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Biomedical subjects

R Spreafico

Publications and source records attributed to R Spreafico.

At least 109 records · Page 6Linked to original sources
PubMed1985

Transneuronal transport of wheatgerm agglutinin conjugated with horseradish peroxidase in the somatosensory system of the rat: a light- and electron-microscopic study.

Experiments were performed in order to investigate, at the light- and electron-microscopic levels, the transneuronal transport of wheatgerm agglutinin conjugated with horseradish peroxidase (WGA:HRP) in the somatosensory system of rats. In five adult albino rats, various amounts of WGA:HRP at different concentrations were bilaterally injected in the dorsal column nuclei (DCN). In one additional animal, WGA:HRP was injected in one side, whereas free HRP was injected in the contralateral DCN. In another five rats, WGA:HRP was injected in the first somatosensory cortex (SI). The postinjection survival time of the animals ranged from 30 to 48 hr. The histochemical visualization of the enzyme was performed using either paraphenylenediamine-pyrocatechol (PPD-PC) or tetraethylbenzidine (TMB) as chromogens on adjacent horizontal serial sections. All the reacted samples were studied at the light-microscopic level, and sections from four animals were processed for the ultrastructural investigation. After DCN injections, a massive anterograde labeling was always observed in nucleus ventralis posterolateralis (VPL) of the thalamus, where also labeled neurons and glial cells were detected at both the light- and the electron-microscopic levels. Labeled neurons and terminals in the lateral border of nucleus reticularis (Re) of the thalamus were also observed after either DCN or SI injection of WGA:HRP. Our results show that WGA:HRP is effectively transported not only anterogradely and retrogradely through the somatosensory system of the rat, but also transneuronally. The transneuronal transfer of the tracer seems to be mainly related to the postlabeling survival time of the animal, and it does not occur when free HRP is injected. In controlled experimental conditions, WGA:HRP can therefore be useful for tracing secondary projections. Moreover, in the present report, the existence of a mediolateral arrangement of the projections of the somatosensory-related area of Re toward VPL is directly demonstrated. As for the histochemical procedure employed, differences in sensitivity are shown between PPD-PC and TMB, although the same general pattern of labeling is present with both chromogens.

Afferent Pathways↗
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↗
PubMed1980

Brain stem projections in the pulvinar-lateralis posterior complex of the cat.

The present experiments were undertaken to define the areas of projection of pretectum and superior colliculus to the pulvinar and n. lateralis posterior, respectively, and to define other brain stem structures projecting to these thalamic nuclei in cats. For this purpose of technique of retrograde transport of horseradish peroxidase (HRP) has been used. After injection of the enzyme in the pulvinar, neurons were labeled in all subdivisions of the pretectal area. The majority of the labeled cells were located in the n pretectalis anterior pars compacta and area pretectalis medialis. Neurons projecting to the pulvinar were also found in the periaqueductal gray, reticular formation and locus coeruleus. When HRP was injected in the n. lateralis posterior, labeled neurons were present in the II and III subdivisions of the second layer of the superior colliculus. The location of these cells shifted from medial to lateral as the injections were shifted from posterior to anterior within the lateralis posterior. Neurons projecting to this nucleus were also present in the intermediate layers of the superior colliculus, lateral hypothalamus and parabigeminal nucleus. The possible role of the pretectal area and superior colliculus in mediating somesthetic input to the pulvinar and lateralis posterior, respectively, and the role of these structures in the control of ocular movements, are discussed.

Animals↗
PubMed1980

Multisensory convergence and interaction in the pulvinar-lateralis posterior complex of the cat's thalamus.

Responsiveness to visual, acoustic and somesthesic stimuli was studied in 260 units recorded within the associative thalamic nuclei of the cat (pulvinar-lateralis posterior complex and posterior group). Of the 123 units responding to one or more stimuli 41 (corresponding to 15% of the total) showed multisensory convergence. Bimodal, visual-somesthesic convergence was the most common finding, occurring in 33 units. Visual-somesthesic inhibitory interaction was observed only in the pulvinar nucleus, suggesting a peculiar synaptic organization of multisensory input to this nucleus.

Animals↗
PubMed1979

Oculomotor disorders in Huntington's chorea.

Electro-oculographic recordings were obtained from 11 patients with Huntington's disease. Significant reduction of saccadic velocity was constantly found. In all the patients vertical saccades were much more impaired than horizontal. When present, vertical saccades showed long latency, low amplitude, low velocity, and disturbances related to blinking. Following movements were jerky, and ability to perform repeated rhythmic movements was impaired. These results are in agreement with previous observations and underline the selective defect of rapid movements as a characteristic feature of Huntington's disease. Further, they suggest a possible correlation between the difficulty in performing repeated ocular movements and the impaired execution of gestural sequences involving a succession of different fundamental movements.

Adult↗
PubMed1977

Biochemical aspects of Huntington's chorea.

