Thymus Hyperplasia: Enlargement of the thymus. A condition described in the late 1940's and 1950's as pathological thymic hypertrophy was status thymolymphaticus and was treated with radiotherapy. Unnecessary removal of the thymus was also practiced. It later became apparent that the thymus undergoes normal physiological hypertrophy, reaching a maximum at puberty and involuting thereafter. The concept of status thymolymphaticus has been abandoned. Thymus hyperplasia is present in two thirds of all patients with myasthenia gravis. (From Segen, Dictionary of Modern Medicine, 1992; Cecil Textbook of Medicine, 19th ed, p1486)Hyperplasia: An increase in the number of cells in a tissue or organ without tumor formation. It differs from HYPERTROPHY, which is an increase in bulk without an increase in the number of cells.Congenital Disorders of Glycosylation: A genetically heterogeneous group of heritable disorders resulting from defects in protein N-glycosylation.Education, Distance: Education via communication media (correspondence, radio, television, computer networks) with little or no in-person face-to-face contact between students and teachers. (ERIC Thesaurus, 1997)Computer-Assisted Instruction: A self-learning technique, usually online, involving interaction of the student with programmed instructional materials.Time and Motion Studies: The observation and analysis of movements in a task with an emphasis on the amount of time required to perform the task.Online Systems: Systems where the input data enter the computer directly from the point of origin (usually a terminal or workstation) and/or in which output data are transmitted directly to that terminal point of origin. (Sippl, Computer Dictionary, 4th ed)Carbohydrate Metabolism, Inborn ErrorsThymus Gland: A single, unpaired primary lymphoid organ situated in the MEDIASTINUM, extending superiorly into the neck to the lower edge of the THYROID GLAND and inferiorly to the fourth costal cartilage. It is necessary for normal development of immunologic function early in life. By puberty, it begins to involute and much of the tissue is replaced by fat.Encyclopedias as Topic: Works containing information articles on subjects in every field of knowledge, usually arranged in alphabetical order, or a similar work limited to a special field or subject. (From The ALA Glossary of Library and Information Science, 1983)Stromal Cells: Connective tissue cells of an organ found in the loose connective tissue. These are most often associated with the uterine mucosa and the ovary as well as the hematopoietic system and elsewhere.Mediastinum: A membrane in the midline of the THORAX of mammals. It separates the lungs between the STERNUM in front and the VERTEBRAL COLUMN behind. It also surrounds the HEART, TRACHEA, ESOPHAGUS, THYMUS, and LYMPH NODES.Hematopoietic Stem Cells: Progenitor cells from which all blood cells derive.Mediastinal Neoplasms: Tumors or cancer of the MEDIASTINUM.Lymphoid Tissue: Specialized tissues that are components of the lymphatic system. They provide fixed locations within the body where a variety of LYMPHOCYTES can form, mature and multiply. The lymphoid tissues are connected by a network of LYMPHATIC VESSELS.Carcinoma, Mucoepidermoid: A tumor of both low- and high-grade malignancy. The low-grade grow slowly, appear in any age group, and are readily cured by excision. The high-grade behave aggressively, widely infiltrate the salivary gland and produce lymph node and distant metastases. Mucoepidermoid carcinomas account for about 21% of the malignant tumors of the parotid gland and 10% of the sublingual gland. They are the most common malignant tumor of the parotid. (From DeVita Jr et al., Cancer: Principles & Practice of Oncology, 3d ed, p575; Holland et al., Cancer Medicine, 3d ed, p1240)Adenolymphoma: A benign tumor characterized histologically by tall columnar epithelium within a lymphoid tissue stroma. It is usually found in the salivary glands, especially the parotid.Carcinoma, Acinar Cell: A malignant tumor arising from secreting cells of a racemose gland, particularly the salivary glands. Racemose (Latin racemosus, full of clusters) refers, as does acinar (Latin acinus, grape), to small saclike dilatations in various glands. Acinar cell carcinomas are usually well differentiated and account for about 13% of the cancers arising in the parotid gland. Lymph node metastasis occurs in about 16% of cases. Local recurrences and distant metastases many years after treatment are common. This tumor appears in all age groups and is most common in women. (Stedman, 25th ed; Holland et al., Cancer Medicine, 3d ed, p1240; from DeVita Jr et al., Cancer: Principles & Practice of Oncology, 3d ed, p575)Paraneoplastic