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Biomedical subjects

A Ducati

Publications and source records attributed to A Ducati.

At least 37 records · Page 2Linked to original sources
PubMed1987

Pattern-reversal visual evoked potentials in phenylketonuric children.

Pattern-reversal visual evoked potentials (PR-VEPs) and EEG were recorded in 14 phenylketonuric (PKU) children on a low-phenylalanine (phe) diet; the data obtained were correlated with metabolic parameters, namely, the actual phe plasma level, the mean phe plasma level in the last year, an the beginning of the diet. PR-VEPs seem to be more sensitive than EEG in detecting neurophysiological derangements in these subjects; in fact PR-VEPs were pathological in six patients while EEG detected three; no significant alterations were found in the neurophysiological tests among the children with good metabolic control, and only one child was abnormal among the six on an early dietetic regimen; in contrast, six of the nine subjects presenting with high mean phe plasma levels (greater than 10 mg/100 ml) and five of the eight whose diet started after the 2nd month of life showed pathological PR-VEPs.

Adolescent↗
PubMed1985

Changes in visual evoked potentials in children on chronic dialysis treatment.

Visual evoked potentials (VEP) were recorded in 20 children undergoing dialysis for chronic renal failure. VEP before treatment (72 h after last dialysis) were pathological in 17 patients (85%); responses obtained 3 h after treatment were abnormal in only 6 cases (30%). Furthermore, all patients improved after treatment, except two who were unchanged. However, VEP recorded immediately after dialysis were worse in 4 of 7 patients than before treatment, probably as an effect of the dysequilibrium syndrome; they improved spontaneously afterwards. The acute changes caused by dialysis seem to be more evident in children than in adults. No correlations have been found between blood chemistry indexes and VEP modifications. Finally, VEP have proved to be more sensitive than EEG in identifying a central nervous system (CNS) dysfunction in these uremic patients.

Adolescent↗
PubMed1984

Short-latency cortical potentials evoked by tactile air-jet stimulation of body and face in man.

Natural cutaneous stimulation was performed in 10 healthy volunteers by means of a brief, localized air jet directed to the glabrous skin of the face, finger or toe. Neurograms (from finger stimulation) and somatosensory evoked potentials (SEPs) were recorded and, in the case of finger and toe stimulation, compared with the SEPs obtained by low intensity electrical stimulation. Comparing the latencies at wrist and elbow of the respective neurograms, it appears that a 2 msec period accounts for skin indentation and build-up of the generator potential in the receptors activated by the air jet. A slightly lower conduction velocity was obtained on natural than on electrical stimulation, and the cortical SEPs accordingly had a longer latency. In spite of the much smaller amplitude of the air-jet evoked neurograms, the amplitudes of the SEPs from finger and toe were similar to the amplitudes of the SEPs on electrical stimulation of the same regions. Natural stimulation in the regions innervated by the 3 branches of the trigeminal nerve (tongue included) yielded consistent SEPs, comparable with those reported in the literature to electrical stimulation. These potentials were distinguishable from the electrical activity due to the blink reflex, which invariably takes place on air-jet stimulation of the first trigeminal branch.

Adult↗
PubMed1984

Effects of deep barbiturate coma on acute spinal cord injury in the cat.

The effects of barbiturate administration on experimental balloon-induced spinal cord injury were tested in cats. Somatosensory evoked potentials from sciatic nerve stimulation were obtained before trauma and every 60 minutes after it up to the sixth hour, when the animals were killed. Eight cats received no barbiturate treatment. On histologic examination the traumatic lesion was found to be extensive (mean, 72.8% of total cross section of the cord area), sparing dorsal columns only in six cats. Somatosensory evoked potentials were absent in two cats and profoundly modified (that is, the late waves were absent) in six cats at the sixth hour. Eight cats were given a continuous infusion for 1 hour of intravenous thiopental sodium (total dose, 65-90 mg/kg) starting 30 minutes after trauma. In these eight cats, the extent of the traumatic lesion was significantly reduced (8.8% of the cord area). Among them, three animals presented with unaltered somatosensory evoked potentials (that is, with the presence of both primary components and late waves) at the sixth hour. It was concluded that thiopental sodium improves the response of the spinal cord to trauma, both at an anatomic and at a functional level.

Acute Disease↗
PubMed1982

Simulation of post-tetanic potentiation and fatigue in muscle using a visco-elastic model.

Post-tetanic potentiation (PTP) in single motor units was simulated using a simple visco-elastic model. Single isometric twitches and unfused tetani were obtained using a wide range of physiological input rates. Values of model parameters were chosen to simulate contraction times close to those of fast and slow muscle fibers. PTP has been attributed either to i) an augmented plateau level of active state or ii) an increase in time constant of active state decay. Our results show that a prolonged decay time of active state can account for most of the experimental data obtained in amphibian and mammalian preparations. In particular, potentiation is more marked in unfused tetani than in single twitches. Moreover the model accounts for PTP even in the case of a reduction of active state plateau due to fatigue.

