Simulated cell trajectories in a stratified gas–liquid flow tubular photobioreactor

The fluid dynamic environment within a photobioreactor is critical for performance as it controls mass transfer of photosynthetic gases (CO₂ and O₂) and the mixing environment of the algal culture. At a cellular level, light fluctuation will occur when cells move between the “light”, well-illuminated volume of the culture near the light source and the “dark”, self-shaded zone of the culture. Controlled light/dark frequency may increase the light to biomass yield and prevent photoinhibition. Knowledge of cell trajectories within the reactor is therefore important to optimize culture performance. This study examines the cell trajectories and light/dark frequencies in a stratified gas–liquid flow tubular photobioreactor. Commercially available computational fluid dynamics software, ANSYS Fluent, was used to investigate cell trajectories within the half-full solar receivers at different liquid velocities and reactor tube diameters. In the standard configuration 96-mm solar receiver tube, the light/dark cycle frequencies ranged from 0.104 to 0.612?Hz over the liquid velocity range of 0.1 to 1?m s^?1. In comparison, the smaller diameter 48- and 24-mm tubes exhibit higher light/dark frequencies, 0.219 to 1.30?Hz and 0.486 to 2.67?Hz, respectively.     

Characterization of the viral microbiome in patients with severe lower respiratory tract infections, using metagenomic sequencing

The human respiratory tract is heavily exposed to microorganisms. Viral respiratory tract pathogens, like RSV, influenza and rhinoviruses cause major morbidity and mortality from respiratory tract disease. Furthermore, as viruses have limited means of transmission, viruses that cause pathogenicity in other tissues may be transmitted through the respiratory tract. It is therefore important to chart the human virome in this compartment. We have studied nasopharyngeal aspirate samples submitted to the Karolinska University Laboratory, Stockholm, Sweden from March 2004 to May 2005 for diagnosis of respiratory tract infections. We have used a metagenomic sequencing strategy to characterize viruses, as this provides the most unbiased view of the samples. Virus enrichment followed by 454 sequencing resulted in totally 703,790 reads and 110,931 of these were found to be of viral origin by using an automated classification pipeline. The snapshot of the respiratory tract virome of these 210 patients revealed 39 species and many more strains of viruses. Most of the viral sequences were classified into one of three major families; Paramyxoviridae, Picornaviridae or Orthomyxoviridae. The study also identified one novel type of Rhinovirus C, and identified a number of previously undescribed viral genetic fragments of unknown origin.     

Characteristics of Biofilms from Urinary Tract Catheters and Presence of Biofilm-Related Components in Escherichia coli

Long term catheterization of the urinary tract leads to bacterial colonization of the urine, whereby adherence to the catheter surface is a major determinative factor for colonization. Collection of bacterial isolates from urine and urinary catheters of 45 patients showed multi-species catheter-colonization, while Escherichia coli isolates were frequently found in the urine in high numbers. Biofilm formation of catheter and urine-derived E. coli isolates was associated with the presence of the fluA gene, loss of O-antigen, and expression of type 1 fimbriae. The second messenger cyclic di-GMP (cdiGMP), a major regulator of biofilm formation, regulated adherence to the catheter surface in a selected clinical isolate suggesting that the cdiGMP second messenger pathway may be a target for anti-biofilm therapeutic approaches.     

The erythropoietin analogue ARA290 modulates the innate immune response and reduces Escherichia coli invasion into urothelial cells

Urinary tract infections (UTI) are one of the most common infectious diseases worldwide. The majority is caused by uropathogenic Escherichia coli. Emerging resistances against conventional antimicrobial therapy requires novel treatment strategies. Beside its role in erythropoiesis, erythropoietin has been recognized to exert tissue-protective and immunomodulatory properties. Here, we investigated the nonerythropoietic erythropoietin analogue ARA290 for potential properties to modulate uroepithelial infection by E. coli in a cell culture model. Expression of the erythropoietin receptor was increased by bacterial stimuli and further enhanced by ARA290 in bladder epithelial cell lines and primary cells as well as in the monocytic cell line THP-1. Stimulation with ARA290 promoted an immune response, inducing a strong initial, but temporarily limited interleukin-8 induction. Moreover, the invasion of bladder epithelial cells by E. coli was significantly reduced in cells costimulated with ARA290. Our results indicate that the erythropoietin analogue ARA290 might be a candidate for the development of novel treatment strategies against UTI, by boosting an early immune response and reducing bacterial invasion as a putative source for recurrent infections.     

Porphyromonas gingivalis Facilitates the Development and Progression of Destructive Arthritis through Its Unique Bacterial Peptidylarginine Deiminase (PAD)

Rheumatoid arthritis and periodontitis are two prevalent chronic inflammatory diseases in humans and are associated with each other both clinically and epidemiologically. Recent findings suggest a causative link between periodontal infection and rheumatoid arthritis via bacteria-dependent induction of a pathogenic autoimmune response to citrullinated epitopes. Here we showed that infection with viable periodontal pathogen Porphyromonas gingivalis strain W83 exacerbated collagen-induced arthritis (CIA) in a mouse model, as manifested by earlier onset, accelerated progression and enhanced severity of the disease, including significantly increased bone and cartilage destruction. The ability of P. gingivalis to augment CIA was dependent on the expression of a unique P. gingivalis peptidylarginine deiminase (PPAD), which converts arginine residues in proteins to citrulline. Infection with wild type P. gingivalis was responsible for significantly increased levels of autoantibodies to collagen type II and citrullinated epitopes as a PPAD-null mutant did not elicit similar host response. High level of citrullinated proteins was also detected at the site of infection with wild-type P. gingivalis. Together, these results suggest bacterial PAD as the mechanistic link between P. gingivalis periodontal infection and rheumatoid arthritis.     

