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Medical Dictionary


parthenogenesis (par′the-no-jen′e-sis)
A form of nonsexual reproduction, or agamogenesis, in which the female reproduces its kind without fecundation by the male. SYN: apogamia, apogamy, apomixia, virgin generation. [G. parthenos, virgin, + genesis, product]

parthenophobia (par′the-no-fo′be-a)
Morbid fear of girls. [G. parthenos, virgin, + phobos, fear]

particle (par′ti-kl)
1. A very small piece or portion of anything. 2. An elementary p. such as a proton or electron. [L. particula, dim. of pars, part] alpha p. (α) a p. consisting of two neutrons and two protons, with a positive charge (2e+); emitted energetically from the nuclei of unstable isotopes of high atomic number (elements of mass number from 82 up); identical to the helium nucleus. SYN: alpha ray. beta p. an electron, either positively (positron, β+) or negatively (negatron, β−) charged, emitted during beta decay of a radionuclide. SEE ALSO: cathode rays, under ray. SYN: beta ray. chromatin particles fine bluish dots thought to represent remnants of the nucleus, occasionally seen in stained erythrocytes. core p. p. released by partial enzymatic digestion of chromatin. Dane particles the larger spherical forms of hepatitis-associated antigens; they compose the virion of hepatitis B virus, containing a 27-nm “core” in which DNA-dependent DNA polymerase and circular, double-stranded DNA have been found. defective interfering p. an incomplete virus that is unable to replicate and interferes with replication of an infectious virus. D.I. p. abbreviation for defective interfering p.. electron transport particles (ETP) fragments of mitochondria still capable of transporting electrons. SYN: submitochondrial particles. elementary p. 1. SYN: platelet. 2. one of the units occurring on the matrical surface of mitochondrial cristae; the head of the p., which measures about 9 nm, attaches to the membrane of the crista by a stalk 5 nm long; the p. may be concerned with the electron transport system. kappa particles inheritable cytoplasmic symbionts, once thought to be particles mainly or exclusively of DNA, occurring in some strains of Paramecium; capable of producing a product lethal to other strains. signal recognition p. (SRP) a small RNA-protein complex that interacts with the signal sequence of nascent secretory proteins. Binding of the signal recognition p. results in arrest of translation until interaction with docking protein, an integral part of the endoplasmic reticulum membrane. submitochondrial particles SYN: electron transport particles. Zimmermann elementary p. obsolete term for platelet.

particulate (par-tik′u-lat)
Relating to or occurring in the form of fine particles.

particulates (par-tik′u-lats)
Formed elements, discrete bodies, as contrasted with the surrounding liquid or semiliquid material; e.g., granules or mitochondria in cells.

partogram (par′to-gram)
Graph of labor parameters of time and dilation with alert and action lines to prompt intervention if the curve deviates from expected. SYN: Friedman curve, labor curve. [L. partus, childbirth, + -gram]

parturient (par-too′re-ent)
Relating to or in the process of childbirth. [L. parturio, to be in labor]

parturifacient (par-toor-e-fa′shent)
1. Inducing or accelerating labor. 2. An agent that induces or accelerates labor. SYN: oxytocic (2) . [L. parturio, to be in labor, + facio, to make]

parturition (par-toor-ish′un)
SYN: childbirth. [L. parturitio, fr. parturio, to be in labor]

part. vic.
Abbreviation for L. partes vicibus, in divided doses.

parulis, pl .parulides (pa-roo′lis, -li-dez)
SYN: gingival abscess. [G. paroulis, gumboil, fr. para, beside, + oulon, gum]

parumbilical (par′um-bil′i-kal)
SYN: paraumbilical.

paruresis (par-u-re′sis)
Inhibited urination, especially in the presence of strangers. [para- + G. ouresis, urination]

parvalbumin (par-val-bu′min)
Any of a group of small water-soluble calcium-binding proteins distinct from calmodulin and other calcium-binding proteins; found in the brain, skeletal muscle, and retina, but not in the heart, liver, or spleen, of various species. [L. parvus, small, + albumin]

Parvobacteriaceae (par′vo-bak-ter-e-a′se-e)
A family name regarded as a former name for the bacterial family Brucellaceae. No type genus has ever been proposed for the family P..

parvocellular (par-vo-sel′u-lar)
Relating to or composed of cells of small size. [L. parvus, small, + Mod. L. cellularis, cellular]

parvoline (par′vo-len)
A ptomaine, C9H13N, from decaying fish.

