Increase In Ribosomes Research Articles

Genome-wide profiling reveals a role for T-cell intracellular antigens TIA1 and TIAR in the control of translational specificity in HeLa cells.

TIA (T-cell intracellular antigens)-knockdown HeLa cells show an increase in ribosomes and translational machinery components. This increase correlates with specific changes in translationally up-regulated mRNAs involved in cell-cycle progression and DNA repair, as shown in polysomal profiling analysis. Our data support the hypothesis that a concerted activation of both global and selective translational rates leads to the transition to a more proliferative status in TIA-knockdown HeLa cells.

Proliferation of mitochondria in chronically stimulated rabbit skeletal muscle--transcription of mitochondrial genes and copy number of mitochondrial DNA.

Mitochondrial proliferation was studied in chronically stimulated rabbit skeletal muscle over a period of 50 days. After this time, subunits of COX had increased about fourfold. Corresponding mRNAs, encoded on mitochondrial DNA as well as on nuclear genes, were unchanged when related to total tissue RNA, however, they were elevated two- to fivefold when the massive increase of ribosomes per unit mass of muscle was taken into account. The same was true for the mRNA encoding mitochondrial transcription factor A. Surprisingly, tissue levels of mtTFA protein were reduced about twofold, together with mitochondrial DNA. In conclusion, mitochondria are able to maintain high rates of mitochondrial transcription even in the presence of reduced mtTFA protein and mtDNA levels. Therefore, stimulated mtTFA gene expression accompanies stimulated mitochondrial transcription, as in other models, but it is not sufficient for an increase of mtDNA copy number and other, yet unknown, factors have to be postulated.

The Effects of MPL-Ligand, Interleukin-6 and Interleukin-11 on Megakaryocyte and Platelet Alpha-granule Proteins

Thrombopoietin (Mpl ligand), interleukin-6 (IL-6), and interleukin-11 (IL-11) differ in their effects on megakaryocyte maturation and development. In the present study, the impact of these thrombocytopoietic cytokines on biochemical and structural granule and membrane components was examined. Western blotting was performed on equivalent amounts of isolated megakaryocyte or platelet protein and the relative intensities of the enhanced chemiluminescent-visualized bands were quantitated by densitometry. Megakaryocyte growth and development factor (MGDF), a recombinant thrombopoietin-related molecule, significantly increased megakaryocyte fibronectin (72%), thrombospondin (55%), von Willebrand factor (28%) and p-selectin (CD62p) (37%) when compared to equivalent amounts of protein from saline-treated controls (p<0.01). Megakaryocyte fibrinogen was not increased. Ultrastructurally, there was a marked increase in ribosomes and rough endoplasmic reticulum even in mature-appearing megakaryocytes. Platelets from MGDF-treated mice showed small increases in fibronectin (8%), and CD62p (18%), but did not show increases in other measured alpha-granule proteins. Neither IL-6 nor IL-11 increased megakaryocyte or platelet alpha-granule proteins over levels observed in saline controls. IL-11 treated megakaryocytes, while also exhibiting an increase in ribosomes, were characterized by prominent cytoplasmic fragmentation. The study demonstrates the impact of Mpl ligand in increasing synthesized megakaryocyte alpha-granule proteins and of IL-11 in promoting megakaryocyte fragmentation.

Regulation of eukaryotic translation initiation factor expression during T-cell activation

Primary T-cells are metabolically quiescent, with little DNA, RNA or protein synthesis. Upon mitogenic stimulation the rate of protein synthesis increases 10-fold. We have studied the role of eIF-2 and eIF-4α (eIF-4E) expression in the mechanism of translational activation. During this period, the levels of eIF-2α and eIF-4α mRNA increase some 50-fold. Similar to the increase in ribosomes and mRNA, the number of eIF-2α, eIF-2β, and eIF-4α molecules per cell also increase 2–3-fold. This suggests that in addition to an increase in the pool size of translational components, an additional mechanism exists which results in an increased efficiency of factor utilization. We have looked at initiation factor phosphorylation. We find that eIF-2α does not undergo significant changes in its phosphorylation state nor is there a change in the efficiency of eIF-2 utilization. However, there is a rapid increase in the phosphorylation state of eIF-4α which correlates with the rapid increase in translational activity. It thus appears there are 2 distinct components responsible for the translational activation of quiescent T-cells during mitogenic stimulation. The first is the phosphorylation of eIF-4α, with a concomitant increase in the efficiency of eIF-4α utilization. The second is an increase in the pool sizes of eIF-2 and eIF-4α.

