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Biomedical subjects

B Hofer

Publications and source records attributed to B Hofer.

At least 19 recordsLinked to original sources
PubMed1999

Regiospecificity of dioxygenation of di- to pentachlorobiphenyls and their degradation to chlorobenzoates by the bph-encoded catabolic pathway of Burkholderia sp. strain LB400.

Burkholderia sp. strain LB400 is one of the most potent aerobic polychlorobiphenyl (PCB)-degrading microorganisms that have been characterized. Its PCB-dioxygenating activity originates predominantly or exclusively from the biphenyl dioxygenase encoded by its bph gene cluster. Analysis of the dioxygenation products of several di- to pentachlorinated biphenyls formed by this enzyme revealed a complex dependence of the regiospecificity and the yield of dioxygenation on the substitution patterns of both the oxidized and the nonoxidized rings. No dioxygenolytic attack involving chlorinated meta or para carbons was observed. Therefore, the ability of the enzyme to hydroxylate chlorinated carbons appears to be limited to the ortho position. However, it is not limited to monochlorinated rings, as evidenced by dioxygenation of the 2, 4-disubstituted ring at carbons 2 and 3. This site of attack is strikingly different from that of the 2,5-dichlorinated ring, which has been shown to be dihydroxylated at positions 3 and 4 (J. D. Haddock, J. R. Horton, and D. T. Gibson, J. Bacteriol. 177:20-26, 1995). These results demonstrate that a second substituent of ortho-chlorinated rings crucially influences the site of dioxygenation at this ring and thereby determines whether or not the initial chlorobiphenyl oxidation product is further metabolized through the bph-encoded pathway. The 2,4-dichlorinated ring can alternatively be attacked at carbons 5 and 6. The preferred site crucially depends on the substitution pattern of the other ring. The formation of more than a single dioxygenation product was found predominantly with congeners that contain two chlorinated rings, both of which are similarly prone to dioxygenation or one is substituted only at carbon 3.

Biodegradation, Environmental↗
PubMed1998

Crystal structure of cis-biphenyl-2,3-dihydrodiol-2,3-dehydrogenase from a PCB degrader at 2.0 A resolution.

cis-Biphenyl-2,3-dihydrodiol-2,3-dehydrogenase (BphB) is involved in the aerobic biodegradation of polychlorinated biphenyls (PCBs). The crystal structure of the NAD+-enzyme complex was determined by molecular replacement and refined to an R-value of 17.9% at 2.0 A. As a member of the short-chain alcohol dehydrogenase/reductase (SDR) family, the overall protein fold and positioning of the catalytic triad in BphB are very similar to those observed in other SDR enzymes, although small differences occur in the cofactor binding site. Modeling studies indicate that the substrate is bound in a deep hydrophobic cleft close to the nicotinamide moiety of the NAD+ cofactor. These studies further suggest that Asn143 is a key determinant of substrate specificity. A two-step reaction mechanism is proposed for cis-dihydrodiol dehydrogenases.

Asparagine↗
PubMed1998

[Changes in the clinical picture and surgical therapy of Crohn disease. 10 years experiences].

Changes in clinical presentation of Crohn's disease (CD), patients' age at the time of disease manifestation and operation, general condition and duration of medical management were investigated in a retrospective study. 395 operations for CD were divided into consecutive groups and analysed. In an increasing number of cases patients presented with the "fibrostenotic type" rather than the "fistulizing type" of complaints. The duration of disease and of medical management increased. Patients in later groups were younger and in better general condition. We found a rise in frequency of patients with recurrent CD or prior abdominal surgery for other reasons. Primary surgery for CD increasingly consisted of resection of solitary segments of gut; in the case of recurrence, of multiple, minimal resections. The average total length of the resected intestine could be significantly reduced. The complication rate was equal in elective and emergency surgery.