Parvoviridae (par-vo-vir′i-de)
A family of small viruses containing single-stranded DNA. Virions are 18–26 nm in diameter, are not enveloped, and are ether-resistant. Capsids are of cubic symmetry, with 32 capsomeres. Replication and assembly occur in the nucleus of infected cells. Three genera in the subfamily Parvovirinae are recognized: Parvovirus, Erythrovirus, and Dependovirus, which includes the adeno-associated virus. A second subfamily, Densovirinae, has 3 additional genera, all of which infect arthropods.

Parvovirus (par′vo-vi-rus)
A genus of viruses (family Parvoviridae) that replicate autonomously in suitable cells. Strain B19 infects humans, causing erythema infectiosum and aplastic crisis in hemolytic anemia. [L. parvus, small, + virus]

Parvovirus B19
A single-stranded DNA virus belonging to the family Parvoviridae; the cause of erythema infectiosum (fifth disease) and aplastic crises.P. (B19V) was first isolated in 1975 from a specimen of healthy donor blood. In 1983 it was linked to erythema infectiosum, also called fifth disease, a generally benign febrile exanthem of children. B19V infection occurs worldwide and can attack persons of any age. It is most often contracted in childhood; 30–60% of adults have protective IgG antibody to the virus. Infection is asymptomatic in 20–50% of persons who acquire it. Transmission is usually by respiratory secretions. The virus replicates in bone marrow. Classical erythema infectiosum typically occurs in children 4–15 years of age. Sporadic outbreaks are common, and the peak incidence is during the winter and spring. After an incubation period of 4–14 days, the child develops prodromal symptoms, usually mild, consisting of headache, fever, chills, joint pains, and malaise. About 1 week later, a bright red “slapped cheek” rash appears on the face, and over the next 3–4 days the rash spreads to the rest of the body (proximal extremities, then trunk and distal extremities, including palms and soles), where it has a reticular or maculopapular appearance. Itching, if any, is slight. The rash is an immune response, heralding the appearance of IgM antibody and the end of the period of communicability. The disease typically runs a benign course, and treatment is purely symptomatic. (Like certain other viruses, B19V also occasionally causes a benign exanthem known as papular-purpuric gloves-and-socks syndrome.) Infection in adults follows a different pattern: the “slapped cheek” appearance does not occur, and the rash on the trunk and limbs tends to be milder and more subtle, but 15–20% of adult patients, virtually all of them women, develop significant joint involvement. Deposition of immune complexes in joint membranes leads to sudden onset of symmetric polyarthritis, affecting particularly the metacarpophalangeal and proximal interphalangeal joints, the wrists, and the knees. Swelling may or may not occur. Pain and disability can be severe, and symptoms can persist for weeks or months, although eventual spontaneous resolution is the rule. Because B19V infects the bone marrow, most patients experience a transient decline in red blood cells, white blood cells, and platelets. Generally this is of no consequence, but occasionally it progresses to a transient aplastic crisis (TAC), in which red blood cell production virtually stops and the red blood cell count falls rapidly. The risk of this complication is much greater in sickle cell anemia, autoimmune hemolytic anemias, immunodeficiency, and pregnancy. With the formation of IgG antibody by the immune system, red blood cell formation resumes and the anemia resolves. In patients with congenital or acquired immune deficiency, however, failure to form antibody can lead to prolonged anemia. Infection in a pregnant woman has about 1 chance in 3 of being passed to the fetus and inducing a fetal aplastic crisis. This in turn can result in congestive heart failure and fetal hydrops. Spontaneous recovery is typical, but fetal death occurs in as many as 10% of cases. Fetal infection with B19V apparently does not cause congenital anomalies. Acute B19V infection can be confirmed by a rapid rise and fall of IgM antibody. Diagnosis can also be established by culturing the virus from bone marrow or by ELISA detection of the antigen in serum. The treatment of all forms of B19V infection is purely symptomatic and supportive, since specific antiviral therapy is not available. Hospitalized patients with B19V are isolated, and pregnant workers are advised to avoid contact with them. Severe anemia may require blood transfusions. When prolonged anemia results from inability to form IgM antibody, intravenous immune globulin may help.

