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B L Nielsen

Publications and source records attributed to B L Nielsen.

At least 37 records · Page 2Linked to original sources
PubMed1993

Characterization of the pea chloroplast DNA OriA region.

One of the two origins of replication in pea chloroplast DNA (oriA) maps in the rRNA spacer region downstream of the 16S rRNA gene, and further characterization of this origin is presented here. End-labeling of nascent DNA strands from in vivo replicating ctDNA was used to generate probes for Southern hybridization. Hybridization data identified the same region that was previously mapped to contain D-loops by electron microscopy. Subclones of the oriA region were tested for their ability to support in vitro DNA replication using a partially purified pea ctDNA replication system. Two-dimensional agarose gel electrophoresis identified replication intermediates for clones from the region just downstream of the 16S rRNA gene, with a 450-bp SacI-EcoRI clone showing the strongest activity. The experiments presented in this paper identify the 940 base pair region in the rRNA spacer between the 3' end of the 16S rRNA gene and the EcoRI site as containing oriA. Previous studies by electron microscopy localized the D-loop in the spacer region just to the right of the BamHI site, but the experiments presented here show that sequences to the left of the BamHI site are required for replication initiation from oriA. DNA sequence analysis of this region of pea ctDNA shows the presence of characteristic elements of DNA replication origins, including several direct and inverted repeat sequences, an A + T rich region, and dnaA-like binding sites, most of which are unique to the pea ctDNA oriA region when compared with published rRNA spacer sequences from other chloroplast genomes.

Base Sequence↗
PubMed1991

Pea chloroplast DNA primase: characterization and role in initiation of replication.

A DNA primase activity was isolated from pea chloroplasts and examined for its role in replication. The DNA primase activity was separated from the majority of the chloroplast RNA polymerase activity by linear salt gradient elution from a DEAE-cellulose column, and the two enzyme activities were separately purified through heparin-Sepharose columns. The primase activity was not inhibited by tagetitoxin, a specific inhibitor of chloroplast RNA polymerase, or by polyclonal antibodies prepared against purified pea chloroplast RNA polymerase, while the RNA polymerase activity was inhibited completely by either tagetitoxin or the polyclonal antibodies. The DNA primase activity was capable of priming DNA replication on single-stranded templates including poly(dT), poly(dC), M13mp19, and M13mp19 + 2.1, which contains the AT-rich pea chloroplast origin of replication. The RNA polymerase fraction was incapable of supporting incorporation of 3H-TTP in in vitro replication reactions using any of these single-stranded DNA templates. Glycerol gradient analysis indicated that the pea chloroplast DNA primase (115-120 kDa) separated from the pea chloroplast DNA polymerase (90 kDa), but is much smaller than chloroplast RNA polymerase. Because of these differences in size, template specificity, sensitivity to inhibitors, and elution characteristics, it is clear that the pea chloroplast DNA primase is an distinct enzyme form RNA polymerase. In vitro replication activity using the DNA primase fraction required all four rNTPs for optimum activity. The chloroplast DNA primase was capable of priming DNA replication activity on any single-stranded M13 template, but shows a strong preference for M13mp19 + 2.1. Primers synthesized using M13mp19 + 2.1 are resistant to DNase I, and range in size from 4 to about 60 nucleotides.

Antibodies↗
PubMed1990

Transient foreign gene expression in chloroplasts of cultured tobacco cells after biolistic delivery of chloroplast vectors.

