Biomedical subjects

D Lima

Publications and source records attributed to D Lima.

46 records · Page 3Linked to original sources

PubMed1991

Fine structure and synaptic architecture of HRP-labelled primary afferent terminations in lamina IIi of the rat dorsal horn.

The fine structure and synaptic architecture of the afferent terminations in dorsal horn lamina II are studied using a combined light and electron microscopic procedure after anterograde labelling with horseradish peroxidase. Vibratome parasagittal sections, stained with heavy metal intensified diaminobenzidine after tracer application to the dorsal roots, were flat-embedded in Epon. The five types of labelled terminal arbors occurring in lamina IIi (Cruz et al., '87: J. Comp. Neurol. 261:221-236) were drawn and relocated in 5-microns sections cut serially from the thick sections. Ultrathin sections were then cut from the 5-microns sections so that the terminal fibers and swellings observed in the light microscope could be traced in the electron microscope. The flame-shaped arbors arose from fine myelinated stem fibers. Terminal strands generated large oval central terminals of type II synaptic glomeruli (CII), which established frequent axoaxonal contacts. Similar terminals have been labelled in the cat after tracer injections into hair-follicle fibers (Réthelyi et al., '82: J. Comp. Neurol. 207:381-393). The other four plexuses arose from unmyelinated stem fibers. The swarms of ultrafine boutons consisted of extremely thin terminal fibers generating very small, round, or polygonal glomerular terminals containing tightly packed agranular synaptic vesicles of variable size and one mitochondrion at best. The terminal strands of the bouquet plexus bore long and scalloped central varicosities of type I synaptic glomeruli (CI) with pleomorphic agranular vesicles and a relative abundance of dendroaxonal contacts. These features, together with the location in dorsal lamina IIi, suggest their belonging to the fluoride resistant acid phosphatase (FRAP)-reactive population. The boutons of the undulating fibers and those of the lateral plexus were, like those of the bouquets, scalloped and elongated rostrocaudally (CI), but contained a few large granular vesicles. The occurrence of the swarm, undulating, and lateral plexuses in ventral lamina IIi, which seems to lack FRAP or peptidergic terminals, suggests an origin from other, still unidentified neurochemical populations of fine primary afferents.

Animals↗

PubMed1991

The spino-latero-reticular system of the rat: projections from the superficial dorsal horn and structural characterization of marginal neurons involved.

The projections of the superficial dorsal horn to the lateral reticular nucleus of the medulla oblongata of the rat, and the morphological types of spinal cord lamina I neurons involved were studied after injecting the retrograde tracer cholera toxin subunit B in the caudal portion of the lateral reticular nucleus. Only injection sites located in the lateral part of the lateral reticular nucleus caused retrograde cell labelling in the superficial dorsal horn (laminae I-III). However, injection sites covering the lateral half of the lateral reticular nucleus and the region intermediate between its lateral border and the ventrocaudal tip of the trigeminal spinal nucleus also labelled cells in the neck of the dorsal horn. In contrast, injection sites confined to the intermediate region gave rise to an almost exclusive cell labelling in laminae I-III. Because the lateral part of the lateral reticular nucleus and the adjoining lateral region are rich in noradrenergic cells, it is suggested that these may be the specific targets of laminae I-III neurons. On the basis of the solid dendritic filling achieved, labelled lamina I cells were classified structurally. Most were fusiform cells (80%) and a minority pyramidal or flattened cells (10% each). Since fusiform cells also project selectively to the parabrachial nuclei, which together with the lateral reticular nucleus have been implicated in respiratory and cardiovascular reflexes, it is suggested that this cell type may convey nociceptive input originating autonomic responses. The pyramidal cells project also in large numbers to the mesencephalic periaqueductal gray which, like the lateral reticular nucleus, exerts descending inhibition on the dorsal horn nociceptive neurons. This suggests that this cell type may activate the spinal-midbrain pain modulatory loops centred on both nuclei.

Afferent Pathways↗

PubMed1990

A spinomedullary projection terminating in the dorsal reticular nucleus of the rat.

Spinal afferents to the medullary dorsal reticular nucleus were studied using the following retrograde tracers: horseradish peroxidase (diluted in dimethylsulfoxide), wheat germ agglutinin conjugated with horseradish peroxidase, and cholera toxin subunit B. Spinal cord cells projecting to that medullary region were located predominantly in medial lamina I and lamina X. Cell labelling was moderate in the medial part of laminae II-IV and sparse throughout laminae V-VII. Labelling was predominantly ipsilateral in the dorsal horn and bilateral in laminae VII and X. After mechanical lesions of the dorsal white matter which severed most of the ipsilateral cuneate fasciculus, the numbers of superficial dorsal horn cells that were labelled from the dorsal reticular nucleus were considerably decreased caudal to the lesion, which suggests that their axons utilize mostly the cuneate fasciculus. Since the medullary dorsal reticular nucleus of the rat has a predominant population of nociceptive specific neurons, it is suggested that this spino-dorsomedullary reticular pathway is involved in pain processing.

