Search PubMed⌕ Search

Biomedical subjects

J Zimmer

Publications and source records attributed to J Zimmer.

At least 145 records · Page 8Linked to original sources
PubMed1987

Growth of hippocampal mossy fibers: a lesion and coculture study of organotypic slice cultures.

In hippocampal slice cultures, the mossy fibers from the dentate granule cells project as normally to cells in the dentate hilus (CA4) and the hippocampal CA3 pyramidal cells. After lesions in vivo and intracerebral transplantation, the mossy fibers can alter their normal distribution within CA3 and even contact CA1 pyramidal cells. The present study examined whether similar changes could be induced in the more simple, virtual two-dimensionally organized slice cultures. For this purpose slices of 7-day-old hippocampi were prepared and subjected to one of the two following manipulations: (1) transection of the mossy fiber layer in CA3 or (2) rearrangement of the geometrical relations between the dentate granule cells in their potential targets (CA3 and CA1) by coculturing dentate slices with CA3 or CA1 slices. Two to 8 weeks later the distribution of the mossy fiber system was visualized by histochemical Timm sulphide silver staining of the terminals. The distribution of the mossy fiber system observed in previous studies of ordinary hippocampal slice cultures was confirmed. In addition, mossy fibers were found to cross the cuts through the mossy fiber layer with formation of a reduced number of characteristic Timm-stained terminals in CA3 distal to the lesion. Close proximity and contiguity of the cut surfaces were important for such growth to occur. Significantly fewer mossy fiber terminals were found when separate slices of dentate and CA3 tissue were joined and grown as cocultures. Similar apposition of slices of dentate and CA1 tissue only rarely resulted in the ingrowth of mossy fibers into CA1. The Timm-stained mossy fiber terminals were then of subnormal size. The results show the potentials of the slice culture technique in supplementing lesion and transplant studies in situ. The growth of mossy fibers across a transection of their pathway is thus a new observation, difficult to demonstrate in the brain. The limited growth in the cocultures of aberrant mossy fibers into Ca1 does, on the other hand, emphasize the importance of close structural contact for the formation of nerve connections, and such contact is apparently more easily obtained in the brain. When the growth of the mossy fibers and that of the cholinergic septohippocampal fibers are compared, it is evident that the cholinergic axons grow better both in vitro and in vivo after lesions and transplantation.

Animals↗
PubMed1987

Difference in monoamine oxidase B activity between C57 black and albino NMRI mouse strains may explain differential effects of the neurotoxin MPTP.

Monoamine oxidase B (MAO-B) is the key enzyme in the conversion of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP) to N-methyl-4-phenyl-pyridinium ion (MPP+) which causes degeneration of dopaminergic nigral neurons. Using a histochemical tetrazolium method for MAO-B with tyramine as substrate and chlorgyline for the inhibition of MAO-A, black C57 mice were found to have a higher brain MAO-B activity than similar aged albino NMRI mice. The difference, which was in general density rather than distribution, included the basal ganglia and the substantia nigra. The higher activity in C57 mice may explain differences in the susceptibility to MPTP.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1987

Nerve connections between mouse and rat hippocampal brain tissue: ultrastructural observations after intracerebral xenografting.

Fascia dentata tissue from embryonic mice was grafted to the hippocampal region of newborn Kyoto rats. After 1-7 months the recipients received lesions of the entorhinal cortex on the side of transplantation. Three days later their brains were processed for electron microscopy. The xenografts were identified by their content of mouse dentate granule cells which have smaller cell nuclei with more nucleoli than the corresponding host rat granule cells. Electron dense, degenerating host rat entorhinal fibers terminated in the outer parts of the mouse dentate molecular layer corresponding to the normal perforant path zones. They formed the normal type of synaptic contacts with dendritic spines. The findings demonstrate that precise synaptic contacts can be made across a species barrier.

Animals↗
PubMed1987

GABAergic nonpyramidal neurons in intracerebral transplants of the rat hippocampus and fascia dentata: a combined light and electron microscopic immunocytochemical study.

