Evolution of the structural proteins of human immunodeficiency virus: selective constraints on nucleotide substitution

We have estimated the frequency of synonymous (KS) and amino acid replacement nucleotide substitutions (KA) among gag and env genes of published HIV sequences. The ratio of KS to KA can be used as an indicator of the intensity of the selective constraints on the amino acid sequence of a protein. By this approach we have shown that for both gp120 and gp41, the rate of change in amino acid sequence relative to the overall rate of change in nucleotide sequence is higher than for any other protein yet analyzed. The gag proteins p15 and p17 evolve slightly less rapidly, but p24 is relatively strongly conserved. We have compared the env gene of HIV with those of two other retroviruses for which appropriate data are available. In neither murine leukemia virus nor feline leukemia virus do the envelope glycoproteins evolve particularly rapidly. These results suggest that HIV is unusual among retroviruses in that both gp120 and gp41 are evolving under extremely weak selective constraints relative to the rest of the viral genome; accordingly, much of the observed variation may be selectively neutral.

A new member of the ras gene superfamily identified in a rat liver cell line

A new member of the ras genes superfamily was isolated from a cDNA library derived from a rat liver cell line (BRL-3A). The predicted 201 amino acids ras-like protein shows 30-35% homology with other members of the ras and ras-related gene products so far described. Conserved features include the GTP-binding and hydrolysis domains and the carboxyl terminal cysteine residues. A protein of the expected size (Mr 23,000) was synthesized in an in vitro transcription-translation system. The BRL-ras gene is present in single copy in the rat genome and is ubiquitously expressed at high levels in all tissues and cell lines examined.

Structure of the rat insulin-like growth factor II transcriptional unit: heterogeneous transcripts are generated from two promoters by use of multiple polyadenylation sites and differential ribonucleic acid splicing

The rat insulin-like growth factor II (rIGF-II) gene, which exists as a single copy in the genome, is expressed as a multitranscript family of mRNA molecules ranging in size from 4.6 to 1 kilobases. Part of this heterogeneity can be ascribed to the presence of two different promoters, each transcribing alternative 5'-noncoding regions which are spliced to common coding exons. In the present study we use a combination of DNA sequence analysis of the gene, mapping of the mRNA molecules by Northern analysis and ribonuclease protection experiments, and DNA sequence analysis of cDNA clones complementary to different regions of the genome to establish the structure of several rIGF-II mRNA species. These results indicate that RNA heterogeneity also arises from the use of different polyadenylation sites. In addition, a variant 2 kilobases RNA was observed that was colinear with the distal 1700 base pairs of the 3147 base pair long exon 3, and may arise by alternative RNA splicing. These posttranscriptional modifications of RNAs arising from the rIGF-II transcription unit may generate molecules with different functional potential.

Cardiovascular and renal effects of dopamine and dobutamine in healthy, conscious piglets

The pharmacologic effects of dopamine and dobutamine (2 to 32 micrograms/kg.min) were evaluated in 12 1 to 2-month-old piglets. Dopamine increased cardiac output at 16 to 32 micrograms/kg.min (p less than .05) and increased heart rate (HR) at 4 to 32 micrograms/kg.min (p less than .05). Dobutamine produced an increased cardiac output at doses of 16 to 32 micrograms/kg.min (p less than .05), and increased HR at 32 micrograms/kg.min (p less than .05), decreased systemic arterial pressure and systemic vascular resistance at 16 to 32 micrograms/kg.min (p less than .05), decreased renal vascular resistance at 16 to 32 micrograms/kg.min, and increased renal blood flow at 4.8 and 32 micrograms/kg.min (p less than .05). We conclude that dopamine and dobutamine increase cardiac output in healthy, conscious piglets primarily by increasing HR. Neither agent was effective in increasing stroke volume, although a positive inotropic effect obscured by tachycardia cannot be ruled out. Dobutamine was the superior agent for renal vasodilation, whereas neither agent produced significant pulmonary vasodilation.

