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Biomedical subjects

F Fischer

Publications and source records attributed to F Fischer.

At least 19 recordsLinked to original sources
PubMed1997

The internal open reading frame within the nucleocapsid gene of mouse hepatitis virus encodes a structural protein that is not essential for viral replication.

The coronavirus mouse hepatitis virus (MHV) contains a large open reading frame embedded entirely within the 5' half of its nucleocapsid (N) gene. This internal gene (designated I) is in the +1 reading frame with respect to the N gene, and it encodes a mostly hydrophobic 23-kDa polypeptide. We have found that this protein is expressed in MHV-infected cells and that it is a previously unrecognized structural protein of the virion. To analyze the potential biological importance of the I gene, we disrupted its expression by site-directed mutagenesis using targeted RNA recombination. The start codon for I was replaced by a threonine codon, and a stop codon was introduced at a short interval downstream. Both alterations created silent changes in the N reading frame. In vitro translation studies showed that these mutations completely abolished synthesis of I protein, and immunological analysis of infected cell lysates confirmed this conclusion. The MHV I mutant was viable and grew to high titer. However, the I mutant had a reduced plaque size in comparison with its isogenic wild-type counterpart, suggesting that expression of I confers some minor growth advantage to the virus. The engineered mutations were stable during the course of experimental infection in mice, and the I mutant showed no significant differences from wild type in its ability to replicate in the brains or livers of infected animals. These results demonstrate that I protein is not essential for the replication of MHV either in tissue culture or in its natural host.

Animals↗
PubMed1997

Influence of the perfusate temperature on lung preservation: is there an optimum?

The optimal temperature of the pulmonary flush perfusate is still a matter of controversy. At present, a temperature of 10 degrees C is favored. This study deals with the structural and functional impact of different perfusate temperatures on lung preservation. In an extracorporeal rat heart-lung model lungs were preserved with Perfadex solution of 4, 15 and 25 degrees C and submitted to 2 h ischemia. Heart-lung blocks harvested from male rats were perfused with Krebs-Henseleit solution and ventilated with room air. Lungs were perfused with deoxygenated perfusate via the working right ventricle while the coronary arteries were retrogradely perfused with oxygenated perfusate. Oxygenation capacity (dPO2), peak inspiratory pressure (PIP) and pulmonary vascular resistance were measured. After establishment of baseline functional parameters hearts were arrested with 10 ml St. Thomas cardioplegia and lungs were flushed with 20 ml Perfadex solution. The heart-lung block was then stored for 2 h at 10 degrees C. Reperfusion was performed thereafter under the same conditions. At the end of the trial the lung tissue water was measured by the wet/dry ratio. The perfusion time of the groups flushed with 15 or 25 degrees C perfusate was significantly lower than that of the 4 degrees C group. After 20 min reperfusion dPO2 of the groups flushed with 15 or 25 degrees C was superior to those submitted to a 4 degrees C flush perfusion. PIP was significantly lower in the 15 degrees C group than in the 4 and 25 degrees C groups. The wet/dry ratio revealed the smallest water content in the 15 degrees C group. We conclude that the post-ischemic lung function is dependent on the temperature of the flush perfusate. Among the tested temperatures, perfusion at 15 degrees C showed the best results. The optimum may therefore lie in this range.

Animals↗
PubMed1996

Comparison of acamprosate and placebo in long-term treatment of alcohol dependence.

BACKGROUND: About 50% of alcoholic patients relapse within 3 months of treatment. Previous studies have suggested that acamprosate may help to prevent such relapse. The aim of our study was to assess the efficacy and safety of long-term acamprosate treatment in alcohol dependence. METHODS: In this multicentre, double-blind, placebo-controlled study, we recruited 455 patients, aged 18-65 years, with chronic or episodic alcohol dependence. Patients were randomly allocated treatment with acamprosate (1998 mg daily for bodyweight > 60 kg; 1332 mg daily for < or = kg) or placebo for 360 days. Patients were assessed on the day treatment started and on days 30, 90, 180, 270, and 360 by interview, self-report, questionnaire, and laboratory screening. Patients were classified as abstinent, relapsing, or non-attending. Time to first treatment failure (relapse or non-attendance) was the primary outcome measure. FINDINGS: Seven patients were excluded from the intention-to-treat analysis because they did not attend on the first treatment day and therefore received no medication. The acamprosate (n = 224) and placebo (n = 224) groups were well matched in terms of baseline demographic and alcohol-related variables. 94 acamprosate-treated and 85 placebo-treated patients completed the treatment phase: of those withdrawn, 104 (52 in each group) relapsed, 69 (33 vs 36, respectively) were lost to follow-up, 63 (31 vs 32) refused to continue treatment, 16 (15 vs 11) had concurrent illness, three (two vs one) died, ten (six vs four) had adverse side-effects, one (acamprosate treated) received the wrong medication, and three (placebo treated) were non-compliant. The proportion without treatment failure was higher in the acamprosate than in the placebo group throughout the treatment period (p < 0.001, Mantel-Cox). At the end of treatment, 41 (18.3%) acamprosate-treated and 16 (7.1%) placebo-treated patients had been continuously abstinent (p = 0.007). Mean cumulative abstinence duration was significantly greater in the acamprosate group than in the placebo group (138.8 [SD 137.5] vs 103.8 [119.0] days; p = 0.012). 148 patients (79 acamprosate, 69 placebo) completed 27 months follow-up: 27 (11.9%) acamprosate-treated and 11 (4.9%) placebo-treated patients remained continuously abstinent, and the mean cumulative abstinence duration was 230.8 days (259.1) and 183.0 days (235.2), respectively. Apart from occasional diarrhoea, there was no difference in side-effects between groups. INTERPRETATION: Acamprosate is an effective and well-tolerated pharmacological adjunct to psychosocial and behavioural treatment programmes for treatment of alcohol-dependent patients.

