Transcriptional repression by Suppressor of Hairless involves the binding of a Hairless-dCtBP complex in Drosophila

Notch is the receptor for a conserved signaling pathway that regulates numerous cell fate decisions during development [1]. Signal transduction involves the presenilin-dependent intracellular processing of Notch and the nuclear translocation of the intracellular domain of Notch, NICD [2-6]. NICD associates with Suppressor of Hairless [Su(H)], a DNA binding protein, and Mastermind (Mam), a transcriptional coactivator [7-9]. In the absence of Notch signaling, Su(H) acts as a transcriptional repressor [10, 11]. Repression by Su(H) is relieved by the activation of Notch [12-16]. In the Drosophila embryo, this transcriptional switch from repression to activation is important for patterning the expression of the single-minded (sim) gene along the dorsoventral axis [12]. Here, we investigate the mechanisms by which Su(H) inhibits the expression of Notch target genes in Drosophila. We show that Hairless, an antagonist of Notch signaling [17-19], is required to repress the transcription of the sim gene. Hairless forms a DNA-bound complex with Su(H). Furthermore, it directly binds the Drosophila C-terminal Binding Protein (dCtBP), which acts as a transcriptional corepressor. The dCtBP binding motif of Hairless is essential for the function of Hairless in vivo. We propose that Hairless mediates transcriptional repression by Su(H) via the recruitment of dCtBP.

Static compression of articular cartilage can reduce solute diffusivity and partitioning: implications for the chondrocyte biological response

Chondrocytes depend upon solute transport within the avascular extracellular matrix of adult articular cartilage for many of their biological activities. Alterations to bioactive solute transport may, therefore, represent a mechanism by which cartilage compression is transduced into cellular metabolic responses. We investigated the effects of cartilage static compression on diffusivity and partitioning of a range of model solutes including dextrans of molecular weights 3 and 40 kDa, and tetramethylrhodamine (a 430 Da fluorophore). New fluorescence methods were developed for real-time visualization and measurement of transport within compressed cartilage explants. Experimental design allowed for multiple measurements on individual explants at different compression levels in order to minimize confounding influences of compositional variations. Results demonstrate that physiological levels of static compression may significantly decrease solute diffusivity and partitioning in cartilage. Effects of compression were most dramatic for the relatively high molecular weight solutes. For 40 kDa dextran, diffusivity decreased significantly (p<0.01) between 8% and 23% compression, while partitioning of 3 and 40 kDa dextran decreased significantly (p<0.01) between free-swelling conditions and 8% compression. Since diffusivity and partitioning can influence pericellular concentrations of bioactive solutes, these observations support a role for perturbations to solute transport in mediating the cartilage biological response to compression.

Genetic recombination of the hepatitis C virus: clinical implications

Genetic recombination is a well-known feature of RNA viruses that plays a significant role in their evolution. Although recombination is well documented for Flaviviridae family viruses, the first natural recombinant strain of hepatitis C virus (HCV) was identified as recently as 2002. Since then, a few other natural inter-genotypic, intra-genotypic and intra-subtype recombinant HCV strains have been described. However, the frequency of recombination may have been underestimated because not all known HCV recombinants are screened for in routine practice. Furthermore, the choice of treatment regimen and its predictive outcome remain problematic as the therapeutic strategy for HCV infection is genotype dependent. HCV recombination also raises many questions concerning its mechanisms and effects on the epidemiological and physiopathological features of the virus. This review provides an update on recombinant HCV strains, the process that gives rise to recombinants and clinical implications of recombination.

Quality of web-based information on bipolar disorder

OBJECTIVE

To evaluate web-based information on bipolar disorder and to assess particular content quality indicators.

METHODS

Two keywords, "bipolar disorder" and "manic depressive illness" were entered into popular World Wide Web search engines. Websites were assessed with a standardized proforma designed to rate sites on the basis of accountability, presentation, interactivity, readability and content quality. "Health on the Net" (HON) quality label, and DISCERN scale scores were used to verify their efficiency as quality indicators.

RESULTS

Of the 80 websites identified, 34 were included. Based on outcome measures, the content quality of the sites turned-out to be good. Content quality of web sites dealing with bipolar disorder is significantly explained by readability, accountability and interactivity as well as a global score.

CONCLUSIONS

The overall content quality of the studied bipolar disorder websites is good.

