Autocalibration based on dilution of a single concentrated standard is used for the determination of silicate in sea water by the modified molybdenum blue method.

The silicate (Si) molybdenum blue method was modified by combining oxalate and ascorbic acid into a single reagent and was used for determining Si in sea water samples. The first step of this automated assay protocol was designed to perform either a calibration by a single Si standard prepared in deionized (DI) water, or to dilute samples in the range of 0-160 µM Si to fit into 0-20 µM Si calibration range using a 20 cm flow cell. By designing the assay protocol to function in batch mode, the influence of salinity on calibration was eliminated, thus making the method suitable for analysis of samples collected in the open ocean, coastal areas, or rivers. Reproducibility and accuracy of this method were evaluated by analysis of certified sea water reference materials. Phosphate (P) does not interfere significantly if the Si:P ratio is 4:1 or larger. The limit of detection was 514 nM Si, r.s.d. 2.1 %, sampling frequency 40 s/h, reagent consumption 700 µL/sample, and using deionized water as the carrier solution.

Developmental models of the carrion beetle Thanatophilus rugosus (Linnaeus, 1758) (Coleoptera: Silphidae).

Coleoptera are currently considered a fundamental tool to help solve criminal investigations, allowing forensic entomologists to estimate post-mortem intervals and obtain other ecology-related information. Thanatophilus rugosus (Linnaeus, 1758) is an important necrophagous beetle distributed through most of the Palaearctic region, where it is readily found on human bodies and animal carcasses. In this study, the new thermal summation models for all the developmental stages of Thanatophilus rugosus are provided. Beetles were reared at six different constant and ecologically relevant temperatures (12, 14, 16, 18, 20, and 22 °C), and their developmental times were measured. Thermal summation constants were calculated for each developmental stage (egg, three larval instars, post-feeding stage, and pupa).

Hyperbaric oxygen enhances collagen III formation in wound of ZDF rat.

Diabetic foot ulcer (DFU) is a serious complication of diabetes and hyperbaric oxygen therapy (HBOT) is also considered in comprehensive treatment. The evidence supporting the use of HBOT in DFU treatment is controversial. The aim of this work was to introduce a DFU model in ZDF rat by creating a wound on the back of an animal and to investigate the effect of HBOT on the defect by macroscopic evaluation, quantitative histological evaluation of collagen (types I and III), evaluation of angiogenesis and determination of interleukin 6 (IL6) levels in the plasma. The study included 10 rats in the control group (CONT) and 10 in the HBOT group, who underwent HBOT in standard clinical regimen. Histological evaluation was performed on the 18th day after induction of defect. The results show that HBOT did not affect the macroscopic size of the defect nor IL6 plasma levels. A volume fraction of type I collagen was slightly increased by HBOT without reaching statistical significance (1.35+/-0.49 and 1.94+/-0.67 %, CONT and HBOT, respectively). In contrast, the collagen type III volume fraction was ~120 % higher in HBOT wounds (1.41+/-0.81 %) than in CONT ones (0.63+/-0.37 %; p=0.046). In addition, the ratio of the volume fraction of both collagens in the wound ((I+III)w) to the volume fraction of both collagens in the adjacent healthy skin ((I+III)h) was ~65 % higher in rats subjected to HBOT (8.9+/-3.07 vs. 5.38+/-1.86 %, HBOT and CONT, respectively; p=0.028). Vessels density (number per 1 mm2) was found to be higher in CONT vs. HBOT (206.5+/-41.8 and 124+/-28.2, respectively, p<0.001). Our study suggests that HBOT promotes collagen III formation and decreases the number of newly formed vessels at the early phases of healing.

Hyperbaric oxygen influences chronic wound healing - a cellular level review.

Chronic wound is a serious medical issue due to its high prevalence and complications; hyperbaric oxygen therapy (HBOT) is also considered in comprehensive treatment. Clinical trials, including large meta-analyses bring inconsistent results about HBOT efficacy. This review is summarizing the possible effect of HBOT on the healing of chronic wound models at the cellular level. HBOT undoubtedly escalates the production of reactive oxygen and nitrogen radicals (ROS and RNS), which underlie both the therapeutic and toxic effects of HBOT on certain tissues. HBOT paradoxically elevates the concentration of Hypoxia inducible factor (HIF) 1 by diverting the HIF-1 degradation to pathways that are independent of the oxygen concentration. Elevated HIF-1 stimulates the production of different growth factors, boosting the healing process. HBOT supports synthesis of Heat shock proteins (HSP), which are serving as chaperones of HIF-1. HBOT has antimicrobial effect, increases the effectiveness of some antibiotics, stimulates fibroblasts growth, collagen synthesis and suppresses the activity of proteolytic enzymes like matrix metalloproteinases. All effects of HBOT were investigated on cell cultures and animal models, the limitation of their translation is discussed at the end of this review.

