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Biomedical subjects

G Zanette

Publications and source records attributed to G Zanette.

At least 73 records · Page 4Linked to original sources
PubMed1995

Effect of pharmacologically induced mydriasis on the normal variability of retinal oscillatory potentials in man.

In this study we describe certain aspects of normal variability of oscillatory potentials, with particular reference to interaction between pupil size and stimulus intensity. The mean latencies of the earlier oscillatory potentials, O1 and O2, were significantly shorter when adopting the dilated pupil condition than when stimulating with a normal pupil. This occurred at various light intensities, although the difference was more significant at the highest intensity. O1 and O2 latencies became significantly longer as the stimulus intensity was progressively reduced. The latencies of the later components O3 and O4 were unaffected. The O1 and O2 amplitudes were not influenced by pupil size, but a significant reduction occurred with the progressive decrease in stimulus intensity. The later components O3 and O4 are greatly reduced in amplitude after pupil dilatation using higher stimulus intensities; the O4 potential may even disappear in 10% of the cases. These data provide further support for the existence of two distinct behavior patterns for earlier and later oscillatory potentials. Although light adaptation may affect oscillatory potentials, we suggest that in our experimental conditions, oscillatory potential changes may occur as a result of the activity of the neural modulating system, not only as a result of photoreceptor interaction.

Adult↗
PubMed1995

Neurophysiological and urodynamic examinations in the functional assessment of the spinal cord below the injury site.

We examined the characteristics of specific components of the evoked electrospinogram (EESG) in response to tibial nerve stimulation in 28 patients with traumatic injury of the dorsal and cervical spinal cord. The data were correlated with clinical, urodynamic and additional neurophysiological findings. In the majority of patients (82%), 11 with complete and 12 with partial spinal cord lesions, the lumbar components of the EESG were normal. In 4 of these patients with complete lesion above T2 the dorsal EESG was absent. In 5 cases (18%), the lumbosacral EESG was altered in the presence of an atypical clinical syndrome characterized by persistent urinary retention associated with lower leg atrophy and reduced tendon jerks. In these cases, MRI provided evidence of an unexpected sacral lesion. Unlike the dorsal EESG reflecting the afferent dorsal column volley, the lumbar components of the EESG are usually unaffected by interruption of the cord pathways; these last events thus originate from segmental neuronal activity, the involvement of which bears witness to additional lumbosacral damage.

Adolescent↗
PubMed1995

[Influence of droperidol on the hypnotic effect of thiopental].

We studied the effect of DBP on thiopentone hypnosis in 580 patients aged 20 to 30 and 560 patients aged 40 to 50. The hypnotic effect of thiopentone was evaluated after 5, 15, 30, 45 and 60 minutes from intravenous administration of 0.05 mg.kg-1 of DBP by using dose-effect curves to identify the ED50 dose. The ED50 value of thiopentone decreased up to 15 minutes after DBP (about 1.1 mg.kg-1 in both age groups) and increased after 30, 45 and 60 minutes, the increase being higher in the patients aged 40 to 50. We concluded that DBP has a synergic effect with thiopentone and the pharmacokinetic and alpha 1-lytic effects of DBP are responsible of an increased need of barbituric in the patients aged 40 to 50.

Adjuvants, Anesthesia↗
PubMed1995

Dynamic F wave from lower limbs: value and clinical application.

We evaluated changes in F wave from the lower limbs after walking in normals. Twenty-two healthy subjects ranging in age from 24 to 74 years (mean 40.2 SD 15.2) were investigated. The peroneal nerve was examined in 16 subjects and the posterior tibial nerve in 22 subjects on the dominant side. F waves were evaluated at rest and 1 minute and 10 minutes after effort testing consisting in prolonged walking for 15 minutes. F wave minimum, maximum and mean latencies, chronodispersion, duration, persistence and amplitude were evaluated. Only chronodispersion showed a significant decrease for both the peroneal and tibial nerve (p < 0.05) after walking. Moreover we evaluated the F wave after effort in five patients affected by neurogenic claudication: three patients presented a further slowing of proximal conduction, while two patients exhibited a transitory conduction block. In conclusion, F wave changes observed in dynamic conditions in normals probably reflect a synchronization of motorneuron firing requiring a certain amount of descending facilitation. On the other hand, the marked F wave changes after effort observed in patients increase the sensitivity of this method in the clinical setting and may provide insights into the pathophysiologic basis of neurogenic claudication.

Adult↗
PubMed1994

Evidence of higher insulin resistance in NIDDM patients with ischaemic heart disease.

