Mild traumatic brain injury: improving quality of care in the paediatric emergency department setting

AIM

Traumatic brain injury (TBI) in childhood can impose a significant threat to life and longer-term disability. This study investigated the extent to which the documentation of key indicators of healthcare quality in the emergency department (ED) setting was consistent with clinical guidelines for the management of children with mild TBI (MTBI).

METHODS

The clinical records of a random sample of 60 children (stratified by ethnicity and age group), who were seen and discharged from a large metropolitan paediatric hospital ED following a head injury, were systematically reviewed to examine the processes of care and follow-up.

RESULTS

Based on the documentation in clinical records, processes designed to identify and manage potentially life-threatening acute complications (e.g. computed tomography scanning to identify intracranial haemorrhage) were consistent with best practice standards. However gaps existed between current and best practice for some aspects of care that could minimise risks of longer-term disability from MTBI. For example, relevant clinical criteria were well documented, but this information did not appear to be applied systematically to identify and to follow up children with definite or possible MTBI.

CONCLUSION

The apparent absence of a systematic approach to the diagnosis and follow-up of MTBI in children presenting to ED suggests a missed opportunity to minimise the risk of disability following these injuries. Greater attention to an integrated care pathway that improves the identification, documentation, and follow-up of children with MTBI presenting to ED is required.

Randomized, double-blind comparison of growth in infants receiving goat milk formula versus cow milk infant formula

OBJECTIVE

To compare growth of infants fed goat milk infant formula (GMF) or cow milk infant formula (CMF) and to compare tolerability and safety of the two formulas.

METHODS

The study was conducted in Auckland, New Zealand. This was a double-blind randomized controlled trial. Newborn term infants were randomized within 72 h of birth to GMF or CMF. Milk formula powder in single serve sachets were reconstituted and fed to infants from trial commencement until age 168 days. No other formula given from randomization until age 168 days. Infant weight, length and head circumference were measured at birth and age 14, 28, 56, 84, 112, 140 and 168 days. Bowel motion frequency and consistency, sleeping and crying patterns and adverse events were also measured.

RESULTS

Seventy-two infants were randomized, 36 each to GMF or CMF, with 62 infants completing the intervention. At enrollment the average weight of infants in the GMF group (mean +/- SD) was 3.33 +/- 0.43 kg and in the CMF group 3.43 +/- 0.47 kg; and at study completion 8.07 +/- 0.90 kg (GMF) and 7.87 +/- 0.99 kg (CMF). The difference in average weight gain over the study period for the GMF group versus the CMF group was not significant (+309 g; 95% CI = -49 to +668, P = 0.09). Median daily bowel motion frequency was greater in the GMF group than the CMF group (2.4 vs 1.7, P = 0.01). There were no group differences in bowel motion consistency, duration of crying, ease of settling, or frequency of adverse events.

CONCLUSION

Growth of infants fed GMF is not different to that of infants-fed CMF.

Short-term repeatability of a food frequency questionnaire in New Zealand children aged 1–14 y

OBJECTIVE

To evaluate the repeatability of a children's food frequency questionnaire (FFQ) by gender, ethnicity, and age group.

DESIGN

A 117-item FFQ asking about food intake patterns over the past 4 weeks was developed using food records from 428 children (204 boys and 224 girls) and the reproducibility on average 13 days apart was tested in 130 children (78 boys and 52 girls). Children were recruited using clustered probability sampling (n=103), and a convenience sample of 25 Maori children.

SETTING

Children aged 1-14 y from Auckland, Feilding and Shannon, New Zealand.

SUBJECTS

There were 71 Maori, 20 Pacific, and 39 Other children.

RESULTS

Spearman correlations between the two FFQs ranged from 0.50 for bread to 0.82 for fruit, with a median of 0.76 for spreads and nonmilk drinks, and Cronbach's coefficient alpha's ranged from 0.59 for bread to 0.92 for nonmilk drinks, with a median of 0.85 for mixed meat dishes. There were no significant differences between the two administrations, apart from reporting higher intakes of vegetables and snacks & sweets in the first FFQ. Correlation coefficients tended to be slightly higher in boys than in girls, and in Other ethnic groups compared to Maori and Pacific children. Correlations were slightly higher for the 1-4 y age group, intermediate in the 10-14 y age group, and lowest in the 5-9 y-old age group.

