粗唇(鱼危)精巢显微结构和精子发生的研究

采用光镜和透射电镜观察了粗唇(鱼危)(Leiocassis crassilabris)精巢结构和精子发生.光镜结果显示:粗唇(鱼危)的精巢各小叶由数个小囊组成.从第Ⅱ期到第V期时,初级精母细胞逐渐发育成为次级精母细胞、精子细胞和精子,第Ⅵ期为排精后退化时期.透射电镜观察粗唇(鱼危)的精原细胞、初级精母细胞、次级精母细胞、精子细胞和精子的形态以及细胞核和线粒体等的结果表明:在精子发生各期中线粒体和细胞核有明显的变化;精原细胞时期细胞器较丰富,到精子细胞后期,细胞器的形态和数量发生了较大变化;随着精母细胞的发育,核质凝聚程度逐渐增强;粗唇(鱼危) 的精子具有椭圆的头部和复杂的中片,并具有由外膜折叠形成的波浪形的结构.     

粗唇鮠精巢显微结构和精子发生的研究

采用光镜和透射电镜观察了粗唇鮠(Leiocassis crassilabris)精巢结构和精子发生。光镜结果显示:粗唇鮠的精巢各小叶由数个小囊组成。从第Ⅱ期到第V期时,初级精母细胞逐渐发育成为次级精母细胞、精子细胞和精子,第Ⅵ期为排精后退化时期。透射电镜观察粗唇鮠的精原细胞、初级精母细胞、次级精母细胞、精子细胞和精子的形态以及细胞核和线粒体等的结果表明:在精子发生各期中线粒体和细胞核有明显的变化;精原细胞时期细胞器较丰富,到精子细胞后期,细胞器的形态和数量发生了较大变化;随着精母细胞的发育,核质凝聚程度逐渐增强;粗唇鮠的精子具有椭圆的头部和复杂的中片,并具有由外膜折叠形成的波浪形的结构。     

嫁(虫戚)精巢的组织学研究

本文研究了嫁Qi雄性生殖系统的组织学。嫁Qi的精巢结构同贻贝、栉孔扇贝的相似，也是由外膜及其内的无数生殖小管构成。外膜较薄，由平滑肌和少量结缔组织组成，只在局部区域含有单层柱状上皮细胞。生殖小管间充填着结缔组织及来自外膜的薄层肌肉，结缔组织中含有血管。生殖小管由位于基膜上的生殖上皮及由生殖上皮增殖出的精原细胞、初级精母细胞、次级精母细胞、精细胞和精子组成。精原细胞较大，圆形或椭圆形，核较大，与细胞同形，染色质呈颗粒状靠近核膜分布，核仁1个，圆形，明显。初级精母细胞和次级精母细胞结构相似。精细胞圆形，核染色深。精子呈长棒状，悬浮于生殖小管腔内。     

嫁虫戚精巢的组织学研究

本文研究了嫁虫戚雄性生殖系统的组织学。嫁虫戚的精巢结构同贻贝、栉孔扇贝的相似,也是由外膜及其内的无数生殖小管构成。外膜较薄,由平滑肌和少量结缔组织组成,只在局部区域含有单层柱状上皮细胞。生殖小管间充填着结缔组织及来自外膜的薄层肌肉,结缔组织中含有血管。生殖小管由位于基膜上的生殖上皮及由生殖上皮增殖出的精原细胞、初级精母细胞、次级精母细胞、精细胞和精子组成。精原细胞较大,圆形或椭圆形,核较大,与细胞同形,染色质呈颗粒状靠近核膜分布,核仁1个,圆形,明显。初级精母细胞和次级精母细胞结构相似。精细胞圆形,核染色深。精子呈长棒状,悬浮于生殖小管腔内。     

