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Medical Dictionary


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leptotene (lep′to-ten)
Early stage of prophase in meiosis in which the chromosomes contract and become visible as long filaments well separated from each other. SYN: leptonema. [lepto- + G. tainia, band, tape]

leptothricosis (lep′to-thri-ko′sis)
Obsolete term for any disease caused by the now invalid genus Leptothrix.

Leptothrix (lep′to-thriks)
A now invalid genus of sheathed organisms closely related to the genus Sphaerotilus found in fresh water.

Leptotrichia (lep-to-trik′e-a)
A genus of anaerobic, nonmotile bacteria containing Gram-negative, straight or slightly curved rods, 5–15 μm in length, with one or both ends rounded, often pointed. Granules are distributed evenly along the long axis, and one or more large granules may localize near the end of the cell. Branched or clubbed forms do not occur. Two or more cells join together and form septate filaments of varying length; in older cultures, filaments up to 200 μm may form and twist around each other; large, coccoid bodies may be found within a filament as a cell lyses. Carbon dioxide is essential for optimal growth. Lactic acid is produced from glucose. These organisms occur in the oral cavity of humans. The type species is L. buccalis. [lepto- + G. thrix, hair] L. buccalis a bacterial species found in the human mouth rarely found in the blood of immunocompromised patients; it is the type species of the genus L..

Leptotrombidium (lep′to-trom-bid′e-um)
An important genus of trombiculid mites, formerly considered a subgenus of the genus Trombicula, which includes all of the vectors of scrub typhus (tsutsugamushi disease). Members of L. that serve as vectors of scrub typhus are within the L. deliense group: L. akamushi is the classical vector in Japan; L. deliense is the primary vector, extending from New Guinea, Australia, the Philippines, China, and Southeast Asia to western Pakistan; L. fletcheri is found in Malaysia, New Guinea, and the Philippines. Some eight other species have also been implicated in scrub typhus transmission in more limited areas. L. akamushi one of two species, the other being L. deliensis (T. deliensis), implicated in the transmission of Rickettsia tsutsugamushi, agent of tsutsugamushi disease in Japan and elsewhere in the Orient; the larvae of these species are characteristic parasites of rodents, which therefore are reservoirs of human infections, although the mites themselves are also reservoirs, as their rickettsial parasites are transovarially transmitted from generation to generation (a requirement for transmission to humans as only larval mites feed parasitically and then only once in their lifetimes). SYN: Trombicula akamushi.

lergotrile (ler′go-tril)
A derivative of ergot which exerts agonistic properties on dopamine receptors; similar to bromocriptine and lisuride.

Leri
André, French orthopedic surgeon, 1875–1930. See L. pleonosteosis, L. sign, L.-Weill disease, L.-Weill syndrome.

Leriche
René, French surgeon, 1879–1955. See L. operation, L. syndrome.

Lermoyez
Marcel, French otolaryngologist, 1858–1929. See L. syndrome.

Lerner
I.M., U.S. population geneticist, 1910–1967. See L. homeostasis.

Leroy
Edgar August, French physician, *1883. See Fiessinger-L.-Reiter syndrome.

LES
Acronym for lower esophageal sphincter; Lambert-Eaton syndrome.

lesbian (lez′be-an)
1. A female homosexual. 2. Pertaining to homosexuality between women. See gay.

lesbianism (lez′be-an-izm)
Homosexuality between women. SYN: sapphism. [G. lesbios, relating to the island of Lesbos]

Lesch
Michael, U.S. pediatrician, *1939. See L.-Nyhan syndrome.

