scholarly journals Differential Uptake of Tritiated Thymidine into Hetero- and Euchromatin in Melanoplus and Secale

1959 ◽  
Vol 6 (3) ◽  
pp. 457-466 ◽  
Author(s):  
A. Lima-de-Faria
Keyword(s):  
Sex Chromosome ◽  
Unit Area ◽  
Tritiated Thymidine ◽  
Early Prophase ◽  
Chromosome Counts ◽  
Heterochromatic Block ◽  
Melanoplus Differentialis ◽  
Photometric Measurements ◽  
Silver Grains ◽  
Prophase Of Meiosis

Grasshoppers of the species Melanoplus differentialis were injected with tritium-labelled thymidine. At intervals thereafter autoradiographic stripping film was applied over Feulgen squashes and sections. In this species during early prophase of meiosis the sex chromosome forms a heterochromatic block large enough to be resolved in tritium autoradiographs. A study of the squash preparations reveals that the sex chromosome is synthesizing DNA at a different period of time from the euchromatic autosomes. Since there is a developmental sequence of spermatocyte cysts along the testicular tubes it is possible from the sections to show that the heterochromatin synthesizes DNA later than does the euchromatin. To find out whether the results obtained in Melanoplus were characteristic of heterochromatin in general, young seedlings of rye were grown in a tritiated thymidine solution and Feulgen squashes were made as for Melanoplus. In rye leaf nuclei there is a large block of heterochromatin constituted by the proximal regions of the chromosomes and a euchromatic one formed by the median and distal regions of the same chromosomes. Here also the heterochromatin synthesizes DNA at a different period of time from the euchromatin. It is concluded that in rye the asynchrony of synthesis occurs within each chromosome. Counts of silver grains over the two types of chromatin in nuclei of Melanoplus and Secale disclosed that the number of grains per unit area was two to three times higher over the heterochromatin. To check the DNA content, Feulgen photometric measurements were made of Melanoplus nuclei at the same stage. The Feulgen and grain counts agree in showing that the heterochromatin contains two to three times more DNA per unit area than the euchromatin.

scholarly journals XXY Mice

1961 ◽  
Vol 2 (1) ◽  
pp. 156-158 ◽  
Author(s):  
Bruce M. Cattanach
Keyword(s):  
Y Chromosome ◽  
X Chromosome ◽  
Sex Chromosome ◽  
Mouse Testis ◽  
Chromosome Counts ◽  
Cleavage Division ◽  
Chromosomal Constitution ◽  
Sister Chromatids

Welshons & Russell (1959) have presented data to show that the XO chromosomal constitution in the mouse is female. This conclusion was based on results of genetical tests with sex-linked markers and on chromosome counts. All XO females were matroclinous, that is, they had inherited their X-chromosome from their mother. Females of this type will arise when non-disjunction occurs in the meiotic divisions of the father and results in spermatozoa without a sex-chromosome. Alternatively, the paternal sex-chromosome may be lost from the fertilized ovum if non-disjunction of sister-chromatids occurs during the first cleavage division. This latter explanation has been urged by Ohno, Kaplan & Kinosita (1959), who found no evidence for non-disjunction of the X-and Y-chromosome in an extensive cytolosical examination of the mouse testis.

scholarly journals DISTRIBUTION OF LEUCINE-3H DURING AXOPLASMIC TRANSPORT WITHIN REGENERATING NEURONS AS DETERMINED BY ELECTRON-MICROSCOPE RADIOAUTOGRAPHY

1972 ◽  
Vol 52 (3) ◽  
pp. 719-732 ◽  
Author(s):  
Thomas L. Lentz
Keyword(s):  
Electron Microscope ◽  
Short Distance ◽  
Unit Area ◽  
Trophic Factors ◽  
Nerve Terminals ◽  
Sensory Ganglia ◽  
Successive Addition ◽  
Myelinated Nerves ◽  
Almost All ◽  
Silver Grains