Glutamate decarboxylase (GAD) immunocytochemistry was used to study GABAergic neurons and synapses in intracerebral allografts of the rat hippocampus and fascia dentata. Tissue blocks of regio inferior of Ammon's horn (hippocampal field CA3) or of the fascia dentata were taken from newborn rats and transplanted to the hippocampal region of young adult rats. After 6 1/2 months' survival the recipient brains were fixed by perfusion and serially sectioned on a Vibratome. Sections containing the transplant and/or the host hippocampal region were immunostained for GAD and flat-embedded in Araldite for a correlated light and electron microscopic analysis. Immunostained neurons and terminals in the transplants were compared to immunoreactive elements in the hippocampus and fascia dentata of the hosts and other, normal rats. As in the hippocampal formation in situ, GAD-immunoreactive neurons and terminals in the transplants were observed in all layers. In dentate transplants a preponderance of immunostained cells was found just beneath the granule cell layer. In both hippocampal and dentate transplants, immunoreactive terminals were most abundant in the cell layers where they formed characteristic pericellular baskets around the pyramidal and granule cell bodies. In the electron microscope, the transplant GAD-immunoreactive neurons exhibited numerous cytoplasmic organelles, deeply infolded nuclei, and nuclear rods. Immunoreactive terminals formed symmetric synaptic contacts on the cell bodies, dendritic shafts, and spines of transplant pyramidal cells, granule cells, and hilar neurons. These are normal characteristics of GAD-immunoreactive neurons and terminals as also observed in the hippocampus of the host rats and the normal controls. Our results demonstrate that GABAergic neurons survive transplantation and develop a cell-specific morphology that includes the axonal projections.

Animals↗
PubMed1987

Fetal cortical transplants in the cerebral hemisphere of newborn rats: a retrograde fluorescent analysis of connections.

Fetal cerebral neocortex (E15-17) was grafted into the cortex of newborn (0-1 day old) rats. In some animals the tissue was grafted just caudal to cortical aspiration lesions made immediately prior to grafting. At maturity, transplant efferents were examined by use of the retrogradely transported fluorescent dyes Fast Blue and Diamidino Yellow. Dyes were principally injected in various combinations into the host pyramidal tract decussation and into cervical and lumbar spinal cord levels. In addition some of these animals received injections into the host cortex opposite the transplant, into the ipsilateral thalamus or into the transplant. Transplants were recovered in 26 of 30 animals, and they were typically larger in recipients sustaining aspiration lesions. Histologically, transplants commonly demonstrated laminar patterns that resembled normal cortical supra- and infragranular laminae. Numerous retrogradely-labeled neurons were counted within transplants after injections of fluorescent tracers into the host pyramidal tract decussation or cervical spinal cord. These cells were often located appropriately in areas resembling infragranular layers. Retrogradely labeled neurons were also found within transplants after injections into the host cortex or thalamus. Additionally, numerous host neurons were labeled after Diamidino Yellow injections into the transplant. These findings demonstrate an exchange of connections between host and transplant and suggest the establishment of normal connection patterns.

Animals↗
PubMed1987

Early loss of somatostatin neurons in dentate hilus after cerebral ischemia in the rat precedes CA-1 pyramidal cell loss.

Somatostatin (SS)- and cholecystokinin (CCK)-immunopositive cell somata in the rat hippocampus were quantitated at day 1, 2, 3 and 4 after cerebral ischemia. A significant (P less than 0.01) 60%-80% loss of hilar and CA-3c SS neurons took place. No CCK neurons were lost. Damage to SS neurons was significant on the second postischemic day and preceded the delayed loss of CA-1 neurons. We speculate that loss of SS neurons, which presumably innervate the inhibitory GABAergic (gamma-aminobutyric acid) interneurons, may induce hyperactivity stimulating the Ca-1 neurons to death.

Animals↗
PubMed1987

Cryopreservation of fetal rat brain tissue later used for intracerebral transplantation.

Intracerebral grafting of immature brain tissue is now widely used as a tool to study neuronal development and regeneration in the brain and spinal cord. This has stimulated the interest in methods for storage of such tissue before transplantation. In this study a method for cryopreservation of immature rat central nervous tissue is presented and discussed in relation to current cryobiological principles. The method was applied to brain tissue from 16- and 17-day-old fetal rats, including the neocortex, habenula, septum and basal forebrain, cerebellum, and retina. After storage in liquid nitrogen from 6 to 52 days the tissue was grafted into the brain of adult rats. The recipients survived for 23 to 673 days before their brains were processed by current neuroanatomical, histological methods. The presence of graft tissues was recorded and their cellular and connective organization was examined, including their exchange of nerve connections with the host brain. The results obtained were comparable with results from other studies where the same tissues were grafted immediately after removal from the donor, and a study of cryopreservation of developing hippocampal tissue. We conclude that cryopreservation is a reliable method for storage of immature neural tissue later to be used for intracerebral grafting.