四指马鲅精巢发育及精子发生的组织学和超微结构

为了解四指马鲅（）精巢的组织结构和精巢发育及精子发生的组织学和超微结构变化，运用组织切片HE染色和透射电镜技术对养殖四指马鲅的精巢发育过程进行观察。结果显示，四指马鲅精巢位于腹腔背侧，紧贴中肾和鳔的腹面，为一对延长的扁平带状器官，呈灰白色，两条精巢于后端融合，呈“Y”字形，组织学上属典型小叶型精巢；根据精巢发育及精子发生的组织学特点可将其分为6个时期：3月龄精巢发育至第I期（精原细胞增殖期），4月龄发育至第II期（精母细胞增长期），5~7月龄发育至第III期（精母细胞成熟期），7~9月龄发育至第IV期（精子开始出现期），最早在10月龄发育至第V期（精子完全成熟期）达到初次性成熟；参与生殖排精后的精巢为第VI期（精子退化吸收期）；精子发生过程经历初级精原细胞、次级精原细胞、初级精母细胞、次级精母细胞、精细胞和精子6个时相，其细胞及细胞核直径逐级减小，核质比发生规律性变化；电镜下显示精子发生过程中，细胞核内染色体逐渐浓缩，电子密度增加，线粒体数量减少，体积增大，內嵴结构逐渐丰富；精子由头部、中部和尾部组成，鞭毛轴丝为典型“9+2”结构。本研究阐述了四指马鲅雄鱼精巢的组织结构及初次性成熟精巢发育及精子发生过程的组织学和超微结构变化，丰富了四指马鲅的繁殖生物学内容，为掌握四指马鲅的繁殖规律和提高人工繁育技术提供理论参考。     

二倍体和三倍体皱纹盘鲍精子发生过程的超微结构

比较了二倍体和三倍体皱纹盘鲍精子发生过程中细胞和细胞器的超微结构变化。结果表明，二倍体皱纹盘鲍的精子发生经历了精原细胞、初级精母细胞、次级精母细胞、精子细胞和精子5个阶段。其形态结构发生了一系列变化，主要包括：核染色质浓缩、线粒体的发达与融合、顶体形成和胞质的减少。三倍体皱纹盘鲍各种生精细胞的直径和核径均大于二倍体，精原细胞结构与二倍体相似；初级、次级精母细胞的胞质中，除溶酶体外，线粒体、内质网等细胞器少于二倍体，线粒体大小与二倍体没有差别，但形态不典型，层状嵴不发达；三倍体皱纹盘鲍的精子发生停滞在精子细胞阶段，表现出各种畸形状态，很多趋于解体，没有发现成熟精子。     

双须骨舌鱼性腺发育的组织学观察

通过组织学研究方法,分别对双须骨舌鱼Ⅱ~Ⅴ期的卵巢及Ⅱ~Ⅵ期精巢的形态结构、特征及生殖细胞变化进行描述。结果显示,Ⅱ时相卵母细胞的细胞核较大,约为细胞体积的一半;Ⅲ时相卵母细胞出现卵黄斑及卵黄颗粒;Ⅳ时相卵母细胞中卵黄迅速积累且细胞膜出现褶皱;Ⅴ时相卵母细胞膜表面的褶皱消失。雄性双须骨舌鱼精巢发育的Ⅱ期,只含有初级精母细胞。Ⅲ期精巢分布有初级和次级精母细胞,精小管形成且小管中充满精细胞;Ⅳ期精巢主要含有初级和次级精母细胞以及精原细胞,精小管中出现空腔;Ⅴ期精巢中包含次级精母细胞、精原细胞和精子细胞,精小管中的空腔增大;Ⅵ期精巢则显示出高度血管化和结缔组织增多等特点。本研究将为双须骨舌鱼人工繁殖提供参考。     

