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T Samuelsson

Publications and source records attributed to T Samuelsson.

At least 19 recordsLinked to original sources
PubMed1992

A Mycoplasma protein homologous to mammalian SRP54 recognizes a highly conserved domain of SRP RNA.

A protein homologous to SRP54, a subunit of the mammalian signal recognition particle (SRP), was identified in Mycoplasma mycoides. The mycoplasma protein was expressed in E.coli and purified to near homogeneity. It was shown to bind specifically in vitro to a small mycoplasma RNA with structural features related to the RNA component of SRP. These findings provide evidence of a ribonucleoprotein complex in mycoplasma reminiscent of SRP. A part of the RNA was protected from ribonuclease digestion in the presence of the SRP54 homologue. The protected region contains structural elements that have been highly conserved in SRP RNAs during evolution.

Amino Acid Sequence↗
PubMed1991

Interactions of transfer RNA pseudouridine synthases with RNAs substituted with fluorouracil.

We have previously purified and characterized two different S. cerevisiae enzymes that produce pseudouridine specifically in nucleotide positions 13 and 55, respectively, in their tRNA substrates. The interactions of these enzymes with fluorinated tRNAs have now been studied. Such RNAs were produced by in vitro transcription using as templates synthetic genes that encode variants of a yeast glycine tRNA. RNAs substituted with fluorouracil were found to markedly inhibit pseudouridine synthase activity and the inhibitory effect of a tRNA was to a large extent dependent on the presence of fluorouracil in the nucleotide position where normally pseudouridylation occurs. Pseudouridine synthases were shown to form highly stable, non-covalent complexes with fluorinated tRNAs and we demonstrate that this interaction may be used to further characterize and purify these enzymes. The use of 5-fluorouracil as a cancer therapeutic agent is discussed in relation to our results.

Base Sequence↗
PubMed1990

Codon reading properties of an unmodified transfer RNA.

We have previously shown that the Mycoplasma mycoides glycine tRNA (anticodon UCC) effectively reads the codons GGU and GGC in violation of the classic codon reading rules. We have attempted to elucidate what structural elements in this tRNA molecule confer this translational property and in the course of this investigation T7 RNA polymerase transcription of the corresponding gene was used to produce a tRNA devoid of modified nucleosides. Using an in vitro translation system the ability of this tRNA to read the 4 glycine codons (GGU, GGC, and GGG) was tested and it was shown to be as efficient as its normal, fully modified counterpart in the reading of all four codons. This result demonstrates that a tRNA devoid of modified nucleosides is able to efficiently sustain protein synthesis in vitro and, furthermore, that the normal modification pattern of the Mycoplasma glycine tRNA is not essential for the ability of this tRNA to read the glycine codons GGU and GGC effectively.

Base Sequence↗
PubMed1990

Transfer RNA pseudouridine synthases in Saccharomyces cerevisiae.

A transfer RNA lacking modified nucleosides was produced by transcription in vitro of a cloned gene that encodes a Saccharomyces cerevisiae glycine tRNA. At least three different uridines (in nucleotide positions 13, 32, and 55) of this transcript tRNA are modified to pseudouridine by an extract of S. cerevisiae. Variants of the RNA substrate were also constructed that each had only one of these sites, thus allowing specific monitoring of pseudouridylation at different nucleotide positions. Using such RNAs to assay pseudouridine synthesis, enzymes producing this nucleoside were purified from an extract of S. cerevisiae. The activities corresponding to positions 13, 32, and 55 in the tRNA substrate could all be separated chromatographically, indicating that there is a separate enzyme for each of these sites. The enzyme specific for position 55 (denoted pseudouridine synthase 55) was purified approximately 4000-fold using a combination of DEAE-Sepharose, heparin-Sepharose, and hydroxylapatite.

Base Sequence↗
PubMed1989

Unconventional codon reading by Mycoplasma mycoides tRNAs as revealed by partial sequence analysis.