Adult↗
PubMed1997

Heterologous expression of biphenyl dioxygenase-encoding genes from a gram-positive broad-spectrum polychlorinated biphenyl degrader and characterization of chlorobiphenyl oxidation by the gene products.

The bphA1A2A3A4 gene cluster, encoding a biphenyl dioxygenase from Rhodococcus globerulus P6, a gram-positive microorganism able to degrade a wide spectrum of polychlorobiphenyls (PCBs), was expressed in Pseudomonas putida, thereby allowing characterization of chlorobiphenyl oxidation by this enzyme. While P6 biphenyl dioxygenase activity was observed in P. putida containing bphA1A2A3A4, no activity was detected in Escherichia coli cells containing the same gene cluster. In E. coli, transcription of genes bphB and bphCl, located downstream of bphA1A2A3A4, was shown to be driven solely by a vector promoter, which indicated that the lack of biphenyl dioxygenase activity was not due to a lack of mRNA synthesis. Radioactive labelling of bph gene products in E. coli implied inefficient translation of the bphA gene cluster or rapid degradation of the gene products. The biosynthesis of functional P6 biphenyl dioxygenase in P. putida cells containing the same plasmid construct that yielded no activity in E. coli emphasizes the importance of the host strain for heterologous expression and shows that synthesis, correct folding, and assembly of a Rhodococcus biphenyl dioxygenase can be achieved in a gram-negative organism. Dioxygenation of six mono- and dichlorinated PCB congeners by P. putida containing the P6 bphA gene cluster indicates the following ring substitution preference for this reaction (from most to least preferred): un-, meta-, para-, and ortho-substitution. No indications were found for dioxygenation of meta/para carbon pairs, or for hydroxylation of chlorinated carbons at any position of a monochlorinated ring, suggesting a strict specificity of this biphenyl dioxygenase for attack at nonhalogenated ortho/meta vicinal carbons. This contrasts the properties of an analogous enzyme from Pseudomonas sp. strain LB400, which can both dioxygenate at meta and para positions and dehalogenate substituted ortho carbons during ortho and meta dioxygenation.

Biodegradation, Environmental↗
PubMed1997

[Temporary colostomies after sigmoid colon and rectum interventions--are they still justified?].

Primary anastomosis is increasingly favored even in emergency colorectal surgery. Two-stage procedures are frequently considered obsolete. The aim of this study is to define conditions when a two-staged operative strategy with a temporary colostomy is still appropriate. We analyzed a series of 126 patients who were treated by a colostomy following resection and subsequent closure of the colostomy. In 44 cases the primary operation was a Hartmann resection, in 39 cases a resection with colostomy and mucous fistula and in 43 cases a resection with primary anastomosis and proximal loop colostomy. Complications of diverticular or neoplastic disease were generally managed by resection without primary anastomosis. Protective loop colostomy was done after low anterior resection of the rectum or in cases of anastomotic leakage. Patients were hospitalized again after an average of 6 months for closure of the colostomy. Restoration of intestinal continuity carried no significant risk of severe intra- or post-operative complications. Disturbances of wound healing occurred in 4.5% (Hartmann resection), 17.9% (colostomy and mucous fistula) and 20.9% (loop colostomy) of patients. We found an anastomotic dehiscence rate of 2.4% after discontinuity resections and of 4.7% after closure of loop colostomies. Only one patient with anastomotic leakage required surgical reintervention. The mortality after closure of a colostomy was zero. The rate of anastomotic leakage of 2.4% was lower than in published series with more than 7.2% after primary anastomosis, thus emphasizing the beneficial effect of a two-stage operative strategy. In emergency situations of sigmoidal and rectal surgery or in cases of low anastomosis of the distal rectum, unnecessary surgical complications can be avoided by resection without primary anastomosis or by performing protective loop colostomies.

Aged↗
PubMed1995

Degradation of chlorobiphenyls catalyzed by the bph-encoded biphenyl-2,3-dioxygenase and biphenyl-2,3-dihydrodiol-2,3-dehydrogenase of Pseudomonas sp. LB400.

