Biomedical subjects

R Schmidt-Kastner

Publications and source records attributed to R Schmidt-Kastner.

At least 37 records · Page 2Linked to original sources

PubMed1995

Decrease of neurotrophin-3 mRNA in adult rat hippocampus after pilocarpine seizures.

Neurotrophins such as NT-3 are subject to complex regulation during epileptic seizures. Pilocarpine at a dose of 250 mg/kg induced either limbic seizures (LS) or limbic motor status epilepticus (LMSE) in adult rats. In situ hybridization signals for NT-3 mRNA declined moderately after LS and were nearly lost in LMSE at 3-4 h. Loss of NT-3 mRNA expression does not correlate with cell death and may reflect a functional down-regulation in certain hippocampal neurons.

Animals↗

PubMed1995

Altered pattern of immunohistochemical staining for glial fibrillary acidic protein (GFAP) in the forebrain and cerebellum of the mutant spastic rat.

The spastic rat is a neurological mutant of the Han-Wistar strain with prominent spasticity, tremor, and ataxia. Neurodegeneration is found in the CA3 sector of the hippocampus and in Purkinje cells of the cerebellum. We examined the forebrain and cerebellum of spastic rats for glial reactions by using immunolabelling for the astrocytic marker, glial fibrillary acidic protein (GFAP). First, a map of the GFAP-distribution was made representing a systematic series of frontal sections in controls. Reactive astrocytes with increased GFAP should occur in the areas with established neuronal degeneration, but they could also demarcate further regions with pathology in this rat strain. Since the baseline levels of GFAP-immunoreactivity differ between brain regions, control rats and clinically normal littermates served as controls to judge relative increases in major structures. In the CA3 sector and hilus of the dorsal hippocampus, a massive gliosis was detected. In the cerebellum, a patchy increase of GFAP labelling in Bergmann glia was found. Further increases of GFAP-labelling in reactive astrocytes occurred in fiber tracts, the ventral thalamic nuclei, medial geniculate nuclei, pontine region and optic layer of the superior colliculus. Inconsistent changes were noted in cortex and pallidum. No defects of glial labelling or malformations in glial architectonics were found. The reactive changes of astroglial cells in hippocampus and cerebellum are in proportion to the neuronal degeneration. The glial reactions in the other brain regions possibly reflect a reaction to fiber degeneration and incipient neuronal degeneration or functional alterations of glial cells in response to neuronal dysfunction.

Animals↗

PubMed1994

Transient immunohistochemical labelling of rat retinal axons during Wallerian degeneration by a monoclonal antibody to neurofilaments.

Immunohistochemical labelling with the monoclonal antibody SMI32 to non-phosphorylated epitopes on neurofilament proteins of high molecular weight class was low in rat central optic fibers of controls. After unilateral transection of optic nerve, a strong, transient increase of labelling with SMI32 occurred in degenerating fibers of optic tract at 2 and 4 days, which then declined at 8 and remained low at 21 days. Consequently, immunostaining with SMI32 may serve as a positive marker for degenerating fibers in rat optic system.

Animals↗

PubMed1994

Loss of immunoreactivity for glial fibrillary acidic protein (GFAP) in astrocytes as a marker for profound tissue damage in substantia nigra and basal cortical areas after status epilepticus induced by pilocarpine in rat.

Status epilepticus induced by pilocarpine in rats induces massive tissue damage comprising neurons and astrocytes (incomplete infarction) in substantia nigra pars reticulata (SNR) and in basal cortical areas (BCTX). Immunohistochemistry with a polyclonal antiserum and a monoclonal antibody to GFAP were used here to study the astroglial damage in these regions. Control sections showed a strong labeling for glial fibrillary acidic protein (GFAP) for both antibodies in SNR and BCTX. At 1 day after induction of seizures, labeling with the polyclonal antibodies showed diffuse increase within the lesioned areas and enhanced staining of astrocytes at the border zones. However, staining with the monoclonal antibody was abolished. At 3 days, labeling with both the polyclonal antiserum and the monoclonal antibody was severely reduced within the damaged regions. Reactive astrocytes in the surround of the infarct showed enhanced labeling with both antibodies. This combination of enhanced labeling with polyclonal antibodies and decreased labeling with the specific monoclonal antibody for GFAP can be taken as indicator for acute glial cell damage in seizures and related experimental conditions.

Animals↗

PubMed1994

Immunohistochemical markers for neurons and astrocytes show pan-necrosis following infusion of high-dose NMDA into rat cortex.

