Evaluation of 1047-nm photoacoustic instruments and photoelectric aerosol sensors in source-sampling of black carbon aerosol and particle-bound PAHs from gasoline and diesel powered vehicles.

A series of measurements have been performed at Hill Air Force Base to evaluate real-time instruments for measurements of black carbon aerosol and particle-bound PAHs emitted from spark and ignition compression vehicles. Vehicles were operated at idle or fast idle in one set of measurements and were placed under load on a dynamometer during the second series. Photoacoustic instruments were developed that operated at a wavelength of 1047 nm where gaseous interference is negligible, although sensitivity to black carbon is good. Compact, efficient, solid-state lasers with direct electronic modulation capabilities are used in these instruments. Black carbon measurements are compared with samples collected on quartz fiber filters that were evaluated using the thermal optical reflectance method. A measure of total particle-bound PAH was provided by photoelectric aerosol sensors (PAS) and is evaluated against a sum of PAH mass concentrations obtained with a filter-denuder combination. The PAS had to be operated with a dilution system held at approximately 150 degrees C for most of the source sampling to prevent spurious behavior, thus perhaps compromising detection of lighter PAHs. PA and PAS measurements were found to have a high degree of correlation, perhaps suggesting that the PAS can respond to the polycyclic nature of the black carbon aerosol. The PAS to PA ratio for ambient air in Fresno, CA is 3.7 times as large in winter than in summer months, suggesting that the PAS clearly does respond to compounds other than BC when the instrument is used without the heated inlet.

Phase and size distribution of polycyclic aromatic hydrocarbons in diesel and gasoline vehicle emissions.

Emission measurements were obtained for a variety of military vehicles at Hill Air Force Base (Ogden, UT) in November 2000 as part of a Strategic Environmental Research and Development Program. Aircraft ground support equipment vehicles using gasoline, diesel, and JP8 fuels were tested using chassis dynamometers under predetermined load. The exhaust from the tested vehicle was passed to a dilution tunnel where it was diluted 30-40 times and collected using Micro-Orifice Uniform Deposit Impactor (MOUDI) fitted with aluminum substrates, an XAD-coated annular denuder, and a filter followed by a solid adsorbent. All MOUDI substrates were analyzed for mass and for organic and elemental (EC) carbon by the thermal/optical reflectance method and for polycyclic aromatic hydrocarbons (PAHs) by GC/MS. Black carbon was measured with a photoacoustic instrument. The denuder and filter/solid adsorbent samples were analyzed for semivolatile PAH. Overall, there is more mass and higher EC contribution when the vehicle is run under higher load in comparison with the low load. However, older vehicles generally show more mass and EC emissions than newer vehicles, and there is a shift toward smaller particle sizes for the low load, which is most pronounced for newer vehicles. The particle-associated semivolatile PAHs and nonvolatile four-through six-ring PAHs are present predominantly on the submicron particles collected on MOUDI stages 0.1-0.18, 0.18-0.32, and 0.32-0.56 microm. For the low-load runs, the distribution of PAHs seems to be shifted toward smaller size particles. The gas-particle phase distribution of semivolatile PAHs depends also on the engine loading. For idle, not only are the more volatile two- and three-ring PAHs, from naphthalene to dimethylphenanthrenes, retained on the denuder portion, but also less volatile four-ring PAHs, such as fluoranthene and pyrene, are retained by the denuder at the 80-90% range, which implies that they are present predominantly in the gas phase. In contrast, for engines under high loads, a much larger portion of three- and four-ring PAHs are partitioned to the particle phase.

Time-resolved characterization of diesel particulate emissions. 2. Instruments for elemental and organic carbon measurements.

