A comparison of two methods for prediction of response and rates of inbreeding in selected populations with the results obtained in two selection experiments

Selection programmes are mainly concerned with increasing genetic gain. However, short-term progress should not be obtained at the expense of the within-population genetic variability. Different prediction models for the evolution within a small population of the genetic mean of a selected trait, its genetic variance and its inbreeding have been developed but have mainly been validated through Monte Carlo simulation studies. The purpose of this study was to compare theoretical predictions to experimental results. Two deterministic methods were considered, both grounded on a polygenic additive model. Differences between theoretical predictions and experimental results arise from differences between the true and the assumed genetic model, and from mathematical simplifications applied in the prediction methods. Two sets of experimental lines of chickens were used in this study: the Dutch lines undergoing true truncation mass selection, the other lines (French) undergoing mass selection with a restriction on the representation of the different families. This study confirmed, on an experimental basis, that modelling is an efficient approach to make useful predictions of the evolution of selected populations although the basic assumptions considered in the models (polygenic additive model, normality of the distribution, base population at the equilibrium, etc.) are not met in reality. The two deterministic methods compared yielded results that were close to those observed in real data, especially when the selection scheme followed the rules of strict mass selection: for instance, both predictions overestimated the genetic gain in the French experiment, whereas both predictions were close to the observed values in the Dutch experimen

Delayed-type hypersensitivity response to KLH in F2 and backcrosses of two immune selected chicken lines: effect of immunisation and selection

Cell-mediated immune response to keyhole limpet hemocyanin (KLH) was studied in 13 different progeny groups belonging to a second generation cross between two lines of White Leghorn previously selected for 10 generations for high antibody response to Newcastle disease vaccine (ND3) and high cell-mediated response to phytohemagglutinin (PHA) measured as wing web swelling. The cutaneous hypersensitivity response to KLH was assessed in KLH immunized and non-immunized birds. Wing thickness was measured at three time points: before the injection and 4 and 24 hours after the injection. The effect of previous immunization and genetic background was assessed. While no differences were present between progeny types or to a randomly bred control line at any of the three time points, significant differences were present between immunized and not immunized birds 24 hours after challenge. Results demonstrate that KLH immunized birds perform better and that the previous selection and crossbreeding scheme has not influenced the intensity of the skin swelling response to KLH. Apparently, neither selection for antibody responsiveness to ND3 nor selection for enhanced responsiveness to a T cell mitogen affected delayed-type hypersensitivity (DTH) to the Th 2 antigen KLH. These results may serve to facilitate further selection based on independent immune parameters

Absence of high affinity dopamine receptor in GH3 cells: a prolactin-secreting clone resistant to the inhibitory action of dopamine

Dopamine (DA) and DA agonists bind with high affinity to anterior pituitary receptors which mediate the inhibition of PRL release. Spiperone (SPIP), a DA antagonist, has also been successfully used to characterize pituitary DA receptors with a dissociation constant (Kd) of less than 1 nM. We studied the binding of SPIP to GH3D6 cells which secrete only PRL and GH. This clone was derived from a radiation-induced tumor of the rat anterior pituitary. Equilibrium binding of [3H]SPIP to living GH3 cells showed no high affinity receptors, but a low affinity (Kd = 0.83 microM) and saturable (0.06 fmol/cell) population of sites was observed. In addition, saturable binding with a similar affinity (Kd = 0.57 microM) was noted in broken GH3 cells. The interaction was completely reversible and temperature dependent. The concentration of various ligands required to compete for half of the [3H]SPIP binding to whole cells were: chlorpromazine, 0.17 microM; haloperidol, 0.68 microM; pimozide, 0.77 microM; d-butaclamol, 1.16 microM; 1-butaclamol, 1.30 microM; SPIP, 1.49 microM; bromergocryptine, 4.98 microM; apomorphine, 13.9 microM; and DA, 100 microM. The absence of a high affinity site in GH3 cells is consistent with the decreased effectiveness of various agonists and antagonists on PRL secretion. It is possible that the low affinity interactions observed in GH3 cells are normally present in the anterior pituitary and brain and do not simply represent an alteration of receptor affinity

Circulating corticosterone reaction to restraint and adrenocorticotropin hormone administration in white leghorns selected for immune response traits

Corticosterone plasma concentration was measured in a random-bred control line and in 3 White Leghorn chicken lines previously selected over 9 generations for 3 different in vivo immune responses: high antibody response to Newcastle disease virus vaccine 3 wk after vaccination (ND3), high cell-mediated immune response (response to phytohemagglutinin, PHA), and high phagocytic activity measured as carbon clearance (CC). The objective of the study was to estimate if selection on immune response had an effect on the response to stress assessed by measures of corticosterone concentration before and after physical stress or adrenocorticotropin hormone injection and if the effect was dependent on the immune response trait that had been selected for, by joint analyses of immune responses and concentrations. The mean values of plasma corticosterone measures did not differ between lines, indicating that selection for different high immune responses had little effect on response to stress. Within line, however, significant negative correlations (?0.46 64 r 64 ?0.39) were found between cell-mediated immunity and corticosterone plasma concentrations in 3 of the 4 lines. Moreover, in the line selected for high antibody titers (ND3-L), corticosterone levels were positively correlated to ND3 (r = 0.41 and 0.47) and negatively correlated to CC (r = ?0.48). \ua92008 Poultry Science Association Inc