Biomedical subjects

W Zuschratter

Publications and source records attributed to W Zuschratter.

28 records · Page 2Linked to original sources

PubMed1995

Comparison of frequency-specific c-Fos expression and fluoro-2-deoxyglucose uptake in auditory cortex of gerbils (Meriones unguiculatus).

Induction of c-Fos in the auditory cortex of gerbils was investigated immunocytochemically 1 h after single, triple or 1 h continuous stimulation with a series of narrow band frequency-modulated tone bursts. With single stimulation c-Fos immunoreactive neurons were chiefly found in the primary auditory field (AI), where they formed a narrow frequency-specific column across layers II-VI. Side-band-like patterns adjacent to this column appeared characteristically with triple stimulation. Immunoreactive cell density in the anterior auditory field and the caudal fields was sparse and location not frequency specific with single or triple stimulation. Spatial comparisons of c-Fos immunoreactive neuron density with 2-deoxy-2-fluoro-D-glucose (FDG) autoradiography in the same animals after 1 h of stimulation revealed spreading of c-Fos expression in neurons across the tonotopic maps of the AI and in the rostral and caudal fields of the auditory cortex. The pattern of the highest density of c-Fos labelled cells in the AI still matched the peak labelling of FDG autoradiographs. The results show that the postsynaptic marker c-Fos reflects the frequency representation in the AI with single or triple stimulation yet with a higher spatial resolution than the deoxyglucose technique. Longer stimulation causes nontonotopic intracortical spreading of the c-Fos-inducing message, a phenomenon potentially reflecting the effects of cooperativity in the maps.

Animals↗

PubMed1995

Mapping of stimulus features and meaning in gerbil auditory cortex with 2-deoxyglucose and c-Fos antibodies.

The basic functional organization of gerbil auditory cortex was previously mapped with unit recording of best frequency and with the fluoro-2-deoxyglucose mapping (FDG) technique. Among at least seven subfields in this cortex the primary auditory cortex (AI) and the anterior auditory field (AAF) showed prominent tonotopic organization with parallel dorsoventral iso-frequency contours (electrophysiology) in correspondence to FDG labelling of frequency band laminae. In an approach to mechanisms of learning aversive tone conditioning paradigms were found to reshape frequency receptive fields of single units in AI and also produced spatial shifts of tone representation in the tonotopic maps of AI and AAF. Both results suggest that spectral features as well as aspects of behavioural meaning of sounds may be represented even in primary auditory cortex. General meaningfulness in terms of occurrence of novel and salient stimuli may be reflected by expression of immediate early genes. Mapping with an antibody against the immediate early gene product c-Fos was performed in order to identify the spatial distribution of neurons in auditory cortex which change metabolism as a result of stimulation with auditory signals in a new environment. Very short e.g. less than 3 min repetitive stimulation with a tone led to frequency-specific columnar expression of c-Fos in AI and to spare non-tonotopic expression in other fields. Longer stimulation or longer aversive conditioning with the same tone led to spreading of expression, i.e. to accessory non-tonotopic labelling in AI and other fields, particularly pronounced in the output layers V and VI. It is assumed that this spreading relates to the formation of output schemes from auditory cortex in terms of implicit behavioural meaning of stimuli.

Animals↗

PubMed1995

Transection of rat fimbria-fornix induces lasting expression of c-Jun protein in axotomized septal neurons immunonegative for choline acetyltransferase and nitric oxide synthase.

The fimbria-fornix (FF) fiber tract was unilaterally transected in adult rats by a stereotaxic knife cut. In the axotomized neurons of the medial septal nucleus (MS) and ventral diagonal band of Broca (VDB), the expression of Jun, Fos, Krox, CREB transcription factors, choline acetyltransferase (ChAT) and nitric oxide synthase (NOS) were studied by immunocytochemistry. In addition, NADPH-diaphorase (NDP) and acetylcholine esterase (AChE) were visualized by activity assays. For retrograde tracing of axotomized neurons, either HRP-coupled gold was injected in the entorhinal cortex prior to axotomy, or Fast Blue was injected into the transection site subsequently to FF transection. Following FF transection c-Jun and in a less extend JunD were expressed in axotomized MS and VDB neurons. Expression levels rose at 24 h, but not at 18 h, postaxotomy, reached their maximal levels between 5 and 7 days, and then gradually declined. Up to 100 days, c-Jun was still present in a substantial number of septal neurons. JunB, Krox-20, Krox-24, c-Fos, and pan-Fos immunoreactivities (IR) were not detectable in axotomized septal neurons and CREB-IR did not change compared to the intact contralateral side. ChAT-IR dramatically declined over 36 h, and furthermore AChE reactivity had substantially fallen after 5 days. The number and intensity of cytoplasmic neuronal NOS-IR and NDP which generated congruent temporospatial patterns gradually fell between 3 and 5 days postaxotomy. The surviving neurons labeled by NOS and NDP showed a high coexpression of c-Jun, whereas c-Jun was almost completely absent in neurons stained for ChAT and AChE. Finally, ChAT-IR and NDP reaction labeled different subpopulations. Our findings demonstrate a lasting expression of the c-Jun transcription factor in axotomized MS and VDB neurons that might indicate the regenerative propensity of damaged neurons. The decrease of NOS and NDP in MS and VDB neurons demonstrates that neuronal populations respond to axotomy with an individual regulation of NOS expression.