Ultrastructural relationships of the developing syncytium induced by Heterodera schachtii (Nematoda) in root tissues of rape

The growth and development of the syncytium induced by the beet cyst nematode (Heterodera schachtii Schmidt) in rape (Brassica napus var. oleifera) and its relationships to adjacent root tissues were studied by serial sectioning and electron microscopy. In a 5-day-old syncytium, xylem parenchyma cells formed the largest part of the syncytium volume, while pericycle cells constituted the smallest fraction. Xylem parenchyma cells outside the confluent part of the syncytium were the first cells to differentiate into syncytium-component cells at the leading edges of syncytia. Early stages of differentiation were characterized by an increase in ribosomes and rough endoplasmic reticulum. Later stages involved formation of tubular structures and cell wall ingrowths. In lateral roots, into which main root syncytia extended, xylem differentiation was disturbed by strong hypertrophy of xylem parenchyma cells. Here, xylem tracheary elements similar to graniferous tracheary elements occurred. The parasitism of H. schachtii in rape induced dramatic changes in root morphogenesis, and the response of xylem parenchyma cells was of fundamental importance in this host–parasite system. Key words: Brassica napus, Heterodera schachtii, syncytium, ultrastructure.

Spinal neuronal pathology associated with continuous intrathecal infusion ofN-methyl-d-aspartate in the rat

Continuous intrathecal infusion of N-methyl-D-aspartate (NMDA) at the level of the lumbar enlargement of the spinal cord in middle-aged rats produced dose-dependent toxicity of spinal cord neuronal systems. Toxicity was enhanced by coadministration of glycine, but was significantly reduced when NMDA was co-administered with the competitive inhibitor DL-2-amino-5-phosphovaleric acid or the noncompetitive inhibitor MgSO4. The toxic effects of NMDA were manifest most dramatically and at the lowest concentrations in the neuropil, while neuronal loss was obvious at higher concentrations. The distribution and intensity of reactive astrocytosis was consistent with the known regional and subcellular distribution of NMDA receptors in the spinal cord of rats. The increase in ribosomes and rough endoplasmic reticulum observed in anterior horn cells suggested an increase of cell metabolism reflecting either a nonspecific response to injury or a specific increase in cell metabolism secondary to sustained activation of NMDA receptors. The present studies implicate excitatory amino acid receptors of the NMDA type in producing toxicity to selected neuronal populations of the spinal cord. This model provides a system for studies of the protective effects and rescue of neuronal populations susceptible to the toxic effects of excitatory amino acids.

Effect of ginsenoside-Rb2 on nitrogen compounds in streptozotocin-diabetic rats.

The effects of ginsenoside-Rb2 on nitrogen compounds in streptozotocin-diabetic rats were investigated. A marked decrease in blood urea nitrogen level was observed in the ginsenoside-Rb2 administered group. Administration of ginsenoside-Rb2 induced increases of total protein and Lys, Gly, Glu, Arg, etc. in serum, while no significant change of serum albumin was observed. In the liver, the urea content was decreased with a concomitant increase of ribonucleic acid content. A quantitative study on the distribution of free and membrane-bound ribosomes indicated that the increase in ribosomes caused by the Administration of ginsenoside-Rb2 is mainly due to the increase in membrane-bound ribosomes. Ginsenoside-Rb2 exhibited a normalizing action on the hepatic concentrations of Glu, Thy, Phe, and Tyr. Furthermore, body weight significantly increased in diabetic rats receiving ginsenoside-Rb2, even though they took less food than the control group. Ginsenoside-Rb2 remarkably improved diabetic symptoms such as over-eating, polyuria, etc.

