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Biomedical subjects

M Zampolini

Publications and source records attributed to M Zampolini.

At least 19 recordsLinked to original sources
PubMed1997

Reciprocating gait orthoses: a multicenter study of their use by spinal cord injured patients.

OBJECTIVE: Use of reciprocating orthosis (RGO, ARGO, HGO) by 74 patients with complete traumatic spinal cord injury was studied. Lesion levels ranged from T1 to T12. STUDY DESIGN: Patients were enrolled in seven Italian rehabilitation centers an average of 37 weeks after acute trauma. The training period averaged 39 days. Discontinued use of the device was recorded at follow-up. Before discharge, functional walking, gait velocity, donning and doffing time, and the ability to climb stairs were recorded. The same items were evaluated at 6-month follow-up. RESULTS: At follow-up, 24 patients had abandoned the orthosis, 19 used the device for therapeutic exercise, 31 used it for functional gait, and 9 also used it outside the home. Functional walking was correlated with age, level of lesion, ability to climb stairs, duration of training, and lapse of use of the orthosis. The results showed a correlation between use of the orthosis and the ability to climb stairs, as well as a high Garrett score. CONCLUSION: This orthosis is not considered as an alternative to the wheelchair, despite its greater speed, simplicity of use, and greater autonomy provided to the user.

Adolescent↗
PubMed1996

Low-frequency stimulation cancels the high-frequency-induced long-lasting effects in the rat medial vestibular nuclei.

In rat brainstem slices, we investigated the effects of low-frequency stimulation (LFS) of the primary vestibular afferents on the amplitude of the field potentials evoked in the medial vestibular nuclei (MVN). LFS induced long-term effects, the sign of which depended on whether the vestibular neurons were previously conditioned by HFS. In unconditioned slices, LFS evoked modifications of the responses that were similar to those observed after HFS but had a smaller extension. In fact, LFS caused long-lasting potentiation of the N1 wave in the MVN ventral portion (Vp) and long-lasting depression of the N2 wave in the MVN dorsal portion (Dp), whereas it provoked small and variable effects on the N1 wave. By contrast, when the synaptic transmission was already conditioned, LFS influenced the synaptic responses oppositely, reducing or annulling the HFS long-term effects. This phenomenon was specifically induced by LFS, because HFS was not able to cause it. The involvement of NMDA receptors in mediating the LFS long-term effects was supported by the fact that AP-5 prevented their induction. In addition, the annulment of HFS long-term effects by LFS was also demonstrated by the shift in the latency of the evoked unitary potentials after LFS. In conclusion, we suggest that the reduction of the previously induced conditioning could represent a cancellation mechanism, useful to quickly adapt the vestibular system to continuous different needs and to avoid saturation.

2-Amino-5-phosphonovalerate↗
PubMed1995

The role of GABA in NMDA-dependent long term depression (LTD) of rat medial vestibular nuclei.

The role of GABA in NMDA-dependent long term depression (LTD) in the medial vestibular nuclei (MVN) was studied on rat brainstem slices. High frequency stimulation (HFS) of the primary vestibular afferents induces a long lasting reduction of the polysynaptic (N2) component of the field potentials recorded in the dorsal portion of the MVN. The induction but not the maintenance of this depression was abolished by AP5, a specific blocking agent for glutamate NMDA receptors. The involvement of GABA in mediating the depression was checked by applying the GABAA and GABAB receptor antagonists, bicuculline and saclofen, before and after HFS. Under bicuculline and saclofen perfusion, HFS provoked a slight potentiation of the N2 wave, while the N2 depression clearly emerged after drug wash-out. This indicates that GABA is not involved in inducing the long term effect, but it is necessary for its expression. Similarly, the LTD reversed and a slight potentiation appeared when both drugs were administered after its induction. Most of these effects were due to the bicuculline, suggesting that GABAA receptors contribute to LTD more than GABAB do. According to our results, it is unlikely that the long lasting vestibular depression is the result of a homosynaptic LTD. On the contrary, our findings suggest that the depression is due to an enhancement of the GABA inhibitory effect, caused by an HFS dependent increase in gabaergic interneuron activity, which resets vestibular neuron excitability at a lower level.

