Tracking image correlation: combining single-particle tracking and image correlation.

The interactions and coordination of biomolecules are crucial for most cellular functions. The observation of protein interactions in live cells may provide a better understanding of the underlying mechanisms. After fluorescent labeling of the interacting partners and live-cell microscopy, the colocalization is generally analyzed by quantitative global methods. Recent studies have addressed questions regarding the individual colocalization of moving biomolecules, usually by using single-particle tracking (SPT) and comparing the fluorescent intensities in both color channels. Here, we introduce a new method that combines SPT and correlation methods to obtain a dynamical 3D colocalization analysis along single trajectories of dual-colored particles. After 3D tracking, the colocalization is computed at each particle's position via the local 3D image cross correlation of the two detection channels. For every particle analyzed, the output consists of the 3D trajectory, the time-resolved 3D colocalization information, and the fluorescence intensity in both channels. In addition, the cross-correlation analysis shows the 3D relative movement of the two fluorescent labels with an accuracy of 30 nm. We apply this method to the tracking of viral fusion events in live cells and demonstrate its capacity to obtain the time-resolved colocalization status of single particles in dense and noisy environments.

Time trends for alendronate prescription practices in women with chronic obstructive pulmonary disease and women exposed to systemic glucocorticoids.

UNLABELLED: Chronic obstructive pulmonary disease (COPD) and systemic glucocorticoid exposure are well-known risk factors of osteoporosis. We evaluated alendronate prescription practices related to COPD and exposure to systemic corticosteroids from 1996 to 2008 and showed an increasing targeting of alendronate treatment in patients with COPD and patients with systemic corticosteroid exposure. INTRODUCTION: COPD and systemic glucocorticoid exposure are well-known risk factors of osteoporosis and fragility fracture, but osteoporosis is often underdiagnosed and undertreated in these patients. This study aims to evaluate alendronate prescription practices related to COPD and/or to exposure to systemic glucocorticoids among Danish women. METHODS: A total of 388,314 female subjects >50 years old, 64,719 of whom initiated treatment with alendronate, and 323,595 age- and gender-matched controls were retrospectively identified between 1996 and 2008 from national health registers. Multivariate logistic regression was used for examining prescription practices, specifically if these risk factors (COPD or glucocorticoid exposure) increased or decreased the likelihood of beginning alendronate therapy. RESULTS: A diagnosis of COPD was associated with an increased likelihood of using alendronate (odds ratio (OR) 1.4, 95 % confidence interval (CI) 1.4-1.5, p < 0.001). Further, a diagnosis of COPD was associated with an increasing tendency of initiating alendronate treatment in the study period (OR 1.3 (95 % CI 1.1-1.5, years 1996-1999) to 1.5 (95 % CI 1.4-1.6, years 2006-2008), p < 0.01). Exposure to systemic glucocorticoids was associated with a significantly increasing (OR 3.6, 95 % CI 3.3-3.9 to OR 5.5, 95 % CI 5.3-5.8) probability of receiving alendronate treatment in the same observation period. CONCLUSION: This nationwide register-based study on alendronate prescription practices in Denmark shows an increasing targeting of alendronate treatment in patients with COPD and an even stronger trend for patients with systemic glucocorticoid exposure, perhaps indicating increased awareness of well-known and associated conditions.

[Transplantation of corneal endothelium--chances and challenges]. / Die Transplantation des kornealen Endothels--Möglichkeiten und Grenzen.

