Staphylococcus aureus SigS Induces Expression of a Regulatory Protein Pair That Modulates Its mRNA Stability

SigS is the sole extracytoplasmic function sigma factor in Staphylococcus aureus and is necessary for virulence, immune evasion, and adaptation to toxic chemicals and environmental stressors. Despite the contribution of SigS to a myriad of critical phenotypes, the downstream effectors of SigS-dependent pathogenesis, immune evasion, and stress adaptation remain elusive. To address this knowledge gap, we analyzed the S. aureus transcriptome following transient overexpression of SigS. We identified a bicistronic transcript, upregulated 1,000-fold, containing two midsized genes, each containing single domains of unknown function (DUFs). We renamed these genes SigS-regulated orfA (sroA) and SigS-regulated orfB (sroB). We demonstrated that SigS regulation of the sroAB operon is direct by using in vitro transcription analysis. Using Northern blot analysis, we also demonstrated that SroA and SroB have opposing autoregulatory functions on the transcriptional architecture of the sigS locus, with SroA stimulating SigS mRNA levels and SroB stimulating s750 (SigS antisense) levels. We hypothesized that these opposing regulatory effects were due to a direct interaction. We subsequently demonstrated a direct interaction between SroA and SroB using an in vivo surrogate genetics approach via bacterial adenylate cyclase-based two-hybrid (BACTH) analysis. We demonstrated that the SroA effect on SigS is at the posttranscriptional level of mRNA stability, highlighting a mechanism likely used by S. aureus to tightly control SigS levels. Finally, we demonstrate that the sroAB locus promotes virulence in a murine pneumonia model of infection. IMPORTANCE SigS is necessary for S. aureus virulence, immune evasion, and adaptation to chemical and environmental stressors. These processes are critically important for the ability of S. aureus to cause disease. However, the SigS-dependent transcriptome has not been identified, hindering our ability to identify downstream effectors of SigS that contribute to these pathogenic and adaptive phenotypes. Here, we identify a regulatory protein pair that is a major direct target of SigS, known as SroA and SroB. SroA also acts to stimulate SigS expression at the posttranscriptional level of RNA turnover, providing insight into intrinsically low levels of SigS. The discovery of SroA and SroB increases our understanding of SigS and the S. aureus pathogenesis process.

Post-Transcriptional Regulation of RseA by Small RNAs RyhB and FnrS in Escherichia coli

RseA is the critical central regulator of the σ^E-dependent stress response in E. coli and other related bacteria. The synthesis of RseA is controlled at the transcriptional level by several promoters and transcriptional regulators, including σ^E itself at two σ^E-dependent promoters: rpoE_P and rseA_P3. The presence of these two independent polycistrons encoding rseA is potentially redundant. We hypothesized that post-transcriptional control of the rseA_P3 transcript was necessary to overcome this redundancy. However, to date, nothing is known about the post-transcriptional control of the rseA_P3 transcript. We executed a targeted genetic screen to identify small RNA regulators of the rseA_P3 transcript and identified RyhB and FnrS as small RNA activators of the RseA P3 transcript. Through genetic analysis, we confirmed that a direct interaction occurs between RyhB and RseA. We also identified sequences within the 5′ untranslated region (UTR) of RseA that were inhibitory for RseA expression. Point mutations predicted to prevent an interaction between RyhB and RseA resulted in increased RseA expression. Taken together, this suggests that the 5’ UTR of the RseAP3 transcript prevents optimal expression of RseA, preventing redundancy due to RseA expression from the σ^E-dependent rpoE_P, and this is overcome by the stimulatory activity of RyhB and FnrS.

The Yersinia pseudotuberculosis Cpx envelope stress system contributes to transcriptional activation of rovM

The Gram-negative enteropathogen Yersinia pseudotuberculosis possesses a number of regulatory systems that detect cell envelope damage caused by noxious extracytoplasmic stresses. The CpxA sensor kinase and CpxR response regulator two-component regulatory system is one such pathway. Active Cpx signalling upregulates various factors designed to repair and restore cell envelope integrity. Concomitantly, this pathway also down-regulates key determinants of virulence. In Yersinia, cpxA deletion accumulates high levels of phosphorylated CpxR (CpxR~P). Accumulated CpxR~P directly repressed rovA expression and this limited expression of virulence-associated processes. A second transcriptional regulator, RovM, also negatively regulates rovA expression in response to nutrient stress. Hence, this study aimed to determine if CpxR~P can influence rovA expression through control of RovM levels. We determined that the active CpxR~P isoform bound to the promoter of rovM and directly induced its expression, which naturally associated with a concurrent reduction in rovA expression. Site-directed mutagenesis of the CpxR~P binding sequence in the rovM promoter region desensitised rovM expression to CpxR~P. These data suggest that accumulated CpxR~P inversely manipulates the levels of two global transcriptional regulators, RovA and RovM, and this would be expected to have considerable influence on Yersinia pathophysiology and metabolism.

Ketamine interactions with gut-microbiota in rats: relevance to its antidepressant and anti-inflammatory properties

BACKGROUND

Appreciable evidence suggest that dysbiosis in microbiota, reflected in gut microbial imbalance plays a key role in the pathogenesis of neuropsychiatric disorders including depression and inflammatory diseases. Recently, the antidepressant properties of ketamine have gained prominence due to its fast and long lasting effects. Additional uses for ketamine in inflammatory disorders such as irritable bowel syndrome have been suggested. However, ketamine's exact mechanism of action and potential effects on microbiome is not known. Here, we examined the effects of low dose ketamine, known to induce antidepressant effects, on stool microbiome profile in adult male Wistar rats. Animals (5/group) were injected intraperitoneally with ketamine (2.5 mg/kg) or saline, daily for 7 days and sacrificed on day 8 when intestinal stools were collected and stored at - 80 °C. DNA was extracted from the samples and the 16 S rRNA gene-based microbiota analysis was performed using 16S Metagenomics application.

RESULTS

At genus-level, ketamine strikingly amplified Lactobacillus, Turicibacter and Sarcina by 3.3, 26 and 42 fold, respectively. Conversely, opportunistic pathogens Mucispirillum and Ruminococcus were reduced by approximately 2.6 and 26 fold, respectively, in ketamine group. Low levels of Lactobacillus and Turicibacter are associated with various disorders including depression and administration of certain species of Lactobacillus ameliorates depressive-like behavior in animal models. Hence, some of the antidepressant effects of ketamine might be mediated through its interaction with these gut bacteria. Additionally, high level of Ruminococcus is positively associated with the severity of irritable bowel syndrome (IBS), and some species of Mucispirillum have been associated with intestinal inflammation. Indirect evidence of anti-inflammatory role of Sarcina has been documented. Hence, some of the anti-inflammatory effects of ketamine and its usefulness in specific inflammatory diseases including IBS may be mediated through its interaction with these latter bacteria.

CONCLUSION

Our data suggest that at least some of the antidepressant and anti-inflammatory effects of daily ketamine treatment for 7 days may be mediated via its interaction with specific gut bacteria. These findings further validate the usefulness of microbiome as a target for therapeutic intervention and call for more detailed investigation of microbiome interaction with central mediators of mood and/or inflammatory disorders.

An essential Staphylococcus aureus cell division protein directly regulates FtsZ dynamics

Binary fission has been well studied in rod-shaped bacteria, but the mechanisms underlying cell division in spherical bacteria are poorly understood. Rod-shaped bacteria harbor regulatory proteins that place and remodel the division machinery during cytokinesis. In the spherical human pathogen Staphylococcus aureus, we found that the essential protein GpsB localizes to mid-cell during cell division and co-constricts with the division machinery. Depletion of GpsB arrested cell division and led to cell lysis, whereas overproduction of GpsB inhibited cell division and led to the formation of enlarged cells. We report that S. aureus GpsB, unlike other Firmicutes GpsB orthologs, directly interacts with the core divisome component FtsZ. GpsB bundles and organizes FtsZ filaments and also stimulates the GTPase activity of FtsZ. We propose that GpsB orchestrates the initial stabilization of the Z-ring at the onset of cell division and participates in the subsequent remodeling of the divisome during cytokinesis.

