Lipid dynamics in zebrafish embryonic development observed by DESI-MS imaging and nanoelectrospray-MS.

The zebrafish Danio rerio is a model vertebrate organism for understanding biological mechanisms. Recent studies have explored using zebrafish as a model for lipid-related diseases, for in vivo fish bioassays, and for embryonic toxicity experiments. Mass spectrometry (MS) and MS imaging are established tools for lipid profiling and spatial mapping of biomolecules and offer rapid, sensitive, and simple analytical protocols for zebrafish analysis. When ambient ionization techniques are used, ions are generated in native environmental conditions, requiring neither sample preparation nor separation of molecules prior to MS. We used two direct MS techniques to describe the dynamics of the lipid profile during zebrafish embryonic development from 0 to 96 hours post-fertilization and to explore these analytical approaches as molecular diagnostic assays. Desorption electrospray ionization (DESI) MS imaging followed by nanoelectrospray (nESI) MS and tandem MS (MS/MS) were used in positive and negative ion modes, allowing the detection of a large variety of phosphatidylglycerols, phosphatidylcholines, phosphatidylinositols, free fatty acids, triacylglycerols, ubiquinone, squalene, and other lipids, and revealed information on the spatial distributions of lipids within the embryo and on lipid molecular structure. Differences were observed in the relative ion abundances of free fatty acids, triacylglycerols, and ubiquinone - essentially localized to the yolk - across developmental stages, whereas no relevant differences were found in the distribution of complex membrane glycerophospholipids, indicating conserved lipid constitution. Embryos exposed to trichloroethylene for 72 hours exhibited an altered lipid profile, indicating the potential utility of this technique for testing the effects of environmental contaminants.

Does overwinter temperature affect maternal body composition and egg traits in yellow perch Perca flavescens?

Female yellow perch Perca flavescens exposed to three overwinter temperature regimes (4, 8 and 13° C) for 150 days spawned in markedly different proportions upon spring warming (37% of females in 4° C v. 64 and 91% in 8 and 13° C treatments, respectively), but exhibited no differences in fecundity, egg size or egg lipid content. Females held at 4° C also exhibited less within-clutch egg size variation than females held at 13° C. Moreover, eggs differed among temperature treatments in the overall proportions of 18 fatty acids, with the colder treatments resulting in potentially higher quality eggs containing more of the unsaturated fatty acids C16:1, C22:6-n3 and C18:2 cis. Female somatic condition also varied with temperature. Maternal somatic growth and protein content increased while lipid content decreased in 13° C compared to the colder treatments. There were, however, no differences among treatments in the fatty acid composition of maternal muscle. These results suggest that the temperatures experienced during winter may be less influential to P. flavescens egg size or number, which may exhibit relatively little plasticity in this species, but can alter both the number of females that spawn and the overall composition of eggs and maternal somatic tissues, which may have implications for future reproductive success.

Regulation of apical H⁺-ATPase activity and intestinal HCO3⁻ secretion in marine fish osmoregulation.

The absorption of Cl(-) and water from ingested seawater in the marine fish intestine is accomplished partly through Cl(-)/HCO(3)(-) exchange. Recently, a H(+) pump (vacuolar-type H(+)-ATPase) was found to secrete acid into the intestinal lumen, and it may serve to titrate luminal HCO(3)(-) and facilitate further Cl(-)/HCO(3)(-) exchange, especially in the posterior intestine, where adverse concentration gradients could limit Cl(-)/HCO(3)(-) exchange. The H(+) pump is expressed in all intestinal segments and in gill tissue of gulf toadfish (Opsanus beta) maintained in natural seawater. After acute transfer of toadfish to 60 ppt salinity, H(+) pump expression increased 20-fold in the posterior intestine. In agreement with these observations was a fourfold-increased H(+)-ATPase activity in the posterior intestine of animals acclimated to 60 ppt salinity. Interestingly, Na(+)-K(+)-ATPase activity was elevated in the anterior intestine and gill, but not in the posterior intestine. Apical acid secretion by isolated intestinal tissue mounted in Ussing chambers fitted with pH-stat titration systems increased after acclimation to hypersalinity in the anterior and posterior intestine, titrating >20% of secreted bicarbonate. In addition, net base secretion increased in hypersalinity-acclimated fish and was ∼70% dependent on serosal HCO(3)(-). Protein localization by immunohistochemistry confirmed the presence of the vacuolar-type H(+)-ATPase in the apical region of intestinal enterocytes. These results show that the H(+) pump, especially in the posterior intestine, plays an important role in hypersaline osmoregulation and that it likely has significant effects on HCO(3)(-) accumulation in the intestinal lumen and, therefore, the continued absorption of Cl(-) and water.

Air sampling at the chest and ear as representative of the breathing zone.

