OBJECTIVE

To demonstrate the value of item response theory (IRT) and differential item functioning (DIF) methods in examining a health-related quality-of-life measure in children and adolescents.

METHODS

This illustration uses data from 5,429 children using the four subscales of the PedsQL 4.0 Generic Core Scales. The IRT model-based likelihood ratio test was used to detect and evaluate DIF between healthy children and children with a chronic condition.

RESULTS

DIF was detected for a majority of items but canceled out at the total test score level due to opposing directions of DIF. Post hoc analysis indicated that this pattern of results may be due to multidimensionality. We discuss issues in detecting and handling DIF.

CONCLUSIONS

This article describes how to perform DIF analyses in validating a questionnaire to ensure that scores have equivalent meaning across subgroups. It offers insight into ways information gained through the analysis can be used to evaluate an existing scale.

We have studied the growth and division of xerC, xerD and dif mutants of Escherichia coli, which are unable to resolve dimer chromosomes. These mutants express the Dif phenotype, which includes reduced viability, SOS induction and filamentation, and abnormal nucleoid morphology. Growth was studied in synchronous cultures and in microcolonies derived from single cells. SOS induction and filamentation commenced after an apparently normal cell division, which sheared unresolved dimer chromosomes. This has been called guillotining. Microcolony analysis demonstrated that cell division in the two daughter cells was inhibited after guillotining, and microcolonies formed that consisted of two filaments lying side by side. Growth of these filaments was severely reduced in hipA+ strains. We propose that guillotining at dif destroys the expression of the adjacent hipBA genes and, in the absence of continued formation of HipB, HipA inhibits growth. The length of the filaments was also affected by SfiA: sfiA dif hipA mutants initially formed filaments, but cell division at the ends of the filaments ultimately produced a number of DNA-negative cells. If SOS induction was blocked by lexA3 (Ind-), filaments did not form, and cell division was not inhibited. However, pedigree analysis of cells in microcolonies demonstrated that lethal sectoring occurred as a result of limited growth and division of dead cells produced by guillotining.

The Dictyostelium slug contains a simple anterior-posterior pattern of prestalk and prespore cells. It is likely that DIF, the morphogen which induces stalk cells, is involved in establishing this pattern. Previous work has shown that a number of distinct species of DIF are released by developing cells and that cell-associated DIF activity increases rapidly during the slug stage of development. In this paper we describe a comparison of the DIF extracted from slugs with the DIF released into the medium. Analysis by high-pressure liquid chromatography (HPLC) using different solvent systems shows that the major species of DIF activity extracted from slugs coelutes with DIF-1, the major species of released DIF and is similarly sensitive to sodium borohydride reduction. Since DIF specifically induces the differentiation of prestalk cells, the anterior cells of the slug, it could be anticipated that DIF is localized in the prestalk region. We have therefore determined the distribution of DIF within the slug. Migrating slugs from strain V12M2 were manually dissected into anterior one-third and posterior two-third fragments and the DIF activity extracted. Surprisingly, we found that DIF was not restricted to the prestalk fragment. Instead there appears to be a reverse gradient of DIF in the slug with at least twice the specific activity of total DIF in the prespore region than in the prestalk region.

FtsK translocates dsDNA directionally at >5 kb/s, even under strong forces. In vivo, the action of FtsK at the bacterial division septum is required to complete the final stages of chromosome unlinking and segregation. Despite the availability of translocase structures, the mechanism by which ATP hydrolysis is coupled to DNA translocation is not understood. Here, we use covalently linked translocase subunits to gain insight into the DNA translocation mechanism. Covalent trimers of wild-type subunits dimerized efficiently to form hexamers with high translocation activity and an ability to activate XerCD-dif chromosome unlinking. Covalent trimers with a catalytic mutation in the central subunit formed hexamers with two mutated subunits that had robust ATPase activity. They showed wild-type translocation velocity in single-molecule experiments, activated translocation-dependent chromosome unlinking, but had an impaired ability to displace either a triplex oligonucleotide, or streptavidin linked to biotin-DNA, during translocation along DNA. This separation of translocation velocity and ability to displace roadblocks is more consistent with a sequential escort mechanism than stochastic, hand-off, or concerted mechanisms.