Prospective studies have shown a relationship between hyperinsulinaemia, an indirect index of insulin resistance, and IHD in men with normal glucose tolerance. In NIDDM this association is less clear possibly due to the poor significance of insulin and C-peptide concentrations as an index of insulin resistance. Therefore, only a direct measurement of insulin sensitivity could clarify the possible relationship between insulin resistance and IHD in NIDDM. We have evaluated insulin sensitivity, by means of an ITT, and some risk factors for IHD in 72 men with NIDDM, 36 with and 36 without IHD, attending our out-patient Diabetic Clinic. The two groups were of similar age, duration of diabetes, glycaemic control and body composition. Subjects with IHD were more insulin resistant (K(ITT) index 2.45 +/- 0.18 vs 3.12 +/- 0.13% per min, in patients with and without IHD, respectively, p < 0.004), had higher total (p = 0.011) and LDL serum cholesterol levels (p = 0.010) and greater prevalence of hypertension (p = 0.001) compared to subjects without IHD. Using step-wise logistic regression analysis, insulin resistance (odds ratio 2.57, 95% CI 1.87-3.28, p = 0.008), hypertension (odds ratio 8.17, 95% CI 6.86-9.48, p = 0.002), total serum cholesterol levels (odds ratio 1.02, 95% CI 1.005-1.035, p = 0.015) and BMI (0.79, 95% CI 0.67-0.97, p = 0.049) were independently associated with IHD. After adjustment for age and duration of diabetes, only insulin sensitivity was directly related to the age of onset of IHD, independently from other clinical and metabolic parameters (p < 0.015).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Cortical output modulation after rapid repetitive movements.

Transcranial magnetic stimulation was used to evaluate changes in motor cortex excitability after rapid repetitive movements in five healthy subjects aged 23-30 years, by considering the amplitude of motor evoked potentials (MEPs) at rest and after one minute of maximal frequency repetitive abduction-adduction movements of the thumb. In addition, M and F waves were evaluated by stimulating the median nerve at the wrist. All of the examined subjects showed a clear modification in post-exercise MEP amplitudes, with a mean maximal reduction of 50-60% in comparison with basal values and complete recovery after a period of about 35 minutes. The time course of this phenomenon showed a triphasic pattern: (I) a rapid decrease phase up to the fifth minute; (II) a maximal depression phase for a period of about ten minutes; (III) a slow return to basal values. No significant changes were observed in post-exercise M and F waves. These results show the existence of a reversible modulation of the excitability of the upper motor neuron after rapid repetitive movements. It is likely that this modulation takes place at the level of the motor cortex and that its anatomo-functional substrate is represented by the activation of inhibitory intracortical circuits.

Adult↗
PubMed1994

Spinal somatosensory evoked potentials in patients with tethered cord syndrome.

We studied the electrophysiological changes occurring in six patients with tethered cord syndrome. Evidence of spinal malformations was provided by magnetic resonance imaging. The functional assessment of the spinal cord was performed by analysing both spinal and cortical somatosensory evoked potentials. The evoked electrospinogram was recorded from the thoracic and lumbosacral spinous processes. The N22 lumbosacral potential was selectively affected, being rostrocaudally displaced and reduced in amplitude or even absent in patients with neurological signs indicating a segmental lower cord lesion. Inter-peak somatosensory evoked potentials latency was normal in all cases, suggesting that ascending axonal potentials in the dorsal column fibres may be synchronized. Segmental potentials of the lumbosacral response, originating from the post-synaptic activity of dorsal horn interneurons, are selectively affected in this syndrome resulting from the rostrocaudal displacement of the spinal cord due to tethering. Our findings in the clinical field are consistent with previous experimental evidence indicating a different sensitivity of the gray vs. white matter to progressive stretching.

Adult↗
PubMed1994

October 1942: a strange epidemic paralysis in Saval, Verona, Italy. Revision and diagnosis 50 years later of tri-ortho-cresyl phosphate poisoning.

In the autumn of 1942 a strange epidemic paralysis started in Saval, at that time a country area but now part of the city of Verona. The epidemic went on for several months and affected 41 people, all working as owners or labourers on the same farm. Some of the farm animals (chickens, horses, cattle, pigs) also became ill. About 20 patients were admitted to the nearby city hospital. The outbreak was diagnosed as polyneuritis with a probable viral cause. Fifty years later, seven people with sequelae of the disease were examined. The most severe cases present a spastic paraplegia and lower leg muscle atrophy without sensory impairment, resembling an amyotrophic lateral sclerosis "frozen" for 50 years. The clinical syndrome can now be attributed confidently to organophosphate induced delayed polyneuropathy. All the epidemiological data obtained from the survivors were evaluated and a careful review of the literature was made. Contamination of the ground from a rubbish dump near the farmyard would explain the epidemiology of the Saval outbreak.

Adolescent↗
PubMed1994

Hemiparkinsonism-hemiatrophy syndrome: neuroradiological and neurophysiological findings.

