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Medical Dictionary - Dictionary of Medicine and Human Biology

Medical Dictionary


picokatal (pkat) (pi′ko-kat′al; pe′ko-kat′al)
One trillionth of a katal (10−12 katal).

picolinic acid (pik-o-lin′ik)
Pyridine-4-carboxylic acid;an isomer of nicotinic acid.

picolinuric acid (pik-o-li-noor′ik)
N-Picolinoylglycine;the amide, with glycine, of picolinic acid; a hippuric acid analog in which picolinic acid, rather than benzoic acid, is conjugated with glycine and excreted.

picometer (pm) (pi′ko-me-ter)
One-trillionth of a meter. SYN: bicron.

picomole (pmol) (pe′ko-mol; pi′ko-mol)
One-trillionth of a mole (10−12 mol).

Picornaviridae (pi-kor-na-vir′i-de)
A family of very small (20–30 nm) ether-resistant, nonenveloped viruses having a core of positive sense single-stranded infectious RNA enclosed in a capsid of icosahedral symmetry with 60 capsomeres. Numerous species (including the polioviruses, coxsackieviruses, and echoviruses) are included in the family. There are five accepted genera: Enterovirus, Rhinovirus, Hepatovirus, Cardiovirus, and Aphthovirus. [It. piccolo, very small, + RNA + -viridae]

picornavirus (pi-kor-na-vi′rus)
A virus of the family Picornaviridae.

picramic acid (pi-kram′ik)
Red crystals sometimes found in the blood of persons poisoned with picric acid; the crystals are formed as a result of partial reduction of picric acid.

Picrasma (pi-kraz′ma)
See quassia. [L., fr. G. pikrasmos, bitterness]

picrate (pik′rat)
A salt of picric acid.

picric acid (pik′rik)
Has been used as an application in burns, eczema, erysipelas, and pruritus. SYN: carbazotic acid, nitroxanthic acid. [G. pikros, bitter]

picrocarmine (pik-ro-kar′min, -men)
See p. stain.

picroformol (pik′ro-for′mol)
See p. fixative.

picronigrosin (pik′ro-ni′gro-sin)
See p. stain.

picrotoxin (pik′ro-tok′sin)
A very bitter neutral principle derived from the fruit of Anamirta cocculus (family Menispermaceae); a central nervous system stimulant, used as an antidote for poisoning by barbiturates and certain other CNS-depressant drugs; a convulsant and GABA antagonist used extensively in experimental procedures studying seizure mechanisms. SYN: cocculin. [G. pikros, bitter, + toxicon, poison]

picrotoxinin (pik-ro-tok′si-nin)
A lactone breakdown product of picrotoxin; pharmacologic properties resemble those of picrotoxin.

picryl (pik′ril)
The organic radical derived from picric acid by removal of the hydroxyl group.

pictograph (pik′to-graf)
A vision test chart for illiterates.

Abbreviation for pelvic inflammatory disease.

Pidgin Sign English (PSE) (pij′in)
A system of communication that is a manual representation of English in which American Sign Language signs are used in English word order; there are no inflectional signs, and finger spelling is used for proper names.

piebaldism (pi′bawld-izm) [MIM*172800]
Patchy absence of the pigment of scalp hair, giving a streaked appearance; patches of vitiligo may be present in other areas due to absence of melanocytes; often transmitted as an autosomal dominant trait caused by mutation in the KIT protooncogene on 4q and may be associated with neurologic defects [MIM*172850] or eye changes [MIM*172870]. Cf.:Waardenburg syndrome. SYN: cutaneous albinism, piebald skin, piebaldness.

piebaldness (pi′bawld-ness)
SYN: piebaldism.

piece (pes)
A part or portion. end p. a part of the spermatozoon consisting of an axoneme surrounded only by the flagellar membrane. Fab p. SYN: Fab fragment. Fc p. SYN: Fc fragment. middle p. a part of the spermatozoon characterized by an axoneme and by a sheath of mitochondria arranged in a tight helix. principal p. the principal part of the spermatozoon, which is about 45 μm long and has a characteristic fibrous sheath surrounding the axoneme.