Acamprosate↗
PubMed1996

Guidelines for cost-effective implementation of Picture Archiving and Communication Systems. An approach building on practical experiences in three European hospitals.

This paper describes a comprehensive approach for the assessment of the impact of (partial) Picture Archiving and Communication Systems (PACS). The approach is developed, based on actual clinical experience in three European hospitals and tested in these environments. The approach departs from a thorough analysis of the working procedures and information flows before implementation, both descriptive and quantitative. On the basis of this analysis, quantitative (and hence testable) objectives of the implementation are defined. The implementation strategy is defined after comparison of various scenarios, taking costs and effects for both the final and the transition phases into account. The approach is supported by a comprehensive evaluation protocol and a software package (PACER). The approach is demonstrated in this paper by applying it on a hypothetical PACS implementation for CT, ultrasound and for the part of the radiology department serving ICU. The objectives of this PACS are: (1)--to shorten the turn around time between the radiology department and ICU from 4 h to 30 min, (2)--to save 2000 m2 of film per year and (3)--to save personnel time. In this case the PACS is introduced in three phases and completed after three years. The cost analysis shows that, if started in 1995, a financial break even point is reached after 6 years, when comparing costs for the film-based system with those of the PACS. Experiences in the three sites show that the approach helps to harvest potential benefits, allowing a cost-effective implementation of PACS.

Cost-Benefit Analysis↗
PubMed1996

Influence of dextrans on lung preservation: is the molecular weight important?

BACKGROUND: The addition of dextran with a molecular weight of 40,000 Dalton in pulmonary preservation solutions has proved to be beneficial. However, dextrans of other size have not yet been investigated. Therefore, it is unclear whether dextran 40,000 represents the optimal additive for lung preservation solutions. METHOD: In a working rat heart-lung model, lung were preserved with regular Euro-Collins solution or with Euro-Collins solution containing 5% dextran of different sizes: 40,000 Dalton molecular weight; 70,000 Dalton molecular weight; 160,000 Dalton molecular weight. After 2 hours of ischemia functional (oxygenation; pulmonary vascular resistance) and structural (wet/dry-ratio, light microscopy) data were assessed and the amount of dextran in the lung tissue was measured. RESULTS: Lungs preserved with Euro-Collins solution 70,000 Dalton molecular weight or Euro-Collins solution 160,000 Dalton molecular weight exhibited superior functional and structural results when compared with Euro-Collins solution and Euro-Collins solution 40,000 Dalton molecular weight. Additionally, the least amount of dextran in the lung tissue was found in organs preserved with Euro-Collins solution 160,000 Dalton molecular weight after ischemia and reperfusion. CONCLUSIONS: Dextrans are useful additives for lung preservation solutions. However, the size of the molecules is important because dextrans of 160,000 Dalton molecular weight were superior to dextrans of lower molecular weight in our study.

Animals↗
PubMed1996

Noninvasive continuous blood pressure control by pulse wave velocity.

A comparison of arterial pulse wave velocity (PWV) detected by ultrasonic Doppler probes and invasive blood pressure data was performed. For accurate assessment of PWV beat-to-beat detection of the pulse transit time (PTT) was performed by means of two 8 Mhz ultrasonic Doppler probes placed externally over the right brachial resp. radial artery, as a reference the continuous invasive blood pressure (IAP) of the contralateral radial artery was collected. Comparing the PWV associated blood pressure (APPWV) and IAP yielded a correlation coefficient of r = 0.86, and Bland-Altman plotting proved 95% (+/- 2 SEM) of APPWV values to differ within +/- 10 mm Hg from IAP. With this clinical study we found that beat-to-beat PWV measurement noninvasively, continuously and reliably monitors arterial blood pressure especially with respect to rapid blood pressure changes.

