Search PubMed⌕ Search

Biomedical subjects

M L Rossi

Publications and source records attributed to M L Rossi.

At least 109 records · Page 6Linked to original sources
PubMed1988

An immunohistological study of 66 ependymomas.

Sixty-six ependymomas were examined immunohistologically to determine their distribution of glial fibrillary acidic proteins, S-100 protein and vimentin. The neoplasms were subdivided into four groups: (1) ependymomas from the cauda equina, predominantly of the myxopapillary type; (2) benign ependymomas; (3) malignant ependymomas; and (4) ependymoblastomas. Marked differences in antigen reactivity were observed between each group. The intensity of the reaction with the three antibodies was strongest in malignant ependymomas. Ependymomas from the cauda equina showed a patchy distribution of positivity for the three antigens in cells surrounding blood vessels but there was no staining of collagenous septa or the myxoid areas. In ependymoblastomas, the cells of the rosettes were negative for glial fibrillary acidic protein, but there was focal positivity for vimentin and S-100. Other areas showed tumour cells containing moderate amounts of vimentin and small amounts of S-100, and a few bands of filaments positive for glial fibrillary acidic protein. The cytogenetic and biological implications of these findings are discussed.

Cauda Equina↗
PubMed1988

Immunocytochemical study of the cellular immune response in meningiomas.

Twenty four meningiomas (17 benign and seven "atypical" were reacted with a panel of monoclonal antibodies to macrophages, lymphocytes, and HLA DR antigens. All the tumours contained macrophages but these cells were more numerous in the atypical meningiomas. Lymphocytes, almost exclusively of the CD8 subtype, were also present in 70% of benign meningiomas and in all atypical meningiomas and were more abundant in the latter. B lymphocytes were present in minimal numbers in three atypical meningiomas and in one benign meningioma. CD4 positive T lymphocytes were present in small numbers in one benign meningioma and in moderate numbers in one atypical meningioma. HLA DR antigen expression on tumour cells was present in about 60% of both tumour groups. The numbers of macrophages and T and CD8 lymphocytes in meningiomas seem to be related to atypical histological features, and the presence of these cells raises questions about host immune response and the relation of this to prognosis.

B-Lymphocytes↗
PubMed1987

Immunohistological study of mononuclear cell infiltrate in malignant gliomas.

Sixty-five malignant gliomas (astrocytomas grade 3 and 4 and glioblastomas) were examined by means of immunoperoxidase staining on frozen tissue using various monoclonal antibodies directed against macrophages, lymphocytes and natural killer cells. Depending on the antibody used, the presence of macrophages in tumours ranged from 85%-100%. Many of the tumours contained substantial numbers of macrophages not only, as expected, in necrotic areas but also in intact tumour tissue. Eighty-nine percent of 39 tumours tested contained Fc receptor-bearing mononuclear cells in viable tumour. In 100% of 44 tumours tested for HLADR class 2 major histocompatibility complex antigen this antigen was detected in the macrophages. In 40% of these 44 cases, HLADR antigen was also present on the tumour cells. Eighty-eight percent of 53 tumours tested contained T cells in viable tumour and the majority of these cells were T cytotoxic/suppressor (T8). Twenty-four percent of 33 tumours contained no T helper/inducer (T4) lymphocytes and in the other 76% there were few positive cells. Only 9% of 21 tumours contained natural killer cells (NK). B cells were absent from 88% of 61 tumours and almost all of the remainder contained only a small number of B cells. The findings are discussed with reference to a possible host immune response to gliomas and relevant literature is reviewed.

Antibodies, Monoclonal↗
PubMed1987

Pituicytoma (pilocytic astrocytoma). Case report.

Tumors of the posterior pituitary are rare and the previous nomenclature has been confusing. A 40-year-old man presented with visual failure and disconnection hyperprolactinemia (830 mU/liter) due to a large invasive pituitary tumor shown to be a pituicytoma (pilocytic astrocytoma). Its astrocytic nature was confirmed by positive immunostaining for glial fibrillary acidic protein and the finding of cytoplasmic filaments on electron microscopy. This case report contains the pathological description of a pituicytoma and illustrates that a non-adenomatous pituitary lesion may masquerade as a pituitary adenoma. Large pituitary lesions associated with serum prolactin concentrations of less than 3000 mU/liter require early surgical biopsy.

Adult↗
PubMed1986

Some hydrodynamic properties of the posterior canal in the frog labyrinth related to neuronal responses.

Measurements of the posterior-canal radius of curvature (R), the semicircular-duct radius (r) and the cupula radius (rC) were performed in the frog labyrinth. The Steinhausen-van Egmond equation led to an estimate of the canal endolymph flow, cupula deflection and sensory hair bending during constant angular accelerations (0.2-64 degrees/s2) of opposite directions and increasing duration (1.2-12 s). This analysis suggests that the non-linear canal afferent discharge behaviour exhibited by some units may not arise at the presynaptic level but rather postsynaptically, at the encoder site.

