scholarly journals Ribonucleic acid stimulation of mammalian liver nuclear-envelope nucleoside triphosphatase. A possible enzymic marker for the nuclear envelope

1977 ◽  
Vol 162 (3) ◽  
pp. 671-679 ◽  
Author(s):  
P S Agutter ◽  
J R Harris ◽  
I Stevenson
Keyword(s):  
Nuclear Envelope ◽  
Specific Activity ◽  
Assay Medium ◽  
Exogenous Rna ◽  
Mammalian Liver ◽  
High Concentrations ◽  
Enzymic Marker ◽  
Stimulation Of ◽  
Nucleoside Triphosphatase

1. The specific activity of rat and pig liver nuclear-envelope nucleoside triphosphatase (EC 3.6.1.3) decreases when the system is depleted of RNA. The activity can be restored by adding high concentrations of yeast RNA to the assay medium. 2. Exogenous RNA also increases the activity of the enzyme in control envelopes (not RNA-depleted). The effect appears to be largely specific for poly(A) and poly(G); it is not stimulated by rRNA or tRNA preparations, ribonuclease-hydrolysed RNA, AMP, or double- or single-stranded DNA. 3. Inhibitors of the enzyme, in concentrations at which half-maximal inhibition of the enzyme is achieved, do not affect the percentage stimulation of the enzyme by yeast RNA. 4. The simulation is abolished by the inclusion of 150 mM-KCl or -NaCl in the assay medium, but not by increasing the assay pH to 8.5. 5. The results are discussed in the light of the possible role of the nucleoside triphosphatase in vivo in nucleo-cytoplasmic ribonucleoprotein translocation. 6. It is proposed that poly(G)-stimulated Mg2+-activated adenosine triphosphatase activity should be adopted as an enzymic marker for the nuclear envelope.

scholarly journals Inhibition of ribonucleic acid efflux from isolated SV40-3T3 cell nuclei by 3′-deoxyadenosine (cordycepin)

1979 ◽  
Vol 180 (2) ◽  
pp. 371-378 ◽  
Author(s):  
P S Agutter ◽  
B McCaldin
Keyword(s):  
Nuclear Envelope ◽  
Ribonucleic Acid ◽  
Actinomycin D ◽  
Cell Nuclei ◽  
Maximal Inhibition ◽  
Degree Of Protection ◽  
Substantial Degree ◽  
Stimulation Of ◽  
Nucleoside Triphosphatase

The effect of 3′-deoxyadenosine (cordycepin) on mRNA efflux from isolated SV40-3T3 cell nuclei has been studied and compared with its effect on the nucleoside triphosphatase activity in the isolated nuclear envelope. Inhibition of mRNA efflux occurs rapidly, but is dependent on the presence of ATP. Half-maximal inhibition occurs with 40 microM-cordycepin. The effect is not simulated by 2′-deoxyadenosine or by actinomycin D, and adenosine provides a substantial degree of protection against it. Cordycepin does not directly inhibit the nucleoside triphosphatase. The stimulation of this enzyme by poly(A) is not affected unless the poly(A) and cordycepin are incubated together with nuclear lysate in the presence of ATP; in this case the stimulation is significantly reduced. Possible interpretations of these results and their relevance for understanding the system in vivo for nucleo-cytoplasmic messenger transport are discussed.

Stimulation of transport of alpha-aminoisobutyric acid into the testes of immature mice in vivo by follicle-stimulating hormone

1982 ◽  
Vol 100 (1) ◽  
pp. 137-142
Author(s):  
Nila Oza ◽  
Sarah J. Meanock ◽  
A. G. Davies
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Specific Activity ◽  
Follicle Stimulating Hormone ◽  
Acid Transport ◽  
Aminoisobutyric Acid ◽  
Old Mice ◽  
Stimulation Of