Leser
Edmund, German surgeon, 1828–1916. See L.-Trélat sign.

lesion (le′zhun)
1. A wound or injury. 2. A pathologic change in the tissues. 3. One of the individual points or patches of a multifocal disease. [L. laedo, pp. laesus, to injure] Baehr-Lohlein l. SYN: Lohlein-Baehr l.. Bankart l. a tear of the anterior glenoid labrum accompanying detachment of the inferior glenohumeral ligament. benign lymphoepithelial l. benign tumor-like masses of lymphoid tissue in the parotid gland, containing scattered small, mainly solid islands of epithelial cells. SYN: Godwin tumor. Bracht-Wächter l. a focal collection of lymphocytes and mononuclear cells within the myocardium in bacterial endocarditis. caviar l. a dilated vein or varicule existing in the venous collecting system under the tongue. coin l. of lungs SYN: nodular opacity. Dieulafoy l. an abnormally large submucosal artery located in the proximal stomach that may be the site of acute and recurrent episodes of massive hemorrhage. Duret l. small hemorrhage(s) in the floor of the fourth ventricle or beneath the aqueduct of Sylvius. Ghon primary l. SYN: Ghon tubercle. gross l. a l. plainly visible to the naked eye. high-grade squamous intraepithelial l. (HSIL, HGSIL) term used in the Bethesda system for reporting cervical/vaginal cytologic diagnosis to describe a spectrum of noninvasive cervical epithelial abnormalities, including moderate and severe dysplasia, carcinoma in situ, and cervical intraepithelial neoplasia grades 2 and 3. SEE ALSO: Bethesda system, ASCUS, atypical glandular cells of undetermined significance, under cell, low-grade squamous intraepithelial l.. Hill-Sachs l. an irregularity seen in the head of the humerus following anterior dislocation of the shoulder; caused by impaction of posterolateral portion of the head of the humerus against the anterior edge of the glenoid. Janeway l. one of the stigmata of infectious endocarditis: irregular, erythematous, flat, painless macules on the palms, soles, thenar and hypothenar eminences of the hands, tips of the fingers, and plantar surfaces of the toes; rarely a diffuse rash. In acute endocarditis the lesions may be hemorrhagic or purple. Lohlein-Baehr l. focal embolic glomerulonephritis occurring in bacterial endocarditis. SYN: Baehr-Lohlein l.. lower motor neuron l. injury to motor cells in the brainstem or spinal cord, or of the axons derived from them. low-grade squamous intraepithelial l. (LGSIL, LSIL) term used in the Bethesda system for reporting cervical/vaginal cytologic diagnosis to describe a spectrum of noninvasive cervical epithelial abnormalities; these lesions include the cellular changes associated with human papilloma virus cytopathologic effect and mild dysplasia (cervical intraepithelial neoplasia grade 1). SEE ALSO: Bethesda system, reactive changes, under change, ASCUS, atypical glandular cells of undetermined significance, under cell. Mallory-Weiss l. SYN: Mallory-Weiss syndrome. precancerous l. a noninvasive l. with a predictable likelihood of becoming malignant; e.g., actinic keratosis. radial sclerosing l. a variant of sclerosing adenosis of the breast with central scar formation and radiating hyperplastic ducts. SYN: radial scar. ring-wall l. a small ring hemorrhage in the brain that stimulates proliferation of a glial ring. supranuclear l. injury to cerebral descending (corticonuclear) fibers above the brainstem or spinal motor nerve nucleus. SYN: upper motor neuron l.. upper motor neuron l. SYN: supranuclear l.. wire-loop l. thickening of the basement membrane, with fibrinoid staining, of scattered peripheral capillaries in renal glomeruli; characteristic of renal involvement in systemic lupus erythematosus; the appearance of an affected capillary wall resembles a loop used in microbiology.

Lesser
Ladislaus Leo, German surgeon born in Poland, 1846–1925. See L. triangle.

Lesshaft
Pjotr F., Russian physician, 1836–1909. See L. triangle.

LET
Abbreviation for linear energy transfer.

lethal (le′thal)
Pertaining to or causing death; denoting especially the causal agent. [L. letalis, fr. letum, death] clinical l. a disorder that culminates in premature death. genetic l. a disorder that prevents effective reproduction by those affected; e.g., Klinefelter syndrome.

lethality (le-thal′i-te)
The quality or state of being lethal.

lethargy (leth′ar-je)
Relatively mild impairment of consciousness resulting in reduced alertness and awareness; this condition has many causes but is ultimately due to generalized brain dysfunction. [G. lethargia, drowsiness]

LETS
Acronym for large, external transformation-sensitive fibronectin. See fibronectins.

