A method to quantify infectious airborne pathogens at concentrations below the threshold of quantification by culture.

In aerobiology, dose-response studies are used to estimate the risk of infection to a susceptible host presented by exposure to a specific dose of an airborne pathogen. In the research setting, host- and pathogen-specific factors that affect the dose-response continuum can be accounted for by experimental design, but the requirement to precisely determine the dose of infectious pathogen to which the host was exposed is often challenging. By definition, quantification of viable airborne pathogens is based on the culture of micro-organisms, but some airborne pathogens are transmissible at concentrations below the threshold of quantification by culture.

Median infectious dose (ID₅₀) of porcine reproductive and respiratory syndrome virus isolate MN-184 via aerosol exposure.

The median infectious dose (ID(50)) of porcine reproductive and respiratory syndrome (PRRS) virus isolate MN-184 was determined for aerosol exposure. In 7 replicates, 3-week-old pigs (n=58) respired 10l of airborne PRRS virus from a dynamic aerosol toroid (DAT) maintained at -4°C. Thereafter, pigs were housed in isolation and monitored for evidence of infection.

Pulse-driven switching in one-dimensional nonlinear photonic band gap materials: a numerical study.

We numerically examine the time-dependent properties of nonlinear bistable multilayer structures for constant wave illumination. We find that our system exhibits both steady-state and self-pulsing solutions. In the steady-state regime, we examine the dynamics of driving the system between different transmission states by injecting pulses, and we find optimal pulse parameters.

Capillary isoelectric focusing-electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry for protein characterization.

On-line combination of capillary isoelectric focusing (CIEF) with electrospray ionization Fourier transform ion cyclotron resonance (ESI-FTICR) mass spectrometry is demonstrated for high-resolution analysis of model proteins, human hemoglobin variants, and Escherichia coli proteins. The acquisition of high-resolution mass spectra of hemoglobin beta chains allows direct identification of hemoglobin variants A and C, differing in molecular mass by 1 Da. Direct mass determination of cellular proteins separated in the CIEF capillary is achieved using their isotopic envelopes obtained from ESI-FTICR.

Direct analysis of single rat peritoneal mast cells with laser vaporization/ionization mass spectrometry.

A linear time-of-flight mass spectrometer was used as a detector for flow cytometry. These two techniques were coupled by a laser vaporization/ionization interface. The estimated mass detection limit of the combined system was 20 amol of serotonin standard with one laser pulse.

Mass resolution of 11,000 to 22,000 with a multiple pass quadrupole mass analyzer.

CO+ and N+2 are separated with resolution of 11,000 [full width half maximum (FWHM)] using a conventional quadrupole mass spectrometer by applying square wave voltages to the entrance and exit lenses to trap or reflect the ions for multiple passes. A resolution of 22,000 (FWHM) with 63% of the total signal remaining is attained using multiple passes when ions are stored between injection pulses. Gated ion extraction also reduces the mass shift and number and intensity of artifact peaks and permits better resolution compared to the performance obtained when the ions are injected continuously.

Study of single cells by using capillary electrophoresis and native fluorescence detection.

Capillary electrophoresis is known for its compatibility with biological materials and with small samples. It is an ideal tool for the study of single biological cells. Either whole cells or the material secreted from cells can be quantified.

Capillary electrophoretic study of individual exocytotic events in single mast cells.

In this work we have demonstrated the application of on-column dynamic release of serotonin from individual granules within rat peritoneal mast cells (RPMCs). These granules are approximately 0.25 fl in volume and represent some of the smallest entities studied by capillary electrophoresis (CE).

Enhancement of molecular fluorescence near the surface of colloidal metal films.

Fluorescence enhancement was studied on silver colloidal metal films (CMFs) using two systems: (1) Langmuir--Blodgett monolayers of fluorescein-labeled phospholipids separated from the surface of the films by spacer layers of octadecanoic acid and (2) biotin--fluorescein conjugates captured by avidin molecules adsorbed on top of a multilayer structure formed by alternating layers of bovine serum albumin--biotin conjugate (BSA--biotin) and avidin. The dependence of fluorescence intensity on the number of lipid or protein spacer layers deposited on the surface of the CMF was investigated. The results demonstrate the requirement for adsorbate location within the region between Ag particles for maximal enhancement.

