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Biomedical subjects

G F Rossi

Publications and source records attributed to G F Rossi.

At least 37 records · Page 2Linked to original sources
PubMed1993

Hemispheric control of unilateral and bilateral responses to lateralized light stimuli after callosotomy and in callosal agenesis.

Normally, simple digital or manual responses to a light stimulus in the right or left visual hemifields are performed faster with uncrossed hand-field combinations than with crossed hand-field combinations. Because of the organization of visual and motor pathways, the integration of uncrossed responses is assumed to occur within a single hemisphere, whereas a time-consuming interhemispheric transfer via the corpus callosum is considered to be necessary for the integration of crossed responses. However, callosal transfer may be dispensable for those crossed responses which can be controlled through ipsilaterally descending motor pathways by the hemisphere receiving the visual stimulus. We investigated crossed-uncrossed differences (CUDs) in speed of simple visuomotor responses to lateralized flashes in one subject with total section of the corpus callosum and two subjects with complete callosal agenesis. We recorded the reaction times as well as the premotor times, as indicated by the electromyographic latencies of the prime movers, of three types of responses: a distal response involving a thumb flexion, a proximal response chiefly involving a forearm flexion and an axial response involving a shoulder elevation. Further, the three types of responses to a single lateralised flash were performed both unilaterally and bilaterally. The three acallosal subjects showed CUDs greatly exceeding normal values on distal responses, either unilateral or bilateral, and on unilateral proximal responses. These abnormally long CUDs stood in sharp contrast to the insignificant CUDs exhibited by the same subjects on bilateral proximal responses and on unilateral and bilateral axial responses in agreement with correspondingly insignificant CUDs reported for normal subjects. These results confirm that a callosal contribution is important for the execution of fast distal and unilateral proximal responses to a visual stimulus directed to the hemisphere ipsilateral to the responding hand. By contrast, the other types of crossed responses appear to be efficiently coordinated across the midline without the aid of the corpus callosum. This is in keeping with the hypothesis that they are governed by a bilaterally distributed motor system which is preferentially activated for the execution of symmetrical bilateral movements, employing axial and proximal limb muscles.

Accidents, Traffic↗
PubMed1993

Callosotomy for generalized seizures associated with hypothalamic hamartoma.

A case is reported of intractable epilepsy associated with a hypothalamic hamartoma in an 18 year old man. The patient underwent a two-third anterior callsotomy and, subsequently, removal of the hamartoma. Callosotomy did not affect the generalized seizure pattern. The authors believe this to be the first documented case of hypothalamic hamartoma in which callosotomy for seizure control was attempted. The poor response to callosotomy suggests the extracallosal diffusion of the generalized seizures from hypothalamic hamartomas.

Adolescent↗
PubMed1992

Levocarnitine acetyl prevents cell death following long-term section of the vagus nerve in rats.

Levocarnitine acetyl has previously been found to significantly prevent axotomy-induced cell death in the spinal cord motor nucleus 9 and 12 months after section of the sciatic nerve in rats. In the present paper, the effects of levocarnitine acetyl on axotomy-induced cell death in the brain stem motor nuclei 90 days after section of the vagus nerve were studied. The right vagus nerve was cut at the neck. To prevent regeneration, a 5 mm-long segment of the vagus nerve was excised and the distal stump was displaced caudally. After surgery, a group of rats (n = 6) was treated with levocarnitine acetyl dissolved in the drinking water (75 mg/kg/day) (Group I). A second group of operated rats (n = 4) received drinking water alone. (Group II). Ninety days postoperatively, in the rats of both groups the proximal nerve stump of the vagus nerve was injected with horseradish peroxidase to label retrogradely the brain stem motoneurons of the dorsal motor vagal and the ambiguus nuclei. The brain stem nuclei were also labelled by horseradish peroxidase in three unoperated control rats (Group III). In the Group II rats, the number of horseradish peroxidase-labelled motoneurons of the dorsal motor vagal nucleus was found to be significantly smaller than in either the Group I (p < 0.01) or the Group III (p < 0.02) animals. In the Group I rats, the number of motoneurons of the dorsal motor vagal nucleus was not significantly smaller compared to the Group III rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcarnitine↗
PubMed1991

Bone metastasis associated with shunt-related peritoneal deposits from a pineal germinoma. Case report and review of the literature.

