Routes to turbulence in Taylor-Couette flow.

Fluid flows between rotating concentric cylinders exhibit two distinct routes to turbulence. In flows dominated by inner-cylinder rotation, a sequence of linear instabilities leads to temporally chaotic dynamics as the rotation speed is increased. The resulting flow patterns occupy the whole system and sequentially lose spatial symmetry and coherence in the transition process. In flows dominated by outer-cylinder rotation, the transition is abrupt and leads directly to turbulent flow regions that compete with laminar ones. We here review the main features of these two routes to turbulence. Bifurcation theory rationalizes the origin of temporal chaos in both cases. However, the catastrophic transition of flows dominated by outer-cylinder rotation can only be understood by accounting for the spatial proliferation of turbulent regions with a statistical approach. We stress the role of the rotation number (the ratio of Coriolis to inertial forces) and show that it determines the lower border for the existence of intermittent laminar-turbulent patterns. This article is part of the theme issue 'Taylor-Couette and related flows on the centennial of Taylor's seminal Philosophical Transactions paper (Part 2)'.

Which factors are associated with bone marrow oedema suspicious of axial spondyloarthritis as detected by MRI in the sacroiliac joints and the spine in the general population?

OBJECTIVE: Identify factors associated with presence and extension of spinal and sacroiliac joints (SIJ)-MRI lesions suggestive of axial spondyloarthritis (axSpA) in a population-based cohort (Study of Health in Pomerania) aged <45 years. METHODS: Spinal (sagittal T1/T2) and SIJ (semicoronal STIR sequences) MRIs were evaluated by two trained blinded readers. The presence (yes/no) and extension (Berlin MRI Score) of bone marrow oedema (BME) were captured. Degenerative spinal lesions were excluded and discrepancies resolved by consensus. Cross-sectional associations between clinical factors and presence/extension of BME were analysed by logistic/negative binomial regression. Record linkage of claims data was applied to identify participants with axSpA. RESULTS: MRIs of 793 volunteers were evaluated. The presence of SIJ-BME (odds ratio) was strongly associated delivery during the last year (4.47, 1.49-13.41). For SIJ-BME extension, associations (incidence rate ratios, 95% CI) were found for delivery ((during last year) 4.52, 1.48-13.84), human leucocyte antigen (HLA)-B27+ (2.32, 1.30-4.14), body mass index (25-30 vs <25 kg/m²; 1.86 (1.19-2.89)) and back pain ((last 3 months) 1.55, 1.04-2.31), while for spinal BME, associations were found for age per decade (1.46, 1.13-1.90) and physically demanding work (1.46, 1.06-2.00). Record linkage was available for 694 (87.5%) participants and 9/694 (1.3%) had a record of axSpA (ICD M45.09). CONCLUSION: These population-based data support the hypothesis of mechanic strain contributing to BME in the general population aged <45 years and the role of HLA-B27+ as a severity rather than a susceptibility factor for SIJ-BME.

Frequency of MRI changes suggestive of axial spondyloarthritis in the axial skeleton in a large population-based cohort of individuals aged <45 years.

OBJECTIVE: To investigate the frequency of bone marrow oedema (BME) and fatty lesions (FL) suggestive of axial spondyloarthritis (axSpA) on MRI of the spine and sacroiliac joints (SIJ) in a general population sample. METHODS: As part of a community-based cohort project (Study of Health in Pomerania), volunteers underwent spinal (sagittal T1/T2) and SIJ (semicoronal short tau inversion recovery) MRI examinations. Two calibrated readers evaluated the images to detect BME in SIJ and vertebral corners (VC) and FL in VC suggestive of axSpA using Assessment of SpondyloArthritis international Society definitions. RESULTS: MRIs of 793 volunteers (49.4% males, mean age 37.3±6.3 years, 8.4% human leucocyte antigen-B27+) aged <45 years were evaluated. SIJ BME was seen in 136 (17.2%), VC BME in 218 (27.5%) and FL in 645 (81.4%) volunteers. SIJ BME in ≥1, ≥3 and ≥5 SIJ quadrants was seen in 136 (17.2%), 7 (0.9%) and 1 (0.1%) volunteers, respectively. In VC, BME≥1, ≥3 and ≥5 lesions were seen in 218 (27.5%), 38 (4.8%) and 6 (0.8%) volunteers, respectively, while FL≥1, ≥3 and ≥5 were seen in 645 (81.3%), 351 (44.3%) and 185 (23.3%) volunteers, respectively. Logistic regression analysis showed that BME and FL in VC were related to increasing age: OR 1.33, 95% CI 1.02 to 1.72, and OR 1.73, 95% CI 1.32 to 2.27, per decade increase, respectively. CONCLUSIONS: In this large population-based study, a high frequency of inflammatory and fatty MRI lesions suggestive of axSpA was found, especially in the spine. This indicates a limited value of such MRI findings for diagnosis and classification of axSpA. The increasing frequency with age suggests that mechanical factors could play a role.