Adult↗
PubMed1995

Mutagenesis of the genome of mouse hepatitis virus by targeted RNA recombination.

Our laboratory has described a method for introducing site-specific mutations into the genome of the coronavirus mouse hepatitis virus (MHV) by RNA recombination between cotransfected genomic RNA and a synthetic subgenomic mRNA. By using a thermolabile N protein mutant of MHV as the recipient virus and synthetic RNA7 (the mRNA for the nucleocapsid protein N) as the donor, engineered recombinant viruses were selected as heat-stable progeny resulting from cotransfection. We have recently reported an optimization of the efficiency of targeted recombination in this process by using a synthetic defective interfering (DI) RNA in place of RNA7. The frequency of recombination is sufficiently high that recombinants can often be directly identified without employing a thermal selection. We present here a progress report on our use of this system to map MHV mutants and to construct N gene mutants which include (1) a mutant in which the internal open reading frame within the N gene (the I gene) has been disrupted, and (2) a series of recombinants in which portions of the MHV N gene have been replaced by the homologous regions from the N gene of bovine coronavirus. We also report on some mutants we have not been able to construct.

Amino Acid Sequence↗
PubMed1995

Escherichia coli genes required for cytochrome c maturation.

The so-called aeg-46.5 region of Escherichia coli contains genes whose expression is induced under anaerobic growth conditions in the presence of nitrate or nitrite as the terminal electron acceptor. In this work, we have examined more closely several genes of this cluster, here designated ccmABCDEFGH, that are homologous to two separate Bradyrhizobium japonicum gene clusters required for the biogenesis of c-type cytochromes. A deletion mutant of E. coli which lacked all of these genes was constructed. Maturation of indigenous c-type cytochromes synthesized under anaerobic respiratory conditions, with nitrite, nitrate, or trimethylamine N-oxide as the electron acceptor, was found to be defective in the mutant. The biogenesis of foreign cytochromes, such as the soluble B. japonicum cytochrome c550 and the membrane-bound Bacillus subtilis cytochrome c550, was also investigated. None of these cytochromes was synthesized in its mature form when expressed in the mutant, as opposed to the situation in the wild type. The results suggest that the E. coli ccm gene cluster present in the aeg-46.5 region is required for a general pathway involved in cytochrome c maturation.

Anaerobiosis↗
PubMed1995

Analytic isocenter calibration. A new approach for accurate x-ray gantries.

Isocenter calibration transforms cardiac structures in digitized biplane angiograms to absolute dimensions, calculating their radiological magnification and video transformation. Since a scaling device is not required, isocenter calibration yields to more accurate measurements than the widely used reference object calibration. Both isocenter methods reported so far, regarding geometrically inaccurate x-ray gantries, yield to different and complex computational formulas. Since these formulas are hard to understand, isocenter calibration is less widely used. To facilitate the implementation of the isocenter calibration, the basic formulas for accurate x-ray gantries are derived. Shifting virtually one x-ray system onto the other, basic isocenter calibration is derived geometrically in three simple steps. The radiological magnification of an object is illustrated as a ratio of planes. The calculation of all parameters entering the computations is demonstrated geometrically, by use of the isocenter of the x-ray gantry. The derivation gives a clear idea of isocenter calibration. It is simple to derive and facilitates the understanding of the error regarding developments. When geometrical inaccuracies vanish, all formulas become equivalent. However, even if the inaccuracies increase, all methods provide nearly identical results, indicating the robustness of isocenter calibration.

Angiocardiography↗
PubMed1995

Quantitative coronary arteriography: efficient correction of catheter calibrated vessel measurement.