Ultrastructural changes of monensin‐oleandomycin myopathy in broiler chicks

Light microscopical and ultrastructural changes of skeletal muscles were described in chicks treated with monensin and oleandomycin in the food and water for 3 to 6 days. Simultaneously, or slightly subsequent to necrosis of some myofibres on days 3 and 4 of treatment, many myofibres exhibited reversible alterations initiated by focal myofibrillar lysis and degeneration of mitochondria. Reparative changes appearing on day 6 of treatment showed proliferation of the mitochondria, marked increase of ribosomes and polysomes, and enlargement of the Golgi apparatus in the sarcoplasm of degenerated myofibres. The morphological findings of monensin-oleandomycin myopathy in chicks were indistinguishable from monensin-tiamulin myopathy. Possible factors contributing to the unique morphology of this myopathy were discussed.

Aging of Cylinders Excised from Pulp Tissues of the `Golden Delicious' Apple

Aging cylinders excised from ;Golden Delicious' apple (Pyrus malus L.) pulp, like the intact fruit, exhibit some characteristic phenomena such as rise in respiration (climacteric), ethylene synthesis, enzymic changes, and increase in ribosomes and mRNA. Aging of cylinders of pulp tissues may offer a useful physiological tool for the study of maturation and senescence.

Hepatocellular glycogenosis and related pattern of enzymatic changes during hepatocarcinogenesis

Systematic studies of the sequence of cellular changes during hepatocarcinogenesis induced predominantly in rats by stop experiments with N-nitrosomorphine (NNM) led to the following main results and conclusions: 1. 1.|The development of hepatocellular tumors is preceded by a multifocal hepatic glycogen storage disease (glycogenosis). 2. 2.|Cytomorphological and cytochemical findings suggest a sequence of focal changes leading from clear and acidophilic glycogen storage foci through mixed cell foci and neoplastic nodules to hepatocellular carcinomas. The clear and acidophilic glycogen storage cells persisting after withdrawal of the carcinogen apparently represent a preneoplastic cell population, the neoplastic transformation of which is accompanied by a gradual reduction of glycogen and a concomitant increase in ribosomes (basophilia). 3. 3.|The first appearance and frequency of the different liver lesions investigated was shown to depend on the dose of carcinogen administered. With increasing dose of NNM, the number of focal lesionsn considerably increased, and this was accompanied by an earlier development of mixed and basophilic cell populations. There was no indication of any reversibility of pronounced focal lesions under the experimental conditions chosen. On the contrary, the foci became larger and acquired phenotypic markers closer to neoplasia independent of further action of the carinogen. 4. 4.|Enzyme histochemically, the majority of the pronounced glycogen storage foci showed a reduction in the activities of glycogen phosphorylase and glucose-6-phosphatase while the activity of glucose-6-phosphate dehydrogenase, a key enzyme for the pentose phosphate pathway, was increased. The mixed cell foci, neoplastic nodules and carcinomas which emerged at later stages were characterized by a progressive shift away from glycogen metabolism towards glycolysis and the pentose phosphate pathway, as indicated by an increase in glyceraldehyde-3-phosphate dehydrogenase and glucose-6-phosphate dehdyrogenase activities. These changes in enzyme pattern are in keeping with a developmental sequence leading fromm glycogen storage foci through mixed cell foci and neoplastic nodules to hepatocellular carcinomas. 5. 5.|Biochemical microanalysis of dissected glycogen storage foci and mixed cell foci revealed that the foci composed exclusively of storage cells contained on an average 100% more glycogen than the normal liver tissue. The overall glycogen content of the mixed cell foci, which were composed of both glycogenotic and glycogen-poor basophilic cells, was not distinguishable from that of normal tissue. The activity of the glucose-6-phosphate dehydrogenase showed a clear tendency to higher values in the majority of the small glycogen storage foci. However, in large glycogenetic foci and especially in mixed cell foci the activity of this enzyme was significantly higher than in the normal liver tissue. The data support the concept that hepatocarcinogens induce a focal glycogen storage disease of the liver. In consequence, adaptive enzymatic changes appear to be elicited which gradually redirect the disturbed carbohydrate metabolism towards alternative metabolic pathways.