A bacterium called Staphylococcus aureus causes many infections in humans, especially in hospital patients with weakened immune systems. These infections are generally treated with drugs known as antibiotics that interact with specific proteins in the bacteria to kill the cells, or stop them from growing. However, some S. aureus infections are resistant to the antibiotics currently available so there is a need to develop new drugs that target different bacterial proteins.

Bacteria multiply by dividing to make identical copies of themselves. When a bacterium is preparing to divide, filaments made of a protein called FtsZ form a ring at the site where the cell will split. Many other proteins are involved in controlling how and when a cell divides. For example, several species of bacteria harbor a dispensable cell division protein called GpsB. In at least one organism, it helps to maintain the proper shape of the cell during cell division. In S. aureus, though, GpsB is essential for cells to survive and could therefore be a potential target for new antibiotics. However, its role in S. aureus has not been studied.

Eswara et al. have now used genetic and biochemical approaches to study the S. aureus form of the GpsB protein. The experiments show that GpsB moves to the middle of S. aureus cells just before they begin to divide and binds directly to FtsZ. This helps to secure the position of FtsZ across the middle of the cell and activates the protein so that the cell can begin to divide into two. In cells that produce too much GpsB, the FtsZ proteins become active too early, leading to the cells growing larger and larger until they burst.

The findings of Eswara et al. reveal that GpsB plays a different role in S. aureus cells than in some other species of bacteria. Further studies into such differences could help researchers to develop new antibiotics, as well as improving our understanding of why bacteria are so diverse.

RpoS-dependent sRNA RgsA regulates Fis and AcpP in Pseudomonas aeruginosa

RgsA is a phylogenetically conserved small regulatory RNA (sRNA) in Pseudomonas species. This sRNA has been shown to be directly controlled by the major stationary phase and stress sigma factor σ^S (RpoS), and also indirectly regulated by the GacS/GacA two-component system. However, the role and the regulatory targets of this sRNA remain unclear. Here, two direct regulatory targets of RgsA, the mRNAs coding for the global transcriptional regulator Fis and the acyl carrier protein AcpP, were identified in P. aeruginosa. RgsA downregulates the synthesis of Fis and AcpP by base-pairing, and this regulation requires the RNA chaperone protein Hfq. Alignment of RgsA homologs in Pseudomonas revealed a conserved core region, which is strictly required for RgsA target recognition. Specifically, RgsA inhibits fis expression via an 11 + 11 bp RNA duplex, whereas this interaction region is not sufficient for repression and the 35 nt downstream region is also required. Interestingly, two functional start codons initiate fis mRNA translation and both are repressed by RgsA. Furthermore, deletion of rgsA significantly increased swarming motility in P. aeruginosa. Together, this study suggests a novel regulatory role of sRNA in which the versatile transcriptional regulator Fis and the stress regulator RpoS are connected by RgsA.

The i6A37 tRNA modification is essential for proper decoding of UUX-Leucine codons during rpoS and iraP translation

The translation of rpoS(σ(S)), the general stress/stationary phase sigma factor, is tightly regulated at the post-transcriptional level by several factors via mechanisms that are not clearly defined. One of these factors is MiaA, the enzyme necessary for the first step in theN(6)-isopentyl-2-thiomethyl adenosinemethyl adenosine 37 (ms(2)i(6)A37) tRNA modification. We tested the hypothesis that an elevated UUX-Leucine/total leucine codon ratio can be used to identify transcripts whose translation would be sensitive to loss of the MiaA-dependent modification. We identified iraPas another candidate MiaA-sensitive gene, based on the UUX-Leucine/total leucine codon ratio. AniraP-lacZ fusion was significantly decreased in the abse nce of MiaA, consistent with our predictive model. To determine the role of MiaA in UUX-Leucine decoding in rpoS and iraP, we measured β-galactosidase-specific activity of miaA(-)rpo Sandira P translational fusions upon overexpression of leucine tRNAs. We observed suppression of the MiaA effect on rpoS, and notira P, via overexpression of tRNA(LeuX)but not tRNA(LeuZ) We also tested the hypothesis that the MiaA requirement for rpoS and iraP translation is due to decoding of UUX-Leucine codons within the rpoS and iraP transcripts, respectively. We observed a partial suppression of the MiaA requirement for rpoS and iraP translational fusions containing one or both UUX-Leucine codons removed. Taken together, this suggests that MiaA is necessary for rpoS and iraP translation through proper decoding of UUX-Leucine codons and that rpoS and iraP mRNAs are both modification tunable transcripts (MoTTs) via the presence of the modification.

Environmental Regulation of Yersinia Pathophysiology

Hallmarks of Yersinia pathogenesis include the ability to form biofilms on surfaces, the ability to establish close contact with eukaryotic target cells and the ability to hijack eukaryotic cell signaling and take over control of strategic cellular processes. Many of these virulence traits are already well-described. However, of equal importance is knowledge of both confined and global regulatory networks that collaborate together to dictate spatial and temporal control of virulence gene expression. This review has the purpose to incorporate historical observations with new discoveries to provide molecular insight into how some of these regulatory mechanisms respond rapidly to environmental flux to govern tight control of virulence gene expression by pathogenic Yersinia.

Prevention Across the Spectrum: a randomized controlled trial of three programs to reduce risk factors for both eating disorders and obesity

BACKGROUND

A randomized controlled trial of three school-based programs and a no-intervention control group was conducted to evaluate their efficacy in reducing eating disorder and obesity risk factors.

METHOD

A total of 1316 grade 7 and 8 girls and boys (mean age = 13.21 years) across three Australian states were randomly allocated to: Media Smart; Life Smart; the Helping, Encouraging, Listening and Protecting Peers (HELPP) initiative; or control (usual school class). Risk factors were measured at baseline, post-program (5 weeks later), and at the 6- and 12-month follow-ups.

RESULTS

Media Smart girls had half the rate of onset of clinically significant concerns about shape and weight than control girls at the 12-month follow-up. Media Smart and HELPP girls reported significantly lower weight and shape concern than Life Smart girls at the 12-month follow-up. Media Smart and control girls scored significantly lower than HELPP girls on eating concerns and perceived pressure at the 6-month follow-up. Media Smart and HELPP boys experienced significant benefit on media internalization compared with control boys and these were sustained at the 12-month follow-up in Media Smart boys. A group × time effect found that Media Smart participants reported more physical activity than control and HELPP participants at the 6-month follow-up, while a main effect for group found Media Smart participants reported less screen time than controls.

CONCLUSIONS

Media Smart was the only program to show benefit on both disordered eating and obesity risk factors. Whilst further investigations are indicated, this study suggests that this program is a promising approach to reducing risk factors for both problems.

Discovery and development of therapeutic aptamers

Therapeutic aptamers are single-stranded structured oligonucleotides that bind to protein targets with high affinity and specificity and modulate protein function. Aptamers are discovered by iterative rounds of selection for binding to the target protein, partitioning, and amplification of binding clones from a diverse starting library (SELEX). Postselection optimization of clones using chemical modification is directed at improving affinity, potency, and metabolic stability. A key attribute of therapeutic aptamers is the ability to tailor the pharmacokinetic profile by modulating the degree of metabolic stability and modulating renal clearance and rate of distribution by conjugation to various sizes of polyethylene glycol (PEG). In toxicology studies, therapeutic aptamers have been largely devoid of the previously reported oligonucleotide class effects of immune stimulation, complement activation, and anticoagulation; and the principal finding is the histologically visible accumulation of drug-related material in mononuclear phagocytes, a finding generally not considered an adverse effect. Good safety margins between the pharmacologically effective dose and toxicologically established no-adverse-effect levels have been observed consistently. There are presently seven aptamers either on the market or in clinical trials, but there is still much to be demonstrated in terms of chronic systemic use to fully realize the potential of this promising new class of drugs.