西埔湾黄鳍鲷精子发生和形成

本文在超微结构水平上,着重研究了西埔湾黄鳍鲷精子发生和形成过程中各级精细胞形态结构的变化、线粒体和高尔基体等细胞器的演变特点以及精巢内一些体细胞的形态结构与功能。研究结果证实了黄鳍鲷雄性性腺能在半封闭的西埔湾内发育成熟。精子发生和形成可分为原始精原细胞、精原细胞、初级精母细胞、次级精母细胞、精子细胞和精子形成等6个发育阶段。成熟精子由头部、中段和尾部组成,头部近圆形,细胞核呈马蹄形,核内染色质高度浓缩,核上方不具顶体。尾部轴丝为“9×2+2”结构。     

塑膜大棚内中华鳖发育过程血清性激素与性腺发育的研究

以塑膜大棚内养殖的不同龄的中华鳖为试验材料,观察其性腺形态学和组织学的变化,并用酶联免疫吸附法测定血清中睾酮和雌二醇的含量。研究发现,塑膜大棚内中华鳖不仅生长速度加快,而且性腺发育也提前。大棚内养殖的中华鳖的性腺质量和性腺指数明显大于露天池塘养殖的同等鳖龄的中华鳖的性腺质量和性腺指数。半年龄鳖精巢的曲细精管中填塞精原细胞;1龄鳖的精巢,曲细精管中精原细胞2～3层,分布较散;2龄鳖的精巢,生精上皮层数很多,包括精原细胞、初级与次级精母细胞、精子细胞,并且已见圆形精子细胞和拉长的精子出现在管腔中;3龄鳖的精巢,管腔明显增大,生精上皮比2龄鳖的生精上皮层数少,可见靠近基膜的极少量精原细胞、初级与次级精母细胞,变态后的精子细胞的数量最多。半年龄鳖的卵巢内卵泡已经发育至初级卵泡期,1龄鳖的卵泡处于生长卵泡期,2龄鳖的卵巢处于卵黄发生期,3龄鳖处于排卵期。雄性鳖的睾酮的峰值出现于2龄鳖,即生精活动的旺盛期;雌性鳖的睾酮峰值出现于1龄时,即卵泡的生长期;而2龄、3龄的雌鳖的睾酮含量明显降低,即在卵黄形成期和排卵期,睾酮含量是降低的。雌性鳖的雌二醇,在3龄时即卵黄的沉积期和成熟卵的形成期达到最高值。雄性鳖的雌二醇,在2龄时出现最高值,此时生精活动最为旺盛。     

广东鲂性腺发育组织学研究

利用组织学方法,对珠江下游野生广东鲂(Megalobrama terminalis)性腺进行了显微观察和研究,描述了其卵巢、精巢的结构特征以及各类型生殖细胞形态。结果显示,广东鲂属于一次性产卵类型,卵巢发育类型为部分同步型。其卵巢为细线或条状,卵巢发育经历卵原细胞期、单层滤泡细胞期、卵黄泡期、卵黄充满期、成熟期和退化期。卵细胞发生经历3个阶段:卵原细胞、初级卵母细胞和次级卵母细胞;卵巢初级卵母细胞中核仁外排现象出现在第2时相末期至第3时相早期;精巢呈线状或直棒状,精巢为叶状型结构。精细胞发生经历5个阶段:精原细胞、初级精母细胞、次级精母细胞、精子细胞及精子;繁殖季节精子充满于精小叶内,精小囊消失。     

Immunohistochemical localization of rainbow trout androgen receptors in the testis

SUMMARY: We examined the distribution of two rainbow trout androgen receptors (rtAR: rtAR-α and rtAR-β) in the testis immunohistochemically using a specific antibody to clarify the target cells of androgen in spermatogenesis. Positive rtAR immunoreactivity in paraffin-embedded sections was revealed using microwave treatment, and was detected in the nuclei of Sertoli cells, Leydig cells, and other interstitial cells. The presence of rtAR in Leydig cells suggested that fish androgens regulate Leydig cell activity in an autocrine fashion similar to mammalian androgens. In addition, we found that not all Leydig cells exhibited rtAR immunoreactivity in the mature testis by double staining using anti-3β-hydroxysteroid dehydrogenase (3β-HSD) antibody. Furthermore, rtAR immunoreactivity was also detected in the nuclei of spermatogonia, spermatocytes, and spermatids. The intensity of rtAR immunoreactivity in the nuclei of spermatogonia seemed to be weaker than those of spermatocytes and spermatids. These results suggested that androgens act directly on both germ cells and somatic cells in the regulation of spermatogenesis in the rainbow trout.     

