Nanoparticle inhalation augments particle-dependent systemic microvascular dysfunction

Background  

We have shown that pulmonary exposure to fine particulate matter (PM) impairs endothelium dependent dilation in systemic arterioles. Ultrafine PM has been suggested to be inherently more toxic by virtue of its increased surface area. The purpose of this study was to determine if ultrafine PM (or nanoparticle) inhalation produces greater microvascular dysfunction than fine PM. Rats were exposed to fine or ultrafine TiO₂ aerosols (primary particle diameters of ~1 μm and ~21 nm, respectively) at concentrations which do not alter bronchoalveolar lavage markers of pulmonary inflammation or lung damage.     

Physical Characterization of the University of Toronto Coarse,Fine, and Ultrafine High-Volume Particle Concentrator Systems

Particle concentrators allow exposure to controlled levels of concentrated ambient particulate matter (PM) over a broad range of concentrations. The performance of these systems can be influenced by the physicochemical characteristics of PM and so it is vital to characterize the concentrators at a given site. The quasi-ultrafine PM (<0.2 μm), fine PM (0.15–2.5 μm), and coarse PM (2.5–10 μm) concentrators at the Southern Ontario Center for Atmospheric Aerosol Research (SOCAAR), University of Toronto, were characterized as a part of the “Health Effects of Aerosols in Toronto (HEAT)” campaign held during February–March, 2010. The full size distributions of ambient and concentrated particles were simultaneously measured in terms of number, surface area, and volume using high time-resolution instruments. Examination of the complete size distribution, including the unconcentrated particles beyond the cutpoints of the concentrator systems, revealed that particles in the unconcentrated size ranges made significant contributions to the particle number and surface area present in the concentrated airstreams of fine and coarse concentrators. Further transients in the ambient ultrafine particle concentrations were evident as dampened signals in these concentrated airstreams. The ultrafine concentrator exhibited a significant size shift when the ambient particle size distribution had a mode ≤30 nm. Overall the fine and coarse concentrators provided a reasonable concentrated reproduction of the ambient PM mass while questions remain regarding the representativeness of the ultrafine concentrator.

Copyright 2012 American Association for Aerosol Research     

Ambient fine particulate air pollution triggers ST-elevation myocardial infarction, but not non-ST elevation myocardial infarction: a case-crossover study

Background

We and others have shown that increases in particulate air pollutant (PM) concentrations in the previous hours and days have been associated with increased risks of myocardial infarction, but little is known about the relationships between air pollution and specific subsets of myocardial infarction, such as ST-elevation myocardial infarction (STEMI) and non ST-elevation myocardial infarction (NSTEMI).

Methods

Using data from acute coronary syndrome patients with STEMI (n?=?338) and NSTEMI (n?=?339) and case-crossover methods, we estimated the risk of STEMI and NSTEMI associated with increased ambient fine particle (<2.5 um) concentrations, ultrafine particle (10-100 nm) number concentrations, and accumulation mode particle (100-500 nm) number concentrations in the previous few hours and days.

Results

We found a significant 18% increase in the risk of STEMI associated with each 7.1 μg/m³ increase in PM_2.5 concentration in the previous hour prior to acute coronary syndrome onset, with smaller, non-significantly increased risks associated with increased fine particle concentrations in the previous 3, 12, and 24 hours. We found no pattern with NSTEMI. Estimates of the risk of STEMI associated with interquartile range increases in ultrafine particle and accumulation mode particle number concentrations in the previous 1 to 96 hours were all greater than 1.0, but not statistically significant. Patients with pre-existing hypertension had a significantly greater risk of STEMI associated with increased fine particle concentration in the previous hour than patients without hypertension.

Conclusions

Increased fine particle concentrations in the hour prior to acute coronary syndrome onset were associated with an increased risk of STEMI, but not NSTEMI. Patients with pre-existing hypertension and other cardiovascular disease appeared particularly susceptible. Further investigation into mechanisms by which PM can preferentially trigger STEMI over NSTEMI within this rapid time scale is needed.     

Occupational exposure to airborne isocyanates during brush/roller application of 2-pack polyurethane paints in a tropical climate

Shipboard and laboratory trials were conducted to determine airborne occupational exposure to isocyanates by brush/roller application of 2-pack polyurethane paints. Airborne concentrations in the breathing zones of the operators were found to be <0.1 μg/m³ during the paint application to a vessel deck, in a tropical climate, in the open air. Similarly, brush/roller application of the paints in an enclosed space generated airborne isocyanate concentrations <3 μg/m³. The dust generated during light sanding of the polyurethane paint, 24 h after curing, did not show detectable levels of isocyanates.     

