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Biomedical subjects

M Dressler

Publications and source records attributed to M Dressler.

8 recordsLinked to original sources
PubMed2000

Efficient intracellular retrotransposition of an exogenous primate retrovirus genome.

The foamy virus (FV) subgroup of Retroviridae reverse transcribe their RNA (pre-)genome late in the replication cycle before leaving an infected cell. We studied whether a marker gene-transducing FV vector is able to shuttle to the nucleus and integrate into host cell genomic DNA. While a potential intracellular retrotransposition of vectors derived from other retroviruses was below the detection limit of our assay, we found that up to 5% of cells transfected with the FV vector were stably transduced, harboring 1 to approximately 10 vector integrants. Generation of the integrants depended on expression of functional capsid, reverse transcriptase and integrase proteins, and did not involve an extracellular step. PCR analysis of the U3 region of the 5' long terminal repeat and determination of proviral integration sites showed that a reverse transcription step had taken place to generate the integrants. Co-expression of a mutated envelope allowing particle egress and avoiding extracellular infection resulted in a significantly increased rescue of cells harboring integrants, suggesting that accumulation of proviruses via intracellular retrotransposition represents an integral part of the FV replication strategy.

Animals↗
PubMed2000

Complex effects of deletions in the 5' untranslated region of primate foamy virus on viral gene expression and RNA packaging.

Due to various advantageous features there is current interest in retroviral vectors derived from primate foamy viruses (PFVs). Two PFV cis-acting sequences have been mapped in the 5' region of the RNA (pre-)genome and in the 3' pol genomic region. In order to genetically separate PFV packaging constructs from vector constructs, we investigated the effect of deletions in the 5' untranslated region (UTR) of PFV packaging constructs and vectors on gene expression and RNA incorporation into viral particles. Our results indicate that the 5' UTR serves different previously unknown functions. First, the R region of the long terminal repeat was found to be required for PFV gag gene expression. This regulation of gene expression appeared to be mainly posttranscriptional. Second, constructs with sequence deletions between the R region and the gag gene start codon packaged as much viral mRNA into particles as the undeleted construct, and RNA from such a 5'-UTR-deleted packaging construct was copackaged into vector-virus particles, together with vector RNA which was preferentially packaged. Finally, in the U5 region a sequence was identified that was required to allow cleavage of the Gag precursor protein by the pol gene-encoded protease, suggesting a role of RNA in PFV particle formation. Taken together, the results indicate that complex interactions of the viral RNA, capsid, and polymerase proteins take place during PFV particle formation and that a clear separation of PFV vector and packaging construct sequences may be difficult to achieve.

5' Untranslated Regions↗
PubMed1993

[Liquid ventilation. 2].

The authors made two series of experiments in rabbits, using liquid ventilation. The first group was ventilated manually using RM 101 solution with an equilibration period of 30 and 60 sec., Tv = 10 ml/kg after previous administration of 30 ml/kg RM 101 at the beginning. The second group was ventilated using a specially developed liquid ventilator--part of the animals was ventilated with an equilibration interval of 30-90 sec., Tv = 10 ml/kg with administration of an initial dose od 30 ml/kg of RM 101 solution, a part of the animals in a continual manner, i.e. without an equilibration period and without administration of the initial dose of the solution. From the results it is apparent that the optimal way as regards blood gases and minimal manner of liquid ventilation. When this method was used during the 180 minutes of liquid ventilation paO2, paCO2 and pH were within the normal range. The other methods of liquid ventilation led rapidly to hypercapnia and a drop of pH as well as to serious changes in the circulation (hypertension, bradyarrhythmia).

Animals↗
PubMed1993

[Liquid ventilation--1].

The authors investigated in detail the sorption and desorption of oxygen and carbon dioxide in a solution of perfluorocarbons (solution RM 101, Miteni, Italy). From the results of the investigation ensues that maximal oxygen saturation of 77.3 vol.% can be achieved at 8 degrees C. With rising temperature the oxygen concentration in the solution declines (67.6 vol.% at 37 degrees). The saturation of the RM 101 solution corresponds to a linear equation of seventh order (fig. 2). Desorption of the RM 101 solution fully saturated with carbon dioxide, is on the other hand, most rapid at 37 degrees C (after the 13th minute the RM 101 solution contains less than 2% carbon dioxide as compared with 25 vol.% at 8 degrees C during the same period. In general the kinetics of desorption of carbon dioxide in solution correspond to a linear equation of fifth order (fig. 4). From the practical aspect it is not expedient to saturate the RM 101 solution with oxygen longer than 15-20 minutes. The mentioned kinetic parameters are important for the construction of a special liquid membrane or bubble oxygenator. In particular the latter is useful as with its use the authors achieved a 1.9 x higher oxygen concentration in the RM 101 solution than declared by the manufacturer.

Carbon Dioxide↗
PubMed1981

Neural contrast sensitivity measurements with a laser interference system for clinical and screening application.

A He-Ne laser interference device for clinical measurements of the neural contrast sensitivity fraction (CSF) is described. The system uses planoparallel glass plates for the generation of sinusoidal gratings on the retina. Incoherent light from two light-emitting diodes is superimposed for reducing the contrast to a range from 2 X 10-3 to 0.5. The device is coupled with a microcomputer that calculates the contrast sensitivity (CS) and permits control of the system by a dialogue program. The mean CSF for normal observers (95 eyes) is presented, and the data are compared with overall CS values from other authors. Pathologic CSFs of three patients are shown as examples for the clinical application. For screening purposes the CS values for five spatial frequencies are compared with the normal CSF. And loss-of-contrast values are calculated.

Equipment Safety↗
PubMed1979

[Optical properties and clinical performance of the Topcon retinal camera TRC-FET 3 (author's transl)].

A Topcon Retinal Camera TRC-FET 3 was tested for several weeks under laboratory and clinical routine conditions. The optical properties turned out as good and meet the requirements for retinal cameras in all details. Remarkable is the high speed of the imaging system, which allows working with low flash energies and with high flash frequency. The resolving power is high (8 microns at the center) and decreases slowly to the periphery. The illumination of the fundus is fairly homogeneous. Many filters of good performance are provided. There was no problem in handling the camera, and the test photographs as well as the clinical routine photographs were of high quality.

Clinical Trials as Topic↗