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Biomedical subjects

J M Swanson

Publications and source records attributed to J M Swanson.

11 recordsLinked to original sources
PubMed1979

Erythrosin B inhibition of neurotransmitter accumulation by rat brain homogenate.

A mixture of seven food dyes inhibited the accumulation of eight neurotransmitters or neurotransmitter precursors by rat brain homogenate. At a low concentration (1 microgram per milliliter), erythrosin B (FD&C red 3) was the only dye that inhibited dopamine accumulation. Erythrosin also was effective in decreasing the accumulation of all the other transmitter substances, suggesting that the inhibition is nonspecific and probably secondary to general membrane alteration.

Animals↗
PubMed1979

Liquid-chromatographic analysis for methylphenidate (Ritalin) in serum.

We describe a "high performance" liquid chromatographic method for quantitating methylphenidate in serum. The internal standard, 4,5-diphenylimidazole, and serum or plasma sample are extracted in chloroform, evaporated, and redissolved in 20 mmol/L potassium phosphate (pH 3.5)/high-purity acetonitrile, 80/20 by vol. A centrifuged aliquot is chromatographed on mu-Bondapak C-18 with the phosphate/acetonitrile solvent as mobile phase, a flow rate of 1.6 mL/min, and a column temperature of 40 degrees C. Absorbances are read at 192 nm. This method reliably measures concentrations greater than 20 micrograms/L and has analytical recoveries of 74%.

Child↗
PubMed1979

A liquid-chromatographic analysis for ritalinic acid [alpha-phenyl-alpha-(2-piperidyl) acetic acid] in serum.

We describe a "high-performance" liquid-chromatographic assay for measuring ritalinic acid in 300 muL of serum. The procedure includes adsorption of ritalinic acid and internal standard (alpha,alpha-dimethyl-beta-emthylsuccinimide) from serum onto charcoal, from which both compounds are eluted with methanol. The methanol extract is evaporated, the residue dissolved in a 93/7 (by volume) mixture of potassium phosphate buffer (20 mmol/L, pH 3.8) and acetonitrile, and an aliquot of this solution is chromatographed. We used a mu-Bondapak C-18 column with the above-mentioned buffer system as mobile phase, a flow rate of 2.0 mL/min, and a column temperature of 40 degrees C. Ritalinic acid and internal standard are detected by their absorbance at 192 nm and quantitated by measuring peak heights. The procedure allows for the reliable analysis for ritalinic acid in serum at concentrations greater than 50 microgram/L. Analytical recoveries were greater than 73% and the method affords good day-to-day precision (CV, less than 12%).

Chromatography, High Pressure Liquid↗
PubMed1978

Differences in reaction times and average evoked potentials as a function of direct and indirect neural pathways.

Average evoked potentials and manula response latencies were collected during a simple detection task in which brief visual stimuli were presented to the left and right visual fields. Latencies generated by the ipsilateral stimulus-hand combinations were shorter than contralateral combinations only under certain conditions, impugning the hypothesis that the reaction time difference reflects interhemispheric transfer time. Certain evoked potential components recorded contralateral to the stimulus occurred earlier than their ipsilateral counterparts, but whether this difference can be interpreted as representing interhemispheric transfer time is also questioned.

Adult↗
PubMed1978

Reaction times and evoked potentials as indicators of hemispheric differences for laterally presented name and physical matches.

Letter pairs, which could be name matches, physical matches, or mismatches, were presented at fixation or 2.5 degrees left or right of fixation. During different experimental sessions, the locations and the types of matches were fixed (and therefore known in advance by the subject) or were randomized. Right visual field superiority in reaction time occurred for name matches only when location was randomized, and then the extent of the superiority depended on whether the types of match called for were predictable. Evoked potentials to the letter pairs during this task revealed hemispheric and neural pathway differences that were independent of expectancy condition. Right hemisphere responses were larger than left. For some components, amplitudes were smaller and latencies were shorter for direct than for indirect projection of stimuli to each cerebral hemisphere. Indirect-direct differences in P300 amplitude varied for each cerebral hemisphere according to whether a physical or name match occurred. The P130 and N170 components manifested hemispheric differences that depended on whether the two letters of a pair were in the same or different cases.

Adult↗
PubMed1977

Hyperactive children's underuse of learning time: correction by stimulant treatment.

This study investigates the effects of methylphenidate (Ritalin) on hyperactive children's performance on a paired-associate learning task under 3 presentation rates (4, 8, and 12 sec per item). The total-time hypothesis states that a fixed amount of time is necessary to learn a fixed amount of material, regardless of the number of trials into which that time is divided. In a double-blind crossover design, the total-time hypothesis was supported by performance in a drug state, but not by performance in a placebo state, where slower presentation rates were not utilized effectively. These results are discussed in terms of inattention in the placebo state and improved attention and use of learning time in the drug state. The methodology presented is suggested as a means of assessing attentional deficits as well as providing a diagnostic procedure for objectively evaluating the appropriateness of stimulant treatment for children referred for symptoms of hyperactivity.

Adolescent↗
PubMed1976

Stimulant-related state-dependent learning in hyperactive children.

Hyperactive and nonhyperactive children performed a learning task in two states, while being treated with stimulant medication (methylphenidate) and while taking a placebo, and were tested for retention of each class of learned material in both states. Symmetrical state-dependent learning was demonstrated in the hyperactive group but not in the nonhyperactive group. The state-dependent effect was contingent on the presence of drug-induced facilitation during initial learning. This is apparently the first report on record of state-dependent learning with a drug agent that facilitates rather than impairs performance of human subjects.

Child↗