Syndromes: In patients with neoplastic diseases a wide variety of clinical pictures which are indirect and usually remote effects produced by tumor cell metabolites or other products.Parotid Neoplasms: Tumors or cancer of the PAROTID GLAND.Adenoma, Pleomorphic: A benign, slow-growing tumor, most commonly of the salivary gland, occurring as a small, painless, firm nodule, usually of the parotid gland, but also found in any major or accessory salivary gland anywhere in the oral cavity. It is most often seen in women in the fifth decade. Histologically, the tumor presents a variety of cells: cuboidal, columnar, and squamous cells, showing all forms of epithelial growth. (Dorland, 27th ed)Bone Marrow Transplantation: The transference of BONE MARROW from one human or animal to another for a variety of purposes including HEMATOPOIETIC STEM CELL TRANSPLANTATION or MESENCHYMAL STEM CELL TRANSPLANTATION.Bone Marrow: The soft tissue filling the cavities of bones. Bone marrow exists in two types, yellow and red. Yellow marrow is found in the large cavities of large bones and consists mostly of fat cells and a few primitive blood cells. Red marrow is a hematopoietic tissue and is the site of production of erythrocytes and granular leukocytes. Bone marrow is made up of a framework of connective tissue containing branching fibers with the frame being filled with marrow cells.Transplantation, Homologous: Transplantation between individuals of the same species. Usually refers to genetically disparate individuals in contradistinction to isogeneic transplantation for genetically identical individuals.Myasthenia Gravis: A disorder of neuromuscular transmission characterized by weakness of cranial and skeletal muscles. Autoantibodies directed against acetylcholine receptors damage the motor endplate portion of the NEUROMUSCULAR JUNCTION, impairing the transmission of impulses to skeletal muscles. Clinical manifestations may include diplopia, ptosis, and weakness of facial, bulbar, respiratory, and proximal limb muscles. The disease may remain limited to the ocular muscles. THYMOMA is commonly associated with this condition. (Adams et al., Principles of Neurology, 6th ed, p1459)Bone Marrow Cells: Cells contained in the bone marrow including fat cells (see ADIPOCYTES); STROMAL CELLS; MEGAKARYOCYTES; and the immediate precursors of most blood cells.Seminoma: A radiosensitive, malignant neoplasm of the testis, thought to be derived from primordial germ cells of the sexually undifferentiated embryonic gonad. There are three variants: classical (typical), the most common type; anaplastic; and spermatocytic. The classical seminoma is composed of fairly well differentiated sheets or cords of uniform polygonal or round cells (seminoma cells), each cell having abundant clear cytoplasm, distinct cell membranes, a centrally placed round nucleus, and one or more nucleoli. In the female, a grossly and histologically identical neoplasm, known as dysgerminoma, occurs. (Dorland, 27th ed)Pseudolymphoma: A group of disorders having a benign course but exhibiting clinical and histological features suggestive of malignant lymphoma. Pseudolymphoma is characterized by a benign infiltration of lymphoid cells or histiocytes which microscopically resembles a malignant lymphoma. (From Dorland, 28th ed & Stedman, 26th ed)Testicular Neoplasms: Tumors or cancer of the TESTIS. Germ cell tumors (GERMINOMA) of the testis constitute 95% of all testicular neoplasms.Neuroendocrine Cells: Specialized NEURONS that produce hormones, such as NEUROPEPTIDES or BIOGENIC AMINES. They generally are in the NERVOUS SYSTEM, such as HYPOTHALAMUS, but can be found in other organs or systems. These neurons contain dense neurosecretory granules and PROPROTEIN CONVERTASES allowing the rapidly release of NEUROHORMONES into the blood circulation upon stimulation.Carcinoid Tumor: A usually small, slow-growing neoplasm composed of islands of rounded, oxyphilic, or spindle-shaped cells of medium size, with moderately small vesicular nuclei, and covered by intact mucosa with a yellow cut surface. The tumor can occur anywhere in the gastrointestinal tract (and in the lungs and other sites); approximately 90% arise in the appendix. It is now established that these tumors are of neuroendocrine origin and derive from a primitive stem cell. (From Stedman, 25th ed & Holland et al., Cancer Medicine, 3d ed, p1182)Hyperostosis, Diffuse Idiopathic Skeletal: A disease of elderly men characterized by large osteophytes that bridge vertebrae and ossification of ligaments and tendon insertions.Neurosecretory Systems: A system of NEURONS that has the specialized function to produce and secrete HORMONES, and that constitutes, in whole or in part, an