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M Langmeier

Publications and source records attributed to M Langmeier.

At least 19 recordsLinked to original sources
PubMed1998

[Developmental neuronal plasticity and its importance in the recovery and function of neural tissue].

Plasticity is understand as a natural ability of the nervous tissue to respond to intrinsic and extrinsic stimuli by means of functional or structural changes. All its manifestations, including the developmental changes and processes of recovery are controlled by general genetic programs. One of the major research goals in the field of neuroplasticity is to design a strategy for the activation of the functional recovery. Enough evidence has shown that the internal environment of the nervous tissue is one of the decisive factors which determine the degree of both the developmental and regenerative plasticity. To improve capacity for the recovery it is therefore necessary to activate these intrinsic neuroplastic mechanisms. One alternative is the method of implantation of the embryonal nerve cells suspension into the site of neuronal lesion. The grafted cells can either replace the lost cells or they might become a source of stimulating factors which may activate the process of recovery. In the model of the intrahippocampal pathways interruption (experimental partial elimination of granule cells in the dorsal blade of the dentate gyrus), the subsequent implantation of embryonal neurons of the same origin into the site of lesion can partly restore the structural pattern of the gyrus dentatus and probably preserve some of the afferent connections. However, the outgrow of efferent fibers probably remains limited to the grafted tissue.

Animals↗
PubMed1998

[Intermittent hypobaric hypoxia during development--morphologic changes in the neocortex and hippocampus].

Infant rats, together with their mother, were exposed to the simulated altitude of 7,000 m for 8 hours per day since birth to the age of 18 days. Animals were studied the 25th day, 7 days after the last exposure to hypoxia. The experimental and control animals were killed the 25th day by the transaortic perfusion with 4% buffered neutral formaldehyde under ether anaesthesia. Brains were processed for classical neurohistological analysis (Nissl staining). 1. Cortical area in the AP plane 3 mm posterior to bregma were subjected to quantification and "laminar analysis" of the neuron count. 2. Hilus of the dentate gyrus between the AP plane 2.5 mm and 4 mm posterior to bregma were subjected to quantification of the neurons. The findings were as follows: a) The cytoarchitectonics of the brain in animals exposed to hypoxia was not severely damaged. b) The thickness of neocortex is in the experimental animals lower than that in the controls. c) The "laminar analysis" of neocortex showed a relative increase of neuronal density in layers I., II., V. and VI. of the cortex. d) The quantification of the neuron count showed a decrease in hilus of the dentate gyrus. These results demonstrate that the intermittent hypobaric hypoxia has a profound effect on morphological maturation of central nervous system in infant rats.

Altitude↗
PubMed1997

Synaptic vesicle size and shape profile in the kindling model of epileptogenesis.

Excitatory synapses were studied in the dentate gyrus ipsilateral to stimulated entorhinal cortex in fully kindled rats 2 weeks after the last (3rd) stage 5 seizure. In previous studies of the same model marked redistribution of synaptic vesicles to a 'strategic position' in the vicinity of the synaptic cleft and a significant enlargement of postsynaptic element were described. In this study the size and shape of synaptic vesicles were evaluated in three zones parallel to the presynaptic membrane of the synaptic cleft. The first zone (0.1 micron) directly adjoined the active zone of presynaptic membrane, the second was from 0.1 to 0.2 micron and the third from 0.2 to 0.3 micron from the presynaptic membrane. The vesicles of both the experimental and control animals were significantly smaller in zone I than in zone II and III and, in the control animals there was a tendency of vesicles to diminish towards the active zone. Such a tendency was not observed in the experimental animals, the largest vesicles were in the middle of zone II and were significantly more rounded in comparison to the vesicles in the controls. On the contrary, the vesicles in zone I and III were more elongated in the experimental animals than in controls. Our results may be taken as a sign of active reconstruction of synaptic apparatus in relation to increased functional readiness of the synapses. Possible mechanisms as well as significance for the kindling and epileptogenesis are discussed.

Animals↗
PubMed1997

Effects of a subconvulsant dose of kainic acid on afterdischarges elicited by cortical stimulation in rats.

The aim of this study was to test the hypothesis that nonconvulsive seizures elicited by a low dose of kainic acid may induce acute as well as chronic changes in brain function. Cortical epileptic afterdischarges (ADs) characterized by spike-and-wave rhythm and clonic seizures of facial and forelimb muscles were elicited in adult male rats with chronically implanted electrodes. Four stimulations were given in each of four weekly sessions. In the second session, 26 animals were injected with kainic acid (6 mg/kg i.p.) and 19 rats received no injection. The acute effects of kainic acid were to increase the intensity of movements accompanying stimulation and abruptly prolong ADs. Epileptic ADs were followed by a depression of electrocorticographic activity in both noninjected and kainic acid groups. In addition, when kainate was administered, interictal spike activity was registered mostly in the occipital region. One and two weeks after kainate administration, i.e. in the third and fourth stimulation sessions, there was an increased incidence of transitions from spike-and-wave ADs to another, limbic type of afterdischarge. This functional change persisted although no obvious neuronal death was found in the hippocampi of 12 other rats that received the same dose of kainic acid.

