Search PubMed⌕ Search

Biomedical subjects

S M Rao

Publications and source records attributed to S M Rao.

At least 55 records · Page 3Linked to original sources
PubMed1995

The relationship between seizure subtype and interictal personality. Results from the Vietnam Head Injury Study.

A wide variety of interictal personality traits has been associated with complex partial (CP) epilepsy. However, the specificity of these behavioural changes to CP epilepsy has been questioned in several controlled studies. To address this issue, we examined personality and behavioural characteristics in 467 Vietnam veterans 15 years post penetrating head injury. Of this sample, 238 (51%) had developed seizure disorders which were classified as follows: 39 simple partial (SP), 59 CP, 76 partial with secondary generalization (PG), and 64 generalized (G). Seizure patients were compared with two demographically matched control groups: 229 penetrating head-injured Veterans without seizures (PHI-C) and 84 uninjured veterans (UC). Dependent measures included self-report and examiner rating scales, and history of psychiatric treatment. Pre-injury intelligence, brain volume loss (CT scan), seizure frequency and duration of epilepsy served as covariates. We found statistically significant increases in interictal psychopathology in the CP, PG and G groups when compared with the two control groups (PHI-C and UC). No group differences were observed across seizure subtypes. These results suggest that interictal personality and behavioural abnormalities are not specific to individuals with CP seizures. Furthermore, the increased psychopathology in seizure groups when compared with the PHI-C group suggests that personality changes cannot be accounted for by structural brain damage alone.

Adult↗
PubMed1995

Neuropsychology of multiple sclerosis.

Neuropsychological investigations have demonstrated that cognitive disorders are common (45-65%) in patients with multiple sclerosis. This review summarizes our current understanding of the nature and etiology of these disorders. Specifically, neuropsychological deficits regularly occur on measures of recent memory, attention, information-processing speed, executive functions, and visuospatial perception. In contrast, general intelligence, language, and certain aspects of memory (short-term capacity and implicit) are preserved. The degree and pattern of cognitive dysfunction is highly correlated with the amount and location of white-matter disease within the cerebral hemispheres. Natural history studies indicate that changes in cognitive test performance are correlated with increasing lesion load on magnetic resonance imaging. The development of brief cognitive-testing instruments for clinical screening and measuring treatment effects in clinical trials is underway. A clear weakness in the literature is the dearth of studies evaluating potential treatments for cognitive disorders.

Brain↗
PubMed1995

Somatotopic mapping of the human primary motor cortex with functional magnetic resonance imaging.

We applied functional magnetic resonance imaging (FMRI) to map the somatotopic organization of the primary motor cortex using voluntary movements of the hand, arm, and foot. Eight right-handed healthy subjects performed self-paced, repetitive, flexion/extension movements of the limbs while undergoing echo-planar imaging. Four subjects performed movements of the right fingers and toes, while the remaining subjects performed movements of the right fingers and elbow joint. There was statistically significant functional activity in the left primary motor cortex in all subjects. The pattern of functional activity followed a topographic representation: finger movements resulted in signal intensity changes over the convexity of the left motor cortex, whereas toe movements produced changes either at the interhemispheric fissure or on the dorsolateral surface adjacent to the interhemispheric fissure. Elbow movements overlapped the more medial signal intensity changes observed with finger movements. Functionally active regions were confined to the cortical ribbon and followed the gyral anatomy closely. These findings indicate that FMRI is capable of generating somatotopic maps of the primary motor cortex in individual subjects.

Adult↗
PubMed1994

Functional magnetic resonance imaging of human auditory cortex.

