Filter Elution Research Articles

Environmental Surveillance for Polioviruses in Haïti (2017-2019): The Dynamic Process for the Establishment and Monitoring of Sampling Sites.

Haïti is at risk for wild poliovirus (WPV) importation and circulation, as well as vaccine-derived poliovirus (VDPV) emergence. Environmental surveillance (ES) for polioviruses was established in Port au Prince and Gonaïves in 2016. During 2017–2019, initial ES sites were re-evaluated, and ES was expanded into Cap Haïtien and Saint Marc. Wastewater samples and data on weather, hour of collection, and sample temperature and pH were collected every 4 weeks during March 2017–December 2019 (272 sampling events) from 21 sites in Cap Haïtien, Gonaïves, Port au Prince, and Saint Marc. Samples were processed for the detection of polio and non-polio enteroviruses using the two-phase and “Concentration and Filter Elution” methodologies. Polioviruses were serotyped and underwent intra-typic characterization. No WPV or VDPVs were isolated. Sabin-like polioviruses (oral vaccine strain) of serotypes 1 and 3 were sporadically detected. Five of six (83%), one of six (17%), five of six (83%), and two of three (67%) sites evaluated in Cap Haïtien, Gonaïves, Port au Prince, and Saint Marc, respectively, had enterovirus isolation from >50% of sampling events; these results and considerations, such as watershed population size and overlap, influence of sea water, and excessive particulates in samples, were factors in site retention or termination. The evaluation of 21 ES sampling sites in four Haïtian cities led to the termination of 11 sites. Every-four-weekly sampling continues at the remaining 10 sites across the four cities as a core Global Polio Eradication Initiative activity.

Piloting and implementation of quality assessment and quality control procedures in RBC-Omics: a large multi-center study of red blood cell hemolysis during storage.

The major aims of the RBC-Omics study were to evaluate the genomic and metabolomic determinants of spontaneous and stress-induced hemolysis during RBC storage. This study was unique in scale and design to allow evaluation of RBC donations from a sufficient number of donors across the spectrum of race, ethnicity, sex, and donation intensity. Study procedures were carefully piloted, optimized, and controlled to enable high-quality data collection. The enrollment goal of 14,000 RBC donors across four centers, with characterization of RBC hemolysis across two testing laboratories, required rigorous piloting and optimization and establishment of a quality assurance (QA) and quality control (QC) program. Optimization of WBC elution from leukoreduction (LR) filters, development and validation of small-volume transfer bags, impact of manufacturing and sample-handling procedures on hemolysis parameters, and testing consistency across laboratories and technicians and over time were part of this quality assurance/quality control program. LR filter elution procedures were optimized for obtaining DNA for analysis. Significant differences between standard and pediatric storage bags led to use of an alternative LR-RBC transfer bag. The impact of sample preparation and freezing methods on metabolomics analyses was evaluated. Proficiency testing monitored and documented testing consistency across laboratories and technicians. Piloting and optimization, and establishment of a robust quality assurance/quality control program documented process consistency throughout the study and was essential in executing this large-scale multicenter study. This program supports the validity of the RBC-Omics study results and a sample repository that can be used in future studies.

Polyvinylidene Fluoride Micropore Membranes as Solid-Phase Extraction Disk for Preconcentration of Nanoparticulate Silver in Environmental Waters.

Efficient separation and preconcentration of trace nanoparticulate silver (NAg) from large-volume environmental waters is a prerequisite for reliable analysis and therefore understanding the environmental processes of silver nanoparticles (AgNPs). Herein, we report the novel use of polyvinylidene fluoride (PVDF) filter membrane for disk-based solid phase extraction (SPE) of NAg in 1 L of water samples with the disk-based SPE system, which consists of a syringe pump and a syringe filter holder to embed the filter membrane. While the PVDF membrane can selectively adsorb NAg in the presence of Ag+, aqueous solution of 2% (m/v) FL-70 is found to efficiently elute NAg. Analysis of NAg is performed following optimization of filter membrane and elution conditions with an enrichment factor of 1000. Additionally, transmission electron microscopy (TEM), UV-vis spectroscopy, and size-exclusion chromatography coupled with ICP-MS (SEC-ICP-MS) analysis showed that the extraction gives rise to no change in NAg size or shape, making this method attractive for practical applications. Furthermore, feasibility of the protocol is verified by applying it to extract NAg in four real waters with recoveries of 62.2-80.2% at 0.056-0.58 μg/L spiked levels. This work will facilitate robust studies of trace NAg transformation and their hazard assessments in the environment.

