Analogical transfer in very young children: combining two separately learned solutions to reach a goal

In 5 studies, the learning and transfer abilities of 2-4-year-old children were examined on a task in which they were required to combine 2 separately learned solutions to reach a goal. The 3 main findings are very early competence on the task if it is situated in familiar settings, a developmental trend in the ability to notice the similarity across analogous versions of the problem that differ in surface format but share the same underlying logic, and the success of 2 forms of assistance in promoting transfer. Both emphasizing task similarity and encouraging the children to talk about the rules ensure that they will notice problem similarity and hence afford them the opportunity to apply the learned rules appropriately. Difficulties with noticing similarity, rather than in applying the rule, lead to transfer failure. Given a hospitable environment, children as young as 2-3 years of age can combine information and apply a reasoning rule quite broadly.

Coordinate developmental regulation of high and low molecular weight mRNAs for rat insulin-like growth factor II

Insulin-like growth factor II (IGF-II) is a mitogenic polypeptide that is thought to play a role in fetal growth and development. To study the hormonal and developmental regulation of IGF-II gene expression, we have isolated a cDNA clone for rat IGF-II (rIGF-II) from a 12S [1.2-kilobase-pair (kbp)] fraction of mRNA from a rat liver cell line (BRL-3A) that directs the cell-free synthesis of pre-pro-rIGF-II. In the present study, the rIGF-II probe was used to determine the size of IGF-II RNA. Surprisingly, in BRL-3A cells and in neonatal liver, the probe hybridized under stringent conditions 10-20 times more strongly to a larger (4 kbp) RNA than to 1.2-kbp RNA. The 4-kbp RNA is almost exclusively cytoplasmic and is colinear with a 551-base fragment of the rIGF-II cDNA insert containing coding and 3' noncoding regions. The 4-kbp and 1.2-kbp RNA species are regulated coordinately with developmental age, being high in liver from neonatal rats but not detectable in liver from older animals, suggesting that both IGF-II mRNA species arise from a single primary transcript by alternative RNA processing. Although oligodeoxynucleotide hybridization and S1 nuclease protection experiments suggest that the 4-kbp RNA contains an intact protein-coding region, fractions enriched in 4-kbp RNA do not direct the translation of pre-pro-rIGF-II in vitro. This may indicate that the 4-kbp RNA specifies an altered protein product that has not yet been recognized, or alternatively that it contains a normal protein-coding region but requires further RNA processing to be activated for translation.

General practitioner referrals to a clinical child psychologist

An analysis of the problems that are referred by general practitioners to a clinical child psychologist working in the community is presented. To illustrate some of the principles of assessment and management an example from each of three main categories--behaviour problems, emotional disturbances, and disorders of function--is given.

Cerebrospinal fluid penetration of imipenem and cilastatin (primaxin) in children with central nervous system infections

Cerebrospinal fluid (CSF) penetration of imipenem-cilastatin was evaluated in 20 children (aged 4 months to 11 years) with central nervous system infections. A total of 10 children received a single 25-mg/kg intravenous dose, and 10 received three 25-mg/kg intravenous doses at 6-h intervals. Blood and CSF were obtained 1.5 to 2.5 h after the last dose during the early (days 1 to 3) and the late (days 7 to 10) stages of infection. Imipenem concentrations after single-dose infusion in serum and CSF during the early phase of treatment (8.59 +/- 0.95 and 1.36 +/- 0.32 micrograms/ml, respectively) were similar to those during the late phase (9.96 +/- 2.36 and 2.08 +/- 1.14 micrograms/ml, respectively). Concentrations of imipenem in serum and CSF after multiple-dose infusion during the early phase (11.97 +/- 2.03 and 1.87 +/- 0.29 micrograms/ml, respectively) were similar to those during the late phase (9.57 +/- 1.76 and 1.22 +/- 0.11 micrograms/ml, respectively). There were no significant differences in the serum or CSF imipenem concentrations between the single- and multiple-dose groups during the early or late treatment stages. Cilastatin concentrations in serum and CSF were similar in all groups with the exception of the multiple-dose, early- versus late-phase evaluation of CSF cilastatin concentration. There was no correlation between age or absolute CSF neutrophil count and the serum or CSF concentrations of imipenem or cilastatin. We found a mean CSF penetration of 15 to 27% for imipenem and 16 to 66% for cilastatin in children. These findings suggest that imipenem-cilastatin sufficiently penetrates into CSF in children to warrant further investigation of this compound in pediatric central nervous system infections.

