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Biomedical subjects

B Bauer

Publications and source records attributed to B Bauer.

At least 199 records · Page 11Linked to original sources
PubMed1984

Detection and quantitation of coronary artery stenoses from digital subtraction angiograms compared with 35-millimeter film cineangiograms.

To assess the ability to detect coronary artery narrowings from computer-acquired angiograms, a panel of 4 observers independently identified and measured focal coronary narrowings from digital subtraction angiograms and compared the results to those obtained from standard 35-mm cine film angiograms. Both cine and digital angiograms were obtained sequentially using selective intracoronary artery injection of standard amounts of iodinated contrast media. Digital images were obtained at 8 frames/s with a 512 X 512 X 8-bit pixel matrix. Modifications in the imaging chain for computer acquisition included a slower pulsed radiographic mode, a progressive scan camera, and initial storage of the images on an 80-megabyte digital hard disk. Postprocessing computer algorithms were used to enhance the unsubtracted digital images; these included single-frame, mask-mode subtraction, vessel boundary edge enhancement, and 4-fold pixel magnification. In 19 patient studies, 32 arteries were reduced more than 25% in diameter according to at least 1 of 4 observers on either the digital or cine film angiograms. There was no significant difference in the mean percent diameter narrowing for all the narrowings between the digital angiograms (53 +/- 31%) and the cineangiograms (52 +/- 31%). In addition, a 2-way analysis of variance yielded no significant difference between the amount of variability in the measurements between the cine film and the digital technique. This similar variability persisted when subsets of patients based on the degrees of stenosis were considered (e.g., only narrowings from 50 to 90% diameter reduction).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

[Radiologic studies of the correlation between the mineral content of the peripheral and axial skeleton].

Estimations of mineral content of normal human skeletons using three radiological methods have led to the following conclusions: 1. Bone density of vertebral bodies increases from T.6 to L.5. Average values for thoracic and lumbar vertebrae are 0.71 and 0.88 g./cm2. 2. There is no linear correlation between the mineral content of an easily accessible peripheral bone and of the vertebrae. 3. The method for bone mineral estimation, using thulium170, which was developed in Dresden, can be used for the peripheral and central skeleton. 4. 125-photon absorption us useful for measurements on the peripheral skeleton, where it is the most elegant and accurate method. It is, however, useless for measurements of the central skeleton.

Adolescent↗
PubMed1984

The release of (3H)-GABA from the rabbit retina.

The neuronal and glial release of (3H)-GABA from rabbit retina has been studied. The results indicate, that neither are there any glutamate, aspartate or glycine receptors on the GABA accumulating neurons, nor any GABA autoreceptors. (3H)-GABA was found to be released by 40 mM K+ from retinal neurons, but not from glia, and the release was not dependent on extracellular Ca++. This indicates a release from a non vesicular transmitter pool. Ouabain has been proposed as a pharmacological tool for studying the release of (3H)-GABA located in neuronal cytoplasm. However, it induced an increased release of (3H)-GABA from both neurons and glia and it is therefore unlikely that it can be used for the specific purpose of studying release from neuronal cytoplasm.

Amino Acids↗
PubMed1984

[Results of radiculomyelography with dimer-X following lumbar intervertebral disk operations].

In radiculomyelogram after operation of lumbar intervertebral disk has been investigated an adhesive arachnopathy in 24 out of 86 patients. It appears increased in patients with two operations of the intervertebral disk, revision of several intervertebral spaces and after massed prolapses. The etiological importance of hyperosmolar X-ray contrast media is comparatively slight. Characteristical clinical findings were not evident in patients with arachnopathy. In some patients the protein content in cerebrospinal fluid was raised, it could be observed as an unspecific reaction and a relative monocytosis in the cytogram. Two third of the patients with recurrent nucleus pulposus prolapse were diagnosed rightly by radiculomyelography, though there are difficulties in the differentiation of adhesive-fibrotic changes.

Adult↗
PubMed1983

Hysteretic behaviour of citrate synthase. Alternating sites during the catalytic cycle.

Chemically and stereochemically pure (3S)-citryl-CoA was prepared enzymically and used as a substrate for citrate synthase to investigate the previously determined unexpectedly low rate of hydrolysis of the (3RS)-substrate. The unnatural R-diastereomer of this mixture is not inhibitory. At low enzyme concentrations the rate of citryl-CoA hydrolysis was linear until the reaction went near to completion; the hydrolysis approached Michaelis-Menten kinetics at high enzyme concentrations. In between these concentration extremes a biphasic rate dependence was detectable, where a fast initial phase lasting a few seconds was followed by a slow steady-state phase. Citrate synthase was characterized as a hysteretic enzyme existing in two interconvertible forms, which were designated according to their functions as hydrolase E and ligase E'. The hysteretic behaviour originates in the cleavage of citryl-CoA to acetyl-CoA and oxaloacetate. This reaction occurs on the ligase form E', which represents a trap for enzyme form E, the hydrolase. The conclusions given above are strengthened by the ordinary hydrolysis kinetics of (2S)-malyl-CoA, a substrate that is not subject to cleavage of the C-C bond on the synthase. The results satisfy the kinetic criterion for citryl-CoA being an intermediate of the physiological synthase reaction and, therefore, establish the oscillation of the synthase between hydrolase and ligase states during the catalytic cycle. A disorganization of these oscillations can be achieved by limited tryptic proteolysis of the synthase.

Binding Sites↗
PubMed1983

[Combination treatment of malignant brain tumors. Results of initial experiences].

