Exudates and Transudates: Exudates are fluids, CELLS, or other cellular substances that are slowly discharged from BLOOD VESSELS usually from inflamed tissues. Transudates are fluids that pass through a membrane or squeeze through tissue or into the EXTRACELLULAR SPACE of TISSUES. Transudates are thin and watery and contain few cells or PROTEINS.Pleural Effusion: Presence of fluid in the pleural cavity resulting from excessive transudation or exudation from the pleural surfaces. It is a sign of disease and not a diagnosis in itself.Pleural Effusion, Malignant: Presence of fluid in the PLEURAL CAVITY as a complication of malignant disease. Malignant pleural effusions often contain actual malignant cells.Plant Exudates: Substances released by PLANTS such as PLANT GUMS and PLANT RESINS.Hydrothorax: A collection of watery fluid in the pleural cavity. (Dorland, 27th ed)Tuberculosis, Pleural: Tuberculosis of the serous membrane lining the thoracic cavity and surrounding the lungs.Paracentesis: A procedure in which fluid is withdrawn from a body cavity or organ via a trocar and cannula, needle, or other hollow instrument.Pleura: The thin serous membrane enveloping the lungs (LUNG) and lining the THORACIC CAVITY. Pleura consist of two layers, the inner visceral pleura lying next to the pulmonary parenchyma and the outer parietal pleura. Between the two layers is the PLEURAL CAVITY which contains a thin film of liquid.L-Lactate Dehydrogenase: A tetrameric enzyme that, along with the coenzyme NAD+, catalyzes the interconversion of LACTATE and PYRUVATE. In vertebrates, genes for three different subunits (LDH-A, LDH-B and LDH-C) exist.Euthanasia: The act or practice of killing or allowing death from natural causes, for reasons of mercy, i.e., in order to release a person from incurable disease, intolerable suffering, or undignified death. (from Beauchamp and Walters, Contemporary Issues in Bioethics, 5th ed)Sensitivity and Specificity: Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)ROC Curve: A graphic means for assessing the ability of a screening test to discriminate between healthy and diseased persons; may also be used in other studies, e.g., distinguishing stimuli responses as to a faint stimuli or nonstimuli.Biological Markers: Measurable and quantifiable biological parameters (e.g., specific enzyme concentration, specific hormone concentration, specific gene phenotype distribution in a population, presence of biological substances) which serve as indices for health- and physiology-related assessments, such as disease risk, psychiatric disorders, environmental exposure and its effects, disease diagnosis, metabolic processes, substance abuse, pregnancy, cell line development, epidemiologic studies, etc.Blood Proteins: Proteins that are present in blood serum, including SERUM ALBUMIN; BLOOD COAGULATION FACTORS; and many other types of proteins.Plant Roots: The usually underground portions of a plant that serve as support, store food, and through which water and mineral nutrients enter the plant. (From American Heritage Dictionary, 1982; Concise Dictionary of Biology, 1990)Proteins: Linear POLYPEPTIDES that are synthesized on RIBOSOMES and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of AMINO ACIDS determines the shape the polypeptide will take, during PROTEIN FOLDING, and the function of the protein.Ascitic Fluid: The serous fluid of ASCITES, the accumulation of fluids in the PERITONEAL CAVITY.