OBJECTIVE

This study examined the construct validity, and improved the test reliability and the estimation accuracy for the correlation between domains of the WHOQOL-BREF using multidimensional Rasch analysis.

METHODS

A total of 13,083 adults were administered the 28-item WHOQOL-BREF Taiwan version, which consists of 4 subscales (domains). The multidimensional form of the partial credit model was used to examine the fit of the 4 subscales. For comparison, each subscale individually was also fitted to the unidimensional partial credit model. Standard item fit statistics and analysis of differential item functioning (DIF) were used to check model-data fit.

RESULTS

After excluding 2 overall items and deleting 7 DIF items, the remaining items of each subscale in the WHOQOL-BREF constituted a single construct. The test reliabilities and correlations between domains obtained from the multidimensional approach, (0.82-0.86) and (0.79-0.89), respectively, were much higher than those obtained from the unidimensional approach, (0.67-0.75) and (0.53-0.65), respectively.

CONCLUSIONS

The 19-item WHOQOL-BREF measures more succinct latent traits than the original design. The multidimensional approach yields not only more accurate estimates for the correlation between domains but also substantially higher reliabilities, than the standard unidimensional approach.

BACKGROUND

Since its first publication, the Clinical Global Impression Scale (CGI) has become one of the most widely used assessment instruments in psychiatry. Although some conflicting data has been presented, studies investigating the CGI's validity have only rarely been conducted so far. It is unclear whether the improvement index CGI-I or a difference score of the severity index CGI-S (dif) is more valid in depicting clinical change. The current study examined the validity of these two measures and investigated whether therapists' CGI ratings correspond to the view the patients themselves have on their condition.

METHODS

Thirty-one inpatients of a German psychotherapeutic hospital suffering from a major depressive disorder (age M = 45.3, SD = 17.2; 58.1% women) participated. Patients filled in the Beck Depression Inventory (BDI). CGI-S and CGI-I were rated from three perspectives: the treating therapist (THER), the team of therapists involved in the patient's treatment (TEAM), and the patient (PAT). BDI and CGI-S were filled in at admission and discharge, CGI-I at discharge only. Data was analysed using effect sizes, Spearman's ρ and intra-class correlations (ICC).

RESULTS

Effect sizes between CGI-I and CGI-S (dif) ratings were large for all three perspectives with substantially higher change scores on CGI-I than on CGI-S (dif). BDI (dif) correlated moderately with PAT ratings, but did not correlate significantly with TEAM or THER ratings. Congruence between CGI-ratings from the three perspectives was low for CGI-S (dif) (ICC = .37; Confidence Interval [CI] .15 to .59; F(30,60) = 2.77, p < .001; mean ρ = 0.36) and moderate for CGI-I (ICC = .65 (CI .47 to .80; F(30,60) = 6.61, p < .001; mean ρ = 0.59).

CONCLUSIONS

Results do not suggest a definite recommendation for whether CGI-I or CGI-S (dif) should be used since no strong evidence for the validity of neither of them could be found. As congruence between CGI ratings from patients' and staff's perspective was not convincing it cannot be assumed that CGI THER or TEAM ratings fully represent the view of the patient on the severity of his impairment. Thus, we advocate for the incorporation of multiple self- and clinician-reported scales into the design of clinical trials in addition to CGI in order to gain further insight into CGI's relation to the patients' perspective.

