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A Rustioni

Publications and source records attributed to A Rustioni.

At least 73 records · Page 4Linked to original sources
PubMed1986

Intracellular staining study of the feline cuneate nucleus. I. Terminal patterns of primary afferent fibers.

The terminal arborizations of single identified cutaneous hair follicle and slowly adapting type I receptors and muscle (Ia) afferents have been studied in the cuneate nucleus of cats after intra-axonal injection of horseradish peroxidase. Penetrations were mainly at the middle and caudal levels of the nucleus--i.e., from obex to approximately 7 mm caudal to it. Following histochemical processing, the injected axons, along with their collateral branches and synaptic terminals, were visualized and examined with light and electron microscopy. Cutaneous afferents in middle cuneate (from obex to approximately 4 mm caudal to it) issued collateral branches, along the rostrocaudal axis of the nucleus, at intervals between 100 and 1,000 microns. The terminal field of each collateral's branches encompassed an area elongated largely rostrocaudally and virtually confined to the dorsal part of the middle cuneate. Although adjacent collaterals had nonoverlapping terminal arborizations, each one could give rise to separate foci of terminations. Muscle afferents differed, on the whole, from cutaneous afferents in the location and extent of collateral branching and terminal arborizations. However, because muscle fibers terminated primarily in the ventral region of the cuneate, but nevertheless exhibited sparser terminations in the dorsal part of the middle cuneate, there was some spatial overlap between zones of muscle and cutaneous projection. Synaptic boutons of cutaneous afferent fibers contained round clear vesicles, contacted dendritic profiles (sometimes more than one), and were postsynaptic to small boutons containing polymorphic vesicles. In contrast, boutons of muscle afferent fibers contacted somatic and dendritic profiles and were not postsynaptic to other boutons. The results are in general agreement with previous anatomical and electrophysiological work; however, the extent of the terminal field of single collateral branches may provide for a greater convergence of different receptor classes and of receptive fields on neurons in the middle cuneate than estimated by previous electrophysiological investigations.

Afferent Pathways↗
PubMed1986

Intracellular staining study of the feline cuneate nucleus. II. Thalamic projecting neurons.

Morphological and physiological features of thalamic projecting neurons in the middle region of the cuneate nucleus of cats (from obex to 4 mm below it) have been studied, using intracellular recording and iontophoresis of horseradish peroxidase. All cuneothalamic neurons in the present sample) responded to movement of hairs on wrist, paw, or digits. However, approximately 50% of the neurons could be activated by other types of stimulation (e.g., light or maintained pressure on the skin, movement of claws, etc.). No clear differences were apparent in the physiological responses correlated with the varied dendritic pattern of stained neurons. Dendritic arborizations of most cuneothalamic neurons were more extensive than assumed previously, from Golgi impregnated material. As a consequence, only a few neurons have dendrites ramifying within a restricted region--i.e., corresponding to a typical cluster of the middle cuneate nucleus. Dendrites extending in various directions and spanning a distance up to 500 microns provide cuneothalamic neurons with the ability to receive input from relatively widespread areas. Collateral branches of axons of cuneothalamic neurons were observed in 50% of the stained neurons. Most of these collaterals terminated ventrally within the cuneate nucleus. Extensive collateral arborizations were observed in the dorsal as well as the ventral cuneate. These results, together with those reported in the previous paper, suggest complex interactions of afferent inputs on cuneothalamic neurons. In particular, such neurons are likely to be influenced by convergent input from different receptor classes and, because of their axonal collaterals, probably affect the excitability of other neurons, projecting or intrinsic, in their immediate vicinity or in other nuclear regions.

Afferent Pathways↗
PubMed1985

Sensorimotor cortical projections to the primate cuneate nucleus.

