scholarly journals THE INTRACELLULAR DISTRIBUTION AND HETEROGENEITY OF RIBONUCLEIC ACID IN STARFISH OOCYTES

1961 ◽  
Vol 11 (3) ◽  
pp. 549-557 ◽  
Author(s):  
Jan-Erik Edström ◽  
Wolfgang Grampp ◽  
Norberto Schor
Keyword(s):  
Ribosomal Rna ◽  
Messenger Rna ◽  
The Other ◽  
Asterias Rubens ◽  
Cell Component ◽  
Cytoplasmic Rna ◽  
Stable Part ◽  
Unstable Part ◽  
Nucleolar Rna ◽  
Purine Pyrimidine

A study has been made of the content and composition of RNA in cytoplasm, nucleoplasm, and nucleoli from growing oocytes of the starfish Asterias rubens. The determinations were carried out, using ultramicrochemical methods, on units isolated by microdissection from fixed sections. Macrochemical and interferometric control experiments show that RNA can be quantitatively evaluated in this way. The results show that the growing oocyte represents a system in which the relations between the quantities of nucleolar, nucleoplasmic, and cytoplasmic RNA undergo great changes. These changes are continuous for nucleolar and cytoplasmic RNA so that their amounts may be predicted from the size of the cell. Nucleoplasmic RNA, on the other hand, shows great variations among different cells, independent of cell size. Purine-pyrimidine analyses show that each cell component contains an RNA which differs significantly from that of the other two. Cytoplasmic and nucleolar RNA are closely related, the only difference being a slightly higher guanine/uracil quotient for the nucleolar RNA. They are both of the usual tissue RNA type, i.e., they show a preponderance of guanine and cytosine over adenine and uracil. Nucleoplasmic RNA deviates grossly from the RNA of the other two components. Here the concentrations of adenine and uracil are higher than those of guanine and cytosine, respectively. This RNA consequently shows some resemblance to the general type of animal DNA although the purine/pyrimidine ratio is far from unity. Our data favor a nucleolar origin for the stable part of the ribosomal RNA and a nucleoplasmic one for the unstable part (the messenger RNA).

scholarly journals COMPOSITION OF RIBONUCLEIC ACID FROM VARIOUS PARTS OF SPIDER OOCYTES

1960 ◽  
Vol 8 (1) ◽  
pp. 47-51 ◽  
Author(s):  
Jan-Erik Edström
Keyword(s):  
Ribonucleic Acid ◽  
The Other ◽  
Total Rna ◽  
Other Hand ◽  
Cytoplasmic Rna ◽  
The Difference ◽  
Nucleolar Rna ◽  
Purine Pyrimidine ◽  
Different Parts

Microphoretic purine-pyrimidine analyses of the ribonucleic acid (RNA) in nucleoli, nucleoplasm, cytoplasm, and yolk nuclei of spider oocytes have been carried out. The material necessary for the analyses was isolated by micromanipulation. Determinations of the amounts of RNA in the different parts of the cell were also performed. No differences between the composition of RNA in the nucleolus and the cytoplasm could be disclosed. Nucleoplasmic RNA was, on the other hand, distinctly different from that in the nucleolus and in the cytoplasm. The difference lies in the content of adenine, which is highest in nucleoplasmic RNA. The few analyses carried out on yolk nuclei showed their RNA to be variable in composition with a tendency to high purine values. The cytoplasm contains about 99 per cent of the total RNA in these cells, the nucleoplasm about 1 per cent, and the nucleolus not more than 0.3 per cent, although the highest concentrations are found in these latter structures. When considered in the light of other recent findings the results are compatible with the view that nucleolar RNA is the precursor of cytoplasmic RNA.

scholarly journals Evidence for Two Metabolically Distinct Types of Ribonucleic Acid in Chromatin and Nucleoli

1958 ◽  
Vol 4 (1) ◽  
pp. 5-11 ◽  
Author(s):  
Rachel McMaster-Kaye ◽  
J. Herbert Taylor
Keyword(s):  
Maximum Activity ◽  
The Other ◽  
Precise Localization ◽  
Isolated Nuclei ◽  
Metabolic Characteristics ◽  
Nucleolar Activity ◽  
Cytoplasmic Rna ◽  
Nuclear Rna ◽  
Time Courses ◽  
Nucleolar Rna

