Terms Starting with Letter: M Magnetic resonance (MR) spectroscopy Spectroscopic method of measuring the magnetic interactions between elementary particles by providing radiofrequency spectra. marker protein Protein that is highly specific for a disease and can be detected with a sufficient sensitivity by means of imaging or in vitro diagnostics. medial Toward or at the midline of the body; on the inner side of. messenger RNA (mRNA) A transcript of on of the strands of DNA that specifies the order of amino acids, as a sequence of codons, in protein synthesis. metastasis The shifting of a disease, typically cancer, from one location in the body to another. It usually involves dissemination of tumor cells by the lymphatics or blood vessels. methionine A sulfur-containing essential amino acid. micelle Spherical aggregate of amphipathic molecules that is dispersed in solution such as a liposome or a colloid. Micro MR, CT, PET, and single photon emission CT Dedicated devices for use in small animals, with higher spatial resolution than the counterparts used for clinical imaging in humans. microarray technology New way of studying how large numbers of genes interact with each other and how the regulatory networks of a cell control numerous genes simultaneously. The method uses a robot to print tiny amounts of functional DNA samples precisely onto glass slides. Researchers then attach fluorescent labels to DNA from the cell they are studying. The labeled probes are allowed to bind to complementary DNA strands on the slides. The slides are put into a scanning microscope that can measure the brightness of each fluorescent dot; brightness reveals how much of a specific DNA fragment is present, an indicator of how active it is. microbubbles Used in ultrasound (US) imaging, microbubbles are gas-filled, lipid spheres which can be engineered to burst on focused ultrasounds delivering contrast agents or drugs. As the bubbles are filled with gas, they behave as contrast agents for ultrasound without a need for bursting. microdissection The extraction of specific cells from a microscopicaly heterogeneous tissue sample. This is useful in identifying genetic differences across the sample. See LCM. microimaging The imaging of intact small animals at appropriately high spatial resolution to visualize the small (by human standards) features of the research animal. molecular imaging Growing research discipline aimed at developing and testing novel tools, reagents, and methods to image specific molecular pathways in vivo, particularly those that are key targets in disease processes. molecular modeling Three-dimensional representation, either graphic or computational, for the structure of a molecule. Utilized to aid in drug design. molecular probe In molecular biology, labeled DNA or RNA used to detect complementary nucleic acid sequences. In molecular imaging, highly specific agent that reports on a single molecular event. molecular profiling Study of specific patterns (finger-prints) of proteins, DNA, and/or mRNA and how these patterns correlate with an individual’s physical characteristics or symptoms of disease. molecular target assessment Assess the effectiveness of a given therapeutic drug on it's intended molecular target by imaging or other technique. monoclonal antibodies (MAbs) Antibodies produced during an immune reaction in response to antigen immunization. The antibodies are all identical. mouse imaging Imaging technologies optimized for mice (e.g., animal MRI, microPET, microSPECT, microCT) muscarinic Receptors that respond to the neurotransmitter acetylcholine are divided into two types - muscarinic and nicotinic. These receptors are so named because they are stimulated by the drugs muscarine or nicotine. The cholinergic receptors of the target organs of the autonomic nervous system are generally muscarinic, while those in the autonomic ganglia and neuromuscular junction are typically nicotinic. The CNS contains both types of receptors. mutagen An agent, either chemical or radiation, that causes heritable change in DNA sequences. mutation A permanent, heritable change in the nucleotide sequence of a chromosome usually leading to a change in or loss of function.