Biomedical subjects

S P Diamond

Publications and source records attributed to S P Diamond.

16 recordsLinked to original sources

PubMed1992

EEG coherence as a predictor of spike propagation.

The relationship between resting EEG coherence and the propagation of spike activity from an experimental cortical focus was investigated in 6 rats. EEG was collected from an array of 6 epicortical electrodes positioned over the posterior hind limb sensorimotor (HL) and frontal (Fr1, Fr2) cortices. Coherence decreased non-linearly for all frequency bands with increasing interelectrode distance. The greatest decrement in coherence occurred in the region corresponding to the junction between hind limb (HL) and frontal (Fr1) cortices. The decrease in coherence was greatest for the highest frequency band for all interelectrode pairs. A spike focus was induced in all 6 animals following the application of bicuculline at the most posterior electrode of the cortical array. In 5 of the 6 animals spike propagation was delayed at the junction of HL and Fr1 cortices, where the greatest decrease in coherence was observed. In one animal spike activity never advanced across this region. These results demonstrate an association between intracortical coherence and the spatial propagation of spike activity. The function of short and long cortico-cortical pathways as mediators of both EEG coherence and cortical spike propagation are discussed.

Action Potentials↗

PubMed1990

Allergic contact dermatitis to nasturtium.

In conclusion, oil of mustard, contained in many plants and recognized mainly as a skin irritant, is also capable of causing an allergic contact dermatitis. Nasturtium, which contains mustard oil, should be added to the list of plants capable of causing this dermatitis and must be suspected in any patient who handles plants and presents with hand dermatitis.

Adrenal Cortex Hormones↗

PubMed1986

Nitrous oxide: clinical and electrophysiologic investigation of neurologic complications.

Prolonged exposure to nitrous oxide produces a recognized neurologic syndrome. We report clinical and electrophysiologic studies of nervous system involvement in a 25-year-old student who abused nitrous oxide. He developed signs of a sensorimotor polyneuropathy and of myelopathy. Routine blood studies, CSF examination, and myelogram were normal. Clinical electrophysiologic studies were performed serially. Nerve conduction studies demonstrated reduced amplitude and slowed sensory potentials, and mildly prolonged late responses. Sensory evoked potentials revealed prolonged latency of scalp-evoked potentials from tibial nerve stimulation with normal median nerve values. The foveal visual evoked potential was delayed in the right eye, with normal visual acuity, funduscopic examination, and spatial contrast sensitivity. Repeat electrophysiologic studies demonstrated improvement. Nitrous oxide produces multifocal reversible dysfunction within the nervous system similar to that described in patients with vitamin B12 deficiency.

Adult↗

PubMed1983

Visual exploration of non-verbal material by dyslexic children.

Eye movements were recorded from fifteen matched pairs of dyslexic children and normal readers (boys) during a field of search task. The task required the subjects to locate a target that matched a central standard. The relative familiarity of elements in the array, the array density, and the tilt of the elements with respect to the central standard were varied. Results showed that the dyslexic children took significantly longer than controls to find the matching target when the elements in the array were tilted, and somewhat (though not significantly) longer when the material was unfamiliar. Within the dyslexic group, search durations were related to graphomotor skills and to WRAT reading level. Two explanations for the results were proposed: (1) dyslexic children may have a specific difficulty in processing directionally confusing information; (2) some dyslexic children may have a pervasive difficulty in motoric gating of visual information.

Adolescent↗

PubMed1979

The interaction of 2,6,8-triaminopurine with poly(uridylic acid).

Equilibrium dialysis measurements have shown that poly(uridylic acid) binds 2,6,8-triaminopurine in a strongly cooperative manner to form a stable 2 : 1 complex at pH 7.8, 0.15 M Na+. The thermal dissociation of the complex has been characterized by ultraviolet absorbance versus temperature profiles. From the variation of Tm with the concentration of uncomplexed triaminopurine at this temperature, the partial molar enthalpy and entropy of formation of the complex have been calculated as --87 (+/- 2) kJ/mol of triaminopurine and --236 (+/- 7) J/mol of triaminopurine per K, respectively. In terms of Tm, the complex is approximately 4 degrees C more stable than the corresponding 2 : 1 complex of poly(U) with 2-aminoadenine. This stabilization is attributed to the existence of an additional hydrogen-bonding interaction, in the poly(U)-triaminopurine complex, between the 8-amino group of 2,6,8-triaminopurine and O(2) of the uracil moiety which is base paired with it in Hoogsteen fashion.

Adenine↗

PubMed1978

The complexing of guanine nucleosides by poly(inosinic acid).

Under conditions where it is single-stranded (pH 7.0, 0.05 M Na+), poly(inosinic acid) complexes guanosine and 2'-deoxyguanosine in a strongly cooperative process that ultimately results in gel formation. The binding isotherm for formation of the poly(I).deoxyguanosine complex at 3.5 degrees C shows that it contains approximately one molecule of deoxyguanosine bound per IMP residue of the poly(I). This is compatible with the complex having a structure similar to that of the four-stranded secondary structure of poly(I) in which two of the poly(I) strands are replaced by helical arrays of deoxyguanosine molecules. The complex is laevorotatory at wavelengths longer than 300 nm. Optical rotation and ultraviolet absorbance versus temperature profiles show that on thermal dissociation the complex undergoes a co-operative helix-coil transition with Tm in the range 10--20 degrees C.

Deoxyguanosine↗

PubMed1976

The measurement of spatial contrast sensitivity in cases of blurred vision associated with cerebral lesions.

Thirty-five patients with known cerebral lesions complained of recently acquired blurred vision. None of them had evident oculomotor or pupillary abnormalities, and each had intact central fields and normal visual acuity by conventional standards. Examination of spatial contrast sensitivity was carried out with sinusoidal grating patterns, by determining the minimum contrast between alternate light and dark bars required to distinguish the pattern from a homogeneous field. This was done at each of several spatial frequencies which were established by varying the width of the bars and hence the coarseness of the pattern. The contrast sensitivities were plotted as "visuograms" which, by analogy to audiograms, record the sensitivities in comparison to normal standards. Of the 35 patients, most showed significant losses, amounting to greater than 50 per cent elevation of contrast thresholds. Eighteen showed high frequency losses; 11 had uniform reductions over the entire visible spatial frequency range and 6 had selective frequency losses in the intermediate frequency ranges. These defects in spatial contrast sensitivity, which were not predictable from standard acuity scores, indicate that the visual symptoms in our patients may have been caused by damage to frequency-selective neural elements in the central visual systems. The method may be used to advantage in clinical investigations as well as in physiological investigations of the functional pathways subserving central vision.

Adolescent↗

PubMed1973