Animals↗
PubMed1986

Intracephalic transplants of freeze-stored rat hippocampal tissue.

The survival and cellular and connective organization of intracephalic transplants of developing, freeze-stored rat hippocampal tissue were examined. Blocks of tissue containing the hippocampus and fascia dentata were obtained from late embryonic (E16-E22) and early postnatal rats (P0-P4) and immersed in a tissue culture medium with 10% of the cryoprotective agent DMSO, frozen at a cooling rate of approximately 1 degree C/minute, and stored for 1-226 days in liquid nitrogen. After quick thawing and washing out of the DMSO the tissue blocks were transplanted to the brain of adult rats. From 2 weeks to 3 months later the recipient brains were processed histologically. The cellular and connective organization of the transplants and their interaction with the host brains were analyzed after thionin cell staining, Timm's staining for hippocampal and dentate afferents, immunohistochemical staining for enkephalin-, CCK-, and somatostatin-reactive neurons and afferents, AChE staining for cholinergic afferents, and silver stains for fiber architectonics and tracing of connections by anterograde axonal degeneration. Freeze-storage narrowed the range of donor ages with good transplant survival. The best surviving hippocampal and dentate transplants thus came from 17-21-day-old embryos. There was no correlation between the length of storage and survival. Structurally the transplants of stored tissue were more frequently fragmented than the transplants of fresh tissue when located outside the brain parenchyma in the brain ventricles. This was in accordance with the results of a previous study of grafts of freeze-stored and fresh hippocampal tissue placed in the anterior eye chamber. Despite the decrease in survival and the tendency for fragmentation many well-structured and organotypically organized hippocampal and dentate transplants were recovered corresponding to the donor ages E19-E21. In addition to the main cell types (granule cells and pyramidal cells) the freeze-stored transplants also contained peptidergic nerve cells reacting for CCK, somatostatin, and enkephalin. The organization of the intrinsic nerve connections and the exchange of connections with the host brain were similar for transplants of stored and fresh tissue. Besides the consistent innervation of the hippocampal and dentate transplants by host cholinergic afferents monitored by AChE staining, several appropriately located dentate transplants thus sent mossy fibers to the host CA3. Others received host perforant path projections. A CA3-associated transplant projection to the denervated perforant path zones in the host fascia dentata was also observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Age Factors↗
PubMed1986

Intracerebral transplants of the rat fascia dentata: a Golgi/electron microscope study of dentate granule cells.

In the present study we describe the morphological characteristics of dentate granule cells in intracerebral allografts of the rat fascia dentata. Blocks of hippocampal tissue containing the fascia dentata were taken from late embryonic and newborn rats and transplanted to the hippocampal region of other newborn and young adult rats. After survival periods of several months the recipient brains were fixed by perfusion and serially sectioned on a Vibratome. Some sections were stained with thionin to determine the localization and general histological organization of the transplants, while others were Golgi stained with a modification of the section Golgi technique. Well-impregnated transplant granule cells were gold-toned and deimpregnated thus allowing a correlated, light and electron microscopic analysis of identified neurons to be done. At the light microscopic level the morphology of the dentate granule cells in the transplants was very similar to Golgi-impregnated, gold-toned granule cells in the fascia dentata of normal rats (controls). A few irregular, more obliquely curved dendrites occurred, but basal dendrites passing into the hilar region were never observed. Following an initial spine-free segment granule cell dendrites were densely covered with spines. The axon, the mossy fiber, originated as usual from the basal pole of the cell body. In the electron microscope, both small and larger complex spines (v and w types) were seen to emerge from the gold-toned dendrites of the identified granule cells. The thin unmyelinated granule cell axons gave rise to giant mossy fiber boutons in the dentate hilus, but in addition numerous aberrant mossy fiber terminals were found innermost in the dentate molecular layer just above the granule cell layer. The results demonstrate that dentate granule cells that have gone through the major part of their differentiation after transplantation develop characteristic dendritic and axonal elements very similar to those of granule cells in the fascia dentata in situ. The minor changes observed correspond to the redistribution of intrinsic connections that results from the absence of major extrinsic afferents.