In order to characterize the metabolites produced in vivo by biphenyl-2,3-dioxygenase and biphenyl-2,3-dihydrodiol-2,3-dehydrogenase, the first two enzymes of the (polychloro)biphenyl catabolic pathway encoded by the bph locus of Pseudomonas sp. LB400, recombinant E. coli strains expressing the respective genes were constructed. Biphenyl-2,3-dioxygenase attack on 2,2'- or 2,4'-dichlorobiphenyl was shown to give rise to virtually quantitative ortho-dechlorination of these congeners by hydroxylation at the chlorinated carbon 2 and its unsubstituted neighbour. Elimination of hydrochloric acid directly leads to 2,3-dihydroxy-chlorobiphenyls and obviates the need for biphenyl-2,3-dihydrodiol-2,3-dehydrogenase for the catabolism of such congeners.

Biphenyl Compounds↗
PubMed1995

Conversion of chlorobiphenyls into phenylhexadienoates and benzoates by the enzymes of the upper pathway for polychlorobiphenyl degradation encoded by the bph locus of Pseudomonas sp. strain LB400.

Metabolism of 21 chlorobiphenyls by the enzymes of the upper biphenyl catabolic pathway encoded by the bph locus of Pseudomonas sp. strain LB400 was investigated by using recombinant strains harboring gene cassettes containing bphABC or bphABCD. The enzymes of the upper pathway were generally able to metabolize mono- and dichlorinated biphenyls but only partially transform most trichlorinated congeners investigated: 14 of 15 mono- and dichlorinated and 2 of 6 trichlorinated congeners were converted into benzoates. All mono- and at least 8 of 12 dichlorinated congeners were attacked by the bphA-encoded biphenyl dioxygenase virtually exclusively at ortho and meta carbons. This enzyme exhibited a high degree of selectivity for the aromatic ring to be attacked, with the order of ring preference being non- > ortho- > meta- > para-substituted for mono- and dichlorinated congeners. The influence of the chlorine substitution pattern of the metabolized ring on benzoate formation resembled its influence on the reactivity of initial dioxygenation, suggesting that the rate of benzoate formation may frequently be determined by the rate of initial attack. The absorption spectra of phenylhexadienoates formed correlated with the presence or absence of a chlorine substituent at an ortho position.

Benzoates↗
PubMed1995

The superinfection exclusion gene (sieA) of bacteriophage P22: identification and overexpression of the gene and localization of the gene product.

Previous work has shown that the sieA gene of Salmonella bacteriophage P22 is located between the genes mnt and 16. We cloned DNA fragments of the region into multicopy vectors and tested the transformants for mediating superinfection exclusion. Subcloning, phenotypical tests, and DNA sequencing resulted in the identification of the sieA gene. There are two possible initiation codons within one open reading frame of 492 or 480 bp. The deduced amino acid sequence leads to a hypothetical polypeptide with a calculated molecular mass of 18.8 or 18.3 kDa, respectively. According to three hydrophobic regions, all of which are long enough to span the membrane, the product of sieA should be a protein of the inner membrane of a P22-lysogenic cell of Salmonella typhimurium. The SieA protein was moderately overproduced from an expression vector in cultures of Escherichia coli and could be recovered from the membrane fraction.

Amino Acid Sequence↗
PubMed1994

[Erosive osteochondrosis is not spondylitis].

Technetium-99m-DPD and gallium bone scanning were concomitantly performed in patients suffering from either infectious spondylitis or erosive spondylopathy. This comparative study in 5 patients with spinal infections and in 7 patients with lumbar erosive intervertebral osteochondrosis shows a distinct enhancement of the isotopes used such that differentiation between infections and aggressive degeneration is possible. Combined scintigraphy may be a helpful diagnostic tool in such cases.

