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Biomedical subjects

M Olsson

Publications and source records attributed to M Olsson.

At least 127 records · Page 7Linked to original sources
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↗
PubMed1990

Modification of deoxyribose-phosphate residues by extracts of ataxia telangiectasia cells.

The release of DNA 5'-terminal deoxyribose-phosphate residues from enzymatically incised apurinic/apyrimidinic sites by human cell extracts has been under investigation. During the course of these studies, we observed that ataxia telangiectasia cell extracts modify deoxyribose-phosphate (dRp) residues by converting them to an altered form, dRp-X, which shows altered chromatographic properties on HPLC analysis. The chemical nature of the adduct is as yet unknown, but dRp-X is stable to both heat and acid. The modification requires an enzymatic activity and a low-molecular weight co-factor. Extracts of normal cells contain a dialyzable inhibitor that suppresses the reaction occurring with ataxia telangiectasia cell extracts. Formation of dRp-X has been observed in 7 out of 7 ataxia telangiectasia lymphoblastoid lines which represent at least 3 genetic complementation groups. Similar modification of dRp did not occur with extracts of cells of normal origin, nor those representing Fanconi's anaemia, xeroderma pigmentosum, Bloom's syndrome, Werner's syndrome or Friedreich's ataxia.

Ataxia Telangiectasia↗
PubMed1990

Measurement of histamine in nasal lavage fluid: comparison of a glass fiber-based fluorometric method with two radioimmunoassays.

The determination of histamine in nasal secretions and nasal lavage fluid may be of importance to monitor activation of histamine containing cells in the nasal cavity. However, such studies have been besieged by controversy, specifically to findings of changes in histamine levels in relation to allergenic stimulation. This controversy may be due to the specificity and accuracy of the various methods used to determine histamine in the nasal fluid. We have therefore applied and compared three new methods to determine histamine in nasal lavage fluids obtained before and after allergen challenge in normal subjects and patients with allergic rhinitis. We used a fluorometric glass fiber-based histamine method (FHR) and two RIAs, I and II. The FHR (detection limit, 7.0 nmol) and the RIA II (detection limit, 0.2 nmol) are specific for histamine itself, whereas the RIA I (detection limit, 18.0 nmol) measures mainly methylhistamine and cross-reacts to some extent with histamine. The histamine levels in the nasal lavage fluids from the nasal challenges demonstrated histamine values between 100 and 2000 nmol/L of histamine with significantly higher levels in the postallergen challenges for the allergic subjects as compared to the normal control subjects. The FHR correlated well with the RIA I and RIA II methods with correlation coefficients of 0.77 to 0.88 (p less than 0.001), respectively. However, the RIA I (methylhistamine antibody) always demonstrated absolute histamine values 5% to 20% of values measured by the RIA II (at the level of cross-reactivity to histamine).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

MRI contrast media for the liver. Efficacy in conditions of acute biliary obstruction.

The authors investigated in a rat model the efficacy of magnetic resonance imaging (MRI) contrast media for evaluating the liver in conditions of acute biliary obstruction. Two liver-specific MRI contrast media, Cr-DEHIDA and Mn-DPDP, and the nonspecific agent Gd-DTPA were studied in normal rats and in rats whose bile ducts had been ligated before administration of the contrast medium. Images were made using a 2.4 T animal MRI system, and intensity enhancement of liver after contrast medium injection was calculated. Metal analyses of serum and liver tissue and T1 and T2 measurements on liver samples in vitro were performed. The differences in image intensity enhancement of liver between normal rats and rats with ligated bile ducts were not significant for any of the three contrast media. Imaging with Mn-DPDP resulted in the highest intensity enhancement of the liver compared with Cr-DEHIDA and Gd-DTPA. Contrast media concentrations in liver tissue were not significantly different between normal rats and rats with ligated bile ducts; however, Cr-DEHIDA concentrations in serum were higher after bile duct ligation. In vitro measurements of liver tissue indicated unique relaxation properties for Mn-DPDP. This investigation indicates that the contrast media studied may be useful in situations where suspected liver pathology is complicated by acute biliary obstruction.

Animals↗
PubMed1990

Unnecessary deaths from valvular aortic stenosis.

