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B Heimrich

Publications and source records attributed to B Heimrich.

53 records · Page 3Linked to original sources
PubMed1993

Expression of the cholecystokinin gene in organotypic slice cultures of immature rat somatosensory cortex.

The preprocholecystokinin gene is expressed in a subpopulation of cortical interneurons containing gamma-aminobutyric acid. Slices of neonatal rat cortex were cultivated for 12 +/- 2 days and examined for the presence and distribution of these neurons by in situ hybridization and immunocytochemistry. Like in situ, two layers of preprocholecystokinin-mRNA-expressing cells were present. Immunopositive fibers formed a dense network and established symmetric contacts on dendritic shafts and spines. It is concluded that cholecystokinin-expressing interneurons survive in cultured slices of rat cerebral cortex. These organotypic cultures may be useful to study the cellular interactions which regulate neuronal cholecystokinin expression.

Animals↗
PubMed1993

Loss of layer-specific astrocytic glutamine synthetase immunoreactivity in slice cultures of hippocampus.

Glutamine synthetase (GS) supposedly inactivates the excitatory neurotransmitter glutamate. By using immunocytochemistry for GS, we recently demonstrated a layer-specific, perisynaptic distribution of GS-immunoreactive astrocytes and their processes in perfusion-fixed rat hippocampi. Highest levels of immunoreactivity were found in well defined termination zones of glutamatergic hippocampal afferents. In the present study we analysed the developmental aspect of this neuron-glia interaction by using hippocampal slice cultures lacking all extrinsic afferents. Under these conditions, no layer-specific distribution of astrocytic GS immunoreactivity could be demonstrated. This suggests that the laminated distribution of GS immunoreactivity is formed in parallel with the segregated termination of hippocampal afferents. Thus, there is no predetermined pattern of GS-containing astrocytes playing a role in the segregation of extrinsic fibres. The ultrastructural localization of GS immunoreactivity in fine astrocytic processes around asymmetric, probably glutamatergic excitatory spine synapses confirms earlier in situ findings, which suggests that this arrangement is a global phenomenon of glutamatergic systems.

Animals↗
PubMed1993

Formation of the septohippocampal projection in vitro: an electron microscopic immunocytochemical study of cholinergic synapses.

Cholinergic neurons in the medial septum/diagonal band complex project to the hippocampus and fascia dentata and establish characteristic types of synapses on a variety of target neurons. At present we do not know the principles that underlie the development of this projection and the formation of the cholinergic synapses. Here we have used co-cultured slices of septum and hippocampus of one- to six-day-old rat pups to study the development of the septohippocampal pathway and the formation of cholinergic synapses on hippocampal target neurons in vitro. Slices of septum and hippocampus were incubated together for 10-46 days applying the roller-tube technique. The fluorescent dye dioctadecyltetramethylindocarbocyanine perchlorate and histochemical staining for acetylcholinesterase labeled many fibers connecting both explants. Combined light- and electron-microscopic immunocytochemistry for choline acetyltransferase, the acetylcholine-synthesizing enzyme, revealed multipolar immunopositive neurons with long aspiny dendrites in the septal culture. Numerous varicose immunoreactive, supposedly cholinergic fibers could be followed from the septal to the hippocampal culture where they ramified and formed a three-dimensional network. As in situ, cholinergic terminals formed characteristic symmetric synapses on cell bodies, spines and, most often, on dendritic shafts of the hippocampal target neurons. No immunoreactive fibers and synapses were observed in single cultures of hippocampus. These results demonstrate that the cholinergic septohippocampal projection develops in vitro and that similar types of cholinergic synapses are established on co-cultured hippocampal target neurons as observed in situ.

Acetylcholinesterase↗
PubMed1991

Differentiation of dentate granule cells in slice cultures of rat hippocampus: a Golgi/electron microscopic study.

The differentiation of granule cells in organotypic cultures of rat hippocampus was studied by means of the Golgi/electron microscopic (EM) technique. Like in vivo, the granule cells have a small round or avoid cell body which gives rise to apical dendrites densely covered with spines. However, the apical dendrites of the cultured granule cells are more horizontally oriented than in the normal fascia dentata where they form a cone-shaped dendritic arbor. Granule cells in slice cultures occasionally have basal dendrites invading the hilar region. Electron microscopic examination revealed many synaptic contacts on identified apical and basal dendrites of the gold-toned granule cells in culture. This suggests that a considerable synaptic reorganization takes place since all extrinsic afferents normally innervating the granule cells are lost. Several granule cells displayed deep infoldings of their nuclei which are known from in vivo studies to be a characteristic feature of non-granule cells in this region. i.e. basket cells. The presence of basal dendrites and nuclear infolding indicates an increased variability of this cell type which is situ displays a rather stereotyped morphology.