parvule (par′vool)
A very small pill. [L. parvulus, very small, fr. parvus, small]

parvus (par′vus)
Small. [L.]

Abbreviation for p-aminosalicylic acid; periodic acid-Schiff stain.

Abbreviation for p-aminosalicylic acid.

Blaise, French scientist, 1623–1662. See p., P. law.

pascal (Pa) (pas′kal)
A derived unit of pressure or stress in the SI system, expressed in newtons per square meter; equal to 10−5 bar or 7.50062 × 10−3 torr. [B. P.]

Pascheff, Pashev
Konstantin M., Bulgarian ophthalmologist, 1873–1961. See P. conjunctivitis.

Enrique, German pathologist, 1860–1936. See P. bodies, under body.

See Pascheff.

Augustine, 20th century Argentinian dermatologist. See atrophoderma of P. and Pierini.

paspalism (pas′pal-izm)
Poisoning by seeds of a species of grass, Paspalum scrobiculatum. [G. paspalos, a kind of millet, fr. pas, all, + pale, meal]

passage (pas′ij)
1. The act of passing. 2. A discharge, as from the bowels or of urine. 3. Inoculation of a series of animals with the same strain of a pathogenic microorganism whereby the virulence usually is increased, but is sometimes diminished. 4. A channel, duct, pore, or opening. [Mediev. L. passo, to pass] blind p. successive transfer of an agent through cultures or animals without apparent replication or disease. nasopharyngeal p. SYN: nasopharyngeal meatus. oropharyngeal p. SYN: fauces. serial p. successive transfer of an infectious agent through a series of cultures or experimental animals, usually to attenuate pathogenicity.

Passalurus ambiguus (pa-sal′u-rus am-big′u-us)
The rabbit pinworm, an oxyurid nematode found abundantly in the cecum and large intestine of rabbits.

Philippas G., German physician, 1815–1893. See P. bar, P. cushion, P. pad, P. ridge.

R.D., 20th century British pathologist. See Harding-P. melanoma.

passiflora (pas-i-flo′ra)
The passion-flower, P. incarnata (family Passifloraceae), a climbing herb of the southern U.S.; the dried flowering and fruiting top has been used in neuralgia, dysmenorrhea, and insomnia, and as an application to hemorrhoids and for burns. [L. passio, passion, + flos (flor-), flower]

passion (pash′un)
1. Intense emotion. 2. Obsolete term for suffering or pain. [L. passio, fr. patior, pp. passus, to suffer]

passive (pas′iv)
Not active; submissive. [L. passivus, fr. patior, to endure]

passivism (pas′iv-izm)
1. An attitude of submission. 2. A sexual practice in which the subject is submissive to the will of the partner in behavior that usually requires the consent of both participants ( e.g., anal intercourse). SEE ALSO: pathic. [see passive]

passivity (pas-iv′i-te)
1. The condition of a metal having formed a protective oxide coating; e.g., rustless metals and aluminum become passive in air. 2. In dentistry, the quality or condition of inactivity or rest assumed by the teeth, tissues, and denture when a removable partial denture is in place but not under masticatory pressure.

pasta, gen. and pl. pastae (pas′ta, -te)
SYN: paste. [L.]

paste (past)
A soft semisolid of firmer consistency than pap, but soft enough to flow slowly and not to retain its shape. SYN: pasta. [L. pasta] dermatologic p. a class of preparations consisting of starch, dextrin, sulfur, calcium carbonate, or zinc oxide made into a p. with glycerin, soft soap, petrolatum, or some fat, with which is incorporated some medicinal substance. desensitizing p. an ointment, usually caustic, coagulating or cytotoxic, formulated to be applied to the cervix of a tooth for the purpose of obtunding pain from sensitive, exposed cementum or dentin.

paster (pa′ster)
The segment forming the part for near vision in two-piece bifocal lenses.

