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Biomedical subjects

M Heldal

Publications and source records attributed to M Heldal.

12 recordsLinked to original sources
PubMed1997

Bacterial population dynamics in a meromictic lake.

Polyclonal antibodies against nine different bacteria isolated from Lake Saelenvannet in western Norway were produced, and the population dynamics of these strains in the lake were monitored through two spring seasons by immunofluorescence staining. The total counts of bacteria varied over time and space from 1.5 x 10(6) to 1.5 x 10(7) cells ml-1. The counts of specific bacteria were in the range of 10(3) to 10(4) cells ml-1 or less; in sum, they generally made up less than 1% of the bacterial community. Some populations showed significant changes in abundance, with blooms lasting 1 to 3 weeks. The rate of change (increase and decrease) in abundance during blooms was estimated to be 0.2 to 0.6 day-1. The average virus-to-bacteria ratio was 50, and there was a significant correlation between the abundances of virus and bacteria. Both protozoan grazing and lytic virus infection were assessed as possible mechanisms driving the variations in bacterial population density.

Antibodies, Bacterial↗
PubMed1996

Simple clinical data are useful in predicting effect of exercise training after myocardial infarction.

OBJECTIVES: The aim of the present study was to determine whether simple clinical variables can predict the effect of intensive exercise training in an unselected population early after myocardial infarction. METHODS: Starting 5 weeks after the qualifying myocardial infarction, 105 patients, 68 years old or younger, completed a 4 week period of intensive exercise training. The training effect was defined as an absolute increase in cumulative work at bicycle ergometry. Using univariate and multivariate analysis, 28 variables were tested against the training effect. RESULTS: The mean exercise capacity increased from 46.7 +/- 22.7 kJ to 69.5 +/- 31.1 kJ (P = 0.0001). Multivariate analysis identified five independent predictors of the training effect. Myocardial infarct size was associated with a better training effect (P = 0.0018), as was male gender (P = 0.0042) and ability to exercise to exhaustion at the baseline exercise test (P = 0.0124). Older age (P = 0.0017) and treatment with beta-adrenergic blocking agents (P = 0.0241) were associated with a lower effect from training. These five variables explained 33% of the variations in effect from training. Patients suffering in-hospital cardiac complications or congestive heart failure achieved a training effect at least as great as patients without cardiac complications. CONCLUSIONS: Five simple clinical variables, including infarct size, can assist in the selection of patients for exercise training after myocardial infarction.

Aged↗
PubMed1995

[Radiofrequency ablation of heart arrhythmias. Results in the first 150 patients treated at the Arrhythmia center in Oslo].

The authors review the first 150 patients with cardiac arrhythmias who were treated with radio-frequency ablation at a Norwegian arrhythmia centre. The clinical success rate (either electrophysiological cure or a dramatic reduction in the severity and frequency of the attacks) was 97%. 11 patients were treated for two or more arrhythmias. In 27 patients two, occasionally three, sessions were required to obtain a satisfactory clinical result. Repeat ablation is scheduled for three cases where the treatment was unsuccessful. Among 190 ablations, 13 complications occurred, none of which resulted in permanent sequelae. The time spent on each procedure, and particularly the long time spent on fluoroscopy during the earlier procedures, demonstrates the existence of a learning curve for ablation. This lends support to the authorities' restriction of treatment of arrhythmias by ablation to only two laboratories in a population of four million.

Adolescent↗
PubMed1994

Effects of intensive exercise training on lipid levels in high risk post-MI patients.