Ribonucleic acid changes in medial cells in evans blue positive regions of the dog aorta

Evidence is presented supporting the feasibility of using cytophotometric analysis of cellular azure B-RNA dye binding as a cytochemical marker of metabolic alterations in medial smooth muscle cells underlying aortic areas having spontaneously occurring increased uptake of Evans blue dye. Focal areas of enhanced permeability or intra-aortic macromolecular accumulation (demarcated by in vivo uptake of Evans blue dye) exhibited 20–40% higher extents of azure B staining in intimal, medial, and adventitial compartments when compared to corresponding compartments in dye-impermeable regions. No discernible differences were evidenced in deoxyribonucleic acid levels (using Feulgen-DNA cytophotometry) or in the histological appearance (using conventional staining) between Evans blue-positive and negative aortic specimens. The overall data suggest that (1) focal differences in cellular azurophilia are attributable to differences in rates of uptake or accumulation of plasma constituents in Evans blue-permeable and impermeable aortic regions, and (2) the permeability-associated increase in azurophilia is due to an increase in ribosomes and reflects a compensatory activation of metabolic processes in response to an increased uptake and transmural transport of plasma macromolecules.

Ribosomal RNA Synthesis Throughout Epidermal Hyperplastic Growth Induced by Abrasion or Treatment with 12-0-Tetradecanoyl-phorbol-13-acetate

During the production of an epidermal hyperplasia following abrasion, or the application of 17 nmoles of 21-0-tetradecanoyl-phorbol-13-acetate (TPA) on the back skin of female CD-1 mice there is a marked increase in ribosomes. During the period of regression, when the epidermis returns to its normal size, the ribosome content also returns to normal. To determine the contribution of ribosome synthesis to the accumulation of ribosomes, mice at varying intervals after abrasion or treatment with 17 nmoles of TPA were injected with (5-3H) uridine (100 muCi, I.P.), 3 hr later the mice were sacrificed, the cytoplasmic ribosomes isolated, and the incorporation of (5-3H) uridine into the cytoplasmic ribosomes was determined. During the production of epidermal hyperplasia, following either abrasion or TPA treatment, there is a significant increase in the incorporation of (5-3H) uridine into the rRNA of the cytoplasmic ribosomes, suggesting that there is an increase in ribosome synthesis. During the period of epidermal regression, ribosome synthesis returns toward normal levels. There is a rough correlation between the amount of hyperplastic growth and the degree of ribosome synthesis. Abrasion induces about a 2-fold greater increase in epidermal mass, compared to TPA treatment. Accordingly, at its peak ribosome synthesis is about 2 times greater after abrasion than after TPA treatment.

Histometric and Fine-Structural Analysis of Pig Glomeruli after Experimental Protracted Shock

Glomeruli of control and shock-treated, 6-8-week-old pigs (n = 16 specific pathogen-free) were analyzed by light microscopy, transmission electron microscopy and morphometry. In eight of the animals the shock was induced using a neurotoxin of the E. coli serotype O 139: k82 (B). The animals were killed 47 to 264 hours post injection. In semithin sections a significant mesangial widening and increase of the mesangial nuclei count was demonstrated. The volume of the mesangium was 11.1% in the control animals and increased to 19.6% after protracted shock. By electron microscopy we ascertained a distinct activation of the mesangial cells concomitant with an increase of ribosomes, rough endoplasmatic reticulum, lysosomes and a fusion of the epithelial pedicles. The surrounding mesangial matrix was enlarged. In this paper the significance of this mesenchymal reaction in relation to shock situations is discussed.

Polyribosomes from Pear Fruit

Polysome profiles were examined from lyophilized peel tissue of ripening pear (Pyrus communis, L. var. Passe-Crassane). Messenger RNA chains bearing up to eight ribosomes (octamers) were resolved and exhibited the highest absorption peak when ribonuclease activity was eliminated during extraction. Neither normal ripening nor the increase of large polyribosomes that normally accompanies ripening and senescence of the fruit occurred when pretreatment at 0 C was omitted. Normal ripening and increase of large polyribosomes would, however, be initiated by an ethylene treatment. The size distribution of the polyribosomes remained essentially constant throughout a 4-month cold storage; there was, however, a large increase in ribosomes by the 12th week of storage.

