Faculty Bibliography

Following MPTP administration, 4 Cynomolgus monkeys developed a parkinsonian syndrome, accompanied by specific changes of both pattern visual evoked potential and electroretinogram. Retinal dopamine and dihydroxyphenylacetic acid contents were measured in the 4 MPTP-treated monkeys and in 3 normal monkeys. Dopamine and dihydroxyphenylacetic acid levels were significantly lower in the retinas of the MPTP-treated animals (p less than 0.001), suggesting that dopamine has a specific function in the visual system of primates

Endogenous components of evoked potentials resembling P300 in human beings were sequentially studied in four cynomolgus monkeys (Macaca fascicularis using an auditory 'oddball' paradigm, after classical conditioning training. When robust P300-like signals were obtained, each animal underwent further recording sessions in which a placebo, L-carnitine or L-acetylcarnitine (LAC) was injected. Only LAC induced an amplitude increment of P300 waves in all the animals and a latency decrement in two animals. Furthermore a transient effect with amplitude reduction on the primary cortical auditory evoked potentials (AEP) both to rare and frequent tones was also recorded in all the animals. This effect resembled the AEP amplitude reduction induced by physostigmine administration. The findings suggest an effect of LAC on normal processes accompanying cognition

We examined the hemispheric distribution of the pattern visual evoked potential in 3 Cynomolgus monkeys, before and after right optic tractotomy or left occipital lobectomy. The stimuli were vertical gratings of 4 spatial frequencies, presented using counterphase and on-off modulation at 1 and 8 Hz. In the normal monkey, the amplitude and latency of the PVEPs elicited by 1 Hz stimulation were similar across all electrode sites. While no differences were found in the phase of the PVEP elicited by 8 Hz stimulation across the different derivations, PVEP amplitude generally decreased over the lateral electrodes. Once experimental hemianopia was created, PVEPs recorded over the midline and the intact hemisphere were normal. However, partially polarity-inverted PVEPs of smaller amplitude were recorded over the deafferented hemisphere. In addition, the interhemispheric phase difference became more prominent in the PVEP recorded over the deafferented hemisphere as the spatial frequency was increased

The present study evaluates the reproducibility of five cardiovascular reflex tests, deep breathing (DB), Valsalva maneuver (VM), sustained hand-grip (SHG), postural hypotension (PH) and lying to standing (LS) in normal subjects and in insulin dependent (type I) diabetic patients. The study was carried out in 10 normal subjects, in 10 diabetics with autonomic neuropathy and in 10 diabetics without autonomic neuropathy. The five cardiovascular reflex tests were performed five times on five consecutive days by the same investigator and in identical basal conditions. The intraindividual variability of DB, LS and VM was significantly reduced in diabetics with autonomic neuropathy compared with normal controls, but there was no difference between diabetics without neuropathy and normal controls. The intraindividual variability of PH was significantly increased in diabetics with autonomic neuropathy compared with diabetics without autonomic neuropathy and with normal controls. There was no difference among the three groups in the reproducibility of SHG. In normal subjects the intraindividual variability only exceptionally produced a shift from normal to abnormal values or vice versa; in diabetics with autonomic neuropathy this shift was more frequent

VEPs were recorded with three different spatial frequencies of stimulation in patients affected by idiopathic Parkinsonism and by Parkinsonian syndromes. The detection of VEP abnormalities in Parkinson's disease was dependent on the spatial frequency of the visual stimulus (a vertical square wave grating). The VEP latency was normal in Parkinsonian syndrome patients (except in one patient affected by familial Parkinsonism). Dopamine precursor therapy differently reduced the VEP latency, depending on the spatial frequency of the visual stimulus. These findings suggest that the dopaminergic mechanism involved in the generation of VEP delays is sensitive to stimulus spatial frequency. The study of VEPs before and after the administration of haloperidol confirmed this hypothesis. VEP latency did not correlate with the major clinical symptoms of Parkinson's disease and could not predict the results of chronic dopaminergic therapy

Endogenous components of evoked potentials resembling P300 in humans were sequentially studied in 3 cynomolgus monkeys (Macaca fascicularis) using an auditory 'oddball' paradigm. The two different auditory stimuli were 500 Hz and 4000 Hz tones, designated as the 'frequent' and 'rare' stimuli, respectively. The probability of 'rare' tone presentation was initially 0.2. We further used probabilities of 0.1, 0.3 and 0.5. The 'rare' stimulus was reinforced by electrical stimulation, which followed the onset of the high tone by 700 msec. After 3-5 training sessions, a late positive wave was observed following the 'rare' tone. The latency of this P300-like signal was 314 +/- 16.2 msec, and the amplitude was 23.6 +/- 3.14 microV. The amplitude of this potential was modified by changes in stimulus presentation probability and by withholding reinforcement

Common thought is that diabetic neuropathy is a predisposing factor to entrapment syndromes. Carpal tunnel syndrome (CTS) is the most frequent entrapment neuropathy; females and old people are most frequently affected (Comi et al., 1978). Prevalence of CTS in diabetics and associated risk factors were studied in 401 patients (208 males and 193 females) with insulin-dependent and non-insulin-dependent diabetes using electrophysiological techniques. Median nerve sensory and motor conduction velocity, ulnar and peroneal nerve motor conduction velocity and sural nerve sensory conduction velocity were investigated in all patients. Diagnostic criteria for CTS were the presence of delayed median nerve sensory conduction velocity in the palm-wrist tract and of increased distal motor latency. Polyneuropathy was defined by slowing-down of conduction velocity in two or more nerves. Forty-five patients (11.2%), 36 females and 9 males, showed CTS. One-hundred-sixty-eight patients (41.8%), 74 females and 94 males, were suffering from peripheral neuropathy. The strongest risk factors for CTS, in order of importance, were: female sex, older age and presence of neuropathy. Polyneuropathy but not CTS was related to duration of diabetes