Continuing our investigation of the tRNA genes and gene products in Mycoplasma mycoides, we report the sequence of the gene for tRNALeu (CAA) as well as partial primary structures of the following tRNAs: Leu (CAA), Leu (UAG), Arg (UCU), Thr (AGU) and Ile (CAU). It is suggested that in M. mycoides, at least some of the family codon boxes are read by only one tRNA each, using an unconventional method which does not discriminate between the nucleotides in the third codon position. M. mycoides is the first free-living organism known to use an unconventional method of this kind.

Base Sequence↗
PubMed1989

Codon discrimination and anticodon structural context.

Site-directed mutagenesis has been used to change the nucleotide C in the wobble position of tRNA(1Gly) (CCC) to U. The mutated tRNA was tested for its ability to read glycine codons in an in vitro protein-synthesizing system programmed with the phage message MS2-RNA that had been modified by site-directed mutagenesis so as to make it possible to monitor conveniently the reading of all four glycine codons. The results showed that while the efficiency of tRNA(1Gly) (UCC) was comparable to that of mycoplasma tRNA(Gly) (UCC) in the reading of the codon GGA, the mycoplasma tRNA(Gly) was far more efficient than the tRNA(1Gly) (UCC) in the reading of the codons GGU and GGC. Thus, the anticodon UCC, when present in the structural context of the tRNA(1Gly) molecule, behaved as predicted by the wobble rules while in the structural context of the mycoplasma tRNA(Gly) it read without discrimination between the nucleotides in the third codon position, in violation of the wobble restrictions. The result with the codon GGG showed that the anticodon UCC, when present in tRNA(1Gly), was considerably less efficient in reading this codon than it was in the structural context of the mycoplasma tRNA(Gly). It would therefore seem that the anticodon UCC, when present in a certain tRNA, can be an efficient wobbler, while in the molecular environment of another tRNA it is markedly restricted in its ability to wobble.

Amino Acid Sequence↗
PubMed1989

Accumulation of hyaluronan (hyaluronic acid) in the lung in adult respiratory distress syndrome.

The concentrations of hyaluronan (HA) were measured in bronchoalveolar lavage (BAL) fluid and serum from 12 patients with adult respiratory distress syndrome (ARDS). The median BAL fluid HA concentration was 353 micrograms/L, about six times higher than that seen in control patients (p less than 0.001). The median serum HA value was 619 micrograms/L, which was a 30-fold increase compared with that in the control patients (p less than 0.001). Another connective tissue component, type III procollagen peptide, was not recovered in significant amounts during lavage in patients with ARDS, but it appeared in the bloodstream in increased concentrations (p less than 0.001). Obtained recovery of HA during lavage of patients with ARDS cannot be explained by an enhanced passive leakage from the bloodstream because of increased alveolar-capillary permeability, but rather could reflect a mobilization of HA from lung interstitial tissue because of hydrostatic mechanisms. Alternatively, the appearance of HA in the alveolar space in ARDS might reflect an enhanced lung synthesis of HA. An increased HA production can possibly be mediated, directly or indirectly, by activated complement components, since a significant relationship was seen between increased plasma concentrations of C3a des Arg and BAL fluid HA (r = 0.61; p less than 0.05). The observed accumulation of HA in the small airways in ARDS may be expected to immobilize water and thereby contribute to the interstitial and alveolar edema. The inverse correlation (r = 0.71; p less than 0.01) seen between BAL fluid HA and pulmonary oxygenation index (PaO2/inspired oxygen fraction) supports such a hypothesis.

Adult↗
PubMed1988

Properties of a transfer RNA lacking modified nucleosides.

A transfer RNA complete devoid of modified nucleosides was synthesized by in vitro transcription, and some of its properties in aminoacylation and protein synthesis in vitro were studied. For this purpose, a plasmid was constructed which contained a glycine tRNA gene from Mycoplasma mycoides under the promoter of the T7 RNA polymerase, as well as a BstNI restriction site at the 3'-end of the tRNA gene. Cleavage of plasmid DNA with BstNI followed by T7 RNA polymerase transcription in vitro yielded an RNA which was processed with M1 RNA, the catalytic subunit of ribonuclease P, to give a tRNA of mature length. The tRNA synthesized in this manner can be esterified with glycine in vitro, and the rate of aminoacylation is the same as when using the corresponding fully modified glycine tRNA from M. mycoides. Furthermore, in protein synthesis in vitro, the tRNA lacking modified nucleosides was essentially as efficient as the corresponding normal glycine tRNA. However, the Escherichia coli extract used in our protein-synthesizing system introduced one modification, pseudouridine, into the in vitro-synthesized tRNA, and it cannot be excluded that this modification has an essential role in protein synthesis.