2-Amino-5-phosphonovalerate↗
PubMed1995

Gaba mediated long-term depression (LTD) in the rat medial vestibular nuclei.

As previously demonstrated, high frequency stimulation (HFS) of the primary vestibular afferents always induces a clear, long lasting depression of the polysynaptic (N2) component of the field potentials recorded in the dorsal portion of the medial vestibular nuclei (MVN). The induction of the HFS effect was mediated by the activation of glutamate NMDA receptors, since it was blocked by AP5. The mechanisms at the basis of such a depression were studied. Our results demonstrate that Gaba, acting on both GabaA and GabaB receptors, is involved in mediating this phenomenon. In fact, HFS applied during Bicuculline and Saclofen perfusion, was no longer able to induce an N2 depression, but provoked a slight potentiation. However, the N2 depression clearly emerged after drug wash-out. Furthermore, Bicuculline and Saclofen fully abolished the N2 depression and highlighted the potentiation, when administered after HFS. The possibility that the N2 depression is the result of a homosynaptic LTD can be excluded on the basis of our results. On the contrary, our findings suggest that the depression is due to an enhancement of the Gaba inhibitory effect due to an HFS dependent increase in gabaergic interneuron activity, which resets vestibular neuron excitability at a lower level.

Afferent Pathways↗
PubMed1994

Comparability and validity of two clinical scores in the early differential diagnosis of acute stroke.

OBJECTIVE: To compare two available clinical scores for the differential diagnosis of cerebral ischaemia and haemorrhage in acute stroke patients. DESIGN: Prospective, multicentre study of acute stroke patients evaluated with computed tomography and Allen and Siriraj scores; the scores were tested for comparability (kappa statistic) and validity (sensitivity, specificity, positive and negative predictive values, diagnostic gain). The effect of a policy of using Allen and Siriraj scores to determine pathological type of stroke before computed tomography was calculated. SETTING: Three hospitals in Italy, all participating in the international stroke trial, with different access facilities to computed tomography. SUBJECTS: 231 consecutive patients who were screened in the three hospitals for possible inclusion in the international stroke trial from 1 November 1991 to 31 May 1993. RESULTS: The prevalence of haemorrhage (diagnosed with computed tomography) was 14.7% (95% confidence interval 10.1% to 19.3%). Allen scores were "uncertain" in 44 cases and Siriraj scores in 38 cases; in the 164 cases with both the scores in the range of "certainty" kappa was 0.72. Sensitivity, specificity, positive and negative predictive values, and diagnostic gain for haemorrhage were 0.38, 0.98, 0.71, 0.91, and 0.58 for Allen scores and 0.61, 0.94, 0.63, 0.93, and 0.48 for Siriraj scores; positive predictive values for infarction were 91% for Allen scores and 93% for Siriraj scores. According to these data, of 1000 patients with acute stroke, 680 would be correctly and 70 wrongly diagnosed as "ischaemic" with the Allen score; the figures would be 671 and 48 with Siriraj score. CONCLUSION: When computed tomography is not immediately available and the clinician wishes to start antithrombotic treatment (or randomise patients in a clinical trial), the Siriraj score (and possibly the Allen score) can be useful to identify patients at low risk of intracerebral haemorrhage.

Acute Disease↗
PubMed1992

Theta burst stimulation is optimal for induction of LTP at both apical and basal dendritic synapses on hippocampal CA1 neurons.

The efficacy of stimulation patterns consisting of brief high frequency bursts repeated at various intervals to induce long-term potentiation (LTP) at synapses on apical and basal dendrites of CA1 hippocampal neurons was tested in vitro. Both apical and basal dendritic synapses exhibited maximal LTP after bursts repeated at 5-10 Hz, i.e. close to the frequency of the endogenous hippocampal theta rhythm. As at apical dendritic synapses, LTP at basal dendritic synapses was blocked by an antagonist of NMDA receptors. Basal dendritic LTP was significantly greater in magnitude than apical dendritic LTP, although the reason for this is unknown.

