Biomedical subjects

J R Wolff

Publications and source records attributed to J R Wolff.

At least 91 records · Page 5Linked to original sources

PubMed1989

Quantitative analysis of the number and distribution of neurons richly innervated by GABA-immunoreactive axons in the rat superior cervical ganglion.

The superior cervical ganglion of rats contains a considerable number of nerve fibers with GABA-like immunoreactivity which show a nonuniform distribution within the ganglion. The topography of these fibers has been analyzed by using antibodies raised against GABA-BSA-glutaraldehyde complexes. GABA-positive axons and axon varicosities accumulated around a subpopulation of principal ganglion cells forming basketlike patterns. These neurons richly innervated by GABA-positive axons (RIG-neurons) in turn were aggregated in patches with strong immunoreactivity. The size and packing density of the patches containing RIG-neurons and GABA-positive axons approaching them had rostral-to-caudal and medial-to-lateral gradients. Similar patterns were found in right and left ganglia. In five ganglia, a quantitative analysis revealed on average 1,344 RIG-neurons per ganglion representing about 5% of the total neuron population, with small variations (standard deviation 122) despite the highly variable shape of the ganglia. The distribution of RIG-neurons resembles that of neurons sending their axons into the internal carotid nerve. To check this possible correlation, HRP was injected into the eye and applied to the transected external carotid nerve. Double staining for the retrogradely transported peroxidase and GABA immunohistochemistry revealed that RIG-neurons formed a small subpopulation of retrogradely labelled neurons in both experiments. This suggests that RIG-neurons innervate various target organs. This conclusion is in agreement with the observation that RIG-neurons also exist in other sympathetic ganglia. Data presented suggest that sympathetic ganglion cells can be classified on the basis of non-uniform innervation patterns formed by axons that use different neurotransmitters.

Animals↗

PubMed1989

Immunohistochemical localization of glutamate decarboxylase in the rat oviduct and ovary: further evidence for non-neural GABA systems.

The distribution of L-glutamate decarboxylase (GAD), a major biosynthetic enzyme for gamma-aminobutyric acid (GABA), was examined in the oviduct and ovary of the rat by means of an immunohistochemical technique. The polyclonal antiserum raised against brain GAD showed specific immunoreaction in some non-neuronal elements of the sex organs. In the oviduct, the inner layer of the mucosa was predominantly labelled. The selective distribution of GAD immunoreactivity in epithelial cells of the oviduct is consistent with former findings for GABA-like immunoreactivity in the same organ, indicating that the GAD-catalyzed reaction may be a major biosynthetic pathway for GABA even in these cells. In the ovary, vacuole-like formations within the follicular fluid and oocytes showed intense, specific staining. The occurrence of GAD immunoreactivity inside developing ovarian follicles including the oocyte may suggest a role for GABA related to follicular development and certain functions concerning the ovum.

Animals↗

PubMed1989

Pronase treatment increases the staining intensity of GABA-immunoreactive structures in the paravertebral sympathetic ganglia.

A novel tissue preparation technique for improving gamma-aminobutyric acid (GABA) immunocytochemistry has been developed. The influence of the glutaraldehyde concentration in the fixative and the effect of pronase treatment on the GABA immunostaining were tested. This method includes fixation with a high concentration of glutaraldehyde, gelatin embedding and treatment of the sections with pronase. In sympathetic (paravertebral) ganglia and their connectives, the most intense and specific immunoreaction was obtained with the following procedure: immersion fixation in 5% glutaraldehyde, infiltration and embedding in 15% gelatin, secondary fixation of the samples with 4% formaldehyde, floating frozen sections and digestion with 0.1% pronase for 15-20 min. With this technique, the GABA-containing structures (cells and nerve fibers with varicosities forming basket-like networks around some principal neurons) were selectively labeled. The data presented suggest that (1) a high concentration (5%) of glutaraldehyde in the primary fixative is necessary to preserve a large proportion of the GABA content; (2) this glutaraldehyde fixation partly masks the GABA immunoreactivity; and (3) this masking may be overcome by a proteolytic treatment preceding the immunostaining. This method has been extensively tested for the light microscopic visualization of GABA-containing tissue components in the sympathetic ganglion chain, but it may probably also be used for the immunocytochemical detection of other small molecules in other parts of the nervous system.