EPA Method 1615. Measurement of Enterovirus and Norovirus Occurrence in Water by Culture and RT-qPCR. II. Total Culturable Virus Assay

A standardized method is required when national studies on virus occurrence in environmental and drinking waters utilize multiple analytical laboratories. The U.S Environmental Protection Agency’s (USEPA) Method 1615 was developed with the goal of providing such a standard for measuring Enterovirus and Norovirus in these waters. Virus is concentrated from water using an electropositive filter, eluted from the filter surface with beef extract, and then concentrated further using organic flocculation. Herein we present the protocol from Method 1615 for filter elution, secondary concentration, and measurement of total culturable viruses. A portion of the concentrated eluate from each sample is inoculated onto ten replicate flasks of Buffalo Green Monkey kidney cells. The number of flasks demonstrating cytopathic effects is used to quantify the most probable number (MPN) of infectious units per liter. The method uses a number of quality controls to increase data quality and to reduce interlaboratory and intralaboratory variation. Laboratories must meet defined performance standards. Method 1615 was evaluated by examining virus recovery from reagent-grade and ground waters seeded with Sabin poliovirus type 3. Mean poliovirus recoveries with the total culturable assay were 111% in reagent grade water and 58% in groundwaters.

EPA Method 1615. Measurement of Enterovirus and Norovirus Occurrence in Water by Culture and RT-qPCR. II. Total Culturable Virus Assay.

A standardized method is required when national studies on virus occurrence in environmental and drinking waters utilize multiple analytical laboratories. The U.S Environmental Protection Agency’s (USEPA) Method 1615 was developed with the goal of providing such a standard for measuring Enterovirus and Norovirus in these waters. Virus is concentrated from water using an electropositive filter, eluted from the filter surface with beef extract, and then concentrated further using organic flocculation. Herein we present the protocol from Method 1615 for filter elution, secondary concentration, and measurement of total culturable viruses. A portion of the concentrated eluate from each sample is inoculated onto ten replicate flasks of Buffalo Green Monkey kidney cells. The number of flasks demonstrating cytopathic effects is used to quantify the most probable number (MPN) of infectious units per liter. The method uses a number of quality controls to increase data quality and to reduce interlaboratory and intralaboratory variation. Laboratories must meet defined performance standards. Method 1615 was evaluated by examining virus recovery from reagent-grade and ground waters seeded with Sabin poliovirus type 3. Mean poliovirus recoveries with the total culturable assay were 111% in reagent grade water and 58% in groundwaters.

DNA Double-Strand Break Analysis by γ-H2AX Foci: A Useful Method for Determining the Overreactors to Radiation-Induced Acute Reactions Among Head-and-Neck Cancer Patients

Interindividual variability in normal tissue toxicity during radiation therapy is a limiting factor for successful treatment. Predicting the risk of developing acute reactions before initiation of radiation therapy may have the benefit of opting for altered radiation therapy regimens to achieve minimal adverse effects with improved tumor cure. DNA double-strand break (DSB) induction and its repair kinetics in lymphocytes of head-and-neck cancer patients undergoing chemoradiation therapy was analyzed by counting γ-H2AX foci, neutral comet assay, and a modified version of neutral filter elution assay. Acute normal tissue reactions were assessed by Radiation Therapy Oncology Group criteria. The correlation between residual DSBs and the severity of acute reactions demonstrated that residual γ-H2AX foci in head-and-neck cancer patients increased with the severity of oral mucositis and skin reaction. Our results suggest that γ-H2AX analysis may have predictive implications for identifying the overreactors to mucositis and skin reactions among head-and-neck cancer patients prior to initiation of radiation therapy.