Transcriptional antitermination activity of the synthetic nut elements of coliphage lambda. I. Assembly of the nutR recognition site from boxA and nut core elements

An active nutR antiterminator was reconstructed from two synthetic modules, one containing the 8-bp boxA (5'-CGCTCTTA) and the other the 17-bp nutR core (5'-AGCCCTGAAAAAGGGCA) sequence. The modules were synthesized with HindIII cohesive ends, which upon annealing and ligation created an 8-bp spacer (5'-CAAAGCTT) between the boxA and nutR core. The 8-bp length was the same as in the native nutR (5'-CACATTCC), but the sequence showed less than 38% homology. The antitermination mediated by the synthetic nutR was 68-80% efficient when tested in the pp-nutR-N-tL1-galK expression plasmid, analogous to that used by Drahos and Szybalski [Gene, 16 (1981) 261-274]. The cloned boxA by itself has no activity, while the nutR core alone shows only marginal (5-10%) antiterminator function. Increasing the distance between boxA and the nutR core from 8 bp to 20-28 bp, i.e., by one to two turns of the DNA helix (about 10 bp per turn), has little effect on the antiterminator function, whereas use of spacers with length about halfway between 8 and 20 bp results in reduced antitermination. It appears that both the sequences and spacial arrangement of the boxA and nut elements are important for efficient antiterminator function.

Cefotaxime and desacetylcefotaxime pharmacokinetics in infants and children with meningitis

The pharmacokinetics and cerebrospinal fluid (CSF) penetration of cefotaxime (Ctx) and desacetylcefotaxime (dCtx) were evaluated in 13 infants and children with meningitis after dose 6 of Ctx in a multiple-dose intermittent intravenous infusion regimen (50 mg/kg every 6 h). Model-dependent and noncompartmental pharmacokinetic parameters were determined and were found to be congruous. The disposition of both Ctx and dCtx was described adequately by a one-compartment, open model. Noncompartmental pharmacokinetic parameters are reported. The mean Ctx serum concentration at 0.25 h postinfusion was 121.2 micrograms/ml, and the mean CSF concentration at 1 h postinfusion was 6.2 micrograms/ml. The CSF/serum ratio was variable (0 to 20%), with a mean penetration of 10.1%. The mean Ctx elimination half-life, apparent steady-state volume of distribution, and total body clearance were 0.8 h, 0.361 liter/kg, and 0.289 liter/h per kg, respectively. For Ctx, 61% of the dose was excreted unchanged in the urine during the 6-h postinfusion period, and the estimated renal clearance was 0.174 liter/h per kg. No significant correlations were observed between Ctx pharmacokinetic parameters and demographic parameters. The mean peak concentration of dCtx in serum (21.6 micrograms/ml) occurred at approximately 1.5 h postinfusion, and the mean concentration in CSF at 1 h postinfusion was 5.6 micrograms/ml. The CSF/serum ratio was extremely variable (0 to 103%), and the mean penetration was 28.8%. The mean apparent elimination half-life for dCtx was 2.1 h. In infants and children with normal renal function, a 50-mg/kg dose of Ctx administered every 6 h should provide adequate concentrations in serum and CSF in the majority of patients with meningitis.

Metacognition reconsidered: implications for intervention research

Metacognitive training techniques have been used successfully to improve children's problem-solving skills. The concept of metacognition needs further refinement, however, if it is to continue to be useful as an explanatory construct. Specifically, we argue that more attention needs to be paid to how metacognitive abilities are acquired, how this knowledge could be used to help improve the performance of children with learning difficulties, and how metacognition may be related to other self-evaluation processes.