Animals↗

PubMed1989

Evidence for GABAergic fibers entering the superior cervical ganglion of rat from the preganglionic nerve trunk.

The origin of gamma-aminobutyric acid immunoreactive (GABA-IR) nerve fibers present in the superior cervical ganglion (SCG) of rat was investigated. With immunocytochemical techniques many nerve fibers showed GABA-like positivity in the cervical sympathetic trunk, whereas similar staining could not be revealed in the internal carotid nerve or in the external carotid nerve. Ligation of the cervical sympathetic trunk for 24 h resulted a dramatic reduction in the staining density in the ganglion and in the cervical sympathetic trunk distal to the ligature. After transection of the preganglionic nerve fibers for eleven days or more, very few fibers staining for GABA were seen in the ganglion. The immunohistochemical results suggest that a major source of GABA within the SCG is a population of GABAergic axons entering from the preganglionic trunk.

Animals↗

PubMed1989

Functional consequences of modification of callosal connections by perinatal enucleation in rat visual cortex.

The effects of neonatal monocular enucleation (right eye) on the callosal connections in the rat visual cortex were studied by physiological and morphological methods. Evoked activity was recorded in the left hemisphere, i.e. contralaterally to the enucleated eye. After enucleation, trans-callosally evoked responses were recorded in a widened stripe of the lateral visual cortex. Compared with the controls, the responsive area was expanded laterally and medially, i.e. into the lateral part of the primary visual area and within the secondary visual cortex (lateral part). Within about 0.5 mm of the expansion, the responses did not differ from those recorded in areas with "normal" callosal connections. Morphological evidence is presented suggesting that this expansion of evoked responses with high amplitudes and short latencies corresponds to an extension of callosal connections with a high density of axon terminals in layers two and three. Further medially within the primary visual cortex, callosally evoked responses with low amplitudes and longer latencies were recorded. The main types of unit responses and characteristic interactions between visually and callosally evoked responses are shown and discussed. These results suggest that following neonatal enucleation (1) the callosal connections expand and form functional synapses in the lateral part of the visual cortex, (2) these connections can activate cortical neurons either directly or by mediation of associational connections between the lateral secondary and primary visual cortex areas and (3) callosal connections can interact with visually evoked potentials and unit responses.

Animals↗

PubMed1989

Age-related loss of t-[35S]butylbicyclophosphorothionate binding to the gamma-aminobutyric acidA receptor-coupled chloride ionophore in rat cerebral cortex.

Muscimol and t-butylbicyclophosphorothionate (TBPS) are known to label two distinct sites within the gamma-aminobutyric acidA (GABAA) receptor complex, i.e., the GABA recognition site and the chloride ionophore, respectively. Age-dependent changes in the specific binding of [3H]muscimol and [35S]TBPS were compared in membranes prepared from the cerebral cortex of rats, 2-800 days old. Perinatal (day 2) binding of muscimol and TBPS represented 8 and 20% of the respective values for adults (day 180). After the first week, muscimol binding increased more rapidly than TBPS binding. Levels near those of adults were reached at day 20 and remained practically unchanged in adulthood (day 180). In aged (780-day-old) rats, the binding of TBPS was significantly reduced, whereas muscimol binding did not change compared with adult values. This decrease of TBPS binding derived from a reduced density of binding sites, rather than from affinity changes. The allosteric responsiveness of TBPS binding to exogenous GABA was also reduced in aged animals. These findings indicate an age-related change in the molecular (structural) organization of the GABAA receptor-chloride ionophore complex in rat cerebral cortex.

