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Biomedical subjects

S Dörr

Publications and source records attributed to S Dörr.

10 recordsLinked to original sources
PubMed2002

Single preoperative oral application of ascorbic acid does not affect postoperative plasma levels of ascorbic acid.

BACKGROUND AND AIMS: A decrease in ascorbic acid (AA) plasma concentration is well known during the postoperative period and postulated to be caused by increased radical scavenging activity in response to surgical trauma. This often affects postoperative patients and is associated with multiple organ failure. Therefore, substitution of AA could potentially decrease the risk of postoperative complications. This study examines the effect of preoperative oral administration of 1,000 mg AA on the postoperative AA plasma concentration. METHODS: 54 patients were randomly split into two groups; patients in group 1 received no AA preoperatively while group 2 received oral AA (1,000 mg). Plasma samples were obtained preoperatively and on the first postoperative day for AA analysis (HPLC). RESULTS: In both groups the AA concentration was normal preoperatively and reduced postoperatively. CONCLUSION: A preoperative substitution of 1,000 mg AA is not sufficient to prevent postoperative lowered plasma concentration.

Administration, Oral↗
PubMed2001

Phenotypic findings due to trisomy 7p15.3-pter including the TWIST locus.

We report on a three-month-old boy with a 46,XY,der(Y)t(Y;7)(p11.32;p15.3) karyotype and growth deficiency, postnatal microcephaly with large fontanels, wide sagittal and metopic sutures, hypertelorism, choanal stenosis, micrognathia, bilateral cryptorchidism, hypospadias, abnormal fingers and toes, and severe developmental delay. FISH studies showed partial trisomy 7p resulting from a de novo unbalanced translocation. The application of molecular probes from the TWIST gene region (7p15.3-p21.1) and probes from the pseudoautosomal region (PAR) demonstrated that the 7p15.3-pter fragment was translocated onto Yp with the breakpoint within approximately 20 kb from the Yp telomere. We discuss the possible role of the TWIST gene in abnormal skull development and suggest that trisomy 7p cases with delayed closure of fontanels can be a result of TWIST gene dosage effect.

Abnormalities, Multiple↗
PubMed2001

Kabuki syndrome-like features associated with a small ring chromosome X and XIST gene expression.

Although clinical features in Kabuki syndrome (KS; Niikawa-Kuroki syndrome) have been well defined, the underlying genetic mechanism still remains unclear. We report a 9-year-old girl with typical KS-like facial appearance, skeletal and dermatoglyphic abnormalities, severe mental retardation, and growth deficiency. In 60 of 100 GTG-banded metaphases from peripheral blood lymphocytes, a ring chromosome smaller than a G group chromosome was found, which, according to reverse painting, consisted of Xq11.1q13. The proband's karyotype was described as mos45,X/46,X,+r(X). Several loci were analyzed with fluorescence in situ hybridization (FISH) and microsatellite markers revealing that one r(X) breakpoint mapped proximal to DXS422 (Xp11.21) and the second mapped distal to XIST gene, between loci DXS128E and DXS441 (Xq13.2). Uniparental disomy for X and r(X) was excluded and the paternal origin of r(X) was identified. XIST expression was demonstrated by nested reverse transcription polymerase chain reaction (RT-PCR) using primers spanning exons 5, 6i, and 6 in RNA prepared from lymphocytes. The observation of XIST expression is in contrast to two other cases in which the XIST gene was either not present on r(X) or not expressed. To our knowledge, this is the first case of Kabuki-like syndrome manifestations with r(X) and XIST expression.

Abnormalities, Multiple↗
PubMed2001

Construction of a detailed physical and transcript map of the candidate region for Russell-Silver syndrome on chromosome 17q23-q24.