The organization of the corticocuneate pathway was investigated in monkeys by using the anterograde and retrograde axonal transport of either horseradish peroxidase (HRP) or wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). Injection of either tracer into the precentral cortex (centered on area 4) results in heavy anterograde labeling in the tegmental region, which lies immediately ventrolateral to the cuneate nucleus, particularly at levels caudal to the obex. On the other hand, injections of the same tracers involving areas 3b, 1, and 2 cause anterograde labeling mainly within the core (pars rotunda of Ferraro and Barrera, '35, Arch. Neurol. Psychol. 33:262-75) of the cuneate nucleus. Anterograde labeling is also evident in the rostral parts of the cuneate nucleus, especially after injections involving areas 1 and 2. Injections restricted largely to area 3b cause anterograde labeling preferentially in the core of the cuneate nucleus. After injection of HRP or WGA-HRP into the dorsal medulla, retrogradely labeled neurons are present both in the pre- and postcentral gyrus, but their location depends upon the sites and extent of the injection site. When the tracer diffuses into the underlying tegmental area, many retrogradely labeled neurons appear in the precentral motor cortex, principally in area 4 although some of them also occur in area 6. With smaller injections, largely restricted within the cuneate nucleus, most labeled neurons are present in the postcentral gyrus, with the largest population in areas 1 and 2; a smaller number of small neurons in area 3b are best demonstrated with WGA-HRP; and area 3a contains the smallest complement of retrogradely labeled neurons. The data from these studies suggest a segregation of pre- and postcentral afferents in the ventral tegmental region and the cuneate nucleus, respectively. These findings pertaining to the corticocuneate projection in the monkey are discussed in relation to the parallelism between monkeys and cats possible physiological implications of the anatomical organization described, and conflicting evidence in the neurophysiological observations obtained, by earlier investigators, by antidromic and orthodromic activation of this pathway.

Animals↗
PubMed1985

A new double-labeling method demonstrates transmitter-specific projections.

We report a method which combines retrograde transport of the fluorescent dye, diamidino yellow dihydrochloride (DY), with peroxidase immunocytochemical staining for glutamic acid decarboxylase (GAD), an enzyme essential for the synthesis of gamma-aminobutyric acid (GABA). Cells exhibiting both retrograde fluorescent label and GAD-positive immunoreactivity were observed in the cerebellar cortex, the striatum and the ventrobasal complex following injections of DY into the superior vestibular nucleus, substantia nigra and dorsal thalamus. The method, which can in principle be applied to any antigen, takes advantage of the differential nuclear/cytoplasmic distribution of the two stains. By using appropriate filter combinations and balanced epi- and transillumination, double-labeled cells are readily identifiable.

Amidines↗
PubMed1985

Retrograde labeling of dorsal root ganglion neurons after injection of tritiated amino acids in the spinal cord of rats and cats.

The present experiments are based upon evidence that neurons may selectively take up at their terminals, and retrogradely transport, the same chemical they use as a neurotransmitter or its analogues. In an attempt to identify dorsal root ganglion (DRG) neurons that use glutamic acid as a neurotransmitter, [3H]D-aspartate ([3H]D-Asp) was chosen as a marker, since it is a metabolically inert amino acid known to be taken up by the same affinity mechanism as L-aspartate and L-glutamate. Adult rats and cats received injections of 50 nl to 1.5 microliter of [3H]D-Asp (500 microCi/microliter) in the dorsal horn of cervical segments (C3 to C6). At 9 to 48 hr after injection, all animals were perfused with 5% glutaraldehyde. After sections were processed for autoradiography, the DRG neurons situated most closely to the injection site were chosen from representative cases, and the number and cross-sectional area of labeled and unlabeled perikarya with a nucleolus in the plane of the section were calculated. In rats, about 4% of the sampled DRG neurons were autoradiographically labeled, and the mean perikaryal area of these neurons was about twice that of unlabeled perikarya. In cats, the percentage of labeled perikarya ranged between 6.5% and 13.27% of the sampled population. The ratio of the mean perikaryal area of labeled neurons to that of unlabeled neurons ranged between 1.6 and 2.5. In a control cat injected with [3H]proline at C7, all perikarya in the C7 DRG were autoradiographically labeled. However, with injection of [3H]gamma-aminobutyric acid ([3H]GABA) selective retrograde labeling was observed. Quantitative data in rat showed that perikarya labeled at the C6 level after injection of this amino acid constituted about 8% of the sample population in C6 DRG. The ratio of the size of labeled to unlabeled perikarya was 2.02. In one cat injected with [3H]GABA at caudal C3, the largest number of labeled perikarya were in C4 DRG and comprised up to 5.32% of the sampled population. The ratio of the size of labeled to unlabeled perikarya was 1.57. The results in cases of injection with [3H]D-Asp may be interpreted as consistent with the idea that a fraction of DRG neurons use glutamate and/or aspartate as neurotransmitter(s).(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acids↗
PubMed1984

