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Biomedical subjects

B Meier

Publications and source records attributed to B Meier.

At least 361 records · Page 20Linked to original sources
PubMed1990

Acute infarction during triple-vessel coronary angioplasty due to acute occlusion of a nonattempted vessel.

During angioplasty of the left coronary artery, an acute thrombotic occlusion of the right coronary artery occurred at the site of a borderline stenosis. The source of the unexplained chest pain at the end of the procedure was identified but the next day when inferior Q-waves appeared. It was documented by repeat angiography. The coronary angiogram of the right coronary artery preceding the angioplasty of the left coronary artery is likely to have triggered the occlusion. Chest pain during or after angioplasty without apparent cause in the dilated artery must prompt a contrast medium injection into the nonattempted artery, particularly if the latter had undergone a diagnostic study at the beginning of the procedure.

Adult↗
PubMed1990

Initiation of translation at a UAG stop codon in the aldolase gene of Plasmodium falciparum.

The gene coding for the key glycolytic enzyme fructose-1,6-diphosphate aldolase of the human malaria parasite Plasmodium falciparum lacks a functional AUG initiation codon for translation. Protein sequences of natural or in vitro translated aldolase include the candidate start methionine residue at internal positions. No additional AUG start codon is found in genomic DNA, cDNA or mRNA sequences. Instead, a UAG chain termination codon is recognized as the start signal of protein synthesis in vivo and in vitro.

Amino Acid Sequence↗
PubMed1990

Computerized determination of lactate threshold during three modes of exercise.

The lactate threshold (LT) and corresponding exercise levels (rate-pressure product, workload, and exercise duration) have been proposed as objective quantitative parameters of functional capacity and cardiovascular status. The purpose of the present study was to compare three modes of exercise and to evaluate the influence of the body position, using a rapid lactate analyser and computerized determination of the LT. Eight healthy male subjects were studied. No significant difference was found between the LT measured during treadmill (1.55 +/- 0.22 mmol/l), upright bicycle (1.61 +/- 0.17 mmol/l), and supine bicycle (1.41 +/- 0.05 mmol/l) exercises. However, while exercise levels corresponding to the lactate threshold were similar in running and upright bicycling, the supine bicycle was associated with lower exercise duration and workload corresponding to the LT.

Adult↗
PubMed1990

Early assessment of tissue viability with radioiodinated heptadecanoic acid in reperfused canine myocardium: comparison with thallium-201.

Myocardial scintigraphy with heptadecanoic acid labeled with iodine-123 (123I-HDA) may allow early noninvasive delineation of viable myocardium after reperfusion. In this study myocardial uptake of 123I-HDA was compared with that of thallium-201 in six closed-chest dogs after 5 hours of occlusion followed by 1 hour of reperfusion of the left anterior descending coronary artery. Myocardial blood flow was measured with microspheres, and myocardial viability was assessed by means of triphenyltetrazolium chloride staining. In viable areas of the reperfused region, 123I-HDA uptake, thallium-201 uptake, and myocardial blood flow were similar to those measured in the control circumflex region. However, in infarcted areas they were reduced to 48 +/- 2% (mean +/- SEM; p less than 0.001), 59 +/- 3% (p less than 0.001), and 74 +/- 5% (p less than 0.001) of control values, respectively. Results of multiple regression analysis showed that thallium-201 uptake primarily reflected the level of flow during reperfusion, whereas 123I-HDA uptake was dependent on both myocardial blood flow and viability. At each level of flow, 123I-HDA uptake was significantly lower in infarcted than in viable myocardium. By means of discriminant analysis, 123I-HDA uptake was found to be the single most important predictor of viability, whereas thallium-201 was only of limited importance. Myocardial 123I-HDA uptake greater than or equal to 71% or myocardial thallium-201 uptake greater than or equal to 73% best differentiated viable from infarcted myocardium. According to these criteria, 123I-HDA predicted myocardial viability with a sensitivity of 77%, a specificity of 84% and a predictive accuracy of 81%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Interleukin 1-alpha and tumor necrosis factor-alpha induce oxygen radical production in mesangial cells.

