scholarly journals Initiation factors in protein synthesis by free and membrane-bound polyribosomes of liver and hepatoma

1975 ◽  
Vol 152 (1) ◽  
pp. 143-151 ◽  
Author(s):  
C N Murty ◽  
E Verney ◽  
H Sidransky
Keyword(s):  
Protein Synthesis ◽  
Initiation Factors ◽  
Ionic Detergent ◽  
Membrane Bound ◽  
Triton X ◽  
Stimulation Of

The activity of initiation factors obtained from free and membrane-bound polyribosomes of liver and of transplantable H5123 hepatoma of rats was investigated by using an assay of protein synthesis in vitro in which poly (U)-directed polyphenylalanine synthesis was measured. Initiation factors of membrane-bound polyribosomes prepared by using the anionic detergent deoxycholate exhibited less activity in incorporating [14C]phenylalanyltRNA into polypetides than did initiation factors of free polyribosomes. However, when membrane-bound polyribosomes were prepared after using the non-ionic detergent Triton X-100, no significant differences in activities in polyphenylalanine synthesis were observed between the initiation factors of free and membrane-bound polyribosomes. These results suggest that Triton X-100 is preferable to deoxycholate in the isolation of of initiation factors from polyribosomes. Initiation factors, prepared by using Triton X-100, of free polyribosomes of hepatoma exhibited greater activity in the stimulation of polyphenylalanine synthesis than did the initiation factors of free or membrane-bound polyribosomes of host livers or of membrane-bound polyribosomes of hepatomas.

EFFECT OF ACTINOMYCIN D ON TSH-INDUCED STIMULATION OF THYROIDAL PROTEIN SYNTHESIS IN THE RAT

1974 ◽  
Vol 77 (1) ◽  
pp. 64-70 ◽  
Author(s):  
Gustav Wägar
Keyword(s):  
Protein Synthesis ◽  
Actinomycin D ◽  
The Other ◽  
Leucine Incorporation ◽  
Short Term ◽  
Other Hand ◽  
Thyroid Glands ◽  
Translational Level ◽  
Stimulation Of

ABSTRACT Whether the short-term regulation of thyroidal protein synthesis by TSH occurs at the transcriptional or the translational level was tested by measuring the effect of actinomycin D (act D) on the TSH-induced stimulation of L-14C-leucine incorporation into the thyroidal proteins of rats. TSH was injected 6 h before the rats were killed. The thyroid glands were then removed and incubated in vitro in the presence of L-14C-leucine for 2 h. The pronounced stimulation of leucine incorporation in the TSH-treated animals was depressed as compared with controls but still significant even when the animals had been pre-treated with 100 μg act D 24 and 7 h before sacrifice. On the other hand, act D strongly decreased incorporation of 3H-uridine into RNA. Short-term regulation of thyroidal protein synthesis by TSH appears to be partly but not wholly dependent on neosynthesis of RNA. Hence regulation may partly occur at the translation level of protein synthesis.

scholarly journals Differences in size, structure and function of free and membrane-bound polyribosomes of rat liver. Evidence for a single class of membrane-bound polyribosomes

1977 ◽  
Vol 168 (1) ◽  
pp. 1-8 ◽  
Author(s):  
J C Ramsey ◽  
W J Steele
Keyword(s):  
Protein Synthesis ◽  
Rat Liver ◽  
Size Structure ◽  
Large Fraction ◽  
Liver Homogenate ◽  
Structure And Function ◽  
Structural And Functional Properties ◽  
Membrane Bound ◽  
And Function

Free loosely bound and tightly bound polyribosomes were separated from rat liver homogenate by salt extraction followed by differential centrifugation, and several of their structural and functional properties were compared to resolve the existence of loosely bound polyribosomes and verify the specificity of the separation. The free and loosely bound polyribosomes have similar sedimentation profiles and polyribosome contents, their subunit proteins have similar electrophoretic patterns and their products of protein synthesis in vitro show a close correspondence in size and amounts synthesized. In contrast, the tightly bound polyribosomes have different properties from those of the free and loosely bound polyribosomes; their average size is significantly smaller; their polyribosome content is higher; their 60 S-subunit proteins lack two components and contain four or more components not found elsewhere; their products of protein synthesis in vitro differ in size and amounts synthesized. These observations show that rat liver membranes entrap a large fraction of the free polyribosomes at low salt concentrations and that these polyribosomes are similar to those of the free-polyribosome fraction and are different from those of the tightly bound polyribosome fraction in size, structure and function.

