Phytosampling-a supplementary tool for particulate matter (PM) speciation characterization

Ambient air particulate matter (PM) and PM-associated environmentally persistent free radicals (EPFRs) have been documented to contribute to pollution-related health effects. Studies of ambient air PM potentially bear artifacts stemming from the collection methods. We have investigated the applicability of PM phytosampling (PHS) as a supplementary tool to a classic PM sampler in respect of achieving better PM chemical composition assessment (primarily organic fraction). Phytosampling is a static PM collection method relying on the particle entrapment by the plant's leaf through electrostatic forces and surface trichomes. We have investigated the differences in the EPFR and polycyclic aromatic hydrocarbon (PAH) speciation and concentration on ambient air PM for PHS and high-volume PM sampler (HVS). The advantages of PHS are easy particle recovery from the matrix, collection under natural environmental conditions, and the ability to apply a dense collection network to accurately represent spatial pollutant distribution. The experimental results show that the PHS can provide valuable speciation information, sometimes different from that observed for HVS. For PM collected by PHS, we detected the larger contribution of oxygen-centered EPFRs, different decay behavior, and more consistent PAH distribution between different PM sizes compared to the PM from HVS. These results indicate that the isolation of samples from the ambient during HVS sampling and exposure to high-volume airflow may alter the chemical composition of the samples, while the PHS method could provide details on the original speciation and concentration and be more representative of the PM surface. However, PHS cannot evaluate an absolute air concentration of PM, so it serves as an excellent supplementary tool to work in conjunction with the standard PM collection method.

VOC Emissions and Formation Mechanisms from Carbon Nanotube Composites during 3D Printing

A commercially available, 3D printer nanocomposite filament of carbon nanotubes (CNTs) and acrylonitrile-butadiene-styrene (ABS) was analyzed with respect to its VOC emissions during simulated fused deposition modeling (FDM) and compared with a regular ABS filament. VOC emissions were quantified and characterized under a variety of conditions to simulate the thermal degradation that takes place during FDM. Increasing the residence time and temperature resulted in significant increases in VOC emissions, and the oxygen content of the reaction gas influenced the VOC profile. In agreement with other studies, the primary emitted VOC was styrene. Multiple compounds are reported in this work for the first time as having formed during FDM, including 4-vinylcyclohexene and 2-phenyl-2-propanol. Our results show that printing 222.0 g of filament is enough to surpass the reference concentration for inhalation exposure of 1 mg/m³ according to the EPA's Integrated Risk Information System (IRIS). The presence of CNTs in the filament influenced VOC yields and product ratios through three types of surface interactions: (1) adsorption of O₂ on CNTs lowers the available O₂ for oxidation of primary backbone cleavage intermediates, (2) adsorption of styrene and other VOCs to CNTs leads to surface-catalyzed degradation, and (3) CNTs act as a trap for certain VOCs and prevent them from entering vapor emissions. While the presence of CNTs in the filament lowered the total VOC emission under most experimental conditions, they increased the emission of the most hazardous VOCs, such as α-methylstyrene and benzaldehyde. The present study has identified an increased risk associated with the use of CNT nanocomposites in 3D printing.

Postmortem photonic imaging of lux-modified Salmonella Typhimurium within the gastrointestinal tract of swine after oral inoculation in vivo