Expression of chloramphenicol acetyltransferase (cat) by suitable vectors in chloroplasts of cultured tobacco cells, delivered by high-velocity microprojectiles, is reported here. Several chloroplast expression vectors containing bacterial cat genes, placed under the control of either psbA promoter region from pea (pHD series) or rbcL promoter region from maize (pAC series) have been used in this study. In addition, chloroplast expression vectors containing replicon fragments from pea, tobacco, or maize chloroplast DNA have also been tested for efficiency and duration of cat expression in chloroplasts of tobacco cells. Cultured NT1 tobacco cells collected on filter papers were bombarded with tungsten particles coated with pUC118 (negative control), 35S-CAT (nuclear expression vector), pHD312 (repliconless chloroplast expression vector), and pHD407, pACp18, and pACp19 (chloroplast expression vectors with replicon). Sonic extracts of cells bombarded with pUC118 showed no detectable cat activity in the autoradiograms. Nuclear expression of cat reached two-thirds of the maximal 48 hr after bombardment and the maximal at 72 hr. Cells bombarded with chloroplast expression vectors showed a low level of expression until 48 hr of incubation. A dramatic increase in the expression of cat was observed 24 hr after the addition of fresh medium to cultured cells in samples bombarded with pHD407; the repliconless vector pHD312 showed about 50% of this maximal activity. The expression of nuclear cat and the repliconless chloroplast vector decreased after 72 hr, but a high level of chloroplast cat expression was maintained in cells bombarded with pHD407. Organelle-specific expression of cat in appropriate compartments was checked by introducing various plasmid constructions into tobacco protoplasts by electroporation. Although the nuclear expression vector 35S-CAT showed expression of cat, no activity was observed with any chloroplast vectors.

Cells, Cultured↗
PubMed1989

[Treatment of acute myocardial infarction--an elucidative report].

The present-day optimal treatment of patients with acute myocardial infarction (AMI) is reviewed. The prehospital phase should be as brief as possible. Emergency observation and treatment in hospital should be initiated without delay. Schematic stages for mobilization have been discarded and free mobilization is recommended. Routine acute intervention with thrombolysis is recommended for patients in whom symptoms have been present for 6-12 hours and treatment with Aspirin is recommended. Beta-blocking agents are recommended for patients with increased risk after discharge. Treatment of ventricular and supraventricular arrhythmias, block and cardiac failure are reviewed in detail. Patients without complications should be monitored for three to five days and may be discharged after seven to ten days. Exercise ECG should be carried out at discharge to assess the working capacity, ischaemia and subjective reaction. The importance of good patient information is emphasized. Cessation of smoking, control of lipids and blood pressure are important as secondary interventions. As far as possible, outpatient control should be offered after discharge. The criteria for referral to specialized cardiological departments are established both for emergency and elective referral. Patients under the age of 70 years with high risk for repeated AMI or death after discharge (with residual ischaemia) should possibly be referred for coronary arteriography.

Adrenergic beta-Antagonists↗
PubMed1989

Subjective consequences of permanent pacemaker therapy in patients under the age of retirement.

During a 5-year period, 81 patients ages 20 to 60 years old had implantation of a permanent cardiac pacemaker at the University Hospital, Odense. At follow-up, during 1985, the 73 survivors received a semi-structured questionnaire regarding subjective consequences of pacemaker therapy, and 72 people (98.6%) agreed to participate. The mean pacing period (range) was 33.8 (11-72) months. Surgical intervention was required in 14 patients (19.4%) during follow-up. Regarding all symptoms 67 patients (93.1%) perceived benefit from the pacemaker. The effectiveness of cardiac pacing was most pronounced in subjects suffering from syncope and/or dizziness. Eight patients (11.1%) perceived anxiety most frequently due to fear of pacing failure. Physical complaints were present in 17 patients (23.6%), and the discomfort was mainly due to the size of generator, pain/tenderness from the scar or a sensation of "impulses"/palpitations. To the majority (49 patients or 68.1%) pacemaker treatment did not influence quality of sexual activity. Six patients (8.3%) perceived an improvement, whereas a corresponding number felt deterioration in sexual activity following pacemaker implantation. Pacemaker therapy had not affected life quality in 30 (41.7%) of the patients. However 31 patients (43%) felt an improvement, and only a minority of ten patients (13.9%) perceived deterioration in quality of life owed to pacemaker therapy.

Adult↗
PubMed1985

Purification and subunit characterization of Rhizobium meliloti RNA polymerase.