Light and electron microscopic evidence for a direct corticospinal projection to superficial laminae of the dorsal horn in cats and monkeys.

The anterograde transport of horseradish peroxidase (HRP) and wheat germ agglutin conjugated to horseradish peroxidase (WGA-HRP) was employed in cats and monkeys to investigate, at both the light and electron microscopical levels, the contribution of the corticospinal tract (CST) to the superficial laminae of the dorsal horn. At the light microscopic level, this approach not only confirmed the previously documented pattern of CST termination, but also revealed a sparse projection to laminae VIII and IX of the cat and a prominent projection to the most superficial parts of the brachial dorsal horn, i.e., laminae I and II. Discrete injections involving particular cytoarchitectonic areas (4, 3a, 3b, and 1-2) of monkeys showed that the superficial laminae receive their corticofugal inputs primarily from areas 3b, 1, and 2. Electron microscopic observations were made on CST fibers and boutons which were labelled, after histochemical processing, with the reaction product of anterogradely transported WGA-HRP. The labelled fibers in the superficial laminae were small (+/- 0.5 micron), and boutons established mainly axodendritic contacts, contained mostly clear, spherical, or pleomorphic vesicles, but sometimes also displayed dense core vesicles. These boutons were primarily in lamina I and outer lamina II, but not in inner lamina II. The possible role of a direct monosynaptic pathway from the cerebral cortex to the superficial laminae of the dorsal horn is discussed in relation to the previous reports that laminae I and II play a significant role in nociception.

Animals↗
PubMed1984

Arborizations of single corticofugal axons in the feline cuneate nucleus stained by iontophoretic injection of horseradish peroxidase.

Terminal aborizations and synaptic boutons of cortical afferents to the cuneate nucleus were examined by light and electromicroscopy following intra-axonal staining with HRP. Two populations of afferents are described: (1) direct corticocuneate fibers, and (2) fibers destined for the spinal cord which issue collateral branches to the cuneate nucleus. Corticocuneate terminals primarily contact fine dendrites located in the ventral parts of the nucleus. These results are discussed in relation to previous anatomical findings and to new concepts of cuneate nucleus organization.

Animals↗
PubMed1984

Glutamic acid decarboxylase-containing neurons in the dorsal column nuclei of the cat.

The retrograde transport of horseradish peroxidase (HRP) and immunocytochemistry for glutamic acid decarboxylase (GAD) have been employed to examine whether local circuit neurons (LCNs) exist in the dorsal column nuclei (DCN) and whether these neurons may be GABA-ergic. Observations focused on the dorsal part of the middle cuneate nucleus (MCd), since this region has been previously shown to contain projecting neurons whose axons terminate almost exclusively in the contralateral thalamus. After large injections of HRP in the nucleus ventralis posterolateralis and surrounding structures of the feline thalamus, the majority of neurons in MCd are labeled. These represent about 89% of the neurons in MCd as counted in 40-microns frozen sections, and about 69% as counted in plastic-embedded, 2.5-microns-thick section. Unlabeled by the same injections are some medium to large neurons at the dorsal rim of MCd, and many characteristically small (mean = +/- 250 microns2) neurons at the periphery of the cell clusters formed by thalamic-projecting neurons. These small neurons represent 10-12% of the neuronal population of MCd, as counted in 40-microns-thick frozen sections, and about 30%, as counted in plastic-embedded, 2.5-microns-thick sections. Neurons in this size range are also unlabeled after injection of retrograde tracer in the pretectal area, inferior and superior colliculi, inferior olivary complex, and/or spinal cord. These injections, however, result in the labeling of neurons along the dorsal rim of MCd and/or in other regions of the cuneate nucleus. In adult, colchicine-treated cats, the use of anti-GAD serum reveals a population of labeled neurons uniformly distributed throughout the DCN. In MCd, these are small (mean = +/- 235 microns2) neurons mainly intercalated between cell clusters, and represent about 25% of the neuronal population of this nuclear subdivision as counted in plastic-embedded, 2.5-microns-thick sections. Labeled processes densely infiltrate the cell clusters, and labeled varicosities appear to cover the soma and dendrites of unlabeled neurons. At the electron-microscopic level, most labeled profiles contain vesicles and correspond to F boutons usually involved in "axoaxonic" contacts with terminals of dorsal root afferent and presynaptic to dendrites. Other vesicle-containing, GAD-positive endings seem to correspond to the P boutons described by Ellis and Rustioni (1981) and are believed to be, at least in part, of dendritic origin. It is suggested that GAD-positive neurons are GABA-ergic LCNs and that these can mediate both pre- and postsynaptic inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

