| 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) |
| 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) |
| zinco-polar | <physics> Electrically polarized like the surface of the zinc presented to the acid in a battery, which has zincous affinity. Source: Websters Dictionary (01 Mar 1998) |
| law of polar excitation | A given segment of a nerve is irritated by the development of catelectrotonus and the disappearance of anelectrotonus, but the reverse does not hold; i.e., excitation occurs at the cathode when the circuit is closed and at the anode when it is opened. Synonym: Pfluger's law. (05 Mar 2000) |