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Biomedical subjects

R C Gur

Publications and source records attributed to R C Gur.

At least 127 records · Page 7Linked to original sources
PubMed1989

Laterality and frontality of cerebral blood flow and metabolism in schizophrenia: relationship to symptom specificity.

Two of the hypotheses on regional brain dysfunction in schizophrenia that have received some support in studies of cerebral blood flow (CBF) and cerebral metabolic rate (CMR) are: (1) left hemispheric dysfunction and overactivation (laterality) and (2) frontal lobe deactivation or failure to activate (frontality). Although these hypotheses are not mutually exclusive, their relative importance for providing clues to neural underpinnings of symptoms specific to schizophrenia depends on their ability to predict variation in symptomatology. A potentially efficient strategy for such study is to start with physiological parameters of laterality and frontality, and correlate them with measures of severity of clinical symptoms specific to schizophrenia. For two schizophrenic samples reported earlier, we derived laterality (left-right hemispheres) and frontality (frontal-posterior regions) measures of CBF (Study 1) and CMR (Study 2), and correlated them with symptom specificity, defined as the difference in severity of symptoms specific and nonspecific to schizophrenia assessed by the Brief Psychiatric Rating Scale. In both studies, low but significant positive correlations were obtained between the specificity score and laterality for CBF in Study 1 and for CMR in Study 2, but not frontality. The results suggest that in these samples disturbances in lateralized activity are more prominently associated with the phenomenology of schizophrenia than disturbed frontal lobe activity.

Blood Glucose↗
PubMed1989

Memory deficits before and after temporal lobectomy: effect of laterality and age of onset.

Laterality and age of onset effects on semantic and figural memory were evaluated in 30 right-handed, left speech dominant (amobarbital test) patients with epilepsy before and after temporal lobectomy. There were no effects of focus on WAIS-R IQ scores. Early onset (less than or equal to 5 years) was associated with lower IQ and memory (WMS). Left Temporal (LT) patients showed worse semantic than figural memory preoperatively. Unexpectedly, early onset LT had marked postoperative decline of figural memory, whereas late onset LT patients showed the previously reported worsening of semantic memory. Right Temporal (RT) lobectomy patients, in contrast, improved in both semantic and figural memory regardless of age of onset. A "crowding effect" was suggested by the decline in figural memory following surgery in the early onset LT patients who remained stable or improved in semantic memory. Results indicate the need to incorporate age of onset of seizures into laterality models of memory function following unilateral temporal-hippocampal resection.

Adult↗
PubMed1989

Neuropsychological functioning in hemiparkinsonism.

A standardized neuropsychological battery including measures of intellectual cognitive, memory, attention-concentration, language, abstraction and mental flexibility, and sensory and motor functions was administered to 21 hemiparkinsonian patients (14 with right side and 7 with left side symptoms) and 17 controls matched for age and education. Patients were impaired in all functions except sensory. For motor functions, impairment was ipsilateral to the side of symptoms. For cognitive functions, right side symptoms were associated with verbal deficits whereas left side symptoms were associated with spatial deficits. Thus, a pattern of neuropsychological deficits consistent with the lateralization of motor symptoms may appear in the early stages of the disease.

Aged↗
PubMed1989

Selective expression of epitopes in multiphosphorylation repeats of the high and middle molecular weight neurofilament proteins in Alzheimer neurofibrillary tangles.

Here we review our recent "epitope analyses" of a few of the fibrous intraneuronal inclusions that are distinctive hallmarks of human neurodenerative conditions using a large library of monoclonal antibodies (MAbs) raised to normal neuronal cytoskeletal proteins. Analyses of the low (NF-L), middle (NF-M), and high (NF-M), and high (NF-H) molecular weight neurofilament (NF) proteins with greater than 500 MAbs enumerated epitopes shared by NF proteins and the intraneuronal neurofibrillary tangles (NFTs) that occur in the hippocampus and brainstem of Alzheimer's disease (AD) subjects. We identified the NF-H multi-phosphorylation repeat domain, i.e. repeats of Lys-Ser-Pro-X (where X is a small uncharged amino acid and Ser acts as a phosphate acceptor), as the determinant recognized by 15/16 MAbs that detected NFTs in sections of AD hippocampus, and 11 of the same 16 MAbs recognised NF-M multi-phosphorylation repeats. Further, the antigen binding regions of these MAbs were shown to comprise 13 separate classes based on their differential binding to 12 synthetic peptides derived from the NF-H and NF-M multi-phosphorylation sites, NF subunits of 10 diverse mammalian and sub-mammalian species, and normal human tau (tau). None of these anti-NF MAbs recognized NFTs in the brainstem of subjects with progressive supranuclear palsy (PSP), but NFTs in AD brainstem sections were reactive with five of these MAbs. Both PSP and AD brainstem NFTs were recognized by MAbs specific for tau and paired helical filament antigens.(ABSTRACT TRUNCATED AT 400 WORDS)

Alzheimer Disease↗
PubMed1988

Intraneuronal and extracellular neurofibrillary tangles exhibit mutually exclusive cytoskeletal antigens.

