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Jaundice: yellow pigmentation of the skin and whites of the eyes caused by elevated blood levels of bilirubin. The condition is associated with either liver or gallbladder disease or excessive destruction of red blood cells.

Karnofsky Performance Score: a measure given by a physician to a patient.s ability to perform certain ordinary tasks: 100-normal; no complaints; 70-unable to carry on normal activity; 50-requires considerable assistance; 40 - disabled; 30 - hospitalization recommended.

Kcat a parameter in enzymekinetics. Under the conditions of the Michaelis Menten mechanism, this parameter is the first order rate constant for the chemical conversion of the enzyme substrate complex into the enzyme the product complex. In more complicated reactions, the meaning of this parameter changes. Kcat is also referred as the turnover parameter since it represents the maximum number of substrate molecules converted to producs per active site per unit of time.

Latency: A quiescent period during a disease process. For example in AIDS is an asymptomnatic period in the early years of HIV infection. The period of latency is characterized in the peripheral blood by near normal CD4 counts and HIV levels. Recent research indicates that HIV remains quite active in the lymph nodes during this period. Cellular latency is the period after HIV has integrated its genome into a cell.s DNA but has not yet begun to replicate.

Lead discovery is the process of identifying active new chemical entities, which by subsequent modification may be transformed into a clinically useful drug.

Lead generation is the term applied to strategies developed to identify compounds which possess a desired but non-optimized biological activity.

Lead optimization is the synthetic modification of a biologically active compound, to fulfill all stereoelectronic, physicochemical, pharmacokinetic and toxicologic required for clinical usefulness.

Lesion: a disturbed area of tissue -a wound, injury, nodule or tumor on the skin or elsewhere.

Leukocyte: any of the various white blood cells, which together make up the immune system. Neutrophils, lymphocytes and monocytes are all leukocytes.

Leukocytosis: an abnormally high number of leukocytes in the blood. This condition can occur during many types of infection and inflammation.

Leukopenia: an abnormally low number of leukocytes circulating in the blood.

Lipophilicity represents the affinity of a molecule or a moiety for a lipophilic environment. It is commonly measured by its distribution behavior in a biphasic system, either liquid-liquid (e.g., partition coefficient in octan-1-ol/water) or solid/liquid (retention on reversed-phase high performance liquid chromatography (RP-HPLC) or thin-layer chromatography (TLC) system). (See also Hydrophobicity).

Liposomes are microscopic spherical vesicles that form when phospholipids are hydrated. When mixed in water under low shear conditions, the phospholipids arrange themselves in sheets, the molecules aligning side by side in like orientation, .heads. up and .tails. down. These sheets then join tails-to-tails to form a bi-layer membrane, which encloses some of the water in a phospholipid sphere. Typically, several of these vesicles will form one inside the other in diminishing size, creating a multilamellar structure of concentric phosphlipid spheres separated by layers of water.

Lymph: a transparent, slightly yellow fluid that carries lymphocytes and collects foreign microbes. Lymph is derived from tissue fluids. The fluid passes through the lymphatic ducts and then enters the bloodstream.

Lymph Node (Lymph Gland): small bean-sized organs made up mostly of lymphocytes (see), lymph fluid and connective tissue. Clusters of lymph nodes are widely distributed in the body and are essential to the functioning of the immune system. They are connected with each other and other lymphoid tissue by the lymphatic vessels.

Lymphadenopathy: swelling or enlargement of the lymph nodes due to infection or cancer. The swollen nodes may be palpable or visible from outside the body.

Lymphatic Vessel: one of a body-wide network of channels, similar to the blood vessels, that transports lymph to the lymphoid tissue and into the bloodstream.

Lymphocyte: white blood cells that mature and reside in the lymphoid organs and are responsible for the acquired immune response (see Immune System). The two major types of lymphocytes are T-cells and B-cells.

Lymphokine: a substance produced by lymphocytes to precipitate various immune reactions. Lymphokines include the interferons and interleukins and are a subset of the cytokine family.

Lymphoma: a cancer of the lymphoid tissue, usually a solid tumor with cells arising from proliferating lymphocytes. Symptoms may include lymph-node swelling, weight loss and fever. Some examples of lymphomas are Burkitt.s, Hodgkin.s and non-Hodgkin.s. Treatment involves radiotherapy or chemotherapy or both.

Lyophilic are colloids are solvent solving colloids, which form systems called gels.

Lyophobic are colloids are solvent hating colloids which form systems called sols.

Lysis: the splitting and dissolution of cellular, bacterial or viral material by chemical action.

LogP is the decimal logarithm of the partition coefficient of a drug.