Identification of two porcine brush border glycoproteins that bind the K88ac adhesin of Escherichia coli and correlation of these glycoproteins with the adhesive phenotype.

In this study, we identified two brush border glycoproteins (210 and 240 kDa) that bind both K88ac+ Escherichia coli and purified K88ac adhesin. The specificity of these binding glycoproteins for the K88ac adhesin was demonstrated in studies in which the binding of 35S-labeled K88ac+ E. coli and biotinylated K88ac adhesin to these glycoproteins was blocked in the presence of a 100-fold molar excess of unlabeled K88ac adhesin but not in the presence of the K99 adhesin. Pretreatment of adhesive brush borders with sodium metaperiodate destroyed both binding activities, indicating that the interaction between the K88ac adhesin and the binding glycoproteins requires the glycoprotein carbohydrate moiety. It was demonstrated previously that K88ac+ E. coli binds to adhesive brush borders but not to nonadhesive brush borders (R. Sellwood, R. A. Gibbons, G. W. Jones, and J. M. Rutter, J. Med. Microbiol. 8:405-411, 1975). In the present study, brush borders isolated from 10 different pigs were tested first for brush border adhesiveness and then for the presence of the binding glycoproteins. In all cases, the binding glycoproteins were detected only in the adhesive brush border preparations. These two binding glycoproteins may be the receptors used by K88ac+ ETEC to adhere to intestinal brush border cells. Their presence on adhesive brush borders and absence on nonadhesive brush borders may be the basis for resistance and susceptibility of pigs to K88ac+ ETEC infections.

Endocrine and body growth traits in heifers exposed to testosterone-propionate during early fetal development.

This study was conducted to determine the effects of testosterone-propionate exposure during fetal development on sexual differentiation and growth rates in heifers. Ten pregnant cows were given subcutaneous injections of testosterone-propionate (250 mg/injection) every other day during d 40 to 60 of gestation. Four cows aborted after the end of testosterone treatment, while four heifers (androgenized females) and two bulls (androgenized males) were produced from the six remaining pregnant, testosterone-propionate treated cows. Calves from cows that did not receive exogenous hormone treatment were used as controls. At 8 mo of age, the androgenized heifers and control heifers and control steers were challenged with 1 mg estradiol-17 beta to induce a preovulatory luteinizing hormone (LH) surge. Two weeks later, pituitary responsiveness to exogenous luteinizing hormone releasing hormone (LHRH; 75 micrograms) was evaluated in androgenized heifers and in control heifers and control steers. To monitor growth rates, all animals were weighed at 28-d intervals from birth to 380 d of age. Androgenized females exhibited a partially masculinized phenotype as well as internal male reproductive structures. Treatment with estradiol-17 beta first depressed (P less than .05) serum LH concentrations in all animals, then induced (P less than .05) a preovulatory-like LH surge in control and androgenized females. Control steers did not (P greater than .05) exhibit a preovulatory-like LH surge following administration of estradiol-17 beta. Exogenous LHRH treatment stimulated peak LH concentrations (P less than .05) to a greater extent in control and androgenized females than in control steers.(ABSTRACT TRUNCATED AT 250 WORDS)

Active immunization of heifers against prostaglandin F2 alpha: potential as a sterilization vaccine.

Four experiments were conducted with 210 heifers in an attempt to develop a sterilization vaccine by active immunization against prostaglandin F2 alpha (PGF2 alpha) and to evaluate feedlot performance following immunization against the combination of PGF2 alpha and estrogens. The objectives were: development of a PGF2 alpha-ovalbumin conjugate that would induce antibody formation when used with complete Freund's adjuvant (CFA); comparison of CFA with other adjuvants in relation to PGF2 alpha antibody binding and maintenance of the corpus luteum; examination of growth performance in immunized heifers against both PGF2 alpha and estradiol-17 beta and evaluation of sterilization in PGF2 alpha-immunized heifers maintained with bulls. A PGF2 alpha-ovalbumin conjugate was developed that resulted in antibody production against PGF2 alpha, although antibody binding was quite low. The antibody response in heifers was higher in Exp. I and II than in Exp. III and IV (P less than .05). Complete Freund's adjuvant was the best adjuvant in inducing antibody formation compared with all other adjuvants tested (P less than .01). Corpus luteum (CL) function was maintained for 2.5 mo and ovulation was apparently blocked in Exp. I. The results of Exp. II confirmed those of Exp. I. Fewer than half of the heifers in Exp. III and IV had prolonged estrous cycles. In Exp. IV, immunized heifers became sterile for at least 4 mo when kept with bulls, although the success rate was only 37%. The low levels of antibody titers to PGF2 alpha in Exp. III and IV may be the reason for the failure to maintain CL function in some heifers.(ABSTRACT TRUNCATED AT 250 WORDS)