Nucleolar structure and synthetic activity during meiotic prophase and spermiogenesis in the rat.
Nucleolar structure and synthetic activity during meiotic prophase and spermiogenesis in the rat.
复制标题
大鼠减数分裂前期和精子发生期间的核仁结构和合成活性。
DOI：
10.1002/aja.1001890102
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
C. P. Leblond
中科院分区：
文献类型：
--
作者：
Michael C. Schultz;C. P. Leblond
应用连续切片技术，对发育中的大鼠精母细胞和精子细胞核仁的超微结构进行了观察。此外，大鼠睾丸内注射3 H(5‘)-尿苷后1小时，核仁放射自显影反应以此作为核糖体RNA(RRNA)合成速度的指标。从前细线期到合子线期的初级精母细胞具有小的核仁，通常由纤维中心、纤维成分和颗粒成分组成，其中有狭窄的间隙。在粗线期的早期和中期，核仁扩大到初始大小的9倍左右，纤维和颗粒成分形成广泛的索状网络--核线体--其中有广泛的间质空间。同时，出现与颗粒成分相同但与核仁不同的结构，称为核外颗粒成分。最后，从粗线期晚期到第一次成熟分裂，核仁发生凝聚，表现为纤维中心收缩成小块，而纤维和颗粒成分相互凝聚和分离，间质逐渐减少。在次级精母细胞中，核仁致密而相当小，而在年轻的精子细胞中，核仁也致密甚至更小。在伸长的精子细胞中，核仁消失。在~3H-尿苷放射自显影中，核仁标记在年轻的初级精母细胞中很弱，在粗线期早期逐渐增加，中期粗线期结束时核仁标记较强，但在粗线期晚期至第一次成熟分裂时核仁标记逐渐减少。在次级精母细胞和精子细胞中，没有明显的核仁标记。总之，在年轻的精母细胞中，核仁合成rRNA的水平很低。粗线期，随着核仁的增大形成花边状核仁，rRNA合成逐渐增加，到粗线期中期达到较高水平。然而，从粗线期开始，在核仁成分的凝聚和分离过程中，合成逐渐减少和消失。第二次成熟分裂产生的小而致密的精子细胞不合成rRNA。
The ultrastructure of nucleoli was examined in developing rat spermatocytes and spermatids, with the help of serial sections. In addition, the radioautographic reaction of nucleoli as examined in rats sacrificed 1 hr after intratesticular injection of 3H(5')-uridine and taken as an index of the rate of synthesis of ribosomal RNA (rRNA). Primary spermatocytes from preleptotene to zygotene have small nucleoli typically composed of fibrillar centers, a fibrillar component, and a granular component, within which are narrow interstitial spaces. During early and mid-pachytene, nucleoli enlarge to about nine times their initial size, with the fibrillar and granular components forming an extensive network of cords--a nucleolonema--within which are wide interstitial spaces. Meanwhile, there appear structures identical to the granular component but distinct from nucleoli; they are referred to as extranucleolar granular elements. Finally, from late pachytene to the first maturation division, nucleoli undergo condensation, as shown by contraction of fibrillar centers into small clumps, while fibrillar and granular components condense and segregate from each other, with a gradual decrease in interstitial spaces. In secondary spermatocytes, nucleoli are compact and rather small, while in young spermatids they are also compact and even smaller. Nucleoli disappear in elongating spermatids. In 3H-uridine radioautographs, nucleolar label is weak in young primary spermatocytes, increases progressively during early pachytene, is strong by the end of mid pachytene, but gradually decreases during late pachytene up to the first maturation division. In secondary spermatocytes and spermatids, there is no significant nucleolar label. In conclusion, rRNA synthesis by nucleoli is low in young spermatocytes. During pachytene, while nucleoli enlarge and form a lacy nucleolonema, rRNA synthesis increases gradually to a high level by the end of mid pachytene. However, during the condensation and segregation of nucleolar components occurring from late pachytene onward, the synthesis gradually decreases and disappears. The small, compact spermatids arising from the second maturation division do not synthesize rRNA.
影响因子：
3.6
作者：
MEISTRICH, ML;LONGTIN, J;MACE, ML
通讯作者：
MACE, ML