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J R Wolff

Publications and source records attributed to J R Wolff.

At least 109 records · Page 6Linked to original sources
PubMed1986

GABA receptor binding in rat cerebral cortex and superior cervical ganglion in the absence of GABAergic synapses.

High affinity binding of [3H]gamma-aminobutyric acid (GABA) to membrane-containing homogenates prepared from rat cerebral cortex (neonatal or adult) or from adult rat superior cervical ganglion (SCG) was tested for sensitivity to baclofen, bicuculline and several other analogues of GABA. Since no major differences were found between the tissues free of GABAergic synapses (SCG and neonatal cortex) and GABAergic synapse-rich adult rat cortex, it is suggested that the presence of GABAergic synapses does not play a decisive role in the determination of pharmacological sensitivities of high-affinity GABA receptors.

Aging↗
PubMed1986

Spatial correlation between sensory regions and the drainage fields of pial veins in rat cerebral cortex.

Visual and somatosensory evoked potentials were mapped in the cerebral cortex of adult rats and, after filling the cerebral arteries and veins with dye, the mappings were then compared to the distribution of pial veins. A close relationship was found between the position, size and shape of the occipital venous drainage field and the distribution of visual evoked potentials with high amplitudes and short latencies. Accordingly, such potentials evoked by stimulation of the forepaw and tailroot were confined to the fronto-parietal drainage field. In the case of individual variations in the expansion and shape of sensory areas, the medial and lateral borders of the occipital drainage field and the medial border of the fronto-parietal drainage field covaried. Only at the common border between these two drainage fields, visual evoked potentials with small amplitudes and long latencies extended into the parietal drainage field and overlapped with somatosensory evoked potentials. This overlapping area corresponds in position to the anterior part of the peristriate cortex. A comparison between the vascular organization and cytoarchitectonic maps of the rat cortex indicates that other parts of the characteristic pattern of venous drainage fields may also correlate with the cytoarchitectonic and functional organization of the cerebral cortex. These observations suggest that during morphogenesis the formation of sensory projections to the cerebral cortex may interact with the angiogenesis, mainly with the development of veins.

Animals↗
PubMed1986

Self-stabilization of neuronal networks. I. The compensation algorithm for synaptogenesis.

Between the extreme views concerning ontogenesis (genetic vs. environmental determination), we use a moderate approach: a somehow pre-established neuronal model network reacts to activity deviations (reflecting input to be compensated), and stabilizes itself during a complex feed-back process. Morphogenesis is based on an algorithm formalizing the compensation theory of synaptogenesis (Wolff and Wagner 1983). This algorithm is applied to randomly connected McCulloch-Pitts networks that are able to maintain oscillations of their activity patterns over time. The algorithm can lead to networks which are morphogenetically stable but preserve self-maintained oscillations in activity. This is in contrast to most of the current models of synaptogenesis and synaptic modification based on Hebbian rules of plasticity. Hebbian networks are morphogenetically unstable without additional assumptions. The effects of compensation on structural and functional properties of the networks are described. It is concluded that the compensation theory of synaptogenesis can account for the development of morphogenetically stable neuronal networks out of randomly connected networks via selective stabilization and elimination of synapses. The logic of the compensation algorithm is based on experimental results. The present paper shows that the compensation theory can not only predict the behavior of synaptic populations (Wagner and Wolff, in preparation), but it can also describe the behavior of neurons interconnected in a network, with the resulting additional system properties. The neuronal interactions--leading to equilibrium in certain cases--are a self-organizing process in the sense that all decisions are performed on the individual cell level without knowing the overall network situation or goal.

Animals↗
PubMed1986

A method for common undercutting of interactive regions in rat cerebral cortex.

A method is described by which several cortical areas can be isolated from subcortical afferent and corticofugal efferent connections, but the operation leaves associative and commissural connections with each other and with non-isolated areas intact. The common isolation of interactive cortical regions offers new possibilities to study morphologically, biochemically and electrophysiologically the complex process of synaptic reorganization and cortical functions in the absence of subcortical afferent and efferent connections.

Animals↗
PubMed1986

Sensory interactive zones in the rat cerebral cortex.

The acoustic, somatosensory and visual areas of the rat cerebral cortex were mapped in view of overlapping regions, giving polysensory evoked responses. In case of each pair of modalities overlapping areas were found between the cortical representations. The evoked potentials of two different modalities show occlusive and facilitatory interactions in these overlapping areas. In the "core" region of these areas, points with especially high values of occlusion are concentrated while at the periphery weak occlusion or even facilitation is characteristic. It is supposed that the polysensory areas interposed between primary sensory fields represent not only areas with mixed responsiveness but also stage for real physiological interactions between different sensory systems.