The measurement of elemental carbon (EC) and organic carbon (OC) mass for particles emitted by diesel vehicles is currently accomplished using particle collection on filters, followed by analysis using the thermal/optical reflectance carbon analysis method (TOR) or one of its variations. Such filter methods limit time resolution to a minimum of several minutes, making it impossible to study emissions during transient operating conditions. Testing of five different measurement methods has demonstrated that fast response measurement of diesel exhaust particulate EC and OC concentrations, consistent with TOR filter measurements, is feasible using existing technology. EC mass concentrations are best measured through determination of particulate light absorption with a photoacoustic instrument or determination of light extinction with a smoke meter. The photoacoustic instrument has the better dynamic range and sensitivity, whereas the smoke meter is a simpler instrument. Fast response OC measurements cannot be made with any single instrument tested. However, a combination of real time weighing as implemented in the tapered element oscillating microbalance with the photoacoustic instrument has been shown to be capable of determining OC concentrations with good time response. The addition of a nephelometer to the OC measurement could potentially improve time resolution, freedom from interferences, and sensitivity.

Time resolved characterization of diesel particulate emissions. 1. Instruments for particle mass measurements.

The measurement of diesel vehicle exhaust particulate mass is currently accomplished using filter collection methods according to the Code of Federal Regulations (CFR). Such filter methods limit time resolution to a minimum of several minutes, making it impossible to study emissions during transient operating conditions. Extensive testing of five different measurement methods has demonstrated that fast response measurements of diesel exhaust particulate mass concentrations, consistent with CFR filter measurements, are feasible using existing technology. The measurement principles of choice are the real time weighing of exhaust samples as implemented in the tapered element oscillating microbalance (TEOM) and the measurement of light scattering from exhaust particles as implemented in the DustTrak nephelometer. Each of these two instruments has distinctive strengths. The TEOM excels in the area of constant calibration, independent of vehicle. For the DustTrak, this calibration varies by vehicle. On the other hand, the DustTrak has an excellent signal-to-noise ratio, freedom from interference due to other exhaust sample properties, good time resolution, and simplicity. The strengths of the two measurement methods are complimentary, so an obvious suggestion is to integrate them. The nephelometer would obtain a fast response signal, with near real time calibration provided by the microbalance.

Psychoneuroendocrine immunology: perception of stress can alter body temperature and natural killer cell activity.

Psychoimmunology has been credited with using the mind as a way to alter immunity. The problem with this concept is that many of the current psychoimmunology techniques in use are aimed at alleviating stress effects on the immune system rather than at direct augmentation of immunity by the brain. Studies in animals provide a model that permits us to approach the difficulties associated with gaining an understanding of the CNS-immune system connection. A particular advantage of using animals over humans is that psychological and social contributions play a less prominent role for animals than for human subjects, since the animals are all inbred and reared under identical controlled conditions. If the insightful information provided by animal studies is correct, then psychotherapy for the treatment of diseases might be made more effective if some aspect of this knowledge is included in the design of the treatment. We emphasize conditioning as a regimen and an acceptable way to train the brain to remember an output pathway to raise immunity. We propose that a specific drug or perception (mild stress, represented by rotation, total body heating or handling) could substitute and kindle the same output pathway without the need for conditioning. If this view is correct, then instead of using conditioning, it may be possible to use an antigen to activate desired immune cells, and substitute a drug or an external environmental sensory stimulus (perception) to energize the output pathway to these cells. Alternatively, monitoring alterations of body temperature in response to a drug or perception might allow us to follow how effectively the brain is performing in altering immunity. Studies with animals suggest that there are alternative ways to use the mind to raise natural or acquired immunity in man.

Middle- and Neighborhood-Scale Variations of PM10 Source Contributions in Las Vegas, Nevada.

The Las Vegas Valley PM10 Study was conducted during 1995 to determine the contributions to PM10 aerosol from fugitive dust, motor vehicle exhaust, residential wood combustion, and secondary aerosol sources. Twenty-four-hr PM10 samples were collected at two neighborhood-scale sites every sixth day for 13 months. Five week-long intensive studies were conducted over a middle-scale sub-region at 29 locations that contained many construction projects emitting fugitive dust. The study found that the zone of influence around individual emitters was less than 1 km. Most of the sampling sites in residential and commercial areas yielded equivalent PM10 concentrations in the neighborhood region, even though they were more distant from each other than they were from the nearby construction sources. Based on chemical mass balance (CMB) receptor modeling, fugitive dust accounted for 80-90% of the PM10, and motor vehicle exhaust accounted for 3-9% of the PM10 in the Las Vegas Valley.

