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Biomedical subjects

A Bauer

Publications and source records attributed to A Bauer.

At least 181 records · Page 10Linked to original sources
PubMed1994

High-resolution one- and two-dimensional 1H MRS of human brain tumor and normal glial cells.

Astrocytoma (WHO grade II, III), glioblastoma, malignant melanoma, and normal glial cell cultures, established from biopsies, were investigated by 1H MRS. At a 1H resonance frequency of 500 MHz (11.75 T) a high spectral resolution was achieved in 1D 1H spectra; in conjunction with 2D shift-correlated (COSY) MRS, resonances of alanine, aspartate, choline, creatine, glutamate, glutamine, hypotaurine, myo-inositol, phosphocreatine, phosphoryl-ethanolamine, phosphoryl-choline, lactate, lysine, N-acetylaspartate, taurine, threonine and valine could be identified. T1 relaxation times for the most prominent compounds are presented. T1 values of lactate ranged between 450 ms and 850 ms. The intensity of the lactate signal revealed differences between individual spectra, but exhibited no correlation between different tumor specimens or degree of malignancy. It was shown that the lactate signal at 1.3 ppm is covered by peaks arising from threonine and fatty acids. The choline signal level varied among spectra of different tumors, among tumors with similar degree of malignancy, and within the same tumor. Further preliminary differences due to aspartate, inositol and glutamine/glutamate were found in 1D and 2D COSY spectra between normal glial cells as well as different tumors. These results indicate that some differences observed in in vivo spectra may be attributable to secondary macroscopic structural changes (hypoxia, necrosis) and not to tumor inherent characteristics. Further correlation between in vivo and in vitro spectroscopy is therefore required.

Astrocytoma↗
PubMed1994

An improved pair potential to recognize native protein folds.

We present a novel method to improve a simple pair potential of mean force, derived from experimentally determined protein structures, in such a way that it recognizes native protein folds with high reliability. This improvement is based on the use of mutation data matrices to overcome difficulties arising from the poor statistics of small sample sizes. A set of 167 protein chains taken from the Brookhaven Protein Structure Data Base, selected from high-resolution structures and avoiding homologous proteins, is used for generation of the potential set. The potential describes interresidue pair energies depending on distance and sequential separation, and is calculated using the Boltzmann equation. Its performance is evaluated by jackknife tests that try to identify the native fold for a given sequence among a large number of possible threadings on all structures in the set without allowing for gaps. Up to 94% of the protein chains are correctly assigned to their native folds, so that all proper single-chain domains are recognized.

Computer Simulation↗
PubMed1994

[Multicentric reticulohistiocytosis and myelodysplastic syndrome].

Multicentric reticulohistiocytosis (MRH) is a rare disorder of skin and joints, and its aetiology is unknown. We describe a male patient who had first developed osteoblastic lesions of the skeleton in 1976 at the age of 59 years. Three years later, he presented with multiple papular and nodular skin lesions, predominantly on the limbs and upper trunk, and 4 years later he developed painful arthropathy. In 1988 skin examination showed multiple brownish-red papulo-nodules, some of which, at mechanically stressed areas, were ulcerated. The patient complained of pronounced arthrotic disorders with reduced joint mobility. Examination of biopsy specimens from active skin lesions demonstrated extensive numbers of macrophages with partial confluence to giant cells with typical ground-glass cytoplasm. Electron microscopy revealed phagocytosis of collagen-like-structures. Examination of bone marrow biopsy specimens revealed diffuse infiltration by histiocytic cells. The diagnosis made was therefore MRH. The patient was treated for several years with different therapeutic regimens, including azathioprin, dapsone, prednisolon, chlorambucil and cyclophosphamide, and complete remission of skin lesions and of bone marrow infiltration was observed. However, a myelodysplastic syndrome with refractory anaemia and ring sideroblasts developed, which is generally understood to be a preleukaemic condition. Myelodysplastic syndromes commonly develop between 3 and 10 years after the start of a therapy with antineoplastic agents.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1994

Cocaine alters the onset and maintenance of maternal behavior in lactating rats.

Though much attention has been devoted to the behavioral and physiological consequences of cocaine abuse in offspring, little is known regarding the effects on the maternal behavior of the cocaine-exposed dam. We examined whether cocaine affects the initiation (late pregnancy) and/or maintenance (postpartum [PP]) phases of full maternal behavior (FMB; retrieving, grouping, and crouching over six pups) in Sprague-Dawley female rats. In Experiment 1, cocaine (5.0 or 10.0 mg/kg) or saline was administered on PP day 5 or 6 and FMB scored. Both dosages significantly disrupted FMB, particularly crouching, though 10.0 mg/kg had a greater effect on FMB. Experiment 2 (using 10.0 mg/kg cocaine) examined specific elements of the disruption and found significant reductions in proportion of females engaging in FMB, as well as increases in the latencies to contact, retrieve, lick, group, and crouch over pups. In Experiment 3 osmotic pumps containing 20 mg cocaine/kg/day or saline were implanted SC in day 14 pregnant rats. FMB testing was performed on days 1-2 postpartum together with a T-maze pup-retrieval test on postpartum days 3-5. Cocaine disrupted FMB in the homecage, in general, rendering the females less attentive to young, but was without effect in the T-maze tests. Cocaine--perhaps owing to its purported dopaminergic activity--may operate through motivational mechanisms to disrupt FMB in the postpartum maintenance phase; and through effects on late pregnancy levels of prolactin (a hormone which stimulates FMB), to disrupt maternal behavior during the initiation phase.

Animals↗
PubMed1994

Modulation of the electrically evoked blink reflex by different levels of tonic preinnervation of the orbicularis oculi muscle.