AIM:To study the effects of arsenic trioxide and HCPT on dif ferent degrees of differentiated gastric cancer cells (SGC-7901, MKN-45, MKN-28) with respect to both cytotoxicity and induction of apoptosis in vitro.METHODS:The cytotoxicity of As(2)O(3) and HCPT on gastric cancer cells was det ermined by MTT assay.Morphologic changes of apoptosis of gastric cancer cells were observed by light microscopy and transmission electron microscopy.Apoptosis and cell cycle changes of gastric cancer cells induced by HCPT and As(2)O(3) we re investigated by TUNEL method and flow cytometry.RESULTS:As(2)O(3) and HCPT had remarkable cytotoxic effects on different degrees of differentiated gastric cancer cells. The IC(50) of As(2)O(3) on well differentiated gastric cancer cell MKN-28, moderately differentiated gastric cancer cell SGC-7901, and poorly differentiated gastric cancer cell MKN-28 were 8.91 &mgr;mol/L, 10.57 &mgr;mol/L, and 11.65&mgr;mol/L, respectively. The IC(50) of HCP T on MKN-28, SGC-7901, and MKN-45 were 9.35 mg/L, 10.21 mg/L,and 12.63 mg/L respectively after 48 h treatment. After 12 h of exposure to both drugs, gastric cancer cells exhibited morphologic features of apoptosis, includ ing cell shrinkage,nuclear condensation, and formation of apoptotic bodies. A ty pical subdiploid peak before G(0)/G(1) phase was observed by flow cytometry. The apoptotic rates of SGC-7901, MKN-45, and MKN-28 were 13.84%, 22.52%, and 9.68%, respectively after48 h exposure to 10&mgr;mol/L As(2)O(3). The apoptotic ra tes of SGC-7901, MKN-45, and MKN-28 were 21.88%, 12.35%, and 30.26%, resp ectively after 48 h exposure to 10 mg/L HCPT. The apoptotic indice were 7%-15% a s assessed by TUNEL method. The effect of As(2)O(3) on SGC-7901 showed remarkab le cell cycle specificity, which induced cell death in G(1) phase, and blocked G(2)/M phase.HCPT also showed a remarkable cell cycle specificity, by inducing cell death and apoptosis in G(1) phase and arrest of proliferation at Sphase.CONCLUSION:As(2)O(3) and HCPT exhibit significant cytotoxicity on gastric canc er cells by induction of apoptosis. As(2)O(3) and HCPT might have a promising pr ospect in the treatment of gastric cancer, which needs to be further studied.

Differentiation-inducing factor (DIF)-1 is a chlorinated alkyl phenone released by developing Dictyostelium amoebae, which induces them to differentiate into stalk cells. A biosynthetic pathway for DIF-1 is proposed from labeling, inhibitor, and enzymological experiments. Cells incorporate 36Cl- into DIF-1 during development, showing that the chlorine atoms originate from chloride ions; peak incorporation is at the first finger stage. DIF-1 synthesis can be blocked by cerulenin, a polyketide synthase inhibitor, suggesting that it is made from a polyketide. This is most likely the C12 polyketide (2,4,6-trihydroxyphenyl)-1-hexan-1-one (THPH). Feeding experiments confirm that living cells can convert THPH to DIF-1. Conversion requires both chlorination and methylation of THPH, and enzymatic activities able to do this exist in cell lysates. The chlorinating activity, assayed using 36Cl-, is stimulated by H2O2 and requires both soluble and particulate components. It is specific for THPH and does not use this compound after O-methylation. The methyltransferase is soluble, uses S-adenosyl-L-methionine as a co-substrate, has a Km for dichloro-THPH of about 1.1 microM, and strongly prefers this substrate to close analogues. Both chlorinating and methyltransferase activities increase in development in parallel with DIF-1 production, and both are greatly reduced in a mutant strain that makes little DIF-1. It is proposed that DIF-1 is made by the initial assembly of a C12 polyketide skeleton, which is then chlorinated and methylated.

BACKGROUND

Quality of life (QoL) in persons with spinal cord injury (SCI) has been found to differ across countries. However, comparability of measurement results between countries depends on the cross-cultural validity of the applied instruments. The study examined the metric quality and cross-cultural validity of the Satisfaction with Life Scale (SWLS), the Life Satisfaction Questionnaire (LISAT-9), the Personal Well-Being Index (PWI) and the 5-item World Health Organization Quality of Life Assessment (WHOQoL-5) across six countries in a sample of persons with spinal cord injury (SCI).

METHODS

A cross-sectional multi-centre study was conducted and the data of 243 out-patients with SCI from study centers in Australia, Brazil, Canada, Israel, South Africa, and the United States were analyzed using Rasch-based methods.

