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Biomedical subjects

B Hofer

Publications and source records attributed to B Hofer.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1989

A high efficiency method for site-directed mutagenesis with any plasmid.

A procedure is described which allows for the site-directed mutagenesis of DNA segments in any double-stranded plasmid with high efficiency. There are no limitations as to the position of the mutation. The protocol involves only simple enzymatic manipulations and no difficult to control operations, such as partial digestions, are required. The method was developed and used to mutagenize two different genes (encoding human interferon-beta and interleukin-2) cloned in a eukaryotic expression vector. For ten mutageneses with different oligodeoxyribonucleotides the average yield of mutants was 60%.

Base Sequence↗
PubMed1987

Escherichia coli RNA polymerase binding to a DNA terminus prevents formation of a closed promoter complex.

A 302 bp DNA fragment and a 113 bp subfragment of the former, both containing the fd gene VIII promoter (P VIII), were found to exhibit temperature-dependent differential behaviour in RNA chain initiation from P VIII. At 37 degrees C no significant differences were observed, while at 17 degrees C chain initiation was strongly suppressed only with the 113 bp fragment. This phenomenon depended on the presence of the (blunt) DNA terminus upstream from P VIII (position -70). Footprinting revealed that at 17 degrees C RNA polymerase was bound to this DNA fragment in a different mode. Contacts were observed only upstream from position -25. On the contrary, at 37 degrees C only the promoter complex footprint was visible. These results indicate that at 17 degrees C formation of the non-initiating complex is more favourable than formation of the promoter complex (which is closed at 17 degrees C; Hofer, B., Müller, D. and Köster, H. (1985) Nucleic Acids Res. 13, 5995-6013) and that formation of both complexes is mutually exclusive. No footprints of RNA polymerase were observed at other DNA termini. This indicates a sequence-specificity for the interaction at the terminus of the 113 bp fragment. The footprint pattern, together with features of the DNA sequence, suggests that the contacts involved in this interaction are similar to those promoter contacts formed upstream from position -20 and that DNA without a -10 region can be specifically recognized by RNA polymerase.

Bacterial Proteins↗
PubMed1987

Construction and stability of a sixfold repeated artificial gene.

The concatenation of an artificial gene consisting of 69 base pairs is described. A simple and versatile procedure was employed which is applicable to any DNA segment bordered by different restriction sites. If applied in the 'continuous duplication mode', it does not necessitate the isolation of any DNA fragment. The addition of adaptor oligonucleotides to one terminus of the segment is required to create complementary ends. The ligation of single-stranded oligonucleotides to single-stranded DNA termini was analyzed and optimized. A simple procedure is described for the separation of excess adaptor molecules. The in vivo stability of constructs containing up to six directly repeated genes was investigated. Up to four copies of the gene appeared stable during transformation of strain HB101. With six copies exact excision of ony copy was occasionally observed after transformations of rec+, recA, and recBC host cells. During long-term growth the hexameric construct appeared stable in all three strains.

Base Sequence↗
PubMed1987

[The value of various imaging technics in the preoperative diagnosis of choledocholithiasis].

In a retrospective study different methods of detecting choledocholithiasis-sonography, intravenous cholangiography, computed tomography and transhepatic cholangiography-have been compared to evaluate their accuracy. A total of 130 investigations in 93 patients were analysed. Choledocholithiasis could be predicted by sonography in 42.9%, by intravenous cholangiography in 60% and by transhepatic cholangiography in 85.7%. The overall accuracy rate with a single investigation was 51.6%. The combination of different methods increased the accuracy rate of 81.6%. We use sonography as the screening examination. In unclear cases transhepatic cholangiography has proven helpful in demonstrating choledocholithiasis. Only cholangiography, together with cholangioscopy, is performed intraoperatively. Due to high cost and limited availability, computed tomography should not be used as a basic examination.

Cholangiography↗
PubMed1987

[Acquired cystic renal changes--a clinically relevant problem in long-term dialysis].

While dialysis patients survive renal failure for years and even decades, multiple morphologic alterations take place in their kidneys. One of these (so to speak) "postmortem" changes is the formation of secondary renal cysts. A patient with end stage renal failure due to amyloidosis is described who was dialysed at home for 9 years. Intravenous pyelography and renal biopsy in the predialysis period likewise documented the presence of amyloidosis and the absence of cystic disease. Ultrasonography of both kidneys, a suspicious increase in hematocrit and the autopsy finding of numerous large cysts also showed the presence of acquired cystic disease. The frequency and complications of this newly recognized disease in longterm dialysed patients are discussed. Recommendations are given concerning follow-up of these patients, with a view to early detection of tumor development within the cysts.

Amyloidosis↗
PubMed1985

The pathway of E. coli RNA polymerase-promoter complex formation as visualized by footprinting.

The pathway of E. coli RNA polymerase-promoter complex formation was probed by characterization of low temperature intermediates at the major coat protein promoter of phage fd DMA. Three different complexes could be distinguished. One of them represents the active 'open' complex, the other two have to be regarded as 'closed'. The promoter contacts of the lower temperature complexes were totally comprised within the contacts of the higher temperature complexes. Increase in temperature led to extension of contacts into the downstream direction, while the upstream border of the complexes remained virtually unchanged. Only in the 'open' complex contacts were extended beyond the start site of transcription.

Base Sequence↗
PubMed1985

A diagnostic approach to lytic lesions of the mandible.

Fifty seven patients with histologically proven cyst-like lesions of the mandible are reviewed. The importance of combining radiographic with scintigraphic imaging is stressed. These two imaging modalities are complementary in demonstrating both the biological activity and the extent of the lesion. In osteomyelitis the bone scan, which is more sensitive than the radiograph, is also the method of choice in assessing the result of treatment.

Adolescent↗