Magnetic nanoparticle-based immunosensor for electrochemical detection of hepatitis B surface antigen

An electrochemical immunosensor was developed for the detection of hepatitis B surface antigen (HBsAg). The biotinylated hepatitis B surface antibody was immobilized on streptavidin magnetic nanoparticles and used for targeting the HBsAg. By the addition of horseradish peroxidase conjugated with secondary antibody (HRP–HBsAb), a sandwich-type immunoassay format was formed. Aminophenol as substrate for conjugated HRP was enzymatically changed into 3-aminophenoxazone (3-APZ). This electroactive enzymatic production (3-APZ) was transferred into an electrochemical cell and monitored by cyclic voltammetry. Under optimal conditions, the cathodic current response of 3-APZ, which was proportional to the HBsAg concentration, was measured by a glassy carbon electrode. The immunosensor response was linear toward HBsAg in the concentration range from 0.001 to 0.015 ng/ml with a detection limit of 0.9 pg/ml at a signal/noise ratio of 3.     

Towards tropomyosin-related kinase B (TrkB) receptor ligands for brain imaging with PET: Radiosynthesis and evaluation of 2-(4-[18F]fluorophenyl)-7,8-dihydroxy-4H-chromen-4-one and 2-(4-([N-methyl-11C]-dimethylamino)phenyl)-7,8-dihydroxy-4H-chromen-4-one

The interaction of tropomyosin-related kinase B (TrkB) with the cognate ligand brain-derived neurotrophic factor (BDNF) mediates fundamental pathways in the development of the nervous system. TrkB signaling alterations are linked to numerous neurodegenerative diseases and conditions. Herein we report the synthesis, biological evaluation and radiosynthesis of the first TrkB radioligands based on the recently identified 7,8-dihydroxyflavone chemotype. 2-(4-[¹⁸F]fluorophenyl)-7,8-dihydroxy-4H-chromen-4-one ([¹⁸F]10b) was synthesized in high radiochemical yields via an efficient S_NAr radiofluorination involving a para-Michael acceptor substituted aryl followed by BBr₃-promoted double demethylation. Selective N-[¹¹C]methylation afforded 2-(4-([N-methyl-¹¹C]-dimethylamino)phenyl)-7,8-dihydroxy-4H-chromen-4-one ([¹¹C]10c) from the fully deprotected catechol-bearing normethyl precursor 13 with [¹¹C]MeOTf. In vitro autoradiography of [¹⁸F]10b with transverse rat brain sections revealed high specific binding in the cortex, striatum, hippocampus and thalamus in accordance with expected TrkB distribution. Blockade experiments with both 7,8-dihydroxyflavone (1a) and TrkB cognate ligand, BDNF, led to decreases of 80% and 85% of radioligand binding strongly supporting the hypothesis that 7,8-dihydroxyflavones exert their effect on TrkB phosphorylation via direct TrkB extracellular domain (ECD) binding. Positron emission tomography (PET) studies revealed that [¹⁸F]10b and [¹¹C]10c brain uptake is minimal and that they are rapidly eliminated from the plasma (effective plasma half-life 5–10 min) via hepatic secretion. Nevertheless, the high specific binding and TrkB specificity derived from in vitro experiments suggests that the 7,8-disubstituted flavone chemotype represents a promising scaffold for the development of TrkB radiotracers for PET.     

The influence of flow cell geometry related shear stresses on the distribution,structure and susceptibility of Pseudomonas aeruginosa 01 biofilms

The effects of non-uniform hydrodynamic conditions resulting from flow cell geometry (square and rectangular cross-section) on Pseudomonas aeruginosa 01 (PAO1) biofilm formation, location, and structure were investigated for nominally similar flow conditions using a combination of confocal scanning laser microscope (CSLM) and computational fluid dynamics (CFD). The thickness and surface coverage of PAO1 biofilms were observed to vary depending on the location in the flow cell and thus also the local wall shear stress. The biofilm structure in a 5:1 (width to height) aspect ratio rectangular flow cell was observed to consist mainly of a layer of bacterial cells with thicker biofilm formation observed in the flow cell corners. For square cross-section (1:1 aspect ratio) flow cells, generally thicker and more uniform surface coverage biofilms were observed. Mushroom shaped structures with hollow centers and wall breaks, indicative of ‘seeding’ dispersal structures, were found exclusively in the square cross-section tubes. Exposure of PAO1 biofilms grown in the flow cells to gentamicin revealed a difference in susceptibility. Biofilms grown in the rectangular flow cell overall exhibited a greater susceptibility to gentamicin compared to those grown in square flow cells. However, even within a given flow cell, differences in susceptibility were observed depending on location. This study demonstrates that the spanwise shear stress distribution within the flow cells has an important impact on the location of colonization and structure of the resultant biofilm. These differences in biofilm structure have a significant impact on the susceptibility of the biofilms grown within flow channels. The impact of flow modification due to flow cell geometry should be considered when designing flow cells for laboratory investigation of bacterial biofilms.     

Does survivin overexpression enhance the efficiency of fibroblast cell-based wound therapy?

Molecular Biology Reports - Cell-based wound therapy is faced with some limiting factors that decrease the therapeutic efficacy of transplanted cells. In this study, we aimed to genetically modify...     

