Quantitative comparison between two phase contrast techniques: diffraction enhanced imaging and phase propagation imaging

Two x-ray phase contrast imaging techniques are compared in a quantitative way for future mammographic applications: diffraction enhanced imaging (DEI) and phase propagation imaging (PPI). DEI involves, downstream of the sample, an analyser crystal acting as an angular filter for x-rays refracted by the sample. PPI simply uses the propagation (Fresnel diffraction) of the monochromatic and partially coherent x-ray beam over large distances. The information given by the two techniques is assessed by theoretical simulations and compared at the level of the experimental results for different kinds of samples (phantoms and real tissues). The imaging parameters such as the energy, the angular position of the analyser crystal in the DEI case or the sample to detector distance in the PPI case were varied in order to optimize the image quality in terms of contrast, visibility and figure of merit.     

Listeria monocytogenes-infected human dendritic cells: uptake and host cell response

Dendritic cells (DCs) are potent antigen-presenting cells and play a crucial role in initiation and modulation of specific immune responses. Various pathogens are able to persist inside DCs. However, internalization of the gram-positive bacterium Listeria monocytogenes into human DCs has not yet been shown. In the present study, we demonstrate that human monocyte-derived immature DCs can efficiently phagocytose L. monocytogenes. This uptake is independent of listerial adhesion factors internalin A and internalin B but requires cytoskeletal motion and factors present in human plasma. A major portion of internalized bacteria is found in membrane-bound phagosomes and is rarely free in the cytosol, as shown by transmission electron microscopy and by using an L. monocytogenes strain expressing green fluorescent protein when in the host cell cytosol. The infection caused maturation of the immature DCs into mature DCs displaying high levels of CD83, CD25, major histocompatibility complex class II, and the CD86 costimulator molecule. This effect appeared to be largely mediated by listerial lipoteichoic acid. Although L. monocytogenes infection is known to induce death in other cell types, infection of human DCs was found to induce necrotic but not apoptotic death in fewer than 20% of DCs. Therefore, the ability of DCs to act as effective antigen-presenting cells for listerial immunity is probably enhanced by their resistance to cell death, as well as their ability to rapidly differentiate into mature, immunostimulatory DCs upon encountering bacteria.     

Telomere und Telomerase

Zusammenfassung In letzter Zeit fanden spezielle Abschnitte des menschlichen Genoms in der Tumorforschung besondere Beachtung: die Telomere. Telomere, d.h. die Enden aller linearen eukaryotischen Chromosomen, bestehen aus repetitiven DNA-Sequenzen und aus spezifischen Proteinen. Die Funktion der Telomere besteht im Schutz der Chromosomenenden vor Degradation, Fusion und Rekombination. In den meisten somatischen Zellen verkürzen sich die Telomere mit jedem Zellzyklus. Im übertragenen Sinn kann dieser Verlust an telomeren DNA-Sequenzen als eine mitotische Uhr aufgefa?t werden, mit der eine Zelle die Anzahl der Zellteilungen z?hlt und Lebensspanne und Zellalterung dirigiert. Sind die Telomere bis zu einem kritischen Punkt verkürzt, erfolgt die Einleitung des Apoptoseprozesses. Einige wenige Zelltypen entgehen der zellul?ren Seneszenz durch die Expression des Enzyms Telomerase. Dieses Ribonukleoprotein katalysiert die De-Novo-Addition von Nukleotiden an den Telomerenden. Das Enzym ist in den meisten somatischen Zellen in vivo nicht nachweisbar, wurde aber in der Mehrzahl aller Tumorgewebe gefunden. Die Aktivierung der Telomerase scheint Tumorzellen zu unbegrenzter Proliferation und zum Erreichen der Immortalit?t zu bef?higen. Aktuelle Studien zur Telomeraseaktivit?t in Tumoren unterstreichen, da? die Progression eines Tumorzellklons u.a. ma?geblich von der Aktivierung der Telomerase abh?ngt. Deshalb k?nnten Telomeraseinhibitoren neue M?glichkeiten in der Tumortherapie er?ffnen.      

