Development of a DNA-liposome complex for gene delivery applications.

The association structures formed by cationic liposomes and DNA (Deoxyribonucleic acid)-liposome have been effectively utilized as gene carriers in transfection assays. In this research study, cationic liposomes were prepared using a modified lipid film hydration method consisting of a lyophilization step for gene delivery applications. The obtained results demonstrated that the mean particle size had no significant change while the polydispersity (PDI) increased after lyophilization. The mean particle size slightly reduced after lyophilization (520±12nm to 464±25nm) while the PDI increased after lyophilization (0.094±0.017 to 0.220±0.004). In addition. The mean particle size of vesicles increases when DNA is incorporated to the liposomes (673±27nm). According to the Scanning Electron Microscopy (SEM) and transmission electron microscopy (TEM) images, the spherical shape of liposomes confirmed their successful preservation and reconstitution from the powder. It was found that liposomal formulation has enhanced transfection considerably compared to the naked DNA as negative control. Finally, liposomal formulation in this research had a better function than Lipofectamine® 2000 as a commercialized product because the cellular activity (cellular protein) was higher in the prepared lipoplex than Lipofectamine® 2000.

In Silico Prediction of Mechanism of Action for Cancer Therapeutics.

Cancer is currently the second leading cause of death in the U.S. and is projected to become the principal cause in the near future. While radiation and surgery are common cancer treatment methods, chemotherapy remains a key treatment option, offering distinct advantages over other therapy options, especially in the management of metastasized tumors. Understanding the mechanism of action (MoA) of current and newly developed drugs is crucial to ongoing drug development research. Foreknowledge of how a candidate drug works can yield a wealth of information, including which cancers a drug may treat more effectively based on the susceptibility of the cancer to drugs with the same MoA. Previous studies concerning prediction of MoA have relied on costly experimental measurements as input for their predictions. We have developed an a priori quantitative structure-activity relationship (QSAR) for the in silico prediction of MoA without the need for experimental measurements. This model enables us to relate structural features of a chemical to its efficacy with a predictive accuracy of over 80 %, thus identifying the MoA of a candidate drug without costly, time-consuming experimental tests.

On meta-analyses of imaging data and the mixture of records.

Neumann et al. (2010) aim to find directed graphical representations of the independence and dependence relations among activities in brain regions by applying a search procedure to merged fMRI activity records from a large number of contrasts obtained under a variety of conditions. To that end, Neumann et al., obtain three graphical models, justifying their search procedure with simulations that find that merging the data sampled from probability distributions characterized by two distinct Bayes net graphs results in a graphical object that combines the edges in the individual graphs. We argue that the graphical objects they obtain cannot be interpreted as representations of conditional independence and dependence relations among localized neural activities; specifically, directed edges and directed pathways in their graphical results may be artifacts of the manner in which separate studies are combined in the meta-analytic procedure. With a larger simulation study, we argue that their simulation results with combined data sets are an artifact of their choice of examples. We provide sufficient conditions and necessary conditions for the merger of two or more probability distributions, each characterized by the Markov equivalence class of a directed acyclic graph, to be describable by a Markov equivalence class whose edges are a union of those for the individual distributions. Contrary to Neumann et al., we argue that the scientific value of searches for network representations from imaging data lies in attempting to characterize large scaled neural mechanisms, and we suggest several alternative strategies for combining data from multiple experiments.

Six problems for causal inference from fMRI.

Neuroimaging (e.g. fMRI) data are increasingly used to attempt to identify not only brain regions of interest (ROIs) that are especially active during perception, cognition, and action, but also the qualitative causal relations among activity in these regions (known as effective connectivity; Friston, 1994). Previous investigations and anatomical and physiological knowledge may somewhat constrain the possible hypotheses, but there often remains a vast space of possible causal structures. To find actual effective connectivity relations, search methods must accommodate indirect measurements of nonlinear time series dependencies, feedback, multiple subjects possibly varying in identified regions of interest, and unknown possible location-dependent variations in BOLD response delays. We describe combinations of procedures that under these conditions find feed-forward sub-structure characteristic of a group of subjects. The method is illustrated with an empirical data set and confirmed with simulations of time series of non-linear, randomly generated, effective connectivities, with feedback, subject to random differences of BOLD delays, with regions of interest missing at random for some subjects, measured with noise approximating the signal to noise ratio of the empirical data.