Letterer
Erich, German pathologist, *1895. See L.-Siwe disease.

Leu
Symbol for leucine; leucyl.

leuc-, leuco-
White; white blood cell. See leuko-, leuk-. [G. leukos, white]

leucin (loo′sin)
SYN: leukin.

leucine (L, Leu) (loo′sen)
2-Amino-4-methylvaleric acid;the l-isomer is one of the amino acids found in proteins; a nutritionally essential amino acid. l. aminopeptidase aminopeptidase (cytosol). l. dehydrogenase an enzyme that catalyzes the reaction of l-l., water, and NAD+ to produce NADH, ammonia, and 4-methyl-2-oxopentanoate; used in the treatment of certain tumors. l. zipper a structural motif found in a number of proteins ( e.g., some of the DNA-binding regulatory proteins) in which leucyl residues align along one edge of the helix and can interdigitate with a similar structure on another protein molecule. [Zipper, orig. a trademark for a fastening device with two rows of interlocking teeth]

leucinosis (loo′si-no′sis)
A condition in which there is an abnormally large proportion of leucine in the tissues and body fluids.

leucinuria (loo-si-noo′re-a)
The excretion of leucine in the urine.

leucoharmine (loo-ko-har′men)
SYN: harmine.

leucoline (loo′ko-len)
SYN: quinoline (1) .

leucomethylene blue (lu′ko-meth′i-len)
The reduced and colorless form of methylene blue. SYN: methylene white.

Leuconostoc (loo-ko-nos′tok)
A genus of microaerophilic to facultatively anaerobic bacteria (family Lactobacillaceae) containing Gram-positive, spherical cells which may, under certain conditions, lengthen and become pointed and even form rods. Lactic and acetic acids are produced by these organisms. They are found in plant juices and in milk. The type species is L. mesenteroides. [G. leukos, white, + nostoc, a genus of algae (a word coined by Paracelsus)] L. mesenteroides a species found in fermenting vegetables and other plant materials and in prepared meat products; it is an active slime (dextran) producer, the dextran commonly used as a plasma expander; it is the type species of the genus L..

leuco patent blue (loo′ko pat′ent) [C.I. 42051]
A sulfonated triphenylmethane dye reduced and decolorized with zinc and acetic acid to produce a stable solution; used to demonstrate hemoglobin peroxidase. SYN: patent blue V.

leucovorin (loo′ko-vor-in)
SYN: folinic acid. l. calcium the calcium salt of l. (folinic acid); used to counteract toxic effects of folic acid antagonists, for the treatment of megaloblastic anemias, and as an adjunct to cyanocobalamin in pernicious anemia. SYN: calcium folinate.

Leudet
Théodor E., French physician, 1825–1887. See L. tinnitus.

leuenkephalin (loo-en-kef′a-lin)
See enkephalins.

leuk-
See leuko-.

leukanemia (loo-ka-ne′me-a)
Obsolete term for erythroleukemia. [leukemia + anemia]

leukapheresis (look′a-fe-re′sis)
A procedure, analogous to plasmapheresis, in which leukocytes are removed from the withdrawn blood and the remainder of the blood is retransfused into the donor. [leuko- + G. aphairesis, a withdrawal]