Adherent human mesangial cells (HMC) were unable to phagocytose serum-treated zymosan (STZ), nevertheless this stimulus (1 mg/ml) induced a marked immediate increase of H2O2 and O2- release at a rate of 3.15 +/- 0.35 and 3.40 +/- 0.12 nmol/10(6) HMC/hr, respectively. Zymosan alone resulted in no release of either H2O2 or O2-. Phorbol myristate acetate (PMA, 2 X 10(-6) M) had only marginal effects on HMC leading to the generation of 0.273 +/- 0.014 nmol O2-/10(6) HMC/hr. After a lag period, human recombinant tumor necrosis factor-alpha (TNF-alpha) and human recombinant interleukin 1-alpha IL-1 alpha) both induced significant O2- production measured as SOD inhibitable reduction of cytochrome c, 5 X 10(-5) M, by adherent HMC for up to five hours, the maximum rates being 3.04 +/- 0.08 and 3.2 +/- 0.08 nmol/10(6) HMC/hr for IL-1 alpha and TNF-alpha, respectively. Significant O2- release was detectable at 0.625 ng/ml (37 pM) IL-1 alpha or 1 ng/ml (59 pM) TNF-alpha (P less than 0.05). Catalase inhibitable H2O2 production was also induced by IL-1 alpha and TNF-alpha in a dose dependent manner. Using scopoletin (40 nM) and 1 microM peroxidase we fluorimetrically measured 1.73 +/- 0.14 and 1.49 +/- 0.19 nmol H2O2/10(6) HMC/hr induced by IL-1 alpha (25 ng/ml) and TNF-alpha (20 ng/ml). Finally, we ascertained the type of radical species produced by HMC stimulated by cytokines employing ESR-spin-trapping with DMPO.2+ These results demonstrated that O2- was the primary radical species formed.(ABSTRACT TRUNCATED AT 250 WORDS)

Glomerular Mesangium↗
PubMed1990

Human fibroblasts release low amounts of reactive oxygen species in response to the potent phagocyte stimulants, serum-treated zymosan, N-formyl-methionyl-leucyl-phenylalanine, leukotriene B4 or 12-O-tetradecanoylphorbol 13-acetate.

Cell lines of human fibroblasts from primary cultures released reactive oxygen species, and displayed an increase in low-level chemiluminescence when stimulated with serum-treated zymosan, N-formyl-methionyl-leucyl-phenylalanine, leukotriene B4, or 12-O-tetradecanoylphorbol 13-acetate, all of which are known stimulants of respiratory burst in phagocytic cells. Non-serum-treated zymosan, interleukin-6, interleukin-2, interferon-gamma or complement factor C3b were ineffective. The primary radical species produced was O theta.2. Radical formation was continuous for up to 4 h, and it did not occur as an oxidative burst. The low level chemiluminescence probably arose from the excitation of carbonyl groups, since it remained unchanged in the presence of azide and 1,4-diazabicyclo[2.2.2]octane. While the release of reactive oxygen species in phagocytes has a function in defense mechanisms, the sustained production of such species in tissue cells may have a role in signaling mechanisms. The amounts of reactive oxygen species released by the fibroblasts upon stimulation with the stimulants mentioned above were low in comparison with the known stimulatory effects of cytokines [Meier et al. (1989) Biochem. J. 263, 539-545].

Electron Spin Resonance Spectroscopy↗
PubMed1990

Human fibroblasts release reactive oxygen species in response to treatment with synovial fluids from patients suffering from arthritis.

Human fibroblasts in primary culture released reactive oxygen species upon exposure to synovial fluid obtained by joint aspiration from twelve patients suffering from rheumatoid arthritis. The primary radical produced was O2- as determined by ESR spin trapping and cytochrome c reduction. In contrast to the oxidative burst in granulocytes and monocytes, radical formation proceeded continuously for at least four hours. Low-level chemiluminescence was increased upon exposure to inflammatory human synovial fluids. Spectral characteristics and effects of azide and 1,4-diazabicyclo-(2,2,2)-octane led to the conclusion that the photoemissive species were excited carbonyls. Radical production and light emission were not altered either by xanthine or allopurinol, nor by azide, cyanide or rotenone. The O2- production increased in the presence of NADH or NADPH, making an NAD(P)H oxidase a likely source. The liberation of reactive oxygen species correlated with the number of leukocytes present in the inflammatory joint fluids, but not with the concentrations of immunoglobulins and complement factor C3.

Arthritis, Rheumatoid↗
PubMed1989

Human fibroblasts release reactive oxygen species in response to interleukin-1 or tumour necrosis factor-alpha.

Human fibroblasts in primary culture released reactive oxygen species upon stimulation with cytokines such as interleukin-1 alpha (IL-1) or tumour necrosis factor-alpha (TNF). The primary radical produced was O2.- as determined by e.s.r. spin trapping and cytochrome c reduction. In contrast to the oxidative burst in granulocytes and monocytes, radical formation took place continuously for at least 4 h. Low-level chemiluminescence was increased by stimulation with IL-1 and TNF. Spectral characteristics and tests with azide led to the conclusion that the photoemissive species were excited carbonyls and not singlet oxygen. Further, there was a liberation of ethane from the cells. Radical production and light emission were not altered by either xanthine or allopurinol, nor by azide, cyanide or rotenone. O2.- production increased in the presence of NADH or NADPH, making an NAD(P)H oxidase a likely source.

Cytochrome c Group↗
PubMed1989

[Heart valve replacement in active infectious endocarditis].

