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Biomedical subjects

H Nielsen

Publications and source records attributed to H Nielsen.

At least 289 records · Page 16Linked to original sources
PubMed1987

Prediction of cardiac risk in non-cardiac surgery.

This prospective study was carried out to develop a model for the prediction of cardiac risk in non-cardiac surgery. Detailed data were collected concerning the preoperative status of 2609 consecutive patients, who were followed closely during the postoperative course. Fatal or life-threatening cardiac complications occurred in 68 patients (2.6%). By utilizing logistic regression, a model for prediction of cardiac risk was developed. The model contained six significant preoperative predictor variables: Congestive heart failure (with 3 degrees of severity); ischaemic heart disease (with 2 degrees of severity); diabetes mellitus; serum creatinine above 0.13 mmol l-1; emergency operation; and the type of operation (two categories). With this model it seems possible to discriminate between patients with very different levels of cardiac risk.

Adult↗
PubMed1987

Vasospastic angina: control of disease activity and efficacy of drug treatment using the prolonged hyperventilation test.

Sixteen consecutive patients with vasospastic angina underwent a control provocation test in the coronary care unit or the cardiac catheterization laboratory in order to evaluate the disease activity and the efficacy of long-term calcium antagonist treatment. In patients without angina at rest, the prolonged hyperventilation test was negative in 10/10 patients on calcium antagonist treatment (group A + B) and in 4/5 patients without medication (group C). The test was positive in 1/1 patient with angina at rest without medication (group D). However, the test provoked vasospastic angina in 1/5 patients who were asymptomatic without medication. In both the latter patients the prolonged hyperventilation test became negative after the restart of calcium antagonist treatment. During a mean follow-up period of 18 months (range 16-19) after the control hyperventilation test, no relapse of angina at rest, arrhythmias, syncopes, deaths or myocardial infarctions were registered. Thus, a negative test is compatible with low disease activity and/or efficacy of calcium antagonist treatment. Further, the test may reveal a subclinical tendency to coronary artery spasm.

Adult↗
PubMed1987

Isolation and functional activity of human blood monocytes after adherence to plastic surfaces: comparison of different detachment methods.

The recovery and purity of monocytes were assessed after adherence of human blood mononuclear cells to plastic surfaces, with subsequent detachment after exposure to EDTA, lidocaine, trypsin or low temperature (4 degrees C). No differences in purity were observed (81-90%) but the recovery was highest after treatment with lidocaine and trypsin. Pretreatment of the plastic surface with fetal calf serum increased the recovery to approximately 60%. The chemotactic response of the manipulated monocytes was decreased when trypsin had been used, compared with monocytes detached after exposure to low temperature, lidocaine or EDTA. In conclusion, for the measurement of chemotaxis the best results are obtained with monocytes after lidocaine detachment from a serum-pretreated plastic surface.

Adult↗
PubMed1987

Bactericidal effect of polymorphonuclear leukocytes on Pseudomonas aeruginosa pre-incubated in ofloxacin.

The in vitro effect of human polymorphonuclear leukocytes on sub-MIC-ofloxacin-treated Pseudomonas aeruginosa was studied. Two bacteria strains were selected: one serum-sensitive and one serum-resistant. Exposure of the bacteria to subinhibitory concentrations of ofloxacin caused the bacteria to elongate into filaments. Pseudomonas aeruginosa was incubated with polymorphonuclear leukocytes and the bactericidal effect was quantitated by the reduction of CFUs. The killing of untreated and ofloxacin-treated bacteria did not differ when normal human serum was used for opsonization. However, when heat-inactivated serum or buffer was used, the killing of ofloxacin-treated bacteria was increased from 40% to 63% (P less than 0.05). Kinetic studies showed that this effect increased with prolonged incubation time. In addition, polymorphonuclear leukocytes incubated with ofloxacin had an increased bactericidal activity, probably due to intracellular uptake of the drug. Phagocytic ingestion of the bacteria was not influenced by ofloxacin-treatment. These findings support other investigations with DNA-gyrase inhibitors, which show that exposed bacteria become more susceptible to killing and that antibiotic-treated polymorphonuclear leukocytes react more strongly.

Anti-Bacterial Agents↗
PubMed1987

Antibiotics and human monocyte function. I. Chemotaxis.

The influence of thirteen commonly used antibacterial drugs on the chemotactic responsiveness of human blood monocytes in vitro was investigated. Tetracyklin, trimethoprim and fusidic acid at high concentrations produced a significant inhibition of the monocyte response, whereas normal therapeutic concentrations produced insignificant inhibition. Benzylpenicillin, ampicillin, tobramycin, chloramphenicol, metronidazole, rifampicin, clindamycin, sulfametoxazole, cefotaxime and ofloxacin did not alter monocyte migration. From these observations it can be expected that at normal dosages none of the tested drugs will affect monocyte chemotaxis in vivo.

Adult↗
PubMed1987

Erythrocyte CR1 (C3b/C4b receptor) levels and disease activity in patients with SLE.