Adult↗
PubMed1994

The biphenyl/polychlorinated biphenyl-degradation locus (bph) of Pseudomonas sp. LB400 encodes four additional metabolic enzymes.

The bph locus of Pseudomonas sp. LB400, encoding biphenyl/polychlorinated biphenyl (PCB) degradation, contains a region of about 3.5 kb of hitherto unknown function, between bphC and bphD. This DNA segment has now been characterized. Four structural genes have been located and identified by a combination of expression cloning, enzyme activity tests and DNA sequencing. The region contains four closely spaced cistrons (bphKHJI) encoding a glutathione S-transferase (GST), a 2-hydroxypenta-2,4-dienoate hydratase, an acetaldehyde dehydrogenase (acylating) and a 4-hydroxy-2-oxovalerate aldolase, respectively. The latter three are enzymes required for conversion of the aliphatic end product of bphABCD-encoded catabolism of biphenyls to Krebs cycle intermediates. The discovery of these genes provides a rationale for growth of the strain on chlorinated biphenyls which yield chlorinated benzoates as dead-end metabolites. The sequences of the enzymes involved are 54-71% identical to those of homologous enzymes encoded by the dmp and xyl operons. The role of the GST in the degradation of biphenyls is less clear, but since it was found to contain, in the putative xenobiotic substrate-binding domain, a region which shares about 29% of identical amino acids with a bacterial tetrachlorohydroquinone dehalogenase, it may be involved in dehalogenation of PCB-degradative intermediates.

Aldehyde Oxidoreductases↗
PubMed1993

Genetic analysis of a Pseudomonas locus encoding a pathway for biphenyl/polychlorinated biphenyl degradation.

The cistronic organization of the bph locus, encoding a biphenyl/polychlorinated biphenyl (PCB) degradation pathway in Pseudomonas sp. LB400, has been elucidated. Seven structural genes, encoding biphenyl dioxygenase (bphA1A2A3A4), biphenyl-2,3-dihydrodiol-2,3-dehydrogenase (bphB), biphenyl-2,3-diol-1,2-dioxygenase (bphC) and 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate hydrolase (bphD), have been located. The complete sequences of bphB, bphC and bphD are reported. Taken together with the data of Erickson and Mondello [J. Bacteriol. 174 (1992) 2903-2912], Pseudomonas sp. LB400 is now the first strain for which the sequences of all genes encoding the catabolism from biphenyls to benzoates have been determined. Comparisons of the deduced amino acid (aa) sequences of BphB, BphC and BphD with those of related proteins led to predictions about catalytically important aa residues. Six Bph have been detected and identified. Five of them could be obtained as the most abundant proteins when their genes were expressed in Escherichia coli.

Amino Acid Sequence↗
PubMed1993

Biosynthesis and secretion of human interleukin 2 glycoprotein variants from baculovirus-infected Sf21 cells. Characterization of polypeptides and posttranslational modifications.

Human interleukin 2 (IL-2) and human IL-2 mutant proteins, with artificially introduced N-glycosylation or O-glycosylation sites, have been expressed in a lepidopteran cell line (Sf21, Spodoptera frugiperda) using recombinant baculovirus vectors. Only approximately 25% of the total recombinant IL-2 protein synthesized by Sf21 cells was secreted into the culture medium. Significant N-terminal truncations were detected in the secreted polypeptides (up to 85% of the molecules). Alanine and proline were absent in the major truncated forms; the first 3-5 amino acids were also absent in a small proportion of the purified proteins. The introduction of potential artificial O-glycosylation peptide sequences (..GGKAPTPPPK..), to the C-terminus or between positions 80 and 81 of the IL-2 polypeptide chain, resulted in the secretion of unglycosylated and O-glycosylated variant forms. Fast atom bombardment mass spectrometry, compositional analysis and methylation analysis, of the tryptic glycopeptide APTPPPK, revealed the presence of either GalNAc or the disaccharide Gal(beta 1-3)GalNAc as the only carbohydrate constituents attached exclusively to Thr in this peptide, in a specific ratio for each individual IL-2 mutant protein. The Gal(beta 1-3)GalNAc protein forms could be partially altered in vitro to mammalian-type glycoforms by porcine liver beta-galactoside alpha-2,3-sialyltransferase in the presence of CMP-N-acetylneuraminic acid. An IL-2 mutant form, with an 11-amino-acid peptide of human interferon-beta at position 4, which includes its only N-glycosylation site, had exclusively truncated proximally fucosylated oligomannosidic glycans; Man3GlcNAc[Fuc(alpha 1-6)]GlcNAc or Man2GlcNAc[Fuc(alpha 1-6)]GlcNAc structures, in a ratio of 3:1, were detected in the secreted proteins. No evidence was obtained for the presence of secreted proteins with complex oligosaccharide chains, irrespective of the cell-culture conditions used or the harvesting time, for infected cells with recombinant baculovirus constructs.