CONCLUSIONS

Overall, the FFQ described here shows similar or better repeatability in New Zealand children of all major ethnic groups compared to other child or adolescent FFQs.

Analysis of SIV-specific CTL in the rhesus macaque model of AIDS: the use of simian fibroblasts as an alternative source of target cells for chromium release assays

The simian immunodeficiency virus (SIV) model of AIDS is widely used for the development of human immunodeficiency virus (HIV) vaccine strategies, particularly for the analysis of correlates of protective immunity. As it is not always possible to establish autologous B-lymphoblastoid cell lines (B-LCL) for use as targets in the analysis of cytotoxic T cell (CTL) activity, we have compared B-LCL with primary simian skin cells. Using a well-defined SIV gag-encoded CTL epitope restricted by Mamu A*01 major histocompatibility complex (MHC) class I, we have shown that peripheral blood mononuclear cells (PBMC) from vaccinated and infected macaques can kill MHC class I-matched skin fibroblasts presenting the cognate epitope but that skin fibroblasts are a less sensitive target than B-LCL for the detection of CTL.

Structural implications of a Val-->Glu mutation in transmembrane peptides from the EGF receptor

Certain specific point mutations within the transmembrane domains of class I receptor tyrosine kinases are known to induce altered behavior in the host cell. An internally controlled pair of peptides containing the transmembrane portion of the human epidermal growth factor (EGF) receptor (ErbB-1) was examined in fluid, fully hydrated lipid bilayers by wide-line 2H-NMR for insight into the physical basis of this effect. One member of the pair encompassed the native transmembrane sequence from ErbB-1, while in the other the valine residue at position 627 was replaced by glutamic acid to mimic a substitution that produces a transformed phenotype in cells. Heteronuclear probes having a defined relationship to the peptide backbone were incorporated by deuteration of the methyl side chains of natural alanine residues. 2H-NMR spectra were recorded in the range 35 degrees C to 65 degrees C in membranes composed of 1-palmitoyl-2-oleoyl phosphatidylcholine. Narrowed spectral components arising from species rotating rapidly and symmetrically within the membrane persisted to very high temperature and appeared to represent monomeric peptide. Probes at positions 623 and 629 within the EGF receptor displayed changes in quadrupole splitting when Val(627) was replaced by Glu, while probes downstream at position 637 were relatively unaffected. The results demonstrate a measurable spatial reorientation in the region of the 5-amino acid motif (residues 624-628) often suggested to be involved in side-to-side interactions of the receptor transmembrane domain. Spectral changes induced by the Val-->Glu mutation in ErbB-1 were smaller than those induced by the analogous oncogenic mutation in the homologous human receptor, ErbB-2 (Sharpe, S., K. R. Barber, and C. W. M. Grant. 2000. Biochemistry. 39:6572-6580). Quadrupole splittings at probe sites examined were only modestly sensitive to temperature, suggesting that each transmembrane peptide behaved as a motionally ordered unit possessing considerable conformational stability.

Lack of a role for transforming growth factor-beta in cytotoxic T lymphocyte antigen-4-mediated inhibition of T cell activation

Similarities in the phenotypes of mice deficient for cytotoxic T lymphocyte antigen-4 (CTLA-4) or transforming growth factor-beta1 (TGF-beta1) and other observations have led to speculation that CTLA-4 mediates its inhibitory effect on T cell activation via costimulation of TGF-beta production. Here, we examine the role of TGF-beta in CTLA-4-mediated inhibition of T cell activation and of CTLA-4 in the regulation of TGF-beta production. Activation of AND TCR transgenic mouse T cells with costimulatory receptor-specific antigen presenting cells results in efficient costimulation of proliferation by CD28 ligation and inhibition by CTLA-4 ligation. Neutralizing antibody to TGF-beta does not reverse CTLA-4-mediated inhibition. Also, CTLA-4 ligation equally inhibits proliferation of wild-type, TGF-beta1(-/-), and Smad3(-/-) T cells. Further, CTLA-4 engagement does not result in the increased production of either latent or active TGF-beta by CD4(+) T cells. These results indicate that CTLA-4 ligation does not regulate TGF-beta production and that CTLA-4-mediated inhibition can occur independently of TGF-beta. Collectively, these data demonstrate that CTLA-4 and TGF-beta represent distinct mechanisms for regulation of T cell responses.