Animals↗
PubMed1986

Tangential organization of the infragranular fiber plexus in rat cerebral cortex.

Cylindrical lesions (diameter 300-500 microns) were formed by poking needles into various parts of the cerebral cortex of adult albino rats. Degenerating axons were visualized in horizontal sections through the 'flattened' cortex using the silver impregnation method of Gallyas et al. [Stain Technol. 55: 291-297 (1980)] which stains degenerating axoplasm. The density and distribution of tangentially oriented axons were evaluated in the infragranular layers by TV image analysis. The sampling fields were concentrically arranged around the lesion at distances of 200, 400, 700 and 1,100 microns. The results indicate that the distribution patterns of degenerating (associational) axons covary with the cytoarchitectonic regions into which the lesions were placed. In the motor cortex, the majority of axons run in the antero-posterior direction. The density is generally lower around lesions in frontal regions than in parietal regions. The most extended degeneration was found around lesions near the border of or within the retrosplenial cortex, indicating an exceptionally strong internal connectivity in this area. Since only few degenerating axons were seen around lesions in the center of area 17, the high density of myelinated axons in the primary visual cortex seems to be due to fibers that originate in peristrate areas. It is concluded that the number and extension of fibers that degenerate tends to covary with some aspects of cortical architecture, but it is not area-specific.

Animals↗
PubMed1986

Metal-catalyzed oxidation renders silver intensification selective. Applications for the histochemistry of diaminobenzidine and neurofibrillary changes.

Physical developers can increase the visibility of end products of certain histochemical reactions, such as oxidative polymerization of diaminobenzidine and selective binding of complex silver iodide ions to Alzheimer's neurofibrillary changes. Unfortunately, this intensification by silver coating is generally superimposed on a nonspecific staining originating from the argyrophil III reaction, which also takes place when tissue sections are treated with physical developers. The present study reveals that the argyrophil III reaction can be suppressed when tissue sections are treated with certain metal ions and hydrogen peroxide before they are transferred to the physical developer. The selective intensification of Alzheimer's neurofibrillary changes requires a pre-treatment with lanthanum nitrate (10 mM/liter) and 3% hydrogen peroxide for 1 hr. The diaminobenzidine reaction can be selectively intensified when physical development is preceded by consecutive treatments with copper sulfate (10 mM/liter, pH 5, 10 min) and hydrogen peroxide (3%, pH 7, 10 min). In peroxidase histochemistry, this high-grade intensification may help to increase specificity and reduce the threshold of detectability in tracing neurons with horseradish peroxidase or in immunohistochemistry when the peroxidase-antiperoxidase method is used.

3,3'-Diaminobenzidine↗
PubMed1986

Cytochemical demonstration of cyclic 3',5'--AMP phosphodiesterase in the superior cervical ganglion of the rat.

The localization of cyclic 3',5'-phosphodiesterase in the superior cervical ganglion of the rat was studied by an ultrastructural cytochemical method. Large amounts of evenly distributed electron dense granular reaction products were detectable on the cytoplasmic processes of Schwann cells while a discontinuous and rough reaction product was observed in the postganglionic neurones. Usually, a significant number of lead phosphate deposits was found in the capillaries but endothelial cells sometimes were free from the reaction product. Abundant lead phosphate deposits were accumulated in the long processes of macrophages situated in the connective tissue of the ganglion. In the synaptic and non-synaptic neuropil, fine granulated reaction products were associated with microtubular and microfilamentar elements, pre- and postsynaptic membrane thickenings, mitochondria, rough surface endoplasmic reticulum, and multivesicular bodies as well. The wide ranging occurrence of cyclic phosphodiesterase positive reaction product in the superior cervical ganglion reflected the fundamental intra and extracellular regulatory role of this enzyme in cyclic nucleotide metabolism.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1985

Neurogenesis of GABAergic neurons in the rat dentate gyrus: a combined autoradiographic and immunocytochemical study.

Neurogenesis of GABAergic neurons in the rat area dentata was studied combining [3H]thymidine autoradiography with immunostaining for glutamate decarboxylase (GAD), the gamma-aminobutyric acid (GABA) synthesizing enzyme. GAD immunocytochemistry stained many neurons located mainly in the hilar region but also in the granular and molecular layers. Granule cells were not immunoreactive. On embryonic day (E) 14, [3H]thymidine injection labelled 12.8% of GAD-positive (+) neurons in sections of the area dentata processed at an age of 40 days postnatally. This proportion decreased to 1.8% on E17 and to 1% on E18. No GAD (+) neurons were labelled by thymidine injection on E19, while non-immunoreactive granule cells and CA4 pyramids were still labelled, indicating persisting neurogenesis of those cells.