A rare form of secondary parkinsonism has been recently described as 'hemiparkinsonism-hemiatrophy syndrome'. We report a case with such clinical features. A neurophysiological study of the evoked potentials, somatosensory and motor, has been conducted. We stress the neuroradiological findings at nuclear magnetic resonance, which documented the presence of an area of altered signal in the mesencephalon, between the cerebral pedunculus and the red nucleus on the right side. The etiopathogenetic considerations and diagnostic criteria are discussed. Moreover we evaluate the efficacy of levodopa therapy.

Adult↗
PubMed1994

Variability of tibial nerve early cortical potentials in normal subjects.

The aim of the study was to calculate and test the variability of several tibial nerve SEP parameters, particularly scalp amplitude distribution, with a view to obtaining more reliable clinico-electrophysiological correlations. The parameters were evaluated in 20 healthy subjects using a simple, easily reproducible recording method. The absolute latency of the P40 wave was greater than that of the N37 wave, except in two cases. Paradoxical lateralization was present in all subjects. On the basis of the scalp amplitude distribution of the ipsi- and contralateral potentials, three distinct groups were identified: a) dominance of ipsilateral P40, 29 sides; b) dominance of P37, 15 sides; and c) equivalent amplitude of P37 and ipsilateral P40, 5 sides. The individual amplitude values of these potentials were plotted on a normogram. The results suggest that (i) the absence of one or more early cortical SEPs may be considered abnormal; (ii) when SEP scalp lateralization is present, it may be useful to compare the amplitude distribution of the individual components in normal and pathological populations; and (iii) for this purpose, lateralized potentials are more reliable owing to their lower degree of amplitude dispersion.

Adult↗
PubMed1993

Atypical syndromes caudal to the injury site in patients following spinal cord injury. A clinical, neurophysiological and MRI study.

Some patients with a cervical or a high thoracic spinal cord injury show atypical signs and symptoms such as atrophy of lower leg muscles, reduced tendon jerks or urinary retention, either persisting from the acute phase or developing in the course of time. A series of 35 patients was prospectively examined from this point of view with neurophysiological, urodynamic and MRI studies. Seven patients (20%) presented atypical findings; in two there was an isolated areflexic bladder, but no signs of functional or structural sacral damage were found. In five patients (14.2%) a definite cause for the sacral lesion could be detected. The syndrome caudal to the level of the lesion is neither obvious at the beginning nor immutable in time. Treatment requires to be adapted to the changing patterns of somatic and visceral activity.

Adolescent↗
PubMed1993

IDPN impairs post-traumatic regeneration of rat sciatic nerve.

The role played by cytoskeletal proteins in nerve regeneration was investigated in a model in which the axonal transport of neurofilaments (NF) is almost selectively impaired. The administration of beta, beta'-iminodipropionitrile (IDPN), a synthetic lathyrogenic compound, induces an axonopathy characterized by proximal axonal enlargements, due to NF accumulation, and by diffuse atrophic changes associated with spatial segregation of NF from microtubules (MT). We investigated post-axotomy regeneration of rat sciatic nerve following IDPN administration. Changes induced by IDPN, as examined in the proximal and distal nerve stump at 15 and 30 days after lesion, consisted of a statistically significant reduction of the mean axonal diameter (P < 0.0001) as compared to control rats. In addition, the number of regenerating myelinated fibres was smaller in dosed rats (P < 0.001) 15 days after crush, whereas at the later stage the number of axons approached that of control animals. Electrophysiological investigation revealed a delay in target reinnervation in dosed rats. Regenerating IDPN axons, both 15 and 30 days after crush contained fewer NF (P < 0.001), while the number of MT was slightly increased as compared to controls. Taken together, our results suggest that severe alteration of NF transport, coupled with mild alteration of other components of cytoskeletal proteins, impairs the longitudinal and radial growth of regenerating myelinated axons and confirm that the number of NF is the major determinant of the cross-sectional area of each segment of the axon.

Animals↗
PubMed1992

Retinal oscillatory potential abnormalities in patients with chronic renal failure, before and after dialytic treatment.

Nineteen patients with chronic renal failure were studied, oscillatory potentials (OPs) being recorded shortly before and after dialytic treatment. Mean values of either onset latency (O1 latency) and duration of the complex (O1-N4 inter-peak latency) were found to be significantly longer in patients than in controls (p < 0.001). Most of the patients (12) showed a pathological prolongation of latency (> 2.5 SD). Amplitude changes also affected OPs, but earlier components were reduced to a lesser degree than the later ones, as shown by statistical analysis. Moreover, seven patients showed an almost complete loss of O3 and O4 peaks. Latency changes may be transiently reversed by dialysis, suggesting a functional impairment of the retinal response; the loss of later components is a more persistent abnormality probably related with a structural damage.