Animals↗

PubMed1990

Structural types of marginal (lamina I) neurons projecting to the dorsal reticular nucleus of the medulla oblongata.

The morphological features of lamina I neurons labelled from the medullary dorsal reticular nucleus with free or wheat germ agglutinin conjugated horseradish peroxidase and cholera toxin subunit B, were studied in the three standard anatomical planes in the rat. Orientation and way of branching of the dendritic arbors were further analysed by the method of Sholl in cells labelled with cholera toxin subunit B. Most marginal cells belong to the multipolar type (70%) of our Golgi-based classification, and a minority to the pyramidal (15%) and flattened (15%) types. Following unilateral lesions severing the greatest part of the cuneate fasciculus, a considerable decrease of the numbers of labeled cells of the three types was observed caudal and ipsilaterally to the lesion. Contralateral labelling of multipolar and pyramidal cells was less decreased, and that of flattened cells was apparently unchanged. While multipolar cells, which make up the bulk of marginal spinobulbar neurons, appear to have no other supraspinal target, pyramidal and flattened cells have been labelled from the mesencephalon and the thalamus, respectively. It is suggested that the three structural cell types subserve different aspects of the spinofugal nociceptive output.

Animals↗

PubMed1989

Morphological types of spinomesencephalic neurons in the marginal zone (lamina I) of the rat spinal cord, as shown after retrograde labelling with cholera toxin subunit B.

Retrogradely labelled lamina I neurons were studied after intramesencephalic injections of subunit B of cholera toxin. The tracer was visualized with a mixture of two monoclonal antibodies followed by the peroxidase-antiperoxidase technique that produced Golgi-like staining of the labelled cells. A morphological and morphometric analysis in the three anatomical viewing planes disclosed two structural neuronal types which were recognized as the fusiform and pyramidal cells of our Golgi-based classification of rat marginal cells. Fusiform cells had a bipolar longitudinally elongated dendritic arbor, were located in the lateral third of lamina I, and appeared to project mainly to the contralateral parabrachial nuclei. It is asserted that these cells may convey the spinal input which elicits visceral responses generated in that area. Pyramidal cells were longitudinally oriented pyramids with the triangular base straddling the dorsal horn/white matter border and a dendritic arbor extending lateromedially and mainly rostrocaudally throughout superficial lamina I and the dorsal funiculus. These cells occurred along the entire mediolateral extent of lamina I and seemed to have a prevalent projection to the contralateral caudal ventrolateral periaqueductal gray. They may represent the ascending branch of the spinal-midbrain loop centered in that zone which controls nociceptive transmission postsynaptically in the dorsal horn.

Animals↗

PubMed1988

The spinothalamic system of the rat: structural types of retrogradely labelled neurons in the marginal zone (lamina I).

Retrogradely labelled lamina I neurons were studied after intrathalamic injections of free horseradish peroxidase mixed with dimethylsulphoxide, wheat germ agglutinin conjugated with horseradish peroxidase, and subunit B of cholera toxin. The first two tracers revealed only the perikaryal shape and the orientation of primary dendrites, while cholera toxin subunit B produced Golgi-like stainings. The morphological and morphometric analysis of the labelled marginal neurons in different planes showed them to belong to the pyramidal and the flattened types of our Golgi-based classification. These cells were located predominantly in the intermediate lateromedial portion of lamina I at all spinal levels, and it is suggested that their structural duality is matched by different functional properties. Distributions of the remaining spinothalamic cells labelled with the two horseradish peroxidase tracers were rather similar to those previously reported in the literature, including the almost exclusive occurrence of labelled cells, at lumbar levels, in the internal basilar column group. Cholera toxin subunit B labelled many more spinal cells and revealed considerable numbers of labelled cells in all cell groups at the lumbar enlargement.

Animals↗

PubMed1987

Several morphological types of terminal arborizations of primary afferents in laminae I-II of the rat spinal cord, as shown after HRP labeling and Golgi impregnation.

The morphology of the terminal arborizations in laminae I-II of primary afferent fibers was studied in sections stained by the heavy metal (nickel and cobalt) intensification of diaminobenzidine (DAB) after crushing one dorsal root with horseradish peroxidase (HRP) crystals, and with the mixed Golgi method which duplicated the staining provided by the first method. Besides the flame-shaped arbors located in deep lamina IIi as an extension of the arbors of lamina III, which were derived from 1.7-micron thick stem fibers (probably A alpha beta fibers), six types of terminal arbors, all rostrocaudally oriented, arising from fine stem fibers and having preferential locations, were disclosed. The lateral third of laminae I-II contained a longitudinal plexus of parallel 0.8-micron thick stem fibers (C fibers) with longitudinal side branches generating many boutons en passant. Laminae I and IIo, in their middle third, contained dichotomizing longitudinal fibers with elongated boutons, arising from 1-micron thick stem fibers (C or A delta), and, in the medial third, a dense plexus with terminal networks carrying large boutons, which arose from 1.3-micron thick stem fibers (A delta). Fibers ending in terminal bouquets and issuing from 1-micron thick stem fibers (C or A delta) occupied the dorsal part of middle and medial lamina IIi, while the intermediate part contained clusters (swarms) of ultrafine boutons arising from extremely fine fibers. The whole medial lamina IIi also contained fine undulating fibers arising from 0.3 micron-thick stem fibers (C fibers) with large boutons near their ends. The functional meaning of this multiplicity of morphological types and locations is still unclear. It may be clarified when single unit analysis of HRP-injected fine fibers is made possible, or immunocytochemical stainings disclose the neurotransmitters utilized by each fiber type.

