Vitamin Glossary "P"

• parasympathetic nervous system- the craniosacral division of the autonomic nervous system. Effects of parasympathetic stimulation are the constriction of the pupils, contraction of the smooth muscle of the alimentary canal, constriction of bronchioles, slowing of heart rate and increased secretion by glands, except sweat glands.

   

• pathogens- disease-producing microorganisms and toxins.

   

• peptide- a substance formed by two or more amino acids.

   

• perfuse- to pour over or through.

   

• periosteum- the sheath around the bone.

   

• peripheral nervous system- connects the central nervous system to all body tissues and voluntary muscles.

   

• peristalsis- wavelike contractions of the smooth muscles of the digestive tract; also, the wavelike contraction of the colon muscles that expel waste matter.

   

• peroxidase-an enzyme which catalyzes the breakdown of peroxides in the body.

   

• peroxides-highly oxidized compounds like hydrogen peroxide (H-O-O-H), which not only oxidize lipids directly but in so doing create free radicals which spread in a chain reaction until stopped (quenched) by enzymes like peroxidases, catalases, and superoxide dismutase or by antioxidants like vitamin E and BHT.

   

• peroxidized-a chemical which has been oxidized, so that a peroxide, (relative of hydrogen peroxide, H-O-O-H) forms. Unsaturated fats (lipids) in the body are particularly susceptible to peroxidation.

   

• PGI2-see prostacyclin.

   

• pH balance- a method of measurement used in chemistry to express the degree of acidity or alkalinity of a solution. A pH of 7 represents the neutral point where the solution is neither acid nor alkaline. Any higher alkalinity is expressed by a number greater than 7, and higher acidity, by a number less than 7. The calculations of these numbers are based on logarithms.

   

• phenylpropanolamine-a chemical closely resembling amphetamine which is used in some over-the counter appetite control products. Although it has milder side effects that amphetamine, phenylpropanolamine can, after prolonged use, cause depletion of brain norepinephrine (NE) and possible depression. Phenylalanine is a natural precursor to NE, and its use as an appetite inhibitor does not result in NE depletion.

   

• phlegm- thick mucous secreted in abnormal quantity in the respiratory passages.

   

• pitta- an Ayurvedic dosha which determines an individual's constitution.

   

• pituitary gland- a gland in the brain which produces and releases several hormones, including growth hormone, LH, FSH, TSH,vasopressin, ACTH, and others. An aging clock may be located in the pituitary.

   

• placebo- substances having no pharmacological effect.

   

• plaque- a localized abnormal patch on a body part or surface.

   

• plasma- the liquid part of the lymph and of the blood.

   

• plasma lipids- fats in the bloodstream.

   

• platelet- a round or oval disk found in the blood. Important in blood coagulation.

   

• platelet aggregation-structures found in the bloodstream which aggregate in the formation of blood clots. They are tiny fragments of cells derived form the bone marrow. Lipid peroxides stimulate platelets to make thromboxane A2, which in turn causes platelets to adhere and aggregate, as in the formation of atherosclerotic placques and clotting.

   

• polycyclic aromatic hydrocarbons (PAH)-compounds found in combustion tars, created in the burning of nearly all fuels, which are metabolically activated (especially in the liver) to a mutagenic and carcinogenic form. These are probably the most important human chemical carcinogens and are suspected of being responsible for many of human cancers other than solar ultraviolet induced skin cancers. Tobacco smoke is by far the most important source of humans. They are also found in relatively large quantities on charcoal broiled meats.

   

• polynuclear aromatic hydrocarbons-PAH, same as polycyclic aromatic hydrocarbons.

   

• polypeptide- a molecule resulting from the union of two or more amino acids.

   

• polyunsaturated fats-fats containing two or more sets of double bonds between some of their carbon atoms; these bonds are susceptible to autoxidation attack by oxygen and free radicals, which converts polyunsaturated fats to carcinogenic, immune suppressive, clot promoting cross-linking peroxidized fats. Antioxidants can protect these polyunsaturated fats from such chemical attacks. The more unsaturated (the more double bonds), the more readily autoxidized.

   

• postacute- the period after the rapid and severe onset of symptoms.

   

• postpartum- the period after childbirth.

   

• precursor-a chemical which can be converted to another is a precursor of the latter.

   

• prenatal- the period before childbirth.

   

• primary antioxidant-an antioxidant which blocks formation of peroxides by scavenging free radicals. Examples are vitamins A, C, E, B-1, B-5, B-6, cysteine, zinc, and selenium.

   

• probiotics- substances that promote the growth of beneficial bacteria in the intestines.

   

• progeria-a group of inherited conditions resembling accelerated aging. Victims generally die before their teens of strokes or heart attack, looking like little old men or women, bald, bent over, with wrinkled faces, and so on.

   

• progesterone- a steroid hormone responsible for the changes in the endometrium in the second half of the menstrual cycle preparatory for implantation, development of maternal placenta, and the development of mammary glands. Used to treat menstrual disorders, among other problems.

   

• prolactin-a hormone released by the pituitary gland which has several functions, including stimulating milk production.

   

• prophylactic-as a preventive.

   

• prostacyclin-the prostaglandin hormone PGI2, a natural hormone made by normal artery wall lining cells (intima) to inhibit the formation of abnormal blood clots. Peroxidized lipids can block prostacyclin manufacture, thus fostering the development of blood clots.

   

• prostaglandin E-Z- hormone-like fatty acids, biologically active unsaturated fatty acids.

   

• prostate- gland that surrounds the neck of the bladder and urethra in males and secretes a thin fluid that forms part of the seminal fluid.

   

• proteases-enzymes which break down proteins. An example is bromelain, found in raw pineapple. Some proteases have been found to stimulate the immune system.

   

• protein- complex nitrogenous compounds that occur naturally in plants and animals and yield amino acids. Essential for the growth and repair of animal tissue.

   

• psychobiochemistry-the biochemistry of mental processes.

   

• psychopharmacology-the effects of drugs on mental processes.

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