Medical Dictionary

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penumbra (pe-num′bra)
The region of partial illumination or radiation caused by light or x-rays not originating from a point source; also called geometric unsharpness. [Mod. L., fr. L. paene, almost, + umbra, shadow]

peplomer (pep′lo-mer)
A part or knoblike subunit of the peplos of a virion, the assemblage of which produces the complete peplos; frequently a surface glycoprotein on lipoprotein envelope. [see peplos]

peplos (pep′los)
The coat or envelope of lipoprotein material that surrounds certain virions. [G. an outer garment worn by women]

Pepper
William, Jr., U.S. physician, 1874–1947. See P. syndrome.

peppermint (pep′er-mint)
The dried leaves and flowering tops of Mentha piperita (family Labiatae); a carminative and antiemetic. p. camphor SYN: menthol. p. oil the volatile oil distilled with steam from the fresh, overground parts of the flowering plant of Mentha piperita, rectified by distillation and neither partially nor wholly dementholized; a flavor.

pepsic (pep′sik)
SYN: peptic.

pepsin (pep′sin)
A group of closely related aspartic proteinases. P. A is the principal digestive enzyme of gastric juice, formed from pepsinogen; it hydrolyzes peptide bonds at low pH values (is alkali-labile), preferably adjacent to phenylalanyl and leucyl residues, thus reducing proteins to smaller molecules (referred to as proteoses and peptones); p. B (gelatinase) is similar to p. A, but formed from porcine pepsinogen B and has a more restricted specificity; p. C (gastricsin is human p. C) is also similar to p. A, and structurally related to it, having a more restricted specificity. [G. pepsis, digestion]

pepsinate (pep′si-nat)
To mix pepsin with.

pepsiniferous (pep-si-nif′er-us)
SYN: pepsinogenous.

pepsinogen (pep-sin′o-jen)
A proenzyme or zymogen formed and secreted by the chief cells of the gastric mucosa; the acidity of the gastric juice and pepsin itself remove 44 amino acyl residues from p. to form active pepsin. SYN: propepsin. [pepsin + G. -gen, producing]

pepsinogenous (pep-sin-oj′e-nus)
Producing pepsin. SYN: pepsiniferous.

pepsinuria (pep-si-noo′re-a)
Excretion of pepsin in the urine. [pepsin + G. ouron, urine]

pepstatin (pep-sta′tin)
An inhibitor peptide from actinomycetes that inhibits pepsin and cathepsin D.

peptic (pep′tik)
Relating to the stomach, to gastric digestion, or to pepsin A. SYN: pepsic. [G. peptikos, fr. pepto, to digest]

peptidase (pep′ti-das)
Any enzyme capable of hydrolyzing a peptide bond of a peptide; e.g., carboxypeptidases, aminopeptidases. SYN: peptide hydrolase. p. D SYN: proline dipeptidase. p. P SYN: peptidyl dipeptidase A.

