Dictyostelium has 55 genes encoding seven-transmembrane G-protein-coupled receptors (GPCR) that belong to five of the six GPCR families. GrlA is one of the 17 family 3 GPCRs in Dictyostelium all of which resemble GABA(B) receptors from higher eukaryotes. GrlA is a 90-kDa protein present on the plasma membrane and on membranes of the ER. It has a large extracellular domain with homology to bacterial periplasmic proteins. The GrlA message is present throughout development and shows increased levels during the post aggregation stages. Inactivation of the grlA gene does not severely affect the growth phase, however, it leads to a delay in the development at the post aggregation stage. GrlA deficient strains show an altered DIF-1 response specific to the prestalk-specific ecmA and ecmB gene, reduced car2 and pkaC transcript levels and form a reduced number of spores. Germination of the spores was as in wild type. Transcriptional profiling supported the defect in the sporulation pathway as a large number of genes involved in the biogenesis and organization of the extracellular matrix and the sporulation process were significantly downregulated in the mutant.

OBJECTIVE

To determine whether a Portuguese language version of the Child Perceptions Questionnaire for 11-14-year-olds (CPQ(11-14)) showed differential item functioning (DIF) when compared with the original English language version.

METHODS

CPQ(11-14) data from a school-based Brazilian study (n = 138) was compared with CPQ(11-14) data collected as part of a school-based study conducted in New Zealand (n = 322). In order to detect DIF, ordinal logistic regression analysis was performed with each CPQ(11-14) item as the dependent variable. The independent variables were language group (English versus Portuguese), the CPQ(11-14) sub-scale score of which the item was a part, and an interaction term for language*sub-scale score. Nonuniform DIF was deemed to be present if the interaction term was significant. Moderate to large uniform DIF was deemed to be present if after removing the interaction term the beta coefficient (log odds ratio) for language group was significant and numerically greater than 0.64. Analyses were also undertaken to detect pseudo-DIF.

RESULTS

Nonuniform DIF was found in five items and moderate to large uniform DIF in an additional four items. Analyses using 'purified' sub-scale scores indicated that little of the DIF detected was pseudo-DIF. A comparison of the language groups using DIF affected and DIF-free overall and subscale CPQ(11-14) scores revealed that the DIF detected had only a marginal effect on the differences between language groups in scores.

CONCLUSIONS

Oral health-related quality of life questionnaires, particularly those that have been translated, need to be assessed for DIF and its likely impact on group comparisons.

BACKGROUND

The SF-36 is a very commonly used generic measure of health outcome in osteoarthritis (OA). An important, but frequently overlooked, aspect of validating health outcome measures is to establish if items work in the same way across subgroup of a population. That is, if respondents have the same 'true' level of outcome, does the item give the same score in different subgroups or is it biased towards one subgroup or another. Differential item functioning (DIF) can identify items that may be biased for one group or another and has been applied to measuring patient reported outcomes. Items may show DIF for different conditions and between cultures, however the SF-36 has not been specifically examined in an osteoarthritis population nor in a UK population. Hence, the aim of the study was to apply the DIF method to the SF-36 for a UK OA population.

METHODS

The sample comprised a community sample of 763 people with OA who participated in the Somerset and Avon Survey of Health. The SF-36 was explored for DIF with respect to demographic, social, clinical and psychological factors. Well developed ordinal regression models were used to identify DIF items.

RESULTS

DIF items were found by age (6 items), employment status (6 items), social class (2 items), mood (2 items), hip v knee (2 items), social deprivation (1 item) and body mass index (1 item). Although the impact of the DIF items rarely had a significant effect on the conclusions of group comparisons, in most cases there was a significant change in effect size.

CONCLUSIONS

Overall, the SF-36 performed well with only a small number of DIF items identified, a reassuring finding in view of the frequent use of the SF-36 in OA. Nevertheless, where DIF items were identified it would be advisable to analyse data taking account of DIF items, especially when age effects are the focus of interest.

BACKGROUND

A previous study had identified 45 items assessing the impact of atopic dermatitis (AD) on the whole family. From these it was intended to develop two separate scales, one assessing impact on carers and the other determining the effect on the child.