Narrow ridge waveguide high power single mode 1.3-μm InAs/InGaAs ten-layer quantum dot lasers

Ten-layer InAs/In_0.15Ga_0.85As quantum dot (QD) laser structures have been grown using molecular beam epitaxy (MBE) on GaAs (001) substrate. Using the pulsed anodic oxidation technique, narrow (2 μm) ridge waveguide (RWG) InAs QD lasers have been fabricated. Under continuous wave operation, the InAs QD laser (2 × 2,000 μm²) delivered total output power of up to 272.6 mW at 10 °C at 1.3 μm. Under pulsed operation, where the device heating is greatly minimized, the InAs QD laser (2 × 2,000 μm²) delivered extremely high output power (both facets) of up to 1.22 W at 20 °C, at high external differential quantum efficiency of 96%. Far field pattern measurement of the 2-μm RWG InAs QD lasers showed single lateral mode operation.     

High-temperature resistant ambient pressure-dried aluminum doped silica aerogel from inorganic silicon and aluminum sources

Aluminum doped silica aerogel (ASA) exhibiting improved high-temperature resistance is usually prepared via supercritical drying from organic silicon and/or aluminum precursors, which propels the production cost significantly. Herein we demonstrate a simple and effective method to prepare highly thermal resistant ASA via the sol-gel and ambient pressure drying route by using water glass and aluminum chloride as precursors. Effects of the Al/Si molar ratio in precursor, the calcination temperature and the modifier type on the crystallinity, morphology, pore structure of ASA are investigated. Results show that the Al/Si molar ratio and the calcination temperature have significant effects on the structure and heat resistance performance of ASA at temperature of 600–1000 °C. The sample with Al/Si molar ratio of 0.15 shows the highest specific surface area of 805.9 m²/g and pore volume of 5.038 cm³/g after heated to 600 °C, and retains 179.5 m²/g and 1.295 cm³/g respectively after heated to 1000 °C. Mechanism analysis indicates that, though the actual aluminum content is extremely low (0.18%, wt%), the high-temperature resistance of ASA is greatly improved owing to the effective doping of aluminum in the lattice of SiO₂ and the corresponding electrostatic repulsion between neighboring nanoparticles induced by the replacement of Si⁴⁺ by Al³⁺ ions.     

Preparation and characterization of three-dimensional nanostructured macroporous bacterial cellulose/agarose scaffold for tissue engineering

We fabricated a three-dimensional nanostructured macroporous bacterial cellulose scaffold (3D BC scaffold) and a three-dimensional nanostructured macroporous bacterial cellulose/agarose scaffold (3D BC/A). Results of scanning electron microscopy (SEM) and mercury intrusion porosimeter showed that both the 3D BC and the 3D BC/A have interconnected macropores characterized by nanofibrous pore walls (The diameter of the dominant pores was about 100 μm and ranges from <1 μm to >1,000 μm). 3D BC/A also has high surface area (80 ± 5 m²/g) and sufficient porosity (88.5 ± 0.4%) compare with 3D BC (surface area: 92.81 ± 2.02 m²/g; porosity 90.42 ± 0.24%). 3D BC/A do support C5.18 cell and hBMSC attachment, proliferation evaluated with SEM, confocal microscopy and cell proliferation assay. Furthermore, 3D/ABC has enhanced mechanical property (ultimate compressive strength: 26.26 ± 4.6 kPa, Young’s modulus: 39.26 ± 5.72 kPa)) than that 3D/BC has (ultimate compressive strength: 7.04 ± 2.34 kPa, Young’s modulus: 10.76 ± 3.52 kPa). Overall, the 3D BC/A scaffold had more potential than 3D BC scaffold for using as a scaffold for tissue engineering and tissue repair applications.     

High surface area methyltriethoxysilane-derived aerogels by ambient pressure drying

In this paper we report the synthesis of methyltriethoxysilane (MTES) based aerogels by non-supercritical/ambient pressure drying. The alcogels have been aged in different concentrations of silane precursor solutions before drying and aerogels with low density and high porosity were obtained. The 60% vol silane aged aerogel shows a surface area of 416 m²/g with a pore volume of 0.99 cm³/g and a maximum surface area of 727 m²/g was obtained for 80% vol silane aged aerogel. The non-silane aged sample possess a surface area of 471 m²/g with a total pore volume of 0.83 cm³/g. The aerogels show broad pore-size distribution. The FT-IR studies reveal the retention of Si–C bond in the network and the formation of a hydrophobic gel. The ²⁹Si magic angle spinning nuclear magnetic resonance (²⁹Si MAS-NMR) studies were also employed to characterize the local environment around the silicon atoms and to obtain information on the condensation degree of the gel network. By varying the hydrolysis pH, highly flexible aerogels have also been successfully prepared. The porosity studies on the flexible aerogels are also presented here.     