BACKGROUND: Endothelial keratoplasty is a promising surgical procedure which may replace penetrating keratoplasty in cases of endothelial cell diseases of the cornea. This method may thereby help to prevent postoperative astigmatism and transplant rejection. METHODS AND RESULTS: A survey of publications reporting about results after endothelial keratoplasty shows that the main problem of this transplantation technique is a postoperative endothelial cell loss which is comparable to or even higher than that observed in penetrating keratoplasty. Improving surgical techniques led to a reduction of the endothelial cell loss, however, cell-based strategies to prevent postoperative cell loss or to enhance the cell densities of donor corneas or endothelial lamellae are rare. DISCUSSION: This review presents an overview of clinical results after endothelial keratoplasty. Current strategies in the field of cell biology and tissue cultivation of corneal endothelial cells, genetic manipulation of the corneal endothelium and tissue engineering strategies aiming at the production of transplantable endothelial cell sheets are described. CONCLUSION: The limited availability of donor corneas makes it mandatory to develop methods in the field of tissue engineering in order to improve corneal endothelial cell survival or to increase corneal endothelial cell density, using interdisciplinary approaches.

Osteoporosis pharmacotherapy following bone densitometry: importance of patient beliefs and understanding of DXA results.

SUMMARY: Persistence with osteoporosis therapy remains low and identification of factors associated with better persistence is essential in preventing osteoporosis and fractures. In this study, patient understanding of dual energy X-ray absorptiometry (DXA) results and beliefs in effects of treatment were associated with treatment initiation and persistence. INTRODUCTION: The purpose of this study is to examine patient understanding of their DXA results and evaluate factors associated with initiation of and persistence with prescribed medication in first-time users of anti-osteoporotic agents. Self-reported DXA results reflect patient understanding of diagnosis and may influence acceptance of osteoporosis therapy. To improve patient understanding of DXA results, we provided written information to patients and their referring general practitioner (GP), and evaluated factors associated with osteoporosis treatment initiation and 1-year persistence. METHODS: Information on diagnosis was mailed to 1,000 consecutive patients and their GPs after DXA testing. One year after, a questionnaire was mailed to all patients to evaluate self-report of DXA results, drug initiation and 1-year persistence. Quadratic weighted kappa was used to estimate agreement between self-report and actual DXA results. Multivariable logistic regression was used to evaluate predictors of understanding of diagnosis, and correlates of treatment initiation and persistence. RESULTS: A total of 717 patients responded (72%). Overall, only 4% were unaware of DXA results. Agreement between self-reported and actual DXA results was very good (κ = 0.83); younger age and glucocorticoid use were associated with better understanding. Correctly reported DXA results was associated with treatment initiation (OR 4.3, 95% CI 1.2-15.1, p = 0.02), and greater beliefs in drug treatment benefits were associated with treatment initiation (OR 1.4, 95%CI 1.1-1.9, p = 0.006) and persistence with therapy (OR 1.8, 95% CI 1.2-2.7, p = 0.006). CONCLUSION: Our findings suggest that written information provides over 80% of patients with a basic understanding of their DXA results. Communicating results in writing may improve patient understanding thereby also improve osteoporosis management and prevention.

Recognition of apoptotic cells by macrophages activates the peroxisome proliferator-activated receptor-gamma and attenuates the oxidative burst.

It is appreciated that phagocytosis of apoptotic cells (AC) is an immunological relevant process that shapes the pro- versus anti-inflammatory macrophage phenotype. It was our intention to study the respiratory burst, a prototype marker of macrophage activation, under the impact of AC. Following incubation of RAW264.7 macrophages with AC, we noticed attenuated production of reactive oxygen species (ROS) in response to PMA treatment, and observed a correlation between attenuated ROS formation and suppression of protein kinase Calpha (PKCalpha) activation. EMSA analysis demonstrated an immediate activation of peroxisome proliferator-activated receptor-gamma (PPARgamma) following supplementation of AC to macrophages. In macrophages carrying a dominant-negative PPARgamma mutant, recognition of AC no longer suppressed PKCalpha activation, and the initial phase of ROS formation was largely restored. Interference with actin polymerization and transwell experiments suggest that recognition of AC by macrophages suffices to attenuate the early phase of ROS formation that is attributed to PPARgamma activation.

Foamy virus--adenovirus hybrid vectors.