Magnetic resonance imaging methods recently demonstrated regional cerebral signal changes in response to limb movement and visual stimulation, attributed to blood flow enhancement. We studied 5 normal subjects scanned while listening to auditory stimuli including nonspeech noise, meaningless speech sounds, single words, and narrative text. Imaged regions included the lateral aspects of both hemispheres. Signal changes in the superior temporal gyrus and superior temporal sulcus were observed bilaterally in all subjects. Speech stimuli were associated with significantly more widespread signal changes than was the noise stimulus, while no consistent differences were observed between responses to different speech stimuli. Considerable intersubject variability in the topography of signal changes was observed. These observations confirm the utility of magnetic resonance imaging in the study of human brain structure-function relationships and emphasize the role of the superior temporal gyrus in perception of acoustic-phonetic features of speech, rather than processing of semantic features.

Acoustic Stimulation↗
PubMed1994

Lymphoepithelial cyst of the pancreas with sebaceous differentiation.

Lymphoepithelial cysts of the pancreas are rare cystic lesions that histologically resemble branchial cleft cysts. In this article, we report a case of lymphoepithelial cyst with sebaceous differentiation. Lymphoepithelial cysts may present clinically or may be incidental findings, and they should be considered in the differential diagnosis of cystic lesions of the pancreas. The histogenesis of lymphoepithelial cyst is briefly discussed.

Cell Differentiation↗
PubMed1994

Effects of stimulus rate on signal response during functional magnetic resonance imaging of auditory cortex.

Functional magnetic resonance imaging (FMRI) detects focal MRI signal changes in brain tissue that are believed to result from changes in neuronal activity. We describe the dependence of this response in auditory cortex on the rate of presentation of simple speech stimuli. Speech syllables were presented to five normal subjects at rates ranging from 0.17 to 2.5 Hz, while the subjects performed a phoneme discrimination task. Regions studied with FMRI during this task included the lateral aspect of both temporal lobes. All subjects showed bilateral superior temporal lobe MRI signal increases that were coincident with stimulus presentation and performance of the task. The magnitude of this response increased in a monotonic, non-linear manner with increasing stimulus rate. This rate-response relationship was nearly identical in right and left hemispheres. The relationship may reflect metabolic activity integrated over time and subject to non-linear characteristics of neuronal recovery or blood flow regulation. The dependence of response magnitude on stimulation rate supports the hypothesis that the FMRI phenomenon indirectly reflects neuronal metabolic activity. The measures provided here should assist in the design of optimal activation strategies for the human auditory cortex.

Adult↗
PubMed1994

Relationship between frontal lobe lesions and Wisconsin Card Sorting Test performance in patients with multiple sclerosis.

Conceptual reasoning deficits are common in patients with multiple sclerosis (MS) and are typically associated with focal lesions involving the frontal lobes. In this study, we predicted that MS patients with frontal white matter lesions (MS-F) would be more impaired on a standard conceptual reasoning task (Wisconsin Card Sorting Test; WCST) than patients with minimal frontal lesions (MS-NF), even if the total cerebral lesion area (TLA), measured from MRI, was equivalent across groups. We subdivided 43 definite MS patients into three groups based on MRI findings: seven in the MS-F group (mean TLA = 41.4 cm2) and seven in the MS-NF group (mean TLA = 50.0 cm2); 29 MS patients served as a low lesion burden control group (MS-C; mean TLA = 6.4 cm2). The groups did not differ with regard to demographic and illness characteristics. Although the three subgroups obtained comparable scores on a measure of global cognitive functioning (verbal intelligence), the MS-F group achieved significantly fewer categories and made more total errors on the WCST than did the MS-NF and MS-C groups. The MS-F group made significantly more perseverative responses than the MS-C group and nonsignificantly more than the MS-NF group. These results suggest that the pattern of cognitive decline in MS is a function of the location of demyelinating lesions within the cerebral hemispheric white matter. Finally, we supplement the group study results with a case report of an MS patient who was studied serially with MRI and cognitive testing.

Adult↗
PubMed1994

Functional magnetic resonance imaging of somatosensory stimulation.