Age Factors↗
PubMed1985

Postnatal development of axosomatic synapses in the rat visual cortex: morphogenesis and quantitative evaluation.

Postnatal development of axosomatic synapses was studied in the rat visual cortex in order to obtain experimental data that may explain how the unequal distribution of asymmetric and symmetric synapses evolves on the soma of cortical neurons. Three types of synaptic junctions were identified: asymmetric or type 1 synapses, with postsynaptic densities greater than or equal to 20 nm, symmetric type 2 synapses, and symmetric synapses with an intermediate structure. The third synapse type had a structure similar to that of type 1 synapses, although the postsynaptic densities were thinner than 20 nm. Type 1 synapses developed in three phases. In phase 1, the first postnatal week, there were many free postsynaptic thickenings and immature synapses whereby a higher degree of postsynaptic differentiation was visible in comparison to the presynaptic elements. During the following 10 days, phase 2, type 1 synapses containing thin postsynaptic densities and intermediate synapses temporarily increased in number. Intermediate synapses are interpreted as precursors of type 1 synapses that have relatively immature postsynaptic elements. Toward the end of synaptogenesis, phase 3, the free postsynaptic thickenings reappeared while type 1 synapses containing well developed postsynaptic elements prevailed. Throughout the whole postnatal period, the numerical density of axosomatic type 1 synapses remained very low and the ratio of asymmetric to symmetric synapses at the neuronal somata was inversely proportional to that at the dendrites. Also, there was a significant decrease in the numerical density of type 1 synapses between postnatal days (P) 17 and 30. Data normalized according to cortical growth suggest that this is probably due to a decrease in the number of axosomatic type 1 synapses. This corresponds to the observation that in layers III and V a few type 1 synapses were found on pyramid-like cells up to P10 which then disappeared in later stages. Axosomatic type 2 synapses appear to be formed by two different presynaptic processes. The first presynaptic type contains flocculent material with glycogen granules and resembles axonal growth cones. These junctions contain multiple adhesion patches, intermediate junctions, one or more active zones, narrow synaptic clefts, and small pleomorphic vesicles. All of these are structural features of adult type 2 synapses. The growth-cone-like presynaptic elements disappeared after about 3 weeks. The second presynaptic type is smaller in size and also forms contacts with a structure similar to adult type 2 synapses.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

gamma-Aminobutyric acid enables synaptogenesis in the intact superior cervical ganglion of the adult rat.

Local gamma-aminobutyric acid (GABA) application into the intact superior cervical ganglion (SCG) of the adult rat allows active innervation of a surgically implanted hypoglossal nerve in addition to the normal nerve supply of the ganglion. In GABA-treated SCG of the adult rat, action potentials could be obtained on stimulation of both the preganglionic nerve trunk and the implanted hypoglossal nerve. Both action potentials were reversibly sensitive to hexamethonium bromide indicating new cholinergic synapses established between axons in the hypoglossal nerve and principal sympathetic neurons. If GABA treatment of the ganglion was omitted, the double innervation did not develop after hypoglossal nerve implantation.

Animals↗
PubMed1985

Small lesions in the primary visual cortex of rats cause a specific reorganization of associational connections.

Neuroplastic changes in associational connections were investigated 3 weeks after the intrinsic organization of the visual cortex of rats had been partially damaged by small cylindrical lesions (type I). These lesions caused the degeneration of short intracortical connections and associational connections that form patches in the primary and secondary visual areas. The resulting terminal degeneration disappeared within 20 days p.o. after which only some fiber degeneration was evident in the infragranular layers. Patches of terminal degeneration reappeared in the vicinity of the stab wounds, when the associational connections between the retrosplenial and the primary visual cortex had been secondarily interrupted by elongated lesions (type II), which penetrated the paramedian cortex and subcortical white matter. When type-II lesions were made in the intact cortex, patches of degeneration were absent, although in both cases some terminal degeneration was diffusely distributed in the primary visual cortex. Horseradish peroxidase (HRP) was applied to sites similar to those where type-I lesions were applied. In the intact cortex, HRP caused a granular labeling of numerous neurons in various positions including the retrosplenial cortex and patches of the postero-median visual cortex. HRP was also applied to type-I lesions that had been made 3 weeks earlier. In these cases, apparently HRP labeled the same subpopulations of neurons as it did in the intact cortex. However, a fraction of the labeled neurons showed a Golgi-like staining (e.g., 27% of the labeled neurons in the retrosplenial cortex) only when HRP was applied to stab wounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed1985

Oligodendrocytes in the pons and middle cerebellar peduncle of the cat. Topographical relations to neurons and transverse axon bundles.