Acceleration↗
PubMed1986

Afferent activity recorded during rotation from single fibres of the posterior nerve in the isolated frog labyrinth.

EPSPs and spikes were recorded at rest and during rotation from single fibres of the posterior nerve in the isolated frog labyrinth. The spike discharge properties of 57 units were examined at rest and during repetitive acceleratory-velocity steps. Forty of these units were subjected to excitatory steps of 5-12 s duration and 45% displayed an evident discharge adaptation. In the non-adapting units, the excitatory response also deviated from that expected on the basis of the torsion-pendulum model and exhibited an exponential time-course in only 36% of the fibres examined. The time constant T2 of the response rising phase was significantly longer than that of the decay (2.5 s versus 1.7 s). When all the 57 units were considered, a linear behaviour was found in 67%. The average gain in these linear units was 1.9 +/- 1.4 spikes X s-1/deg X s-1. Adaptive fibres exhibited a lower resting firing rate and a higher gain (3.8 spikes/s and 2.3 spikes X s-1/deg X s-2, respectively) when compared with the non-adapting ones (7.1 spikes/s and 1.5 spikes X s-1/deg X s-2). An undershoot was present in 57% of the units; it increased with acceleration and was not strictly related to adaptation. Fifteen of the 40 units tested with the 5-12 s duration excitatory steps survived repeated inhibitory accelerations of the same duration. In these units a marked response asymmetry was evident since their resting activity could be abolished by accelerations not larger than 10 deg/s2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

[Modulating action of barium and other ions on the sensory activity of frog labyrinth].

The effect of Ba2+, TEA, 4-AP and CoCl2 on the EPSP and spike discharges recorded from single fibres of the posterior nerve in the isolated frog labyrinth has been investigated. In Ca-free solution Ba2+ preserved, at low concentration (0.3 mM), the resting activity and at higher levels (up to 6 mM) it resulted in a pronounced facilitation of the EPSP and spike discharges. Facilitation increased on increasing Ba2+ concentration up to 4-5 mM and it was more evident in those units exhibiting a low resting spike firing. The effect of Ba2+ (1 mM) was completely antagonized by 10 mM Ca2+ X CoCl2 (3 mM) suppressed the resting rate at the normal external Ca2+ concentration; the Co2+ block was partially relieved by 1.8 mM Ba2+ X TEA (20 mM) evoked a clear-cut increase in the EPSP and spike discharges which, however, was less consistent than that produced by Ba2+. By comparing the effect of TEA on the spike frequency with that obtained at different Ba2+ levels, the Ba2+ capacity to carry the Ca2+ current was dissected. Such an effect is dose-dependent and it is more evident in low-frequency units. Conversely, 4-AP did not affect the resting discharge frequency. These results indicate that either the Ca2+ or the Ba2+ current sustain the transmitter release at the cyto-neural junction. The effect of TEA suggests that the Ca2+-dependent K+ current may play an important role in supporting the neurosecretory process by controlling the membrane potential of the hair cells.

4-Aminopyridine↗
PubMed1984

[Physical dimensions influence the functional property of the semicircular canal].

The functional dependence of the semicircular canal upon its physical dimensions was evaluated by measuring the internal radius (r), the radius of curvature (R) and the cupula radius (rC) of the posterior canal in 10 freshly dissected frog labyrinths. These values have been compared to the same parameters of the cat labyrinth. The coefficients I, B, K in the Steinhausen equation were determined for both animals. The A ratio between cupula deflection and endolymph displacement was also calculated by utilizing the Bernard equation. The A ratio is three times larger in the frog than in the cat. It follows that if the same acceleration produces similar endolymph displacements in the posterior canal of both animals, the cupula deflection will be larger in the frog. The solution of the Steinhausen equation in the presence of a constant acceleration, however, reveals that the same stimulus intensity will result in a larger endolymph displacement in the cat posterior canal; similarly, the endolymph displacement directly depends on the duration of the stimulating period in both animals. Contrary to the Bernard assumption, these effects generate a G ratio (psi frog/psi cat) which is less than the Q ratio (A frog/A cat). Moreover, G decreases on increasing the duration of the stimulating period. For stimuli of short duration the semicircular canal of a small animal is expected to exhibit a higher sensitivity than that of a larger one. However, the definitive primary afferent discharge will be largely controlled by the receptor/generator potential properties.

Acoustic Stimulation↗
PubMed1983

[Chronic brucellosis: diagnostic problems and case presentations].

Chronic Brucellosis is an infection disease, which is still of great clinical interest whether due to the difficulties of diagnosis involved or to the peculiar course of the illness. For this reasons, we have considered several cases of Chronic Brucellosis observed over a period of 10 years, which have presented particular problems of diagnosis. Furthermore, we have underlined the importance in the diagnosis, of intradermal reaction and the hemoreaction to the anamelitina injection. We propose therefore, to consider their diagnostic specificity by analyzing the results obtained.