This study pertains to the transition between selective neuronal necrosis and the development of cerebral infarction (pan-necrosis). We infused the neuron selective excitotoxin N-methyl-D-aspartate (NMDA) at a relatively high concentration (10 microliters of 50 mM NMDA in phosphate buffer, pH 7.4) into the rat cortex. Local injection of lactic acid and a minor stab wound in the cortex were used as a reference. The tissue damage was evaluated with immunohistochemical markers for neurons (MAP2, parvalbumin) and for astrocytes (GFAP and S100 protein). The stab wound and infusion of lactic acid led to a small distinct area of pan-necrosis with a sharp border to the surrounding tissue. The NMDA lesions were characterized by a center of pan-necrosis with loss of all tissue elements that were larger and less distinctly demarcated than the other lesions. This study shows that activation of NMDA receptors per se can induce pan-necrosis, and we conclude that the transition from selective neuronal necrosis to infarction depends on the intensity of the neuronal damage process.

Animals↗

PubMed1994

Glial cell-line derived neurotrophic factor (GDNF) mRNA upregulation in striatum and cortical areas after pilocarpine-induced status epilepticus in rats.

Glial cell-line derived neurotrophic factor (GDNF) has recently been cloned and shown to have trophic effects on dopaminergic nigral neurons. However, GDNF mRNA has not been detected in striatum or other forebrain areas of adult rat. Using limbic motor status epilepticus induced by pilocarpine to activate neurons in motor and limbic areas, we now demonstrate GDNF mRNA signals in the striatum, hippocampus and cortex using in situ hybridisation. The finding of GDNF mRNA in the stimulated striatum opens the possibility that GDNF may be a target-derived, trophic factor in the nigro-striatal system. This expression of GDNF mRNA may be linked to excitatory cortical input. Increases in GDNF mRNA after status epilepticus in hippocampus and neocortex indicate additional roles for GDNF.

Animals↗

PubMed1994

Effect of transient reduction of cerebral blood flow on membrane anisotropy and lipid peroxidation in different rat brain areas.

Light-microscopical studies revealed that oligemic hypoxia for 24 and 60 min as produced by bilateral clamping of the carotid arteries (BCCA) in normotension does not produce neuronal cell necrosis in the vast majority of rat brain. Less than 5% of cases showed a pattern of mild selective neuronal necrosis as would be expected in ischemia. However, significant changes in both lipid peroxidation (as measured by MDA formation) and membrane anisotropy (measured by DPH or TMA-DPH, respectively, as a fluorescence probe) in cortical and striatal, but not in hippocampal, membrane fractions could be measured in ex vivo studies. Twenty-four and 60 min of BCCA without reperfusion decreased lipid peroxidation in the cerebral cortex but not in the striatum. BCCA, either for 24 or 60 min, and 60 min of reperfusion produced no changes in lipid peroxidation in either structure. However, 24 and 60 min of BCCA followed by 14 days of reperfusion led to a significant increase in MDA formation in the striatum, while lipid peroxidation in the cortex was only increased after 60 min of BCCA. Cortical as well as striatal membrane anisotropy increased significantly 14 days later in rats submitted to BCCA for 24 or 60 min. The study shows an increased lipid peroxidation 2 weeks after a transient reduction in cerebral blood flow although no neuronal necrosis could be observed in general.

Animals↗

PubMed1994

Lesion-induced transient suppression of inhibitory function in rat neocortex in vitro.

The structural and functional consequences of a local thermolesion were examined in rat neocortex with electrophysiological in vitro techniques and immunocytochemistry. Age-matched untreated and sham-operated animals served as controls and were analysed in the same way. The lesions consisted of a core of coagulated tissue 2-3 mm in diameter and reached ventrally into the deep cortical layers. After two days reactive astrocytes and after nine days a dense gliosis were observed in the immediate vicinity. Modifications in the intrinsic membrane characteristics and the synaptic network properties were investigated with intra- and extracellular recording techniques after survival times of one to eight days. Neurons recorded in the surrounding of lesions in neocortical slices revealed a significantly more depolarized resting membrane potential and a higher neuronal input resistance. In comparison to cells in control slices, maximal discharge rates to injection of depolarizing current pulses of neurons close to a focal lesion were not significantly altered and intrinsic burst firing was never observed. However, between postlesion days 1 and 5, neurons in the surroundings of lesions showed a transient increase in synaptic excitability. This hyperactivity was most clearly pronounced at a distance of 2-3 mm from the centre of the lesion (i.e. about 1-1.5 mm away from the lesion border) and characterized by long-duration field potential responses and multiphasic long-lasting excitatory postsynaptic potentials to orthodromic stimulation of the afferent input. This lesion-induced hyperexcitability was associated with a significant reduction in the peak conductance of the Cl(-)-dependent fast inhibitory postsynaptic potential and the K(+)-dependent long-latency inhibitory postsynaptic potential, suggesting that the intracortical GABAergic system was functionally impaired. The decrease in synaptic inhibition was associated with prolonged N-methyl-D-aspartate receptor-mediated activity, which could be reversibly blocked by D-amino-phosphonovaleric acid. In addition, neurons recorded in the vicinity of the lesion responded to an orthodromic synaptic stimulus with a long-lasting burst. The lesion-induced disturbance in the balance between the excitatory and inhibitory system may not only have profound influences on the mechanisms of intracortical information processing, but may also lead to the expression of epileptiform activity and long-term functional deficits.