Nine novel mutations in maturity-onset diabetes of the young (MODY) candidate genes in 22 Spanish families

The aims of this study were to estimate the prevalence of major maturity-onset diabetes of the young (MODY) subtypes in Spanish MODY families and to analyze genotype-phenotype correlations. Twenty-two unrelated pediatric MODY patients and 97 relatives were screened for mutations in the coding region of the glucokinase (GCK), hepatic nuclear factor- HNF-1alpha and HNF4alpha genes using PCR-single strand conformation polymorphism and/or direct sequencing. In families carrying GCK mutations, the influence of genetic defects on fetal growth was investigated by comparing the birth weights of 32 offspring discordant for the mutations. Mutations in MODY genes were identified in 64% of the families. GCK/MODY2 mutations were the most frequently found, in 41%: seven novel (R369P, S411F, M298K, C252Y, Y108C, A188E, and S383L) and 2 already described mutations. Four pedigrees (18%) harbored mutations in the HNF-1alpha/MODY3 gene, including a previously unreported change (R271G). One family (4%) carried a novel mutation in the HNF-4alpha gene (IVS5-2delA), representing the first report of a MODY1 pedigree in the Spanish population. The age at diagnosis was prepubertal in MODY2 index patients and pubertal in MODY3 patients. Overt diabetes was rare in MODY2 and was invariably present in MODY3 index patients. Chronic complications of diabetes were absent in the MODY2 population and were present in more than 40% of all relatives of MODY3. Birth weight was lower in the presence of a GCK fetal mutation when the mutation was of paternal origin. The MODY1 patient was diagnosed at 15 yr of age. She developed intermittent microalbuminuria despite good metabolic control, and severe late-onset complications were common within her family. Mutations in the GCK/MODY2 gene are the most common cause of MODY in our population as recruited from pediatric and adolescent index patients. The inheritance of GCK defects by the fetus results in a reduction of birth weight. Clinical expression of MODY3 and MODY1 mutations, the second and third groups of defects found, was more severe, including the frequent development of chronic complications.

Effects of damage in the articular surface on the cartilage response to injurious compression in vitro

Macroscopic structural damage to the cartilage articular surface can occur due to slicing in surgery, cracking in mechanical trauma, or fibrillation in early stage osteoarthrosis. These alterations may render cartilage matrix and chondrocytes susceptible to subsequent mechanical injury and contribute to progression of degenerative disease. To examine this hypothesis, single 300 microm deep vertical slices were introduced across a diameter of the articular surface of osteochondral explant disks on day 6 after dissection. Then a single uniaxial unconfined ramp compression at 7 x 10(-5) or 7 x 10(-2) s(-1) strain rate to a peak stress of 3.5 or 14 MPa was applied on day 13 during which mechanical behavior was monitored. Effects of slices alone and together with compression were measured in terms of explant swelling and cell viability on days 10 and 17. Slicing alone induced tissue swelling without significant cell death, while compression alone induced cell death without significant tissue swelling. Under low strain rate loading, no differences in the response to injurious compression were found between sliced and unsliced explants. Under high strain rate loading, slicing rendered cartilage more easily compressible and appeared to slightly reduce compression-induced cell and matrix injury. Findings highlight microphysical factors important to cartilage mechanical injury, and suggest ways that macroscopic structural damage may accelerate or, in certain cases, possibly slow the progression of cartilage degeneration.

Microstructural Modeling of Collagen Network Mechanics and Interactions with the Proteoglycan Gel in Articular Cartilage

Cartilage matrix mechanical function is largely determined by interactions between the collagen fibrillar network and the proteoglycan gel. Although the molecular physics of these matrix constituents have been characterized and modern imaging methods are capable of localized measurement of molecular densities and orientation distributions, theoretical tools for using this information for prediction of cartilage mechanical behavior are lacking. We introduce a means to model collagen network contributions to cartilage mechanics based upon accessible microstructural information (fibril density and orientation distributions) and which self-consistently follows changes in microstructural geometry with matrix deformations. The interplay between the molecular physics of the collagen network and the proteoglycan gel is scaled up to determine matrix material properties, with features such as collagen fibril pre-stress in free-swelling cartilage emerging naturally and without introduction of ad hoc parameters. Methods are developed for theoretical treatment of the collagen network as a continuum-like distribution of fibrils, such that mechanical analysis of the network may be simplified by consideration of the spherical harmonic components of functions of the fibril orientation, strain, and stress distributions. Expressions for the collagen network contributions to matrix stress and stiffness tensors are derived, illustrating that only spherical harmonic components of orders 0 and 2 contribute to the stress, while orders 0, 2, and 4 contribute to the stiffness. Depth- and compression-dependent equilibrium mechanical properties of cartilage matrix are modeled, and advantages of the approach are illustrated by exploration of orientation and strain distributions of collagen fibrils in compressed cartilage. Results highlight collagen-proteoglycan interactions, especially for very small physiological strains where experimental data are relatively sparse. These methods for determining matrix mechanical properties from measurable quantities at the microscale (composition, structure, and molecular physics) may be useful for investigating cartilage structure-function relationships relevant to load-bearing, injury, and repair.