Staphylococcus aureus extracellular adherence protein contributes to biofilm formation in the presence of serum

Staphylococcus aureus extracellular adherence protein (EAP) is secreted, but it can redock on the bacterial cell surface via neutral phosphatase (Nptase). EAP binds to certain blood proteins and to itself, and through these affinities, it contributes to adherence and aggregation. It has been demonstrated previously that EAP expression is iron regulated and it contributes to biofilm formation under iron-deplete conditions. In this study, we found that EAP and Nptase also play a role in biofilm formation under iron-replete conditions in the presence of human serum.

Analysis of CD4+ T-cell gene expression in allergic subjects using two different microarray platforms

BACKGROUND

Allergic diseases are thought to involve dysregulated activation of T cells including CD4+ lymphocytes. T-cell activation results in changes in gene expression, but the optimal method to study gene expression profiles in T cells, and how this changes over time, are not known.

METHODS

Circulating CD4+ T cells were obtained from subjects with atopic asthma, nonatopic asthma or nonallergic controls, and total mRNA was rapidly isolated. Atopy was defined as positive skin prick test to one of nine allergens. Gene expression was analyzed using hybridization and Affymetrix oligonucleotide arrays (Hu133A and Hu133B chips, n = 84), or by reverse transcription-polymerase chain reaction (RT-PCR) with a pathway-targeted array (Human Th1-Th2-Th3 RT(2) Profiler PCR Array, Superarray, n = 16).

RESULTS

Using Affymetrix arrays, it was difficult to discern a dominant allergy-associated profile because of heterogeneity in gene expression profiles. In contrast, a Th2-like signature was evident using RT-PCR arrays with increased expression of expected genes (e.g. IL-4, 5, 9, and 13, all P < 0.05) as well as unexpected gene transcripts (e.g. osteopontin). Gene expression profiles were relatively stable over time in circulating CD4+ T cells from two subjects using both platforms.

CONCLUSIONS

Unstimulated CD4+ T cells isolated from allergic subjects express a characteristic profile of genes when analyzed using RT-PCR based microarrays.

T cells from multiple sclerosis patients recognize multiple epitopes on Self-IgG

The highly diversified variable regions of immunoglobulin (Ig) molecules contain immunogenic determinants denoted idiotopes. We have previously reported that T cells from multiple sclerosis (MS) patients recognize IgG from autologous cerebrospinal fluid (CSF), and mapped a T-cell epitope to an IgG idiotope. To test the ability of CSF IgG molecules to elicit a broad polyclonal T-cell response in MS, we have analysed T-cell responses in the blood and CSF against idiotope peptides spanning complementarity determining region (CDR) 3 and somatic mutations within the variable regions of monoclonal CSF IgG. Consistent with a diversified idiotope-specific T-cell repertoire, CD4(+) T cells from both patients recognized several idiotope peptides presented by HLA-DR molecules. Mutations were critical for T-cell recognition, as T cells specific for a mutated CDR1 peptide did not recognize corresponding germline-encoded peptides. One T-cell clone recognized both an idiotope peptide and the B-cell clone expressing this idiotope, compatible with endogenous processing and presentation of this idiotope by B cells. These results suggest that mutated CSF IgG from MS patients carry several T-cell epitopes, which could mediate intrathecal IgG production and inflammation in MS through idiotope-driven T-B-cell collaboration.

SigmaE regulates and is regulated by a small RNA in Escherichia coli

RybB is a small, Hfq-binding noncoding RNA originally identified in a screen of conserved intergenic regions in Escherichia coli. Fusions of the rybB promoter to lacZ were used to screen plasmid genomic libraries and genomic transposon mutants for regulators of rybB expression. A number of plasmids, including some carrying rybB, negatively regulated the fusion. An insertion in the rep helicase and one upstream of dnaK decreased expression of the fusion. Multicopy suppressors of these insertions led to identification of two plasmids that stimulated the fusion. One contained the gene for the response regulator OmpR; the second contained mipA, encoding a murein hydrolase. The involvement of MipA and OmpR in cell surface synthesis suggested that the rybB promoter might be dependent on sigma(E). The sequence upstream of the +1 of rybB contains a consensus sigma(E) promoter. The activity of rybB-lacZ was increased in cells lacking the RseA anti-sigma factor and when sigma(E) was overproduced from a heterologous promoter. The activity of rybB-lacZ and the detection of RybB were totally abolished in an rpoE-null strain. In vitro, sigma(E) efficiently transcribes from this promoter. Both a rybB mutation and an hfq mutation significantly increased expression of both rybB-lacZ and rpoE-lacZ fusions, consistent with negative regulation of the sigma(E) response by RybB and other small RNAs. Based on the plasmid screens, NsrR, a repressor sensitive to nitric oxide, was also found to negatively regulate sigma(E)-dependent promoters in an RseA-independent fashion.

Species and response dependent differences in the effects of MAPK inhibitors on P2X(7) receptor function

BACKGROUND

Recent studies have implicated the mitogen activated protein kinase (MAPK) in cellular permeability changes following P2X(7) receptor activation in native tissues. In this study we have further studied the effect of MAPK inhibitors on recombinant and native P2X(7) receptors.

EXPERIMENTAL APPROACH

The MAPK inhibitors SB-203580, SB-202190 and SB-242235 were examined in HEK293 cells expressing recombinant P2X(7) receptors and in THP-1 cells expressing native human P2X(7) receptors using a range of experimental approaches.

KEY RESULTS

At human recombinant P2X(7) receptors, SB-203580 and SB-202190 were weak, non-competitive inhibitors (pIC(50)= 4.8 - 6.4) of ethidium accumulation stimulated by 2'- & 3'-O-(4benzoylbenzoyl)-ATP (BzATP) but SB-242235 (0.1-10 microM) had no effect. SB-203580 and SB-202190 had no effect on rat or mouse recombinant P2X(7) receptors and studies with chimeric P2X(7) receptors suggested that SB-203580 was only effective in chimeras containing the N-terminal 255aa of the human P2X(7) receptor. SB-203580 did not consistently affect BzATP-mediated increases in cell calcium levels and, in electrophysiological studies, it slightly decreased responses to 30 microM BzATP but potentiated responses to 100 microM BzATP. In THP1 cells, SB-203580 modestly inhibited BzATP-stimulated ethidium accumulation (pIC(50) 5.7 - < 5) but SB-202190 had no effect. Finally, SB-203580 did not block BzATP-stimulated interleukin-1beta release in THP-1 cells.

CONCLUSIONS

This study confirms that high concentrations of SB-203580 and SB-202190 can block human P2X(7) receptor-mediated increases in cellular ethidium accumulation but suggest this is not related to MAPK inhibition. Overall, the data cast doubt on a general role of MAPK in mediating P2X(7) receptor mediated changes in cellular permeability.

Otago Diagnostic Laboratories' (ODL) Method for the detection of beta-lactamases in Enterobacteriaceae

AIM

The rapid evolvement of beta-lactamases in Enterobacteriaceae is an important concern and the clinical microbiology laboratory is required to detect them, where possible, using a rapid, reliable, simple and low cost methodology.

MATERIALS AND METHODS

A disc diffusion method using NCCLS breakpoints, Jarlier's principle and cefoxitin test for AmpC was carried out. It incorporated seven antimicrobial discs in one agar plate: cefotaxime, aztreonam, amoxicillin-clavulanate, ceftazidime, cefpodoxime, cefepime and cefoxitin. NCCLS disc confirmation test for extended-spectrum beta-lactamase (ESBL) was carried out simultaneously.

RESULTS

AmpC, ESBL, CTX-M, and K1 were detected using these tests. The prevalence of ESBL was <1% in the hospital.

CONCLUSION

The method is recommended for the phenotypic detection of beta-lactamases in Enterobacteriaceae or for confirmation after the results are obtained by conventional automated systems.