EGF promotes gastric mucosal restitution by activating Na+/H+exchange of epithelial cells

2002 ◽  
Vol 282 (5) ◽  
pp. G866-G876 ◽  
Author(s):  
Akinori Yanaka ◽  
Hideo Suzuki ◽  
Takeshi Shibahara ◽  
Hirofumi Matsui ◽  
Akira Nakahara ◽  
...  
Keyword(s):  
Electrical Resistance ◽  
Egf Receptor ◽  
Mucous Cells ◽  
Egf Receptors ◽  
Intracellular Acidosis ◽  
Receptor Antibody ◽  
Epidermal Growth ◽  
Triton X ◽  
Stimulation Of

This study was conducted to determine whether the contributions of epidermal growth factor (EGF) to gastric mucosal restitution after injury are mediated by stimulation of Na+/H+exchangers in surface mucous cells (SMC). Intact sheets of guinea pig gastric mucosae were incubated in vitro. Intracellular pH (pHi) in SMC was measured fluorometrically, using 2′,7′- bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein. Restitution after Triton X-100-induced injury was evaluated by recovery of electrical resistance. At neutral luminal pH, exogenous EGF (ex-EGF) increased pHiand enhanced restitution in the absence but not in the presence of serosal HCO[Formula: see text]. During exposure to luminal acid, ex-EGF not only prevented intracellular acidosis but also promoted restitution. These effects of ex-EGF were blocked by serosal amiloride or anti-EGF-receptor antibody. In the absence of ex-EGF, restitution was inhibited by replacement of luminal and serosal solutions with fresh solutions and was blocked more completely by serosal anti-EGF-receptor antibody. These results suggest that both endogenous and ex-EGF contribute to restitution via basolateral EGF receptors, with effects mediated, at least in part, by stimulation of basolateral Na+/H+exchangers.

scholarly journals Biotin-mediated protein biosynthesis

1974 ◽  
Vol 140 (3) ◽  
pp. 549-556 ◽  
Author(s):  
R. L. Boeckx ◽  
K. Dakshinamurti
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Rat Liver ◽  
Intestinal Mucosa ◽  
Protein Biosynthesis ◽  
Amino Acid Incorporation ◽  
Acid Incorporation ◽  
Stimulation Of

The effect of administration of biotin to biotin-deficient rats on protein biosynthesis was studied. Biotin treatment resulted in stimulation by more than twofold of amino acid incorporation into protein, both in vivo and in vitro in rat liver, pancreas, intestinal mucosa and skin. Analysis of the products of amino acid incorporation into liver proteins in vivo and in vitro indicated that the synthesis of some proteins was stimulated more than twofold, but others were not stimulated at all. This indicates a specificity in the stimulation of protein synthesis mediated by biotin.

Proteins synthesized by rabbit reticulocyte membrane-bound ribosomes

1982 ◽  
Vol 60 (5) ◽  
pp. 580-585 ◽  
Author(s):  
Réal Lemieux ◽  
Claude Godin
Keyword(s):  
Protein Synthesis ◽  
Ionic Strength ◽  
Messenger Rna ◽  
Rna Degradation ◽  
Main Protein ◽  
Membrane Bound ◽  
Phenol Treatment

Rabbit reticulocyte membrane-bound ribosomes liberated by deoxycholate treatment contain degraded forms of ribosomal and messenger RNA. This degradation occurs after the liberation of the ribosomes from the membranes by the detergent because intact ribosomal and messenger RNA can be extracted from washed membranes by phenol treatment. Increasing the ionic strength of the detergent buffer prevents this RNA degradation and allows the recovery of membrane-bound ribosomes capable of protein synthesis. Comparison of the proteins synthesized in vitro by the polyribosomes shows that the main protein produced by both free and membrane-bound ribosomes is globin. However, the two types of polyribosomes could be distinguished by the nonglobin proteins they produce.

scholarly journals Stimulation of Toll-like receptor 3 and 4 induces interleukin-1β maturation by caspase-8

2008 ◽  
Vol 205 (9) ◽  
pp. 1967-1973 ◽  
Author(s):  
Jonathan Maelfait ◽  
Elisabeth Vercammen ◽  
Sophie Janssens ◽  
Peter Schotte ◽  
Mira Haegman ◽  
...  
Keyword(s):  
Active Form ◽  
Biologically Active ◽  
Poly I:C ◽  
Caspase 8 ◽  
Caspase 1 ◽  
Polyinosinic:Polycytidylic Acid ◽  
Membrane Bound ◽  
Acute And Chronic Inflammation ◽  
Stimulation Of

