Bhattacharya S, Dey R, Basu A, Maitra S K, Banerji T K
Department of Zoology, University of Burdwan, Burdwan, India.
Endocr Res. 2003 May;29(2):141-56. doi: 10.1081/erc-120022295.
The structure of the pineal complex and the annual reproductive cycle in a major Indian carp, Catla catla, were investigated in the present study. Additionally, given the well-known inhibitory effects of the pineal on reproductive function in mammals, attempts were made to investigate whether or not the pineal exerts an inhibitory influence on reproductive function in this piscine species as well. Sexually adult animals were utilized in all experiments. The cytomorphology of the pineal complex and a number of parameters for testicular function--such as testicular cytology, serum testosterone levels, and testicular activities of two steroidogenic enzymes, 17beta-hydroxysteroid dehydrogenase (17beta-HSD) and delta5-3beta-hydroxysteroid dehydrogenase (delta5-3beta-HSD) were examined over a period of two years. Our studies showed that the pineal complex in this species consists of three separate but distinctly connected components: (a) an end vesicle (EV); (b) a long pineal stalk (PS); and (c) a dorsal sac (DS). Of these, the epithelial lining of the EV consists of cells that have rounded vesicular nuclei and long apical cytoplasmic processes that reach the lumen, features suggestive of photoreceptor cells. The cells of the PS have some similarity with those of the EV, while DS cells appear columnar and ciliated. With regard to gonadal activity, germ cell profiles revealed that this species has four distinct phases during the annual reproductive cycle: (a) preparatory (January-April); (b) pre-spawning (May-June); (c) spawning (July); and (d) post-spawning (August-December). During the spawning phase (July), seminiferous tubular diameter, percentage of late spermatids within seminiferous tubules, and serum testosterone levels showed the highest values compared to those obtained in most of the other phases of the reproductive cycle. Also in July, along with peak serum testosterone levels, the activities of 17beta-HSD and delta5-3beta-HSD were at their highest levels. In a correlation between the pineal cytology and testicular functional status, it was noted that both the nuclear diameter and the apical cytoplasmic projections of the EV photoreceptor cells showed a significant reduction, thus suggesting a reduced synthetic activity, during the month of July, the spawning phase of the reproductive cycle. In contrast, the same features of the EV cells during the other phases of the reproductive cycle showed an increased cellular and metabolic activity--a time when the gonads were less active and in a quiescent stage. These data suggest an inhibitory role of the pineal on gonadal function and thus provide additional credence to the concept that, as in higher mammals, there exists an inverse relationship between the pineal activity and gonadal function in teleost fishes as well.
在本研究中，对印度主要鲤科鱼类印度鲃的松果体复合体结构和年度繁殖周期进行了调查。此外，鉴于松果体对哺乳动物生殖功能具有众所周知的抑制作用，本研究还试图探究松果体对该鱼类的生殖功能是否也有抑制影响。所有实验均使用性成熟的动物。在两年时间里，对松果体复合体的细胞形态以及睾丸功能的一些参数进行了检查，这些参数包括睾丸细胞学、血清睾酮水平以及两种类固醇生成酶（17β-羟基类固醇脱氢酶（17β-HSD）和δ5-3β-羟基类固醇脱氢酶（δ5-3β-HSD））的睾丸活性。我们的研究表明，该物种的松果体复合体由三个独立但明显相连的部分组成：（a）终囊（EV）；（b）长的松果体柄（PS）；（c）背囊（DS）。其中，终囊的上皮衬里由具有圆形泡状核和长的顶端细胞质突起（伸向管腔）的细胞组成，这些特征表明它们是光感受器细胞。松果体柄的细胞与终囊的细胞有一些相似之处，而背囊细胞呈柱状且有纤毛。关于性腺活动，生殖细胞图谱显示该物种在年度繁殖周期中有四个不同阶段：（a）准备期（1月至4月）；（b）产卵前期（5月至6月）；（c）产卵期（7月）；（d）产卵后期（8月至12月）。在产卵期（7月），与繁殖周期的大多数其他阶段相比，生精小管直径、生精小管内晚期精子细胞的百分比以及血清睾酮水平均显示出最高值。同样在7月，随着血清睾酮水平达到峰值，17β-HSD和δ5-3β-HSD的活性也处于最高水平。在松果体细胞学与睾丸功能状态的相关性研究中发现，在繁殖周期的产卵期7月，终囊光感受器细胞的核直径和顶端细胞质突起均显著减小，这表明合成活性降低。相比之下，在繁殖周期的其他阶段，终囊细胞的这些特征显示细胞和代谢活性增加，而此时性腺活性较低且处于静止阶段。这些数据表明松果体对性腺功能具有抑制作用，从而进一步支持了这样一种观点，即与高等哺乳动物一样，硬骨鱼类的松果体活性与性腺功能之间也存在负相关关系。