Sesquiterpene Lactones Downregulate G2/M Cell Cycle Regulator Proteins and Affect the Invasive Potential of Human Soft Tissue Sarcoma Cells

Soft tissue sarcomas (STS) represent a rare group of malignant tumors that frequently exhibit chemotherapeutic resistance and increased metastatic potential. Many studies have demonstrated the great potential of plant-derived agents in the treatment of various malignant entities. The present study investigates the effects of the sesquiterpene lactones costunolide and dehydrocostus lactone on cell cycle, MMP expression, and invasive potential of three human STS cell lines of various origins. Both compounds reduced cell proliferation in a time- and dose-dependent manner. Dehydrocostus lactone significantly inhibited cell proliferation, arrested the cells at the G2/M interface and caused a decrease in the expression of the cyclin-dependent kinase CDK2 and the cyclin-dependent kinase inhibitor p27^Kip1. In addition, accumulation of cells at the G2/M phase transition interface resulted in a significant decrease in cdc2 (CDK1) together with cyclin B1. Costunolide had no effect on the cell cycle. Based on the fact that STS tend to form daughter cell nests and metastasize, the expression levels of matrix metalloproteinases (MMPs), which play a crucial role in extracellular matrix degradation and metastasis, were investigated by Luminex® technology and real-time RT-PCR. In the presence of costunolide, MMP-2 and -9 levels were significantly increased in SW-982 and TE-671 cells. Dehydrocostus lactone treatment significantly reduced MMP-2 and -9 expression in TE-671 cells, but increased MMP-9 level in SW-982 cells. In addition, the invasion potential was significantly reduced after treatment with both sesquiterpene lactones as investigated by the HTS FluoroBlock™ insert system.     

Mutations in Nicastrin Protein Differentially Affect Amyloid β-Peptide Production and Notch Protein Processing

The γ-secretase complex is responsible for intramembrane processing of over 60 substrates and is involved in Notch signaling as well as in the generation of the amyloid β-peptide (Aβ). Aggregated forms of Aβ have a pathogenic role in Alzheimer disease and, thus, reducing the Aβ levels by inhibiting γ-secretase is a possible treatment strategy for Alzheimer disease. Regrettably, clinical trials have shown that inhibition of γ-secretase results in Notch-related side effects. Therefore, it is of great importance to find ways to inhibit amyloid precursor protein (APP) processing without disturbing vital signaling pathways such as Notch. Nicastrin (Nct) is part of the γ-secretase complex and has been proposed to be involved in substrate recognition and selection. We have investigated how the four evenly spaced and conserved cysteine residues in the Nct ectodomain affect APP and Notch processing. We mutated these cysteines to serines and analyzed them in cells lacking endogenous Nct. We found that two mutants, C213S (C2) and C230S (C3), differentially affected APP and Notch processing. Both the formation of Aβ and the intracellular domain of amyloid precursor protein (AICD) were reduced, whereas the production of Notch intracellular domain (NICD) was maintained on a high level, although C230S (C3) showed impaired complex assembly. Our data demonstrate that single residues in a γ-secretase component besides presenilin are able to differentially affect APP and Notch processing.     

Minor contribution of presenilin 2 for γ-secretase activity in mouse embryonic fibroblasts and adult mouse brain

γ-Secretase plays an important function in the development of Alzheimer disease, since it participates in the production of the toxic amyloid β-peptide (Aβ) from the amyloid precursor protein (APP). Besides APP, γ-secretase cleaves many other substrates resulting in adverse side effects when γ-secretase inhibitors are used in clinical trials. γ-Secretase is a membrane bound protein complex consisting of at least four subunits, presenilin (PS), nicastrin, Aph-1 and Pen-2. PS and Aph-1 exist as different homologs (PS1/PS2 and Aph-1a/Aph-1b, respectively), which generates a variation in complex composition. PS1 and PS2 appears to have distinct roles since PS1 is essential during embryonic development whereas PS2 deficient mice are viable with a mild phenotype. The molecular mechanism behind this diversity is, however, largely unknown. In order to investigate whether PS1 and PS2 show different substrate specificity, we used PS1 or PS2 deficient mouse embryonic fibroblasts to study the processing on the γ-secretase substrates APP, Notch, N-cadherin, and ephrinB. We found that whereas depletion of PS1 severely affected the cleavage of all substrates, the effect of PS2 depletion was minor. In addition, less PS2 was found in active γ-secretase complexes. We also studied the effect of PS2 depletion in adult mouse brain and, in concordance with the results from the mouse embryonic fibroblasts, PS2 deficiency did not alter the cleavage of the two most important substrates, APP and Notch. In summary, this study shows that the contribution of PS2 on γ-secretase activity is of less importance, explaining the mild phenotype of PS2-deficient mice.