The annual mortality from aortic valvular stenosis was calculated among potential candidates for surgical replacement of the aortic valve. From the Swedish Central Register of Causes of Death, 70 patients below the age of 80 years who had died from aortic stenosis during a 1-year period in the County of Stockholm (population 1.5 million), were identified. A retrospective analysis of their medical records showed that 37 individuals were suitable candidates for surgery. The presence of aortic stenosis had been verified at autopsy in 31 (84%) patients. The remaining six patients (16%) had their aortic stenosis diagnosis established by a thorough non-invasive investigation performed before death. Although typical signs and symptoms of aortic stenosis were recorded in all 37 patients, only six (16%) of them had been considered by their physicians to be suitable candidates for surgery prior to death. The deceased patients were compared with a group of 68 patients who had undergone aortic valve replacement for aortic stenosis during the same period. There were no significant differences between the two groups with regard to symptoms and clinical findings, except for a higher incidence of syncope in the operated group. It is concluded that, of 105 (68 surgically treated and 37 deceased) eligible patients with aortic stenosis, 37 individuals did not receive surgical care in time. The reason for this was probably insufficient knowledge of the curability of the disease.

Aged↗
PubMed1990

Osseointegrated implants in edentulous jaws: a 2-year longitudinal study.

Osseointegrated implants in 50 edentulous jaws were studied during a 2-year observation period. The implant survival rate was 89% in the maxillae and 97% in the mandibles. The marginal bone loss averaged 1.7 mm in the maxillae and 1.1 mm in the mandibles. Most of this bone loss occurred during the first year. The bone loss was greater in jaws with a preoperatively minor resorption of the alveolar ridge than in those with moderate or advanced resorption. The bone loss was also greater at the medially positioned implants than at those more posterior.

Adult↗
PubMed1989

15-Keto-13,14-dihydroprostaglandin E2- and F2 alpha-metabolite levels in blood from men and women given prostaglandin E2 orally.

Prostaglandin E2 (PGE2) was administered orally in a dose of 1 mg to healthy males (n = 20) and females (n = 10). Blood levels of 15-keto-13,14-dihydroprostaglandin F2 alpha (PGF2 alpha-M) and 15-keto-13,14-dihydroprostaglandin E2 (PGE2-M), determined as the rearrangement product 11-deoxy-15-keto-13,14-dihydro-11 beta, 16-cycloprostaglandin E2 (PGE2-cyclo-M), were measured. The levels of the two PG metabolites increased already 10 minutes after ingestion of the tablet and the mean peak value for PGE2-cyclo-M in the men was 4.64 nmol/l which was reached 50 minutes after PGE2 administration. The mean peak value in women was 4.99 nmol/l which was obtained after 30 minutes. The increase in PGE2-cyclo-M concentration was significantly faster (p less than 0.05) in women than in the men. The mean plasma concentration of PGF2 alpha in males were 0.20 nmol/l prior to treatment and rose after PGE2 ingestion to mean peak level of 0.84 nmol/l after 70 minutes. The corresponding values for the females were 0.18 nmol/l and 0.88 nmol/l 50 minutes into treatment. When the data from both sexes were amalgamated PGE2-cyclo-M peak levels were reached significantly (p = 0.004) sooner than the PGF2 alpha-M peak. The two PG metabolites returned to baseline levels in 70% of the individuals after 240 minutes. The increase in PGF2 alpha-M concentration following oral administration of PGE2 indicates that part of the PGE2 was reduced to PGF2 alpha.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1989

Magnetic resonance imaging and aneurysm clips. Magnetic properties and image artifacts.

The magnetic properties of 12 different types of aneurysm clip were investigated in order to identify which clips allow postoperative magnetic resonance (MR) imaging without risk. Clip-induced MR artifacts were also quantitatively studied using a geometrical phantom. Nonferromagnetic aneurysm clips like the Yaşargil Phynox, Sugita Elgiloy, and Vari-Angle McFadden clips do not appear to contraindicate MR studies performed with a FONAR beta-3000M imager. There is no clip movement upon introduction of the phantom into the MR imager, and the image artifacts caused by the clips are so limited that patients harboring such clips may well be considered for MR imaging. This examination may reveal information not obtainable by any other radiological modality.

Aneurysm↗
PubMed1988

The disposal of an oral glucose load in patients with non-insulin-dependent diabetes.