A long distance-PCR derived FISH probe detects a deletion between p15 and p16 in CML and T-ALL patients

The tumor suppressor genes p15INK4B and p16INK4A, located in the chromosomal region 9p21, are frequently inactivated by homo- or hemizygous deletions, point mutation or promotor methylation in various types of cancer. No commercial probe is yet available that allows the detection of such deletions by FISH. Long distance (LD)-PCR was successfully used to generate a FISH probe, that covers a sequence stretch of 11.68 kb, located between the tumor suppressor genes p15 and p16. The LD-PCR amplicon was cloned and biotinylated by DOP-PCR (degenerated oligonucleotide primed-PCR) or nick translation. The FISH probe was hybridized on different samples of 16 patients with leukemia (3 T-ALL, 13 CML) and normal controls. Loss of at least one FISH-signal was found in 2/3 (67%) of the T-ALL- and 2/13 (15%) of the CML-cases. The new FISH probe presented here was proven to be advantageous for the detection of deletions in chromosomal region 9p21, especially between p15 and p16.     

The changing landscape of percutaneous technology leading to surgical complications

With new technology comes new complications. We discuss the interesting case presented by Bjelic and colleagues regarding a misplaced TAVR (transcatheter aortic valve replacement) valve into the inflow cannula of a left ventricular assist device, leading to hemodynamic collapse. The author describes the pitfalls of the new technology and interesting surgical maneuvers to address these complications.     

Response of the ENPP1-Deficient Skeletal Phenotype to Oral Phosphate Supplementation and/or Enzyme Replacement Therapy: Comparative Studies in Humans and Mice

Inactivating mutations in human ecto-nucleotide pyrophosphatase/phosphodiesterase-1 (ENPP1) may result in early-onset osteoporosis (EOOP) in haploinsufficiency and autosomal recessive hypophosphatemic rickets (ARHR2) in homozygous deficiency. ARHR2 patients are frequently treated with phosphate supplementation to ameliorate the rachitic phenotype, but elevating plasma phosphorus concentrations in ARHR2 patients may increase the risk of ectopic calcification without increasing bone mass. To assess the risks and efficacy of conventional ARHR2 therapy, we performed comprehensive evaluations of ARHR2 patients at two academic medical centers and compared their skeletal and renal phenotypes with ENPP1-deficient Enpp1^asj/asj mice on an acceleration diet containing high phosphate treated with recombinant murine Enpp1-Fc. ARHR2 patients treated with conventional therapy demonstrated improvements in rickets, but all adults and one adolescent analyzed continued to exhibit low bone mineral density (BMD). In addition, conventional therapy was associated with the development of medullary nephrocalcinosis in half of the treated patients. Similar to Enpp1^asj/asj mice on normal chow and to patients with mono- and biallelic ENPP1 mutations, 5-week-old Enpp1^asj/asj mice on the high-phosphate diet exhibited lower trabecular bone mass, reduced cortical bone mass, and greater bone fragility. Treating the Enpp1^asj/asj mice with recombinant Enpp1-Fc protein between weeks 2 and 5 normalized trabecular bone mass, normalized or improved bone biomechanical properties, and prevented the development of nephrocalcinosis and renal failure. The data suggest that conventional ARHR2 therapy does not address low BMD inherent in ENPP1 deficiency, and that ENPP1 enzyme replacement may be effective for correcting low bone mass in ARHR2 patients without increasing the risk of nephrocalcinosis. © 2021 American Society for Bone and Mineral Research (ASBMR).     

Lipoteichoic acid fractions from pathogenic and apathogenic Listeria species and Staphylococcus aureus induce similar amounts of macrophage-derived cytokines

Lipoteichoic acids (LTAs) of pathogenic and apathogenic Listeria species and of Staphylococcus aureus were fractionated and tested for their ability to stimulate production of cytokines (IL-1α, IL-6, TNF-α) in resident peritoneal macrophages (Mϕ) of endotoxin-resistant C3H/HeJ mice using a serum-free medium. For IL-1α and IL-6 there were no detectable differences in the ability of LTA fractions of pathogenic and apathogenic Listeria species and of Staphylococcus aureus. However, LTA-2 fractions of Staphylococcus aureus, which might be less hydrophobic than the LTA-2 fractions of the listeriae-induced lower amounts of TNF-α. Furthermore, the more lipophilic LTA-2 fractions of all LTAs employed were more potent inducers of cytokines than the less lipophilic LTA-1 fractions. The biologic effect of LTAs appears, therefore, to depend mainly on their hydrophobicity.