Adolescent↗
PubMed1982

[Effects of veratridine on labyrinth receptors in the frog].

The action of the veratrum alkaloid veratridine has been tested on the sensory apparatus of the frog semicircular canals. Intracellular and extracellular recordings of the electrical responses evoked by sinusoidal mechanical stimulations of the ampullar organ could not reveal an action of the drug on the hair cells whereas the onset of the impulse discharge at the encoder of the afferent nerve fibres is largely facilitated by veratridine. The mechanism of the drug action is discussed.

Animals↗
PubMed1982

Effectiveness of some anions in sustaining the efferent inhibition in the frog labyrinth.

Efferent inhibition in the frog labyrinth is sustained by the release of acetylcholine (ACh) which opens a Cl(-)-channel in the hair cell membrane. To investigate more closely the nature of the permeability change underlying the ACh reaction, the external Cl(-) was replaced by anions of increasing hydrated size, and to test the possible role of a Cl(-)-pump in the sensory cells, drugs were applied which are known to block active cl(-) pumping in other systems. Experiments indicate that the ACh-operated inhibitory channel of the hair cell is larger than at other inhibitory synapses (or approximately 0.7 nm), while pharmacological treatments (DNP, NaN3, acetazolamide, ammonium acetate, DIDS) fail to demonstrate any active distribution of Cl(-) across the hair cell membrane.

Action Potentials↗
PubMed1981

[Tonic mechanisms of efferent inhibition in the frog labyrinth].

Activation of the efferent system of the isolated group labyrinth inhibits the afferent EPSP and spike discharge by releasing ACh, which opens the Cl- channel of the hair cells membrane. Experiments in which increasing amounts of Cl- in the bath are replaced by equivalent amounts of Br-, NO2-, NO3-, CH3 CO2-, SO4(2-), CH3CH2CO2-, CH3(CH2)2CO2-, CH3(CH2)3CO2- benzoate, indicate that all these anions are able to penetrate the postsynaptic membrane, since full inhibition was invariably elicited. On the other hand, when citrate or isethionate are substituted for Cl- inhibition disappeared. In the presence of anions which are known to chelate calcium, its bath concentration was adequately increased. The presence of inhibition of Ringer-benzoate (benzoate ion size 6.5 A) and its disappearance in Ringer-citrate (8 A) or in Ringer-isethionate (greater than 10 A), suggests that the Cl- channel is at least 7 A in diameter, a size significantly larger than at other inhibitory synapses. Since metabolic inhibitors (DNP 0.1 mM and NaN3 1 mM) or acetazolamide (5 mM) and ammonium acetate (10 mM), which are known to block active Cl- pumping in other systems, do not affect the efferent synapse it appears difficult to interfere with the mechanisms which maintain the Cl- concentration gradient across the hair cell membrane.

Animals↗
PubMed1981

Reduction of venous sequelae of i.v. diazepam with a fat emulsion as solvent.

Venous sequelae were studied in 93 female patients undergoing minor gynaecological procedures. They were premedicated with diazepam i. v. dissolved in a fat emulsion (Diazemuls) injected to a superficial vein of the right hand. The patients observed the site of injection for 14 days and recorded their findings. Twenty-eight per cent reported mild tenderness and 7.5% mild or moderate swelling of short duration. Signs of thrombophlebitis were found in 2.2%. Thrombophlebitis after injection can be prevented effectively and safely using fat emulsion as a solvent for diazepam.

Adolescent↗
PubMed1980

Activation of the efferent system in the isolated frog labyrinth: effects on the afferent EPSPs and spike discharge recorded from single fibres of the posterior nerve.

Intra-axonal recordings were obtained from single afferent fibres of the posterior nerve in the isolated labyrinth of the frog (Rana esculenta). EPSPs and spike discharge were recorded both at rest and during rotatory stimulation of the canal. Electrical stimulation of either the distal end of the cut posterior nerve or of the central stumps of the anterior-horizontal nerves elicited a frequency-dependent inhibitory effect on the afferent discharge arising from the posterior canal. Denervation experiments revealed that inhibition is mediated by efferent fibres exhibiting a high degree of branching in the proximal part of the eighth nerve. The inhibitory effect was selectively cancelled by (1)D-tubocurarine 10(-6) M; (2) atropine 5 x 10(-5) M; (3) acetylcholine or carbachol 10(-4) M; (4) eserine 10(-5) M. Inhibition is thus most likely to be sustained by the release of acetylcholine from the efferent nerve terminals. Experiments in which the ionic composition of the external medium was modified suggest that the transmitter acts mainly by opening the chloride ion channels of the hair cell membrane. In some units the same stimulation pattern evoked a consistent increase in both EPSP and spike discharge, instead of inhibition. Such facilitation was unaffected by drugs for ionic modifications which block the efferent synapse, but disappeared after denervation. Inhibition and facilitation, therefore, act as two control mechanisms which are able to modify substantially, at the first stage of processing, the sensory information which is sent to the vestibular second order neurons.

Acetylcholine↗