Two cases of 'asthma' revealing a diverticulum of Kommerell

Among embryonic aortic vascular malformations, persistence of a right aortic arch and aberrant left subclavian artery associated with a diverticulum of Kommerell is rare, and is estimated to occur in 0.1% of the general population. We report two cases of diverticulum of Kommerell in which tracheal compression due to the vascular ring induced respiratory symptoms such as asthmatic dyspnoea. This reminds us that at least a chest X-ray should be performed in newly diagnosed asthmatic patients, focusing on the trachea and upper mediastinum. In case of vascular abnormality, angiography and magnetic resonance are the best investigations to define the abnormal anatomy and guide surgery.

Prestrain decreases cartilage susceptibility to injury by ramp compression in vitro

BACKGROUND

Injurious mechanical loading of articular cartilage can be an initiating factor in the development of degenerative joint disease. The tissue response to compression depends on the loading conditions and matrix mechanical properties. The short-term loading history of cartilage can affect its water content and microstructural organization, and may thereby modify its susceptibility to injury. We therefore examined the role of prestrain on the response of articular cartilage to injurious compression.

METHODS

The full-thickness cartilage of bovine osteochondral explants was subjected to prestrains of 0, 5, 10, 25 or 50% before application of injurious ramp compression characterized by a strain rate of 7x10(-2) or 7x10(-3)s-1 and peak stress of 3.5 or 14 MPa. Effects of prestrain were evaluated in terms of fluid exudation, tissue mechanical stiffening, and the tissue response to injurious compression as characterized by macroscopic crack formation, cell viability and glycosaminoglycan release to culture media.

RESULTS

Macroscopic crack formation due to injurious compression decreased with increasing prestrain in association with lower cell mortality. Significantly decreased susceptibility to injury was already evident for 10% prestrain. In contrast, explant mechanical stiffness was unchanged up to 25% prestrain.

CONCLUSION

Findings demonstrate that compressive strains due to the short-term loading history of cartilage may strongly reduce its susceptibility to mechanical injury. Conversely, matrix swelling may render cartilage more vulnerable to injury. The cartilage response to injurious compression is therefore strongly influenced by matrix fluid content, and possibly also by other structural parameters such as collagen fiber orientation.

Hepatitis C Virus p7 membrane protein quasispecies variability in chronically infected patients treated with interferon and ribavirin, with or without amantadine

A clinical study was carried out to compare the response rate of two groups of non-responder (NR) hepatitis C virus (HCV) genotype 1 chronically infected patients treated with interferon and ribavirin, with or without amantadine. The viral load decreased more markedly in the group treated by tritherapy including amantadine, but the response rate at the end of treatment was not significantly different between bitherapy and tritherapy. As amantadine could have an antiviral effect on the ion channel activity of the p7 HCV protein, the p7 quasispecies was characterized by cloning and sequencing. Sequence data were analyzed to determine the pattern and significance of p7 genetic heterogeneity and a possible relationship with therapy. Subtype differences were confirmed between p7 HCV genotypes 1a and 1b, and quasispecies analysis showed a reduction of genetic diversity in subtype 1a, but not 1b, during tritherapy. However, the absence of changes at numerous positions, as well as the conservative changes at other positions, indicated the high conservation of the p7 structure. Residue His-17, proposed to interact with amantadine, was fully conserved in both subtypes 1a and 1b, independently of amantadine administration. In conclusion, although the analysis of the p7 sequences revealed a selective pressure during therapy, no specific residues appeared to be linked to the effect of amantadine on viral decline. These results suggest that the potential antiviral effect of amantadine might be non-specific and related to a reduction in endosomal acidification and therefore reduced viral entry of HCV via its pH-dependent pathway.