Large magnetic gap at the Dirac point in Bi2Te3/MnBi2Te4 heterostructures.

Magnetically doped topological insulators enable the quantum anomalous Hall effect (QAHE), which provides quantized edge states for lossless charge-transport applications1-8. The edge states are hosted by a magnetic energy gap at the Dirac point2, but hitherto all attempts to observe this gap directly have been unsuccessful. Observing the gap is considered to be essential to overcoming the limitations of the QAHE, which so far occurs only at temperatures that are one to two orders of magnitude below the ferromagnetic Curie temperature, TC (ref. 8). Here we use low-temperature photoelectron spectroscopy to unambiguously reveal the magnetic gap of Mn-doped Bi2Te3, which displays ferromagnetic out-of-plane spin texture and opens up only below TC. Surprisingly, our analysis reveals large gap sizes at 1 kelvin of up to 90 millielectronvolts, which is five times larger than theoretically predicted9. Using multiscale analysis we show that this enhancement is due to a remarkable structure modification induced by Mn doping: instead of a disordered impurity system, a self-organized alternating sequence of MnBi2Te4 septuple and Bi2Te3 quintuple layers is formed. This enhances the wavefunction overlap and size of the magnetic gap10. Mn-doped Bi2Se3 (ref. 11) and Mn-doped Sb2Te3 form similar heterostructures, but for Bi2Se3 only a nonmagnetic gap is formed and the magnetization is in the surface plane. This is explained by the smaller spin-orbit interaction by comparison with Mn-doped Bi2Te3. Our findings provide insights that will be crucial in pushing lossless transport in topological insulators towards room-temperature applications.

[Choroidal melanoma stage T1 - comparison of the planning protocol for stereotactic radiosurgery and proton beam irradiation]. / Choroidálny melanóm v stádiu T1 - porovnanie plánu oziarenia pri stereotaktickej rádiochirurgii a pri protónovej terapii.

OBJECTIVE: Comparison of two methods of irradiation of patients with malignant choroidal melanoma - stereotactic radiosurgery and proton beam irradiation. External (non-contact) applied irradiation is used as a source of accelerated protons, respectively helium ions. This method allows applications of ionizing irradiation also despite the low radiosensitivity of cells of malignant melanoma of the uvea (MMU). External source of ionizing radiation is modulated current energy electrons, protons or neutrons, accelerated in linear accelerators. From the external medium voltages resources (4-16 MeV) are irradiated tissues with target dose of 5.0-24.0 Gy. Volume protons permeate straight the structures of the eye to a certain distance. The use of proton radiation density of ionized protons increases in the vicinity of the impact due to energy losses for electrons interacting with the environment. At the end of the track there is a huge increase in the ionization dose ("Bragg spike"). Therefore, the structures surrounding the eye at the point of entry and little affected and increasing the dose at the end of the proton beam is ideal for the desired therapeutic effect. Fractionated application is also possible. CASE REPORT: In December 2011 we performed stereotactic radiosurgery to treat female patient (born 1939) with malignant melanoma of the choroid stage T1 N0 M0. Plan has been drawn up for stereotactic irradiation - model for linear accelerator Clinac, Corvus planning system ver. 6.2, verification and OmniPro IMRT planning system Liebinger ver. 4.3. Patient characteristics were compared with the virtual plan for proton radiation therapy, and we used the scheme in Physical parameters FIAN-technical center in the Russian Federation. We compared both planning protocols and assess in particular the extent of radiation surrounding non-tumor tissue. RESULTS: When comparing the two planning schemes irradiation levels of surrounding tissues and risk structures (lens, optic nerve, chiasm) in both methods were corresponding to the required standard. CONCLUSION: Treatment of uveal melanoma through proton beam irradiation in Slovakia is not available yet, although it has several advantages, such as fractionation and the possibility of achieving a higher dose of irradiation to deposit (more than 50.0 Gy). The fundamental difference between the two methods for an eye is particularly the possibility of proton beam irradiation exposure of tumor of iris and ciliary body, which can not be solved through stereotactic radiosurgery. The dose to the tumor during irradiation can be optimized. The model device allowed us to make OPTMI - Therapy (Proton Treatment with Optimized Modulated Intensity).

Xanthan and gellan degradation by bacteria of activated sludge.