Use of ventricular stroke work index and ventricular function curves in assessing myocardial contractility.

Cardiac output and cardiac index values are traditionally used by critical care nurses as indicators of myocardial contractility. Due to the incidence of compensatory tachycardia in many critically ill patients, however, the value of LVSWI as an indicator of myocardial contractility is enhanced, because the formula for its calculation does not emphasize the variable of heart rate. The advantages of using LVSWI are the following: It is easily calculated at the bedside by using an integrated hemodynamic software package or by using the formula provided. It is readily available to the nurse and indicates sensitive changes in myocardial function. When used in LV function curves in the nursing assessment of myocardial contractility of critically ill adults, its use can direct changes in fluid and pharmacologic interventions. Factors that affect ventricular end-diastolic pressure such as altered myocardial compliance or increased transmural pressure alters PCWP. Although LVSWI is not completely independent of these factors and may be less precise with altered PCWP, the LVSWI does enhance the data base used to manage patients with altered ventricular function. Ideal LVSWI values may not be achievable in patients with poor myocardial contractility; however, tracking the LVSWI provides sensitive and immediate feedback on the efficacy of pharmacologic intervention. Critical care nurses should use the LVSWI for any hemodynamically unstable patient whose myocardial contractility might be compromised. This information allows the nurse to optimize the patient's hemodynamic performance with a more accurate assessment of heart function.

Task performance in heat: a review.

A wide array of variable conditions, tasks, subject populations, etc., have been included in studies that have produced data on perceptual motor performance in the heat. This paper uses a methodology for comparing these studies, regardless of the inherent differences, which allows determination of whether thermal effects are dominant enough to persist through diverse combinations of variables. Approximately 160 individual studies of perceptual motor performance reported in the literature were summarized based on thermal level, duration of exposure and the type of task performed. Results indicated no dominant effect of duration of exposure to the heat and no dominant effect of thermal level on mental/cognitive tasks. For perceptual motor tasks other than very simple or mental tasks, an onset of performance decrement was noted in the 30-33 degrees C WBGT range of temperature. This temperature level is consistent with the Recommended Exposure Limits for work in the heat at low levels of metabolic heat.

The predictive accuracy of in vitro measurements for the dermal absorption of a lipophilic penetrant (fluazifop-butyl) through rat and human skin.

The predictive accuracy of in vitro measurements in estimating dermal absorption has been evaluated in rat and human skin using fluazifop-butyl (FB), a lipophilic model compound, at dosage rates of 2.5, 25, and 250 micrograms/cm2. In vitro studies used rat and human epidermal membranes mounted in static diffusion cells with radiolabeled FB and receptor fluids of 50% aqueous ethanol (Aq Et), 6% polyethylene glycol 20 oleyl ether in saline (PEG), or tissue culture medium (TCM). In vivo rat studies with radiolabeled FB were carried out to parallel previously published human volunteer studies. For rat skin, in vitro measurements with all types of receptor fluid provide an adequate prediction (generally within a factor of 3) of in vivo absorption. Absorption data for human epidermal membranes with a receptor fluid of Aq Et were adequately predictive of the in vivo absorption. In contrast, membranes with PEG or TCM significantly underestimated the in vivo absorption. The results support the conclusion that in vitro studies are useful to predict in vivo dermal absorption in rat and man, when appropriate receptor fluids are used.

Modelling dermal pharmacokinetics using in vitro data. Part I. Fluazifop-butyl in the rat.