The case of a 15-year-old boy with a pineal germinoma is reported. The patient first underwent a ventriculoperitoneal (VP) shunt followed by a stereotactic biopsy, then, because of the rapidly deteriorating neurological status, an emergency craniotomy with subtotal removal of the tumour was performed. Two months after surgery, a left femoral metastasis and extensive peritoneal lesions became evident; they were regarded as due to haematogenous and VP shunt spread of the germinoma. At that time, extremely high serum levels of placental alkaline phosphatase were detected. The patient died 6 months after the initial diagnosis. The occurrence of extraneural metastases as well as of shunt related peritoneal deposits from primary intracranial germinoma is discussed. As far as we know this is the first reported case of a combination of haematogenous as well as VP shunt spread of a pineal germinoma.

Adolescent↗
PubMed1991

Recovery cycle of the cerebral neocortex: preliminary observations in epileptic patients.

The recovery cycle of the amplitude of the potential evoked in the cerebral neocortex by paired electrical stimuli of the underlying white matter was studied in 5 epileptic patients with intracerebral electrodes chronically implanted stereotactically. A reproducible pattern was apparent for the late components of the potential (i.e., the peak-to-peak amplitude between the second and the third peak, with an average peak latency of 14 and 35 ms, respectively). There was an early period of facilitation (5-10 ms interstimulus interval) followed by a period of relative or absolute depression (20-100 ms) with recovery at an interstimulus interval of about 150 ms. The recovery function of the early components of the potential (i.e., the peak-to-peak amplitude between the first and the second peak, with an average peak latency of 6 and 14 ms, respectively) was variable; recovery was reached at about 150 ms. The responsiveness seemed less in the most epileptogenic cortical areas.

Afferent Pathways↗
PubMed1991

Sleep and epileptic activity.

Thirteen patients suffering from severe partial epilepsy and potential candidates for surgical treatment were investigated with stereotactically implanted intracerebral electrodes during nocturnal physiological sleep. The recorded electrocerebral activity was automatically analyzed to gain information on interictal epileptic events during wakefulness and the phases of sleep. The interictal epileptic activity shows: (1) great variability in the different subjects, and intra-individually, variability according to the explored cerebral regions; (2) is not influenced by the location of the recorded epileptic events; and (3) is affected by the local level of epileptogenicity. The latter was determined by the assessment of the capacity to give origin to ictal discharges and the disappearance of seizures following surgical removal. The interictal rate of spiking from the most epileptogenic cerebral zone is characterized by a relative stability during the night and by a relatively high degree during REM sleep.

Adolescent↗
PubMed1991

Levocarnitine acetyl promotes the regeneration of peripheral sensory axons and reduces the hypertrophy of axotomized spinal cord motoneurons in rats.

In previous studies, the neurotrophic action of levocarnitine acetyl on the regeneration of the sciatic nerve in rats has been demonstrated. The present study investigated the particular effect of levocarnitine acetyl on the initial stages of sciatic nerve regeneration. In the first 8 days after sciatic nerve lesion caused by crushing (Group A) or cutting (Group B), the rats of both groups were divided into 2 subgroups: treated rats received daily intraperitoneal levocarnitine acetyl (a megadose of 100 mg in saline solution); untreated rats only received saline solution. Treatment started on the day of operation. The regeneration growth rate of sensory fibres was studied using the pinch test. The size of the axotomized spinal motoneurons was studied using retrograde axonal tracers (horseradish peroxidase or Fast blue). The results showed that: (a) levocarnitine acetyl promoted the elongation of sensory fibres in the first 8 days following the crushing or sectioning of the sciatic nerve, but the data were only statistically significant (p less than 0.01) for the first 3 days after crushing; (b) levocarnitine acetyl accelerated the velocity of sensory fibre regeneration when compared to untreated rats by 16% in the first 3 days after nerve crushing, by 14% in the first 4 days after nerve section, and by 32% from the 5th to the 8th day after nerve section; (c) levocarnitine acetyl promoted a significant reduction in spinal motoneuron hypertrophy when compared to untreated rats at both 4 and 8 days after sciatic nerve section.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcarnitine↗
PubMed1990

Principles of surgery for epilepsy.

