Cell culture techniques are routinely used for measuring the infectivity of a wide range of human pathogens. A variety of different cell culture systems and detection methodologies have been applied to Cryptosporidium parvum. However, the correlation between cell culture methods and animal infectivity assays has not been thoroughly investigated. Although many cell culture methods have been developed for C. parvum, it has not been proven that infectivity in cell culture is a good indicator of the ability of oocysts to cause infections in animals. The objective of this research was to compare in-vitro cell culture methods with a mouse assay for measuring infectivity of C. parvum oocysts. The specific objectives were to (1) compare the dose response and sensitivity of cell culture and mouse assays with multiple isolates; (2) compare infectivity methods with oocysts exposed to environmental water samples; (3) determine the reproducibility and variability of the methods; and (4) compare cell culture and animal assays for assessing ozone and UV disinfection.For untreated oocysts, challenge doses were enumerated by flow cytometry. Dose response curves were constructed by regression analysis of oocyst dose against a logistic transformation of the proportional infectivity and the 50% infectious doses for each isolate were calculated by solving the regression for a logit value of zero. Infections in CD-1 mice were detected by microscopy following staining with hematoxylin and eosin. Infection in HCT-8 and Caco-2 cells was detected by C. parvum-specific RT-PCR. In MDCK cells, infection was detected using immunofluorescence. For disinfection studies, oocysts were exposed to UV using a medium-pressure, collimated beam apparatus and inactivation was measured as the difference in ID50 of unexposed and UV-exposed oocysts. Oocysts were exposed to ozone using batch, semi-batch, and single continuously stirred tank reactors at 1, 5, and 15°C.This investigation demonstrated that in-vitro cell culture was equivalent with a mouse assay for measuring infectivity of untreated C. parvum oocysts and should therefore be considered a practical alternative for assessing the potential of oocysts to cause infection. However, the high levels of variability displayed by mouse and cell culture methods indicated that infectivity and disinfection experiments should be limited to discerning relatively large differences. Of the three cell culture assays, the HCT-8/RT-PCR method displayed the closest agreement with the CD-1 mouse assay. C. hominis was infectious in HCT-8 cells but did not infect mice. Similar results were obtained with CD-1 mice and HCT-8 cells for measuring infectivity of oocysts that had been exposed to environmental water for 35 days. There was also very good agreement between HCT-8 cell culture and CD-1 mouse assays for measuring UV inactivation of C. parvum. A medium-pressure UV dosage of 5.6 mJ/cm2 resulted in 2-log10 inactivation. The shapes of ozone inactivation curves were generally the same for mouse and cell culture derived data although the CD-1 mouse assay typically generated 0.5 to 1-log10 higher levels of inactivation than HCT-8 cells. In addition, there was a stimulatory response in oocysts exposed to ozone below 20 mg.min/L when assayed by HCT-8 cell culture. Consequently, further research is necessary to understand the response of oocysts to ozone when inactivation is assessed by cell culture methods. The water industry should adopt in-vitro cell culture as a routine method for measuring the infectivity of waterborne C. parvum and C. hominis oocysts. This project has demonstrated that cell culture has equivalency with the standard CD-1 mouse assay and cell culture assays can be applied to oocysts recovered from water using approved methods. However, there needs to be a thorough, robust, and well-controlled study to compare the various cell culture-based assays for measuring C. parvum and C. hominis infectivity. This evaluation should include inter-laboratory comparisons and round-robin testing. Cell culture-based assays should also be used to assess disinfection of C. hominis isolates. Originally published by AwwaRF for its subscribers in 2004. This publication can also be purchased and downloaded via Pay Per View on Water Intelligence Online - click on the Pay Per View icon below
In the most original and ambitious synthesis yet undertaken in Melanesian scholarship, Marilyn Strathern argues that gender relations have been a particular casualty of unexamined assumptions held by Western anthropologists and feminist scholars alike. The book treats with equal seriousness—and with equal good humor—the insights of Western social science, feminist politics, and ethnographic reporting, in order to rethink the representation of Melanesian social and cultural life. This makes The Gender of the Gift one of the most sustained critiques of cross-cultural comparison that anthropology has seen, and one of its most spirited vindications.
In Jane Addams’s Evolutionary Theorizing, Marilyn Fischer advances the bold and original claim that Addams’s reasoning in her first book, Democracy and Social Ethics, is thoroughly evolutionary. While Democracy and Social Ethics, a foundational text of classical American pragmatism, is praised for advancing a sensitive and sophisticated method of ethical deliberation, Fischer is the first to explore its intellectual roots. Examining essays Addams wrote in the 1890s and showing how they were revised for Democracy and Social Ethics, Fischer draws from philosophy, history, literature, rhetoric, and more to uncover the array of social evolutionary thought Addams engaged with in her texts—from British socialist writings on the evolution of democracy to British and German anthropological accounts of the evolution of morality. By excavating Addams’s evolutionary reasoning and rhetorical strategies, Fischer reveals the depth, subtlety, and richness of Addams’s thought.
In a time of declining resources in institutions of higher education, we grapple with how priorities are to be set for the limited resources available. Most vulnerable are those students labeled underprepared by colleges and universities. Should we argue that the limited resources available ought to be used to support these students through their undergraduate years? And, if we decide that we want to do that, what evidence of their potential for success can we provide that will justify the use of these resources? Through longitudinal research that follows students who have been so labeled over all their college years, we can begin to find answers to these questions. Time to Know Them is the first book that follows the experiences of a group of students over their entire academic experience. No previous studies have brought together the factors incorporated in this study: *examining writing and learning on a true longitudinal basis; *studying a multicultural urban population; *investigating the relationship between writing and learning by examining papers written over time for regularly assigned academic courses across a range of disciplines; and *taking into consideration non-academic factors that influence academic performance such as race, gender, socio-economic status, and ideological orientation. Through interviews twice a semester over six years, the collection of papers written for all courses, observations of instructional settings, and analysis of required institutional tests of writing, the author has been able to pull together a more complete picture of writing and intellectual development over the college years than has previously been available in any study. Students are seen to acquire the ability to handle more complex reasoning tasks as they find themselves in more challenging intellectual settings and where risk-taking and exploration of new ideas are valued. The integration of students' previous life experiences into their academic studies allows them to analyze, critique, modify, and apply their previously held world views to their new learning. These changes are seen to occur over time with instructional settings and support providing key roles in writing development. Personal factors in students' lives present difficulties that require persistence and dedication to overcome. Never before have the complexities of real individual lives as they affect academic performance been so clearly presented.
Based on the author s analysis of in-depth interviews and relevant research literature, this booki nvestigates and explores the experiences, problems and pressures faced by black and ethnic minority women managers in the United Kingdom. To date, research addressing the issues of black managers has been almost exclusively American, predominantly black African-Americans, and the overall amount of published research has been limited. Indeed, studies of black and ethnic minority professional women, especially in corporate settings, have been virtually excluded from the growing body of research on women in management. This book has been written to fill this gap.
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