Netrin receptor deficient mice exhibit functional reorganization of dopaminergic systems and do not sensitize to amphetamine

Netrins are guidance cues that play a fundamental role in organizing the developing brain. The netrin receptor, DCC (deleted in colorectal cancer), is highly expressed by dopaminergic (DA) neurons. DCC may therefore participate in the organization of DA circuitry during development and also influence DA function in the adult. Here we show that adult dcc heterozygous mice exhibit a blunted behavioral response to the indirect DA agonist amphetamine and do not develop sensitization to its effects when treated repeatedly. These behavioral alterations are associated with profound changes in DA function. In the medial prefrontal cortex, dcc heterozygotes exhibit increased tyrosine hydroxylase (TH) protein levels and dramatic increases in basal concentrations of DA and DA metabolites. In contrast, in the nucleus accumbens, dcc heterozygotes show no changes in either TH or DA levels, but exhibit decreased concentrations of DA metabolites, suggesting reduced DA activity. In addition, dcc heterozygous mice exhibit a small, but significant reduction in total number of TH-positive neurons in midbrain DA cell body regions. These results demonstrate for the first time that alterations in dcc expression lead to selective changes in DA function and, in turn, to differences in DA-related behaviors in adulthood. These findings raise the possibility that changes in dcc function early in life are implicated in the development of DA dysregulation observed in certain psychiatric disorders, such as schizophrenia, or following chronic use of drugs of abuse.

Receptor protein tyrosine phosphatase sigma inhibits axonal regeneration and the rate of axon extension

Transgenic mice lacking receptor protein tyrosine phophatase-sigma (RPTPsigma), a type IIa receptor protein tyrosine phosphatase, exhibit severe neural developmental deficits. Continued expression of RPTPsigma in the adult suggests that it plays a functional role in the mature nervous system. To determine if RPTPsigma might influence axonal regeneration, the time course of regeneration following facial nerve crush in wild-type and RPTPsigma (-/-) mice was compared. Mice lacking RPTPsigma exhibited an accelerated rate of functional recovery. Immunocytochemical examination of wild-type neurons in cell culture showed RPTPsigma protein in the growth cone. To determine if RPTPsigma affects the ability of a neuron to extend an axon, the rate of axon growth in neuronal cultures derived from wild-type and RPTPsigma (-/-) embryonic mice was compared. RPTPsigma did not affect the rate of axon initiation, but the rate of axon extension is enhanced in neurons obtained from RPTPsigma (-/-) mice. These findings indicate that RPTPsigma slows axon growth via a mechanism intrinsic to the neuron and identify a role for RPTPsigma regulating axonal regeneration by motoneurons.

Cross-reaction of anti-simian immunodeficiency virus envelope protein antibodies with human immunoglobulins

It has been recently established that retroviral envelope proteins (REPs) have structural features similar to those of immunoglobulins (Igs). In this study, we asked whether anti-REP antibodies cross-react with human Igs (hIgs). To this end, murine monoclonal antibodies (mMoAbs) that had been raised against a simian immunodeficiency virus (SIV) envelope protein, SIVMac251gp120, were screened for their ability to react with human monoclonal Igs (HMIgs). We show that two HMIgs, RFSJ2 (a rheumatoid factor) and PAMLN6 (a human anti-hIg V region antibody), but not a number of other HMIgs, could be weakly, but consistently, bound by anti-SIVMac251gp120 mMoAbs KK17 and KK46, as judged by indirect enzyme-linked immunosorbent assay and a liquid-phase inhibition immunoassay. Both mMoAbs are specific to amino acid residues in the V3 loop of the SIVMac251gp120. The RFSJ2 Ig heavy-chain V region (VH) is coded in part by a human VH gene, VH3-30.3 and includes the idiotope 7B4 (NKYY), which was previously shown to be present in the gp120 protein of a number of HIV-2 and SIV strains. However, an entirely different VH gene codes the PAMLN6 VH region, opening the possibility that epitope(s) shared between SIVMac251gp120 and hIgs may not be limited to the 7B4 idiotope.

The chemokines CCL5, CCL2 and CXCL12 play significant roles in the migration of Th1 cells into rheumatoid synovial tissue

As the T-cell population in the synovial tissue (ST) in rheumatoid arthritis (RA) is dominated by T helper (Th) 1 cells, this study was designed to examine whether there is a preferential migration of polarized T cells to ST, and to identify the chemokines responsible for the migration. This was done by developing 10 T-cell clones specific for an arbitrary antigen (mouse immunoglobulin G (IgG)) from the peripheral blood (PB) of a healthy donor sensitized to mouse IgG. The Th polarizations of the clones were determined by measuring secreted interferon-gamma and interleukin-4, following anti-CD3 stimulation. Migration to pools of RA ST cell-derived supernatants was analysed. Expression of the chemokine receptors CCR1, CCR2, CCR3, CCR4, CCR5, CCR6, CCR7, CCR8, CXCR3 and CXCR4 were analysed by flow cytometry. Th1 clones showed significantly higher migration to RA ST cell-derived supernatant compared with Th2 clones. Blocking of either of the chemokines, CCL5 or CCL2, strongly inhibited migration of the Th1 cells between 56 and 77%, while blocking of CXCL12 inhibited migration between 44 and 61%. Blocking of CXCL10 had only a minor inhibitory effect. Our results demonstrate a selective migration of Th1 cells to RA ST supernatant and that blocking either CCL5, CCL2 or CXCL12 significantly inhibits T-cell migration. This indicates that CCL5, CCL2 and CXCL12 play significant roles in attracting Th1 cells towards the RA ST, and may prove potent targets for obstructing T-cell migration to the synovium.

Clonal analysis of a human antimouse antibody (HAMA) response

Circulating human antimouse antibodies (HAMAs) directed to mouse immunoglobulin G (IgG) are clinically significant, compromising mouse antibody therapy and imaging, and interfering in immunological assays. To investigate the HAMA response, 20 stable cell lines secreting human monoclonal antibodies reactive with mouse IgG were established from a donor with a history of exposure to mice. Their subclass and domain specificities were established by solid-phase binding, indirect haemagglutination assays and immunoblotting, using Igs of known subclass and Ig fragments. The heavy-chain variable region gene usage was determined for 12 HAMAs. Eight HAMAs were IgM, 11 HAMAs were IgG4 and one HAMA was IgG1, indicating an IgG4-dominated response. All of the IgG HAMAs reacted with epitopes present on the Fc portion; one was subclass-specific, nine were subclass-restricted and two were pan-IgG-reactive. Measurement of their affinities gave dissociation constants typically in the nanomolar range. Seven and five HAMAs were derived from variable heavy-chain 3 (VH3) and VH1 gene segments, respectively. The IgG HAMAs used different VH segments to the IgM HAMAs. JH regions were coded by JH4 in eight HAMAs. DH segment usage appeared to be restricted in the IgM HAMAs. Two IgG HAMAs were clonally related. These monoclonal HAMAs are potentially useful as reagents for detecting mouse IgG and as reference reagents for the investigation of the HAMA response in patients undergoing mouse monoclonal antibody therapy and for the investigation of the influence of HAMAs on immunodiagnostic tests.

Troybodies and pepbodies

All antibodies (Abs) with effector function are produced in mammalian cells, whereas bacterial production is restricted to smaller targeting fragments (scFv and Fab) without effector functions. In this project, we isolated different peptides that bind one of several Ab effector molecules. We have developed bacterial expression vectors for direct cloning of these peptides as fusions to scFv and Fab, and have obtained targeting fragments that also have the ability to bind Ab effector molecules. Some of these fusions (pepbodies) may also initiate Ab effector functions. We have also genetically inserted T-cell epitopes into Abs with specificity for antigen-presenting cell (APC) surface molecules to target the Ab-T-cell epitope fusions (Troybodies) to APCs. The approach is to exchange loops in Ig constant domains with single copies of well-defined T-cell epitopes. We have shown that a number of such T-cell epitopes are loaded on to MHC class II on APCs and are presented to specific T-cells. An increase in T-cell activation of up to four orders of magnitude is achieved compared with synthetic peptide. Our current goal is to identify all the loops in all Ig constant domains that may be loaded with T-cell epitopes to produce a multi-vaccine.