Cell-cell interactions in the testis of the dogfish: stage-related changes in protein synthesis

Previous studies have shown that the testis of Selachians is a very suited model to study stage-dependent changes in Sertoli cells during spermatogenesis (Dubois and Callard 1989; Sourdaine et al. 1990). In the dogfish testis (here: Scyliorhinus canicula), germ cells, at an identical stage of spermatogenesis, are associated with Sertoli cells to form spermatocysts, which are arranged in zones corresponding to the different stages of spermatogenesis. Using previously described methods for the isolation and culture of spermatocysts from four spermatogenic stages (spermatogonia, spermatocytes, early spermatids and late spermatids; Sourdaine and Jégou 1989; Sourdaine and Garnier 1992) and electrophoresis techniques (1D and 2D-SDS-PAGE) we have investigated the [³⁵S] methionine incorporation into proteins in the dogfish testis. Our results indicate that protein synthesis reaches a maximum in spermatocysts with spermatocytes. Marked stage-related changes of protein synthesis and secretion were also observed on the autoradiograms of 1D and 2D-SDS-PAGE. Further investigations of the paracrine control of germ cells on Sertoli cell protein synthesis requires the identification of specific Sertoli cell proteins in the dogfish.     

外源性促性腺激素诱导日本鳗鲡卵子发生和卵巢发育成熟的机制

用兔抗促黄体素生成素受体(LHR)或称绒毛膜促性腺激素受体(CGR)、雌激素受体(ER)和孕激素受体(PR)的抗体对LHR,ER和PR进行免疫组织化学定位。目的在于揭示外源性促性腺激素(鲤鱼脑垂体提取物,CPE和人绒毛膜促性腺激素,hCG)诱发日本鳗鲡卵子发生和卵母细胞成熟的内分泌机制。结果表明,注射激素前后卵巢发育和卵子发生出现了十分显著的变化。卵巢组织学切片观察显示激素处理前鳗鲡卵巢发育处于卵黄发生早期,卵母细胞平均直径(220±0.01)μm。第一次注射这两种激素后10d,实验组卵母细胞中卵黄核分散在核的周围,核仁数量显著增加,多达18～20个左右,而对照组8～10个。第3和4次激素处理后,卵母细胞发育进入卵黄发生早-中期至中期,卵黄颗粒数量增加。第6和7次激素处理后,卵母细胞进入卵黄发生中后期到成熟期,卵母细胞胞质中充满卵黄颗粒,胞径和核径增加,分别为(570±1.39)μm和(128±1.19)μm,而对照组没有变化。其次,免疫组织化学染色结果显示LHR、ER和PR均定位在鳗鲡卵巢中卵母细胞胞质、核膜、核质、卵被膜和体细胞上。这里值得指出的是,从第3次和第4次激素处理后,这三种受体的定位各有特点,L...     

