Partial purification and characterization of anhydrotetracycline oxygenase of Streptomyces aureofaciens

Anhydrotetracycline oxygenase was purified both by affinity chromatography and by hydrophobic interaction chromatography. Molecular weight of anhydrotetracycline oxygenase was determined to be 115,000 by Sephadex G-200 gel filtration. Using preparative isoelectric focusing the isoelectric point of the enzyme was estimated to be 5.3. The enzyme showed a sensitivity to thiol-specific inhibitors. During the hydrophobic interaction purification step, the activity dropped considerably. Reactivation occurred when a heat treated crude extract was added to the reaction mixture.     

Properties of visual evoked potentials to onset of movement on a television screen

In 80 subjects the dependence of movement-onset visual evoked potentials on some measures of stimulation was examined, and these responses were compared with pattern-reversal visual evoked potentials to verify the effectiveness of pattern movement application for visual evoked potential acquisition. Horizontally moving vertical gratings were generated on a television screen. The typical movement-onset reactions were characterized by one marked negative peak only, with a peak time between 140 and 200ms. In all subjects the sufficient stimulus duration for acquisition of movement-onset-related visual evoked potentials was 100ms; in some cases it was only 20ms. Higher velocity (5.6°/s) produced higher amplitudes of movement-onset visual evoked potentials than did the lower velocity (2.8°/s). In 80% of subjects, the more distinct reactions were found in the leads from lateral occipital areas (in 60% from the right hemisphere), with no correlation to handedness of subjects. Unlike pattern-reversal visual evoked potentials, the movement-onset responses tended to be larger to extramacular stimulation (annular target of 5°–9°) than to macular stimulation (circular target of 5° diameter).Abbreviation PREP pattern-reversal visual evoked potentials     

SORB-GEL method of analysis of 99mTc-labelled compounds

A SORB-GEL method has been worked out for analysing ^99mTc-labelled compounds which (in a few minutes) enables the pertechnetate content to be determined in a preparation. The method is based upon a different tupe of behaviour of ^99mTc-labelled compound, pertechnetate in the columns packed with Sephadex G-10, and with alumina during elution with saline.Polythene syringes 4.7 cm long and 1 cm in diameter were used as chromotographic columns. A syringe packed with Sephadex G-10 transferred 0.1 ml of ^99mTc-labelled compound into the column, and the activity of the column was then measured in the ionisation chamber. Using a syringe, 20 ml of saline was foreced through this column. The eluate was then removed. Using an injection needle, a second column, packed with alumina, was connected with the first. Similarly, a third column, packed with Sephadex G-10, was connected to the second. Through all of them 40 ml of saline was forced. The third column containing Sephadex G-10 was then disconnected and its activity was measured in the ionisation chamber. The pertechnetate content in the preparation was then calculated from the measured values.The method is suitable for determinating the free pertechnetate content in strong and weak chelate compounds and in particle preparations.     

Analysis of Adenosine Vascular Effect in Isolated Rat Aorta: Possible Role of Na+/K+‐ATPase

Abstract: The present experiments were undertaken in order to examine the effect of adenosine in isolated rat aorta, to investigate the possible role of intact endothelium and endothelial relaxing factors in this action and to determine which population of adenosine receptors is involved in rat aorta response to adenosine. Adenosine (0.1–300 μM) produced concentration‐dependent (intact rings: pD₂=4.39±0.09) and endothelium‐independent (denuded rings: pD₂=4.52±0.12) relaxation of isolated rat aorta. In the presence of high concentration of K⁺ (100 mM) adenosine‐evoked relaxation was significantly reduced (maximal relaxation in denuded rings: control – 92.1±9.8 versus K⁺– 54.4±5.0). Similar results were obtained after incubation of ouabain (100 μM) or glibenclamide (1 μM). In K⁺‐free solution, K⁺ (1–10 mM)‐induced rat aorta relaxant response was significantly inhibited by ouabain (100 μM). Application of indomethacin (10 μM), N^G‐nitro‐L‐arginine (10 μM) or tetraethylammonium (500 μM) did not alter the adenosine‐elicited effect in rat aorta. 8‐(3‐Chlorostyril)‐caffeine (0.3–3 μM), a selective A_2A‐receptor antagonist, significantly reduced adenosine‐induced relaxation of rat aorta in a concentration‐dependent manner (pK_B=6.57). Conversely, 1,3‐dipropyl‐8‐cyclopentylxanthine (10 nM), an A₁‐receptor antagonist, did not affect adenosine‐evoked dilatation. These results indicate that in isolated rat aorta, adenosine produces endothelium‐independent relaxation, which is most probably dependent upon activation of smooth muscle Na⁺/K⁺‐ATPase, and opening of ATP‐sensitive K⁺ channels, to a smaller extent. According to receptor analysis, vasorelaxant action of adenosine in rat aorta is partly induced by activation of smooth muscle adenosine A_2A receptors.     

Aryl hydrocarbon receptor-activating polychlorinated biphenyls and their hydroxylated metabolites induce cell proliferation in contact-inhibited rat liver epithelial cells.