Aging↗

PubMed1989

Binding of [3H]-muscimol to GABAA sites in the guinea-pig urinary bladder: biochemical assay and autoradiography.

1. The specific binding of [3H]-muscimol, a gamma-aminobutyric acidA receptor (GABAA) agonist, to whole membranes of the guinea-pig urinary bladder was examined. In addition, the distribution of specific muscimol binding sites within the bladder was visualized by autoradiography. 2. It was demonstrated that in a frozen-thawed whole membrane preparation of the organ the specific binding of [3H]-muscimol is reproducible, reversible and saturable. 3. Saturable binding was of a single component with an equilibrium dissociation constant (Kd) of 12 nM and a maximal density (Bmax) of about 80 fmol mg-1 protein. 4. In displacement experiments with several model compounds, [3H]-muscimol binding sites showed the characteristics of a GABAA receptor site. 5. Autoradiographic experiments revealed uneven distribution of specifically bound [3H]-muscimol in the bladder. The density of binding sites was high in clusters within the smooth muscle layers of the bladder fundus and of the urethra, while the apex and the neck were not specifically labelled. 6. The present findings show that GABAA type receptor sites in the guinea-pig urinary bladder may be labelled by [3H]-muscimol in a specific and reproducible manner. Moreover, the localization of these binding sites is consistent with the presence of GABAA receptors in only a subpopulation of vesical ganglia.

Animals↗

PubMed1989

Inhibition by sodium bromide of synaptic potentiation and calcium accumulation in the superior cervical ganglion of rat.

Electrophysiological data show that sodium bromide (NaBr) inhibits the development of the post-tetanic potentiation in superior cervical ganglia of rat. NaBr treatment also prevented the accumulation of calcium in synaptic vesicles and dendritic vacuoles otherwise seen for some minutes after a tetanizing stimulation. These observations support the notion that the calcium ions entering into pre- and postsynaptic elements play an important role in the genesis of synaptic potentiation.

Animals↗

PubMed1989

Interaction of soluble and substratum-bound factors influences neurite elongation.

Neurite elongation was investigated in explanted chick dorsal root ganglia (DRG) using either serum-supplemented or defined N1 medium and different culture substrata. The results indicate that there is no substantial difference in neurite elongation on the three substrata when ganglia are grown in N1 medium. In contrast, neurite length depends on the substratum in serum-supplemented medium and in general exceeds that obtained in N1 medium. Optimal neurite growth was observed in N1 medium when culture dishes have been precoated with serum. Our data suggest that while soluble serum molecules inhibit neurite growth adsorbed serum constituents clearly stimulate neurite elongation.

Animals↗

PubMed1988

Releasable, non-neuronal GABA pool in rat stomach.

The uptake and K+-evoked release of [3H] gamma-aminobutyric acid (GABA) was examined in tissue slices from rat gastric antrum. Active [3H]GABA accumulation was observed that could only be partially inhibited by L-diaminobutyric acid (L-DABA), a blocker of neuronal GABA uptake. The L-DABA-insensitive uptake component was saturable, sodium-dependent and of high affinity. Moreover, [3H]GABA could be released from this L-DABA-resistant pool by a high K+ concentration. It is concluded that a releasable, non-neuronal GABA pool, which may have some functional significance, is present in the gastric antrum.

Aminobutyrates↗

PubMed1988

Self-stabilization of neuronal networks. II. Stability conditions for synaptogenesis.

