +/- 35.1 (-42.5%), animals exposed to noise 114,1 +/- 94.6 (+ 38.8%)). These results confirm previous studies on the number of spines along the main apical shaft of CA 1 pyramidal cells (Frotscher et al. 1975) and on the number of synapses in the stratum radiatum of CA 1 (Frotscher et al. 1977) in rats reared under identical experimental conditions. On the basis of these results it seems to be obvious that synaptogenesis in the hippocampus is influenced by the environmental conditions used though this region is not directly involved in the optic or in the acoustic pathway.

Acoustic Stimulation↗
PubMed1978

[Quantitative electron microscopic studies of the environment dependent differentiation of synapses in the hippocampus (CA 1) of the rat].

The influence of environmental factors on synaptogenesis in the rat hippocampus (stratum radiatum of CA 1) was studied by the aid of quantitative electron microscopy. Three groups of newborn Wistar-rats were exposed to different environmental conditions (sensory deprivation and stimulation, respectively). The first group was raised in complete darkness while the second was exposed to permanent noise. The third group (controls) was reared under normal laboratory conditions. The animals were sacrificed either on the 15th or on the 35th postnatal day and prepared for electron microscopy. In the 15 day old dark raised animals the number of synapses in the stratum radiatum of CA 1 was significantly decreased by 24% in comparison with the normal. On the other hand, 15 day old rats exposed to permanent noise exhibit significantly more synapses (+ 28%) in the stratum radiatum of CA 1 (the mean number of synapses/25 micrometer 2 is 4,30 +/- 1,85 in the controls, 3,29 +/- 1,66 in the dark raised group and 5,52 +/- 2,35 in the animals subjected to permanent noise). No significant differences in the number of synapses between experimental animals and controls could be found in 35 day old rats. In accordance with earlier studies on the development of dendritic spines in hippocampal neurons the results of the present paper indicate an environment-dependent differentiation of synaptic structures in the hippocampus of the rat during the early postnatal period.

Animals↗
PubMed1976

[Neuron structure of the rat septum telencephali].

1. The neuronal structure of the septum of adult rats was studied after GOLGI impregnation. On the basis of cytoarchitectonic investigations the septum of the rat was divided into three big nuclei: nuclei septalis lateralis, septalis medialis, and tractus diagonalis (s. ANDY and STEPHAN). 2. The nc. septalis medialis contains cells with pyramidal, oval, round, spindle-shaped, fusiforme or triangular pericarya, while in the nc. septalis lateralis cells with pyramidal pericarya are absent. In the nc. tractus diagonalis four different forms of cells bodies occur: oval, triangular, round, and parymidal ones. 3. The existence of single, characteristic cell forms is not restricted to certain areas within a nucleus; the different kinds of cells are distributed irregularly and arranged ina different distance. 4. Mostly after a dichotome division the dendrites spread into all directions (bipolar to star-shaped dendritic arborisation). An orientation of the dendrites of single neurones into a special direction (i.e. to the ventricle) was not observed. 5. Neurons of the septum have dendritic fields with a mean diameter of 300 mum. The dendritic diameter regularly remains constant in the distance between two branchings and decreases only after the division of the dendrite. 6. The distribution of spines on the dendrites is typical for interneurons. Immediately after their origin from the pericaryon the dividing dendrites have a segment free of spines which extends up to the first outgrowth of a lateral dendrite. In neurons with poorly ramified dendrites this spines-free segment is absent; the first spines are found close by the pericaryon. Bferore and after a ramification of dendrites a different density of spines exists. 7. The neurons of the septum are morphologically and functionally classified as interneurons. Their dendritic fields correspond to those of star cells and are even similar to pyramidal cells. For the cell types described a great structural variability in the dentritic arrangement occurs.

Animals↗
PubMed1975

[Postnatal development of Rattus norvegicus B. cortical neurons and the influence of trauma].

The differentiation of the pyramid neurons during ontogenesis and the effects of a trauma on the process of neuron differentiation and synaptogenesis were investigated in the rat cerebral cortex after Golgi-impregnation. 1. There are temporal differences in the differentiation of the processes of cortical neurons. Axons differentiate earlier than dendrites, apical dendrites earlier than basal ones. 2. Varicosities in the processes of cortical neurons during the early postnatal period are regarded as a feature of growth processes. 3. The appearance of the dendritic spines is an important process in the ontogenetic and phylogenetic development of cortical neurons. 4. The different cortical layers show a different degree of differentiation during development. The deeper layers precede the upper layers in the process of differentiation. 5. Ingrowing afferents have an essential influence on the differentiation - especially on the differentiation of the dendritic postsynaptic structures. 6. The cortex of 6 month old rats shows no principle differences in comparison with 24 days old animals. It is concluded that the visible differentiation processes of cortical neurons are nearly finished 24 days post partum. 7. As an effect of the trauma a considerable loss of dendritic spines of layer III and V pyramid cells is found in addition to general degeneration features. 8. The following factors are thought to be responsible for the loss of spines: (i) transneuronal processes with spine degeneration and subsequent phagocytosis of the synaptosome. (ii) destruction of differentiation furthering afferents results in differentiation defects of the neuron with the failure of further postsynaptic differentiation (spines).

Animals↗
PubMed1975

[Environmentally affected differentiation of dendrite spines of pyramidal neurons in rat hippocampus (CA 1)].

Three groups of newborn WISTAR-rats were exposed to different environmental influences. The first group was raised in darkness from birth onwards, the second was permanently subjected to noise immediately after birth, while the third group (controls) was reared under normal laboratory conditions. The animals of all three groups were killed on the 15th day after birth and handled by a modified Golgi-Kopsch method. Then the distribution of spines on apical dendrites of CA 1-neurons of the hippocampus was investigated. For apical dendrites of a comparable length the mean number of spines per 50 mum as well as the mean total of spines on the apical dendrite was evaluated. Rats reared in darkness show significantly less spines on the apical dendrites of CA 1-neurons in comparison with the control animals. Rats permanently subjected to noise, on the contrary, have significantly more spines in comparison with the controls (total number of spines on the apical dendrite is 89,8 +/- 10,2 in the control animals, 55,0 +/- 16,6 in the animals reared in darkness, and 125,8 +/- 29,4 in the animals subjected to noise). The changes involve the whole apical dendrite; extreme changes in the individual segments of the apical dendrite were not observed. The results suggest that environmental factors have an influence on the differentiation of central neurons, which is not restricted to the specific analyzer concerned.

Animals↗
PubMedDate not supplied

Role of NGF in axotomy-induced c-Jun expression in medial septal cholinergic neurons.

The extent of neuronal regeneration after axotomy largely depends on the survival capacity of the injured cell. It has been shown for a long time that nerve fiber transection results in retrograde changes in the parent neuronal cell body, and that these changes may eventually lead to neuronal degeneration. At present, little is known about the sequence of events initiated in a nerve cell body by the transection of its axonal process. In this report, we will focus on an interaction of nerve growth factor (NGF) with the transcription factor c-Jun in intact and axotomized septohippocampal projection neurons.

Animals↗