Animals↗
PubMed1986

Non-cholinergic afferents determine the distribution of the cholinergic septohippocampal projection: a study of the AChE staining pattern in the rat fascia dentata and hippocampus after lesions, X-irradiation, and intracerebral grafting.

The acetylcholinesterase (AChE) activity of the rat hippocampus and fascia dentata depends on an intact septohippocampal connection, and histochemical staining for AChE is commonly used to monitor the distribution of the cholinergic septohippocampal projection. It is also characteristic that the laminae of low or moderate to dense AChE staining in the hippocampus and fascia dentata coincide with the terminal fields of the major non-cholinergic, afferent pathways. While studying lesion-induced collateral sprouting and aberrant axonal growth of these pathways we observed that the AChE staining pattern changed in accordance with the reorganized distribution of the non-cholinergic pathways, and this occurred even without direct interfering with the septohippocampal projection itself. Widening and narrowing of the medial perforant path and mossy fiber terminal zones thus resulted in corresponding changes in the bands of AChE staining normally associated with these zones. Expansion of the commissural-associational hippocampodentate projections and the lateral perforant path was in a similar way paralleled by a widening of the AChE-poor zones which normally overlap with the termination of these projections. Observations of the same kind were made in intracerebral transplants of fascia dentata innervated by various host afferents, and in rats subjected to neonatal X-irradiation, where the mossy fiber projection is reduced and aberrant perforant pathways project into CA3 due to a reduced formation of granule cells. The observed sets of changes with linkage between the different non-cholinergic projections and the activity of AChE in their respective terminal fields were accordingly reproduced under several different experimental conditions. It could not be explained alone by interaction between the septal afferents and their target cells. We therefore conclude that the density and laminar distribution of the AChE activities within the hippocampus and fascia dentata are determined at least in part by the major afferent, non-cholinergic nerve connections. We suggest that the effect occurs through direct axonal interaction or through changes in the receptiveness of the common dentate and hippocampal target cells.

Acetylcholinesterase↗
PubMed1986

Neonatal hippocampal neurons, retrogradely labeled with granular blue, survive intracerebral grafting and explantation to tissue culture.

Previous studies have shown that developing neocortical neurons labeled in situ by retrograde axonal transport of the fluorescent dye Granular Blue can retain this dye for at least 2 months essentially without fading or leakage. In this study, retrograde labeling with Granular Blue was used to label neonatal rat hippocampal neurons prior to intracerebral grafting to uninjected littermates, and explantation as slice cultures. Hippocampal regio inferior and hilar neurons labeled through their developing commissural axons were found to survive axotomy and subsequent grafting and explantation for at least 3 and 8 weeks, respectively. The labeling helped define the developmental differentiation of the neurons at the time of manipulation and provides a new method for identification of a specific population of transplanted or explanted neurons.

Animals↗
PubMed1986

Timm staining of hippocampal nerve cell bodies in the Kyoto rat. A cell marker in allo- and xenografting of rat and mouse brain tissue, revealing neuronal migration.

Using the histochemical Timm sulphide silver method, a strain-specific, increased stainability of the cell bodies of the dentate granule cells and the hippocampal pyramidal cells was observed in the inbred Kyoto rat. The resulting dense staining which also includes neurons in the neocortex and cerebellum can be used as a cell marker in studies of intracerebral allo- and xenotransplantation of rat and mouse hippocampal tissue. Used in such experiments the marker revealed migration of dentate granule cells from Kyoto transplants into the Wistar host fascia dentata.

Animals↗
PubMed1986

Influence of adenohypophyseal tissue on the development of the rat fascia dentata in vitro.

