Biomedical subjects

S E Jensen

Publications and source records attributed to S E Jensen.

At least 19 recordsLinked to original sources

PubMed1995

The aminoterminal propeptide of type III procollagen provides new information on prognosis after acute myocardial infarction.

The aim of the study was to examine sequential changes in serum levels of the aminoterminal propeptide of type III procollagen (S-PIIINP) after acute myocardial infarction (AMI), and to assess the value of S-PIIINP as a predictor of outcome. The study group comprised 74 patients with AMI, and 24 patients in whom AMI was suspected but disproved. S-PIIINP changed characteristically after AMI, and in patients not receiving thrombolytic therapy or having cardiogenic shock, the changes correlated to peak enzyme values (r = 0.4, p < or = 0.03). S-PIIINP was higher at days 0 to 2 in nonsurviving AMI patients than in survivors (p < 0.05). With use of either the upper quartile for S-PIIINP at day 0 for nonsurviving AMI patients or the mean value of S-PIIINP in a normal population plus 2 SDs as a cutoff, the predictive value of a negative test ranged from 0.79 to 0.87 at days 0 to 2, and the predictive value of a positive test ranged from 0.39 to 0.67. Thus, S-PIIINP on admission and for the following few days after AMI is higher in patients with poor outcome.

Adult↗

PubMed1995

Giant linear plasmids of beta-lactam antibiotic producing Streptomyces.

A survey of the total cellular DNA from five beta-lactam antibiotic-producing Streptomyces spp. by pulsed field gel electrophoresis was conducted to investigate the presence of linear plasmids. Streptomyces clavuligerus NRRL 3585 contained two giant linear plasmids of 120 and 430 kb, in addition to the well-characterized 11.7 kb linear plasmid. Streptomyces griseus NRRL 3851 contained a single giant linear plasmid of 120 kb, and Streptomyces jumonjinensis NRRL 5741 contained two giant linear plasmids (220 and 280 kb), and two smaller linear plasmids. No plasmids were identified in Streptomyces cattleya NRRL 3841 or Streptomyces lipmannii NRRL 3584. Southern hybridization did not reveal any homology shared by these plasmids, and beta-lactam antibiotic synthesis gene clusters were located on the chromosome.

Anti-Bacterial Agents↗

PubMed1995

[Should silent ischemia be diagnosed and treated?].

Silent ischaemia (objective signs of myocardial ischaemia without symptoms) can be diagnosed using a conventional exercise-test or ambulatory Holter monitoring. Silent ischaemia is a frequent phenomenon in patients with ischaemic heart disease, i.e. patients with angina pectoris or previous myocardial infarction. The reason why ischaemia is symptomatic in some cases, and asymptomatic in others is unknown. Different possible mechanisms are discussed. Myocardial ischaemia, symptomatic or not is accompanied by a compromised function of the left ventricle, including reduced ejection fraction during exercise. In selected groups of patients, silent ischaemia is related to an impaired prognosis, while it does not seem to carry any prognostic information in other groups of patients. Silent ischaemia can be treated/reduced using antianginal medication or revascularization, but for the time being it is not known if treatment can improve prognosis. Studies concerning the latter are under way.

Humans↗

PubMed1995

Production of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine by entrapped ACV-synthetase from Streptomyces clavuligerus.

delta-(L-alpha-Aminoadipyl)-L-cysteinyl-D-valine (ACV)-synthetase from Streptomyces clavuligerus was studied under conditions that enabled the reuse of the enzyme. Coupling of ACV-synthetase to DEAE-Trisacryl and aminopropyl-glass resulted in an immobilized enzyme product of little or no catalytic activity. However, an enzyme reactor was designed by physical confinement of partially-purified ACV-synthetase in an ultrafiltration cell. This system was stimulated by phosphoenolpyruvate at lower concentrations of ATP, an effect not observed with purified enzyme. Up to 30% conversion of the limiting substrate, cysteine, to ACV occurred under semi-continuous conditions. Reaction products were investigated as potential inhibitors: AMP was the most inhibitory, but only when used at concentrations in excess of those produced in reaction mixtures. Under a nitrogen atmosphere, both product and enzyme stabilities were greatly improved and the enzyme retained 45-65% of its initial activity after five uses at room temperature during a 24-h period. Extrapolations based on these data suggest that 1.3 g partially purified enzyme (0.13 U g-1) would be capable of producing 411 mg of ACV in a 1-L reaction mixture in this period.

Amino Acid Sequence↗

PubMed1994

Transcriptional analysis and heterologous expression of the gene encoding beta-lactamase inhibitor protein (BLIP) from Streptomyces clavuligerus.