Abstract. Groups of immature mice were injected sc with radiocarbon-labelled alpha-aminoisobutyric acid (AIB) after being given a single sc injection of hFSH or of 0.9% saline. As an index of the transport of AIB, the specific activity of isotope was measured in homogenates of testis and of liver. FSH treatment caused statistically significant increases in the specific activity of isotope in the testes and in the ratio of testicular to liver specific activity. The effect was greatest in 9-day-old mice injected with FSH 16 h before removal of the testes. Uptake of labelled AIB was not stimulated after administration of hCG or testosterone. Doses of cycloheximide sufficient to reduce the rate of protein synthesis by over 99% did not impair testicular uptake of labelled AIB or the influence of FSH on AIB uptake. These results suggest that FSH stimulates amino acid transport into cells of the immature testis and that this action is independent of the stimulatory effect of FSH on testicular protein synthesis.

scholarly journals The formation, distribution and function of ribosomes and microsomal membranes during induced amphibian metamorphosis

1967 ◽  
Vol 105 (2) ◽  
pp. 783-801 ◽  
Author(s):  
J. R. Tata
Keyword(s):  
Endoplasmic Reticulum ◽  
Ribosomal Proteins ◽  
Specific Activity ◽  
Tail Length ◽  
Similar Response ◽  
Carbamoyl Phosphate ◽  
Microsomal Membranes ◽  
Stimulation Of ◽  
Induction Of Metamorphosis

1. A lag period of about 4 days preceded the onset of metamorphosis precociously induced by tri-iodothyronine in tadpoles of the giant American bullfrog (Rana catesbeiana). It was established by the accelerated synthesis or induction of carbamoyl phosphate synthetase and cytochrome oxidase in the liver, serum albumin and adult haemoglobin in the blood, acid phosphatase in the tail, and the increase in the hindleg/tail length ratio. 2. A 4- to 6-fold stimulation, 2 days after the induction of metamorphosis, of the rate of synthesis of rapidly labelled nuclear RNA in liver cells was followed by an increasing amount of RNA appearing in the cytoplasm. Most of the newly formed RNA on induction of metamorphosis was of the ribosomal type. An accelerated turnover at early stages of development preceded a net accumulation of RNA in the cytoplasm, with no change in the amount of DNA per liver. 3. Most hepatic ribosomes of the pre-metamorphic tadpoles were present as 78s monomers and 100s dimers; metamorphosis caused a shift towards larger polysomal aggregates with newly formed ribosomes that were relatively more tightly bound to membranes of the endoplasmic reticulum. 4. The appearance of new polyribosomes in the cytoplasm on induction of metamorphosis was co-ordinated in time with a stimulation of synthesis of phospholipids of the smooth and rough endoplasmic reticulum, followed by a gradual shift in preponderance from the smooth to the rough type of microsomal membranes. 5. Electron- and optical-microscopic examination of intact hepatocytes revealed a striking change in the distribution and nature of ribosomes and microsomal membranes during metamorphosis. 6. Ribosomes prepared from non-metamorphosing and metamorphosing animals were identical in their sedimentation coefficients and in the structural ribosomal proteins. The base composition and sedimentation coefficients of ribosomal RNA were also identical. Induction of metamorphosis also did not alter the incorporation of 32P into the different phospholipid constituents of microsomal membranes. 7. Nascent 14C-labelled protein with the highest specific activity was recovered in the ‘heavy’ rough membrane fraction of microsomes, whereas little 14C was associated with ‘free’ polysomes. Protein synthesis in vivo was most markedly stimulated during metamorphosis in the tightly membrane-bound ribosomal fraction after the appearance of new ribosomes. 8. The rate of synthesis of macromolecules in vivo could not be followed beyond 7–8 days after induction because of variable shifts in precursor pools due to regression of larval tissues. 9. The stimulation of RNA and ribosome formation was specifically associated with the process of metamorphosis since no similar response to thyroid hormones occurred in those species (Axolotl and Necturus) in which the hormones failed to induce metamorphosis.

