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Biomedical subjects

S Gilman

Publications and source records attributed to S Gilman.

At least 127 records · Page 7Linked to original sources
PubMed1988

Motor dysfunction in olivopontocerebellar atrophy is related to cerebral metabolic rate studied with positron emission tomography.

We compared the severity of motor dysfunction with local cerebral metabolic rates for glucose (lCMRGlc) and the degree of tissue atrophy in 30 patients with olivopontocerebellar atrophy (OPCA). We devised a scale to quantitate the degree of ataxia in the neurological examinations. lCMRGlc was measured with 18F-2-fluoro-2-deoxy-D-glucose and positron emission tomography (PET). Tissue atrophy was assessed by visual rating of computed tomographic scans. PET studies revealed marked hypometabolism in the cerebellar vermis, cerebellar hemispheres, and brainstem of OPCA patients compared with 30 control subjects. A significant correlation was found between severity of motor impairment and lCMRGlc within the cerebellar vermis, both cerebellar hemispheres, and the brainstem. A significant but weaker relationship was noted between the degree of tissue atrophy in these regions and clinical severity. Partial correlation analysis revealed that motor dysfunction in OPCA correlated more strongly with lCMRGlc than with the amount of tissue atrophy. These results suggest that the clinical manifestations of OPCA are more closely related to the metabolic state of the tissue than to the structural changes in the cerebellum.

Adult↗
PubMed1988

Thalamic, brainstem, and cerebellar glucose metabolism in the hemiplegic monkey.

Unilateral ablation of cerebral cortical areas 4 and 6 of Brodmann in the macaque monkey results in a contralateral hemiplegia that resolves partially with time. During the phase of dense hemiplegia, local cerebral metabolic rate for glucose (1CMRG1c) is decreased significantly in most of the thalamic nuclei ipsilateral to the ablation, and there are slight contralateral decreases. The lCMRGlc is reduced bilaterally in most of the brainstem nuclei and bilaterally in the deep cerebellar nuclei, but only in the contralateral cerebellar cortex. During the phase of partial motor recovery, lCMRGlc is incompletely restored in many of the thalamic nuclei ipsilateral to the ablation and completely restored in the contralateral nuclei. In the brainstem and deep cerebellar nuclei, poor to moderate recovery occurs bilaterally. Moderate recovery occurs in the contralateral cerebellar cortex. The findings demonstrate that a unilateral cerebral cortical lesion strongly affects lCMRGlc in the thalamus ipsilaterally and in the cerebellar cortex contralaterally, but in the brainstem bilaterally. Partial recovery of lCMRGlc accompanies the progressive motor recovery. The structures affected include those with direct, and also those with indirect, connections to the areas ablated.

Animals↗
PubMed1988

A microdrive positioning adapter for chronic single unit recording.

A new micropositioner design for use in chronic, transdural single unit recording studies is presented. The adapter is used to position an electrode microdrive assembly to any desired location within a surgically implanted recording chamber. The adapter uses a radial positioning technique that requires few moving parts. In comparison with the X-Y slide manipulator it replaces, it is more durable, it provides access to a larger brain area, and it attaches more securely. In addition, provision can be made to mount a second microdrive, permitting two electrodes to be manipulated independently.

Brain↗
PubMed1988

A relationship between metabolism in frontal lobes and cerebellum in normal subjects studied with PET.

Lesions of one cerebral hemisphere are associated with decreased glucose metabolism, oxygen metabolism, and blood flow in the contralateral cerebellar hemisphere. We used positron emission tomography to look for a functional relationship in cerebral metabolism between the cerebral cortex and the contralateral cerebellum in normal human subjects. Twenty-four normal subjects were scanned with [18F]fluoro-2-deoxy-D-glucose while in a resting state. Asymmetry in local CMRglu (LCMRglu) in the frontal cortex was strongly correlated with asymmetry in LCMRglu in the opposite direction in the cerebellar hemispheres (r = -0.60, p less than 0.001). Widespread subregions of the frontal cortex were found to contribute to this relationship. Considering these results together with previous studies demonstrating that frontal lesions are associated with decreased metabolism in the contralateral cerebellum, we conclude that the frontal cortex exerts a strong modulating influence on metabolism in the contralateral cerebellum in normal subjects, and that this influence may be asymmetrical.