2-Amino-5-phosphonovalerate↗
PubMed1992

NMDA receptor-mediated long term modulation of electrically evoked field potentials in the rat medial vestibular nuclei.

The effect of high frequency stimulation (HFS) of the primary vestibular afferents on field potentials recorded in the ipsilateral Medial Vestibular Nuclei (MVN) was studied. Our results show that potentiation and depression can be induced in different portions of MVN, which are distinguishable by their anatomical organization. HFS induces potentiation of the monosynaptic component in the ventral portion of the MVN, whereas it provokes depression of the polysynaptic component in the dorsal portion of the same nucleus. The induction of both potentiation and depression was blocked under AP5 perfusion, thus demonstrating that NMDA receptor activation mediates both phenomena. Furthermore, the finding that the field potentials were not modified during perfusion with DL-AP5, as previously reported, supports the hypothesis that NMDA receptors are not involved in the normal synaptic transmission from the primary vestibular afferent fibres, but are only activated following hyperstimulation of this afferent system. Our results suggest that the mechanisms of long term modification of synaptic efficacy observed in MVN may underlie the plasticity phenomena occurring in vestibular nuclei.

2-Amino-5-phosphonovalerate↗
PubMed1992

Role of NMDA receptors in the compensation of ocular nystagmus induced by hemilabyrinthectomy in the guinea pig.

The possibility that N-methyl-D-aspartate (NMDA) receptor activation plays a role in inducing the vestibular compensation following hemilabyrinthectomy (HL) in guinea pigs, was verified by means of continuous intraventricular osmotic pumping of DL-2-Amino-5-phosphono-valeric acid (APV). Our results show that high doses (40 and 20 mM) of APV decrease both the combined OKR and VOR and the nystagmus following HL. Low doses of APV (2.5 mM), affect the time course of the ocular compensation by maintaining a higher level of nystagmus beat frequency and by delaying the nystagmus disappearance. On the contrary, the compensation time course is not affected by administering APV later on in the compensation period. Therefore, it appears that NMDA receptors are activated during the precocious phase of vestibular compensation, when a large vestibular imbalance is present. This finding is explained by the development of NMDA receptor hypersensitivity, in the functionally inactivated commissural system or by the occurrence of NMDA-mediated long-term potentiation.

2-Amino-5-phosphonovalerate↗
PubMed1987

Creatine kinase BB activity in serum of patients with acute stroke: correlation with the severity of brain damage.

BB-CK activity was measured in 11 patients with stroke and in 10 controls. Blood samples were taken 36 hours after the clinical stroke onset in every patient. Sera were stored at -80 degrees and analyzed within two months. The creatine kinase isoenzymatic pattern was determined by ion-exchange column separation and gradient elution system. The mean BB-CK concentration in patients with stroke was significantly higher than in controls (p less than 0.01). In the group of "stroke" patients we found a correlation between severity of brain damage, as suggested by the clinical picture and CT scans, and serum values of BB-CK.

Adult↗
PubMed1987

Afferent sensillar inputs to the Retzius cell of the leech Hirudo medicinalis.

Water-wave and photic stimulation of the sensilla elicits synaptic potentials identical to those elicited by electrical stimulation of the segmental roots. Mechanical stimulation elicits a localized IPSP and a generalized EPSP in the RCs and an IPSP in the AE motoneurons. Photic stimulation gives rise to a generalized EPSP in the RCs alone. The impulse discharges elicited in the afferent fibers by the two kinds of stimuli is transmitted along the cord both anteriorly and posteriorly to the stimulated segment. This implies that the afferent impulses excite a pool of intersegmental neurons in each ganglion, which distribute their discharges to the adjacent ganglia. The evidence for occlusion between cordal and photically elicited volleys indicates that it shares with the sensillar input a common pool of interneurons. The possible functional significance of the inhibitory and excitatory inputs is discussed.

Afferent Pathways↗