A material of 87 patients who underwent cardiac surgery for active infective endocarditis from 1975 to 1987 is analyzed retrospectively. 91 emergency operations were performed in 19 women and 68 men with a mean age of 48 years. 72 native valves and 19 prosthetic valves were involved. Streptococci (41%) and staphylococci (27%) were the most frequent bacteriological isolates, whereas 19% of the cultures remained negative. Heart failure (52%), embolism (21%), uncontrolled infection (11%), prosthetic valve endocarditis (10%), atrioventricular block (4%) and ventricular septal defect (2%) were the indications for surgery an average of 22 days after diagnosis. 17 patients (19%) died, 9 during hospitalization from heart failure or septicemia and 8 in the later course. 16 patients required reoperation for valvular incompetence (5), paravalvular leak (4) or prosthesis infection (7). Five relapses (5.5%) and two reinfections (2.5%) were treated surgically while two reinfections responded to medical therapy alone. Postoperatively, 34 patients (39%) suffered severe complications such as neurological deficits, prosthetic valve endocarditis or anticoagulant haemorrhage. After a mean observation period of 52 months (range 1-147 months) 64 (91%) of the surviving patients were in NYHA classes I + II and 6 (9%) in NYHA classes III + IV.

Adolescent↗
PubMed1989

[Local development of coronary angioplasty].

From December 1980 to January 1989, over 1600 coronary angioplasty procedures were performed at the University Hospital of Geneva. The increase in interventions per year has been particularly marked since 1983 and coronary angioplasty procedures have since outnumbered coronary bypass operations, although the latter have been increasing too. The shortening of the waiting list for bypass surgery and the ageing of the surgical population can be attributed to coronary angioplasty. In the German-speaking part of Switzerland and in the country as a whole, coronary bypass surgery still dominates angioplasty in terms of numbers. Multivessel coronary angioplasty has decreased in importance in Geneva and accounts currently for about 10% of the procedures. The general growth of coronary angioplasty is therefore due to improvement in early detection of coronary artery disease, thus yielding good candidates for angioplasty, and to more frequent attempts at recanalization of chronic total coronary occlusions. This development is in keeping with that observed at the University Hospital of Lausanne but contrasts with those at the University Hospitals of Basel and Zurich. There, coronary angioplasty has gained importance only over the last 2 years, due to extension of indications to multivessel angioplasty. Primary success of the most recent 1500 interventions in Geneva was 85% with an incidence of major complications of 6% (infarction 3.5%, emergency surgery 2.0%, death 0.5%). In spite of technical improvements, there has been no persistent amelioration of results of coronary angioplasty over time. This may be explained by the fact that technically more intricate lesions (e.g., chronic total occlusions) have been tackled.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1989

Magnum wire for balloon recanalization of chronic total coronary occlusions.

A new guidewire (Magnum wire, Schneider) was developed for balloon recanalization of chronic total coronary occlusions. This 0.021-inch solid-steel wire with a floppy tip equipped with a 1-mm diameter "olive" is used like an ordinary guidewire, fits conventional balloon catheters and provides excellent steerability. Magnum wires were used in 50 consecutive chronic total coronary occlusions (mean +/- standard deviation duration 8 +/- 21 months, range 1 day to 10 years; mean length 1.1 +/- 0.8 cm, range 0.2 to 4.0). All occlusions were reached (in 23 right, 18 left anterior descending, 8 left circumflex coronary arteries and 1 diagonal branch) and 30 (60%) were recanalized (1 reoccluded during the procedure, and in 3 patients the Magnum wire did not completely cross the occlusion but enabled the previously impossible passage of a conventional wire). The mean age of the occlusion was 3 +/- 4 months in successful and 17 +/- 33 months in unsuccessful procedures (p = 0.04) and the mean length was 1.1 +/- 0.9 and 1.3 +/- 0.6 cm, respectively (p = 0.4). In 17 patients, conventional techniques had been exhausted before the Magnum wire attempt, which was successful in 8 (47%). In 33 patients the Magnum wire was tried first, with success in 22 (67%). Conventional techniques were subsequently tried in 9 of the 11 failures (none was successful). Of the 38 procedures carried out with a second, improved version of the Magnum wire, 26 (68%) were successful.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Emergency balloon angioplasty and digital subtraction angiography in the management of an acute iatrogenic occlusive dissection of a saphenous vein graft.

A 63-year-old male with status post quadruple aortocoronary bypass surgery suddenly complained of chest pain and had ST-segment elevation in lead III during routine coronary angiography. Subsequent selective injections showed occlusion of the bypass graft to the right coronary artery, whereas by digital angiography done 15 min earlier it had been patient. Iatrogenic dissection of the graft was assumed, and balloon recanalization was immediately performed. Chest pain and signs of ischemia rapidly resolved, and no evidence of myocardial infarction was found until hospital discharge.

Angiography↗