The development of error correction strategies in young children's manipulative play

The focus of this study was the strategies used by young children between 18 and 42 months for correcting the errors they made as they attempted to nest a set of 5 seriated cups. In the process of combining the cups, the children committed numerous errors (such as putting a cup that was too large on a smaller cup), and they tried to correct the majority of those errors. Detailed examination of the children's correction attempts revealed that the strategies they used changed substantially with age, becoming increasingly more flexible and involving more extensive restructuring of the relations among the cups. Earlier correction attempts tended to focus on a single, nonfitting cup or on a single relation between 2 cups. Later-appearing strategies involved the coordination of relations involving several cups. The same trend toward increasing flexibility of thought and action also appeared in the procedures the children used to combine the cups. This study thus documents a finely graded series of cognitively significant changes in children's constructive activity during a period that has been poorly differentiated by cognitive developmental research. In so doing, it demonstrates the usefulness for problem-solving research of analyzing how subjects go about trying to rectify their own mistakes.

Ticarcillin/clavulanic acid pharmacokinetics in children and young adults with cystic fibrosis

The single-dose pharmacokinetics of ticarcillin and clavulanic acid (Timentin) were evaluated in children and young adults with cystic fibrosis after a 0.5-hour intravenous infusion of both a 3.1 and a 3.2 gm formulation (representing 3.0 gm ticarcillin combined with 100 mg and 200 mg clavulanic acid, respectively) in a crossover design. A 75 mg/kg dose of the ticarcillin component was used. Model-dependent and noncompartmental pharmacokinetic parameters were congruous. The disposition of ticarcillin and clavulanic acid was characterized adequately by a one-compartment open model. The elimination half-life, apparent steady-state volume of distribution, and total body clearance of ticarcillin from serum were 1.19 hours, 0.231 L/kg, and 0.150 L/hr/kg, respectively, for the 3.1 gm formulation and 1.21 hours, 0.211 L/kg, and 0.123 L/hr/kg, respectively, for the 3.2 gm formulation. For ticarcillin, 86% and 93% of the dose of the 3.1 and 3.2 gm formulations, respectively, were excreted unchanged in urine during the first 6 hours after infusion. Concomitant renal clearance values were 0.120 and 0.112 L/hr/kg for the 3.1 and 3.2 gm formulations, respectively. Approximately 50% of a clavulanic acid dose was excreted unchanged in urine during the 6-hour postinfusion period for both formulations. For ticarcillin, no significant differences were observed between the 3.1 and 3.2 gm formulations. For clavulanic acid, a significant difference between the two formulations was observed in comparison of the area under the serum concentration vs time curve and dose size (P less than 0.01). Linear inverse relationships were identified between demographic factors (e.g., age, weight, height, body surface area) and both the apparent volume of distribution and total body clearance of ticarcillin and clavulanic acid for both formulations. The ticarcillin/clavulanic acid combination in either the 3.1 or 3.2 gm formulation is suitable for microbiologic and clinical evaluation in patients with cystic fibrosis.

Oesophageal stimulation lowers exertional angina threshold

The effect of oesophageal stimulation with acid on the exertional angina threshold was examined in 12 subjects. Each walked until the angina threshold was reached on four successive occasions; during two tests the oesophagus was instilled with 0.1 mol/l hydrochloric acid and during the other two with physiological saline. Oesophageal instillation was carried out for 20 min at rest before each walk. In 10 patients the angina point was reached after walking a significantly shorter distance on the treadmill when acid was instilled than when the saline was instilled. ST-segment changes and rate-pressure product were not significantly different during the acid and saline tests. The mechanism responsible for the reduction of angina threshold is not known. However, the effect was more pronounced in the 6 patients who had experienced regular oesophageal symptoms than in those who had not. Ischaemic heart disease and gastro-oesophageal reflux are both common, and the possibility that acid reflux may aggravate angina should be borne in mind, particularly when oesophageal symptoms are present.

Thermosensitivity of a DNA recognition site: activity of a truncated nutL antiterminator of coliphage lambda

Antitermination is an important transcriptional control. In bacteriophage lambda, the presence of the nut antiterminators between the promoters and terminators results in relatively unhindered transcription when the lambda N gene product and necessary host factors are supplied. This antitermination system has been rendered thermosensitivity by modification of the nut site. A fragment of lambda DNA [74 base pairs (bp) in length]that contained the 17-bp nutL core sequence, but lacked the 8-bp boxA sequence, was cloned in a pp-N-tL1-galK plasmid between the pp promoter and gene N. This fragment mediated antitermination of transcription at 30 degrees C, as measured by assaying galK gene expression in Escherichia coli. At 42 degrees C, however, antitermination at the lambda tL1 terminator was abolished. Antitermination at 42 degrees C was restored by replacing the 74-bp nutL fragment with longer sequences containing both nutL and boxA or by cloning a synthetic boxA sequence ahead of the 74-bp nutL fragment. Thus, efficient antitermination required both boxA and the 17-bp nutL core, with the latter becoming conditionally defective when the boxA sequence was deleted.