Fifteen patients affected by Huntington's chorea were divided into two groups, 'slow' and 'fast', according to IQ scores on the Wechsler-Bellevue scale, and scores on some motor performance tests. A possible correlation was looked for between some biochemical data (cerebrospinal fluid (CSF), homovanillic acid (HVA), and 5-hydroxyindolacetic acid (5HIAA) levels, plasma dopamine-beta-hydroxylase (DBH), dopamine (DA) uptake by platelets), and clinical data (duration of illness, severity of symptoms, age of patients, IQ scores, 'slow' and 'fast' groups). The CSF, HVA, and 5HIAA levels were found to be significantly lowered in comparison with normal controls. DBH activity and DA uptake by platelets did not differ significantly from normal subjects. Treatment with haloperidol in all patients and with dipropylacetic acid in three patients did not appear to modify the CSF, HVA, and 5HIAA concentrations, the plasma DBH activity, or the DA uptake. There were no significant differences in the CSF, HVA, and 5HIAA contents between the two groups of patients, and there was no correlation between biochemical data and clinical features.

Adult↗
PubMed1976

Study of the excitability cycle of the blink reflex in Huntington's chorea.

The trigemino-facial reflex was studied in 7 patients affected by Huntington's chorea and in 10 patients affected by Parkinson's disease. The results show a different behavior of the habituation phenomenon in the two groups of patients: it is enhanced in the choreic and abolished in the parkinsonian patients. The main changes concern the time course of the second phase (the first inhibitory phase) of the reflex excitability cycle, in fact, the inhibitory phase appears very pronounced and prolonged in huntingtonian patients and reduced or abolished in parkinsonian patients. Some pathophysiological mechanisms involved in the control of the trigeminofacial reflex excitability are discussed with particular regard to the role of the hemispheric structures.

Adult↗
PubMedDate not supplied

Burst suppression and impairment of neocortical ontogenesis: electroclinical and neuropathologic findings in two infants with early myoclonic encephalopathy.

We report the electroclinical and neuropathologic correlations in 2 children aged 2.5 months affected by early myoclonic encephalopathy characterized by epileptic seizures, erratic myoclonus, and an EEG pattern of burst suppression. Despite different etiologies, the neuropathologic findings showed similar abnormalities in both cases, with no substantial impairment of the myelination processes. Islands of matrix tissue scattered in the periventricular region and neurons aligned marginally in the bulbar olives were detected. The presence of numerous large spiny neurons dispersed in the white matter along the axons of the cortical gyri was the most striking finding. The neurons have been interpreted as abnormally persisting interstitial cells in 2.5-month-old children. These early generated neurons, normally present during neocortical histogenesis, are programmed to die near the end of gestation or soon after birth. The interstitial cells are regarded as a waiting compartment of afferent fibers during cortical development. Their persistence in our patients represents an anatomic condition for cortical disconnection providing a pathophysiologic basis to burst-suppression phenomena.

Brain↗
PubMedDate not supplied

Calcium-dependent regulation of genetically determined spike and waves by the reticular thalamic nucleus of rats.

The pathophysiologic role of the reticular thalamic nucleus (RT) in rat generalized nonconvulsive epilepsy was investigated in the selected strain GAERS (genetic absence epilepsy rats from Strasbourg). After the RT was lesioned by the excitotoxic agent ibotenic acid stereotaxically injected in previously callosotomized rats, a disruption of ipsilateral spike and wave discharges (SWD) was observed in freely moving animals. In a second group of animals Cd2+ (0.5-1.5 microliter, 1 mM), which is known to block Ca2+ and Ca(2+)-dependent K+ conductances (gK+ (Ca2+)), was injected into the thalamus. Cd2+ reversibly suppressed ipsilateral SWD when injected in RT, whereas it slightly reduced SWD expression when injected in the ventrobasal (VB) complex. The difference was highly significant. We conclude that Ca(2+)-dependent oscillatory properties of the RT are critical for expression of genetically determined SWD in GAERS.

Animals↗
PubMedDate not supplied

[Presentation of 25 cases of post-irradiation lesions of the brachial plexus and their treatment].

A study was carried out on a series of 25 patients who were operated on for breast cancer and who submitted to postoperative radiotherapy, in which lesions of the brachial nervous plexus from ionizing radiations were obtained. In almost all the cases, 24 out of 25, various symptoms such as paresthesiae, pain, and motorial disturbances, were observed even one year after the completion of the treatment. Motorial troubles, which in 13 cases were not detected at the moment of the diagnosis of the other lesions, always occurred later. Etiopathogenesis and diagnosis of these lesions have been considered, as well as the possibility of lowering the incidence of such troubles. The conclusion can be drawn that useful results can be obtained, to a certain extent, only if therapeutic treatment is performed early: in most cases, however, the lesions showed a progressive evolution.

Brachial Plexus↗