piedra (pe-a′dra)
A fungus disease of the hair characterized by the formation of numerous waxy, small, firm, nodular masses on the hair shaft. SEE ALSO: trichosporosis. [Sp. a stone] black p. p. involving the hairs of the scalp, caused by Piedraia hortae and characterized by firmly adherent black, hard, gritty nodules composed of an organized, firmly cemented mass of fungus cells; the fungal growth is always located above the level of the hair follicles; the disease occurs in humid tropical areas of the Americas, Africa, and Asia, and attacks chimpanzees and other primates as well as humans. p. nostras a condition similar to p., but affecting the hair of the beard. white p. p. of the beard, moustache, and genital areas, as well as the scalp, caused by Trichosporon beigelii and found in South America, Europe, and Japan; characterized by soft, mucilaginous, white to light brown nodules, within as well as on the hairs.

Piedraia (pi′e-dri′a)
A genus of fungi, based on P. hortae, which is probably the only species and which causes black piedra. [see piedra]

pieds terminaux (pe-e′ter-me-no′)
SYN: axon terminals, under terminal. [Fr., end feet]

Luigi, 20th century Argentinian dermatologist. See atrophoderma of Pasini and P..

Pierre Robin
See Robin.

piesimeter, piesometer (pi-e-sim′e-ter, pi-e-som′e-ter)
An instrument for measuring the pressure of a gas or a fluid. SYN: piezometer. [G. piesis, pressure] Hales p. a glass tube inserted into an artery at right angles to its axis, the pressure being shown by the height to which the blood ascends in the tube.

piesis (pi′e-sis)
SYN: blood pressure. [G. pressure]

piezochemistry (pi-e-zo-kem′is-tre)
The study of the effect of very high pressures on chemical reactions.

piezoelectric (pi′e-zo-e-lek′trik)
Pertaining to piezoelectricity.

piezoelectricity (pi′e-zo-e-lek-tris′i-te)
Electric currents generated by pressure upon certain crystals, e.g., quartz, mica, calcite. [G. piezo, to press, squeeze, + electricity]

piezogenic (pi′e-zo-jen′ik)
Resulting from pressure. [G. piezo, to press, squeeze, + genesis, origin]

piezometer (pi-e-zom′e-ter)
SYN: piesimeter.

A container, usually made of lead, used for shielding vials or syringes containing radioactive materials. [jargon]

A type of necrotizing enteritis endemic in the Papua New Guinea highlands caused by the B toxin of Clostridium perfringens type C; occurs predominantly in children because of poor immunity to B toxin and a low level of intestinal proteases resulting from a diet low in protein and high in sweet potatoes.

1. Any coloring matter, as that of the red blood cells, hair, iris, etc., or the stains used in histologic or bacteriologic work, or that in paints. 2. A medicinal preparation for external use, applied to the skin like paint, or coloring agents used in paints. [L. pigmentum, paint] bile pigments coloring matter in the bile derived from porphyrins by rupture of a methane bridge; e.g., bilirubin, biliverdin. chymotropic p. a p. dissolved in the vacuole of a plant cell. [G. chymos, juice, + trope, turning, inclination, + -ic] formalin p. a p. formed when acid aqueous solutions of formaldehyde act on blood-rich tissues; characterized by rotation of the plane of polarized light, withstanding extraction in aqueous and lipid solvents, being bleached in acids and hydrogen peroxide; not formed when tissue is fixed with formaldehyde buffered to pH levels above 6. hematogenous p. a p. derived from the hemoglobin of the red blood cells. hepatogenous p. bile p. derived from the destruction of hemoglobin in the liver. malarial p. a dark brown, granular p. that rotates the plane of polarized light and has other properties similar to formalin p.; occurs in parasites, such as Plasmodium malariae, around brain capillaries, and in fixed macrophages of spleen, liver, bone marrow, and lymph nodes; composed of excess protein, an iron porphyrin, and hematin left over from the metabolism of hemoglobin by the malarial parasite within the red blood cell. See malarial p. stain. melanotic p. SYN: melanin. natural p. a naturally occurring colored compound; absorbs light in the visible range of the electromagnetic spectrum. Cf.:structural color. SYN: biochrome. respiratory pigments the oxygen-carrying (colored) substances in blood and tissues (hemoglobin, myoglobin, hemocyanin, etc.). visual pigments the photopigments in the retinal cones and rods that absorb light and initiate the visual process. wear-and-tear p. lipofuscin that accumulates in aging or atrophic cells as a residue of lysosomal digestion.