Tracer gas concentrations were measured on a 60%-sized mannequin holding a pure sulfur hexafluoride source in its hands at waist height while it stood in a wind tunnel. Samplers were placed at the mannequin's mouth, in front of the ear, and at three chest locations at lapel level. Simultaneous 15-min time-weighted average samples were taken by drawing air into different sampling bags with sampling pumps. For the factorial study design, test conditions included cross-draft velocities of 10, 22, 47, and 80 ft/min; three mannequin orientations (facing to, side to, and back to cross-draft), and rotating speed through an 80 degrees arc (fast, slow, and no movement). Each study condition was tested twice. Concentrations at all sampling locations when the mannequin faced to the front and side were less than a tenth of the levels measured at the nose (Cnose) when the mannequin faced downstream. Higher velocities significantly increased concentration at the Back orientation and generally reduced it at the Side and Facing orientations. Concentrations at the nose were different from concentrations at other sites. For 34 of 36 samples the mean chest concentration (Cchest,) was higher than the Cnose (geometric mean three times higher). The ratio of ear (Cear) and Cnose varied with orientation. At the Back orientation, Cear, was lower than Cnose, whereas Cear was higher than Cnose at the Side and Facing to flow orientations. Velocity affected the ratios of concentrations. At the Back orientation, the chest sampler provided lower overestimates of Cnose, at higher velocities than at lower values. Mannequin movement, done only at the Back orientation, proved important only for the ear location. Results showed significant and substantial differences between concentrations at the nose and lapel. However, these findings should be interpreted with caution because a very dense tracer gas and an unheated, nonbreathing mannequin were used. In more realistic conditions, the findings probably would show far smaller differences in concentrations at different sampling sites.

An evaluation of industrial ventilation branch screening methods for obstructions in working exhaust systems.

This research evaluated the effectiveness of screening methods in identifying obstructed branches in industrial ventilation systems. These methods were divided into two categories: pressure comparisons and pressure ratio comparisons. The first category contained techniques that compare measured static pressures with the corresponding design static pressures or with previously measured pressures. Certain aspects of the method suggested in the Industrial Ventilation Manual were also tested. The second category compares the ratios of two measured pressures and includes the new reference ratio method. Data were collected from six industrial ventilation systems. Four of the systems were used to control wood dust, and two were used to control metal shavings from a saw-sharpening operation. Each system was tested for naturally occurring or deliberately inserted obstructions. Appropriate static and velocity pressures were measured to calculate each troubleshooting method's parameter. The change in the parameter was compared with a range of thresholds for the test cases. Receiver operator characteristic curves and bootstrapping techniques were used to identify the best method for determining the presence of obstructions or alterations. The pressure ratio methods were found to be substantially superior to the pressure comparison methods at detecting obstructions.

An evaluation of industrial ventilation troubleshooting methods in experimental systems.

This study determined the efficacy of specific methods of identifying and locating obstructions and alterations to industrial exhaust ventilation systems under challenging conditions when measurement errors were minimized. Two traditional screening methods were evaluated: (1) two variations of the hood static pressure method and (2) a severely modified version of the "Check-out" method. Three proposed pressure ratio methods also were evaluated and compared with the traditional methods. Two full-sized experimental ventilation systems in two ventilation laboratories were tested. One system had five branch ducts, the other had eight, with branch duct diameters ranging from 4 to 7 inches. To create challenge, each system received multiple alterations and, in some cases, the airflow level was changed throughout the system. For each round of measurements (1) different combinations of alterations were made to some ducts; (2) on a given system, relevant pressures and flows were determined for each duct using calibrated pressure sensors and standard pitot tubes held in a traversing device; and (3) the numbers of true and false positives and negatives for each screening method were computed for a broad range of threshold values. Sensitivities were plotted against the false positive rates for all thresholds for each method. The area (AROC) under the resulting "receiver operating characteristic curves" was computed for each method. Variability was simulated using bootstrap methods to determine significance of differences. In addition, the thresholds that would achieve 10 and 20% false positive rates were determined for each method and the accompanying sensitivities compared. The pressure ratio methods detected nearly all nontrivial obstructions with nearly zero false positives (AROC=1). The direct pressure comparison methods showed substantially inferior performance for the substantial challenges presented in these tests. The latter may be useful under less challenging conditions but were of dubious utility in locating obstructions under the ranges of conditions tested.

Hard metal exposures. Part 1: Observed performance of three local exhaust ventilation systems.

Not every ventilation system performs as intended; much can be learned when they do not. The purpose of this study was to compare observed initial performance to expected levels for three saw-reconditioning shop ventilation systems and to characterize the changes in performance of the systems over a one-year period. These three local exhaust ventilation systems were intended to control worker exposures to cobalt, cadmium, and chromium during wet grinding, dry grinding, and welding/brazing activities. Prior to installation the authors provided some design guidance based on Industrial Ventilation, a Manual of Recommended Practice. However, the authors had limited influence on the actual installation and operation and no line authority for the systems. In apparent efforts to cut costs and to respond to other perceived needs, the installed systems deviated from the specifications used in pressure calculations in many important aspects, including adding branch ducts, use of flexible ducts, the choice of fans, and the construction of some hoods. After installation of the three systems, ventilation measurements were taken to determine if the systems met design specifications, and worker exposures were measured to determine effectiveness. The results of the latter will be published as a companion article. The deviations from design and maintenance failures may have adversely affected performance. From the beginning to the end of the study period the distribution of air flow never matched the design specifications for the systems. The observed air flows measured within the first month of installation did not match the predicated design air flows for any of the systems, probably because of the differences between the design and the installed system. Over the first year of operation, hood air flow variability was high due to inadequate cleaning of the sticky process materials which rapidly accumulated in the branch ducts. Poor distribution of air flows among branch ducts frequently produced individual hood air flows that were far below specified design levels even when the total air flow through that system was more than adequate. To experienced practitioners, it is not surprising that deviations from design recommendations and poor maintenance would be associated with poor system performance. Although commonplace, such experiences have not been documented in peer-reviewed publications to date. This publication is a first step in providing that documentation.