leukemia (loo-ke′me-a)
Progressive proliferation of abnormal leukocytes found in hemopoietic tissues, other organs, and usually in the blood in increased numbers. L. is classified by the dominant cell type, and by duration from onset to death. This occurs in acute l. within a few months in most cases, and is associated with acute symptoms including severe anemia, hemorrhages, and slight enlargement of lymph nodes or the spleen. The duration of chronic l. exceeds one year, with a gradual onset of symptoms of anemia or marked enlargement of spleen, liver, or lymph nodes. SYN: leukocytic sarcoma. [leuko- + G. haima, blood] acute lymphocytic l. (ALL) lymphocytic l.. acute promyelocytic l. l. presenting as a severe bleeding disorder, with infiltration of the bone marrow by abnormal promyelocytes and myelocytes, a low plasma fibrinogen, and defective coagulation. adult T-cell l. (ATL) SYN: adult T-cell lymphoma. aleukemic l. l. in which abnormal (or leukemic) cells are absent in the peripheral blood. basophilic l., basophilocytic l. a form of granulocytic l. in which there are unusually great numbers of basophilic granulocytes in the tissues and circulating blood; in some instances, the immature and mature basophilic forms may represent from 40 to 80% of the total numbers of white blood cells. SYN: mast cell l.. chronic granulocytic l. SYN: chronic myelocytic l.. chronic myelocytic l. a heterogeneous group of myeloproliferative disorders that may evolve into acute l. in late stages ( i.e., blast crisis.) SYN: chronic granulocytic l., chronic myelogenous l., chronic myeloid l.. chronic myelogenous l. (CML) SYN: chronic myelocytic l.. chronic myeloid l. SYN: chronic myelocytic l.. l. cutis yellow-brown, red, blue-red, or purple, sometimes nodular lesions associated with diffuse infiltration of leukemic cells in the skin; the involvement may be diffuse and generalized, i.e., so-called universal l. cutis, or it may be localized. embryonal l. SYN: stem cell l.. eosinophilic l., eosinophilocytic l. a form of granulocytic l. in which there are conspicuous numbers of eosinophilic granulocytes in the tissues and circulating blood, or in which such cells are predominant; in chronic disease of this type, the total white blood cell count may be as high as 200,000–250,000 per mm3, with as many as 80 or 90% being eosinophils, chiefly adult forms. granulocytic l. a form of l. characterized by an uncontrolled proliferation of myelopoietic cells in the bone marrow and in extramedullary sites, and the presence of large numbers of immature and mature granulocytic forms in various tissues (and organs) and in the circulating blood; the total count may range from 1000 (aleukemic variety) to several hundred thousand per cu mm. The predominant cell is usually of the neutrophilic series, but, in a few instances, eosinophilic or basophilic granulocytes, or even megakaryocytes, may represent the chief form; early in granulocytic l., the circulating blood may contain excessive numbers of all of the granulocytic forms. SYN: leukemic myelosis (1) , myelocytic l., myelogenic l., myelogenous l., myeloid l.. hairy cell l. a rare, usually chronic disorder characterized by proliferation of hairy cells in reticuloendothelial organs and blood. leukemic l. an obsolete redundant term sometimes used to emphasize the occurrence of abundant numbers of leukemic cells in the circulating blood; this classic form of l. is usually termed simply l.. leukopenic l. a form of lymphocytic, granulocytic, or monocytic l. in which the total number of white blood cells in the circulating blood is in the normal range, or may be diminished to various levels that are significantly less than normal. lymphatic l. SYN: lymphocytic l.. lymphoblastic l. acute lymphocytic l. in which the abnormal cells are chiefly (or almost totally) blast forms of the lymphocytic series, or in which unusually large numbers of the immature forms occur in association with adult lymphocytes. lymphocytic l. a variety of l. characterized by an uncontrolled proliferation and conspicuous enlargement of lymphoid tissue in various sites ( e.g., lymph nodes, spleen, bone marrow, lungs), and the occurrence of increased numbers of cells of the lymphocytic series in the circulating blood and in various tissues and organs; in chronic disease, the cells are adult lymphocytes, whereas conspicuous numbers of lymphoblasts are observed in the more acute syndromes. SYN: lymphatic l., lymphoid l.. lymphoid l. SYN: lymphocytic l.. mast cell l. SYN: basophilic l.. mature cell l. chronic granulocytic l.. megakaryocytic l. an unusual form of myelopoietic disease that is characterized by a seemingly uncontrolled proliferation of megakaryocytes in the bone marrow, and sometimes