To confer adenovirus vectors (AdV), the feature of integration into the host cell genome hybrid vectors were characterized in vitro, which express vectors derived from the prototypic foamy virus (FV) in the backbone of a high-capacity AdV. FVs constitute a subfamily of retroviruses with a distinct replication pathway and no known pathogenicity. In the absence of envelope glycoprotein, the prototypic FV behaves like a retrotransposon, while it behaves like an exogenous retrovirus in its presence. Two principle types of vectors, which either allows the intracellular (HC-FAD-7) or, in addition, the extracellular (HC-FAD-2) pathway were constructed. In both chimeras the expression of the FV vector was controlled by the tetracycline-regulatable system. Hybrids were produced close to 10(10) infectious units/ml. By Southern blotting, the functionality of the hybrid vectors to generate host cell genomic integrants was shown. However, the efficiency of HC-FAD-7 to establish stable transgene expression was rather low, while around 70% of cells were stably transduced in secondary round following primary transduction with HC-FAD-2 at an MOI of 100. Given the benign characteristics of high-capacity adenovirus and FV vectors, hybrids based on HC-FAD-2 are probably suited for an in vivo application.

The foamy virus envelope glycoproteins.

The main functions of retroviral glycoproteins are recognition and binding to the cellular virus receptor as well as fusion of viral and cellular lipid membranes to release the viral particle into the cytoplasm of the host cell. Foamy viruses (FVs) are a special group of retroviruses with a very broad host range that use a currently unknown cellular receptor for entry. Nevertheless, many functions of the FV envelope glycoproteins in the viral replication cycle have been characterized in detail over the last years. Several unique features not found for any other retrovirus were identified. These include the presence of two types of FV Env proteins, gp170(Env-Bet) and gp130Env, and the strict requirement of gp130Env coexpression for the FV budding and particle release process, a function that cannot be compensated for by any other viral glycoprotein tested so far. Furthermore, domains in gp130Env could be characterized that influence its intracellular distribution, cell surface transport, and its specific interaction with the viral capsid during particle egress. In addition, it has recently been shown that gp130Env expression alone induces release of subviral particles from cells. This review summarizes the current knowledge about the nature of the FV Env proteins and their function in the viral replication cycle.

Efficient transduction and long-term retroviral expression of the melanoma-associated tumor antigen tyrosinase in CD34(+) cord blood-derived dendritic cells.

Differentiation of genetically modified CD34(+) hematopoietic stem cells into dendritic cells (DCs) will contribute to the development of immunotherapeutic anticancer protocols. Retroviral vectors that have been used for the transduction of CD34(+) cells face the problem of gene silencing when integrated into the genome of repopulating stem cells. We reasoned that a high copy number of retroviral DNA sequences might overcome silencing of transgene expression during expansion and differentiation of progenitor cells into functional DCs. To prove this, we utilized a retroviral vector with bicistronic expression of the melanoma-associated antigen tyrosinase and the enhanced green fluorescent protein (EGFP). Human cord blood CD34(+) cells were transduced with vesicular stomatitis virus G-protein (VSV-G) pseudotyped Moloney murine leukemia virus (MoMuLV) particles using 100-150 multiplicity of infection. During expansion of transduced cells with immature phenotype, transgene expression was strongly silenced, but upon differentiation into mature DCs, residual transgene expression was retained. Intracellular processing of the provirally expressed tyrosinase was tested in a chromium release assay utilizing a cytotoxic T cell clone specific for a HLA-A*0201-restricted tyrosinase peptide. We suggest that retroviral transduction of tumor-associated antigens in hematopoietic progenitor cells and subsequent differentiation into DCs is a suitable basis for the development of potent anti-tumor vaccines.

Low-level expression of functional foamy virus receptor on hematopoietic progenitor cells.