A novel N-acetylglucosaminidase from neonatal rat enterocytes

The luminal surface of ileal enterocytes in fetal and neonatal mammals is covered by beta-hexosaminidase, which is attached to a fibrillar array. In this study, we have isolated this enzyme and subjected it to kinetic and structural analyses. The enzyme is identified as N-acetyl-beta-glucosaminidase (NA beta G) on the basis of substrate specificity and susceptibility to inhibition by N-acetylgalactosamine. Its catalytic properties and thermal stability are characteristics of the acidic, thermally labile human isoenzyme, but it differs from the human glycosidase in size. The neonatal NA beta G is a species of 225,000 relative mass (Mr), composed of two subunits of 125,000 and 115,000 Mr. Both its cellular location and differences in biophysical properties from the adult rat lysosomal forms and human glycosidases suggest that the neonatal rat NA beta G is a novel isoenzyme.

Potential secondary and tertiary structure in the genomic RNA of foot and mouth disease virus

The nucleotide sequence of the 5' untranslated region of foot and mouth disease virus (FMDV), serotype A10 has been determined. This completes the first total genomic sequence for any one serotype of FMDV. Analysis of the sequence to the 3' side of the poly (C) tract reveals the presence of a 24 nucleotide repeated motif which has homologies with a sequence located upstream of the transcriptional initiation site from several mammalian fibrinogen genes. The function of this element in FMDV is unclear. However, computer analysis of this region predicts the presence of a high degree of secondary and tertiary structure in which these repeats form an important part. The implications of these predictions are discussed.

Investigation of synthetic Escherichia coli heat-stable enterotoxin as an immunogen for swine and cattle

In its native form Escherichia coli heat-stable enterotoxin (STa) is nonantigenic; however, neutralizing antibodies are elicited in animals vaccinated with toxin-carrier conjugates. To study the immunogenicity of STa, peptides STa1-18 and STa5-18 were synthesized, characterized, and conjugated to carrier proteins. Pregnant gilts and heifers were hyperimmunized with the respective conjugates. Following parturition neonates were challenged with virulent E. coli (K99+ STa+). Peptides coupled to ovalbumin and emulsified with Freund adjuvant elicited antibodies that neutralized toxin-induced fluid accumulation in suckling mice. Peptides coupled to particulate carriers, with or without muramyl dipeptide adjuvant, failed to induce a measurable response. Peak antibody levels in sera were observed following three doses of conjugate and persisted for several weeks. The serological response in cattle was superior to that observed in swine; however, antibody levels in porcine colostrum were higher than those observed in cattle. Clinical observations of neonates from vaccinated dams indicated that passively obtained antibody provided partial protection from disease, but not as complete as that demonstrable with whole cell bacterins that induce antibody to pili. However, the data suggest the potential for utility of synthetically prepared antigens.

Congenital hypothyroidism: increased risk of neonatal morbidity results in delayed treatment

In a population-based screen of 617,913 infants, primary congenital hypothyroidism (CH) was confirmed in 100 children. 32 of the 100 infants with CH had an additional defect or complication. In the group with CH the rates of congenital heart disease, non-cardiac malformations, respiratory distress syndrome, and death were higher than in the general population of the same age. Black infants were less likely than whites to have CH, but were at twice the risk of additional impairment. Infants with CH who had an additional complication were screened (12.7 vs 4.8 days) and treated (32.4 vs 19.7 days) significantly later than those infants with isolated CH. Congenital malformations and neonatal complications should not be reasons for deferring screening for CH.

Structure and expression of the rat insulin-like growth factor II (rIGF-II) gene. rIGF-II RNAs are transcribed from two promoters

Insulin-like growth factor II (IGF-II) is a mitogenic polypeptide present in rat plasma at high levels during fetal and early postnatal life and is believed to play an important, although as yet undefined, role in fetal development. Both in humans and rats, expression of the IGF-II gene results in the appearance of several mRNA species. In the present study, cDNA and synthetic oligonucleotide probes were used to isolate and characterize the rat IGF-II gene from genomic libraries. The rat IGF-II gene extends over 12 kilobase pairs and contains two 5'-noncoding exons and three protein-coding exons. The two 5' exons represent alternative 5' regions of different mRNA molecules and are expressed from two distinct promoters. The two promoters are transcribed with different efficiencies but exhibit similar tissue-specific expression and regulation with developmental age.