A transmembrane peptide from the human EGF receptor: behaviour of the cytoplasmic juxtamembrane domain in lipid bilayers

Solid state (2)H NMR spectroscopy was employed to study peptides related to the transmembrane domain of the human epidermal growth factor receptor, for insight into the interaction of its cytoplasmic juxtamembrane domain with the membrane surface. Since such receptors have clusters of (+)charged amino acids in this region, the effect of (-)charged phosphatidylserine at the concentration found naturally in the cytoplasmic leaflet (15 mol%) was considered. Each peptide contained 34 amino acids, which included the hydrophobic 23 amino acid stretch thought to span the membrane and a ten amino acid segment beyond the 'cytoplasmic' surface. Non-perturbing deuterium probe nuclei were located within alanine side chains in intramembranous and extramembranous portions. (2)H NMR spectra were recorded at 35 degrees C and 65 degrees C in fluid lipid bilayers consisting of (zwitterionic) 1-palmitoyl-2-oleoylphosphatidylcholine, with and without 15 mol% (anionic) phosphatidylserine. The cationic extramembranous portion of the receptor backbone was found to be highly rotationally mobile on a time scale of 10(-4)-10(-5) s in both types of membrane - as was the alpha-helical intramembranous portion. Deuterium nuclei in alanine side chains (-CD(3)) detected modest changes in peptide backbone orientation and/or dynamics related to the presence of 1-stearoyl-2-oleoylphosphatidylserine: in the case of the extramembranous portion of the peptide these seemed related to lipid charge. Temperature effects on the peptide backbone external to the membrane were qualitatively different from effects on the helical transmembrane domain - likely reflecting the different physical constraints on these peptide regions and the greater flexibility of the extramembranous domain. Effects related to lipid charge could be detected in the spectrum of CD(3) groups on the internally mobile side chain of Val(650), six residues beyond the membrane surface.

Val(659)-->Glu mutation within the transmembrane domain of ErbB-2: effects measured by (2)H NMR in fluid phospholipid bilayers

Certain point mutations within the hydrophobic transmembrane domains of class I receptor tyrosine kinases have been associated with oncogenic transformation in vitro and in vivo [Gullick, J., and Srinivasan, R. (1998) Breast Cancer Res. Treat. 52, 43-53]. An important example is the replacement of a single (hydrophobic) valine by (charged) glutamate in the rat protein, Neu, and in the homologous human protein, ErbB-2. It has been suggested that the oncogenic nature of this Val-->Glu substitution may derive from alteration of the transmembrane domain's ability to take part in direct side-to-side associations. In the present work, we examined the basis of this phenomenon by studying transmembrane portions of ErbB-2 in fluid bilayer membranes. An expression system was designed to produce such peptides from the wild-type ErbB-2, and from an identical region of the transforming mutant in which Val(659) is replaced by Glu. All peptides were 50-mers, containing the appropriate transmembrane domain plus contiguous stretches of amino acids from the cytoplasmic and extracellular domains. Deuterium heteronuclear probes were incorporated into alanine side chains (thus, each alanine -CH(3) side chain became -CD(3)). Given the presence of natural alanine residues at positions 648 and 657 within ErbB-2, this approach afforded heteronuclear probes within the motif Ser(656)AlaValValGlu(660), thought to be important for homodimer formation, and nine residues upstream of this site. Further peptides were produced, by site-directed mutagenesis, to confirm spectral assignments and to provide an additional probe location at position 670 (11 residues downstream of the motif region). On SDS-polyacrylamide gels, the transmembrane peptides migrated as predominant monomers in equilibrium with smaller populations of homodimers/-oligomers. CD spectra of both wild-type and transforming mutant peptides were consistent with the transmembrane portions being basically alpha-helical. (2)H NMR spectra of each transmembrane peptide were obtained in fluid phospholipid bilayers of 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) from 35 to 65 degrees C. Results were consistent with the concept that the glutamic acid residue characterizing the mutant is uncharged at neutral pH. Narrowed spectral components from species rotating rapidly and symmetrically within the membrane appeared to represent monomeric peptide. Mutation of Val(659) to Glu within the hydrophobic domain induced changes in side chain angulation of at least 6-8 degrees at Ala(657) (i.e., within the five amino acid motif thought to be involved in homodimer formation), and downstream of this site to residue 670. There was little evidence of effect at the upstream site (Ala(648)) at the membrane surface. This result argues that the transforming mutation is associated with significant intramolecular rearrangement of the monomeric transmembrane helix-extending over some four helix turns-which could influence its lateral associations. In addition, temperature effects on spectral quadrupole splittings suggested that there is greater peptide backbone flexibility for the wild-type transmembrane region.

