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E Mugnaini

Publications and source records attributed to E Mugnaini.

At least 109 records · Page 6Linked to original sources
PubMed1982

Central GABAergic innervation of neurointermediate pituitary lobe: biochemical and immunocytochemical study in the rat.

Activity of glutamic acid decarboxylase GluDCase, the biosynthetic enzyme of gamma-aminobutyric acid (GABA) was measured in low-speed homogenate supernatant of the neural and intermediate (neurointermediate) lobe (28--30 pmol of CO2 per microgram of protein per hr) and of the anterior lobe (2--4 pmol of CO2 per microgram of protein per hr). In the neurointermediate lobe, stalk transection reduced the GluDCase activity by more than 95%. By using an antiserum to rat brain GluDCase and the unlabeled antibody--peroxidase method of Sternberger, GluDCase immunoreactivity was localized in many terminals within the neurointermediate lobe of the hypophysis. In pars intermedia, immunoreactive terminals occurred in apposition to secretory cells and to glial cells and were near nonimmunoreactive axonal profiles; in pars neuralis they were apposed to pituicytes and to unlabeled axons including the neurosecretory terminals and were along fenestrated portal capillaries. GluDCase immunoreactive axons terminals exhibited diverse morphological features and would not have been identified as a distinct population without the GluDCase antiserum. No GluDCase-immunoreactivity was found in the anterior pituitary lobe. Stalk transection abolished GluDCase immunoreactivity in the neurointermediate lobe. These data provide biochemical and morphological evidence for a central GABAergic innervation of neural and intermediate lobes of the hypophysis.

Animals↗
PubMed1980

Distribution and light microscopic features of granule cells in the cochlear nuclei of cat, rat, and mouse.

In the present study the cytology and the topography of the cochlear granule cell domain (a comprehensive term introduced here for all granule cell-containing regions of the cochlear nuclear complex) have been studied light microscopically in Nissl, Bielschowsky, and Golgi-Del Rio-Hortega material of cats, rats, and mice; in Golig rapid material of 0-14-day-old kittens; and in sections of 6-week-old kittens following HRP injections in the superficial dorsal cochlear nucleus (DCN). The domain has been parcellated in seven subdivisions which, in spite of some species' differences, are easily identifiable in all of the included animals. The cochlear granule cells are considered as a particular class of neuron, which is slightly different from, but nevertheless principally similar to the cerebellar granule cells in both shape and mode of neuronal connections. The digitiform terminals of the cochlear granule cells differentiate after the first two weeks of extrauterine life. In several respects these cells show larger variation among species than do the cerebellar granules, the similarity between the two classes of granule cells being most conspicuous in the rodent. The silver, Golgi rapid, and HRP material suggest that all, or at least the majority, of the granule cell axons project to the molecular layer of the DCN, forming parallel fibers similar to those of the cerebellar cortex. Also, the cochlear parallel fibers traverse the spiny apical dendrites of principal neurons (the pyramidal cells) and the smoother dendrites of molecular layer stellate cells.

Animals↗
PubMed1980

Fine structure of granule cells and related interneurons (termed Golgi cells) in the cochlear nuclear complex of cat, rat and mouse.

This paper describes the fine structure of granule cells and granule-associated interneurons (termed Golgi cells) in the cochlear nuclei of cat, rat and mouse. Granule cells and Golgi cells are present in defined regions of ventral and dorsal cochlear nuclei collectively termed "cochlear granule cell domain'. The granule cells are small neurons with two or three short dendrites that give rise to a few branches with terminal expansions. These participate in glomerular synaptic arrays similar to those of the cerebellar cortex. In the glomeruli the dendrites form short type 1 synapses with a large, centrally-located mossy bouton containing round synaptic vesicles and type 2 synapses with peripherally located, smaller boutons containing pleomorphic vesicles. The granule cell axons is thin and beaded and, on its way to the molecular layer of the DCN, takes a straight course, which in ventral nucleus is parallel to the pial surface. Neurons of the second category resemble cerebellar Golgi cells and occur everywhere interspersed among the granule cells. They are usually larger than the granule cells and give rise to dendrites which may branch close to and curve around the cell body. The dendrites contain numerous mitochondria and are laden with thin appendages, giving them a hairy appearance. Both the cell body and the stem dendrites participate in glomerular synaptic arrays. Golgi cell glomeruli are distinguishable from the granule cell glomeruli by unique features of the dendritic profiles and by longer, type 1 synaptic junctions with the central mossy bouton. The Golgi cell axon forms a beaded plexus close to the parent cell body. The synaptic vesicle population of the mossy boutons suggests that they are a heterogeneous group and may have multiple origins. Apparently, each of the various classes participates in both granule and Golgi cell glomeruli. The smaller peripheral boutons with pleomorphic vesicles in the two types of glomeruli may represent Golgi cell axons which make synaptic contacts with both granule and Golgi cells. The Golgi cell axons which make synaptic contacts with both granule and Golgi cells. The Golgi cell dendrites, on the other hand, are also contacted by small boutons en passant with round synaptic vesicles, which may represent granule cell axons. A tentative scheme of the circuitry in the cochlear granule cell domain is presented. The similarity with the cerebellar granule cell layer is striking.