The pre-requisite conditions for surgical treatment of epilepsy are: ineffective pharmacotherapy, the unacceptable nature of the seizures and the presence of an organic brain lesion as the basis of the disease. The principles of surgery stem from knowledge of the anatomicofunctional structure and evolution of the epileptic process, which indicate the targets for surgery. Two main groups of surgical approaches are available. The first and most efficient one aims at suppressing the seizures by acting on the nucleus of origin of the epilepsy; the combined removal of both the causative cerebral lesion and the primary epileptogenic zone is considered as the "optimal" type of surgery (hemispherectomy, lobectomy, topectomy); only in rare cases is an ablation limited either to the causative lesion (mainly in children) or to the epileptogenic zone sufficient. The second group of surgical procedures aims at reducing the cerebral epileptogenicity by preventing diffusion of the epileptic discharges (callosotomy, subpial transections), by enhancing inhibitory (cerebellar stimulation) or reducing facilitatory influences (stereotactic deep lesions); these are regarded as a "second choice" treatment. The final surgical indication, the choice of the surgical approach and the surgical prognosis are dependent on accurate presurgical investigations. The very good results which can be obtained should favour the wider use of surgery.

Brain Mapping↗
PubMed1990

Studies on the degenerative and regenerative phenomena occurring after transection and repair of the sciatic nerve in rats: effects of acetyl-L-carnitine.

The effects of acetyl-L-carnitine on some degenerative and regenerative phenomena following sciatic nerve transection in rats, were studied. In Experiment 1, acetyl-L-carnitine was administered intraperitoneally at the dose of 50 mg/kg/day for 28 and 56 days following transection and microsurgical repair of the sciatic nerve. On day 56, the acetyl-L-carnitine-treated rats showed a significantly (p less than 0.05) better motor recovery ("clinical assessment") of the peroneal component of the sciatic nerve than the control rats. Twenty-eight days after nerve repair, the acetyl-L-carnitine-treated rats showed a significantly higher (p less than 0.05) number of myelinated axons in the postlesional nerve stump than control rats. Finally, the treated rats had a significantly lower (p less than 0.05) presence of atrophic fibres in the extensor digitorum longus muscle. In Experiment 2 the sciatic nerve was cut. To prevent spontaneous regeneration, a metallic clip was applied to the distal nerve stump and then the nerve stumps were positioned in different anatomical compartments. After surgery, a group of rats was treated with acetyl-L-carnitine dissolved in the drinking water (75 mg/kg/day). Another group of rats received normal water and served as the control group. Three, 6, 9, 12 and 18 months postoperatively, in the rats of both groups, the proximal sciatic nerve stump was injected with horseradish peroxidase to label the spinal cord neurons of the sciatic nerve nucleus. While in untreated rats the number of horseradish peroxidase-labelled neurons decreased with the increase in denervation time, in acetyl-L-carnitine-treated rats the number of horseradish peroxidase-labelled neurons remained stable for as long as 12 months of denervation and decreased only after 18 months of denervation. Furthermore, acetyl-L-carnitine-treated rats showed a significantly higher (p less than 0.05) number of horseradish peroxidase-labelled neurons with respect to untreated rats both after 9 and 12 months of denervation. In Experiment 3, the sciatic nerve was cut and then repaired after periods of 3, 6, 9, 12, and 18 months. Four months after nerve repair, the sciatic nerve was again cut and the proximal nerve stump was injected with horseradish peroxidase to label the spinal cord neurons of the sciatic nerve nucleus. Both acetyl-L-carnitine-treated and untreated rats showed a tendency to have an increased number of horseradish peroxidase-labelled neurons with respect to intact rats of correspondent ages.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcarnitine↗
PubMed1989

Natural history of neuroepithelial tumours: contribution of stereotactic biopsy.