One hundred and two patients participated in a 4 week programme of intensive exercise training early after myocardial infarction. Lipid levels were measured before and after exercise training. The mean exercise capacity increased by 49% (P = 0.0001). Twenty-one patients who continued smoking and 25 non-beta-blocked patients were considered to have an increased risk of recurrent cardiac events, as were patients with high initial lipid levels. In the smokers and non-beta-blocked patients total cholesterol decreased by 0.30 mmol.l-1 (P = 0.031) and 0.37 mmol.l-1 (P = 0.042) respectively and triglycerides by 0.28 mmol.l-1 (P = 0.058) and 0.13 mmol.l-1 (P = 0.11). Patients with high initial cholesterol and triglyceride levels had the largest cholesterol and triglyceride decrease, r = 0.43 (P = 0.0001) and r = 0.38 (P = 0.001) respectively. After adjusting for initial lipid levels, cholesterol (P = 0.036) as well as triglycerides (P = 0.034) decreased in patients without beta-blocker treatment whereas smoking no longer had an independent effect on lipid level decrease. HDL-cholesterol did not change in any group. Thus, after 4 weeks of exercise training lipid profiles were improved in patients with an increased risk of recurrent cardiac events. Beta-blocker treatment, however, seemed to hinder the beneficial effects of exercise training on lipid levels.

Adrenergic beta-Antagonists↗
PubMed1993

Effects of flecainide on termination of atrial flutter by rapid atrial pacing.

Rapid atrial pacing is effective in terminating atrial flutter, but often results in transient or permanent atrial fibrillation rather than sinus rhythm. Class Ia antiarrhythmic drugs have earlier been shown to facilitate the direct conversion of atrial flutter to sinus rhythm. The present study was performed to test the hypothesis that flecainide, a group 1c antiarrhythmic drug, increases the direct conversion to sinus rhythm. In a series of 30 consecutive clinical episodes of atrial flutter treated with rapid atrial pacing, 12 episodes were in patients on flecainide treatment (group A), while in 13 episodes no patients were on group I antiarrhythmic drugs (group B). Direct conversion to sinus rhythm was achieved more often in group A (75%) than in group B (31%) P = 0.034. Both the flutter rates and the pacing rates used were lower in group A, 240 vs 280 beat.min-1 and 375 vs 430 b.min-1, respectively. Patients with atrial flutter in whom rapid atrial pacing is to be performed should be considered for pretreatment with flecainide.

Adult↗
PubMed1993

Deep vein thrombosis: a 7-year follow-up study.

OBJECTIVES: To study the sequelae of deep venous thrombosis (DVT) in terms of symptoms and objective signs of deep venous insufficiency (DVI) and their relationship to the initial extension of DVT, and to assess the control legs in the same way. DESIGN: Follow-up study after an average of 89 (range 79-102) months. SETTING: Out-patient clinic, University Hospital, Oslo. SUBJECTS: Seventy-six patients with DVT 7 years previously. At follow-up 41 patients were dead and 10 were not available for restudy, thus twenty-five patients were studied in all. MAIN OUTCOME MEASURES: Symptom rating. Objective verification of DVI by invasive pressure recordings (DVI-I) and by the Doppler ultrasound technique (DVI-D). RESULTS: At follow-up, 42% of the patients had symptoms, half of these severe, while 68% had DVI. Eighty-two per cent of symptomatic patients and 60% of the asymptomatic patients had DVI. There were no more symptoms in proximal than in distal DVT, but slightly more DVI. Control legs had neither symptoms nor DVI. CONCLUSIONS: Seven years after DVT few patients had severe symptoms, although objective signs of DVI were common. Symptoms were no more frequent after proximal than after distal DVT. We found no symptoms or DVI in control legs.

Aged↗
PubMed1991

Changes in polyphosphate composition and localization in Propionibacterium acnes after near-ultraviolet irradiation.

Electron microscopy showed that electron-dense granules accumulated in Propionibacterium acnes in larger amounts when the bacteria were grown on a phosphate-rich medium. X-ray microanalysis demonstrated that the granules contained mostly phosphorus and potassium, indicating that the cells contained polyphosphate granules. When cells were grown on a complex Bacto-agar medium, the amount and the size of the polyphosphate granules were reduced. Polyphosphate was also detected with 31P nuclear magnetic resonance (31P-NMR). Of the polyphosphates observed with 31P-NMR, 20% seemed to be located outside the cell membrane. Broad-band near-ultraviolet irradiation (emission maximum 366 nm) corresponding to doses that killed 37% of the cells increased the amount of polyphosphate in cells grown on the phosphate-rich medium. The fluorescent chromophore 4',6-diamidino-2-phenylindole (DAPI) shifted the fluorescence emission from 478 to 538 nm when bound to polyphosphate and excited at 340 nm. DAPI was used to detect polyphosphates generated after near-ultraviolet irradiation of the cells. Nonirradiated cells showed no increased fluorescence at 538 nm, indicating no polyphosphate is presented in the cells. We conclude that DAPI did not have "access" to the intracellular polyphosphate as long as the cells were not light damaged. This observation is important for the interpretation of near-UV damage to cells.

