Atomic-scale desorption through electronic and vibrational excitation mechanisms.

The scanning tunneling microscope has been used to desorb hydrogen from hydrogen-terminated silicon (100) surfaces. As a result of control of the dose of incident electrons, a countable number of desorption sites can be created and the yield and cross section are thereby obtained. Two distinct desorption mechanisms are observed: (i) direct electronic excitation of the Si-H bond by field-emitted electrons and (ii) an atomic resolution mechanism that involves multiple-vibrational excitation by tunneling electrons at low applied voltages.

Effects of 25-hydroxycholesterol and aminoglutethimide in isolated rat adrenal cells. A model for congenital lipoid adrenal hyperplasia?

The production of corticosterone from 25-hydroxycholesterol by isolated rat adrenal cells is inhibited by aminoglutethimide phosphate (AGI); half-maximal inhibition is obtained at ca. 10 muM. AGI also inhibits ACTH-stimulated steroid production from endogeneous substrates; here half-maximal inhibition is obtained with ca.

Studies on isolated rat adrenal cells metabolism of hydroxylated sterols.

Corticosterone production by isolated rat adrenal cells in the absence of ACTH is stimulated by 20alpha-hydroxycholesterol, 22R-hydroxycholesterol and 25-hydroxycholesterol. This effect is also seen at sub-maximal ACTH concentrations. Aminoglutethimide (AGI) inhibits the stimulation caused by the three hydroxylated cholesterols.