Animals↗
PubMed1997

Convulsant action of D,L-homocysteic acid and its stereoisomers in immature rats.

PURPOSE: We wished to characterize the convulsant effect of homocysteic acid (HCA) in developing rats. METHODS: Seizures were induced in 7-, 12-, 18-, and 25-day-old rats by intraperitoneal (i.p.) administration of D,L-HCA and in 12-day-old rats by i.p. injection of L- and D-stereoisomers of HCA. The animals were observed for 30 min after injection. The incidence, latencies, pattern of motor seizures, and all behavioral phenomena were noted. Fifty percent convulsant dose (CD50) values were calculated by probit analysis. Electrocorticograms (ECoG) were recorded after injection. RESULTS: HCA did not elicit minimal clonic seizures whereas generalized tonic-clonic seizures (GTCS) occurred in all the age groups studied. Flexion (emprosthotonic) convulsions occurred to postnatal day 18. ECoG recordings exhibited delta activity in younger pups and sharp graphoelements in older pups, but electroclinical correlation was poor. Young animals were more sensitive to the convulsant effect of D,L-HCA. In addition, D-HCA was significantly more effective than L-HCA in inducing both flexion and generalized seizures. CONCLUSIONS: Our data clearly indicate that seizures induced by HCA differ from those evoked by homocysteine. There are no qualitative differences in the motor pattern of seizures induced by the two stereoisomers of HCA, but marked differences were apparent in the very first signs of their action. These differences might be due to interaction with different glutamate receptor subtypes.

Animals↗
PubMed1995

[Programmed neural cell death?].

During normal development of the nervous system, up to 50 percent or more neuronal and glial cells die by programmed cell death. In the developing neuron, a continual access to neurotrophic factors is required for survival of the cells. The death may be a passive process, and the absence of neurotrophic factors leads to a loss of metabolic activity and, ultimately to cellular degeneration. Alternatively, apoptosis may be a metabolically active process and neurotrophic factors are necessary to repress the "suicide" response of the cell. The role of intracellular calcium, RNA-synthesis, protein synthesis a gene expression is discussed.

Apoptosis↗
PubMed1995

[Magnesium and the transport system].

Magnesium is sometimes denoted as "the overlooked cation" for although it is the second most abundant intracellular cation, the study of its homeostasis and regulation has long been neglected. However, at present it is evident that magnesium plays an important intracellular regulatory role. Magnesium transport systems can be divided into two principal categories: paracellular transport systems and transmembrane transport system. Paracellular pathway plays an important role in the intestinal and renal magnesium transports. The movement of magnesium across biological membranes is discussed from the perspectives of the secondary active transport and specific magnesium channels.

Biological Transport↗
PubMed1995

[Programmed neuronal cell death?].

During normal development of the nervous system, up to 50 percent or more neuronal and glial cells die by programmed cell death. In the developing neuron, a continual access to neurotrophic factors is required for survival of the cells. The death may be a passive process, and the absence of neurotrophic factors leads to a loss of metabolic activity and, ultimately to cellular degeneration. Alternatively, apoptosis may be a metabolically active process and neurotrophic factors are necessary to repress the "suicide" response of the cell. The role of intracellular calcium, RNA-synthesis, protein synthesis a gene expression is discussed.

Apoptosis↗
PubMed1994

[Ion channels].

Explore the source record for details and available documents.

Ion Channel Gating↗
PubMed1992

Morphological changes of the presynaptic and postsynaptic element in excitatory synapses during kindling.

In a previous study of a kindling model using stimulation of the entorhinal cortex we found a redistribution of synaptic vesicles into the close vicinity of the active zone of synapses of Type I (Gray 1959) in the hippocampal gyrus dentatus. In this paper, ultrastructural studies of the same model are being continued using planimetry of the synaptic apparatus. A significant increase of the postsynaptic apparatus, area enlargement by 53%, increase of the perimeter by 28% and shape irregularity are being reported. No changes in shape or in size have been demonstrated in presynaptic structures or in the morphology of presynaptic mitochondria. These findings are discussed in relation to increased functional readiness of the synapses as signs of active reconstruction of the synaptic apparatus.

Animals↗
PubMed1992

Are embryonal neurones used for transplantation "sufficiently immature"?

Live neuronal suspensions, prepared from the hippocampal region of donors aged 20 embryonal days, were observed in the Nomarski Differential Interference Contrast. Many neurones displayed profiles, resembling dendrites or axons and both principal hippocampal neurones (pyramidal and granular cells) were identified. For transplantation studies, donors of a younger embryonal age are thus recommended.