Adult↗
PubMed1992

Erythrocyte Li+/Na+ and Na+/H+ exchange, cardiac anatomy and function in insulin-dependent diabetics.

It has been proposed that an increased activity of cell membrane Na+/H+ exchange, mirrored by increased erythrocyte Li+/Na+ exchange, may facilitate cell hypertrophy and hyperplasia. Patients with insulin-dependent diabetes mellitus may develop a specific cardiomyopathy with systolic and diastolic abnormalities and increased thickness of the left ventricle. Therefore, we have investigated the relationships between erythrocyte Li+/Na+ and Na+/H+ exchange and echocardiographic parameters in 31 male insulin-dependent diabetics (aged 17-68), in good metabolic control. Three had untreated mild hypertension. In all patients the urinary albumin excretion rate was less than 200 micrograms min-1. Ten patients had a Li+/Na+ countertransport higher than 0.37 mmol l-1 cell h-1, the upper normal limit for our laboratory (0.49 +/- 0.10, mean +/- SD). In comparison with the patients with normal countertransport, they had increased interventricular septum thickness and relative wall thickness (h/r). End diastolic volume and cardiac index were reduced while blood pressure and urinary albumin excretion rate were similar. In the whole study group, interventricular septum thickness was significantly correlated to Li+/Na+ exchange (r = 0.61, P less than 0.001) and Na+/H+ exchange (r = 0.35, P less than 0.05), independently of the effect of age and blood pressure. Posterior wall thickness was correlated to Li+/Na+ exchange (r = 0.38, P less than 0.05) and h/r to Li+/Na+ exchange (r = 0.41, P less than 0.05) and to Na+/H+ exchange (r = 0.44, P less than 0.05). Li+/Na+ exchange was negatively correlated to cardiac index (r = -0.37, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Polyneuritis cranialis: clinical and electrophysiological findings.

A 13 year old boy, developed bilateral facial weakness, dysphonia and dysphagia acutely after a febrile illness. Neurological examination and MRI of the brain were normal. The CSF protein level increased. Blink reflex monitoring during clinical recovery was consistent with demyelination of the lower cranial nerves innervating the branchial arch musculature, a rare variant of Guillain-Barré syndrome.

Adolescent↗
PubMed1992

Interaction between thiopentone and subhypnotic doses of ketamine.

The hypnotic effects of thiopentone and ketamine were studied in ASA Grade I female patients aged 20-30 without premedication. The dose-response curves of ketamine 0.4 mg kg-1 and thiopentone following ketamine 0.4 mg kg-1 were determined by probit analysis. The interaction between ketamine and thiopentone was found to be an antagonistic one. This effect can be interpreted as a consequence of the different neurophysiological spectra of action of the two drugs.

Adult↗
PubMed1991

Sodium-lithium countertransport and cardiorenal abnormalities in essential hypertension.

The rate of red blood cell sodium-lithium countertransport is elevated only in a subgroup of patients with essential hypertension. We have therefore compared renal and cardiac function and morphology in two groups of hypertensive patients with high (n = 23) or normal (n = 22) sodium-lithium countertransport (mean +/- SEM: 0.61 +/- 0.10 versus 0.29 +/- 0.07 mmol/l red blood cells.hr). The two groups were similar in age, sex distribution, body mass index, smoking habit, duration of hypertension, and actual levels of untreated blood pressure. Hypertensive patients with elevated sodium-lithium countertransport activity showed elevated glomerular filtration rate (118 +/- 2 versus 109 +/- 2 ml/min.1.73 m2; p less than 0.001), albumin excretion rate (23 +/- 3 versus 14 +/- 2 micrograms/min; p less than 0.001), larger kidney volume (250 +/- 15 versus 203 +/- 13 ml.1.73 m2; p less than 0.01), lower lithium clearance rate (26.7 +/- 0.3 versus 28.9 +/- 0.3 ml/min.1.73 m2; p less than 0.01), and higher total body exchangeable sodium (2,716 +/- 33 versus 2,485 +/- 41 mmol.1.73 m2; p less than 0.01). Left ventricular mass index (139 +/- 6 versus 119 +/- 6 g/m2; p less than 0.05), relative wall thickness (0.39 +/- 0.05 versus 0.29 +/- 0.04 cm; p less than 0.001), and left posterior wall plus intraventricular septum thickness (2.02 +/- 0.04 versus 1.76 +/- 0.03 cm; p less than 0.05) were also higher in patients with high sodium-lithium countertransport. Hypertensive patients with normal sodium-lithium countertransport had renal and cardiac parameters similar to those of a normotensive control group (n = 21) except for a higher glomerular filtration rate and left ventricular mass index.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