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D E Rannels

Publications and source records attributed to D E Rannels.

At least 91 records · Page 5Linked to original sources
PubMed1984

Effect of age on the accumulation of lung protein following unilateral pneumonectomy in rats.

The effects of unilateral pneumonectomy (PNX) on the net synthesis of right lung protein were investigated in vivo using three groups of rats with body weights (BW) ranging from 85 to 330 g. These data were compared to those from sham-operated and normal growing control animals. After PNX, both the 2-day lag prior to the compensatory increase in right lung mass (LW) and the subsequent rate of increase in LW and LW/BW ratio were independent of two-fold differences in the basal rate of lung growth. In all PNX groups, both right LW and LW/BW reached control values for both lungs, but in the older rats the time required for complete compensation was extended from 5 days to 12 days. The rate of net accumulation of right lung protein increased two-fold in the youngest PNX rats and 6 to 8-fold in the older animals, but when these changes were normalized to the protein content of the remaining tissue, the older rats appeared to respond to PNX less efficiently. Increased tissue levels of RNA and the resulting increased capacity of the lungs for protein synthesis could account for the accelerated rate of gain in right lung protein following PNX in both adult and young animals.

Aging↗
PubMed1983

Reversible inhibition of protein synthesis in lung by halothane.

Alterations in the synthesis and degradation of proteins were investigated in intact lungs exposed to the volatile anaesthetic halothane. In rat lungs perfused in situ with Krebs-Henseleit bicarbonate buffer containing 4.5% (w/v) bovine serum albumin, 5.6 mM-glucose, plasma concentrations of 19 amino acids and 690 microM-[U-14C]-phenylalanine and equilibrated with O2/N2/CO2 (4:15:1), protein synthesis, calculated based on the specific radioactivity of aminoacyl-tRNA, was inhibited by halothane. The anaesthetic did not affect degradation of lung proteins. The inhibition of protein synthesis was rapid in onset, dose-dependent, and quickly reversible. It did not appear to be associated with overall energy depletion, with non-specific changes in cellular permeability, or with decreased availability of amino acids as substrates for protein synthesis.

Adenosine Triphosphate↗
PubMed1983

Identification of specific proteins synthesized by type II pneumocytes in primary culture.

Proteins from primary cultures of type II granular pneumocytes have been examined by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis to identify type II cell-specific proteins. The distribution of Coomassie Blue-stained bands in preparations of cellular proteins, culture medium, lavage and lamellar bodies have been compared. The most prominent stained band in the serum-free medium from type II cell cultures (HS1; Mr 39900) corresponds to a major protein in acellular sedimentable (20000 g for 30 min) crude surfactant obtained from rat lungs by saline (0.9% NaCl) lavage. A second protein (HS2; Mr 12000) is also found both in type II cell-conditioned medium and in lavage. Neither rat serum nor donor calf serum (used in the isolation of the type II cells) contains a protein co-migrating with HS1 or HS2 proteins. HS1 is also found in Coomassie Blue-stained gels of cellular proteins and of lamellar bodies isolated from whole lungs. Cultures of type II cells incorporate [14C]phenylalanine into HS1 and HS2 as shown by autoradiography of sodium dodecyl sulphate/polyacrylamide gels of culture medium. Rat lungs perfused in situ incorporate [35S]methionine into HS1 in the lamellar body fraction. A third protein (HS3; Mr 47000) is observed only in autoradiographs of cell culture medium; no corresponding Coomassie Blue-stained band can be identified in medium, in cells or in lung lavage. No protein bands corresponding to HS1, HS2 or HS3 are found in conditioned media from pulmonary alveolar macrophages, rat fibroblasts or bovine aorta endothelial cells. Two-dimensional gel electrophoresis of HS1 shows a single polypeptide with an isoelectric point of 6.3; HS3 appears as a chain of spots with a range of isoelectric points from 6.3 to 6.6. HS2 has not been identified on two-dimensional gels. The amino acid composition of HS1 does not differ significantly from that of surfactant apoproteins studied previously; however, HS1 is not detected by glycoprotein stains, nor does it appear to be a subunit of a thiol-linked multimer.

Animals↗
PubMed1983

Effect of halothane on metabolism of 5-hydroxytryptamine by rat lungs perfused in situ.