Improved visualization of neurons labeled with horseradish peroxidase: silver-intensification of the pyrocatechol/p-phenylenediamine reaction product.

A silver intensification procedure suitable for use with pyrocatechol/p-phenylenediamine (PC-PPD) product of the horseradish peroxidase (HRP) reaction is described. Qualitative and quantitative results from retrogradely labeled neurons in the cat cortex after thalamic injection of HRP demonstrate an increase of the intensity of labeling and in the number of darkly labeled cells after the intensification procedure. In both the non-intensified and the intensified PC-PPD reacted tissue the sensitivity was comparable to that of TMB-treated material. The ratio of lightly to darkly labeled neurons was very similar in intensified PC-PPD and TMB material, suggesting that the lightly labeled cells may have fewer terminals present at the level of the injected target.

Animals↗
PubMed1983

Cortical relay neurons and interneurons in the N. ventralis posterolateralis of cats: a horseradish peroxidase, electron-microscopic, Golgi and immunocytochemical study.

After injections of horseradish peroxidase involving the whole primary (SI) and secondary somatosensory (SII) areas of adult cats, 16-21% out of 2220 counted neurons in the nucleus ventralis posterolateralis were unlabelled. The mean areas of perikarya of these neurons varied between 111.8 +/- 32.3 microns2 and 180.8 +/- 48.6 microns2. The size of perikarya of retrogradely-labelled neuron ranged from 256.9 +/- 100.4 microns2 to 409 +/- 163 microns2. Retrogradely-labelled and unlabelled neurons were examined under light- and high-voltage electron-microscopy. Besides 'large', mainly multipolar or oval fusiform perikarya, retrogradely-labelled neurons may display perikarya of 'small' size. Both types of neurons correlate well with Golgi-impregnated cells with a tufted dendritic pattern usually identified as thalamocortical neurons. On the other hand, the size and morphology of perikarya and initial dendrites of neurons unlabelled by retrograde transport of horseradish peroxidase correlate well with that of Golgi-impregnated neurons which are markedly different from the thalamocortical neurons, have very characteristic and profuse dendritic appendages and have been identified by previous investigators as Golgi Type II neurons. In order to probe further whether these may correspond to the GABAergic interneurons proposed by previous evidence, an immunocytochemical approach was also applied at the light- and electron-microscope level, using an antiserum prepared in sheep against rat brain glutamate decarboxylase. By this method it is shown that 19-21% of neurons in the nucleus ventralis posterolateralis of adult cats are glutamate decarboxylase-positive and that the perikaryal size of these labelled neurons ranges between 134.6 +/- 44.5 microns2 and 164.4 +/- 47.3 microns2. Histogram distribution of the number and areas of the counted immunoreactive neurons closely matches that of unlabelled neurons in experiments with retrograde transport of horseradish peroxidase. The results give support to previous evidence suggesting that part of population of neurons in the nucleus ventralis posterolateralis is represented by a distinct class of neurons which are apparently GABAergic.

