Single neonatal estrogen implant sterilizes female animals by decreasing hypothalamic KISS1 expression.

Reproductive sterilization by surgical gonadectomy is strongly advocated to help manage animal populations, especially domesticated pets, and to prevent reproductive behaviors and diseases. This study explored the use of a single-injection method to induce sterility in female animals as an alternative to surgical ovariohysterectomy. The idea was based on our recent finding that repetitive daily injection of estrogen into neonatal rats disrupted hypothalamic expression of Kisspeptin (KISS1), the neuropeptide that triggers and regulates pulsatile secretion of GnRH. Neonatal female rats were dosed with estradiol benzoate (EB) either by daily injections for 11 days or by subcutaneous implantation of an EB-containing silicone capsule designed to release EB over 2-3 weeks. Rats treated by either method did not exhibit estrous cyclicity, were anovulatory, and became infertile. The EB-treated rats had fewer hypothalamic Kisspeptin neurons, but the GnRH-LH axis remained responsive to Kisspeptin stimulation. Because it would be desirable to use a biodegradable carrier that is also easier to handle, an injectable EB carrier was developed from PLGA microspheres to provide pharmacokinetics comparable to the EB-containing silicone capsule. A single neonatal injection of EB-microspheres at an equivalent dosage resulted in sterility in the female rat. In neonatal female Beagle dogs, implantation of an EB-containing silicone capsule also reduced ovarian follicle development and significantly inhibited KISS1 expression in the hypothalamus. None of the treatments produced any concerning health effects, other than infertility. Therefore, further development of this technology for sterilization in domestic female animals, such as dogs and cats is worthy of investigation.

Effects of Lithium and Phosphorus on the Efficacy of a Liner for Increasing the Shear Bond Strength Between Lithium Disilicate and Zirconia.

PURPOSE: To evaluate the effect of the chemical formulation of liners on the shear bond strength (SBS) between lithium disilicate veneering ceramic and zirconia core. MATERIALS AND METHODS: Four experimental groups (n = 12) were designed according to liner composition: negative control group (lithium and phosphorus removed from the conventional liner), Li group (lithium added to the negative control group), P group (phosphorus added to the negative control group), and Li+P group as the positive control (conventional liner). After applying the liner, lithium disilicate was pressed on zirconia. Specimens were stored in distilled water (37°C, 24 h) before testing the SBS. To test the SBS, shear force was applied perpendicular to the lithium disilicate-zirconia interface. The differences in the SBS between the veneer lithium disilicate and zirconia substructure were evaluated with one-way ANOVA (significance level of 0.05). RESULTS: The presence or absence of lithium and phosphorus influenced the efficacy of the liner. The negative control and P groups showed mainly cohesive failures, and the Li group mainly showed mixed failures. Both adhesive and mixed failures were observed in the Li+P group. The groups including lithium showed significantly higher SBS than the negative control or Li+P group (p < 0.05). The group including phosphorus, which showed higher crystallinity, showed significantly lower SBS than the negative control and Li+P groups (p < 0.05). CONCLUSIONS: The differences in the composition of the liner can affect the wettability and reactivity, and as a result, the SBS was different.