Animals↗
PubMed1991

Proliferation and differentiation of glial fibrillary acidic protein-immunoreactive glial cells in organotypic slice cultures of rat hippocampus.

The present paper deals with the proliferation and differentiation of glial cells in organotypic slice cultures of the rat hippocampal formation. Transverse slices of hippocampus of newborn to five-day-old rats were cultivated using the roller tube technique. To study the development of glial cells under these conditions, the slice cultures were processed for immunostaining employing antibodies against the glial fibrillary acidic protein. The proliferation of glial cells was studied in double-labeling experiments employing glial fibrillary acidic protein-immunostaining and the bromodeoxyuridine technique. The three-dimensional glial scaffold in the cultures was analysed in semithin and ultrathin cross-sections through the slice cultures after varying periods following explanation. Our results can be summarized as follows: 1. At all intervals after explanation of the slices there are numerous glial fibrillary acidic protein-positive cells with morphological characteristics of astrocytes. 2. With some modifications, the differentiation of astrocytes and their processes follows similar rules as observed in the hippocampus in vivo. A radial glial scaffold is also formed in the cultures. However, in cultures, a regular pattern of radial fibers is more obvious in the hippocampus proper than in the dentate gyrus. This glial scaffold persists after 20 days in vitro whereas it is known to disappear after the first postnatal week in vivo. 3. Bromodeoxyuridine-positive nuclei of glial cells were found at all time periods after explanation. After short incubation periods, they were most frequent in the "ventricular" zones of the cultures. Following longer incubation periods after bromodeoxyuridine administration, proliferating cells were found throughout the cultures, covering and underlying the cultured tissue. A rim of laterally migrating astrocytes completely surrounds the cultures. Our results demonstrate that glial cells proliferate and differentiate under the present culture conditions. After three weeks of incubation the whole slice culture is surrounded by a glial cover which may play an important role for the survival and differentiation of the cultured hippocampal neurons.

Animals↗
PubMed1990

Plasticity of identified neurons in slice cultures of hippocampus: a combined Golgi/electron microscopic and immunocytochemical study.

The combined Golgi/electron microscope (EM) technique and immunocytochemistry for glutamate decarboxylase (GAD) were used to study the differentiation of pyramidal neurons and GABAergic inhibitory non-pyramidal cells in slice cultures of rat and mouse hippocampus. Golgi-impregnated and gold-toned cultures showed the characteristic curved structure of the Ammon's horn. Hippocampal regions CA1, CA3 and fascia dentata could easily be recognized. Pyramidal neurons in CA1 displayed all characteristics of this cell type known from Golgi studies in situ. A triangular cell body gives rise to a main apical dendritic shaft which gives off several side branches. Basal dendrites and the axon originate at the basal pole of the cell body. Apical and basal dendrites are densely covered with spines. As a characteristic feature of the cultured pyramidal cells, numerous spines were observed on the cell body. Most likely due to flattening of the slice during incubation, the pyramidal neurons in CA1 are no longer arranged in a densely packed layer. This results in more space between cell bodies which is filled in by numerous horizontal and basal dendrites originating from the pyramidal cell perikaryon. CA1 pyramidal neurons in slice cultures of the rat or mouse thus resemble the pyramidal neurons in the CA1 region of the primate hippocampus where a similar loose distribution of cell bodies is found. In the electron microscope, cell bodies and dendritic shafts of the gold-toned pyramidal cells formed symmetric synaptic contacts with presynaptic terminals. Numerous boutons were observed that established asymmetric synaptic contacts on gold-toned spines of peripheral pyramidal cell dendrites. This suggests that considerable synaptic reorganization takes place because in situ spines on peripheral dendritic segments are contacted mainly by extrinsic afferents. Like in situ, at least some of the terminals that establish symmetric synaptic contacts are GABAergic. In our immunocytochemical study we observed numerous GAD-positive terminals that formed a dense pericellular plexus around immunonegative cell bodies of pyramidal neurons. In the electron microscope these structures were identified as presynaptic boutons which formed symmetric synaptic contacts on cell bodies and dendritic shafts. They most likely originated from the GAD-positive neurons scattered in all layers of the slice culture. Our results have shown that the main cell types in the hippocampus, pyramidal neurons and GABAergic inhibitory non-pyramidal cells, survive and differentiate under the present culture conditions.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

Using genetically-defined rodent strains for the identification of hippocampal traits relevant for two-way avoidance behavior: a non-invasive approach.

