Extracting dust from soil: a simple solution to a tricky task

Air quality is commonly assessed by the ambient concentration of airborne particles sized smaller than 10 microm (PM10). However, in addition to concentration, particle shape as well as the type and bioaccessibility of elements adsorbed to this particulate fraction are likely to be related to subsequent respiratory health effects. In order to investigate this relationship, a relatively large mass of the relevant size fraction is needed since sample preparation is necessary prior to analysis. Most existing methods for sampling dust have been developed for analysing the dust directly, without prior handling or digestion. In order to provide sufficient material to be used for subsequent bioaccessibility analysis, these methods require repetitive and time consuming sampling as well as special equipment and procedures which are high in both cost and maintenance. This paper describes an inexpensive and relatively simple procedure for extracting the PM10 fraction from soil to be used for lung bioaccessibility studies. The method described involves dry and wet sieving in order to exclude larger size fractions as far as possible. Vacuum filtering of the wet-sieved soil solution through a 10 microm mesh was then employed to extract the required fraction. In order to avoid frequent blocking of the mesh, Stokes's law was applied in the construction of a tube which enables separation of the solution holding the smallest fraction.     

On the reassessment of doses in TL-dosimetry by measuring the residual dose

Second readouts and the photo-transferred thermoluminscence (PTTL) method are sometimes used to reassess high doses. When using the common LiF:Mg,Ti, if the second readout is performed by a regular readout cycle of 13.3 s, its efficiency is low and the estimations cannot be obtained with acceptable accuracy for low doses in the 10-100 mSv range. By applying the PTTL method, the efficiency is much higher, but a high background is also present, deteriorating the quality of the reassessment. A simple and efficient method was studied, which consists of expanding the heating time to 30 s. Although the efficiency relative to a standard readout is improved by only a factor of 3, the low background enables to obtain results with the same uncertainty as the more complicated PTTL method. By applying region of integration discrimination, the errors can be further diminished.     

Use of statistical checks as maintenance tools for TLD readers

Although the values of different parameters may remain within permissible limits during the operation of a thermoluminescent dosemeter (TLD) reader, certain effects can become apparent only when a long-term followup of these parameters is performed. In order to ensure an accurate and reliable operation of a TLD reader, the system characteristics must be monitored continuously. Long-term statistical checks of key system parameters may give a broader insight into the operational characteristics of the TLD reader and may help for proper maintenance of the system. The photomultipliers noise, the internal reference light source stability and the A to D reference voltage were found to be critical parameters, which have a major influence on the accuracy and stability of the system. A followup of these parameters for a period of about 10 y is presented, and some problems are seen to be reflected in the distributions.     

On the reassessment of thermal neutron doses in TLD-100 by measuring the residual dose

By employing second readouts and the Phototransferred thermoluminescence (PTTL) method, high doses may be reassessed on the basis of residual dose information. It was shown in the past that for TLD-100, gamma doses can be reassessed by using a simple and efficient method, which consists of expanding the heating time to 30 s. In the present study, the 'extended time' method and the PTTL residual dose evaluations are used for reassessing thermal neutron doses when using TLD-100 crystals. Reassessment characteristics are presented for relatively low thermal neutron doses, in the range between approximately 1 and 18 mSv gamma dose equivalent.     

The changing molecular epidemiology and establishment of endemicity of vancomycin resistance in enterococci at one hospital over a 6-year period

The contributions of clonal spread, transfer of genetic elements, and introduction of new strains to the establishment of endemicity of vancomycin-resistant enterococci (VRE) were determined. The study took place at one hospital between 1990, when VRE were first detected, and 1996, when endemicity had become established. Isolates from 183 patients were categorized into 24 strain types by pulsed-field gel electrophoresis; the resistance genotype was determined by polymerase chain reaction. Between 1990 and 1993, 69% of patients were infected with the same vanB Enterococcus faecium strain. VanA resistance was not detected until 1993, but in 1996, the ratio of vanA to vanB was 2.2:1. Over time, 8 vanA strains were detected; a 35- or 40-kb conjugative vanA plasmid was found in 4 of the 8 strains. Clonal spread was a major factor in the establishment of endemicity. Transfer of genetic elements and introduction of new strain types were detected less often. However, these events may have been equally important evolutionarily.     