Adolescent↗
PubMed1988

The role of anticoagulation in cavernous sinus thrombosis.

Prior to the antibiotic (AB) era, cavernous sinus thrombosis (CST) was almost uniformly fatal. AB therapy has significantly reduced mortality, but additional treatment with anticoagulants (AC) has remained controversial. We reviewed our experience with seven cases, as well as the literature since Lyons' 1941 introduction of AC treatment, to determine effectiveness, complications, and morbidity among survivors. We divided the cases into (1) those treated with AB alone, and (2) those treated with a combination of AB and AC. We found no conclusive evidence for reduction of mortality when AC was used in combination with AB. However, early AC therapy reduced morbidity (blindness, stroke, ophthalmoplegia, hypopituitarism, focal seizures, and vascular steal syndrome), whereas delayed or inadequate use provided no apparent benefit above AB therapy alone. Complications of AC therapy were rare; cerebral venous thrombosis occurred frequently, but in association with dural sinus thrombosis as a direct result of the disease. We conclude that AC therapy is indicated early in the treatment of CST to reduce morbidity among survivors.

Adolescent↗
PubMed1987

Cortical blindness: etiology, diagnosis, and prognosis.

We examined 15 patients with cortical blindness, reviewed the records of 10 others, and compared these 25 patients to those in previous studies of cortical blindness. Although cerebrovascular disease was the most common cause in our series, surgery, particularly cardiac surgery, and cerebral angiography were also major causes. Only 3 patients denied their blindness, although 4 others were unaware of their visual loss. Electroencephalograms (EEGs) were performed during the period of blindness in 20 patients and all recordings were abnormal, with absent alpha rhythm. Visual evoked potentials recorded during blindness were abnormal in 15 of 19 patients, but did not correlate with the severity of visual loss or with outcome. Bioccipital lucencies were found in computed tomographic (CT) scans of 14 patients; none of the 14 regained good vision. Recovery of vision was poor in all 8 patients who had a spontaneous stroke, but fair or good in 11 of the other 17 patients. Prognosis was best in patients under the age of 40 years, in those without a history of hypertension or diabetes mellitus, and in those without associated cognitive, language, or memory impairments. We conclude that the prognosis in cortical blindness is poor when caused by stroke; EEGs are more useful than visual evoked potentials for diagnosis; and bioccipital abnormalities shown on CT scan are associated with a poor prognosis.

Blindness↗
PubMed1987

Experimental hemiplegia in the monkey: basal ganglia glucose activity during recovery.

Unilateral ablation of cerebral cortical areas 4 and 6 of Brodmann in the macaque monkey results in a dense contralateral hemiplegia that recovers partially with time. During the phase of dense hemiplegia, the local cerebral metabolic rate for glucose (lCMRGlc) is decreased significantly in the caudate nucleus, putamen, globus pallidus, subthalamic nucleus, substantia nigra, and red nucleus of the hemisphere ipsilateral to the lesion. In the present study, lCMRGlc in the basal ganglia was studied during the phase of partial recovery of motor activity. lCMRGlc was partially restored, and the greatest degree of restoration occurred in structures with direct connections to the cerebral cortex (caudate nucleus, putamen, subthalamic nucleus, substantia nigra, and red nucleus). Restoration was least in structures that do not receive direct connections from the cerebral cortex (the internal and external segments of the globus pallidus). The findings support the hypothesis that corticofugal activity accounts for a substantial degree of functional recovery.

Animals↗
PubMed1987

Positron emission tomography studies of cerebral glucose metabolism in chronic partial epilepsy.