1. BACKGROUND. To quantify coronary dimensions from digitized angiograms, the coronary catheter is commonly used as a scaling device. However, significant errors may result due to different angiographic magnification (DM) of the vessel and of the catheter resulting from deviating locations in the X-ray field. These errors can be corrected by biplane angiography. Since this correction needs a gantry measurement system, DM correction is less widely used. We analyzed the magnitude of DM that affects the accuracy of catheter calibrated vessel dimensions and developed DM corrections requiring low computational and measurement effort. 2. MATERIAL AND METHODS. We filmed biplane a perspex bloc of vessel phantoms (0.3 - 4.5 mm) in the isocenter of the x-ray system to get the true pixel sizes before any calibration. The phantoms were detected in the digitized images using a cardiac workstation (Kontron Cardio 500) and calibrated with differently located catheters. The calibration error was then calculated for increasing distances phantom-catheter. For DM correction, we developed procedures decreasing: (i) the computational effort (E) by approximated (A) formulas, as well as (ii) the measurement effort; this decrease approximates measured gantry settings (M) through fixed pre-settings for distances (D) and videochain (V). The several DM corrections were applied on the phantom images to analyze their correction performance and remaining calibration error. 3. RESULTS. The calibration of correctly detected pixel dimensions by a differentially magnified catheter causes a deviation of the absolute vessel dimensions, increasing with the vessel size. However, as shown in Table 1, DM correction reduces this calibration error substantially. Table 1: Calibration errors of catheter calibration and performance of DM corrections with decreasing effort (50 mm location distance phantom-catheter) 4. CONCLUSIONS. DM causes errors of vessel diameters of up to 15%. Even a measurement-free procedure (fixed presettings) corrects 71% of DM. Thus, the only additional effort of selecting an angiogram from the opposite view and marking the vessel and catheter locations in both images should be accepted.

Calibration↗
PubMed1992

[Self-instruction expert systems in medicine. Presentation of knowledge, acquisition of knowledge, prediction of suicide as an example].

AIMS: 1. Description of how self-learning expert systems work, and 2. comparison of various algorithms for the establishment of a data base for suicide prediction. POINTS DISCUSSED: from exemplary patient data, self-learning expert systems obtain their expert knowledge which they subsequently employ to establish the diagnosis in new patients. Various possibilities of storing knowledge may be employed, for example the decision tree, classes of rules or neuronal networks. The various forms of representing knowledge are also presented. Taking the prediction of suicidal risk as an example, the effectiveness of the algorithm is tested with the aid of a patient questionnaire. CONCLUSIONS: Different fields of application require different systems. The diagnosis of such expert systems can at least prompt the care-providing physician to reconsider his own diagnosis.

Artificial Intelligence↗
PubMed1992

A DNA library from an individual Beta patellaris chromosome conferring nematode resistance obtained by microdissection of meiotic metaphase chromosomes.

We have used a standard protocol established for human chromosomes to create a chromosome-specific plasmid library from a Beta patellaris chromosome conferring nematode resistance. A monosomic addition line was chosen carrying 18 sugar-beet (Beta vulgaris L.) and one wild-beet (B. patellaris) chromosome. The wild-beet chromosome can readily be identified as a univalent during metaphase I of meiosis. Highly synchronized meiotic material was used to excise the univalents from four pollen mother cells. The chromatin was lysed in a 1 nl collection drop, the DNA purified and restricted with Rsa I, ligated into a vector containing universal sequencing primers, and amplified by the polymerase chain reaction. The amplified DNA was inserted into a standard plasmid vector and cloned. Approximately 23,000 recombinant plasmids were obtained of which 15,800 could be utilized. Their insert sizes ranged from 80 to 700 bp with an average of 130 bp. 61 clones were tested in more detail by genomic Southern hybridization with sugar-beet and wild-beet DNA. Of these 32 plasmids (52%) contained single-copy inserts, 11 (18%) were specific for wild-beet DNA indicating that the DNA cloned originates in the univalent chromosome. The application of this technique for establishing high-density RFLP maps for discrete regions of plant genomes is discussed.

Animals↗
PubMed1992

DNA markers closely linked to nematode resistance genes in sugar beet (Beta vulgaris L.) mapped using chromosome additions and translocations originating from wild beets of the Procumbentes section.

Genes conferring resistance to the beet cyst nematode (Heterodera schachtii Schm.) have been transferred to sugar beet (Beta vulgaris L.) from three wild species of the Procumbentes section using monosomic addition and translocation lines, because no meiotic recombination occurs between chromosomes of cultured and wild species. In the course of a project to isolate the nematode resistance genes by strategies of reverse genetics, probes were cloned from DNA of a fragmented B. procumbens chromosome carrying a resistance gene, which had been isolated by pulsed-field gel electrophoresis. One probe (pRK643) hybridized with a short dispersed repetitive DNA element, which was found only in wild beets, and thus may be used as a molecular marker for nematode resistance to progeneis of monosomic addition lines segregating resistant and susceptible individuals. Additional probes for the resistance gene region were obtained with a polymerase chain reaction (PCR)-based strategy using repetitive primers to amplify DNA located between repetitive elements. One of these probes established the existence of at least six different chromosomes from wild beet species, each conferring resistance independently of the others. A strict correlation between the length of the wild beet chromatin introduced in fragment addition and translocation lines and the repeat copy number has been used physically to map the region conferring resistance to a chromosome segment of 0.5-3 Mb.

Animals↗