Animals↗
PubMed1982

Brainstem auditory evoked potentials in a case of 'Manto syndrome', or spasmodic torticollis with thoracic outlet syndrome.

A case of spasmodic torticollis with thoracic outlet syndrome observed for over 18 months is presented and discussed. Maximal head rotation (determining backward gaze) was associated with compression of the brachial plexus between the scaleni muscles and motor, sensory and trophic troubles in the hand. This new syndrome is called after the diviner Manto, quoted by Dante Alighieri in his 'Divina Commedia' (Inferno, XX, 52-56). The etiology was ascribed to subacute toxic effects of methylparathion. Brainstem Auditory Evoked Potentials (BAEPs) demonstrated severe brainstem involvement, maximal in the mesencephalic structures. Clinical and neurophysiological data improved on treatment with L-5-hydroxytryptophan. Finally, BAEPs returned to normal.

5-Hydroxytryptophan↗
PubMed1981

Effects of stimulus intensity, cervical cord tractotomies and cerebellectomy on somatosensory evoked potentials from skin and muscle afferents of cat hind limb.

The somatosensory evoked potentials (SEPs) recorded from the sensory cortex were investigated by using graded stimulation of skin and muscle nerves from contralateral hind limb in the cat. Sections were made of the middle cervical cord to assess the pathways involved in mediating SEPs evoked by large and small diameter fibers. Dorsal column (DC) section caused a decrease of SEPs from skin group I afferents, and a small increase in those from group I muscle afferents. A subsequent section of dorso-lateral fasciculus (DLF) further decreased SEPs from skin and eliminated SEPs from muscle, evoked at low stimulus intensity. When the stimulus recruited group III fibres, SEPs were still present after DC and DLF section, both from skin and muscle nerves. Section of ALT in addition to DC confirmed a major role played by DLF (mainly spino-cervical tract of Morin) in transmitting impulses from muscle afferents; the role of DLF in mediating potentials evoked from skin is less remarkable than that of DC. Cerebellectomy did not change any SEP, however evoked. Previous results in the literature are discussed, taking into account the methodologies employed by various authors, and the possible interactions among pathways mediating SEPs.

Afferent Pathways↗
PubMed1975

Properties of motor units in the first deep lumbrical muscle of the cat's foot.

Isometric contractions of single motor units were studied in the first deep lumbrical muscle of the cat's hind-foot. Motor units with short twitch contraction times (15-20 msec) generally differed from those with longer ones (23-50 msec; contraction time measured in unpotentiated twitches) in showing (1) a greater maximum tetanic tension, (2) a smaller resistance to fatigue, (3) more post-tetanic potentiation of twitch tension, and (4) no post-tetanic occurrence of repetitive activity in response to single nerve stimuli (such "post-tetanic repetitive activity" was seen in several of the slower units). The ratio between unpotentiated twitch tension and maximum tetanic tension was similar for units with brief and long contraction times. The peak-to-peak amplitude of a single motor unit spike, recorded with gross electrodes, tended to be directly proportional to the maximum tetanic tension of the same motor unit.

Animals↗
PubMedDate not supplied

Neuronal generators of the visual evoked potentials: intracerebral recording in awake humans.

Flash and pattern reversal visual evoked potentials were recorded in awake patients undergoing stereotactic procedures for severe dyskinetic disorders resistant to medical treatment. The nucleus ventralis lateralis thalami was reached via an occipital approach. VEPs were recorded on the scalp at the entrance of the intracerebral electrode, and serially from sites at different depths. A polarity reversal of the surface recorded wave form took place as the intracerebral electrode was advanced beneath the surface cortical layers. As concerns F-VEPs, most of the scalp activity mirrored the potentials recorded down to the depth of 70-65 mm from the thalamus. The largest amplitude of intracerebral F-VEPs was obtained from recording sites at 50-70 mm from the thalamus, i.e., in the depth of the calcarine fissure. A negative wave, peaking around 47-50 msec, became evident in recording sites at 30-40 mm from the thalamus but vanished as the electrode was advanced farther. In only one patient could we record a small negative wave, peaking at 33 msec, in the vicinity of the corpus geniculatum externum. Furthermore, the oscillatory activity recorded from the scalp appeared to be generated in the cortical layers. PR-VEPs also underwent polarity reversal as the electrode traversed the cortex. PR-VEPs disappeared more superficially than F-VEPs. No PR-evoked activity could be recorded in the vicinity of the corpus geniculatum externum. We conclude that slow and fast components of VEPs recorded from the scalp are entirely generated in cortical layers.

Brain Mapping↗
PubMedDate not supplied

Role of SEP in identifying patients requiring temporary shunt during carotid endarterectomy.