by the presence of a considerable number of megakaryocytes in the circulating blood. When bone marrow is examined at various intervals in some instances of chronic myelocytic l., the proliferation of megakaryocytes is more prominent than that of the granulocytes; at such times, the circulating blood may contain megakaryocytes or fragments of megakaryocytic nuclei and cytoplasm, or both, amounting to as much as 5 or 6% of the total number of leukocytes. meningeal l. infiltration of the meninges by leukemic cells, a common occurrence in relapse following systemic administration of chemotherapeutic agents to l. patients. micromyeloblastic l. a form of myelocytic l. in which relatively large proportions of micromyeloblasts are found in the circulating blood and in bone marrow and other tissues. mixed l., mixed cell l. term infrequently used as a designation for granulocytic l., thereby emphasizing the occurrence of different types of cells in the myeloid series ( i.e., neutrophilic, eosinophilic, and basophilic granulocytes), in contrast to the comparatively monotonous pattern observed in lymphocytic and monocytic l.. monocytic l. a form of l. characterized by large numbers of cells that can be definitely identified as monocytes, in addition to larger, apparently related cells formed from the uncontrolled proliferation of the reticuloendothelial tissue; l. in which these two types of cells seem to “overrun” the usual sites of the reticuloendothelial system, and occur in conspicuous numbers in the circulating blood, is frequently referred to as the Schilling type of monocytic l., or sometimes as true monocytic l. The disease runs an acute or subacute course in older persons, and is characterized by swelling of gums, oral ulceration, bleeding in skin or mucous membranes, secondary infection, and splenomegaly. murine l. a leukemic disorder of mice caused by a number of different type C retroviruses. myeloblastic l. a form of granulocytic l. in which there are large numbers of myeloblasts in various tissues (and organs) and in the circulating blood; the immature forms may amount to 30–60% (or even a greater proportion) of the increased total number of white blood cells. Used synonymously with acute granulocytic l.. SYN: leukemic myelosis (2) . myelocytic l., myelogenic l., myelogenous l., myeloid l. SYN: granulocytic l.. myelomonocytic l. a variant of granulocytic l. with monocytosis in the peripheral blood. SYN: Naegeli type of monocytic l.. Naegeli type of monocytic l. SYN: myelomonocytic l.. natural killer cell l. a l. originating from cells of natural killer cell origin; often associated with the presence of monoclonal Epstein-Barr virus infecting tumor cells; usually indicates a leukemic subtype of poor prognosis. neutrophilic l. an unusual form of chronic granulocytic l. in which the greatly increased number of leukocytes in the circulating blood are mature polymorphonuclear neutrophils, with virtually no young or immature granulocytes being observed. plasma cell l. an unusual disease characterized by leukocytosis and other signs and symptoms that are suggestive of l., in association with diffuse infiltrations and aggregates of plasma cells in the spleen, liver, bone marrow, and lymph nodes, and the presence of considerable numbers of plasma cells in the circulating blood; the total number of leukocytes in the latter may range from normal levels to 80,000 or 90,000/mm3, and 5–90% may be plasma cells; multiple myelomas are observed in some examples of plasma cell l., but discrete nodules are not formed in bone. Although there are other clinicopathologic differences in the two conditions, they may be phases of the same basic process. polymorphocytic l. granulocytic l., especially any variety in which the predominant cells are mature, segmented granulocytes. Rieder cell l. a special form of acute granulocytic l. in which the affected tissues and the circulating blood contain relatively large numbers of atypical myeloblasts ( i.e., Rieder cells) that have the usual, faintly granular, immature type of cytoplasm, and a bizarre, comparatively mature nucleus with several wide and deep indentations (suggestive of lobulation). Schilling type of monocytic l. monocytic l.. splenic l. a form of l. in which there is an unusually great degree of enlargement of the spleen, as observed frequently in chronic granulocytic l.. stem cell l. a form of l. in which the abnormal cells are thought to be the precursors of lymphoblasts, myeloblasts, or monoblasts. SYN: embryonal l.. subleukemic l. a form of l. in which abnormal cells are present in the peripheral blood, but the total leukocyte count is not elevated. SYN: hypoleukemia, leukopenic myelosis, subleukemic myelosis, subleukemia.