Volunteer peer counselors increase breastfeeding duration among rural low-income women.

Background: The purpose of this demonstration project was to test the effectiveness of a volunteer peer counseling program for promoting breastfeeding in a community.

Methods: The two-year project was conducted in Iowa from September 1994 to September 1996. Both intervention and control groups were rural low-income pregnant and postpartum women who qualified for the Women, Infants and Children's (WIC) nutritional program.

Fast DNA separations using poly(ethylene oxide) in non-denaturing medium with temperature programming.

We demonstrated fast DNA separations in low viscosity entangled solutions with a temperature gradient in a non-denaturing separation medium. The separations were carried out in a solution of commercially available poly(ethylene oxide) (PEO) [1 x Tris(hydroxymethyl)aminomethane borate buffer, without urea] with a temperature gradient of 2 degrees C/min. The performance was compared with that of a solution of PEO with urea at ambient temperature.

Monitoring protein refolding induced by disulfide formation using capillary isoelectric focusing-electrospray ionization mass spectrometry.

Rapid growth in the biotechnology industry has led to a dramatic increase in attention to the protein folding problem. Understanding protein-folding pathways is essential to the production of biopharmaceuticals since commercial production of recombinant proteins often requires a protein-refolding process for recovery of high yields. Protein folding coupled to the formation of disulfide bonds presents one of the simplest approaches to studying folding intermediates.

Separation of DNA sequencing fragments up to 1000 bases by using poly(ethylene oxide)-filled capillary electrophoresis.

We have demonstrated that DNA bases up to 1000 base pairs (bp) in a sequencing ladder can be separated using poly(ethylene oxide)-filled capillary electrophoresis (resolution of raw data = 0.5 at 966 bp). Separation performance of this sieving matrix has been tested under different experimental conditions.

Application of capillary electrophoresis-fluorescence line-narrowing spectroscopy for on-line spectral characterization of closely related analytes.

Capillary electrophoresis (CE) interfaced with low-temperature (4.2 K) fluorescence line-narrowing spectroscopy (FLNS) is used for the separation and spectral characterization of closely related analytes. In this paper, the CE-FLNS system is applied to the analysis of a mixture of deuterated and protonated benzo[a]pyrene, a mixture of structurally similar benzo[a]pyrene and benzo[e]pyrene, and mixtures of dibenzo[a,l]pyrene-derived adenine DNA adducts.

Laser photodissociation of insulin ions generated by matrix-assisted laser desorption.

A novel method for studying the ionization step of matrix-assisted laser desorption/ionization (MALDI) is demonstrated. A 193-nm pulse from an ArF excimer laser is used to photodissociate a portion of a plume of insulin ions generated by MALDI. Laser photodissociation (LPD) creates a "hole", i.

Monitoring single-cell pharmacokinetics by capillary electrophoresis and laser-induced native fluorescence.

The quantification of insulin released from single cells of the insulin-secreting cell line beta TC3 permeabilized by digitonin is demonstrated. A simple method for monitoring the on-column release process by using capillary electrophoresis and laser-induced native fluorescence detection is described. Quantitative measurements of both the amount of insulin released and the amount remaining in the cell can be achieved simultaneously.

Cognitive reactions to smoking relapse: the reciprocal relation between dissonance and self-esteem.

Perceptions of health risk associated with smoking, commitment to quitting, and self-concept were assessed among smokers before, during, and after their participation in cessation clinics. Consistent with expectations derived from cognitive dissonance theory, results indicated that relapsers' perception of risk declined after they resumed smoking, although the decline was significant only for relapsers with high self-esteem; high self-esteem relapsers experienced a significantly greater decline in commitment to quitting than did low self-esteem relapsers; and decline in risk perception among relapsers was associated with maintenance of self-esteem. The implications of these results for dissonance theory and the study of smoking relapse and cessation are discussed.