Animals↗
PubMed1983

The corticocuneate pathway in the cat: relations among terminal distribution patterns, cytoarchitecture, and single neuron functional properties.

A combined anatomical and physiological strategy was used to investigate the organization of the corticocuneate pathway in the cat. The distribution of the corticocuneate projection was mapped by means of the anterograde horseradish peroxidase (HRP) labeling technique and correlated with the nuclear cytoarchitecture in Nissl and Golgi material, the distribution of retrogradely labeled relay cells after HRP injections in the ventrobasal complex of the thalamus, and the topographic organization derived from single- and multiunit recordings in the decerebrate, unanesthetized cat. This approach provided details about the arrangement of the corticocuneate pathway that were not available from previous studies with anterograde degeneration methods. On the basis of cytoarchitectonic and connectional features, a number of subdivisions are identified in the cuneate nucleus, each of which is associated with characteristic functional properties. In agreement with previous studies, it is found that a large portion of the cuneate nucleus, the middle dorsal part (MCd), is exclusively devoted to the representation of cutaneous receptive fields on the digits. This "core" region contains more thalamic projecting neurons than any other subdivision of the cuneate nucleus. A topographic arrangement also exists in the subdivisions of the rostral cuneate and of the nuclear region ventral to MCd, although in these, receptive fields are larger and predominantly, but not exclusively, related to deep receptors and involve the arm, shoulder, and trunk. Observations on corticocuneate projections were based on injections, mainly focused on functional subdivisions of the primary somatosensory cortex (SI) as described by McKenna et al. (1981). Although cortical projections are mainly to cuneate regions other than its core, a significant proportion of fibers from the region of SI where the digits are represented (particularly area 3b) do project to the MCd region of the cuneate nucleus. Similarly, nuclear areas associated with receptive fields on the arm and trunk are labeled after injection in SI arm and trunk regions, respectively. Thus, a close topographic relationship appears to exist between the somatosensory cortex and cuneate regions related to the same body representation, although nuclear regions in which receptive fields on the neck area are represented receive very sparse or no detectable cortical projections even when the injection of the tracer involves the entire sensorimotor cortex.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1982

Selective retrograde transport of D-aspartate in spinal interneurons and cortical neurons of rats.

Retrograde labeling of neuronal elements in the brain and spinal cord has been investigated by autoradiographic techniques following injections of D-[3H]aspartate (asp), [3H] gamma-aminobutyric acid (GABA) or horseradish peroxidase (HRP) in the medulla and spinal cord of rats. Twenty-four hours after D-[3H]asp injections focused upon the cuneate nucleus, autoradiographic labeling is present over fibers in the pyramidal tract, internal capsule and over layer V pyramids in the forelimb representation of the sensorimotor cortex. After [3H]GABA injections in the same nucleus no labeling attributable to retrograde translocation can be detected in spinal segments, brain stem or cortex. Conversely, injections of 30% HRP in the cuneate nucleus label neurons in several brain stem nuclei, in spinal gray and in layer V of the sensorimotor cortex. These observations give further support to the proposed existence of a selective retrograde transport of D-[3H]asp and are consistent with the available evidence which indicates that the corticodorsal column nuclei path use glutamate and/or aspartate as neurotransmitter(s). D-[3H]Asp injections focused on the dorsal horn at cervical segments label a fraction of perikarya of the substantia gelatinosa and a sparser population of larger neurons in laminae IV to VI for a distance of 3-5 segments above and below the injection point. No brain stem neuronal perikarya appear labeled following spinal injections of D-[3H]asp although autoradiographic grains overlie pyramidal tract fibers on the side contralateral to the injection. This labeling however has not been observed rostral to lower pontine levels nor over cortical neurons at any of the survival times used in the present experiments (6-72 h). As in cases with cuneate injections this pattern of labeling contracts with that obtained after spinal injections of either [3H]GABA or HRP. Although labeling of neocortical neurons has not been observed after spinal injections of D [3H]asp, possibly as a result of the length of corticospinal axons, retrograde labeling of these elements for at least some distance may be taken as suggestive of a special affinity of their terminals for glutamate and/or aspartate.