Adenosine↗
PubMed1987

Prevention by granulocyte depletion of endotoxin-induced adult respiratory distress syndrome. An experimental study in pigs.

To see whether circulating granulocytes are of importance in mediating endotoxin-induced pulmonary failure with similar characteristics to the human adult respiratory distress syndrome (ARDS), we made pigs granulocytopenic by injecting hydroxyurea via a central venous line for 10 days. The circulating granulocyte count decreased by 95% prior to the start of the continuous (6 h) endotoxin infusion (n = 8), whereas pigs sham-infused for 10 days had a normal granulocyte count before starting the continuous endotoxin infusion (n = 8). Four granulocyte depleted pigs served as controls and received physiological saline instead of endotoxin. No physiological changes occurred in controls during the observation period of 6 h and all animals survived. Granulocyte depletion in response to endotoxin was associated with significantly attenuated pulmonary hypertension, significantly better preservation of cardiac output, significantly better maintained arterial oxygenation and a significantly smaller increase in extravascular lung water throughout the observation period as compared with non-granulocytopenic animals. Seven out of 8 granulocytopenic animals survived the observation period as against 4 out of 8 in non-granulocytopenic animals. Although one should be extremely careful in applying experimental results to the clinical situation, our findings might support the potential use of agents which interfere with granulocyte activation in septic-induced ARDS.

Agranulocytosis↗
PubMed1987

Apparent lack of discrimination in the reading of certain codons in Mycoplasma mycoides.

We report a cluster of four tRNA genes from Mycoplasma mycoides as well as the sequence of the alanine, proline, and valine tRNAs and the serine tRNA reading the UCN codons (where N stands for G, A, C, or U). This brings the total number of tRNA genes that we have so far characterized in this organism to 14, 6 of which code for tRNAs that read the codons of family boxes. In each of these latter cases, we found only one gene per family box, and the gene sequence contains a thymidine in the position corresponding to the wobble nucleotide, with the exception of the arginine tRNA gene that has an adenosine in this position. Furthermore, all of the tRNA structures reported here have an unsubstituted uridine in the wobble position. These findings are similar to those reported for mitochondria, especially yeast mitochondria, that contain an arginine tRNA with the anticodon ACG. However, the resemblance is not complete since we have demonstrated the presence of two isoacceptor tRNAs for threonine having uridine and adenosine, respectively, in the wobble position. It is suggested that in the M. mycoides at least some of the family codon boxes are read by only one tRNA each, using an unconventional method without discrimination between the nucleotides in the third codon position.

Base Sequence↗
PubMed1987

Complement activation and increased alveolar-capillary permeability after major surgery and in adult respiratory distress syndrome.

The concentrations of C3a des Arg were measured in bronchoalveolar fluid (BAL) and plasma from 12 patients with adult respiratory distress syndrome (ARDS). Compared with 32 controls, all patients had increased BAL fluid levels (p less than .001), and nine of 12 had increased plasma levels (p less than .001) of this split product from the third complement component. Reduced total hemolytic activity (CH50) in serum was seen in five patients (p less than .01). As an indication of damage to the alveolar-capillary barrier, ten of the 12 ARDS patients had elevated albumin concentrations in BAL fluid (p less than .001). These signs of complement activation and lung tissue damage are not specific for ARDS. Thus, in 15 patients investigated preoperatively and postoperatively, we found that major surgery induced a significant increase of BAL fluid C3a (p less than .01) and plasma C3a (p less than .02), a significant reduction of CH50 (p less than .001), and a significant increase of BAL fluid albumin (p less than .02). Similar values of CH50 and plasma C3a were seen in ARDS and after surgery (p greater than .05). Of the 12 ARDS patients, eight had increased BAL fluid concentrations of C3a (p less than .001), and ten had increased BAL fluid levels of albumin (p less than .001) compared with the post-surgical patients. Measuring complement consumption in blood by these techniques is of limited value in ARDS due to the lack of specificity. BAL fluid albumin has a similar degree of sensitivity and specificity for ARDS as does BAL fluid C3a.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Eosinophil activation in the lung is related to lung damage in adult respiratory distress syndrome.