METHODS

The 45 items were included in three clinical trials designed to test the efficacy of a new topical treatment (pimecrolimus, Elidel cream 1%) in the treatment of AD in infants and children and in validation studies in the UK, US, Germany, France and the Netherlands. Rasch analyses were undertaken to determine whether an internationally valid, unidimensional scale could be developed that would inform on the direct impact of AD on the child.

RESULTS

Rasch analyses applied to the data from the trials indicated that the draft measure consisted of two scales, one assessing the QoL of the carer and the other (consisting of 12 items) measuring the impact of AD on the child. Three of the 12 potential items failed to fit the measurement model in Europe and five in the US. In addition, four items exhibiting differential item functioning (DIF) by country were identified. After removing the misfitting items and controlling for DIF it was possible to derive a scale; The Childhood Impact of Atopic Dermatitis (CIAD) with good item fit for each trial analysis. Analysis of the validation data from each of the different countries confirmed that the CIAD had adequate internal consistency, reproducibility and construct validity. The CIAD demonstrated the benefits of treatment with Elidel over placebo in the European trial. A similar (non-significant) trend was found for the US trials.

CONCLUSIONS

The study represents a novel method of dealing with the problem of DIF associated with different cultures. Such problems are likely to arise in any multinational study involving patient-reported outcome measures, as items in the scales are likely to be valued differently in different cultures. However, where all items in a scale fit both a single theoretical construct and the Rasch measurement model, it is feasible to conceive of outcome measures with a different set of items in each language.

BACKGROUND

The alexithymia construct is mainly characterized by a difficulty in identifying and expressing feelings that is thought to reflect a deficit in cognitive processing and regulation of emotional states. During the last decade, alexithymia has been associated with a large variety of medical and psychiatric disorders in the adult population. Although adolescence is probably an opportune time to explore processes of emotion regulation, alexithymia has been rarely examined during this period. The 20-item Toronto alexithymia scale (TAS-20) is the most widely used self-report measure of alexithymia. For this scale, a three-factor structure was proposed: difficulty identifying feelings (DIF), difficulty describing feelings (DDF) and externally oriented thinking (EOT). Research has yielded considerable evidence that the TAS-20 is a reliable and valid measure of alexithymia in normal and clinical adult samples. To date, no psychometric data concerning the use of the TAS-20 with adolescent samples are available.

OBJECTIVE

The aim of the study is to provide psychometric data concerning the TAS-20 when administered to healthy adolescents. Furthermore, in a developmental perspective, this study explores the evolution of alexithymia across age groups in adolescence.

METHODS

The TAS-20 was administered to a sample of 264 adolescents aged from 14 to 19 years. In order to compare alexithymia across age groups, the sample was divided into three groups: group 1 (<16 years old), group 2 (16-17 years old) and group 3 (>17 years old).

RESULTS

Results of a confirmatory factor analysis (CFA) confirmed that the data fitted well to the three-factor model of the TAS-20 (chi(2)/df=2.22, GFI=0.88, AGFI=0.84 and RMSEA=0.068). The internal reliability coefficients and mean interitem correlations are acceptable for DIF (alpha>0.60; mean interitem correlation=0.22) and good for DDF (alpha>0.70, mean interitem correlation=0.33). As often reported in most translations of the TAS-20, the internal reliability of EOT is poor. Results of a one-way Anova showed a significant linear trend indicating that, with age, the level of alexithymia (TAS-20 total score), the difficulty in identifying feelings and the externally oriented thinking decreased.

CONCLUSIONS

This study demonstrated that the TAS-20 has sufficient construct validity in a non-clinical sample of adolescents. Our results support the idea that adolescence period is associated with the development of the ability to regulate emotions.

Using fluorescence-activated cell sorting (FACS), we have studied the effect of the differentiation-inducing factor (DIF) on cellular Ca2+ in Dictyostelium discoideum. We have shown previously that freshly starved or postaggregation amoebae are heterogenous with respect to the amounts of cellular Ca2+ that they contain; the L or "low Ca2+" class exhibits a prespore tendency and the H or "high Ca2+" class exhibits a prestalk tendency. Upon adding DIF, within 2 min there is an approximately twofold increase in the relative fraction of amoebae falling in the H class. A major part of the increase is caused by Ca2+ influx from the extracellular medium. Therefore a rise in the level of cellular Ca2+ is an early step in the signal transduction pathway following stimulation by DIF. Also, in parallel with the cellular heterogeneity in respect of Ca2+ content, there is a heterogeneity in the response to DIF, which appears to be restricted to L cells.