Mechanisms of Pi regulation of the skeletal muscle SR Ca2+ release channel

2000 ◽  
Vol 278 (3) ◽  
pp. C601-C611 ◽  
Author(s):  
Edward M. Balog ◽  
Bradley R. Fruen ◽  
Patricia K. Kane ◽  
Charles F. Louis
Keyword(s):  
Skeletal Muscle ◽  
Single Channel ◽  
Adenine Nucleotides ◽  
Muscle Fibers ◽  
Open Probability ◽  
Release Channel ◽  
High Concentrations ◽  
Channel Open Time ◽  
Stimulation Of

Inorganic phosphate (Pi) accumulates in the fibers of actively working muscle where it acts at various sites to modulate contraction. To characterize the role of Pi as a regulator of the sarcoplasmic reticulum (SR) calcium (Ca2+) release channel, we examined the action of Pi on purified SR Ca2+ release channels, isolated SR vesicles, and skinned skeletal muscle fibers. In single channel studies, addition of Pi to the cis chamber increased single channel open probability ( P o; 0.079 ± 0.020 in 0 Pi, 0.157 ± 0.034 in 20 mM Pi) by decreasing mean channel closed time; mean channel open times were unaffected. In contrast, the ATP analog, β,γ-methyleneadenosine 5′-triphosphate (AMP-PCP), enhanced P o by increasing single channel open time and decreasing channel closed time. Pi stimulation of [3H]ryanodine binding by SR vesicles was similar at all concentrations of AMP-PCP, suggesting Pi and adenine nucleotides act via independent sites. In skinned muscle fibers, 40 mM Pi enhanced Ca2+-induced Ca2+ release, suggesting an in situ stimulation of the release channel by high concentrations of Pi. Our results support the hypothesis that Pi may be an important endogenous modulator of the skeletal muscle SR Ca2+ release channel under fatiguing conditions in vivo, acting via a mechanism distinct from adenine nucleotides.

scholarly journals Differential regulation of Igf1 and Igf2 mRNA levels in tilapia hepatocytes: effects of insulin and cortisol on GH sensitivity

2011 ◽  
Vol 211 (2) ◽  
pp. 201-210 ◽  
Author(s):  
Andrew L Pierce ◽  
Jason P Breves ◽  
Shunsuke Moriyama ◽  
Tetsuya Hirano ◽  
E Gordon Grau
Keyword(s):  
Growth And Development ◽  
Mrna Level ◽  
Differential Regulation ◽  
Postnatal Life ◽  
Mrna Levels ◽  
Primary Cultured Hepatocytes ◽  
Mammalian Liver ◽  
Growth Promoting ◽  
Stimulation Of

Igf1 and Igf2 stimulate growth and development of vertebrates. In mammals, liver-derived endocrine Igf1 mediates the growth promoting effects of GH during postnatal life, whereas Igf2 stimulates placental and fetal growth and is not regulated by GH. Insulin enhances Igf1 production by the mammalian liver directly, and by increasing hepatocyte sensitivity to GH. We examined the regulation ofigf1andigf2mRNA levels by GH, insulin, and cortisol, and the effects of insulin and cortisol on GH sensitivity in primary cultured hepatocytes of tilapia, a cichlid teleost. GH increased mRNA levels of bothigf1andigf2in a concentration-related and biphasic manner over the physiological range, with a greater effect onigf2mRNA level. Insulin increased basaligf2mRNA level, and strongly increased GH-stimulatedigf2mRNA level, but slightly reduced basaligf1mRNA level and did not affect GH-stimulatedigf1mRNA level. Cortisol inhibited GH stimulation ofigf1, but increased GH stimulation ofigf2mRNA level. The synergistic effect of insulin and GH onigf2mRNA level was confirmedin vivo. These results indicate that insulin and cortisol differentially modulate the response ofigf1andigf2mRNA to GH in tilapia hepatocytes, and suggest that the regulation of liver Igf2 production differs between fish and mammals. Regulation of liver Igf2 production in fish appears to be similar to regulation of liver Igf1 production in mammals.

