Model of cellular mechanotransduction via actin stress fibers

Mechanical stresses due to blood flow regulate vascular endothelial cell structure and function and play a key role in arterial physiology and pathology. In particular, the development of atherosclerosis has been shown to correlate with regions of disturbed blood flow where endothelial cells are round and have a randomly organized cytoskeleton. Thus, deciphering the relation between the mechanical environment, cell structure, and cell function is a key step toward understanding the early development of atherosclerosis. Recent experiments have demonstrated very rapid (\(\sim \)100 ms) and long-distance (\(\sim \)10 \(\upmu \)m) cellular mechanotransduction in which prestressed actin stress fibers play a critical role. Here, we develop a model of mechanical signal transmission within a cell by describing strains in a network of prestressed viscoelastic stress fibers following the application of a force to the cell surface. We find force transmission dynamics that are consistent with experimental results. We also show that the extent of stress fiber alignment and the direction of the applied force relative to this alignment are key determinants of the efficiency of mechanical signal transmission. These results are consistent with the link observed experimentally between cytoskeletal organization, mechanical stress, and cellular responsiveness to stress. Based on these results, we suggest that mechanical strain of actin stress fibers under force constitutes a key link in the mechanotransduction chain.     

Increased Reactive Oxygen Species Formation and Oxidative Stress in Rheumatoid Arthritis

BackgroundRheumatoid arthritis (RA) is an autoimmune inflammatory disorder. Highly reactive oxygen free radicals are believed to be involved in the pathogenesis of the disease. In this study, RA patients were sub-grouped depending upon the presence or absence of rheumatoid factor, disease activity score and disease duration. RA Patients (120) and healthy controls (53) were evaluated for the oxidant—antioxidant status by monitoring ROS production, biomarkers of lipid peroxidation, protein oxidation and DNA damage. The level of various enzymatic and non-enzymatic antioxidants was also monitored. Correlation analysis was also performed for analysing the association between ROS and various other parameters.MethodsIntracellular ROS formation, lipid peroxidation (MDA level), protein oxidation (carbonyl level and thiol level) and DNA damage were detected in the blood of RA patients. Antioxidant status was evaluated by FRAP assay, DPPH reduction assay and enzymatic (SOD, catalase, GST, GR) and non-enzymatic (vitamin C and GSH) antioxidants.ResultsRA patients showed a higher ROS production, increased lipid peroxidation, protein oxidation and DNA damage. A significant decline in the ferric reducing ability, DPPH radical quenching ability and the levels of antioxidants has also been observed. Significant correlation has been found between ROS and various other parameters studied.ConclusionRA patients showed a marked increase in ROS formation, lipid peroxidation, protein oxidation, DNA damage and decrease in the activity of antioxidant defence system leading to oxidative stress which may contribute to tissue damage and hence to the chronicity of the disease.     

Spectroscopic (UV/VIS,Raman) and Electrophoresis Study of Cytosine-Guanine Oligonucleotide DNA Influenced by Magnetic Field

Studying the effect of a magnetic field on oligonucleotide DNA can provide a novel DNA manipulation technique for potential application in bioengineering and medicine. In this work, the optical and electrochemical response of a 100 bases oligonucleotides DNA, cytosine-guanine (CG₁₀₀), is investigated via exposure to different magnetic fields (250, 500, 750, and 1000 mT). As a result of the optical response of CG₁₀₀ to the magnetic field, the ultra-violet-visible spectrum indicated a slight variation in the band gap of CG₁₀₀ of about 0.3 eV. Raman spectroscopy showed a significant deviation in hydrogen and phosphate bonds’ vibration after exposure to the magnetic field. Oligonucleotide DNA mobility was investigated in the external electric field using the gel electrophoresis technique, which revealed a small decrease in the migration of CG₁₀₀ after exposure to the magnetic field.     

Copper Oxide Nanomaterials Derived from Zanthoxylum armatum DC. and Berberis lycium Royle Plant Species: Characterization,Assessment of Free Radical Scavenging and Antibacterial Activity

Copper oxide nanomaterials were synthesized by a facile sustainable biological method using two plant species (Zanthoxylum armatum DC. and Berberis lycium Royle ). The formation of materials was confirmed by FT‐IR, ATR, UV‐visible, XRD, TEM, SEM, EDX, TGA and PL. The antibacterial activity was evaluated by agar well diffusion method to ascertain the efficacy of plant species extract and extract derived copper oxide nanomaterials against six Gram‐positive bacteria namely Staphylococcus aureus, Streptococcus mutans, Streptococcus pyogenes, Corynebacterium diphtheriae, Corynebacterium xerosis, Bacillus cereus and four Gram‐negative bacteria such as Klebsiella pneumonia, Escherichia coli, Pseudomonas aeruginosa and Proteus vulgaris against the standard drug, Ciprofloxacin for Gram‐positive and Gentamicin for Gram‐negative bacteria, respectively. In both cases, copper oxide nanomaterials were found to be sensitive in all the bacterial species. Sensitivity of copper oxide nanomaterials shows an be higher as compared to plant species extract against different bacteria. Scavenging activity of plant extracts along with nanomaterials have been accessed using previously reported protocols employing ascorbic acid as standard. Scavenging activity of copper oxide nanomaterials shows an increase with increase in concentration. The biological activity (bactericidal and scavenging efficiency) of plant derived copper oxide nanomaterials revealed that these materials can be used as potent antimicrobial agent and DPPH scavengers in industrial as well as pharmacological fields.     

Recent developments in bioreactor scale production of bacterial polyhydroxyalkanoates

Bioprocess and Biosystems Engineering - Polyhydroxyalkanoates (PHAs) are biological plastics that are sustainable alternative to synthetic ones. Numerous microorganisms have been identified as PHAs...