Search PubMed⌕ Search

Biomedical subjects

B Frey

Publications and source records attributed to B Frey.

At least 109 records · Page 6Linked to original sources
PubMed1993

Use of specific oligonucleotide duplexes to stimulate cleavage of refractory DNA sites by restriction endonucleases.

There are numerous restriction endonucleases (ENases) which are known never to achieve total cleavage of certain unmethylated target DNAs. In addition to EcoRII we found seven ENases (AtuBI, Cfr9I, Eco57I, Ksp632I, NaeI, NarI, and SauBMKI) that were stimulated by oligodeoxyribonucleotide (oligo) duplexes containing enzyme-specific recognition sequences to cut the target DNAs much more efficiently and in most cases even to completion. These enzymes are class-II and class-IIS Enases isolated from different bacterial species and possess a varying number of specific sites in the refractory DNA substrates. For DNA analysis and large-scale preparation of certain restriction fragments where complete digestions are essential we recommend taking into account the fact that various ENases can be activated by specific oligo duplexes to drive restriction digestions to completion.

Base Sequence↗
PubMed1992

SwaI, a unique restriction endonuclease from Staphylococcus warneri, which recognizes 5'-ATTTAAAT-3'.

A novel class-II restriction endonuclease designated SwaI was purified from Staphylococcus warneri. This enzyme cleaves adenovirus 2 DNA, SV40 DNA and M13mp7 at one site each, but does not cleave lambda, PhiX174, pBR322 or pBR328 DNA. SwaI recognizes the octanucleotide sequence 5'-ATTTAAAT-3', cleaving in the center of the recognition sequence creating blunt ended DNA fragments. SwaI was used to digest chromosomal DNA from various microorganisms and human cells.

DNA↗
PubMed1992

Antiadrenergic cardiovascular adverse effects of high-dose amiodarone loading regimen.

A 55-year-old patient with inferior wall infarction was treated effectively for ventricular tachycardia with high-dose oral amiodarone loading regimen (5 g within 16 hours). Serial pharmacokinetic studies demonstrated a rapid temporary increase in amiodarone plasma concentration to a maximum of 3.40 micrograms/ml 17 hours after initiation of therapy followed by a return to normal plasma concentration within 8 hours. During fast drug evasion the patient developed acute low-output syndrome with syncope successfully controlled with intravenous catecholamine administration. Our findings suggest that the cardiovascular collapse was caused by the non-competitive adrenoceptor antagonism of amiodarone resulting in secondary autonomic insufficiency.

Administration, Oral↗
PubMed1992

Prognostic value of heart rate variability in patients awaiting cardiac transplantation.

Time and frequency domain parameters of heart rate variability (HRV) were determined in patients with severe endstage heart failure awaiting cardiac transplantation (HTX). These parameters were then correlated with mortality to investigate the performance of HRV in discriminating between groups with high and low risk of death. The standard deviation of five consecutive RR intervals (SDANN) was found to be the parameter with the greatest sensitivity (90%) and specificity (91%). Patients with SDANN values of < 55 msec had a twenty-fold increased risk of death (90% confidence limits: 4-118, P < 0.001). The results furthermore suggest that measurements of HRV are superior to other prognostic markers such as left ventricular ejection fraction, pulmonary artery wedge pressure, cardiac index, and serum sodium levels. We conclude that HRV is a powerful, noninvasive tool to assess the risk of death in candidates for HTX. HRV measurements can therefore be used as a supplement to other markers of risk to determine the optimal therapeutic strategy in patients with severe congestive heart failure.

Adult↗
PubMed1991

[Radiotherapy as an emergency measure].

An emergency in radiotherapy is a case calling for such urgent treatment that the usual stages of planning are abbreviated and radiation is started within a few hours. After a short summary of the biological effects of radiotherapy, we will discuss the emergency situations one has to deal with. Most frequent are those in the course of malignant disease. Yet, in the context of increasingly practised transfusion- and transplantation-techniques, the number of other emergencies is rising.

Airway Obstruction↗
PubMed1991

Plasma propafenone concentration in the evaluation of anti-arrhythmic efficacy.