leukemic (loo-ke′mik)
Pertaining to, or having the characteristics of, any form of leukemia.

leukemid (loo-kem′id)
Any nonspecific type of cutaneous lesion that is frequently associated with leukemia, but is not a localized accumulation of leukemic cells; e.g., petechiae, vesicles, wheals, bullae, hematomas, and the lesions of exfoliative dermatitis and herpes zoster. [leuko- + G. haima, blood, + id (1)]

leukemogen (loo-ke′mo-jen)
Any substance or entity ( e.g., benzene, ionizing radiation) considered to be a causal factor in the occurrence of leukemia.

leukemogenesis (loo-ke-mo-jen′e-sis)
The causation (or induction), development, and progression of a leukemic disease. [leukemia + G. genesis, production]

leukemogenic (loo-ke-mo-jen′ik)
Pertaining to the causation, induction, and development of leukemia; manifesting the ability to cause leukemia.

leukemoid (loo-ke′moyd)
Resembling leukemia in various signs and symptoms, especially with reference to changes in the circulating blood. SEE ALSO: l. reaction. [leukemia + G. eidos, resemblance]

leukemoid reaction
A moderate, advanced, or sometimes extreme degree of leukocytosis in the circulating blood, similar to that occurring in various forms of leukemia, but not the result of leukemic disease; usually, there is a disproportionate increase in the number of forms (including immature stages) in one series of leukocytes, and various examples of myelocytic, lymphocytic, monocytic, or plasmocytic l. may be also indistinguishable from leukocytosis that is associated with certain forms of leukemia. Leukemoid reactions are sometimes observed as a feature of: 1) infectious disease caused by certain bacteria and other biologic agents, e.g., tuberculosis, diphtheria, and chickenpox; 2) intoxication of various types, e.g., eclampsia, serious burns, and mustard gas poisoning; 3) malignant neoplasms, e.g., carcinoma of the colon, of the lung, of the kidney, or of other organs; 4) acute hemorrhage or hemolysis. lymphocytic l. leukocytosis of varying degree, with adult lymphocytes and immature forms amounting to 40% (or more) of the total number of white blood cells in the circulating blood; may be observed in association with pertussis, infectious mononucleosis, gonorrhea, chickenpox, and sarcoidosis. monocytic l. leukocytosis of varying degree, e.g., 30,000–40,000/mm3, with adult monocytes and immature forms amounting to 30% (or more) of the total number of white blood cells in the circulating blood; may be observed in association with tuberculosis, especially the first infection, miliary type. myelocytic l. leukocytosis of at least moderate degree, e.g., 50,000 or more per mm3, with a few immature forms, e.g., 1 or 2% myelocytes, but chiefly mature polymorphonuclear leukocytes in the circulating blood; may be observed in association with tuberculosis, chronic osteomyelitis, various types of empyema, malaria, pneumococcal pneumonia, meningococcal meningitis, Hodgkin disease, and metastases of carcinoma in the bone marrow. plasmocytic l. the presence of unusual numbers of plasma cells, i.e., plasmocytosis, in the bone marrow; may be observed in association with sarcoidosis, rheumatoid arthritis, cirrhosis, Hodgkin disease, and certain of the so-called vascular collagen diseases.

leukin (loo′kin)
A thermostable bactericidal substance extracted from leukocytes. SYN: leucin. [leukocyte + -in]

leuko-, leuk-
White; white blood cells. For some words beginning thus, see leuc- and leuco-. [G. leukos, white]

leukoagglutinin (loo′ko-a-gloo′ti-nin)
An antibody that agglutinates white blood cells.