First experiences with the combined treatment of malignant gliomas (29 cases) are presented in connection with the results reported in literature. The cytostatic therapy has been carried out according to the modified Israel-Scheme of Heiss et al. Using the combined treatment (resection of tumor, radiotherapy and polychemotherapy) a prolongation of survival time to 55 till 80 weeks is noticeable. The patients observed in our study survived on an average 79,8 weeks (operation and chemotherapy) resp. 94,7 weeks (operation, radiotherapy and chemotherapy). Special problems of the cytostatic therapy of malignant brain tumors are considered, among others in relation to the blood-brain-barrier and the tumorcell-kinetics; a further optimation of therapy is necessary.

Adolescent↗
PubMed1982

Enzyme induction in Streptomyces hydrogenans. Comparison of the effects of different steroids to increase the activity of 3 alpha, 20 beta-hydroxysteroid dehydrogenase and of 3 beta, 17 beta-hydroxysteroid dehydrogenase.

After cultivation of Streptomyces hydrogenans in the presence of different steroids the activity of both 3 alpha, 20 beta-hydroxysteroid dehydrogenase and 3 beta, 17 beta-hydroxysteroid dehydrogenase was determined in the cell homogenate of the microorganism. By comparing the efficacy of the steroids to increase enzyme activities, steroids could be divided into 3 groups: a) steroids which stimulated preferentially the activity of 3 alpha, 20 beta-hydroxysteroid dehydrogenase (e. g., corticosterone), b) steroids which stimulated preferentially 3 beta, 17 beta-hydroxysteroid dehydrogenase (estradiol-17 beta), and c) those behaving intermediately (e. g., progesterone, 5 alpha -dihydrotestosterone). Highest 3 beta, 17 beta-hydroxysteroid dehydrogenase activity could be measured 2 h after addition of 5 alpha-dihydrotestosterone to the culture medium. The activity of 3 alpha, 20 beta-hydroxysteroid dehydrogenase, however, increased continuously up to 4 h. 3 alpha, 20 beta-hydroxysteroid dehydrogenase and 3 beta, 17 beta-hydroxysteroid dehydrogenase syntheses seemed to be controlled by steroids in a non-coordinate manner.

17-Hydroxysteroid Dehydrogenases↗
PubMed1982

Circular forms of viral DNA in Marek's disease virus-transformed lymphoblastoid cells.

The state of viral DNA in three Marek's disease virus (MDV)-transformed chicken cell lines (MDCC-MSB-1, MDCC-HP-2, MDCC-RP-1) was investigated by CsCl-density gradient centrifugation, and sedimentation analysis in neutral glycerol gradients. Each cell line contained MDV DNA integrated into the host cell genome. Additionally, free viral DNA could be identified in MDCC-MSB-1 and MDCC-HP-2 cells, sedimenting at about 100 S, and banding at the position of circular DNA in CsCl-ethidiumbromide gradients. Thus, MDV DNA with properties of circular plasmid DNA could be demonstrated in 2 virus-transformed cell lines. The significance of circular plasmid forms of viral DNA remains yet to be clarified, since these are apparently not regularly found in MDV-transformed cells.

Animals↗
PubMed1982

Stimulated release of 3H-glycine from retina.

The release of 3H-glycine was studied from rabbit retinas. Kainic acid (10(-5) M), a glutamate agonist, evoked prompt CA2+-dependent increased release of 3H-glycine. However, nuciferine (10(-4) M) could not suppress the effect of kainic acid. The effect of glutamic acid (10(-5) M) was significantly reduced in the presence of nuciferine (10(-4) M). The GABA analogues, muscimol and THIP, had no effect on the release of 3H-glycine. Aspartate and cystic acid were also without effect.

Animals↗
PubMed1981

Evidence from inhibitor studies for conformational changes of citrate synthase.

1. Substrate analogue CoA derivatives were applied as inhibitors of citrate synthase. Substitution of the acyl-CoA oxygen next to sulfur by hydrogen was without marked influence on the affinity. 2. Carboxymethyl-CoA, a structural analogue of enolic acetyl-CoA, was characterized as a transition state analogue by an affinity 100-fold higher than that of acetyl-CoA. Ks of the binary inhibitor-enzyme complex was high (230 microM) but that of the ternary inhibitor-oxaloacetate-enzyme complex was 0.07 microM. Both enzyme subunits bound the inhibitor independently, also in the presence of oxaloacetate. 3. (3R,S)-3,4-Dicarboxy-3-hydroxybutyl-CoA, an analogue of citryl-CoA, inhibited the overall reaction noncompetitively against acetyl-CoA and against oxaloacetate; it was a competitive inhibitor against the hydrolysis and cleavage reactions of (3S)-citryl-CoA. Kinetic data suggest that this inhibitor represents an intermediate analogue. 4. The results given above indicate conformational changes of the synthase during the catalytic cycle. In the proposed mechanism the free enzyme represents a hydrolase which in the presence of oxaloacetate, by a well-known conformational change, is converted into a ligase. If both substrates are present, the ligase is reconverted into the hydrolase upon formation of the intermediate, (3S)-citryl-CoA.

Acetyl Coenzyme A↗
PubMed1981

[Psychological factors in duodenal ulcers].

With the aid of a clinical questionnaire and the I-N-R-personality test of Eysenck (as modified by Böttcher), we examined 127 male patients with clinically and radiologically proven ulcer compared to 145 age-matched persons without gastric affections. The features extraversion, neuroticism (emotional lability) and rigidity were determined and the question of an association with symptoms, age at onset of disease as well as occupational and familial factors statistically analyzed. With high significance, duodenal ulcer patients are more often emotionally labile and psychically more rigid. In the event the disease manifests under the age of 30, in ulcer patients introversion too is pronounced with highly significant frequency. Those patients complaining of conflicts with collaborators, lack of sleep, occupational overexertion, noise, draught at work place, present, compared to others without these complaints, a frequently emotional lability with high significance.

Adult↗