Morphology, microtopography and numerical density of oligodendrocytes were analyzed by light microscopy in the pontine gray and middle cerebellar peduncle of adult cats. The cells were selectively stained by use of the dicyanoargentate technique (Ogawa et al. 1975) that visualizes the entire cell population including perikarya and characteristic features of processes. On the basis of different microtopographical relations to neuronal perikarya and/or transversely oriented axon bundles, six groups of oligodendrocytes were separately analyzed: interfascicular, intrafascicular, perifascicular, perineuronal satellite, perifascicular-perineuronal, and "neuropil" cells. The cell morphology did not co-vary with any of these groups, but the shape of oligodendrocytes was on an average more elongated in the peduncle than in the pontine gray. The average cell density was similar in the gray and white matter (55000-56000 cells/mm3). However, 76% of the cells were concentrated near neuronal perikarya and axon bundles in a volume fraction of only 34%. Between adjacent neurons and axon bundles the cell density was even higher suggesting an additive behavior of these two topographical groups of oligodendrocytes. Axon bundles within the pontine gray contained only very few oligodendrocytes (density 6% that of the peduncle). These observations and quantitative data suggest that the perifascicular cells belong to the group of oligodendrocytes that are topographically related to axons (similar to interfascicular glia of the white matter) rather than to neuronal perikarya or neuropil.

Animals↗
PubMed1985

Oxalate pretreatment and use of a physical developer render the Kossa method selective and sensitive for calcium.

Based on experiments on agarose gels and tissue, a procedure has been developed which greatly improves the sensitivity and the specifity of the Kossa method for demonstrating calcium in tissue. Tissue calcium is immobilized by acetonic oxalic acid, which simultaneously removes the other sorts of anions capable of precipitating silver ions (e.g. phosphate, carbonate). The resulting submicroscopic grains of calcium oxalate are converted first into silver oxalate then into metallic silver by a treatment with silver nitrate followed by an ultra-violet irradiation (Kossa reaction). These submicroscopic metallic silver grains are enlarged up to microscopic visibility by means of physical development, which makes the staining highly sensitive. Co-staining of the argyrophil sites in the tissue is totally suppressed by various tricks, which render the silver staining selective for calcium.

Animals↗
PubMed1985

Modulation of the acetylcholine system in the superior cervical ganglion of rat: effects of GABA and hypoglossal nerve implantation after in vivo GABA treatment.

gamma-Aminobutyric acid (GABA) was applied to the superior cervical ganglion (SCG) of CFY rats in vitro and in vivo, with or without implantation of a hypoglossal nerve, to evaluate the effects of these experimental interventions on the acetylcholine (ACh) system, which mainly serves the synaptic transmission of the preganglionic input. Long-lasting GABA microinfusion into the SCG in vivo apparently resulted in a "functional denervation." This treatment reduced the acetylcholinesterase (AChE; EC 3.1.1.7) activity by 30% (p less than 0.01) and transiently increased the number of nicotinic acetylcholine receptors, but had no significant effect on the choline acetyltransferase (acetyl-coenzyme A:choline-O-acetyltransferase; EC 2.3.1.6) activity, the ACh level, or the number of muscarinic acetylcholine receptors. The relative amounts of the different molecular forms of AChE did not change under these conditions. In vivo GABA application to the SCG with a hypoglossal nerve implanted in the presence of intact preganglionic afferent synapses exerted a significant modulatory effect on the AChE activity and its molecular forms. The "hyperinnervation" of the ganglia led to increases in the AChE activity (to 142.5%, p less than 0.01) and the 16S molecular form (to 200%, p less than 0.01). It is concluded that in vivo GABA microinfusion and GABA treatment in the presence of additional cholinergic synapses has a modulatory effect on the elements of the ACh system in the SCG of CFY rats.

Acetylcholine↗
PubMed1984

Development of GABAergic neurons in rat visual cortex as identified by glutamate decarboxylase-like immunoreactivity.

The development of glutamate decarboxylase (GAD)-like immunoreactivity was studied in albino rats. GAD-positive structures appeared and accumulated in a characteristic temporo-spatial sequence: from embryonic day 18 onwards in lamina (L) I and subplate; after birth in L I-II, L IV-V and deep L VI including white matter; after two weeks in superficial L I, L II to L III-IV border, L V and L VI-white matter. GAD-positive axon varicosities formed perisomatic 'baskets' on L V pyramids on postnatal day 8 and a few days later on those L II-III. During the third week GAD-positive structures attained adult densities and established different laminar patterns in the primary and secondary visual areas.

Animals↗