Quantitative tumour growth into the brain (stage of the disease) and qualitative tumour evolution in the time (progression) are the two basic aspects of the natural history of the cerebral neoplastic disease. Recently the development of neuroradiological imaging (CT and MR) and the progress in biopathology of the nervous system tumours introduced new concepts like heterogeneity of neuroepithelial tumours or evolution to anaplasia. The findings obtained in 159 neuroepithelial tumours studied with stereotactic biopsy from 1980 to 1987 are presented. Most of them were glioblastomas (n = 43; 27%) and astrocytic tumours (n = 81; 50.9%). Twenty-nine cases of fibrillary astrocytomas (35.8% of all astrocytic tumours) showed focal anaplasia (progression). In 10 out of the 43 glioblastomas (23.3%) signs of astrocytic differentiation were clearly evident (secondary glioblastoma?). Our data confirm that neuroectodermal tumours, particularly of astrocytic series, undergo progression through anaplasia, which may be at the beginning a circumscribed phenomenon (focal anaplasia). The staging of the disease (tumour growth) into cerebral nervous system in some cases can not be correctly expressed through the neuroradiological imaging. Sometime CT scan may underestimate the true extension of the lesion. On the contrary, MR may overrate the extension of the lesion. Such mistakes in evaluation of tumour staging may be corrected through seriate stereotactic biopsy.

Astrocytoma↗
PubMed1989

Comments on brachycurie therapy of cerebral tumours.

Between 1980 and 1987 thirty patients harbouring cerebral neuroepithelial tumours have been treated with stereotactic brachycurie therapy (18 males, 12 females), either alone (n = 16) or combined with surgery (n = 7) and/or external radiotherapy (n = 10). There were 25 slowly growing tumours (grade I n = 1; grade II n = 24). The remaining 5 were malignant tumours (grade III n = 3; grade IV n = 2). The radioactive sources utilized were 192Ir in 26 cases and 125I in 4. Twenty-eight patients underwent permanent implantation, the other two received temporary irradiation with removable after-loaded catheters. Target volume was less than 15 cm3 in 6 cases, between 16-60 cm3 in 17 and more than 60 cm3 in 7. Tumour dose at the periphery of the target volume was: 70-100 Gy in 19 and 100-130 Gy in 9 of the cases treated with permanent implantation; the patients irradiated with removable implants received 40-60 Gy in 5-7 days. General follow-up ranged between 0.3 and 6.9 years (mean = 2.5 years). The results are analyzed with reference to the following aspects: 1) natural history of the disease; 2) modalities and goal of the treatment; 3) place of brachy therapy as sole treatment and combined with the other available therapeutical means.

Adult↗
PubMed1989

Effect of magnesium valproate on amygdala-kindled seizures in the rat: comparison with sodium valproate.

The anticonvulsant activity of a salt of valproic acid (VA), magnesium valproate (MgV), was assessed against amygdala-kindled seizures in rats. The anti-epileptic power of MgV was compared with that of sodium valproate (NaV). Kindling was obtained by delivering daily to one of the amygdala a 2 s train of monophasic square-wave pulses (1 ms, 60 c.p.s., 100-130 microA) via chronically implanted electrodes. Magnesium valproate and NaV were tested once kindling was stabilized and the post-kindling threshold for generalized convulsions was determined. The drugs were administered intraperitoneally in doses ranging from 25 to 200 mg/kg. The injection/test interval was 30 min. Each animal received a single dose every 24 h. Magnesium valproate exhibited an anticonvulsant activity qualitatively and quantitatively similar to that of NaV. Statistically significant differences were not found between the two drugs with respect to the reduction of seizure severity and afterdischarge (AD) duration. The calculated ED50's were 94.58 and 97.41 mg/kg for the suppression of generalized seizures, 176.96 and 129.26 mg/kg for the suppression of partial seizures, 275.96 and 224.13 mg/kg for the suppression of the local AD in the MgV and NaV treated groups, respectively.