Anoxia induces thermotolerance in the locust flight system

Heat shock and anoxia are environmental stresses that are known to trigger similar cellular responses. In this study, we used the locust to examine stress cross-tolerance by investigating the consequences of a prior anoxic stress on the effects of a subsequent high-temperature stress. Anoxic stress and heat shock induced thermotolerance by increasing the ability of intact locusts to survive normally lethal temperatures. To determine whether induced thermotolerance observed in the intact animal was correlated with electrophysiological changes, we measured whole-cell K+ currents and action potentials from locust neurons. K+ currents recorded from thoracic neuron somata were reduced after anoxic stress and decreased with increases in temperature. Prior anoxic stress and heat shock increased the upper temperature limit for generation of an action potential during a subsequent heat stress. Although anoxia induced thermotolerance in the locust flight system, a prior heat shock did not protect locusts from a subsequent anoxic stress. To determine whether changes in bioenergetic status were implicated in whole-animal cross-tolerance, phosphagen levels and rates of mitochondrial respiration were assayed. Heat shock alone had no effect on bioenergetic status. Prior heat shock allowed rapid recovery after normally lethal heat stress but afforded no protection after a subsequent anoxic stress. Heat shock also afforded no protection against disruption of bioenergetic status after a subsequent exercise stress. These metabolite studies are consistent with the electrophysiological data that demonstrate that a prior exposure to anoxia can have protective effects against high-temperature stress but that heat shock does not induce tolerance to anoxia.

Association of antigen specificity and migratory capacity of memory T cells in rheumatoid arthritis

Among the T cell pool of multiple specificities in the rheumatoid synovial tissues (ST) we have previously shown a lack of proliferative response of T cells to Acanthamoeba polyphaga [1]. In contrast, peripheral blood (PB) derived T cells proliferate to the antigen. The aim of the present study was to establish whether there is a preferential migration of some T cell specificities to the joint in rheumatoid arthritis (RA) patients dependent on the chemokine system, and to identify which chemokine receptors are involved in the migratory process. For this purpose, PB-derived T cell lines and clones from RA patients specific for A. polyphaga, herpes simplex virus (HSV) and Campylobacter jejuni were developed. Their migratory capacities towards ST-derived chemokine supernatants were analysed. Expression of CCR1, CCR2, CCR5, CCR6, CCR7, CXCR3 and CXCR4 were analysed by FACS, and attracting chemokines were identified by blocking studies. We found that the migratory capacities of T cells specific for C. jejuni and HSV were markedly higher against synovial chemokines than T cells specific for A. polyphaga. CCR5 and CXCR3 were expressed by all high-migrating T cell lines and clones. CCR2 was expressed at higher levels on the high-migrating T cell lines compared with the low-migrating A. polyphaga lines. Neutralization of RANTES (regulated upon activation normal T cell expressed and secreted) in the ST cell-derived supernatant reduced T cell migration of all T cell lines and clones by 60-90%, while neutralization of MCP-1 reduced the migratory capacity of CCR2-expressing T cells by 45-80%. In conclusion, the ability of T cells to migrate towards chemokines produced by ST cells is associated with the T cell specificity. Blocking of single chemokines substantially reduced the migratory capacity of memory T cells to ST cell-derived supernatant indicating unique roles for each chemokine receptor in the process of T cell migration.

Eating disturbance and sexual trauma in childhood and adulthood

OBJECTIVE

This study examined the relationship between sexual trauma and eating disorder behavior, taking into account the effects of developmental stage of the victim and the effects of multiple sexual assaults.

METHOD

Four groups of adult women took part in this study. Subjects were either victims of childhood sexual abuse, victims of rape in adulthood, victims of both childhood sexual abuse and rape, and controls who were not traumatized sexually. All subjects were assessed with semistructured interviews and self-report inventories that assessed eating disorder behavior, general psychopathology, and impulsivity.

RESULTS

Victims of childhood sexual abuse differed from controls on measures of eating disorder behavior and individuals who had experienced both childhood sexual abuse and rape in adulthood were most likely to display eating disorder-related psychopathology. Victims of childhood sexual abuse also distinguished themselves with high levels of eating disorder behavior plus multiple forms of impulsive self-destructive behavior.

DISCUSSION

This study provides additional support for the association between childhood sexual abuse and eating disorder behavior. Childhood sexual abuse may be particularly linked to the presence of binge eating behavior and several other forms of impulsive self-destructive behavior.

The risk of groundling fatalities from unintentional airplane crashes

The crashes of four hijacked commercial planes on September 11, 2001, and the repeated televised images of the consequent collapse of the World Trade Center and one side of the Pentagon will inevitably change people's perceptions of the mortality risks to people on the ground from crashing airplanes. Goldstein and colleagues were the first to quantify the risk for Americans of being killed on the ground from a crashing airplane for unintentional events, providing average point estimates of 6 in a hundred million for annual risk and 4.2 in a million for lifetime risk. They noted that the lifetime risk result exceeded the commonly used risk management threshold of 1 in a million, and suggested that the risk to "groundlings" could be a useful risk communication tool because (a) it is a man-made risk (b) arising from economic activities (c) from which the victims derive no benefit and (d) exposure to which the victims cannot control. Their results have been used in risk communication. This analysis provides updated estimates of groundling fatality risks from unintentional crashes using more recent data and a geographical information system approach to modeling the population around airports. The results suggest that the average annual risk is now 1.2 in a hundred million and the lifetime risk is now 9 in ten million (below the risk management threshold). Analysis of the variability and uncertainty of this estimate, however, suggests that the exposure to groundling fatality risk varies by about a factor of approximately 100 in the spatial dimension of distance to an airport, with the risk declining rapidly outside the first 2 miles around an airport. We believe that the risk to groundlings from crashing airplanes is more useful in the context of risk communication when information about variability and uncertainty in the risk estimates is characterized, but we suspect that recent events will alter its utility in risk communication.

Bm1-Bm5 classification of peripheral blood B cells reveals circulating germinal center founder cells in healthy individuals and disturbance in the B cell subpopulations in patients with primary Sjögren's syndrome

Analyses of B cells in the bone marrow and secondary lymphoid tissues have revealed a broad range of cell surface markers defining B cell subpopulations, but only a few of these have been used to analyze B cell subpopulations in peripheral blood (PB). We report here the delineation of circulating PB B cell subpopulations by staining for CD19, CD38, and IgD in combination with CD10, CD44, CD77, CD95, CD23, IgM, and the B cell memory marker CD27. The utility of this approach is shown by the demonstration of disturbances of circulating B cell subpopulations in patients with autoimmune disease. Five mature B cell (Bm) subpopulations were identified in normal PB that were comparable with the tonsillar Bm1, Bm2, early Bm5, Bm5 subpopulations and, surprisingly, to the germinal center (GC) founder cell subpopulation (Bm2' and Bm3delta-4delta), suggesting that some GC founder cells are circulating. No PB B cells resembled the Bm3 and Bm4 GC cells. Remarkably, some cells with the CD38-IgD+ phenotype, previously known as naive Bm1 cells, expressed CD27. The CD38-IgD+ subpopulation therefore includes both naive Bm1 cells and IgD+ memory B cells. This new classification of B cell developmental stages reveals disturbances in the proportions of B cell subpopulations in primary Sjögren's syndrome (pSS) patients compared with healthy donors and rheumatoid arthritis patients. Patients with pSS contained a significantly higher percentage of B cells in two activated stages, which might reflect a disturbance in B cell trafficking and/or alteration in B cell differentiation. These findings could be of diagnostic significance for pSS.

T-cell responses to viral, bacterial and protozoan antigens in rheumatoid inflammation. Selective migration of T cells to synovial tissue

OBJECTIVE

To identify any preferential or selective migration of T-cell specificities to inflamed tissues of rheumatoid arthritis (RA) patients.

METHODS

Lymphocytes from peripheral blood (PB) and synovial tissue (ST) were isolated from RA patients and stimulated with a panel of crude antigen preparations from 18 bacterial, protozoan and viral sources. Proliferative responses of the T lymphocytes to each antigen and group of antigens were compared in PB and ST. Antigen-specific T-cell clones were developed and their migratory capacities towards synovial chemokines were compared.

RESULTS

ST-derived T cells showed a small but significantly higher stimulation index (SI) to the group of intestinal bacteria compared with PB T cells. Conversely, responses of ST-derived T cells to Acanthamoeba polyphaga (AP) were both profoundly and significantly lower compared with PB-derived T cells. The viral antigens as a whole gave comparable reactivities in blood and ST. The migratory capacity of AP-specific T-cell clones towards chemokines produced by ST was profoundly poorer compared with Campylobacter jejuni- and herpes simplex virus-specific T-cell clones.

