Characterizing the Indoor-Outdoor Relationship of Fine Particulate Matter in Non-Heating Season for Urban Residences in Beijing

Objective

Ambient fine particulate matter (PM_2.5) pollution is currently a major public health concern in Chinese urban areas. However, PM_2.5 exposure primarily occurs indoors. Given such, we conducted this study to characterize the indoor-outdoor relationship of PM_2.5 mass concentrations for urban residences in Beijing.

Methods

In this study, 24-h real-time indoor and ambient PM_2.5 mass concentrations were concurrently collected for 41 urban residences in the non-heating season. The diurnal variation of pollutant concentrations was characterized. Pearson correlation analysis was used to examine the correlation between indoor and ambient PM_2.5 mass concentrations. Regression analysis with ordinary least square was employed to characterize the influences of a variety of factors on PM_2.5 mass concentration.

Results

Hourly ambient PM_2.5 mass concentrations were 3–280 μg/m³ with a median of 58 μg/m³, and hourly indoor counterpart were 4–193 μg/m³ with a median of 34 μg/m³. The median indoor/ambient ratio of PM_2.5 mass concentration was 0.62. The diurnal variation of residential indoor and ambient PM_2.5 mass concentrations tracked with each other well. Strong correlation was found between indoor and ambient PM_2.5 mass concentrations on the community basis (coefficients: r≥0.90, p<0.0001), and the ambient data explained ≥84% variance of the indoor data. Regression analysis suggested that the variables, such as traffic conditions, indoor smoking activities, indoor cleaning activities, indoor plants and number of occupants, had significant influences on the indoor PM_2.5 mass concentrations.

Conclusions

PM_2.5 of ambient origin made dominant contribution to residential indoor PM_2.5 exposure in the non-heating season under the high ambient fine particle pollution condition. Nonetheless, the large inter-residence variability of infiltration factor of ambient PM_2.5 raised the concern of exposure misclassification when using ambient PM_2.5 mass concentrations as exposure surrogates. PM_2.5 of indoor origin still had minor influence on indoor PM_2.5 mass concentrations, particularly at 11:00–13:00 and 22:00–0:00. The predictive models suggested that particles from traffic emission, secondary aerosols, particles from indoor smoking, resuspended particles due to indoor cleaning and particles related to indoor plants contributed to indoor PM_2.5 mass concentrations in this study. Real-time ventilation measurements and improvement of questionnaire design to involve more variables subject to built environment were recommended to enhance the performance of the predictive models.     

Detection of Phosphatidylcholine-Coated Gold Nanoparticles in Orthotopic Pancreatic Adenocarcinoma using Hyperspectral Imaging

Nanoparticle uptake and distribution to solid tumors are limited by reticuloendothelial system systemic filtering and transport limitations induced by irregular intra-tumoral vascularization. Although vascular enhanced permeability and retention can aid targeting, high interstitial fluid pressure and dense extracellular matrix may hinder local penetration. Extravascular diffusivity depends upon nanoparticle size, surface modifications, and tissue vascularization. Gold nanoparticles functionalized with biologically-compatible layers may achieve improved uptake and distribution while enabling cytotoxicity through synergistic combination of chemotherapy and thermal ablation. Evaluation of nanoparticle uptake in vivo remains difficult, as detection methods are limited. We employ hyperspectral imaging of histology sections to analyze uptake and distribution of phosphatidylcholine-coated citrate gold nanoparticles (CGN) and silica-gold nanoshells (SGN) after tail-vein injection in mice bearing orthotopic pancreatic adenocarcinoma. For CGN, the liver and tumor showed 26.5±8.2 and 23.3±4.1 particles/100μm² within 10μm from the nearest source and few nanoparticles beyond 50μm, respectively. The spleen had 35.5±9.3 particles/100μm² within 10μm with penetration also limited to 50μm. For SGN, the liver showed 31.1±4.1 particles/100μm² within 10μm of the nearest source with penetration hindered beyond 30μm. The spleen and tumor showed uptake of 22.1±6.2 and 15.8±6.1 particles/100μm² within 10μm, respectively, with penetration similarly hindered. CGH average concentration (nanoparticles/μm²) was 1.09±0.14 in the liver, 0.74±0.12 in the spleen, and 0.43±0.07 in the tumor. SGN average concentration (nanoparticles/μm²) was 0.43±0.07 in the liver, 0.30±0.06 in the spleen, and 0.20±0.04 in the tumor. Hyperspectral imaging of histology sections enables analysis of phosphatidylcholine-coated gold-based nanoparticles in pancreatic tumors with the goal to improve nanotherapeutic efficacy.     