Glass Wool Filters for Concentrating Waterborne Viruses and Agricultural Zoonotic Pathogens

The key first step in evaluating pathogen levels in suspected contaminated water is concentration. Concentration methods tend to be specific for a particular pathogen group, for example US Environmental Protection Agency Method 1623 for Giardia and Cryptosporidium, which means multiple methods are required if the sampling program is targeting more than one pathogen group. Another drawback of current methods is the equipment can be complicated and expensive, for example the VIRADEL method with the 1MDS cartridge filter for concentrating viruses. In this article we describe how to construct glass wool filters for concentrating waterborne pathogens. After filter elution, the concentrate is amenable to a second concentration step, such as centrifugation, followed by pathogen detection and enumeration by cultural or molecular methods. The filters have several advantages. Construction is easy and the filters can be built to any size for meeting specific sampling requirements. The filter parts are inexpensive, making it possible to collect a large number of samples without severely impacting a project budget. Large sample volumes (100s to 1,000s L) can be concentrated depending on the rate of clogging from sample turbidity. The filters are highly portable and with minimal equipment, such as a pump and flow meter, they can be implemented in the field for sampling finished drinking water, surface water, groundwater, and agricultural runoff. Lastly, glass wool filtration is effective for concentrating a variety of pathogen types so only one method is necessary. Here we report on filter effectiveness in concentrating waterborne human enterovirus, Salmonella enterica, Cryptosporidium parvum, and avian influenza virus.

Glass Wool Filters for Concentrating Waterborne Viruses and Agricultural Zoonotic Pathogens

The key first step in evaluating pathogen levels in suspected contaminated water is concentration. Concentration methods tend to be specific for a particular pathogen group, for example US Environmental Protection Agency Method 1623 for Giardia and Cryptosporidium1, which means multiple methods are required if the sampling program is targeting more than one pathogen group. Another drawback of current methods is the equipment can be complicated and expensive, for example the VIRADEL method with the 1MDS cartridge filter for concentrating viruses2. In this article we describe how to construct glass wool filters for concentrating waterborne pathogens. After filter elution, the concentrate is amenable to a second concentration step, such as centrifugation, followed by pathogen detection and enumeration by cultural or molecular methods. The filters have several advantages. Construction is easy and the filters can be built to any size for meeting specific sampling requirements. The filter parts are inexpensive, making it possible to collect a large number of samples without severely impacting a project budget. Large sample volumes (100s to 1,000s L) can be concentrated depending on the rate of clogging from sample turbidity. The filters are highly portable and with minimal equipment, such as a pump and flow meter, they can be implemented in the field for sampling finished drinking water, surface water, groundwater, and agricultural runoff. Lastly, glass wool filtration is effective for concentrating a variety of pathogen types so only one method is necessary. Here we report on filter effectiveness in concentrating waterborne human enterovirus, Salmonella enterica, Cryptosporidium parvum, and avian influenza virus.

Protective Effects of Tannic Acid against Methomyl-Induced-Oxidative Stress

Methomyl carbamate is a pesticide widely used in the control of insects. The present work aims at studying the effect of tannic acid on the antioxidant system of methomyl-treated-mice. Swiss albino mice were intraperitoneally administered a single dose of methomyl (7 mg/Kg b.wt). Mice of another group were injected with tannic acid (20 mg/ Kg b.wt.) 3 hrs before methomyl intoxication. After 24 hours, methomyl exposure resulted in significant increase in lactic dehydrogenase activity (LDH). The antioxidant capacity of hepatic cells in terms of the activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione-S-transferase (GST) and glutathione (GSH) content was diminished. It appears that methomyl exerts its toxic effect via peroxidative damage to hepatic, renal and splenic cell membranes. Also, methomyl induced DNA damage in these organs as detected by alkaline filter elution technique. The distribution of methomyl in different organs of mice was detected by HPLC. Tannic acid administration prior to methomyl injection produced pronounced protective action against methomyl effects. It is observed that tannic acid enhances the endogenous antioxidant capacity of the cells by increasing the activities of SOD, CAT, GR and GST as well as increasing GSH content. The activity of LDH was decreased in liver and the damage of DNA was suppressed comparable to controls. In conclusion, this study concludes that tannic acid has a potential in mitigating most of the adverse effects induced by methomyl toxicity.

