scholarly journals Effect of post-ischaemic recovery on albumin synthesis and relative amount of translatable albumin messenger RNA in rat liver

1982 ◽  
Vol 204 (1) ◽  
pp. 197-202 ◽  
Author(s):  
G Cairo ◽  
L Schiaffonati ◽  
M G Aletti ◽  
A Bernelli-Zazzera
Keyword(s):  
Protein Synthesis ◽  
Total Protein ◽  
Messenger Rna ◽  
Relative Proportion ◽  
Liver Homogenate ◽  
Albumin Synthesis ◽  
Specific Proteins ◽  
Membrane Bound ◽  
Albumin Mrna

In liver cells recovering from reversible ischaemia, total protein synthesis by postmitochondrial supernatant and membrane-bound and free polyribosomes is not different from that in sham-operated controls. However, the relative proportion of specific proteins is changed, since the incorporation of [3H]leucine in vivo into liver albumin, relative to incorporation into total protein, as determined by precipitation of labelled albumin with the specific antibody, decreases by 40-50% in post-ischaemic livers. Cell-free synthesis by membrane-bound polyribosomes and poly(A)-enriched RNA isolated from unfractionated liver homogenate shows that the decrease in albumin synthesis in liver of rats recovering from ischaemia is due to the relative decrease in translatable albumin mRNA.

Time course of changes in albumin synthesis and mRNA in diabetic and insulin-treated diabetic rats

1985 ◽  
Vol 248 (6) ◽  
pp. E656-E663 ◽  
Author(s):  
D. E. Peavy ◽  
J. M. Taylor ◽  
L. S. Jefferson
Keyword(s):  
Total Protein ◽  
Time Course ◽  
Insulin Treatment ◽  
Relative Rate ◽  
Cdna Probe ◽  
Diabetic Rats ◽  
Rate Of Change ◽  
Albumin Synthesis ◽  
Albumin Mrna

Albumin synthesis in rat liver in vivo decreased from 12.7 to 2.2% of total protein synthesis during the first 3 days after the induction of diabetes and then remained relatively constant at this depressed rate for another 3 days. Insulin treatment begun on the 3rd day after the induction of diabetes restored albumin synthesis to control values within 3 days. Hybridization of total polyadenylate-containing RNA with a specific albumin cDNA probe revealed a close correspondence between the relative abundance of albumin mRNA and the relative rate of albumin synthesis after induction of diabetes and in response to insulin treatment. The apparent half-life of albumin mRNA, based on the rate of change of the message from one steady-state level to another, was approximately 22 h in both diabetic and insulin-treated diabetic rats. Diabetes of 3-day duration had no effect on the average sizes of total and albumin-synthesizing polysomes or on the ribosomal half-transit time for total protein and albumin. However, the number of albumin-synthesizing polysomes decreased as a result of diabetes to approximately one-third the number found in control livers. Taken together the results indicate that albumin synthesis was regulated by the availability of albumin mRNA and not by alterations in degradation, sequestration, or translation of message.

Synthesis of Albumin with Exogenous Mouse-Liver Messenger RNA in a Homologous Cell-Free System

1974 ◽  
Vol 52 (5) ◽  
pp. 429-432 ◽  
Author(s):  
A. J. Faber ◽  
S. H. Miall ◽  
T. Tamaoki
Keyword(s):  
Protein Synthesis ◽  
Total Protein ◽  
Gel Electrophoresis ◽  
Messenger Rna ◽  
Mouse Liver ◽  
Polyacrylamide Gel Electrophoresis ◽  
Polyacrylamide Gel ◽  
Free System ◽  
Cell Free System ◽  
Membrane Bound

RNA extracted from total and membrane-bound polysomes of mouse liver was capable of directing protein synthesis in a homologous cell-free system in the presence of a 0.5 M KCl ribosomal wash fraction. Analysis of the products by polyacrylamide gel electrophoresis and immunoprecipitation showed that newly formed albumin could account for up to 8% of the total protein synthesized.

scholarly journals Alterations in albumin secretion and total protein synthesis in livers of thyroidectomized rats

1981 ◽  
Vol 198 (2) ◽  
pp. 289-299 ◽  
Author(s):  
D E Peavy ◽  
J M Taylor ◽  
L S Jefferson
Keyword(s):  
Protein Synthesis ◽  
Total Protein ◽  
Rat Hepatocytes ◽  
Secretory Protein ◽  
Secretory Proteins ◽  
Isolated Rat Hepatocytes ◽  
Transit Times ◽  
Free Translation ◽  
Albumin Mrna

Perfused rat livers and isolated rat hepatocytes exhibited a 50% decrease in the secretion of both albumin and total secretory proteins after thyroidectomy. In contrast, synthesis of non-secretory proteins was decreased by only 20% from the rates observed in liver preparations from euthyroid rats. These observations suggested a disproportionate effect of thyroidectomy on the synthesis of secretory proteins compared with non-secretory proteins. Disproportionate decreases in the synthesis of albumin in other endocrine-deficient states such as hypophysectomy and diabetes had previously been shown to be associated with decreases of similar magnitude in the relative abundance of albumin-mRNA sequences. In contrast, thyroidectomy did not affect the activity or amount of albumin mRNA in total liver poly(A)-containing RNA when assayed by cell-free translation and by hybridization with complementary DNA, respectively. Furthermore, labelling experiments in vivo demonstrated that albumin synthesis represented 12.9 +/- 0.5% and 12.4 +/- 0.4% of total protein synthesis in livers of thyroidectomized and euthyroid rats respectively. Therefore the fall in secretion of albumin and total secretory protein after thyroidectomy did not appear to be a reflection of disproportionate decreases in the synthesis of these proteins. Instead, defects in steps involved in the post-synthetic processing and secretion of albumin are suggested. A number of comparisons, including ribosome half-transit times, the size distributions of total and albumin-synthesizing polyribosomes, and the fraction of RNA present as inactive ribosomes, provided evidence that the overall decrease in protein synthesis after thyroidectomy was not due to generalized alterations in translational processes. Instead, the decrease in total protein synthesis appeared to reflect the RNA content of the liver, which fell in proportion to th decrease in protein synthesis.