The distribution of leucine-3H in neurons was determined by electron-microscope radioautography after infusion of label into the spinal cord or sensory ganglia of regenerating newts. In the nerve cell bodies 3 days after infusion, the highest concentration of label per unit area occurred over the rough-surfaced endoplasmic reticulum. In the large brachial nerves, the silver grains were not distributed uniformly in the axoplasm, indicating that the labeled materials are restricted in their movement to certain regions of the axon. Almost all of the radioautographic grains observed in myelinated nerves could be accounted for by the presence of a uniformly labeled band occupying the area 1500–9000 A inside the axolemma. This region of the axon was rich in microtubules and organelles while the unlabeled central core of the axon contained mainly neurofilaments. This observation supports the hypothesis that microtubules are related to axonal transport. In small, vesicle-filled nerve terminals in the blastema, labeled material was restricted to a thin zone a short distance beneath the plasma membrane while the central region of the terminal was largely unlabeled. The peripheral pattern of labeling in the nerve endings is consistent with successive addition of newly synthesized proteins at the periphery of the growth cone and release of substances such as trophic factors at the nerve terminal.

Quantitative high resolution light and EM autoradiography of fluorophosphate-esterase in developing mouse liver

1978 ◽  
Vol 36 (2) ◽  
pp. 66-67
Author(s):  
C. Budd
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Mouse Liver ◽  
Unit Area ◽  
Irreversible Inhibitor ◽  
Adult Mice ◽  
Quantitative Measurements ◽  
Em Autoradiography ◽  
Old Mice ◽  
Silver Grains

The distribution and concentration of fluorophosphate reactive (FPR) esterases in the liver of developing and adult mice was determined quantitatively from light and electron microscope autoradiograms of liver reacted with 3H - diisopropylfluorophosphate (3H-DFP) an irreversible inhibitor of carboxylesterases.The majority of labeled cells in the liver of 2, 8, 14 and 28- day-old mice and in adult mice (60-180 days old) were hepatocytes, but in the liver from 2-day-old mice and to a lesser extent 8-day-old mice, the autoradiographic silver grains were also concentrated over granulocytes of the intrahepatic hemopoietic population.Quantitative measurements of grain density (developed silver grains/unit area) in light microscope autoradiograms revealed an increase in the predominantly cytoplasmic concentration of FPR esterase sites in hepatocytes from 137o of the adult concentration in 2-day-old mice, to 497, and 78% of the adult concentration in 8- and 14-day-old animals, respectively.

The Cytoplasmic Incorporation of Tritiated Thymidine During Oogenesis in Pteridium Aquilinum

1971 ◽  
Vol 8 (2) ◽  
pp. 467-487
Author(s):  
D. C. SIGEE ◽  
P. R. BELL
Keyword(s):  
Electron Microscope ◽  
Tritiated Thymidine ◽  
Pteridium Aquilinum ◽  
Egg Cell ◽  
Cell Periphery ◽  
Short Term ◽  
Electron Microscope Autoradiography ◽  
Microscope Autoradiography ◽  
Silver Grains ◽  
Stable Molecule

The short-term incorporation of tritiated thymidine into the cytoplasm of cells undergoing oogenesis was investigated in Pteridium aquilinum using electron-microscope autoradiography. There was substantial uptake into the central cell and egg cell during the 6-h labelling period. The quantity and distribution of the label incorporated into the cytoplasm were closely similar in cells fixed immediately after the labelling period and in those immersed for a further 18 h in unlabelled thymidine. This suggested that incorporation was into a stable molecule, with little nucleoside turnover and no subsequent migration within the cytoplasm. Enzyme studies indicated that the tritiated thymidine was incorporated almost entirely into DNA, most probably the DNA undergoing replication. Within the cytoplasm the label was markedly and consistently concentrated in plastids and mitochondria. This localization was not, however, complete and 5-40% was attributable to sites in the ground cytoplasm. A gradient of incorporated label was demonstrated within the cytoplasm in both central cells and egg cells. Concentration was high adjacent to the nucleus and low at the cell periphery. This gradient could be satisfactorily explained by the distribution of the plastids and mitochondria within the cytoplasm, the labelling of the organelles being irrespective of their position. The results of statistical examination of the frequencies of the silver grains associated with the mitochondria and plastids were considered to indicate general uptake of label directly into the DNA of these organelles without nuclear participation.