Nanoparticle-Mediated Gene Silencing for Sensitization of Lung Cancer to Cisplatin Therapy.

Platinum-based chemotherapy remains a mainstay treatment for the management of advanced non-small cell lung cancer. A key cellular factor that contributes to sensitivity to platinums is the 5'-3' structure-specific endonuclease excision repair cross-complementation group 1 (ERCC1)/ xeroderma pigmentosum group F (XPF). ERCC1/XPF is critical for the repair of platinum-induced DNA damage and has been the subject of intense research efforts to identify small molecule inhibitors of its nuclease activity for the purpose of enhancing patient response to platinum-based chemotherapy. As an alternative to small molecule inhibitors, small interfering RNA (siRNA) has often been described to be more efficient in interrupting protein-protein interactions. The goal of this study was therefore to determine whether biocompatible nanoparticles consisting of an amphiphilic triblock copolymer (polyethylenimine-polycaprolactone-polyethylene glycol (PEI-PCL-PEG)) and carrying siRNA targeted to ERCC1 and XPF made by microfluidic assembly are capable of efficient gene silencing and able to sensitize lung cancer cells to cisplatin. First, we show that our PEI-PCL-PEG micelleplexes carrying ERCC1 and XPF siRNA efficiently knocked down ERCC1/XPF protein expression to the same extent as the standard siRNA transfection reagent, Lipofectamine. Second, we show that our siRNA-carrying nanoparticles enhanced platinum sensitivity in a p53 wildtype model of non-small cell lung cancer in vitro. Our results suggest that nanoparticle-mediated targeting of ERCC1/XPF is feasible and could represent a novel therapeutic strategy for targeting ERCC1/XPF in vivo.

Spatiotemporal Intermittency in Pulsatile Pipe Flow.

Despite its importance in cardiovascular diseases and engineering applications, turbulence in pulsatile pipe flow remains little comprehended. Important advances have been made in the recent years in understanding the transition to turbulence in such flows, but the question remains of how turbulence behaves once triggered. In this paper, we explore the spatiotemporal intermittency of turbulence in pulsatile pipe flows at fixed Reynolds and Womersley numbers (Re=2400, Wo=8) and different pulsation amplitudes. Direct numerical simulations (DNS) were performed according to two strategies. First, we performed DNS starting from a statistically steady pipe flow. Second, we performed DNS starting from the laminar Sexl-Womersley flow and disturbed with the optimal helical perturbation according to a non-modal stability analysis. Our results show that the optimal perturbation is unable to sustain turbulence after the first pulsation period. Spatiotemporally intermittent turbulence only survives for multiple periods if puffs are triggered. We find that puffs in pulsatile pipe flow do not only take advantage of the self-sustaining lift-up mechanism, but also of the intermittent stability of the mean velocity profile.

The impact of microfluidic mixing of triblock micelleplexes on in vitro / in vivo gene silencing and intracellular trafficking.

