甲状腺激素在鱼类繁殖中的作用

<正>甲状腺激素(Thyroid hormone,TH),包括三碘甲状腺原氨酸(T3)和四碘甲状腺原氨酸(T4),存在于所有的脊椎动物中。研究表明,TH对哺乳类和两栖类的早期发育和变态过程发挥着至关重要的作用,而在鱼类(尤其是鲆鲽类)的变态过程中,TH的调控作用更加明显[1,2]。近期研究发现,TH在鱼类发育的各阶段都起着重要的调节作用,其中对鱼类繁殖过程的调控作用尤为显著[3]。作者旨在阐述鱼类甲状腺的结构特征,及TH在鱼类繁殖过程中的作用。     

鱼类甲状腺轴对胚胎发育、仔鱼变态及性别分化的调控作用研究进展

鱼类甲状腺轴由下丘脑、垂体、甲状腺组成,下丘脑通过分泌促甲状腺激素释放激素、促肾上腺皮质激素释放激素调节垂体促甲状腺激素的合成和分泌,促甲状腺激素促进甲状腺滤泡合成并释放甲状腺激素(主要为甲状腺素—T4),T4运输至肝脏等外周组织中,经过脱碘转化形成生物活性更强的三碘甲腺原氨酸(T3),T3主要通过同核受体结合发挥生物学功能。甲状腺激素对鱼类胚胎发育、仔鱼变态及性别分化等早期生长发育过程具有重要调控作用:甲状腺激素为鱼类胚胎发育期所必须,外加适量甲状腺激素能够提高胚胎或仔鱼存活率;仔鱼变态过程中,某些外部形态变化及相关组织分化依赖甲状腺激素的调控,牙鲆等仔鱼变态期体内甲状腺激素水平及其受体表达量会显著升高;性腺发育期,甲状腺激素对调控鱼类性别分化方向可能具有一定作用。     

强化管理依法行政促进食盐加碘消除碘缺乏危害

“碘”是甲状腺合成甲状腺激素所必需的微量元素。甲状腺素对人和动物的正常生长都是必不可缺的,凡是甲状腺激素所具有的各种生物学功能,诸如维持能量代谢、调节新陈代谢、对垂体功能的支持作用、促进体格发育、促进中枢神经系统的结构发育与功能的建立等均与“碘”直接有关。     

外源污染物对硬骨鱼甲状腺干扰作用机制的研究进展

甲状腺激素在鱼类生长发育、变态、生殖、渗透调节以及摄食和营养代谢中发挥着重要作用,外源化合物对硬骨鱼的甲状腺干扰作用会导致发育和孵化延迟、运动性降低。本文首先对鱼类甲状腺激素的中枢调控、合成、转运、代谢和发挥作用的相关过程进行简要介绍,随后从核受体介导途径、非受体介导途径两个方面综述了外源污染物对硬骨鱼甲状腺的干扰作用机制,最后从物种特异性、检测指标、膜受体介导途径三个方面提出了目前研究的不足之处以及解决方法,以期为今后探究外源污染物对鱼类甲状腺系统干扰作用机制的研究提供更多的参考。     

降海鲑渗透生理及入海窗口期的研究进展

在过去30年中,降海鲑的发育得到了大量关注,研究降海鲑的发育,特别是如何调控降海鲑发育的时间和品质,以便幼鲑移入海水网箱。洄游型鲑科鱼类幼鲑向降海鲑的转变包含了一系列的行为、形态、生理的改变,这都为降海洄游进入河口做准备。降海鲑发育受几种激素的促进,包括生长激素、胰岛素样生长因子-I、皮质醇、甲状腺素,而催乳素通常会抑制发育。鳃氯细胞中特殊的离子转运蛋白(NKA、Na+/K+/Cl-协同转运蛋白和Cl-通道)丰度的增加引起盐分泌能力的提高,从而有利于降海鲑在海水中生长、游泳和存活。具银化期的鲑科鱼类(如大西洋鲑(Salmo salar)、硬头鳟(Oncorhyunchus mykiss)、银大麻哈鱼(Oncorhynchus kisutch)至少在淡水中生活一年,达到临界最小规格之后才可改变其对光周期的响应。如果在银化前未达到这个最小规格,则需等到下一年(或更长)。鲑科鱼类如何在一年中合适的时间确定其规格或生长率,并增加对光周期的响应性,这一重要的领域还未得到大量的关注。因此,了解降海鲑渗透生理及入海窗口期,查明不同鱼类适宜生长盐度,入海时间和方式非常重要,可为鲑科鱼类(如虹鳟(Oncorhynchus mykiss)、硬头鳟等)在黄海冷水团规模化养殖提供理论支持。     

