Seven male patients previously exposed to industrial solvents and diagnosed with chronic toxic encephalopathy (aged 38 to 69 years; mean age, 56 years) were investigated by dynamic posturography and compared with healthy, age-matched male control patients. Dynamic posturography comprises two phases: a sensory organization (SO) phase, in which the support surface and visual surround are either stable or referenced to the patient's sway, with eyes open or closed, and a movement coordination (MC) phase, in which the platform makes active movements. In SO testing, the patient group showed significantly impaired equilibrium performance compared with the control group in most test conditions. The MC test revealed no differences between groups. A relationship was found between the equilibrium score resulting from SO testing with stable support and visual surround and the sway area of the confidence ellipse elicited 3 years previously by static posturography with eyes open. We conclude that patients with chronic toxic encephalopathy have impaired equilibrium, as demonstrated by dynamic posturography testing.

Adult↗

PubMedDate not supplied

Restricted expression of HIV1 in human astrocytes: molecular basis for viral persistence in the CNS.

Besides macrophages and microglial cells, cells of astroglial origin are thought to be targets of HIV1 in the brain. HIV1 infection of astroglial cells results in restricted production of the virus. To analyse the molecular basis of this restricted infection phenotype, we established a chronically HIV1-infected low-producer astrocytoma cell line. These cells show only low levels of mRNA encoding structural proteins, due to a cell-determined blockage in the Rev/RRE regulatory axis. The low-producer state could not be overcome by treatment with known stimulators of virus expression such as phorbol ester, (12-O-tetradecanoylphorbol-13-acetate), tumour necrosis factor alpha or sodium butyrate. This indicates that the molecular mechanisms involved in restricting virus production in astroglial cells differ from those in latently infected T cells and monocytes.

Astrocytes↗

PubMedDate not supplied

The effect of stimulus predictability and age on human tracking eye movements.

Human tracking eye movements were recorded in healthy volunteers of varying age. The target motion was either predictable (pure sinusoids or sinusoidal frequency sweep) or unpredictable (pseudorandomized). Gain and phase values for the tracking and the smooth pursuit eye movement signal were calculated as a function of target frequency from 0.2 to 2 Hz. Max. target velocity was 20 or 40 deg/sec. In the low frequency area the smooth pursuit gain for predictable stimulation was higher than the gain elicited by the pseudorandomized stimulation. In the high-frequency area, gain values did not differ significantly. For the predictable stimulation, the phase of the smooth component was always a lag, increasing with increasing frequency. At low frequencies of the pseudorandomized signal a phase lead was observed. At higher frequencies the lead turned into a lag that was greater than for the predictable stimulation. The young and old groups showed reduced smooth pursuit gain values, compared with the main group specially when the target waveform was pseudorandomized. The reduced smooth pursuit ability was mostly compensated for by an increased amount of saccades.

Adult↗

PubMedDate not supplied

The plasticity of compensatory eye movements in bilateral vestibular loss. A study with low and high frequency rotatory tests.

Twelve subjects with bilateral vestibular loss, with a mean age of 27 years (18-49) were studied. The loss was based on symptoms of oscillopsia and ice-water caloric tests. Nine subjects were evaluated by low-frequency sinusoidal harmonic acceleration (SHA) rotatory tests (0.01-0.32 Hz), and 3 subjects with high broad-frequency band rotatory tests (0.25-3.25 Hz). During alertness tests (darkness) all subjects had absent or very low gains. When tested with a stationary light in the middle of the swing, the SHA tests showed perfect compensatory eye movements with gains of 1 and phases of approximately 0 degrees. In the broad-frequency test, the gain was near 1 below 1 Hz, decreasing rapidly at higher frequencies. In imaginary stationary target tests (darkness), the gain was enhanced to 'normal' values (0.5) with a phase lead in the low-frequency range (SHA). This could not be replicated in the high-frequency tests. Testing with stationary acoustic guidance (darkness), further enhanced the gain in the SHA tests. A small increase of gain could also be found in the high-frequency tests. Compensatory eye movements, when tested in low-frequency rotatory tests (less than 1 Hz), are to a large extent influenced by non-vestibular mechanisms. By voluntary modifications, normal gains could be produced by patients with 'bilateral vestibular loss'. The phase lead found is proposed to be of central non-vestibular origin. Testing in higher frequency ranges (greater than 1 Hz) could not replicate these findings, thus the broad-frequency band rotatory test should be preferred for adequate vestibular quantification.

Adaptation, Physiological↗

PubMedDate not supplied

Otoneurological findings in psycho-organic syndrome caused by industrial solvent exposure.

Nine subjects with long-term (8-30 years) occupational exposure to industrial solvents and a confirmed diagnosis of psycho-organic syndrome (POS) have been studied with audiological and otoneurological test batteries. The results were compared to a matched control group of nine industrial workers not exposed to solvents and to normal data from healthy volunteers. In the clinical examination, the Romberg test identified 5/9 workers as pathologic and concurrently the stabilometry showed significantly larger sway areas in the POS-group. In the audiological test battery, the significantly pathologic tests were discrimination of interrupted speech and evoked cortical responses to frequency glides (CRA-delta-f). The saccade test disclosed abnormal findings in 5/9 workers. In the smooth pursuit test, abnormality was found at some test frequencies using pseudorandomized stimulus. The VOR-suppression test was significantly abnormal at all test frequencies. The test battery used strongly indicates CNS lesions due to industrial solvents.

Adult↗

PubMedDate not supplied

Posturography findings in workers exposed to industrial solvents.

Postural control was investigated by static posturography in 18 workers exposed to industrial solvents, 9 patients with psycho-organic syndrome due to industrial solvent exposure, and 52 controls. Both groups of exposed subjects showed larger sway areas with eyes open as well as closed, compared with the controls. No differences were found in the Romberg quotient (the relationship between sway areas with eyes closed/open). The correlation between static posturography and the otoneurological test battery was positive for the visual suppression test in the styrene group. In the industrial solvent group no significant correlations were found. The visual suppression test and some auditory tests were pathological in the exposed groups. The otoneurological test battery--especially the visual suppression test and static posturography--seems to contribute in the assessment of solvent related CNS lesions.

Adult↗