The anti-arrhythmic drug efficacy of oral propafenone therapy (300 mg to 900 mg per day) was studied in relation to propafenone and hydroxy-propafenone plasma concentrations in 70 outpatients (46 males, 24 females, mean age 57 +/- 12 years) followed up for 24 +/- 32 months. On average 1.7 plasma concentration measurements were performed per patient. The arrhythmias were effectively controlled in 32 patients, but in another 32 patients propafenone therapy was ineffective; in six patients the evaluation was unclear. The therapy was effective in 66% of patients with ventricular premature beats, in 50% with complex ventricular arrhythmias, in 40% with ventricular tachycardia and in 20% with supraventricular tachycardia. Fifty per cent of patients with coronary heart disease and electrical disease, but only 20% with dilated cardiomyopathy and Wolff-Parkinson-White syndrome were effectively treated. Measurement of peak plasma propafenone levels performed 4.5 +/- 2 h after oral drug administration revealed no statistically significant dose-plasma concentration relation. Optimal propafenone drug efficacy was documented at propafenone plasma concentrations ranging from 0.20 to 0.60 micrograms/ml (63% of patients considered as effectively treated). There was a trend to decrease propafenone efficacy at plasma concentrations below 0.20 micrograms/ml and above 0.60 micrograms/ml. Analysis of hydroxypropafenone identified four patients as poor metabolizers with unusually high propafenone and low hydroxypropafenone plasma concentrations; only one of these four patients showed drug efficacy. Monitoring of propafenone and hydroxypropafenone plasma concentrations was a practical procedure to assess patient's compliance, to identify poor metabolizers and to guide anti-arrhythmic drug therapy.

Adult↗
PubMed1990

Transient cholestatic hepatitis in a neonate associated with carbamazepine exposure during pregnancy and breast-feeding.

We report a 3-week-old boy with cholestatic hepatitis, most likely due to carbamazepine exposure during pregnancy and breastfeeding. Cholestasis resolved after cessation of nursing. Liver function test results and histological findings were compatible with a drug-induced hepatitis. Other causes were excluded. While carbamazepine-induced hepatitis is well known in children and adults, it has never been described in association with prenatal exposure and/or breast-feeding.

Breast Feeding↗
PubMed1989

Mutations in the Escherichia coli fnr and tgt genes: control of molybdate reductase activity and the cytochrome d complex by fnr.

In eubacteria, the tRNA transglycosylase (Tgt) in specific tRNAs exchanges a guanine in the anticodon for 7-aminomethyl-7-deazaguanine, which is finally converted to queuosine. The tgt gene of Escherichia coli has been mapped at 9 min on the genome, and mutant pairs containing an intact or mutated tgt allele were obtained after transduction of the tgt locus by P1 bacteriophages into a genetically defined E. coli strain (S. Noguchi, Y. Nishimura, Y. Hirota, and S. Nishimura, J. Biol. Chem. 257:6544-6550, 1982). These tgt mutants grew anerobically with fumarate as an electron acceptor, while nitrate or trimethylamine N-oxide could not be reduced. Furthermore, molybdate reductase activity was almost lacking and the characteristic absorption maxima, corresponding to cytochrome a1 and the cytochrome d complex, were not detectable in low-temperature reduced-minus-oxidized difference spectra in anaerobically grown cells. Transduction of the mutated tgt locus into another E. coli recipient resulted in tgt mutants without anaerobic defects. Transformation of the original tgt mutants with an fnr gene-containing plasmid reversed the anaerobic defects. Clearly, the original tgt mutants harbor a second mutation, affecting the anaerobic regulator protein Fnr. The results suggest that fnr is involved in anaerobic control of components of the cytochrome d complex and of the redox system that transfers electrons to molybdate. F' plasmids containing a fused lacI-lacZ gene with the nonsense codon UAG at different positions in the lacI part were transferred to E. coli strains with a mutated or nonmutated tgt locus but intact in fnr. A twofold increase in the frequency of incorrect readthrough of the UAG codon, dependent on the codon context, was observed in the tgt mutant and is suggested to be caused by a tRNA(Tyr) with G in place of queuosine.

Base Sequence↗