BACKGROUND

The Hospital Anxiety and Depression Scale (HADS) is frequently used in cancer studies, yet its utility for comparing people with cancer with people in the community is uncertain.

METHODS

HADS scores were obtained from population-based samples of women with (n = 731) and without (n = 158) early-onset breast cancer. Psychometric properties were examined using differential item functioning (DIF) which is the presence of systematic group differences in certain response items independent of the trait being measured.

RESULTS

Women with breast cancer scored lower than reference women on anxiety (mean (SD) 7.5 (4.3) vs. 8.2 (4.0); p = 0.06) and depression (3.3 (3.2) vs. 4.2 (3.0); p = 0.003). Group differences remained following adjustment for demographics. Time since diagnosis was not related to anxiety or depression scores. DIF was present in two anxiety and five depression items. Adjustment for DIF did not substantially change the anxiety or depression group differences.

CONCLUSIONS

Specific sampling or DIF effects do not explain the observation that women with breast cancer have lower levels of anxiety and depression than population controls. The psychometric properties of the HADS appear to be acceptable in these groups.

Signaling by Drosophila Toll pathway activates two Rel/NF-kappaB transcription factors, Dorsal (Dl) and Dorsal-related immune factor (Dif). Dl plays a central role in the establishment of dorsoventral polarity during early embryogenesis, whereas Dif mediates the Toll receptor-dependent antifungal immune response in adult Drosophila. The absence of a Dif ortholog in mosquito genomes suggests that Dl may play its functional role in the mosquito Toll-mediated innate immune responses. We have cloned and molecularly characterized the gene homologous to Drosophila Dl and to Anopheles gambiae REL1 (Gambif1) from the yellow fever mosquito Aedes aegypti, named AaREL1. AaREL1 alternative transcripts encode two isoforms, AaREL1-A and AaREL1-B. Both transcripts are enriched during embryogenesis and are inducible by septic injury in larval and female mosquitoes. AaREL1 and AaREL2 (Aedes Relish) selectively bind to different kappaB motifs from insect immune gene promoters. Ectopic expression of AaREL1-A in both Drosophila mbn-2 cells and transgenic flies specifically activates Drosomycin and results in increased resistance against the fungus Beauveria bassiana. AaREL1-B acted cooperatively with AaREL1-A to enhance the immune gene activation in Aag-2 cells. The RNA interference knock-outs revealed that AaREL1 affected the expression of Aedes homologue of Drosophila Serpin-27A and mediated specific antifungal immune response against B. bassiana. These results indicate that the homologue of Dl, but not that of Dif, is a key regulator of the Toll antifungal immune pathway in A. aegypti female mosquitoes.

The innate immune response in Drosophila involves the inducible expression of antimicrobial peptide genes mediated by the Toll and IMD signaling pathways. Dorsal and DIF act downstream of Toll, whereas Relish acts downstream of IMD to regulate target gene expression. Dorsal, DIF, and Relish are NF-kappaB-related transcription factors and function as obligate dimers, but it is not clear how the various dimer combinations contribute to the innate immune response. We systematically examined the dimerization tendency of these proteins through the use of transgenic assays. The results show that all combinations of homo- and heterodimers are formed, but with varying degrees of efficiency. The formation of the DIF-Relish heterodimer is particularly interesting because it may mediate signaling for the seemingly independent Toll and IMD pathways. By incorporating a flexible peptide linker, we specifically tested the functions of the DIF;Relish (a ; sign represents the peptide linker) linked heterodimer. Our results demonstrate that the linked heterodimer can activate target genes of both the Toll and IMD pathways. The DIF and Relish complex is detectable in whole animal extracts, suggesting that this heterodimer may function in vivo to increase the spectrum and level of antimicrobial peptide production in response to different infections.

