Vascular turnover of a continuously growing organ: The rat incisor

Abstract

The vascular tissue supplying the pulp of the continuously growing and developing rat incisor was quantitatively analyzed in six female rats, weighing approximately 200 gm each. One hour after a single administration of 3H-TdR, 1 microCi/gm body weight, the rats were sacrificed and the lower left jaws excised and processed histologically. Every 20th section was evaluated for venular and arterial count, endothelial cell count, and percentage of labeled endothelial cells. It was found that the proliferative capacity of the vascular tissue of the rat incisor is confined to its most apical 3.0 mm-a zone defined as the vascular progenitor compartment. Daily production of endothelial vein cells and of veins within the progenitor compartment were calculated to be 7,392 cells/day and two veins/day, respectively. Generation time of these cells was found to be 3.56 days. Endothelial cell production within the progenitor compartment provides for the formation of new vessels and for the enlargement and elongation of existing ones. The vessels originating within the progenitor compartment move in an incisal and centripetal direction, while simultaneously undergoing a continuous process of aging, until their ultimate disintegration.

Anatomy and developmental chronology of the rat inferior alveolar nerve

“…Growth rates are reported to be some 0.5 m d d a y (Chiba et al, 1973). Tooth growth includes generation of new blood vessels (Pitaru et al, 1982) as well as growth and degeneration of pulpal axons (Bishop, 1981). We have not seen any features in the adult rat IAN trunk that may be linked to the de-and regenerative events at terminal levels in the incisor.…”

A method for sampling the stages of amelogenesis on mandibular rat incisors using the molars as a reference for dissection

“…Hence, if the position of a group of cells within the length of the tooth is known, then the absolute and relative ages of the cells can be estimated by distance measurements (Smith and Warshawsky, 1975). The same relationship also exists for any of the extracellular hard and soft tissues of the tooth (Smith and Warshawsky, 1975;Zajicek, 1979;Pitaru et al, 1982;Robinson and Kirkham, 1984a;Weinreb et al, 1985;Beertsen and Hoeben, 1987). It has been estimated that 1 hour of time represents approximately 27 km of tooth length under normal conditions of impeded eruption in mandibular incisors of rats weighing about 100 g (Smith and Warshawsky, 1975;McKee and Warshawsky, 1986).…”

Proliferative responses of endothelial cell populations to experimentally induced inflammatory lesions of gingival connective tissues in the cynomolgus monkey (Macaca fascicularis)

“…Cognizant of these limitations and because of the very slow turnover of endothelial cells in virtually all healthy, adult mammalian tissues (Hobson and Denekamp, 1984), we have examined angiogenesis in periodontal connective tissues. The periodontium provides a n excellent model to study the response of endothelial cells to inflammation in part because the relatively rapid basal cell turnover rates (Pitaru et al, 1982;McCulloch and Melcher, 1983) facilitate kinetic studies of cells in well-delineated anatomical compartments. There are also data to indicate that in inflamed gingiva there is increased capillary loop formation, coiling, and tortuous widening of small vessels (Egelberg, 1966;Hansson et al, 1968;Hock and Nuki, 1971;Soderholm and Egelberg, 1973), but it is still controversial whether these alterations in vessel morphology are the result of endothelial cell proliferation, vessel remodelling, or hemodynamic changes.…”