pigmentary (pig′men-tar-e)
Relating to a pigment.

pigmentation (pig-men-ta′shun)
Coloration, either normal or pathologic, of the skin or tissues resulting from a deposit of pigment. arsenic p. generalized but spotty increased melanin p. of the skin in chronic arsenic poisoning. exogenous p. discoloration of the skin or tissues by a pigment introduced from without.

pigmented (pig′men-ted)
Colored as the result of a deposit of pigment.

pigmentolysin (pig-men-tol′i-sin)
An antibody causing destruction of pigment. [L. pigmentum, pigment, + G. lysis, a loosening]

pigmentum nigrum (pig-men′tum ni′grum)
Melanin of the choroid coat of the eye.

pigmy (pig′me)
SYN: pygmy.

Maurice-C.J., French surgeon, *1871. See P. formula.

pilar, pilary (pi′lar, pil′a-re)
SYN: hairy. [L. pilus, hair]

pile (pil)
1. A series of plates of two different metals imposed alternately one on the other, separated by a sheet of material moistened with a dilute acid solution, used to produce a current of electricity. [L. pila, pillar] 2. An individual hemorrhoidal tumor. See hemorrhoids. [L. pila, ball] sentinel p. a circumscribed thickening of the mucous membrane at the lower end of a fissure of the anus. thermoelectric p. SYN: thermopile.

piles (pilz)
SYN: hemorrhoids. [L. pila, a ball]

pileus (pi′le-us)
SYN: greater omentum. [L. pileum or p., a felt cap]

pili (pi′li)
Plural of pilus. [L.]

pilimiction (pi-li-mik′shun)
Passage of hairs in the urine, as in cases of dermoid tumors, or of threads of mucus in the urine. [L. pilus, hair, + mictio, urination]

pilin (pi′lin)
The protein component of bacterial adhesive appendages that help the bacterium to stick to tissue or container surfaces, often the glycoproteins on the surface of eukaryotic cells. [pilus 2. + -in]

1. A small globular mass of some coherent, but soluble, substance containing a medicinal substance to be swallowed. SEE ALSO: tablet. 2. The P.; a colloquial term for oral contraceptives. [L. pilula; dim. of pila, ball] bread p. a placebo made of bread crumbs or other inactive substances. morning after p. an oral drug that, when taken by a woman within 2–3 days after intercourse, reduces the probability that she will become pregnant. SYN: emergency hormonal contraception.Usually the term refers to oral contraceptive tablets (birth control pills) taken briefly in higher-than-usual dosage. Use of oral contraceptives has been approved by the U.S. Food and Drug Administration as a means of “emergency contraception” after rape or unplanned and unprotected intercourse, but not as a regular means of preventing pregnancy. The Yupze regimen consists of a combination of progestogen (levonorgestrel 0.25 mg or norgestrel 0.5 mg) and estrogen (ethinyl estradiol 0.05 mg) taken at once and repeated in 12 hours. Depending on the product used, this regimen requires taking 2–4 tablets of a standard oral contraceptive. The first dose should preferably be taken within 24 hours after intercourse, and no later than 72 hours after. The method reduces the likelihood of pregnancy by about 75%. About 50% of women experience uterine bleeding within 1 week and most of the rest within 3 weeks unless conception has occurred. If taken early enough, the hormones may prevent fertilization from taking place by altering tubal function or exerting toxicity against the ovum. Probably, however, they usually act by preventing implantation of a fertilized ovum. At this hormone dosage the incidence of nausea is about 50% and of vomiting about 20%; headache, fluid retention, and breast tenderness may also occur. (Levonorgestrel administered alone has been reported to cause less nausea than combination therapy and to yield comparable or better protection against pregnancy.) This procedure is contraindicated in women for whom oral contraceptives are contraindicated, such as those with hypertension or a history of stroke or thromboembolic disease. The short course of high-dose hormones probably does not interrupt a pregnancy once implantation has occurred, and there is no evidence that fetal harm has occurred when such a pregnancy has continued to term. However, hormone use is contraindicated in known pregnancy or if the woman has had unprotected intercourse within the preceding 3–10 days. pep pills colloquialism for tablets containing a central nervous system stimulant, especially amphetamine.