Transcriptional activators interact with diverse proteins and recruit transcriptional machinery to the activated promoter. Recruitment of the Mediator complex by transcriptional activators is usually the key step in transcriptional activation. However, it is unclear how Mediator recognizes different types of activator proteins. To systematically identify the subunits responsible for the signal- and activator-specific functions of Mediator in Drosophila melanogaster, each Mediator subunit was depleted by RNA interference, and its effect on transcriptional activation of endogenous as well as synthetic promoters was examined. The depletion of some Mediator gene products caused general transcriptional defects, whereas depletion of others caused defects specifically related to activation. In particular, MED16 and MED23 were required for lipopolysaccharide- and heat-shock-specific gene expression, respectively, and their activator-specific functions appeared to result from interaction with specific activators. The corequirement of MED16 for other forms of differentiation-inducing factor-induced transcription was confirmed by microarray analysis of differentiation-inducing factor (DIF)- and MED16-depleted cells individually. These results suggest that distinct Mediator subunits interact with specific activators to coordinate and transfer activator-specific signals to the transcriptional machinery.

The signaling pathways governing pathophysiologically important autophagic (ACD) and necrotic (NCD) cell death are not entirely known. In the Dictyostelium eukaryote model, which benefits from both unique analytical and genetic advantages and absence of potentially interfering apoptotic machinery, the differentiation factor DIF leads from starvation-induced autophagy to ACD, or, if atg1 is inactivated, to NCD. Here, through random insertional mutagenesis, we found that inactivation of the iplA gene, the only gene encoding an inositol 1,4,5-trisphosphate receptor (IP3R) in this organism, prevented ACD. The IP3R is a ligand-gated channel governing Ca(2+) efflux from endoplasmic reticulum stores to the cytosol. Accordingly, Ca(2+)-related drugs also affected DIF signaling leading to ACD. Thus, in this system, a main pathway signaling ACD requires IP3R and further Ca(2+)-dependent steps. This is one of the first insights in the molecular understanding of a signaling pathway leading to autophagic cell death.

The recombination site dif is the target on the Escherichia coli chromosome of the site-specific recombinases XerC and XerD. The dif/XerC-D system plays a role during the cell cycle, probably by favoring sister chromosome monomerization or separation. A phenomenon of regional control over dif activity, also analyzed in this issue, is demonstrated here by translocation of dif to a series of loci close to the normal locus. We found that the site is physiologically active only within a narrow zone around its natural position. Competence for dif activity does not depend on the sequence of the normal dif activity zone (DAZ), because delta(dif) deletions larger than the DAZ result in Dif+ bacteria when dif is reinserted at the junction point. Although dif maps where replication normally terminates, termination of replication is not the elicitor. A strain with a large inversion that places dif and its surrounding region close to oriC remains Dif+, even when a Tus- mutation allows replication to terminate far away from it. Preliminary data suggest the possibility that specialized sequences separate the competent zone from the rest of the chromosome. We suspect that these sequences are members of a set of sequences involved in a polarized process of postreplicative reconstruction of the nucleoid structure. We propose that this reconstruction forces catenation links between sister chromosomes to accumulate within the DAZ, where they eventually favor recombination at dif.

A reverse transcription-PCR (RT-PCR) assay based on automated fluorescent capillary electrophoresis and GeneScan software analysis was developed to detect six common respiratory viruses in clinical specimens from young children. Assays for human respiratory syncytial virus (HRSV); human parainfluenza viruses 1, 2, and 3 (HPIV1, -2, and -3, respectively); and influenza A and B viruses were incorporated into a single standard assay format. The optimized assay panel was used to test 470 respiratory specimens obtained from 462 children hospitalized with acute respiratory illness that had been previously tested by viral culture (405 specimens) or direct immunofluorescence staining (DIF) (65 specimens). Of 93 specimens positive for respiratory viruses by culture or DIF, 86 (92%) were positive by RT-PCR, including 66 HRSV, 2 HPIV2, 5 HPIV3, 3 influenza A virus, and 10 influenza B virus specimens. An additional 119 respiratory viruses were identified by RT-PCR in 116 patients for whom results were negative by viral isolation or DIF. We conclude that the GeneScan RT-PCR panel can markedly improve detection of acute respiratory virus infections in young children.

OBJECTIVE

The S-QoL 41 is a French self-administered questionnaire that assesses quality of life (QoL) among people with schizophrenia. This study aims to validate a shortened version of the S-QoL for more widespread use in clinical practice.