We examined the possibility that neurofibrillary tangles (NFTs) were heterogeneous in postmortem hippocampus from 22 patients with or without senile dementia of the Alzheimer type. Intraneuronal NFTs and extracellular, or "ghost," NFTs were recognized in situ by only one or the other of two monoclonal antibodies. The first monoclonal antibody, RMO87, stained only intraneuronal NFTs and is specific for phosphate-dependent epitopes in tau and the two high molecular weight neurofilament proteins. The second monoclonal antibody, 2.2B10, is specific for glial fibrillary acidic protein, and it stained only the RMO87-negative extracellular NFTs. Treatment of sections with alkaline phosphatase or sodium dodecyl sulfate, and the isolation of NFTs from hippocampus, did not expose RMO87 binding sites in extracellular NFTs. These observations indicate that neurofilament-like and tau-like epitopes can be lost from NFTs in situ, and that at least two populations of morphologically and immunochemically distinct NFTs exist.

Aged↗
PubMed1988

Validation of the lateral limits technique with a callosotomy patient.

The lateral limits technique, presented by Myers and Sperry, was evaluated with a right-handed callosotomy patient. Consistent with traditional tachistoscopic findings, right visual-field presentations were superior for naming of letters and pictures, as well as rhyming. Left field presentations were superior for line orientation. Determination of the testing fields was insufficiently precise when the blind spot was used as a reference. An eye asymmetry was observed in both location of lateral limits and visual acuity. However, complete lateralization of input without interhemispheric transfer was achieved when presentation was made to fields of equal acuity. We conclude that the technique is valid and valuable for prolonged unilateral stimulation, but that care must be taken in determining appropriate and comparable testing fields.

Adult↗
PubMed1988

Positron emission tomography and subcortical glucose metabolism in schizophrenia.

Our previous observation of a disturbed subcortical-to-cortical gradient of activity in schizophrenia was further elucidated by examining glucose metabolism in three subcortical structures: lenticular nucleus, caudate nucleus, and thalamus. Local cerebral glucose metabolism was determined with 18F-fluorodeoxyglucose using positron emission tomography (PET) in a sample of 20 unmedicated schizophrenics and 18 normal volunteers. Repeated evaluations were performed for 12 schizophrenics following treatment with psychotropic medications and for 11 controls. Unmedicated schizophrenics had lower cortical and caudate absolute metabolic rates. Subcortical-to-cortical ratios for the lenticular nucleus and thalamus were increased in schizophrenics compared with controls, reflecting a preservation of activity in these structures relative to decreased cortical metabolism. When patients were grouped by length of medication-free period before the initial study, there was a trend for patients who had been medication free less than 6 months to have higher subcortical ratios. However, there were no consistent effects of medication in the subsample of patients whose PET studies were repeated following treatment. The results demonstrate relative hypermetabolism in structures implicated in dopamine pathways. An understanding of the physiological significance of this finding awaits the combined measurement of metabolic activity and neuroreceptors in schizophrenics.

Adult↗
PubMed1988

Reliability of psychiatric scales in patients with dementia of the Alzheimer type.

For 43 patients with probable Alzheimer's disease who were screened for psychiatric disorders, the interrater reliability of the Global Deterioration Scale, BPRS, and Hamilton Rating Scale for Depression was high (intraclass correlation, 0.82-0.998). As expected, the prevalence of psychiatric symptoms in this sample was low. The score on the Zung Self-Rating Depression Scale correlated with the score on the rater-administered Hamilton depression scale in patients whose Alzheimer's disease was of low severity (N = 24) but not high severity (N = 19).

Aged↗
PubMed1987

Regional brain function in schizophrenia. I. A positron emission tomography study.

Local cerebral glucose metabolism was determined with 18-F-fluorodeoxyglucose using positron emission tomography in a sample of 12 unmedicated schizophrenics and 12 matched normal controls. The data were analyzed for absolute metabolic rates and region/whole-brain ratios using the cortical-subcortical, antero-posterior, and laterality dimensions. Lobar areas within cortical regions were also compared. Across groups, subcortical metabolism was higher than cortical metabolism. Patients had lower metabolism, cortically and subcortically, and a steeper subcortical to cortical gradient. Patients with higher scores on the Brief Psychiatric Rating Scale had higher absolute metabolism and higher left relative to right hemispheric metabolism than did patients with lesser severity. The results did not show "hypofrontality" in schizophrenia. These findings provide some support for cerebral dysfunction in schizophrenia and indicate the need for further examination of the cortical-subcortical dimension.

Brain↗
PubMed1987

Regional brain function in schizophrenia. II. Repeated evaluation with positron emission tomography.

Cerebral glucose metabolism was measured twice in a sample of 15 schizophrenics and eight controls, using positron emission tomography (PET) with 18-F-fluorodeoxyglucose. Studies were separated by three to 33 weeks. Patients were unmedicated during the first study, and the majority were receiving neuroleptics during the second study. There were no changes from study 1 to study 2 in average whole-brain metabolic rates, regional cortical activity, or the gradient of subcortical to cortical activity. The steeper subcortical to cortical gradient in schizophrenics, present in the first study, persisted in the second. Changes in this gradient were uncorrelated with changes in clinical status. Laterality (right-left) was stable across studies, and changes toward higher right relative to left hemispheric metabolism were correlated with clinical improvement. The results support the hypothesis of abnormal hemispheric activity in schizophrenia and implicate the subcortical-cortical gradient as another dimension that merits further exploration.