The study objective was to monitor Salmonella progression by photonic detection through segments of the gastrointestinal tract after oral inoculation. Pigs (~80 kg) were inoculated orally with 3.1 or 4.1 x 10(10) cfu of Salmonella Typhimurium transformed with plasmid pAK1-lux for a 6-h (n = 6) or 12-h (n = 6) incubation in vivo and then were killed for tissue harvest. Intestinal regions (duodenum, jejunum, ileum, large intestine) were divided into 5 replicates of 4 segments (5 cm) each for imaging. For each replicate, n = 2 segments of each region were intact, whereas n = 2 segments were opened to expose the digesta. Subsamples of digesta were analyzed to determine actual colony-forming units, and images were analyzed for relative light units per second. At 6 h, a greater (P < 0.05) concentration of emitting bacteria, and consequently a greater (P < 0.05) detection of photonic emissions, was observed in the small intestine than in the large intestine. The correlations (6 h) of photonic emissions in exposed segments to bacterial colony-forming units were r = 0.73, 0.62, 0.56, and 0.52 (P < 0.05) in duodenum, jejunum, ileum, and large intestine, respectively. Photonic emissions were greater (P < 0.05) in intact jejunum, ileum, and large intestine than in the duodenum after a 6-h incubation. At 12 h, a greater (P < 0.05) concentration of emitting bacteria in jejunum and ileum of exposed segments was observed than in duodenum and large intestine of exposed segments. Photonic emissions were greater in ileum than duodenum, jejunum, and large intestine of exposed segments (P < 0.05). The correlations (12 h) of photonic emissions in exposed segments to bacterial colony-forming units were r = 0.71 and 0.62 for jejunum and ileum, respectively (P < 0.05). At 12 h, a greater (P < 0.05) concentration of emitting bacteria in jejunum and ileum of intact segments was observed than in duodenum and large intestine. These data indicate that colony-forming units of introduced bacteria remained greater in the small intestine after 6- and 12-h incubations; we have determined that a minimum of 2.0 x 10(5) cfu generates detection through these tissues (~1.0 to 21.0 relative light units/s). This study demonstrates the feasibility of using biophotonics in research models ex vivo for monitoring the pathogenicity of Salmonella in swine, in place of, or in conjunction with, traditional microbiological assessments and whether a greater level of sensitivity of detection and correlation to actual bacterial concentrations can be achieved.

ARF- and coatomer-mediated peroxisomal vesiculation

The authors characterized on a molecular level the clofibrate-inducible 26-kDa integral peroxisomal membrane protein (Pmp26p, Pex11-1p) of rat liver. By screening cDNA databases with the obtained Pex11-1p-cDNA, a second homologous cDNA was identified that codes for a polypeptide with slightly larger molecular mass than Pex11-1p. The authors call this polypeptide Pex11-2p. Studies on the topology of Pex11-1p revealed two transmembrane domains with the N- and C-terminus facing the cytoplasm. The C-terminal tail of Pex11-1p ends in a consensus dilysine motif of the type -KXKXX-COOH, which is known to be involved in the ADP-ribosylation factor (ARF)1-coat protein (COP) I coat (ARF)1-dependent membrane recruitment to Golgi membranes. Studies with isolated peroxisomes incubated in the presence of cytosol, adenosine triphosphate and GTP gamma S, indeed, provided evidence for specific binding of ARF and coatomer to peroxisomes. Expression of Pex11-1p in Chinese hamster ovary (CHO) wild-type cells led to a twofold increase in the number of peroxisomes, but expression in a temperature-sensitive CHO mutant, defective in coatomer, induced elongation and tubulation of peroxisomal structures, rather than numerical proliferation. The obtained results for the first time offer a mechanism explaining Pex11-1p-, as well as ARF- and coatomer-mediated peroxisomal vesiculation. Two models are presented that may explain how these observations fit in with peroxisome biogenesis.

Myocardial injury during radiofrequency catheter ablation: comparison of focal and linear lesions

The aim of study was to investigate the extent of myocardial injury incurred by creation of continuous RF current induced linear ablation lesions (LL; ablation of atrial fibrillation, right atrial procedure) in comparison to focal RF lesions (FL; AV node reentry tachycardia, WPW tachycardia). In 23 patients with LL (age 51.3 +/- 11.2 years, 18 men, 5 women) and in 16 patients with FL (age 53.9 +/- 5.1 years, 8 men and 8 women), levels of creatine kinase (CK), myoglobin (MG), CKMB mass (CKMB M), CKMB activity (CKMB A), and cardiac troponin T (cTnT) were determined before and 2, 4, 8, 24, and 48 hours after ablation. CKMB A was normal in 87% in LL and 100% in FL (< 6% of CK) with median maximum CK values of 214 (45-1583) U/L in LL and 36 (29-212) U/L in FL. Peak values of all parameters were significantly higher in LL than in FL. The sensitivity of cTnT was 50% in FL and 100% in LL. In FL MG, total CK, and CKMB M were abnormal in only 12.5% of cases while in LL MG and CKMB M were pathological in 100% and total CK was abnormal in 91.3% of patients. The amount of energy and number of RF applications correlated with cTnT, MG, and CKMB M (P = 0.01). In conclusion, (1) long linear RF current lesions for ablation of atrial fibrillation are associated with significantly greater myocardial injury than focal ablations. (2) In focal lesions only cTnT provided a sensitivity of 50% in the detection of myocardial injury while in linear lesions cTnT, CKMBM, and CKMB M seemed suitable for detection of RF current induced myocardial damage with 100% sensitivity. All biochemical parameters do not differentiate patients with coronary ischemia up to 48 hours after an ablation. (3) Further investigations are necessary to determine if RF current linear lesions lead to impaired atrial contractility in cases of extensive tissue damage.