疏肝健脾方结合左甲状腺素钠片治疗桥本甲状腺炎35 例总结

目的：观察疏肝健脾方结合左甲状腺素钠片治疗桥本甲状腺炎的临床疗效。方法：选取70 例桥本甲状腺炎患者作为研究对象,按随机数字表法将其分为治疗组和对照组,每组各35 例。对照组采取左甲状腺素钠片治疗,治疗组在对照组基础上采用疏肝健脾方治疗。疗程均为3个月。比较2组综合疗效及抗甲状腺球蛋白抗体（TGAb）、抗甲状腺过氧化物酶抗体（TPOAb）水平。结果：总有效率治疗组为94.3%（33/35）,对照组为77.1%（27/35）,组间比较,差异有统计学意义;治疗组TGAb、TPOAb指标改善情况明显优于对照组,差异均有统计学意义（P＜0.05）。结论：疏肝健脾方联合左甲状腺素钠片治疗桥本甲状腺炎,疗效理想,可提升患者甲状腺自身抗体,值得临床借鉴。     

鱼类生长激素的体内代谢、分泌调控和作用机制研究的进展

主要对１９８３－１９９６年间关于鱼类生长激素的体内代谢、分泌调控和作用机制的研究进展予以综合评述。通过鱼类划性放射免疫测定法的建立和体风代谢动力学研究，证实，外源生长激素在鱼体内不会产生积累。鱼类生长激素的分泌调控受下丘脑分泌的生长激素释放因子（ＧＨＲＦ）和释放抑制因子（ＳＲＩＦ）的双重；促性腺激素释放激素（ＧｎＲＨ）、雌二醇（Ｅ２）、促甲状腺素释放激素（ＴＲＨ）和神经肽（ＮＹＰ）对鱼类生长激素的     

文昌鱼幼虫变态的内分泌调节研究进展

本文对头索动物文昌鱼幼虫变态的内分泌调节研究所取得的新进展进行综述.现已证实文昌鱼内柱分泌甲状腺素(TH)及其衍生物三碘甲腺醋酸与甲状腺素受体(TR)结合触发幼虫变态.同时,文昌鱼脑泡神经细胞分泌促甲状腺素释放激素(TRH)或促肾上腺激素释放激素(CRH)和哈氏窝上皮细胞分泌促甲状腺素(TSH)及其受体的发现将表明文昌鱼存在甲状腺调控轴,这就为文昌鱼幼虫变态受内分泌基因网络调节提供新证据.因而本综述可为人工控制文昌鱼幼虫变态和提高成活率提供科学依据.     

鱼类免疫系统的早期发生

鱼类养殖业的发展极大促进了近10年来对鱼类早期免疫系统发生的研究,并取得一些新进展。本文就母体免疫因子向卵子转移和早期胚胎免疫、胚胎血细胞发生、淋巴器官和淋巴细胞发生以及体液免疫的发育4个方面,对鱼类早期免疫系统的发育做简要评述。     

控制光照期促进鱼类性腺成熟

大多数鱼类的性腺仅在一年的某个特定的季节内成熟,在这些季节内,鱼类生活的环境条件必需与鱼类性腺发育所必需的条件相符合,其性腺才能发育成熟。由于每一个地区的环境条件都不一样,因而在不同的地区内,即令是同一品种的鱼类,其性腺成熟的具体时间也是不一致的。而在温度、光照、海流、盐度和食物等环境条件中,以温度     

Development of thyroid abnormalities in mummichogs,Fundulus heteroclitus,from a polluted site