scholarly journals DNA SYNTHESIS IN THE OOPLASM OF DROSOPHILA MELANOGASTER

1966 ◽  
Vol 28 (2) ◽  
pp. 199-208 ◽  
Author(s):  
F. A. Muckenthaler ◽  
A. P. Mahowald
Keyword(s):  
Drosophila Melanogaster ◽  
Tritiated Thymidine ◽  
Follicle Cells ◽  
Nurse Cells ◽  
Cell Nuclei ◽  
Electron Microscopic ◽  
Tissue Sections ◽  
Electron Microscopes ◽  
High Level ◽  
Silver Grains

Tritiated thymidine was injected into 2-day-old Drosophila melanogaster females, and tissue sections were prepared from the ovary for radioautography with both the light and electron microscopes. Besides the expected incorporation of H3-thymidine into nuclei of nurse cells and follicle cells, there was a relatively high level of incorporation of label into ooplasmic DNA. The highest level of incorporation occurred at stage 12. At the same time, the 15 nurse cell nuclei also incorporate thymidine in spite of the fact that they are breaking down and degenerating. The label in the ooplasm is not removed by extraction with DNase (although this removes nuclear label) unless extraction is preceded by a treatment with protease. Electron microscopic radioautography revealed that 36% of the silver grains resulting from decay of H3-thymidine are found over mitochondria, with a further 28% being located within 0.25 µ of these organelles. The remaining 36% of the silver grains was not found to be associated with any organelles, and it probably represents synthesis in the cytoplasm by the "storage DNA" characteristic of many eggs. It is suggested that one mechanism acting throughout the egg chamber is responsible for the synchronous synthesis of DNA in the degenerating nurse cells, in the mitochondria of the egg, and in the "storage DNA" of the ooplasm.

scholarly journals Sex chromosome pairing mediated by euchromatic homology in Drosophila male meiosis

2019 ◽  
Author(s):  
Christopher A. Hylton ◽  
Katie Hansen ◽  
Andrew Bourgeois ◽  
John E. Tomkiel
Keyword(s):  
Sex Chromosomes ◽  
Sex Chromosome ◽  
Intergenic Spacer ◽  
Male Meiosis ◽  
Early Prophase ◽  
Dna Breaks ◽  
Late Prophase ◽  
Prophase I ◽  
Y Chromosomes ◽  
Meiosis I

ABSTRACTTo maintain proper ploidy, haploid sex cells must undergo two subsequent meiotic divisions. During meiosis I, homologs pair and remain conjoined until segregation at anaphase. Drosophila melanogaster spermatocytes are unique in that the canonical events of meiosis I including synaptonemal complex (SC) formation, double-strand DNA breaks, and chiasmata are absent. Sex chromosomes pair at intergenic spacer sequences within the heterochromatic rDNA while euchromatin is required to pair and segregate autosomal homologies, suggesting that pairing may be limited to specific sequences. However, previous work generated from genetic segregation assays or observations of late prophase I/prometaphase I chromosome associations fail to differentiate pairing from conjunction. Here, we separately examined the capability of X euchromatin to pair and conjoin using an rDNA-deficient X and a series of Dp(1;Y) chromosomes. Genetic assays showed that duplicated X euchromatin can substitute for endogenous rDNA pairing sites. Segregation was not proportional to homology length, and pairing could be mapped to nonoverlapping sequences within a single Dp(1;Y). Using fluorescent in situ hybridization (FISH) to early prophase I spermatocytes, we showed that pairing occurred with high fidelity at all homologies tested. Pairing was unaffected by the presence of X rDNA, nor could it be explained by rDNA magnification. By comparing genetic and cytological data, we determined that centromere proximal pairings were best at segregation. Segregation was dependent on the conjunction protein Stromalin in Meiosis while the autosomal-specific Teflon was dispensable. Overall, our results suggest that pairing may occur at all homologies, but there may be sequence or positional requirements for conjunction.ARTICLE SUMMARYDrosophila males have evolved a unique system of chromosome segregation in meiosis that lacks recombination. Chromosomes pair at selected sequences suggesting that early steps of meiosis may also differ in this organism. Using Y chromosomes carrying portions of X material, we show that pairing between sex chromosomes can be mediated by sequences other than the previously identified rDNA pairing sites. We propose that pairing may simply be homology-based and may not differ from canonical meiosis observed in females. The main difference in males may be that conjunctive mechanisms that join homologs in the absence of crossovers.

