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41.
S. Devin McLennan Lauren A. Peterson Joan B. Rose 《Applied and environmental microbiology》2009,75(22):7283-7286
Four point-of-use disinfection technologies for treating sewage-contaminated well water were compared. Three systems, based on flocculant-disinfectant packets and N-halamine chlorine and bromine contact disinfectants, provided a range of 4.0 to >6.6 log10 reductions (LR) of naturally occurring fecal indicator and heterotrophic bacteria and a range of 0.9 to >1.9 LR of coliphage.Disasters and flooding can overwhelm sanitation infrastructure, leading to sewage contamination of potable waters. This may be routine during the wet season in many parts of the world and spreads numerous waterborne diseases (21). Point-of-use (POU) water treatment has reduced the incidence of diarrheal disease when used for household drinking water (3, 4, 6, 13) and is now being promoted for disaster relief. While POU systems have recently been reviewed (14), to our knowledge there has been no direct, experimental comparison for treating actual sewage-contaminated waters. In this study, the efficacies of four POU disinfection systems (based on sodium dichloroisocyanurate [NaDCC] tablets, a flocculent-disinfectant powder, and chlorine and bromine contact disinfectant cartridges) in reducing the concentrations of six microbial indicators in well water contaminated with raw sewage were compared.The NaDCC tablets (67 mg; Aquatabs; Medentech, Wexford, Ireland), used for disinfection in low-turbidity water, have shown preliminary efficacy for routine household drinking water treatment (3, 4). The flocculant-disinfectant packet (4 g; PUR; Procter & Gamble Co., Cincinnati, OH) includes Fe2(SO4)3, bentonite, Na2CO3, chitosan, polyacrylamide, KMnO4, and Ca(OCl)2 (13). It achieved >7.3 log10 reductions (LR) of 24 bacteria species; >4.6 LR of poliovirus and rotavirus in EPA no. 2 test water (turbidity, >30 nephelometric turbidity units [NTU]) (15); and reduced diarrheal illness in Guatemala, Liberia, Kenya, and Pakistan (6, 7, 11, 13).HaloPure canisters (Eureka Forbes, Mumbai, India) contain N-halamine polymer disinfectant beads, poly[1,2-dichloro-5-methyl-5-(4′-vinylphenyl)hydrantoin] for chlorine canisters, and poly[1,2-dibromo-5-methyl-5-(4′-vinylphenyl)hydrantoin] for bromine canisters. Seeded laboratory trials achieved >6.8 LR for Escherichia coli and Staphylococcus aureus as water was passed through the canisters (2). The Cl-contact (producing residuals ranging from 0 to 0.6 mg/liter) and Br-contact (with residuals of 0.68 to 1.8 mg/liter) disinfectants achieved 2.9 LR and 5.0 LR of the bacteriophage MS2, respectively, and 27.5% and 88.5% reductions of the algal toxin microcystin, respectively (5).Sewage-contaminated water was prepared by mixing 9 liters of potable, nonchlorinated well water (pH 7.8; turbidity, 0.33 NTU; Williamston, MI) with 1 liter of raw sewage (City of East Lansing Wastewater Treatment Plant, MI) with an average pH of 6.6 ± 0.1, a biochemical oxygen demand of 144 ± 36 mg/liter, a concentration of total suspended solids of 146 ± 31 mg/liter, and a turbidity of 132 ± 12 NTU. Three disinfection trials were conducted at room temperature for each POU system on three different days to allow for variance in sewage strength. The turbidities of 1:10 dilutions of raw sewage averaged 7.5 ± 2.0 NTU. Table Table11 lists the indicator microorganism concentrations in the influent and effluent for each system.