Gender differences in health: evidence from the Czech Republic.

Gender differences in health have been linked to gender stratification in the United States. Women's relation to production, paid and unpaid work, and their experience of this gender inequality disadvantage their self-rated health compared to men. Men's consumption or health lifestyles disfavors their comparative health.

Determination of lactate dehydrogenase isoenzymes in single lymphocytes from normal and leukemia cell lines.

This work demonstrates that our previously developed technique for single-erythrocyte analysis by capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) can be applied to study individual lymphocytes, with some modification in the cell lysing procedure. A tesla coil was shown to be capable of lysing the lymphocyte cells inside the capillary. The electromagnetic field induced by the tesla coil was believed to be responsible for breaking the cell membrane.

The use of differential transverse relaxation to detect mobile species in solids.

Delayed acquisition of the proton NMR in selected organic molecular solids (L-alanine, durene, ethyl fumarate, and p-hydroxybenzoic acid) is shown to allow the observation of mobile species in the presence of relatively rigid bulk molecules. The mobility is found to be thermally activated. The combination of the thermally activated motion and magic-angle spinning leads to a fraction of these species moving nearly isotropically on the time scale of the inverse of the homonuclear dipolar splitting.

Exercise training mode affects the hemodynamic responses to lower body negative pressure in women.

To determine if different exercise modes used to improve cardiovascular fitness result in differing cardiovascular responses to lower body negative pressure (LBNP) in exercise-trained women, seven chronically exercising female runners (RUN) and 11 swimmers (SWIM) of similar fitness levels maximal oxygen uptake, [VO(2max), mean (SEM) = 50 (2) and 45 (2) ml*kg(-1)*min(-1), respectively; P > 0.05] underwent serial exposures to LBNP at pressures of 0, -1.3, -2.

Electroosmotic control of chiral separation in capillary zone electrophoresis.

The resolution in capillary zone electrophoresis (CZE), with the assumption of diffusion control only, is strongly dependent on the direction and magnitude of electroosmotic flow. In fact, excellent separation resolution will be obtained if the electroosmotic flow is in the opposite direction of the electrophoretic migration. By applying various radial electric potential gradients across the capillary wall, the direct control of the zeta potential and the electroosmotic flow results in a great enhancement of chiral resolution in cyclodextrin-modified CZE.

Computer networked scanning electron microscope for teaching, research, and industry applications.

A laboratory designed for teaching the operation of a scanning electron microscope (SEM) has been developed. The laboratory makes use of a computer network to allow remote operation of the SEM. Movable teaching stations, consisting of a computer, TV monitor, and joystick control, enable students to view the image on the SEM screen, move the sample, control the basic operating parameters of the microscope, and acquire X-ray spectra.

Formation and persistence of benzo[a]pyrene-DNA adducts in mouse epidermis in vivo: importance of adduct conformation.

The formation and repair of benzo[a]pyrene diol epoxide-N2-deoxyguanosine adducts (BPDE-N2-dG) in DNA isolated from the skin of mice treated topically with benzo[a]pyrene (BP) was studied by 32P-postlabeling and by low-temperature fluorescence spectroscopy under low resolution and under high resolution fluorescence line narrowing (FLN) conditions. In agreement with earlier studies, total BP-DNA binding reached a maximum at 24 h after treatment (dose: 1 mumol/mouse), then declined rapidly until 4 days after treatment and much more slowly thereafter. An HPLC method was developed which resolved the 32P-postlabeled (-)-trans- from (-)-cis-anti-BPDE-N2-dG, and (+)-trans-from (+)-cis-anti-BPDE-N2-dG.

Poly(ethyleneoxide) for high-resolution and high-speed separation of DNA by capillary electrophoresis.

Capillary electrophoresis (CE) with polyacrylamide gels has already been demonstrated to allow single-base resolution of single-stranded DNA. However, linear polyacrylamide is not an ideal matrix because of a high viscosity and difficulties in preparing the polymer with well defined pore sizes. Alternatively, poly(ethyleneoxide) (PEO) with a large range of molecular masses from 300,000 to 8,000,000 is available commercially.