Expression and membrane assembly of a transmembrane region from Neu

Transmembrane domains of receptor tyrosine kinases are increasingly seen as key modulatory elements in signaling pathways. The present work addresses problems surrounding expression, isolation, secondary structure recovery, and assembly into membranes, of the relatively large quantities of transmembrane peptides needed to investigate these pathways by NMR spectroscopy. We demonstrate significant correspondence between SDS-PAGE behavior of such peptides and their (2)H NMR spectra in lipid bilayer membranes. A 50-residue peptide, Neu(exp), containing the transmembrane portion of the receptor tyrosine kinase, Neu, was designed for expression in Escherichia coli. The sequence also contained 11-12 amino acids from each side of the transmembrane domain. The common problem of low expressivity of transmembrane peptides was encountered-likely associated with membrane toxicity of the desired gene product. This difficulty was overcome by expressing the peptide as a TrpE fusion protein in a pATH vector to target expression products to inclusion bodies, and subsequently removing the TrpE portion by cyanogen bromide cleavage. Inclusion bodies offered the additional benefits of reduced proteolytic degradation and simplified purification. The presence of a hexa-His tag allowed excellent recovery of the final peptide, while permitting use of denaturing solvents and avoiding the need for HPLC with its attendant adsorption losses. Isolated expressed peptides were found to be pure, but existed as high oligomers rich in beta-structure as evidenced by CD spectroscopy and SDS-PAGE behavior. Dissolution in certain acidic organic solvents led to material with increased alpha-helix content, which behaved in detergent as mixtures of predominantly monomers and dimers-a situation often considered to exist in cell membranes. For purposes of NMR spectroscopy, peptide alanine residues were deuterated in high yield during expression. The same acidic organic solvents used to dissolve and dissociate expressed transmembrane peptides proved invaluable for their assembly into lipid bilayers. Analogous transmembrane peptides from the human receptor tyrosine kinase, ErbB-2, demonstrated related phenomena.

Alloantigen-stimulated anti-HIV activity

A number of studies have suggested that an immune response to human leukocyte antigen (HLA) alloantigens may contribute to protection against HIV infection. In the present study, we examined the effect of alloantigen-stimulated cell lines obtained from peripheral blood mononuclear cells (PBMC) of HIV-uninfected (HIV-) individuals and the soluble factors produced by these cell lines on HIV-1 replication. Multiple in vitro restimulation with irradiated allogeneic PBMC from HIV- donors resulted in the expansion of CD8(+) T-cell lines that inhibited HIV-1 replication when cocultured with either autologous or heterologous in vitro-infected phytohemagglutinin (PHA) blasts. Supernatants from the alloantigen-stimulated cell lines also inhibited HIV replication in both PHA blasts and a chronically infected cell line. The alloantigen-stimulated cell lines and the factors they produced inhibited both T-cell-tropic (T) and macrophage-tropic (M) isolates of HIV-1. Blocking experiments using anti-chemokine antibodies suggested that this inhibition of HIV replication was not due to the beta-chemokines present in cocultures of cell lines with HIV-infected blasts. These results indicate that alloantigen-stimulation of PBMC from HIV- individuals activates CD8(+) T cells that produce soluble factor(s) that inhibit HIV replication of a wide spectrum of HIV-1 isolates through a chemokine-independent mechanism. This is a US government work. There are no restrictions on its use.