scholarly journals Protein synthesis in the dendrite

2002 ◽  
Vol 357 (1420) ◽  
pp. 521-529 ◽  
Author(s):  
Shao Jun Tang ◽  
Erin M. Schuman
Keyword(s):  
Protein Synthesis ◽  
Neural Plasticity ◽  
Messenger Rna ◽  
Mrna Translation ◽  
Synaptic Activity ◽  
Synaptic Proteins ◽  
Local Source ◽  
Synaptic Protein ◽  
Specific Proteins ◽  
Molecular Nature

In neurons, many proteins that are involved in the transduction of synaptic activity and the expression of neural plasticity are specifically localized at synapses. How these proteins are targeted is not clearly understood. One mechanism is synaptic protein synthesis. According to this idea, messenger RNA (mRNA) translation from the polyribosomes that are observed at the synaptic regions provides a local source of synaptic proteins. Although an increasing number of mRNA species has been detected in the dendrite, information about the synaptic synthesis of specific proteins in a physiological context is still limited. The physiological function of synaptic synthesis of specific proteins in synaptogenesis and neural plasticity expression remains to be shown. Experiments aimed at understanding the mechanisms and functions f synaptic protein synthesis might provide important information about the molecular nature of neural plasticity.

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.

Aortic perfusion pressure as early determinant of beta-isomyosin expression in perfused hearts

1992 ◽  
Vol 263 (5) ◽  
pp. H1537-H1545
Author(s):  
C. Delcayre ◽  
D. Klug ◽  
V. T. Nguyen ◽  
C. Mouas ◽  
B. Swynghedauw
Keyword(s):  
Protein Synthesis ◽  
Total Protein ◽  
Stress Protein ◽  
Pressure Overload ◽  
Aortic Pressure ◽  
Mechanical Stimulus ◽  
Beating Heart ◽  
Specific Gene ◽  
Coronary Pressure

Pressure overload in vivo induces an increase in cardiac protooncogene and stress protein expression that may initiate the long-term genetic changes observed in hypertrophy. To known whether mechanical stimulus is linked to specific gene transcription, expression of immediate early genes and synthesis of total proteins and myosin heavy chains (MHCs) were studied in beating and KCl-arrested isolated rat hearts perfused for 2 h under various coronary pressures. The main result of this study is that in the beating heart an augmentation of aortic pressure from 60 to 120 mmHg results in a pronounced enhancement of the synthesis of MHC (+59%) and of the expression of the beta-MHC isomyosin mRNA (iso-mRNA; +104%). Also, total protein synthesis and the amounts of poly-(A)+, c-fos, c-myc, and heat-shock protein HSP68 mRNAs were increased. To arrest the heart at 60 mmHg has no effect on total protein synthesis and on the amounts of poly(A)+, alpha-MHC and beta-MHC iso-mRNAs, and mRNAs coding for oncoproteins, but the synthesis of MHC decreased by 24%. By contrast with what we have observed in the beating heart, the augmentation of the coronary pressure in the arrested heart stimulates total protein synthesis and increases the amount of poly(A)+, c-fos, c-myc, and HSP68 mRNAs but has no effect on the expression of both MHC iso-mRNAs. In conclusion, the activation of myosin synthesis by high coronary pressure in this model has mainly a pretranslational origin when the heart is beating.(ABSTRACT TRUNCATED AT 250 WORDS)

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 Studies on the mechanism for entry of vesicular stomatitis virus glycoprotein g mRNA into membrane-bound polyribosome complexes

1977 ◽  
Vol 74 (1) ◽  
pp. 43-57 ◽  
Author(s):  
MJ Grubman ◽  
JA Weinstein ◽  
DA Shafritz
Keyword(s):  
Protein Synthesis ◽  
Vesicular Stomatitis Virus ◽  
Cytosol Fraction ◽  
Initial Event ◽  
Glycoprotein G ◽  
Nonspecific Effects ◽  
Membrane Bound ◽  
Vesicular Stomatitis

Glycoprotein mRNA (G mRNA) of vesicular stomatitis virus is synthesized in the cytosol fraction of infected HeLa cells. Shortly after synthesis, this mRNA associates with 40S ribosomal subunits and subsequently forms 80S monosomes in the cytosol fraction. The bulk of labeled G mRNA is then found in polysomes associated with the membrane, without first appearing in the subunit or monomer pool of the membrane-bound fraction. Inhibition of the initiation of protein synthesis by pactamycin or muconomycin A blocks entry of newly synthesized G m RNA into membrane-bound polysomes. Under these circumstances, labeled G mRNA accumulates into the cytosol. Inhibition of the elongation of protein synthesis by cucloheximide, however, allows entry of 60 percent of newly synthesized G mRNA into membrane-bound polysomes. Furthermore, prelabeled G mRNA associated with membrane-bound polysomes is released from the membrane fraction in vivo by pactamycin or mucomycon A and in vitro by 1mM puromycin - 0.5 M KCI. This release is not due to nonspecific effects of the drugs. These results demonstrate that association of G mRNA with membrane-bound polysomes is dependent upon polysome formation and initiation of protein synthesis. Therefore, direct association of the 3' end of G mRNA with the membrane does not appear to be the initial event in the formation of membrane-bound polysomes.

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