Cell population kinetics was studied by bromodeoxyuridine (BrdU) histochemical and 3H thymidine radioautographic labelling in dog thyroids. In-vivo labelling with BrdU and in-vitro labelling of incubated slices with 3H thymidine gave similar results. This validates the use of in-vitro labelling of slices for the study of cell kinetics in the thyroid. In-vitro labelling of human thyroid slices demonstrated a labelling index of 13.4 x 10(-5) for follicular cells; assuming an S phase of 10 h, this corresponds to a turnover time of the order of 8.5 years for the follicular cells. Stromal cells appear to turn over faster. These results show for the first time that human thyroid cells divide about five times during adulthood and therefore that the steady state level of thyroid cell mass results from a balance between cell division and cell loss. A shorter turnover time was found as expected in the thyroid of an adolescent and in follicular colloid nodules.

The use of ultrasound (US) in the diagnosis of renal vein thrombosis (RVT) remains ill defined because the classical features lack specificity. The authors report three cases of renal vein thrombosis with a common US pattern: hyperechoic streaks in the interlobulary spaces confirming previous reports with the same pattern. The pattern has been observed in neonates as well as in utero. Associated vena cava thrombosis was present in two cases. This sign might be a specific sign of RVT.

The acute effect of in vitro deendothelialization on the production of prostacyclin (PG12) by the rabbit aorta has been investigated. The effectiveness of removing endothelium by rubbing it against filter paper or scraping it with a scalpel was demonstrated by scanning electron microscopy and en face examination after silver staining. Endothelium removal produced an immediate stimulation of PGI2 release, resulting in 408% of the control after rubbing and 367% of the control after scraping, during the first 30-min period of incubation. This increased production of PG12 gradually declined over time to reach values similar to the control after 2 h. At that time, the deendothelialized aorta was totally unresponsive to the stimuli that increase PG12 release in the intact aorta (acetylcholine, ADP, ionophore A23187, and arachidonic acid). The enhanced production of PG12 in the deendothelialized aorta was associated with an increased release of free arachidonic acid (353% of the control): in contrast with PG12, this stimulation was maintained for at least 150 min. A transient exposure of the deendothelialized aorta to ibuprofen (250 1M) was followed by a rebound of PG12 production, which was also prolonged by BW-755C (3-10 ;&M). In conclusion, removal of the endothelium triggered an immediate and sustained mobilization of free arachidonic acid in the rabbit aorta: the resulting increase of P012 production was short-lived, probably as a consequence of cyclooxygenase self-inactivation. Our results indicate that the subendothelium has a significant capacity to produce PGI2, but that this capacity is expressed only briefly.

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