Modeling and Mapping of Atmospheric Mercury Deposition in Adirondack Park,New York

The Adirondacks of New York State, USA is a region that is sensitive to atmospheric mercury (Hg) deposition. In this study, we estimated atmospheric Hg deposition to the Adirondacks using a new scheme that combined numerical modeling and limited experimental data. The majority of the land cover in the Adirondacks is forested with 47% of the total area deciduous, 20% coniferous and 10% mixed. We used litterfall plus throughfall deposition as the total atmospheric Hg deposition to coniferous and deciduous forests during the leaf-on period, and wet Hg deposition plus modeled atmospheric dry Hg deposition as the total Hg deposition to the deciduous forest during the leaf-off period and for the non-forested areas year-around. To estimate atmospheric dry Hg deposition we used the Big Leaf model. The average atmospheric Hg deposition to the Adirondacks was estimated as 17.4 g m yr with a range of −3.7–46.0 g m yr. Atmospheric Hg dry deposition (370 kg yr) was found to be more important than wet deposition (210 kg yr) to the entire Adirondacks (2.4 million ha). The spatial pattern showed a large variation in atmospheric Hg deposition with scattered areas in the eastern Adirondacks having total Hg deposition greater than 30 μg m⁻² yr⁻¹, while the southwestern and the northern areas received Hg deposition ranging from 25–30 μg m⁻² yr⁻¹.     

Lacrimal Cytokines Assessment in Subjects Exposed to Different Levels of Ambient Air Pollution in a Large Metropolitan Area

Background

Air pollution is one of the most environmental health concerns in the world and has serious impact on human health, particularly in the mucous membranes of the respiratory tract and eyes. However, ocular hazardous effects to air pollutants are scarcely found in the literature.

Design

Panel study to evaluate the effect of different levels of ambient air pollution on lacrimal film cytokine levels of outdoor workers from a large metropolitan area.

Methods

Thirty healthy male workers, among them nineteen professionals who work on streets (taxi drivers and traffic controllers, high pollutants exposure, Group 1) and eleven workers of a Forest Institute (Group 2, lower pollutants exposure compared to group 1) were evaluated twice, 15 days apart. Exposure to ambient PM_2.5 (particulate matter equal or smaller than 2.5 μm) was 24 hour individually collected and the collection of tears was performed to measure interleukins (IL) 2, 4, 5 and 10 and interferon gamma (IFN-γ) levels. Data from both groups were compared using Student’s t test or Mann- Whitney test for cytokines. Individual PM_2.5 levels were categorized in tertiles (lower, middle and upper) and compared using one-way ANOVA. Relationship between PM_2.5 and cytokine levels was evaluated using generalized estimating equations (GEE).

Results

PM_2.5 levels in the three categories differed significantly (lower: ≤22 μg/m³; middle: 23–37.5 μg/m³; upper: >37.5 μg/m³; p<0.001). The subjects from the two groups were distributed unevenly in the lower category (Group 1 = 8%; Group 2 = 92%), the middle category (Group 1 = 89%; Group 2 = 11%) and the upper category (Group 1 = 100%). A significant relationship was found between IL-5 and IL-10 and PM_2.5 levels of the group 1, with an average decrease of 1.65 pg/mL of IL-5 level and of 0.78 pg/mL of IL-10 level in tear samples for each increment of 50 μg/m3 of PM_2.5 (p = 0.01 and p = 0.003, respectively).

Conclusion

High levels of PM_2.5 exposure is associated with decrease of IL-5 and IL-10 levels suggesting a possible modulatory action of ambient air pollution on ocular surface immune response.     

