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Biomedical subjects

M Hübner

Publications and source records attributed to M Hübner.

15 recordsLinked to original sources
PubMed1990

[Computed tomographic detection of liver hemangiomas].

A 67-year old woman had noticed increasing growth of hair on the face and extremities for eight months. The testosterone level was raised at 2.6 micrograms/l and 24-hour urinary cortisol excretion was 160 micrograms. Ultrasound scanning showed a tumour measuring 14 x 10 x 10 cm in the left suprarenal, as well as several irregular space-occupying lesions in the liver, some of which were echo-rich. By computed tomography these structures were hypodense and did not concentrate any contrast medium. A provisional diagnosis of suprarenal carcinoma with hepatic metastases was accordingly made. After surgical removal of the suprarenal carcinoma the hormonal parameters unexpectedly returned to normal. Repetition of the computed tomography failed to elucidate the nature of the liver lesions. However, superselective hepatic angiography revealed the typical picture of haemangiomas of the liver. The existing computed tomograms were therefore reviewed. The diagnostic error was found to be due to incorrect timing of the interval between injection of contrast medium and performance of computed tomography.

Adrenal Gland Neoplasms↗
PubMed1988

On the discrimination of compound Gabor signals and textures.

We compared the discrimination of compound Gabor signals when presented pairwise and in isolation to that of textures consisting of an array of such signals. Textures composed of mirror-image compound Gabor signals were found indistinguishable even when the individual micropatterns were easily discriminated. No such blindness exists for textures composed of non-mirror-image compound Gabor signals. These results are analogous to earlier findings concerning the foveal and extrafoveal rapid discrimination of compound gratings [Rentschler and Treutwein, Nature 313, 308-310 (1985)]. This suggests that both texture perception and extrafoveal vision are, under the conditions of the given experiments, characterized by the absence of neural interactions that otherwise allow the analysis of form. Our results do also imply that the texton concept of Julesz can be extended to grey-level Gabor textures, irrespectively of whether the space domain (geometric features) or the spatial frequency domain (local spectral characteristics) representations of the micropatterns are referred to.

Discrimination, Psychological↗
PubMed1986

On the discrimination of micropatterns and textures.

The Perceptron-type of approach of texture perception argues for decomposition of the patterns by detectors or filters which can interact to result in classification of spatial information. We consider a case of texture discrimination where textures composed of discriminable grey-level micropatterns may or may not be distinguished. Two types of models involving linear pattern decomposition are shown to be insufficient for explaining such results. This suggests that observers encode the signals by means of signal dependent or adaptive feature extractors. Such a concept of texture perception is related to connectionist ideas of information processing as pursued by Julesz in his texton theory.

Animals↗
PubMed1986

[Bovine serum albumin conjugates of the new progestagen dienogest, synthesis and immunogenic properties].

In order to develop a radioimmunoassay for the new progestagen dienogest (STS 557, 17 alpha-cyanomethyl-17 beta-hydroxy-estra-4,9-dien-3-one), bovine serum albumin (BSA) conjugates of STS 557-3-carboxymethyloxime and of STS 557-11-hemisuccinate were synthesized as antigens for the production of antisera. It was proved that an excess of isobutylchlorocarbonate in the coupling reaction using the "mixed anhydride method" results in an acylation of free NH2-groups in the BSA. By the immunization of rabbits with the STS 557-antigen-antisera of high specificity and affinity to STS 557 were produced. Endogenous steroids show no cross reaction with the STS 557-antisera. Steroids with a 17 alpha-CH2CN-group, being obtained by chemical synthesis or microbial transformation, compete with STS 557 for the binding positions of the antibodies to a different extent.

Animals↗
PubMed1985

A-ring conformational stability and progesterone-receptor binding affinity of 4-en-3-one steroids.

The molecular structure and strain energy of 4-en-3-one steroids in two different A-ring conformations are calculated by means of a molecular mechanics technique. The computations for the isolated molecules provide the following order of increasing stability of the inverted A-ring conformers: 10-methyl, 19-nor, 9-ene compound. This tendency is in agreement with X-ray structure data for single crystals. The normal 1 alpha, 2 beta-half chair conformation of 10-methyl steroids is found to be stabilized by bond angles, mainly at C10, and non-bonded interactions from the 10-methyl group. Pitzer strains favour the inverted 1 beta, 2 alpha-half chair conformation in the case of 4,9-diene-3-one compounds. Binding affinities to the progesterone receptor decrease in the series: 19-nor, 9-ene, 10-methyl compound. In view of this ordering, the calculated relative stabilities of A-ring conformers are in conflict with a conformation-controlled receptor binding. Variations of receptor bond strengths are supposed to be more strongly influenced by a steric hindrance of the 10-methyl group and/or steroid-backbone flexibility.

Animals↗
PubMed1985

Signal detection analysis of residual vision in a field defect due to a post-geniculate lesion.

A patient's ability to discriminate between 'blank trials' and small visual targets presented tachistoscopically within his blind hemifield was tested at five positions within the scotoma. For each position a Receiver-Operating-Characteristic curve (ROC) was determined. Results show the patient's discrimination between the target and no-target conditions to be better than expected by guessing at three positions along the horizontal meridian, whereas in the natural Blind Spot within the scotoma no significant discrimination is found. Thus, light scatter produced by the visual target cannot explain the observed residual vision. At least three anatomical pathways could be responsible for the discrimination: the retino-collicular projection, the retino-geniculo-striatal projection, and the retino-geniculo-extrastriatal projection.

Aged↗
PubMed1985

Hidden-face recognition: comparing foveal and extrafoveal performance.

Ambiguous stimulus material was computer-generated by superimposing image components of a target-face and either a random checkerboard texture or a masking face. The recognition of the target-face was studied both for foveal and extrafoveal vision. Compensation of the peripheral disadvantage in image discrimination by rescaling the stimulus size was possible only in the case of texture. Comparable results were obtained from combining band-pass image components of the portraits. Results suggest that it is the relative inability to recover a signal from spatially correlated noise that characterizes visual discrimination in the peripheral visual field.

Adult↗
PubMed1979

[Partial effects of estrogens and 19-nortestoron derivatives].

In the present review the extragenital effects of steroidal estrogens and 19-norandrogen derivatives on mammalian organs and tissues are described. In detail experimental and clinical findings concerning the influence of these compounds on carbohydrate-, lipid- and protein metabolism, on the cardio-vascular system, the blood coagulation, the bone-tissue, the connective-tissue, the central nervous system and the immune system are summarised. These effects are mainly discussed as possible side effects and also as base for new therapeutic concepts.

Blood Coagulation↗