Spermatogenesis and its endocrine regulation

Three major phases compose spermatogenesis: mitotic proliferation of spermatogonia, meiosis of spermatocytes, and spermiogenesis, the restructuring of spermatids into flagellated spermatozoa. The process is fuelled by stem cells that, when dividing, either self-renew or produce spermatogonia that are committed to proliferation, meiosis, and spermiogenesis. During all phases, germ cells are in close contact with and require the structural and functional support of Sertoli cells. In contrast to germ cells, these somatic cells express receptors for sex steroids and follicle-stimulating hormone (FSH), the most important hormones that regulate spermatogenesis. A typical Sertoli cell response to an endocrine stimulus would be to change the release of a growth factor that would then mediate the hormone's effect to the germ cells. Recent studies in the Japanese eel have shown, for example, that in the absence of gonadotropin Sertoli cells produce a growth factor (an orthologue of anti-Müllerian hormone) that restricts stem cell divisions to the self-renewal pathway; also estrogens stimulate stem cell renewal divisions but not spermatogonial proliferation. Gonadotropin or 11-ketotestosterone (11-KT) stimulation, however, induces spermatogonial proliferation, which is in part mimicked by another Sertoli cell-derived growth factor (activin B). Since FSH (besides luteinizing hormone, LH) stimulates steroidogenesis in fish, and since FSH is the only gonadotropin detected in the plasma of sexually immature salmonids, increased FSH signalling may be sufficient to initiate spermatogenesis by activating both Sertoli cell functions and 11-KT production. Another important androgen is testosterone (T), which seems to act via feedback mechanisms that can compromise FSH-dependent signalling or steroidogenesis. The testicular production of T and 11-KT therefore needs to be balanced adequately. Further research is required to elucidate in what way(s) 11-KT stimulates later stages of development, such as entry into meiosis and spermiogenesis. At this period, LH becomes increasingly important for the regulation of androgen production. Results from mammalian models suggest that during the later phases, the control of germ cell apoptosis via Sertoli cell factors is an important regulatory mechanism. In many species, sperm cells cannot fertilize eggs until having passed a maturation process known as capacitation, which includes the acquisition of motility. Progestins that are produced under the influence of LH appear to play an important role in this context, which involves the control of the composition of the seminal plasma (e.g., pH values). This revised version was published online in July 2006 with corrections to the Cover Date.     

Androgen secretion activity of recombinant follicle-stimulating hormone of Japanese eel, Anguilla japonica in immature and maturing eel testes

The androgen secretion activities of recombinant Japanese eel follicle-stimulating hormone (rjeFSH) were investigated in immature and maturing eel testes. The rjeFSH stimulated testosterone (T) and 11-ketotestosterone (11-KT) secretion in immature testis but not in maturing testis. This result suggests that eel FSH plays an important role through the sex steroid secretion in immature testis rather than in maturing testis.     

Differentiation and development of Leydig cell, and induction of spermatogenesis during testicular differentiation in the Japanese eel, Anguilla japonica

The initial appearance and the development of Leydig cells (LCs), the sites of steroid hormone production in the testis, were investigated ultrastructurally during testicular differentiation in the Japanese eel, Anguilla japonica. In addition, the effects of a single injection of human chorionic gonadotropin (HCG; 5 IU g body weight^-1) on histological changes of the testes and serum 11-ketotestosterone (11-KT) were examined at various stages (15–18, 20–23, 26–29, 32–35, 38–41 and 46–50 cm body length (BL)) of testicular differentiation. Testicular differentiation was morphologically characterized by the development of loose connective tissue on the medial side in animals 18–29 cm in BL. Ultrastructurally, LCs were first identified in the loose connective tissue of the testis of the 23 cm fish. In the testes of fish over 32 cm, clusters of LCs were distributed throughout the interstitial region accompanying the increase in number of spermatogonia. In fish larger than 32 cm, spermatogenesis was induced by administration of HCG; serum 11-KT levels were also raised. On the other hand, there was no effect on spermatogenesis or serum 11-KT levels in fish less than 29 cm, or in the controls. These result suggests that morphological differentiation of LCs occurs in testis of the 23 cm eel, and subsequently, the testes of eels of BL more than 32 cm acquire the capability to produce steroid hormones.     