BACKGROUND

Dexamethasone cyclophosphamide pulse (DCP) therapy is an established mode of treatment for pemphigus in India.

OBJECTIVE

To assess the therapeutic benefit of additional DCPs (phase II, consolidation phase) versus immediate oral cyclophosphamide, usually used in phase III (maintenance phase), after initial DCP therapy (phase I) and to assess which laboratory test (DIF or ELISA) will reflect the clinical relapse best.

METHODS

Nineteen newly recruited patients of pemphigus vulgaris (PV) received monthly DCPs in phase I and were then randomized into two groups. Group A (10 patients) received monthly DCPs for nine months and Group B (nine patients) received only oral cyclophosphamide for nine months. Direct immunofluorescence (DIF) and enzyme-linked immunosorbent assay (ELISA) were tested before starting DCP regimen, and at 0,3,6,9 months after randomization.

RESULTS

Clinical relapse by the end of follow-up period occurred in only one patient in each group. In these cases, DIF became (again) positive before the relapse. No statistically significant difference between the two groups was found at three, six and nine months by ELISA indices and DIF grading.

CONCLUSIONS

Although the DCP regimen is the standard therapy for pemphigus in India, we found no difference in the clinical outcome between patients receiving nine DCPs in phase II and patients shifted directly from phase I to III. Periodic testing using DIF and Dsg ELISA were found to be useful to monitor disease activity and predict a relapse. Further large scale studies are required to assess if patients can be shifted directly from phase I to III and maintained only on oral cyclophosphamide.

OBJECTIVE

To correlate disease course and complications in children with juvenile dermatomyositis (JDM) and polymyositis (JPM) with specific features of muscle pathology on biopsy.

METHODS

This is a retrospective cohort analysis of 59 children diagnosed with JDM or JPM between 1965 and 1998 and followed at the Cincinnati Children's Hospital Medical Center (CCHMC) for a mean duration of 7.3 years (range 1.1-24.5 years). Disease course was characterized as limited, chronic non-ulcerative or chronic ulcerative, similar to previously defined disease course subtypes reported by Crowe et al.(1). All subjects had diagnostic muscle biopsies performed at CCHMC and had disease for at least two years' duration in order to classify their disease course as either limited or chronic. Features of muscle histopathology that were evaluated included loss of the intramuscular capillary bed, infarct, perifascicular myopathy, direct immunofluorescence (DIF) staining of the intramuscular vasculature and specifically, the locale of DIF staining, i.e., small arteries or capillaries. Disease complications that were assessed included calcinosis, contractures, muscle atrophy, lipodystrophy, gastrointestinal ulceration, cutaneous ulceration and death. Data analysis was completed using Chi-square or Fisher's exact tests and logistic regression modeling.

RESULTS

Twenty-two children (37%) had limited disease, 24 (41%) had chronic non-ulcerative disease and 13 (22%) had chronic ulcerative disease. Neither loss of the intramuscular capillary bed nor perifascicular myopathy on muscle biopsy significantly correlated with disease course or the various complications evaluated in this study. DIF staining of intramuscular vessels overall was not significantly associated with clinical disease course, but the localization of DIF staining to intramuscular arteries (rather than to capillaries) was significantly associated with the outcome of chronic ulcerative disease. Nine of the 13 children with chronic ulcerative disease had DIF-arterial staining on muscle biopsy (69%), significantly greater than DIF-arterial staining in children with limited disease (32% had DIF-arterial staining) (p = 0.04), chronic non-ulcerative disease (8% had DIF-arterial staining) (p = 0.0002), and non-ulcerative disease overall (limited + chronic non-ulcerative disease groups combined) (20% had DIF-arterial staining), with p = 0.001. Additionally, lack of DIF-arterial staining on biopsy was significantly correlated with patients not having gastrointestinal ulceration (p = 0.002), cutaneous ulceration (p = 0.004) and/or death (p = 0.02) as disease-related complications. Infarct on muscle biopsy was significantly associated with the development of chronic ulcerative disease (p = 0.02), being present on biopsy in 23% of children with chronic ulcerative disease compared with none of the patients with chronic non-ulcerative disease and 4% of those with limited disease. Infarct on muscle biopsy correlated with the outcomes of death (p = 0.01) and gastrointestinal ulceration (p = 0.03), but not with the development of cutaneous ulceration (p = 0.18).