Positron emission tomography (PET) performed with [18F]-2-fluoro-2-deoxy-D-glucose ([18F]FDG) was used to measure local cerebral metabolic rate for glucose (lCMRGlc) interictally in 31 patients with chronic partial epilepsy and 16 age-matched normal subjects. Hypometabolic zones were visualized in 25 patients (81%). Cortical lCMRGlc in hypometabolic zones was within 2 standard deviations of the mean for normal temporal cortex in all but 8 patients. However, in 24 patients asymmetry between the hypometabolic cortex and homologous contralateral cortex was more than 2 standard deviations above the mean cortical asymmetry for normals. There was good correlation between hypometabolic zones and electroencephalogram (EEG) foci in patients with unilateral well-defined EEG foci. Diffuse or shifting EEG abnormalities were often associated with normal PET scans. Of 28 patients who underwent magnetic resonance imaging, 10 showed focal temporal lobe abnormalities corresponding to focal hypometabolism. While the [18F]FDG PET scan cannot currently localize an epileptogenic zone independently, the absence of focal hypometabolism or its presence contralateral to a presumed EEG focus suggests the need for additional electrophysiological data.

Adolescent↗
PubMed1987

The effect of diazepam sedation on cerebral glucose metabolism in Alzheimer's disease as measured using positron emission tomography.

The effect of sedation induced by intravenous diazepam on cerebral glucose metabolic activity was examined with [18F]2-fluoro-2-deoxy-D-glucose (FDG) and positron emission tomography (PET) in five patients with probable Alzheimer's disease. Each subject was studied on 2 separate days: on one occasion at rest with eyes patched and ears open, and on the second when sedated with intravenous diazepam titrated to maintain stage II sleep by clinical and EEG criteria. Similar patterns of glucose uptake were observed in both the presence and the absence of sedation, but overall glucose utilization was depressed an average of 20% and was closely correlated with the amount of diazepam administered prior to the injection of FDG. The predominant temporoparietal hypometabolism and relative sparing of frontal metabolism observed in this disease are therefore not explained by differences in anxiety or activity level in this patient group. Utilization of diazepam sedation for PET study appears to be safe and may permit the study of patients otherwise unable to cooperate with FDG-PET procedures.

Aged↗
PubMed1986

Accumulation of gentamicin by Staphylococcus aureus: the role of the transmembrane electrical potential.

Accumulation of gentamicin by gentamicin-susceptible Staphylococcus aureus was examined by using the ionophorous antibiotic, valinomycin and the protontranslocating ATPase inhibitor N,N'-dicyclohexylcarbodiimide. The effects of these inhibitors on the transmembrane electrical potential (delta psi) were determined by measuring the equilibrium distribution of the tetraphenylphosphonium ion. The results indicate a direct correlation between delta psi and the extent of gentamicin uptake. However, under conditions where a significant delta psi existed across the plasma membrane, uptake of gentamicin was negligible. A threshold delta psi may thus be required to initiate gentamicin uptake. The proposed threshold delta psi appears to vary depending upon the external concentration of gentamicin.

Dicyclohexylcarbodiimide↗
PubMed1986

Uptake of gentamicin by Staphylococcus aureus possessing gentamicin-modifying enzymes: enhancement of uptake by puromycin and N,N'-dicyclohexylcarbodiimide.

Uptake of gentamicin by a gentamicin-resistant strain of Staphylococcus aureus possessing the aminoglycoside-modifying phosphotransferase enzyme APH(2") was enhanced by the protein synthesis inhibitor, puromycin or by the proton-translocating ATPase inhibitor, N,N'-dicylohexylcarbodiimide. Such enhanced uptake was inhibited by carbonyl cyanide p trifluoromethoxyphenylhydrazone or by valinomycin in the presence of potassium ions, suggesting a role for the transmembrane proton motive force in the process. The accumulated gentamicin did not cause loss of cell viability and exhibited altered chromatographic mobility compared with a control (unmodified) preparation of gentamicin.

Carbodiimides↗
PubMed1986

Acoustics of ear canal measurement of eardrum SPL in simulators.