A modified fluorimetric neutral filter elution method for analyzing radiation-induced double strand break and repair

Neutral filter elution assay is one of the methods used for detection of DNA double strand breaks (DSBs). However, it is laborious, expensive, and hazardous (radiolabeled precursors for DSB detection and scintillation counter for quantification), making it a less preferred method for DSB detection. In the present study, an attempt was made to improve the existing neutral filter elution assay by making use of fluorescent dye (PicoGreen) and microfiltration assembly for eluting the fragmented DNA, thereby reducing the cost and time required for the assay. We studied the effect of dye dilution, pH conditions, and cell number as a part of method standardization. X-ray dose–response and repair kinetics in lymphocytes as well as cell lines were studied for validating the sensitivity of the assay. A linear dose–response relationship for DSBs was observed at a cell number of 4 × 10 5 cells, a dye dilution of 500-fold, and at pH 10. Repair kinetics revealed a time-dependent repair of DSBs up to 360 min of posttreatment, indicating its usefulness in DSB repair studies. In conclusion, the present modified method is more efficient (in terms of cell number), cost effective, less time-consuming, and less hazardous compared to the existing method.

258 POSTER Tricyclic triazin 1,4-dioxides: a new class of hypoxia-selective cytotoxins with improved extravascular transport compared to tirapazamine

SR 4233 (3-amino-1,2,4-benzotriazine 1,4-dioxide) is a bioreductive agent which exhibits highly selective killing of hypoxic cells in a variety of mammalian cell lines in vitro and in murine tumors in vivo. The selective toxicity of the drug results from its one-electron reduction under hypoxic conditions to form a free radical intermediate capable of damaging DNA, through the formation of strand breaks. Using the neutral filter elution assay, SR 4233 was found to be more efficient at producing DNA double strand breaks in Chinese hamster ovary (CHO) cells than an equitoxic dose of γ-rays. Drug and radiation sequencing experiments were also performed, with both cell survival and DNA strand break rejoining used as endpoints. As a result of these studies, we now describe two additional properties of SR .4233: (a) radiosensitization of aerobic cells in culture produced by hypoxic incubation with drug either before or after irradiation, and (b) the inhibition of subsequent rejoining of radiation-induced DNA double strand breaks after hypoxic pretreatment with drug. The magnitude of the radiosensitization produced did not vary for drug treatments which, when given alone, reduced cell survival over a range from 30% to 2%. The extent of DNA repair inhibition increased with increasing severity of the SR 4233 pretreatment, but was quite small for non-lethal drug exposures.

DNA–DNA cross-links contribute to the mutagenic potential of the mycotoxin patulin

The mycotoxin patulin (PAT), which occurs in various foods, induces mutations in cultured mammalian cells. However, the mechanism underlying the mutagenic potential of PAT is far from clear. In order to further clarify the mutagenic mode of action of PAT, we investigated the potential of PAT to induce DNA strand breaks, oxidative DNA modifications, and DNA–DNA cross-links using an alkaline filter elution technique and a fluorescence-based assay. In concentrations known to induce mutations in V79 cells (0.5–2.5 μM), PAT also induced DNA–DNA cross-links. In contrast, no effect on the number of DNA strand breaks (i.e., DNA single and double strand breaks as well as alkali-labile sites) or fpg-sensitive sites (i.e., oxidative DNA modifications) was observed in the non-cytotoxic concentration range. Thus, the present study demonstrates for the first time the direct reactivity of PAT towards DNA in a cellular system, which might have implications for the toxicological evaluation of this widespread mycotoxin.