Developmental regulation of insulin-like growth factor II mRNA in different rat tissues

Insulin-like growth factor II (IGF-II) is present at high levels in fetal and early neonatal rat plasma, and decreases profoundly following birth. In the present study, the levels of IGF-II RNA in different rat tissues at different ages were determined by hybridization to a rat IGF-II cDNA probe. IGF-II RNA was present in 11 of 13 fetal or neonatal tissues examined: at higher levels in muscle, skin, lung, liver, intestine, and thymus; at lower levels in brain stem, heart, cerebral cortex, kidney, and hypothalamus; and undetectable in spleen and pancreas (although the latter RNA was partially degraded). In each tissue, Northern blot hybridization revealed the presence of six IGF-II RNAs: 6, 4, 3.8, 2.2, 1.7, and 1.2 kilobase pairs, consistent with results previously observed in the BRL-3A rat liver cell line and attributed to alternative RNA processing. Although differences in the relative abundance of these RNAs were observed in different tissues, the same size species occurred in all tissues with the 4-kilobase pair RNA the most abundant species. RNAs from the different tissues were examined at six developmental ages (days 16 and 21 of gestation; days 2, 11, 22, and 75 after birth) by hybridization to slot blots and Northern blots. In lung, thymus, kidney, and brain stem, IGF-II RNA was expressed at higher levels in the fetus than after birth, whereas in muscle, skin, liver, heart, and intestine, the high fetal levels of IGF-II RNA continued through day 11 or day 22 after birth. IGF-II RNA persisted into adulthood in cerebral cortex and hypothalamus. Although the significance of these tissue-specific differences in the developmental regulation of the expression of IGF-II RNA remains to be established, they exhibit intriguing temporal correlations with major maturational events in some tissues such as lung and muscle.

Children's learning and transfer of inductive reasoning rules: studies of proximal development

An initial study examined the relation between current developmental levels, as estimated by IQ, and proximal levels of development, as estimated by the efficiency of learning and transfer in assisted contexts. 8-11-year-old children learned to solve letter series completion problems with the aid of graduated sequences of prompts. Maintenance and transfer were later assessed using similar prompting procedures. Both IQ and age effects were found. Average-IQ (and younger) children required more assistance than high-IQ (and older) children to achieve the same mastery level on the original problem types. In addition to this difference in learning efficiency, average-versus high-IQ students, and younger versus older children, subsequently diverged in the number of prompts they needed as the transfer problems differed increasingly from the ones originally learned. In a second study, amount of assistance required in learning was found to be quite stable across moderately related tasks (letter series and progressive matrices). Assistance needed in maintenance and transfer appeared less stable but was also significantly correlated across tasks. Theoretical and clinical implications are discussed.

Growth hormone regulates the abundance of insulin-like growth factor I RNA in adult rat liver

Insulin-like growth factor I (IGF-I) is a mitogenic polypeptide present in the plasma of man and rat that is thought to mediate the actions of pituitary growth hormone on cartilage to promote skeletal elongation. In the rat, plasma levels of IGF-I show both developmental and hormonal regulation: levels are low at birth, increase with age, and are decreased in growth hormone-deficient adult animals. The present study demonstrates that these changes in plasma IGF-I reflect the abundance of IGF-I RNA in rat liver. A human IGF-I cDNA probe hybridized to multiple RNA species in adult rat liver with sizes 8.6, 4.6, 3.2, 2.1, and 1.0-1.4 kilobases. These RNA species were decreased by greater than 80% in neonatal (2- and 12-day-old) rat liver and by greater than 90% in liver from adult rats made growth hormone-deficient by hypophysectomy. Treatment of hypophysectomized rats with growth hormone increased the abundance of all species of IGF-I RNA. These results suggest that growth hormone regulates the expression of its physiological mediator by altering the synthesis, stability, or both of IGF-I RNA in rat liver.