Cytokine release from alveolar macrophages exposed to ambient particulate matter: Heterogeneity in relation to size,city and season

Background  

Several studies have demonstrated an association between exposure to ambient particulate matter (PM) and respiratory and cardiovascular diseases. Inflammation seems to play an important role in the observed health effects. However, the predominant particle component(s) that drives the inflammation is still not fully clarified. In this study representative coarse (2.5–10 μm) and fine (0.1–2.5 μm) particulate samples from a western, an eastern, a northern and a southern European city (Amsterdam, Lodz, Oslo and Rome) were collected during three seasons (spring, summer and winter). All fractions were investigated with respect to cytokine-inducing potential in primary macrophages isolated from rat lung. The results were related to the physical and chemical parameters of the samples in order to disclose possible connections between inflammatory potential and specific characteristics of the particles.     

Shape matters: effects of silver nanospheres and wires on human alveolar epithelial cells

Background

Ambient particulate matter (PM) exposure is associated with respiratory and cardiovascular morbidity and mortality. To what extent such effects are different for PM obtained from different sources or locations is still unclear. This study investigated the in vitro toxicity of ambient PM collected at different sites in the Netherlands in relation to PM composition and oxidative potential.

Method

PM was sampled at eight sites: three traffic sites, an underground train station, as well as a harbor, farm, steelworks, and urban background location. Coarse (2.5-10 μm), fine (< 2.5 μm) and quasi ultrafine PM (qUF; < 0.18 μm) were sampled at each site. Murine macrophages (RAW 264.7 cells) were exposed to increasing concentrations of PM from these sites (6.25-12.5-25-50-100 μg/ml; corresponding to 3.68-58.8 μg/cm²). Following overnight incubation, MTT-reduction activity (a measure of metabolic activity) and the release of pro-inflammatory markers (Tumor Necrosis Factor-alpha, TNF-α; Interleukin-6, IL-6; Macrophage Inflammatory Protein-2, MIP-2) were measured. The oxidative potential and the endotoxin content of each PM sample were determined in a DTT- and LAL-assay respectively. Multiple linear regression was used to assess the relationship between the cellular responses and PM characteristics: concentration, site, size fraction, oxidative potential and endotoxin content.

Results

Most PM samples induced a concentration-dependent decrease in MTT-reduction activity and an increase in pro-inflammatory markers with the exception of the urban background and stop & go traffic samples. Fine and qUF samples of traffic locations, characterized by a high concentration of elemental and organic carbon, induced the highest pro-inflammatory activity. The pro-inflammatory response to coarse samples was associated with the endotoxin level, which was found to increase dramatically during a three-day sample concentration procedure in the laboratory. The underground samples, characterized by a high content of transition metals, showed the largest decrease in MTT-reduction activity. PM size fraction was not related to MTT-reduction activity, whereas there was a statistically significant difference in pro-inflammatory activity between Fine and qUF PM. Furthermore, there was a statistically significant negative association between PM oxidative potential and MTT-reduction activity.

Conclusion

The response of RAW264.7 cells to ambient PM was markedly different using samples collected at various sites in the Netherlands that differed in their local PM emission sources. Our results are in support of other investigations showing that the chemical composition as well as oxidative potential are determinants of PM induced toxicity in vitro.     

Enzyme hydrolysis of babassu oil in a membrane bioreactor

This work deals with the enzymatic hydrolysis of babassu oil by immobilized lipase in a membrane bioreactor using unmixed aqueous and lipid streams. The experimental work was carried out in a flat plate membrane module with two different membranes: hydrophobic (nylon) and hydrophilic [mixed cellulose esters (MCE)], with different nominal pore sizes ranging from 0.10 to 0.65 μm. Candida cylindracea lipase was adsorbed on the membrane surface area, and the reactor was operated in batch mode. The initial enzymatic rate increased from 80 to 150 μmol H⁺/min when the organic phase velocity increased from 1.0×10⁻³ to 3.0×10⁻³ m/s, indicating that mass transfer in that phase was the process-limiting step. Calcium ions had a marked effect on immobilized lipase activity, increasing around twofold the lipolytic activity. Long-term experimental runs showed that the immobilized lipase remained stable for at least 8 d. The values for immobilized protein and maximal productivities observed for 0.45 μm membranes were: 1.01 g/m² and 193 μmol H⁺/m²·s for MCE membrane and 0.78 g/m² and 220 μmol H⁺/m²·s for nylon membrane. The productivities obtained are among the highest values reported in the technical literature.     