The RNA polymerase of the symbiotic, nitrogen-fixing bacterium Rhizobium meliloti was purified, and its subunit composition was determined. The cells were disrupted in the presence of protease inhibitors, and holoenzyme fractions were purified by fractionation by using DEAE-cellulose and DNA-agarose chromatography. The core polymerase was purified by additional chromatography on phosphocellulose. The subunit structure is beta prime (155,000 molecular weight), beta (151,000), alpha (43,000), and sigma (93,000), with an additional polypeptide of 29,000 molecular weight, which we have designated tau, found associated with both core and holoenzyme fractions. The measured stoichiometry of the holoenzyme complex was found to be 2 alpha:1 beta':1 beta:0.7 sigma:1 tau. The 93,000 molecular-weight protein subunit was identified as the sigma subunit based upon stimulation of specific transcription in assays with reconstituted polymerase.

DNA-Directed RNA Polymerases↗
PubMed1984

The basis for colored silver-protein complex formation in stained polyacrylamide gels.

Using a modified silver stain of Merril et al. [(1981) Science 211, 1437-1438] for staining polypeptides in sodium dodecyl sulfate-polyacrylamide gels, protein bands reproducibly stain different shades of blue, yellow, red, and gray. The procedure is highly temperature dependent, with optimal color formation at 42 degrees C. The procedure may be completed within 2 h. Color formation is due to silver ion complexes with charged amino acid side chains. The color of the silver-protein complex can be predicted if the amino acid sequence is known, although some exceptions are discussed. This provides another dimension to the characterization of proteins by gel electrophoresis.

Chemical Phenomena↗
PubMed1984

Analgetic treatment in acute myocardial infarction. A controlled clinical comparison of morphine, nicomorphine and pethidine.

In a randomized double-blind study with flexible dosage, morphine, nicomorphine and pethidine were compared with regard to analgetic effect, dose requirements, dose intervals and adverse reactions. A total of 275 patients were included, and 28 patients were excluded due to adverse reactions (n = 16) and for practical reasons, etc. Acute myocardial infarction (AMI) was diagnosed in about 60% of the patients, and about 30% had ischemic heart disease without AMI. All three analgesics provided equally efficient pain relief in relative doses of morphine 10, nicomorphine 10 and pethidine 75 mg/ml. Severe adverse reactions were few (allergy 3 cases, respiratory insufficiency 4, severe bradycardia 4), whereas nausea was recorded in 20-30%, vomiting in 5-15% and dizziness in 10-30% of the patients, with no difference between the three drugs. Significant blood pressure drop (greater than 30 mmHg) was seen in 3-8% of the patients, with no significant differences between the drugs.

Aged↗
PubMed1983

Limitation of enzymatic models for predicting myocardial infarct size.

The possibility of predicting myocardial infarct size from early enzyme measurements was studied using a physiological two compartment distribution model. Based on this the time dependent appearance function in plasma was calculated for creatine kinase, aspartate aminotransferase, and lactate dehydrogenase in 29 patients suffering from acute myocardial infarction. On average, the appearance function of the three enzymes started four hours after the onset of symptoms, and the maximum was reached after 12 hours for creatine kinase, 13 hours for aspartate aminotransferase, and 22 hours for lactate dehydrogenase. The cumulated appearance function was used as an acceptable estimate of infarct size. The prediction of infarct size from defined points of the appearance function curve for each of the three enzymes was attempted according to a set schedule during the first 25 hours after the onset of myocardial infarction. The prediction using creatine kinase was superior to the other enzymes. Even so, a reliable prediction could only be established at the very earliest from nine hours and this is too late, as irreversible loss of myocardium occurs rapidly after the onset of symptoms. This, together with the fact that other models have unacceptable variability of the prediction, lead to the conclusion that enzymatic predictive models are of no practical value in clinical intervention studies to reduce infarct size.

Adult↗
PubMed1981

Praecordial ECG mapping in acute anterior myocardial infarction. The evolution of ST segment and Q and R waves.