Papel del selenio sobre la capacidad antioxidante en ratones tratados con metomil

Methomyl carbamate is a pesticide widely used in the control of insects. The present work aims at studying the effect of selenium on the antioxidant system of methomyl-treated mice. Swiss albino mice were intraperitoneally administered a single dose of methomyl (7 mg/Kg body weight). Mice of another group were injected with sodium selenite (5 pmole/Kg b.wt.) 7 days before methomyl intoxication. After 24 hours, methomyl exposure resulted in significant increase in lactic dehydrogenase activity (LDH). The antioxidant capacity of hepatic cells in terms of the activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione-S-transferase (GST) and glutathione (GSH) content was diminished. It appears that methomyl exerts its toxic effect via peroxidative damage to hepatic, renal and splenic cell membranes. Also, methomyl induced DNA damage in these organs as detected by alkaline filter elution technique. The distribution of methomyl in different organs of mice was detected by HPLC. Selenium administration prior to methomyl injection produced pronounced protective action against methomyl effects. It is observed that selenium enhances the endogenous antioxidant capacity of the cells by increasing the activities of SOD, CAT, GR and GST as well as increasing GSH content. The activity of LDH was decreased in blood and the damage of DNA was suppressed comparable to controls. In conclusion, the adverse effects of methomyl in mice could be ameliorated by selenium.

Filter Buffy Coats (FBC): A source of peripheral blood leukocytes recovered from leukocyte depletion filters

In compliance with federal regulations, blood banks routinely use leukocyte depletion filters to eliminate contaminating leukocytes from blood products such as red blood cell and platelet concentrates. We developed and optimized conditions to elute leukocytes adsorbed to these filters; resulting in leukocyte suspensions which we termed Filter Buffy Coats (FBCs). These Filter Buffy Coats can replace standard buffy coats for various research applications. After optimizing both the filter elution medium as well as elution protocols, we compared commonly used leukocyte depletion filters from four different manufacturers. Relative fractions as well as total recoveries of leukocyte subsets, such as lymphocytes, monocytes and granulocytes, found in Filter Buffy Coats were identified and compared among the filters as well as to standard buffy coats and whole blood. Flow cytometric analysis of Filter Buffy Coats confirmed the presence of T- and B-lymphocytes, NK cells and monocytes. Furthermore, a significant quantity of CD34 + hematopoietic stem or progenitor cells (HSC/HPC) was detected in Filter Buffy Coats prepared from different filters, thus making FBCs a valuable source for research on HSC/HPC. Colony assays revealed that most of these CD34 + cells are functional. Using immunomagnetic cell sorting (MACS), we isolated a variety of leukocyte populations from FBC mononuclear cells (Filter-PBMCs) including T lymphocytes (CD4 +, CD8 +, CD3 +), B lymphocytes (CD19 +), NK cells (CD56 +), HSC/HPC (CD34 +, CD133 +) or dendritic cells (BDCA-4 +). Functional properties of Filter-PBMCs, as well as of some of these isolated leukocyte populations, were confirmed using standard assays. In summary, Filter Buffy Coats are a valuable and convenient source of different peripheral leukocyte populations and can replace standard buffy coat preparations for research applications.

Monocyte enrichment of mononuclear apheresis preparations with a multistep back‐flush procedure on a cord blood filter

