THE BASE COMPOSITION OF NUCLEIC ACIDS IN CHROMOSOMES, PUFFS, NUCLEOLI, AND CYTOPLASM OF CHIRONOMUS SALIVARY GLAND CELLS

The base composition of RNA from individually isolated giant chromosomes, puffed chromosome segments, nucleoli, and samples of cytoplasm from Chironomus salivary gland cells was determined by microelectrophoresis. Data on the adenine: guanine quotient of the chromosomal DNA were also obtained. The results show that: 1) Chromosomal, nucleolar, and cytoplasmic RNA's differ significantly from each other in base composition. 2) Nucleolar and cytoplasmic RNA's, in spite of the difference, show great similarities with regard to the base composition and are both rich in adenine and uracil. 3) The RNA extracted from chromosome I differs significantly from the RNA's extracted from different segments of chromosome IV, and the latter differ significantly from each other. 4) The values for the RNA: DNA quotients of chromosome segments parallel the development of synthetically active genes, so-called Balbiani rings. 5) The chromosomal RNA does not show a base symmetry in any of the investigated cases, nor is the content of guanine + cytosine the same as that for DNA. The first of these two facts excludes the possibility that the chromosomal RNA is a complete copy of both strands of the chromosomal DNA. In spite of the difference in guanine + cytosine content between the two nucleic acids the RNA may still partly or completely be a single strand copy depending upon how representative the DNA values are for the synthetically active DNA.

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Unusual germ line limited chromosomes in Acricotopus lucidus (Diptera, Chironomidae)

Genome ◽

10.1139/g87-120 ◽

1987 ◽

Vol 29 (5) ◽

pp. 702-705 ◽

Cited By ~ 6

Author(s):

W. Staiber

Keyword(s):

Salivary Gland ◽

Polytene Chromosome ◽

Germ Line ◽

Chromosome Elimination ◽

Male Meiosis ◽

Laboratory Stock ◽

Gland Cells ◽

Salivary Gland Cells ◽

Chromosome I ◽

Acricotopus Lucidus

A small supernumerary polytene chromosome was found during the last 8 years in some rare cases in larval salivary gland cells of Acricotopus lucidus (Diptera, Chironomidae). The chromosome may be derived from the germ line restricted parts of the genome. It consists of a short heterochromatic segment and of euchromatic sections with banding patterns homologous to sections of the short arm of soma chromosome I. When examining male meiosis, an exceptional small germ line limited chromosome was found. It is believed that this chromosome was not always recognized during soma elimination as a germ line limited chromosome, probably because of its partial homology to one of the soma chromosomes, and was then polytenized in salivary gland cells. Another germ line limited chromosome with a characteristic morphology and with a special behavior in differential gonial mitosis was found to have existed for more than 12 years in a laboratory stock. In differential gonial mitosis this special germ line limited chromosome partly pairs with the long arm of soma chromosome I. The present results strongly support the idea that the germ line limited chromosomes of A. lucidus are derived from the soma chromosomes, and show that chromosomes of the germ line restricted part of the genome can persist for many generations in a laboratory stock in spite of complex chromosome elimination mechanisms in the primary germ cells. Key words: germ line limited chromosomes, supernumerary polytene chromosome, salivary gland, Acricotopus lucidus.

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An ultrastructural and histochemical developmental study of Drosophila auraria salivary gland cells during the third-instar period

Canadian Journal of Zoology ◽

10.1139/z89-063 ◽

1989 ◽

Vol 67 (2) ◽

pp. 421-429 ◽

Cited By ~ 4

Author(s):

George N. Thomopoulos ◽

Eleftherios P. Neophytou ◽

Costas D. Kastritsis

Keyword(s):

Salivary Gland ◽

Electron Density ◽

Developmental Stages ◽

Secretory Granules ◽

Polytene Chromosomes ◽

Developmental Study ◽

The Third ◽

Gland Cells ◽

Salivary Gland Cells ◽

Balbiani Rings

Early in the third-instar stage of Drosophila auraria, the salivary gland cells produce small secretory granules of low electron density which empty their flocculent contents into the lumen of the gland. At that stage, the Golgi complexes consist of vesiculated, round cisternae which, as middle third instar is approached, change to their classical appearance. Cytoplasmic protrusions, intramitochondrial granules, and close contacts of mitochondria with lipid droplets are observed during the early developmental stages. At about the middle of the third instar the glue secretory granules start being produced. These secretory granules contain a granular material (where small amounts of vicinal glycol and sulfated groups of complex carbohydrates have been detected) of medium electron density. The glue secretory granules can be classified according to their electron density into two populations. Before exocytosis large amounts of glycogen particles are observed, providing some of the energy needed during the final step of exocytosis. Two different types of ribonucleoprotein particles in puffing sites of the chromosomes are observed. Of these, the larger ones consist of a core surrounded by smaller particles; we suspect that they may be produced in the Balbiani rings observed in the polytene chromosomes of this species. Nuclear blebs and oval bodies are common, particularly during the late developmental stages. The functional significance of these findings during development is discussed.

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IN SITU DEMONSTRATION OF DNA HYBRIDIZING WITH CHROMOSOMAL AND NUCLEAR SAP RNA IN CHIRONOMUS TENTANS

The Journal of Cell Biology ◽

10.1083/jcb.53.2.407 ◽

1972 ◽

Vol 53 (2) ◽

pp. 407-418 ◽

Cited By ~ 37

Author(s):

B. Lambert ◽

L. Wieslander ◽

B. Daneholt ◽

E. Egyházi ◽

U. Ringborg

Keyword(s):

Salivary Gland ◽

Dna Sequences ◽

Chironomus Tentans ◽

Gland Cells ◽

Salivary Gland Cells ◽

Labeled Rna ◽

Chromosome I ◽

Nucleolar Rna ◽

Diffuse Distribution

Cytological hybridization combined with microdissection of Chironomus tentans salivary gland cells was used to locate DNA complementary to newly synthesized RNA from chromosomes and nuclear sap and from a single chromosomal puff, the Balbiani ring 2 (BR 2). Salivary glands were incubated with tritiated nucleosides. The labeled RNA was extracted from microdissected nuclei and hybridized to denatured squash preparations of salivary gland cells under conditions which primarily allow repeated sequences to interact. The bound RNA, resistant to ribonuclease treatment, was detected radioautographically. It was found that BR 2 RNA hybridizes specifically with the BR 2 region of chromosome IV. Nuclear sap RNA was fractionated into high and low molecular-weight RNA; the former hybridizes with the BR 2 region of chromosome IV, the latter in a diffuse distribution over the whole chromosome set. RNA from chromosome I hybridizes diffusely with all chromosomes. Nucleolar RNA hybridizes specifically with the nucleolar organizers, contained in chromosomes II and III. It is concluded that the BR 2 region of chromosome IV contains repeated DNA sequences and that nuclear sap contains BR 2 RNA.

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