scholarly journals RNA TRANSPORT FROM NUCLEUS TO CYTOPLASM IN CHIRONOMUS SALIVARY GLANDS

1966 ◽  
Vol 31 (1) ◽  
pp. 55-77 ◽  
Author(s):  
Barbara J. Stevens ◽  
Hewson Swift
Keyword(s):  
Nuclear Envelope ◽  
Messenger Rna ◽  
Rna Transport ◽  
Central Channel ◽  
Balbiani Ring ◽  
Apparent Effect ◽  
Nuclear Pores ◽  
Balbiani Rings ◽  
Rna Puffs ◽  
Chironomus Thummi

The fine structure and cytochemistry of the extremely large RNA puffs, or Balbiani rings, in salivary gland nuclei of midge, Chironomus thummi, larvae have been investigated. The Balbiani rings are composed of a diffuse mass of electron-opaque 400 to 500 A granules, short threads about 180 to 220 A in diameter and associated fine chromatin fibrils. These components appear to be organized into brushlike elements which form the ring. Electron microscope cytochemistry has shown that the granules and short threads contain RNA. After ribonuclease digestion, only 50 to 100 A chromatin fibrils were apparent in the Balbiani ring, and the granules were no longer demonstrable. Deoxyribonuclease digestion had no apparent effect on these structures. Observations indicate that the granules are formed from the short threads and released into the nucleoplasm in which they are evenly distributed. At the nuclear envelope, many granules have been observed partially or completely within the nuclear pores. These granules become elongated and are shown to penetrate the center of the pore in a rodlike form, about 200 A in diameter. The Balbiani ring granules are not normally visible within the cytoplasm adjacent to the nuclear envelope, but have been rarely found in this region. It is suggested that the granules represent the product of the Balbiani ring, possibly a messenger RNA bound to protein, and that they regularly pass into the cytoplasm through a narrow central channel in the pores of the nuclear envelope.

FINE STRUCTURE OF NUCLEOLI AND RNA-CONTAINING CHROMOSOME REGIONS OF SALIVARY GLAND CHROMOSOMES OF CHIRONOMIDS AND THEIR INTERRELATIONSHIP

1964 ◽  
Vol 42 (6) ◽  
pp. 1147-1155 ◽  
Author(s):  
V. I. Kalnins ◽  
H. F. Stich ◽  
S. A. Bencosme
Keyword(s):  
Fine Structure ◽  
Salivary Gland ◽  
Electron Microscope ◽  
Light Microscopy ◽  
Messenger Rna ◽  
Balbiani Ring ◽  
Electron Microscopic ◽  
Chironomid Species ◽  
Balbiani Rings ◽  
Chromosome Regions

Electron microscope studies of salivary gland nuclei of four chironomid species have shown that the RNA-containing chromosome regions and associated structures, which by light microscopy exhibit a great variety of structures such as bands, granules, micronucleoli, nucleoli, puffs, and Balbiani rings, consist of only few basic units: pars amorpha, nucleolonema, and Balbiani ring granules. The fine structure of the nucleoli and spherical micronucleoli located at various chromosome regions appears to be identical, consisting of pars amorpha, which contains fibers of varying diameters, and strands of nucleolonema composed of fibers and ribosome-like granules. The arrangement of pars amorpha and nucleolonema of nucleoli and spherical micronucleoli follows a consistent pattern. Chromosome fibers are closely associated with pars amorpha, whereas strands of nucleolonema border only the surfaces of pars amorpha. Balbiani ring granules, which have a diameter of 300 Å to 500 Å and are characterized by a particular structure, accumulate in Balbiani rings, in many chromosome regions, and in nuclear sap. In the Balbiani ring these granules seem to be attached to 100 Å chromosome fibers. They are absent in nucleoli and micronucleoli. The possible correlation between our electron microscopic observations and the present-day concept of ribosomal and messenger RNA production is discussed.

scholarly journals Large-sized polysomes in Chironomus tentans salivary glands and their relation to Balbiani ring 75S RNA.

1977 ◽  
Vol 73 (1) ◽  
pp. 149-160 ◽  
Author(s):  
B Daneholt ◽  
K Anderson ◽  
M Fagerlind
Keyword(s):  
Salivary Glands ◽  
Messenger Rna ◽  
High Yield ◽  
Chironomus Tentans ◽  
Balbiani Ring ◽  
Rna Molecules ◽  
Large Size ◽  
Present Information ◽  
Balbiani Rings ◽  
Available Information

