The ascertainment of consistent diurnal variations in human epidermal cell proliferation may have important implications for the treatment of many skin diseases. For the evaluation of diurnal rhythms in the growth of human epidermis, skin biopsies were taken every 4th hour for 48 h from each of two persons under synchronized living conditions. The epidermal cell proliferation was assessed by the fraction of cells in S and in G2-M phase as determined by measurements of the DNA content in the individual cells in single-cell suspensions. The existence of diurnally consistent body functions in the test persons was verified by monitoring the excretion of cortisol by urine. The fraction of cells in G2-M phase indicated circadian rhythmicity for the first 32 h of the test period. No regular variation according to time of day could be established in the fraction of cells in S-phase.

In 16 acute stroke patients with focal cerebral hyperemia angiography and regional cerebral blood flow (rCBF) were studied 1 to 4 days post stroke. CT was performed twice with and without contrast enhancement 3 +/- 1 days and 16 +/- 4 days post stroke. Angiographic evidence of focal cerebral hyperemia was seen in 8 patients in the form of early filling veins. In 5 of these the hyperemic areas were located within infarcted areas and in 3 patients in areas which appeared normal on CT. In the remaining 8 patients the hyperemias were located perifocally around ischemic infarcts. Early filling veins were not seen in this type of hyperemia. The blood flow was higher and the transit time of the contrast medium was faster in the former type of hyperemia probably because of arteriovenous shunting. Contrast enhancement was not observed on the early CT but was typically seen in the infarcts on the late CT at a time when the hyperemic state is known to have vanished. It is concluded that focal cerebral hyperemia is not responsible for contrast enhancement on CT.