A novel automatic flow method with direct-injection photometric detector for determination of dissolved reactive phosphorus in wastewater and freshwater samples

The novel automatic flow system, direct-injection detector (DID) integrated with multi-pumping flow system (MPFS), dedicated for the photometric determination of orthophosphates in wastewater and freshwater samples is for the first time described. All reagents and the sample were injected simultaneously, in counter-current into the reaction-detection chamber by the system of specially selected for this purpose solenoid micro-pumps. The micro-pumps provided good precision and accuracy of the injected volumes. For the determination of orthophosphates, the molybdenum blue method was employed. The developed method can be used to detect orthophosphate in the range 0.1-12 mg L^-1, with the repeatability (RSD) about 2.2% at 4 mg L^-1 and a very high injection throughput of 120 injections h^-1. It was possible to achieve a very small consumption of reagents (10 μL of ammonium molybdate and 10 μL of ascorbic acid) and sample (20 μL). The volume of generated waste was only 440 μL per analysis. The method has been successfully applied, giving a good accuracy, to determination of orthophosphates in complex matrix samples: treated wastewater, lake water and reference sample of groundwater. The developed system is compact, small in both size and weight, requires 12 V in supply voltage, which are desirable for truly portable equipment used in routine analysis. The simplicity of the system should result in its greater long-time reliability comparing to other flow methods previously described.

[Pain, fear of falling and functional performance in nursing home residents - a cross-sectional study]

Pain and fear of falling (FOF) are modifiable factors that might play an important role in functional performance of nursing homes residents (NHR). Both factors are characterised by deficits in research and provision of long-term care services. The purpose of this study was to examine the functional performance of NHR with and without pain or FOF. Quantitative data were collected on NHR in Berlin and Brandenburg using a cross-sectional design. The cognitive status was assessed using the Minimental state test. Existing pain and FOF were assessed as a question part of interview. Functional performance was examined using the Barthel Index (BI) the Timed «up & go»-Test. Multiple linear regression analyses were performed to investigate the research question and the influence of additional explanatory variables (age, sex, relevant somatic morbidity). 217 NHR without considerable cognitive impairment (MMST >= 20) participated. 65 % of the NHR suffered from pain and 48 % had FOF. There was a statistically significant association between Pain or FOF und lower functional mobility. With respect to NHR able to walk, there was statistically significant association between Pain or FOF und lower performance in activities of daily living. Possibilities for interventions which might have positive effects on functional performance of NHR are an improved pain treatment and interventions to reduce FOF.

Application of the PEDD flow detector for analysis of natural dissolved organic substances in coloured water

The automated techniques of measurement of water parameters are developed based on flow analysis (flow injection analysis, sequential injection analysis). PEDD detectors (paired emitter-detector diode), built with the use of two paired light-emitting diodes (LEDs) - emission and detection, can serve that purpose. The aim of the studies was to optimize the system for determination of the dissolved organic substances in coloured water with the use of PEDDs in the flowing-stream measurement system. The investigations were conducted for a number of concentrations of the humic, fulvic and tannic acids, which were measured as the dissolved organic carbon (DOC). Three arrangements of diodes (PEDD) with a selected emission spectrum and absorption characteristics were used. A two-beam flow cell was designed for the measurements. The signal from the detection diode was recorded and converted into absorbance through software written for that purpose. The results obtained showed a high sensitivity in relation to the concentration as well as the selectivity in the type of substances studied. A miniature and cheap photometric flow analysis set was proposed, adapted to work with one or several light wavelengths and steered by a microprocessor unit.

Antipsychotic drugs predominate in pharmacotherapy of nursing home residents with dementia

INTRODUCTION

The aim of this study was to investigate the frequency of benzodiazepines, antidementia and antipsychotic drug prescriptions in nursing home residents (NHR).Data of a German health insurance company were retrospectively analyzed for the year 2008.