The effect of halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) on the uptake of 14C-labelled 5-hydroxytryptamine (5-HT) and its metabolism to 5-hydroxyindol-3-ylacetic acid (5-HIAA) was investigated in rat lungs perfused in situ. The rate of accumulation of 14C-labelled 5-HIAA in the tissue, monitored as an index of 5-HT metabolism, was linear with time, displayed saturation kinetics and remained stable for at least 180 min of perfusion. Exposure of the lungs to halothane (4%) for 60 min reversibly reduced production of 5-HIAA through an increase in the apparent Km for metabolism of the amine from 1.45 to 3.52 microM (P less than 0.001); the anaesthetic had no effect on the Vmax. of the process. The magnitude of the inhibition increased with time of exposure to the anaesthetic. Halothane exposure did not alter the distribution of [3H]sorbitol or [14C]5-HT, pulmonary vascular resistance, levels of ATP or the kinetics of amino acid transport in the tissue. Inhibition of protein synthesis by cycloheximide did not mimic the effect of the anaesthetic. These observations, together with those made in lungs exposed to inhibitors of 5-HT uptake and metabolism, were consistent with a halothane-mediated inhibition of 5-HT uptake, which did not appear to involve non-specific changes in membrane permeability.

Animals↗
PubMed1983

Pinocytosis and intracellular degradation of exogenous protein: modulation by amino acids.

Intracellular degradation of exogenous (serum) proteins provides a source of amino acids for cellular protein synthesis. Pinocytosis serves as the mechanism for delivering exogenous protein to the lysosomes, the major site of intracellular degradation of exogenous protein. To determine whether the availability of extracellular free amino acids altered pinocytic function, we incubated monolayers of pulmonary alveolar macrophages with the fluid-phase marker, [14C]sucrose, and we dissected the pinocytic process by kinetic analysis. Additionally, intracellular degradation of endogenous and exogenous protein was monitored by measuring phenylalanine released from the cell monolayers in the presence of cycloheximide. Results revealed that in response to a subphysiological level of essential amino acids or to amino acid deprivation, (a) the rate of fluid-phase pinocytosis increased in such a manner as to preferentially increase both delivery to and size of an intracellular compartment believed to be the lysosomes, (b) the degradation of exogenously supplied albumin increased, and (c) the fraction of phenylalanine derived from degradation of exogenous albumin and reutilized for de novo protein synthesis increased. Thus, modulation of the pinosome-lysosome pathway may represent a homeostatic mechanism sensitive to the availability of extracellular free amino acids.

Amino Acids↗
PubMed1983

Regulation of protein synthesis in lung by amino acids and insulin.

Acute effects of amino acid availability and insulin on protein synthesis were investigated in rat lungs perfused in situ with buffer containing either 4.5% fraction V bovine serum albumin (FrV BSA), 4.5% essentially fatty acid-free (FAF) BSA, or 4.5% dextran to maintain colloid osmotic pressure. In the presence of FrV BSA, protein synthesis was unaffected by perfusion for 1 or 3 h with buffer containing no added amino acids (0X), as compared with amino acids at concentrations one (1X) or five (5X) times those in rat plasma. Regardless of the amino acid concentration, addition of insulin was without effect. Likewise, in lungs perfused for 1 h with either FAF BSA or dextran, protein synthesis was insensitive to amino acid availability or to insulin. After 3 h, however, protein synthesis decreased 34 and 37%, respectively, when these lungs were perfused in the absence of both amino acids and insulin. In both cases, the inhibition was prevented by addition of insulin to the perfusate; addition of the hormone to perfusate containing 1X amino acids or elevating perfusate amino acids to 5X did not affect protein synthesis. The deficit in protein synthesis observed in the absence of both amino acids and insulin was not accompanied by ATP depletion or by lower intracellular concentrations of amino acids. Similarly, the effect of insulin was not associated with a general elevation in intracellular amino acid concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1983

Effect of halothane on synthesis and secretion of liver proteins.

The effect of halothane on synthesis of retained and secreted proteins was investigated using isolated perfused rat livers. Anesthetic exposure rapidly inhibited synthesis of total liver proteins in a dose-dependent manner by a mechanism which appeared to involve reduced rates of both peptide chain initiation and elongation. While halothane concentrations comparable to the clinical dose resulted in small changes in protein metabolism, higher concentrations (4%) of the anesthetic had marked effects. At early time points, relative rates of albumin synthesis were unaffected by halothane, but, as anesthetic exposure was prolonged, production of albumin and of total secreted plasma proteins was inhibited more extensively than that of retained liver proteins. Thus, halothane appeared to exert differential inhibitory effects on synthesis of these two classes of liver proteins.

Albumins↗
PubMed1982

The measurement of protein synthesis in biological systems.

Attempts to quantitate metabolism in the lung and other tissues using radioactive precursors may be subject to significant errors arising from inappropriate assumptions regarding precursor metabolism, compartmentation and specific radioactivity. This article reviews the type and magnitude of error which may complicate such measurements by presenting specific data from experiments using radioactive amino acids to estimate the rate of protein synthesis. The applicability of these observations to other metabolic systems is discussed briefly in order to develop a more general awareness of the errors which may result from incomplete validation of experimental measurements using radioisotopes.