Monocytes or mononuclear cells have been investigated for the treatment of chronic wounds and spinal cord injuries, as well as serve as a source for dendritic or endothelial cell culture. Because these cells may have clinical benefit yet no rapid and inexpensive closed system for monocyte purification is commercially available, a method was investigated to enrich monocytes from mononuclear apheresis units using a cord blood filter. A 4-step method for monocyte enrichment was developed which involved 1) filtering a mononuclear apheresis unit through a cord blood filter, 2) chasing with medium to remove non-adherent residual cells and plasma, 3) back-flushing under low shear conditions to remove loosely adherent lymphocytes, and 4) back-flushing under high shear conditions to collect a fraction enriched in monocytes. Apheresis units and enriched monocyte preparations were characterized by cell count and differential, filter-isolated preparations were cryopreserved, and thawed preparations were assayed for viability, and phagocytosis. Enriched monocyte preparations were also assayed for inflammatory cytokines secretion and secretion of prostaglandin E2 during short-term culture. Monocytes were viable, capable of phagocytosis, and enriched using the multistep filter elution technique to represent 42 +/- 13-percent of white cells in the final preparation. Fifty-three-percent of monocytes were recovered in the final preparation, while total cell counts of red cells, platelets, neutrophils and lymphocytes were reduced to 3.0, 3.0, 4.5 and 16-percent, respectively, from levels present in mononuclear apheresis units. Filter enriched monocyte preparations secreted IL-8, IL-6, MCP-1, and MIP-1alpha, during short term culture. The use of a multi-step back flush procedure with a cord blood filter resulted in rapid enrichment of viable and functional monocytes from mononuclear apheresis units with significant reduction of contaminating platelets and red cells.

A novel combination antimetabolite, TAS-102, exhibits antitumor activity in FU-resistant human cancer cells through a mechanism involving FTD incorporation in DNA

TAS-102 is a new antimetabolite agent composed of a alpha, alpha, alpha-trifluorothymidine (FTD; 1 M) and thymidine phosphorylase inhibitor (TPI; 0.5 M). Here, we investigated the antitumor effect and mechanism of TAS-102 against 5-FU, or FdUrd, resistant human cancer cell lines. The respective tumor growth inhibition rate of orally administered FTD against 5-FU-resistant NUGC-3 was about 70% at a dose level of 200 mg/kg/day; this value was comparable to that against the parental NUGC-3. On the other hand, the tumor inhibition rates of 5-FU, FdUrd, and TS-1 against 5-FU-resistant NUGC-3 were lower than those against parental NUGC-3. Similar observations were made in an FdUrd-resistant human colorectal cancer cell line (DLD-1). TAS-102 was also effective in 5-FU-less sensitive human pancreatic cancer cell lines (PAN-12 and BxPC-3) and human esophagus cancer (T.T.) when compared with 5-FU or UFT. Our hypothesis was that a relatively short and high dosage of TAS-102 results in an additional mechanism of FTD incorporation into DNA other than thymidylate synthase (TS) inhibition. We then examined the effects of FTD on DNA at the cellular level. After treatment with FTD or FdUrd, the DNA fragmentation pattern was examined using filter elution and in situ nick translation. Treatment with FTD for 2 h resulted in marked DNA fragmentation. When the tumor cells were treated with FTD for 72 h or with FdUrd for 2 or 72 h, only a small amount of DNA fragmentation was observed, and the appearance of the tumor cells did not differ markedly from that of untreated cells. Moreover, the DNA fragmentation rate in the TAS-102 treatment group was significantly higher than that in the control group in vivo. These results suggest that when tumor cells are exposed to high concentrations of FTD for short periods of time, FTD manifests its antitumor activity primarily through the induction of DNA fragmentation after FTD incorporation into the DNA. We conclude that TAS-102 is expected to manifest antitumor effects against 5-FU-resistant tumors that are similar to those exerted in 5-FU-sensitive tumors.

Interspecies differences in DNA single strand breaks caused by benzo( a)pyrene and marine environment

The presence of DNA single strand breaks in untreated specimens of selected species, mosquito fish Gambusia affinis, painted comber Serranus scriba, blue mussel Mytilus galloprovincialis, spiny crab Maja crispata and sea cucumber Holothuria tubulosa as well as in 10 μg/g benzo( a)pyrene (BaP) treated mosquito fish, blue mussel and spiny crab was measured, using alkaline filter elution. Interspecies differences in alkaline elution profiles were observed and attributed to different lengths of DNA from different sources and to differences in the number of strand breaks present during normal cellular events in different phyla. Spiny crab hemocytes are more sensitive to action of BaP then blue mussel hemocytes and mosquito fish hepatocytes that could be explained by differences in the rates of distinct metabolic reactions and DNA repair among the investigated species. In field study, DNA single strand breaks were measured in hepatocytes of painted comber and in hemocytes of blue mussel and spiny crab from natural population specimens collected at eight sampling sites along Istrian coast, Croatia. Spatial variations in DNA integrity for each species were detected and revealed for the first time that spiny crab is responsive to different environmental conditions. Interspecies variations in the DNA integrity due to environmental conditions, confirmed species specific susceptibility to genotoxicity of certain environment that in long-term may modify the structure of marine communities. The multi-species approach in designing biomonitoring studies was suggested.