Centrifugation, Density Gradient↗
PubMed1990

Enumeration and biomass estimation of planktonic bacteria and viruses by transmission electron microscopy.

Bacteria and virus particles were harvested from water samples by ultracentrifugation directly onto Formvar-coated electron microscopy grids and counted in a transmission electron microscope. With this technique, we have counted and sized bacteria and viruses in marine water samples and during laboratory incubations. By X-ray microanalysis, we could determine the elemental composition and dry-matter content of individual bacteria. The dry weight/volume ratio for the bacteria was 600 fg of dry weight microns-3. The potassium content of the bacteria was normal compared with previous estimates from other bacterial assemblages; thus, this harvesting procedure did not disrupt the bacterial cells. Virus particles were, by an order of magnitude, more abundant than bacteria in marine coastal waters. During the first 5 to 7 days of incubation, the total number of viruses increased exponentially at a rate of 0.4 day-1 and thereafter declined. The high proliferation rate suggests that viral parasitism may affect mortality of bacteria in aquatic environments.

Bacteria↗
PubMed1989

[Atrial flutter with 1:1 AV conduction during intravenous flecainide treatment].

Acute drug treatment of recent onset atrial flutter may reduce the ventricular rate by increasing block in the A-V node (digitalis/verapamil) or act by directly affecting the atria by reducing the atrial rate or converting flutter to sinus rhythm (1a and 1c antiarrthythmic drugs). Treatment that reduces the atrial rate may cause 1:1 A-V conduction. Quinidine and disopyramide are well known for increasing A-V conduction to 1:1 in some patients, because of their anticholinergic effect on the A-V node. Flecainide, a 1c antiarrhythmic drug, slows down atrial conduction, reducing flutter rate by 1/3. Clinical studies have shown flecainide to be effective in converting atrial fibrillation, atrial tachycardia, A-V reentry and A-V nodal reentry tachycardias to sinus rhythm. The effect on atrial flutter has been less impressive. Flecainide prolongs A-V conduction and increases Wenckebach cycle length. In spite of this, 1:1 A-V conduction may occur during treatment with intravenous flecainide for atrial flutter. We present a case where this is demonstrated and review the literature.

Aged↗
PubMed1989

High abundance of viruses found in aquatic environments.

The concentration of bacteriophages in natural unpolluted waters is in general believed to be low, and they have therefore been considered ecologically unimportant. Using a new method for quantitative enumeration, we have found up to 2.5 x 10(8) virus particles per millilitre in natural waters. These concentrations indicate that virus infection may be an important factor in the ecological control of planktonic micro-organisms, and that viruses might mediate genetic exchange among bacteria in natural aquatic environments.

Bacteria↗
PubMed1985

X-ray microanalytic method for measurement of dry matter and elemental content of individual bacteria.

A method for the determination of dry matter and elemental content of individual bacterial cells is described. The method is based on energy-dispersive X-ray microanalysis in a transmission electron microscope. A theory for area correction of intensity is developed. Escherichia coli in the late exponential phase of growth and early stationary phase (glucose limited) had an average dry matter content of 278 and 154 fg/cell, respectively. Of the elements detected, sodium, magnesium, phosphorus, sulphur, chlorine, potassium, and calcium together made up 15 to 17% of the dry matter content. A phosphorus content of 4.2 to 5.4% of the dry matter was found in these cells. Volume measurements of air-dried cells gave an average of 1.20 to 1.25 micron3. These results emphasize that dry matter content and elemental composition can be measured directly on single cells from complex microbial communities.

Electron Probe Microanalysis↗