Amino Acids↗
PubMed1982

Additive effects of pentobarbital and halothane to inhibit synthesis of lung proteins.

The effect of pentobarbital on synthesis of lung proteins was investigated, both when administered alone and in combination with halothane. When rat lungs perfused in situ with Krebs-Henseleit bicarbonate buffer containing plasma levels of 19 amino acids, 690 microM phenylalanine, 5.6 mM glucose, and 4.5 per cent fraction V bovine serum albumin were exposed to pentobarbital, a dose-related inhibition of [14C]phenylalanine incorporation into protein was observed, with a maximal inhibition (74 per cent) at a pentobarbital concentration of 324 micrograms/ml. Halothane (1-4 per cent equilibrated with O2/N2/CO2, 4:15:1) also rapidly inhibited synthesis of lung proteins in a dose-dependent manner. At the maximally effective concentration of pentobarbital, exposure of the lungs to halothane enhanced the inhibition of protein synthesis; halothane concentrations ranging from 1 to 4 per cent were equally effective. Furthermore, when lungs were exposed to a combination of pentobarbital (100 micrograms/ml) and halothane (1 per cent) at doses which had no effect when given alone, protein synthesis was inhibited 35 per cent (P less than 0.001). Thus, the metabolic effects of the anesthetics were potentiated when the drugs were administered in combination. The inhibition of protein synthesis by pentobarbital (324 micrograms/ml), with or without 4 per cent halothane, was fully reversible. A similar inhibitory effect of pentobarbital was observed in perfused rat hearts.

Adenosine Triphosphate↗
PubMed1982

Effect of diabetes on metabolism of 5-hydroxytryptamine by rat lungs perfused in situ.

The effect of diabetes induced by treatment of rats with streptozotocin on metabolism of circulating 5-hydroxytryptamine (5HT) was investigated using an in situ lung perfusion preparation. Tissue uptake of 5HT and production of its metabolite, 5-hydroxyindolacetic acid, were unaffected in lungs of diabetic animals provided 2 or 20 microM exogenous 5HT. At constant perfusion pressure, pulmonary flow was not altered by substrate concentration or by streptozotocin treatment. Thus, in the experimental models of diabetes used, metabolism of circulating 5HT by the pulmonary endothelium remained unaffected.

Animals↗
PubMed1982

Use of radioisotopes in quantitative studies of lung metabolism.

Quantitatively accurate studies of macromolecule and lipid synthesis in lung and other tissues by using radioactive substrates require detailed knowledge of the specific radioactivity of the appropriate pool of precursor molecules serving the synthetic pathway. A brief summary is provided of how considerations of precursor availability, metabolism, and compartmentation, as well as product remodeling, may affect the accuracy with which rates of protein, DNA, RNA, and lipid synthesis can be measured. Where possible, the application of this material to studies of lung metabolism is discussed, along with approaches that may minimize experimental uncertainties.

Amino Acids↗
PubMed1981

Protein turnover in pulmonary macrophages. Utilization of amino acids derived from protein degradation.

Conditions were defined under which rates of protein synthesis and degradation could be estimated in alveolar macrophages isolated from rabbits by pulmonary lavage and incubated in the presence of plasma concentrations of amino acids and 5.6 mM-glucose. Phenylalanine was validated as suitable precursor for use in these studies: it was not metabolized appreciably, except in the pathways of protein synthesis and degradation; it entered the cells rapidly; it maintained a stable intracellular concentration; and it was incorporated into protein at measurable rates. When extracellular phenylalanine was raised to a concentration sufficient to minimize dilution of the specific radioactivity of the precursor for protein synthesis with amino acid derived from protein degradation, the specific radioactivity of phenylalanyl-tRNA was only 60% of that of the extracellular amino acid. This relationship was unchanged in cells where proteolysis increased 2.5-fold after uptake and degradation of exogenous bovine serum albumin. In contrast, albumin prevented the decrease in phenylalanine incorporation observed in macrophages deprived of an exogenous source of amino acids. These observations suggested that macrophages preferentially re-utilized amino acids derived from the degradation of endogenous, but not from exogenous (albumin), protein. However, when the extracellular supply of amino acids was restricted, substrates derived from albumin catabolism could support the protein-synthetic pathway.

Amino Acids↗
PubMed1981

Effects of halothane on protein synthesis and degradation in rabbit pulmonary macrophages.