Previous studies showed that adult and 6-month-old young-of-year Fundulus heteroclitus from a polluted site have enlarged thyroid follicles and (in adults) higher thyroxine levels compared to fish from an unpolluted reference site. This study's purpose was to discover when in development these differences begin to appear. For 15-20 mm fish, the average follicle size of the polluted population was significantly larger than that of the reference population, similar to the pattern found in older fish. However, for the smaller size (12-14.5 mm), the average follicle size of fish from the polluted site was significantly smaller. Although not statistically significant, radioimmunoassay measurements of thyroxine levels were consistent with follicle differences: in larger sizes (20-25 and 15-20 mm) fish from the polluted site had higher thyroxine levels but the smaller size (12-14.5 mm) had lower levels. Therefore, the thyroid abnormalities seen in adults begin when the fish are approximately 15-20 mm long. However, the follicle size reversal for the 12-14.5 mm range may also indicate abnormality at that developmental stage.     

Endocrine disruption: thyroid dysfunction in mummichogs (Fundulus heteroclitus) from a polluted habitat.

Mummichogs (Fundulus heteroclitus) from Piles Creeks (PC), New Jersey (a polluted site), are sluggish and show poorer prey capture and predator avoidance than reference fish from Tuckerton (TK). The behavioral dysfunction of the PC fish may be associated with thyroid impairment due to endocrine disruption. In this study, we compared thyroid histology and thyroid hormones in the two populations and determined experimentally whether the polluted environment could alter thyroid hormone levels. PC fish had larger thyroid follicles, greater follicle cell heights, and contained higher plasma thyroxine (T4) levels than TK fish. However, there were no significant differences in either plasma or tissue triiodothyronine (T3). TK fish held in simulated PC environments had higher plasma T4 and lower plasma T3 than field-sampled fish. PC fish held in clean water had lower plasma T4 and T3 than field-sampled fish. In either case, there was no significant difference in tissue T3 content. The contaminants in PC alter thyroid structure and function, which may relate to the behavioral differences between fish from the polluted and reference sites.     

Changes in serum thyroid hormone levels and thyroid gland activity of artificially maturing female Japanese eel(Anguilla japonica)

In order to evaluate the involvement of the thyroid gland in reproduction, thyroid functioning was described in female cultivated Japanese eel (Anguilla japonica) in progressive stages of sexual maturation induced by chum salmon pituitary homogenate (SPH) treatment. Serum thyroid hormones, thyroxine (T4) and triiodothyronine (T3) were also measured in each stage. Thyroid gland activity (epithelial cell height) was high before SPH injection (previtellogenic stage), further increasing at the early vitellogenic stage, thereafter decreasing to late vitellogenic and migratory nucleus stages. The profiles of both T3 and T4 changed during vitellogenesis, being high during previtellogenic and early vitellogenic stages, and subsequently declining, thus mimicking thyroid gland activity. These results suggest that the thyroid has relation with eel ovarian development during artificial maturation.     

Stage‐dependent thyroxine effects on sea urchin development

Thyroxine, one of the iodinated hormones produced by vertebrate thyroids, has been reported to accelerate late larval development in several sea urchins (Chino et al. 1994) and in the crown‐of‐thorns starfish (Johnson & Cartwright 1996), but thyroxine effects on earlier portions of echinoderm development have not been reported. I investigated thyroxine effects on developmental rates during several periods spanning development from early cleavage to metamorphosis in the New Zealand sea urchin Evechinus chloroticus (Valenciennes). Thyroxine treatment slowed development between the eight‐cell stage and assembly of the four‐armed pluteus and mid‐larval development between the four‐armed and six‐armed stages. Thyroxine treatment accelerated progress of eight‐armed plutei toward settling, but did not alter the final percentages of larvae that settled and metamorphosed to juvenile urchins. Acceleration of late larval echinoderm development by thyroxine may indicate a relatively ancient evolutionary origin of thyroxine's effects on developmental processes (Johnson 1997).     