Instability of Mammalian Liver Nuclear-Envelope Nucleoside Triphosphatase

1978 ◽  
Vol 6 (6) ◽  
pp. 1174-1177 ◽  
Author(s):  
ELIZABETH R. PORTEOUS ◽  
SARAH A. JAMIESON ◽  
PAUL S. AGUTTER
Keyword(s):  
Nuclear Envelope ◽  
Mammalian Liver ◽  
Nucleoside Triphosphatase

Extreme hyperinsulinemia unmasks insulin’s effect to stimulate protein synthesis in the human forearm

1998 ◽  
Vol 274 (6) ◽  
pp. E1067-E1074 ◽  
Author(s):  
Teresa A. Hillier ◽  
David A. Fryburg ◽  
Linda A. Jahn ◽  
Eugene J. Barrett
Keyword(s):  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
In Vivo Studies ◽  
Skeletal Muscle Protein ◽  
High Concentrations ◽  
Arterial Plasma ◽  
Stimulation Of

Insulin clearly stimulates skeletal muscle protein synthesis in vitro. Surprisingly, this effect has been difficult to reproduce in vivo. As in vitro studies have typically used much higher insulin concentrations than in vivo studies, we examined whether these concentration differences could explain the discrepancy between in vitro and in vivo observations. In 14 healthy volunteers, we raised forearm insulin concentrations 1,000-fold above basal levels while maintaining euglycemia for 4 h. Amino acids (AA) were given to either maintain basal arterial ( n = 4) or venous plasma ( n = 6) AA or increment arterial plasma AA by 100% ( n = 4) in the forearm. We measured forearm muscle glucose, lactate, oxygen, phenylalanine balance, and [3H]phenylalanine kinetics at baseline and at 4 h of insulin infusion. Extreme hyperinsulinemia strongly reversed postabsorptive muscle’s phenylalanine balance from a net release to an uptake ( P < 0.001). This marked anabolic effect resulted from a dramatic stimulation of protein synthesis ( P < 0.01) and a modest decline in protein degradation. Furthermore, this effect was seen even when basal arterial or venous aminoacidemia was maintained. With marked hyperinsulinemia, protein synthesis increased further when plasma AA concentrations were also increased ( P< 0.05). Forearm blood flow rose at least twofold with the combined insulin and AA infusion ( P< 0.01), and this was consistent in all groups. These results demonstrate an effect of high concentrations of insulin to markedly stimulate muscle protein synthesis in vivo in adults, even when AA concentrations are not increased. This is similar to prior in vitro reports but distinct from physiological hyperinsulinemia in vivo where stimulation of protein synthesis does not occur. Therefore, the current findings suggest that the differences in insulin concentrations used in prior studies may largely explain the previously reported discrepancy between insulin action on protein synthesis in adult muscle in vivo vs. in vitro.

scholarly journals Importance of mammalian nuclear-envelope nucleoside triphosphatase in nucleo-cytoplasmic transport of ribonucleoproteins

1979 ◽  
Vol 182 (3) ◽  
pp. 811-819 ◽  
Author(s):  
P S Agutter ◽  
B McCaldin ◽  
H J McArdle
Keyword(s):  
Ionic Strength ◽  
Substrate Specificity ◽  
Nuclear Envelope ◽  
Nucleoside Triphosphate ◽  
Rna Transport ◽  
Isolated Nuclei ◽  
Cytoplasmic Rna ◽  
Cytoplasmic Transport ◽  
Nucleoside Triphosphatase

The nucleoside triphosphate-stimulated efflux of RNA from isolated nuclei was studied under a range of conditions, and the effects of these conditions on the process were compared with the properties of the nucleoside triphosphatase located in the pore complex. A marked similarity between the rate of efflux and the rate of nucleoside triphosphate hydrolysis was apparent, in terms of substrate specificity, sensitivity to treatment with insolubilized trypsin, kinetics and the effects of increased ionic strength and of many inhibitors. These results are taken, in view of earlier evidence, to suggest that the activity of the nucleoside triphosphatase is a prerequisite for nucleo-cytoplasmic RNA transport in vivo. There are some indications that the nuclear-envelope lipid is also involved in regulating the efflux process.