The triblock copolymer polyethylenimine-polycaprolactone-polyethylene glycol (PEI-PCL-PEG) has been shown to spontaneously assemble into nano-sized particulate carriers capable of complexing with nucleic acids for gene delivery. The objective of this study was to investigate micelleplex characteristics, their in vitro and in vivo fate following microfluidic preparation of siRNA nanoparticles compared to the routinely used batch reactor mixing technique. Herein, PEI-PCL-PEG nanoparticles were prepared with batch reactor or microfluidic mixing techniques and characterized by various biochemical assays and in cell culture. Microfluidic nanoparticles showed a reduction of overall particle size as well as a more uniform size distribution when compared to batch reactor pipette mixing. Confocal microscopy, flow cytometry and qRT-PCR displayed the subcellular delivery of the microfluidic formulation and confirmed the ability to achieve mRNA knockdown. Intratracheal instillation of microfluidic formulation resulted in a significantly more efficient (p < 0.05) knockdown of GAPDH compared to treatment with the batch reactor formulation. The use of microfluidic mixing techniques yields an overall smaller and more uniform PEG-PCL-PEI nanoparticle that is able to more efficiently deliver siRNA in vivo. This preparation method may prove to be useful when a scaled up production of well-defined polyplexes is required.

Comparison of single and two-tunnel techniques during open treatment of acromioclavicular joint disruption.

BACKGROUND: Coracoclavicular (CC) ligament reconstruction with semitendinosus tendon (ST) grafts has become more popular and has achieved relatively good results; however optimal reconstruction technique, single-tunnel or two-tunnel, still remains controversial. This paper is to compare the clinical and radiographic data of allogenous ST grafting with single- or two-tunnel reconstruction techniques of the AC joint. METHODS: The outcomes of 21 consecutive patients who underwent anatomical reduction and ST grafting for AC joint separation were reviewed retrospectively. Patients were divided into two groups: single-tunnel group (11) and two-tunnel group (10). All patients were evaluated clinically and radiographically using a modified UCLA rating scale. RESULTS: The majority of separations (18 of 21) were Rockwood type V, with one each in type III, IV and VI categories. The overall mean follow-up time was 16 months, and at the time of the latest follow-up, the overall mean UCLA rating score was 14.1 (range 8-20).The percentage of good-to-excellent outcomes was significantly higher for patients with the two-tunnel technique than for those with the one-tunnel technique (70% vs. 18%, respectively, p = 0.03). Within the single-tunnel group, there was no statistically significant difference in percentage of good-to-excellent outcomes between patients with vs. without tightrope augmentation (17% vs 20%, p > 0.99). Similarly, within the two-tunnel group, there was no significant difference in the percentage of good-to-excellent outcomes between the graft only and augment groups (67% vs. 75%, p > 0.99). CONCLUSION: Anatomical reduction of the AC joint and reconstruction CC ligaments are crucial for optimal joint stability and function. Two-tunnel CC reconstruction with an allogenous ST graft provides superior significantly better radiographic and clinical results compared to the single-tunnel reconstruction technique.

Inhibition of SARS-CoV-2 replication in the lung with siRNA/VIPER polyplexes.

SARS-CoV-2 has been the cause of a global pandemic since 2019 and remains a medical urgency. siRNA-based therapies are a promising strategy to fight viral infections. By targeting a specific region of the viral genome, siRNAs can efficiently downregulate viral replication and suppress viral infection. However, to achieve the desired therapeutic activity, siRNA requires a suitable delivery system. The VIPER (virus-inspired polymer for endosomal release) block copolymer has been reported as promising delivery system for both plasmid DNA and siRNA in the past years. It is composed of a hydrophilic block for condensation of nucleic acids as well as a hydrophobic, pH-sensitive block that, at acidic pH, exposes the membrane lytic peptide melittin, which enhances endosomal escape. In this study, we aimed at developing a formulation for pulmonary administration of siRNA to suppress SARS-CoV-2 replication in lung epithelial cells. After characterizing siRNA/VIPER polyplexes, the activity and safety profile were confirmed in a lung epithelial cell line. To further investigate the activity of the polyplexes in a more sophisticated cell culture system, an air-liquid interface (ALI) culture was established. siRNA/VIPER polyplexes reached the cell monolayer and penetrated through the mucus layer secreted by the cells. Additionally, the activity against wild-type SARS-CoV-2 in the ALI model was confirmed by qRT-PCR. To investigate translatability of our findings, the activity against SARS-CoV-2 was tested ex vivo in human lung explants. Here, siRNA/VIPER polyplexes efficiently inhibited SARS-CoV-2 replication. Finally, we verified the delivery of siRNA/VIPER polyplexes to lung epithelial cells in vivo, which represent the main cellular target of viral infection in the lung. In conclusion, siRNA/VIPER polyplexes efficiently delivered siRNA to lung epithelial cells and mediated robust downregulation of viral replication both in vitro and ex vivo without toxic or immunogenic side effects in vivo, demonstrating the potential of local siRNA delivery as a promising antiviral therapy in the lung.

