Earticle

The present study was aimed to investigate the molecular mechanisms of active immunization against GnRH by focusing on effects of active immunization against GnRH on hypothalamic-pituitary-testicular axis. Adult male rats (n=36) were randomly and equally allocated into three groups: control (no treatment), surgically castrated, or immunized against 50 ug D-Lys6-GnRH-tandem-dimer peptide conjugated to ovalbumin in Specol adjuvant at 12 weeks of age (with a booster 8 weeks later). Blood samples (for antibody titers and hormone concentrations) were collected at 2-week intervals until rats were killed at 20 weeks of age. At decapitation, testes weight /volume and pituitary weight were recorded. Hypothalamus, pituitary and testis were collected to detect the mRNA expressions of reproduction-related genes with real-time fluorescence quantitative PCR, and the hypothalamus and testes were excised for tissue GnRH detection and morphological observation, respectively. Compared to intact controls, immunocastration reduced (p<0.05) serum concentrations of testosterone, LH and FSH, and the GnRH content in the median eminence, reduced the weight of the hypohysis (p<0.01), and induced testicular atrophy (suppression of spermatogenesis). Furthermore, mRNA expression of GnRH in the hypothalamus, GnRH receptor, LH-β and FSH-β in the pituitary, LH receptor and FSH receptor in the testes, and genes in sex steroid feedback loops (androgen receptor (AR), kisspeptin encoded gene (Kiss-1) and kisspeptin receptor (GPR54) in the hypothalamus were decreased in immunocastrated rats compared to intact controls (p<0.05). Similarly, surgical castration reduced GnRH in the median eminence as well as mRNA expression of GnRH, AR, Kiss-1 and GPR54 in the hypothalamus (p<0.05). These results suggest that active immunization against GnRH reduces GnRH synthesis in the hypothalamus by decreasing androgen-androgen receptor-Kisspeptin-GPR54 signaling pathways and causes dysfunction of the pituitarytesticular axis. Both the loss of GnRH synthesis and dysfunction of the pituitary- testicular axis seem to be mechanisms underlying immunocastration.

There are rare reports about equine industrial data especially equine neonatology and pediatrics in Korea. The object of this study was to evaluate incidence of death and rate of entering stable in foals. A retrospective study was carried out to investigate numbers of survival foals by 45 days old and entering stable of racing authority in mainland and Jeju island from 2001 to 2010. And incidence of death and euthanasia caused by disorders in a population of Thoroughbred foals during their first 12 months post partum in Jeju in 2010 only. Among 11,321 foals, 1,210 did not survive to 45 days of age. In addition, 9,034 foals entered racing stables without veterinary problems. So, rate of survival foal and entering stable were 89.3% and 79.8% respectively during 10 years. Of 79 foals were dead through growing in Jeju: respiratory infection was the most common cause of death (27.8%, 22/79 foals) followed by catastrophic fractures (24.0%, 19/79), neonatal maladjustment syndrome (20.2%, 16/79), non-infectious gastrointestinal problems (13.9%, 11/79), septicemia (7.6%, 6/79) and congenital defects (6.5%, 5/79). Infection was the single most common cause of death accounting for 35.5% (28/79) of all death incidents in this population. Young animal infection remains a leading cause of mortality in the equine industry, despite advances in prevention and treatment. Findings from this study provide information regarding the causes of death in the young Korean Thoroughbred horses.