Animals↗
PubMed1982

Thalamic projecting neurons in the feline nucleus cuneatus. A combined horseradish peroxidase and high voltage electron microscopic study.

The retrograde transport of horseradish peroxidase (HRP) has been employed to identify thalamic projection neurons (TPN) in the feline nucleus cuneatus by means of light microscopy and high voltage electron microscopy. Forty-eight hours after injection of HRP in the contralateral ventrobasal complex of the thalamus, labelled neurons at levels caudal to the obex are concentrated in the cell clusters of the dorsal two-thirds of the nucleus. In plastic sections, labelled TPN are identified by the presence of HRP-positive granules in the perinuclear cytoplasm. TPN are typically about 25 micrometers in diameter, have a round nucleus with a smooth contour and abundant cytoplasm. In contrast, neurons unlabelled after thalamic injection are located at the periphery of clusters of TPN. Unlabelled neurons are characterized by their fusiform shape (hence, round when encountered in cross-section), small diameter (10-15 micrometers), a nucleus with an irregular or highly indented contour, and sparse cytoplasm. At the ultrastructural level, TPN are identified by the presence of HRP-positive, membrane-bound, dense bodies in the perinuclear cytoplasm. Furthermore, the presence of such dense bodies in cross-sections of dendrites allows their identification as processes of TPN. The perikarya of adjacent neurons in a cluster are often closely apposed and separated by an extracellular space of 20 to 25 nm. Adjacent to such sites of apposition, small boutons are often presynaptic to one or both of the neurons. The possible functional implications of such an arrangement are discussed.

Afferent Pathways↗
PubMed1981

Descending projections from brainstem and sensorimotor cortex to spinal enlargements in the cat. Single and double retrograde tracer studies.

Single and double retrograde tracer techniques were employed in cats to investigate: (1) the topographical relationships between supraspinal neurons projecting to either the brachial or lumbosacral enlargement, (2) the distribution and relative frequency of single supraspinal neurons which project to both enlargements by means of axonal branching. In one group of cats large injections of horseradish peroxidase (HRP) were made throughout either the brachial or lumbosacral enlargement. The results from these experiments support recent observations on the multiplicity of brainstem centers giving origin to descending spinal pathways and provide evidence for a population of corticospinal neurons in area 6. In a second set of experiments, HRP was injected in one enlargement, and 3H-apo-HRP (enzymatically inactive) was injected in the other enlargement. Relatively large numbers of neurons with collateral projections to both enlargements (double-labeled) were observed in the medullary and pontine reticular formation, the medial and inferior vestibular nuclei bilaterally, the ipsilateral lateral vestibular nucleus, Edinger-Westphal nucleus, caudal midline raphe nuclei and nuclear regions surrounding the brachium conjunctivum. By contrast, double-labeled neurons were infrequently observed in the red nucleus and sensorimotor cortex, contralateral to the injections. In the red nucleus, lateral vestibular nucleus and sensorimotor cortex, neurons projecting to the brachial enlargement were largely segregated topographically from neurons projecting to the lumbosacral enlargement. However, there was some overlap, and double-labeled neurons were consistently observed within the region of overlap. In the sensorimotor cortex, the overlap between brachial- and lumbar-projecting neurons was most prominent in areas 4 and 3a, along the cruciate sulcus, but also involved other cytoarchitectonic regions in the medial aspect of the hemisphere.

Animals↗
PubMed1981

Corticospinal tract collaterals to the dorsal column nuclei of cats. An anatomical single and double retrograde tracer study.

A double-labelling anatomical strategy employing horseradish peroxidase and tritiated, enzymatically inactive horseradish peroxidase allowed simultaneous visualization of corticospinal neurones and cortical neurones projecting to the dorsal column nuclei in cats. By this approach it is shown that although most cortical fibres to these nuclei are not branches of corticospinal axons, neurones projecting to both targets are present in all areas of the sensorimotor cortex and especially in area 3a. Thus, cortical control upon the dorsal column nuclei is mediated via descending fibres that differ as to their origin and to their branching pattern.

Animals↗