METHODS

We used data from four studies conducted in four psychiatric hospitals in France (n=507). The item reduction and validation processes were based on both item response theory and classical test theory. The final version of the S-QoL was tested for construct validity, reliability, external validity, reproducibility and sensitivity to change. In addition, differential item functioning (DIF) analyses were performed to see whether all items behave in the same way in subgroups divided by age, gender, educational level and clinical form.

RESULTS

The S-QoL 18 evaluates eight dimensions: psychological well-being, self-esteem, family relationships, relationships with friends, resilience, physical well-being, autonomy and sentimental life. The factor structure accounted for 78% of the total variance. Internal consistency was satisfactory (item-internal consistency greater than 0.40; Cronbach's alpha coefficients ranged from 0.72 to 0.84). The scalability was satisfactory, with INFIT statistics within an acceptable range. In addition, the results confirmed the absence of DIF and supported the invariance of the item calibrations.

CONCLUSIONS

The S-QoL 18 is a short self-administered QoL instrument that has a high degree of comparability with S-QoL 41 and presents satisfactory psychometric properties. Future studies should confirm its sensitivity to change.

The Microviridae comprises icosahedral lytic viruses with circular single-stranded DNA genomes. The family is divided into two distinct groups based on genome characteristics and virion structure. Viruses infecting enterobacteria belong to the genus Microvirus, whereas those infecting obligate parasitic bacteria, such as Chlamydia, Spiroplasma and Bdellovibrio, are classified into a subfamily, the Gokushovirinae. Recent metagenomic studies suggest that members of the Microviridae might also play an important role in marine environments. In this study we present the identification and characterization of Microviridae-related prophages integrated in the genomes of species of the Bacteroidetes, a phylum not previously known to be associated with microviruses. Searches against metagenomic databases revealed the presence of highly similar sequences in the human gut. This is the first report indicating that viruses of the Microviridae lysogenize their hosts. Absence of associated integrase-coding genes and apparent recombination with dif-like sequences suggests that Bacteroidetes-associated microviruses are likely to rely on the cellular chromosome dimer resolution machinery. Phylogenetic analysis of the putative major capsid proteins places the identified proviruses into a group separate from the previously characterized microviruses and gokushoviruses, suggesting that the genetic diversity and host range of bacteriophages in the family Microviridae is wider than currently appreciated.

A simple, effective method of unlabeled, stable gene insertion into bacterial chromosomes has been developed. This utilizes an insertion cassette consisting of an antibiotic resistance gene flanked by dif sites and regions homologous to the chromosomal target locus. dif is the recognition sequence for the native Xer site-specific recombinases responsible for chromosome and plasmid dimer resolution: XerC/XerD in Escherichia coli and RipX/CodV in Bacillus subtilis. Following integration of the insertion cassette into the chromosomal target locus by homologous recombination, these recombinases act to resolve the two directly repeated dif sites to a single site, thus excising the antibiotic resistance gene. Previous approaches have required the inclusion of exogenous site-specific recombinases or transposases in trans; our strategy demonstrates that this is unnecessary, since an effective recombination system is already present in bacteria. The high recombination frequency makes the inclusion of a counter-selectable marker gene unnecessary.

BACKGROUND

Differential item functioning (DIF) methods can be used to determine whether different subgroups respond differently to particular items within a health-related quality of life (HRQoL) subscale, after allowing for overall subgroup differences in that scale. This article reviews issues that arise when testing for DIF in HRQoL instruments. We focus on logistic regression methods, which are often used because of their efficiency, simplicity and ease of application.

METHODS

A review of logistic regression DIF analyses in HRQoL was undertaken. Methodological articles from other fields and using other DIF methods were also included if considered relevant.

RESULTS

There are many competing approaches for the conduct of DIF analyses and many criteria for determining what constitutes significant DIF. DIF in short scales, as commonly found in HRQL instruments, may be more difficult to interpret. Qualitative methods may aid interpretation of such DIF analyses.

CONCLUSIONS

A number of methodological choices must be made when applying logistic regression for DIF analyses, and many of these affect the results. We provide recommendations based on reviewing the current evidence. Although the focus is on logistic regression, many of our results should be applicable to DIF analyses in general. There is a need for more empirical and theoretical work in this area.