Open in a separate windowaValues shown are numbers of CFU/ml except those for coliphage, which are numbers of PFU/ml. The percentage of samples below the detection limit (n = 3 for all systems) is 0% if not shown.All systems were used in accordance with the manufacturer''s directions for 10 liters of water. For NaDCC trials, one tablet was added and allowed 30 min of contact time (total dose of 3.2 mg/liter of hypochlorite; in deionized water, one tablet produced 2.1 mg/liter free Cl residual). For flocculant-disinfectant trials, one packet was added, stirred vigorously for 5 min, strained through cheesecloth after 10 min, and allowed 20 min of further contact time. The amount of hypochlorite included in one packet was not indicated, but one packet provided 1.5 mg/liter free Cl residual in 10 liters of deionized water. Samples were taken at 1, 3, 5, 10, 15, and 30 min for both systems.For the Cl-contact and Br-contact trials, disinfectant cartridges were installed in AquaSure housings consisting of an upper reservoir for influent, which flows by gravity through the disinfectant cartridge to a lower reservoir with a tap for dispensing (Fig. (Fig.1).1). The housings usually include cloth and activated charcoal prefilters, but these were removed in order to directly evaluate the disinfectant. With the tap open, 10 liters of influent was added and samples were collected at first flow (6 to 12 min) and after 15 and 30 min of flow. A single chlorine canister was used for all trials; the bromine canister was replaced for the third trial because the original clogged.Open in a separate windowFIG. 1.Flow schematic for contact disinfectant cartridges. Arrows indicate the directions of water flow from the upper reservoir (U), through the halogen (chlorine or bromine) disinfectant cartridge (H) containing packed N-halamine beads (N), to the lower reservoir (L) and out through the open tap.Microbial indicators in the influent and effluent (collection tubes contained sodium thiosulfate) in triplicate were quantified as numbers of CFU/ml by using mENDO agar for total coliforms (9), mHPC agar for heterotrophic plate counts (8), mTEC medium for E. coli (19), mEI agar for the genus Enterococcus (18), and mCP agar for the genus Clostridium (1) (Becton, Dickinson and Co., Franklin Lakes, NJ). Coliphage (PFU/ml) were measured with a double agar overlay assay, EPA method 1601 (17). Residuals (mg/liter) were measured using a Hach chlorine (free and total) test kit, model CN66 (Hach Co., Loveland, CO) (used for bromine in accordance with Hach method 8016 [10], with the instrument reading multiplied by 2.25 [the ratio of the atomic weights of bromine and chlorine], as advised by Hach Co. technical support).Comparison of water quality levels was done at 30 minutes. LR were calculated, with zeros replaced with the detection limits (Fig. (Fig.2).2). All POU systems reduced microbial concentrations below the detection limit in some trials (Table (Table1),1), making the calculated reductions the lower bound for those trials.Open in a separate windowFIG. 2.Average LR of naturally occurring microorganisms at 30 min for sewage-contaminated well water (1:10 dilution of raw sewage in well water) with the use of four POU disinfection systems (error bars represent 1 standard error). * indicates that effluent was below the limit of detection for all samples. Limit of detection was substituted to calculate LR and actual reductions may be greater than shown.Average LR for each POU system were compared using two-way analysis of variance with post hoc least-significant-difference (LSD) tests, performed with SPSS 11.0.1 (SPSS, Inc.). LR at 30 min differed significantly between systems (analysis of variance; F3,5 = 20.6; P < 0.001). There was no significant difference between the LR achieved by flocculant-disinfectant and contact disinfectants (LSD; mean difference, 0.2 to 0.5 LR; P > 0.05), while the NaDCC tablets induced significantly lower reductions (LSD; mean difference, 1.5 to 2.0 LR; P < 0.001).There was detectable residual free chlorine after 30 min for one NaDCC trial (0.4 mg/liter) and two flocculant-disinfectant trials (0.1 and 0.4 mg/liter). No contact disinfectant trial produced a measurable residual.No system in this study reliably produced residuals for safe storage after POU treatment or ideal virus reduction. Except for the NaDCC system, the POU systems achieved approximately 5.5 LR for E. coli and coliforms, 4.5 LR for enterococci, 4.0 LR for heterotrophs, 2.5 LR for clostridia, and 1.0 LR for coliphage. Coliphage was reduced below detection limits in all trials with Br-contact, similar to what was found in previous research (5). Bromine disinfection has proved safe and effective for large-scale maritime applications, like U.S. Navy vessels (20), and appears promising for household treatment. Further assessment of the Br-contact system is warranted, as is field comparison of POU systems in disaster relief. 相似文献
TABLE 1.