Particulate emission rates for unpaved shoulders along a paved road.

This paper reports the first empirical estimate of particle emissions from unpaved shoulders along paved roads. Its objectives are to develop and demonstrate an emission rate measurement methodology that can be applied in different areas; identify the mechanisms that suspend dust from unpaved shoulders and the observables related to this suspension process; and quantify PM10 mass emissions in the form of an emission rate. To achieve these objectives, fast-response observations from nephelometers and a sonic anemometer were used to characterize short-lived dust plumes generated by passing vehicles. In addition, detailed soil surface measurements determined the mechanical properties of the shoulder surfaces. Large traffic-induced turbulence events that led to significant dust entrainment were almost exclusively caused by "large" vehicles such as trucks, semis, and vehicles pulling trailers, all traveling 50-65 mph. PM10 emission rates for these large, fast-traveling vehicles were determined to be 8 +/- 4 grams per vehicle kilometer traveled under dry conditions. Emissions due to smaller vehicles such as cars, vans, and sport utility vehicles were negligible for normal on-road driving. These results indicate that the majority of PM10 emissions from unpaved shoulders is caused by relatively few vehicles.

Afferent signals to the CNS appear not to condition the modulation of interleukin-1 receptors in the hippocampus.

Conditioned alteration of natural killer (NK) cell activity was used as an indicator of the functional bidirectional communication between the immune and central nervous systems. Poly I:C and lipopolysaccharide (LPS) from Escherichia coli and Salmonella typhimurium were used as unconditioned stimuli and odor of camphor as the conditioned stimulus. An attempt was made to demonstrate the role of central interleukin (IL-1) receptors in this communication process. Brain IL-1 receptors were down-regulated by treatment with 50 microg/mouse of LPS from S. typhimurium, but not with the same dose of LPS from E. coli or poly I:C. A significant level of conditioned augmentation of NK cell activity was observed with poly I:C. Conditioned alteration in NK cell activity was also observed with LPS from E. coli, but at much lower level than poly I:C. NK cell activity was not conditioned with LPS from S. typhimurium at the same dose as E. coli LPS, but conditioned enhancement of NK cell activity was observed with a higher dose (100 microg) of S. typhimurium LPS. These results suggest that modulation of central IL-1 receptors do not seem to play a role in the conditioned augmentation of NK cell activity.

Psychoneuroendocrine immunology: site of recognition, learning and memory in the immune system and the brain.

How the interaction between the brain and immune system takes place has not been clearly defined. Because multiple changes are occurring simultaneously in all organ systems (e.g., cardiovascular, gastrointestinal, reproductive, renal, respiratory, immune, CNS), how many single systems interacts with the brain becomes extraordinarily difficult to understand. The problem boils down to developing an approach that not only allows one to study the whole organism and define the mediators of the interacting systems, but also permit one to establish the connection and physiologic relevance of the responses that are being evaluated. Conditioning, a phenomenon made popular by the work of Pavlov (1906, 1927), may provide insight into the pathways of communication between the brain and possibly any organ system of the body. Conditioning allows one to separate the afferent from the efferent circuits. That is, signals from the immune system to the CNS (IS-->CNS) can be effectively separated from signals from the CNS to immune system (CNS-->IS). This permits one to study each pathway individually. Simple, single association trial models to condition fever, natural killer (NK) cell and cytotoxic lymphocyte (CTL) activities have been developed to evaluate the pathways. Single trial learning is not new. Pavlov has observed that "The electric buzzer set going before administration of food established a conditioned alimentary reflex after only a single combination," whereas the reverse order of presentation failed to condition the animal (Pavlov 1927 p. 27). Thus, conditioning can be used to train the brain to activate the immune system and other organ systems participating in the response. During the course of the conditioned response, presumably the CNS via the hypothalamus integrates in a cohesive orderly fashion all input and output signals and coordinates the responses made by the brain to the organ systems. The odor of camphor, the conditioned stimulus (CS) can be associated with the response produced by an unconditioned stimulus (US). The unconditioned stimuli used are poly I:C to raise fever and nonimmunospecific NK cell activity or alloantigens to raise immunospecific CTL activity. The unconditioned stimulus serves only as a means to activate the immune system and unbalance the homeostasis so that a transient but new bidirectional communication loop can be established between the immune system and the CNS (IS<-->CNS). The expression of the conditioned response (i.e., elevation of fever, NK cell, or CTL activity) induced with the CS (odor stimulus) is an outcome of neural activity (CNS-->IS). This infers that during conditioning, the signals generated by the CS and US imprints a neural pathway located within the central nervous system and leaves behind a CS/US memory of the association. The immune activity (NK cell or CTL activity) which is modulated indicate that the memory pathway was activated in the brain of the animal expressing the conditioned response. The immune cells that are modulated can be considered to be casual bystander cells. These cells however must be in the proper (ready) state of activation to receive salient signals from the brain. Along with changes in the indicator cell population, other complex physiological processes are altered by the brain via sympathetic and neuroendocrine pathways to raise the fever response. These observations suggest that the physiological changes which are being evaluated such as fever, NK cell or CTL activities or perhaps blood pressure, heart rate, fat metabolism, oxygen consumption serve only as indicators (readouts), and infer that the CNS has made a coordinated reply in response to the CS signal.