The effects of exposure to the volatile anesthetic halothane on the synthesis and degradation of rabbit pulmonary macrophage proteins were investigated. Protein synthesis was inhibited rapidly and reversibly when macrophages were exposed to halothane. The magnitude of the inhibition was dependent upon the dose of anesthetic and upon the composition of the medium. The effect of halothane was not associated with increased cell death or with depletion of cellular ATP. Halothane exposure did not affect the ability of the cells to degrade either endogenous proteins or exogenous bovine serum albumin. These results suggested that halothane exposure favored protein catabolism in pulmonary alveolar macrophages though an inhibition of protein synthesis with no change in protein degradation.

Adenosine Triphosphate↗
PubMed1980

Measurement of protein synthesis in rat lungs perfused in situ.

Compartmentalization of amino acid was investigated to define conditions required for accurate measurements of rates of protein synthesis in rat lungs perfused in situ. Lungs were perfused with Krebs-Henseleit bicarbonate buffer containing 4.5% (w/v) bovine serum albumin, 5.6mm-glucose, normal plasma concentrations of 19 amino acids, and 8.6-690mum-[U-(14)C]phenylalanine. The perfusate was equilibrated with the same humidified gas mixture used to ventilate the lungs [O(2)/CO(2) (19:1) or O(2)/N(2)/CO(2) (4:15:1)]. [U-(14)C]Phenylalanine was shown to be a suitable precursor for studies of protein synthesis in perfused lungs: it entered the tissue rapidly (t((1/2)), 81s) and was not converted to other compounds. As perfusate phenylalanine was decreased below 5 times the normal plasma concentration, the specific radioactivity of the pool of phenylalanine serving as precursor for protein synthesis, and thus [(14)C]phenylalanine incorporation into protein, declined. In contrast, incorporation of [(14)C]histidine into lung protein was unaffected. At low perfusate phenylalanine concentrations, rates of protein synthesis that were based on the specific radioactivity of phenylalanyl-tRNA were between rates calculated from the specific radioactivity of phenylalanine in the extracellular or intracellular pools. Rates based on the specific radioactivities of these three pools of phenylalanine were the same when extracellular phenylalanine was increased. These observations suggested that: (1) phenylalanine was compartmentalized in lung tissue; (2) neither the extracellular nor the total intracellular pool of phenylalanine served as the sole source of precursor for protein; (3) at low extracellular phenylalanine concentrations, rates of protein synthesis were in error if calculated from the specific radioactivity of the free amino acid; (4) at high extracellular phenylalanine concentrations, the effects of compartmentalization were negligible and protein synthesis could be calculated accurately from the specific radioactivity of the free or tRNA-bound phenylalanine pool.

Animals↗
PubMed1980

Effects of glucocorticoids on peptide chain initiation in heart and skeletal muscle.

Treatment of rats for 5 days with cortisone acetate reduced synthesis of skeletal muscle protein by 56% compared to untreated controls, but had no effect on protein synthesis in heart. The reduction in synthesis in skeletal muscle was accounted for by both a loss of tissue RNA and development of a block in peptide-chain initiation. Activity of an eIF-2-like initiation factor decreased in psoas muscle of hormone-treated rats in proportion to the loss of RNA. Peptide-chain initiation, RNA content, and initiation factor activity were unaffected in heart muscle. In skeletal muscle of rats treated for 4 hr with dexamethasone, peptide-chain initiation was inhibited, whereas tissue RNA content and initiation factor activity were unchanged. These experiments suggested that total activity of eIF-2 did not always correlate with the rate of initiation, but that there did appear to be a relationship between initiation factor activity and tissue RNA content. Purification of eIF-2 from bovine heart muscle was undertaken in order to directly investigate the mechanism by which glucocorticoids modify eIF-2-activity and control peptide-chain initiation.

Animals↗
PubMed1980

Inhibition of protein degradation in the energy-poor heart.

Hypoxia and anoxia were induced in isolated perfused rat hearts by reduction of perfusate oxygen. Ischemia was produced by restricting coronary flow in hearts working against high resistance. Protein degradation, estimated from release of phenylalanine into the perfusate in the presence of cycloheximide, was inhibited in both anoxic and ischemia as compared to aerobic hearts. The effect of ischemia was greater than that of anoxia. A similar inhibitory effect was observed in energy-poor hearts when insulin was present in the perfusate. Other experiments indicated that the effects of energy depletion were exerted at a step early in the degradative pathway, since peptide products of partial proteolysis did not accumulate. A graded reduction in perfusate oxygen tension (hypoxia) led to a significant inhibition of proteolysis with unaltered tissue levels of nucleotides and creatine phosphate. Protein degradation was inhibited in aerobic and anoxic hearts exposed to increasing extracellular levels of hydrogen ions and lactate, suggesting that reduced proteolysis in hearts that are provided limited oxygen may result from accumulation of metabolites as well as from energy depletion per se.

Adenosine Triphosphate↗