CONCLUSIONS

DIF-arterial staining and infarct on muscle biopsy are significantly associated with the development of chronic ulcerative disease in JDM and JPM, while perifascicular myopathy and loss of the intramuscular capillary network are not associated with disease course. The presence of DIF-arterial staining and infarct on biopsy should suggest early use of second-line therapeutic agents to more quickly bring disease activity under control.

The Drosophila immune response is characterized by the rapid and robust production of a battery of antimicrobial peptides immediately following infection. The genes encoding these antimicrobial peptides are controlled by two NF-κB signaling pathways that respond to microbial infection. The IMD pathway is triggered by DAP-type peptidoglycan, from the cell wall of most Gram-negative and certain Gram-positive bacteria, and activates the NF-κB precursor protein Relish. The Toll pathway, on the other hand, is stimulated by lysine-type peptidoglycan from many Gram-positive bacteria, β 1,3 glucans from many fungi, as well as by microbial proteases. Toll signaling leads to the activation and nuclear translocation of DIF or Dorsal, two other NF-κB homologs. This review presents our current understanding of the molecular mechanisms involved in microbial recognition and signal transduction in these two innate immune pathways.

OBJECTIVE

To study the diagnostic utility and clinical associations of immunoglobulin deposition, determined by direct immunofluorescence (DIF) in cutaneous leukocytoclastic vasculitis (LCV).

METHODS

We performed a retrospective study of all biopsy-proven LCV cases seen at Cleveland Clinic between 2007 and 2012. All LCV cases in which DIF was performed were included.

RESULTS

Of the 218 LCV cases, 106 cases had DIF performed and data from 88 cases were available: median (SD) age 53.3 (19.4), 52% male, 64.1% white, duration of rash 5.5 (20.8) months; follow-up 14 (19.7) months. DIF results showed any immunoglobulin and/or complement and/or fibrinogen in 70.5%, immunoglobulin A (IgA) in 36.4%, immunoglobulin M (IgM) in 21.6%, immunoglobulin G (IgG) in 11.4%. Patients with IgA deposition by DIF, compared with those without IgA, were younger, 44 (19) versus 56 (17) (P = 0.006), more likely to be white (P = 0.025) and had more organs affected by vasculitis (P = 0.002), higher incidence of gastrointestinal tract involvement (P = 0.0001) and renal disease (P = 0.006). No differences between rates of infection or malignancy were seen between DIF IgA, IgM, or IgG-positive versus negative patients.

CONCLUSIONS

In patients with cutaneous LCV, IgA is the most common immunoglobulin found by DIF. IgA deposition, but not IgM or IgG, is predictive of associated renal and gastrointestinal organ involvement by vasculitis. No association between the type of immunoglobulin and preexisting infection or malignancy was found. DIF results add information that is clinically relevant to the diagnosis and management of LCV.

BACKGROUND

The DSM-IV age at onset criterion for attention-deficit/hyperactivity disorder (ADHD) has been a subject of debate. In DSM-5, the required age at onset (ie, the age by which impairing symptoms must have been present) has increased from 7 years to 12 years. The present study examined measurement properties of ADHD symptoms according to age at onset.

METHODS

Data were derived from the 2004-2005 National Epidemiologic Survey on Alcohol and Related Conditions, which included 34,653 US participants. Among participants with a lifetime DSM-IV diagnosis of ADHD (assessed using the Alcohol Use Disorder and Associated Disabilities Interview Schedule-IV), we compared the psychometric properties of the 18 ADHD symptoms according to 3 categories of age at onset (≤ 7 years,>> 7 and ≤ 12 years, and>> 12 and ≤ 18 years). A 2-parameter item response model was used to estimate differential item functioning (DIF) between these groups.

