Glossary Terms (Simple List)
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Tissue Culture Infectious Dose – TCID50
The dilution of virus that results in the probability of infection of 50% in replicate tissue-culture inoculations. (TR41)
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Titer
The concentration of infectious virus calculated, taking into account the dilution factor. (TR41)
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Titer Reduction (TR)
A measure of the degree to which a particular filter removes a microorganism under specified test conditions. Calculated as the ratio of the total number of microorganisms used to challenge the filter divided by the total number of microorganisms that passed through the filter. (TR75)
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Toll-like Receptor (TLR)
A class of single membrane-spanning non-catalytic receptors that recognize structurally conserved molecules derived from microbes. They can activate immune cell responses when microbes have breached physical barriers such as the skin or intestinal tract mucosa. (TR50)
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Total Impurities
The sum of all impurities observed. (TR38)
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Total Organic Carbon (TOC)
An indirect measure of organic molecules present in pharmaceutical waters measured as carbon. (TR45)
Measurement term for the total organic carbon in a sample. (TR70)
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Touchdown PCR
A technique to reduce appearance of non-specific amplicons in PCR reactions. The earliest cycles of a touchdown PCR method have high annealing temperatures. The annealing temperature is decreased in increments for subsequent cycles until a fixed point is reached. (TR50)
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Toxicity
The capacity of a substance to confer morbidity or mortality. In the context of virus assays, the ability of a buffer or other process components to kill or otherwise harm the functionality of indicator cell lines. This is independent of the infection by the virus. (TR41)
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Toxicity Studies (also referred to as “Tox” studies)
In vivo or in vitro experiments in which test articles are studied prospectively in test systems under laboratory conditions with the primary goals of identifying the following: 1) an initial safe dose and subsequent dose escalation schemes in humans; 2) potential target organs for toxicity and for the study of whether such toxicity is reversible; and, 3) safety parameters for clinical monitoring after the appropriate dosing and administering schedule is followed (relevant to the drug being studied). In toxicity studies, the test animals are examined by histological or serological methods in order to identify toxic, mutagenic, or teratogenic effects of the drug. It is sometimes possible to collect physiological data from the animals prior to sacrifice. Some toxicity studies may be performed using cell culture methods. Toxicity studies are also described by the U.S. FDA as “nonclinical laboratory studies” and by ICH as “preclinical safety evaluations”.
The definition does not include studies using human subjects or clinical studies, field trials in animals, or any basic exploratory studies carried out to determine whether a test article has any potential utility or to determine physical or chemical characteristics as described in ICH S6 and 21 CFR Part 58 (GLP). (TR56)
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Transcription-Mediated Amplification (TMA)
An isothermal NAT method that can amplify RNA or DNA targets a billion-fold in less than one hour. TMA technology uses two primers and two enzymes: RNA polymerase and reverse transcriptase. (TR50)