Vasoactive intestinal peptide (VIP) has potent PRL-releasing activity, but its physiological role in the regulation of PRL release during the avian reproductive cycle is not known. We used indirect immunofluorescence to determine if changes in hypothalamic VIP are associated with the shifts in circulating PRL during the reproductive cycle of the domestic turkey. In the naturally hyperprolactinemic incubating hen, the majority of VIP immunoreactivity (VIP-IR) existed within neurons of the infundibular nuclear complex (INF) and fibers in the external layer of the median eminence. Within the INF, the numbers of VIP-IR cells increased during the cycle, paralleling increases in serum PRL. In the reproductively inactive, nonphotostimulated hen with low serum PRL, essentially no positive cells were noted, whereas the incubating hen exhibited 32.1 +/- 2.2 cells/pair of adjacent sections in the anterior INF and 59.6 +/- 2.0 cells in the posterior INF. Exposure of inactive hens to a stimulatory photoperiod resulted in a 2.6-fold increase in serum PRL with the appearance of VIP-IR cells in the INF. During laying and incubation, further increases were observed in the number of positive cells in the INF and serum PRL as well as a greater fiber density in the median eminence. To further examine the association between changes in VIP-IR and serum PRL, circulating PRL was artificially lowered by depriving incubating hens of their nests for 0, 2, 5, and 10 days. On day 2 of nest deprivation, serum PRL declined markedly to 12% of day 0 levels, with VIP-IR cell numbers at 64% and 46% in the anterior and posterior INF, respectively. By day 10, birds exhibited cell numbers in the INF averaging 20% of those observed in the day 0 incubating hens, with serum PRL at 6% of day 0 levels. The results of these studies indicate a possible causal relationship between hypothalamic VIP and changes in PRL secretion during the avian reproductive cycle, providing a basis for further research on the importance of this peptide as well as factors responsible for the modulation of its expression in hypothalamic INF neurons.

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Intracranial perfusion of ovine prolactin (oPrl) via osmotic pump in laying turkey hens caused a sudden onset in incubation behavior, defined as an increase in nest visits. The hens also displayed a gradual decrease in egg laying during the time they were receiving oPrl, another indicator of the onset of incubation. Circulating immunoreactive turkey Prl levels fell during the perfusion period, even though the hens were displaying persistent nesting activity and reduced egg laying. No effects on serum LH were noted. Perfusion of oPrl during the first 14 days of photostimulation delayed the onset of egg laying by several days. No effects on serum Prl or serum LH were noted. It is suggested that incubation behavior is facilitated by central levels of Prl.

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The use of glutaraldehyde-treated biological tissue in heart valve substitutes is an important option in the treatment of heart valve disease. These devices have limited durability, in part, because of tissue calcification and subsequent tearing of the valve leaflets. Components thought to induce calcification include lipids, cell remnants, and residual glutaraldehyde. We hypothesized that treatment of glutaraldehyde-treated bioprosthetic heart valve material using a short and long chain alcohol (LCA) combination, composed of 5% 1,2-octanediol in an ethanolic buffered solution, would reduce phospholipid content and subsequently lower the propensity of these tissues to calcify in vivo. Phospholipid content of glutaraldehyde-treated porcine valve leaflets and bovine pericardium was found to be 10.1 +/- 4.3 (n = 7) and 3.9 +/- 0.48 (n = 2) microg/mg dry tissue, respectively, which was reduced to 0.041 +/- 0.06 (n = 7) and 0.21 +/- 0.05 (n = 4) microg/mg dry tissue, respectively, after LCA treatment. Calcification potential of the treated tissues was assessed using a rat subcutaneous implant model. After 60 days of implantation, calcium levels were found to be 171 +/- 32 (n = 11) and 83 +/- 70 (n = 12) mg/g dry weight for glutaraldehyde-treated porcine leaflets and bovine pericardium, respectively, whereas prior LCA treatment resulted in reduced calcium levels of 1.1 +/- 0.6 (n = 12) and 0.82 +/- 0.1 (n = 12) mg/g dry weight, respectively. These data, taken together, support the notion that treatment of glutaraldehyde-treated tissue with a short and long chain alcohol combination will reduce both extractable phospholipids and the propensity for in vivo calcification.