leukobilin (loo-ko-bil′in)
SYN: white bile. [leuko- + L. bilis, bile]

leukoblast (loo′ko-blast)
An immature granular leukocyte. SYN: proleukocyte. [leuko- + G. blastos, germ]

leukoblastosis (loo′ko-blas-to′sis)
A general term for the abnormal proliferation of leukocytes, especially that occurring in myelocytic and lymphocytic leukemia.

leukochloroma (loo′ko-klo-ro′ma)
Obsolete term for myelocytomatosis. [leuko- + G. chloros, green, + -oma, tumor]

leukocidin (loo-kos′i-din, loo-ko-si′din)
A heat-labile substance that is elaborated by many strains of Staphylococcus aureus, Streptococcus pyogenes, and pneumococci and manifests a destructive action on leukocytes, with or without lysis of the cells. [leukocyte + L. caedo, to kill]

leukocoria, leukokoria (loo-ko-ko′re-a, loo-ko-ko′re-a)
Reflection from a white mass within the eye giving the appearance of a white pupil. SYN: leukokoria, white pupillary reflex. [leuko- white, + G. kore, pupil]

leukocytactic (loo′ko-si-tak′tik)
SYN: leukocytotactic.

leukocytal (loo-ko-si′tal)
SYN: leukocytic.

leukocytaxia, leukocytaxis (loo′ko-si-tak′se-a, -tak′sis)
SYN: leukocytotaxia.