RESULTS

The analyses showed high reliability for all 4 instruments (person reliability index .78-.92). Unidimensionality of measurement was supported for the WHOQoL-5 (Chi2 = 16.43, df = 10, p = .088), partially supported for the PWI (Chi2 = 15.62, df = 16, p = .480), but rejected for the LISAT-9 (Chi2 = 50.60, df = 18, p = .000) and the SWLS (Chi2 = 78.54, df = 10, p = .000) based on overall and item-wise Chi2 tests, principal components analyses and independent t-tests. The response scales showed the expected ordering for the WHOQoL-5 and the PWI, but not for the other two instruments. Using differential item functioning (DIF) analyses potential cross-country bias was found in two items of the SWLS and the WHOQoL-5, three items of the LISAT-9 and four items of the PWI. However, applying Rasch-based statistical methods, especially subtest analyses, it was possible to identify optimal strategies to enhance the metric properties and the cross-country equivalence of the instruments post-hoc. Following the post-hoc procedures the WHOQOL-5 and the PWI worked in a consistent and expected way in all countries.

CONCLUSIONS

QoL assessment using the summary scores of the WHOQOL-5 and the PWI appeared cross-culturally valid in persons with SCI. In contrast, summary scores of the LISAT-9 and the SWLS have to be interpreted with caution. The findings of the current study can be especially helpful to select instruments for international research projects in SCI.

BACKGROUND

The construct validity of alexithymia and its assessment using the 20-item Toronto Alexithymia Scale (TAS-20) in Japan is unknown. Low reliability has been found for the third factor of the TAS-20 in some cultures, and the factor structure for psychosomatic disorder patients has not been adequately investigated. Although alexithymia most likely has certain developmental aspects, this has infrequently been investigated.

METHODS

The newly-developed Japanese TAS-20 was administered to a normative sample (n = 2,718; 14-84 y.o.), along with the NEO Five-Factor Inventory (NEO-FFI) for cross validation. Psychosomatic patients (n = 1,924, 12-87 y.o.) were tested to evaluate the factor structure in a clinical sample. College students (n = 196) were used for a test-retest study. Internal reliability and consistency were assessed, and the factorial structure was evaluated using confirmatory and exploratory factor analyses for both the normative and the clinical samples. The correlations between the TAS-20 and the NEO-FFI factor scores were evaluated. Age-related and gender differences in the TAS-20 were explored using analysis of variance in the normative sample.

RESULTS

The original three-factor model of the TAS-20 was confirmed to be valid for these Japanese samples, although a 4-factor solution that included negatively keyed items (NKI) as an additional factor was more effective. Significant correlations of the TAS-20 with the NEO-FFI were found, as has been previously reported. Factor analyses of the normative and patient samples showed similar patterns. The TAS-20 total, difficulty in identifying feelings (DIF), and difficulty in describing feelings (DDF) scores were high for teenagers, decreased with age, and from 30s did not change significantly. In contrast, externally oriented thinking (EOT) scores showed an almost linear positive correlation with age. DIF scores were higher for females, while EOT scores were higher for males, without any interaction between gender and age differences.

CONCLUSIONS

The original three-factor concept of the TAS-20 was generally supported for practical use. Age-related differences in TAS-20 scores indicate developmental aspects of alexithymia. Alexithymia is made up of two components with different developmental paths: DIF/DDF and EOT.

A number of cytokines have been found to be potent regulators of bone resorption and to share the properties originally attributed to osteoclast-activating factor. One such activity, differentiation-inducing factor (DIF, D-factor) from mouse spleen cells, shares a number of biological and biochemical properties with the recently characterized and cloned leukemia inhibitory factor (LIF). We have assessed the effects of recombinant LIF on bone resorption and other parameters in neonatal mouse calvaria. Both recombinant murine and human (h) LIFs stimulated 45Ca release from prelabeled calvaria in a dose-dependent manner. The increase in bone resorption was associated with an increase in the number of osteoclasts per mm2 bone. The osteolytic effect of hLIF were blocked by 10(-7) M indomethacin. hLIF also stimulated incorporation of [3H] thymidine into calvaria, but the dose-response relationship was distinct from that for bone resorption, and this effect was not blocked by indomethacin. Similarly, hLIF increased [3H]phenylalanine incorporation into calvaria, and this was also not inhibited by indomethacin. It is concluded that LIF stimulates bone resorption by a mechanism involving prostaglandin production, but that a distinct mechanism is responsible for its stimulation of DNA and protein synthesis. The primary structure of LIF differs from that of other fully characterized, bone-active cytokines, and it, thus, represents a novel factor which may be involved in the normal regulation of bone cell function.