Radioiodinated N-(2-diethylaminoethyl)benzamide derivatives with high melanoma uptake: structure-affinity relationships, metabolic fate, and intracellular localization

Several radioiodinated N-(dialkylaminoalkyl)benzamides have been used for planar scintigraphy and single-photon emission computed tomography (SPECT) of melanoma metastases. In a quest for improved melanoma uptake and tissue selectivity, structure-activity studies for N-(2-diethylaminoethyl)benzamides with variation of phenyl substituents were performed using C57Bl/6 mice bearing B16 melanoma. Compounds 2 (4-amino-5-bromo-N-(2-diethylaminoethyl)-3-[(131)I]iodo-2-methoxybenz amide) and 6 (4-acetamido-N-(2-diethylaminoethyl)-5-[(131)I]iodo-2-methoxybenzamid e) showed at 6 h post iv injection, for example, melanoma uptake of 16.6 and 23.2% ID/g, respectively (mean values, n = 3). Uptake was 3-5 times higher (P < 0.01) than observed with benzamides known from the literature and was probably facilitated by the relatively slow urinary excretion of 2 or 6. In contrast, analogues lacking either the MeO, Ac, AcNH, or Br substituents exhibited reduced tumor uptake and high urinary excretion of radioactivity in various benzamide metabolites. Uptake of radioiodinated benzamides in B16 melanoma is not mediated by a specific mechanism such as sigma-receptor binding. 2 and 6 exhibited similar melanoma uptake values but quite different sigma(1)-receptor affinities of K(i) = 0.278 +/- 0.018 and 5.19 +/- 0.40 microM, respectively. Uptake studies with IMBA (N-(2-diethylaminoethyl)-3-[(131)I]iodo-4-methoxybenzamide) or BZA (N-(2-diethylaminoethyl)-4-[(131)I]iodobenzamide) showed that with increasing dose of unlabeled compound the measured uptake of label was unchanged (IMBA) or even enhanced (BZA) while receptor binding of label decreased. Differential and equilibrium density-gradient centrifugation revealed that most of the radioactivity from labeled IMBA was associated with fractions containing melanin granules. Thus, structure-activity studies indicate that blood clearance rates and metabolic stability are the main determinants for benzamide uptake in melanoma. The high uptake and slow clearance of 6 offer considerable potential for melanoma imaging in patients, and this compound may also prove to be useful for radionuclide therapy.

Peroxisome biogenesis: involvement of ARF and coatomer

Peroxisomal membrane protein (Pmp)26p (RnPex11p), a major constituent of induced rat liver peroxisomal membrane, was found to contain a COOH-terminal, cytoplasmically exposed consensus dilysine motif with the potential to bind coatomer. Biochemical as well as immunocytochemical evidence is presented showing that peroxisomes incubated with preparations of bovine brain or rat liver cytosol recruit ADP-ribosylation factor (ARF) and coatomer in a strictly guanosine 5'-O-(3-thiotriphosphate)-dependent manner. Consistent with this observation, ldlF cells expressing a temperature-sensitive mutant version of the epsilon-subunit of coatomer exhibit elongated tubular peroxisomes possibly due to impaired vesiculation at the nonpermissive temperature. Since overexpression of Pex11p in Chinese hamster ovary wild-type cells causes proliferation of peroxisomes, these data suggest that Pex11p plays an important role in peroxisome biogenesis by supporting ARF- and coatomer-dependent vesiculation of the organelles.