Foamy viruses have several qualities favorable for vector development: they are not known to cause disease; they can transduce stationary cells; and the foamy virus receptor is expressed on a wide variety of cells. Here, we analyzed the level of virus receptor expression on hematopoietic progenitor cells. Foamy virus binding was measured by a flow cytometric assay and was found to be considerably reduced in hematopoietic progenitors cell lines as well as in primary CD34(+) cells when compared to fibroblasts. Retroviral vectors based on murine leukemia virus (MLV) pseudotyped with a foamy virus envelope transduced hematopoietic cell lines with a more than 10-fold lower efficiency than fibroblasts. Moreover, less than 1% of primary CD34(+) hematopoietic progenitor cells were transduced with the foamy virus pseudotypes, while gene transfer efficiencies of 8-40% were achieved using pseudotypes with amphotropic envelope or the G protein of vesicular stomatitis virus. In conclusion, the expression of functional foamy virus receptors on hematopoietic progenitors cells was found to be insufficient to achieve high levels of gene transfer into CD34(+) hematopoietic progenitor cells with cell-free vector supernatants using current transduction protocols.

Extracellular signal regulated kinase 5 (ERK5) is required for the differentiation of muscle cells.

Extracellular signal regulated kinase 5 (ERK5) is a novel member of the mitogen-activated protein kinase (MAPK) family with a poorly defined physiological function. Since ERK5 and its upstream activator MEK5 are abundant in skeletal muscle we examined a function of the cascade during muscle differentiation. We show that ERK5 is activated upon induction of differentiation in mouse myoblasts and that selective activation of the pathway results in promoter activation of differentiation-specific genes. Moreover, myogenic differentiation is completely blocked when ERK5 expression is inhibited by antisense RNA. Thus, we conclude that the MEK5/ERK5 MAP kinase cascade is critical for early steps of muscle cell differentiation.

Self-reported exercise before age 40: influence on quantitative skeletal ultrasound and fall risk in the elderly.

OBJECTIVES: To compare musculoskeletal factors with bone structure, as measured by quantitative ultrasound (QUS) at the calcaneus, and their potential to predict fall risk in geriatric inpatients. DESIGN: Longitudinal. SETTING: Two geriatric hospitals in Switzerland. PARTICIPANTS: A total of 134 of 207 long-stay geriatric patients (96 women, 38 men) who were able to perform the timed up and go (TUG) test. INTERVENTIONS: Five musculoskeletal tests: 2 functional tests (TUG, for mobility; functional reach test, for balance), and 3 muscle strength tests (knee flexor, knee extensor, grip). Falls were monitored prospectively in a subgroup of 94 mobile subjects of 1 geriatric hospital throughout each individual length of stay (median, 31.4wk: interquartile range, 16-56.4wk). MAIN OUTCOME MEASUREMENTS: Functional and strength tests, mobility status, and self-reported exercise before age 40 were musculoskeletal factors to be compared with QUS. RESULTS: QUS was higher in mobile subjects without walking aid (p < .0001) and correlated significantly with muscle strength (knee flexor: r = .36; knee extensor: r = .30) and functional tests (TUG: r = -.25; functional reach: r = .16). Women who reported regular exercise before age 40 had higher QUS (p = .01) and fewer falls (p = .01). Falls were less frequent in subjects with walking aid (p = .03). No single musculoskeletal test, but rather a combination of demographic variables, musculoskeletal factors, and QUS could predict 76% of total variation of fall risk. CONCLUSION: This study showed the important impact of current mobility and muscle strength status on bone structure, as measured by QUS at the calcaneus. In addition, a beneficial effect of former exercise on QUS and fall risk at advanced age could be documented in women. Both findings support life-long engagement in exercise, which might be particularly meaningful for women.

A particle-associated glycoprotein signal peptide essential for virus maturation and infectivity.