CONCLUSIONS

The results indicate a selective migration of T cells of given specificities to the inflamed rheumatoid synovium.

Significantly depressed percentage of CD27+ (memory) B cells among peripheral blood B cells in patients with primary Sjögren's syndrome

CD27 has been found to be expressed on somatically mutated B cells and is thus a positive marker for memory B cells in peripheral blood (PB). Since abnormal immunogloblin (Ig) production is characteristic of the autoimmune diseases primary Sjögren's syndrome (pSS) and rheumatoid arthritis (RA), we have analyzed in detail the CD27 expression on PB B cell from these patient groups. Staining of PB B cells with monoclonal antibodies (MoAb) specific for CD19 and CD27 revealed a significantly depressed percentage of CD27+ PB B cells in patients with pSS (14.8 +/- 1.6%) compared to both healthy donors (31.3 +/- 4.7%, P = 0.005) and patients with RA (40.8 +/- 4.1%, P = 0.0001). In addition, the percentages of both the IgD+CD27+ and the IgD-CD27+ B-cell subpopulations were significantly lower in pSS patients compared to RA patients and healthy donors. However, the relative proportion of IgD- and IgD+ cells among the CD27+B cells were almost the same for the three groups. Our data suggest a disturbance in the differentiation of peripheral B cells and possibly a bias towards plasma cell differentiation, resulting in a depressed percentage of CD27+ memory PB B cells in pSS. These results are potentially of pathological significance and of diagnostic value.

A dynamic programming approach to the efficient design of clinical trials

If the prospective evaluation of all feasible strategies of patient management is not possible or efficient then this poses a number of questions: (i) which clinical decision problems will be worth evaluating through prospective clinical research; (ii) if a clinical decision problem is worth evaluating which of the many competing alternatives should be considered "relevant" and be compared in the evaluation; (iii) what is the optimal (technically efficient) scale of this prospective research; (iv) what is an optimal allocation of trial entrants between the competing alternatives; and (v) what is the value of this proposed research? The purpose of this paper is to present a Bayesian decision theoretic approach to the value of information which can provide answers to each of these questions. An analysis of the value of sample information was combined with dynamic programming and applied to numerical examples of sequential decision problems. The analysis demonstrates that this approach can be used to establish: optimal sample size; optimal sample allocation; and the societal payoff to proposed research. This approach provides a consistent way to identify which of the competing alternatives can be regarded as "relevant" and should be included in any evaluative study design. Bayesian decision theory can provide a general methodological framework that can ensure consistency in decision making between service provision, research and development, and the design, conduct and interpretation clinical research.

An assessment of the recidivism rates of substantiated and unsubstantiated maltreatment cases

OBJECTIVE

This study assembles information about the large number of maltreatment reports that are determined by social services to be unsubstantiated. Specifically, we assess whether the status of a maltreatment case (substantiated vs. unsubstantiated) has implications for recidivism. Recidivism rates for substantiated and unsubstantiated maltreated juveniles were also compared to juvenile offenders.

METHOD

Juvenile court records for 15,812 juveniles were assessed over a 3 year period. The data included 2558 maltreatment cases. Fifty-four percent of these cases were unsubstantiated. Logistic regression analysis was employed to assess the probability of recidivism based on time one referral status.

RESULTS

Youth whose maltreatment allegations were unsubstantiated had significantly lower odds of recidivating than abused youth. Having a case recorded as unsubstantiated lowered a youth's odds of subsequent offending by 55% relative to being abused. The probability of recidivating was highest for juvenile offenders, followed in order by maltreated youth and youth whose reports were unsubstantiated.

DISCUSSION

This is one of the first studies to examine the court histories of substantiated and unsubstantiated maltreatment cases. If the subsequent outcomes following maltreatment investigations are used as an indicator of seriousness, our results suggest that assessment caseworkers are successfully sorting out the serious from the less serious cases.

Violence in E-rated video games

CONTEXT

Children's exposure to violence, alcohol, tobacco and other substances, and sexual messages in the media are a source of public health concern; however, content in video games commonly played by children has not been quantified.

OBJECTIVES

To quantify and characterize the depiction of violence, alcohol, tobacco and other substances, and sex in video games rated E (for "Everyone"), analogous to the G rating of films, which suggests suitability for all audiences.

DESIGN

We created a database of all existing E-rated video games available for rent or sale in the United States by April 1, 2001, to identify the distribution of games by genre and to characterize the distribution of content descriptors associated with these games. We played and assessed the content of a convenience sample of 55 E-rated video games released for major home video game consoles between 1985 and 2000.

MAIN OUTCOME MEASURES

Game genre; duration of violence; number of fatalities; types of weapons used; whether injuring characters or destroying objects is rewarded or is required to advance in the game; depiction of alcohol, tobacco and other substances; and sexual content.

RESULTS

Based on analysis of the 672 current E-rated video games played on home consoles, 77% were in sports, racing, or action genres and 57% did not receive any content descriptors. We found that 35 of the 55 games we played (64%) involved intentional violence for an average of 30.7% of game play (range, 1.5%-91.2%), and we noted significant differences in the amount of violence among game genres. Injuring characters was rewarded or required for advancement in 33 games (60%). The presence of any content descriptor for violence (n = 23 games) was significantly correlated with the presence of intentional violence in the game (at a 5% significance level based on a 2-sided Wilcoxon rank-sum test, t(53) = 2.59). Notably, 14 of 32 games (44%) that did not receive a content descriptor for violence contained acts of violence. Action and shooting games led to the largest numbers of deaths from violent acts, and we found a significant correlation between the proportion of violent game play and the number of deaths per minute of play. We noted potentially objectionable sexual content in 2 games and the presence of alcohol in 1 game.

CONCLUSIONS

Content analysis suggests a significant amount of violence in some E-rated video games. The content descriptors provide some information to parents and should be used along with the rating, but the game's genre also appears to play a role in the amount of violent play. Physicians and parents should understand that popular E-rated video games may be a source of exposure to violence and other unexpected content for children and that games may reward the players for violent actions.

Estimation of tuberculosis risk and incidence under upper room ultraviolet germicidal irradiation in a waiting room in a hypothetical scenario

Environmental control measures (ventilation, high-efficiency particulate air filtration, and upper room ultraviolet germicidal irradiation [UVGI]) are recommended to effectively control tuberculosis (TB) transmission from unsuspected TB patients in high-risk settings, but the effectiveness of their use is not often clear. This study presents a simulation model for a hypothetical hospital waiting room, in which the number of susceptible immunocompetent people in the waiting room follows a Poisson distribution (M = 5) in either low (annual number of TB patients = 5) or high TB risk settings (annual number of TB patients = 50), and used the model to evaluate the reduction of TB transmission risk by upper room UVGI. An exponential dose-response model was used for TB transmission and a two-zone model was used for evaluating the effect of upper room UVGI. Upper room UVGI reduced TB risk by 1.6-fold at 3 microW/cm2 UV irradiance in the upper room in the low TB risk setting and by 4.1-fold at 15 microW/cm2 UV irradiance in the upper room in the high TB risk setting. Use of upper room UVGI also reduced the mean annual new infection rate from 2.2 to 1.3 infections per year at 3 microW/cm2 and to 0.6 infections per year at 15 microW/cm2 in our hypothetical high-risk settings. The effect of upper room UVGI was sensitive to both vertical air velocity (air mixing) and UV irradiance level. Results from partitioning variability indicate that most variability of TB transmission risk came from waiting time in our hypothetical hospital.