RESULTS

364 participants with a lifetime DSM-IV diagnosis of ADHD had an age at onset ≤ 7 years, 252 had an age at onset>> 7 and ≤ 12 years, and 148 had an age at onset>> 12 and ≤ 18 years. In both dimensions of ADHD (ie, inattention and hyperactivity-impulsivity), there was no significant DIF between age at onset groups.

CONCLUSIONS

Expression of DSM-IVADHD symptoms was not affected by age at onset in the 3 groups considered. This study provides psychometric support to the change in the age criterion introduced by DSM-5 and further suggests that the age at onset criterion could be extended to 18 years without changing the psychometric properties of the ADHD symptoms.

BACKGROUND

Alexithymia, the difficulty in describing or recognizing emotions, has been associated with various psychosomatic pathologies including psoriasis. The aim of this study was to examine the prevalence of alexithymia and its association with anxiety and depression in patients with psoriasis compared with healthy participants, while taking into consideration demographic and clinical variables.

METHODS

One hundred and eight psoriatic patients and 100 healthy participants from the general population completed the Toronto Alexithymia Scale (TAS-20) and the Hospital Anxiety and Depression Scale (HADS). The severity of patients' psoriasis was clinically assessed using the Psoriasis Area and Severity Index (PASI).

RESULTS

Psoriatic patients had higher levels of alexithymia compared with healthy participants. While a rather high rate of psoriatic patients presented anxiety and depression as defined by the HADS, the differences that were found in comparison with the control group were not significant. Neither alexithymia nor its dimensions, difficulty in identifying feelings (DIF), difficulty in describing feelings (DDF) and externally oriented thinking (EOT), were associated with gender or psoriasis severity. Age was associated only with EOT, which was independent of depression and anxiety. Higher anxiety and depression were connected with higher alexithymia and DIF, while higher anxiety with higher DDF as well.

CONCLUSIONS

The alexithymia prevalence was higher in psoriatic patients than that in healthy participants, while it was positively correlated with anxiety and depression. Difficulty in identifying feelings was connected with both anxiety and depression, whereas difficulty in describing them was only with anxiety. Finally, externally oriented thinking was predicted only from age.

Direct (DIF) and indirect (IIF) immunofluorescence, indirect immunoperoxidase conjugate (IPC) and unlabelled antibody peroxidase antiperoxidase (PAP) staining was performed on sections of artificial substrate containing different concentrations of human immunoglobulin (Ig)A or IgG. Detection sensitivity, in terms of the lowest amount of discernible antigen, was evaluated by direct microscopy and by microphotometry. Staining efficiency (signal-to-noise ratio) was evaluated by microphotometry. Only minor differences in antigen detection sensitivity were found when IPC and PAP were compared with DIF and IIF under appropriate conditions. The sensitivity of DIF was only marginally improved by raised conjugate concentration and prolonged incubation time. Microphotometry of DIF on ethanol-fixed IgA substrate revealed that the staining intensity increased proportionally with the antigen concentration whereas on formaldehyde-fixed substrate a progressive masking of the antigen was indicated which, however, could be overcome by applying raised conjugate concentration and prolonged incubation time. Such antigenic self masking was of relatively little importance to IPC and PAP staining, probably because of the inherent amplification in these methods. An additional masking effect due to extraneous protein was revealed by DIF when ethanol-fixed sections had been soaked in bovine serum albumin and postfixed with formaldehyde; unmasking was achieved by proteolytic treatment of the sections.

OBJECTIVE

Use multidimensional polytomous item response modeling (MPIRM) to evaluate the psychometric properties of a television (TV) parenting practices (PP) instrument. Perform differential item functioning (DIF) analysis to test whether item parameter estimates differed across education, language, or age groups.

METHODS

Secondary analyses of data from three studies that included 358 children between the ages of 3 and 12 years old in Houston, Texas. TV PP included 15 items with three subscales: social co-viewing, instructive parental mediation, and restrictive parenting. The multidimensional partial credit model was used to assess the performance. DIF was used to investigate the differences in psychometric properties across subgroups.

