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Biomedical subjects

C L Carlson

Publications and source records attributed to C L Carlson.

29 records · Page 2Linked to original sources
PubMed1991

Effects of methylphenidate on the persistence of ADHD boys following failure experiences.

We examined the effects of methylphenidate on the task persistence of 21 boys with attention-deficit hyperactivity disorder (ADHD), after they had been exposed to both solvable and insolvable problems. The boys attempted to solve 10 different find-a-word puzzles on each of 4 days, involving the crossing of medication (placebo vs. 0.3 mg/kg) and prior task difficulty (solvable vs. insolvable). The results revealed that medication prevented the decrement in performance following the insolvable problems that was evident with the placebo days. In addition, on medication compared with placebo, the boys were more likely to make external attributions for failure and internal attributions for success. The results are discussed in terms of the impact of medication on ADHD boys' performance as mediated by cognitive-motivational state mechanisms.

Achievement↗
PubMed1991

A divided attention analysis of the effects of methylphenidate on the arithmetic performance of children with attention-deficit hyperactivity disorder.

Thirteen boys with Attention-Deficit Hyperactivity Disorder (ADHD) completed 80 arithmetic problems presented on a computer screen by typing a two digit answer. On half the trials, a foot press was required to terminate a computer-generated tone presented 2 seconds before, 1 second before, 1 second after, and 2 seconds after arithmetic problem presentation. Compared to placebo, methylphenidate resulted in significantly faster reaction times (RTs) to tone probes and faster answers to arithmetic problems when the two tasks did not overlap in time, but not when simultaneous processing was required when the probe was presented 2 seconds after arithmetic problems. When dual processing taxed cognitive capacity, methylphenidate still improved accuracy on the primary arithmetic task relative to placebo, but at the expense of speed of performance on the secondary RT task. When ADHD children fail to allocate available resources to a primary cognitive task, treatment with methylphenidate may result in reallocation of existing cognitive capacity from a secondary task to the primary task.

Attention↗
PubMed1991

Validity of the diagnostic category of attention deficit disorder without hyperactivity: a review of the literature.

The validity of the diagnostic category of Attention Deficit Disorder Without Hyperactivity (ADD/WO) has been the subject of debate since it was first introduced in DSM-III. The differentiation of two syndromes of ADD is supported by factor analytic studies that indicate two dimensions of maladjustment: (1) inattention and disorganization, and (2) motor hyperactivity and impulsive responding. Cluster analyses of these two dimensions have yielded two profiles of deviance that correspond to the DSM-III subtypes. Furthermore, clinic-referred children who meet DSM-III criteria for ADD/WO have been shown to exhibit less serious conduct problems, are less impulsive, are more likely to be characterized as sluggish and drowsy, are less rejected by peers but more socially withdrawn, and are more likely to exhibit depressed mood and symptoms of anxiety disorder than children with Attention Deficit Disorder with Hyperactivity (ADD/H).

Attention↗
PubMed1987

Sociometric status of clinic-referred children with attention deficit disorders with and without hyperactivity.

Peer sociometric nominations of clinic-referred children given the diagnosis of Attention) Deficit Disorder with Hyperactivity (ADD/H) or Attention Deficit Disorder without Hyperactivity (ADD/WO) were compared to one another and to those of normal control children. Only children with ADD diagnoses in the absence of other major diagnoses were included. Both children with ADD/H (n = 16) and ADD/WO (n = 11) received significantly fewer "liked most" nominations, more "liked least" nominations, and lower social preference scores than normal control (n = 45) children. These results confirm previous findings of social deficits in children with ADD/H, even when codiagnoses are excluded. In addition, they support the validity of the diagnostic category of ADD/WO by demonstrating that the ADD/WO behavior pattern is apparently "psychopathological" in being associated with peer unpopularity after codiagnoses are excluded. When larger groups including all codiagnoses (primarily Conduct Disorder) of children with ADD/H (n = 36) and ADD/WO (n = 20) were compared, identical patterns of peer unpopularity were found, except that children with ADD/H also were significantly more likely to be nominated as a child who "fights most."

Attention↗
PubMed1984

Peer assessment of the social behavior of accepted, rejected, and neglected children.