Transcription of bli, the gene encoding beta-lactamase (Bla) inhibitor protein (BLIP) of Streptomyces clavuligerus, was analyzed by promoter-probe studies, Northern hybridization and high-resolution S1 nuclease mapping. The 1-kb SalI DNA fragment immediately upstream from the bli open reading frame (ORF) showed promoter activity when tested using the xylE-based promoter-probe vector, pIJ4083. The promoter activity was approx. 36-fold higher in S. clavuligerus than in S. lividans. Northern hybridization analysis of S. clavuligerus RNA revealed that bli was expressed as a 0.7-kb monocistronic transcript. High-resolution S1 nuclease mapping identified the transcription start point as an A residue 47 bp upstream from the bli start codon. When the bli ORF, along with 111 bp of upstream sequence including the promoter, was introduced into S. lividans, the transformants produced BLIP, but in amounts approx. 12-fold lower than that produced by S. clavuligerus. Involvement of some additional regulatory element that is present in S. clavuligerus, but absent in S. lividans, could explain the difference in the promoter activities and therefore the difference in the overall expression of bli in the two hosts.

Bacterial Proteins↗

PubMed1993

Production kinetics and stability properties of delta(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase from Streptomyces clavuligerus.

Delta-(L-alpha-Aminoadipyl)-L-cysteinyl-D-valine (ACV)-synthetase is a key enzyme that channels primary metabolites to a tripeptide common to cephalosporin and cephamycin biosynthesis in Streptomyces clavuligerus. Time-course studies indicated that the S. clavuligerus ACV-synthetase was stable during the cephamycin C fermentation: the enzyme was produced early in the growth phase and its activity remained high up to 96 h of growth. The detection of crude ACV-synthetase activity in older cultures was best achieved with an assay medium supplemented with 5 mM phosphoenolpyruvate, at lower ATP concentrations. During storage at 4 degrees C, a progressive decrease in the stability of crude ACV-synthetase was observed with increasing culture age. Although a proteinolytic activity with a pH optimum at 8.2 was detected in crude cell-free extracts, no significant variation was observed in its activity with increasing culture age to account for the instability of ACV-synthetase in vitro. Addition of proteinase inhibitors did not improve the stability of the enzyme. However, a stabilization cocktail containing dithiothreitol, MgCl2, the three substrate amino acids, and glycerol increased the stability of the enzyme isolated from cultures grown for 30-40 h, which was shortly after the appearance of antibiotics in the culture fluid. This stabilized enzyme retained half of its initial activity after 6 days at 4 degrees C.

Anti-Bacterial Agents↗

PubMed1992

Molecular structure of the acyl-enzyme intermediate in beta-lactam hydrolysis at 1.7 A resolution.

The X-ray crystal structure of the molecular complex of penicillin G with a deacylation-defective mutant of the RTEM-1 beta-lactamase from Escherichia coli shows how these antibiotics are recognized and destroyed. Penicillin G is covalently bound to Ser 70 0 gamma as an acyl-enzyme intermediate. The deduced catalytic mechanism uses Ser 70 0 gamma as the attacking nucleophile during acylation. Lys 73 N zeta acts as a general base in abstracting a proton from Ser 70 and transferring it to the thiazolidine ring nitrogen atom via Ser 130 0 gamma. Deacylation is accomplished by nucleophilic attack on the penicilloyl carbonyl carbon by a water molecule assisted by the general base, Glu 166.

Acylation↗

PubMed1992

[Atrial flutter with paroxysmal 1:1 atrioventricular conduction].

Three patients with "lone" paroxysmal atrial flutter complicated by paroxysms of 1:1 AV conduction are presented. One patient (42 years of age) had been misdiagnosed as an neurotic for 18 years. The mechanism, diagnosis and treatment of the condition are outlined. The most characteristic symptoms are dizzy spells and fainting. The recommended diagnostic procedures include long term ECG recording by telemetry or Holter, exercise-ECG and oesophageal-ECG.

Adult↗

PubMed1992

Transcriptional analysis of the isopenicillin N synthase-encoding gene of Streptomyces clavuligerus.

The gene (pcbC) encoding isopenicillin N synthase of Streptomyces clavuligerus is separated from an upstream open reading frame (ORF) by a 31-bp intergenic region. Inspection of the sequence of this intergenic region did not identify a promoter sequence. The promoter probe plasmid, pIJ4083, which contains the promoter-less catechol-2,3-dioxygenase (C23O)-encoding gene (xylE) as a reporter gene, was used to analyze the sequence upstream from the pcbC gene for promoter activity. Introduction of an SphI site at the start codon of pcbC by site-directed mutagenesis allowed the cloning of a 335-bp fragment (-334 to +1 in relation to the pcbC start codon) immediately upstream from xylE in pIJ4083. C23O activity was detected in both Streptomyces lividans and S. clavuligerus cultures that contained the upstream fragment, suggesting the presence of a promoter sequence. Northern analysis of total RNA extracted from S. clavuligerus identified a monocistronic 1.2-kb transcript hybridizing to a pcbC-specific probe. When RNA was isolated at various times during growth in liquid culture, the presence of a transcript was first detected during stationary phase. Analysis of the pcbC transcript by primer extension located the transcription start point to a C residue within the upstream ORF, 91 bp upstream from the pcbC start codon.