Animals↗
PubMed1979

The cerebellar projection of the vestibular nerve in the cat.

The projection of the vestibular nerve to the cerebellum of the cat was examined with silver degeneration methods after complete lesions of the vestibular ganglion. The majority of the primary vestibular afferents were traced to the cortex of the ipsilateral nodulus and uvula, relatively fewer entering the ipsilateral flocculus. Fibers were not traced to the paraflocculus, lingula or lateral cerebellar nucleus. A sparse projection to the ipsilateral fastigial nucleus may exist, but it remains equivocal until confirmed with additional methods. Light microscopic examination of plastic sections confirmed these observations and showed further details of the organization of the primary vestibular projection to the nodulus and uvula. These results show that the region of the cerebellum densely innervated by primary vestibular afferents is smaller than previously believed.

Afferent Pathways↗
PubMed1978

Temporal and spatial sequence of anterograde degeneration in the cochlear nerve fibers of the cat. A light microscopic study.

This study deals with anterograde degeneration in the cochlear nerve fibers following cochlear lesions. The observations are based on 2-mum thick sections of material embedded in resin according to procedures used in electron microscopy and stained with toluidine blue. Among the various operative approaches used in this study, sparing of the modiolus afforded the least local reaction and furnished the material best suited for anterograde degneration studies in this nerve only 2 mm long. The anterograde degeneration of the cochlear nerve is characterized by segmental swelling of myelinated nerve fibers followed by shrinkage of the axoplasm and collapse of the distended myelin sheaths. The swelling, which begins at the nodal-paranodal region of the axon, is preceded by accumulation in the cytoplasm of granular organelles, presumably mitochondria and lysosomes. The portions of the cochlear fibers situated in the nerve root, i.e., within the cochlear nuclei and including the axon terminals, follow essentially the same pattern of degeneration as those in the peripheral portion of the nerve. Both peripherally and centrally degenerative changes occur first in the basal, high frequency fibers and centrally degenerative changes occur first in the basal, high frequency fibers and progress to the apical, low frequency fibers. The difference between the two extremes in the onset of degeneration is, approximately, 24 hours. Once initiated, however, the pace of degeneration is the same along the whole fiber spectrum.

Animals↗
PubMed1976

Fulminant Purkinje cell death following axotomy and its use for analysis of the dendritic arborization.

Young and adult cats were operated upon and a number of the vermal cerebellar folia were either transected with a vertical incision or isolated by a horizontal cut. In the proximity of the lesion, Purkinje cell bodies and their dendritic trees became stainable with the Fink-Heimer method. Electron microscopy of the silver stained sections show that the argyrophilic Purkinje neurons undergo an electron dense type of degeneration. Stellate cell dendrites adjacent to the degenerating Purkinje trees are normal, suggesting that the cause of cell death is axotomy close to the perikaryon rather than direct injury. The retrograde Purkinje cell degeneration is fulminant since it is evident 6 hours after the lesion. In Fink-Heimer stained sections the entire dendritic tree is impregnated 1-3 days after the lesion. 4-10 days post-operatively, the flattened dendritic tree becomes fragmented and is partially phagocytized. The silver stained arborizations are approximately 280 mu in width and have an uneven thickness (8-16 mu). In longitudinal and horizontal silver stained sections of lesioned cerebellar folia, uninterrupted fields of degenerating Purkinje cell arborizations can be seen, suggesting that the arborizations overlap. The overlap was demonstrated in electron micrographs of single degenerating arborizations surrounded by normal dendritic trees. The degree of overlap varies with the thickness of the arborization and is in the order of 1-2 mu. This approach indicates that each Purkinje tree occupies an exclusive sheet of molecular layer 8 mu thick and may overlap for as much as 2 mu on each side with neighboring trees. The average thickness of the Purkinje tree is approximately 12 mu.

Animals↗
PubMed1976

The length of parallel fibers in the cat cerebellar cortex. An experimental light and electron microscopic study.

Experimental light and electron microscopic studies were carried out to determine the length of parallel fibers in the cat cerebellar cortex. Using a fine surgical knife, vermal and hemispheral folia were cut perpendicular to their long axis. The animals were sacrificed 1-10 days after the operation. Sections of the transected folia were then stained with a Fink-Heimer procedure. The resulting degeneration appeared as fine dots that extended lateral to the lesion, as predictable from the course of the parallel fibers. Densitometer readings indicate that the density of degeneration declines gradually lateral to the lesion. The specificity of the silver impregnation was checked by processing silver stained sections for electron microscopy. This confirmed the location of the silver precipitate on degenerating parallel fibers. The pattern of parallel fiber degeneration in the molecular layer has a trapezoidal configuration centered on the lesion. The shorter parallel fibers are located at the base of the molecular layer and extend for 5 mm. The parallel fibers become progressively longer as they approach the pial surface where they attain a maximum length of 7 mm. Our studies suggest that in folia longer than 7 mm parallel fibers are 6 mm long on the average. In addition, it was determined on Golgi sections that the average center-to-center distance between en passant boutons of individual parallel fibers is 5.2 mum. The data indicate that an average parallel fiber, 6 mm long, forming approximately 1100 boutons, may synapse with each Purkinje dendritic tree it traverses.