To examine variations in the manifestation of depressive symptomatology across racial/ethnic groups, analyses of differential item functioning (DIF) on the Center for Epidemiologic Studies Depression Scale (CES-D) were separately conducted for representative samples of young adults in the following groups: African-Americans (n = 434), Hispanics born in the US (n = 493), and Hispanics born outside the US (n = 395). Non-Hispanic whites (n = 463) were employed as the reference group in all analyses. The effects of gender and age were controlled. DIF analyses indicated that: (1) about half of the CES-D items functioned differently among non-Hispanic whites compared to each of the other racial/ethnic groups; (2) the manifestation of symptoms seemed to be similar for both Hispanic groups, except for low positive affect; (3) African-Americans tended to favor somatic symptoms over affective (depressive) symptoms; (4) Immigrant Hispanics appeared to inhibit the expression of positive affect, and thus more high scorers on the total CES-D were observed within this subgroup. In contrast, no differences were observed when only negative items were considered. The use of positive affect items might artifactually induce spurious differences among people who were born outside the United States or North America.

At least three distinct types of cell arise from a population of similar amoebae during Dictyostelium development: prespore, prestalk A and prestalk B cells. We report evidence suggesting that this cellular diversification can be brought about by the combinatorial action of two diffusible signals, cAMP and DIF-1. Cells at different stages of normal development were transferred to shaken suspension, challenged with various combinations of signal molecules and the expression of cell-type-specific mRNA markers measured 1-2 h later. pDd63, pDd56 and D19 mRNAs were used for prestalk A, prestalk B and prespore cells respectively. We find the following results. (1) Cells first become responsive to DIF-1 for prestalk A differentiation and to cAMP for prespore differentiation at the end of aggregation, about 2 h before these cell types normally appear. (2) At the first finger stage of development, when the rate of accumulation of the markers is maximal, the expression of each is favoured by a unique combination of effectors: prespore differentiation is stimulated by cAMP and inhibited by DIF-1; prestalk A differentiation is stimulated by both cAMP and DIF-1 and prestalk B differentiation is stimulated by DIF-1 and inhibited by cAMP. (3) Half-maximal effects are produced by 10-70 nM DIF-1, which is in the physiological range. (4) Ammonia and adenosine, which can affect cell differentiation in other circumstances, have no significant pathway-specific effect in our conditions. These results suggest that cell differentiation could be brought about in normal development by the localized action of cAMP and DIF-1.

This study demonstrated the application of an innovative item response theory (IRT) based approach to evaluating measurement equivalence, comparing a newly developed Spanish version of the Posttraumatic Stress Disorder Checklist-Civilian Version (PCL-C) with the established English version. Basic principles and practical issues faced in the application of IRT methods for instrument evaluation are discussed. Data were derived from a study of the mental health consequences of community violence in both Spanish speakers (n = 102) and English speakers (n = 284). Results of differential item functioning (DIF) analyses revealed that the 2 versions were not fully equivalent on an item-by-item basis in that 6 of the 17 items displayed uniform DIF. No bias was observed, however, at the composite PCL-C scale score, indicating that the 2 language versions can be combined for scale-level analyses.

To investigate whether a history of hematolymphoproliferative cancers (HLP) and other cancers among a parent or sibling is a risk factor for specific subtypes of leukemia and non-Hodgkin's lymphoma (NHL), data from a population-based case-control study, in Iowa and Minnesota, of 578 leukemia cases, 622 NHL cases and 1245 controls were evaluated. Having at least one sibling with HLP significantly increased the risk for all leukemias combined (odds ratio (OR) = 2.3) and for NHL (OR = 2.7). In particular, chronic lymphocytic leukemia (CLL) was significantly increased among those reporting a sibling with leukemia (OR = 3.0) or lymphoma (OR = 4.3). Elevated risks of small lymphocytic NHL (SML) (OR = 7.3) and diffuse NHL (DIF) (OR = 5.4) were also observed among subjects who had a sibling with lymphoma (primarily Hodgkin's disease). A significantly increased risk of follicular NHL was noted among those with a sibling history of pancreatic cancer (OR = 4.8) and colorectal cancer (OR = 2.7). Parental history of HLP was not associated with any type of leukemia or NHL. A history of stomach cancer among parents was associated with a 2-fold elevation of CLL and DIF compared to controls. Increased risks of CLL and DIF were also linked to breast cancer among sisters and mothers, respectively. Prostate cancer among fathers increased the risk 2-fold for CLL and 3-fold for SML. This study confirms some familial cancer associations previously reported for leukemia and NHL, and provides new information regarding the various subtypes of leukemia and NHL.