Fifty-four patients with systemic lupus erythematosus (SLE) were examined for (1) CR1 (C3b/C4b receptor) levels on erythrocytes by an enzyme-linked immunosorbent assay, (2) levels of circulating immune complexes (IC) by a polyethylene glycol precipitation complement consumption method, and (3) concentrations of C3d split products in plasma by intermediate gel rocket immunoelectrophoresis. A preponderance of low CR1 levels was found among patients with SLE (mean 40%, range 13-106) as compared with normal controls (mean 70%, range 24-130) (p less than 0.001). The concentrations of circulating IC were elevated in 38% of 58 samples. The concentrations of C3d were elevated in 72%, and were positively correlated with the levels of IC (tau = 0.28; p less than 0.005) and with disease activity as assessed by a modification of the UCH/Middlesex criteria. Negative correlations were seen between the CR1 numbers and disease activity (p = 0.01), concentrations of circulating IC (tau = -0.14; p less than 0.005), and C3d (tau = -0.21; p less than 0.005). The changes found in CR1 levels on repeated study were, however, relatively small (less than or equal to 27%; median 5), even during periods of changing disease activity.

Adult↗
PubMed1986

Phylogenetic evidence for the acquisition of ribosomal RNA introns subsequent to the divergence of some of the major Tetrahymena groups.

Previous work has demonstrated the presence of a self-splicing intron in the large subunit ribosomal RNA coding region in some strains of the ciliate protozoan Tetrahymena. Sequence comparisons of the intron regions from six Tetrahymena species showed these to fall into three homology groups. In an attempt to evaluate the evolutionary origins of the intervening sequences, we have now determined complete small subunit ribosomal RNA gene sequences from 13 species of Tetrahymena and the absolute number of nucleotide differences between the sequences was used to construct a phylogenetic tree. This phylogeny was consistent with the groupings suggested by comparisons of other biochemical characters including cytoskeletal proteins, isozyme analyses, and restriction maps of complete rRNA transcription units. The homology groupings that were based upon the intron sequence data do not agree with the relationships inferred from the small subunit rRNA sequence data. These observations are taken to indicate that the intron character has been acquired independently in different species at a stage later than the branching out of the species.

Animals↗
PubMed1986

Characterization of detergent-solubilized sarcoplasmic reticulum Ca2+-ATPase by high-performance liquid chromatography.

Sarcoplasmic reticulum Ca2+-ATPase solubilized by the nonionic detergent octaethylene glycol monododecyl ether was studied by molecular sieve high-performance liquid chromatography (HPLC) and analytical ultracentrifugation. Significant irreversible aggregation of soluble Ca2+-ATPase occurred within a few hours in the presence of less than or equal to 50 microM Ca2+. The aggregates were inactive and were primarily held together by hydrophobic forces. In the absence of reducing agent, secondary formation of disulfide bonds occurred. The stability of the inactive dimer upon dilution permitted unambiguous assignment of its elution position and sedimentation coefficient. At high Ca2+ concentration (500 microM), monomeric Ca2+-ATPase was stable for several hours. Reversible self-association induced by variation in protein, detergent, and lipid concentrations was studied by large-zone HPLC. The association constant for dimerization of active Ca2+-ATPase was found to be 10(5)-10(6) M-1 depending on the detergent concentration. More detergent was bound to monomeric than to dimeric Ca2+-ATPase, even above the critical micellar concentration of the detergent. Binding of Ca2+ and vanadate as well as ATP-dependent phosphorylation was studied in monomeric and in reversibly associated dimeric preparations. In both forms, two high-affinity Ca2+ binding sites per phosphorylation site existed. The delipidated monomer purified by HPLC was able to form ADP-insensitive phosphoenzyme and to bind ATP and vanadate simultaneously. These results suggest that formation of Ca2+-ATPase oligomers in the membrane is governed by nonspecific forces (low affinity) and that each polypeptide chain constitutes a functional unit.

Animals↗
PubMed1986

Site specificity of psoralen-DNA interstrand cross-linking determined by nuclease Bal31 digestion.

A novel method for determination of psoralen photo-cross-linking sites in double-stranded DNA is described, which is based on a pronounced inhibition of Bal31 exonuclease activity by psoralen-DNA interstrand cross-links. The results using a 51 base pair fragment of plasmid pUC19 and a 346 base pair fragment of pBR322 show that 5'-TA sequences are preferred cross-linking sites compared to 3'-TA sequences. They also indicate that sequences flanking the 5'-TA site influence the cross-linking efficiency at the site. The DNA photo-cross-linking by 4,5',8-trimethylpsoralen and 8-methoxypsoralen was analyzed, and these two psoralens showed identical site specificity. The 5'-TA preference is rationalized on the basis of the local DNA structure in terms of the pi-pi electronic interaction between the thymines and the intercalated psoralens, as well as on the base tilt angles of the DNA.

Base Sequence↗
PubMed1986

Use of enzymatic solubilization of tissues and direct injection on pre-columns of large volumes for analysing biological samples by high-performance liquid chromatography.

A pre-column technique, which can be used to introduce all types of biological samples into high-performance liquid chromatographic systems, is described. Fluids are injected directly, whereas faeces are homogenized and centrifuged and tissue samples are solubilized by the enzyme subtilisin A. Acetonitrile is added to all samples (no precipitation of proteins is seen), fluids (10%), solubilized tissue (25%) and faeces (20%), to obtain better wettability of the packing and to counteract binding. Samples of up to 50 ml are injected onto a 6 X 4 mm I.D. pre-column from which the compounds are backflushed onto the analytical column. Different packing materials for the pre-column have been used; LiChroprep RP-18 gave the best results. This system has been used for a series of different drugs, using different analytical columns and different detectors. Both gradient and isocratic elution have been used. High recoveries, good reproducibility and low detection limits are seen for routine analysis. For metabolic work, a very large enrichment factor is obtained.

Biotransformation↗