Zygosity diagnosis in the absence of genotypic data: An approach using latent class analysis

For zygosity diagnosis in the absence of genotypic data, or in the recruitment phase of a twin study where only single twins from same-sex pairs are being screened, or to provide a test for sample duplication leading to the false identification of a dizygotic pair as monozygotic, the appropriate analysis of respondents' answers to questions about zygosity is critical. Using data from a young adult Australian twin cohort (N = 2094 complete pairs and 519 singleton twins from same-sex pairs with complete responses to all zygosity items), we show that application of latent class analysis (LCA), fitting a 2-class model, yields results that show good concordance with traditional methods of zygosity diagnosis, but with certain important advantages. These include the ability, in many cases, to assign zygosity with specified probability on the basis of responses of a single informant (advantageous when one zygosity type is being oversampled); and the ability to quantify the probability of misassignment of zygosity, allowing prioritization of cases for genotyping as well as identification of cases of probable laboratory error. Out of 242 twins (from 121 like-sex pairs) where genotypic data were available for zygosity confirmation, only a single case was identified of incorrect zygosity assignment by the latent class algorithm. Zygosity assignment for that single case was identified by the LCA as uncertain (probability of being a monozygotic twin only 76%), and the co-twin's responses clearly identified the pair as dizygotic (probability of being dizygotic 100%). In the absence of genotypic data, or as a safeguard against sample duplication, application of LCA for zygosity assignment or confirmation is strongly recommended.

Susy Glaubach working in a laboratory; Vienna Portraits Women

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Group portrait at the farewell banquet for Dr. William Antopol from the laboratory staff of Mount Sinai Hospital; Ken's Chop House, New York city Portraits Groups

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Tracking and identifying wastewater toxicants and assessing their biodegradation products

Screening of wastewater effluents from municipal and industrial wastewater treatment plants with biotests showed that the treated wastewater effluents possess only minor acute toxic properties towards whole organisms (e.g. bacteria, algae, daphnia), if any. In vitro tests (sub-mitochondrial membranes and fish hepatocytes) were generally more susceptible to the effluents. Most of the effluents indicated the presence of hormonally active compounds, as the production of vitellogenin, an egg yolk precursor protein, was induced in fish hepatocytes exposed to wastewater. In addition, indications of slight genotoxic potential was found in one effluent concentrate with a recombinant bacteria test. Reverse electron transport (RET) of mitochondrial membranes was used as a model test to conduct effluent assessment followed by toxicant characterisations and identifications. Using a modified U.S. EPA Toxicity Identification Evaluation Phase I scheme and additional case-specific methods, the main compound in a pulp and paper mill effluent causing RET inhibition was characterised to be an organic, relatively hydrophilic high molecular weight (HMW) compound. The toxicant could be verified as HMW lignin by structural analyses using nuclear magnetic resonance. In the confirmation step commercial and in-house extracted lignin products were used. The possible toxicity related structures were characterised by statistical analysis of the chemical breakdown structures of laboratory-scale pulping and bleaching effluents and the toxicities of these effluents. Finally, the biological degradation of the identified toxicant and other wastewater constituents was evaluated using bioassays in combination with chemical analyses. Biological methods have not been used routinely in establishing effluent discharge limits in Finland. However, the biological effects observed in this study could not have been predicted using only routine physical and chemical effluent monitoring parameters. Therefore chemical parameters cannot be considered to be sufficient in controlling effluent discharges especially in case of unknown, possibly bioaccumulative, compounds that may be present in small concentrations and may cause chronic effects.

Students of Willy Marckwald working in laboratory; Friedrich-Wilhelms-Universitaet Berlin Institutions; Universities

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Students of Willy Marckwaldeating lunch, still wearing laboratory coats; Friedrich-Wilhelms-Universitaet Berlin Institutions; Universities

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Students of Willy Marckwald working in laboratory; Friedrich-Wilhelms-Universitaet Berlin Institutions; Universities

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Students of Willy Marckwald working in laboratory; Friedrich-Wilhelms-Universitaet Berlin Institutions; Universities

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Students of Willy Marckwald working in laboratory; Friedrich-Wilhelms-Universitaet Berlin Institutions; Universities

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Students of Willy Marckwald working in laboratory; Friedrich-Wilhelms-Universitaet Berlin Institutions; Universities

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Students of Willy Marckwald working in laboratory; Friedrich-Wilhelms-Universitaet Berlin Institutions; Universities

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Students of Willy Marckwald working in laboratory; Friedrich-Wilhelms-Universitaet Berlin Institutions; Universities

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Students of Willy Marckwald working in laboratory; Friedrich-Wilhelms-Universitaet Berlin Institutions; Universities

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Students of Willy Marckwald working in laboratory; Friedrich-Wilhelms-Universitaet Berlin Institutions; Universities

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Students of Willy Marckwald working in laboratory; Friedrich-Wilhelms-Universitaet Berlin Institutions; Universities

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