RESULTS

Classical test theory analyses revealed acceptable internal consistency reliability (Cronbach's α: 0.72 to 0.83). More items displaying significant DIF were found across children's age groups than parental education or language groups. A Wright map revealed that items covered only a restricted range of the distribution, at the easier to respond end of the trait.

CONCLUSIONS

TV PP scales functioned differently on the basis of parental education, parental language, and child age, with the highest DIF among the latter. Additional research is needed to modify the scales to minimize these moderating influences. Some items may be age specific.

This study examined the effects of a 14-week running program on VO2max, as well as cardiac output (Q) and arterial-venous O2 difference (a-vO2 dif) at submaximal intensities corresponding to 50 and 75% of VO2max. Thirteen boys (mean age 10.6 +/- 1.2 yrs) served as experimental subjects while 13 other boys of similar age (mean age 10.2 +/- 1.2 yrs) served as controls. Mean VO2max in the runners increased 13%, from 44.2 +/- 7.0 to 49.9 +/- 6.3 ml.kg-1.min-1. Posttraining VO2 during submaximal and maximal exercise was significantly (p < 0.05) greater in the runners than in the controls. Q and SV exhibited an increase of 10% at each intensity, but posttraining differences between groups were not significant (p>> 0.05). A-vO2 dif increased by 8% at 50% of VO2max and by 6% at 75% of VO2max, and was significantly greater in the runners following training. These results indicate that increases in submaximal relative VO2 in children are mediated by increases in a-vO2 dif and Q.

Chlorinated compounds are important environmental pollutants whose biodegradation may be limited by inefficient dechlorinating enzymes. Dictyostelium amoebae produce a chlorinated alkyl phenone called DIF which induces stalk cell differentiation during their multicellular development. Here we describe the identification of DIF dechlorinase. DIF dechlorinase is active when expressed in bacteria, and activity is lost from Dictyostelium cells when its gene, drcA, is knocked out. It has a K(m) for DIF of 88 nM and K(cat) of 6.7 s(-1). DrcA is related to glutathione S-transferases, but with a key asparagine-to-cysteine substitution in the catalytic pocket. When this change is reversed, the enzyme reverts to a glutathione S-transferase, thus suggesting a catalytic mechanism. DrcA offers new possibilities for the rational design of bioremediation strategies.

A previous report described an intracellular factor (differentiation-inducing factor I, or DIF-I) that seems to play a role in erythroid differentiation in mouse erythroleukemia (MEL) cells. We have detected another erythroid-inducing factor in cell-free extracts from dimethyl sulfoxide- or hexamethylenebis(acetamide)-treated MEL cells, which acts synergistically with DIF-I. The partially purified factor (termed DIF-II) triggered erythroid differentiation when introduced into undifferentiated MEL cells that had been potentiated by the induction of DIF-I. The activity in the extracts appeared in an inducible manner after addition of dimethyl sulfoxide or hexamethylenebis(acetamide), reached a maximum at 6 hr, and then rapidly decreased. The induction was inhibited by phorbol 12-myristate 13-acetate and also by cycloheximide. No induction was observed in a mutant MEL cell line defective in erythroid differentiation. These characteristics are consistent with the supposition that DIF-II is one of the putative dimethyl sulfoxide-inducible factors detected in previously reported cell-fusion and cytoplast-fusion experiments. The role of DIF-II in MEL-cell differentiation and in vitro differentiation in general is discussed.

OBJECTIVE

We have previously validated the English version of the Systemic Lupus Erythematosus Quality of Life Questionnaire (SLEQOL) in our patients with lupus. Many of our Chinese patients are not fluent in English and therefore a Chinese version (SLEQOL-C) has been adapted for their use.

METHODS

Two independent translators translated the SLEQOL into Chinese. A consensus version was derived from both sets of translations. Back translation of this version was performed by another 2 independent translators who had neither been involved in the forward translation nor encountered the SLEQOL. The final version, SLEQOL-C, was finalized after rectifying the discrepancies revealed by the back translation. Linguistic validity was tested in open interviews with bilingual patients with lupus. The SLEQOL-C and SLEQOL were administered to patients to determine whether they displayed differential item functioning (DIF).