Lipopolysaccharide and IL-1 alpha activate CNS pathways as measured by NK cell activity.

The effect of lipopolysaccharide (LPS) on murine unstimulated and prestimulated natural killer (NK) cells and its ability to serve as an unconditioned stimulus was investigated. LPS injection induced a statistically significant increase in NK cell activity when compared with saline-treated control groups. To demonstrate the existence of communication between the peripheral immune system and the central nervous system (CNS), we used a single-trial conditioning paradigm in which camphor served as the conditioned stimulus (CS) and LPS as the unconditioned stimulus (US). Once a CS/US association is made, exposure of animals to the CS alone results in the conditioned response (i.e., increase in NK cell activity). Using 50 micrograms of LPS as the US produced a low but significant increase in NK cell activity when compared to control groups. However, 10 micrograms of LPS did not show a significant increase in NK cell activity. We also observed that interleukin-1 alpha (IL-1 alpha) injected intracisternally can serve as a US to condition a central neuroendocrine pathway. Because the dose of IL-1 alpha employed was too small to raise NK cell activity in the spleen, the NK cells themselves were formally not subjected to conditioning. These observations suggest that LPS and IL-1 alpha conditions the brain and that NK cell activity can be used as an indicator system to detect neuroendocrine signals arising from the activated pathway(s).

Arecoline a muscarinic cholinergic agent conditions central pathways that modulate natural killer cell activity.

The central nervous system plays an active role in the regulation of the immune system. Modulation of immune activities appears to be in part under the control of the hypothalamic-pituitary-adrenal (HPA) axis. We investigated the effect of a muscarinic cholinergic agonist, arecoline, which stimulates the secretion of corticotropin-releasing hormone (CRF) and adrenocorticotropic hormone (ACTH) on the immune system. In this report we demonstrate that peripherally administered arecoline or ACTH can increase activity of pre-activated NK cells. Second, we show that central administration of arecoline at a dose too low to alter peripheral events is sufficient to induce a significant increase in the activity of pre-activated natural killer (NK) cells. Finally, we demonstrate by using a Pavlovian conditioning paradigm that the pairing of a novel odor (camphor) with administration of arecoline can be used to alter NK cell activity. Subsequent to the conditioning trial, exposure to the odor alone is sufficient to raise NK cell activity. From these observations, we infer that the pathway(s) that are conditioned reside in sites located within the CNS and the conditioned response is evoked in the peripheral compartment (NK cell activity).

Lidocaine interrupts the conditioned natural killer cell response by interfering with the conditioned stimulus.