Humidity,density, and inlet aspiration efficiency correction improve accuracy of a low-cost sensor during field calibration at a suburban site in the North-Western Indo-Gangetic plain (NW-IGP)

Abstract

Low-cost particulate matter (PM) sensors are now widely used by concerned citizens to monitor PM exposure despite poor validation under field conditions. Here, we report the field calibration of a modified version of the Laser Egg (LE), against Class III US EPA Federal Equivalent Method PM₁₀ and PM_2.5 β-attenuation analyzers. The calibration was performed at a site in the north-western Indo-Gangetic Plain from 27 April 2016 to 25 July 2016. At ambient PM mass loadings ranging from <1–838?µg m^?3 and <1–228?µg m^?3 for PM₁₀ and PM_2.5, respectively, measurements of PM₁₀, PM_2.5 from the LE were precise, with a Pearson correlation coefficient (r) >0.9 and a percentage coefficient of variance (CV) <12%. The original Mean Bias Error (MBE) of ～?90?µg m^?3 decreased to ?30.9?µg m^?3 (Sensor 1) and ?23.2?µg m^?3 (Sensor 2) during the summer period (27 April–15 June 2016) after correcting for particle density and aspiration losses. During the monsoon period (16 June–25 July 2016) the MBE of the PM_2.5 measurements decreased from 19.1?µg m^?3 to 8.7?µg m^?3 and from 28.3?µg m^?3 to 16.5?µg m^?3 for Sensor 1 and Sensor 2, respectively, after correcting for particle density and hygroscopic growth. The corrections reduced the overall MBE to <20?µg m^?3 for PM₁₀ and <3?µg m^?3 for PM_2.5, indicating that modified version of the LE could be used for ambient PM monitoring with appropriate correction and meteorological observations. However, users of the original product may underestimate their PM₁₀ exposure.

Copyright © 2020 American Association for Aerosol Research     

Design and performance evaluation of plasma air cleaning systems for removing yellow sand dust

Yellow sand dust (Asian dust storms) causes harmful damage indoors and outdoors during the springtime, and the removal of Yellow sand dust has become an issue for suitable indoor conditions. An air cleaner is required to remove Yellow sand dust efficiently to improve indoor air quality, and the removal characteristics of Yellow sand dust should be studied. The size distribution and mass concentration of Yellow sand dust observed in China and Korea are analyzed, and the removal efficiency of a plasma air cleaning system based on the principle of electrostatic precipitation is evaluated by using Yellow sand dust. Mass median diameter of Yellow sand dust sampled in Beijing and Seoul ranges from 7.0 to 8.0 μm with a mass concentration of 300-1,462 μg/m³. For a single-pass test, the efficiency of dust removal increases with increasing particle size and decreasing flow rate. The removal efficiency of Yellow sand dust in a plasma air cleaning system at a face velocity of 1.0 m/s is higher than 80%. For a multi-pass test in occupied spaces, the operation time required to reduce Yellow sand dust concentration from an initial concentration of 300 μg/m³ to 150 μg/m³ is 10 minutes for a test room of 27 m³.     

Preparation,microstructure and mechanical properties of MoAlB-0.15% Si ceramics with superior strength and toughness

MoAlB has been regarded as a promising high-temperature structural ceramic, but the strength and toughness are still insufficient in the practical application. In this work, MoAlB ceramic bulk with superior hardness, strength and toughness has been fabricated by adding 0.15 mol. % Si. The MoAlB-0.15Si bulk is composed of Si-doped MoAlB, Mo(Al, Si)₂ and ultrafine Al₂O₃. The Vickers hardness ranges from 14.2 to 12.5 GPa with the tested load increasing from 10 to 200 N. The Vickers indentation remains the intact tetragonum in spite of the appearance of corner cracks, indicating the excellent damage tolerance. The flexural strength, fracture toughness and compressive strength of MoAlB-0.15Si are 518.46 MPa, 7.01 MPa m^1/2 and 2.62 GPa, respectively, obviously superior to the present MoAlB polycrystalline bulk. Si doping, grain refinement, strengthening effect of ultrafine Al₂O₃ and phase transformation from Al₈Mo₃ to Mo(Al, Si)₂ jointly account for the improvement of comprehensive properties of MoAlB bulk.     