Evaluating the Regulation of Cytokine Levels After siRNA Treatment in Antigen-Specific Target Cell Populations via Intracellular Staining.

RNA interference (RNAi) offers a promising base for therapeutic knockdown of clinically relevant genes. Local delivery routes as well as targeted delivery to specific cell populations have been shown to circumvent several hurdles of successful siRNA delivery in vivo. To evaluate and quantify the treatment effect in a precise way, next to measuring the downregulation on gene and protein levels, it is equally essential to investigate the influence on downstream factors such as generated cytokines. Here, we describe an expressive method to specifically isolate the desired target cells and determine their levels of intracellular cytokines by flow cytometry using the example of murine lungs after pulmonary in vivo transfection with siRNA.Therefore, the lungs of treated mice are harvested and processed into single cell suspensions, in which CD4 positive T cells are marked by antibody-coupled magnetic beads and isolated via magnetic separation. These purified target cells are then fixed and permeabilized, making their intracellular interleukins accessible for staining with fluorescently labeled antibodies. Thus, the cytokine levels and hence the precise influence of the siRNA treatment on intracellular conditions can be measured.

Microfluidic Assembly of siRNA-Loaded Micelleplexes for Tumor Targeting in an Orthotopic Model of Ovarian Cancer.

The use of cationic polymers to interact with negatively charged siRNA via charge complexation to form polyelectrolyte complexes has been widely studied ever since the 1998 report on RNA interference. These polyelectrolyte complex formulations aim to overcome the many pitfalls associated with the use of RNA interference as a potential cancer therapy. The triblock copolymer polyethylenimine-polycaprolactone-polyethylene glycol (PEI-PCL-PEG) contains the cation PEI and has been shown to be an efficient carrier capable of complexing with nucleic acids for gene delivery. This copolymer system also allows for targeting moieties to be linked to the micelleplex, thereby exploiting overexpressed receptors (such as the folate receptor) located within tumors. Additionally, we demonstrated recently that microfluidic mixing of PEI-PCL-PEG nanoparticles allows for the rapid, scaled-up production of micelleplexes while maintaining small and uniform particle distributions. The preparation of small and reproducible particles is imperative for clinical translation of nanomedicine and for tumor targeting via systemic administration. Furthermore, to enable tracing of its deposition in vivo after its administration, micelleplexes can be radiolabeled. To assess tumor targeting over time, the noninvasive imaging technique single-photon emission computed tomography (SPECT) offers the ability to examine the same subject at multiple time points and generate biodistribution profiles. Since the biodistribution and tumor targeting of the therapeutic load of micelleplexes is of foremost interest, we recently described an approach to modify siRNA with a DTPA (diethylenetriaminepentaacetic acid) chelator. Herein, we explain the details of encapsulating indium-labeled siRNA via microfluidic mixing in PEI-PCL-PEG nanoparticles with a folic acid targeting ligand for assessment of their in vivo tumor targeting in an orthotopic ovarian cancer model.

Characterization of spray dried powders with nucleic acid-containing PEI nanoparticles.

