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Biomedical subjects

R E Hicks

Publications and source records attributed to R E Hicks.

At least 37 records · Page 2Linked to original sources
PubMed1986

A neuropathic substrate for stimulant drug effects in hyperactive children.

Behavioral, physiological, and cognitive data are presented from a sample of 55 hyperactive children undergoing methylphenidate treatment. Consistent with previous research, considerable variability exists on these measures in this clinical population with little evidence for a consistent profile on any of these dimensions. A theoretical discussion is offered reflecting these findings with reference to a proposed pathophysiologic basis for the disorder. The proposed model postulates a particular emphasis on the functional responsibilities of the frontal-striatal system. A neural substrate for the abnormal oscillations that characterize hyperactive children, the correction of which is germane to therapeutic stimulant effects, is presented in terms of the regulatory functions of the frontal lobe.

Antisocial Personality Disorder↗
PubMed1986

Methylphenidate and exercise: additive effects on motor performance, variable effects on the neuroendocrine response.

It has been suggested that the effects of intensive environmental stressors and of psychostimulant drugs may be interchangeable. A specific test of this hypothesis was undertaken in a double-blind, placebo controlled, cross-over study of the stimulant drug, methylphenidate (MPH), and of intense exercise, alone and in combination. On measures of motor performance the effects of MPH and of exercise were additive while on measures of neuroendocrine response the individual and interactive effects were variable. The effects of MPH and of intense exercise are probably mediated by mechanisms that overlap to a degree but are by no means identical.

Adolescent↗
PubMed1985

Separating the effects of lead and social factors on IQ.

Initial evaluations of 104 low-socioeconomic status black children screened by the local community health departments in North Carolina showed significant effects of lead in the range 6-59 micrograms/dl on IQ after controlling for concomitant social factors, such as socioeconomic status, home environment, and maternal IQ. The main concomitant variable was socioeconomic status, which was multicolinear with other social factors. Five years later, when all blood lead levels were 30 micrograms/dl or less, lead effects on IQ were no longer significant. The correlation between maternal and child IQ, which had been suppressed initially in children with higher lead levels, returned to expected levels when decreases in blood lead level occurred, while concomitant variables remained stable over the 5-year period.

Child↗
PubMed1985

Neuropharmacology of methylphenidate and a neural substrate for childhood hyperactivity.

What began as a simple chemical question about the clinical utility of MPH SL measurement has led our group across a broad expanse of research endeavors, from the problem of nonintercorrelated stimulant effects to a theory of hyperactivity as a dysregulatory disorder based on frontal-striatal dysfunction or dysmaturation. The transition has been from a traditional and fairly circumscribed question in psychopharmacology to a new interest in the neuropsychological approach to hyperactivity and its treatment. Biologic psychiatry and neuropsychology have developed as distinct disciplines well insulated from one another, but a degree of cross-fertilization is beginning to occur. Rather than thinking of childhood hyperactivity in terms of vague metapsychological concepts such as "attention" or "arousal," it will be perhaps more constructive to base a model for the disorder on the foundation of known elements of brain function. Perhaps the most interesting research areas to pursue will be neuropsychological and neurodiagnostic (for example, PET). The specific locus of disorders, such as the HKS and the specific mechanisms of drug action, may not be so elusive after all.

Antipsychotic Agents↗
PubMed1984

Influence of sex of antecedent siblings on the human sex ratio.

Analysis of family configurations in a population of 649,366 American secondary school students confirmed that sex of later-born children is influenced by the sex of antecedent siblings. Antecedent brothers decrease the probability of subsequent male births. This observation, a confirmation of an earlier report in a substantially smaller sample, is consistent with an immunologic influence on human sex determination.

Child↗
PubMed1984

The persistence of stimulant effects in chronically treated children: further evidence of an inverse relationship between drug effects and placebo levels of response.

Seventeen hyperactive children who had been treated for 1-5 years with methylphenidate were studied in a double-blind placebo-controlled crossover study. Specific measures of stimulant response were found to be inversely related to the subject's level of response in the placebo condition. This inverse relationship was previously found to characterize the clinical effects of hyperactive children in an acute-treatment paradigm. It is equally valid in a chronic-treatment study. "State-contingency" is not, therefore, simply a function of the "novelty" of initial drug treatment.

Adolescent↗
PubMed1984

Pathological left-handedness and familial sinistrality in relation to degree of mental retardation.