Signal peptides (SP) are key determinants for targeting glycoproteins to the secretory pathway. Here we describe the involvement in particle maturation as an additional function of a viral glycoprotein SP. The SP of foamy virus (FV) envelope glycoprotein is predicted to be unusually long. Using an SP-specific antiserum, we demonstrate that its proteolytic removal occurs posttranslationally by a cellular protease and that the major N-terminal cleavage product, gp18, is found in purified viral particles. Analysis of mutants in proposed signal peptidase cleavage positions and N-glycosylation sites revealed an SP about 148 amino acids (aa) in length. FV particle release from infected cells requires the presence of cognate envelope protein and cleavage of its SP sequence. An N-terminal 15-aa SP domain with two conserved tryptophan residues was found to be essential for the egress of FV particles. While the SP N terminus was found to mediate the specificity of FV Env to interact with FV capsids, it was dispensable for Env targeting to the secretory pathway and FV envelope-mediated infectivity of murine leukemia virus pseudotypes.

Activation of NF-kappa B via the Ikappa B kinase complex is both essential and sufficient for proinflammatory gene expression in primary endothelial cells.

Activation of the transcription factor NF-kappaB is necessary for full expression of tumor necrosis factor alpha (TNF-alpha)-inducible endothelial chemokines and adhesion molecules. However, a detailed analysis regarding contribution of the different NF-kappaB upstream components to endothelial activation has not been performed yet. We employed a retroviral infection approach to stably express transdominant (TD) mutants of IkappaBalpha, IkappaBbeta, or IkappaBepsilon and dominant negative (dn) versions of IkappaB kinases (IKK) 1 or 2 as well as a constitutively active version of IKK2 in human endothelial cells. TD IkappaBalpha, IkappaBbeta, and IkappaBepsilon were not degraded upon TNF-alpha exposure, and each prevented NF-kappaB activation. These TD IkappaB mutants almost completely inhibited the induction of monocyte chemoattractant protein-1, interleukin-8, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin expression by TNF-alpha, whereas interferon-gamma-mediated up-regulation of intercellular adhesion molecule-1 and HLA-DR was not affected. Expression of dn IKK2 completely blocked TNF-alpha-induced up-regulation, whereas dn IKK1 showed a partial inhibition of expression of these molecules. Importantly, expression of constitutively active IKK2 was sufficient to drive full expression of all chemokines and adhesion molecules in the absence of cytokine. We conclude that the IKK/IkappaB/NF-kappaB pathway is crucial and sufficient for proinflammatory activation of endothelium.

Glucocorticoids inhibit lipopolysaccharide-induced up-regulation of arginase in rat alveolar macrophages.

1. As arginase by limiting nitric oxide (NO) synthesis may play a role in airway hyperresponsiveness and glucocorticoids are known to induce the expression of arginase I in hepatic cells, glucocorticoid effects on arginase in alveolar macrophages (AM Phi) were studied. 2. Rat AM Phi were cultured in absence or presence of test substances. Thereafter, nitrite accumulation, arginase activity, and the expression pattern of inducible NO synthase, arginase I and II mRNA (RT - PCR) and proteins (immunoblotting) were determined. 3. Lipopolyssacharides (LPS, 20 h) caused an about 2 fold increase in arginase activity, whereas interferon-gamma (IFN-gamma), like LPS a strong inducer of NO synthesis, had no effect. 4. Dexamethasone decreased arginase activity by about 25% and prevented the LPS-induced increase. Mifepristone (RU-486) as partial glucocorticoid receptor agonist inhibited LPS-induced increase by 45% and antagonized the inhibitory effect of dexamethasone. 5. Two different inhibitors of the NF-kappa B-pathway also prevented LPS-induced increase in arginase activity. 6. Rat AM Phi expressed mRNA and protein of arginase I and II, but arginase I expression was stronger. Arginase I mRNA and protein was not affected by IFN-gamma, but increased by LPS and this effect was prevented by dexamethasone. Both, LPS and IFN-gamma enhanced the levels of arginase II mRNA and protein, effects also inhibited by dexamethasone. As IFN-gamma did not affect total arginase activity, arginase II may represent only a minor fraction of total arginase activity. 7. In rat AM Phi glucocorticoids inhibit LPS-induced up-regulation of arginase activity, an effect which may contribute to the beneficial effects of glucocorticoids in the treatment of inflammatory airway diseases.