This study is concerned with synaptic reorganization in local neuronal networks. Within networks of 30 neurons, an initial disequilibrium in connectivity has to be compensated by reorganization of synapses. Such plasticity is not a genetically determined process, but depends on results of neuronal interaction. Neurobiological experiments have lead to a model of the behavior of individual neurons during neuroplastic reorganization, formalized as a "synaptogenetic rule" that governs changes in the amount of synaptic elements on each neuron. When this synaptogenetic rule is applied to a system of neurons, there is some freedom left to the choice of further conditions. In this study it is examined, which assumptions additional to the synaptogenetic rule are essential in order to obtain morphogenetic stability. By explicating these assumptions, their plausibility can be tested. It is analysed, in which respect these conditions are important, in which part of the model they exert their influence, and what kind of instability and degeneration happens if the assumptions are violated. Our essentials for reaching morphogenetic stability are: (1) A network structure that guarantees the possibility of oscillations, (2) a compensation algorithm that guarantees a smooth morphogenesis, (3) kinetic parameters that guarantee convergence in the synaptic elements' change, and (4) a synaptic modification rule that prohibits Hebb-like as well as anti-Hebb-like synaptic changes. It is concluded that many structural features of the mammalian cerebral cortex are in accordance with the requirements of the model.

Algorithms↗

PubMed1988

Heterogeneous distribution of GABA-immunoreactive nerve fibers and axon terminals in the superior cervical ganglion of adult rat.

The distribution of axons and axon varicosities containing GABA was studied in the superior cervical ganglion of rat by light and electron microscopic immunohistochemistry. Two different polyclonal antibodies were used, which had been made against GABA conjugated by glutardialdehyde to bovine serum albumin. GABA-like immunoreactivity occurred in many axons within the cervical sympathetic trunk and in axons and axon varicosities around the principal nerve cells in the superior cervical ganglion. GABA-positive axons were intermingled with non-stained axons, except for a small group of fibers in the trunk where the staining was absent. The rostral part of the ganglion and some scattered patches were more densely innervated by GABA-positive axons than the middle and caudal parts. Within dense areas, some of the large ganglion cells were abundantly surrounded by GABA-positive nerve fibers, while the vicinity of others was devoid of any immunoreactive axon terminals. None of the principal ganglion cells contained GABA-like immunoreactivity, although a class of small cells scattered within the ganglion was stained. Transection of the cervical sympathetic trunk for 11 days caused the disappearance of GABA-like positivity from most of the fibers, and only very little GABA-like staining was revealed in some small cells, which resembled satellite cells. Ultrastructurally, the GABA-positive nerve fibers were unmyelinated. However, their terminal branches and varicosities accumulated around the perikarya and dendrites of certain principal ganglion cells were partly wrapped in glial processes. The present results provide evidence that the superior cervical ganglion of adult rat receives a significant number of GABA-positive axons from the cervical sympathetic trunk and that these axons provide an innervation which is heterogeneously distributed within the superior cervical ganglion and on ganglionic cells. The source and function of the GABA-positive axons remain to be elucidated.

Animals↗

PubMed1988

Modified distribution patterns of responses in rat visual cortex induced by monocular enucleation.

Monocular enucleation was performed on rats at birth or on the 8th or 15th day, respectively. The animals were raised and from the age of 3 months the evoked activity was tested in the visual cortex. It was found that monocular enucleation changed the distribution of visually evoked responses. In the right hemisphere (contralateral to the preserved eye) two focuses of evoked potentials appeared with large amplitudes shifted to both sides, towards the lateral and medial borders of the primary visual area. In the left hemisphere the focus of the evoked potentials was shifted slightly laterally and posteriorly. Early enucleation caused an expansion of the somatosensory responses into the visual area. Bimodal neurons (responsive to visual and somatosensory stimuli) were observed in the anterior part of the primary and secondary visual areas contralateral to the enucleation. These changes became moderate with increasing age at which enucleation was performed and were not found in animals enucleated on the 15th day after birth.

Animals↗

PubMed1987

Fine-structural changes of synapses in the superior cervical ganglion of adult rats after long-term administration of GABA. A morphometric analysis.