Estimating Mortality Derived from Indoor Exposure to Particles of Outdoor Origin

Following an extensive review of the literature, we further analyze the published data to examine the health effects of indoor exposure to particulate matter (PM) of outdoor origin. We obtained data on all-cause, cardiovascular, and respiratory mortality per 10 μg/m³ increase in outdoor PM₁₀ or PM_2.5; the infiltration factors for buildings; and estimated time spent outdoors by individuals in the United States, Europe, China, and globally. These data were combined log-linear exposure–response model to estimate the all-cause, cardiovascular, and respiratory mortality of exposure to indoor PM pollution of outdoor origin. Indoor PM pollution of outdoor origin is a cause of considerable mortality, accounting for 81% to 89% of the total increase in mortality associated with exposure to outdoor PM pollution for the studied regions. The findings suggest that enhancing the capacity of buildings to protect occupants against exposure to outdoor PM pollution has significant potential to improve public health outcomes.     

Penetration of Rhizopus oligosporus into Soybeans in Tempeh

Histological observations were made on the penetration of hyphae of Rhizopus oligosporus into soybean cotyledons in tempeh, an Indonesian soybean food. Hyphal penetrations averaged one per 1,400 μm² (±390 μm²) on the curved (outer) cotyledon surface and one per 1,010 μm² (±340 μm²) on the flat (inner) one. Hyphae infiltrated to a depth of 742 μm, or about 25% of the average width of a soybean cotyledon. This previously unreported degree of penetration offers partial explanation for the rapid physical and chemical changes in soybeans during tempeh fermentation.     

Carbon- and Nitrogen-to-Volume Ratios of Bacterioplankton Grown under Different Nutritional Conditions

Carbon- and nitrogen-to-volume (C/V and N/V) ratios were determined for freshwater bacterial assemblages grown in lake water filtrate or in water enriched with nutrients (aqueous extract of lake seston, glucose, arginine, phosphate, or ammonium). Biovolume was measured by epifluorescence microphotography, and carbon and nitrogen biomasses were measured with a CHN analyzer. Despite large variations of nutritional conditions (i.e., the composition and concentration of the dissolved organic carbon) and different mean cell sizes of the bacterial assemblage (0.17 to 1.8 μm³ per cell), the C/V, N/V, and carbon-to-nitrogen weight ratios varied little (C/V ratio, 0.14 pg of C per μm³ [standard deviation, 0.057; n = 15]; N/V ratio, 0.027 pg of N per μm³ [standard deviation; 0.011, n = 15]; carbon-to-nitrogen weight ratio, 5.6 [standard deviation, 2.2, n = 15]). An average C/V ratio of 0.12 pg of C per μm³ that was derived from natural and cultured bacterial assemblages is proposed as an appropriate conversion factor for estimation of the biomass of freshwater bacteria.     

myo-Inositol homeostasis in foetal rabbit lung

In several species, lung maturation is accompanied by a decline in the phosphatidylinositol content of lung surfactant and a concomitant increase in its phosphatidylglycerol content. To examine the possibility that this developmental change is influenced by the availability of myo-inositol, potential sources of myo-inositol for the developing rabbit lung were investigated. On day 28 of gestation the myo-inositol content of foetal rabbit lung tissue (2.3±0.5μmol/g of tissue) was not significantly different from that of adult lung tissue but the activity of d-glucose 6-phosphate:1l-myo-inositol 1-phosphate cyclase (cyclase) in foetal lung tissue (81.0±9.0nmol·h⁻¹·g of tissue⁻¹) was higher than that found in adult lung tissue (23.2±1.0nmol·h⁻¹·g of tissue⁻¹). Day 28 foetal rabbit lung tissue was found also to take up myo-inositol by a specific, energy-dependent, Na⁺-requiring mechanism. Half-maximal uptake of myo-inositol by foetal rabbit lung slices was observed when the concentration of myo-inositol in the incubation medium was 85μm. When the myo-inositol concentration was 1mm (but not 100μm) the addition of glucose (5.5mm) stimulated myo-inositol uptake. myo-Inositol uptake was observed also in adult rabbit lung and was found to be sub-maximal at the concentration of myo-inositol found in adult rabbit serum. The concentration of myo-inositol in the serum of pregnant adult rabbits (47.5±5.5μm) was significantly lower than that of non-pregnant adult female rabbits (77.9±9.2μm). On day 28 of gestation the concentration of myo-inositol in foetal serum (175.1±12.0μm) was much less than on day 25, but more than that found on day 30. A transient post-partum increase in the concentration of myo-inositol in serum was followed by a rapid decline. Much of the myo-inositol in foetal rabbit serum probably originates from the placenta, where on day 28 of gestation a high cyclase activity (527±64nmol·h⁻¹·g of tissue⁻¹) was measured. The gestational decline in serum myo-inositol concentration, together with the decreasing cyclase activity of the lungs, is consistent with the view that maturation of the lungs is accompanied by decreased availability of myo-inositol to this tissue.     