Eleven subjects were instructed to maintain different levels of tonic pre-innervation of the two orbicularis oculi muscles: relaxation, 25%, 50%, 75% and 100% of maximum voluntary contraction. Surface electromyographic activity was recorded unilaterally from the left orbicularis oculi muscle while cutaneous reflex responses were evoked electrically during different levels of pre-innervation. Latencies of the early (R1) and late (R2) blink reflex responses were significantly shorter during moderate pre-innervation level (25%) compared to relaxation, with no further latency decrease under stronger tonic pre-innervation. The amplitude of the R1 component increased significantly until a pre-innervation level of 50% of maximum voluntary contraction was reached. There was no further amplitude enhancement with stronger pre-innervation. R2 amplitudes linearly increased with the increasing pre-innervation levels, possibly reflecting recruitment of a greater number of motor units for the late component or a postponement of motoneuron synchronization of the late component.

Adult↗
PubMed1994

[Not Available].

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Emblems and Insignia↗
PubMed1993

[American football in Germany--aspects of trauma surgery].

While football injuries in the USA are well documented and thoroughly studied, informations on injuries caused by this spreading sport in Germany are not available. For this reason the Berufsgenossenschaftliche Unfallklinik in Frankfurt conducted a prospective study to register all injuries in major league football in southern Germany in 1991. In 49 games that were evaluated we found 281 minor injuries, mainly skin lesions and concussions of extremities. In addition 33 significant injuries were registered, amongst them 30% injuries of knee ligaments. The only severe injury was an abdominal hit causing a intrahepatic hematoma. The results of our study are comparable to the injury risks found in US college football as well as to those found in German statistics on soccer and hockey. Although no fatal injuries in our study were registered, this should not lead to neglecting the potential risks in football.

Adult↗
PubMed1993

Imaging ischemic tissue at risk of infarction during stroke.

Autoradiograms obtained after middle cerebral artery occlusion (MCAO) in spontaneously hypertensive rats show that the 99mTc complex of a 2-nitroimidazole-derivatized propylene amine oxime (BMS-181321) is selectively retained in acutely ischemic brain before disruption of the blood-brain barrier (BBB), but not in the ischemic infarct. BMS-181321 is therefore a marker of ischemic tissue at risk of infarction and its uptake, unlike that of x-ray and magnetic resonance contrast agents, does not require disruption of the BBB. In keeping with this conclusion, we have found that the single-pass cerebral extraction fraction of BMS-181321 is 0.67 at normal rat whole-brain blood flow. Sequential single-photon emission computed tomographic images obtained from cats after MCAO show that the initial distribution of BMS-181321 approximates regional CBF and that selective retention subsequently produces a positive image within the ischemic territory. BMS-181321 is the first Tc complex able to indicate not only ischemia, but also ischemic tissue at risk of infarction. Use of this novel Tc complex to monitor biochemical events during ischemia may contribute to the clinical management of acute stroke.

Animals↗
PubMed1993

[Not Available].

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Historiography↗
PubMed1992

Muscarinic desensitization after septal lesions in rat hippocampus: evidence for the involvement of G-proteins.

Three days after bilateral septal lesions, regional and laminar densities of the muscarinic acetylcholine receptors of the dorsal rat hippocampus were studied. The concentration of [3H]N-methylscopolamine binding sites and muscarinic M1 and M2 receptor subtypes, as well as the affinity of muscarinic receptors and their sensitivity to modulation by 5-guanylylimidodiphosphate were analysed by quantitative receptor autoradiography. The measurement of these parameters was performed with a computerized image-processing system allowing a spatial resolution down to the level of single hippocampal layers. No postlesional changes of the density of M1 receptors were detected. M2 receptors showed a remarkable decrease in concentration (less than 21%) in some hippocampal layers after septal lesions. In competition experiments the affinity of muscarinic receptors for the cholinergic agonist carbamylcholine chloride decreased significantly in all hippocampal subregions and layers of the lesioned animals. In contrast to controls, the sensitivity of muscarinic receptors of the lesioned animals could not be modulated by 5-guanylylimidodiphosphate. These findings demonstrate a desensitization of muscarinic receptors in the rat hippocampus three days after septal lesions, which is caused by changes of the coupling of guanine nucleotide-binding proteins to muscarinic receptors. Therefore, the lesion-induced alteration of the muscarinic receptor-effector complex is a major aspect of the hippocampal plasticity after cholinergic denervation.

Animals↗
PubMed1992

Nonspecific immunostimulation with low doses of cyclophosphamide (LDCY), thymostimulin, and Echinacea purpurea extracts (echinacin) in patients with far advanced colorectal cancers: preliminary results.

Outpatients (n = 15) with metastasizing far advanced colorectal cancers received immunotherapy consisting of low-dose cyclophosphamide (LDCY) 300 mg/m2 every 28 days i.v., thymostimulin 30 mg/m2, days 3-10 after low-dose cyclophosphamide i.m. once daily, then twice a week, and echinacin 60 mg/m2 together with thymostimulin i.m. All patients had had previous surgery and/or chemotherapy and had progressive disease upon entering the study. Two months after onset of therapy a partial tumor regression was documented in one and a stable disease in 6 other patients by abdominal ultrasonography, decrease of the tumor markers carcinoembryonic antigen (CEA), CA 19-9, CA 15-3, and/or chest roentgenography, which may also be attributed to the natural course of disease. Mean survival time was 4 months, 2 patients survived for more than 8 months. Immunotherapy was well tolerated by all patients without side effects.

Adjuvants, Immunologic↗
PubMed1992

[Not Available].

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Education, Medical↗