金钱鱼促性腺激素受体基因克隆及其在性腺发育不同时期mRNA表达水平的分析

为了解金钱鱼促性腺激素受体基因(GtHRs)在金钱鱼性腺发育中的作用,采用反转录PCR(Rt-PCR)与cDNA末端快速克隆(RACE)首次克隆了金钱鱼卵泡刺激素受体(FSHR)和促黄体生成素受体(LHR)的cDNA序列全长。FSHR的cDNA全长2538 bp,编码702个氨基酸,LHR的cDNA全长3315 bp,编码722个氨基酸,它们都含有属于糖蛋白激素受体(GHR)家族的典型跨膜螺旋结构区域(TM helix)。同源性分析显示金钱鱼GtHRs与欧洲鲈的相似性最高,且GtHRs在进化中具有一定的保守性。性腺不同时期表达分析表明,在卵巢Ⅰ期时,FSHR高水平表达,Ⅱ、Ⅲ、Ⅳ期时在较低水平表达。在精巢中,FSHR的表达水平在Ⅰ、Ⅱ、Ⅲ期逐渐升高并在Ⅲ期达到最高,Ⅳ期开始下降。LHR在金钱鱼卵巢和精巢的Ⅰ、Ⅱ、Ⅲ期低水平表达,在Ⅳ期表达水平达到最高。研究表明,FSHR在金钱鱼性腺发育早期扮演重要作用,LHR与卵子和精子的成熟有关。     

Gonadotropins, gonadotropin receptors and their expressions during sexual maturation in yellowtail, a carangid fish

To study the physiological roles of gonadotropins (GtHs) in the yellowtail, the cDNAs encoding each GtH subunit (GPHα, FSHβ and LHβ) and their receptors (FSHR and LHR) were isolated from the pituitary gland and gonads using the polymerase chain reaction (PCR). In addition, thyrotropin (TSH) and its receptor (TSHR) cDNAs, were isolated from the pituitary gland, ovary and testis. The changes in the mRNA levels of each subunit were determined at different stages of maturation. The isolated cDNAs of GPHα, FSHβ, LHβ and TSHβ were 662, 545, 595 and 879 bp long, respectively. The amino acid sequence identity of the yellowtail GPHα, FSHβ, LHβ and TSHβ subunits was 85–63, 68–33, 93–65 and 74–46%, respectively, as compared with other fish species. Northern blot analysis showed that GPHα and FSHβ were strongly expressed in pituitary at the early vitellogenic stage and during spermatogenesis, whereas LHβ was expressed significantly in the late vitellogenic stage, and in both spermatogenesis and spermiation. Full-length cDNAs encoding FSHR, LHR, and TSHR were obtained from the testes and ovaries. The FSHR, LHR and TSHR cDNA encoded a protein of 680, 702 and 778 amino acids, and showed the highest identity with tilapia FSHR (76%), tilapia LHR (84%) and striped bass TSHR (94%), respectively. Northern blot analyses indicated that all of these receptors are expressed differently at different stages in the ovaries and testes.     

Spermatogenesis in teleost: insights from the Nile tilapia (Oreochromis niloticus) model

The morphometric study of spermatogenic cysts in sexually mature tilapias, during the evolution of spermatogenesis, showed a dramatic increase in both number of germ cells and cyst volume. However, the opposite trend was observed for germ cell size. Nevertheless, the number of Sertoli cells increased gradually up to leptotene/zygotene cysts, stabilizing thereafter. Based on the number of spermatids supported by each Sertoli cell and compared to mammals, Sertoli cell efficiency in tilapias is remarkably high. Sertoli cell proliferation was frequently observed, mainly in spermatogonial cysts, and probably is the major factor related to the testis growth and the increase in sperm production that normally occurs in adult tilapias. The combined duration of spermatocytes (5 days) and spermiogenic (5–6 days) phases of spermatogenesis in fish kept at 25 °C was 10–11 days. Mainly due to acceleration in meiosis, these two phases lasted a total of 6 days in tilapias kept at 30 °C, in the opposite way, at 20 °C spermatogenesis was arrested at pachytene spermatocytes. To our knowledge, this is the most comprehensive investigation performed up to date on testis morphometry and function in adult tilapias.