OBJECTIVE

To evaluate whether items of the Patient Health Questionnaire 9 (PHQ-9) function differently in persons with traumatic brain injury (TBI) than in persons from a primary care sample.

METHODS

This study was a retrospective analysis of responses to the PHQ-9 collected in 2 previous studies. Responses to the PHQ-9 were modeled using item response theory, and the presence of DIF was evaluated using ordinal logistic regression.

METHODS

Eight primary care sites and a single trauma center in Washington state.

METHODS

Participants (N=3365) were persons from 8 primary care sites (n=3000) and a consecutive sample of persons with complicated mild to severe TBI from a trauma center who were 1 year postinjury (n=365).

METHODS

Not applicable.

METHODS

PHQ-9.

RESULTS

No PHQ-9 item demonstrated statistically significant or meaningful DIF attributable to TBI. A sensitivity analysis failed to show that the cumulative effects of nonsignificant DIF resulted in a systematic inflation of PHQ-9 total scores. Therefore, the results also do not support the hypothesis that cumulative DIF for PHQ-9 items spuriously inflates the numbers of persons with TBI screened as potentially having major depressive disorder.

CONCLUSIONS

The PHQ-9 is a valid screener of major depressive disorder in people with complicated mild to severe TBI, and all symptoms can be counted toward the diagnosis of major depressive disorder without special concern about overdiagnosis or unnecessary treatment.

5,6-Dichloro-1-(beta-D-ribofuranosyl)benzimidazole (DiCl-RB) is a powerful inhibitor of casein kinase-2 (CK-2) [Zandomeni, R. et al. (1986) J. Biol. Chem. 261, 3414-3420]. Here a series of 17 analogues of DiCl-RB has been employed for studying the specificity and the mode of action of this family of CK-2 inhibitors. The two halogen substituents on the benzene ring are shown to play a prominent role in inhibition, the 5,6-dibromo derivative (DiBr-RB) being fivefold more effective than DiCl-RB (Ki = 2 microM, with GTP as substrate), whereas the difluoro derivative (DiF-RB) is nearly as ineffective as unsubstituted 1-(beta-D-ribofuranosyl)benzimidazole. On the other hand, although some modifications of the ribose group significantly decrease the inhibitory efficiency, the sugar moiety is not strictly required, since dichlorobenzimidazole itself (DiCl-Bz) is an inhibitor almost as good as DiCl-RB. Inhibition of CK-2 by DiCl-RB and by its analogues, DiCl-Bz included, is of the competitive type with respect to the nucleotide substrate, the Ki values being lower with GTP than with ATP. The Ki values of the most potent inhibitor, DiBr-RB, with ATP and GTP, are 6 microM and 2 microM, respectively, denoting an affinity for the enzyme higher than that of the physiological substrates, ATP and GTP. DiBr-RB has been assayed for its inhibitory capacity toward several protein kinase other than CK-2. Protein kinase-C, cAMP-dependent protein kinase, the Ser/Thr protein kinase expressed by Pseudorabies virus, and four different tyrosine protein kinases from spleen, proved insensitive to DiBr-RB concentrations capable of almost entirely suppressing the activity of rat liver and maize seedling CK-2. Casein kinase-1 however is nearly as sensitive as CK-2 to DiBr-RB. Inhibition of CK-1 is also of the competitive type with respect to ATP (Ki = 14 microM). Although the inhibitory spectrum of CK-1 by the various analogues is reminiscent of that observed with CK-2, a remarkable difference is revealed by 5'-phosphorylation of ribose which increases the Ki with CK-2 while decreasing that with CK-1.

Recent results showed the critical role of the mammalian p62-atypical protein kinase C (aPKC) complex in the activation of NF-kappaB in response to different stimuli. Here we demonstrate using the RNA interference technique on Schneider cells that the Drosophila aPKC (DaPKC) is required for the stimulation of the Toll-signaling pathway, which activates the NF-kappaB homologues Dif and Dorsal. However, DaPKC does not appear to be important for the other Drosophila NF-kappaB signaling cascade, which activates the NF-kappaB homologue Relish in response to lipopolysaccharides. Interestingly, DaPKC functions downstream of the nuclear translocation of Dorsal or Dif, controlling the transcriptional activity of the Drosomycin promoter. We also show that the Drosophila Ref(2)P protein is the homologue of mammalian p62 as it binds to DaPKC, its overexpression is sufficient to activate the Drosomycin but not the Attacin promoter, and its depletion severely impairs Toll signaling. Collectively, these results demonstrate the conservation of the p62-aPKC complex for the control of innate immunity signal transduction in Drosophila melanogaster.