peptide (pep′tid)
A compound of two or more amino acids in which a carboxyl group of one is united with an amino group of another, with the elimination of a molecule of water, thus forming a p. bond, –CO–NH–; i.e., a substituted amide. Cf.:eupeptide bond, isopeptide bond. adrenocorticotropic p. a p. with ACTH activity, isolated from pituitary extracts. anionic neutrophil-activating p. (ANAP) SYN: interleukin-8. antigen peptides the protein fragments that bind to MHC molecules. atrial natriuretic p. (ANP) (na′tre-oo-ret′ik) a 28–amino acid p. (α-ANP), derived from cardiac atria, several smaller fragments of α-ANP, and a dimer of α-ANP with 56 amino acids (β-ANP) that are present in plasma in heart failure. ANP actions include increasing capillary filtration, and renal salt and water excretion, and decreasing arterial pressure and the secretion of renin, angiotensin, aldosterone, and antidiuretic hormone. SYN: atriopeptin, cardionatrin. bitter peptides peptides that have a bitter taste and may spoil certain foods; often contain high proportions of leucyl, valyl, and aromatic amino acyl residues. bradykinin-potentiating p. SYN: teprotide. calcitonin gene-related p. (CGRP) a second product transcribed from the calcitonin gene. CGRP is found in a number of tissues including nervous tissue. It is a vasodilator that may participate in the cutaneous triple response. cyclic p. a p. that forms a ring structure; E.G., tyrocidin A, an antibiotic, is a cyclic decapeptide; valinomycin is a cyclic depsipeptide. gastric inhibitory p. (GIP) SYN: gastric inhibitory polypeptide. glucagonlike p. a gut hormone that slows gastric emptying and stimulates insulin secretion. It may become useful in the future in the treatment of noninsulin-dependent diabetes mellitus, perhaps administered by patch, inhaler, or buccal pellet formulation. glucagonlike insulinotropic p. an insulinotropic substance originating in the gastrointestinal tract and released into the circulation following ingestion of a meal containing glucose. heterodetic p. a p. that contains p. bonds as well as covalent linkages between certain amino acyl residues that are not p. bonds; e.g., valinomycin, oxytocin. [hetero- + G. detos, bound, fr. deo, to bind, + -ic] heteromeric p. a p. that, on hydrolysis, yields substances other than amino acids in addition to amino acids; e.g., pteroylglutamic acid. homodetic p. a p. in which all of the covalent linkages between the constituent amino acids are p. bonds; E.G., bradykinin. [homo- + G. detos, bound, fr. deo, to bind, + -ic] homomeric p. 1. a p. that, on hydrolysis, yields only amino acids; e.g., glutathione; 2. a p. that consists of only one particular amino acid; e.g., alanylalanylalanine. p. hydrolase [EC subclass 3.4] SYN: peptidase. parathyroid hormone-related p. a hormone that can be produced by tumors, especially of the squamous cell type; massive overproduction can lead to hypercalcemia and other manifestations of hyperparathyroidism. PTHrP exerts a biologic action similar to that of parathyroid hormone (PTH), acting via the same receptor, which is expressed in many tissues but most abundantly in kidney, bone, and growth plate cartilage. It apparently has significant actions during development, but it is uncertain whether PTHrP circulates at all or has any function in normal human adults. The structure of the gene for human PTHrP is more complex than that of PTH, and varying molecular forms exist, including proteins of 141, 139, and 173 amino acids, which share a significant homology with parathyroid hormone. phenylthiocarbamoyl p., PTC p. the p. formed by combination of phenylisothiocyanate and an α-amino group of a p.. SEE ALSO: phenylthiohydantoin. S p. S protein. sigma p. a p. with one end bonded to a point within the chain, usually by means of the disulfide group of a cystine residue, so that only one end of the p. is free; so called since the p. chain has then the rough shape of the Greek letter sigma; e.g., oxytocin. p. synthetase [EC 6.3.2.x] any enzyme that catalyzes the synthesis of p. bonds, with the concomitant hydrolysis of a nucleoside triphosphate. vasoactive intestinal p. SYN: vasoactive intestinal polypeptide.

peptidergic (pep-ti-der′jik)
Referring to nerve cells or fibers that are believed to employ small peptide molecules as their neurotransmitter. [peptide + G. ergon, work]

peptidoglycan (pep′ti-do-gli′kan)
A compound containing amino acids (or peptides) linked to sugars, with the latter preponderant. Cf.:glycopeptide. SYN: mucopeptide (2) .

peptidoid (pep′ti-doyd)
A condensation product of two amino acids involving at least one condensing group other than the α-carboxyl or α-amino group; e.g., glutathione.

peptidolytic (pep′ti-do-lit′ik)
Causing the cleavage or digestion of peptides. [peptide + G. lytikos, solvent]

peptidyl dipeptidase A (pep′ti-dil)
A zinc-containing hydrolase cleaving C-terminal dipeptides from a variety of substrates, including angiotensin I, which is converted to angiotensin II and histidylleucine (an important step in the metabolism of certain vasopressor agents). Drugs that inhibit it are used to treat hypertension and congestive heart failure. SYN: angiotensin-converting enzyme, carboxycathepsin, dipeptidyl carboxypeptidase, kinase II, peptidase P.

peptidyltransferase (pep-ti′dil-trans′fer-as)
The enzyme responsible for the formation of the peptide bond on the ribosome during protein biosynthesis, peptidyl-tRNA1 + aminoacyl-tRNA2 → tRNA1 + peptidylaminoacyl-tRNA2.

peptization (pep-ti-za′shun)
In colloid chemistry, an increase in the degree of dispersion, tending toward a uniform distribution of the dispersed phase.

Peptococcaceae (pep′to-kok-a′se-e)
A family of nonmotile, nonsporeforming, anaerobic bacteria (order Eubacteriales) containing Gram-positive (staining may be equivocal) cocci, 0.5–1.6 μm in diameter, which occur singly, in pairs, chains, tetrads, and irregular masses but not in three-dimensional, cubic packets. These organisms are chemoorganotrophic and have complex nutritional requirements. Carbohydrates may or may not be fermented by these organisms, which produce gas, principally CO2 and usually H2, from amino acids, or carbohydrates, or both. They are found in the mouth and intestinal and respiratory tracts of humans and other animals; they are frequently found in normal and pathologic human female urogenital tracts.