Amino Acid Sequence↗
PubMed1993

Implantable transvenous cardioverter-defibrillators.

BACKGROUND: Implantable transvenous cardioverter-defibrillators offer a significant opportunity to decrease procedural morbidity and medical costs in the care of patients with life-threatening ventricular arrhythmias who otherwise would have required a sternotomy or thoracotomy for device insertion. The purpose of this study was to examine prospectively the safety, efficacy, and limitations associated with the use of a transvenously implanted, tiered-therapy cardioverter-defibrillator with antitachycardia pacing function in a consecutive population of 84 ventricular fibrillation (VF) and sustained ventricular tachycardia (VT) survivors. METHODS AND RESULTS: The index arrhythmia promoting transvenous cardioverter-defibrillator implantation was VF in 41 patients, VT in 27, and both VF and VT in 16. In each patient, transvenous defibrillation via a coronary sinus, a right ventricular, a superior vena caval, and/or a subcutaneous chest patch lead system was attempted. The pulsing methods used include two-electrode single-pathway pulsing or three-electrode dual-pathway simultaneous or sequential pulsing. A transvenous cardioverter-defibrillator was inserted if the defibrillation threshold (DFT) was < or = 20 J. Successful implantation of a transvenous cardioverter-defibrillator was possible in 80 of 84 (95%) patients. The mean implant DFT was 10.9 +/- 4.8 J. After cardioverter-defibrillator implantation, all patients were extubated in the operating room and sent to a standard telemetry ward for monitoring. No patient suffered a postoperative pulmonary complication or perioperative flurry of cardiac arrhythmias. Postoperative complications included lead dislodgments in eight, transient long thoracic nerve injury in one, asymptomatic left subclavian vein occlusion in two, asymptomatic small pericardial effusion in one, subcutaneous patch pocket hematomas in four, pulse generator pocket infection in one, and lead fracture in one. As experience was gained with the procedure, it was routine to discharge patients 3 days after surgery. The mean hospital stay was 6.0 +/- 2.4 days. Upon discharge, all patients returned to their prehospital activities including those with complications except for the patient with a pocket infection, who required intravenous antibiotic therapy. Patient survival using an intention-to-treat analysis was 98% over an 11 +/- 7-month follow-up period. During this time period, 31 of the 80 patients (39%) with transvenous lead systems were successfully treated by their device for sustained VT or VF. Antitachycardia pacing was used in 424 episodes of monomorphic VT and was successful in 371 (88%). All episodes of VF were aborted by the device. Antiarrhythmic drugs were used after device implantation in only eight of 80 patients (10%). CONCLUSIONS: Transvenous cardioverter-defibrillator implantation is practical in most candidates. Implant DFTs are usually low, surgical morbidity and postoperative complications are modest, therapy of VT and VF is efficient, and survival is excellent.

Algorithms↗
PubMed1993

A simplified, single-lead unipolar transvenous cardioversion-defibrillation system.