OBJECTIVE

Clinical trials and community-based studies often include the Center for Epidemiologic Studies-Depression scale (CES-D) as a measure of depression outcome. We compared responses to symptom-related items on the CES-D by depressed stroke and primary-care patients for several purposes: 1) to illustrate the use of Item Response Theory (IRT)-based (Rasch) models for comparing scale functioning across different patient subgroups; and 2) to inform clinicians and outcome researchers about scale functioning and depressive symptomatology in stroke- compared with primary care-based depression.

METHODS

Two data sources were analyzed, including 32 depressed patients who were 3 months poststroke, and 366 depressed primary-care patients. Presence of depression was based on a CES-D score 16 or higher. Rasch models were used to assess item fit and compare item hierarchies between depressed primary-care and stroke patients.

RESULTS

Item hierarchies were similar for poststroke depression and primary care-based depression. Interpersonal disruption items were the most difficult to endorse for both groups. No items misfit the scale in primary-care depression. Items relating to restless sleep, unfriendliness, and crying slightly misfit the scale in stroke patients, that is, may measure a different trait. Differential item functioning (DIF) between the groups was identified for items relating to appetite, restless sleep, crying, and feeling disliked.

CONCLUSIONS

Results generally supported the use of the CES-D as measure of depression outcome, particularly in primary care-based depression. DIF may imply that slightly different clusters of depressive symptoms are reported by depressed stroke patients compared with primary care, but this is conjectural given the small stroke sample size and the same items have been previously associated with bias in studies of large nonstroke samples. This study found Rasch models to be useful tools to investigate scale performance for different clinical applications.

Highly conserved during evolution, the enzyme Ubc9 activates the small ubiquitin-like modifier (SUMO) prior to its covalent ligation to target proteins. We have used mutations in the Drosophila Ubc9 (dUbc9) gene to understand Ubc9 functions in vivo. Loss-of-function mutations in dUbc9 cause strong mitotic defects in larval hematopoietic tissues, an increase in the number of hematopoietic precursors in the lymph gland and of mature blood cells in circulation, and an increase in the proportion of cyclin-B-positive cells. Some blood cells are polyploid and multinucleate, exhibiting signs of genomic instability. We also observe an overabundance of highly differentiated blood cells (lamellocytes), normally not found in healthy larvae. Lamellocytes in mutants are either free in circulation or recruited to form tumorous masses. Hematopoietic defects of dUbc9 mutants are strongly suppressed in the absence of the Rel/NF-kappaB-family transcription factors Dorsal and Dif or in the presence of a non-signaling allele of Cactus, the IkappaB protein in Drosophila. In the larval fat body, dUbc9 negatively regulates the expression of the antifungal peptide gene drosomycin, which is constitutively expressed in dUbc9 mutants in the absence of immune challenge. dUbc9-mediated drosomycin expression requires Dorsal and Dif. Together, our results support a role for dUbc9 in the negative regulation of the Drosophila NF-kappaB signaling pathways in larval hematopoiesis and humoral immunity.

