Abstract
Thin sections of the testicular follicles of the grasshopper Laplatacris dispar were studied under the electron microscope. In the primary spermatocytes, during meiotic prophase, three main regions can be recognized within the nucleus: (1) the nucleolus and associated nucleolar material; (2) the interchromosomal regions with the dense particles; and (3) the chromosomes. The nucleolus is generally compact and is surrounded by nucleolar bodies that comprise aggregations of dense round particles 100 to 250 A in diameter. A continuous transition can be observed between these particles and those found isolated or in short chains in the interchromosomal spaces. Particles of similar size (mean diameter of 160 A) can be found associated with the nuclear membrane and in the cytoplasm. The chromosomes show different degrees of condensation in different stages of meiotic prophase. The bulk of the chromosome appears to be made of very fine and irregularly coiled filaments of macromolecular dimensions. Their length cannot be determined because of the thinness of the section but some of them can be followed without interruption for about 1000 to 2000 A. The thickness of the chromosome filaments seems to vary with different stages of prophase and in metaphase. In early prophase, filaments vary between 28 ± 7 A and 84 ± 7 A with a mean of 47 A, in late prophase the mean is about 70 A. In metaphase the filaments vary between 60 and 170 A with a mean of about 100 A. Neither the prophase nor the metaphase chromosomes have a membrane or other inhomogeneities. The finding of a macromolecular filamentous component of chromosomes is discussed in relation to the physicochemical literature on nucleoproteins and nucleic acids and as a result it is suggested that the thinnest chromosome filaments (28 ± 7 A) probably represent single deoxyribonucleoprotein molecules.
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- BAHR G. F. Continued studies about the fixation with osmium tetroxide. Exp Cell Res. 1955 Oct;9(2):277–285. doi: 10.1016/0014-4827(55)90100-2. [DOI] [PubMed] [Google Scholar]
- BERNSTEIN M. H., MAZIA D. The desoxyribonucleoprotein of sea urchin sperm. I. Isolation and analysis. Biochim Biophys Acta. 1953 Apr;10(4):600–606. doi: 10.1016/0006-3002(53)90303-5. [DOI] [PubMed] [Google Scholar]
- FAWCETT D. W. The fine structure of chromosomes in the meiotic prophase of vertebrate spermatocytes. J Biophys Biochem Cytol. 1956 Jul 25;2(4):403–406. doi: 10.1083/jcb.2.4.403. [DOI] [PMC free article] [PubMed] [Google Scholar]
- FEUGHELMAN M., LANGRIDGE R., SEEDS W. E., STOKES A. R., WILSON H. R., HOOPER C. W., WILKINS M. H., BARCLAY R. K., HAMILTON L. D. Molecular structure of deoxyribose nucleic acid and nucleoprotein. Nature. 1955 May 14;175(4463):834–838. [PubMed] [Google Scholar]
- KAHLER H., LLOYD B. J., Jr The electron microscopy of sodium desoxyribonucleate. Biochim Biophys Acta. 1953 Mar;10(3):355–359. doi: 10.1016/0006-3002(53)90265-0. [DOI] [PubMed] [Google Scholar]
- MOSES M. J. Chromosomal structures in crayfish spermatocytes. J Biophys Biochem Cytol. 1956 Mar 25;2(2):215–218. doi: 10.1083/jcb.2.2.215. [DOI] [PMC free article] [PubMed] [Google Scholar]
- MOSES M. J. Studies on nuclei using correlated cytochemical, light, and electron microscope techniques. J Biophys Biochem Cytol. 1956 Jul 25;2(4 Suppl):397–406. doi: 10.1083/jcb.2.4.397. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Mazia D. THE PARTICULATE ORGANIZATION OF THE CHROMOSOME. Proc Natl Acad Sci U S A. 1954 Jun;40(6):521–527. doi: 10.1073/pnas.40.6.521. [DOI] [PMC free article] [PubMed] [Google Scholar]
- PORTER K. R., BLUM J. A study in microtomy for electron microscopy. Anat Rec. 1953 Dec;117(4):685–710. doi: 10.1002/ar.1091170403. [DOI] [PubMed] [Google Scholar]
- PORTER K. R. Electron microscopy of basophilic components of cytoplasm. J Histochem Cytochem. 1954 Sep;2(5):346–375. doi: 10.1177/2.5.346. [DOI] [PubMed] [Google Scholar]
- WILLIAMS R. C. Electron microscopy of sodium desoxyribonucleate by use of a new freeze-drying method. Biochim Biophys Acta. 1952 Sep;9(3):237–239. doi: 10.1016/0006-3002(52)90157-1. [DOI] [PubMed] [Google Scholar]