Recycled water: potential health risks from volatile organic compounds and use of 1,4-dichlorobenzene as treatment performance indicator

Characterisation of the concentrations and potential health risks of chemicals in recycled water is important if this source of water is to be safely used to supplement drinking water sources. This research was conducted to: (i) determine the concentration of volatile organic compounds (VOCs) in secondary treated effluent (STE) and, post-reverse osmosis (RO) treatment and to; (ii) assess the health risk associated with VOCs for indirect potable reuse (IPR). Samples were examined pre and post-RO in one full-scale and one pilot plant in Perth, Western Australia. Risk quotients (RQ) were estimated by expressing the maximum and median concentration as a function of the health value. Of 61 VOCs analysed over a period of three years, twenty one (21) were detected in STE, with 1,4-dichlorobenzene (94%); tetrachloroethene (88%); carbon disulfide (81%) and; chloromethane (58%) most commonly detected. Median concentrations for these compounds in STE ranged from 0.81 μg/L for 1,4-dichlorobenzene to 0.02 μg/L for carbon disulphide. After RO, twenty six (26) VOCs were detected, of which 1,4-dichlorobenzene (89%); acrylonitrile (83%) chloromethane (63%) and carbon disulfide (40%) were the more frequently detected. RQ(max) were all below health values in the STE and after RO. Median removal efficiency for RO was variable, ranging from −77% (dichlorodifluoromethane) to 91.2% (tetrachloroethene). The results indicate that despite the detection of VOCs in STE and after RO, their human health impact in IPR is negligible due to the low concentrations detected. The results indicate that 1,4-dichlorobenzene is a potential treatment chemical indicator for assessment of VOCs in IPR using RO treatment.     

Challenges in nucleic acid‐lipid films for transfection

The use of surface‐based methods for the delivery of therapeutics has recently generated increasing interest. These platforms have tremendous potential to minimize detrimental side effects associated with systemic delivery by localizing the therapeutic vehicle, and thus provide higher local doses for improved efficacy. Cationic lipids are one of the most commonly used synthetic carriers for the delivery of genetic cargo, such as DNA and RNA. However, reports on the use of lipid‐based films for gene delivery are scarce. Here we investigate the use of a lipid‐based film for the in vitro delivery of plasmid DNA. Solid DNA‐lipid films show very low levels of transfection, while identical complexes prepared for bolus delivery provide high levels of transfection when used directly. We investigate the mechanism, whereby the activity of these solid‐state films is lost and suggest methods for circumventing these challenges and restoring the efficacy of these films as gene delivery platforms. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3203–3213, 2013     

Genes Involved in the Endoplasmic Reticulum N-Glycosylation Pathway of the Red Microalga Porphyridium sp.: A Bioinformatic Study

N-glycosylation is one of the most important post-translational modifications that influence protein polymorphism, including protein structures and their functions. Although this important biological process has been extensively studied in mammals, only limited knowledge exists regarding glycosylation in algae. The current research is focused on the red microalga Porphyridium sp., which is a potentially valuable source for various applications, such as skin therapy, food, and pharmaceuticals. The enzymes involved in the biosynthesis and processing of N-glycans remain undefined in this species, and the mechanism(s) of their genetic regulation is completely unknown. In this study, we describe our pioneering attempt to understand the endoplasmic reticulum N-Glycosylation pathway in Porphyridium sp., using a bioinformatic approach. Homology searches, based on sequence similarities with genes encoding proteins involved in the ER N-glycosylation pathway (including their conserved parts) were conducted using the TBLASTN function on the algae DNA scaffold contigs database. This approach led to the identification of 24 encoded-genes implicated with the ER N-glycosylation pathway in Porphyridium sp. Homologs were found for almost all known N-glycosylation protein sequences in the ER pathway of Porphyridium sp.; thus, suggesting that the ER-pathway is conserved; as it is in other organisms (animals, plants, yeasts, etc.).     

Intercellular junctions in FANFT-induced carcinomas of rat urinary bladder in tissue culture: in situ thin-section, freeze-fracture, and scanning electron microscopy studies.

This paper describes a set of simple methods for comparative light and electron microscopy studies on tissue cultured tumour cells derived from both noninvasive and invasive carcinogen-induced rat urinary bladder carcinomas. Cells are grown on Thermanox plastic coverslips and fixed in situ. Each plastic coverslip is then divided with scissors into four parts: the first is processed for light microscopy, the second for thin-section electron microscopy, the third for freeze-fracture electron microscopy, and the fourth for scanning electron microscopy. In some experiments, portions of the culture which have first been examined by light microscopy are subsequently prepared for electron microscopy. In this way, the culture conditions are kept constant and comparison of structural features (i.e. intercellular junctions) by several preparative techniques is possible. Noninvasive and invasive rat bladder tumour cells, characterized by numerous pleomorphic microvilli, have normal zonulae occludentes at the apices of lateral surfaces of tumour cells in all cultures. In some areas of invasive tumour cells, occludens junctions are focally attenuated, consisting of only one or two strands, and occasionally the strands are discontinuous. Gap junctions, type PF-1, as well as numerous demosomes are present in all cell lines. Thus, intercellular junctions in noninvasive and invasive rate bladder epithelial cell lines bear a striking resemblance to those previously described in the comparable solid primary tumours. These culture systems may be useful for studying factors which influence the formation of intercellular junctions during malignant transformation.