Following glucose ingestion, tissue glucose uptake is enhanced and endogenous glucose production is inhibited, thus contributing to the maintenance of normal glucose tolerance. To examine whether these responses are disturbed in diabetes, glucose kinetics after oral glucose administration were studied in 12 non-insulin-dependent diabetic and 10 age- and weight-matched control subjects. A double tracer approach was used, whereby the endogenous glucose pool was labeled with 3-3H-glucose and the oral load with 1-14C-glucose. The two glucose tracers were separated in plasma by a two-step chromatographic procedure, and the two sets of isotopic data were analyzed according to a two-compartment model for the glucose system. Basally, glucose production was slightly higher in diabetics than in controls (2.51 +/- 0.24 v 2.28 +/- 0.11 mg/kg.min, NS) even though the former had higher plasma glucose (189 +/- 19 v 93 +/- 2 mg/dL, P less than .001) and insulin (23 +/- 4 v 12 +/- 1 microU/mL, P less than .05) concentrations. Following the ingestion of 1 g/kg of glucose, oral glucose appeared in the peripheral circulation in similar time-course and amount in the two groups (75 +/- 2% of the load over 3.5 hours in the diabetics v 76 +/- 3% in controls). Endogenous glucose production was promptly inhibited in diabetic and normal subjects alike, but the mean residual hepatic glucose production after glucose ingestion was significantly greater in the diabetic group (17 +/- 2 v 10 +/- 3 g/3.5 h, P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1988

Splanchnic metabolism of amino acids in healthy subjects: effect of 60 hours of fasting.

Brief starvation is accompanied by decreased circulating levels of most amino acids, which has been attributed to an increased splanchnic uptake of amino acids, primarily alanine, for gluconeogenesis. However, quantitative data on splanchnic exchange of amino acids and gluconeogenic precursors is lacking. Consequently, arterial concentrations and splanchnic exchange of whole blood amino acids, ketone bodies, glucose, and gluconeogenic precursors were measured in 16 prolonged fasted (60 to 64 hours) and 15 overnight fasted (12 to 14 hours) healthy, nonobese subjects. After the 60-hour fast net splanchnic glucose production decreased by 41% to 0.31 +/- 0.02 mumol/L (P less than .001), whereas the splanchnic uptake of gluconeogenic precursors increased and could account for the total glucose output. Net splanchnic uptake of taurine, threonine, serine, glycine, lysine, histidine, and arginine rose significantly in response to fasting (P less than .05 to .01) due to increased splanchnic fractional extraction. Although the splanchnic fractional extraction of alanine was augmented by 40% (P less than .001), net splanchnic uptake was not influenced by fasting. Total net splanchnic uptake of amino acids increased by 68%, from 231 +/- 44 mumol/min in the postabsorptive state to 388 +/- 63 mumol/min (mean +/- SEM) (P less than .05) in the 60-hour fasted state. However, only one half of this rise was accounted for by gluconeogenic amino acids.

Adult↗
PubMed1988

Comparison of MR imaging and CT in patients with intracranial aneurysm clips.

CT and MR imaging of the brain were performed without complications in 16 patients who had undergone surgery for a ruptured aneurysm with the use of nonferromagnetic Yasargil 316 or Sugita Elgiloy clips. MR was performed on a 0.3-T Fonar beta-3000M imaging system. The artifacts caused by the clips were smaller on MR than on CT, and, therefore, anatomic structures such as the brainstem and temporal lobes were better visualized on MR. Brain-tissue lesions corresponding to the frontotemporal surgical approach were seen with MR in seven patients and with CT in six. In three patients temporal-lobe lesions seen on MR were not seen on CT because of beam-hardening artifacts. Lesions unrelated to the region of surgery were seen with MR in nine patients and with CT in five. In conclusion, MR was safe and superior to CT both in demonstrating anatomic details and in detecting tissue lesions in patients with aneurysm clips.

Alloys↗
PubMed1988

An improved standardized procedure for urine mutagenicity testing.

The aim of the present study was to optimize the procedures for urinary mutagenicity testing in order to lower the baseline variation in mutagenic activity found in urine from unexposed subjects and to increase the sensitivity of the method. This was accomplished by using urine from nonsmokers and smokers as well as chemically spiked nonsmokers' urine. Diet was standardized. The number of mutants per ml of urine calculated from the linear portion of the dose-response curve was used as a measure of mutagenicity. The parameters investigated were (i) the total volume of urine per resin volume, (ii) the flow rate, (iii) the pH, (iv) the ionic strength of the urine, and (v) elimination of histidine. XAD-2 and C18 Sep-Pak resins recovered mutagens in smokers' urine and in chemically spiked urine with the same efficiency when an optimized procedure was adopted. The optimized procedure using a maximum volume of 50 ml acidified urine per Sep-Pak cartridge, or equal amount of XAD-2 resin, gave well over ten times greater recovery of mutagens from smokers' urine than in earlier reports. Histidine was effectively eliminated, and the background variation was also lowered.

Humans↗