Action Potentials↗

PubMed1994

Ischemic damage visualized in flat mounts of rat retina after photochemically induced thrombosis.

The method of photochemically induced thrombosis was used to produce severe ischemia in the rat retina. Flat mounts of the retina were prepared at 3 h, and 1, 2, 3, 4, 6, 7, and 22 days after lesioning and Nissl-stained, which facilitated the study of the topography of the ischemic lesions. The regional variability of ischemic damage and the cytological features of ischemic cell death in the ganglion cell layer were evaluated. Neuropathological analysis showed ischemic cell damage of ganglion cells at 3 h, an infarction-type lesion at 1 to 7 days, and scar formation at 3 weeks. As an additional parameter of ischemic ganglion cell death, the degeneration of retinal axons was visualized in the contralateral dorsal lateral geniculate nucleus by Fink-Heimer silver impregnation and by immunohistochemical staining for glial fibrillary acidic protein (GFAP) in reactive astrocytes.

Animals↗

PubMed1994

[Increased spontaneous and evoked response in the area of model infarcts of the visual cortex of cats].

Ischemic lesions were produced in the cat visual cortex and changes of responses to visual stimuli were studied in single cells with extracellular recordings. The spontaneous and the visually driven activity were quantitatively analyzed and compared with those in normal controls. While the normal control cells showed a mean response strength of 52.7 impulses/s, this value was increased to 69.3 impulses/s in the vicinity of ischemic lesions. The spontaneous activity was also increased. Epileptiform burst activity with frequencies above 500 I/s was observed in 37.7% of the cells. Directional and orientational specificity was significantly reduced in these regions because of an increase in responses to stimuli in non-preferred directions and with non-preferred orientations. Thus, an increase in activity-dependent energy consumption occurs in the vicinity of lesions in the ischemically severed cortex.

Animals↗

PubMed1993

Immunohistochemical studies on neurofilamentous hypertrophy in degenerating retinal terminals of the olivary pretectal nucleus in the rat.

Following section of the optic nerve, degenerating retinal terminals reveal an accumulation of neurofilaments (neurofilamentous hypertrophy) as demonstrated by silver impregnation techniques or electron microscopy. The present study examined degenerating retinal terminals by means of immunohistochemistry and antibodies specific for the triplet of neurofilament proteins of low (NF-L), medium (NF-M), and high (NF-H) molecular weight class. Following unilateral optic nerve section in the rat and survival of 1, 2, 4, 8, and 21 days, brains were perfused with aldehyde fixative, sliced on a vibratome and stained for neurofilaments by using the peroxidase-antiperoxidase technique. Other brains were frozen, cut in the native state, and slide-mounted sections were fixed by acetone. Side comparisons in visual pathways were made in frontal sections, taking advantage of the near complete crossing of retinal fibers in the rat. Anterograde degeneration of axons occurred in the optic tract and branchium colliculi. Changes of terminals were investigated in the olivary pretectal nucleus, which contains a dense aggregation of retinal terminals in the core region. The optic tract and branchium colliculi showed a reduction in immunostaining for neurofilament proteins following axotomy. Within the core region of the olivary pretectal nucleus, strong increases of immunoreactivity of NF-L and NF-M were detected beginning at 2 days postlesion and persisting at 8 days. No changes in NF-H proteins were found in the terminal regions with three different antibody probes. The increase in immunostaining reflects the accumulation of neurofilament proteins in the degenerating retinal terminals, i.e., neurofilamentous hypertrophy.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Immunohistochemical studies with antibodies to neurofilament proteins on axonal damage in experimental focal lesions in rat.