Patterns of radioisotope incorporation are useful characteristics in describing cellular RNA fractions, and have indicated a distinctive "nuclear" RNA. In order to characterize the RNA fractions of the two nuclear components, nucleoli and chromatin, and to determine thereby the precise localization of the RNA typical of isolated nuclei, time-courses of P32 incorporation into nucleolar, chromosomal, and cytoplasmic RNA of Drosophila salivary glands have been determined from autoradiograms. Two experiments are reported which cover 12 and 18 hour periods, including an initial 2 hour feeding on P32. Concentrations of RNA-P32 (identified by ribonuclease digestion) were determined by grain counts. After 1 hour only the nucleolar RNA is labelled. Activity is detectible in chromosomal and cytoplasmic RNA after the 2nd hour. The nucleolar fraction reaches its maximum activity shortly after transfer of the larvae to non-radioactive food, the other fractions several hours later. Maximum activities persist in the chromosomal and cytoplasmic fractions; nucleolar activity decreases after the 9th hour. The observed differences in times at which incorporation begins and maximum activities are reached, and in maintenance of maximum activities indicate that chromosomal and nucleolar RNA are distinct fractions. The metabolic characteristics which have been ascribed to "nuclear" RNA apply only to the nucleolar fraction.

Phylogeny of hymenolepidids (Cestoda: Cyclophyllidea) from mammals: sequences of 18S rRNA and COI genes confirm major clades revealed by the 28S rRNA analyses

2021 ◽  
Vol 95 ◽  
Author(s):  
B. Neov ◽  
G.P. Vasileva ◽  
G. Radoslavov ◽  
P. Hristov ◽  
D.T.J. Littlewood ◽  
...  
Keyword(s):  
Ribosomal Rna ◽  
18S Rrna ◽  
Phylogenetic Analyses ◽  
The Other ◽  
Rrna Genes ◽  
Host Switching ◽  
28S Rrna ◽  
Mitochondrial Cytochrome ◽  
Rapid Radiation ◽  
18S Rrna Genes

Abstract The aim of the study is to test a hypothesis for the phylogenetic relationships among mammalian hymenolepidid tapeworms, based on partial (D1–D3) nuclear 28S ribosomal RNA (rRNA) genes, by estimating new molecular phylogenies for the group based on partial mitochondrial cytochrome c oxidase I (COI) and nuclear 18S rRNA genes, as well as a combined analysis using all three genes. New sequences of COI and 18S rRNA genes were obtained for Coronacanthus integrus, C. magnihamatus, C. omissus, C. vassilevi, Ditestolepis diaphana, Lineolepis scutigera, Spasskylepis ovaluteri, Staphylocystis tiara, S. furcata, S. uncinata, Vaucherilepis trichophorus and Neoskrjabinolepis sp. The phylogenetic analyses confirmed the major clades identified by Haukisalmi et al. (Zoologica Scripta 39: 631–641, 2010): Ditestolepis clade, Hymenolepis clade, Rodentolepis clade and Arostrilepis clade. While the Ditestolepis clade is associated with soricids, the structure of the other three clades suggests multiple evolutionary events of host switching between shrews and rodents. Two of the present analyses (18S rRNA and COI genes) show that the basal relationships of the four mammalian clades are branching at the same polytomy with several hymenolepidids from birds (both terrestrial and aquatic). This may indicate a rapid radiation of the group, with multiple events of colonizations of mammalian hosts by avian parasites.