METHODS

The study cohort comprised 13,042 NHR (82% women, mean age 83.6 ± 7 years). Following analgetics, antipsychotic drugs were the second most frequently prescribed drug group with 13.3% of all prescriptions. Dementia was diagnosed in 8 017 (61.5%) NHR. Thereof 51.6% received an antipsychotic, 17.3% a benzodiazepine and 15.2% an antidementia pharmaceutical, respectively. 18.1% of NHR with dementia and antipsychotic drug prescriptions were in combined treatment with antidementia pharmaceuticals. The rate of antipsychotic drug prescribing was significantly doubled in NHR with dementia compared to those without this diagnosis (p<0.01); the most frequently prescribed antipsychotics were melperone, risperidone and pipamperone.

DISCUSSION

This study demonstrates the wide-spread use of psychotropic drugs in NHR. Moreover, dementia in NHR was associated with antipsychotic drug prescribing in every second patient. This highlights the need for further studies analyzing alternative treatments for dementia-related symptoms.

Application of direct-injection detector integrated with the multi-pumping flow system to photometric stop-flow determination of total iron

A novel direct-injection detector (DID) integrated with multi-pumping flow system (MPFS) for the photometric determination of iron is proposed. Paired emitter-detector diodes have been used as a photometric detection system. The sample and reagent were injected using appropriate solenoid pulse micro-pumps directly into the detection chamber where effective mixing occured. The use of proposed stop-flow detector considerably simplified the analytical procedure. The potassium thiocyanate has been chosen as a chromogenic reagent for photometric Fe(III) detection. The total volume of reagent and sample/standard solutions involved in the detection process was adjusted to the volume of the reaction-detection chamber. Calibration graph was found to be linear in the range up to 10mgL(-1). The detection limit (3s(b)/S) was 0.15mgL(-1). The repeatability (R.S.D.), calculated from 10 analyses of sample containing 5mgL(-1) Fe(III), was 1.5% and the sample throughput 180 determinations per hour. The consumption of sample and reagent was 20μL each with the waste generation at the level of 0.24mL. The applicability of the proposed method to the determination of total iron in groundwater samples has been proved. The analytical parameters are compared to those obtained exploiting the MPFS system with typical configuration containing a confluence point and reaction coil.

A novel direct-injection photometric detector integrated with solenoid pulse-pump flow system

A novel flow photometric detector based on paired emitter-detector diodes (PEDD), coupled with solenoid pulse micro-pumps is presented. The photometric detection chamber also plays a role of the reaction chamber. Both solutions, a sample and a reagent, are injected by solenoid micro-pumps directly and simultaneously into the chamber in countercurrent. This method ensures fast and effective mixing of the injected solutions. A good accuracy and precision of the injected volumes assure the pulse micro-pumps. This method, in comparison with other flow methods, does not require the application of the reaction coil. Thanks to this, the dispersion of the sample is minimized. The presented flow network is easy to control, miniaturize and exhibits a very low consumption of reagents and the sample. Two chemical systems were chosen and presented as models of photometric reactions: the first - Fe(III) with thiocyanate, and the second - Cr(VI) with 1,5-diphenylcarbazide. To obtain the highest repeatability, the total volume of the solutions should be smaller than the volume of the reaction-detection chamber. In this case, the whole coloured product remains in the chamber. The use of the proposed direct-injection PEDD detector considerably simplifies analytical procedures. The shape of analytical signals and their potential applications have been discussed.

Ascorbic Acid determination in commercial fruit juice samples by cyclic voltammetry

A method was developed for assessing ascorbic acid concentration in commercial fruit juice by cyclic voltammetry. The anodic oxidation peak for ascorbic acid occurs at about 490 mV on a Pt disc working electrode (versus SCE). The influence of the potential sweep speed on the peak height was studied. The obtained calibration graph shows a linear dependence between peak height and ascorbic acid concentration in the domain (0.1-10 mmol.L(-1)). The equation of the calibration graph was y = 6.391x + 0.1903 (where y represents the value of intensity measured for the anodic peak height, expressed as muA and x the analyte concentration, as mmol.L(-1), r(2) = 0.9995, r.s.d. = 1.14%, n = 10, C(ascorbic acid) = 2 mmol.L(-1)). The developed method was applied to ascorbic acid assessment in fruit juice. The ascorbic acid content determined ranged from 0.83 to 1.67 mmol.L(-1) for orange juice, from 0.58 to 1.93 mmol.L(-1) for lemon juice, and from 0.46 to 1.84 mmol.L(-1) for grapefruit juice. Different ascorbic acid concentrations (from standard solutions) were added to the analysed samples, the degree of recovery being comprised between 94.35% and 104%. Ascorbic acid determination results obtained by cyclic voltammetry were compared with those obtained by the volumetric method with dichlorophenol indophenol. The results obtained by the two methods were in good agreement.