Precursors of mnemonic strategies in very young children's memory

In 4 studies with 18-24-month-old children, evidence was obtained of strategy-like behaviors in a memory-for-location task in which the child had to remember in what natural location a toy had been hidden. The children exhibited behaviors that resemble the mature strategies of rehearsal and monitoring, including talking about the toy or its hiding place and looking or pointing at it during the delay interval. In Experiments 1 and 2, these strategy-like behaviors were engaged in differentially as a function of familiarity, both of the setting in which the task was embedded and of the task itself. Significantly more target behaviors occurred in an unfamiliar than in a familiar setting, and more target behaviors occurred on the first than on the second day of observation. In Experiment 3, when the basic memory task was modified to remove the memory demands from the child, very few of the strategy-like behaviors occurred, indicating that they were indeed memory specific. In the fourth experiment, the rehearsal-like behaviors were shown to be related to subsequent retrieval. We interpret these results as evidence of an early natural propensity to keep alive what must be remembered, a rudimentary and imperfect version of what will later become more elaborate and planful mnemonic strategies.

Transcriptional antitermination activity of the synthetic nut elements of coliphage lambda. I. Assembly of the nutR recognition site from boxA and nut core elements

An active nutR antiterminator was reconstructed from two synthetic modules, one containing the 8-bp boxA (5'-CGCTCTTA) and the other the 17-bp nutR core (5'-AGCCCTGAAAAAGGGCA) sequence. The modules were synthesized with HindIII cohesive ends, which upon annealing and ligation created an 8-bp spacer (5'-CAAAGCTT) between the boxA and nutR core. The 8-bp length was the same as in the native nutR (5'-CACATTCC), but the sequence showed less than 38% homology. The antitermination mediated by the synthetic nutR, was 68-80% efficient when tested in the pp-nutR-N-tL1-galK expression plasmid, analogous to that used by Drahos and Szybalski [Gene, 16 (1981) 261-274]. The cloned boxA by itself has no activity, while the nutR core alone shows only marginal (5-10%) antiterminator function. Increasing the distance between boxA and the nutR core from 8 bp to 20-28 bp, i.e., by one to two turns of the DNA helix (about 10 bp per turn), has little effect on the antiterminator function, whereas use of spacers with length about halfway between 8 and 20 bp results in reduced antitermination. It appears that both the sequences and spacial arrangement of the boxA and nut elements are important for efficient antiterminator function.

Rapid estimation of serum theophylline clearance in children with acute asthma

Serum theophylline clearance was estimated prior to reaching steady state in 29 asthmatic children, aged 1-14 years, using methods described by Chiou et al. and Vozeh et al. Comparison of the estimated clearance by the Vozeh method (0.094 +/- 0.005 L/kg/h) did not differ significantly from that estimated by the Chiou method (0.094 +/- 0.005 L/kg/h). Neither estimate of serum theophylline clearance differed significantly from the calculated clearance at steady state (0.092 +/- 0.006 L/kg/h). Linear correlations between predicted and observed serum theophylline clearances were found for both the Chiou (p = 0.002, r = 0.54) and Vozeh (p = 0.02, r = 0.49) methods. Estimates of the steady-state serum theophylline concentrations by the Vozeh method (10.32 +/- 0.56 mg/L) and the Chiou method (10.28 +/- 0.52 mg/L) did not differ significantly from each other or from the observed steady-state serum theophylline concentration (10.54 +/- 0.48 mg/L). A linear correlation between predicted and observed serum theophylline concentrations was found for both the Chiou (p = 0.02, r = 0.43) and Vozeh (p = 0.001, r = 0.57) methods. These results suggest that either method of estimating serum theophylline clearance can be used to rapidly individualize therapy in children with acute asthma.