OBJECTIVE

To illustrate the application of the Differential Item and Test Functioning (DFIT) method using English and Spanish versions of the Mini-Mental State Examination (MMSE).

METHODS

Study participants were 65 years of age or older and lived in North Manhattan, New York. Of the 1578 study participants who were administered the MMSE 665 completed it in Spanish.

METHODS

: The MMSE contains 20 items that measure the degree of cognitive impairment in the areas of orientation, attention and calculation, registration, recall and language, as well as the ability to follow verbal and written commands.

METHODS

After assessing the dimensionality of the MMSE scale, item response theory person and item parameters were estimated separately for the English and Spanish sample using Samejima's 2-parameter graded response model. Then the DFIT framework was used to assess differential item functioning (DIF) and differential test functioning (DTF).

RESULTS

Nine items were found to show DIF; these were items that ask the respondent to name the correct season, day of the month, city, state, and 2 nearby streets, recall 3 objects, repeat the phrase no ifs, no ands, no buts, follow the command, "close your eyes," and the command, "take the paper in your right hand, fold the paper in half with both hands, and put the paper down in your lap." At the scale level, however, the MMSE did not show differential functioning.

CONCLUSIONS

Respondents to the English and Spanish versions of the MMSE are comparable on the basis of scale scores. However, assessments based on individual MMSE items may be misleading.

Brief and culturally compatible measures of depression are necessary, yet most depression scales are translated without regard for cultural biases. In this study, 292 medical outpatients completed an English or a Spanish-translated and back-translated version of the Beck Depression Inventory (BDI). The BDI items were analyzed for bias between Spanish and English-speaking patients to determine the equivalence of the scale. A Differential Item Function (DIF) using a Mantel Haenszel Approach for Ordered Response Categories was used to analyze how likely subjects in the two ethnic groups were to endorse each response category. The results suggest that regardless of level of depression, Latinos are more likely to endorse items reflecting tearfulness and punishment, and less likely to endorse inability to work. Cultural interpretations and recommendations for use of the BDI are discussed.

Cell fate in Dictyostelium development depends on intrinsic differences between cells, dating from their growth period, and on cell interactions occurring during development. We have sought for a mechanism linking these two influences on cell fate. First, we confirmed earlier work showing that the vegetative differences are biases, not commitments, since cells that are stalky-biased when developed with one partner are sporey with another. Then we tested the idea that these biases operate by modulating the sensitivity of cells to the signals controlling cell fate during development. Cells grown without glucose are stalky-biased when developed with cells grown with glucose. We find, using monolayer culture conditions, that they are more sensitive to each of the stalk-inducing signals, DIFs 1-3. Mixing experiments show that this bias is a cell-intrinsic property. Cells initiating development early in the cell cycle are stalky compared to those initiating development later in the cycle. Likewise, they are more sensitive to DIF-1. Assays of standard markers for prestalk and prespore cell differentiation reveal similar differences in DIF-1 sensitivity between biased cells; DIF-1 dechlorinase (an early prestalk cell marker enzyme) behaves in a consistent manner. We propose that cell-fate biases are manifest as differences in sensitivity to DIF.

Drugs that inhibit dopamine (DA) reuptake through actions at the dopamine transporter (DAT) have been proposed as candidates for development as pharmacotherapies for cocaine abuse. Accordingly, it is important to understand the potential pharmacological interactions of cocaine with other drugs acting at the DAT. Effects of combinations of cocaine with a cocaine analog, 2beta-carbomethoxy-3beta-(4-fluorophenyl)tropane (WIN 35,428), were compared quantitatively with the combinations of cocaine with the N-butyl,4',4''-diF benztropine analog, 3-(bis(4-fluorophenyl)methoxy)-8-butyl-8-azabicyclo[3.2.1]octane (JHW 007), to determine whether their effects on DA levels in the shell of the nucleus accumbens (NAC) in mice differed. Each of the drugs alone produced dose-related elevations in NAC DA levels. In contrast to the other drugs, JHW 007 was less effective, producing maximal effects that approached 400% of control versus approximately 700% with the other drugs. In addition, the JHW 007 dose-effect curve was not as steep as those for cocaine and WIN 35,428. Combinations of cocaine with its analog, WIN 35,428, were most often greater than those predicted based on dose additivity. In contrast, combinations of cocaine with JHW 007 were most often subadditive. This outcome is consistent with recent studies suggesting that structurally divergent DA uptake inhibitors bind to different domains of the DAT, which can result in different DAT conformations. The conformational changes occurring with JHW 007 binding may result in functional outcomes that alter its abuse liability and its effects in combination with cocaine.