Concentrations of influent and 30-min-effluent microorganisms for POU disinfectant systems treating sewage-contaminated waterMicroorganism group | Geometric mean concn (range) [% of samples below detection limit]a | |||||||
---|---|---|---|---|---|---|---|---|
NaDCC | Flocculant-disinfectant | Cl-contact | Br-contact | |||||
Influent | Effluent at 30 min | Influent | Effluent at 30 min | Influent | Effluent at 30 min | Influent | Effluent at 30 min | |
Total coliforms | 2.7 × 104 (6.7 × 103 to 7.6 × 104) | 4.3 (4.0 × 10−2 to 1.6 × 102) | 1.7 × 104 (1.2 × 104 to 2.7 × 104) | 4.0 × 10−2 (<1.0 × 10−2 to 2.4 × 10−1) [33] | 2.9 × 104 (2.3 × 104 to 4.0 × 104) | <1.0 × 10−2 [100] | 4.5 × 104 (1.9 × 104 to 7.2 × 104) | 1.1 × 10−2 (<1.0 × 10−2 to 1.3 × 10−2) [66] |
Heterotrophic plate counts | 8.7 × 104 (2.7 × 104 to 1.8 × 105) | 6.4 × 101 (2.1 × 101 to 4.5 × 102) | 8.9 × 104 (2.9 × 104 to 4.3 × 105) | 8.5 (4.7 to 2.7 × 101) | 6.6 × 104 (3.5 × 104 to 1.1 × 105) | 3.9 (3.5 to 4.2) | 8.3 × 104 (2.4 × 104 to 2.0 × 105) | 4.6 (2.2 to 7.7) |
E. coli | 3.3 × 103 (7.7 × 102 to 1.1 × 104) | 1.8 × 101 (9.0 × 10−1 to 5.3 × 102) | 6.7 × 103 (2.3 × 103 to 4.3 × 104) | 1.1 × 10−2 (<1.0 × 10−2 to 1.3 × 10−2) [66] | 4.7 × 103 (2.3 × 103 to 1.1 × 104) | <1.0 × 10−2 [100] | 1.5 × 104 (6.3 × 103 to 4.6 × 104) | <1.0 × 10−2 [100] |
Enterococci | 8.8 × 102 (5.7 × 102 to 1.3 × 103) | 2.3 (<1.0 × 10−2 to 4.9 × 101) [33] | 6.3 × 102 (5.0 × 102 to 8.7 × 102) | <1.0 × 10−2 [100] | 9.9 × 102 (5.3 × 102 to 1.7 × 103) | <1.0 × 10−2 [100] | 1.3 × 103 (7.3 × 102 to 2.3 × 103) | <1.0 × 10−2 [100] |
Clostridia | 1.6 × 102 (6.0 × 101 to 3.0 × 102) | 6.4 (6.7 × 10−1 to 7.7 × 101) | 2.0 × 102 (7.0 × 101 to 6.0 × 102) | 7.9 × 10−1 (4.5 × 10−1 to 1.4) | 3.4 × 101 (2.0 × 101 to 6.3 × 101) | 2.4 × 10−2 (<1.0 × 10−2 to 6.0 × 10−2) [33] | 4.4 × 101 (2.7 × 101 to 9.3 × 101) | 7.4 × 10−2 (<1.0 × 10−2 to 3.6 × 10−1) [33] |
Coliphage | 1.5 × 102 (1.2 × 102 to 2.2 × 102) | 3.1 × 101 (<1.0 to 1.8 × 102) [33] | 1.4 × 102 (1.3 × 102 to 1.4 × 102) | 1.9 × 101 (<1.0 to 1.1 × 102) [33] | 9.4 × 101 (4.3 × 101 to 1.6 × 102) | 7.3 (1.3 to 4.7 × 101) | 7.7 × 101 (4.0 × 101 to 1.2 × 102) | <1.0 [100] |
42.
Michael F McNitt-Gray Luc M Bidaut Samuel G Armato III Charles R Meyer Marios A Gavrielides Charles Fenimore Geoffrey McLennan Nicholas Petrick Binsheng Zhao Anthony P Reeves Reinhard Beichel Hyun-Jung Kim Lisa Kinnard 《Translational oncology》2009,2(4):216-222
RATIONALE AND OBJECTIVES: This article describes issues and methods that are specific to the measurement of change in tumor volume as measured from computed tomographic (CT) images and how these would relate to the establishment of CT tumor volumetrics as a biomarker of patient response to therapy. The primary focus is on the measurement of lung tumors, but the approach should be generalizable to other anatomic regions. MATERIALS AND METHODS: The first issues addressed are the various sources of bias and variance in the measurement of tumor volumes, which are discussed in the context of measurement variation and its impact on the early detection of response to therapy. RESULTS AND RESOURCES: Research that seeks to identify the magnitude of some of these sources of error is ongoing, and several of these efforts are described herein. In addition, several resources for these investigations are being made available through the National Institutes of Health-funded Reference Image Database to Evaluate Response to therapy in cancer project, and these are described as well. Other measures derived from CT image data that might be predictive of patient response are described briefly, as well as the additional issues that each of these metrics may encounter in real-life applications. CONCLUSIONS: The article concludes with a brief discussion of moving from the assessment of measurement variation to the steps necessary to establish the efficacy of a metric as a biomarker for response. 相似文献
43.