scholarly journals Sex Chromosome Mosaicism in Liver, Thymus, Spleen and Regenerating Liver of Perameles Nasuta and Isoodon Macrourus

1979 ◽  
Vol 32 (6) ◽  
pp. 615
Author(s):  
RL Close
Keyword(s):  
Developmental Stages ◽  
Sex Chromosome ◽  
Early Stage ◽  
Chromosome Complement ◽  
Regenerating Liver ◽  
Chromosome Counts ◽  
Histological Studies ◽  
Haematopoietic Cells ◽  
Somatic Tissues ◽  
Dividing Cells

An X chromosome disappears from female cells and the Y chromosome disappears from male cells during development in some somatic tissues of the bandicoots P. nasuta and l. macrourus leaving the cells with a 2n = 13 (Le. XO) chromosome complement. In order to determine time of disappearance of the relevant sex chromosome, counts were made from dividing cells in liver, thymus and spleen of both species at various stages of development. Histological studies of liver and thymus were made at the same developmental stages. Frequencies of 2n = 14 cells (Le. those containing both sex chromosomes) were high in the liver and thymus of animals 1-4 days old but were low at 15 days of age when haematopoietic cells predominated. While most cells of thymus and spleen remained 2n = 13, the frequency of 2n = 14 cells rose again in the liver of animals aged over 20 days at which time blood-forming activity was considerably diminished. It is suggested that blood-forming cells of both species of bandicoot discard a sex chromosome at an early stage of differentiation.

Extra-Chromosomal DNA in Early Stages of Oogenesis in Acheta Domesticus

1969 ◽  
Vol 4 (3) ◽  
pp. 593-609
Author(s):  
M. D. CAVE ◽  
E. R. ALLEN
Keyword(s):  
Acheta Domesticus ◽  
The Body ◽  
Early Prophase ◽  
Chromosomal Dna ◽  
Late Pachytene ◽  
Diplotene Stage ◽  
Stage Of Development ◽  
Interphase Cells ◽  
Chromatin Material ◽  
Prophase Of Meiosis

A large extra-chromosomal DNA body is found in gonial and oocyte nuclei of Acheta domesticus. Somatic cells within the ovary do not contain the DNA body which is limited to the nuclei of gametogenic cells. During early prophase of meiosis this body is spherically shaped and intensely Feulgen positive. Electron microscopy shows it to be composed of tightly packed fibrogranular material. The body is formed in the nuclei of premeiotic interphase cells where it first appears and a mass of dense chromatin material located within the nucleolus. In nuclei of early prophase cells the body is closely associated with the nuclear membrane. It increases in size, reaching a maximum in mid-pachytene nuclei. During late pachytene-early diplotene stage of meiosis the tight fibrillar material within the body loosens and takes on a less compact appearance. At the same time large fascicles of RNA-containing material accumulate within and around the DNA body. The amount of RNA material surrounding the body increases as the oocytes proceed into an arrested diplotene stage of development.

