ABSTRACT
To assess the age-dependent vitamin A status of children, liver samples taken at autopsy from 170 American children 0-15 yr of age were analyzed for vitamin A and carotenoids. The median liver vitamin A concentration at birth was low (11 micrograms retinol/g), remained constant to 3 mo, rapidly increased to 4 yr (130 micrograms/g) and then remained constant into adolescence. In contrast the vitamin A status of premature infants deteriorated after birth. Of infants less than 3 mo, approximately one-fourth and two-thirds showed liver vitamin A concentrations less than or equal to 5 micrograms retinol/g and less than or equal to 20 micrograms/g, respectively. On the other hand, essentially all infants greater than or equal to 6 months showed an adequate vitamin A status, defined as liver stores greater than 20 micrograms retinol/g liver. Liver carotenoid concentrations did not meaningfully correlate with age or with vitamin A concentrations. Parameters that did not significantly affect the vitamin A concentration were: 1) height and weight in infants less than 1 mo, except in the highest weight-height groups, 2) sex, although values of females were slightly higher than males, and 3) causes of death.
Subject(s)
Liver/analysis , Vitamin A/analysis , Accidents , Adolescent , Age Factors , Birth Weight , Body Height , Carotenoids/analysis , Child , Child, Preschool , Disease/metabolism , Female , Humans , Infant , Infant, Newborn , Infant, Premature , Male , Sex FactorsABSTRACT
Through the use of radiative collisions, sometimes called photon-induced collisions, and the autoionizing properties of N(2)*(X, nu), a system using He-N(2) is presented as a high-efficiency (~15%) ultraviolet laser amplifier when an intense (>1 MW/cm(2)) photon field, tuned to the transition of interest, is directed into the system. The model is described using rate-equation analysis, and calculations are presented to describe this system.