RESULTS

In general, most of the items in English could be expressed in Chinese precisely, although a few instructions had to be altered slightly to make them more idiomatic. The forward and back translations of the SLEQOL were accomplished without major difficulties. A total of 638 patients were interviewed (62.8% with the SLEQOL and 37.2% with the SLEQOL-C). Using DIF analysis, there was no detectable test bias due to language use after controlling for repeated observations, age, sex, and ethnicity.

CONCLUSIONS

The SLEQOL-C has semantic, idiomatic, and conceptual equivalence to the SLEQOL. The rigorous process of cross-cultural translation provides some measure of quality in the content validity.

BACKGROUND

Although much is known about the higher prevalence of anxiety and depressive disorders among adolescent females, less is known about the differential item endorsement due to gender in items of scales commonly used to measure anxiety and depression.

OBJECTIVE

We conducted a study to examine if adolescent males and females from Chile differed on how they endorsed the items of the Youth Self Report (YSR) anxious/depressed problem scale. We used data from a cross-sectional sample consisting of 925 participants (mean age = 14, SD 1.3, 49% females) of low to lower-middle socioeconomic status.

METHODS

A two-parameter logistic (2PL) IRT DIF model was fit.

RESULTS

RESULTS

s revealed differential item functioning (DIF) by gender for six of the 13 items, with adolescent females being more likely to endorse a depression item while males were found more likely to endorse anxiety items.

CONCLUSIONS

Findings suggest that items found in commonly used measures of anxiety and depression symptoms may not equally capture the true levels of these behavioural problems in adolescent males and females. Given the high levels of mental disorders in Chile and the surrounding countries, further attention should be focused on increasing the number of empirical studies examining potential gender differences in the assessment of mental health problems among Latin American populations to better aid our understanding of the phenomenology and determinants of these problems in the region.

We have previously reported that chronic hypertension develops consistently in Wistar rats with a 25% reduction in renal mass (RRM) following the induction of insulin dependent diabetes mellitus (IDDM) with streptozotocin (STZ, 65 mg/kg body weight, intravenously). In this study, we examined the role of the endogenous digitalis-like substance in the development of hypertension. Four groups of rats were studied: 1) 25% RRM rats with STZ-induced IDDM (25-DM), 2) normal rats with STZ-induced IDDM (2K-DM), 3) 25% RRM rats with vehicle treatment (25-V), and 4) normal rats with vehicle treatment (2K-V). In 25-DM rats, blood pressure progressively increased during the 3 weeks after STZ treatment and was associated with microalbuminuria, low plasma renin activity, and extracellular volume expansion. In contrast, the 2K-DM, 25-V, and 2K-V rats remained normotensive. Furthermore, the plasma and urine levels of digoxin-like immunoreactive factor (DIF), determined by digoxin radioimmunoassay (Baxter), were significantly higher in hypertensive 25-DM rats than in their controls. The same was the case for plasma digitalis-like substance (DLS), determined by exposing canine Na+,K(+)-ATPase to plasma fractions and observing the percent inhibition. Increased DIF and DLS in hypertensive 25-DM rats was associated with a significant decrease in Na+,K(+)-ATPase activity of microsomes prepared from the left and right ventricles, when compared with microsomes from normotensive 2K-DM animals. Microsomal 5'-nucleotidase, a plasma membrane marker, was unchanged. The DIF and DLS correlated significantly with each other and with myocardial Na+,K(+)-ATPase activity and mean blood pressure. These results suggest that increased endogenous digitalis-like substance, which inhibits cardiovascular muscle cell Na(+)-K(+)-pump activity, may be involved in the mechanism of hypertension associated with IDDM in 25% RRM rats.

OBJECTIVE

In order to test the difference between group means, the construct measured must have the same meaning for all groups under investigation. This study examined the measurement invariance of responses to the patient-reported outcomes measurement information system (PROMIS) pain behavior (PB) item bank in two samples: the PROMIS calibration sample (Wave 1, N = 426) and a sample recruited from the American Chronic Pain Association (ACPA, N = 750). The ACPA data were collected to increase the number of participants with higher levels of pain.

