- - antigenic s. mutation, i.e., sudden change in molecular structure of RNA/DNA in microorganisms, especially viruses, which produces new strains; hosts previously exposed to other strains have little or no acquired immunity to the new strain; antigenic s. is believed to be the explanation for the occurrence of new strains of influenza virus, which occur by recombination or genetic reassortment of 2 different viral strains in a given host, and is associated with large-scale epidemics.- chemical s. dependence of the resonance frequency of a nucleus on the chemical binding of the atom or molecule in which it is contained. See chemical s. artifact.- chloride s. when CO2 enters the blood from the tissues, it passes into the red blood cell and is converted by carbonate dehydratase to bicarbonate (HCO3−); HCO3− ion passes out into the plasma while Cl− migrates into the red blood cell. Reverse changes occur in the lungs when CO2 is eliminated from the blood. SYN: Hamburger phenomenon.- Doppler s. the magnitude of the frequency change in hertz when sound and observer are in relative motion away from or toward each other. SEE ALSO: Doppler effect.- s. to the left 1. a marked increase in the percentage of immature cells in the circulating blood, based on the premise in hematology that the bone marrow with its immature myeloid cells is on the left, while the circulating blood with its mature neutrophils is on the right; SYN: deviation to the left. 2. See maturation index.- luteoplacental s. the change in site of production of the estrogen and progesterone essential for human pregnancy from the corpus luteum to the placenta; ovariectomy always terminates pregnancy in most mammals because their placentas never produce enough estrogen and progesterone, but, after the sixth week of pregnancy, a human placenta can produce enough of these hormones to prevent abortion despite ovariectomy.- permanent threshold s. the irreversible hearing loss that results from exposure to intense impulse or continuous sound, as opposed to the reversible temporary threshold s. that also results from such exposure.- phase s. in nuclear magnetic resonance, the change in phase caused by movement of the spins, which can be used to show fluid flow.- s. to the right 1. in a differential count of white blood cells in the peripheral blood, the absence of young and immature forms; SYN: deviation to the right. 2. See maturation index.- temporary threshold s. the reversible hearing loss that results from exposure to intense impulse or continuous sound, as opposed to the irreversible permanent threshold s. that may result from such exposure.- threshold s. the degree of hearing loss or impairment in terms of a decibel s. from an individual's previous audiogram. After exposure to intense sound, there may be temporary threshold s. with recovery in hours or days or permanent threshold s. (noise-induced hearing loss).
* * *a) a change in frequency resulting in a change in position of a spectral line or band compare DOPPLER EFFECT
* * *(shift) a change, as of position or status.
Medical dictionary. 2011.