Localized aerosol delivery of gene therapies is a promising treatment of severe pulmonary diseases including lung cancer, cystic fibrosis, COPD and asthma. The administration of drugs by inhalation features multiple benefits including an enhanced patient acceptability and compliance. The application of a spray dried powder formulation has advantages over solutions due to their increased stability and shelf life. Furthermore, optimal sizes of the powder can be obtained by spray drying to allow a deep lung deposition. The present study optimized the parameters involved with spray drying polyplexes formed by polyethylenimine (PEI) and nucleic acids in inert excipients to generate a nano-embedded microparticle (NEM) powder with appropriate aerodynamic diameter. Furthermore, the effects of the excipient matrix used to generate the NEM powder on the biological activity of the nucleic acid and the ability to recover the embedded nanoparticles was investigated. The study showed that bioactivity and nucleic acid integrity was preserved after spray drying, and that polyplexes could be reconstituted from the dry powders made with trehalose but not mannitol as a stabilizer. Scanning electron microscopy (SEM) showed trehalose formulations that formed fused, lightly corrugated spherical particles in the range between 1 and 5 µm, while mannitol formulations had smooth surfaces and consisted of more defined particles. After redispersion of the microparticles in water, polyplex dispersions are obtained that are comparable to the initial formulations before spray drying. Cellular uptake and transfection studies conducted in lung adenocarcinoma cells show that redispersed trehalose particles performed similar to or better than polyplexes that were not spray dried. A method for quantifying polymer and nucleic acid loss following spray drying was developed in order to ensure that equal nucleic acid amounts were used in all in vitro experiments. The results confirm that spray dried NEM formulations containing nucleic acids can be prepared with characteristics known to be optimal for inhalation therapy.

PARP-1/PAR Activity in Cultured Human Lens Epithelial Cells Exposed to Two Levels of UVB Light.

This study investigated poly(ADP-ribose) polymerase-1 (PARP-1) activation in cultured human lens epithelial cells exposed to two levels of UVB light (312 nm peak wavelength), 0.014 and 0.14 J cm-2 ("low" and "high" dose, respectively). At the low dose, PARP-1 and poly(ADP-ribose) (PAR) polymers acted to repair DNA strand breaks rapidly with no subsequent major effects on either cell morphology or viability. However, following the high UVB dose, there was a dramatic second phase of PARP-1 activation, 90 min later, which included a sudden reappearance of DNA strand breaks, bursts of reactive oxygen species (ROS) formation within both the mitochondria and nucleus, a translocation of PAR from the nucleus to the mitochondria and an ultimate 70% loss of cell viability occurring after 24 h. The results provide evidence for an important role for PARP-1 in protecting the human lens epithelium against low levels of UVB light, and possibly participating in the triggering of cell death following exposure to toxic levels of radiation.

In vitro and in vivo delivery of siRNA via VIPER polymer system to lung cells.

The block copolymer VIPER (virus-inspired polymer for endosomal release) has been reported to be a promising novel delivery system of DNA plasmids both in vitro and in vivo. VIPER is comprised of a polycation segment for condensation of nucleic acids as well as a pH-sensitive segment that exposes the membrane lytic peptide melittin in acidic environments to facilitate endosomal escape. The objective of this study was to investigate VIPER/siRNA polyplex characteristics, and compare their in vitro and in vivo performance with commercially available transfection reagents and a control version of VIPER lacking melittin. VIPER/siRNA polyplexes were formulated and characterized at various charge ratios and shown to be efficiently internalized in cultured cells. Target mRNA knockdown was confirmed by both flow cytometry and qRT-PCR and the kinetics of knockdown was monitored by live cell spinning disk microscopy, revealing knockdown starting by 4 h post-delivery. Intratracheal instillation of VIPER particles formulated with sequence specific siRNA to the lung of mice resulted in a significantly more efficient knockdown of GAPDH compared to treatment with VIPER particles formulated with scrambled sequence siRNA. We also demonstrated using pH-sensitive labels that VIPER particles experience less acidic environments compared to control polyplexes. In summary, VIPER/siRNA polyplexes efficiently deliver siRNA in vivo resulting in robust gene silencing (>75% knockdown) within the lung.

Revisiting the value of competition assays in folate receptor-mediated drug delivery.