ENDOCRINE SYSTEM or organ.Carcinoma, Neuroendocrine: A group of carcinomas which share a characteristic morphology, often being composed of clusters and trabecular sheets of round "blue cells", granular chromatin, and an attenuated rim of poorly demarcated cytoplasm. Neuroendocrine tumors include carcinoids, small ("oat") cell carcinomas, medullary carcinoma of the thyroid, Merkel cell tumor, cutaneous neuroendocrine carcinoma, pancreatic islet cell tumors, and pheochromocytoma. Neurosecretory granules are found within the tumor cells. (Segen, Dictionary of Modern Medicine, 1992)Neuroendocrine Tumors: Tumors whose cells possess secretory granules and originate from the neuroectoderm, i.e., the cells of the ectoblast or epiblast that program the neuroendocrine system. Common properties across most neuroendocrine tumors include ectopic hormone production (often via APUD CELLS), the presence of tumor-associated antigens, and isozyme composition.Local Lymph Node Assay: The local lymph node assay (LLNA) is an alternative method for the identification of chemicals that have the ability to cause skin sensitization and allergic contact dermatitis. Endpoints have been established so fewer animals are required and less painful procedures are used.Myasthenia Gravis, Autoimmune, Experimental: Any autoimmune animal disease model used in the study of MYASTHENIA GRAVIS. Injection with purified neuromuscular junction acetylcholine receptor (AChR) (see RECEPTORS, CHOLINERGIC) components results in a myasthenic syndrome that has acute and chronic phases. The motor endplate pathology, loss of acetylcholine receptors, presence of circulating anti-AChR antibodies, and electrophysiologic changes make this condition virtually identical to human myasthenia gravis. Passive transfer of AChR antibodies or lymphocytes from afflicted animals to normals induces passive transfer experimental autoimmune myasthenia gravis. (From Joynt, Clinical Neurology, 1997, Ch 54, p3)Autoimmune Diseases: Disorders that are characterized by the production of antibodies that react with host tissues or immune effector cells that are autoreactive to endogenous peptides.Lupus Erythematosus, Systemic: A chronic, relapsing, inflammatory, and often febrile multisystemic disorder of connective tissue, characterized principally by involvement of the skin, joints, kidneys, and serosal membranes. It is of unknown etiology, but is thought to represent a failure of the regulatory mechanisms of the autoimmune system. The disease is marked by a wide range of system dysfunctions, an elevated erythrocyte sedimentation rate, and the formation of LE cells in the blood or bone marrow.Thymectomy: Surgical removal of the thymus gland. (Dorland, 28th ed)Receptors, Cholinergic: Cell surface proteins that bind acetylcholine with high affinity and trigger intracellular changes influencing the behavior of cells. Cholinergic receptors are divided into two major classes, muscarinic and nicotinic, based originally on their affinity for nicotine and muscarine. Each group is further subdivided based on pharmacology, location, mode of action, and/or molecular biology.Thymoma: A neoplasm originating from thymic tissue, usually benign, and frequently encapsulated. Although it is occasionally invasive, metastases are extremely rare. It consists of any type of thymic epithelial cell as well as lymphocytes that are usually abundant. Malignant lymphomas that involve the thymus, e.g., lymphosarcoma, Hodgkin's disease (previously termed granulomatous thymoma), should not be regarded as thymoma. (From Stedman, 25th ed)MassachusettsHospitals, General: Large hospitals with a resident medical staff which provides continuous care to maternity, surgical and medical patients.Alfaxalone Alfadolone Mixture: A 3:1 mixture of alfaxalone with alfadolone acetate that previously had been used as a general anesthetic. It is no longer actively marketed. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1445)BostonSister Mary Joseph's Nodule: Metastatic lesion of the UMBILICUS associated with intra-abdominal neoplasms especially of the GASTROINTESTINAL TRACT or OVARY.Umbilicus: The pit in the center of the ABDOMINAL WALL marking the point where the UMBILICAL CORD entered in the FETUS.Education, Graduate: Studies beyond the bachelor's degree at an institution having graduate programs for the purpose of preparing for entrance into a specific field, and obtaining a higher degree.History, 19th Century: Time period from 1801 through 1900 of the common era.History, 20th Century: Time period from 1901 through 2000 of the common era.Nobel PrizeFaculty: The teaching staff and members of the administrative staff having academic rank in an educational institution.