Acetylcholine-induced relaxation of the rabbit aorta is preload-independent but markedly dependent upon the degree of excitatory agonist-induced tone.

1. The aim of the present study was to investigate the relationship between endothelium-dependent relaxation evoked by acetylcholine, tissue preload and the degree of noradrenaline-induced tone in the isolated rabbit aorta. 2.

A t(5p-;21q+) translocation in a family with Down syndrome.

A mother and daughter carrying a t(5;21)(p13;q22) chromosome were discovered after they had contacted us for genetic counseling. They were concerned because of two cases of Down syndrome in their family. Four of the mother's eight pregnancies had resulted in miscarriages; the chromosome complements of the abortuses is not known.