Owing to increasing amounts of xanthan and gellan in food, cosmetics and pharmaceuticals, as well as in some technical spheres, studies were carried out on the xanthan and gellan degrading bacteria present in activated sludge. The activated sludge used in the study was able to degrade both carbohydrates over 7 days, with levels of xanthan and gellan utilizing microbes estimated at 10(5) cells/g of dry sludge weight. Isolating key degrading bacteria revealed the important role of genus Paenibacillus in xanthan degradation and prosthecate bacterium Verrucomicrobium sp. GD, which was capable of gellan utilization. Further tests performed with both strains showed they were able to degrade other types of carbohydrate polymers, and that Verrucomicrobium sp. GD did not possess extracellular free gellan depolymerase.

Irresistible bouquet of death--how are burying beetles (Coleoptera: Silphidae: Nicrophorus) attracted by carcasses.

Chemical composition of volatiles emitted from fresh mouse carcasses (laboratory mice, Mus musculus) was studied using solid sample injection technique (solid-phase micro-extraction), two-dimensional gas chromatography with time of flight mass spectrometric detection and gas chromatography with electroantennographic detection. Electroantennography (EAG) and laboratory olfactometric behavioural observations were used to study the antennal sensitivity to identified infochemicals and their attractiveness for burying beetles Nicrophorus vespillo and Nicrophorus vespilloides (Silphidae: Nicrophorinae). Chemical analysis showed that immediately after death, emitted volatiles did not differ from those emitted by a living organism. However, in the course of time, sulphur-containing chemicals, specifically methanethiol, methyl thiolacetate, dimethyl sulphide, dimethyl disulphide and dimethyl trisulphide appear. EAG measurements revealed antennal sensitivity to these compounds. Behavioural tests in laboratory olfactometer showed that dimethyl sulphide, dimethyl disulphide and dimethyl trisulphide are highly attractive to both studied species. The data suggest that sulphur-containing chemicals are involved in mediating the fresh carcass attractiveness for N. vespillo and N. vespilloides.

Pyramid projection - validation of a new method of skin defect measurement.

This paper presents a new method for the determination of the volume, surface area and depth of skin defects. The method is based on the description of a spatial defect using a pyramid (made, for example, from injection needles), which is placed over the defect. The projection of the pyramid on to the defect is photographed using a digital camera and subsequently compared with the projection of the same pyramid on to a sheet of grid paper. The defect is mathematically reconstructed on a computer, and an optimal body shape describing the defect is found, using a number of simplifications and assumptions. The method was then validated using a plaster mold of a real foot with 19 defects simulating real wounds. These plaster wounds were molded using alginate hydrocolloid, and the volume, surface area and depth were measured and compared with the results of the pyramid projection by means of regression analysis.This method correlates in all variables with correlation coefficients higher than 0.9. It can be concluded that the projection pyramid method correlates well with the reference mold method and can be used with good results for a whole range of variables.

Biological effects of noble gases.

Noble gases are known for their inertness. They do not react chemically with any element at normal temperature and pressure. Through that, some of them are known to be biologically active by their sedative, hypnotic and analgesic properties. Common inhalation anesthetics are characterized by some disadvantages (toxicity, decreased cardiac output, etc). Inhalation of xenon introduces anesthesia and has none of the above disadvantages, hence xenon seems to be the anesthetic gas of the future (with just one disadvantage - its cost). It is known that argon has similar anesthetic properties (under hyperbaric conditions), which is much cheaper and easily accessible. The question is if this could be used in clinical practice, in anesthesia of patients who undergo treatment in the hyperbaric chamber. Xenon was found to be organ-protective. Recent animal experiments indicated that xenon decreases infarction size after ischemic attack on brain or heart. The goal of our study is to check if hyperbaric argon has properties similar to those of xenon.

Biotransformation of trichloroethene by pure bacterial cultures.

From natural samples 11 isolates able to remove trichloroethene (CCl2CHCl) from an aqueous environment were obtained which were capable of cometabolic degradation of CCl2CHCl by an enzyme system for phenol degradation. At an initial CCl2CHCl concentration of 1 mg/L, the resting cells of particular cultures degraded 33-94% CCl2CHCl during 1 d and their transformation capacity ranged from 0.3 to 3.1 mg CCl2CHCl per g organic fraction. An analysis of a mixed phenol-fed culture with an excellent trichloroethene-degrading ability found a markedly minority isolate represented in the consortium to be responsible for this property. This culture degraded CCl2CHCl even at a low inoculum concentration and attained a transformation capacity of 14.7 mg CCl2CHCl per g. The increase in chloride concentration after degradation was quantitative when compared with the decrease in organically bound chlorine. The degree of CCl2CHCl degradation was affected by Me2S2; this substance can significantly reduce the degrading ability of some tested cultures (> 60%); however, it does not cause this inhibition with others.