Polymeric nanoparticles have been studied for gene and drug delivery. These nanoparticles can be modified to utilize a targeted delivery approach to selectively deliver their payload to specific cells, while avoiding unwanted delivery to healthy cells. One commonly over-expressed receptor which can be targeted by ligand-conjugated nanoparticles is the folate receptor alpha (FRα). The ability to target FRα remains a promising concept, and therefore, understanding the binding dynamics of the receptor with the ligand of the nanoparticle therapeutic can provide valuable insight. This manuscript focuses on the interaction between self-assembled nanoparticles decorated with a folic acid (FA) ligand and FRα. The nanoparticles consist of micelles formed with a FA conjugated triblock copolymer (PEI-g-PCL-b-PEG-FA) which condensed siRNA to form micelleplexes. By combining biological and biophysical approaches, this manuscript explores the binding kinetics and force of the targeted siRNA containing nanoparticles to FRα in comparison with free FA. We demonstrate via flow cytometry and atomic force microscopy that multivalent micelleplexes bind to FRα with a higher binding probability and binding force than monovalent FA. Furthermore, we revisited why competitive inhibition studies of binding of multivalent nanoparticles to their respective receptor are often reported in literature to be inconclusive evidence of effective receptor targeting. In conclusion, the results presented in this paper suggest that multivalent targeted nanoparticles display strong receptor binding that a monovalent ligand may not be able to compete with under in vitro conditions and that high concentrations of competing monovalent ligands can lead to measurement artifacts.

Return to play following surgical treatment of meniscal and chondral injuries to the knee.

Much has been written in the sports medicine literature regarding return to competition following anterior cruciate ligament reconstruction; however, little scientific work has been done regarding the return to competition following meniscal surgery or cartilage surgery. This article reviews the basic science of meniscal surgery and cartilage surgery in an attempt to promote rational rehabilitative protocols rooted in scientific investigation. A twofold approach is used. One approach is from a biologic standpoint; that is, when are the repaired tissues healed enough to withstand physiologic activity? The second approach is from a rehabilitative standpoint; when is the patient strong enough to play without recurrent injury?

Bone marrow adipocytes promote tumor growth in bone via FABP4-dependent mechanisms.

Incidence of skeletal metastases and death from prostate cancer greatly increases with age and obesity, conditions which increase marrow adiposity. Bone marrow adipocytes are metabolically active components of bone metastatic niche that modulate the function of neighboring cells; yet the mechanisms of their involvement in tumor behavior in bone have not been explored. In this study, using experimental models of intraosseous tumor growth and diet-induced obesity, we demonstrate the promoting effects of marrow fat on growth and progression of skeletal prostate tumors. We reveal that exposure to lipids supplied by marrow adipocytes induces expression of lipid chaperone FABP4, pro-inflammatory interleukin IL-1ß, and oxidative stress protein HMOX-1 in metastatic tumor cells and stimulates their growth and invasiveness. We show that FABP4 is highly overexpressed in prostate skeletal tumors from obese mice and in bone metastasis samples from prostate cancer patients. In addition, we provide results suggestive of bi-directional interaction between FABP4 and PPARγ pathways that may be driving aggressive tumor cell behavior in bone. Together, our data provide evidence for functional relationship between bone marrow adiposity and metastatic prostate cancers and unravel the FABP4/IL-1ß axis as a potential therapeutic target for this presently incurable disease.

Dermatomiosite/polimiosite infanto-juvenil / Juvenile dermatomyositis/polymyositis

O melhor tratamento para dermatomiosite/polimiosite nao está ainda estabelecido. Embora o corticosteróide seja considerado a droga de eleiçao para o controle inicial da doença, outras drogas podem ser utilizadas sobretudo nas formas mais agressivas e nao responsivas. Dentro deste contexto, destacam-se o metotrexato e a ciclosporina A. O uso da imunoglobulina intravenosa e da plasmaferese ainda é restrito principalmente em decorrência de seu elevado custo. A reposiçao nutricional e o tratamento precoce das infecçoes intercorrentes sao de extrema importância na abordagem terapêutica dessa enfermidade