Proteins that bind to DNA and package it into compact structures to form nucleosomes —integral structural components of chromosomes. The compact packaging of DNA must be relaxed somewhat for DNA copying (replication) and gene expression (‘transcription’) to occur. Modification of histones through the attachment of acetyl (-COCH3) or methyl (-CH3) groups (acetylation or methylation), and of biotin (biotinylation) has been shown to affect the structure of histones, thereby affecting replication and transcription of DNA.


A sulfur-containing amino acid, which is an intermediate in the metabolism of methionine, another sulfur-containing amino acid.  Homocysteine appears to be a nerve and vessel toxin, promoting mortality and cardiovascular disease as well as strokeAlzheimer's disease, birth defects, recurrent pregnancy loss, and eye disorders.

Elevated homocysteine levels in the blood have been associated with increased risk of cardiovascular disease. Most research indicates that a blood plasma homocysteine level of less than 10 micromoles/liter is associated with a lower risk of cardiovascular disease and a reasonable treatment goal for individuals at high risk. However, it is not yet clear whether lowering homocysteine levels will reduce cardiovascular disease risk.

The metabolism of homocysteine provides an example of the interrelationships among nutrients necessary for optimum physiological function and health: the amount of homocysteine in the blood is regulated by three vitamins: vitamin B9, vitamin B12, and vitamin B6.


A molecule released by cells into the blood to act as chemical “messenger”, transporting a signal from one cell to another. Cells respond to a hormone when they produce a specific receptor for that hormone. The hormone binds to the receptor protein, resulting in the activation of a signal transduction mechanism that ultimately leads to cell type-specific responses.

Huntington's disease

An inherited degenerative disorder of the brain. Symptoms include movement disorders and impaired cognitive function. Symptoms typically develop in the fourth decade of life and progressively deteriorate over time.


A medical condition in which the blood pressure is permanently (chronically) elevated. Persistent hypertension is one of the risk factors for strokes, heart attacks and heart failure, and is a leading cause of chronic kidney (renal) failure. Beginning at a systolic pressure of 115 mmHg and a diastolic pressure of 75 mmHg (commonly written as 115/75 mmHg), cardiovascular disease risk doubles for each increment of 20/10 mmHg. A normal blood pressure is 90–119/60–79 mmHg.