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H

habituation

A condition characterized by a psychological craving for the effects produced by the administration of a drug, as a desire rather than a compulsion, and an absence of physical dependence.

haemolysis (hemolysis)

Haemolysis is the rupture (lysis) or destruction of erythrocytes. Haemolysis can be caused by bacterial toxins (e.g. Gram +ve Streptococcal, Enterococcal or Staphylococcal toxins), parasites (e.g. Plasmodium sp.), autoimmune or genetic disorders, and can lead to haemoglobinemia (hemoglobinemia).

half-life

Half-life (t½) is an important pharmacokinetic measurement. The metabolic half-life of a drug in vivo is the time taken for its concentration in plasma to decline to half its original level. Half-life confers the duration of action of a drug and depends upon how quickly the drug is eliminated from the plasma. The clearance and distribution of a drug from the plasma are therefore important parameters for the determination of its half-life.

heterochromatin

A tightly packed form of chromatin that is not actively being transcribed or is less accessible for transcription

histones

Eukaryotic proteins around which DNA is tightly wound. Histones function to condense and package DNA in the nucleus.

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