In hippocampal slice cultures, the mossy fibers from the dentate granule cells were previously shown by Timm staining to retain their normal connections to CA4 and CA3 pyramidal cells. While the granule cells of the suprapyramidal (hidden) blade remained in a distinct layer, the granule cells of the infrapyramidal (free) blade of the fascia dentata, however, often spread. This aberrant trait was strikingly enhanced in the presence of a co-cultured adenohypophyseal explant. This infrapyramidal blade of the fascia dentata largely disappeared as a cell layer; granule cell-like neurons, displaying a monopolar dendritic structure directed towards the pituitary, would migrate toward the hypophyseal explant, whilst their axons still functionally innervated CA3 pyramidal cells. Axon collaterals projected in the opposite direction and presumably terminated on dendrites, thus giving rise to the intense black labelling which was observed in Timm-stained preparations as a bridge connecting the two explants. The morphological alterations induced in the fascia dentata by co-cultured adenohypophysis were tissue-specific since co-cultured neurohypophysis, pineal gland and cerebellum failed to produce similar effects. These results suggest that cultured adenohypophyseal tissue is capable of releasing yet unidentified factors which apparently enhance neuronal migration.

Animals↗
PubMed1986

Toward early diagnosis of myotonic dystrophy: construction and characterization of a somatic cell hybrid with a single human der(19) chromosome.

We have constructed a somatic cell hybrid line, designated 908K1, with a single human der(19) chromosome on a Chinese hamster background by employing conventional as well as microcell-mediated cell fusion techniques. The der(19) chromosome comprises the 19p13.1----q13.2 segment, as well as the distal (Xq24----qter) portion of the X chromosome long arm, and is stably retained by HAT selection. Extensive characterization of this hybrid line and comparison with other somatic cell hybrids has enabled us to regionally assign PGK2 to the distal short arm of chromosome 19 and to narrow down the assignments of CYP1, TGFB, and ERCC1 on 19q. Moreover, a cosmid library has been constructed from this microcell hybrid. By screening this library, as well as a chromosome 19-enriched library obtained elsewhere, 14 single-copy probes have been isolated that map on the 19p13.1----q13.2 segment, and 5 probes were assigned to the distal Xq. It is anticipated that these probes will be useful for the diagnosis of myotonic dystrophy and fra(X) mental retardation.

Animals↗
PubMed1985

Transplantation of fetal cortex to the brain of newborn rats: a retrograde fluorescent analysis of callosal and thalamic projections from transplant to host.

Fetal cerebral cortical tissue was transplanted into the cerebral hemisphere of 0-1-day-old rats. In some cases, the transplants were placed into or adjacent to cortical lesion cavities made immediately prior to transplantation. Injections at maturity of fast blue and diamidino yellow into the host contralateral cortex and ipsilateral thalamus demonstrated the presence of callosal and thalamic projections from transplant to host. Numerous single-labeled neurons were often arranged in cell bands or clusters. This apparent topography and the absence of double-labeling resembled normal labeling patterns.

Animals↗
PubMed1985

Resonance Raman evidence for the activation of dioxygen in horseradish oxyperoxidase.

Resonance Raman spectroscopy has been employed to investigate the molecular bases for the markedly different properties of horseradish oxyperoxidase and oxymyoglobin. The porphyrin core of oxyperoxidase is slightly more expanded with the iron atom closer to the porphyrin plane, and there is greater iron d pi-to-oxygen pi backbonding compared to oxymyoglobin. The iron-oxygen (stretching or bending) bands are observed at 570 and 562 cm-1, respectively, for oxymyoglobin and oxyperoxidase, and the iron-His stretching bands have been tentatively identified at 276 and 289 cm-1, respectively. It is suggested that the stronger iron-His bond in oxyperoxidase facilitates greater iron d pi-to-oxygen pi backdonation by raising the energy of the iron d pi orbitals closer to the energy of the oxygen pi orbitals. This weakens the O-O bond and activates dioxygen for use as an electron acceptor in the peroxidase-oxidase reaction.

Horseradish Peroxidase↗
PubMed1985

X inactivation patterns in two syndromes with probable X-linked dominant, male lethal inheritance.

For Incontinentia pigmenti Bloch-Sulzberger (IP) and Aicardi syndrome, an X-linked dominant transmission with lethality in hemizygous males has been proposed. The typical transition from inflammation to verrucous hypertrophy and hyperpigmented skin areas in IP suggests a gradual replacement of defective cells by normal cells. This would imply a preferential inactivation of the X chromosome carrying the IP gene with a proliferative advantage of this cell population. We have confirmed this hypothesis by demonstrating that the same X chromosome is preferentially active in fibroblasts grown from normal and hyperpigmented skin of an affected girl. In contrast, X inactivation was random in a girl with Aicardi syndrome.

Abnormalities, Multiple↗