Search PubMed⌕ Search

Biomedical subjects

C Claesson

Publications and source records attributed to C Claesson.

10 recordsLinked to original sources
PubMed2000

ADP-ribosylation factor 1 and its activation of phospholipase D are important for the assembly of very low density lipoproteins.

The role of ADP-ribosylation factor 1 (ARF-1) in the assembly of very low density lipoproteins (VLDL) was investigated by expressing dominant-negative mutants in McA-RH7777 cells. Transient expression of ARF-1(T31N), a GDP-restrictive mutant, significantly inhibited apolipoprotein B-100 (apoB-100) VLDL production without influencing the biosynthesis of apoB-100 low density lipoproteins or total apoB production (indicating that it inhibited the second step of VLDL assembly) and without altering total protein production or biosynthesis of transferrin, phosphatidylcholine, or triglycerides. These effects were confirmed in stable inducible transfectants. In contrast, expression of an ARF-1 mutant lacking the N-terminal 17 amino acids, which has no myristoylation site and cannot interact with the microsomal membrane, did not affect VLDL assembly. Thus, active ARF-1 is needed for the second step of the process. To further explore these observations, we developed a cell-free system based on the postnuclear supernatant isolated from McA-RH7777 cells. In this system, 10-15% of the apoB-100 pool was converted to VLDL in a time- and temperature-dependent way. The assembly process was highly dependent on a heat-stable factor in the d > 1.21 g/ml infranatant of fetal calf serum; this factor was not present in low density lipoproteins or VLDL. Brefeldin A inhibited VLDL assembly in this system, as did a synthetic peptide (corresponding to N-terminal amino acids 2-17 of ARF-1) that displaces ARF-1 from the membrane. Thus, active ARF-1 is also needed for cell-free assembly of VLDL. Guanosine 5'-3-O-(thio)triphosphate also inhibited VLDL assembly in this system, indicating that the process requires ongoing hydrolysis of GTP. 1-Butanol, which inhibits the formation of phosphatidic acid (PA) and instead gives rise to phosphatidylbutanol, inhibited VLDL assembly, whereas 2-butanol, which does not inhibit PA formation, failed to do so. Thus, phospholipase D (PLD)-catalyzed formation of PA from phosphatidylcholine is essential for VLDL assembly. In support of this conclusion, exogenous PLD prevented brefeldin A from inhibiting the assembly process. Our results indicate that ARF-1 participates in the second step of VLDL assembly through a process that involves activation of PLD and production of PA.

1-Butanol↗
PubMed1999

The Brief Medication Questionnaire: a tool for screening patient adherence and barriers to adherence.

Self-report tools for monitoring adherence can be useful in identifying patients who need assistance with their medications, assessing patient concerns, and evaluating new programs. The aim of this study is to test the validity of the Brief Medication Questionnaire (BMQ), a new self-report tool for screening adherence and barriers to adherence. The tool includes a 5-item Regimen Screen that asks patients how they took each medication in the past week, a 2-item Belief Screen that asks about drug effects and bothersome features, and a 2-item Recall Screen about potential difficulties remembering. Validity was assessed in 20 patients using the Medication Events Monitoring System (MEMS). Results varied by type of non-adherence, with the Regimen and Belief Screens having 80-100% sensitivity for "repeat" non-adherence and the Recall Screen having 90% sensitivity for "sporadic" non-adherence. The BMQ appears more sensitive than existing tools and may be useful in identifying and diagnosing adherence problems.

Adult↗
PubMed1999

Assembly of very low density lipoprotein: a two-step process of apolipoprotein B core lipidation.

The liver plays a primary role in lipid metabolism. Important functions include the synthesis and incorporation of hydrophobic lipids, triacylglycerols and cholesteryl esters into the core of water-miscible particles called lipoproteins and the secretion of these particles into the circulation for transport to distant tissues. In this article, we present a brief overview of one aspect of the assembly process of very low density lipoproteins, namely, possible mechanisms for combining core lipids with apolipoprotein B. This is a complex process in which apolipoprotein B interacts with core lipids to form very low density lipoproteins by a two-step process that can be dissociated biochemically.