3,3'-Diaminobenzidine↗

PubMed1986

A Golgi study of the neuronal population of the marginal zone (lamina I) of the rat spinal cord.

On the basis of dendroarchitecture and cell body shape, complemented with morphometry of dendritic ramification, four major neuronal types were distinguished in lamina I of the spinal cord of the rat. (I) Fusiform spiny cells (39% of impregnated neurons) have longitudinal spindle-shaped perikarya with bipolar, less frequently unipolar, dendritic trees rich in pedicled spines and a thin, beaded longitudinal axon; such neurons occur mainly in the lateral marginal zone. In type IA cells (33% of the total), the dendritic domain occupies a narrow longitudinal area, while in type Ib cells (6%) the polar dendritic trees partly arborize ventrally. Fusiform neurons are considered intrinsic cells connected with the longitudinal afferent plexus in lateral lamina I, and in type IB cells also receiving primary input in the substantia gelatinosa. (II) Multipolar cells (23%) have a dense dendritic arbor originating from numerous primary trunks and they predominate in the medial marginal zone. The dendritic arbor is moderately extended dorsoventrally in type IIA cells and reaches lamina III in the larger type IIB cells. The former possess a variety of spines, axonlike processes and sometimes an unmyelinated axon, and are presumably interneurons, while type IIB cells show a thick tapering axon that is probably myelinated. (III) Flattened aspiny neurons (13%) with a polygonal body flattened in the horizontal plane, and a horizontal dendritic arbor confined to lamina I; these cells predominate in middle lamina I. (IV) Pyramidal neurons (25%) have longitudinally elongated perikarya that bulge into the white matter. The arbor has a large longitudinal and lateromedial spread and includes branches which ramify in the white matter. Types III and IV show the classical lateromedially elongated orientation of the marginal cells of the old literature; they show thick tapering axons and probably make up the bulk of the projection neurons of rat lamina I.

Animals↗

PubMed1983

The neuronal population of the marginal zone (lamina I) of the rat spinal cord. A study based on reconstructions of serially sectioned cells.

Complete series of silver-stained semithin transverse sections were used to reconstruct 177 nerve cells of rat lamina I. According to the three-dimensional shape of the perikarya and the number and orientation of primary dendritic trunks, lamina I cells formed four distinct groups: (1) Fusiform cells with long rostrocaudal axis and having 1-4 primary dendrites oriented rostrocaudally or ventrally, which were the most numerous (50%) and predominated in the lateral third of lamina I. (2) Flattened cells (12%) which were thin discs of angular contour, spread out parallel to the lamina dorsal border; they emitted thick lateral and medial, but no dorsal or ventral, primary dendrites, and were mainly located in the middle third. (3) Multipolar cells (20%) with polyhedric somata emitting 4-12 primary dendritic trunks in several directions, which were practically confined to the medial third of the lamina. (4) Prismatic, wedge-shaped cells (18%), partly situated or encased, in the white matter, emitting one dorsal interstitial dendrite and several transversely oriented dendrites, which were distributed throughout the whole dorsal border of lamina I, though more abundant in its lateral portion. A subpopulation of large cells was identified in all groups, except in the multipolar one. These four cell types may help establish a basic morphologic classification of the neuronal population of lamina I, and may explain the different appearances under which local cells have previously been described in preparations using different planes of section and varied staining methods.

Animals↗

PubMedDate not supplied

Morphological characterization of marginal (lamina I) neurons immunoreactive for substance P, enkephalin, dynorphin and gamma-aminobutyric acid in the rat spinal cord.

Neurons of the rat spinal cord were immunostained for substance P, enkephalin and dynorphin in colchicine-treated animals, and for gamma-aminobutyric acid (GABA). Lamina I stained cells were classified in the four neuronal groups of our previous morphological classification of marginal cells (See Lima and Coimbra, 1986), according to their configuration in the three main anatomical planes. Most lamina I cells exhibiting substance P-immunoreactivity belonged in the group of flattened neurons. Most enkephalinergic cells were pyramidal neurons, while GABA-immunoreactive cells included all multipolar stained neurons and some fusiform neurons. Dynorphin-immunoreactive cells could be fusiform, pyramidal or flattened. The different neurochemical nature and supraspinal projection patterns are suggestive of functional specificity for each group. It is likely that each immunocytochemical subset in each cell group includes tract cells acting at their projection target and intrinsic neurons with local functional roles.

Animals↗