Anti-major histocompatibility complex antibody responses to simian B cells do not protect macaques against SIVmac infection

Macaques have been protected against infection with human cell-grown SIVmac by immunization with antigens encoded by the human major histocompatibility complex (MHC). Here, we investigated the efficacy of alloimmunization with simian B cells expressing high levels of MHC class I and class II molecules to confer protection against systemic challenge with simian-grown SIVmac. Eight rhesus macaques were vaccinated with glutaraldehyde-fixed and beta-propiolactone-inactivated herpesvirus papio-transformed B cells. Four of the macaques received 5 doses, the others 10. Animals were challenged with rhesus macaque spleen-derived cell-free SIVmac. Allogeneic B cells elicited antibody responses to rhesus MHC class I and II but failed to protect animals against infection. Anti-MHC class I antibodies were restricted in specificity and failed to recognize MHC class I from some B lymphoblastoid cell lines (B-LCLs) including a B-LCL from the animal in whose cells the challenge virus was grown. Vaccinated animals responded to self-MHC class I antigens but not to self-MHC class II antigens from peripheral blood mononuclear cells (PBMCs). Animals that underwent the shorter immunization regimen had transiently enhanced PBMC-associated virus loads after challenge, whereas the average virus-infected cell load was reduced in animals that underwent the more extensive immunization. These results suggest that antibody responses to allogeneic MHC molecules do not protect against infection with immunodeficiency lentiviruses.

Neutralization of a clade B primary isolate by sera from human immunodeficiency virus-uninfected recipients of candidate AIDS vaccines

The inability of antibodies induced by experimental human immunodeficiency virus type 1 (HIV-1) vaccines to neutralize HIV-1 primary isolates may be due to a failure to elicit such antibodies, antigenic differences between the vaccine and the strains tested, insensitivity of the assays used, or to a combination of factors. New neutralization assays were used to determine the ability of candidate AIDS vaccines to generate neutralizing antibodies for clade B primary isolate BZ167, which is closely related in portions of its envelope to the immunizing strains. Sera from HIV-uninfected volunteers in vaccine trials were tested, and neutralizing activity was found in recipients of recombinant (r) gp120MN or of rgp160MN-containing canarypox boosted with rgp120SF-2. Detection of antibodies that neutralize primary isolate BZ167 correlated with neutralizing activity for homologous vaccine strains. These data demonstrate that certain candidate AIDS vaccines can elicit antibodies that neutralize a primary isolate of HIV-1.

Dietary fat and asthma: is there a connection?

The last two decades have seen an increase in the prevalence of asthma, eczema, and allergic rhinitis in developed countries. This increase has been paralleled by a fall in the consumption of saturated fat and an increase in the amount of polyunsaturated fat in the diet. This is due to a reduction in the consumption of animal fat and an increase in the use of margarine and vegetable oils containing omega-6 polyunsaturated fatty acids (PUFAs), such as linoleic acid. There is also evidence for a decrease in the consumption of oily fish which contain omega-3 PUFAs, such as eicosapentaenoic acid. In a number of countries, there are social class and regional differences in the prevalence of allergic disease, which are associated with differences in the consumption of PUFAs. Linoleic acid is a precursor of arachidonic acid, which can be converted to prostaglandin E2 (PGE2), whereas eicosapentaenoic acid inhibits the formation of PGE2. PGE2 acts on T-lymphocytes to reduce the formation of interferon-gamma (IFN-gamma) without affecting the formation of interleukin-4 (IL-4). This may lead to the development of allergic sensitization, since IL-4 promotes the synthesis of immunoglobulin E (IgE), whereas IFN-gamma has the opposite effect. Changes in the diet may explain the increase in the prevalence of asthma, eczema and allergic rhinitis. The effects of diet may be mediated through an increase in the synthesis of prostaglandin E2 which in turn can promote the formation of immunoglobulin E.