Louis, French chemist and bacteriologist, 1822–1895. See P. vaccine, P. effect, P. pipette.

Pasteurella (pas-ter-el′a)
A genus of aerobic to facultatively anaerobic, nonmotile bacteria (family Brucellaceae) containing very small, Gram-negative, cocci or ellipsoidal to elongated rods which, with special methods, may show bipolar staining. These organisms are parasites of humans and other animals, including birds. The type species is P. multocida. [L. Pasteur] P. aerogenes a species found in swine that may cause human wound infections following pig bites. P. multocida a bacterial species that causes fowl cholera and hemorrhagic septicemia in warm-blooded animals and may infect dog or cat bites or scratches and cause cellulitis and septicemia in humans with chronic disease. Most common pathogen associated with cat and dog bites. Cause of pasteurellosis. It is the type species of the genus P.. P. pestis SYN: Yersinia pestis. P. pseudotuberculosis SYN: Yersinia pseudotuberculosis. P. “SP” a rarely encountered organism of problematic taxonomy that can cause infections after a guinea pig bite; human infections are quite rare, probably because the bacterium is not widespread and is of low virulence. P. tularensis SYN: Francisella tularensis.

pasteurella, pl .pasteurellae (pas-ter-el′a, pas-ter-el′e)
A vernacular term used to refer to any member of the genus P..

pasteurellosis (pas′ter-e-lo′sis)
Infection with bacteria of the genus Pasteurella.

pasteurization (pas′ter-i-za′shun)
The heating of milk, wines, fruit juices, etc., for about 30 minutes at 68°C (154.4°F) whereby living bacteria are destroyed, but the flavor or bouquet is preserved; the spores are unaffected, but are kept from developing by immediately cooling the liquid to 10°C (50°F) or lower. SEE ALSO: sterilization. [L. Pasteur]

pasteurize (pas′ter-iz)
To treat by pasteurization.

pasteurizer (pas′ter-i-zer)
An apparatus used in pasteurization.

Constantin C., Roumanian physician, 1883–1926. See P. sign.

pastil, pastille (pas′til, pas-tel′)
1. A small mass of benzoin and other aromatic substances to be burned for fumigation. 2. SYN: troche. [Fr. pastille; L. pastillus, a roll (of bread), dim. of panis, bread] Sabouraud pastils disks containing barium platinocyanide that undergo a color change when exposed to x-rays; previously used to indicate the administered dose.

past-pointing (past′poynt′ing)
A test of the integrity of the vestibular system: the subject, seated in a revolving chair, is rotated to the right 10 times with eyes closed; then with the arm held horizontal, the right index finger is brought in touch with the tip of the examiner's finger; the arm is then raised vertically and the subject is instructed to touch the examiner's finger on bringing the arm once more to the horizontal; if the vestibular apparatus is normal, the finger will be brought down several inches to the right of the examiner's finger; the reverse is true on rotation to the left. In cerebellar disease, a patient attempting to reach a point with the finger will overshoot it. The test is also used in connection with caloric stimulation. In some vestibular disorders, p. occurs without rotation or caloric stimulation.

patagium, pl .patagia (pa-ta′je-um, -a)
A winglike membrane. [L. a gold edging on a woman's gown]

Klaus, 20th century U.S. cytogeneticist. See P. syndrome.