Kinetic correlation between degradation and dechlorination of perchloroethylene in the Fenton reaction

In the Fenton reaction, degradation and dechlorination are directly affected by the concentrations of hydrogen peroxide and Fe³⁺. Although there is considerable research on the biodegradation of chlorinated compounds combined with the Fenton reaction, the kinetics of degradation and dechlorination of the reaction, with various concentrations of hydrogen peroxide and Fe³⁺, have been rarely investigated. Therefore, we investigated the degradation and dechlorination of PCE with various concentrations of hydrogen peroxide and Fe³⁺. The initial concentration of PCE (10 μM) decreased from a value of 8.9 μM (with 0.1 mM of hydrogen peroxide and 5 mM of Fe³⁺) to 1.1 μM (with 10 mM of hydrogen peroxide and 5 mM of Fe³⁺); the respective values for chloride ions produced were 0.9 and 21.6 μM. Also, the initial 10 μM of PCE decreased from 8.9 (with 0.1 mM of Fe³⁺ and 5 mM of hydrogen peroxide) to 2.2 μM (with 10mM of Fe³⁺ and 5 mM of hydrogen peroxide); the respective chloride ions produced were 0.7 and 14.5 μM. The logarithmic correlations between the degradation and dechlorination coefficients were 0.7682 and 0.7834 for concentrations of hydrogen peroxide and Fe³⁺, respectively. Both coefficients were used, from all possible cases, to derive six models which displayed both the ratio of degradation and dechlorination and the hydrogen peroxide and Fe³⁺ concentrations. The dechlorination of PCE could then be predicted with the model obtained by the coefficient with the concentration of hydrogen peroxide and Fe³⁺. The models could be applied to various Fenton reactions for optimization of degradation or dechlorination, such as biodegradation of PCE which is scarcely degraded by aerobic bacteria.     

Influence of magnesium and aluminium ions on the copper a.c. deposition into aluminium anodic oxide film nanotubes

The influence of Mg²⁺ and Al³⁺ ions on a.c. deposition of copper nanowires into aluminium anodic oxide film (AOF) nanotubes has been studied using cyclic voltammetry and d.c. plasma emission spectrometry. From the analysis of copper quantities deposited into the Al AOF nanotubes (m _Cu), 0.02 M MgSO₄ concentration was found to be optimal for Cu(II) solutions. Moreover, it was shown that Mg²⁺ and Al³⁺ ions not only prevent the breakdown of the barrier layer of AOF, but change the rate of copper deposition and modify the shape of the m _Cu against pH plots depending on the a.c. voltage applied. From the analysis of the quantities of magnesium (m _Mg) incorporated into the Al AOF nanotubes, presumably in the form of Mg(OH)₂, the m _Mg against pH dependences were determined in MgSO₄ and MgSO₄ + CuSO₄ solutions. An increase in m _Mg from 30 g dm^–2 to 1 mg dm^–2 at pH 1.5 and from 6 g dm^–2 to 16 g dm^–2 at pH 7.0 was found under the same a.c. treatment conditions from MgSO₄ solutions without and with Cu²⁺ ions, respectively, indicating the incorporation of Mg(OH)₂ into the Al AOF nanotubes to be lower up to about one hundred times in the case of Cu deposition. Based on the experimental results, it was suggested that incorporation of the Mg(OH)₂ particles into the Al AOF nanotubes occurred simultaneously with growing copper nanowires under a.c. bias is insignificant, if the pH of the CuSO₄ + MgSO₄ solution is 2.5.     

Effects of particulate matter on the pulmonary and vascular system: time course in spontaneously hypertensive rats

Background  

This study was performed within the scope of two multi-center European Commission-funded projects (HEPMEAP and PAMCHAR) concerning source-composition-toxicity relationship for particulate matter (PM) sampled in Europe. The present study aimed to optimize the design for PM in vivo toxicity screening studies in terms of dose and time between a single exposure and the determination of the biological responses in a rat model mimicking human disease resulting in susceptibility to ambient PM. Dust in thoracic PM size-range (aerodynamic diameter <10 μm) was sampled nearby a road tunnel (RTD) using a high volume cascade impactor. Spontaneously hypertensive rats were exposed to urban dust collected in Ottawa, Canada (EHC-93 10 mg/kg of body weight; reference PM) or different RTD doses (0.3, 1, 3, 10 mg/kg of body weight) by intratracheal instillation. Necropsy was performed at 4, 24, or 48 hr after exposure.     