Inability of tributyltin-induced chloride/hydroxyl exchange to stimulate calcium transport in mitochondria isolated from flight muscle of the sheep blowfly Lucilia cuprina

Tributyltin in the concentration range 1–4μm failed to stimulate Ca²⁺ transport by Lucilia flight-muscle mitochondria in a medium containing KCl and respiratory substrate but devoid of P_i, despite its promotion of a rapid Cl⁻/OH⁻ exchange. When 2mm-P_i was present, concentrations of tributyltin greater than 1μm inhibited the initial rate of Ca²⁺ transport and induced efflux of the ion from the mitochondria in Cl⁻- or NO₃⁻-containing media. Lower concentrations had little effect. Oligomycin added at up to 10μg/mg of mitochondrial protein had no effect on Ca²⁺ transport. By contrast, approx. 0.3μm-tributyltin completely inhibited respiration supported by α-glycerophosphate in either the presence or absence of added ADP. The data suggest that tributyltin can inhibit Ca²⁺ transport in Lucilia flight-muscle mitochondria other than by facilitating a Cl⁻/OH⁻ exchange or producing an oligomycin-like effect.     

Laboratory Evaluation of the Shinyei PPD42NS Low-Cost Particulate Matter Sensor

Objective

Finely resolved PM2.5 exposure measurements at the level of individual participants or over a targeted geographic area can be challenging due to the cost, size and weight of the monitoring equipment. We propose re-purposing the low-cost, portable and lightweight Shinyei PPD42NS particle counter as a particle counting device. Previous field deployment of this sensor suggests that it captures trends in ambient PM2.5 concentrations, but important characteristics of the sensor response have yet to be determined. Laboratory testing was undertaken in order to characterize performance.

Methods

The Shinyei sensors, in-line with a TSI Aerosol Particle Sizer (APS) model 3321, tracked particle decay within an aerosol exposure chamber. Test atmospheres were composed of monodisperse polystyrene spheres with diameters of 0.75, 1, 2 3 and 6 um as well as a polydisperse atmosphere of ASHRAE test dust #1.

Results

Two-minute block averages of the sensor response provide a measurement with low random error, within sensor, for particles in the 0.75–6μm range with a limit of detection of 1 μg/m3. The response slope of the sensors is idiomatic, and each sensor requires a unique response curve. A linear model captures the sensor response for concentrations below 50 μg/m3 and for concentrations above 50 μg/m³ a non-linear function captures the response and saturates at 800 μg/m³. The Limit of Detection (LOD) is 1 μg/m³. The response time is on the order of minutes, making it appropriate for tracking short-term changes in concentration.

Conclusions

When paired with prior evaluation, these sensors are appropriate for use as ambient particle counters for low and medium concentrations of respirable particles (< 100 ug/m³). Multiple sensors deployed over a spatial grid would provide valuable spatio-temporal variability in PM2.5 and could be used to validate exposure models. When paired with GPS tracking, these devices have the potential to provide time and space resolved exposure measurements for a large number of participants, thus increasing the power of a study.     