Praecordial ECG mapping (42 leads) was carried out in 16 patients with anterior myocardial infarction, admitted up to 3 hours after the onset of symptoms. The mappings were performed according to a set time schedule throughout the acute phase and one year after the infarction. For each ECG map the number of leads with ST elevation greater than or equal to 1.5 mm (NST) and the sum of these (epsilon ST) were calculated. In addition, the sum of Q amplitudes (epsilon Q) and R amplitudes (epsilon R) were determined. On average, the initial epsilon ST elevation decreased from 2 to 8 hours. A secondary increase, occurring in 14 patients, was maximal during days 2-5. Based on the appearance function of creatine kinase in plasma and the QRS alterations, it is suggested that this re-elevation of the St segment was due to infarct extension (5 pats.) or expansion (9 pats.). The course of the average NST was similar to epsilon ST. epsilon Q began to develop at 3 hours, the maximum deflection being reached after about 24 hours (range 8-45). epsilon R was falling at 2 hours; the maximum rate of decrease occurred, on average, within the first 24 hours (range 12-54). One year after the infarction, both epsilon Q and epsilon R had the same level as at 8 hours. The ST elevation at 4 hours was related to the development of Q and R waves within 24 hours, but only a weak or no correlation was found. Thus, there was very little value in predicting the development of QR changes from the ST elevation at 4 hours.

Adult↗
PubMed1981

Plasma enzymes in myocardial infarction. An appraisal of quantitative, clinical and pathophysiological information.

In twenty-nine patients suffering from acute myocardial infarction changes of concentrations in plasma of creatine kinase, aspartate aminotransferase and lactate dehydrogenase were monitored 1 week following onset of infarction. The temporal characteristics of enzyme changes described are (i) the time lag from onset of chest pain until increasing enzyme concentrations occur, (ii) the time of maximum concentrations, and (iii) the period during which enzyme is released into blood. Three estimates for the extent of the infarct (i) the peak value of the plasma enzyme curves,(ii the value of the cumulated plasma curves, and (iii) the size of the infarct in grams of necrotic myocardial tissue were, as expected, closely correlated. It is concluded, that the three types of quantification of infarct size are of almost identical value for clinical, prognostic usage, From a pathophysiological point of view they are of limited interest being based on assumptions that are either unlikely to occur or cannot be tested in man.

Adult↗
PubMed1980

Sinus node dysfunction in 128 patients. A retrospective study with follow-up.

A retrospective study covering all admissions during a 6-year period revealed 128 patients with sinus node dysfunction (SND). The patients were grouped according to the ECG criteria chosen: group I 33 patients with sinus bradycardia, group II 37 with sinoatrial block/sinus arrest, group III 58 with brady-tachy syndrome. Additional heart disease, predominantly ischaemic, was found in 56%. The frequency and severity of symptoms increased from group I to group III. Pacemaker treatment was given to 40% of the cases, while medical treatment alone was successful in 17%. A follow-up including 104 patients was carried out after a mean observation period of approximately three years. Sixteen patients had died. The cause of death may have been SND per se in only one case. Five patients died of apoplectic insults or complications to such. In total, nine possible or proven systemic embolic events were found--all occurring in patients with brady-tachy syndrome. A progression of the ECG abnormality from a lower to a higher group took place in nine patients during the observation period. It is concluded that SND is a condition with a broad clinical spectrum and a stationary or slowly progressive course. In general, it carries a good prognosis. A substantial number of deaths of disabilities in patients with brady-tachy syndrome may be ascribed to systemic embolism. Long-term anticoagulant therapy is proposed in this subgroup of patients with SND.

Adult↗
PubMed1980

Sinus node dysfunction in acute myocardial infarction.

In a retrospective study of patients admitted for acute myocardial infarction (AMI) during six years, sinus node dysfunction (SND) was detected in 20 (1.04%). Twelve had persistent sinus bradycardia, 11 sinotrial block or sinus arrest and six bradytachy syndrome. Symptoms occurred in 17 patients, 12 of whom required temporary pacing for periods up to three weeks. A permanent cardiac pacemaker was implanted in three patients with brady-tachy syndrome. Three patients died during the primary admission and six during the observation period. Follow-up after a mean observation period of 34 months showed continuous signs of SND in 11 out of 19 patients. The arrhythmia caused symptoms in five patients, two of whom had a cardiac pacemaker and two received medical treatment. It is concluded that SND appearing during an AMI persists in a high number of these patients.

Aged↗