The effect of standing waves on the ear canal measurement of eardrum sound pressure level (SPL) was determined by both calculation and measurement. Transmission line calculations of the standing wave were made using the dimensions of the ANSI S3.25-1979 ear simulator and three different eardrum impedances. Standing wave curves have been obtained for the standard eardrum impedance at 1-kHz intervals in the range of 1-8 kHz. The changes in standing wave position due to each of the three eardrum impedances and their effects on ear canal measurements of SPL were computed for each of the eardrum impedances. Ear canal SPL measurements conducted on simulators modified to correspond to the eardrum impedances used in the calculations were compared to the computed values. Differences between eardrum SPLs and those measured at different locations in the ear canal approached a standing wave ratio (SWR) of 10-12 dB as the position of the measuring probe approached the standing wave minimum at each frequency. These maximum differences compared favorably with data developed by other investigators from real ears. Differences due to the eardrum impedance were found to be significant only in the frequency region of 2-5 kHz. Calibration of probes in a standard or modified ANSI simulator at the same distance from the eardrum as in the real ear reduces the eardrum SPL measurement errors to those resulting from differences in eardrum impedance.

Acoustic Stimulation↗
PubMed1985

Basal ganglia glucose utilization after recent precentral ablation in the monkey.

In the macaque monkey, unilateral ablation of areas 4 and 6 of Brodmann results initially in a significant decrease of glucose metabolic activity in the ipsilateral caudate nucleus, putamen, globus pallidus, substantia nigra, and subthalamic nucleus. The contralateral hemisphere shows nonsignificant but consistently decreased activity in the caudate nucleus, putamen, and globus pallidus. Cerebral blood flow is decreased in the same pattern as the glucose metabolic activity. The change in glucose metabolic activity results from loss of neurons known to project directly from the cerebral cortex to the basal ganglia and also from indirect effects (diaschisis) in basal ganglia structures that do not receive connections from the cerebral cortex.

Animals↗
PubMed1985

The initial diagnosis of multiple sclerosis: clinical impact of magnetic resonance imaging.

Thirty patients in whom the initial diagnosis of multiple sclerosis was clinically entertained underwent cranial magnetic resonance imaging (MRI) in close temporal relationship to cranial x-ray computed tomography (CT), electrodiagnostic studies (visual evoked responses, brainstem auditory evoked responses, and somatosensory evoked responses), and cerebrospinal fluid analyses (oligoclonal bands, myelin basic protein, and IgG/albumin ratio). In 26 of the 30 patients, MRI demonstrated lesions consistent with multiple sclerosis that corresponded, at least in part, with the clinically expected neuroanatomical lesion distribution. Two of the 4 patients with normal MRI had normal electrodiagnostic studies and cerebrospinal fluid analyses, and the other 2 had a single abnormal or equivocal electrodiagnostic study. All 26 patients with abnormal MRI had at least one other abnormal laboratory test. CT revealed only the largest lesions, and in the patients with abnormal CT, MRI demonstrated even more lesions. MRI, in this limited series, proved to be a strong tool in the initial diagnosis of multiple sclerosis; it may prove to be the single best test, with a sensitivity exceeding that of electrodiagnostic studies and cerebrospinal fluid analysis.

Adolescent↗
PubMed1985

Probe-determined hearing-aid gain compared to functional and coupler gains.

In this investigation, hearing-aid gain as measured by a probe-earmold system was compared with gain determined from couplers (HA-2 coupler and ear simulator) and functional-gain measurements. Fifteen subjects with moderate sensorineural hearing loss were tested under aided and unaided conditions in the sound field. In order to determine the effect of the occluded ear canal length on these results, an optical method was developed using an operating microscope to measure the length of the individual subject's occluded ear canal. The results indicate that gain, as measured by the probe-earmold system, corrected for effects of occluded ear canal length, agrees closely with functional and ear-simulator gain through 4.0 kHz. At the frequencies of 5.0 and 6.0 kHz the probe-earmold system underestimated gain particularly when compared to measurements conducted with the ear simulator. Other comparisons were also made between gain measured in a HA-2 coupler and functional gain. The average differences between these measurements of gain agree with several previous investigations, but individual variation around the average difference was smaller than previously reported.

Adult↗