Paul M Kulesa Jessica M Teddy Miranda Smith Richard Alexander Cameron HJ Cooper Rusty Lansford Rebecca McLennan 《BMC developmental biology》2010,10(1):101
Background
Tracing cell dynamics in the embryo becomes tremendously difficult when cell trajectories cross in space and time and tissue density obscure individual cell borders. Here, we used the chick neural crest (NC) as a model to test multicolor cell labeling and multispectral confocal imaging strategies to overcome these roadblocks. 相似文献44.
Hanna J. McLennan Avishkar Saini Georgina M. Sylvia Erik P. Schartner Kylie R. Dunning Malcolm S. Purdey Tanya M. Monro Andrew D. Abell Jeremy G. Thompson 《Journal of biophotonics》2020,13(3)
Unfertilised eggs (oocytes) release chemical biomarkers into the medium surrounding them. This provides an opportunity to monitor cell health and development during assisted reproductive processes if detected in a non‐invasive manner. Here we report the measurement of pH using an optical fibre probe, OFP1, in 5 μL drops of culture medium containing single mouse cumulus oocyte complexes (COCs). This allowed for the detection of statistically significant differences in pH between COCs in culture medium with no additives and those incubated with either a chemical (cobalt chloride) or hormonal treatment (follicle stimulating hormone); both of which serve to induce the release of lactic acid into the medium immediately surrounding the COC. Importantly, OFP1 was shown to be cell‐safe with no inherent cell toxicity or light‐induced phototoxicity indicated by negative DNA damage staining. Pre‐measurement photobleaching of the probe reduced fluorescence signal variability, providing improved measurement precision (0.01‐0.05 pH units) compared to previous studies. This optical technology presents a promising platform for the measurement of pH and the detection of other extracellular biomarkers to assess cell health during assisted reproduction. 相似文献
45.
Bruce M Carlson Jean A Carlson Eduard I Dedkov Ian S McLennan 《The journal of histochemistry and cytochemistry》2003,51(9):1113-1118
Caveolin-3, a muscle-specific member of the caveolin family, is strongly localized to the neuromuscular junction (NMJ) in adult rat muscle fibers, where it co-localizes with alpha-bungarotoxin staining. In 24-month-old rats, less distinct staining corresponds with the normal aging changes in the NMJ. After denervation, the pattern and intensity of staining begin to break up as early as 3 days, and by 10 days little staining remains. The functional implications of this concentration of caveolin-3 at the NMJ remain obscure, but it is possible that its absence could account for some of the phenotypic characteristics of individuals with caveolin-3 mutations. 相似文献
46.
Citizen science in schools: Engaging students in research on urban habitat for pollinators
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Manu E. Saunders Erin Roger William L. Geary Floret Meredith Dustin J. Welbourne Alex Bako Emily Canavan Francesca Herro Charlotte Herron Olivia Hung Madeline Kunstler Jade Lin Natasha Ludlow Mayling Paton Sunny Salt Tallulah Simpson Ariana Wang Nikki Zimmerman Kalani B. Drews Hayley F. Dawson Lachlan W. J. Martin Jack B. Sutton Chiquita C. Webber Amy L. Ritchie Leigham D. Berns Bella A. Winch Holly R. Reeves Eiron C. McLennan Jordan M. Gardner Charli G. Butler Emily I. Sutton Max M. Couttie Jake B. Hildebrand Isabella A. Blackney Justine A. Forsyth Deborah M. Keating Angela T. Moles 《Austral ecology》2018,43(6):635-642
Citizen science can play an important role in school science education. Citizen science is particularly relevant to addressing current societal environmental sustainability challenges, as it engages the students directly with environmental science and gives students an understanding of the scientific process. In addition, it allows students to observe local representations of global challenges. Here, we report a citizen science programme designed to engage school‐age children in real‐world scientific research. The programme used standardized methods deployed across multiple schools through scientist–school partnerships to engage students with an important conservation problem: habitat for pollinator insects in urban environments. Citizen science programmes such as the programme presented here can be used to enhance scientific literacy and skills. Provided key challenges to maintain data quality are met, this approach is a powerful way to contribute valuable citizen science data for understudied, but ecologically important study systems, particularly in urban environments across broad geographical areas. 相似文献
47.