METHODS

Multi-group confirmatory factor analysis (MG-CFA) and two item response theory (IRT)-based differential item functioning (DIF) approaches were employed to evaluate the existence of measurement invariance.

RESULTS

MG-CFA results supported metric invariance of the PROMIS-PB, indicating unstandardized factor loadings with equal across samples. DIF analyses revealed that impact of 6 DIF items was negligible.

CONCLUSIONS

Based on the results of both MG-CFA and IRT-based DIF approaches, we recommend retaining the original parameter estimates obtained from the combined samples based on the results of MG-CFA.

In E. coli, 10 to 15% of growing bacteria produce dimeric chromosomes during DNA replication. These dimers are resolved by XerC and XerD, two tyrosine recombinases that target the 28-nucleotide motif (dif) associated with the chromosome's replication terminus. In streptococci and lactococci, an alternative system is composed of a unique, Xer-like recombinase (XerS) genetically linked to a dif-like motif (dif(SL)) located at the replication terminus. Preliminary observations have suggested that the dif/Xer system is commonly found in bacteria with circular chromosomes but that assumption has not been confirmed in an exhaustive analysis. The aim of the present study was to extensively characterize the dif/Xer system in the proteobacteria, since this taxon accounts for the majority of genomes sequenced to date. To that end, we analyzed 234 chromosomes from 156 proteobacterial species and showed that most species (87.8%) harbor XerC and XerD-like recombinases and a dif-related sequence which (i) is located in non-coding sequences, (ii) is close to the replication terminus (as defined by the cumulative GC skew) (iii) has a palindromic structure, (iv) is encoded by a low G+C content and (v) contains a highly conserved XerD binding site. However, not all proteobacteria display this dif/XerCD system. Indeed, a sub-group of pathogenic epsilon-proteobacteria (including Helicobacter sp and Campylobacter sp) harbors a different recombination system, composed of a single recombinase (XerH) which is phylogenetically distinct from the other Xer recombinases and a motif (dif(H)) sharing homologies with dif(SL). Furthermore, no homologs to dif or Xer recombinases could be detected in small endosymbiont genomes or in certain bacteria with larger chromosomes like the Legionellales. This raises the question of the presence of other chromosomal deconcatenation systems in these species. Our study highlights the complexity of dif/Xer recombinase systems in proteobacteria and paves the way for systematic detection of these components in prokaryotes.

We recently proposed that guillotining of dimer chromosomes occurs at cell division in resolvase mutants of Escherichia coli. This was based on the abnormal pattern of cell division observed in 10-14% of the cells in microcolonies of xerC, xerD and dif mutants. A prediction of this guillotining is that DNA degradation should occur in the terminus region, in the vicinity of the dif locus. We have tested this by DNA-DNA hybridization and have observed that dif was absent in about 22% of the chromosomes in exponentially growing xerC mutants. A locus 206 kb from dif was not affected by this degradation. We have also observed that degradation did not occur in xerC recD mutants, and that the low efficiency of plating associated with the Dif phenotype was suppressed in this strain. A model is proposed in which rapid degradation of the terminus region does not occur in recD mutants following guillotining, and that this permits the initiation of repair of broken dimer chromosomes prior to completion of cell division.

The FtsK dsDNA translocase functions in bacterial chromosome unlinking by activating XerCD-dif recombination in the replication terminus region. To analyze FtsK assembly and translocation, and the subsequent activation of XerCD-dif recombination, we extended the tethered fluorophore motion technique, using two spectrally distinct fluorophores to monitor two effective lengths along the same tethered DNA molecule. We observed that FtsK assembled stepwise on DNA into a single hexamer, and began translocation rapidly (∼ 0.25 s). Without extruding DNA loops, single FtsK hexamers approached XerCD-dif and resided there for ∼ 0.5 s irrespective of whether XerCD-dif was synapsed or unsynapsed. FtsK then dissociated, rather than reversing. Infrequently, FtsK activated XerCD-dif recombination when it encountered a preformed synaptic complex, and dissociated before the completion of recombination, consistent with each FtsK-XerCD-dif encounter activating only one round of recombination.