The gametogenesis of the digenetic trematode Sphaerostoma bramae (Müller) Lühe

Parasitology ◽  
1958 ◽  
Vol 48 (3-4) ◽  
pp. 293-302 ◽  
Author(s):  
R. A. R. Gresson
Keyword(s):  
Germ Cells ◽  
Diploid Number ◽  
Digenetic Trematode ◽  
Early Prophase ◽  
Chromosome Counts ◽  
Golgi Bodies ◽  
Digenetic Trematodes ◽  
Primary Oocyte ◽  
Central Disk ◽  
Single Mass

The stages of spermatogenesis and the structure of the primary oocyte of Sphaerostoma bramae were studied in material fixed in Bouin and Flemming's fluid and in preparations treated according to the Kolatchev and the Feulgen techniques.Chromosome counts of primary and secondary spermatocytes indicate that the diploid number is twenty-four.The stages of spermatogenesis, in general, conform to the usual pattern of this process in digenetic trematodes. The spermatogonia, spermatocytes and early spermatids are not connected together by central strands, nor by a central disk, as is claimed for some other species. A study of sections stained in haematoxylin and of Feulgen preparations showed that the spermatozoon is composed of an elongate nucleus and a tail. It was not possible, with the methods employed during the present investigation, to determine the fine structure of the tail.The primary ovarian oocytes are in the interphase or in early prophase of the first maturation division. There is evidence that material is extruded from the nucleus to the cytoplasm.The Golgi elements of the male germ-cells are revealed in Kolatchev preparations as short rods and filaments. The Golgi elements of the spermatid are eliminated in the residual cytoplasm. Mitochondria, in the form of granular bodies and short rods, were visible in spermatogonia, spermatocytes and spermatids. Those of the spermatid remain in the residual cytoplasm.Short, rod-like Golgi bodies are present in the primary oocytes. In the young cells they form a compact mass situated close to or in contact with the nuclear membrane. Later, the elements spread out through the cell. Granular and rod-shaped mitochondria are concentrated in a single mass at one pole of the nucleus or in two masses at opposite sides of the nucleus. A few mitochondria are scattered through the cytoplasm.

scholarly journals THE FINE STRUCTURE OF THE DNP COMPONENT OF THE NUCLEUS

1963 ◽  
Vol 16 (1) ◽  
pp. 29-51 ◽  
Author(s):  
Elizabeth D. Hay ◽  
J. P. Revel
Keyword(s):  
Fine Structure ◽  
Dna Synthesis ◽  
Interphase Nucleus ◽  
Deoxyribonucleic Acid ◽  
Tritiated Thymidine ◽  
Proliferating Cells ◽  
Interphase Nuclei ◽  
Ultrathin Sections ◽  
Silver Grains ◽  
Dense Chromatin

In the present investigation, the sites of deoxyribonucleic acid (DNA) synthesis and the fate of labeled deoxyribonucleoprotein (DNP) were studied in autoradiographs of ultrathin sections viewed with the electron microscope. Tritiated thymidine was employed as a label for DNA in the nuclei of proliferating cells of regenerating salamander limbs. In the autoradiographic method reported here, dilute NaOH was used to remove the gelatin of the emulsion after exposure and development. The exposed silver grains are not displaced by this treatment and the resolution of fine structure in the underlying section is greatly improved. Our observations suggest that the DNP component is a meshwork of interconnected filaments 50 to 75 A in diameter, which may be cross-linked to form what Frey-Wyssling would term a "reticular gel." The filamentous DNP meshwork is dispersed throughout the interphase nucleus during DNA synthesis, whereas in chromosomes, which are relatively inert metabolically, the meshwork is denser and is aggregated into compact masses. Dense chromatin centers in interphase nuclei are similar in fine structure to chromosomes and are also inert with respect to DNA synthesis. In the Discussion, the structure of the filamentous meshwork in chromatin is compared with that in chromosomes, and speculations are made as to the functional significance of the variations in DNP fine structure observed.

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