Morphometric analysis of gap junctions in regenerating arterial endothelium

Gap junctions may provide the structural basis for communication between arterial and endothelial cells and modulate their response to injury. We have utilized autoradiography and freeze fracture techniques to correlate proliferative activity with changes in the organization, density, and surface area of gap junctions in healing arterial endothelium. A well-circumscribed, reproducible area of endothelial loss was produced in the common carotid artery of the rabbit by desiccation of the intima. The lesion healed in 15 days by centripetal proliferation and migration of endothelial cells from adjacent uninjured areas. As controls, we used the uninjured contralateral artery. In parallel experiments, the vascular endothelium was sampled either for autoradiography after administration of 3H-thymidine or for freeze fracturing. Proliferative activity was measured by calculating the labeling index in autoradiographs of endothelium. The surface areas of gap junctions and that of the lateral endothelial membranes was measured by planimetry in electron micrographs of freeze fracture replicas. Two days after injury, cells at the growing edge of the endothelium revealed a marked decrease in the density and surface area of gap junctions, loss of tight junctions, and high labeling index (232 +/- 55 S.E.M.). At seven days, the labeling index was lower (61 +/- 31 S.E.M.), gap junctions were small but numerous, and short segments of tight junctions were present. At fifteen days, the endothelial integrity was restored, the labeling index was at control levels (3.32 +/- 3 S.E.M.), and both gap and tight junctions were well developed and indistinguishable from controls. The study shows that loss of junctions between endothelial cells is associated with high proliferative activity. As a corollary, well-developed gap junctions may prevent the response of the uninjured endothelium to circulating mitogens

[Occult carcinoma of the thyroid gland: an epidemiological study of autopsy material]

The occurrence of occult thyroid carcinoma at autopsy was examined in 507 consecutive autopsies performed over one-year in subjects without clinical evidence of thyroid cancer, from different regions of Italy, including areas of endemic goiter. We found 54 (10.65%) occult thyroid carcinomas. In 37 cases the histologic pattern was of the papillary type, with diameter ranging between 176 and 6000 microns, 12 of these cases showed a typical papillary pattern, 6 had a marked fibrosis, 2 had a cystic pattern, one showed a lymphoid stroma, and 17 had a follicular pattern. The remaining 17 cases were medullary carcinomas, with a diameter ranging from 50 to 1600 microns. The percentage of occult thyroid carcinomas reported in the present study may constitute real value of the occurrence of this tumor in the Italian population

Correlation between increased serum and tissue L-carnitine levels and improved muscle symptoms in hemodialyzed patients

A group of 14 uremic patients on intermittent hemodialysis was admitted to a cross-over double-blind trial in order to evaluate serum and muscle carnitine levels before and after 60 days of L-carnitine oral (2 g/day) treatment. The morphology of muscle fragments was studied by light and electron microscopy. Symptoms (asthenia, cramps) occurring during hemodialysis were also recorded. After L-carnitine treatment the blood and muscle levels of the metabolite increased simultaneously to reduced asthenia and cramps. Morphological examination of the muscle of 13 of 14 patients did not reveal any pre- or posttreatment pathological alterations. The presence of nemaline rods was morphologically diagnosed in only one case and was no longer observed at the second biopsy at 2 months of L-carnitine treatment