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

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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.

Very young children's memory for the location of objects in a large-scale environment

2 experiments were carried out to investigate 18- to 30-month-old children's memory for the location of a hidden object. In the first experiment, young children were observed in 2 different memory-for-location tasks, both conducted in their own homes. In 1, a toy was hidden in a natural location, and in the other it was hidden in one of a set of boxes with picture cues on top of them. Memory performance was significantly better when the toy was hidden within the natural environment. The effect of different types of hiding locations was examined further in the second experiment. No age differences were found when an object was hidden either in the natural environment or in 1 of a set of unmarked boxes (although performance was better in the former condition). However, in the third condition the older subjects (24-30 months) effectively used a landmark cue (a nearby piece of furniture) to help them remember in which plain box a toy had been hidden, but the young subjects (18-22 months) did not profit from such potential cues. The results, as well as some previous research with delayed-response tasks, were interpreted as reflecting developmental changes in very young children's ability to exploit available cues. The pattern of results suggested the possibility that 2-year-old children are capable of a simple form of mnemonic strategy, actively associating an available cue with the information to be remembered.

Chronic camphor ingestion mimicking Reye's syndrome

Camphor is a potentially dangerous drug which nevertheless remains popular as a home remedy. Because of its hepatoneurotoxic effects, camphor toxicity may clinically mimic Reye's syndrome. The differentiation between the two requires histologic examination of liver tissue, further emphasizing the need for a liver biopsy to establish the diagnosis of Reye's syndrome.

Coordinated system for comprehensive newborn metabolic screening

In September 1978 phenylketonuria (PKU) screening in the state of Georgia was expanded to include testing for five additional metabolic disorders. Our goal was to begin therapy within the first three weeks of an infant's life. During the first 22 months, 167,458 specimens were received; 151,250 from infants less than or equal to 1 week of age. During this period 157,893 live births were reported. More than 90% of 2,299 infants with abnormal screening results were retested. The number of cases and incidence of each disease detected were hyperphenylalaninemia, five (1/31,579); maple syrup urine disease, 0 (0/151,250); homocystinuria, one (1/151,250); galactosemia, two (1/63,352); transient tyrosinemia (greater than or equal to 12 mg/dl), 50 (1/3,158); primary congenital hypothyroidism, 17 (1/7,453); and thyroid binding globulin deficiency, ten (1/12,670). For eight children with either hyperphenylalaninemia, homocystinuria, or galactosemia, the average time for retrieval between the initial abnormal screening result ad the first follow-up test was 6.2 days (range three to ten days). Therapy was started by 9.9 days of age (range seven to 17). For the 17 children with congenital hypothyroidism, the retrieval time was 11.6 days (range three to 27) and treatment began by 21.3 days of age (range ten to 69 days).

Salmonella Minnesota Re 595 lipid A induced nephritis

Injection of heat killed bacteria into kidney parenchyma results in pathologic lesions similar to chronic pyelonephritis while immunosuppression reverses this phenomenon. These observations and the propensity of lipid A to bind to cell membranes suggest that the lipid component of bacterial lipopolysaccharide antigens may be important in the pathogenesis of kidney tubule cell death. The right kidneys of syngeneic Fischer 344 rats were repeatedly injected with glycolipid prepared from Salmonella minnesota Re 595 cell walls. As a control, the contralateral kidney was injected with normal saline. The inflammatory response observed in the glycolipid injected kidney was significantly greater (p less than 0.005) than the response detected in the contralateral saline injected control kidney. Electron microscopy of kidney tubule cells incubated with peroxidase conjugated glycolipid demonstrated glycolipid bound to the kidney tubule cell plasma membranes. These studies suggest that individual antigenic components can induce kidney lesions and tubule cell death similar to that seen in chronic pyelonephritis.