The cytokine interleukin (IL)-1β is a key mediator of the inflammatory response and has been implicated in the pathophysiology of acute and chronic inflammation. IL-1β is synthesized in response to many stimuli as an inactive pro–IL-1β precursor protein that is further processed by caspase-1 into mature IL-1β, which is the secreted biologically active form of the cytokine. Although stimulation of membrane-bound Toll-like receptors (TLRs) up-regulates pro–IL-1β expression, activation of caspase-1 is believed to be mainly initiated by cytosolic Nod-like receptors. In this study, we show that polyinosinic:polycytidylic acid (poly[I:C]) and lipopolysaccharide stimulation of macrophages induces pro–IL-1β processing via a Toll/IL-1R domain–containing adaptor-inducing interferon-β–dependent signaling pathway that is initiated by TLR3 and TLR4, respectively. Ribonucleic acid interference (RNAi)–mediated knockdown of the intracellular receptors NALP3 or MDA5 did not affect poly(I:C)-induced pro–IL-1β processing. Surprisingly, poly(I:C)- and LPS-induced pro–IL-1β processing still occurred in caspase-1–deficient cells. In contrast, pro–IL-1β processing was inhibited by caspase-8 peptide inhibitors, CrmA or vFLIP expression, and caspase-8 knockdown via RNAi, indicating an essential role for caspase-8. Moreover, recombinant caspase-8 was able to cleave pro–IL-1β in vitro at exactly the same site as caspase-1. These results implicate a novel role for caspase-8 in the production of biologically active IL-1β in response to TLR3 and TLR4 stimulation.

The stimulation of sodium transport by aldosterone

1971 ◽  
Vol 262 (842) ◽  
pp. 323-332 ◽  
Keyword(s):  
Protein Synthesis ◽  
Active Transport ◽  
Sodium Transport ◽  
Apical Plasma Membrane ◽  
Transport Pathway ◽  
Receptor Sites ◽  
Rna And Protein Synthesis ◽  
Inhibitor Of Protein Synthesis ◽  
Stimulation Of

Aldosterone, the major sodium retaining hormone in man, will stimulate active transport of sodium across the urinary bladder of the toad, Bufo marinus in vitro , at physiological concentrations of the hormone.The in vitro action of aldosterone is mimicked by steroid hormones with known mineralocorticoid properties and it is competitively inhibited by other analogues, e.g. spironolactone and cortisone. Aldosterone is bound to physiological receptor sites within the transporting epithelial cells, chiefly within the nuclei, and is displaced from these binding sites specifically by structural analogues including other mineralocorticoids. Effects of aldosterone are dependent upon availability of metabolizable substrates to support the active transport of sodium. Although the stimulation of sodium transport by aldosterone can be specifically inhibited by actinomycin D, an inhibitor of RNA synthesis, and by puromycin, an inhibitor of protein synthesis, direct evidence of stimulation of new RNA and protein synthesis during the latent period with physiological concentrations of aldosterone is still lacking. It is possible, however, that the amounts of RNA and protein that are involved are too small to be detected by available techniques. Evidence is summarized which leads us to conclude that the increased sodium transport induced by aldosterone is the consequence of a reduced resistance of the apical plasma membrane of the transporting epithelia to the entry of sodium into the transport pathway.

scholarly journals Stimulation of collagen galactosyltransferase and glucosyltransferase activities by lysophosphatidylcholine

1976 ◽  
Vol 160 (1) ◽  
pp. 29-35 ◽  
Author(s):  
H Anttinen
Keyword(s):  
Chick Embryo ◽  
High Speed ◽  
Membrane Structures ◽  
Embryo Extract ◽  
Chick Embryo Extract ◽  
Triton X ◽  
Regulatory Significance ◽  
Stimulation Of

Lysophosphatidylcholine stimulated the activities of collagen galactosyl- and glucosyl-transferases in chick-embryo extract and its particulate fractions in vitro, whereas essentially no stimulation was noted in the high-speed supernatant, where the enzymes are soluble and membrane-free. The stimulatory effect of lysophosphatidylcholine was masked by 0.1% Triton X-100. In kinetic experiments lysophosphatidylcholine raised the maximum velocities with respect to the substrates and co-substrates, whereas no changes were observed in the apparant Km values. Phospholipase A preincubation of the chick-embryo extract resulted in stimulation of both transferase activities, probably gy generating lysophosphatides from endogenous phospholipids. No stimulation by lysophosphatidylcholine was found when tested with 500-fold-purified glycosyltransferase. The results suggest that collagen glycosyltransferases must be associated with the membrane structures of the cell in order to be stimulated by lysophosphatidylcholine. Lysophosphatidylcholine could have some regulatory significance in vivo, since its concentration in the cell is comparable with that which produced marked stimulation in vitro.

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