The superior cervical ganglion (SCG) of adult rats was exposed to gamma-aminobutyric acid (GABA) by means of long-term microapplication. Serial sections were cut from GABA-treated and control ganglia, and subsequently the fine structure of individual synapses was investigated. The quantitative analysis of structural parameters of studied synapses showed that significant changes consisting of (1) a reduction in size of presynaptic axon terminals, (2) a decrease in the number of synaptic vesicles, and (3) a diminution in the extent of the postsynaptic membrane thickening at the dendritic side developed as an effect of GABA-treatment. These results provide morphological evidence that long-term application of GABA to the SCG exerts a combination of effects on both presynaptic and postsynaptic elements. It is suggested that the structural changes observed in the fine structure of individual synapses within the SCG may play an integral role in the development of the synaptogenetic action of GABA.

Animals↗

PubMed1987

Transient increase of calcium in pre- and postsynaptic organelles of rat superior cervical ganglion after tetanizing stimulation.

The stimulation-dependent translocation and redistribution of intracellular calcium was studied in synapses of the rat superior cervical ganglion. For the cytochemical demonstration of calcium at the ultrastructural level the oxalate-pyroantimonate technique was used. Calcium-containing deposits were observed as electron-dense particles in synaptic vesicles and occasionally in presynaptic mitochondria. On the postsynaptic side, vesicles and vacuoles in dendrites contained increased amounts of reaction product. Following a short train of impulses (20 s, 20 c.p.s.), the ganglionic response to a single stimulus was increased. This potentiation effect which lasted about 1-5 min was accompanied by a change in the distribution of calcium at fine structural level. In ganglia fixed 1 and 5 min after the train, but not later, the number of calcium-containing synaptic vesicles and postsynaptic vacuoles increased significantly.

Animals↗

PubMed1987

Neurochemistry of GABAergic system in cerebral cortex chronically exposed to bromide in vivo.

Neurochemical correlates of GABAergic synaptic transmission [binding, uptake, metabolism, and tissue content of gamma-aminobutyric acid (GABA)] were investigated in the cortex of rats that had been given 27 mM bromide in drinking water for periods of time ranging from 1 day to 1 month. No effect of bromide on any of the parameters was found and it is concluded that chronic administration of bromide has no profound effect on GABAergic inhibitory system in the rat cortex.

4-Aminobutyrate Transaminase↗

PubMed1986

Presence of neurons with GABA-like immunoreactivity in the superior cervical ganglion of the rat.

Using antibodies raised against gamma-aminobutyric acid (GABA)-glutaraldehyde complexes, we have found neurons with GABA-like immunoreactivity in the superior cervical ganglion of adult rats. The processes of these neurons formed pericellular networks around the principal ganglion cells. Electron microscopy revealed that the immunoreactive dendrites were innervated by non-reactive axon terminals which formed asymmetrical synapses and probably originated from the preganglionic nerve. Axons with GABA-like immunoreactivity, especially axonal varicosities filled with synaptic vesicles, were found in direct apposition to principal ganglion cells. The GABA-positive axons and axon varicosities persisted in experimentally decentralized (deafferented) ganglia, suggesting that the perikarya of the immunoreactive neurons were intrinsic to the superior cervical ganglion. Taken together with data on inhibitory effects of GABA in sympathetic ganglia, these findings suggest that the superior cervical ganglion of rats contains a subpopulation of inhibitory interneurons which is GABAergic. This would indicate that GABAergic neurons do not only occur in the central but also in the peripheral nervous system.

Animals↗

PubMed1986

Promotion by sodium bromide of functional synapse formation from foreign nerves in the superior cervical ganglion of adult rat with intact preganglionic nerve supply.

The possible effect of sodium bromide (NaBr) (a substance with known inhibitory action on synaptic transmission) was studied on synapse formation with foreign nerves, implanted into the superior cervical ganglion of adult rats. It was found that in spite of the presence of preganglionic nerve supply, both implanted nerves (n.XII and n.X, respectively) were enabled to establish functional synapses with the principal ganglion cells in NaBr-treated animals. In contrast, synapse formation was almost absent in ganglia of sodium chloride drinking (control) rats with intact preganglionic nerve supply. This effect of NaBr is considered to be analogous to that of GABA, whose promoting action on synaptogenesis in adult rat superior cervical ganglion has been previously described.

Animals↗