1. A small circumscribed area differing in color or structure from the surrounding surface. 2. In dermatology, a flat area greater than 1.0 cm in diameter. 3. An intermediate stage in the formation of a cap on the surface of a cell. butterfly p. SYN: butterfly (2) . p. clamping a technique used in the study of ion channels in which the movement of ions across a small p. of isolated membrane is measured when the membrane is electrically polarized or hyperpolarized and maintained at that potential. SYN: p. clamp. cotton-wool patches white, fuzzy areas on the surface of the retina (accumulations of cellular organelles) caused by damage (usually infarction) of the retinal fiber layer. SYN: cotton-wool spots. herald p. the initial rapidly enlarging oval-shaped red papulosquamous lesion, usually on the trunk, heralding the widespread eruption of pityriasis rosea, and preceding the latter by 7–14 days. Hutchinson p. SYN: salmon p.. mucous p. an oval to round, yellow-gray to white, membrane-covered lesion or lesions occurring on the mucous membranes; usually seen in secondary syphilis. Peyer patches SYN: aggregated lymphoid nodules of small intestine, under nodule. salmon p. 1. an intraretinal hemorrhage seen in sickle cell retinopathy; 2. the appearance of an orbital lymphoid tumor as seen in the subconjunctival space; 3. a common macular orange-pink to red vascular malformation present at or near birth on the head and neck that involutes during childhood. SYN: Hutchinson p.. shagreen p. SYN: shagreen skin. smoker's patches SYN: leukoplakia. soldier's patches SYN: milk spots (1) , under spot.

G., French physician, 1857–1928. See P. albumin.

patella, gen. and pl. patellae (pa-tel′a, -e) [TA]
The large sesamoid bone, in the combined tendon of the extensors of the leg, covering the anterior surface of the knee. SYN: kneecap. [L. a small plate, the kneecap, dim. of patina, a shallow disk, fr. pateo, to lie open] p. alta term used to describe a somewhat more proximal position of the p. than anticipated when it is visualized on a lateral radiograph of the knee. [p. + L. alta, high] p. baja term used to describe a somewhat more distal position of the p. than anticipated when it is visualized on a lateral radiograph of the knee. [p. + Sp. baja, low] floating p. a p. elevated by the presence of a knee effusion. slipping p. spontaneous or easily provoked dislocation of the p..

patellar (pa-tel′ar)
Relating to the patella.

patellectomy (pat′e-lek′to-me)
Excision of the patella. [patella + G. ektome, excision]

patelliform (pa-tel′i-form)
Of the shape of the patella.

patency (pa′ten-se)
The state of being freely open or exposed. probe p. (of foramen ovale), a term introduced by B.M. Patten to cover incomplete fibrous adhesion of an adequate valvula foraminis ovalis in the postnatal closure of the foramen ovale.

patent (pa′tent, pa′tent)
Open or exposed. SYN: patulous. [L. patens, pres. p. of pateo, to lie open]

patent blue V
SYN: leuco patent blue.

Donald R., English otolaryngologist, 1863–1939. See P.-Kelly syndrome, P.-Brown-Kelly syndrome.

A road or way; the course taken by an electric current or by nervous impulses. SEE ALSO: pathway. [A.S. paeth] clinical p. a map that outlines the entire track or p. a patient is expected to follow throughout the course of treatment and beyond. condyle p. the p. traveled by the mandibular condyle in the temporomandibular joint during the various mandibular movements. generated occlusal p. a registration of the paths of movement of the occlusal surfaces of mandibular teeth on a plastic or abrasive surface attached to the maxillary arch. SEE ALSO: functional chew-in record. incisal p. SYN: incisal guidance. p. of insertion the direction in which a dental prosthesis is placed upon or removed from the supporting tissues or abutment teeth. milled-in paths 1. contours carved by various mandibular movements into the occluding surface of an occlusion rim, by teeth or studs placed in the opposing occlusion rim; the curves or contours may be carved into wax, modeling plastic, or plaster of Paris; 2. occlusal curves developed by masticatory or gliding movements of occlusion rims that are composed of materials including abrasives. SEE ALSO: functional chew-in record. SYN: milled-in curves. occlusal p. 1. a gliding occlusal contact; 2. the p. of movement of an occlusal surface.

path-, -pathy, patho-, pathic
Disease. [G. pathos, feeling, suffering, disease]

pathema (pa-the′ma)
Obsolete term for a disease or morbid condition. [G. p., suffering]


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