Experimental study on mercury transformation and removal in coal-fired boiler flue gases

This paper reported mercury speciation and emissions from five coal-fired power stations in China. The standard Ontario Hydro Method (OHM) was used into the flue gas mercury sampling before and after fabric filter (FF)/electrostatic precipitator (ESP) locations in these coal-fired power stations, and then various mercury speciation such as Hg⁰, Hg²⁺ and Hg^P in flue gas, was analyzed by using EPA method. The solid samples such as coal, bottom ash and ESP ash, were analyzed by DMA 80 based on EPA Method 7473. Through analysis the mercury speciation varied greatly when flue gas went through FF/ESP. Of the total mercury in flue gas, the concentration of Hg²⁺ is in the range of 0.11–14.76 μg/N m³ before FF/ESP and 0.02–21.20 μg/N m³ after FF/ESP; the concentration of Hg⁰ ranges in 1.18–33.63 μg/N m³ before FF/ESP and 0.77–13.57 μg/N m³ after FF/ESP, and that of Hg^P is in the scope of 0–12.11 μg/N m³ before FF/ESP and 0–0.54 μg/N m³ after FF/ESP. The proportion of Hg²⁺ ranges from 4.87%–50.93% before FF/ESP and 2.02%–75.55% after FF/ESP, while that of Hg⁰ is between 13.81% – 94.79% before FF/ESP and 15.69%–98% after FF/ESP, with that of Hg^P is in the range of 0%–45.13% before FF/ESP and 0%–11.03% after FF/ESP. The mercury in flue gas mainly existed in the forms of Hg⁰ and Hg²⁺. The concentrations of chlorine and sulfur in coal and flue gas influence the species of Hg that are formed in the flue gas entering air pollution control devices. The concentrations of chlorine, sulfur and mercury in coal and the compositions of fly ash had significant effects on mercury emissions.     

Morphological Analysis of Polyethylene Foams with Post-use Material Incorporated

Summary This study investigated the morphology of low-density polyethylene (LDPE) foams with post-use polyethylene (p-PE) incorporated. Samples manufactured using compression molding were analyzed through scanning electron microscopy. Micrographs were treated using the software Image Tool for Windows, version 3.00. This allowed the determination of cell size (0–2500 μm) and cell area (0–1500 .10³ μm²) distributions. The research found that all compositions with p-PE material incorporated (15, 30, 40, 50 and 70% w/w) had similar morphologies, except the composition with 70% of p-PE, which gave a more significant increase in the amount of smaller cells. In comparison to samples with virgin LDPE only, all samples with p-PE showed an increase in cells with smaller areas (< 60 μm) and smaller diameters (< 850 μm²), especially those with 70% p-PE. This finding may be explained by the smaller melt flow index of the p-PE (0.60 g.min^-1) in relation to LDPE (l.74 g.min^-1), which hinders cell growth. The addition up to 70%, of p-PE in formulations which contain 5% of azodicarbonamide leads to PE foams with ideal density ranges for use as packaging (30 to 70 kg.m³).     

Fetal Bovine Serum Concentration Affects Δ<Superscript>9</Superscript> Desaturase Activity of <Emphasis Type="Italic">Trypanosoma cruzi</Emphasis>

Fetal bovine serum (FBS) is an important factor in the culture of Trypanosoma cruzi, since this parasite obtains and metabolizes fatty acids (FAs) from the culture medium, and changes in FBS concentration reduce the degree of unsaturation of FAs in phosphoinositides. When T. cruzi epimastigotes were cultured with 5% instead of 10% FBS, and stearic acid was used as the substrate, ∆⁹ desaturase activity decreased by 50%. Apparent K _m and V _m values for stearic acid, determined from Lineaweaver–Burk plots, were 2 μM and 219 pmol/min/mg of protein, respectively. In studies of the requirement for reduced pyridine nucleotide, ∆⁹ desaturase activity reached a maximum with 8 μM NADH and then remained constant; the apparent K _m and V _m were 4.3 μM and 46.8 pmol/min/mg of protein, respectively. The effect of FBS was observed only for ∆⁹ desaturase activity; ∆¹² desaturase activity was not affected. The results suggest that decreased FBS in culture medium is a signal that modulates ∆⁹ desaturase activity in T. cruzi epimastigotes.