BACKGROUND

Methods based on item response theory (IRT) that can be used to examine differential item functioning (DIF) are illustrated. An IRT-based approach to the detection of DIF was applied to physical function and general distress item sets. DIF was examined with respect to gender, age and race. The method used for DIF detection was the item response theory log-likelihood ratio (IRTLR) approach. DIF magnitude was measured using the differences in the expected item scores, expressed as the unsigned probability differences, and calculated using the non-compensatory DIF index (NCDIF). Finally, impact was assessed using expected scale scores, expressed as group differences in the total test (measure) response functions.

METHODS

The example for the illustration of the methods came from a study of 1,714 patients with cancer or HIV/AIDS. The measure contained 23 items measuring physical functioning ability and 15 items addressing general distress, scored in the positive direction.

RESULTS

The substantive findings were of relatively small magnitude DIF. In total, six items showed relatively larger magnitude (expected item score differences greater than the cutoff) of DIF with respect to physical function across the three comparisons: "trouble with a long walk" (race), "vigorous activities" (race, age), "bending, kneeling stooping" (age), "lifting or carrying groceries" (race), "limited in hobbies, leisure" (age), "lack of energy" (race). None of the general distress items evidenced high magnitude DIF; although "worrying about dying" showed some DIF with respect to both age and race, after adjustment.

CONCLUSIONS

The fact that many physical function items showed DIF with respect to age, even after adjustment for multiple comparisons, indicates that the instrument may be performing differently for these groups. While the magnitude and impact of DIF at the item and scale level was minimal, caution should be exercised in the use of subsets of these items, as might occur with selection for clinical decisions or computerized adaptive testing. The issues of selection of anchor items, and of criteria for DIF detection, including the integration of significance and magnitude measures remain as issues requiring investigation. Further research is needed regarding the criteria and guidelines appropriate for DIF detection in the context of health-related items.

OBJECTIVE

To develop psychometrically sound, culturally relevant, and linguistically equivalent English and Spanish self-report measures of social health guided by a comprehensive conceptual model and applicable across chronic illnesses.

METHODS

The Patient-Reported Outcomes Measurement Information System (PROMIS) Social Health Workgroup implemented a mixed methods approach to evaluate earlier results (v1.0); expand and refine domain definitions and items; translate items into Spanish; and obtain qualitative feedback. Computer-based and paper/pencil questionnaire administration was conducted with a variety of U.S. respondent samples during 2009-2012. Analyses included exploratory factor analysis (EFA), confirmatory factor analysis (CFA), two-parameter logistic item response theory (IRT) modeling, evaluation of differential item functioning (DIF), and evaluation of criterion and construct validity.

RESULTS

Qualitative feedback supported the conceptualization of the Social Health domain framework (Social Function and Social Relationships subcomponents). Validation testing participants (n = 2,208 English; n = 644 Spanish) were diverse in terms of gender, age, education, and ethnicity/race. EFA, CFA, and IRT identified 7 unidimensional factors with good model fit. There was no DIF by language, and good evidence of criterion and construct validity.

CONCLUSIONS

PROMIS English and Spanish language instruments (v2.0), including computer-adaptive tests and fixed-length short forms, are publicly available for assessment of Social Function (Ability to Participate in Social Roles and Activities, and Satisfaction with Social Roles and Activities) and Social Relationships (Companionship; Emotional, Informational and Instrumental Support; and Social Isolation). Measures of social health will play a key role in applications that use ecologic (or determinants of health) models that emphasize how patients' social environments influence their health.

