Nucleolar structure and synthetic activity during meiotic prophase and spermiogenesis in the rat

Journal Article · Sat Sep 01 00:00:00 EDT 1990 · American Journal of Anatomy; (USA)

DOI:https://doi.org/10.1002/aja.1001890102· OSTI ID:6171126

Schultz, M C; Leblond, C P ^[1]

---

1. McGill Univ., Montreal, Quebec (Canada)

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.

• OSTI ID: 6171126
• Journal Information: American Journal of Anatomy; (USA), Journal Name: American Journal of Anatomy; (USA) Journal Issue: 1 Vol. 189:1; ISSN AJANA; ISSN 0002-9106
• Country of Publication: United States
• Language: English

Related Subjects

550301* -- Cytology-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
AUTORADIOGRAPHY
AZINES
BIOSYNTHESIS
CELL CONSTITUENTS
CELL DIVISION
CELL NUCLEI
ELECTRON MICROSCOPY
GAMETOGENESIS
GERM CELLS
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
MAMMALS
MICROSCOPY
MITOSIS
MOLECULAR STRUCTURE
NUCLEIC ACIDS
NUCLEOSIDES
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PYRIMIDINES
RATS
RIBOSIDES
RIBOSOMAL RNA
RNA
RODENTS
SPERMATOCYTES
SPERMATOGENESIS
SYNTHESIS
TRITIUM COMPOUNDS
URACILS
URIDINE
VERTEBRATES