EEGs and short-latency somatosensory evoked potentials (SEPs) to median nerve stimulation were recorded during 151 carotid endarterectomies, performed under general anaesthesia. Carotid occlusion did not affect either EEG or SEP in 120 cases (group A). In 31 cases the EEG showed "ischaemic" abnormalities (group B). A temporary shunt was inserted only in 16 B patients showing also severely depressed cortical SEPs within 2 min after carotid occlusion (group B shunt). In 15 B patients in whom SEPs were less affected, the operation was completed without shunt (group B no shunt). One intraoperative stroke occurred in group A and two in group B shunt. No neurological complications occurred in group B no shunt. Overall stroke rate was 2%. On retrospective analysis, latency and amplitude of N20 and P25 waves proved to be uninfluenced by carotid occlusion in group A, but were significantly affected in group B shunt. P25 amplitude alone was reduced in B no shunt. An arbitrary index (need-for-shunt index, NSI) was made in order to rate changes of P25 latency and amplitude. Its mean values were significantly different in the 3 groups. A threshold value is suggested above which shunt is required, as a useful adjunct to EEG, in order to balance prevention of brain ischaemia against the risks of shunt.

Aged↗
PubMedDate not supplied

Treatment of malignant gliomas: a new approach.

The aim of this study is to describe the authors' experience with intra-arterial ACNU chemotherapy of malignant gliomas. The prognosis of cerebral malignant gliomas remains poor, whatever traditional therapy is applied. ACNU is a well tolerated nitrosourea with a strong antimitotic effect on neurogenic cells both in vitro and in vivo; this drug has enhanced efficacy when used at high concentrations, particularly as an intraarterial infusion. Seventy-six patients have been studied to date, 68 of whom are evaluable; these patients were treated by intra-arterial infusion of ACNU (100 mg/m2) every 6 weeks, with a mean of 2.5 courses per patient. The objective response (OR) was 28% and analysis of pretreatment factors revealed that survival was influenced by histological grade, other types of therapy applied, and age. In general IAC is well tolerated and the response and survival appear to be better than with systemic chemotherapy.

Adult↗
PubMedDate not supplied

Evaluation of spinal cord function by means of lower limb somatosensory evoked potentials in reparative aortic surgery.

A group of patients undergoing aortic replacement of thoracic and abdominal aneurysms were studied by intraoperative recording of Somatosensory Evoked Potentials (SEPs). Lower limb nerves were stimulated and SEPs recorded at spinal and cortical level. Progressive changes of cortical SEPs until their disappearance were observed. In operations on the thoracic aorta, the spinal response was essentially unmodified, so that the observed alterations reflected true dysfunction of the spinal cord. The only patient who developed an intraoperative anterior spinal infarct had the longest period of absent SEPs and a striking latency prolongation when they returned. Postoperative recordings were absolutely normal. When the abdominal aorta was occluded, SEP alterations involved both cortical and spinal responses, so that it is difficult to distinguish between the relative roles of peripheral nerve and spinal cord ischemia. These findings indicate that SEPs can be reliably applied to spinal cord monitoring in the course of aortic surgery, even though they are mainly conducted in the posterior cord tracts.

Aged↗
PubMedDate not supplied

Evaluation of brainstem function, using acoustic evoked potentials, in 26 patients harbouring a CSF shunt for non-tumoral aqueductal stenosis hydrocephalus.

26 patients harbouring a CSF shunt for non-tumoral aqueductal stenosis hydrocephalus underwent Brainstem Acoustic Evoked Potentials (BAEPs) recording, to evaluate brainstem function. Only 6 patients presented with normal responses both at standard and at sensitized tests. In the remaining 19 patients, BAEPs were abnormal, bilaterally in 10 cases, monolaterally in 9. Four out of the 6 normal responses belonged to the group recognized of congenital origin. As refers to ventricular size BAEPs were abnormal in 62% of patients with normal ventricle and in 92% of patients with enlarged ventricles. The most significant BAEPs abnormalities were found in patients with maximal ventricular dilation. It appears that BAEPs abnormalities are to the ascribed to both primary and secondary brainstem dysfunction: no reliable criterion to differentiate between these two possibilities is evident. In the individual patient, serial BAEPs recording may contribute to recognize the early phase of supratentorial hypertension due to shunt dysfunction.

Adolescent↗
PubMedDate not supplied

Respiratory complications during artificial barbiturate coma.

Artificial barbiturate coma was induced in 13 patients with disorders of consciousness from traumatic or spontaneous diseases. Early respiratory complications consisting with Adult Respiratory Distress Syndrome (ARDS) were found in 10 out of these 13 patients; on the contrary, only 2 out of 13 patients, treated with routine intensive care therapy without barbiturate, showed analogous respiratory complications. The literature on the subject and the possible pathophysiological mechanism of respiratory distress are discussed.

Anesthesia↗