Estimation of the Yield Coefficient of Pseudomonas sp. Strain DP-4 with a Low Substrate (2,4-Dichlorophenol [DCP]) Concentration in a Mineral Medium from Which Uncharacterized Organic Compounds Were Eliminated by a Non-DCP-Degrading Organism

The yield coefficient (YC) of Pseudomonas sp. strain DP-4, a 2,4-dichlorophenol (DCP)-degrading organism, was estimated from the number of CFU produced at the expense of 1 unit amount of DCP at low concentrations. At a low concentration of DCP, the YC can be overestimated in pure culture, because DP-4 assimilated not only DCP but also uncharacterized organic compounds contaminating a mineral salt medium. The concentration of these uncharacterized organic compounds was nutritionally equivalent to 0.7 μg of DCP-C ml⁻¹. A mixed culture with non-DCP-degrading organisms resulted in elimination of ca. 99.9% of the uncharacterized organic compounds, and then DP-4 assimilated only DCP as a substrate. In a mixed culture, DP-4 degraded an initial concentration of 0.1 to 10 μg of C ml of DCP⁻¹ and the number of CFU of DP-4 increased. In the mixed culture, DCP at an initial concentration of 0.07 μg of C ml⁻¹ was degraded. However, the number of CFU of DP-4 did not increase. DCP at an extremely low initial concentration of 0.01 μg of C ml⁻¹ was not degraded in mixed culture even by a high density, 10⁵ CFU ml⁻¹, of DP-4. When glucose was added to this mixed culture to a final concentration of 1 μg of C ml⁻¹, the initial concentration of 0.01 μg of C ml of DCP⁻¹ was degraded. These results suggested that DP-4 required cosubstrates to degrade DCP at an extremely low initial concentration of 0.01 μg of C ml⁻¹. The YCs of DP-4 at the expense of DCP alone decreased discontinuously with the decrease of the initial concentration of DCP, i.e., 1.5, 0.19, or 0 CFU per pg of DCP-C when 0.7 to 10, 0.1 to 0.5, or 0.07 μg of C ml of DCP⁻¹ was degraded, respectively. In this study, we developed a new method to eliminate uncharacterized organic compounds, and we estimated the YC of DP-4 at the expense of DCP as a sole source of carbon.     

Effects of Condensed Tannins on Endoglucanase Activity and Filter Paper Digestion by Fibrobacter succinogenes S85

The effect of condensed tannins from birdsfoot trefoil (Lotus corniculatus L.) on the cellulolytic rumen bacterium Fibrobacter succinogenes S85 was examined. Condensed tannins inhibited endoglucanase activity in the extracellular culture fluid, at concentrations as low as 25 μg ml^-1. In contrast, cell-associated endoglucanase activity increased in concentrations of condensed tannins between 100 and 300 μg ml^-1. Inhibition of endoglucanase activity in both the extracellular and the cell-associated fractions was virtually complete at 400 μg of condensed tannins ml^-1. Despite the sharp decline in extracellular endoglucanase activity with increasing concentrations of condensed tannins, filter paper digestion declined only moderately between 0 and 200 μg of condensed tannins ml^-1. However, at 300 μg ml^-1, filter paper digestion was dramatically reduced and at 400 μg ml^-1, almost no filter paper was digested. F. succinogenes S85 was seen to form digestive grooves on the surface of cellulose, and at 200 μg ml^-1, digestive pits were formed which penetrated into the interior of cellulose fibers. Cells grown with condensed tannins (100 to 300 μg ml^-1) possessed large amounts of surface material, and although this material may have been capsular carbohydrate, its osmiophilic nature suggested that it had arisen from the formation of tannin-protein complexes on the cell surface. The presence of electron-dense extracellular material suggested that similar complexes were formed with extracellular protein.     