Single-dose pharmacokinetics of imipenem in children

The single-dose pharmacokinetics of imipenem (N-formimidoyl thienamycin) was evaluated in 13 pediatric patients (mean age 5.2 +/- 3.5 years). Imipenem was administered in combination with cilastatin as either a 10 mg/kg or 25 mg/kg dose (not to exceed 500 mg) over 15 minutes. Plasma disposition in children was best described by a two-compartment open model. The distribution phase was rapid (t1/2 lambda 1 = 0.18 hours) and was followed by a monoexponential elimination phase (t1/2 lambda 2 = 1.2 hours). The calculated value for the apparent volume of distribution (0.66 L/kg) was similar to that of total body water. The total plasma clearance was rapid (0.36 L/hr/kg). Direct proportionality was exhibited between administered dose and either resultant plasma concentration or area under the plasma concentration versus time curve. Comparison of imipenem plasma pharmacokinetic data derived from these children with data reported from adult subjects revealed disparities for both the apparent volume of distribution and plasma clearance. Based on preliminary pharmacokinetic simulations using parameters generated from our study, a 25.0 mg/kg dose of imipenem administered every 6 hours appears adequate for initiation of therapy in children.

Renal clearance of imipenem in children

Imipenem renal clearance was studied in six children (three males, three females; 2.9-11.2 years of age) following a single intravenous dose (21.7 +/- 5.1 mg/kg) of imipenem/cilastatin (1:1). In an approximately six-hour period following drug administration, 65.3 +/- 9.7% of the imipenem dose was excreted in the urine unchanged. The renal clearance (280.03 +/- 24.34 ml/min/1.73 m2) of imipenem was found to account for 69.2% of the corresponding plasma imipenem clearance (404.89 +/- 24.83 ml/min/1.73 m2). Contrary to existing adult data, the imipenem renal clearance in our subjects was 1.95-fold greater than the estimated creatinine clearance, suggesting significant tubular secretion of imipenem in children. Examination of urinary imipenem excretion rate versus plasma concentration relationships in three of the children revealed a potential renal tubular reabsorption component for imipenem in children. Comparison of renal imipenem clearance data in these children to similar data from adults suggests that quantitatively important developmental differences may exist for the renal handling of imipenem.

Cefotaxime therapy of bacterial meningitis in children

Thirty children with bacterial meningitis were randomized to receive either ampicillin and chloramphenicol in standard doses or cefotaxime (50 mg/kg/dose every 6 h) for 10 to 14 days. Eighteen patients received ampicillin and chloramphenicol and 12 patients received cefotaxime. Cerebrospinal fluid isolated included: Haemophilus influenzae (20), Streptococcus pneumoniae (4), Neisseria meningitidis (3), Group B streptococcus (2), and Salmonella enteritidis (1). Five of the H. influenzae isolates were ampicillin resistant but no isolates were resistant to cefotaxime. The minimum inhibitory concentrations of cefotaxime for 30 isolates ranged from 0.0004 to 0.06 mg/l, while the minimum bactericidal concentrations ranged from 0.007 to 0.12 mg/l. The cerebrospinal fluid bactericidal titres for the cefotaxime-treated group ranged from 1:64 to 1:1024. On the second day of therapy the mean cefotaxime serum concentrations were 56.9 +/- 28.7 mg/l at 1 h and 3.66 +/- 5.65 mg/l at 6 h after administration of the drug whilst mean desacetyl-cefotaxime serum concentrations were 12.31 +/- 7.56 mg/l at one hour and 7.96 +/- 8.26 mg/l at 6 h respectively. Cerebrospinal fluid concentrations of cefotaxime and desacetylcefotaxime measured one hour after drug administration were 3.72 +/- 5.57 mg/l and 4.35 +/- 7.12 mg/l, respectively. No adverse drug reactions were noted in either treatment group. Cefotaxime proved to be both as safe and as efficacious as standard therapy for the treatment of bacterial meningitis in children.

Life changes. Leaving school

Images

Inclusion of social problem categories in disease registers

The reliability of a disease register as a record of the number and type of social problems was investigated in one practice of approximately 12,000 patients. A comparison with a randomly selected sample of the practice population, matched for age and sex, indicated that some social problems were not included. The types of problem concerned, and the reasons why they were not included, are discussed.