A simple flow injection system with bead injection for trace iron determination.

A simple and low cost flow injection (FI) system with bead injection (BI) was developed for determination of low concentration (mumol l(-1)) of iron in water samples. Chelex-100 chelating resin beads, trapped in a jet ring cell, were employed. The intensity of red complex of 1,10-phenanthroline with Fe(2+) was monitored using colorimetric detector with a LED green light source. Amount of total Fe (Fe(2+) and Fe(3+)) and Fe(2+) can be evaluated by with and without reduction of Fe(3+) using ascorbic acid. Lowest detectable levels of Fe(2+) were 0.90 and 0.45 mumol l(-1) for sample loading time of 3 and 5 min, respectively. Working range was up to 3.90 mumol l(-1) using 0.3% w/v 1, 10-phenanthroline. Percent recoveries of spiked water samples (0.90-2.33 mumol l(-1) of Fe(2+)) were 100-110%.

Stopped-flow injection simultaneous determination of phosphate and silicate using molybdenum blue.

Kinetic information for the phosphate-molybdate-ascorbic acid reaction can be obtained by making use of a very simple manually operated stopped-flow injection (FI) system. Various parameters (concentrations of reagents, flow rate, mixing coils, and volume of flow cell) were investigated for determination of phosphate. A stopped-FI system should be arranged for low degree of mixing (of reactants) and low dispersion so that good signals of rate changes will be observed. Simultaneous determination of phosphate and silicate by the stopped-FI technique is proposed, using a laboratory-made semi-automatic stopped-FI Analyzer with LED-based photometer. It is based on kinetic separation of phosphate and silicate using molybdenum blue. The proposed procedure has been demonstrated for the application to water samples. The results obtained agree with that of a standard method.

[Transcutaneous oxygen tension in hyperbaric condition as a predictor of ischaemia in non-healing diabetic foot ulcers]. / Transkutánní tlak kyslíku v hyperbarii jako prediktor ischemie u nehojících se diabetických vredu.

UNLABELLED: The aim of the study was to evaluate the contribution of basal and modify transcutaneous oxygen tension measurement (TcpO2) to diagnosis of ischaemia and indication of angiography in non-healing diabetes foot ulcers: METHOD: 69 patients with non-healing diabetic ulcers localised on 76 legs underwent angiography (DSA) and basal and modify TcpO2 measurement after 100 % O2 exposition under normo- and hyperbaric conditions. CHARACTERISTIC OF PATIENTS: mean age 66 years (42 81), diabetes duration 14.3 years (1 - 36), glycated hemoglobin 7.9 % (+/-1,35). RESULTS: Clinically important angiographic findings were obtained in 80 % (61/76) all ulcers. Basal TcpO2 < or = = 30 mm Hg was detected in 82 % diabetic ulcers with positive DSA (sensitivity - SN). The specificity (SP), positive and negative predictive value (PPV, NPV), relative risk (RR) and accuracy (A) of test were 60 %, 89 %, 47 %, 1.7 and 78 % respectively. TcpO2 with hyperbaric 100 % O2 was determined as the strongest predictor of ischaemia by statistical logistic regression. SN (91%), SP (77%), PPV (94 %), NPV (67 %, RR (2.8) and A (88 %) of test were increased (cut off 270 mmHg). CONCLUSION: TcpO2 measurement contributes to the diagnosis of ischaemia in non-healing diabetic ulcers. Modify TcpO2 increases the test value.

Micro sequential injection: fermentation monitoring of ammonia, glycerol, glucose, and free iron using the novel lab-on-valve system.

Using an integrated lab-on-valve manifold in a microfluidic sequential injection format (microSI), automated sample processing has been developed for off-line and on-line monitoring of small-scale fermentations. Spectrophotometric assays of ammonia, glucose, glycerol, and free iron were downscaled to use micro-quantities of commercial reagents. By monitoring the reaction rate, the response curves in a stopped-flow mode generate linear calibration curves for ammonia [r2 = 1.000 (0.9% SE)], glycerol [r2 = 0.999 (1.1% SE)], glucose [r2 = 0.999 (1.1% SE)], and free iron [r2 = 0.999 (1.5% SE)]. Since sample dilution and reagent quantities are easily adjusted within the programmable SI format, the lab-on-valve system can accommodate samples over a wide concentration range (ammonia: 3-1200 ppm; glycerol: 20-120 ppm; glucose: 35-1000 ppm; and free iron: 80-400 ppm). This work demonstrates the key advantages of miniaturization through the reduction of sample and reagent use, minimizing waste and providing a compact yet reliable instrument. The lab-on-valve manifold uses a universal hardware configuration for all analyses, only requiring changes in software protocol and choice of reagents. All of these features are of particular importance to small-scale experimental fermentation where multiple analyte analyses are needed in real-time using small sample volumes. It is hoped that this first real-life application of the lab-on-valve manifold will serve not only as a model system to downscale assays in a practical fashion, but will also inspire and promote the use of the integrated microSI manifold approach for a wider range of biotechnological applications.

