Paradoxical effects of bovine somatotropin treatment on the ovarian follicular population and in vitro embryo production of lactating buffalo donors submitted to ovum pick-up.

The aim of the present study was to evaluate the effect of bovine somatotropin (bST; 500mg) administration on lactating buffalo donors submitted to two different ovum pick-up (OPU) and in vitro embryo production schemes with a 7 or 14d intersession OPU interval. A total of 16 lactating buffalo cows were randomly assigned into one of four experimental groups according to the bST treatment (bST or No-bST) and the OPU intersession interval (7 or 14d) in a 2×2 factorial design (16 weeks of OPU sessions). The females submitted to OPU every 14d had a larger (P<0.001) number of ovarian follicles suitable for puncture (15.6±0.7 vs. 12.8±0.4) and an increased (P=0.004) number of cumulus-oocyte complexes (COCs) recovered (10.0±0.5 vs. 8.5±0.3) compared to the 7d interval group. However, a 7 or 14d interval between OPU sessions had no effect (P=0.34) on the number of blastocysts produced per OPU (1.0±0.1 vs. 1.3±0.2, respectively). In addition, bST treatment increased (P<0.001) the number of ovarian follicles suitable for puncture (15.3±0.5 vs. 12.1±0.4) but reduced the percentage (18.9% vs. 10.9%; P=0.009) and the number (1.4±0.2 vs. 0.8±0.1; P=0.003) of blastocysts produced per OPU session compared with the non-bST-treated buffaloes. In conclusion, the 14d interval between OPU sessions and bST treatment efficiently increased the number of ovarian follicles suitable for puncture. However, the OPU session interval had no effect on embryo production, and bST treatment reduced the in vitro blastocyst outcomes in lactating buffalo donors.

Specific suppression of hybridoma immunoglobulin secretion by hapten-conjugated mouse IgG: a model of B-cell tolerance.

In an effort to establish a model system for studying B-cell tolerance, the effects of hapten-conjugated isologous mouse IgG on the secretion of antibody by a mouse hybridoma cell line were studied. The hybridoma cell line 35-12 (HC) secretes IgM antibody to the hapten dinitrophenyl (DNP). After HC cells are injected intraperitoneally into BALB/c mice, the cells initially undergo a marked reduction in the proportion of PFC/10(6) followed by a return of PFC to pretransfer levels by 7-10 days. Hapten-conjugated mouse IgG (DNP-MGG), which induces tolerance to DNP in normal mouse B cells, also induces suppression of HC PFC when administered within the first 2 days after the transfer. Administration of tolerogen either 2 days before injection of HC or after the PFC response has returned to preinjection levels fails to give suppression. Suppression is dose dependent and hapten specific since immunogenic hapten-carrier conjugates (e.g., DNP-KLH, DNP-Ficoll) and fluorescein-MGG are not suppressive. T cells may not be required for suppression since hybridoma cells inoculated into nude mice are also suppressed by DNP-MGG. These results suggest that hybridoma cells undergo a change from nonsecreting to secreting cells during in vivo growth and that administration of tolerogen during the nonsecreting stage inhibits antibody secretion.