Functional magnetic resonance imaging (FMRI) has detected changes in regional cerebral blood flow and volume in response to motor movements, visual stimuli, and auditory stimuli in each of their respective primary cortices. This experiment was conducted to determine whether signal changes in the somatosensory cortex secondary to tactile stimulation could be demonstrated. The palm of the right hand was periodically stimulated while the subject was undergoing echo-planar imaging with a 1.5-T magnetic resonance scanner equipped with local gradient and radio frequency coils. Sagittal and coronal images of 10- to 15-mm slice thickness were selected to include the postcentral gyrus and surrounding regions. Temporally correlated signal changes of 1% to 5% occurred in the peri-rolandic region in each of six subjects. The time course of signal changes was comparable to that found in other primary sensory and motor cortices. The results provide preliminary evidence of the sensitivity of FMRI to activation of the somatosensory cortex with tactile stimulation and support FMRI as a promising noninvasive technique for study of the functional organization and integrity of the cerebrum.

Adult↗
PubMed1993

cis-acting elements in the 5'-untranslated region of rat testis proenkephalin mRNA regulate translation of the precursor protein.

We found that a rat testis cDNA library contained two types of proenkephalin cDNA, corresponding to somatic and germ cell-specific transcripts. The somatic form is identical in primary sequence to previously characterized transcripts from rat brain and heart. The longer germ cell-specific cDNA contains a novel 5' terminus derived from the somatic intron A. We found that germ cell-specific transcripts translate in vitro with significantly lower efficiency than do somatic-type transcripts. Deletion analysis indicated that translational inefficiency is mediated primarily by the presence of four upstream AUG codons followed by short open reading frames within the leader sequence. Secondary structure in the form of a stem-and-loop upstream of the initiator codon for proenkephalin was found to have a slightly inhibitory effect on translation. These results, coupled with the very low abundance of the somatic transcript, provide a possible explanation for the low levels of opioid peptides found in adult rat testis in spite of the abundant quantity of germ cell-specific proenkephalin transcript.

Animals↗
PubMed1993

Functional magnetic resonance imaging of complex human movements.

Functional magnetic resonance imaging (FMRI) is a new, noninvasive imaging tool thought to measure changes related to regional cerebral blood flow (rCBF). Previous FMRI studies have demonstrated functional changes within the primary cerebral cortex in response to simple activation tasks, but it is unknown whether FMRI can also detect changes within the nonprimary cortex in response to complex mental activities. We therefore scanned six right-handed healthy subjects while they performed self-paced simple and complex finger movements with the right and left hands. Some subjects also performed the tasks at a fixed rate (2 Hz) or imagined performing the complex task. Functional changes occurred (1) in the contralateral primary motor cortex during simple, self-paced movements; (2) in the contralateral (and occasionally ipsilateral) primary motor cortex, the supplementary motor area (SMA), the premotor cortex of both hemispheres, and the contralateral somatosensory cortex during complex, self-paced movements; (3) with less intensity during paced movements, presumably due to the slower movement rates associated with the paced (relative to self-paced) condition; and (4) in the SMA and, to a lesser degree, the premotor cortex during imagined complex movements. These preliminary results are consistent with hierarchical models of voluntary motor control.

Adult↗
PubMed1992

Molecular cloning, sequence analysis and translation of proenkephalin mRNA from rat heart.

Proenkephalin mRNA is abundant in rat cardiac ventricles but surprisingly low levels of opioid peptides or precursor forms derived from proenkephalin are present in tissue extracts. Proenkephalin mRNA in rat heart was characterized at the molecular level with the use of cDNA sequencing, in vitro translation, and primer extension. Two positive proenkephalin cDNA clones were obtained by screening approx. 20,000 recombinant phages from a heart cDNA library. Sequence analysis of the cDNA clones indicated that the heart transcript was the same form as in rat brain, but differed from the germ cell-specific testis transcript that utilizes a different transcriptional start site. Heart proenkephalin cRNA translated efficiently, resulting in the synthesis of a 35 kDa protein that was immunoprecipitated by an antibody specific to the protein. The transcriptional initiation sites utilized in the heart were the same as in the brain, based on primer extension studies. These data suggest that the proenkephalin transcript found in abundance in rat heart is the same form as found in the brain, and differs from the testis-type transcript. We conclude that the scant level of proenkephalin-derived peptides in the heart is not due to an intrinsic inability of the proenkephalin transcript to translate.