Polychlorinated biphenyls (PCBs) exhibit tumor-promoting effects in experimental animals. We investigated effects of six model PCB congeners and hydroxylated PCB metabolites on proliferation of contact-inhibited rat liver epithelial WB-F344 cells. The 'dioxin-like' PCB congeners, PCB 126, PCB 105, and 4'-OH-PCB 79, a metabolite of the planar PCB 77 congener, induced cell proliferation in a concentration-dependent manner. In contrast, the 'non-dioxin-like' compounds that are not aryl hydrocarbon receptor (AhR) agonists, PCB 47, PCB 153, and 4-OH-PCB 187, an abundant noncoplanar PCB metabolite, had no effect on cell proliferation at concentrations up to 10 muM. The concentrations of dioxin-like PCBs leading to cell proliferation corresponded with the levels inducing the expression of cytochrome P450 1A1 mRNA, suggesting that the release from contact inhibition was associated with AhR activation. The effects of PCB 126 and PCB 153 on expression of proteins controlling G0/G1-S-phase transition and S-phase progression were compared. Only PCB 126 was found to upregulate cyclin A and D2 protein levels, and to increase both total cyclin-dependent kinase 2 (cdk2) and cyclin A/cdk2 complex activities. Despite the observed upregulation of cyclin D2, no increase in cdk4 activity was observed. The expression of cdk inhibitor p27Kip1 was not affected by either PCB 126 or PCB 153. These results suggest that dioxin-like PCBs can induce cell proliferation of contact-inhibited rat liver epithelial cells by increasing cyclin A protein levels, a process that then leads to upregulation of cyclin A/cdk2 activity and initiation of DNA replication. This mechanism could be involved in tumor-promoting effects of dioxin-like PCBs.     

Post-synthetically modified metal–porphyrin framework GaTCPP for carbon dioxide adsorption and energy storage in Li–S batteries

Lithium–sulphur batteries attract increasing interest due to their high theoretical specific capacity, advantageous economy, and “eco-friendliness”. In this study, a metal–organic framework (MOF) GaTCPP containing a porphyrinic base ligand was used as a conductive additive for sulphur. GaTCPP was synthesized, characterized, and post-synthetically modified by the transition metal ions (Co²⁺/Ni²⁺). The doping of GaTCPP ensured an increase in the carbon dioxide adsorption capacities, which were measured under different conditions. Post-synthetic modification of GaTCPP with Co²⁺/Ni²⁺ ions has been shown to increase carbon dioxide storage capacity from 22.8 wt% for unmodified material to 23.1 wt% and 26.5 wt% at 0 °C and 1 bar for Co²⁺ and Ni²⁺-doped analogues, respectively. As a conductive part of cathode material, MOFs displayed successful sulphur capture and encapsulation proven by stable charge/discharge cycle performances, high-capacity retention, and coulombic efficiency. The electrodes with pristine GaTCPP showed a discharge capacity of 699 mA h g⁻¹ at 0.2C in the fiftieth cycle. However, the doping of GaTCPP by Ni²⁺ has a positive impact on the electrochemical properties, the capacity increased to 778 mA h g⁻¹ in the fiftieth cycle at 0.2C.

Metal–porphyrin framework GaTCPP was used for carbon dioxide adsorption and as a host for preparation of a Li–S battery cathode material.     

The frequency and characteristics of ultrasonographic ankle joint involvement in systemic lupus erythematosus: A prospective cross-sectional single-center study

The involvement of ankles in systemic lupus erythematosus (SLE) has not been widely studied. The aim of our prospective study was to determine the characteristics of the ankle joint and tendon involvement in SLE using ultrasound (US) as an imaging modality. Sixty consecutive patients with SLE underwent a detailed clinical evaluation and US examination. Gray-scale and power Doppler US of the bilateral tibiotalar (TT) joints, subtalar (ST) joints, and ankle tendons were performed using a multiplanar scanning technique. Joint effusion, synovitis, tenosynovitis, enthesitis, and vascularization were assessed according to the OMERACT recommendations. The Total Ankle Ultrasound Score (TAUSS) was calculated as the sum of the grades of joint effusion and synovial hypertrophy for both TT and ST joints bilaterally (ranging from 0–24) and power Doppler activity was assessed separately. Finally, US findings were correlated with physical evaluation, laboratory parameters, and SLE activity scores. US ankle joint involvement was present in 32/60 (53.3%) patients. TT joints were affected in 26 (43.3%) and ST joints in 16 (26.7%) patients. Thirteen (21.7%) patients had US tendons and/or enthesal involvement. TT joint effusion was the most frequent finding, present in 55/240 (22.9%) examined joints, followed by synovial hypertrophy detected in 18/240 (7.5%) joints. The median (interquartile range; range) TAUSS of the US-affected joints was 1 (0–2; range 1–10). There were no significant correlations between US findings and inflammatory parameters or serological parameters of disease activity, but we found a weak positive correlation between TAUSS and the European Consensus Lupus Activity Measurement (r = 0.281, P = .029). This study revealed a high prevalence of pathological US ankle changes in patients with SLE and a positive correlation between ankle US involvement and disease activity score (European Consensus Lupus Activity Measurement).     

Bis(2,2′-bipyridil)Copper(II) Chloride Complex: Tyrosinase Biomimetic Catalyst or Redox Mediator?

In this article, construction of amperometric sensor(s) based on screen-printed carbon electrodes covered by thin layers of two types of carbon nanomaterials serving as amplifiers, and containing [Cu(bipy)₂Cl]Cl∙5H₂O complex is reported. Their performance and biomimetic activity towards two selected neurotransmitters (dopamine and serotonin) was studied mainly using flow injection analysis (FIA). The important parameters of FIA such as working potential, flow rate, and pH were optimized. The mechanism of the catalytic activity is explained and experimentally confirmed. It reveals that presence of hydrogen peroxide plays a crucial role which leads to answer the title question: can presented complex really be considered as a tyrosinase biomimetic catalyst or only as a redox mediator?