The terminus region of the Escherichia coli chromosome is the scene of frequent homologous recombination. This can be demonstrated by formation of deletions between directly repeated sequences which flank a genetic marker whose loss can be easily detected. We report here that terminal recombination events are restricted to a relatively large terminal recombination zone (TRZ). On one side of the TRZ, the transition from the region with a high excision rate to the normal (low) excision rates of the rest of the chromosome occurs along a DNA stretch of less than 1 min. No specific border of this domain has been defined. To identify factors inducing terminal recombination, we examined its relation to two other phenomena affecting the same region, site-specific recombination at the dif locus and site-specific replication pausing. Both the location and the efficiency of terminal recombination remained unchanged after inactivation of the dif-specific recombination system. Similarly, inactivation of site-specific replication pausing or displacement of the replication fork trap so that termination occurs about 200 kb away from the normal region had no clear effect on this phenomenon. Therefore, terminal recombination is not a direct consequence of either dif-specific recombination or replication termination. Furthermore, deletions encompassing the wild-type TRZ do not eliminate hyperrecombination. Terminal recombination therefore cannot be attributed to the activity of some unique sequence of the region. A possible explanation of terminal hyperrecombination involves nucleoid organization and its remodeling after replication: we propose that post replicative reconstruction of the nucleoid organization results in a displacement of the catenation links between sister chromosomes to the last chromosomal domain to be rebuilt. Unrelated to replication termination, this process would facilitate interactions between the catenated molecules and would make the domain highly susceptible to recombination between sister chromosomes.

PstA and pstO cells are the two major populations in the prestalk region of the Dictyostelium slug and DIF-1 is a low molecular weight signalling molecule that selectively induces pstO cell-specific gene expression. The two cell types are defined by their differential use of spatially separated regions of the ecmA promoter. Additionally, there are anterior-like cells (ALCs) scattered throughout the rear, prespore region of the slug. They, like the pstO cells, use a cap-site distal ecmA promoter segment termed the ecmO region. When multimerised, a 22-nucleotide subsegment of the ecmO region directs expression in pstA cells, pstO cells and ALCs. It also directs DIF-inducible gene expression. The 22-nucleotide region was used to purify MybE, a protein with a single MYB DNA-binding domain of a type previously found only in a large family of plant transcription factors. Slugs of a mybE-null (mybE-) strain express an ecmAO:lacZ fusion gene (i.e. a reporter construct containing the ecmA and ecmO promoter regions) in pstA cells but there is little or no expression in pstO cells and ALCs. The ecmA gene is not induced by DIF-1 in a mybE-strain. Thus, MybE is necessary for DIF-1 responsiveness and for the correct differentiation of pstO cells and ALCs.

The Escherichia coli chromosome contains two opposed sets of unidirectional DNA replication pause (Ter) sites that, according to the replication fork trap theory, control the termination of chromosome replication by restricting replication fork fusion to the terminus region. In contrast, a recent hypothesis suggested that termination occurs at the dif locus instead. Using two-dimensional agarose gel electrophoresis, we examined DNA replication intermediates at the Ter sites and at dif in wild-type cells. Two definitive signatures of site-specific termination--specific replication fork arrest and converging replication forks--were clearly detected at Ter sites, but not at dif. We also detected a significant pause during the latter stages of replication fork convergence at Ter sites. Quantification of fork pausing at the Ter sites in both their native chromosomal context and the plasmid context further supported the fork trap model.

We prospectively studied 42 adult patients with acute dermis and soft-tissue infections (27 with erysipelas and 15 with acute cellulitis) involving the lower limb in all except one case. Streptococcus organisms (groups A, C, D, and G) were researched in skin biopsy specimens by a direct immunofluorescent (DIF) technique using commercially available antibodies. Our results showed that DIF gives a sensitivity of 0.70 for the in situ detection of streptococci in cases of erysipelas and cellulitis. With the obvious contribution of this DIF technique, streptococcal pathogens could be detected in situ and grouped in 19 of 27 cases of erysipelas (group A, 13; group B, 1; group C, 1; and group G, 4) and in ten of 15 cases of cellulitis (group A, 9; group B, 1). Combined data, including conventional cultures, DIF studies, and serologic findings, established that Streptococcus organisms, especially Streptococcus pyogenes (A), were, in nearly all cases, responsible for both erysipelas (26/27 cases) and acute cellulitis (11/15 cases) involving the lower limb in adults.

BACKGROUND

During the replication process of bacteria with circular chromosomes, an odd number of homologous recombination events results in concatenated dimer chromosomes that cannot be partitioned into daughter cells. However, many bacteria harbor a conserved dimer resolution machinery consisting of one or two tyrosine recombinases, XerC and XerD, and their 28-bp target site, dif.

