The effect of ethynyl oestradiol and chlormadinone acetate, separately and combined, on the aorta, carotid, mesenteric and renal arteries of female rats was studied using light and scanning electron microscopy. The hormones were injected daily for either 30 or 90 days. The most constant finding was intimal thickening which consisted mainly of areas of subendothelially located smooth muscle cells. Each artery was given a score from 0 to 3 according to the degree of development of these areas. Ethynyl oestradiol, unlike chlormadinone acetate, was associated with sustained significant enhancement of both incidence and degree of intimal thickening. With the combined treatment, the degree of intimal thickening in the 30-day group was not appreciably different from that obtained with oestrogen alone. However, in the 90-day group it was significantly less in arteries other than the aorta, suggesting that the progestogen inhibited the enhancing effect of the oestrogen on the proliferative process in these arteries.
A combination of thin-layer and gas-liquid chromatography was used to determine the concentration of 7,12-dimethylbenz(α)anthracene in mammary tissue of female rats at various intervals after its intragastric administration. Peak concentration was reached after 6 hours and measurable amounts were still present after 5 days. The method is as sensitive as spectrofluorometry, offers greater specificity and is applicable to the determination of other polynuclear hydrocarbons.
The concentration of 7,12-dimethylbenz( α )anthracene (DMBA) in mammary tissue was determined at different time intervals following its administration, in a single dose, to female Sprague-Dawley rats maintained on 3 different semisynthetic diets: low fat, high coconut oil, and high corn oil. In general, the rate of uptake and clearance of the carcinogen was similar in the 3 groups, with a peak concentration occurring 6 to 12 hours after its administration. At 6 hours the tissue level of DMBA in coconut oil fed rats was significantly lower than in the other 2 groups. However, the data obtained could not fully explain the effects of dietary fat upon DMBA mammary carcinogenesis.
The villous syncytium of the placenta of the macaque was found to contain channel-like formations bounded by syncytial membrane. They were present in placental specimens obtained from rhesus monkeys at periods of gestation varying from 90 to 164 days and were identifiable only by electron microscopy. These syncytial channels communicated with the intervillous space but were quite distinct from junctional complexes described in the syncytium of human placental villi. They appeared to be extensions of the intervillous space whereby areas of the syncytium would come in contact with maternal plasma flowing at a greatly reduced rate. Features of these channels, of their bounding membrane and of the adjacent cytoplasm, could point to a phenomenon of regional specialisation in the syncytiotrophoblast.