Positive and negative sociometric nominations were used with second and fifth-grade children to select 26 socially accepted, 32 rejected, and 28 neglected children. A total of 358 of their classmates evaluated these children by indicating whether each of 19 descriptions of social behavior was characteristic of each child. Rejected children were perceived by their peers as being more aggressive, disruptive, irritable, domineering , dishonest , and selfish than accepted and/or neglected children. Neglected children, in contrast, differed from accepted children only in being less likely to brag about physical prowess . While the low sociometric status of rejected children appears to be related to the negative impact of their behavior on peers, this does not appear to be the case for neglected children. Females were generally perceived as behaving more positively with peers, but no interactions were found between sex and sociometric status. In general, the test-retest reliability of peer evaluation items was higher for fifth- than for second-grade children, but significant grade by sociometric status interactions were found for only two items.

Age Factors↗
PubMed1983

Intrathecal penetration of N-formimidoyl thienamycin in normal rabbits: potentiation by coadministration of renal dipeptidase enzyme inhibitor.

The intrathecal penetration of N-formimidoyl thienamycin (MK0787) with or without coadministration of the renal dipeptidase enzyme inhibitor (MK791) in normal rabbits was studied immediately before and after the third dose of 40 mg/kg infused intravenously at daily 6-h intervals. Mean +/- standard error peak concentrations in cerebrospinal fluid were 0.23 +/- 0.02 and 0.53 +/- 0.12 micrograms/ml without and with coadministration of MK791, respectively (P less than 0.05, Student's t test). Penetration into cerebrospinal fluid (based on the ratio of cerebrospinal fluid to plasma area under the concentration-time curves) were 4.4 and 6.0%, respectively. N-Formimidoyl thienamycin penetrated uninflamed meninges, and peak concentrations were significantly augmented by coadministration of MK791.

Animals↗
PubMed1983

Ocular penetration of N-formimidoyl thienamycin (MK-787) and potentiation by dipeptidase inhibitor (MK-791).

N-formimidoyl thienamycin (MK-787) is a new beta-lactam with potent activity against both aerobic and anaerobic gram-positive and gram-negative bacteria. Its spectrum and activity suggest it may be useful in treatment of complicated intraocular infections. Its ocular penetration was studied in New Zealand white rabbits immediately before and after the third dose of 40 mg/kg administered intravenously at q6h intervals. Plasma, aqueous humor, and vitreous humor were obtained by direct aspiration, and antibiotic levels were assayed using an agar well diffusion method. MK-787 penetrated uninflamed intraocular fluids, including vitreous humor, although vitreous concentrations achieved (0.1-0.2 micrograms/ml) were significantly lower than the mean peak plasma (15 micrograms/ml) and aqueous concentrations (7 micrograms/ml). Nevertheless, the intraocular levels attained approached or exceeded the MIC90 for most sensitive organisms including some gram-negative bacilli important in bacterial endophthalmitis. When administered in combination with the renal enzyme inhibitor MK-791, plasma and aqueous concentrations of MK-787 were markedly potentiated, although vitreous concentrations were minimally affected. The potential usefulness of MK-787 in conjunction with MK-791 in the infected eye should be examined further in an animal model of bacterial endophthalmitis.

Animals↗
PubMedDate not supplied

Developmental neurotoxicity of polybrominated biphenyls.

Female F0 generation Sprague-Dawley rats received daily oral doses of 0, 0.2, or 2 mg/kg polybrominated biphenyls (PBB) as fireMaster BP-6 from Day 6 of gestation through Day 24 postpartum. Maternal parameters were assessed, and F1 generation offspring were evaluated for growth and survival, as well as physical and behavioral development. No adverse maternal effects were observed nor were there PBB-related effects on survival of the F1 generation or acquisition of developmental landmarks. Crown-rump length of 0.2 and 2 mg/kg male offspring was significantly less than that of controls and 2 mg/kg male and female offspring gained significantly less weight than did controls for the entire 60-day postnatal observation period. An overall evaluation of behavior by multivariate analysis of variance revealed significant PBB-related effects for acquisition of forward locomotion, cliff avoidance, cage emergence, and open-field activity of male and female offspring from dams administered 2 mg/kg. Delays in acquisition of forward locomotion and suppressed open-field activity were the most prominent effects. These indications of growth retardation and neurobehavioral toxicity occurred at concentrations of PBB in offspring body fat in the range of those which have been reported for highly exposed human subjects with neurological sequelae.

Aging↗