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Biomedical subjects

N Kapur

Publications and source records attributed to N Kapur.

15 recordsLinked to original sources
PubMed1992

Focal retrograde amnesia following bilateral temporal lobe pathology. A neuropsychological and magnetic resonance study.

A patient who suffered a severe closed head injury was left with a dense retrograde amnesia for events which she had experienced prior to her injury, but she showed only mild, patchy anterograde memory impairment. Her retrograde amnesia included both public events and autobiographical material, and it extended back to her childhood. Previously learned skills such as playing a piano and driving a car were spared, even though she had no recollection at all of the original learning experience. A series of focused magnetic resonance scan images revealed major pathology in the anterior portion of both temporal lobes. No significant abnormality was found in the hippocampus, thalamus or other medial structures in the limbic-diencephalic system. Our findings indicate the independence of anterograde and retrograde memory mechanisms, and point to structures and pathways in the anterior temporal lobes as playing a critical role in memory for past events.

Adult↗
PubMed1991

Studies on the mode of action of tolnaftate in Microsporum gypseum.

Studies were performed on the mode of action of tolnaftate and resistance to this drug in Microsporum gypseum. Cells grown in the presence of tolnaftate (at the IC 50) showed a reduced content of total phospholipids and sterols whereas there was an increase in total RNA content. Incubation of cells with tolnaftate (at 10 x MIC), followed by addition of different macromolecule precursors revealed inhibition of the biosynthesis of all macromolecules except for RNA. The activity of membrane-bound enzymes did not change on treatment with tolnaftate (10 x MIC) whereas an increase in the leakage of intracellular 32P was observed. The content of total phospholipids was higher in tolnaftate-resistant cells, whereas the content of total sterols, DNA, RNA and protein was comparable to that of susceptible cultures. Activity of phosphodiesterase decreased and 5'-nucleotidase increased in tolnaftate-resistant cells. Our results suggest that the antifungal activity of tolnaftate is due to differential action on various targets site(s) which are modified in strains resistant to the drug.

DNA, Fungal↗
PubMed1991

Amnesia in relation to fugue states--distinguishing a neurological from a psychogenic basis.

A case of transient amnesia is described in which a patient reported memory loss for five days, during which he had wandered extensively. Analysis showed that he did not have selective amnesia for the public events which had occurred during the five days for which he professed memory loss. This finding was incompatible with our case having a neurologically based global memory disorder during the fugue state. These findings offer support for a distinction between personal and public episodic memory.

Adult↗
PubMed1990

The role of diencephalic pathology in human memory disorder. Evidence from a penetrating paranasal brain injury.

A patient (B.J.) is reported who developed severe memory impairment following a penetrating brain injury caused by a snooker cue which entered through his left nostril into the basal regions of the brain. Initially, his memory disorder had the clinical features of a dense amnesic syndrome, with both anterograde and retrograde amnesia, but B.J. subsequently showed significant recovery of memory function. Formal memory testing was carried out 21 months after injury. This demonstrated marked verbal memory impairment, as severe as that seen in patients with the amnesic syndrome. On nonverbal memory tests, his impairment was relatively mild and patchy. His retrograde amnesia had regressed mainly to affect a 6 month period before the injury. On other cognitive tasks, he performed at an average or above average level, and there was no neuropsychological evidence of frontal lobe dysfunction. Neuroradiological investigations at various stages after his injury failed to demonstrate a lesion in any of the thalamic nuclei. Magnetic resonance imaging showed a lesion in the hypothalamus in the region of the mamillary bodies. Our study demonstrates that marked, relatively focal, memory disorder after diencephalic injury can occur without direct pathology to the body of the thalamus. It also indicates that structures in or adjacent to the hypothalamus, such as the mamillary bodies, may play a more important role in human memory functioning than has hitherto been considered.

Adult↗
PubMed1989

Focal retrograde amnesia: a long term clinical and neuropsychological follow-up.