Type III TGF-beta receptor-independent signalling of TGF-beta2 via TbetaRII-B, an alternatively spliced TGF-beta type II receptor.

Transforming growth factor-beta (TGF-beta) signals through membrane-bound serine/threonine kinase receptors, which upon stimulation phosphorylate Smad proteins and thereby trigger their nuclear translocation and transcriptional activity. Although the three mammalian isoforms of TGF-beta are highly homologous at the level of sequence, analysis of their in vivo function by gene knockouts revealed striking differences, suggesting no significant functional redundancy between TGF-beta1, -2 and -3. While signal transduction by TGF-beta1 has been well characterized, receptor binding and activation by the TGF-beta2 isoform is less well understood. Here, we show that TbetaRII-B, an alternatively spliced variant of the TGF-beta type II receptor, is a TGF-beta2 binding receptor, which mediates signalling via the Smad pathway in the absence of any TGF-beta type III receptor (TbetaRIII). L6 cells lacking endogenous TbetaRIII as well as TbetaRII-B do not respond to TGF-beta2. Transfection of these cells with TbetaRII-B restores TGF-beta2 sensitivity. The expression of TbetaRII-B is restricted to cells originating from tissues such as bone where the isoform TGF-beta2 has a predominant role. This reflects the importance of this receptor in TGF-beta isoform-specific signalling.

C/EBPbeta enhances IL-4 but impairs IL-2 and IFN-gamma induction in T cells.

C/EBP transcription factors have been described to control the activity of the human IL-4 promoter. The C/EBP binding sites within the IL-4 promoter overlap with composite NF-AT and AP-1 binding motifs. We show here that similar binding sites are part of the murine IL-4 promoter. Retroviral overexpression of C/EBPbeta in murine EL-4 thymoma cells led to a strong induction of endogenous IL-4 and a reduction in IL-2 and IFN-gamma expression. Similarily, in primary murine T cells C/EBPbeta induction resulted in an increase in IL-4 levels, whereas in human Jurkat T cells a decrease in IL-2 RNA was detected. Like AP-1, C/EBP factors belong to the large class of basic leucine zipper proteins. However, unlike AP-1, C/EBPbeta does not act in synergy with NF-AT in the induction of the murine IL-4 promoter. Instead, both factors compete in their binding to the P4/Pu-bD site, one of the most important sequence elements of the IL-4 promoter. Whereas NF-AT factors require high levels of free Ca2+ and calcineurin activity for induction, C/EBP induction in T cells is Ca2+/calcineurin independent. These observations suggest that various induction conditions lead to the activation of transcription factors, inducing IL-4 promoter activity at specific developmental stages of T cells.

Efficient intracellular retrotransposition of an exogenous primate retrovirus genome.

The foamy virus (FV) subgroup of Retroviridae reverse transcribe their RNA (pre-)genome late in the replication cycle before leaving an infected cell. We studied whether a marker gene-transducing FV vector is able to shuttle to the nucleus and integrate into host cell genomic DNA. While a potential intracellular retrotransposition of vectors derived from other retroviruses was below the detection limit of our assay, we found that up to 5% of cells transfected with the FV vector were stably transduced, harboring 1 to approximately 10 vector integrants. Generation of the integrants depended on expression of functional capsid, reverse transcriptase and integrase proteins, and did not involve an extracellular step. PCR analysis of the U3 region of the 5' long terminal repeat and determination of proviral integration sites showed that a reverse transcription step had taken place to generate the integrants. Co-expression of a mutated envelope allowing particle egress and avoiding extracellular infection resulted in a significantly increased rescue of cells harboring integrants, suggesting that accumulation of proviruses via intracellular retrotransposition represents an integral part of the FV replication strategy.