Towards the proteome of the rhodopsin-bearing post-Golgi compartment of retinal photoreceptor cells

Polarized sorting of rhodopsin in retinal rod photoreceptor cells is mediated by post-Golgi carrier membranes that bud from the trans-Golgi network and fuse with the specialized domain of the plasma membrane in the rod inner segment. The identity of the majority of the resident proteins of this organelle still remains elusive, despite multifaceted approaches to study this compartment. In the present study we have taken a proteomic approach to the analysis of the post-Golgi carriers. First, we modified the previously established fractionation protocols in order to achieve greater purity of the isolated membranes. Specifically, the new fractionation scheme depleted the post-Golgi fraction of cytosolic proteins that were the most abundant contaminants complicating analysis of two-dimensional (2-D) gel profiles in our previous preparations. The isolated membranes were subjected to 2-D gel electrophoresis, immunoblotting and microsequencing. This analysis showed that the improved subcellular fractionation yielded a fraction highly enriched in rhodopsin-bearing post-Golgi carrier membranes. Two-dimensional mapping revealed 29 proteins that are preferentially found in this fraction and therefore represent candidates for post-Golgi membrane-specific proteins. This preparation of rhodopsin-bearing post-Golgi carriers is a first step towards the proteomics of this important organelle.

Bone and joint complications in patients with hereditary hemochromatosis: a cross-sectional study of 93 patients

Background

The aim of this study was to determine the frequency and characteristics of bone and joint complications, specifically bone fragility, joint replacement surgery, and arthropathy, in hereditary hemochromatosis (HH) and related factors.

Methods

This study was a cross-sectional observational study of 93 patients with HH. Radiographs of the hands, wrists, knees, and ankles were scored for joint space narrowing, erosions and cysts, osteophytes, and chondrocalcinosis. Prevalent (vertebral and non-vertebral) fragility fractures were recorded and bone mineral density (BMD) was systematically evaluated by dual energy X-ray absorptiometry. Bone fragility was defined as (i) a T-score ⩽ -2.5 at any site with or without a prevalent fragility fracture, or (ii) a T-score between -1.0 and -2.5 at any site and a prevalent fragility fracture.

Results

The mean age of the patients was 60.0 (11.2) years, and 58.0% of them were men. The frequency of radiographic MCP2-3 arthropathy was 37.6% (95% CI 0.28-0.48). Radiographic MCP2-3 arthropathy was independently associated with older age [OR 1.17 (1.09-1.26) per year, p < 0.0001], male sex [OR 3.89 (1.17-12.97), p = 0.027] and C282Y+/+ genotype [OR 4.78 (1.46-15.68), p = 0.010]. The frequency of joint replacement surgery was 12.9% (95% CI 0.07-0.21). The frequency of bone fragility was 20.4% (95% CI 0.13-0.30). Bone fragility was independently associated with hepatic cirrhosis [OR 8.20 (1.74-38.68), p = 0.008].

Discussion

Radiographic MCP2-3 arthropathy was found to occur in 37.6% of patients with HH. The association observed between this form of arthropathy and C282Y homozygosity, male sex, and older age suggests that demographic characteristics and genetic background are likely to be major determinants of this joint disorder and play a more important role than severity of iron overload. Bone fragility was observed in a fifth of the patients with HH, independently of genetic background and severity of iron overload, and was strongly associated with hepatic cirrhosis.

Conclusion

Future investigations should focus on pathogenesis and early identification of patients at risk of developing bone and joint complications secondary to HH.

Occurrence of an HIV-1 gp160 endoproteolytic activity in low-density vesicles and evidence for a distinct density distribution from endogenously expressed furin and PC7/LPC convertases

Human immunodeficiency virus (HIV) glycoprotein (gp) 160 processing by host cell proteinases is an essential step for viral fusion and infectivity. We have identified a rat liver subcellular fraction which specifically processes gp160 into gp120 and gp41. Using equilibration of microsomes in sucrose gradients, the gp160 cleavage activity was associated with particles equilibrating at low densities, well-separated from the endoplasmic reticulum, cis-Golgi network, Golgi stacks, lysosomes and plasma membrane. Its density distribution was compatible with light secretory vesicles derived from the trans-Golgi network (TGN) or to endosomes, but association with endosomes was not supported by free flow electrophoresis. Although furin and pro-protein convertase (PC) 7/LPC have been proposed as the major gp160 processing convertases, the rat liver microsomal gp160 processing activity was essentially resolved from furin and only partially overlapped PC7/LPC. These data suggest that proteinase(s) other than furin and PC7/LPC, presumably located in TGN-derived vesicles, may participate in the gp160 processing into gp120 and gp41.

Bronchoscopy with the Vision Sciences BF100 Disposable-Sheath Device: French Experience after 328 Procedures

BACKGROUND

In spite of adhesion to recommended disinfection procedures, the transmission of infections by bronchoscopes is a permanent problem.