The pharmacokinetics of the herbicide fluazifop-butyl have been determined in female rats following oral and intravenous dosing, and described by a mathematical model. Penetration of fluazifop-butyl through epidermal membranes has been determined using three different receptor fluids. It is demonstrated how this in vitro absorption data can be used with a pharmacokinetic model derived from oral and i.v. dosing studies to predict plasma concentrations and urinary excretion profiles following dermal dosing. Model predictions are compared with experimental measurements and found to be in good agreement.

Modelling dermal pharmacokinetics using in vitro data. Part II. Fluazifop-butyl in man.

In a previous paper it was demonstrated that dermal absorption of the herbicide fluazifop-butyl in the rat could be modelled by combining a knowledge of the pharmacokinetics following intravenous and oral dosing with in vitro measurements of dermal absorption. This paper demonstrates the validation of a similar model for the dermal absorption of fluazifop-butyl in man. Pharmacokinetic parameters derived from an oral dosing study are combined in a mathematical model with in vitro measurements of dermal absorption of fluazifop-butyl. Model predictions of the rate and extent of dermal absorption of fluazifop-butyl are compared with the results of dermal absorption studies in human volunteers. Good agreement is found between the model predictions and the experimental measurements. These results have implications for improved risk assessment. The model provides a tool for risk assessment based on both internal dose (e.g. peak plasma concentration, plasma area under the curve) as well as total absorbed dose. However, further work is required to evaluate whether the same techniques are applicable to a wider range of compounds.

Further validation of an in vitro method to reduce the need for in vivo studies for measuring the absorption of chemicals through rat skin.

Current requirements for the registration of agrochemicals, particularly in the U.S.A., often require the provision of dermal absorption data. In this process the rat is often used and complex in vivo studies, using large numbers of animals, are performed. We have compared the data obtained from in vivo and in vitro dermal absorption studies using eight pesticides with a range of physicochemical properties. Measurements were made of the 14C-labeled pesticides which could be washed from the skin, were associated with (on/in) skin, or absorbed through the skin following dermal applications in vivo and in vitro at various time points over a 24-hr exposure period. Good agreement was found between the amounts washed from and associated with the skin in vivo and in vitro. Over the time period 4-24 hr after application the in vitro experiments predicted the in vivo absorption within a factor of 2-3. These results show that, with a range of pesticide molecules, the in vitro method accurately predicted in vivo absorption supporting the utilization of the in vitro method for risk assessment from exposure to pesticides and other chemicals.

Pharmacokinetics of fluazifop-butyl in human volunteers. II: Dermal dosing.

1. The absorption of the herbicide fluazifop-butyl (f-b), has been determined from plasma and urine measurements in groups of six male volunteers following dermal administration of 2.5, 25 and 250 micrograms cm-2 from standardized formulations containing 0.05, 0.5 and 5.0% (w/v) fluazifop-butyl to a skin area of 800 cm2. 2. Urinary excretion rate of the principal metabolite fluazifop, following dosing with the 5% formulation, was described by a two-compartment pharmacokinetic model; the average elimination half-lives of initial and terminal phases were 18 h and approximately 70 h, respectively. For the other dose levels the elimination half-life was estimated to be 17 h; urine concentrations at later time points were too low to characterize a second compartment. 3. The estimated total fluazifop-butyl absorbed was 8.0, 3.4 and 1.6% of the applied dose for the 0.05, 0.5 and 5.0% formulations, respectively. 4. Up to 50% of the applied fluazifop-butyl was readily removed by skin washing and the majority of the remainder was transferred to clothing during the 24 h following application. 5. When six volunteers were given a daily dermal dose of the 0.5% formulation for five consecutive days, the plasma and urinary excretion kinetics of fluazifop could be accurately predicted by simple mathematical extrapolation of the kinetic data from the single exposure study at the equivalent daily dose. 6. It is concluded that fluazifop-butyl is only slowly and poorly absorbed through human skin and has a low potential to accumulate in man.

Detection and identification of volatile substances by headspace capillary gas chromatography to aid the diagnosis of acute poisoning.

