Incorporation of labelled thymidine into DNA of different rat brain regions was studied after 30 min of forebrain ischaemia and recirculation periods up to 24 hours. The amount of label incorporated into DNA showed a different pattern in the brain. After 1 hour of recirculation, the incorporation was reduced in the cortex and in the striatum, without any significant change in the hippocampus. After 3 to 9 hours the incorporation remained depressed in the cortex, diminished in the hippocampus, and increased by 2-2.5 fold in the striatum. Later, after 24 hours, the DNA labelling returned to control values in the striatum and in the cortex, but was increased in the hippocampus.
The effect of propylthiouracil (PTU) on the growth activity of intact liver and liver regenerating after partial (65-70 %) hepatectomy (PH) was studied in rats. FEU (Propycil, Kali-Chcmie, FRG) was dissolved in drinking water (1 g PTU per litre) and this was given to the rats, as their sole source of fluids, three days before PI I and then up to the end of the experiment. In rats given FPU, marked inhibition of liver DNA synthesis and the mitotic activity of hepatocytes was found after PH. This effect was potentiated to some extent by partial inanition of the experimental animals given FITJ, as demonstrated in a paired feeding test in control rats. PTU inhibition of DNA synthesis in intact and regenerating liver also took effect in thyroidectomized rats, even with substitution (thyroid hormone) therapy. The experiments demonstrated that the effect of propylthiouracil on DNA synthesis in the liver is mediated primarily by way of its direct effect on the liver.
The morphology and proliferation of vascular smooth muscle cells (VSMC) were studied in cultures prepared from the aorta of newborn male and female Wistar rats. The doubling times (DT) of the male-derived population were 16.4 ±0.7 h and 30.0 ±2.2 h in the exponential and post-exponential growth phases, respectively. In the female donor cells, the corresponding DT values were significantly longer, i.e. 21.9 ± 1.8 h and 38.0 ±2.2 h. In addition, the period of growth was shorter in the female-derived cultures. The percentage of 3H-thymidine labelled cells in male cultures was 61.0±3.1, 92.8± 1.9 and 98.7±0.6 % at 2, 27 and 52 h, respectively. In the female-derived populations, only 24.6 ±4.4, 66.1 ±3.8 and 82.8 ±2.0 % of cells were labelled at the corresponding incubation intervals. As a consequence, the final population density in male cultures was 5.6 times higher. In addition, the male-derived VSMC were mainly spindle-shaped and bulgy in appearance while those from female donors were flat and polygonal which means that the cells were adhering to the growth support to a different extent. The study revealed early determination and long-term persistence of lower adhesiveness as well as higher growth potential of male VSMC, i.e. properties which may be of importance for explaining the higher incidence of vascular wall disorders in males.