BACKGROUND

The inducible production of antimicrobial peptides is a major immune response in Drosophila. The genes encoding these peptides are activated by NF-kappaB transcription factors that are controlled by two independent signaling cascades: the Toll pathway that regulates the NF-kappaB homologs, Dorsal and DIF; and the IMD pathway that regulates the compound NF-kappaB-like protein, Relish. Although numerous components of each pathway that are required to induce antimicrobial gene expression have been identified, less is known about the mechanisms that either repress antimicrobial genes in the absence of infection or that downregulate these genes after infection.

RESULTS

In a screen for factors that negatively regulate the IMD pathway, we isolated two partial loss-of-function mutations in the SkpA gene that constitutively induce the antibacterial peptide gene, Diptericin, a target of the IMD pathway. These mutations do not affect the systemic expression of the antifungal peptide gene, Drosomycin, a target of the Toll pathway. SkpA encodes a homolog of the yeast and human Skp1 proteins. Skp1 proteins function as subunits of SCF-E3 ubiquitin ligases that target substrates to the 26S proteasome, and mutations affecting either the Drosophila SCF components, Slimb and dCullin1, or the proteasome also induce Diptericin expression. In cultured cells, inhibition of SkpA and Slimb via RNAi increases levels of both the full-length Relish protein and the processed Rel-homology domain.

CONCLUSIONS

In contrast to other NF-kappaB activation pathways, the Drosophila IMD pathway is repressed by the ubiquitin-proteasome system. A possible target of this proteolytic activity is the Relish transcription factor, suggesting a mechanism for NF-kappaB downregulation in Drosophila.

Homologous recombination between circular sister chromosomes during DNA replication in bacteria can generate chromosome dimers that must be resolved into monomers prior to cell division. In Escherichia coli, dimer resolution is achieved by site-specific recombination, Xer recombination, involving two paralogous tyrosine recombinases, XerC and XerD, and a 28-bp recombination site (dif) located at the junction of the two replication arms. Xer recombination is tightly controlled by the septal protein FtsK. XerCD recombinases and FtsK are found on most sequenced eubacterial genomes, suggesting that the Xer recombination system as described in E. coli is highly conserved among prokaryotes. We show here that Streptococci and Lactococci carry an alternative Xer recombination machinery, organized in a single recombination module. This corresponds to an atypical 31-bp recombination site (dif(SL)) associated with a dedicated tyrosine recombinase (XerS). In contrast to the E. coli Xer system, only a single recombinase is required to recombine dif(SL), suggesting a different mechanism in the recombination process. Despite this important difference, XerS can only perform efficient recombination when dif(SL) sites are located on chromosome dimers. Moreover, the XerS/dif(SL) recombination requires the streptococcal protein FtsK(SL), probably without the need for direct protein-protein interaction, which we demonstrated to be located at the division septum of Lactococcus lactis. Acquisition of the XerS recombination module can be considered as a landmark of the separation of Streptococci/Lactococci from other firmicutes and support the view that Xer recombination is a conserved cellular function in bacteria, but that can be achieved by functional analogs.

OBJECTIVE

To evaluate, by age, the performance of 2 disability measures based on needing help: one using 5 classic activities of daily living (ADL) and another using an expanded set of 14 activities including instrumental activities of daily living (IADL), walking, getting outside, and ADL (IADL/ADL).

METHODS

Guttman and item response theory (IRT) scaling methods are used with a large (N = 25,470) nationally representative household survey of individuals aged 18 years and older.

RESULTS

Guttman scalability of the ADL items increases steadily with age, reaching a high level at ages 75 years and older. That is reflected in an IRT model by age-related differential item functioning (DIF) resulting in age-biased measurement of ADL. Guttman scalability of the IADL/ADL items also increases with age but is lower than the ADL. Although age-related DIF also occurs with IADL/ADL items, DIF is lower in magnitude and balances out without causing age bias.

CONCLUSIONS

An IADL/ADL scale measuring need for help is hierarchical, unidimensional, and unbiased by age. It has greater content validity for measuring need for help in the community and shows greater sensitivity by age than the classic ADL measure. As demand for community services is increasing among adults of all ages, an expanded IADL/ADL measure is more useful than ADL.