Animals↗
PubMed1989

Effects of L-carnitine, L-acetylcarnitine and gangliosides on the regeneration of the transected sciatic nerve in rats.

Three pharmacological agents, L-carnitine, L-acetylcarnitine and gangliosides, were tested for their ability to enhance the regeneration of the rat sciatic nerve following transection and microsurgical repair. The drugs were administered intraperitoneally at the dose of 50 mg/kg/d for 28 and 56 d postoperatively. At the end of treatment, the motor function recovery of the peroneal component of the sciatic nerve was assessed and the regenerated nerves were analysed morphometrically on histological semi-thin sections. Also, the reinnervated extensor digitorum longus (EDL) muscles were studied histochemically using the adenosine-triphosphatase (ATP-ase) technique 56 d after surgery. Motor function assessment at 56 d after nerve repair revealed that L-acetylcarnitine-treated animals recovered a clinical grade significantly higher (p less than 0.05) than the control animals. Twenty-eight days after nerve repair, the number of myelinated fibres was significantly higher (p less than 0.05) in L-acetylcarnitine and ganglioside-treated animals than in control animals. However, 56 d after nerve repair the number of regenerated fibres in all the drug-treated groups was not significantly different from that of the control group. The EDL muscles of the drug-treated animals did not show significant differences from those of control animals with respect to fibre composition and fibre diameter although the L-acetylcarnitine-treated animals exhibited a significantly lower (p less than 0.05) degree of muscle atrophy than did the control animals. The results of the present work seem to indicate that L-acetylcarnitine and to a lesser extent gangliosides exert some favourable effect on the regeneration of the transected sciatic nerve in rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcarnitine↗
PubMed1989

Spinal cord stimulation in management of chronic pain. A 9-year experience.

Between 1978 and 1986, 109 patients with chronic pain underwent spinal cord stimulation (SCS) at the authors' institute as part of their pain treatment program. The results of SCS in these patients at the end of the test period and at the latest follow-up examination are analyzed in relation to the etiology of their pain. In 40 patients pain was associated with an obstructive peripheral vasculopathy, in 10 with a previous herpes zoster infection, in 15 with an incomplete traumatic spinal cord lesion, in nine with root and/or nerve damage, in 11 with cancer, and in 19 with previous back surgery. The etiology of the pain in five patients was uncertain. This experience supports the conclusion that the best indications for SCS are vasculopathic pain and post-herpetic neuralgia. No clinical usefulness was found for SCS in cancer pain or in central deafferentation types of pain.

Adult↗
PubMed1988

Subspecialization in neurosurgery.

The main aim of neurosurgery is to provide the patient with the best possible care. However, high priority should also be given to active contributions to the advancement of neuroscience, of which neurosurgery is a part. Clinical neurosurgery is continuously expanding and the trend is towards increased neurosurgical manpower which in turn leads to an unavoidable dilution of surgical experience. Progress in neuroscience is impressive. It appears unlikely that a neurosurgeon will be able to master all aspects of clinical neurosurgery and actively participate in research. Subspecialization permits optimum qualification in any one area of neurosurgery with regard to surgical skill and research. Thus the above difficulties would be overcome and the demands of neurosurgery fully satisfied. Subspecialization should be regarded as an inherent part of the neurosurgical field rather than an independent biomedical discipline. All specialists should receive a solid, general neurosurgical training and, with only few exceptions, should practice within an organized clinical framework.

Humans↗
PubMed1987

The spatial and morphological assessment of cerebral neuroectodermal tumors through stereotactic biopsy.

Stereotactic biopsies were carried out in an attempt to define the grading of 99 neuroectodermal tumors with respect to their modalities of growth and their degree of malignancy. Valuable data has been obtained in all explored tumors. The reliability of the information provided by stereotactic biopsy depends on the careful planning of the procedure by exploring different parts of the tumor as well as of the surrounding brain tissue.

Biopsy↗