The relationship between personal and familial hand preference and mental retardation was examined. Six unimanual tasks were performed by 232 subjects within four mental retardation severity groups. Family handedness histories were obtained. Right hand preference varied inversely with severity of mental retardation. The handedness of mentally retarded groups at the different functional levels paralleled, but tended much more to the sinistral, than that of the corresponding parent groups. The parent-proband handedness correlations were largely insignificant, especially in lower functioning groups. The findings support both pathological left-handedness theory and an association between brain damage causing mental retardation and familial sinistrality.

Brain Damage, Chronic↗
PubMed1984

A developmental study of temporal duration judgments.

First, third, fifth, and seventh graders and college students (18 per grade) made four serial reproductions of each of three time intervals, 8, 13, and 32 sec. The results paralleled those of other studies using only adults since both the psychophysical function and the Weber fraction were typical, and magnitude of judgments was an increasing, negatively accelerated function of trials. None of these effects was a function of age nor were there any age effects in an analysis of variable errors. Analysis of first-degree sequential dependency of judgments (using lag correlations) revealed a slight negative recency which was also invariant with age of Ss.

Adult↗
PubMed1984

Clinical correlates of methylphenidate blood levels.

The clinical correlates of methylphenidate blood levels in hyper-active children and normal adults were examined in five studies. Although occasional correlations between blood levels and neuroendocrine response were noted within subjects along the pharmacokinetic time profile of the drug, no significant associations were found between blood levels and clinical response in behavioral measures or laboratory tests of attention or activity. It is unlikely that routine methylphenidate blood level determinations will become a part of the routine clinical management of hyperactive children.

Adult↗
PubMed1984

Cannabis, atropine, and temporal information processing.

In experiment 1, subjects judged time by duration production under no-counting instructions. The productions were made following intravenous injection of atropine sulfate or saline, and after smoking cigarettes with and without (-)-delta 9-tetrahydrocannabinol (THC). THC increased the subjective time rate (STR); i.e., the rate at which subjective time passes relative to clock time, whereas atropine had no effect on STR. Thus, reduction in central acetylcholine activity is not a sufficient explanation of THC's effect on STR. Experiment 2 replicated the THC effect on STR when subjects were counting subjective seconds. This result indicates that THC affects the experience of time as it is passing, and not solely the memory for duration experience after a time period.

Adult↗
PubMed1984

Tardive dyskinesia and other clinical consequences of neuroleptic treatment in children and adolescents.

Of 41 children, adolescents, and young adults who were withdrawn from chronic neuroleptic treatment, 18 developed tardive dyskinesia, withdrawal dyskinesia, nondyskinetic withdrawal symptoms, or transient behavior deterioration. Development of neuroleptic-related problems seemed to be associated with cumulative neuroleptic dose and possibly with the sex of the subject. Only 12 of the 41 subjects required resumption of neuroleptic treatment after a prolonged trial withdrawal period.

Adolescent↗
PubMed1983

An improved gas chromatographic method for measuring glucosamine and muramic acid concentrations.

A method of simultaneously measuring glucosamine and muramic acid concentrations in marsh grass litter was developed. Spartina alterniflora samples were preextracted with acetone to remove lipids containing amino sugars and then hydrolyzed in 6 N HCl (100 degrees C, 4.5 h). Amino sugars in the hydrolysates were isolated by ion-exchange chromatography, which gave good recoveries (greater than 90%) and reproducibility (CV less than 5%). Isolated amino sugars were converted to O-methyloxime acetates. beta-Phenylglucose and N-methylglucamine were added as internal standards. Sample derivatives were quantified by capillary column gas chromatography. OV-101 and SE-54 capillary columns completely separated glucosamine and muramic acid from other amino sugars. The detection limit of glucosamine and muramic acid during gas chromatographic analysis was below 30 pmol using splitless-mode injection (SE-54 column). Filamentous fungal and procaryotic biomasses may be estimated simultaneously by using glucosamine and muramic acid biomass conversion factors in conjunction with this method.

Animals↗
PubMed1983

Effects of response language and stimulus context upon judgments of visual and temporal extent.

College-student subjects judged duration (Experiment 1) or line length (Experiment 2) using conventional measurement units (sec and in.) and cross-modality matching. In each experiment, three stimulus contexts were created varying in average stimulus value. Judgmental contrast was observed in the cross-modality judgments, but not in the conventional-units judgments. It was inferred that the context effects were operating on response-translation processes.

Female↗