Headspace gas chromatography with split flame-ionization-electron-capture detection is a simple method of screening for a wide range of volatile substances in biological fluids. A 60 m x 0.53 mm i.d. thick-film (5 microns) fused-silica capillary coated with SPB-1 (Supelchem) with split flame-ionization-electron-capture detection provides a valuable alternative to packed columns in this work. Most commonly abused compounds, including many with very low boiling-points such as bromochlorodifluoromethane (BCF), butane, dimethyl ether, FC 11, FC 12, isobutane and propane, can be retained and differentiated at an initial column temperature of 40 degrees C followed by programming to 200 degrees C. The total analysis time is 26 min. Retention and detector response data were generated for 244 compounds. Good peak shapes are obtained for polar analytes such as ethanol and injections of up to 0.30 cm3 of headspace can be performed with no discernable loss of efficiency. The sensitivity is thus at least as good as that attainable with packed columns. Of the commonly encountered compounds, only isobutane-methanol and paraldehyde-toluene are at all difficult to differentiate. Quantitative measurements can be performed either isothermally or by using the temperature programme.

The response of evidential breath alcohol testing instruments with subjects exposed to organic solvents and gases. I. Toluene, 1,1,1-trichloroethane and butane.

Experimental work has been undertaken to investigate the potential interference of toluene, 1,1,1-trichloroethane and butane with the evidential breath alcohol testing instruments used in Great Britain (Lion Intoximeter 3000 and Camic Breath Analyser). Volunteers inhaled the volatile substances in an exposure chamber for up to 4 hours, at concentrations of 100, 350 and 600ppm respectively. Subsequently breath was tested on leaving the chamber. No interference was observed with the breath alcohol instruments when the subjects were exposed to toluene and 1,1,1-trichloroethane. A short-term response immediately after exposure was observed for subjects exposed to butane. Further analytical work involving blood and breath samples demonstrated that all three volatile substances were absorbed during exposure and were detectable in blood for at least 3 hours post-exposure. Their elimination post-exposure followed an exponential decay.

The response of evidential breath alcohol testing instruments with subjects exposed to organic solvents and gases. II. White spirit and nonane.

Following exposure to white spirit vapour, the effect of the expired solvent on evidential breath alcohol equipment was investigated under controlled exposure chamber conditions and in a simulated painting exercise. Five volunteers inhaled the solvent in an exposure chamber at a concentration of 100ppm for periods up to 4h 17min. Two other volunteers were exposed to white spirit while painting with domestic gloss paint in an unventilated room under which conditions exposure concentrations reached 185ppm for 20min. Following all white spirit exposures, volunteers underwent breath tests with the Lion Intoximeter 3000. In all instances the apparent alcohol responses were very small and never exceeded a reading of 1 microgram/100ml for breath samples more than 10min post-exposure. Simultaneous analytical work was conducted to demonstrate that white spirit was absorbed during exposure and was present in the breath and blood after the volunteers had left the exposure atmospheres. A further study involved the exposure of a volunteer to nonane vapour at 100ppm, demonstrating that this compound, being one of the principal components of white spirit, appears to be a good model for studying the uptake and elimination of white spirit.

The response of evidential breath alcohol testing instruments with subjects exposed to organic solvents and gases. III. White spirit exposure during domestic painting.

The concentration of white spirit vapour in the breathing zone of a volunteer engaged in domestic painting activities has been investigated. Air was continuously sampled and analysed using an infra-red gas analyser (Miran) during painting experiments. Both indoor and outdoor painting tasks were undertaken using commercial paints in a wide variety of situations. For each task the time weighted average (TWA) exposure has been determined. In no case did the TWA exposure exceed the Occupational Exposure Limit-Long Term Exposure Limit (OEL-LTEL) of 100 ppm. The results have been used to discuss the significance of previous studies in which volunteers were exposed to white spirit vapour in an exposure chamber to test for possible interference in breath alcohol testing.