In the present study, lidocaine, a local anesthetic that inhibits the initiation or conduction of nerve impulses, was used to differentiate between the memory for the conditioned stimulus (CS) and the memory for the CS and unconditioned stimulus (US) association. Lidocaine was used to block memory formation. It was administered into the cisterna magna to localize the inhibition to the central nervous system (CNS) where circuits for the CS and US exist. The results show that lidocaine specifically blocks the ability of the CS to stimulate the circuits responsible for storing the CS/US association, but it does not interfere with the inherent ability of the US to signal the CNS and trigger a peripheral response. The observation that the CS circuit can be interrupted independently of the US circuit suggests that these signals come together to form a new circuit for the memory of the association. The association memory forms later and is independent of the memory for the CS.

Role of arcuate nucleus of the hypothalamus in the acquisition of association memory between the CS and US.

A single trial association protocol was used to demonstrate a conditioned increase in natural killer (NK) cell activity. The signals used were odor of camphor as the conditioned stimulus (CS) and polyinosinic-polycytidylic acid (poly I:C) as the unconditioned stimulus (US). This model has been used to dissect the underlying mechanisms of interaction between the central nervous system (CNS) and the immune system (IS) and vice versa. Here, we demonstrate the potential role played by the arcuate nucleus of the hypothalamus in the acquisition of association memory between the CS and the US. Chemical destruction of the arcuate nucleus with monosodium glutamate (MSG) was used for this purpose. Mice with arcuate nucleus lesion prior to the association protocol did not demonstrate a conditioned increase in NK cell activity. However, the lesion has no effect if produced prior to exposure to the CS at recall. These studies demonstrate the significant role played by the hypothalamus (arcuate nucleus) in a conditioned response.

Conditioning of the allogeneic cytotoxic lymphocyte response.

Allogeneic cytotoxic T-lymphocyte (CTL) response can be obtained following immunization of BALB/c mice with C57BL/6 spleen cells. We investigated the possibility of behaviorally conditioning this response by associating the C57BL/6 spleen cell immunization [unconditioned stimulus (US)] with camphor odor [conditioned stimulus (CS)]. We reported the possible mechanisms involved in the conditioning of natural killer cell activity. Similar approaches were used to investigate the mechanisms that participate in the conditioned CTL activity. The first mechanism of investigation utilized opioid receptor blockers naltrexone and quaternary naltrexone. Naltrexone, which blocks both the central and peripheral opioid receptors, blocked the recall of the conditioned response, whereas quaternary naltrexone, which does not penetrate the blood-brain barrier, was unable to block the conditioned response, demonstrating that centrally located opioid receptors play a role in the recall of the conditioned response. The studies are of interest because they indicate that resistance or susceptibility to various diseases such as cancer, autoimmunity, and infectious diseases might be influenced by the regulatory network of the CNS.

A simple, single, trial-learning paradigm for conditioned increase in natural killer cell activity.

A change in natural killer (NK) cell activity can be conditioned with one trial learning when conditioned stimulus (CS) precedes the unconditioned stimulus (US). To avoid the problems associated with two reexposures in our earlier studies, we have developed a reliable and simple conditioning protocol utilizing the one trial learning and one reexposure to the odor CS. The conditioned change in NK cell activity was significantly different (P less than 0.05) from the control groups of mice. The paradigm is short and simple in that the conditioned change could be demonstrated within 3 days. We have also compared the effects of temporal association of CS and US on conditioned increase in NK cell activity. Forward conditioning (CS preceded the US) demonstrated a conditioned change, but the backward conditioning protocol did not. The paradigm provides a reliable approach to the study of mechanisms of the phenomenon of odor-NK conditioning.

In vivo enhancement of NK cell activity with met-enkephalin and glycyl-glutamine: their possible role in the conditioned response.