Induced glial differentiation of fetal rat brain cells in culture: An ultrastructural study

Primary and secondary cultures of fetal rat brain cells (FBC) from 18th day of gestation have been investigated by scanning and transmission electron microscopy. Primary cultures consisted of a monolayer of flat, undifferentiated epithelioid cells, with some oligodendrocytes, astrocytes and immature neuronal cells. In secondary cultures, cells with glia morphology disappeared. Following addition of extracts from adult rat brains to secondary cultures, a dramatic change of the epithelioid cells took place. They detached from the palstic surface, extruded long cytoplasmic processes with numerous microvilli and cytoplasmic blebs as well as parallel arrays of microtubules and filaments. The differentiated cells resembled astrocytes, and characteristic glia filaments were also observed. An increase of ribosomes and rough endoplasmatic reticulum suggested enhancement of protein synthesis. At the same time S-100 protein and glial fibrillary acidic protein accumulated within the cells. The morphological changes were mostly reversible within 48 h of removal of the brain extract.

Effect of castration and testosterone administration on the neuromuscular junction in the levator ani muscle of the rat

The ultrastructure of the neuromuscular junction (n.m.j.) of the androgen-sensitive levator ani muscle was studied in normal adult male rats, in 8-month-old rats castrated at the age of one month and in castrated rats treated with testosterone propionate (TP). Castration does not result in significant changes of the n.m.j. The density of synaptic vesicles and the postsynaptic junctional folds remain practically normal inspite of marked atrophy of the muscle. TP administration for 7 days results in marked changes in pre- and postsynaptic structures. There is slow progressive depletion of synaptic vesicles, appearance of cisternae and coated vesicles in axon terminals, and coalescence of coated vesicles with the plasma membrane. Coated vesicles are also found inside Schwann cells and among junctional folds. Dense core vesicles appear both in the axon terminals and in the postsynaptic area. Collateral sprouting of terminal axons with the formation of new immature junctions is observed. After 35 days of TP administration depletion of synaptic vesicles continues. Glycogen beta-particles, mostly freely dispersed, occasionally seen in axon terminals 7 days after TP administration, subsequently increase in number. In the endplate zone of the muscle fibre increased protein synthesis is indicated by a rapid increase in ribosomes and irregularly located myofilaments and myofibrils. The appearance of n.m.j. after testosterone administration resembles that described after nerve stimulation; the degree of change is however less pronounced.

Early changes in the ultrastructure of denervated rat skeletal muscle

The activities of peptide hydrolase and cathepsin B1, thought to be lysosomal, increase shortly after denervation in the rat soleus and extensor digitorum longus (EDL) muscles. In order to look for evidence of a concomitant formation of lysosomes the ultrastructure was examined at 3 days after denervation, when the activities reach a maximum in the soleus, and at 6 days after denervation, when they reach a peak in the EDL. Morphometry was carried out to quantify some of the changes in the fiber constituents. Both types of muscle showed a heterogeneous range of secondary lysosomes including autophagic vacuoles, multivesicular bodies, myelin figures, and lipofuscin granules. These constituted up to 1% of the volume of the denervated fibers. Also present were small dense bodies which, because of their morphological characterization and their location, were thought to be primary lysosomes. These were often in close association with Golgi complexes which became more numerous after denervation. There was also an increase in ribosomes and rough endoplasmic reticulum (RER). Earlier work suggested that this protein-synthetic machinery is involved in the production of new acetylcholine receptors in the plasma membrane, but the present authors make an alternative suggestion that the new RER and Golgi apparatus are involved in the manufacture and sequestering of the enzymes entering into the lysosomes.