Blotting, Northern↗

PubMed1992

High-level expression of the Streptomyces clavuligerus isopenicillin N synthase gene in Escherichia coli.

The pcbC gene, which encodes isopenicillin N synthase (IPNS), was subcloned from Streptomyces clavuligerus into Escherichia coli by using the pT7 series of plasmid vectors. The polymerase chain reaction was used to introduce an NdeI site at the translation initiation codon of pcbC, allowing the gene to be inserted behind an E. coli type of ribosome binding site. This construction directed high-level expression of IPNS, but the IPNS was in an inactive form in inclusion bodies. Active IPNS was recovered by solubilizing and renaturing the protein.

Base Sequence↗

PubMed1990

[Selective screening for hypercholesterolemia. Results from a screening model in general practice].

At present, it appears to be probable that both dietary changes and medicinal treatment can reduce the risk of development of coronary disease in middle-aged men with moderately to severely raised blood cholesterol values. Internationally, the limits for cholesterol intervention are considerably lower than in Denmark. Extensive cholesterol screening is, however, very expensive and the identified persons with high cholesterol values will frequently be found in sex and age groups where the beneficial effect of intervention is probably limited. A model for selective cholesterol screening in high risk groups in general practice is described here. In 20 general practices, all of the men aged 45-59 years belonging to the practice were invited to examination of cholesterol and blood pressure. Plasma cholesterol was measured by means of a Reflotron (results are available within three minutes) and the blood pressure and tobacco consumption were registered. After this, the patient's own general practitioner calculated with each of the persons the risk for development of myocardial infarction within the next ten years and intervention could be commenced immediately. 41% of those invited came for examination. Out of these, 29% had cholesterol values greater than or equal to 7.0 mmol/l (Danish limiting value), 44% greater than or equal to 6.5 mmol/l (limiting value in the remainder of Western Europe), and 5% greater than or equal to 9.0 mmol/l (severe hypercholesterolaemia) while only 18% had completely normal cholesterol less than 5.2 mmol/l. In every practice, two patients on an average were found with severe hypercholesterolaemia greater than or equal to 9.0 mmol/l. 28% of the participants had at least two of the three risk factors investigated. (ABSTRACT TRUNCATED AT 250 WORDS)

Denmark↗

PubMed1990

[Formalized dietary advice in hypercholesterolemia. Results in 110 men diagnosed by selective screening in general practice].

In connection with a screening investigation for high blood cholesterol in middle-aged men in general practice in the Municipality of Copenhagen, all participants with cholesterol values greater than or equal to 7.5 mmol/l were given brief advice by their own general practitioner and were invited to come for fasting blood lipid tests approximately ten days later. In cases with continued cholesterol greater than or equal to 6.8 mmol/l, the participants together with wives or partners were invited to formalized dietary advice in small groups. Already before the formalized dietary advice, an average decrease in serum cholesterol of 10% was observed. This was attributed to biological variation, absence of fasting, the degree of error between the measuring methods and also a genuine decrease on the basis of the brief dietary advice by the general practitioner. On control after dietary advice, a further decrease in cholesterol of 15% was observed while low density lipoprotein cholesterol fell by 20% and triglycerides by 23%. These decreases must be considered to result mainly from the dietary advice. It is concluded that a single but professional session of dietary advice in small groups and with involvement of the wives or partners is an effective method of treatment in hypercholesterolaemia. If the decrease in cholesterol obtained can be maintained, the literature suggests that the risk of development of ischaemic heart disease during the subsequent 5-7 years is reduced by 20-30%.

Denmark↗

PubMed1990

[Measurement of blood cholesterol, decentralized, using a Reflotron, or centralized in a laboratory. A comparison].

In connection with an extensive screening programme for blood cholesterol, the cholesterol values in 105 participants were measured on a sample of capillary blood employing a Reflotron and, simultaneously, samples of venous blood were examined by conventional enzymatic analysis in a laboratory. Whereas the day-to-day variation and the scatter involved were quite limited in the laboratory, the variation scatter between the two methods of measurement was 0.65 mmol/l. This figure was, however, no greater than that described between different laboratories in USA. Nevertheless, it is an important problem with the Reflotron method that even slight deviations from the recommended procedure of withdrawing blood involve a systematic risk for erroneously low cholesterol results.

