Effects of cyclic steroid hormone replacement on prolactin and luteinizing hormone surges in female rats.

The ability of steroid hormones to produce an LH or prolactin (PRL) surge was determined in rats ovariectomized at 6, 9 or 13 weeks of age and subjected to one, three or six cycles of estrogen and progesterone replacement. Sensitivity to steroid replacement was dependent on the age of the animal at the time of ovariectomy. Repeated cyclic steroid hormone replacement significantly increased the magnitude of the PRL response, but not the LH response, in animals ovariectomized at 6 weeks. The LH response was significantly altered by cyclic steroid replacement only in animals ovariectomized at 13 weeks. These results indicate that the mechanisms involved in the regulation of PRL secretion are influenced by steroid hormone replacement and that cyclic steroid hormone exposure increases the magnitude of the PRL secretory response.

Effects of age and gender on the AII-induced stimulation of prolactin release and inositol phosphate accumulation in rat anterior pituitary cells in vitro.

The stimulatory effects of Angiotensin II (AII) on prolactin secretion and inositol phosphate accumulation were examined in dispersed anterior pituitary cells collected from young (3-4 month), mature (7-8 month) and old (18-20 month) male and female rats. Physiological doses of AII (0.01-10 nM) stimulated prolactin release from cells collected from mature female rats only. This effect was antagonized by pretreatment with Saralasin, an AII receptor antagonist. Significant accumulation of the inositol phosphates was observed in cells obtained from the mature, female donors and this increase preceded the prolactin response. Although there was a small increase in total inositol phosphate accumulation in cells obtained from the old female rats, this was transient and did not coincide with a similar increase in prolactin release. These results indicate that pituitary sensitivity to AII stimulation is related to the age and the gender of the donor animal. The physiological role of pituitary AII needs to be examined in sexually mature female animals.

Combined orthodontic-endodontic therapy: case report of orthodontic movement of a recalcified lateral incisor.

Unlike most cases of combined orthodontic and endodontic therapy that have been reported, in this case endodontic treatment with calcium hydroxide-induced calcification was utilized prior to orthodontic treatment. A 14-yr-old female required orthodontic therapy due to anterior crowding. Preoperative periapical radiographs indicated that the maxillary right lateral incisor demonstrated advanced lateral root resorption of the distal surface. It was decided to use calcium hydroxide therapy to halt any further resorption prior to orthodontic movement. Approximately 1 yr was required to gain calcification, fill the canal with gutta-percha, and place the maxillary closing arch. Subsequent orthodontic treatment did align the teeth in a desirable manner without jeopardy to the recalcified root.

Access cavity preparation.

The endodontic access cavity is an essential component of the endodontic triad upon which all subsequent canal preparation and filling is based. It is probably the most frequently underemphasized aspect of endodontic therapy. This results in great clinical frustration and poor immediate and long-term results for the practitioner. The access cavity must provide clear and unobstructed access to each and every orifice and must be designed in such a way so as not to interfere with the often difficult intracanal procedures to follow. An understanding of root development, chamber, and canal anatomy will allow the practitioner to more easily debride and seal each canal through proper access cavity preparation.