A New Sensitive Bioassay for Determination of Microbially Available Phosphorus in Water

The content of assimilable organic carbon has been proposed to control the growth of microbes in drinking water. However, recent results have shown that there are regions where it is predominantly phosphorus which determines the extent of microbial growth in drinking waters. Even a very low concentration of phosphorus (below 1 μg of P liter⁻¹) can promote extensive microbial growth. We present here a new sensitive method to determine microbially available phosphorus concentrations in water down to 0.08 μg of P liter⁻¹. The method is a bioassay in which the analysis of phosphorus in a water sample is based on maximum growth of Pseudomonas fluorescens P17 when the energy supply and inorganic nutrients, with the exception of phosphorus, do not limit bacterial growth. Maximum growth (CFU) in the water sample is related to the concentration of phosphorus with the factor 373,200 ± 9,400 CFU/μg of PO₄-P. A linear relationship was found between cell growth and phosphorus concentration between 0.05 to 10 μg of PO₄-P liter⁻¹. The content of microbially available phosphorus in Finnish drinking waters varied from 0.1 to 10.2 μg of P liter⁻¹ (median, 0.60 μg of P liter⁻¹).     

Greenhouse Gas Fluxes from Salt Marshes Exposed to Chronic Nutrient Enrichment

We assessed the impact of nutrient additions on greenhouse gas fluxes using dark static chambers in a microtidal and a macrotidal marsh along the coast of New Brunswick, Canada approximately monthly over a year. Both were experimentally fertilized for six years with varying levels of N and P. For unfertilized, N and NPK treatments, average yearly CO₂ emissions (which represent only respiration) at the microtidal marsh (13, 19, and 28 mmoles CO₂ m^-2 hr^-1, respectively) were higher than at the macrotidal marsh (12, 15, and 19 mmoles m^-2 hr^-1, respectively, with a flux under the additional high N/low P treatment of 21 mmoles m^-2 hr^-1). Response of CH₄ to fertilization was more variable. At the macrotidal marsh average yearly fluxes were 1.29, 1.26, and 0.77 μmol CH₄ m^-2 hr^-1 with control, N, and NPK treatments, respectively and 1.21 μmol m^-2 hr^-1 under high N/low P treatment. At the microtidal marsh CH₄ fluxes were 0.23, 0.16, and -0.24 μmol CH₄ m^-2 hr^-1 in control, N, and NPK and treatments, respectively. Fertilization changed soils from sinks to sources of N₂O. Average yearly N₂O fluxes at the macrotidal marsh were -0.07, 0.08, and 1.70, μmol N₂O m^-2 hr^-1 in control, N, NPK and treatments, respectively and 0.35 μmol m^-2 hr^-1 under high N/low P treatment. For the control, N, and NPK treatments at the microtidal marsh N₂O fluxes were -0.05, 0.30, and 0.52 μmol N₂O m^-2 hr^-1, respectively. Our results indicate that N₂O fluxes are likely to vary with the source of pollutant nutrients but emissions will be lower if N is not accompanied by an adequate supply of P (e.g., atmospheric deposition vs sewage or agricultural runoff). With chronic fertilization the global warming potential of the increased N₂O emissions may be enough to offset the global cooling potential of the C sequestered by salt marshes.     

The sodium, potassium and chloride of cerebral tissues: maintenance, change on stimulation and subsequent recovery

1. Cerebral tissues were prepared for incubation by cutting them from the brain rapidly and in situ, and the calcium concentration in the incubating medium was altered from the customary 2·8mm to 0·75mm. This provided incubated cerebral cortex with fluid and ion content more closely resembling that of the brain in vivo than hitherto obtained. 2. From a systematic difference in size between inulin spaces of slices with one and those with two cut surfaces, it was estimated that cutting directly affected a layer 0·02mm. thick. On the basis of the volume of this layer, it was calculated that the portion of the tissue not affected by cutting had an inulin space of 258 μl./g. initial wt., and during the process of preparation and incubation had gained 30μequiv. of sodium and 17 μequiv. of chloride/g. and had lost 14 μequiv. of potassium/g. 3. Several aspects of the ion content of the incubated tissue were compatible with the observed membrane potential of −60mv between cellular and extracellular phases. 4. In response to electrical stimulation, sodium of the non-inulin space increased from 28 to 57 μequiv./g., potassium decreased from 68 to 48 μequiv./g. and chloride increased from 16 to 22 μequiv./g. in the non-inulin space. These changes were complete in about 6min., and thereafter the concentrations remained steady during continued stimulation. Initial rates of change were 460 μequiv./g./hr. for sodium and 480 μequiv./g./hr. for potassium. 5. After stimulation was stopped the ionic composition of the tissue returned completely to its pre-stimulation state within 10min. Initial rates for extrusion of sodium and gain of potassium were 160 and 230 μequiv./g./hr. respectively.     