pillar (pil′ar)
A structure or part having a resemblance to a column or p.. [L. pila] anterior p. of fauces palatoglossal arch. anterior p. of fornix SYN: column of fornix. Corti pillars SYN: p. cells, under cell. pillars of fauces palatoglossal arch, palatopharyngeal arch. pillars of fornix the columna fornicis [TA] and crus fornicis [TA]. p. of iris SYN: trabecular tissue of sclera. posterior p. of fauces palatopharyngeal arch. posterior p. of fornix SYN: crus fornicis.

pillet (pil′et)
A small pill.

pill mass
SYN: pilular mass.

pill-rolling (pil′rol′ing)
A circular movement of the opposed tips of the thumb and the index finger appearing as a form of tremor in paralysis agitans.

Hair. [L. pilus]

pilocarpine (pi-lo-kar′pen)
An alkaloid obtained from the leaves of Pilocarpus; Microphyllus or P. jaborandi (family Rutaceae), shrubs of the West Indies and tropical America; a parasympathomimetic agent used as a diaphoretic, sialogogue, and stimulant of intestinal motility, and externally as a miotic and in the treatment of glaucoma; used as the hydrochloride and the nitrate salts. [G. pilos, a felt hat, + karpos, fruit]

pilocarpus (pil′o-kar-pus)
A genus of trees and shrubs found in Central and South America and in the West Indies. Constitutes the botanical source for pilocarpine, an alkaloid that activates cholinergic muscarinic receptors. Pilocarpine is used in the treatment of glaucoma, in which it is instilled in the eye. Sudorific; miotic. SYN: Jaborandi.

pilocystic (pi′lo-sis′tik)
Denoting a dermoid cyst containing hair. [pilo- + G. kystis, bladder]

piloerection (pi′lo-e-rek′shun)
Erection of hair due to action of arrectores pilorum muscles.

piloid (pi′loyd)
Hairlike; resembling hair. [pilo- + G. eidos, resemblance]

pilomatrixoma (pi′lo-ma-trik-so′ma)
A benign solitary hair follicle tumor, often starting in childhood, containing cells resembling basal cell carcinoma and areas of epithelial necrosis forming eosinophilic ghost cells with variable calcification and foreign body giant cell reaction in the fibrous stroma. SYN: Malherbe calcifying epithelioma. [pilo- + matrix + G. -oma, tumor]

pilomotor (pi′lo-mo′ter)
Moving the hair; denoting the arrectores pilorum muscles of the skin and the postganglionic sympathetic nerve fibers innervating these small smooth muscles. [pilo- + L. motor, mover]

pilonidal (pi-lo-ni′dal)
Denoting the presence of hair in a dermoid cyst or in a sinus opening on the skin. [pilo- + L. nidus, nest]

pilose (pi′los)
SYN: hairy. [L. pilosus]


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