These studies investigated the effect of met-enkephalin, glycyl-glutamine, and naltrexone on NK cell activity in vivo and in vitro. It was found that both met-enkephalin (which shares the amino-terminal end of beta-endorphin) and glycyl-glutamine (which reflects the carboxyl-terminal end of beta-endorphin) can enhance the NK cell activity of mice prestimulated with a low dose (1 microgram/mouse) of poly I:C. Naltrexone had no effect. In vivo prestimulation of the mice with 1 microgram poly I:C was necessary as mice which were not pretreated with poly I:C did not show enhanced NK cell activity when treated with either met-enkephalin or glycyl-glutamine. In vitro studies however indicate that the drugs when cultured together with the NK cells from mice preactivated with poly I:C did not have a direct stimulatory effect on the NK cells. These studies imply that while beta-endorphin released from the pituitary could be involved in enhancement of activated NK cells in vivo other indirect peripheral pathways might be involved. The results suggest beta-endorphin probably reacts with other accessory type cells which in turn release the mediators which are required for the stimulation of NK cells in vivo.

Conditioning the elevation of body temperature, a host defensive reflex response.

We hypothesize that a number of host defense responses such as natural killer (NK) cell activity, cytotoxic lymphocyte (CTL) activity, antibody production, and elevated body temperature (TR) might be conditionable. We have designated such specifically learned response to be a defensive reflex response. Here we describe a simple single trial association paradigm for conditioning the TR response in BALB/c mice. Animals are conditioned on day 0 by exposing them to the odor of camphor for 1 hr, followed by injection of the pyrogen poly I:C 20 microgram ip. Control groups are injected with either poly I:C or saline and not exposed to the camphor odor. Reexposure of all groups to the conditioned stimulus (CS) on day 2 or 3 cause elevation of body temperature in the conditioned group mice but not in the nonconditioned or saline control groups. Since we have conditioned the natural killer cell response with the same paradigm, these results suggest that multiple defensive responses might be conditionable simultaneously and they might have important survival value for the species.

NaCl does not affect hypothalamic noradrenergic input in deoxycorticosterone acetate/NaCl and Dahl salt-sensitive rats.

Previous studies from our laboratories demonstrated that dietary NaCl supplementation in NaCl-sensitive spontaneously hypertensive rats elevates blood pressure, increases peripheral sympathetic nervous system activity, and depresses endogenous norepinephrine stores and turnover in the anterior hypothalamus. These findings suggest that reduced noradrenergic input to sympathoinhibitory neurons in anterior hypothalamus contributes to NaCl-sensitive hypertension in spontaneously hypertensive rats. The current study tested the hypothesis that dietary NaCl supplementation depresses endogenous norepinephrine stores and turnover in anterior hypothalamus of two other NaCl-sensitive models of hypertension, the Dahl salt-sensitive rat and the deoxycorticosterone acetate/NaCl hypertensive rat, thus increasing blood pressure by reducing noradrenergic input to the anterior hypothalamus. Dahl salt-sensitive rats were fed a high (8%) NaCl diet, and deoxycorticosterone acetate/NaCl rats rats drank 1% NaCl solution ad libitum for 2 or 4 weeks. Age-matched Dahl salt-sensitive rats fed a basal 1% NaCl diet and uninephrectomized Sprague-Dawley rats drinking tap water were controls. Regional brain catecholamines were determined by high-performance liquid chromatography with electrochemical detection. Norepinephrine turnover in hypothalamus (anterior, posterior, and ventral regions) and brain stem (pons and medulla) was assessed using the dopamine beta-hydroxylase inhibitor 1-cyclohexyl-2-mercapto-imidazole. High NaCl treatment caused significant elevations in blood pressure in Dahl salt-sensitive and deoxycorticosterone acetate/NaCl rats, but endogenous norepinephrine levels and turnover rates were not significantly different in anterior hypothalamus or any other brain region studied between the NaCl-supplemented and control groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurements of cloud condensation nuclei in the stratosphere around the plume of mount st. Helens.

Measurements of cloud condensation nuclei were made from small samples of stratospheric air taken from a U-2 aircraft at altitudes ranging from 13 to 19 kilometers. The measured concentrations of nuclei both in and outside the plume from the May and June 1980 eruptions of Mount St. Helens were higher than expected, ranging from about 100 to about 1000 per cubic centimeter active at 1 percent supersaturation.