Air Pollution in China: Mapping of Concentrations and Sources

China has recently made available hourly air pollution data from over 1500 sites, including airborne particulate matter (PM), SO₂, NO₂, and O₃. We apply Kriging interpolation to four months of data to derive pollution maps for eastern China. Consistent with prior findings, the greatest pollution occurs in the east, but significant levels are widespread across northern and central China and are not limited to major cities or geologic basins. Sources of pollution are widespread, but are particularly intense in a northeast corridor that extends from near Shanghai to north of Beijing. During our analysis period, 92% of the population of China experienced >120 hours of unhealthy air (US EPA standard), and 38% experienced average concentrations that were unhealthy. China’s population-weighted average exposure to PM_2.5 was 52 μg/m³. The observed air pollution is calculated to contribute to 1.6 million deaths/year in China [0.7–2.2 million deaths/year at 95% confidence], roughly 17% of all deaths in China.     

Triazole Susceptibilities in Thermotolerant Fungal Isolates from Outdoor Air in the Seoul Capital Area in South Korea

Emerging fungi resistant to triazoles are a concern because of the increased use of medical triazoles and exposure to agricultural triazoles. However, little is known about the levels of triazole susceptibility in outdoor airborne fungi making it difficult to assess the risks of inhalation exposure to airborne, antifungal-resistant fungi. This study examined triazole susceptibilities of the airborne thermotolerant fungi isolated from the ambient air of the Seoul Capital Area of South Korea. We used impactor air sampling with triazole-containing nutrient agar plates as the collection substrates to screen for airborne fungal isolates based on their triazole susceptibilities. This study estimated that 0.17% of all the culturable fungi belong to the pathogenic thermotolerant taxa, among which each isolate of Aspergillus niger and Aspergillus tubingensis showed a minimum inhibitory concentration (MIC) of 2 μg/mL or greater for itraconazole. Their concentration in air was 0.4 CFU/m³. Seven human pathogenic Paecilomyces variotii isolates had MICs of 32 μg/mL or greater and lower than 2 μg/mL for the agricultural fungicide tebuconazole and the medical triazole itraconazole, respectively. Though the concentration was low, our results confirm the presence of airborne fungi with high MICs for itraconazole in ambient air. Inhalation is an important exposure route because people inhale more than 10 m³ of air each day. Vigilance is preferred over monitoring for the emergence of triazole-resistant fungal pathogens in ambient outdoor air.     

Hydrogel-Forming Microneedle Arrays Allow Detection of Drugs and Glucose In Vivo: Potential for Use in Diagnosis and Therapeutic Drug Monitoring