The Activities of the Tube Feet of Asterias Rubens L

1947 ◽  
Vol s3-88 (1) ◽  
pp. 1-14
Author(s):  
J. E. SMITH
Keyword(s):  
Forward Direction ◽  
The Other ◽  
Asterias Rubens ◽  
Ideal Form ◽  
First Time ◽  
Intrinsic Musculature ◽  
Tube Feet ◽  
Postural Muscles ◽  
The Ideal

1. An account is given of the muscular anatomy of the foot and ampulla of Asterias rubens. An intrinsic musculature of the sucker figured by Cuénot (1891) and Chadwick (1923) is shown not to be present; on the other hand, postural muscles responsible for orientating the podium, levator fibres which ‘cup’ the sucker, and radial fibres which flatten it are described and figured for the first time. 2. The role of the different muscle systems, the collagen connective tissue, and the fluid of the hydrocoel in protracting and retracting the foot, and in effecting the attachment and detachment of the sucker, is discussed. 3. Evidence is presented, to show that postural pointing of the foot is brought about by the contraction of a ring of muscles encircling the base of the podium. The orienting muscles are functionally, but not anatomically, distinct from the longitudinal fibres of the retractor sheath. 4. The ambulatory step is shown to comprise a series of linked phases of static posture and of movement. Each phase is characterized by the contraction of one member of each of the two opposing pairs of muscles engaged in the development of the step. The two pairs of muscles are (1) the anterior and posterior orienting fibres, and (2) the protractors and retractors of the foot. In its ideal form the step comprises four phases of static posture alternating with four movements. Each movement is ushered in by a reversal of the contraction-relaxation relationships of one of the two pairs of opposing muscle systems. Four such changes are possible and they occur in a sequence that ensures the orderly succession of the four movements of protraction, swing back, retraction, and swing forward, of which movements the idealized stepping cycle is composed. 5. The actual locomotory step departs from the ideal form in two respects: (1) it is liable to become disrupted by a delay in the initiation of the protraction or of the backswing movement, and (2) withdrawal of the podium occurs simultaneously with its re-orientation in the forward direction. It is pointed out that these variations are explicable on the assumption that, in the two series of opposing muscle pairs, the retractor fibres are more readily excited to contract than are their antagonists, and the anterior postural muscles than the posterior postural fibres.

Changes in the size and structure of the nucleolus of columnar cells during their migration from crypt base to villus top in rat jejunum

1982 ◽  
Vol 56 (1) ◽  
pp. 83-99
Author(s):  
G.G. Altmann ◽  
C.P. Leblond
Keyword(s):  
Ribosomal Rna ◽  
The Other ◽  
Rat Jejunum ◽  
Differentiated Cells ◽  
Image Analyser ◽  
Single Structure ◽  
Columnar Cells ◽  
Crypt Base ◽  
Size And Structure ◽  
Nucleolar Components

An image analyser was used to measure the area of the nucleolus and its component parts in columnar cells at six levels of the jejunal epithelium, corresponding to stages in cell migration from crypt base to villus top. In columnar cells of crypt base, which function as stem cells for the epithelium, the nucleolus is large (3.1 micron2), irregular and reticulated. As cells migrate up the crypt, divide and differentiate, the nucleolus decreases in size (1.7 micron2) and becomes spherical, but remains reticulated. In the fully differentiated cells of the midvillus, however, the nucleolus becomes small (0.9 micron2) and compact. At the villus top, as the cells display early signs of degeneration, the nucleolus is further compacted (0.5 micron2). Most nucleolar components also decrease in size. Pars fibrosa (about 19% of the nucleolar area in crypt base) and pars granulosa (about 70%) decrease in proportion to the rest of the nucleolus, except in mid-villus and villus top where loss of pars granulosa predominates. In contrast, the total area of fibrillar centres remains constant (about 0.1 micron2), even though individual centres are small and numerous in crypt base, larger and fewer at higher levels, and they coalesce into a single structure in villus top. The other nucleolar components are also segregated into distinct, but adjacent, areas at this level. The changes in size and structure of the nucleolus taking place during the migration of columnar cells can be correlated with the maturation of the cells and the loss of their ability to synthesize ribosomal RNA.

scholarly journals Rex-induced recombination implies bipolar organization of the ribosomal RNA genes of Drosophila melanogaster.

Genetics ◽  
1988 ◽  
Vol 120 (4) ◽  
pp. 1053-1059
Author(s):  
L G Robbins ◽  
E E Swanson
Keyword(s):  
Drosophila Melanogaster ◽  
Ribosomal Rna ◽  
Mitotic Recombination ◽  
Ribosomal Rna Genes ◽  
The Other ◽  
Other Orientation ◽  
Rna Genes ◽  
Nucleolus Organizers

Abstract Rex-induced mitotic recombination was used to determine whether nucleolus organizers can pair in both inverted and noninverted orientations. Two target chromosomes, each duplicated for the rDNA region, were exposed to maternal Rex activity. Recombination in one orientation should yield deletion of the material between the two nucleolus organizers, recombination in the other orientation should yield inversion of the same material. Both products were recovered from both target chromosomes. The generality of using Rex-mediated recombination for analysis of the rDNA is considered.