Animals↗
PubMed1992

Endocytotic activity of the presynaptic membrane and the morphometric differences of cortical synapses during the excitability changes in the initial phases of kindling.

Cortical sensorimotor areas of the laboratory rats was repeatedly stimulated at 10 min intervals. It led to progressive lengthening of the self-sustained after discharges (SSAD). Ten minutes after termination of the third SSAD the synapses of type I were examined. The ten minutes interval corresponds in electrophysiological experiments with a marked increase of excitability of the investigated cortical area. At the some time, it coincides with the intensification of endocytotic activity on the presynaptic membrane, and with an increase of complex and dense-core vesicles. The exocytotic activity was not changed. The area of the presynaptic elements increased together with their perimeter and maximal diameter. Mitochondria within the presynaptic bags had larger section area. Also the postsynaptic elements became larger, their section area, perimeter and maximal diameter increased. We consider the theory of presynaptic membrane recycling, ion permeability changes, activity of proteosynthesis and the role of contractile proteins during the repeated hyperfunction.

Animals↗
PubMed1991

[Changes in the configuration of synapses in the cerebral cortex in laboratory rats after termination of epileptic seizures during kindling].

The sensorimotor area of the cerebral cortex of the laboratory rat was repeatedly stimulated by electric current after 10-minute intervals which led to the development a gradual prolongation of self-sustained after-discharges (SSAD). One and 10 minutes after termination of the third SSAD the authors analyzed under the electron microscope synapses type I after to Gray from the second cortical homotopic area of the unstimulated hemisphere. They evaluated the curvature of the active zone of synapses. Evidence was provided that one minute after termination of the fit the number of negatively curved synapses increased and the number of synapses with a straight active zone decreased. The number of synapses with a positively curved active zone does not change. Ten minutes after termination of SSAD in the experimental animals the number of positively curved elements declines and the number of negatively curved synapses increases. There is no significant difference in the number of synapses with a straight active zone. The authors discuss possible functional consequences of the mentioned changes.

Animals↗
PubMed1991

[Presynaptic terminals in the sensorimotor area of the cerebral cortex in old laboratory rats].

In male laboratory rats, Wistar strain, 2 and a half years old, quantitative morphometric analysis of synapses (type I after to Gray) from the second layer of the sensorimotor area of the neocortical region was performed. Evidence was provided of enlargement of the area of presynaptic formations, their circumference and of prolongation of the active zone of the synapse. The absolute number of agranular synaptic vesicles does not change, however, the number of vesicles per area unit declines (1 micron 2). This change was proved in all regions of the presynaptic ending. The enlargement of the area of synaptic endings is discussed in relation to possible shifts of water and electrolytes between the extracellular and intracellular space as a result of ageing of nervous tissue. The authors discuss also the passive change caused by a decrease of neuropil structures and narrowing of the extracellular space. The relative decline of the number of synaptic vesicles in the entire synapse and thus in the vicinity of the active zone is taken to be the morphological basis of a certain restriction of synaptic transmission in the sensorimotor area of the cortex in old age.

Aging↗
PubMed1991

Postnatal neuronal plasticity of the pyramidal cells of CA1 area of the hippocampus as a reaction to neurotoxic damage.

Kainic acid (KA) was injected into both lateral ventricles of the brain of adult laboratory rats with the aim of verifying whether damage to afferent fibres in the hippocampal CA1 area would also be reflected in changes in the dendritic arborization of the neurones after maturation of these structures was completed. A significant proportion of the afferent fibres ending in area CA1 comes from CA3-4. The neurodegenerative effect of KA on the neurones in CA3-4 thus leads to marked reconstruction of the dendritic network of the pyramidal cells in the CA1 area. In the CA1 area of the experimental animals, there are fewer segments in the proximal part of the basal dendrites and in the lateral branches of the apical dendrites. The total number of segments in the apical dendrites is smaller and the higher order segments are likewise reduced. In the experimental group, the segments of both the basal and the apical dendrites are shorter. In the experimental animals, dendritic spine density in the lateral preterminal branches, the distal part of the apical shaft, the terminal segments of the lateral branches and the apical preterminal branches are smaller than in the controls, whereas in the segments proximal to the soma of the pyramidal cells it is greater. It can be seen from the results that area CA1 of the hippocampus is endowed, even in adulthood, not only with high functional plasticity, but also with surprisingly high morphological plasticity.

Animals↗
PubMed1991

Survival and maturation of hippocampal suspension grafts.

Implantation of an embryonal hippocampal tissue suspension into the area of the kainic acid lesion brought about an increase of the number of neurons. These neurons formed dendritic trees of an irregular pattern. Only neurons located within the pyramidal layer had the typical arrangement of pyramidal cells, but their dendrites were shorter and less branched.

Animals↗