Acetylcholinesterase↗

PubMed1995

Hypoglycemia-elicited immediate early gene expression in neurons and glia of the hippocampus: novel patterns of FOS, JUN, and KROX expression following excitotoxic injury.

In the hippocampus there is a graded vulnerability of neuronal subpopulations to hypoglycemia-induced degeneration, most likely due to excitotoxic activation of glutamate receptors. The present study was conducted to investigate whether the induction of transcription factors of the immediate early gene (IEG) family after hypoglycemia reflects these different grades of neuronal vulnerability. We studied the expression profile of seven IEG-coded proteins in the rat hippocampus following severe insulin-induced hypoglycemia with 30 min of EEG isoelectricity and various survival periods for up to 42 h after glucose replenishment. Immunocytochemistry was performed on vibratome sections with specific polyclonal antisera directed against c-FOS, FOS B, c-JUN, JUN B, JUN D, KROX-24, and KROX-20. To unequivocally define the type of glial cells showing IEG induction, we investigated coexpression of c-FOS and glial marker proteins (glial fibrillary acid protein [GFAP], OX-42) by confocal laser scanning microscopy. Up to 3 h after glucose replenishment, differential temporospatial induction of IEG-coded transcription factors of the FOS, JUN and KROX families were observed in moderately injured neuronal subpopulations, including the majority of dentate granule cells and CA3 neurons. At later time points, however, a delayed and persistent c-JUN expression was found in severely, but reversibly, injured CA1 neurons and in neurons in the immediate vicinity of irreversibly damaged neurons in the crest of the dentate gyrus. Similar to the results with experimental models of central and peripheral axotomy, selective c-JUN induction in these neurons may represent an initial event in the regeneration process of sublethally injured neurons. In contrast to other models of excitotoxic injury such as ischemia and epilepsy, marked glial c-FOS expression was restricted to astrocytes, as assessed by confocal laser scanning microscopy.

Animals↗

PubMed1991

Distribution of (fucogalactosyl-)epitope expressing glycoconjugates in rat brain.

Glycoconjugates are known to be concentrated in plasma membranes, especially in synaptic junctions, where they subserve various functions in neural connectivity. Here we report the cellular distribution of a new monoclonal antibody recognizing (fucogalactosyl) sequences in carbohydrate structures. The most pronounced immunoreactivity was found in fibrous astrocytes, in many parts of the brain and with lower density in various neuronal elements. This points to the expression of identical carbohydrate sequences on molecules within certain glial and neuronal elements. Previous intracerebral injections of the antibody interfered with long term memory formation. Therefore, functions mediated by corresponding glycoproteins in neurons and glia cells or even neuron-glial interactions, might be relevant for information-processing.

Animals↗

PubMed1990

Distribution of choline acetyltransferase and acetylcholinesterase in the vocal motor system of zebra finches.

The distribution of choline acetyltransferase immunoreactivity (ChAT-IR) was surveyed in the vocal motor system of adult male and female zebra finches and was compared with the pattern of histochemical acetylcholinesterase (AChE-His). In the vocal motor system the most prominent accumulation of ChAT-IR somata was found in lobus parolfactorius (LPO) including Area X. Immunoreactive neuropil was found to be concentrated in pericellular networks of fibers in male's Area X while the corresponding area in females could not be demarcated within the LPO. The density of ChAT-IR fiber networks was much higher in LPO, paleostriatum augmentatum and in a shelf region around nucleus robustus archistriatalis (RA) than in neostriatal and hyperstriatal parts of the telencephalon. AChE positive neurons and neuropil were observed in all ChAT-IR regions and, in addition, in the vocal motor nuclei nucleus hyperstriatum ventrale pars caudalis (HVc), nucleus magnocellularis in the anterior neostriatum (MAN), nucleus interfacialis (NIF) and RA. However, none of the latter nuclei contained ChAT-IR cell bodies. They were characterized by rare ChAT-IR neuropil. MAN and RA exhibited shelf regions with a higher degree of stained fibers. The discrepancy between the localization of AChE-His and ChAT-IR can hardly be explained by different classes of ChAT isoenzymes in neurons within the basal forebrain and the neostriatal, hyperstriatal and archistriatal vocal control nuclei not detected by our antibody. On the other hand, vocal control centers while receiving cholinergic inputs, might - except for Area X - not possess cholinergic efferent projections within the telencephalon.

Acetylcholinesterase↗

PubMed1989

System-specific distribution of zinc in the chick brain. A light- and electron-microscopic study using the Timm method.