Amino Acid Sequence↗
PubMed1992

Quantitative MR in the diagnosis of multiple sclerosis.

In patients with multiple sclerosis (MS), the apparently uninvolved cerebral white matter between demyelinated plaques may have biochemical abnormalities. To what degree the changes in the white matter contribute to symptomatology in MS is unknown. In 39 patients with multiple sclerosis, and in 39 age-matched nondiseased volunteers, T1 and T2 were calculated from spin-echo images in four regions of apparently uninvolved white matter. In three of four white matter areas, the average T1 and T2 were significantly longer in the patients than in the controls. The T1 correlated with the disability, measured by the Kurtzke Extended Disability Status Scale, although the correlation was marginally significant. The results suggest that in patients with MS, white matter disease that is not visualized in MR as distinct foci of abnormal signal intensity may contribute to disease burden and disability.

Brain↗
PubMed1992

Emotional changes with multiple sclerosis and Parkinson's disease.

Multiple sclerosis (MS) and Parkinson's disease (PD) are relatively common neurological disorders. Both disorders are chronic and progressive, produce varying degrees of physical disability, and result in characteristic neuropathological changes to a variety of subcortical brain structures. Patients with MS or PD also exhibit a higher prevalence of emotional disorders relative to other patient groups with comparable degrees of physical disability. The present review (a) examines specific methodological issues associated with research in this area, (b) describes the range and severity of emotional disorders in MS and PD, and (c) examines both endogenous and reactive explanations to account for the increased prevalence of emotional dysfunction in these two disorders. Suggestions for future research are offered, as well as implications for treatment.

Adult↗
PubMed1992

Viscosity and social cohesion in temporal lobe epilepsy.

Clinical case reports suggest that viscosity, the behavioural tendency to talk repetitively and circumstantially about a restricted range of topics, is common in patients with temporal lobe epilepsy (TLE). Such patients are also reported to exhibit heightened levels of social cohesion, the tendency to become interpersonally "clingy". This "sticky" interpersonal style may be particularly common in TLE patients with a left sided temporal lobe seizure focus. To test this hypothesis, self-report and observer rating scales were developed to assess both viscosity and social cohesion. Subjects consisted of patients with right, left, or bilateral temporal lobe seizure foci, absence or primary generalised tonic-clonic seizures, psychiatric controls (panic disorder patients), and normal controls. Elevations on the viscosity scale were observed primarily in TLE patients with left or bilateral seizure foci. Viscosity scores also correlated with seizure duration and left handedness. No group differences were observed on the social cohesion scale. These findings are consistent with the hypothesis that viscosity results from subtle interictal language disturbances, although other pathogenetic mechanisms are discussed.

Anomia↗
PubMed1991

Visual evoked potentials and visual acuity after transurethral resection of the prostate.

Changes in visual evoked potentials, visual acuity, blood ammonia levels and serum electrolytes (Na+ and K+) after transurethral resection of the prostate using glycine as an irrigating fluid performed under subarachnoid block were studied in 12 patients, in the pre-operative and immediate postoperative periods. Visual evoked potentials (p100 latency), recorded by shift of a checkerboard pattern, increased significantly from a pre-operative value of mean (SEM) 101.18 (1.63) msec in the right eye, and 102.5 (1.47) msec in the left eye to 108.91 (1.8) msec (p less than 0.01) and 108.08 (2.53) msec (p less than 0.01) respectively in the postoperative phase. There were no changes in visual acuity as assessed by a Snellen's chart, blood ammonia levels and serum electrolyte concentrations. The amount of glycine used intra-operatively for irrigation ranged from 3 to 31 litres.

Aged↗