DIFFERENTIAL STIMULATION BY PARATHYROID HORMONE OF BONE AND KIDNEY RIBONUCLEIC ACID SYNTHESIS

1971 ◽  
Vol 49 (3) ◽  
pp. 493-506 ◽  
Author(s):  
J. STEINBERG ◽  
G. NICHOLS
Keyword(s):  
Parathyroid Hormone ◽  
Specific Activity ◽  
Acid Synthesis ◽  
Hormonal Stimulation ◽  
Precursor Pool ◽  
Hormonal Effect ◽  
Parathyroid Extract ◽  
Apparent Shift ◽  
Stimulation Of

SUMMARY The effects of parathyroid extract (PTE) on the synthesis in vivo of free nucleotide and RNA were compared in rat metaphysial bone and kidney. The incorporation of 32P into chromatographically pure acid-soluble 5′-AMP and purified bulk RNA was examined at various times after PTE administration. Pulse-labelled RNA was further characterized by sedimentation in sucrose density gradients and by ribomononucleotide analysis. In both organs the labelling of 5′-AMP and its turnover were accelerated after administration of the hormone. The pool size of free AMP of kidney was approximately 3 times that of bone; neither was affected by PTE. The specific activity of pulse-labelled kidney AMP was always greater, and hormonal stimulation of its labelling was more rapid than in bone. Despite more extensive precursor labelling, the stimulation of renal RNA synthesis was negligible, and was delayed for several hours, the overall hormonal effect being inseparable from its effect on phosphate entry into the nucleotide precursor pool. In bone, the hormonal stimulation of RNA labelling was immediate, and continued to increase at a linear rate for up to 12 h. Initially, stimulation of RNA polymerization accounted for the total hormonal effect, while after 4 h an increasing proportion of the total increase in RNA labelling was attributable to enhanced precursor labelling. Newly synthesized bone RNA differed qualitatively from kidney RNA in its sedimentation properties and composition. Although the labelling of all RNA species and RNA-nucleotides in bone was stimulated by PTE, there was a proportionately greater effect on the labelling of ribosomal RNA, and an apparent shift towards GMP-rich molecules, neither change being manifest in kidney. It is concluded that while bone and kidney share certain mechanisms, they show changes in RNA biosynthesis in response to parathyroid hormone which are both quantitatively and qualitatively different and which are in accord with the RNA requirements for the respective physiological response of each.

scholarly journals Breakdown of phosphatidylinositol provoked by muscarinic cholinergic stimulation of rat parotid-gland fragments

1974 ◽  
Vol 142 (3) ◽  
pp. 583-590 ◽  
Author(s):  
Lynne M. Jones ◽  
Robert H. Michell
Keyword(s):  
Lipid Metabolism ◽  
Cholinergic Stimulation ◽  
Muscarinic Cholinergic Receptors ◽  
The Past ◽  
Rat Parotid Gland ◽  
Muscarinic Cholinergic ◽  
High Concentrations ◽  
Rat Parotid ◽  
Stimulation Of

When rat parotid fragments that had been labelled with32P in vivo were exposed to high concentrations of acetylcholine, radioactivity was lost from phosphatidylinositol but not from other phospholipids. Simultaneously the concentration of phosphatidylinositol in the tissue decreased. If previously unlabelled tissue was incubated with32Pi an increase in incorporation of radioactivity into phosphatidylinositol was observed during this decrease in concentration. The effects of acetylcholine were blocked by atropine, but not by tubocurarine. The response to acetylcholine was rapid, with up to one-third of the tissue's phosphatidylinositol disappearing within 5min. Similar effects were evoked by stimulation with methacholine and by high concentrations of tetramethylammonium ion; these responses were also atropine-sensitive and tubocurarine-insensitive. It is concluded that the event in inositol lipid metabolism that is affected by acetylcholine stimulation is removal of the phosphorylinositol group from the molecule; this is mediated through muscarinic cholinergic receptors. This is followed by a compensatory increase in the rate of synthesis of phosphatidylinositol, which has been described in detail in the past. These observations are compared with those of previous workers and are discussed in relation to the existing hypotheses relating to the significance of stimulus-provoked phosphatidylinositol turnover.

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