The concentrations of eosinophil cationic protein (ECP), a specific granule constituent of eosinophil granulocytes, were measured in bronchoalveolar lavage (BAL) fluid from patients with adult respiratory distress syndrome (ARDS). The mean level was 163 +/- 85 (SD) micrograms/L and significantly increased (p less than 0.001) compared with the levels in control subjects (19 +/- 18 micrograms/L). The BAL fluid concentrations of myeloperoxidase (MPO) were also significantly increased in ARDS, indicating a local neutrophil activation. A significant correlation was found between BAL fluid ECP and MPO, suggesting a common activator of eosinophils and neutrophils. No relation was seen between BAL fluid ECP or MPO and degree of complement consumption, suggesting that other mechanisms besides complement activation may underlie granulocyte activation in ARDS. Lavage ECP levels correlated strongly with the severity of lung damage defined by pulmonary oxygenation index (PaO2/inspired fraction of O2). Activation of eosinophils, neutrophils, and the complement system is not specific for ARDS but was also observed in patients after major surgery, but at a significantly lower level (p less than 0.001). It is concluded that eosinophil activation is part of the inflammatory process in the lung in ARDS. The association observed between elevated lavage fluid levels of ECP and reduced pulmonary function in ARDS might reflect a pathophysiologic role for ECP and other cytotoxic eosinophil products in this syndrome and should be evaluated.

Adult↗
PubMed1987

Volume substitution and treatment with prostaglandin E1 in a porcine model of endotoxaemia-induced pulmonary and cardiovascular failure.

The effects of prostaglandin E1 (PGE1) and volume substitution (5% albumin) on pulmonary haemodynamics and oxygen transport were evaluated in a porcine model of pulmonary and cardiovascular failure. Albumin was infused i.v. to maintain baseline mean left atrial pressure throughout the experiments. Ten pigs received endotoxin + albumin and showed ten-fold increase in venous admixture, 90% increased extravascular lung water and 25% fall in cardiac output. Oxygen delivery and base excess decreased significantly and four pigs died. In ten other endotoxin-albumin-treated pigs PGE1 infusion (0.25 micrograms X kg-1 X min-1) was begun after established pulmonary and cardiovascular dysfunction, for closer mimicking of clinical use. The raised pulmonary vascular resistance thereafter normalized and extravascular lung water increased by only 15%, but the increase in venous admixture was not influenced. Cardiac output was maintained at baseline. PGE1 prevented further derangement of oxygen delivery and base excess. All the animals survived. The clinical implications may be that volume infusion, even optimally titrated, is not optimum treatment in endotoxemic pulmonary and cardiovascular failure. PGE1 added to optimum volume treatment may be a useful adjuvant in endotoxaemia.

Albumins↗
PubMed1986

The predictive and discriminative value of biologically active products of eosinophils, neutrophils and complement in bronchoalveolar lavage and blood in patients with adult respiratory distress syndrome.

To determine whether biologically active products of eosinophils, neutrophils and complement contribute to the development of adult respiratory distress system (ARDS) we measured eosinophil cationic protein (ECP), lactoferrin (LF) and C3a in bronchoalveolar lavage (BAL) and blood by means of radioimmunoassays. Seventeen patients served as controls. Fifteen patients were studied before and after major surgery to evaluate the influence of the surgical procedure, and 12 patients with ARDS were investigated 4-12 h after the onset of the disease. Major surgery per se significantly increased ECP in BAL, LF in serum and C3a in BAL and plasma. ECP, LF and C3a levels in BAL and blood were all significantly higher in ARDS patients as compared with levels in controls and those observed after major surgery. The higher ECP levels in BAL were associated with the more severe ARDS as was also the case for C3a in BAL and plasma and LF in serum. One out of 15 patients subjected to major surgery developed ARDS postoperatively and had very high levels of ECP, LF and C3a in BAL and blood at sampling 3 h prior to onset of ARDS, and these levels were similar to those observed in ARDS patients. One out of 12 ARDS patients died from the disease and this patient had the highest level of ECP in BAL and serum. Our results strongly support the role of activated polymorphonuclears, and notably the activated eosinophils, in the pathogenesis of ARDS. Evidence is also presented that ECP can be used as a predictor of impending ARDS.