leukocyte (loo′ko-sit)
A type of cell formed in the myelopoietic, lymphoid, and reticular portions of the reticuloendothelial system in various parts of the body, and normally present in those sites and in the circulating blood (rarely in other tissues). Under various abnormal conditions, the total numbers or proportions, or both, may be characteristically increased, decreased, or not altered, and they may be present in other tissues and organs. Leukocytes represent three lines of development from primitive elements: myeloid, lymphoid, and monocytic series. On the basis of features observed with various methods of staining with polychromatic dyes ( e.g., Wright stain). cells of the myeloid series are frequently termed granular leukocytes, or granulocytes; cells of the lymphoid and monocytic series also have granules in the cytoplasm but, owing to their tiny, inconspicuous size and different properties (frequently not clearly visualized with routine methods), lymphocytes and monocytes are sometimes termed nongranular or agranular leukocytes. Granulocytes are commonly known as polymorphonuclear leukocytes (also polynuclear or multinuclear leukocytes), inasmuch as the mature nucleus is divided into two to five rounded or ovoid lobes that are connected with thin strands or small bands of chromatin; they consist of three distinct types: neutrophils, eosinophils, and basophils, named on the basis of the staining reactions of the cytoplasmic granules. Cells of the lymphocytic series occur as two, somewhat arbitrary, normal varieties: small and large lymphocytes; the former represent the ordinary forms and are conspicuously more numerous in the circulating blood and normal lymphoid tissue; the latter may be found in normal circulating blood, but are more easily observed in lymphoid tissue. The small lymphocytes have nuclei that are deeply or densely stained (the chromatin is coarse and bulky) and almost fill the cells, with only a slight rim of cytoplasm around the nuclei; the large lymphocytes have nuclei that are approximately the same size as, or only slightly larger than, those of the small forms, but there is a broader, easily visualized band of cytoplasm around the nuclei. Cells of the monocytic series are usually larger than the other leukocytes, and are characterized by a relatively abundant, slightly opaque, pale blue or blue-gray cytoplasm that contains myriad extremely fine reddish-blue granules. Monocytes are usually indented, reniform, or shaped similarly to a horseshoe, but are sometimes rounded or ovoid; their nuclei are usually large and centrally placed and, even when eccentrically located, are completely surrounded by at least a small band of cytoplasm. SYN: white blood cell. [leuko- + G. kytos, cell] acidophilic l. SYN: eosinophilic l.. agranular l. SYN: nongranular l.. basophilic l. a polymorphonuclear l. characterized by many large, coarse, metachromatic granules (dark purple or blue-black when treated with Wright or similar stains) that usually fill the cytoplasm and may almost mask the nucleus; these leukocytes are unique in that they usually do not occur in increased numbers as the result of acute infectious disease, and their phagocytic qualities are probably not significant; the granules, which contain heparin and histamine, may degranulate in response to hypersensitivity reactions and can be of significance in general inflammation. SYN: basocyte, basophilocyte, mast l.. cystinotic l. a l. having an enhanced content of cystine, found in patients with disorders characterized by the storage of cystine; within the l., the cystine, largely in noncrystalline form, is associated with dense lysosomal particles. endothelial l. obsolete term for a monocyte, a type of l. thought to be derived from reticuloendothelial tissue. eosinophilic l. a polymorphonuclear l. characterized by many large or prominent, refractile, cytoplasmic granules that are fairly uniform in size and bright yellow-red or orange when treated with Wright or similar stains; the nuclei are usually larger than those of neutrophils, do not stain as deeply, and characteristically have two lobes (a third lobe is sometimes interposed on the connecting strand of chromatin); these leukocytes are motile phagocytes with distinctive antiparasitic functions. SYN: acidophilic l., eosinocyte, eosinophil, eosinophile, oxyphil (2) , oxyphile, oxyphilic l.. filament polymorphonuclear l. any mature polymorphonuclear l., especially a neutrophilic l., in which the lobes of the nucleus are interconnected with a thin strand or filament of chromatin. globular l. a type of wandering cell with a small, round nucleus found in the epithelium and lamina propria of the intestinal mucosa of many animals; its cytoplasm contains large eosinophilic globules or droplets. granular l. any one of the polymorphonuclear leukocytes, especially a neutrophilic l.. SEE ALSO: granulocyte, basophilic l., eosinophilic l.. hyaline l. obsolete term for a monocyte, and for a mononuclear macrophage in various lesions. mast l. SYN: basophilic l.. motile l. any l. that manifests active ameboid movement, especially a mature granulocytic l. (eosinophils are less motile than neutrophils or basophils); monocytes manifest a slow, but persistent, wavelike movement. multinuclear l. SYN: polymorphonuclear l.. neutrophilic l. a neutrophilic granulocyte, the most frequent of the polymorphonuclear leukocytes, and also the most active phagocyte among the various types of white blood cells; when treated with Wright stain (or similar preparations), the fairly abundant cytoplasm is faintly pink, and numerous tiny, slightly refractile, relatively bright pink or violet-pink, diffusely scattered granules are recognizable in the cytoplasm; the deeply stained blue or purple-blue nucleus is sharply distinguished from the cytoplasm and is distinctly lobated, with thin strands of chromatin connecting the three to five lobes. nonfilament polymorphonuclear l. a neutrophil, basophil, or eosinophil that is not completely matured, i.e., the lobes of the nuclei remain connected with bands of chromatin, in contrast to the thin strands observed in mature cells. nongranular l. a general, nonspecific term frequently used with reference to lymphocytes, monocytes, and plasma cells; although the cytoplasm of a lymphocyte or monocyte contains tiny granules, it is “nongranular” in comparison with that of a neutrophil, basophil, or eosinophil. SEE ALSO: l.. SYN: agranular l.. nonmotile l. a term sometimes used with reference to lymphocytes, monocytes, and plasma cells; although such forms actually have some degree of motility, they are “nonmotile” in comparison with the actively ameboid neutrophilic, basophilic, and eosinophilic leukocytes. oxyphilic l. SYN: eosinophilic l.. polymorphonuclear l., polynuclear l. common term for granulocyte or granulocytic l.; the term includes basophilic, eosinophilic, and neutrophilic leukocytes, but is usually used especially with reference to the neutrophilic leukocytes. SYN: multinuclear l.. segmented l. any mature polymorphonuclear l., especially a neutrophilic l.. transitional l. obsolete term for a monocyte. Türk l. SYN: Türk cell.

leukocythemia (loo′ko-si-the′me-a)
Obsolete term for leukemia. [leukocyte + G. haima, blood]




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