On the relevance of genotoxicity for fish populations II: genotoxic effects in zebrafish ( Danio rerio) exposed to 4-nitroquinoline-1-oxide in a complete life-cycle test

In order to characterize the impact of genotoxic potentials on populations of aquatic organisms in surface waters, zebrafish ( Danio rerio) were exposed to the model genotoxicant 4-nitroquinoline-1-oxide (NQO) in a complete life-cycle test. Fish exposed to mean NQO concentrations of 0, 0.1, 0.3, 1.1, and 2.9 μg/l were examined by several genotoxicity assays with different endpoints. Assays included the unscheduled DNA synthesis (UDS) test, the comet assay, the alkaline filter elution, and the micronucleus test. The genotoxicity assays revealed an increasing genotoxicity, ranging from induction of DNA repair (even at the lowest concentration tested) to primary and secondary DNA alterations at higher concentrations of 1.1 and 2.9 μg/l NQO. Whether the lowered reproductivity observed in the life-cycle test is caused by genotoxic pathways of NQO, remains unclear. However, the results indicate a contradiction to an earlier assumption that genotoxicants as found in the environment are likely to not impact natural populations.

Carcinogenesis switched on by DNA cross-link between complementary bases aroused by aflatoxin and N-nitroso compounds *

Abstract The di-region theory put forward by Dai Qianhuan, a molecular mechanism of chemical carcinogenesis, concluded that the carcinogenesis induced by most of the environmental carcinogens is switched on by the cross-linking between DNA complementary bases aroused by the bifunctional alkylation of their metabolic intermediates. It was evidenced in this paper with DNA filter elution method that one carcinogenic mycotoxin, aflatoxin G1, four carcinogenic N-nitroso compounds. N-nitrosodiethyl-amine, N-nitrosodibutyl-amine, N-nitrosomorpholine and N-nitrosopyrrolidine, one carcinogenic diazo color, 4-dimethylaminodiazobenzene and one carcinogenic nitrogen-containing heterocyclic compound, quinoline, all induced DNA interstrands cross-linking with dosage correlation after metabolic activation. However, the non-carcinogens in corresponding series for control, aflatoxin B2, N-nitroso-diphenylamine, 4′-bromo-4-dimethylamino-diazobenzene and isoquinoline, cannot induce DNA interstrands cross-linking at all in t...

An improved filter elution and cell culture assay procedure for evaluating public groundwater systems for culturable enteroviruses.

Large-scale virus studies of groundwater systems require practical and sensitive procedures for both sample processing and viral assay. Filter adsorption-elution procedures have traditionally been used to process large-volume water samples for viruses. In this study, five filter elution procedures using cartridge filters were evaluated for their effectiveness in processing samples. Of the five procedures tested, the third method, which incorporated two separate beef extract elutions (one being an overnight filter immersion in beef extract), recovered 95% of seeded poliovirus compared with recoveries of 36 to 70% for the other methods. For viral enumeration, an expanded roller bottle quantal assay was evaluated using seeded poliovirus. This cytopathic-based method was considerably more sensitive than the standard plaque assay method. The roller bottle system was more economical than the plaque assay for the evaluation of comparable samples. Using roller bottles required less time and manipulation than the plaque procedure and greatly facilitated the examination of large numbers of samples. The combination of the improved filter elution procedure and the roller bottle assay for viral analysis makes large-scale virus studies of groundwater systems practical. This procedure was subsequently field tested during a groundwater study in which large-volume samples (exceeding 800 L) were processed through the filters.