Adult↗
PubMed1986

Treatment with prostaglandin E1 in a porcine model of early adult respiratory distress syndrome.

The effects of treatment with PGE1 were evaluated in a porcine model of early adult respiratory distress syndrome induced by endotoxaemia. Spontaneously breathing pigs under ketamine anaesthesia were infused i.v. with E. coli endotoxin (10 micrograms X kg-1 X h-1) for 6 h. Thirteen pigs were given endotoxin, and 11 pigs were treated with a continuous infusion of PGE1, 0.25 microgram X kg-1 X min-1 for 4 h, beginning 2 h after start of endotoxin and established lung injury. Four pigs served as controls and receiving only PGE1 (0.25 microgram X kg-1 X min-1) during the whole observation period of 6 h. PGE1 treatment did not influence the decline in platelet and polymorphonuclear cell counts, whereas it markedly decreased the pulmonary hypertension induced by endotoxaemia. The increased extravascular lung water returned towards baseline after institution of PGE1. The increased venous admixture was not significantly influenced by PGE1. Treatment with PGE1 induced an exacerbated hypotensive state in the endotoxaemic animals primarily due to vasodilation. The decline in cardiac output and oxygen delivery noted in endotoxaemic pigs were not influenced by PGE1 and survival was not improved. Although one should be extremely careful in extrapolating these data to the clinical situation the results from the present study suggest the need for optimum volume replacement when starting PGE1 infusion in endotoxin-induced ARDS.

Alprostadil↗
PubMed1985

Cloning and nucleotide sequence analysis of transfer RNA genes from Mycoplasma mycoides.

As part of an investigation of the tRNA genes of Mycoplasma mycoides, two HindIII fragments of mycoplasma DNA comprising 0.4 and 2.5 kilobases (kb), respectively, were cloned in pBR322 and their nucleotide sequences determined. Only one tRNA gene was found in the 0.4 kb fragment, the gene for tRNAArg with the anticodon TCT, while the 2.5 kb fragment contained nine different tRNA genes arranged in a cluster which presumably constitutes a transcriptional unit. The clustered tRNA genes, with their respective anticodons, were as follows: Arg (ACG), Pro (TGG), Ala (TGC), Met (CAT), Ile (CAT), Ser (TGA), fMet (CAT), Asp (GTC), and Phe (GAA).

Base Sequence↗
PubMed1983

Unconventional reading of the glycine codons.

We have used a protein-synthesizing in vitro system programmed with the phage message MS2-RNA to investigate the ability of glycyl-tRNAs with different anticodons to read the glycine codons. Under conditions of no competition, when the glycyl-tRNA analyzed was the only source of glycine for protein synthesis, each of the isoacceptors tested, tRNA1Gly (anticodon CCC), tRNA2Gly (anticodon N/UCC), tRNA3Gly (anticodon GCC) from Escherichia coli, and tRNAGly (anticodon UCC) from Mycoplasma mycoides, could read all of the glycine codons in the MS2 coat protein cistron (GGU, GGC, GGA, and GGG). However, tRNA1Gly seemed to have difficulties reading through the whole cistron. Experiments in which two glycyl-tRNAs competed for the same codon showed that the mycoplasma tRNAGly (anticodon UCC) was almost as efficient in the unorthodox reading of the codons GGU and GGC as it was in conventional reading. It would seem to be the only tRNAGly present in Mycoplasma mycoides and our results are consistent with this finding since the mycoplasma tRNAGly appears to have been designed to read all four glycine codons with approximately equal efficiency. The competition experiments furthermore showed that E. coli tRNA1Gly (anticodon CCC) reads the codon GGA more efficiently than it reads GGU and GGC suggesting that the mispair C . A between the wobble position of the anticodon and the third codon position might have appreciable stability.

Amino Acid Sequence↗