RESULTS

To study the evolution of the dif/XerCD system and its relationship with replication termination, we report the comprehensive prediction of dif sequences in silico using a phylogenetic prediction approach based on iterated hidden Markov modeling. Using this method, dif sites were identified in 641 organisms among 16 phyla, with a 97.64% identification rate for single-chromosome strains. The dif sequence positions were shown to be strongly correlated with the GC skew shift-point that is induced by replicational mutation/selection pressures, but the difference in the positions of the predicted dif sites and the GC skew shift-points did not correlate with the degree of replicational mutation/selection pressures.

CONCLUSIONS

The sequence of dif sites is widely conserved among many bacterial phyla, and they can be computationally identified using our method. The lack of correlation between dif position and the degree of GC skew suggests that replication termination does not occur strictly at dif sites.

BACKGROUND

Urticarial vasculitis is characterized by persistent urticarial lesions with histologic evidence of leukocytoclastic vasculitis. Hypocomplementemic urticarial vasculitis (HUV) is a distinct clinical entity in a subset of patients with urticarial vasculitis.

OBJECTIVE

We examined presentation of urticarial vasculitis and factors predictive of connective tissue disease.

METHODS

The clinical, histologic, and immunologic characteristics of 132 patients with urticarial vasculitis seen at the Mayo Clinic were examined, and features of the hypocomplementemic patients were compared with those of the normocomplementemic patients.

RESULTS

Twenty-four patients (18%) had hypocomplementemia; all were female. Interstitial dermal neutrophilia was seen in 19 biopsy specimens (83%). On direct immunofluorescence (DIF) testing of lesional skin, 23 patients (96%) had a continuous strong granular deposition of immunoreactants along the basement membrane zone compatible with lupus erythematosus in addition to vascular fluorescence. Systemic lupus erythematosus (SLE) was present or occurred in 13 (54%). One hundred eight patients (82%) had normocomplementemia; 65 (60%) were female. Interstitial dermal neutrophilia was seen in 11 of 26 (42%) randomly selected biopsy specimens. On DIF, one patient (1%) had the lupus band. SLE occurred in three patients (3%).

CONCLUSIONS

Patients with HUV were more likely to be female, to have diffuse neutrophilia on biopsy specimens stained with hematoxylin and eosin, to have continuous strong granular deposition of immunoreactants along the basement membrane zone on DIF, and to have SLE than normocomplementemic patients. We submit that HUV represents a subset of SLE with shared clinical, laboratory, and immunologic features.

In physiological settings, DNA translocases will encounter DNA-bound proteins, which must be dislodged or bypassed to allow continued translocation. FtsK is a bacterial translocase that promotes chromosome dimer resolution and decatenation by activating XerCD-dif recombination. To better understand how translocases act in crowded environments, we used single-molecule imaging to visualize FtsK in real time as it collided with other proteins. We show that FtsK can push, evict, and even bypass DNA-bound proteins. The primary factor dictating the outcome of collisions was the relative affinity of the proteins for their specific binding sites. Importantly, protein-protein interactions between FtsK and XerD help prevent removal of XerCD from DNA by promoting rapid reversal of FtsK. Finally, we demonstrate that RecBCD always overwhelms FtsK when these two motor proteins collide while traveling along the same DNA molecule, indicating that RecBCD is capable of exerting a much greater force than FtsK when translocating along DNA.

The present study examined the role of acculturation in manifestation of depressive symptoms among 230 Korean-American older adults (M age = 69.8, SD = 7.05) in Florida. Given the cultural emphasis on modesty and self-effacement in the traditional Korean society, we hypothesized that older Korean-Americans who were less acculturated to American culture, when compared to the more acculturated ones, would be more likely to inhibit positive affects in depressive symptom reports. Using two validated measures of depressive symptoms, the short forms of the Geriatric Depression Scale (GDS-SF) and the Center for Epidemiologic Studies-Depression Scale (CES-D), different response patterns for low and high acculturation groups were identified. First, there was low comparability in the factor structures for both the GDS-SF and the CES-D across low and high acculturation groups. A differential item function (DIF) analysis based on partial correlations indicated that older adults in the low acculturation group inhibited endorsing positive affect items; one item in the GDS-SF (#7 'feel happy') and two items in the CES-D (# 5 'felt hopeful' and # 8 'was happy'). The finding suggests the substantial cultural influences in expressing emotions, especially those related to positive affects. Implications are discussed from a cultural perspective.