Peptococcus (pep′to-kok′us)
A genus of nonmotile, anaerobic, chemoorganotrophic bacteria (family Peptococcaceae) containing Gram-positive, spherical cells that occur singly, in pairs, tetrads, or irregular masses, and rarely in short chains. They are frequently found in association with pathologic conditions. The type species is P. niger. [G. pepto, to digest, + kokkos, berry] P. aerogenes former name for Peptostreptococcus asaccharolyticus. P. constellatus a bacterial species found in tonsils, purulent pleurisy, appendix, the nose, throat, and gums, and infrequently on the skin and in the vagina. P. niger a bacterial species found once, in the urine of an aged woman; type species of the genus P..

peptocrinine (pep-to-krin′en)
An extract of the intestinal mucosa resembling secretin.

peptogenic, peptogenous (pep-to-jen′ik, pep-toj′e-nus)
1. Producing peptones. 2. Promoting digestion.

peptoid (pep′toyd)
A peptide with one or more non—amino acyl groups ( e.g., sugar, lipid, etc.) covalently linked to the peptide.

peptolide (pep′to-lid)
1. A cyclic depsipeptide; e.g., valinomycin. 2. A heteromeric depsipeptide.

peptolysis (pep-tol′i-sis)
The hydrolysis of peptones.

peptolytic (pep-to-lit′ik)
1. Pertaining to peptolysis. 2. Denoting an enzyme or other agent that hydrolyzes peptones.

peptone (pep′ton)
Descriptive term applied to intermediate polypeptide products, formed in partial hydrolysis of proteins, that are soluble in water, diffusible, and not coagulable by heat; used in bacterial culture media.

peptonic (pep-ton′ik)
Relating to or containing peptone.

peptonization (pep′ton-i-za′shun)
Conversion by enzymic action of native protein into soluble peptone.

Peptostreptococcus (pep′to-strep-to-kok′us)
A genus of nonmotile, anaerobic, chemoorganotrophic bacteria (family Peptococcaceae) containing spherical to ovoid, Gram-positive cells that occur in pairs and short or long chains. These organisms are found in normal and pathologic female genital tracts and blood in puerperal fever, in respiratory and intestinal tracts of normal humans and other animals, in the oral cavity, and in pyogenic infections, putrefactive war wounds, and appendicitis; they may be pathogenic. The type species is P. anaerobius. [G. pepto, to digest, + streptos, curved, + kokkos, berry] P. anaerobius a bacterial species found in the mouth, intestinal and respiratory tracts, and cavities, especially the vagina, of humans and other animals; it may be pathogenic; it is the type species of the genus P.. P. asaccharolyticus a bacterial species found in the human large intestine, buccal cavity, pleura, uterus, and vagina; also found in cases of puerperal fever; characterized by its inability to metabolize sugars. P. evolutus a bacterial species found in the human respiratory tract, mouth, and vagina. P. foetidus a bacterial species found in abscesses, blood, the intestinal tract, vagina, and mouth of humans and other animals; it is sometimes fatal. P. intermedius SYN: Streptococcus intermedius. P. magnus a bacterial species found in putrefying butcher's meat and in a case of appendicitis. P. micros a bacterial species found in natural cavities of humans and other animals; it has been isolated from various pathologic conditions. P. morbillorum a bacterial species found in the nose, throat, eyes, ears, mucous secretions, and blood in cases of measles, being irrelevant, however, to the etiology of measles; probably present normally, developing as a secondary invader. SYN: Streptococcus morbillorum. P. paleopneumoniae a bacterial species found in the buccal pharyngeal cavity and the upper respiratory tract of humans. P. parvulus former name for Atopobium parvulus. P. plagarumbelli a bacterial species commonly found in septic war wounds. P. productus former name for Ruminococcus productus. P. putridus a bacterial species found in the human mouth and intestinal tract but especially in the vagina.

per-
1. Through, conveying intensity. 2. In chemistry, a prefix denoting either 1) more or most, with respect to the amount of a given element (usually oxygen, as in perchloric acid) or radical contained in a compound, or 2) the degree of substitution for hydrogen, as in peroxides, peroxy acids ( e.g., hydrogen peroxide, peroxyformic acid). SEE ALSO: peroxy-. [L. through, throughout, extremely]

peracephalus (per-a-sef′a-lus)
An omphalosite lacking head and arms, and with a defective thorax; typically, the body consists of little more than pelvis and legs. [per- + G. a- priv. + kephale, head]

peracid (per-as′id)
An acid containing a peroxide group (–O–OH); e.g., peracetic acid. SYN: peroxy acid.

peracute (per-a-kyut′)
Very acute; said of a disease. [L. peracutus, very sharply]

per anum (per a′num)
By or through the anus. [L.]

perarticulation (per′ar-tik′u-la′shun)
SYN: synovial joint. [per- + L. articulatio, joint]

peratodynia (per′a-to-din′e-a)
Obsolete term for pyrosis. [G. peratos, on the opposite side, + odyne, pain]

peraxillary (per-ak′si-lar-e)
Through the axilla.

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