Blood Chemical Analysis↗

PubMed1990

[Screening for cardiovascular risk factors in a large workplace].

A screening investigation was carried out in a large industry in the Copenhagen region and 1,472 of the employees were offered examination of blood cholesterol and measurement of blood pressure. At this examination the employees completed a one-page questionnaire about other cardiovascular risk factors. 45% of those invited participated in the investigation, the poorest participation was among women and the greatest among the male officials. On account of the limited number of female employees, the majority of results were only calculated for men. Over 1/3 of these had hypercholesteremia (greater than or equal to 7.0 mmol/l) and nearly 1/3 had, simultaneously, at least two cardiovascular risk factors in addition to age and male sex. Extensive occupational investigations under the auspices of WHO have demonstrated that energetic intervention at the place of work aimed at the cardiovascular risk factors can reduce the risk of development of coronary heart disease and death within a six-year follow-up period. It is therefore emphasized that similar interventions are very necessary also in Denmark.

Adult↗

PubMed1990

Production of Streptomyces clavuligerus isopenicillin N synthase in Escherichia coli using two-cistron expression systems.

Streptomyces clavuligerus isopenicillin N synthase (IPNS) gene expression was achieved in Escherichia coli by the construction of two-cistron expression systems formed in the high copy number plasmid vector pUC119. These two-cistron constructions were composed of the IPNS gene and its flanking sequences which encoded an upstream open reading frame (ORF), the IPNS ribosome binding site and a putative transcription terminator. No E. coli- like Streptomyces promoter motif was present upstream of the IPNS gene therefore transcriptional regulation of the two-cistron system was provided by the lac promoter of pUC119. Enzymatically active IPNS was detected in E. coli cells harboring the recombinant plasmids thereby providing evidence for the activity of the IPNS ORF and for the feasibility of production of S. clavuligerus IPNS in E. coli. These results indicate that simple two-cistron constructions involving foreign gene flanking sequences may be used to express foreign proteins in E. coli.

Base Sequence↗

PubMed1990

Oxygen derepresses deacetoxycephalosporin C synthase and increases the conversion of penicillin N to cephamycin C in Streptomyces clavuligerus.

When dissolved oxygen (DO) was maintained at saturation level during batch fermentations of Streptomyces clavuligerus (NRRL 3585), the accumulation of the intermediate penicillin N was lowered while formation of the end product cephamycin C was increased relative to fermentations without DO control. The specific activity of the penicillin ring-expansion enzyme deacetoxycephalosporin C synthase (DAOCS) was increased 2.3-fold under oxygen saturated conditions, whereas the penicillin ring-cyclizing enzyme isopenicillin N synthase (IPNS) showed only a 1.3-fold increase. Thus oxygen derepression of DAOCS appears to be an important regulatory mechanism in the conversion of penicillin N to cephamycin C in S. clavuligerus. IPNS, an early acting enzyme in cephamycin C biosynthesis, and DAOCS, which acts late in the pathway, both disappeared from cell extracts at 60 h, just prior to cessation of cephamycin production.

Cephamycins↗

PubMed1990

Discovery of an insertion sequence, IS116, from Streptomyces clavuligerus and its relatedness to other transposable elements from actinomycetes.

We have identified an insertion sequence, IS116, present in Streptomyces clavuligerus at one copy per genome. The element was discovered as a 1.4 kb insertion into the multicopy plasmid pIJ702 after propagation in S. clavuligerus. The nucleotide sequence of IS116 and the flanking sequences from pIJ702 have been determined. The junctions with pIJ702 show no target site duplication and there are no inverted repeats at the ends of the element. One putative coding open reading frame of 1197 bp was identified which would code for a protein product of 399 amino acids. This protein resembles deduced integrase/transposase proteins specified by three other transposable elements of actinomycetes: IS110 and the mini-circle from Streptomyces coelicolor A3(2), and--most particularly--IS900 of Mycobacterium paratuberculosis. Two regions that are relatively conserved among these gene products show features found in similar positions in many reverse transcriptases. IS116 and IS900 are also closely similar in their general organization and (apparently) in their insertion site specificity, whereas IS110 and the mini-circle are quite different in these features.

Actinomycetales↗

PubMed1990

Purification and partial characterization of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase from Streptomyces clavuligerus.

delta-(L-alpha-Aminoadipyl)-L-cysteinyl-D-valine synthetase (ACVS) was purified from Streptomyces clavuligerus by a combination of salt precipitation, ultrafiltration, and anion-exchange chromatography. The final purified material gave two protein bands with molecular weights of 283,000 and 32,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Electrophoresis in nondenaturing gels gave a single protein band with an estimated molecular weight of 560,000. These results suggest that ACVS is a multimer composed of nonidentical subunits.

Chromatography↗