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D Pfeifer

Publications and source records attributed to D Pfeifer.

At least 37 records · Page 2Linked to original sources
PubMed1994

The sequence complexity of exons trapped from the mouse genome.

BACKGROUND: A central issue in genome analysis is the identification and characterization of coding regions. Estimating the coding complexity of vertebrate genomes by measuring the kinetic complexity of mRNA populations and by sequence analysis of cDNAs is limited by the fact that any given source of mRNA represents a very biased sample of all genes. Exon trapping is a method that enables the identification of genes irrespective of their transcriptional status. RESULTS: Exons were trapped from the entire mouse genome, and the resulting fragments cloned. About 7% of a random sample of exons taken from this library have significant structural homology or sequence similarity to previously sequenced genes. Using cDNAs derived from several stages of mouse development, evidence for expression of about 62% of this sample of exons was found. These data suggest that the great majority of 'exons' in the library are derived from genes. We estimate that the fraction of the genome contained in trapped exons is 2.4%; this corresponds to a sequence complexity of about 72 megabases. CONCLUSIONS: The library of exons trapped from the entire mouse genome probably represents one of the least biased and most comprehensive libraries of mouse coding regions, and should therefore prove very useful for finding genes during genome mapping and sequencing.

Amino Acid Sequence↗
PubMed1994

[Non-pharmacologic therapy of atrial fibrillation].

Since patients with recurrent atrial fibrillation are prone to recurrences, even under treatment with antiarrhythmic agents, alternative treatment modalities are being sought. Today, the non-pharmacological treatment modalities such as modification or ablation of the AV node or the operative procedures ("maze" or "corridor" operation) do not cure these patients. The non-pharmacological therapies are indicated if severe symptoms are due to high ventricular rate with hemodynamic compromise. In such cases, His bundle ablation followed by rate adaptive pacing can achieve control of symptoms in the majority of patients. In the future, more refined techniques for ablation or the introduction of automatic atrial cardioverters will extend therapeutic options.

Anti-Arrhythmia Agents↗
PubMed1994

Exon amplification from complete libraries of genomic DNA using a novel phage vector with automatic plasmid excision facility: application to the mouse neurofibromatosis-1 locus.

The identification of transcription units in the vicinity of chromosomal lesions found in tumours is an essential step in the identification of new oncogenes. Here, we describe a lambda phage vector system for genomic exon-trapping (lambda GET), which dramatically simplifies the task of exon amplification from genomic DNA. The vector accommodates about 6.5 to 19 kb of DNA and allows inserts to be automatically subcloned as multi-copy plasmids containing splice donor and acceptor sites positioned flanking the inserted genomic DNA. RNA transcripts derived from such plasmids are processed in vivo and exons contained within the inserted genomic fragments become flanked by known sequences in the resulting mRNAs. RNA-based PCR can then be used for subsequent cloning and sequence analysis of trapped exons. We have exploited the large cloning capacity of lambda GET to construct highly redundant complete genomic libraries from Sau3AI partially digested vertebrae DNAs. Using this system, we have analysed a region of about 1 MB around the mouse neurofibromatosis-1 locus and have identified novel transcription units flanking the Nf-1 gene.

Amino Acid Sequence↗
PubMed1993

Growth and cholesterol oxidation by Mycobacterium species in Tween 80 medium.

Mycobacterium strain DP was isolated from marine coastal sediment and tested for its ability to oxidize cholesterol in Tween 80-cholesterol (2.59 mM) medium. Strain DP degraded cholesterol to 4-cholesten-3-one (cholestenone), 4-androsten-3,17-dione (AD), 1,4-androstadien-3,17-dione (ADD), testosterone, and 1-dehydrotestosterone (DHT). Cholesterol disappeared in about 4 days. Cholestenone, AD, testosterone, and DHT accumulations were transient with peak concentrations of 300, 600, 30 to 40, and 21 microM. ADD production peaked after 6 days with a concentration of 1,100 microM. Peak ADD concentrations and production rates compared well with those reported for strain NRRL B3683 on cyclodextrin medium. Tween 80 medium was superior to finely dispersed cholesterol particles for both strains. In comparison, NRRL B3683 (patented for its ability to accumulate AD and ADD) on Tween 80 medium transiently accumulated more AD (approximately 1,000 microM) than did strain DP, but ADD accumulations (200 microM) were significantly lower than those for strain DP. Strain DP could be adapted to grow on ADD, which was initially inhibitory at 3.25 mM. ADD-adapted strain DP cultures produced approximately four times as much DHT from ADD than unadapted cultures did from cholesterol, showing that additional manipulation might enhance testosterone production. We believe that ADD toxicity might account for the low ADD accumulations by NRRL B3683 in Tween 80 medium.

Androstadienes↗
PubMed1992

Distinguishing between respiratory syncytial virus subgroups by protein profile analysis.

We subgrouped 75 strains of respiratory syncytial virus by a protein profile method (PPM) which relies on different mobilities of the phosphoprotein in one-dimensional polyacrylamide gel electrophoresis and does not require monoclonal antibodies. When compared with enzyme immunoassay, PPM correctly subgrouped 54 of 56 subgroup A and all 19 subgroup B strains.