Marijuana use among adolescents: trends, patterns, and influences

This article reviews current marijuana conditions, trends, and influences among adolescents. Data show that prevalence rates vary markedly among youth, showing higher usage rates in the United States and Western Europe and lower rates among Mediterranean and Scandinavian youth. Urianalysis studies show that American juvenile arrestees are testing positive for cannabis at increasing rates. Influences that are central to marijuana use include being older, being male, experiencing family conflict, having peer models for use, and suffering from mood and anxiety disorders. More information is needed on how much gene-based evolutionary traits are relevant to marijuana abuse. Criticisms of school-based drug education programs have lead to the emergence of more comprehensive and enduring prevention programs. Concern about rising levels of marijuana abuse, lack of accountability, and dual diagnoses have given rise to juvenile drug courts. Preliminary reports suggest that these two strategies could show promise in reducing marijuana use and abuse, although rising THC yields could counteract these efforts.

Proposed occupational exposure limits for select ethylene glycol ethers using PBPK models and Monte Carlo simulations

Methoxyethanol (ethylene glycol monomethyl ether, EGME), ethoxyethanol (ethylene glycol monoethyl ether, EGEE), and ethoxyethyl acetate (ethylene glycol monoethyl ether acetate, EGEEA) are all developmental toxicants in laboratory animals. Due to the imprecise nature of the exposure data in epidemiology studies of these chemicals, we relied on human and animal pharmacokinetic data, as well as animal toxicity data, to derive 3 occupational exposure limits (OELs). Physiologically based pharmacokinetic (PBPK) models for EGME, EGEE, and EGEEA in pregnant rats and humans have been developed (M. L. Gargas et al., 2000, Toxicol. Appl. Pharmacol. 165, 53-62; M. L. Gargas et al., 2000, Toxicol. Appl. Pharmacol. 165, 63-73). These models were used to calculate estimated human-equivalent no adverse effect levels (NAELs), based upon internal concentrations in rats exposed to no observed effect levels (NOELs) for developmental toxicity. Estimated NAEL values of 25 ppm for EGEEA and EGEE and 12 ppm for EGME were derived using average values for physiological, thermodynamic, and metabolic parameters in the PBPK model. The uncertainties in the point estimates for the NOELs and NAELs were estimated from the distribution of internal dose estimates obtained by varying key parameter values over expected ranges and probability distributions. Key parameters were identified through sensitivity analysis. Distributions of the values of these parameters were sampled using Monte Carlo techniques and appropriate dose metrics calculated for 1600 parameter sets. The 95th percentile values were used to calculate interindividual pharmacokinetic uncertainty factors (UFs) to account for variability among humans (UF(h,pk)). These values of 1.8 for EGEEA/EGEE and 1.7 for EGME are less than the default value of 3 for this area of uncertainty. The estimated human equivalent NAELs were divided by UF(h,pk) and the default UFs for pharmacodynamic variability among animals and among humans to calculate the proposed OELs. This methodology indicates that OELs (8-h time-weighted average) that should protect workers from the most sensitive adverse effects of these chemicals are 2 ppm EGEEA and EGEE (11 mg/m(3) EGEEA, 7 mg/m(3) EGEE) and 0.9 ppm (3 mg/m(3)) EGME. These recommendations assume that dermal exposure will be minimal or nonexistent.

Widespread expression of netrin-1 by neurons and oligodendrocytes in the adult mammalian spinal cord

Netrins are a family of secreted proteins that function as chemotropic axon guidance cues during neural development. Here we demonstrate that netrin-1 continues to be expressed in the adult rat spinal cord at a level similar to that in the embryonic CNS. In contrast, netrin-3, which is also expressed in the embryonic spinal cord, was not detected in the adult. In situ hybridization analysis demonstrated that cells in the white matter and the gray matter of the adult spinal cord express netrin-1. Colocalization studies using the neuronal marker NeuN revealed that netrin-1 is expressed by multiple classes of spinal interneurons and motoneurons. Markers identifying glial cell types indicated that netrin-1 is expressed by most, if not all, oligodendrocytes but not by astrocytes. During neural development, netrin-1 has been proposed to function as a diffusible long-range cue for growing axons. We show that in the adult spinal cord the majority of netrin-1 protein is not freely soluble but is associated with membranes or the extracellular matrix. Fractionation of adult spinal cord white matter demonstrated that netrin-1 was absent from fractions enriched for compact myelin but was enriched in fractions containing periaxonal myelin and axolemma, indicating that netrin-1 protein may be localized to the periaxonal space. These findings suggest that in addition to its role as a long-range guidance cue for developing axons, netrin may have a short-range function associated with the cell surface that contributes to the maintenance of appropriate neuronal and axon-oligodendroglial interactions in the mature nervous system.

Depiction of alcohol, tobacco, and other substances in G-rated animated feature films

OBJECTIVE

To quantify and characterize the depiction of alcohol, tobacco, and other substances in G-rated animated feature films.

METHOD

The content of all G-rated animated feature films released in theaters between 1937 and 2000, recorded in English, and available on videocassette in the United States by October 31, 2000, was reviewed for portrayals of alcohol, tobacco, and other substances and their use. Duration of scenes depicting alcohol, tobacco, or other substances; type of characters using them (good, neutral, or bad); and correlation of amount and type used with character type and movie type were evaluated.

RESULTS

Of the 81 films reviewed, 38 films (47%) showed alcohol use (mean exposure: 42 seconds per film; range: 2 seconds to 2.9 minutes) and 35 films (43%) showed tobacco use (mean exposure: 2.1 minutes per film; range: 2 seconds to 10.5 minutes). Analysis of time trends showed a significant decrease in both tobacco and alcohol use over time (both corrected for total screen duration and uncorrected.) No films showed the use of illicit drugs, although 3 films showed characters consuming a substance that transfigured them and 2 films showed characters injected with a drug. Analysis of the correlation of alcohol and tobacco depiction revealed several scenes in which alcohol and tobacco were shown in use in the same scene and that bar scenes in these movies depict a significant amount of drinking, smoking, and violence. Three films contained a message that a character should stop smoking but none contained messages about restricting consumption of alcohol.

CONCLUSIONS

The depiction of alcohol and tobacco use in G-rated animated films seems to be decreasing over time. Nonetheless, parents should be aware that nearly half of the G-rated animated feature films available on videocassette show alcohol and tobacco use as normative behavior and do not convey the long-term consequences of this use.

Species- and agonist-dependent differences in the deactivation-kinetics of P2X7 receptors

In this study we have expressed recombinant P2X7 receptors in HEK293 cells and examined the reasons for the species- and agonist-dependent differences in the time taken for the closure of the P2X7 receptor ion-channels after agonist removal. Channel closure times, measured in electrophysiological studies or by measuring cellular permeability to ethidium cations, were slower at rat than at human or mouse P2X7 channels following washout of the P2X7 agonist 2'- and 3'-O-(4-benzoylbenzoyl)-ATP (BzATP). In contrast, there were no species differences in channel closure times when ATP was the agonist. BzATP was more potent than ATP at the three species homologues and exhibited highest potency for rat P2X7 receptors suggesting that channel closure time was related to agonist potency. Furthermore, BzATP potency for the P2X7 receptor could be modified by changing extracellular ionic concentrations or by mutating the receptor and modifications which increased agonist potency also increased the time taken for channel closure. The dependence of channel closure time on agonist potency suggests it reflects agonist dissociation from the P2X7 receptor rather being an intrinsic property of the ion-channel. Consistent with this, our previous studies have shown that agonist potency increases after repeated agonist applications and in this study channel closure time at rat P2X7 receptors increased after repeated agonist applications. Overall these results suggest that the species differences in channel closure times reflect differences in agonist dissociation rates which arise as a consequence of the marked species differences in agonist potency.