BACKGROUND: Transvenous implantable cardioverter-defibrillators provide significant advantages in the treatment of patients with life-threatening ventricular arrhythmias. However, present technology requires considerable electrophysiology expertise, multiple incisions, and long operative times for successful implementation. METHODS AND RESULTS: In this study, we present a prototype of a new, easy-to-insert unipolar transvenous defibrillation system that has the reliability of epicardial defibrillation but the ease of pacemaker insertion. This system incorporates a single anodal right ventricular defibrillation electrode using a 65% tilt biphasic pulse delivered to a 108-cm2 surface area pulse generator titanium alloy shell as an active cathode placed in a left infraclavicular pocket. Testing of this system was performed before implantation of a standard nonthoracotomy-transvenous defibrillation system in 40 consecutive patients with a history of ventricular tachycardia or fibrillation. The simplified unipolar single-lead system resulted in a defibrillation threshold of 9.3 +/- 6.0 J with 37 of 40 patients (93%) having a defibrillation threshold of less than 20 J. Moreover, the unipolar defibrillation system was efficiently used requiring only 3.4 +/- 0.8 ventricular fibrillation inductions to measure the defibrillation threshold and 100 +/- 28 minutes to implement. CONCLUSIONS: This new unipolar transvenous defibrillation system is as simple to insert as a pacemaker, requires few ventricular fibrillation inductions, demands less technical expertise, and provides defibrillation at energy levels comparable to that reported with epicardial lead systems. It should substantially reduce the morbidity, time, and cost of defibrillator implantation.

Adult↗
PubMed1992

Clinical experience with a tiered-therapy, multiprogrammable antiarrhythmia device.

BACKGROUND: The purpose of this report is to describe our initial experience with a tiered-therapy, variable detection criteria, multiprogrammable antiarrhythmia device capable of antitachycardia pacing, cardioversion, and defibrillation in 50 cardiac arrest survivors. METHODS AND RESULTS: An epicardial lead system was used in 35 patients. A transvenous lead system was used in 15 patients. The index arrhythmia leading to device implantation was ventricular fibrillation (VF) in 23 patients, ventricular tachycardia (VT) in 21 patients, and both VT and VF in six patients. Postoperatively, all 50 patients benefited from the additional functions available in the new device compared with a device capable only of high-energy termination of arrhythmias using a simple rate detection algorithm. Total patient survival over a mean follow-up period of 15 +/- 5 months was 96%, with no patient succumbing to sudden arrhythmic death, cardiac death, or surgical death. Nine patients (18%) avoided the need for a bradycardia pacemaker because of the device's backup bradycardia pacing function. A programmable tachycardia cycle length stability algorithm prevented inappropriate device intervention into atrial fibrillation in 11 patients (22%). Detection schema flexibility, antitachycardia pacing capabilities, and low-energy cardioversion options allowed the elimination or avoidance of antiarrhythmic drugs in 41 patients (82%). Device data storage facilitated troubleshooting and reprogramming of detection algorithms and therapeutic schema in all 50 patients. Finally, the ability to perform noninvasive programmed electrical stimulation obviated the need for invasive cardiac catheterization in 35 of 35 patients who required electrophysiological testing after device implantation. CONCLUSIONS: These findings indicate that a multiprogrammable antiarrhythmia device can provide a substantial advance in the treatment of patients with disabling or life-threatening ventricular arrhythmias by minimizing the use of painful shocks, reducing the need for antiarrhythmic drugs, lowering the incidence of inappropriate shocks, facilitating electrophysiological evaluation, and obviating the need for dual-device therapy.

Adolescent↗
PubMed1990

[Status of scintigraphy in small bowel diseases].

Radionuclide studies have an established place in the evaluation of small bowel disease; in particular they allow the demonstration of active bowel bleeding with the aid of labeled erythrocytes and the diagnosis of an inflammatory bowel process or formation of an abscess with the aid of labeled leukocytes.

Enteritis↗