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To resolve controversy over umbilical vessels structure, a morphological review was undertaken of the histology of blood vessels in 130 fetal umbilical cords varying in gestational age and the ultrastructure of blood vessels in 6 umbilical cords. Arteries and veins were lined by endothelium. The internal elastic lamina was frequently interrupted when associated with intimal thickening of longitudinally orientated smooth muscle cells. Fragments of elastic laminae developed in the intima and inner media both of which were thicker in arteries than in vein. No external elastic laminae or distinct adventitia were found. Most notable was the accumulation of cell debris developed from blebs derived from polypoid cytoplasmic protrusions of smooth muscle cells of both arteries and veins. They underwent hydropic change and became detached and fragmented particularly after 20 weeks' gestation. Similar hydropic degeneration occurred in endothelial cells of arteries and veins, such changes being consistent with the destructive pattern of hemodynamic stresses.

A rapid method for preparing Leydig cells from rat testes is described. An interstitial cell suspension, prepared by collagenase treatment of decapsulated testes, was centrifugal for 10 min over a cushion of 60% (v/v) Percoll to remove red blood cells, and then centrifuged for 20 min in a 0-60% linear density gradient of Percoll. Seventy-four per cent of the cells present in that fraction of the gradient comprising 35-50% Percoll were Leydig cells; the yield from each testis was about 1.5 x 10(6) cells. The Leydig cells appeared viable, excluded Trypan blue, possessed high-affinity binding sites for human chorionic gonadotrophin (hCG) and synthesized increased quantities of testosterone in response to hCG. The cells could be stored overnight in 20% (v/v) glycerol at -20 degrees C, with only minimal effect on the specific activities of a number of enzymes used as markers of subcellular components. Testosterone production in vitro by the cells after storage for 20 h was greater than that of hCG-stimulated fresh cells and was not further increased by hCG.