An evolutionarily conserved positively charged amino acid in the putative membrane-spanning domain of the foamy virus envelope protein controls fusion activity.

Foamy viruses (FVs) are highly fusogenic, and their replication induces massive syncytium formation in infected cell cultures which is believed to be mediated by expression of the envelope (Env) protein. The FV Env is essential for virus particle egress. The unusually long putative membrane-spanning domain (MSD) of the transmembrane subunit carries dispersed charged amino acids and has an important function for particle envelopment. To better understand the capsid-envelope interaction and Env-mediated cell fusion, we generated a variety of FV MSD mutations. C-terminal deletions revealed the cytoplasmic domain to be dispensable but the full-length MSD to be required for fusogenic activity. The N-terminal 15 amino acids of the MSD were found to be sufficient for membrane anchorage and promotion of FV particle release. Expression of wild-type Env protein rarely induced syncytia due to intracellular retention. Coexpression with FV Gag-Pol resulted in particle export and a dramatic increase in fusion activity. A nonconservative mutation of K(959) in the middle of the putative MSD resulted in increased fusogenic activity of Env in the absence of Gag-Pol due to enhanced cell surface expression as well as structural changes in the mutant proteins. Coexpression with Gag-Pol resulted in a further increase in the fusion activity of mutant FV Env proteins. Our results suggest that an interaction between the viral capsid and Env is required for FV-induced giant-cell formation and that the positive charge in the MSD is an important determinant controlling intracellular transport and fusogenic activity of the FV Env protein.

No influence of osteoarthritis of the hand on phalangeal osteography in elderly women.

We investigate the influence of hand osteoarthritis on skeletal quantitative ultrasound (QUS) measurement through the proximal phalanges in female geriatric inpatients. In a cross-sectional study, bone status was assessed with QUS at the distal metaphysis of the first phalanges of fingers II-V. Thirty-three of 101 female geriatric inpatients met the clinical criteria of the American College of Rheumatology for osteoarthritis of the hands (median age: 85 years) and were compared to 68 female inpatients without swellings of the small finger joints (median age: 88 years). Amplitude-dependent speed of sound at the distal metaphysis, the electronic signal of the ultrasonic wave after crossing the phalanx (graphic trace), and the thickness of the each phalanx were measured and compared between the two groups by a phalangeal QUS device (DBM-Sonic 1200). There were no significant differences between the phalangeal QUS readings of both groups. The only statistically significant difference was observed in the comparison of the small finger thickness with a lower value in the osteoarthritis group (p = 0.02). These findings suggest that at the metaphyseal level of phalanges, the degenerative process of osteoarthritis doesn't influence the QUS assessment. This could be explained by the finger thickness at metaphyseal level, which was not increased in patients with osteoarthritis compared with control subjects, at least as detected by the applied finger ultrasound method.

Reversal of Blimp-1-mediated apoptosis by A1, a member of the Bcl-2 family.

Blimp-1 (B lymphocyte-induced maturation protein 1) is strongly expressed during the late stages of B cell differentiation to immunoglobulin-secreting plasma cells. Overexpression of Blimp-1 in B lymphoma cells has been reported to induce either growth arrest and cell death or Ig secretion and terminal differentiation, depending on the developmental stage of the recipient lymphomas. By using a retroviral expression system we show that Blimp-1-transduced immature WEHI 231 murine B lymphoma cells produce J chain, increased levels of the secretory form of micro heavy chain mRNA and secrete IgM for a short period of time. Concomitantly, they exhibit altered ratios of c-myc/mad4 mRNA levels, a reduction in the expression of the anti-apoptotic bcl-2 family member A1 and a distinct growth disadvantage, followed by cell death. Reintroduction of A1 by retroviral transduction greatly extends the life span of Blimp-1-expressing WEHI 231 cells which continue to secrete IgM. These data suggest that levels of A1 may determine the checkpoint between death and survival of Blimp-1-expressing B cells at different stages of differentiation.