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T

Toxicity

Toxicity is the degree to which a chemical or biological substance can damage a living organism. It can refer to harm to specific organs, tissues or cells, or to the whole organism.

Medicines development is a step-by-step process involving the evaluation of both animal and human safety information. Non-clinical safety studies (before human testing) should be able to identify potential toxic effects that might occur under the conditions of the later clinical trial.

Toxicokinetics

A specific type of pharmacokinetics that studies what the body does to a medicinal product at toxic doses. These studies assess how a substance enters the body and what happens to it in the body depending on the absorption, distribution, metabolism and excretion of the substance. Toxicokinetic measurements that determine the severity of toxicity are:

  • Duration and concentration of substance at the site of entry.
  • Rate and amount that can be absorbed.
  • Distribution in the body and concentration at specific sites.
  • Metabolic efficiency and nature of the metabolites.
  • Ability of the substance or its metabolites to pass through cell membranes and come into contact with specific cell components (e.g. DNA).
  • The amount and duration of storage of the substance (or its metabolites) in body tissues.
  • The rate and sites of excretion.

Different dose levels used in toxicokinetics, compared to pharmacokinetics, give rise to technological changes in such factors as solubility, stability, absorption, pre-systemic clearance, protein binding, and metabolism that may be influenced by dose size, and may give rise to profound differences in the design and interpretation of studies.

Toxicology

Toxicology is the study of the toxic effects of substances on living organisms. It includes symptoms, mechanisms, treatments and detection of poisoning, especially the poisoning of people. The main criterion regarding the toxicity of a substance is the dose, i.e. the amount of exposure to the substance.

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Toxoid vaccine

Toxoid vaccines use an inactivated toxin of a pathogenic micro-organism to stimulate a response by the immune system.

TQTc

TQTc stands for 'thorough QT/QTc study'. The test studies the effect of a compound on the electrical activity of the heart. In cardiology, the QT interval is a measure of the time between the start of the Q wave and the end of the T wave in the heart's electrical cycle. The QT interval represents the electrical activity associated with the contraction and relaxation of the heart chambers. A lengthened QT interval is used as an (imperfect) biomarker to assess the risk that a medicine may provoke arrhythmia.

Transcribed

Transcription is the process by which genetic information is transferred from DNA to RNA (this is accomplished by an enzyme called RNA polymerase). This RNA will in turn serve as a template to create a protein.

Transcriptome

To produce proteins, genes are first ˜transcribed™ into messenger RNA (mRNA). The transcriptome represents the whole set of mRNA molecules present in a specific cell or tissue at a certain time. By analysing the transcriptome, researchers can determine when each gene is turned on or off in a cell or tissue, how that type of cell normally functions, and how changes in the normal level of gene activity may be altered by or contribute to disease.

Transdermal

Transdermal meaning ˜through the skin™ is a route of medicine administration to deliver a specific dose of medication through the skin and into the bloodstream e.g. transdermal patches or ointments. Examples include nicotine patches and scopolamine patches for motion sickness.

Transfusion

Transfer of blood or blood components (red and white blood cells, plasma, clotting factors, or platelets) into the bloodstream intravenously.

Transgenic

A transgenic organism (otherwise known as a genetically modified organism (GMO)) is an organism whose genetic material has been altered. Genetic modifications are made to produce certain traits (such as disease resistance in crops) or to cause the organism to produce specific biological products (for example, bacteria have been altered in order to produce insulin for diabetes treatment, and plants have been altered to make antibodies for blood-clotting factors).

Transgenic organisms are used in the production of medicines, in new forms of medicine such as gene therapy, and in agriculture.

Genetic modification is also a useful tool for scientists in many areas of research, including those who study the mechanisms of human and other diseases.


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