Immunohistochemistry with monoclonal antibodies against neurofilament (NF) proteins of middle and high molecular weight class, NF-M and NF-H, was used to study axonal injury in the borderzone of focal lesions in rats. Focal injury in the cortex was produced by infusion of lactate at acid pH or by stab caused by needle insertion. Infarcts in substantia nigra pars reticulata were evoked by prolonged pilocarpine-induced status epilepticus. Immunohistochemical staining for NFs showed characteristic terminal clubs of axons in the borderzone of lesions. Differences in the labelling pattern occurred with different antibodies which apparently depended on molecular weight class of NFs and phosphorylation state. These immunohistochemical changes of NFs can serve as a marker for axonal damage in various experimental traumatic or ischemic lesions.

Animals↗

PubMed1993

A one-step immunohistochemical method for detection of blood-brain barrier disturbances for immunoglobulins in lesioned rat brain with special reference to false-positive labelling in immunohistochemistry.

Disturbances of the blood-brain barrier (BBB) following brain lesions lead to extravasation of serum proteins that can be detected by immunohistochemical methods in tissue sections. Here, extravasated immunoglobulins were visualized by a 1-step technique using rabbit anti-rat immunoglobulins conjugated to horseradish peroxidase (HRP). This method is associated with a lower background staining than the conventional 3-step peroxidase-antiperoxidase (PAP) technique using rabbit antibodies against rat whole-serum proteins or immunoglobulins (IgG). Further tests using a direct conjugate of rabbit anti-rat immunoglobulins to fluorescein isothiocyanate (FITC) showed usefulness of the approach for fluorescence microscopy. Additional experiments showed that antibodies directed against mouse immunoglobulins as used for detection of mouse monoclonal antibodies can cross-react with extravasated rat immunoglobulins. Therefore, immunohistochemical studies on lesioned rat brain should routinely include a visualization of areas containing extravasated serum proteins including immunoglobulins.

Animals↗

PubMed1993

Metabolic changes during and after transient clamping of carotid arteries in normotensive rats.

In the present experiments changes of local metabolism in the striatum, hippocampus, and frontal cortex during and after transient clamping of carotid arteries in normotensive rats (BCCA) were studied by continuous measurement of local cerebral temperature, partial oxygen tension (PO2), and extracellular levels of lactate. Local temperature in the striatum, hippocampus, and frontal cortex fell between 1.7 and 2.3 degrees C upon occlusion and quickly returned to preocclusion values after free flow had been established. Local PO2 was reduced in the striatum, hippocampus, and frontal cortex to values between 70 and 30% during BCCA. Immediately after termination of BCCA the PO2 showed a tendency to recover in the striatum and frontal cortex, whereas in the hippocampus, this process started later. Extracellular levels of lactate within these three structures increased during BCCA and went down to preocclusion values within the observed period of reperfusion. The results suggest that BCCA induces a transient anaerobic metabolism that seems to be sufficient to evoke functional changes without neuronal damage.

Animals↗

PubMed1993

Immunohistochemical staining for glial fibrillary acidic protein (GFAP) after deafferentation or ischemic infarction in rat visual system: features of reactive and damaged astrocytes.

Immunohistochemical staining for glial fibrillary acidic protein (GFAP) is standard for visualization of reactive astrocytes in tissue sections, whereas various forms of astrocytic damage remain to be described in detail. In this study we tested differences in GFAP labeling in reactive astrocytes and in glial cells damaged by ischemia and edema. Studies were performed in the anatomically well defined visual system of rat. Basic staining patterns for GFAP were established in subcortical visual nuclei and visual cortex. In the first model, deafferentation of visual centers was performed by unilateral optic nerve lesion, and characteristic changes of GFAP labeling in reactive astrocytes were studied at 0.5, 1, 1.5, 2, 4, 8 and 21 days after lesion. Initial changes were seen in the deafferented superior colliculus at 1 day after deafferentation with a diffuse increase and stellate types of reactive cells formed at 2-8 days. In the second model, small ischemic infarcts were produced in the visual cortex of rats using the method of photochemically-induced thrombosis. GFAP labeling with a polyclonal antiserum was massively enhanced in the infarct at 4 hr. Characteristic morphological changes in damaged astrocytes were seen which were also identified in experiments with simulated global ischemia. In the surround of the infarct, swelling of astrocytes also caused increased labeling. At 3-4 days infarction typical reactive astrocytes surrounded the lesioned area. In conclusion, these immunohistochemical studies on GFAP in rat visual system allow for the following classifications. (a) Normal astrocytes vary in labeling at different anatomical localizations. (b) Reactive astrocytes show enhanced labeling and larger cell-size within an interval of 1-2 days after lesion. (c) Astrocytes damaged by ischemia reveal increased labeling of disintegrating cellular elements within hours after a lesion. (d) Swollen astrocytes undergo enhanced labeling in areas with vasogenic edema.