Intranuclear Accumulation of Rna Resembling the Smaller Ribosomal Rna Component

1970 ◽  
Vol 6 (1) ◽  
pp. 53-72
Author(s):  
M. E. BRAMWELL
Keyword(s):  
Ribosomal Rna ◽  
Base Composition ◽  
Actinomycin D ◽  
Total Radioactivity ◽  
16S Ribosomal Rna ◽  
Low Concentrations ◽  
Rapid Accumulation ◽  
Nuclear Rna ◽  
Step Down ◽  
Nucleolar Rna

A study was made of the nuclear RNA in HeLa cells with particular reference to the rapidly labelled fractions. It was found that if cells were incubated at a high density, that is, under ‘step-down’ conditions, there was a rapid accumulation of RNA in the nucleus. The fraction of the nuclear RNA which includes rapidly labelled RNA and which binds tightly to columns of methylated albumin on kieselguhr increased in amount and reached levels which permitted enough of the material to be isolated for direct measurement of its base composition. This was found to be very similar to that of 16s ribosomal RNA. When cells growing logarithmically were treated with low concentrations of actinomycin D and then incubated in the presence of [3H]uridine it was found that an RNA fraction which bound tightly to methylated albumin on kieselguhr again accumulated in the nucleus. This fraction resembled that which accumulated under ‘step-down’ conditions. It contained over 85% of the total radioactivity in the nuclear RNA and again had a base composition very similar to 16s ribosomal RNA. Since nucleolar RNA synthesis was inhibited by the concentrations of actinomycin D used, it appeared that an RNA closely resembling 16s ribosomal RNA was synthesized outside the nucleolus. Sedimentation patterns on sucrose density gradients and thermal denaturation profiles lent support to the view that the RNA which binds tightly to columns of methylated albumin on kieselguhr probably represents ‘nascent’ 16s ribosomal RNA.

The appearance and quantitation of cytoplasmic ribonucleic acid in the early chick embryo

Development ◽  
1972 ◽  
Vol 28 (2) ◽  
pp. 367-384
Author(s):  
C. C. Wylie
Keyword(s):  
Chick Embryo ◽  
Ribosomal Rna ◽  
Rna Synthesis ◽  
Specific Activity ◽  
Cell Number ◽  
Present Knowledge ◽  
Precursor Pool ◽  
Cytoplasmic Rna ◽  
Labelling Experiment ◽  
Neurula Stage

This paper seeks to extend our knowledge about RNA synthesis in early embryogenesis to the domestic fowl, Gallus domesticus. Using this species for research, apart from increasing our knowledge of higher vertebrate embryology, has certain advantages such as rapid uptake of isotopic precursors and ease of microdissection in culture. The following results are presented: (1) The cell number in the whole chick embryos is shown to be increasing logarithmically between the time of laying and the early neurula stage; with a doubling time of 7·4 h. (2) The onset of ribosomal RNA synthesis has been shown to be during mid-cleavage of the chick embryo, while development is taking place in the oviduct and uterus of the mother. (3) In a cumulative labelling experiment, embryos were labelled at the unincubated-egg stage, allowed to develop to various morphological stages up to neurulation, and their cytoplasmic RNA prepared and analysed by gel electrophoresis. (4) The specific activity of the precursor pool for RNA synthesis was measured at several stages, using the same labelling conditions, and the results were used to quantitate the RNA synthesis from the incorporated radioactivity. (5) Using these techniques, it was found that newly synthesized cytoplasmic RNA accumulates steadily in the whole chick embryo, reaching a level of 104 μg by the early neurula stage. On a per cell basis, however, the amount of newly synthesized cytoplasmic RNA seems to decrease slightly. These findings are discussed in the light of present knowledge about embryos of other vertebrates and certain invertebrates.

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