A resting cell assay for improved detection of antibody-mediated neutralization of HIV type 1 primary isolates

The sensitivity with which antibody-mediated neutralization is detected in vitro is dependent on the virus, the antibody, the target cells, and the culture conditions used in the assay. Using activated and transformed target cells, the ability of various culture-adapted and primary strains of HIV-1 to be neutralized by different polyclonal and monoclonal antibody preparations has been thoroughly studied. However, the vast majority of HIV-1-susceptible CD4+ cells in vivo are not activated or transformed, but are quiescent. Because resting lymphocytes can be infected with HIV-1, we initiated studies to determine (1) if the use of resting lymphocytes as target cells would result in a neutralization assay with increased sensitivity, (2) if the degree of target cell activation had a measurable effect on the sensitivity with which antibody-mediated neutralization could be detected, and (3) whether, using a more sensitive assay, neutralizing antibodies in patients' sera might be detectable that had been below the threshold of detection when using "conventional" assays. The experiments described in the studies below reveal that an inverse relationship exists between the level of target cell activation and the sensitivity with which neutralization can be detected. Moreover, using an assay in which unstimulated peripheral blood mononuclear cells serve as target cells, experiments show that antibody-mediated neutralization of primary and prototype laboratory isolates of HIV-1 can be detected with 10- to 100-fold greater sensitivity than when stimulated peripheral blood mononuclear cells are used as target cells. With this resting cell assay, neutralizing activity can be detected in the sera of HIV-positive subjects that, by previously used "conventional" neutralization assays, was undetectable.

Repair and evolution of nef in vivo modulates simian immunodeficiency virus virulence

Experimental evidence from the simian immunodeficiency virus (SIV) model of AIDS has shown that the nef gene is critical in the pathogenesis of AIDS. Consequently, nef is of considerable interest in both antiviral drug and vaccine development. Preliminary findings in two rhesus macaques indicated that a deletion of only 12 bp found in the overlapping nef/3' long terminal repeat (LTR) region (9501 to 9512) of the SIVmacC8 molecular clone was associated with reduced virus isolation frequency. We show that this deletion can be repaired in vivo by a sequence duplication event and that sequence evolution continues until the predicted amino acid sequence of the repair is virtually indistinguishable from that of the virulent wild type. These changes occurred concomitantly with reversion to virulence, evidenced by a high virus isolation frequency and load, decline in anti-p27 antibody, substantial reduction in the CD4/CD8 ratio, and development of opportunistic infections associated with AIDS. These findings clearly illustrate the capacity for repair of small attenuating deletions in primate lentiviruses and also strongly suggest that the region from 9501 to 9512 in the SIV nef/3' LTR region is of biological relevance. In addition, the ability of attenuated virus to revert to virulence raises fundamental questions regarding the nature of superinfection immunity.

Antibodies to the HIV-1 V3 loop in serum from infected persons contribute a major proportion of immune effector functions including complement activation, antibody binding, and neutralization

Previous studies have shown that the V3 region of the HIV envelope is both critical to viral functions and immunogenic. However, the relative contribution of anti-V3 antibodies in the sera of infected individuals in mediating immune effector functions directed at whole intact virus and infected cells has not been determined. This study used peptides corresponding to several regions of the HIV envelope as inhibitors of antibody binding and antibody effector functions directed at virions and virus-infected cells in order to assess the relative importance of V3-specific antibodies in sera from infected persons. Approximately 40% of the antibody in serum which could bind to native viral proteins on HIVMN-infected cells was blocked by a peptide corresponding to the central 15 amino acids of the V3 loop. In contrast, little if any blocking of serum antibody binding was observed with peptides corresponding to flanking regions of HIVMN V3 or three regions of gp41. Since antiviral antibody can also activate immune effector functions, we determined whether peptides could block antibody-dependent activation of the complement system by HIV-infected cells or free virus. Surprisingly, the V3 loop peptide blocked 75-95% of complement activation on HIV-infected cells. While the V3 loop peptide also blocked a substantial portion of the neutralizing activity in serum from infected persons for free virus it was again more effective in inhibiting complement-mediated effects on free virus. Accordingly, antibody-dependent, complement-mediated virolysis was inhibited by 61-79%. The results of these experiments indicate that (1) a substantial portion (30-40%) of the antibody in sera from infected persons that is capable of binding to HIV-infected cells and HIV virions is V3-specific, and (2) these V3-specific antibodies are particularly important for complement activation on infected cells and virions. This indicates that the central portion of the V3 loop, while constituting less than 3% of the amino acid sequence of the HIV envelope, apparently provides a major gp160 site for immune effector functions, especially complement activation.