Effect of estradiol-17β on pituitary-thyroidal axis of Japanese eel (Anguilla japonica)

In teleost sPeCies, it is well accepted that estradiol--l75 (E2 )is generated from ovarian fOl-licles stimulated by pituitary gonadOtropins (GTH) (Nagahama, l987). FUrthermore, E2 canstimulate hepatic vitellngenesis and elevate plasrna yOlk protein precursor vite1lOgenin, totalCa and W levels in several teleosts (KorSgaard and Petersen, l976, l978; Whiteheadet al., l978; Elliott et al., l979; Pertersen et al., l983; Wallace, 1985; tapigliati etal., 1999). On the other hand, many stud…     

闽南-台湾浅滩渔场鱼类食物网研究

海洋鱼类食物网是海洋生态学基础理论研究之一,从多种海洋鱼类食性类型的综合分析,阐明食物网营养级的能流途径,为改造海洋生态系统,减少食物链的环数而提高水域生产力。因此,深入研究海洋鱼类食物网,对于合理利用海洋渔业资源具有一定的实践意义。近年来,国外在河口红树林群落,以残屑(detritus)为基础的食物网研究已有报道[1];对河口游泳动物食物网也发表过综合论述[2]。     

鱼类精液超低温冷冻保存的研究展望

精液的超低温冷冻保存是从上世纪50年代开始的，此项技术发展至今已取得很大成就。国外学者的工作主要集中在冷水性鲑鳟鱼类及某些海水鱼上，而国内以研究四大家鱼及其他淡水鱼类精液的超低温保存居多，只有少数学者研究如真鲷、黑鲷、花鲈、大弹涂鱼等海水鱼类精液的超低温保存。本文就开展鱼类精液冷冻保存研究的意义、鱼类精子超低温保存的基本生物学原理，及有关鱼类精液冷冻保存的研究现状等作一综合评述。     

Demersal fish and habitat associations from visual surveys on the central California shelf

In 2004, we surveyed demersal fishes and habitats on the continental shelf off central California (65–110 m depth) using the occupied submersible Delta. Our objectives were to estimate the relative abundance of habitats and to examine demersal fish species composition, diversity, density, and sizes relative to these habitats. A total of 112 transects were completed covering 32 km of seafloor. A higher density of fishes was estimated in boulder and cobble habitats than in mud and brachiopod beds. More than 80% of the fishes were small, measuring 20 cm or less in total length. Species with small maximum size (primarily pygmy rockfish, Sebastes wilsoni, and blackeye gobies, Rhinogobiops nicholsii) accounted for nearly half (49%) of the total number of 12,441 fishes. Most fishes were immature, with only 4 of 20 harvested species having more than 50% of the individuals larger than the size at first maturity. Our study area on the continental shelf may be an ontogenetic transition zone for immature fishes before they move to their adult habitat on the slope. Alternatively, historical fishing pressure may have contributed to the lack of large, mature fishes in the survey area. Understanding the importance of these habitats to fishes at various life stages will improve our ability to assess these deepwater fish stocks and effectively manage these living resources on an ecosystem basis.     

基于氮稳定同位素的九龙江口鱼类营养级研究

采用氮稳定同位素技术对2013年6—8月九龙江口采集到的隶属于13目42科61属共71种鱼类的营养级进行研究。结果表明,九龙江口鱼类的δ15 N值跨度较大,介于7.23‰~14.66‰之间。以菲律宾蛤仔(Ruditapes philippinarum)为基准生物估算出鱼类的营养级介于1.70~3.89之间,营养级最低与最高的鱼类分别为少牙斑鲆(Pseudorhombus oligodon)与多鳞鱚(Sillago sihama)。与Fishbase同种鱼类的营养级数据进行比较,83.1%的鱼类的营养级均值处于Fishbase同种鱼类的营养级范围内,但81.7%的鱼类的营养级均值比Fishbase同种鱼类的营养级均值略低;与传统的胃含物分析结果比较,58.3%的鱼类的营养级在0.5个营养级的误差范围内。基于氮稳定同位素估算的鱼类营养级较低的原因可能与本研究样品中低龄鱼及幼鱼比例较大有关。与其他方法相比,稳定同位素法在研究体型较小的幼鱼和低龄鱼营养级更具优势。鱼类营养级随其个体大小的变化明显,但存在种的差异性:不同体长的髭缟鰕虎鱼(Tridentiger barbatus)和绿鳍鱼(Chelidonichthys kumu)的营养级跨度较大,分别为1.54和1.43;而鳓(Ilisha elongata)等的营养级则跨度较小,这可能与不同鱼类的食性变化有关。