B D Schanbacher

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The working hypotheses in this experiment were: that ovarian estradiol would inhibit luteinizing hormone (LH) secretion in heifers that were anestrus as a result of restricted dietary energy intake and the responsiveness of LH secretion to estradiol negative feedback would decrease during the period when restoration of estrous cycles occurred following(More)
Sexually mature rams were left intact, castrated (wethers), castrated and implanted with testosterone, or castrated, implanted with testosterone and pulse-infused every hour with LHRH. Serum concentrations of LH increased rapidly during the first week after castration and at 14 days had reached values of 13.1 +/- 2.2 ng/ml (mean +/- s.e.m.) and were(More)
Alterations in testicular morphology were studied in boars actively immunized against gonadotropin hormone releasing hormone (GnRH). Ten boars were divided equally into two experimental groups (five GnRH-immunized, and five controls). Antibody production was achieved by conjugating GnRH to human serum globulin (hSG). The GnRH-hSG conjugate was emulsified in(More)
SUMMARY Concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were determined in serum of crossbred beef bulls during pubertal development. Serum LH ranged between .5 and 2.0 ng/ml with highest concentrations observed as 12 months of age. Serum FSH varied considerably among individuals but mean concentrations were within the(More)
Five intact male mongrel dogs, characterized by an episodic secretory pattern of LH and normal serum testosterone concentrations, were actively immunized against LHRH by subcutaneous injections of 200 micrograms of a LHRH-human serum albumin conjugate at 0, 4, and 8 weeks. After 12 weeks, two dogs having the highest antibody titers to LHRH (25% and 51%(More)
Morphologic changes in the male reproductive system of mongrel dogs immunized against LHRH were quantitated using linear measurements and morphometric techniques at the light-microscopic level. Two experimental groups (5 nonimmunized control animals and 5 actively immunized animals) were killed 12 weeks after the primary immunization. No significant(More)
This mini-review aims to summarize some of our recent findings relating to testicular function and feedback control of the hypothalamic-pituitary axis by testicular steroids in rams and bulls. Testosterone secretion in intact males is not tonic, but is characterized by episodic pulses. This pattern of secretion is dictated by inputs of the central nervous(More)
The effects of contrasting photoperiods (16L:8D vs 8L:16D) and ambient temperatures (5 C vs 18 C vs 31 C) on performance traits of ewe lambs have been evaluated. Seventy-two lambs were paired and allotted to one of six treatment groups in a 2 x 3 factorial experiment. The lambs were fed a pelleted diet ad libitum. throughout the 14-wk study (i.e., as lambs(More)
SUMMARY Acute and chronic effects of gonadotropin releasing hormone (GnRH) administration on reproductive characteristics of 32 rams have been assessed during the nonbreeding season. Rams injected intramuscularly with 50 /ag of GnRH had elevated (P<.01)concentrations of serum testosterone and noticeably higher (60%) mating activities when compared to(More)
Pituitaries were collected from intact rams and rams that had been rendered bilaterally cryptorchid by surgery to examine the effects of cryptorchidism on gonadotropin heterogeneity, levels of uncombined luteinizing hormone (LH) subunits, and the apparent molecular sizes of LH and follicle-stimulating hormone (FSH). Cryptorchid rams had higher pituitary(More)