Polysomes from the salivary glands of Chironomus tentans were investigated to determine whether Balbiani ring 75S RNA is incorporated into polysomal structures, and thus probably acts as messenger RNA. A new extraction technique for obtaining ribonucleoproteins was applied that gives a high yield of polysomes with only moderate degradation of the cytoplasmic, high molecular weight RNA. The polysomes sedimented in a broad region (200-2,000S) with a peak value of about 700S, which suggested that they were partly of very large sizes. This was confirmed by visualization of the polysomes in the electron microscope: 400S polysomes contained mainly 11-16 ribosomes, and 1,500S polysomes about 60 ribosomes per polysome. However, polysomes containing 100 or more ribosomes were also observed. It was further established that most of the cytoplasmic 75S RNA was located in polysomes, preferentially in the most rapidly sedimenting ones. From the available information on Balbiani ring RNA in cytoplasm and the present demonstration of 75S RNA molecules in polysomes, it was concluded that at least some Balbiani ring RNA, generated as 75S RNA within the Balbiani rings, eventually enters polysomes without being measurably changed in size. The present information on the potential amino acid coding sequences in 75S RNA is discussed in relation to the large size of the polysomes observed.

High-voltage cytochemistry for three-dimensional observation of nuclei and calculation of total numbers of nuclear pores in retinal Mueller glia

1990 ◽  
Vol 48 (3) ◽  
pp. 956-957
Author(s):  
H. Ishigooka ◽  
S. Ueno ◽  
L.M. Hjelmeland ◽  
M.B. Landers ◽  
K. Ogawa
Keyword(s):  
Nuclear Envelope ◽  
High Voltage ◽  
Three Dimensional ◽  
Reaction Medium ◽  
Nuclear Pores ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
G6pase Activity ◽  
Mueller Glia

Introduction: We have demonstrated that Glucose-6-phosphatase (G6Pase) activity is localized to the endoplasmic reticulum and nuclear envelope of Mueller glia in the normal and pathological guinea pig retina. Using a combination of this cytochemical technique and high voltage electron microscopy, the distribution of nuclear pores could be clearly observed on the nuclear envelope of Mueller glia because of their anatomical lack of reaction products. This technique was developed to study the three-dimensional structure of nuclei and to calculate total numbers of nuclear pores utilizing a computer graphic analysis system in the normal and pathological retina.Materials and methods: Normal and photocoagulated retina of pigmented adult guinea pigs were perfused with a cold mixture of 0.25% glutaraldehyde and 2% paraformaldehyde in 0.1M cacodylate buffer, and the enucleated globes were hemisected and immersed in the same fixative for 30 min. After sectioning and incubation in the reaction medium for the detection of G6Pase activity by the method of Wachstein-Meisel, the sections were postfixed, dehydrated and embedded in Spurr’s epoxy resin. Serial thick sections (1.0um) were prepared for the observation by a Hitachi high voltage electron microscope (H 1250-M) with an accelerating voltage of 1000 Kv. and pictures were analyzed and three-dimensionally reconstructed by TRI (RATOC Co., Ltd.).

scholarly journals Structural interaction between the nuclear pore complex and a specific translocating RNP particle.

1995 ◽  
Vol 129 (5) ◽  
pp. 1205-1216 ◽  
Author(s):  
H Mehlin ◽  
B Daneholt ◽  
U Skoglund
Keyword(s):  
Nuclear Pore Complex ◽  
Nuclear Pore ◽  
Initial Contact ◽  
Chironomus Tentans ◽  
Central Channel ◽  
Balbiani Ring ◽  
Salivary Gland Cells ◽  
Larval Salivary Gland ◽  
Nuclear Ring ◽  
Precise Area

The transport of Balbiani ring (BR) premessenger RNP particles in the larval salivary gland cells of the dipteran Chironomus tentans can be followed using electron microscopy. A BR RNP particle consists of an RNP ribbon bent into a ringlike structure. Upon translocation through the nuclear pore complex (NPC), the ribbon is straightened and enters the central channel of the NPC with the 5' end of the transcript in the lead. The translocating ribbon is likely to interact with the central channel but, in addition, the remaining portion of the ribbon ring makes contact with the periphery of the NPC. To determine the nature of this latter interaction, we have now studied the connections between the RNP particle and the border of the NPC during different stages of translocation using electron microscope tomography. It was observed that the 3' terminal domain of the ribbon always touches the nuclear ring of the NPC, but the precise area of contact is variable. Sometimes also a region on the opposite side of the ribbon ring reaches the nuclear ring. The pattern of contacts could be correlated to the stage of translocation, and it was concluded that the particle-nuclear ring interactions reflect a rotation of the ribbon ring in front of the central channel, the rotation being secondary to the successive translocation of the ribbon through the channel. The particle's mode of interaction with the NPC suggests that the initial contact between the 5' end domain of the ribbon and the entrance to the central channel is probably crucial to accomplish the ordered translocation of the premessenger RNP particle through the NPC.

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