RESUMO
The greater amberjack (Seriola dumerili), a pelagic marine species with a global distribution, has considerable worldwide potential as an aquaculture species. However, difficulties have been encountered in inducing spontaneous spawning in cultured fish stocks. In this study, we analysed the key regulatory factors, secretoneurin (SN) and gonadotropin-releasing hormone (GnRH), in greater amberjack. Active peptides of SN and GnRH, SdSNa, and SdGnRH, respectively, were obtained by comparative analysis of homologous proteins from different species. Amino acid substitutions of the SdGnRH decapeptide at position 6 with a dextrorotatory (D) amino acid and at position 10 with an ethylamide group yielded a super-active agonist (SdGnRHa). The injection of SdSNa and SdGnRHa elevated luteinizing hormone, thyroid-stimulating hormone, and oxytocin levels in the sera of sexually mature fish, whereas it reduced the level of follicle-stimulating hormone. Furthermore, in response to the SdSNa and SdGnRHa injections, we detected an increase in the expression of genes associated with oocyte development and spermatogenesis. We established that the greater amberjack cultured along the southern coast of China reached sexual maturity at three years of age, and its reproductive season extended from February to April. Spawning of the cultured greater amberjack was successfully induced with a single injection of SdGnRHa/SdSN/DOM/HCG. Our findings indicate that similar to GnRHa, SNa is a potential stimulator of reproduction that can be used to artificially induce spawning in marine fish.
RESUMO
Objective To introduce the competing risk model into outcome prediction of mild cognitive impairment (MCI) of seniors and to explore influencing factors for the prognosis of MCI to Alzheimer' s disease (AD).Methods Data were collected from six follow-up visits to 600 seniors from communities in Taiyuan city,which were conducted at an interval of six months from October 2010 to May 2013.MCI state was defined as the transient state,AD and death before AD as two absorbing states (death before AD in which was regarded as a competing risk event),building the competing risk model to identify the model parameters,and to explore influencing factors on MCI prognosis to AD.In the meantime,the 3-year MCI-AD transition probability was estimated based on the multi-state Markov model.Results Based on screening with the multivariate competing risk model analysis,factors such as higher age (estimate HR=1.56,95％CI:1.01-2.39),female gender (HR=1.72,95％CI:1.02-2.92),higher education(HR=0.64,95％CI:0.41-1.00),reading frequently (HR=0.57,95％CI:0.32-0.99),hypertension (HR=3.43,95％CI:1.08-10.85) and high SBP(HR=1.67,95％CI:1.04-2.66),were statistically significant for transition from MCI to AD in three years.3-year MCI-AD transition probability was 10.7％(95％CI:8.6％-13.2％).Conclusion Age,gender,education,reading and blood pressure were the influencing factors for the prognosis of MCI to AD.Competing risk model was advantageous in studying longitudinal data with multiple potential outcomes.