We describe, for the first time the use of hydrogel-forming microneedle (MN) arrays for minimally-invasive extraction and quantification of drug substances and glucose from skin in vitro and in vivo. MN prepared from aqueous blends of hydrolysed poly(methyl-vinylether-co-maleic anhydride) (11.1% w/w) and poly(ethyleneglycol) 10,000 daltons (5.6% w/w) and crosslinked by esterification swelled upon skin insertion by uptake of fluid. Post-removal, theophylline and caffeine were extracted from MN and determined using HPLC, with glucose quantified using a proprietary kit. In vitro studies using excised neonatal porcine skin bathed on the underside by physiologically-relevant analyte concentrations showed rapid (5 min) analyte uptake. For example, mean concentrations of 0.16 μg/mL and 0.85 μg/mL, respectively, were detected for the lowest (5 μg/mL) and highest (35 μg/mL) Franz cell concentrations of theophylline after 5 min insertion. A mean concentration of 0.10 μg/mL was obtained by extraction of MN inserted for 5 min into skin bathed with 5 μg/mL caffeine, while the mean concentration obtained by extraction of MN inserted into skin bathed with 15 μg/mL caffeine was 0.33 μg/mL. The mean detected glucose concentration after 5 min insertion into skin bathed with 4 mmol/L was 19.46 nmol/L. The highest theophylline concentration detected following extraction from a hydrogel-forming MN inserted for 1 h into the skin of a rat dosed orally with 10 mg/kg was of 0.363 μg/mL, whilst a maximum concentration of 0.063 μg/mL was detected following extraction from a MN inserted for 1 h into the skin of a rat dosed with 5 mg/kg theophylline. In human volunteers, the highest mean concentration of caffeine detected using MN was 91.31 μg/mL over the period from 1 to 2 h post-consumption of 100 mg Proplus^® tablets. The highest mean blood glucose level was 7.89 nmol/L detected 1 h following ingestion of 75 g of glucose, while the highest mean glucose concentration extracted from MN was 4.29 nmol/L, detected after 3 hours skin insertion in human volunteers. Whilst not directly correlated, concentrations extracted from MN were clearly indicative of trends in blood in both rats and human volunteers. This work strongly illustrates the potential of hydrogel-forming MN in minimally-invasive patient monitoring and diagnosis. Further studies are now ongoing to reduce clinical insertion times and develop mathematical algorithms enabling determination of blood levels directly from MN measurements.     

Determination of Bacterial Cell Dry Mass by Transmission Electron Microscopy and Densitometric Image Analysis

We applied transmission electron microscopy and densitometric image analysis to measure the cell volume (V) and dry weight (DW) of single bacterial cells. The system was applied to measure the DW of Escherichia coli DSM 613 at different growth phases and of natural bacterial assemblages of two lakes, Piburger See and Gossenköllesee. We found a functional allometric relationship between DW (in femtograms) and V (in cubic micrometers) of bacteria (DW = 435 · V^0.86); i.e., smaller bacteria had a higher ratio of DW to V than larger cells. The measured DW of E. coli cells ranged from 83 to 1,172 fg, and V ranged from 0.1 to 3.5 μm³ (n = 678). Bacterial cells from Piburger See and Gossenköllesee (n = 465) had DWs from 3 fg (V = 0.003 μm³) to 1,177 fg (V = 3.5 μm³). Between 40 and 50% of the cells had a DW of less than 20 fg. By assuming that carbon comprises 50% of the DW, the ratio of carbon content to V of individual cells varied from 466 fg of C μm⁻³ for Vs of 0.001 to 0.01 μm³ to 397 fg of C μm⁻³ (0.01 to 0.1 μm³) and 288 fg of C μm⁻³ (0.1 to 1 μm³). Exponentially growing and stationary cells of E. coli DSM 613 showed conversion factors of 254 fg of C μm⁻³ (0.1 to 1 μm³) and 211 fg of C μm⁻³ (1 to 4 μm³), respectively. Our data suggest that bacterial biomass in aquatic environments is higher and more variable than previously assumed from volume-based measurements.     

Control of logarithmic growth rates of tobacco callus tissue by cytokinins

The growth rates of tobacco callus tissues on media containing 10⁻⁶ to 10 μm 6-(γ,γ-dimethylallylamino)purine (2iP) were measured. At concentrations of 10⁻⁴ μm and above growth rates were exponential and dependent on cytokinin concentration. At 2iP concentrations of 10⁻⁴ to 0.33 μm, the exponential rate was maintained for 4 to 5 doublings of fresh and dry weight. After this period a linear phase, resulting in approximately 1 doubling of weight, occurred. The growth of tissues on media containing higher than 0.33 μm 2iP was exponential for only about 15 days. At the end of this time, and well before they achieved half their final weight, they exhibited growth which was less rapid than logarithmic but more rapid than linear. Comparisons with zeatin, 6-benzylaminopurine and kinetin indicated that, although the maximum growth rates obtained with relatively high concentrations (0.1-1 μm) were similar, the naturally occurring cytokinins, 2iP and zeatin, promoted faster rates at lower concentrations (10⁻³-10⁻² μm) than did 6-benzylaminopurine and kinetin.