Lack of Effect of Dietary Chromium Supplementation on Growth Performance and Serum Insulin, Glucose, and Lipoprotein Levels in Broilers Reared Under Heat Stress Condition

This study evaluated the effects of supplemental dietary chromium (Cr) on the performance, carcass traits, and some serum parameters of broilers under a heat stress (23.9 to 37 °C cycling) condition. A total of 150 1-day-old broiler chicks (Cobb 500) according to a completely randomized design were assigned into five treatment groups. Each treatment consisted of three replicates and each replicate contained ten chicks. Treatments were supplemented with 0 (control), 600, and 1,200 μg kg^?1 Cr in the form of Cr chloride (CrCl₃) and Cr L-methionine from 1 to 49 days of age. Blood samples were collected from two birds in each replicate to determine serum parameters at 35 and 49 days of age. The body mass, feed intake, and conversion ratio were not influenced by dietary Cr (P?>?0.05). Dietary supplementation of Cr from either CrCl₃ or Cr L-methionine caused increased serum concentrations of Cr (P?<?0.05), but had no effect on serum insulin and glucose concentrations at both sampling times (P?>?0.05). Serum triglycerides, very low-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol were also not significantly affected (P?>?0.05) by dietary treatments, whereas total cholesterol concentration decreased in chicks fed Cr L-methionine compared to the control (P?<?0.05).     

Introduction of Beauveria bassiana as a biological control agent for Tribolium castaneum in Kerman province

Barley, Hordeum vulgare, one of the important crops in the word, is used in malting, feed and food industries. The red flour beetle, Tribolium castaneum, was found wherever grains or other dried foods are stored. Disinfestations of barley using chemical methods to kill insects, in this research, for the first time we isolated the pathogenic KB512 of entomopathogenic fungi Beauveria bassiana from soil and insects, which produced aerial and submerged conidia and blastospores in laboratory conditions. We investigated the best conditions for the production and utilisation of spore suspension to spray the larvae of T. castaneum, which is one of the important pests in Kerman province (Iran). One hundred and eighty isolates that naturally infected by T. castaneum were reared during spring and summer seasons 2010–2011. The pathogenicity test was carried out with direct spray. To bioassay the isolates, three concentrations of the spore suspension were prepared as follows: 1?×?10⁶ and 1?×?10⁸ conidia/ml. The pests were sprayed by aerial conidial suspension, which was prepared by 0.01% Tween 80 in distilled water, and the controls were sprayed by 0.01% Tween 80 in distilled water. After spraying the pests, the plates were incubated at 25?±?1?°C and 80% of relative humidity. Then, the treated pests were monitored every day for the fungal growth and mortality.     

New immunological investigations on Helicobacter pylori‐induced gastric ulcer in patients

Although Helicobacter pylori (Hp) plays an important role in the pathogenesis of chronic gastritis and gastric ulcer, little is known about the probable mechanisms of these types of gastrointestinal damage. To determine the precise mechanisms involved in ulcer formation, immune responses in patients with gastric ulcer (GUP) caused by Hp infection (Hp⁺) were compared with those of other gastritis patients (GP). The sensitivity and proliferation of peripheral blood mononuclear cells (PBMNCs) obtained from patients were evaluated by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay against exposure with complex Hp crude antigen (HPCA) and mitogen (phytohemagglutinin, PHA). Production of inflammatory cytokines, including interleukin (IL)‐1β and IL‐8, in serum and supernatants of PBMNCs were then measured by ELISA. It was found that, after stimulation with PHA, both IL‐8 and IL‐1β concentrations in sera and supernatants as well as proliferation and sensitivity were statistically greater in GUP Hp⁺ than GP Hp^?. Furthermore, HPCA inhibited the proliferation of PBMNCs dose‐dependently; however, it stimulated IL‐8 and IL‐1β production in supernatants of mononuclear cells. Therefore, the up‐regulated concentrations of IL‐8 and IL‐1β may have been caused by increase in the size of mononuclear cell subpopulations or in their cytokine secretory activity, indicating the greatest cell responsiveness in GUP Hp⁺ patients. These results suggest that tissue damage and ulcers occur in patients who produce more IL‐8 and IL‐1β than patients who do not develop ulcers; the former consequently have more activated immune cells at the site of infection. Therefore, both host responses and Hp virulence factors may be involved in the development of gastric ulcers.

     

Structural insight into the binding complex: β-arrestin/CCR5 complex

The chemokine receptor 5 (CCR5) belongs to the superfamily of serpentine G protein-coupled receptors (GPCRs). The DRY motif (Asp, Arg, Tyr) of the intracellular loop 2 (ICL2), which is highly conserved in the GPCRs has been shown to be essential for the stability of folding of CCR5 and the interaction with β-arrestin. But the molecular mechanism by which it recognizes and interacts with β-arrestin has not been elucidated. In the present study, we described the active state of the β-arrestin structure using normal mode analysis and characterized the binding cleft of CCR5-ICL2 with β-arrestin using SABRE© docking tool and molecular dynamics simulation. Based on our computational results, we proposed a mode of binding between the ICL2 loop of CCR5 and β-arrestin structure, and modeled the energetically stable β-arrestin/CCR5 complex. In view of CCR5’s importance as a therapeutic target for the treatment of HIV, this observation provides novel insight into the β-arrestin/CCR5 pathway. As a result, the current computational study of the detailed β-arrestin/CCR5 binding complex could provide the rationale for the development of next generation of HIV peptide inhibitors as therapeutic agents.