OBJECTIVE

The new device may prevent nosocomial infections because it consists of two parts: a specific bronchoscope Vision Sciences BF100 and a single-use protective sheath for each procedure. The aim of this paper is to report our practice and the difficulties encountered when using this system.

METHODS

We report our experience from 1997 to 2002 after 328 elective and emergency endoscopic procedures with the BF100 device. In a retrospective study, we describe the population and the incidents during procedure. We discuss the impact of the use of BF100 on the cost of bronchoscopies.

RESULTS

The major constraint is the care required in assembling the optical device and disposable sheath. The intrinsic qualities of the optics are confirmed; any sample may be taken although image quality and suction capacity are inferior to videoscopes. Maneuverability is inferior to videoscopes, but improves with a short experience. In addition, this device is expensive.

CONCLUSIONS

The technical performances of the BF100 device are inferior to those of videoscopes but the concept of sterile single-use sheaths is able to prevent the nosocomial infections related to bronchoscopes. Because of the cost, examination with the BF100 should be reserved to patients with proved or suspected infection (multiresistant bacteria, tuberculosis, hepatitis C and B virus, HIV, prions) and immunosuppression (hematologic diseases).

Epidemiological and quantitative study of GBV-C infection in french polytransfused children

From 1999 to 2002, 246 serum samples taken from polytransfused children were tested for the presence of GB virus C (GBV-C) RNA using a real-time reverse transcription-polymerase chain reaction (RT-PCR) assay. This assay was based on the TaqMan technology and allowed viral load determination in infected children with a dynamic range from 10(3) to 10(7) genome equivalent (gEq) copies/ml. The limit of detection was estimated to 619 gEq copies/ml with a > or = 95% probability of a positive result. Thirty five sera were found to be GBV-C RNA positive, corresponding to a prevalence of GBV-C of 14.2%. The mean viral load was high, i.e., 6 +/- 1.4 log (range 3.22-7.42) gEq copies/ml, but low viral loads were also detected. Sequencing of the 5'-untranslated region (UTR) identified a majority of genotype 2 strains (82%) distributed into two subtypes, 88.5% genotype 2a and 11.5% genotype 2b. In conclusion, GBV-C active infection is very frequent in exposed populations such as polytransfused children. GBV-C RNA quantitation using real-time assay may be useful for diagnosis and follow-up of the natural history of GBV-C infection.

Genetic features of polioviruses isolated in Tunisia, 1991-2006

BACKGROUND

Genetic characterisation of polioviruses remains highly important even in countries where wild poliovirus circulation has been interrupted. Sequence data on representative wild strains from all geographical regions is required for surveillance purposes and surveillance for vaccine-related isolates with increased potential for transmissibility in humans should continue.

OBJECTIVE

To report the genetic characteristics of wild and vaccine-related polioviruses isolated in Tunisia from 1991 to 2006.

STUDY DESIGN

Wild isolates were sequenced in the VP1 genomic region and compared to each other. Vaccine-related isolates were assessed for genetic recombination by PCR/RFLP and sequence analysis of the 3D region. Recombinant viruses were assessed for genetic drift in the VP1 region.

RESULTS

The VP1 sequences of the last wild isolates, all from serotype3, showed 97.7-98.7% nucleotide homology. Nineteen percent of vaccine-related isolates were vaccine/vaccine intertypic recombinants. No recombinant with non-poliovirus enteroviruses was identified. Mutational differences in the VP1 sequences of recombinant viruses ranged from 0.0% to 0.7% indicating a limited replication period.

CONCLUSIONS

This study provides sequence data on wild polioviruses from Tunisia/North Africa and shows that in countries with continuous high vaccine coverage transmission of vaccine-related polioviruses is time-limited.

Search for DNA sequence variations using a MutS-based technology

The search for DNA sequence variations (DSV) is emphasized with genetic studies of a large number of multifactorial diseases. Saturation of regions of interest with diallelic polymorphisms will be an essential step to pinpoint, through association studies, predisposing genes. We have developed a solid-phase method based on the ability of mismatch binding protein MutS to recognize single nucleotide mismatches. This approach was applied to the study of 83 sequence-tagged sites (STSs) extracted from an eight centimorgans (cM) chromosome 21 region. One-third of tested STSs were found to be polymorphic leading to a frequency of one DSV every 822 base pairs (bp). Sequencing of analyzed STSs showed the high reliability of the MutS-based technology for mismatches up to 2 bp in DNA fragments ranging in size from 200 bp to 1 kilobase (kb). The entire assay which is performed in a solid-phase format without the need of electrophoresis or sequencing, will provide an efficient tool for new polymorphism detection.