Thomas GH; Newbern EC; Korte CC; Bales MA; Muse SV; Clark AG; Kiehart DP 《Molecular biology and evolution》1997,14(12):1285-1295
Many structural, signaling, and adhesion molecules contain tandemly
repeated amino acid motifs. The alpha-actinin/spectrin/dystrophin
superfamily of F-actin-crosslinking proteins contains an array of triple
alpha-helical motifs (spectrin repeats). We present here the complete
sequence of the novel beta-spectrin isoform beta(Heavy)- spectrin (beta H).
The sequence of beta H supports the origin of alpha- and beta-spectrins
from a common ancestor, and we present a novel model for the origin of the
spectrins from a homodimeric actin-crosslinking precursor. The pattern of
similarity between the spectrin repeat units indicates that they have
evolved by a series of nested, nonuniform duplications. Furthermore, the
spectrins and dystrophins clearly have common ancestry, yet the repeat unit
is of a different length in each family. Together, these observations
suggest a dynamic period of increase in repeat number accompanied by
homogenization within each array by concerted evolution. However, today,
there is greater similarity of homologous repeats between species than
there is across repeats within species, suggesting that concerted evolution
ceased some time before the arthropod/vertebrate split. We propose a
two-phase model for the evolution of the spectrin repeat arrays in which an
initial phase of concerted evolution is subsequently retarded as each new
protein becomes constrained to a specific length and the repeats diverge at
the DNA level. This evolutionary model has general applicability to the
origins of the many other proteins that have tandemly repeated motifs.
相似文献
48.
Higher‐order assemblies of oligomeric cargo receptor complexes form the membrane scaffold of the Cvt vesicle
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Arjen J Jakobi Abul K Tarafder Yury S Bykov Andrea Picco Wanda Kukulski Jan Kosinski Wim JH Hagen Arvind C Ravichandran Matthias Wilmanns Marko Kaksonen John AG Briggs Carsten Sachse 《EMBO reports》2016,17(7):1044-1060
Selective autophagy is the mechanism by which large cargos are specifically sequestered for degradation. The structural details of cargo and receptor assembly giving rise to autophagic vesicles remain to be elucidated. We utilize the yeast cytoplasm‐to‐vacuole targeting (Cvt) pathway, a prototype of selective autophagy, together with a multi‐scale analysis approach to study the molecular structure of Cvt vesicles. We report the oligomeric nature of the major Cvt cargo Ape1 with a combined 2.8 Å X‐ray and negative stain EM structure, as well as the secondary cargo Ams1 with a 6.3 Å cryo‐EM structure. We show that the major dodecameric cargo prApe1 exhibits a tendency to form higher‐order chain structures that are broken upon interaction with the receptor Atg19 in vitro. The stoichiometry of these cargo–receptor complexes is key to maintaining the size of the Cvt aggregate in vivo. Using correlative light and electron microscopy, we further visualize key stages of Cvt vesicle biogenesis. Our findings suggest that Atg19 interaction limits Ape1 aggregate size while serving as a vehicle for vacuolar delivery of tetrameric Ams1. 相似文献
49.
In the course of a freeze-cleave study on intercellular junctions in the regenerating rat liver, we observed an unusual array of intramembranous particles located in regions of contact between endothelial cells lining the hepatic sinusoids. These arrays were characterized by an accumulation of particles which resembled a zonula occludens in their linear deployment but differed in that the contact regions were composed of individual particles which remained separated from each other by regular particle-free intervals. 相似文献
50.
I S McLennan 《Developmental biology》1983,97(1):229-238
The pattern of innervation in 13 chicken hindlimb muscles was studied at various stages of development in order to examine the mechanisms which regulate its formation. The pattern of innervation was visualized by examining the distribution of fiber types within each muscle. It was found that the fiber type which a myotube acquired was influenced by both its time of formation and its position within a muscle. The earliest generation of myotubes (primary) had a marked tendency to become type I fibers, whereas, in contrast, the later generation of myotubes (secondary) tended to differentiate into type II fibers. There were regions of muscle, however, in which primary myotubes differentiated into type II fibers and other regions in which secondary myotubes acquired type I characteristics. During the development of some muscles the pattern of fiber types changed as a result of either a selective loss of type I fibers or, in other cases, a rearrangement of some of the initial neuromuscular contacts. These observations are consistent with the pattern of innervation of a muscle being established as a result of differential projection patterns of fast and slow motoneurons and the existence of some type of chemoaffinity where particular myotubes are preferentially innervated by particular motoneurons. 相似文献