Genetically-defined rodent strains permit the identification of hippocampal traits which are of functional relevance for the performance of two-way avoidance behavior. This is exemplified here by analyzing the relationship between infrapyramidal mossy fibers (a tiny projection terminating upon the basal dendrites of hippocampal pyramidal neurons) and two-way avoidance learning in about 800 animals. The necessary steps include 1) identification of structural traits sensitive to selective breeding for extremes in two-way avoidance, 2) testing the robustness of the associations found by studying individual and genetical correlations between hippocampal traits and behavior, 3) establishing causal relationships by Mendelian crossing of strains with extreme structural traits and studying the behavioral consequences of such structural 'randomization', 4) confirming causal relationships by manipulating the structural variable in inbred (isogenic) strains, thereby eliminating the possibility of genetic linkage, and 5) ruling out the possibility of spurious associations by studying the correlations between the hippocampal trait and other behaviors known to depend on hippocampal functioning. In comparison with the classical lesion approach for identifying relationships between brain and behavior, the present procedure appears to be superior in two aspects: it is non-invasive, and it focuses automatically on those brain traits which are used by natural selection to shape behaviorally-defined animal populations, i.e., it reveals the natural regulators of behavior.

Animals↗
PubMed1989

Hippocampal mossy fiber distribution and long-term potentiation in two inbred mouse strains.

We studied long-term potentiation in the inbred mouse strains DBA/2 and C3H/He known to be different in both hippocampal mossy fiber distribution and several aspects of learning. Tetanic stimulation of mossy fibers resulted in a significantly stronger increase of the population spike amplitude in the CA3 pyramidal cell layer of C3H mice. This result suggests that the extent of the CA3 hippocampal mossy fiber projection correlates with synaptic efficacy in mice.

Action Potentials↗
PubMed1989

Identification of a cell surface-associated protein involved in mouse neural cell aggregation by means of antibodies against the sponge aggregation factor.

Polyclonal antibodies were raised against the purified aggregation factor (AF) from the sponge Geodia cydonium to elucidate possible immunological relationships between adhesion molecules of lower multicellular eukaryotic systems (sponges) and those of vertebrates. This anti-AF recognized a series of polypeptides associated with the AF, among them also a polypeptide with a Mr of 47,000 (p47). The formation of the antibody-p47 immunocomplexes could be prevented by adsorbing the anti-AF with a brain extract from DBA/2J mice. Moreover, this brain polypeptide inhibited the AF-mediated aggregation of sponge cells. Interestingly, the anti-AF recognized a p37 molecule in the brains of 2- to 3-day-old mice; no reaction could be traced using brain extracts from animals older than 2 months. The anti-AF failed to interact with polypeptides from mouse liver or spleen. By indirect immunofluorescence staining the p37 was found to be localized on the plasma membranes of brain cells. Moreover, Fab' fragments of the anti-AF inhibited aggregation of mouse brain cells. These data indicate that the sponge anti-AF recognizes a p37 molecule in mouse brain cells which is either directly or indirectly involved in brain cell aggregation.

Animals↗
PubMed1988

Strain-specific development of the mossy fiber system in organotypic cultures of the mouse hippocampus.

The postnatal development of the hippocampus of the inbred mice strains BALB/c, C57BL/6, and DBA/2 was studied in organotypic explant cultures using the roller-tube technique. In vivo, mice exhibit strain-specific mossy fiber distribution patterns. As a main result we found, that after cultivation of 3-4 weeks, similar strain-specific patterns became apparent in vitro, as visualized by a modified Timm staining. From this experiment we can conclude that a postnatal extrinsic influence cannot be the cause of the strain-specific hippocampal features.

Animals↗
PubMed1988

Organotypic culture of central histamine neurons.

Organotypic cultures of histaminergic tuberomammillary (TM) neurons were grown using explants obtained from newborn rats. The cultures were examined after immunohistochemical localization of the histamine synthetic enzyme, L-histidine decarboxylase (HDC). The morphological properties of the somata, dendrites and axons of HDC-immunoreactive TM neurons in organotypic culture were virtually indistinguishable from those seen in situ. Extensive plexuses of HDC-immunopositive axons, including growth cones, were seen within the hypothalamus, the plasma surrounding the explant and co-cultured hippocampus. Organotypic cultures of TM histamine neurons, and co-cultures with their targets, provide a useful model system for studying several aspects of central histaminergic neurobiology.