Animals↗
PubMed1976

The paranodal axo-glial junction in the central nervous system studied with thin sections and freeze-fracture.

The lateral belts of the myelin sheath wind helically around the paranodal region of the axon. The lateral belt coil leaves an imprint on the axon and thus confers a conspicuous, indented configuration to the freeze-fracture faces of the axolemma. The contact area between the axolemma and the lateral belt membrane is the site of an extensive and unusual cell junction (axo-glial junction). In thin sections the junctional membranes are undulated, the peaks in one membrane mirroring the peaks in the other. The transverse bands (intercellular septa) are in register with the undulations. The intercellular space measures about 30 A. In freeze-fracture replicas, the undulations are evident as alternating ridges and grooves which run strictly parallel and are oriented at an angle with respect to the helical path of the lateral belt. Both junctional membranes contain parallel rows of intramembrane particles which coincide with the ridges and grooves and, therefore, with the intercellular septa. The center-to-center distance between septa or, equivalently, between adjacent rows of particles measures approximately 250 A. Although the axo-glial junction possesses structurally symmetrical features, there exist important differences between the two junctional membranes. The intramembrane particles of the glial and the axonal membrane differ in cleaving properties. Furthermore, in some of the fibres the E face of the junctional axolemma displays a crystalline array which is not present in the fracture faces of the glial membrane. The axo-glial junction is limited to the paranodal region, although the inner belt of the myelin sheath may form occasional junctional spots with the internodal region proper of the axolemma. The classification and the presumptive functions of the paranodal axo-glial junction are briefly discussed.

Animals↗
PubMed1976

Freeze-fracture properties of central myelin in the bullfrog.

The freeze-fractured membrane of the central myelin sheath has three classes of particulate components: (i) Particles inherent to the compact myelin lamellae. These are distributed at random and cleave predominantly with the P (protoplasmic) face. (ii) Particles which comprise the intramyelinic tight junctions. These are arranged in strands and are located at the inner and outer mesaxon, the paranodal loops, the cytoplasmic incisures, and occasionally within the compact regions of the myelin sheath. (iii) Particles localized exclusively at the portion of the paranodal loop membrane involved in the septate-like junction with the axolemma. These are regularly spaced and are organized in parallel rows. In the central myelin sheaths of bullfrogs fixed by perfusion with aldehydes and cryoprotected in 30% glycerol, the randomly distributed particles differ in size and shape from those of the axolemma. They possess a reasonably well defined bimodal distribution with respect to particle shape--most can be described either as globules or as ellipsoids. The globular particles range in diameter from 60 to 150 A. The ellipsoidal particles are 100-200 A long and 15-50 A wide. The total number of particles per square micron on the P face is approximately 1500. About half of these are of the globular type and half of the ellipsoidal type. In poorly fixed specimens, loss of interlamellar adhesion and loss of randomly distributed particles seem to coincide. Evidence is presented against the hypothesis that the tight junctions between compact myelin lamellae represent the radial component of the myelin. The possible relation between the types of particulate components seen in freeze-fracture and the classes of protein isolated from central myelin fractions is briefly discussed.

Animals↗
PubMed1975

Mode of distribution of aminergic fibers in the cerebellar cortex of the chicken.

The cerebellar cortex of adult hens contains a dense plexus of thin varicose nerve fibers which display a formaldehyde-induced green fluorescence. This plexus is not distributed at random in the cortical layers. Within the granular layer the plexus forms a netlike pattern. The fiber branches, which have numerous varicosities, are predominantly oriented in the traverse plane of the folium. In the molecular layer the fluorescent plexus shows some variations in the convex, flat and concave portions of the folia. Many of the fluorescent branches are oriented parallel to the course of the folium. They arise from a T-division of radially oriented axons resembling parallel fibers in Golgi sections. The meshes of the fluorescent plexus in the granular layer measure 10-60 mu. In the molecular layer (top of the folia) there are about 30 fluorescent fibers per 100 mu2. The fluorescent fibers originate from the locus coeruleus and form a rostral and a caudal bundle in the cerebellar peduncle. The mode of distribution of the fluorescent fibers in the cortical layers seems to depend on the organization of the innervated tissue. Light microscopy suggests that the aminergic fibers innervate more than one class of cerebellar neurons.

Amines↗