The brain of young domestic chicks was investigated using a Timm sulfide silver method. Serial Vibratome sections were analyzed under the light microscope, and the localization of zinc-positive structures in selected areas was determined at the ultrastructural level. Both strong and differential staining was visible in the avian telencephalon whereas most subtelencephalic structures showed a pale reaction. The highest staining intensity was found in the nonprimary sensory regions of the telencephalon such as the hyperstriatum dorsale, hyperstriatum ventrale, hippocampus, palaeostriatum augmentatum, lobus parolfactorius and caudal parts of neostriatum. There was an overall gradient of staining intensity in neostriatal areas from rostral to caudal with the heaviest zinc deposits in the caudal neostriatum. Primary sensory projection areas, such as the ectostriatum (visual), hyperstriatum intercalatum superius (visual), nucleus basalis (beak representation), the input layer L2 of the auditory field L and the somatosensory area rostral to field L were selectively left unstained. Fiber tracts throughout the brain were free of zinc deposits except for glial cells. In electron micrographs of stained regions, silver grains were localized in some presynaptic boutons of asymmetric synpases (Gray type I), within the cytoplasm of neuronal somata and sporadically in the nucleus. The possible involvement of zinc in synaptic transmission and other processes is discussed.

Animals↗

PubMed1988

Postnatal development of parvalbumin-, calbindin- and adult GABA-immunoreactivity in two visual nuclei of zebra finches.

The characterization of neuron populations by their immunoreactivity against parvalbumin- and calbindin (28-kDa)-antisera has been used to study the postnatal development of the visual diencephalic nucleus rotundus and the mesencephalic nucleus isthmi complex in zebra finches. In nucleus rotundus, parvalbumin-immunoreactivity was restricted to the neuropil during the first 10 days and appears additionally in somata around day 12 where it remains until adulthood. Calbindin-immunoreactivity of the very scarce neuropil and the few somata, which can be observed during the first two weeks, disappears until adulthood. Thus, the adult nucleus rotundus shows an almost complementary distribution of calbindin- and parvalbumin-immunoreactive structures: the numerous, heavily parvalbumin-positive somata, which are surrounded by dense immunoreactive neuropil are in sharp contrast to the complete absence of calbindin-immunoreactive somata. Only a thin rim surrounding this nucleus contains punctate calbindin-positive neuropil. In the nucleus isthmi complex, parvalbumin and calbindin staining patterns show markedly different developmental profiles. While the density of parvalbumin-immunoreactive neuropil in the parvocellular part of the nucleus isthmi continuously increases and the somata remain unstained, the initially heavily calbindin-positive somata gradually lose their immunoreactivity during the first two weeks. In the adult nucleus isthmi complex, parvalbumin- and calbindin show nearly identical staining patterns. A comparison between the two calcium-binding proteins and GABA-immunoreactivity in adult brains revealed different relationships in the two nuclei: while in nucleus rotundus GABA-staining pattern neither resembles that of parvalbumin nor of calbindin, in the nucleus isthmi complex all three staining patterns coincide.

Animals↗

PubMed1985

Ultrastructural localization of the calcium-binding protein parvalbumin in neurons of the song system of the zebra finch, Poephila guttata.

The distribution of parvalbumin (PV) within neurons of the vocal motor nucleus hyperstriatum ventralepars caudalis (HVc) was investigated in the forebrain of adult male zebra finches by means of light and electron microscopy using the indirect immunoperoxidase technique. Parvalbumin-reaction product was located in the amorphous material of perikarya, dendrites and nuclei, and associated to microtubuli, postsynaptic densities and intracellular membranes; it was found in some axons and Gray type-2 boutons, but rarely in type-1 boutons and never in the Golgi apparatus. These observations suggest that parvalbumin may regulate calcium-dependent processes at the postsynaptic membrane and in the cytosol. Furthermore, the partial association of parvalbumin to microtubuli points to an involvement in calcium-dependent tubular functions. Calcium currents and microtubular assembly or transport may be relevant for the known functions of HVc in song learning.

Animals↗

PubMedDate not supplied

Suppression of c-fos induction in rat brain impairs retention of a brightness discrimination reaction.

Recently, the induction of transcription factor-encoding immediate-early genes such as c-fos was observed in distinct brain regions of rats trained to acquire a footshock-motivated brightness discrimination in a Y-maze. The functional relevance of inducible transcription factors for learning and memory formation is, however, not clear. To address this question in the present study, we have used a synthetic antisense phosphorothioate oligodeoxynucleotide to suppress in vivo the expression of c-fos in rat brain. Intrahippocampal application of the oligodeoxynucleotide 10 hr and 2 hr before starting a brightness discrimination training drastically reduced the induction of c-Fos immunoreactivity normally observed in limbic and cortical areas after the training session. Acquisition of the discrimination reaction was not affected by this treatment. In a relearning test 24 hr after the first training, retention of the discrimination reaction was specifically impaired compared with rats pretreated with control oligodeoxynucleotide or saline. Our findings are consistent with the hypothesis that the inducible transcription factor c-Fos is involved in processes underlying the formation of long-term memory.

Animals↗