Effects of focused laser radiation on dental enamel.
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Dental Enamel↗
Biomedical subjects
A Hedin
Publications and source records attributed to A Hedin.
In vitro studies of biological effects of cigarette smoke condensate. I. Genotoxic and cytotoxic effects of neutral, semivolatile constituents.
Much of the biological activity of cigarette smoke resides in the neutral fraction of the particulate phase. Since the volatile constituents of this material, the semivolatiles, are accessible to selective filtration, some of the biological activity of cigarette smoke might be reduced. In view of this, the genotoxic and cytotoxic effects and the chemical composition of the semivolatile neutral material of a cigarette smoke condensate was investigated. Cigarette smoke condensate obtained from domestic American blend type cigarettes, was separated into a volatile, a nonvolatile and a semivolatile fraction. The semivolatile constituents were fractionated by liquid-liquid extraction into 4 subfractions: acids, phenols, bases and neutrals. The neutral material was separated further by silica gel chromatography into 7 subfractions of varying polarity. The major components of these were identified by gas chromatography-mass spectrometry. These fractions were studied using 4 in vitro short-term tests, of which 2, the Ames test and induction of sister-chromatid exchanges, provided information on their genotoxicity and the other 2 provided information on their cytotoxicity by measuring inhibition of cell growth and inhibition of oxidative metabolism. Sister-chromatid exchanges were induced by the neutral fraction and the 7 subfractions, the activities of which increased with increasing polarity. Neither the total neutral material, nor the subfractions showed any mutagenic activity in the Ames test. The cytotoxic effect of the fractions of medium polarity, was greater than that of the total neutral material, while the most and the least polar fractions were less toxic.
Adipose Tissue, Brown↗
A modified letter matching chart for testing young children's visual acuity.
A new chart for testing children's visual acuity was designed. It was based on the matching principle and showed rows of the four letters H, O, T, and V at a distance of 3 m. A geometric progression of leter size was used. In order to disclose the crowding phenomenon, the distance between letters was equal to the letter width in each line. Fifty children's testability and visual acuity was studied with this chart and an E chart. It was found that the children performed better when the letter matching chart was used and that the letter matching visual acuity values were higher in about 2/3 of the eyes. The more interesting matching game and the closer viewing distance are possible causes of these differences.
Age Factors↗