Animals↗
PubMed1988

Infrapyramidal mossy fibers and two-way avoidance learning: developmental modification of hippocampal circuitry and adult behavior of rats and mice.

The extent of the intra- and infrapyramidal mossy fiber projection (IIP-MF) in the hippocampus of mice and rats is strain-specific, and correlates negatively with the strain-specific capacity of avoidance learning. If variations of the IIP-MF influence the capacity for 2-way avoidance learning, then developmental modification of the IIP-MF projection in an individual member of a strain should remain correlated with its adult behavior. Pups of strains with high avoidance capacity and small IIP-MF projections (RHA rats, DBA/2 and BALB/c mice) were injected with varying doses of thyroxine during the postnatal period. This transient hyperthyroidism resulted in a strong, yet largely unpredictable, variability of the IIP-MF projection in the adult animals. Furthermore, postnatal saline injections also increased the variability of the IIP-MF projection; however, this was to a lesser degree than when using thyroxine. The animals were tested for 2-way avoidance learning at the age of 90-120 d. Many showed strain-atypical avoidance scores. These deviations from the inherited level of 2-way avoidance learning were strongly correlated with the magnitude of the IIP-MF projection, regardless of whether the structural changes resulted from thyroxine or saline injections. A multivariate analysis showed that the observed correlations could neither be explained by thyroxine-induced changes in brain weight nor by individual differences of other terminal fields in the hippocampal region CA3. These results suggest that the extent of the IIP-MF projection is influenced by several genetic and epigenetic factors. Irrespective of the underlying causes, the magnitude of the IIP-MF (or of an unknown but well-correlated variable) appears to bias the adult capacity for 2-way avoidance learning predictably.

Animals↗
PubMed1987

Strain-specific correlations between hippocampal structural traits and habituation in a spatial novelty situation.

The rat strains Naples high-excitable (NHE) and Naples low-excitable (NLE) have been selectively bred since 1976 for behavioral arousal in a spatial novelty situation. The Timm-stained hippocampi of 20 NHE and 18 NLE rats were examined morphometrically for differences in the proportions (volume percentages) of terminal fields in the fascia dentata and CA3/CA4 at the mid-septotemporal level. Prior to histology animals were tested on 2 days for exploratory activity in a square alley system (Làt box). Overall, the two strains differed significantly in the percentage of stratum lacunosum molecular (NHE greater than NLE, P less than 0.001), of the intra/infrapyramidal mossy fiber (IIP-MF) projection (NLE greater than NHE, P less than 0.001), of the granule cell layer (NLE greater than NHE, P less than 0.05) and of the outer molecular layer (NHE greater than NLE, P less than 0.05). Both strains had an IIP-MF projection smaller than in any other rat strain. Most of the strain differences, however, appear to reflect genetic drift rather than a response to selective breeding. Unexpectedly, the highly active line (NHE) showed a strong correlation between the IIP-MF and overnight habituation; the larger the IIP-MF projection, the lesser the long-term habituation (r = -0.70, P less than 0.001). In the NLE rats, the IIP-MF correlated positively with overnight habituation (though not significantly, because of an outlier). In both lines, stratum oriens was negatively correlated with short-term habituation in the second exposure (NHE: r = -0.68, P less than 0.001; NLE: r = -0.66, P less than 0.01). Thus, hippocampal variability of non-genetic origin appears to be correlated with processes which modulate strain-characteristic responses to a spatial novelty situation.

Animals↗
PubMed1985

Hippocampal variation between the inbred mouse strains C3H/HeJ and DBA/2: a quantitative-genetic analysis.

A classical cross-breeding study involving the inbred mouse strains DBA/2 and C3H/HeJ revealed a rather complex mode of inheritance for the following hippocampal variables: size of stratum pyramidale, number of supra-, intra- and infrapyramidal mossy fiber synapses, and the size of terminal fields receiving entorhinal input. A polygenic mode of inheritance was inferred for these phenotypes. For the size of the regio inferior a model containing additive genetic effects only was sufficient to explain the variation between generations. The strain difference may be caused by one genetic factor only. In agreement with previous experiments a strong negative correlation between the number of intra- and infrapyramidal mossy fiber synapses and shuttle-box avoidance performance was found in the genetically heterogeneous F2 population.

Animals↗