Cytochemical and subcellular organization of root apical meristems of dry and germinating jack pine embryos

By cytochemical and electron microscopic methods, the emerging radicle of Pinusbanksiana Lamb. was shown to contain an abundance of food reserves largely proteins, lipids, and starch grains. After 4 days of imbibition, the food reserves were dispersed to the daughter cells that tended to form through a sequence of divisions, linear arrays of adhering cells. The main cytochemical changes were associated with the later stages of imbibition and the consumption of carbohydrates and nitrogenous compounds for the synthesis of newly dispersed macromolecules. Peroxidase (EC 1.11.1.7) not found to any significant extent in the dry embryo, appeared by day 4 in the root cap and epidermal cells. As for DNA synthesis, cells of the quiescent zone were shown by autoradiography to incorporate very little [methyl-3H]thymidine. By contrast, most cells in the radicle incorporated thymidine in advance of the first wave of cell division between 3 to 4 days.The initial tight packing of subcellular organelles and the high lipid content of dry cells made the evaluation of subcellular changes difficult. In the nucleus and cytoplasm, the increase of ribosomes and polysomes was supported by the increased cytoplasmic staining for total RNA and acidic proteins. In emerging radicles, the overall redistribution of organic reserves and the associated subcellular reorganization related to the tactical displacement of cells and to new channels for the initial uptake of water and nutrients from the soil.

Pollen Ultrastructure in Anther Cultures ofNicotiana tabacum

Ultrathin sections of 2- and of 5-day-old cultured tobacco anthers inoculated at the stage of the first pollen mitosis were examined in the electron microscope in an attempt to identify early structural changes associated with pollen embryogenesis. On both sampling occasions grains were observed with structural features of typical bicellular gametophytes but lacking starch. Some of these grains were atypical in that they possessed numerous small vacuoles in both cells. There was no obvious change in organelle structure in either cell from 2 to 5 d, though there was evidence of an increase in ribosomes and other organelles in the vegetative cell. Gametophytes possessing starch were also present but in relatively low numbers. At 5 d, pollen tubes and grains having structure characteristic of germinating pollen were also encountered. It is concluded that embryogenesis begins after a short period of normal gametophytic differentiation which, during the first 2 d of culture, proceeds at much the same rate as in vivo. Subsequently the rate declines and gametophytic processes gradually come to a halt. Starch formation is suppressed.

Influence of Auxin and Incubation on the Relative Level of Polyribosomes in Excised Soybean Hypocotyl

The influence of incubation and auxin (2,4-D) on polyribosome level in soybean hypocotyl was studied.A marked drop in the relative level of polyribosomes in excised apical or meristematic tissue (0 to 5 millimeters below the cotyledons) occurred during incubation. The addition of auxin to the incubation medium did not affect polyribosome level. A similar decrease in polyribosome level occurred in excised elongating tissue (5 to 15 millimeters below cotyledons) during incubation. Auxin, however, caused a small but highly reproducible stabilization of polyribosomes in this tissue. There was a rapid, but small, auxin-independent increase in polyribosomes of basal or nongrowing hypocotyl (from 20 to 40 millimeters below cotyledons) during incubation, followed by a larger auxin-dependent increase in polyribosomes. While auxin is known to cause an increase in total ribosomes during incubation of the excised basal hypocotyl, the observed transformation from monoribosomes to polyribosomes was not dependent on new ribosome synthesis.Protein synthetic activity (poly U-directed phenylalanine incorporation) of the 80S monoribosomes at low Mg(2+) levels increased during incubation of the excised basal hypocotyl. The increase in ribosome activity was biphasic (an initial auxin-independent phase followed by an auxin-dependent increase in activity) correlating with the biphasic increase in polyribosomes. The enhanced activity of 80S monoribosomes was related, at least in part, to an increase in the level of peptidyl-tRNA associated with the ribosome population. Removal of peptidyl-tRNA from the ribosomes reversed the auxin effect.The hypothesis is advanced that the increase in polyribosomes in response to incubation and to auxin is preceded by and dependent upon the activation of 80S monoribosomes. This activation is in addition to a requirement for continued RNA synthesis, at least in part mRNA, for the transition from monoribosomes to polyribosomes.