Antigens, Viral↗
PubMed1991

Automated localization and identification of lower spinal anatomy in magnetic resonance images.

Clinical interpretation of the subtle changes present in MR images in the setting of disease currently relies on subjective image analysis. Image evaluation could potentially be improved by computerized segmentation and precise quantification of the image anatomy. However, this cannot be automated unless reliable navigation within an image is established, capable of compensating for unpredictable factors such as anatomical variability, positioning of an image plane in the body, and variable image characteristics. Focusing on the lower spinal region, this paper explores the presence of image- and anatomy-invariant features which facilitate automated, unconstrained identification, and localization of basic lower spine anatomy.

Algorithms↗
PubMed1989

Protein fingerprinting: a novel virus identification system.

Viral proteins separated by one-dimensional SDS-PAGE produce protein binding patterns (fingerprints) which are unique for different viruses. We have applied this concept successfully for the development of a practical and objective virus identification system which is applicable to most viruses. The method is simple, specific, and, unlike the currently available methods, free from all virus-specific reagents. Interference by host protein bands in SDS-PAGE preparations of virus-infected cell lysates was eliminated consistently by treating virus infected cell cultures with optimum concentration of NaCl for selective inhibition of host protein synthesis. The method utilizes the comparison of protein fingerprints of 'unknown' viruses with protein fingerprints of reference viruses stored in a computer data base, using pattern recognition software. All 113 'unknown' virus strains were correctly identified to the genus level by the protein fingerprint method, when compared with the conventional virus identification methods.

Animals↗
PubMed1980

IS4 is still found at its chromosomal site after transposition to galT.

IS4-DNA has been hybridized to separated DNA fragments of E. coli K12 strain M28 and to three mutants caused by transposition of IS4 to galT. The parental strain shows one band hybridizing to IS4 representing one copy of IS4 in the chromosome. The mutants have this copy retained and show in addition a second band corresponding to the IS4 copy in galT. The experiments support the hypothesis that transposition of IS4 is accompanied by replication of the element.

DNA Replication↗
PubMed1980

Utilization of D-phenylglycyl-glycine in Escherichia coli.

Escherichia coli K 12 is able to utilize the dipeptide D-phenylglycyl-glycine as a source of glycine. Growth experiments with a glycine auxotrophic mutant show that utilization of there dipeptide is competitively inhibited by D-alanine at a Ki of 4 x 10(-4) M. In contrast, L-alanyl-L-alanine which is transported via the system specific for dipeptides does not interfere with the utilization of D-phenylglycyl-glycine. This indicates that the dipeptide is hydrolyzed prior to uptake, and D-alanine therefore competes with the uptake of glycine via the transport system common for both amino acids. This was confirmed by examining the growth response of various transport mutants. A mutant deficient in the transport of oligo- and dipeptides grows as well as the wild type on D-phenylglycyl-glycine, whereas the growth of mutants deficient in the transport of glycine is severely impaired or prevented with this dipeptide. It is therefore demonstrated that D-phenylglycyl-glycine is hydrolyzed prior to uptake. This is a mechanism of peptide utilization in E. coli K 12 which is distinct from that described so far for other dipeptides.

Alanine↗
PubMed1980

[Use of solubilization for the preparation of samples for determination of heavy metals in biological materials using atomic absorption spectrophotometry].

Solubilisation was tested for its suitability to prepare organic samples for metal determination. Flameless atomic-absorption spectrophotometry was used as test method. Copper, manganese, zinc, and chromium levels were determined from various organ systems of Wistar rat, in response to "normal" feeding of pelletised standard feed. A comparison between experimentally established concentrations, on the one hand, and literature data, on the other, suggested that solubilisation was applicable with good success to the preparation of samples from which to determine reliable values, in ppm and ppb, of the above elements.

Animal Feed↗
PubMed1980

[Control of trace elements in the rat using the heavy metal antidote "Unithiol" (sodium-2,3- dimercaptopropane sulfonate)].

The trace element balance in laboratory rats was found to be affected by somewhat lasting application of "Unitiol". Unambiguous decline of manganese, copper, and zinc concentrations was recorded from blood and liver. Complex fixation of copper was stronger than that of the other elements tested. No dose-dependent changes were observed with the experimental arrangement described. The chromium levels in all examined organs were affected but slightly or not at all. The proposal is made that long-term therapeutic use of chelate formers should be accompanied by properly balanced application of essential trace elements.

Animals↗
PubMed1979

Burns as a manifestation of child abuse and neglect.

A multidisciplinary child abuse team investigated children with burns admitted to a general hospital in Tulsa, Okla. Of the 26 burn cases investigated, 14 were found to be accidental, seven accidental with extreme degrees of neglect, and five nonaccidental burns. There are correlations between physical findings and social characteristics, which may aid in the identification and disposition of children with burns. A multiplicity of injuries suggests that nonaccidental burns are not spontaneous abuse, but a planned form of aggression. The high mortality of the abused group indicates the seriousness and severity of nonaccidental injuries. This experience has also shown that nonaccidental burns in children demand a thorough investigation of medical, social, and emotional factors.

Accidents, Home↗