| polar lobe | <marine biology> In some molluscs a polar lobe appears as a clear protrusion close to the vegetal pole of the cell prior to the first cleavage and becomes associated with only one of the daughter cells. Removal of the first polar lobe or of any polar lobe that forms at a subsequent mitosis, leads to defects in the embryo, it seems that the polar lobe contains special morphogenetic factors. (18 Nov 1997) |
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| polar mutation | <molecular biology> A mutation in a single gene which affects the rate of expression of other genes that are near it on a chromosome. (09 Oct 1997) |
| polar plasm | <cell biology, embryology> Differentiated cytoplasm associated with the animal or vegetal pole of an oocyte, egg or early embryo. (18 Nov 1997) |
| polar plates | Condensed platelike bodies at the ends of the spindle during mitosis of certain types of cells. (05 Mar 2000) |
| polar presentation | The presentation of either pole of the foetal oval; may be either a cephalic or breech presentation, or a longitudinal lie. (05 Mar 2000) |
| polar ring | A thickened, electron-dense ring at the anterior end of certain stages of the Apicomplexa; part of the apical complex characteristic of these sporozoans. (05 Mar 2000) |
| polar solvents | Solvent's that exhibit polar forces on solutes, due to high dipole moment, wide separation of charges, or tight association; e.g., water, alcohols, acids. (05 Mar 2000) |
| polar star | One of the figures forming the diaster. Synonym: polar star. (05 Mar 2000) |
| polar zone | The region in the vicinity of an electrode applied to the body. See: electrotonus. (05 Mar 2000) |
| cradle cap | <dermatology> A form of seborrheic dermatitis of the scalp in infants that is characterised by flaky or scaly skin which may be reddened. May involve the skin on the nose, eyebrows, scalp, ears and skin of the trunk (in skin folds). A weak 0.5% hydrocortisone cream can be effective in controlling this problem. (27 Sep 1997) |
| head cap | A collapsed membranous vesicle that covers the anterior part of the nucleus of the spermatozoon, derived from the acrosomal granule; the carbohydrate-rich substance of the cap is associated with hydrolytic enzymes that aid in sperm penetration of the zona pellucida of the ovum. Synonym: head cap. (05 Mar 2000) |
| pyloric cap | Archaic term for duodenal cap. (05 Mar 2000) |
| duodenal cap | The first portion of the duodenum, as seen in a roentgenogram or by fluoroscopy. Synonym: duodenal bulb. (05 Mar 2000) |
| electro-polar | <physics> Possessing electrical polarity; positively electrified at one end, or on one surface, and negatively at the other; said of a conductor. Source: Websters Dictionary (01 Mar 1998) |
| enamel cap | The enamel covering the crown of a tooth. (05 Mar 2000) |