Modeling the induction of lipid membrane electropermeabilization

Experiments show significant effects of an electric field on lipid membrane, leading to a pore formation when a high intensity field is applied. The phenomenon of electroporation is preceded by the induction and expansion of defects, responsible for the pre-pore excitation. We examine the mechanism of the induction of the field-driven defects by Monte Carlo simulations. The study is based on the improved Pink's model, which includes explicit interactions between the polar heads and energy of interactions between the heads and the field. No anomalous deformation of the molecules is considered. The study, provided for bilayer dipalmitoyl-phosphatidylcholine (DPPC) membrane in the gel (300 K) and fluid (330 K) phases, shows dependence of the membrane conformational and energetical state on the value of the electric field. We observe that the electric field affects the number of molecules in the gel and in the fluid states. In the layer at the negative potential, when the transmembrane voltage is above U(c) approximately 280 mV, lipid heads abruptly reorient and the number of local spots with fluid conformation increases. The other layer slightly tends to tighten its structure, producing additional mechanical stress between layers. Lipids showed complete insensitivity to the electric field within physiological limits, U<70 mV.

Simulation of electroporated cell by chronopotentiometry

Chronopotentiometry on planar lipid bilayer (BLM) is proposed as a method for modeling the electrical phenomena in electroporated cell. Two techniques are discussed: constant-current and linear-current chronopotentiometry. It is proposed that the constant-current chronopotentiometry may provide basis for modeling the electroporated cell shortly after the removal of the electric field, when activity of cellular pumps counteracts ionic fluxes through the electropore and ionic channels. The linear-current method can be considered for modeling the cell in the later stage after electroporation, when energetical resources of the cell are gradually getting exhausted and the activity of pumps decreases. Based on this idea, it may be postulated that the electropore in the cell has fluctuating dynamics whose stochastic characteristics, similarly as biological channels, shows 1/f noise. The model implies that the fluctuations would disappear leaving the electropore with a constant resistance when efficiency of the pumps becomes very small. The results of chronopotentiometry also may suggest that opening time, conductivity and selectivity of the electropore can be controlled by the cell environment or membrane composition.

Self-similar processes and flicker noise from a fluctuating nanopore in a lipid membrane

Stochastic properties of a fluctuating nanopore generated and sustained by an electric field in a lipid bilayer membrane are studied. It is shown that the process of voltage fluctuations, in the current clamp experiment, is a stochastic fractal with long memory, which is the main reason for its nonstationarity. The aging process contributes to the nonstationarity if molecular interactions in the membrane are weak. An attempt to classify the process reveals a non-Gaussian distribution with long tails, which contradicts the hypothesis of fractional Brownian motion, showing that stable motion may be possible. The self-similarity index, estimated by three different methods, depends on current value and membrane sensitivity to electric field in a well defined and explicable manner. The stochastic analysis provided for calculated conductance of nanopore revealed the process close to 1/f noise, the result observed only for the pores not exceeding 1 nm in diameter, induced in membranes with strong molecular interactions. Our results show that such a pore is the simplest biological system needed for flicker noise to occur, and the complexity of highly regulated protein channel is not a necessary factor. A case of noise 1/f(2), observed for a pore with impeded dynamics, suggests a process without memory in such a situation. A physical interpretation is presented for some of the results.

Changes of structural and dynamic properties of model lipid membranes induced by alpha-tocopherol: implication to the membrane stabilization under external electric field

The effects of alpha-tocopherol on electric properties of bilayer lipid membranes were investigated. Planar bilayer membranes formed by the Mueller-Rudin method were used. Voltammetric and chronopotentiometric measurements were performed using a four-electrode potentiostat-galvanostat. It was demonstrated that registration of membrane capacitance, resistance, and voltammetric characteristics provided information about the change in the structure and permeability of bilayer lipid membranes. The results suggested that incorporation of alpha-tocopherol into lipid membrane destabilized its structure and facilitated the electrogeneration of pores. The possible role of observed changes in physiological functions of alpha-tocopherol was discussed.