Animals↗
PubMed1995

Glycine codon discrimination and the nucleotide in position 32 of the anticodon loop.

Using an in vitro protein-synthesizing system that allowed us to monitor separately the reading of each glycine codon, we have previously shown, that in constructs based on glycine tRNA1 from Escherichia coli the nature of the nucleotide in position 32 determines the ability of the anticodon UCC to discriminate between the glycine codons. Thus, with a U in position 32 the anticodon UCC discriminated according to the wobble rules, but with a C in this position it had lost its ability to discriminate. In the present paper we show that the same is true also for constructs based on mycoplasma glycine tRNA. When C32 in the wild type was changed to U32, the anticodon UCC discriminated between the glycine codons, while in wild type mycoplasma glycine tRNA it did not. Furthermore, when U32 was changed to C32 in glycine tRNA1(CCC), the anticodon CCC loses its ability to discriminate. We therefore conclude that the nature of the nucleotide in position 32 determines the discriminatory ability of both anticodons UCC and CCC in the glycine tRNA1 structural background, and that the same is true for the anticodon UCC in the mycoplasma glycine tRNA background.

Anticodon↗
PubMed1993

The nucleotide in position 32 of the tRNA anticodon loop determines ability of anticodon UCC to discriminate among glycine codons.

We have investigated the influence of structures in the tRNA anticodon loop and stem on the ability of the anticodon to discriminate among codons. We had previously shown that anticodon UCC, when placed in the structural context of tRNA(Gly1) from Escherichia coli, discriminated efficiently between the glycine codons, as required by the wobble rules. Thus, this anticodon read GGA and GGG but did not read GGU and GGC, whereas in mycoplasma tRNA(Gly), the same anticodon did not discriminate among the glycine codons. We have now determined the reading properties of three constructions based on tRNA(Gly1) containing the anticodon UCC in different structural contexts. In one of these constructs, tRNA(Gly1-ASL), the anticodon loop and stem are the same as in mycoplasma tRNA(Gly). The second construct, tRNA(Gly1-AS), has an anticodon stem identical with the mycoplasma tRNA(Gly), whereas in the last construct, tRNA(Gly1-C32), the only difference from tRNA(Gly1)(UCC) is that the uridine in position 32 of the anticodon loop has been replaced by cytidine. These constructs were tested for ability to read glycine codons in an in vitro protein-synthesizing system that allowed us to monitor separately the reading of each codon. We found that the anticodon UCC, when present in tRNA(Gly1-AS), discriminated among the glycine codons, whereas in the constructs tRNA(Gly1-ASL) and tRNA(Gly1-C32), the same anticodon had lost its ability to discriminate--i.e., it behaved as in mycoplasma tRNA(Gly). These results strongly suggest that nt 32 of the anticodon loop of tRNA(Gly1)(UCC) decisively influences the reading properties of the anticodon UCC.

Anticodon↗
PubMed1993

Undiscriminating codon reading with adenosine in the wobble position.

To investigate the reading properties of adenosine in the wobble position we have used site-directed mutagenesis of the Escherichia coli glycine tRNA1(CCC) gene to substitute the nucleotide A in the wobble position of the corresponding tRNA. The effect of this change on the ability of the tRNA to discriminate between the nucleotides in the third position of the glycine codons has been investigated. We have compared the ability of the mutant glycine tRNA1(UCC) and glycine tRNA1(ACC) as well as the mycoplasma glycine tRNA(UCC) to read the glycine codons. The results showed that glycine tRNA1(ACC) unlike glycine tRNA1(UCC) did not fully discriminate between the glycine codons. These experiments were carried out using a new in vitro protein synthesizing system that allows us to monitor the reading of all four glycine codons. In the present paper we give a detailed description of this new in vitro system.

Adenosine↗
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↗
PubMedDate not supplied

International pharmacy.

Several worldwide initiatives involve pharmacy education and practice; however, the International Pharmaceutical Federation is the only worldwide pharmacy organization currently in existence. This is the first report of the good pharmacy practice initiative published in the United States. We hope that it will stimulate interest in international pharmacy.

Drug Utilization↗