Effects of ultrafiltration, dialysis, and temperature on gas exchange during hemodiafiltration: a laboratory experiment.

To study gas exchange in the filter during continuous venovenous hemodiafiltration (CVVHDF), an air-tight heated mixing chamber with adjustable CO2 supply was constructed and connected to a CVVHDF monitor. Bicarbonate-free crystalloid (Part 1) and packed red blood cell (Part 2) solutions were circulated at 150 ml x min(-1). Gas exchange expressed as pre-postfilter difference in CO2 and O2 contents was measured at different CVVHDF settings and temperatures of circulating and dialysis solutions. Ultrafiltration was most efficacious for CO2 removal (at 1,000 ml x h(-1) ultrafiltration CO2 losses reached 13% of prefilter CO2 content). Addition of dialysis (1,000 ml x h(-1)) increased CO2 loss to 17% and at maximal parameters (filtration 3,000 ml x h(-1), dialysis 2,500 ml x h(-1)), the loss of CO2 amounted to 35% of prefilter content. Temperature changes of circulating and/or dialysis fluids had no significant impact on CO2 losses. The O2 exchange during CVVHDF was negligible. Currently used CVVHDF is only marginally effective in CO2 removal. Higher volume ultrafiltration combined with dialysis can be expected to reach clinical significance.

Micro sequential injection: environmental monitoring of nitrogen and phosphate in water using a "Lab-on-Valve" system furnished with a microcolumn.

A "Lab-on-Valve" manifold operated in the micro sequential injection (microSI) mode was adopted to accommodate EPA-approved methods for spectrophotometric determinations of nitrate, nitrite and orthophosphate in the ppb (N or P) concentration range. A computer programmable microSI protocol, utilizing stopped-flow within a copperized Cd-foil filled microcolumn was developed for nitrate reduction to nitrite with subsequent colorimetric measurement, yielding concentration ranges for nitrate of 100.0-4000.0 ppb (N) and for nitrite of 30.0-4000.0 ppb (N) and linear calibration responses of r2 = 0.9999 for nitrate and 0.9995 for nitrite. Using a stopped-flow reaction rate measurement, phosphate was determined in the range 1.0-30.0 ppb (P) with a calibration response of r2 = 0.9997. The technical improvement of this methodology, apart from micro miniaturization, is the use of the stopped-flow technique, that resulted in improved detection limits and allowed reagent consumption to be reduced 1500-fold compared with conventional procedure while the amount of metallic cadmium was reduced 20-fold compared with the EPA-approved continuous-flow assay.

Nutrition, HIV, and drug abuse: the molecular basis of a unique role for selenium.

HIV-infected injection drug users (IDUs) often suffer from serious nutritional deficiencies. This is a concern because plasma levels of micronutrients such as vitamin B12, zinc, and selenium have been correlated with mortality risk in HIV-positive populations. Injection drug use also increases lipid peroxidation and other indicators of oxidative stress, which, combined with antioxidant deficiencies, can stimulate HIV-1 replication through activation of NF-kappaB transcription factors, while weakening immune defenses. As detailed herein, these prooxidant stimuli can also increase the pathogenic effects of HIV-1 by another mechanism, involving viral selenoproteins. Overlapping the envelope coding region, HIV-1 encodes a truncated glutathione peroxidase (GPx) gene (see #6 in reference list). Sequence analysis and molecular modeling show that this viral GPx (vGPx) module has highly significant structural similarity to known mammalian GPx, with conservation of the catalytic triad of selenocysteine (Sec), glutamine, and tryptophan. In addition to other functions, HIV-1 vGPx may serve as a negative regulator of proviral transcription, by acting as an NF-kappaB inhibitor (a known property of cellular GPx). Another potential selenoprotein coding function of HIV-1 is associated with the 3' end of the nef gene, which terminates in a conserved UGA (potential Sec) codon in the context of a sequence (Cys-Sec) identical to the C-terminal redox center of thioredoxin reductase, another cellular regulator of NF-kappaB. Thus, in combination with known cellular mechanisms involving Se, viral selenoproteins may represent a unique mechanism by which HIV-1 monitors and exploits an essential micronutrient to optimize its replication relative to the host.