Russell-Silver syndrome (RSS) is a heterogeneous disorder characterized mainly by pre- and postnatal growth retardation and characteristic dysmorphic features. The genetic cause of this syndrome is unknown. However, two autosomal translocations involving chromosome 17q25 were reported in association with RSS. Molecular analysis of the breakpoint on chromosome 17 of the de novo translocation previously described as t(1;17)(q31;q25) enabled us to refine the localization of the chromosome 17 breakpoint to 17q23-q24. Since no detailed mapping data were available for this region, we established a contig of yeast artificial chromosomes, P1 artificial chromosomes, bacterial artificial chromosomes, and cosmid clones for a 17q segment flanked by the sequence-tagged site (STS) markers D17S1557 and D17S940. This contig covers a physical distance of 4-5 Mb encompassing several novel markers. A transcript map was constructed by assigning genes and expressed sequence tags to the clone contig, and altogether 74 STS markers were mapped. Furthermore, the locus order and content provide insight into several duplication events that have occurred in the chromosomal region 17q23-q24. On the basis of our refined map, we have reduced the translocation breakpoint region to 65 kb between the newly derived markers 58T7 and CF20b. These data provide the molecular tools for the final identification of the RSS gene in 17q23-q24.

Abnormalities, Multiple↗
PubMed2000

Color constancy in goldfish: the limits.

Color constancy was investigated in behavioral training experiments on colors ranging from blue to yellow, located in the color space close to Planck's locus representing the main changes in natural skylight. Two individual goldfish were trained to peck at a test field of medium hue out of a series of 13-15 yellowish and bluish test fields presented simultaneously on a black background. During training the tank in which the fish were swimming freely was illuminated with white light. Correct choices were rewarded with food. During the tests differently saturated yellow or blue illumination was used. The degree of color constancy was inferred from the choice behavior under these illuminations. Perfect color constancy was found up to a certain degree of saturation of the colored light. Beyond this level test fields other than the training test field were chosen, indicating imperfect color constancy. Color constancy was quantified by applying color metrics on the basis of the goldfish cone sensitivity functions.

Animals↗
PubMed1997

Simultaneous color contrast in goldfish--a quantitative study.

A set of 9-15 colored test fields was presented to goldfish. In Experiment 1, test field hues ranged from green through yellow to red; in Experiment 2, the hues varied from blue through gray to yellow. In the training conditions, the test fields were presented with a gray or black surround. The fish learned to choose one intermediate test field hue by rewarding them with food. In the test conditions, the color of the surround was changed from gray to green, or red (Experiment 1), and from black to blue, or yellow (Experiment 2). The choice behavior of the goldfish changed substantially: one of the test fields other than the training test field was preferred. Direction and strength of simultaneous color contrast was quantified in goldfish color space. The effect of spatial stimulus configuration was investigated by changing test field size and using narrow annular surrounds. With test field radii ranging between 2 and 7.5 mm simultaneous color contrast was optimal whenever the ratio between surround width and test field radius had a value of about 1:1.

Algorithms↗
PubMed1996

The goldfish--a colour-constant animal.

A series of either thirteen or fifteen coloured test fields with hues from blue through grey to yellow were presented on a black background. Goldfish were trained on a bluish-grey test field by food reward. In the training situation, the setup with the coloured papers was illuminated with white light. In the test situation, the colour of the illumination was changed to blue or yellow. In both test illuminations the goldfish preferred the training field in the same way as under white illumination despite the fact that this test field stimulated the cone types very differently from the training situation. As test fields were present that excited the cones in exactly the same way as under white light, but were not chosen, colour constancy can be concluded. By means of colour metrics, it was possible to quantify direction and strength of colour constancy.

Animals↗
PubMed1994

Wavelength discrimination of the goldfish in the ultraviolet spectral range.

Wavelength discrimination ability of the goldfish was measured with a behavioural training technique in the UV spectral range. First, spectral sensitivity was determined for the two fish to adjust the monochromatic lights (between 334 and 450 nm) to equal subjective brightness. The results of the wavelength discrimination experiment show that, independent of which wavelength the fish were trained on, the relative choice frequency reached values above 70% only at wavelengths longer than 410 nm. Wavelength discrimination between 344 and 404 nm was not possible. Accordingly, the delta lambda function increases steeply between 400 and 380 nm, with values between about 12 and 90 nm, respectively. Model computations indicate that the delta lambda function cannot be explained on the basis of the cone sensitivity spectra. Instead, inhibitory interactions have to be assumed which suppress the short wavelength flanks of the short-, mid-, and long-wavelength sensitive cone types in the UV range.

Animals↗