Chronopotentiometric studies of electroporation of bilayer lipid membranes

The constant-intensity current chronopotentiometric measurements of egg yolk phosphatidylcholine bilayer membranes (BLM) are presented. It is demonstrated that a constant-intensity current flowing through the bilayer membranes generates the pores in their structures. For the current intensity from 0.1 to 2.0 nA, the generated pores open and close cyclically. The frequency of oscillations depends on the current intensity: the higher current intensity, the higher frequency of pore oscillations. It is suggested that the presented method may allow to create one pore in BLM and to observe its dynamical behaviour. Based on chronopotentiometric curves, a method of pore conductance calculations is presented. It is demonstrated that the value of obtained conductance can be applied for pore diameter estimation. The hypothetical application of constant-current method as a biotechnological tool for selective and controlled incorporation of molecules into microorganisms is discussed.

Genetic variation of major histocompatibility complex and microsatellite loci: a comparison in bighorn sheep

Examining and comparing genetic variation for major histocompatibility complex (MHC) and micro-satellite (MS) loci in the same individuals provides an opportunity to understand the forces influencing genetic variation. We examined five MHC and three MS loci in 235 bighorn sheep (Ovis canadensis) from 14 populations and found that both types of loci were highly variable and were in Hardy-Weinberg proportions. Mean FST values for both markers were very similar and MHC and MS genetic variability was predominantly distributed within rather than among populations. However, analyses of genetic distances and tree topologies revealed different spatial patterns of variation for the two types of loci. Collectively, these results indicated that neutral forces substantially influenced MS and MHC variation, and they provided limited evidence for selection acting on the MHC.

Expression of human hepatic glucokinase in transgenic mice liver results in decreased glucose levels and reduced body weight

Glucokinase is the predominant hexokinase in pancreatic beta-cells and liver parenchymal cells and functions as a critical component of the glucose-sensing apparatus in these glucose-responsive cell types. In the beta-cells, the sensing leads to insulin secretion, while the role in hepatocytes is thought to be in hepatic glucose uptake. To determine the physiological response to an increase in hepatic glucokinase expression, transgenic mice expressing the human hepatic glucokinase gene under the control of a liver-specific human apolipoprotein A-I gene enhancer were generated. Transgenic mice had twofold higher total fasting hepatic glucokinase mRNA, which resulted in a modest 20% increase in fasting glucokinase activity. These animals showed lower fasting plasma glucose, insulin, and lactate levels and improved tolerance to glucose. In addition, glucokinase transgenic animals weighed less and had lower BMI than nontransgenic animals. Thus, glucokinase transgenic animals demonstrate that a modest change in hepatic glucokinase activity enhances the metabolism of glucose.

A new system for bilayer lipid membrane capacitance measurements: method, apparatus and applications

A new method and a new apparatus for capacitance measurements on bilayer lipid membranes are described. The membrane is charged and discharged with a constant current during the measurement. The charge-discharge cycle duration, which is proportional to the membrane capacitance, is measured. The measured time period is converted into a binary number by digital systems and then this number is either further converted into a constant capacity-proportional voltage or read out by the computer. The apparatus makes it possible to measure the capacitances of voltage-polarized membranes. Application of the apparatus to capacitance measurements of bilayer lipid membranes during their potential on the capacitance is presented. The capacitances of membranes stimulated by rectangular voltage pulses and of those stimulated by a linearly varying potential were reported.

Abnormal differentiation of human papillomavirus-induced laryngeal papillomas

We studied the proliferation and differentiation of human laryngeal papillomas, which are benign tumors induced by human papillomaviruses. Immunofluorescent stains of tissues for a number of differentiation-specific proteins showed abnormal differentiation. Papilloma tissue fragments in vitro showed a slightly decreased fraction of proliferating cells that incorporated tritiated thymidine and a markedly reduced incorporation of tritiated uridine when compared with normal tissue. We propose that papillomavirus infection results in normal basal cell proliferation but abnormal terminal differentiation and that this abnormality significantly contributes to the hyperplasia of the papillomas.