Adult↗
PubMed1987

Age and regional cerebral blood flow at rest and during cognitive activity.

The relationship between age and regional cerebral blood flow (rCBF) activation for cognitive tasks was investigated with the xenon Xe 133 inhalation technique. The sample consisted of 55 healthy subjects, ranging in age from 18 to 72 years, who were studied during rest and during the performance of verbal analogy and spatial orientation tasks. The dependent measures were indexes of gray-matter rCBF and average rCBF (gray and white matter) as well as the percentage of gray-matter tissue. Advanced age was associated with reduced flow, particularly pronounced in anterior regions. However, the extent and pattern of rCBF changes during cognition was unaffected by age. For the percentage of gray matter, there was a specific reduction in anterior regions of the left hemisphere. The findings suggest the utility of this research paradigm for investigating neural underpinnings of the effects of dementia on cognitive functioning, relative to the effects of normal aging.

Adolescent↗
PubMed1987

Contralateral and ipsilateral control of fingers following callosotomy.

The extent of ipsilateral control of the distal limbs is not documented. In this experiment visuo-motor control of fingers was investigated in two callosotomy patients. A substantial amount of ipsilateral control was evident, especially for the left hand fingers. Ipsilateral control of the right hand was evident for the thumb and index fingers, but not for the other fingers. Left hand fingers did not vary significantly in degree of ipsilateral control.

Adult↗
PubMed1987

The reproducibility of the 133Xe inhalation technique in resting studies: task order and sex related effects in healthy young adults.

Repeated applications of the 133Xe inhalation technique for measuring regional CBF (rCBF) were made during consecutive resting conditions in a sample of young healthy subjects. Subjects were grouped by order and by sex [nine had resting studies as the initial two measurements in a series of four measurement (six men, three women) and six had these measurements later (two men, four women)]. Three flow parameters were examined: f1 (fast flow) and IS (initial slope) for gray matter CBF, and CBF-15 for mean CBF (gray and white matter over 15-min integration), as well as w1, the percentage of tissue with fast clearing characteristics. With all groups combined, there were no significant differences between the two resting measurements, and high test-retest correlations were obtained for the flow parameters and w1. Analyses by order and sex grouping revealed, for the flow parameters, significant interactions of test-retest difference with order. Repeated initial studies showed reduced CBF from the first to second measurement, whereas resting studies performed later in the series showed no reduction. Interactions for test-retest difference with sex indicated that reduced CBF in serial measures was more pronounced for women. No hemispheric or regional specificity to account for these effects was found. Correction for PaCO2 differences did not alter these results. The results resemble data regarding habituation effects measured for other psychophysiologic measures, and suggest that reduction in CBF for consecutive measurements made on the same day may reflect habituation. This underscores the importance of controlling for effects of habituation on serial measurements of CBF and metabolism.

Administration, Intranasal↗
PubMed1987

The effect of anxiety on cortical cerebral blood flow and metabolism.

The relation between anxiety and cortical activity was compared in two samples of normal volunteers. One group was studied with the noninvasive xenon-133 inhalation technique for measuring cerebral blood flow (CBF) and the other with positron emission tomography (PET) using 18Flurodeoxyglucose (18FDG) for measuring cerebral metabolic rates (CMR) for glucose. The inhalation technique produced less anxiety than the PET procedure, and for low anxiety subjects, there was a linear increase in CBF with anxiety. For higher anxiety subjects, however, there was a linear decrease in CBF with increased anxiety. The PET group manifested a linear decrease in CMR with increased anxiety. The results indicate that anxiety can have systematic effects on cortical activity, and this should be taken into consideration when comparing data from different procedures. They also suggest a physiologic explanation of a fundamental behavioral law that stipulates a curvilinear, inverted-U relationship between anxiety and performance.

Adolescent↗
PubMed1987

Clinical significance of sleep apnea in the elderly.

The generally accepted polysomnographic criteria for diagnosis of sleep apnea is exceeded by elderly subjects with such frequency that the validity of its application to this age group has been questioned. We studied a group of elderly volunteers with nocturnal polysomnography and partitioned them into 2 groups based upon an apnea index of greater than or less than 5 per hour. The results of a protocol evaluating the presence of potential complications of sleep apnea including cardiac arrhythmias, systemic hypertension, cor pulmonale, daytime sleepiness, and cognitive impairment were compared for the 2 groups. No excess incidence of cardiovascular complications was found. Although an increase in daytime sleep tendency was shown for the group with more frequent apneas, no appreciable deficits in cognitive performance were demonstrated. Although apnea during sleep in the elderly may be associated with an increase in daytime sleepiness, it may not necessarily result in other physiologic or neuropsychologic consequences. Therapeutic intervention for these abnormalities should be carefully considered prior to the institution of treatment in light of these observations.

Aged↗