Hard metal exposures. Part 2: Prospective exposure assessment.

Hard metal exposures may precipitate lung disease in exposed workers. This article reports on a project investigating the relationship between local exhaust hood air flow levels and workplace hard metal exposures. Airborne cobalt, chromium, and cadmium exposure concentrations, and ventilation system function were monitored for three consecutive days prior to installation of three new ventilation systems, and then were followed monthly for one year. Work activities included wet and dry grinding of saw blades, brazing, welding, and setup. Work task exposures were highly variable over the period of the study. Ventilation air flows failed to meet design goals due to low total air volume and poor distribution; however, worker exposures to metals were controlled in most cases. Hood design, worker acceptance, and use of the hoods were as important in controlling exposures as were exhaust hood air flow levels.

Experimental investigation of power loss coefficients and static pressure ratios in an industrial exhaust ventilation system.

A study tested whether measures of equivalent resistance (X values) and ratios of static pressure (SPratio) for given ducts of contaminant control exhaust ventilation systems were independent of substantial changes to airflow level and to changes to resistance of other ducts within the same full-scale five-branch system. In a factorial study design, four airflow levels were achieved by changing fan rotation rate while resistances to flow for specific branch ducts were changed independently by adjusting slidegate dampers to various settings. For each damper insertion depth (including fully open), the results demonstrated substantial invariance for branch X values (few greater than 5%), SPratio (few greater than 3%), and fraction of airflow to each duct (few greater than 2%). X-values for submains were much less stable, changing by 20% or more with changes to other parts of the system. For the same conditions, hood static pressures changed by as much as 96% (with standard deviation of 40%). The results suggest that before and after values of X and SPratios should be more reliable bases for indicating alterations than comparison of observed static pressures. The stability of airflow distributions with substantial changes in airflow suggests that one could adjust airflow distribution (e.g., with dampers) without considering whether the fan speed was set correctly, leaving fan adjustments for a final step.

Comparison of pitot traverses taken at varying distances downstream of obstructions.

This study determined the deviations between pitot traverses taken under "ideal" conditions--at least seven duct diameter's lengths (i.e., distance = 7D) from obstructions, elbows, junction fittings, and other disturbances to flows--with those taken downstream from commonplace disturbances. Two perpendicular 10-point, log-linear velocity pressure traverses were taken at various distances downstream of tested upstream conditions. Upstream conditions included a plain duct opening, a junction fitting, a single 90 degrees elbow, and two elbows rotated 90 degrees from each other into two orthogonal planes. Airflows determined from those values were compared with the values measured more than 40D downstream of the same obstructions under ideal conditions. The ideal measurements were taken on three traverse diameters in the same plane separated by 120 degrees in honed drawn-over-mandrel tubing. In all cases the pitot tubes were held in place by devices that effectively eliminated alignment errors and insertion depth errors. Duct velocities ranged from 1500 to 4500 ft/min. Results were surprisingly good if one employed two perpendicular traverses. When the averages of two perpendicular traverses was taken, deviations from ideal value were 6% or less even for traverses taken as close as 2D distance from the upstream disturbances. At 3D distance, deviations seldom exceeded 5%. With single diameter traverses, errors seldom exceeded 5% at 6D or more downstream from the disturbance. Interestingly, percentage deviations were about the same at high and low velocities. This study demonstrated that two perpendicular pitot traverses can be taken as close as 3D from these disturbances with acceptable (< or = 5%) deviations from measurements taken under ideal conditions.

Effects of shape, size, and air velocity on entry loss factors of suction hoods.

This study further elucidated the effects of air velocity, aspect ratio (face length to face width), and area ratio (face area to duct area) on entry loss factors of suction hoods. A full scale ventilation system was utilized to determine the entry loss factor attributable to each of 20 square and rectangular hoods with a 90 degrees included angle. Static and velocity pressures were measured using Pitot tubes connected by tubing to piezo-resistive pressure transducers and inclined tube manometers. The entry loss factor, Fh, is the ratio of hood total pressure loss to mean velocity pressure. Values of Fh determined in this study ranged from 0.17-1.85. The values of Fh were a hyperbolic function of area ratio with a region rapidly increasing change for area ratios less than 5. For area ratios greater than 5, the values of Fh approached an asymptote of 0.17. Among hoods with a given area ratio (e.g., 2.5, 5.1, or 10.2), values of Fh were independent of aspect ratio. To a limited extent, Fh values decreased as mean air velocities increased from 319-1770 m/min (1046-5807 feet/min).