Complexities of measuring antagonist potency at P2X(7) receptor orthologs

The ability of P2 antagonists to affect agonist-stimulated fluorescent dye accumulation in cells expressing human, rat, or mouse P2X(7) receptors was examined. Several compounds, including pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), which was previously thought to be a weak P2X(7) receptor antagonist, possessed high potency (nanomolar IC(50)) at human and rat P2X(7) receptors. However, there were species differences in antagonist potency with PPADS, pyridoxal 5'-phosphate (P5P), and periodate-oxidized ATP (OxATP) exhibiting 20- to 500-fold higher potency for human than for mouse P2X(7) receptors. HMA (5-(N,N-hexamethylene)amiloride) was also selective for human over rat P2X(7) receptors but potentiated responses at mouse P2X(7) receptors. Coomassie Brilliant Blue G (CBB) was a nonselective antagonist with high potency at mouse P2X(7) receptors (IC(50) approximately 100 nM). All compounds were noncompetitive antagonists, and potency could only be quantified by measuring IC(50) values. These values were similar when determined against EC(50) concentrations of ATP or 2'- and 3'-O-4(-benzoylbenzoyl)-ATP and, for most compounds, only slightly (3- to 5-fold) affected by agonist concentration. However, IC(50) values for KN62 (1-[N,O-bis(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine) and suramin, varied up to 25-fold depending upon agonist concentration. Furthermore, IC(50) values for KN62 and OxATP were 10-fold lower at 22 degrees C than at 37 degrees C, whereas IC(50) values for PPADS, P5P, suramin, and OxATP were up to 20-fold lower in NaCl than in sucrose buffer. Potency estimates for CBB and PPADS decreased 5-fold in the presence of bovine serum albumin, possibly due to protein binding. Given the species differences, and the effects of assay conditions on antagonist potency, caution must be exercised when interpreting results obtained with the available antagonists.

Sexual violence and weight control techniques among adolescent girls

OBJECTIVE

Research has linked childhood sexual abuse and eating disturbances among adult females. Less is known about whether sexual abuse in the form of dating violence has implications for deviant weight control techniques among adolescent girls. This study assesses the association between sexual violence and weight control practices among girls. We also attempt to untangle the effects of family environment from this association and to determine if weak impulse control mediates the association.

METHOD

Survey data were gathered from 2,629 girls in Grades 9-12 to assess health risks. Girls responded to questions regarding dating violence, unwanted sexual contact, purging, and diet pill consumption. Logistic regression was used to assess the unique contribution of sexual violence on weight control techniques.

RESULTS

Dating violence and unwanted sexual contact elevated the probability that girls would report practicing weight control techniques by 6-13%. Controls for family environment did not eliminate these associations. Weak impulse control did not significantly mediate these associations.

DISCUSSION

These findings suggest that sexual violence has immediate implications as a risk factor for weight control techniques in adolescence.

Sexual victimization and adolescent weight regulation practices: a test across three community based samples

OBJECTIVE

This study had four objectives: 1) to examine the association between sexual victimization and weight regulation across three samples of adolescent girls, 2) to assess whether sexual victimization is associated with more extreme forms of weight regulation in girls, 3) to discern whether sexual victimization has implications for the use of multiple forms of weight regulation, and 4) to address the role of physical victimization in explaining these relationships.

METHOD

Data from three separate samples of 9th-12th graders were used to test these hypotheses. Girls from the upper Midwest responded to survey questions related to victimization and weight regulation in a largely urban sample (N = 2,086), a rural sample (N = 2,629), and a statewide sample (N = 966).

RESULTS

Logistic regression revealed that sexual victimization was consistently associated with weight regulation in adolescent girls, independent of the effects of physical victimization. In the urban sample, being sexually victimized was associated with an increase in the probability of purging by 18% relative to not being sexually victimized. Sexual victimization was associated more strongly with extreme forms of weight regulation and significantly discriminated whether girls would choose multiple weight regulation forms.

CONCLUSIONS

Sexual victimization contributes unique variance to the probability that girls will practice weight regulation techniques. Data from three independent samples confirms that being violated sexually places girls at risk for various health compromising eating behaviors.

Characterization and V(H) sequences of human monoclonal anti-F(ab')(2) autoantibodies from normals and Sjögren's syndrome patients

To investigate the genetic background of anti-F(ab')(2) autoantibodies and the mechanism behind their production we have analyzed 10 human monoclonal antibodies directed against IgG F(ab')(2) and IgG Fab. They were all derived from peripheral blood by the EBV/hybridoma technique. Eight were from three healthy individuals and two from two patients with primary Sjögren's syndrome (pSS). They react with epitopes on distinct regions of IgG, including epitopes present on or near the hinge of IgG, epitopes on the Fd gamma, and an antigenic determinant(s) present on lambda light chains. These determinants are either exposed on the intact IgG molecule or revealed following pepsin or papain digestion. The V(H) germline gene repertoire used is diverse and with considerable overlap with that used by rheumatoid factors (RF). The two IgG antibodies from normals are extensively mutated (13 and 24 mutations/V(H)), but with a replacement to silent mutation ratio in the CDR(H)1 + 2 of only 3.7. The IgM antibodies from normals are also heavily mutated (mean 10 mutations/V(H)). This suggests that anti-F(ab')(2) from normals are generated by an antigen-driven somatic hypermutation mechanism. In contrast, the two IgM antibodies from pSS are virtually unmutated in both V(H) and V(L). Together with published data of pSS RF and anti-Ro 52-kDa sequences (1-3), this suggests that there is an expanded population of naïve B cells with autoantibody specificities in the peripheral blood of pSS patients.

An observational study of object mouthing behavior by young children

OBJECTIVE

Mouthing behavior in infants and young children <3 years old is a poorly quantified yet normal part of early childhood development. Increasingly, safety and risk assessments involving materials that may be mouthed depend on accurate estimates of oral contact time. This study reports the results of an observational study performed to investigate and obtain data on mouthing behavior of objects for children up to 3 years old.

METHODOLOGY

The study used a standard diary form with instructions for participating parents to observe their child in a normal environment (primarily home), and to document both the type and duration of each item mouthed. Phase I (pilot) consisted of 30 children each observed for 1 day, divided equally between the ages of 0 to 18 months (n = 15) and 19 to 36 months (n = 15), whereas Phase II included more participants (n = 92 aged 0-18 months; n = 95 aged 19-36 months). Phase III included observations for 5 nonconsecutive days over a 2-month period on 168 children between the ages of 3 to 18 months (at study initiation), and focused on total mouthing time of objects, exclusive of pacifiers.

RESULTS

The data collected during the first 2 phases were pooled and analyzed together. For all participants between the ages of 0 and 18 months (n = 107), the average daily duration of mouthing objects included: pacifiers (108 minutes), plastic toys (17 minutes), teethers (6 minutes), and other objects (9 minutes). The results for children 19 to 36 months old (n = 110) included: pacifiers (126 minutes), plastic toys (2 minutes), teethers (0 minutes), and other objects (2 minutes). Although no significant difference existed between the 2 age ranges for pacifier mouthing duration, a statistically significant difference was observed for nonpacifier objects. For Phase III, the average daily mouthing time for all objects (excluding pacifiers), based on 5 nonconsecutive days of observation for 168 children, was 36 minutes (n = 793 valid child observation days).

CONCLUSIONS

Results of this study indicate that mouthing behavior is dependent on age and the types of items that are mouthed. Duration of mouthing varies among children, with some consistently not mouthing any objects and with a very small number mouthing objects for >2 hours a day. The study also revealed wide variability in the types of objects mouthed, including many nontoy objects. Children mouth pacifiers significantly longer than other objects, regardless of age. Significantly increased mouthing time of all nonpacifier objects is reported for children in the 0- to 18-month range compared with the 19- to 36-month range.

Smoking and weight control in adolescent females

This paper examines the association between smoking and various weight control techniques among adolescent girls in two school-based samples. Previous studies have relied heavily on clinical trials of adults and have focused mainly on dietary restraint rather than purging behavior. This study seeks to determine whether purging is associated with smoking and if purging and dietary restraint effects upon smoking are additive or synergistic. Data from adolescent girls were gathered from two school-based surveys conducted in the upper Midwest. Assessments were conducted for smoking, dietary restraint, diet pill use, and purging. Logistic regression was used to test for main and interaction effects. Analysis revealed significant associations between smoking and weight control. Purging was more highly associated with smoking than dietary restraint or diet pill use. The form of these associations was interactive rather than additive in both data sets. Nonpurging girls were significantly more likely to smoke if they were dieting or using diet pills than if they were not practicing dieting behavior. Thus, the effect of dieting and diet pill use on smoking is dependent on purging behavior. Weight control is associated with smoking behavior in adolescent girls but the form of these associations may be more complex than originally thought. Future research is needed to determine if there are two subtypes of smoking-weight control girls.