A patient (E.D.) who had displayed a selective retrograde amnesia in association with transient amnesic episodes (Kapur et al., 1986) was reexamined five years after initial assessment. At the clinical level, his transient amnesic attacks continued, but some of these had clear epileptic features. In addition, EEG investigation indicated temporal lobe abnormality, more prominent in the left temporal region, and supported a clinical diagnosis of temporal lobe epilepsy. Both CT scanning and magnetic resonance imaging were unable to detect the presence of any structural lesion. At the neuropsychological level, there was no evidence of dementia in the form of generalized cognitive dysfunction nor significant deterioration in cognitive functioning since the earlier assessment. Our patient continued to show marked memory loss for public events over the past 20-30 years, in the context of normal or near normal performance on most tests of anterograde memory functioning. While memory for famous scenes and famous faces was markedly impaired, our patient's memory for famous cars was within normal limits and his memory for autobiographical events showed only patchy impairment. Although E.D. performed at an average or above average level on most standard tests of anterograde memory functioning, our patient did show evidence of significant memory loss for public events which had occurred over the past ten years (i.e. since the onset of his illness). The possibility is raised that E.D.'s memory disorder may represent a form of disconnection syndrome.

Aged↗
PubMed1989

Genetic analysis of temperature-sensitive lethal mutants of Salmonella typhimurium.

We have isolated 440 mutants of Salmonella typhimurium that show temperature-sensitive growth on complex medium at 44 degrees. Approximately 16% of the mutations in these strains have been mapped to 17 chromosomal locations; two of these chromosomal locations seem to include several essential genes. Genetic analysis of the mutations suggests that the collection saturates the genes readily mutable to a ts lethal phenotype in S. typhimurium. Physiological characteristics of the ts lethal mutants were tested: 6% of the mutants can grow at high temperature under anaerobic conditions, 17% can grow when the medium includes 0.5 M KCl, and 9% of the mutants die after a 2-hr incubation at the nonpermissive temperature. Most ts lethal mutations in this collection probably affect genes required for growth at all temperatures (not merely during high temperature growth) since Tn10 insertions that cause a temperature-sensitive lethal phenotype are rare.

Chromosome Mapping↗
PubMed1989

How to write your first book.

Many doctors have, at some time or other, the idea of writing a book. This article considers some of the practical problems involved, including dealing with publishers, the formulation of a book proposal, writing individual chapters and desirable features of computer software.

Books↗
PubMed1985

Double dissociation between perseveration in memory and problem solving tasks.

This study reports a double dissociation between perseverative responses on a short-term verbal memory test and a card sorting task, as shown by two patients with cerebral tumours. The two patients were matched for number of correct responses on the memory task. The first patient, with a craniopharyngioma and associated dilatation of the third ventricle and lateral ventricles, showed perseveration on the short-term memory task but not on the card sorting task. The second patient, with a subfrontal tumour involving the anterior corpus callosum, perseverated on the card sorting task but not on the short-term memory task. The presence of this double dissociation demonstrates the functional specificity of perseveration in certain memory and problem solving contexts and suggests that distinct subcortical/frontal mechanisms may underly specific types of perseveration.

Amnesia↗
PubMed1978

Recognition reading in paralexia.

Reading aloud and recognition reading were examined in a paralexic patient. Certainty ratings made by the patient during oral reading indicated that he was usually unaware of paralexic errors which he made. In an auditory recognition reading task for words previously misread, the patient still performed poorly, often chosing his paralexic response as the correct alternative. Possible mechanisms underlying paralexia are discussed in the light of these findings.

Adult↗
PubMed1975

Retraining of dysgraphia - a case study.

A patient with dysgraphia resulting from a gunshot wound of the brain is presented. Analysis of the functional status of component operations involved in the skill of writing is described. A retraining scheme based on this analysis brought about a significant improvement in the patient's handwriting.

Adult↗