Animals↗

PubMed1992

Immunohistochemical changes of neuronal calcium-binding proteins parvalbumin and calbindin-D-28k following unilateral deafferentation in the rat visual system.

The neuron-specific calcium-binding proteins, parvalbumin and calbindin-D-28k, were studied in the subcortical visual system of normal and unilaterally deafferented albino rats. Immunohistochemistry with monoclonal antibodies was used on vibratome sections through optic tract (OT), dorsal lateral geniculate nucleus (dLGN), olivary pretectal nucleus (OPN), and superior colliculus (SC). In controls, OT stained strongly for parvalbumin and weakly for calbindin-D-28k. The dLGN contained a plexus of parvalbumin-positive fibers. In dLGN, calbindin-D-28k-antibodies showed strong labeling of some neurons with long dendrites and weak staining of the cytoplasm in other neurons. In OPN, parvalbumin stained a ring of neurons and terminals in the shell region, whereas calbindin-D-28k was contained in medial cell populations. In SC, parvalbumin was contained in fibers, terminals, and neurons throughout the visual layer. Calbindin-D-28k showed a laminar distribution of neurons with a predominance in deep portions of superficial grey matter and in ventral portions of stratum opticum. Following unilateral deafferentation induced by optic nerve section, retinal axons showed immunohistochemical changes related to Wallerian degeneration and target neurons reacted by changes of calcium-binding proteins. Parvalbumin and calbindin-D-28k immunostaining decreased during Wallerian degeneration of OT. In the deafferented dLGN, immunohistochemical labeling for calbindin-D-28k declined in strongly stained neurons from 4 to 21 days after lesion. Measurement of dendritic length per number of cells or per area of dLGN showed a significant decline for the contralateral side at 4, 8, and 21 days (ANOVA, P less than 0.05). In deafferented OPN, terminal-like staining for parvalbumin decreased and neuronal labeling was enhanced. In deafferented SC, the neuronal and dendritic staining for parvalbumin increased beginning from Day 1 on and persisting at Day 21, whereas fibers and terminal-like elements decreased in staining. Measurement of parvalbumin-positive neurons per area of SC showed a significant increase of labeling in the contralateral side from Day 1 to Day 21 (ANOVA, P less than 0.05). These studies show that cellular responses to deafferentation of visual neurons involve a regulation of calcium-binding proteins. The decline in staining for calbindin-D-28k in dLGN may relate to reduced retinal afferent activity. The progressive cellular changes in parvalbumin staining may be related to unmasking of intrinsic neurons after removal of parvalbumin-containing, afferent fibers and terminals. Additionally, the changes of parvalbumin labeling in SC neurons may reflect a plastic reorganization of local circuits known to occur in rat SC in response to deafferentation.

Afferent Pathways↗

PubMed1991

Neuronal dysfunction at the border of focal lesions in cat visual cortex.

Traditional concepts assume that traumatic or ischemic brain lesions are surrounded by regions with depressed neuronal function. More recently hyperactivity gained increasing attention as excitotoxic mechanisms become effective at certain stages of neuronal injury. Single cell recordings in the surrounding of small focal lesions in the cat visual cortex revealed both types of functional pathology 1-30 days after lesioning. A rim of suppressed neurons surrounded a completely silent core. Cells further away from the lesion showed bursts and long lasting hyperactivity with extremely high discharge rates. Consequently, the volume of disturbed tissue was considerably larger than the region of initial cell death. This halo of dysfunction may be important for neurological symptoms evoked by cortical lesions.

Animals↗

PubMed1991

Neuronal degeneration in hippocampus and cerebellum of mutant spastic Han-Wistar rats.

The neuropathology of the brain of mutant spastic Han-Wistar rats (Han-Wist SPA/SPA) was investigated using histological techniques. A surprising result was the detection of neuronal degeneration in the hippocampus and cerebellum of mutant spastic rat brains, whereas other regions, e.g. neocortex, isocortex, basal ganglia and thalamus, were overall normal. The CA3 sector in the septal third of the hippocampus including the cell band reaching into the hilus ('CA3c') showed a severe neuronal degeneration, whereas the granule cells of the dentate gyrus, several hilar neurons ('CA4') and the pyramidal cells in CA1 were found normal. In the cerebellum, a variable patchy degeneration of Purkinje cells was detected while the general layering was normal and granule cells and Golgi cells appeared preserved.

Animals↗